Rustc complains about seemingly valid string slice passed to a closure.

[simias]

The following code:

�pub fn main() {
    let error = | err | {
        println!("error: {}", err);
    };

    {
        let str = "foo".to_string();

        error(str.as_slice());
    }
}

Produces the following error:

test.rs:9:15: 9:18 error: `str` does not live long enough
test.rs:9         error(str.as_slice());
                        ^~~
test.rs:1:15: 11:2 note: reference must be valid for the block at 1:14...
test.rs:1 pub fn main() {
test.rs:2     let error = | err | {
test.rs:3         println!("error: {}", err);
test.rs:4     };
test.rs:5 
test.rs:6     {
          ...
test.rs:6:5: 10:6 note: ...but borrowed value is only valid for the block at 6:4
test.rs:6     {
test.rs:7         let str = "foo".to_string();
test.rs:8 
test.rs:9         error(str.as_slice());
test.rs:10     }
error: aborting due to previous error

The code builds if I annotate the closure with | err: &str|

[steveklabnik]

This is intended. Closures capture references to their environment, and your str goes out of scope at the end of the block, just like the error says. This would be a dangling pointer otherwise.