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Give opaque types a better coherence error

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This commit is contained in:
Oli Scherer 2022-12-21 17:44:30 +00:00
parent 1d12c3cea3
commit a9af75cdbc
2 changed files with 16 additions and 9 deletions
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23
compiler/rustc_hir_analysis/src/coherence/orphan.rs
View file

@ -184,11 +184,19 @@ fn emit_orphan_check_error<'tcx>(
ty::Adt(def, _) => tcx.mk_adt(*def, ty::List::empty()), ty::Adt(def, _) => tcx.mk_adt(*def, ty::List::empty()),
_ => ty, _ => ty,
}; };
let this = "this".to_string(); let msg = |ty: &str, postfix: &str| {
let (ty, postfix) = match &ty.kind() { format!("{ty} is not defined in the current crate{postfix}")
ty::Slice(_) => (this, " because slices are always foreign"), };
ty::Array(..) => (this, " because arrays are always foreign"), let this = |name: &str| msg("this", &format!(" because {name} are always foreign"));
ty::Tuple(..) => (this, " because tuples are always foreign"), let msg = match &ty.kind() {
ty::Slice(_) => this("slices"),
ty::Array(..) => this("arrays"),
ty::Tuple(..) => this("tuples"),
ty::Alias(ty::Opaque, ..) => {
"type alias impl trait is treated as if it were foreign, \
because its hidden type could be from a foreign crate"
.to_string()
}
ty::RawPtr(ptr_ty) => { ty::RawPtr(ptr_ty) => {
emit_newtype_suggestion_for_raw_ptr( emit_newtype_suggestion_for_raw_ptr(
full_impl_span, full_impl_span,
@ -198,12 +206,11 @@ fn emit_orphan_check_error<'tcx>(
&mut err, &mut err,
); );
(format!("`{}`", ty), " because raw pointers are always foreign") msg(&format!("`{ty}`"), " because raw pointers are always foreign")
} }
_ => (format!("`{}`", ty), ""), _ => msg(&format!("`{ty}`"), ""),
}; };
let msg = format!("{} is not defined in the current crate{}", ty, postfix);
if is_target_ty { if is_target_ty {
// Point at `D<A>` in `impl<A, B> for C<B> in D<A>` // Point at `D<A>` in `impl<A, B> for C<B> in D<A>`
err.span_label(self_ty_span, &msg); err.span_label(self_ty_span, &msg);

2
src/test/ui/type-alias-impl-trait/coherence.stderr
View file

@ -4,7 +4,7 @@ error[E0117]: only traits defined in the current crate can be implemented for ar
LL | impl<T> foreign_crate::ForeignTrait for AliasOfForeignType<T> {} LL | impl<T> foreign_crate::ForeignTrait for AliasOfForeignType<T> {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^--------------------- | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---------------------
| | | | | |
| | `AliasOfForeignType<T>` is not defined in the current crate | | type alias impl trait is treated as if it were foreign, because its hidden type could be from a foreign crate
| impl doesn't use only types from inside the current crate | impl doesn't use only types from inside the current crate
| |
= note: define and implement a trait or new type instead = note: define and implement a trait or new type instead