https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91259
--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> --- (In reply to David Stone from comment #0) > libstdc++ contains many expressions that are not parenthesized Many? > that do not meet these requirements (this was not true of the Concepts TS, > but as changed as part of standardization). For instance, in <memory>, we > have `requires ! _Std_pair<_Tp>`. I'm pretty sure that's the only use of concepts in the whole library.
