142 struct BitString {  struct
143   using StorageType = BitStringChar::StorageType;  argument
151   // How many bits are needed to represent BitString[0..position)?  argument
171   // How many bits are needed for a BitStringChar at the position?  argument
181   // See also "BitString[N]" in the doc header.  argument
193   void SetAt(size_t idx, BitStringChar bitchar) {  in SetAt()  argument
206   // See also "StrLen(BitString)" in the doc header.  argument
211       BitStringChar bc = (*this)[i];  in Length()  argument
235   BitString() = default;  argument
249     return (*this) == BitString{};  in IsEmpty()  argument
255   BitString Truncate(size_t end) {  in Truncate()  argument
277 static_assert(BitSizeOf<BitString::StorageType>() >=  argument