Try the following line of code in both 3.5 and 3.6:

[1/0] on: Error do: [:e | e signal]

In 3.5, when the debugger comes up, the top context is the send to #/.  In
3.6, it is the handler block, with the send to #/ several frames down.

Which is correct?  I personally much prefer the 3.5 behavior.

Another symptom of what I think is the same bug:

[1/0. self inform: 'inner']
  on: Error
  do: [:e | e defaultAction. self inform: 'outer'].

Try this code.  When the notifier pops up, click Proceed.

In 3.5, you will see 'inner'.  In 3.6, you will see 'outer'.

Again, I would prefer the 3.5 behavior here.

Does anyone know what exactly has changed, and how easy it is to fix?