23 Strings library [strings]

23.3 String view classes [string.view]

23.3.6 Hash support [string.view.hash]

template<> struct hash<string_view>; template<> struct hash<u8string_view>; template<> struct hash<u16string_view>; template<> struct hash<u32string_view>; template<> struct hash<wstring_view>;
The specialization is enabled ([unord.hash]).
[Note 1: 
The hash value of a string view object is equal to the hash value of the corresponding string object ([basic.string.hash]).
— end note]