bjoernager/rust
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Improve spans for specialization error

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This commit is contained in:
Michael Goulet 2022-07-01 14:41:28 -07:00
parent 46b8c23f3e
commit a368830d10
6 changed files with 31 additions and 18 deletions
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27
compiler/rustc_typeck/src/impl_wf_check/min_specialization.rs
View file

@ -279,11 +279,16 @@ fn check_predicates<'tcx>(
span: Span,
) {
let tcx = infcx.tcx;
let impl1_predicates: Vec<_> = traits::elaborate_predicates(
let instantiated = tcx.predicates_of(impl1_def_id).instantiate(tcx, impl1_substs);
let impl1_predicates: Vec<_> = traits::elaborate_predicates_with_span(
tcx,
tcx.predicates_of(impl1_def_id).instantiate(tcx, impl1_substs).predicates.into_iter(),
std::iter::zip(
instantiated.predicates,
// Don't drop predicates (unsound!) because `spans` is too short
instantiated.spans.into_iter().chain(std::iter::repeat(span)),
),
)
.map(|obligation| obligation.predicate)
.map(|obligation| (obligation.predicate, obligation.cause.span))
.collect();
let mut impl2_predicates = if impl2_node.is_from_trait() {
@ -321,7 +326,7 @@ fn check_predicates<'tcx>(
// which is sound because we forbid impls like the following
//
// impl<D: Debug> AlwaysApplicable for D { }
let always_applicable_traits = impl1_predicates.iter().copied().filter(|&predicate| {
let always_applicable_traits = impl1_predicates.iter().copied().filter(|&(predicate, _)| {
matches!(
trait_predicate_kind(tcx, predicate),
Some(TraitSpecializationKind::AlwaysApplicable)
@ -345,11 +350,11 @@ fn check_predicates<'tcx>(
}
}
impl2_predicates.extend(
traits::elaborate_predicates(tcx, always_applicable_traits)
traits::elaborate_predicates_with_span(tcx, always_applicable_traits)
.map(|obligation| obligation.predicate),
);
for predicate in impl1_predicates {
for (predicate, span) in impl1_predicates {
if !impl2_predicates.contains(&predicate) {
check_specialization_on(tcx, predicate, span)
}
@ -384,9 +389,17 @@ fn check_specialization_on<'tcx>(tcx: TyCtxt<'tcx>, predicate: ty::Predicate<'tc
.emit();
}
}
ty::PredicateKind::Projection(ty::ProjectionPredicate { projection_ty, term }) => {
tcx.sess
.struct_span_err(
span,
&format!("cannot specialize on associated type `{projection_ty} == {term}`",),
)
.emit();
}
_ => {
tcx.sess
.struct_span_err(span, &format!("cannot specialize on `{:?}`", predicate))
.struct_span_err(span, &format!("cannot specialize on predicate `{}`", predicate))
.emit();
}
}