[erlang-questions] Deforesting tuple updates

[James Hague]

> you are likely to end up with some pointers from the old generation into
> the new generation, and this breaks the main invariant that the GC is
> based on. The result will be an emulator crash.

That's only if you put a pointer into a tuple, right?  If the VM
verified new value was a fixnum or atom, then destructive updates
should be okay (after the compiler verifies that the array isn't
shared, as Joel originally mentioned).