https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91953
--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jason Merrill <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:8fda2c274ac66d60c1dfc1349e9efb4e8c2a3580 commit r10-6416-g8fda2c274ac66d60c1dfc1349e9efb4e8c2a3580 Author: Jason Merrill <ja...@redhat.com> Date: Mon Feb 3 11:11:55 2020 -0500 c++: Allow parm of empty class type in constexpr. Since copying a class object is defined in terms of the copy constructor, copying an empty class is OK even if it would otherwise not be usable in a constant expression. Relatedly, using a parameter as an lvalue is no more problematic than a local variable, and calling a member function uses the object as an lvalue. PR c++/91953 * constexpr.c (potential_constant_expression_1) [PARM_DECL]: Allow empty class type. [COMPONENT_REF]: A member function reference doesn't use the object as an rvalue.
