Issue Description:

Given the following code:

class ClassA<T> {
    init(someVar: Int = 0) {}
}

class ClassB {
    private let classA: ClassA<String>

    init() {
        classA = ClassA<String>()
    }
}

A source.request.indexsource response does not include a source.lang.swift.ref.function.constructor reference for ClassA<String>() to the declaration init(someVar:). The constructor has the USR s:4test6ClassACACyxGSi7someVar_tcfc and it is not referenced anywhere in the index.

This issue appears to only affect classes with generic types. If I remove the generic type from ClassA, the ClassB constructor declaration will contain a reference to init(someVar:).

Full index response is here: https://gist.github.com/ileitch/2b6b08ab247d712da752c5c24b5fca85

/cc @nkcsgexi @benlangmuir