[CSFix] Allow invalid property wrapper type to be diagnosed in ambiguous context

Adds `diagnoseForAmbiguity` to `AllowInvalidPropertyWrapperType` fix
because it could be attached to a closure parameter that has ambiguity
in the body so it has to be diagnosable in ambiguous contexts.

Resolves: rdar://116522161

Author: xedin

include/swift/Sema/CSFix.h

@@ -1368,6 +1368,10 @@ class AllowInvalidPropertyWrapperType final : public ConstraintFix {
     return "allow invalid property wrapper type";
   }
 
+  bool diagnoseForAmbiguity(CommonFixesArray commonFixes) const override {
+    return diagnose(*commonFixes.front().first);
+  }
+
   bool diagnose(const Solution &solution, bool asNote = false) const override;
 
   static bool classof(const ConstraintFix *fix) {

test/Sema/property_wrapper_parameter_invalid.swift

@@ -279,3 +279,15 @@ func testInvalidWrapperInference() {
   // expected-error@+1 {{contextual closure type '() -> Void' expects 0 arguments, but 1 was used in closure body}}
   testExtraParameter { $value in }
 }
+
+// rdar://116522161 - failed to produce a diagnostic on invalid projection use
+func testInvalidProjectionInAmbiguousContext() {
+  func test<T>(_: [T], _: (T) -> Void) {}
+
+  func ambiguous() -> Int { 42 }
+  func ambiguous() -> String { "" }
+
+  test([42]) { $v in // expected-error {{inferred projection type 'Int' is not a property wrapper}}
+    ambiguous()
+  }
+}