message: [lang] Add tests for messages with no arguments and messages not starting with self
diff: @@ -26,7 +26,39 @@ fn using_self_val_in_message() {
  pub(external) fn with_self_value(self) {}
  }
  },
  - "contract messages must start with `&self` or `&mut self`"
  + "contract messages must operate on `&self` or `&mut self`"
  + )
  +}
  +
  +#[test]
  +fn using_non_self_in_message() {
  + assert_failure(
  + quote!{
  + struct TestContract {}
  + impl Deploy for TestContract {
  + fn deploy(&mut self) {}
  + }
  + impl TestContract {
  + pub(external) fn with_self_value(not_self: u32) {}
  + }
  + },
  + "contract messages must operate on `&self` or `&mut self`"
  + )
  +}
  +
  +#[test]
  +fn using_empty_message_args() {
  + assert_failure(
  + quote!{
  + struct TestContract {}
  + impl Deploy for TestContract {
  + fn deploy(&mut self) {}
  + }
  + impl TestContract {
  + pub(external) fn with_self_value() {}
  + }
  + },
  + "contract messages must operate on `&self` or `&mut self`"
  )
  }
  