Add description to assert

llvm-svn: 227291

llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp

@@ -627,7 +627,7 @@ static uint64_t getBaseTypeSize(DwarfDebug *DD, DIDerivedType Ty) {
 
   DIType BaseType = DD->resolve(Ty.getTypeDerivedFrom());
 
-  assert(BaseType.isValid());
+  assert(BaseType.isValid() && "Unexpected invalid base type");
 
   // If this is a derived type, go ahead and get the base type, unless it's a
   // reference then it's just the size of the field. Pointer types have no need