[TypeChecker] NFC: Add test-case for rdar://75978086

Author: xedin

test/Constraints/static_member_on_protocol_with_opaque_result.swift

@@ -0,0 +1,19 @@
+// RUN: %target-swift-frontend -disable-availability-checking -typecheck -verify %s
+
+// rdar://75978086 - static member lookup doesn't work with opaque types
+
+protocol Intent {}
+
+extension Intent where Self == Intents.List {
+  static func orderedList() -> Self {
+    return Intents.List.orderedList(nestedIn: nil)
+  }
+}
+
+enum Intents {
+  enum List: Intent {
+  case orderedList(nestedIn: Any?)
+  }
+}
+
+let rdar75978086: some Intent = .orderedList() // Ok