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Rollup merge of #119506 - compiler-errors:visibilities-for-object-safety-error, r=Nilstrieb

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Use `resolutions(()).effective_visiblities` to avoid cycle errors in `report_object_error`

Inside of `report_object_error`, using the `effective_visibilities` query causes cycles since it calls `type_of`, which itself may call `typeck`, which may end up reporting its own object-safety errors.

Fixes #119346
Fixes #119502
This commit is contained in:
Matthias Krüger 2024-01-05 20:39:52 +01:00 committed by GitHub
commit 8309063e0a
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3 changed files with 110 additions and 1 deletions
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5
compiler/rustc_infer/src/traits/error_reporting/mod.rs
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@ -152,7 +152,10 @@ pub fn report_object_safety_error<'tcx>(
};
let externally_visible = if !impls.is_empty()
&& let Some(def_id) = trait_def_id.as_local()
&& tcx.effective_visibilities(()).is_exported(def_id)
// We may be executing this during typeck, which would result in cycle
// if we used effective_visibilities query, which looks into opaque types
// (and therefore calls typeck).
&& tcx.resolutions(()).effective_visibilities.is_exported(def_id)
{
true
} else {

28
tests/ui/impl-trait/in-trait/cycle-effective-visibilities-during-object-safety.rs Normal file
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@ -0,0 +1,28 @@
trait Marker {}
impl Marker for u32 {}
trait MyTrait {
fn foo(&self) -> impl Marker;
}
struct Outer;
impl MyTrait for Outer {
fn foo(&self) -> impl Marker {
42
}
}
impl dyn MyTrait {
//~^ ERROR the trait `MyTrait` cannot be made into an object
fn other(&self) -> impl Marker {
//~^ ERROR the trait `MyTrait` cannot be made into an object
MyTrait::foo(&self)
//~^ ERROR the trait bound `&dyn MyTrait: MyTrait` is not satisfied
//~| ERROR the trait bound `&dyn MyTrait: MyTrait` is not satisfied
//~| ERROR the trait bound `&dyn MyTrait: MyTrait` is not satisfied
//~| ERROR the trait `MyTrait` cannot be made into an object
}
}
fn main() {}

78
tests/ui/impl-trait/in-trait/cycle-effective-visibilities-during-object-safety.stderr Normal file
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@ -0,0 +1,78 @@
error[E0277]: the trait bound `&dyn MyTrait: MyTrait` is not satisfied
--> $DIR/cycle-effective-visibilities-during-object-safety.rs:20:22
|
LL | MyTrait::foo(&self)
| ------------ ^^^^^ the trait `MyTrait` is not implemented for `&dyn MyTrait`
| |
| required by a bound introduced by this call
|
= help: the trait `MyTrait` is implemented for `Outer`
error[E0038]: the trait `MyTrait` cannot be made into an object
--> $DIR/cycle-effective-visibilities-during-object-safety.rs:20:9
|
LL | MyTrait::foo(&self)
| ^^^^^^^^^^^^ `MyTrait` cannot be made into an object
|
note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
--> $DIR/cycle-effective-visibilities-during-object-safety.rs:5:22
|
LL | trait MyTrait {
| ------- this trait cannot be made into an object...
LL | fn foo(&self) -> impl Marker;
| ^^^^^^^^^^^ ...because method `foo` references an `impl Trait` type in its return type
= help: consider moving `foo` to another trait
= help: only type `Outer` implements the trait, consider using it directly instead
error[E0277]: the trait bound `&dyn MyTrait: MyTrait` is not satisfied
--> $DIR/cycle-effective-visibilities-during-object-safety.rs:20:9
|
LL | MyTrait::foo(&self)
| ^^^^^^^^^^^^^^^^^^^ the trait `MyTrait` is not implemented for `&dyn MyTrait`
|
= help: the trait `MyTrait` is implemented for `Outer`
error[E0277]: the trait bound `&dyn MyTrait: MyTrait` is not satisfied
--> $DIR/cycle-effective-visibilities-during-object-safety.rs:20:9
|
LL | MyTrait::foo(&self)
| ^^^^^^^^^^^^ the trait `MyTrait` is not implemented for `&dyn MyTrait`
|
= help: the trait `MyTrait` is implemented for `Outer`
error[E0038]: the trait `MyTrait` cannot be made into an object
--> $DIR/cycle-effective-visibilities-during-object-safety.rs:16:6
|
LL | impl dyn MyTrait {
| ^^^^^^^^^^^ `MyTrait` cannot be made into an object
|
note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
--> $DIR/cycle-effective-visibilities-during-object-safety.rs:5:22
|
LL | trait MyTrait {
| ------- this trait cannot be made into an object...
LL | fn foo(&self) -> impl Marker;
| ^^^^^^^^^^^ ...because method `foo` references an `impl Trait` type in its return type
= help: consider moving `foo` to another trait
= help: only type `Outer` implements the trait, consider using it directly instead
error[E0038]: the trait `MyTrait` cannot be made into an object
--> $DIR/cycle-effective-visibilities-during-object-safety.rs:18:15
|
LL | fn other(&self) -> impl Marker {
| ^^^^ `MyTrait` cannot be made into an object
|
note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
--> $DIR/cycle-effective-visibilities-during-object-safety.rs:5:22
|
LL | trait MyTrait {
| ------- this trait cannot be made into an object...
LL | fn foo(&self) -> impl Marker;
| ^^^^^^^^^^^ ...because method `foo` references an `impl Trait` type in its return type
= help: consider moving `foo` to another trait
= help: only type `Outer` implements the trait, consider using it directly instead
error: aborting due to 6 previous errors
Some errors have detailed explanations: E0038, E0277.
For more information about an error, try `rustc --explain E0038`.