Improper parenthesis addition when using `clippy_lints::utils::Sugg::maybe_par`

[booleancoercion]

While working on #6717, I noticed that sometimes an expression like (1+2) would be (falsely?) converted to a Sugg::BinOp, which coupled with the maybe_par method would produce the suggestion ((1+2)).

I'm not sure where the issue is: should the expression have been converted into a NonParen in the first place, or does maybe_par need to have an additional check when working with BinOp? If it's the latter, care must be taken because a simple check that the boundaries are () is wrong: for example, (1+2) + (3+4).

Also related - shouldn't the MaybeParen branch always return a NonParen?

It should be noted that this bug affects the following lints:

• floating_point_log
• from_str_radix_10 (WIP)
• manual_memcpy