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};
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::print::with_forced_trimmed_paths;
71 use rustc_middle::ty::relate::{self, RelateResult, TypeRelation};
72 use rustc_middle::ty::{
73 self, error::TypeError, List, Region, Ty, TyCtxt, TypeFoldable, TypeSuperVisitable,
76 use rustc_span::{sym, symbol::kw, BytePos, DesugaringKind, Pos, Span};
77 use rustc_target::spec::abi;
78 use std::ops::{ControlFlow, Deref};
79 use std::path::PathBuf;
80 use std::{cmp, fmt, iter};
86 pub(crate) mod need_type_info;
87 pub use need_type_info::TypeAnnotationNeeded;
89 pub mod nice_region_error;
91 /// A helper for building type related errors. The `typeck_results`
92 /// field is only populated during an in-progress typeck.
93 /// Get an instance by calling `InferCtxt::err` or `FnCtxt::infer_err`.
94 pub struct TypeErrCtxt<'a, 'tcx> {
95 pub infcx: &'a InferCtxt<'tcx>,
96 pub typeck_results: Option<std::cell::Ref<'a, ty::TypeckResults<'tcx>>>,
97 pub fallback_has_occurred: bool,
99 pub normalize_fn_sig: Box<dyn Fn(ty::PolyFnSig<'tcx>) -> ty::PolyFnSig<'tcx> + 'a>,
102 Box<dyn Fn(Ty<'tcx>) -> Vec<(Ty<'tcx>, Vec<PredicateObligation<'tcx>>)> + 'a>,
105 impl TypeErrCtxt<'_, '_> {
106 /// This is just to avoid a potential footgun of accidentally
107 /// dropping `typeck_results` by calling `InferCtxt::err_ctxt`
108 #[deprecated(note = "you already have a `TypeErrCtxt`")]
110 pub fn err_ctxt(&self) -> ! {
111 bug!("called `err_ctxt` on `TypeErrCtxt`. Try removing the call");
115 impl<'tcx> Deref for TypeErrCtxt<'_, 'tcx> {
116 type Target = InferCtxt<'tcx>;
117 fn deref(&self) -> &InferCtxt<'tcx> {
122 pub(super) fn note_and_explain_region<'tcx>(
124 err: &mut Diagnostic,
126 region: ty::Region<'tcx>,
128 alt_span: Option<Span>,
130 let (description, span) = match *region {
131 ty::ReEarlyBound(_) | ty::ReFree(_) | ty::ReStatic => {
132 msg_span_from_free_region(tcx, region, alt_span)
135 ty::RePlaceholder(_) => return,
137 // FIXME(#13998) RePlaceholder should probably print like
138 // ReFree rather than dumping Debug output on the user.
140 // We shouldn't really be having unification failures with ReVar
141 // and ReLateBound though.
142 ty::ReVar(_) | ty::ReLateBound(..) | ty::ReErased => {
143 (format!("lifetime {:?}", region), alt_span)
147 emit_msg_span(err, prefix, description, span, suffix);
150 fn explain_free_region<'tcx>(
152 err: &mut Diagnostic,
154 region: ty::Region<'tcx>,
157 let (description, span) = msg_span_from_free_region(tcx, region, None);
159 label_msg_span(err, prefix, description, span, suffix);
162 fn msg_span_from_free_region<'tcx>(
164 region: ty::Region<'tcx>,
165 alt_span: Option<Span>,
166 ) -> (String, Option<Span>) {
168 ty::ReEarlyBound(_) | ty::ReFree(_) => {
169 let (msg, span) = msg_span_from_early_bound_and_free_regions(tcx, region);
172 ty::ReStatic => ("the static lifetime".to_owned(), alt_span),
173 _ => bug!("{:?}", region),
177 fn msg_span_from_early_bound_and_free_regions<'tcx>(
179 region: ty::Region<'tcx>,
180 ) -> (String, Span) {
181 let scope = region.free_region_binding_scope(tcx).expect_local();
183 ty::ReEarlyBound(ref br) => {
184 let mut sp = tcx.def_span(scope);
186 tcx.hir().get_generics(scope).and_then(|generics| generics.get_named(br.name))
190 let text = if br.has_name() {
191 format!("the lifetime `{}` as defined here", br.name)
193 "the anonymous lifetime as defined here".to_string()
197 ty::ReFree(ref fr) => {
198 if !fr.bound_region.is_named()
199 && let Some((ty, _)) = find_anon_type(tcx, region, &fr.bound_region)
201 ("the anonymous lifetime defined here".to_string(), ty.span)
203 match fr.bound_region {
204 ty::BoundRegionKind::BrNamed(_, name) => {
205 let mut sp = tcx.def_span(scope);
207 tcx.hir().get_generics(scope).and_then(|generics| generics.get_named(name))
211 let text = if name == kw::UnderscoreLifetime {
212 "the anonymous lifetime as defined here".to_string()
214 format!("the lifetime `{}` as defined here", name)
218 ty::BrAnon(idx, span) => (
219 format!("the anonymous lifetime #{} defined here", idx + 1),
222 None => tcx.def_span(scope)
226 format!("the lifetime `{}` as defined here", region),
237 err: &mut Diagnostic,
243 let message = format!("{}{}{}", prefix, description, suffix);
245 if let Some(span) = span {
246 err.span_note(span, &message);
253 err: &mut Diagnostic,
259 let message = format!("{}{}{}", prefix, description, suffix);
261 if let Some(span) = span {
262 err.span_label(span, &message);
268 #[instrument(level = "trace", skip(tcx))]
269 pub fn unexpected_hidden_region_diagnostic<'tcx>(
273 hidden_region: ty::Region<'tcx>,
274 opaque_ty: ty::OpaqueTypeKey<'tcx>,
275 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
276 let opaque_ty = tcx.mk_opaque(opaque_ty.def_id.to_def_id(), opaque_ty.substs);
277 let mut err = struct_span_err!(
281 "hidden type for `{opaque_ty}` captures lifetime that does not appear in bounds",
284 // Explain the region we are capturing.
285 match *hidden_region {
286 ty::ReEarlyBound(_) | ty::ReFree(_) | ty::ReStatic => {
287 // Assuming regionck succeeded (*), we ought to always be
288 // capturing *some* region from the fn header, and hence it
289 // ought to be free. So under normal circumstances, we will go
290 // down this path which gives a decent human readable
293 // (*) if not, the `tainted_by_errors` field would be set to
294 // `Some(ErrorGuaranteed)` in any case, so we wouldn't be here at all.
298 &format!("hidden type `{}` captures ", hidden_ty),
302 if let Some(reg_info) = tcx.is_suitable_region(hidden_region) {
303 let fn_returns = tcx.return_type_impl_or_dyn_traits(reg_info.def_id);
304 nice_region_error::suggest_new_region_bound(
308 hidden_region.to_string(),
310 format!("captures `{}`", hidden_region),
312 Some(reg_info.def_id),
317 // Ugh. This is a painful case: the hidden region is not one
318 // that we can easily summarize or explain. This can happen
320 // `tests/ui/multiple-lifetimes/ordinary-bounds-unsuited.rs`:
323 // fn upper_bounds<'a, 'b>(a: Ordinary<'a>, b: Ordinary<'b>) -> impl Trait<'a, 'b> {
324 // if condition() { a } else { b }
328 // Here the captured lifetime is the intersection of `'a` and
329 // `'b`, which we can't quite express.
331 // We can at least report a really cryptic error for now.
332 note_and_explain_region(
335 &format!("hidden type `{}` captures ", hidden_ty),
346 impl<'tcx> InferCtxt<'tcx> {
347 pub fn get_impl_future_output_ty(&self, ty: Ty<'tcx>) -> Option<Ty<'tcx>> {
348 let (def_id, substs) = match *ty.kind() {
349 ty::Alias(_, ty::AliasTy { def_id, substs, .. })
351 self.tcx.def_kind(def_id),
352 DefKind::OpaqueTy | DefKind::ImplTraitPlaceholder
360 let future_trait = self.tcx.require_lang_item(LangItem::Future, None);
361 let item_def_id = self.tcx.associated_item_def_ids(future_trait)[0];
363 self.tcx.bound_explicit_item_bounds(def_id).subst_iter_copied(self.tcx, substs).find_map(
367 .map_bound(|kind| match kind {
368 ty::PredicateKind::Clause(ty::Clause::Projection(projection_predicate))
369 if projection_predicate.projection_ty.def_id == item_def_id =>
371 projection_predicate.term.ty()
382 impl<'tcx> TypeErrCtxt<'_, 'tcx> {
383 pub fn report_region_errors(
385 generic_param_scope: LocalDefId,
386 errors: &[RegionResolutionError<'tcx>],
388 debug!("report_region_errors(): {} errors to start", errors.len());
390 // try to pre-process the errors, which will group some of them
391 // together into a `ProcessedErrors` group:
392 let errors = self.process_errors(errors);
394 debug!("report_region_errors: {} errors after preprocessing", errors.len());
396 for error in errors {
397 debug!("report_region_errors: error = {:?}", error);
399 if !self.try_report_nice_region_error(&error) {
400 match error.clone() {
401 // These errors could indicate all manner of different
402 // problems with many different solutions. Rather
403 // than generate a "one size fits all" error, what we
404 // attempt to do is go through a number of specific
405 // scenarios and try to find the best way to present
406 // the error. If all of these fails, we fall back to a rather
407 // general bit of code that displays the error information
408 RegionResolutionError::ConcreteFailure(origin, sub, sup) => {
409 if sub.is_placeholder() || sup.is_placeholder() {
410 self.report_placeholder_failure(origin, sub, sup).emit();
412 self.report_concrete_failure(origin, sub, sup).emit();
416 RegionResolutionError::GenericBoundFailure(origin, param_ty, sub) => {
417 self.report_generic_bound_failure(
426 RegionResolutionError::SubSupConflict(
435 if sub_r.is_placeholder() {
436 self.report_placeholder_failure(sub_origin, sub_r, sup_r).emit();
437 } else if sup_r.is_placeholder() {
438 self.report_placeholder_failure(sup_origin, sub_r, sup_r).emit();
440 self.report_sub_sup_conflict(
441 var_origin, sub_origin, sub_r, sup_origin, sup_r,
446 RegionResolutionError::UpperBoundUniverseConflict(
453 assert!(sup_r.is_placeholder());
455 // Make a dummy value for the "sub region" --
456 // this is the initial value of the
457 // placeholder. In practice, we expect more
458 // tailored errors that don't really use this
460 let sub_r = self.tcx.lifetimes.re_erased;
462 self.report_placeholder_failure(sup_origin, sub_r, sup_r).emit();
469 // This method goes through all the errors and try to group certain types
470 // of error together, for the purpose of suggesting explicit lifetime
471 // parameters to the user. This is done so that we can have a more
472 // complete view of what lifetimes should be the same.
473 // If the return value is an empty vector, it means that processing
474 // failed (so the return value of this method should not be used).
476 // The method also attempts to weed out messages that seem like
477 // duplicates that will be unhelpful to the end-user. But
478 // obviously it never weeds out ALL errors.
481 errors: &[RegionResolutionError<'tcx>],
482 ) -> Vec<RegionResolutionError<'tcx>> {
483 debug!("process_errors()");
485 // We want to avoid reporting generic-bound failures if we can
486 // avoid it: these have a very high rate of being unhelpful in
487 // practice. This is because they are basically secondary
488 // checks that test the state of the region graph after the
489 // rest of inference is done, and the other kinds of errors
490 // indicate that the region constraint graph is internally
491 // inconsistent, so these test results are likely to be
494 // Therefore, we filter them out of the list unless they are
495 // the only thing in the list.
497 let is_bound_failure = |e: &RegionResolutionError<'tcx>| match *e {
498 RegionResolutionError::GenericBoundFailure(..) => true,
499 RegionResolutionError::ConcreteFailure(..)
500 | RegionResolutionError::SubSupConflict(..)
501 | RegionResolutionError::UpperBoundUniverseConflict(..) => false,
504 let mut errors = if errors.iter().all(|e| is_bound_failure(e)) {
507 errors.iter().filter(|&e| !is_bound_failure(e)).cloned().collect()
510 // sort the errors by span, for better error message stability.
511 errors.sort_by_key(|u| match *u {
512 RegionResolutionError::ConcreteFailure(ref sro, _, _) => sro.span(),
513 RegionResolutionError::GenericBoundFailure(ref sro, _, _) => sro.span(),
514 RegionResolutionError::SubSupConflict(_, ref rvo, _, _, _, _, _) => rvo.span(),
515 RegionResolutionError::UpperBoundUniverseConflict(_, ref rvo, _, _, _) => rvo.span(),
520 /// Adds a note if the types come from similarly named crates
521 fn check_and_note_conflicting_crates(&self, err: &mut Diagnostic, terr: TypeError<'tcx>) {
522 use hir::def_id::CrateNum;
523 use rustc_hir::definitions::DisambiguatedDefPathData;
524 use ty::print::Printer;
525 use ty::subst::GenericArg;
527 struct AbsolutePathPrinter<'tcx> {
531 struct NonTrivialPath;
533 impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
534 type Error = NonTrivialPath;
536 type Path = Vec<String>;
539 type DynExistential = !;
542 fn tcx<'a>(&'a self) -> TyCtxt<'tcx> {
546 fn print_region(self, _region: ty::Region<'_>) -> Result<Self::Region, Self::Error> {
550 fn print_type(self, _ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> {
554 fn print_dyn_existential(
556 _predicates: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
557 ) -> Result<Self::DynExistential, Self::Error> {
561 fn print_const(self, _ct: ty::Const<'tcx>) -> Result<Self::Const, Self::Error> {
565 fn path_crate(self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
566 Ok(vec![self.tcx.crate_name(cnum).to_string()])
571 _trait_ref: Option<ty::TraitRef<'tcx>>,
572 ) -> Result<Self::Path, Self::Error> {
578 _print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
579 _disambiguated_data: &DisambiguatedDefPathData,
581 _trait_ref: Option<ty::TraitRef<'tcx>>,
582 ) -> Result<Self::Path, Self::Error> {
587 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
588 disambiguated_data: &DisambiguatedDefPathData,
589 ) -> Result<Self::Path, Self::Error> {
590 let mut path = print_prefix(self)?;
591 path.push(disambiguated_data.to_string());
594 fn path_generic_args(
596 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
597 _args: &[GenericArg<'tcx>],
598 ) -> Result<Self::Path, Self::Error> {
603 let report_path_match = |err: &mut Diagnostic, did1: DefId, did2: DefId| {
604 // Only external crates, if either is from a local
605 // module we could have false positives
606 if !(did1.is_local() || did2.is_local()) && did1.krate != did2.krate {
608 |def_id| AbsolutePathPrinter { tcx: self.tcx }.print_def_path(def_id, &[]);
610 // We compare strings because DefPath can be different
611 // for imported and non-imported crates
612 let same_path = || -> Result<_, NonTrivialPath> {
613 Ok(self.tcx.def_path_str(did1) == self.tcx.def_path_str(did2)
614 || abs_path(did1)? == abs_path(did2)?)
616 if same_path().unwrap_or(false) {
617 let crate_name = self.tcx.crate_name(did1.krate);
619 "perhaps two different versions of crate `{}` are being used?",
626 TypeError::Sorts(ref exp_found) => {
627 // if they are both "path types", there's a chance of ambiguity
628 // due to different versions of the same crate
629 if let (&ty::Adt(exp_adt, _), &ty::Adt(found_adt, _)) =
630 (exp_found.expected.kind(), exp_found.found.kind())
632 report_path_match(err, exp_adt.did(), found_adt.did());
635 TypeError::Traits(ref exp_found) => {
636 report_path_match(err, exp_found.expected, exp_found.found);
638 _ => (), // FIXME(#22750) handle traits and stuff
642 fn note_error_origin(
644 err: &mut Diagnostic,
645 cause: &ObligationCause<'tcx>,
646 exp_found: Option<ty::error::ExpectedFound<Ty<'tcx>>>,
647 terr: TypeError<'tcx>,
649 match *cause.code() {
650 ObligationCauseCode::Pattern { origin_expr: true, span: Some(span), root_ty } => {
651 let ty = self.resolve_vars_if_possible(root_ty);
652 if !matches!(ty.kind(), ty::Infer(ty::InferTy::TyVar(_) | ty::InferTy::FreshTy(_)))
654 // don't show type `_`
655 if span.desugaring_kind() == Some(DesugaringKind::ForLoop)
656 && let ty::Adt(def, substs) = ty.kind()
657 && Some(def.did()) == self.tcx.get_diagnostic_item(sym::Option)
659 err.span_label(span, format!("this is an iterator with items of type `{}`", substs.type_at(0)));
661 err.span_label(span, format!("this expression has type `{}`", ty));
664 if let Some(ty::error::ExpectedFound { found, .. }) = exp_found
665 && ty.is_box() && ty.boxed_ty() == found
666 && let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span)
670 "consider dereferencing the boxed value",
671 format!("*{}", snippet),
672 Applicability::MachineApplicable,
676 ObligationCauseCode::Pattern { origin_expr: false, span: Some(span), .. } => {
677 err.span_label(span, "expected due to this");
679 ObligationCauseCode::MatchExpressionArm(box MatchExpressionArmCause {
689 opt_suggest_box_span,
693 hir::MatchSource::TryDesugar => {
694 if let Some(ty::error::ExpectedFound { expected, .. }) = exp_found {
695 let scrut_expr = self.tcx.hir().expect_expr(scrut_hir_id);
696 let scrut_ty = if let hir::ExprKind::Call(_, args) = &scrut_expr.kind {
697 let arg_expr = args.first().expect("try desugaring call w/out arg");
698 self.typeck_results.as_ref().and_then(|typeck_results| {
699 typeck_results.expr_ty_opt(arg_expr)
702 bug!("try desugaring w/out call expr as scrutinee");
706 Some(ty) if expected == ty => {
707 let source_map = self.tcx.sess.source_map();
709 source_map.end_point(cause.span),
710 "try removing this `?`",
712 Applicability::MachineApplicable,
720 // `prior_arm_ty` can be `!`, `expected` will have better info when present.
721 let t = self.resolve_vars_if_possible(match exp_found {
722 Some(ty::error::ExpectedFound { expected, .. }) => expected,
725 let source_map = self.tcx.sess.source_map();
726 let mut any_multiline_arm = source_map.is_multiline(arm_span);
727 if prior_arms.len() <= 4 {
728 for sp in prior_arms {
729 any_multiline_arm |= source_map.is_multiline(*sp);
730 err.span_label(*sp, format!("this is found to be of type `{}`", t));
732 } else if let Some(sp) = prior_arms.last() {
733 any_multiline_arm |= source_map.is_multiline(*sp);
736 format!("this and all prior arms are found to be of type `{}`", t),
739 let outer = if any_multiline_arm || !source_map.is_multiline(cause.span) {
740 // Cover just `match` and the scrutinee expression, not
741 // the entire match body, to reduce diagram noise.
742 cause.span.shrink_to_lo().to(scrut_span)
746 let msg = "`match` arms have incompatible types";
747 err.span_label(outer, msg);
748 self.suggest_remove_semi_or_return_binding(
757 if let Some(ret_sp) = opt_suggest_box_span {
758 // Get return type span and point to it.
759 self.suggest_boxing_for_return_impl_trait(
762 prior_arms.iter().chain(std::iter::once(&arm_span)).map(|s| *s),
767 ObligationCauseCode::IfExpression(box IfExpressionCause {
773 opt_suggest_box_span,
775 let then_span = self.find_block_span_from_hir_id(then_id);
776 let else_span = self.find_block_span_from_hir_id(else_id);
777 err.span_label(then_span, "expected because of this");
778 if let Some(sp) = outer_span {
779 err.span_label(sp, "`if` and `else` have incompatible types");
781 self.suggest_remove_semi_or_return_binding(
790 if let Some(ret_sp) = opt_suggest_box_span {
791 self.suggest_boxing_for_return_impl_trait(
794 [then_span, else_span].into_iter(),
798 ObligationCauseCode::LetElse => {
799 err.help("try adding a diverging expression, such as `return` or `panic!(..)`");
800 err.help("...or use `match` instead of `let...else`");
803 if let ObligationCauseCode::BindingObligation(_, span)
804 | ObligationCauseCode::ExprBindingObligation(_, span, ..)
805 = cause.code().peel_derives()
806 && let TypeError::RegionsPlaceholderMismatch = terr
808 err.span_note( * span,
809 "the lifetime requirement is introduced here");
815 /// Given that `other_ty` is the same as a type argument for `name` in `sub`, populate `value`
816 /// highlighting `name` and every type argument that isn't at `pos` (which is `other_ty`), and
817 /// populate `other_value` with `other_ty`.
821 /// ^^^^--------^ this is highlighted
823 /// | this type argument is exactly the same as the other type, not highlighted
824 /// this is highlighted
826 /// -------- this type is the same as a type argument in the other type, not highlighted
830 value: &mut DiagnosticStyledString,
831 other_value: &mut DiagnosticStyledString,
833 sub: ty::subst::SubstsRef<'tcx>,
837 // `value` and `other_value` hold two incomplete type representation for display.
838 // `name` is the path of both types being compared. `sub`
839 value.push_highlighted(name);
842 value.push_highlighted("<");
845 // Output the lifetimes for the first type
849 let s = lifetime.to_string();
850 if s.is_empty() { "'_".to_string() } else { s }
854 if !lifetimes.is_empty() {
855 if sub.regions().count() < len {
856 value.push_normal(lifetimes + ", ");
858 value.push_normal(lifetimes);
862 // Highlight all the type arguments that aren't at `pos` and compare the type argument at
863 // `pos` and `other_ty`.
864 for (i, type_arg) in sub.types().enumerate() {
866 let values = self.cmp(type_arg, other_ty);
867 value.0.extend((values.0).0);
868 other_value.0.extend((values.1).0);
870 value.push_highlighted(type_arg.to_string());
873 if len > 0 && i != len - 1 {
874 value.push_normal(", ");
878 value.push_highlighted(">");
882 /// If `other_ty` is the same as a type argument present in `sub`, highlight `path` in `t1_out`,
883 /// as that is the difference to the other type.
885 /// For the following code:
887 /// ```ignore (illustrative)
888 /// let x: Foo<Bar<Qux>> = foo::<Bar<Qux>>();
891 /// The type error output will behave in the following way:
895 /// ^^^^--------^ this is highlighted
897 /// | this type argument is exactly the same as the other type, not highlighted
898 /// this is highlighted
900 /// -------- this type is the same as a type argument in the other type, not highlighted
904 mut t1_out: &mut DiagnosticStyledString,
905 mut t2_out: &mut DiagnosticStyledString,
907 sub: &'tcx [ty::GenericArg<'tcx>],
911 // FIXME/HACK: Go back to `SubstsRef` to use its inherent methods,
912 // ideally that shouldn't be necessary.
913 let sub = self.tcx.intern_substs(sub);
914 for (i, ta) in sub.types().enumerate() {
916 self.highlight_outer(&mut t1_out, &mut t2_out, path, sub, i, other_ty);
919 if let ty::Adt(def, _) = ta.kind() {
920 let path_ = self.tcx.def_path_str(def.did());
921 if path_ == other_path {
922 self.highlight_outer(&mut t1_out, &mut t2_out, path, sub, i, other_ty);
930 /// Adds a `,` to the type representation only if it is appropriate.
933 value: &mut DiagnosticStyledString,
934 other_value: &mut DiagnosticStyledString,
938 if len > 0 && pos != len - 1 {
939 value.push_normal(", ");
940 other_value.push_normal(", ");
944 /// Given two `fn` signatures highlight only sub-parts that are different.
947 sig1: &ty::PolyFnSig<'tcx>,
948 sig2: &ty::PolyFnSig<'tcx>,
949 ) -> (DiagnosticStyledString, DiagnosticStyledString) {
950 let sig1 = &(self.normalize_fn_sig)(*sig1);
951 let sig2 = &(self.normalize_fn_sig)(*sig2);
953 let get_lifetimes = |sig| {
954 use rustc_hir::def::Namespace;
955 let (_, sig, reg) = ty::print::FmtPrinter::new(self.tcx, Namespace::TypeNS)
956 .name_all_regions(sig)
958 let lts: Vec<String> = reg.into_iter().map(|(_, kind)| kind.to_string()).collect();
959 (if lts.is_empty() { String::new() } else { format!("for<{}> ", lts.join(", ")) }, sig)
962 let (lt1, sig1) = get_lifetimes(sig1);
963 let (lt2, sig2) = get_lifetimes(sig2);
965 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
967 DiagnosticStyledString::normal("".to_string()),
968 DiagnosticStyledString::normal("".to_string()),
971 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
973 values.0.push(sig1.unsafety.prefix_str(), sig1.unsafety != sig2.unsafety);
974 values.1.push(sig2.unsafety.prefix_str(), sig1.unsafety != sig2.unsafety);
976 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
978 if sig1.abi != abi::Abi::Rust {
979 values.0.push(format!("extern {} ", sig1.abi), sig1.abi != sig2.abi);
981 if sig2.abi != abi::Abi::Rust {
982 values.1.push(format!("extern {} ", sig2.abi), sig1.abi != sig2.abi);
985 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
987 let lifetime_diff = lt1 != lt2;
988 values.0.push(lt1, lifetime_diff);
989 values.1.push(lt2, lifetime_diff);
991 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
993 values.0.push_normal("fn(");
994 values.1.push_normal("fn(");
996 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
998 let len1 = sig1.inputs().len();
999 let len2 = sig2.inputs().len();
1001 for (i, (l, r)) in iter::zip(sig1.inputs(), sig2.inputs()).enumerate() {
1002 let (x1, x2) = self.cmp(*l, *r);
1003 (values.0).0.extend(x1.0);
1004 (values.1).0.extend(x2.0);
1005 self.push_comma(&mut values.0, &mut values.1, len1, i);
1008 for (i, l) in sig1.inputs().iter().enumerate() {
1009 values.0.push_highlighted(l.to_string());
1011 values.0.push_highlighted(", ");
1014 for (i, r) in sig2.inputs().iter().enumerate() {
1015 values.1.push_highlighted(r.to_string());
1017 values.1.push_highlighted(", ");
1022 if sig1.c_variadic {
1024 values.0.push_normal(", ");
1026 values.0.push("...", !sig2.c_variadic);
1028 if sig2.c_variadic {
1030 values.1.push_normal(", ");
1032 values.1.push("...", !sig1.c_variadic);
1035 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
1037 values.0.push_normal(")");
1038 values.1.push_normal(")");
1040 // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
1042 let output1 = sig1.output();
1043 let output2 = sig2.output();
1044 let (x1, x2) = self.cmp(output1, output2);
1045 if !output1.is_unit() {
1046 values.0.push_normal(" -> ");
1047 (values.0).0.extend(x1.0);
1049 if !output2.is_unit() {
1050 values.1.push_normal(" -> ");
1051 (values.1).0.extend(x2.0);
1056 /// Compares two given types, eliding parts that are the same between them and highlighting
1057 /// relevant differences, and return two representation of those types for highlighted printing.
1062 ) -> (DiagnosticStyledString, DiagnosticStyledString) {
1063 debug!("cmp(t1={}, t1.kind={:?}, t2={}, t2.kind={:?})", t1, t1.kind(), t2, t2.kind());
1066 fn equals<'tcx>(a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
1067 match (a.kind(), b.kind()) {
1068 (a, b) if *a == *b => true,
1069 (&ty::Int(_), &ty::Infer(ty::InferTy::IntVar(_)))
1071 &ty::Infer(ty::InferTy::IntVar(_)),
1072 &ty::Int(_) | &ty::Infer(ty::InferTy::IntVar(_)),
1074 | (&ty::Float(_), &ty::Infer(ty::InferTy::FloatVar(_)))
1076 &ty::Infer(ty::InferTy::FloatVar(_)),
1077 &ty::Float(_) | &ty::Infer(ty::InferTy::FloatVar(_)),
1083 fn push_ty_ref<'tcx>(
1084 region: ty::Region<'tcx>,
1086 mutbl: hir::Mutability,
1087 s: &mut DiagnosticStyledString,
1089 let mut r = region.to_string();
1095 s.push_highlighted(format!("&{}{}", r, mutbl.prefix_str()));
1096 s.push_normal(ty.to_string());
1099 // process starts here
1100 match (t1.kind(), t2.kind()) {
1101 (&ty::Adt(def1, sub1), &ty::Adt(def2, sub2)) => {
1102 let did1 = def1.did();
1103 let did2 = def2.did();
1104 let sub_no_defaults_1 =
1105 self.tcx.generics_of(did1).own_substs_no_defaults(self.tcx, sub1);
1106 let sub_no_defaults_2 =
1107 self.tcx.generics_of(did2).own_substs_no_defaults(self.tcx, sub2);
1108 let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new());
1109 let path1 = self.tcx.def_path_str(did1);
1110 let path2 = self.tcx.def_path_str(did2);
1112 // Easy case. Replace same types with `_` to shorten the output and highlight
1113 // the differing ones.
1114 // let x: Foo<Bar, Qux> = y::<Foo<Quz, Qux>>();
1117 // --- ^ type argument elided
1119 // highlighted in output
1120 values.0.push_normal(path1);
1121 values.1.push_normal(path2);
1123 // Avoid printing out default generic parameters that are common to both
1125 let len1 = sub_no_defaults_1.len();
1126 let len2 = sub_no_defaults_2.len();
1127 let common_len = cmp::min(len1, len2);
1128 let remainder1: Vec<_> = sub1.types().skip(common_len).collect();
1129 let remainder2: Vec<_> = sub2.types().skip(common_len).collect();
1130 let common_default_params =
1131 iter::zip(remainder1.iter().rev(), remainder2.iter().rev())
1132 .filter(|(a, b)| a == b)
1134 let len = sub1.len() - common_default_params;
1135 let consts_offset = len - sub1.consts().count();
1137 // Only draw `<...>` if there are lifetime/type arguments.
1139 values.0.push_normal("<");
1140 values.1.push_normal("<");
1143 fn lifetime_display(lifetime: Region<'_>) -> String {
1144 let s = lifetime.to_string();
1145 if s.is_empty() { "'_".to_string() } else { s }
1147 // At one point we'd like to elide all lifetimes here, they are irrelevant for
1148 // all diagnostics that use this output
1152 // ^^ ^^ --- type arguments are not elided
1154 // | elided as they were the same
1155 // not elided, they were different, but irrelevant
1157 // For bound lifetimes, keep the names of the lifetimes,
1158 // even if they are the same so that it's clear what's happening
1159 // if we have something like
1161 // for<'r, 's> fn(Inv<'r>, Inv<'s>)
1162 // for<'r> fn(Inv<'r>, Inv<'r>)
1163 let lifetimes = sub1.regions().zip(sub2.regions());
1164 for (i, lifetimes) in lifetimes.enumerate() {
1165 let l1 = lifetime_display(lifetimes.0);
1166 let l2 = lifetime_display(lifetimes.1);
1167 if lifetimes.0 != lifetimes.1 {
1168 values.0.push_highlighted(l1);
1169 values.1.push_highlighted(l2);
1170 } else if lifetimes.0.is_late_bound() {
1171 values.0.push_normal(l1);
1172 values.1.push_normal(l2);
1174 values.0.push_normal("'_");
1175 values.1.push_normal("'_");
1177 self.push_comma(&mut values.0, &mut values.1, len, i);
1180 // We're comparing two types with the same path, so we compare the type
1181 // arguments for both. If they are the same, do not highlight and elide from the
1185 // ^ elided type as this type argument was the same in both sides
1186 let type_arguments = sub1.types().zip(sub2.types());
1187 let regions_len = sub1.regions().count();
1188 let num_display_types = consts_offset - regions_len;
1189 for (i, (ta1, ta2)) in type_arguments.take(num_display_types).enumerate() {
1190 let i = i + regions_len;
1191 if ta1 == ta2 && !self.tcx.sess.verbose() {
1192 values.0.push_normal("_");
1193 values.1.push_normal("_");
1195 let (x1, x2) = self.cmp(ta1, ta2);
1196 (values.0).0.extend(x1.0);
1197 (values.1).0.extend(x2.0);
1199 self.push_comma(&mut values.0, &mut values.1, len, i);
1202 // Do the same for const arguments, if they are equal, do not highlight and
1203 // elide them from the output.
1204 let const_arguments = sub1.consts().zip(sub2.consts());
1205 for (i, (ca1, ca2)) in const_arguments.enumerate() {
1206 let i = i + consts_offset;
1207 if ca1 == ca2 && !self.tcx.sess.verbose() {
1208 values.0.push_normal("_");
1209 values.1.push_normal("_");
1211 values.0.push_highlighted(ca1.to_string());
1212 values.1.push_highlighted(ca2.to_string());
1214 self.push_comma(&mut values.0, &mut values.1, len, i);
1217 // Close the type argument bracket.
1218 // Only draw `<...>` if there are lifetime/type arguments.
1220 values.0.push_normal(">");
1221 values.1.push_normal(">");
1226 // let x: Foo<Bar<Qux> = foo::<Bar<Qux>>();
1228 // ------- this type argument is exactly the same as the other type
1244 // let x: Bar<Qux> = y:<Foo<Bar<Qux>>>();
1247 // ------- this type argument is exactly the same as the other type
1262 // We can't find anything in common, highlight relevant part of type path.
1263 // let x: foo::bar::Baz<Qux> = y:<foo::bar::Bar<Zar>>();
1264 // foo::bar::Baz<Qux>
1265 // foo::bar::Bar<Zar>
1266 // -------- this part of the path is different
1268 let t1_str = t1.to_string();
1269 let t2_str = t2.to_string();
1270 let min_len = t1_str.len().min(t2_str.len());
1272 const SEPARATOR: &str = "::";
1273 let separator_len = SEPARATOR.len();
1274 let split_idx: usize =
1275 iter::zip(t1_str.split(SEPARATOR), t2_str.split(SEPARATOR))
1276 .take_while(|(mod1_str, mod2_str)| mod1_str == mod2_str)
1277 .map(|(mod_str, _)| mod_str.len() + separator_len)
1280 debug!(?separator_len, ?split_idx, ?min_len, "cmp");
1282 if split_idx >= min_len {
1283 // paths are identical, highlight everything
1285 DiagnosticStyledString::highlighted(t1_str),
1286 DiagnosticStyledString::highlighted(t2_str),
1289 let (common, uniq1) = t1_str.split_at(split_idx);
1290 let (_, uniq2) = t2_str.split_at(split_idx);
1291 debug!(?common, ?uniq1, ?uniq2, "cmp");
1293 values.0.push_normal(common);
1294 values.0.push_highlighted(uniq1);
1295 values.1.push_normal(common);
1296 values.1.push_highlighted(uniq2);
1303 // When finding T != &T, highlight only the borrow
1304 (&ty::Ref(r1, ref_ty1, mutbl1), _) if equals(ref_ty1, t2) => {
1305 let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new());
1306 push_ty_ref(r1, ref_ty1, mutbl1, &mut values.0);
1307 values.1.push_normal(t2.to_string());
1310 (_, &ty::Ref(r2, ref_ty2, mutbl2)) if equals(t1, ref_ty2) => {
1311 let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new());
1312 values.0.push_normal(t1.to_string());
1313 push_ty_ref(r2, ref_ty2, mutbl2, &mut values.1);
1317 // When encountering &T != &mut T, highlight only the borrow
1318 (&ty::Ref(r1, ref_ty1, mutbl1), &ty::Ref(r2, ref_ty2, mutbl2))
1319 if equals(ref_ty1, ref_ty2) =>
1321 let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new());
1322 push_ty_ref(r1, ref_ty1, mutbl1, &mut values.0);
1323 push_ty_ref(r2, ref_ty2, mutbl2, &mut values.1);
1327 // When encountering tuples of the same size, highlight only the differing types
1328 (&ty::Tuple(substs1), &ty::Tuple(substs2)) if substs1.len() == substs2.len() => {
1330 (DiagnosticStyledString::normal("("), DiagnosticStyledString::normal("("));
1331 let len = substs1.len();
1332 for (i, (left, right)) in substs1.iter().zip(substs2).enumerate() {
1333 let (x1, x2) = self.cmp(left, right);
1334 (values.0).0.extend(x1.0);
1335 (values.1).0.extend(x2.0);
1336 self.push_comma(&mut values.0, &mut values.1, len, i);
1339 // Keep the output for single element tuples as `(ty,)`.
1340 values.0.push_normal(",");
1341 values.1.push_normal(",");
1343 values.0.push_normal(")");
1344 values.1.push_normal(")");
1348 (ty::FnDef(did1, substs1), ty::FnDef(did2, substs2)) => {
1349 let sig1 = self.tcx.fn_sig(*did1).subst(self.tcx, substs1);
1350 let sig2 = self.tcx.fn_sig(*did2).subst(self.tcx, substs2);
1351 let mut values = self.cmp_fn_sig(&sig1, &sig2);
1352 let path1 = format!(" {{{}}}", self.tcx.def_path_str_with_substs(*did1, substs1));
1353 let path2 = format!(" {{{}}}", self.tcx.def_path_str_with_substs(*did2, substs2));
1354 let same_path = path1 == path2;
1355 values.0.push(path1, !same_path);
1356 values.1.push(path2, !same_path);
1360 (ty::FnDef(did1, substs1), ty::FnPtr(sig2)) => {
1361 let sig1 = self.tcx.fn_sig(*did1).subst(self.tcx, substs1);
1362 let mut values = self.cmp_fn_sig(&sig1, sig2);
1363 values.0.push_highlighted(format!(
1365 self.tcx.def_path_str_with_substs(*did1, substs1)
1370 (ty::FnPtr(sig1), ty::FnDef(did2, substs2)) => {
1371 let sig2 = self.tcx.fn_sig(*did2).subst(self.tcx, substs2);
1372 let mut values = self.cmp_fn_sig(sig1, &sig2);
1373 values.1.push_normal(format!(
1375 self.tcx.def_path_str_with_substs(*did2, substs2)
1380 (ty::FnPtr(sig1), ty::FnPtr(sig2)) => self.cmp_fn_sig(sig1, sig2),
1383 if t1 == t2 && !self.tcx.sess.verbose() {
1384 // The two types are the same, elide and don't highlight.
1385 (DiagnosticStyledString::normal("_"), DiagnosticStyledString::normal("_"))
1387 // We couldn't find anything in common, highlight everything.
1389 DiagnosticStyledString::highlighted(t1.to_string()),
1390 DiagnosticStyledString::highlighted(t2.to_string()),
1397 /// Extend a type error with extra labels pointing at "non-trivial" types, like closures and
1398 /// the return type of `async fn`s.
1400 /// `secondary_span` gives the caller the opportunity to expand `diag` with a `span_label`.
1402 /// `swap_secondary_and_primary` is used to make projection errors in particular nicer by using
1403 /// the message in `secondary_span` as the primary label, and apply the message that would
1404 /// otherwise be used for the primary label on the `secondary_span` `Span`. This applies on
1405 /// E0271, like `tests/ui/issues/issue-39970.stderr`.
1408 skip(self, diag, secondary_span, swap_secondary_and_primary, prefer_label)
1410 pub fn note_type_err(
1412 diag: &mut Diagnostic,
1413 cause: &ObligationCause<'tcx>,
1414 secondary_span: Option<(Span, String)>,
1415 mut values: Option<ValuePairs<'tcx>>,
1416 terr: TypeError<'tcx>,
1417 swap_secondary_and_primary: bool,
1420 let span = cause.span();
1422 // For some types of errors, expected-found does not make
1423 // sense, so just ignore the values we were given.
1424 if let TypeError::CyclicTy(_) = terr {
1427 struct OpaqueTypesVisitor<'tcx> {
1428 types: FxIndexMap<TyCategory, FxIndexSet<Span>>,
1429 expected: FxIndexMap<TyCategory, FxIndexSet<Span>>,
1430 found: FxIndexMap<TyCategory, FxIndexSet<Span>>,
1435 impl<'tcx> OpaqueTypesVisitor<'tcx> {
1436 fn visit_expected_found(
1438 expected: impl TypeVisitable<'tcx>,
1439 found: impl TypeVisitable<'tcx>,
1442 let mut types_visitor = OpaqueTypesVisitor {
1443 types: Default::default(),
1444 expected: Default::default(),
1445 found: Default::default(),
1449 // The visitor puts all the relevant encountered types in `self.types`, but in
1450 // here we want to visit two separate types with no relation to each other, so we
1451 // move the results from `types` to `expected` or `found` as appropriate.
1452 expected.visit_with(&mut types_visitor);
1453 std::mem::swap(&mut types_visitor.expected, &mut types_visitor.types);
1454 found.visit_with(&mut types_visitor);
1455 std::mem::swap(&mut types_visitor.found, &mut types_visitor.types);
1459 fn report(&self, err: &mut Diagnostic) {
1460 self.add_labels_for_types(err, "expected", &self.expected);
1461 self.add_labels_for_types(err, "found", &self.found);
1464 fn add_labels_for_types(
1466 err: &mut Diagnostic,
1468 types: &FxIndexMap<TyCategory, FxIndexSet<Span>>,
1470 for (key, values) in types.iter() {
1471 let count = values.len();
1472 let kind = key.descr();
1478 if count == 1 { "the " } else { "one of the " },
1489 impl<'tcx> ty::visit::TypeVisitor<'tcx> for OpaqueTypesVisitor<'tcx> {
1490 fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
1491 if let Some((kind, def_id)) = TyCategory::from_ty(self.tcx, t) {
1492 let span = self.tcx.def_span(def_id);
1493 // Avoid cluttering the output when the "found" and error span overlap:
1495 // error[E0308]: mismatched types
1496 // --> $DIR/issue-20862.rs:2:5
1501 // | the found closure
1502 // | expected `()`, found closure
1504 // = note: expected unit type `()`
1505 // found closure `[closure@$DIR/issue-20862.rs:2:5: 2:14 x:_]`
1507 // Also ignore opaque `Future`s that come from async fns.
1508 if !self.ignore_span.overlaps(span)
1509 && !span.is_desugaring(DesugaringKind::Async)
1511 self.types.entry(kind).or_default().insert(span);
1514 t.super_visit_with(self)
1518 debug!("note_type_err(diag={:?})", diag);
1520 Variable(ty::error::ExpectedFound<Ty<'a>>),
1521 Fixed(&'static str),
1523 let (expected_found, exp_found, is_simple_error, values) = match values {
1524 None => (None, Mismatch::Fixed("type"), false, None),
1526 let values = self.resolve_vars_if_possible(values);
1527 let (is_simple_error, exp_found) = match values {
1528 ValuePairs::Terms(infer::ExpectedFound { expected, found }) => {
1529 match (expected.unpack(), found.unpack()) {
1530 (ty::TermKind::Ty(expected), ty::TermKind::Ty(found)) => {
1532 expected.is_simple_text() && found.is_simple_text();
1533 OpaqueTypesVisitor::visit_expected_found(
1534 self.tcx, expected, found, span,
1540 Mismatch::Variable(infer::ExpectedFound { expected, found }),
1543 (ty::TermKind::Const(_), ty::TermKind::Const(_)) => {
1544 (false, Mismatch::Fixed("constant"))
1546 _ => (false, Mismatch::Fixed("type")),
1549 ValuePairs::Sigs(infer::ExpectedFound { expected, found }) => {
1550 OpaqueTypesVisitor::visit_expected_found(self.tcx, expected, found, span)
1552 (false, Mismatch::Fixed("signature"))
1554 ValuePairs::TraitRefs(_) | ValuePairs::PolyTraitRefs(_) => {
1555 (false, Mismatch::Fixed("trait"))
1557 ValuePairs::Regions(_) => (false, Mismatch::Fixed("lifetime")),
1559 let Some(vals) = self.values_str(values) else {
1560 // Derived error. Cancel the emitter.
1561 // NOTE(eddyb) this was `.cancel()`, but `diag`
1562 // is borrowed, so we can't fully defuse it.
1563 diag.downgrade_to_delayed_bug();
1566 (Some(vals), exp_found, is_simple_error, Some(values))
1570 let mut label_or_note = |span: Span, msg: &str| {
1571 if (prefer_label && is_simple_error) || &[span] == diag.span.primary_spans() {
1572 diag.span_label(span, msg);
1574 diag.span_note(span, msg);
1577 if let Some((sp, msg)) = secondary_span {
1578 if swap_secondary_and_primary {
1579 let terr = if let Some(infer::ValuePairs::Terms(infer::ExpectedFound {
1584 format!("expected this to be `{}`", expected)
1586 terr.to_string(self.tcx).to_string()
1588 label_or_note(sp, &terr);
1589 label_or_note(span, &msg);
1591 label_or_note(span, &terr.to_string(self.tcx));
1592 label_or_note(sp, &msg);
1595 if let Some(values) = values
1596 && let Some((e, f)) = values.ty()
1597 && let TypeError::ArgumentSorts(..) | TypeError::Sorts(_) = terr
1599 let e = self.tcx.erase_regions(e);
1600 let f = self.tcx.erase_regions(f);
1601 let expected = with_forced_trimmed_paths!(e.sort_string(self.tcx));
1602 let found = with_forced_trimmed_paths!(f.sort_string(self.tcx));
1603 if expected == found {
1604 label_or_note(span, &terr.to_string(self.tcx));
1606 label_or_note(span, &format!("expected {expected}, found {found}"));
1609 label_or_note(span, &terr.to_string(self.tcx));
1613 if let Some((expected, found, exp_p, found_p)) = expected_found {
1614 let (expected_label, found_label, exp_found) = match exp_found {
1615 Mismatch::Variable(ef) => (
1616 ef.expected.prefix_string(self.tcx),
1617 ef.found.prefix_string(self.tcx),
1620 Mismatch::Fixed(s) => (s.into(), s.into(), None),
1623 enum Similar<'tcx> {
1624 Adts { expected: ty::AdtDef<'tcx>, found: ty::AdtDef<'tcx> },
1625 PrimitiveFound { expected: ty::AdtDef<'tcx>, found: Ty<'tcx> },
1626 PrimitiveExpected { expected: Ty<'tcx>, found: ty::AdtDef<'tcx> },
1629 let similarity = |ExpectedFound { expected, found }: ExpectedFound<Ty<'tcx>>| {
1630 if let ty::Adt(expected, _) = expected.kind() && let Some(primitive) = found.primitive_symbol() {
1631 let path = self.tcx.def_path(expected.did()).data;
1632 let name = path.last().unwrap().data.get_opt_name();
1633 if name == Some(primitive) {
1634 return Some(Similar::PrimitiveFound { expected: *expected, found });
1636 } else if let Some(primitive) = expected.primitive_symbol() && let ty::Adt(found, _) = found.kind() {
1637 let path = self.tcx.def_path(found.did()).data;
1638 let name = path.last().unwrap().data.get_opt_name();
1639 if name == Some(primitive) {
1640 return Some(Similar::PrimitiveExpected { expected, found: *found });
1642 } else if let ty::Adt(expected, _) = expected.kind() && let ty::Adt(found, _) = found.kind() {
1643 if !expected.did().is_local() && expected.did().krate == found.did().krate {
1644 // Most likely types from different versions of the same crate
1645 // are in play, in which case this message isn't so helpful.
1646 // A "perhaps two different versions..." error is already emitted for that.
1649 let f_path = self.tcx.def_path(found.did()).data;
1650 let e_path = self.tcx.def_path(expected.did()).data;
1652 if let (Some(e_last), Some(f_last)) = (e_path.last(), f_path.last()) && e_last == f_last {
1653 return Some(Similar::Adts{expected: *expected, found: *found});
1660 // If two types mismatch but have similar names, mention that specifically.
1661 TypeError::Sorts(values) if let Some(s) = similarity(values) => {
1662 let diagnose_primitive =
1666 diagnostic: &mut Diagnostic| {
1667 let name = shadow.sort_string(self.tcx);
1668 diagnostic.note(format!(
1669 "{prim} and {name} have similar names, but are actually distinct types"
1672 .note(format!("{prim} is a primitive defined by the language"));
1673 let def_span = self.tcx.def_span(defid);
1674 let msg = if defid.is_local() {
1675 format!("{name} is defined in the current crate")
1677 let crate_name = self.tcx.crate_name(defid.krate);
1678 format!("{name} is defined in crate `{crate_name}")
1680 diagnostic.span_note(def_span, msg);
1684 |expected_adt : ty::AdtDef<'tcx>,
1685 found_adt: ty::AdtDef<'tcx>,
1686 diagnostic: &mut Diagnostic| {
1687 let found_name = values.found.sort_string(self.tcx);
1688 let expected_name = values.expected.sort_string(self.tcx);
1690 let found_defid = found_adt.did();
1691 let expected_defid = expected_adt.did();
1693 diagnostic.note(format!("{found_name} and {expected_name} have similar names, but are actually distinct types"));
1694 for (defid, name) in
1695 [(found_defid, found_name), (expected_defid, expected_name)]
1697 let def_span = self.tcx.def_span(defid);
1699 let msg = if found_defid.is_local() && expected_defid.is_local() {
1702 .parent_module_from_def_id(defid.expect_local())
1704 let module_name = self.tcx.def_path(module).to_string_no_crate_verbose();
1705 format!("{name} is defined in module `crate{module_name}` of the current crate")
1706 } else if defid.is_local() {
1707 format!("{name} is defined in the current crate")
1709 let crate_name = self.tcx.crate_name(defid.krate);
1710 format!("{name} is defined in crate `{crate_name}`")
1712 diagnostic.span_note(def_span, msg);
1717 Similar::Adts{expected, found} => {
1718 diagnose_adts(expected, found, diag)
1720 Similar::PrimitiveFound{expected, found: prim} => {
1721 diagnose_primitive(prim, values.expected, expected.did(), diag)
1723 Similar::PrimitiveExpected{expected: prim, found} => {
1724 diagnose_primitive(prim, values.found, found.did(), diag)
1728 TypeError::Sorts(values) => {
1729 let extra = expected == found;
1730 let sort_string = |ty: Ty<'tcx>, path: Option<PathBuf>| {
1731 let mut s = match (extra, ty.kind()) {
1732 (true, ty::Alias(ty::Opaque, ty::AliasTy { def_id, .. })) => {
1733 let sm = self.tcx.sess.source_map();
1734 let pos = sm.lookup_char_pos(self.tcx.def_span(*def_id).lo());
1736 " (opaque type at <{}:{}:{}>)",
1737 sm.filename_for_diagnostics(&pos.file.name),
1739 pos.col.to_usize() + 1,
1742 (true, ty::Alias(ty::Projection, proj))
1743 if self.tcx.def_kind(proj.def_id)
1744 == DefKind::ImplTraitPlaceholder =>
1746 let sm = self.tcx.sess.source_map();
1747 let pos = sm.lookup_char_pos(self.tcx.def_span(proj.def_id).lo());
1749 " (trait associated opaque type at <{}:{}:{}>)",
1750 sm.filename_for_diagnostics(&pos.file.name),
1752 pos.col.to_usize() + 1,
1755 (true, _) => format!(" ({})", ty.sort_string(self.tcx)),
1756 (false, _) => "".to_string(),
1758 if let Some(path) = path {
1759 s.push_str(&format!(
1760 "\nthe full type name has been written to '{}'",
1766 if !(values.expected.is_simple_text() && values.found.is_simple_text())
1767 || (exp_found.map_or(false, |ef| {
1768 // This happens when the type error is a subset of the expectation,
1769 // like when you have two references but one is `usize` and the other
1770 // is `f32`. In those cases we still want to show the `note`. If the
1771 // value from `ef` is `Infer(_)`, then we ignore it.
1772 if !ef.expected.is_ty_or_numeric_infer() {
1773 ef.expected != values.expected
1774 } else if !ef.found.is_ty_or_numeric_infer() {
1775 ef.found != values.found
1781 diag.note_expected_found_extra(
1786 &sort_string(values.expected, exp_p),
1787 &sort_string(values.found, found_p),
1793 "note_type_err: exp_found={:?}, expected={:?} found={:?}",
1794 exp_found, expected, found
1796 if !is_simple_error || terr.must_include_note() {
1797 diag.note_expected_found(&expected_label, expected, &found_label, found);
1802 let exp_found = match exp_found {
1803 Mismatch::Variable(exp_found) => Some(exp_found),
1804 Mismatch::Fixed(_) => None,
1806 let exp_found = match terr {
1807 // `terr` has more accurate type information than `exp_found` in match expressions.
1808 ty::error::TypeError::Sorts(terr)
1809 if exp_found.map_or(false, |ef| terr.found == ef.found) =>
1815 debug!("exp_found {:?} terr {:?} cause.code {:?}", exp_found, terr, cause.code());
1816 if let Some(exp_found) = exp_found {
1817 let should_suggest_fixes =
1818 if let ObligationCauseCode::Pattern { root_ty, .. } = cause.code() {
1819 // Skip if the root_ty of the pattern is not the same as the expected_ty.
1820 // If these types aren't equal then we've probably peeled off a layer of arrays.
1821 self.same_type_modulo_infer(*root_ty, exp_found.expected)
1826 if should_suggest_fixes {
1827 self.suggest_tuple_pattern(cause, &exp_found, diag);
1828 self.suggest_as_ref_where_appropriate(span, &exp_found, diag);
1829 self.suggest_accessing_field_where_appropriate(cause, &exp_found, diag);
1830 self.suggest_await_on_expect_found(cause, span, &exp_found, diag);
1831 self.suggest_function_pointers(cause, span, &exp_found, diag);
1835 self.check_and_note_conflicting_crates(diag, terr);
1837 self.note_and_explain_type_err(diag, terr, cause, span, cause.body_id.to_def_id());
1838 if let Some(exp_found) = exp_found
1839 && let exp_found = TypeError::Sorts(exp_found)
1840 && exp_found != terr
1842 self.note_and_explain_type_err(
1847 cause.body_id.to_def_id(),
1851 if let Some(ValuePairs::PolyTraitRefs(exp_found)) = values
1852 && let ty::Closure(def_id, _) = exp_found.expected.skip_binder().self_ty().kind()
1853 && let Some(def_id) = def_id.as_local()
1854 && terr.involves_regions()
1856 let span = self.tcx.def_span(def_id);
1857 diag.span_note(span, "this closure does not fulfill the lifetime requirements");
1860 // It reads better to have the error origin as the final
1862 self.note_error_origin(diag, cause, exp_found, terr);
1867 pub fn report_and_explain_type_error(
1869 trace: TypeTrace<'tcx>,
1870 terr: TypeError<'tcx>,
1871 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
1872 use crate::traits::ObligationCauseCode::MatchExpressionArm;
1874 debug!("report_and_explain_type_error(trace={:?}, terr={:?})", trace, terr);
1876 let span = trace.cause.span();
1877 let failure_code = trace.cause.as_failure_code(terr);
1878 let mut diag = match failure_code {
1879 FailureCode::Error0038(did) => {
1880 let violations = self.tcx.object_safety_violations(did);
1881 report_object_safety_error(self.tcx, span, did, violations)
1883 FailureCode::Error0317(failure_str) => {
1884 struct_span_err!(self.tcx.sess, span, E0317, "{}", failure_str)
1886 FailureCode::Error0580(failure_str) => {
1887 struct_span_err!(self.tcx.sess, span, E0580, "{}", failure_str)
1889 FailureCode::Error0308(failure_str) => {
1890 fn escape_literal(s: &str) -> String {
1891 let mut escaped = String::with_capacity(s.len());
1892 let mut chrs = s.chars().peekable();
1893 while let Some(first) = chrs.next() {
1894 match (first, chrs.peek()) {
1895 ('\\', Some(&delim @ '"') | Some(&delim @ '\'')) => {
1897 escaped.push(delim);
1900 ('"' | '\'', _) => {
1904 (c, _) => escaped.push(c),
1909 let mut err = struct_span_err!(self.tcx.sess, span, E0308, "{}", failure_str);
1910 if let Some((expected, found)) = trace.values.ty() {
1911 match (expected.kind(), found.kind()) {
1912 (ty::Tuple(_), ty::Tuple(_)) => {}
1913 // If a tuple of length one was expected and the found expression has
1914 // parentheses around it, perhaps the user meant to write `(expr,)` to
1915 // build a tuple (issue #86100)
1916 (ty::Tuple(fields), _) => {
1917 self.emit_tuple_wrap_err(&mut err, span, found, fields)
1919 // If a byte was expected and the found expression is a char literal
1920 // containing a single ASCII character, perhaps the user meant to write `b'c'` to
1921 // specify a byte literal
1922 (ty::Uint(ty::UintTy::U8), ty::Char) => {
1923 if let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span)
1924 && let Some(code) = code.strip_prefix('\'').and_then(|s| s.strip_suffix('\''))
1925 && code.chars().next().map_or(false, |c| c.is_ascii())
1927 err.span_suggestion(
1929 "if you meant to write a byte literal, prefix with `b`",
1930 format!("b'{}'", escape_literal(code)),
1931 Applicability::MachineApplicable,
1935 // If a character was expected and the found expression is a string literal
1936 // containing a single character, perhaps the user meant to write `'c'` to
1937 // specify a character literal (issue #92479)
1938 (ty::Char, ty::Ref(_, r, _)) if r.is_str() => {
1939 if let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span)
1940 && let Some(code) = code.strip_prefix('"').and_then(|s| s.strip_suffix('"'))
1941 && code.chars().count() == 1
1943 err.span_suggestion(
1945 "if you meant to write a `char` literal, use single quotes",
1946 format!("'{}'", escape_literal(code)),
1947 Applicability::MachineApplicable,
1951 // If a string was expected and the found expression is a character literal,
1952 // perhaps the user meant to write `"s"` to specify a string literal.
1953 (ty::Ref(_, r, _), ty::Char) if r.is_str() => {
1954 if let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span) {
1956 code.strip_prefix('\'').and_then(|s| s.strip_suffix('\''))
1958 err.span_suggestion(
1960 "if you meant to write a `str` literal, use double quotes",
1961 format!("\"{}\"", escape_literal(code)),
1962 Applicability::MachineApplicable,
1967 // For code `if Some(..) = expr `, the type mismatch may be expected `bool` but found `()`,
1968 // we try to suggest to add the missing `let` for `if let Some(..) = expr`
1969 (ty::Bool, ty::Tuple(list)) => if list.len() == 0 {
1970 self.suggest_let_for_letchains(&mut err, &trace.cause, span);
1975 let code = trace.cause.code();
1976 if let &MatchExpressionArm(box MatchExpressionArmCause { source, .. }) = code
1977 && let hir::MatchSource::TryDesugar = source
1978 && let Some((expected_ty, found_ty, _, _)) = self.values_str(trace.values)
1981 "`?` operator cannot convert from `{}` to `{}`",
1983 expected_ty.content(),
1988 FailureCode::Error0644(failure_str) => {
1989 struct_span_err!(self.tcx.sess, span, E0644, "{}", failure_str)
1992 self.note_type_err(&mut diag, &trace.cause, None, Some(trace.values), terr, false, false);
1996 fn emit_tuple_wrap_err(
1998 err: &mut Diagnostic,
2001 expected_fields: &List<Ty<'tcx>>,
2003 let [expected_tup_elem] = expected_fields[..] else { return };
2005 if !self.same_type_modulo_infer(expected_tup_elem, found) {
2009 let Ok(code) = self.tcx.sess().source_map().span_to_snippet(span)
2012 let msg = "use a trailing comma to create a tuple with one element";
2013 if code.starts_with('(') && code.ends_with(')') {
2014 let before_close = span.hi() - BytePos::from_u32(1);
2015 err.span_suggestion(
2016 span.with_hi(before_close).shrink_to_hi(),
2019 Applicability::MachineApplicable,
2022 err.multipart_suggestion(
2024 vec![(span.shrink_to_lo(), "(".into()), (span.shrink_to_hi(), ",)".into())],
2025 Applicability::MachineApplicable,
2032 values: ValuePairs<'tcx>,
2033 ) -> Option<(DiagnosticStyledString, DiagnosticStyledString, Option<PathBuf>, Option<PathBuf>)>
2036 infer::Regions(exp_found) => self.expected_found_str(exp_found),
2037 infer::Terms(exp_found) => self.expected_found_str_term(exp_found),
2038 infer::TraitRefs(exp_found) => {
2039 let pretty_exp_found = ty::error::ExpectedFound {
2040 expected: exp_found.expected.print_only_trait_path(),
2041 found: exp_found.found.print_only_trait_path(),
2043 match self.expected_found_str(pretty_exp_found) {
2044 Some((expected, found, _, _)) if expected == found => {
2045 self.expected_found_str(exp_found)
2050 infer::PolyTraitRefs(exp_found) => {
2051 let pretty_exp_found = ty::error::ExpectedFound {
2052 expected: exp_found.expected.print_only_trait_path(),
2053 found: exp_found.found.print_only_trait_path(),
2055 match self.expected_found_str(pretty_exp_found) {
2056 Some((expected, found, _, _)) if expected == found => {
2057 self.expected_found_str(exp_found)
2062 infer::Sigs(exp_found) => {
2063 let exp_found = self.resolve_vars_if_possible(exp_found);
2064 if exp_found.references_error() {
2067 let (exp, fnd) = self.cmp_fn_sig(
2068 &ty::Binder::dummy(exp_found.expected),
2069 &ty::Binder::dummy(exp_found.found),
2071 Some((exp, fnd, None, None))
2076 fn expected_found_str_term(
2078 exp_found: ty::error::ExpectedFound<ty::Term<'tcx>>,
2079 ) -> Option<(DiagnosticStyledString, DiagnosticStyledString, Option<PathBuf>, Option<PathBuf>)>
2081 let exp_found = self.resolve_vars_if_possible(exp_found);
2082 if exp_found.references_error() {
2086 Some(match (exp_found.expected.unpack(), exp_found.found.unpack()) {
2087 (ty::TermKind::Ty(expected), ty::TermKind::Ty(found)) => {
2088 let (mut exp, mut fnd) = self.cmp(expected, found);
2089 // Use the terminal width as the basis to determine when to compress the printed
2090 // out type, but give ourselves some leeway to avoid ending up creating a file for
2091 // a type that is somewhat shorter than the path we'd write to.
2092 let len = self.tcx.sess().diagnostic_width() + 40;
2093 let exp_s = exp.content();
2094 let fnd_s = fnd.content();
2095 let mut exp_p = None;
2096 let mut fnd_p = None;
2097 if exp_s.len() > len {
2098 let (exp_s, exp_path) = self.tcx.short_ty_string(expected);
2099 exp = DiagnosticStyledString::highlighted(exp_s);
2102 if fnd_s.len() > len {
2103 let (fnd_s, fnd_path) = self.tcx.short_ty_string(found);
2104 fnd = DiagnosticStyledString::highlighted(fnd_s);
2107 (exp, fnd, exp_p, fnd_p)
2110 DiagnosticStyledString::highlighted(exp_found.expected.to_string()),
2111 DiagnosticStyledString::highlighted(exp_found.found.to_string()),
2118 /// Returns a string of the form "expected `{}`, found `{}`".
2119 fn expected_found_str<T: fmt::Display + TypeFoldable<'tcx>>(
2121 exp_found: ty::error::ExpectedFound<T>,
2122 ) -> Option<(DiagnosticStyledString, DiagnosticStyledString, Option<PathBuf>, Option<PathBuf>)>
2124 let exp_found = self.resolve_vars_if_possible(exp_found);
2125 if exp_found.references_error() {
2130 DiagnosticStyledString::highlighted(exp_found.expected.to_string()),
2131 DiagnosticStyledString::highlighted(exp_found.found.to_string()),
2137 pub fn report_generic_bound_failure(
2139 generic_param_scope: LocalDefId,
2141 origin: Option<SubregionOrigin<'tcx>>,
2142 bound_kind: GenericKind<'tcx>,
2145 self.construct_generic_bound_failure(generic_param_scope, span, origin, bound_kind, sub)
2149 pub fn construct_generic_bound_failure(
2151 generic_param_scope: LocalDefId,
2153 origin: Option<SubregionOrigin<'tcx>>,
2154 bound_kind: GenericKind<'tcx>,
2156 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
2157 // Attempt to obtain the span of the parameter so we can
2158 // suggest adding an explicit lifetime bound to it.
2159 let generics = self.tcx.generics_of(generic_param_scope);
2160 // type_param_span is (span, has_bounds)
2161 let mut is_synthetic = false;
2162 let mut ast_generics = None;
2163 let type_param_span = match bound_kind {
2164 GenericKind::Param(ref param) => {
2165 // Account for the case where `param` corresponds to `Self`,
2166 // which doesn't have the expected type argument.
2167 if !(generics.has_self && param.index == 0) {
2168 let type_param = generics.type_param(param, self.tcx);
2169 is_synthetic = type_param.kind.is_synthetic();
2170 type_param.def_id.as_local().map(|def_id| {
2171 // Get the `hir::Param` to verify whether it already has any bounds.
2172 // We do this to avoid suggesting code that ends up as `T: 'a'b`,
2173 // instead we suggest `T: 'a + 'b` in that case.
2174 let hir_id = self.tcx.hir().local_def_id_to_hir_id(def_id);
2175 ast_generics = self.tcx.hir().get_generics(hir_id.owner.def_id);
2177 ast_generics.and_then(|g| g.bounds_span_for_suggestions(def_id));
2178 // `sp` only covers `T`, change it so that it covers
2179 // `T:` when appropriate
2180 if let Some(span) = bounds {
2183 let sp = self.tcx.def_span(def_id);
2184 (sp.shrink_to_hi(), false)
2195 let mut possible = (b'a'..=b'z').map(|c| format!("'{}", c as char));
2197 iter::successors(Some(generics), |g| g.parent.map(|p| self.tcx.generics_of(p)))
2198 .flat_map(|g| &g.params)
2199 .filter(|p| matches!(p.kind, ty::GenericParamDefKind::Lifetime))
2200 .map(|p| p.name.as_str())
2201 .collect::<Vec<_>>();
2203 .find(|candidate| !lts_names.contains(&&candidate[..]))
2204 .unwrap_or("'lt".to_string())
2207 let mut add_lt_suggs: Vec<Option<_>> = vec![];
2209 if let Some(ast_generics) = ast_generics {
2210 let named_lifetime_param_exist = ast_generics.params.iter().any(|p| {
2213 hir::GenericParamKind::Lifetime { kind: hir::LifetimeParamKind::Explicit }
2216 if named_lifetime_param_exist && let [param, ..] = ast_generics.params
2218 add_lt_suggs.push(Some((
2219 self.tcx.def_span(param.def_id).shrink_to_lo(),
2220 format!("{new_lt}, "),
2224 .push(Some((ast_generics.span.shrink_to_hi(), format!("<{new_lt}>"))));
2228 if let [param, ..] = &generics.params[..] && let Some(def_id) = param.def_id.as_local()
2231 .push(Some((self.tcx.def_span(def_id).shrink_to_lo(), format!("{new_lt}, "))));
2235 if let Some(ast_generics) = ast_generics {
2236 for p in ast_generics.params {
2237 if p.is_elided_lifetime() {
2242 .span_to_prev_source(p.span.shrink_to_hi())
2244 .map_or(false, |s| *s.as_bytes().last().unwrap() == b'&')
2249 p.span.shrink_to_hi(),
2250 if let Ok(snip) = self.tcx.sess.source_map().span_to_next_source(p.span)
2251 && snip.starts_with(' ')
2255 format!("{new_lt} ")
2260 add_lt_suggs.push(Some((p.span.shrink_to_hi(), format!("<{new_lt}>"))));
2266 let labeled_user_string = match bound_kind {
2267 GenericKind::Param(ref p) => format!("the parameter type `{}`", p),
2268 GenericKind::Alias(ref p) => match p.kind(self.tcx) {
2269 ty::AliasKind::Projection => format!("the associated type `{}`", p),
2270 ty::AliasKind::Opaque => format!("the opaque type `{}`", p),
2274 if let Some(SubregionOrigin::CompareImplItemObligation {
2280 return self.report_extra_impl_obligation(
2284 &format!("`{}: {}`", bound_kind, sub),
2288 fn binding_suggestion<'tcx, S: fmt::Display>(
2289 err: &mut Diagnostic,
2290 type_param_span: Option<(Span, bool)>,
2291 bound_kind: GenericKind<'tcx>,
2293 add_lt_suggs: Vec<Option<(Span, String)>>,
2295 let msg = "consider adding an explicit lifetime bound";
2296 if let Some((sp, has_lifetimes)) = type_param_span {
2298 if has_lifetimes { format!(" + {}", sub) } else { format!(": {}", sub) };
2299 let mut suggestions = vec![(sp, suggestion)];
2300 for add_lt_sugg in add_lt_suggs {
2301 if let Some(add_lt_sugg) = add_lt_sugg {
2302 suggestions.push(add_lt_sugg);
2305 err.multipart_suggestion_verbose(
2306 format!("{msg}..."),
2308 Applicability::MaybeIncorrect, // Issue #41966
2311 let consider = format!("{} `{}: {}`...", msg, bound_kind, sub);
2312 err.help(&consider);
2316 let new_binding_suggestion =
2317 |err: &mut Diagnostic, type_param_span: Option<(Span, bool)>| {
2318 let msg = "consider introducing an explicit lifetime bound";
2319 if let Some((sp, has_lifetimes)) = type_param_span {
2320 let suggestion = if has_lifetimes {
2321 format!(" + {}", new_lt)
2323 format!(": {}", new_lt)
2326 vec![(sp, suggestion), (span.shrink_to_hi(), format!(" + {}", new_lt))];
2327 for add_lt_sugg in add_lt_suggs.clone() {
2328 if let Some(lt) = add_lt_sugg {
2330 sugg.rotate_right(1);
2333 // `MaybeIncorrect` due to issue #41966.
2334 err.multipart_suggestion(msg, sugg, Applicability::MaybeIncorrect);
2339 enum SubOrigin<'hir> {
2340 GAT(&'hir hir::Generics<'hir>),
2346 let sub_origin = 'origin: {
2348 ty::ReEarlyBound(ty::EarlyBoundRegion { def_id, .. }) => {
2349 let node = self.tcx.hir().get_if_local(def_id).unwrap();
2351 Node::GenericParam(param) => {
2352 for h in self.tcx.hir().parent_iter(param.hir_id) {
2353 break 'origin match h.1 {
2354 Node::ImplItem(hir::ImplItem {
2355 kind: hir::ImplItemKind::Type(..),
2359 | Node::TraitItem(hir::TraitItem {
2360 kind: hir::TraitItemKind::Type(..),
2363 }) => SubOrigin::GAT(generics),
2364 Node::ImplItem(hir::ImplItem {
2365 kind: hir::ImplItemKind::Fn(..),
2368 | Node::TraitItem(hir::TraitItem {
2369 kind: hir::TraitItemKind::Fn(..),
2372 | Node::Item(hir::Item {
2373 kind: hir::ItemKind::Fn(..), ..
2374 }) => SubOrigin::Fn,
2375 Node::Item(hir::Item {
2376 kind: hir::ItemKind::Trait(..),
2378 }) => SubOrigin::Trait,
2379 Node::Item(hir::Item {
2380 kind: hir::ItemKind::Impl(..), ..
2381 }) => SubOrigin::Impl,
2393 debug!(?sub_origin);
2395 let mut err = match (*sub, sub_origin) {
2396 // In the case of GATs, we have to be careful. If we a type parameter `T` on an impl,
2397 // but a lifetime `'a` on an associated type, then we might need to suggest adding
2398 // `where T: 'a`. Importantly, this is on the GAT span, not on the `T` declaration.
2399 (ty::ReEarlyBound(ty::EarlyBoundRegion { name: _, .. }), SubOrigin::GAT(generics)) => {
2400 // Does the required lifetime have a nice name we can print?
2401 let mut err = struct_span_err!(
2405 "{} may not live long enough",
2408 let pred = format!("{}: {}", bound_kind, sub);
2409 let suggestion = format!("{} {}", generics.add_where_or_trailing_comma(), pred,);
2410 err.span_suggestion(
2411 generics.tail_span_for_predicate_suggestion(),
2412 "consider adding a where clause",
2414 Applicability::MaybeIncorrect,
2419 ty::ReEarlyBound(ty::EarlyBoundRegion { name, .. })
2420 | ty::ReFree(ty::FreeRegion { bound_region: ty::BrNamed(_, name), .. }),
2422 ) if name != kw::UnderscoreLifetime => {
2423 // Does the required lifetime have a nice name we can print?
2424 let mut err = struct_span_err!(
2428 "{} may not live long enough",
2431 // Explicitly use the name instead of `sub`'s `Display` impl. The `Display` impl
2432 // for the bound is not suitable for suggestions when `-Zverbose` is set because it
2433 // uses `Debug` output, so we handle it specially here so that suggestions are
2435 binding_suggestion(&mut err, type_param_span, bound_kind, name, vec![]);
2439 (ty::ReStatic, _) => {
2440 // Does the required lifetime have a nice name we can print?
2441 let mut err = struct_span_err!(
2445 "{} may not live long enough",
2448 binding_suggestion(&mut err, type_param_span, bound_kind, "'static", vec![]);
2453 // If not, be less specific.
2454 let mut err = struct_span_err!(
2458 "{} may not live long enough",
2461 note_and_explain_region(
2464 &format!("{} must be valid for ", labeled_user_string),
2469 if let Some(infer::RelateParamBound(_, t, _)) = origin {
2470 let return_impl_trait =
2471 self.tcx.return_type_impl_trait(generic_param_scope).is_some();
2472 let t = self.resolve_vars_if_possible(t);
2475 // fn get_later<G, T>(g: G, dest: &mut T) -> impl FnOnce() + '_
2477 // fn get_later<'a, G: 'a, T>(g: G, dest: &mut T) -> impl FnOnce() + '_ + 'a
2478 ty::Closure(..) | ty::Alias(ty::Opaque, ..) if return_impl_trait => {
2479 new_binding_suggestion(&mut err, type_param_span);
2496 if let Some(origin) = origin {
2497 self.note_region_origin(&mut err, &origin);
2502 fn report_sub_sup_conflict(
2504 var_origin: RegionVariableOrigin,
2505 sub_origin: SubregionOrigin<'tcx>,
2506 sub_region: Region<'tcx>,
2507 sup_origin: SubregionOrigin<'tcx>,
2508 sup_region: Region<'tcx>,
2510 let mut err = self.report_inference_failure(var_origin);
2512 note_and_explain_region(
2515 "first, the lifetime cannot outlive ",
2521 debug!("report_sub_sup_conflict: var_origin={:?}", var_origin);
2522 debug!("report_sub_sup_conflict: sub_region={:?}", sub_region);
2523 debug!("report_sub_sup_conflict: sub_origin={:?}", sub_origin);
2524 debug!("report_sub_sup_conflict: sup_region={:?}", sup_region);
2525 debug!("report_sub_sup_conflict: sup_origin={:?}", sup_origin);
2527 if let infer::Subtype(ref sup_trace) = sup_origin
2528 && let infer::Subtype(ref sub_trace) = sub_origin
2529 && let Some((sup_expected, sup_found, _, _)) = self.values_str(sup_trace.values)
2530 && let Some((sub_expected, sub_found, _, _)) = self.values_str(sub_trace.values)
2531 && sub_expected == sup_expected
2532 && sub_found == sup_found
2534 note_and_explain_region(
2537 "...but the lifetime must also be valid for ",
2543 sup_trace.cause.span,
2544 &format!("...so that the {}", sup_trace.cause.as_requirement_str()),
2547 err.note_expected_found(&"", sup_expected, &"", sup_found);
2552 self.note_region_origin(&mut err, &sup_origin);
2554 note_and_explain_region(
2557 "but, the lifetime must be valid for ",
2563 self.note_region_origin(&mut err, &sub_origin);
2567 /// Determine whether an error associated with the given span and definition
2568 /// should be treated as being caused by the implicit `From` conversion
2569 /// within `?` desugaring.
2570 pub fn is_try_conversion(&self, span: Span, trait_def_id: DefId) -> bool {
2571 span.is_desugaring(DesugaringKind::QuestionMark)
2572 && self.tcx.is_diagnostic_item(sym::From, trait_def_id)
2575 /// Structurally compares two types, modulo any inference variables.
2577 /// Returns `true` if two types are equal, or if one type is an inference variable compatible
2578 /// with the other type. A TyVar inference type is compatible with any type, and an IntVar or
2579 /// FloatVar inference type are compatible with themselves or their concrete types (Int and
2580 /// Float types, respectively). When comparing two ADTs, these rules apply recursively.
2581 pub fn same_type_modulo_infer<T: relate::Relate<'tcx>>(&self, a: T, b: T) -> bool {
2582 let (a, b) = self.resolve_vars_if_possible((a, b));
2583 SameTypeModuloInfer(self).relate(a, b).is_ok()
2587 struct SameTypeModuloInfer<'a, 'tcx>(&'a InferCtxt<'tcx>);
2589 impl<'tcx> TypeRelation<'tcx> for SameTypeModuloInfer<'_, 'tcx> {
2590 fn tcx(&self) -> TyCtxt<'tcx> {
2594 fn intercrate(&self) -> bool {
2595 assert!(!self.0.intercrate);
2599 fn param_env(&self) -> ty::ParamEnv<'tcx> {
2600 // Unused, only for consts which we treat as always equal
2601 ty::ParamEnv::empty()
2604 fn tag(&self) -> &'static str {
2605 "SameTypeModuloInfer"
2608 fn a_is_expected(&self) -> bool {
2612 fn mark_ambiguous(&mut self) {
2616 fn relate_with_variance<T: relate::Relate<'tcx>>(
2618 _variance: ty::Variance,
2619 _info: ty::VarianceDiagInfo<'tcx>,
2622 ) -> relate::RelateResult<'tcx, T> {
2626 fn tys(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>> {
2627 match (a.kind(), b.kind()) {
2628 (ty::Int(_) | ty::Uint(_), ty::Infer(ty::InferTy::IntVar(_)))
2630 ty::Infer(ty::InferTy::IntVar(_)),
2631 ty::Int(_) | ty::Uint(_) | ty::Infer(ty::InferTy::IntVar(_)),
2633 | (ty::Float(_), ty::Infer(ty::InferTy::FloatVar(_)))
2635 ty::Infer(ty::InferTy::FloatVar(_)),
2636 ty::Float(_) | ty::Infer(ty::InferTy::FloatVar(_)),
2638 | (ty::Infer(ty::InferTy::TyVar(_)), _)
2639 | (_, ty::Infer(ty::InferTy::TyVar(_))) => Ok(a),
2640 (ty::Infer(_), _) | (_, ty::Infer(_)) => Err(TypeError::Mismatch),
2641 _ => relate::super_relate_tys(self, a, b),
2647 a: ty::Region<'tcx>,
2648 b: ty::Region<'tcx>,
2649 ) -> RelateResult<'tcx, ty::Region<'tcx>> {
2650 if (a.is_var() && b.is_free_or_static())
2651 || (b.is_var() && a.is_free_or_static())
2652 || (a.is_var() && b.is_var())
2657 Err(TypeError::Mismatch)
2663 a: ty::Binder<'tcx, T>,
2664 b: ty::Binder<'tcx, T>,
2665 ) -> relate::RelateResult<'tcx, ty::Binder<'tcx, T>>
2667 T: relate::Relate<'tcx>,
2669 Ok(a.rebind(self.relate(a.skip_binder(), b.skip_binder())?))
2675 _b: ty::Const<'tcx>,
2676 ) -> relate::RelateResult<'tcx, ty::Const<'tcx>> {
2677 // FIXME(compiler-errors): This could at least do some first-order
2683 impl<'tcx> InferCtxt<'tcx> {
2684 fn report_inference_failure(
2686 var_origin: RegionVariableOrigin,
2687 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
2688 let br_string = |br: ty::BoundRegionKind| {
2689 let mut s = match br {
2690 ty::BrNamed(_, name) => name.to_string(),
2698 let var_description = match var_origin {
2699 infer::MiscVariable(_) => String::new(),
2700 infer::PatternRegion(_) => " for pattern".to_string(),
2701 infer::AddrOfRegion(_) => " for borrow expression".to_string(),
2702 infer::Autoref(_) => " for autoref".to_string(),
2703 infer::Coercion(_) => " for automatic coercion".to_string(),
2704 infer::LateBoundRegion(_, br, infer::FnCall) => {
2705 format!(" for lifetime parameter {}in function call", br_string(br))
2707 infer::LateBoundRegion(_, br, infer::HigherRankedType) => {
2708 format!(" for lifetime parameter {}in generic type", br_string(br))
2710 infer::LateBoundRegion(_, br, infer::AssocTypeProjection(def_id)) => format!(
2711 " for lifetime parameter {}in trait containing associated type `{}`",
2713 self.tcx.associated_item(def_id).name
2715 infer::EarlyBoundRegion(_, name) => format!(" for lifetime parameter `{}`", name),
2716 infer::UpvarRegion(ref upvar_id, _) => {
2717 let var_name = self.tcx.hir().name(upvar_id.var_path.hir_id);
2718 format!(" for capture of `{}` by closure", var_name)
2720 infer::Nll(..) => bug!("NLL variable found in lexical phase"),
2727 "cannot infer an appropriate lifetime{} due to conflicting requirements",
2733 pub enum FailureCode {
2735 Error0317(&'static str),
2736 Error0580(&'static str),
2737 Error0308(&'static str),
2738 Error0644(&'static str),
2741 pub trait ObligationCauseExt<'tcx> {
2742 fn as_failure_code(&self, terr: TypeError<'tcx>) -> FailureCode;
2743 fn as_requirement_str(&self) -> &'static str;
2746 impl<'tcx> ObligationCauseExt<'tcx> for ObligationCause<'tcx> {
2747 fn as_failure_code(&self, terr: TypeError<'tcx>) -> FailureCode {
2748 use self::FailureCode::*;
2749 use crate::traits::ObligationCauseCode::*;
2751 CompareImplItemObligation { kind: ty::AssocKind::Fn, .. } => {
2752 Error0308("method not compatible with trait")
2754 CompareImplItemObligation { kind: ty::AssocKind::Type, .. } => {
2755 Error0308("type not compatible with trait")
2757 CompareImplItemObligation { kind: ty::AssocKind::Const, .. } => {
2758 Error0308("const not compatible with trait")
2760 MatchExpressionArm(box MatchExpressionArmCause { source, .. }) => {
2761 Error0308(match source {
2762 hir::MatchSource::TryDesugar => "`?` operator has incompatible types",
2763 _ => "`match` arms have incompatible types",
2766 IfExpression { .. } => Error0308("`if` and `else` have incompatible types"),
2767 IfExpressionWithNoElse => Error0317("`if` may be missing an `else` clause"),
2768 LetElse => Error0308("`else` clause of `let...else` does not diverge"),
2769 MainFunctionType => Error0580("`main` function has wrong type"),
2770 StartFunctionType => Error0308("`#[start]` function has wrong type"),
2771 IntrinsicType => Error0308("intrinsic has wrong type"),
2772 MethodReceiver => Error0308("mismatched `self` parameter type"),
2774 // In the case where we have no more specific thing to
2775 // say, also take a look at the error code, maybe we can
2778 TypeError::CyclicTy(ty) if ty.is_closure() || ty.is_generator() => {
2779 Error0644("closure/generator type that references itself")
2781 TypeError::IntrinsicCast => {
2782 Error0308("cannot coerce intrinsics to function pointers")
2784 _ => Error0308("mismatched types"),
2789 fn as_requirement_str(&self) -> &'static str {
2790 use crate::traits::ObligationCauseCode::*;
2792 CompareImplItemObligation { kind: ty::AssocKind::Fn, .. } => {
2793 "method type is compatible with trait"
2795 CompareImplItemObligation { kind: ty::AssocKind::Type, .. } => {
2796 "associated type is compatible with trait"
2798 CompareImplItemObligation { kind: ty::AssocKind::Const, .. } => {
2799 "const is compatible with trait"
2801 ExprAssignable => "expression is assignable",
2802 IfExpression { .. } => "`if` and `else` have incompatible types",
2803 IfExpressionWithNoElse => "`if` missing an `else` returns `()`",
2804 MainFunctionType => "`main` function has the correct type",
2805 StartFunctionType => "`#[start]` function has the correct type",
2806 IntrinsicType => "intrinsic has the correct type",
2807 MethodReceiver => "method receiver has the correct type",
2808 _ => "types are compatible",
2813 /// Newtype to allow implementing IntoDiagnosticArg
2814 pub struct ObligationCauseAsDiagArg<'tcx>(pub ObligationCause<'tcx>);
2816 impl IntoDiagnosticArg for ObligationCauseAsDiagArg<'_> {
2817 fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> {
2818 use crate::traits::ObligationCauseCode::*;
2819 let kind = match self.0.code() {
2820 CompareImplItemObligation { kind: ty::AssocKind::Fn, .. } => "method_compat",
2821 CompareImplItemObligation { kind: ty::AssocKind::Type, .. } => "type_compat",
2822 CompareImplItemObligation { kind: ty::AssocKind::Const, .. } => "const_compat",
2823 ExprAssignable => "expr_assignable",
2824 IfExpression { .. } => "if_else_different",
2825 IfExpressionWithNoElse => "no_else",
2826 MainFunctionType => "fn_main_correct_type",
2827 StartFunctionType => "fn_start_correct_type",
2828 IntrinsicType => "intristic_correct_type",
2829 MethodReceiver => "method_correct_type",
2833 rustc_errors::DiagnosticArgValue::Str(kind)
2837 /// This is a bare signal of what kind of type we're dealing with. `ty::TyKind` tracks
2838 /// extra information about each type, but we only care about the category.
2839 #[derive(Clone, Copy, PartialEq, Eq, Hash)]
2840 pub enum TyCategory {
2843 Generator(hir::GeneratorKind),
2848 fn descr(&self) -> &'static str {
2850 Self::Closure => "closure",
2851 Self::Opaque => "opaque type",
2852 Self::Generator(gk) => gk.descr(),
2853 Self::Foreign => "foreign type",
2857 pub fn from_ty(tcx: TyCtxt<'_>, ty: Ty<'_>) -> Option<(Self, DefId)> {
2859 ty::Closure(def_id, _) => Some((Self::Closure, def_id)),
2860 ty::Alias(ty::Opaque, ty::AliasTy { def_id, .. }) => Some((Self::Opaque, def_id)),
2861 ty::Generator(def_id, ..) => {
2862 Some((Self::Generator(tcx.generator_kind(def_id).unwrap()), def_id))
2864 ty::Foreign(def_id) => Some((Self::Foreign, def_id)),
2870 impl<'tcx> InferCtxt<'tcx> {
2871 /// Given a [`hir::Block`], get the span of its last expression or
2872 /// statement, peeling off any inner blocks.
2873 pub fn find_block_span(&self, block: &'tcx hir::Block<'tcx>) -> Span {
2874 let block = block.innermost_block();
2875 if let Some(expr) = &block.expr {
2877 } else if let Some(stmt) = block.stmts.last() {
2878 // possibly incorrect trailing `;` in the else arm
2881 // empty block; point at its entirety
2886 /// Given a [`hir::HirId`] for a block, get the span of its last expression
2887 /// or statement, peeling off any inner blocks.
2888 pub fn find_block_span_from_hir_id(&self, hir_id: hir::HirId) -> Span {
2889 match self.tcx.hir().get(hir_id) {
2890 hir::Node::Block(blk) => self.find_block_span(blk),
2891 // The parser was in a weird state if either of these happen, but
2892 // it's better not to panic.
2893 hir::Node::Expr(e) => e.span,
2894 _ => rustc_span::DUMMY_SP,