Use metacode to read comments #20785

Feature

What about to replace the current way of reading machine-readable comments with a ready-made solution: metacode. This will not only simplify the internal implementation of mypy, but also eliminate some bugs of the current scheme.

Pitch

I have 2 linters that respond to the problem in the same line of code: ruff and mypy. Here is my code:

@classmethod
def from_callable(cls, function: Callable[..., Any], raise_exception: bool = False) -> 'SignatureSeriesMatcher':  # noqa: F821 # type: ignore[name-defined]
    ...

If I shut up ruff first and then mypy, I get an error from mypy:

some_file:227: error: Name "SignatureSeriesMatcher" is not defined  [name-defined]

However, if I swap them like this:

# type: ignore[name-defined] # noqa: F821

... the mypy error disappears.

Obviously, mypy does not know how to correctly handle changing the order of machine-readable comments.

This problem can be solved quickly if you use a ready-made solution for reading such comments: metacode. This "out of the box" can read comments arranged in any order.