[CSFix] Make it possible to diagnose r-value -> l-value fix for ambiguity

Author: xedin

lib/Sema/CSFix.h

@@ -369,6 +369,10 @@ class TreatRValueAsLValue final : public ConstraintFix {
 
   bool diagnose(const Solution &solution, bool asNote = false) const override;
 
+  bool diagnoseForAmbiguity(CommonFixesArray commonFixes) const override {
+    return diagnose(*commonFixes.front().first);
+  }
+
   static TreatRValueAsLValue *create(ConstraintSystem &cs,
                                      ConstraintLocator *locator);
 };