Support for stateful precompiles

[palango]

Motivation

I'm trying to add support for the Celo transfer precompile to anvil. This precompile transfers funds and therefore requires access to the state database.

This also has been requested in #7703.

Solution

Below is what I managed to do so far, along with a couple of questions.

Add the precompile. As far as I can tell I cannot get access to the state from the Env. So I need to use ContextPrecompile instead to access state through InnerEvmContext.

#[derive(Debug, Clone)]
pub struct Transfer;

impl<DB: revm::Database> ContextStatefulPrecompileMut<DB> for Transfer {
    fn call_mut(
        &mut self,
        bytes: &Bytes,
        _gas_price: u64,
        evmctx: &mut revm::InnerEvmContext<DB>,
    ) -> PrecompileResult {
        let amount = U256::from(123);

        evmctx.journaled_state.transfer(&FROM_ADDR, &TO_ADDR, amount, &mut evmctx.db);
        Ok(PrecompileOutput { gas_used: 100, bytes: bytes.clone() })
    }
}

In order to use inject_precompiles(&mut evm, CustomPrecompileFactory.precompiles()); as in the example, a change to the signature of PrecompileFactory is required:

pub trait PrecompileFactory<DB: revm::Database>: Send + Sync + Unpin + Debug {
    /// Returns a set of precompiles to extend the EVM with.
    fn precompiles(&self) -> Vec<(Address, ContextPrecompile<DB>)>;
}

This new generic parameter now leads to errors through the whole codebase which I haven't managed to solve so far.
Is there a simpler way than propagating the generic parameter through the whole codebase? Any ideas or recommendations are appreciated.