c++: 'typename T::X' vs 'struct T::X' lookup [PR109420]

c++: 'typename T::X' vs 'struct T::X' lookup [PR109420]

r13-6098-g46711ff8e60d64 made make_typename_type no longer ignore
non-types during the lookup, unless the TYPENAME_TYPE in question was
followed by the :: scope resolution operator.  But there is another
exception to this rule: we need to ignore non-types during the lookup
also if the TYPENAME_TYPE was named with a tag other than 'typename',
such as 'struct' or 'enum', since in that case we're dealing with an
elaborated-type-specifier and so [basic.lookup.elab] applies.  This
patch implements this additional exception.

	PR c++/109420

gcc/cp/ChangeLog:

	* decl.cc (make_typename_type): Also ignore non-types during the
	lookup if tag_type corresponds to an elaborated-type-specifier.
	* pt.cc (tsubst) <case TYPENAME_TYPE>: Pass class_type or
	enum_type as tag_type to make_typename_type accordingly instead
	of always passing typename_type.

gcc/testsuite/ChangeLog:

	* g++.dg/template/typename27.C: New test.