Incorrect type repr of empty tuples and namedtuples

[sobolevn]

Right now this code will produce:

from typing import NamedTuple

N = NamedTuple('N', [])
n: N
reveal_type(N)  # N: Revealed type is "def () -> Tuple[, fallback=__main__.N]"
reveal_type(n)  # N: Revealed type is "Tuple[, fallback=__main__.N]"

and:

from typing import Tuple

def f() -> Tuple[()]: ...

reveal_type(f)    # N: Revealed type is "def () -> Tuple[]"
reveal_type(f())  # N: Revealed type is "Tuple[]"

This does not look right, because Tuple[] is not a thing in Python:

>>> from typing import Tuple
>>> Tuple[]
  File "<stdin>", line 1
    Tuple[]
          ^
SyntaxError: invalid syntax

I propose to change it to tuple[()] or Tuple[()] with optional fallback= in case of NamedTuple.

This can affect people who assert output (like pytest-mypy-plugins users), but I think that /s/Tuple[]/Tuple[()] is simple enough to fix all output based checks.

But, we will be more correct in terms of typing.