[CSFix] Add a warning fix for situations when trailing closure is matched via backward scan

lib/Sema/CSFix.cpp

@@ -1526,3 +1526,15 @@ UnwrapOptionalBaseKeyPathApplication::attempt(ConstraintSystem &cs, Type baseTy,
   return new (cs.getAllocator())
       UnwrapOptionalBaseKeyPathApplication(cs, baseTy, rootTy, locator);
 }
+
+bool SpecifyLabelToAssociateTrailingClosure::diagnose(const Solution &solution,
+                                                      bool asNote) const {
+  return false;
+}
+
+SpecifyLabelToAssociateTrailingClosure *
+SpecifyLabelToAssociateTrailingClosure::create(ConstraintSystem &cs,
+                                               ConstraintLocator *locator) {
+  return new (cs.getAllocator())
+      SpecifyLabelToAssociateTrailingClosure(cs, locator);
+}