assign_op_pattern misleading on wrongly implemented assign impl.

[letheed]

impl SubAssign for Foo {
    fn sub_assign(&mut self, rhs: Self) {
        *self = *self + rhs; // Copy-paste facepalm
    }
}

Triggers assign_op_pattern, which suggest replace it with: *self += rhs.

Mistake caught but left me wondering for a minute. Had to find this to figure out something else must be going on.

[oli-obk]

duplicate of #1239

[oli-obk]

Oh, this is SubAssign not AddAssign, nevermind me

[Ryan1729]

Given that #2458, which addresses this, landed some time ago, and that #5820 which reduces the false positive rate on the suspicious_arithmetic_impl lint, recently landed, can this issue be closed?

#2458 does mention that the suspicious_arithmetic_impl lint only covers the Add, Sub, Mul and Div, traits, and this is still true currently. Do we want to extend this lint to cover the rest of the binary operations that can be overloaded? Specifically those are BitAnd, BitOr, BitXor, Rem, Shl, and Shr.