Wrong self type only reported upon call if using VarArgs

Bug Report

Mypy does not raise an error if a method accepts nothing but a vararg list, but lacks a self parameter or staticmethod decorator.

This behavior is confusing because Mypy does catch wrong self types for regular parameters.

To Reproduce

class Class:
    def method(*args: int) -> int:
        return sum(args)

print(Class().method(1, 2, 3))

Expected Behavior

foo.py:2: error: Self argument missing for a non-static method (or an invalid type for self)  [misc]

Actual Behavior

foo.py:5: error: Invalid self argument "Class" to attribute function "method" with type "Callable[[VarArg(int)], Any]"  [misc]
Found 1 error in 1 file (checked 1 source file)

Your Environment

• Mypy version used: 1.7.0
• Mypy command-line flags: --strict
• Mypy configuration options from mypy.ini (and other config files): none
• Python version used: 3.9

No source file or test is named. Run the supplied Python 3.9 reproducer with mypy --strict, then trace the existing self-argument validation for methods annotated with VarArg. Done means the expected [misc] diagnostic is reported at the method definition rather than only when the method is called.