Explain HRTB + infer limitations of old solver

This commit is contained in:
Michael Goulet 2023-09-07 02:06:20 +00:00
parent 19dd953540
commit 976d377f7f
7 changed files with 112 additions and 0 deletions

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@ -986,6 +986,8 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
}
}
self.explain_hrtb_projection(&mut err, trait_predicate, obligation.param_env, &obligation.cause);
// Return early if the trait is Debug or Display and the invocation
// originates within a standard library macro, because the output
// is otherwise overwhelming and unhelpful (see #85844 for an

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@ -406,6 +406,14 @@ pub trait TypeErrCtxtExt<'tcx> {
candidate_impls: &[ImplCandidate<'tcx>],
span: Span,
);
fn explain_hrtb_projection(
&self,
diag: &mut Diagnostic,
pred: ty::PolyTraitPredicate<'tcx>,
param_env: ty::ParamEnv<'tcx>,
cause: &ObligationCause<'tcx>,
);
}
fn predicate_constraint(generics: &hir::Generics<'_>, pred: ty::Predicate<'_>) -> (Span, String) {
@ -4027,6 +4035,71 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
}
}
}
fn explain_hrtb_projection(
&self,
diag: &mut Diagnostic,
pred: ty::PolyTraitPredicate<'tcx>,
param_env: ty::ParamEnv<'tcx>,
cause: &ObligationCause<'tcx>,
) {
if pred.skip_binder().has_escaping_bound_vars() && pred.skip_binder().has_non_region_infer()
{
self.probe(|_| {
let ocx = ObligationCtxt::new(self);
let pred = self.instantiate_binder_with_placeholders(pred);
let pred = ocx.normalize(&ObligationCause::dummy(), param_env, pred);
ocx.register_obligation(Obligation::new(
self.tcx,
ObligationCause::dummy(),
param_env,
pred,
));
if !ocx.select_where_possible().is_empty() {
// encountered errors.
return;
}
if let ObligationCauseCode::FunctionArgumentObligation {
call_hir_id,
arg_hir_id,
parent_code: _,
} = cause.code()
{
let arg_span = self.tcx.hir().span(*arg_hir_id);
let mut sp: MultiSpan = arg_span.into();
sp.push_span_label(
arg_span,
"the trait solver is unable to infer the \
generic types that should be inferred from this argument",
);
sp.push_span_label(
self.tcx.hir().span(*call_hir_id),
"add turbofish arguments to this call to \
specify the types manually, even if it's redundant",
);
diag.span_note(
sp,
"this is a known limitation of the trait solver that \
will be lifted in the future",
);
} else {
let mut sp: MultiSpan = cause.span.into();
sp.push_span_label(
cause.span,
"try adding turbofish arguments to this expression to \
specify the types manually, even if it's redundant",
);
diag.span_note(
sp,
"this is a known limitation of the trait solver that \
will be lifted in the future",
);
}
});
}
}
}
/// Add a hint to add a missing borrow or remove an unnecessary one.

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@ -16,6 +16,14 @@ LL | build(Bar);
| required by a bound introduced by this call
|
= help: the trait `for<'a> Send` is not implemented for `impl Future<Output = ()> { <_ as Foo>::bar() }`
note: this is a known limitation of the trait solver that will be lifted in the future
--> $DIR/normalizing-self-auto-trait-issue-109924.rs:23:11
|
LL | build(Bar);
| ------^^^-
| | |
| | the trait solver is unable to infer the generic types that should be inferred from this argument
| add turbofish arguments to this call to specify the types manually, even if it's redundant
note: required by a bound in `build`
--> $DIR/normalizing-self-auto-trait-issue-109924.rs:20:39
|

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@ -7,6 +7,14 @@ LL | test(Foo);
| required by a bound introduced by this call
|
= help: the trait `Marker` is implemented for `()`
note: this is a known limitation of the trait solver that will be lifted in the future
--> $DIR/issue-88460.rs:28:10
|
LL | test(Foo);
| -----^^^-
| | |
| | the trait solver is unable to infer the generic types that should be inferred from this argument
| add turbofish arguments to this call to specify the types manually, even if it's redundant
note: required by a bound in `test`
--> $DIR/issue-88460.rs:15:27
|

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@ -8,6 +8,14 @@ LL | call(f, ());
|
= note: expected a closure with arguments `((),)`
found a closure with arguments `(<_ as ATC<'a>>::Type,)`
note: this is a known limitation of the trait solver that will be lifted in the future
--> $DIR/issue-62529-3.rs:25:14
|
LL | call(f, ());
| -----^-----
| | |
| | the trait solver is unable to infer the generic types that should be inferred from this argument
| add turbofish arguments to this call to specify the types manually, even if it's redundant
note: required by a bound in `call`
--> $DIR/issue-62529-3.rs:9:36
|

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@ -7,6 +7,14 @@ LL | upcast(y)
| required by a bound introduced by this call
|
= help: the trait `IsCovariant<'a>` is implemented for `std::borrow::Cow<'a, T>`
note: this is a known limitation of the trait solver that will be lifted in the future
--> $DIR/issue-90950.rs:50:12
|
LL | upcast(y)
| -------^-
| | |
| | the trait solver is unable to infer the generic types that should be inferred from this argument
| add turbofish arguments to this call to specify the types manually, even if it's redundant
note: required by a bound in `upcast`
--> $DIR/issue-90950.rs:27:42
|

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@ -4,6 +4,11 @@ error[E0277]: the trait bound `for<'a> <_ as Trait<'a>>::Out: Copy` is not satis
LL | let _: () = weird_bound();
| ^^^^^^^^^^^ the trait `for<'a> Copy` is not implemented for `<_ as Trait<'a>>::Out`
|
note: this is a known limitation of the trait solver that will be lifted in the future
--> $DIR/norm-before-method-resolution.rs:22:17
|
LL | let _: () = weird_bound();
| ^^^^^^^^^^^ try adding turbofish arguments to this expression to specify the types manually, even if it's redundant
note: required by a bound in `weird_bound`
--> $DIR/norm-before-method-resolution.rs:18:40
|