``BoundMethod.implicit_parameters`` returns a proper value for ``__new__``

Close PyCQA/pylint#2335

3 files changed, 28 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index 78af48d9..515fd656 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -11,6 +11,10 @@ Release Date: TBA
 
   Closes PyCQA/astroid#725
 
+* ``BoundMethod.implicit_parameters`` returns a proper value for ``__new__``
+
+  Close PyCQA/pylint#2335
+
 * Allow slots added dynamically to a class to still be inferred
 
   Close PyCQA/pylint#2334
diff --git a/astroid/bases.py b/astroid/bases.py
index ae66c7a3..a59cbd12 100644
--- a/astroid/bases.py
+++ b/astroid/bases.py
@@ -391,6 +391,9 @@ class BoundMethod(UnboundMethod):
         self.bound = bound
 
     def implicit_parameters(self):
+        if self.name == "__new__":
+            # __new__ acts as a classmethod but the class argument is not implicit.
+            return 0
         return 1
 
     def is_bound(self):
diff --git a/tests/unittest_inference.py b/tests/unittest_inference.py
index b2210a8d..21dc946d 100644
--- a/tests/unittest_inference.py
+++ b/tests/unittest_inference.py
@@ -5791,5 +5791,26 @@ def test_allow_retrieving_instance_attrs_and_special_attrs_for_functions():
     assert len(attrs) == 2
 
 
+def test_implicit_parameters_bound_method():
+    code = """
+    class A(type):
+        @classmethod
+        def test(cls, first): return first
+        def __new__(cls, name, bases, dictionary):
+            return super().__new__(cls, name, bases, dictionary)
+
+    A.test #@
+    A.__new__ #@
+    """
+    test, dunder_new = extract_node(code)
+    test = next(test.infer())
+    assert isinstance(test, BoundMethod)
+    assert test.implicit_parameters() == 1
+
+    dunder_new = next(dunder_new.infer())
+    assert isinstance(dunder_new, BoundMethod)
+    assert dunder_new.implicit_parameters() == 0
+
+
 if __name__ == "__main__":
     unittest.main()