Function wire_wchar_width_of 

pub const fn wire_wchar_width_of(width: WcharWidth) -> WcharWidth

A scalar wchar’s width, as the byte layer names it.

It used to be read off WstringLengthPolicy::char16_size, on the reading that the scalar and the wstring’s code units cannot disagree. They can: rmw_cyclonedds_cpp writes two octets for a wchar member and four for a wstring’s units, so the width is its own axis and this only carries it down to zerodds-wire, which knows nothing about a policy.