diff --git a/slides/99-scala3-migration-course.md b/slides/99-scala3-migration-course.md new file mode 100644 index 000000000..e2c3247c3 --- /dev/null +++ b/slides/99-scala3-migration-course.md @@ -0,0 +1,225 @@ + + +[//]: # (The following is a hack to move the slide H2 section down) +## ­ +## ­ +## ­ +## Scala 3 migration course + +--- + +## Course overview +## ­ + +* In this course we will: + * Start from an existing sbt build (Scala 2.13) + * Use sbt-scala3-migrate to migrate the build to Scala 3 +### ­ +* The objective is to learn the four steps of migrating a project: + * Updating the dependencies + * Updating the compiler options + * Patching the syntax of the code + * Fixing the type inference errors + + + +--- + +## Dotty/Scala 3 +## ­ + +* Dotty: New research project started in 2012 by Martin Odersky's lab at EPFL +* Dotty announced to become Scala 3 (April 2018) +* 3.0.0 released on May 13, 2021 +* [3.3.0](https://github.com/lampepfl/dotty/releases/tag/3.3.0) relased on May 30th, 2023. First LTS (Long Term Support) release. +* IDE support + * [Visual Studio Code](https://code.visualstudio.com) with [Metals](https://scalameta.org/metals/) + * integrated support in Metals including Scala Worksheet support! + * [IntelliJ](https://www.jetbrains.com/idea/) + * Scala 3 support with the [Scala Plugin](https://lp.jetbrains.com/intellij-scala/) +* There's the [Scala 3 Migration Guide](https://docs.scala-lang.org/scala3/guides/migration/compatibility-intro.html)! + +--- +## Compatibility in Scala 2 +## ­ + +- Before Scala 2.10: no compatibility between any two versions + - Different standard library + - Different binary interface +- Since Scala 2.10: strict binary compatibility in minor versions + - 2.13.11 is compatible with 2.13.8 + - 2.13.11 is not compatible with 2.12.19 + +## ­ +### => Ecosystem jump between 2.12 and 2.13 + +--- + +## Compatibility between Scala 2.13 and Scala 3 +## ­ + +* Scala 3 uses the Scala 2.13 standard library +* Scala 3 produces Scala 2.13 compatible binaries (class files, sjsir, ...) +* Scala 3 can read Scala 2.13 signatures (Pickle format) +* Scala 2.13 can read Scala 3 signatures (TASTy) using -Ytasty-reader + +## ­ + +### => Backward and forward compatibility between Scala 2.13 and Scala 3 + +--- + +## For 3 use 2.13 +## ­ + +![](images/compatibility-3-to-213.svg) + +``` +lazy val foo = project.in(file("foo")) + .settings( + scalaVersion := "3.0.0", + libraryDependencies += + ("org.bar" %% "bar" % "1.0.0").cross(CrossVersion.for3Use2_13) + ) +``` + +--- + +## For 2.13 use 3 (TASTy reader) +## ­ + +![](images/compatibility-213-to-3.svg) + +``` +lazy val foo = project.in(ile("foo")) + .settings( + scalaVersion := "2.13.6", + scalacOptions += "-Ytasty-reader", + libraryDependencies += + ("org.bar" %% "bar" % "1.0.0").cross(CrossVersion.for2_13Use3) + ) +``` + +--- + +## The sandwich pattern +## ­ + +![](images/compatibility-sandwich.svg) + +--- + +## The diamond pattern +## ­ + + + +``` +[error] Modules were resolved with conflicting cross-version suffixes in main: +[error] org.typelevel:cats _3, _2.13 +``` + +--- + +## Metaprogramming +## ­ + +- Scala 2.13 macros are experimental +- Scala 3 macros are based on new foundations. +They are simpler and more stable. +- Scala 2.13 and Scala 3 macros are incompatible +- The community started migrating the macro libraries to Scala 3. +See [Table of macro libraries.](https://scalacenter.github.io/scala-3-migration-guide/docs/macros/macro-libraries.html) + +--- + +## Compiler plugins +## ­ + +- The Scala 3 compiler is completely new +- Scala 2.13 plugins cannot be used in Scala 3 +- Scala 3 plugins are more constrained +- Some important plugins were integrated in the compiler, and can be activated with an option: + - `-Ykind-projector` + - `-scalajs` + - `-semanticdb` + +--- +## Compiler Options (`scalacOptions`) +## ­ + +- Most options are available +- Some are renamed +- Some are dropped +- Some of the most used Scala 2 options are ported to Scala 3. For example, we ported `-Wunused` to Scala 3.3.0. +- See [table of compiler options](https://docs.scala-lang.org/scala3/guides/migration/options-lookup.html). + +--- +## Syntactic changes + +![](images/incompat-syntax.png) + +--- + +## Dropped features + +![](images/incompat-dropped-features.png) +--- + +## Contextual abstractions (Implicits) + +![](images/incompat-context-abstractions.png) + +--- + +## Other changed features + +![](images/incompat-changed-features.png) + +--- + +## Type checker and type inference + +![](images/incompat-types.png) + +--- + +## sbt-scala3-migrate + +- It's an sbt plugin + +![](images/sbt-scala3-migrate-install.png) + +- It can assist you during the migration to Scala 3 of your build + +![](images/sbt-scala3-migrate-welcome.png) + +--- + +## Scala 3 migration course + +![](images/scalacenter-scala3-migration-course.png) + +--- + +## Scala 3 migration course +## ­ + +``` +$ cmtc install -f -s scalacenter/scala3-migration-course +Downloading studentified course from 'https://github.com/scalacenter/scala3-migration-course/releases/download/0.1.0/scala3-migrate-course-student.zip' to courses directory + +Project scalacenter/scala3-migration-course (0.1.0) successfully installed to: + /home/user/Library/Caches/com.lunatech.cmt/Courses/scala3-migration-course + +Current course set to '/home/user/Library/Caches/com.lunatech.cmt/Courses/scala3-migration-course' + +Exercises in repository: + 1. * exercise_000_initial_state + 2. exercise_001_install_sbt_scala3_migrate + 3. exercise_002_migrate_dependencies + 4. exercise_003_migrate_scalac_options + 5. exercise_004_migrate_syntax + 6. exercise_005_migrate_types + 7. exercise_006_update_scala_version +``` diff --git a/slides/images/compatibility-213-to-3.svg b/slides/images/compatibility-213-to-3.svg new file mode 100644 index 000000000..32d5687bc --- /dev/null +++ b/slides/images/compatibility-213-to-3.svg @@ -0,0 +1,3 @@ + + +
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