rust/src/test/run-pass/lambda-infer-unresolved.rs

// This should typecheck even though the type of e is not fully
// resolved when we finish typechecking the fn@.
fn main() {
    let e = @{mut refs: ~[], n: 0};
    let f = fn@ () { log(error, e.n); };
    e.refs += ~[1];
}