Rollup merge of #87960 - hkmatsumoto:suggest-inexisting-field-for-unmentioned-field, r=estebank

Suggest replacing an inexisting field for an unmentioned field

Fix #87938

This PR adds a suggestion to replace an inexisting field for an
unmentioned field. Given the following code:
```rust
enum Foo {
    Bar { alpha: u8, bravo: u8, charlie: u8 },
}

fn foo(foo: Foo) {
    match foo {
        Foo::Bar {
            alpha,
            beta, // `bravo` miswritten as `beta` here.
            charlie,
        } => todo!(),
    }
}
```
the compiler now emits the error messages below.
```text
error[E0026]: variant `Foo::Bar` does not have a field named `beta`
 --> src/lib.rs:9:13
  |
9 |             beta, // `bravo` miswritten as `beta` here.
  |             ^^^^
  |             |
  |             variant `Foo::Bar` does not have this field
  |             help: `Foo::Bar` has a field named `bravo`: `bravo`
```

Note that this suggestion is available iff the number of inexisting
fields and unmentioned fields are both 1.

compiler/rustc_typeck/src/check/pat.rs

@@ -1452,7 +1452,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     plural
                 ),
             );
-            if plural == "" {
+
+            if unmentioned_fields.len() == 1 {
                 let input =
                     unmentioned_fields.iter().map(|(_, field)| field.name).collect::<Vec<_>>();
                 let suggested_name = find_best_match_for_name(&input, ident.name, None);
@@ -1473,6 +1474,18 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         // We don't want to throw `E0027` in case we have thrown `E0026` for them.
                         unmentioned_fields.retain(|&(_, x)| x.name != suggested_name);
                     }
+                } else if inexistent_fields.len() == 1 {
+                    let unmentioned_field = unmentioned_fields[0].1.name;
+                    err.span_suggestion_short(
+                        ident.span,
+                        &format!(
+                            "`{}` has a field named `{}`",
+                            tcx.def_path_str(variant.def_id),
+                            unmentioned_field
+                        ),
+                        unmentioned_field.to_string(),
+                        Applicability::MaybeIncorrect,
+                    );
                 }
             }
         }