EVM: error handling

[jochem-brouwer]

Part of #3712

Excerpt from evm/errors.ts:

export enum EvmErrorCode {
  UNSUPPORTED_FEATURE = 'EVM_ERROR_UNSUPPORTED_FEATURE',
  RUNTIME_ERROR = 'EVM_ERROR_RUNTIME_ERROR',
}

type EvmRuntimeErrorType = {
  code: EvmErrorCode.RUNTIME_ERROR
  reason: RuntimeErrorMessage | EOFError
} & (
  | { reason: RuntimeErrorMessage.REVERT; revertBytes: Uint8Array }
  | { reason: Exclude<RuntimeErrorMessage, RuntimeErrorMessage.REVERT> | EOFError }
)

export type EvmErrorType = { code: EvmErrorCode.UNSUPPORTED_FEATURE } | EvmRuntimeErrorType

export class EvmError extends EthereumJSError<EvmErrorType> {
  constructor(type: EvmErrorType, message?: string) {
    super(type, message)
  }
}

This is a Proof-of-Concept (I still need to do some cycles to clean this up though) which shows that we now have two EVM error types: a UNSUPPORTED_FEATURE or a RUNTIME_ERROR. In case of a RUNTIME_ERROR, typescript now demands a reason field in the error (this could for instance be "stack overflow", "stack underflow", etc.

What is nice: for the REVERT reason it demands a revertBytes field, which is actually the reverted bytes in case the EVM runs into a revert (from these bytes error messages can be derived, such as solidity revert strings!).

Errors now look like this:

(I had added the error.code field but I think we should keep it at error.type.code).

The error handler (taken / inspired from lodestar: https://github.com/ChainSafe/lodestar/blob/unstable/packages/utils/src/errors.ts) allows to add custom error classes (see EvmError class in this case, can add extra constructor arguments for environment situation), and also has a message argument which allows for custom message strings.

Note: super WIP. I am not completely satisfied yet with the results, because now EVM has a huge code bloat due to instantiating these error messages. I have to find a way to go back to the "old versions" (trap(ERROR.OUT_OF_GAS)) but still remaining type-safety (for the REVERT error string for instance).

Note, tests will likely fail because of the updated error format.

[Maliksb11]

Okay 👍