https://gcc.gnu.org/bugzilla/show_bug.cgi?id=48665
--- Comment #16 from Jonathan Wakely <redi at gcc dot gnu.org> --- It's not valid. [expr.typeid] p5 says typeid(cv T) is the same as typeid(T) but that isn't relevant here. 'void () const' is not the cv-qualified version of 'void ()', because there are no cv-qualified function types. See [dcl.fct] p7. 'void () const' is a function type with a cv-qualifier-seq and can only appear in a few specific places, which does not include a typeid expression. See [dcl.fct] p6.
