Merge pull request #3894 from hippo91/bug_pylint_3885

Bug pylint 3885

ChangeLog

@@ -11,6 +11,11 @@ What's New in Pylint 2.6.1?
 ===========================
 Release date: TBA
 
+* Fix a false-positive emission of `no-self-use` and `unused-argument` for methods
+  of generic structural types (`Protocol[T]`)
+
+  Closes #3885
+
 * Fix bug that lead to duplicate messages when using ``--jobs 2`` or more.
 
   Close #3584

pylint/checkers/utils.py

@@ -74,7 +74,9 @@
     "abc.abstractclassmethod",
     "abc.abstractstaticmethod",
 }
-TYPING_PROTOCOLS = frozenset({"typing.Protocol", "typing_extensions.Protocol"})
+TYPING_PROTOCOLS = frozenset(
+    {"typing.Protocol", "typing_extensions.Protocol", ".Protocol"}
+)
 ITER_METHOD = "__iter__"
 AITER_METHOD = "__aiter__"
 NEXT_METHOD = "__next__"

tests/functional/p/protocol_classes.py

@@ -10,3 +10,25 @@ def update(self, blob: bytes):
 
     def digest(self) -> bytes:
         ...
+
+
+Generic = typing.TypeVar("Generic")
+
+
+class HasherGeneric(typing.Protocol[Generic]):
+    """A hashing algorithm, e.g. :func:`hashlib.sha256`."""
+    def update(self, blob: bytes):
+        ...
+    def digest(self) -> bytes:
+        ...
+
+
+class Protocol:  #pylint:disable=too-few-public-methods
+    pass
+
+class HasherFake(Protocol):
+    """A hashing algorithm, e.g. :func:`hashlib.sha256`."""
+    def update(self, blob: bytes): # [no-self-use, unused-argument]
+        ...
+    def digest(self) -> bytes: # [no-self-use]
+        ...

tests/functional/p/protocol_classes.txt

@@ -0,0 +1,3 @@
+no-self-use:31:HasherFake.update:"Method could be a function"
+unused-argument:31:HasherFake.update:"Unused argument 'blob'":INFERENCE
+no-self-use:33:HasherFake.digest:"Method could be a function"