https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118698
--- Comment #19 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The trunk branch has been updated by Jason Merrill <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:94438ca82792063abf05823326695af25ab02d17 commit r15-9325-g94438ca82792063abf05823326695af25ab02d17 Author: Jason Merrill <ja...@redhat.com> Date: Tue Apr 8 15:53:34 2025 -0400 c++: lambda in concept [PR118698] When normalizing is_foo for <T>, we get to normalizing callable<decltype(...),T> for <T,foo>, which means substituting <T,foo> into <decltype(...),T>. Since r14-9938, because in_template_context is false we return the lambda unchanged, just with LAMBDA_EXPR_EXTRA_ARGS set, so the closure type still refers to the is_specialization_of tparms in its CLASSTYPE_TEMPLATE_INFO. So then in normalize_atom caching find_template_parameters walks over the parameter mapping; any_template_parm_r walks into the TREE_TYPE of a LAMBDA_EXPR without considering EXTRA_ARGS and finds a template parm from the wrong parameter list. But since r15-3530 we expect to set tf_partial when substituting with dependent arguments, so we should set that when normalizing. And then tf_partial causes TREE_STATIC to be set on the EXTRA_ARGS, meaning that those args will replace all the template parms in the rest of the lambda, so we can walk just the EXTRA_ARGS and ignore the rest. PR c++/118698 gcc/cp/ChangeLog: * constraint.cc (struct norm_info): Add tf_partial. * pt.cc (any_template_parm_r): Handle LAMBDA_EXPR_EXTRA_ARGS. gcc/testsuite/ChangeLog: * g++.dg/cpp2a/concepts-lambda22.C: New test.
