https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96645
--- Comment #9 from Jason Merrill <jason at gcc dot gnu.org> ---
(In reply to Jason Merrill from comment #8)
> This is related to CWG1890, and the general issue that we don't currently
> parse on demand like we do instantiate on demand for templates.
("We" in this sentence is the C++ standard.)
