Rollup merge of #114913 - beetrees:escape-double-quote, r=davidtwco

Fix suggestion for attempting to define a string with single quotes

Currently attempting to compile `fn main() { let _ = '\\"'; }` will result in the following error message:
```
error: character literal may only contain one codepoint
 --> src/main.rs:1:21
  |
1 | fn main() { let _ = '\\"'; }
  |                     ^^^^^
  |
help: if you meant to write a `str` literal, use double quotes
  |
1 | fn main() { let _ = "\\""; }
  |                     ~~~~~
```
The suggestion is invalid as it fails to escape the `"`. This PR fixes the suggestion so that it now reads:
```
help: if you meant to write a `str` literal, use double quotes
  |
1 | fn main() { let _ = "\\\""; }
  |                     ~~~~~~
```
The relevant test is also updated to ensure that this does not regress in future.

0 files changed, 0 insertions, 0 deletions