template<template<class> class use>
tk::grm::is_keyword struct

Compile-time test functor verifying that type U is a keyword.

This functor is used for triggering a compiler error if any of the expected option values is not in the keywords pool of the grammar. It is used inside of a brigand::for_each to run a compile-time loop over an type sequence, e.g., a list, which verifies that each type in the list is a valid keyword that defines the type 'pegtl_string'.