Currently you must use UFCS form to invoke methods. Here is an [example by @kinghajj](https://github.com/rust-lang/rust/pull/20307#issuecomment-68329294): ``` rust #![feature(associated_types)] trait Foo { fn foo(&self) -> (); } trait Bar { type F: Foo; } struct Wat<B: Bar> { fs: Vec<B::F>, } impl<B: Bar> Wat<B> { fn wat(&mut self) -> () { self.fs.pop().unwrap().foo(); } } fn main() { } ```