Create the basics to work with TypedDict in the future

jedi/inference/value/klass.py

@@ -38,11 +38,11 @@ py__doc__()                            Returns the docstring for a value.
 """
 from jedi import debug
 from jedi._compatibility import use_metaclass
-from jedi.parser_utils import get_cached_parent_scope
+from jedi.parser_utils import get_cached_parent_scope, expr_is_dotted
 from jedi.inference.cache import inference_state_method_cache, CachedMetaClass, \
     inference_state_method_generator_cache
 from jedi.inference import compiled
-from jedi.inference.lazy_value import LazyKnownValues
+from jedi.inference.lazy_value import LazyKnownValues, LazyTreeValue
 from jedi.inference.filters import ParserTreeFilter
 from jedi.inference.names import TreeNameDefinition, ValueName
 from jedi.inference.arguments import unpack_arglist, ValuesArguments
@@ -265,6 +265,35 @@ class ClassValue(use_metaclass(CachedMetaClass, ClassMixin, FunctionAndClassBase
             self.inference_state.builtins_module.py__getattribute__('object')
         )]
 
+    def is_typeddict(self):
+        # TODO Do a proper mro resolution. Currently we are just listing
+        # classes. However, it's a complicated algorithm.
+        from jedi.inference.gradual.typing import TypedDictBase
+        for lazy_cls in self.py__bases__():
+            if not isinstance(lazy_cls, LazyTreeValue):
+                return False
+            tree_node = lazy_cls.data
+            # Only resolve simple classes, stuff like Iterable[str] are more
+            # intensive to resolve and if generics are involved, we know it's
+            # not a TypedDict.
+            if not expr_is_dotted(tree_node):
+                return False
+
+            for cls in lazy_cls.infer():
+                if isinstance(cls, TypedDictBase):
+                    return True
+                try:
+                    method = cls.is_typeddict
+                except AttributeError:
+                    # We're only dealing with simple classes, so just returning
+                    # here should be fine. This only happens with e.g. compiled
+                    # classes.
+                    return False
+                else:
+                    if method():
+                        return True
+        return False
+
     def py__getitem__(self, index_value_set, contextualized_node):
         from jedi.inference.gradual.base import GenericClass
         if not index_value_set: