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ede0a71b9e
The following code is supposed to compile
```rust
use std::ops::BitOr;
pub trait IntWrapper {
type InternalStorage;
}
impl<T> BitOr for dyn IntWrapper<InternalStorage = T>
where
Self: Sized,
T: BitOr + BitOr<Output = T>,
{
type Output = Self;
fn bitor(self, _other: Self) -> Self {
todo!()
}
}
```
Before this change it would ICE. In #70998 the removed logic was added
to provide better suggestions, and the `delay_span_bug` guard was added
to protect against a potential logic error when returning traits. As it
happens, there are cases, like the one above, where traits can indeed be
returned, so valid code was being rejected.
Fix #80207.
For high-level intro to how type checking works in rustc, see the type checking chapter of the rustc dev guide.