:relfileprefix: ../../../
[#boost-urls-grammar-is_rule-0f]

= xref:boost.adoc[pass:[boost]]::xref:boost/urls.adoc[pass:[urls]]::xref:boost/urls/grammar.adoc[pass:[grammar]]::is_rule



== Synopsis

Declared in header `<https://www.github.com/boostorg/url/blob/develop/include/boost/url/grammar/type_traits.hpp#L54[boost/url/grammar/type_traits.hpp,window=blank_]>`

[source,cpp,subs="verbatim,macros,-callouts"]
----
template<class T>
struct xref:boost/urls/grammar/is_rule-0a.adoc[pass:[is_rule]]<T, xref:boost/urls/void_t.adoc[void_t]<decltype(std::declval<system::result<typename T::value_type>&>() =
                std::declval<T const&>().parse(
                    std::declval<char const*&>(),
                    std::declval<char const*>()))>>
    : xref:std.adoc[std]::is_nothrow_copy_constructible<T>;
----