Auto merge of #64271 - Centril:non-exhaustive-peel-refs, r=estebank

check_match: refactor + improve non-exhaustive diagnostics for default binding modes

Refactor `check_match` a bit with more code-reuse and improve the diagnostics for a non-exhaustive pattern match by peeling off any references from the scrutinee type so that the "defined here" label is added in more cases. For example:

```rust
error[E0004]: non-exhaustive patterns: `&mut &B` not covered
 --> foo.rs:4:11
  |
1 | enum E { A, B }
  | ---------------
  | |           |
  | |           not covered
  | `E` defined here
...
4 |     match x {
  |           ^ pattern `&mut &B` not covered
  |
  = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
```

Moreover, wrt. "defined here", we give irrefutable pattern matching (i.e. in `let`, `for`, and `fn` parameters) a more consistent treatment in line with `match`.

r? @estebank

1 files changed, 4 insertions, 4 deletions

diff --git a/src/test/ui/refutable-pattern-errors.stderr b/src/test/ui/refutable-pattern-errors.stderr
index c67ae7c6d48..3b13e25293d 100644
--- a/src/test/ui/refutable-pattern-errors.stderr
+++ b/src/test/ui/refutable-pattern-errors.stderr
@@ -1,14 +1,14 @@
 error[E0005]: refutable pattern in function argument: `(_, _)` not covered
-  --> $DIR/refutable-pattern-errors.rs:1:9
+  --> $DIR/refutable-pattern-errors.rs:3:9
    |
 LL | fn func((1, (Some(1), 2..=3)): (isize, (Option<isize>, isize))) { }
    |         ^^^^^^^^^^^^^^^^^^^^^ pattern `(_, _)` not covered
 
-error[E0005]: refutable pattern in local binding: `(std::i32::MIN..=0i32, _)` not covered
-  --> $DIR/refutable-pattern-errors.rs:5:9
+error[E0005]: refutable pattern in local binding: `(std::i32::MIN..=0i32, _)` and `(2i32..=std::i32::MAX, _)` not covered
+  --> $DIR/refutable-pattern-errors.rs:7:9
    |
 LL |     let (1, (Some(1), 2..=3)) = (1, (None, 2));
-   |         ^^^^^^^^^^^^^^^^^^^^^ pattern `(std::i32::MIN..=0i32, _)` not covered
+   |         ^^^^^^^^^^^^^^^^^^^^^ patterns `(std::i32::MIN..=0i32, _)` and `(2i32..=std::i32::MAX, _)` not covered
 
 error: aborting due to 2 previous errors