False positive on `_` (underscore) as variable name with `disallow-any-expr`

Bug Report

mypy gives a false positive with variable _ (underscore) under certain circumstances (see repro).

To Reproduce

https://mypy-play.net/?mypy=latest&python=3.8&flags=disallow-any-expr&gist=bca874771ec5eba30815133c9bbd4ab7

from typing import Callable, Tuple, TypeVar

T = TypeVar("T")

def wrapper(fn: Callable[[], T]) -> Tuple[T, float]:
    return fn(), 1

def wrapper2(fn: Callable[[], T]) -> T:
    return fn()

def func() -> int:
    x = 1
    return x

def a() -> None:
    _, c = wrapper(func)  # <- 2 errors here
    b, c = wrapper(func)
    _ = wrapper2(func)

_, c = wrapper(func)

Interestingly only one line causes the error:

• statement inside a function
• variable named _
• wrapper returns a tuple

Actual Behavior

main.py:16: error: Expression type contains "Any" (has type "Tuple[Any, float]")  [misc]
main.py:16: error: Expression has type "Any"  [misc]
Found 2 errors in 1 file (checked 1 source file)

Your Environment

(environment of the playground)

• Mypy version used: 1.3.0
• Mypy command-line flags: --disallow-any-expr
• Python version used: 3.8 (same for other versions)

Start with the linked mypy-play reproduction and run it using Python 3.8 with --disallow-any-expr, checking the diagnostic on the underscore tuple assignment inside a function. Trace the type-checking entry point for tuple unpacking and underscore variables; done means this case produces no false positives while the other assignments retain their expected diagnostics.