Rewrite the next function.

jedi/evaluate/__init__.py

@@ -93,6 +93,7 @@ class Evaluator(object):
         self.analysis = []
         self.dynamic_params_depth = 0
         self.is_analysis = False
+        self.python_version = sys.version_info[:2]
 
         if sys_path is None:
             sys_path = sys.path

jedi/evaluate/compiled/fake/builtins.pym

@@ -6,17 +6,6 @@ possible for the auto completion.
 """
 
 
-def next(iterator, default=None):
-    if random.choice([0, 1]):
-        if hasattr("next"):
-            return iterator.next()
-        else:
-            return iterator.__next__()
-    else:
-        if default is not None:
-            return default
-
-
 def iter(collection, sentinel=None):
     if sentinel:
         yield collection()

jedi/evaluate/iterable.py

@@ -123,7 +123,7 @@ def has_builtin_methods(cls):
 
 def register_builtin_method(method_name, python_version_match=None):
     def wrapper(func):
-        if python_version_match and python_version_match + int(is_py3) == 3:
+        if python_version_match and python_version_match == 2 + int(is_py3):
             # Some functions do only apply to certain versions.
             return func
         dct = func.__dict__.setdefault('registered_builtin_methods', {})

jedi/evaluate/stdlib.py

@@ -106,6 +106,25 @@ def argument_clinic(string, want_obj=False, want_context=False, want_arguments=F
     return f
 
 
+@argument_clinic('iterator[, default], /')
+def builtins_next(evaluator, iterators, defaults):
+    if evaluator.python_version[0] == 2:
+        name = 'next'
+    else:
+        name = '__next__'
+
+    types = set()
+    for iterator in iterators:
+        if isinstance(iterator, AbstractInstanceContext):
+            for filter in iterator.get_filters(include_self_names=True):
+                for n in filter.get(name):
+                    for context in n.infer():
+                        types |= context.execute_evaluated()
+    if types:
+        return types
+    return defaults
+
+
 @argument_clinic('object, name[, default], /')
 def builtins_getattr(evaluator, objects, names, defaults=None):
     # follow the first param
@@ -249,6 +268,7 @@ def _return_first_param(evaluator, firsts):
 
 _implemented = {
     'builtins': {
+        'next': builtins_next,
         'getattr': builtins_getattr,
         'type': builtins_type,
         'super': builtins_super,