1 //! Error Reporting Code for the inference engine
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.
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
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.
21 //! # Region Inference
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.
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.
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.
48 use super::lexical_region_resolve::RegionResolutionError;
49 use super::region_constraints::GenericKind;
50 use super::{InferCtxt, RegionVariableOrigin, SubregionOrigin, TypeTrace, ValuePairs};
53 use crate::infer::error_reporting::nice_region_error::find_anon_type::find_anon_type;
54 use crate::infer::ExpectedFound;
55 use crate::traits::error_reporting::report_object_safety_error;
57 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 fallback_has_occurred: bool,
97 pub normalize_fn_sig: Box<dyn Fn(ty::PolyFnSig<'tcx>) -> ty::PolyFnSig<'tcx> + 'a>,
100 Box<dyn Fn(Ty<'tcx>) -> Vec<(Ty<'tcx>, Vec<PredicateObligation<'tcx>>)> + 'a>,
103 impl TypeErrCtxt<'_, '_> {
104 /// This is just to avoid a potential footgun of accidentally
105 /// dropping `typeck_results` by calling `InferCtxt::err_ctxt`
106 #[deprecated(note = "you already have a `TypeErrCtxt`")]
108 pub fn err_ctxt(&self) -> ! {
109 bug!("called `err_ctxt` on `TypeErrCtxt`. Try removing the call");
113 impl<'tcx> Deref for TypeErrCtxt<'_, 'tcx> {
114 type Target = InferCtxt<'tcx>;
115 fn deref(&self) -> &InferCtxt<'tcx> {
120 pub(super) fn note_and_explain_region<'tcx>(
122 err: &mut Diagnostic,
124 region: ty::Region<'tcx>,
126 alt_span: Option<Span>,
128 let (description, span) = match *region {
129 ty::ReEarlyBound(_) | ty::ReFree(_) | ty::ReStatic => {
130 msg_span_from_free_region(tcx, region, alt_span)
133 ty::RePlaceholder(_) => return,
135 // FIXME(#13998) RePlaceholder should probably print like
136 // ReFree rather than dumping Debug output on the user.
138 // We shouldn't really be having unification failures with ReVar
139 // and ReLateBound though.
140 ty::ReVar(_) | ty::ReLateBound(..) | ty::ReErased => {
141 (format!("lifetime {:?}", region), alt_span)
145 emit_msg_span(err, prefix, description, span, suffix);
148 fn explain_free_region<'tcx>(
150 err: &mut Diagnostic,
152 region: ty::Region<'tcx>,
155 let (description, span) = msg_span_from_free_region(tcx, region, None);
157 label_msg_span(err, prefix, description, span, suffix);
160 fn msg_span_from_free_region<'tcx>(
162 region: ty::Region<'tcx>,
163 alt_span: Option<Span>,
164 ) -> (String, Option<Span>) {
166 ty::ReEarlyBound(_) | ty::ReFree(_) => {
167 let (msg, span) = msg_span_from_early_bound_and_free_regions(tcx, region);
170 ty::ReStatic => ("the static lifetime".to_owned(), alt_span),
171 _ => bug!("{:?}", region),
175 fn msg_span_from_early_bound_and_free_regions<'tcx>(
177 region: ty::Region<'tcx>,
178 ) -> (String, Span) {
179 let scope = region.free_region_binding_scope(tcx).expect_local();
181 ty::ReEarlyBound(ref br) => {
182 let mut sp = tcx.def_span(scope);
184 tcx.hir().get_generics(scope).and_then(|generics| generics.get_named(br.name))
188 let text = if br.has_name() {
189 format!("the lifetime `{}` as defined here", br.name)
191 "the anonymous lifetime as defined here".to_string()
195 ty::ReFree(ref fr) => {
196 if !fr.bound_region.is_named()
197 && let Some((ty, _)) = find_anon_type(tcx, region, &fr.bound_region)
199 ("the anonymous lifetime defined here".to_string(), ty.span)
201 match fr.bound_region {
202 ty::BoundRegionKind::BrNamed(_, name) => {
203 let mut sp = tcx.def_span(scope);
205 tcx.hir().get_generics(scope).and_then(|generics| generics.get_named(name))
209 let text = if name == kw::UnderscoreLifetime {
210 "the anonymous lifetime as defined here".to_string()
212 format!("the lifetime `{}` as defined here", name)
216 ty::BrAnon(idx, span) => (
217 format!("the anonymous lifetime #{} defined here", idx + 1),
220 None => tcx.def_span(scope)
224 format!("the lifetime `{}` as defined here", region),
235 err: &mut Diagnostic,
241 let message = format!("{}{}{}", prefix, description, suffix);
243 if let Some(span) = span {
244 err.span_note(span, &message);
251 err: &mut Diagnostic,
257 let message = format!("{}{}{}", prefix, description, suffix);
259 if let Some(span) = span {
260 err.span_label(span, &message);
266 #[instrument(level = "trace", skip(tcx))]
267 pub fn unexpected_hidden_region_diagnostic<'tcx>(
271 hidden_region: ty::Region<'tcx>,
272 opaque_ty: ty::OpaqueTypeKey<'tcx>,
273 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
274 let opaque_ty = tcx.mk_opaque(opaque_ty.def_id.to_def_id(), opaque_ty.substs);
275 let mut err = struct_span_err!(
279 "hidden type for `{opaque_ty}` captures lifetime that does not appear in bounds",
282 // Explain the region we are capturing.
283 match *hidden_region {
284 ty::ReEarlyBound(_) | ty::ReFree(_) | ty::ReStatic => {
285 // Assuming regionck succeeded (*), we ought to always be
286 // capturing *some* region from the fn header, and hence it
287 // ought to be free. So under normal circumstances, we will go
288 // down this path which gives a decent human readable
291 // (*) if not, the `tainted_by_errors` field would be set to
292 // `Some(ErrorGuaranteed)` in any case, so we wouldn't be here at all.
296 &format!("hidden type `{}` captures ", hidden_ty),
300 if let Some(reg_info) = tcx.is_suitable_region(hidden_region) {
301 let fn_returns = tcx.return_type_impl_or_dyn_traits(reg_info.def_id);
302 nice_region_error::suggest_new_region_bound(
306 hidden_region.to_string(),
308 format!("captures `{}`", hidden_region),
310 Some(reg_info.def_id),
315 // Ugh. This is a painful case: the hidden region is not one
316 // that we can easily summarize or explain. This can happen
318 // `tests/ui/multiple-lifetimes/ordinary-bounds-unsuited.rs`:
321 // fn upper_bounds<'a, 'b>(a: Ordinary<'a>, b: Ordinary<'b>) -> impl Trait<'a, 'b> {
322 // if condition() { a } else { b }
326 // Here the captured lifetime is the intersection of `'a` and
327 // `'b`, which we can't quite express.
329 // We can at least report a really cryptic error for now.
330 note_and_explain_region(
333 &format!("hidden type `{}` captures ", hidden_ty),
344 impl<'tcx> InferCtxt<'tcx> {
345 pub fn get_impl_future_output_ty(&self, ty: Ty<'tcx>) -> Option<Ty<'tcx>> {
346 let (def_id, substs) = match *ty.kind() {
347 ty::Alias(_, ty::AliasTy { def_id, substs, .. })
349 self.tcx.def_kind(def_id),
350 DefKind::OpaqueTy | DefKind::ImplTraitPlaceholder
358 let future_trait = self.tcx.require_lang_item(LangItem::Future, None);
359 let item_def_id = self.tcx.associated_item_def_ids(future_trait)[0];
361 self.tcx.bound_explicit_item_bounds(def_id).subst_iter_copied(self.tcx, substs).find_map(
365 .map_bound(|kind| match kind {
366 ty::PredicateKind::Clause(ty::Clause::Projection(projection_predicate))
367 if projection_predicate.projection_ty.def_id == item_def_id =>
369 projection_predicate.term.ty()
380 impl<'tcx> TypeErrCtxt<'_, 'tcx> {
381 pub fn report_region_errors(
383 generic_param_scope: LocalDefId,
384 errors: &[RegionResolutionError<'tcx>],
386 debug!("report_region_errors(): {} errors to start", errors.len());
388 // try to pre-process the errors, which will group some of them
389 // together into a `ProcessedErrors` group:
390 let errors = self.process_errors(errors);
392 debug!("report_region_errors: {} errors after preprocessing", errors.len());
394 for error in errors {
395 debug!("report_region_errors: error = {:?}", error);
397 if !self.try_report_nice_region_error(&error) {
398 match error.clone() {
399 // These errors could indicate all manner of different
400 // problems with many different solutions. Rather
401 // than generate a "one size fits all" error, what we
402 // attempt to do is go through a number of specific
403 // scenarios and try to find the best way to present
404 // the error. If all of these fails, we fall back to a rather
405 // general bit of code that displays the error information
406 RegionResolutionError::ConcreteFailure(origin, sub, sup) => {
407 if sub.is_placeholder() || sup.is_placeholder() {
408 self.report_placeholder_failure(origin, sub, sup).emit();
410 self.report_concrete_failure(origin, sub, sup).emit();
414 RegionResolutionError::GenericBoundFailure(origin, param_ty, sub) => {
415 self.report_generic_bound_failure(
424 RegionResolutionError::SubSupConflict(
433 if sub_r.is_placeholder() {
434 self.report_placeholder_failure(sub_origin, sub_r, sup_r).emit();
435 } else if sup_r.is_placeholder() {
436 self.report_placeholder_failure(sup_origin, sub_r, sup_r).emit();
438 self.report_sub_sup_conflict(
439 var_origin, sub_origin, sub_r, sup_origin, sup_r,
444 RegionResolutionError::UpperBoundUniverseConflict(
451 assert!(sup_r.is_placeholder());
453 // Make a dummy value for the "sub region" --
454 // this is the initial value of the
455 // placeholder. In practice, we expect more
456 // tailored errors that don't really use this
458 let sub_r = self.tcx.lifetimes.re_erased;
460 self.report_placeholder_failure(sup_origin, sub_r, sup_r).emit();
467 // This method goes through all the errors and try to group certain types
468 // of error together, for the purpose of suggesting explicit lifetime
469 // parameters to the user. This is done so that we can have a more
470 // complete view of what lifetimes should be the same.
471 // If the return value is an empty vector, it means that processing
472 // failed (so the return value of this method should not be used).
474 // The method also attempts to weed out messages that seem like
475 // duplicates that will be unhelpful to the end-user. But
476 // obviously it never weeds out ALL errors.
479 errors: &[RegionResolutionError<'tcx>],
480 ) -> Vec<RegionResolutionError<'tcx>> {
481 debug!("process_errors()");
483 // We want to avoid reporting generic-bound failures if we can
484 // avoid it: these have a very high rate of being unhelpful in
485 // practice. This is because they are basically secondary
486 // checks that test the state of the region graph after the
487 // rest of inference is done, and the other kinds of errors
488 // indicate that the region constraint graph is internally
489 // inconsistent, so these test results are likely to be
492 // Therefore, we filter them out of the list unless they are
493 // the only thing in the list.
495 let is_bound_failure = |e: &RegionResolutionError<'tcx>| match *e {
496 RegionResolutionError::GenericBoundFailure(..) => true,
497 RegionResolutionError::ConcreteFailure(..)
498 | RegionResolutionError::SubSupConflict(..)
499 | RegionResolutionError::UpperBoundUniverseConflict(..) => false,
502 let mut errors = if errors.iter().all(|e| is_bound_failure(e)) {
505 errors.iter().filter(|&e| !is_bound_failure(e)).cloned().collect()
508 // sort the errors by span, for better error message stability.
509 errors.sort_by_key(|u| match *u {
510 RegionResolutionError::ConcreteFailure(ref sro, _, _) => sro.span(),
511 RegionResolutionError::GenericBoundFailure(ref sro, _, _) => sro.span(),
512 RegionResolutionError::SubSupConflict(_, ref rvo, _, _, _, _, _) => rvo.span(),
513 RegionResolutionError::UpperBoundUniverseConflict(_, ref rvo, _, _, _) => rvo.span(),
518 /// Adds a note if the types come from similarly named crates
519 fn check_and_note_conflicting_crates(&self, err: &mut Diagnostic, terr: TypeError<'tcx>) {
520 use hir::def_id::CrateNum;
521 use rustc_hir::definitions::DisambiguatedDefPathData;
522 use ty::print::Printer;
523 use ty::subst::GenericArg;
525 struct AbsolutePathPrinter<'tcx> {
529 struct NonTrivialPath;
531 impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
532 type Error = NonTrivialPath;
534 type Path = Vec<String>;
537 type DynExistential = !;
540 fn tcx<'a>(&'a self) -> TyCtxt<'tcx> {
544 fn print_region(self, _region: ty::Region<'_>) -> Result<Self::Region, Self::Error> {
548 fn print_type(self, _ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> {
552 fn print_dyn_existential(
554 _predicates: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
555 ) -> Result<Self::DynExistential, Self::Error> {
559 fn print_const(self, _ct: ty::Const<'tcx>) -> Result<Self::Const, Self::Error> {
563 fn path_crate(self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
564 Ok(vec![self.tcx.crate_name(cnum).to_string()])
569 _trait_ref: Option<ty::TraitRef<'tcx>>,
570 ) -> Result<Self::Path, Self::Error> {
576 _print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
577 _disambiguated_data: &DisambiguatedDefPathData,
579 _trait_ref: Option<ty::TraitRef<'tcx>>,
580 ) -> Result<Self::Path, Self::Error> {
585 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
586 disambiguated_data: &DisambiguatedDefPathData,
587 ) -> Result<Self::Path, Self::Error> {
588 let mut path = print_prefix(self)?;
589 path.push(disambiguated_data.to_string());
592 fn path_generic_args(
594 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
595 _args: &[GenericArg<'tcx>],
596 ) -> Result<Self::Path, Self::Error> {
601 let report_path_match = |err: &mut Diagnostic, did1: DefId, did2: DefId| {
602 // Only external crates, if either is from a local
603 // module we could have false positives
604 if !(did1.is_local() || did2.is_local()) && did1.krate != did2.krate {
606 |def_id| AbsolutePathPrinter { tcx: self.tcx }.print_def_path(def_id, &[]);
608 // We compare strings because DefPath can be different
609 // for imported and non-imported crates
610 let same_path = || -> Result<_, NonTrivialPath> {
611 Ok(self.tcx.def_path_str(did1) == self.tcx.def_path_str(did2)
612 || abs_path(did1)? == abs_path(did2)?)
614 if same_path().unwrap_or(false) {
615 let crate_name = self.tcx.crate_name(did1.krate);
617 "perhaps two different versions of crate `{}` are being used?",
624 TypeError::Sorts(ref exp_found) => {
625 // if they are both "path types", there's a chance of ambiguity
626 // due to different versions of the same crate
627 if let (&ty::Adt(exp_adt, _), &ty::Adt(found_adt, _)) =
628 (exp_found.expected.kind(), exp_found.found.kind())
630 report_path_match(err, exp_adt.did(), found_adt.did());
633 TypeError::Traits(ref exp_found) => {
634 report_path_match(err, exp_found.expected, exp_found.found);
636 _ => (), // FIXME(#22750) handle traits and stuff
640 fn note_error_origin(
642 err: &mut Diagnostic,
643 cause: &ObligationCause<'tcx>,
644 exp_found: Option<ty::error::ExpectedFound<Ty<'tcx>>>,
645 terr: TypeError<'tcx>,
647 match *cause.code() {
648 ObligationCauseCode::Pattern { origin_expr: true, span: Some(span), root_ty } => {
649 let ty = self.resolve_vars_if_possible(root_ty);
650 if !matches!(ty.kind(), ty::Infer(ty::InferTy::TyVar(_) | ty::InferTy::FreshTy(_)))
652 // don't show type `_`
653 if span.desugaring_kind() == Some(DesugaringKind::ForLoop)
654 && let ty::Adt(def, substs) = ty.kind()
655 && Some(def.did()) == self.tcx.get_diagnostic_item(sym::Option)
657 err.span_label(span, format!("this is an iterator with items of type `{}`", substs.type_at(0)));
659 err.span_label(span, format!("this expression has type `{}`", ty));
662 if let Some(ty::error::ExpectedFound { found, .. }) = exp_found
663 && ty.is_box() && ty.boxed_ty() == found
664 && let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span)
668 "consider dereferencing the boxed value",
669 format!("*{}", snippet),
670 Applicability::MachineApplicable,
674 ObligationCauseCode::Pattern { origin_expr: false, span: Some(span), .. } => {
675 err.span_label(span, "expected due to this");
677 ObligationCauseCode::MatchExpressionArm(box MatchExpressionArmCause {
687 opt_suggest_box_span,
691 hir::MatchSource::TryDesugar => {
692 if let Some(ty::error::ExpectedFound { expected, .. }) = exp_found {
693 let scrut_expr = self.tcx.hir().expect_expr(scrut_hir_id);
694 let scrut_ty = if let hir::ExprKind::Call(_, args) = &scrut_expr.kind {
695 let arg_expr = args.first().expect("try desugaring call w/out arg");
696 self.typeck_results.as_ref().and_then(|typeck_results| {
697 typeck_results.expr_ty_opt(arg_expr)
700 bug!("try desugaring w/out call expr as scrutinee");
704 Some(ty) if expected == ty => {
705 let source_map = self.tcx.sess.source_map();
707 source_map.end_point(cause.span),
708 "try removing this `?`",
710 Applicability::MachineApplicable,
718 // `prior_arm_ty` can be `!`, `expected` will have better info when present.
719 let t = self.resolve_vars_if_possible(match exp_found {
720 Some(ty::error::ExpectedFound { expected, .. }) => expected,
723 let source_map = self.tcx.sess.source_map();
724 let mut any_multiline_arm = source_map.is_multiline(arm_span);
725 if prior_arms.len() <= 4 {
726 for sp in prior_arms {
727 any_multiline_arm |= source_map.is_multiline(*sp);
728 err.span_label(*sp, format!("this is found to be of type `{}`", t));
730 } else if let Some(sp) = prior_arms.last() {
731 any_multiline_arm |= source_map.is_multiline(*sp);
734 format!("this and all prior arms are found to be of type `{}`", t),
737 let outer = if any_multiline_arm || !source_map.is_multiline(cause.span) {
738 // Cover just `match` and the scrutinee expression, not
739 // the entire match body, to reduce diagram noise.
740 cause.span.shrink_to_lo().to(scrut_span)
744 let msg = "`match` arms have incompatible types";
745 err.span_label(outer, msg);
746 self.suggest_remove_semi_or_return_binding(
755 if let Some(ret_sp) = opt_suggest_box_span {
756 // Get return type span and point to it.
757 self.suggest_boxing_for_return_impl_trait(
760 prior_arms.iter().chain(std::iter::once(&arm_span)).map(|s| *s),
765 ObligationCauseCode::IfExpression(box IfExpressionCause {
771 opt_suggest_box_span,
773 let then_span = self.find_block_span_from_hir_id(then_id);
774 let else_span = self.find_block_span_from_hir_id(else_id);
775 err.span_label(then_span, "expected because of this");
776 if let Some(sp) = outer_span {
777 err.span_label(sp, "`if` and `else` have incompatible types");
779 self.suggest_remove_semi_or_return_binding(
788 if let Some(ret_sp) = opt_suggest_box_span {
789 self.suggest_boxing_for_return_impl_trait(
792 [then_span, else_span].into_iter(),
796 ObligationCauseCode::LetElse => {
797 err.help("try adding a diverging expression, such as `return` or `panic!(..)`");
798 err.help("...or use `match` instead of `let...else`");
801 if let ObligationCauseCode::BindingObligation(_, span)
802 | ObligationCauseCode::ExprBindingObligation(_, span, ..)
803 = cause.code().peel_derives()
804 && let TypeError::RegionsPlaceholderMismatch = terr
806 err.span_note( * span,
807 "the lifetime requirement is introduced here");
813 /// Given that `other_ty` is the same as a type argument for `name` in `sub`, populate `value`
814 /// highlighting `name` and every type argument that isn't at `pos` (which is `other_ty`), and
815 /// populate `other_value` with `other_ty`.
819 /// ^^^^--------^ this is highlighted
821 /// | this type argument is exactly the same as the other type, not highlighted
822 /// this is highlighted
824 /// -------- this type is the same as a type argument in the other type, not highlighted
828 value: &mut DiagnosticStyledString,
829 other_value: &mut DiagnosticStyledString,
831 sub: ty::subst::SubstsRef<'tcx>,
835 // `value` and `other_value` hold two incomplete type representation for display.
836 // `name` is the path of both types being compared. `sub`
837 value.push_highlighted(name);
840 value.push_highlighted("<");
843 // Output the lifetimes for the first type
847 let s = lifetime.to_string();
848 if s.is_empty() { "'_".to_string() } else { s }
852 if !lifetimes.is_empty() {
853 if sub.regions().count() < len {
854 value.push_normal(lifetimes + ", ");
856 value.push_normal(lifetimes);
860 // Highlight all the type arguments that aren't at `pos` and compare the type argument at
861 // `pos` and `other_ty`.
862 for (i, type_arg) in sub.types().enumerate() {
864 let values = self.cmp(type_arg, other_ty);
865 value.0.extend((values.0).0);
866 other_value.0.extend((values.1).0);
868 value.push_highlighted(type_arg.to_string());
871 if len > 0 && i != len - 1 {
872 value.push_normal(", ");
876 value.push_highlighted(">");
880 /// If `other_ty` is the same as a type argument present in `sub`, highlight `path` in `t1_out`,
881 /// as that is the difference to the other type.
883 /// For the following code:
885 /// ```ignore (illustrative)
886 /// let x: Foo<Bar<Qux>> = foo::<Bar<Qux>>();
889 /// The type error output will behave in the following way:
893 /// ^^^^--------^ this is highlighted
895 /// | this type argument is exactly the same as the other type, not highlighted
896 /// this is highlighted
898 /// -------- this type is the same as a type argument in the other type, not highlighted
902 mut t1_out: &mut DiagnosticStyledString,
903 mut t2_out: &mut DiagnosticStyledString,
905 sub: &'tcx [ty::GenericArg<'tcx>],
909 // FIXME/HACK: Go back to `SubstsRef` to use its inherent methods,
910 // ideally that shouldn't be necessary.
911 let sub = self.tcx.intern_substs(sub);
912 for (i, ta) in sub.types().enumerate() {
914 self.highlight_outer(&mut t1_out, &mut t2_out, path, sub, i, other_ty);
917 if let ty::Adt(def, _) = ta.kind() {
918 let path_ = self.tcx.def_path_str(def.did());
919 if path_ == other_path {
920 self.highlight_outer(&mut t1_out, &mut t2_out, path, sub, i, other_ty);
928 /// Adds a `,` to the type representation only if it is appropriate.
931 value: &mut DiagnosticStyledString,
932 other_value: &mut DiagnosticStyledString,
936 if len > 0 && pos != len - 1 {
937 value.push_normal(", ");
938 other_value.push_normal(", ");
942 /// Given two `fn` signatures highlight only sub-parts that are different.
945 sig1: &ty::PolyFnSig<'tcx>,
946 sig2: &ty::PolyFnSig<'tcx>,
947 ) -> (DiagnosticStyledString, DiagnosticStyledString) {
948 let sig1 = &(self.normalize_fn_sig)(*sig1);
949 let sig2 = &(self.normalize_fn_sig)(*sig2);
951 let get_lifetimes = |sig| {
952 use rustc_hir::def::Namespace;
953 let (_, sig, reg) = ty::print::FmtPrinter::new(self.tcx, Namespace::TypeNS)
954 .name_all_regions(sig)
956 let lts: Vec<String> = reg.into_iter().map(|(_, kind)| kind.to_string()).collect();
957 (if lts.is_empty() { String::new() } else { format!("for<{}> ", lts.join(", ")) }, sig)
960 let (lt1, sig1) = get_lifetimes(sig1);
961 let (lt2, sig2) = get_lifetimes(sig2);
963 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
965 DiagnosticStyledString::normal("".to_string()),
966 DiagnosticStyledString::normal("".to_string()),
969 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
971 values.0.push(sig1.unsafety.prefix_str(), sig1.unsafety != sig2.unsafety);
972 values.1.push(sig2.unsafety.prefix_str(), sig1.unsafety != sig2.unsafety);
974 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
976 if sig1.abi != abi::Abi::Rust {
977 values.0.push(format!("extern {} ", sig1.abi), sig1.abi != sig2.abi);
979 if sig2.abi != abi::Abi::Rust {
980 values.1.push(format!("extern {} ", sig2.abi), sig1.abi != sig2.abi);
983 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
985 let lifetime_diff = lt1 != lt2;
986 values.0.push(lt1, lifetime_diff);
987 values.1.push(lt2, lifetime_diff);
989 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
991 values.0.push_normal("fn(");
992 values.1.push_normal("fn(");
994 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
996 let len1 = sig1.inputs().len();
997 let len2 = sig2.inputs().len();
999 for (i, (l, r)) in iter::zip(sig1.inputs(), sig2.inputs()).enumerate() {
1000 let (x1, x2) = self.cmp(*l, *r);
1001 (values.0).0.extend(x1.0);
1002 (values.1).0.extend(x2.0);
1003 self.push_comma(&mut values.0, &mut values.1, len1, i);
1006 for (i, l) in sig1.inputs().iter().enumerate() {
1007 values.0.push_highlighted(l.to_string());
1009 values.0.push_highlighted(", ");
1012 for (i, r) in sig2.inputs().iter().enumerate() {
1013 values.1.push_highlighted(r.to_string());
1015 values.1.push_highlighted(", ");
1020 if sig1.c_variadic {
1022 values.0.push_normal(", ");
1024 values.0.push("...", !sig2.c_variadic);
1026 if sig2.c_variadic {
1028 values.1.push_normal(", ");
1030 values.1.push("...", !sig1.c_variadic);
1033 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
1035 values.0.push_normal(")");
1036 values.1.push_normal(")");
1038 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
1040 let output1 = sig1.output();
1041 let output2 = sig2.output();
1042 let (x1, x2) = self.cmp(output1, output2);
1043 if !output1.is_unit() {
1044 values.0.push_normal(" -> ");
1045 (values.0).0.extend(x1.0);
1047 if !output2.is_unit() {
1048 values.1.push_normal(" -> ");
1049 (values.1).0.extend(x2.0);
1054 /// Compares two given types, eliding parts that are the same between them and highlighting
1055 /// relevant differences, and return two representation of those types for highlighted printing.
1060 ) -> (DiagnosticStyledString, DiagnosticStyledString) {
1061 debug!("cmp(t1={}, t1.kind={:?}, t2={}, t2.kind={:?})", t1, t1.kind(), t2, t2.kind());
1064 fn equals<'tcx>(a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
1065 match (a.kind(), b.kind()) {
1066 (a, b) if *a == *b => true,
1067 (&ty::Int(_), &ty::Infer(ty::InferTy::IntVar(_)))
1069 &ty::Infer(ty::InferTy::IntVar(_)),
1070 &ty::Int(_) | &ty::Infer(ty::InferTy::IntVar(_)),
1072 | (&ty::Float(_), &ty::Infer(ty::InferTy::FloatVar(_)))
1074 &ty::Infer(ty::InferTy::FloatVar(_)),
1075 &ty::Float(_) | &ty::Infer(ty::InferTy::FloatVar(_)),
1081 fn push_ty_ref<'tcx>(
1082 region: ty::Region<'tcx>,
1084 mutbl: hir::Mutability,
1085 s: &mut DiagnosticStyledString,
1087 let mut r = region.to_string();
1093 s.push_highlighted(format!("&{}{}", r, mutbl.prefix_str()));
1094 s.push_normal(ty.to_string());
1097 // process starts here
1098 match (t1.kind(), t2.kind()) {
1099 (&ty::Adt(def1, sub1), &ty::Adt(def2, sub2)) => {
1100 let did1 = def1.did();
1101 let did2 = def2.did();
1102 let sub_no_defaults_1 =
1103 self.tcx.generics_of(did1).own_substs_no_defaults(self.tcx, sub1);
1104 let sub_no_defaults_2 =
1105 self.tcx.generics_of(did2).own_substs_no_defaults(self.tcx, sub2);
1106 let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new());
1107 let path1 = self.tcx.def_path_str(did1);
1108 let path2 = self.tcx.def_path_str(did2);
1110 // Easy case. Replace same types with `_` to shorten the output and highlight
1111 // the differing ones.
1112 // let x: Foo<Bar, Qux> = y::<Foo<Quz, Qux>>();
1115 // --- ^ type argument elided
1117 // highlighted in output
1118 values.0.push_normal(path1);
1119 values.1.push_normal(path2);
1121 // Avoid printing out default generic parameters that are common to both
1123 let len1 = sub_no_defaults_1.len();
1124 let len2 = sub_no_defaults_2.len();
1125 let common_len = cmp::min(len1, len2);
1126 let remainder1: Vec<_> = sub1.types().skip(common_len).collect();
1127 let remainder2: Vec<_> = sub2.types().skip(common_len).collect();
1128 let common_default_params =
1129 iter::zip(remainder1.iter().rev(), remainder2.iter().rev())
1130 .filter(|(a, b)| a == b)
1132 let len = sub1.len() - common_default_params;
1133 let consts_offset = len - sub1.consts().count();
1135 // Only draw `<...>` if there are lifetime/type arguments.
1137 values.0.push_normal("<");
1138 values.1.push_normal("<");
1141 fn lifetime_display(lifetime: Region<'_>) -> String {
1142 let s = lifetime.to_string();
1143 if s.is_empty() { "'_".to_string() } else { s }
1145 // At one point we'd like to elide all lifetimes here, they are irrelevant for
1146 // all diagnostics that use this output
1150 // ^^ ^^ --- type arguments are not elided
1152 // | elided as they were the same
1153 // not elided, they were different, but irrelevant
1155 // For bound lifetimes, keep the names of the lifetimes,
1156 // even if they are the same so that it's clear what's happening
1157 // if we have something like
1159 // for<'r, 's> fn(Inv<'r>, Inv<'s>)
1160 // for<'r> fn(Inv<'r>, Inv<'r>)
1161 let lifetimes = sub1.regions().zip(sub2.regions());
1162 for (i, lifetimes) in lifetimes.enumerate() {
1163 let l1 = lifetime_display(lifetimes.0);
1164 let l2 = lifetime_display(lifetimes.1);
1165 if lifetimes.0 != lifetimes.1 {
1166 values.0.push_highlighted(l1);
1167 values.1.push_highlighted(l2);
1168 } else if lifetimes.0.is_late_bound() {
1169 values.0.push_normal(l1);
1170 values.1.push_normal(l2);
1172 values.0.push_normal("'_");
1173 values.1.push_normal("'_");
1175 self.push_comma(&mut values.0, &mut values.1, len, i);
1178 // We're comparing two types with the same path, so we compare the type
1179 // arguments for both. If they are the same, do not highlight and elide from the
1183 // ^ elided type as this type argument was the same in both sides
1184 let type_arguments = sub1.types().zip(sub2.types());
1185 let regions_len = sub1.regions().count();
1186 let num_display_types = consts_offset - regions_len;
1187 for (i, (ta1, ta2)) in type_arguments.take(num_display_types).enumerate() {
1188 let i = i + regions_len;
1189 if ta1 == ta2 && !self.tcx.sess.verbose() {
1190 values.0.push_normal("_");
1191 values.1.push_normal("_");
1193 let (x1, x2) = self.cmp(ta1, ta2);
1194 (values.0).0.extend(x1.0);
1195 (values.1).0.extend(x2.0);
1197 self.push_comma(&mut values.0, &mut values.1, len, i);
1200 // Do the same for const arguments, if they are equal, do not highlight and
1201 // elide them from the output.
1202 let const_arguments = sub1.consts().zip(sub2.consts());
1203 for (i, (ca1, ca2)) in const_arguments.enumerate() {
1204 let i = i + consts_offset;
1205 if ca1 == ca2 && !self.tcx.sess.verbose() {
1206 values.0.push_normal("_");
1207 values.1.push_normal("_");
1209 values.0.push_highlighted(ca1.to_string());
1210 values.1.push_highlighted(ca2.to_string());
1212 self.push_comma(&mut values.0, &mut values.1, len, i);
1215 // Close the type argument bracket.
1216 // Only draw `<...>` if there are lifetime/type arguments.
1218 values.0.push_normal(">");
1219 values.1.push_normal(">");
1224 // let x: Foo<Bar<Qux> = foo::<Bar<Qux>>();
1226 // ------- this type argument is exactly the same as the other type
1242 // let x: Bar<Qux> = y:<Foo<Bar<Qux>>>();
1245 // ------- this type argument is exactly the same as the other type
1260 // We can't find anything in common, highlight relevant part of type path.
1261 // let x: foo::bar::Baz<Qux> = y:<foo::bar::Bar<Zar>>();
1262 // foo::bar::Baz<Qux>
1263 // foo::bar::Bar<Zar>
1264 // -------- this part of the path is different
1266 let t1_str = t1.to_string();
1267 let t2_str = t2.to_string();
1268 let min_len = t1_str.len().min(t2_str.len());
1270 const SEPARATOR: &str = "::";
1271 let separator_len = SEPARATOR.len();
1272 let split_idx: usize =
1273 iter::zip(t1_str.split(SEPARATOR), t2_str.split(SEPARATOR))
1274 .take_while(|(mod1_str, mod2_str)| mod1_str == mod2_str)
1275 .map(|(mod_str, _)| mod_str.len() + separator_len)
1278 debug!(?separator_len, ?split_idx, ?min_len, "cmp");
1280 if split_idx >= min_len {
1281 // paths are identical, highlight everything
1283 DiagnosticStyledString::highlighted(t1_str),
1284 DiagnosticStyledString::highlighted(t2_str),
1287 let (common, uniq1) = t1_str.split_at(split_idx);
1288 let (_, uniq2) = t2_str.split_at(split_idx);
1289 debug!(?common, ?uniq1, ?uniq2, "cmp");
1291 values.0.push_normal(common);
1292 values.0.push_highlighted(uniq1);
1293 values.1.push_normal(common);
1294 values.1.push_highlighted(uniq2);
1301 // When finding T != &T, highlight only the borrow
1302 (&ty::Ref(r1, ref_ty1, mutbl1), _) if equals(ref_ty1, t2) => {
1303 let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new());
1304 push_ty_ref(r1, ref_ty1, mutbl1, &mut values.0);
1305 values.1.push_normal(t2.to_string());
1308 (_, &ty::Ref(r2, ref_ty2, mutbl2)) if equals(t1, ref_ty2) => {
1309 let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new());
1310 values.0.push_normal(t1.to_string());
1311 push_ty_ref(r2, ref_ty2, mutbl2, &mut values.1);
1315 // When encountering &T != &mut T, highlight only the borrow
1316 (&ty::Ref(r1, ref_ty1, mutbl1), &ty::Ref(r2, ref_ty2, mutbl2))
1317 if equals(ref_ty1, ref_ty2) =>
1319 let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new());
1320 push_ty_ref(r1, ref_ty1, mutbl1, &mut values.0);
1321 push_ty_ref(r2, ref_ty2, mutbl2, &mut values.1);
1325 // When encountering tuples of the same size, highlight only the differing types
1326 (&ty::Tuple(substs1), &ty::Tuple(substs2)) if substs1.len() == substs2.len() => {
1328 (DiagnosticStyledString::normal("("), DiagnosticStyledString::normal("("));
1329 let len = substs1.len();
1330 for (i, (left, right)) in substs1.iter().zip(substs2).enumerate() {
1331 let (x1, x2) = self.cmp(left, right);
1332 (values.0).0.extend(x1.0);
1333 (values.1).0.extend(x2.0);
1334 self.push_comma(&mut values.0, &mut values.1, len, i);
1337 // Keep the output for single element tuples as `(ty,)`.
1338 values.0.push_normal(",");
1339 values.1.push_normal(",");
1341 values.0.push_normal(")");
1342 values.1.push_normal(")");
1346 (ty::FnDef(did1, substs1), ty::FnDef(did2, substs2)) => {
1347 let sig1 = self.tcx.bound_fn_sig(*did1).subst(self.tcx, substs1);
1348 let sig2 = self.tcx.bound_fn_sig(*did2).subst(self.tcx, substs2);
1349 let mut values = self.cmp_fn_sig(&sig1, &sig2);
1350 let path1 = format!(" {{{}}}", self.tcx.def_path_str_with_substs(*did1, substs1));
1351 let path2 = format!(" {{{}}}", self.tcx.def_path_str_with_substs(*did2, substs2));
1352 let same_path = path1 == path2;
1353 values.0.push(path1, !same_path);
1354 values.1.push(path2, !same_path);
1358 (ty::FnDef(did1, substs1), ty::FnPtr(sig2)) => {
1359 let sig1 = self.tcx.bound_fn_sig(*did1).subst(self.tcx, substs1);
1360 let mut values = self.cmp_fn_sig(&sig1, sig2);
1361 values.0.push_highlighted(format!(
1363 self.tcx.def_path_str_with_substs(*did1, substs1)
1368 (ty::FnPtr(sig1), ty::FnDef(did2, substs2)) => {
1369 let sig2 = self.tcx.bound_fn_sig(*did2).subst(self.tcx, substs2);
1370 let mut values = self.cmp_fn_sig(sig1, &sig2);
1371 values.1.push_normal(format!(
1373 self.tcx.def_path_str_with_substs(*did2, substs2)
1378 (ty::FnPtr(sig1), ty::FnPtr(sig2)) => self.cmp_fn_sig(sig1, sig2),
1381 if t1 == t2 && !self.tcx.sess.verbose() {
1382 // The two types are the same, elide and don't highlight.
1383 (DiagnosticStyledString::normal("_"), DiagnosticStyledString::normal("_"))
1385 // We couldn't find anything in common, highlight everything.
1387 DiagnosticStyledString::highlighted(t1.to_string()),
1388 DiagnosticStyledString::highlighted(t2.to_string()),
1395 /// Extend a type error with extra labels pointing at "non-trivial" types, like closures and
1396 /// the return type of `async fn`s.
1398 /// `secondary_span` gives the caller the opportunity to expand `diag` with a `span_label`.
1400 /// `swap_secondary_and_primary` is used to make projection errors in particular nicer by using
1401 /// the message in `secondary_span` as the primary label, and apply the message that would
1402 /// otherwise be used for the primary label on the `secondary_span` `Span`. This applies on
1403 /// E0271, like `tests/ui/issues/issue-39970.stderr`.
1406 skip(self, diag, secondary_span, swap_secondary_and_primary, prefer_label)
1408 pub fn note_type_err(
1410 diag: &mut Diagnostic,
1411 cause: &ObligationCause<'tcx>,
1412 secondary_span: Option<(Span, String)>,
1413 mut values: Option<ValuePairs<'tcx>>,
1414 terr: TypeError<'tcx>,
1415 swap_secondary_and_primary: bool,
1418 let span = cause.span();
1420 // For some types of errors, expected-found does not make
1421 // sense, so just ignore the values we were given.
1422 if let TypeError::CyclicTy(_) = terr {
1425 struct OpaqueTypesVisitor<'tcx> {
1426 types: FxIndexMap<TyCategory, FxIndexSet<Span>>,
1427 expected: FxIndexMap<TyCategory, FxIndexSet<Span>>,
1428 found: FxIndexMap<TyCategory, FxIndexSet<Span>>,
1433 impl<'tcx> OpaqueTypesVisitor<'tcx> {
1434 fn visit_expected_found(
1436 expected: impl TypeVisitable<'tcx>,
1437 found: impl TypeVisitable<'tcx>,
1440 let mut types_visitor = OpaqueTypesVisitor {
1441 types: Default::default(),
1442 expected: Default::default(),
1443 found: Default::default(),
1447 // The visitor puts all the relevant encountered types in `self.types`, but in
1448 // here we want to visit two separate types with no relation to each other, so we
1449 // move the results from `types` to `expected` or `found` as appropriate.
1450 expected.visit_with(&mut types_visitor);
1451 std::mem::swap(&mut types_visitor.expected, &mut types_visitor.types);
1452 found.visit_with(&mut types_visitor);
1453 std::mem::swap(&mut types_visitor.found, &mut types_visitor.types);
1457 fn report(&self, err: &mut Diagnostic) {
1458 self.add_labels_for_types(err, "expected", &self.expected);
1459 self.add_labels_for_types(err, "found", &self.found);
1462 fn add_labels_for_types(
1464 err: &mut Diagnostic,
1466 types: &FxIndexMap<TyCategory, FxIndexSet<Span>>,
1468 for (key, values) in types.iter() {
1469 let count = values.len();
1470 let kind = key.descr();
1471 let mut returned_async_output_error = false;
1473 if sp.is_desugaring(DesugaringKind::Async) && !returned_async_output_error {
1474 if [sp] != err.span.primary_spans() {
1475 let mut span: MultiSpan = sp.into();
1476 span.push_span_label(
1479 "checked the `Output` of this `async fn`, {}{} {}{}",
1480 if count > 1 { "one of the " } else { "" },
1488 "while checking the return type of the `async fn`",
1494 "checked the `Output` of this `async fn`, {}{} {}{}",
1495 if count > 1 { "one of the " } else { "" },
1501 err.note("while checking the return type of the `async fn`");
1503 returned_async_output_error = true;
1509 if count == 1 { "the " } else { "one of the " },
1521 impl<'tcx> ty::visit::TypeVisitor<'tcx> for OpaqueTypesVisitor<'tcx> {
1522 fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
1523 if let Some((kind, def_id)) = TyCategory::from_ty(self.tcx, t) {
1524 let span = self.tcx.def_span(def_id);
1525 // Avoid cluttering the output when the "found" and error span overlap:
1527 // error[E0308]: mismatched types
1528 // --> $DIR/issue-20862.rs:2:5
1533 // | the found closure
1534 // | expected `()`, found closure
1536 // = note: expected unit type `()`
1537 // found closure `[closure@$DIR/issue-20862.rs:2:5: 2:14 x:_]`
1538 if !self.ignore_span.overlaps(span) {
1539 self.types.entry(kind).or_default().insert(span);
1542 t.super_visit_with(self)
1546 debug!("note_type_err(diag={:?})", diag);
1548 Variable(ty::error::ExpectedFound<Ty<'a>>),
1549 Fixed(&'static str),
1551 let (expected_found, exp_found, is_simple_error, values) = match values {
1552 None => (None, Mismatch::Fixed("type"), false, None),
1554 let values = self.resolve_vars_if_possible(values);
1555 let (is_simple_error, exp_found) = match values {
1556 ValuePairs::Terms(infer::ExpectedFound { expected, found }) => {
1557 match (expected.unpack(), found.unpack()) {
1558 (ty::TermKind::Ty(expected), ty::TermKind::Ty(found)) => {
1560 expected.is_simple_text() && found.is_simple_text();
1561 OpaqueTypesVisitor::visit_expected_found(
1562 self.tcx, expected, found, span,
1568 Mismatch::Variable(infer::ExpectedFound { expected, found }),
1571 (ty::TermKind::Const(_), ty::TermKind::Const(_)) => {
1572 (false, Mismatch::Fixed("constant"))
1574 _ => (false, Mismatch::Fixed("type")),
1577 ValuePairs::Sigs(infer::ExpectedFound { expected, found }) => {
1578 OpaqueTypesVisitor::visit_expected_found(self.tcx, expected, found, span)
1580 (false, Mismatch::Fixed("signature"))
1582 ValuePairs::TraitRefs(_) | ValuePairs::PolyTraitRefs(_) => {
1583 (false, Mismatch::Fixed("trait"))
1585 ValuePairs::Regions(_) => (false, Mismatch::Fixed("lifetime")),
1587 let Some(vals) = self.values_str(values) else {
1588 // Derived error. Cancel the emitter.
1589 // NOTE(eddyb) this was `.cancel()`, but `diag`
1590 // is borrowed, so we can't fully defuse it.
1591 diag.downgrade_to_delayed_bug();
1594 (Some(vals), exp_found, is_simple_error, Some(values))
1598 let mut label_or_note = |span: Span, msg: &str| {
1599 if (prefer_label && is_simple_error) || &[span] == diag.span.primary_spans() {
1600 diag.span_label(span, msg);
1602 diag.span_note(span, msg);
1605 if let Some((sp, msg)) = secondary_span {
1606 if swap_secondary_and_primary {
1607 let terr = if let Some(infer::ValuePairs::Terms(infer::ExpectedFound {
1612 format!("expected this to be `{}`", expected)
1616 label_or_note(sp, &terr);
1617 label_or_note(span, &msg);
1619 label_or_note(span, &terr.to_string());
1620 label_or_note(sp, &msg);
1623 label_or_note(span, &terr.to_string());
1626 if let Some((expected, found, exp_p, found_p)) = expected_found {
1627 let (expected_label, found_label, exp_found) = match exp_found {
1628 Mismatch::Variable(ef) => (
1629 ef.expected.prefix_string(self.tcx),
1630 ef.found.prefix_string(self.tcx),
1633 Mismatch::Fixed(s) => (s.into(), s.into(), None),
1636 enum Similar<'tcx> {
1637 Adts { expected: ty::AdtDef<'tcx>, found: ty::AdtDef<'tcx> },
1638 PrimitiveFound { expected: ty::AdtDef<'tcx>, found: Ty<'tcx> },
1639 PrimitiveExpected { expected: Ty<'tcx>, found: ty::AdtDef<'tcx> },
1642 let similarity = |ExpectedFound { expected, found }: ExpectedFound<Ty<'tcx>>| {
1643 if let ty::Adt(expected, _) = expected.kind() && let Some(primitive) = found.primitive_symbol() {
1644 let path = self.tcx.def_path(expected.did()).data;
1645 let name = path.last().unwrap().data.get_opt_name();
1646 if name == Some(primitive) {
1647 return Some(Similar::PrimitiveFound { expected: *expected, found });
1649 } else if let Some(primitive) = expected.primitive_symbol() && let ty::Adt(found, _) = found.kind() {
1650 let path = self.tcx.def_path(found.did()).data;
1651 let name = path.last().unwrap().data.get_opt_name();
1652 if name == Some(primitive) {
1653 return Some(Similar::PrimitiveExpected { expected, found: *found });
1655 } else if let ty::Adt(expected, _) = expected.kind() && let ty::Adt(found, _) = found.kind() {
1656 if !expected.did().is_local() && expected.did().krate == found.did().krate {
1657 // Most likely types from different versions of the same crate
1658 // are in play, in which case this message isn't so helpful.
1659 // A "perhaps two different versions..." error is already emitted for that.
1662 let f_path = self.tcx.def_path(found.did()).data;
1663 let e_path = self.tcx.def_path(expected.did()).data;
1665 if let (Some(e_last), Some(f_last)) = (e_path.last(), f_path.last()) && e_last == f_last {
1666 return Some(Similar::Adts{expected: *expected, found: *found});
1673 // If two types mismatch but have similar names, mention that specifically.
1674 TypeError::Sorts(values) if let Some(s) = similarity(values) => {
1675 let diagnose_primitive =
1679 diagnostic: &mut Diagnostic| {
1680 let name = shadow.sort_string(self.tcx);
1681 diagnostic.note(format!(
1682 "{prim} and {name} have similar names, but are actually distinct types"
1685 .note(format!("{prim} is a primitive defined by the language"));
1686 let def_span = self.tcx.def_span(defid);
1687 let msg = if defid.is_local() {
1688 format!("{name} is defined in the current crate")
1690 let crate_name = self.tcx.crate_name(defid.krate);
1691 format!("{name} is defined in crate `{crate_name}")
1693 diagnostic.span_note(def_span, msg);
1697 |expected_adt : ty::AdtDef<'tcx>,
1698 found_adt: ty::AdtDef<'tcx>,
1699 diagnostic: &mut Diagnostic| {
1700 let found_name = values.found.sort_string(self.tcx);
1701 let expected_name = values.expected.sort_string(self.tcx);
1703 let found_defid = found_adt.did();
1704 let expected_defid = expected_adt.did();
1706 diagnostic.note(format!("{found_name} and {expected_name} have similar names, but are actually distinct types"));
1707 for (defid, name) in
1708 [(found_defid, found_name), (expected_defid, expected_name)]
1710 let def_span = self.tcx.def_span(defid);
1712 let msg = if found_defid.is_local() && expected_defid.is_local() {
1715 .parent_module_from_def_id(defid.expect_local())
1717 let module_name = self.tcx.def_path(module).to_string_no_crate_verbose();
1718 format!("{name} is defined in module `crate{module_name}` of the current crate")
1719 } else if defid.is_local() {
1720 format!("{name} is defined in the current crate")
1722 let crate_name = self.tcx.crate_name(defid.krate);
1723 format!("{name} is defined in crate `{crate_name}`")
1725 diagnostic.span_note(def_span, msg);
1730 Similar::Adts{expected, found} => {
1731 diagnose_adts(expected, found, diag)
1733 Similar::PrimitiveFound{expected, found: prim} => {
1734 diagnose_primitive(prim, values.expected, expected.did(), diag)
1736 Similar::PrimitiveExpected{expected: prim, found} => {
1737 diagnose_primitive(prim, values.found, found.did(), diag)
1741 TypeError::Sorts(values) => {
1742 let extra = expected == found;
1743 let sort_string = |ty: Ty<'tcx>, path: Option<PathBuf>| {
1744 let mut s = match (extra, ty.kind()) {
1745 (true, ty::Alias(ty::Opaque, ty::AliasTy { def_id, .. })) => {
1746 let sm = self.tcx.sess.source_map();
1747 let pos = sm.lookup_char_pos(self.tcx.def_span(*def_id).lo());
1749 " (opaque type at <{}:{}:{}>)",
1750 sm.filename_for_diagnostics(&pos.file.name),
1752 pos.col.to_usize() + 1,
1755 (true, ty::Alias(ty::Projection, proj))
1756 if self.tcx.def_kind(proj.def_id)
1757 == DefKind::ImplTraitPlaceholder =>
1759 let sm = self.tcx.sess.source_map();
1760 let pos = sm.lookup_char_pos(self.tcx.def_span(proj.def_id).lo());
1762 " (trait associated opaque type at <{}:{}:{}>)",
1763 sm.filename_for_diagnostics(&pos.file.name),
1765 pos.col.to_usize() + 1,
1768 (true, _) => format!(" ({})", ty.sort_string(self.tcx)),
1769 (false, _) => "".to_string(),
1771 if let Some(path) = path {
1772 s.push_str(&format!(
1773 "\nthe full type name has been written to '{}'",
1779 if !(values.expected.is_simple_text() && values.found.is_simple_text())
1780 || (exp_found.map_or(false, |ef| {
1781 // This happens when the type error is a subset of the expectation,
1782 // like when you have two references but one is `usize` and the other
1783 // is `f32`. In those cases we still want to show the `note`. If the
1784 // value from `ef` is `Infer(_)`, then we ignore it.
1785 if !ef.expected.is_ty_or_numeric_infer() {
1786 ef.expected != values.expected
1787 } else if !ef.found.is_ty_or_numeric_infer() {
1788 ef.found != values.found
1794 diag.note_expected_found_extra(
1799 &sort_string(values.expected, exp_p),
1800 &sort_string(values.found, found_p),
1806 "note_type_err: exp_found={:?}, expected={:?} found={:?}",
1807 exp_found, expected, found
1809 if !is_simple_error || terr.must_include_note() {
1810 diag.note_expected_found(&expected_label, expected, &found_label, found);
1815 let exp_found = match exp_found {
1816 Mismatch::Variable(exp_found) => Some(exp_found),
1817 Mismatch::Fixed(_) => None,
1819 let exp_found = match terr {
1820 // `terr` has more accurate type information than `exp_found` in match expressions.
1821 ty::error::TypeError::Sorts(terr)
1822 if exp_found.map_or(false, |ef| terr.found == ef.found) =>
1828 debug!("exp_found {:?} terr {:?} cause.code {:?}", exp_found, terr, cause.code());
1829 if let Some(exp_found) = exp_found {
1830 let should_suggest_fixes =
1831 if let ObligationCauseCode::Pattern { root_ty, .. } = cause.code() {
1832 // Skip if the root_ty of the pattern is not the same as the expected_ty.
1833 // If these types aren't equal then we've probably peeled off a layer of arrays.
1834 self.same_type_modulo_infer(*root_ty, exp_found.expected)
1839 if should_suggest_fixes {
1840 self.suggest_tuple_pattern(cause, &exp_found, diag);
1841 self.suggest_as_ref_where_appropriate(span, &exp_found, diag);
1842 self.suggest_accessing_field_where_appropriate(cause, &exp_found, diag);
1843 self.suggest_await_on_expect_found(cause, span, &exp_found, diag);
1847 // In some (most?) cases cause.body_id points to actual body, but in some cases
1848 // it's an actual definition. According to the comments (e.g. in
1849 // rustc_hir_analysis/check/compare_impl_item.rs:compare_predicate_entailment) the latter
1850 // is relied upon by some other code. This might (or might not) need cleanup.
1851 let body_owner_def_id =
1852 self.tcx.hir().opt_local_def_id(cause.body_id).unwrap_or_else(|| {
1853 self.tcx.hir().body_owner_def_id(hir::BodyId { hir_id: cause.body_id })
1855 self.check_and_note_conflicting_crates(diag, terr);
1856 self.tcx.note_and_explain_type_err(diag, terr, cause, span, body_owner_def_id.to_def_id());
1858 if let Some(ValuePairs::PolyTraitRefs(exp_found)) = values
1859 && let ty::Closure(def_id, _) = exp_found.expected.skip_binder().self_ty().kind()
1860 && let Some(def_id) = def_id.as_local()
1861 && terr.involves_regions()
1863 let span = self.tcx.def_span(def_id);
1864 diag.span_note(span, "this closure does not fulfill the lifetime requirements");
1867 // It reads better to have the error origin as the final
1869 self.note_error_origin(diag, cause, exp_found, terr);
1874 pub fn report_and_explain_type_error(
1876 trace: TypeTrace<'tcx>,
1877 terr: TypeError<'tcx>,
1878 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
1879 use crate::traits::ObligationCauseCode::MatchExpressionArm;
1881 debug!("report_and_explain_type_error(trace={:?}, terr={:?})", trace, terr);
1883 let span = trace.cause.span();
1884 let failure_code = trace.cause.as_failure_code(terr);
1885 let mut diag = match failure_code {
1886 FailureCode::Error0038(did) => {
1887 let violations = self.tcx.object_safety_violations(did);
1888 report_object_safety_error(self.tcx, span, did, violations)
1890 FailureCode::Error0317(failure_str) => {
1891 struct_span_err!(self.tcx.sess, span, E0317, "{}", failure_str)
1893 FailureCode::Error0580(failure_str) => {
1894 struct_span_err!(self.tcx.sess, span, E0580, "{}", failure_str)
1896 FailureCode::Error0308(failure_str) => {
1897 fn escape_literal(s: &str) -> String {
1898 let mut escaped = String::with_capacity(s.len());
1899 let mut chrs = s.chars().peekable();
1900 while let Some(first) = chrs.next() {
1901 match (first, chrs.peek()) {
1902 ('\\', Some(&delim @ '"') | Some(&delim @ '\'')) => {
1904 escaped.push(delim);
1907 ('"' | '\'', _) => {
1911 (c, _) => escaped.push(c),
1916 let mut err = struct_span_err!(self.tcx.sess, span, E0308, "{}", failure_str);
1917 if let Some((expected, found)) = trace.values.ty() {
1918 match (expected.kind(), found.kind()) {
1919 (ty::Tuple(_), ty::Tuple(_)) => {}
1920 // If a tuple of length one was expected and the found expression has
1921 // parentheses around it, perhaps the user meant to write `(expr,)` to
1922 // build a tuple (issue #86100)
1923 (ty::Tuple(fields), _) => {
1924 self.emit_tuple_wrap_err(&mut err, span, found, fields)
1926 // If a byte was expected and the found expression is a char literal
1927 // containing a single ASCII character, perhaps the user meant to write `b'c'` to
1928 // specify a byte literal
1929 (ty::Uint(ty::UintTy::U8), ty::Char) => {
1930 if let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span)
1931 && let Some(code) = code.strip_prefix('\'').and_then(|s| s.strip_suffix('\''))
1932 && code.chars().next().map_or(false, |c| c.is_ascii())
1934 err.span_suggestion(
1936 "if you meant to write a byte literal, prefix with `b`",
1937 format!("b'{}'", escape_literal(code)),
1938 Applicability::MachineApplicable,
1942 // If a character was expected and the found expression is a string literal
1943 // containing a single character, perhaps the user meant to write `'c'` to
1944 // specify a character literal (issue #92479)
1945 (ty::Char, ty::Ref(_, r, _)) if r.is_str() => {
1946 if let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span)
1947 && let Some(code) = code.strip_prefix('"').and_then(|s| s.strip_suffix('"'))
1948 && code.chars().count() == 1
1950 err.span_suggestion(
1952 "if you meant to write a `char` literal, use single quotes",
1953 format!("'{}'", escape_literal(code)),
1954 Applicability::MachineApplicable,
1958 // If a string was expected and the found expression is a character literal,
1959 // perhaps the user meant to write `"s"` to specify a string literal.
1960 (ty::Ref(_, r, _), ty::Char) if r.is_str() => {
1961 if let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span) {
1963 code.strip_prefix('\'').and_then(|s| s.strip_suffix('\''))
1965 err.span_suggestion(
1967 "if you meant to write a `str` literal, use double quotes",
1968 format!("\"{}\"", escape_literal(code)),
1969 Applicability::MachineApplicable,
1974 // For code `if Some(..) = expr `, the type mismatch may be expected `bool` but found `()`,
1975 // we try to suggest to add the missing `let` for `if let Some(..) = expr`
1976 (ty::Bool, ty::Tuple(list)) => if list.len() == 0 {
1977 self.suggest_let_for_letchains(&mut err, &trace.cause, span);
1982 let code = trace.cause.code();
1983 if let &MatchExpressionArm(box MatchExpressionArmCause { source, .. }) = code
1984 && let hir::MatchSource::TryDesugar = source
1985 && let Some((expected_ty, found_ty, _, _)) = self.values_str(trace.values)
1988 "`?` operator cannot convert from `{}` to `{}`",
1990 expected_ty.content(),
1995 FailureCode::Error0644(failure_str) => {
1996 struct_span_err!(self.tcx.sess, span, E0644, "{}", failure_str)
1999 self.note_type_err(&mut diag, &trace.cause, None, Some(trace.values), terr, false, false);
2003 fn emit_tuple_wrap_err(
2005 err: &mut Diagnostic,
2008 expected_fields: &List<Ty<'tcx>>,
2010 let [expected_tup_elem] = expected_fields[..] else { return };
2012 if !self.same_type_modulo_infer(expected_tup_elem, found) {
2016 let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span)
2019 let msg = "use a trailing comma to create a tuple with one element";
2020 if code.starts_with('(') && code.ends_with(')') {
2021 let before_close = span.hi() - BytePos::from_u32(1);
2022 err.span_suggestion(
2023 span.with_hi(before_close).shrink_to_hi(),
2026 Applicability::MachineApplicable,
2029 err.multipart_suggestion(
2031 vec![(span.shrink_to_lo(), "(".into()), (span.shrink_to_hi(), ",)".into())],
2032 Applicability::MachineApplicable,
2039 values: ValuePairs<'tcx>,
2040 ) -> Option<(DiagnosticStyledString, DiagnosticStyledString, Option<PathBuf>, Option<PathBuf>)>
2043 infer::Regions(exp_found) => self.expected_found_str(exp_found),
2044 infer::Terms(exp_found) => self.expected_found_str_term(exp_found),
2045 infer::TraitRefs(exp_found) => {
2046 let pretty_exp_found = ty::error::ExpectedFound {
2047 expected: exp_found.expected.print_only_trait_path(),
2048 found: exp_found.found.print_only_trait_path(),
2050 match self.expected_found_str(pretty_exp_found) {
2051 Some((expected, found, _, _)) if expected == found => {
2052 self.expected_found_str(exp_found)
2057 infer::PolyTraitRefs(exp_found) => {
2058 let pretty_exp_found = ty::error::ExpectedFound {
2059 expected: exp_found.expected.print_only_trait_path(),
2060 found: exp_found.found.print_only_trait_path(),
2062 match self.expected_found_str(pretty_exp_found) {
2063 Some((expected, found, _, _)) if expected == found => {
2064 self.expected_found_str(exp_found)
2069 infer::Sigs(exp_found) => {
2070 let exp_found = self.resolve_vars_if_possible(exp_found);
2071 if exp_found.references_error() {
2074 let (exp, fnd) = self.cmp_fn_sig(
2075 &ty::Binder::dummy(exp_found.expected),
2076 &ty::Binder::dummy(exp_found.found),
2078 Some((exp, fnd, None, None))
2083 fn expected_found_str_term(
2085 exp_found: ty::error::ExpectedFound<ty::Term<'tcx>>,
2086 ) -> Option<(DiagnosticStyledString, DiagnosticStyledString, Option<PathBuf>, Option<PathBuf>)>
2088 let exp_found = self.resolve_vars_if_possible(exp_found);
2089 if exp_found.references_error() {
2093 Some(match (exp_found.expected.unpack(), exp_found.found.unpack()) {
2094 (ty::TermKind::Ty(expected), ty::TermKind::Ty(found)) => {
2095 let (mut exp, mut fnd) = self.cmp(expected, found);
2096 // Use the terminal width as the basis to determine when to compress the printed
2097 // out type, but give ourselves some leeway to avoid ending up creating a file for
2098 // a type that is somewhat shorter than the path we'd write to.
2099 let len = self.tcx.sess().diagnostic_width() + 40;
2100 let exp_s = exp.content();
2101 let fnd_s = fnd.content();
2102 let mut exp_p = None;
2103 let mut fnd_p = None;
2104 if exp_s.len() > len {
2105 let (exp_s, exp_path) = self.tcx.short_ty_string(expected);
2106 exp = DiagnosticStyledString::highlighted(exp_s);
2109 if fnd_s.len() > len {
2110 let (fnd_s, fnd_path) = self.tcx.short_ty_string(found);
2111 fnd = DiagnosticStyledString::highlighted(fnd_s);
2114 (exp, fnd, exp_p, fnd_p)
2117 DiagnosticStyledString::highlighted(exp_found.expected.to_string()),
2118 DiagnosticStyledString::highlighted(exp_found.found.to_string()),
2125 /// Returns a string of the form "expected `{}`, found `{}`".
2126 fn expected_found_str<T: fmt::Display + TypeFoldable<'tcx>>(
2128 exp_found: ty::error::ExpectedFound<T>,
2129 ) -> Option<(DiagnosticStyledString, DiagnosticStyledString, Option<PathBuf>, Option<PathBuf>)>
2131 let exp_found = self.resolve_vars_if_possible(exp_found);
2132 if exp_found.references_error() {
2137 DiagnosticStyledString::highlighted(exp_found.expected.to_string()),
2138 DiagnosticStyledString::highlighted(exp_found.found.to_string()),
2144 pub fn report_generic_bound_failure(
2146 generic_param_scope: LocalDefId,
2148 origin: Option<SubregionOrigin<'tcx>>,
2149 bound_kind: GenericKind<'tcx>,
2152 self.construct_generic_bound_failure(generic_param_scope, span, origin, bound_kind, sub)
2156 pub fn construct_generic_bound_failure(
2158 generic_param_scope: LocalDefId,
2160 origin: Option<SubregionOrigin<'tcx>>,
2161 bound_kind: GenericKind<'tcx>,
2163 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
2164 // Attempt to obtain the span of the parameter so we can
2165 // suggest adding an explicit lifetime bound to it.
2166 let generics = self.tcx.generics_of(generic_param_scope);
2167 // type_param_span is (span, has_bounds)
2168 let mut is_synthetic = false;
2169 let mut ast_generics = None;
2170 let type_param_span = match bound_kind {
2171 GenericKind::Param(ref param) => {
2172 // Account for the case where `param` corresponds to `Self`,
2173 // which doesn't have the expected type argument.
2174 if !(generics.has_self && param.index == 0) {
2175 let type_param = generics.type_param(param, self.tcx);
2176 is_synthetic = type_param.kind.is_synthetic();
2177 type_param.def_id.as_local().map(|def_id| {
2178 // Get the `hir::Param` to verify whether it already has any bounds.
2179 // We do this to avoid suggesting code that ends up as `T: 'a'b`,
2180 // instead we suggest `T: 'a + 'b` in that case.
2181 let hir_id = self.tcx.hir().local_def_id_to_hir_id(def_id);
2182 ast_generics = self.tcx.hir().get_generics(hir_id.owner.def_id);
2184 ast_generics.and_then(|g| g.bounds_span_for_suggestions(def_id));
2185 // `sp` only covers `T`, change it so that it covers
2186 // `T:` when appropriate
2187 if let Some(span) = bounds {
2190 let sp = self.tcx.def_span(def_id);
2191 (sp.shrink_to_hi(), false)
2202 let mut possible = (b'a'..=b'z').map(|c| format!("'{}", c as char));
2204 iter::successors(Some(generics), |g| g.parent.map(|p| self.tcx.generics_of(p)))
2205 .flat_map(|g| &g.params)
2206 .filter(|p| matches!(p.kind, ty::GenericParamDefKind::Lifetime))
2207 .map(|p| p.name.as_str())
2208 .collect::<Vec<_>>();
2210 .find(|candidate| !lts_names.contains(&&candidate[..]))
2211 .unwrap_or("'lt".to_string())
2214 let mut add_lt_suggs: Vec<Option<_>> = vec![];
2216 if let Some(ast_generics) = ast_generics {
2217 let named_lifetime_param_exist = ast_generics.params.iter().any(|p| {
2220 hir::GenericParamKind::Lifetime { kind: hir::LifetimeParamKind::Explicit }
2223 if named_lifetime_param_exist && let [param, ..] = ast_generics.params
2225 add_lt_suggs.push(Some((
2226 self.tcx.def_span(param.def_id).shrink_to_lo(),
2227 format!("{new_lt}, "),
2231 .push(Some((ast_generics.span.shrink_to_hi(), format!("<{new_lt}>"))));
2235 if let [param, ..] = &generics.params[..] && let Some(def_id) = param.def_id.as_local()
2238 .push(Some((self.tcx.def_span(def_id).shrink_to_lo(), format!("{new_lt}, "))));
2242 if let Some(ast_generics) = ast_generics {
2243 for p in ast_generics.params {
2244 if p.is_elided_lifetime() {
2249 .span_to_prev_source(p.span.shrink_to_hi())
2251 .map_or(false, |s| *s.as_bytes().last().unwrap() == b'&')
2256 p.span.shrink_to_hi(),
2257 if let Ok(snip) = self.tcx.sess.source_map().span_to_next_source(p.span)
2258 && snip.starts_with(' ')
2262 format!("{new_lt} ")
2267 add_lt_suggs.push(Some((p.span.shrink_to_hi(), format!("<{new_lt}>"))));
2273 let labeled_user_string = match bound_kind {
2274 GenericKind::Param(ref p) => format!("the parameter type `{}`", p),
2275 GenericKind::Alias(ref p) => match p.kind(self.tcx) {
2276 ty::AliasKind::Projection => format!("the associated type `{}`", p),
2277 ty::AliasKind::Opaque => format!("the opaque type `{}`", p),
2281 if let Some(SubregionOrigin::CompareImplItemObligation {
2287 return self.report_extra_impl_obligation(
2291 &format!("`{}: {}`", bound_kind, sub),
2295 fn binding_suggestion<'tcx, S: fmt::Display>(
2296 err: &mut Diagnostic,
2297 type_param_span: Option<(Span, bool)>,
2298 bound_kind: GenericKind<'tcx>,
2300 add_lt_suggs: Vec<Option<(Span, String)>>,
2302 let msg = "consider adding an explicit lifetime bound";
2303 if let Some((sp, has_lifetimes)) = type_param_span {
2305 if has_lifetimes { format!(" + {}", sub) } else { format!(": {}", sub) };
2306 let mut suggestions = vec![(sp, suggestion)];
2307 for add_lt_sugg in add_lt_suggs {
2308 if let Some(add_lt_sugg) = add_lt_sugg {
2309 suggestions.push(add_lt_sugg);
2312 err.multipart_suggestion_verbose(
2313 format!("{msg}..."),
2315 Applicability::MaybeIncorrect, // Issue #41966
2318 let consider = format!("{} `{}: {}`...", msg, bound_kind, sub);
2319 err.help(&consider);
2323 let new_binding_suggestion =
2324 |err: &mut Diagnostic, type_param_span: Option<(Span, bool)>| {
2325 let msg = "consider introducing an explicit lifetime bound";
2326 if let Some((sp, has_lifetimes)) = type_param_span {
2327 let suggestion = if has_lifetimes {
2328 format!(" + {}", new_lt)
2330 format!(": {}", new_lt)
2333 vec![(sp, suggestion), (span.shrink_to_hi(), format!(" + {}", new_lt))];
2334 for add_lt_sugg in add_lt_suggs.clone() {
2335 if let Some(lt) = add_lt_sugg {
2337 sugg.rotate_right(1);
2340 // `MaybeIncorrect` due to issue #41966.
2341 err.multipart_suggestion(msg, sugg, Applicability::MaybeIncorrect);
2346 enum SubOrigin<'hir> {
2347 GAT(&'hir hir::Generics<'hir>),
2353 let sub_origin = 'origin: {
2355 ty::ReEarlyBound(ty::EarlyBoundRegion { def_id, .. }) => {
2356 let node = self.tcx.hir().get_if_local(def_id).unwrap();
2358 Node::GenericParam(param) => {
2359 for h in self.tcx.hir().parent_iter(param.hir_id) {
2360 break 'origin match h.1 {
2361 Node::ImplItem(hir::ImplItem {
2362 kind: hir::ImplItemKind::Type(..),
2366 | Node::TraitItem(hir::TraitItem {
2367 kind: hir::TraitItemKind::Type(..),
2370 }) => SubOrigin::GAT(generics),
2371 Node::ImplItem(hir::ImplItem {
2372 kind: hir::ImplItemKind::Fn(..),
2375 | Node::TraitItem(hir::TraitItem {
2376 kind: hir::TraitItemKind::Fn(..),
2379 | Node::Item(hir::Item {
2380 kind: hir::ItemKind::Fn(..), ..
2381 }) => SubOrigin::Fn,
2382 Node::Item(hir::Item {
2383 kind: hir::ItemKind::Trait(..),
2385 }) => SubOrigin::Trait,
2386 Node::Item(hir::Item {
2387 kind: hir::ItemKind::Impl(..), ..
2388 }) => SubOrigin::Impl,
2400 debug!(?sub_origin);
2402 let mut err = match (*sub, sub_origin) {
2403 // In the case of GATs, we have to be careful. If we a type parameter `T` on an impl,
2404 // but a lifetime `'a` on an associated type, then we might need to suggest adding
2405 // `where T: 'a`. Importantly, this is on the GAT span, not on the `T` declaration.
2406 (ty::ReEarlyBound(ty::EarlyBoundRegion { name: _, .. }), SubOrigin::GAT(generics)) => {
2407 // Does the required lifetime have a nice name we can print?
2408 let mut err = struct_span_err!(
2412 "{} may not live long enough",
2415 let pred = format!("{}: {}", bound_kind, sub);
2416 let suggestion = format!("{} {}", generics.add_where_or_trailing_comma(), pred,);
2417 err.span_suggestion(
2418 generics.tail_span_for_predicate_suggestion(),
2419 "consider adding a where clause",
2421 Applicability::MaybeIncorrect,
2426 ty::ReEarlyBound(ty::EarlyBoundRegion { name, .. })
2427 | ty::ReFree(ty::FreeRegion { bound_region: ty::BrNamed(_, name), .. }),
2429 ) if name != kw::UnderscoreLifetime => {
2430 // Does the required lifetime have a nice name we can print?
2431 let mut err = struct_span_err!(
2435 "{} may not live long enough",
2438 // Explicitly use the name instead of `sub`'s `Display` impl. The `Display` impl
2439 // for the bound is not suitable for suggestions when `-Zverbose` is set because it
2440 // uses `Debug` output, so we handle it specially here so that suggestions are
2442 binding_suggestion(&mut err, type_param_span, bound_kind, name, vec![]);
2446 (ty::ReStatic, _) => {
2447 // Does the required lifetime have a nice name we can print?
2448 let mut err = struct_span_err!(
2452 "{} may not live long enough",
2455 binding_suggestion(&mut err, type_param_span, bound_kind, "'static", vec![]);
2460 // If not, be less specific.
2461 let mut err = struct_span_err!(
2465 "{} may not live long enough",
2468 note_and_explain_region(
2471 &format!("{} must be valid for ", labeled_user_string),
2476 if let Some(infer::RelateParamBound(_, t, _)) = origin {
2477 let return_impl_trait =
2478 self.tcx.return_type_impl_trait(generic_param_scope).is_some();
2479 let t = self.resolve_vars_if_possible(t);
2482 // fn get_later<G, T>(g: G, dest: &mut T) -> impl FnOnce() + '_
2484 // fn get_later<'a, G: 'a, T>(g: G, dest: &mut T) -> impl FnOnce() + '_ + 'a
2485 ty::Closure(..) | ty::Alias(ty::Opaque, ..) if return_impl_trait => {
2486 new_binding_suggestion(&mut err, type_param_span);
2503 if let Some(origin) = origin {
2504 self.note_region_origin(&mut err, &origin);
2509 fn report_sub_sup_conflict(
2511 var_origin: RegionVariableOrigin,
2512 sub_origin: SubregionOrigin<'tcx>,
2513 sub_region: Region<'tcx>,
2514 sup_origin: SubregionOrigin<'tcx>,
2515 sup_region: Region<'tcx>,
2517 let mut err = self.report_inference_failure(var_origin);
2519 note_and_explain_region(
2522 "first, the lifetime cannot outlive ",
2528 debug!("report_sub_sup_conflict: var_origin={:?}", var_origin);
2529 debug!("report_sub_sup_conflict: sub_region={:?}", sub_region);
2530 debug!("report_sub_sup_conflict: sub_origin={:?}", sub_origin);
2531 debug!("report_sub_sup_conflict: sup_region={:?}", sup_region);
2532 debug!("report_sub_sup_conflict: sup_origin={:?}", sup_origin);
2534 if let infer::Subtype(ref sup_trace) = sup_origin
2535 && let infer::Subtype(ref sub_trace) = sub_origin
2536 && let Some((sup_expected, sup_found, _, _)) = self.values_str(sup_trace.values)
2537 && let Some((sub_expected, sub_found, _, _)) = self.values_str(sub_trace.values)
2538 && sub_expected == sup_expected
2539 && sub_found == sup_found
2541 note_and_explain_region(
2544 "...but the lifetime must also be valid for ",
2550 sup_trace.cause.span,
2551 &format!("...so that the {}", sup_trace.cause.as_requirement_str()),
2554 err.note_expected_found(&"", sup_expected, &"", sup_found);
2559 self.note_region_origin(&mut err, &sup_origin);
2561 note_and_explain_region(
2564 "but, the lifetime must be valid for ",
2570 self.note_region_origin(&mut err, &sub_origin);
2574 /// Determine whether an error associated with the given span and definition
2575 /// should be treated as being caused by the implicit `From` conversion
2576 /// within `?` desugaring.
2577 pub fn is_try_conversion(&self, span: Span, trait_def_id: DefId) -> bool {
2578 span.is_desugaring(DesugaringKind::QuestionMark)
2579 && self.tcx.is_diagnostic_item(sym::From, trait_def_id)
2582 /// Structurally compares two types, modulo any inference variables.
2584 /// Returns `true` if two types are equal, or if one type is an inference variable compatible
2585 /// with the other type. A TyVar inference type is compatible with any type, and an IntVar or
2586 /// FloatVar inference type are compatible with themselves or their concrete types (Int and
2587 /// Float types, respectively). When comparing two ADTs, these rules apply recursively.
2588 pub fn same_type_modulo_infer(&self, a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
2589 let (a, b) = self.resolve_vars_if_possible((a, b));
2590 SameTypeModuloInfer(self).relate(a, b).is_ok()
2594 struct SameTypeModuloInfer<'a, 'tcx>(&'a InferCtxt<'tcx>);
2596 impl<'tcx> TypeRelation<'tcx> for SameTypeModuloInfer<'_, 'tcx> {
2597 fn tcx(&self) -> TyCtxt<'tcx> {
2601 fn intercrate(&self) -> bool {
2602 assert!(!self.0.intercrate);
2606 fn param_env(&self) -> ty::ParamEnv<'tcx> {
2607 // Unused, only for consts which we treat as always equal
2608 ty::ParamEnv::empty()
2611 fn tag(&self) -> &'static str {
2612 "SameTypeModuloInfer"
2615 fn a_is_expected(&self) -> bool {
2619 fn mark_ambiguous(&mut self) {
2623 fn relate_with_variance<T: relate::Relate<'tcx>>(
2625 _variance: ty::Variance,
2626 _info: ty::VarianceDiagInfo<'tcx>,
2629 ) -> relate::RelateResult<'tcx, T> {
2633 fn tys(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>> {
2634 match (a.kind(), b.kind()) {
2635 (ty::Int(_) | ty::Uint(_), ty::Infer(ty::InferTy::IntVar(_)))
2637 ty::Infer(ty::InferTy::IntVar(_)),
2638 ty::Int(_) | ty::Uint(_) | ty::Infer(ty::InferTy::IntVar(_)),
2640 | (ty::Float(_), ty::Infer(ty::InferTy::FloatVar(_)))
2642 ty::Infer(ty::InferTy::FloatVar(_)),
2643 ty::Float(_) | ty::Infer(ty::InferTy::FloatVar(_)),
2645 | (ty::Infer(ty::InferTy::TyVar(_)), _)
2646 | (_, ty::Infer(ty::InferTy::TyVar(_))) => Ok(a),
2647 (ty::Infer(_), _) | (_, ty::Infer(_)) => Err(TypeError::Mismatch),
2648 _ => relate::super_relate_tys(self, a, b),
2654 a: ty::Region<'tcx>,
2655 b: ty::Region<'tcx>,
2656 ) -> RelateResult<'tcx, ty::Region<'tcx>> {
2657 if (a.is_var() && b.is_free_or_static())
2658 || (b.is_var() && a.is_free_or_static())
2659 || (a.is_var() && b.is_var())
2664 Err(TypeError::Mismatch)
2670 a: ty::Binder<'tcx, T>,
2671 b: ty::Binder<'tcx, T>,
2672 ) -> relate::RelateResult<'tcx, ty::Binder<'tcx, T>>
2674 T: relate::Relate<'tcx>,
2676 Ok(a.rebind(self.relate(a.skip_binder(), b.skip_binder())?))
2682 _b: ty::Const<'tcx>,
2683 ) -> relate::RelateResult<'tcx, ty::Const<'tcx>> {
2684 // FIXME(compiler-errors): This could at least do some first-order
2690 impl<'tcx> InferCtxt<'tcx> {
2691 fn report_inference_failure(
2693 var_origin: RegionVariableOrigin,
2694 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
2695 let br_string = |br: ty::BoundRegionKind| {
2696 let mut s = match br {
2697 ty::BrNamed(_, name) => name.to_string(),
2705 let var_description = match var_origin {
2706 infer::MiscVariable(_) => String::new(),
2707 infer::PatternRegion(_) => " for pattern".to_string(),
2708 infer::AddrOfRegion(_) => " for borrow expression".to_string(),
2709 infer::Autoref(_) => " for autoref".to_string(),
2710 infer::Coercion(_) => " for automatic coercion".to_string(),
2711 infer::LateBoundRegion(_, br, infer::FnCall) => {
2712 format!(" for lifetime parameter {}in function call", br_string(br))
2714 infer::LateBoundRegion(_, br, infer::HigherRankedType) => {
2715 format!(" for lifetime parameter {}in generic type", br_string(br))
2717 infer::LateBoundRegion(_, br, infer::AssocTypeProjection(def_id)) => format!(
2718 " for lifetime parameter {}in trait containing associated type `{}`",
2720 self.tcx.associated_item(def_id).name
2722 infer::EarlyBoundRegion(_, name) => format!(" for lifetime parameter `{}`", name),
2723 infer::UpvarRegion(ref upvar_id, _) => {
2724 let var_name = self.tcx.hir().name(upvar_id.var_path.hir_id);
2725 format!(" for capture of `{}` by closure", var_name)
2727 infer::Nll(..) => bug!("NLL variable found in lexical phase"),
2734 "cannot infer an appropriate lifetime{} due to conflicting requirements",
2740 pub enum FailureCode {
2742 Error0317(&'static str),
2743 Error0580(&'static str),
2744 Error0308(&'static str),
2745 Error0644(&'static str),
2748 pub trait ObligationCauseExt<'tcx> {
2749 fn as_failure_code(&self, terr: TypeError<'tcx>) -> FailureCode;
2750 fn as_requirement_str(&self) -> &'static str;
2753 impl<'tcx> ObligationCauseExt<'tcx> for ObligationCause<'tcx> {
2754 fn as_failure_code(&self, terr: TypeError<'tcx>) -> FailureCode {
2755 use self::FailureCode::*;
2756 use crate::traits::ObligationCauseCode::*;
2758 CompareImplItemObligation { kind: ty::AssocKind::Fn, .. } => {
2759 Error0308("method not compatible with trait")
2761 CompareImplItemObligation { kind: ty::AssocKind::Type, .. } => {
2762 Error0308("type not compatible with trait")
2764 CompareImplItemObligation { kind: ty::AssocKind::Const, .. } => {
2765 Error0308("const not compatible with trait")
2767 MatchExpressionArm(box MatchExpressionArmCause { source, .. }) => {
2768 Error0308(match source {
2769 hir::MatchSource::TryDesugar => "`?` operator has incompatible types",
2770 _ => "`match` arms have incompatible types",
2773 IfExpression { .. } => Error0308("`if` and `else` have incompatible types"),
2774 IfExpressionWithNoElse => Error0317("`if` may be missing an `else` clause"),
2775 LetElse => Error0308("`else` clause of `let...else` does not diverge"),
2776 MainFunctionType => Error0580("`main` function has wrong type"),
2777 StartFunctionType => Error0308("`#[start]` function has wrong type"),
2778 IntrinsicType => Error0308("intrinsic has wrong type"),
2779 MethodReceiver => Error0308("mismatched `self` parameter type"),
2781 // In the case where we have no more specific thing to
2782 // say, also take a look at the error code, maybe we can
2785 TypeError::CyclicTy(ty) if ty.is_closure() || ty.is_generator() => {
2786 Error0644("closure/generator type that references itself")
2788 TypeError::IntrinsicCast => {
2789 Error0308("cannot coerce intrinsics to function pointers")
2791 _ => Error0308("mismatched types"),
2796 fn as_requirement_str(&self) -> &'static str {
2797 use crate::traits::ObligationCauseCode::*;
2799 CompareImplItemObligation { kind: ty::AssocKind::Fn, .. } => {
2800 "method type is compatible with trait"
2802 CompareImplItemObligation { kind: ty::AssocKind::Type, .. } => {
2803 "associated type is compatible with trait"
2805 CompareImplItemObligation { kind: ty::AssocKind::Const, .. } => {
2806 "const is compatible with trait"
2808 ExprAssignable => "expression is assignable",
2809 IfExpression { .. } => "`if` and `else` have incompatible types",
2810 IfExpressionWithNoElse => "`if` missing an `else` returns `()`",
2811 MainFunctionType => "`main` function has the correct type",
2812 StartFunctionType => "`#[start]` function has the correct type",
2813 IntrinsicType => "intrinsic has the correct type",
2814 MethodReceiver => "method receiver has the correct type",
2815 _ => "types are compatible",
2820 /// Newtype to allow implementing IntoDiagnosticArg
2821 pub struct ObligationCauseAsDiagArg<'tcx>(pub ObligationCause<'tcx>);
2823 impl IntoDiagnosticArg for ObligationCauseAsDiagArg<'_> {
2824 fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> {
2825 use crate::traits::ObligationCauseCode::*;
2826 let kind = match self.0.code() {
2827 CompareImplItemObligation { kind: ty::AssocKind::Fn, .. } => "method_compat",
2828 CompareImplItemObligation { kind: ty::AssocKind::Type, .. } => "type_compat",
2829 CompareImplItemObligation { kind: ty::AssocKind::Const, .. } => "const_compat",
2830 ExprAssignable => "expr_assignable",
2831 IfExpression { .. } => "if_else_different",
2832 IfExpressionWithNoElse => "no_else",
2833 MainFunctionType => "fn_main_correct_type",
2834 StartFunctionType => "fn_start_correct_type",
2835 IntrinsicType => "intristic_correct_type",
2836 MethodReceiver => "method_correct_type",
2840 rustc_errors::DiagnosticArgValue::Str(kind)
2844 /// This is a bare signal of what kind of type we're dealing with. `ty::TyKind` tracks
2845 /// extra information about each type, but we only care about the category.
2846 #[derive(Clone, Copy, PartialEq, Eq, Hash)]
2847 pub enum TyCategory {
2850 Generator(hir::GeneratorKind),
2855 fn descr(&self) -> &'static str {
2857 Self::Closure => "closure",
2858 Self::Opaque => "opaque type",
2859 Self::Generator(gk) => gk.descr(),
2860 Self::Foreign => "foreign type",
2864 pub fn from_ty(tcx: TyCtxt<'_>, ty: Ty<'_>) -> Option<(Self, DefId)> {
2866 ty::Closure(def_id, _) => Some((Self::Closure, def_id)),
2867 ty::Alias(ty::Opaque, ty::AliasTy { def_id, .. }) => Some((Self::Opaque, def_id)),
2868 ty::Generator(def_id, ..) => {
2869 Some((Self::Generator(tcx.generator_kind(def_id).unwrap()), def_id))
2871 ty::Foreign(def_id) => Some((Self::Foreign, def_id)),
2877 impl<'tcx> InferCtxt<'tcx> {
2878 /// Given a [`hir::Block`], get the span of its last expression or
2879 /// statement, peeling off any inner blocks.
2880 pub fn find_block_span(&self, block: &'tcx hir::Block<'tcx>) -> Span {
2881 let block = block.innermost_block();
2882 if let Some(expr) = &block.expr {
2884 } else if let Some(stmt) = block.stmts.last() {
2885 // possibly incorrect trailing `;` in the else arm
2888 // empty block; point at its entirety
2893 /// Given a [`hir::HirId`] for a block, get the span of its last expression
2894 /// or statement, peeling off any inner blocks.
2895 pub fn find_block_span_from_hir_id(&self, hir_id: hir::HirId) -> Span {
2896 match self.tcx.hir().get(hir_id) {
2897 hir::Node::Block(blk) => self.find_block_span(blk),
2898 // The parser was in a weird state if either of these happen, but
2899 // it's better not to panic.
2900 hir::Node::Expr(e) => e.span,
2901 _ => rustc_span::DUMMY_SP,