Fix to c++/9336 introduces segfault

[Michael Matz <matz at suse dot de>]

Hi Mark,

me again ;)  The patch

        PR c++/9336
        * decl2.c (do_nonmember_using_decl): Do not call duplicate decls
        to merge old and new declarations.

introduces a segfault with the below snippet.  If tree-checking is active,
it results in a check failure, namely:

  bla.cc:7: internal compiler error: tree check: expected tree_list,
   have type_decl in compparms, at cp/typeck.c:1418

, which is at:
1418      if (!same_type_p (TREE_VALUE (t2), TREE_VALUE (t1)))

The segfault acutally happens inside same_type_p().  The underlying
reason, I believe is, that compparms() is called with a function and a
record type, because do_nonmember_using_decl() does call it so, although
it's parameters look like:

4245                  else if (compparms (TYPE_ARG_TYPES (TREE_TYPE (new_fn)),
4246                                      TYPE_ARG_TYPES (TREE_TYPE (old_fn))))
% p debug_tree(new_fn)
 <function_decl 0x401960d8 f
    type <function_type 0x4015f0d8
        type <void_type 0x40159b64 void VOID
 ...
% p debug_tree(old_fn)
 <type_decl 0x401965e8 f
    type <record_type 0x401964a4 f type_1 type_5 QI
        size <integer_cst 0x4014ed00 constant 8>
 ...

The snippet showing this is:
-------- snip ---------
namespace A {
  void f();
}
int g()
{
  struct f { };
  using A::f;
}
-------- snap ---------

This happens on 3.3 branch and HEAD.


Ciao,
Michael.