Open Radar

 
Summary:
Normally when you nest a type within a generic type you get this error:

error: type 'S' nested in generic type 'Foo' is not allowed

If you do it within an extension, it crashes instead.


Steps to Reproduce:
1. This:

enum Foo<T> {
	case Bar(T)
}
extension Foo {
	struct S {}
}


or equivalently, this:

extension Optional {
	struct S {}
}



Expected Results:
I expected the error (or else for it to compile because that restriction is just terrible).


Actual Results:
Crash.


Regression:
N/A


Notes:
N/A