add comment to explain rlp_unsigned_bytes (#1367)

* add comment for rlp_unsigned_bytes

* rename chain_id

Author: DreamWuGit

bus-mapping/src/circuit_input_builder/transaction.rs

@@ -194,7 +194,8 @@ pub struct Transaction {
     pub signature: Signature,
     /// RLP bytes
     pub rlp_bytes: Vec<u8>,
-    /// RLP bytes for signing
+    /// RLP bytes for signing, only used for PreEip155 tx without chain_id
+    /// for other tx types: rlp == rlp_unsigned.
     pub rlp_unsigned_bytes: Vec<u8>,
     /// RLP bytes for signed tx
     pub rlp_signed_bytes: Vec<u8>,

eth-types/src/geth_types.rs

@@ -287,7 +287,8 @@ pub struct Transaction {
 
     /// RLP bytes
     pub rlp_bytes: Vec<u8>,
-    /// RLP unsigned bytes
+    /// RLP unsigned bytes, only used for PreEip155 tx without chain_id
+    /// for other tx types: rlp == rlp_unsigned.
     pub rlp_unsigned_bytes: Vec<u8>,
     // TODO: add rlp_signed_bytes as well ?
     /// Transaction hash