deriving(Hash) on enum generates method call on generic integer (1.hash())

[klutzy]

#[deriving(Hash)]
enum E {
    A = 1,
    B,
}

error: unable to infer enough type information to locate the impl of the trait `collections::hash::Hash` for the type `_`; type annotations required
#[deriving(Hash)]
           ^~~~

rustc --pretty=expanded output:

#![crate_type = "lib"]
#![feature(phase)]
#![no_std]
#![feature(globs)]
#[phase(plugin, link)]
extern crate "std" as std;
#[prelude_import]
use std::prelude::*;

enum E { A = 1, B, }
#[automatically_derived]
impl ::std::hash::Hash for E {
    #[inline]
    fn hash(&self, __arg_0: &mut ::std::hash::sip::SipState) {
        match (&*self,) {
            (&A,) => { 1.hash(__arg_0); }
            (&B,) => { 1u.hash(__arg_0); }
        }
    }
}

For A = 1, rustc generates 1.hash(__arg_0) but it doesn't compile because 1 is generic integer.

Moreoever, for B rustc generates 1u.hash(__arg_0) but it should be 2u.

[steveklabnik]

This compiles fine today.

[klutzy]

This compiles because 1 is now 1i32. It still hashes 1 for A and 1us for B, thus causes collision on 32-bit machine:

use std::hash::{hash, SipHasher};

#[derive(Hash)]
enum E {
    A = 1,
    B,
}

fn main() {
    let a = hash::<_,   SipHasher>(&E::A);
    let b = hash::<_,   SipHasher>(&E::B);

    println!("{}, {}, {}", a, b, a == b);
}

$ rustc a.rs --target=i686-unknown-linux-gnu && ./a
13715208377448023093, 13715208377448023093, true

[klutzy]

(Opened #21714 for the collision issue)