Index: include/clang/AST/TemplateBase.h
===================================================================
--- include/clang/AST/TemplateBase.h
+++ include/clang/AST/TemplateBase.h
@@ -465,7 +465,13 @@
 
   TemplateArgumentLoc(const TemplateArgument &Argument, Expr *E)
       : Argument(Argument), LocInfo(E) {
-    assert(Argument.getKind() == TemplateArgument::Expression);
+
+    // Permit any kind of template argument that can be represented 
+    // with an expression
+    assert(Argument.getKind() == TemplateArgument::NullPtr ||
+           Argument.getKind() == TemplateArgument::Integral ||
+           Argument.getKind() == TemplateArgument::Declaration ||
+           Argument.getKind() == TemplateArgument::Expression);
   }
 
   TemplateArgumentLoc(const TemplateArgument &Argument, 
Index: test/SemaObjCXX/class-templ-error-null-init.mm
===================================================================
--- /dev/null
+++ test/SemaObjCXX/class-templ-error-null-init.mm
@@ -0,0 +1,7 @@
+// RUN: %clang_cc1 -fsyntax-only -std=c++17  -verify %s
+// expected-no-diagnostics
+template <typename a, int* = nullptr>
+struct e {
+    e(a) {}
+};
+e c(0);