Index: clang/lib/AST/DeclPrinter.cpp
===================================================================
--- clang/lib/AST/DeclPrinter.cpp
+++ clang/lib/AST/DeclPrinter.cpp
@@ -144,6 +144,8 @@
       BaseType = RTy->getPointeeType();
     else if (const AutoType *ATy = BaseType->getAs<AutoType>())
       BaseType = ATy->getDeducedType();
+    else if (isa<BuiltinType>(BaseType))
+      break;
     else
       llvm_unreachable("Unknown declarator!");
   }
Index: clang/test/Sema/ast-print-cxx.cpp
===================================================================
--- /dev/null
+++ clang/test/Sema/ast-print-cxx.cpp
@@ -0,0 +1,6 @@
+// RUN: %clang_cc1 -std=c++11 %s -ast-print | FileCheck %s
+// RUN: %clang_cc1 -std=c++11 %s -ast-print \
+// RUN:      | %clang_cc1 -std=c++11 -x c++ -fsyntax-only -
+
+// CHECK: typedef decltype(nullptr) nullptr_t;
+typedef decltype(nullptr) nullptr_t;