https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104641
--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Patrick Palka <ppa...@gcc.gnu.org>: https://gcc.gnu.org/g:d3b0dc686c00bfe9e7f4fe0490def68e9b92157a commit r12-7633-gd3b0dc686c00bfe9e7f4fe0490def68e9b92157a Author: Patrick Palka <ppa...@redhat.com> Date: Sat Mar 12 15:00:51 2022 -0500 c++: naming a dependently-scoped template for CTAD [PR104641] In order to be able to perform CTAD for a dependently-scoped template (such as A<T>::B in the testcase below), we need to permit a typename-specifier to resolve to a template as per [dcl.type.simple]/3, at least when it appears in a CTAD-enabled context. This patch implements this using a new tsubst flag tf_tst_ok to control when a TYPENAME_TYPE is allowed to name a template, and sets this flag when substituting into the type of a CAST_EXPR, CONSTRUCTOR or VAR_DECL (each of which is a CTAD-enabled context). PR c++/104641 gcc/cp/ChangeLog: * cp-tree.h (tsubst_flags::tf_tst_ok): New flag. * decl.cc (make_typename_type): Allow a typename-specifier to resolve to a template when tf_tst_ok, in which case return a CTAD placeholder for the template. * pt.cc (tsubst_decl) <case VAR_DECL>: Set tf_tst_ok when substituting the type. (tsubst): Clear tf_tst_ok and remember if it was set. <case TYPENAME_TYPE>: Pass tf_tst_ok to make_typename_type appropriately. (tsubst_copy) <case CAST_EXPR>: Set tf_tst_ok when substituting the type. (tsubst_copy_and_build) <case CAST_EXPR>: Likewise. <case CONSTRUCTOR>: Likewise. gcc/testsuite/ChangeLog: * g++.dg/cpp1z/class-deduction107.C: New test.
