[Core Protocol] Why have the L2 Smart Contracts been implemented as predeploys instead of precompiles?

[PaulRBerg]

Did you check the documentation?

• Yes

Did you read the specs?

• Yes
• No

Did you check for duplicate questions?

• Yes

Issue Description

I was looking at the Smart Contracts overview in the docs, and I was wondering - why have the L2 contracts been implemented as predeploys instead of precompiles?

That is, why write these in Solidity instead of in the client software (in op-geth)? Wouldn't it have been more efficient and less error-prone to do that? I imagine that upgrading the client software is easier than upgrading smart contracts via the upgradeability pattern.

• BaseFeeVault
• GasPriceOracle
• L1Block
• L1FeeVault
• L2CrossDomainMessenger
• L2ERC721Bridge
• L2StandardBridge
• L2ToL1MessagePasser
• SequencerFeeVault ​

[hash1go]

Hello.
Perhaps the decision was made to have the same specifications as other contracts for better interoperability.
However, I would need to ask the engineers on the OP team to know for sure. If resolving this question is a high priority, I will ask the OP team.

[PaulRBerg]

Got it.

Not high-priority, no. But thanks for offering to ask.

[PaulRBerg]

Could the rationale behind this have been to make Optimism easier to fault proof via Cannon?

cc @IaroslavMazur

[sbvegan]

I suspect part of the reason is to not modify the EVM further. A guiding development foundation is evm equivalence and handling the L2 smart contracts outside of the evm adheres to that.

[PaulRBerg]

Thank you for your answer.

[sbvegan]

Yeah sorry for the late reply. I did confirm this is the reason with an engineer internally.