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Improve spans for specialization error
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compiler-errors committed Jul 1, 2022
1 parent 46b8c23 commit a368830
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Showing 6 changed files with 31 additions and 18 deletions.
27 changes: 20 additions & 7 deletions compiler/rustc_typeck/src/impl_wf_check/min_specialization.rs
Original file line number Diff line number Diff line change
Expand Up @@ -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() {
Expand Down Expand Up @@ -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)
Expand All @@ -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)
}
Expand Down Expand Up @@ -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();
}
}
Expand Down
Original file line number Diff line number Diff line change
@@ -1,8 +1,8 @@
error: cannot specialize on `Binder(ProjectionPredicate(ProjectionTy { substs: [V], item_def_id: DefId(0:6 ~ repeated_projection_type[54ea]::Id::This) }, Ty((I,))), [])`
--> $DIR/repeated_projection_type.rs:19:1
error: cannot specialize on associated type `<V as Id>::This == (I,)`
--> $DIR/repeated_projection_type.rs:19:15
|
LL | impl<I, V: Id<This = (I,)>> X for V {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| ^^^^^^^^^^^

error: aborting due to previous error

Original file line number Diff line number Diff line change
@@ -1,8 +1,8 @@
error: cannot specialize on trait `HasMethod`
--> $DIR/spec-marker-supertraits.rs:22:1
--> $DIR/spec-marker-supertraits.rs:22:9
|
LL | impl<T: Marker> Spec for T {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^
| ^^^^^^

error: aborting due to previous error

Original file line number Diff line number Diff line change
@@ -1,8 +1,8 @@
error: cannot specialize on trait `Default`
--> $DIR/specialization_super_trait.rs:13:1
--> $DIR/specialization_super_trait.rs:13:9
|
LL | impl<T: Default> SpecMarker for T {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| ^^^^^^^

error: aborting due to previous error

Original file line number Diff line number Diff line change
Expand Up @@ -11,10 +11,10 @@ LL | impl<T> SpecMarker for (T, T) {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: cannot specialize on trait `Clone`
--> $DIR/specialization_trait.rs:21:1
--> $DIR/specialization_trait.rs:21:9
|
LL | impl<T: Clone> SpecMarker for [T] {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| ^^^^^

error: aborting due to 3 previous errors

Original file line number Diff line number Diff line change
@@ -1,8 +1,8 @@
error: cannot specialize on trait `SpecMarker`
--> $DIR/specialize_on_trait.rs:15:1
--> $DIR/specialize_on_trait.rs:15:9
|
LL | impl<T: SpecMarker> X for T {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^
| ^^^^^^^^^^

error: aborting due to previous error

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