duplicates:

• SR-5650 Remove parent field from type metadata

relates to:

• SR-3779 Program with struct nested in generic struct crashes because of “cyclic metadata dependency”
• SR-5432 Using nested type as a superclass generic parameter leads to a crash

Issue Description:

The following code compiles without warning but when run crashes instantiating Subclass instance, prior to entering Subclass.init. Would appear to be due to having nested struct A defined within Subclass and this being used as generic parameter. Refactoring struct A so its not nested and no crash. If this is not valid to use nested type as generic parameter like this should not the compiler give an error? If it is valid code the runtime crash should be fixed.

$ swiftc --version
Apple Swift version 3.1 (swiftlang-802.0.51 clang-802.0.41)

class Base<T> {}

class Subclass: Base<Subclass.A> {
    
    struct A {}
    
    override init() {
        super.init()
    }    
}

let _ = Subclass()