Fix argument search for methods and classmethods.

2 files changed, 41 insertions, 0 deletions

diff --git a/inference.py b/inference.py
index 29c97be..35cce33 100644
--- a/inference.py
+++ b/inference.py
@@ -72,6 +72,11 @@ class CallContext:
                         return iter((boundnode,))
                     if funcnode.type == 'classmethod':
                         return iter((boundnode,))
+                # if we have a method, extract one position
+                # from the index, so we'll take in account
+                # the extra parameter represented by `self` or `cls`
+                if funcnode.type in ('method', 'classmethod'):
+                    argindex -= 1
                 # 2. search arg index
                 try:
                     return self.args[argindex].infer(context)
diff --git a/test/unittest_inference.py b/test/unittest_inference.py
index ce02f99..c417e1a 100644
--- a/test/unittest_inference.py
+++ b/test/unittest_inference.py
@@ -1183,6 +1183,42 @@ B = namedtuple('B', 'a b')
         self.assertIn('a', bclass.instance_attrs)
         self.assertIn('b', bclass.instance_attrs)
 
+    def test_infer_arguments(self):
+        code = '''
+class A(object):
+    def first(self, arg1, arg2):
+        return arg1
+    @classmethod
+    def method(cls, arg1, arg2):
+        return arg2
+    @classmethod
+    def empty(cls):
+        return 2
+    @staticmethod
+    def static(arg1, arg2):
+        return arg1
+    def empty_method(self):
+        return []
+x = A().first(1, [])
+y = A.method(1, [])
+z = A.static(1, [])
+empty = A.empty()
+empty_list = A().empty_method()
+        '''
+        astroid = builder.string_build(code, __name__, __file__)
+        int_node = astroid['x'].infered()[0]
+        self.assertIsInstance(int_node, nodes.Const)
+        self.assertEqual(int_node.value, 1)
+        list_node = astroid['y'].infered()[0]
+        self.assertIsInstance(list_node, nodes.List)
+        int_node = astroid['z'].infered()[0]
+        self.assertIsInstance(int_node, nodes.Const)
+        self.assertEqual(int_node.value, 1)
+        empty = astroid['empty'].infered()[0]
+        self.assertIsInstance(empty, nodes.Const)
+        self.assertEqual(empty.value, 2)
+        empty_list = astroid['empty_list'].infered()[0]
+        self.assertIsInstance(empty_list, nodes.List)
 
 if __name__ == '__main__':
     unittest_main()