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),
310 // Ugh. This is a painful case: the hidden region is not one
311 // that we can easily summarize or explain. This can happen
313 // `src/test/ui/multiple-lifetimes/ordinary-bounds-unsuited.rs`:
316 // fn upper_bounds<'a, 'b>(a: Ordinary<'a>, b: Ordinary<'b>) -> impl Trait<'a, 'b> {
317 // if condition() { a } else { b }
321 // Here the captured lifetime is the intersection of `'a` and
322 // `'b`, which we can't quite express.
324 // We can at least report a really cryptic error for now.
325 note_and_explain_region(
328 &format!("hidden type `{}` captures ", hidden_ty),
339 impl<'tcx> InferCtxt<'tcx> {
340 pub fn get_impl_future_output_ty(&self, ty: Ty<'tcx>) -> Option<Ty<'tcx>> {
341 let (def_id, substs) = match *ty.kind() {
342 ty::Alias(_, ty::AliasTy { def_id, substs, .. })
344 self.tcx.def_kind(def_id),
345 DefKind::OpaqueTy | DefKind::ImplTraitPlaceholder
353 let future_trait = self.tcx.require_lang_item(LangItem::Future, None);
354 let item_def_id = self.tcx.associated_item_def_ids(future_trait)[0];
356 self.tcx.bound_explicit_item_bounds(def_id).subst_iter_copied(self.tcx, substs).find_map(
360 .map_bound(|kind| match kind {
361 ty::PredicateKind::Clause(ty::Clause::Projection(projection_predicate))
362 if projection_predicate.projection_ty.def_id == item_def_id =>
364 projection_predicate.term.ty()
375 impl<'tcx> TypeErrCtxt<'_, 'tcx> {
376 pub fn report_region_errors(
378 generic_param_scope: LocalDefId,
379 errors: &[RegionResolutionError<'tcx>],
381 debug!("report_region_errors(): {} errors to start", errors.len());
383 // try to pre-process the errors, which will group some of them
384 // together into a `ProcessedErrors` group:
385 let errors = self.process_errors(errors);
387 debug!("report_region_errors: {} errors after preprocessing", errors.len());
389 for error in errors {
390 debug!("report_region_errors: error = {:?}", error);
392 if !self.try_report_nice_region_error(&error) {
393 match error.clone() {
394 // These errors could indicate all manner of different
395 // problems with many different solutions. Rather
396 // than generate a "one size fits all" error, what we
397 // attempt to do is go through a number of specific
398 // scenarios and try to find the best way to present
399 // the error. If all of these fails, we fall back to a rather
400 // general bit of code that displays the error information
401 RegionResolutionError::ConcreteFailure(origin, sub, sup) => {
402 if sub.is_placeholder() || sup.is_placeholder() {
403 self.report_placeholder_failure(origin, sub, sup).emit();
405 self.report_concrete_failure(origin, sub, sup).emit();
409 RegionResolutionError::GenericBoundFailure(origin, param_ty, sub) => {
410 self.report_generic_bound_failure(
419 RegionResolutionError::SubSupConflict(
428 if sub_r.is_placeholder() {
429 self.report_placeholder_failure(sub_origin, sub_r, sup_r).emit();
430 } else if sup_r.is_placeholder() {
431 self.report_placeholder_failure(sup_origin, sub_r, sup_r).emit();
433 self.report_sub_sup_conflict(
434 var_origin, sub_origin, sub_r, sup_origin, sup_r,
439 RegionResolutionError::UpperBoundUniverseConflict(
446 assert!(sup_r.is_placeholder());
448 // Make a dummy value for the "sub region" --
449 // this is the initial value of the
450 // placeholder. In practice, we expect more
451 // tailored errors that don't really use this
453 let sub_r = self.tcx.lifetimes.re_erased;
455 self.report_placeholder_failure(sup_origin, sub_r, sup_r).emit();
462 // This method goes through all the errors and try to group certain types
463 // of error together, for the purpose of suggesting explicit lifetime
464 // parameters to the user. This is done so that we can have a more
465 // complete view of what lifetimes should be the same.
466 // If the return value is an empty vector, it means that processing
467 // failed (so the return value of this method should not be used).
469 // The method also attempts to weed out messages that seem like
470 // duplicates that will be unhelpful to the end-user. But
471 // obviously it never weeds out ALL errors.
474 errors: &[RegionResolutionError<'tcx>],
475 ) -> Vec<RegionResolutionError<'tcx>> {
476 debug!("process_errors()");
478 // We want to avoid reporting generic-bound failures if we can
479 // avoid it: these have a very high rate of being unhelpful in
480 // practice. This is because they are basically secondary
481 // checks that test the state of the region graph after the
482 // rest of inference is done, and the other kinds of errors
483 // indicate that the region constraint graph is internally
484 // inconsistent, so these test results are likely to be
487 // Therefore, we filter them out of the list unless they are
488 // the only thing in the list.
490 let is_bound_failure = |e: &RegionResolutionError<'tcx>| match *e {
491 RegionResolutionError::GenericBoundFailure(..) => true,
492 RegionResolutionError::ConcreteFailure(..)
493 | RegionResolutionError::SubSupConflict(..)
494 | RegionResolutionError::UpperBoundUniverseConflict(..) => false,
497 let mut errors = if errors.iter().all(|e| is_bound_failure(e)) {
500 errors.iter().filter(|&e| !is_bound_failure(e)).cloned().collect()
503 // sort the errors by span, for better error message stability.
504 errors.sort_by_key(|u| match *u {
505 RegionResolutionError::ConcreteFailure(ref sro, _, _) => sro.span(),
506 RegionResolutionError::GenericBoundFailure(ref sro, _, _) => sro.span(),
507 RegionResolutionError::SubSupConflict(_, ref rvo, _, _, _, _, _) => rvo.span(),
508 RegionResolutionError::UpperBoundUniverseConflict(_, ref rvo, _, _, _) => rvo.span(),
513 /// Adds a note if the types come from similarly named crates
514 fn check_and_note_conflicting_crates(&self, err: &mut Diagnostic, terr: TypeError<'tcx>) {
515 use hir::def_id::CrateNum;
516 use rustc_hir::definitions::DisambiguatedDefPathData;
517 use ty::print::Printer;
518 use ty::subst::GenericArg;
520 struct AbsolutePathPrinter<'tcx> {
524 struct NonTrivialPath;
526 impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
527 type Error = NonTrivialPath;
529 type Path = Vec<String>;
532 type DynExistential = !;
535 fn tcx<'a>(&'a self) -> TyCtxt<'tcx> {
539 fn print_region(self, _region: ty::Region<'_>) -> Result<Self::Region, Self::Error> {
543 fn print_type(self, _ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> {
547 fn print_dyn_existential(
549 _predicates: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
550 ) -> Result<Self::DynExistential, Self::Error> {
554 fn print_const(self, _ct: ty::Const<'tcx>) -> Result<Self::Const, Self::Error> {
558 fn path_crate(self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
559 Ok(vec![self.tcx.crate_name(cnum).to_string()])
564 _trait_ref: Option<ty::TraitRef<'tcx>>,
565 ) -> Result<Self::Path, Self::Error> {
571 _print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
572 _disambiguated_data: &DisambiguatedDefPathData,
574 _trait_ref: Option<ty::TraitRef<'tcx>>,
575 ) -> Result<Self::Path, Self::Error> {
580 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
581 disambiguated_data: &DisambiguatedDefPathData,
582 ) -> Result<Self::Path, Self::Error> {
583 let mut path = print_prefix(self)?;
584 path.push(disambiguated_data.to_string());
587 fn path_generic_args(
589 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
590 _args: &[GenericArg<'tcx>],
591 ) -> Result<Self::Path, Self::Error> {
596 let report_path_match = |err: &mut Diagnostic, did1: DefId, did2: DefId| {
597 // Only external crates, if either is from a local
598 // module we could have false positives
599 if !(did1.is_local() || did2.is_local()) && did1.krate != did2.krate {
601 |def_id| AbsolutePathPrinter { tcx: self.tcx }.print_def_path(def_id, &[]);
603 // We compare strings because DefPath can be different
604 // for imported and non-imported crates
605 let same_path = || -> Result<_, NonTrivialPath> {
606 Ok(self.tcx.def_path_str(did1) == self.tcx.def_path_str(did2)
607 || abs_path(did1)? == abs_path(did2)?)
609 if same_path().unwrap_or(false) {
610 let crate_name = self.tcx.crate_name(did1.krate);
612 "perhaps two different versions of crate `{}` are being used?",
619 TypeError::Sorts(ref exp_found) => {
620 // if they are both "path types", there's a chance of ambiguity
621 // due to different versions of the same crate
622 if let (&ty::Adt(exp_adt, _), &ty::Adt(found_adt, _)) =
623 (exp_found.expected.kind(), exp_found.found.kind())
625 report_path_match(err, exp_adt.did(), found_adt.did());
628 TypeError::Traits(ref exp_found) => {
629 report_path_match(err, exp_found.expected, exp_found.found);
631 _ => (), // FIXME(#22750) handle traits and stuff
635 fn note_error_origin(
637 err: &mut Diagnostic,
638 cause: &ObligationCause<'tcx>,
639 exp_found: Option<ty::error::ExpectedFound<Ty<'tcx>>>,
640 terr: TypeError<'tcx>,
642 match *cause.code() {
643 ObligationCauseCode::Pattern { origin_expr: true, span: Some(span), root_ty } => {
644 let ty = self.resolve_vars_if_possible(root_ty);
645 if !matches!(ty.kind(), ty::Infer(ty::InferTy::TyVar(_) | ty::InferTy::FreshTy(_)))
647 // don't show type `_`
648 if span.desugaring_kind() == Some(DesugaringKind::ForLoop)
649 && let ty::Adt(def, substs) = ty.kind()
650 && Some(def.did()) == self.tcx.get_diagnostic_item(sym::Option)
652 err.span_label(span, format!("this is an iterator with items of type `{}`", substs.type_at(0)));
654 err.span_label(span, format!("this expression has type `{}`", ty));
657 if let Some(ty::error::ExpectedFound { found, .. }) = exp_found
658 && ty.is_box() && ty.boxed_ty() == found
659 && let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span)
663 "consider dereferencing the boxed value",
664 format!("*{}", snippet),
665 Applicability::MachineApplicable,
669 ObligationCauseCode::Pattern { origin_expr: false, span: Some(span), .. } => {
670 err.span_label(span, "expected due to this");
672 ObligationCauseCode::MatchExpressionArm(box MatchExpressionArmCause {
682 opt_suggest_box_span,
686 hir::MatchSource::TryDesugar => {
687 if let Some(ty::error::ExpectedFound { expected, .. }) = exp_found {
688 let scrut_expr = self.tcx.hir().expect_expr(scrut_hir_id);
689 let scrut_ty = if let hir::ExprKind::Call(_, args) = &scrut_expr.kind {
690 let arg_expr = args.first().expect("try desugaring call w/out arg");
691 self.typeck_results.as_ref().and_then(|typeck_results| {
692 typeck_results.expr_ty_opt(arg_expr)
695 bug!("try desugaring w/out call expr as scrutinee");
699 Some(ty) if expected == ty => {
700 let source_map = self.tcx.sess.source_map();
702 source_map.end_point(cause.span),
703 "try removing this `?`",
705 Applicability::MachineApplicable,
713 // `prior_arm_ty` can be `!`, `expected` will have better info when present.
714 let t = self.resolve_vars_if_possible(match exp_found {
715 Some(ty::error::ExpectedFound { expected, .. }) => expected,
718 let source_map = self.tcx.sess.source_map();
719 let mut any_multiline_arm = source_map.is_multiline(arm_span);
720 if prior_arms.len() <= 4 {
721 for sp in prior_arms {
722 any_multiline_arm |= source_map.is_multiline(*sp);
723 err.span_label(*sp, format!("this is found to be of type `{}`", t));
725 } else if let Some(sp) = prior_arms.last() {
726 any_multiline_arm |= source_map.is_multiline(*sp);
729 format!("this and all prior arms are found to be of type `{}`", t),
732 let outer = if any_multiline_arm || !source_map.is_multiline(cause.span) {
733 // Cover just `match` and the scrutinee expression, not
734 // the entire match body, to reduce diagram noise.
735 cause.span.shrink_to_lo().to(scrut_span)
739 let msg = "`match` arms have incompatible types";
740 err.span_label(outer, msg);
741 self.suggest_remove_semi_or_return_binding(
750 if let Some(ret_sp) = opt_suggest_box_span {
751 // Get return type span and point to it.
752 self.suggest_boxing_for_return_impl_trait(
755 prior_arms.iter().chain(std::iter::once(&arm_span)).map(|s| *s),
760 ObligationCauseCode::IfExpression(box IfExpressionCause {
766 opt_suggest_box_span,
768 let then_span = self.find_block_span_from_hir_id(then_id);
769 let else_span = self.find_block_span_from_hir_id(else_id);
770 err.span_label(then_span, "expected because of this");
771 if let Some(sp) = outer_span {
772 err.span_label(sp, "`if` and `else` have incompatible types");
774 self.suggest_remove_semi_or_return_binding(
783 if let Some(ret_sp) = opt_suggest_box_span {
784 self.suggest_boxing_for_return_impl_trait(
787 [then_span, else_span].into_iter(),
791 ObligationCauseCode::LetElse => {
792 err.help("try adding a diverging expression, such as `return` or `panic!(..)`");
793 err.help("...or use `match` instead of `let...else`");
796 if let ObligationCauseCode::BindingObligation(_, span)
797 | ObligationCauseCode::ExprBindingObligation(_, span, ..)
798 = cause.code().peel_derives()
799 && let TypeError::RegionsPlaceholderMismatch = terr
801 err.span_note( * span,
802 "the lifetime requirement is introduced here");
808 /// Given that `other_ty` is the same as a type argument for `name` in `sub`, populate `value`
809 /// highlighting `name` and every type argument that isn't at `pos` (which is `other_ty`), and
810 /// populate `other_value` with `other_ty`.
814 /// ^^^^--------^ this is highlighted
816 /// | this type argument is exactly the same as the other type, not highlighted
817 /// this is highlighted
819 /// -------- this type is the same as a type argument in the other type, not highlighted
823 value: &mut DiagnosticStyledString,
824 other_value: &mut DiagnosticStyledString,
826 sub: ty::subst::SubstsRef<'tcx>,
830 // `value` and `other_value` hold two incomplete type representation for display.
831 // `name` is the path of both types being compared. `sub`
832 value.push_highlighted(name);
835 value.push_highlighted("<");
838 // Output the lifetimes for the first type
842 let s = lifetime.to_string();
843 if s.is_empty() { "'_".to_string() } else { s }
847 if !lifetimes.is_empty() {
848 if sub.regions().count() < len {
849 value.push_normal(lifetimes + ", ");
851 value.push_normal(lifetimes);
855 // Highlight all the type arguments that aren't at `pos` and compare the type argument at
856 // `pos` and `other_ty`.
857 for (i, type_arg) in sub.types().enumerate() {
859 let values = self.cmp(type_arg, other_ty);
860 value.0.extend((values.0).0);
861 other_value.0.extend((values.1).0);
863 value.push_highlighted(type_arg.to_string());
866 if len > 0 && i != len - 1 {
867 value.push_normal(", ");
871 value.push_highlighted(">");
875 /// If `other_ty` is the same as a type argument present in `sub`, highlight `path` in `t1_out`,
876 /// as that is the difference to the other type.
878 /// For the following code:
880 /// ```ignore (illustrative)
881 /// let x: Foo<Bar<Qux>> = foo::<Bar<Qux>>();
884 /// The type error output will behave in the following way:
888 /// ^^^^--------^ this is highlighted
890 /// | this type argument is exactly the same as the other type, not highlighted
891 /// this is highlighted
893 /// -------- this type is the same as a type argument in the other type, not highlighted
897 mut t1_out: &mut DiagnosticStyledString,
898 mut t2_out: &mut DiagnosticStyledString,
900 sub: &'tcx [ty::GenericArg<'tcx>],
904 // FIXME/HACK: Go back to `SubstsRef` to use its inherent methods,
905 // ideally that shouldn't be necessary.
906 let sub = self.tcx.intern_substs(sub);
907 for (i, ta) in sub.types().enumerate() {
909 self.highlight_outer(&mut t1_out, &mut t2_out, path, sub, i, other_ty);
912 if let ty::Adt(def, _) = ta.kind() {
913 let path_ = self.tcx.def_path_str(def.did());
914 if path_ == other_path {
915 self.highlight_outer(&mut t1_out, &mut t2_out, path, sub, i, other_ty);
923 /// Adds a `,` to the type representation only if it is appropriate.
926 value: &mut DiagnosticStyledString,
927 other_value: &mut DiagnosticStyledString,
931 if len > 0 && pos != len - 1 {
932 value.push_normal(", ");
933 other_value.push_normal(", ");
937 /// Given two `fn` signatures highlight only sub-parts that are different.
940 sig1: &ty::PolyFnSig<'tcx>,
941 sig2: &ty::PolyFnSig<'tcx>,
942 ) -> (DiagnosticStyledString, DiagnosticStyledString) {
943 let sig1 = &(self.normalize_fn_sig)(*sig1);
944 let sig2 = &(self.normalize_fn_sig)(*sig2);
946 let get_lifetimes = |sig| {
947 use rustc_hir::def::Namespace;
948 let (_, sig, reg) = ty::print::FmtPrinter::new(self.tcx, Namespace::TypeNS)
949 .name_all_regions(sig)
951 let lts: Vec<String> = reg.into_iter().map(|(_, kind)| kind.to_string()).collect();
952 (if lts.is_empty() { String::new() } else { format!("for<{}> ", lts.join(", ")) }, sig)
955 let (lt1, sig1) = get_lifetimes(sig1);
956 let (lt2, sig2) = get_lifetimes(sig2);
958 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
960 DiagnosticStyledString::normal("".to_string()),
961 DiagnosticStyledString::normal("".to_string()),
964 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
966 values.0.push(sig1.unsafety.prefix_str(), sig1.unsafety != sig2.unsafety);
967 values.1.push(sig2.unsafety.prefix_str(), sig1.unsafety != sig2.unsafety);
969 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
971 if sig1.abi != abi::Abi::Rust {
972 values.0.push(format!("extern {} ", sig1.abi), sig1.abi != sig2.abi);
974 if sig2.abi != abi::Abi::Rust {
975 values.1.push(format!("extern {} ", sig2.abi), sig1.abi != sig2.abi);
978 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
980 let lifetime_diff = lt1 != lt2;
981 values.0.push(lt1, lifetime_diff);
982 values.1.push(lt2, lifetime_diff);
984 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
986 values.0.push_normal("fn(");
987 values.1.push_normal("fn(");
989 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
991 let len1 = sig1.inputs().len();
992 let len2 = sig2.inputs().len();
994 for (i, (l, r)) in iter::zip(sig1.inputs(), sig2.inputs()).enumerate() {
995 let (x1, x2) = self.cmp(*l, *r);
996 (values.0).0.extend(x1.0);
997 (values.1).0.extend(x2.0);
998 self.push_comma(&mut values.0, &mut values.1, len1, i);
1001 for (i, l) in sig1.inputs().iter().enumerate() {
1002 values.0.push_highlighted(l.to_string());
1004 values.0.push_highlighted(", ");
1007 for (i, r) in sig2.inputs().iter().enumerate() {
1008 values.1.push_highlighted(r.to_string());
1010 values.1.push_highlighted(", ");
1015 if sig1.c_variadic {
1017 values.0.push_normal(", ");
1019 values.0.push("...", !sig2.c_variadic);
1021 if sig2.c_variadic {
1023 values.1.push_normal(", ");
1025 values.1.push("...", !sig1.c_variadic);
1028 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
1030 values.0.push_normal(")");
1031 values.1.push_normal(")");
1033 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
1035 let output1 = sig1.output();
1036 let output2 = sig2.output();
1037 let (x1, x2) = self.cmp(output1, output2);
1038 if !output1.is_unit() {
1039 values.0.push_normal(" -> ");
1040 (values.0).0.extend(x1.0);
1042 if !output2.is_unit() {
1043 values.1.push_normal(" -> ");
1044 (values.1).0.extend(x2.0);
1049 /// Compares two given types, eliding parts that are the same between them and highlighting
1050 /// relevant differences, and return two representation of those types for highlighted printing.
1055 ) -> (DiagnosticStyledString, DiagnosticStyledString) {
1056 debug!("cmp(t1={}, t1.kind={:?}, t2={}, t2.kind={:?})", t1, t1.kind(), t2, t2.kind());
1059 fn equals<'tcx>(a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
1060 match (a.kind(), b.kind()) {
1061 (a, b) if *a == *b => true,
1062 (&ty::Int(_), &ty::Infer(ty::InferTy::IntVar(_)))
1064 &ty::Infer(ty::InferTy::IntVar(_)),
1065 &ty::Int(_) | &ty::Infer(ty::InferTy::IntVar(_)),
1067 | (&ty::Float(_), &ty::Infer(ty::InferTy::FloatVar(_)))
1069 &ty::Infer(ty::InferTy::FloatVar(_)),
1070 &ty::Float(_) | &ty::Infer(ty::InferTy::FloatVar(_)),
1076 fn push_ty_ref<'tcx>(
1077 region: ty::Region<'tcx>,
1079 mutbl: hir::Mutability,
1080 s: &mut DiagnosticStyledString,
1082 let mut r = region.to_string();
1088 s.push_highlighted(format!("&{}{}", r, mutbl.prefix_str()));
1089 s.push_normal(ty.to_string());
1092 // process starts here
1093 match (t1.kind(), t2.kind()) {
1094 (&ty::Adt(def1, sub1), &ty::Adt(def2, sub2)) => {
1095 let did1 = def1.did();
1096 let did2 = def2.did();
1097 let sub_no_defaults_1 =
1098 self.tcx.generics_of(did1).own_substs_no_defaults(self.tcx, sub1);
1099 let sub_no_defaults_2 =
1100 self.tcx.generics_of(did2).own_substs_no_defaults(self.tcx, sub2);
1101 let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new());
1102 let path1 = self.tcx.def_path_str(did1);
1103 let path2 = self.tcx.def_path_str(did2);
1105 // Easy case. Replace same types with `_` to shorten the output and highlight
1106 // the differing ones.
1107 // let x: Foo<Bar, Qux> = y::<Foo<Quz, Qux>>();
1110 // --- ^ type argument elided
1112 // highlighted in output
1113 values.0.push_normal(path1);
1114 values.1.push_normal(path2);
1116 // Avoid printing out default generic parameters that are common to both
1118 let len1 = sub_no_defaults_1.len();
1119 let len2 = sub_no_defaults_2.len();
1120 let common_len = cmp::min(len1, len2);
1121 let remainder1: Vec<_> = sub1.types().skip(common_len).collect();
1122 let remainder2: Vec<_> = sub2.types().skip(common_len).collect();
1123 let common_default_params =
1124 iter::zip(remainder1.iter().rev(), remainder2.iter().rev())
1125 .filter(|(a, b)| a == b)
1127 let len = sub1.len() - common_default_params;
1128 let consts_offset = len - sub1.consts().count();
1130 // Only draw `<...>` if there are lifetime/type arguments.
1132 values.0.push_normal("<");
1133 values.1.push_normal("<");
1136 fn lifetime_display(lifetime: Region<'_>) -> String {
1137 let s = lifetime.to_string();
1138 if s.is_empty() { "'_".to_string() } else { s }
1140 // At one point we'd like to elide all lifetimes here, they are irrelevant for
1141 // all diagnostics that use this output
1145 // ^^ ^^ --- type arguments are not elided
1147 // | elided as they were the same
1148 // not elided, they were different, but irrelevant
1150 // For bound lifetimes, keep the names of the lifetimes,
1151 // even if they are the same so that it's clear what's happening
1152 // if we have something like
1154 // for<'r, 's> fn(Inv<'r>, Inv<'s>)
1155 // for<'r> fn(Inv<'r>, Inv<'r>)
1156 let lifetimes = sub1.regions().zip(sub2.regions());
1157 for (i, lifetimes) in lifetimes.enumerate() {
1158 let l1 = lifetime_display(lifetimes.0);
1159 let l2 = lifetime_display(lifetimes.1);
1160 if lifetimes.0 != lifetimes.1 {
1161 values.0.push_highlighted(l1);
1162 values.1.push_highlighted(l2);
1163 } else if lifetimes.0.is_late_bound() {
1164 values.0.push_normal(l1);
1165 values.1.push_normal(l2);
1167 values.0.push_normal("'_");
1168 values.1.push_normal("'_");
1170 self.push_comma(&mut values.0, &mut values.1, len, i);
1173 // We're comparing two types with the same path, so we compare the type
1174 // arguments for both. If they are the same, do not highlight and elide from the
1178 // ^ elided type as this type argument was the same in both sides
1179 let type_arguments = sub1.types().zip(sub2.types());
1180 let regions_len = sub1.regions().count();
1181 let num_display_types = consts_offset - regions_len;
1182 for (i, (ta1, ta2)) in type_arguments.take(num_display_types).enumerate() {
1183 let i = i + regions_len;
1184 if ta1 == ta2 && !self.tcx.sess.verbose() {
1185 values.0.push_normal("_");
1186 values.1.push_normal("_");
1188 let (x1, x2) = self.cmp(ta1, ta2);
1189 (values.0).0.extend(x1.0);
1190 (values.1).0.extend(x2.0);
1192 self.push_comma(&mut values.0, &mut values.1, len, i);
1195 // Do the same for const arguments, if they are equal, do not highlight and
1196 // elide them from the output.
1197 let const_arguments = sub1.consts().zip(sub2.consts());
1198 for (i, (ca1, ca2)) in const_arguments.enumerate() {
1199 let i = i + consts_offset;
1200 if ca1 == ca2 && !self.tcx.sess.verbose() {
1201 values.0.push_normal("_");
1202 values.1.push_normal("_");
1204 values.0.push_highlighted(ca1.to_string());
1205 values.1.push_highlighted(ca2.to_string());
1207 self.push_comma(&mut values.0, &mut values.1, len, i);
1210 // Close the type argument bracket.
1211 // Only draw `<...>` if there are lifetime/type arguments.
1213 values.0.push_normal(">");
1214 values.1.push_normal(">");
1219 // let x: Foo<Bar<Qux> = foo::<Bar<Qux>>();
1221 // ------- this type argument is exactly the same as the other type
1237 // let x: Bar<Qux> = y:<Foo<Bar<Qux>>>();
1240 // ------- this type argument is exactly the same as the other type
1255 // We can't find anything in common, highlight relevant part of type path.
1256 // let x: foo::bar::Baz<Qux> = y:<foo::bar::Bar<Zar>>();
1257 // foo::bar::Baz<Qux>
1258 // foo::bar::Bar<Zar>
1259 // -------- this part of the path is different
1261 let t1_str = t1.to_string();
1262 let t2_str = t2.to_string();
1263 let min_len = t1_str.len().min(t2_str.len());
1265 const SEPARATOR: &str = "::";
1266 let separator_len = SEPARATOR.len();
1267 let split_idx: usize =
1268 iter::zip(t1_str.split(SEPARATOR), t2_str.split(SEPARATOR))
1269 .take_while(|(mod1_str, mod2_str)| mod1_str == mod2_str)
1270 .map(|(mod_str, _)| mod_str.len() + separator_len)
1273 debug!(?separator_len, ?split_idx, ?min_len, "cmp");
1275 if split_idx >= min_len {
1276 // paths are identical, highlight everything
1278 DiagnosticStyledString::highlighted(t1_str),
1279 DiagnosticStyledString::highlighted(t2_str),
1282 let (common, uniq1) = t1_str.split_at(split_idx);
1283 let (_, uniq2) = t2_str.split_at(split_idx);
1284 debug!(?common, ?uniq1, ?uniq2, "cmp");
1286 values.0.push_normal(common);
1287 values.0.push_highlighted(uniq1);
1288 values.1.push_normal(common);
1289 values.1.push_highlighted(uniq2);
1296 // When finding T != &T, highlight only the borrow
1297 (&ty::Ref(r1, ref_ty1, mutbl1), _) if equals(ref_ty1, t2) => {
1298 let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new());
1299 push_ty_ref(r1, ref_ty1, mutbl1, &mut values.0);
1300 values.1.push_normal(t2.to_string());
1303 (_, &ty::Ref(r2, ref_ty2, mutbl2)) if equals(t1, ref_ty2) => {
1304 let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new());
1305 values.0.push_normal(t1.to_string());
1306 push_ty_ref(r2, ref_ty2, mutbl2, &mut values.1);
1310 // When encountering &T != &mut T, highlight only the borrow
1311 (&ty::Ref(r1, ref_ty1, mutbl1), &ty::Ref(r2, ref_ty2, mutbl2))
1312 if equals(ref_ty1, ref_ty2) =>
1314 let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new());
1315 push_ty_ref(r1, ref_ty1, mutbl1, &mut values.0);
1316 push_ty_ref(r2, ref_ty2, mutbl2, &mut values.1);
1320 // When encountering tuples of the same size, highlight only the differing types
1321 (&ty::Tuple(substs1), &ty::Tuple(substs2)) if substs1.len() == substs2.len() => {
1323 (DiagnosticStyledString::normal("("), DiagnosticStyledString::normal("("));
1324 let len = substs1.len();
1325 for (i, (left, right)) in substs1.iter().zip(substs2).enumerate() {
1326 let (x1, x2) = self.cmp(left, right);
1327 (values.0).0.extend(x1.0);
1328 (values.1).0.extend(x2.0);
1329 self.push_comma(&mut values.0, &mut values.1, len, i);
1332 // Keep the output for single element tuples as `(ty,)`.
1333 values.0.push_normal(",");
1334 values.1.push_normal(",");
1336 values.0.push_normal(")");
1337 values.1.push_normal(")");
1341 (ty::FnDef(did1, substs1), ty::FnDef(did2, substs2)) => {
1342 let sig1 = self.tcx.bound_fn_sig(*did1).subst(self.tcx, substs1);
1343 let sig2 = self.tcx.bound_fn_sig(*did2).subst(self.tcx, substs2);
1344 let mut values = self.cmp_fn_sig(&sig1, &sig2);
1345 let path1 = format!(" {{{}}}", self.tcx.def_path_str_with_substs(*did1, substs1));
1346 let path2 = format!(" {{{}}}", self.tcx.def_path_str_with_substs(*did2, substs2));
1347 let same_path = path1 == path2;
1348 values.0.push(path1, !same_path);
1349 values.1.push(path2, !same_path);
1353 (ty::FnDef(did1, substs1), ty::FnPtr(sig2)) => {
1354 let sig1 = self.tcx.bound_fn_sig(*did1).subst(self.tcx, substs1);
1355 let mut values = self.cmp_fn_sig(&sig1, sig2);
1356 values.0.push_highlighted(format!(
1358 self.tcx.def_path_str_with_substs(*did1, substs1)
1363 (ty::FnPtr(sig1), ty::FnDef(did2, substs2)) => {
1364 let sig2 = self.tcx.bound_fn_sig(*did2).subst(self.tcx, substs2);
1365 let mut values = self.cmp_fn_sig(sig1, &sig2);
1366 values.1.push_normal(format!(
1368 self.tcx.def_path_str_with_substs(*did2, substs2)
1373 (ty::FnPtr(sig1), ty::FnPtr(sig2)) => self.cmp_fn_sig(sig1, sig2),
1376 if t1 == t2 && !self.tcx.sess.verbose() {
1377 // The two types are the same, elide and don't highlight.
1378 (DiagnosticStyledString::normal("_"), DiagnosticStyledString::normal("_"))
1380 // We couldn't find anything in common, highlight everything.
1382 DiagnosticStyledString::highlighted(t1.to_string()),
1383 DiagnosticStyledString::highlighted(t2.to_string()),
1390 /// Extend a type error with extra labels pointing at "non-trivial" types, like closures and
1391 /// the return type of `async fn`s.
1393 /// `secondary_span` gives the caller the opportunity to expand `diag` with a `span_label`.
1395 /// `swap_secondary_and_primary` is used to make projection errors in particular nicer by using
1396 /// the message in `secondary_span` as the primary label, and apply the message that would
1397 /// otherwise be used for the primary label on the `secondary_span` `Span`. This applies on
1398 /// E0271, like `src/test/ui/issues/issue-39970.stderr`.
1401 skip(self, diag, secondary_span, swap_secondary_and_primary, prefer_label)
1403 pub fn note_type_err(
1405 diag: &mut Diagnostic,
1406 cause: &ObligationCause<'tcx>,
1407 secondary_span: Option<(Span, String)>,
1408 mut values: Option<ValuePairs<'tcx>>,
1409 terr: TypeError<'tcx>,
1410 swap_secondary_and_primary: bool,
1413 let span = cause.span();
1415 // For some types of errors, expected-found does not make
1416 // sense, so just ignore the values we were given.
1417 if let TypeError::CyclicTy(_) = terr {
1420 struct OpaqueTypesVisitor<'tcx> {
1421 types: FxIndexMap<TyCategory, FxIndexSet<Span>>,
1422 expected: FxIndexMap<TyCategory, FxIndexSet<Span>>,
1423 found: FxIndexMap<TyCategory, FxIndexSet<Span>>,
1428 impl<'tcx> OpaqueTypesVisitor<'tcx> {
1429 fn visit_expected_found(
1435 let mut types_visitor = OpaqueTypesVisitor {
1436 types: Default::default(),
1437 expected: Default::default(),
1438 found: Default::default(),
1442 // The visitor puts all the relevant encountered types in `self.types`, but in
1443 // here we want to visit two separate types with no relation to each other, so we
1444 // move the results from `types` to `expected` or `found` as appropriate.
1445 expected.visit_with(&mut types_visitor);
1446 std::mem::swap(&mut types_visitor.expected, &mut types_visitor.types);
1447 found.visit_with(&mut types_visitor);
1448 std::mem::swap(&mut types_visitor.found, &mut types_visitor.types);
1452 fn report(&self, err: &mut Diagnostic) {
1453 self.add_labels_for_types(err, "expected", &self.expected);
1454 self.add_labels_for_types(err, "found", &self.found);
1457 fn add_labels_for_types(
1459 err: &mut Diagnostic,
1461 types: &FxIndexMap<TyCategory, FxIndexSet<Span>>,
1463 for (key, values) in types.iter() {
1464 let count = values.len();
1465 let kind = key.descr();
1466 let mut returned_async_output_error = false;
1468 if sp.is_desugaring(DesugaringKind::Async) && !returned_async_output_error {
1469 if [sp] != err.span.primary_spans() {
1470 let mut span: MultiSpan = sp.into();
1471 span.push_span_label(
1474 "checked the `Output` of this `async fn`, {}{} {}{}",
1475 if count > 1 { "one of the " } else { "" },
1483 "while checking the return type of the `async fn`",
1489 "checked the `Output` of this `async fn`, {}{} {}{}",
1490 if count > 1 { "one of the " } else { "" },
1496 err.note("while checking the return type of the `async fn`");
1498 returned_async_output_error = true;
1504 if count == 1 { "the " } else { "one of the " },
1516 impl<'tcx> ty::visit::TypeVisitor<'tcx> for OpaqueTypesVisitor<'tcx> {
1517 fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
1518 if let Some((kind, def_id)) = TyCategory::from_ty(self.tcx, t) {
1519 let span = self.tcx.def_span(def_id);
1520 // Avoid cluttering the output when the "found" and error span overlap:
1522 // error[E0308]: mismatched types
1523 // --> $DIR/issue-20862.rs:2:5
1528 // | the found closure
1529 // | expected `()`, found closure
1531 // = note: expected unit type `()`
1532 // found closure `[closure@$DIR/issue-20862.rs:2:5: 2:14 x:_]`
1533 if !self.ignore_span.overlaps(span) {
1534 self.types.entry(kind).or_default().insert(span);
1537 t.super_visit_with(self)
1541 debug!("note_type_err(diag={:?})", diag);
1543 Variable(ty::error::ExpectedFound<Ty<'a>>),
1544 Fixed(&'static str),
1546 let (expected_found, exp_found, is_simple_error, values) = match values {
1547 None => (None, Mismatch::Fixed("type"), false, None),
1549 let values = self.resolve_vars_if_possible(values);
1550 let (is_simple_error, exp_found) = match values {
1551 ValuePairs::Terms(infer::ExpectedFound { expected, found }) => {
1552 match (expected.unpack(), found.unpack()) {
1553 (ty::TermKind::Ty(expected), ty::TermKind::Ty(found)) => {
1555 expected.is_simple_text() && found.is_simple_text();
1556 OpaqueTypesVisitor::visit_expected_found(
1557 self.tcx, expected, found, span,
1563 Mismatch::Variable(infer::ExpectedFound { expected, found }),
1566 (ty::TermKind::Const(_), ty::TermKind::Const(_)) => {
1567 (false, Mismatch::Fixed("constant"))
1569 _ => (false, Mismatch::Fixed("type")),
1572 ValuePairs::TraitRefs(_) | ValuePairs::PolyTraitRefs(_) => {
1573 (false, Mismatch::Fixed("trait"))
1575 ValuePairs::Regions(_) => (false, Mismatch::Fixed("lifetime")),
1577 let Some(vals) = self.values_str(values) else {
1578 // Derived error. Cancel the emitter.
1579 // NOTE(eddyb) this was `.cancel()`, but `diag`
1580 // is borrowed, so we can't fully defuse it.
1581 diag.downgrade_to_delayed_bug();
1584 (Some(vals), exp_found, is_simple_error, Some(values))
1588 let mut label_or_note = |span: Span, msg: &str| {
1589 if (prefer_label && is_simple_error) || &[span] == diag.span.primary_spans() {
1590 diag.span_label(span, msg);
1592 diag.span_note(span, msg);
1595 if let Some((sp, msg)) = secondary_span {
1596 if swap_secondary_and_primary {
1597 let terr = if let Some(infer::ValuePairs::Terms(infer::ExpectedFound {
1602 format!("expected this to be `{}`", expected)
1606 label_or_note(sp, &terr);
1607 label_or_note(span, &msg);
1609 label_or_note(span, &terr.to_string());
1610 label_or_note(sp, &msg);
1613 label_or_note(span, &terr.to_string());
1616 if let Some((expected, found, exp_p, found_p)) = expected_found {
1617 let (expected_label, found_label, exp_found) = match exp_found {
1618 Mismatch::Variable(ef) => (
1619 ef.expected.prefix_string(self.tcx),
1620 ef.found.prefix_string(self.tcx),
1623 Mismatch::Fixed(s) => (s.into(), s.into(), None),
1626 enum Similar<'tcx> {
1627 Adts { expected: ty::AdtDef<'tcx>, found: ty::AdtDef<'tcx> },
1628 PrimitiveFound { expected: ty::AdtDef<'tcx>, found: Ty<'tcx> },
1629 PrimitiveExpected { expected: Ty<'tcx>, found: ty::AdtDef<'tcx> },
1632 let similarity = |ExpectedFound { expected, found }: ExpectedFound<Ty<'tcx>>| {
1633 if let ty::Adt(expected, _) = expected.kind() && let Some(primitive) = found.primitive_symbol() {
1634 let path = self.tcx.def_path(expected.did()).data;
1635 let name = path.last().unwrap().data.get_opt_name();
1636 if name == Some(primitive) {
1637 return Some(Similar::PrimitiveFound { expected: *expected, found });
1639 } else if let Some(primitive) = expected.primitive_symbol() && let ty::Adt(found, _) = found.kind() {
1640 let path = self.tcx.def_path(found.did()).data;
1641 let name = path.last().unwrap().data.get_opt_name();
1642 if name == Some(primitive) {
1643 return Some(Similar::PrimitiveExpected { expected, found: *found });
1645 } else if let ty::Adt(expected, _) = expected.kind() && let ty::Adt(found, _) = found.kind() {
1646 if !expected.did().is_local() && expected.did().krate == found.did().krate {
1647 // Most likely types from different versions of the same crate
1648 // are in play, in which case this message isn't so helpful.
1649 // A "perhaps two different versions..." error is already emitted for that.
1652 let f_path = self.tcx.def_path(found.did()).data;
1653 let e_path = self.tcx.def_path(expected.did()).data;
1655 if let (Some(e_last), Some(f_last)) = (e_path.last(), f_path.last()) && e_last == f_last {
1656 return Some(Similar::Adts{expected: *expected, found: *found});
1663 // If two types mismatch but have similar names, mention that specifically.
1664 TypeError::Sorts(values) if let Some(s) = similarity(values) => {
1665 let diagnose_primitive =
1669 diagnostic: &mut Diagnostic| {
1670 let name = shadow.sort_string(self.tcx);
1671 diagnostic.note(format!(
1672 "{prim} and {name} have similar names, but are actually distinct types"
1675 .note(format!("{prim} is a primitive defined by the language"));
1676 let def_span = self.tcx.def_span(defid);
1677 let msg = if defid.is_local() {
1678 format!("{name} is defined in the current crate")
1680 let crate_name = self.tcx.crate_name(defid.krate);
1681 format!("{name} is defined in crate `{crate_name}")
1683 diagnostic.span_note(def_span, msg);
1687 |expected_adt : ty::AdtDef<'tcx>,
1688 found_adt: ty::AdtDef<'tcx>,
1689 diagnostic: &mut Diagnostic| {
1690 let found_name = values.found.sort_string(self.tcx);
1691 let expected_name = values.expected.sort_string(self.tcx);
1693 let found_defid = found_adt.did();
1694 let expected_defid = expected_adt.did();
1696 diagnostic.note(format!("{found_name} and {expected_name} have similar names, but are actually distinct types"));
1697 for (defid, name) in
1698 [(found_defid, found_name), (expected_defid, expected_name)]
1700 let def_span = self.tcx.def_span(defid);
1702 let msg = if found_defid.is_local() && expected_defid.is_local() {
1705 .parent_module_from_def_id(defid.expect_local())
1707 let module_name = self.tcx.def_path(module).to_string_no_crate_verbose();
1708 format!("{name} is defined in module `crate{module_name}` of the current crate")
1709 } else if defid.is_local() {
1710 format!("{name} is defined in the current crate")
1712 let crate_name = self.tcx.crate_name(defid.krate);
1713 format!("{name} is defined in crate `{crate_name}`")
1715 diagnostic.span_note(def_span, msg);
1720 Similar::Adts{expected, found} => {
1721 diagnose_adts(expected, found, diag)
1723 Similar::PrimitiveFound{expected, found: prim} => {
1724 diagnose_primitive(prim, values.expected, expected.did(), diag)
1726 Similar::PrimitiveExpected{expected: prim, found} => {
1727 diagnose_primitive(prim, values.found, found.did(), diag)
1731 TypeError::Sorts(values) => {
1732 let extra = expected == found;
1733 let sort_string = |ty: Ty<'tcx>, path: Option<PathBuf>| {
1734 let mut s = match (extra, ty.kind()) {
1735 (true, ty::Alias(ty::Opaque, ty::AliasTy { def_id, .. })) => {
1736 let sm = self.tcx.sess.source_map();
1737 let pos = sm.lookup_char_pos(self.tcx.def_span(*def_id).lo());
1739 " (opaque type at <{}:{}:{}>)",
1740 sm.filename_for_diagnostics(&pos.file.name),
1742 pos.col.to_usize() + 1,
1745 (true, ty::Alias(ty::Projection, proj))
1746 if self.tcx.def_kind(proj.def_id)
1747 == DefKind::ImplTraitPlaceholder =>
1749 let sm = self.tcx.sess.source_map();
1750 let pos = sm.lookup_char_pos(self.tcx.def_span(proj.def_id).lo());
1752 " (trait associated opaque type at <{}:{}:{}>)",
1753 sm.filename_for_diagnostics(&pos.file.name),
1755 pos.col.to_usize() + 1,
1758 (true, _) => format!(" ({})", ty.sort_string(self.tcx)),
1759 (false, _) => "".to_string(),
1761 if let Some(path) = path {
1762 s.push_str(&format!(
1763 "\nthe full type name has been written to '{}'",
1769 if !(values.expected.is_simple_text() && values.found.is_simple_text())
1770 || (exp_found.map_or(false, |ef| {
1771 // This happens when the type error is a subset of the expectation,
1772 // like when you have two references but one is `usize` and the other
1773 // is `f32`. In those cases we still want to show the `note`. If the
1774 // value from `ef` is `Infer(_)`, then we ignore it.
1775 if !ef.expected.is_ty_infer() {
1776 ef.expected != values.expected
1777 } else if !ef.found.is_ty_infer() {
1778 ef.found != values.found
1784 diag.note_expected_found_extra(
1789 &sort_string(values.expected, exp_p),
1790 &sort_string(values.found, found_p),
1796 "note_type_err: exp_found={:?}, expected={:?} found={:?}",
1797 exp_found, expected, found
1799 if !is_simple_error || terr.must_include_note() {
1800 diag.note_expected_found(&expected_label, expected, &found_label, found);
1805 let exp_found = match exp_found {
1806 Mismatch::Variable(exp_found) => Some(exp_found),
1807 Mismatch::Fixed(_) => None,
1809 let exp_found = match terr {
1810 // `terr` has more accurate type information than `exp_found` in match expressions.
1811 ty::error::TypeError::Sorts(terr)
1812 if exp_found.map_or(false, |ef| terr.found == ef.found) =>
1818 debug!("exp_found {:?} terr {:?} cause.code {:?}", exp_found, terr, cause.code());
1819 if let Some(exp_found) = exp_found {
1820 let should_suggest_fixes =
1821 if let ObligationCauseCode::Pattern { root_ty, .. } = cause.code() {
1822 // Skip if the root_ty of the pattern is not the same as the expected_ty.
1823 // If these types aren't equal then we've probably peeled off a layer of arrays.
1824 self.same_type_modulo_infer(*root_ty, exp_found.expected)
1829 if should_suggest_fixes {
1830 self.suggest_tuple_pattern(cause, &exp_found, diag);
1831 self.suggest_as_ref_where_appropriate(span, &exp_found, diag);
1832 self.suggest_accessing_field_where_appropriate(cause, &exp_found, diag);
1833 self.suggest_await_on_expect_found(cause, span, &exp_found, diag);
1837 // In some (most?) cases cause.body_id points to actual body, but in some cases
1838 // it's an actual definition. According to the comments (e.g. in
1839 // rustc_hir_analysis/check/compare_impl_item.rs:compare_predicate_entailment) the latter
1840 // is relied upon by some other code. This might (or might not) need cleanup.
1841 let body_owner_def_id =
1842 self.tcx.hir().opt_local_def_id(cause.body_id).unwrap_or_else(|| {
1843 self.tcx.hir().body_owner_def_id(hir::BodyId { hir_id: cause.body_id })
1845 self.check_and_note_conflicting_crates(diag, terr);
1846 self.tcx.note_and_explain_type_err(diag, terr, cause, span, body_owner_def_id.to_def_id());
1848 if let Some(ValuePairs::PolyTraitRefs(exp_found)) = values
1849 && let ty::Closure(def_id, _) = exp_found.expected.skip_binder().self_ty().kind()
1850 && let Some(def_id) = def_id.as_local()
1851 && terr.involves_regions()
1853 let span = self.tcx.def_span(def_id);
1854 diag.span_note(span, "this closure does not fulfill the lifetime requirements");
1857 // It reads better to have the error origin as the final
1859 self.note_error_origin(diag, cause, exp_found, terr);
1864 pub fn report_and_explain_type_error(
1866 trace: TypeTrace<'tcx>,
1867 terr: TypeError<'tcx>,
1868 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
1869 use crate::traits::ObligationCauseCode::MatchExpressionArm;
1871 debug!("report_and_explain_type_error(trace={:?}, terr={:?})", trace, terr);
1873 let span = trace.cause.span();
1874 let failure_code = trace.cause.as_failure_code(terr);
1875 let mut diag = match failure_code {
1876 FailureCode::Error0038(did) => {
1877 let violations = self.tcx.object_safety_violations(did);
1878 report_object_safety_error(self.tcx, span, did, violations)
1880 FailureCode::Error0317(failure_str) => {
1881 struct_span_err!(self.tcx.sess, span, E0317, "{}", failure_str)
1883 FailureCode::Error0580(failure_str) => {
1884 struct_span_err!(self.tcx.sess, span, E0580, "{}", failure_str)
1886 FailureCode::Error0308(failure_str) => {
1887 fn escape_literal(s: &str) -> String {
1888 let mut escaped = String::with_capacity(s.len());
1889 let mut chrs = s.chars().peekable();
1890 while let Some(first) = chrs.next() {
1891 match (first, chrs.peek()) {
1892 ('\\', Some(&delim @ '"') | Some(&delim @ '\'')) => {
1894 escaped.push(delim);
1897 ('"' | '\'', _) => {
1901 (c, _) => escaped.push(c),
1906 let mut err = struct_span_err!(self.tcx.sess, span, E0308, "{}", failure_str);
1907 if let Some((expected, found)) = trace.values.ty() {
1908 match (expected.kind(), found.kind()) {
1909 (ty::Tuple(_), ty::Tuple(_)) => {}
1910 // If a tuple of length one was expected and the found expression has
1911 // parentheses around it, perhaps the user meant to write `(expr,)` to
1912 // build a tuple (issue #86100)
1913 (ty::Tuple(fields), _) => {
1914 self.emit_tuple_wrap_err(&mut err, span, found, fields)
1916 // If a character was expected and the found expression is a string literal
1917 // containing a single character, perhaps the user meant to write `'c'` to
1918 // specify a character literal (issue #92479)
1919 (ty::Char, ty::Ref(_, r, _)) if r.is_str() => {
1920 if let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span)
1921 && let Some(code) = code.strip_prefix('"').and_then(|s| s.strip_suffix('"'))
1922 && code.chars().count() == 1
1924 err.span_suggestion(
1926 "if you meant to write a `char` literal, use single quotes",
1927 format!("'{}'", escape_literal(code)),
1928 Applicability::MachineApplicable,
1932 // If a string was expected and the found expression is a character literal,
1933 // perhaps the user meant to write `"s"` to specify a string literal.
1934 (ty::Ref(_, r, _), ty::Char) if r.is_str() => {
1935 if let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span) {
1937 code.strip_prefix('\'').and_then(|s| s.strip_suffix('\''))
1939 err.span_suggestion(
1941 "if you meant to write a `str` literal, use double quotes",
1942 format!("\"{}\"", escape_literal(code)),
1943 Applicability::MachineApplicable,
1948 // For code `if Some(..) = expr `, the type mismatch may be expected `bool` but found `()`,
1949 // we try to suggest to add the missing `let` for `if let Some(..) = expr`
1950 (ty::Bool, ty::Tuple(list)) => if list.len() == 0 {
1951 self.suggest_let_for_letchains(&mut err, &trace.cause, span);
1956 let code = trace.cause.code();
1957 if let &MatchExpressionArm(box MatchExpressionArmCause { source, .. }) = code
1958 && let hir::MatchSource::TryDesugar = source
1959 && let Some((expected_ty, found_ty, _, _)) = self.values_str(trace.values)
1962 "`?` operator cannot convert from `{}` to `{}`",
1964 expected_ty.content(),
1969 FailureCode::Error0644(failure_str) => {
1970 struct_span_err!(self.tcx.sess, span, E0644, "{}", failure_str)
1973 self.note_type_err(&mut diag, &trace.cause, None, Some(trace.values), terr, false, false);
1977 fn emit_tuple_wrap_err(
1979 err: &mut Diagnostic,
1982 expected_fields: &List<Ty<'tcx>>,
1984 let [expected_tup_elem] = expected_fields[..] else { return };
1986 if !self.same_type_modulo_infer(expected_tup_elem, found) {
1990 let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span)
1993 let msg = "use a trailing comma to create a tuple with one element";
1994 if code.starts_with('(') && code.ends_with(')') {
1995 let before_close = span.hi() - BytePos::from_u32(1);
1996 err.span_suggestion(
1997 span.with_hi(before_close).shrink_to_hi(),
2000 Applicability::MachineApplicable,
2003 err.multipart_suggestion(
2005 vec![(span.shrink_to_lo(), "(".into()), (span.shrink_to_hi(), ",)".into())],
2006 Applicability::MachineApplicable,
2013 values: ValuePairs<'tcx>,
2014 ) -> Option<(DiagnosticStyledString, DiagnosticStyledString, Option<PathBuf>, Option<PathBuf>)>
2017 infer::Regions(exp_found) => self.expected_found_str(exp_found),
2018 infer::Terms(exp_found) => self.expected_found_str_term(exp_found),
2019 infer::TraitRefs(exp_found) => {
2020 let pretty_exp_found = ty::error::ExpectedFound {
2021 expected: exp_found.expected.print_only_trait_path(),
2022 found: exp_found.found.print_only_trait_path(),
2024 match self.expected_found_str(pretty_exp_found) {
2025 Some((expected, found, _, _)) if expected == found => {
2026 self.expected_found_str(exp_found)
2031 infer::PolyTraitRefs(exp_found) => {
2032 let pretty_exp_found = ty::error::ExpectedFound {
2033 expected: exp_found.expected.print_only_trait_path(),
2034 found: exp_found.found.print_only_trait_path(),
2036 match self.expected_found_str(pretty_exp_found) {
2037 Some((expected, found, _, _)) if expected == found => {
2038 self.expected_found_str(exp_found)
2046 fn expected_found_str_term(
2048 exp_found: ty::error::ExpectedFound<ty::Term<'tcx>>,
2049 ) -> Option<(DiagnosticStyledString, DiagnosticStyledString, Option<PathBuf>, Option<PathBuf>)>
2051 let exp_found = self.resolve_vars_if_possible(exp_found);
2052 if exp_found.references_error() {
2056 Some(match (exp_found.expected.unpack(), exp_found.found.unpack()) {
2057 (ty::TermKind::Ty(expected), ty::TermKind::Ty(found)) => {
2058 let (mut exp, mut fnd) = self.cmp(expected, found);
2059 // Use the terminal width as the basis to determine when to compress the printed
2060 // out type, but give ourselves some leeway to avoid ending up creating a file for
2061 // a type that is somewhat shorter than the path we'd write to.
2062 let len = self.tcx.sess().diagnostic_width() + 40;
2063 let exp_s = exp.content();
2064 let fnd_s = fnd.content();
2065 let mut exp_p = None;
2066 let mut fnd_p = None;
2067 if exp_s.len() > len {
2068 let (exp_s, exp_path) = self.tcx.short_ty_string(expected);
2069 exp = DiagnosticStyledString::highlighted(exp_s);
2072 if fnd_s.len() > len {
2073 let (fnd_s, fnd_path) = self.tcx.short_ty_string(found);
2074 fnd = DiagnosticStyledString::highlighted(fnd_s);
2077 (exp, fnd, exp_p, fnd_p)
2080 DiagnosticStyledString::highlighted(exp_found.expected.to_string()),
2081 DiagnosticStyledString::highlighted(exp_found.found.to_string()),
2088 /// Returns a string of the form "expected `{}`, found `{}`".
2089 fn expected_found_str<T: fmt::Display + TypeFoldable<'tcx>>(
2091 exp_found: ty::error::ExpectedFound<T>,
2092 ) -> Option<(DiagnosticStyledString, DiagnosticStyledString, Option<PathBuf>, Option<PathBuf>)>
2094 let exp_found = self.resolve_vars_if_possible(exp_found);
2095 if exp_found.references_error() {
2100 DiagnosticStyledString::highlighted(exp_found.expected.to_string()),
2101 DiagnosticStyledString::highlighted(exp_found.found.to_string()),
2107 pub fn report_generic_bound_failure(
2109 generic_param_scope: LocalDefId,
2111 origin: Option<SubregionOrigin<'tcx>>,
2112 bound_kind: GenericKind<'tcx>,
2115 self.construct_generic_bound_failure(generic_param_scope, span, origin, bound_kind, sub)
2119 pub fn construct_generic_bound_failure(
2121 generic_param_scope: LocalDefId,
2123 origin: Option<SubregionOrigin<'tcx>>,
2124 bound_kind: GenericKind<'tcx>,
2126 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
2127 // Attempt to obtain the span of the parameter so we can
2128 // suggest adding an explicit lifetime bound to it.
2129 let generics = self.tcx.generics_of(generic_param_scope);
2130 // type_param_span is (span, has_bounds)
2131 let type_param_span = match bound_kind {
2132 GenericKind::Param(ref param) => {
2133 // Account for the case where `param` corresponds to `Self`,
2134 // which doesn't have the expected type argument.
2135 if !(generics.has_self && param.index == 0) {
2136 let type_param = generics.type_param(param, self.tcx);
2137 type_param.def_id.as_local().map(|def_id| {
2138 // Get the `hir::Param` to verify whether it already has any bounds.
2139 // We do this to avoid suggesting code that ends up as `T: 'a'b`,
2140 // instead we suggest `T: 'a + 'b` in that case.
2141 let hir_id = self.tcx.hir().local_def_id_to_hir_id(def_id);
2142 let ast_generics = self.tcx.hir().get_generics(hir_id.owner.def_id);
2144 ast_generics.and_then(|g| g.bounds_span_for_suggestions(def_id));
2145 // `sp` only covers `T`, change it so that it covers
2146 // `T:` when appropriate
2147 if let Some(span) = bounds {
2150 let sp = self.tcx.def_span(def_id);
2151 (sp.shrink_to_hi(), false)
2162 let mut possible = (b'a'..=b'z').map(|c| format!("'{}", c as char));
2164 iter::successors(Some(generics), |g| g.parent.map(|p| self.tcx.generics_of(p)))
2165 .flat_map(|g| &g.params)
2166 .filter(|p| matches!(p.kind, ty::GenericParamDefKind::Lifetime))
2167 .map(|p| p.name.as_str())
2168 .collect::<Vec<_>>();
2170 .find(|candidate| !lts_names.contains(&&candidate[..]))
2171 .unwrap_or("'lt".to_string())
2174 let add_lt_sugg = generics
2177 .and_then(|param| param.def_id.as_local())
2178 .map(|def_id| (self.tcx.def_span(def_id).shrink_to_lo(), format!("{}, ", new_lt)));
2180 let labeled_user_string = match bound_kind {
2181 GenericKind::Param(ref p) => format!("the parameter type `{}`", p),
2182 GenericKind::Projection(ref p) => format!("the associated type `{}`", p),
2183 GenericKind::Opaque(def_id, substs) => {
2184 format!("the opaque type `{}`", self.tcx.def_path_str_with_substs(def_id, substs))
2188 if let Some(SubregionOrigin::CompareImplItemObligation {
2194 return self.report_extra_impl_obligation(
2198 &format!("`{}: {}`", bound_kind, sub),
2202 fn binding_suggestion<S: fmt::Display>(
2203 err: &mut Diagnostic,
2204 type_param_span: Option<(Span, bool)>,
2205 bound_kind: GenericKind<'_>,
2207 add_lt_sugg: Option<(Span, String)>,
2209 let msg = "consider adding an explicit lifetime bound";
2210 if let Some((sp, has_lifetimes)) = type_param_span {
2212 if has_lifetimes { format!(" + {}", sub) } else { format!(": {}", sub) };
2213 let mut suggestions = vec![(sp, suggestion)];
2214 if let Some(add_lt_sugg) = add_lt_sugg {
2215 suggestions.push(add_lt_sugg);
2217 err.multipart_suggestion_verbose(
2218 format!("{msg}..."),
2220 Applicability::MaybeIncorrect, // Issue #41966
2223 let consider = format!("{} `{}: {}`...", msg, bound_kind, sub);
2224 err.help(&consider);
2228 let new_binding_suggestion =
2229 |err: &mut Diagnostic, type_param_span: Option<(Span, bool)>| {
2230 let msg = "consider introducing an explicit lifetime bound";
2231 if let Some((sp, has_lifetimes)) = type_param_span {
2232 let suggestion = if has_lifetimes {
2233 format!(" + {}", new_lt)
2235 format!(": {}", new_lt)
2238 vec![(sp, suggestion), (span.shrink_to_hi(), format!(" + {}", new_lt))];
2239 if let Some(lt) = add_lt_sugg.clone() {
2241 sugg.rotate_right(1);
2243 // `MaybeIncorrect` due to issue #41966.
2244 err.multipart_suggestion(msg, sugg, Applicability::MaybeIncorrect);
2249 enum SubOrigin<'hir> {
2250 GAT(&'hir hir::Generics<'hir>),
2256 let sub_origin = 'origin: {
2258 ty::ReEarlyBound(ty::EarlyBoundRegion { def_id, .. }) => {
2259 let node = self.tcx.hir().get_if_local(def_id).unwrap();
2261 Node::GenericParam(param) => {
2262 for h in self.tcx.hir().parent_iter(param.hir_id) {
2263 break 'origin match h.1 {
2264 Node::ImplItem(hir::ImplItem {
2265 kind: hir::ImplItemKind::Type(..),
2269 | Node::TraitItem(hir::TraitItem {
2270 kind: hir::TraitItemKind::Type(..),
2273 }) => SubOrigin::GAT(generics),
2274 Node::ImplItem(hir::ImplItem {
2275 kind: hir::ImplItemKind::Fn(..),
2278 | Node::TraitItem(hir::TraitItem {
2279 kind: hir::TraitItemKind::Fn(..),
2282 | Node::Item(hir::Item {
2283 kind: hir::ItemKind::Fn(..), ..
2284 }) => SubOrigin::Fn,
2285 Node::Item(hir::Item {
2286 kind: hir::ItemKind::Trait(..),
2288 }) => SubOrigin::Trait,
2289 Node::Item(hir::Item {
2290 kind: hir::ItemKind::Impl(..), ..
2291 }) => SubOrigin::Impl,
2303 debug!(?sub_origin);
2305 let mut err = match (*sub, sub_origin) {
2306 // In the case of GATs, we have to be careful. If we a type parameter `T` on an impl,
2307 // but a lifetime `'a` on an associated type, then we might need to suggest adding
2308 // `where T: 'a`. Importantly, this is on the GAT span, not on the `T` declaration.
2309 (ty::ReEarlyBound(ty::EarlyBoundRegion { name: _, .. }), SubOrigin::GAT(generics)) => {
2310 // Does the required lifetime have a nice name we can print?
2311 let mut err = struct_span_err!(
2315 "{} may not live long enough",
2318 let pred = format!("{}: {}", bound_kind, sub);
2319 let suggestion = format!("{} {}", generics.add_where_or_trailing_comma(), pred,);
2320 err.span_suggestion(
2321 generics.tail_span_for_predicate_suggestion(),
2322 "consider adding a where clause",
2324 Applicability::MaybeIncorrect,
2329 ty::ReEarlyBound(ty::EarlyBoundRegion { name, .. })
2330 | ty::ReFree(ty::FreeRegion { bound_region: ty::BrNamed(_, name), .. }),
2332 ) if name != kw::UnderscoreLifetime => {
2333 // Does the required lifetime have a nice name we can print?
2334 let mut err = struct_span_err!(
2338 "{} may not live long enough",
2341 // Explicitly use the name instead of `sub`'s `Display` impl. The `Display` impl
2342 // for the bound is not suitable for suggestions when `-Zverbose` is set because it
2343 // uses `Debug` output, so we handle it specially here so that suggestions are
2345 binding_suggestion(&mut err, type_param_span, bound_kind, name, None);
2349 (ty::ReStatic, _) => {
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 binding_suggestion(&mut err, type_param_span, bound_kind, "'static", None);
2363 // If not, be less specific.
2364 let mut err = struct_span_err!(
2368 "{} may not live long enough",
2371 note_and_explain_region(
2374 &format!("{} must be valid for ", labeled_user_string),
2379 if let Some(infer::RelateParamBound(_, t, _)) = origin {
2380 let return_impl_trait =
2381 self.tcx.return_type_impl_trait(generic_param_scope).is_some();
2382 let t = self.resolve_vars_if_possible(t);
2385 // fn get_later<G, T>(g: G, dest: &mut T) -> impl FnOnce() + '_
2387 // fn get_later<'a, G: 'a, T>(g: G, dest: &mut T) -> impl FnOnce() + '_ + 'a
2388 ty::Closure(..) | ty::Alias(ty::Opaque, ..) if return_impl_trait => {
2389 new_binding_suggestion(&mut err, type_param_span);
2406 if let Some(origin) = origin {
2407 self.note_region_origin(&mut err, &origin);
2412 fn report_sub_sup_conflict(
2414 var_origin: RegionVariableOrigin,
2415 sub_origin: SubregionOrigin<'tcx>,
2416 sub_region: Region<'tcx>,
2417 sup_origin: SubregionOrigin<'tcx>,
2418 sup_region: Region<'tcx>,
2420 let mut err = self.report_inference_failure(var_origin);
2422 note_and_explain_region(
2425 "first, the lifetime cannot outlive ",
2431 debug!("report_sub_sup_conflict: var_origin={:?}", var_origin);
2432 debug!("report_sub_sup_conflict: sub_region={:?}", sub_region);
2433 debug!("report_sub_sup_conflict: sub_origin={:?}", sub_origin);
2434 debug!("report_sub_sup_conflict: sup_region={:?}", sup_region);
2435 debug!("report_sub_sup_conflict: sup_origin={:?}", sup_origin);
2437 if let infer::Subtype(ref sup_trace) = sup_origin
2438 && let infer::Subtype(ref sub_trace) = sub_origin
2439 && let Some((sup_expected, sup_found, _, _)) = self.values_str(sup_trace.values)
2440 && let Some((sub_expected, sub_found, _, _)) = self.values_str(sub_trace.values)
2441 && sub_expected == sup_expected
2442 && sub_found == sup_found
2444 note_and_explain_region(
2447 "...but the lifetime must also be valid for ",
2453 sup_trace.cause.span,
2454 &format!("...so that the {}", sup_trace.cause.as_requirement_str()),
2457 err.note_expected_found(&"", sup_expected, &"", sup_found);
2462 self.note_region_origin(&mut err, &sup_origin);
2464 note_and_explain_region(
2467 "but, the lifetime must be valid for ",
2473 self.note_region_origin(&mut err, &sub_origin);
2477 /// Determine whether an error associated with the given span and definition
2478 /// should be treated as being caused by the implicit `From` conversion
2479 /// within `?` desugaring.
2480 pub fn is_try_conversion(&self, span: Span, trait_def_id: DefId) -> bool {
2481 span.is_desugaring(DesugaringKind::QuestionMark)
2482 && self.tcx.is_diagnostic_item(sym::From, trait_def_id)
2485 /// Structurally compares two types, modulo any inference variables.
2487 /// Returns `true` if two types are equal, or if one type is an inference variable compatible
2488 /// with the other type. A TyVar inference type is compatible with any type, and an IntVar or
2489 /// FloatVar inference type are compatible with themselves or their concrete types (Int and
2490 /// Float types, respectively). When comparing two ADTs, these rules apply recursively.
2491 pub fn same_type_modulo_infer(&self, a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
2492 let (a, b) = self.resolve_vars_if_possible((a, b));
2493 SameTypeModuloInfer(self).relate(a, b).is_ok()
2497 struct SameTypeModuloInfer<'a, 'tcx>(&'a InferCtxt<'tcx>);
2499 impl<'tcx> TypeRelation<'tcx> for SameTypeModuloInfer<'_, 'tcx> {
2500 fn tcx(&self) -> TyCtxt<'tcx> {
2504 fn intercrate(&self) -> bool {
2505 assert!(!self.0.intercrate);
2509 fn param_env(&self) -> ty::ParamEnv<'tcx> {
2510 // Unused, only for consts which we treat as always equal
2511 ty::ParamEnv::empty()
2514 fn tag(&self) -> &'static str {
2515 "SameTypeModuloInfer"
2518 fn a_is_expected(&self) -> bool {
2522 fn mark_ambiguous(&mut self) {
2526 fn relate_with_variance<T: relate::Relate<'tcx>>(
2528 _variance: ty::Variance,
2529 _info: ty::VarianceDiagInfo<'tcx>,
2532 ) -> relate::RelateResult<'tcx, T> {
2536 fn tys(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>> {
2537 match (a.kind(), b.kind()) {
2538 (ty::Int(_) | ty::Uint(_), ty::Infer(ty::InferTy::IntVar(_)))
2540 ty::Infer(ty::InferTy::IntVar(_)),
2541 ty::Int(_) | ty::Uint(_) | ty::Infer(ty::InferTy::IntVar(_)),
2543 | (ty::Float(_), ty::Infer(ty::InferTy::FloatVar(_)))
2545 ty::Infer(ty::InferTy::FloatVar(_)),
2546 ty::Float(_) | ty::Infer(ty::InferTy::FloatVar(_)),
2548 | (ty::Infer(ty::InferTy::TyVar(_)), _)
2549 | (_, ty::Infer(ty::InferTy::TyVar(_))) => Ok(a),
2550 (ty::Infer(_), _) | (_, ty::Infer(_)) => Err(TypeError::Mismatch),
2551 _ => relate::super_relate_tys(self, a, b),
2557 a: ty::Region<'tcx>,
2558 b: ty::Region<'tcx>,
2559 ) -> RelateResult<'tcx, ty::Region<'tcx>> {
2560 if (a.is_var() && b.is_free_or_static())
2561 || (b.is_var() && a.is_free_or_static())
2562 || (a.is_var() && b.is_var())
2567 Err(TypeError::Mismatch)
2573 a: ty::Binder<'tcx, T>,
2574 b: ty::Binder<'tcx, T>,
2575 ) -> relate::RelateResult<'tcx, ty::Binder<'tcx, T>>
2577 T: relate::Relate<'tcx>,
2579 Ok(a.rebind(self.relate(a.skip_binder(), b.skip_binder())?))
2585 _b: ty::Const<'tcx>,
2586 ) -> relate::RelateResult<'tcx, ty::Const<'tcx>> {
2587 // FIXME(compiler-errors): This could at least do some first-order
2593 impl<'tcx> InferCtxt<'tcx> {
2594 fn report_inference_failure(
2596 var_origin: RegionVariableOrigin,
2597 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
2598 let br_string = |br: ty::BoundRegionKind| {
2599 let mut s = match br {
2600 ty::BrNamed(_, name) => name.to_string(),
2608 let var_description = match var_origin {
2609 infer::MiscVariable(_) => String::new(),
2610 infer::PatternRegion(_) => " for pattern".to_string(),
2611 infer::AddrOfRegion(_) => " for borrow expression".to_string(),
2612 infer::Autoref(_) => " for autoref".to_string(),
2613 infer::Coercion(_) => " for automatic coercion".to_string(),
2614 infer::LateBoundRegion(_, br, infer::FnCall) => {
2615 format!(" for lifetime parameter {}in function call", br_string(br))
2617 infer::LateBoundRegion(_, br, infer::HigherRankedType) => {
2618 format!(" for lifetime parameter {}in generic type", br_string(br))
2620 infer::LateBoundRegion(_, br, infer::AssocTypeProjection(def_id)) => format!(
2621 " for lifetime parameter {}in trait containing associated type `{}`",
2623 self.tcx.associated_item(def_id).name
2625 infer::EarlyBoundRegion(_, name) => format!(" for lifetime parameter `{}`", name),
2626 infer::UpvarRegion(ref upvar_id, _) => {
2627 let var_name = self.tcx.hir().name(upvar_id.var_path.hir_id);
2628 format!(" for capture of `{}` by closure", var_name)
2630 infer::Nll(..) => bug!("NLL variable found in lexical phase"),
2637 "cannot infer an appropriate lifetime{} due to conflicting requirements",
2643 pub enum FailureCode {
2645 Error0317(&'static str),
2646 Error0580(&'static str),
2647 Error0308(&'static str),
2648 Error0644(&'static str),
2651 pub trait ObligationCauseExt<'tcx> {
2652 fn as_failure_code(&self, terr: TypeError<'tcx>) -> FailureCode;
2653 fn as_requirement_str(&self) -> &'static str;
2656 impl<'tcx> ObligationCauseExt<'tcx> for ObligationCause<'tcx> {
2657 fn as_failure_code(&self, terr: TypeError<'tcx>) -> FailureCode {
2658 use self::FailureCode::*;
2659 use crate::traits::ObligationCauseCode::*;
2661 CompareImplItemObligation { kind: ty::AssocKind::Fn, .. } => {
2662 Error0308("method not compatible with trait")
2664 CompareImplItemObligation { kind: ty::AssocKind::Type, .. } => {
2665 Error0308("type not compatible with trait")
2667 CompareImplItemObligation { kind: ty::AssocKind::Const, .. } => {
2668 Error0308("const not compatible with trait")
2670 MatchExpressionArm(box MatchExpressionArmCause { source, .. }) => {
2671 Error0308(match source {
2672 hir::MatchSource::TryDesugar => "`?` operator has incompatible types",
2673 _ => "`match` arms have incompatible types",
2676 IfExpression { .. } => Error0308("`if` and `else` have incompatible types"),
2677 IfExpressionWithNoElse => Error0317("`if` may be missing an `else` clause"),
2678 LetElse => Error0308("`else` clause of `let...else` does not diverge"),
2679 MainFunctionType => Error0580("`main` function has wrong type"),
2680 StartFunctionType => Error0308("`#[start]` function has wrong type"),
2681 IntrinsicType => Error0308("intrinsic has wrong type"),
2682 MethodReceiver => Error0308("mismatched `self` parameter type"),
2684 // In the case where we have no more specific thing to
2685 // say, also take a look at the error code, maybe we can
2688 TypeError::CyclicTy(ty) if ty.is_closure() || ty.is_generator() => {
2689 Error0644("closure/generator type that references itself")
2691 TypeError::IntrinsicCast => {
2692 Error0308("cannot coerce intrinsics to function pointers")
2694 _ => Error0308("mismatched types"),
2699 fn as_requirement_str(&self) -> &'static str {
2700 use crate::traits::ObligationCauseCode::*;
2702 CompareImplItemObligation { kind: ty::AssocKind::Fn, .. } => {
2703 "method type is compatible with trait"
2705 CompareImplItemObligation { kind: ty::AssocKind::Type, .. } => {
2706 "associated type is compatible with trait"
2708 CompareImplItemObligation { kind: ty::AssocKind::Const, .. } => {
2709 "const is compatible with trait"
2711 ExprAssignable => "expression is assignable",
2712 IfExpression { .. } => "`if` and `else` have incompatible types",
2713 IfExpressionWithNoElse => "`if` missing an `else` returns `()`",
2714 MainFunctionType => "`main` function has the correct type",
2715 StartFunctionType => "`#[start]` function has the correct type",
2716 IntrinsicType => "intrinsic has the correct type",
2717 MethodReceiver => "method receiver has the correct type",
2718 _ => "types are compatible",
2723 /// Newtype to allow implementing IntoDiagnosticArg
2724 pub struct ObligationCauseAsDiagArg<'tcx>(pub ObligationCause<'tcx>);
2726 impl IntoDiagnosticArg for ObligationCauseAsDiagArg<'_> {
2727 fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> {
2728 use crate::traits::ObligationCauseCode::*;
2729 let kind = match self.0.code() {
2730 CompareImplItemObligation { kind: ty::AssocKind::Fn, .. } => "method_compat",
2731 CompareImplItemObligation { kind: ty::AssocKind::Type, .. } => "type_compat",
2732 CompareImplItemObligation { kind: ty::AssocKind::Const, .. } => "const_compat",
2733 ExprAssignable => "expr_assignable",
2734 IfExpression { .. } => "if_else_different",
2735 IfExpressionWithNoElse => "no_else",
2736 MainFunctionType => "fn_main_correct_type",
2737 StartFunctionType => "fn_start_correct_type",
2738 IntrinsicType => "intristic_correct_type",
2739 MethodReceiver => "method_correct_type",
2743 rustc_errors::DiagnosticArgValue::Str(kind)
2747 /// This is a bare signal of what kind of type we're dealing with. `ty::TyKind` tracks
2748 /// extra information about each type, but we only care about the category.
2749 #[derive(Clone, Copy, PartialEq, Eq, Hash)]
2750 pub enum TyCategory {
2753 Generator(hir::GeneratorKind),
2758 fn descr(&self) -> &'static str {
2760 Self::Closure => "closure",
2761 Self::Opaque => "opaque type",
2762 Self::Generator(gk) => gk.descr(),
2763 Self::Foreign => "foreign type",
2767 pub fn from_ty(tcx: TyCtxt<'_>, ty: Ty<'_>) -> Option<(Self, DefId)> {
2769 ty::Closure(def_id, _) => Some((Self::Closure, def_id)),
2770 ty::Alias(ty::Opaque, ty::AliasTy { def_id, .. }) => Some((Self::Opaque, def_id)),
2771 ty::Generator(def_id, ..) => {
2772 Some((Self::Generator(tcx.generator_kind(def_id).unwrap()), def_id))
2774 ty::Foreign(def_id) => Some((Self::Foreign, def_id)),
2780 impl<'tcx> InferCtxt<'tcx> {
2781 /// Given a [`hir::Block`], get the span of its last expression or
2782 /// statement, peeling off any inner blocks.
2783 pub fn find_block_span(&self, block: &'tcx hir::Block<'tcx>) -> Span {
2784 let block = block.innermost_block();
2785 if let Some(expr) = &block.expr {
2787 } else if let Some(stmt) = block.stmts.last() {
2788 // possibly incorrect trailing `;` in the else arm
2791 // empty block; point at its entirety
2796 /// Given a [`hir::HirId`] for a block, get the span of its last expression
2797 /// or statement, peeling off any inner blocks.
2798 pub fn find_block_span_from_hir_id(&self, hir_id: hir::HirId) -> Span {
2799 match self.tcx.hir().get(hir_id) {
2800 hir::Node::Block(blk) => self.find_block_span(blk),
2801 // The parser was in a weird state if either of these happen, but
2802 // it's better not to panic.
2803 hir::Node::Expr(e) => e.span,
2804 _ => rustc_span::DUMMY_SP,