rust/tests/ui/consts/const-eval/ub-invalid-values.rs

const fn bool_cast(ptr: *const bool) { unsafe {
    let _val = *ptr as u32; //~ NOTE inside `bool_cast`
    //~^ NOTE the failure occurred here
}}

const _: () = {
    let v = 3_u8;
    bool_cast(&v as *const u8 as *const bool); //~ ERROR: evaluation of constant value failed
    //~^ NOTE interpreting an invalid 8-bit value as a bool
};

fn main() {}