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Rollup merge of #111039 - compiler-errors:foreign-span-rpitit, r=tmiasko
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Encode def span for foreign return-position `impl Trait` in trait

Fixes #111031, yet another def-span encoding issue :/

Includes a smaller repro than the issue, but I can confirm it ICEs:

```
query stack during panic:
#0 [def_span] looking up span for `rpitit::Foo::bar::{opaque#0}`
#1 [object_safety_violations] determining object safety of trait `rpitit::Foo`
#2 [check_is_object_safe] checking if trait `rpitit::Foo` is object safe
#3 [typeck] type-checking `main`
#4 [used_trait_imports] finding used_trait_imports `main`
#5 [analysis] running analysis passes on this crate
```

Luckily since this only affects nightly, this desn't need to be backported.
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matthiaskrgr authored May 4, 2023
2 parents 6387eda + ed468ee commit b194b43
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Showing 5 changed files with 32 additions and 7 deletions.
3 changes: 2 additions & 1 deletion compiler/rustc_metadata/src/rmeta/encoder.rs
Original file line number Diff line number Diff line change
Expand Up @@ -837,11 +837,12 @@ fn should_encode_span(def_kind: DefKind) -> bool {
| DefKind::AnonConst
| DefKind::InlineConst
| DefKind::OpaqueTy
| DefKind::ImplTraitPlaceholder
| DefKind::Field
| DefKind::Impl { .. }
| DefKind::Closure
| DefKind::Generator => true,
DefKind::ForeignMod | DefKind::ImplTraitPlaceholder | DefKind::GlobalAsm => false,
DefKind::ForeignMod | DefKind::GlobalAsm => false,
}
}

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4 changes: 2 additions & 2 deletions tests/ui/impl-trait/in-trait/auxiliary/rpitit.rs
Original file line number Diff line number Diff line change
Expand Up @@ -5,10 +5,10 @@
use std::ops::Deref;

pub trait Foo {
fn bar() -> impl Deref<Target = impl Sized>;
fn bar(self) -> impl Deref<Target = impl Sized>;
}

pub struct Foreign;
impl Foo for Foreign {
fn bar() -> &'static () { &() }
fn bar(self) -> &'static () { &() }
}
8 changes: 8 additions & 0 deletions tests/ui/impl-trait/in-trait/foreign-dyn-error.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,8 @@
// aux-build: rpitit.rs

extern crate rpitit;

fn main() {
let _: &dyn rpitit::Foo = todo!();
//~^ ERROR the trait `Foo` cannot be made into an object
}
15 changes: 15 additions & 0 deletions tests/ui/impl-trait/in-trait/foreign-dyn-error.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,15 @@
error[E0038]: the trait `Foo` cannot be made into an object
--> $DIR/foreign-dyn-error.rs:6:12
|
LL | let _: &dyn rpitit::Foo = todo!();
| ^^^^^^^^^^^^^^^^ `Foo` 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/auxiliary/rpitit.rs:8:21
|
LL | fn bar(self) -> impl Deref<Target = impl Sized>;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait cannot be made into an object because method `bar` references an `impl Trait` type in its return type

error: aborting due to previous error

For more information about this error, try `rustc --explain E0038`.
9 changes: 5 additions & 4 deletions tests/ui/impl-trait/in-trait/foreign.rs
Original file line number Diff line number Diff line change
Expand Up @@ -5,17 +5,18 @@

extern crate rpitit;

use rpitit::{Foo, Foreign};
use std::sync::Arc;

// Implement an RPITIT from another crate.
struct Local;
impl rpitit::Foo for Local {
fn bar() -> Arc<String> { Arc::new(String::new()) }
impl Foo for Local {
fn bar(self) -> Arc<String> { Arc::new(String::new()) }
}

fn main() {
// Witness an RPITIT from another crate.
let &() = <rpitit::Foreign as rpitit::Foo>::bar();
let &() = Foreign.bar();

let x: Arc<String> = <Local as rpitit::Foo>::bar();
let x: Arc<String> = Local.bar();
}

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