fix timelock nits (#39)

* - add nice error message for queueing a canceled set of calls
- prevent cancel from being called twice

* revert change to declare script

src/timelock.cairo

@@ -144,6 +144,7 @@ pub mod Timelock {
             let id = to_calls_id(calls);
             let execution_state = self.execution_state.read(id);
 
+            assert(execution_state.executed.is_zero(), 'ALREADY_EXECUTED');
             assert(execution_state.canceled.is_zero(), 'HAS_BEEN_CANCELED');
             assert(execution_state.created.is_zero(), 'ALREADY_QUEUED');
 
@@ -164,6 +165,7 @@ pub mod Timelock {
             let execution_state = self.execution_state.read(id);
             assert(execution_state.created.is_non_zero(), 'DOES_NOT_EXIST');
             assert(execution_state.executed.is_zero(), 'ALREADY_EXECUTED');
+            assert(execution_state.canceled.is_zero(), 'ALREADY_CANCELED');
 
             self
                 .execution_state

src/timelock_test.cairo

@@ -92,6 +92,23 @@ fn test_queue_cancel() {
     timelock.execute(single_call(transfer_call(token, recipient, 500_u256)));
 }
 
+#[test]
+#[should_panic(expected: ('ALREADY_CANCELED', 'ENTRYPOINT_FAILED'))]
+fn test_queue_cancel_twice() {
+    set_block_timestamp(1);
+    let timelock = deploy(get_contract_address(), 86400, 3600);
+
+    let token = deploy_token(get_contract_address(), 12345);
+    token.transfer(timelock.contract_address, 12345);
+
+    let recipient = contract_address_const::<12345>();
+
+    let id = timelock.queue(single_call(transfer_call(token, recipient, 500_u256)));
+
+    timelock.cancel(id);
+    timelock.cancel(id);
+}
+
 #[test]
 #[should_panic(expected: ('ALREADY_EXECUTED', 'ENTRYPOINT_FAILED'))]
 fn test_queue_execute_twice() {