@Fidget-Spinner,
Since @markshannon prefers to use the current specializer pipeline (and I am also fine with this option), I opened a new PR.

@vstinner @corona10

This breaks STORE_SUBSCR_DICT as it allows stores to frozen dicts.
Please revert or fix.

To fix this you'll need to add a new guard for any dict. Use that for loads, and keep the old dict-only guard for stores.

And please add tests that specialized stores to frozen dicts fail.

I will fix this today

BTW, it's quite tricky to write the test, you'll need a non-branching way to get a dict for specializing and a frozendict once specialized. This is a pattern we've used before:

dicts = [ {...}, frozendict(...) ]
...
for i in range(...):
    d = dicts[i == 100]
    d[...] = ...

Actually, that's only necessary for JIT tests, a simple d = frozendict() if i == 100 else {} should work as well.