We were doing a number of things wrong:
- Switching to the parent context in the else meant that we couldn't
break out of the else section anymore
- We were not validating the resulting values, and so the stack was
in a relatively unknown state after 'else'
This commit fixes these issues :^)
This isn't a complete conversion to ErrorOr<void>, but a good chunk.
The end goal here is to propagate buffer allocation failures to the
caller, and allow the use of TRY() with formatting functions.
