https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68683
Bug ID: 68683 Summary: [concepts] function satisfy_argument_deduction_constraint modifies a type tree node but leaves TYPE_CANONICAL unchanged Product: gcc Version: 6.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: ryan.burn at gmail dot com Target Milestone: --- The below code causes a "same canonical type node for different types" ICE because the function satisfy_argument_deduction_constraint changes the PLACEHOLDER_TYPE_CONSTRAINTS for a tree node but leaves the TYPE_CANONICAL value unchanged. Since PLACEHOLDER_TYPE_CONSTRAINTS are used when checking for equality, \ the TYPE_CANONICAL value is no longer valid for the changed type which triggers the ICE. /////////////////////////////////////////////////////////////////// template <typename, typename> struct is_same { static constexpr bool value = true; }; template <typename T, typename U> concept bool Same = is_same<T, U>::value; template <typename T> concept bool Integral = requires{ { T() } -> Same<typename T::value_type>; }; struct A { using value_type = bool; }; int main() { Integral<A>; Integral<A>; return 0; } ///////////////////////////////////////////////////////////////////