+ /// toNullTerminatedStringRef - This returns the twine as a single null
+ /// terminated StringRef if it can be represented as such. Otherwise the
+ /// twine is written into the given SmallVector and a StringRef to the
+ /// SmallVector's data is returned.
+ ///
+ /// The returned StringRef's size does not include the null terminator.
+ StringRef toNullTerminatedStringRef(SmallVectorImpl<char> &Out) const;
+