example.rs

import io::*;
import to_str::*;

impl <T : to_str copy> of to_str for @[mut T] {
    fn to_str() -> str {
        let tmp = self;
        tmp.map(|x| { x.to_str() }).to_str()
    }
}

fn main() {
    println((@[mut 1, 2, 3]).to_str());
}

gistfile1.txt

user@note ~/soft/mine/rust $ rustc example.rs 
example.rs:7:8: 7:11 error: internal compiler error: aliased ptr with a non-none lp
example.rs:7         tmp.map(|x| { x.to_str() }).to_str()
                     ^~~