address comments

Author: colinlyguo

rollup/internal/controller/relayer/l2_relayer_sanity.go

@@ -131,9 +131,17 @@ func (r *Layer2Relayer) getBatchesFromCalldata(info *CalldataInfo) ([]*dbBatchWi
 					return nil, nil, fmt.Errorf("failed to get L2 blocks for chunk %d: %w", chunk.Index, err)
 				}
 				for _, block := range blockWithL1Messages {
+					bn := block.Header.Number.Uint64()
+					seenL2 := false
 					for _, tx := range block.Transactions {
 						if tx.Type == types.L1MessageTxType {
-							l1MessagesWithBlockNumbers[block.Header.Number.Uint64()] = append(l1MessagesWithBlockNumbers[block.Header.Number.Uint64()], tx)
+							if seenL2 {
+								// Invariant violated: found an L1 after an L2 in the same block.
+								return nil, nil, fmt.Errorf("L1 message after L2 tx in block %d", bn)
+							}
+							l1MessagesWithBlockNumbers[bn] = append(l1MessagesWithBlockNumbers[bn], tx)
+						} else {
+							seenL2 = true
 						}
 					}
 				}