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Mention traits being upcasted, types being coerced

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This commit is contained in:
Michael Goulet 2022-04-24 21:07:46 -07:00
parent 4c5f6e6277
commit 0de7568e41
3 changed files with 16 additions and 9 deletions
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19
compiler/rustc_typeck/src/check/coercion.rs
View File

@ -615,7 +615,7 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
)];
let mut has_unsized_tuple_coercion = false;
let mut has_trait_upcasting_coercion = false;
let mut has_trait_upcasting_coercion = None;
// Keep resolving `CoerceUnsized` and `Unsize` predicates to avoid
// emitting a coercion in cases like `Foo<$1>` -> `Foo<$2>`, where
@ -635,7 +635,7 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
&& data_a.principal_def_id() != data_b.principal_def_id()
{
debug!("coerce_unsized: found trait upcasting coercion");
has_trait_upcasting_coercion = true;
has_trait_upcasting_coercion = Some((self_ty, unsize_ty));
}
if let ty::Tuple(..) = unsize_ty.kind() {
debug!("coerce_unsized: found unsized tuple coercion");
@ -706,14 +706,19 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
.emit();
}
if has_trait_upcasting_coercion && !self.tcx().features().trait_upcasting {
feature_err(
if let Some((sub, sup)) = has_trait_upcasting_coercion
&& !self.tcx().features().trait_upcasting
{
// Renders better when we erase regions, since they're not really the point here.
let (sub, sup) = self.tcx.erase_regions((sub, sup));
let mut err = feature_err(
&self.tcx.sess.parse_sess,
sym::trait_upcasting,
self.cause.span,
"trait upcasting coercion is experimental",
)
.emit();
&format!("cannot cast `{sub}` to `{sup}`, trait upcasting coercion is experimental"),
);
err.note(&format!("required when coercing `{source}` into `{target}`"));
err.emit();
}
Ok(coercion)

3
src/test/ui/feature-gates/feature-gate-trait_upcasting.stderr
View File

@ -1,4 +1,4 @@
error[E0658]: trait upcasting coercion is experimental
error[E0658]: cannot cast `dyn Bar` to `dyn Foo`, trait upcasting coercion is experimental
--> $DIR/feature-gate-trait_upcasting.rs:11:25
|
LL | let foo: &dyn Foo = bar;
@ -6,6 +6,7 @@ LL | let foo: &dyn Foo = bar;
|
= note: see issue #65991 <https://github.com/rust-lang/rust/issues/65991> for more information
= help: add `#![feature(trait_upcasting)]` to the crate attributes to enable
= note: required when coercing `&dyn Bar` into `&dyn Foo`
error: aborting due to previous error

3
src/test/ui/issues/issue-11515.stderr
View File

@ -1,4 +1,4 @@
error[E0658]: trait upcasting coercion is experimental
error[E0658]: cannot cast `dyn Fn()` to `dyn FnMut()`, trait upcasting coercion is experimental
--> $DIR/issue-11515.rs:9:33
|
LL | let test = box Test { func: closure };
@ -6,6 +6,7 @@ LL | let test = box Test { func: closure };
|
= note: see issue #65991 <https://github.com/rust-lang/rust/issues/65991> for more information
= help: add `#![feature(trait_upcasting)]` to the crate attributes to enable
= note: required when coercing `Box<(dyn Fn() + 'static)>` into `Box<(dyn FnMut() + 'static)>`
error: aborting due to previous error