1 pub mod on_unimplemented;
5 ConstEvalFailure, EvaluationResult, FulfillmentError, FulfillmentErrorCode,
6 MismatchedProjectionTypes, Obligation, ObligationCause, ObligationCauseCode,
7 OnUnimplementedDirective, OnUnimplementedNote, OutputTypeParameterMismatch, Overflow,
8 PredicateObligation, SelectionContext, SelectionError, TraitNotObjectSafe,
11 use crate::infer::error_reporting::{TyCategory, TypeAnnotationNeeded as ErrorCode};
12 use crate::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
13 use crate::infer::{self, InferCtxt, TyCtxtInferExt};
14 use rustc_data_structures::fx::FxHashMap;
15 use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticBuilder, ErrorReported};
17 use rustc_hir::def_id::{DefId, LOCAL_CRATE};
19 use rustc_middle::mir::interpret::ErrorHandled;
20 use rustc_middle::ty::error::ExpectedFound;
21 use rustc_middle::ty::fold::TypeFolder;
22 use rustc_middle::ty::{
23 self, fast_reject, AdtKind, SubtypePredicate, ToPolyTraitRef, ToPredicate, Ty, TyCtxt,
24 TypeFoldable, WithConstness,
26 use rustc_session::DiagnosticMessageId;
27 use rustc_span::{ExpnKind, Span, DUMMY_SP};
30 use crate::traits::query::evaluate_obligation::InferCtxtExt as _;
31 use crate::traits::query::normalize::AtExt as _;
32 use on_unimplemented::InferCtxtExt as _;
33 use suggestions::InferCtxtExt as _;
35 pub use rustc_infer::traits::error_reporting::*;
37 pub trait InferCtxtExt<'tcx> {
38 fn report_fulfillment_errors(
40 errors: &[FulfillmentError<'tcx>],
41 body_id: Option<hir::BodyId>,
42 fallback_has_occurred: bool,
45 fn report_overflow_error<T>(
47 obligation: &Obligation<'tcx, T>,
48 suggest_increasing_limit: bool,
51 T: fmt::Display + TypeFoldable<'tcx>;
53 fn report_overflow_error_cycle(&self, cycle: &[PredicateObligation<'tcx>]) -> !;
55 fn report_selection_error(
57 obligation: &PredicateObligation<'tcx>,
58 error: &SelectionError<'tcx>,
59 fallback_has_occurred: bool,
63 /// Given some node representing a fn-like thing in the HIR map,
64 /// returns a span and `ArgKind` information that describes the
65 /// arguments it expects. This can be supplied to
66 /// `report_arg_count_mismatch`.
67 fn get_fn_like_arguments(&self, node: Node<'_>) -> Option<(Span, Vec<ArgKind>)>;
69 /// Reports an error when the number of arguments needed by a
70 /// trait match doesn't match the number that the expression
72 fn report_arg_count_mismatch(
75 found_span: Option<Span>,
76 expected_args: Vec<ArgKind>,
77 found_args: Vec<ArgKind>,
79 ) -> DiagnosticBuilder<'tcx>;
82 impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
83 fn report_fulfillment_errors(
85 errors: &[FulfillmentError<'tcx>],
86 body_id: Option<hir::BodyId>,
87 fallback_has_occurred: bool,
90 struct ErrorDescriptor<'tcx> {
91 predicate: ty::Predicate<'tcx>,
92 index: Option<usize>, // None if this is an old error
95 let mut error_map: FxHashMap<_, Vec<_>> = self
96 .reported_trait_errors
99 .map(|(&span, predicates)| {
104 .map(|&predicate| ErrorDescriptor { predicate, index: None })
110 for (index, error) in errors.iter().enumerate() {
111 // We want to ignore desugarings here: spans are equivalent even
112 // if one is the result of a desugaring and the other is not.
113 let mut span = error.obligation.cause.span;
114 let expn_data = span.ctxt().outer_expn_data();
115 if let ExpnKind::Desugaring(_) = expn_data.kind {
116 span = expn_data.call_site;
119 error_map.entry(span).or_default().push(ErrorDescriptor {
120 predicate: error.obligation.predicate,
124 self.reported_trait_errors
128 .push(error.obligation.predicate);
131 // We do this in 2 passes because we want to display errors in order, though
132 // maybe it *is* better to sort errors by span or something.
133 let mut is_suppressed = vec![false; errors.len()];
134 for (_, error_set) in error_map.iter() {
135 // We want to suppress "duplicate" errors with the same span.
136 for error in error_set {
137 if let Some(index) = error.index {
138 // Suppress errors that are either:
139 // 1) strictly implied by another error.
140 // 2) implied by an error with a smaller index.
141 for error2 in error_set {
142 if error2.index.map_or(false, |index2| is_suppressed[index2]) {
143 // Avoid errors being suppressed by already-suppressed
144 // errors, to prevent all errors from being suppressed
149 if self.error_implies(&error2.predicate, &error.predicate)
150 && !(error2.index >= error.index
151 && self.error_implies(&error.predicate, &error2.predicate))
153 info!("skipping {:?} (implied by {:?})", error, error2);
154 is_suppressed[index] = true;
162 for (error, suppressed) in errors.iter().zip(is_suppressed) {
164 self.report_fulfillment_error(error, body_id, fallback_has_occurred);
169 /// Reports that an overflow has occurred and halts compilation. We
170 /// halt compilation unconditionally because it is important that
171 /// overflows never be masked -- they basically represent computations
172 /// whose result could not be truly determined and thus we can't say
173 /// if the program type checks or not -- and they are unusual
174 /// occurrences in any case.
175 fn report_overflow_error<T>(
177 obligation: &Obligation<'tcx, T>,
178 suggest_increasing_limit: bool,
181 T: fmt::Display + TypeFoldable<'tcx>,
183 let predicate = self.resolve_vars_if_possible(&obligation.predicate);
184 let mut err = struct_span_err!(
186 obligation.cause.span,
188 "overflow evaluating the requirement `{}`",
192 if suggest_increasing_limit {
193 self.suggest_new_overflow_limit(&mut err);
196 self.note_obligation_cause_code(
198 &obligation.predicate,
199 &obligation.cause.code,
204 self.tcx.sess.abort_if_errors();
208 /// Reports that a cycle was detected which led to overflow and halts
209 /// compilation. This is equivalent to `report_overflow_error` except
210 /// that we can give a more helpful error message (and, in particular,
211 /// we do not suggest increasing the overflow limit, which is not
213 fn report_overflow_error_cycle(&self, cycle: &[PredicateObligation<'tcx>]) -> ! {
214 let cycle = self.resolve_vars_if_possible(&cycle.to_owned());
215 assert!(!cycle.is_empty());
217 debug!("report_overflow_error_cycle: cycle={:?}", cycle);
219 self.report_overflow_error(&cycle[0], false);
222 fn report_selection_error(
224 obligation: &PredicateObligation<'tcx>,
225 error: &SelectionError<'tcx>,
226 fallback_has_occurred: bool,
230 let span = obligation.cause.span;
232 let mut err = match *error {
233 SelectionError::Unimplemented => {
234 if let ObligationCauseCode::CompareImplMethodObligation {
239 | ObligationCauseCode::CompareImplTypeObligation {
243 } = obligation.cause.code
245 self.report_extra_impl_obligation(
250 &format!("`{}`", obligation.predicate),
255 match obligation.predicate {
256 ty::Predicate::Trait(ref trait_predicate, _) => {
257 let trait_predicate = self.resolve_vars_if_possible(trait_predicate);
259 if self.tcx.sess.has_errors() && trait_predicate.references_error() {
262 let trait_ref = trait_predicate.to_poly_trait_ref();
263 let (post_message, pre_message, type_def) = self
264 .get_parent_trait_ref(&obligation.cause.code)
267 format!(" in `{}`", t),
268 format!("within `{}`, ", t),
269 s.map(|s| (format!("within this `{}`", t), s)),
272 .unwrap_or_default();
274 let OnUnimplementedNote { message, label, note, enclosing_scope } =
275 self.on_unimplemented_note(trait_ref, obligation);
276 let have_alt_message = message.is_some() || label.is_some();
281 .span_to_snippet(span)
284 let is_from = format!("{}", trait_ref.print_only_trait_path())
285 .starts_with("std::convert::From<");
287 { Some(trait_ref.def_id()) == self.tcx.lang_items().unsize_trait() };
288 let (message, note) = if is_try && is_from {
291 "`?` couldn't convert the error to `{}`",
295 "the question mark operation (`?`) implicitly performs a \
296 conversion on the error value using the `From` trait"
304 let mut err = struct_span_err!(
309 message.unwrap_or_else(|| format!(
310 "the trait bound `{}` is not satisfied{}",
311 trait_ref.without_const().to_predicate(),
316 let should_convert_option_to_result =
317 format!("{}", trait_ref.print_only_trait_path())
318 .starts_with("std::convert::From<std::option::NoneError");
319 let should_convert_result_to_option = format!("{}", trait_ref)
320 .starts_with("<std::option::NoneError as std::convert::From<");
321 if is_try && is_from {
322 if should_convert_option_to_result {
323 err.span_suggestion_verbose(
325 "consider converting the `Option<T>` into a `Result<T, _>` \
326 using `Option::ok_or` or `Option::ok_or_else`",
327 ".ok_or_else(|| /* error value */)".to_string(),
328 Applicability::HasPlaceholders,
330 } else if should_convert_result_to_option {
331 err.span_suggestion_verbose(
333 "consider converting the `Result<T, _>` into an `Option<T>` \
336 Applicability::MachineApplicable,
339 if let Some(ret_span) = self.return_type_span(obligation) {
342 &format!("expected `{}` because of this", trait_ref.self_ty()),
348 if obligation.cause.code == ObligationCauseCode::MainFunctionType {
349 "consider using `()`, or a `Result`".to_owned()
352 "{}the trait `{}` is not implemented for `{}`",
354 trait_ref.print_only_trait_path(),
359 if self.suggest_add_reference_to_arg(
366 self.note_obligation_cause(&mut err, obligation);
370 if let Some(ref s) = label {
371 // If it has a custom `#[rustc_on_unimplemented]`
372 // error message, let's display it as the label!
373 err.span_label(span, s.as_str());
374 err.help(&explanation);
376 err.span_label(span, explanation);
378 if let Some((msg, span)) = type_def {
379 err.span_label(span, &msg);
381 if let Some(ref s) = note {
382 // If it has a custom `#[rustc_on_unimplemented]` note, let's display it
383 err.note(s.as_str());
385 if let Some(ref s) = enclosing_scope {
386 let enclosing_scope_span = tcx.def_span(
388 .opt_local_def_id(obligation.cause.body_id)
390 tcx.hir().body_owner_def_id(hir::BodyId {
391 hir_id: obligation.cause.body_id,
397 err.span_label(enclosing_scope_span, s.as_str());
400 self.suggest_borrow_on_unsized_slice(&obligation.cause.code, &mut err);
401 self.suggest_fn_call(&obligation, &mut err, &trait_ref, points_at_arg);
402 self.suggest_remove_reference(&obligation, &mut err, &trait_ref);
403 self.suggest_semicolon_removal(&obligation, &mut err, span, &trait_ref);
404 self.note_version_mismatch(&mut err, &trait_ref);
405 if self.suggest_impl_trait(&mut err, span, &obligation, &trait_ref) {
411 // If the obligation failed due to a missing implementation of the
412 // `Unsize` trait, give a pointer to why that might be the case
414 "all implementations of `Unsize` are provided \
415 automatically by the compiler, see \
416 <https://doc.rust-lang.org/stable/std/marker/trait.Unsize.html> \
417 for more information",
421 // Try to report a help message
422 if !trait_ref.has_infer_types_or_consts()
423 && self.predicate_can_apply(obligation.param_env, trait_ref)
425 // If a where-clause may be useful, remind the
426 // user that they can add it.
428 // don't display an on-unimplemented note, as
429 // these notes will often be of the form
430 // "the type `T` can't be frobnicated"
431 // which is somewhat confusing.
432 self.suggest_restricting_param_bound(
435 obligation.cause.body_id,
438 if !have_alt_message {
439 // Can't show anything else useful, try to find similar impls.
440 let impl_candidates = self.find_similar_impl_candidates(trait_ref);
441 self.report_similar_impl_candidates(impl_candidates, &mut err);
443 // Changing mutability doesn't make a difference to whether we have
444 // an `Unsize` impl (Fixes ICE in #71036)
446 self.suggest_change_mut(
455 // If this error is due to `!: Trait` not implemented but `(): Trait` is
456 // implemented, and fallback has occurred, then it could be due to a
457 // variable that used to fallback to `()` now falling back to `!`. Issue a
458 // note informing about the change in behaviour.
459 if trait_predicate.skip_binder().self_ty().is_never()
460 && fallback_has_occurred
462 let predicate = trait_predicate.map_bound(|mut trait_pred| {
463 trait_pred.trait_ref.substs = self.tcx.mk_substs_trait(
465 &trait_pred.trait_ref.substs[1..],
469 let unit_obligation = Obligation {
470 predicate: ty::Predicate::Trait(
472 hir::Constness::NotConst,
476 if self.predicate_may_hold(&unit_obligation) {
478 "the trait is implemented for `()`. \
479 Possibly this error has been caused by changes to \
480 Rust's type-inference algorithm (see issue #48950 \
481 <https://github.com/rust-lang/rust/issues/48950> \
482 for more information). Consider whether you meant to use \
483 the type `()` here instead.",
491 ty::Predicate::Subtype(ref predicate) => {
492 // Errors for Subtype predicates show up as
493 // `FulfillmentErrorCode::CodeSubtypeError`,
494 // not selection error.
495 span_bug!(span, "subtype requirement gave wrong error: `{:?}`", predicate)
498 ty::Predicate::RegionOutlives(ref predicate) => {
499 let predicate = self.resolve_vars_if_possible(predicate);
501 .region_outlives_predicate(&obligation.cause, &predicate)
508 "the requirement `{}` is not satisfied (`{}`)",
514 ty::Predicate::Projection(..) | ty::Predicate::TypeOutlives(..) => {
515 let predicate = self.resolve_vars_if_possible(&obligation.predicate);
520 "the requirement `{}` is not satisfied",
525 ty::Predicate::ObjectSafe(trait_def_id) => {
526 let violations = self.tcx.object_safety_violations(trait_def_id);
527 report_object_safety_error(self.tcx, span, trait_def_id, violations)
530 ty::Predicate::ClosureKind(closure_def_id, closure_substs, kind) => {
531 let found_kind = self.closure_kind(closure_substs).unwrap();
533 self.tcx.sess.source_map().guess_head_span(
534 self.tcx.hir().span_if_local(closure_def_id).unwrap(),
536 let hir_id = self.tcx.hir().as_local_hir_id(closure_def_id.expect_local());
537 let mut err = struct_span_err!(
541 "expected a closure that implements the `{}` trait, \
542 but this closure only implements `{}`",
549 format!("this closure implements `{}`, not `{}`", found_kind, kind),
552 obligation.cause.span,
553 format!("the requirement to implement `{}` derives from here", kind),
556 // Additional context information explaining why the closure only implements
557 // a particular trait.
558 if let Some(tables) = self.in_progress_tables {
559 let tables = tables.borrow();
560 match (found_kind, tables.closure_kind_origins().get(hir_id)) {
561 (ty::ClosureKind::FnOnce, Some((span, name))) => {
565 "closure is `FnOnce` because it moves the \
566 variable `{}` out of its environment",
571 (ty::ClosureKind::FnMut, Some((span, name))) => {
575 "closure is `FnMut` because it mutates the \
589 ty::Predicate::WellFormed(ty) => {
590 if !self.tcx.sess.opts.debugging_opts.chalk {
591 // WF predicates cannot themselves make
592 // errors. They can only block due to
593 // ambiguity; otherwise, they always
594 // degenerate into other obligations
596 span_bug!(span, "WF predicate not satisfied for {:?}", ty);
598 // FIXME: we'll need a better message which takes into account
599 // which bounds actually failed to hold.
600 self.tcx.sess.struct_span_err(
602 &format!("the type `{}` is not well-formed (chalk)", ty),
607 ty::Predicate::ConstEvaluatable(..) => {
608 // Errors for `ConstEvaluatable` predicates show up as
609 // `SelectionError::ConstEvalFailure`,
610 // not `Unimplemented`.
613 "const-evaluatable requirement gave wrong error: `{:?}`",
620 OutputTypeParameterMismatch(ref found_trait_ref, ref expected_trait_ref, _) => {
621 let found_trait_ref = self.resolve_vars_if_possible(&*found_trait_ref);
622 let expected_trait_ref = self.resolve_vars_if_possible(&*expected_trait_ref);
624 if expected_trait_ref.self_ty().references_error() {
628 let found_trait_ty = found_trait_ref.self_ty();
630 let found_did = match found_trait_ty.kind {
631 ty::Closure(did, _) | ty::Foreign(did) | ty::FnDef(did, _) => Some(did),
632 ty::Adt(def, _) => Some(def.did),
636 let found_span = found_did
637 .and_then(|did| self.tcx.hir().span_if_local(did))
638 .map(|sp| self.tcx.sess.source_map().guess_head_span(sp)); // the sp could be an fn def
640 if self.reported_closure_mismatch.borrow().contains(&(span, found_span)) {
641 // We check closures twice, with obligations flowing in different directions,
642 // but we want to complain about them only once.
646 self.reported_closure_mismatch.borrow_mut().insert((span, found_span));
648 let found = match found_trait_ref.skip_binder().substs.type_at(1).kind {
649 ty::Tuple(ref tys) => vec![ArgKind::empty(); tys.len()],
650 _ => vec![ArgKind::empty()],
653 let expected_ty = expected_trait_ref.skip_binder().substs.type_at(1);
654 let expected = match expected_ty.kind {
655 ty::Tuple(ref tys) => tys
657 .map(|t| ArgKind::from_expected_ty(t.expect_ty(), Some(span)))
659 _ => vec![ArgKind::Arg("_".to_owned(), expected_ty.to_string())],
662 if found.len() == expected.len() {
663 self.report_closure_arg_mismatch(
670 let (closure_span, found) = found_did
672 let node = self.tcx.hir().get_if_local(did)?;
673 let (found_span, found) = self.get_fn_like_arguments(node)?;
674 Some((Some(found_span), found))
676 .unwrap_or((found_span, found));
678 self.report_arg_count_mismatch(
683 found_trait_ty.is_closure(),
688 TraitNotObjectSafe(did) => {
689 let violations = self.tcx.object_safety_violations(did);
690 report_object_safety_error(self.tcx, span, did, violations)
693 ConstEvalFailure(ErrorHandled::TooGeneric) => {
694 // In this instance, we have a const expression containing an unevaluated
695 // generic parameter. We have no idea whether this expression is valid or
696 // not (e.g. it might result in an error), but we don't want to just assume
697 // that it's okay, because that might result in post-monomorphisation time
698 // errors. The onus is really on the caller to provide values that it can
699 // prove are well-formed.
703 .struct_span_err(span, "constant expression depends on a generic parameter");
704 // FIXME(const_generics): we should suggest to the user how they can resolve this
705 // issue. However, this is currently not actually possible
706 // (see https://github.com/rust-lang/rust/issues/66962#issuecomment-575907083).
707 err.note("this may fail depending on what value the parameter takes");
711 // Already reported in the query.
712 ConstEvalFailure(ErrorHandled::Reported(ErrorReported)) => {
713 // FIXME(eddyb) remove this once `ErrorReported` becomes a proof token.
714 self.tcx.sess.delay_span_bug(span, "`ErrorReported` without an error");
718 // Already reported in the query, but only as a lint.
719 // This shouldn't actually happen for constants used in types, modulo
720 // bugs. The `delay_span_bug` here ensures it won't be ignored.
721 ConstEvalFailure(ErrorHandled::Linted) => {
722 self.tcx.sess.delay_span_bug(span, "constant in type had error reported as lint");
727 bug!("overflow should be handled before the `report_selection_error` path");
731 self.note_obligation_cause(&mut err, obligation);
732 self.point_at_returns_when_relevant(&mut err, &obligation);
737 /// Given some node representing a fn-like thing in the HIR map,
738 /// returns a span and `ArgKind` information that describes the
739 /// arguments it expects. This can be supplied to
740 /// `report_arg_count_mismatch`.
741 fn get_fn_like_arguments(&self, node: Node<'_>) -> Option<(Span, Vec<ArgKind>)> {
742 let sm = self.tcx.sess.source_map();
743 let hir = self.tcx.hir();
745 Node::Expr(&hir::Expr {
746 kind: hir::ExprKind::Closure(_, ref _decl, id, span, _),
749 sm.guess_head_span(span),
754 if let hir::Pat { kind: hir::PatKind::Tuple(ref args, _), span, .. } =
761 sm.span_to_snippet(pat.span)
763 .map(|snippet| (snippet, "_".to_owned()))
765 .collect::<Option<Vec<_>>>()?,
768 let name = sm.span_to_snippet(arg.pat.span).ok()?;
769 Some(ArgKind::Arg(name, "_".to_owned()))
772 .collect::<Option<Vec<ArgKind>>>()?,
774 Node::Item(&hir::Item { span, kind: hir::ItemKind::Fn(ref sig, ..), .. })
775 | Node::ImplItem(&hir::ImplItem {
777 kind: hir::ImplItemKind::Fn(ref sig, _),
780 | Node::TraitItem(&hir::TraitItem {
782 kind: hir::TraitItemKind::Fn(ref sig, _),
785 sm.guess_head_span(span),
789 .map(|arg| match arg.clone().kind {
790 hir::TyKind::Tup(ref tys) => ArgKind::Tuple(
792 vec![("_".to_owned(), "_".to_owned()); tys.len()],
794 _ => ArgKind::empty(),
796 .collect::<Vec<ArgKind>>(),
798 Node::Ctor(ref variant_data) => {
799 let span = variant_data.ctor_hir_id().map(|id| hir.span(id)).unwrap_or(DUMMY_SP);
800 let span = sm.guess_head_span(span);
801 (span, vec![ArgKind::empty(); variant_data.fields().len()])
803 _ => panic!("non-FnLike node found: {:?}", node),
807 /// Reports an error when the number of arguments needed by a
808 /// trait match doesn't match the number that the expression
810 fn report_arg_count_mismatch(
813 found_span: Option<Span>,
814 expected_args: Vec<ArgKind>,
815 found_args: Vec<ArgKind>,
817 ) -> DiagnosticBuilder<'tcx> {
818 let kind = if is_closure { "closure" } else { "function" };
820 let args_str = |arguments: &[ArgKind], other: &[ArgKind]| {
821 let arg_length = arguments.len();
822 let distinct = match &other[..] {
823 &[ArgKind::Tuple(..)] => true,
826 match (arg_length, arguments.get(0)) {
827 (1, Some(&ArgKind::Tuple(_, ref fields))) => {
828 format!("a single {}-tuple as argument", fields.len())
833 if distinct && arg_length > 1 { "distinct " } else { "" },
834 pluralize!(arg_length)
839 let expected_str = args_str(&expected_args, &found_args);
840 let found_str = args_str(&found_args, &expected_args);
842 let mut err = struct_span_err!(
846 "{} is expected to take {}, but it takes {}",
852 err.span_label(span, format!("expected {} that takes {}", kind, expected_str));
854 if let Some(found_span) = found_span {
855 err.span_label(found_span, format!("takes {}", found_str));
858 // ^^^^^^^^-- def_span
862 let prefix_span = self.tcx.sess.source_map().span_until_non_whitespace(found_span);
866 if let Some(span) = found_span.trim_start(prefix_span) { span } else { found_span };
868 // Suggest to take and ignore the arguments with expected_args_length `_`s if
869 // found arguments is empty (assume the user just wants to ignore args in this case).
870 // For example, if `expected_args_length` is 2, suggest `|_, _|`.
871 if found_args.is_empty() && is_closure {
872 let underscores = vec!["_"; expected_args.len()].join(", ");
873 err.span_suggestion_verbose(
876 "consider changing the closure to take and ignore the expected argument{}",
877 pluralize!(expected_args.len())
879 format!("|{}|", underscores),
880 Applicability::MachineApplicable,
884 if let &[ArgKind::Tuple(_, ref fields)] = &found_args[..] {
885 if fields.len() == expected_args.len() {
888 .map(|(name, _)| name.to_owned())
889 .collect::<Vec<String>>()
891 err.span_suggestion_verbose(
893 "change the closure to take multiple arguments instead of a single tuple",
894 format!("|{}|", sugg),
895 Applicability::MachineApplicable,
899 if let &[ArgKind::Tuple(_, ref fields)] = &expected_args[..] {
900 if fields.len() == found_args.len() && is_closure {
905 .map(|arg| match arg {
906 ArgKind::Arg(name, _) => name.to_owned(),
909 .collect::<Vec<String>>()
911 // add type annotations if available
912 if found_args.iter().any(|arg| match arg {
913 ArgKind::Arg(_, ty) => ty != "_",
920 .map(|(_, ty)| ty.to_owned())
921 .collect::<Vec<String>>()
928 err.span_suggestion_verbose(
930 "change the closure to accept a tuple instead of individual arguments",
932 Applicability::MachineApplicable,
942 trait InferCtxtPrivExt<'tcx> {
943 // returns if `cond` not occurring implies that `error` does not occur - i.e., that
944 // `error` occurring implies that `cond` occurs.
945 fn error_implies(&self, cond: &ty::Predicate<'tcx>, error: &ty::Predicate<'tcx>) -> bool;
947 fn report_fulfillment_error(
949 error: &FulfillmentError<'tcx>,
950 body_id: Option<hir::BodyId>,
951 fallback_has_occurred: bool,
954 fn report_projection_error(
956 obligation: &PredicateObligation<'tcx>,
957 error: &MismatchedProjectionTypes<'tcx>,
960 fn fuzzy_match_tys(&self, a: Ty<'tcx>, b: Ty<'tcx>) -> bool;
962 fn describe_generator(&self, body_id: hir::BodyId) -> Option<&'static str>;
964 fn find_similar_impl_candidates(
966 trait_ref: ty::PolyTraitRef<'tcx>,
967 ) -> Vec<ty::TraitRef<'tcx>>;
969 fn report_similar_impl_candidates(
971 impl_candidates: Vec<ty::TraitRef<'tcx>>,
972 err: &mut DiagnosticBuilder<'_>,
975 /// Gets the parent trait chain start
976 fn get_parent_trait_ref(
978 code: &ObligationCauseCode<'tcx>,
979 ) -> Option<(String, Option<Span>)>;
981 /// If the `Self` type of the unsatisfied trait `trait_ref` implements a trait
982 /// with the same path as `trait_ref`, a help message about
983 /// a probable version mismatch is added to `err`
984 fn note_version_mismatch(
986 err: &mut DiagnosticBuilder<'_>,
987 trait_ref: &ty::PolyTraitRef<'tcx>,
990 fn mk_obligation_for_def_id(
994 cause: ObligationCause<'tcx>,
995 param_env: ty::ParamEnv<'tcx>,
996 ) -> PredicateObligation<'tcx>;
998 fn maybe_report_ambiguity(
1000 obligation: &PredicateObligation<'tcx>,
1001 body_id: Option<hir::BodyId>,
1004 fn predicate_can_apply(
1006 param_env: ty::ParamEnv<'tcx>,
1007 pred: ty::PolyTraitRef<'tcx>,
1010 fn note_obligation_cause(
1012 err: &mut DiagnosticBuilder<'_>,
1013 obligation: &PredicateObligation<'tcx>,
1016 fn suggest_unsized_bound_if_applicable(
1018 err: &mut DiagnosticBuilder<'_>,
1019 obligation: &PredicateObligation<'tcx>,
1022 fn is_recursive_obligation(
1024 obligated_types: &mut Vec<&ty::TyS<'tcx>>,
1025 cause_code: &ObligationCauseCode<'tcx>,
1029 impl<'a, 'tcx> InferCtxtPrivExt<'tcx> for InferCtxt<'a, 'tcx> {
1030 // returns if `cond` not occurring implies that `error` does not occur - i.e., that
1031 // `error` occurring implies that `cond` occurs.
1032 fn error_implies(&self, cond: &ty::Predicate<'tcx>, error: &ty::Predicate<'tcx>) -> bool {
1037 let (cond, error) = match (cond, error) {
1038 (&ty::Predicate::Trait(..), &ty::Predicate::Trait(ref error, _)) => (cond, error),
1040 // FIXME: make this work in other cases too.
1045 for obligation in super::elaborate_predicates(self.tcx, std::iter::once(*cond)) {
1046 if let ty::Predicate::Trait(implication, _) = obligation.predicate {
1047 let error = error.to_poly_trait_ref();
1048 let implication = implication.to_poly_trait_ref();
1049 // FIXME: I'm just not taking associated types at all here.
1050 // Eventually I'll need to implement param-env-aware
1051 // `Γ₁ ⊦ φ₁ => Γ₂ ⊦ φ₂` logic.
1052 let param_env = ty::ParamEnv::empty();
1053 if self.can_sub(param_env, error, implication).is_ok() {
1054 debug!("error_implies: {:?} -> {:?} -> {:?}", cond, error, implication);
1063 fn report_fulfillment_error(
1065 error: &FulfillmentError<'tcx>,
1066 body_id: Option<hir::BodyId>,
1067 fallback_has_occurred: bool,
1069 debug!("report_fulfillment_error({:?})", error);
1071 FulfillmentErrorCode::CodeSelectionError(ref selection_error) => {
1072 self.report_selection_error(
1075 fallback_has_occurred,
1076 error.points_at_arg_span,
1079 FulfillmentErrorCode::CodeProjectionError(ref e) => {
1080 self.report_projection_error(&error.obligation, e);
1082 FulfillmentErrorCode::CodeAmbiguity => {
1083 self.maybe_report_ambiguity(&error.obligation, body_id);
1085 FulfillmentErrorCode::CodeSubtypeError(ref expected_found, ref err) => {
1086 self.report_mismatched_types(
1087 &error.obligation.cause,
1088 expected_found.expected,
1089 expected_found.found,
1097 fn report_projection_error(
1099 obligation: &PredicateObligation<'tcx>,
1100 error: &MismatchedProjectionTypes<'tcx>,
1102 let predicate = self.resolve_vars_if_possible(&obligation.predicate);
1104 if predicate.references_error() {
1110 let mut err = &error.err;
1111 let mut values = None;
1113 // try to find the mismatched types to report the error with.
1115 // this can fail if the problem was higher-ranked, in which
1116 // cause I have no idea for a good error message.
1117 if let ty::Predicate::Projection(ref data) = predicate {
1118 let mut selcx = SelectionContext::new(self);
1119 let (data, _) = self.replace_bound_vars_with_fresh_vars(
1120 obligation.cause.span,
1121 infer::LateBoundRegionConversionTime::HigherRankedType,
1124 let mut obligations = vec![];
1125 let normalized_ty = super::normalize_projection_type(
1127 obligation.param_env,
1129 obligation.cause.clone(),
1135 "report_projection_error obligation.cause={:?} obligation.param_env={:?}",
1136 obligation.cause, obligation.param_env
1140 "report_projection_error normalized_ty={:?} data.ty={:?}",
1141 normalized_ty, data.ty
1144 let is_normalized_ty_expected = match &obligation.cause.code {
1145 ObligationCauseCode::ItemObligation(_)
1146 | ObligationCauseCode::BindingObligation(_, _)
1147 | ObligationCauseCode::ObjectCastObligation(_) => false,
1151 if let Err(error) = self.at(&obligation.cause, obligation.param_env).eq_exp(
1152 is_normalized_ty_expected,
1156 values = Some(infer::ValuePairs::Types(ExpectedFound::new(
1157 is_normalized_ty_expected,
1167 let msg = format!("type mismatch resolving `{}`", predicate);
1168 let error_id = (DiagnosticMessageId::ErrorId(271), Some(obligation.cause.span), msg);
1169 let fresh = self.tcx.sess.one_time_diagnostics.borrow_mut().insert(error_id);
1171 let mut diag = struct_span_err!(
1173 obligation.cause.span,
1175 "type mismatch resolving `{}`",
1178 self.note_type_err(&mut diag, &obligation.cause, None, values, err);
1179 self.note_obligation_cause(&mut diag, obligation);
1185 fn fuzzy_match_tys(&self, a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
1186 /// returns the fuzzy category of a given type, or None
1187 /// if the type can be equated to any type.
1188 fn type_category(t: Ty<'_>) -> Option<u32> {
1190 ty::Bool => Some(0),
1191 ty::Char => Some(1),
1193 ty::Int(..) | ty::Uint(..) | ty::Infer(ty::IntVar(..)) => Some(3),
1194 ty::Float(..) | ty::Infer(ty::FloatVar(..)) => Some(4),
1195 ty::Ref(..) | ty::RawPtr(..) => Some(5),
1196 ty::Array(..) | ty::Slice(..) => Some(6),
1197 ty::FnDef(..) | ty::FnPtr(..) => Some(7),
1198 ty::Dynamic(..) => Some(8),
1199 ty::Closure(..) => Some(9),
1200 ty::Tuple(..) => Some(10),
1201 ty::Projection(..) => Some(11),
1202 ty::Param(..) => Some(12),
1203 ty::Opaque(..) => Some(13),
1204 ty::Never => Some(14),
1205 ty::Adt(adt, ..) => match adt.adt_kind() {
1206 AdtKind::Struct => Some(15),
1207 AdtKind::Union => Some(16),
1208 AdtKind::Enum => Some(17),
1210 ty::Generator(..) => Some(18),
1211 ty::Foreign(..) => Some(19),
1212 ty::GeneratorWitness(..) => Some(20),
1213 ty::Placeholder(..) | ty::Bound(..) | ty::Infer(..) | ty::Error => None,
1214 ty::UnnormalizedProjection(..) => bug!("only used with chalk-engine"),
1218 match (type_category(a), type_category(b)) {
1219 (Some(cat_a), Some(cat_b)) => match (&a.kind, &b.kind) {
1220 (&ty::Adt(def_a, _), &ty::Adt(def_b, _)) => def_a == def_b,
1221 _ => cat_a == cat_b,
1223 // infer and error can be equated to all types
1228 fn describe_generator(&self, body_id: hir::BodyId) -> Option<&'static str> {
1229 self.tcx.hir().body(body_id).generator_kind.map(|gen_kind| match gen_kind {
1230 hir::GeneratorKind::Gen => "a generator",
1231 hir::GeneratorKind::Async(hir::AsyncGeneratorKind::Block) => "an async block",
1232 hir::GeneratorKind::Async(hir::AsyncGeneratorKind::Fn) => "an async function",
1233 hir::GeneratorKind::Async(hir::AsyncGeneratorKind::Closure) => "an async closure",
1237 fn find_similar_impl_candidates(
1239 trait_ref: ty::PolyTraitRef<'tcx>,
1240 ) -> Vec<ty::TraitRef<'tcx>> {
1241 let simp = fast_reject::simplify_type(self.tcx, trait_ref.skip_binder().self_ty(), true);
1242 let all_impls = self.tcx.all_impls(trait_ref.def_id());
1245 Some(simp) => all_impls
1246 .filter_map(|def_id| {
1247 let imp = self.tcx.impl_trait_ref(def_id).unwrap();
1248 let imp_simp = fast_reject::simplify_type(self.tcx, imp.self_ty(), true);
1249 if let Some(imp_simp) = imp_simp {
1250 if simp != imp_simp {
1257 None => all_impls.map(|def_id| self.tcx.impl_trait_ref(def_id).unwrap()).collect(),
1261 fn report_similar_impl_candidates(
1263 impl_candidates: Vec<ty::TraitRef<'tcx>>,
1264 err: &mut DiagnosticBuilder<'_>,
1266 if impl_candidates.is_empty() {
1270 let len = impl_candidates.len();
1271 let end = if impl_candidates.len() <= 5 { impl_candidates.len() } else { 4 };
1273 let normalize = |candidate| {
1274 self.tcx.infer_ctxt().enter(|ref infcx| {
1275 let normalized = infcx
1276 .at(&ObligationCause::dummy(), ty::ParamEnv::empty())
1277 .normalize(candidate)
1280 Some(normalized) => format!("\n {:?}", normalized.value),
1281 None => format!("\n {:?}", candidate),
1286 // Sort impl candidates so that ordering is consistent for UI tests.
1287 let mut normalized_impl_candidates =
1288 impl_candidates.iter().map(normalize).collect::<Vec<String>>();
1290 // Sort before taking the `..end` range,
1291 // because the ordering of `impl_candidates` may not be deterministic:
1292 // https://github.com/rust-lang/rust/pull/57475#issuecomment-455519507
1293 normalized_impl_candidates.sort();
1296 "the following implementations were found:{}{}",
1297 normalized_impl_candidates[..end].join(""),
1298 if len > 5 { format!("\nand {} others", len - 4) } else { String::new() }
1302 /// Gets the parent trait chain start
1303 fn get_parent_trait_ref(
1305 code: &ObligationCauseCode<'tcx>,
1306 ) -> Option<(String, Option<Span>)> {
1308 &ObligationCauseCode::BuiltinDerivedObligation(ref data) => {
1309 let parent_trait_ref = self.resolve_vars_if_possible(&data.parent_trait_ref);
1310 match self.get_parent_trait_ref(&data.parent_code) {
1313 let ty = parent_trait_ref.skip_binder().self_ty();
1315 TyCategory::from_ty(ty).map(|(_, def_id)| self.tcx.def_span(def_id));
1316 Some((ty.to_string(), span))
1324 /// If the `Self` type of the unsatisfied trait `trait_ref` implements a trait
1325 /// with the same path as `trait_ref`, a help message about
1326 /// a probable version mismatch is added to `err`
1327 fn note_version_mismatch(
1329 err: &mut DiagnosticBuilder<'_>,
1330 trait_ref: &ty::PolyTraitRef<'tcx>,
1332 let get_trait_impl = |trait_def_id| {
1333 let mut trait_impl = None;
1334 self.tcx.for_each_relevant_impl(trait_def_id, trait_ref.self_ty(), |impl_def_id| {
1335 if trait_impl.is_none() {
1336 trait_impl = Some(impl_def_id);
1341 let required_trait_path = self.tcx.def_path_str(trait_ref.def_id());
1342 let all_traits = self.tcx.all_traits(LOCAL_CRATE);
1343 let traits_with_same_path: std::collections::BTreeSet<_> = all_traits
1345 .filter(|trait_def_id| **trait_def_id != trait_ref.def_id())
1346 .filter(|trait_def_id| self.tcx.def_path_str(**trait_def_id) == required_trait_path)
1348 for trait_with_same_path in traits_with_same_path {
1349 if let Some(impl_def_id) = get_trait_impl(*trait_with_same_path) {
1350 let impl_span = self.tcx.def_span(impl_def_id);
1351 err.span_help(impl_span, "trait impl with same name found");
1352 let trait_crate = self.tcx.crate_name(trait_with_same_path.krate);
1353 let crate_msg = format!(
1354 "perhaps two different versions of crate `{}` are being used?",
1357 err.note(&crate_msg);
1362 fn mk_obligation_for_def_id(
1365 output_ty: Ty<'tcx>,
1366 cause: ObligationCause<'tcx>,
1367 param_env: ty::ParamEnv<'tcx>,
1368 ) -> PredicateObligation<'tcx> {
1370 ty::TraitRef { def_id, substs: self.tcx.mk_substs_trait(output_ty, &[]) };
1371 Obligation::new(cause, param_env, new_trait_ref.without_const().to_predicate())
1374 fn maybe_report_ambiguity(
1376 obligation: &PredicateObligation<'tcx>,
1377 body_id: Option<hir::BodyId>,
1379 // Unable to successfully determine, probably means
1380 // insufficient type information, but could mean
1381 // ambiguous impls. The latter *ought* to be a
1382 // coherence violation, so we don't report it here.
1384 let predicate = self.resolve_vars_if_possible(&obligation.predicate);
1385 let span = obligation.cause.span;
1388 "maybe_report_ambiguity(predicate={:?}, obligation={:?} body_id={:?}, code={:?})",
1389 predicate, obligation, body_id, obligation.cause.code,
1392 // Ambiguity errors are often caused as fallout from earlier
1393 // errors. So just ignore them if this infcx is tainted.
1394 if self.is_tainted_by_errors() {
1398 let mut err = match predicate {
1399 ty::Predicate::Trait(ref data, _) => {
1400 let trait_ref = data.to_poly_trait_ref();
1401 let self_ty = trait_ref.self_ty();
1402 debug!("self_ty {:?} {:?} trait_ref {:?}", self_ty, self_ty.kind, trait_ref);
1404 if predicate.references_error() {
1407 // Typically, this ambiguity should only happen if
1408 // there are unresolved type inference variables
1409 // (otherwise it would suggest a coherence
1410 // failure). But given #21974 that is not necessarily
1411 // the case -- we can have multiple where clauses that
1412 // are only distinguished by a region, which results
1413 // in an ambiguity even when all types are fully
1414 // known, since we don't dispatch based on region
1417 // This is kind of a hack: it frequently happens that some earlier
1418 // error prevents types from being fully inferred, and then we get
1419 // a bunch of uninteresting errors saying something like "<generic
1420 // #0> doesn't implement Sized". It may even be true that we
1421 // could just skip over all checks where the self-ty is an
1422 // inference variable, but I was afraid that there might be an
1423 // inference variable created, registered as an obligation, and
1424 // then never forced by writeback, and hence by skipping here we'd
1425 // be ignoring the fact that we don't KNOW the type works
1426 // out. Though even that would probably be harmless, given that
1427 // we're only talking about builtin traits, which are known to be
1428 // inhabited. We used to check for `self.tcx.sess.has_errors()` to
1429 // avoid inundating the user with unnecessary errors, but we now
1430 // check upstream for type errors and don't add the obligations to
1431 // begin with in those cases.
1436 .map_or(false, |sized_id| sized_id == trait_ref.def_id())
1438 self.need_type_info_err(body_id, span, self_ty, ErrorCode::E0282).emit();
1441 let mut err = self.need_type_info_err(body_id, span, self_ty, ErrorCode::E0283);
1442 err.note(&format!("cannot satisfy `{}`", predicate));
1443 if let ObligationCauseCode::ItemObligation(def_id) = obligation.cause.code {
1444 self.suggest_fully_qualified_path(&mut err, def_id, span, trait_ref.def_id());
1447 ObligationCauseCode::BindingObligation(ref def_id, _),
1449 (self.tcx.sess.source_map().span_to_snippet(span), &obligation.cause.code)
1451 let generics = self.tcx.generics_of(*def_id);
1452 if generics.params.iter().any(|p| p.name.as_str() != "Self")
1453 && !snippet.ends_with('>')
1455 // FIXME: To avoid spurious suggestions in functions where type arguments
1456 // where already supplied, we check the snippet to make sure it doesn't
1457 // end with a turbofish. Ideally we would have access to a `PathSegment`
1458 // instead. Otherwise we would produce the following output:
1460 // error[E0283]: type annotations needed
1461 // --> $DIR/issue-54954.rs:3:24
1463 // LL | const ARR_LEN: usize = Tt::const_val::<[i8; 123]>();
1464 // | ^^^^^^^^^^^^^^^^^^^^^^^^^^
1466 // | cannot infer type
1467 // | help: consider specifying the type argument
1468 // | in the function call:
1469 // | `Tt::const_val::<[i8; 123]>::<T>`
1471 // LL | const fn const_val<T: Sized>() -> usize {
1472 // | - required by this bound in `Tt::const_val`
1474 // = note: cannot satisfy `_: Tt`
1476 err.span_suggestion_verbose(
1477 span.shrink_to_hi(),
1479 "consider specifying the type argument{} in the function call",
1480 pluralize!(generics.params.len()),
1487 .map(|p| p.name.to_string())
1488 .collect::<Vec<String>>()
1491 Applicability::HasPlaceholders,
1498 ty::Predicate::WellFormed(ty) => {
1499 // Same hacky approach as above to avoid deluging user
1500 // with error messages.
1501 if ty.references_error() || self.tcx.sess.has_errors() {
1504 self.need_type_info_err(body_id, span, ty, ErrorCode::E0282)
1507 ty::Predicate::Subtype(ref data) => {
1508 if data.references_error() || self.tcx.sess.has_errors() {
1509 // no need to overload user in such cases
1512 let &SubtypePredicate { a_is_expected: _, a, b } = data.skip_binder();
1513 // both must be type variables, or the other would've been instantiated
1514 assert!(a.is_ty_var() && b.is_ty_var());
1515 self.need_type_info_err(body_id, span, a, ErrorCode::E0282)
1517 ty::Predicate::Projection(ref data) => {
1518 let trait_ref = data.to_poly_trait_ref(self.tcx);
1519 let self_ty = trait_ref.self_ty();
1520 let ty = data.skip_binder().ty;
1521 if predicate.references_error() {
1524 if self_ty.needs_infer() && ty.needs_infer() {
1525 // We do this for the `foo.collect()?` case to produce a suggestion.
1526 let mut err = self.need_type_info_err(body_id, span, self_ty, ErrorCode::E0284);
1527 err.note(&format!("cannot satisfy `{}`", predicate));
1530 let mut err = struct_span_err!(
1534 "type annotations needed: cannot satisfy `{}`",
1537 err.span_label(span, &format!("cannot satisfy `{}`", predicate));
1543 if self.tcx.sess.has_errors() {
1546 let mut err = struct_span_err!(
1550 "type annotations needed: cannot satisfy `{}`",
1553 err.span_label(span, &format!("cannot satisfy `{}`", predicate));
1557 self.note_obligation_cause(&mut err, obligation);
1561 /// Returns `true` if the trait predicate may apply for *some* assignment
1562 /// to the type parameters.
1563 fn predicate_can_apply(
1565 param_env: ty::ParamEnv<'tcx>,
1566 pred: ty::PolyTraitRef<'tcx>,
1568 struct ParamToVarFolder<'a, 'tcx> {
1569 infcx: &'a InferCtxt<'a, 'tcx>,
1570 var_map: FxHashMap<Ty<'tcx>, Ty<'tcx>>,
1573 impl<'a, 'tcx> TypeFolder<'tcx> for ParamToVarFolder<'a, 'tcx> {
1574 fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
1578 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
1579 if let ty::Param(ty::ParamTy { name, .. }) = ty.kind {
1580 let infcx = self.infcx;
1581 self.var_map.entry(ty).or_insert_with(|| {
1582 infcx.next_ty_var(TypeVariableOrigin {
1583 kind: TypeVariableOriginKind::TypeParameterDefinition(name, None),
1588 ty.super_fold_with(self)
1594 let mut selcx = SelectionContext::new(self);
1597 pred.fold_with(&mut ParamToVarFolder { infcx: self, var_map: Default::default() });
1599 let cleaned_pred = super::project::normalize(
1602 ObligationCause::dummy(),
1607 let obligation = Obligation::new(
1608 ObligationCause::dummy(),
1610 cleaned_pred.without_const().to_predicate(),
1613 self.predicate_may_hold(&obligation)
1617 fn note_obligation_cause(
1619 err: &mut DiagnosticBuilder<'_>,
1620 obligation: &PredicateObligation<'tcx>,
1622 // First, attempt to add note to this error with an async-await-specific
1623 // message, and fall back to regular note otherwise.
1624 if !self.maybe_note_obligation_cause_for_async_await(err, obligation) {
1625 self.note_obligation_cause_code(
1627 &obligation.predicate,
1628 &obligation.cause.code,
1631 self.suggest_unsized_bound_if_applicable(err, obligation);
1635 fn suggest_unsized_bound_if_applicable(
1637 err: &mut DiagnosticBuilder<'_>,
1638 obligation: &PredicateObligation<'tcx>,
1641 ty::Predicate::Trait(pred, _),
1642 ObligationCauseCode::BindingObligation(item_def_id, span),
1643 ) = (&obligation.predicate, &obligation.cause.code)
1645 if let (Some(generics), true) = (
1646 self.tcx.hir().get_if_local(*item_def_id).as_ref().and_then(|n| n.generics()),
1647 Some(pred.def_id()) == self.tcx.lang_items().sized_trait(),
1649 for param in generics.params {
1650 if param.span == *span
1651 && !param.bounds.iter().any(|bound| {
1652 bound.trait_ref().and_then(|trait_ref| trait_ref.trait_def_id())
1653 == self.tcx.lang_items().sized_trait()
1656 let (span, separator) = match param.bounds {
1657 [] => (span.shrink_to_hi(), ":"),
1658 [.., bound] => (bound.span().shrink_to_hi(), " + "),
1660 err.span_suggestion_verbose(
1662 "consider relaxing the implicit `Sized` restriction",
1663 format!("{} ?Sized", separator),
1664 Applicability::MachineApplicable,
1673 fn is_recursive_obligation(
1675 obligated_types: &mut Vec<&ty::TyS<'tcx>>,
1676 cause_code: &ObligationCauseCode<'tcx>,
1678 if let ObligationCauseCode::BuiltinDerivedObligation(ref data) = cause_code {
1679 let parent_trait_ref = self.resolve_vars_if_possible(&data.parent_trait_ref);
1681 if obligated_types.iter().any(|ot| ot == &parent_trait_ref.skip_binder().self_ty()) {
1689 pub fn recursive_type_with_infinite_size_error(
1692 ) -> DiagnosticBuilder<'tcx> {
1693 assert!(type_def_id.is_local());
1694 let span = tcx.hir().span_if_local(type_def_id).unwrap();
1695 let span = tcx.sess.source_map().guess_head_span(span);
1696 let mut err = struct_span_err!(
1700 "recursive type `{}` has infinite size",
1701 tcx.def_path_str(type_def_id)
1703 err.span_label(span, "recursive type has infinite size");
1705 "insert indirection (e.g., a `Box`, `Rc`, or `&`) \
1706 at some point to make `{}` representable",
1707 tcx.def_path_str(type_def_id)
1712 /// Summarizes information
1715 /// An argument of non-tuple type. Parameters are (name, ty)
1716 Arg(String, String),
1718 /// An argument of tuple type. For a "found" argument, the span is
1719 /// the locationo in the source of the pattern. For a "expected"
1720 /// argument, it will be None. The vector is a list of (name, ty)
1721 /// strings for the components of the tuple.
1722 Tuple(Option<Span>, Vec<(String, String)>),
1726 fn empty() -> ArgKind {
1727 ArgKind::Arg("_".to_owned(), "_".to_owned())
1730 /// Creates an `ArgKind` from the expected type of an
1731 /// argument. It has no name (`_`) and an optional source span.
1732 pub fn from_expected_ty(t: Ty<'_>, span: Option<Span>) -> ArgKind {
1734 ty::Tuple(ref tys) => ArgKind::Tuple(
1736 tys.iter().map(|ty| ("_".to_owned(), ty.to_string())).collect::<Vec<_>>(),
1738 _ => ArgKind::Arg("_".to_owned(), t.to_string()),