fix some "labeled" bugs

[Taraflex]

Ast traversing is buggy. I fix some errors and mark with "todo" some suspicious places for which I didn't come up with test cases.

All places with return node; and return; require checks.

I think it would be a good idea to rewrite the tree traversal so that there is only one return for the function. This would help to avoid errors related to forgetting to traversing child nodes.

[Taraflex]

The last commit should not have been included in the pull request. My mistake.