https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121822
--- Comment #5 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-15 branch has been updated by Patrick Palka <[email protected]>: https://gcc.gnu.org/g:7f7101cdc372c47e070e356e3e8fe980f5a1676e commit r15-10838-g7f7101cdc372c47e070e356e3e8fe980f5a1676e Author: Patrick Palka <[email protected]> Date: Tue Feb 17 11:21:45 2026 -0500 c++: void(concept-id) evaluation [PR121822] Similar to r16-7056-g22f51c0f5e62a4, here the expression within the decltype void(Derived<T>) is non-dependent enough that we instantiate/fold it immediately, during which however convert_to_void tries to evaluate the concept-id, which fails. When in an unevaluated context such as decltype I don't think convert_to_void should be evaluating concept-ids. PR c++/121822 gcc/cp/ChangeLog: * cvt.cc (convert_to_void): Don't evaluate a concept-id in an unevaluated context. gcc/testsuite/ChangeLog: * g++.dg/cpp2a/concepts-decltype6.C: New test. Reviewed-by: Jason Merrill <[email protected]> (cherry picked from commit 44a51e8c7037eacd4315df0e84bf51e6e4021088)
