Test and preparations for better call signatures with builtins, see #515.

jedi/api/classes.py

@@ -326,7 +326,7 @@ class BaseDefinition(object):
             raise AttributeError()
         followed = followed[0]  # only check the first one.
 
-        if followed.isinstance(er.Function):
+        if followed.type == 'funcdef':
             if isinstance(followed, er.InstanceElement):
                 params = followed.params[1:]
             else:

jedi/evaluate/compiled/__init__.py

@@ -85,6 +85,8 @@ class CompiledObject(Base):
     def params(self):
         params_str, ret = self._parse_function_doc()
         tokens = params_str.split(',')
+        if inspect.ismethoddescriptor(self._cls().obj):
+            tokens.insert(0, 'self')
         params = []
         for p in tokens:
             parts = [FakeName(part) for part in p.strip().split('=')]