Fix &mut removal suggestion

Author: estebank

compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs

@@ -449,8 +449,8 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, '_, 'infcx, 'tcx> {
                     .is_ok_and(|snippet| snippet.starts_with("&mut ")) =>
             {
                 err.span_label(span, format!("cannot {act}"));
-                err.span_suggestion(
-                    span,
+                err.span_suggestion_verbose(
+                    span.with_hi(span.lo() + BytePos(5)),
                     "try removing `&mut` here",
                     "",
                     Applicability::MaybeIncorrect,

tests/ui/borrowck/issue-33819.stderr

@@ -2,10 +2,13 @@ error[E0596]: cannot borrow `v` as mutable, as it is not declared as mutable
   --> $DIR/issue-33819.rs:4:34
    |
 LL |         Some(ref v) => { let a = &mut v; },
-   |                                  ^^^^^^
-   |                                  |
-   |                                  cannot borrow as mutable
-   |                                  help: try removing `&mut` here
+   |                                  ^^^^^^ cannot borrow as mutable
+   |
+help: try removing `&mut` here
+   |
+LL -         Some(ref v) => { let a = &mut v; },
+LL +         Some(ref v) => { let a = v; },
+   |
 
 error: aborting due to 1 previous error
 

tests/ui/did_you_mean/issue-34337.stderr

@@ -2,10 +2,13 @@ error[E0596]: cannot borrow `key` as mutable, as it is not declared as mutable
   --> $DIR/issue-34337.rs:6:9
    |
 LL |     get(&mut key);
-   |         ^^^^^^^^
-   |         |
-   |         cannot borrow as mutable
-   |         help: try removing `&mut` here
+   |         ^^^^^^^^ cannot borrow as mutable
+   |
+help: try removing `&mut` here
+   |
+LL -     get(&mut key);
+LL +     get(key);
+   |
 
 error: aborting due to 1 previous error
 

tests/ui/did_you_mean/issue-37139.stderr

@@ -2,10 +2,13 @@ error[E0596]: cannot borrow `x` as mutable, as it is not declared as mutable
   --> $DIR/issue-37139.rs:12:18
    |
 LL |             test(&mut x);
-   |                  ^^^^^^
-   |                  |
-   |                  cannot borrow as mutable
-   |                  help: try removing `&mut` here
+   |                  ^^^^^^ cannot borrow as mutable
+   |
+help: try removing `&mut` here
+   |
+LL -             test(&mut x);
+LL +             test(x);
+   |
 
 error: aborting due to 1 previous error