Identity/erasing operation lints #2136
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For expressions that can be replaced by a zero.
clippy_lints/src/identity_op.rs
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| @@ -58,15 +58,28 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for IdentityOp { | |||
| } | |||
| } | |||
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| fn no_zeros(v: &ConstInt) -> bool { | |||
| match *v { | |||
| ConstInt::I8(i) => i.count_zeros() == 0, | |||
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can we just compare with !0 or something?
clippy_lints/src/erasing_op.rs
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| /// **What it does:** Checks for erasing operations, e.g. `x * 0`. | ||
| /// | ||
| /// **Why is this bad?** The whole expression can be replaced by zero. | ||
| /// Most likely mistake was made and code should be reviewed or simplified. |
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I'd rather write "This is most likely not the intended outcome and should probably be corrected."
| declare_lint! { | ||
| pub ERASING_OP, | ||
| Warn, | ||
| "using erasing operations, e.g. `x * 0` or `y & 0`" |
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There is also x | -1 (signed) / x | !0 (unsigned), though those return -1 and !0 respectively. It's ok if we extend this later, though.
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Yes, I can add this lint. We might also change the lint name. Something about expression with a constant result, I'm not sure.
clippy_lints/src/erasing_op.rs
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| cx, | ||
| ERASING_OP, | ||
| span, | ||
| "the operation is ineffective. Consider reducing it to `0`", |
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I don't quite like our message here, as it implies the zero would be correct, where this will most likely not be the case. I'd rather warn "this operation will always return zero. This is likely not the intended outcome."
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Thanks! |
#2086