Defining a method called "format" on an enum triggers incorrect errors

[ruuda]

Please provide more information to help us understand the issue:

• Are you reporting a bug, or opening a feature request? I am reporting a bug.

• Please insert below the code you are checking with mypy.

  from enum import Enum, auto
  
  class Widget(Enum):
      vanilla = auto()
      chocolate = auto()
  
      def format(self, n: int) -> str:
          return f'{self.name} {n}'
  
  print(Widget.vanilla.format(10))

• What is the actual behavior/output?

  repro.py:10: error: Not all arguments converted during string formatting
  Found 1 error in 1 file (checked 1 source file)
  

  This happens at the call to format.

• What is the behavior/output you expect? The file should typecheck without errors.

• What are the versions of mypy and Python you are using? Mypy 0.740 on Python 3.7.5.
  Do you see the same issue after installing mypy from Git master? Yes, on 09c1fc7 the problem is still present.

• What are the mypy flags you are using? None, just the default.

Issue #7563 seemed superficially related, but now that I am taking a closer look, I’m not sure any more.

[ilevkivskyi]

Yes, this looks like a separate issue. I think this is relatively low priority.