add slot uniqueness check and test for EIP-7928

core/types/bal/bal_encoding.go

@@ -159,6 +159,19 @@ func (e *AccountAccess) validate() error {
 		return errors.New("storage read slots not in lexicographic order")
 	}
 
+	// EIP-7928: a slot must not appear in both storage_changes and storage_reads.
+	if len(e.StorageWrites) > 0 && len(e.StorageReads) > 0 {
+		changeSlots := make(map[common.Hash]struct{}, len(e.StorageWrites))
+		for _, sc := range e.StorageWrites {
+			changeSlots[sc.Slot] = struct{}{}
+		}
+		for _, key := range e.StorageReads {
+			if _, exists := changeSlots[key]; exists {
+				return fmt.Errorf("storage key %s in both changes and reads", key)
+			}
+		}
+	}
+
 	// Check the balance changes are sorted in order
 	if !slices.IsSortedFunc(e.BalanceChanges, func(a, b encodingBalanceChange) int {
 		return cmp.Compare[uint16](a.TxIdx, b.TxIdx)

core/types/bal/bal_test.go

@@ -252,3 +252,26 @@ func TestBlockAccessListValidation(t *testing.T) {
 		t.Fatalf("Unexpected validation error: %v", err)
 	}
 }
+
+func TestBlockAccessListSlotUniqueness(t *testing.T) {
+	var addr common.Address
+	addr[19] = 0x01
+	slot := common.HexToHash("0x01")
+
+	ac := AccountAccess{
+		Address: addr,
+		StorageWrites: []encodingSlotWrites{
+			{
+				Slot: slot,
+				Accesses: []encodingStorageWrite{
+					{TxIdx: 0, ValueAfter: [32]byte{1}},
+				},
+			},
+		},
+		StorageReads: [][32]byte{slot},
+	}
+	bal := BlockAccessList{[]AccountAccess{ac}}
+	if err := bal.Validate(); err == nil {
+		t.Fatal("expected error for slot in both changes and reads")
+	}
+}