https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104606
--- Comment #13 from Jonathan Wakely <redi at gcc dot gnu.org> --- (In reply to Andrew Pinski from comment #5) > (In reply to Jakub Jelinek from comment #4) > > Just wild guess, perhaps the PR98842 changes between 11.1 and 11.2? > > That would mean it is a bug in GCC 10.4 also :(. It's not, even though 10.4 has the library change. Compiling the test case with 10.4 works. But preprocessing with 10.4 and then compiling with 11.1 fails, confirming a front end change is to blame. Bisection shows it started to error with r11-2774 c++: Check satisfaction before non-dep convs. [CWG2369] It's very hard to use concepts to protect a template from hard errors due to unwanted instantiation if constraints aren't checked until after doing all substitution and checking of non-dependent conversions. It was pretty straightforward to insert the satisfaction check into the logic, but I needed to make the 3-parameter version of satisfy_declaration_constraints call push_tinst_level like the 2-parameter version already does. For simplicity, I also made it add any needed outer template arguments from the TEMPLATE_DECL to the args. The testsuite changes are mostly because this change causes unsatisfaction to cause deduction to fail rather than reject the candidate later in overload resolution. gcc/cp/ChangeLog: DR 2369 * cp-tree.h (push_tinst_level, push_tinst_level_loc): Declare. * constraint.cc (satisfy_declaration_constraints): Use add_outermost_template_args and push_tinst_level. * pt.c (add_outermost_template_args): Handle getting a TEMPLATE_DECL as the first argument. (push_tinst_level, push_tinst_level_loc): No longer static. (fn_type_unification): Check satisfaction before non-dependent conversions.
