"assignment to discriminant changes object branch"

[stefantalpalaru]

Compile time:

/mnt/sda3/storage/CODE/status/nim-beacon-chain/vendor/nim-confutils/confutils.nim(597, 27) Warning: Potential object case transition, instantiate new object instead [CaseTransition]
/mnt/sda3/storage/CODE/status/nim-beacon-chain/vendor/nim-confutils/confutils.nim(599, 27) Warning: Potential object case transition, instantiate new object instead [CaseTransition]

Run time (in nim-beacon-chain, running make eth2_network_simulation):

Error while processing the 'cmd' parameter:
assignment to discriminant changes object branch; compile with -d:nimOldCaseObjects for a transition period

[zah]

The new more restrictive behavior of the Nim case object makes life too difficult for libraries such as nim-seriazation and nim-confutils. For this reason, I recommend setting -d:nimOldCaseObjects globally for all of our projects. I'll try to negotiate a new Nim feature that will solve the problem in the long run.

[stefantalpalaru]

setting -d:nimOldCaseObjects globally

I just did that for nim-beacon-chain. Will do the same for Nimbus.

[mratsim]

See also: nim-lang/RFCs#56

[jangko]

still need support from nim compiler to fix this issue, see this bug nim-lang/Nim#19547