[Bug c/88566] -Wconversion not using value range information

[hoganmeier at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88566

--- Comment #1 from krux <hoganmeier at gmail dot com> ---
Even simpler example:
uint8_t foo(uint8_t pin)
{
        return pin > 0 ? pin - 1 : 0;
}