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// build-fail
trait Tr {
const A: u8 = 255;
// This should not be a constant evaluation error (overflow). The value of
// `Self::A` must not be assumed to hold inside the trait.
const B: u8 = Self::A + 1;
//~^ ERROR any use of this value will cause an error
//~| WARN this was previously accepted by the compiler but is being phased out
}
// An impl that doesn't override any constant will NOT cause a const eval error
// just because it's defined, but only if the bad constant is used anywhere.
// This matches the behavior without defaults.
impl Tr for () {}
// An impl that overrides either constant with a suitable value will be fine.
impl Tr for u8 {
const A: u8 = 254;
}
impl Tr for u16 {
const B: u8 = 0;
}
impl Tr for u32 {
const A: u8 = 254;
const B: u8 = 0;
}
fn main() {
assert_eq!(<() as Tr>::A, 255);
assert_eq!(<() as Tr>::B, 0); // causes the error above
//~^ ERROR evaluation of constant value failed
//~| ERROR erroneous constant used
//~| WARN this was previously accepted by the compiler but is being phased out
assert_eq!(<u8 as Tr>::A, 254);
assert_eq!(<u8 as Tr>::B, 255);
assert_eq!(<u16 as Tr>::A, 255);
assert_eq!(<u16 as Tr>::B, 0);
assert_eq!(<u32 as Tr>::A, 254);
assert_eq!(<u32 as Tr>::B, 0);
}
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