Merge pull request #69642 from xedin/rdar-117871338

[CSSimplify] Fix handling of holes by OptionalObject constraint

Author: xedin

lib/Sema/CSSimplify.cpp

@@ -9184,8 +9184,8 @@ ConstraintSystem::simplifyOptionalObjectConstraint(
   }
 
   if (optTy->isPlaceholder()) {
-    if (auto *typeVar = second->getAs<TypeVariableType>())
-      recordPotentialHole(typeVar);
+    // object type should be simplified because it could be already bound.
+    recordAnyTypeVarAsPotentialHole(simplifyType(second));
     return SolutionKind::Solved;
   }
 

test/stmt/switch_stmt2.swift

@@ -150,3 +150,25 @@ func fallthrough_not_last(i: Int) {
     break
   }
 }
+
+// rdar://117871338 - incorrect diagnostic - type of expression is ambiguous when member is missing.
+func test_invalid_optional_chaining() {
+  func test(_: (E) -> Void) {
+  }
+
+  enum E {
+  case a
+  case b
+  }
+
+  struct S {
+    var prop: E
+  }
+
+  test {
+    switch $0.prop? { // expected-error {{value of type 'E' has no member 'prop'}}
+    case .a: break
+    case .b: break
+    }
+  }
+}