rustc weirdness

gistfile1.rs

fn sum(a: int, b: int) -> int { a + b }                                                           
                                                                                                    
fn main() {                                                                                         
    let a = |x:int| { |y:int| -> int { x + y } };                                                     
    let b = a(2);                                                                                   
                                                                                                    
    io::println(int::to_str(sum(2, 3)));                                                            
    io::println(int::to_str(a(2)(3)));                                                              
    io::println(int::to_str(b(3)));                                                                 
}         

// Which when run outputs

> 5
> 6
> 39739523 // random value

// meanwhile in the REPL

[jaen@yuuki ~]$ rust sketch
WARNING: The Rust REPL is experimental and may be
unstable. If you encounter problems, please use the
compiler instead.
rusti> fn sum(a: int, b: int) -> int { a + b }     
()
rusti> let a = |x:int| { |y:int| -> int { x + y } };
<anon>:36:4: 36:7 warning: unused variable: `a`
<anon>:36 let a = |x:int| { |y:int| -> int { x + y } };
              ^~~
()
rusti> let b = a(2);
<anon>:38:4: 38:7 warning: unused variable: `b`
<anon>:38 let b = a(2);
              ^~~
()
rusti> sum(2, 3)
<anon>:37:4: 37:7 warning: unused variable: `b`
<anon>:37 let b = a(2);
              ^~~
5
rusti> a(2)(3)
<anon>:37:4: 37:7 warning: unused variable: `b`
<anon>:37 let b = a(2);
              ^~~
5
rusti> b(3)
5
rusti>