https://gcc.gnu.org/g:2bf057c53e97004034ed1528d850a214372305b8
commit r16-6141-g2bf057c53e97004034ed1528d850a214372305b8 Author: Patrick Palka <[email protected]> Date: Mon Dec 15 14:30:53 2025 -0500 c++: nested typename type resolving to wildcard type [PR122752] Here typename A<S>::VertexSet::size_type within the out-of-line declaration is initially parsed at namespace scope, so the LHS A<S>::VertexSet is treated as a dependent name and represented as a TYPENAME_TYPE with tag_type as class_type.[1] Once we realize we're parsing a member declarator we call maybe_update_decl_type to reprocess the TYPENAME_TYPE relative to the class template scope, during which make_typename_type succeeds in resolving the lookup and returns the member typedef VertexSet (to the TEMPLATE_TYPE_PARM S). But then the caller tsubst complains that this result isn't a class type as per the tag_type. This patch just relaxes tsubst to allow TYPENAME_TYPE getting resolved to a wildcard type regardless of the tag_type. This does mean we lose information about the tag_type during a subsequent tsubst, but that's probably harmless (famous last words). [1]: The tag_type should probably be scope_type. Changing this seems to be a matter of changing cp_parser_qualifying_entity to pass scope_type instead of class_type, but I don't feel confident about that and it seems risky. I then got confused as to why that function passes none_type in the !type_p case; to me it should use scope_type unconditionally, but doing so breaks things. This approach seems safer to backport. PR c++/122752 gcc/cp/ChangeLog: * pt.cc (tsubst) <case TYPENAME_TYPE>: Allow TYPENAME_TYPE resolving to another wildcard type. gcc/testsuite/ChangeLog: * g++.dg/template/dependent-name19.C: New test. Reviewed-by: Jason Merrill <[email protected]> Diff: --- gcc/cp/pt.cc | 2 +- gcc/testsuite/g++.dg/template/dependent-name19.C | 22 ++++++++++++++++++++++ 2 files changed, 23 insertions(+), 1 deletion(-) diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc index f13b3436eb3f..a5d932ac9ea6 100644 --- a/gcc/cp/pt.cc +++ b/gcc/cp/pt.cc @@ -17342,7 +17342,7 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl) f = TREE_TYPE (f); } - if (TREE_CODE (f) != TYPENAME_TYPE) + if (!WILDCARD_TYPE_P (f)) { if (TYPENAME_IS_ENUM_P (t) && TREE_CODE (f) != ENUMERAL_TYPE) { diff --git a/gcc/testsuite/g++.dg/template/dependent-name19.C b/gcc/testsuite/g++.dg/template/dependent-name19.C new file mode 100644 index 000000000000..87fe7c7e5c04 --- /dev/null +++ b/gcc/testsuite/g++.dg/template/dependent-name19.C @@ -0,0 +1,22 @@ +// PR c++/122752 + +struct set { + typedef unsigned size_type; + unsigned size() { return 42; } +}; + +template<class S> +struct A { + typedef S VertexSet; + typename VertexSet::size_type size(); + VertexSet vertices_; +}; + +template<class S> +inline typename A<S>::VertexSet::size_type A<S>::size() +{ return vertices_.size(); } + +int main() { + A<set> a; + a.size(); +}
