Fixed length array type with high un-suffixed count literal incorrectly treated as negative count

[lilyball]

A fixed-length array expression with a repeat count with the high bit set and no suffix is incorrectly treated as a negative count.

On a 64-bit machine:

fn main() {
    let x = [0u, ..9223372036854775808];
}

This results in

unnamed.rs:2:20: 2:39 error: expected positive integer for repeat count but found negative integer
unnamed.rs:2     let x = [0u, ..9223372036854775808];
                                ^~~~~~~~~~~~~~~~~~~
error: aborting due to previous error

[hirschenberger]

Can be easily fixed after #15709 landed

[bombless]

fn main() {
    let x = [0usize; 9223372036854775808];
//~^ error: the type `[usize; 9223372036854775808]` is too big for the current architecture
}

Seems that it is not an issue any more.

[bombless]

I'm thinking that if it behave differently on different platforms, is it making it an undefined behavior?
And I think designating an exact behavior for UB cannot possibly be a breaking change?

[lilyball]

@bombless This does not make it undefined behavior. It's very much defined behavior. If it were undefined behavior, then any usize or isize literal would be undefined behavior as well, because the range of valid values is architecture-dependent.