[SR-12890] Unable to explicitly qualify a shadowed type alias

[swift-ci]

Previous ID	SR-12890
Radar	None
Original Reporter	andrewchang-bird (JIRA User)
Type	Bug

Environment

Apple Swift version 5.2.2 (swiftlang-1103.0.32.6 clang-1103.0.32.51)
Target: x86_64-apple-darwin19.4.0

Additional Detail from JIRA

Votes	0
Component/s
Labels	Bug
Assignee	None
Priority	Medium

md5: 91dc18a2dde2fd5052dc515d364a25f8

Issue Description:

Shadowing a type alias declared by an inherited protocol breaks explicit type qualification.

protocol One {
  typealias Nominal = String
  typealias Generic<T> = Array<T>
}


class Two: One {
  typealias Nominal = Int
  typealias Generic<T> = Dictionary<String, T>
  
  func method(nominal: Nominal) {}
  func method(oneNominal: One.Nominal) {}
  func method(twoNominal: Two.Nominal) {} // Ambiguous type name 'Nominal' in 'Two'
  
  func method(generic: Generic<Bool>) {}
  func method(oneGeneric: One.Generic<Bool>) {} // Type alias 'Generic' can only be used with a concrete type or generic parameter base
  func method(twoGeneric: Two.Generic<Bool>) {} // Ambiguous type name 'Generic' in 'Two'
}

It feels like references to `Nominal` vs `Two.Nominal` should be treated the same within `Two`.