Document support for Python 3.6 features.

docs/source/index.rst

@@ -28,6 +28,7 @@ Mypy is a static type checker for Python.
    additional_features
    command_line
    config_file
+   python36
    faq
    cheat_sheet
    revision_history

docs/source/python36.rst

@@ -0,0 +1,64 @@
+.. python36:
+
+New features in Python 3.6
+==========================
+
+Python 3.6 will be `released
+<https://www.python.org/dev/peps/pep-0494>`_ in December 2016.  The
+`first beta <https://www.python.org/downloads/release/python-360b1/>`_
+came out in September and adds some exciting features.  Here's the
+support matrix for these in mypy (to be updated with each new mypy
+release).  The intention is to support all of these by the time Python
+3.6 is released.
+
+Syntax for variable annotations (`PEP 526 <https://www.python.org/dev/peps/pep-0526>`_)
+---------------------------------------------------------------------------------------
+
+Python 3.6 feature: variables (in global, class or local scope) can
+now have type annotations using either of the two forms:
+
+.. code-block:: python
+
+   foo: Optional[int]
+   bar: List[str] = []
+
+Mypy fully supports this syntax, interpreting them as equivalent to
+
+.. code-block:: python
+
+   foo = None  # type: Optional[int]
+   bar = []  # type: List[str]
+
+Literal string formatting (`PEP 498 <https://www.python.org/dev/peps/pep-0498>`_)
+---------------------------------------------------------------------------------
+
+Python 3.6 feature: string literals of the form
+``f"text {expression} text"`` evaluate ``expression`` using the
+current evaluation context (locals and globals).
+
+Mypy does not yet support this.
+
+Underscores in numeric literals (`PEP 515 <https://www.python.org/dev/peps/pep-0515>`_)
+---------------------------------------------------------------------------------------
+
+Python 3.6 feature: numeric literals can contain underscores,
+e.g. ``1_000_000``.
+
+Mypy does not yet support this.
+
+Asynchronous generators (`PEP 525 <https://www.python.org/dev/peps/pep-0525>`_)
+-------------------------------------------------------------------------------
+
+Python 3.6 feature: coroutines defined with ``async def`` (PEP 492)
+can now also be generators, i.e. contain ``yield`` expressions.
+
+Mypy does not yet support this.
+
+Asynchronous comprehensions (`PEP 530 <https://www.python.org/dev/peps/pep-0530>`_)
+-----------------------------------------------------------------------------------
+
+Python 3.6 feature: coroutines defined with ``async def`` (PEP 492)
+can now also contain list, set and dict comprehensions that use
+``async for`` syntax.
+
+Mypy does not yet support this.