@singledispatchmethod fails mypy validation

[cosenal]

I am trying to validate the following example straight from the docs -- Here I renamed the two methods _ from the example to _int and _bool to obviate an issue already reported, i.e., python/mypy#2904

from functools import singledispatchmethod

class Negator:
 @singledispatchmethod
 def neg(self, arg):
 raise NotImplementedError("Cannot negate a")

 @neg.register
 def _int(self, arg: int):
 return -arg

 @neg.register
 def _bool(self, arg: bool):
 return not arg

n = Negator()
n.neg(2)
n.neg(True)

When I run mypy checks on this file, I get the following errors:

negator.py:17: error: "singledispatchmethod[Any]" not callable
negator.py:18: error: "singledispatchmethod[Any]" not callable
Found 2 errors in 1 file (checked 1 source file)

Python 3.8.2
mypy 0.770

[hauntsaninja]

Thanks for the report! Linked PR fixes your repro for me locally.