False positive for accessing enum "instance fields"

For example, let’s assume a Money message (containing amount and currency) and a Money.Currency enum.

This should be valid:

some_money = Money()
some_money.amount = 200
some_money.currency = Money.USD

and

some_money.currency = Money.Currency.Value('CAD')

However, this should be invalid (but is currently valid):

cad = some_money.currency.Value('CAD')

Similarly, this is a false positive:

Money.Currency('CAD')

since it finds int.__init__ although in runtime it would result in:

TypeError: 'EnumTypeWrapper' object is not callable

One way to solve it would be introduce a CurrencyValue:

class Money(google___protobuf___message___Message):
  CurrencyValue = NewType('int')
  class Currency:
    DESCRIPTOR: ...
    ...
  USD = typing___cast(CurrencyValue, 1)
  ...

This would be a breaking change since it’ll require changing any signature accepting Money.Currency. Also, since it exists only in the type stubs, you’d have to quote it, i.e.

def do_something(currency: 'Money.CurrencyValue'):

Alternatively, there might be some (new?) mypy construct that allows to designate fields and functions as class-access only – basically the same as its built-in (hardcoded, from what I could tell) support for enum.

[nipunn1313]

I’m not sure I follow. I can try to play with it later to get a better understanding. Can you provide a full example (with contents of proto file, python callsite, expected mypy error, actual runtime result)

Would be great to have a testcase to really spell it out.

[nipunn1313]

I believe #79 should cover