Merge pull request #46 from TheBlueMatt/main
[ldk-c-bindings] / c-bindings-gen / src / types.rs
index 13c3b0ed0c2b7b3b00b4af8e58728a117614d6cb..7f53019785a971af285dc3a4dd1127e9d8e08992 100644 (file)
@@ -173,13 +173,13 @@ pub fn is_enum_opaque(e: &syn::ItemEnum) -> bool {
 /// concrete C container struct, etc).
 #[must_use]
 pub struct GenericTypes<'a, 'b> {
-       self_ty: Option<(String, &'a syn::Path)>,
+       self_ty: Option<String>,
        parent: Option<&'b GenericTypes<'b, 'b>>,
-       typed_generics: HashMap<&'a syn::Ident, (String, Option<&'a syn::Path>)>,
+       typed_generics: HashMap<&'a syn::Ident, String>,
        default_generics: HashMap<&'a syn::Ident, (syn::Type, syn::Type)>,
 }
 impl<'a, 'p: 'a> GenericTypes<'a, 'p> {
-       pub fn new(self_ty: Option<(String, &'a syn::Path)>) -> Self {
+       pub fn new(self_ty: Option<String>) -> Self {
                Self { self_ty, parent: None, typed_generics: HashMap::new(), default_generics: HashMap::new(), }
        }
 
@@ -192,6 +192,7 @@ impl<'a, 'p: 'a> GenericTypes<'a, 'p> {
 
        /// 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 {
+               let mut new_typed_generics = HashMap::new();
                // First learn simple generics...
                for generic in generics.params.iter() {
                        match generic {
@@ -205,14 +206,13 @@ impl<'a, 'p: 'a> GenericTypes<'a, 'p> {
                                                        if path_matches_nongeneric(&trait_bound.path, &["core", "clone", "Clone"]) { continue; }
 
                                                        assert_simple_bound(&trait_bound);
-                                                       if let Some(mut path) = types.maybe_resolve_path(&trait_bound.path, None) {
+                                                       if let Some(path) = types.maybe_resolve_path(&trait_bound.path, None) {
                                                                if types.skip_path(&path) { continue; }
                                                                if path == "Sized" { continue; }
                                                                if non_lifetimes_processed { return false; }
                                                                non_lifetimes_processed = true;
-                                                               let new_ident = if path != "std::ops::Deref" && path != "core::ops::Deref" {
-                                                                       path = "crate::".to_string() + &path;
-                                                                       Some(&trait_bound.path)
+                                                               if path != "std::ops::Deref" && path != "core::ops::Deref" {
+                                                                       new_typed_generics.insert(&type_param.ident, Some(path));
                                                                } else if trait_bound.path.segments.len() == 1 {
                                                                        // If we're templated on Deref<Target = ConcreteThing>, store
                                                                        // the reference type in `default_generics` which handles full
@@ -231,11 +231,11 @@ impl<'a, 'p: 'a> GenericTypes<'a, 'p> {
                                                                                                _ => unimplemented!(),
                                                                                        }
                                                                                }
-                                                                               None
-                                                                       } else { None }
-                                                               } else { None };
-                                                               self.typed_generics.insert(&type_param.ident, (path, new_ident));
-                                                       } else { return false; }
+                                                                       } else {
+                                                                               new_typed_generics.insert(&type_param.ident, None);
+                                                                       }
+                                                               }
+                                                       }
                                                }
                                        }
                                        if let Some(default) = type_param.default.as_ref() {
@@ -254,9 +254,9 @@ impl<'a, 'p: 'a> GenericTypes<'a, 'p> {
                                                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.get_mut(&p_iter.next().unwrap().ident) {
-                                                       if gen.0 != "std::ops::Deref" && gen.0 != "core::ops::Deref" { return false; }
-                                                       if &format!("{}", p_iter.next().unwrap().ident) != "Target" { return false; }
+                                               if let Some(gen) = new_typed_generics.get_mut(&p_iter.next().unwrap().ident) {
+                                                       if gen.is_some() { return false; }
+                                                       if &format!("{}", p_iter.next().unwrap().ident) != "Target" {return false; }
 
                                                        let mut non_lifetimes_processed = false;
                                                        for bound in t.bounds.iter() {
@@ -267,8 +267,7 @@ impl<'a, 'p: 'a> GenericTypes<'a, 'p> {
                                                                        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, None),
-                                                                               Some(&trait_bound.path));
+                                                                       *gen = Some(types.resolve_path(&trait_bound.path, None));
                                                                }
                                                        }
                                                } else { return false; }
@@ -276,8 +275,10 @@ impl<'a, 'p: 'a> GenericTypes<'a, 'p> {
                                }
                        }
                }
-               for (_, (_, ident)) in self.typed_generics.iter() {
-                       if ident.is_none() { return false; }
+               for (key, value) in new_typed_generics.drain() {
+                       if let Some(v) = value {
+                               assert!(self.typed_generics.insert(key, v).is_none());
+                       } else { return false; }
                }
                true
        }
@@ -292,17 +293,15 @@ impl<'a, 'p: 'a> GenericTypes<'a, 'p> {
                                        match bounds_iter.next().unwrap() {
                                                syn::TypeParamBound::Trait(tr) => {
                                                        assert_simple_bound(&tr);
-                                                       if let Some(mut path) = types.maybe_resolve_path(&tr.path, None) {
+                                                       if let Some(path) = types.maybe_resolve_path(&tr.path, None) {
                                                                if types.skip_path(&path) { continue; }
                                                                // In general we handle Deref<Target=X> as if it were just X (and
                                                                // implement Deref<Target=Self> for relevant types). We don't
                                                                // bother to implement it for associated types, however, so we just
                                                                // ignore such bounds.
-                                                               let new_ident = if path != "std::ops::Deref" && path != "core::ops::Deref" {
-                                                                       path = "crate::".to_string() + &path;
-                                                                       Some(&tr.path)
-                                                               } else { None };
-                                                               self.typed_generics.insert(&t.ident, (path, new_ident));
+                                                               if path != "std::ops::Deref" && path != "core::ops::Deref" {
+                                                                       self.typed_generics.insert(&t.ident, path);
+                                                               }
                                                        } else { unimplemented!(); }
                                                },
                                                _ => unimplemented!(),
@@ -318,10 +317,10 @@ impl<'a, 'p: 'a> GenericTypes<'a, 'p> {
        pub fn maybe_resolve_ident<'b>(&'b self, ident: &syn::Ident) -> Option<&'b String> {
                if let Some(ty) = &self.self_ty {
                        if format!("{}", ident) == "Self" {
-                               return Some(&ty.0);
+                               return Some(&ty);
                        }
                }
-               if let Some(res) = self.typed_generics.get(ident).map(|(a, _)| a) {
+               if let Some(res) = self.typed_generics.get(ident) {
                        return Some(res);
                }
                if let Some(parent) = self.parent {
@@ -333,14 +332,14 @@ impl<'a, 'p: 'a> GenericTypes<'a, 'p> {
 
        /// 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)> {
+       pub fn maybe_resolve_path<'b>(&'b self, path: &syn::Path) -> Option<&'b String> {
                if let Some(ident) = path.get_ident() {
                        if let Some(ty) = &self.self_ty {
                                if format!("{}", ident) == "Self" {
-                                       return Some((&ty.0, ty.1));
+                                       return Some(&ty);
                                }
                        }
-                       if let Some(res) = self.typed_generics.get(ident).map(|(a, b)| (a, b.unwrap())) {
+                       if let Some(res) = self.typed_generics.get(ident) {
                                return Some(res);
                        }
                } else {
@@ -349,7 +348,7 @@ impl<'a, 'p: 'a> GenericTypes<'a, 'p> {
                        let mut it = path.segments.iter();
                        if path.segments.len() == 2 && format!("{}", it.next().unwrap().ident) == "Self" {
                                let ident = &it.next().unwrap().ident;
-                               if let Some(res) = self.typed_generics.get(ident).map(|(a, b)| (a, b.unwrap())) {
+                               if let Some(res) = self.typed_generics.get(ident) {
                                        return Some(res);
                                }
                        }
@@ -581,12 +580,12 @@ impl<'mod_lifetime, 'crate_lft: 'mod_lifetime> ImportResolver<'mod_lifetime, 'cr
                } else { None }
        }
 
-       pub fn maybe_resolve_path(&self, p_arg: &syn::Path, generics: Option<&GenericTypes>) -> Option<String> {
-               let p = if let Some(gen_types) = generics {
-                       if let Some((_, synpath)) = gen_types.maybe_resolve_path(p_arg) {
-                               synpath
-                       } else { p_arg }
-               } else { p_arg };
+       pub fn maybe_resolve_path(&self, p: &syn::Path, generics: Option<&GenericTypes>) -> Option<String> {
+               if let Some(gen_types) = generics {
+                       if let Some(resp) = gen_types.maybe_resolve_path(p) {
+                               return Some(resp.clone());
+                       }
+               }
 
                if p.leading_colon.is_some() {
                        let mut res: String = p.segments.iter().enumerate().map(|(idx, seg)| {
@@ -798,8 +797,8 @@ pub struct TypeResolver<'mod_lifetime, 'crate_lft: 'mod_lifetime> {
 enum EmptyValExpectedTy {
        /// A type which has a flag for being empty (eg an array where we treat all-0s as empty).
        NonPointer,
-       /// A pointer that we want to dereference and move out of.
-       OwnedPointer,
+       /// A Option mapped as a COption_*Z
+       OptionType,
        /// A pointer which we want to convert to a reference.
        ReferenceAsPointer,
 }
@@ -868,10 +867,6 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                        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)
 
@@ -889,7 +884,10 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                        "std::time::SystemTime" => Some("u64"),
                        "std::io::Error" => Some("crate::c_types::IOError"),
 
+                       "core::convert::Infallible" => Some("crate::c_types::NotConstructable"),
+
                        "bech32::u5" => Some("crate::c_types::u5"),
+                       "core::num::NonZeroU8" => Some("u8"),
 
                        "bitcoin::secp256k1::key::PublicKey"|"bitcoin::secp256k1::PublicKey"|"secp256k1::key::PublicKey"
                                => Some("crate::c_types::PublicKey"),
@@ -904,12 +902,17 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                        "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" => Some("crate::lightning::chain::transaction::OutPoint"),
-                       "bitcoin::blockdata::transaction::Transaction" => Some("crate::c_types::Transaction"),
+                       "bitcoin::blockdata::transaction::Transaction"|"bitcoin::Transaction" => Some("crate::c_types::Transaction"),
                        "bitcoin::blockdata::transaction::TxOut" if !is_ref => Some("crate::c_types::TxOut"),
                        "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"),
 
+                       "bitcoin::hash_types::PubkeyHash"|"bitcoin::hash_types::WPubkeyHash"|"bitcoin::hash_types::ScriptHash"
+                               if is_ref => Some("*const [u8; 20]"),
+                       "bitcoin::hash_types::WScriptHash"
+                               if is_ref => Some("*const [u8; 32]"),
+
                        // Newtypes that we just expose in their original form.
                        "bitcoin::hash_types::Txid"|"bitcoin::hash_types::BlockHash"|"bitcoin_hashes::sha256::Hash"
                                if is_ref  => Some("*const [u8; 32]"),
@@ -925,6 +928,8 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                        // Override the default since Records contain an fmt with a lifetime:
                        "lightning::util::logger::Record" => Some("*const std::os::raw::c_char"),
 
+                       "lightning::io::Read" => Some("crate::c_types::u8slice"),
+
                        _ => None,
                }
        }
@@ -959,10 +964,13 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                        // Note that we'll panic for String if is_ref, as we only have non-owned memory, we
                        // cannot create a &String.
 
+                       "core::convert::Infallible" => Some("panic!(\"You must never construct a NotConstructable! : "),
+
                        "std::time::Duration"|"core::time::Duration" => Some("std::time::Duration::from_secs("),
                        "std::time::SystemTime" => Some("(::std::time::SystemTime::UNIX_EPOCH + std::time::Duration::from_secs("),
 
                        "bech32::u5" => Some(""),
+                       "core::num::NonZeroU8" => Some("core::num::NonZeroU8::new("),
 
                        "bitcoin::secp256k1::key::PublicKey"|"bitcoin::secp256k1::PublicKey"|"secp256k1::key::PublicKey"
                                if is_ref => Some("&"),
@@ -977,13 +985,23 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                                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::blockdata::transaction::Transaction"|"bitcoin::Transaction" if is_ref => Some("&"),
+                       "bitcoin::blockdata::transaction::Transaction"|"bitcoin::Transaction" => Some(""),
+                       "bitcoin::blockdata::transaction::OutPoint" => Some("crate::c_types::C_to_bitcoin_outpoint("),
                        "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("),
 
+                       "bitcoin::hash_types::PubkeyHash" if is_ref =>
+                               Some("&bitcoin::hash_types::PubkeyHash::from_hash(bitcoin::hashes::Hash::from_inner(unsafe { *"),
+                       "bitcoin::hash_types::WPubkeyHash" if is_ref =>
+                               Some("&bitcoin::hash_types::WPubkeyHash::from_hash(bitcoin::hashes::Hash::from_inner(unsafe { *"),
+                       "bitcoin::hash_types::ScriptHash" if is_ref =>
+                               Some("&bitcoin::hash_types::ScriptHash::from_hash(bitcoin::hashes::Hash::from_inner(unsafe { *"),
+                       "bitcoin::hash_types::WScriptHash" if is_ref =>
+                               Some("&bitcoin::hash_types::WScriptHash::from_hash(bitcoin::hashes::Hash::from_inner(unsafe { *"),
+
                        // 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(&"),
@@ -997,6 +1015,8 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                        // List of traits we map (possibly during processing of other files):
                        "crate::util::logger::Logger" => Some(""),
 
+                       "lightning::io::Read" => Some("&mut "),
+
                        _ => None,
                }.map(|s| s.to_owned())
        }
@@ -1024,10 +1044,13 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                        "alloc::string::String"|"String" => Some(".into_string()"),
                        "std::io::Error" if !is_ref => Some(".to_rust()"),
 
+                       "core::convert::Infallible" => Some("\")"),
+
                        "std::time::Duration"|"core::time::Duration" => Some(")"),
                        "std::time::SystemTime" => Some("))"),
 
                        "bech32::u5" => Some(".into()"),
+                       "core::num::NonZeroU8" => Some(").expect(\"Value must be non-zero\")"),
 
                        "bitcoin::secp256k1::key::PublicKey"|"bitcoin::secp256k1::PublicKey"|"secp256k1::key::PublicKey"
                                => Some(".into_rust()"),
@@ -1039,12 +1062,17 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                                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" => Some(".into_bitcoin()"),
+                       "bitcoin::blockdata::transaction::Transaction"|"bitcoin::Transaction" => Some(".into_bitcoin()"),
+                       "bitcoin::blockdata::transaction::OutPoint" => Some(")"),
                        "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()"),
 
+                       "bitcoin::hash_types::PubkeyHash"|"bitcoin::hash_types::WPubkeyHash"|
+                       "bitcoin::hash_types::ScriptHash"|"bitcoin::hash_types::WScriptHash"
+                               if is_ref => Some(" }.clone()))"),
+
                        // 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()"),
@@ -1058,6 +1086,8 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                        // List of traits we map (possibly during processing of other files):
                        "crate::util::logger::Logger" => Some(""),
 
+                       "lightning::io::Read" => Some(".to_reader()"),
+
                        _ => None,
                }.map(|s| s.to_owned())
        }
@@ -1107,6 +1137,8 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                        "std::time::SystemTime" => Some(""),
                        "std::io::Error" if !is_ref => Some("crate::c_types::IOError::from_rust("),
 
+                       "core::convert::Infallible" => Some("panic!(\"Cannot construct an Infallible: "),
+
                        "bech32::u5" => Some(""),
 
                        "bitcoin::secp256k1::key::PublicKey"|"bitcoin::secp256k1::PublicKey"|"secp256k1::key::PublicKey"
@@ -1121,8 +1153,8 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                                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 => Some("crate::c_types::Transaction::from_bitcoin("),
-                       "bitcoin::blockdata::transaction::Transaction" => Some("crate::c_types::Transaction::from_bitcoin(&"),
+                       "bitcoin::blockdata::transaction::Transaction"|"bitcoin::Transaction" if is_ref => Some("crate::c_types::Transaction::from_bitcoin("),
+                       "bitcoin::blockdata::transaction::Transaction"|"bitcoin::Transaction" => Some("crate::c_types::Transaction::from_bitcoin(&"),
                        "bitcoin::blockdata::transaction::OutPoint" => Some("crate::c_types::bitcoin_to_C_outpoint("),
                        "bitcoin::blockdata::transaction::TxOut" if !is_ref => Some("crate::c_types::TxOut::from_rust("),
                        "bitcoin::network::constants::Network" => Some("crate::bitcoin::network::Network::from_bitcoin("),
@@ -1146,6 +1178,8 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                        // Override the default since Records contain an fmt with a lifetime:
                        "lightning::util::logger::Record" => Some("local_"),
 
+                       "lightning::io::Read" => Some("crate::c_types::u8slice::from_vec(&crate::c_types::reader_to_vec("),
+
                        _ => None,
                }.map(|s| s.to_owned())
        }
@@ -1177,6 +1211,8 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                        "std::time::SystemTime" => Some(".duration_since(::std::time::SystemTime::UNIX_EPOCH).expect(\"Times must be post-1970\").as_secs()"),
                        "std::io::Error" if !is_ref => Some(")"),
 
+                       "core::convert::Infallible" => Some("\")"),
+
                        "bech32::u5" => Some(".into()"),
 
                        "bitcoin::secp256k1::key::PublicKey"|"bitcoin::secp256k1::PublicKey"|"secp256k1::key::PublicKey"
@@ -1191,7 +1227,7 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                                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" => Some(")"),
+                       "bitcoin::blockdata::transaction::Transaction"|"bitcoin::Transaction" => Some(")"),
                        "bitcoin::blockdata::transaction::OutPoint" => Some(")"),
                        "bitcoin::blockdata::transaction::TxOut" if !is_ref => Some(")"),
                        "bitcoin::network::constants::Network" => Some(")"),
@@ -1215,6 +1251,8 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                        // Override the default since Records contain an fmt with a lifetime:
                        "lightning::util::logger::Record" => Some(".as_ptr()"),
 
+                       "lightning::io::Read" => Some("))"),
+
                        _ => None,
                }.map(|s| s.to_owned())
        }
@@ -1228,6 +1266,18 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                }
        }
 
+       /// When printing a reference to the source crate's rust type, if we need to map it to a
+       /// different "real" type, it can be done so here.
+       /// This is useful to work around limitations in the binding type resolver, where we reference
+       /// a non-public `use` alias.
+       /// TODO: We should never need to use this!
+       fn real_rust_type_mapping<'equiv>(&self, thing: &'equiv str) -> &'equiv str {
+               match thing {
+                       "lightning::io::Read" => "std::io::Read",
+                       _ => thing,
+               }
+       }
+
        // ****************************
        // *** Container Processing ***
        // ****************************
@@ -1245,15 +1295,17 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
 
        /// Returns true if the path containing the given args is a "transparent" container, ie an
        /// Option or a container which does not require a generated continer class.
-       fn is_transparent_container<'i, I: Iterator<Item=&'i syn::Type>>(&self, full_path: &str, _is_ref: bool, mut args: I) -> bool {
+       fn is_transparent_container<'i, I: Iterator<Item=&'i syn::Type>>(&self, full_path: &str, _is_ref: bool, mut args: I, generics: Option<&GenericTypes>) -> bool {
                if full_path == "Option" {
                        let inner = args.next().unwrap();
                        assert!(args.next().is_none());
                        match inner {
                                syn::Type::Reference(_) => true,
                                syn::Type::Path(p) => {
-                                       if let Some(resolved) = self.maybe_resolve_path(&p.path, None) {
-                                               if self.is_primitive(&resolved) { false } else { true }
+                                       if let Some(resolved) = self.maybe_resolve_path(&p.path, generics) {
+                                               if self.c_type_has_inner_from_path(&resolved) { return true; }
+                                               if self.is_primitive(&resolved) { return false; }
+                                               if self.c_type_from_path(&resolved, false, false).is_some() { true } else { false }
                                        } else { true }
                                },
                                syn::Type::Tuple(_) => false,
@@ -1273,7 +1325,7 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                        }),
                        syn::PathArguments::Parenthesized(_) => unimplemented!(),
                };
-               self.is_transparent_container(&self.resolve_path(full_path, generics), is_ref, inner_iter)
+               self.is_transparent_container(&self.resolve_path(full_path, generics), is_ref, inner_iter, generics)
        }
        /// Returns true if this is a known, supported, non-transparent container.
        fn is_known_container(&self, full_path: &str, is_ref: bool) -> bool {
@@ -1309,23 +1361,28 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                                        } else { None }
                                } else { None };
                                if let Some(inner_path) = contained_struct {
-                                       if self.is_primitive(&inner_path) {
-                                               return Some(("if ", vec![
-                                                       (format!(".is_none() {{ {}::COption_{}Z::None }} else {{ ", Self::generated_container_path(), inner_path),
-                                                        format!("{}::COption_{}Z::Some({}.unwrap())", Self::generated_container_path(), inner_path, var_access))
-                                                       ], " }", ContainerPrefixLocation::NoPrefix));
-                                       } else if self.c_type_has_inner_from_path(&inner_path) {
+                                       if self.c_type_has_inner_from_path(&inner_path) {
                                                let is_inner_ref = if let Some(syn::Type::Reference(_)) = single_contained { true } else { false };
                                                if is_ref {
                                                        return Some(("if ", vec![
-                                                               (".is_none() { std::ptr::null() } else { ".to_owned(),
+                                                               (".is_none() { std::ptr::null() } else { ObjOps::nonnull_ptr_to_inner(".to_owned(),
                                                                        format!("({}{}.unwrap())", var_access, if is_inner_ref { "" } else { ".as_ref()" }))
-                                                               ], " }", ContainerPrefixLocation::OutsideConv));
+                                                               ], ") }", ContainerPrefixLocation::OutsideConv));
                                                } else {
                                                        return Some(("if ", vec![
                                                                (".is_none() { std::ptr::null_mut() } else { ".to_owned(), format!("({}.unwrap())", var_access))
                                                                ], " }", ContainerPrefixLocation::OutsideConv));
                                                }
+                                       } else if self.is_primitive(&inner_path) || self.c_type_from_path(&inner_path, false, false).is_none() {
+                                               let inner_name = self.get_c_mangled_container_type(vec![single_contained.unwrap()], generics, "Option").unwrap();
+                                               return Some(("if ", vec![
+                                                       (format!(".is_none() {{ {}::None }} else {{ {}::Some(",
+                                                               inner_name, inner_name),
+                                                        format!("{}.unwrap()", var_access))
+                                                       ], ") }", ContainerPrefixLocation::PerConv));
+                                       } else {
+                                               // If c_type_from_path is some (ie there's a manual mapping for the inner
+                                               // type), lean on write_empty_rust_val, below.
                                        }
                                }
                                if let Some(t) = single_contained {
@@ -1385,14 +1442,11 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                                                                        return Some(("if ", vec![
                                                                                (format!("{} {{ None }} else {{ Some(", s), format!("unsafe {{ &mut *{} }}", var_access))
                                                                        ], ") }", ContainerPrefixLocation::NoPrefix)),
-                                                               EmptyValExpectedTy::OwnedPointer => {
-                                                                       if let syn::Type::Slice(_) = t {
-                                                                                       panic!();
-                                                                       }
-                                                                       return Some(("if ", vec![
-                                                                               (format!("{} {{ None }} else {{ Some(", s), format!("unsafe {{ *Box::from_raw({}) }}", var_access))
-                                                                       ], ") }", ContainerPrefixLocation::NoPrefix));
-                                                               }
+                                                               EmptyValExpectedTy::OptionType =>
+                                                                       return Some(("{ /* ", vec![
+                                                                               (format!("*/ let {}_opt = {};", var_name, var_access),
+                                                                               format!("}} if {}_opt{} {{ None }} else {{ Some({{ {}_opt.take()", var_name, s, var_name))
+                                                                       ], ") } }", ContainerPrefixLocation::PerConv)),
                                                                EmptyValExpectedTy::NonPointer =>
                                                                        return Some(("if ", vec![
                                                                                (format!("{} {{ None }} else {{ Some(", s), format!("{}", var_access))
@@ -1410,6 +1464,49 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                }
        }
 
+       /// Constructs a reference to the given type, possibly tweaking the type if relevant to make it
+       /// convertable to C.
+       pub fn create_ownable_reference(&self, t: &syn::Type, generics: Option<&GenericTypes>) -> Option<syn::Type> {
+               let default_value = Some(syn::Type::Reference(syn::TypeReference {
+                       and_token: syn::Token!(&)(Span::call_site()), lifetime: None, mutability: None,
+                       elem: Box::new(t.clone()) }));
+               match generics.resolve_type(t) {
+                       syn::Type::Path(p) => {
+                               if let Some(resolved_path) = self.maybe_resolve_path(&p.path, generics) {
+                                       if resolved_path != "Vec" { return default_value; }
+                                       if p.path.segments.len() != 1 { unimplemented!(); }
+                                       let only_seg = p.path.segments.iter().next().unwrap();
+                                       if let syn::PathArguments::AngleBracketed(args) = &only_seg.arguments {
+                                               if args.args.len() != 1 { unimplemented!(); }
+                                               let inner_arg = args.args.iter().next().unwrap();
+                                               if let syn::GenericArgument::Type(ty) = &inner_arg {
+                                                       let mut can_create = self.c_type_has_inner(&ty);
+                                                       if let syn::Type::Path(inner) = ty {
+                                                               if inner.path.segments.len() == 1 &&
+                                                                               format!("{}", inner.path.segments[0].ident) == "Vec" {
+                                                                       can_create = true;
+                                                               }
+                                                       }
+                                                       if !can_create { return default_value; }
+                                                       if let Some(inner_ty) = self.create_ownable_reference(&ty, generics) {
+                                                               return Some(syn::Type::Reference(syn::TypeReference {
+                                                                       and_token: syn::Token![&](Span::call_site()),
+                                                                       lifetime: None,
+                                                                       mutability: None,
+                                                                       elem: Box::new(syn::Type::Slice(syn::TypeSlice {
+                                                                               bracket_token: syn::token::Bracket { span: Span::call_site() },
+                                                                               elem: Box::new(inner_ty)
+                                                                       }))
+                                                               }));
+                                                       } else { return default_value; }
+                                               } else { unimplemented!(); }
+                                       } else { unimplemented!(); }
+                               } else { return None; }
+                       },
+                       _ => default_value,
+               }
+       }
+
        // *************************************************
        // *** Type definition during main.rs processing ***
        // *************************************************
@@ -1421,12 +1518,14 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
        pub fn c_type_has_inner_from_path(&self, full_path: &str) -> bool {
                self.crate_types.opaques.get(full_path).is_some()
        }
+
        /// Returns true if the object at the given path is mapped as X { inner: *mut origX, .. }.
        pub fn c_type_has_inner(&self, ty: &syn::Type) -> bool {
                match ty {
                        syn::Type::Path(p) => {
-                               let full_path = self.resolve_path(&p.path, None);
-                               self.c_type_has_inner_from_path(&full_path)
+                               if let Some(full_path) = self.maybe_resolve_path(&p.path, None) {
+                                       self.c_type_has_inner_from_path(&full_path)
+                               } else { false }
                        },
                        syn::Type::Reference(r) => {
                                self.c_type_has_inner(&*r.elem)
@@ -1475,7 +1574,7 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                                // If we're printing a generic argument, it needs to reference the crate, otherwise
                                // the original crate:
                                } else if self.maybe_resolve_path(&path, None).as_ref() == Some(&resolved) {
-                                       write!(w, "{}", resolved).unwrap();
+                                       write!(w, "{}", self.real_rust_type_mapping(&resolved)).unwrap();
                                } else {
                                        write!(w, "crate::{}", resolved).unwrap();
                                }
@@ -1649,8 +1748,8 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                                                // We may eventually need to allow empty_val_check_suffix_from_path to specify if we need a deref or not
                                                EmptyValExpectedTy::NonPointer
                                        } else {
-                                               write!(w, " == std::ptr::null_mut()").unwrap();
-                                               EmptyValExpectedTy::OwnedPointer
+                                               write!(w, ".is_none()").unwrap();
+                                               EmptyValExpectedTy::OptionType
                                        }
                                }
                        },
@@ -1788,6 +1887,8 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                                } 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, generics)), None)).unwrap();
+                                       } else if let syn::Type::Slice(_) = &*r.elem {
+                                               write!(w, "{}", sliceconv(false, None)).unwrap();
                                        } else { unimplemented!(); }
                                } else if let syn::Type::Tuple(t) = &*s.elem {
                                        assert!(!t.elems.is_empty());
@@ -1845,16 +1946,16 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                                                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 => {
+                                                       if !ptr_for_ref { write!(w, "&").unwrap(); }
+                                                       write!(w, "crate::{} {{ inner: unsafe {{ ObjOps::nonnull_ptr_to_inner((", 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(),
+                                                       write!(w, "crate::{} {{ inner: ObjOps::heap_alloc(", decl_path).unwrap(),
                                                DeclType::Trait(_) if is_ref => write!(w, "").unwrap(),
-                                               DeclType::Trait(_) if !is_ref => {},
+                                               DeclType::Trait(_) if !is_ref => write!(w, "Into::into(").unwrap(),
                                                _ => panic!("{:?}", decl_path),
                                        }
                                });
@@ -1869,20 +1970,18 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                                        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(),
+                                               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::EnumIgnored|DeclType::StructImported if !is_ref => write!(w, "), is_owned: true }}").unwrap(),
                                        DeclType::Trait(_) if is_ref => {},
                                        DeclType::Trait(_) => {
                                                // This is used when we're converting a concrete Rust type into a C trait
                                                // for use when a Rust trait method returns an associated type.
                                                // Because all of our C traits implement From<RustTypesImplementingTraits>
                                                // we can just call .into() here and be done.
-                                               write!(w, ".into()").unwrap()
+                                               write!(w, ")").unwrap()
                                        },
                                        _ => unimplemented!(),
                                });
@@ -1891,13 +1990,11 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                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) {
+       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_".to_owned(),
                                |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(),
+                               |w, decl_type, _full_path, is_ref, _is_mut| match decl_type {
+                                       DeclType::StructImported if is_ref => write!(w, "").unwrap(),
                                        DeclType::StructImported if !is_ref => write!(w, "*unsafe {{ Box::from_raw(").unwrap(),
                                        DeclType::MirroredEnum if is_ref => write!(w, "&").unwrap(),
                                        DeclType::MirroredEnum => {},
@@ -1917,9 +2014,10 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                                        (true, Some(_)) => unreachable!(),
                                },
                                |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(),
+                               |w, decl_type, _full_path, is_ref, is_mut| match decl_type {
+                                       DeclType::StructImported if is_ref && ptr_for_ref => write!(w, "XXX unimplemented").unwrap(),
+                                       DeclType::StructImported if is_mut && is_ref => write!(w, ".get_native_mut_ref()").unwrap(),
+                                       DeclType::StructImported if is_ref => write!(w, ".get_native_ref()").unwrap(),
                                        DeclType::StructImported if !is_ref => write!(w, ".take_inner()) }}").unwrap(),
                                        DeclType::MirroredEnum if is_ref => write!(w, ".to_native()").unwrap(),
                                        DeclType::MirroredEnum => write!(w, ".into_native()").unwrap(),
@@ -1940,7 +2038,7 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                                        } else { None }
                                },
                                |w, decl_type, _full_path, is_ref, _is_mut| match decl_type {
-                                       DeclType::StructImported if !is_ref => write!(w, "unsafe {{ &*").unwrap(),
+                                       DeclType::StructImported if !is_ref => write!(w, "").unwrap(),
                                        _ => unimplemented!(),
                                });
        }
@@ -1954,7 +2052,7 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                                },
                                |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(),
+                                       DeclType::StructImported if !is_ref => write!(w, ".get_native_ref()").unwrap(),
                                        _ => unimplemented!(),
                                });
        }
@@ -2043,14 +2141,14 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                                                if prefix_location == ContainerPrefixLocation::PerConv {
                                                        var_prefix(w, conv_ty, generics, is_ref && ty_has_inner, ptr_for_ref, false);
                                                } else if !is_ref && !needs_ref_map && to_c && only_contained_has_inner {
-                                                       write!(w, "Box::into_raw(Box::new(").unwrap();
+                                                       write!(w, "ObjOps::heap_alloc(").unwrap();
                                                }
 
                                                write!(w, "{}{}", if contains_slice { "local_" } else { "" }, if new_var { new_var_name } else { var_access }).unwrap();
                                                if prefix_location == ContainerPrefixLocation::PerConv {
                                                        var_suffix(w, conv_ty, generics, is_ref && ty_has_inner, ptr_for_ref, false);
                                                } else if !is_ref && !needs_ref_map && to_c && only_contained_has_inner {
-                                                       write!(w, "))").unwrap();
+                                                       write!(w, ")").unwrap();
                                                }
                                                write!(w, " }}").unwrap();
                                        }
@@ -2091,7 +2189,7 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                                        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
+                                                               generics.resolve_type(ty)
                                                        } else { unimplemented!(); }
                                                }));
                                        } else { unimplemented!(); }
@@ -2124,7 +2222,7 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                                } else if let syn::Type::Reference(ty) = &*s.elem {
                                        let tyref = [&*ty.elem];
                                        is_ref = true;
-                                       convert_container!("Slice", 1, || tyref.iter().map(|t| *t));
+                                       convert_container!("Slice", 1, || tyref.iter().map(|t| generics.resolve_type(*t)));
                                        unimplemented!("convert_container should return true as container_lookup should succeed for slices");
                                } else if let syn::Type::Tuple(t) = &*s.elem {
                                        // When mapping into a temporary new var, we need to own all the underlying objects.
@@ -2354,7 +2452,7 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
        fn write_c_mangled_container_path_intern<W: std::io::Write>
                        (&self, w: &mut W, args: Vec<&syn::Type>, generics: Option<&GenericTypes>, 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, args.iter().map(|a| *a)) {
+               if !self.is_transparent_container(ident, is_ref, args.iter().map(|a| *a), generics) {
                        write!(w, "C{}_", ident).unwrap();
                        write!(mangled_type, "C{}_", ident).unwrap();
                } else { assert_eq!(args.len(), 1); }
@@ -2362,7 +2460,7 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                        macro_rules! write_path {
                                ($p_arg: expr, $extra_write: expr) => {
                                        if let Some(subtype) = self.maybe_resolve_path(&$p_arg.path, generics) {
-                                               if self.is_transparent_container(ident, is_ref, args.iter().map(|a| *a)) {
+                                               if self.is_transparent_container(ident, is_ref, args.iter().map(|a| *a), generics) {
                                                        if !in_type {
                                                                if self.c_type_has_inner_from_path(&subtype) {
                                                                        if !self.write_c_path_intern(w, &$p_arg.path, generics, is_ref, is_mut, ptr_for_ref) { return false; }
@@ -2399,64 +2497,70 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                                        } 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 if let syn::Type::Reference(refelem) = elem {
-                                                       if let syn::Type::Path(p) = &*refelem.elem {
+                       match generics.resolve_type(arg) {
+                               syn::Type::Tuple(tuple) => {
+                                       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 if let syn::Type::Reference(refelem) = elem {
+                                                               if let syn::Type::Path(p) = &*refelem.elem {
+                                                                       write_path!(p, Some(&mut mangled_tuple_type));
+                                                               } else { return false; }
                                                        } else { return false; }
-                                               } else { return false; }
-                                       }
-                                       write!(w, "Z").unwrap();
-                                       write!(mangled_type, "Z").unwrap();
-                                       write!(mangled_tuple_type, "Z").unwrap();
-                                       if !self.check_create_container(String::from_utf8(mangled_tuple_type).unwrap(),
-                                                       &format!("{}Tuple", tuple.elems.len()), tuple.elems.iter().collect(), generics, is_ref) {
-                                               return false;
+                                               }
+                                               write!(w, "Z").unwrap();
+                                               write!(mangled_type, "Z").unwrap();
+                                               write!(mangled_tuple_type, "Z").unwrap();
+                                               if !self.check_create_container(String::from_utf8(mangled_tuple_type).unwrap(),
+                                                               &format!("{}Tuple", tuple.elems.len()), tuple.elems.iter().collect(), generics, is_ref) {
+                                                       return false;
+                                               }
                                        }
-                               }
-                       } else if let syn::Type::Path(p_arg) = arg {
-                               write_path!(p_arg, None);
-                       } else if let syn::Type::Reference(refty) = arg {
-                               if let syn::Type::Path(p_arg) = &*refty.elem {
+                               },
+                               syn::Type::Path(p_arg) => {
                                        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.
-                                       if args.len() != 1 { return false; }
-                                       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, generics);
-                                       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();
+                               },
+                               syn::Type::Reference(refty) => {
+                                       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.
+                                               if args.len() != 1 { return false; }
+                                               write!(w, "*mut ").unwrap();
+                                               self.write_c_type(w, arg, None, true);
                                        } else { return false; }
-                               } else { return false; }
-                       } else { return false; }
+                               },
+                               syn::Type::Array(a) => {
+                                       if let syn::Type::Path(p_arg) = &*a.elem {
+                                               let resolved = self.resolve_path(&p_arg.path, generics);
+                                               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; }
+                               },
+                               _ => { return false; },
+                       }
                }
-               if self.is_transparent_container(ident, is_ref, args.iter().map(|a| *a)) { return true; }
+               if self.is_transparent_container(ident, is_ref, args.iter().map(|a| *a), generics) { return true; }
                // Push the "end of type" Z
                write!(w, "Z").unwrap();
                write!(mangled_type, "Z").unwrap();
@@ -2465,7 +2569,7 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                self.check_create_container(String::from_utf8(mangled_type).unwrap(), ident, args, generics, is_ref)
        }
        fn write_c_mangled_container_path<W: std::io::Write>(&self, w: &mut W, args: Vec<&syn::Type>, generics: Option<&GenericTypes>, ident: &str, is_ref: bool, is_mut: bool, ptr_for_ref: bool) -> bool {
-               if !self.is_transparent_container(ident, is_ref, args.iter().map(|a| *a)) {
+               if !self.is_transparent_container(ident, is_ref, args.iter().map(|a| *a), generics) {
                        write!(w, "{}::", Self::generated_container_path()).unwrap();
                }
                self.write_c_mangled_container_path_intern(w, args, generics, ident, is_ref, is_mut, ptr_for_ref, false)
@@ -2580,6 +2684,20 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
                                                } else { return false; };
                                                write!(w, "{}::{}", Self::generated_container_path(), mangled_container).unwrap();
                                                self.check_create_container(mangled_container, "Vec", vec![&*r.elem], generics, false)
+                                       } else if let syn::Type::Slice(sl2) = &*r.elem {
+                                               if let syn::Type::Reference(r2) = &*sl2.elem {
+                                                       if let syn::Type::Path(p) = &*r2.elem {
+                                                               // Slices with slices with opaque types (with is_owned flags) are mapped as non-ref Vecs
+                                                               let resolved = self.resolve_path(&p.path, generics);
+                                                               let mangled_container = if let Some(ident) = self.crate_types.opaques.get(&resolved) {
+                                                                       format!("CVec_CVec_{}ZZ", ident)
+                                                               } else { return false; };
+                                                               write!(w, "{}::{}", Self::generated_container_path(), mangled_container).unwrap();
+                                                               let inner = &r2.elem;
+                                                               let vec_ty: syn::Type = syn::parse_quote!(Vec<#inner>);
+                                                               self.check_create_container(mangled_container, "Vec", vec![&vec_ty], generics, false)
+                                                       } else { false }
+                                               } else { false }
                                        } else { false }
                                } else if let syn::Type::Tuple(_) = &*s.elem {
                                        let mut args = syn::punctuated::Punctuated::<_, syn::token::Comma>::new();