u8::MAX as usize is 2^64 when used in array syntax

[silven]

Long story short. When trying to use the ::MAX properties of sized integers and converting them to usize, they get the wrong value. Like so:

let a: [u8; 255] = [0; core::u8::MAX as usize];
14:54 error: mismatched types:
expected [u8; 255],
found [u8; 18446744073709551615]

https://play.rust-lang.org/?code=%23![feature%28asm,+simd,+thread_local,+unsafe_destructor%29]%0A%23![feature%28core,+libc,+collections,+std_misc,+io,+path%29]%0A%23![allow%28dead_code,+unused_variables%29]%0A%23![allow%28unused_features%29]%0A%0Aextern+crate+libc;%0A%0Astatic+VERSION:+%26%27static+str+%3D+%22rustc+1.0.0-nightly+%28ba2f13ef0+2015-02-04+20:03:55+%2B0000%29%22;%0A%0Afn+show%3CT:+std::fmt::Debug%3E%28e:+T%29+{+println!%28%22{:%3F}%22,+e%29+}%0A%0Afn+main%28%29+{%0A++++show%28{%0A++++++++let+a:+[u8;+255]+%3D+[0;+std::u8::MAX+as+usize];%0A++++}%29;%0A}&run=1

[Gankra]

Probably a consequence of the fact that these are consts and defined thusly:

pub const MIN: $T = 0 as $T;
pub const MAX: $T = 0 as $T - 1 as $T;

[daboross]

Noting that u8::MAX as usize works fine in other places, just not in array decelerations. e.g. println!("{}", u8::MAX as usize); works as expected.

[mitaa]

dup of #13768

[alexcrichton]

Thanks @mitaa!