@rough-minister-58256 For weird reasons that I still don’t understand, there are actually two different things that look like `Type<Other>`: On a struct they’re called generic type parameters. Their existence is defined:

struct S<Param> {
  field: Param,
}

and they’re used

fn foo() -> S<String>

. On a trait, they’re called associated types, and they have names. They’re defined:

trait T {
  type Param;
}

and they’re used:

fn foo() -> T<Param=String>