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

   1 // This file is Copyright its original authors, visible in version control
   2 // history.
   3 //
   4 // This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE>
   5 // or the MIT license <LICENSE-MIT>, at your option.
   6 // You may not use this file except in accordance with one or both of these
   7 // licenses.
   8
   9 //! Printing logic for basic blocks of Rust-mapped code - parts of functions and declarations but
  10 //! not the full mapping logic.
  11
  12 use std::fs::File;
  13 use std::io::Write;
  14
  15 use proc_macro2::TokenTree;
  16 use quote::format_ident;
  17
  18 use crate::types::*;
  19
  20 /// Writes out a C++ wrapper class for the given type, which contains various utilities to access
  21 /// the underlying C-mapped type safely avoiding some common memory management issues by handling
  22 /// resource-freeing and prevending accidental raw copies.
  23 pub fn write_cpp_wrapper(cpp_header_file: &mut File, ty: &str, has_destructor: bool, trait_methods: Option<Vec<(String, String)>>) {
  24         writeln!(cpp_header_file, "class {} {{", ty).unwrap();
  25         writeln!(cpp_header_file, "private:").unwrap();
  26         writeln!(cpp_header_file, "\tLDK{} self;", ty).unwrap();
  27         writeln!(cpp_header_file, "public:").unwrap();
  28         writeln!(cpp_header_file, "\t{}(const {}&) = delete;", ty, ty).unwrap();
  29         writeln!(cpp_header_file, "\t{}({}&& o) : self(o.self) {{ memset(&o, 0, sizeof({})); }}", ty, ty, ty).unwrap();
  30         writeln!(cpp_header_file, "\t{}(LDK{}&& m_self) : self(m_self) {{ memset(&m_self, 0, sizeof(LDK{})); }}", ty, ty, ty).unwrap();
  31         writeln!(cpp_header_file, "\toperator LDK{}() && {{ LDK{} res = self; memset(&self, 0, sizeof(LDK{})); return res; }}", ty, ty, ty).unwrap();
  32         if has_destructor {
  33                 writeln!(cpp_header_file, "\t~{}() {{ {}_free(self); }}", ty, ty).unwrap();
  34                 writeln!(cpp_header_file, "\t{}& operator=({}&& o) {{ {}_free(self); self = o.self; memset(&o, 0, sizeof({})); return *this; }}", ty, ty, ty, ty).unwrap();
  35         } else {
  36                 writeln!(cpp_header_file, "\t{}& operator=({}&& o) {{ self = o.self; memset(&o, 0, sizeof({})); return *this; }}", ty, ty, ty).unwrap();
  37         }
  38         writeln!(cpp_header_file, "\tLDK{}* operator &() {{ return &self; }}", ty).unwrap();
  39         writeln!(cpp_header_file, "\tLDK{}* operator ->() {{ return &self; }}", ty).unwrap();
  40         writeln!(cpp_header_file, "\tconst LDK{}* operator &() const {{ return &self; }}", ty).unwrap();
  41         writeln!(cpp_header_file, "\tconst LDK{}* operator ->() const {{ return &self; }}", ty).unwrap();
  42         if let Some(methods) = trait_methods {
  43                 for (meth_name, meth_docs) in methods {
  44                         cpp_header_file.write_all(meth_docs.as_bytes()).unwrap();
  45                         // Note that we have zero logic to print C/C__ code for a given function. Instead, we
  46                         // simply use sed to replace the following in genbindings.sh
  47                         writeln!(cpp_header_file, "XXX {} {}", ty, meth_name).unwrap();
  48                 }
  49         }
  50         writeln!(cpp_header_file, "}};").unwrap();
  51 }
  52
  53 /// Writes out a C-callable concrete Result<A, B> struct and utility methods
  54 pub fn write_result_block<W: std::io::Write>(w: &mut W, mangled_container: &str, ok_type: &str, err_type: &str, clonable: bool) {
  55         writeln!(w, "#[repr(C)]").unwrap();
  56         writeln!(w, "/// The contents of {}", mangled_container).unwrap();
  57         writeln!(w, "pub union {}Ptr {{", mangled_container).unwrap();
  58         if ok_type != "()" {
  59                 writeln!(w, "\t/// A pointer to the contents in the success state.").unwrap();
  60                 writeln!(w, "\t/// Reading from this pointer when `result_ok` is not set is undefined.").unwrap();
  61                 writeln!(w, "\tpub result: *mut {},", ok_type).unwrap();
  62         } else {
  63                 writeln!(w, "\t/// Note that this value is always NULL, as there are no contents in the OK variant").unwrap();
  64                 writeln!(w, "\tpub result: *mut core::ffi::c_void,").unwrap();
  65         }
  66         if err_type != "()" {
  67                 writeln!(w, "\t/// A pointer to the contents in the error state.").unwrap();
  68                 writeln!(w, "\t/// Reading from this pointer when `result_ok` is set is undefined.").unwrap();
  69                 writeln!(w, "\tpub err: *mut {},", err_type).unwrap();
  70         } else {
  71                 writeln!(w, "\t/// Note that this value is always NULL, as there are no contents in the Err variant").unwrap();
  72                 writeln!(w, "\tpub err: *mut core::ffi::c_void,").unwrap();
  73         }
  74         writeln!(w, "}}").unwrap();
  75         writeln!(w, "#[repr(C)]").unwrap();
  76         writeln!(w, "/// A {} represents the result of a fallible operation,", mangled_container).unwrap();
  77         writeln!(w, "/// containing a {} on success and a {} on failure.", ok_type, err_type).unwrap();
  78         writeln!(w, "/// `result_ok` indicates the overall state, and the contents are provided via `contents`.").unwrap();
  79         writeln!(w, "pub struct {} {{", mangled_container).unwrap();
  80         writeln!(w, "\t/// The contents of this {}, accessible via either", mangled_container).unwrap();
  81         writeln!(w, "\t/// `err` or `result` depending on the state of `result_ok`.").unwrap();
  82         writeln!(w, "\tpub contents: {}Ptr,", mangled_container).unwrap();
  83         writeln!(w, "\t/// Whether this {} represents a success state.", mangled_container).unwrap();
  84         writeln!(w, "\tpub result_ok: bool,").unwrap();
  85         writeln!(w, "}}").unwrap();
  86
  87         writeln!(w, "#[no_mangle]").unwrap();
  88         if ok_type != "()" {
  89                 writeln!(w, "/// Creates a new {} in the success state.", mangled_container).unwrap();
  90                 writeln!(w, "pub extern \"C\" fn {}_ok(o: {}) -> {} {{", mangled_container, ok_type, mangled_container).unwrap();
  91         } else {
  92                 writeln!(w, "/// Creates a new {} in the success state.", mangled_container).unwrap();
  93                 writeln!(w, "pub extern \"C\" fn {}_ok() -> {} {{", mangled_container, mangled_container).unwrap();
  94         }
  95         writeln!(w, "\t{} {{", mangled_container).unwrap();
  96         writeln!(w, "\t\tcontents: {}Ptr {{", mangled_container).unwrap();
  97         if ok_type != "()" {
  98                 writeln!(w, "\t\t\tresult: Box::into_raw(Box::new(o)),").unwrap();
  99         } else {
 100                 writeln!(w, "\t\t\tresult: core::ptr::null_mut(),").unwrap();
 101         }
 102         writeln!(w, "\t\t}},").unwrap();
 103         writeln!(w, "\t\tresult_ok: true,").unwrap();
 104         writeln!(w, "\t}}").unwrap();
 105         writeln!(w, "}}").unwrap();
 106
 107         writeln!(w, "#[no_mangle]").unwrap();
 108         if err_type != "()" {
 109                 writeln!(w, "/// Creates a new {} in the error state.", mangled_container).unwrap();
 110                 writeln!(w, "pub extern \"C\" fn {}_err(e: {}) -> {} {{", mangled_container, err_type, mangled_container).unwrap();
 111         } else {
 112                 writeln!(w, "/// Creates a new {} in the error state.", mangled_container).unwrap();
 113                 writeln!(w, "pub extern \"C\" fn {}_err() -> {} {{", mangled_container, mangled_container).unwrap();
 114         }
 115         writeln!(w, "\t{} {{", mangled_container).unwrap();
 116         writeln!(w, "\t\tcontents: {}Ptr {{", mangled_container).unwrap();
 117         if err_type != "()" {
 118                 writeln!(w, "\t\t\terr: Box::into_raw(Box::new(e)),").unwrap();
 119         } else {
 120                 writeln!(w, "\t\t\terr: core::ptr::null_mut(),").unwrap();
 121         }
 122         writeln!(w, "\t\t}},").unwrap();
 123         writeln!(w, "\t\tresult_ok: false,").unwrap();
 124         writeln!(w, "\t}}").unwrap();
 125         writeln!(w, "}}").unwrap();
 126
 127         writeln!(w, "/// Checks if the given object is currently in the success state").unwrap();
 128         writeln!(w, "#[no_mangle]").unwrap();
 129         writeln!(w, "pub extern \"C\" fn {}_is_ok(o: &{}) -> bool {{", mangled_container, mangled_container).unwrap();
 130         writeln!(w, "\to.result_ok").unwrap();
 131         writeln!(w, "}}").unwrap();
 132
 133         writeln!(w, "#[no_mangle]").unwrap();
 134         writeln!(w, "/// Frees any resources used by the {}.", mangled_container).unwrap();
 135         writeln!(w, "pub extern \"C\" fn {}_free(_res: {}) {{ }}", mangled_container, mangled_container).unwrap();
 136         writeln!(w, "impl Drop for {} {{", mangled_container).unwrap();
 137         writeln!(w, "\tfn drop(&mut self) {{").unwrap();
 138         writeln!(w, "\t\tif self.result_ok {{").unwrap();
 139         if ok_type != "()" {
 140                 writeln!(w, "\t\t\tif unsafe {{ !(self.contents.result as *mut ()).is_null() }} {{").unwrap();
 141                 writeln!(w, "\t\t\t\tlet _ = unsafe {{ Box::from_raw(self.contents.result) }};").unwrap();
 142                 writeln!(w, "\t\t\t}}").unwrap();
 143         }
 144         writeln!(w, "\t\t}} else {{").unwrap();
 145         if err_type != "()" {
 146                 writeln!(w, "\t\t\tif unsafe {{ !(self.contents.err as *mut ()).is_null() }} {{").unwrap();
 147                 writeln!(w, "\t\t\t\tlet _ = unsafe {{ Box::from_raw(self.contents.err) }};").unwrap();
 148                 writeln!(w, "\t\t\t}}").unwrap();
 149         }
 150         writeln!(w, "\t\t}}").unwrap();
 151         writeln!(w, "\t}}").unwrap();
 152         writeln!(w, "}}").unwrap();
 153
 154         writeln!(w, "impl From<crate::c_types::CResultTempl<{}, {}>> for {} {{", ok_type, err_type, mangled_container).unwrap();
 155         writeln!(w, "\tfn from(mut o: crate::c_types::CResultTempl<{}, {}>) -> Self {{", ok_type, err_type).unwrap();
 156         writeln!(w, "\t\tlet contents = if o.result_ok {{").unwrap();
 157         if ok_type != "()" {
 158                 writeln!(w, "\t\t\tlet result = unsafe {{ o.contents.result }};").unwrap();
 159                 writeln!(w, "\t\t\tunsafe {{ o.contents.result = core::ptr::null_mut() }};").unwrap();
 160                 writeln!(w, "\t\t\t{}Ptr {{ result }}", mangled_container).unwrap();
 161         } else {
 162                 writeln!(w, "\t\t\tlet _ = unsafe {{ Box::from_raw(o.contents.result) }};").unwrap();
 163                 writeln!(w, "\t\t\to.contents.result = core::ptr::null_mut();").unwrap();
 164                 writeln!(w, "\t\t\t{}Ptr {{ result: core::ptr::null_mut() }}", mangled_container).unwrap();
 165         }
 166         writeln!(w, "\t\t}} else {{").unwrap();
 167         if err_type != "()" {
 168                 writeln!(w, "\t\t\tlet err = unsafe {{ o.contents.err }};").unwrap();
 169                 writeln!(w, "\t\t\tunsafe {{ o.contents.err = core::ptr::null_mut(); }}").unwrap();
 170                 writeln!(w, "\t\t\t{}Ptr {{ err }}", mangled_container).unwrap();
 171         } else {
 172                 writeln!(w, "\t\t\tlet _ = unsafe {{ Box::from_raw(o.contents.err) }};").unwrap();
 173                 writeln!(w, "\t\t\to.contents.err = core::ptr::null_mut();").unwrap();
 174                 writeln!(w, "\t\t\t{}Ptr {{ err: core::ptr::null_mut() }}", mangled_container).unwrap();
 175         }
 176         writeln!(w, "\t\t}};").unwrap();
 177         writeln!(w, "\t\tSelf {{").unwrap();
 178         writeln!(w, "\t\t\tcontents,").unwrap();
 179         writeln!(w, "\t\t\tresult_ok: o.result_ok,").unwrap();
 180         writeln!(w, "\t\t}}").unwrap();
 181         writeln!(w, "\t}}").unwrap();
 182         writeln!(w, "}}").unwrap();
 183
 184         if clonable {
 185                 writeln!(w, "impl Clone for {} {{", mangled_container).unwrap();
 186                 writeln!(w, "\tfn clone(&self) -> Self {{").unwrap();
 187                 writeln!(w, "\t\tif self.result_ok {{").unwrap();
 188                 writeln!(w, "\t\t\tSelf {{ result_ok: true, contents: {}Ptr {{", mangled_container).unwrap();
 189                 if ok_type != "()" {
 190                         writeln!(w, "\t\t\t\tresult: Box::into_raw(Box::new(<{}>::clone(unsafe {{ &*self.contents.result }})))", ok_type).unwrap();
 191                 } else {
 192                         writeln!(w, "\t\t\t\tresult: core::ptr::null_mut()").unwrap();
 193                 }
 194                 writeln!(w, "\t\t\t}} }}").unwrap();
 195                 writeln!(w, "\t\t}} else {{").unwrap();
 196                 writeln!(w, "\t\t\tSelf {{ result_ok: false, contents: {}Ptr {{", mangled_container).unwrap();
 197                 if err_type != "()" {
 198                         writeln!(w, "\t\t\t\terr: Box::into_raw(Box::new(<{}>::clone(unsafe {{ &*self.contents.err }})))", err_type).unwrap();
 199                 } else {
 200                         writeln!(w, "\t\t\t\terr: core::ptr::null_mut()").unwrap();
 201                 }
 202                 writeln!(w, "\t\t\t}} }}").unwrap();
 203                 writeln!(w, "\t\t}}").unwrap();
 204                 writeln!(w, "\t}}").unwrap();
 205                 writeln!(w, "}}").unwrap();
 206                 writeln!(w, "#[no_mangle]").unwrap();
 207                 writeln!(w, "/// Creates a new {} which has the same data as `orig`", mangled_container).unwrap();
 208                 writeln!(w, "/// but with all dynamically-allocated buffers duplicated in new buffers.").unwrap();
 209                 writeln!(w, "pub extern \"C\" fn {}_clone(orig: &{}) -> {} {{ Clone::clone(&orig) }}", mangled_container, mangled_container, mangled_container).unwrap();
 210         }
 211 }
 212
 213 /// Writes out a C-callable concrete Vec<A> struct and utility methods
 214 pub fn write_vec_block<W: std::io::Write>(w: &mut W, mangled_container: &str, inner_type: &str, clonable: bool) {
 215         writeln!(w, "#[repr(C)]").unwrap();
 216         writeln!(w, "/// A dynamically-allocated array of {}s of arbitrary size.", inner_type).unwrap();
 217         writeln!(w, "/// This corresponds to std::vector in C++").unwrap();
 218         writeln!(w, "pub struct {} {{", mangled_container).unwrap();
 219         writeln!(w, "\t/// The elements in the array.").unwrap();
 220         writeln!(w, "\t/// If datalen is non-0 this must be a valid, non-NULL pointer allocated by malloc().").unwrap();
 221         writeln!(w, "\tpub data: *mut {},", inner_type).unwrap();
 222         writeln!(w, "\t/// The number of elements pointed to by `data`.").unwrap();
 223         writeln!(w, "\tpub datalen: usize").unwrap();
 224         writeln!(w, "}}").unwrap();
 225
 226         writeln!(w, "impl {} {{", mangled_container).unwrap();
 227         writeln!(w, "\t#[allow(unused)] pub(crate) fn into_rust(&mut self) -> Vec<{}> {{", inner_type).unwrap();
 228         writeln!(w, "\t\tif self.datalen == 0 {{ return Vec::new(); }}").unwrap();
 229         writeln!(w, "\t\tlet ret = unsafe {{ Box::from_raw(core::slice::from_raw_parts_mut(self.data, self.datalen)) }}.into();").unwrap();
 230         writeln!(w, "\t\tself.data = core::ptr::null_mut();").unwrap();
 231         writeln!(w, "\t\tself.datalen = 0;").unwrap();
 232         writeln!(w, "\t\tret").unwrap();
 233         writeln!(w, "\t}}").unwrap();
 234         writeln!(w, "\t#[allow(unused)] pub(crate) fn as_slice(&self) -> &[{}] {{", inner_type).unwrap();
 235         writeln!(w, "\t\tunsafe {{ core::slice::from_raw_parts_mut(self.data, self.datalen) }}").unwrap();
 236         writeln!(w, "\t}}").unwrap();
 237         writeln!(w, "}}").unwrap();
 238
 239         writeln!(w, "impl From<Vec<{}>> for {} {{", inner_type, mangled_container).unwrap();
 240         writeln!(w, "\tfn from(v: Vec<{}>) -> Self {{", inner_type).unwrap();
 241         writeln!(w, "\t\tlet datalen = v.len();").unwrap();
 242         writeln!(w, "\t\tlet data = Box::into_raw(v.into_boxed_slice());").unwrap();
 243         writeln!(w, "\t\tSelf {{ datalen, data: unsafe {{ (*data).as_mut_ptr() }} }}").unwrap();
 244         writeln!(w, "\t}}").unwrap();
 245         writeln!(w, "}}").unwrap();
 246
 247         writeln!(w, "#[no_mangle]").unwrap();
 248         writeln!(w, "/// Frees the buffer pointed to by `data` if `datalen` is non-0.").unwrap();
 249         writeln!(w, "pub extern \"C\" fn {}_free(_res: {}) {{ }}", mangled_container, mangled_container).unwrap();
 250         writeln!(w, "impl Drop for {} {{", mangled_container).unwrap();
 251         writeln!(w, "\tfn drop(&mut self) {{").unwrap();
 252         writeln!(w, "\t\tif self.datalen == 0 {{ return; }}").unwrap();
 253         writeln!(w, "\t\tunsafe {{ Box::from_raw(core::slice::from_raw_parts_mut(self.data, self.datalen)) }};").unwrap();
 254         writeln!(w, "\t}}").unwrap();
 255         writeln!(w, "}}").unwrap();
 256         if clonable {
 257                 writeln!(w, "impl Clone for {} {{", mangled_container).unwrap();
 258                 writeln!(w, "\tfn clone(&self) -> Self {{").unwrap();
 259                 writeln!(w, "\t\tlet mut res = Vec::new();").unwrap();
 260                 writeln!(w, "\t\tif self.datalen == 0 {{ return Self::from(res); }}").unwrap();
 261                 writeln!(w, "\t\tres.extend_from_slice(unsafe {{ core::slice::from_raw_parts_mut(self.data, self.datalen) }});").unwrap();
 262                 writeln!(w, "\t\tSelf::from(res)").unwrap();
 263                 writeln!(w, "\t}}").unwrap();
 264                 writeln!(w, "}}").unwrap();
 265         }
 266 }
 267
 268 /// Writes out a C-callable concrete (A, B, ...) struct and utility methods
 269 pub fn write_tuple_block<W: std::io::Write>(w: &mut W, mangled_container: &str, types: &[String], clonable: bool) {
 270         writeln!(w, "#[repr(C)]").unwrap();
 271         writeln!(w, "/// A tuple of {} elements. See the individual fields for the types contained.", types.len()).unwrap();
 272         writeln!(w, "pub struct {} {{", mangled_container).unwrap();
 273         for (idx, ty) in types.iter().enumerate() {
 274                 writeln!(w, "\t/// The element at position {}", idx).unwrap();
 275                 if ty.starts_with("&'static ") {
 276                         writeln!(w, "\tpub {}: {},", ('a' as u8 + idx as u8) as char, &ty[9..]).unwrap();
 277                 } else {
 278                         writeln!(w, "\tpub {}: {},", ('a' as u8 + idx as u8) as char, ty).unwrap();
 279                 }
 280         }
 281         writeln!(w, "}}").unwrap();
 282
 283         let mut tuple_str = "(".to_owned();
 284         for (idx, ty) in types.iter().enumerate() {
 285                 if idx != 0 { tuple_str += ", "; }
 286                 if ty.starts_with("&'static ") {
 287                         tuple_str += &ty[9..];
 288                 } else {
 289                         tuple_str += ty;
 290                 }
 291         }
 292         tuple_str += ")";
 293
 294         writeln!(w, "impl From<{}> for {} {{", tuple_str, mangled_container).unwrap();
 295         writeln!(w, "\tfn from (tup: {}) -> Self {{", tuple_str).unwrap();
 296         writeln!(w, "\t\tSelf {{").unwrap();
 297         for idx in 0..types.len() {
 298                 writeln!(w, "\t\t\t{}: tup.{},", ('a' as u8 + idx as u8) as char, idx).unwrap();
 299         }
 300         writeln!(w, "\t\t}}").unwrap();
 301         writeln!(w, "\t}}").unwrap();
 302         writeln!(w, "}}").unwrap();
 303         writeln!(w, "impl {} {{", mangled_container).unwrap();
 304         writeln!(w, "\t#[allow(unused)] pub(crate) fn to_rust(mut self) -> {} {{", tuple_str).unwrap();
 305         write!(w, "\t\t(").unwrap();
 306         for idx in 0..types.len() {
 307                 write!(w, "{}self.{}", if idx != 0 {", "} else {""}, ('a' as u8 + idx as u8) as char).unwrap();
 308         }
 309         writeln!(w, ")").unwrap();
 310         writeln!(w, "\t}}").unwrap();
 311         writeln!(w, "}}").unwrap();
 312
 313         if clonable {
 314                 writeln!(w, "impl Clone for {} {{", mangled_container).unwrap();
 315                 writeln!(w, "\tfn clone(&self) -> Self {{").unwrap();
 316                 writeln!(w, "\t\tSelf {{").unwrap();
 317                 for (idx, ty) in types.iter().enumerate() {
 318                         if ty.starts_with("&'static ") {
 319                                 // Assume blindly the type is opaque. If its not we'll fail to build.
 320                                 // Really we should never have derived structs with a reference type.
 321                                 write!(w, "\t\t\t{}: {} {{ inner: self.{}.inner, is_owned: false}},", ('a' as u8 + idx as u8) as char, &ty[9..], ('a' as u8 + idx as u8) as char).unwrap();
 322                         } else{
 323                                 writeln!(w, "\t\t\t{}: Clone::clone(&self.{}),", ('a' as u8 + idx as u8) as char, ('a' as u8 + idx as u8) as char).unwrap();
 324                         }
 325                 }
 326                 writeln!(w, "\t\t}}").unwrap();
 327                 writeln!(w, "\t}}").unwrap();
 328                 writeln!(w, "}}").unwrap();
 329                 writeln!(w, "#[no_mangle]").unwrap();
 330                 writeln!(w, "/// Creates a new tuple which has the same data as `orig`").unwrap();
 331                 writeln!(w, "/// but with all dynamically-allocated buffers duplicated in new buffers.").unwrap();
 332                 writeln!(w, "pub extern \"C\" fn {}_clone(orig: &{}) -> {} {{ Clone::clone(&orig) }}", mangled_container, mangled_container, mangled_container).unwrap();
 333         }
 334
 335         writeln!(w, "/// Creates a new {} from the contained elements.", mangled_container).unwrap();
 336         write!(w, "#[no_mangle]\npub extern \"C\" fn {}_new(", mangled_container).unwrap();
 337         for (idx, gen) in types.iter().enumerate() {
 338                 write!(w, "{}{}: ", if idx != 0 { ", " } else { "" }, ('a' as u8 + idx as u8) as char).unwrap();
 339                 //if !self.write_c_type_intern(&mut created_container, gen, generics, false, false, false) { return false; }
 340                 write!(w, "{}", gen).unwrap();
 341         }
 342         writeln!(w, ") -> {} {{", mangled_container).unwrap();
 343         write!(w, "\t{} {{ ", mangled_container).unwrap();
 344         for (idx, ty) in types.iter().enumerate() {
 345                 if ty.starts_with("&'static ") {
 346                         // Assume blindly the type is opaque. If its not we'll fail to build.
 347                         // Really we should never have derived structs with a reference type.
 348                         write!(w, "{}: {} {{ inner: {}.inner, is_owned: false}}, ", ('a' as u8 + idx as u8) as char, &ty[9..], ('a' as u8 + idx as u8) as char).unwrap();
 349                 } else {
 350                         write!(w, "{}, ", ('a' as u8 + idx as u8) as char).unwrap();
 351                 }
 352         }
 353         writeln!(w, "}}\n}}\n").unwrap();
 354
 355         writeln!(w, "#[no_mangle]").unwrap();
 356         writeln!(w, "/// Frees any resources used by the {}.", mangled_container).unwrap();
 357         writeln!(w, "pub extern \"C\" fn {}_free(_res: {}) {{ }}", mangled_container, mangled_container).unwrap();
 358 }
 359
 360 /// Writes out a C-callable concrete Option<A> struct and utility methods
 361 pub fn write_option_block<W: std::io::Write>(w: &mut W, mangled_container: &str, inner_type: &str, clonable: bool) {
 362         writeln!(w, "#[repr(C)]").unwrap();
 363         if clonable {
 364                 writeln!(w, "#[derive(Clone)]").unwrap();
 365         }
 366         writeln!(w, "/// An enum which can either contain a {} or not", inner_type).unwrap();
 367         writeln!(w, "pub enum {} {{", mangled_container).unwrap();
 368         writeln!(w, "\t/// When we're in this state, this {} contains a {}", mangled_container, inner_type).unwrap();
 369         if inner_type != "" {
 370                 writeln!(w, "\tSome({}),", inner_type).unwrap();
 371         } else {
 372                 writeln!(w, "\tSome,").unwrap();
 373         }
 374         writeln!(w, "\t/// When we're in this state, this {} contains nothing", mangled_container).unwrap();
 375         writeln!(w, "\tNone").unwrap();
 376         writeln!(w, "}}").unwrap();
 377
 378         writeln!(w, "impl {} {{", mangled_container).unwrap();
 379         writeln!(w, "\t#[allow(unused)] pub(crate) fn is_some(&self) -> bool {{").unwrap();
 380         writeln!(w, "\t\tif let Self::None = self {{ false }} else {{ true }}").unwrap();
 381         writeln!(w, "\t}}").unwrap();
 382         writeln!(w, "\t#[allow(unused)] pub(crate) fn is_none(&self) -> bool {{").unwrap();
 383         writeln!(w, "\t\t!self.is_some()").unwrap();
 384         writeln!(w, "\t}}").unwrap();
 385         if inner_type != "" {
 386                 writeln!(w, "\t#[allow(unused)] pub(crate) fn take(mut self) -> {} {{", inner_type).unwrap();
 387                 writeln!(w, "\t\tif let Self::Some(v) = self {{ v }} else {{ unreachable!() }}").unwrap();
 388                 writeln!(w, "\t}}").unwrap();
 389         }
 390         writeln!(w, "}}").unwrap();
 391
 392         writeln!(w, "#[no_mangle]").unwrap();
 393         writeln!(w, "/// Constructs a new {} containing a {}", mangled_container, inner_type).unwrap();
 394         if inner_type != "" {
 395                 writeln!(w, "pub extern \"C\" fn {}_some(o: {}) -> {} {{", mangled_container, inner_type, mangled_container).unwrap();
 396                 writeln!(w, "\t{}::Some(o)", mangled_container).unwrap();
 397         } else {
 398                 writeln!(w, "pub extern \"C\" fn {}_some() -> {} {{", mangled_container, mangled_container).unwrap();
 399                 writeln!(w, "\t{}::Some", mangled_container).unwrap();
 400         }
 401         writeln!(w, "}}").unwrap();
 402
 403         writeln!(w, "#[no_mangle]").unwrap();
 404         writeln!(w, "/// Constructs a new {} containing nothing", mangled_container).unwrap();
 405         writeln!(w, "pub extern \"C\" fn {}_none() -> {} {{", mangled_container, mangled_container).unwrap();
 406         writeln!(w, "\t{}::None", mangled_container).unwrap();
 407         writeln!(w, "}}").unwrap();
 408
 409         writeln!(w, "#[no_mangle]").unwrap();
 410         writeln!(w, "/// Frees any resources associated with the {}, if we are in the Some state", inner_type).unwrap();
 411         writeln!(w, "pub extern \"C\" fn {}_free(_res: {}) {{ }}", mangled_container, mangled_container).unwrap();
 412         if clonable {
 413                 writeln!(w, "#[no_mangle]").unwrap();
 414                 writeln!(w, "/// Creates a new {} which has the same data as `orig`", mangled_container).unwrap();
 415                 writeln!(w, "/// but with all dynamically-allocated buffers duplicated in new buffers.").unwrap();
 416                 writeln!(w, "pub extern \"C\" fn {}_clone(orig: &{}) -> {} {{ Clone::clone(&orig) }}", mangled_container, mangled_container, mangled_container).unwrap();
 417         }
 418 }
 419
 420 /// Prints the docs from a given attribute list unless its tagged no export
 421 pub fn writeln_fn_docs<'a, W: std::io::Write, I>(w: &mut W, attrs: &[syn::Attribute], prefix: &str, types: &mut TypeResolver, generics: Option<&GenericTypes>, args: I, ret: &syn::ReturnType) where I: Iterator<Item = &'a syn::FnArg> {
 422         writeln_docs_impl(w, attrs, prefix, Some((types, generics,
 423                 args.filter_map(|arg| if let syn::FnArg::Typed(ty) = arg {
 424                                 if let syn::Pat::Ident(id) = &*ty.pat {
 425                                         Some((id.ident.to_string(), &*ty.ty))
 426                                 } else { unimplemented!() }
 427                         } else { None }),
 428                 if let syn::ReturnType::Type(_, ty) = ret { Some(&**ty) } else { None },
 429                 None
 430         )));
 431 }
 432
 433 /// Prints the docs from a given attribute list unless its tagged no export
 434 pub fn writeln_docs<W: std::io::Write>(w: &mut W, attrs: &[syn::Attribute], prefix: &str) {
 435         writeln_docs_impl(w, attrs, prefix, None::<(_, _, std::vec::Drain<'_, (String, &syn::Type)>, _, _)>);
 436 }
 437
 438 pub fn writeln_arg_docs<'a, W: std::io::Write, I>(w: &mut W, attrs: &[syn::Attribute], prefix: &str, types: &mut TypeResolver, generics: Option<&GenericTypes>, args: I, ret: Option<&syn::Type>) where I: Iterator<Item = (String, &'a syn::Type)> {
 439         writeln_docs_impl(w, attrs, prefix, Some((types, generics, args, ret, None)))
 440 }
 441
 442 pub fn writeln_field_docs<W: std::io::Write>(w: &mut W, attrs: &[syn::Attribute], prefix: &str, types: &mut TypeResolver, generics: Option<&GenericTypes>, field: &syn::Type) {
 443         writeln_docs_impl(w, attrs, prefix, Some((types, generics, vec![].drain(..), None, Some(field))))
 444 }
 445
 446 /// Prints the docs from a given attribute list unless its tagged no export
 447 fn writeln_docs_impl<'a, W: std::io::Write, I>(w: &mut W, attrs: &[syn::Attribute], prefix: &str, method_args_ret: Option<(&mut TypeResolver, Option<&GenericTypes>, I, Option<&syn::Type>, Option<&syn::Type>)>) where I: Iterator<Item = (String, &'a syn::Type)> {
 448         for attr in attrs.iter() {
 449                 let tokens_clone = attr.tokens.clone();
 450                 let mut token_iter = tokens_clone.into_iter();
 451                 if let Some(token) = token_iter.next() {
 452                         match token {
 453                                 TokenTree::Punct(c) if c.as_char() == '=' => {
 454                                         // syn gets '=' from '///' or '//!' as it is syntax for #[doc = ""]
 455                                 },
 456                                 TokenTree::Group(_) => continue, // eg #[derive()]
 457                                 _ => unimplemented!(),
 458                         }
 459                 } else { continue; }
 460                 match attr.style {
 461                         syn::AttrStyle::Inner(_) => {
 462                                 match token_iter.next().unwrap() {
 463                                         TokenTree::Literal(lit) => {
 464                                                 // Drop the first and last chars from lit as they are always "
 465                                                 let doc = format!("{}", lit);
 466                                                 writeln!(w, "{}//!{}", prefix, &doc[1..doc.len() - 1]).unwrap();
 467                                         },
 468                                         _ => unimplemented!(),
 469                                 }
 470                         },
 471                         syn::AttrStyle::Outer => {
 472                                 match token_iter.next().unwrap() {
 473                                         TokenTree::Literal(lit) => {
 474                                                 // Drop the first and last chars from lit as they are always "
 475                                                 let doc = format!("{}", lit);
 476                                                 writeln!(w, "{}///{}", prefix, &doc[1..doc.len() - 1]).unwrap();
 477                                         },
 478                                         _ => unimplemented!(),
 479                                 }
 480                         },
 481                 }
 482         }
 483         if let Some((types, generics, inp, outp, field)) = method_args_ret {
 484                 let mut nullable_found = false;
 485                 for (name, inp) in inp {
 486                         if types.skip_arg(inp, generics) { continue; }
 487                         if if let syn::Type::Reference(syn::TypeReference { elem, .. }) = inp {
 488                                 if let syn::Type::Path(syn::TypePath { ref path, .. }) = &**elem {
 489                                         types.is_path_transparent_container(path, generics, true)
 490                                 } else { false }
 491                         } else if let syn::Type::Path(syn::TypePath { ref path, .. }) = inp {
 492                                 types.is_path_transparent_container(path, generics, true)
 493                         } else { false } {
 494                                 // Note downstream clients match this text exactly so any changes may require
 495                                 // changes in the Java and Swift bindings, at least.
 496                                 if !nullable_found { writeln!(w, "{}///", prefix).unwrap(); }
 497                                 nullable_found = true;
 498                                 writeln!(w, "{}/// Note that {} (or a relevant inner pointer) may be NULL or all-0s to represent None", prefix, name).unwrap();
 499                         }
 500                 }
 501                 if if let Some(syn::Type::Reference(syn::TypeReference { elem, .. })) = outp {
 502                         if let syn::Type::Path(syn::TypePath { ref path, .. }) = &**elem {
 503                                 types.is_path_transparent_container(path, generics, true)
 504                         } else { false }
 505                 } else if let Some(syn::Type::Path(syn::TypePath { ref path, .. })) = outp {
 506                         types.is_path_transparent_container(path, generics, true)
 507                 } else { false } {
 508                         // Note downstream clients match this text exactly so any changes may require
 509                         // changes in the Java and Swift bindings, at least.
 510                         if !nullable_found { writeln!(w, "{}///", prefix).unwrap(); }
 511                         nullable_found = true;
 512                         writeln!(w, "{}/// Note that the return value (or a relevant inner pointer) may be NULL or all-0s to represent None", prefix).unwrap();
 513                 }
 514                 if if let Some(syn::Type::Reference(syn::TypeReference { elem, .. })) = field {
 515                         if let syn::Type::Path(syn::TypePath { ref path, .. }) = &**elem {
 516                                 types.is_path_transparent_container(path, generics, true)
 517                         } else { false }
 518                 } else if let Some(syn::Type::Path(syn::TypePath { ref path, .. })) = field {
 519                         types.is_path_transparent_container(path, generics, true)
 520                 } else { false } {
 521                         // Note downstream clients match this text exactly so any changes may require
 522                         // changes in the Java and Swift bindings, at least.
 523                         if !nullable_found { writeln!(w, "{}///", prefix).unwrap(); }
 524                         writeln!(w, "{}/// Note that this (or a relevant inner pointer) may be NULL or all-0s to represent None", prefix).unwrap();
 525                 }
 526         }
 527
 528 }
 529
 530 /// Print the parameters in a method declaration, starting after the open parenthesis, through and
 531 /// including the closing parenthesis and return value, but not including the open bracket or any
 532 /// trailing semicolons.
 533 ///
 534 /// Usable both for a function definition and declaration.
 535 ///
 536 /// this_param is used when returning Self or accepting a self parameter, and should be the
 537 /// concrete, mapped type.
 538 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) {
 539         if sig.constness.is_some() || sig.asyncness.is_some() || sig.unsafety.is_some() ||
 540                         sig.abi.is_some() || sig.variadic.is_some() {
 541                 unimplemented!();
 542         }
 543         if sig.generics.lt_token.is_some() {
 544                 for generic in sig.generics.params.iter() {
 545                         match generic {
 546                                 syn::GenericParam::Type(_)|syn::GenericParam::Lifetime(_) => {
 547                                         // We ignore these, if they're not on skipped args, we'll blow up
 548                                         // later, and lifetimes we just hope the C client enforces.
 549                                 },
 550                                 _ => unimplemented!(),
 551                         }
 552                 }
 553         }
 554
 555         let mut first_arg = true;
 556         let mut num_unused = 0;
 557         for inp in sig.inputs.iter() {
 558                 match inp {
 559                         syn::FnArg::Receiver(recv) => {
 560                                 if !recv.attrs.is_empty() { unimplemented!(); }
 561                                 write!(w, "{}this_arg: {}{}", if recv.reference.is_none() { "mut " } else { "" },
 562                                         if recv.reference.is_some() {
 563                                                 match (self_ptr, recv.mutability.is_some()) {
 564                                                         (true, true) => "*mut ",
 565                                                         (true, false) => "*const ",
 566                                                         (false, true) => "&mut ",
 567                                                         (false, false) => "&",
 568                                                 }
 569                                         } else { "" }, this_param).unwrap();
 570                                 assert!(first_arg);
 571                                 first_arg = false;
 572                         },
 573                         syn::FnArg::Typed(arg) => {
 574                                 if types.skip_arg(&*arg.ty, generics) { continue; }
 575                                 if !arg.attrs.is_empty() { unimplemented!(); }
 576                                 // First get the c type so that we can check if it ends up being a reference:
 577                                 let mut c_type = Vec::new();
 578                                 types.write_c_type(&mut c_type, &*arg.ty, generics, false);
 579                                 match &*arg.pat {
 580                                         syn::Pat::Ident(ident) => {
 581                                                 if !ident.attrs.is_empty() || ident.subpat.is_some() {
 582                                                         unimplemented!();
 583                                                 }
 584                                                 write!(w, "{}{}{}: ", if first_arg { "" } else { ", " }, if !fn_decl || c_type[0] == '&' as u8 || c_type[0] == '*' as u8 { "" } else { "mut " }, ident.ident).unwrap();
 585                                                 first_arg = false;
 586                                         },
 587                                         syn::Pat::Wild(wild) => {
 588                                                 if !wild.attrs.is_empty() { unimplemented!(); }
 589                                                 write!(w, "{}unused_{}: ", if first_arg { "" } else { ", " }, num_unused).unwrap();
 590                                                 num_unused += 1;
 591                                         },
 592                                         _ => unimplemented!(),
 593                                 }
 594                                 w.write(&c_type).unwrap();
 595                         }
 596                 }
 597         }
 598         write!(w, ")").unwrap();
 599         match &sig.output {
 600                 syn::ReturnType::Type(_, rtype) => {
 601                         write!(w, " -> ").unwrap();
 602                         if let Some(mut remaining_path) = first_seg_self(&*rtype) {
 603                                 if remaining_path.next().is_none() {
 604                                         write!(w, "{}", this_param).unwrap();
 605                                         return;
 606                                 }
 607                         }
 608                         types.write_c_type(w, &*rtype, generics, true);
 609                 },
 610                 _ => {},
 611         }
 612 }
 613
 614 /// Print the main part of a method declaration body, starting with a newline after the function
 615 /// open bracket and converting each function parameter to or from C-mapped types. Ends with "let
 616 /// mut ret = " assuming the next print will be the unmapped Rust function to call followed by the
 617 /// parameters we mapped to/from C here.
 618 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) {
 619         let mut num_unused = 0u32;
 620         for inp in sig.inputs.iter() {
 621                 match inp {
 622                         syn::FnArg::Receiver(_) => {},
 623                         syn::FnArg::Typed(arg) => {
 624                                 if types.skip_arg(&*arg.ty, generics) { continue; }
 625                                 if !arg.attrs.is_empty() { unimplemented!(); }
 626                                 macro_rules! write_new_var {
 627                                         ($ident: expr, $ty: expr) => {
 628                                                 if to_c {
 629                                                         if types.write_to_c_conversion_new_var(w, &$ident, &$ty, generics, false) {
 630                                                                 write!(w, "\n\t{}", extra_indent).unwrap();
 631                                                         }
 632                                                 } else {
 633                                                         if types.write_from_c_conversion_new_var(w, &$ident, &$ty, generics) {
 634                                                                 write!(w, "\n\t{}", extra_indent).unwrap();
 635                                                         }
 636                                                 }
 637                                         }
 638                                 }
 639                                 match &*arg.pat {
 640                                         syn::Pat::Ident(ident) => {
 641                                                 if !ident.attrs.is_empty() || ident.subpat.is_some() {
 642                                                         unimplemented!();
 643                                                 }
 644                                                 write_new_var!(ident.ident, *arg.ty);
 645                                         },
 646                                         syn::Pat::Wild(w) => {
 647                                                 if !w.attrs.is_empty() { unimplemented!(); }
 648                                                 write_new_var!(format_ident!("unused_{}", num_unused), *arg.ty);
 649                                                 num_unused += 1;
 650                                         },
 651                                         _ => unimplemented!(),
 652                                 }
 653                         }
 654                 }
 655         }
 656         match &sig.output {
 657                 syn::ReturnType::Type(_, _) => {
 658                         write!(w, "let mut ret = ").unwrap();
 659                 },
 660                 _ => {},
 661         }
 662 }
 663
 664 /// Prints the parameters in a method call, starting after the open parenthesis and ending with a
 665 /// final return statement returning the method's result. Should be followed by a single closing
 666 /// bracket.
 667 ///
 668 /// The return value is expected to be bound to a variable named `ret` which is available after a
 669 /// method-call-ending semicolon.
 670 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) {
 671         let mut first_arg = true;
 672         let mut num_unused = 0;
 673         for inp in sig.inputs.iter() {
 674                 match inp {
 675                         syn::FnArg::Receiver(recv) => {
 676                                 if !recv.attrs.is_empty() { unimplemented!(); }
 677                                 if to_c {
 678                                         if recv.reference.is_none() { unimplemented!(); }
 679                                         write!(w, "self.this_arg").unwrap();
 680                                         first_arg = false;
 681                                 }
 682                         },
 683                         syn::FnArg::Typed(arg) => {
 684                                 if types.skip_arg(&*arg.ty, generics) {
 685                                         if !to_c {
 686                                                 if !first_arg {
 687                                                         write!(w, ", ").unwrap();
 688                                                 }
 689                                                 first_arg = false;
 690                                                 types.no_arg_to_rust(w, &*arg.ty, generics);
 691                                         }
 692                                         continue;
 693                                 }
 694                                 if !arg.attrs.is_empty() { unimplemented!(); }
 695                                 macro_rules! write_ident {
 696                                         ($ident: expr) => {
 697                                                 if !first_arg {
 698                                                         write!(w, ", ").unwrap();
 699                                                 }
 700                                                 first_arg = false;
 701                                                 if to_c {
 702                                                         types.write_to_c_conversion_inline_prefix(w, &*arg.ty, generics, false);
 703                                                         write!(w, "{}", $ident).unwrap();
 704                                                         types.write_to_c_conversion_inline_suffix(w, &*arg.ty, generics, false);
 705                                                 } else {
 706                                                         types.write_from_c_conversion_prefix(w, &*arg.ty, generics);
 707                                                         write!(w, "{}", $ident).unwrap();
 708                                                         types.write_from_c_conversion_suffix(w, &*arg.ty, generics);
 709                                                 }
 710                                         }
 711                                 }
 712                                 match &*arg.pat {
 713                                         syn::Pat::Ident(ident) => {
 714                                                 if !ident.attrs.is_empty() || ident.subpat.is_some() {
 715                                                         unimplemented!();
 716                                                 }
 717                                                 write_ident!(ident.ident);
 718                                         },
 719                                         syn::Pat::Wild(w) => {
 720                                                 if !w.attrs.is_empty() { unimplemented!(); }
 721                                                 write_ident!(format!("unused_{}", num_unused));
 722                                                 num_unused += 1;
 723                                         },
 724                                         _ => unimplemented!(),
 725                                 }
 726                         }
 727                 }
 728         }
 729         write!(w, ")").unwrap();
 730         match &sig.output {
 731                 syn::ReturnType::Type(_, rtype) => {
 732                         write!(w, ";\n\t{}", extra_indent).unwrap();
 733
 734                         let self_segs_iter = first_seg_self(&*rtype);
 735                         if to_c && first_seg_self(&*rtype).is_some() {
 736                                 // Assume rather blindly that we're returning an associated trait from a C fn call to a Rust trait object.
 737                                 write!(w, "ret").unwrap();
 738                         } else if !to_c && self_segs_iter.is_some() && self_segs_iter.unwrap().next().is_none() {
 739                                 // If we're returning "Self" (and not "Self::X"), just do it manually
 740                                 write!(w, "{} {{ inner: ObjOps::heap_alloc(ret), is_owned: true }}", this_type).unwrap();
 741                         } else if to_c {
 742                                 let new_var = types.write_from_c_conversion_new_var(w, &format_ident!("ret"), rtype, generics);
 743                                 if new_var {
 744                                         write!(w, "\n\t{}", extra_indent).unwrap();
 745                                 }
 746                                 types.write_from_c_conversion_prefix(w, &*rtype, generics);
 747                                 write!(w, "ret").unwrap();
 748                                 types.write_from_c_conversion_suffix(w, &*rtype, generics);
 749                         } else {
 750                                 let new_var = types.write_to_c_conversion_new_var(w, &format_ident!("ret"), &rtype, generics, true);
 751                                 if new_var {
 752                                         write!(w, "\n\t{}", extra_indent).unwrap();
 753                                 }
 754                                 types.write_to_c_conversion_inline_prefix(w, &rtype, generics, true);
 755                                 write!(w, "ret").unwrap();
 756                                 types.write_to_c_conversion_inline_suffix(w, &rtype, generics, true);
 757                         }
 758                 }
 759                 _ => {},
 760         }
 761 }
 762
 763 /// Prints concrete generic parameters for a struct/trait/function, including the less-than and
 764 /// greater-than symbols, if any generic parameters are defined.
 765 pub fn maybe_write_generics<W: std::io::Write>(w: &mut W, generics: &syn::Generics, types: &TypeResolver, concrete_lifetimes: bool) {
 766         let mut gen_types = GenericTypes::new(None);
 767         assert!(gen_types.learn_generics(generics, types));
 768         if generics.params.is_empty() { return; }
 769         for generic in generics.params.iter() {
 770                 match generic {
 771                         syn::GenericParam::Type(type_param) => {
 772                                 for bound in type_param.bounds.iter() {
 773                                         match bound {
 774                                                 syn::TypeParamBound::Trait(t) => {
 775                                                         if let Some(trait_bound) = types.maybe_resolve_path(&t.path, None) {
 776                                                                 if types.skip_path(&trait_bound) {
 777                                                                         // Just hope rust deduces generic params if some bounds are skipable.
 778                                                                         return;
 779                                                                 }
 780                                                         }
 781                                                 }
 782                                                 _ => {},
 783                                         }
 784                                 }
 785                         }
 786                         _ => {},
 787                 }
 788         }
 789
 790         write!(w, "<").unwrap();
 791         for (idx, generic) in generics.params.iter().enumerate() {
 792                 match generic {
 793                         syn::GenericParam::Type(type_param) => {
 794                                 write!(w, "{}", if idx != 0 { ", " } else { "" }).unwrap();
 795                                 let type_ident = &type_param.ident;
 796                                 types.write_c_type_in_generic_param(w, &syn::parse_quote!(#type_ident), Some(&gen_types), false);
 797                         },
 798                         syn::GenericParam::Lifetime(lt) => {
 799                                 if concrete_lifetimes {
 800                                         write!(w, "'static").unwrap();
 801                                 } else {
 802                                         write!(w, "{}'{}", if idx != 0 { ", " } else { "" }, lt.lifetime.ident).unwrap();
 803                                 }
 804                         },
 805                         _ => unimplemented!(),
 806                 }
 807         }
 808         write!(w, ">").unwrap();
 809 }
 810
 811 pub fn maybe_write_lifetime_generics<W: std::io::Write>(w: &mut W, generics: &syn::Generics, types: &TypeResolver) {
 812         let mut gen_types = GenericTypes::new(None);
 813         assert!(gen_types.learn_generics(generics, types));
 814         if generics.params.iter().any(|param| if let syn::GenericParam::Lifetime(_) = param { true } else { false }) {
 815                 write!(w, "<").unwrap();
 816                 for (idx, generic) in generics.params.iter().enumerate() {
 817                         match generic {
 818                                 syn::GenericParam::Type(_) => {},
 819                                 syn::GenericParam::Lifetime(lt) => {
 820                                         write!(w, "{}'{}", if idx != 0 { ", " } else { "" }, lt.lifetime.ident).unwrap();
 821                                 },
 822                                 _ => unimplemented!(),
 823                         }
 824                 }
 825                 write!(w, ">").unwrap();
 826         }
 827 }