bsl::operator+

template<
    class CHAR_TYPE,
    class CHAR_TRAITS,
    class ALLOCATOR,
    class STRING_VIEW_LIKE_TYPE>
bsl::basic_string<CHAR_TYPE, CHAR_TRAITS, ALLOCATOR>
operator+(
    STRING_VIEW_LIKE_TYPE const& lhs,
    basic_string<CHAR_TYPE, CHAR_TRAITS, ALLOCATOR>&& rhs);