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Rollup merge of #55638 - pnkfelix:issue-55608-ice-reempty-msg_span_from_free_region, r=estebank

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Fix ICE in msg_span_from_free_region on ReEmpty

On an example like this:

```rust
#![feature(conservative_impl_trait)]

fn server() -> impl FilterBase2 {
    segment2(|| { loop { } }).map2(|| "")
}

trait FilterBase2 {
    fn map2<F>(self, _fn: F) -> Map2<F> where Self: Sized { loop { } }
}

struct Map2<F> { _func: F }

impl<F> FilterBase2 for Map2<F> { }

fn segment2<F>(_fn: F) -> Map2<F> where F: Fn() -> Result<(), ()> {
    loop { }
}
```

we now, instead of ICE'ing, get a diagnostic like:

```
error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
 --> issue-55608.rs:3:16
  |
3 | fn server() -> impl FilterBase2 {
  |                ^^^^^^^^^^^^^^^^
  |
  = note: hidden type `Map2<[closure@issue-55608.rs:4:36: 4:41]>` captures an empty lifetime
```

Fix #55608
This commit is contained in:
Mark Rousskov 2018-11-08 18:14:51 -07:00 • committed by GitHub
commit 4805a97274
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22
src/test/ui/impl-trait/issue-55608-captures-empty-region.rs Normal file
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@ -0,0 +1,22 @@
// This used to ICE because it creates an `impl Trait` that captures a
// hidden empty region.
#![feature(conservative_impl_trait)]
fn server() -> impl FilterBase2 { //~ ERROR [E0700]
segment2(|| { loop { } }).map2(|| "")
}
trait FilterBase2 {
fn map2<F>(self, _fn: F) -> Map2<F> where Self: Sized { loop { } }
}
struct Map2<F> { _func: F }
impl<F> FilterBase2 for Map2<F> { }
fn segment2<F>(_fn: F) -> Map2<F> where F: Fn() -> Result<(), ()> {
loop { }
}
fn main() { server(); }

11
src/test/ui/impl-trait/issue-55608-captures-empty-region.stderr Normal file
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@ -0,0 +1,11 @@
error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
--> $DIR/issue-55608-captures-empty-region.rs:6:16
|
LL | fn server() -> impl FilterBase2 { //~ ERROR [E0700]
| ^^^^^^^^^^^^^^^^
|
= note: hidden type `Map2<[closure@$DIR/issue-55608-captures-empty-region.rs:7:36: 7:41]>` captures an empty lifetime
error: aborting due to previous error
For more information about this error, try `rustc --explain E0700`.