use Infallible for memory db's error type (bluealloy#196)

* use Infallible for memory db's error type

* std to core

* chore: rustfmt

crates/revm/src/db/in_memory_db.rs

@@ -2,6 +2,7 @@ use super::{DatabaseCommit, DatabaseRef};
 use crate::{interpreter::bytecode::Bytecode, Database, KECCAK_EMPTY};
 use crate::{Account, AccountInfo, Log};
 use alloc::vec::Vec;
+use core::convert::Infallible;
 use hashbrown::{hash_map::Entry, HashMap as Map};
 use primitive_types::{H160, H256, U256};
 use sha3::{Digest, Keccak256};
@@ -325,7 +326,7 @@ impl<ExtDB: DatabaseRef> DatabaseRef for CacheDB<ExtDB> {
 pub struct EmptyDB();
 
 impl DatabaseRef for EmptyDB {
- type Error = ();
+ type Error = Infallible;
  /// Get basic account information.
  fn basic(&self, _address: H160) -> Result<Option<AccountInfo>, Self::Error> {
  Ok(None)
@@ -361,7 +362,7 @@ impl BenchmarkDB {
 }
 
 impl Database for BenchmarkDB {
- type Error = ();
+ type Error = Infallible;
  /// Get basic account information.
  fn basic(&mut self, address: H160) -> Result<Option<AccountInfo>, Self::Error> {
  if address == H160::zero() {