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
::fx
::FxHashSet
;
11 use rustc_data_structures
::stack
::ensure_sufficient_stack
;
12 use rustc_errors
::{error_code, struct_span_err, Applicability, DiagnosticBuilder, Style}
;
14 use rustc_hir
::def
::DefKind
;
15 use rustc_hir
::def_id
::DefId
;
16 use rustc_hir
::intravisit
::Visitor
;
17 use rustc_hir
::lang_items
::LangItem
;
18 use rustc_hir
::{AsyncGeneratorKind, GeneratorKind, Node}
;
19 use rustc_middle
::ty
::{
20 self, suggest_constraining_type_param
, AdtKind
, DefIdTree
, Infer
, InferTy
, ToPredicate
, Ty
,
21 TyCtxt
, TypeFoldable
, WithConstness
,
23 use rustc_middle
::ty
::{TypeAndMut, TypeckResults}
;
24 use rustc_span
::symbol
::{kw, sym, Ident, Symbol}
;
25 use rustc_span
::{BytePos, MultiSpan, Span, DUMMY_SP}
;
26 use rustc_target
::spec
::abi
;
29 use super::InferCtxtPrivExt
;
30 use crate::traits
::query
::evaluate_obligation
::InferCtxtExt
as _
;
33 pub enum GeneratorInteriorOrUpvar
{
34 // span of interior type
40 // This trait is public to expose the diagnostics methods to clippy.
41 pub trait InferCtxtExt
<'tcx
> {
42 fn suggest_restricting_param_bound(
44 err
: &mut DiagnosticBuilder
<'_
>,
45 trait_ref
: ty
::PolyTraitRef
<'tcx
>,
49 fn suggest_dereferences(
51 obligation
: &PredicateObligation
<'tcx
>,
52 err
: &mut DiagnosticBuilder
<'tcx
>,
53 trait_ref
: ty
::PolyTraitRef
<'tcx
>,
60 err
: &mut DiagnosticBuilder
<'_
>,
66 obligation
: &PredicateObligation
<'tcx
>,
67 err
: &mut DiagnosticBuilder
<'_
>,
68 trait_ref
: ty
::Binder
<ty
::TraitRef
<'tcx
>>,
72 fn suggest_add_reference_to_arg(
74 obligation
: &PredicateObligation
<'tcx
>,
75 err
: &mut DiagnosticBuilder
<'_
>,
76 trait_ref
: &ty
::Binder
<ty
::TraitRef
<'tcx
>>,
78 has_custom_message
: bool
,
81 fn suggest_remove_reference(
83 obligation
: &PredicateObligation
<'tcx
>,
84 err
: &mut DiagnosticBuilder
<'_
>,
85 trait_ref
: ty
::Binder
<ty
::TraitRef
<'tcx
>>,
88 fn suggest_change_mut(
90 obligation
: &PredicateObligation
<'tcx
>,
91 err
: &mut DiagnosticBuilder
<'_
>,
92 trait_ref
: ty
::Binder
<ty
::TraitRef
<'tcx
>>,
96 fn suggest_semicolon_removal(
98 obligation
: &PredicateObligation
<'tcx
>,
99 err
: &mut DiagnosticBuilder
<'_
>,
101 trait_ref
: ty
::Binder
<ty
::TraitRef
<'tcx
>>,
104 fn return_type_span(&self, obligation
: &PredicateObligation
<'tcx
>) -> Option
<Span
>;
106 fn suggest_impl_trait(
108 err
: &mut DiagnosticBuilder
<'_
>,
110 obligation
: &PredicateObligation
<'tcx
>,
111 trait_ref
: ty
::Binder
<ty
::TraitRef
<'tcx
>>,
114 fn point_at_returns_when_relevant(
116 err
: &mut DiagnosticBuilder
<'_
>,
117 obligation
: &PredicateObligation
<'tcx
>,
120 fn report_closure_arg_mismatch(
123 found_span
: Option
<Span
>,
124 expected_ref
: ty
::PolyTraitRef
<'tcx
>,
125 found
: ty
::PolyTraitRef
<'tcx
>,
126 ) -> DiagnosticBuilder
<'tcx
>;
128 fn suggest_fully_qualified_path(
130 err
: &mut DiagnosticBuilder
<'_
>,
136 fn maybe_note_obligation_cause_for_async_await(
138 err
: &mut DiagnosticBuilder
<'_
>,
139 obligation
: &PredicateObligation
<'tcx
>,
142 fn note_obligation_cause_for_async_await(
144 err
: &mut DiagnosticBuilder
<'_
>,
145 interior_or_upvar_span
: GeneratorInteriorOrUpvar
,
146 interior_extra_info
: Option
<(Option
<Span
>, Span
, Option
<hir
::HirId
>, Option
<Span
>)>,
147 inner_generator_body
: Option
<&hir
::Body
<'tcx
>>,
148 outer_generator
: Option
<DefId
>,
149 trait_ref
: ty
::TraitRef
<'tcx
>,
151 typeck_results
: &ty
::TypeckResults
<'tcx
>,
152 obligation
: &PredicateObligation
<'tcx
>,
153 next_code
: Option
<&ObligationCauseCode
<'tcx
>>,
156 fn note_obligation_cause_code
<T
>(
158 err
: &mut DiagnosticBuilder
<'_
>,
160 cause_code
: &ObligationCauseCode
<'tcx
>,
161 obligated_types
: &mut Vec
<&ty
::TyS
<'tcx
>>,
162 seen_requirements
: &mut FxHashSet
<DefId
>,
166 fn suggest_new_overflow_limit(&self, err
: &mut DiagnosticBuilder
<'_
>);
168 /// Suggest to await before try: future? => future.await?
169 fn suggest_await_before_try(
171 err
: &mut DiagnosticBuilder
<'_
>,
172 obligation
: &PredicateObligation
<'tcx
>,
173 trait_ref
: ty
::Binder
<ty
::TraitRef
<'tcx
>>,
178 fn predicate_constraint(generics
: &hir
::Generics
<'_
>, pred
: String
) -> (Span
, String
) {
180 generics
.where_clause
.tail_span_for_suggestion(),
183 if !generics
.where_clause
.predicates
.is_empty() { "," }
else { " where" }
,
189 /// Type parameter needs more bounds. The trivial case is `T` `where T: Bound`, but
190 /// it can also be an `impl Trait` param that needs to be decomposed to a type
191 /// param for cleaner code.
192 fn suggest_restriction(
194 generics
: &hir
::Generics
<'tcx
>,
196 err
: &mut DiagnosticBuilder
<'_
>,
197 fn_sig
: Option
<&hir
::FnSig
<'_
>>,
198 projection
: Option
<&ty
::ProjectionTy
<'_
>>,
199 trait_ref
: ty
::PolyTraitRef
<'tcx
>,
200 super_traits
: Option
<(&Ident
, &hir
::GenericBounds
<'_
>)>,
202 // When we are dealing with a trait, `super_traits` will be `Some`:
203 // Given `trait T: A + B + C {}`
204 // - ^^^^^^^^^ GenericBounds
207 let span
= generics
.where_clause
.span_for_predicates_or_empty_place();
208 if span
.from_expansion() || span
.desugaring_kind().is_some() {
211 // Given `fn foo(t: impl Trait)` where `Trait` requires assoc type `A`...
212 if let Some((bound_str
, fn_sig
)) =
213 fn_sig
.zip(projection
).and_then(|(sig
, p
)| match p
.self_ty().kind() {
214 // Shenanigans to get the `Trait` from the `impl Trait`.
215 ty
::Param(param
) => {
216 // `fn foo(t: impl Trait)`
217 // ^^^^^ get this string
218 param
.name
.as_str().strip_prefix("impl").map(|s
| (s
.trim_start().to_string(), sig
))
223 // We know we have an `impl Trait` that doesn't satisfy a required projection.
225 // Find all of the ocurrences of `impl Trait` for `Trait` in the function arguments'
226 // types. There should be at least one, but there might be *more* than one. In that
227 // case we could just ignore it and try to identify which one needs the restriction,
228 // but instead we choose to suggest replacing all instances of `impl Trait` with `T`
230 let mut ty_spans
= vec
![];
231 let impl_trait_str
= format
!("impl {}", bound_str
);
232 for input
in fn_sig
.decl
.inputs
{
233 if let hir
::TyKind
::Path(hir
::QPath
::Resolved(
235 hir
::Path { segments: [segment], .. }
,
238 if segment
.ident
.as_str() == impl_trait_str
.as_str() {
239 // `fn foo(t: impl Trait)`
240 // ^^^^^^^^^^ get this to suggest `T` instead
242 // There might be more than one `impl Trait`.
243 ty_spans
.push(input
.span
);
248 let type_param_name
= generics
.params
.next_type_param_name(Some(&bound_str
));
249 // The type param `T: Trait` we will suggest to introduce.
250 let type_param
= format
!("{}: {}", type_param_name
, bound_str
);
252 // FIXME: modify the `trait_ref` instead of string shenanigans.
253 // Turn `<impl Trait as Foo>::Bar: Qux` into `<T as Foo>::Bar: Qux`.
254 let pred
= trait_ref
.without_const().to_predicate(tcx
).to_string();
255 let pred
= pred
.replace(&impl_trait_str
, &type_param_name
);
257 // Find the last of the generic parameters contained within the span of
262 .map(|p
| p
.bounds_span().unwrap_or(p
.span
))
263 .filter(|&span
| generics
.span
.contains(span
) && span
.desugaring_kind().is_none())
264 .max_by_key(|span
| span
.hi())
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
271 Some(span
) => (span
.shrink_to_hi(), format
!(", {}", type_param
)),
273 // `fn foo(t: impl Trait)`
274 // ^ suggest `where <T as Trait>::A: Bound`
275 predicate_constraint(generics
, pred
),
277 sugg
.extend(ty_spans
.into_iter().map(|s
| (s
, type_param_name
.to_string())));
279 // Suggest `fn foo<T: Trait>(t: T) where <T as Trait>::A: Bound`.
280 // FIXME: once `#![feature(associated_type_bounds)]` is stabilized, we should suggest
281 // `fn foo(t: impl Trait<A: Bound>)` instead.
282 err
.multipart_suggestion(
283 "introduce a type parameter with a trait bound instead of using `impl Trait`",
285 Applicability
::MaybeIncorrect
,
288 // Trivial case: `T` needs an extra bound: `T: Bound`.
289 let (sp
, suggestion
) = match super_traits
{
290 None
=> predicate_constraint(
292 trait_ref
.without_const().to_predicate(tcx
).to_string(),
294 Some((ident
, bounds
)) => match bounds
{
296 bound
.span().shrink_to_hi(),
297 format
!(" + {}", trait_ref
.print_only_trait_path().to_string()),
300 ident
.span
.shrink_to_hi(),
301 format
!(": {}", trait_ref
.print_only_trait_path().to_string()),
306 err
.span_suggestion_verbose(
308 &format
!("consider further restricting {}", msg
),
310 Applicability
::MachineApplicable
,
315 impl<'a
, 'tcx
> InferCtxtExt
<'tcx
> for InferCtxt
<'a
, 'tcx
> {
316 fn suggest_restricting_param_bound(
318 mut err
: &mut DiagnosticBuilder
<'_
>,
319 trait_ref
: ty
::PolyTraitRef
<'tcx
>,
322 let self_ty
= trait_ref
.skip_binder().self_ty();
323 let (param_ty
, projection
) = match self_ty
.kind() {
324 ty
::Param(_
) => (true, None
),
325 ty
::Projection(projection
) => (false, Some(projection
)),
329 // FIXME: Add check for trait bound that is already present, particularly `?Sized` so we
330 // don't suggest `T: Sized + ?Sized`.
331 let mut hir_id
= body_id
;
332 while let Some(node
) = self.tcx
.hir().find(hir_id
) {
334 hir
::Node
::Item(hir
::Item
{
336 kind
: hir
::ItemKind
::Trait(_
, _
, generics
, bounds
, _
),
338 }) if self_ty
== self.tcx
.types
.self_param
=> {
340 // Restricting `Self` for a single method.
349 Some((ident
, bounds
)),
354 hir
::Node
::TraitItem(hir
::TraitItem
{
356 kind
: hir
::TraitItemKind
::Fn(..),
358 }) if self_ty
== self.tcx
.types
.self_param
=> {
360 // Restricting `Self` for a single method.
362 self.tcx
, &generics
, "`Self`", err
, None
, projection
, trait_ref
, None
,
367 hir
::Node
::TraitItem(hir
::TraitItem
{
369 kind
: hir
::TraitItemKind
::Fn(fn_sig
, ..),
372 | hir
::Node
::ImplItem(hir
::ImplItem
{
374 kind
: hir
::ImplItemKind
::Fn(fn_sig
, ..),
377 | hir
::Node
::Item(hir
::Item
{
378 kind
: hir
::ItemKind
::Fn(fn_sig
, generics
, _
), ..
379 }) if projection
.is_some() => {
380 // Missing restriction on associated type of type parameter (unmet projection).
384 "the associated type",
393 hir
::Node
::Item(hir
::Item
{
395 hir
::ItemKind
::Trait(_
, _
, generics
, _
, _
)
396 | hir
::ItemKind
::Impl { generics, .. }
,
398 }) if projection
.is_some() => {
399 // Missing restriction on associated type of type parameter (unmet projection).
403 "the associated type",
413 hir
::Node
::Item(hir
::Item
{
415 hir
::ItemKind
::Struct(_
, generics
)
416 | hir
::ItemKind
::Enum(_
, generics
)
417 | hir
::ItemKind
::Union(_
, generics
)
418 | hir
::ItemKind
::Trait(_
, _
, generics
, ..)
419 | hir
::ItemKind
::Impl { generics, .. }
420 | hir
::ItemKind
::Fn(_
, generics
, _
)
421 | hir
::ItemKind
::TyAlias(_
, generics
)
422 | hir
::ItemKind
::TraitAlias(generics
, _
)
423 | hir
::ItemKind
::OpaqueTy(hir
::OpaqueTy { generics, .. }
),
426 | hir
::Node
::TraitItem(hir
::TraitItem { generics, .. }
)
427 | hir
::Node
::ImplItem(hir
::ImplItem { generics, .. }
)
430 // Missing generic type parameter bound.
431 let param_name
= self_ty
.to_string();
432 let constraint
= trait_ref
.print_only_trait_path().to_string();
433 if suggest_constraining_type_param(
439 Some(trait_ref
.def_id()),
445 hir
::Node
::Crate(..) => return,
450 hir_id
= self.tcx
.hir().get_parent_item(hir_id
);
454 /// When after several dereferencing, the reference satisfies the trait
455 /// binding. This function provides dereference suggestion for this
456 /// specific situation.
457 fn suggest_dereferences(
459 obligation
: &PredicateObligation
<'tcx
>,
460 err
: &mut DiagnosticBuilder
<'tcx
>,
461 trait_ref
: ty
::PolyTraitRef
<'tcx
>,
464 // It only make sense when suggesting dereferences for arguments
468 let param_env
= obligation
.param_env
;
469 let body_id
= obligation
.cause
.body_id
;
470 let span
= obligation
.cause
.span
;
471 let real_trait_ref
= match &obligation
.cause
.code
{
472 ObligationCauseCode
::ImplDerivedObligation(cause
)
473 | ObligationCauseCode
::DerivedObligation(cause
)
474 | ObligationCauseCode
::BuiltinDerivedObligation(cause
) => cause
.parent_trait_ref
,
477 let real_ty
= match real_trait_ref
.self_ty().no_bound_vars() {
482 if let ty
::Ref(region
, base_ty
, mutbl
) = *real_ty
.kind() {
483 let mut autoderef
= Autoderef
::new(self, param_env
, body_id
, span
, base_ty
, span
);
484 if let Some(steps
) = autoderef
.find_map(|(ty
, steps
)| {
486 let ty
= self.tcx
.mk_ref(region
, TypeAndMut { ty, mutbl }
);
488 self.mk_trait_obligation_with_new_self_ty(param_env
, real_trait_ref
, ty
);
489 Some(steps
).filter(|_
| self.predicate_may_hold(&obligation
))
492 if let Ok(src
) = self.tcx
.sess
.source_map().span_to_snippet(span
) {
493 // Don't care about `&mut` because `DerefMut` is used less
494 // often and user will not expect autoderef happens.
495 if src
.starts_with('
&'
) && !src
.starts_with("&mut ") {
496 let derefs
= "*".repeat(steps
);
499 "consider adding dereference here",
500 format
!("&{}{}", derefs
, &src
[1..]),
501 Applicability
::MachineApplicable
,
510 /// Given a closure's `DefId`, return the given name of the closure.
512 /// This doesn't account for reassignments, but it's only used for suggestions.
516 err
: &mut DiagnosticBuilder
<'_
>,
518 ) -> Option
<String
> {
520 |err
: &mut DiagnosticBuilder
<'_
>, kind
: &hir
::PatKind
<'_
>| -> Option
<String
> {
521 // Get the local name of this closure. This can be inaccurate because
522 // of the possibility of reassignment, but this should be good enough.
524 hir
::PatKind
::Binding(hir
::BindingAnnotation
::Unannotated
, _
, name
, None
) => {
525 Some(format
!("{}", name
))
534 let hir
= self.tcx
.hir();
535 let hir_id
= hir
.local_def_id_to_hir_id(def_id
.as_local()?
);
536 let parent_node
= hir
.get_parent_node(hir_id
);
537 match hir
.find(parent_node
) {
538 Some(hir
::Node
::Stmt(hir
::Stmt { kind: hir::StmtKind::Local(local), .. }
)) => {
539 get_name(err
, &local
.pat
.kind
)
541 // Different to previous arm because one is `&hir::Local` and the other
542 // is `P<hir::Local>`.
543 Some(hir
::Node
::Local(local
)) => get_name(err
, &local
.pat
.kind
),
548 /// We tried to apply the bound to an `fn` or closure. Check whether calling it would
549 /// evaluate to a type that *would* satisfy the trait binding. If it would, suggest calling
550 /// it: `bar(foo)` → `bar(foo())`. This case is *very* likely to be hit if `foo` is `async`.
553 obligation
: &PredicateObligation
<'tcx
>,
554 err
: &mut DiagnosticBuilder
<'_
>,
555 trait_ref
: ty
::Binder
<ty
::TraitRef
<'tcx
>>,
558 let self_ty
= match trait_ref
.self_ty().no_bound_vars() {
563 let (def_id
, output_ty
, callable
) = match *self_ty
.kind() {
564 ty
::Closure(def_id
, substs
) => (def_id
, substs
.as_closure().sig().output(), "closure"),
565 ty
::FnDef(def_id
, _
) => (def_id
, self_ty
.fn_sig(self.tcx
).output(), "function"),
568 let msg
= format
!("use parentheses to call the {}", callable
);
570 // `mk_trait_obligation_with_new_self_ty` only works for types with no escaping bound
571 // variables, so bail out if we have any.
572 let output_ty
= match output_ty
.no_bound_vars() {
578 self.mk_trait_obligation_with_new_self_ty(obligation
.param_env
, trait_ref
, output_ty
);
580 match self.evaluate_obligation(&new_obligation
) {
582 EvaluationResult
::EvaluatedToOk
583 | EvaluationResult
::EvaluatedToOkModuloRegions
584 | EvaluationResult
::EvaluatedToAmbig
,
588 let hir
= self.tcx
.hir();
589 // Get the name of the callable and the arguments to be used in the suggestion.
590 let (snippet
, sugg
) = match hir
.get_if_local(def_id
) {
591 Some(hir
::Node
::Expr(hir
::Expr
{
592 kind
: hir
::ExprKind
::Closure(_
, decl
, _
, span
, ..),
595 err
.span_label(*span
, "consider calling this closure");
596 let name
= match self.get_closure_name(def_id
, err
, &msg
) {
600 let args
= decl
.inputs
.iter().map(|_
| "_").collect
::<Vec
<_
>>().join(", ");
601 let sugg
= format
!("({})", args
);
602 (format
!("{}{}", name
, sugg
), sugg
)
604 Some(hir
::Node
::Item(hir
::Item
{
606 kind
: hir
::ItemKind
::Fn(.., body_id
),
609 err
.span_label(ident
.span
, "consider calling this function");
610 let body
= hir
.body(*body_id
);
614 .map(|arg
| match &arg
.pat
.kind
{
615 hir
::PatKind
::Binding(_
, _
, ident
, None
)
616 // FIXME: provide a better suggestion when encountering `SelfLower`, it
617 // should suggest a method call.
618 if ident
.name
!= kw
::SelfLower
=> ident
.to_string(),
619 _
=> "_".to_string(),
623 let sugg
= format
!("({})", args
);
624 (format
!("{}{}", ident
, sugg
), sugg
)
629 // When the obligation error has been ensured to have been caused by
630 // an argument, the `obligation.cause.span` points at the expression
631 // of the argument, so we can provide a suggestion. This is signaled
632 // by `points_at_arg`. Otherwise, we give a more general note.
633 err
.span_suggestion_verbose(
634 obligation
.cause
.span
.shrink_to_hi(),
637 Applicability
::HasPlaceholders
,
640 err
.help(&format
!("{}: `{}`", msg
, snippet
));
644 fn suggest_add_reference_to_arg(
646 obligation
: &PredicateObligation
<'tcx
>,
647 err
: &mut DiagnosticBuilder
<'_
>,
648 trait_ref
: &ty
::Binder
<ty
::TraitRef
<'tcx
>>,
650 has_custom_message
: bool
,
656 let span
= obligation
.cause
.span
;
657 let param_env
= obligation
.param_env
;
658 let trait_ref
= trait_ref
.skip_binder();
660 if let ObligationCauseCode
::ImplDerivedObligation(obligation
) = &obligation
.cause
.code
{
661 // Try to apply the original trait binding obligation by borrowing.
662 let self_ty
= trait_ref
.self_ty();
663 let found
= self_ty
.to_string();
664 let new_self_ty
= self.tcx
.mk_imm_ref(self.tcx
.lifetimes
.re_static
, self_ty
);
665 let substs
= self.tcx
.mk_substs_trait(new_self_ty
, &[]);
666 let new_trait_ref
= ty
::TraitRef
::new(obligation
.parent_trait_ref
.def_id(), substs
);
667 let new_obligation
= Obligation
::new(
668 ObligationCause
::dummy(),
670 new_trait_ref
.without_const().to_predicate(self.tcx
),
673 if self.predicate_must_hold_modulo_regions(&new_obligation
) {
674 if let Ok(snippet
) = self.tcx
.sess
.source_map().span_to_snippet(span
) {
675 // We have a very specific type of error, where just borrowing this argument
676 // might solve the problem. In cases like this, the important part is the
677 // original type obligation, not the last one that failed, which is arbitrary.
678 // Because of this, we modify the error to refer to the original obligation and
679 // return early in the caller.
682 "the trait bound `{}: {}` is not satisfied",
684 obligation
.parent_trait_ref
.skip_binder().print_only_trait_path(),
686 if has_custom_message
{
689 err
.message
= vec
![(msg
, Style
::NoStyle
)];
691 if snippet
.starts_with('
&'
) {
692 // This is already a literal borrow and the obligation is failing
693 // somewhere else in the obligation chain. Do not suggest non-sense.
699 "expected an implementor of trait `{}`",
700 obligation
.parent_trait_ref
.skip_binder().print_only_trait_path(),
704 // This if is to prevent a special edge-case
705 if !span
.from_expansion() {
706 // We don't want a borrowing suggestion on the fields in structs,
709 // the_foos: Vec<Foo>
715 "consider borrowing here",
716 format
!("&{}", snippet
),
717 Applicability
::MaybeIncorrect
,
727 /// Whenever references are used by mistake, like `for (i, e) in &vec.iter().enumerate()`,
728 /// suggest removing these references until we reach a type that implements the trait.
729 fn suggest_remove_reference(
731 obligation
: &PredicateObligation
<'tcx
>,
732 err
: &mut DiagnosticBuilder
<'_
>,
733 trait_ref
: ty
::Binder
<ty
::TraitRef
<'tcx
>>,
735 let span
= obligation
.cause
.span
;
737 if let Ok(snippet
) = self.tcx
.sess
.source_map().span_to_snippet(span
) {
739 snippet
.chars().filter(|c
| !c
.is_whitespace()).take_while(|c
| *c
== '
&'
).count();
740 if let Some('
\''
) = snippet
.chars().filter(|c
| !c
.is_whitespace()).nth(refs_number
) {
741 // Do not suggest removal of borrow from type arguments.
745 let mut suggested_ty
= match trait_ref
.self_ty().no_bound_vars() {
750 for refs_remaining
in 0..refs_number
{
751 if let ty
::Ref(_
, inner_ty
, _
) = suggested_ty
.kind() {
752 suggested_ty
= inner_ty
;
754 let new_obligation
= self.mk_trait_obligation_with_new_self_ty(
755 obligation
.param_env
,
760 if self.predicate_may_hold(&new_obligation
) {
765 .span_take_while(span
, |c
| c
.is_whitespace() || *c
== '
&'
);
767 let remove_refs
= refs_remaining
+ 1;
769 let msg
= if remove_refs
== 1 {
770 "consider removing the leading `&`-reference".to_string()
772 format
!("consider removing {} leading `&`-references", remove_refs
)
775 err
.span_suggestion_short(
779 Applicability
::MachineApplicable
,
790 /// Check if the trait bound is implemented for a different mutability and note it in the
792 fn suggest_change_mut(
794 obligation
: &PredicateObligation
<'tcx
>,
795 err
: &mut DiagnosticBuilder
<'_
>,
796 trait_ref
: ty
::Binder
<ty
::TraitRef
<'tcx
>>,
799 let span
= obligation
.cause
.span
;
800 if let Ok(snippet
) = self.tcx
.sess
.source_map().span_to_snippet(span
) {
802 snippet
.chars().filter(|c
| !c
.is_whitespace()).take_while(|c
| *c
== '
&'
).count();
803 if let Some('
\''
) = snippet
.chars().filter(|c
| !c
.is_whitespace()).nth(refs_number
) {
804 // Do not suggest removal of borrow from type arguments.
807 let trait_ref
= self.resolve_vars_if_possible(trait_ref
);
808 if trait_ref
.has_infer_types_or_consts() {
809 // Do not ICE while trying to find if a reborrow would succeed on a trait with
810 // unresolved bindings.
814 if let ty
::Ref(region
, t_type
, mutability
) = *trait_ref
.skip_binder().self_ty().kind() {
815 if region
.is_late_bound() || t_type
.has_escaping_bound_vars() {
816 // Avoid debug assertion in `mk_obligation_for_def_id`.
818 // If the self type has escaping bound vars then it's not
819 // going to be the type of an expression, so the suggestion
820 // probably won't apply anyway.
824 let suggested_ty
= match mutability
{
825 hir
::Mutability
::Mut
=> self.tcx
.mk_imm_ref(region
, t_type
),
826 hir
::Mutability
::Not
=> self.tcx
.mk_mut_ref(region
, t_type
),
829 let new_obligation
= self.mk_trait_obligation_with_new_self_ty(
830 obligation
.param_env
,
834 let suggested_ty_would_satisfy_obligation
= self
835 .evaluate_obligation_no_overflow(&new_obligation
)
836 .must_apply_modulo_regions();
837 if suggested_ty_would_satisfy_obligation
{
842 .span_take_while(span
, |c
| c
.is_whitespace() || *c
== '
&'
);
843 if points_at_arg
&& mutability
== hir
::Mutability
::Not
&& refs_number
> 0 {
844 err
.span_suggestion_verbose(
846 "consider changing this borrow's mutability",
848 Applicability
::MachineApplicable
,
852 "`{}` is implemented for `{:?}`, but not for `{:?}`",
853 trait_ref
.print_only_trait_path(),
855 trait_ref
.skip_binder().self_ty(),
863 fn suggest_semicolon_removal(
865 obligation
: &PredicateObligation
<'tcx
>,
866 err
: &mut DiagnosticBuilder
<'_
>,
868 trait_ref
: ty
::Binder
<ty
::TraitRef
<'tcx
>>,
871 |ty
: ty
::Binder
<Ty
<'_
>>| *ty
.skip_binder().kind() == ty
::Tuple(ty
::List
::empty());
873 let hir
= self.tcx
.hir();
874 let parent_node
= hir
.get_parent_node(obligation
.cause
.body_id
);
875 let node
= hir
.find(parent_node
);
876 if let Some(hir
::Node
::Item(hir
::Item
{
877 kind
: hir
::ItemKind
::Fn(sig
, _
, body_id
), ..
880 let body
= hir
.body(*body_id
);
881 if let hir
::ExprKind
::Block(blk
, _
) = &body
.value
.kind
{
882 if sig
.decl
.output
.span().overlaps(span
)
883 && blk
.expr
.is_none()
884 && is_empty_tuple(trait_ref
.self_ty())
886 // FIXME(estebank): When encountering a method with a trait
887 // bound not satisfied in the return type with a body that has
888 // no return, suggest removal of semicolon on last statement.
889 // Once that is added, close #54771.
890 if let Some(ref stmt
) = blk
.stmts
.last() {
891 let sp
= self.tcx
.sess
.source_map().end_point(stmt
.span
);
892 err
.span_label(sp
, "consider removing this semicolon");
899 fn return_type_span(&self, obligation
: &PredicateObligation
<'tcx
>) -> Option
<Span
> {
900 let hir
= self.tcx
.hir();
901 let parent_node
= hir
.get_parent_node(obligation
.cause
.body_id
);
902 let sig
= match hir
.find(parent_node
) {
903 Some(hir
::Node
::Item(hir
::Item { kind: hir::ItemKind::Fn(sig, ..), .. }
)) => sig
,
907 if let hir
::FnRetTy
::Return(ret_ty
) = sig
.decl
.output { Some(ret_ty.span) }
else { None }
910 /// If all conditions are met to identify a returned `dyn Trait`, suggest using `impl Trait` if
911 /// applicable and signal that the error has been expanded appropriately and needs to be
913 fn suggest_impl_trait(
915 err
: &mut DiagnosticBuilder
<'_
>,
917 obligation
: &PredicateObligation
<'tcx
>,
918 trait_ref
: ty
::Binder
<ty
::TraitRef
<'tcx
>>,
920 match obligation
.cause
.code
.peel_derives() {
921 // Only suggest `impl Trait` if the return type is unsized because it is `dyn Trait`.
922 ObligationCauseCode
::SizedReturnType
=> {}
926 let hir
= self.tcx
.hir();
927 let parent_node
= hir
.get_parent_node(obligation
.cause
.body_id
);
928 let node
= hir
.find(parent_node
);
929 let (sig
, body_id
) = if let Some(hir
::Node
::Item(hir
::Item
{
930 kind
: hir
::ItemKind
::Fn(sig
, _
, body_id
),
938 let body
= hir
.body(*body_id
);
939 let trait_ref
= self.resolve_vars_if_possible(trait_ref
);
940 let ty
= trait_ref
.skip_binder().self_ty();
941 let is_object_safe
= match ty
.kind() {
942 ty
::Dynamic(predicates
, _
) => {
943 // If the `dyn Trait` is not object safe, do not suggest `Box<dyn Trait>`.
946 .map_or(true, |def_id
| self.tcx
.object_safety_violations(def_id
).is_empty())
948 // We only want to suggest `impl Trait` to `dyn Trait`s.
949 // For example, `fn foo() -> str` needs to be filtered out.
953 let ret_ty
= if let hir
::FnRetTy
::Return(ret_ty
) = sig
.decl
.output
{
959 // Use `TypeVisitor` instead of the output type directly to find the span of `ty` for
960 // cases like `fn foo() -> (dyn Trait, i32) {}`.
961 // Recursively look for `TraitObject` types and if there's only one, use that span to
962 // suggest `impl Trait`.
964 // Visit to make sure there's a single `return` type to suggest `impl Trait`,
965 // otherwise suggest using `Box<dyn Trait>` or an enum.
966 let mut visitor
= ReturnsVisitor
::default();
967 visitor
.visit_body(&body
);
969 let typeck_results
= self.in_progress_typeck_results
.map(|t
| t
.borrow()).unwrap();
971 let mut ret_types
= visitor
974 .filter_map(|expr
| typeck_results
.node_type_opt(expr
.hir_id
))
975 .map(|ty
| self.resolve_vars_if_possible(ty
));
976 let (last_ty
, all_returns_have_same_type
, only_never_return
) = ret_types
.clone().fold(
978 |(last_ty
, mut same
, only_never_return
): (std
::option
::Option
<Ty
<'_
>>, bool
, bool
),
980 let ty
= self.resolve_vars_if_possible(ty
);
982 !matches
!(ty
.kind(), ty
::Error(_
))
983 && last_ty
.map_or(true, |last_ty
| {
984 // FIXME: ideally we would use `can_coerce` here instead, but `typeck` comes
985 // *after* in the dependency graph.
986 match (ty
.kind(), last_ty
.kind()) {
987 (Infer(InferTy
::IntVar(_
)), Infer(InferTy
::IntVar(_
)))
988 | (Infer(InferTy
::FloatVar(_
)), Infer(InferTy
::FloatVar(_
)))
989 | (Infer(InferTy
::FreshIntTy(_
)), Infer(InferTy
::FreshIntTy(_
)))
991 Infer(InferTy
::FreshFloatTy(_
)),
992 Infer(InferTy
::FreshFloatTy(_
)),
997 (Some(ty
), same
, only_never_return
&& matches
!(ty
.kind(), ty
::Never
))
1000 let all_returns_conform_to_trait
=
1001 if let Some(ty_ret_ty
) = typeck_results
.node_type_opt(ret_ty
.hir_id
) {
1002 match ty_ret_ty
.kind() {
1003 ty
::Dynamic(predicates
, _
) => {
1004 let cause
= ObligationCause
::misc(ret_ty
.span
, ret_ty
.hir_id
);
1005 let param_env
= ty
::ParamEnv
::empty();
1007 || ret_types
.all(|returned_ty
| {
1008 predicates
.iter().all(|predicate
| {
1009 let pred
= predicate
.with_self_ty(self.tcx
, returned_ty
);
1010 let obl
= Obligation
::new(cause
.clone(), param_env
, pred
);
1011 self.predicate_may_hold(&obl
)
1021 let sm
= self.tcx
.sess
.source_map();
1022 let snippet
= if let (true, hir
::TyKind
::TraitObject(..), Ok(snippet
), true) = (
1023 // Verify that we're dealing with a return `dyn Trait`
1024 ret_ty
.span
.overlaps(span
),
1026 sm
.span_to_snippet(ret_ty
.span
),
1027 // If any of the return types does not conform to the trait, then we can't
1028 // suggest `impl Trait` nor trait objects: it is a type mismatch error.
1029 all_returns_conform_to_trait
,
1035 err
.code(error_code
!(E0746
));
1036 err
.set_primary_message("return type cannot have an unboxed trait object");
1037 err
.children
.clear();
1038 let impl_trait_msg
= "for information on `impl Trait`, see \
1039 <https://doc.rust-lang.org/book/ch10-02-traits.html\
1040 #returning-types-that-implement-traits>";
1041 let trait_obj_msg
= "for information on trait objects, see \
1042 <https://doc.rust-lang.org/book/ch17-02-trait-objects.html\
1043 #using-trait-objects-that-allow-for-values-of-different-types>";
1044 let has_dyn
= snippet
.split_whitespace().next().map_or(false, |s
| s
== "dyn");
1045 let trait_obj
= if has_dyn { &snippet[4..] }
else { &snippet[..] }
;
1046 if only_never_return
{
1047 // No return paths, probably using `panic!()` or similar.
1048 // Suggest `-> T`, `-> impl Trait`, and if `Trait` is object safe, `-> Box<dyn Trait>`.
1049 suggest_trait_object_return_type_alternatives(
1055 } else if let (Some(last_ty
), true) = (last_ty
, all_returns_have_same_type
) {
1056 // Suggest `-> impl Trait`.
1057 err
.span_suggestion(
1060 "use `impl {1}` as the return type, as all return paths are of type `{}`, \
1061 which implements `{1}`",
1064 format
!("impl {}", trait_obj
),
1065 Applicability
::MachineApplicable
,
1067 err
.note(impl_trait_msg
);
1070 // Suggest `-> Box<dyn Trait>` and `Box::new(returned_value)`.
1071 // Get all the return values and collect their span and suggestion.
1072 if let Some(mut suggestions
) = visitor
1076 let snip
= sm
.span_to_snippet(expr
.span
).ok()?
;
1077 Some((expr
.span
, format
!("Box::new({})", snip
)))
1079 .collect
::<Option
<Vec
<_
>>>()
1081 // Add the suggestion for the return type.
1082 suggestions
.push((ret_ty
.span
, format
!("Box<dyn {}>", trait_obj
)));
1083 err
.multipart_suggestion(
1084 "return a boxed trait object instead",
1086 Applicability
::MaybeIncorrect
,
1090 // This is currently not possible to trigger because E0038 takes precedence, but
1091 // leave it in for completeness in case anything changes in an earlier stage.
1093 "if trait `{}` was object safe, you could return a trait object",
1097 err
.note(trait_obj_msg
);
1099 "if all the returned values were of the same type you could use `impl {}` as the \
1103 err
.note(impl_trait_msg
);
1104 err
.note("you can create a new `enum` with a variant for each returned type");
1109 fn point_at_returns_when_relevant(
1111 err
: &mut DiagnosticBuilder
<'_
>,
1112 obligation
: &PredicateObligation
<'tcx
>,
1114 match obligation
.cause
.code
.peel_derives() {
1115 ObligationCauseCode
::SizedReturnType
=> {}
1119 let hir
= self.tcx
.hir();
1120 let parent_node
= hir
.get_parent_node(obligation
.cause
.body_id
);
1121 let node
= hir
.find(parent_node
);
1122 if let Some(hir
::Node
::Item(hir
::Item { kind: hir::ItemKind::Fn(_, _, body_id), .. }
)) =
1125 let body
= hir
.body(*body_id
);
1126 // Point at all the `return`s in the function as they have failed trait bounds.
1127 let mut visitor
= ReturnsVisitor
::default();
1128 visitor
.visit_body(&body
);
1129 let typeck_results
= self.in_progress_typeck_results
.map(|t
| t
.borrow()).unwrap();
1130 for expr
in &visitor
.returns
{
1131 if let Some(returned_ty
) = typeck_results
.node_type_opt(expr
.hir_id
) {
1132 let ty
= self.resolve_vars_if_possible(returned_ty
);
1133 err
.span_label(expr
.span
, &format
!("this returned value is of type `{}`", ty
));
1139 fn report_closure_arg_mismatch(
1142 found_span
: Option
<Span
>,
1143 expected_ref
: ty
::PolyTraitRef
<'tcx
>,
1144 found
: ty
::PolyTraitRef
<'tcx
>,
1145 ) -> DiagnosticBuilder
<'tcx
> {
1146 crate fn build_fn_sig_string
<'tcx
>(
1148 trait_ref
: ty
::PolyTraitRef
<'tcx
>,
1150 let inputs
= trait_ref
.skip_binder().substs
.type_at(1);
1151 let sig
= if let ty
::Tuple(inputs
) = inputs
.kind() {
1153 inputs
.iter().map(|k
| k
.expect_ty()),
1154 tcx
.mk_ty_infer(ty
::TyVar(ty
::TyVid { index: 0 }
)),
1156 hir
::Unsafety
::Normal
,
1161 std
::iter
::once(inputs
),
1162 tcx
.mk_ty_infer(ty
::TyVar(ty
::TyVid { index: 0 }
)),
1164 hir
::Unsafety
::Normal
,
1168 trait_ref
.rebind(sig
).to_string()
1171 let argument_is_closure
= expected_ref
.skip_binder().substs
.type_at(0).is_closure();
1172 let mut err
= struct_span_err
!(
1176 "type mismatch in {} arguments",
1177 if argument_is_closure { "closure" }
else { "function" }
1180 let found_str
= format
!("expected signature of `{}`", build_fn_sig_string(self.tcx
, found
));
1181 err
.span_label(span
, found_str
);
1183 let found_span
= found_span
.unwrap_or(span
);
1185 format
!("found signature of `{}`", build_fn_sig_string(self.tcx
, expected_ref
));
1186 err
.span_label(found_span
, expected_str
);
1191 fn suggest_fully_qualified_path(
1193 err
: &mut DiagnosticBuilder
<'_
>,
1198 if let Some(assoc_item
) = self.tcx
.opt_associated_item(def_id
) {
1199 if let ty
::AssocKind
::Const
| ty
::AssocKind
::Type
= assoc_item
.kind
{
1201 "{}s cannot be accessed directly on a `trait`, they can only be \
1202 accessed through a specific `impl`",
1203 assoc_item
.kind
.as_def_kind().descr(def_id
)
1205 err
.span_suggestion(
1207 "use the fully qualified path to an implementation",
1208 format
!("<Type as {}>::{}", self.tcx
.def_path_str(trait_ref
), assoc_item
.ident
),
1209 Applicability
::HasPlaceholders
,
1215 /// Adds an async-await specific note to the diagnostic when the future does not implement
1216 /// an auto trait because of a captured type.
1219 /// note: future does not implement `Qux` as this value is used across an await
1220 /// --> $DIR/issue-64130-3-other.rs:17:5
1222 /// LL | let x = Foo;
1223 /// | - has type `Foo`
1224 /// LL | baz().await;
1225 /// | ^^^^^^^^^^^ await occurs here, with `x` maybe used later
1227 /// | - `x` is later dropped here
1230 /// When the diagnostic does not implement `Send` or `Sync` specifically, then the diagnostic
1231 /// is "replaced" with a different message and a more specific error.
1234 /// error: future cannot be sent between threads safely
1235 /// --> $DIR/issue-64130-2-send.rs:21:5
1237 /// LL | fn is_send<T: Send>(t: T) { }
1238 /// | ---- required by this bound in `is_send`
1240 /// LL | is_send(bar());
1241 /// | ^^^^^^^ future returned by `bar` is not send
1243 /// = help: within `impl std::future::Future`, the trait `std::marker::Send` is not
1244 /// implemented for `Foo`
1245 /// note: future is not send as this value is used across an await
1246 /// --> $DIR/issue-64130-2-send.rs:15:5
1248 /// LL | let x = Foo;
1249 /// | - has type `Foo`
1250 /// LL | baz().await;
1251 /// | ^^^^^^^^^^^ await occurs here, with `x` maybe used later
1253 /// | - `x` is later dropped here
1256 /// Returns `true` if an async-await specific note was added to the diagnostic.
1257 fn maybe_note_obligation_cause_for_async_await(
1259 err
: &mut DiagnosticBuilder
<'_
>,
1260 obligation
: &PredicateObligation
<'tcx
>,
1263 "maybe_note_obligation_cause_for_async_await: obligation.predicate={:?} \
1264 obligation.cause.span={:?}",
1265 obligation
.predicate
, obligation
.cause
.span
1267 let hir
= self.tcx
.hir();
1269 // Attempt to detect an async-await error by looking at the obligation causes, looking
1270 // for a generator to be present.
1272 // When a future does not implement a trait because of a captured type in one of the
1273 // generators somewhere in the call stack, then the result is a chain of obligations.
1275 // Given a `async fn` A that calls a `async fn` B which captures a non-send type and that
1276 // future is passed as an argument to a function C which requires a `Send` type, then the
1277 // chain looks something like this:
1279 // - `BuiltinDerivedObligation` with a generator witness (B)
1280 // - `BuiltinDerivedObligation` with a generator (B)
1281 // - `BuiltinDerivedObligation` with `std::future::GenFuture` (B)
1282 // - `BuiltinDerivedObligation` with `impl std::future::Future` (B)
1283 // - `BuiltinDerivedObligation` with `impl std::future::Future` (B)
1284 // - `BuiltinDerivedObligation` with a generator witness (A)
1285 // - `BuiltinDerivedObligation` with a generator (A)
1286 // - `BuiltinDerivedObligation` with `std::future::GenFuture` (A)
1287 // - `BuiltinDerivedObligation` with `impl std::future::Future` (A)
1288 // - `BuiltinDerivedObligation` with `impl std::future::Future` (A)
1289 // - `BindingObligation` with `impl_send (Send requirement)
1291 // The first obligation in the chain is the most useful and has the generator that captured
1292 // the type. The last generator (`outer_generator` below) has information about where the
1293 // bound was introduced. At least one generator should be present for this diagnostic to be
1295 let (mut trait_ref
, mut target_ty
) = match obligation
.predicate
.skip_binders() {
1296 ty
::PredicateAtom
::Trait(p
, _
) => (Some(p
.trait_ref
), Some(p
.self_ty())),
1299 let mut generator
= None
;
1300 let mut outer_generator
= None
;
1301 let mut next_code
= Some(&obligation
.cause
.code
);
1303 let mut seen_upvar_tys_infer_tuple
= false;
1305 while let Some(code
) = next_code
{
1306 debug
!("maybe_note_obligation_cause_for_async_await: code={:?}", code
);
1308 ObligationCauseCode
::DerivedObligation(derived_obligation
)
1309 | ObligationCauseCode
::BuiltinDerivedObligation(derived_obligation
)
1310 | ObligationCauseCode
::ImplDerivedObligation(derived_obligation
) => {
1311 let ty
= derived_obligation
.parent_trait_ref
.skip_binder().self_ty();
1313 "maybe_note_obligation_cause_for_async_await: \
1314 parent_trait_ref={:?} self_ty.kind={:?}",
1315 derived_obligation
.parent_trait_ref
,
1320 ty
::Generator(did
, ..) => {
1321 generator
= generator
.or(Some(did
));
1322 outer_generator
= Some(did
);
1324 ty
::GeneratorWitness(..) => {}
1325 ty
::Tuple(_
) if !seen_upvar_tys_infer_tuple
=> {
1326 // By introducing a tuple of upvar types into the chain of obligations
1327 // of a generator, the first non-generator item is now the tuple itself,
1328 // we shall ignore this.
1330 seen_upvar_tys_infer_tuple
= true;
1332 _
if generator
.is_none() => {
1333 trait_ref
= Some(derived_obligation
.parent_trait_ref
.skip_binder());
1334 target_ty
= Some(ty
);
1339 next_code
= Some(derived_obligation
.parent_code
.as_ref());
1345 // Only continue if a generator was found.
1347 "maybe_note_obligation_cause_for_async_await: generator={:?} trait_ref={:?} \
1349 generator
, trait_ref
, target_ty
1351 let (generator_did
, trait_ref
, target_ty
) = match (generator
, trait_ref
, target_ty
) {
1352 (Some(generator_did
), Some(trait_ref
), Some(target_ty
)) => {
1353 (generator_did
, trait_ref
, target_ty
)
1358 let span
= self.tcx
.def_span(generator_did
);
1360 // Do not ICE on closure typeck (#66868).
1361 if !generator_did
.is_local() {
1365 // Get the typeck results from the infcx if the generator is the function we are
1366 // currently type-checking; otherwise, get them by performing a query.
1367 // This is needed to avoid cycles.
1368 let in_progress_typeck_results
= self.in_progress_typeck_results
.map(|t
| t
.borrow());
1369 let generator_did_root
= self.tcx
.closure_base_def_id(generator_did
);
1371 "maybe_note_obligation_cause_for_async_await: generator_did={:?} \
1372 generator_did_root={:?} in_progress_typeck_results.hir_owner={:?} span={:?}",
1375 in_progress_typeck_results
.as_ref().map(|t
| t
.hir_owner
),
1378 let query_typeck_results
;
1379 let typeck_results
: &TypeckResults
<'tcx
> = match &in_progress_typeck_results
{
1380 Some(t
) if t
.hir_owner
.to_def_id() == generator_did_root
=> t
,
1382 query_typeck_results
= self.tcx
.typeck(generator_did
.expect_local());
1383 &query_typeck_results
1387 let generator_body
= generator_did
1389 .map(|def_id
| hir
.local_def_id_to_hir_id(def_id
))
1390 .and_then(|hir_id
| hir
.maybe_body_owned_by(hir_id
))
1391 .map(|body_id
| hir
.body(body_id
));
1392 let mut visitor
= AwaitsVisitor
::default();
1393 if let Some(body
) = generator_body
{
1394 visitor
.visit_body(body
);
1396 debug
!("maybe_note_obligation_cause_for_async_await: awaits = {:?}", visitor
.awaits
);
1398 // Look for a type inside the generator interior that matches the target type to get
1400 let target_ty_erased
= self.tcx
.erase_regions(target_ty
);
1401 let ty_matches
= |ty
| -> bool
{
1402 // Careful: the regions for types that appear in the
1403 // generator interior are not generally known, so we
1404 // want to erase them when comparing (and anyway,
1405 // `Send` and other bounds are generally unaffected by
1406 // the choice of region). When erasing regions, we
1407 // also have to erase late-bound regions. This is
1408 // because the types that appear in the generator
1409 // interior generally contain "bound regions" to
1410 // represent regions that are part of the suspended
1411 // generator frame. Bound regions are preserved by
1412 // `erase_regions` and so we must also call
1413 // `erase_late_bound_regions`.
1414 let ty_erased
= self.tcx
.erase_late_bound_regions(ty
);
1415 let ty_erased
= self.tcx
.erase_regions(ty_erased
);
1416 let eq
= ty
::TyS
::same_type(ty_erased
, target_ty_erased
);
1418 "maybe_note_obligation_cause_for_async_await: ty_erased={:?} \
1419 target_ty_erased={:?} eq={:?}",
1420 ty_erased
, target_ty_erased
, eq
1425 let mut interior_or_upvar_span
= None
;
1426 let mut interior_extra_info
= None
;
1428 if let Some(upvars
) = self.tcx
.upvars_mentioned(generator_did
) {
1429 interior_or_upvar_span
= upvars
.iter().find_map(|(upvar_id
, upvar
)| {
1430 let upvar_ty
= typeck_results
.node_type(*upvar_id
);
1431 let upvar_ty
= self.resolve_vars_if_possible(upvar_ty
);
1432 if ty_matches(ty
::Binder
::dummy(upvar_ty
)) {
1433 Some(GeneratorInteriorOrUpvar
::Upvar(upvar
.span
))
1440 // The generator interior types share the same binders
1441 if let Some(cause
) =
1442 typeck_results
.generator_interior_types
.as_ref().skip_binder().iter().find(
1443 |ty
::GeneratorInteriorTypeCause { ty, .. }
| {
1444 ty_matches(typeck_results
.generator_interior_types
.rebind(ty
))
1448 // Check to see if any awaited expressions have the target type.
1449 let from_awaited_ty
= visitor
1452 .map(|id
| hir
.expect_expr(id
))
1453 .find(|await_expr
| {
1454 let ty
= typeck_results
.expr_ty_adjusted(&await_expr
);
1456 "maybe_note_obligation_cause_for_async_await: await_expr={:?}",
1459 ty_matches(ty
::Binder
::dummy(ty
))
1461 .map(|expr
| expr
.span
);
1462 let ty
::GeneratorInteriorTypeCause { span, scope_span, yield_span, expr, .. }
= cause
;
1464 interior_or_upvar_span
= Some(GeneratorInteriorOrUpvar
::Interior(*span
));
1465 interior_extra_info
= Some((*scope_span
, *yield_span
, *expr
, from_awaited_ty
));
1469 "maybe_note_obligation_cause_for_async_await: interior_or_upvar={:?} \
1470 generator_interior_types={:?}",
1471 interior_or_upvar_span
, typeck_results
.generator_interior_types
1473 if let Some(interior_or_upvar_span
) = interior_or_upvar_span
{
1474 self.note_obligation_cause_for_async_await(
1476 interior_or_upvar_span
,
1477 interior_extra_info
,
1492 /// Unconditionally adds the diagnostic note described in
1493 /// `maybe_note_obligation_cause_for_async_await`'s documentation comment.
1494 fn note_obligation_cause_for_async_await(
1496 err
: &mut DiagnosticBuilder
<'_
>,
1497 interior_or_upvar_span
: GeneratorInteriorOrUpvar
,
1498 interior_extra_info
: Option
<(Option
<Span
>, Span
, Option
<hir
::HirId
>, Option
<Span
>)>,
1499 inner_generator_body
: Option
<&hir
::Body
<'tcx
>>,
1500 outer_generator
: Option
<DefId
>,
1501 trait_ref
: ty
::TraitRef
<'tcx
>,
1502 target_ty
: Ty
<'tcx
>,
1503 typeck_results
: &ty
::TypeckResults
<'tcx
>,
1504 obligation
: &PredicateObligation
<'tcx
>,
1505 next_code
: Option
<&ObligationCauseCode
<'tcx
>>,
1507 let source_map
= self.tcx
.sess
.source_map();
1509 let is_async
= inner_generator_body
1510 .and_then(|body
| body
.generator_kind())
1511 .map(|generator_kind
| matches
!(generator_kind
, hir
::GeneratorKind
::Async(..)))
1513 let (await_or_yield
, an_await_or_yield
) =
1514 if is_async { ("await", "an await") }
else { ("yield", "a yield") }
;
1515 let future_or_generator
= if is_async { "future" }
else { "generator" }
;
1517 // Special case the primary error message when send or sync is the trait that was
1519 let is_send
= self.tcx
.is_diagnostic_item(sym
::send_trait
, trait_ref
.def_id
);
1520 let is_sync
= self.tcx
.is_diagnostic_item(sym
::sync_trait
, trait_ref
.def_id
);
1521 let hir
= self.tcx
.hir();
1522 let trait_explanation
= if is_send
|| is_sync
{
1523 let (trait_name
, trait_verb
) =
1524 if is_send { ("`Send`", "sent") }
else { ("`Sync`", "shared") }
;
1527 err
.set_primary_message(format
!(
1528 "{} cannot be {} between threads safely",
1529 future_or_generator
, trait_verb
1532 let original_span
= err
.span
.primary_span().unwrap();
1533 let mut span
= MultiSpan
::from_span(original_span
);
1535 let message
= outer_generator
1536 .and_then(|generator_did
| {
1537 Some(match self.tcx
.generator_kind(generator_did
).unwrap() {
1538 GeneratorKind
::Gen
=> format
!("generator is not {}", trait_name
),
1539 GeneratorKind
::Async(AsyncGeneratorKind
::Fn
) => self
1541 .parent(generator_did
)
1542 .and_then(|parent_did
| parent_did
.as_local())
1543 .map(|parent_did
| hir
.local_def_id_to_hir_id(parent_did
))
1544 .and_then(|parent_hir_id
| hir
.opt_name(parent_hir_id
))
1546 format
!("future returned by `{}` is not {}", name
, trait_name
)
1548 GeneratorKind
::Async(AsyncGeneratorKind
::Block
) => {
1549 format
!("future created by async block is not {}", trait_name
)
1551 GeneratorKind
::Async(AsyncGeneratorKind
::Closure
) => {
1552 format
!("future created by async closure is not {}", trait_name
)
1556 .unwrap_or_else(|| format
!("{} is not {}", future_or_generator
, trait_name
));
1558 span
.push_span_label(original_span
, message
);
1561 format
!("is not {}", trait_name
)
1563 format
!("does not implement `{}`", trait_ref
.print_only_trait_path())
1566 let mut explain_yield
=
1567 |interior_span
: Span
, yield_span
: Span
, scope_span
: Option
<Span
>| {
1568 let mut span
= MultiSpan
::from_span(yield_span
);
1569 if let Ok(snippet
) = source_map
.span_to_snippet(interior_span
) {
1570 // #70935: If snippet contains newlines, display "the value" instead
1571 // so that we do not emit complex diagnostics.
1572 let snippet
= &format
!("`{}`", snippet
);
1573 let snippet
= if snippet
.contains('
\n'
) { "the value" }
else { snippet }
;
1574 // The multispan can be complex here, like:
1575 // note: future is not `Send` as this value is used across an await
1576 // --> $DIR/issue-70935-complex-spans.rs:13:9
1578 // LL | baz(|| async{
1579 // | __________^___-
1582 // LL | || foo(tx.clone());
1583 // LL | || }).await;
1584 // | || - ^- value is later dropped here
1585 // | ||_________|______|
1586 // | |__________| await occurs here, with value maybe used later
1587 // | has type `closure` which is not `Send`
1589 // So, detect it and separate into some notes, like:
1591 // note: future is not `Send` as this value is used across an await
1592 // --> $DIR/issue-70935-complex-spans.rs:13:9
1594 // LL | / baz(|| async{
1595 // LL | | foo(tx.clone());
1597 // | |________________^ first, await occurs here, with the value maybe used later...
1598 // note: the value is later dropped here
1599 // --> $DIR/issue-70935-complex-spans.rs:15:17
1604 // If available, use the scope span to annotate the drop location.
1605 if let Some(scope_span
) = scope_span
{
1606 let scope_span
= source_map
.end_point(scope_span
);
1608 yield_span
.overlaps(scope_span
) || yield_span
.overlaps(interior_span
);
1610 span
.push_span_label(
1613 "first, {} occurs here, with {} maybe used later...",
1614 await_or_yield
, snippet
1620 "{} {} as this value is used across {}",
1621 future_or_generator
, trait_explanation
, an_await_or_yield
1624 if source_map
.is_multiline(interior_span
) {
1627 &format
!("{} is later dropped here", snippet
),
1632 "this has type `{}` which {}",
1633 target_ty
, trait_explanation
1637 let mut span
= MultiSpan
::from_span(scope_span
);
1638 span
.push_span_label(
1640 format
!("has type `{}` which {}", target_ty
, trait_explanation
),
1642 err
.span_note(span
, &format
!("{} is later dropped here", snippet
));
1645 span
.push_span_label(
1648 "{} occurs here, with {} maybe used later",
1649 await_or_yield
, snippet
1652 span
.push_span_label(
1654 format
!("{} is later dropped here", snippet
),
1656 span
.push_span_label(
1658 format
!("has type `{}` which {}", target_ty
, trait_explanation
),
1663 "{} {} as this value is used across {}",
1664 future_or_generator
, trait_explanation
, an_await_or_yield
1669 span
.push_span_label(
1672 "{} occurs here, with {} maybe used later",
1673 await_or_yield
, snippet
1676 span
.push_span_label(
1678 format
!("has type `{}` which {}", target_ty
, trait_explanation
),
1683 "{} {} as this value is used across {}",
1684 future_or_generator
, trait_explanation
, an_await_or_yield
1690 match interior_or_upvar_span
{
1691 GeneratorInteriorOrUpvar
::Interior(interior_span
) => {
1692 if let Some((scope_span
, yield_span
, expr
, from_awaited_ty
)) = interior_extra_info
{
1693 if let Some(await_span
) = from_awaited_ty
{
1694 // The type causing this obligation is one being awaited at await_span.
1695 let mut span
= MultiSpan
::from_span(await_span
);
1696 span
.push_span_label(
1699 "await occurs here on type `{}`, which {}",
1700 target_ty
, trait_explanation
1706 "future {not_trait} as it awaits another future which {not_trait}",
1707 not_trait
= trait_explanation
1711 // Look at the last interior type to get a span for the `.await`.
1713 "note_obligation_cause_for_async_await generator_interior_types: {:#?}",
1714 typeck_results
.generator_interior_types
1716 explain_yield(interior_span
, yield_span
, scope_span
);
1719 if let Some(expr_id
) = expr
{
1720 let expr
= hir
.expect_expr(expr_id
);
1721 debug
!("target_ty evaluated from {:?}", expr
);
1723 let parent
= hir
.get_parent_node(expr_id
);
1724 if let Some(hir
::Node
::Expr(e
)) = hir
.find(parent
) {
1725 let parent_span
= hir
.span(parent
);
1726 let parent_did
= parent
.owner
.to_def_id();
1729 // fn foo(&self) -> i32 {}
1732 // ^^^^^^^ a temporary `&T` created inside this method call due to `&self`
1735 let is_region_borrow
= typeck_results
1736 .expr_adjustments(expr
)
1738 .any(|adj
| adj
.is_region_borrow());
1741 // struct Foo(*const u8);
1742 // bar(Foo(std::ptr::null())).await;
1743 // ^^^^^^^^^^^^^^^^^^^^^ raw-ptr `*T` created inside this struct ctor.
1745 debug
!("parent_def_kind: {:?}", self.tcx
.def_kind(parent_did
));
1746 let is_raw_borrow_inside_fn_like_call
=
1747 match self.tcx
.def_kind(parent_did
) {
1748 DefKind
::Fn
| DefKind
::Ctor(..) => target_ty
.is_unsafe_ptr(),
1752 if (typeck_results
.is_method_call(e
) && is_region_borrow
)
1753 || is_raw_borrow_inside_fn_like_call
1757 "consider moving this into a `let` \
1758 binding to create a shorter lived borrow",
1765 GeneratorInteriorOrUpvar
::Upvar(upvar_span
) => {
1766 let mut span
= MultiSpan
::from_span(upvar_span
);
1767 span
.push_span_label(
1769 format
!("has type `{}` which {}", target_ty
, trait_explanation
),
1771 err
.span_note(span
, &format
!("captured value {}", trait_explanation
));
1775 // Add a note for the item obligation that remains - normally a note pointing to the
1776 // bound that introduced the obligation (e.g. `T: Send`).
1777 debug
!("note_obligation_cause_for_async_await: next_code={:?}", next_code
);
1778 self.note_obligation_cause_code(
1780 &obligation
.predicate
,
1783 &mut Default
::default(),
1787 fn note_obligation_cause_code
<T
>(
1789 err
: &mut DiagnosticBuilder
<'_
>,
1791 cause_code
: &ObligationCauseCode
<'tcx
>,
1792 obligated_types
: &mut Vec
<&ty
::TyS
<'tcx
>>,
1793 seen_requirements
: &mut FxHashSet
<DefId
>,
1799 ObligationCauseCode
::ExprAssignable
1800 | ObligationCauseCode
::MatchExpressionArm { .. }
1801 | ObligationCauseCode
::Pattern { .. }
1802 | ObligationCauseCode
::IfExpression { .. }
1803 | ObligationCauseCode
::IfExpressionWithNoElse
1804 | ObligationCauseCode
::MainFunctionType
1805 | ObligationCauseCode
::StartFunctionType
1806 | ObligationCauseCode
::IntrinsicType
1807 | ObligationCauseCode
::MethodReceiver
1808 | ObligationCauseCode
::ReturnNoExpression
1809 | ObligationCauseCode
::UnifyReceiver(..)
1810 | ObligationCauseCode
::MiscObligation
=> {}
1811 ObligationCauseCode
::SliceOrArrayElem
=> {
1812 err
.note("slice and array elements must have `Sized` type");
1814 ObligationCauseCode
::TupleElem
=> {
1815 err
.note("only the last element of a tuple may have a dynamically sized type");
1817 ObligationCauseCode
::ProjectionWf(data
) => {
1818 err
.note(&format
!("required so that the projection `{}` is well-formed", data
,));
1820 ObligationCauseCode
::ReferenceOutlivesReferent(ref_ty
) => {
1822 "required so that reference `{}` does not outlive its referent",
1826 ObligationCauseCode
::ObjectTypeBound(object_ty
, region
) => {
1828 "required so that the lifetime bound of `{}` for `{}` is satisfied",
1832 ObligationCauseCode
::ItemObligation(item_def_id
) => {
1833 let item_name
= tcx
.def_path_str(item_def_id
);
1834 let msg
= format
!("required by `{}`", item_name
);
1835 if let Some(sp
) = tcx
.hir().span_if_local(item_def_id
) {
1836 let sp
= tcx
.sess
.source_map().guess_head_span(sp
);
1837 err
.span_label(sp
, &msg
);
1842 ObligationCauseCode
::BindingObligation(item_def_id
, span
) => {
1843 let item_name
= tcx
.def_path_str(item_def_id
);
1844 let msg
= format
!("required by this bound in `{}`", item_name
);
1845 if let Some(ident
) = tcx
.opt_item_name(item_def_id
) {
1846 let sm
= tcx
.sess
.source_map();
1848 match (sm
.lookup_line(ident
.span
.hi()), sm
.lookup_line(span
.lo())) {
1849 (Ok(l
), Ok(r
)) => l
.line
== r
.line
,
1852 if !ident
.span
.overlaps(span
) && !same_line
{
1853 err
.span_label(ident
.span
, "required by a bound in this");
1856 if span
!= DUMMY_SP
{
1857 err
.span_label(span
, &msg
);
1862 ObligationCauseCode
::ObjectCastObligation(object_ty
) => {
1864 "required for the cast to the object type `{}`",
1865 self.ty_to_string(object_ty
)
1868 ObligationCauseCode
::Coercion { source: _, target }
=> {
1869 err
.note(&format
!("required by cast to type `{}`", self.ty_to_string(target
)));
1871 ObligationCauseCode
::RepeatVec(suggest_const_in_array_repeat_expressions
) => {
1873 "the `Copy` trait is required because the repeated element will be copied",
1875 if suggest_const_in_array_repeat_expressions
{
1877 "this array initializer can be evaluated at compile-time, see issue \
1878 #49147 <https://github.com/rust-lang/rust/issues/49147> \
1879 for more information",
1881 if tcx
.sess
.opts
.unstable_features
.is_nightly_build() {
1883 "add `#![feature(const_in_array_repeat_expressions)]` to the \
1884 crate attributes to enable",
1889 ObligationCauseCode
::VariableType(hir_id
) => {
1890 let parent_node
= self.tcx
.hir().get_parent_node(hir_id
);
1891 match self.tcx
.hir().find(parent_node
) {
1892 Some(Node
::Local(hir
::Local
{
1893 init
: Some(hir
::Expr { kind: hir::ExprKind::Index(_, _), span, .. }
),
1896 // When encountering an assignment of an unsized trait, like
1897 // `let x = ""[..];`, provide a suggestion to borrow the initializer in
1898 // order to use have a slice instead.
1899 err
.span_suggestion_verbose(
1900 span
.shrink_to_lo(),
1901 "consider borrowing here",
1903 Applicability
::MachineApplicable
,
1905 err
.note("all local variables must have a statically known size");
1907 Some(Node
::Param(param
)) => {
1908 err
.span_suggestion_verbose(
1909 param
.ty_span
.shrink_to_lo(),
1910 "function arguments must have a statically known size, borrowed types \
1911 always have a known size",
1913 Applicability
::MachineApplicable
,
1917 err
.note("all local variables must have a statically known size");
1920 if !self.tcx
.features().unsized_locals
{
1921 err
.help("unsized locals are gated as an unstable feature");
1924 ObligationCauseCode
::SizedArgumentType(sp
) => {
1925 if let Some(span
) = sp
{
1926 err
.span_suggestion_verbose(
1927 span
.shrink_to_lo(),
1928 "function arguments must have a statically known size, borrowed types \
1929 always have a known size",
1931 Applicability
::MachineApplicable
,
1934 err
.note("all function arguments must have a statically known size");
1936 if tcx
.sess
.opts
.unstable_features
.is_nightly_build()
1937 && !self.tcx
.features().unsized_fn_params
1939 err
.help("unsized fn params are gated as an unstable feature");
1942 ObligationCauseCode
::SizedReturnType
=> {
1943 err
.note("the return type of a function must have a statically known size");
1945 ObligationCauseCode
::SizedYieldType
=> {
1946 err
.note("the yield type of a generator must have a statically known size");
1948 ObligationCauseCode
::AssignmentLhsSized
=> {
1949 err
.note("the left-hand-side of an assignment must have a statically known size");
1951 ObligationCauseCode
::TupleInitializerSized
=> {
1952 err
.note("tuples must have a statically known size to be initialized");
1954 ObligationCauseCode
::StructInitializerSized
=> {
1955 err
.note("structs must have a statically known size to be initialized");
1957 ObligationCauseCode
::FieldSized { adt_kind: ref item, last, span }
=> {
1959 AdtKind
::Struct
=> {
1962 "the last field of a packed struct may only have a \
1963 dynamically sized type if it does not need drop to be run",
1967 "only the last field of a struct may have a dynamically sized type",
1972 err
.note("no field of a union may have a dynamically sized type");
1975 err
.note("no field of an enum variant may have a dynamically sized type");
1978 err
.help("change the field's type to have a statically known size");
1979 err
.span_suggestion(
1980 span
.shrink_to_lo(),
1981 "borrowed types always have a statically known size",
1983 Applicability
::MachineApplicable
,
1985 err
.multipart_suggestion(
1986 "the `Box` type always has a statically known size and allocates its contents \
1989 (span
.shrink_to_lo(), "Box<".to_string()),
1990 (span
.shrink_to_hi(), ">".to_string()),
1992 Applicability
::MachineApplicable
,
1995 ObligationCauseCode
::ConstSized
=> {
1996 err
.note("constant expressions must have a statically known size");
1998 ObligationCauseCode
::InlineAsmSized
=> {
1999 err
.note("all inline asm arguments must have a statically known size");
2001 ObligationCauseCode
::ConstPatternStructural
=> {
2002 err
.note("constants used for pattern-matching must derive `PartialEq` and `Eq`");
2004 ObligationCauseCode
::SharedStatic
=> {
2005 err
.note("shared static variables must have a type that implements `Sync`");
2007 ObligationCauseCode
::BuiltinDerivedObligation(ref data
) => {
2008 let parent_trait_ref
= self.resolve_vars_if_possible(data
.parent_trait_ref
);
2009 let ty
= parent_trait_ref
.skip_binder().self_ty();
2010 if parent_trait_ref
.references_error() {
2015 // If the obligation for a tuple is set directly by a Generator or Closure,
2016 // then the tuple must be the one containing capture types.
2017 let is_upvar_tys_infer_tuple
= if !matches
!(ty
.kind(), ty
::Tuple(..)) {
2020 if let ObligationCauseCode
::BuiltinDerivedObligation(ref data
) =
2023 let parent_trait_ref
= self.resolve_vars_if_possible(data
.parent_trait_ref
);
2024 let ty
= parent_trait_ref
.skip_binder().self_ty();
2025 matches
!(ty
.kind(), ty
::Generator(..))
2026 || matches
!(ty
.kind(), ty
::Closure(..))
2032 // Don't print the tuple of capture types
2033 if !is_upvar_tys_infer_tuple
{
2034 err
.note(&format
!("required because it appears within the type `{}`", ty
));
2037 obligated_types
.push(ty
);
2039 let parent_predicate
= parent_trait_ref
.without_const().to_predicate(tcx
);
2040 if !self.is_recursive_obligation(obligated_types
, &data
.parent_code
) {
2041 // #74711: avoid a stack overflow
2042 ensure_sufficient_stack(|| {
2043 self.note_obligation_cause_code(
2053 ObligationCauseCode
::ImplDerivedObligation(ref data
) => {
2054 let mut parent_trait_ref
= self.resolve_vars_if_possible(data
.parent_trait_ref
);
2055 let parent_def_id
= parent_trait_ref
.def_id();
2057 "required because of the requirements on the impl of `{}` for `{}`",
2058 parent_trait_ref
.print_only_trait_path(),
2059 parent_trait_ref
.skip_binder().self_ty()
2062 let mut parent_predicate
= parent_trait_ref
.without_const().to_predicate(tcx
);
2063 let mut data
= data
;
2065 seen_requirements
.insert(parent_def_id
);
2066 while let ObligationCauseCode
::ImplDerivedObligation(child
) = &*data
.parent_code
{
2067 // Skip redundant recursive obligation notes. See `ui/issue-20413.rs`.
2068 let child_trait_ref
= self.resolve_vars_if_possible(child
.parent_trait_ref
);
2069 let child_def_id
= child_trait_ref
.def_id();
2070 if seen_requirements
.insert(child_def_id
) {
2075 parent_predicate
= child_trait_ref
.without_const().to_predicate(tcx
);
2076 parent_trait_ref
= child_trait_ref
;
2079 err
.note(&format
!("{} redundant requirements hidden", count
));
2081 "required because of the requirements on the impl of `{}` for `{}`",
2082 parent_trait_ref
.print_only_trait_path(),
2083 parent_trait_ref
.skip_binder().self_ty()
2086 // #74711: avoid a stack overflow
2087 ensure_sufficient_stack(|| {
2088 self.note_obligation_cause_code(
2097 ObligationCauseCode
::DerivedObligation(ref data
) => {
2098 let parent_trait_ref
= self.resolve_vars_if_possible(data
.parent_trait_ref
);
2099 let parent_predicate
= parent_trait_ref
.without_const().to_predicate(tcx
);
2100 // #74711: avoid a stack overflow
2101 ensure_sufficient_stack(|| {
2102 self.note_obligation_cause_code(
2111 ObligationCauseCode
::CompareImplMethodObligation { .. }
=> {
2113 "the requirement `{}` appears on the impl method but not on the corresponding \
2118 ObligationCauseCode
::CompareImplTypeObligation { .. }
=> {
2120 "the requirement `{}` appears on the associated impl type but not on the \
2121 corresponding associated trait type",
2125 ObligationCauseCode
::CompareImplConstObligation
=> {
2127 "the requirement `{}` appears on the associated impl constant \
2128 but not on the corresponding associated trait constant",
2132 ObligationCauseCode
::ReturnType
2133 | ObligationCauseCode
::ReturnValue(_
)
2134 | ObligationCauseCode
::BlockTailExpression(_
) => (),
2135 ObligationCauseCode
::TrivialBound
=> {
2136 err
.help("see issue #48214");
2137 if tcx
.sess
.opts
.unstable_features
.is_nightly_build() {
2138 err
.help("add `#![feature(trivial_bounds)]` to the crate attributes to enable");
2144 fn suggest_new_overflow_limit(&self, err
: &mut DiagnosticBuilder
<'_
>) {
2145 let current_limit
= self.tcx
.sess
.recursion_limit();
2146 let suggested_limit
= current_limit
* 2;
2148 "consider adding a `#![recursion_limit=\"{}\"]` attribute to your crate (`{}`)",
2149 suggested_limit
, self.tcx
.crate_name
,
2153 fn suggest_await_before_try(
2155 err
: &mut DiagnosticBuilder
<'_
>,
2156 obligation
: &PredicateObligation
<'tcx
>,
2157 trait_ref
: ty
::Binder
<ty
::TraitRef
<'tcx
>>,
2161 "suggest_await_before_try: obligation={:?}, span={:?}, trait_ref={:?}, trait_ref_self_ty={:?}",
2167 let body_hir_id
= obligation
.cause
.body_id
;
2168 let item_id
= self.tcx
.hir().get_parent_node(body_hir_id
);
2170 if let Some(body_id
) = self.tcx
.hir().maybe_body_owned_by(item_id
) {
2171 let body
= self.tcx
.hir().body(body_id
);
2172 if let Some(hir
::GeneratorKind
::Async(_
)) = body
.generator_kind
{
2173 let future_trait
= self.tcx
.require_lang_item(LangItem
::Future
, None
);
2175 let self_ty
= self.resolve_vars_if_possible(trait_ref
.self_ty());
2177 // Do not check on infer_types to avoid panic in evaluate_obligation.
2178 if self_ty
.has_infer_types() {
2181 let self_ty
= self.tcx
.erase_regions(self_ty
);
2183 let impls_future
= self.tcx
.type_implements_trait((
2185 self_ty
.skip_binder(),
2187 obligation
.param_env
,
2190 let item_def_id
= self
2192 .associated_items(future_trait
)
2193 .in_definition_order()
2197 // `<T as Future>::Output`
2198 let projection_ty
= ty
::ProjectionTy
{
2200 substs
: self.tcx
.mk_substs_trait(
2201 trait_ref
.self_ty().skip_binder(),
2202 self.fresh_substs_for_item(span
, item_def_id
),
2208 let mut selcx
= SelectionContext
::new(self);
2210 let mut obligations
= vec
![];
2211 let normalized_ty
= normalize_projection_type(
2213 obligation
.param_env
,
2215 obligation
.cause
.clone(),
2221 "suggest_await_before_try: normalized_projection_type {:?}",
2222 self.resolve_vars_if_possible(normalized_ty
)
2224 let try_obligation
= self.mk_trait_obligation_with_new_self_ty(
2225 obligation
.param_env
,
2229 debug
!("suggest_await_before_try: try_trait_obligation {:?}", try_obligation
);
2230 if self.predicate_may_hold(&try_obligation
) && impls_future
{
2231 if let Ok(snippet
) = self.tcx
.sess
.source_map().span_to_snippet(span
) {
2232 if snippet
.ends_with('?'
) {
2233 err
.span_suggestion_verbose(
2234 span
.with_hi(span
.hi() - BytePos(1)).shrink_to_hi(),
2235 "consider `await`ing on the `Future`",
2236 ".await".to_string(),
2237 Applicability
::MaybeIncorrect
,
2247 /// Collect all the returned expressions within the input expression.
2248 /// Used to point at the return spans when we want to suggest some change to them.
2250 pub struct ReturnsVisitor
<'v
> {
2251 pub returns
: Vec
<&'v hir
::Expr
<'v
>>,
2252 in_block_tail
: bool
,
2255 impl<'v
> Visitor
<'v
> for ReturnsVisitor
<'v
> {
2256 type Map
= hir
::intravisit
::ErasedMap
<'v
>;
2258 fn nested_visit_map(&mut self) -> hir
::intravisit
::NestedVisitorMap
<Self::Map
> {
2259 hir
::intravisit
::NestedVisitorMap
::None
2262 fn visit_expr(&mut self, ex
: &'v hir
::Expr
<'v
>) {
2263 // Visit every expression to detect `return` paths, either through the function's tail
2264 // expression or `return` statements. We walk all nodes to find `return` statements, but
2265 // we only care about tail expressions when `in_block_tail` is `true`, which means that
2266 // they're in the return path of the function body.
2268 hir
::ExprKind
::Ret(Some(ex
)) => {
2269 self.returns
.push(ex
);
2271 hir
::ExprKind
::Block(block
, _
) if self.in_block_tail
=> {
2272 self.in_block_tail
= false;
2273 for stmt
in block
.stmts
{
2274 hir
::intravisit
::walk_stmt(self, stmt
);
2276 self.in_block_tail
= true;
2277 if let Some(expr
) = block
.expr
{
2278 self.visit_expr(expr
);
2281 hir
::ExprKind
::Match(_
, arms
, _
) if self.in_block_tail
=> {
2283 self.visit_expr(arm
.body
);
2286 // We need to walk to find `return`s in the entire body.
2287 _
if !self.in_block_tail
=> hir
::intravisit
::walk_expr(self, ex
),
2288 _
=> self.returns
.push(ex
),
2292 fn visit_body(&mut self, body
: &'v hir
::Body
<'v
>) {
2293 assert
!(!self.in_block_tail
);
2294 if body
.generator_kind().is_none() {
2295 if let hir
::ExprKind
::Block(block
, None
) = body
.value
.kind
{
2296 if block
.expr
.is_some() {
2297 self.in_block_tail
= true;
2301 hir
::intravisit
::walk_body(self, body
);
2305 /// Collect all the awaited expressions within the input expression.
2307 struct AwaitsVisitor
{
2308 awaits
: Vec
<hir
::HirId
>,
2311 impl<'v
> Visitor
<'v
> for AwaitsVisitor
{
2312 type Map
= hir
::intravisit
::ErasedMap
<'v
>;
2314 fn nested_visit_map(&mut self) -> hir
::intravisit
::NestedVisitorMap
<Self::Map
> {
2315 hir
::intravisit
::NestedVisitorMap
::None
2318 fn visit_expr(&mut self, ex
: &'v hir
::Expr
<'v
>) {
2319 if let hir
::ExprKind
::Yield(_
, hir
::YieldSource
::Await { expr: Some(id) }
) = ex
.kind
{
2320 self.awaits
.push(id
)
2322 hir
::intravisit
::walk_expr(self, ex
)
2326 pub trait NextTypeParamName
{
2327 fn next_type_param_name(&self, name
: Option
<&str>) -> String
;
2330 impl NextTypeParamName
for &[hir
::GenericParam
<'_
>] {
2331 fn next_type_param_name(&self, name
: Option
<&str>) -> String
{
2332 // This is the list of possible parameter names that we might suggest.
2333 let name
= name
.and_then(|n
| n
.chars().next()).map(|c
| c
.to_string().to_uppercase());
2334 let name
= name
.as_deref();
2335 let possible_names
= [name
.unwrap_or("T"), "T", "U", "V", "X", "Y", "Z", "A", "B", "C"];
2336 let used_names
= self
2338 .filter_map(|p
| match p
.name
{
2339 hir
::ParamName
::Plain(ident
) => Some(ident
.name
),
2342 .collect
::<Vec
<_
>>();
2346 .find(|n
| !used_names
.contains(&Symbol
::intern(n
)))
2347 .unwrap_or(&"ParamName")
2352 fn suggest_trait_object_return_type_alternatives(
2353 err
: &mut DiagnosticBuilder
<'_
>,
2356 is_object_safe
: bool
,
2358 err
.span_suggestion(
2360 "use some type `T` that is `T: Sized` as the return type if all return paths have the \
2363 Applicability
::MaybeIncorrect
,
2365 err
.span_suggestion(
2368 "use `impl {}` as the return type if all return paths have the same type but you \
2369 want to expose only the trait in the signature",
2372 format
!("impl {}", trait_obj
),
2373 Applicability
::MaybeIncorrect
,
2376 err
.span_suggestion(
2379 "use a boxed trait object if all return paths implement trait `{}`",
2382 format
!("Box<dyn {}>", trait_obj
),
2383 Applicability
::MaybeIncorrect
,