[Feature] change `EvmFactory` trait to let implementers use a stricter trait for the generic `DB` to give to the EVM

[Alessandro Mazza]

Describe the feature you would like

Right now the EvmFactory trait in the alloy-evm crate has an associated type called Evm that has a generic DB: alloy_evm::Database.

evm/crates/evm/src/evm.rs

Line 197 in 224bf74

     type Evm<DB: Database, I: Inspector<Self::Context<DB>>>: Evm< 

This makes it impossible in the concrete implementation to use a trait that is stricter than the alloy_evm::Database trait because of how Rust compiler works with generic defined on associated types (instead of the generic being defined in the trait itself - something like pub trait EvmFactory<DB: Database>.

Do you think it could make sense to change the trait such that it lets implementers use a stricter (meaning it's at least Database, but it may have additional requirements such as thread safety Send + Sync or clonable Clone) trait on the DB.

I'm down to help here if you give me some guidance and find the proposal appealing.

Additional context

No response

[Matthias Seitz]

pub trait EvmFactory<DB: Database>

this doesn't really work for how we intend to use it because this then requires slapping a generic all over the pace

have you tried restricting you impl like this

evm/crates/evm/src/tracing.rs

Lines 140 to 142 in 224bf74

 impl<E, T, Txs, F, O, Err> Iterator for TracerIter<'_, E, Txs, F> 
 where 
     E: Evm<DB: DatabaseCommit, Inspector: Clone>, 

maybe this could work for your use case?

[Alessandro Mazza]

maybe this could work for your use case?

thanks for the answer. As of now I'm trying to use a different strategy to overcome this issue - i.e. trying to make the DB implements alloy_evm::Database and move the stricter traits in different places.

I don't think what you suggest can be applied in the EvmFactory trait, specifically for the DB generic on the Evm associated type