Build FunctionDef.__get__ to use positional only arguments when inferring the bound method

2 files changed, 20 insertions, 6 deletions

diff --git a/astroid/interpreter/objectmodel.py b/astroid/interpreter/objectmodel.py
index 34f65279..cc4a2ba4 100644
--- a/astroid/interpreter/objectmodel.py
+++ b/astroid/interpreter/objectmodel.py
@@ -293,7 +293,7 @@ class FunctionModel(ObjectModel):
                 return 0
 
             def infer_call_result(self, caller, context=None):
-                if len(caller.args) != 2:
+                if len(caller.args) > 2 or len(caller.args) < 1:
                     raise exceptions.InferenceError(
                         "Invalid arguments for descriptor binding",
                         target=self,
@@ -343,11 +343,15 @@ class FunctionModel(ObjectModel):
                 we get a new object which has two parameters, *self* and *type*.
                 """
                 nonlocal func
-                params = func.args.args.copy()
-                params.append(astroid.AssignName(name="type"))
+                positional_or_keyword_params = func.args.args.copy()
+                positional_or_keyword_params.append(astroid.AssignName(name="type"))
+
+                positional_only_params = func.args.posonlyargs.copy()
+
                 arguments = astroid.Arguments(parent=func.args.parent)
                 arguments.postinit(
-                    args=params,
+                    args=positional_or_keyword_params,
+                    posonlyargs=positional_only_params,
                     defaults=[],
                     kwonlyargs=[],
                     kw_defaults=[],
diff --git a/astroid/tests/unittest_object_model.py b/astroid/tests/unittest_object_model.py
index 0cacf20d..ac42485a 100644
--- a/astroid/tests/unittest_object_model.py
+++ b/astroid/tests/unittest_object_model.py
@@ -13,7 +13,7 @@ import xml
 import pytest
 
 import astroid
-from astroid import builder
+from astroid import builder, util
 from astroid import exceptions
 from astroid import MANAGER
 from astroid import test_utils
@@ -343,6 +343,17 @@ class FunctionModelTest(unittest.TestCase):
         self.assertEqual(len(args), 2)
         self.assertEqual([arg.name for arg in args], ["self", "type"])
 
+    @test_utils.require_version(minver="3.8")
+    def test__get__and_positional_only_args(self):
+        node = builder.extract_node(
+            """
+        def test(self, a, b, /, c): return a + b + c
+        test.__get__(test)(1, 2, 3)
+        """
+        )
+        inferred = next(node.infer())
+        assert inferred is util.Uninferable
+
     @unittest.expectedFailure
     def test_descriptor_not_inferrring_self(self):
         # We can't infer __get__(X, Y)() when the bounded function
@@ -366,7 +377,6 @@ class FunctionModelTest(unittest.TestCase):
         class A: pass
         def test(self): return 42
         test.__get__()() #@
-        test.__get__(1)() #@
         test.__get__(2, 3, 4) #@
         """
         )