c++: pack expansion arg vs non-pack parm checking ICE [PR118454]

c++: pack expansion arg vs non-pack parm checking ICE [PR118454]

During ahead of time template argument coercion, we handle the case of
passing a pack expansion to a non-pack parameter by breaking out early
and using the original unconverted arguments, deferring coercion until
instantiation time where we have concrete arguments.

This PR illustrates we still need to strip typedefs from the original
arguments in this case as in the ordinary case, for sake of our template
argument hashing/equivalence routines which assume template arguments
went through strip_typedefs.

Since we're using the unconverted arguments we need to preserve
injected-class-name typedefs because we use them to distinguish passing
an injected-class-name vs the corresponding specialization as the
argument to a template template parameter (the former is valid, the
latter isn't).

	PR c++/118454

gcc/cp/ChangeLog:

	* cp-tree.h (STF_KEEP_INJ_CLASS_NAME): Define.
	* pt.cc (iterative_hash_template_argument) <case tcc_type>:
	Clarify comment for when we'd see an alias template
	specialization here.
	(coerce_template_parms): Strip typedefs (except for
	injected-class-names) in the pack expansion early break cases
	that defer coercion.
	* tree.cc (strip_typedefs): Don't strip an injected-class-name
	if STF_KEEP_INJ_CLASS_NAME is set.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/variadic187.C: New test.

Reviewed-by: Jason Merrill <jason@redhat.com>