Auto merge of #59044 - petrochenkov:uiui, r=davidtwco

Filter away test annotations from UI test output

If you worked with UI tests for some time you could notice one issue affecting their readability and also readability of diffs when the tests change.
Look at the output of this test.
```rust
fn main() {
    let 1 = 2; //~ ERROR refutable pattern in local binding
}
```
```
error[E0005]: refutable pattern in local binding: `-2147483648i32..=0i32` not covered
 --> src/main.rs:2:9
  |
2 |     let 1 = 2; //~ ERROR refutable pattern in local binding
  |         ^ pattern `-2147483648i32..=0i32` not covered

error: aborting due to previous error

For more information about this error, try `rustc --explain E0005`.
```
You can see that the "refutable pattern in local binding" is duplicated.
One instance is the actual error, and the second instance is the expected error annotation.
This annotation is useful in the test input, but in the output it clutters the text and makes it harder to see what text refers to actual errors and what is just comments, especially if there are many errors in a single test file.

@estebank [reported](https://github.com/rust-lang/rust/pull/57379#discussion_r245523361) using the next trick to avoid the clutter
```rust
fn main() {
    let 1 = 2;
    //~^ ERROR refutable pattern in local binding
}
```
```
error[E0005]: refutable pattern in local binding: `-2147483648i32..=0i32` not covered
 --> src/main.rs:2:9
  |
2 |     let 1 = 2;
  |         ^ pattern `-2147483648i32..=0i32` not covered

error: aborting due to previous error

For more information about this error, try `rustc --explain E0005`.
```
, i.e. using `//~^` and placing the annotation one line below will remove the annotation from the output.

However, this doesn't always works (consider errors with multi-line spans), and shouldn't be necessary in general!
`compiletest` could automatically filter away its own annotations from the output instead.
This is exactly what this PR does.

r? @davidtwco

0 files changed, 0 insertions, 0 deletions