ensure proper writing of codeunits

[ExpandingMan]

There is a really nasty fallback for writing codeunits in Base:

write(io::IO, s::CodeUnits) = write(io, s.s)

what this means for InlineString is that it is writing the canonical binary representation of the InlineString, not the code units that are correctly returned by codeunits. This leads to confusing disasters like this.

This is a good demonstration of why it's really bad not to have a formal AbstractString interface. We really ought to open an issue in Base but it might take some background research to open an intelligent and actionable issue.

[quinnj]

Oof, that is indeed unfortunate. Sorry for the hassle and thanks for the fix here.

[ExpandingMan]

Yeah no worries, that would have been incredibly hard to catch for sure. Again, it's really more of a Base problem in my opinion.

[ExpandingMan]

This could use a tag when you get a chance.