Index: clang/lib/Sema/SemaInit.cpp
===================================================================
--- clang/lib/Sema/SemaInit.cpp
+++ clang/lib/Sema/SemaInit.cpp
@@ -5936,6 +5936,7 @@
   // We're at the end of the line for C: it's either a write-back conversion
   // or it's a C assignment. There's no need to check anything else.
   if (!S.getLangOpts().CPlusPlus) {
+    assert(Initializer && "Initializer must be non-null");
     // If allowed, check whether this is an Objective-C writeback conversion.
     if (allowObjCWritebackConversion &&
         tryObjCWritebackConversion(S, *this, Entity, Initializer)) {
@@ -5962,7 +5963,8 @@
     if (Kind.getKind() == InitializationKind::IK_Direct ||
         (Kind.getKind() == InitializationKind::IK_Copy &&
          (Context.hasSameUnqualifiedType(SourceType, DestType) ||
-          S.IsDerivedFrom(Initializer->getBeginLoc(), SourceType, DestType))))
+          (Initializer &&
+           S.IsDerivedFrom(Initializer->getBeginLoc(), SourceType, DestType)))))
       TryConstructorInitialization(S, Entity, Kind, Args,
                                    DestType, DestType, *this);
     //     - Otherwise (i.e., for the remaining copy-initialization cases),
@@ -5971,9 +5973,11 @@
     //       used) to a derived class thereof are enumerated as described in
     //       13.3.1.4, and the best one is chosen through overload resolution
     //       (13.3).
-    else
+    else {
+      assert(Initializer && "Initializer must be non-null");
       TryUserDefinedConversion(S, DestType, Kind, Initializer, *this,
                                TopLevelOfInitList);
+    }
     return;
   }
 
@@ -6022,6 +6026,7 @@
   //    - Otherwise, if the source type is a (possibly cv-qualified) class
   //      type, conversion functions are considered.
   if (!SourceType.isNull() && SourceType->isRecordType()) {
+    assert(Initializer && "Initializer must be non-null");
     // For a conversion to _Atomic(T) from either T or a class type derived
     // from T, initialize the T object then convert to _Atomic type.
     bool NeedAtomicConversion = false;