https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124297
--- Comment #4 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Patrick Palka <[email protected]>: https://gcc.gnu.org/g:d0d3d4dde0b4712a3c39970ec8dcfe0782434d3e commit r16-7937-gd0d3d4dde0b4712a3c39970ec8dcfe0782434d3e Author: Patrick Palka <[email protected]> Date: Fri Mar 6 17:59:11 2026 -0500 c++: ICE mangling C auto... tparm [PR124297] After r16-7491, the constraint on a C auto... tparm is represented as a fold-expression (in TEMPLATE_PARM_CONSTRAINTS) instead of a concept-id (in PLACEHOLDER_TYPE_CONSTRAINTS). So we now need to strip this fold-expression before calling write_type_constraint, like we do in the type template parameter case a few lines below. PR c++/124297 gcc/cp/ChangeLog: * mangle.cc (write_template_param_decl) <case PARM_DECL>: Strip fold-expression before calling write_type_constraint. gcc/testsuite/ChangeLog: * g++.dg/cpp2a/concepts-variadic4.C: New test. Reviewed-by: Jason Merrill <[email protected]>
