Error -> Except migration
ganesh at earth.li
Tue Mar 3 07:32:09 UTC 2015
In recent versions of transformers, 'ErrorT' has been deprecated in
favour of 'ExceptT':
This doesn't seem like a trivial like-for-like replacement since the
implementation of 'fail' is different - in ErrorT it produces an
exception within the ErrorT itself, and in ExceptT it just calls fail in
the underlying monad.
Is there any guidance or simple trick to find if a program is relying on
the old behaviour? Otherwise migrating could be rather
painful/dangerous, particularly as tests often don't cover exceptional
I've spent a while searching for past discussion of the change, but
haven't found anything, so please do point me at anything relevant if
this has already been discussed.
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