Implement typing.cast

jedi/evaluate/gradual/typing.py

@@ -114,8 +114,7 @@ class TypingModuleName(NameWrapper):
             yield OverloadFunction.create_cached(evaluator, self.parent_context, self.tree_name)
         elif name == 'cast':
             # TODO implement cast
-            for c in self._wrapped_name.infer():  # Fuck my life Python 2
-                yield c
+            yield CastFunction.create_cached(evaluator, self.parent_context, self.tree_name)
         elif name == 'TypedDict':
             # TODO doesn't even exist in typeshed/typing.py, yet. But will be
             # added soon.
@@ -449,6 +448,12 @@ class OverloadFunction(_BaseTypingContext):
         return func_context_set
 
 
+class CastFunction(_BaseTypingContext):
+    @repack_with_argument_clinic('type, object, /')
+    def py__call__(self, type_context_set, object_context_set):
+        return type_context_set.execute_annotation()
+
+
 class BoundTypeVarName(AbstractNameDefinition):
     """
     This type var was bound to a certain type, e.g. int.

test/completion/pep0484_typing.py

@@ -351,3 +351,14 @@ def foo(a: typing.List, b: typing.Dict, c: typing.MutableMapping) -> typing.Type
     c['asdf']
 #? int
 foo()
+
+def cast_tests():
+    x = 3.0
+    y = typing.cast(int, x)
+    #? int()
+    y
+    return typing.cast(str, x)
+
+
+#? str()
+cast_tests()