1 //! Error Reporting Code for the inference engine
2 //!
3 //! Because of the way inference, and in particular region inference,
4 //! works, it often happens that errors are not detected until far after
5 //! the relevant line of code has been type-checked. Therefore, there is
6 //! an elaborate system to track why a particular constraint in the
7 //! inference graph arose so that we can explain to the user what gave
8 //! rise to a particular error.
9 //!
10 //! The system is based around a set of "origin" types. An "origin" is the
11 //! reason that a constraint or inference variable arose. There are
12 //! different "origin" enums for different kinds of constraints/variables
13 //! (e.g., `TypeOrigin`, `RegionVariableOrigin`). An origin always has
14 //! a span, but also more information so that we can generate a meaningful
15 //! error message.
16 //!
17 //! Having a catalog of all the different reasons an error can arise is
18 //! also useful for other reasons, like cross-referencing FAQs etc, though
19 //! we are not really taking advantage of this yet.
20 //!
21 //! # Region Inference
22 //!
23 //! Region inference is particularly tricky because it always succeeds "in
24 //! the moment" and simply registers a constraint. Then, at the end, we
25 //! can compute the full graph and report errors, so we need to be able to
26 //! store and later report what gave rise to the conflicting constraints.
27 //!
28 //! # Subtype Trace
29 //!
30 //! Determining whether `T1 <: T2` often involves a number of subtypes and
31 //! subconstraints along the way. A "TypeTrace" is an extended version
32 //! of an origin that traces the types and other values that were being
33 //! compared. It is not necessarily comprehensive (in fact, at the time of
34 //! this writing it only tracks the root values being compared) but I'd
35 //! like to extend it to include significant "waypoints". For example, if
36 //! you are comparing `(T1, T2) <: (T3, T4)`, and the problem is that `T2
37 //! <: T4` fails, I'd like the trace to include enough information to say
38 //! "in the 2nd element of the tuple". Similarly, failures when comparing
39 //! arguments or return types in fn types should be able to cite the
40 //! specific position, etc.
41 //!
42 //! # Reality vs plan
43 //!
44 //! Of course, there is still a LOT of code in typeck that has yet to be
45 //! ported to this system, and which relies on string concatenation at the
46 //! time of error detection.
47
48 use super::lexical_region_resolve::RegionResolutionError;
49 use super::region_constraints::GenericKind;
50 use super::{InferCtxt, RegionVariableOrigin, SubregionOrigin, TypeTrace, ValuePairs};
51
52 use crate::errors::{self, ObligationCauseFailureCode, TypeErrorAdditionalDiags};
53 use crate::infer;
54 use crate::infer::error_reporting::nice_region_error::find_anon_type::find_anon_type;
55 use crate::infer::ExpectedFound;
56 use crate::traits::{
57 IfExpressionCause, MatchExpressionArmCause, ObligationCause, ObligationCauseCode,
58 PredicateObligation,
59 };
60
61 use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
62 use rustc_errors::{pluralize, struct_span_err, Diagnostic, ErrorGuaranteed, IntoDiagnosticArg};
63 use rustc_errors::{Applicability, DiagnosticBuilder, DiagnosticStyledString};
64 use rustc_hir as hir;
65 use rustc_hir::def::DefKind;
66 use rustc_hir::def_id::{DefId, LocalDefId};
67 use rustc_hir::intravisit::Visitor;
68 use rustc_hir::lang_items::LangItem;
69 use rustc_hir::Node;
70 use rustc_middle::dep_graph::DepContext;
71 use rustc_middle::ty::print::with_forced_trimmed_paths;
72 use rustc_middle::ty::relate::{self, RelateResult, TypeRelation};
73 use rustc_middle::ty::{
74 self, error::TypeError, List, Region, Ty, TyCtxt, TypeFoldable, TypeSuperVisitable,
75 TypeVisitable, TypeVisitableExt,
76 };
77 use rustc_span::{sym, symbol::kw, BytePos, DesugaringKind, Pos, Span};
78 use rustc_target::spec::abi;
79 use std::borrow::Cow;
80 use std::ops::{ControlFlow, Deref};
81 use std::path::PathBuf;
82 use std::{cmp, fmt, iter};
83
84 mod note;
85 mod note_and_explain;
86 mod suggest;
87
88 pub(crate) mod need_type_info;
89 pub use need_type_info::TypeAnnotationNeeded;
90
91 pub mod nice_region_error;
92
93 /// Makes a valid string literal from a string by escaping special characters (" and \),
94 /// unless they are already escaped.
escape_literal(s: &str) -> String95 fn escape_literal(s: &str) -> String {
96 let mut escaped = String::with_capacity(s.len());
97 let mut chrs = s.chars().peekable();
98 while let Some(first) = chrs.next() {
99 match (first, chrs.peek()) {
100 ('\\', Some(&delim @ '"') | Some(&delim @ '\'')) => {
101 escaped.push('\\');
102 escaped.push(delim);
103 chrs.next();
104 }
105 ('"' | '\'', _) => {
106 escaped.push('\\');
107 escaped.push(first)
108 }
109 (c, _) => escaped.push(c),
110 };
111 }
112 escaped
113 }
114
115 /// A helper for building type related errors. The `typeck_results`
116 /// field is only populated during an in-progress typeck.
117 /// Get an instance by calling `InferCtxt::err_ctxt` or `FnCtxt::err_ctxt`.
118 ///
119 /// You must only create this if you intend to actually emit an error.
120 /// This provides a lot of utility methods which should not be used
121 /// during the happy path.
122 pub struct TypeErrCtxt<'a, 'tcx> {
123 pub infcx: &'a InferCtxt<'tcx>,
124 pub typeck_results: Option<std::cell::Ref<'a, ty::TypeckResults<'tcx>>>,
125 pub fallback_has_occurred: bool,
126
127 pub normalize_fn_sig: Box<dyn Fn(ty::PolyFnSig<'tcx>) -> ty::PolyFnSig<'tcx> + 'a>,
128
129 pub autoderef_steps:
130 Box<dyn Fn(Ty<'tcx>) -> Vec<(Ty<'tcx>, Vec<PredicateObligation<'tcx>>)> + 'a>,
131 }
132
133 impl Drop for TypeErrCtxt<'_, '_> {
drop(&mut self)134 fn drop(&mut self) {
135 if let Some(_) = self.infcx.tcx.sess.has_errors_or_delayed_span_bugs() {
136 // ok, emitted an error.
137 } else {
138 self.infcx
139 .tcx
140 .sess
141 .delay_good_path_bug("used a `TypeErrCtxt` without raising an error or lint");
142 }
143 }
144 }
145
146 impl TypeErrCtxt<'_, '_> {
147 /// This is just to avoid a potential footgun of accidentally
148 /// dropping `typeck_results` by calling `InferCtxt::err_ctxt`
149 #[deprecated(note = "you already have a `TypeErrCtxt`")]
150 #[allow(unused)]
err_ctxt(&self) -> !151 pub fn err_ctxt(&self) -> ! {
152 bug!("called `err_ctxt` on `TypeErrCtxt`. Try removing the call");
153 }
154 }
155
156 impl<'tcx> Deref for TypeErrCtxt<'_, 'tcx> {
157 type Target = InferCtxt<'tcx>;
deref(&self) -> &InferCtxt<'tcx>158 fn deref(&self) -> &InferCtxt<'tcx> {
159 &self.infcx
160 }
161 }
162
note_and_explain_region<'tcx>( tcx: TyCtxt<'tcx>, err: &mut Diagnostic, prefix: &str, region: ty::Region<'tcx>, suffix: &str, alt_span: Option<Span>, )163 pub(super) fn note_and_explain_region<'tcx>(
164 tcx: TyCtxt<'tcx>,
165 err: &mut Diagnostic,
166 prefix: &str,
167 region: ty::Region<'tcx>,
168 suffix: &str,
169 alt_span: Option<Span>,
170 ) {
171 let (description, span) = match *region {
172 ty::ReEarlyBound(_) | ty::ReFree(_) | ty::RePlaceholder(_) | ty::ReStatic => {
173 msg_span_from_named_region(tcx, region, alt_span)
174 }
175
176 ty::ReError(_) => return,
177
178 // We shouldn't really be having unification failures with ReVar
179 // and ReLateBound though.
180 ty::ReVar(_) | ty::ReLateBound(..) | ty::ReErased => {
181 (format!("lifetime `{region}`"), alt_span)
182 }
183 };
184
185 emit_msg_span(err, prefix, description, span, suffix);
186 }
187
explain_free_region<'tcx>( tcx: TyCtxt<'tcx>, err: &mut Diagnostic, prefix: &str, region: ty::Region<'tcx>, suffix: &str, )188 fn explain_free_region<'tcx>(
189 tcx: TyCtxt<'tcx>,
190 err: &mut Diagnostic,
191 prefix: &str,
192 region: ty::Region<'tcx>,
193 suffix: &str,
194 ) {
195 let (description, span) = msg_span_from_named_region(tcx, region, None);
196
197 label_msg_span(err, prefix, description, span, suffix);
198 }
199
msg_span_from_named_region<'tcx>( tcx: TyCtxt<'tcx>, region: ty::Region<'tcx>, alt_span: Option<Span>, ) -> (String, Option<Span>)200 fn msg_span_from_named_region<'tcx>(
201 tcx: TyCtxt<'tcx>,
202 region: ty::Region<'tcx>,
203 alt_span: Option<Span>,
204 ) -> (String, Option<Span>) {
205 match *region {
206 ty::ReEarlyBound(ref br) => {
207 let scope = region.free_region_binding_scope(tcx).expect_local();
208 let span = if let Some(param) =
209 tcx.hir().get_generics(scope).and_then(|generics| generics.get_named(br.name))
210 {
211 param.span
212 } else {
213 tcx.def_span(scope)
214 };
215 let text = if br.has_name() {
216 format!("the lifetime `{}` as defined here", br.name)
217 } else {
218 "the anonymous lifetime as defined here".to_string()
219 };
220 (text, Some(span))
221 }
222 ty::ReFree(ref fr) => {
223 if !fr.bound_region.is_named()
224 && let Some((ty, _)) = find_anon_type(tcx, region, &fr.bound_region)
225 {
226 ("the anonymous lifetime defined here".to_string(), Some(ty.span))
227 } else {
228 let scope = region.free_region_binding_scope(tcx).expect_local();
229 match fr.bound_region {
230 ty::BoundRegionKind::BrNamed(_, name) => {
231 let span = if let Some(param) =
232 tcx.hir().get_generics(scope).and_then(|generics| generics.get_named(name))
233 {
234 param.span
235 } else {
236 tcx.def_span(scope)
237 };
238 let text = if name == kw::UnderscoreLifetime {
239 "the anonymous lifetime as defined here".to_string()
240 } else {
241 format!("the lifetime `{}` as defined here", name)
242 };
243 (text, Some(span))
244 }
245 ty::BrAnon(span) => (
246 "the anonymous lifetime as defined here".to_string(),
247 Some(match span {
248 Some(span) => span,
249 None => tcx.def_span(scope)
250 })
251 ),
252 _ => (
253 format!("the lifetime `{}` as defined here", region),
254 Some(tcx.def_span(scope)),
255 ),
256 }
257 }
258 }
259 ty::ReStatic => ("the static lifetime".to_owned(), alt_span),
260 ty::RePlaceholder(ty::PlaceholderRegion {
261 bound: ty::BoundRegion { kind: ty::BoundRegionKind::BrNamed(def_id, name), .. },
262 ..
263 }) => (format!("the lifetime `{name}` as defined here"), Some(tcx.def_span(def_id))),
264 ty::RePlaceholder(ty::PlaceholderRegion {
265 bound: ty::BoundRegion { kind: ty::BoundRegionKind::BrAnon(Some(span)), .. },
266 ..
267 }) => (format!("the anonymous lifetime defined here"), Some(span)),
268 ty::RePlaceholder(ty::PlaceholderRegion {
269 bound: ty::BoundRegion { kind: ty::BoundRegionKind::BrAnon(None), .. },
270 ..
271 }) => (format!("an anonymous lifetime"), None),
272 _ => bug!("{:?}", region),
273 }
274 }
275
emit_msg_span( err: &mut Diagnostic, prefix: &str, description: String, span: Option<Span>, suffix: &str, )276 fn emit_msg_span(
277 err: &mut Diagnostic,
278 prefix: &str,
279 description: String,
280 span: Option<Span>,
281 suffix: &str,
282 ) {
283 let message = format!("{}{}{}", prefix, description, suffix);
284
285 if let Some(span) = span {
286 err.span_note(span, message);
287 } else {
288 err.note(message);
289 }
290 }
291
label_msg_span( err: &mut Diagnostic, prefix: &str, description: String, span: Option<Span>, suffix: &str, )292 fn label_msg_span(
293 err: &mut Diagnostic,
294 prefix: &str,
295 description: String,
296 span: Option<Span>,
297 suffix: &str,
298 ) {
299 let message = format!("{}{}{}", prefix, description, suffix);
300
301 if let Some(span) = span {
302 err.span_label(span, message);
303 } else {
304 err.note(message);
305 }
306 }
307
308 #[instrument(level = "trace", skip(tcx))]
unexpected_hidden_region_diagnostic<'tcx>( tcx: TyCtxt<'tcx>, span: Span, hidden_ty: Ty<'tcx>, hidden_region: ty::Region<'tcx>, opaque_ty_key: ty::OpaqueTypeKey<'tcx>, ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>309 pub fn unexpected_hidden_region_diagnostic<'tcx>(
310 tcx: TyCtxt<'tcx>,
311 span: Span,
312 hidden_ty: Ty<'tcx>,
313 hidden_region: ty::Region<'tcx>,
314 opaque_ty_key: ty::OpaqueTypeKey<'tcx>,
315 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
316 let mut err = tcx.sess.create_err(errors::OpaqueCapturesLifetime {
317 span,
318 opaque_ty: Ty::new_opaque(tcx, opaque_ty_key.def_id.to_def_id(), opaque_ty_key.substs),
319 opaque_ty_span: tcx.def_span(opaque_ty_key.def_id),
320 });
321
322 // Explain the region we are capturing.
323 match *hidden_region {
324 ty::ReEarlyBound(_) | ty::ReFree(_) | ty::ReStatic => {
325 // Assuming regionck succeeded (*), we ought to always be
326 // capturing *some* region from the fn header, and hence it
327 // ought to be free. So under normal circumstances, we will go
328 // down this path which gives a decent human readable
329 // explanation.
330 //
331 // (*) if not, the `tainted_by_errors` field would be set to
332 // `Some(ErrorGuaranteed)` in any case, so we wouldn't be here at all.
333 explain_free_region(
334 tcx,
335 &mut err,
336 &format!("hidden type `{}` captures ", hidden_ty),
337 hidden_region,
338 "",
339 );
340 if let Some(reg_info) = tcx.is_suitable_region(hidden_region) {
341 let fn_returns = tcx.return_type_impl_or_dyn_traits(reg_info.def_id);
342 nice_region_error::suggest_new_region_bound(
343 tcx,
344 &mut err,
345 fn_returns,
346 hidden_region.to_string(),
347 None,
348 format!("captures `{}`", hidden_region),
349 None,
350 Some(reg_info.def_id),
351 )
352 }
353 }
354 ty::ReError(_) => {
355 err.delay_as_bug();
356 }
357 _ => {
358 // Ugh. This is a painful case: the hidden region is not one
359 // that we can easily summarize or explain. This can happen
360 // in a case like
361 // `tests/ui/multiple-lifetimes/ordinary-bounds-unsuited.rs`:
362 //
363 // ```
364 // fn upper_bounds<'a, 'b>(a: Ordinary<'a>, b: Ordinary<'b>) -> impl Trait<'a, 'b> {
365 // if condition() { a } else { b }
366 // }
367 // ```
368 //
369 // Here the captured lifetime is the intersection of `'a` and
370 // `'b`, which we can't quite express.
371
372 // We can at least report a really cryptic error for now.
373 note_and_explain_region(
374 tcx,
375 &mut err,
376 &format!("hidden type `{}` captures ", hidden_ty),
377 hidden_region,
378 "",
379 None,
380 );
381 }
382 }
383
384 err
385 }
386
387 impl<'tcx> InferCtxt<'tcx> {
get_impl_future_output_ty(&self, ty: Ty<'tcx>) -> Option<Ty<'tcx>>388 pub fn get_impl_future_output_ty(&self, ty: Ty<'tcx>) -> Option<Ty<'tcx>> {
389 let (def_id, substs) = match *ty.kind() {
390 ty::Alias(_, ty::AliasTy { def_id, substs, .. })
391 if matches!(self.tcx.def_kind(def_id), DefKind::OpaqueTy) =>
392 {
393 (def_id, substs)
394 }
395 ty::Alias(_, ty::AliasTy { def_id, substs, .. })
396 if self.tcx.is_impl_trait_in_trait(def_id) =>
397 {
398 (def_id, substs)
399 }
400 _ => return None,
401 };
402
403 let future_trait = self.tcx.require_lang_item(LangItem::Future, None);
404 let item_def_id = self.tcx.associated_item_def_ids(future_trait)[0];
405
406 self.tcx.explicit_item_bounds(def_id).subst_iter_copied(self.tcx, substs).find_map(
407 |(predicate, _)| {
408 predicate
409 .kind()
410 .map_bound(|kind| match kind {
411 ty::ClauseKind::Projection(projection_predicate)
412 if projection_predicate.projection_ty.def_id == item_def_id =>
413 {
414 projection_predicate.term.ty()
415 }
416 _ => None,
417 })
418 .no_bound_vars()
419 .flatten()
420 },
421 )
422 }
423 }
424
425 impl<'tcx> TypeErrCtxt<'_, 'tcx> {
report_region_errors( &self, generic_param_scope: LocalDefId, errors: &[RegionResolutionError<'tcx>], ) -> ErrorGuaranteed426 pub fn report_region_errors(
427 &self,
428 generic_param_scope: LocalDefId,
429 errors: &[RegionResolutionError<'tcx>],
430 ) -> ErrorGuaranteed {
431 if let Some(guaranteed) = self.infcx.tainted_by_errors() {
432 return guaranteed;
433 }
434
435 debug!("report_region_errors(): {} errors to start", errors.len());
436
437 // try to pre-process the errors, which will group some of them
438 // together into a `ProcessedErrors` group:
439 let errors = self.process_errors(errors);
440
441 debug!("report_region_errors: {} errors after preprocessing", errors.len());
442
443 for error in errors {
444 debug!("report_region_errors: error = {:?}", error);
445
446 if !self.try_report_nice_region_error(&error) {
447 match error.clone() {
448 // These errors could indicate all manner of different
449 // problems with many different solutions. Rather
450 // than generate a "one size fits all" error, what we
451 // attempt to do is go through a number of specific
452 // scenarios and try to find the best way to present
453 // the error. If all of these fails, we fall back to a rather
454 // general bit of code that displays the error information
455 RegionResolutionError::ConcreteFailure(origin, sub, sup) => {
456 if sub.is_placeholder() || sup.is_placeholder() {
457 self.report_placeholder_failure(origin, sub, sup).emit();
458 } else {
459 self.report_concrete_failure(origin, sub, sup).emit();
460 }
461 }
462
463 RegionResolutionError::GenericBoundFailure(origin, param_ty, sub) => {
464 self.report_generic_bound_failure(
465 generic_param_scope,
466 origin.span(),
467 Some(origin),
468 param_ty,
469 sub,
470 );
471 }
472
473 RegionResolutionError::SubSupConflict(
474 _,
475 var_origin,
476 sub_origin,
477 sub_r,
478 sup_origin,
479 sup_r,
480 _,
481 ) => {
482 if sub_r.is_placeholder() {
483 self.report_placeholder_failure(sub_origin, sub_r, sup_r).emit();
484 } else if sup_r.is_placeholder() {
485 self.report_placeholder_failure(sup_origin, sub_r, sup_r).emit();
486 } else {
487 self.report_sub_sup_conflict(
488 var_origin, sub_origin, sub_r, sup_origin, sup_r,
489 );
490 }
491 }
492
493 RegionResolutionError::UpperBoundUniverseConflict(
494 _,
495 _,
496 _,
497 sup_origin,
498 sup_r,
499 ) => {
500 assert!(sup_r.is_placeholder());
501
502 // Make a dummy value for the "sub region" --
503 // this is the initial value of the
504 // placeholder. In practice, we expect more
505 // tailored errors that don't really use this
506 // value.
507 let sub_r = self.tcx.lifetimes.re_erased;
508
509 self.report_placeholder_failure(sup_origin, sub_r, sup_r).emit();
510 }
511 }
512 }
513 }
514
515 self.tcx
516 .sess
517 .delay_span_bug(self.tcx.def_span(generic_param_scope), "expected region errors")
518 }
519
520 // This method goes through all the errors and try to group certain types
521 // of error together, for the purpose of suggesting explicit lifetime
522 // parameters to the user. This is done so that we can have a more
523 // complete view of what lifetimes should be the same.
524 // If the return value is an empty vector, it means that processing
525 // failed (so the return value of this method should not be used).
526 //
527 // The method also attempts to weed out messages that seem like
528 // duplicates that will be unhelpful to the end-user. But
529 // obviously it never weeds out ALL errors.
process_errors( &self, errors: &[RegionResolutionError<'tcx>], ) -> Vec<RegionResolutionError<'tcx>>530 fn process_errors(
531 &self,
532 errors: &[RegionResolutionError<'tcx>],
533 ) -> Vec<RegionResolutionError<'tcx>> {
534 debug!("process_errors()");
535
536 // We want to avoid reporting generic-bound failures if we can
537 // avoid it: these have a very high rate of being unhelpful in
538 // practice. This is because they are basically secondary
539 // checks that test the state of the region graph after the
540 // rest of inference is done, and the other kinds of errors
541 // indicate that the region constraint graph is internally
542 // inconsistent, so these test results are likely to be
543 // meaningless.
544 //
545 // Therefore, we filter them out of the list unless they are
546 // the only thing in the list.
547
548 let is_bound_failure = |e: &RegionResolutionError<'tcx>| match *e {
549 RegionResolutionError::GenericBoundFailure(..) => true,
550 RegionResolutionError::ConcreteFailure(..)
551 | RegionResolutionError::SubSupConflict(..)
552 | RegionResolutionError::UpperBoundUniverseConflict(..) => false,
553 };
554
555 let mut errors = if errors.iter().all(|e| is_bound_failure(e)) {
556 errors.to_owned()
557 } else {
558 errors.iter().filter(|&e| !is_bound_failure(e)).cloned().collect()
559 };
560
561 // sort the errors by span, for better error message stability.
562 errors.sort_by_key(|u| match *u {
563 RegionResolutionError::ConcreteFailure(ref sro, _, _) => sro.span(),
564 RegionResolutionError::GenericBoundFailure(ref sro, _, _) => sro.span(),
565 RegionResolutionError::SubSupConflict(_, ref rvo, _, _, _, _, _) => rvo.span(),
566 RegionResolutionError::UpperBoundUniverseConflict(_, ref rvo, _, _, _) => rvo.span(),
567 });
568 errors
569 }
570
571 /// Adds a note if the types come from similarly named crates
check_and_note_conflicting_crates(&self, err: &mut Diagnostic, terr: TypeError<'tcx>)572 fn check_and_note_conflicting_crates(&self, err: &mut Diagnostic, terr: TypeError<'tcx>) {
573 use hir::def_id::CrateNum;
574 use rustc_hir::definitions::DisambiguatedDefPathData;
575 use ty::print::Printer;
576 use ty::subst::GenericArg;
577
578 struct AbsolutePathPrinter<'tcx> {
579 tcx: TyCtxt<'tcx>,
580 }
581
582 struct NonTrivialPath;
583
584 impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
585 type Error = NonTrivialPath;
586
587 type Path = Vec<String>;
588 type Region = !;
589 type Type = !;
590 type DynExistential = !;
591 type Const = !;
592
593 fn tcx<'a>(&'a self) -> TyCtxt<'tcx> {
594 self.tcx
595 }
596
597 fn print_region(self, _region: ty::Region<'_>) -> Result<Self::Region, Self::Error> {
598 Err(NonTrivialPath)
599 }
600
601 fn print_type(self, _ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> {
602 Err(NonTrivialPath)
603 }
604
605 fn print_dyn_existential(
606 self,
607 _predicates: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
608 ) -> Result<Self::DynExistential, Self::Error> {
609 Err(NonTrivialPath)
610 }
611
612 fn print_const(self, _ct: ty::Const<'tcx>) -> Result<Self::Const, Self::Error> {
613 Err(NonTrivialPath)
614 }
615
616 fn path_crate(self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
617 Ok(vec![self.tcx.crate_name(cnum).to_string()])
618 }
619 fn path_qualified(
620 self,
621 _self_ty: Ty<'tcx>,
622 _trait_ref: Option<ty::TraitRef<'tcx>>,
623 ) -> Result<Self::Path, Self::Error> {
624 Err(NonTrivialPath)
625 }
626
627 fn path_append_impl(
628 self,
629 _print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
630 _disambiguated_data: &DisambiguatedDefPathData,
631 _self_ty: Ty<'tcx>,
632 _trait_ref: Option<ty::TraitRef<'tcx>>,
633 ) -> Result<Self::Path, Self::Error> {
634 Err(NonTrivialPath)
635 }
636 fn path_append(
637 self,
638 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
639 disambiguated_data: &DisambiguatedDefPathData,
640 ) -> Result<Self::Path, Self::Error> {
641 let mut path = print_prefix(self)?;
642 path.push(disambiguated_data.to_string());
643 Ok(path)
644 }
645 fn path_generic_args(
646 self,
647 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
648 _args: &[GenericArg<'tcx>],
649 ) -> Result<Self::Path, Self::Error> {
650 print_prefix(self)
651 }
652 }
653
654 let report_path_match = |err: &mut Diagnostic, did1: DefId, did2: DefId| {
655 // Only report definitions from different crates. If both definitions
656 // are from a local module we could have false positives, e.g.
657 // let _ = [{struct Foo; Foo}, {struct Foo; Foo}];
658 if did1.krate != did2.krate {
659 let abs_path =
660 |def_id| AbsolutePathPrinter { tcx: self.tcx }.print_def_path(def_id, &[]);
661
662 // We compare strings because DefPath can be different
663 // for imported and non-imported crates
664 let same_path = || -> Result<_, NonTrivialPath> {
665 Ok(self.tcx.def_path_str(did1) == self.tcx.def_path_str(did2)
666 || abs_path(did1)? == abs_path(did2)?)
667 };
668 if same_path().unwrap_or(false) {
669 let crate_name = self.tcx.crate_name(did1.krate);
670 let msg = if did1.is_local() || did2.is_local() {
671 format!(
672 "the crate `{crate_name}` is compiled multiple times, possibly with different configurations"
673 )
674 } else {
675 format!(
676 "perhaps two different versions of crate `{crate_name}` are being used?"
677 )
678 };
679 err.note(msg);
680 }
681 }
682 };
683 match terr {
684 TypeError::Sorts(ref exp_found) => {
685 // if they are both "path types", there's a chance of ambiguity
686 // due to different versions of the same crate
687 if let (&ty::Adt(exp_adt, _), &ty::Adt(found_adt, _)) =
688 (exp_found.expected.kind(), exp_found.found.kind())
689 {
690 report_path_match(err, exp_adt.did(), found_adt.did());
691 }
692 }
693 TypeError::Traits(ref exp_found) => {
694 report_path_match(err, exp_found.expected, exp_found.found);
695 }
696 _ => (), // FIXME(#22750) handle traits and stuff
697 }
698 }
699
note_error_origin( &self, err: &mut Diagnostic, cause: &ObligationCause<'tcx>, exp_found: Option<ty::error::ExpectedFound<Ty<'tcx>>>, terr: TypeError<'tcx>, )700 fn note_error_origin(
701 &self,
702 err: &mut Diagnostic,
703 cause: &ObligationCause<'tcx>,
704 exp_found: Option<ty::error::ExpectedFound<Ty<'tcx>>>,
705 terr: TypeError<'tcx>,
706 ) {
707 match *cause.code() {
708 ObligationCauseCode::Pattern { origin_expr: true, span: Some(span), root_ty } => {
709 let ty = self.resolve_vars_if_possible(root_ty);
710 if !matches!(ty.kind(), ty::Infer(ty::InferTy::TyVar(_) | ty::InferTy::FreshTy(_)))
711 {
712 // don't show type `_`
713 if span.desugaring_kind() == Some(DesugaringKind::ForLoop)
714 && let ty::Adt(def, substs) = ty.kind()
715 && Some(def.did()) == self.tcx.get_diagnostic_item(sym::Option)
716 {
717 err.span_label(span, format!("this is an iterator with items of type `{}`", substs.type_at(0)));
718 } else {
719 err.span_label(span, format!("this expression has type `{}`", ty));
720 }
721 }
722 if let Some(ty::error::ExpectedFound { found, .. }) = exp_found
723 && ty.is_box() && ty.boxed_ty() == found
724 && let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span)
725 {
726 err.span_suggestion(
727 span,
728 "consider dereferencing the boxed value",
729 format!("*{}", snippet),
730 Applicability::MachineApplicable,
731 );
732 }
733 }
734 ObligationCauseCode::Pattern { origin_expr: false, span: Some(span), .. } => {
735 err.span_label(span, "expected due to this");
736 }
737 ObligationCauseCode::MatchExpressionArm(box MatchExpressionArmCause {
738 arm_block_id,
739 arm_span,
740 arm_ty,
741 prior_arm_block_id,
742 prior_arm_span,
743 prior_arm_ty,
744 source,
745 ref prior_arms,
746 scrut_hir_id,
747 opt_suggest_box_span,
748 scrut_span,
749 ..
750 }) => match source {
751 hir::MatchSource::TryDesugar => {
752 if let Some(ty::error::ExpectedFound { expected, .. }) = exp_found {
753 let scrut_expr = self.tcx.hir().expect_expr(scrut_hir_id);
754 let scrut_ty = if let hir::ExprKind::Call(_, args) = &scrut_expr.kind {
755 let arg_expr = args.first().expect("try desugaring call w/out arg");
756 self.typeck_results.as_ref().and_then(|typeck_results| {
757 typeck_results.expr_ty_opt(arg_expr)
758 })
759 } else {
760 bug!("try desugaring w/out call expr as scrutinee");
761 };
762
763 match scrut_ty {
764 Some(ty) if expected == ty => {
765 let source_map = self.tcx.sess.source_map();
766 err.span_suggestion(
767 source_map.end_point(cause.span),
768 "try removing this `?`",
769 "",
770 Applicability::MachineApplicable,
771 );
772 }
773 _ => {}
774 }
775 }
776 }
777 _ => {
778 // `prior_arm_ty` can be `!`, `expected` will have better info when present.
779 let t = self.resolve_vars_if_possible(match exp_found {
780 Some(ty::error::ExpectedFound { expected, .. }) => expected,
781 _ => prior_arm_ty,
782 });
783 let source_map = self.tcx.sess.source_map();
784 let mut any_multiline_arm = source_map.is_multiline(arm_span);
785 if prior_arms.len() <= 4 {
786 for sp in prior_arms {
787 any_multiline_arm |= source_map.is_multiline(*sp);
788 err.span_label(*sp, format!("this is found to be of type `{}`", t));
789 }
790 } else if let Some(sp) = prior_arms.last() {
791 any_multiline_arm |= source_map.is_multiline(*sp);
792 err.span_label(
793 *sp,
794 format!("this and all prior arms are found to be of type `{}`", t),
795 );
796 }
797 let outer = if any_multiline_arm || !source_map.is_multiline(cause.span) {
798 // Cover just `match` and the scrutinee expression, not
799 // the entire match body, to reduce diagram noise.
800 cause.span.shrink_to_lo().to(scrut_span)
801 } else {
802 cause.span
803 };
804 let msg = "`match` arms have incompatible types";
805 err.span_label(outer, msg);
806 if let Some(subdiag) = self.suggest_remove_semi_or_return_binding(
807 prior_arm_block_id,
808 prior_arm_ty,
809 prior_arm_span,
810 arm_block_id,
811 arm_ty,
812 arm_span,
813 ) {
814 err.subdiagnostic(subdiag);
815 }
816 if let Some(ret_sp) = opt_suggest_box_span {
817 // Get return type span and point to it.
818 self.suggest_boxing_for_return_impl_trait(
819 err,
820 ret_sp,
821 prior_arms.iter().chain(std::iter::once(&arm_span)).map(|s| *s),
822 );
823 }
824 }
825 },
826 ObligationCauseCode::IfExpression(box IfExpressionCause {
827 then_id,
828 else_id,
829 then_ty,
830 else_ty,
831 outer_span,
832 opt_suggest_box_span,
833 }) => {
834 let then_span = self.find_block_span_from_hir_id(then_id);
835 let else_span = self.find_block_span_from_hir_id(else_id);
836 err.span_label(then_span, "expected because of this");
837 if let Some(sp) = outer_span {
838 err.span_label(sp, "`if` and `else` have incompatible types");
839 }
840 if let Some(subdiag) = self.suggest_remove_semi_or_return_binding(
841 Some(then_id),
842 then_ty,
843 then_span,
844 Some(else_id),
845 else_ty,
846 else_span,
847 ) {
848 err.subdiagnostic(subdiag);
849 }
850 // don't suggest wrapping either blocks in `if .. {} else {}`
851 let is_empty_arm = |id| {
852 let hir::Node::Block(blk) = self.tcx.hir().get(id)
853 else {
854 return false;
855 };
856 if blk.expr.is_some() || !blk.stmts.is_empty() {
857 return false;
858 }
859 let Some((_, hir::Node::Expr(expr))) = self.tcx.hir().parent_iter(id).nth(1)
860 else {
861 return false;
862 };
863 matches!(expr.kind, hir::ExprKind::If(..))
864 };
865 if let Some(ret_sp) = opt_suggest_box_span
866 && !is_empty_arm(then_id)
867 && !is_empty_arm(else_id)
868 {
869 self.suggest_boxing_for_return_impl_trait(
870 err,
871 ret_sp,
872 [then_span, else_span].into_iter(),
873 );
874 }
875 }
876 ObligationCauseCode::LetElse => {
877 err.help("try adding a diverging expression, such as `return` or `panic!(..)`");
878 err.help("...or use `match` instead of `let...else`");
879 }
880 _ => {
881 if let ObligationCauseCode::BindingObligation(_, span)
882 | ObligationCauseCode::ExprBindingObligation(_, span, ..)
883 = cause.code().peel_derives()
884 && let TypeError::RegionsPlaceholderMismatch = terr
885 {
886 err.span_note( * span,
887 "the lifetime requirement is introduced here");
888 }
889 }
890 }
891 }
892
893 /// Given that `other_ty` is the same as a type argument for `name` in `sub`, populate `value`
894 /// highlighting `name` and every type argument that isn't at `pos` (which is `other_ty`), and
895 /// populate `other_value` with `other_ty`.
896 ///
897 /// ```text
898 /// Foo<Bar<Qux>>
899 /// ^^^^--------^ this is highlighted
900 /// | |
901 /// | this type argument is exactly the same as the other type, not highlighted
902 /// this is highlighted
903 /// Bar<Qux>
904 /// -------- this type is the same as a type argument in the other type, not highlighted
905 /// ```
highlight_outer( &self, value: &mut DiagnosticStyledString, other_value: &mut DiagnosticStyledString, name: String, sub: ty::subst::SubstsRef<'tcx>, pos: usize, other_ty: Ty<'tcx>, )906 fn highlight_outer(
907 &self,
908 value: &mut DiagnosticStyledString,
909 other_value: &mut DiagnosticStyledString,
910 name: String,
911 sub: ty::subst::SubstsRef<'tcx>,
912 pos: usize,
913 other_ty: Ty<'tcx>,
914 ) {
915 // `value` and `other_value` hold two incomplete type representation for display.
916 // `name` is the path of both types being compared. `sub`
917 value.push_highlighted(name);
918 let len = sub.len();
919 if len > 0 {
920 value.push_highlighted("<");
921 }
922
923 // Output the lifetimes for the first type
924 let lifetimes = sub
925 .regions()
926 .map(|lifetime| {
927 let s = lifetime.to_string();
928 if s.is_empty() { "'_".to_string() } else { s }
929 })
930 .collect::<Vec<_>>()
931 .join(", ");
932 if !lifetimes.is_empty() {
933 if sub.regions().count() < len {
934 value.push_normal(lifetimes + ", ");
935 } else {
936 value.push_normal(lifetimes);
937 }
938 }
939
940 // Highlight all the type arguments that aren't at `pos` and compare the type argument at
941 // `pos` and `other_ty`.
942 for (i, type_arg) in sub.types().enumerate() {
943 if i == pos {
944 let values = self.cmp(type_arg, other_ty);
945 value.0.extend((values.0).0);
946 other_value.0.extend((values.1).0);
947 } else {
948 value.push_highlighted(type_arg.to_string());
949 }
950
951 if len > 0 && i != len - 1 {
952 value.push_normal(", ");
953 }
954 }
955 if len > 0 {
956 value.push_highlighted(">");
957 }
958 }
959
960 /// If `other_ty` is the same as a type argument present in `sub`, highlight `path` in `t1_out`,
961 /// as that is the difference to the other type.
962 ///
963 /// For the following code:
964 ///
965 /// ```ignore (illustrative)
966 /// let x: Foo<Bar<Qux>> = foo::<Bar<Qux>>();
967 /// ```
968 ///
969 /// The type error output will behave in the following way:
970 ///
971 /// ```text
972 /// Foo<Bar<Qux>>
973 /// ^^^^--------^ this is highlighted
974 /// | |
975 /// | this type argument is exactly the same as the other type, not highlighted
976 /// this is highlighted
977 /// Bar<Qux>
978 /// -------- this type is the same as a type argument in the other type, not highlighted
979 /// ```
cmp_type_arg( &self, mut t1_out: &mut DiagnosticStyledString, mut t2_out: &mut DiagnosticStyledString, path: String, sub: &'tcx [ty::GenericArg<'tcx>], other_path: String, other_ty: Ty<'tcx>, ) -> Option<()>980 fn cmp_type_arg(
981 &self,
982 mut t1_out: &mut DiagnosticStyledString,
983 mut t2_out: &mut DiagnosticStyledString,
984 path: String,
985 sub: &'tcx [ty::GenericArg<'tcx>],
986 other_path: String,
987 other_ty: Ty<'tcx>,
988 ) -> Option<()> {
989 // FIXME/HACK: Go back to `SubstsRef` to use its inherent methods,
990 // ideally that shouldn't be necessary.
991 let sub = self.tcx.mk_substs(sub);
992 for (i, ta) in sub.types().enumerate() {
993 if ta == other_ty {
994 self.highlight_outer(&mut t1_out, &mut t2_out, path, sub, i, other_ty);
995 return Some(());
996 }
997 if let ty::Adt(def, _) = ta.kind() {
998 let path_ = self.tcx.def_path_str(def.did());
999 if path_ == other_path {
1000 self.highlight_outer(&mut t1_out, &mut t2_out, path, sub, i, other_ty);
1001 return Some(());
1002 }
1003 }
1004 }
1005 None
1006 }
1007
1008 /// Adds a `,` to the type representation only if it is appropriate.
push_comma( &self, value: &mut DiagnosticStyledString, other_value: &mut DiagnosticStyledString, len: usize, pos: usize, )1009 fn push_comma(
1010 &self,
1011 value: &mut DiagnosticStyledString,
1012 other_value: &mut DiagnosticStyledString,
1013 len: usize,
1014 pos: usize,
1015 ) {
1016 if len > 0 && pos != len - 1 {
1017 value.push_normal(", ");
1018 other_value.push_normal(", ");
1019 }
1020 }
1021
1022 /// Given two `fn` signatures highlight only sub-parts that are different.
cmp_fn_sig( &self, sig1: &ty::PolyFnSig<'tcx>, sig2: &ty::PolyFnSig<'tcx>, ) -> (DiagnosticStyledString, DiagnosticStyledString)1023 fn cmp_fn_sig(
1024 &self,
1025 sig1: &ty::PolyFnSig<'tcx>,
1026 sig2: &ty::PolyFnSig<'tcx>,
1027 ) -> (DiagnosticStyledString, DiagnosticStyledString) {
1028 let sig1 = &(self.normalize_fn_sig)(*sig1);
1029 let sig2 = &(self.normalize_fn_sig)(*sig2);
1030
1031 let get_lifetimes = |sig| {
1032 use rustc_hir::def::Namespace;
1033 let (_, sig, reg) = ty::print::FmtPrinter::new(self.tcx, Namespace::TypeNS)
1034 .name_all_regions(sig)
1035 .unwrap();
1036 let lts: Vec<String> = reg.into_values().map(|kind| kind.to_string()).collect();
1037 (if lts.is_empty() { String::new() } else { format!("for<{}> ", lts.join(", ")) }, sig)
1038 };
1039
1040 let (lt1, sig1) = get_lifetimes(sig1);
1041 let (lt2, sig2) = get_lifetimes(sig2);
1042
1043 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
1044 let mut values = (
1045 DiagnosticStyledString::normal("".to_string()),
1046 DiagnosticStyledString::normal("".to_string()),
1047 );
1048
1049 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
1050 // ^^^^^^
1051 values.0.push(sig1.unsafety.prefix_str(), sig1.unsafety != sig2.unsafety);
1052 values.1.push(sig2.unsafety.prefix_str(), sig1.unsafety != sig2.unsafety);
1053
1054 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
1055 // ^^^^^^^^^^
1056 if sig1.abi != abi::Abi::Rust {
1057 values.0.push(format!("extern {} ", sig1.abi), sig1.abi != sig2.abi);
1058 }
1059 if sig2.abi != abi::Abi::Rust {
1060 values.1.push(format!("extern {} ", sig2.abi), sig1.abi != sig2.abi);
1061 }
1062
1063 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
1064 // ^^^^^^^^
1065 let lifetime_diff = lt1 != lt2;
1066 values.0.push(lt1, lifetime_diff);
1067 values.1.push(lt2, lifetime_diff);
1068
1069 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
1070 // ^^^
1071 values.0.push_normal("fn(");
1072 values.1.push_normal("fn(");
1073
1074 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
1075 // ^^^^^
1076 let len1 = sig1.inputs().len();
1077 let len2 = sig2.inputs().len();
1078 if len1 == len2 {
1079 for (i, (l, r)) in iter::zip(sig1.inputs(), sig2.inputs()).enumerate() {
1080 let (x1, x2) = self.cmp(*l, *r);
1081 (values.0).0.extend(x1.0);
1082 (values.1).0.extend(x2.0);
1083 self.push_comma(&mut values.0, &mut values.1, len1, i);
1084 }
1085 } else {
1086 for (i, l) in sig1.inputs().iter().enumerate() {
1087 values.0.push_highlighted(l.to_string());
1088 if i != len1 - 1 {
1089 values.0.push_highlighted(", ");
1090 }
1091 }
1092 for (i, r) in sig2.inputs().iter().enumerate() {
1093 values.1.push_highlighted(r.to_string());
1094 if i != len2 - 1 {
1095 values.1.push_highlighted(", ");
1096 }
1097 }
1098 }
1099
1100 if sig1.c_variadic {
1101 if len1 > 0 {
1102 values.0.push_normal(", ");
1103 }
1104 values.0.push("...", !sig2.c_variadic);
1105 }
1106 if sig2.c_variadic {
1107 if len2 > 0 {
1108 values.1.push_normal(", ");
1109 }
1110 values.1.push("...", !sig1.c_variadic);
1111 }
1112
1113 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
1114 // ^
1115 values.0.push_normal(")");
1116 values.1.push_normal(")");
1117
1118 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
1119 // ^^^^^^^^
1120 let output1 = sig1.output();
1121 let output2 = sig2.output();
1122 let (x1, x2) = self.cmp(output1, output2);
1123 if !output1.is_unit() {
1124 values.0.push_normal(" -> ");
1125 (values.0).0.extend(x1.0);
1126 }
1127 if !output2.is_unit() {
1128 values.1.push_normal(" -> ");
1129 (values.1).0.extend(x2.0);
1130 }
1131 values
1132 }
1133
1134 /// Compares two given types, eliding parts that are the same between them and highlighting
1135 /// relevant differences, and return two representation of those types for highlighted printing.
cmp( &self, t1: Ty<'tcx>, t2: Ty<'tcx>, ) -> (DiagnosticStyledString, DiagnosticStyledString)1136 pub fn cmp(
1137 &self,
1138 t1: Ty<'tcx>,
1139 t2: Ty<'tcx>,
1140 ) -> (DiagnosticStyledString, DiagnosticStyledString) {
1141 debug!("cmp(t1={}, t1.kind={:?}, t2={}, t2.kind={:?})", t1, t1.kind(), t2, t2.kind());
1142
1143 // helper functions
1144 fn equals<'tcx>(a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
1145 match (a.kind(), b.kind()) {
1146 (a, b) if *a == *b => true,
1147 (&ty::Int(_), &ty::Infer(ty::InferTy::IntVar(_)))
1148 | (
1149 &ty::Infer(ty::InferTy::IntVar(_)),
1150 &ty::Int(_) | &ty::Infer(ty::InferTy::IntVar(_)),
1151 )
1152 | (&ty::Float(_), &ty::Infer(ty::InferTy::FloatVar(_)))
1153 | (
1154 &ty::Infer(ty::InferTy::FloatVar(_)),
1155 &ty::Float(_) | &ty::Infer(ty::InferTy::FloatVar(_)),
1156 ) => true,
1157 _ => false,
1158 }
1159 }
1160
1161 fn push_ty_ref<'tcx>(
1162 region: ty::Region<'tcx>,
1163 ty: Ty<'tcx>,
1164 mutbl: hir::Mutability,
1165 s: &mut DiagnosticStyledString,
1166 ) {
1167 let mut r = region.to_string();
1168 if r == "'_" {
1169 r.clear();
1170 } else {
1171 r.push(' ');
1172 }
1173 s.push_highlighted(format!("&{}{}", r, mutbl.prefix_str()));
1174 s.push_normal(ty.to_string());
1175 }
1176
1177 // process starts here
1178 match (t1.kind(), t2.kind()) {
1179 (&ty::Adt(def1, sub1), &ty::Adt(def2, sub2)) => {
1180 let did1 = def1.did();
1181 let did2 = def2.did();
1182 let sub_no_defaults_1 =
1183 self.tcx.generics_of(did1).own_substs_no_defaults(self.tcx, sub1);
1184 let sub_no_defaults_2 =
1185 self.tcx.generics_of(did2).own_substs_no_defaults(self.tcx, sub2);
1186 let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new());
1187 let path1 = self.tcx.def_path_str(did1);
1188 let path2 = self.tcx.def_path_str(did2);
1189 if did1 == did2 {
1190 // Easy case. Replace same types with `_` to shorten the output and highlight
1191 // the differing ones.
1192 // let x: Foo<Bar, Qux> = y::<Foo<Quz, Qux>>();
1193 // Foo<Bar, _>
1194 // Foo<Quz, _>
1195 // --- ^ type argument elided
1196 // |
1197 // highlighted in output
1198 values.0.push_normal(path1);
1199 values.1.push_normal(path2);
1200
1201 // Avoid printing out default generic parameters that are common to both
1202 // types.
1203 let len1 = sub_no_defaults_1.len();
1204 let len2 = sub_no_defaults_2.len();
1205 let common_len = cmp::min(len1, len2);
1206 let remainder1: Vec<_> = sub1.types().skip(common_len).collect();
1207 let remainder2: Vec<_> = sub2.types().skip(common_len).collect();
1208 let common_default_params =
1209 iter::zip(remainder1.iter().rev(), remainder2.iter().rev())
1210 .filter(|(a, b)| a == b)
1211 .count();
1212 let len = sub1.len() - common_default_params;
1213 let consts_offset = len - sub1.consts().count();
1214
1215 // Only draw `<...>` if there are lifetime/type arguments.
1216 if len > 0 {
1217 values.0.push_normal("<");
1218 values.1.push_normal("<");
1219 }
1220
1221 fn lifetime_display(lifetime: Region<'_>) -> String {
1222 let s = lifetime.to_string();
1223 if s.is_empty() { "'_".to_string() } else { s }
1224 }
1225 // At one point we'd like to elide all lifetimes here, they are irrelevant for
1226 // all diagnostics that use this output
1227 //
1228 // Foo<'x, '_, Bar>
1229 // Foo<'y, '_, Qux>
1230 // ^^ ^^ --- type arguments are not elided
1231 // | |
1232 // | elided as they were the same
1233 // not elided, they were different, but irrelevant
1234 //
1235 // For bound lifetimes, keep the names of the lifetimes,
1236 // even if they are the same so that it's clear what's happening
1237 // if we have something like
1238 //
1239 // for<'r, 's> fn(Inv<'r>, Inv<'s>)
1240 // for<'r> fn(Inv<'r>, Inv<'r>)
1241 let lifetimes = sub1.regions().zip(sub2.regions());
1242 for (i, lifetimes) in lifetimes.enumerate() {
1243 let l1 = lifetime_display(lifetimes.0);
1244 let l2 = lifetime_display(lifetimes.1);
1245 if lifetimes.0 != lifetimes.1 {
1246 values.0.push_highlighted(l1);
1247 values.1.push_highlighted(l2);
1248 } else if lifetimes.0.is_late_bound() {
1249 values.0.push_normal(l1);
1250 values.1.push_normal(l2);
1251 } else {
1252 values.0.push_normal("'_");
1253 values.1.push_normal("'_");
1254 }
1255 self.push_comma(&mut values.0, &mut values.1, len, i);
1256 }
1257
1258 // We're comparing two types with the same path, so we compare the type
1259 // arguments for both. If they are the same, do not highlight and elide from the
1260 // output.
1261 // Foo<_, Bar>
1262 // Foo<_, Qux>
1263 // ^ elided type as this type argument was the same in both sides
1264 let type_arguments = sub1.types().zip(sub2.types());
1265 let regions_len = sub1.regions().count();
1266 let num_display_types = consts_offset - regions_len;
1267 for (i, (ta1, ta2)) in type_arguments.take(num_display_types).enumerate() {
1268 let i = i + regions_len;
1269 if ta1 == ta2 && !self.tcx.sess.verbose() {
1270 values.0.push_normal("_");
1271 values.1.push_normal("_");
1272 } else {
1273 let (x1, x2) = self.cmp(ta1, ta2);
1274 (values.0).0.extend(x1.0);
1275 (values.1).0.extend(x2.0);
1276 }
1277 self.push_comma(&mut values.0, &mut values.1, len, i);
1278 }
1279
1280 // Do the same for const arguments, if they are equal, do not highlight and
1281 // elide them from the output.
1282 let const_arguments = sub1.consts().zip(sub2.consts());
1283 for (i, (ca1, ca2)) in const_arguments.enumerate() {
1284 let i = i + consts_offset;
1285 if ca1 == ca2 && !self.tcx.sess.verbose() {
1286 values.0.push_normal("_");
1287 values.1.push_normal("_");
1288 } else {
1289 values.0.push_highlighted(ca1.to_string());
1290 values.1.push_highlighted(ca2.to_string());
1291 }
1292 self.push_comma(&mut values.0, &mut values.1, len, i);
1293 }
1294
1295 // Close the type argument bracket.
1296 // Only draw `<...>` if there are lifetime/type arguments.
1297 if len > 0 {
1298 values.0.push_normal(">");
1299 values.1.push_normal(">");
1300 }
1301 values
1302 } else {
1303 // Check for case:
1304 // let x: Foo<Bar<Qux> = foo::<Bar<Qux>>();
1305 // Foo<Bar<Qux>
1306 // ------- this type argument is exactly the same as the other type
1307 // Bar<Qux>
1308 if self
1309 .cmp_type_arg(
1310 &mut values.0,
1311 &mut values.1,
1312 path1.clone(),
1313 sub_no_defaults_1,
1314 path2.clone(),
1315 t2,
1316 )
1317 .is_some()
1318 {
1319 return values;
1320 }
1321 // Check for case:
1322 // let x: Bar<Qux> = y:<Foo<Bar<Qux>>>();
1323 // Bar<Qux>
1324 // Foo<Bar<Qux>>
1325 // ------- this type argument is exactly the same as the other type
1326 if self
1327 .cmp_type_arg(
1328 &mut values.1,
1329 &mut values.0,
1330 path2,
1331 sub_no_defaults_2,
1332 path1,
1333 t1,
1334 )
1335 .is_some()
1336 {
1337 return values;
1338 }
1339
1340 // We can't find anything in common, highlight relevant part of type path.
1341 // let x: foo::bar::Baz<Qux> = y:<foo::bar::Bar<Zar>>();
1342 // foo::bar::Baz<Qux>
1343 // foo::bar::Bar<Zar>
1344 // -------- this part of the path is different
1345
1346 let t1_str = t1.to_string();
1347 let t2_str = t2.to_string();
1348 let min_len = t1_str.len().min(t2_str.len());
1349
1350 const SEPARATOR: &str = "::";
1351 let separator_len = SEPARATOR.len();
1352 let split_idx: usize =
1353 iter::zip(t1_str.split(SEPARATOR), t2_str.split(SEPARATOR))
1354 .take_while(|(mod1_str, mod2_str)| mod1_str == mod2_str)
1355 .map(|(mod_str, _)| mod_str.len() + separator_len)
1356 .sum();
1357
1358 debug!(?separator_len, ?split_idx, ?min_len, "cmp");
1359
1360 if split_idx >= min_len {
1361 // paths are identical, highlight everything
1362 (
1363 DiagnosticStyledString::highlighted(t1_str),
1364 DiagnosticStyledString::highlighted(t2_str),
1365 )
1366 } else {
1367 let (common, uniq1) = t1_str.split_at(split_idx);
1368 let (_, uniq2) = t2_str.split_at(split_idx);
1369 debug!(?common, ?uniq1, ?uniq2, "cmp");
1370
1371 values.0.push_normal(common);
1372 values.0.push_highlighted(uniq1);
1373 values.1.push_normal(common);
1374 values.1.push_highlighted(uniq2);
1375
1376 values
1377 }
1378 }
1379 }
1380
1381 // When finding T != &T, highlight only the borrow
1382 (&ty::Ref(r1, ref_ty1, mutbl1), _) if equals(ref_ty1, t2) => {
1383 let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new());
1384 push_ty_ref(r1, ref_ty1, mutbl1, &mut values.0);
1385 values.1.push_normal(t2.to_string());
1386 values
1387 }
1388 (_, &ty::Ref(r2, ref_ty2, mutbl2)) if equals(t1, ref_ty2) => {
1389 let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new());
1390 values.0.push_normal(t1.to_string());
1391 push_ty_ref(r2, ref_ty2, mutbl2, &mut values.1);
1392 values
1393 }
1394
1395 // When encountering &T != &mut T, highlight only the borrow
1396 (&ty::Ref(r1, ref_ty1, mutbl1), &ty::Ref(r2, ref_ty2, mutbl2))
1397 if equals(ref_ty1, ref_ty2) =>
1398 {
1399 let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new());
1400 push_ty_ref(r1, ref_ty1, mutbl1, &mut values.0);
1401 push_ty_ref(r2, ref_ty2, mutbl2, &mut values.1);
1402 values
1403 }
1404
1405 // When encountering tuples of the same size, highlight only the differing types
1406 (&ty::Tuple(substs1), &ty::Tuple(substs2)) if substs1.len() == substs2.len() => {
1407 let mut values =
1408 (DiagnosticStyledString::normal("("), DiagnosticStyledString::normal("("));
1409 let len = substs1.len();
1410 for (i, (left, right)) in substs1.iter().zip(substs2).enumerate() {
1411 let (x1, x2) = self.cmp(left, right);
1412 (values.0).0.extend(x1.0);
1413 (values.1).0.extend(x2.0);
1414 self.push_comma(&mut values.0, &mut values.1, len, i);
1415 }
1416 if len == 1 {
1417 // Keep the output for single element tuples as `(ty,)`.
1418 values.0.push_normal(",");
1419 values.1.push_normal(",");
1420 }
1421 values.0.push_normal(")");
1422 values.1.push_normal(")");
1423 values
1424 }
1425
1426 (ty::FnDef(did1, substs1), ty::FnDef(did2, substs2)) => {
1427 let sig1 = self.tcx.fn_sig(*did1).subst(self.tcx, substs1);
1428 let sig2 = self.tcx.fn_sig(*did2).subst(self.tcx, substs2);
1429 let mut values = self.cmp_fn_sig(&sig1, &sig2);
1430 let path1 = format!(" {{{}}}", self.tcx.def_path_str_with_substs(*did1, substs1));
1431 let path2 = format!(" {{{}}}", self.tcx.def_path_str_with_substs(*did2, substs2));
1432 let same_path = path1 == path2;
1433 values.0.push(path1, !same_path);
1434 values.1.push(path2, !same_path);
1435 values
1436 }
1437
1438 (ty::FnDef(did1, substs1), ty::FnPtr(sig2)) => {
1439 let sig1 = self.tcx.fn_sig(*did1).subst(self.tcx, substs1);
1440 let mut values = self.cmp_fn_sig(&sig1, sig2);
1441 values.0.push_highlighted(format!(
1442 " {{{}}}",
1443 self.tcx.def_path_str_with_substs(*did1, substs1)
1444 ));
1445 values
1446 }
1447
1448 (ty::FnPtr(sig1), ty::FnDef(did2, substs2)) => {
1449 let sig2 = self.tcx.fn_sig(*did2).subst(self.tcx, substs2);
1450 let mut values = self.cmp_fn_sig(sig1, &sig2);
1451 values.1.push_normal(format!(
1452 " {{{}}}",
1453 self.tcx.def_path_str_with_substs(*did2, substs2)
1454 ));
1455 values
1456 }
1457
1458 (ty::FnPtr(sig1), ty::FnPtr(sig2)) => self.cmp_fn_sig(sig1, sig2),
1459
1460 _ => {
1461 if t1 == t2 && !self.tcx.sess.verbose() {
1462 // The two types are the same, elide and don't highlight.
1463 (DiagnosticStyledString::normal("_"), DiagnosticStyledString::normal("_"))
1464 } else {
1465 // We couldn't find anything in common, highlight everything.
1466 (
1467 DiagnosticStyledString::highlighted(t1.to_string()),
1468 DiagnosticStyledString::highlighted(t2.to_string()),
1469 )
1470 }
1471 }
1472 }
1473 }
1474
1475 /// Extend a type error with extra labels pointing at "non-trivial" types, like closures and
1476 /// the return type of `async fn`s.
1477 ///
1478 /// `secondary_span` gives the caller the opportunity to expand `diag` with a `span_label`.
1479 ///
1480 /// `swap_secondary_and_primary` is used to make projection errors in particular nicer by using
1481 /// the message in `secondary_span` as the primary label, and apply the message that would
1482 /// otherwise be used for the primary label on the `secondary_span` `Span`. This applies on
1483 /// E0271, like `tests/ui/issues/issue-39970.stderr`.
1484 #[instrument(
1485 level = "debug",
1486 skip(self, diag, secondary_span, swap_secondary_and_primary, prefer_label)
1487 )]
note_type_err( &self, diag: &mut Diagnostic, cause: &ObligationCause<'tcx>, secondary_span: Option<(Span, Cow<'static, str>)>, mut values: Option<ValuePairs<'tcx>>, terr: TypeError<'tcx>, swap_secondary_and_primary: bool, prefer_label: bool, )1488 pub fn note_type_err(
1489 &self,
1490 diag: &mut Diagnostic,
1491 cause: &ObligationCause<'tcx>,
1492 secondary_span: Option<(Span, Cow<'static, str>)>,
1493 mut values: Option<ValuePairs<'tcx>>,
1494 terr: TypeError<'tcx>,
1495 swap_secondary_and_primary: bool,
1496 prefer_label: bool,
1497 ) {
1498 let span = cause.span();
1499
1500 // For some types of errors, expected-found does not make
1501 // sense, so just ignore the values we were given.
1502 if let TypeError::CyclicTy(_) = terr {
1503 values = None;
1504 }
1505 struct OpaqueTypesVisitor<'tcx> {
1506 types: FxIndexMap<TyCategory, FxIndexSet<Span>>,
1507 expected: FxIndexMap<TyCategory, FxIndexSet<Span>>,
1508 found: FxIndexMap<TyCategory, FxIndexSet<Span>>,
1509 ignore_span: Span,
1510 tcx: TyCtxt<'tcx>,
1511 }
1512
1513 impl<'tcx> OpaqueTypesVisitor<'tcx> {
1514 fn visit_expected_found(
1515 tcx: TyCtxt<'tcx>,
1516 expected: impl TypeVisitable<TyCtxt<'tcx>>,
1517 found: impl TypeVisitable<TyCtxt<'tcx>>,
1518 ignore_span: Span,
1519 ) -> Self {
1520 let mut types_visitor = OpaqueTypesVisitor {
1521 types: Default::default(),
1522 expected: Default::default(),
1523 found: Default::default(),
1524 ignore_span,
1525 tcx,
1526 };
1527 // The visitor puts all the relevant encountered types in `self.types`, but in
1528 // here we want to visit two separate types with no relation to each other, so we
1529 // move the results from `types` to `expected` or `found` as appropriate.
1530 expected.visit_with(&mut types_visitor);
1531 std::mem::swap(&mut types_visitor.expected, &mut types_visitor.types);
1532 found.visit_with(&mut types_visitor);
1533 std::mem::swap(&mut types_visitor.found, &mut types_visitor.types);
1534 types_visitor
1535 }
1536
1537 fn report(&self, err: &mut Diagnostic) {
1538 self.add_labels_for_types(err, "expected", &self.expected);
1539 self.add_labels_for_types(err, "found", &self.found);
1540 }
1541
1542 fn add_labels_for_types(
1543 &self,
1544 err: &mut Diagnostic,
1545 target: &str,
1546 types: &FxIndexMap<TyCategory, FxIndexSet<Span>>,
1547 ) {
1548 for (key, values) in types.iter() {
1549 let count = values.len();
1550 let kind = key.descr();
1551 for &sp in values {
1552 err.span_label(
1553 sp,
1554 format!(
1555 "{}{} {}{}",
1556 if count == 1 { "the " } else { "one of the " },
1557 target,
1558 kind,
1559 pluralize!(count),
1560 ),
1561 );
1562 }
1563 }
1564 }
1565 }
1566
1567 impl<'tcx> ty::visit::TypeVisitor<TyCtxt<'tcx>> for OpaqueTypesVisitor<'tcx> {
1568 fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
1569 if let Some((kind, def_id)) = TyCategory::from_ty(self.tcx, t) {
1570 let span = self.tcx.def_span(def_id);
1571 // Avoid cluttering the output when the "found" and error span overlap:
1572 //
1573 // error[E0308]: mismatched types
1574 // --> $DIR/issue-20862.rs:2:5
1575 // |
1576 // LL | |y| x + y
1577 // | ^^^^^^^^^
1578 // | |
1579 // | the found closure
1580 // | expected `()`, found closure
1581 // |
1582 // = note: expected unit type `()`
1583 // found closure `[closure@$DIR/issue-20862.rs:2:5: 2:14 x:_]`
1584 //
1585 // Also ignore opaque `Future`s that come from async fns.
1586 if !self.ignore_span.overlaps(span)
1587 && !span.is_desugaring(DesugaringKind::Async)
1588 {
1589 self.types.entry(kind).or_default().insert(span);
1590 }
1591 }
1592 t.super_visit_with(self)
1593 }
1594 }
1595
1596 debug!("note_type_err(diag={:?})", diag);
1597 enum Mismatch<'a> {
1598 Variable(ty::error::ExpectedFound<Ty<'a>>),
1599 Fixed(&'static str),
1600 }
1601 let (expected_found, exp_found, is_simple_error, values) = match values {
1602 None => (None, Mismatch::Fixed("type"), false, None),
1603 Some(values) => {
1604 let values = self.resolve_vars_if_possible(values);
1605 let (is_simple_error, exp_found) = match values {
1606 ValuePairs::Terms(infer::ExpectedFound { expected, found }) => {
1607 match (expected.unpack(), found.unpack()) {
1608 (ty::TermKind::Ty(expected), ty::TermKind::Ty(found)) => {
1609 let is_simple_err =
1610 expected.is_simple_text() && found.is_simple_text();
1611 OpaqueTypesVisitor::visit_expected_found(
1612 self.tcx, expected, found, span,
1613 )
1614 .report(diag);
1615
1616 (
1617 is_simple_err,
1618 Mismatch::Variable(infer::ExpectedFound { expected, found }),
1619 )
1620 }
1621 (ty::TermKind::Const(_), ty::TermKind::Const(_)) => {
1622 (false, Mismatch::Fixed("constant"))
1623 }
1624 _ => (false, Mismatch::Fixed("type")),
1625 }
1626 }
1627 ValuePairs::Sigs(infer::ExpectedFound { expected, found }) => {
1628 OpaqueTypesVisitor::visit_expected_found(self.tcx, expected, found, span)
1629 .report(diag);
1630 (false, Mismatch::Fixed("signature"))
1631 }
1632 ValuePairs::TraitRefs(_) | ValuePairs::PolyTraitRefs(_) => {
1633 (false, Mismatch::Fixed("trait"))
1634 }
1635 ValuePairs::Aliases(infer::ExpectedFound { expected, .. }) => {
1636 (false, Mismatch::Fixed(self.tcx.def_descr(expected.def_id)))
1637 }
1638 ValuePairs::Regions(_) => (false, Mismatch::Fixed("lifetime")),
1639 };
1640 let Some(vals) = self.values_str(values) else {
1641 // Derived error. Cancel the emitter.
1642 // NOTE(eddyb) this was `.cancel()`, but `diag`
1643 // is borrowed, so we can't fully defuse it.
1644 diag.downgrade_to_delayed_bug();
1645 return;
1646 };
1647 (Some(vals), exp_found, is_simple_error, Some(values))
1648 }
1649 };
1650
1651 let mut label_or_note = |span: Span, msg: Cow<'static, str>| {
1652 if (prefer_label && is_simple_error) || &[span] == diag.span.primary_spans() {
1653 diag.span_label(span, msg);
1654 } else {
1655 diag.span_note(span, msg);
1656 }
1657 };
1658 if let Some((sp, msg)) = secondary_span {
1659 if swap_secondary_and_primary {
1660 let terr = if let Some(infer::ValuePairs::Terms(infer::ExpectedFound {
1661 expected,
1662 ..
1663 })) = values
1664 {
1665 Cow::from(format!("expected this to be `{}`", expected))
1666 } else {
1667 terr.to_string(self.tcx)
1668 };
1669 label_or_note(sp, terr);
1670 label_or_note(span, msg);
1671 } else {
1672 label_or_note(span, terr.to_string(self.tcx));
1673 label_or_note(sp, msg);
1674 }
1675 } else {
1676 if let Some(values) = values
1677 && let Some((e, f)) = values.ty()
1678 && let TypeError::ArgumentSorts(..) | TypeError::Sorts(_) = terr
1679 {
1680 let e = self.tcx.erase_regions(e);
1681 let f = self.tcx.erase_regions(f);
1682 let expected = with_forced_trimmed_paths!(e.sort_string(self.tcx));
1683 let found = with_forced_trimmed_paths!(f.sort_string(self.tcx));
1684 if expected == found {
1685 label_or_note(span, terr.to_string(self.tcx));
1686 } else {
1687 label_or_note(span, Cow::from(format!("expected {expected}, found {found}")));
1688 }
1689 } else {
1690 label_or_note(span, terr.to_string(self.tcx));
1691 }
1692 }
1693
1694 if let Some((expected, found, exp_p, found_p)) = expected_found {
1695 let (expected_label, found_label, exp_found) = match exp_found {
1696 Mismatch::Variable(ef) => (
1697 ef.expected.prefix_string(self.tcx),
1698 ef.found.prefix_string(self.tcx),
1699 Some(ef),
1700 ),
1701 Mismatch::Fixed(s) => (s.into(), s.into(), None),
1702 };
1703
1704 enum Similar<'tcx> {
1705 Adts { expected: ty::AdtDef<'tcx>, found: ty::AdtDef<'tcx> },
1706 PrimitiveFound { expected: ty::AdtDef<'tcx>, found: Ty<'tcx> },
1707 PrimitiveExpected { expected: Ty<'tcx>, found: ty::AdtDef<'tcx> },
1708 }
1709
1710 let similarity = |ExpectedFound { expected, found }: ExpectedFound<Ty<'tcx>>| {
1711 if let ty::Adt(expected, _) = expected.kind() && let Some(primitive) = found.primitive_symbol() {
1712 let path = self.tcx.def_path(expected.did()).data;
1713 let name = path.last().unwrap().data.get_opt_name();
1714 if name == Some(primitive) {
1715 return Some(Similar::PrimitiveFound { expected: *expected, found });
1716 }
1717 } else if let Some(primitive) = expected.primitive_symbol() && let ty::Adt(found, _) = found.kind() {
1718 let path = self.tcx.def_path(found.did()).data;
1719 let name = path.last().unwrap().data.get_opt_name();
1720 if name == Some(primitive) {
1721 return Some(Similar::PrimitiveExpected { expected, found: *found });
1722 }
1723 } else if let ty::Adt(expected, _) = expected.kind() && let ty::Adt(found, _) = found.kind() {
1724 if !expected.did().is_local() && expected.did().krate == found.did().krate {
1725 // Most likely types from different versions of the same crate
1726 // are in play, in which case this message isn't so helpful.
1727 // A "perhaps two different versions..." error is already emitted for that.
1728 return None;
1729 }
1730 let f_path = self.tcx.def_path(found.did()).data;
1731 let e_path = self.tcx.def_path(expected.did()).data;
1732
1733 if let (Some(e_last), Some(f_last)) = (e_path.last(), f_path.last()) && e_last == f_last {
1734 return Some(Similar::Adts{expected: *expected, found: *found});
1735 }
1736 }
1737 None
1738 };
1739
1740 match terr {
1741 // If two types mismatch but have similar names, mention that specifically.
1742 TypeError::Sorts(values) if let Some(s) = similarity(values) => {
1743 let diagnose_primitive =
1744 |prim: Ty<'tcx>,
1745 shadow: Ty<'tcx>,
1746 defid: DefId,
1747 diagnostic: &mut Diagnostic| {
1748 let name = shadow.sort_string(self.tcx);
1749 diagnostic.note(format!(
1750 "{prim} and {name} have similar names, but are actually distinct types"
1751 ));
1752 diagnostic
1753 .note(format!("{prim} is a primitive defined by the language"));
1754 let def_span = self.tcx.def_span(defid);
1755 let msg = if defid.is_local() {
1756 format!("{name} is defined in the current crate")
1757 } else {
1758 let crate_name = self.tcx.crate_name(defid.krate);
1759 format!("{name} is defined in crate `{crate_name}`")
1760 };
1761 diagnostic.span_note(def_span, msg);
1762 };
1763
1764 let diagnose_adts =
1765 |expected_adt : ty::AdtDef<'tcx>,
1766 found_adt: ty::AdtDef<'tcx>,
1767 diagnostic: &mut Diagnostic| {
1768 let found_name = values.found.sort_string(self.tcx);
1769 let expected_name = values.expected.sort_string(self.tcx);
1770
1771 let found_defid = found_adt.did();
1772 let expected_defid = expected_adt.did();
1773
1774 diagnostic.note(format!("{found_name} and {expected_name} have similar names, but are actually distinct types"));
1775 for (defid, name) in
1776 [(found_defid, found_name), (expected_defid, expected_name)]
1777 {
1778 let def_span = self.tcx.def_span(defid);
1779
1780 let msg = if found_defid.is_local() && expected_defid.is_local() {
1781 let module = self
1782 .tcx
1783 .parent_module_from_def_id(defid.expect_local())
1784 .to_def_id();
1785 let module_name = self.tcx.def_path(module).to_string_no_crate_verbose();
1786 format!("{name} is defined in module `crate{module_name}` of the current crate")
1787 } else if defid.is_local() {
1788 format!("{name} is defined in the current crate")
1789 } else {
1790 let crate_name = self.tcx.crate_name(defid.krate);
1791 format!("{name} is defined in crate `{crate_name}`")
1792 };
1793 diagnostic.span_note(def_span, msg);
1794 }
1795 };
1796
1797 match s {
1798 Similar::Adts{expected, found} => {
1799 diagnose_adts(expected, found, diag)
1800 }
1801 Similar::PrimitiveFound{expected, found: prim} => {
1802 diagnose_primitive(prim, values.expected, expected.did(), diag)
1803 }
1804 Similar::PrimitiveExpected{expected: prim, found} => {
1805 diagnose_primitive(prim, values.found, found.did(), diag)
1806 }
1807 }
1808 }
1809 TypeError::Sorts(values) => {
1810 let extra = expected == found;
1811 let sort_string = |ty: Ty<'tcx>, path: Option<PathBuf>| {
1812 let mut s = match (extra, ty.kind()) {
1813 (true, ty::Alias(ty::Opaque, ty::AliasTy { def_id, .. })) => {
1814 let sm = self.tcx.sess.source_map();
1815 let pos = sm.lookup_char_pos(self.tcx.def_span(*def_id).lo());
1816 format!(
1817 " (opaque type at <{}:{}:{}>)",
1818 sm.filename_for_diagnostics(&pos.file.name),
1819 pos.line,
1820 pos.col.to_usize() + 1,
1821 )
1822 }
1823 (true, ty::Alias(ty::Projection, proj))
1824 if self.tcx.is_impl_trait_in_trait(proj.def_id) =>
1825 {
1826 let sm = self.tcx.sess.source_map();
1827 let pos = sm.lookup_char_pos(self.tcx.def_span(proj.def_id).lo());
1828 format!(
1829 " (trait associated opaque type at <{}:{}:{}>)",
1830 sm.filename_for_diagnostics(&pos.file.name),
1831 pos.line,
1832 pos.col.to_usize() + 1,
1833 )
1834 }
1835 (true, _) => format!(" ({})", ty.sort_string(self.tcx)),
1836 (false, _) => "".to_string(),
1837 };
1838 if let Some(path) = path {
1839 s.push_str(&format!(
1840 "\nthe full type name has been written to '{}'",
1841 path.display(),
1842 ));
1843 }
1844 s
1845 };
1846 if !(values.expected.is_simple_text() && values.found.is_simple_text())
1847 || (exp_found.is_some_and(|ef| {
1848 // This happens when the type error is a subset of the expectation,
1849 // like when you have two references but one is `usize` and the other
1850 // is `f32`. In those cases we still want to show the `note`. If the
1851 // value from `ef` is `Infer(_)`, then we ignore it.
1852 if !ef.expected.is_ty_or_numeric_infer() {
1853 ef.expected != values.expected
1854 } else if !ef.found.is_ty_or_numeric_infer() {
1855 ef.found != values.found
1856 } else {
1857 false
1858 }
1859 }))
1860 {
1861 if let Some(ExpectedFound { found: found_ty, .. }) = exp_found {
1862 // `Future` is a special opaque type that the compiler
1863 // will try to hide in some case such as `async fn`, so
1864 // to make an error more use friendly we will
1865 // avoid to suggest a mismatch type with a
1866 // type that the user usually are not using
1867 // directly such as `impl Future<Output = u8>`.
1868 if !self.tcx.ty_is_opaque_future(found_ty) {
1869 diag.note_expected_found_extra(
1870 &expected_label,
1871 expected,
1872 &found_label,
1873 found,
1874 &sort_string(values.expected, exp_p),
1875 &sort_string(values.found, found_p),
1876 );
1877 }
1878 }
1879 }
1880 }
1881 _ => {
1882 debug!(
1883 "note_type_err: exp_found={:?}, expected={:?} found={:?}",
1884 exp_found, expected, found
1885 );
1886 if !is_simple_error || terr.must_include_note() {
1887 diag.note_expected_found(&expected_label, expected, &found_label, found);
1888 }
1889 }
1890 }
1891 }
1892 let exp_found = match exp_found {
1893 Mismatch::Variable(exp_found) => Some(exp_found),
1894 Mismatch::Fixed(_) => None,
1895 };
1896 let exp_found = match terr {
1897 // `terr` has more accurate type information than `exp_found` in match expressions.
1898 ty::error::TypeError::Sorts(terr)
1899 if exp_found.is_some_and(|ef| terr.found == ef.found) =>
1900 {
1901 Some(terr)
1902 }
1903 _ => exp_found,
1904 };
1905 debug!("exp_found {:?} terr {:?} cause.code {:?}", exp_found, terr, cause.code());
1906 if let Some(exp_found) = exp_found {
1907 let should_suggest_fixes =
1908 if let ObligationCauseCode::Pattern { root_ty, .. } = cause.code() {
1909 // Skip if the root_ty of the pattern is not the same as the expected_ty.
1910 // If these types aren't equal then we've probably peeled off a layer of arrays.
1911 self.same_type_modulo_infer(*root_ty, exp_found.expected)
1912 } else {
1913 true
1914 };
1915
1916 if should_suggest_fixes {
1917 self.suggest_tuple_pattern(cause, &exp_found, diag);
1918 self.suggest_accessing_field_where_appropriate(cause, &exp_found, diag);
1919 self.suggest_await_on_expect_found(cause, span, &exp_found, diag);
1920 self.suggest_function_pointers(cause, span, &exp_found, diag);
1921 }
1922 }
1923
1924 self.check_and_note_conflicting_crates(diag, terr);
1925
1926 self.note_and_explain_type_err(diag, terr, cause, span, cause.body_id.to_def_id());
1927 if let Some(exp_found) = exp_found
1928 && let exp_found = TypeError::Sorts(exp_found)
1929 && exp_found != terr
1930 {
1931 self.note_and_explain_type_err(
1932 diag,
1933 exp_found,
1934 cause,
1935 span,
1936 cause.body_id.to_def_id(),
1937 );
1938 }
1939
1940 if let Some(ValuePairs::PolyTraitRefs(exp_found)) = values
1941 && let ty::Closure(def_id, _) = exp_found.expected.skip_binder().self_ty().kind()
1942 && let Some(def_id) = def_id.as_local()
1943 && terr.involves_regions()
1944 {
1945 let span = self.tcx.def_span(def_id);
1946 diag.span_note(span, "this closure does not fulfill the lifetime requirements");
1947 self.suggest_for_all_lifetime_closure(span, self.tcx.hir().get_by_def_id(def_id), &exp_found, diag);
1948 }
1949
1950 // It reads better to have the error origin as the final
1951 // thing.
1952 self.note_error_origin(diag, cause, exp_found, terr);
1953
1954 debug!(?diag);
1955 }
1956
type_error_additional_suggestions( &self, trace: &TypeTrace<'tcx>, terr: TypeError<'tcx>, ) -> Vec<TypeErrorAdditionalDiags>1957 pub fn type_error_additional_suggestions(
1958 &self,
1959 trace: &TypeTrace<'tcx>,
1960 terr: TypeError<'tcx>,
1961 ) -> Vec<TypeErrorAdditionalDiags> {
1962 use crate::traits::ObligationCauseCode::MatchExpressionArm;
1963 let mut suggestions = Vec::new();
1964 let span = trace.cause.span();
1965 let values = self.resolve_vars_if_possible(trace.values);
1966 if let Some((expected, found)) = values.ty() {
1967 match (expected.kind(), found.kind()) {
1968 (ty::Tuple(_), ty::Tuple(_)) => {}
1969 // If a tuple of length one was expected and the found expression has
1970 // parentheses around it, perhaps the user meant to write `(expr,)` to
1971 // build a tuple (issue #86100)
1972 (ty::Tuple(fields), _) => {
1973 suggestions.extend(self.suggest_wrap_to_build_a_tuple( span, found, fields))
1974 }
1975 // If a byte was expected and the found expression is a char literal
1976 // containing a single ASCII character, perhaps the user meant to write `b'c'` to
1977 // specify a byte literal
1978 (ty::Uint(ty::UintTy::U8), ty::Char) => {
1979 if let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span)
1980 && let Some(code) = code.strip_prefix('\'').and_then(|s| s.strip_suffix('\''))
1981 && !code.starts_with("\\u") // forbid all Unicode escapes
1982 && code.chars().next().is_some_and(|c| c.is_ascii()) // forbids literal Unicode characters beyond ASCII
1983 {
1984 suggestions.push(TypeErrorAdditionalDiags::MeantByteLiteral { span, code: escape_literal(code) })
1985 }
1986 }
1987 // If a character was expected and the found expression is a string literal
1988 // containing a single character, perhaps the user meant to write `'c'` to
1989 // specify a character literal (issue #92479)
1990 (ty::Char, ty::Ref(_, r, _)) if r.is_str() => {
1991 if let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span)
1992 && let Some(code) = code.strip_prefix('"').and_then(|s| s.strip_suffix('"'))
1993 && code.chars().count() == 1
1994 {
1995 suggestions.push(TypeErrorAdditionalDiags::MeantCharLiteral { span, code: escape_literal(code) })
1996 }
1997 }
1998 // If a string was expected and the found expression is a character literal,
1999 // perhaps the user meant to write `"s"` to specify a string literal.
2000 (ty::Ref(_, r, _), ty::Char) if r.is_str() => {
2001 if let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span) {
2002 if let Some(code) =
2003 code.strip_prefix('\'').and_then(|s| s.strip_suffix('\''))
2004 {
2005 suggestions.push(TypeErrorAdditionalDiags::MeantStrLiteral { span, code: escape_literal(code) })
2006 }
2007 }
2008 }
2009 // For code `if Some(..) = expr `, the type mismatch may be expected `bool` but found `()`,
2010 // we try to suggest to add the missing `let` for `if let Some(..) = expr`
2011 (ty::Bool, ty::Tuple(list)) => if list.len() == 0 {
2012 suggestions.extend(self.suggest_let_for_letchains(&trace.cause, span));
2013 }
2014 (ty::Array(_, _), ty::Array(_, _)) => suggestions.extend(self.suggest_specify_actual_length(terr, trace, span)),
2015 _ => {}
2016 }
2017 }
2018 let code = trace.cause.code();
2019 if let &MatchExpressionArm(box MatchExpressionArmCause { source, .. }) = code
2020 && let hir::MatchSource::TryDesugar = source
2021 && let Some((expected_ty, found_ty, _, _)) = self.values_str(trace.values)
2022 {
2023 suggestions.push(TypeErrorAdditionalDiags::TryCannotConvert { found: found_ty.content(), expected: expected_ty.content() });
2024 }
2025 suggestions
2026 }
2027
suggest_specify_actual_length( &self, terr: TypeError<'_>, trace: &TypeTrace<'_>, span: Span, ) -> Option<TypeErrorAdditionalDiags>2028 fn suggest_specify_actual_length(
2029 &self,
2030 terr: TypeError<'_>,
2031 trace: &TypeTrace<'_>,
2032 span: Span,
2033 ) -> Option<TypeErrorAdditionalDiags> {
2034 let hir = self.tcx.hir();
2035 let TypeError::FixedArraySize(sz) = terr else {
2036 return None;
2037 };
2038 let tykind = match hir.find_by_def_id(trace.cause.body_id) {
2039 Some(hir::Node::Item(hir::Item { kind: hir::ItemKind::Fn(_, _, body_id), .. })) => {
2040 let body = hir.body(*body_id);
2041 struct LetVisitor<'v> {
2042 span: Span,
2043 result: Option<&'v hir::Ty<'v>>,
2044 }
2045 impl<'v> Visitor<'v> for LetVisitor<'v> {
2046 fn visit_stmt(&mut self, s: &'v hir::Stmt<'v>) {
2047 if self.result.is_some() {
2048 return;
2049 }
2050 // Find a local statement where the initializer has
2051 // the same span as the error and the type is specified.
2052 if let hir::Stmt {
2053 kind: hir::StmtKind::Local(hir::Local {
2054 init: Some(hir::Expr {
2055 span: init_span,
2056 ..
2057 }),
2058 ty: Some(array_ty),
2059 ..
2060 }),
2061 ..
2062 } = s
2063 && init_span == &self.span {
2064 self.result = Some(*array_ty);
2065 }
2066 }
2067 }
2068 let mut visitor = LetVisitor { span, result: None };
2069 visitor.visit_body(body);
2070 visitor.result.map(|r| &r.peel_refs().kind)
2071 }
2072 Some(hir::Node::Item(hir::Item { kind: hir::ItemKind::Const(ty, _), .. })) => {
2073 Some(&ty.peel_refs().kind)
2074 }
2075 _ => None,
2076 };
2077 if let Some(tykind) = tykind
2078 && let hir::TyKind::Array(_, length) = tykind
2079 && let hir::ArrayLen::Body(hir::AnonConst { hir_id, .. }) = length
2080 && let Some(span) = self.tcx.hir().opt_span(*hir_id)
2081 {
2082 Some(TypeErrorAdditionalDiags::ConsiderSpecifyingLength { span, length: sz.found })
2083 } else {
2084 None
2085 }
2086 }
2087
report_and_explain_type_error( &self, trace: TypeTrace<'tcx>, terr: TypeError<'tcx>, ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>2088 pub fn report_and_explain_type_error(
2089 &self,
2090 trace: TypeTrace<'tcx>,
2091 terr: TypeError<'tcx>,
2092 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
2093 debug!("report_and_explain_type_error(trace={:?}, terr={:?})", trace, terr);
2094
2095 let span = trace.cause.span();
2096 let failure_code = trace.cause.as_failure_code_diag(
2097 terr,
2098 span,
2099 self.type_error_additional_suggestions(&trace, terr),
2100 );
2101 let mut diag = self.tcx.sess.create_err(failure_code);
2102 self.note_type_err(&mut diag, &trace.cause, None, Some(trace.values), terr, false, false);
2103 diag
2104 }
2105
suggest_wrap_to_build_a_tuple( &self, span: Span, found: Ty<'tcx>, expected_fields: &List<Ty<'tcx>>, ) -> Option<TypeErrorAdditionalDiags>2106 fn suggest_wrap_to_build_a_tuple(
2107 &self,
2108 span: Span,
2109 found: Ty<'tcx>,
2110 expected_fields: &List<Ty<'tcx>>,
2111 ) -> Option<TypeErrorAdditionalDiags> {
2112 let [expected_tup_elem] = expected_fields[..] else { return None};
2113
2114 if !self.same_type_modulo_infer(expected_tup_elem, found) {
2115 return None;
2116 }
2117
2118 let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span)
2119 else { return None };
2120
2121 let sugg = if code.starts_with('(') && code.ends_with(')') {
2122 let before_close = span.hi() - BytePos::from_u32(1);
2123 TypeErrorAdditionalDiags::TupleOnlyComma {
2124 span: span.with_hi(before_close).shrink_to_hi(),
2125 }
2126 } else {
2127 TypeErrorAdditionalDiags::TupleAlsoParentheses {
2128 span_low: span.shrink_to_lo(),
2129 span_high: span.shrink_to_hi(),
2130 }
2131 };
2132 Some(sugg)
2133 }
2134
values_str( &self, values: ValuePairs<'tcx>, ) -> Option<(DiagnosticStyledString, DiagnosticStyledString, Option<PathBuf>, Option<PathBuf>)>2135 fn values_str(
2136 &self,
2137 values: ValuePairs<'tcx>,
2138 ) -> Option<(DiagnosticStyledString, DiagnosticStyledString, Option<PathBuf>, Option<PathBuf>)>
2139 {
2140 match values {
2141 infer::Regions(exp_found) => self.expected_found_str(exp_found),
2142 infer::Terms(exp_found) => self.expected_found_str_term(exp_found),
2143 infer::Aliases(exp_found) => self.expected_found_str(exp_found),
2144 infer::TraitRefs(exp_found) => {
2145 let pretty_exp_found = ty::error::ExpectedFound {
2146 expected: exp_found.expected.print_only_trait_path(),
2147 found: exp_found.found.print_only_trait_path(),
2148 };
2149 match self.expected_found_str(pretty_exp_found) {
2150 Some((expected, found, _, _)) if expected == found => {
2151 self.expected_found_str(exp_found)
2152 }
2153 ret => ret,
2154 }
2155 }
2156 infer::PolyTraitRefs(exp_found) => {
2157 let pretty_exp_found = ty::error::ExpectedFound {
2158 expected: exp_found.expected.print_only_trait_path(),
2159 found: exp_found.found.print_only_trait_path(),
2160 };
2161 match self.expected_found_str(pretty_exp_found) {
2162 Some((expected, found, _, _)) if expected == found => {
2163 self.expected_found_str(exp_found)
2164 }
2165 ret => ret,
2166 }
2167 }
2168 infer::Sigs(exp_found) => {
2169 let exp_found = self.resolve_vars_if_possible(exp_found);
2170 if exp_found.references_error() {
2171 return None;
2172 }
2173 let (exp, fnd) = self.cmp_fn_sig(
2174 &ty::Binder::dummy(exp_found.expected),
2175 &ty::Binder::dummy(exp_found.found),
2176 );
2177 Some((exp, fnd, None, None))
2178 }
2179 }
2180 }
2181
expected_found_str_term( &self, exp_found: ty::error::ExpectedFound<ty::Term<'tcx>>, ) -> Option<(DiagnosticStyledString, DiagnosticStyledString, Option<PathBuf>, Option<PathBuf>)>2182 fn expected_found_str_term(
2183 &self,
2184 exp_found: ty::error::ExpectedFound<ty::Term<'tcx>>,
2185 ) -> Option<(DiagnosticStyledString, DiagnosticStyledString, Option<PathBuf>, Option<PathBuf>)>
2186 {
2187 let exp_found = self.resolve_vars_if_possible(exp_found);
2188 if exp_found.references_error() {
2189 return None;
2190 }
2191
2192 Some(match (exp_found.expected.unpack(), exp_found.found.unpack()) {
2193 (ty::TermKind::Ty(expected), ty::TermKind::Ty(found)) => {
2194 let (mut exp, mut fnd) = self.cmp(expected, found);
2195 // Use the terminal width as the basis to determine when to compress the printed
2196 // out type, but give ourselves some leeway to avoid ending up creating a file for
2197 // a type that is somewhat shorter than the path we'd write to.
2198 let len = self.tcx.sess().diagnostic_width() + 40;
2199 let exp_s = exp.content();
2200 let fnd_s = fnd.content();
2201 let mut exp_p = None;
2202 let mut fnd_p = None;
2203 if exp_s.len() > len {
2204 let (exp_s, exp_path) = self.tcx.short_ty_string(expected);
2205 exp = DiagnosticStyledString::highlighted(exp_s);
2206 exp_p = exp_path;
2207 }
2208 if fnd_s.len() > len {
2209 let (fnd_s, fnd_path) = self.tcx.short_ty_string(found);
2210 fnd = DiagnosticStyledString::highlighted(fnd_s);
2211 fnd_p = fnd_path;
2212 }
2213 (exp, fnd, exp_p, fnd_p)
2214 }
2215 _ => (
2216 DiagnosticStyledString::highlighted(exp_found.expected.to_string()),
2217 DiagnosticStyledString::highlighted(exp_found.found.to_string()),
2218 None,
2219 None,
2220 ),
2221 })
2222 }
2223
2224 /// Returns a string of the form "expected `{}`, found `{}`".
expected_found_str<T: fmt::Display + TypeFoldable<TyCtxt<'tcx>>>( &self, exp_found: ty::error::ExpectedFound<T>, ) -> Option<(DiagnosticStyledString, DiagnosticStyledString, Option<PathBuf>, Option<PathBuf>)>2225 fn expected_found_str<T: fmt::Display + TypeFoldable<TyCtxt<'tcx>>>(
2226 &self,
2227 exp_found: ty::error::ExpectedFound<T>,
2228 ) -> Option<(DiagnosticStyledString, DiagnosticStyledString, Option<PathBuf>, Option<PathBuf>)>
2229 {
2230 let exp_found = self.resolve_vars_if_possible(exp_found);
2231 if exp_found.references_error() {
2232 return None;
2233 }
2234
2235 Some((
2236 DiagnosticStyledString::highlighted(exp_found.expected.to_string()),
2237 DiagnosticStyledString::highlighted(exp_found.found.to_string()),
2238 None,
2239 None,
2240 ))
2241 }
2242
report_generic_bound_failure( &self, generic_param_scope: LocalDefId, span: Span, origin: Option<SubregionOrigin<'tcx>>, bound_kind: GenericKind<'tcx>, sub: Region<'tcx>, )2243 pub fn report_generic_bound_failure(
2244 &self,
2245 generic_param_scope: LocalDefId,
2246 span: Span,
2247 origin: Option<SubregionOrigin<'tcx>>,
2248 bound_kind: GenericKind<'tcx>,
2249 sub: Region<'tcx>,
2250 ) {
2251 self.construct_generic_bound_failure(generic_param_scope, span, origin, bound_kind, sub)
2252 .emit();
2253 }
2254
construct_generic_bound_failure( &self, generic_param_scope: LocalDefId, span: Span, origin: Option<SubregionOrigin<'tcx>>, bound_kind: GenericKind<'tcx>, sub: Region<'tcx>, ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>2255 pub fn construct_generic_bound_failure(
2256 &self,
2257 generic_param_scope: LocalDefId,
2258 span: Span,
2259 origin: Option<SubregionOrigin<'tcx>>,
2260 bound_kind: GenericKind<'tcx>,
2261 sub: Region<'tcx>,
2262 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
2263 // Attempt to obtain the span of the parameter so we can
2264 // suggest adding an explicit lifetime bound to it.
2265 let generics = self.tcx.generics_of(generic_param_scope);
2266 // type_param_span is (span, has_bounds)
2267 let mut is_synthetic = false;
2268 let mut ast_generics = None;
2269 let type_param_span = match bound_kind {
2270 GenericKind::Param(ref param) => {
2271 // Account for the case where `param` corresponds to `Self`,
2272 // which doesn't have the expected type argument.
2273 if !(generics.has_self && param.index == 0) {
2274 let type_param = generics.type_param(param, self.tcx);
2275 is_synthetic = type_param.kind.is_synthetic();
2276 type_param.def_id.as_local().map(|def_id| {
2277 // Get the `hir::Param` to verify whether it already has any bounds.
2278 // We do this to avoid suggesting code that ends up as `T: 'a'b`,
2279 // instead we suggest `T: 'a + 'b` in that case.
2280 let hir_id = self.tcx.hir().local_def_id_to_hir_id(def_id);
2281 ast_generics = self.tcx.hir().get_generics(hir_id.owner.def_id);
2282 let bounds =
2283 ast_generics.and_then(|g| g.bounds_span_for_suggestions(def_id));
2284 // `sp` only covers `T`, change it so that it covers
2285 // `T:` when appropriate
2286 if let Some(span) = bounds {
2287 (span, true)
2288 } else {
2289 let sp = self.tcx.def_span(def_id);
2290 (sp.shrink_to_hi(), false)
2291 }
2292 })
2293 } else {
2294 None
2295 }
2296 }
2297 _ => None,
2298 };
2299
2300 let new_lt = {
2301 let mut possible = (b'a'..=b'z').map(|c| format!("'{}", c as char));
2302 let lts_names =
2303 iter::successors(Some(generics), |g| g.parent.map(|p| self.tcx.generics_of(p)))
2304 .flat_map(|g| &g.params)
2305 .filter(|p| matches!(p.kind, ty::GenericParamDefKind::Lifetime))
2306 .map(|p| p.name.as_str())
2307 .collect::<Vec<_>>();
2308 possible
2309 .find(|candidate| !lts_names.contains(&&candidate[..]))
2310 .unwrap_or("'lt".to_string())
2311 };
2312
2313 let mut add_lt_suggs: Vec<Option<_>> = vec![];
2314 if is_synthetic {
2315 if let Some(ast_generics) = ast_generics {
2316 let named_lifetime_param_exist = ast_generics.params.iter().any(|p| {
2317 matches!(
2318 p.kind,
2319 hir::GenericParamKind::Lifetime { kind: hir::LifetimeParamKind::Explicit }
2320 )
2321 });
2322 if named_lifetime_param_exist && let [param, ..] = ast_generics.params
2323 {
2324 add_lt_suggs.push(Some((
2325 self.tcx.def_span(param.def_id).shrink_to_lo(),
2326 format!("{new_lt}, "),
2327 )));
2328 } else {
2329 add_lt_suggs
2330 .push(Some((ast_generics.span.shrink_to_hi(), format!("<{new_lt}>"))));
2331 }
2332 }
2333 } else {
2334 if let [param, ..] = &generics.params[..] && let Some(def_id) = param.def_id.as_local()
2335 {
2336 add_lt_suggs
2337 .push(Some((self.tcx.def_span(def_id).shrink_to_lo(), format!("{new_lt}, "))));
2338 }
2339 }
2340
2341 if let Some(ast_generics) = ast_generics {
2342 for p in ast_generics.params {
2343 if p.is_elided_lifetime() {
2344 if self
2345 .tcx
2346 .sess
2347 .source_map()
2348 .span_to_prev_source(p.span.shrink_to_hi())
2349 .ok()
2350 .is_some_and(|s| *s.as_bytes().last().unwrap() == b'&')
2351 {
2352 add_lt_suggs
2353 .push(Some(
2354 (
2355 p.span.shrink_to_hi(),
2356 if let Ok(snip) = self.tcx.sess.source_map().span_to_next_source(p.span)
2357 && snip.starts_with(' ')
2358 {
2359 format!("{new_lt}")
2360 } else {
2361 format!("{new_lt} ")
2362 }
2363 )
2364 ));
2365 } else {
2366 add_lt_suggs.push(Some((p.span.shrink_to_hi(), format!("<{new_lt}>"))));
2367 }
2368 }
2369 }
2370 }
2371
2372 let labeled_user_string = match bound_kind {
2373 GenericKind::Param(ref p) => format!("the parameter type `{}`", p),
2374 GenericKind::Alias(ref p) => match p.kind(self.tcx) {
2375 ty::AliasKind::Projection | ty::AliasKind::Inherent => {
2376 format!("the associated type `{}`", p)
2377 }
2378 ty::AliasKind::Weak => format!("the type alias `{}`", p),
2379 ty::AliasKind::Opaque => format!("the opaque type `{}`", p),
2380 },
2381 };
2382
2383 if let Some(SubregionOrigin::CompareImplItemObligation {
2384 span,
2385 impl_item_def_id,
2386 trait_item_def_id,
2387 }) = origin
2388 {
2389 return self.report_extra_impl_obligation(
2390 span,
2391 impl_item_def_id,
2392 trait_item_def_id,
2393 &format!("`{}: {}`", bound_kind, sub),
2394 );
2395 }
2396
2397 fn binding_suggestion<'tcx, S: fmt::Display>(
2398 err: &mut Diagnostic,
2399 type_param_span: Option<(Span, bool)>,
2400 bound_kind: GenericKind<'tcx>,
2401 sub: S,
2402 add_lt_suggs: Vec<Option<(Span, String)>>,
2403 ) {
2404 let msg = "consider adding an explicit lifetime bound";
2405 if let Some((sp, has_lifetimes)) = type_param_span {
2406 let suggestion =
2407 if has_lifetimes { format!(" + {}", sub) } else { format!(": {}", sub) };
2408 let mut suggestions = vec![(sp, suggestion)];
2409 for add_lt_sugg in add_lt_suggs.into_iter().flatten() {
2410 suggestions.push(add_lt_sugg);
2411 }
2412 err.multipart_suggestion_verbose(
2413 format!("{msg}..."),
2414 suggestions,
2415 Applicability::MaybeIncorrect, // Issue #41966
2416 );
2417 } else {
2418 let consider = format!("{} `{}: {}`...", msg, bound_kind, sub);
2419 err.help(consider);
2420 }
2421 }
2422
2423 let new_binding_suggestion =
2424 |err: &mut Diagnostic, type_param_span: Option<(Span, bool)>| {
2425 let msg = "consider introducing an explicit lifetime bound";
2426 if let Some((sp, has_lifetimes)) = type_param_span {
2427 let suggestion = if has_lifetimes {
2428 format!(" + {}", new_lt)
2429 } else {
2430 format!(": {}", new_lt)
2431 };
2432 let mut sugg =
2433 vec![(sp, suggestion), (span.shrink_to_hi(), format!(" + {}", new_lt))];
2434 for lt in add_lt_suggs.clone().into_iter().flatten() {
2435 sugg.push(lt);
2436 sugg.rotate_right(1);
2437 }
2438 // `MaybeIncorrect` due to issue #41966.
2439 err.multipart_suggestion(msg, sugg, Applicability::MaybeIncorrect);
2440 }
2441 };
2442
2443 #[derive(Debug)]
2444 enum SubOrigin<'hir> {
2445 GAT(&'hir hir::Generics<'hir>),
2446 Impl,
2447 Trait,
2448 Fn,
2449 Unknown,
2450 }
2451 let sub_origin = 'origin: {
2452 match *sub {
2453 ty::ReEarlyBound(ty::EarlyBoundRegion { def_id, .. }) => {
2454 let node = self.tcx.hir().get_if_local(def_id).unwrap();
2455 match node {
2456 Node::GenericParam(param) => {
2457 for h in self.tcx.hir().parent_iter(param.hir_id) {
2458 break 'origin match h.1 {
2459 Node::ImplItem(hir::ImplItem {
2460 kind: hir::ImplItemKind::Type(..),
2461 generics,
2462 ..
2463 })
2464 | Node::TraitItem(hir::TraitItem {
2465 kind: hir::TraitItemKind::Type(..),
2466 generics,
2467 ..
2468 }) => SubOrigin::GAT(generics),
2469 Node::ImplItem(hir::ImplItem {
2470 kind: hir::ImplItemKind::Fn(..),
2471 ..
2472 })
2473 | Node::TraitItem(hir::TraitItem {
2474 kind: hir::TraitItemKind::Fn(..),
2475 ..
2476 })
2477 | Node::Item(hir::Item {
2478 kind: hir::ItemKind::Fn(..), ..
2479 }) => SubOrigin::Fn,
2480 Node::Item(hir::Item {
2481 kind: hir::ItemKind::Trait(..),
2482 ..
2483 }) => SubOrigin::Trait,
2484 Node::Item(hir::Item {
2485 kind: hir::ItemKind::Impl(..), ..
2486 }) => SubOrigin::Impl,
2487 _ => continue,
2488 };
2489 }
2490 }
2491 _ => {}
2492 }
2493 }
2494 _ => {}
2495 }
2496 SubOrigin::Unknown
2497 };
2498 debug!(?sub_origin);
2499
2500 let mut err = match (*sub, sub_origin) {
2501 // In the case of GATs, we have to be careful. If we a type parameter `T` on an impl,
2502 // but a lifetime `'a` on an associated type, then we might need to suggest adding
2503 // `where T: 'a`. Importantly, this is on the GAT span, not on the `T` declaration.
2504 (ty::ReEarlyBound(ty::EarlyBoundRegion { name: _, .. }), SubOrigin::GAT(generics)) => {
2505 // Does the required lifetime have a nice name we can print?
2506 let mut err = struct_span_err!(
2507 self.tcx.sess,
2508 span,
2509 E0309,
2510 "{} may not live long enough",
2511 labeled_user_string
2512 );
2513 let pred = format!("{}: {}", bound_kind, sub);
2514 let suggestion = format!("{} {}", generics.add_where_or_trailing_comma(), pred,);
2515 err.span_suggestion(
2516 generics.tail_span_for_predicate_suggestion(),
2517 "consider adding a where clause",
2518 suggestion,
2519 Applicability::MaybeIncorrect,
2520 );
2521 err
2522 }
2523 (
2524 ty::ReEarlyBound(ty::EarlyBoundRegion { name, .. })
2525 | ty::ReFree(ty::FreeRegion { bound_region: ty::BrNamed(_, name), .. }),
2526 _,
2527 ) if name != kw::UnderscoreLifetime => {
2528 // Does the required lifetime have a nice name we can print?
2529 let mut err = struct_span_err!(
2530 self.tcx.sess,
2531 span,
2532 E0309,
2533 "{} may not live long enough",
2534 labeled_user_string
2535 );
2536 // Explicitly use the name instead of `sub`'s `Display` impl. The `Display` impl
2537 // for the bound is not suitable for suggestions when `-Zverbose` is set because it
2538 // uses `Debug` output, so we handle it specially here so that suggestions are
2539 // always correct.
2540 binding_suggestion(&mut err, type_param_span, bound_kind, name, vec![]);
2541 err
2542 }
2543
2544 (ty::ReStatic, _) => {
2545 // Does the required lifetime have a nice name we can print?
2546 let mut err = struct_span_err!(
2547 self.tcx.sess,
2548 span,
2549 E0310,
2550 "{} may not live long enough",
2551 labeled_user_string
2552 );
2553 binding_suggestion(&mut err, type_param_span, bound_kind, "'static", vec![]);
2554 err
2555 }
2556
2557 _ => {
2558 // If not, be less specific.
2559 let mut err = struct_span_err!(
2560 self.tcx.sess,
2561 span,
2562 E0311,
2563 "{} may not live long enough",
2564 labeled_user_string
2565 );
2566 note_and_explain_region(
2567 self.tcx,
2568 &mut err,
2569 &format!("{} must be valid for ", labeled_user_string),
2570 sub,
2571 "...",
2572 None,
2573 );
2574 if let Some(infer::RelateParamBound(_, t, _)) = origin {
2575 let return_impl_trait =
2576 self.tcx.return_type_impl_trait(generic_param_scope).is_some();
2577 let t = self.resolve_vars_if_possible(t);
2578 match t.kind() {
2579 // We've got:
2580 // fn get_later<G, T>(g: G, dest: &mut T) -> impl FnOnce() + '_
2581 // suggest:
2582 // fn get_later<'a, G: 'a, T>(g: G, dest: &mut T) -> impl FnOnce() + '_ + 'a
2583 ty::Closure(..) | ty::Alias(ty::Opaque, ..) if return_impl_trait => {
2584 new_binding_suggestion(&mut err, type_param_span);
2585 }
2586 _ => {
2587 binding_suggestion(
2588 &mut err,
2589 type_param_span,
2590 bound_kind,
2591 new_lt,
2592 add_lt_suggs,
2593 );
2594 }
2595 }
2596 }
2597 err
2598 }
2599 };
2600
2601 if let Some(origin) = origin {
2602 self.note_region_origin(&mut err, &origin);
2603 }
2604 err
2605 }
2606
report_sub_sup_conflict( &self, var_origin: RegionVariableOrigin, sub_origin: SubregionOrigin<'tcx>, sub_region: Region<'tcx>, sup_origin: SubregionOrigin<'tcx>, sup_region: Region<'tcx>, )2607 fn report_sub_sup_conflict(
2608 &self,
2609 var_origin: RegionVariableOrigin,
2610 sub_origin: SubregionOrigin<'tcx>,
2611 sub_region: Region<'tcx>,
2612 sup_origin: SubregionOrigin<'tcx>,
2613 sup_region: Region<'tcx>,
2614 ) {
2615 let mut err = self.report_inference_failure(var_origin);
2616
2617 note_and_explain_region(
2618 self.tcx,
2619 &mut err,
2620 "first, the lifetime cannot outlive ",
2621 sup_region,
2622 "...",
2623 None,
2624 );
2625
2626 debug!("report_sub_sup_conflict: var_origin={:?}", var_origin);
2627 debug!("report_sub_sup_conflict: sub_region={:?}", sub_region);
2628 debug!("report_sub_sup_conflict: sub_origin={:?}", sub_origin);
2629 debug!("report_sub_sup_conflict: sup_region={:?}", sup_region);
2630 debug!("report_sub_sup_conflict: sup_origin={:?}", sup_origin);
2631
2632 if let infer::Subtype(ref sup_trace) = sup_origin
2633 && let infer::Subtype(ref sub_trace) = sub_origin
2634 && let Some((sup_expected, sup_found, _, _)) = self.values_str(sup_trace.values)
2635 && let Some((sub_expected, sub_found, _, _)) = self.values_str(sub_trace.values)
2636 && sub_expected == sup_expected
2637 && sub_found == sup_found
2638 {
2639 note_and_explain_region(
2640 self.tcx,
2641 &mut err,
2642 "...but the lifetime must also be valid for ",
2643 sub_region,
2644 "...",
2645 None,
2646 );
2647 err.span_note(
2648 sup_trace.cause.span,
2649 format!("...so that the {}", sup_trace.cause.as_requirement_str()),
2650 );
2651
2652 err.note_expected_found(&"", sup_expected, &"", sup_found);
2653 if sub_region.is_error() | sup_region.is_error() {
2654 err.delay_as_bug();
2655 } else {
2656 err.emit();
2657 }
2658 return;
2659 }
2660
2661 self.note_region_origin(&mut err, &sup_origin);
2662
2663 note_and_explain_region(
2664 self.tcx,
2665 &mut err,
2666 "but, the lifetime must be valid for ",
2667 sub_region,
2668 "...",
2669 None,
2670 );
2671
2672 self.note_region_origin(&mut err, &sub_origin);
2673 if sub_region.is_error() | sup_region.is_error() {
2674 err.delay_as_bug();
2675 } else {
2676 err.emit();
2677 }
2678 }
2679
2680 /// Determine whether an error associated with the given span and definition
2681 /// should be treated as being caused by the implicit `From` conversion
2682 /// within `?` desugaring.
is_try_conversion(&self, span: Span, trait_def_id: DefId) -> bool2683 pub fn is_try_conversion(&self, span: Span, trait_def_id: DefId) -> bool {
2684 span.is_desugaring(DesugaringKind::QuestionMark)
2685 && self.tcx.is_diagnostic_item(sym::From, trait_def_id)
2686 }
2687
2688 /// Structurally compares two types, modulo any inference variables.
2689 ///
2690 /// Returns `true` if two types are equal, or if one type is an inference variable compatible
2691 /// with the other type. A TyVar inference type is compatible with any type, and an IntVar or
2692 /// FloatVar inference type are compatible with themselves or their concrete types (Int and
2693 /// Float types, respectively). When comparing two ADTs, these rules apply recursively.
same_type_modulo_infer<T: relate::Relate<'tcx>>(&self, a: T, b: T) -> bool2694 pub fn same_type_modulo_infer<T: relate::Relate<'tcx>>(&self, a: T, b: T) -> bool {
2695 let (a, b) = self.resolve_vars_if_possible((a, b));
2696 SameTypeModuloInfer(self).relate(a, b).is_ok()
2697 }
2698 }
2699
2700 struct SameTypeModuloInfer<'a, 'tcx>(&'a InferCtxt<'tcx>);
2701
2702 impl<'tcx> TypeRelation<'tcx> for SameTypeModuloInfer<'_, 'tcx> {
tcx(&self) -> TyCtxt<'tcx>2703 fn tcx(&self) -> TyCtxt<'tcx> {
2704 self.0.tcx
2705 }
2706
param_env(&self) -> ty::ParamEnv<'tcx>2707 fn param_env(&self) -> ty::ParamEnv<'tcx> {
2708 // Unused, only for consts which we treat as always equal
2709 ty::ParamEnv::empty()
2710 }
2711
tag(&self) -> &'static str2712 fn tag(&self) -> &'static str {
2713 "SameTypeModuloInfer"
2714 }
2715
a_is_expected(&self) -> bool2716 fn a_is_expected(&self) -> bool {
2717 true
2718 }
2719
relate_with_variance<T: relate::Relate<'tcx>>( &mut self, _variance: ty::Variance, _info: ty::VarianceDiagInfo<'tcx>, a: T, b: T, ) -> relate::RelateResult<'tcx, T>2720 fn relate_with_variance<T: relate::Relate<'tcx>>(
2721 &mut self,
2722 _variance: ty::Variance,
2723 _info: ty::VarianceDiagInfo<'tcx>,
2724 a: T,
2725 b: T,
2726 ) -> relate::RelateResult<'tcx, T> {
2727 self.relate(a, b)
2728 }
2729
tys(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>>2730 fn tys(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>> {
2731 match (a.kind(), b.kind()) {
2732 (ty::Int(_) | ty::Uint(_), ty::Infer(ty::InferTy::IntVar(_)))
2733 | (
2734 ty::Infer(ty::InferTy::IntVar(_)),
2735 ty::Int(_) | ty::Uint(_) | ty::Infer(ty::InferTy::IntVar(_)),
2736 )
2737 | (ty::Float(_), ty::Infer(ty::InferTy::FloatVar(_)))
2738 | (
2739 ty::Infer(ty::InferTy::FloatVar(_)),
2740 ty::Float(_) | ty::Infer(ty::InferTy::FloatVar(_)),
2741 )
2742 | (ty::Infer(ty::InferTy::TyVar(_)), _)
2743 | (_, ty::Infer(ty::InferTy::TyVar(_))) => Ok(a),
2744 (ty::Infer(_), _) | (_, ty::Infer(_)) => Err(TypeError::Mismatch),
2745 _ => relate::structurally_relate_tys(self, a, b),
2746 }
2747 }
2748
regions( &mut self, a: ty::Region<'tcx>, b: ty::Region<'tcx>, ) -> RelateResult<'tcx, ty::Region<'tcx>>2749 fn regions(
2750 &mut self,
2751 a: ty::Region<'tcx>,
2752 b: ty::Region<'tcx>,
2753 ) -> RelateResult<'tcx, ty::Region<'tcx>> {
2754 if (a.is_var() && b.is_free_or_static())
2755 || (b.is_var() && a.is_free_or_static())
2756 || (a.is_var() && b.is_var())
2757 || a == b
2758 {
2759 Ok(a)
2760 } else {
2761 Err(TypeError::Mismatch)
2762 }
2763 }
2764
binders<T>( &mut self, a: ty::Binder<'tcx, T>, b: ty::Binder<'tcx, T>, ) -> relate::RelateResult<'tcx, ty::Binder<'tcx, T>> where T: relate::Relate<'tcx>,2765 fn binders<T>(
2766 &mut self,
2767 a: ty::Binder<'tcx, T>,
2768 b: ty::Binder<'tcx, T>,
2769 ) -> relate::RelateResult<'tcx, ty::Binder<'tcx, T>>
2770 where
2771 T: relate::Relate<'tcx>,
2772 {
2773 Ok(a.rebind(self.relate(a.skip_binder(), b.skip_binder())?))
2774 }
2775
consts( &mut self, a: ty::Const<'tcx>, _b: ty::Const<'tcx>, ) -> relate::RelateResult<'tcx, ty::Const<'tcx>>2776 fn consts(
2777 &mut self,
2778 a: ty::Const<'tcx>,
2779 _b: ty::Const<'tcx>,
2780 ) -> relate::RelateResult<'tcx, ty::Const<'tcx>> {
2781 // FIXME(compiler-errors): This could at least do some first-order
2782 // relation
2783 Ok(a)
2784 }
2785 }
2786
2787 impl<'tcx> InferCtxt<'tcx> {
report_inference_failure( &self, var_origin: RegionVariableOrigin, ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>2788 fn report_inference_failure(
2789 &self,
2790 var_origin: RegionVariableOrigin,
2791 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
2792 let br_string = |br: ty::BoundRegionKind| {
2793 let mut s = match br {
2794 ty::BrNamed(_, name) => name.to_string(),
2795 _ => String::new(),
2796 };
2797 if !s.is_empty() {
2798 s.push(' ');
2799 }
2800 s
2801 };
2802 let var_description = match var_origin {
2803 infer::MiscVariable(_) => String::new(),
2804 infer::PatternRegion(_) => " for pattern".to_string(),
2805 infer::AddrOfRegion(_) => " for borrow expression".to_string(),
2806 infer::Autoref(_) => " for autoref".to_string(),
2807 infer::Coercion(_) => " for automatic coercion".to_string(),
2808 infer::LateBoundRegion(_, br, infer::FnCall) => {
2809 format!(" for lifetime parameter {}in function call", br_string(br))
2810 }
2811 infer::LateBoundRegion(_, br, infer::HigherRankedType) => {
2812 format!(" for lifetime parameter {}in generic type", br_string(br))
2813 }
2814 infer::LateBoundRegion(_, br, infer::AssocTypeProjection(def_id)) => format!(
2815 " for lifetime parameter {}in trait containing associated type `{}`",
2816 br_string(br),
2817 self.tcx.associated_item(def_id).name
2818 ),
2819 infer::EarlyBoundRegion(_, name) => format!(" for lifetime parameter `{}`", name),
2820 infer::UpvarRegion(ref upvar_id, _) => {
2821 let var_name = self.tcx.hir().name(upvar_id.var_path.hir_id);
2822 format!(" for capture of `{}` by closure", var_name)
2823 }
2824 infer::Nll(..) => bug!("NLL variable found in lexical phase"),
2825 };
2826
2827 struct_span_err!(
2828 self.tcx.sess,
2829 var_origin.span(),
2830 E0495,
2831 "cannot infer an appropriate lifetime{} due to conflicting requirements",
2832 var_description
2833 )
2834 }
2835 }
2836
2837 pub enum FailureCode {
2838 Error0317,
2839 Error0580,
2840 Error0308,
2841 Error0644,
2842 }
2843
2844 pub trait ObligationCauseExt<'tcx> {
as_failure_code(&self, terr: TypeError<'tcx>) -> FailureCode2845 fn as_failure_code(&self, terr: TypeError<'tcx>) -> FailureCode;
2846
as_failure_code_diag( &self, terr: TypeError<'tcx>, span: Span, subdiags: Vec<TypeErrorAdditionalDiags>, ) -> ObligationCauseFailureCode2847 fn as_failure_code_diag(
2848 &self,
2849 terr: TypeError<'tcx>,
2850 span: Span,
2851 subdiags: Vec<TypeErrorAdditionalDiags>,
2852 ) -> ObligationCauseFailureCode;
as_requirement_str(&self) -> &'static str2853 fn as_requirement_str(&self) -> &'static str;
2854 }
2855
2856 impl<'tcx> ObligationCauseExt<'tcx> for ObligationCause<'tcx> {
as_failure_code(&self, terr: TypeError<'tcx>) -> FailureCode2857 fn as_failure_code(&self, terr: TypeError<'tcx>) -> FailureCode {
2858 use self::FailureCode::*;
2859 use crate::traits::ObligationCauseCode::*;
2860 match self.code() {
2861 IfExpressionWithNoElse => Error0317,
2862 MainFunctionType => Error0580,
2863 CompareImplItemObligation { .. }
2864 | MatchExpressionArm(_)
2865 | IfExpression { .. }
2866 | LetElse
2867 | StartFunctionType
2868 | IntrinsicType
2869 | MethodReceiver => Error0308,
2870
2871 // In the case where we have no more specific thing to
2872 // say, also take a look at the error code, maybe we can
2873 // tailor to that.
2874 _ => match terr {
2875 TypeError::CyclicTy(ty) if ty.is_closure() || ty.is_generator() => Error0644,
2876 TypeError::IntrinsicCast => Error0308,
2877 _ => Error0308,
2878 },
2879 }
2880 }
as_failure_code_diag( &self, terr: TypeError<'tcx>, span: Span, subdiags: Vec<TypeErrorAdditionalDiags>, ) -> ObligationCauseFailureCode2881 fn as_failure_code_diag(
2882 &self,
2883 terr: TypeError<'tcx>,
2884 span: Span,
2885 subdiags: Vec<TypeErrorAdditionalDiags>,
2886 ) -> ObligationCauseFailureCode {
2887 use crate::traits::ObligationCauseCode::*;
2888 match self.code() {
2889 CompareImplItemObligation { kind: ty::AssocKind::Fn, .. } => {
2890 ObligationCauseFailureCode::MethodCompat { span, subdiags }
2891 }
2892 CompareImplItemObligation { kind: ty::AssocKind::Type, .. } => {
2893 ObligationCauseFailureCode::TypeCompat { span, subdiags }
2894 }
2895 CompareImplItemObligation { kind: ty::AssocKind::Const, .. } => {
2896 ObligationCauseFailureCode::ConstCompat { span, subdiags }
2897 }
2898 MatchExpressionArm(box MatchExpressionArmCause { source, .. }) => match source {
2899 hir::MatchSource::TryDesugar => {
2900 ObligationCauseFailureCode::TryCompat { span, subdiags }
2901 }
2902 _ => ObligationCauseFailureCode::MatchCompat { span, subdiags },
2903 },
2904 IfExpression { .. } => ObligationCauseFailureCode::IfElseDifferent { span, subdiags },
2905 IfExpressionWithNoElse => ObligationCauseFailureCode::NoElse { span },
2906 LetElse => ObligationCauseFailureCode::NoDiverge { span, subdiags },
2907 MainFunctionType => ObligationCauseFailureCode::FnMainCorrectType { span },
2908 StartFunctionType => ObligationCauseFailureCode::FnStartCorrectType { span, subdiags },
2909 IntrinsicType => ObligationCauseFailureCode::IntrinsicCorrectType { span, subdiags },
2910 MethodReceiver => ObligationCauseFailureCode::MethodCorrectType { span, subdiags },
2911
2912 // In the case where we have no more specific thing to
2913 // say, also take a look at the error code, maybe we can
2914 // tailor to that.
2915 _ => match terr {
2916 TypeError::CyclicTy(ty) if ty.is_closure() || ty.is_generator() => {
2917 ObligationCauseFailureCode::ClosureSelfref { span }
2918 }
2919 TypeError::IntrinsicCast => {
2920 ObligationCauseFailureCode::CantCoerce { span, subdiags }
2921 }
2922 _ => ObligationCauseFailureCode::Generic { span, subdiags },
2923 },
2924 }
2925 }
2926
as_requirement_str(&self) -> &'static str2927 fn as_requirement_str(&self) -> &'static str {
2928 use crate::traits::ObligationCauseCode::*;
2929 match self.code() {
2930 CompareImplItemObligation { kind: ty::AssocKind::Fn, .. } => {
2931 "method type is compatible with trait"
2932 }
2933 CompareImplItemObligation { kind: ty::AssocKind::Type, .. } => {
2934 "associated type is compatible with trait"
2935 }
2936 CompareImplItemObligation { kind: ty::AssocKind::Const, .. } => {
2937 "const is compatible with trait"
2938 }
2939 ExprAssignable => "expression is assignable",
2940 IfExpression { .. } => "`if` and `else` have incompatible types",
2941 IfExpressionWithNoElse => "`if` missing an `else` returns `()`",
2942 MainFunctionType => "`main` function has the correct type",
2943 StartFunctionType => "`#[start]` function has the correct type",
2944 IntrinsicType => "intrinsic has the correct type",
2945 MethodReceiver => "method receiver has the correct type",
2946 _ => "types are compatible",
2947 }
2948 }
2949 }
2950
2951 /// Newtype to allow implementing IntoDiagnosticArg
2952 pub struct ObligationCauseAsDiagArg<'tcx>(pub ObligationCause<'tcx>);
2953
2954 impl IntoDiagnosticArg for ObligationCauseAsDiagArg<'_> {
into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static>2955 fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> {
2956 use crate::traits::ObligationCauseCode::*;
2957 let kind = match self.0.code() {
2958 CompareImplItemObligation { kind: ty::AssocKind::Fn, .. } => "method_compat",
2959 CompareImplItemObligation { kind: ty::AssocKind::Type, .. } => "type_compat",
2960 CompareImplItemObligation { kind: ty::AssocKind::Const, .. } => "const_compat",
2961 ExprAssignable => "expr_assignable",
2962 IfExpression { .. } => "if_else_different",
2963 IfExpressionWithNoElse => "no_else",
2964 MainFunctionType => "fn_main_correct_type",
2965 StartFunctionType => "fn_start_correct_type",
2966 IntrinsicType => "intrinsic_correct_type",
2967 MethodReceiver => "method_correct_type",
2968 _ => "other",
2969 }
2970 .into();
2971 rustc_errors::DiagnosticArgValue::Str(kind)
2972 }
2973 }
2974
2975 /// This is a bare signal of what kind of type we're dealing with. `ty::TyKind` tracks
2976 /// extra information about each type, but we only care about the category.
2977 #[derive(Clone, Copy, PartialEq, Eq, Hash)]
2978 pub enum TyCategory {
2979 Closure,
2980 Opaque,
2981 OpaqueFuture,
2982 Generator(hir::GeneratorKind),
2983 Foreign,
2984 }
2985
2986 impl TyCategory {
descr(&self) -> &'static str2987 fn descr(&self) -> &'static str {
2988 match self {
2989 Self::Closure => "closure",
2990 Self::Opaque => "opaque type",
2991 Self::OpaqueFuture => "future",
2992 Self::Generator(gk) => gk.descr(),
2993 Self::Foreign => "foreign type",
2994 }
2995 }
2996
from_ty(tcx: TyCtxt<'_>, ty: Ty<'_>) -> Option<(Self, DefId)>2997 pub fn from_ty(tcx: TyCtxt<'_>, ty: Ty<'_>) -> Option<(Self, DefId)> {
2998 match *ty.kind() {
2999 ty::Closure(def_id, _) => Some((Self::Closure, def_id)),
3000 ty::Alias(ty::Opaque, ty::AliasTy { def_id, .. }) => {
3001 let kind =
3002 if tcx.ty_is_opaque_future(ty) { Self::OpaqueFuture } else { Self::Opaque };
3003 Some((kind, def_id))
3004 }
3005 ty::Generator(def_id, ..) => {
3006 Some((Self::Generator(tcx.generator_kind(def_id).unwrap()), def_id))
3007 }
3008 ty::Foreign(def_id) => Some((Self::Foreign, def_id)),
3009 _ => None,
3010 }
3011 }
3012 }
3013
3014 impl<'tcx> InferCtxt<'tcx> {
3015 /// Given a [`hir::Block`], get the span of its last expression or
3016 /// statement, peeling off any inner blocks.
find_block_span(&self, block: &'tcx hir::Block<'tcx>) -> Span3017 pub fn find_block_span(&self, block: &'tcx hir::Block<'tcx>) -> Span {
3018 let block = block.innermost_block();
3019 if let Some(expr) = &block.expr {
3020 expr.span
3021 } else if let Some(stmt) = block.stmts.last() {
3022 // possibly incorrect trailing `;` in the else arm
3023 stmt.span
3024 } else {
3025 // empty block; point at its entirety
3026 block.span
3027 }
3028 }
3029
3030 /// Given a [`hir::HirId`] for a block, get the span of its last expression
3031 /// or statement, peeling off any inner blocks.
find_block_span_from_hir_id(&self, hir_id: hir::HirId) -> Span3032 pub fn find_block_span_from_hir_id(&self, hir_id: hir::HirId) -> Span {
3033 match self.tcx.hir().get(hir_id) {
3034 hir::Node::Block(blk) => self.find_block_span(blk),
3035 // The parser was in a weird state if either of these happen, but
3036 // it's better not to panic.
3037 hir::Node::Expr(e) => e.span,
3038 _ => rustc_span::DUMMY_SP,
3039 }
3040 }
3041 }
3042