[clang] False-positive warning for integer promotion [-Wimplicit-int-conversion]

[Mephistophiles]

#include <stdint.h>

_Static_assert(__builtin_types_compatible_p(typeof(UINT8_C(1)), int), "");
_Static_assert(__builtin_types_compatible_p(typeof(UINT8_C(1)), uint8_t) == 0, "");

int foo(uint8_t b)
{
    uint8_t a = ((uint8_t)1) << b;
    return __builtin_types_compatible_p(typeof(((uint8_t)1) << b), int);
}

https://godbolt.org/z/s1f64449b

Code snippet gives a warning:

<source>:8:30: warning: implicit conversion loses integer precision: 'int' to 'uint8_t' (aka 'unsigned char') [-Wimplicit-int-conversion]
    8 |     uint8_t a = ((uint8_t)1) << b;
      |             ~   ~~~~~~~~~~~~~^~~~

However, this behavior is not considered an error in gcc (there is no warning):
https://godbolt.org/z/d1KjrbKdd

[frederick-vs-ja]

I think Clang is doing the right thing.

[shafik]

Shift will perform promotions on its operands see expr.shift p1:

... and integral promotions are performed. ... result is that of the promoted left operand

and based on conv.prom the result will be int.