Need proper tip for range syntax

[bombless]

For

fn foo() {
    for i in 0 .. 9us {
        println!("{}", i)
    }
}

it compiles fine, and for

fn bar(len: usize) {
    for i in 0 .. len {
        println!("{}", i)
    }
}

compiler shows

3:10: 3:11 error: expected `:`, found `!`

It should give a tip that parentheses are missing anyway.

Rustc version:

rustc 1.0.0-dev (1028e185f 2015-01-20 18:12:41 +0800)
binary: rustc
commit-hash: 1028e185f91482551f629e97b8c3ad7ce0ade2f7
commit-date: 2015-01-20 18:12:41 +0800
host: i686-pc-windows-gnu
release: 1.0.0-dev

[klutzy]

#20241?

[bombless]

@klutzy Thanks!
Dup of #20241, so I'm closing it.