[cargo fix] `identity_conversion` removes parenthesis with inner expression, that needs them.

[soruh]

When running cargo fix --clippy -Z unstable-options the following happens:

This

let int_c = i32::from(int_a + int_b) * 3;

will be turned into this

let int_c = int_a + int_b * 3;

, which is obviously incorrect.
It should instead be turned into this:

let int_c = (int_a + int_b) * 3;

Only tested on this version:

$ cargo clippy -V
clippy 0.0.212 (e8d5a9e 2019-10-22)
$ cargo -V
cargo 1.40.0-nightly (3a9abe3f0 2019-10-15)
$ rustc -V
rustc 1.40.0-nightly (4a8c5b20c 2019-10-23)

[basil-cow]

Is it ok to just always emit (...) regardless of whether they are needed?

[flip1995]

There is the unused_parens lint, that would deal with this afterwards. But there already is

rust-clippy/clippy_lints/src/utils/sugg.rs

Lines 22 to 30 in b4f1769

	pub enum Sugg<'a> {
	/// An expression that never needs parenthesis such as `1337` or `[0; 42]`.
	NonParen(Cow<'a, str>),
	/// An expression that does not fit in other variants.
	MaybeParen(Cow<'a, str>),
	/// A binary operator expression, including `as`-casts and explicit type
	/// coercion.
	BinOp(AssocOp, Cow<'a, str>),
	}

which can be helpful on fixing this issue.

[basil-cow]

Cool, I'll make a pr once clippy is buildable