Just `mut` alongside `let mut`

There is an assumed condition in my response seeing how I was replying to a post that objected to this proposal on grounds that it would "be harder to detect shadowing in your code" (emphasis added).

For those of us that want to detect or prevent shadowing , most likely use lints to detect it. Existing lints that do that could easily be extended to detect additional forms of shadowing caused from this proposal; thus it wouldn't be "harder" from a programmatic view.

I edited my post to make this conditional explicit.