macro_rules! ty { ($($body:tt)*) => { ... }; }
This macro takes type paths of the form my_crate::my_mod::FooBar and <my_crate::my_mod::FooBar as my_crate::my_mod::MyTrait>::MyType and turns them into a syn::Type.
my_crate::my_mod::FooBar
<my_crate::my_mod::FooBar as my_crate::my_mod::MyTrait>::MyType
syn::Type