Get typing.NewType working (#1344)

Squashed from the following commits:

* Update pep0484.py

(I don't think I want to know why the cursor jumped to the beginning of the line with every keystroke in GitHub's online editor. Change was entered backwards.)

* Added test for inline use of NewType. Currently assuming that wrapped instances should get the underlying type.

* Altered tests per https://github.com/davidhalter/jedi/issues/1015#issuecomment-356131566

* Add NewTypeFunction to typing evaluation module

* Update AUTHORS.txt

* Add a new test, and a speculative justification

For now, address only the second comment

* Copy code from third comment on the PR

From inspection, I *believe* I understand what this code is doing, and as such, I believe this should cause the new test I added in response to the second comment to fail, because that test is based on faulty assumptions.

* Explicitly discard the key from the tuple

* Update pep0484_typing.py

* Test for the wrapped type, not the wrapper "type"

* Change the return value from calling a NewType

AUTHORS.txt

@@ -51,5 +51,6 @@ Maksim Novikov (@m-novikov) <mnovikov.work@gmail.com>
 Tobias Rzepka (@TobiasRzepka)
 micbou (@micbou)
 Dima Gerasimov (@karlicoss) <karlicoss@gmail.com>
+Max Woerner Chase (@mwchase) <max.chase@gmail.com>
 
 Note: (@user) means a github user name.

jedi/evaluate/gradual/typing.py

@@ -115,6 +115,8 @@ class TypingModuleName(NameWrapper):
             yield builtin_from_name(evaluator, u'True')
         elif name == 'overload':
             yield OverloadFunction.create_cached(evaluator, self.parent_context, self.tree_name)
+        elif name == 'NewType':
+            yield NewTypeFunction.create_cached(evaluator, self.parent_context, self.tree_name)
         elif name == 'cast':
             # TODO implement cast
             yield CastFunction.create_cached(evaluator, self.parent_context, self.tree_name)
@@ -459,6 +461,32 @@ class OverloadFunction(_BaseTypingContext):
         return func_context_set
 
 
+class NewTypeFunction(_BaseTypingContext):
+    def py__call__(self, arguments):
+        ordered_args = arguments.unpack()
+        next(ordered_args, (None, None))
+        _, second_arg = next(ordered_args, (None, None))
+        if second_arg is None:
+            return NO_CONTEXTS
+        return ContextSet(
+            NewType(
+                self.evaluator,
+                contextualized_node.context,
+                contextualized_node.node,
+                second_arg.infer(),
+            ) for contextualized_node in arguments.get_calling_nodes())
+
+
+class NewType(Context):
+    def __init__(self, evaluator, parent_context, tree_node, type_context_set):
+        super(NewType, self).__init__(evaluator, parent_context)
+        self._type_context_set = type_context_set
+        self.tree_node = tree_node
+
+    def py__call__(self, arguments):
+        return self._type_context_set.execute_annotation()
+
+
 class CastFunction(_BaseTypingContext):
     @repack_with_argument_clinic('type, object, /')
     def py__call__(self, type_context_set, object_context_set):

test/completion/pep0484_typing.py

@@ -256,6 +256,31 @@ for key in x.keys():
 for value in x.values():
     #? int()
     value
+
+WrappingType = typing.NewType('WrappingType', str) # Chosen arbitrarily
+y = WrappingType(0) # Per https://github.com/davidhalter/jedi/issues/1015#issuecomment-355795929
+#? str()
+y
+
+def testnewtype(y):
+    """
+    :type y: WrappingType
+    """
+    #? str()
+    y
+    #? ["upper"]
+    y.u
+
+WrappingType2 = typing.NewType()
+
+def testnewtype2(y):
+    """
+    :type y: WrappingType2
+    """
+    #?
+    y
+    #? []
+    y.
 # python >= 3.4
 
 class TestDefaultDict(typing.DefaultDict[str, int]):