2 EvaluationResult
, Obligation
, ObligationCause
, ObligationCauseCode
, PredicateObligation
,
6 use crate::autoderef
::Autoderef
;
7 use crate::infer
::InferCtxt
;
8 use crate::traits
::normalize_projection_type
;
10 use rustc_data_structures
::stack
::ensure_sufficient_stack
;
11 use rustc_errors
::{error_code, struct_span_err, Applicability, DiagnosticBuilder, Style}
;
13 use rustc_hir
::def
::DefKind
;
14 use rustc_hir
::def_id
::DefId
;
15 use rustc_hir
::intravisit
::Visitor
;
16 use rustc_hir
::lang_items
::LangItem
;
17 use rustc_hir
::{AsyncGeneratorKind, GeneratorKind, Node}
;
18 use rustc_middle
::ty
::{
19 self, suggest_constraining_type_param
, AdtKind
, DefIdTree
, Infer
, InferTy
, ToPredicate
, Ty
,
20 TyCtxt
, TypeFoldable
, WithConstness
,
22 use rustc_middle
::ty
::{TypeAndMut, TypeckResults}
;
23 use rustc_span
::symbol
::{kw, sym, Ident, Symbol}
;
24 use rustc_span
::{MultiSpan, Span, DUMMY_SP}
;
27 use super::InferCtxtPrivExt
;
28 use crate::traits
::query
::evaluate_obligation
::InferCtxtExt
as _
;
31 pub enum GeneratorInteriorOrUpvar
{
32 // span of interior type
38 // This trait is public to expose the diagnostics methods to clippy.
39 pub trait InferCtxtExt
<'tcx
> {
40 fn suggest_restricting_param_bound(
42 err
: &mut DiagnosticBuilder
<'_
>,
43 trait_ref
: ty
::PolyTraitRef
<'tcx
>,
47 fn suggest_dereferences(
49 obligation
: &PredicateObligation
<'tcx
>,
50 err
: &mut DiagnosticBuilder
<'tcx
>,
51 trait_ref
: &ty
::PolyTraitRef
<'tcx
>,
58 err
: &mut DiagnosticBuilder
<'_
>,
64 obligation
: &PredicateObligation
<'tcx
>,
65 err
: &mut DiagnosticBuilder
<'_
>,
66 trait_ref
: &ty
::Binder
<ty
::TraitRef
<'tcx
>>,
70 fn suggest_add_reference_to_arg(
72 obligation
: &PredicateObligation
<'tcx
>,
73 err
: &mut DiagnosticBuilder
<'_
>,
74 trait_ref
: &ty
::Binder
<ty
::TraitRef
<'tcx
>>,
76 has_custom_message
: bool
,
79 fn suggest_remove_reference(
81 obligation
: &PredicateObligation
<'tcx
>,
82 err
: &mut DiagnosticBuilder
<'_
>,
83 trait_ref
: &ty
::Binder
<ty
::TraitRef
<'tcx
>>,
86 fn suggest_change_mut(
88 obligation
: &PredicateObligation
<'tcx
>,
89 err
: &mut DiagnosticBuilder
<'_
>,
90 trait_ref
: &ty
::Binder
<ty
::TraitRef
<'tcx
>>,
94 fn suggest_semicolon_removal(
96 obligation
: &PredicateObligation
<'tcx
>,
97 err
: &mut DiagnosticBuilder
<'_
>,
99 trait_ref
: &ty
::Binder
<ty
::TraitRef
<'tcx
>>,
102 fn return_type_span(&self, obligation
: &PredicateObligation
<'tcx
>) -> Option
<Span
>;
104 fn suggest_impl_trait(
106 err
: &mut DiagnosticBuilder
<'_
>,
108 obligation
: &PredicateObligation
<'tcx
>,
109 trait_ref
: &ty
::Binder
<ty
::TraitRef
<'tcx
>>,
112 fn point_at_returns_when_relevant(
114 err
: &mut DiagnosticBuilder
<'_
>,
115 obligation
: &PredicateObligation
<'tcx
>,
118 fn report_closure_arg_mismatch(
121 found_span
: Option
<Span
>,
122 expected_ref
: ty
::PolyTraitRef
<'tcx
>,
123 found
: ty
::PolyTraitRef
<'tcx
>,
124 ) -> DiagnosticBuilder
<'tcx
>;
126 fn suggest_fully_qualified_path(
128 err
: &mut DiagnosticBuilder
<'_
>,
134 fn maybe_note_obligation_cause_for_async_await(
136 err
: &mut DiagnosticBuilder
<'_
>,
137 obligation
: &PredicateObligation
<'tcx
>,
140 fn note_obligation_cause_for_async_await(
142 err
: &mut DiagnosticBuilder
<'_
>,
143 interior_or_upvar_span
: GeneratorInteriorOrUpvar
,
144 interior_extra_info
: Option
<(Option
<Span
>, Span
, Option
<hir
::HirId
>, Option
<Span
>)>,
145 inner_generator_body
: Option
<&hir
::Body
<'tcx
>>,
146 outer_generator
: Option
<DefId
>,
147 trait_ref
: ty
::TraitRef
<'tcx
>,
149 typeck_results
: &ty
::TypeckResults
<'tcx
>,
150 obligation
: &PredicateObligation
<'tcx
>,
151 next_code
: Option
<&ObligationCauseCode
<'tcx
>>,
154 fn note_obligation_cause_code
<T
>(
156 err
: &mut DiagnosticBuilder
<'_
>,
158 cause_code
: &ObligationCauseCode
<'tcx
>,
159 obligated_types
: &mut Vec
<&ty
::TyS
<'tcx
>>,
163 fn suggest_new_overflow_limit(&self, err
: &mut DiagnosticBuilder
<'_
>);
165 /// Suggest to await before try: future? => future.await?
166 fn suggest_await_before_try(
168 err
: &mut DiagnosticBuilder
<'_
>,
169 obligation
: &PredicateObligation
<'tcx
>,
170 trait_ref
: &ty
::Binder
<ty
::TraitRef
<'tcx
>>,
175 fn predicate_constraint(generics
: &hir
::Generics
<'_
>, pred
: String
) -> (Span
, String
) {
177 generics
.where_clause
.tail_span_for_suggestion(),
180 if !generics
.where_clause
.predicates
.is_empty() { "," }
else { " where" }
,
186 /// Type parameter needs more bounds. The trivial case is `T` `where T: Bound`, but
187 /// it can also be an `impl Trait` param that needs to be decomposed to a type
188 /// param for cleaner code.
189 fn suggest_restriction(
191 generics
: &hir
::Generics
<'tcx
>,
193 err
: &mut DiagnosticBuilder
<'_
>,
194 fn_sig
: Option
<&hir
::FnSig
<'_
>>,
195 projection
: Option
<&ty
::ProjectionTy
<'_
>>,
196 trait_ref
: ty
::PolyTraitRef
<'tcx
>,
197 super_traits
: Option
<(&Ident
, &hir
::GenericBounds
<'_
>)>,
199 // When we are dealing with a trait, `super_traits` will be `Some`:
200 // Given `trait T: A + B + C {}`
201 // - ^^^^^^^^^ GenericBounds
204 let span
= generics
.where_clause
.span_for_predicates_or_empty_place();
205 if span
.from_expansion() || span
.desugaring_kind().is_some() {
208 // Given `fn foo(t: impl Trait)` where `Trait` requires assoc type `A`...
209 if let Some((bound_str
, fn_sig
)) =
210 fn_sig
.zip(projection
).and_then(|(sig
, p
)| match p
.self_ty().kind() {
211 // Shenanigans to get the `Trait` from the `impl Trait`.
212 ty
::Param(param
) => {
213 // `fn foo(t: impl Trait)`
214 // ^^^^^ get this string
215 param
.name
.as_str().strip_prefix("impl").map(|s
| (s
.trim_start().to_string(), sig
))
220 // We know we have an `impl Trait` that doesn't satisfy a required projection.
222 // Find all of the ocurrences of `impl Trait` for `Trait` in the function arguments'
223 // types. There should be at least one, but there might be *more* than one. In that
224 // case we could just ignore it and try to identify which one needs the restriction,
225 // but instead we choose to suggest replacing all instances of `impl Trait` with `T`
227 let mut ty_spans
= vec
![];
228 let impl_trait_str
= format
!("impl {}", bound_str
);
229 for input
in fn_sig
.decl
.inputs
{
230 if let hir
::TyKind
::Path(hir
::QPath
::Resolved(
232 hir
::Path { segments: [segment], .. }
,
235 if segment
.ident
.as_str() == impl_trait_str
.as_str() {
236 // `fn foo(t: impl Trait)`
237 // ^^^^^^^^^^ get this to suggest `T` instead
239 // There might be more than one `impl Trait`.
240 ty_spans
.push(input
.span
);
245 let type_param_name
= generics
.params
.next_type_param_name(Some(&bound_str
));
246 // The type param `T: Trait` we will suggest to introduce.
247 let type_param
= format
!("{}: {}", type_param_name
, bound_str
);
249 // FIXME: modify the `trait_ref` instead of string shenanigans.
250 // Turn `<impl Trait as Foo>::Bar: Qux` into `<T as Foo>::Bar: Qux`.
251 let pred
= trait_ref
.without_const().to_predicate(tcx
).to_string();
252 let pred
= pred
.replace(&impl_trait_str
, &type_param_name
);
257 .filter(|p
| match p
.kind
{
258 hir
::GenericParamKind
::Type
{
259 synthetic
: Some(hir
::SyntheticTyParamKind
::ImplTrait
),
266 // `fn foo(t: impl Trait)`
267 // ^ suggest `<T: Trait>` here
268 None
=> (generics
.span
, format
!("<{}>", type_param
)),
269 // `fn foo<A>(t: impl Trait)`
270 // ^^^ suggest `<A, T: Trait>` here
272 param
.bounds_span().unwrap_or(param
.span
).shrink_to_hi(),
273 format
!(", {}", type_param
),
276 // `fn foo(t: impl Trait)`
277 // ^ suggest `where <T as Trait>::A: Bound`
278 predicate_constraint(generics
, pred
),
280 sugg
.extend(ty_spans
.into_iter().map(|s
| (s
, type_param_name
.to_string())));
282 // Suggest `fn foo<T: Trait>(t: T) where <T as Trait>::A: Bound`.
283 // FIXME: once `#![feature(associated_type_bounds)]` is stabilized, we should suggest
284 // `fn foo(t: impl Trait<A: Bound>)` instead.
285 err
.multipart_suggestion(
286 "introduce a type parameter with a trait bound instead of using `impl Trait`",
288 Applicability
::MaybeIncorrect
,
291 // Trivial case: `T` needs an extra bound: `T: Bound`.
292 let (sp
, suggestion
) = match super_traits
{
293 None
=> predicate_constraint(
295 trait_ref
.without_const().to_predicate(tcx
).to_string(),
297 Some((ident
, bounds
)) => match bounds
{
299 bound
.span().shrink_to_hi(),
300 format
!(" + {}", trait_ref
.print_only_trait_path().to_string()),
303 ident
.span
.shrink_to_hi(),
304 format
!(": {}", trait_ref
.print_only_trait_path().to_string()),
309 err
.span_suggestion_verbose(
311 &format
!("consider further restricting {}", msg
),
313 Applicability
::MachineApplicable
,
318 impl<'a
, 'tcx
> InferCtxtExt
<'tcx
> for InferCtxt
<'a
, 'tcx
> {
319 fn suggest_restricting_param_bound(
321 mut err
: &mut DiagnosticBuilder
<'_
>,
322 trait_ref
: ty
::PolyTraitRef
<'tcx
>,
325 let self_ty
= trait_ref
.skip_binder().self_ty();
326 let (param_ty
, projection
) = match self_ty
.kind() {
327 ty
::Param(_
) => (true, None
),
328 ty
::Projection(projection
) => (false, Some(projection
)),
332 // FIXME: Add check for trait bound that is already present, particularly `?Sized` so we
333 // don't suggest `T: Sized + ?Sized`.
334 let mut hir_id
= body_id
;
335 while let Some(node
) = self.tcx
.hir().find(hir_id
) {
337 hir
::Node
::Item(hir
::Item
{
339 kind
: hir
::ItemKind
::Trait(_
, _
, generics
, bounds
, _
),
341 }) if self_ty
== self.tcx
.types
.self_param
=> {
343 // Restricting `Self` for a single method.
352 Some((ident
, bounds
)),
357 hir
::Node
::TraitItem(hir
::TraitItem
{
359 kind
: hir
::TraitItemKind
::Fn(..),
361 }) if self_ty
== self.tcx
.types
.self_param
=> {
363 // Restricting `Self` for a single method.
365 self.tcx
, &generics
, "`Self`", err
, None
, projection
, trait_ref
, None
,
370 hir
::Node
::TraitItem(hir
::TraitItem
{
372 kind
: hir
::TraitItemKind
::Fn(fn_sig
, ..),
375 | hir
::Node
::ImplItem(hir
::ImplItem
{
377 kind
: hir
::ImplItemKind
::Fn(fn_sig
, ..),
380 | hir
::Node
::Item(hir
::Item
{
381 kind
: hir
::ItemKind
::Fn(fn_sig
, generics
, _
), ..
382 }) if projection
.is_some() => {
383 // Missing restriction on associated type of type parameter (unmet projection).
387 "the associated type",
396 hir
::Node
::Item(hir
::Item
{
398 hir
::ItemKind
::Trait(_
, _
, generics
, _
, _
)
399 | hir
::ItemKind
::Impl { generics, .. }
,
401 }) if projection
.is_some() => {
402 // Missing restriction on associated type of type parameter (unmet projection).
406 "the associated type",
416 hir
::Node
::Item(hir
::Item
{
418 hir
::ItemKind
::Struct(_
, generics
)
419 | hir
::ItemKind
::Enum(_
, generics
)
420 | hir
::ItemKind
::Union(_
, generics
)
421 | hir
::ItemKind
::Trait(_
, _
, generics
, ..)
422 | hir
::ItemKind
::Impl { generics, .. }
423 | hir
::ItemKind
::Fn(_
, generics
, _
)
424 | hir
::ItemKind
::TyAlias(_
, generics
)
425 | hir
::ItemKind
::TraitAlias(generics
, _
)
426 | hir
::ItemKind
::OpaqueTy(hir
::OpaqueTy { generics, .. }
),
429 | hir
::Node
::TraitItem(hir
::TraitItem { generics, .. }
)
430 | hir
::Node
::ImplItem(hir
::ImplItem { generics, .. }
)
433 // Missing generic type parameter bound.
434 let param_name
= self_ty
.to_string();
435 let constraint
= trait_ref
.print_only_trait_path().to_string();
436 if suggest_constraining_type_param(
442 Some(trait_ref
.def_id()),
448 hir
::Node
::Crate(..) => return,
453 hir_id
= self.tcx
.hir().get_parent_item(hir_id
);
457 /// When after several dereferencing, the reference satisfies the trait
458 /// binding. This function provides dereference suggestion for this
459 /// specific situation.
460 fn suggest_dereferences(
462 obligation
: &PredicateObligation
<'tcx
>,
463 err
: &mut DiagnosticBuilder
<'tcx
>,
464 trait_ref
: &ty
::PolyTraitRef
<'tcx
>,
467 // It only make sense when suggesting dereferences for arguments
471 let param_env
= obligation
.param_env
;
472 let body_id
= obligation
.cause
.body_id
;
473 let span
= obligation
.cause
.span
;
474 let real_trait_ref
= match &obligation
.cause
.code
{
475 ObligationCauseCode
::ImplDerivedObligation(cause
)
476 | ObligationCauseCode
::DerivedObligation(cause
)
477 | ObligationCauseCode
::BuiltinDerivedObligation(cause
) => &cause
.parent_trait_ref
,
480 let real_ty
= match real_trait_ref
.self_ty().no_bound_vars() {
485 if let ty
::Ref(region
, base_ty
, mutbl
) = *real_ty
.kind() {
486 let mut autoderef
= Autoderef
::new(self, param_env
, body_id
, span
, base_ty
, span
);
487 if let Some(steps
) = autoderef
.find_map(|(ty
, steps
)| {
489 let ty
= self.tcx
.mk_ref(region
, TypeAndMut { ty, mutbl }
);
491 self.mk_trait_obligation_with_new_self_ty(param_env
, real_trait_ref
, ty
);
492 Some(steps
).filter(|_
| self.predicate_may_hold(&obligation
))
495 if let Ok(src
) = self.tcx
.sess
.source_map().span_to_snippet(span
) {
496 // Don't care about `&mut` because `DerefMut` is used less
497 // often and user will not expect autoderef happens.
498 if src
.starts_with('
&'
) && !src
.starts_with("&mut ") {
499 let derefs
= "*".repeat(steps
);
502 "consider adding dereference here",
503 format
!("&{}{}", derefs
, &src
[1..]),
504 Applicability
::MachineApplicable
,
513 /// Given a closure's `DefId`, return the given name of the closure.
515 /// This doesn't account for reassignments, but it's only used for suggestions.
519 err
: &mut DiagnosticBuilder
<'_
>,
521 ) -> Option
<String
> {
523 |err
: &mut DiagnosticBuilder
<'_
>, kind
: &hir
::PatKind
<'_
>| -> Option
<String
> {
524 // Get the local name of this closure. This can be inaccurate because
525 // of the possibility of reassignment, but this should be good enough.
527 hir
::PatKind
::Binding(hir
::BindingAnnotation
::Unannotated
, _
, name
, None
) => {
528 Some(format
!("{}", name
))
537 let hir
= self.tcx
.hir();
538 let hir_id
= hir
.local_def_id_to_hir_id(def_id
.as_local()?
);
539 let parent_node
= hir
.get_parent_node(hir_id
);
540 match hir
.find(parent_node
) {
541 Some(hir
::Node
::Stmt(hir
::Stmt { kind: hir::StmtKind::Local(local), .. }
)) => {
542 get_name(err
, &local
.pat
.kind
)
544 // Different to previous arm because one is `&hir::Local` and the other
545 // is `P<hir::Local>`.
546 Some(hir
::Node
::Local(local
)) => get_name(err
, &local
.pat
.kind
),
551 /// We tried to apply the bound to an `fn` or closure. Check whether calling it would
552 /// evaluate to a type that *would* satisfy the trait binding. If it would, suggest calling
553 /// it: `bar(foo)` → `bar(foo())`. This case is *very* likely to be hit if `foo` is `async`.
556 obligation
: &PredicateObligation
<'tcx
>,
557 err
: &mut DiagnosticBuilder
<'_
>,
558 trait_ref
: &ty
::Binder
<ty
::TraitRef
<'tcx
>>,
561 let self_ty
= match trait_ref
.self_ty().no_bound_vars() {
566 let (def_id
, output_ty
, callable
) = match *self_ty
.kind() {
567 ty
::Closure(def_id
, substs
) => (def_id
, substs
.as_closure().sig().output(), "closure"),
568 ty
::FnDef(def_id
, _
) => (def_id
, self_ty
.fn_sig(self.tcx
).output(), "function"),
571 let msg
= format
!("use parentheses to call the {}", callable
);
573 // `mk_trait_obligation_with_new_self_ty` only works for types with no escaping bound
574 // variables, so bail out if we have any.
575 let output_ty
= match output_ty
.no_bound_vars() {
581 self.mk_trait_obligation_with_new_self_ty(obligation
.param_env
, trait_ref
, output_ty
);
583 match self.evaluate_obligation(&new_obligation
) {
585 EvaluationResult
::EvaluatedToOk
586 | EvaluationResult
::EvaluatedToOkModuloRegions
587 | EvaluationResult
::EvaluatedToAmbig
,
591 let hir
= self.tcx
.hir();
592 // Get the name of the callable and the arguments to be used in the suggestion.
593 let (snippet
, sugg
) = match hir
.get_if_local(def_id
) {
594 Some(hir
::Node
::Expr(hir
::Expr
{
595 kind
: hir
::ExprKind
::Closure(_
, decl
, _
, span
, ..),
598 err
.span_label(*span
, "consider calling this closure");
599 let name
= match self.get_closure_name(def_id
, err
, &msg
) {
603 let args
= decl
.inputs
.iter().map(|_
| "_").collect
::<Vec
<_
>>().join(", ");
604 let sugg
= format
!("({})", args
);
605 (format
!("{}{}", name
, sugg
), sugg
)
607 Some(hir
::Node
::Item(hir
::Item
{
609 kind
: hir
::ItemKind
::Fn(.., body_id
),
612 err
.span_label(ident
.span
, "consider calling this function");
613 let body
= hir
.body(*body_id
);
617 .map(|arg
| match &arg
.pat
.kind
{
618 hir
::PatKind
::Binding(_
, _
, ident
, None
)
619 // FIXME: provide a better suggestion when encountering `SelfLower`, it
620 // should suggest a method call.
621 if ident
.name
!= kw
::SelfLower
=> ident
.to_string(),
622 _
=> "_".to_string(),
626 let sugg
= format
!("({})", args
);
627 (format
!("{}{}", ident
, sugg
), sugg
)
632 // When the obligation error has been ensured to have been caused by
633 // an argument, the `obligation.cause.span` points at the expression
634 // of the argument, so we can provide a suggestion. This is signaled
635 // by `points_at_arg`. Otherwise, we give a more general note.
636 err
.span_suggestion_verbose(
637 obligation
.cause
.span
.shrink_to_hi(),
640 Applicability
::HasPlaceholders
,
643 err
.help(&format
!("{}: `{}`", msg
, snippet
));
647 fn suggest_add_reference_to_arg(
649 obligation
: &PredicateObligation
<'tcx
>,
650 err
: &mut DiagnosticBuilder
<'_
>,
651 trait_ref
: &ty
::Binder
<ty
::TraitRef
<'tcx
>>,
653 has_custom_message
: bool
,
659 let span
= obligation
.cause
.span
;
660 let param_env
= obligation
.param_env
;
661 let trait_ref
= trait_ref
.skip_binder();
663 if let ObligationCauseCode
::ImplDerivedObligation(obligation
) = &obligation
.cause
.code
{
664 // Try to apply the original trait binding obligation by borrowing.
665 let self_ty
= trait_ref
.self_ty();
666 let found
= self_ty
.to_string();
667 let new_self_ty
= self.tcx
.mk_imm_ref(self.tcx
.lifetimes
.re_static
, self_ty
);
668 let substs
= self.tcx
.mk_substs_trait(new_self_ty
, &[]);
669 let new_trait_ref
= ty
::TraitRef
::new(obligation
.parent_trait_ref
.def_id(), substs
);
670 let new_obligation
= Obligation
::new(
671 ObligationCause
::dummy(),
673 new_trait_ref
.without_const().to_predicate(self.tcx
),
676 if self.predicate_must_hold_modulo_regions(&new_obligation
) {
677 if let Ok(snippet
) = self.tcx
.sess
.source_map().span_to_snippet(span
) {
678 // We have a very specific type of error, where just borrowing this argument
679 // might solve the problem. In cases like this, the important part is the
680 // original type obligation, not the last one that failed, which is arbitrary.
681 // Because of this, we modify the error to refer to the original obligation and
682 // return early in the caller.
685 "the trait bound `{}: {}` is not satisfied",
687 obligation
.parent_trait_ref
.skip_binder().print_only_trait_path(),
689 if has_custom_message
{
692 err
.message
= vec
![(msg
, Style
::NoStyle
)];
694 if snippet
.starts_with('
&'
) {
695 // This is already a literal borrow and the obligation is failing
696 // somewhere else in the obligation chain. Do not suggest non-sense.
702 "expected an implementor of trait `{}`",
703 obligation
.parent_trait_ref
.skip_binder().print_only_trait_path(),
707 // This if is to prevent a special edge-case
708 if !span
.from_expansion() {
709 // We don't want a borrowing suggestion on the fields in structs,
712 // the_foos: Vec<Foo>
718 "consider borrowing here",
719 format
!("&{}", snippet
),
720 Applicability
::MaybeIncorrect
,
730 /// Whenever references are used by mistake, like `for (i, e) in &vec.iter().enumerate()`,
731 /// suggest removing these references until we reach a type that implements the trait.
732 fn suggest_remove_reference(
734 obligation
: &PredicateObligation
<'tcx
>,
735 err
: &mut DiagnosticBuilder
<'_
>,
736 trait_ref
: &ty
::Binder
<ty
::TraitRef
<'tcx
>>,
738 let span
= obligation
.cause
.span
;
740 if let Ok(snippet
) = self.tcx
.sess
.source_map().span_to_snippet(span
) {
742 snippet
.chars().filter(|c
| !c
.is_whitespace()).take_while(|c
| *c
== '
&'
).count();
743 if let Some('
\''
) = snippet
.chars().filter(|c
| !c
.is_whitespace()).nth(refs_number
) {
744 // Do not suggest removal of borrow from type arguments.
748 let mut suggested_ty
= match trait_ref
.self_ty().no_bound_vars() {
753 for refs_remaining
in 0..refs_number
{
754 if let ty
::Ref(_
, inner_ty
, _
) = suggested_ty
.kind() {
755 suggested_ty
= inner_ty
;
757 let new_obligation
= self.mk_trait_obligation_with_new_self_ty(
758 obligation
.param_env
,
763 if self.predicate_may_hold(&new_obligation
) {
768 .span_take_while(span
, |c
| c
.is_whitespace() || *c
== '
&'
);
770 let remove_refs
= refs_remaining
+ 1;
772 let msg
= if remove_refs
== 1 {
773 "consider removing the leading `&`-reference".to_string()
775 format
!("consider removing {} leading `&`-references", remove_refs
)
778 err
.span_suggestion_short(
782 Applicability
::MachineApplicable
,
793 /// Check if the trait bound is implemented for a different mutability and note it in the
795 fn suggest_change_mut(
797 obligation
: &PredicateObligation
<'tcx
>,
798 err
: &mut DiagnosticBuilder
<'_
>,
799 trait_ref
: &ty
::Binder
<ty
::TraitRef
<'tcx
>>,
802 let span
= obligation
.cause
.span
;
803 if let Ok(snippet
) = self.tcx
.sess
.source_map().span_to_snippet(span
) {
805 snippet
.chars().filter(|c
| !c
.is_whitespace()).take_while(|c
| *c
== '
&'
).count();
806 if let Some('
\''
) = snippet
.chars().filter(|c
| !c
.is_whitespace()).nth(refs_number
) {
807 // Do not suggest removal of borrow from type arguments.
810 let trait_ref
= self.resolve_vars_if_possible(trait_ref
);
811 if trait_ref
.has_infer_types_or_consts() {
812 // Do not ICE while trying to find if a reborrow would succeed on a trait with
813 // unresolved bindings.
817 if let ty
::Ref(region
, t_type
, mutability
) = *trait_ref
.skip_binder().self_ty().kind() {
818 if region
.is_late_bound() || t_type
.has_escaping_bound_vars() {
819 // Avoid debug assertion in `mk_obligation_for_def_id`.
821 // If the self type has escaping bound vars then it's not
822 // going to be the type of an expression, so the suggestion
823 // probably won't apply anyway.
827 let suggested_ty
= match mutability
{
828 hir
::Mutability
::Mut
=> self.tcx
.mk_imm_ref(region
, t_type
),
829 hir
::Mutability
::Not
=> self.tcx
.mk_mut_ref(region
, t_type
),
832 let new_obligation
= self.mk_trait_obligation_with_new_self_ty(
833 obligation
.param_env
,
837 let suggested_ty_would_satisfy_obligation
= self
838 .evaluate_obligation_no_overflow(&new_obligation
)
839 .must_apply_modulo_regions();
840 if suggested_ty_would_satisfy_obligation
{
845 .span_take_while(span
, |c
| c
.is_whitespace() || *c
== '
&'
);
846 if points_at_arg
&& mutability
== hir
::Mutability
::Not
&& refs_number
> 0 {
847 err
.span_suggestion_verbose(
849 "consider changing this borrow's mutability",
851 Applicability
::MachineApplicable
,
855 "`{}` is implemented for `{:?}`, but not for `{:?}`",
856 trait_ref
.print_only_trait_path(),
858 trait_ref
.skip_binder().self_ty(),
866 fn suggest_semicolon_removal(
868 obligation
: &PredicateObligation
<'tcx
>,
869 err
: &mut DiagnosticBuilder
<'_
>,
871 trait_ref
: &ty
::Binder
<ty
::TraitRef
<'tcx
>>,
874 |ty
: ty
::Binder
<Ty
<'_
>>| *ty
.skip_binder().kind() == ty
::Tuple(ty
::List
::empty());
876 let hir
= self.tcx
.hir();
877 let parent_node
= hir
.get_parent_node(obligation
.cause
.body_id
);
878 let node
= hir
.find(parent_node
);
879 if let Some(hir
::Node
::Item(hir
::Item
{
880 kind
: hir
::ItemKind
::Fn(sig
, _
, body_id
), ..
883 let body
= hir
.body(*body_id
);
884 if let hir
::ExprKind
::Block(blk
, _
) = &body
.value
.kind
{
885 if sig
.decl
.output
.span().overlaps(span
)
886 && blk
.expr
.is_none()
887 && is_empty_tuple(trait_ref
.self_ty())
889 // FIXME(estebank): When encountering a method with a trait
890 // bound not satisfied in the return type with a body that has
891 // no return, suggest removal of semicolon on last statement.
892 // Once that is added, close #54771.
893 if let Some(ref stmt
) = blk
.stmts
.last() {
894 let sp
= self.tcx
.sess
.source_map().end_point(stmt
.span
);
895 err
.span_label(sp
, "consider removing this semicolon");
902 fn return_type_span(&self, obligation
: &PredicateObligation
<'tcx
>) -> Option
<Span
> {
903 let hir
= self.tcx
.hir();
904 let parent_node
= hir
.get_parent_node(obligation
.cause
.body_id
);
905 let sig
= match hir
.find(parent_node
) {
906 Some(hir
::Node
::Item(hir
::Item { kind: hir::ItemKind::Fn(sig, ..), .. }
)) => sig
,
910 if let hir
::FnRetTy
::Return(ret_ty
) = sig
.decl
.output { Some(ret_ty.span) }
else { None }
913 /// If all conditions are met to identify a returned `dyn Trait`, suggest using `impl Trait` if
914 /// applicable and signal that the error has been expanded appropriately and needs to be
916 fn suggest_impl_trait(
918 err
: &mut DiagnosticBuilder
<'_
>,
920 obligation
: &PredicateObligation
<'tcx
>,
921 trait_ref
: &ty
::Binder
<ty
::TraitRef
<'tcx
>>,
923 match obligation
.cause
.code
.peel_derives() {
924 // Only suggest `impl Trait` if the return type is unsized because it is `dyn Trait`.
925 ObligationCauseCode
::SizedReturnType
=> {}
929 let hir
= self.tcx
.hir();
930 let parent_node
= hir
.get_parent_node(obligation
.cause
.body_id
);
931 let node
= hir
.find(parent_node
);
932 let (sig
, body_id
) = if let Some(hir
::Node
::Item(hir
::Item
{
933 kind
: hir
::ItemKind
::Fn(sig
, _
, body_id
),
941 let body
= hir
.body(*body_id
);
942 let trait_ref
= self.resolve_vars_if_possible(trait_ref
);
943 let ty
= trait_ref
.skip_binder().self_ty();
944 let is_object_safe
= match ty
.kind() {
945 ty
::Dynamic(predicates
, _
) => {
946 // If the `dyn Trait` is not object safe, do not suggest `Box<dyn Trait>`.
949 .map_or(true, |def_id
| self.tcx
.object_safety_violations(def_id
).is_empty())
951 // We only want to suggest `impl Trait` to `dyn Trait`s.
952 // For example, `fn foo() -> str` needs to be filtered out.
956 let ret_ty
= if let hir
::FnRetTy
::Return(ret_ty
) = sig
.decl
.output
{
962 // Use `TypeVisitor` instead of the output type directly to find the span of `ty` for
963 // cases like `fn foo() -> (dyn Trait, i32) {}`.
964 // Recursively look for `TraitObject` types and if there's only one, use that span to
965 // suggest `impl Trait`.
967 // Visit to make sure there's a single `return` type to suggest `impl Trait`,
968 // otherwise suggest using `Box<dyn Trait>` or an enum.
969 let mut visitor
= ReturnsVisitor
::default();
970 visitor
.visit_body(&body
);
972 let typeck_results
= self.in_progress_typeck_results
.map(|t
| t
.borrow()).unwrap();
974 let mut ret_types
= visitor
977 .filter_map(|expr
| typeck_results
.node_type_opt(expr
.hir_id
))
978 .map(|ty
| self.resolve_vars_if_possible(&ty
));
979 let (last_ty
, all_returns_have_same_type
, only_never_return
) = ret_types
.clone().fold(
981 |(last_ty
, mut same
, only_never_return
): (std
::option
::Option
<Ty
<'_
>>, bool
, bool
),
983 let ty
= self.resolve_vars_if_possible(&ty
);
985 !matches
!(ty
.kind(), ty
::Error(_
))
986 && last_ty
.map_or(true, |last_ty
| {
987 // FIXME: ideally we would use `can_coerce` here instead, but `typeck` comes
988 // *after* in the dependency graph.
989 match (ty
.kind(), last_ty
.kind()) {
990 (Infer(InferTy
::IntVar(_
)), Infer(InferTy
::IntVar(_
)))
991 | (Infer(InferTy
::FloatVar(_
)), Infer(InferTy
::FloatVar(_
)))
992 | (Infer(InferTy
::FreshIntTy(_
)), Infer(InferTy
::FreshIntTy(_
)))
994 Infer(InferTy
::FreshFloatTy(_
)),
995 Infer(InferTy
::FreshFloatTy(_
)),
1000 (Some(ty
), same
, only_never_return
&& matches
!(ty
.kind(), ty
::Never
))
1003 let all_returns_conform_to_trait
=
1004 if let Some(ty_ret_ty
) = typeck_results
.node_type_opt(ret_ty
.hir_id
) {
1005 match ty_ret_ty
.kind() {
1006 ty
::Dynamic(predicates
, _
) => {
1007 let cause
= ObligationCause
::misc(ret_ty
.span
, ret_ty
.hir_id
);
1008 let param_env
= ty
::ParamEnv
::empty();
1010 || ret_types
.all(|returned_ty
| {
1011 predicates
.iter().all(|predicate
| {
1012 let pred
= predicate
.with_self_ty(self.tcx
, returned_ty
);
1013 let obl
= Obligation
::new(cause
.clone(), param_env
, pred
);
1014 self.predicate_may_hold(&obl
)
1024 let sm
= self.tcx
.sess
.source_map();
1025 let snippet
= if let (true, hir
::TyKind
::TraitObject(..), Ok(snippet
), true) = (
1026 // Verify that we're dealing with a return `dyn Trait`
1027 ret_ty
.span
.overlaps(span
),
1029 sm
.span_to_snippet(ret_ty
.span
),
1030 // If any of the return types does not conform to the trait, then we can't
1031 // suggest `impl Trait` nor trait objects: it is a type mismatch error.
1032 all_returns_conform_to_trait
,
1038 err
.code(error_code
!(E0746
));
1039 err
.set_primary_message("return type cannot have an unboxed trait object");
1040 err
.children
.clear();
1041 let impl_trait_msg
= "for information on `impl Trait`, see \
1042 <https://doc.rust-lang.org/book/ch10-02-traits.html\
1043 #returning-types-that-implement-traits>";
1044 let trait_obj_msg
= "for information on trait objects, see \
1045 <https://doc.rust-lang.org/book/ch17-02-trait-objects.html\
1046 #using-trait-objects-that-allow-for-values-of-different-types>";
1047 let has_dyn
= snippet
.split_whitespace().next().map_or(false, |s
| s
== "dyn");
1048 let trait_obj
= if has_dyn { &snippet[4..] }
else { &snippet[..] }
;
1049 if only_never_return
{
1050 // No return paths, probably using `panic!()` or similar.
1051 // Suggest `-> T`, `-> impl Trait`, and if `Trait` is object safe, `-> Box<dyn Trait>`.
1052 suggest_trait_object_return_type_alternatives(
1058 } else if let (Some(last_ty
), true) = (last_ty
, all_returns_have_same_type
) {
1059 // Suggest `-> impl Trait`.
1060 err
.span_suggestion(
1063 "use `impl {1}` as the return type, as all return paths are of type `{}`, \
1064 which implements `{1}`",
1067 format
!("impl {}", trait_obj
),
1068 Applicability
::MachineApplicable
,
1070 err
.note(impl_trait_msg
);
1073 // Suggest `-> Box<dyn Trait>` and `Box::new(returned_value)`.
1074 // Get all the return values and collect their span and suggestion.
1075 if let Some(mut suggestions
) = visitor
1079 let snip
= sm
.span_to_snippet(expr
.span
).ok()?
;
1080 Some((expr
.span
, format
!("Box::new({})", snip
)))
1082 .collect
::<Option
<Vec
<_
>>>()
1084 // Add the suggestion for the return type.
1085 suggestions
.push((ret_ty
.span
, format
!("Box<dyn {}>", trait_obj
)));
1086 err
.multipart_suggestion(
1087 "return a boxed trait object instead",
1089 Applicability
::MaybeIncorrect
,
1093 // This is currently not possible to trigger because E0038 takes precedence, but
1094 // leave it in for completeness in case anything changes in an earlier stage.
1096 "if trait `{}` was object safe, you could return a trait object",
1100 err
.note(trait_obj_msg
);
1102 "if all the returned values were of the same type you could use `impl {}` as the \
1106 err
.note(impl_trait_msg
);
1107 err
.note("you can create a new `enum` with a variant for each returned type");
1112 fn point_at_returns_when_relevant(
1114 err
: &mut DiagnosticBuilder
<'_
>,
1115 obligation
: &PredicateObligation
<'tcx
>,
1117 match obligation
.cause
.code
.peel_derives() {
1118 ObligationCauseCode
::SizedReturnType
=> {}
1122 let hir
= self.tcx
.hir();
1123 let parent_node
= hir
.get_parent_node(obligation
.cause
.body_id
);
1124 let node
= hir
.find(parent_node
);
1125 if let Some(hir
::Node
::Item(hir
::Item { kind: hir::ItemKind::Fn(_, _, body_id), .. }
)) =
1128 let body
= hir
.body(*body_id
);
1129 // Point at all the `return`s in the function as they have failed trait bounds.
1130 let mut visitor
= ReturnsVisitor
::default();
1131 visitor
.visit_body(&body
);
1132 let typeck_results
= self.in_progress_typeck_results
.map(|t
| t
.borrow()).unwrap();
1133 for expr
in &visitor
.returns
{
1134 if let Some(returned_ty
) = typeck_results
.node_type_opt(expr
.hir_id
) {
1135 let ty
= self.resolve_vars_if_possible(&returned_ty
);
1136 err
.span_label(expr
.span
, &format
!("this returned value is of type `{}`", ty
));
1142 fn report_closure_arg_mismatch(
1145 found_span
: Option
<Span
>,
1146 expected_ref
: ty
::PolyTraitRef
<'tcx
>,
1147 found
: ty
::PolyTraitRef
<'tcx
>,
1148 ) -> DiagnosticBuilder
<'tcx
> {
1149 crate fn build_fn_sig_string
<'tcx
>(
1151 trait_ref
: ty
::TraitRef
<'tcx
>,
1153 let inputs
= trait_ref
.substs
.type_at(1);
1154 let sig
= if let ty
::Tuple(inputs
) = inputs
.kind() {
1156 inputs
.iter().map(|k
| k
.expect_ty()),
1157 tcx
.mk_ty_infer(ty
::TyVar(ty
::TyVid { index: 0 }
)),
1159 hir
::Unsafety
::Normal
,
1160 ::rustc_target
::spec
::abi
::Abi
::Rust
,
1164 ::std
::iter
::once(inputs
),
1165 tcx
.mk_ty_infer(ty
::TyVar(ty
::TyVid { index: 0 }
)),
1167 hir
::Unsafety
::Normal
,
1168 ::rustc_target
::spec
::abi
::Abi
::Rust
,
1171 ty
::Binder
::bind(sig
).to_string()
1174 let argument_is_closure
= expected_ref
.skip_binder().substs
.type_at(0).is_closure();
1175 let mut err
= struct_span_err
!(
1179 "type mismatch in {} arguments",
1180 if argument_is_closure { "closure" }
else { "function" }
1183 let found_str
= format
!(
1184 "expected signature of `{}`",
1185 build_fn_sig_string(self.tcx
, found
.skip_binder())
1187 err
.span_label(span
, found_str
);
1189 let found_span
= found_span
.unwrap_or(span
);
1190 let expected_str
= format
!(
1191 "found signature of `{}`",
1192 build_fn_sig_string(self.tcx
, expected_ref
.skip_binder())
1194 err
.span_label(found_span
, expected_str
);
1199 fn suggest_fully_qualified_path(
1201 err
: &mut DiagnosticBuilder
<'_
>,
1206 if let Some(assoc_item
) = self.tcx
.opt_associated_item(def_id
) {
1207 if let ty
::AssocKind
::Const
| ty
::AssocKind
::Type
= assoc_item
.kind
{
1209 "{}s cannot be accessed directly on a `trait`, they can only be \
1210 accessed through a specific `impl`",
1211 assoc_item
.kind
.as_def_kind().descr(def_id
)
1213 err
.span_suggestion(
1215 "use the fully qualified path to an implementation",
1216 format
!("<Type as {}>::{}", self.tcx
.def_path_str(trait_ref
), assoc_item
.ident
),
1217 Applicability
::HasPlaceholders
,
1223 /// Adds an async-await specific note to the diagnostic when the future does not implement
1224 /// an auto trait because of a captured type.
1227 /// note: future does not implement `Qux` as this value is used across an await
1228 /// --> $DIR/issue-64130-3-other.rs:17:5
1230 /// LL | let x = Foo;
1231 /// | - has type `Foo`
1232 /// LL | baz().await;
1233 /// | ^^^^^^^^^^^ await occurs here, with `x` maybe used later
1235 /// | - `x` is later dropped here
1238 /// When the diagnostic does not implement `Send` or `Sync` specifically, then the diagnostic
1239 /// is "replaced" with a different message and a more specific error.
1242 /// error: future cannot be sent between threads safely
1243 /// --> $DIR/issue-64130-2-send.rs:21:5
1245 /// LL | fn is_send<T: Send>(t: T) { }
1246 /// | ---- required by this bound in `is_send`
1248 /// LL | is_send(bar());
1249 /// | ^^^^^^^ future returned by `bar` is not send
1251 /// = help: within `impl std::future::Future`, the trait `std::marker::Send` is not
1252 /// implemented for `Foo`
1253 /// note: future is not send as this value is used across an await
1254 /// --> $DIR/issue-64130-2-send.rs:15:5
1256 /// LL | let x = Foo;
1257 /// | - has type `Foo`
1258 /// LL | baz().await;
1259 /// | ^^^^^^^^^^^ await occurs here, with `x` maybe used later
1261 /// | - `x` is later dropped here
1264 /// Returns `true` if an async-await specific note was added to the diagnostic.
1265 fn maybe_note_obligation_cause_for_async_await(
1267 err
: &mut DiagnosticBuilder
<'_
>,
1268 obligation
: &PredicateObligation
<'tcx
>,
1271 "maybe_note_obligation_cause_for_async_await: obligation.predicate={:?} \
1272 obligation.cause.span={:?}",
1273 obligation
.predicate
, obligation
.cause
.span
1275 let hir
= self.tcx
.hir();
1277 // Attempt to detect an async-await error by looking at the obligation causes, looking
1278 // for a generator to be present.
1280 // When a future does not implement a trait because of a captured type in one of the
1281 // generators somewhere in the call stack, then the result is a chain of obligations.
1283 // Given a `async fn` A that calls a `async fn` B which captures a non-send type and that
1284 // future is passed as an argument to a function C which requires a `Send` type, then the
1285 // chain looks something like this:
1287 // - `BuiltinDerivedObligation` with a generator witness (B)
1288 // - `BuiltinDerivedObligation` with a generator (B)
1289 // - `BuiltinDerivedObligation` with `std::future::GenFuture` (B)
1290 // - `BuiltinDerivedObligation` with `impl std::future::Future` (B)
1291 // - `BuiltinDerivedObligation` with `impl std::future::Future` (B)
1292 // - `BuiltinDerivedObligation` with a generator witness (A)
1293 // - `BuiltinDerivedObligation` with a generator (A)
1294 // - `BuiltinDerivedObligation` with `std::future::GenFuture` (A)
1295 // - `BuiltinDerivedObligation` with `impl std::future::Future` (A)
1296 // - `BuiltinDerivedObligation` with `impl std::future::Future` (A)
1297 // - `BindingObligation` with `impl_send (Send requirement)
1299 // The first obligation in the chain is the most useful and has the generator that captured
1300 // the type. The last generator (`outer_generator` below) has information about where the
1301 // bound was introduced. At least one generator should be present for this diagnostic to be
1303 let (mut trait_ref
, mut target_ty
) = match obligation
.predicate
.skip_binders() {
1304 ty
::PredicateAtom
::Trait(p
, _
) => (Some(p
.trait_ref
), Some(p
.self_ty())),
1307 let mut generator
= None
;
1308 let mut outer_generator
= None
;
1309 let mut next_code
= Some(&obligation
.cause
.code
);
1310 while let Some(code
) = next_code
{
1311 debug
!("maybe_note_obligation_cause_for_async_await: code={:?}", code
);
1313 ObligationCauseCode
::DerivedObligation(derived_obligation
)
1314 | ObligationCauseCode
::BuiltinDerivedObligation(derived_obligation
)
1315 | ObligationCauseCode
::ImplDerivedObligation(derived_obligation
) => {
1316 let ty
= derived_obligation
.parent_trait_ref
.skip_binder().self_ty();
1318 "maybe_note_obligation_cause_for_async_await: \
1319 parent_trait_ref={:?} self_ty.kind={:?}",
1320 derived_obligation
.parent_trait_ref
,
1325 ty
::Generator(did
, ..) => {
1326 generator
= generator
.or(Some(did
));
1327 outer_generator
= Some(did
);
1329 ty
::GeneratorWitness(..) => {}
1330 _
if generator
.is_none() => {
1331 trait_ref
= Some(derived_obligation
.parent_trait_ref
.skip_binder());
1332 target_ty
= Some(ty
);
1337 next_code
= Some(derived_obligation
.parent_code
.as_ref());
1343 // Only continue if a generator was found.
1345 "maybe_note_obligation_cause_for_async_await: generator={:?} trait_ref={:?} \
1347 generator
, trait_ref
, target_ty
1349 let (generator_did
, trait_ref
, target_ty
) = match (generator
, trait_ref
, target_ty
) {
1350 (Some(generator_did
), Some(trait_ref
), Some(target_ty
)) => {
1351 (generator_did
, trait_ref
, target_ty
)
1356 let span
= self.tcx
.def_span(generator_did
);
1358 // Do not ICE on closure typeck (#66868).
1359 if !generator_did
.is_local() {
1363 // Get the typeck results from the infcx if the generator is the function we are
1364 // currently type-checking; otherwise, get them by performing a query.
1365 // This is needed to avoid cycles.
1366 let in_progress_typeck_results
= self.in_progress_typeck_results
.map(|t
| t
.borrow());
1367 let generator_did_root
= self.tcx
.closure_base_def_id(generator_did
);
1369 "maybe_note_obligation_cause_for_async_await: generator_did={:?} \
1370 generator_did_root={:?} in_progress_typeck_results.hir_owner={:?} span={:?}",
1373 in_progress_typeck_results
.as_ref().map(|t
| t
.hir_owner
),
1376 let query_typeck_results
;
1377 let typeck_results
: &TypeckResults
<'tcx
> = match &in_progress_typeck_results
{
1378 Some(t
) if t
.hir_owner
.to_def_id() == generator_did_root
=> t
,
1380 query_typeck_results
= self.tcx
.typeck(generator_did
.expect_local());
1381 &query_typeck_results
1385 let generator_body
= generator_did
1387 .map(|def_id
| hir
.local_def_id_to_hir_id(def_id
))
1388 .and_then(|hir_id
| hir
.maybe_body_owned_by(hir_id
))
1389 .map(|body_id
| hir
.body(body_id
));
1390 let mut visitor
= AwaitsVisitor
::default();
1391 if let Some(body
) = generator_body
{
1392 visitor
.visit_body(body
);
1394 debug
!("maybe_note_obligation_cause_for_async_await: awaits = {:?}", visitor
.awaits
);
1396 // Look for a type inside the generator interior that matches the target type to get
1398 let target_ty_erased
= self.tcx
.erase_regions(&target_ty
);
1399 let ty_matches
= |ty
| -> bool
{
1400 // Careful: the regions for types that appear in the
1401 // generator interior are not generally known, so we
1402 // want to erase them when comparing (and anyway,
1403 // `Send` and other bounds are generally unaffected by
1404 // the choice of region). When erasing regions, we
1405 // also have to erase late-bound regions. This is
1406 // because the types that appear in the generator
1407 // interior generally contain "bound regions" to
1408 // represent regions that are part of the suspended
1409 // generator frame. Bound regions are preserved by
1410 // `erase_regions` and so we must also call
1411 // `erase_late_bound_regions`.
1412 let ty_erased
= self.tcx
.erase_late_bound_regions(&ty
::Binder
::bind(ty
));
1413 let ty_erased
= self.tcx
.erase_regions(&ty_erased
);
1414 let eq
= ty
::TyS
::same_type(ty_erased
, target_ty_erased
);
1416 "maybe_note_obligation_cause_for_async_await: ty_erased={:?} \
1417 target_ty_erased={:?} eq={:?}",
1418 ty_erased
, target_ty_erased
, eq
1423 let mut interior_or_upvar_span
= None
;
1424 let mut interior_extra_info
= None
;
1426 if let Some(upvars
) = self.tcx
.upvars_mentioned(generator_did
) {
1427 interior_or_upvar_span
= upvars
.iter().find_map(|(upvar_id
, upvar
)| {
1428 let upvar_ty
= typeck_results
.node_type(*upvar_id
);
1429 let upvar_ty
= self.resolve_vars_if_possible(&upvar_ty
);
1430 if ty_matches(&upvar_ty
) {
1431 Some(GeneratorInteriorOrUpvar
::Upvar(upvar
.span
))
1439 .generator_interior_types
1441 .find(|ty
::GeneratorInteriorTypeCause { ty, .. }
| ty_matches(ty
))
1443 // Check to see if any awaited expressions have the target type.
1444 let from_awaited_ty
= visitor
1447 .map(|id
| hir
.expect_expr(id
))
1448 .find(|await_expr
| {
1449 let ty
= typeck_results
.expr_ty_adjusted(&await_expr
);
1451 "maybe_note_obligation_cause_for_async_await: await_expr={:?}",
1456 .map(|expr
| expr
.span
);
1457 let ty
::GeneratorInteriorTypeCause { span, scope_span, yield_span, expr, .. }
=
1460 interior_or_upvar_span
= Some(GeneratorInteriorOrUpvar
::Interior(*span
));
1461 interior_extra_info
= Some((*scope_span
, *yield_span
, *expr
, from_awaited_ty
));
1465 "maybe_note_obligation_cause_for_async_await: interior_or_upvar={:?} \
1466 generator_interior_types={:?}",
1467 interior_or_upvar_span
, typeck_results
.generator_interior_types
1469 if let Some(interior_or_upvar_span
) = interior_or_upvar_span
{
1470 self.note_obligation_cause_for_async_await(
1472 interior_or_upvar_span
,
1473 interior_extra_info
,
1488 /// Unconditionally adds the diagnostic note described in
1489 /// `maybe_note_obligation_cause_for_async_await`'s documentation comment.
1490 fn note_obligation_cause_for_async_await(
1492 err
: &mut DiagnosticBuilder
<'_
>,
1493 interior_or_upvar_span
: GeneratorInteriorOrUpvar
,
1494 interior_extra_info
: Option
<(Option
<Span
>, Span
, Option
<hir
::HirId
>, Option
<Span
>)>,
1495 inner_generator_body
: Option
<&hir
::Body
<'tcx
>>,
1496 outer_generator
: Option
<DefId
>,
1497 trait_ref
: ty
::TraitRef
<'tcx
>,
1498 target_ty
: Ty
<'tcx
>,
1499 typeck_results
: &ty
::TypeckResults
<'tcx
>,
1500 obligation
: &PredicateObligation
<'tcx
>,
1501 next_code
: Option
<&ObligationCauseCode
<'tcx
>>,
1503 let source_map
= self.tcx
.sess
.source_map();
1505 let is_async
= inner_generator_body
1506 .and_then(|body
| body
.generator_kind())
1507 .map(|generator_kind
| matches
!(generator_kind
, hir
::GeneratorKind
::Async(..)))
1509 let (await_or_yield
, an_await_or_yield
) =
1510 if is_async { ("await", "an await") }
else { ("yield", "a yield") }
;
1511 let future_or_generator
= if is_async { "future" }
else { "generator" }
;
1513 // Special case the primary error message when send or sync is the trait that was
1515 let is_send
= self.tcx
.is_diagnostic_item(sym
::send_trait
, trait_ref
.def_id
);
1516 let is_sync
= self.tcx
.is_diagnostic_item(sym
::sync_trait
, trait_ref
.def_id
);
1517 let hir
= self.tcx
.hir();
1518 let trait_explanation
= if is_send
|| is_sync
{
1519 let (trait_name
, trait_verb
) =
1520 if is_send { ("`Send`", "sent") }
else { ("`Sync`", "shared") }
;
1523 err
.set_primary_message(format
!(
1524 "{} cannot be {} between threads safely",
1525 future_or_generator
, trait_verb
1528 let original_span
= err
.span
.primary_span().unwrap();
1529 let mut span
= MultiSpan
::from_span(original_span
);
1531 let message
= outer_generator
1532 .and_then(|generator_did
| {
1533 Some(match self.tcx
.generator_kind(generator_did
).unwrap() {
1534 GeneratorKind
::Gen
=> format
!("generator is not {}", trait_name
),
1535 GeneratorKind
::Async(AsyncGeneratorKind
::Fn
) => self
1537 .parent(generator_did
)
1538 .and_then(|parent_did
| parent_did
.as_local())
1539 .map(|parent_did
| hir
.local_def_id_to_hir_id(parent_did
))
1540 .and_then(|parent_hir_id
| hir
.opt_name(parent_hir_id
))
1542 format
!("future returned by `{}` is not {}", name
, trait_name
)
1544 GeneratorKind
::Async(AsyncGeneratorKind
::Block
) => {
1545 format
!("future created by async block is not {}", trait_name
)
1547 GeneratorKind
::Async(AsyncGeneratorKind
::Closure
) => {
1548 format
!("future created by async closure is not {}", trait_name
)
1552 .unwrap_or_else(|| format
!("{} is not {}", future_or_generator
, trait_name
));
1554 span
.push_span_label(original_span
, message
);
1557 format
!("is not {}", trait_name
)
1559 format
!("does not implement `{}`", trait_ref
.print_only_trait_path())
1562 let mut explain_yield
= |interior_span
: Span
,
1564 scope_span
: Option
<Span
>| {
1565 let mut span
= MultiSpan
::from_span(yield_span
);
1566 if let Ok(snippet
) = source_map
.span_to_snippet(interior_span
) {
1567 span
.push_span_label(
1569 format
!("{} occurs here, with `{}` maybe used later", await_or_yield
, snippet
),
1571 // If available, use the scope span to annotate the drop location.
1572 if let Some(scope_span
) = scope_span
{
1573 span
.push_span_label(
1574 source_map
.end_point(scope_span
),
1575 format
!("`{}` is later dropped here", snippet
),
1579 span
.push_span_label(
1581 format
!("has type `{}` which {}", target_ty
, trait_explanation
),
1587 "{} {} as this value is used across {}",
1588 future_or_generator
, trait_explanation
, an_await_or_yield
1592 match interior_or_upvar_span
{
1593 GeneratorInteriorOrUpvar
::Interior(interior_span
) => {
1594 if let Some((scope_span
, yield_span
, expr
, from_awaited_ty
)) = interior_extra_info
{
1595 if let Some(await_span
) = from_awaited_ty
{
1596 // The type causing this obligation is one being awaited at await_span.
1597 let mut span
= MultiSpan
::from_span(await_span
);
1598 span
.push_span_label(
1601 "await occurs here on type `{}`, which {}",
1602 target_ty
, trait_explanation
1608 "future {not_trait} as it awaits another future which {not_trait}",
1609 not_trait
= trait_explanation
1613 // Look at the last interior type to get a span for the `.await`.
1615 "note_obligation_cause_for_async_await generator_interior_types: {:#?}",
1616 typeck_results
.generator_interior_types
1618 explain_yield(interior_span
, yield_span
, scope_span
);
1621 if let Some(expr_id
) = expr
{
1622 let expr
= hir
.expect_expr(expr_id
);
1623 debug
!("target_ty evaluated from {:?}", expr
);
1625 let parent
= hir
.get_parent_node(expr_id
);
1626 if let Some(hir
::Node
::Expr(e
)) = hir
.find(parent
) {
1627 let parent_span
= hir
.span(parent
);
1628 let parent_did
= parent
.owner
.to_def_id();
1631 // fn foo(&self) -> i32 {}
1634 // ^^^^^^^ a temporary `&T` created inside this method call due to `&self`
1637 let is_region_borrow
= typeck_results
1638 .expr_adjustments(expr
)
1640 .any(|adj
| adj
.is_region_borrow());
1643 // struct Foo(*const u8);
1644 // bar(Foo(std::ptr::null())).await;
1645 // ^^^^^^^^^^^^^^^^^^^^^ raw-ptr `*T` created inside this struct ctor.
1647 debug
!("parent_def_kind: {:?}", self.tcx
.def_kind(parent_did
));
1648 let is_raw_borrow_inside_fn_like_call
=
1649 match self.tcx
.def_kind(parent_did
) {
1650 DefKind
::Fn
| DefKind
::Ctor(..) => target_ty
.is_unsafe_ptr(),
1654 if (typeck_results
.is_method_call(e
) && is_region_borrow
)
1655 || is_raw_borrow_inside_fn_like_call
1659 "consider moving this into a `let` \
1660 binding to create a shorter lived borrow",
1667 GeneratorInteriorOrUpvar
::Upvar(upvar_span
) => {
1668 let mut span
= MultiSpan
::from_span(upvar_span
);
1669 span
.push_span_label(
1671 format
!("has type `{}` which {}", target_ty
, trait_explanation
),
1673 err
.span_note(span
, &format
!("captured value {}", trait_explanation
));
1677 // Add a note for the item obligation that remains - normally a note pointing to the
1678 // bound that introduced the obligation (e.g. `T: Send`).
1679 debug
!("note_obligation_cause_for_async_await: next_code={:?}", next_code
);
1680 self.note_obligation_cause_code(
1682 &obligation
.predicate
,
1688 fn note_obligation_cause_code
<T
>(
1690 err
: &mut DiagnosticBuilder
<'_
>,
1692 cause_code
: &ObligationCauseCode
<'tcx
>,
1693 obligated_types
: &mut Vec
<&ty
::TyS
<'tcx
>>,
1699 ObligationCauseCode
::ExprAssignable
1700 | ObligationCauseCode
::MatchExpressionArm { .. }
1701 | ObligationCauseCode
::Pattern { .. }
1702 | ObligationCauseCode
::IfExpression { .. }
1703 | ObligationCauseCode
::IfExpressionWithNoElse
1704 | ObligationCauseCode
::MainFunctionType
1705 | ObligationCauseCode
::StartFunctionType
1706 | ObligationCauseCode
::IntrinsicType
1707 | ObligationCauseCode
::MethodReceiver
1708 | ObligationCauseCode
::ReturnNoExpression
1709 | ObligationCauseCode
::UnifyReceiver(..)
1710 | ObligationCauseCode
::MiscObligation
=> {}
1711 ObligationCauseCode
::SliceOrArrayElem
=> {
1712 err
.note("slice and array elements must have `Sized` type");
1714 ObligationCauseCode
::TupleElem
=> {
1715 err
.note("only the last element of a tuple may have a dynamically sized type");
1717 ObligationCauseCode
::ProjectionWf(data
) => {
1718 err
.note(&format
!("required so that the projection `{}` is well-formed", data
,));
1720 ObligationCauseCode
::ReferenceOutlivesReferent(ref_ty
) => {
1722 "required so that reference `{}` does not outlive its referent",
1726 ObligationCauseCode
::ObjectTypeBound(object_ty
, region
) => {
1728 "required so that the lifetime bound of `{}` for `{}` is satisfied",
1732 ObligationCauseCode
::ItemObligation(item_def_id
) => {
1733 let item_name
= tcx
.def_path_str(item_def_id
);
1734 let msg
= format
!("required by `{}`", item_name
);
1735 if let Some(sp
) = tcx
.hir().span_if_local(item_def_id
) {
1736 let sp
= tcx
.sess
.source_map().guess_head_span(sp
);
1737 err
.span_label(sp
, &msg
);
1742 ObligationCauseCode
::BindingObligation(item_def_id
, span
) => {
1743 let item_name
= tcx
.def_path_str(item_def_id
);
1744 let msg
= format
!("required by this bound in `{}`", item_name
);
1745 if let Some(ident
) = tcx
.opt_item_name(item_def_id
) {
1746 let sm
= tcx
.sess
.source_map();
1748 match (sm
.lookup_line(ident
.span
.hi()), sm
.lookup_line(span
.lo())) {
1749 (Ok(l
), Ok(r
)) => l
.line
== r
.line
,
1752 if !ident
.span
.overlaps(span
) && !same_line
{
1753 err
.span_label(ident
.span
, "required by a bound in this");
1756 if span
!= DUMMY_SP
{
1757 err
.span_label(span
, &msg
);
1762 ObligationCauseCode
::ObjectCastObligation(object_ty
) => {
1764 "required for the cast to the object type `{}`",
1765 self.ty_to_string(object_ty
)
1768 ObligationCauseCode
::Coercion { source: _, target }
=> {
1769 err
.note(&format
!("required by cast to type `{}`", self.ty_to_string(target
)));
1771 ObligationCauseCode
::RepeatVec(suggest_const_in_array_repeat_expressions
) => {
1773 "the `Copy` trait is required because the repeated element will be copied",
1775 if suggest_const_in_array_repeat_expressions
{
1777 "this array initializer can be evaluated at compile-time, see issue \
1778 #49147 <https://github.com/rust-lang/rust/issues/49147> \
1779 for more information",
1781 if tcx
.sess
.opts
.unstable_features
.is_nightly_build() {
1783 "add `#![feature(const_in_array_repeat_expressions)]` to the \
1784 crate attributes to enable",
1789 ObligationCauseCode
::VariableType(hir_id
) => {
1790 let parent_node
= self.tcx
.hir().get_parent_node(hir_id
);
1791 match self.tcx
.hir().find(parent_node
) {
1792 Some(Node
::Local(hir
::Local
{
1793 init
: Some(hir
::Expr { kind: hir::ExprKind::Index(_, _), span, .. }
),
1796 // When encountering an assignment of an unsized trait, like
1797 // `let x = ""[..];`, provide a suggestion to borrow the initializer in
1798 // order to use have a slice instead.
1799 err
.span_suggestion_verbose(
1800 span
.shrink_to_lo(),
1801 "consider borrowing here",
1803 Applicability
::MachineApplicable
,
1805 err
.note("all local variables must have a statically known size");
1807 Some(Node
::Param(param
)) => {
1808 err
.span_suggestion_verbose(
1809 param
.ty_span
.shrink_to_lo(),
1810 "function arguments must have a statically known size, borrowed types \
1811 always have a known size",
1813 Applicability
::MachineApplicable
,
1817 err
.note("all local variables must have a statically known size");
1820 if !self.tcx
.features().unsized_locals
{
1821 err
.help("unsized locals are gated as an unstable feature");
1824 ObligationCauseCode
::SizedArgumentType(sp
) => {
1825 if let Some(span
) = sp
{
1826 err
.span_suggestion_verbose(
1827 span
.shrink_to_lo(),
1828 "function arguments must have a statically known size, borrowed types \
1829 always have a known size",
1831 Applicability
::MachineApplicable
,
1834 err
.note("all function arguments must have a statically known size");
1836 if tcx
.sess
.opts
.unstable_features
.is_nightly_build()
1837 && !self.tcx
.features().unsized_locals
1839 err
.help("unsized locals are gated as an unstable feature");
1842 ObligationCauseCode
::SizedReturnType
=> {
1843 err
.note("the return type of a function must have a statically known size");
1845 ObligationCauseCode
::SizedYieldType
=> {
1846 err
.note("the yield type of a generator must have a statically known size");
1848 ObligationCauseCode
::AssignmentLhsSized
=> {
1849 err
.note("the left-hand-side of an assignment must have a statically known size");
1851 ObligationCauseCode
::TupleInitializerSized
=> {
1852 err
.note("tuples must have a statically known size to be initialized");
1854 ObligationCauseCode
::StructInitializerSized
=> {
1855 err
.note("structs must have a statically known size to be initialized");
1857 ObligationCauseCode
::FieldSized { adt_kind: ref item, last, span }
=> {
1859 AdtKind
::Struct
=> {
1862 "the last field of a packed struct may only have a \
1863 dynamically sized type if it does not need drop to be run",
1867 "only the last field of a struct may have a dynamically sized type",
1872 err
.note("no field of a union may have a dynamically sized type");
1875 err
.note("no field of an enum variant may have a dynamically sized type");
1878 err
.help("change the field's type to have a statically known size");
1879 err
.span_suggestion(
1880 span
.shrink_to_lo(),
1881 "borrowed types always have a statically known size",
1883 Applicability
::MachineApplicable
,
1885 err
.multipart_suggestion(
1886 "the `Box` type always has a statically known size and allocates its contents \
1889 (span
.shrink_to_lo(), "Box<".to_string()),
1890 (span
.shrink_to_hi(), ">".to_string()),
1892 Applicability
::MachineApplicable
,
1895 ObligationCauseCode
::ConstSized
=> {
1896 err
.note("constant expressions must have a statically known size");
1898 ObligationCauseCode
::InlineAsmSized
=> {
1899 err
.note("all inline asm arguments must have a statically known size");
1901 ObligationCauseCode
::ConstPatternStructural
=> {
1902 err
.note("constants used for pattern-matching must derive `PartialEq` and `Eq`");
1904 ObligationCauseCode
::SharedStatic
=> {
1905 err
.note("shared static variables must have a type that implements `Sync`");
1907 ObligationCauseCode
::BuiltinDerivedObligation(ref data
) => {
1908 let parent_trait_ref
= self.resolve_vars_if_possible(&data
.parent_trait_ref
);
1909 let ty
= parent_trait_ref
.skip_binder().self_ty();
1910 err
.note(&format
!("required because it appears within the type `{}`", ty
));
1911 obligated_types
.push(ty
);
1913 let parent_predicate
= parent_trait_ref
.without_const().to_predicate(tcx
);
1914 if !self.is_recursive_obligation(obligated_types
, &data
.parent_code
) {
1915 // #74711: avoid a stack overflow
1916 ensure_sufficient_stack(|| {
1917 self.note_obligation_cause_code(
1926 ObligationCauseCode
::ImplDerivedObligation(ref data
) => {
1927 let parent_trait_ref
= self.resolve_vars_if_possible(&data
.parent_trait_ref
);
1929 "required because of the requirements on the impl of `{}` for `{}`",
1930 parent_trait_ref
.print_only_trait_path(),
1931 parent_trait_ref
.skip_binder().self_ty()
1933 let parent_predicate
= parent_trait_ref
.without_const().to_predicate(tcx
);
1934 // #74711: avoid a stack overflow
1935 ensure_sufficient_stack(|| {
1936 self.note_obligation_cause_code(
1944 ObligationCauseCode
::DerivedObligation(ref data
) => {
1945 let parent_trait_ref
= self.resolve_vars_if_possible(&data
.parent_trait_ref
);
1946 let parent_predicate
= parent_trait_ref
.without_const().to_predicate(tcx
);
1947 // #74711: avoid a stack overflow
1948 ensure_sufficient_stack(|| {
1949 self.note_obligation_cause_code(
1957 ObligationCauseCode
::CompareImplMethodObligation { .. }
=> {
1959 "the requirement `{}` appears on the impl method \
1960 but not on the corresponding trait method",
1964 ObligationCauseCode
::CompareImplTypeObligation { .. }
=> {
1966 "the requirement `{}` appears on the associated impl type \
1967 but not on the corresponding associated trait type",
1971 ObligationCauseCode
::CompareImplConstObligation
=> {
1973 "the requirement `{}` appears on the associated impl constant \
1974 but not on the corresponding associated trait constant",
1978 ObligationCauseCode
::ReturnType
1979 | ObligationCauseCode
::ReturnValue(_
)
1980 | ObligationCauseCode
::BlockTailExpression(_
) => (),
1981 ObligationCauseCode
::TrivialBound
=> {
1982 err
.help("see issue #48214");
1983 if tcx
.sess
.opts
.unstable_features
.is_nightly_build() {
1984 err
.help("add `#![feature(trivial_bounds)]` to the crate attributes to enable");
1990 fn suggest_new_overflow_limit(&self, err
: &mut DiagnosticBuilder
<'_
>) {
1991 let current_limit
= self.tcx
.sess
.recursion_limit();
1992 let suggested_limit
= current_limit
* 2;
1994 "consider adding a `#![recursion_limit=\"{}\"]` attribute to your crate (`{}`)",
1995 suggested_limit
, self.tcx
.crate_name
,
1999 fn suggest_await_before_try(
2001 err
: &mut DiagnosticBuilder
<'_
>,
2002 obligation
: &PredicateObligation
<'tcx
>,
2003 trait_ref
: &ty
::Binder
<ty
::TraitRef
<'tcx
>>,
2007 "suggest_await_before_try: obligation={:?}, span={:?}, trait_ref={:?}, trait_ref_self_ty={:?}",
2013 let body_hir_id
= obligation
.cause
.body_id
;
2014 let item_id
= self.tcx
.hir().get_parent_node(body_hir_id
);
2016 if let Some(body_id
) = self.tcx
.hir().maybe_body_owned_by(item_id
) {
2017 let body
= self.tcx
.hir().body(body_id
);
2018 if let Some(hir
::GeneratorKind
::Async(_
)) = body
.generator_kind
{
2019 let future_trait
= self.tcx
.require_lang_item(LangItem
::Future
, None
);
2021 let self_ty
= self.resolve_vars_if_possible(&trait_ref
.self_ty());
2023 // Do not check on infer_types to avoid panic in evaluate_obligation.
2024 if self_ty
.has_infer_types() {
2027 let self_ty
= self.tcx
.erase_regions(&self_ty
);
2029 let impls_future
= self.tcx
.type_implements_trait((
2031 self_ty
.skip_binder(),
2033 obligation
.param_env
,
2036 let item_def_id
= self
2038 .associated_items(future_trait
)
2039 .in_definition_order()
2043 // `<T as Future>::Output`
2044 let projection_ty
= ty
::ProjectionTy
{
2046 substs
: self.tcx
.mk_substs_trait(
2047 trait_ref
.self_ty().skip_binder(),
2048 self.fresh_substs_for_item(span
, item_def_id
),
2054 let mut selcx
= SelectionContext
::new(self);
2056 let mut obligations
= vec
![];
2057 let normalized_ty
= normalize_projection_type(
2059 obligation
.param_env
,
2061 obligation
.cause
.clone(),
2067 "suggest_await_before_try: normalized_projection_type {:?}",
2068 self.resolve_vars_if_possible(&normalized_ty
)
2070 let try_obligation
= self.mk_trait_obligation_with_new_self_ty(
2071 obligation
.param_env
,
2075 debug
!("suggest_await_before_try: try_trait_obligation {:?}", try_obligation
);
2076 if self.predicate_may_hold(&try_obligation
) && impls_future
{
2077 if let Ok(snippet
) = self.tcx
.sess
.source_map().span_to_snippet(span
) {
2078 if snippet
.ends_with('?'
) {
2079 err
.span_suggestion(
2081 "consider using `.await` here",
2082 format
!("{}.await?", snippet
.trim_end_matches('?'
)),
2083 Applicability
::MaybeIncorrect
,
2093 /// Collect all the returned expressions within the input expression.
2094 /// Used to point at the return spans when we want to suggest some change to them.
2096 pub struct ReturnsVisitor
<'v
> {
2097 pub returns
: Vec
<&'v hir
::Expr
<'v
>>,
2098 in_block_tail
: bool
,
2101 impl<'v
> Visitor
<'v
> for ReturnsVisitor
<'v
> {
2102 type Map
= hir
::intravisit
::ErasedMap
<'v
>;
2104 fn nested_visit_map(&mut self) -> hir
::intravisit
::NestedVisitorMap
<Self::Map
> {
2105 hir
::intravisit
::NestedVisitorMap
::None
2108 fn visit_expr(&mut self, ex
: &'v hir
::Expr
<'v
>) {
2109 // Visit every expression to detect `return` paths, either through the function's tail
2110 // expression or `return` statements. We walk all nodes to find `return` statements, but
2111 // we only care about tail expressions when `in_block_tail` is `true`, which means that
2112 // they're in the return path of the function body.
2114 hir
::ExprKind
::Ret(Some(ex
)) => {
2115 self.returns
.push(ex
);
2117 hir
::ExprKind
::Block(block
, _
) if self.in_block_tail
=> {
2118 self.in_block_tail
= false;
2119 for stmt
in block
.stmts
{
2120 hir
::intravisit
::walk_stmt(self, stmt
);
2122 self.in_block_tail
= true;
2123 if let Some(expr
) = block
.expr
{
2124 self.visit_expr(expr
);
2127 hir
::ExprKind
::Match(_
, arms
, _
) if self.in_block_tail
=> {
2129 self.visit_expr(arm
.body
);
2132 // We need to walk to find `return`s in the entire body.
2133 _
if !self.in_block_tail
=> hir
::intravisit
::walk_expr(self, ex
),
2134 _
=> self.returns
.push(ex
),
2138 fn visit_body(&mut self, body
: &'v hir
::Body
<'v
>) {
2139 assert
!(!self.in_block_tail
);
2140 if body
.generator_kind().is_none() {
2141 if let hir
::ExprKind
::Block(block
, None
) = body
.value
.kind
{
2142 if block
.expr
.is_some() {
2143 self.in_block_tail
= true;
2147 hir
::intravisit
::walk_body(self, body
);
2151 /// Collect all the awaited expressions within the input expression.
2153 struct AwaitsVisitor
{
2154 awaits
: Vec
<hir
::HirId
>,
2157 impl<'v
> Visitor
<'v
> for AwaitsVisitor
{
2158 type Map
= hir
::intravisit
::ErasedMap
<'v
>;
2160 fn nested_visit_map(&mut self) -> hir
::intravisit
::NestedVisitorMap
<Self::Map
> {
2161 hir
::intravisit
::NestedVisitorMap
::None
2164 fn visit_expr(&mut self, ex
: &'v hir
::Expr
<'v
>) {
2165 if let hir
::ExprKind
::Yield(_
, hir
::YieldSource
::Await { expr: Some(id) }
) = ex
.kind
{
2166 self.awaits
.push(id
)
2168 hir
::intravisit
::walk_expr(self, ex
)
2172 pub trait NextTypeParamName
{
2173 fn next_type_param_name(&self, name
: Option
<&str>) -> String
;
2176 impl NextTypeParamName
for &[hir
::GenericParam
<'_
>] {
2177 fn next_type_param_name(&self, name
: Option
<&str>) -> String
{
2178 // This is the list of possible parameter names that we might suggest.
2179 let name
= name
.and_then(|n
| n
.chars().next()).map(|c
| c
.to_string().to_uppercase());
2180 let name
= name
.as_deref();
2181 let possible_names
= [name
.unwrap_or("T"), "T", "U", "V", "X", "Y", "Z", "A", "B", "C"];
2182 let used_names
= self
2184 .filter_map(|p
| match p
.name
{
2185 hir
::ParamName
::Plain(ident
) => Some(ident
.name
),
2188 .collect
::<Vec
<_
>>();
2192 .find(|n
| !used_names
.contains(&Symbol
::intern(n
)))
2193 .unwrap_or(&"ParamName")
2198 fn suggest_trait_object_return_type_alternatives(
2199 err
: &mut DiagnosticBuilder
<'_
>,
2202 is_object_safe
: bool
,
2204 err
.span_suggestion(
2206 "use some type `T` that is `T: Sized` as the return type if all return paths have the \
2209 Applicability
::MaybeIncorrect
,
2211 err
.span_suggestion(
2214 "use `impl {}` as the return type if all return paths have the same type but you \
2215 want to expose only the trait in the signature",
2218 format
!("impl {}", trait_obj
),
2219 Applicability
::MaybeIncorrect
,
2222 err
.span_suggestion(
2225 "use a boxed trait object if all return paths implement trait `{}`",
2228 format
!("Box<dyn {}>", trait_obj
),
2229 Applicability
::MaybeIncorrect
,