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}
;
18 use rustc_hir
::intravisit
::Visitor
;
20 use rustc_middle
::mir
::interpret
::ErrorHandled
;
21 use rustc_middle
::ty
::error
::ExpectedFound
;
22 use rustc_middle
::ty
::fold
::TypeFolder
;
23 use rustc_middle
::ty
::{
24 self, fast_reject
, AdtKind
, SubtypePredicate
, ToPolyTraitRef
, ToPredicate
, Ty
, TyCtxt
,
25 TypeFoldable
, WithConstness
,
27 use rustc_session
::DiagnosticMessageId
;
28 use rustc_span
::symbol
::{kw, sym}
;
29 use rustc_span
::{ExpnKind, MultiSpan, Span, DUMMY_SP}
;
32 use crate::traits
::query
::evaluate_obligation
::InferCtxtExt
as _
;
33 use crate::traits
::query
::normalize
::AtExt
as _
;
34 use on_unimplemented
::InferCtxtExt
as _
;
35 use suggestions
::InferCtxtExt
as _
;
37 pub use rustc_infer
::traits
::error_reporting
::*;
39 pub trait InferCtxtExt
<'tcx
> {
40 fn report_fulfillment_errors(
42 errors
: &[FulfillmentError
<'tcx
>],
43 body_id
: Option
<hir
::BodyId
>,
44 fallback_has_occurred
: bool
,
47 fn report_overflow_error
<T
>(
49 obligation
: &Obligation
<'tcx
, T
>,
50 suggest_increasing_limit
: bool
,
53 T
: fmt
::Display
+ TypeFoldable
<'tcx
>;
55 fn report_overflow_error_cycle(&self, cycle
: &[PredicateObligation
<'tcx
>]) -> !;
57 fn report_selection_error(
59 obligation
: &PredicateObligation
<'tcx
>,
60 error
: &SelectionError
<'tcx
>,
61 fallback_has_occurred
: bool
,
65 /// Given some node representing a fn-like thing in the HIR map,
66 /// returns a span and `ArgKind` information that describes the
67 /// arguments it expects. This can be supplied to
68 /// `report_arg_count_mismatch`.
69 fn get_fn_like_arguments(&self, node
: Node
<'_
>) -> Option
<(Span
, Vec
<ArgKind
>)>;
71 /// Reports an error when the number of arguments needed by a
72 /// trait match doesn't match the number that the expression
74 fn report_arg_count_mismatch(
77 found_span
: Option
<Span
>,
78 expected_args
: Vec
<ArgKind
>,
79 found_args
: Vec
<ArgKind
>,
81 ) -> DiagnosticBuilder
<'tcx
>;
84 impl<'a
, 'tcx
> InferCtxtExt
<'tcx
> for InferCtxt
<'a
, 'tcx
> {
85 fn report_fulfillment_errors(
87 errors
: &[FulfillmentError
<'tcx
>],
88 body_id
: Option
<hir
::BodyId
>,
89 fallback_has_occurred
: bool
,
92 struct ErrorDescriptor
<'tcx
> {
93 predicate
: ty
::Predicate
<'tcx
>,
94 index
: Option
<usize>, // None if this is an old error
97 let mut error_map
: FxHashMap
<_
, Vec
<_
>> = self
98 .reported_trait_errors
101 .map(|(&span
, predicates
)| {
106 .map(|&predicate
| ErrorDescriptor { predicate, index: None }
)
112 for (index
, error
) in errors
.iter().enumerate() {
113 // We want to ignore desugarings here: spans are equivalent even
114 // if one is the result of a desugaring and the other is not.
115 let mut span
= error
.obligation
.cause
.span
;
116 let expn_data
= span
.ctxt().outer_expn_data();
117 if let ExpnKind
::Desugaring(_
) = expn_data
.kind
{
118 span
= expn_data
.call_site
;
121 error_map
.entry(span
).or_default().push(ErrorDescriptor
{
122 predicate
: error
.obligation
.predicate
,
126 self.reported_trait_errors
130 .push(error
.obligation
.predicate
);
133 // We do this in 2 passes because we want to display errors in order, though
134 // maybe it *is* better to sort errors by span or something.
135 let mut is_suppressed
= vec
![false; errors
.len()];
136 for (_
, error_set
) in error_map
.iter() {
137 // We want to suppress "duplicate" errors with the same span.
138 for error
in error_set
{
139 if let Some(index
) = error
.index
{
140 // Suppress errors that are either:
141 // 1) strictly implied by another error.
142 // 2) implied by an error with a smaller index.
143 for error2
in error_set
{
144 if error2
.index
.map_or(false, |index2
| is_suppressed
[index2
]) {
145 // Avoid errors being suppressed by already-suppressed
146 // errors, to prevent all errors from being suppressed
151 if self.error_implies(error2
.predicate
, error
.predicate
)
152 && !(error2
.index
>= error
.index
153 && self.error_implies(error
.predicate
, error2
.predicate
))
155 info
!("skipping {:?} (implied by {:?})", error
, error2
);
156 is_suppressed
[index
] = true;
164 for (error
, suppressed
) in errors
.iter().zip(is_suppressed
) {
166 self.report_fulfillment_error(error
, body_id
, fallback_has_occurred
);
171 /// Reports that an overflow has occurred and halts compilation. We
172 /// halt compilation unconditionally because it is important that
173 /// overflows never be masked -- they basically represent computations
174 /// whose result could not be truly determined and thus we can't say
175 /// if the program type checks or not -- and they are unusual
176 /// occurrences in any case.
177 fn report_overflow_error
<T
>(
179 obligation
: &Obligation
<'tcx
, T
>,
180 suggest_increasing_limit
: bool
,
183 T
: fmt
::Display
+ TypeFoldable
<'tcx
>,
185 let predicate
= self.resolve_vars_if_possible(&obligation
.predicate
);
186 let mut err
= struct_span_err
!(
188 obligation
.cause
.span
,
190 "overflow evaluating the requirement `{}`",
194 if suggest_increasing_limit
{
195 self.suggest_new_overflow_limit(&mut err
);
198 self.note_obligation_cause_code(
200 &obligation
.predicate
,
201 &obligation
.cause
.code
,
206 self.tcx
.sess
.abort_if_errors();
210 /// Reports that a cycle was detected which led to overflow and halts
211 /// compilation. This is equivalent to `report_overflow_error` except
212 /// that we can give a more helpful error message (and, in particular,
213 /// we do not suggest increasing the overflow limit, which is not
215 fn report_overflow_error_cycle(&self, cycle
: &[PredicateObligation
<'tcx
>]) -> ! {
216 let cycle
= self.resolve_vars_if_possible(&cycle
.to_owned());
217 assert
!(!cycle
.is_empty());
219 debug
!("report_overflow_error_cycle: cycle={:?}", cycle
);
221 self.report_overflow_error(&cycle
[0], false);
224 fn report_selection_error(
226 obligation
: &PredicateObligation
<'tcx
>,
227 error
: &SelectionError
<'tcx
>,
228 fallback_has_occurred
: bool
,
232 let span
= obligation
.cause
.span
;
234 let mut err
= match *error
{
235 SelectionError
::Unimplemented
=> {
236 if let ObligationCauseCode
::CompareImplMethodObligation
{
241 | ObligationCauseCode
::CompareImplTypeObligation
{
245 } = obligation
.cause
.code
247 self.report_extra_impl_obligation(
252 &format
!("`{}`", obligation
.predicate
),
258 match obligation
.predicate
.skip_binders() {
259 ty
::PredicateAtom
::Trait(trait_predicate
, _
) => {
260 let trait_predicate
= ty
::Binder
::bind(trait_predicate
);
261 let trait_predicate
= self.resolve_vars_if_possible(&trait_predicate
);
263 if self.tcx
.sess
.has_errors() && trait_predicate
.references_error() {
266 let trait_ref
= trait_predicate
.to_poly_trait_ref();
267 let (post_message
, pre_message
, type_def
) = self
268 .get_parent_trait_ref(&obligation
.cause
.code
)
271 format
!(" in `{}`", t
),
272 format
!("within `{}`, ", t
),
273 s
.map(|s
| (format
!("within this `{}`", t
), s
)),
276 .unwrap_or_default();
278 let OnUnimplementedNote { message, label, note, enclosing_scope }
=
279 self.on_unimplemented_note(trait_ref
, obligation
);
280 let have_alt_message
= message
.is_some() || label
.is_some();
285 .span_to_snippet(span
)
288 let is_from
= self.tcx
.get_diagnostic_item(sym
::from_trait
)
289 == Some(trait_ref
.def_id());
291 { Some(trait_ref.def_id()) == self.tcx.lang_items().unsize_trait() }
;
292 let (message
, note
) = if is_try
&& is_from
{
295 "`?` couldn't convert the error to `{}`",
296 trait_ref
.skip_binder().self_ty(),
299 "the question mark operation (`?`) implicitly performs a \
300 conversion on the error value using the `From` trait"
308 let mut err
= struct_span_err
!(
313 message
.unwrap_or_else(|| format
!(
314 "the trait bound `{}` is not satisfied{}",
315 trait_ref
.without_const().to_predicate(tcx
),
320 if is_try
&& is_from
{
321 let none_error
= self
323 .get_diagnostic_item(sym
::none_error
)
324 .map(|def_id
| tcx
.type_of(def_id
));
325 let should_convert_option_to_result
=
326 Some(trait_ref
.skip_binder().substs
.type_at(1)) == none_error
;
327 let should_convert_result_to_option
=
328 Some(trait_ref
.self_ty().skip_binder()) == none_error
;
329 if should_convert_option_to_result
{
330 err
.span_suggestion_verbose(
332 "consider converting the `Option<T>` into a `Result<T, _>` \
333 using `Option::ok_or` or `Option::ok_or_else`",
334 ".ok_or_else(|| /* error value */)".to_string(),
335 Applicability
::HasPlaceholders
,
337 } else if should_convert_result_to_option
{
338 err
.span_suggestion_verbose(
340 "consider converting the `Result<T, _>` into an `Option<T>` \
343 Applicability
::MachineApplicable
,
346 if let Some(ret_span
) = self.return_type_span(obligation
) {
350 "expected `{}` because of this",
351 trait_ref
.skip_binder().self_ty()
358 if obligation
.cause
.code
== ObligationCauseCode
::MainFunctionType
{
359 "consider using `()`, or a `Result`".to_owned()
362 "{}the trait `{}` is not implemented for `{}`",
364 trait_ref
.print_only_trait_path(),
365 trait_ref
.skip_binder().self_ty(),
369 if self.suggest_add_reference_to_arg(
376 self.note_obligation_cause(&mut err
, obligation
);
380 if let Some(ref s
) = label
{
381 // If it has a custom `#[rustc_on_unimplemented]`
382 // error message, let's display it as the label!
383 err
.span_label(span
, s
.as_str());
384 if !matches
!(trait_ref
.skip_binder().self_ty().kind(), ty
::Param(_
)) {
385 // When the self type is a type param We don't need to "the trait
386 // `std::marker::Sized` is not implemented for `T`" as we will point
387 // at the type param with a label to suggest constraining it.
388 err
.help(&explanation
);
391 err
.span_label(span
, explanation
);
393 if let Some((msg
, span
)) = type_def
{
394 err
.span_label(span
, &msg
);
396 if let Some(ref s
) = note
{
397 // If it has a custom `#[rustc_on_unimplemented]` note, let's display it
398 err
.note(s
.as_str());
400 if let Some(ref s
) = enclosing_scope
{
403 .opt_local_def_id(obligation
.cause
.body_id
)
405 tcx
.hir().body_owner_def_id(hir
::BodyId
{
406 hir_id
: obligation
.cause
.body_id
,
410 let enclosing_scope_span
=
411 tcx
.hir().span_with_body(tcx
.hir().local_def_id_to_hir_id(body
));
413 err
.span_label(enclosing_scope_span
, s
.as_str());
416 self.suggest_dereferences(&obligation
, &mut err
, &trait_ref
, points_at_arg
);
417 self.suggest_fn_call(&obligation
, &mut err
, &trait_ref
, points_at_arg
);
418 self.suggest_remove_reference(&obligation
, &mut err
, &trait_ref
);
419 self.suggest_semicolon_removal(&obligation
, &mut err
, span
, &trait_ref
);
420 self.note_version_mismatch(&mut err
, &trait_ref
);
422 if Some(trait_ref
.def_id()) == tcx
.lang_items().try_trait() {
423 self.suggest_await_before_try(&mut err
, &obligation
, &trait_ref
, span
);
426 if self.suggest_impl_trait(&mut err
, span
, &obligation
, &trait_ref
) {
432 // If the obligation failed due to a missing implementation of the
433 // `Unsize` trait, give a pointer to why that might be the case
435 "all implementations of `Unsize` are provided \
436 automatically by the compiler, see \
437 <https://doc.rust-lang.org/stable/std/marker/trait.Unsize.html> \
438 for more information",
443 self.tcx
.lang_items().fn_trait(),
444 self.tcx
.lang_items().fn_mut_trait(),
445 self.tcx
.lang_items().fn_once_trait(),
447 .contains(&Some(trait_ref
.def_id()));
448 let is_target_feature_fn
= if let ty
::FnDef(def_id
, _
) =
449 *trait_ref
.skip_binder().self_ty().kind()
451 !self.tcx
.codegen_fn_attrs(def_id
).target_features
.is_empty()
455 if is_fn_trait
&& is_target_feature_fn
{
457 "`#[target_feature]` functions do not implement the `Fn` traits",
461 // Try to report a help message
462 if !trait_ref
.has_infer_types_or_consts()
463 && self.predicate_can_apply(obligation
.param_env
, trait_ref
)
465 // If a where-clause may be useful, remind the
466 // user that they can add it.
468 // don't display an on-unimplemented note, as
469 // these notes will often be of the form
470 // "the type `T` can't be frobnicated"
471 // which is somewhat confusing.
472 self.suggest_restricting_param_bound(
475 obligation
.cause
.body_id
,
478 if !have_alt_message
{
479 // Can't show anything else useful, try to find similar impls.
480 let impl_candidates
= self.find_similar_impl_candidates(trait_ref
);
481 self.report_similar_impl_candidates(impl_candidates
, &mut err
);
483 // Changing mutability doesn't make a difference to whether we have
484 // an `Unsize` impl (Fixes ICE in #71036)
486 self.suggest_change_mut(
495 // If this error is due to `!: Trait` not implemented but `(): Trait` is
496 // implemented, and fallback has occurred, then it could be due to a
497 // variable that used to fallback to `()` now falling back to `!`. Issue a
498 // note informing about the change in behaviour.
499 if trait_predicate
.skip_binder().self_ty().is_never()
500 && fallback_has_occurred
502 let predicate
= trait_predicate
.map_bound(|mut trait_pred
| {
503 trait_pred
.trait_ref
.substs
= self.tcx
.mk_substs_trait(
505 &trait_pred
.trait_ref
.substs
[1..],
509 let unit_obligation
=
510 obligation
.with(predicate
.without_const().to_predicate(tcx
));
511 if self.predicate_may_hold(&unit_obligation
) {
513 "the trait is implemented for `()`. \
514 Possibly this error has been caused by changes to \
515 Rust's type-inference algorithm (see issue #48950 \
516 <https://github.com/rust-lang/rust/issues/48950> \
517 for more information). Consider whether you meant to use \
518 the type `()` here instead.",
526 ty
::PredicateAtom
::Subtype(predicate
) => {
527 // Errors for Subtype predicates show up as
528 // `FulfillmentErrorCode::CodeSubtypeError`,
529 // not selection error.
530 span_bug
!(span
, "subtype requirement gave wrong error: `{:?}`", predicate
)
533 ty
::PredicateAtom
::RegionOutlives(predicate
) => {
534 let predicate
= ty
::Binder
::bind(predicate
);
535 let predicate
= self.resolve_vars_if_possible(&predicate
);
537 .region_outlives_predicate(&obligation
.cause
, predicate
)
544 "the requirement `{}` is not satisfied (`{}`)",
550 ty
::PredicateAtom
::Projection(..) | ty
::PredicateAtom
::TypeOutlives(..) => {
551 let predicate
= self.resolve_vars_if_possible(&obligation
.predicate
);
556 "the requirement `{}` is not satisfied",
561 ty
::PredicateAtom
::ObjectSafe(trait_def_id
) => {
562 let violations
= self.tcx
.object_safety_violations(trait_def_id
);
563 report_object_safety_error(self.tcx
, span
, trait_def_id
, violations
)
566 ty
::PredicateAtom
::ClosureKind(closure_def_id
, closure_substs
, kind
) => {
567 let found_kind
= self.closure_kind(closure_substs
).unwrap();
569 self.tcx
.sess
.source_map().guess_head_span(
570 self.tcx
.hir().span_if_local(closure_def_id
).unwrap(),
573 self.tcx
.hir().local_def_id_to_hir_id(closure_def_id
.expect_local());
574 let mut err
= struct_span_err
!(
578 "expected a closure that implements the `{}` trait, \
579 but this closure only implements `{}`",
586 format
!("this closure implements `{}`, not `{}`", found_kind
, kind
),
589 obligation
.cause
.span
,
590 format
!("the requirement to implement `{}` derives from here", kind
),
593 // Additional context information explaining why the closure only implements
594 // a particular trait.
595 if let Some(typeck_results
) = self.in_progress_typeck_results
{
596 let typeck_results
= typeck_results
.borrow();
597 match (found_kind
, typeck_results
.closure_kind_origins().get(hir_id
)) {
598 (ty
::ClosureKind
::FnOnce
, Some((span
, name
))) => {
602 "closure is `FnOnce` because it moves the \
603 variable `{}` out of its environment",
608 (ty
::ClosureKind
::FnMut
, Some((span
, name
))) => {
612 "closure is `FnMut` because it mutates the \
626 ty
::PredicateAtom
::WellFormed(ty
) => {
627 if !self.tcx
.sess
.opts
.debugging_opts
.chalk
{
628 // WF predicates cannot themselves make
629 // errors. They can only block due to
630 // ambiguity; otherwise, they always
631 // degenerate into other obligations
633 span_bug
!(span
, "WF predicate not satisfied for {:?}", ty
);
635 // FIXME: we'll need a better message which takes into account
636 // which bounds actually failed to hold.
637 self.tcx
.sess
.struct_span_err(
639 &format
!("the type `{}` is not well-formed (chalk)", ty
),
644 ty
::PredicateAtom
::ConstEvaluatable(..) => {
645 // Errors for `ConstEvaluatable` predicates show up as
646 // `SelectionError::ConstEvalFailure`,
647 // not `Unimplemented`.
650 "const-evaluatable requirement gave wrong error: `{:?}`",
655 ty
::PredicateAtom
::ConstEquate(..) => {
656 // Errors for `ConstEquate` predicates show up as
657 // `SelectionError::ConstEvalFailure`,
658 // not `Unimplemented`.
661 "const-equate requirement gave wrong error: `{:?}`",
666 ty
::PredicateAtom
::TypeWellFormedFromEnv(..) => span_bug
!(
668 "TypeWellFormedFromEnv predicate should only exist in the environment"
673 OutputTypeParameterMismatch(ref found_trait_ref
, ref expected_trait_ref
, _
) => {
674 let found_trait_ref
= self.resolve_vars_if_possible(&*found_trait_ref
);
675 let expected_trait_ref
= self.resolve_vars_if_possible(&*expected_trait_ref
);
677 if expected_trait_ref
.self_ty().references_error() {
681 let found_trait_ty
= match found_trait_ref
.self_ty().no_bound_vars() {
686 let found_did
= match *found_trait_ty
.kind() {
687 ty
::Closure(did
, _
) | ty
::Foreign(did
) | ty
::FnDef(did
, _
) => Some(did
),
688 ty
::Adt(def
, _
) => Some(def
.did
),
692 let found_span
= found_did
693 .and_then(|did
| self.tcx
.hir().span_if_local(did
))
694 .map(|sp
| self.tcx
.sess
.source_map().guess_head_span(sp
)); // the sp could be an fn def
696 if self.reported_closure_mismatch
.borrow().contains(&(span
, found_span
)) {
697 // We check closures twice, with obligations flowing in different directions,
698 // but we want to complain about them only once.
702 self.reported_closure_mismatch
.borrow_mut().insert((span
, found_span
));
704 let found
= match found_trait_ref
.skip_binder().substs
.type_at(1).kind() {
705 ty
::Tuple(ref tys
) => vec
![ArgKind
::empty(); tys
.len()],
706 _
=> vec
![ArgKind
::empty()],
709 let expected_ty
= expected_trait_ref
.skip_binder().substs
.type_at(1);
710 let expected
= match expected_ty
.kind() {
711 ty
::Tuple(ref tys
) => tys
713 .map(|t
| ArgKind
::from_expected_ty(t
.expect_ty(), Some(span
)))
715 _
=> vec
![ArgKind
::Arg("_".to_owned(), expected_ty
.to_string())],
718 if found
.len() == expected
.len() {
719 self.report_closure_arg_mismatch(
726 let (closure_span
, found
) = found_did
728 let node
= self.tcx
.hir().get_if_local(did
)?
;
729 let (found_span
, found
) = self.get_fn_like_arguments(node
)?
;
730 Some((Some(found_span
), found
))
732 .unwrap_or((found_span
, found
));
734 self.report_arg_count_mismatch(
739 found_trait_ty
.is_closure(),
744 TraitNotObjectSafe(did
) => {
745 let violations
= self.tcx
.object_safety_violations(did
);
746 report_object_safety_error(self.tcx
, span
, did
, violations
)
748 ConstEvalFailure(ErrorHandled
::TooGeneric
) => {
749 bug
!("too generic should have been handled in `is_const_evaluatable`");
751 // Already reported in the query.
752 ConstEvalFailure(ErrorHandled
::Reported(ErrorReported
)) => {
753 // FIXME(eddyb) remove this once `ErrorReported` becomes a proof token.
754 self.tcx
.sess
.delay_span_bug(span
, "`ErrorReported` without an error");
758 // Already reported in the query, but only as a lint.
759 // This shouldn't actually happen for constants used in types, modulo
760 // bugs. The `delay_span_bug` here ensures it won't be ignored.
761 ConstEvalFailure(ErrorHandled
::Linted
) => {
762 self.tcx
.sess
.delay_span_bug(span
, "constant in type had error reported as lint");
767 bug
!("overflow should be handled before the `report_selection_error` path");
771 self.note_obligation_cause(&mut err
, obligation
);
772 self.point_at_returns_when_relevant(&mut err
, &obligation
);
777 /// Given some node representing a fn-like thing in the HIR map,
778 /// returns a span and `ArgKind` information that describes the
779 /// arguments it expects. This can be supplied to
780 /// `report_arg_count_mismatch`.
781 fn get_fn_like_arguments(&self, node
: Node
<'_
>) -> Option
<(Span
, Vec
<ArgKind
>)> {
782 let sm
= self.tcx
.sess
.source_map();
783 let hir
= self.tcx
.hir();
785 Node
::Expr(&hir
::Expr
{
786 kind
: hir
::ExprKind
::Closure(_
, ref _decl
, id
, span
, _
),
789 sm
.guess_head_span(span
),
794 if let hir
::Pat { kind: hir::PatKind::Tuple(ref args, _), span, .. }
=
801 sm
.span_to_snippet(pat
.span
)
803 .map(|snippet
| (snippet
, "_".to_owned()))
805 .collect
::<Option
<Vec
<_
>>>()?
,
808 let name
= sm
.span_to_snippet(arg
.pat
.span
).ok()?
;
809 Some(ArgKind
::Arg(name
, "_".to_owned()))
812 .collect
::<Option
<Vec
<ArgKind
>>>()?
,
814 Node
::Item(&hir
::Item { span, kind: hir::ItemKind::Fn(ref sig, ..), .. }
)
815 | Node
::ImplItem(&hir
::ImplItem
{
817 kind
: hir
::ImplItemKind
::Fn(ref sig
, _
),
820 | Node
::TraitItem(&hir
::TraitItem
{
822 kind
: hir
::TraitItemKind
::Fn(ref sig
, _
),
825 sm
.guess_head_span(span
),
829 .map(|arg
| match arg
.clone().kind
{
830 hir
::TyKind
::Tup(ref tys
) => ArgKind
::Tuple(
832 vec
![("_".to_owned(), "_".to_owned()); tys
.len()],
834 _
=> ArgKind
::empty(),
836 .collect
::<Vec
<ArgKind
>>(),
838 Node
::Ctor(ref variant_data
) => {
839 let span
= variant_data
.ctor_hir_id().map(|id
| hir
.span(id
)).unwrap_or(DUMMY_SP
);
840 let span
= sm
.guess_head_span(span
);
841 (span
, vec
![ArgKind
::empty(); variant_data
.fields().len()])
843 _
=> panic
!("non-FnLike node found: {:?}", node
),
847 /// Reports an error when the number of arguments needed by a
848 /// trait match doesn't match the number that the expression
850 fn report_arg_count_mismatch(
853 found_span
: Option
<Span
>,
854 expected_args
: Vec
<ArgKind
>,
855 found_args
: Vec
<ArgKind
>,
857 ) -> DiagnosticBuilder
<'tcx
> {
858 let kind
= if is_closure { "closure" }
else { "function" }
;
860 let args_str
= |arguments
: &[ArgKind
], other
: &[ArgKind
]| {
861 let arg_length
= arguments
.len();
862 let distinct
= match &other
[..] {
863 &[ArgKind
::Tuple(..)] => true,
866 match (arg_length
, arguments
.get(0)) {
867 (1, Some(&ArgKind
::Tuple(_
, ref fields
))) => {
868 format
!("a single {}-tuple as argument", fields
.len())
873 if distinct
&& arg_length
> 1 { "distinct " }
else { "" }
,
874 pluralize
!(arg_length
)
879 let expected_str
= args_str(&expected_args
, &found_args
);
880 let found_str
= args_str(&found_args
, &expected_args
);
882 let mut err
= struct_span_err
!(
886 "{} is expected to take {}, but it takes {}",
892 err
.span_label(span
, format
!("expected {} that takes {}", kind
, expected_str
));
894 if let Some(found_span
) = found_span
{
895 err
.span_label(found_span
, format
!("takes {}", found_str
));
898 // ^^^^^^^^-- def_span
902 let prefix_span
= self.tcx
.sess
.source_map().span_until_non_whitespace(found_span
);
906 if let Some(span
) = found_span
.trim_start(prefix_span
) { span }
else { found_span }
;
908 // Suggest to take and ignore the arguments with expected_args_length `_`s if
909 // found arguments is empty (assume the user just wants to ignore args in this case).
910 // For example, if `expected_args_length` is 2, suggest `|_, _|`.
911 if found_args
.is_empty() && is_closure
{
912 let underscores
= vec
!["_"; expected_args
.len()].join(", ");
913 err
.span_suggestion_verbose(
916 "consider changing the closure to take and ignore the expected argument{}",
917 pluralize
!(expected_args
.len())
919 format
!("|{}|", underscores
),
920 Applicability
::MachineApplicable
,
924 if let &[ArgKind
::Tuple(_
, ref fields
)] = &found_args
[..] {
925 if fields
.len() == expected_args
.len() {
928 .map(|(name
, _
)| name
.to_owned())
929 .collect
::<Vec
<String
>>()
931 err
.span_suggestion_verbose(
933 "change the closure to take multiple arguments instead of a single tuple",
934 format
!("|{}|", sugg
),
935 Applicability
::MachineApplicable
,
939 if let &[ArgKind
::Tuple(_
, ref fields
)] = &expected_args
[..] {
940 if fields
.len() == found_args
.len() && is_closure
{
945 .map(|arg
| match arg
{
946 ArgKind
::Arg(name
, _
) => name
.to_owned(),
949 .collect
::<Vec
<String
>>()
951 // add type annotations if available
952 if found_args
.iter().any(|arg
| match arg
{
953 ArgKind
::Arg(_
, ty
) => ty
!= "_",
960 .map(|(_
, ty
)| ty
.to_owned())
961 .collect
::<Vec
<String
>>()
968 err
.span_suggestion_verbose(
970 "change the closure to accept a tuple instead of individual arguments",
972 Applicability
::MachineApplicable
,
982 trait InferCtxtPrivExt
<'tcx
> {
983 // returns if `cond` not occurring implies that `error` does not occur - i.e., that
984 // `error` occurring implies that `cond` occurs.
985 fn error_implies(&self, cond
: ty
::Predicate
<'tcx
>, error
: ty
::Predicate
<'tcx
>) -> bool
;
987 fn report_fulfillment_error(
989 error
: &FulfillmentError
<'tcx
>,
990 body_id
: Option
<hir
::BodyId
>,
991 fallback_has_occurred
: bool
,
994 fn report_projection_error(
996 obligation
: &PredicateObligation
<'tcx
>,
997 error
: &MismatchedProjectionTypes
<'tcx
>,
1000 fn fuzzy_match_tys(&self, a
: Ty
<'tcx
>, b
: Ty
<'tcx
>) -> bool
;
1002 fn describe_generator(&self, body_id
: hir
::BodyId
) -> Option
<&'
static str>;
1004 fn find_similar_impl_candidates(
1006 trait_ref
: ty
::PolyTraitRef
<'tcx
>,
1007 ) -> Vec
<ty
::TraitRef
<'tcx
>>;
1009 fn report_similar_impl_candidates(
1011 impl_candidates
: Vec
<ty
::TraitRef
<'tcx
>>,
1012 err
: &mut DiagnosticBuilder
<'_
>,
1015 /// Gets the parent trait chain start
1016 fn get_parent_trait_ref(
1018 code
: &ObligationCauseCode
<'tcx
>,
1019 ) -> Option
<(String
, Option
<Span
>)>;
1021 /// If the `Self` type of the unsatisfied trait `trait_ref` implements a trait
1022 /// with the same path as `trait_ref`, a help message about
1023 /// a probable version mismatch is added to `err`
1024 fn note_version_mismatch(
1026 err
: &mut DiagnosticBuilder
<'_
>,
1027 trait_ref
: &ty
::PolyTraitRef
<'tcx
>,
1030 /// Creates a `PredicateObligation` with `new_self_ty` replacing the existing type in the
1033 /// For this to work, `new_self_ty` must have no escaping bound variables.
1034 fn mk_trait_obligation_with_new_self_ty(
1036 param_env
: ty
::ParamEnv
<'tcx
>,
1037 trait_ref
: &ty
::PolyTraitRef
<'tcx
>,
1038 new_self_ty
: Ty
<'tcx
>,
1039 ) -> PredicateObligation
<'tcx
>;
1041 fn maybe_report_ambiguity(
1043 obligation
: &PredicateObligation
<'tcx
>,
1044 body_id
: Option
<hir
::BodyId
>,
1047 fn predicate_can_apply(
1049 param_env
: ty
::ParamEnv
<'tcx
>,
1050 pred
: ty
::PolyTraitRef
<'tcx
>,
1053 fn note_obligation_cause(
1055 err
: &mut DiagnosticBuilder
<'tcx
>,
1056 obligation
: &PredicateObligation
<'tcx
>,
1059 fn suggest_unsized_bound_if_applicable(
1061 err
: &mut DiagnosticBuilder
<'tcx
>,
1062 obligation
: &PredicateObligation
<'tcx
>,
1065 fn is_recursive_obligation(
1067 obligated_types
: &mut Vec
<&ty
::TyS
<'tcx
>>,
1068 cause_code
: &ObligationCauseCode
<'tcx
>,
1072 impl<'a
, 'tcx
> InferCtxtPrivExt
<'tcx
> for InferCtxt
<'a
, 'tcx
> {
1073 // returns if `cond` not occurring implies that `error` does not occur - i.e., that
1074 // `error` occurring implies that `cond` occurs.
1075 fn error_implies(&self, cond
: ty
::Predicate
<'tcx
>, error
: ty
::Predicate
<'tcx
>) -> bool
{
1080 // FIXME: It should be possible to deal with `ForAll` in a cleaner way.
1081 let (cond
, error
) = match (cond
.skip_binders(), error
.skip_binders()) {
1082 (ty
::PredicateAtom
::Trait(..), ty
::PredicateAtom
::Trait(error
, _
)) => {
1083 (cond
, ty
::Binder
::bind(error
))
1086 // FIXME: make this work in other cases too.
1091 for obligation
in super::elaborate_predicates(self.tcx
, std
::iter
::once(cond
)) {
1092 if let ty
::PredicateAtom
::Trait(implication
, _
) = obligation
.predicate
.skip_binders() {
1093 let error
= error
.to_poly_trait_ref();
1094 let implication
= ty
::Binder
::bind(implication
.trait_ref
);
1095 // FIXME: I'm just not taking associated types at all here.
1096 // Eventually I'll need to implement param-env-aware
1097 // `Γ₁ ⊦ φ₁ => Γ₂ ⊦ φ₂` logic.
1098 let param_env
= ty
::ParamEnv
::empty();
1099 if self.can_sub(param_env
, error
, implication
).is_ok() {
1100 debug
!("error_implies: {:?} -> {:?} -> {:?}", cond
, error
, implication
);
1109 fn report_fulfillment_error(
1111 error
: &FulfillmentError
<'tcx
>,
1112 body_id
: Option
<hir
::BodyId
>,
1113 fallback_has_occurred
: bool
,
1115 debug
!("report_fulfillment_error({:?})", error
);
1117 FulfillmentErrorCode
::CodeSelectionError(ref selection_error
) => {
1118 self.report_selection_error(
1121 fallback_has_occurred
,
1122 error
.points_at_arg_span
,
1125 FulfillmentErrorCode
::CodeProjectionError(ref e
) => {
1126 self.report_projection_error(&error
.obligation
, e
);
1128 FulfillmentErrorCode
::CodeAmbiguity
=> {
1129 self.maybe_report_ambiguity(&error
.obligation
, body_id
);
1131 FulfillmentErrorCode
::CodeSubtypeError(ref expected_found
, ref err
) => {
1132 self.report_mismatched_types(
1133 &error
.obligation
.cause
,
1134 expected_found
.expected
,
1135 expected_found
.found
,
1140 FulfillmentErrorCode
::CodeConstEquateError(ref expected_found
, ref err
) => {
1141 self.report_mismatched_consts(
1142 &error
.obligation
.cause
,
1143 expected_found
.expected
,
1144 expected_found
.found
,
1152 fn report_projection_error(
1154 obligation
: &PredicateObligation
<'tcx
>,
1155 error
: &MismatchedProjectionTypes
<'tcx
>,
1157 let predicate
= self.resolve_vars_if_possible(&obligation
.predicate
);
1159 if predicate
.references_error() {
1165 let mut err
= &error
.err
;
1166 let mut values
= None
;
1168 // try to find the mismatched types to report the error with.
1170 // this can fail if the problem was higher-ranked, in which
1171 // cause I have no idea for a good error message.
1172 if let ty
::PredicateAtom
::Projection(data
) = predicate
.skip_binders() {
1173 let mut selcx
= SelectionContext
::new(self);
1174 let (data
, _
) = self.replace_bound_vars_with_fresh_vars(
1175 obligation
.cause
.span
,
1176 infer
::LateBoundRegionConversionTime
::HigherRankedType
,
1177 &ty
::Binder
::bind(data
),
1179 let mut obligations
= vec
![];
1180 let normalized_ty
= super::normalize_projection_type(
1182 obligation
.param_env
,
1184 obligation
.cause
.clone(),
1190 "report_projection_error obligation.cause={:?} obligation.param_env={:?}",
1191 obligation
.cause
, obligation
.param_env
1195 "report_projection_error normalized_ty={:?} data.ty={:?}",
1196 normalized_ty
, data
.ty
1199 let is_normalized_ty_expected
= match &obligation
.cause
.code
{
1200 ObligationCauseCode
::ItemObligation(_
)
1201 | ObligationCauseCode
::BindingObligation(_
, _
)
1202 | ObligationCauseCode
::ObjectCastObligation(_
) => false,
1206 if let Err(error
) = self.at(&obligation
.cause
, obligation
.param_env
).eq_exp(
1207 is_normalized_ty_expected
,
1211 values
= Some(infer
::ValuePairs
::Types(ExpectedFound
::new(
1212 is_normalized_ty_expected
,
1222 let msg
= format
!("type mismatch resolving `{}`", predicate
);
1223 let error_id
= (DiagnosticMessageId
::ErrorId(271), Some(obligation
.cause
.span
), msg
);
1224 let fresh
= self.tcx
.sess
.one_time_diagnostics
.borrow_mut().insert(error_id
);
1226 let mut diag
= struct_span_err
!(
1228 obligation
.cause
.span
,
1230 "type mismatch resolving `{}`",
1233 self.note_type_err(&mut diag
, &obligation
.cause
, None
, values
, err
);
1234 self.note_obligation_cause(&mut diag
, obligation
);
1240 fn fuzzy_match_tys(&self, a
: Ty
<'tcx
>, b
: Ty
<'tcx
>) -> bool
{
1241 /// returns the fuzzy category of a given type, or None
1242 /// if the type can be equated to any type.
1243 fn type_category(t
: Ty
<'_
>) -> Option
<u32> {
1245 ty
::Bool
=> Some(0),
1246 ty
::Char
=> Some(1),
1248 ty
::Int(..) | ty
::Uint(..) | ty
::Infer(ty
::IntVar(..)) => Some(3),
1249 ty
::Float(..) | ty
::Infer(ty
::FloatVar(..)) => Some(4),
1250 ty
::Ref(..) | ty
::RawPtr(..) => Some(5),
1251 ty
::Array(..) | ty
::Slice(..) => Some(6),
1252 ty
::FnDef(..) | ty
::FnPtr(..) => Some(7),
1253 ty
::Dynamic(..) => Some(8),
1254 ty
::Closure(..) => Some(9),
1255 ty
::Tuple(..) => Some(10),
1256 ty
::Projection(..) => Some(11),
1257 ty
::Param(..) => Some(12),
1258 ty
::Opaque(..) => Some(13),
1259 ty
::Never
=> Some(14),
1260 ty
::Adt(adt
, ..) => match adt
.adt_kind() {
1261 AdtKind
::Struct
=> Some(15),
1262 AdtKind
::Union
=> Some(16),
1263 AdtKind
::Enum
=> Some(17),
1265 ty
::Generator(..) => Some(18),
1266 ty
::Foreign(..) => Some(19),
1267 ty
::GeneratorWitness(..) => Some(20),
1268 ty
::Placeholder(..) | ty
::Bound(..) | ty
::Infer(..) | ty
::Error(_
) => None
,
1272 match (type_category(a
), type_category(b
)) {
1273 (Some(cat_a
), Some(cat_b
)) => match (a
.kind(), b
.kind()) {
1274 (&ty
::Adt(def_a
, _
), &ty
::Adt(def_b
, _
)) => def_a
== def_b
,
1275 _
=> cat_a
== cat_b
,
1277 // infer and error can be equated to all types
1282 fn describe_generator(&self, body_id
: hir
::BodyId
) -> Option
<&'
static str> {
1283 self.tcx
.hir().body(body_id
).generator_kind
.map(|gen_kind
| match gen_kind
{
1284 hir
::GeneratorKind
::Gen
=> "a generator",
1285 hir
::GeneratorKind
::Async(hir
::AsyncGeneratorKind
::Block
) => "an async block",
1286 hir
::GeneratorKind
::Async(hir
::AsyncGeneratorKind
::Fn
) => "an async function",
1287 hir
::GeneratorKind
::Async(hir
::AsyncGeneratorKind
::Closure
) => "an async closure",
1291 fn find_similar_impl_candidates(
1293 trait_ref
: ty
::PolyTraitRef
<'tcx
>,
1294 ) -> Vec
<ty
::TraitRef
<'tcx
>> {
1295 let simp
= fast_reject
::simplify_type(self.tcx
, trait_ref
.skip_binder().self_ty(), true);
1296 let all_impls
= self.tcx
.all_impls(trait_ref
.def_id());
1299 Some(simp
) => all_impls
1300 .filter_map(|def_id
| {
1301 let imp
= self.tcx
.impl_trait_ref(def_id
).unwrap();
1302 let imp_simp
= fast_reject
::simplify_type(self.tcx
, imp
.self_ty(), true);
1303 if let Some(imp_simp
) = imp_simp
{
1304 if simp
!= imp_simp
{
1311 None
=> all_impls
.map(|def_id
| self.tcx
.impl_trait_ref(def_id
).unwrap()).collect(),
1315 fn report_similar_impl_candidates(
1317 impl_candidates
: Vec
<ty
::TraitRef
<'tcx
>>,
1318 err
: &mut DiagnosticBuilder
<'_
>,
1320 if impl_candidates
.is_empty() {
1324 let len
= impl_candidates
.len();
1325 let end
= if impl_candidates
.len() <= 5 { impl_candidates.len() }
else { 4 }
;
1327 let normalize
= |candidate
| {
1328 self.tcx
.infer_ctxt().enter(|ref infcx
| {
1329 let normalized
= infcx
1330 .at(&ObligationCause
::dummy(), ty
::ParamEnv
::empty())
1331 .normalize(candidate
)
1334 Some(normalized
) => format
!("\n {}", normalized
.value
),
1335 None
=> format
!("\n {}", candidate
),
1340 // Sort impl candidates so that ordering is consistent for UI tests.
1341 let mut normalized_impl_candidates
=
1342 impl_candidates
.iter().map(normalize
).collect
::<Vec
<String
>>();
1344 // Sort before taking the `..end` range,
1345 // because the ordering of `impl_candidates` may not be deterministic:
1346 // https://github.com/rust-lang/rust/pull/57475#issuecomment-455519507
1347 normalized_impl_candidates
.sort();
1350 "the following implementations were found:{}{}",
1351 normalized_impl_candidates
[..end
].join(""),
1352 if len
> 5 { format!("\nand {} others
", len - 4) } else { String::new() }
1356 /// Gets the parent trait chain start
1357 fn get_parent_trait_ref(
1359 code: &ObligationCauseCode<'tcx>,
1360 ) -> Option<(String, Option<Span>)> {
1362 &ObligationCauseCode::BuiltinDerivedObligation(ref data) => {
1363 let parent_trait_ref = self.resolve_vars_if_possible(&data.parent_trait_ref);
1364 match self.get_parent_trait_ref(&data.parent_code) {
1367 let ty = parent_trait_ref.skip_binder().self_ty();
1369 TyCategory::from_ty(ty).map(|(_, def_id)| self.tcx.def_span(def_id));
1370 Some((ty.to_string(), span))
1378 /// If the `Self` type of the unsatisfied trait `trait_ref` implements a trait
1379 /// with the same path as `trait_ref`, a help message about
1380 /// a probable version mismatch is added to `err`
1381 fn note_version_mismatch(
1383 err: &mut DiagnosticBuilder<'_>,
1384 trait_ref: &ty::PolyTraitRef<'tcx>,
1386 let get_trait_impl = |trait_def_id| {
1387 let mut trait_impl = None;
1388 self.tcx.for_each_relevant_impl(
1390 trait_ref.skip_binder().self_ty(),
1392 if trait_impl.is_none() {
1393 trait_impl = Some(impl_def_id);
1399 let required_trait_path = self.tcx.def_path_str(trait_ref.def_id());
1400 let all_traits = self.tcx.all_traits(LOCAL_CRATE);
1401 let traits_with_same_path: std::collections::BTreeSet<_> = all_traits
1403 .filter(|trait_def_id| **trait_def_id != trait_ref.def_id())
1404 .filter(|trait_def_id| self.tcx.def_path_str(**trait_def_id) == required_trait_path)
1406 for trait_with_same_path in traits_with_same_path {
1407 if let Some(impl_def_id) = get_trait_impl(*trait_with_same_path) {
1408 let impl_span = self.tcx.def_span(impl_def_id);
1409 err.span_help(impl_span, "trait impl with same name found
");
1410 let trait_crate = self.tcx.crate_name(trait_with_same_path.krate);
1411 let crate_msg = format!(
1412 "perhaps two different versions of
crate `{}` are being used?
",
1415 err.note(&crate_msg);
1420 fn mk_trait_obligation_with_new_self_ty(
1422 param_env: ty::ParamEnv<'tcx>,
1423 trait_ref: &ty::PolyTraitRef<'tcx>,
1424 new_self_ty: Ty<'tcx>,
1425 ) -> PredicateObligation<'tcx> {
1426 assert!(!new_self_ty.has_escaping_bound_vars());
1428 let trait_ref = trait_ref.map_bound_ref(|tr| ty::TraitRef {
1429 substs: self.tcx.mk_substs_trait(new_self_ty, &tr.substs[1..]),
1434 ObligationCause::dummy(),
1436 trait_ref.without_const().to_predicate(self.tcx),
1440 fn maybe_report_ambiguity(
1442 obligation: &PredicateObligation<'tcx>,
1443 body_id: Option<hir::BodyId>,
1445 // Unable to successfully determine, probably means
1446 // insufficient type information, but could mean
1447 // ambiguous impls. The latter *ought* to be a
1448 // coherence violation, so we don't report it here.
1450 let predicate = self.resolve_vars_if_possible(&obligation.predicate);
1451 let span = obligation.cause.span;
1454 "maybe_report_ambiguity(predicate
={:?}
, obligation
={:?} body_id
={:?}
, code
={:?}
)",
1455 predicate, obligation, body_id, obligation.cause.code,
1458 // Ambiguity errors are often caused as fallout from earlier
1459 // errors. So just ignore them if this infcx is tainted.
1460 if self.is_tainted_by_errors() {
1464 let mut err = match predicate.skip_binders() {
1465 ty::PredicateAtom::Trait(data, _) => {
1466 let trait_ref = ty::Binder::bind(data.trait_ref);
1467 let self_ty = trait_ref.skip_binder().self_ty();
1468 debug!("self_ty {:?} {:?} trait_ref {:?}
", self_ty, self_ty.kind(), trait_ref);
1470 if predicate.references_error() {
1473 // Typically, this ambiguity should only happen if
1474 // there are unresolved type inference variables
1475 // (otherwise it would suggest a coherence
1476 // failure). But given #21974 that is not necessarily
1477 // the case -- we can have multiple where clauses that
1478 // are only distinguished by a region, which results
1479 // in an ambiguity even when all types are fully
1480 // known, since we don't dispatch based on region
1483 // This is kind of a hack: it frequently happens that some earlier
1484 // error prevents types from being fully inferred, and then we get
1485 // a bunch of uninteresting errors saying something like "<generic
1486 // #0> doesn't implement Sized". It may even be true that we
1487 // could just skip over all checks where the self-ty is an
1488 // inference variable, but I was afraid that there might be an
1489 // inference variable created, registered as an obligation, and
1490 // then never forced by writeback, and hence by skipping here we'd
1491 // be ignoring the fact that we don't KNOW the type works
1492 // out. Though even that would probably be harmless, given that
1493 // we're only talking about builtin traits, which are known to be
1494 // inhabited. We used to check for `self.tcx.sess.has_errors()` to
1495 // avoid inundating the user with unnecessary errors, but we now
1496 // check upstream for type errors and don't add the obligations to
1497 // begin with in those cases.
1498 if self.tcx
.lang_items().sized_trait() == Some(trait_ref
.def_id()) {
1499 self.emit_inference_failure_err(
1508 let mut err
= self.emit_inference_failure_err(
1514 err
.note(&format
!("cannot satisfy `{}`", predicate
));
1515 if let ObligationCauseCode
::ItemObligation(def_id
) = obligation
.cause
.code
{
1516 self.suggest_fully_qualified_path(&mut err
, def_id
, span
, trait_ref
.def_id());
1519 ObligationCauseCode
::BindingObligation(ref def_id
, _
),
1521 (self.tcx
.sess
.source_map().span_to_snippet(span
), &obligation
.cause
.code
)
1523 let generics
= self.tcx
.generics_of(*def_id
);
1524 if generics
.params
.iter().any(|p
| p
.name
!= kw
::SelfUpper
)
1525 && !snippet
.ends_with('
>'
)
1527 // FIXME: To avoid spurious suggestions in functions where type arguments
1528 // where already supplied, we check the snippet to make sure it doesn't
1529 // end with a turbofish. Ideally we would have access to a `PathSegment`
1530 // instead. Otherwise we would produce the following output:
1532 // error[E0283]: type annotations needed
1533 // --> $DIR/issue-54954.rs:3:24
1535 // LL | const ARR_LEN: usize = Tt::const_val::<[i8; 123]>();
1536 // | ^^^^^^^^^^^^^^^^^^^^^^^^^^
1538 // | cannot infer type
1539 // | help: consider specifying the type argument
1540 // | in the function call:
1541 // | `Tt::const_val::<[i8; 123]>::<T>`
1543 // LL | const fn const_val<T: Sized>() -> usize {
1544 // | - required by this bound in `Tt::const_val`
1546 // = note: cannot satisfy `_: Tt`
1548 err
.span_suggestion_verbose(
1549 span
.shrink_to_hi(),
1551 "consider specifying the type argument{} in the function call",
1552 pluralize
!(generics
.params
.len()),
1559 .map(|p
| p
.name
.to_string())
1560 .collect
::<Vec
<String
>>()
1563 Applicability
::HasPlaceholders
,
1570 ty
::PredicateAtom
::WellFormed(arg
) => {
1571 // Same hacky approach as above to avoid deluging user
1572 // with error messages.
1573 if arg
.references_error() || self.tcx
.sess
.has_errors() {
1577 self.emit_inference_failure_err(body_id
, span
, arg
, ErrorCode
::E0282
)
1580 ty
::PredicateAtom
::Subtype(data
) => {
1581 if data
.references_error() || self.tcx
.sess
.has_errors() {
1582 // no need to overload user in such cases
1585 let SubtypePredicate { a_is_expected: _, a, b }
= data
;
1586 // both must be type variables, or the other would've been instantiated
1587 assert
!(a
.is_ty_var() && b
.is_ty_var());
1588 self.emit_inference_failure_err(body_id
, span
, a
.into(), ErrorCode
::E0282
)
1590 ty
::PredicateAtom
::Projection(data
) => {
1591 let trait_ref
= ty
::Binder
::bind(data
).to_poly_trait_ref(self.tcx
);
1592 let self_ty
= trait_ref
.skip_binder().self_ty();
1594 if predicate
.references_error() {
1597 if self_ty
.needs_infer() && ty
.needs_infer() {
1598 // We do this for the `foo.collect()?` case to produce a suggestion.
1599 let mut err
= self.emit_inference_failure_err(
1605 err
.note(&format
!("cannot satisfy `{}`", predicate
));
1608 let mut err
= struct_span_err
!(
1612 "type annotations needed: cannot satisfy `{}`",
1615 err
.span_label(span
, &format
!("cannot satisfy `{}`", predicate
));
1621 if self.tcx
.sess
.has_errors() {
1624 let mut err
= struct_span_err
!(
1628 "type annotations needed: cannot satisfy `{}`",
1631 err
.span_label(span
, &format
!("cannot satisfy `{}`", predicate
));
1635 self.note_obligation_cause(&mut err
, obligation
);
1639 /// Returns `true` if the trait predicate may apply for *some* assignment
1640 /// to the type parameters.
1641 fn predicate_can_apply(
1643 param_env
: ty
::ParamEnv
<'tcx
>,
1644 pred
: ty
::PolyTraitRef
<'tcx
>,
1646 struct ParamToVarFolder
<'a
, 'tcx
> {
1647 infcx
: &'a InferCtxt
<'a
, 'tcx
>,
1648 var_map
: FxHashMap
<Ty
<'tcx
>, Ty
<'tcx
>>,
1651 impl<'a
, 'tcx
> TypeFolder
<'tcx
> for ParamToVarFolder
<'a
, 'tcx
> {
1652 fn tcx
<'b
>(&'b
self) -> TyCtxt
<'tcx
> {
1656 fn fold_ty(&mut self, ty
: Ty
<'tcx
>) -> Ty
<'tcx
> {
1657 if let ty
::Param(ty
::ParamTy { name, .. }
) = *ty
.kind() {
1658 let infcx
= self.infcx
;
1659 self.var_map
.entry(ty
).or_insert_with(|| {
1660 infcx
.next_ty_var(TypeVariableOrigin
{
1661 kind
: TypeVariableOriginKind
::TypeParameterDefinition(name
, None
),
1666 ty
.super_fold_with(self)
1672 let mut selcx
= SelectionContext
::new(self);
1675 pred
.fold_with(&mut ParamToVarFolder { infcx: self, var_map: Default::default() }
);
1677 let cleaned_pred
= super::project
::normalize(
1680 ObligationCause
::dummy(),
1685 let obligation
= Obligation
::new(
1686 ObligationCause
::dummy(),
1688 cleaned_pred
.without_const().to_predicate(selcx
.tcx()),
1691 self.predicate_may_hold(&obligation
)
1695 fn note_obligation_cause(
1697 err
: &mut DiagnosticBuilder
<'tcx
>,
1698 obligation
: &PredicateObligation
<'tcx
>,
1700 // First, attempt to add note to this error with an async-await-specific
1701 // message, and fall back to regular note otherwise.
1702 if !self.maybe_note_obligation_cause_for_async_await(err
, obligation
) {
1703 self.note_obligation_cause_code(
1705 &obligation
.predicate
,
1706 &obligation
.cause
.code
,
1709 self.suggest_unsized_bound_if_applicable(err
, obligation
);
1713 fn suggest_unsized_bound_if_applicable(
1715 err
: &mut DiagnosticBuilder
<'tcx
>,
1716 obligation
: &PredicateObligation
<'tcx
>,
1718 let (pred
, item_def_id
, span
) =
1719 match (obligation
.predicate
.skip_binders(), obligation
.cause
.code
.peel_derives()) {
1721 ty
::PredicateAtom
::Trait(pred
, _
),
1722 &ObligationCauseCode
::BindingObligation(item_def_id
, span
),
1723 ) => (pred
, item_def_id
, span
),
1728 self.tcx
.hir().get_if_local(item_def_id
),
1729 Some(pred
.def_id()) == self.tcx
.lang_items().sized_trait(),
1731 (Some(node
), true) => node
,
1734 let generics
= match node
.generics() {
1735 Some(generics
) => generics
,
1738 for param
in generics
.params
{
1739 if param
.span
!= span
1740 || param
.bounds
.iter().any(|bound
| {
1741 bound
.trait_ref().and_then(|trait_ref
| trait_ref
.trait_def_id())
1742 == self.tcx
.lang_items().sized_trait()
1753 hir
::ItemKind
::Enum(..)
1754 | hir
::ItemKind
::Struct(..)
1755 | hir
::ItemKind
::Union(..),
1759 // Suggesting `T: ?Sized` is only valid in an ADT if `T` is only used in a
1760 // borrow. `struct S<'a, T: ?Sized>(&'a T);` is valid, `struct S<T: ?Sized>(T);`
1762 let mut visitor
= FindTypeParam
{
1763 param
: param
.name
.ident().name
,
1764 invalid_spans
: vec
![],
1767 visitor
.visit_item(item
);
1768 if !visitor
.invalid_spans
.is_empty() {
1769 let mut multispan
: MultiSpan
= param
.span
.into();
1770 multispan
.push_span_label(
1772 format
!("this could be changed to `{}: ?Sized`...", param
.name
.ident()),
1774 for sp
in visitor
.invalid_spans
{
1775 multispan
.push_span_label(
1778 "...if indirection was used here: `Box<{}>`",
1786 "you could relax the implicit `Sized` bound on `{T}` if it were \
1787 used through indirection like `&{T}` or `Box<{T}>`",
1788 T
= param
.name
.ident(),
1796 let (span
, separator
) = match param
.bounds
{
1797 [] => (span
.shrink_to_hi(), ":"),
1798 [.., bound
] => (bound
.span().shrink_to_hi(), " +"),
1800 err
.span_suggestion_verbose(
1802 "consider relaxing the implicit `Sized` restriction",
1803 format
!("{} ?Sized", separator
),
1804 Applicability
::MachineApplicable
,
1810 fn is_recursive_obligation(
1812 obligated_types
: &mut Vec
<&ty
::TyS
<'tcx
>>,
1813 cause_code
: &ObligationCauseCode
<'tcx
>,
1815 if let ObligationCauseCode
::BuiltinDerivedObligation(ref data
) = cause_code
{
1816 let parent_trait_ref
= self.resolve_vars_if_possible(&data
.parent_trait_ref
);
1818 if obligated_types
.iter().any(|ot
| ot
== &parent_trait_ref
.skip_binder().self_ty()) {
1826 /// Look for type `param` in an ADT being used only through a reference to confirm that suggesting
1827 /// `param: ?Sized` would be a valid constraint.
1828 struct FindTypeParam
{
1829 param
: rustc_span
::Symbol
,
1830 invalid_spans
: Vec
<Span
>,
1834 impl<'v
> Visitor
<'v
> for FindTypeParam
{
1835 type Map
= rustc_hir
::intravisit
::ErasedMap
<'v
>;
1837 fn nested_visit_map(&mut self) -> hir
::intravisit
::NestedVisitorMap
<Self::Map
> {
1838 hir
::intravisit
::NestedVisitorMap
::None
1841 fn visit_ty(&mut self, ty
: &hir
::Ty
<'_
>) {
1842 // We collect the spans of all uses of the "bare" type param, like in `field: T` or
1843 // `field: (T, T)` where we could make `T: ?Sized` while skipping cases that are known to be
1844 // valid like `field: &'a T` or `field: *mut T` and cases that *might* have further `Sized`
1845 // obligations like `Box<T>` and `Vec<T>`, but we perform no extra analysis for those cases
1846 // and suggest `T: ?Sized` regardless of their obligations. This is fine because the errors
1847 // in that case should make what happened clear enough.
1849 hir
::TyKind
::Ptr(_
) | hir
::TyKind
::Rptr(..) | hir
::TyKind
::TraitObject(..) => {}
1850 hir
::TyKind
::Path(hir
::QPath
::Resolved(None
, path
))
1851 if path
.segments
.len() == 1 && path
.segments
[0].ident
.name
== self.param
=>
1854 self.invalid_spans
.push(ty
.span
);
1857 hir
::TyKind
::Path(_
) => {
1858 let prev
= self.nested
;
1860 hir
::intravisit
::walk_ty(self, ty
);
1864 hir
::intravisit
::walk_ty(self, ty
);
1870 pub fn recursive_type_with_infinite_size_error(
1875 assert
!(type_def_id
.is_local());
1876 let span
= tcx
.hir().span_if_local(type_def_id
).unwrap();
1877 let span
= tcx
.sess
.source_map().guess_head_span(span
);
1878 let path
= tcx
.def_path_str(type_def_id
);
1880 struct_span_err
!(tcx
.sess
, span
, E0072
, "recursive type `{}` has infinite size", path
);
1881 err
.span_label(span
, "recursive type has infinite size");
1882 for &span
in &spans
{
1883 err
.span_label(span
, "recursive without indirection");
1886 "insert some indirection (e.g., a `Box`, `Rc`, or `&`) to make `{}` representable",
1889 if spans
.len() <= 4 {
1890 err
.multipart_suggestion(
1896 (span
.shrink_to_lo(), "Box<".to_string()),
1897 (span
.shrink_to_hi(), ">".to_string()),
1902 Applicability
::HasPlaceholders
,
1910 /// Summarizes information
1913 /// An argument of non-tuple type. Parameters are (name, ty)
1914 Arg(String
, String
),
1916 /// An argument of tuple type. For a "found" argument, the span is
1917 /// the locationo in the source of the pattern. For a "expected"
1918 /// argument, it will be None. The vector is a list of (name, ty)
1919 /// strings for the components of the tuple.
1920 Tuple(Option
<Span
>, Vec
<(String
, String
)>),
1924 fn empty() -> ArgKind
{
1925 ArgKind
::Arg("_".to_owned(), "_".to_owned())
1928 /// Creates an `ArgKind` from the expected type of an
1929 /// argument. It has no name (`_`) and an optional source span.
1930 pub fn from_expected_ty(t
: Ty
<'_
>, span
: Option
<Span
>) -> ArgKind
{
1932 ty
::Tuple(tys
) => ArgKind
::Tuple(
1934 tys
.iter().map(|ty
| ("_".to_owned(), ty
.to_string())).collect
::<Vec
<_
>>(),
1936 _
=> ArgKind
::Arg("_".to_owned(), t
.to_string()),