https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109160
--- Comment #2 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:a5de246535db1b4fdc61287f27de0fdd074fc4b3 commit r13-6971-ga5de246535db1b4fdc61287f27de0fdd074fc4b3 Author: Patrick Palka <ppa...@redhat.com> Date: Sat Apr 1 12:01:30 2023 -0400 c++: NTTP constraint depending on outer parms [PR109160] Here we're crashing during satisfaction for the NTTP 'C<B> auto V' ultimately because convert_template_argument / unify don't pass all outer template arguments to do_auto_deduction, and during satisfaction we need to know all arguments. While these callers do pass some outer arguments, they are only sufficient to properly substitute the (level-lowered) 'auto' and are not necessarily the entire set. Fortunately it seems these callers have access to the full set of outer arguments via convert_template_argument's 'in_decl' parameter and unify's 'tparms' parameter. So this patch adds a new parameter to do_auto_deduction, used only during adc_unify deduction, through which these callers can pass the enclosing (partially instantiated) template and from which do_auto_deduction can obtain _all_ outer template arguments for sake of satisfaction. This patch also ensures that the 'in_decl' argument passed to coerce_template_parms is always a TEMPLATE_DECL, which in turn allows us to pass it as-is to do_auto_deduction; the only coerce_template_parms caller that needed adjustment was tsubst_decl it seems. PR c++/109160 gcc/cp/ChangeLog: * cp-tree.h (do_auto_deduction): Add defaulted tmpl parameter. * pt.cc (convert_template_argument): Pass 'in_decl' as 'tmpl' to do_auto_deduction. (tsubst_decl) <case VAR_/TYPE_DECL>: Pass 'tmpl' instead of 't' as 'in_decl' to coerce_template_parms. (unify) <case TEMPLATE_PARM_INDEX>: Pass TPARMS_PRIMARY_TEMPLATE as 'tmpl' to do_auto_deduction. (do_auto_deduction): Document default arguments. Rename local variable 'tmpl' to 'ctmpl'. Use 'tmpl' to obtain a full set of template arguments for satisfaction in the adc_unify case. gcc/testsuite/ChangeLog: * g++.dg/cpp2a/concepts-placeholder12.C: New test.
