Lint `let mut x = x;` where `x` is a function argument

[oli-obk]

The argument should be made mutable instead of rebinding it to mutable.

[Evrey]

Except if we are talking about quickcheck!, which does not support mutable arguments. This macro does allow adding an #[allow(const_argument_mut_rebinding)] or whatever attribute, however. Just wanted to mention this one case.

[clarfonthey]

@Evrey IMHO quickcheck should eventually be able to convert their macro into a proc_macro, removing that need.

[oli-obk]

We can just bail out inside macros

[cauebs]

I'll see if I can help with this one. Expect a PR this week, or a somewhat sad comment of me giving up. 🤣