]> git.bitcoin.ninja Git - rust-lightning/commitdiff
Add tool to read a Rust crate and generate C-compatible wrappers
authorMatt Corallo <git@bluematt.me>
Tue, 12 May 2020 18:49:29 +0000 (14:49 -0400)
committerMatt Corallo <git@bluematt.me>
Fri, 11 Sep 2020 01:58:44 +0000 (21:58 -0400)
In general, it maps:
 * Traits to a struct with a void* and a list of function pointers,
   emulating what the compiler will do for a dyn trait anyway,
 * Structs as a struct with a single opaque pointer to the
   underlying type and a flag to indicate ownership. While this is
   a bit less effecient than just a direct pointer, it neatly lets
   us expose in the public interface the concept of ownership by
   setting a flag in the generated struct.
 * Unit enums as enums with each type copied over and conversion
   functions,
 * Non-unit enums have each field converted back and forth with a
   type flag and a union across all the C-mapped fields.

c-bindings-gen/Cargo.toml [new file with mode: 0644]
c-bindings-gen/src/blocks.rs [new file with mode: 0644]
c-bindings-gen/src/main.rs [new file with mode: 0644]
c-bindings-gen/src/types.rs [new file with mode: 0644]

diff --git a/c-bindings-gen/Cargo.toml b/c-bindings-gen/Cargo.toml
new file mode 100644 (file)
index 0000000..6f4716e
--- /dev/null
@@ -0,0 +1,12 @@
+[package]
+name = "c-bindings-gen"
+version = "0.0.1"
+authors = ["Matt Corallo"]
+edition = "2018"
+
+[dependencies]
+syn = { version = "1", features = ["full", "extra-traits"] }
+proc-macro2 = "1"
+
+# We're not in the workspace as we're just a binary code generator:
+[workspace]
diff --git a/c-bindings-gen/src/blocks.rs b/c-bindings-gen/src/blocks.rs
new file mode 100644 (file)
index 0000000..9e255a1
--- /dev/null
@@ -0,0 +1,373 @@
+//! Printing logic for basic blocks of Rust-mapped code - parts of functions and declarations but
+//! not the full mapping logic.
+
+use std::collections::HashMap;
+use std::fs::File;
+use std::io::Write;
+use proc_macro2::{TokenTree, Span};
+
+use crate::types::*;
+
+/// Writes out a C++ wrapper class for the given type, which contains various utilities to access
+/// the underlying C-mapped type safely avoiding some common memory management issues by handling
+/// resource-freeing and prevending accidental raw copies.
+pub fn write_cpp_wrapper(cpp_header_file: &mut File, ty: &str, has_destructor: bool) {
+       writeln!(cpp_header_file, "class {} {{", ty).unwrap();
+       writeln!(cpp_header_file, "private:").unwrap();
+       writeln!(cpp_header_file, "\tLDK{} self;", ty).unwrap();
+       writeln!(cpp_header_file, "public:").unwrap();
+       writeln!(cpp_header_file, "\t{}(const {}&) = delete;", ty, ty).unwrap();
+       if has_destructor {
+               writeln!(cpp_header_file, "\t~{}() {{ {}_free(self); }}", ty, ty).unwrap();
+       }
+       writeln!(cpp_header_file, "\t{}({}&& o) : self(o.self) {{ memset(&o, 0, sizeof({})); }}", ty, ty, ty).unwrap();
+       writeln!(cpp_header_file, "\t{}(LDK{}&& m_self) : self(m_self) {{ memset(&m_self, 0, sizeof(LDK{})); }}", ty, ty, ty).unwrap();
+       writeln!(cpp_header_file, "\toperator LDK{}() {{ LDK{} res = self; memset(&self, 0, sizeof(LDK{})); return res; }}", ty, ty, ty).unwrap();
+       writeln!(cpp_header_file, "\tLDK{}* operator &() {{ return &self; }}", ty).unwrap();
+       writeln!(cpp_header_file, "\tLDK{}* operator ->() {{ return &self; }}", ty).unwrap();
+       writeln!(cpp_header_file, "\tconst LDK{}* operator &() const {{ return &self; }}", ty).unwrap();
+       writeln!(cpp_header_file, "\tconst LDK{}* operator ->() const {{ return &self; }}", ty).unwrap();
+       writeln!(cpp_header_file, "}};").unwrap();
+}
+
+/// Prints the docs from a given attribute list unless its tagged no export
+pub fn writeln_docs<W: std::io::Write>(w: &mut W, attrs: &[syn::Attribute], prefix: &str) {
+       for attr in attrs.iter() {
+               let tokens_clone = attr.tokens.clone();
+               let mut token_iter = tokens_clone.into_iter();
+               if let Some(token) = token_iter.next() {
+                       match token {
+                               TokenTree::Punct(c) if c.as_char() == '=' => {
+                                       // syn gets '=' from '///' or '//!' as it is syntax for #[doc = ""]
+                               },
+                               TokenTree::Group(_) => continue, // eg #[derive()]
+                               _ => unimplemented!(),
+                       }
+               } else { continue; }
+               match attr.style {
+                       syn::AttrStyle::Inner(_) => {
+                               match token_iter.next().unwrap() {
+                                       TokenTree::Literal(lit) => {
+                                               // Drop the first and last chars from lit as they are always "
+                                               let doc = format!("{}", lit);
+                                               writeln!(w, "{}//!{}", prefix, &doc[1..doc.len() - 1]).unwrap();
+                                       },
+                                       _ => unimplemented!(),
+                               }
+                       },
+                       syn::AttrStyle::Outer => {
+                               match token_iter.next().unwrap() {
+                                       TokenTree::Literal(lit) => {
+                                               // Drop the first and last chars from lit as they are always "
+                                               let doc = format!("{}", lit);
+                                               writeln!(w, "{}///{}", prefix, &doc[1..doc.len() - 1]).unwrap();
+                                       },
+                                       _ => unimplemented!(),
+                               }
+                       },
+               }
+       }
+}
+
+/// Print the parameters in a method declaration, starting after the open parenthesis, through and
+/// including the closing parenthesis and return value, but not including the open bracket or any
+/// trailing semicolons.
+///
+/// Usable both for a function definition and declaration.
+///
+/// this_param is used when returning Self or accepting a self parameter, and should be the
+/// concrete, mapped type.
+pub fn write_method_params<W: std::io::Write>(w: &mut W, sig: &syn::Signature, associated_types: &HashMap<&syn::Ident, &syn::Ident>, this_param: &str, types: &mut TypeResolver, generics: Option<&GenericTypes>, self_ptr: bool, fn_decl: bool) {
+       if sig.constness.is_some() || sig.asyncness.is_some() || sig.unsafety.is_some() ||
+                       sig.abi.is_some() || sig.variadic.is_some() {
+               unimplemented!();
+       }
+       if sig.generics.lt_token.is_some() {
+               for generic in sig.generics.params.iter() {
+                       match generic {
+                               syn::GenericParam::Type(_)|syn::GenericParam::Lifetime(_) => {
+                                       // We ignore these, if they're not on skipped args, we'll blow up
+                                       // later, and lifetimes we just hope the C client enforces.
+                               },
+                               _ => unimplemented!(),
+                       }
+               }
+       }
+
+       let mut first_arg = true;
+       let mut num_unused = 0;
+       for inp in sig.inputs.iter() {
+               match inp {
+                       syn::FnArg::Receiver(recv) => {
+                               if !recv.attrs.is_empty() || recv.reference.is_none() { unimplemented!(); }
+                               write!(w, "this_arg: {}{}",
+                                       match (self_ptr, recv.mutability.is_some()) {
+                                               (true, true) => "*mut ",
+                                               (true, false) => "*const ",
+                                               (false, true) => "&mut ",
+                                               (false, false) => "&",
+                                       }, this_param).unwrap();
+                               assert!(first_arg);
+                               first_arg = false;
+                       },
+                       syn::FnArg::Typed(arg) => {
+                               if types.skip_arg(&*arg.ty, generics) { continue; }
+                               if !arg.attrs.is_empty() { unimplemented!(); }
+                               let mut is_ref = if let syn::Type::Reference(_) = *arg.ty { true } else { false };
+                               if let syn::Type::Reference(syn::TypeReference { ref elem, .. }) = *arg.ty {
+                                       if let syn::Type::Slice(_) = &**elem {
+                                               // Slices are mapped to non-ref Vec types, so we want them to be mut
+                                               // letting us drain(..) the underlying Vec.
+                                               is_ref = false;
+                                       }
+                               }
+                               match &*arg.pat {
+                                       syn::Pat::Ident(ident) => {
+                                               if !ident.attrs.is_empty() || ident.subpat.is_some() {
+                                                       unimplemented!();
+                                               }
+                                               write!(w, "{}{}{}: ", if first_arg { "" } else { ", " }, if is_ref || !fn_decl { "" } else { "mut " }, ident.ident).unwrap();
+                                               first_arg = false;
+                                       },
+                                       syn::Pat::Wild(wild) => {
+                                               if !wild.attrs.is_empty() { unimplemented!(); }
+                                               write!(w, "{}unused_{}: ", if first_arg { "" } else { ", " }, num_unused).unwrap();
+                                               num_unused += 1;
+                                       },
+                                       _ => unimplemented!(),
+                               }
+                               types.write_c_type(w, &*arg.ty, generics, false);
+                       }
+               }
+       }
+       write!(w, ")").unwrap();
+       match &sig.output {
+               syn::ReturnType::Type(_, rtype) => {
+                       write!(w, " -> ").unwrap();
+                       if let Some(mut remaining_path) = first_seg_self(&*rtype) {
+                               if let Some(associated_seg) = get_single_remaining_path_seg(&mut remaining_path) {
+                                       // We're returning an associated type in a trait impl. Its probably a safe bet
+                                       // that its also a trait, so just return the trait type.
+                                       let real_type = associated_types.get(associated_seg).unwrap();
+                                       types.write_c_type(w, &syn::Type::Path(syn::TypePath { qself: None,
+                                               path: syn::PathSegment {
+                                                       ident: (*real_type).clone(),
+                                                       arguments: syn::PathArguments::None
+                                               }.into()
+                                       }), generics, true);
+                               } else {
+                                       write!(w, "{}", this_param).unwrap();
+                               }
+                       } else {
+                               if let syn::Type::Reference(r) = &**rtype {
+                                       // We can't return a reference, cause we allocate things on the stack.
+                                       types.write_c_type(w, &*r.elem, generics, true);
+                               } else {
+                                       types.write_c_type(w, &*rtype, generics, true);
+                               }
+                       }
+               },
+               _ => {},
+       }
+}
+
+/// Print the main part of a method declaration body, starting with a newline after the function
+/// open bracket and converting each function parameter to or from C-mapped types. Ends with "let
+/// mut ret = " assuming the next print will be the unmapped Rust function to call followed by the
+/// parameters we mapped to/from C here.
+pub fn write_method_var_decl_body<W: std::io::Write>(w: &mut W, sig: &syn::Signature, extra_indent: &str, types: &TypeResolver, generics: Option<&GenericTypes>, to_c: bool) {
+       let mut num_unused = 0;
+       for inp in sig.inputs.iter() {
+               match inp {
+                       syn::FnArg::Receiver(_) => {},
+                       syn::FnArg::Typed(arg) => {
+                               if types.skip_arg(&*arg.ty, generics) { continue; }
+                               if !arg.attrs.is_empty() { unimplemented!(); }
+                               macro_rules! write_new_var {
+                                       ($ident: expr, $ty: expr) => {
+                                               if to_c {
+                                                       if types.write_to_c_conversion_new_var(w, &$ident, &$ty, generics, false) {
+                                                               write!(w, "\n\t{}", extra_indent).unwrap();
+                                                       }
+                                               } else {
+                                                       if types.write_from_c_conversion_new_var(w, &$ident, &$ty, generics) {
+                                                               write!(w, "\n\t{}", extra_indent).unwrap();
+                                                       }
+                                               }
+                                       }
+                               }
+                               match &*arg.pat {
+                                       syn::Pat::Ident(ident) => {
+                                               if !ident.attrs.is_empty() || ident.subpat.is_some() {
+                                                       unimplemented!();
+                                               }
+                                               write_new_var!(ident.ident, *arg.ty);
+                                       },
+                                       syn::Pat::Wild(w) => {
+                                               if !w.attrs.is_empty() { unimplemented!(); }
+                                               write_new_var!(syn::Ident::new(&format!("unused_{}", num_unused), Span::call_site()), *arg.ty);
+                                               num_unused += 1;
+                                       },
+                                       _ => unimplemented!(),
+                               }
+                       }
+               }
+       }
+       match &sig.output {
+               syn::ReturnType::Type(_, _) => {
+                       write!(w, "let mut ret = ").unwrap();
+               },
+               _ => {},
+       }
+}
+
+/// Prints the parameters in a method call, starting after the open parenthesis and ending with a
+/// final return statement returning the method's result. Should be followed by a single closing
+/// bracket.
+///
+/// The return value is expected to be bound to a variable named `ret` which is available after a
+/// method-call-ending semicolon.
+pub fn write_method_call_params<W: std::io::Write>(w: &mut W, sig: &syn::Signature, associated_types: &HashMap<&syn::Ident, &syn::Ident>, extra_indent: &str, types: &TypeResolver, generics: Option<&GenericTypes>, this_type: &str, to_c: bool) {
+       let mut first_arg = true;
+       let mut num_unused = 0;
+       for inp in sig.inputs.iter() {
+               match inp {
+                       syn::FnArg::Receiver(recv) => {
+                               if !recv.attrs.is_empty() || recv.reference.is_none() { unimplemented!(); }
+                               if to_c {
+                                       write!(w, "self.this_arg").unwrap();
+                                       first_arg = false;
+                               }
+                       },
+                       syn::FnArg::Typed(arg) => {
+                               if types.skip_arg(&*arg.ty, generics) {
+                                       if !to_c {
+                                               if !first_arg {
+                                                       write!(w, ", ").unwrap();
+                                               }
+                                               first_arg = false;
+                                               types.no_arg_to_rust(w, &*arg.ty, generics);
+                                       }
+                                       continue;
+                               }
+                               if !arg.attrs.is_empty() { unimplemented!(); }
+                               macro_rules! write_ident {
+                                       ($ident: expr) => {
+                                               if !first_arg {
+                                                       write!(w, ", ").unwrap();
+                                               }
+                                               first_arg = false;
+                                               if to_c {
+                                                       types.write_to_c_conversion_inline_prefix(w, &*arg.ty, generics, false);
+                                                       write!(w, "{}", $ident).unwrap();
+                                                       types.write_to_c_conversion_inline_suffix(w, &*arg.ty, generics, false);
+                                               } else {
+                                                       types.write_from_c_conversion_prefix(w, &*arg.ty, generics);
+                                                       write!(w, "{}", $ident).unwrap();
+                                                       types.write_from_c_conversion_suffix(w, &*arg.ty, generics);
+                                               }
+                                       }
+                               }
+                               match &*arg.pat {
+                                       syn::Pat::Ident(ident) => {
+                                               if !ident.attrs.is_empty() || ident.subpat.is_some() {
+                                                       unimplemented!();
+                                               }
+                                               write_ident!(ident.ident);
+                                       },
+                                       syn::Pat::Wild(w) => {
+                                               if !w.attrs.is_empty() { unimplemented!(); }
+                                               write_ident!(format!("unused_{}", num_unused));
+                                               num_unused += 1;
+                                       },
+                                       _ => unimplemented!(),
+                               }
+                       }
+               }
+       }
+       write!(w, ")").unwrap();
+       match &sig.output {
+               syn::ReturnType::Type(_, rtype) => {
+                       write!(w, ";\n\t{}", extra_indent).unwrap();
+
+                       if to_c && first_seg_self(&*rtype).is_some() {
+                               // Assume rather blindly that we're returning an associated trait from a C fn call to a Rust trait object.
+                               write!(w, "ret").unwrap();
+                       } else if !to_c && first_seg_self(&*rtype).is_some() {
+                               if let Some(mut remaining_path) = first_seg_self(&*rtype) {
+                                       if let Some(associated_seg) = get_single_remaining_path_seg(&mut remaining_path) {
+                                               let real_type = associated_types.get(associated_seg).unwrap();
+                                               if let Some(t) = types.crate_types.traits.get(&types.maybe_resolve_ident(&real_type).unwrap()) {
+                                                       // We're returning an associated trait from a Rust fn call to a C trait
+                                                       // object.
+                                                       writeln!(w, "let mut rust_obj = {} {{ inner: Box::into_raw(Box::new(ret)), is_owned: true }};", this_type).unwrap();
+                                                       writeln!(w, "\t{}let mut ret = {}_as_{}(&rust_obj);", extra_indent, this_type, t.ident).unwrap();
+                                                       writeln!(w, "\t{}// We want to free rust_obj when ret gets drop()'d, not rust_obj, so wipe rust_obj's pointer and set ret's free() fn", extra_indent).unwrap();
+                                                       writeln!(w, "\t{}rust_obj.inner = std::ptr::null_mut();", extra_indent).unwrap();
+                                                       writeln!(w, "\t{}ret.free = Some({}_free_void);", extra_indent, this_type).unwrap();
+                                                       writeln!(w, "\t{}ret", extra_indent).unwrap();
+                                                       return;
+                                               }
+                                       }
+                               }
+                               write!(w, "{} {{ inner: Box::into_raw(Box::new(ret)), is_owned: true }}", this_type).unwrap();
+                       } else if to_c {
+                               let new_var = types.write_from_c_conversion_new_var(w, &syn::Ident::new("ret", Span::call_site()), rtype, generics);
+                               if new_var {
+                                       write!(w, "\n\t{}", extra_indent).unwrap();
+                               }
+                               types.write_from_c_conversion_prefix(w, &*rtype, generics);
+                               write!(w, "ret").unwrap();
+                               types.write_from_c_conversion_suffix(w, &*rtype, generics);
+                       } else {
+                               let ret_returned = if let syn::Type::Reference(_) = &**rtype { true } else { false };
+                               let new_var = types.write_to_c_conversion_new_var(w, &syn::Ident::new("ret", Span::call_site()), &rtype, generics, true);
+                               if new_var {
+                                       write!(w, "\n\t{}", extra_indent).unwrap();
+                               }
+                               types.write_to_c_conversion_inline_prefix(w, &rtype, generics, true);
+                               write!(w, "{}ret", if ret_returned && !new_var { "*" } else { "" }).unwrap();
+                               types.write_to_c_conversion_inline_suffix(w, &rtype, generics, true);
+                       }
+               }
+               _ => {},
+       }
+}
+
+/// Prints concrete generic parameters for a struct/trait/function, including the less-than and
+/// greater-than symbols, if any generic parameters are defined.
+pub fn maybe_write_generics<W: std::io::Write>(w: &mut W, generics: &syn::Generics, types: &TypeResolver, concrete_lifetimes: bool) {
+       let mut gen_types = GenericTypes::new();
+       assert!(gen_types.learn_generics(generics, types));
+       if !generics.params.is_empty() {
+               write!(w, "<").unwrap();
+               for (idx, generic) in generics.params.iter().enumerate() {
+                       match generic {
+                               syn::GenericParam::Type(type_param) => {
+                                       let mut printed_param = false;
+                                       for bound in type_param.bounds.iter() {
+                                               if let syn::TypeParamBound::Trait(trait_bound) = bound {
+                                                       assert_simple_bound(&trait_bound);
+                                                       write!(w, "{}{}", if idx != 0 { ", " } else { "" }, gen_types.maybe_resolve_ident(&type_param.ident).unwrap()).unwrap();
+                                                       if printed_param {
+                                                               unimplemented!("Can't print generic params that have multiple non-lifetime bounds");
+                                                       }
+                                                       printed_param = true;
+                                               }
+                                       }
+                               },
+                               syn::GenericParam::Lifetime(lt) => {
+                                       if concrete_lifetimes {
+                                               write!(w, "'static").unwrap();
+                                       } else {
+                                               write!(w, "{}'{}", if idx != 0 { ", " } else { "" }, lt.lifetime.ident).unwrap();
+                                       }
+                               },
+                               _ => unimplemented!(),
+                       }
+               }
+               write!(w, ">").unwrap();
+       }
+}
+
+
diff --git a/c-bindings-gen/src/main.rs b/c-bindings-gen/src/main.rs
new file mode 100644 (file)
index 0000000..52ee3b0
--- /dev/null
@@ -0,0 +1,1283 @@
+//! Converts a rust crate into a rust crate containing a number of C-exported wrapper functions and
+//! classes (which is exportable using cbindgen).
+//! In general, supports convering:
+//!  * structs as a pointer to the underlying type (either owned or not owned),
+//!  * traits as a void-ptr plus a jump table,
+//!  * enums as an equivalent enum with all the inner fields mapped to the mapped types,
+//!  * certain containers (tuples, slices, Vecs, Options, and Results currently) to a concrete
+//!    version of a defined container template.
+//!
+//! It also generates relevant memory-management functions and free-standing functions with
+//! parameters mapped.
+
+use std::collections::HashMap;
+use std::env;
+use std::fs::File;
+use std::io::{Read, Write};
+use std::path::Path;
+use std::process;
+
+use proc_macro2::{TokenTree, TokenStream, Span};
+
+mod types;
+mod blocks;
+use types::*;
+use blocks::*;
+
+// *************************************
+// *** Manually-expanded conversions ***
+// *************************************
+
+/// Because we don't expand macros, any code that we need to generated based on their contents has
+/// to be completely manual. In this case its all just serialization, so its not too hard.
+fn convert_macro<W: std::io::Write>(w: &mut W, macro_path: &syn::Path, stream: &TokenStream, types: &TypeResolver) {
+       assert_eq!(macro_path.segments.len(), 1);
+       match &format!("{}", macro_path.segments.iter().next().unwrap().ident) as &str {
+               "impl_writeable" | "impl_writeable_len_match" => {
+                       let struct_for = if let TokenTree::Ident(i) = stream.clone().into_iter().next().unwrap() { i } else { unimplemented!(); };
+                       if let Some(s) = types.maybe_resolve_ident(&struct_for) {
+                               if !types.crate_types.opaques.get(&s).is_some() { return; }
+                               writeln!(w, "#[no_mangle]").unwrap();
+                               writeln!(w, "pub extern \"C\" fn {}_write(obj: *const {}) -> crate::c_types::derived::CVec_u8Z {{", struct_for, struct_for).unwrap();
+                               writeln!(w, "\tcrate::c_types::serialize_obj(unsafe {{ &(*(*obj).inner) }})").unwrap();
+                               writeln!(w, "}}").unwrap();
+                               writeln!(w, "#[no_mangle]").unwrap();
+                               writeln!(w, "pub extern \"C\" fn {}_read(ser: crate::c_types::u8slice) -> {} {{", struct_for, struct_for).unwrap();
+                               writeln!(w, "\tif let Ok(res) = crate::c_types::deserialize_obj(ser) {{").unwrap();
+                               writeln!(w, "\t\t{} {{ inner: Box::into_raw(Box::new(res)), is_owned: true }}", struct_for).unwrap();
+                               writeln!(w, "\t}} else {{").unwrap();
+                               writeln!(w, "\t\t{} {{ inner: std::ptr::null_mut(), is_owned: true }}", struct_for).unwrap();
+                               writeln!(w, "\t}}\n}}").unwrap();
+                       }
+               },
+               _ => {},
+       }
+}
+
+/// Convert "impl trait_path for for_obj { .. }" for manually-mapped types (ie (de)serialization)
+fn maybe_convert_trait_impl<W: std::io::Write>(w: &mut W, trait_path: &syn::Path, for_obj: &syn::Ident, types: &TypeResolver) {
+       if let Some(t) = types.maybe_resolve_path(&trait_path) {
+               let s = types.maybe_resolve_ident(for_obj).unwrap();
+               if !types.crate_types.opaques.get(&s).is_some() { return; }
+               match &t as &str {
+                       "util::ser::Writeable" => {
+                               writeln!(w, "#[no_mangle]").unwrap();
+                               writeln!(w, "pub extern \"C\" fn {}_write(obj: *const {}) -> crate::c_types::derived::CVec_u8Z {{", for_obj, for_obj).unwrap();
+                               writeln!(w, "\tcrate::c_types::serialize_obj(unsafe {{ &(*(*obj).inner) }})").unwrap();
+                               writeln!(w, "}}").unwrap();
+                       },
+                       "util::ser::Readable" => {
+                               writeln!(w, "#[no_mangle]").unwrap();
+                               writeln!(w, "pub extern \"C\" fn {}_read(ser: crate::c_types::u8slice) -> {} {{", for_obj, for_obj).unwrap();
+                               writeln!(w, "\tif let Ok(res) = crate::c_types::deserialize_obj(ser) {{").unwrap();
+                               writeln!(w, "\t\t{} {{ inner: Box::into_raw(Box::new(res)), is_owned: true }}", for_obj).unwrap();
+                               writeln!(w, "\t}} else {{").unwrap();
+                               writeln!(w, "\t\t{} {{ inner: std::ptr::null_mut(), is_owned: true }}", for_obj).unwrap();
+                               writeln!(w, "\t}}\n}}").unwrap();
+                       },
+                       _ => {},
+               }
+       }
+}
+
+// *******************************
+// *** Per-Type Printing Logic ***
+// *******************************
+
+macro_rules! walk_supertraits { ($t: expr, $types: expr, ($( $pat: pat => $e: expr),*) ) => { {
+       if $t.colon_token.is_some() {
+               for st in $t.supertraits.iter() {
+                       match st {
+                               syn::TypeParamBound::Trait(supertrait) => {
+                                       if supertrait.paren_token.is_some() || supertrait.lifetimes.is_some() {
+                                               unimplemented!();
+                                       }
+                                       if let Some(ident) = supertrait.path.get_ident() {
+                                               match (&format!("{}", ident) as &str, &ident) {
+                                                       $( $pat => $e, )*
+                                               }
+                                       } else {
+                                               let path = $types.resolve_path(&supertrait.path);
+                                               match (&path as &str, &supertrait.path.segments.iter().last().unwrap().ident) {
+                                                       $( $pat => $e, )*
+                                               }
+                                       }
+                               },
+                               syn::TypeParamBound::Lifetime(_) => unimplemented!(),
+                       }
+               }
+       }
+} } }
+
+/// Gets a HashMap from name idents to the bounding trait for associated types.
+/// eg if a native trait has a "type T = TraitA", this will return a HashMap containing a mapping
+/// from "T" to "TraitA".
+fn learn_associated_types<'a>(t: &'a syn::ItemTrait) -> HashMap<&'a syn::Ident, &'a syn::Ident> {
+       let mut associated_types = HashMap::new();
+       for item in t.items.iter() {
+               match item {
+                       &syn::TraitItem::Type(ref t) => {
+                               if t.default.is_some() || t.generics.lt_token.is_some() { unimplemented!(); }
+                               let mut bounds_iter = t.bounds.iter();
+                               match bounds_iter.next().unwrap() {
+                                       syn::TypeParamBound::Trait(tr) => {
+                                               assert_simple_bound(&tr);
+                                               associated_types.insert(&t.ident, assert_single_path_seg(&tr.path));
+                                       },
+                                       _ => unimplemented!(),
+                               }
+                               if bounds_iter.next().is_some() { unimplemented!(); }
+                       },
+                       _ => {},
+               }
+       }
+       associated_types
+}
+
+/// Prints a C-mapped trait object containing a void pointer and a jump table for each function in
+/// the original trait.
+/// Implements the native Rust trait and relevant parent traits for the new C-mapped trait.
+///
+/// Finally, implements Deref<MappedTrait> for MappedTrait which allows its use in types which need
+/// a concrete Deref to the Rust trait.
+fn writeln_trait<'a, 'b, W: std::io::Write>(w: &mut W, t: &'a syn::ItemTrait, types: &mut TypeResolver<'b, 'a>, extra_headers: &mut File, cpp_headers: &mut File) {
+       let trait_name = format!("{}", t.ident);
+       match export_status(&t.attrs) {
+               ExportStatus::Export => {},
+               ExportStatus::NoExport|ExportStatus::TestOnly => return,
+       }
+       writeln_docs(w, &t.attrs, "");
+
+       writeln!(w, "#[repr(C)]\npub struct {} {{", trait_name).unwrap();
+       writeln!(w, "\tpub this_arg: *mut c_void,").unwrap();
+       let associated_types = learn_associated_types(t);
+       let mut generated_fields = Vec::new(); // Every field's name except this_arg, used in Clone generation
+       for item in t.items.iter() {
+               match item {
+                       &syn::TraitItem::Method(ref m) => {
+                               match export_status(&m.attrs) {
+                                       ExportStatus::NoExport => {
+                                               // NoExport in this context means we'll hit an unimplemented!() at runtime,
+                                               // so add a comment noting that this needs to change in the output.
+                                               writeln!(w, "\t//XXX: Need to export {}", m.sig.ident).unwrap();
+                                               continue;
+                                       },
+                                       ExportStatus::Export => {},
+                                       ExportStatus::TestOnly => continue,
+                               }
+                               if m.default.is_some() { unimplemented!(); }
+
+                               writeln_docs(w, &m.attrs, "\t");
+
+                               if let syn::ReturnType::Type(_, rtype) = &m.sig.output {
+                                       if let syn::Type::Reference(r) = &**rtype {
+                                               // We have to do quite a dance for trait functions which return references
+                                               // - they ultimately require us to have a native Rust object stored inside
+                                               // our concrete trait to return a reference to. However, users may wish to
+                                               // update the value to be returned each time the function is called (or, to
+                                               // make C copies of Rust impls equivalent, we have to be able to).
+                                               //
+                                               // Thus, we store a copy of the C-mapped type (which is just a pointer to
+                                               // the Rust type and a flag to indicate whether deallocation needs to
+                                               // happen) as well as provide an Option<>al function pointer which is
+                                               // called when the trait method is called which allows updating on the fly.
+                                               write!(w, "\tpub {}: ", m.sig.ident).unwrap();
+                                               generated_fields.push(format!("{}", m.sig.ident));
+                                               types.write_c_type(w, &*r.elem, None, false);
+                                               writeln!(w, ",").unwrap();
+                                               writeln!(w, "\t/// Fill in the {} field as a reference to it will be given to Rust after this returns", m.sig.ident).unwrap();
+                                               writeln!(w, "\t/// Note that this takes a pointer to this object, not the this_ptr like other methods do").unwrap();
+                                               writeln!(w, "\t/// This function pointer may be NULL if {} is filled in when this object is created and never needs updating.", m.sig.ident).unwrap();
+                                               writeln!(w, "\tpub set_{}: Option<extern \"C\" fn(&{})>,", m.sig.ident, trait_name).unwrap();
+                                               generated_fields.push(format!("set_{}", m.sig.ident));
+                                               // Note that cbindgen will now generate
+                                               // typedef struct Thing {..., set_thing: (const Thing*), ...} Thing;
+                                               // which does not compile since Thing is not defined before it is used.
+                                               writeln!(extra_headers, "struct LDK{};", trait_name).unwrap();
+                                               writeln!(extra_headers, "typedef struct LDK{} LDK{};", trait_name, trait_name).unwrap();
+                                               continue;
+                                       }
+                                       // Sadly, this currently doesn't do what we want, but it should be easy to get
+                                       // cbindgen to support it. See https://github.com/eqrion/cbindgen/issues/531
+                                       writeln!(w, "\t#[must_use]").unwrap();
+                               }
+
+                               write!(w, "\tpub {}: extern \"C\" fn (", m.sig.ident).unwrap();
+                               generated_fields.push(format!("{}", m.sig.ident));
+                               write_method_params(w, &m.sig, &associated_types, "c_void", types, None, true, false);
+                               writeln!(w, ",").unwrap();
+                       },
+                       &syn::TraitItem::Type(_) => {},
+                       _ => unimplemented!(),
+               }
+       }
+       // Add functions which may be required for supertrait implementations.
+       walk_supertraits!(t, types, (
+               ("Clone", _) => {
+                       writeln!(w, "\tpub clone: Option<extern \"C\" fn (this_arg: *const c_void) -> *mut c_void>,").unwrap();
+                       generated_fields.push("clone".to_owned());
+               },
+               ("std::cmp::Eq", _) => {
+                       writeln!(w, "\tpub eq: extern \"C\" fn (this_arg: *const c_void, other_arg: *const c_void) -> bool,").unwrap();
+                       generated_fields.push("eq".to_owned());
+               },
+               ("std::hash::Hash", _) => {
+                       writeln!(w, "\tpub hash: extern \"C\" fn (this_arg: *const c_void) -> u64,").unwrap();
+                       generated_fields.push("hash".to_owned());
+               },
+               ("Send", _) => {}, ("Sync", _) => {},
+               (s, i) => {
+                       // For in-crate supertraits, just store a C-mapped copy of the supertrait as a member.
+                       if types.crate_types.traits.get(s).is_none() { unimplemented!(); }
+                       writeln!(w, "\tpub {}: crate::{},", i, s).unwrap();
+                       generated_fields.push(format!("{}", i));
+               }
+       ) );
+       writeln!(w, "\tpub free: Option<extern \"C\" fn(this_arg: *mut c_void)>,").unwrap();
+       generated_fields.push("free".to_owned());
+       writeln!(w, "}}").unwrap();
+       // Implement supertraits for the C-mapped struct.
+       walk_supertraits!(t, types, (
+               ("Send", _) => writeln!(w, "unsafe impl Send for {} {{}}", trait_name).unwrap(),
+               ("Sync", _) => writeln!(w, "unsafe impl Sync for {} {{}}", trait_name).unwrap(),
+               ("std::cmp::Eq", _) => {
+                       writeln!(w, "impl std::cmp::Eq for {} {{}}", trait_name).unwrap();
+                       writeln!(w, "impl std::cmp::PartialEq for {} {{", trait_name).unwrap();
+                       writeln!(w, "\tfn eq(&self, o: &Self) -> bool {{ (self.eq)(self.this_arg, o.this_arg) }}\n}}").unwrap();
+               },
+               ("std::hash::Hash", _) => {
+                       writeln!(w, "impl std::hash::Hash for {} {{", trait_name).unwrap();
+                       writeln!(w, "\tfn hash<H: std::hash::Hasher>(&self, hasher: &mut H) {{ hasher.write_u64((self.hash)(self.this_arg)) }}\n}}").unwrap();
+               },
+               ("Clone", _) => {
+                       writeln!(w, "impl Clone for {} {{", trait_name).unwrap();
+                       writeln!(w, "\tfn clone(&self) -> Self {{").unwrap();
+                       writeln!(w, "\t\tSelf {{").unwrap();
+                       writeln!(w, "\t\tthis_arg: if let Some(f) = self.clone {{ (f)(self.this_arg) }} else {{ self.this_arg }},").unwrap();
+                       for field in generated_fields.iter() {
+                               writeln!(w, "\t\t\t{}: self.{}.clone(),", field, field).unwrap();
+                       }
+                       writeln!(w, "\t\t}}\n\t}}\n}}").unwrap();
+               },
+               (s, i) => {
+                       if s != "util::events::MessageSendEventsProvider" { unimplemented!(); }
+                       // XXX: We straight-up cheat here - instead of bothering to get the trait object we
+                       // just print what we need since this is only used in one place.
+                       writeln!(w, "impl lightning::{} for {} {{", s, trait_name).unwrap();
+                       writeln!(w, "\tfn get_and_clear_pending_msg_events(&self) -> Vec<lightning::util::events::MessageSendEvent> {{").unwrap();
+                       writeln!(w, "\t\t<crate::{} as lightning::{}>::get_and_clear_pending_msg_events(&self.{})", s, s, i).unwrap();
+                       writeln!(w, "\t}}\n}}").unwrap();
+               }
+       ) );
+
+       // Finally, implement the original Rust trait for the newly created mapped trait.
+       writeln!(w, "\nuse {}::{}::{} as rust{};", types.orig_crate, types.module_path, t.ident, trait_name).unwrap();
+       write!(w, "impl rust{}", t.ident).unwrap();
+       maybe_write_generics(w, &t.generics, types, false);
+       writeln!(w, " for {} {{", trait_name).unwrap();
+       for item in t.items.iter() {
+               match item {
+                       syn::TraitItem::Method(m) => {
+                               if let ExportStatus::TestOnly = export_status(&m.attrs) { continue; }
+                               if m.default.is_some() { unimplemented!(); }
+                               if m.sig.constness.is_some() || m.sig.asyncness.is_some() || m.sig.unsafety.is_some() ||
+                                               m.sig.abi.is_some() || m.sig.variadic.is_some() {
+                                       unimplemented!();
+                               }
+                               write!(w, "\tfn {}", m.sig.ident).unwrap();
+                               types.write_rust_generic_param(w, m.sig.generics.params.iter());
+                               write!(w, "(").unwrap();
+                               for inp in m.sig.inputs.iter() {
+                                       match inp {
+                                               syn::FnArg::Receiver(recv) => {
+                                                       if !recv.attrs.is_empty() || recv.reference.is_none() { unimplemented!(); }
+                                                       write!(w, "&").unwrap();
+                                                       if let Some(lft) = &recv.reference.as_ref().unwrap().1 {
+                                                               write!(w, "'{} ", lft.ident).unwrap();
+                                                       }
+                                                       if recv.mutability.is_some() {
+                                                               write!(w, "mut self").unwrap();
+                                                       } else {
+                                                               write!(w, "self").unwrap();
+                                                       }
+                                               },
+                                               syn::FnArg::Typed(arg) => {
+                                                       if !arg.attrs.is_empty() { unimplemented!(); }
+                                                       match &*arg.pat {
+                                                               syn::Pat::Ident(ident) => {
+                                                                       if !ident.attrs.is_empty() || ident.by_ref.is_some() ||
+                                                                                       ident.mutability.is_some() || ident.subpat.is_some() {
+                                                                               unimplemented!();
+                                                                       }
+                                                                       write!(w, ", {}{}: ", if types.skip_arg(&*arg.ty, None) { "_" } else { "" }, ident.ident).unwrap();
+                                                               }
+                                                               _ => unimplemented!(),
+                                                       }
+                                                       types.write_rust_type(w, &*arg.ty);
+                                               }
+                                       }
+                               }
+                               write!(w, ")").unwrap();
+                               match &m.sig.output {
+                                       syn::ReturnType::Type(_, rtype) => {
+                                               write!(w, " -> ").unwrap();
+                                               types.write_rust_type(w, &*rtype)
+                                       },
+                                       _ => {},
+                               }
+                               write!(w, " {{\n\t\t").unwrap();
+                               match export_status(&m.attrs) {
+                                       ExportStatus::NoExport => {
+                                               writeln!(w, "unimplemented!();\n\t}}").unwrap();
+                                               continue;
+                                       },
+                                       _ => {},
+                               }
+                               if let syn::ReturnType::Type(_, rtype) = &m.sig.output {
+                                       if let syn::Type::Reference(r) = &**rtype {
+                                               assert_eq!(m.sig.inputs.len(), 1); // Must only take self!
+                                               writeln!(w, "if let Some(f) = self.set_{} {{", m.sig.ident).unwrap();
+                                               writeln!(w, "\t\t\t(f)(self);").unwrap();
+                                               write!(w, "\t\t}}\n\t\t").unwrap();
+                                               types.write_from_c_conversion_to_ref_prefix(w, &*r.elem, None);
+                                               write!(w, "self.{}", m.sig.ident).unwrap();
+                                               types.write_from_c_conversion_to_ref_suffix(w, &*r.elem, None);
+                                               writeln!(w, "\n\t}}").unwrap();
+                                               continue;
+                                       }
+                               }
+                               write_method_var_decl_body(w, &m.sig, "\t", types, None, true);
+                               write!(w, "(self.{})(", m.sig.ident).unwrap();
+                               write_method_call_params(w, &m.sig, &associated_types, "\t", types, None, "", true);
+
+                               writeln!(w, "\n\t}}").unwrap();
+                       },
+                       &syn::TraitItem::Type(ref t) => {
+                               if t.default.is_some() || t.generics.lt_token.is_some() { unimplemented!(); }
+                               let mut bounds_iter = t.bounds.iter();
+                               match bounds_iter.next().unwrap() {
+                                       syn::TypeParamBound::Trait(tr) => {
+                                               writeln!(w, "\ttype {} = crate::{};", t.ident, types.resolve_path(&tr.path)).unwrap();
+                                       },
+                                       _ => unimplemented!(),
+                               }
+                               if bounds_iter.next().is_some() { unimplemented!(); }
+                       },
+                       _ => unimplemented!(),
+               }
+       }
+       writeln!(w, "}}\n").unwrap();
+       writeln!(w, "// We're essentially a pointer already, or at least a set of pointers, so allow us to be used").unwrap();
+       writeln!(w, "// directly as a Deref trait in higher-level structs:").unwrap();
+       writeln!(w, "impl std::ops::Deref for {} {{\n\ttype Target = Self;", trait_name).unwrap();
+       writeln!(w, "\tfn deref(&self) -> &Self {{\n\t\tself\n\t}}\n}}").unwrap();
+
+       writeln!(w, "/// Calls the free function if one is set").unwrap();
+       writeln!(w, "#[no_mangle]\npub extern \"C\" fn {}_free(this_ptr: {}) {{ }}", trait_name, trait_name).unwrap();
+       writeln!(w, "impl Drop for {} {{", trait_name).unwrap();
+       writeln!(w, "\tfn drop(&mut self) {{").unwrap();
+       writeln!(w, "\t\tif let Some(f) = self.free {{").unwrap();
+       writeln!(w, "\t\t\tf(self.this_arg);").unwrap();
+       writeln!(w, "\t\t}}\n\t}}\n}}").unwrap();
+
+       write_cpp_wrapper(cpp_headers, &trait_name, true);
+       types.trait_declared(&t.ident, t);
+}
+
+/// Write out a simple "opaque" type (eg structs) which contain a pointer to the native Rust type
+/// and a flag to indicate whether Drop'ing the mapped struct drops the underlying Rust type.
+///
+/// Also writes out a _free function and a C++ wrapper which handles calling _free.
+fn writeln_opaque<W: std::io::Write>(w: &mut W, ident: &syn::Ident, struct_name: &str, generics: &syn::Generics, attrs: &[syn::Attribute], types: &TypeResolver, extra_headers: &mut File, cpp_headers: &mut File) {
+       // If we directly read the original type by its original name, cbindgen hits
+       // https://github.com/eqrion/cbindgen/issues/286 Thus, instead, we import it as a temporary
+       // name and then reference it by that name, which works around the issue.
+       write!(w, "\nuse {}::{}::{} as native{}Import;\ntype native{} = native{}Import", types.orig_crate, types.module_path, ident, ident, ident, ident).unwrap();
+       maybe_write_generics(w, &generics, &types, true);
+       writeln!(w, ";\n").unwrap();
+       writeln!(extra_headers, "struct native{}Opaque;\ntypedef struct native{}Opaque LDKnative{};", ident, ident, ident).unwrap();
+       writeln_docs(w, &attrs, "");
+       writeln!(w, "#[must_use]\n#[repr(C)]\npub struct {} {{\n\t/// Nearly everyhwere, inner must be non-null, however in places where", struct_name).unwrap();
+       writeln!(w, "\t/// the Rust equivalent takes an Option, it may be set to null to indicate None.").unwrap();
+       writeln!(w, "\tpub inner: *mut native{},\n\tpub is_owned: bool,\n}}\n", ident).unwrap();
+       writeln!(w, "impl Drop for {} {{\n\tfn drop(&mut self) {{", struct_name).unwrap();
+       writeln!(w, "\t\tif self.is_owned && !self.inner.is_null() {{").unwrap();
+       writeln!(w, "\t\t\tlet _ = unsafe {{ Box::from_raw(self.inner) }};\n\t\t}}\n\t}}\n}}").unwrap();
+       writeln!(w, "#[no_mangle]\npub extern \"C\" fn {}_free(this_ptr: {}) {{ }}", struct_name, struct_name).unwrap();
+       writeln!(w, "#[allow(unused)]").unwrap();
+       writeln!(w, "/// Used only if an object of this type is returned as a trait impl by a method").unwrap();
+       writeln!(w, "extern \"C\" fn {}_free_void(this_ptr: *mut c_void) {{", struct_name).unwrap();
+       writeln!(w, "\tunsafe {{ let _ = Box::from_raw(this_ptr as *mut native{}); }}\n}}", struct_name).unwrap();
+       writeln!(w, "#[allow(unused)]").unwrap();
+       writeln!(w, "/// When moving out of the pointer, we have to ensure we aren't a reference, this makes that easy").unwrap();
+       writeln!(w, "impl {} {{", struct_name).unwrap();
+       writeln!(w, "\tpub(crate) fn take_ptr(mut self) -> *mut native{} {{", struct_name).unwrap();
+       writeln!(w, "\t\tassert!(self.is_owned);").unwrap();
+       writeln!(w, "\t\tlet ret = self.inner;").unwrap();
+       writeln!(w, "\t\tself.inner = std::ptr::null_mut();").unwrap();
+       writeln!(w, "\t\tret").unwrap();
+       writeln!(w, "\t}}\n}}").unwrap();
+
+       'attr_loop: for attr in attrs.iter() {
+               let tokens_clone = attr.tokens.clone();
+               let mut token_iter = tokens_clone.into_iter();
+               if let Some(token) = token_iter.next() {
+                       match token {
+                               TokenTree::Group(g) => {
+                                       if format!("{}", single_ident_generic_path_to_ident(&attr.path).unwrap()) == "derive" {
+                                               for id in g.stream().into_iter() {
+                                                       if let TokenTree::Ident(i) = id {
+                                                               if i == "Clone" {
+                                                                       writeln!(w, "impl Clone for {} {{", struct_name).unwrap();
+                                                                       writeln!(w, "\tfn clone(&self) -> Self {{").unwrap();
+                                                                       writeln!(w, "\t\tSelf {{").unwrap();
+                                                                       writeln!(w, "\t\t\tinner: Box::into_raw(Box::new(unsafe {{ &*self.inner }}.clone())),").unwrap();
+                                                                       writeln!(w, "\t\t\tis_owned: true,").unwrap();
+                                                                       writeln!(w, "\t\t}}\n\t}}\n}}").unwrap();
+                                                                       writeln!(w, "#[allow(unused)]").unwrap();
+                                                                       writeln!(w, "/// Used only if an object of this type is returned as a trait impl by a method").unwrap();
+                                                                       writeln!(w, "pub(crate) extern \"C\" fn {}_clone_void(this_ptr: *const c_void) -> *mut c_void {{", struct_name).unwrap();
+                                                                       writeln!(w, "\tBox::into_raw(Box::new(unsafe {{ (*(this_ptr as *mut native{})).clone() }})) as *mut c_void", struct_name).unwrap();
+                                                                       writeln!(w, "}}").unwrap();
+                                                                       break 'attr_loop;
+                                                               }
+                                                       }
+                                               }
+                                       }
+                               },
+                               _ => {},
+                       }
+               }
+       }
+
+       write_cpp_wrapper(cpp_headers, &format!("{}", ident), true);
+}
+
+/// Writes out all the relevant mappings for a Rust struct, deferring to writeln_opaque to generate
+/// the struct itself, and then writing getters and setters for public, understood-type fields and
+/// a constructor if every field is public.
+fn writeln_struct<'a, 'b, W: std::io::Write>(w: &mut W, s: &'a syn::ItemStruct, types: &mut TypeResolver<'b, 'a>, extra_headers: &mut File, cpp_headers: &mut File) {
+       let struct_name = &format!("{}", s.ident);
+       let export = export_status(&s.attrs);
+       match export {
+               ExportStatus::Export => {},
+               ExportStatus::TestOnly => return,
+               ExportStatus::NoExport => {
+                       types.struct_ignored(&s.ident);
+                       return;
+               }
+       }
+
+       writeln_opaque(w, &s.ident, struct_name, &s.generics, &s.attrs, types, extra_headers, cpp_headers);
+
+       eprintln!("exporting fields for {}", struct_name);
+       if let syn::Fields::Named(fields) = &s.fields {
+               let mut gen_types = GenericTypes::new();
+               assert!(gen_types.learn_generics(&s.generics, types));
+
+               let mut all_fields_settable = true;
+               for field in fields.named.iter() {
+                       if let syn::Visibility::Public(_) = field.vis {
+                               let export = export_status(&field.attrs);
+                               match export {
+                                       ExportStatus::Export => {},
+                                       ExportStatus::NoExport|ExportStatus::TestOnly => {
+                                               all_fields_settable = false;
+                                               continue
+                                       },
+                               }
+
+                               if let Some(ident) = &field.ident {
+                                       let ref_type = syn::Type::Reference(syn::TypeReference {
+                                               and_token: syn::Token!(&)(Span::call_site()), lifetime: None, mutability: None,
+                                               elem: Box::new(field.ty.clone()) });
+                                       if types.understood_c_type(&ref_type, Some(&gen_types)) {
+                                               writeln_docs(w, &field.attrs, "");
+                                               write!(w, "#[no_mangle]\npub extern \"C\" fn {}_get_{}(this_ptr: &{}) -> ", struct_name, ident, struct_name).unwrap();
+                                               types.write_c_type(w, &ref_type, Some(&gen_types), true);
+                                               write!(w, " {{\n\tlet mut inner_val = &mut unsafe {{ &mut *this_ptr.inner }}.{};\n\t", ident).unwrap();
+                                               let local_var = types.write_to_c_conversion_new_var(w, &syn::Ident::new("inner_val", Span::call_site()), &ref_type, Some(&gen_types), true);
+                                               if local_var { write!(w, "\n\t").unwrap(); }
+                                               types.write_to_c_conversion_inline_prefix(w, &ref_type, Some(&gen_types), true);
+                                               if local_var {
+                                                       write!(w, "inner_val").unwrap();
+                                               } else {
+                                                       write!(w, "(*inner_val)").unwrap();
+                                               }
+                                               types.write_to_c_conversion_inline_suffix(w, &ref_type, Some(&gen_types), true);
+                                               writeln!(w, "\n}}").unwrap();
+                                       }
+
+                                       if types.understood_c_type(&field.ty, Some(&gen_types)) {
+                                               writeln_docs(w, &field.attrs, "");
+                                               write!(w, "#[no_mangle]\npub extern \"C\" fn {}_set_{}(this_ptr: &mut {}, mut val: ", struct_name, ident, struct_name).unwrap();
+                                               types.write_c_type(w, &field.ty, Some(&gen_types), false);
+                                               write!(w, ") {{\n\t").unwrap();
+                                               let local_var = types.write_from_c_conversion_new_var(w, &syn::Ident::new("val", Span::call_site()), &field.ty, Some(&gen_types));
+                                               if local_var { write!(w, "\n\t").unwrap(); }
+                                               write!(w, "unsafe {{ &mut *this_ptr.inner }}.{} = ", ident).unwrap();
+                                               types.write_from_c_conversion_prefix(w, &field.ty, Some(&gen_types));
+                                               write!(w, "val").unwrap();
+                                               types.write_from_c_conversion_suffix(w, &field.ty, Some(&gen_types));
+                                               writeln!(w, ";\n}}").unwrap();
+                                       } else { all_fields_settable = false; }
+                               } else { all_fields_settable = false; }
+                       } else { all_fields_settable = false; }
+               }
+
+               if all_fields_settable {
+                       // Build a constructor!
+                       write!(w, "#[must_use]\n#[no_mangle]\npub extern \"C\" fn {}_new(", struct_name).unwrap();
+                       for (idx, field) in fields.named.iter().enumerate() {
+                               if idx != 0 { write!(w, ", ").unwrap(); }
+                               write!(w, "mut {}_arg: ", field.ident.as_ref().unwrap()).unwrap();
+                               types.write_c_type(w, &field.ty, Some(&gen_types), false);
+                       }
+                       write!(w, ") -> {} {{\n\t", struct_name).unwrap();
+                       for field in fields.named.iter() {
+                               let field_name = format!("{}_arg", field.ident.as_ref().unwrap());
+                               if types.write_from_c_conversion_new_var(w, &syn::Ident::new(&field_name, Span::call_site()), &field.ty, Some(&gen_types)) {
+                                       write!(w, "\n\t").unwrap();
+                               }
+                       }
+                       writeln!(w, "{} {{ inner: Box::into_raw(Box::new(native{} {{", struct_name, s.ident).unwrap();
+                       for field in fields.named.iter() {
+                               write!(w, "\t\t{}: ", field.ident.as_ref().unwrap()).unwrap();
+                               types.write_from_c_conversion_prefix(w, &field.ty, Some(&gen_types));
+                               write!(w, "{}_arg", field.ident.as_ref().unwrap()).unwrap();
+                               types.write_from_c_conversion_suffix(w, &field.ty, Some(&gen_types));
+                               writeln!(w, ",").unwrap();
+                       }
+                       writeln!(w, "\t}})), is_owned: true }}\n}}").unwrap();
+               }
+       }
+
+       types.struct_imported(&s.ident, struct_name.clone());
+}
+
+/// Prints a relevant conversion for impl *
+///
+/// For simple impl Struct {}s, this just outputs the wrapper functions as Struct_fn_name() { .. }.
+///
+/// For impl Trait for Struct{}s, this non-exported generates wrapper functions as
+/// Trait_Struct_fn_name and a Struct_as_Trait(&struct) -> Trait function which returns a populated
+/// Trait struct containing a pointer to the passed struct's inner field and the wrapper functions.
+///
+/// A few non-crate Traits are hard-coded including Default.
+fn writeln_impl<W: std::io::Write>(w: &mut W, i: &syn::ItemImpl, types: &mut TypeResolver) {
+       if let &syn::Type::Path(ref p) = &*i.self_ty {
+               if p.qself.is_some() { unimplemented!(); }
+               if let Some(ident) = single_ident_generic_path_to_ident(&p.path) {
+                       if let Some(resolved_path) = types.maybe_resolve_non_ignored_ident(&ident) {
+                               let mut gen_types = GenericTypes::new();
+                               if !gen_types.learn_generics(&i.generics, types) {
+                                       eprintln!("Not implementing anything for impl {} due to not understood generics", ident);
+                                       return;
+                               }
+
+                               if i.defaultness.is_some() || i.unsafety.is_some() { unimplemented!(); }
+                               if let Some(trait_path) = i.trait_.as_ref() {
+                                       if trait_path.0.is_some() { unimplemented!(); }
+                                       if types.understood_c_path(&trait_path.1) {
+                                               let full_trait_path = types.resolve_path(&trait_path.1);
+                                               let trait_obj = *types.crate_types.traits.get(&full_trait_path).unwrap();
+                                               // We learn the associated types maping from the original trait object.
+                                               // That's great, except that they are unresolved idents, so if we learn
+                                               // mappings from a trai defined in a different file, we may mis-resolve or
+                                               // fail to resolve the mapped types.
+                                               let trait_associated_types = learn_associated_types(trait_obj);
+                                               let mut impl_associated_types = HashMap::new();
+                                               for item in i.items.iter() {
+                                                       match item {
+                                                               syn::ImplItem::Type(t) => {
+                                                                       if let syn::Type::Path(p) = &t.ty {
+                                                                               if let Some(id) = single_ident_generic_path_to_ident(&p.path) {
+                                                                                       impl_associated_types.insert(&t.ident, id);
+                                                                               }
+                                                                       }
+                                                               },
+                                                               _ => {},
+                                                       }
+                                               }
+
+                                               let export = export_status(&trait_obj.attrs);
+                                               match export {
+                                                       ExportStatus::Export => {},
+                                                       ExportStatus::NoExport|ExportStatus::TestOnly => return,
+                                               }
+                                               write!(w, "#[no_mangle]\npub extern \"C\" fn {}_as_{}(this_arg: *const {}) -> crate::{} {{\n", ident, trait_obj.ident, ident, full_trait_path).unwrap();
+                                               writeln!(w, "\tcrate::{} {{", full_trait_path).unwrap();
+                                               writeln!(w, "\t\tthis_arg: unsafe {{ (*this_arg).inner as *mut c_void }},").unwrap();
+                                               writeln!(w, "\t\tfree: None,").unwrap();
+
+                                               macro_rules! write_meth {
+                                                       ($m: expr, $trait: expr, $indent: expr) => {
+                                                               let trait_method = $trait.items.iter().filter_map(|item| {
+                                                                       if let syn::TraitItem::Method(t_m) = item { Some(t_m) } else { None }
+                                                               }).find(|trait_meth| trait_meth.sig.ident == $m.sig.ident).unwrap();
+                                                               match export_status(&trait_method.attrs) {
+                                                                       ExportStatus::Export => {},
+                                                                       ExportStatus::NoExport => {
+                                                                               write!(w, "{}\t\t//XXX: Need to export {}\n", $indent, $m.sig.ident).unwrap();
+                                                                               continue;
+                                                                       },
+                                                                       ExportStatus::TestOnly => continue,
+                                                               }
+
+                                                               let mut printed = false;
+                                                               if let syn::ReturnType::Type(_, rtype) = &$m.sig.output {
+                                                                       if let syn::Type::Reference(r) = &**rtype {
+                                                                               write!(w, "\n\t\t{}{}: ", $indent, $m.sig.ident).unwrap();
+                                                                               types.write_empty_rust_val(w, &*r.elem);
+                                                                               writeln!(w, ",\n{}\t\tset_{}: Some({}_{}_set_{}),", $indent, $m.sig.ident, ident, trait_obj.ident, $m.sig.ident).unwrap();
+                                                                               printed = true;
+                                                                       }
+                                                               }
+                                                               if !printed {
+                                                                       write!(w, "{}\t\t{}: {}_{}_{},\n", $indent, $m.sig.ident, ident, trait_obj.ident, $m.sig.ident).unwrap();
+                                                               }
+                                                       }
+                                               }
+                                               for item in trait_obj.items.iter() {
+                                                       match item {
+                                                               syn::TraitItem::Method(m) => {
+                                                                       write_meth!(m, trait_obj, "");
+                                                               },
+                                                               _ => {},
+                                                       }
+                                               }
+                                               walk_supertraits!(trait_obj, types, (
+                                                       ("Clone", _) => {
+                                                               writeln!(w, "\t\tclone: Some({}_clone_void),", ident).unwrap();
+                                                       },
+                                                       (s, t) => {
+                                                               if s.starts_with("util::") {
+                                                                       let supertrait_obj = types.crate_types.traits.get(s).unwrap();
+                                                                       writeln!(w, "\t\t{}: crate::{} {{", t, s).unwrap();
+                                                                       writeln!(w, "\t\t\tthis_arg: unsafe {{ (*this_arg).inner as *mut c_void }},").unwrap();
+                                                                       writeln!(w, "\t\t\tfree: None,").unwrap();
+                                                                       for item in supertrait_obj.items.iter() {
+                                                                               match item {
+                                                                                       syn::TraitItem::Method(m) => {
+                                                                                               write_meth!(m, supertrait_obj, "\t");
+                                                                                       },
+                                                                                       _ => {},
+                                                                               }
+                                                                       }
+                                                                       write!(w, "\t\t}},\n").unwrap();
+                                                               }
+                                                       }
+                                               ) );
+                                               write!(w, "\t}}\n}}\nuse {}::{} as {}TraitImport;\n", types.orig_crate, full_trait_path, trait_obj.ident).unwrap();
+
+                                               macro_rules! impl_meth {
+                                                       ($m: expr, $trait: expr, $indent: expr) => {
+                                                               let trait_method = $trait.items.iter().filter_map(|item| {
+                                                                       if let syn::TraitItem::Method(t_m) = item { Some(t_m) } else { None }
+                                                               }).find(|trait_meth| trait_meth.sig.ident == $m.sig.ident).unwrap();
+                                                               match export_status(&trait_method.attrs) {
+                                                                       ExportStatus::Export => {},
+                                                                       ExportStatus::NoExport|ExportStatus::TestOnly => continue,
+                                                               }
+
+                                                               if let syn::ReturnType::Type(_, _) = &$m.sig.output {
+                                                                       writeln!(w, "#[must_use]").unwrap();
+                                                               }
+                                                               write!(w, "extern \"C\" fn {}_{}_{}(", ident, trait_obj.ident, $m.sig.ident).unwrap();
+                                                               gen_types.push_ctx();
+                                                               assert!(gen_types.learn_generics(&$m.sig.generics, types));
+                                                               write_method_params(w, &$m.sig, &trait_associated_types, "c_void", types, Some(&gen_types), true, true);
+                                                               write!(w, " {{\n\t").unwrap();
+                                                               write_method_var_decl_body(w, &$m.sig, "", types, Some(&gen_types), false);
+                                                               let mut takes_self = false;
+                                                               for inp in $m.sig.inputs.iter() {
+                                                                       if let syn::FnArg::Receiver(_) = inp {
+                                                                               takes_self = true;
+                                                                       }
+                                                               }
+                                                               if takes_self {
+                                                                       write!(w, "unsafe {{ &mut *(this_arg as *mut native{}) }}.{}(", ident, $m.sig.ident).unwrap();
+                                                               } else {
+                                                                       write!(w, "{}::{}::{}(", types.orig_crate, resolved_path, $m.sig.ident).unwrap();
+                                                               }
+
+                                                               let mut real_type = "".to_string();
+                                                               match &$m.sig.output {
+                                                                       syn::ReturnType::Type(_, rtype) => {
+                                                                               if let Some(mut remaining_path) = first_seg_self(&*rtype) {
+                                                                                       if let Some(associated_seg) = get_single_remaining_path_seg(&mut remaining_path) {
+                                                                                               real_type = format!("{}", impl_associated_types.get(associated_seg).unwrap());
+                                                                                       }
+                                                                               }
+                                                                       },
+                                                                       _ => {},
+                                                               }
+                                                               write_method_call_params(w, &$m.sig, &trait_associated_types, "", types, Some(&gen_types), &real_type, false);
+                                                               gen_types.pop_ctx();
+                                                               write!(w, "\n}}\n").unwrap();
+                                                               if let syn::ReturnType::Type(_, rtype) = &$m.sig.output {
+                                                                       if let syn::Type::Reference(r) = &**rtype {
+                                                                               assert_eq!($m.sig.inputs.len(), 1); // Must only take self
+                                                                               writeln!(w, "extern \"C\" fn {}_{}_set_{}(trait_self_arg: &{}) {{", ident, trait_obj.ident, $m.sig.ident, trait_obj.ident).unwrap();
+                                                                               writeln!(w, "\t// This is a bit race-y in the general case, but for our specific use-cases today, we're safe").unwrap();
+                                                                               writeln!(w, "\t// Specifically, we must ensure that the first time we're called it can never be in parallel").unwrap();
+                                                                               write!(w, "\tif ").unwrap();
+                                                                               types.write_empty_rust_val_check(w, &*r.elem, &format!("trait_self_arg.{}", $m.sig.ident));
+                                                                               writeln!(w, " {{").unwrap();
+                                                                               writeln!(w, "\t\tunsafe {{ &mut *(trait_self_arg as *const {}  as *mut {}) }}.{} = {}_{}_{}(trait_self_arg.this_arg);", trait_obj.ident, trait_obj.ident, $m.sig.ident, ident, trait_obj.ident, $m.sig.ident).unwrap();
+                                                                               writeln!(w, "\t}}").unwrap();
+                                                                               writeln!(w, "}}").unwrap();
+                                                                       }
+                                                               }
+                                                       }
+                                               }
+
+                                               for item in i.items.iter() {
+                                                       match item {
+                                                               syn::ImplItem::Method(m) => {
+                                                                       impl_meth!(m, trait_obj, "");
+                                                               },
+                                                               syn::ImplItem::Type(_) => {},
+                                                               _ => unimplemented!(),
+                                                       }
+                                               }
+                                               walk_supertraits!(trait_obj, types, (
+                                                       (s, t) => {
+                                                               if s.starts_with("util::") {
+                                                                       writeln!(w, "use {}::{} as native{}Trait;", types.orig_crate, s, t).unwrap();
+                                                                       let supertrait_obj = *types.crate_types.traits.get(s).unwrap();
+                                                                       for item in supertrait_obj.items.iter() {
+                                                                               match item {
+                                                                                       syn::TraitItem::Method(m) => {
+                                                                                               impl_meth!(m, supertrait_obj, "\t");
+                                                                                       },
+                                                                                       _ => {},
+                                                                               }
+                                                                       }
+                                                               }
+                                                       }
+                                               ) );
+                                               write!(w, "\n").unwrap();
+                                       } else if let Some(trait_ident) = trait_path.1.get_ident() {
+                                               //XXX: implement for other things like ToString
+                                               match &format!("{}", trait_ident) as &str {
+                                                       "From" => {},
+                                                       "Default" => {
+                                                               write!(w, "#[must_use]\n#[no_mangle]\npub extern \"C\" fn {}_default() -> {} {{\n", ident, ident).unwrap();
+                                                               write!(w, "\t{} {{ inner: Box::into_raw(Box::new(Default::default())), is_owned: true }}\n", ident).unwrap();
+                                                               write!(w, "}}\n").unwrap();
+                                                       },
+                                                       "PartialEq" => {},
+                                                       // If we have no generics, try a manual implementation:
+                                                       _ if p.path.get_ident().is_some() => maybe_convert_trait_impl(w, &trait_path.1, &ident, types),
+                                                       _ => {},
+                                               }
+                                       } else if p.path.get_ident().is_some() {
+                                               // If we have no generics, try a manual implementation:
+                                               maybe_convert_trait_impl(w, &trait_path.1, &ident, types);
+                                       }
+                               } else {
+                                       let declared_type = (*types.get_declared_type(&ident).unwrap()).clone();
+                                       for item in i.items.iter() {
+                                               match item {
+                                                       syn::ImplItem::Method(m) => {
+                                                               if let syn::Visibility::Public(_) = m.vis {
+                                                                       match export_status(&m.attrs) {
+                                                                               ExportStatus::Export => {},
+                                                                               ExportStatus::NoExport|ExportStatus::TestOnly => continue,
+                                                                       }
+                                                                       if m.defaultness.is_some() { unimplemented!(); }
+                                                                       writeln_docs(w, &m.attrs, "");
+                                                                       if let syn::ReturnType::Type(_, _) = &m.sig.output {
+                                                                               writeln!(w, "#[must_use]").unwrap();
+                                                                       }
+                                                                       write!(w, "#[no_mangle]\npub extern \"C\" fn {}_{}(", ident, m.sig.ident).unwrap();
+                                                                       let ret_type = match &declared_type {
+                                                                               DeclType::MirroredEnum => format!("{}", ident),
+                                                                               DeclType::StructImported => format!("{}", ident),
+                                                                               _ => unimplemented!(),
+                                                                       };
+                                                                       gen_types.push_ctx();
+                                                                       assert!(gen_types.learn_generics(&m.sig.generics, types));
+                                                                       write_method_params(w, &m.sig, &HashMap::new(), &ret_type, types, Some(&gen_types), false, true);
+                                                                       write!(w, " {{\n\t").unwrap();
+                                                                       write_method_var_decl_body(w, &m.sig, "", types, Some(&gen_types), false);
+                                                                       let mut takes_self = false;
+                                                                       let mut takes_mut_self = false;
+                                                                       for inp in m.sig.inputs.iter() {
+                                                                               if let syn::FnArg::Receiver(r) = inp {
+                                                                                       takes_self = true;
+                                                                                       if r.mutability.is_some() { takes_mut_self = true; }
+                                                                               }
+                                                                       }
+                                                                       if takes_mut_self {
+                                                                               write!(w, "unsafe {{ &mut (*(this_arg.inner as *mut native{})) }}.{}(", ident, m.sig.ident).unwrap();
+                                                                       } else if takes_self {
+                                                                               write!(w, "unsafe {{ &*this_arg.inner }}.{}(", m.sig.ident).unwrap();
+                                                                       } else {
+                                                                               write!(w, "{}::{}::{}(", types.orig_crate, resolved_path, m.sig.ident).unwrap();
+                                                                       }
+                                                                       write_method_call_params(w, &m.sig, &HashMap::new(), "", types, Some(&gen_types), &ret_type, false);
+                                                                       gen_types.pop_ctx();
+                                                                       writeln!(w, "\n}}\n").unwrap();
+                                                               }
+                                                       },
+                                                       _ => {},
+                                               }
+                                       }
+                               }
+                       } else {
+                               eprintln!("Not implementing anything for {} due to no-resolve (probably the type isn't pub or its marked not exported)", ident);
+                       }
+               }
+       }
+}
+
+/// Returns true if the enum will be mapped as an opaue (ie struct with a pointer to the underlying
+/// type), otherwise it is mapped into a transparent, C-compatible version of itself.
+fn is_enum_opaque(e: &syn::ItemEnum) -> bool {
+       for var in e.variants.iter() {
+               if let syn::Fields::Unit = var.fields {
+               } else if let syn::Fields::Named(fields) = &var.fields {
+                       for field in fields.named.iter() {
+                               match export_status(&field.attrs) {
+                                       ExportStatus::Export|ExportStatus::TestOnly => {},
+                                       ExportStatus::NoExport => return true,
+                               }
+                       }
+               } else {
+                       return true;
+               }
+       }
+       false
+}
+
+/// Print a mapping of an enum. If all of the enum's fields are C-mapped in some form (or the enum
+/// is unitary), we generate an equivalent enum with all types replaced with their C mapped
+/// versions followed by conversion functions which map between the Rust version and the C mapped
+/// version.
+fn writeln_enum<'a, 'b, W: std::io::Write>(w: &mut W, e: &'a syn::ItemEnum, types: &mut TypeResolver<'b, 'a>, extra_headers: &mut File, cpp_headers: &mut File) {
+       match export_status(&e.attrs) {
+               ExportStatus::Export => {},
+               ExportStatus::NoExport|ExportStatus::TestOnly => return,
+       }
+
+       if is_enum_opaque(e) {
+               eprintln!("Skipping enum {} as it contains non-unit fields", e.ident);
+               writeln_opaque(w, &e.ident, &format!("{}", e.ident), &e.generics, &e.attrs, types, extra_headers, cpp_headers);
+               types.enum_ignored(&e.ident);
+               return;
+       }
+       writeln_docs(w, &e.attrs, "");
+
+       if e.generics.lt_token.is_some() {
+               unimplemented!();
+       }
+       types.mirrored_enum_declared(&e.ident);
+
+       let mut needs_free = false;
+
+       writeln!(w, "#[must_use]\n#[derive(Clone)]\n#[repr(C)]\npub enum {} {{", e.ident).unwrap();
+       for var in e.variants.iter() {
+               assert_eq!(export_status(&var.attrs), ExportStatus::Export); // We can't partially-export a mirrored enum
+               writeln_docs(w, &var.attrs, "\t");
+               write!(w, "\t{}", var.ident).unwrap();
+               if let syn::Fields::Named(fields) = &var.fields {
+                       needs_free = true;
+                       writeln!(w, " {{").unwrap();
+                       for field in fields.named.iter() {
+                               if export_status(&field.attrs) == ExportStatus::TestOnly { continue; }
+                               write!(w, "\t\t{}: ", field.ident.as_ref().unwrap()).unwrap();
+                               types.write_c_type(w, &field.ty, None, false);
+                               writeln!(w, ",").unwrap();
+                       }
+                       write!(w, "\t}}").unwrap();
+               }
+               if var.discriminant.is_some() { unimplemented!(); }
+               writeln!(w, ",").unwrap();
+       }
+       writeln!(w, "}}\nuse {}::{}::{} as native{};\nimpl {} {{", types.orig_crate, types.module_path, e.ident, e.ident, e.ident).unwrap();
+
+       macro_rules! write_conv {
+               ($fn_sig: expr, $to_c: expr, $ref: expr) => {
+                       writeln!(w, "\t#[allow(unused)]\n\tpub(crate) fn {} {{\n\t\tmatch {} {{", $fn_sig, if $to_c { "native" } else { "self" }).unwrap();
+                       for var in e.variants.iter() {
+                               write!(w, "\t\t\t{}{}::{} ", if $to_c { "native" } else { "" }, e.ident, var.ident).unwrap();
+                               if let syn::Fields::Named(fields) = &var.fields {
+                                       write!(w, "{{").unwrap();
+                                       for field in fields.named.iter() {
+                                               if export_status(&field.attrs) == ExportStatus::TestOnly { continue; }
+                                               write!(w, "{}{}, ", if $ref { "ref " } else { "mut " }, field.ident.as_ref().unwrap()).unwrap();
+                                       }
+                                       write!(w, "}} ").unwrap();
+                               }
+                               write!(w, "=>").unwrap();
+                               if let syn::Fields::Named(fields) = &var.fields {
+                                       write!(w, " {{\n\t\t\t\t").unwrap();
+                                       for field in fields.named.iter() {
+                                               if export_status(&field.attrs) == ExportStatus::TestOnly { continue; }
+                                               let mut sink = ::std::io::sink();
+                                               let mut out: &mut dyn std::io::Write = if $ref { &mut sink } else { w };
+                                               let new_var = if $to_c {
+                                                       types.write_to_c_conversion_new_var(&mut out, field.ident.as_ref().unwrap(), &field.ty, None, false)
+                                               } else {
+                                                       types.write_from_c_conversion_new_var(&mut out, field.ident.as_ref().unwrap(), &field.ty, None)
+                                               };
+                                               if $ref || new_var {
+                                                       if $ref {
+                                                               write!(w, "let mut {}_nonref = (*{}).clone();\n\t\t\t\t", field.ident.as_ref().unwrap(), field.ident.as_ref().unwrap()).unwrap();
+                                                               if new_var {
+                                                                       let nonref_ident = syn::Ident::new(&format!("{}_nonref", field.ident.as_ref().unwrap()), Span::call_site());
+                                                                       if $to_c {
+                                                                               types.write_to_c_conversion_new_var(w, &nonref_ident, &field.ty, None, false);
+                                                                       } else {
+                                                                               types.write_from_c_conversion_new_var(w, &nonref_ident, &field.ty, None);
+                                                                       }
+                                                                       write!(w, "\n\t\t\t\t").unwrap();
+                                                               }
+                                                       } else {
+                                                               write!(w, "\n\t\t\t\t").unwrap();
+                                                       }
+                                               }
+                                       }
+                               } else { write!(w, " ").unwrap(); }
+                               write!(w, "{}{}::{}", if $to_c { "" } else { "native" }, e.ident, var.ident).unwrap();
+                               if let syn::Fields::Named(fields) = &var.fields {
+                                       write!(w, " {{").unwrap();
+                                       for field in fields.named.iter() {
+                                               if export_status(&field.attrs) == ExportStatus::TestOnly { continue; }
+                                               write!(w, "\n\t\t\t\t\t{}: ", field.ident.as_ref().unwrap()).unwrap();
+                                               if $to_c {
+                                                       types.write_to_c_conversion_inline_prefix(w, &field.ty, None, false);
+                                               } else {
+                                                       types.write_from_c_conversion_prefix(w, &field.ty, None);
+                                               }
+                                               write!(w, "{}{}",
+                                                       field.ident.as_ref().unwrap(),
+                                                       if $ref { "_nonref" } else { "" }).unwrap();
+                                               if $to_c {
+                                                       types.write_to_c_conversion_inline_suffix(w, &field.ty, None, false);
+                                               } else {
+                                                       types.write_from_c_conversion_suffix(w, &field.ty, None);
+                                               }
+                                               write!(w, ",").unwrap();
+                                       }
+                                       writeln!(w, "\n\t\t\t\t}}").unwrap();
+                                       write!(w, "\t\t\t}}").unwrap();
+                               }
+                               writeln!(w, ",").unwrap();
+                       }
+                       writeln!(w, "\t\t}}\n\t}}").unwrap();
+               }
+       }
+
+       write_conv!(format!("to_native(&self) -> native{}", e.ident), false, true);
+       write_conv!(format!("into_native(self) -> native{}", e.ident), false, false);
+       write_conv!(format!("from_native(native: &native{}) -> Self", e.ident), true, true);
+       write_conv!(format!("native_into(native: native{}) -> Self", e.ident), true, false);
+       writeln!(w, "}}").unwrap();
+
+       if needs_free {
+               writeln!(w, "#[no_mangle]\npub extern \"C\" fn {}_free(this_ptr: {}) {{ }}", e.ident, e.ident).unwrap();
+       }
+       write_cpp_wrapper(cpp_headers, &format!("{}", e.ident), needs_free);
+}
+
+fn writeln_fn<'a, 'b, W: std::io::Write>(w: &mut W, f: &'a syn::ItemFn, types: &mut TypeResolver<'b, 'a>) {
+       match export_status(&f.attrs) {
+               ExportStatus::Export => {},
+               ExportStatus::NoExport|ExportStatus::TestOnly => return,
+       }
+       writeln_docs(w, &f.attrs, "");
+
+       let mut gen_types = GenericTypes::new();
+       if !gen_types.learn_generics(&f.sig.generics, types) { return; }
+
+       write!(w, "#[no_mangle]\npub extern \"C\" fn {}(", f.sig.ident).unwrap();
+       write_method_params(w, &f.sig, &HashMap::new(), "", types, Some(&gen_types), false, true);
+       write!(w, " {{\n\t").unwrap();
+       write_method_var_decl_body(w, &f.sig, "", types, Some(&gen_types), false);
+       write!(w, "{}::{}::{}(", types.orig_crate, types.module_path, f.sig.ident).unwrap();
+       write_method_call_params(w, &f.sig, &HashMap::new(), "", types, Some(&gen_types), "", false);
+       writeln!(w, "\n}}\n").unwrap();
+}
+
+// ********************************
+// *** File/Crate Walking Logic ***
+// ********************************
+
+/// Simple utility to walk the modules in a crate - iterating over the modules (with file paths) in
+/// a single File.
+struct FileIter<'a, I: Iterator<Item = &'a syn::Item>> {
+       in_dir: &'a str,
+       path: &'a str,
+       module: &'a str,
+       item_iter: I,
+}
+impl<'a, I: Iterator<Item = &'a syn::Item>> Iterator for FileIter<'a, I> {
+       type Item = (String, String, &'a syn::ItemMod);
+       fn next(&mut self) -> std::option::Option<<Self as std::iter::Iterator>::Item> {
+               loop {
+                       match self.item_iter.next() {
+                               Some(syn::Item::Mod(m)) => {
+                                       if let syn::Visibility::Public(_) = m.vis {
+                                               match export_status(&m.attrs) {
+                                                       ExportStatus::Export => {},
+                                                       ExportStatus::NoExport|ExportStatus::TestOnly => continue,
+                                               }
+
+                                               let f_path = format!("{}/{}.rs", (self.path.as_ref() as &Path).parent().unwrap().display(), m.ident);
+                                               let new_mod = if self.module.is_empty() { format!("{}", m.ident) } else { format!("{}::{}", self.module, m.ident) };
+                                               if let Ok(_) = File::open(&format!("{}/{}", self.in_dir, f_path)) {
+                                                       return Some((f_path, new_mod, m));
+                                               } else {
+                                                       return Some((
+                                                               format!("{}/{}/mod.rs", (self.path.as_ref() as &Path).parent().unwrap().display(), m.ident),
+                                                               new_mod, m));
+                                               }
+                                       }
+                               },
+                               Some(_) => {},
+                               None => return None,
+                       }
+               }
+       }
+}
+fn file_iter<'a>(file: &'a syn::File, in_dir: &'a str, path: &'a str, module: &'a str) ->
+               impl Iterator<Item = (String, String, &'a syn::ItemMod)> + 'a {
+       FileIter { in_dir, path, module, item_iter: file.items.iter() }
+}
+
+/// A struct containing the syn::File AST for each file in the crate.
+struct FullLibraryAST {
+       files: HashMap<String, syn::File>,
+}
+
+/// Do the Real Work of mapping an original file to C-callable wrappers. Creates a new file at
+/// `out_path` and fills it with wrapper structs/functions to allow calling the things in the AST
+/// at `module` from C.
+fn convert_file<'a, 'b>(libast: &'a FullLibraryAST, crate_types: &mut CrateTypes<'a>, in_dir: &str, out_dir: &str, path: &str, orig_crate: &str, module: &str, header_file: &mut File, cpp_header_file: &mut File) {
+       eprintln!("Converting {}...", path);
+
+       let syntax = if let Some(ast) = libast.files.get(module) { ast } else { return };
+
+       assert!(syntax.shebang.is_none()); // Not sure what this is, hope we dont have one
+
+       let new_file_path = format!("{}/{}", out_dir, path);
+       let _ = std::fs::create_dir((&new_file_path.as_ref() as &std::path::Path).parent().unwrap());
+       let mut out = std::fs::OpenOptions::new().write(true).create(true).truncate(true)
+               .open(new_file_path).expect("Unable to open new src file");
+
+       assert_eq!(export_status(&syntax.attrs), ExportStatus::Export);
+       writeln_docs(&mut out, &syntax.attrs, "");
+
+       if path.ends_with("/lib.rs") {
+               // Special-case the top-level lib.rs with various lint allows and a pointer to the c_types
+               // and bitcoin hand-written modules.
+               writeln!(out, "#![allow(unknown_lints)]").unwrap();
+               writeln!(out, "#![allow(non_camel_case_types)]").unwrap();
+               writeln!(out, "#![allow(non_snake_case)]").unwrap();
+               writeln!(out, "#![allow(unused_imports)]").unwrap();
+               writeln!(out, "#![allow(unused_variables)]").unwrap();
+               writeln!(out, "#![allow(unused_mut)]").unwrap();
+               writeln!(out, "#![allow(unused_parens)]").unwrap();
+               writeln!(out, "#![allow(unused_unsafe)]").unwrap();
+               writeln!(out, "#![allow(unused_braces)]").unwrap();
+               writeln!(out, "mod c_types;").unwrap();
+               writeln!(out, "mod bitcoin;").unwrap();
+       } else {
+               writeln!(out, "\nuse std::ffi::c_void;\nuse bitcoin::hashes::Hash;\nuse crate::c_types::*;\n").unwrap();
+       }
+
+       for (path, new_mod, m) in file_iter(&syntax, in_dir, path, &module) {
+               writeln_docs(&mut out, &m.attrs, "");
+               writeln!(out, "pub mod {};", m.ident).unwrap();
+               convert_file(libast, crate_types, in_dir, out_dir, &path,
+                       orig_crate, &new_mod, header_file, cpp_header_file);
+       }
+
+       let mut type_resolver = TypeResolver::new(orig_crate, module, crate_types);
+
+       for item in syntax.items.iter() {
+               match item {
+                       syn::Item::Use(u) => type_resolver.process_use(&mut out, &u),
+                       syn::Item::Static(_) => {},
+                       syn::Item::Enum(e) => {
+                               if let syn::Visibility::Public(_) = e.vis {
+                                       writeln_enum(&mut out, &e, &mut type_resolver, header_file, cpp_header_file);
+                               }
+                       },
+                       syn::Item::Impl(i) => {
+                               writeln_impl(&mut out, &i, &mut type_resolver);
+                       },
+                       syn::Item::Struct(s) => {
+                               if let syn::Visibility::Public(_) = s.vis {
+                                       writeln_struct(&mut out, &s, &mut type_resolver, header_file, cpp_header_file);
+                               }
+                       },
+                       syn::Item::Trait(t) => {
+                               if let syn::Visibility::Public(_) = t.vis {
+                                       writeln_trait(&mut out, &t, &mut type_resolver, header_file, cpp_header_file);
+                               }
+                       },
+                       syn::Item::Mod(_) => {}, // We don't have to do anything - the top loop handles these.
+                       syn::Item::Const(c) => {
+                               // Re-export any primitive-type constants.
+                               if let syn::Visibility::Public(_) = c.vis {
+                                       if let syn::Type::Path(p) = &*c.ty {
+                                               let resolved_path = type_resolver.resolve_path(&p.path);
+                                               if type_resolver.is_primitive(&resolved_path) {
+                                                       writeln!(out, "\n#[no_mangle]").unwrap();
+                                                       writeln!(out, "pub static {}: {} = {}::{}::{};", c.ident, resolved_path, orig_crate, module, c.ident).unwrap();
+                                               }
+                                       }
+                               }
+                       },
+                       syn::Item::Type(t) => {
+                               if let syn::Visibility::Public(_) = t.vis {
+                                       match export_status(&t.attrs) {
+                                               ExportStatus::Export => {},
+                                               ExportStatus::NoExport|ExportStatus::TestOnly => continue,
+                                       }
+                                       if t.generics.lt_token.is_none() {
+                                               writeln_opaque(&mut out, &t.ident, &format!("{}", t.ident), &t.generics, &t.attrs, &type_resolver, header_file, cpp_header_file);
+                                       }
+                               }
+                       },
+                       syn::Item::Fn(f) => {
+                               if let syn::Visibility::Public(_) = f.vis {
+                                       writeln_fn(&mut out, &f, &mut type_resolver);
+                               }
+                       },
+                       syn::Item::Macro(m) => {
+                               if m.ident.is_none() { // If its not a macro definition
+                                       convert_macro(&mut out, &m.mac.path, &m.mac.tokens, &type_resolver);
+                               }
+                       },
+                       syn::Item::Verbatim(_) => {},
+                       syn::Item::ExternCrate(_) => {},
+                       _ => unimplemented!(),
+               }
+       }
+
+       out.flush().unwrap();
+}
+
+/// Load the AST for each file in the crate, filling the FullLibraryAST object
+fn load_ast(in_dir: &str, path: &str, module: String, ast_storage: &mut FullLibraryAST) {
+       eprintln!("Loading {}{}...", in_dir, path);
+
+       let mut file = File::open(format!("{}/{}", in_dir, path)).expect("Unable to open file");
+       let mut src = String::new();
+       file.read_to_string(&mut src).expect("Unable to read file");
+       let syntax = syn::parse_file(&src).expect("Unable to parse file");
+
+       assert_eq!(export_status(&syntax.attrs), ExportStatus::Export);
+
+       for (path, new_mod, _) in file_iter(&syntax, in_dir, path, &module) {
+               load_ast(in_dir, &path, new_mod, ast_storage);
+       }
+       ast_storage.files.insert(module, syntax);
+}
+
+/// Walk the FullLibraryAST, deciding how things will be mapped and adding tracking to CrateTypes.
+fn walk_ast<'a>(in_dir: &str, path: &str, module: String, ast_storage: &'a FullLibraryAST, crate_types: &mut CrateTypes<'a>) {
+       let syntax = if let Some(ast) = ast_storage.files.get(&module) { ast } else { return };
+       assert_eq!(export_status(&syntax.attrs), ExportStatus::Export);
+
+       for (path, new_mod, _) in file_iter(&syntax, in_dir, path, &module) {
+               walk_ast(in_dir, &path, new_mod, ast_storage, crate_types);
+       }
+
+       for item in syntax.items.iter() {
+               match item {
+                       syn::Item::Struct(s) => {
+                               if let syn::Visibility::Public(_) = s.vis {
+                                       match export_status(&s.attrs) {
+                                               ExportStatus::Export => {},
+                                               ExportStatus::NoExport|ExportStatus::TestOnly => continue,
+                                       }
+                                       let struct_path = format!("{}::{}", module, s.ident);
+                                       crate_types.opaques.insert(struct_path, &s.ident);
+                               }
+                       },
+                       syn::Item::Trait(t) => {
+                               if let syn::Visibility::Public(_) = t.vis {
+                                       match export_status(&t.attrs) {
+                                               ExportStatus::Export => {},
+                                               ExportStatus::NoExport|ExportStatus::TestOnly => continue,
+                                       }
+                                       let trait_path = format!("{}::{}", module, t.ident);
+                                       crate_types.traits.insert(trait_path, &t);
+                               }
+                       },
+                       syn::Item::Enum(e) if is_enum_opaque(e) => {
+                               if let syn::Visibility::Public(_) = e.vis {
+                                       match export_status(&e.attrs) {
+                                               ExportStatus::Export => {},
+                                               ExportStatus::NoExport|ExportStatus::TestOnly => continue,
+                                       }
+                                       let enum_path = format!("{}::{}", module, e.ident);
+                                       crate_types.opaques.insert(enum_path, &e.ident);
+                               }
+                       },
+                       syn::Item::Enum(e) => {
+                               if let syn::Visibility::Public(_) = e.vis {
+                                       match export_status(&e.attrs) {
+                                               ExportStatus::Export => {},
+                                               ExportStatus::NoExport|ExportStatus::TestOnly => continue,
+                                       }
+                                       let enum_path = format!("{}::{}", module, e.ident);
+                                       crate_types.mirrored_enums.insert(enum_path, &e);
+                               }
+                       },
+                       _ => {},
+               }
+       }
+}
+
+fn main() {
+       let args: Vec<String> = env::args().collect();
+       if args.len() != 7 {
+               eprintln!("Usage: source/dir target/dir source_crate_name derived_templates.rs extra/includes.h extra/cpp/includes.hpp");
+               process::exit(1);
+       }
+
+       let mut derived_templates = std::fs::OpenOptions::new().write(true).create(true).truncate(true)
+               .open(&args[4]).expect("Unable to open new header file");
+       let mut header_file = std::fs::OpenOptions::new().write(true).create(true).truncate(true)
+               .open(&args[5]).expect("Unable to open new header file");
+       let mut cpp_header_file = std::fs::OpenOptions::new().write(true).create(true).truncate(true)
+               .open(&args[6]).expect("Unable to open new header file");
+
+       writeln!(header_file, "#if defined(__GNUC__)\n#define MUST_USE_STRUCT __attribute__((warn_unused))").unwrap();
+       writeln!(header_file, "#else\n#define MUST_USE_STRUCT\n#endif").unwrap();
+       writeln!(header_file, "#if defined(__GNUC__)\n#define MUST_USE_RES __attribute__((warn_unused_result))").unwrap();
+       writeln!(header_file, "#else\n#define MUST_USE_RES\n#endif").unwrap();
+       writeln!(cpp_header_file, "#include <string.h>\nnamespace LDK {{").unwrap();
+
+       // First parse the full crate's ASTs, caching them so that we can hold references to the AST
+       // objects in other datastructures:
+       let mut libast = FullLibraryAST { files: HashMap::new() };
+       load_ast(&args[1], "/lib.rs", "".to_string(), &mut libast);
+
+       // ...then walk the ASTs tracking what types we will map, and how, so that we can resolve them
+       // when parsing other file ASTs...
+       let mut libtypes = CrateTypes { traits: HashMap::new(), opaques: HashMap::new(), mirrored_enums: HashMap::new(),
+               templates_defined: HashMap::new(), template_file: &mut derived_templates };
+       walk_ast(&args[1], "/lib.rs", "".to_string(), &libast, &mut libtypes);
+
+       // ... finally, do the actual file conversion/mapping, writing out types as we go.
+       convert_file(&libast, &mut libtypes, &args[1], &args[2], "/lib.rs", &args[3], "", &mut header_file, &mut cpp_header_file);
+
+       // For container templates which we created while walking the crate, make sure we add C++
+       // mapped types so that C++ users can utilize the auto-destructors available.
+       for (ty, has_destructor) in libtypes.templates_defined.iter() {
+               write_cpp_wrapper(&mut cpp_header_file, ty, *has_destructor);
+       }
+       writeln!(cpp_header_file, "}}").unwrap();
+
+       header_file.flush().unwrap();
+       cpp_header_file.flush().unwrap();
+       derived_templates.flush().unwrap();
+}
diff --git a/c-bindings-gen/src/types.rs b/c-bindings-gen/src/types.rs
new file mode 100644 (file)
index 0000000..56bb4e6
--- /dev/null
@@ -0,0 +1,2021 @@
+use std::collections::HashMap;
+use std::fs::File;
+use std::io::Write;
+
+use proc_macro2::{TokenTree, Span};
+
+// The following utils are used purely to build our known types maps - they break down all the
+// types we need to resolve to include the given object, and no more.
+
+pub fn first_seg_self<'a>(t: &'a syn::Type) -> Option<impl Iterator<Item=&syn::PathSegment> + 'a> {
+       match t {
+               syn::Type::Path(p) => {
+                       if p.qself.is_some() || p.path.leading_colon.is_some() {
+                               return None;
+                       }
+                       let mut segs = p.path.segments.iter();
+                       let ty = segs.next().unwrap();
+                       if !ty.arguments.is_empty() { return None; }
+                       if format!("{}", ty.ident) == "Self" {
+                               Some(segs)
+                       } else { None }
+               },
+               _ => None,
+       }
+}
+
+pub fn get_single_remaining_path_seg<'a, I: Iterator<Item=&'a syn::PathSegment>>(segs: &mut I) -> Option<&'a syn::Ident> {
+       if let Some(ty) = segs.next() {
+               if !ty.arguments.is_empty() { unimplemented!(); }
+               if segs.next().is_some() { return None; }
+               Some(&ty.ident)
+       } else { None }
+}
+
+pub fn assert_single_path_seg<'a>(p: &'a syn::Path) -> &'a syn::Ident {
+       if p.leading_colon.is_some() { unimplemented!(); }
+       get_single_remaining_path_seg(&mut p.segments.iter()).unwrap()
+}
+
+pub fn single_ident_generic_path_to_ident(p: &syn::Path) -> Option<&syn::Ident> {
+       if p.segments.len() == 1 {
+               Some(&p.segments.iter().next().unwrap().ident)
+       } else { None }
+}
+
+#[derive(Debug, PartialEq)]
+pub enum ExportStatus {
+       Export,
+       NoExport,
+       TestOnly,
+}
+/// Gets the ExportStatus of an object (struct, fn, etc) given its attributes.
+pub fn export_status(attrs: &[syn::Attribute]) -> ExportStatus {
+       for attr in attrs.iter() {
+               let tokens_clone = attr.tokens.clone();
+               let mut token_iter = tokens_clone.into_iter();
+               if let Some(token) = token_iter.next() {
+                       match token {
+                               TokenTree::Punct(c) if c.as_char() == '=' => {
+                                       // Really not sure where syn gets '=' from here -
+                                       // it somehow represents '///' or '//!'
+                               },
+                               TokenTree::Group(g) => {
+                                       if format!("{}", single_ident_generic_path_to_ident(&attr.path).unwrap()) == "cfg" {
+                                               let mut iter = g.stream().into_iter();
+                                               if let TokenTree::Ident(i) = iter.next().unwrap() {
+                                                       if i == "any" {
+                                                               // #[cfg(any(test, feature = ""))]
+                                                               if let TokenTree::Group(g) = iter.next().unwrap() {
+                                                                       if let TokenTree::Ident(i) = g.stream().into_iter().next().unwrap() {
+                                                                               if i == "test" || i == "feature" {
+                                                                                       // If its cfg(feature(...)) we assume its test-only
+                                                                                       return ExportStatus::TestOnly;
+                                                                               }
+                                                                       }
+                                                               }
+                                                       } else if i == "test" || i == "feature" {
+                                                               // If its cfg(feature(...)) we assume its test-only
+                                                               return ExportStatus::TestOnly;
+                                                       }
+                                               }
+                                       }
+                                       continue; // eg #[derive()]
+                               },
+                               _ => unimplemented!(),
+                       }
+               } else { continue; }
+               match token_iter.next().unwrap() {
+                       TokenTree::Literal(lit) => {
+                               let line = format!("{}", lit);
+                               if line.contains("(C-not exported)") {
+                                       return ExportStatus::NoExport;
+                               }
+                       },
+                       _ => unimplemented!(),
+               }
+       }
+       ExportStatus::Export
+}
+
+pub fn assert_simple_bound(bound: &syn::TraitBound) {
+       if bound.paren_token.is_some() || bound.lifetimes.is_some() { unimplemented!(); }
+       if let syn::TraitBoundModifier::Maybe(_) = bound.modifier { unimplemented!(); }
+}
+
+/// A stack of sets of generic resolutions.
+///
+/// This tracks the template parameters for a function, struct, or trait, allowing resolution into
+/// a concrete type. By pushing a new context onto the stack, this can track a function's template
+/// parameters inside of a generic struct or trait.
+///
+/// It maps both direct types as well as Deref<Target = X>, mapping them via the provided
+/// TypeResolver's resolve_path function (ie traits map to the concrete jump table, structs to the
+/// concrete C container struct, etc).
+pub struct GenericTypes<'a> {
+       typed_generics: Vec<HashMap<&'a syn::Ident, (String, Option<&'a syn::Path>)>>,
+}
+impl<'a> GenericTypes<'a> {
+       pub fn new() -> Self {
+               Self { typed_generics: vec![HashMap::new()], }
+       }
+
+       /// push a new context onto the stack, allowing for a new set of generics to be learned which
+       /// will override any lower contexts, but which will still fall back to resoltion via lower
+       /// contexts.
+       pub fn push_ctx(&mut self) {
+               self.typed_generics.push(HashMap::new());
+       }
+       /// pop the latest context off the stack.
+       pub fn pop_ctx(&mut self) {
+               self.typed_generics.pop();
+       }
+
+       /// Learn the generics in generics in the current context, given a TypeResolver.
+       pub fn learn_generics<'b, 'c>(&mut self, generics: &'a syn::Generics, types: &'b TypeResolver<'a, 'c>) -> bool {
+               for generic in generics.params.iter() {
+                       match generic {
+                               syn::GenericParam::Type(type_param) => {
+                                       let mut non_lifetimes_processed = false;
+                                       for bound in type_param.bounds.iter() {
+                                               if let syn::TypeParamBound::Trait(trait_bound) = bound {
+                                                       if let Some(ident) = single_ident_generic_path_to_ident(&trait_bound.path) {
+                                                               match &format!("{}", ident) as &str { "Send" => continue, "Sync" => continue, _ => {} }
+                                                       }
+
+                                                       assert_simple_bound(&trait_bound);
+                                                       if let Some(mut path) = types.maybe_resolve_path(&trait_bound.path) {
+                                                               if types.skip_path(&path) { continue; }
+                                                               if non_lifetimes_processed { return false; }
+                                                               non_lifetimes_processed = true;
+                                                               let new_ident = if path != "std::ops::Deref" {
+                                                                       path = "crate::".to_string() + &path;
+                                                                       Some(&trait_bound.path)
+                                                               } else { None };
+                                                               self.typed_generics.last_mut().unwrap().insert(&type_param.ident, (path, new_ident));
+                                                       } else { return false; }
+                                               }
+                                       }
+                               },
+                               _ => {},
+                       }
+               }
+               if let Some(wh) = &generics.where_clause {
+                       for pred in wh.predicates.iter() {
+                               if let syn::WherePredicate::Type(t) = pred {
+                                       if let syn::Type::Path(p) = &t.bounded_ty {
+                                               if p.qself.is_some() { return false; }
+                                               if p.path.leading_colon.is_some() { return false; }
+                                               let mut p_iter = p.path.segments.iter();
+                                               if let Some(gen) = self.typed_generics.last_mut().unwrap().get_mut(&p_iter.next().unwrap().ident) {
+                                                       if gen.0 != "std::ops::Deref" { return false; }
+                                                       if &format!("{}", p_iter.next().unwrap().ident) != "Target" { return false; }
+
+                                                       let mut non_lifetimes_processed = false;
+                                                       for bound in t.bounds.iter() {
+                                                               if let syn::TypeParamBound::Trait(trait_bound) = bound {
+                                                                       if non_lifetimes_processed { return false; }
+                                                                       non_lifetimes_processed = true;
+                                                                       assert_simple_bound(&trait_bound);
+                                                                       *gen = ("crate::".to_string() + &types.resolve_path(&trait_bound.path),
+                                                                               Some(&trait_bound.path));
+                                                               }
+                                                       }
+                                               } else { return false; }
+                                       } else { return false; }
+                               }
+                       }
+               }
+               for (_, (_, ident)) in self.typed_generics.last().unwrap().iter() {
+                       if ident.is_none() { return false; }
+               }
+               true
+       }
+
+       /// Attempt to resolve an Ident as a generic parameter and return the full path.
+       pub fn maybe_resolve_ident<'b>(&'b self, ident: &syn::Ident) -> Option<&'b String> {
+               for gen in self.typed_generics.iter().rev() {
+                       if let Some(res) = gen.get(ident).map(|(a, _)| a) {
+                               return Some(res);
+                       }
+               }
+               None
+       }
+       /// Attempt to resolve a Path as a generic parameter and return the full path. as both a string
+       /// and syn::Path.
+       pub fn maybe_resolve_path<'b>(&'b self, path: &syn::Path) -> Option<(&'b String, &'a syn::Path)> {
+               if let Some(ident) = path.get_ident() {
+                       for gen in self.typed_generics.iter().rev() {
+                               if let Some(res) = gen.get(ident).map(|(a, b)| (a, b.unwrap())) {
+                                       return Some(res);
+                               }
+                       }
+               }
+               None
+       }
+}
+
+#[derive(Clone, PartialEq)]
+// The type of declaration and the object itself
+pub enum DeclType<'a> {
+       MirroredEnum,
+       Trait(&'a syn::ItemTrait),
+       StructImported,
+       StructIgnored,
+       EnumIgnored,
+}
+
+/// Top-level struct tracking everything which has been defined while walking the crate.
+pub struct CrateTypes<'a> {
+       /// This may contain structs or enums, but only when either is mapped as
+       /// struct X { inner: *mut originalX, .. }
+       pub opaques: HashMap<String, &'a syn::Ident>,
+       /// Enums which are mapped as C enums with conversion functions
+       pub mirrored_enums: HashMap<String, &'a syn::ItemEnum>,
+       /// Traits which are mapped as a pointer + jump table
+       pub traits: HashMap<String, &'a syn::ItemTrait>,
+       /// Template continer types defined, map from mangled type name -> whether a destructor fn
+       /// exists.
+       ///
+       /// This is used at the end of processing to make C++ wrapper classes
+       pub templates_defined: HashMap<String, bool>,
+       /// The output file for any created template container types, written to as we find new
+       /// template containers which need to be defined.
+       pub template_file: &'a mut File,
+}
+
+/// A struct which tracks resolving rust types into C-mapped equivalents, exists for one specific
+/// module but contains a reference to the overall CrateTypes tracking.
+pub struct TypeResolver<'mod_lifetime, 'crate_lft: 'mod_lifetime> {
+       pub orig_crate: &'mod_lifetime str,
+       pub module_path: &'mod_lifetime str,
+       imports: HashMap<syn::Ident, String>,
+       // ident -> is-mirrored-enum
+       declared: HashMap<syn::Ident, DeclType<'crate_lft>>,
+       pub crate_types: &'mod_lifetime mut CrateTypes<'crate_lft>,
+}
+
+impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
+       pub fn new(orig_crate: &'a str, module_path: &'a str, crate_types: &'a mut CrateTypes<'c>) -> Self {
+               let mut imports = HashMap::new();
+               // Add primitives to the "imports" list:
+               imports.insert(syn::Ident::new("bool", Span::call_site()), "bool".to_string());
+               imports.insert(syn::Ident::new("u64", Span::call_site()), "u64".to_string());
+               imports.insert(syn::Ident::new("u32", Span::call_site()), "u32".to_string());
+               imports.insert(syn::Ident::new("u16", Span::call_site()), "u16".to_string());
+               imports.insert(syn::Ident::new("u8", Span::call_site()), "u8".to_string());
+               imports.insert(syn::Ident::new("usize", Span::call_site()), "usize".to_string());
+               imports.insert(syn::Ident::new("str", Span::call_site()), "str".to_string());
+               imports.insert(syn::Ident::new("String", Span::call_site()), "String".to_string());
+
+               // These are here to allow us to print native Rust types in trait fn impls even if we don't
+               // have C mappings:
+               imports.insert(syn::Ident::new("Result", Span::call_site()), "Result".to_string());
+               imports.insert(syn::Ident::new("Vec", Span::call_site()), "Vec".to_string());
+               imports.insert(syn::Ident::new("Option", Span::call_site()), "Option".to_string());
+               Self { orig_crate, module_path, imports, declared: HashMap::new(), crate_types }
+       }
+
+       // *************************************************
+       // *** Well know type and conversion definitions ***
+       // *************************************************
+
+       /// Returns true we if can just skip passing this to C entirely
+       fn skip_path(&self, full_path: &str) -> bool {
+               full_path == "bitcoin::secp256k1::Secp256k1" ||
+               full_path == "bitcoin::secp256k1::Signing" ||
+               full_path == "bitcoin::secp256k1::Verification"
+       }
+       /// Returns true we if can just skip passing this to C entirely
+       fn no_arg_path_to_rust(&self, full_path: &str) -> &str {
+               if full_path == "bitcoin::secp256k1::Secp256k1" {
+                       "&bitcoin::secp256k1::Secp256k1::new()"
+               } else { unimplemented!(); }
+       }
+
+       /// Returns true if the object is a primitive and is mapped as-is with no conversion
+       /// whatsoever.
+       pub fn is_primitive(&self, full_path: &str) -> bool {
+               match full_path {
+                       "bool" => true,
+                       "u64" => true,
+                       "u32" => true,
+                       "u16" => true,
+                       "u8" => true,
+                       "usize" => true,
+                       _ => false,
+               }
+       }
+       /// Gets the C-mapped type for types which are outside of the crate, or which are manually
+       /// ignored by for some reason need mapping anyway.
+       fn c_type_from_path<'b>(&self, full_path: &'b str, is_ref: bool, ptr_for_ref: bool) -> Option<&'b str> {
+               if self.is_primitive(full_path) {
+                       return Some(full_path);
+               }
+               match full_path {
+                       "Result" => Some("crate::c_types::derived::CResult"),
+                       "Vec" if !is_ref => Some("crate::c_types::derived::CVec"),
+                       "Option" => Some(""),
+
+                       // Note that no !is_ref types can map to an array because Rust and C's call semantics
+                       // for arrays are different (https://github.com/eqrion/cbindgen/issues/528)
+
+                       "[u8; 32]" if !is_ref => Some("crate::c_types::ThirtyTwoBytes"),
+                       "[u8; 16]" if !is_ref => Some("crate::c_types::SixteenBytes"),
+                       "[u8; 10]" if !is_ref => Some("crate::c_types::TenBytes"),
+                       "[u8; 4]" if !is_ref => Some("crate::c_types::FourBytes"),
+                       "[u8; 3]" if !is_ref => Some("crate::c_types::ThreeBytes"), // Used for RGB values
+
+                       "str" if is_ref => Some("crate::c_types::Str"),
+                       "String" if !is_ref => Some("crate::c_types::derived::CVec_u8Z"),
+                       "String" if is_ref => Some("crate::c_types::Str"),
+
+                       "std::time::Duration" => Some("u64"),
+
+                       "bitcoin::secp256k1::key::PublicKey" => Some("crate::c_types::PublicKey"),
+                       "bitcoin::secp256k1::Signature" => Some("crate::c_types::Signature"),
+                       "bitcoin::secp256k1::key::SecretKey" if is_ref  => Some("*const [u8; 32]"),
+                       "bitcoin::secp256k1::key::SecretKey" if !is_ref => Some("crate::c_types::SecretKey"),
+                       "bitcoin::secp256k1::Error" if !is_ref => Some("crate::c_types::Secp256k1Error"),
+                       "bitcoin::blockdata::script::Script" if is_ref => Some("crate::c_types::u8slice"),
+                       "bitcoin::blockdata::script::Script" if !is_ref => Some("crate::c_types::derived::CVec_u8Z"),
+                       "bitcoin::blockdata::transaction::OutPoint" if is_ref => Some("crate::chain::transaction::OutPoint"),
+                       "bitcoin::blockdata::transaction::Transaction" if is_ref && !ptr_for_ref => Some("crate::c_types::Transaction"),
+                       "bitcoin::blockdata::transaction::Transaction" => Some("crate::c_types::derived::CVec_u8Z"),
+                       "bitcoin::blockdata::transaction::TxOut" if !is_ref => Some("crate::c_types::TxOut"),
+                       "bitcoin::OutPoint" => Some("crate::chain::transaction::OutPoint"),
+                       "bitcoin::network::constants::Network" => Some("crate::bitcoin::network::Network"),
+                       "bitcoin::blockdata::block::BlockHeader" if is_ref  => Some("*const [u8; 80]"),
+                       "bitcoin::blockdata::block::Block" if is_ref  => Some("crate::c_types::u8slice"),
+
+                       // Newtypes that we just expose in their original form.
+                       "bitcoin::hash_types::Txid" if is_ref  => Some("*const [u8; 32]"),
+                       "bitcoin::hash_types::Txid" if !is_ref => Some("crate::c_types::ThirtyTwoBytes"),
+                       "bitcoin::hash_types::BlockHash" if is_ref  => Some("*const [u8; 32]"),
+                       "bitcoin::hash_types::BlockHash" if !is_ref => Some("crate::c_types::ThirtyTwoBytes"),
+                       "ln::channelmanager::PaymentHash" if is_ref => Some("*const [u8; 32]"),
+                       "ln::channelmanager::PaymentHash" if !is_ref => Some("crate::c_types::ThirtyTwoBytes"),
+                       "ln::channelmanager::PaymentPreimage" if is_ref => Some("*const [u8; 32]"),
+                       "ln::channelmanager::PaymentPreimage" if !is_ref => Some("crate::c_types::ThirtyTwoBytes"),
+                       "ln::channelmanager::PaymentSecret" if is_ref => Some("crate::c_types::ThirtyTwoBytes"),
+                       "ln::channelmanager::PaymentSecret" if !is_ref => Some("crate::c_types::ThirtyTwoBytes"),
+
+                       // Override the default since Records contain an fmt with a lifetime:
+                       "util::logger::Record" => Some("*const std::os::raw::c_char"),
+
+                       // List of structs we map that aren't detected:
+                       "ln::features::InitFeatures" if is_ref && ptr_for_ref => Some("crate::ln::features::InitFeatures"),
+                       "ln::features::InitFeatures" if is_ref => Some("*const crate::ln::features::InitFeatures"),
+                       "ln::features::InitFeatures" => Some("crate::ln::features::InitFeatures"),
+                       _ => {
+                               eprintln!("    Type {} (ref: {}) unresolvable in C", full_path, is_ref);
+                               None
+                       },
+               }
+       }
+
+       fn from_c_conversion_new_var_from_path<'b>(&self, _full_path: &str, _is_ref: bool) -> Option<(&'b str, &'b str)> {
+               None
+       }
+       fn from_c_conversion_prefix_from_path<'b>(&self, full_path: &str, is_ref: bool) -> Option<String> {
+               if self.is_primitive(full_path) {
+                       return Some("".to_owned());
+               }
+               match full_path {
+                       "Vec" if !is_ref => Some("local_"),
+                       "Result" if !is_ref => Some("local_"),
+                       "Option" if is_ref => Some("&local_"),
+                       "Option" => Some("local_"),
+
+                       "[u8; 32]" if is_ref => Some("unsafe { &*"),
+                       "[u8; 32]" if !is_ref => Some(""),
+                       "[u8; 16]" if !is_ref => Some(""),
+                       "[u8; 10]" if !is_ref => Some(""),
+                       "[u8; 4]" if !is_ref => Some(""),
+                       "[u8; 3]" if !is_ref => Some(""),
+
+                       "[u8]" if is_ref => Some(""),
+                       "[usize]" if is_ref => Some(""),
+
+                       "str" if is_ref => Some(""),
+                       "String" if !is_ref => Some("String::from_utf8("),
+                       // Note that we'll panic for String if is_ref, as we only have non-owned memory, we
+                       // cannot create a &String.
+
+                       "std::time::Duration" => Some("std::time::Duration::from_secs("),
+
+                       "bitcoin::secp256k1::key::PublicKey" if is_ref => Some("&"),
+                       "bitcoin::secp256k1::key::PublicKey" => Some(""),
+                       "bitcoin::secp256k1::Signature" if is_ref => Some("&"),
+                       "bitcoin::secp256k1::Signature" => Some(""),
+                       "bitcoin::secp256k1::key::SecretKey" if is_ref => Some("&::bitcoin::secp256k1::key::SecretKey::from_slice(&unsafe { *"),
+                       "bitcoin::secp256k1::key::SecretKey" if !is_ref => Some(""),
+                       "bitcoin::blockdata::script::Script" if is_ref => Some("&::bitcoin::blockdata::script::Script::from(Vec::from("),
+                       "bitcoin::blockdata::script::Script" if !is_ref => Some("::bitcoin::blockdata::script::Script::from("),
+                       "bitcoin::blockdata::transaction::Transaction" if is_ref => Some("&"),
+                       "bitcoin::blockdata::transaction::Transaction" => Some("::bitcoin::consensus::encode::deserialize(&"),
+                       "bitcoin::blockdata::transaction::TxOut" if !is_ref => Some(""),
+                       "bitcoin::network::constants::Network" => Some(""),
+                       "bitcoin::blockdata::block::BlockHeader" => Some("&::bitcoin::consensus::encode::deserialize(unsafe { &*"),
+                       "bitcoin::blockdata::block::Block" if is_ref => Some("&::bitcoin::consensus::encode::deserialize("),
+
+                       // Newtypes that we just expose in their original form.
+                       "bitcoin::hash_types::Txid" if is_ref => Some("&::bitcoin::hash_types::Txid::from_slice(&unsafe { &*"),
+                       "bitcoin::hash_types::Txid" if !is_ref => Some("::bitcoin::hash_types::Txid::from_slice(&"),
+                       "bitcoin::hash_types::BlockHash" => Some("::bitcoin::hash_types::BlockHash::from_slice(&"),
+                       "ln::channelmanager::PaymentHash" if !is_ref => Some("::lightning::ln::channelmanager::PaymentHash("),
+                       "ln::channelmanager::PaymentHash" if is_ref => Some("&::lightning::ln::channelmanager::PaymentHash(unsafe { *"),
+                       "ln::channelmanager::PaymentPreimage" if !is_ref => Some("::lightning::ln::channelmanager::PaymentPreimage("),
+                       "ln::channelmanager::PaymentPreimage" if is_ref => Some("&::lightning::ln::channelmanager::PaymentPreimage(unsafe { *"),
+                       "ln::channelmanager::PaymentSecret" => Some("::lightning::ln::channelmanager::PaymentSecret("),
+
+                       // List of structs we map (possibly during processing of other files):
+                       "ln::features::InitFeatures" if !is_ref => Some("*unsafe { Box::from_raw("),
+
+                       // List of traits we map (possibly during processing of other files):
+                       "crate::util::logger::Logger" => Some(""),
+
+                       _ => {
+                               eprintln!("    Type {} unconvertable from C", full_path);
+                               None
+                       },
+               }.map(|s| s.to_owned())
+       }
+       fn from_c_conversion_suffix_from_path<'b>(&self, full_path: &str, is_ref: bool) -> Option<String> {
+               if self.is_primitive(full_path) {
+                       return Some("".to_owned());
+               }
+               match full_path {
+                       "Vec" if !is_ref => Some(""),
+                       "Option" => Some(""),
+                       "Result" if !is_ref => Some(""),
+
+                       "[u8; 32]" if is_ref => Some("}"),
+                       "[u8; 32]" if !is_ref => Some(".data"),
+                       "[u8; 16]" if !is_ref => Some(".data"),
+                       "[u8; 10]" if !is_ref => Some(".data"),
+                       "[u8; 4]" if !is_ref => Some(".data"),
+                       "[u8; 3]" if !is_ref => Some(".data"),
+
+                       "[u8]" if is_ref => Some(".to_slice()"),
+                       "[usize]" if is_ref => Some(".to_slice()"),
+
+                       "str" if is_ref => Some(".into()"),
+                       "String" if !is_ref => Some(".into_rust()).unwrap()"),
+
+                       "std::time::Duration" => Some(")"),
+
+                       "bitcoin::secp256k1::key::PublicKey" => Some(".into_rust()"),
+                       "bitcoin::secp256k1::Signature" => Some(".into_rust()"),
+                       "bitcoin::secp256k1::key::SecretKey" if !is_ref => Some(".into_rust()"),
+                       "bitcoin::secp256k1::key::SecretKey" if is_ref => Some("}[..]).unwrap()"),
+                       "bitcoin::blockdata::script::Script" if is_ref => Some(".to_slice()))"),
+                       "bitcoin::blockdata::script::Script" if !is_ref => Some(".into_rust())"),
+                       "bitcoin::blockdata::transaction::Transaction" if is_ref => Some(".into_bitcoin()"),
+                       "bitcoin::blockdata::transaction::Transaction" => Some(".into_rust()[..]).unwrap()"),
+                       "bitcoin::blockdata::transaction::TxOut" if !is_ref => Some(".into_rust()"),
+                       "bitcoin::network::constants::Network" => Some(".into_bitcoin()"),
+                       "bitcoin::blockdata::block::BlockHeader" => Some(" }).unwrap()"),
+                       "bitcoin::blockdata::block::Block" => Some(".to_slice()).unwrap()"),
+
+                       // Newtypes that we just expose in their original form.
+                       "bitcoin::hash_types::Txid" if is_ref => Some(" }[..]).unwrap()"),
+                       "bitcoin::hash_types::Txid" => Some(".data[..]).unwrap()"),
+                       "bitcoin::hash_types::BlockHash" if !is_ref => Some(".data[..]).unwrap()"),
+                       "ln::channelmanager::PaymentHash" if !is_ref => Some(".data)"),
+                       "ln::channelmanager::PaymentHash" if is_ref => Some(" })"),
+                       "ln::channelmanager::PaymentPreimage" if !is_ref => Some(".data)"),
+                       "ln::channelmanager::PaymentPreimage" if is_ref => Some(" })"),
+                       "ln::channelmanager::PaymentSecret" => Some(".data)"),
+
+                       // List of structs we map (possibly during processing of other files):
+                       "ln::features::InitFeatures" if is_ref => Some(".inner) }"),
+                       "ln::features::InitFeatures" if !is_ref => Some(".take_ptr()) }"),
+
+                       // List of traits we map (possibly during processing of other files):
+                       "crate::util::logger::Logger" => Some(""),
+
+                       _ => {
+                               eprintln!("    Type {} unconvertable from C", full_path);
+                               None
+                       },
+               }.map(|s| s.to_owned())
+       }
+
+       fn to_c_conversion_new_var_from_path<'b>(&self, full_path: &str, is_ref: bool) -> Option<(&'b str, &'b str)> {
+               if self.is_primitive(full_path) {
+                       return None;
+               }
+               match full_path {
+                       "[u8]" if is_ref => Some(("crate::c_types::u8slice::from_slice(", ")")),
+                       "[usize]" if is_ref => Some(("crate::c_types::usizeslice::from_slice(", ")")),
+
+                       "bitcoin::blockdata::transaction::Transaction" if is_ref => Some(("::bitcoin::consensus::encode::serialize(", ")")),
+                       "bitcoin::blockdata::transaction::Transaction" if !is_ref => Some(("::bitcoin::consensus::encode::serialize(&", ")")),
+                       "bitcoin::blockdata::block::BlockHeader" if is_ref => Some(("{ let mut s = [0u8; 80]; s[..].copy_from_slice(&::bitcoin::consensus::encode::serialize(", ")); s }")),
+                       "bitcoin::blockdata::block::Block" if is_ref => Some(("::bitcoin::consensus::encode::serialize(", ")")),
+                       "bitcoin::hash_types::Txid" => None,
+
+                       // Override the default since Records contain an fmt with a lifetime:
+                       // TODO: We should include the other record fields
+                       "util::logger::Record" => Some(("std::ffi::CString::new(format!(\"{}\", ", ".args)).unwrap()")),
+                       _ => None,
+               }.map(|s| s.to_owned())
+       }
+       fn to_c_conversion_inline_prefix_from_path(&self, full_path: &str, is_ref: bool, ptr_for_ref: bool) -> Option<String> {
+               if self.is_primitive(full_path) {
+                       return Some("".to_owned());
+               }
+               match full_path {
+                       "Result" if !is_ref => Some("local_"),
+                       "Vec" if !is_ref => Some("local_"),
+                       "Option" => Some("local_"),
+
+                       "[u8; 32]" if !is_ref => Some("crate::c_types::ThirtyTwoBytes { data: "),
+                       "[u8; 32]" if is_ref => Some("&"),
+                       "[u8; 16]" if !is_ref => Some("crate::c_types::SixteenBytes { data: "),
+                       "[u8; 10]" if !is_ref => Some("crate::c_types::TenBytes { data: "),
+                       "[u8; 4]" if !is_ref => Some("crate::c_types::FourBytes { data: "),
+                       "[u8; 3]" if is_ref => Some("&"),
+
+                       "[u8]" if is_ref => Some("local_"),
+                       "[usize]" if is_ref => Some("local_"),
+
+                       "str" if is_ref => Some(""),
+                       "String" => Some(""),
+
+                       "std::time::Duration" => Some(""),
+
+                       "bitcoin::secp256k1::key::PublicKey" => Some("crate::c_types::PublicKey::from_rust(&"),
+                       "bitcoin::secp256k1::Signature" => Some("crate::c_types::Signature::from_rust(&"),
+                       "bitcoin::secp256k1::key::SecretKey" if is_ref  => Some(""),
+                       "bitcoin::secp256k1::key::SecretKey" if !is_ref => Some("crate::c_types::SecretKey::from_rust("),
+                       "bitcoin::secp256k1::Error" if !is_ref => Some("crate::c_types::Secp256k1Error::from_rust("),
+                       "bitcoin::blockdata::script::Script" if is_ref => Some("crate::c_types::u8slice::from_slice(&"),
+                       "bitcoin::blockdata::script::Script" if !is_ref => Some(""),
+                       "bitcoin::blockdata::transaction::Transaction" if is_ref && !ptr_for_ref => Some("crate::c_types::Transaction::from_slice(&local_"),
+                       "bitcoin::blockdata::transaction::Transaction" => Some("local_"),
+                       "bitcoin::blockdata::transaction::TxOut" if !is_ref => Some("crate::c_types::TxOut::from_rust("),
+                       "bitcoin::blockdata::block::BlockHeader" if is_ref => Some("&local_"),
+                       "bitcoin::blockdata::block::Block" if is_ref => Some("crate::c_types::u8slice::from_slice(&local_"),
+
+                       "bitcoin::hash_types::Txid" if !is_ref => Some("crate::c_types::ThirtyTwoBytes { data: "),
+
+                       // Newtypes that we just expose in their original form.
+                       "bitcoin::hash_types::Txid" if is_ref => Some(""),
+                       "bitcoin::hash_types::BlockHash" if is_ref => Some(""),
+                       "bitcoin::hash_types::BlockHash" => Some("crate::c_types::ThirtyTwoBytes { data: "),
+                       "ln::channelmanager::PaymentHash" if is_ref => Some("&"),
+                       "ln::channelmanager::PaymentHash" if !is_ref => Some("crate::c_types::ThirtyTwoBytes { data: "),
+                       "ln::channelmanager::PaymentPreimage" if is_ref => Some("&"),
+                       "ln::channelmanager::PaymentPreimage" => Some("crate::c_types::ThirtyTwoBytes { data: "),
+                       "ln::channelmanager::PaymentSecret" if !is_ref => Some("crate::c_types::ThirtyTwoBytes { data: "),
+
+                       // Override the default since Records contain an fmt with a lifetime:
+                       "util::logger::Record" => Some("local_"),
+
+                       // List of structs we map (possibly during processing of other files):
+                       "ln::features::InitFeatures" if is_ref && ptr_for_ref => Some("crate::ln::features::InitFeatures { inner: &mut "),
+                       "ln::features::InitFeatures" if is_ref => Some("Box::into_raw(Box::new(crate::ln::features::InitFeatures { inner: &mut "),
+                       "ln::features::InitFeatures" if !is_ref => Some("crate::ln::features::InitFeatures { inner: Box::into_raw(Box::new("),
+
+                       _ => {
+                               eprintln!("    Type {} (is_ref: {}) unconvertable to C", full_path, is_ref);
+                               None
+                       },
+               }.map(|s| s.to_owned())
+       }
+       fn to_c_conversion_inline_suffix_from_path(&self, full_path: &str, is_ref: bool, ptr_for_ref: bool) -> Option<String> {
+               if self.is_primitive(full_path) {
+                       return Some("".to_owned());
+               }
+               match full_path {
+                       "Result" if !is_ref => Some(""),
+                       "Vec" if !is_ref => Some(".into()"),
+                       "Option" => Some(""),
+
+                       "[u8; 32]" if !is_ref => Some(" }"),
+                       "[u8; 32]" if is_ref => Some(""),
+                       "[u8; 16]" if !is_ref => Some(" }"),
+                       "[u8; 10]" if !is_ref => Some(" }"),
+                       "[u8; 4]" if !is_ref => Some(" }"),
+                       "[u8; 3]" if is_ref => Some(""),
+
+                       "[u8]" if is_ref => Some(""),
+                       "[usize]" if is_ref => Some(""),
+
+                       "str" if is_ref => Some(".into()"),
+                       "String" if !is_ref => Some(".into_bytes().into()"),
+                       "String" if is_ref => Some(".as_str().into()"),
+
+                       "std::time::Duration" => Some(".as_secs()"),
+
+                       "bitcoin::secp256k1::key::PublicKey" => Some(")"),
+                       "bitcoin::secp256k1::Signature" => Some(")"),
+                       "bitcoin::secp256k1::key::SecretKey" if !is_ref => Some(")"),
+                       "bitcoin::secp256k1::key::SecretKey" if is_ref => Some(".as_ref()"),
+                       "bitcoin::secp256k1::Error" if !is_ref => Some(")"),
+                       "bitcoin::blockdata::script::Script" if is_ref => Some("[..])"),
+                       "bitcoin::blockdata::script::Script" if !is_ref => Some(".into_bytes().into()"),
+                       "bitcoin::blockdata::transaction::Transaction" if is_ref && !ptr_for_ref => Some(")"),
+                       "bitcoin::blockdata::transaction::Transaction" => Some(".into()"),
+                       "bitcoin::blockdata::transaction::TxOut" if !is_ref => Some(")"),
+                       "bitcoin::blockdata::block::BlockHeader" if is_ref => Some(""),
+                       "bitcoin::blockdata::block::Block" if is_ref => Some(")"),
+
+                       "bitcoin::hash_types::Txid" if !is_ref => Some(".into_inner() }"),
+
+                       // Newtypes that we just expose in their original form.
+                       "bitcoin::hash_types::Txid" if is_ref => Some(".as_inner()"),
+                       "bitcoin::hash_types::BlockHash" if is_ref => Some(".as_inner()"),
+                       "bitcoin::hash_types::BlockHash" => Some(".into_inner() }"),
+                       "ln::channelmanager::PaymentHash" if is_ref => Some(".0"),
+                       "ln::channelmanager::PaymentHash" => Some(".0 }"),
+                       "ln::channelmanager::PaymentPreimage" if is_ref => Some(".0"),
+                       "ln::channelmanager::PaymentPreimage" => Some(".0 }"),
+                       "ln::channelmanager::PaymentSecret" if !is_ref => Some(".0 }"),
+
+                       // Override the default since Records contain an fmt with a lifetime:
+                       "util::logger::Record" => Some(".as_ptr()"),
+
+                       // List of structs we map (possibly during processing of other files):
+                       "ln::features::InitFeatures" if is_ref && ptr_for_ref => Some(", is_owned: false }"),
+                       "ln::features::InitFeatures" if is_ref => Some(", is_owned: false }))"),
+                       "ln::features::InitFeatures" => Some(")), is_owned: true }"),
+
+                       _ => {
+                               eprintln!("    Type {} unconvertable to C", full_path);
+                               None
+                       },
+               }.map(|s| s.to_owned())
+       }
+
+       fn empty_val_check_suffix_from_path(&self, full_path: &str) -> Option<&str> {
+               match full_path {
+                       "ln::channelmanager::PaymentSecret" => Some(".data == [0; 32]"),
+                       _ => None
+               }
+       }
+
+       // ****************************
+       // *** Container Processing ***
+       // ****************************
+
+       /// Returns the module path in the generated mapping crate to the containers which we generate
+       /// when writing to CrateTypes::template_file.
+       fn generated_container_path() -> &'static str {
+               "crate::c_types::derived"
+       }
+       /// Returns the module path in the generated mapping crate to the container templates, which
+       /// are then concretized and put in the generated container path/template_file.
+       fn container_templ_path() -> &'static str {
+               "crate::c_types"
+       }
+
+       /// Returns true if this is a "transparent" container, ie an Option or a container which does
+       /// not require a generated continer class.
+       fn is_transparent_container(&self, full_path: &str, _is_ref: bool) -> bool {
+               full_path == "Option"
+       }
+       /// Returns true if this is a known, supported, non-transparent container.
+       fn is_known_container(&self, full_path: &str, is_ref: bool) -> bool {
+               (full_path == "Result" && !is_ref) || (full_path == "Vec" && !is_ref) || full_path.ends_with("Tuple")
+       }
+       fn to_c_conversion_container_new_var<'b>(&self, full_path: &str, is_ref: bool, single_contained: Option<&syn::Type>, var_name: &syn::Ident, var_access: &str)
+                       // Returns prefix + Vec<(prefix, var-name-to-inline-convert)> + suffix
+                       // expecting one element in the vec per generic type, each of which is inline-converted
+                       -> Option<(&'b str, Vec<(String, String)>, &'b str)> {
+               match full_path {
+                       "Result" if !is_ref => {
+                               Some(("match ",
+                                               vec![(" { Ok(mut o) => crate::c_types::CResultTempl::ok(".to_string(), "o".to_string()),
+                                                       ("), Err(mut e) => crate::c_types::CResultTempl::err(".to_string(), "e".to_string())],
+                                               ") }"))
+                       },
+                       "Vec" if !is_ref => {
+                               Some(("Vec::new(); for item in ", vec![(format!(".drain(..) {{ local_{}.push(", var_name), "item".to_string())], "); }"))
+                       },
+                       "Slice" => {
+                               Some(("Vec::new(); for item in ", vec![(format!(".iter() {{ local_{}.push(", var_name), "**item".to_string())], "); }"))
+                       },
+                       "Option" => {
+                               if let Some(syn::Type::Path(p)) = single_contained {
+                                       if self.c_type_has_inner_from_path(&self.resolve_path(&p.path)) {
+                                               if is_ref {
+                                                       return Some(("if ", vec![
+                                                               (".is_none() { std::ptr::null() } else { ".to_owned(), format!("({}.as_ref().unwrap())", var_access))
+                                                               ], " }"));
+                                               } else {
+                                                       return Some(("if ", vec![
+                                                               (".is_none() { std::ptr::null_mut() } else { ".to_owned(), format!("({}.unwrap())", var_access))
+                                                               ], " }"));
+                                               }
+                                       }
+                               }
+                               if let Some(t) = single_contained {
+                                       let mut v = Vec::new();
+                                       self.write_empty_rust_val(&mut v, t);
+                                       let s = String::from_utf8(v).unwrap();
+                                       return Some(("if ", vec![
+                                               (format!(".is_none() {{ {} }} else {{ ", s), format!("({}.unwrap())", var_access))
+                                               ], " }"));
+                               } else { unreachable!(); }
+                       },
+                       _ => None,
+               }
+       }
+
+       /// only_contained_has_inner implies that there is only one contained element in the container
+       /// and it has an inner field (ie is an "opaque" type we've defined).
+       fn from_c_conversion_container_new_var<'b>(&self, full_path: &str, is_ref: bool, single_contained: Option<&syn::Type>, var_name: &syn::Ident, var_access: &str)
+                       // Returns prefix + Vec<(prefix, var-name-to-inline-convert)> + suffix
+                       // expecting one element in the vec per generic type, each of which is inline-converted
+                       -> Option<(&'b str, Vec<(String, String)>, &'b str)> {
+               match full_path {
+                       "Result" if !is_ref => {
+                               Some(("match ",
+                                               vec![(".result_ok { true => Ok(".to_string(), format!("(*unsafe {{ Box::from_raw({}.contents.result.take_ptr()) }})", var_name)),
+                                                    ("), false => Err(".to_string(), format!("(*unsafe {{ Box::from_raw({}.contents.err.take_ptr()) }})", var_name))],
+                                               ")}"))
+                       },
+                       "Vec"|"Slice" if !is_ref => {
+                               Some(("Vec::new(); for mut item in ", vec![(format!(".into_rust().drain(..) {{ local_{}.push(", var_name), "item".to_string())], "); }"))
+                       },
+                       "Slice" if is_ref => {
+                               Some(("Vec::new(); for mut item in ", vec![(format!(".as_slice().iter() {{ local_{}.push(", var_name), "item".to_string())], "); }"))
+                       },
+                       "Option" => {
+                               if let Some(syn::Type::Path(p)) = single_contained {
+                                       if self.c_type_has_inner_from_path(&self.resolve_path(&p.path)) {
+                                               if is_ref {
+                                                       return Some(("if ", vec![(".inner.is_null() { None } else { Some((*".to_string(), format!("{}", var_name))], ").clone()) }"))
+                                               } else {
+                                                       return Some(("if ", vec![(".inner.is_null() { None } else { Some(".to_string(), format!("{}", var_name))], ") }"));
+                                               }
+                                       }
+                               }
+
+                               if let Some(t) = single_contained {
+                                       let mut v = Vec::new();
+                                       let needs_deref = self.write_empty_rust_val_check_suffix(&mut v, t);
+                                       let s = String::from_utf8(v).unwrap();
+                                       if needs_deref {
+                                               return Some(("if ", vec![
+                                                       (format!("{} {{ None }} else {{ Some(", s), format!("unsafe {{ &mut *{} }}", var_access))
+                                               ], ") }"));
+                                       } else {
+                                               return Some(("if ", vec![
+                                                       (format!("{} {{ None }} else {{ Some(", s), format!("{}", var_access))
+                                               ], ") }"));
+                                       }
+                               } else { unreachable!(); }
+                       },
+                       _ => None,
+               }
+       }
+
+       // *************************************************
+       // *** Type definition during main.rs processing ***
+       // *************************************************
+
+       fn process_use_intern<W: std::io::Write>(&mut self, w: &mut W, u: &syn::UseTree, partial_path: &str) {
+               match u {
+                       syn::UseTree::Path(p) => {
+                               let new_path = format!("{}::{}", partial_path, p.ident);
+                               self.process_use_intern(w, &p.tree, &new_path);
+                       },
+                       syn::UseTree::Name(n) => {
+                               let full_path = format!("{}::{}", partial_path, n.ident);
+                               self.imports.insert(n.ident.clone(), full_path);
+                       },
+                       syn::UseTree::Group(g) => {
+                               for i in g.items.iter() {
+                                       self.process_use_intern(w, i, partial_path);
+                               }
+                       },
+                       syn::UseTree::Rename(r) => {
+                               let full_path = format!("{}::{}", partial_path, r.ident);
+                               self.imports.insert(r.rename.clone(), full_path);
+                       },
+                       syn::UseTree::Glob(_) => {
+                               eprintln!("Ignoring * use for {} - this may result in resolution failures", partial_path);
+                       },
+               }
+       }
+       pub fn process_use<W: std::io::Write>(&mut self, w: &mut W, u: &syn::ItemUse) {
+               if let syn::Visibility::Public(_) = u.vis {
+                       // We actually only use these for #[cfg(fuzztarget)]
+                       eprintln!("Ignoring pub(use) tree!");
+                       return;
+               }
+               match &u.tree {
+                       syn::UseTree::Path(p) => {
+                               let new_path = format!("{}", p.ident);
+                               self.process_use_intern(w, &p.tree, &new_path);
+                       },
+                       _ => unimplemented!(),
+               }
+               if u.leading_colon.is_some() { unimplemented!() }
+       }
+
+       pub fn mirrored_enum_declared(&mut self, ident: &syn::Ident) {
+               eprintln!("{} mirrored", ident);
+               self.declared.insert(ident.clone(), DeclType::MirroredEnum);
+       }
+       pub fn enum_ignored(&mut self, ident: &'c syn::Ident) {
+               self.declared.insert(ident.clone(), DeclType::EnumIgnored);
+       }
+       pub fn struct_imported(&mut self, ident: &'c syn::Ident, named: String) {
+               eprintln!("Imported {} as {}", ident, named);
+               self.declared.insert(ident.clone(), DeclType::StructImported);
+       }
+       pub fn struct_ignored(&mut self, ident: &syn::Ident) {
+               eprintln!("Not importing {}", ident);
+               self.declared.insert(ident.clone(), DeclType::StructIgnored);
+       }
+       pub fn trait_declared(&mut self, ident: &syn::Ident, t: &'c syn::ItemTrait) {
+               eprintln!("Trait {} created", ident);
+               self.declared.insert(ident.clone(), DeclType::Trait(t));
+       }
+       pub fn get_declared_type(&'a self, ident: &syn::Ident) -> Option<&'a DeclType<'c>> {
+               self.declared.get(ident)
+       }
+       /// Returns true if the object at the given path is mapped as X { inner: *mut origX, .. }.
+       fn c_type_has_inner_from_path(&self, full_path: &str) -> bool{
+               self.crate_types.opaques.get(full_path).is_some()
+       }
+
+       pub fn maybe_resolve_ident(&self, id: &syn::Ident) -> Option<String> {
+               if let Some(imp) = self.imports.get(id) {
+                       Some(imp.clone())
+               } else if self.declared.get(id).is_some() {
+                       Some(self.module_path.to_string() + "::" + &format!("{}", id))
+               } else { None }
+       }
+
+       pub fn maybe_resolve_non_ignored_ident(&self, id: &syn::Ident) -> Option<String> {
+               if let Some(imp) = self.imports.get(id) {
+                       Some(imp.clone())
+               } else if let Some(decl_type) = self.declared.get(id) {
+                       match decl_type {
+                               DeclType::StructIgnored => None,
+                               _ => Some(self.module_path.to_string() + "::" + &format!("{}", id)),
+                       }
+               } else { None }
+       }
+
+       pub fn maybe_resolve_path(&self, p: &syn::Path) -> Option<String> {
+               if p.leading_colon.is_some() {
+                       // At some point we may need this, but for now, its unused, so just fail.
+                       return None;
+               } else if let Some(id) = p.get_ident() {
+                       self.maybe_resolve_ident(id)
+               } else {
+                       if p.segments.len() == 1 {
+                               let seg = p.segments.iter().next().unwrap();
+                               return self.maybe_resolve_ident(&seg.ident);
+                       }
+                       let mut seg_iter = p.segments.iter();
+                       let first_seg = seg_iter.next().unwrap();
+                       let remaining: String = seg_iter.map(|seg| {
+                               if let syn::PathArguments::None = seg.arguments {
+                                       format!("{}", seg.ident)
+                               } else {
+                                       format!("{}", seg.ident)
+                               }
+                       }).collect();
+                       if let Some(imp) = self.imports.get(&first_seg.ident) {
+                               if remaining != "" {
+                                       Some(imp.clone() + "::" + &remaining)
+                               } else {
+                                       Some(imp.clone())
+                               }
+                       } else { None }
+               }
+       }
+       pub fn resolve_path(&self, p: &syn::Path) -> String {
+               self.maybe_resolve_path(p).unwrap()
+       }
+
+       // ***********************************
+       // *** Original Rust Type Printing ***
+       // ***********************************
+
+       fn write_rust_path<W: std::io::Write>(&self, w: &mut W, path: &syn::Path) {
+               if let Some(resolved) = self.maybe_resolve_path(&path) {
+                       if self.is_primitive(&resolved) {
+                               write!(w, "{}", path.get_ident().unwrap()).unwrap();
+                       } else {
+                               if resolved.starts_with("ln::") || resolved.starts_with("chain::") || resolved.starts_with("util::") {
+                                       write!(w, "lightning::{}", resolved).unwrap();
+                               } else {
+                                       write!(w, "{}", resolved).unwrap(); // XXX: Probably doens't work, get_ident().unwrap()
+                               }
+                       }
+                       if let syn::PathArguments::AngleBracketed(args) = &path.segments.iter().last().unwrap().arguments {
+                               self.write_rust_generic_arg(w, args.args.iter());
+                       }
+               } else {
+                       if path.leading_colon.is_some() {
+                               write!(w, "::").unwrap();
+                       }
+                       for (idx, seg) in path.segments.iter().enumerate() {
+                               if idx != 0 { write!(w, "::").unwrap(); }
+                               write!(w, "{}", seg.ident).unwrap();
+                               if let syn::PathArguments::AngleBracketed(args) = &seg.arguments {
+                                       self.write_rust_generic_arg(w, args.args.iter());
+                               }
+                       }
+               }
+       }
+       pub fn write_rust_generic_param<'b, W: std::io::Write>(&self, w: &mut W, generics: impl Iterator<Item=&'b syn::GenericParam>) {
+               let mut had_params = false;
+               for (idx, arg) in generics.enumerate() {
+                       if idx != 0 { write!(w, ", ").unwrap(); } else { write!(w, "<").unwrap(); }
+                       had_params = true;
+                       match arg {
+                               syn::GenericParam::Lifetime(lt) => write!(w, "'{}", lt.lifetime.ident).unwrap(),
+                               syn::GenericParam::Type(t) => {
+                                       write!(w, "{}", t.ident).unwrap();
+                                       if t.colon_token.is_some() { write!(w, ":").unwrap(); }
+                                       for (idx, bound) in t.bounds.iter().enumerate() {
+                                               if idx != 0 { write!(w, " + ").unwrap(); }
+                                               match bound {
+                                                       syn::TypeParamBound::Trait(tb) => {
+                                                               if tb.paren_token.is_some() || tb.lifetimes.is_some() { unimplemented!(); }
+                                                               self.write_rust_path(w, &tb.path);
+                                                       },
+                                                       _ => unimplemented!(),
+                                               }
+                                       }
+                                       if t.eq_token.is_some() || t.default.is_some() { unimplemented!(); }
+                               },
+                               _ => unimplemented!(),
+                       }
+               }
+               if had_params { write!(w, ">").unwrap(); }
+       }
+
+       pub fn write_rust_generic_arg<'b, W: std::io::Write>(&self, w: &mut W, generics: impl Iterator<Item=&'b syn::GenericArgument>) {
+               write!(w, "<").unwrap();
+               for (idx, arg) in generics.enumerate() {
+                       if idx != 0 { write!(w, ", ").unwrap(); }
+                       match arg {
+                               syn::GenericArgument::Type(t) => self.write_rust_type(w, t),
+                               _ => unimplemented!(),
+                       }
+               }
+               write!(w, ">").unwrap();
+       }
+       pub fn write_rust_type<W: std::io::Write>(&self, w: &mut W, t: &syn::Type) {
+               match t {
+                       syn::Type::Path(p) => {
+                               if p.qself.is_some() || p.path.leading_colon.is_some() {
+                                       unimplemented!();
+                               }
+                               self.write_rust_path(w, &p.path);
+                       },
+                       syn::Type::Reference(r) => {
+                               write!(w, "&").unwrap();
+                               if let Some(lft) = &r.lifetime {
+                                       write!(w, "'{} ", lft.ident).unwrap();
+                               }
+                               if r.mutability.is_some() {
+                                       write!(w, "mut ").unwrap();
+                               }
+                               self.write_rust_type(w, &*r.elem);
+                       },
+                       syn::Type::Array(a) => {
+                               write!(w, "[").unwrap();
+                               self.write_rust_type(w, &a.elem);
+                               if let syn::Expr::Lit(l) = &a.len {
+                                       if let syn::Lit::Int(i) = &l.lit {
+                                               write!(w, "; {}]", i).unwrap();
+                                       } else { unimplemented!(); }
+                               } else { unimplemented!(); }
+                       }
+                       syn::Type::Slice(s) => {
+                               write!(w, "[").unwrap();
+                               self.write_rust_type(w, &s.elem);
+                               write!(w, "]").unwrap();
+                       },
+                       syn::Type::Tuple(s) => {
+                               write!(w, "(").unwrap();
+                               for (idx, t) in s.elems.iter().enumerate() {
+                                       if idx != 0 { write!(w, ", ").unwrap(); }
+                                       self.write_rust_type(w, &t);
+                               }
+                               write!(w, ")").unwrap();
+                       },
+                       _ => unimplemented!(),
+               }
+       }
+
+       /// Prints a constructor for something which is "uninitialized" (but obviously not actually
+       /// unint'd memory).
+       pub fn write_empty_rust_val<W: std::io::Write>(&self, w: &mut W, t: &syn::Type) {
+               match t {
+                       syn::Type::Path(p) => {
+                               let resolved = self.resolve_path(&p.path);
+                               if self.crate_types.opaques.get(&resolved).is_some() {
+                                       write!(w, "crate::{} {{ inner: std::ptr::null_mut(), is_owned: true }}", resolved).unwrap();
+                               } else {
+                                       // Assume its a manually-mapped C type, where we can just define an null() fn
+                                       write!(w, "{}::null()", self.c_type_from_path(&resolved, false, false).unwrap()).unwrap();
+                               }
+                       },
+                       syn::Type::Array(a) => {
+                               if let syn::Expr::Lit(l) = &a.len {
+                                       if let syn::Lit::Int(i) = &l.lit {
+                                               if i.base10_digits().parse::<usize>().unwrap() < 32 {
+                                                       // Blindly assume that if we're trying to create an empty value for an
+                                                       // array < 32 entries that all-0s may be a valid state.
+                                                       unimplemented!();
+                                               }
+                                               let arrty = format!("[u8; {}]", i.base10_digits());
+                                               write!(w, "{}", self.to_c_conversion_inline_prefix_from_path(&arrty, false, false).unwrap()).unwrap();
+                                               write!(w, "[0; {}]", i.base10_digits()).unwrap();
+                                               write!(w, "{}", self.to_c_conversion_inline_suffix_from_path(&arrty, false, false).unwrap()).unwrap();
+                                       } else { unimplemented!(); }
+                               } else { unimplemented!(); }
+                       }
+                       _ => unimplemented!(),
+               }
+       }
+
+       /// Prints a suffix to determine if a variable is empty (ie was set by write_empty_rust_val),
+       /// returning whether we need to dereference the inner value before using it (ie it is a
+       /// pointer).
+       pub fn write_empty_rust_val_check_suffix<W: std::io::Write>(&self, w: &mut W, t: &syn::Type) -> bool {
+               match t {
+                       syn::Type::Path(p) => {
+                               let resolved = self.resolve_path(&p.path);
+                               if self.crate_types.opaques.get(&resolved).is_some() {
+                                       write!(w, ".inner.is_null()").unwrap();
+                                       false
+                               } else {
+                                       if let Some(suffix) = self.empty_val_check_suffix_from_path(&resolved) {
+                                               write!(w, "{}", suffix).unwrap();
+                                               false // We may eventually need to allow empty_val_check_suffix_from_path to specify if we need a deref or not
+                                       } else {
+                                               write!(w, ".is_null()").unwrap();
+                                               false
+                                       }
+                               }
+                       },
+                       syn::Type::Array(a) => {
+                               if let syn::Expr::Lit(l) = &a.len {
+                                       if let syn::Lit::Int(i) = &l.lit {
+                                               write!(w, " == [0; {}]", i.base10_digits()).unwrap();
+                                               false
+                                       } else { unimplemented!(); }
+                               } else { unimplemented!(); }
+                       },
+                       syn::Type::Slice(_) => {
+                               // Option<[]> always implies that we want to treat len() == 0 differently from
+                               // None, so we always map an Option<[]> into a pointer.
+                               write!(w, ".is_null()").unwrap();
+                               true
+                       },
+                       _ => unimplemented!(),
+               }
+       }
+
+       /// Prints a suffix to determine if a variable is empty (ie was set by write_empty_rust_val).
+       pub fn write_empty_rust_val_check<W: std::io::Write>(&self, w: &mut W, t: &syn::Type, var_access: &str) {
+               match t {
+                       syn::Type::Path(_) => {
+                               write!(w, "{}", var_access).unwrap();
+                               self.write_empty_rust_val_check_suffix(w, t);
+                       },
+                       syn::Type::Array(a) => {
+                               if let syn::Expr::Lit(l) = &a.len {
+                                       if let syn::Lit::Int(i) = &l.lit {
+                                               let arrty = format!("[u8; {}]", i.base10_digits());
+                                               // We don't (yet) support a new-var conversion here.
+                                               assert!(self.from_c_conversion_new_var_from_path(&arrty, false).is_none());
+                                               write!(w, "{}{}{}",
+                                                       self.from_c_conversion_prefix_from_path(&arrty, false).unwrap(),
+                                                       var_access,
+                                                       self.from_c_conversion_suffix_from_path(&arrty, false).unwrap()).unwrap();
+                                               self.write_empty_rust_val_check_suffix(w, t);
+                                       } else { unimplemented!(); }
+                               } else { unimplemented!(); }
+                       }
+                       _ => unimplemented!(),
+               }
+       }
+
+       // ********************************
+       // *** Type conversion printing ***
+       // ********************************
+
+       /// Returns true we if can just skip passing this to C entirely
+       pub fn skip_arg(&self, t: &syn::Type, generics: Option<&GenericTypes>) -> bool {
+               match t {
+                       syn::Type::Path(p) => {
+                               if p.qself.is_some() { unimplemented!(); }
+                               if let Some(gen_types) = generics {
+                                       if let Some(resolved) = gen_types.maybe_resolve_path(&p.path) {
+                                               return self.skip_path(resolved.0);
+                                       }
+                               }
+                               if let Some(full_path) = self.maybe_resolve_path(&p.path) {
+                                       self.skip_path(&full_path)
+                               } else { false }
+                       },
+                       syn::Type::Reference(r) => {
+                               self.skip_arg(&*r.elem, generics)
+                       },
+                       _ => false,
+               }
+       }
+       pub fn no_arg_to_rust<W: std::io::Write>(&self, w: &mut W, t: &syn::Type, generics: Option<&GenericTypes>) {
+               match t {
+                       syn::Type::Path(p) => {
+                               if p.qself.is_some() { unimplemented!(); }
+                               if let Some(gen_types) = generics {
+                                       if let Some(resolved) = gen_types.maybe_resolve_path(&p.path) {
+                                               write!(w, "{}", self.no_arg_path_to_rust(resolved.0)).unwrap();
+                                               return;
+                                       }
+                               }
+                               if let Some(full_path) = self.maybe_resolve_path(&p.path) {
+                                       write!(w, "{}", self.no_arg_path_to_rust(&full_path)).unwrap();
+                               }
+                       },
+                       syn::Type::Reference(r) => {
+                               self.no_arg_to_rust(w, &*r.elem, generics);
+                       },
+                       _ => {},
+               }
+       }
+
+       fn write_conversion_inline_intern<W: std::io::Write,
+                       LP: Fn(&str, bool, bool) -> Option<String>, DL: Fn(&mut W, &DeclType, &str, bool, bool), SC: Fn(bool) -> &'static str>
+                       (&self, w: &mut W, t: &syn::Type, generics: Option<&GenericTypes>, is_ref: bool, is_mut: bool, ptr_for_ref: bool,
+                        tupleconv: &str, prefix: bool, sliceconv: SC, path_lookup: LP, decl_lookup: DL) {
+               match t {
+                       syn::Type::Reference(r) => {
+                               self.write_conversion_inline_intern(w, &*r.elem, generics, true, r.mutability.is_some(),
+                                       ptr_for_ref, tupleconv, prefix, sliceconv, path_lookup, decl_lookup);
+                       },
+                       syn::Type::Path(p) => {
+                               if p.qself.is_some() || p.path.leading_colon.is_some() {
+                                       unimplemented!();
+                               }
+
+                               if let Some(gen_types) = generics {
+                                       if let Some((_, synpath)) = gen_types.maybe_resolve_path(&p.path) {
+                                               let genpath = self.resolve_path(&synpath);
+                                               assert!(!self.is_known_container(&genpath, is_ref) && !self.is_transparent_container(&genpath, is_ref));
+                                               if let Some(c_type) = path_lookup(&genpath, is_ref, ptr_for_ref) {
+                                                       write!(w, "{}", c_type).unwrap();
+                                                       return;
+                                               } else {
+                                                       let synident = single_ident_generic_path_to_ident(synpath).unwrap();
+                                                       if let Some(t) = self.crate_types.traits.get(&genpath) {
+                                                               decl_lookup(w, &DeclType::Trait(t), &genpath, is_ref, is_mut);
+                                                               return;
+                                                       } else if let Some(_) = self.imports.get(synident) {
+                                                               // crate_types lookup has to have succeeded:
+                                                               panic!("Failed to print inline conversion for {}", synident);
+                                                       } else if let Some(decl_type) = self.declared.get(synident) {
+                                                               decl_lookup(w, decl_type, &self.maybe_resolve_path(synpath).unwrap(), is_ref, is_mut);
+                                                               return;
+                                                       } else { unimplemented!(); }
+                                               }
+                                       }
+                               }
+
+                               let resolved_path = self.resolve_path(&p.path);
+                               if let Some(c_type) = path_lookup(&resolved_path, is_ref, ptr_for_ref) {
+                                       write!(w, "{}", c_type).unwrap();
+                               } else if self.crate_types.opaques.get(&resolved_path).is_some() {
+                                       decl_lookup(w, &DeclType::StructImported, &resolved_path, is_ref, is_mut);
+                               } else if self.crate_types.mirrored_enums.get(&resolved_path).is_some() {
+                                       decl_lookup(w, &DeclType::MirroredEnum, &resolved_path, is_ref, is_mut);
+                               } else if let Some(ident) = single_ident_generic_path_to_ident(&p.path) {
+                                       if let Some(_) = self.imports.get(ident) {
+                                               // crate_types lookup has to have succeeded:
+                                               panic!("Failed to print inline conversion for {}", ident);
+                                       } else if let Some(decl_type) = self.declared.get(ident) {
+                                               decl_lookup(w, decl_type, &self.maybe_resolve_ident(ident).unwrap(), is_ref, is_mut);
+                                       } else { unimplemented!(); }
+                               }
+                       },
+                       syn::Type::Array(a) => {
+                               // We assume all arrays contain only [int_literal; X]s.
+                               // This may result in some outputs not compiling.
+                               if let syn::Expr::Lit(l) = &a.len {
+                                       if let syn::Lit::Int(i) = &l.lit {
+                                               write!(w, "{}", path_lookup(&format!("[u8; {}]", i.base10_digits()), is_ref, ptr_for_ref).unwrap()).unwrap();
+                                       } else { unimplemented!(); }
+                               } else { unimplemented!(); }
+                       },
+                       syn::Type::Slice(s) => {
+                               // We assume all slices contain only literals or references.
+                               // This may result in some outputs not compiling.
+                               if let syn::Type::Path(p) = &*s.elem {
+                                       let resolved = self.resolve_path(&p.path);
+                                       assert!(self.is_primitive(&resolved));
+                                       write!(w, "{}", path_lookup("[u8]", is_ref, ptr_for_ref).unwrap()).unwrap();
+                               } else if let syn::Type::Reference(r) = &*s.elem {
+                                       if let syn::Type::Path(p) = &*r.elem {
+                                               write!(w, "{}", sliceconv(self.c_type_has_inner_from_path(&self.resolve_path(&p.path)))).unwrap();
+                                       } else { unimplemented!(); }
+                               } else { unimplemented!(); }
+                       },
+                       syn::Type::Tuple(t) => {
+                               if t.elems.is_empty() {
+                                       // cbindgen has poor support for (), see, eg https://github.com/eqrion/cbindgen/issues/527
+                                       // so work around it by just pretending its a 0u8
+                                       write!(w, "{}", tupleconv).unwrap();
+                               } else {
+                                       if prefix { write!(w, "local_").unwrap(); }
+                               }
+                       },
+                       _ => unimplemented!(),
+               }
+       }
+
+       fn write_to_c_conversion_inline_prefix_inner<W: std::io::Write>(&self, w: &mut W, t: &syn::Type, generics: Option<&GenericTypes>, is_ref: bool, ptr_for_ref: bool, from_ptr: bool) {
+               self.write_conversion_inline_intern(w, t, generics, is_ref, false, ptr_for_ref, "0u8 /*", true, |_| "local_",
+                               |a, b, c| self.to_c_conversion_inline_prefix_from_path(a, b, c),
+                               |w, decl_type, decl_path, is_ref, _is_mut| {
+                                       match decl_type {
+                                               DeclType::MirroredEnum if is_ref && ptr_for_ref => write!(w, "crate::{}::from_native(&", decl_path).unwrap(),
+                                               DeclType::MirroredEnum if is_ref => write!(w, "&crate::{}::from_native(&", decl_path).unwrap(),
+                                               DeclType::MirroredEnum => write!(w, "crate::{}::native_into(", decl_path).unwrap(),
+                                               DeclType::EnumIgnored|DeclType::StructImported if is_ref && ptr_for_ref && from_ptr =>
+                                                       write!(w, "crate::{} {{ inner: unsafe {{ (", decl_path).unwrap(),
+                                               DeclType::EnumIgnored|DeclType::StructImported if is_ref && ptr_for_ref =>
+                                                       write!(w, "crate::{} {{ inner: unsafe {{ ( (&(", decl_path).unwrap(),
+                                               DeclType::EnumIgnored|DeclType::StructImported if is_ref =>
+                                                       write!(w, "&crate::{} {{ inner: unsafe {{ (", decl_path).unwrap(),
+                                               DeclType::EnumIgnored|DeclType::StructImported if !is_ref && from_ptr =>
+                                                       write!(w, "crate::{} {{ inner: ", decl_path).unwrap(),
+                                               DeclType::EnumIgnored|DeclType::StructImported if !is_ref =>
+                                                       write!(w, "crate::{} {{ inner: Box::into_raw(Box::new(", decl_path).unwrap(),
+                                               DeclType::Trait(_) if is_ref => write!(w, "&").unwrap(),
+                                               _ => panic!("{:?}", decl_path),
+                                       }
+                               });
+       }
+       pub fn write_to_c_conversion_inline_prefix<W: std::io::Write>(&self, w: &mut W, t: &syn::Type, generics: Option<&GenericTypes>, ptr_for_ref: bool) {
+               self.write_to_c_conversion_inline_prefix_inner(w, t, generics, false, ptr_for_ref, false);
+       }
+       fn write_to_c_conversion_inline_suffix_inner<W: std::io::Write>(&self, w: &mut W, t: &syn::Type, generics: Option<&GenericTypes>, is_ref: bool, ptr_for_ref: bool, from_ptr: bool) {
+               self.write_conversion_inline_intern(w, t, generics, is_ref, false, ptr_for_ref, "*/", false, |_| ".into()",
+                               |a, b, c| self.to_c_conversion_inline_suffix_from_path(a, b, c),
+                               |w, decl_type, _full_path, is_ref, _is_mut| match decl_type {
+                                       DeclType::MirroredEnum => write!(w, ")").unwrap(),
+                                       DeclType::EnumIgnored|DeclType::StructImported if is_ref && ptr_for_ref && from_ptr =>
+                                               write!(w, " as *const _) as *mut _ }}, is_owned: false }}").unwrap(),
+                                       DeclType::EnumIgnored|DeclType::StructImported if is_ref && ptr_for_ref =>
+                                               write!(w, ") as *const _) as *mut _) }}, is_owned: false }}").unwrap(),
+                                       DeclType::EnumIgnored|DeclType::StructImported if is_ref =>
+                                               write!(w, " as *const _) as *mut _ }}, is_owned: false }}").unwrap(),
+                                       DeclType::EnumIgnored|DeclType::StructImported if !is_ref && from_ptr =>
+                                               write!(w, ", is_owned: true }}").unwrap(),
+                                       DeclType::EnumIgnored|DeclType::StructImported if !is_ref => write!(w, ")), is_owned: true }}").unwrap(),
+                                       DeclType::Trait(_) if is_ref => {},
+                                       _ => unimplemented!(),
+                               });
+       }
+       pub fn write_to_c_conversion_inline_suffix<W: std::io::Write>(&self, w: &mut W, t: &syn::Type, generics: Option<&GenericTypes>, ptr_for_ref: bool) {
+               self.write_to_c_conversion_inline_suffix_inner(w, t, generics, false, ptr_for_ref, false);
+       }
+
+       fn write_from_c_conversion_prefix_inner<W: std::io::Write>(&self, w: &mut W, t: &syn::Type, generics: Option<&GenericTypes>, is_ref: bool, ptr_for_ref: bool) {
+               self.write_conversion_inline_intern(w, t, generics, is_ref, false, false, "() /*", true, |_| "&local_",
+                               |a, b, _c| self.from_c_conversion_prefix_from_path(a, b),
+                               |w, decl_type, _full_path, is_ref, is_mut| match decl_type {
+                                       DeclType::StructImported if is_ref && ptr_for_ref => write!(w, "unsafe {{ &*(*").unwrap(),
+                                       DeclType::StructImported if is_mut && is_ref => write!(w, "unsafe {{ &mut *").unwrap(),
+                                       DeclType::StructImported if is_ref => write!(w, "unsafe {{ &*").unwrap(),
+                                       DeclType::StructImported if !is_ref => write!(w, "*unsafe {{ Box::from_raw(").unwrap(),
+                                       DeclType::MirroredEnum if is_ref => write!(w, "&").unwrap(),
+                                       DeclType::MirroredEnum => {},
+                                       DeclType::Trait(_) => {},
+                                       _ => unimplemented!(),
+                               });
+       }
+       pub fn write_from_c_conversion_prefix<W: std::io::Write>(&self, w: &mut W, t: &syn::Type, generics: Option<&GenericTypes>) {
+               self.write_from_c_conversion_prefix_inner(w, t, generics, false, false);
+       }
+       fn write_from_c_conversion_suffix_inner<W: std::io::Write>(&self, w: &mut W, t: &syn::Type, generics: Option<&GenericTypes>, is_ref: bool, ptr_for_ref: bool) {
+               self.write_conversion_inline_intern(w, t, generics, is_ref, false, false, "*/", false,
+                               |has_inner| match has_inner {
+                                       false => ".iter().collect::<Vec<_>>()[..]",
+                                       true => "[..]",
+                               },
+                               |a, b, _c| self.from_c_conversion_suffix_from_path(a, b),
+                               |w, decl_type, _full_path, is_ref, _is_mut| match decl_type {
+                                       DeclType::StructImported if is_ref && ptr_for_ref => write!(w, ").inner }}").unwrap(),
+                                       DeclType::StructImported if is_ref => write!(w, ".inner }}").unwrap(),
+                                       DeclType::StructImported if !is_ref => write!(w, ".take_ptr()) }}").unwrap(),
+                                       DeclType::MirroredEnum if is_ref => write!(w, ".to_native()").unwrap(),
+                                       DeclType::MirroredEnum => write!(w, ".into_native()").unwrap(),
+                                       DeclType::Trait(_) => {},
+                                       _ => unimplemented!(),
+                               });
+       }
+       pub fn write_from_c_conversion_suffix<W: std::io::Write>(&self, w: &mut W, t: &syn::Type, generics: Option<&GenericTypes>) {
+               self.write_from_c_conversion_suffix_inner(w, t, generics, false, false);
+       }
+       // Note that compared to the above conversion functions, the following two are generally
+       // significantly undertested:
+       pub fn write_from_c_conversion_to_ref_prefix<W: std::io::Write>(&self, w: &mut W, t: &syn::Type, generics: Option<&GenericTypes>) {
+               self.write_conversion_inline_intern(w, t, generics, false, false, false, "() /*", true, |_| "&local_",
+                               |a, b, _c| {
+                                       if let Some(conv) = self.from_c_conversion_prefix_from_path(a, b) {
+                                               Some(format!("&{}", conv))
+                                       } else { None }
+                               },
+                               |w, decl_type, _full_path, is_ref, _is_mut| match decl_type {
+                                       DeclType::StructImported if !is_ref => write!(w, "unsafe {{ &*").unwrap(),
+                                       _ => unimplemented!(),
+                               });
+       }
+       pub fn write_from_c_conversion_to_ref_suffix<W: std::io::Write>(&self, w: &mut W, t: &syn::Type, generics: Option<&GenericTypes>) {
+               self.write_conversion_inline_intern(w, t, generics, false, false, false, "*/", false,
+                               |has_inner| match has_inner {
+                                       false => ".iter().collect::<Vec<_>>()[..]",
+                                       true => "[..]",
+                               },
+                               |a, b, _c| self.from_c_conversion_suffix_from_path(a, b),
+                               |w, decl_type, _full_path, is_ref, _is_mut| match decl_type {
+                                       DeclType::StructImported if !is_ref => write!(w, ".inner }}").unwrap(),
+                                       _ => unimplemented!(),
+                               });
+       }
+
+       fn write_conversion_new_var_intern<'b, W: std::io::Write,
+               LP: Fn(&str, bool) -> Option<(&str, &str)>,
+               LC: Fn(&str, bool, Option<&syn::Type>, &syn::Ident, &str) ->  Option<(&'b str, Vec<(String, String)>, &'b str)>,
+               VP: Fn(&mut W, &syn::Type, Option<&GenericTypes>, bool, bool, bool),
+               VS: Fn(&mut W, &syn::Type, Option<&GenericTypes>, bool, bool, bool)>
+                       (&self, w: &mut W, ident: &syn::Ident, var: &str, t: &syn::Type, generics: Option<&GenericTypes>,
+                        mut is_ref: bool, mut ptr_for_ref: bool, to_c: bool,
+                        path_lookup: &LP, container_lookup: &LC, var_prefix: &VP, var_suffix: &VS) -> bool {
+
+               macro_rules! convert_container {
+                       ($container_type: expr, $args_len: expr, $args_iter: expr) => { {
+                               // For slices (and Options), we refuse to directly map them as is_ref when they
+                               // aren't opaque types containing an inner pointer. This is due to the fact that,
+                               // in both cases, the actual higher-level type is non-is_ref.
+                               let ty_has_inner = if self.is_transparent_container(&$container_type, is_ref) || $container_type == "Slice" {
+                                       let ty = $args_iter().next().unwrap();
+                                       if $container_type == "Slice" && to_c {
+                                               // "To C ptr_for_ref" means "return the regular object with is_owned
+                                               // set to false", which is totally what we want in a slice if we're about to
+                                               // set ty_has_inner.
+                                               ptr_for_ref = true;
+                                       }
+                                       if let syn::Type::Reference(t) = ty {
+                                               if let syn::Type::Path(p) = &*t.elem {
+                                                       self.c_type_has_inner_from_path(&self.resolve_path(&p.path))
+                                               } else { false }
+                                       } else if let syn::Type::Path(p) = ty {
+                                               self.c_type_has_inner_from_path(&self.resolve_path(&p.path))
+                                       } else { false }
+                               } else { true };
+
+                               // Options get a bunch of special handling, since in general we map Option<>al
+                               // types into the same C type as non-Option-wrapped types. This ends up being
+                               // pretty manual here and most of the below special-cases are for Options.
+                               let mut needs_ref_map = false;
+                               let mut only_contained_type = None;
+                               let mut only_contained_has_inner = false;
+                               let mut contains_slice = false;
+                               if $args_len == 1 && self.is_transparent_container(&$container_type, is_ref) {
+                                       only_contained_has_inner = ty_has_inner;
+                                       let arg = $args_iter().next().unwrap();
+                                       if let syn::Type::Reference(t) = arg {
+                                               only_contained_type = Some(&*t.elem);
+                                               if let syn::Type::Path(_) = &*t.elem {
+                                                       is_ref = true;
+                                               } else if let syn::Type::Slice(_) = &*t.elem {
+                                                       contains_slice = true;
+                                               } else { return false; }
+                                               needs_ref_map = true;
+                                       } else if let syn::Type::Path(_) = arg {
+                                               only_contained_type = Some(&arg);
+                                       } else { unimplemented!(); }
+                               }
+
+                               if let Some((prefix, conversions, suffix)) = container_lookup(&$container_type, is_ref && ty_has_inner, only_contained_type, ident, var) {
+                                       assert_eq!(conversions.len(), $args_len);
+                                       write!(w, "let mut local_{}{} = ", ident, if !to_c && needs_ref_map {"_base"} else { "" }).unwrap();
+                                       if only_contained_has_inner && to_c {
+                                               var_prefix(w, $args_iter().next().unwrap(), generics, is_ref, ptr_for_ref, true);
+                                       }
+                                       write!(w, "{}{}", prefix, var).unwrap();
+
+                                       for ((pfx, var_name), (idx, ty)) in conversions.iter().zip($args_iter().enumerate()) {
+                                               let mut var = std::io::Cursor::new(Vec::new());
+                                               write!(&mut var, "{}", var_name).unwrap();
+                                               let var_access = String::from_utf8(var.into_inner()).unwrap();
+
+                                               let conv_ty = if needs_ref_map { only_contained_type.as_ref().unwrap() } else { ty };
+
+                                               write!(w, "{} {{ ", pfx).unwrap();
+                                               let new_var_name = format!("{}_{}", ident, idx);
+                                               let new_var = self.write_conversion_new_var_intern(w, &syn::Ident::new(&new_var_name, Span::call_site()),
+                                                               &var_access, conv_ty, generics, contains_slice || (is_ref && ty_has_inner), ptr_for_ref, to_c, path_lookup, container_lookup, var_prefix, var_suffix);
+                                               if new_var { write!(w, " ").unwrap(); }
+                                               if (!only_contained_has_inner || !to_c) && !contains_slice {
+                                                       var_prefix(w, conv_ty, generics, is_ref && ty_has_inner, ptr_for_ref, false);
+                                               }
+
+                                               if !is_ref && !needs_ref_map && to_c && only_contained_has_inner {
+                                                       write!(w, "Box::into_raw(Box::new(").unwrap();
+                                               }
+                                               write!(w, "{}{}", if contains_slice { "local_" } else { "" }, if new_var { new_var_name } else { var_access }).unwrap();
+                                               if (!only_contained_has_inner || !to_c) && !contains_slice {
+                                                       var_suffix(w, conv_ty, generics, is_ref && ty_has_inner, ptr_for_ref, false);
+                                               }
+                                               if !is_ref && !needs_ref_map && to_c && only_contained_has_inner {
+                                                       write!(w, "))").unwrap();
+                                               }
+                                               write!(w, " }}").unwrap();
+                                       }
+                                       write!(w, "{}", suffix).unwrap();
+                                       if only_contained_has_inner && to_c {
+                                               var_suffix(w, $args_iter().next().unwrap(), generics, is_ref, ptr_for_ref, true);
+                                       }
+                                       write!(w, ";").unwrap();
+                                       if !to_c && needs_ref_map {
+                                               write!(w, " let mut local_{} = local_{}_base.as_ref()", ident, ident).unwrap();
+                                               if contains_slice {
+                                                       write!(w, ".map(|a| &a[..])").unwrap();
+                                               }
+                                               write!(w, ";").unwrap();
+                                       }
+                                       return true;
+                               }
+                       } }
+               }
+
+               match t {
+                       syn::Type::Reference(r) => {
+                               if let syn::Type::Slice(_) = &*r.elem {
+                                       self.write_conversion_new_var_intern(w, ident, var, &*r.elem, generics, is_ref, ptr_for_ref, to_c, path_lookup, container_lookup, var_prefix, var_suffix)
+                               } else {
+                                       self.write_conversion_new_var_intern(w, ident, var, &*r.elem, generics, true, ptr_for_ref, to_c, path_lookup, container_lookup, var_prefix, var_suffix)
+                               }
+                       },
+                       syn::Type::Path(p) => {
+                               if p.qself.is_some() || p.path.leading_colon.is_some() {
+                                       unimplemented!();
+                               }
+                               if let Some(gen_types) = generics {
+                                       if let Some(resolved) = gen_types.maybe_resolve_path(&p.path) {
+                                               assert!(!self.is_known_container(&resolved.0, is_ref) && !self.is_transparent_container(&resolved.0, is_ref));
+                                               if let Some((prefix, suffix)) = path_lookup(&resolved.0, is_ref) {
+                                                       write!(w, "let mut local_{} = {}{}{};", ident, prefix, var, suffix).unwrap();
+                                                       return true;
+                                               } else { return false; }
+                                       }
+                               }
+                               let resolved_path = self.resolve_path(&p.path);
+                               if self.is_known_container(&resolved_path, is_ref) || self.is_transparent_container(&resolved_path, is_ref) {
+                                       if let syn::PathArguments::AngleBracketed(args) = &p.path.segments.iter().next().unwrap().arguments {
+                                               convert_container!(resolved_path, args.args.len(), || args.args.iter().map(|arg| {
+                                                       if let syn::GenericArgument::Type(ty) = arg {
+                                                               ty
+                                                       } else { unimplemented!(); }
+                                               }));
+                                       } else { unimplemented!(); }
+                               }
+                               if self.is_primitive(&resolved_path) {
+                                       false
+                               } else if let Some(ty_ident) = single_ident_generic_path_to_ident(&p.path) {
+                                       if let Some((prefix, suffix)) = path_lookup(&resolved_path, is_ref) {
+                                               write!(w, "let mut local_{} = {}{}{};", ident, prefix, var, suffix).unwrap();
+                                               true
+                                       } else if self.declared.get(ty_ident).is_some() {
+                                               false
+                                       } else { false }
+                               } else { false }
+                       },
+                       syn::Type::Array(_) => {
+                               // We assume all arrays contain only primitive types.
+                               // This may result in some outputs not compiling.
+                               false
+                       },
+                       syn::Type::Slice(s) => {
+                               if let syn::Type::Path(p) = &*s.elem {
+                                       let resolved = self.resolve_path(&p.path);
+                                       assert!(self.is_primitive(&resolved));
+                                       let slice_path = format!("[{}]", resolved);
+                                       if let Some((prefix, suffix)) = path_lookup(&slice_path, true) {
+                                               write!(w, "let mut local_{} = {}{}{};", ident, prefix, var, suffix).unwrap();
+                                               true
+                                       } else { false }
+                               } else if let syn::Type::Reference(ty) = &*s.elem {
+                                       let tyref = [&*ty.elem];
+                                       is_ref = true;
+                                       convert_container!("Slice", 1, || tyref.iter());
+                                       unimplemented!("convert_container should return true as container_lookup should succeed for slices");
+                               } else { unimplemented!() }
+                       },
+                       syn::Type::Tuple(t) => {
+                               if !t.elems.is_empty() {
+                                       // We don't (yet) support tuple elements which cannot be converted inline
+                                       write!(w, "let (").unwrap();
+                                       for idx in 0..t.elems.len() {
+                                               if idx != 0 { write!(w, ", ").unwrap(); }
+                                               write!(w, "{} orig_{}_{}", if is_ref { "ref" } else { "mut" }, ident, idx).unwrap();
+                                       }
+                                       write!(w, ") = {}{}; ", var, if !to_c { ".to_rust()" } else { "" }).unwrap();
+                                       // Like other template types, tuples are always mapped as their non-ref
+                                       // versions for types which have different ref mappings. Thus, we convert to
+                                       // non-ref versions and handle opaque types with inner pointers manually.
+                                       for (idx, elem) in t.elems.iter().enumerate() {
+                                               if let syn::Type::Path(p) = elem {
+                                                       let v_name = format!("orig_{}_{}", ident, idx);
+                                                       let tuple_elem_ident = syn::Ident::new(&v_name, Span::call_site());
+                                                       if self.write_conversion_new_var_intern(w, &tuple_elem_ident, &v_name, elem, generics,
+                                                                       false, ptr_for_ref, to_c,
+                                                                       path_lookup, container_lookup, var_prefix, var_suffix) {
+                                                               write!(w, " ").unwrap();
+                                                               // Opaque types with inner pointers shouldn't ever create new stack
+                                                               // variables, so we don't handle it and just assert that it doesn't
+                                                               // here.
+                                                               assert!(!self.c_type_has_inner_from_path(&self.resolve_path(&p.path)));
+                                                       }
+                                               }
+                                       }
+                                       write!(w, "let mut local_{} = (", ident).unwrap();
+                                       for (idx, elem) in t.elems.iter().enumerate() {
+                                               let ty_has_inner = {
+                                                               if to_c {
+                                                                       // "To C ptr_for_ref" means "return the regular object with
+                                                                       // is_owned set to false", which is totally what we want
+                                                                       // if we're about to set ty_has_inner.
+                                                                       ptr_for_ref = true;
+                                                               }
+                                                               if let syn::Type::Reference(t) = elem {
+                                                                       if let syn::Type::Path(p) = &*t.elem {
+                                                                               self.c_type_has_inner_from_path(&self.resolve_path(&p.path))
+                                                                       } else { false }
+                                                               } else if let syn::Type::Path(p) = elem {
+                                                                       self.c_type_has_inner_from_path(&self.resolve_path(&p.path))
+                                                               } else { false }
+                                                       };
+                                               if idx != 0 { write!(w, ", ").unwrap(); }
+                                               var_prefix(w, elem, generics, is_ref && ty_has_inner, ptr_for_ref, false);
+                                               if is_ref && ty_has_inner {
+                                                       // For ty_has_inner, the regular var_prefix mapping will take a
+                                                       // reference, so deref once here to make sure we keep the original ref.
+                                                       write!(w, "*").unwrap();
+                                               }
+                                               write!(w, "orig_{}_{}", ident, idx).unwrap();
+                                               if is_ref && !ty_has_inner {
+                                                       // If we don't have an inner variable's reference to maintain, just
+                                                       // hope the type is Clonable and use that.
+                                                       write!(w, ".clone()").unwrap();
+                                               }
+                                               var_suffix(w, elem, generics, is_ref && ty_has_inner, ptr_for_ref, false);
+                                       }
+                                       write!(w, "){};", if to_c { ".into()" } else { "" }).unwrap();
+                                       true
+                               } else { false }
+                       },
+                       _ => unimplemented!(),
+               }
+       }
+
+       pub fn write_to_c_conversion_new_var_inner<W: std::io::Write>(&self, w: &mut W, ident: &syn::Ident, var_access: &str, t: &syn::Type, generics: Option<&GenericTypes>, ptr_for_ref: bool) -> bool {
+               self.write_conversion_new_var_intern(w, ident, var_access, t, generics, false, ptr_for_ref, true,
+                       &|a, b| self.to_c_conversion_new_var_from_path(a, b),
+                       &|a, b, c, d, e| self.to_c_conversion_container_new_var(a, b, c, d, e),
+                       // We force ptr_for_ref here since we can't generate a ref on one line and use it later
+                       &|a, b, c, d, e, f| self.write_to_c_conversion_inline_prefix_inner(a, b, c, d, e, f),
+                       &|a, b, c, d, e, f| self.write_to_c_conversion_inline_suffix_inner(a, b, c, d, e, f))
+       }
+       pub fn write_to_c_conversion_new_var<W: std::io::Write>(&self, w: &mut W, ident: &syn::Ident, t: &syn::Type, generics: Option<&GenericTypes>, ptr_for_ref: bool) -> bool {
+               self.write_to_c_conversion_new_var_inner(w, ident, &format!("{}", ident), t, generics, ptr_for_ref)
+       }
+       pub fn write_from_c_conversion_new_var<W: std::io::Write>(&self, w: &mut W, ident: &syn::Ident, t: &syn::Type, generics: Option<&GenericTypes>) -> bool {
+               self.write_conversion_new_var_intern(w, ident, &format!("{}", ident), t, generics, false, false, false,
+                       &|a, b| self.from_c_conversion_new_var_from_path(a, b),
+                       &|a, b, c, d, e| self.from_c_conversion_container_new_var(a, b, c, d, e),
+                       // We force ptr_for_ref here since we can't generate a ref on one line and use it later
+                       &|a, b, c, d, e, _f| self.write_from_c_conversion_prefix_inner(a, b, c, d, e),
+                       &|a, b, c, d, e, _f| self.write_from_c_conversion_suffix_inner(a, b, c, d, e))
+       }
+
+       // ******************************************************
+       // *** C Container Type Equivalent and alias Printing ***
+       // ******************************************************
+
+       fn write_template_constructor<W: std::io::Write>(&mut self, w: &mut W, container_type: &str, mangled_container: &str, args: &Vec<&syn::Type>, is_ref: bool) {
+               if container_type == "Result" {
+                       assert_eq!(args.len(), 2);
+                       macro_rules! write_fn {
+                               ($call: expr) => { {
+                                       writeln!(w, "#[no_mangle]\npub extern \"C\" fn {}_{}() -> {} {{", mangled_container, $call, mangled_container).unwrap();
+                                       writeln!(w, "\t{}::CResultTempl::{}(0)\n}}\n", Self::container_templ_path(), $call).unwrap();
+                               } }
+                       }
+                       macro_rules! write_alias {
+                               ($call: expr, $item: expr) => { {
+                                       write!(w, "#[no_mangle]\npub static {}_{}: extern \"C\" fn (", mangled_container, $call).unwrap();
+                                       if let syn::Type::Path(syn::TypePath { path, .. }) = $item {
+                                               let resolved = self.resolve_path(path);
+                                               if self.is_known_container(&resolved, is_ref) || self.is_transparent_container(&resolved, is_ref) {
+                                                       self.write_c_mangled_container_path_intern(w, Self::path_to_generic_args(path),
+                                                               &format!("{}", single_ident_generic_path_to_ident(path).unwrap()), is_ref, false, false, false);
+                                               } else {
+                                                       self.write_template_generics(w, &mut [$item].iter().map(|t| *t), is_ref, true);
+                                               }
+                                       } else if let syn::Type::Tuple(syn::TypeTuple { elems, .. }) = $item {
+                                               self.write_c_mangled_container_path_intern(w, elems.iter().collect(),
+                                                       &format!("{}Tuple", elems.len()), is_ref, false, false, false);
+                                       } else { unimplemented!(); }
+                                       write!(w, ") -> {} =\n\t{}::CResultTempl::<", mangled_container, Self::container_templ_path()).unwrap();
+                                       self.write_template_generics(w, &mut args.iter().map(|t| *t), is_ref, true);
+                                       writeln!(w, ">::{};\n", $call).unwrap();
+                               } }
+                       }
+                       match args[0] {
+                               syn::Type::Tuple(t) if t.elems.is_empty() => write_fn!("ok"),
+                               _ => write_alias!("ok", args[0]),
+                       }
+                       match args[1] {
+                               syn::Type::Tuple(t) if t.elems.is_empty() => write_fn!("err"),
+                               _ => write_alias!("err", args[1]),
+                       }
+               } else if container_type.ends_with("Tuple") {
+                       write!(w, "#[no_mangle]\npub extern \"C\" fn {}_new(", mangled_container).unwrap();
+                       for (idx, gen) in args.iter().enumerate() {
+                               write!(w, "{}{}: ", if idx != 0 { ", " } else { "" }, ('a' as u8 + idx as u8) as char).unwrap();
+                               self.write_c_type_intern(None, w, gen, false, false, false);
+                       }
+                       writeln!(w, ") -> {} {{", mangled_container).unwrap();
+                       writeln!(w, "\t{} {{", mangled_container).unwrap();
+                       for idx in 0..args.len() {
+                               writeln!(w, "\t\t{}: Box::into_raw(Box::new({})),", ('a' as u8 + idx as u8) as char, ('a' as u8 + idx as u8) as char).unwrap();
+                       }
+                       writeln!(w, "\t}}\n}}\n").unwrap();
+               } else {
+                       writeln!(w, "").unwrap();
+               }
+       }
+
+       fn write_template_generics<'b, W: std::io::Write>(&self, w: &mut W, args: &mut dyn Iterator<Item=&'b syn::Type>, is_ref: bool, in_crate: bool) {
+               for (idx, t) in args.enumerate() {
+                       if idx != 0 {
+                               write!(w, ", ").unwrap();
+                       }
+                       if let syn::Type::Tuple(tup) = t {
+                               if tup.elems.is_empty() {
+                                       write!(w, "u8").unwrap();
+                               } else {
+                                       write!(w, "{}::C{}TupleTempl<", Self::container_templ_path(), tup.elems.len()).unwrap();
+                                       self.write_template_generics(w, &mut tup.elems.iter(), is_ref, in_crate);
+                                       write!(w, ">").unwrap();
+                               }
+                       } else if let syn::Type::Path(p_arg) = t {
+                               let resolved_generic = self.resolve_path(&p_arg.path);
+                               if self.is_primitive(&resolved_generic) {
+                                       write!(w, "{}", resolved_generic).unwrap();
+                               } else if let Some(c_type) = self.c_type_from_path(&resolved_generic, is_ref, false) {
+                                       if self.is_known_container(&resolved_generic, is_ref) {
+                                                       write!(w, "{}::C{}Templ<", Self::container_templ_path(), single_ident_generic_path_to_ident(&p_arg.path).unwrap()).unwrap();
+                                               assert_eq!(p_arg.path.segments.len(), 1);
+                                               if let syn::PathArguments::AngleBracketed(args) = &p_arg.path.segments.iter().next().unwrap().arguments {
+                                                       self.write_template_generics(w, &mut args.args.iter().map(|gen|
+                                                               if let syn::GenericArgument::Type(t) = gen { t } else { unimplemented!() }),
+                                                               is_ref, in_crate);
+                                               } else { unimplemented!(); }
+                                               write!(w, ">").unwrap();
+                                       } else if resolved_generic == "Option" {
+                                               if let syn::PathArguments::AngleBracketed(args) = &p_arg.path.segments.iter().next().unwrap().arguments {
+                                                       self.write_template_generics(w, &mut args.args.iter().map(|gen|
+                                                               if let syn::GenericArgument::Type(t) = gen { t } else { unimplemented!() }),
+                                                               is_ref, in_crate);
+                                               } else { unimplemented!(); }
+                                       } else if in_crate {
+                                               write!(w, "{}", c_type).unwrap();
+                                       } else {
+                                               self.write_rust_type(w, &t);
+                                       }
+                               } else {
+                                       // If we just write out resolved_generic, it may mostly work, however for
+                                       // original types which are generic, we need the template args. We could
+                                       // figure them out and write them out, too, but its much easier to just
+                                       // reference the native{} type alias which exists at least for opaque types.
+                                       if in_crate {
+                                               write!(w, "crate::{}", resolved_generic).unwrap();
+                                       } else {
+                                               let path_name: Vec<&str> = resolved_generic.rsplitn(2, "::").collect();
+                                               if path_name.len() > 1 {
+                                                       write!(w, "crate::{}::native{}", path_name[1], path_name[0]).unwrap();
+                                               } else {
+                                                       write!(w, "crate::native{}", path_name[0]).unwrap();
+                                               }
+                                       }
+                               }
+                       } else if let syn::Type::Reference(r_arg) = t {
+                               if let syn::Type::Path(p_arg) = &*r_arg.elem {
+                                       let resolved = self.resolve_path(&p_arg.path);
+                                       if single_ident_generic_path_to_ident(&p_arg.path).is_some() {
+                                               if self.crate_types.opaques.get(&resolved).is_some() {
+                                                       write!(w, "crate::{}", resolved).unwrap();
+                                               } else { unimplemented!(); }
+                                       } else { unimplemented!(); }
+                               } else { unimplemented!(); }
+                       } else if let syn::Type::Array(a_arg) = t {
+                               if let syn::Type::Path(p_arg) = &*a_arg.elem {
+                                       let resolved = self.resolve_path(&p_arg.path);
+                                       assert!(self.is_primitive(&resolved));
+                                       if let syn::Expr::Lit(syn::ExprLit { lit: syn::Lit::Int(len), .. }) = &a_arg.len {
+                                               write!(w, "{}",
+                                                       self.c_type_from_path(&format!("[{}; {}]", resolved, len.base10_digits()), is_ref, false).unwrap()).unwrap();
+                                       }
+                               }
+                       }
+               }
+       }
+       fn check_create_container(&mut self, mangled_container: String, container_type: &str, args: Vec<&syn::Type>, is_ref: bool) {
+               if !self.crate_types.templates_defined.get(&mangled_container).is_some() {
+                       self.crate_types.templates_defined.insert(mangled_container.clone(), true);
+                       let mut created_container: Vec<u8> = Vec::new();
+
+                       write!(&mut created_container, "#[no_mangle]\npub type {} = ", mangled_container).unwrap();
+                       write!(&mut created_container, "{}::C{}Templ<", Self::container_templ_path(), container_type).unwrap();
+                       self.write_template_generics(&mut created_container, &mut args.iter().map(|t| *t), is_ref, true);
+                       writeln!(&mut created_container, ">;").unwrap();
+
+                       write!(&mut created_container, "#[no_mangle]\npub static {}_free: extern \"C\" fn({}) = ", mangled_container, mangled_container).unwrap();
+                       write!(&mut created_container, "{}::C{}Templ_free::<", Self::container_templ_path(), container_type).unwrap();
+                       self.write_template_generics(&mut created_container, &mut args.iter().map(|t| *t), is_ref, true);
+                       writeln!(&mut created_container, ">;").unwrap();
+
+                       self.write_template_constructor(&mut created_container, container_type, &mangled_container, &args, is_ref);
+
+                       self.crate_types.template_file.write(&created_container).unwrap();
+               }
+       }
+       fn path_to_generic_args(path: &syn::Path) -> Vec<&syn::Type> {
+               if let syn::PathArguments::AngleBracketed(args) = &path.segments.iter().next().unwrap().arguments {
+                       args.args.iter().map(|gen| if let syn::GenericArgument::Type(t) = gen { t } else { unimplemented!() }).collect()
+               } else { unimplemented!(); }
+       }
+       fn write_c_mangled_container_path_intern<W: std::io::Write>
+                       (&mut self, w: &mut W, args: Vec<&syn::Type>, ident: &str, is_ref: bool, is_mut: bool, ptr_for_ref: bool, in_type: bool) -> bool {
+               let mut mangled_type: Vec<u8> = Vec::new();
+               if !self.is_transparent_container(ident, is_ref) {
+                       write!(w, "C{}_", ident).unwrap();
+                       write!(mangled_type, "C{}_", ident).unwrap();
+               } else { assert_eq!(args.len(), 1); }
+               for arg in args.iter() {
+                       macro_rules! write_path {
+                               ($p_arg: expr, $extra_write: expr) => {
+                                       let subtype = self.resolve_path(&$p_arg.path);
+                                       if self.is_transparent_container(ident, is_ref) {
+                                               // We dont (yet) support primitives or containers inside transparent
+                                               // containers, so check for that first:
+                                               if self.is_primitive(&subtype) { return false; }
+                                               if self.is_known_container(&subtype, is_ref) { return false; }
+                                               if !in_type {
+                                                       if self.c_type_has_inner_from_path(&subtype) {
+                                                               if !self.write_c_path_intern(w, &$p_arg.path, is_ref, is_mut, ptr_for_ref) { return false; }
+                                                       } else {
+                                                               if !self.write_c_path_intern(w, &$p_arg.path, true, is_mut, true) { return false; }
+                                                       }
+                                               } else {
+                                                       if $p_arg.path.segments.len() == 1 {
+                                                               write!(w, "{}", $p_arg.path.segments.iter().next().unwrap().ident).unwrap();
+                                                       } else {
+                                                               return false;
+                                                       }
+                                               }
+                                       } else if self.is_known_container(&subtype, is_ref) || self.is_transparent_container(&subtype, is_ref) {
+                                               if !self.write_c_mangled_container_path_intern(w, Self::path_to_generic_args(&$p_arg.path),
+                                                               &subtype, is_ref, is_mut, ptr_for_ref, true) {
+                                                       return false;
+                                               }
+                                               self.write_c_mangled_container_path_intern(&mut mangled_type, Self::path_to_generic_args(&$p_arg.path),
+                                                       &subtype, is_ref, is_mut, ptr_for_ref, true);
+                                               if let Some(w2) = $extra_write as Option<&mut Vec<u8>> {
+                                                       self.write_c_mangled_container_path_intern(w2, Self::path_to_generic_args(&$p_arg.path),
+                                                               &subtype, is_ref, is_mut, ptr_for_ref, true);
+                                               }
+                                       } else if let Some(id) = single_ident_generic_path_to_ident(&$p_arg.path) {
+                                               write!(w, "{}", id).unwrap();
+                                               write!(mangled_type, "{}", id).unwrap();
+                                               if let Some(w2) = $extra_write as Option<&mut Vec<u8>> {
+                                                       write!(w2, "{}", id).unwrap();
+                                               }
+                                       } else { return false; }
+                               }
+                       }
+                       if let syn::Type::Tuple(tuple) = arg {
+                               if tuple.elems.len() == 0 {
+                                       write!(w, "None").unwrap();
+                                       write!(mangled_type, "None").unwrap();
+                               } else {
+                                       let mut mangled_tuple_type: Vec<u8> = Vec::new();
+
+                                       // Figure out what the mangled type should look like. To disambiguate
+                                       // ((A, B), C) and (A, B, C) we prefix the generic args with a _ and suffix
+                                       // them with a Z. Ideally we wouldn't use Z, but not many special chars are
+                                       // available for use in type names.
+                                       write!(w, "C{}Tuple_", tuple.elems.len()).unwrap();
+                                       write!(mangled_type, "C{}Tuple_", tuple.elems.len()).unwrap();
+                                       write!(mangled_tuple_type, "C{}Tuple_", tuple.elems.len()).unwrap();
+                                       for elem in tuple.elems.iter() {
+                                               if let syn::Type::Path(p) = elem {
+                                                       write_path!(p, Some(&mut mangled_tuple_type));
+                                               } else { return false; }
+                                       }
+                                       write!(w, "Z").unwrap();
+                                       write!(mangled_type, "Z").unwrap();
+                                       write!(mangled_tuple_type, "Z").unwrap();
+                                       self.check_create_container(String::from_utf8(mangled_tuple_type).unwrap(),
+                                               &format!("{}Tuple", tuple.elems.len()), tuple.elems.iter().collect(), is_ref);
+                               }
+                       } else if let syn::Type::Path(p_arg) = arg {
+                               write_path!(p_arg, None);
+                       } else if let syn::Type::Reference(refty) = arg {
+                               if args.len() != 1 { return false; }
+                               if let syn::Type::Path(p_arg) = &*refty.elem {
+                                       write_path!(p_arg, None);
+                               } else if let syn::Type::Slice(_) = &*refty.elem {
+                                       // write_c_type will actually do exactly what we want here, we just need to
+                                       // make it a pointer so that its an option. Note that we cannot always convert
+                                       // the Vec-as-slice (ie non-ref types) containers, so sometimes need to be able
+                                       // to edit it, hence we use *mut here instead of *const.
+                                       write!(w, "*mut ").unwrap();
+                                       self.write_c_type(w, arg, None, true);
+                               } else { return false; }
+                       } else if let syn::Type::Array(a) = arg {
+                               if let syn::Type::Path(p_arg) = &*a.elem {
+                                       let resolved = self.resolve_path(&p_arg.path);
+                                       if !self.is_primitive(&resolved) { return false; }
+                                       if let syn::Expr::Lit(syn::ExprLit { lit: syn::Lit::Int(len), .. }) = &a.len {
+                                               if self.c_type_from_path(&format!("[{}; {}]", resolved, len.base10_digits()), is_ref, ptr_for_ref).is_none() { return false; }
+                                               write!(w, "_{}{}", resolved, len.base10_digits()).unwrap();
+                                               write!(mangled_type, "_{}{}", resolved, len.base10_digits()).unwrap();
+                                       } else { return false; }
+                               } else { return false; }
+                       } else { return false; }
+               }
+               if self.is_transparent_container(ident, is_ref) { return true; }
+               // Push the "end of type" Z
+               write!(w, "Z").unwrap();
+               write!(mangled_type, "Z").unwrap();
+
+               // Make sure the type is actually defined:
+               self.check_create_container(String::from_utf8(mangled_type).unwrap(), ident, args, is_ref);
+               true
+       }
+       fn write_c_mangled_container_path<W: std::io::Write>(&mut self, w: &mut W, args: Vec<&syn::Type>, ident: &str, is_ref: bool, is_mut: bool, ptr_for_ref: bool) -> bool {
+               if !self.is_transparent_container(ident, is_ref) {
+                       write!(w, "{}::", Self::generated_container_path()).unwrap();
+               }
+               self.write_c_mangled_container_path_intern(w, args, ident, is_ref, is_mut, ptr_for_ref, false)
+       }
+
+       // **********************************
+       // *** C Type Equivalent Printing ***
+       // **********************************
+
+       fn write_c_path_intern<W: std::io::Write>(&self, w: &mut W, path: &syn::Path, is_ref: bool, is_mut: bool, ptr_for_ref: bool) -> bool {
+//eprintln!("pcpi ({} {} {}): {:?}", is_ref, is_mut, ptr_for_ref, path);
+               let full_path = match self.maybe_resolve_path(&path) {
+                       Some(path) => path, None => return false };
+               if let Some(c_type) = self.c_type_from_path(&full_path, is_ref, ptr_for_ref) {
+                       write!(w, "{}", c_type).unwrap();
+                       true
+               } else if self.crate_types.traits.get(&full_path).is_some() {
+                       if is_ref && ptr_for_ref {
+                               write!(w, "*{} crate::{}", if is_mut { "mut" } else { "const" }, full_path).unwrap();
+                       } else if is_ref {
+                               write!(w, "&{}crate::{}", if is_mut { "mut " } else { "" }, full_path).unwrap();
+                       } else {
+                               write!(w, "crate::{}", full_path).unwrap();
+                       }
+                       true
+               } else if self.crate_types.opaques.get(&full_path).is_some() || self.crate_types.mirrored_enums.get(&full_path).is_some() {
+                       if is_ref && ptr_for_ref {
+                               // ptr_for_ref implies we're returning the object, which we can't really do for
+                               // opaque or mirrored types without box'ing them, which is quite a waste, so return
+                               // the actual object itself (for opaque types we'll set the pointer to the actual
+                               // type and note that its a reference).
+                               write!(w, "crate::{}", full_path).unwrap();
+                       } else if is_ref {
+                               write!(w, "&{}crate::{}", if is_mut { "mut " } else { "" }, full_path).unwrap();
+                       } else {
+                               write!(w, "crate::{}", full_path).unwrap();
+                       }
+                       true
+               } else {
+                       false
+               }
+       }
+       fn write_c_type_intern<W: std::io::Write>(&mut self, generics: Option<&GenericTypes>, w: &mut W, t: &syn::Type, is_ref: bool, is_mut: bool, ptr_for_ref: bool) -> bool {
+               match t {
+                       syn::Type::Path(p) => {
+                               if p.qself.is_some() || p.path.leading_colon.is_some() {
+                                       return false;
+                               }
+                               if let Some(gen_types) = generics {
+                                       if let Some(resolved) = gen_types.maybe_resolve_path(&p.path) {
+                                               if self.is_known_container(&resolved.0, is_ref) { return false; }
+                                               if self.is_transparent_container(&resolved.0, is_ref) { return false; }
+                                               return self.write_c_path_intern(w, &resolved.1, is_ref, is_mut, ptr_for_ref);
+                                       }
+                               }
+                               if let Some(full_path) = self.maybe_resolve_path(&p.path) {
+                                       if self.is_known_container(&full_path, is_ref) || self.is_transparent_container(&full_path, is_ref) {
+                                               return self.write_c_mangled_container_path(w, Self::path_to_generic_args(&p.path), &full_path, is_ref, is_mut, ptr_for_ref);
+                                       }
+                               }
+                               if p.path.leading_colon.is_some() { return false; }
+                               self.write_c_path_intern(w, &p.path, is_ref, is_mut, ptr_for_ref)
+                       },
+                       syn::Type::Reference(r) => {
+                               if let Some(lft) = &r.lifetime {
+                                       if format!("{}", lft.ident) != "static" { return false; }
+                               }
+                               self.write_c_type_intern(generics, w, &*r.elem, true, r.mutability.is_some(), ptr_for_ref)
+                       },
+                       syn::Type::Array(a) => {
+                               if is_ref && is_mut {
+                                       write!(w, "*mut [").unwrap();
+                                       if !self.write_c_type_intern(generics, w, &a.elem, false, false, ptr_for_ref) { return false; }
+                               } else if is_ref {
+                                       write!(w, "*const [").unwrap();
+                                       if !self.write_c_type_intern(generics, w, &a.elem, false, false, ptr_for_ref) { return false; }
+                               } else {
+                                       let mut typecheck = Vec::new();
+                                       if !self.write_c_type_intern(generics, &mut typecheck, &a.elem, false, false, ptr_for_ref) { return false; }
+                                       if typecheck[..] != ['u' as u8, '8' as u8] { return false; }
+                               }
+                               if let syn::Expr::Lit(l) = &a.len {
+                                       if let syn::Lit::Int(i) = &l.lit {
+                                               if !is_ref {
+                                                       if let Some(ty) = self.c_type_from_path(&format!("[u8; {}]", i.base10_digits()), false, ptr_for_ref) {
+                                                               write!(w, "{}", ty).unwrap();
+                                                               true
+                                                       } else { false }
+                                               } else {
+                                                       write!(w, "; {}]", i).unwrap();
+                                                       true
+                                               }
+                                       } else { false }
+                               } else { false }
+                       }
+                       syn::Type::Slice(s) => {
+                               if !is_ref || is_mut { return false; }
+                               if let syn::Type::Path(p) = &*s.elem {
+                                       let resolved = self.resolve_path(&p.path);
+                                       if self.is_primitive(&resolved) {
+                                               write!(w, "{}::{}slice", Self::container_templ_path(), resolved).unwrap();
+                                               true
+                                       } else { false }
+                               } else if let syn::Type::Reference(r) = &*s.elem {
+                                       if let syn::Type::Path(p) = &*r.elem {
+                                               // Slices with "real types" inside are mapped as the equivalent non-ref Vec
+                                               let resolved = self.resolve_path(&p.path);
+                                               let mangled_container = if let Some(ident) = self.crate_types.opaques.get(&resolved) {
+                                                       format!("CVec_{}Z", ident)
+                                               } else if let Some(en) = self.crate_types.mirrored_enums.get(&resolved) {
+                                                       format!("CVec_{}Z", en.ident)
+                                               } else if let Some(id) = p.path.get_ident() {
+                                                       format!("CVec_{}Z", id)
+                                               } else { return false; };
+                                               write!(w, "{}::{}", Self::generated_container_path(), mangled_container).unwrap();
+                                               self.check_create_container(mangled_container, "Vec", vec![&*r.elem], false);
+                                               true
+                                       } else { false }
+                               } else { false }
+                       },
+                       syn::Type::Tuple(t) => {
+                               if t.elems.len() == 0 {
+                                       true
+                               } else {
+                                       self.write_c_mangled_container_path(w, t.elems.iter().collect(),
+                                               &format!("{}Tuple", t.elems.len()), is_ref, is_mut, ptr_for_ref)
+                               }
+                       },
+                       _ => false,
+               }
+       }
+       pub fn write_c_type<W: std::io::Write>(&mut self, w: &mut W, t: &syn::Type, generics: Option<&GenericTypes>, ptr_for_ref: bool) {
+               assert!(self.write_c_type_intern(generics, w, t, false, false, ptr_for_ref));
+       }
+       pub fn understood_c_path(&mut self, p: &syn::Path) -> bool {
+               if p.leading_colon.is_some() { return false; }
+               self.write_c_path_intern(&mut std::io::sink(), p, false, false, false)
+       }
+       pub fn understood_c_type(&mut self, t: &syn::Type, generics: Option<&GenericTypes>) -> bool {
+               self.write_c_type_intern(generics, &mut std::io::sink(), t, false, false, false)
+       }
+}