identity_op lint fix for '&' with unsigned types

This commit is contained in:
Yury Krivopalov 2017-09-30 11:33:15 +03:00
parent f0aa2c1587
commit f68e408cb6
3 changed files with 28 additions and 6 deletions

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@ -1,9 +1,9 @@
use consts::{constant_simple, Constant};
use rustc::lint::*;
use rustc::hir::*;
use rustc::lint::*;
use rustc_const_math::ConstInt;
use syntax::codemap::Span;
use utils::{in_macro, snippet, span_lint};
use syntax::attr::IntType::{SignedInt, UnsignedInt};
/// **What it does:** Checks for identity operations, e.g. `x + 0`.
///
@ -58,15 +58,28 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for IdentityOp {
}
}
fn no_zeros(v: &ConstInt) -> bool {
match *v {
ConstInt::I8(i) => i.count_zeros() == 0,
ConstInt::I16(i) => i.count_zeros() == 0,
ConstInt::I32(i) => i.count_zeros() == 0,
ConstInt::I64(i) => i.count_zeros() == 0,
ConstInt::I128(i) => i.count_zeros() == 0,
ConstInt::U8(i) => i.count_zeros() == 0,
ConstInt::U16(i) => i.count_zeros() == 0,
ConstInt::U32(i) => i.count_zeros() == 0,
ConstInt::U64(i) => i.count_zeros() == 0,
ConstInt::U128(i) => i.count_zeros() == 0,
_ => false
}
}
#[allow(cast_possible_wrap)]
fn check(cx: &LateContext, e: &Expr, m: i8, span: Span, arg: Span) {
if let Some(Constant::Int(v)) = constant_simple(cx, e) {
if match m {
0 => v.to_u128_unchecked() == 0,
-1 => match v.int_type() {
SignedInt(_) => (v.to_u128_unchecked() as i128 == -1),
UnsignedInt(_) => false,
},
-1 => no_zeros(&v),
1 => v.to_u128_unchecked() == 1,
_ => unreachable!(),
} {

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@ -27,4 +27,7 @@ fn main() {
x & NEG_ONE; //no error, as we skip lookups (for now)
-1 & x;
let u : u8 = 0;
u & 255;
}

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@ -42,3 +42,9 @@ error: the operation is ineffective. Consider reducing it to `x`
29 | -1 & x;
| ^^^^^^
error: the operation is ineffective. Consider reducing it to `u`
--> $DIR/identity_op.rs:32:5
|
32 | u & 255;
| ^^^^^^^