diff --git a/include/clang/Sema/Sema.h b/include/clang/Sema/Sema.h
index 22d5db2..775dc12 100644
--- a/include/clang/Sema/Sema.h
+++ b/include/clang/Sema/Sema.h
@@ -5652,13 +5652,11 @@
 
   ExprResult PerformImplicitConversion(Expr *From, QualType ToType,
                                        AssignmentAction Action,
-                                       bool AllowExplicit = false,
-                                       bool Diagnose = true);
+                                       bool AllowExplicit = false);
   ExprResult PerformImplicitConversion(Expr *From, QualType ToType,
                                        AssignmentAction Action,
                                        bool AllowExplicit,
-                                       ImplicitConversionSequence& ICS,
-                                       bool Diagnose = true);
+                                       ImplicitConversionSequence& ICS);
   ExprResult PerformImplicitConversion(Expr *From, QualType ToType,
                                        const ImplicitConversionSequence& ICS,
                                        AssignmentAction Action,
diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index 60f8418..79db724 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -5540,9 +5540,23 @@
       // C++ 5.17p3: If the left operand is not of class type, the
       // expression is implicitly converted (C++ 4) to the
       // cv-unqualified type of the left operand.
-      ExprResult Res = PerformImplicitConversion(RHS.get(),
-                                                 LHSType.getUnqualifiedType(),
-                                                 AA_Assigning, Diagnose);
+      ExprResult Res;
+      if (Diagnose) {
+        Res = PerformImplicitConversion(RHS.get(), LHSType.getUnqualifiedType(),
+                                        AA_Assigning);
+      } else {
+        ImplicitConversionSequence ICS =
+            TryImplicitConversion(RHS.get(), LHSType.getUnqualifiedType(),
+                                  /*SuppressUserConversions=*/false,
+                                  /*AllowExplicit=*/false,
+                                  /*InOverloadResolution=*/false,
+                                  /*CStyle=*/false,
+                                  /*AllowObjCWritebackConversion=*/false);
+        if (ICS.isFailure())
+          return Incompatible;
+        Res = PerformImplicitConversion(RHS.get(), LHSType.getUnqualifiedType(),
+                                        ICS, AA_Assigning);
+      }
       if (Res.isInvalid())
         return Incompatible;
       Sema::AssignConvertType result = Compatible;
diff --git a/lib/Sema/SemaOverload.cpp b/lib/Sema/SemaOverload.cpp
index b0dd5e2..440c2d1 100644
--- a/lib/Sema/SemaOverload.cpp
+++ b/lib/Sema/SemaOverload.cpp
@@ -912,18 +912,15 @@
 /// explicit user-defined conversions are permitted.
 ExprResult
 Sema::PerformImplicitConversion(Expr *From, QualType ToType,
-                                AssignmentAction Action, bool AllowExplicit,
-                                bool Diagnose) {
+                                AssignmentAction Action, bool AllowExplicit) {
   ImplicitConversionSequence ICS;
-  return PerformImplicitConversion(From, ToType, Action, AllowExplicit, ICS,
-                                   Diagnose);
+  return PerformImplicitConversion(From, ToType, Action, AllowExplicit, ICS);
 }
 
 ExprResult
 Sema::PerformImplicitConversion(Expr *From, QualType ToType,
                                 AssignmentAction Action, bool AllowExplicit,
-                                ImplicitConversionSequence& ICS,
-                                bool Diagnose) {
+                                ImplicitConversionSequence& ICS) {
   // Objective-C ARC: Determine whether we will allow the writeback conversion.
   bool AllowObjCWritebackConversion
     = getLangOptions().ObjCAutoRefCount && 
@@ -935,8 +932,6 @@
                                      /*InOverloadResolution=*/false,
                                      /*CStyle=*/false,
                                      AllowObjCWritebackConversion);
-  if (!Diagnose && ICS.isFailure())
-    return ExprError();
   return PerformImplicitConversion(From, ToType, ICS, Action);
 }