#![crate_type = "lib"] #![crate_name = "default_param_test"] #![feature(default_type_parameter_fallback)] use std::marker::PhantomData; pub struct Foo<A, B>(PhantomData<(A, B)>); pub fn bleh<A=i32, X=char>() -> Foo<A, X> { Foo(PhantomData) }