It's not calling methods on a type that is the issue. It's passing parameters to a method or function when that method or function has a generic type for that p

It's not calling methods on a type that is the issue. It's passing parameters to a method or function when that method or function has a generic type for that parameter. In Rust this is something like fn foo<A>(a: A): A (which can only have one implementation, the identity, if you don't break the abstraction barrier provided by generic types.)