Dotty: Scala 3 SIPs, meta-issue for tracking

[sjrd]

Here is the list of Scala 3 removals/additions/changes that should be turned into SIPs.

For the October meeting (22.10.2018)

• [x] Trait parameters http://dotty.epfl.ch/docs/reference/trait-parameters.html (@liufengyun )
• [x] Intersection types http://dotty.epfl.ch/docs/reference/intersection-types.html (@liufengyun )
• [x] Union types http://dotty.epfl.ch/docs/reference/union-types.html (@smarter)
• [x] Dependent function types http://dotty.epfl.ch/docs/reference/dependent-function-types.html (@olivier)
• [x] Implicit function types http://dotty.epfl.ch/docs/reference/implicit-function-types.html (@olivier)

For the Nov. meetings

• New features
  
  
  
  • [x] Type Lambdas https://dotty.epfl.ch/docs/reference/type-lambdas.html (@odersky)
  
  
  • [x] Multiversal Equality https://dotty.epfl.ch/docs/reference/multiversal-equality.html (@allanrenucci)
  
  
  • [x] Auto Parameter Tupling https://dotty.epfl.ch/docs/reference/auto-parameter-tupling.html (@nicolasstucki)
  
  
  • [x] Named Type Arguments https://dotty.epfl.ch/docs/reference/named-typeargs.html (@smarter)
  
  
  • [ ] Enums https://dotty.epfl.ch/docs/reference/enums/enums.html (@smarter)
  
  
• Changed Features
  
  
  
  • [ ] Volatile Lazy Vals https://dotty.epfl.ch/docs/reference/changed/lazy-vals.html (@allanrenucci)
  
  
  • [x] Structural Types https://dotty.epfl.ch/docs/reference/changed/structural-types.html (@Duhemm)
  
  
  • [ ] Implicit Resolution https://dotty.epfl.ch/docs/reference/changed/implicit-resolution.html
  
  
  • [x] Implicit Conversions https://dotty.epfl.ch/docs/reference/changed/implicit-conversions.html (@Duhemm)
  
  
  • [x] Vararg Patterns https://dotty.epfl.ch/docs/reference/changed/vararg-patterns.html (@allanrenucci)
  
  
  • [ ] Pattern matching https://dotty.epfl.ch/docs/reference/changed/pattern-matching.html
  
  
  • [ ] Eta Expansion https://dotty.epfl.ch/docs/reference/changed/eta-expansion.html (@biboudis)
  
  
• Dropped Features
  
  
  
  • [ ] Existential Types https://dotty.epfl.ch/docs/reference/dropped/existential-types.html (@Blaisorblade)
  
  
  • [ ] Type Projection https://dotty.epfl.ch/docs/reference/dropped/type-projection.html (@Blaisorblade)
  
  
  • [x] Class Shadowing https://dotty.epfl.ch/docs/reference/dropped/class-shadowing.html (@olivier)
  
  
  • [ ] Weak Conformance https://dotty.epfl.ch/docs/reference/dropped/weak-conformance.html (@sjrd?)
  
  
• Already in batch 1 or 2 or earlier SIP
  
  
  
  • [ ] DelayedInit https://dotty.epfl.ch/docs/reference/dropped/delayed-init.html
  
  
  • [ ] Auto-Application https://dotty.epfl.ch/docs/reference/dropped/auto-apply.html
  
  
  • [x] By-Name Implicits https://dotty.epfl.ch/docs/reference/implicit-by-name-parameters.html https://docs.scala-lang.org/sips/byname-implicits.html (@darjutak)
  
  
  • [x] Trait Parameters https://dotty.epfl.ch/docs/reference/trait-parameters.html
  
  

Feel free to edit/refine/etc.

[allanrenucci]

@lampepfl/dotty-core To avoid duplicate work: if you choose to work on one item, edit the issue by adding your name next to the item

[allanrenucci]

trait parameters already have a SIP: https://docs.scala-lang.org/sips/trait-parameters.html

@sjrd Is it good as is?

[liufengyun]

Regarding trait/class parameters, there is a change from Scalac. The following code compiles in Dotty, but not Scalac:

class A(a: Int) {
  trait Y {
    val y = a
  }

  class Z(val o: A) extends o.Y {
    val z = a
  }
}

However, trait parameters cannot be used as parent arguments:

class A(a: Int) {
  trait Y {
    val y = a
  }

  trait Z(val o: A) extends o.Y { // error
    val z = a
  }
}

Related discussion https://github.com/lampepfl/dotty/pull/5099#issuecomment-420776248

[sjrd]

trait parameters already have a SIP: https://docs.scala-lang.org/sips/trait-parameters.html

Yes, this one looks good :+1:

[darjutak]

This is a gentle reminder:
SIP November meetings start on the 1st Nov. at 9 AM. and go on for the next 2 days.
Many of the Committee members are flying in just for this (total number 8 members joining), and it would be great if they could get some of the writeups beforehand to prepare. Suggestion deadline: October 22nd.
Please don't shoot the messenger (o:

[darjutak]

Hi there Everyone, I've been speaking with some of you and I found out that this suggestion might be helpful to you as a guideline going forward, proposed by Eugene: https://gist.github.com/xeno-by/fdf652967727f94a9274ff62773acee0

[smarter]

It looks like the documentation shown on dotty.epfl.ch is outdated: it's missing recent specs addition, e.g. http://dotty.epfl.ch/docs/reference/intersection-types-spec.html is 404 but http://lampepfl.github.io/dotty/docs/reference/intersection-types-spec.html is working. @allanrenucci can you have a look ?

[smarter]

Due to issues with github webhooks, even http://lampepfl.github.io/dotty/docs isn't up to date currently, I recommend going directly to the source: https://github.com/lampepfl/dotty/tree/master/docs/docs/reference

[SethTisue]

should top level definitions be on this list? https://github.com/lampepfl/dotty/blob/cd3b1ed79cda47e99b7c2730677d9f1beac0f96f/docs/docs/reference/dropped-features/package-objects.md

this came up over at https://github.com/scala/scala/pull/7662 /cc @godenji

[OlivierBlanvillain]

I think we can close this one now :smiley_cat: