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

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

Friendly pinging this patch.

Dodji Seketeli <dodji@redhat.com> writes:

> 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>();
> +}
> +

Let's move the alias template case from primary_template_instantiation_p 
into alias_template_specialization_p and call the latter from the 
former.  And also call it from tsubst.

Jason