I just need to add some tests; then, this will be ready to merge.

@JairusSW Heads up: this change definitely breaks transforms. Do you have anything to comment on this PR?

It looks like I forgot aboutif...

Okay, it appears that my code breaks something related to Flow flags, so more work on this PR is needed.

One issue is thatbreaking out of a labeled block sets theBreaks flag on the outer flow and messes with the function not appearing to always terminate.

Another issue is that acontinue (and likelybreak as well) from inside an inner loop to an outer loop won't set theContinues/ConditionallyContinues flow flag on the outer loop body's flow. This is a much more significant issue (since nested loops are the most common use of labels) and seems to be more difficult to fix...

In TS, there are new ASTNodeLabeledStatement to identifier this labeled statement, could we use the same concept?

@HerrCai0907 I considered that before, and it might be a pretty good idea. It would be better for transform users for sure.

Still, there's the issue of setting the properFlowFlags for acontinue to an outer loop...maybe the class I use to keep track of labels should contain the flow, and I can use something likedo flow.set(...) while ((flow = flow.parent) != targetFlow). (Of course, the actual code would look nicer than that.)