Blog Post: Announcing Dotty 0.6.0 and 0.7.0-RC1 #4053

allanrenucci · 2018-03-01T13:41:01Z

@lampepfl/dotty-core Feel free to edit

allanrenucci · 2018-03-01T13:45:49Z

docs/blog/_posts/2018-03-05-seventh-dotty-milestone-release.md

+You can visit our website for more information about [enumerations](/docs/reference/enums/enums.html)
+and how we can use them to model [Algebraic Data Types](/docs/reference/enums/adts.html).
+
+### Unused Parameters [#3342](https://github.com/lampepfl/dotty/pull/3342)


@nicolasstucki Do you want to do this?

@nicolasstucki Probably we should say a couple words about going from phantom types to unused parameters (#2040 (comment)), probably in the release notes rather than in the docs for the latest release (to avoid confusing new users). Starting point:

TL;DR: With unused parameters you can mark values of arbitrary types to be erased at runtime, instead of having to implement separate phantom types.

smarter · 2018-03-01T15:27:03Z

This needs a section on improved GADT support and a section on improved completions in the IDE. I'm not available to write this myself thid week unfortunately.

Blaisorblade · 2018-03-01T13:49:53Z

docs/blog/_posts/2018-03-05-seventh-dotty-milestone-release.md

+```
+
+You can visit our website for more information about [enumerations](/docs/reference/enums/enums.html)
+and how we can use them to model [Algebraic Data Types](/docs/reference/enums/adts.html).


Are these links up-date?

These links will become valid once the page is generated. An alternative would be to write absolute links (e.g. http://dotty.epfl.ch/docs/reference/enums/enums.html) so that they are also valid links in GitHub

Sorry: I was asking if the docs in the target pages have been updated (and I thought not).

Blaisorblade · 2018-03-01T15:46:12Z

docs/blog/_posts/2018-03-05-seventh-dotty-milestone-release.md

+You can visit our website for more information about [enumerations](/docs/reference/enums/enums.html)
+and how we can use them to model [Algebraic Data Types](/docs/reference/enums/adts.html).
+
+### Unused Parameters [#3342](https://github.com/lampepfl/dotty/pull/3342)


@nicolasstucki Probably we should say a couple words about going from phantom types to unused parameters (#2040 (comment)), probably in the release notes rather than in the docs for the latest release (to avoid confusing new users). Starting point:

TL;DR: With unused parameters you can mark values of arbitrary types to be erased at runtime, instead of having to implement separate phantom types.

allanrenucci · 2018-03-01T16:05:09Z

This needs a section on improved GADT support and a section on improved completions in the IDE.

For reference, the PR which improved IDE completions is #3960.

@smarter What improvements do you have in mind regarding GADT support? #3990?

Blaisorblade · 2018-03-01T16:21:00Z

@allanrenucci PRs on GADTs include #3918, #4034 (finding more...)

smarter · 2018-03-01T16:21:18Z

What improvements do you have in mind regarding GADT support? #3990

Soundness was improved by #3918, although there are still holes related to variance until #4013 is merged. @liufengyun also did work related to gadt exhaustiveness checking

Blaisorblade · 2018-03-01T16:32:00Z

So #3645 was in fact fixed in December (so for last release), though it fits well under "ongoing GADT improvements". IIUC, even without #4013, invariant GADTs appear fixed, and with #4013 variant GADTs will be fixed as well.
EDIT: it was merged after 0.6.0-RC1.

Technically `case some =>` works (and binds `some` to `this`) but I don't think this was intended.

The example showcases both scala#3666 and scala#1754.

Duhemm · 2018-03-05T10:58:45Z

docs/blog/_posts/2018-03-05-seventh-dotty-milestone-release.md

+
+## What’s new in the 0.7.0-RC1 technology preview?
+
+### Enums Simplicification [#4003](https://github.com/lampepfl/dotty/pull/4003)


Typo: Simplification

allanrenucci · 2018-03-05T13:22:34Z

docs/blog/_posts/2018-03-05-seventh-dotty-milestone-release.md

+[#3645](https://github.com/lampepfl/dotty/issues/3645),
+and improved handling of matches using repeated type variables
+[#4030](https://github.com/lampepfl/dotty/issues/4030).
+More test cases appear in [#3999](https://github.com/lampepfl/dotty/pull/3999).


I would drop this line.

allanrenucci · 2018-03-05T13:23:23Z

docs/blog/_posts/2018-03-05-seventh-dotty-milestone-release.md

+}
+```
+
+Earlier Dotty releases had issues typechecking such interpreters.


I would say versions instead of releases.

smarter · 2018-03-05T13:45:47Z

docs/blog/_posts/2018-03-05-seventh-dotty-milestone-release.md

+}
+```
+
+Earlier Dotty releases had issues typechecking such interpreters.


I think it's important to note that Scala 2 also has unresolved issues typechecking GADTs, like with the neg example in https://github.com/lampepfl/dotty/pull/3990/files#diff-e7b3b26b928fa129081481ffc513af95

Added a bit; I think Dotty's already much better than Scalac, but I haven't tried enough personally to make strong claims this in release notes. Feel free to add stronger claims you feel comfortable with.

smarter · 2018-03-05T14:41:27Z

docs/blog/_posts/2018-03-05-seventh-dotty-milestone-release.md

@@ -162,7 +162,7 @@ object Interpreter {
 }
 ```

-Earlier Dotty releases had issues typechecking such interpreters.
+Earlier Scalac and Dotty releases had issues typechecking such interpreters.


This makes it sound like recent releases of scalac have fixed this, but they haven't. Also I would use the term "Scala 2" and not "Scalac".

The most convincing thing to do would be to give an example that doesn't typecheck in Dotty but does in Scala 2.

This program works in Scalac, while trickier ones trigger bugs in Scalac or Dotty. I propose to write "Scala 2 and Dotty have issues [...]", since we fixed some.

case class MapS[S, T](xs: Exp[List[S]], f: Exp[S => T]) extends Exp[List[T]] case class Map[S, T, That](xs: Exp[List[S]], f: Exp[S => T])(implicit val cbf: CanBuildFrom[List[S], T, That]) extends Exp[That] //... case m @ Map(xs, f) => //val f1: Exp[Any => Any] = f //accepted by Scalac, rejected by Dotty! eval(xs).map(eval(f))(m.cbf) case MapS(xs, f) => eval(xs) map eval(f) //rejected by Dotty, not 100% sure why. Passing the //alternatively: case m: MapS[s, t] => //(eval(m.xs) map eval(m.f))(List.canBuildFrom) //fails in Dotty (eval(m.xs) map eval(m.f))(List.canBuildFrom[t]) //succeeds in Dotty

Failures in #4069 might be relevant.

EDIT: full example in #4076.

Blaisorblade · 2018-03-06T10:55:06Z

docs/blog/_posts/2018-03-05-seventh-dotty-milestone-release.md

-Earlier Scalac and Dotty releases had issues typechecking such interpreters.
-We fixed multiple bugs about GADT type checking and exhaustiveness checking, including
+Scala 2 and Dotty have issues typechecking such interpreters.
+In this release we fixed multiple bugs about GADT type checking and exhaustiveness checking, including


@smarter @allanrenucci WDYT? A bit less bold, which seems appropriate.

smarter · 2018-03-06T12:08:08Z

I've written an alternative version of the GADT section, I'll let others decide which one is better.

allanrenucci added the stat:wip label Mar 1, 2018

Blog Post: Announcing Dotty 0.6.0 and 0.7.0-RC1

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allanrenucci commented Mar 1, 2018

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Drop dup link

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Add section on unused

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nicolasstucki and others added 5 commits March 2, 2018 12:01

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Emphasize phantom types are being replaced

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Fix typos in code snippets

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Technically `case some =>` works (and binds `some` to `this`) but I don't think this was intended.

Update ghost section with real life example

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allanrenucci force-pushed the 0.7.0-blogpost branch from bf7b0e5 to dc81fd3 Compare March 4, 2018 10:02

allanrenucci and others added 4 commits March 4, 2018 11:41

Add IDE section and use absolute links (better when read on GitHub)

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List GADT issues fixed

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Small example of GADTs WIP

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Add proper GADT example, adapted from scala#3666

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The example showcases both scala#3666 and scala#1754.

Duhemm reviewed Mar 5, 2018

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Rename ghost parameter to erased

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Blaisorblade added 4 commits March 5, 2018 14:51

Fix code snippet, thanks to Allan for pointing it out

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Address review, point out Scalac had issues

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Blog Post: Announcing Dotty 0.6.0 and 0.7.0-RC1 #4053

Blog Post: Announcing Dotty 0.6.0 and 0.7.0-RC1 #4053

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smarter commented Mar 6, 2018


		## What’s new in the 0.7.0-RC1 technology preview?

		### Enums Simplicification [#4003](https://github.com/lampepfl/dotty/pull/4003)

Blog Post: Announcing Dotty 0.6.0 and 0.7.0-RC1 #4053

Blog Post: Announcing Dotty 0.6.0 and 0.7.0-RC1 #4053

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