State of the Scala 2 Union Adriaan Moors Scala Team Lead Scala - PowerPoint PPT Presentation

State of the Scala 2 Union Adriaan Moors Scala Team Lead

Scala 2.13

Developer survey! scala-lang.org/news/survey-2018.html

Apache v2.0! � scala-lang.org/news/license-change.html (deadline for any concerns: Aug 10)

Library release scala/scala-dev#324 M4 out now M5 early August Final: October

Headlines Simpler collections Smaller core lib Faster compiler Java 9 support (minimal) User-friendliness

Simpler Collections Fix common gotchas Simplify implementation & usage Improved type inference of overloaded HO method Available now (M4)

2.13.0-M4 upgrade scala/community-builds#710 Thank you, @xuwei-k ! � × 18

Smaller core lib Parallel collections: ✅ compact1 profile: ✅ #6164 Make way for new modules #5677 Looking at you, scala.io, scala.sys

Faster Compiler Optimization Automated Benchmarking & Charting 20% improvement (last 12 months, hot compiler)

User-friendliness Improve tooling Scala Center Better docs Great way to start contributing

Scalafix use for upgrade to 2.14 procedure syntax add sigs for implicits (& non-private members?) collections also, style checking / linting (built on scala.meta's semantic api)

LSP: modern IDE support Dotty presentation compiler TASTY and SemanticDB

BSP / Build tools Bloop (not a build tool) Mill (bazel-ish) Fury (source dependencies) <insert your build tool here>

Typelevel & friends! literal singleton types implicit search type constructor inference

#help-wanted Configurable error reporting Suppress warnings Nicer REPL

Revamp REPL syntax highlighting nicer editing cleaner wrapping improve embeddability (e.g. Spark) parity with Ammonite

Intermezzo

Scala?

Fusion!

Fusion ⇒ Flexibility Powerful Also, challenging!

OO & FP objects = modules functions = small objects

Safe & Concise Static types: safety + understanding Type inference: elide details Together: refactoring �

Impure ↔ Pure Strict ↔ Lazy Orthogonal concerns

Scala Spectrum Challenge: pick right point (At least you have the choice.)

GTD ↔ Correctness Type checker = lightweight verifier Cost of Failure ↔ Verification?

Cost of Abstraction See: Why the free monad is not free

Empathy-Driven Development Math is good to recognize patterns But we need to communicate intent

Math ↔ Practice math / fun: inspires structure, not names modules: names, mutual recursion

Future correctness checks? Effect system? Ownership?

Scala Spectrum More opinionated in 3.0 Keep essential flexibility

Scala 2.14

Close the Scala 3 Gap stdlib identical (2.13 & 3.0) TASTY interop shared compiler (post-typer) tooling

T-AST-y? Source code, fully type checked Full semantic information

Binary Compatibility? TASTY: Source compat == bin compat Not about: API evolution

Simplify github.com/scala/scala-dev/milestone/18

Drop: early initializers trait parameters procedure syntax

Deprecate: forSome: only wildcards value classes: opaque types whitebox macros: typelevel fun / codegen package object inheritance? vast implicit scope? (ignore packages in prefix)

Add trait parameters opaque types type lambda

Implicits must have explicit return type lazy implicit (see: shapeless) multiple implicit parameter lists (see: Aux in shapeless)

(Maybe) New JVM shiny varhandles minimal value types? …

Scala 3

Kinda like 2.15 Just more exciting :-)

Excitement Implicit function types Union types transparent + principled meta-programming New macros enum @static

Fin

Grateful Contributors Community Scala Center Dotty Team

Thank you Any Questions!?!