Concise conditional Copyable conformances

[xwu (Xiaodi Wu)]

@vns

Isn't this changing type from being conditionally copyable to unconditionally copyable? And then there is no way to define such type with the suggested syntax?

That's correct: this already has a meaning in the language—

struct S<T>: Foo where T: Foo means that S unconditionally conforms to Foo and T is constrained unconditionally to conform to Foo; it does not mean that S<T> conforms to Foo conditionally when T conforms to Foo.