Add mypy roadmap

ROADMAP.md

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+# Mypy Roadmap
+
+The goal of the roadmap is to document areas the mypy core team is
+planning to work on in the future or is currently working on. PRs
+targeting these areas are very welcome, but please check first with a
+core team member that nobody else is working on the same thing.
+
+**Note:** This doesn’t include everything that the core team will work
+on, and everything is subject to change. Near-term plans are likely
+more accurate.
+
+## April-June 2017
+
+- Add more comprehensive testing for `--incremental` and `--quick`
+  modes to improve reliability. At least write more unit tests with
+  focus on areas that have previously had bugs.
+  ([issue](https://github.com/python/mypy/issues/3455))
+
+- Speed up `--quick` mode to better support million+ line codebases
+  through some of these:
+
+  - Make it possible to use remote caching for incremental cache
+    files. This would speed up a cold run with no local cache data.
+    We need to update incremental cache to use hashes to determine
+    whether files have changes to allow
+    [sharing cache data](https://github.com/python/mypy/issues/3403).
+
+  - See if we can speed up deserialization of incremental cache
+    files. Initial experiments aren’t very promising though so there
+    might not be any easy wins left.
+    ([issue](https://github.com/python/mypy/issues/3456))
+
+- Improve support for complex signatures such as `open(fn, 'rb')` and
+  specific complex decorators such as `contextlib.contextmanager`
+  through type checker plugins/hooks.
+  ([issue](https://github.com/python/mypy/issues/1240))
+
+- Document basic properties of all type operations used within mypy,
+  including compatibility, proper subtyping, joins and meets.
+  ([issue](https://github.com/python/mypy/issues/3454))
+
+- Make TypedDict an officially supported mypy feature. This makes it
+  possible to give precise types for dictionaries that represent JSON
+  objects, such as `{"path": "/dir/fnam.ext", "size": 1234}`.
+  ([issue](https://github.com/python/mypy/issues/3453))
+
+- Make error messages more useful and informative.
+  ([issue](https://github.com/python/mypy/labels/topic-usability))
+
+- Resolve [#2008](https://github.com/python/mypy/issues/2008) (we are
+  converging on approach 4).
+
+## July-December 2017
+
+- Invest some effort into systematically filling in missing
+  annotations and stubs in typeshed, with focus on features heavily
+  used at Dropbox. Better support for ORMs will be a separate
+  project.
+
+- Improve opt-in warnings about `Any` types to make it easier to keep
+  code free from unwanted `Any` types. For example, warn about using
+  `list` (instead of `List[x]`) and calling `open` if we can’t infer a
+  precise return type, or using types imported from ignored modules
+  (they are implicitly `Any`).
+
+- Add support for protocols and structural subtyping (PEP 544).
+
+- Switch completely to pytest and remove the custom testing framework.
+  ([issue](https://github.com/python/mypy/issues/1673))
+
+- Make it possible to run mypy as a daemon to avoid reprocessing the
+  entire program on each run. This will improve performance
+  significantly. Even when using the incremental mode, processing a
+  large number of files is not cheap.
+
+- Refactor and simplify specific tricky parts of mypy internals, such
+  as the [conditional type binder](https://github.com/python/mypy/issues/3457),
+  [symbol tables](https://github.com/python/mypy/issues/3458) or
+  the various [semantic analysis passes](https://github.com/python/mypy/issues/3459).
+
+- Implement a general type system plugin architecture. It should be
+  able to support some typical ORM features at least, such as
+  metaclasses that add methods with automatically inferred signatures
+  and complex descriptors such as those used by Django models.
+  ([issue](https://github.com/python/mypy/issues/1240))
+
+- Add support for statically typed
+  [protobufs](https://developers.google.com/protocol-buffers/).
+
+- Provide much faster, reliable interactive feedback through
+  fine-grained incremental type checking, built on top the daemon
+  mode.
+
+- Start work on editor plugins and support for selected IDE features.