Dotty 0.10.0-RC1 blog post

docs/blog/_posts/2018-10-10-10th-dotty-milestone-release.md

@@ -0,0 +1,249 @@
+---
+layout: blog-page
+title: Announcing Dotty 0.10.0-RC1
+author: Allan Renucci
+authorImg: /images/allan.jpg
+date: 2018-10-10
+---
+
+After a long summer break, we are excited to release Dotty version 0.10.0-RC1.
+This release serves as a technology preview that demonstrates new language features and the
+compiler supporting them.
+
+Dotty is the project name for technologies that are considered for inclusion in Scala 3. Scala has
+pioneered the fusion of object-oriented and functional programming in a typed setting. Scala 3 will
+be a big step towards realising the full potential of these ideas. Its main objectives are to
+
+- become more opinionated by promoting programming idioms we found to work well,
+- simplify where possible,
+- eliminate inconsistencies and surprising behaviours,
+- build on strong foundations to ensure the design hangs well together,
+- consolidate language constructs to improve the language’s consistency, safety, ergonomics, and
+  performance.
+
+You can learn more about Dotty on our [website](https://dotty.epfl.ch).
+
+<!--more-->
+
+This is our 10th scheduled release according to our
+[6-week release schedule](https://dotty.epfl.ch/docs/usage/version-numbers.html).
+
+## What’s new in the 0.10.0-RC1 technology preview?
+
+### Java 9+
+
+Dotty now supports the latest versions of Java including Java 11!
+
+### Type-level programming: Match Types
+
+We've introduced a new form of types called match types. A match types is a mechanism for checking a
+type against a pattern. A match type reduces to one of a number of right hand sides, depending on a
+scrutinee type. E.g:
+
+```scala
+type Elem[X] = X match {
+  case String => Char
+  case Array[t] => t
+  case Iterable[t] => t
+}
+```
+
+This defines a type that, depending on the scrutinee type `X`, can reduce to one of its right hand
+sides. For instance,
+
+```scala
+Elem[String]       =:=  Char
+Elem[Array[Int]]   =:=  Int
+Elem[List[Float]]  =:=  Float
+Elem[Nil]          =:=  Nothing
+```
+
+Here `=:=` is understood to mean that left and right hand sides are mutually subtypes of each other.
+
+This feature is still experimental and subject to changes. For more information, visit the
+[Match Types](http://dotty.epfl.ch/docs/reference/match-types.html) section of our documentation.
+
+### Documentation in the REPL
+
+The previous release added documentation support for the IDE. Users can now query the documentation
+of sources previously compiled with Dotty within the REPL:
+
+```scala
+scala> /** An object */ object O { /** A def */ def foo = 0 }
+// defined object O
+
+scala> :doc O
+/** An object */
+
+scala> :doc O.foo
+/** A def */
+```
+
+### Tail-recursive methods can now be polymorphic
+
+Previously, a tail recursive call would be optimised only if the type arguments of the method
+or the enclosing class did not change at call site. E.g.
+
+```scala
+@tailrec def loop[T](x: T): Int = {
+  ...
+  loop[Int](1)
+}
+```
+
+```shell
+   loop[Int](1)
+   ^^^^^^^^^^^^
+  Cannot rewrite recursive call: it changes type arguments on a polymorphic recursive call
+```
+
+This restriction has now been removed. We also  improve upon `scalac` which is not able to optimise
+methods that change the type of `this` on a polymorphic recursive call.
+[Examples](https://github.com/lampepfl/dotty/blob/7a45a4a386d33180e5b7b21aa74271a77cce4707/tests/neg-tailcall/tailrec.scala#L43-L44)
+can be found in our test suite.
+
+### Experimental support for generic Tuples
+
+We augmented the `Tuple` class with generic methods such as `head`, `tail`, `apply`, `*:` and `++`.
+
+```scala
+scala> val t0 = (1, "2", 3L)
+val t0: (Int, String, Long) = (1,2,3)
+
+scala> val head = t0.head
+val head: Int = 1
+
+scala> val tail = t0.tail
+val tail: (String, Long) = (2,3)
+
+scala> val t1 = 0.0 *: t0
+val t1: (Double, Int, String, Long) = (0.0,1,2,3)
+
+scala> val t2 = t0 ++ t0
+val t2: (Int, String, Long, Int, String, Long) = (1,2,3,1,2,3)
+```
+
+### And much more!
+
+Please read our [release notes](https://github.com/lampepfl/dotty/releases/tag/0.10.0-RC1)
+for more details!
+
+## Breaking changes
+
+Dotty 0.10.0-RC1 requires sbt-dotty 0.2.4 and sbt 1.2.3 or newer.
+
+## Trying out Dotty
+
+### sbt
+
+You can setup a new sbt project with Dotty as the compiler by running:
+
+```shell
+sbt new lampepfl/dotty.g8
+```
+
+For more details on using Dotty with sbt, see the
+[example project](https://github.com/lampepfl/dotty-example-project).
+
+### [Mill](http://www.lihaoyi.com/mill/)
+
+The Mill build tool version 0.2.6 introduced experimental support for Dotty. For more details on
+using Dotty with Mill, see the
+[example project](https://github.com/lampepfl/dotty-example-project/tree/mill).
+
+### IDE support
+
+Start using the Dotty IDE in any Dotty project by following
+the [IDE guide](https://dotty.epfl.ch/docs/usage/ide-support.html).
+
+### Standalone installation
+
+Releases are available for download on the _Releases_
+section of the Dotty repository:
+[https://github.com/lampepfl/dotty/releases](https://github.com/lampepfl/dotty/releases)
+
+For MacOs users, we also provide a [homebrew](https://brew.sh/) package that can be installed by
+running:
+
+```shell
+brew install lampepfl/brew/dotty
+```
+
+In case you have already installed Dotty via `brew`, you should instead update it:
+
+```shell
+brew upgrade dotty
+```
+
+## Let us know what you think!
+
+If you have questions or any sort of feedback, feel free to send us a message on our
+[Gitter channel](https://gitter.im/lampepfl/dotty). If you encounter a bug, please
+[open an issue on GitHub](https://github.com/lampepfl/dotty/issues/new).
+
+## Contributing
+
+Thank you to all the contributors who made this release possible!
+
+According to `git shortlog -sn --no-merges 0.9.0..0.10.0-RC1` these are:
+
+```
+   219  Martin Odersky
+   142  Nicolas Stucki
+    67  Paolo G. Giarrusso
+    52  Allan Renucci
+    48  Guillaume Martres
+    39  Martin Duhem
+    23  Liu Fengyun
+    15  Olivier Blanvillain
+    10  Dmytro Melnychenko
+    10  Abel Nieto
+    10  Sébastien Doeraene
+     7  Jaemin Hong
+     7  Eugene Melekhov
+     5  Saloni Vithalani
+     3  Daniel Li
+     3  Dale Wijnand
+     3  Jasper Moeys
+     2  lloydmeta
+     2  Aggelos Biboudis
+     2  Greg Pevnev
+     1  Adriaan Moors
+     1  Lukas Rytz
+     1  Kazuhiro Sera
+     1  Justin du Coeur, AKA Mark Waks
+     1  Jan Rock
+     1  Fengyun Liu
+     1  Szymon Pajzert
+     1  Chris Birchall
+     1  benkobalog
+     1  Martijn Hoekstra
+```
+
+If you want to get your hands dirty and contribute to Dotty, now is a good time to get involved!
+Head to our [Getting Started page for new contributors](https://dotty.epfl.ch/docs/contributing/getting-started.html),
+and have a look at some of the [good first issues](https://github.com/lampepfl/dotty/issues?q=is%3Aissue+is%3Aopen+label%3Aexp%3Anovice).
+They make perfect entry points into hacking on the compiler.
+
+We are looking forward to having you join the team of contributors.
+
+## Library authors: Join our community build
+
+Dotty now has a set of widely-used community libraries that are built against every nightly Dotty
+snapshot. Currently this includes ScalaPB, algebra, scalatest, scopt and squants.
+Join our [community build](https://github.com/lampepfl/dotty-community-build)
+to make sure that our regression suite includes your library.
+
+[Scastie]: https://scastie.scala-lang.org/?target=dotty
+
+[@odersky]: https://github.com/odersky
+[@DarkDimius]: https://github.com/DarkDimius
+[@smarter]: https://github.com/smarter
+[@felixmulder]: https://github.com/felixmulder
+[@nicolasstucki]: https://github.com/nicolasstucki
+[@liufengyun]: https://github.com/liufengyun
+[@OlivierBlanvillain]: https://github.com/OlivierBlanvillain
+[@biboudis]: https://github.com/biboudis
+[@allanrenucci]: https://github.com/allanrenucci
+[@Blaisorblade]: https://github.com/Blaisorblade
+[@Duhemm]: https://github.com/Duhemm