Re: Benefit of the effect system?

[mratsim]

We use it in our code to:

  * Enforce noSideEffect (i.e. no access to globals, including stdin/stdout).
  * Enforce handling of recoverable exceptions and make sure all kinds of 
exceptions that can be thrown in inner function calls are accounted for or 
handled or considered irrecoverable:
    * Serialization 
[https://github.com/status-im/nim-beacon-chain/blob/db92c2f25/beacon_chain/ssz/ssz_serialization.nim#L4](https://github.com/status-im/nim-beacon-chain/blob/db92c2f25/beacon_chain/ssz/ssz_serialization.nim#L4)
    * Fuzzing 
[https://github.com/status-im/nim-beacon-chain/blob/4a2e1806/nfuzz/libnfuzz.nim#L37](https://github.com/status-im/nim-beacon-chain/blob/4a2e1806/nfuzz/libnfuzz.nim#L37)
  * You can force `{.noSideEffect.}` and `{.gcsafe.}` with a block
    * 
[https://github.com/status-im/nim-beacon-chain/blob/4a2e1806/beacon_chain/fork_choice/fork_choice.nim#L161-L166](https://github.com/status-im/nim-beacon-chain/blob/4a2e1806/beacon_chain/fork_choice/fork_choice.nim#L161-L166)