Deniz Mert Edincik

This is on FVM side unfortunately.

Tracked here: https://github.com/onflow/flow-go/issues/3387

I looked into this little, I believe fvm should be the place for the fix. ( they are already planning parallel pre processing already afaik )

@janezpodhostnik any chance you can retry this test with the `--persist` option ? I think can be memstore to blame.

This is fixed with new badger InMemory backend, I tried with 10k random transactions.

Very good idea, also we can add something like `borrowNFTSafe(id: UInt64): &NFT?` for convenience. I think computation there will be not much problem, checking should be `O(logN)` Maybe in Cadence...

Very good and much better than the current standard. I left few minor comments.

> In the future, if you're submitting a Cadence FLIP, please add some people from the Cadence team (e.g. myself, @turbolent, @SupunS and @robert-e-davidson3) as reviewers; otherwise we don't get...

> Allowing addition would lead to effectively allowing field updates, i.e. changing the type of a field, by first removing the field, then adding it back with a different type....

For me, also I think in the design of Cadence, optional variable means more than variable can be nil. ( though I can be wrong, maybe @turbolent can clarify more...