1use crate::syntax::atom::Atom::{self, *};
2use crate::syntax::report::Errors;
3use crate::syntax::visit::{self, Visit};
4use crate::syntax::{
5 error, ident, trivial, Api, Array, Enum, ExternFn, ExternType, Impl, Lang, Lifetimes,
6 NamedType, Ptr, Receiver, Ref, Signature, SliceRef, Struct, Trait, Ty1, Type, TypeAlias, Types,
7};
8use proc_macro2::{Delimiter, Group, Ident, TokenStream};
9use quote::{quote, ToTokens};
10use std::fmt::Display;
11use syn::{GenericParam, Generics, Lifetime};
12
13pub(crate) struct Check<'a> {
14 apis: &'a [Api],
15 types: &'a Types<'a>,
16 errors: &'a mut Errors,
17 generator: Generator,
18}
19
20pub(crate) enum Generator {
21 #[allow(dead_code)]
23 Build,
24 #[allow(dead_code)]
30 Macro,
31}
32
33pub(crate) fn typecheck(cx: &mut Errors, apis: &[Api], types: &Types, generator: Generator) {
34 do_typecheck(&mut Check {
35 apis,
36 types,
37 errors: cx,
38 generator,
39 });
40}
41
42fn do_typecheck(cx: &mut Check) {
43 ident::check_all(cx, cx.apis);
44
45 for ty in cx.types {
46 match ty {
47 Type::Ident(ident) => check_type_ident(cx, ident),
48 Type::RustBox(ptr) => check_type_box(cx, ptr),
49 Type::RustVec(ty) => check_type_rust_vec(cx, ty),
50 Type::UniquePtr(ptr) => check_type_unique_ptr(cx, ptr),
51 Type::SharedPtr(ptr) => check_type_shared_ptr(cx, ptr),
52 Type::WeakPtr(ptr) => check_type_weak_ptr(cx, ptr),
53 Type::CxxVector(ptr) => check_type_cxx_vector(cx, ptr),
54 Type::Ref(ty) => check_type_ref(cx, ty),
55 Type::Ptr(ty) => check_type_ptr(cx, ty),
56 Type::Array(array) => check_type_array(cx, array),
57 Type::Fn(ty) => check_type_fn(cx, ty),
58 Type::SliceRef(ty) => check_type_slice_ref(cx, ty),
59 Type::Str(_) | Type::Void(_) => {}
60 }
61 }
62
63 for api in cx.apis {
64 match api {
65 Api::Include(_) => {}
66 Api::Struct(strct) => check_api_struct(cx, strct),
67 Api::Enum(enm) => check_api_enum(cx, enm),
68 Api::CxxType(ety) | Api::RustType(ety) => check_api_type(cx, ety),
69 Api::CxxFunction(efn) | Api::RustFunction(efn) => check_api_fn(cx, efn),
70 Api::TypeAlias(alias) => check_api_type_alias(cx, alias),
71 Api::Impl(imp) => check_api_impl(cx, imp),
72 }
73 }
74}
75
76impl Check<'_> {
77 pub(crate) fn error(&mut self, sp: impl ToTokens, msg: impl Display) {
78 self.errors.error(sp, msg);
79 }
80}
81
82fn check_type_ident(cx: &mut Check, name: &NamedType) {
83 let ident = &name.rust;
84 if Atom::from(ident).is_none()
85 && !cx.types.structs.contains_key(ident)
86 && !cx.types.enums.contains_key(ident)
87 && !cx.types.cxx.contains(ident)
88 && !cx.types.rust.contains(ident)
89 {
90 let msg = format!("unsupported type: {}", ident);
91 cx.error(ident, msg);
92 }
93}
94
95fn check_type_box(cx: &mut Check, ptr: &Ty1) {
96 if let Type::Ident(ident) = &ptr.inner {
97 if cx.types.cxx.contains(&ident.rust)
98 && !cx.types.aliases.contains_key(&ident.rust)
99 && !cx.types.structs.contains_key(&ident.rust)
100 && !cx.types.enums.contains_key(&ident.rust)
101 {
102 cx.error(ptr, error::BOX_CXX_TYPE.msg);
103 }
104
105 if Atom::from(&ident.rust).is_none() {
106 return;
107 }
108 }
109
110 cx.error(ptr, "unsupported target type of Box");
111}
112
113fn check_type_rust_vec(cx: &mut Check, ty: &Ty1) {
114 match &ty.inner {
115 Type::Ident(ident) => {
116 if cx.types.cxx.contains(&ident.rust)
117 && !cx.types.aliases.contains_key(&ident.rust)
118 && !cx.types.structs.contains_key(&ident.rust)
119 && !cx.types.enums.contains_key(&ident.rust)
120 {
121 cx.error(ty, "Rust Vec containing C++ type is not supported yet");
122 return;
123 }
124
125 match Atom::from(&ident.rust) {
126 None
127 | Some(
128 Bool | Char | U8 | U16 | U32 | U64 | Usize | I8 | I16 | I32 | I64 | Isize | F32
129 | F64 | RustString,
130 ) => return,
131 Some(CxxString) => {}
132 }
133 }
134 Type::Str(_) => return,
135 _ => {}
136 }
137
138 cx.error(ty, "unsupported element type of Vec");
139}
140
141fn check_type_unique_ptr(cx: &mut Check, ptr: &Ty1) {
142 if let Type::Ident(ident) = &ptr.inner {
143 if cx.types.rust.contains(&ident.rust) {
144 cx.error(ptr, "unique_ptr of a Rust type is not supported yet");
145 return;
146 }
147
148 match Atom::from(&ident.rust) {
149 None | Some(CxxString) => return,
150 _ => {}
151 }
152 } else if let Type::CxxVector(_) = &ptr.inner {
153 return;
154 }
155
156 cx.error(ptr, "unsupported unique_ptr target type");
157}
158
159fn check_type_shared_ptr(cx: &mut Check, ptr: &Ty1) {
160 if let Type::Ident(ident) = &ptr.inner {
161 if cx.types.rust.contains(&ident.rust) {
162 cx.error(ptr, "shared_ptr of a Rust type is not supported yet");
163 return;
164 }
165
166 match Atom::from(&ident.rust) {
167 None
168 | Some(
169 Bool | U8 | U16 | U32 | U64 | Usize | I8 | I16 | I32 | I64 | Isize | F32 | F64
170 | CxxString,
171 ) => return,
172 Some(Char | RustString) => {}
173 }
174 } else if let Type::CxxVector(_) = &ptr.inner {
175 cx.error(ptr, "std::shared_ptr<std::vector> is not supported yet");
176 return;
177 }
178
179 cx.error(ptr, "unsupported shared_ptr target type");
180}
181
182fn check_type_weak_ptr(cx: &mut Check, ptr: &Ty1) {
183 if let Type::Ident(ident) = &ptr.inner {
184 if cx.types.rust.contains(&ident.rust) {
185 cx.error(ptr, "weak_ptr of a Rust type is not supported yet");
186 return;
187 }
188
189 match Atom::from(&ident.rust) {
190 None
191 | Some(
192 Bool | U8 | U16 | U32 | U64 | Usize | I8 | I16 | I32 | I64 | Isize | F32 | F64
193 | CxxString,
194 ) => return,
195 Some(Char | RustString) => {}
196 }
197 } else if let Type::CxxVector(_) = &ptr.inner {
198 cx.error(ptr, "std::weak_ptr<std::vector> is not supported yet");
199 return;
200 }
201
202 cx.error(ptr, "unsupported weak_ptr target type");
203}
204
205fn check_type_cxx_vector(cx: &mut Check, ptr: &Ty1) {
206 if let Type::Ident(ident) = &ptr.inner {
207 if cx.types.rust.contains(&ident.rust) {
208 cx.error(
209 ptr,
210 "C++ vector containing a Rust type is not supported yet",
211 );
212 return;
213 }
214
215 match Atom::from(&ident.rust) {
216 None
217 | Some(
218 U8 | U16 | U32 | U64 | Usize | I8 | I16 | I32 | I64 | Isize | F32 | F64 | CxxString,
219 ) => return,
220 Some(Char) => { }
221 Some(Bool | RustString) => {}
222 }
223 }
224
225 cx.error(ptr, "unsupported vector element type");
226}
227
228fn check_type_ref(cx: &mut Check, ty: &Ref) {
229 if ty.mutable && !ty.pinned {
230 if let Some(requires_pin) = match &ty.inner {
231 Type::Ident(ident) if ident.rust == CxxString || is_opaque_cxx(cx, &ident.rust) => {
232 Some(ident.rust.to_string())
233 }
234 Type::CxxVector(_) => Some("CxxVector<...>".to_owned()),
235 _ => None,
236 } {
237 cx.error(
238 ty,
239 format!(
240 "mutable reference to C++ type requires a pin -- use Pin<&mut {}>",
241 requires_pin,
242 ),
243 );
244 }
245 }
246
247 match ty.inner {
248 Type::Fn(_) | Type::Void(_) => {}
249 Type::Ref(_) => {
250 cx.error(ty, "C++ does not allow references to references");
251 return;
252 }
253 _ => return,
254 }
255
256 cx.error(ty, "unsupported reference type");
257}
258
259fn check_type_ptr(cx: &mut Check, ty: &Ptr) {
260 match ty.inner {
261 Type::Fn(_) | Type::Void(_) => {}
262 Type::Ref(_) => {
263 cx.error(ty, "C++ does not allow pointer to reference as a type");
264 return;
265 }
266 _ => return,
267 }
268
269 cx.error(ty, "unsupported pointer type");
270}
271
272fn check_type_slice_ref(cx: &mut Check, ty: &SliceRef) {
273 let supported = !is_unsized(cx, &ty.inner)
274 || match &ty.inner {
275 Type::Ident(ident) => {
276 cx.types.rust.contains(&ident.rust) || cx.types.aliases.contains_key(&ident.rust)
277 }
278 _ => false,
279 };
280
281 if !supported {
282 let mutable = if ty.mutable { "mut " } else { "" };
283 let mut msg = format!("unsupported &{}[T] element type", mutable);
284 if let Type::Ident(ident) = &ty.inner {
285 if is_opaque_cxx(cx, &ident.rust) {
286 msg += ": opaque C++ type is not supported yet";
287 }
288 }
289 cx.error(ty, msg);
290 }
291}
292
293fn check_type_array(cx: &mut Check, ty: &Array) {
294 let supported = !is_unsized(cx, &ty.inner);
295
296 if !supported {
297 cx.error(ty, "unsupported array element type");
298 }
299}
300
301fn check_type_fn(cx: &mut Check, ty: &Signature) {
302 if ty.throws {
303 cx.error(ty, "function pointer returning Result is not supported yet");
304 }
305
306 for arg in &ty.args {
307 if let Type::Ptr(_) = arg.ty {
308 if ty.unsafety.is_none() {
309 cx.error(
310 arg,
311 "pointer argument requires that the function pointer be marked unsafe",
312 );
313 }
314 }
315 }
316}
317
318fn check_api_struct(cx: &mut Check, strct: &Struct) {
319 let name = &strct.name;
320 check_reserved_name(cx, &name.rust);
321 check_lifetimes(cx, &strct.generics);
322
323 if strct.fields.is_empty() {
324 let span = span_for_struct_error(strct);
325 cx.error(span, "structs without any fields are not supported");
326 }
327
328 if cx.types.cxx.contains(&name.rust) {
329 if let Some(ety) = cx.types.untrusted.get(&name.rust) {
330 let msg = "extern shared struct must be declared in an `unsafe extern` block";
331 cx.error(ety, msg);
332 }
333 }
334
335 for derive in &strct.derives {
336 if derive.what == Trait::ExternType {
337 let msg = format!("derive({}) on shared struct is not supported", derive);
338 cx.error(derive, msg);
339 }
340 }
341
342 for field in &strct.fields {
343 if let Type::Fn(_) = field.ty {
344 cx.error(
345 field,
346 "function pointers in a struct field are not implemented yet",
347 );
348 } else if is_unsized(cx, &field.ty) {
349 let desc = describe(cx, &field.ty);
350 let msg = format!("using {} by value is not supported", desc);
351 cx.error(field, msg);
352 }
353 }
354}
355
356fn check_api_enum(cx: &mut Check, enm: &Enum) {
357 check_reserved_name(cx, &enm.name.rust);
358 check_lifetimes(cx, &enm.generics);
359
360 if enm.variants.is_empty() && !enm.explicit_repr && !enm.variants_from_header {
361 let span = span_for_enum_error(enm);
362 cx.error(
363 span,
364 "explicit #[repr(...)] is required for enum without any variants",
365 );
366 }
367
368 for derive in &enm.derives {
369 if derive.what == Trait::Default || derive.what == Trait::ExternType {
370 let msg = format!("derive({}) on shared enum is not supported", derive);
371 cx.error(derive, msg);
372 }
373 }
374}
375
376fn check_api_type(cx: &mut Check, ety: &ExternType) {
377 check_reserved_name(cx, &ety.name.rust);
378 check_lifetimes(cx, &ety.generics);
379
380 for derive in &ety.derives {
381 if derive.what == Trait::ExternType && ety.lang == Lang::Rust {
382 continue;
383 }
384 let lang = match ety.lang {
385 Lang::Rust => "Rust",
386 Lang::Cxx => "C++",
387 };
388 let msg = format!(
389 "derive({}) on opaque {} type is not supported yet",
390 derive, lang,
391 );
392 cx.error(derive, msg);
393 }
394
395 if !ety.bounds.is_empty() {
396 let bounds = &ety.bounds;
397 let span = quote!(#(#bounds)*);
398 cx.error(span, "extern type bounds are not implemented yet");
399 }
400
401 if let Some(reasons) = cx.types.required_trivial.get(&ety.name.rust) {
402 let msg = format!(
403 "needs a cxx::ExternType impl in order to be used as {}",
404 trivial::as_what(&ety.name, reasons),
405 );
406 cx.error(ety, msg);
407 }
408}
409
410fn check_api_fn(cx: &mut Check, efn: &ExternFn) {
411 match efn.lang {
412 Lang::Cxx => {
413 if !efn.generics.params.is_empty() && !efn.trusted {
414 let ref span = span_for_generics_error(efn);
415 cx.error(span, "extern C++ function with lifetimes must be declared in `unsafe extern \"C++\"` block");
416 }
417 }
418 Lang::Rust => {
419 if !efn.generics.params.is_empty() && efn.unsafety.is_none() {
420 let ref span = span_for_generics_error(efn);
421 let message = format!(
422 "must be `unsafe fn {}` in order to expose explicit lifetimes to C++",
423 efn.name.rust,
424 );
425 cx.error(span, message);
426 }
427 }
428 }
429
430 check_generics(cx, &efn.sig.generics);
431
432 if let Some(receiver) = &efn.receiver {
433 let ref span = span_for_receiver_error(receiver);
434
435 if receiver.ty.rust == "Self" {
436 let mutability = match receiver.mutable {
437 true => "mut ",
438 false => "",
439 };
440 let msg = format!(
441 "unnamed receiver type is only allowed if the surrounding extern block contains exactly one extern type; use `self: &{mutability}TheType`",
442 mutability = mutability,
443 );
444 cx.error(span, msg);
445 } else if cx.types.enums.contains_key(&receiver.ty.rust) {
446 cx.error(
447 span,
448 "unsupported receiver type; C++ does not allow member functions on enums",
449 );
450 } else if !cx.types.structs.contains_key(&receiver.ty.rust)
451 && !cx.types.cxx.contains(&receiver.ty.rust)
452 && !cx.types.rust.contains(&receiver.ty.rust)
453 {
454 cx.error(span, "unrecognized receiver type");
455 } else if receiver.mutable && !receiver.pinned && is_opaque_cxx(cx, &receiver.ty.rust) {
456 cx.error(
457 span,
458 format!(
459 "mutable reference to opaque C++ type requires a pin -- use `self: Pin<&mut {}>`",
460 receiver.ty.rust,
461 ),
462 );
463 }
464 }
465
466 for arg in &efn.args {
467 if let Type::Fn(_) = arg.ty {
468 if efn.lang == Lang::Rust {
469 cx.error(
470 arg,
471 "passing a function pointer from C++ to Rust is not implemented yet",
472 );
473 }
474 } else if let Type::Ptr(_) = arg.ty {
475 if efn.sig.unsafety.is_none() {
476 cx.error(
477 arg,
478 "pointer argument requires that the function be marked unsafe",
479 );
480 }
481 } else if is_unsized(cx, &arg.ty) {
482 let desc = describe(cx, &arg.ty);
483 let msg = format!("passing {} by value is not supported", desc);
484 cx.error(arg, msg);
485 }
486 }
487
488 if let Some(ty) = &efn.ret {
489 if let Type::Fn(_) = ty {
490 cx.error(ty, "returning a function pointer is not implemented yet");
491 } else if is_unsized(cx, ty) {
492 let desc = describe(cx, ty);
493 let msg = format!("returning {} by value is not supported", desc);
494 cx.error(ty, msg);
495 }
496 }
497
498 if efn.lang == Lang::Cxx {
499 check_mut_return_restriction(cx, efn);
500 }
501}
502
503fn check_api_type_alias(cx: &mut Check, alias: &TypeAlias) {
504 check_lifetimes(cx, &alias.generics);
505
506 for derive in &alias.derives {
507 let msg = format!("derive({}) on extern type alias is not supported", derive);
508 cx.error(derive, msg);
509 }
510}
511
512fn check_api_impl(cx: &mut Check, imp: &Impl) {
513 let ty = &imp.ty;
514
515 check_lifetimes(cx, &imp.impl_generics);
516
517 if let Some(negative) = imp.negative_token {
518 let span = quote!(#negative #ty);
519 cx.error(span, "negative impl is not supported yet");
520 return;
521 }
522
523 match ty {
524 Type::RustBox(ty)
525 | Type::RustVec(ty)
526 | Type::UniquePtr(ty)
527 | Type::SharedPtr(ty)
528 | Type::WeakPtr(ty)
529 | Type::CxxVector(ty) => {
530 if let Type::Ident(inner) = &ty.inner {
531 if Atom::from(&inner.rust).is_none() {
532 return;
533 }
534 }
535 }
536 _ => {}
537 }
538
539 cx.error(imp, "unsupported Self type of explicit impl");
540}
541
542fn check_mut_return_restriction(cx: &mut Check, efn: &ExternFn) {
543 if efn.sig.unsafety.is_some() {
544 return;
546 }
547
548 match &efn.ret {
549 Some(Type::Ref(ty)) if ty.mutable => {}
550 Some(Type::SliceRef(slice)) if slice.mutable => {}
551 _ => return,
552 }
553
554 if let Some(receiver) = &efn.receiver {
555 if receiver.mutable {
556 return;
557 }
558 let Some(resolve) = cx.types.try_resolve(&receiver.ty) else {
559 return;
560 };
561 if !resolve.generics.lifetimes.is_empty() {
562 return;
563 }
564 }
565
566 struct FindLifetimeMut<'a> {
567 cx: &'a Check<'a>,
568 found: bool,
569 }
570
571 impl<'t, 'a> Visit<'t> for FindLifetimeMut<'a> {
572 fn visit_type(&mut self, ty: &'t Type) {
573 self.found |= match ty {
574 Type::Ref(ty) => ty.mutable,
575 Type::SliceRef(slice) => slice.mutable,
576 Type::Ident(ident) if Atom::from(&ident.rust).is_none() => {
577 match self.cx.types.try_resolve(ident) {
578 Some(resolve) => !resolve.generics.lifetimes.is_empty(),
579 None => true,
580 }
581 }
582 _ => false,
583 };
584 visit::visit_type(self, ty);
585 }
586 }
587
588 let mut visitor = FindLifetimeMut { cx, found: false };
589
590 for arg in &efn.args {
591 visitor.visit_type(&arg.ty);
592 }
593
594 if visitor.found {
595 return;
596 }
597
598 cx.error(
599 efn,
600 "&mut return type is not allowed unless there is a &mut argument",
601 );
602}
603
604fn check_reserved_name(cx: &mut Check, ident: &Ident) {
605 if ident == "Box"
606 || ident == "UniquePtr"
607 || ident == "SharedPtr"
608 || ident == "WeakPtr"
609 || ident == "Vec"
610 || ident == "CxxVector"
611 || ident == "str"
612 || Atom::from(ident).is_some()
613 {
614 cx.error(ident, "reserved name");
615 }
616}
617
618fn check_reserved_lifetime(cx: &mut Check, lifetime: &Lifetime) {
619 if lifetime.ident == "static" {
620 match cx.generator {
621 Generator::Macro => { }
622 Generator::Build => {
623 cx.error(lifetime, error::RESERVED_LIFETIME);
624 }
625 }
626 }
627}
628
629fn check_lifetimes(cx: &mut Check, generics: &Lifetimes) {
630 for lifetime in &generics.lifetimes {
631 check_reserved_lifetime(cx, lifetime);
632 }
633}
634
635fn check_generics(cx: &mut Check, generics: &Generics) {
636 for generic_param in &generics.params {
637 if let GenericParam::Lifetime(def) = generic_param {
638 check_reserved_lifetime(cx, &def.lifetime);
639 }
640 }
641}
642
643fn is_unsized(cx: &mut Check, ty: &Type) -> bool {
644 match ty {
645 Type::Ident(ident) => {
646 let ident = &ident.rust;
647 ident == CxxString || is_opaque_cxx(cx, ident) || cx.types.rust.contains(ident)
648 }
649 Type::Array(array) => is_unsized(cx, &array.inner),
650 Type::CxxVector(_) | Type::Fn(_) | Type::Void(_) => true,
651 Type::RustBox(_)
652 | Type::RustVec(_)
653 | Type::UniquePtr(_)
654 | Type::SharedPtr(_)
655 | Type::WeakPtr(_)
656 | Type::Ref(_)
657 | Type::Ptr(_)
658 | Type::Str(_)
659 | Type::SliceRef(_) => false,
660 }
661}
662
663fn is_opaque_cxx(cx: &mut Check, ty: &Ident) -> bool {
664 cx.types.cxx.contains(ty)
665 && !cx.types.structs.contains_key(ty)
666 && !cx.types.enums.contains_key(ty)
667 && !(cx.types.aliases.contains_key(ty) && cx.types.required_trivial.contains_key(ty))
668}
669
670fn span_for_struct_error(strct: &Struct) -> TokenStream {
671 let struct_token = strct.struct_token;
672 let mut brace_token = Group::new(Delimiter::Brace, TokenStream::new());
673 brace_token.set_span(strct.brace_token.span.join());
674 quote!(#struct_token #brace_token)
675}
676
677fn span_for_enum_error(enm: &Enum) -> TokenStream {
678 let enum_token = enm.enum_token;
679 let mut brace_token = Group::new(Delimiter::Brace, TokenStream::new());
680 brace_token.set_span(enm.brace_token.span.join());
681 quote!(#enum_token #brace_token)
682}
683
684fn span_for_receiver_error(receiver: &Receiver) -> TokenStream {
685 let ampersand = receiver.ampersand;
686 let lifetime = &receiver.lifetime;
687 let mutability = receiver.mutability;
688 if receiver.shorthand {
689 let var = receiver.var;
690 quote!(#ampersand #lifetime #mutability #var)
691 } else {
692 let ty = &receiver.ty;
693 quote!(#ampersand #lifetime #mutability #ty)
694 }
695}
696
697fn span_for_generics_error(efn: &ExternFn) -> TokenStream {
698 let unsafety = efn.unsafety;
699 let fn_token = efn.fn_token;
700 let generics = &efn.generics;
701 quote!(#unsafety #fn_token #generics)
702}
703
704fn describe(cx: &mut Check, ty: &Type) -> String {
705 match ty {
706 Type::Ident(ident) => {
707 if cx.types.structs.contains_key(&ident.rust) {
708 "struct".to_owned()
709 } else if cx.types.enums.contains_key(&ident.rust) {
710 "enum".to_owned()
711 } else if cx.types.aliases.contains_key(&ident.rust) {
712 "C++ type".to_owned()
713 } else if cx.types.cxx.contains(&ident.rust) {
714 "opaque C++ type".to_owned()
715 } else if cx.types.rust.contains(&ident.rust) {
716 "opaque Rust type".to_owned()
717 } else if Atom::from(&ident.rust) == Some(CxxString) {
718 "C++ string".to_owned()
719 } else if Atom::from(&ident.rust) == Some(Char) {
720 "C char".to_owned()
721 } else {
722 ident.rust.to_string()
723 }
724 }
725 Type::RustBox(_) => "Box".to_owned(),
726 Type::RustVec(_) => "Vec".to_owned(),
727 Type::UniquePtr(_) => "unique_ptr".to_owned(),
728 Type::SharedPtr(_) => "shared_ptr".to_owned(),
729 Type::WeakPtr(_) => "weak_ptr".to_owned(),
730 Type::Ref(_) => "reference".to_owned(),
731 Type::Ptr(_) => "raw pointer".to_owned(),
732 Type::Str(_) => "&str".to_owned(),
733 Type::CxxVector(_) => "C++ vector".to_owned(),
734 Type::SliceRef(_) => "slice".to_owned(),
735 Type::Fn(_) => "function pointer".to_owned(),
736 Type::Void(_) => "()".to_owned(),
737 Type::Array(_) => "array".to_owned(),
738 }
739}