Comment by leibnitz27

I haven't raised mine, as I consider it to be a refinement of the bug noted in https://twitter.com/tagir_valeev/status/1210431331332689920 (Don't know if java devs have responsed to that.)

(again, reachability analysis of unrelated code changes semantics.)

The problem is that this IS defined behaviour - the scope of the instanceof-assigned variable is dependent on whether or not the taken if-statement is provably exiting.

This is intended to allow

  {
    if (!(obj instanceof String s)) return;

    // s exists now.
  }

But it's not been thought through.