ahatanak wrote:
> > Could you help me understand why clang is emitting the warning?
> > Isn't it semantically equivalent to the following code?
> > ```
> > unsigned int foo(unsigned char x)
> > {
> > int i = ~(1<<x); // no -Wimplicit-int-conversion warning.
> > return i; // no -Wimplicit-int-conversion warning.
> > }
> > ```
>
> The conversion isn't implicit in the latter case.
It looks like the warning is emitted because of the following code in
`TryGetExprRange`:
```
case BO_Shl:
// ...except that we want to treat '1 << (blah)' as logically
// positive. It's an important idiom.
if (IntegerLiteral *I
= dyn_cast<IntegerLiteral>(BO->getLHS()->IgnoreParenCasts())) {
if (I->getValue() == 1) {
IntRange R = IntRange::forValueOfType(C, GetExprType(E));
return IntRange(R.Width, /*NonNegative*/ true);
}
}
```
`1<<x` is treated as non-negative even though it can be negative when `x` is
equal to 31.
https://github.com/llvm/llvm-project/pull/126846
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