isinstance(x, Tuple) fails when equivalent expressions don't

reproducer

from typing import Any, Dict, Tuple

x = (1,2)
isinstance(x, tuple)
isinstance(x, Tuple[Any, ...])
isinstance(x, Tuple)

observed behavior

$ pipenv run mypy test.py 
test.py:6: error: Argument 2 to "isinstance" has incompatible type "_SpecialForm"; expected "Union[type, Tuple[Union[type, Tuple[Any, ...]], ...]]"

expected behavior
The python documentation states

A plain Tuple is equivalent to Tuple[Any, ...], and in turn to tuple.

If the above is true, IMO either all of the examples should raise errors, or none of them should. Only the third example is raising an error right now. I'm not quite sure what the error means in any case.

environment
master as of 2019-04-15

$ pipenv graph
mypy==0.710+dev.2c8a809693cf5be0b29d272d7f0711521bd4a55a
  - mypy-extensions [required: >=0.4.0,<0.5.0, installed: 0.4.1]
  - typed-ast [required: >=1.3.1,<1.4.0, installed: 1.3.1]

As always, thanks for all the work you do here!

Inizia con il riproduttore isinstance fornito e confronta il modo in cui mypy gestisce tuple, Tuple[Any, ...] e Tuple semplice. Traccia il punto di ingresso del controllo dei tipi per le chiamate a isinstance e determina il comportamento previsto sulla base della documentazione Python collegata. Il lavoro è completato quando le tre forme equivalenti ricevono diagnosi coerenti e documentate, con test che coprono il riproduttore.