revm: add Database Either helper type (#12240)

crates/revm/src/either.rs

@@ -0,0 +1,52 @@
+use alloy_primitives::{Address, B256, U256};
+use revm::{
+    primitives::{AccountInfo, Bytecode},
+    Database,
+};
+
+/// An enum type that can hold either of two different [`Database`] implementations.
+///
+/// This allows flexible usage of different [`Database`] types in the same context.
+#[derive(Debug, Clone)]
+pub enum Either<L, R> {
+    /// A value of type `L`.
+    Left(L),
+    /// A value of type `R`.
+    Right(R),
+}
+
+impl<L, R> Database for Either<L, R>
+where
+    L: Database,
+    R: Database<Error = L::Error>,
+{
+    type Error = L::Error;
+
+    fn basic(&mut self, address: Address) -> Result<Option<AccountInfo>, Self::Error> {
+        match self {
+            Self::Left(db) => db.basic(address),
+            Self::Right(db) => db.basic(address),
+        }
+    }
+
+    fn code_by_hash(&mut self, code_hash: B256) -> Result<Bytecode, Self::Error> {
+        match self {
+            Self::Left(db) => db.code_by_hash(code_hash),
+            Self::Right(db) => db.code_by_hash(code_hash),
+        }
+    }
+
+    fn storage(&mut self, address: Address, index: U256) -> Result<U256, Self::Error> {
+        match self {
+            Self::Left(db) => db.storage(address, index),
+            Self::Right(db) => db.storage(address, index),
+        }
+    }
+
+    fn block_hash(&mut self, number: u64) -> Result<B256, Self::Error> {
+        match self {
+            Self::Left(db) => db.block_hash(number),
+            Self::Right(db) => db.block_hash(number),
+        }
+    }
+}

crates/revm/src/lib.rs

@@ -22,3 +22,6 @@ pub mod test_utils;
 
 // Convenience re-exports.
 pub use revm::{self, *};
+
+/// Either type for flexible usage of different database types in the same context.
+pub mod either;