once fn/proc() allows use-after-move of captured variable

[ben0x539]

and crashes, inevitably.

fn main() {
    let x = ~"foo";
    let f: proc() = proc() {
        let _a = x;
        drop(x);
    };
    f();
}

[huonw]

cc @nikomatsakis

[nikomatsakis]

Looks bad. :) I'll take a look.

[alexcrichton]

Some other code which compiles and shouldn't compile:

fn foo(_: ~int) {}  

fn main() {         
    let a = ~2;     
    do spawn {      
        loop {      
            foo(a); 
        }           
    }               
}