take the following snippet, debug-it and press "Through":
For me, it makes the debugger hang really long time, as apparently the whole code execution is simulated, searching for the current context (#stepToHome:). "Over", in contrast, is faster by far, calling #completeStep: instead.
Can we speed up "Through" in any way? As the button is explained as "Step into a block", we could call #completeStep: internally if the selected message does not contain a block argument, for example.