Rollup merge of #132498 - uellenberg:typo-and-let-suggestions, r=estebank

Suggest fixing typos and let bindings at the same time

Fixes #132483

Currently, a suggestion for adding a let binding won't be shown if we suggest fixing a typo. This changes that behavior to always show both, if possible. Essentially, this turns the suggestion from
```rust
error[E0425]: cannot find value `x2` in this scope
 --> src/main.rs:4:5
  |
4 |     x2 = 2;
  |     ^^ help: a local variable with a similar name exists: `x1`

For more information about this error, try `rustc --explain E0425`.
```

to
```rust
error[E0425]: cannot find value `x2` in this scope
 --> src/main.rs:4:5
  |
4 |     x2 = 2;
  |     ^^
  |
help: a local variable with a similar name exists
  |
4 |     x1 = 2;
  |     ~~
help: you might have meant to introduce a new binding
  |
4 |     let x2 = 2;
  |     +++

For more information about this error, try `rustc --explain E0425`.
```

for the following code:
```rust
fn main() {
    let x1 = 1;
    x2 = 2;
}
```

The original behavior only shows the suggestion for a let binding if a typo suggestion wasn't already displayed. However, this falls apart in the cases like the one above where we have multiple similar variables. I don't think it makes sense to hide this suggestion if there's a similar variable, since that defeats the purpose of this suggestion in that case (it's meant to help those coming from languages like Python).

1 files changed, 6 insertions, 3 deletions

diff --git a/compiler/rustc_resolve/src/late/diagnostics.rs b/compiler/rustc_resolve/src/late/diagnostics.rs
index f0632a21091..1493d5cc158 100644
--- a/compiler/rustc_resolve/src/late/diagnostics.rs
+++ b/compiler/rustc_resolve/src/late/diagnostics.rs
@@ -894,10 +894,13 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
 
             // If the trait has a single item (which wasn't matched by the algorithm), suggest it
             let suggestion = self.get_single_associated_item(path, &source, is_expected);
-            if !self.r.add_typo_suggestion(err, suggestion, ident_span) {
-                fallback = !self.let_binding_suggestion(err, ident_span);
-            }
+            self.r.add_typo_suggestion(err, suggestion, ident_span);
+        }
+
+        if self.let_binding_suggestion(err, ident_span) {
+            fallback = false;
         }
+
         fallback
     }