Do not diagnose no-self-use or unused-argument for methods of structural types (protocols)

[thejohnfreeman]

I searched, but didn't find any issue exactly like this. Nearest ones:

• unused-argument, pointless-statement, and function-redefined with recommended use of typing.overload #1581
• Do not raise "no-self-use" or "unused-argument" for methods overriding methods in superclass #225

Considered making this a bug, but maybe it just falls under "haven't gotten around to it yet".

Steps to reproduce

import typing_extensions as tex

@tex.runtime
class Hasher(tex.Protocol):
    """A hashing algorithm, e.g. :func:`hashlib.sha256`."""
    def update(self, bs: bytes):
        ...
    def digest(self) -> bytes:
        ...

Current behavior

no-self-use and unused-argument diagnostics on the methods.

Expected behavior

No diagnostics.

pylint --version output

pylint 2.3.1
astroid 2.2.5
Python 3.6.8+ (heads/3.6:e5f9f4a, May  6 2019, 11:53:17)
[GCC 7.4.0]

[thejohnfreeman]

Thank you, @PCManticore!