_ Git - rust-lightning/blob - c-bindings-gen/src/blocks.rs

   1 //! Printing logic for basic blocks of Rust-mapped code - parts of functions and declarations but
   2 //! not the full mapping logic.
   3
   4 use std::fs::File;
   5 use std::io::Write;
   6 use proc_macro2::{TokenTree, Span};
   7
   8 use crate::types::*;
   9
  10 /// Writes out a C++ wrapper class for the given type, which contains various utilities to access
  11 /// the underlying C-mapped type safely avoiding some common memory management issues by handling
  12 /// resource-freeing and prevending accidental raw copies.
  13 pub fn write_cpp_wrapper(cpp_header_file: &mut File, ty: &str, has_destructor: bool) {
  14         writeln!(cpp_header_file, "class {} {{", ty).unwrap();
  15         writeln!(cpp_header_file, "private:").unwrap();
  16         writeln!(cpp_header_file, "\tLDK{} self;", ty).unwrap();
  17         writeln!(cpp_header_file, "public:").unwrap();
  18         writeln!(cpp_header_file, "\t{}(const {}&) = delete;", ty, ty).unwrap();
  19         writeln!(cpp_header_file, "\t{}({}&& o) : self(o.self) {{ memset(&o, 0, sizeof({})); }}", ty, ty, ty).unwrap();
  20         writeln!(cpp_header_file, "\t{}(LDK{}&& m_self) : self(m_self) {{ memset(&m_self, 0, sizeof(LDK{})); }}", ty, ty, ty).unwrap();
  21         writeln!(cpp_header_file, "\toperator LDK{}() && {{ LDK{} res = self; memset(&self, 0, sizeof(LDK{})); return res; }}", ty, ty, ty).unwrap();
  22         if has_destructor {
  23                 writeln!(cpp_header_file, "\t~{}() {{ {}_free(self); }}", ty, ty).unwrap();
  24                 writeln!(cpp_header_file, "\t{}& operator=({}&& o) {{ {}_free(self); self = o.self; memset(&o, 0, sizeof({})); return *this; }}", ty, ty, ty, ty).unwrap();
  25         } else {
  26                 writeln!(cpp_header_file, "\t{}& operator=({}&& o) {{ self = o.self; memset(&o, 0, sizeof({})); return *this; }}", ty, ty, ty).unwrap();
  27         }
  28         writeln!(cpp_header_file, "\tLDK{}* operator &() {{ return &self; }}", ty).unwrap();
  29         writeln!(cpp_header_file, "\tLDK{}* operator ->() {{ return &self; }}", ty).unwrap();
  30         writeln!(cpp_header_file, "\tconst LDK{}* operator &() const {{ return &self; }}", ty).unwrap();
  31         writeln!(cpp_header_file, "\tconst LDK{}* operator ->() const {{ return &self; }}", ty).unwrap();
  32         writeln!(cpp_header_file, "}};").unwrap();
  33 }
  34
  35 /// Writes out a C-callable concrete Result<A, B> struct and utility methods
  36 pub fn write_result_block<W: std::io::Write>(w: &mut W, mangled_container: &str, ok_type: &str, err_type: &str, clonable: bool) {
  37         writeln!(w, "#[repr(C)]").unwrap();
  38         writeln!(w, "pub union {}Ptr {{", mangled_container).unwrap();
  39         if ok_type != "()" {
  40                 writeln!(w, "\tpub result: *mut {},", ok_type).unwrap();
  41         } else {
  42                 writeln!(w, "\t/// Note that this value is always NULL, as there are no contents in the OK variant").unwrap();
  43                 writeln!(w, "\tpub result: *mut std::ffi::c_void,").unwrap();
  44         }
  45         if err_type != "()" {
  46                 writeln!(w, "\tpub err: *mut {},", err_type).unwrap();
  47         } else {
  48                 writeln!(w, "\t/// Note that this value is always NULL, as there are no contents in the Err variant").unwrap();
  49                 writeln!(w, "\tpub err: *mut std::ffi::c_void,").unwrap();
  50         }
  51         writeln!(w, "}}").unwrap();
  52         writeln!(w, "#[repr(C)]").unwrap();
  53         writeln!(w, "pub struct {} {{", mangled_container).unwrap();
  54         writeln!(w, "\tpub contents: {}Ptr,", mangled_container).unwrap();
  55         writeln!(w, "\tpub result_ok: bool,").unwrap();
  56         writeln!(w, "}}").unwrap();
  57
  58         writeln!(w, "#[no_mangle]").unwrap();
  59         if ok_type != "()" {
  60                 writeln!(w, "pub extern \"C\" fn {}_ok(o: {}) -> {} {{", mangled_container, ok_type, mangled_container).unwrap();
  61         } else {
  62                 writeln!(w, "pub extern \"C\" fn {}_ok() -> {} {{", mangled_container, mangled_container).unwrap();
  63         }
  64         writeln!(w, "\t{} {{", mangled_container).unwrap();
  65         writeln!(w, "\t\tcontents: {}Ptr {{", mangled_container).unwrap();
  66         if ok_type != "()" {
  67                 writeln!(w, "\t\t\tresult: Box::into_raw(Box::new(o)),").unwrap();
  68         } else {
  69                 writeln!(w, "\t\t\tresult: std::ptr::null_mut(),").unwrap();
  70         }
  71         writeln!(w, "\t\t}},").unwrap();
  72         writeln!(w, "\t\tresult_ok: true,").unwrap();
  73         writeln!(w, "\t}}").unwrap();
  74         writeln!(w, "}}").unwrap();
  75
  76         writeln!(w, "#[no_mangle]").unwrap();
  77         if err_type != "()" {
  78                 writeln!(w, "pub extern \"C\" fn {}_err(e: {}) -> {} {{", mangled_container, err_type, mangled_container).unwrap();
  79         } else {
  80                 writeln!(w, "pub extern \"C\" fn {}_err() -> {} {{", mangled_container, mangled_container).unwrap();
  81         }
  82         writeln!(w, "\t{} {{", mangled_container).unwrap();
  83         writeln!(w, "\t\tcontents: {}Ptr {{", mangled_container).unwrap();
  84         if err_type != "()" {
  85                 writeln!(w, "\t\t\terr: Box::into_raw(Box::new(e)),").unwrap();
  86         } else {
  87                 writeln!(w, "\t\t\terr: std::ptr::null_mut(),").unwrap();
  88         }
  89         writeln!(w, "\t\t}},").unwrap();
  90         writeln!(w, "\t\tresult_ok: false,").unwrap();
  91         writeln!(w, "\t}}").unwrap();
  92         writeln!(w, "}}").unwrap();
  93
  94         writeln!(w, "#[no_mangle]").unwrap();
  95         writeln!(w, "pub extern \"C\" fn {}_free(_res: {}) {{ }}", mangled_container, mangled_container).unwrap();
  96         writeln!(w, "impl Drop for {} {{", mangled_container).unwrap();
  97         writeln!(w, "\tfn drop(&mut self) {{").unwrap();
  98         writeln!(w, "\t\tif self.result_ok {{").unwrap();
  99         if ok_type != "()" {
 100                 writeln!(w, "\t\t\tif unsafe {{ !(self.contents.result as *mut ()).is_null() }} {{").unwrap();
 101                 writeln!(w, "\t\t\t\tlet _ = unsafe {{ Box::from_raw(self.contents.result) }};").unwrap();
 102                 writeln!(w, "\t\t\t}}").unwrap();
 103         }
 104         writeln!(w, "\t\t}} else {{").unwrap();
 105         if err_type != "()" {
 106                 writeln!(w, "\t\t\tif unsafe {{ !(self.contents.err as *mut ()).is_null() }} {{").unwrap();
 107                 writeln!(w, "\t\t\t\tlet _ = unsafe {{ Box::from_raw(self.contents.err) }};").unwrap();
 108                 writeln!(w, "\t\t\t}}").unwrap();
 109         }
 110         writeln!(w, "\t\t}}").unwrap();
 111         writeln!(w, "\t}}").unwrap();
 112         writeln!(w, "}}").unwrap();
 113
 114         // TODO: Templates should use () now that they can, too
 115         let templ_ok_type = if ok_type != "()" { ok_type } else { "u8" };
 116         let templ_err_type = if err_type != "()" { err_type } else { "u8" };
 117
 118         writeln!(w, "impl From<crate::c_types::CResultTempl<{}, {}>> for {} {{", templ_ok_type, templ_err_type, mangled_container).unwrap();
 119         writeln!(w, "\tfn from(mut o: crate::c_types::CResultTempl<{}, {}>) -> Self {{", templ_ok_type, templ_err_type).unwrap();
 120         writeln!(w, "\t\tlet contents = if o.result_ok {{").unwrap();
 121         if ok_type != "()" {
 122                 writeln!(w, "\t\t\tlet result = unsafe {{ o.contents.result }};").unwrap();
 123                 writeln!(w, "\t\t\tunsafe {{ o.contents.result = std::ptr::null_mut() }};").unwrap();
 124                 writeln!(w, "\t\t\t{}Ptr {{ result }}", mangled_container).unwrap();
 125         } else {
 126                 writeln!(w, "\t\t\tlet _ = unsafe {{ Box::from_raw(o.contents.result) }};").unwrap();
 127                 writeln!(w, "\t\t\to.contents.result = std::ptr::null_mut();").unwrap();
 128                 writeln!(w, "\t\t\t{}Ptr {{ result: std::ptr::null_mut() }}", mangled_container).unwrap();
 129         }
 130         writeln!(w, "\t\t}} else {{").unwrap();
 131         if err_type != "()" {
 132                 writeln!(w, "\t\t\tlet err = unsafe {{ o.contents.err }};").unwrap();
 133                 writeln!(w, "\t\t\tunsafe {{ o.contents.err = std::ptr::null_mut(); }}").unwrap();
 134                 writeln!(w, "\t\t\t{}Ptr {{ err }}", mangled_container).unwrap();
 135         } else {
 136                 writeln!(w, "\t\t\tlet _ = unsafe {{ Box::from_raw(o.contents.err) }};").unwrap();
 137                 writeln!(w, "\t\t\to.contents.err = std::ptr::null_mut();").unwrap();
 138                 writeln!(w, "\t\t\t{}Ptr {{ err: std::ptr::null_mut() }}", mangled_container).unwrap();
 139         }
 140         writeln!(w, "\t\t}};").unwrap();
 141         writeln!(w, "\t\tSelf {{").unwrap();
 142         writeln!(w, "\t\t\tcontents,").unwrap();
 143         writeln!(w, "\t\t\tresult_ok: o.result_ok,").unwrap();
 144         writeln!(w, "\t\t}}").unwrap();
 145         writeln!(w, "\t}}").unwrap();
 146         writeln!(w, "}}").unwrap();
 147
 148         if clonable {
 149                 writeln!(w, "impl Clone for {} {{", mangled_container).unwrap();
 150                 writeln!(w, "\tfn clone(&self) -> Self {{").unwrap();
 151                 writeln!(w, "\t\tif self.result_ok {{").unwrap();
 152                 writeln!(w, "\t\t\tSelf {{ result_ok: true, contents: {}Ptr {{", mangled_container).unwrap();
 153                 if ok_type != "()" {
 154                         writeln!(w, "\t\t\t\tresult: Box::into_raw(Box::new(<{}>::clone(unsafe {{ &*self.contents.result }})))", ok_type).unwrap();
 155                 } else {
 156                         writeln!(w, "\t\t\t\tresult: std::ptr::null_mut()").unwrap();
 157                 }
 158                 writeln!(w, "\t\t\t}} }}").unwrap();
 159                 writeln!(w, "\t\t}} else {{").unwrap();
 160                 writeln!(w, "\t\t\tSelf {{ result_ok: false, contents: {}Ptr {{", mangled_container).unwrap();
 161                 if err_type != "()" {
 162                         writeln!(w, "\t\t\t\terr: Box::into_raw(Box::new(<{}>::clone(unsafe {{ &*self.contents.err }})))", err_type).unwrap();
 163                 } else {
 164                         writeln!(w, "\t\t\t\terr: std::ptr::null_mut()").unwrap();
 165                 }
 166                 writeln!(w, "\t\t\t}} }}").unwrap();
 167                 writeln!(w, "\t\t}}").unwrap();
 168                 writeln!(w, "\t}}").unwrap();
 169                 writeln!(w, "}}").unwrap();
 170                 writeln!(w, "#[no_mangle]").unwrap();
 171                 writeln!(w, "pub extern \"C\" fn {}_clone(orig: &{}) -> {} {{ orig.clone() }}", mangled_container, mangled_container, mangled_container).unwrap();
 172         }
 173 }
 174
 175 /// Prints the docs from a given attribute list unless its tagged no export
 176 pub fn writeln_docs<W: std::io::Write>(w: &mut W, attrs: &[syn::Attribute], prefix: &str) {
 177         for attr in attrs.iter() {
 178                 let tokens_clone = attr.tokens.clone();
 179                 let mut token_iter = tokens_clone.into_iter();
 180                 if let Some(token) = token_iter.next() {
 181                         match token {
 182                                 TokenTree::Punct(c) if c.as_char() == '=' => {
 183                                         // syn gets '=' from '///' or '//!' as it is syntax for #[doc = ""]
 184                                 },
 185                                 TokenTree::Group(_) => continue, // eg #[derive()]
 186                                 _ => unimplemented!(),
 187                         }
 188                 } else { continue; }
 189                 match attr.style {
 190                         syn::AttrStyle::Inner(_) => {
 191                                 match token_iter.next().unwrap() {
 192                                         TokenTree::Literal(lit) => {
 193                                                 // Drop the first and last chars from lit as they are always "
 194                                                 let doc = format!("{}", lit);
 195                                                 writeln!(w, "{}//!{}", prefix, &doc[1..doc.len() - 1]).unwrap();
 196                                         },
 197                                         _ => unimplemented!(),
 198                                 }
 199                         },
 200                         syn::AttrStyle::Outer => {
 201                                 match token_iter.next().unwrap() {
 202                                         TokenTree::Literal(lit) => {
 203                                                 // Drop the first and last chars from lit as they are always "
 204                                                 let doc = format!("{}", lit);
 205                                                 writeln!(w, "{}///{}", prefix, &doc[1..doc.len() - 1]).unwrap();
 206                                         },
 207                                         _ => unimplemented!(),
 208                                 }
 209                         },
 210                 }
 211         }
 212 }
 213
 214 /// Print the parameters in a method declaration, starting after the open parenthesis, through and
 215 /// including the closing parenthesis and return value, but not including the open bracket or any
 216 /// trailing semicolons.
 217 ///
 218 /// Usable both for a function definition and declaration.
 219 ///
 220 /// this_param is used when returning Self or accepting a self parameter, and should be the
 221 /// concrete, mapped type.
 222 pub fn write_method_params<W: std::io::Write>(w: &mut W, sig: &syn::Signature, this_param: &str, types: &mut TypeResolver, generics: Option<&GenericTypes>, self_ptr: bool, fn_decl: bool) {
 223         if sig.constness.is_some() || sig.asyncness.is_some() || sig.unsafety.is_some() ||
 224                         sig.abi.is_some() || sig.variadic.is_some() {
 225                 unimplemented!();
 226         }
 227         if sig.generics.lt_token.is_some() {
 228                 for generic in sig.generics.params.iter() {
 229                         match generic {
 230                                 syn::GenericParam::Type(_)|syn::GenericParam::Lifetime(_) => {
 231                                         // We ignore these, if they're not on skipped args, we'll blow up
 232                                         // later, and lifetimes we just hope the C client enforces.
 233                                 },
 234                                 _ => unimplemented!(),
 235                         }
 236                 }
 237         }
 238
 239         let mut first_arg = true;
 240         let mut num_unused = 0;
 241         for inp in sig.inputs.iter() {
 242                 match inp {
 243                         syn::FnArg::Receiver(recv) => {
 244                                 if !recv.attrs.is_empty() || recv.reference.is_none() { unimplemented!(); }
 245                                 write!(w, "this_arg: {}{}",
 246                                         match (self_ptr, recv.mutability.is_some()) {
 247                                                 (true, true) => "*mut ",
 248                                                 (true, false) => "*const ",
 249                                                 (false, true) => "&mut ",
 250                                                 (false, false) => "&",
 251                                         }, this_param).unwrap();
 252                                 assert!(first_arg);
 253                                 first_arg = false;
 254                         },
 255                         syn::FnArg::Typed(arg) => {
 256                                 if types.skip_arg(&*arg.ty, generics) { continue; }
 257                                 if !arg.attrs.is_empty() { unimplemented!(); }
 258                                 // First get the c type so that we can check if it ends up being a reference:
 259                                 let mut c_type = Vec::new();
 260                                 types.write_c_type(&mut c_type, &*arg.ty, generics, false);
 261                                 match &*arg.pat {
 262                                         syn::Pat::Ident(ident) => {
 263                                                 if !ident.attrs.is_empty() || ident.subpat.is_some() {
 264                                                         unimplemented!();
 265                                                 }
 266                                                 write!(w, "{}{}{}: ", if first_arg { "" } else { ", " }, if !fn_decl || c_type[0] == '&' as u8 || c_type[0] == '*' as u8 { "" } else { "mut " }, ident.ident).unwrap();
 267                                                 first_arg = false;
 268                                         },
 269                                         syn::Pat::Wild(wild) => {
 270                                                 if !wild.attrs.is_empty() { unimplemented!(); }
 271                                                 write!(w, "{}unused_{}: ", if first_arg { "" } else { ", " }, num_unused).unwrap();
 272                                                 num_unused += 1;
 273                                         },
 274                                         _ => unimplemented!(),
 275                                 }
 276                                 w.write(&c_type).unwrap();
 277                         }
 278                 }
 279         }
 280         write!(w, ")").unwrap();
 281         match &sig.output {
 282                 syn::ReturnType::Type(_, rtype) => {
 283                         write!(w, " -> ").unwrap();
 284                         if let Some(mut remaining_path) = first_seg_self(&*rtype) {
 285                                 if remaining_path.next().is_none() {
 286                                         write!(w, "{}", this_param).unwrap();
 287                                         return;
 288                                 }
 289                         }
 290                         if let syn::Type::Reference(r) = &**rtype {
 291                                 // We can't return a reference, cause we allocate things on the stack.
 292                                 types.write_c_type(w, &*r.elem, generics, true);
 293                         } else {
 294                                 types.write_c_type(w, &*rtype, generics, true);
 295                         }
 296                 },
 297                 _ => {},
 298         }
 299 }
 300
 301 /// Print the main part of a method declaration body, starting with a newline after the function
 302 /// open bracket and converting each function parameter to or from C-mapped types. Ends with "let
 303 /// mut ret = " assuming the next print will be the unmapped Rust function to call followed by the
 304 /// parameters we mapped to/from C here.
 305 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) {
 306         let mut num_unused = 0;
 307         for inp in sig.inputs.iter() {
 308                 match inp {
 309                         syn::FnArg::Receiver(_) => {},
 310                         syn::FnArg::Typed(arg) => {
 311                                 if types.skip_arg(&*arg.ty, generics) { continue; }
 312                                 if !arg.attrs.is_empty() { unimplemented!(); }
 313                                 macro_rules! write_new_var {
 314                                         ($ident: expr, $ty: expr) => {
 315                                                 if to_c {
 316                                                         if types.write_to_c_conversion_new_var(w, &$ident, &$ty, generics, false) {
 317                                                                 write!(w, "\n\t{}", extra_indent).unwrap();
 318                                                         }
 319                                                 } else {
 320                                                         if types.write_from_c_conversion_new_var(w, &$ident, &$ty, generics) {
 321                                                                 write!(w, "\n\t{}", extra_indent).unwrap();
 322                                                         }
 323                                                 }
 324                                         }
 325                                 }
 326                                 match &*arg.pat {
 327                                         syn::Pat::Ident(ident) => {
 328                                                 if !ident.attrs.is_empty() || ident.subpat.is_some() {
 329                                                         unimplemented!();
 330                                                 }
 331                                                 write_new_var!(ident.ident, *arg.ty);
 332                                         },
 333                                         syn::Pat::Wild(w) => {
 334                                                 if !w.attrs.is_empty() { unimplemented!(); }
 335                                                 write_new_var!(syn::Ident::new(&format!("unused_{}", num_unused), Span::call_site()), *arg.ty);
 336                                                 num_unused += 1;
 337                                         },
 338                                         _ => unimplemented!(),
 339                                 }
 340                         }
 341                 }
 342         }
 343         match &sig.output {
 344                 syn::ReturnType::Type(_, _) => {
 345                         write!(w, "let mut ret = ").unwrap();
 346                 },
 347                 _ => {},
 348         }
 349 }
 350
 351 /// Prints the parameters in a method call, starting after the open parenthesis and ending with a
 352 /// final return statement returning the method's result. Should be followed by a single closing
 353 /// bracket.
 354 ///
 355 /// The return value is expected to be bound to a variable named `ret` which is available after a
 356 /// method-call-ending semicolon.
 357 pub fn write_method_call_params<W: std::io::Write>(w: &mut W, sig: &syn::Signature, extra_indent: &str, types: &TypeResolver, generics: Option<&GenericTypes>, this_type: &str, to_c: bool) {
 358         let mut first_arg = true;
 359         let mut num_unused = 0;
 360         for inp in sig.inputs.iter() {
 361                 match inp {
 362                         syn::FnArg::Receiver(recv) => {
 363                                 if !recv.attrs.is_empty() || recv.reference.is_none() { unimplemented!(); }
 364                                 if to_c {
 365                                         write!(w, "self.this_arg").unwrap();
 366                                         first_arg = false;
 367                                 }
 368                         },
 369                         syn::FnArg::Typed(arg) => {
 370                                 if types.skip_arg(&*arg.ty, generics) {
 371                                         if !to_c {
 372                                                 if !first_arg {
 373                                                         write!(w, ", ").unwrap();
 374                                                 }
 375                                                 first_arg = false;
 376                                                 types.no_arg_to_rust(w, &*arg.ty, generics);
 377                                         }
 378                                         continue;
 379                                 }
 380                                 if !arg.attrs.is_empty() { unimplemented!(); }
 381                                 macro_rules! write_ident {
 382                                         ($ident: expr) => {
 383                                                 if !first_arg {
 384                                                         write!(w, ", ").unwrap();
 385                                                 }
 386                                                 first_arg = false;
 387                                                 if to_c {
 388                                                         types.write_to_c_conversion_inline_prefix(w, &*arg.ty, generics, false);
 389                                                         write!(w, "{}", $ident).unwrap();
 390                                                         types.write_to_c_conversion_inline_suffix(w, &*arg.ty, generics, false);
 391                                                 } else {
 392                                                         types.write_from_c_conversion_prefix(w, &*arg.ty, generics);
 393                                                         write!(w, "{}", $ident).unwrap();
 394                                                         types.write_from_c_conversion_suffix(w, &*arg.ty, generics);
 395                                                 }
 396                                         }
 397                                 }
 398                                 match &*arg.pat {
 399                                         syn::Pat::Ident(ident) => {
 400                                                 if !ident.attrs.is_empty() || ident.subpat.is_some() {
 401                                                         unimplemented!();
 402                                                 }
 403                                                 write_ident!(ident.ident);
 404                                         },
 405                                         syn::Pat::Wild(w) => {
 406                                                 if !w.attrs.is_empty() { unimplemented!(); }
 407                                                 write_ident!(format!("unused_{}", num_unused));
 408                                                 num_unused += 1;
 409                                         },
 410                                         _ => unimplemented!(),
 411                                 }
 412                         }
 413                 }
 414         }
 415         write!(w, ")").unwrap();
 416         match &sig.output {
 417                 syn::ReturnType::Type(_, rtype) => {
 418                         write!(w, ";\n\t{}", extra_indent).unwrap();
 419
 420                         let self_segs_iter = first_seg_self(&*rtype);
 421                         if to_c && first_seg_self(&*rtype).is_some() {
 422                                 // Assume rather blindly that we're returning an associated trait from a C fn call to a Rust trait object.
 423                                 write!(w, "ret").unwrap();
 424                         } else if !to_c && self_segs_iter.is_some() && self_segs_iter.unwrap().next().is_none() {
 425                                 // If we're returning "Self" (and not "Self::X"), just do it manually
 426                                 write!(w, "{} {{ inner: Box::into_raw(Box::new(ret)), is_owned: true }}", this_type).unwrap();
 427                         } else if to_c {
 428                                 let new_var = types.write_from_c_conversion_new_var(w, &syn::Ident::new("ret", Span::call_site()), rtype, generics);
 429                                 if new_var {
 430                                         write!(w, "\n\t{}", extra_indent).unwrap();
 431                                 }
 432                                 types.write_from_c_conversion_prefix(w, &*rtype, generics);
 433                                 write!(w, "ret").unwrap();
 434                                 types.write_from_c_conversion_suffix(w, &*rtype, generics);
 435                         } else {
 436                                 let ret_returned = if let syn::Type::Reference(_) = &**rtype { true } else { false };
 437                                 let new_var = types.write_to_c_conversion_new_var(w, &syn::Ident::new("ret", Span::call_site()), &rtype, generics, true);
 438                                 if new_var {
 439                                         write!(w, "\n\t{}", extra_indent).unwrap();
 440                                 }
 441                                 types.write_to_c_conversion_inline_prefix(w, &rtype, generics, true);
 442                                 write!(w, "{}ret", if ret_returned && !new_var { "*" } else { "" }).unwrap();
 443                                 types.write_to_c_conversion_inline_suffix(w, &rtype, generics, true);
 444                         }
 445                 }
 446                 _ => {},
 447         }
 448 }
 449
 450 /// Prints concrete generic parameters for a struct/trait/function, including the less-than and
 451 /// greater-than symbols, if any generic parameters are defined.
 452 pub fn maybe_write_generics<W: std::io::Write>(w: &mut W, generics: &syn::Generics, types: &TypeResolver, concrete_lifetimes: bool) {
 453         let mut gen_types = GenericTypes::new();
 454         assert!(gen_types.learn_generics(generics, types));
 455         if !generics.params.is_empty() {
 456                 write!(w, "<").unwrap();
 457                 for (idx, generic) in generics.params.iter().enumerate() {
 458                         match generic {
 459                                 syn::GenericParam::Type(type_param) => {
 460                                         let mut printed_param = false;
 461                                         for bound in type_param.bounds.iter() {
 462                                                 if let syn::TypeParamBound::Trait(trait_bound) = bound {
 463                                                         assert_simple_bound(&trait_bound);
 464                                                         write!(w, "{}{}", if idx != 0 { ", " } else { "" }, gen_types.maybe_resolve_ident(&type_param.ident).unwrap()).unwrap();
 465                                                         if printed_param {
 466                                                                 unimplemented!("Can't print generic params that have multiple non-lifetime bounds");
 467                                                         }
 468                                                         printed_param = true;
 469                                                 }
 470                                         }
 471                                 },
 472                                 syn::GenericParam::Lifetime(lt) => {
 473                                         if concrete_lifetimes {
 474                                                 write!(w, "'static").unwrap();
 475                                         } else {
 476                                                 write!(w, "{}'{}", if idx != 0 { ", " } else { "" }, lt.lifetime.ident).unwrap();
 477                                         }
 478                                 },
 479                                 _ => unimplemented!(),
 480                         }
 481                 }
 482                 write!(w, ">").unwrap();
 483         }
 484 }
 485
 486