re PR c++/6255 (ICE with templatess)

        PR c++/6255
        * decl.c (lookup_name_real): Build a new TYPENAME_TYPE rather than
        modifying the old one.

From-SVN: r60259

gcc/testsuite/g++.dg/ext/typename1.C

+// PR c++/6255
+// { dg-options "-fpermissive -w" }
+
+template <class T> struct A { typedef int X; };
+template <class T> struct B { typedef A<T> Y; void f (Y::X); };
+template <class T, class T1, class T2, class T3> struct C : public B<T> { void g (Y::X); };
+template class B<int>;