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Issue Description:

Given the following class definitions in which two final classes with the same name are declared inside different structs but both inherit from a base class:

open class Base {  ...  }

public struct StructA {
    final public class Homonym: Base {  ... }
}

public struct StructB {
    final public class Homonym: Base { ... }
}

When i declare the following extension in a separate project that links with said framework:

extension StructA.Homonym { 
    convenience init() { ... } 
}

and then i use the convenience init to initialize a StructA.Homonym:

let homonym = StructA.Homonym()

the compiler erroneously creates an object of type StructB.Homonym!

(lldb) po type(of: homonym)
Homonyms.StructB.Homonym

hence the extension seems to be applied to StructB.Homonym instead of StructA.Homonym.

Please run the attached workspace to see the strange behaviour.

Please note that this seems to happen only if the class hierarchy is declared in a separate framework: this behaviour does not seem to be reproducible inside a playground. If the classes are not declared as final, the application behaves as expected. If the extension is declared (as public) inside the framework, the application behaves as expected.