[test] Add test for dynamic member lookup behaviour changed by #15412

Author: hamishknight

test/Constraints/dynamic_lookup.swift

@@ -336,3 +336,51 @@ func testOverloadedWithUnavailable(ao: AnyObject) {
   ao.overloadedWithUnavailableB()
 }
 
+// Test that we correctly diagnose ambiguity for different typed members available
+// through dynamic lookup.
+@objc protocol P3 {
+  var ambiguousProperty: String { get } // expected-note {{found this candidate}}
+  var unambiguousProperty: Int { get }
+
+  func ambiguousMethod() -> String // expected-note 2{{found this candidate}}
+  func unambiguousMethod() -> Int
+
+  func ambiguousMethodParam(_ x: String) // expected-note {{found this candidate}}
+  func unambiguousMethodParam(_ x: Int)
+
+  subscript(ambiguousSubscript _: Int) -> String { get } // expected-note {{found this candidate}}
+  subscript(unambiguousSubscript _: String) -> Int { get } // expected-note {{found this candidate}}
+}
+
+class C1 {
+  @objc var ambiguousProperty: Int { return 0 } // expected-note {{found this candidate}}
+  @objc var unambiguousProperty: Int { return 0 }
+
+  @objc func ambiguousMethod() -> Int { return 0 } // expected-note 2{{found this candidate}}
+  @objc func unambiguousMethod() -> Int { return 0 }
+
+  @objc func ambiguousMethodParam(_ x: Int) {} // expected-note {{found this candidate}}
+  @objc func unambiguousMethodParam(_ x: Int) {}
+
+  @objc subscript(ambiguousSubscript _: Int) -> Int { return 0 } // expected-note {{found this candidate}}
+  @objc subscript(unambiguousSubscript _: String) -> Int { return 0 } // expected-note {{found this candidate}}
+}
+
+func testAnyObjectAmbiguity(_ x: AnyObject) {
+  _ = x.ambiguousProperty // expected-error {{ambiguous use of 'ambiguousProperty'}}
+  _ = x.unambiguousProperty
+
+  _ = x.ambiguousMethod() // expected-error {{ambiguous use of 'ambiguousMethod()'}}
+  _ = x.unambiguousMethod()
+
+  _ = x.ambiguousMethod // expected-error {{ambiguous use of 'ambiguousMethod()'}}
+  _ = x.unambiguousMethod
+
+  _ = x.ambiguousMethodParam // expected-error {{ambiguous use of 'ambiguousMethodParam'}}
+  _ = x.unambiguousMethodParam
+
+  _ = x[ambiguousSubscript: 0] // expected-error {{ambiguous use of 'subscript(ambiguousSubscript:)'}}
+
+  // FIX-ME(SR-8611): This is currently ambiguous but shouldn't be.
+  _ = x[unambiguousSubscript: ""] // expected-error {{ambiguous use of 'subscript(unambiguousSubscript:)'}}
+}