Revert "[CSSimplify] Fix handling of holes by OptionalObject constraint"

This reverts commit 8b5e3848a1.

lib/Sema/CSSimplify.cpp

@@ -9179,8 +9179,8 @@ ConstraintSystem::simplifyOptionalObjectConstraint(
   }
 
   if (optTy->isPlaceholder()) {
-    // object type should be simplified because it could be already bound.
-    recordAnyTypeVarAsPotentialHole(simplifyType(second));
+    if (auto *typeVar = second->getAs<TypeVariableType>())
+      recordPotentialHole(typeVar);
     return SolutionKind::Solved;
   }
 

test/stmt/switch_stmt2.swift

@@ -150,25 +150,3 @@ 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
-    }
-  }
-}