1 // ignore-tidy-filelength
2 //! Error Reporting Code for the inference engine
4 //! Because of the way inference, and in particular region inference,
5 //! works, it often happens that errors are not detected until far after
6 //! the relevant line of code has been type-checked. Therefore, there is
7 //! an elaborate system to track why a particular constraint in the
8 //! inference graph arose so that we can explain to the user what gave
9 //! rise to a particular error.
11 //! The system is based around a set of "origin" types. An "origin" is the
12 //! reason that a constraint or inference variable arose. There are
13 //! different "origin" enums for different kinds of constraints/variables
14 //! (e.g., `TypeOrigin`, `RegionVariableOrigin`). An origin always has
15 //! a span, but also more information so that we can generate a meaningful
18 //! Having a catalog of all the different reasons an error can arise is
19 //! also useful for other reasons, like cross-referencing FAQs etc, though
20 //! we are not really taking advantage of this yet.
22 //! # Region Inference
24 //! Region inference is particularly tricky because it always succeeds "in
25 //! the moment" and simply registers a constraint. Then, at the end, we
26 //! can compute the full graph and report errors, so we need to be able to
27 //! store and later report what gave rise to the conflicting constraints.
31 //! Determining whether `T1 <: T2` often involves a number of subtypes and
32 //! subconstraints along the way. A "TypeTrace" is an extended version
33 //! of an origin that traces the types and other values that were being
34 //! compared. It is not necessarily comprehensive (in fact, at the time of
35 //! this writing it only tracks the root values being compared) but I'd
36 //! like to extend it to include significant "waypoints". For example, if
37 //! you are comparing `(T1, T2) <: (T3, T4)`, and the problem is that `T2
38 //! <: T4` fails, I'd like the trace to include enough information to say
39 //! "in the 2nd element of the tuple". Similarly, failures when comparing
40 //! arguments or return types in fn types should be able to cite the
41 //! specific position, etc.
45 //! Of course, there is still a LOT of code in typeck that has yet to be
46 //! ported to this system, and which relies on string concatenation at the
47 //! time of error detection.
49 use super::lexical_region_resolve::RegionResolutionError;
50 use super::region_constraints::GenericKind;
51 use super::{InferCtxt, RegionVariableOrigin, SubregionOrigin, TypeTrace, ValuePairs};
54 use crate::infer::error_reporting::nice_region_error::find_anon_type::find_anon_type;
55 use crate::infer::ExpectedFound;
56 use crate::traits::error_reporting::report_object_safety_error;
58 IfExpressionCause, MatchExpressionArmCause, ObligationCause, ObligationCauseCode,
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, MultiSpan};
65 use rustc_hir::def::DefKind;
66 use rustc_hir::def_id::{DefId, LocalDefId};
67 use rustc_hir::lang_items::LangItem;
69 use rustc_middle::dep_graph::DepContext;
70 use rustc_middle::ty::relate::{self, RelateResult, TypeRelation};
71 use rustc_middle::ty::{
72 self, error::TypeError, List, Region, Ty, TyCtxt, TypeFoldable, TypeSuperVisitable,
75 use rustc_span::{sym, symbol::kw, BytePos, DesugaringKind, Pos, Span};
76 use rustc_target::spec::abi;
77 use std::ops::{ControlFlow, Deref};
78 use std::path::PathBuf;
79 use std::{cmp, fmt, iter};
84 pub(crate) mod need_type_info;
85 pub use need_type_info::TypeAnnotationNeeded;
87 pub mod nice_region_error;
89 /// A helper for building type related errors. The `typeck_results`
90 /// field is only populated during an in-progress typeck.
91 /// Get an instance by calling `InferCtxt::err` or `FnCtxt::infer_err`.
92 pub struct TypeErrCtxt<'a, 'tcx> {
93 pub infcx: &'a InferCtxt<'tcx>,
94 pub typeck_results: Option<std::cell::Ref<'a, ty::TypeckResults<'tcx>>>,
95 pub normalize_fn_sig: Box<dyn Fn(ty::PolyFnSig<'tcx>) -> ty::PolyFnSig<'tcx> + 'a>,
96 pub fallback_has_occurred: bool,
99 impl TypeErrCtxt<'_, '_> {
100 /// This is just to avoid a potential footgun of accidentally
101 /// dropping `typeck_results` by calling `InferCtxt::err_ctxt`
102 #[deprecated(note = "you already have a `TypeErrCtxt`")]
104 pub fn err_ctxt(&self) -> ! {
105 bug!("called `err_ctxt` on `TypeErrCtxt`. Try removing the call");
109 impl<'tcx> Deref for TypeErrCtxt<'_, 'tcx> {
110 type Target = InferCtxt<'tcx>;
111 fn deref(&self) -> &InferCtxt<'tcx> {
116 pub(super) fn note_and_explain_region<'tcx>(
118 err: &mut Diagnostic,
120 region: ty::Region<'tcx>,
122 alt_span: Option<Span>,
124 let (description, span) = match *region {
125 ty::ReEarlyBound(_) | ty::ReFree(_) | ty::ReStatic => {
126 msg_span_from_free_region(tcx, region, alt_span)
129 ty::RePlaceholder(_) => return,
131 // FIXME(#13998) RePlaceholder should probably print like
132 // ReFree rather than dumping Debug output on the user.
134 // We shouldn't really be having unification failures with ReVar
135 // and ReLateBound though.
136 ty::ReVar(_) | ty::ReLateBound(..) | ty::ReErased => {
137 (format!("lifetime {:?}", region), alt_span)
141 emit_msg_span(err, prefix, description, span, suffix);
144 fn explain_free_region<'tcx>(
146 err: &mut Diagnostic,
148 region: ty::Region<'tcx>,
151 let (description, span) = msg_span_from_free_region(tcx, region, None);
153 label_msg_span(err, prefix, description, span, suffix);
156 fn msg_span_from_free_region<'tcx>(
158 region: ty::Region<'tcx>,
159 alt_span: Option<Span>,
160 ) -> (String, Option<Span>) {
162 ty::ReEarlyBound(_) | ty::ReFree(_) => {
163 let (msg, span) = msg_span_from_early_bound_and_free_regions(tcx, region);
166 ty::ReStatic => ("the static lifetime".to_owned(), alt_span),
167 _ => bug!("{:?}", region),
171 fn msg_span_from_early_bound_and_free_regions<'tcx>(
173 region: ty::Region<'tcx>,
174 ) -> (String, Span) {
175 let scope = region.free_region_binding_scope(tcx).expect_local();
177 ty::ReEarlyBound(ref br) => {
178 let mut sp = tcx.def_span(scope);
180 tcx.hir().get_generics(scope).and_then(|generics| generics.get_named(br.name))
184 let text = if br.has_name() {
185 format!("the lifetime `{}` as defined here", br.name)
187 "the anonymous lifetime as defined here".to_string()
191 ty::ReFree(ref fr) => {
192 if !fr.bound_region.is_named()
193 && let Some((ty, _)) = find_anon_type(tcx, region, &fr.bound_region)
195 ("the anonymous lifetime defined here".to_string(), ty.span)
197 match fr.bound_region {
198 ty::BoundRegionKind::BrNamed(_, name) => {
199 let mut sp = tcx.def_span(scope);
201 tcx.hir().get_generics(scope).and_then(|generics| generics.get_named(name))
205 let text = if name == kw::UnderscoreLifetime {
206 "the anonymous lifetime as defined here".to_string()
208 format!("the lifetime `{}` as defined here", name)
212 ty::BrAnon(idx, span) => (
213 format!("the anonymous lifetime #{} defined here", idx + 1),
216 None => tcx.def_span(scope)
220 format!("the lifetime `{}` as defined here", region),
231 err: &mut Diagnostic,
237 let message = format!("{}{}{}", prefix, description, suffix);
239 if let Some(span) = span {
240 err.span_note(span, &message);
247 err: &mut Diagnostic,
253 let message = format!("{}{}{}", prefix, description, suffix);
255 if let Some(span) = span {
256 err.span_label(span, &message);
262 #[instrument(level = "trace", skip(tcx))]
263 pub fn unexpected_hidden_region_diagnostic<'tcx>(
267 hidden_region: ty::Region<'tcx>,
268 opaque_ty: ty::OpaqueTypeKey<'tcx>,
269 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
270 let opaque_ty = tcx.mk_opaque(opaque_ty.def_id.to_def_id(), opaque_ty.substs);
271 let mut err = struct_span_err!(
275 "hidden type for `{opaque_ty}` captures lifetime that does not appear in bounds",
278 // Explain the region we are capturing.
279 match *hidden_region {
280 ty::ReEarlyBound(_) | ty::ReFree(_) | ty::ReStatic => {
281 // Assuming regionck succeeded (*), we ought to always be
282 // capturing *some* region from the fn header, and hence it
283 // ought to be free. So under normal circumstances, we will go
284 // down this path which gives a decent human readable
287 // (*) if not, the `tainted_by_errors` field would be set to
288 // `Some(ErrorGuaranteed)` in any case, so we wouldn't be here at all.
292 &format!("hidden type `{}` captures ", hidden_ty),
296 if let Some(reg_info) = tcx.is_suitable_region(hidden_region) {
297 let fn_returns = tcx.return_type_impl_or_dyn_traits(reg_info.def_id);
298 nice_region_error::suggest_new_region_bound(
302 hidden_region.to_string(),
304 format!("captures `{}`", hidden_region),
306 Some(reg_info.def_id),
311 // Ugh. This is a painful case: the hidden region is not one
312 // that we can easily summarize or explain. This can happen
314 // `src/test/ui/multiple-lifetimes/ordinary-bounds-unsuited.rs`:
317 // fn upper_bounds<'a, 'b>(a: Ordinary<'a>, b: Ordinary<'b>) -> impl Trait<'a, 'b> {
318 // if condition() { a } else { b }
322 // Here the captured lifetime is the intersection of `'a` and
323 // `'b`, which we can't quite express.
325 // We can at least report a really cryptic error for now.
326 note_and_explain_region(
329 &format!("hidden type `{}` captures ", hidden_ty),
340 impl<'tcx> InferCtxt<'tcx> {
341 pub fn get_impl_future_output_ty(&self, ty: Ty<'tcx>) -> Option<Ty<'tcx>> {
342 let (def_id, substs) = match *ty.kind() {
343 ty::Alias(_, ty::AliasTy { def_id, substs, .. })
345 self.tcx.def_kind(def_id),
346 DefKind::OpaqueTy | DefKind::ImplTraitPlaceholder
354 let future_trait = self.tcx.require_lang_item(LangItem::Future, None);
355 let item_def_id = self.tcx.associated_item_def_ids(future_trait)[0];
357 self.tcx.bound_explicit_item_bounds(def_id).subst_iter_copied(self.tcx, substs).find_map(
361 .map_bound(|kind| match kind {
362 ty::PredicateKind::Clause(ty::Clause::Projection(projection_predicate))
363 if projection_predicate.projection_ty.def_id == item_def_id =>
365 projection_predicate.term.ty()
376 impl<'tcx> TypeErrCtxt<'_, 'tcx> {
377 pub fn report_region_errors(
379 generic_param_scope: LocalDefId,
380 errors: &[RegionResolutionError<'tcx>],
382 debug!("report_region_errors(): {} errors to start", errors.len());
384 // try to pre-process the errors, which will group some of them
385 // together into a `ProcessedErrors` group:
386 let errors = self.process_errors(errors);
388 debug!("report_region_errors: {} errors after preprocessing", errors.len());
390 for error in errors {
391 debug!("report_region_errors: error = {:?}", error);
393 if !self.try_report_nice_region_error(&error) {
394 match error.clone() {
395 // These errors could indicate all manner of different
396 // problems with many different solutions. Rather
397 // than generate a "one size fits all" error, what we
398 // attempt to do is go through a number of specific
399 // scenarios and try to find the best way to present
400 // the error. If all of these fails, we fall back to a rather
401 // general bit of code that displays the error information
402 RegionResolutionError::ConcreteFailure(origin, sub, sup) => {
403 if sub.is_placeholder() || sup.is_placeholder() {
404 self.report_placeholder_failure(origin, sub, sup).emit();
406 self.report_concrete_failure(origin, sub, sup).emit();
410 RegionResolutionError::GenericBoundFailure(origin, param_ty, sub) => {
411 self.report_generic_bound_failure(
420 RegionResolutionError::SubSupConflict(
429 if sub_r.is_placeholder() {
430 self.report_placeholder_failure(sub_origin, sub_r, sup_r).emit();
431 } else if sup_r.is_placeholder() {
432 self.report_placeholder_failure(sup_origin, sub_r, sup_r).emit();
434 self.report_sub_sup_conflict(
435 var_origin, sub_origin, sub_r, sup_origin, sup_r,
440 RegionResolutionError::UpperBoundUniverseConflict(
447 assert!(sup_r.is_placeholder());
449 // Make a dummy value for the "sub region" --
450 // this is the initial value of the
451 // placeholder. In practice, we expect more
452 // tailored errors that don't really use this
454 let sub_r = self.tcx.lifetimes.re_erased;
456 self.report_placeholder_failure(sup_origin, sub_r, sup_r).emit();
463 // This method goes through all the errors and try to group certain types
464 // of error together, for the purpose of suggesting explicit lifetime
465 // parameters to the user. This is done so that we can have a more
466 // complete view of what lifetimes should be the same.
467 // If the return value is an empty vector, it means that processing
468 // failed (so the return value of this method should not be used).
470 // The method also attempts to weed out messages that seem like
471 // duplicates that will be unhelpful to the end-user. But
472 // obviously it never weeds out ALL errors.
475 errors: &[RegionResolutionError<'tcx>],
476 ) -> Vec<RegionResolutionError<'tcx>> {
477 debug!("process_errors()");
479 // We want to avoid reporting generic-bound failures if we can
480 // avoid it: these have a very high rate of being unhelpful in
481 // practice. This is because they are basically secondary
482 // checks that test the state of the region graph after the
483 // rest of inference is done, and the other kinds of errors
484 // indicate that the region constraint graph is internally
485 // inconsistent, so these test results are likely to be
488 // Therefore, we filter them out of the list unless they are
489 // the only thing in the list.
491 let is_bound_failure = |e: &RegionResolutionError<'tcx>| match *e {
492 RegionResolutionError::GenericBoundFailure(..) => true,
493 RegionResolutionError::ConcreteFailure(..)
494 | RegionResolutionError::SubSupConflict(..)
495 | RegionResolutionError::UpperBoundUniverseConflict(..) => false,
498 let mut errors = if errors.iter().all(|e| is_bound_failure(e)) {
501 errors.iter().filter(|&e| !is_bound_failure(e)).cloned().collect()
504 // sort the errors by span, for better error message stability.
505 errors.sort_by_key(|u| match *u {
506 RegionResolutionError::ConcreteFailure(ref sro, _, _) => sro.span(),
507 RegionResolutionError::GenericBoundFailure(ref sro, _, _) => sro.span(),
508 RegionResolutionError::SubSupConflict(_, ref rvo, _, _, _, _, _) => rvo.span(),
509 RegionResolutionError::UpperBoundUniverseConflict(_, ref rvo, _, _, _) => rvo.span(),
514 /// Adds a note if the types come from similarly named crates
515 fn check_and_note_conflicting_crates(&self, err: &mut Diagnostic, terr: TypeError<'tcx>) {
516 use hir::def_id::CrateNum;
517 use rustc_hir::definitions::DisambiguatedDefPathData;
518 use ty::print::Printer;
519 use ty::subst::GenericArg;
521 struct AbsolutePathPrinter<'tcx> {
525 struct NonTrivialPath;
527 impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
528 type Error = NonTrivialPath;
530 type Path = Vec<String>;
533 type DynExistential = !;
536 fn tcx<'a>(&'a self) -> TyCtxt<'tcx> {
540 fn print_region(self, _region: ty::Region<'_>) -> Result<Self::Region, Self::Error> {
544 fn print_type(self, _ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> {
548 fn print_dyn_existential(
550 _predicates: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
551 ) -> Result<Self::DynExistential, Self::Error> {
555 fn print_const(self, _ct: ty::Const<'tcx>) -> Result<Self::Const, Self::Error> {
559 fn path_crate(self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
560 Ok(vec![self.tcx.crate_name(cnum).to_string()])
565 _trait_ref: Option<ty::TraitRef<'tcx>>,
566 ) -> Result<Self::Path, Self::Error> {
572 _print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
573 _disambiguated_data: &DisambiguatedDefPathData,
575 _trait_ref: Option<ty::TraitRef<'tcx>>,
576 ) -> Result<Self::Path, Self::Error> {
581 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
582 disambiguated_data: &DisambiguatedDefPathData,
583 ) -> Result<Self::Path, Self::Error> {
584 let mut path = print_prefix(self)?;
585 path.push(disambiguated_data.to_string());
588 fn path_generic_args(
590 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
591 _args: &[GenericArg<'tcx>],
592 ) -> Result<Self::Path, Self::Error> {
597 let report_path_match = |err: &mut Diagnostic, did1: DefId, did2: DefId| {
598 // Only external crates, if either is from a local
599 // module we could have false positives
600 if !(did1.is_local() || did2.is_local()) && did1.krate != did2.krate {
602 |def_id| AbsolutePathPrinter { tcx: self.tcx }.print_def_path(def_id, &[]);
604 // We compare strings because DefPath can be different
605 // for imported and non-imported crates
606 let same_path = || -> Result<_, NonTrivialPath> {
607 Ok(self.tcx.def_path_str(did1) == self.tcx.def_path_str(did2)
608 || abs_path(did1)? == abs_path(did2)?)
610 if same_path().unwrap_or(false) {
611 let crate_name = self.tcx.crate_name(did1.krate);
613 "perhaps two different versions of crate `{}` are being used?",
620 TypeError::Sorts(ref exp_found) => {
621 // if they are both "path types", there's a chance of ambiguity
622 // due to different versions of the same crate
623 if let (&ty::Adt(exp_adt, _), &ty::Adt(found_adt, _)) =
624 (exp_found.expected.kind(), exp_found.found.kind())
626 report_path_match(err, exp_adt.did(), found_adt.did());
629 TypeError::Traits(ref exp_found) => {
630 report_path_match(err, exp_found.expected, exp_found.found);
632 _ => (), // FIXME(#22750) handle traits and stuff
636 fn note_error_origin(
638 err: &mut Diagnostic,
639 cause: &ObligationCause<'tcx>,
640 exp_found: Option<ty::error::ExpectedFound<Ty<'tcx>>>,
641 terr: TypeError<'tcx>,
643 match *cause.code() {
644 ObligationCauseCode::Pattern { origin_expr: true, span: Some(span), root_ty } => {
645 let ty = self.resolve_vars_if_possible(root_ty);
646 if !matches!(ty.kind(), ty::Infer(ty::InferTy::TyVar(_) | ty::InferTy::FreshTy(_)))
648 // don't show type `_`
649 if span.desugaring_kind() == Some(DesugaringKind::ForLoop)
650 && let ty::Adt(def, substs) = ty.kind()
651 && Some(def.did()) == self.tcx.get_diagnostic_item(sym::Option)
653 err.span_label(span, format!("this is an iterator with items of type `{}`", substs.type_at(0)));
655 err.span_label(span, format!("this expression has type `{}`", ty));
658 if let Some(ty::error::ExpectedFound { found, .. }) = exp_found
659 && ty.is_box() && ty.boxed_ty() == found
660 && let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span)
664 "consider dereferencing the boxed value",
665 format!("*{}", snippet),
666 Applicability::MachineApplicable,
670 ObligationCauseCode::Pattern { origin_expr: false, span: Some(span), .. } => {
671 err.span_label(span, "expected due to this");
673 ObligationCauseCode::MatchExpressionArm(box MatchExpressionArmCause {
683 opt_suggest_box_span,
687 hir::MatchSource::TryDesugar => {
688 if let Some(ty::error::ExpectedFound { expected, .. }) = exp_found {
689 let scrut_expr = self.tcx.hir().expect_expr(scrut_hir_id);
690 let scrut_ty = if let hir::ExprKind::Call(_, args) = &scrut_expr.kind {
691 let arg_expr = args.first().expect("try desugaring call w/out arg");
692 self.typeck_results.as_ref().and_then(|typeck_results| {
693 typeck_results.expr_ty_opt(arg_expr)
696 bug!("try desugaring w/out call expr as scrutinee");
700 Some(ty) if expected == ty => {
701 let source_map = self.tcx.sess.source_map();
703 source_map.end_point(cause.span),
704 "try removing this `?`",
706 Applicability::MachineApplicable,
714 // `prior_arm_ty` can be `!`, `expected` will have better info when present.
715 let t = self.resolve_vars_if_possible(match exp_found {
716 Some(ty::error::ExpectedFound { expected, .. }) => expected,
719 let source_map = self.tcx.sess.source_map();
720 let mut any_multiline_arm = source_map.is_multiline(arm_span);
721 if prior_arms.len() <= 4 {
722 for sp in prior_arms {
723 any_multiline_arm |= source_map.is_multiline(*sp);
724 err.span_label(*sp, format!("this is found to be of type `{}`", t));
726 } else if let Some(sp) = prior_arms.last() {
727 any_multiline_arm |= source_map.is_multiline(*sp);
730 format!("this and all prior arms are found to be of type `{}`", t),
733 let outer = if any_multiline_arm || !source_map.is_multiline(cause.span) {
734 // Cover just `match` and the scrutinee expression, not
735 // the entire match body, to reduce diagram noise.
736 cause.span.shrink_to_lo().to(scrut_span)
740 let msg = "`match` arms have incompatible types";
741 err.span_label(outer, msg);
742 self.suggest_remove_semi_or_return_binding(
751 if let Some(ret_sp) = opt_suggest_box_span {
752 // Get return type span and point to it.
753 self.suggest_boxing_for_return_impl_trait(
756 prior_arms.iter().chain(std::iter::once(&arm_span)).map(|s| *s),
761 ObligationCauseCode::IfExpression(box IfExpressionCause {
767 opt_suggest_box_span,
769 let then_span = self.find_block_span_from_hir_id(then_id);
770 let else_span = self.find_block_span_from_hir_id(else_id);
771 err.span_label(then_span, "expected because of this");
772 if let Some(sp) = outer_span {
773 err.span_label(sp, "`if` and `else` have incompatible types");
775 self.suggest_remove_semi_or_return_binding(
784 if let Some(ret_sp) = opt_suggest_box_span {
785 self.suggest_boxing_for_return_impl_trait(
788 [then_span, else_span].into_iter(),
792 ObligationCauseCode::LetElse => {
793 err.help("try adding a diverging expression, such as `return` or `panic!(..)`");
794 err.help("...or use `match` instead of `let...else`");
797 if let ObligationCauseCode::BindingObligation(_, span)
798 | ObligationCauseCode::ExprBindingObligation(_, span, ..)
799 = cause.code().peel_derives()
800 && let TypeError::RegionsPlaceholderMismatch = terr
802 err.span_note( * span,
803 "the lifetime requirement is introduced here");
809 /// Given that `other_ty` is the same as a type argument for `name` in `sub`, populate `value`
810 /// highlighting `name` and every type argument that isn't at `pos` (which is `other_ty`), and
811 /// populate `other_value` with `other_ty`.
815 /// ^^^^--------^ this is highlighted
817 /// | this type argument is exactly the same as the other type, not highlighted
818 /// this is highlighted
820 /// -------- this type is the same as a type argument in the other type, not highlighted
824 value: &mut DiagnosticStyledString,
825 other_value: &mut DiagnosticStyledString,
827 sub: ty::subst::SubstsRef<'tcx>,
831 // `value` and `other_value` hold two incomplete type representation for display.
832 // `name` is the path of both types being compared. `sub`
833 value.push_highlighted(name);
836 value.push_highlighted("<");
839 // Output the lifetimes for the first type
843 let s = lifetime.to_string();
844 if s.is_empty() { "'_".to_string() } else { s }
848 if !lifetimes.is_empty() {
849 if sub.regions().count() < len {
850 value.push_normal(lifetimes + ", ");
852 value.push_normal(lifetimes);
856 // Highlight all the type arguments that aren't at `pos` and compare the type argument at
857 // `pos` and `other_ty`.
858 for (i, type_arg) in sub.types().enumerate() {
860 let values = self.cmp(type_arg, other_ty);
861 value.0.extend((values.0).0);
862 other_value.0.extend((values.1).0);
864 value.push_highlighted(type_arg.to_string());
867 if len > 0 && i != len - 1 {
868 value.push_normal(", ");
872 value.push_highlighted(">");
876 /// If `other_ty` is the same as a type argument present in `sub`, highlight `path` in `t1_out`,
877 /// as that is the difference to the other type.
879 /// For the following code:
881 /// ```ignore (illustrative)
882 /// let x: Foo<Bar<Qux>> = foo::<Bar<Qux>>();
885 /// The type error output will behave in the following way:
889 /// ^^^^--------^ this is highlighted
891 /// | this type argument is exactly the same as the other type, not highlighted
892 /// this is highlighted
894 /// -------- this type is the same as a type argument in the other type, not highlighted
898 mut t1_out: &mut DiagnosticStyledString,
899 mut t2_out: &mut DiagnosticStyledString,
901 sub: &'tcx [ty::GenericArg<'tcx>],
905 // FIXME/HACK: Go back to `SubstsRef` to use its inherent methods,
906 // ideally that shouldn't be necessary.
907 let sub = self.tcx.intern_substs(sub);
908 for (i, ta) in sub.types().enumerate() {
910 self.highlight_outer(&mut t1_out, &mut t2_out, path, sub, i, other_ty);
913 if let ty::Adt(def, _) = ta.kind() {
914 let path_ = self.tcx.def_path_str(def.did());
915 if path_ == other_path {
916 self.highlight_outer(&mut t1_out, &mut t2_out, path, sub, i, other_ty);
924 /// Adds a `,` to the type representation only if it is appropriate.
927 value: &mut DiagnosticStyledString,
928 other_value: &mut DiagnosticStyledString,
932 if len > 0 && pos != len - 1 {
933 value.push_normal(", ");
934 other_value.push_normal(", ");
938 /// Given two `fn` signatures highlight only sub-parts that are different.
941 sig1: &ty::PolyFnSig<'tcx>,
942 sig2: &ty::PolyFnSig<'tcx>,
943 ) -> (DiagnosticStyledString, DiagnosticStyledString) {
944 let sig1 = &(self.normalize_fn_sig)(*sig1);
945 let sig2 = &(self.normalize_fn_sig)(*sig2);
947 let get_lifetimes = |sig| {
948 use rustc_hir::def::Namespace;
949 let (_, sig, reg) = ty::print::FmtPrinter::new(self.tcx, Namespace::TypeNS)
950 .name_all_regions(sig)
952 let lts: Vec<String> = reg.into_iter().map(|(_, kind)| kind.to_string()).collect();
953 (if lts.is_empty() { String::new() } else { format!("for<{}> ", lts.join(", ")) }, sig)
956 let (lt1, sig1) = get_lifetimes(sig1);
957 let (lt2, sig2) = get_lifetimes(sig2);
959 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
961 DiagnosticStyledString::normal("".to_string()),
962 DiagnosticStyledString::normal("".to_string()),
965 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
967 values.0.push(sig1.unsafety.prefix_str(), sig1.unsafety != sig2.unsafety);
968 values.1.push(sig2.unsafety.prefix_str(), sig1.unsafety != sig2.unsafety);
970 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
972 if sig1.abi != abi::Abi::Rust {
973 values.0.push(format!("extern {} ", sig1.abi), sig1.abi != sig2.abi);
975 if sig2.abi != abi::Abi::Rust {
976 values.1.push(format!("extern {} ", sig2.abi), sig1.abi != sig2.abi);
979 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
981 let lifetime_diff = lt1 != lt2;
982 values.0.push(lt1, lifetime_diff);
983 values.1.push(lt2, lifetime_diff);
985 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
987 values.0.push_normal("fn(");
988 values.1.push_normal("fn(");
990 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
992 let len1 = sig1.inputs().len();
993 let len2 = sig2.inputs().len();
995 for (i, (l, r)) in iter::zip(sig1.inputs(), sig2.inputs()).enumerate() {
996 let (x1, x2) = self.cmp(*l, *r);
997 (values.0).0.extend(x1.0);
998 (values.1).0.extend(x2.0);
999 self.push_comma(&mut values.0, &mut values.1, len1, i);
1002 for (i, l) in sig1.inputs().iter().enumerate() {
1003 values.0.push_highlighted(l.to_string());
1005 values.0.push_highlighted(", ");
1008 for (i, r) in sig2.inputs().iter().enumerate() {
1009 values.1.push_highlighted(r.to_string());
1011 values.1.push_highlighted(", ");
1016 if sig1.c_variadic {
1018 values.0.push_normal(", ");
1020 values.0.push("...", !sig2.c_variadic);
1022 if sig2.c_variadic {
1024 values.1.push_normal(", ");
1026 values.1.push("...", !sig1.c_variadic);
1029 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
1031 values.0.push_normal(")");
1032 values.1.push_normal(")");
1034 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
1036 let output1 = sig1.output();
1037 let output2 = sig2.output();
1038 let (x1, x2) = self.cmp(output1, output2);
1039 if !output1.is_unit() {
1040 values.0.push_normal(" -> ");
1041 (values.0).0.extend(x1.0);
1043 if !output2.is_unit() {
1044 values.1.push_normal(" -> ");
1045 (values.1).0.extend(x2.0);
1050 /// Compares two given types, eliding parts that are the same between them and highlighting
1051 /// relevant differences, and return two representation of those types for highlighted printing.
1056 ) -> (DiagnosticStyledString, DiagnosticStyledString) {
1057 debug!("cmp(t1={}, t1.kind={:?}, t2={}, t2.kind={:?})", t1, t1.kind(), t2, t2.kind());
1060 fn equals<'tcx>(a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
1061 match (a.kind(), b.kind()) {
1062 (a, b) if *a == *b => true,
1063 (&ty::Int(_), &ty::Infer(ty::InferTy::IntVar(_)))
1065 &ty::Infer(ty::InferTy::IntVar(_)),
1066 &ty::Int(_) | &ty::Infer(ty::InferTy::IntVar(_)),
1068 | (&ty::Float(_), &ty::Infer(ty::InferTy::FloatVar(_)))
1070 &ty::Infer(ty::InferTy::FloatVar(_)),
1071 &ty::Float(_) | &ty::Infer(ty::InferTy::FloatVar(_)),
1077 fn push_ty_ref<'tcx>(
1078 region: ty::Region<'tcx>,
1080 mutbl: hir::Mutability,
1081 s: &mut DiagnosticStyledString,
1083 let mut r = region.to_string();
1089 s.push_highlighted(format!("&{}{}", r, mutbl.prefix_str()));
1090 s.push_normal(ty.to_string());
1093 // process starts here
1094 match (t1.kind(), t2.kind()) {
1095 (&ty::Adt(def1, sub1), &ty::Adt(def2, sub2)) => {
1096 let did1 = def1.did();
1097 let did2 = def2.did();
1098 let sub_no_defaults_1 =
1099 self.tcx.generics_of(did1).own_substs_no_defaults(self.tcx, sub1);
1100 let sub_no_defaults_2 =
1101 self.tcx.generics_of(did2).own_substs_no_defaults(self.tcx, sub2);
1102 let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new());
1103 let path1 = self.tcx.def_path_str(did1);
1104 let path2 = self.tcx.def_path_str(did2);
1106 // Easy case. Replace same types with `_` to shorten the output and highlight
1107 // the differing ones.
1108 // let x: Foo<Bar, Qux> = y::<Foo<Quz, Qux>>();
1111 // --- ^ type argument elided
1113 // highlighted in output
1114 values.0.push_normal(path1);
1115 values.1.push_normal(path2);
1117 // Avoid printing out default generic parameters that are common to both
1119 let len1 = sub_no_defaults_1.len();
1120 let len2 = sub_no_defaults_2.len();
1121 let common_len = cmp::min(len1, len2);
1122 let remainder1: Vec<_> = sub1.types().skip(common_len).collect();
1123 let remainder2: Vec<_> = sub2.types().skip(common_len).collect();
1124 let common_default_params =
1125 iter::zip(remainder1.iter().rev(), remainder2.iter().rev())
1126 .filter(|(a, b)| a == b)
1128 let len = sub1.len() - common_default_params;
1129 let consts_offset = len - sub1.consts().count();
1131 // Only draw `<...>` if there are lifetime/type arguments.
1133 values.0.push_normal("<");
1134 values.1.push_normal("<");
1137 fn lifetime_display(lifetime: Region<'_>) -> String {
1138 let s = lifetime.to_string();
1139 if s.is_empty() { "'_".to_string() } else { s }
1141 // At one point we'd like to elide all lifetimes here, they are irrelevant for
1142 // all diagnostics that use this output
1146 // ^^ ^^ --- type arguments are not elided
1148 // | elided as they were the same
1149 // not elided, they were different, but irrelevant
1151 // For bound lifetimes, keep the names of the lifetimes,
1152 // even if they are the same so that it's clear what's happening
1153 // if we have something like
1155 // for<'r, 's> fn(Inv<'r>, Inv<'s>)
1156 // for<'r> fn(Inv<'r>, Inv<'r>)
1157 let lifetimes = sub1.regions().zip(sub2.regions());
1158 for (i, lifetimes) in lifetimes.enumerate() {
1159 let l1 = lifetime_display(lifetimes.0);
1160 let l2 = lifetime_display(lifetimes.1);
1161 if lifetimes.0 != lifetimes.1 {
1162 values.0.push_highlighted(l1);
1163 values.1.push_highlighted(l2);
1164 } else if lifetimes.0.is_late_bound() {
1165 values.0.push_normal(l1);
1166 values.1.push_normal(l2);
1168 values.0.push_normal("'_");
1169 values.1.push_normal("'_");
1171 self.push_comma(&mut values.0, &mut values.1, len, i);
1174 // We're comparing two types with the same path, so we compare the type
1175 // arguments for both. If they are the same, do not highlight and elide from the
1179 // ^ elided type as this type argument was the same in both sides
1180 let type_arguments = sub1.types().zip(sub2.types());
1181 let regions_len = sub1.regions().count();
1182 let num_display_types = consts_offset - regions_len;
1183 for (i, (ta1, ta2)) in type_arguments.take(num_display_types).enumerate() {
1184 let i = i + regions_len;
1185 if ta1 == ta2 && !self.tcx.sess.verbose() {
1186 values.0.push_normal("_");
1187 values.1.push_normal("_");
1189 let (x1, x2) = self.cmp(ta1, ta2);
1190 (values.0).0.extend(x1.0);
1191 (values.1).0.extend(x2.0);
1193 self.push_comma(&mut values.0, &mut values.1, len, i);
1196 // Do the same for const arguments, if they are equal, do not highlight and
1197 // elide them from the output.
1198 let const_arguments = sub1.consts().zip(sub2.consts());
1199 for (i, (ca1, ca2)) in const_arguments.enumerate() {
1200 let i = i + consts_offset;
1201 if ca1 == ca2 && !self.tcx.sess.verbose() {
1202 values.0.push_normal("_");
1203 values.1.push_normal("_");
1205 values.0.push_highlighted(ca1.to_string());
1206 values.1.push_highlighted(ca2.to_string());
1208 self.push_comma(&mut values.0, &mut values.1, len, i);
1211 // Close the type argument bracket.
1212 // Only draw `<...>` if there are lifetime/type arguments.
1214 values.0.push_normal(">");
1215 values.1.push_normal(">");
1220 // let x: Foo<Bar<Qux> = foo::<Bar<Qux>>();
1222 // ------- this type argument is exactly the same as the other type
1238 // let x: Bar<Qux> = y:<Foo<Bar<Qux>>>();
1241 // ------- this type argument is exactly the same as the other type
1256 // We can't find anything in common, highlight relevant part of type path.
1257 // let x: foo::bar::Baz<Qux> = y:<foo::bar::Bar<Zar>>();
1258 // foo::bar::Baz<Qux>
1259 // foo::bar::Bar<Zar>
1260 // -------- this part of the path is different
1262 let t1_str = t1.to_string();
1263 let t2_str = t2.to_string();
1264 let min_len = t1_str.len().min(t2_str.len());
1266 const SEPARATOR: &str = "::";
1267 let separator_len = SEPARATOR.len();
1268 let split_idx: usize =
1269 iter::zip(t1_str.split(SEPARATOR), t2_str.split(SEPARATOR))
1270 .take_while(|(mod1_str, mod2_str)| mod1_str == mod2_str)
1271 .map(|(mod_str, _)| mod_str.len() + separator_len)
1274 debug!(?separator_len, ?split_idx, ?min_len, "cmp");
1276 if split_idx >= min_len {
1277 // paths are identical, highlight everything
1279 DiagnosticStyledString::highlighted(t1_str),
1280 DiagnosticStyledString::highlighted(t2_str),
1283 let (common, uniq1) = t1_str.split_at(split_idx);
1284 let (_, uniq2) = t2_str.split_at(split_idx);
1285 debug!(?common, ?uniq1, ?uniq2, "cmp");
1287 values.0.push_normal(common);
1288 values.0.push_highlighted(uniq1);
1289 values.1.push_normal(common);
1290 values.1.push_highlighted(uniq2);
1297 // When finding T != &T, highlight only the borrow
1298 (&ty::Ref(r1, ref_ty1, mutbl1), _) if equals(ref_ty1, t2) => {
1299 let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new());
1300 push_ty_ref(r1, ref_ty1, mutbl1, &mut values.0);
1301 values.1.push_normal(t2.to_string());
1304 (_, &ty::Ref(r2, ref_ty2, mutbl2)) if equals(t1, ref_ty2) => {
1305 let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new());
1306 values.0.push_normal(t1.to_string());
1307 push_ty_ref(r2, ref_ty2, mutbl2, &mut values.1);
1311 // When encountering &T != &mut T, highlight only the borrow
1312 (&ty::Ref(r1, ref_ty1, mutbl1), &ty::Ref(r2, ref_ty2, mutbl2))
1313 if equals(ref_ty1, ref_ty2) =>
1315 let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new());
1316 push_ty_ref(r1, ref_ty1, mutbl1, &mut values.0);
1317 push_ty_ref(r2, ref_ty2, mutbl2, &mut values.1);
1321 // When encountering tuples of the same size, highlight only the differing types
1322 (&ty::Tuple(substs1), &ty::Tuple(substs2)) if substs1.len() == substs2.len() => {
1324 (DiagnosticStyledString::normal("("), DiagnosticStyledString::normal("("));
1325 let len = substs1.len();
1326 for (i, (left, right)) in substs1.iter().zip(substs2).enumerate() {
1327 let (x1, x2) = self.cmp(left, right);
1328 (values.0).0.extend(x1.0);
1329 (values.1).0.extend(x2.0);
1330 self.push_comma(&mut values.0, &mut values.1, len, i);
1333 // Keep the output for single element tuples as `(ty,)`.
1334 values.0.push_normal(",");
1335 values.1.push_normal(",");
1337 values.0.push_normal(")");
1338 values.1.push_normal(")");
1342 (ty::FnDef(did1, substs1), ty::FnDef(did2, substs2)) => {
1343 let sig1 = self.tcx.bound_fn_sig(*did1).subst(self.tcx, substs1);
1344 let sig2 = self.tcx.bound_fn_sig(*did2).subst(self.tcx, substs2);
1345 let mut values = self.cmp_fn_sig(&sig1, &sig2);
1346 let path1 = format!(" {{{}}}", self.tcx.def_path_str_with_substs(*did1, substs1));
1347 let path2 = format!(" {{{}}}", self.tcx.def_path_str_with_substs(*did2, substs2));
1348 let same_path = path1 == path2;
1349 values.0.push(path1, !same_path);
1350 values.1.push(path2, !same_path);
1354 (ty::FnDef(did1, substs1), ty::FnPtr(sig2)) => {
1355 let sig1 = self.tcx.bound_fn_sig(*did1).subst(self.tcx, substs1);
1356 let mut values = self.cmp_fn_sig(&sig1, sig2);
1357 values.0.push_highlighted(format!(
1359 self.tcx.def_path_str_with_substs(*did1, substs1)
1364 (ty::FnPtr(sig1), ty::FnDef(did2, substs2)) => {
1365 let sig2 = self.tcx.bound_fn_sig(*did2).subst(self.tcx, substs2);
1366 let mut values = self.cmp_fn_sig(sig1, &sig2);
1367 values.1.push_normal(format!(
1369 self.tcx.def_path_str_with_substs(*did2, substs2)
1374 (ty::FnPtr(sig1), ty::FnPtr(sig2)) => self.cmp_fn_sig(sig1, sig2),
1377 if t1 == t2 && !self.tcx.sess.verbose() {
1378 // The two types are the same, elide and don't highlight.
1379 (DiagnosticStyledString::normal("_"), DiagnosticStyledString::normal("_"))
1381 // We couldn't find anything in common, highlight everything.
1383 DiagnosticStyledString::highlighted(t1.to_string()),
1384 DiagnosticStyledString::highlighted(t2.to_string()),
1391 /// Extend a type error with extra labels pointing at "non-trivial" types, like closures and
1392 /// the return type of `async fn`s.
1394 /// `secondary_span` gives the caller the opportunity to expand `diag` with a `span_label`.
1396 /// `swap_secondary_and_primary` is used to make projection errors in particular nicer by using
1397 /// the message in `secondary_span` as the primary label, and apply the message that would
1398 /// otherwise be used for the primary label on the `secondary_span` `Span`. This applies on
1399 /// E0271, like `src/test/ui/issues/issue-39970.stderr`.
1402 skip(self, diag, secondary_span, swap_secondary_and_primary, prefer_label)
1404 pub fn note_type_err(
1406 diag: &mut Diagnostic,
1407 cause: &ObligationCause<'tcx>,
1408 secondary_span: Option<(Span, String)>,
1409 mut values: Option<ValuePairs<'tcx>>,
1410 terr: TypeError<'tcx>,
1411 swap_secondary_and_primary: bool,
1414 let span = cause.span();
1416 // For some types of errors, expected-found does not make
1417 // sense, so just ignore the values we were given.
1418 if let TypeError::CyclicTy(_) = terr {
1421 struct OpaqueTypesVisitor<'tcx> {
1422 types: FxIndexMap<TyCategory, FxIndexSet<Span>>,
1423 expected: FxIndexMap<TyCategory, FxIndexSet<Span>>,
1424 found: FxIndexMap<TyCategory, FxIndexSet<Span>>,
1429 impl<'tcx> OpaqueTypesVisitor<'tcx> {
1430 fn visit_expected_found(
1432 expected: impl TypeVisitable<'tcx>,
1433 found: impl TypeVisitable<'tcx>,
1436 let mut types_visitor = OpaqueTypesVisitor {
1437 types: Default::default(),
1438 expected: Default::default(),
1439 found: Default::default(),
1443 // The visitor puts all the relevant encountered types in `self.types`, but in
1444 // here we want to visit two separate types with no relation to each other, so we
1445 // move the results from `types` to `expected` or `found` as appropriate.
1446 expected.visit_with(&mut types_visitor);
1447 std::mem::swap(&mut types_visitor.expected, &mut types_visitor.types);
1448 found.visit_with(&mut types_visitor);
1449 std::mem::swap(&mut types_visitor.found, &mut types_visitor.types);
1453 fn report(&self, err: &mut Diagnostic) {
1454 self.add_labels_for_types(err, "expected", &self.expected);
1455 self.add_labels_for_types(err, "found", &self.found);
1458 fn add_labels_for_types(
1460 err: &mut Diagnostic,
1462 types: &FxIndexMap<TyCategory, FxIndexSet<Span>>,
1464 for (key, values) in types.iter() {
1465 let count = values.len();
1466 let kind = key.descr();
1467 let mut returned_async_output_error = false;
1469 if sp.is_desugaring(DesugaringKind::Async) && !returned_async_output_error {
1470 if [sp] != err.span.primary_spans() {
1471 let mut span: MultiSpan = sp.into();
1472 span.push_span_label(
1475 "checked the `Output` of this `async fn`, {}{} {}{}",
1476 if count > 1 { "one of the " } else { "" },
1484 "while checking the return type of the `async fn`",
1490 "checked the `Output` of this `async fn`, {}{} {}{}",
1491 if count > 1 { "one of the " } else { "" },
1497 err.note("while checking the return type of the `async fn`");
1499 returned_async_output_error = true;
1505 if count == 1 { "the " } else { "one of the " },
1517 impl<'tcx> ty::visit::TypeVisitor<'tcx> for OpaqueTypesVisitor<'tcx> {
1518 fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
1519 if let Some((kind, def_id)) = TyCategory::from_ty(self.tcx, t) {
1520 let span = self.tcx.def_span(def_id);
1521 // Avoid cluttering the output when the "found" and error span overlap:
1523 // error[E0308]: mismatched types
1524 // --> $DIR/issue-20862.rs:2:5
1529 // | the found closure
1530 // | expected `()`, found closure
1532 // = note: expected unit type `()`
1533 // found closure `[closure@$DIR/issue-20862.rs:2:5: 2:14 x:_]`
1534 if !self.ignore_span.overlaps(span) {
1535 self.types.entry(kind).or_default().insert(span);
1538 t.super_visit_with(self)
1542 debug!("note_type_err(diag={:?})", diag);
1544 Variable(ty::error::ExpectedFound<Ty<'a>>),
1545 Fixed(&'static str),
1547 let (expected_found, exp_found, is_simple_error, values) = match values {
1548 None => (None, Mismatch::Fixed("type"), false, None),
1550 let values = self.resolve_vars_if_possible(values);
1551 let (is_simple_error, exp_found) = match values {
1552 ValuePairs::Terms(infer::ExpectedFound { expected, found }) => {
1553 match (expected.unpack(), found.unpack()) {
1554 (ty::TermKind::Ty(expected), ty::TermKind::Ty(found)) => {
1556 expected.is_simple_text() && found.is_simple_text();
1557 OpaqueTypesVisitor::visit_expected_found(
1558 self.tcx, expected, found, span,
1564 Mismatch::Variable(infer::ExpectedFound { expected, found }),
1567 (ty::TermKind::Const(_), ty::TermKind::Const(_)) => {
1568 (false, Mismatch::Fixed("constant"))
1570 _ => (false, Mismatch::Fixed("type")),
1573 ValuePairs::Sigs(infer::ExpectedFound { expected, found }) => {
1574 OpaqueTypesVisitor::visit_expected_found(self.tcx, expected, found, span)
1576 (false, Mismatch::Fixed("signature"))
1578 ValuePairs::TraitRefs(_) | ValuePairs::PolyTraitRefs(_) => {
1579 (false, Mismatch::Fixed("trait"))
1581 ValuePairs::Regions(_) => (false, Mismatch::Fixed("lifetime")),
1583 let Some(vals) = self.values_str(values) else {
1584 // Derived error. Cancel the emitter.
1585 // NOTE(eddyb) this was `.cancel()`, but `diag`
1586 // is borrowed, so we can't fully defuse it.
1587 diag.downgrade_to_delayed_bug();
1590 (Some(vals), exp_found, is_simple_error, Some(values))
1594 let mut label_or_note = |span: Span, msg: &str| {
1595 if (prefer_label && is_simple_error) || &[span] == diag.span.primary_spans() {
1596 diag.span_label(span, msg);
1598 diag.span_note(span, msg);
1601 if let Some((sp, msg)) = secondary_span {
1602 if swap_secondary_and_primary {
1603 let terr = if let Some(infer::ValuePairs::Terms(infer::ExpectedFound {
1608 format!("expected this to be `{}`", expected)
1612 label_or_note(sp, &terr);
1613 label_or_note(span, &msg);
1615 label_or_note(span, &terr.to_string());
1616 label_or_note(sp, &msg);
1619 label_or_note(span, &terr.to_string());
1622 if let Some((expected, found, exp_p, found_p)) = expected_found {
1623 let (expected_label, found_label, exp_found) = match exp_found {
1624 Mismatch::Variable(ef) => (
1625 ef.expected.prefix_string(self.tcx),
1626 ef.found.prefix_string(self.tcx),
1629 Mismatch::Fixed(s) => (s.into(), s.into(), None),
1632 enum Similar<'tcx> {
1633 Adts { expected: ty::AdtDef<'tcx>, found: ty::AdtDef<'tcx> },
1634 PrimitiveFound { expected: ty::AdtDef<'tcx>, found: Ty<'tcx> },
1635 PrimitiveExpected { expected: Ty<'tcx>, found: ty::AdtDef<'tcx> },
1638 let similarity = |ExpectedFound { expected, found }: ExpectedFound<Ty<'tcx>>| {
1639 if let ty::Adt(expected, _) = expected.kind() && let Some(primitive) = found.primitive_symbol() {
1640 let path = self.tcx.def_path(expected.did()).data;
1641 let name = path.last().unwrap().data.get_opt_name();
1642 if name == Some(primitive) {
1643 return Some(Similar::PrimitiveFound { expected: *expected, found });
1645 } else if let Some(primitive) = expected.primitive_symbol() && let ty::Adt(found, _) = found.kind() {
1646 let path = self.tcx.def_path(found.did()).data;
1647 let name = path.last().unwrap().data.get_opt_name();
1648 if name == Some(primitive) {
1649 return Some(Similar::PrimitiveExpected { expected, found: *found });
1651 } else if let ty::Adt(expected, _) = expected.kind() && let ty::Adt(found, _) = found.kind() {
1652 if !expected.did().is_local() && expected.did().krate == found.did().krate {
1653 // Most likely types from different versions of the same crate
1654 // are in play, in which case this message isn't so helpful.
1655 // A "perhaps two different versions..." error is already emitted for that.
1658 let f_path = self.tcx.def_path(found.did()).data;
1659 let e_path = self.tcx.def_path(expected.did()).data;
1661 if let (Some(e_last), Some(f_last)) = (e_path.last(), f_path.last()) && e_last == f_last {
1662 return Some(Similar::Adts{expected: *expected, found: *found});
1669 // If two types mismatch but have similar names, mention that specifically.
1670 TypeError::Sorts(values) if let Some(s) = similarity(values) => {
1671 let diagnose_primitive =
1675 diagnostic: &mut Diagnostic| {
1676 let name = shadow.sort_string(self.tcx);
1677 diagnostic.note(format!(
1678 "{prim} and {name} have similar names, but are actually distinct types"
1681 .note(format!("{prim} is a primitive defined by the language"));
1682 let def_span = self.tcx.def_span(defid);
1683 let msg = if defid.is_local() {
1684 format!("{name} is defined in the current crate")
1686 let crate_name = self.tcx.crate_name(defid.krate);
1687 format!("{name} is defined in crate `{crate_name}")
1689 diagnostic.span_note(def_span, msg);
1693 |expected_adt : ty::AdtDef<'tcx>,
1694 found_adt: ty::AdtDef<'tcx>,
1695 diagnostic: &mut Diagnostic| {
1696 let found_name = values.found.sort_string(self.tcx);
1697 let expected_name = values.expected.sort_string(self.tcx);
1699 let found_defid = found_adt.did();
1700 let expected_defid = expected_adt.did();
1702 diagnostic.note(format!("{found_name} and {expected_name} have similar names, but are actually distinct types"));
1703 for (defid, name) in
1704 [(found_defid, found_name), (expected_defid, expected_name)]
1706 let def_span = self.tcx.def_span(defid);
1708 let msg = if found_defid.is_local() && expected_defid.is_local() {
1711 .parent_module_from_def_id(defid.expect_local())
1713 let module_name = self.tcx.def_path(module).to_string_no_crate_verbose();
1714 format!("{name} is defined in module `crate{module_name}` of the current crate")
1715 } else if defid.is_local() {
1716 format!("{name} is defined in the current crate")
1718 let crate_name = self.tcx.crate_name(defid.krate);
1719 format!("{name} is defined in crate `{crate_name}`")
1721 diagnostic.span_note(def_span, msg);
1726 Similar::Adts{expected, found} => {
1727 diagnose_adts(expected, found, diag)
1729 Similar::PrimitiveFound{expected, found: prim} => {
1730 diagnose_primitive(prim, values.expected, expected.did(), diag)
1732 Similar::PrimitiveExpected{expected: prim, found} => {
1733 diagnose_primitive(prim, values.found, found.did(), diag)
1737 TypeError::Sorts(values) => {
1738 let extra = expected == found;
1739 let sort_string = |ty: Ty<'tcx>, path: Option<PathBuf>| {
1740 let mut s = match (extra, ty.kind()) {
1741 (true, ty::Alias(ty::Opaque, ty::AliasTy { def_id, .. })) => {
1742 let sm = self.tcx.sess.source_map();
1743 let pos = sm.lookup_char_pos(self.tcx.def_span(*def_id).lo());
1745 " (opaque type at <{}:{}:{}>)",
1746 sm.filename_for_diagnostics(&pos.file.name),
1748 pos.col.to_usize() + 1,
1751 (true, ty::Alias(ty::Projection, proj))
1752 if self.tcx.def_kind(proj.def_id)
1753 == DefKind::ImplTraitPlaceholder =>
1755 let sm = self.tcx.sess.source_map();
1756 let pos = sm.lookup_char_pos(self.tcx.def_span(proj.def_id).lo());
1758 " (trait associated opaque type at <{}:{}:{}>)",
1759 sm.filename_for_diagnostics(&pos.file.name),
1761 pos.col.to_usize() + 1,
1764 (true, _) => format!(" ({})", ty.sort_string(self.tcx)),
1765 (false, _) => "".to_string(),
1767 if let Some(path) = path {
1768 s.push_str(&format!(
1769 "\nthe full type name has been written to '{}'",
1775 if !(values.expected.is_simple_text() && values.found.is_simple_text())
1776 || (exp_found.map_or(false, |ef| {
1777 // This happens when the type error is a subset of the expectation,
1778 // like when you have two references but one is `usize` and the other
1779 // is `f32`. In those cases we still want to show the `note`. If the
1780 // value from `ef` is `Infer(_)`, then we ignore it.
1781 if !ef.expected.is_ty_infer() {
1782 ef.expected != values.expected
1783 } else if !ef.found.is_ty_infer() {
1784 ef.found != values.found
1790 diag.note_expected_found_extra(
1795 &sort_string(values.expected, exp_p),
1796 &sort_string(values.found, found_p),
1802 "note_type_err: exp_found={:?}, expected={:?} found={:?}",
1803 exp_found, expected, found
1805 if !is_simple_error || terr.must_include_note() {
1806 diag.note_expected_found(&expected_label, expected, &found_label, found);
1811 let exp_found = match exp_found {
1812 Mismatch::Variable(exp_found) => Some(exp_found),
1813 Mismatch::Fixed(_) => None,
1815 let exp_found = match terr {
1816 // `terr` has more accurate type information than `exp_found` in match expressions.
1817 ty::error::TypeError::Sorts(terr)
1818 if exp_found.map_or(false, |ef| terr.found == ef.found) =>
1824 debug!("exp_found {:?} terr {:?} cause.code {:?}", exp_found, terr, cause.code());
1825 if let Some(exp_found) = exp_found {
1826 let should_suggest_fixes =
1827 if let ObligationCauseCode::Pattern { root_ty, .. } = cause.code() {
1828 // Skip if the root_ty of the pattern is not the same as the expected_ty.
1829 // If these types aren't equal then we've probably peeled off a layer of arrays.
1830 self.same_type_modulo_infer(*root_ty, exp_found.expected)
1835 if should_suggest_fixes {
1836 self.suggest_tuple_pattern(cause, &exp_found, diag);
1837 self.suggest_as_ref_where_appropriate(span, &exp_found, diag);
1838 self.suggest_accessing_field_where_appropriate(cause, &exp_found, diag);
1839 self.suggest_await_on_expect_found(cause, span, &exp_found, diag);
1843 // In some (most?) cases cause.body_id points to actual body, but in some cases
1844 // it's an actual definition. According to the comments (e.g. in
1845 // rustc_hir_analysis/check/compare_impl_item.rs:compare_predicate_entailment) the latter
1846 // is relied upon by some other code. This might (or might not) need cleanup.
1847 let body_owner_def_id =
1848 self.tcx.hir().opt_local_def_id(cause.body_id).unwrap_or_else(|| {
1849 self.tcx.hir().body_owner_def_id(hir::BodyId { hir_id: cause.body_id })
1851 self.check_and_note_conflicting_crates(diag, terr);
1852 self.tcx.note_and_explain_type_err(diag, terr, cause, span, body_owner_def_id.to_def_id());
1854 if let Some(ValuePairs::PolyTraitRefs(exp_found)) = values
1855 && let ty::Closure(def_id, _) = exp_found.expected.skip_binder().self_ty().kind()
1856 && let Some(def_id) = def_id.as_local()
1857 && terr.involves_regions()
1859 let span = self.tcx.def_span(def_id);
1860 diag.span_note(span, "this closure does not fulfill the lifetime requirements");
1863 // It reads better to have the error origin as the final
1865 self.note_error_origin(diag, cause, exp_found, terr);
1870 pub fn report_and_explain_type_error(
1872 trace: TypeTrace<'tcx>,
1873 terr: TypeError<'tcx>,
1874 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
1875 use crate::traits::ObligationCauseCode::MatchExpressionArm;
1877 debug!("report_and_explain_type_error(trace={:?}, terr={:?})", trace, terr);
1879 let span = trace.cause.span();
1880 let failure_code = trace.cause.as_failure_code(terr);
1881 let mut diag = match failure_code {
1882 FailureCode::Error0038(did) => {
1883 let violations = self.tcx.object_safety_violations(did);
1884 report_object_safety_error(self.tcx, span, did, violations)
1886 FailureCode::Error0317(failure_str) => {
1887 struct_span_err!(self.tcx.sess, span, E0317, "{}", failure_str)
1889 FailureCode::Error0580(failure_str) => {
1890 struct_span_err!(self.tcx.sess, span, E0580, "{}", failure_str)
1892 FailureCode::Error0308(failure_str) => {
1893 fn escape_literal(s: &str) -> String {
1894 let mut escaped = String::with_capacity(s.len());
1895 let mut chrs = s.chars().peekable();
1896 while let Some(first) = chrs.next() {
1897 match (first, chrs.peek()) {
1898 ('\\', Some(&delim @ '"') | Some(&delim @ '\'')) => {
1900 escaped.push(delim);
1903 ('"' | '\'', _) => {
1907 (c, _) => escaped.push(c),
1912 let mut err = struct_span_err!(self.tcx.sess, span, E0308, "{}", failure_str);
1913 if let Some((expected, found)) = trace.values.ty() {
1914 match (expected.kind(), found.kind()) {
1915 (ty::Tuple(_), ty::Tuple(_)) => {}
1916 // If a tuple of length one was expected and the found expression has
1917 // parentheses around it, perhaps the user meant to write `(expr,)` to
1918 // build a tuple (issue #86100)
1919 (ty::Tuple(fields), _) => {
1920 self.emit_tuple_wrap_err(&mut err, span, found, fields)
1922 // If a character was expected and the found expression is a string literal
1923 // containing a single character, perhaps the user meant to write `'c'` to
1924 // specify a character literal (issue #92479)
1925 (ty::Char, ty::Ref(_, r, _)) if r.is_str() => {
1926 if let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span)
1927 && let Some(code) = code.strip_prefix('"').and_then(|s| s.strip_suffix('"'))
1928 && code.chars().count() == 1
1930 err.span_suggestion(
1932 "if you meant to write a `char` literal, use single quotes",
1933 format!("'{}'", escape_literal(code)),
1934 Applicability::MachineApplicable,
1938 // If a string was expected and the found expression is a character literal,
1939 // perhaps the user meant to write `"s"` to specify a string literal.
1940 (ty::Ref(_, r, _), ty::Char) if r.is_str() => {
1941 if let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span) {
1943 code.strip_prefix('\'').and_then(|s| s.strip_suffix('\''))
1945 err.span_suggestion(
1947 "if you meant to write a `str` literal, use double quotes",
1948 format!("\"{}\"", escape_literal(code)),
1949 Applicability::MachineApplicable,
1954 // For code `if Some(..) = expr `, the type mismatch may be expected `bool` but found `()`,
1955 // we try to suggest to add the missing `let` for `if let Some(..) = expr`
1956 (ty::Bool, ty::Tuple(list)) => if list.len() == 0 {
1957 self.suggest_let_for_letchains(&mut err, &trace.cause, span);
1962 let code = trace.cause.code();
1963 if let &MatchExpressionArm(box MatchExpressionArmCause { source, .. }) = code
1964 && let hir::MatchSource::TryDesugar = source
1965 && let Some((expected_ty, found_ty, _, _)) = self.values_str(trace.values)
1968 "`?` operator cannot convert from `{}` to `{}`",
1970 expected_ty.content(),
1975 FailureCode::Error0644(failure_str) => {
1976 struct_span_err!(self.tcx.sess, span, E0644, "{}", failure_str)
1979 self.note_type_err(&mut diag, &trace.cause, None, Some(trace.values), terr, false, false);
1983 fn emit_tuple_wrap_err(
1985 err: &mut Diagnostic,
1988 expected_fields: &List<Ty<'tcx>>,
1990 let [expected_tup_elem] = expected_fields[..] else { return };
1992 if !self.same_type_modulo_infer(expected_tup_elem, found) {
1996 let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span)
1999 let msg = "use a trailing comma to create a tuple with one element";
2000 if code.starts_with('(') && code.ends_with(')') {
2001 let before_close = span.hi() - BytePos::from_u32(1);
2002 err.span_suggestion(
2003 span.with_hi(before_close).shrink_to_hi(),
2006 Applicability::MachineApplicable,
2009 err.multipart_suggestion(
2011 vec![(span.shrink_to_lo(), "(".into()), (span.shrink_to_hi(), ",)".into())],
2012 Applicability::MachineApplicable,
2019 values: ValuePairs<'tcx>,
2020 ) -> Option<(DiagnosticStyledString, DiagnosticStyledString, Option<PathBuf>, Option<PathBuf>)>
2023 infer::Regions(exp_found) => self.expected_found_str(exp_found),
2024 infer::Terms(exp_found) => self.expected_found_str_term(exp_found),
2025 infer::TraitRefs(exp_found) => {
2026 let pretty_exp_found = ty::error::ExpectedFound {
2027 expected: exp_found.expected.print_only_trait_path(),
2028 found: exp_found.found.print_only_trait_path(),
2030 match self.expected_found_str(pretty_exp_found) {
2031 Some((expected, found, _, _)) if expected == found => {
2032 self.expected_found_str(exp_found)
2037 infer::PolyTraitRefs(exp_found) => {
2038 let pretty_exp_found = ty::error::ExpectedFound {
2039 expected: exp_found.expected.print_only_trait_path(),
2040 found: exp_found.found.print_only_trait_path(),
2042 match self.expected_found_str(pretty_exp_found) {
2043 Some((expected, found, _, _)) if expected == found => {
2044 self.expected_found_str(exp_found)
2049 infer::Sigs(exp_found) => {
2050 let exp_found = self.resolve_vars_if_possible(exp_found);
2051 if exp_found.references_error() {
2054 let (exp, fnd) = self.cmp_fn_sig(
2055 &ty::Binder::dummy(exp_found.expected),
2056 &ty::Binder::dummy(exp_found.found),
2058 Some((exp, fnd, None, None))
2063 fn expected_found_str_term(
2065 exp_found: ty::error::ExpectedFound<ty::Term<'tcx>>,
2066 ) -> Option<(DiagnosticStyledString, DiagnosticStyledString, Option<PathBuf>, Option<PathBuf>)>
2068 let exp_found = self.resolve_vars_if_possible(exp_found);
2069 if exp_found.references_error() {
2073 Some(match (exp_found.expected.unpack(), exp_found.found.unpack()) {
2074 (ty::TermKind::Ty(expected), ty::TermKind::Ty(found)) => {
2075 let (mut exp, mut fnd) = self.cmp(expected, found);
2076 // Use the terminal width as the basis to determine when to compress the printed
2077 // out type, but give ourselves some leeway to avoid ending up creating a file for
2078 // a type that is somewhat shorter than the path we'd write to.
2079 let len = self.tcx.sess().diagnostic_width() + 40;
2080 let exp_s = exp.content();
2081 let fnd_s = fnd.content();
2082 let mut exp_p = None;
2083 let mut fnd_p = None;
2084 if exp_s.len() > len {
2085 let (exp_s, exp_path) = self.tcx.short_ty_string(expected);
2086 exp = DiagnosticStyledString::highlighted(exp_s);
2089 if fnd_s.len() > len {
2090 let (fnd_s, fnd_path) = self.tcx.short_ty_string(found);
2091 fnd = DiagnosticStyledString::highlighted(fnd_s);
2094 (exp, fnd, exp_p, fnd_p)
2097 DiagnosticStyledString::highlighted(exp_found.expected.to_string()),
2098 DiagnosticStyledString::highlighted(exp_found.found.to_string()),
2105 /// Returns a string of the form "expected `{}`, found `{}`".
2106 fn expected_found_str<T: fmt::Display + TypeFoldable<'tcx>>(
2108 exp_found: ty::error::ExpectedFound<T>,
2109 ) -> Option<(DiagnosticStyledString, DiagnosticStyledString, Option<PathBuf>, Option<PathBuf>)>
2111 let exp_found = self.resolve_vars_if_possible(exp_found);
2112 if exp_found.references_error() {
2117 DiagnosticStyledString::highlighted(exp_found.expected.to_string()),
2118 DiagnosticStyledString::highlighted(exp_found.found.to_string()),
2124 pub fn report_generic_bound_failure(
2126 generic_param_scope: LocalDefId,
2128 origin: Option<SubregionOrigin<'tcx>>,
2129 bound_kind: GenericKind<'tcx>,
2132 self.construct_generic_bound_failure(generic_param_scope, span, origin, bound_kind, sub)
2136 pub fn construct_generic_bound_failure(
2138 generic_param_scope: LocalDefId,
2140 origin: Option<SubregionOrigin<'tcx>>,
2141 bound_kind: GenericKind<'tcx>,
2143 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
2144 // Attempt to obtain the span of the parameter so we can
2145 // suggest adding an explicit lifetime bound to it.
2146 let generics = self.tcx.generics_of(generic_param_scope);
2147 // type_param_span is (span, has_bounds)
2148 let type_param_span = match bound_kind {
2149 GenericKind::Param(ref param) => {
2150 // Account for the case where `param` corresponds to `Self`,
2151 // which doesn't have the expected type argument.
2152 if !(generics.has_self && param.index == 0) {
2153 let type_param = generics.type_param(param, self.tcx);
2154 type_param.def_id.as_local().map(|def_id| {
2155 // Get the `hir::Param` to verify whether it already has any bounds.
2156 // We do this to avoid suggesting code that ends up as `T: 'a'b`,
2157 // instead we suggest `T: 'a + 'b` in that case.
2158 let hir_id = self.tcx.hir().local_def_id_to_hir_id(def_id);
2159 let ast_generics = self.tcx.hir().get_generics(hir_id.owner.def_id);
2161 ast_generics.and_then(|g| g.bounds_span_for_suggestions(def_id));
2162 // `sp` only covers `T`, change it so that it covers
2163 // `T:` when appropriate
2164 if let Some(span) = bounds {
2167 let sp = self.tcx.def_span(def_id);
2168 (sp.shrink_to_hi(), false)
2179 let mut possible = (b'a'..=b'z').map(|c| format!("'{}", c as char));
2181 iter::successors(Some(generics), |g| g.parent.map(|p| self.tcx.generics_of(p)))
2182 .flat_map(|g| &g.params)
2183 .filter(|p| matches!(p.kind, ty::GenericParamDefKind::Lifetime))
2184 .map(|p| p.name.as_str())
2185 .collect::<Vec<_>>();
2187 .find(|candidate| !lts_names.contains(&&candidate[..]))
2188 .unwrap_or("'lt".to_string())
2191 let add_lt_sugg = generics
2194 .and_then(|param| param.def_id.as_local())
2195 .map(|def_id| (self.tcx.def_span(def_id).shrink_to_lo(), format!("{}, ", new_lt)));
2197 let labeled_user_string = match bound_kind {
2198 GenericKind::Param(ref p) => format!("the parameter type `{}`", p),
2199 GenericKind::Projection(ref p) => format!("the associated type `{}`", p),
2200 GenericKind::Opaque(def_id, substs) => {
2201 format!("the opaque type `{}`", self.tcx.def_path_str_with_substs(def_id, substs))
2205 if let Some(SubregionOrigin::CompareImplItemObligation {
2211 return self.report_extra_impl_obligation(
2215 &format!("`{}: {}`", bound_kind, sub),
2219 fn binding_suggestion<S: fmt::Display>(
2220 err: &mut Diagnostic,
2221 type_param_span: Option<(Span, bool)>,
2222 bound_kind: GenericKind<'_>,
2224 add_lt_sugg: Option<(Span, String)>,
2226 let msg = "consider adding an explicit lifetime bound";
2227 if let Some((sp, has_lifetimes)) = type_param_span {
2229 if has_lifetimes { format!(" + {}", sub) } else { format!(": {}", sub) };
2230 let mut suggestions = vec![(sp, suggestion)];
2231 if let Some(add_lt_sugg) = add_lt_sugg {
2232 suggestions.push(add_lt_sugg);
2234 err.multipart_suggestion_verbose(
2235 format!("{msg}..."),
2237 Applicability::MaybeIncorrect, // Issue #41966
2240 let consider = format!("{} `{}: {}`...", msg, bound_kind, sub);
2241 err.help(&consider);
2245 let new_binding_suggestion =
2246 |err: &mut Diagnostic, type_param_span: Option<(Span, bool)>| {
2247 let msg = "consider introducing an explicit lifetime bound";
2248 if let Some((sp, has_lifetimes)) = type_param_span {
2249 let suggestion = if has_lifetimes {
2250 format!(" + {}", new_lt)
2252 format!(": {}", new_lt)
2255 vec![(sp, suggestion), (span.shrink_to_hi(), format!(" + {}", new_lt))];
2256 if let Some(lt) = add_lt_sugg.clone() {
2258 sugg.rotate_right(1);
2260 // `MaybeIncorrect` due to issue #41966.
2261 err.multipart_suggestion(msg, sugg, Applicability::MaybeIncorrect);
2266 enum SubOrigin<'hir> {
2267 GAT(&'hir hir::Generics<'hir>),
2273 let sub_origin = 'origin: {
2275 ty::ReEarlyBound(ty::EarlyBoundRegion { def_id, .. }) => {
2276 let node = self.tcx.hir().get_if_local(def_id).unwrap();
2278 Node::GenericParam(param) => {
2279 for h in self.tcx.hir().parent_iter(param.hir_id) {
2280 break 'origin match h.1 {
2281 Node::ImplItem(hir::ImplItem {
2282 kind: hir::ImplItemKind::Type(..),
2286 | Node::TraitItem(hir::TraitItem {
2287 kind: hir::TraitItemKind::Type(..),
2290 }) => SubOrigin::GAT(generics),
2291 Node::ImplItem(hir::ImplItem {
2292 kind: hir::ImplItemKind::Fn(..),
2295 | Node::TraitItem(hir::TraitItem {
2296 kind: hir::TraitItemKind::Fn(..),
2299 | Node::Item(hir::Item {
2300 kind: hir::ItemKind::Fn(..), ..
2301 }) => SubOrigin::Fn,
2302 Node::Item(hir::Item {
2303 kind: hir::ItemKind::Trait(..),
2305 }) => SubOrigin::Trait,
2306 Node::Item(hir::Item {
2307 kind: hir::ItemKind::Impl(..), ..
2308 }) => SubOrigin::Impl,
2320 debug!(?sub_origin);
2322 let mut err = match (*sub, sub_origin) {
2323 // In the case of GATs, we have to be careful. If we a type parameter `T` on an impl,
2324 // but a lifetime `'a` on an associated type, then we might need to suggest adding
2325 // `where T: 'a`. Importantly, this is on the GAT span, not on the `T` declaration.
2326 (ty::ReEarlyBound(ty::EarlyBoundRegion { name: _, .. }), SubOrigin::GAT(generics)) => {
2327 // Does the required lifetime have a nice name we can print?
2328 let mut err = struct_span_err!(
2332 "{} may not live long enough",
2335 let pred = format!("{}: {}", bound_kind, sub);
2336 let suggestion = format!("{} {}", generics.add_where_or_trailing_comma(), pred,);
2337 err.span_suggestion(
2338 generics.tail_span_for_predicate_suggestion(),
2339 "consider adding a where clause",
2341 Applicability::MaybeIncorrect,
2346 ty::ReEarlyBound(ty::EarlyBoundRegion { name, .. })
2347 | ty::ReFree(ty::FreeRegion { bound_region: ty::BrNamed(_, name), .. }),
2349 ) if name != kw::UnderscoreLifetime => {
2350 // Does the required lifetime have a nice name we can print?
2351 let mut err = struct_span_err!(
2355 "{} may not live long enough",
2358 // Explicitly use the name instead of `sub`'s `Display` impl. The `Display` impl
2359 // for the bound is not suitable for suggestions when `-Zverbose` is set because it
2360 // uses `Debug` output, so we handle it specially here so that suggestions are
2362 binding_suggestion(&mut err, type_param_span, bound_kind, name, None);
2366 (ty::ReStatic, _) => {
2367 // Does the required lifetime have a nice name we can print?
2368 let mut err = struct_span_err!(
2372 "{} may not live long enough",
2375 binding_suggestion(&mut err, type_param_span, bound_kind, "'static", None);
2380 // If not, be less specific.
2381 let mut err = struct_span_err!(
2385 "{} may not live long enough",
2388 note_and_explain_region(
2391 &format!("{} must be valid for ", labeled_user_string),
2396 if let Some(infer::RelateParamBound(_, t, _)) = origin {
2397 let return_impl_trait =
2398 self.tcx.return_type_impl_trait(generic_param_scope).is_some();
2399 let t = self.resolve_vars_if_possible(t);
2402 // fn get_later<G, T>(g: G, dest: &mut T) -> impl FnOnce() + '_
2404 // fn get_later<'a, G: 'a, T>(g: G, dest: &mut T) -> impl FnOnce() + '_ + 'a
2405 ty::Closure(..) | ty::Alias(ty::Opaque, ..) if return_impl_trait => {
2406 new_binding_suggestion(&mut err, type_param_span);
2423 if let Some(origin) = origin {
2424 self.note_region_origin(&mut err, &origin);
2429 fn report_sub_sup_conflict(
2431 var_origin: RegionVariableOrigin,
2432 sub_origin: SubregionOrigin<'tcx>,
2433 sub_region: Region<'tcx>,
2434 sup_origin: SubregionOrigin<'tcx>,
2435 sup_region: Region<'tcx>,
2437 let mut err = self.report_inference_failure(var_origin);
2439 note_and_explain_region(
2442 "first, the lifetime cannot outlive ",
2448 debug!("report_sub_sup_conflict: var_origin={:?}", var_origin);
2449 debug!("report_sub_sup_conflict: sub_region={:?}", sub_region);
2450 debug!("report_sub_sup_conflict: sub_origin={:?}", sub_origin);
2451 debug!("report_sub_sup_conflict: sup_region={:?}", sup_region);
2452 debug!("report_sub_sup_conflict: sup_origin={:?}", sup_origin);
2454 if let infer::Subtype(ref sup_trace) = sup_origin
2455 && let infer::Subtype(ref sub_trace) = sub_origin
2456 && let Some((sup_expected, sup_found, _, _)) = self.values_str(sup_trace.values)
2457 && let Some((sub_expected, sub_found, _, _)) = self.values_str(sub_trace.values)
2458 && sub_expected == sup_expected
2459 && sub_found == sup_found
2461 note_and_explain_region(
2464 "...but the lifetime must also be valid for ",
2470 sup_trace.cause.span,
2471 &format!("...so that the {}", sup_trace.cause.as_requirement_str()),
2474 err.note_expected_found(&"", sup_expected, &"", sup_found);
2479 self.note_region_origin(&mut err, &sup_origin);
2481 note_and_explain_region(
2484 "but, the lifetime must be valid for ",
2490 self.note_region_origin(&mut err, &sub_origin);
2494 /// Determine whether an error associated with the given span and definition
2495 /// should be treated as being caused by the implicit `From` conversion
2496 /// within `?` desugaring.
2497 pub fn is_try_conversion(&self, span: Span, trait_def_id: DefId) -> bool {
2498 span.is_desugaring(DesugaringKind::QuestionMark)
2499 && self.tcx.is_diagnostic_item(sym::From, trait_def_id)
2502 /// Structurally compares two types, modulo any inference variables.
2504 /// Returns `true` if two types are equal, or if one type is an inference variable compatible
2505 /// with the other type. A TyVar inference type is compatible with any type, and an IntVar or
2506 /// FloatVar inference type are compatible with themselves or their concrete types (Int and
2507 /// Float types, respectively). When comparing two ADTs, these rules apply recursively.
2508 pub fn same_type_modulo_infer(&self, a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
2509 let (a, b) = self.resolve_vars_if_possible((a, b));
2510 SameTypeModuloInfer(self).relate(a, b).is_ok()
2514 struct SameTypeModuloInfer<'a, 'tcx>(&'a InferCtxt<'tcx>);
2516 impl<'tcx> TypeRelation<'tcx> for SameTypeModuloInfer<'_, 'tcx> {
2517 fn tcx(&self) -> TyCtxt<'tcx> {
2521 fn intercrate(&self) -> bool {
2522 assert!(!self.0.intercrate);
2526 fn param_env(&self) -> ty::ParamEnv<'tcx> {
2527 // Unused, only for consts which we treat as always equal
2528 ty::ParamEnv::empty()
2531 fn tag(&self) -> &'static str {
2532 "SameTypeModuloInfer"
2535 fn a_is_expected(&self) -> bool {
2539 fn mark_ambiguous(&mut self) {
2543 fn relate_with_variance<T: relate::Relate<'tcx>>(
2545 _variance: ty::Variance,
2546 _info: ty::VarianceDiagInfo<'tcx>,
2549 ) -> relate::RelateResult<'tcx, T> {
2553 fn tys(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>> {
2554 match (a.kind(), b.kind()) {
2555 (ty::Int(_) | ty::Uint(_), ty::Infer(ty::InferTy::IntVar(_)))
2557 ty::Infer(ty::InferTy::IntVar(_)),
2558 ty::Int(_) | ty::Uint(_) | ty::Infer(ty::InferTy::IntVar(_)),
2560 | (ty::Float(_), ty::Infer(ty::InferTy::FloatVar(_)))
2562 ty::Infer(ty::InferTy::FloatVar(_)),
2563 ty::Float(_) | ty::Infer(ty::InferTy::FloatVar(_)),
2565 | (ty::Infer(ty::InferTy::TyVar(_)), _)
2566 | (_, ty::Infer(ty::InferTy::TyVar(_))) => Ok(a),
2567 (ty::Infer(_), _) | (_, ty::Infer(_)) => Err(TypeError::Mismatch),
2568 _ => relate::super_relate_tys(self, a, b),
2574 a: ty::Region<'tcx>,
2575 b: ty::Region<'tcx>,
2576 ) -> RelateResult<'tcx, ty::Region<'tcx>> {
2577 if (a.is_var() && b.is_free_or_static())
2578 || (b.is_var() && a.is_free_or_static())
2579 || (a.is_var() && b.is_var())
2584 Err(TypeError::Mismatch)
2590 a: ty::Binder<'tcx, T>,
2591 b: ty::Binder<'tcx, T>,
2592 ) -> relate::RelateResult<'tcx, ty::Binder<'tcx, T>>
2594 T: relate::Relate<'tcx>,
2596 Ok(a.rebind(self.relate(a.skip_binder(), b.skip_binder())?))
2602 _b: ty::Const<'tcx>,
2603 ) -> relate::RelateResult<'tcx, ty::Const<'tcx>> {
2604 // FIXME(compiler-errors): This could at least do some first-order
2610 impl<'tcx> InferCtxt<'tcx> {
2611 fn report_inference_failure(
2613 var_origin: RegionVariableOrigin,
2614 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
2615 let br_string = |br: ty::BoundRegionKind| {
2616 let mut s = match br {
2617 ty::BrNamed(_, name) => name.to_string(),
2625 let var_description = match var_origin {
2626 infer::MiscVariable(_) => String::new(),
2627 infer::PatternRegion(_) => " for pattern".to_string(),
2628 infer::AddrOfRegion(_) => " for borrow expression".to_string(),
2629 infer::Autoref(_) => " for autoref".to_string(),
2630 infer::Coercion(_) => " for automatic coercion".to_string(),
2631 infer::LateBoundRegion(_, br, infer::FnCall) => {
2632 format!(" for lifetime parameter {}in function call", br_string(br))
2634 infer::LateBoundRegion(_, br, infer::HigherRankedType) => {
2635 format!(" for lifetime parameter {}in generic type", br_string(br))
2637 infer::LateBoundRegion(_, br, infer::AssocTypeProjection(def_id)) => format!(
2638 " for lifetime parameter {}in trait containing associated type `{}`",
2640 self.tcx.associated_item(def_id).name
2642 infer::EarlyBoundRegion(_, name) => format!(" for lifetime parameter `{}`", name),
2643 infer::UpvarRegion(ref upvar_id, _) => {
2644 let var_name = self.tcx.hir().name(upvar_id.var_path.hir_id);
2645 format!(" for capture of `{}` by closure", var_name)
2647 infer::Nll(..) => bug!("NLL variable found in lexical phase"),
2654 "cannot infer an appropriate lifetime{} due to conflicting requirements",
2660 pub enum FailureCode {
2662 Error0317(&'static str),
2663 Error0580(&'static str),
2664 Error0308(&'static str),
2665 Error0644(&'static str),
2668 pub trait ObligationCauseExt<'tcx> {
2669 fn as_failure_code(&self, terr: TypeError<'tcx>) -> FailureCode;
2670 fn as_requirement_str(&self) -> &'static str;
2673 impl<'tcx> ObligationCauseExt<'tcx> for ObligationCause<'tcx> {
2674 fn as_failure_code(&self, terr: TypeError<'tcx>) -> FailureCode {
2675 use self::FailureCode::*;
2676 use crate::traits::ObligationCauseCode::*;
2678 CompareImplItemObligation { kind: ty::AssocKind::Fn, .. } => {
2679 Error0308("method not compatible with trait")
2681 CompareImplItemObligation { kind: ty::AssocKind::Type, .. } => {
2682 Error0308("type not compatible with trait")
2684 CompareImplItemObligation { kind: ty::AssocKind::Const, .. } => {
2685 Error0308("const not compatible with trait")
2687 MatchExpressionArm(box MatchExpressionArmCause { source, .. }) => {
2688 Error0308(match source {
2689 hir::MatchSource::TryDesugar => "`?` operator has incompatible types",
2690 _ => "`match` arms have incompatible types",
2693 IfExpression { .. } => Error0308("`if` and `else` have incompatible types"),
2694 IfExpressionWithNoElse => Error0317("`if` may be missing an `else` clause"),
2695 LetElse => Error0308("`else` clause of `let...else` does not diverge"),
2696 MainFunctionType => Error0580("`main` function has wrong type"),
2697 StartFunctionType => Error0308("`#[start]` function has wrong type"),
2698 IntrinsicType => Error0308("intrinsic has wrong type"),
2699 MethodReceiver => Error0308("mismatched `self` parameter type"),
2701 // In the case where we have no more specific thing to
2702 // say, also take a look at the error code, maybe we can
2705 TypeError::CyclicTy(ty) if ty.is_closure() || ty.is_generator() => {
2706 Error0644("closure/generator type that references itself")
2708 TypeError::IntrinsicCast => {
2709 Error0308("cannot coerce intrinsics to function pointers")
2711 _ => Error0308("mismatched types"),
2716 fn as_requirement_str(&self) -> &'static str {
2717 use crate::traits::ObligationCauseCode::*;
2719 CompareImplItemObligation { kind: ty::AssocKind::Fn, .. } => {
2720 "method type is compatible with trait"
2722 CompareImplItemObligation { kind: ty::AssocKind::Type, .. } => {
2723 "associated type is compatible with trait"
2725 CompareImplItemObligation { kind: ty::AssocKind::Const, .. } => {
2726 "const is compatible with trait"
2728 ExprAssignable => "expression is assignable",
2729 IfExpression { .. } => "`if` and `else` have incompatible types",
2730 IfExpressionWithNoElse => "`if` missing an `else` returns `()`",
2731 MainFunctionType => "`main` function has the correct type",
2732 StartFunctionType => "`#[start]` function has the correct type",
2733 IntrinsicType => "intrinsic has the correct type",
2734 MethodReceiver => "method receiver has the correct type",
2735 _ => "types are compatible",
2740 /// Newtype to allow implementing IntoDiagnosticArg
2741 pub struct ObligationCauseAsDiagArg<'tcx>(pub ObligationCause<'tcx>);
2743 impl IntoDiagnosticArg for ObligationCauseAsDiagArg<'_> {
2744 fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> {
2745 use crate::traits::ObligationCauseCode::*;
2746 let kind = match self.0.code() {
2747 CompareImplItemObligation { kind: ty::AssocKind::Fn, .. } => "method_compat",
2748 CompareImplItemObligation { kind: ty::AssocKind::Type, .. } => "type_compat",
2749 CompareImplItemObligation { kind: ty::AssocKind::Const, .. } => "const_compat",
2750 ExprAssignable => "expr_assignable",
2751 IfExpression { .. } => "if_else_different",
2752 IfExpressionWithNoElse => "no_else",
2753 MainFunctionType => "fn_main_correct_type",
2754 StartFunctionType => "fn_start_correct_type",
2755 IntrinsicType => "intristic_correct_type",
2756 MethodReceiver => "method_correct_type",
2760 rustc_errors::DiagnosticArgValue::Str(kind)
2764 /// This is a bare signal of what kind of type we're dealing with. `ty::TyKind` tracks
2765 /// extra information about each type, but we only care about the category.
2766 #[derive(Clone, Copy, PartialEq, Eq, Hash)]
2767 pub enum TyCategory {
2770 Generator(hir::GeneratorKind),
2775 fn descr(&self) -> &'static str {
2777 Self::Closure => "closure",
2778 Self::Opaque => "opaque type",
2779 Self::Generator(gk) => gk.descr(),
2780 Self::Foreign => "foreign type",
2784 pub fn from_ty(tcx: TyCtxt<'_>, ty: Ty<'_>) -> Option<(Self, DefId)> {
2786 ty::Closure(def_id, _) => Some((Self::Closure, def_id)),
2787 ty::Alias(ty::Opaque, ty::AliasTy { def_id, .. }) => Some((Self::Opaque, def_id)),
2788 ty::Generator(def_id, ..) => {
2789 Some((Self::Generator(tcx.generator_kind(def_id).unwrap()), def_id))
2791 ty::Foreign(def_id) => Some((Self::Foreign, def_id)),
2797 impl<'tcx> InferCtxt<'tcx> {
2798 /// Given a [`hir::Block`], get the span of its last expression or
2799 /// statement, peeling off any inner blocks.
2800 pub fn find_block_span(&self, block: &'tcx hir::Block<'tcx>) -> Span {
2801 let block = block.innermost_block();
2802 if let Some(expr) = &block.expr {
2804 } else if let Some(stmt) = block.stmts.last() {
2805 // possibly incorrect trailing `;` in the else arm
2808 // empty block; point at its entirety
2813 /// Given a [`hir::HirId`] for a block, get the span of its last expression
2814 /// or statement, peeling off any inner blocks.
2815 pub fn find_block_span_from_hir_id(&self, hir_id: hir::HirId) -> Span {
2816 match self.tcx.hir().get(hir_id) {
2817 hir::Node::Block(blk) => self.find_block_span(blk),
2818 // The parser was in a weird state if either of these happen, but
2819 // it's better not to panic.
2820 hir::Node::Expr(e) => e.span,
2821 _ => rustc_span::DUMMY_SP,