own ID as parent ID exception about tree

[BlueM]

The reason I didn’t use === is that one the one hand, I would not have expected mixed datatypes for the IDs, but also as it might impose more work on users to make the input data type-safe.

However, if string IDs and numeric IDs are used in the same dataset, this is of course a bug. Thanks for reporting. On the other hand, simply using === in my opinion is not the optimal solution, as you can construct cases where the invalid parent reference might not be detected. See a75b2f7#diff-d6a892aa7d058c8f3e87ef9717e5cf4bR300 for a test where === would fail. Instead, I chose to use (string) typecasting plus ===; the test is here: a75b2f7#diff-d6a892aa7d058c8f3e87ef9717e5cf4bR313

One more remark: when submitting a pull request, you should not change the project’s name in composer.json.