Trait rustc_trait_selection::traits::error_reporting::suggestions::TypeErrCtxtExt

pub trait TypeErrCtxtExt<'tcx> {
    // Required methods
    fn suggest_restricting_param_bound(
        &self,
        err: &mut Diag<'_>,
        trait_pred: PolyTraitPredicate<'tcx>,
        associated_ty: Option<(&'static str, Ty<'tcx>)>,
        body_id: LocalDefId
    );
    fn suggest_dereferences(
        &self,
        obligation: &PredicateObligation<'tcx>,
        err: &mut Diag<'_>,
        trait_pred: PolyTraitPredicate<'tcx>
    ) -> bool;
    fn get_closure_name(
        &self,
        def_id: DefId,
        err: &mut Diag<'_>,
        msg: Cow<'static, str>
    ) -> Option<Symbol>;
    fn suggest_fn_call(
        &self,
        obligation: &PredicateObligation<'tcx>,
        err: &mut Diag<'_>,
        trait_pred: PolyTraitPredicate<'tcx>
    ) -> bool;
    fn check_for_binding_assigned_block_without_tail_expression(
        &self,
        obligation: &PredicateObligation<'tcx>,
        err: &mut Diag<'_>,
        trait_pred: PolyTraitPredicate<'tcx>
    );
    fn suggest_add_clone_to_arg(
        &self,
        obligation: &PredicateObligation<'tcx>,
        err: &mut Diag<'_>,
        trait_pred: PolyTraitPredicate<'tcx>
    ) -> bool;
    fn extract_callable_info(
        &self,
        body_id: LocalDefId,
        param_env: ParamEnv<'tcx>,
        found: Ty<'tcx>
    ) -> Option<(DefIdOrName, Ty<'tcx>, Vec<Ty<'tcx>>)>;
    fn suggest_add_reference_to_arg(
        &self,
        obligation: &PredicateObligation<'tcx>,
        err: &mut Diag<'_>,
        poly_trait_pred: PolyTraitPredicate<'tcx>,
        has_custom_message: bool
    ) -> bool;
    fn suggest_borrowing_for_object_cast(
        &self,
        err: &mut Diag<'_>,
        obligation: &PredicateObligation<'tcx>,
        self_ty: Ty<'tcx>,
        target_ty: Ty<'tcx>
    );
    fn suggest_remove_reference(
        &self,
        obligation: &PredicateObligation<'tcx>,
        err: &mut Diag<'_>,
        trait_pred: PolyTraitPredicate<'tcx>
    ) -> bool;
    fn suggest_remove_await(
        &self,
        obligation: &PredicateObligation<'tcx>,
        err: &mut Diag<'_>
    );
    fn suggest_change_mut(
        &self,
        obligation: &PredicateObligation<'tcx>,
        err: &mut Diag<'_>,
        trait_pred: PolyTraitPredicate<'tcx>
    );
    fn suggest_semicolon_removal(
        &self,
        obligation: &PredicateObligation<'tcx>,
        err: &mut Diag<'_>,
        span: Span,
        trait_pred: PolyTraitPredicate<'tcx>
    ) -> bool;
    fn return_type_span(
        &self,
        obligation: &PredicateObligation<'tcx>
    ) -> Option<Span>;
    fn suggest_impl_trait(
        &self,
        err: &mut Diag<'_>,
        obligation: &PredicateObligation<'tcx>,
        trait_pred: PolyTraitPredicate<'tcx>
    ) -> bool;
    fn point_at_returns_when_relevant(
        &self,
        err: &mut Diag<'tcx>,
        obligation: &PredicateObligation<'tcx>
    );
    fn report_closure_arg_mismatch(
        &self,
        span: Span,
        found_span: Option<Span>,
        found: TraitRef<'tcx>,
        expected: TraitRef<'tcx>,
        cause: &ObligationCauseCode<'tcx>,
        found_node: Option<Node<'_>>,
        param_env: ParamEnv<'tcx>
    ) -> Diag<'tcx>;
    fn note_conflicting_fn_args(
        &self,
        err: &mut Diag<'_>,
        cause: &ObligationCauseCode<'tcx>,
        expected: Ty<'tcx>,
        found: Ty<'tcx>,
        param_env: ParamEnv<'tcx>
    );
    fn note_conflicting_closure_bounds(
        &self,
        cause: &ObligationCauseCode<'tcx>,
        err: &mut Diag<'tcx>
    );
    fn suggest_fully_qualified_path(
        &self,
        err: &mut Diag<'_>,
        item_def_id: DefId,
        span: Span,
        trait_ref: DefId
    );
    fn maybe_note_obligation_cause_for_async_await<G: EmissionGuarantee>(
        &self,
        err: &mut Diag<'_, G>,
        obligation: &PredicateObligation<'tcx>
    ) -> bool;
    fn note_obligation_cause_for_async_await<G: EmissionGuarantee>(
        &self,
        err: &mut Diag<'_, G>,
        interior_or_upvar_span: CoroutineInteriorOrUpvar,
        is_async: bool,
        outer_coroutine: Option<DefId>,
        trait_pred: TraitPredicate<'tcx>,
        target_ty: Ty<'tcx>,
        obligation: &PredicateObligation<'tcx>,
        next_code: Option<&ObligationCauseCode<'tcx>>
    );
    fn note_obligation_cause_code<G: EmissionGuarantee, T>(
        &self,
        body_id: LocalDefId,
        err: &mut Diag<'_, G>,
        predicate: T,
        param_env: ParamEnv<'tcx>,
        cause_code: &ObligationCauseCode<'tcx>,
        obligated_types: &mut Vec<Ty<'tcx>>,
        seen_requirements: &mut FxHashSet<DefId>
    )
       where T: ToPredicate<'tcx>;
    fn suggest_await_before_try(
        &self,
        err: &mut Diag<'_>,
        obligation: &PredicateObligation<'tcx>,
        trait_pred: PolyTraitPredicate<'tcx>,
        span: Span
    );
    fn suggest_floating_point_literal(
        &self,
        obligation: &PredicateObligation<'tcx>,
        err: &mut Diag<'_>,
        trait_ref: &PolyTraitRef<'tcx>
    );
    fn suggest_derive(
        &self,
        obligation: &PredicateObligation<'tcx>,
        err: &mut Diag<'_>,
        trait_pred: PolyTraitPredicate<'tcx>
    );
    fn suggest_dereferencing_index(
        &self,
        obligation: &PredicateObligation<'tcx>,
        err: &mut Diag<'_>,
        trait_pred: PolyTraitPredicate<'tcx>
    );
    fn note_function_argument_obligation<G: EmissionGuarantee>(
        &self,
        body_id: LocalDefId,
        err: &mut Diag<'_, G>,
        arg_hir_id: HirId,
        parent_code: &ObligationCauseCode<'tcx>,
        param_env: ParamEnv<'tcx>,
        failed_pred: Predicate<'tcx>,
        call_hir_id: HirId
    );
    fn suggest_option_method_if_applicable<G: EmissionGuarantee>(
        &self,
        failed_pred: Predicate<'tcx>,
        param_env: ParamEnv<'tcx>,
        err: &mut Diag<'_, G>,
        expr: &Expr<'_>
    );
    fn look_for_iterator_item_mistakes<G: EmissionGuarantee>(
        &self,
        assocs_in_this_method: &[Option<(Span, (DefId, Ty<'tcx>))>],
        typeck_results: &TypeckResults<'tcx>,
        type_diffs: &[TypeError<'tcx>],
        param_env: ParamEnv<'tcx>,
        path_segment: &PathSegment<'_>,
        args: &[Expr<'_>],
        err: &mut Diag<'_, G>
    );
    fn point_at_chain<G: EmissionGuarantee>(
        &self,
        expr: &Expr<'_>,
        typeck_results: &TypeckResults<'tcx>,
        type_diffs: Vec<TypeError<'tcx>>,
        param_env: ParamEnv<'tcx>,
        err: &mut Diag<'_, G>
    );
    fn probe_assoc_types_at_expr(
        &self,
        type_diffs: &[TypeError<'tcx>],
        span: Span,
        prev_ty: Ty<'tcx>,
        body_id: HirId,
        param_env: ParamEnv<'tcx>
    ) -> Vec<Option<(Span, (DefId, Ty<'tcx>))>>;
    fn suggest_convert_to_slice(
        &self,
        err: &mut Diag<'_>,
        obligation: &PredicateObligation<'tcx>,
        trait_ref: PolyTraitRef<'tcx>,
        candidate_impls: &[ImplCandidate<'tcx>],
        span: Span
    );
    fn explain_hrtb_projection(
        &self,
        diag: &mut Diag<'_>,
        pred: PolyTraitPredicate<'tcx>,
        param_env: ParamEnv<'tcx>,
        cause: &ObligationCause<'tcx>
    );
    fn suggest_desugaring_async_fn_in_trait(
        &self,
        err: &mut Diag<'_>,
        trait_ref: PolyTraitRef<'tcx>
    );
    fn ty_kind_suggestion(
        &self,
        param_env: ParamEnv<'tcx>,
        ty: Ty<'tcx>
    ) -> Option<String>;
}

Required Methods

fn suggest_restricting_param_bound( &self, err: &mut Diag<'_>, trait_pred: PolyTraitPredicate<'tcx>, associated_ty: Option<(&'static str, Ty<'tcx>)>, body_id: LocalDefId )

fn suggest_dereferences( &self, obligation: &PredicateObligation<'tcx>, err: &mut Diag<'_>, trait_pred: PolyTraitPredicate<'tcx> ) -> bool

When after several dereferencing, the reference satisfies the trait binding. This function provides dereference suggestion for this specific situation.

fn get_closure_name( &self, def_id: DefId, err: &mut Diag<'_>, msg: Cow<'static, str> ) -> Option<Symbol>

Given a closure’s DefId, return the given name of the closure.

This doesn’t account for reassignments, but it’s only used for suggestions.

fn suggest_fn_call( &self, obligation: &PredicateObligation<'tcx>, err: &mut Diag<'_>, trait_pred: PolyTraitPredicate<'tcx> ) -> bool

We tried to apply the bound to an fn or closure. Check whether calling it would evaluate to a type that would satisfy the trait binding. If it would, suggest calling it: bar(foo) → bar(foo()). This case is very likely to be hit if foo is async.

fn check_for_binding_assigned_block_without_tail_expression( &self, obligation: &PredicateObligation<'tcx>, err: &mut Diag<'_>, trait_pred: PolyTraitPredicate<'tcx> )

fn suggest_add_clone_to_arg( &self, obligation: &PredicateObligation<'tcx>, err: &mut Diag<'_>, trait_pred: PolyTraitPredicate<'tcx> ) -> bool

fn extract_callable_info( &self, body_id: LocalDefId, param_env: ParamEnv<'tcx>, found: Ty<'tcx> ) -> Option<(DefIdOrName, Ty<'tcx>, Vec<Ty<'tcx>>)>

Extracts information about a callable type for diagnostics. This is a heuristic – it doesn’t necessarily mean that a type is always callable, because the callable type must also be well-formed to be called.

fn suggest_add_reference_to_arg( &self, obligation: &PredicateObligation<'tcx>, err: &mut Diag<'_>, poly_trait_pred: PolyTraitPredicate<'tcx>, has_custom_message: bool ) -> bool

fn suggest_borrowing_for_object_cast( &self, err: &mut Diag<'_>, obligation: &PredicateObligation<'tcx>, self_ty: Ty<'tcx>, target_ty: Ty<'tcx> )

fn suggest_remove_reference( &self, obligation: &PredicateObligation<'tcx>, err: &mut Diag<'_>, trait_pred: PolyTraitPredicate<'tcx> ) -> bool

Whenever references are used by mistake, like for (i, e) in &vec.iter().enumerate(), suggest removing these references until we reach a type that implements the trait.

fn suggest_remove_await( &self, obligation: &PredicateObligation<'tcx>, err: &mut Diag<'_> )

fn suggest_change_mut( &self, obligation: &PredicateObligation<'tcx>, err: &mut Diag<'_>, trait_pred: PolyTraitPredicate<'tcx> )

Check if the trait bound is implemented for a different mutability and note it in the final error.

fn suggest_semicolon_removal( &self, obligation: &PredicateObligation<'tcx>, err: &mut Diag<'_>, span: Span, trait_pred: PolyTraitPredicate<'tcx> ) -> bool

fn return_type_span( &self, obligation: &PredicateObligation<'tcx> ) -> Option<Span>

fn suggest_impl_trait( &self, err: &mut Diag<'_>, obligation: &PredicateObligation<'tcx>, trait_pred: PolyTraitPredicate<'tcx> ) -> bool

If all conditions are met to identify a returned dyn Trait, suggest using impl Trait if applicable and signal that the error has been expanded appropriately and needs to be emitted.

fn point_at_returns_when_relevant( &self, err: &mut Diag<'tcx>, obligation: &PredicateObligation<'tcx> )

fn report_closure_arg_mismatch( &self, span: Span, found_span: Option<Span>, found: TraitRef<'tcx>, expected: TraitRef<'tcx>, cause: &ObligationCauseCode<'tcx>, found_node: Option<Node<'_>>, param_env: ParamEnv<'tcx> ) -> Diag<'tcx>

fn note_conflicting_fn_args( &self, err: &mut Diag<'_>, cause: &ObligationCauseCode<'tcx>, expected: Ty<'tcx>, found: Ty<'tcx>, param_env: ParamEnv<'tcx> )

fn note_conflicting_closure_bounds( &self, cause: &ObligationCauseCode<'tcx>, err: &mut Diag<'tcx> )

fn suggest_fully_qualified_path( &self, err: &mut Diag<'_>, item_def_id: DefId, span: Span, trait_ref: DefId )

fn maybe_note_obligation_cause_for_async_await<G: EmissionGuarantee>( &self, err: &mut Diag<'_, G>, obligation: &PredicateObligation<'tcx> ) -> bool

Adds an async-await specific note to the diagnostic when the future does not implement an auto trait because of a captured type.

note: future does not implement `Qux` as this value is used across an await
  --> $DIR/issue-64130-3-other.rs:17:5
   |
LL |     let x = Foo;
   |         - has type `Foo`
LL |     baz().await;
   |     ^^^^^^^^^^^ await occurs here, with `x` maybe used later
LL | }
   | - `x` is later dropped here

When the diagnostic does not implement Send or Sync specifically, then the diagnostic is “replaced” with a different message and a more specific error.

error: future cannot be sent between threads safely
  --> $DIR/issue-64130-2-send.rs:21:5
   |
LL | fn is_send<T: Send>(t: T) { }
   |               ---- required by this bound in `is_send`
...
LL |     is_send(bar());
   |     ^^^^^^^ future returned by `bar` is not send
   |
   = help: within `impl std::future::Future`, the trait `std::marker::Send` is not
           implemented for `Foo`
note: future is not send as this value is used across an await
  --> $DIR/issue-64130-2-send.rs:15:5
   |
LL |     let x = Foo;
   |         - has type `Foo`
LL |     baz().await;
   |     ^^^^^^^^^^^ await occurs here, with `x` maybe used later
LL | }
   | - `x` is later dropped here

Returns true if an async-await specific note was added to the diagnostic.

fn note_obligation_cause_for_async_await<G: EmissionGuarantee>( &self, err: &mut Diag<'_, G>, interior_or_upvar_span: CoroutineInteriorOrUpvar, is_async: bool, outer_coroutine: Option<DefId>, trait_pred: TraitPredicate<'tcx>, target_ty: Ty<'tcx>, obligation: &PredicateObligation<'tcx>, next_code: Option<&ObligationCauseCode<'tcx>> )

Unconditionally adds the diagnostic note described in maybe_note_obligation_cause_for_async_await’s documentation comment.

fn note_obligation_cause_code<G: EmissionGuarantee, T>( &self, body_id: LocalDefId, err: &mut Diag<'_, G>, predicate: T, param_env: ParamEnv<'tcx>, cause_code: &ObligationCauseCode<'tcx>, obligated_types: &mut Vec<Ty<'tcx>>, seen_requirements: &mut FxHashSet<DefId> )

where T: ToPredicate<'tcx>,

fn suggest_await_before_try( &self, err: &mut Diag<'_>, obligation: &PredicateObligation<'tcx>, trait_pred: PolyTraitPredicate<'tcx>, span: Span )

fn suggest_floating_point_literal( &self, obligation: &PredicateObligation<'tcx>, err: &mut Diag<'_>, trait_ref: &PolyTraitRef<'tcx> )

fn suggest_derive( &self, obligation: &PredicateObligation<'tcx>, err: &mut Diag<'_>, trait_pred: PolyTraitPredicate<'tcx> )

fn suggest_dereferencing_index( &self, obligation: &PredicateObligation<'tcx>, err: &mut Diag<'_>, trait_pred: PolyTraitPredicate<'tcx> )

fn note_function_argument_obligation<G: EmissionGuarantee>( &self, body_id: LocalDefId, err: &mut Diag<'_, G>, arg_hir_id: HirId, parent_code: &ObligationCauseCode<'tcx>, param_env: ParamEnv<'tcx>, failed_pred: Predicate<'tcx>, call_hir_id: HirId )

fn suggest_option_method_if_applicable<G: EmissionGuarantee>( &self, failed_pred: Predicate<'tcx>, param_env: ParamEnv<'tcx>, err: &mut Diag<'_, G>, expr: &Expr<'_> )

fn look_for_iterator_item_mistakes<G: EmissionGuarantee>( &self, assocs_in_this_method: &[Option<(Span, (DefId, Ty<'tcx>))>], typeck_results: &TypeckResults<'tcx>, type_diffs: &[TypeError<'tcx>], param_env: ParamEnv<'tcx>, path_segment: &PathSegment<'_>, args: &[Expr<'_>], err: &mut Diag<'_, G> )

fn point_at_chain<G: EmissionGuarantee>( &self, expr: &Expr<'_>, typeck_results: &TypeckResults<'tcx>, type_diffs: Vec<TypeError<'tcx>>, param_env: ParamEnv<'tcx>, err: &mut Diag<'_, G> )

fn probe_assoc_types_at_expr( &self, type_diffs: &[TypeError<'tcx>], span: Span, prev_ty: Ty<'tcx>, body_id: HirId, param_env: ParamEnv<'tcx> ) -> Vec<Option<(Span, (DefId, Ty<'tcx>))>>

fn suggest_convert_to_slice( &self, err: &mut Diag<'_>, obligation: &PredicateObligation<'tcx>, trait_ref: PolyTraitRef<'tcx>, candidate_impls: &[ImplCandidate<'tcx>], span: Span )

If the type that failed selection is an array or a reference to an array, but the trait is implemented for slices, suggest that the user converts the array into a slice.

fn explain_hrtb_projection( &self, diag: &mut Diag<'_>, pred: PolyTraitPredicate<'tcx>, param_env: ParamEnv<'tcx>, cause: &ObligationCause<'tcx> )

fn suggest_desugaring_async_fn_in_trait( &self, err: &mut Diag<'_>, trait_ref: PolyTraitRef<'tcx> )

fn ty_kind_suggestion( &self, param_env: ParamEnv<'tcx>, ty: Ty<'tcx> ) -> Option<String>

Object Safety

This trait is not object safe.

Implementors

impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx>