``` type actor<T> = { unused: bool }; type self<T> = { unused: bool }; fn act<T:send>(+behavior: sendfn(self<T>)) -> actor<T> { {unused: true} } tag in { preprocess([u8]); exit; } fn mk() -> actor<in> { act {|self| } } fn main() { } ``` ``` ../src/test/run-pass/block-infer.rs:19:4: 19:7 error: cannot determine a type for this expression ../src/test/run-pass/block-infer.rs:19 act {|self| ``` Writing `act::<in>` allows it to work.