Merge pull request #9174 from dotty-staging/25th-release-article

0.25.0-RC2 release blog article

Author: anatoliykmetyuk

docs/blog/_posts/2020-06-22-25th-dotty-milestone-release.md

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+---
+layout: blog-page
+title: Announcing Dotty 0.25.0-RC2 - speed-up of givens and change in the tuple API
+author: Anatolii Kmetiuk
+authorImg: /images/anatolii.png
+date: 2020-06-22
+---
+
+Hello! We are excited to announce 0.25.0-RC2 of Dotty. In this version, following feedback of the community, we have improved compilation speeds when programming with givens. We have also made some improvements to the tuple API.
+
+You can try out this version right now, from the comfort of your SBT, by visiting the [home page](https://dotty.epfl.ch/) and scrolling down to the "Create a Dotty Project" section.
+
+Alternatively, you can try this version of Scala online via [Scastie](https://scastie.scala-lang.org/). Once you're there, click "Build Settings" and set "Target" to "Dotty".
+
+Enjoy the ride🚀!
+
+<!--more-->
+# Dedicated type for empty tuples
+We have added a type `EmptyTuple` to represent empty tuples. Previously empty tuples were represented by `Unit`. This change was done so that all the tuples are a subtype of `Product`. Now, tuples have the following type hierarchy:
+
+```scala
+Product -- Tuple -+- EmptyTuple
+                  |
+                  +- NonEmptyTuple -- *:[Head, Tail <: Tuple]
+```
+
+This change impacts existing typeclass derivation codebases in that they now should use `EmptyTuple` instead of `Unit` in the tuple context.
+
+# Avoid excessive slowdowns when suggesting missing imports in error messages
+Dotty brings to the user an enhanced error reporting when it comes to programming with givens. This better error reporting, however, proved to be a trade-off. Sometimes it takes an unreasonable amount of time and space to compute a quality suggestion to the end user.
+
+A number of users reported considerable slowdowns when it comes to programming with implicits. To address this issue, we have modified the logic for given imports suggestion. We introduced a per-run budget of 10 seconds, so it is guaranteed that it won't take longer than that time to compute all the given imports.
+
+This default budget is configurable via a compiler flag `-Ximport-suggestion-timeout`.
+
+This change should speed up the compiler when it comes to programming with givens.
+
+For more information, see PR [#9167](https://github.com/lampepfl/dotty/pull/9167).
+
+# 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 0.24.0-RC1..0.25.0-RC2` these are:
+
+```
+   190  Nicolas Stucki
+   175  Martin Odersky
+    67  Liu Fengyun
+    32  Guillaume Martres
+    17  Robert Stoll
+    17  bishabosha
+     9  Anatolii Kmetiuk
+     7  yu-croco
+     6  Reto Hablützel
+     5  Akhtiam Sakaev
+     5  odersky
+     4  Raphael Jolly
+     4  Ruslan Shevchenko
+     4  Olivier Blanvillain
+     3  Jamie Thompson
+     3  Chris Birchall
+     2  Radosław Waśko
+     2  Aleksander Boruch-Gruszecki
+     2  Eric Loots
+     2  Jens Kat
+     2  Miles Sabin
+     2  noti0na1
+     1  Krzysztof Bochenek
+     1  Seth Tisue
+     1  Tobias Kahlert
+     1  Yilin Wei
+     1  ansvonwa
+     1  FabioPinheiro
+     1  december32
+     1  yytyd
+     1  Ara Adkins
+     1  squid314
+     1  typeness
+     1  xuwei-k
+     1  Alex Zolotko
+     1  Julien Richard-Foy
+```
+
+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 shapeless, ScalaPB, algebra, scalatest, scopt and squants.
+Join our [community build](https://github.com/lampepfl/dotty/tree/master/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
+[@AleksanderBG]: https://github.com/AleksanderBG
+[@milessabin]: https://github.com/milessabin
+[@anatoliykmetyuk]: https://github.com/anatoliykmetyuk