[PATCH] PR c++/53540 - using fails to be equivalent to typedef

[Dodji Seketeli <dodji at redhat dot com>]

Hello,

In the example of this problem report, during the substituting of int
into 'function', tsubst_aggr_type fails for the alias ctxt1.  This is
because TYPE_TEMPLATE_INFO looks for the TEMPLATE_INFO of the ctxt1
alias at the wrong place and was wrongly finding it to be NULL.
Namely, it was looking for it in the DECL_TEMPLATE_INFO of the
declaration of the type -- as if ctxt1 was an alias template
specialization -- rather than looking of it in its
CLASSTYPE_TEMPLATE_INFO.

Fixed thus.  The second hunk of the patch is just to prevent the
compiler from crashing when primary_template_instantiation_p is passed
an alias of a class template instantiation.

Bootstrapped and tested on x86_64-unknown-linux-gnu against trunk.

gcc/cp

	* cp-tree.h (TYPE_TEMPLATE_INFO): For an alias that is not an
	instance of alias template, don't look for its TEMPLATE_INFO in
	its declaration.
	* pt.c (primary_template_instantiation_p): Don't crash on an alias
	that is not an instance of a template.

gcc/testsuite/

	* g++.dg/cpp0x/alias-decl-21.C: New test.
---
 gcc/cp/cp-tree.h                           |    4 ++--
 gcc/cp/pt.c                                |    1 +
 gcc/testsuite/g++.dg/cpp0x/alias-decl-21.C |   24 ++++++++++++++++++++++++
 3 files changed, 27 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/alias-decl-21.C

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 44f3ac1..64a8830 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -2634,8 +2634,8 @@ extern void decl_shadowed_for_var_insert (tree, tree);
    template info for the alias template, not the one (if any) for the
    template of the underlying type.  */
 #define TYPE_TEMPLATE_INFO(NODE)					\
-  (TYPE_ALIAS_P (NODE)							\
-   ? ((TYPE_NAME (NODE) && DECL_LANG_SPECIFIC (TYPE_NAME (NODE)))	\
+  ((TYPE_ALIAS_P (NODE) && DECL_LANG_SPECIFIC (TYPE_NAME (NODE)))	\
+   ? (DECL_LANG_SPECIFIC (TYPE_NAME (NODE))				\
       ? DECL_TEMPLATE_INFO (TYPE_NAME (NODE))				\
       : NULL_TREE)							\
    : ((TREE_CODE (NODE) == ENUMERAL_TYPE)				\
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index ad81bab..3163bd4 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -2854,6 +2854,7 @@ primary_template_instantiation_p (const_tree t)
   else if (TYPE_P (t)
 	   && TYPE_TEMPLATE_INFO (t)
 	   && PRIMARY_TEMPLATE_P (TYPE_TI_TEMPLATE (t))
+	   && DECL_LANG_SPECIFIC (TYPE_NAME (t))
 	   && DECL_TEMPLATE_INSTANTIATION (TYPE_NAME (t)))
     return true;
   return false;
diff --git a/gcc/testsuite/g++.dg/cpp0x/alias-decl-21.C b/gcc/testsuite/g++.dg/cpp0x/alias-decl-21.C
new file mode 100644
index 0000000..b68fa93
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/alias-decl-21.C
@@ -0,0 +1,24 @@
+// Origin: PR c++/53540
+// { dg-do compile { target c++11 } }
+
+template <typename T>
+struct context
+{
+  typedef int type;
+};
+
+template <typename T>
+void function()
+{
+  using ctx1 = context<T>;
+  typename ctx1::type f1;
+
+  typedef context<T> ctx2;
+  typename ctx2::type f2;
+}
+
+int main()
+{
+  function<int>();
+}
+
-- 
		Dodji