Add memoize_function to cache and use it in fake.get_faked

The previously added test should now pass.

Fix #591

jedi/cache.py

@@ -163,6 +163,18 @@ def memoize_method(method):
     return wrapper
 
 
+def memoize_function(obj):
+    """ A normal memoize function for memoizing free functions. """
+    cache = obj.cache = {}
+
+    def memoizer(*args, **kwargs):
+        key = str(args) + str(kwargs)
+        if key not in cache:
+            cache[key] = obj(*args, **kwargs)
+        return cache[key]
+    return memoizer
+
+
 def cache_star_import(func):
     @time_cache("star_import_cache_validity")
     def wrapper(self):

jedi/evaluate/compiled/fake.py

@@ -8,6 +8,7 @@ import os
 import inspect
 
 from jedi._compatibility import is_py3, builtins, unicode
+from jedi.cache import memoize_function
 from jedi.parser import Parser, load_grammar
 from jedi.parser import tree as pt
 from jedi.evaluate.helpers import FakeName
@@ -97,6 +98,7 @@ def _faked(module, obj, name):
             return search_scope(cls, name)
 
 
+@memoize_function
 def get_faked(module, obj, name=None):
     obj = obj.__class__ if is_class_instance(obj) else obj
     result = _faked(module, obj, name)