Inline Traits & Specialized Traits

.github/ISSUE_TEMPLATE/bug.md

@@ -1,6 +1,6 @@
 ---
 name: "\U0001F41B Bug report"
-about: Report a bug about the Dotty Compiler
+about: Report a bug about the Scala 3 compiler
 title: ''
 labels: itype:bug, stat:needs triage
 assignees: ''

.github/ISSUE_TEMPLATE/crash.md

@@ -1,6 +1,6 @@
 ---
 name: "\U0001F4A5 Crash report"
-about: Report a Dotty compiler crash
+about: Report a Scala 3 compiler crash
 title: ''
 labels: itype:bug, itype:crash, stat:needs triage
 assignees: ''

.github/ISSUE_TEMPLATE/feature.md

@@ -7,4 +7,4 @@ assignees: ''
 
 ---
 
-Please create a feature request in the [Dotty Discussions](https://github.com/scala/scala3/discussions/new?category=feature-requests).
+Please create a feature request in the [Scala 3 Discussions](https://github.com/scala/scala3/discussions/new?category=feature-requests).

.github/ISSUE_TEMPLATE/other-issue.md

@@ -1,6 +1,6 @@
 ---
 name: Other issue
-about: Report an issue about the Dotty Compiler (not bug or crash)
+about: Report an issue about the Scala 3 compiler (not a bug or a crash)
 title: ''
 labels: stat:needs triage
 assignees: ''

.github/pull_request_template.md

@@ -1,42 +1,23 @@
-<!-- Fixes #XYZ (where XYZ is the issue number from the issue tracker) -->
+Fixes #XYZ
 
-<!-- TODO description of the change -->
-<!-- Ideally should have a title like "Fix #XYZ: Short fix description" -->
-
-<!--
-  TODO first sign the CLA
-  https://contribute.akka.io/cla/scala
--->
-
-<!-- if the PR is still a WIP, create it as a draft PR (or convert it into one) -->
+<!-- where #XYZ is the issue number; create as draft if this is still a WIP;
+     if in doubt about your contribution, refer to: https://github.com/scala/scala3/blob/main/CONTRIBUTING.md
+     don't forget to sign the CLA: https://contribute.akka.io/cla/scala -->
 
 ## How much have you relied on LLM-based tools in this contribution?
 
-<!-- 
-  State clearly in the pull request description, 
-  whether LLM-based tools were used and to what extent 
-
-  (extensively/moderately/minimally/not at all)
--->
+<!-- Pick one; refer to https://github.com/scala/scala3/blob/main/LLM_POLICY.md for details -->
 
-<!--
-  Refer to our [LLM usage policy](https://github.com/scala/scala3/blob/main/LLM_POLICY.md) for rules and guidelines
-  regarding usage of LLM-based tools in contributions.
--->
+Extensively, for ...
+Moderately, for ...
+Minimally, for ...
+Not at all
 
 ## How was the solution tested?
 
-<!-- 
-  If automated tests are included, mention it.
-  If they are not, explain why and how the solution was tested.
--->
-
-## Additional notes
-
-<!-- Placeholder for any extra context regarding this contribution. -->
+<!-- Pick one; exceptions must have a very good reason -->
 
-<!--
-  When in doubt, and for support regarding contributions to a particular component of the compiler, 
-  refer to [our contribution guide](https://github.com/scala/scala3/blob/main/CONTRIBUTING.md),
-  and feel free to tag the maintainers listed there for the area(s) you are modifying.
--->
+New automated tests (including the issue's reproducer, if applicable)
+Covered by existing tests (this is a refactoring)
+Non-code change, no tests needed
+Manual tests because writing automated tests is impractical, described below (in detail)

.github/workflows/ci.yaml

@@ -1,4 +1,4 @@
-name: Dotty
+name: Scala 3
 
 on:
   push:
@@ -126,7 +126,7 @@ jobs:
 
       # Extract the release tag
       - name: Extract the release tag
-        run : echo "RELEASE_TAG='${GITHUB_REF#*refs/tags/}'" >> $GITHUB_ENV
+        run : echo "RELEASE_TAG=${GITHUB_REF#*refs/tags/}" >> $GITHUB_ENV
 
       - name: Check compiler version
         shell: bash
@@ -276,5 +276,5 @@ jobs:
         with:
           fetch-depth: 0
       - uses: coursier/cache-action@v8
-      - uses: VirtusLab/scala-cli-setup@v1.12.5
+      - uses: VirtusLab/scala-cli-setup@v1.14
       - run: scala-cli format --check

.github/workflows/lts-backport.yaml

@@ -24,7 +24,7 @@ jobs:
         with:
           fetch-depth: 0
       - uses: coursier/cache-action@v8
-      - uses: VirtusLab/scala-cli-setup@v1.12.3
+      - uses: VirtusLab/scala-cli-setup@v1.14
       - run: scala-cli ./project/scripts/addToBackportingProject.scala -- ${{ github.sha }}
         env:
           GRAPHQL_API_TOKEN: ${{ steps.app-token.outputs.token }}

.github/workflows/scaladoc.yaml

@@ -73,7 +73,7 @@ jobs:
         uses: actions/checkout@v6
 
       - uses: coursier/cache-action@v8
-      - uses: VirtusLab/scala-cli-setup@v1.12.3
+      - uses: VirtusLab/scala-cli-setup@v1.14
 
       - name: Validate docs sidebars
         run: scala-cli ./project/scripts/checkSidebarDocs.scala
@@ -148,7 +148,7 @@ jobs:
     steps:
       - uses: actions/checkout@v6
       - uses: coursier/cache-action@v8
-      - uses: VirtusLab/scala-cli-setup@v1.11
+      - uses: VirtusLab/scala-cli-setup@v1.14
         with:
           jvm: temurin:17
           apps: sbt

.github/workflows/spec.yml

@@ -49,7 +49,7 @@ jobs:
         env:
           USER_FOR_TEST: ${{ secrets.SPEC_DEPLOY_USER }}
         if: ${{ env.USER_FOR_TEST != '' }}
-        uses: burnett01/rsync-deployments@8.0.4
+        uses: burnett01/rsync-deployments@8.0.5
         with:
           switches: -rzv
           path: docs/_spec/_site/

.github/workflows/stdlib.yaml

@@ -167,10 +167,17 @@ jobs:
           distribution: 'temurin'
           java-version: 17
           cache: 'sbt'
+
       - uses: sbt/setup-sbt@v1
+
       - name: Test `scala3-compiler-nonbootstrapped`
         run: ./project/scripts/sbt scala3-compiler-nonbootstrapped/test
 
+      - name: Cmd Tests
+        run: |
+          ./project/scripts/sbt scala3-nonbootstrapped/publishLocal
+          ./project/scripts/cmdTests
+
   test-scala3-compiler-bootstrapped:
     runs-on: ubuntu-latest
     steps:
@@ -183,10 +190,17 @@ jobs:
           distribution: 'temurin'
           java-version: 17
           cache: 'sbt'
+
       - uses: sbt/setup-sbt@v1
+
       - name: Test `scala3-compiler-bootstrapped`
         run: ./project/scripts/sbt scala3-compiler-bootstrapped/test
 
+      - name: Cmd Tests
+        run: |
+          ./project/scripts/sbt scala3-bootstrapped/publishLocal
+          ./project/scripts/bootstrappedOnlyCmdTests
+
   test-scala3-bootstrapped-compilation-coverage:
     runs-on: ubuntu-latest
     steps:

.gitignore

@@ -69,6 +69,7 @@ testlogs/
 
 before-pickling.txt
 after-pickling.txt
+after-printing.txt
 bench/compile.txt
 
 community-build/scala3-bootstrapped.version
@@ -104,4 +105,4 @@ docs/_spec/.jekyll-metadata
 scaladoc/output/
 
 # only used in local development
-.enable_bsp_all_projects
+.enable_bsp_all_projects

README.md

@@ -4,12 +4,7 @@ Scala 3
 [![Join the chat at https://discord.com/invite/scala](https://img.shields.io/discord/632150470000902164)](https://discord.com/invite/scala)
 
 This is the home of the [Scala 3](https://www.scala-lang.org) standard library, compiler, and language spec.
-
-* [Documentation](https://docs.scala-lang.org/scala3/)
-
-Try it out
-==========
-To try it in your project see also the [Getting Started User Guide](https://docs.scala-lang.org/scala3/getting-started.html).
+More documentation [here](https://docs.scala-lang.org/scala3/).
 
 Building a Local Distribution
 =============================
@@ -18,16 +13,16 @@ Building a Local Distribution
 
 Code of Conduct
 ===============
-Dotty uses the [Scala Code of Conduct](https://www.scala-lang.org/conduct.html)
+Scala 3 uses the [Scala Code of Conduct](https://www.scala-lang.org/conduct.html)
 for all communication and discussion. This includes both GitHub, Discord and
 other more direct lines of communication such as email.
 
 How to Contribute
 =================
-* [Getting Started as Contributor](https://docs.scala-lang.org/scala3/guides/contribution/contribution-intro.html)
-* [Issues](https://github.com/scala/scala3/issues?q=is%3Aissue+is%3Aopen+label%3A%22help+wanted%22)
-* [Policy regarding usage of LLM-based tools in contributions to the Scala project](LLM_POLICY.md)
+* [Contributing guide](./CONTRIBUTING.md)
+* [Issues where help is wanted](https://github.com/scala/scala3/issues?q=is%3Aissue+is%3Aopen+label%3A%22help+wanted%22)
+* [Policy regarding the use of LLM-based tools](LLM_POLICY.md)
 
 License
 =======
-Scala 3 is licensed under the [Apache License Version 2.0](https://www.apache.org/licenses/LICENSE-2.0)
+Scala 3 is licensed under the [Apache License Version 2.0](https://www.apache.org/licenses/LICENSE-2.0)

bench-micro/src/main/scala/dotty/tools/benchmarks/SpecializedTraitsBenchmark.scala

@@ -0,0 +1,100 @@
+// Run with: scala-cli --power --jmh bench-micro/src/main/scala/dotty/tools/benchmarks/SpecializedTraitsBenchmark.scala
+// May have to run it again / delete .scala-build and rerun if you get a class not found
+// error from scala-cli first time - the --jmh flag is still experimental.
+// Don't forget to publish the compiler first and check that the version below corresponds to the generated version,
+// as well as to kill the bloop server if you are republishing the same version as before.
+// scala-cli --power bloop exit
+
+//> using scala 3.9.0-RC1-bin-SNAPSHOT-nonbootstrapped
+//> using options -language:experimental.specializedTraits
+
+package dotty.tools.benchmarks
+
+import org.openjdk.jmh.annotations.*
+import java.util.concurrent.TimeUnit
+
+class VecManual(elems: Array[Int]):
+  private val num = summon[Numeric[Int]]
+
+  def length = elems.length
+
+  def apply(i: Int): Int = elems(i)
+
+  def scalarProduct(other: VecManual): Int =
+    require(this.length == other.length)
+    var result = num.fromInt(0)
+    for i <- 0 until length do
+      result = num.plus(result, num.times(this(i), other(i)))
+    result
+
+class VecGeneric[T: Numeric](elems: Array[T]):
+  private val num = summon[Numeric[T]]
+
+  def length = elems.length
+
+  def apply(i: Int): T = elems(i)
+
+  def scalarProduct(other: VecGeneric[T]): T =
+    require(this.length == other.length)
+    var result = num.fromInt(0)
+    for i <- 0 until length do
+      result = num.plus(result, num.times(this(i), other(i)))
+    result
+
+inline trait VecSpecialized[T: {Specialized, Numeric2}](elems: Array[T]):
+  private val num = summon[Numeric2[T]]
+
+  def length = elems.length
+
+  def apply(i: Int): T = elems(i)
+
+  def scalarProduct(other: VecSpecialized[T]): T =
+    require(this.length == other.length)
+    var result = num.fromInt(0)
+    for i <- 0 until length do
+      result = num.plus(result, num.times(this(i), other(i)))
+    result
+
+@State(Scope.Benchmark)
+class Arrays:
+  var arr1 = Array.fill(100_000_000) {math.round(math.random().floatValue * 4)}
+  var arr2 = Array.fill(100_000_000) {math.round(math.random().floatValue * 4)}
+  val target = arr1.zip(arr2).map((x, y) => x * y).fold(0)(_ + _)
+
+@State(Scope.Benchmark)
+@BenchmarkMode(Array(Mode.AverageTime))
+@OutputTimeUnit(TimeUnit.MILLISECONDS)
+@Warmup(iterations = 5, time = 100, timeUnit = TimeUnit.MILLISECONDS)
+@Measurement(iterations = 15, time = 100, timeUnit = TimeUnit.MILLISECONDS)
+@Fork(1)
+class VecBench:
+  @Benchmark
+  def manual(arr: Arrays) =
+    val x = VecManual(arr.arr1)
+    val y = VecManual(arr.arr2)
+    assert(x.scalarProduct(y) == arr.target)
+
+  @Benchmark
+  def generic(arr: Arrays) =
+    val x = VecGeneric[Int](arr.arr1)
+    val y = VecGeneric[Int](arr.arr2)
+    assert(x.scalarProduct(y) == arr.target)
+
+  @Benchmark
+  def specialized(arr: Arrays) =
+    val x = new VecSpecialized[Int](arr.arr1) {}
+    val y = new VecSpecialized[Int](arr.arr2) {}
+    assert(x.scalarProduct(y) == arr.target)
+
+// You can really see the impact of Specialized on the interface usage here
+// Remove Specialized and see that the generated code gets much more boxing and unboxing
+// which slows it down substantially. 
+inline trait Numeric2[T: Specialized]:
+  def fromInt(x: Int): T
+  def plus(x: T, y: T): T
+  def times(x: T, y: T): T
+
+implicit object IntIsIntegral extends Numeric2[Int]:
+  override def fromInt(x: Int): Int = x
+  override def plus(x: Int, y: Int): Int = x + y
+  override def times(x: Int, y: Int): Int = x * y

community-build/src/scala/dotty/communitybuild/projects.scala

@@ -117,12 +117,14 @@ final case class SbtCommunityProject(
     val sbtProps = Option(System.getProperty("sbt.ivy.home")) match
       case Some(ivyHome) => List(s"-Dsbt.ivy.home=$ivyHome")
       case _ => Nil
-    extraSbtArgs ++ sbtProps ++ List("-sbt-version", "1.11.5", "-Dsbt.supershell=false", s"--addPluginSbtFile=$sbtPluginFilePath")
+    extraSbtArgs ++ sbtProps ++ List("-sbt-version", "1.12.1", "-Dsbt.supershell=false", s"--addPluginSbtFile=$sbtPluginFilePath")
 
 object SbtCommunityProject:
   def scalacOptions = List(
     "-Xcheck-macros",
     "-Wsafe-init",
+    "-Yexplicit-nulls",
+    "-language:unsafeNulls",
   )
 
 object projects:
@@ -134,7 +136,7 @@ object projects:
 
   private def removeRelease8(projects: String*): String =
     projects.map(project =>
-      s"""set $project/Compile/scalacOptions := ($project/Compile/scalacOptions).value.filterNot(opt => opt == "-release" || opt == "8")"""
+      s"""set $project/Compile/scalacOptions := ($project/Compile/scalacOptions).value.filterNot(opt => opt == "-release" || opt == "-java-output-version" || opt == "8")"""
     ).mkString("; ")
 
   private def aggregateDoc(in: String)(projects: String*) =
@@ -426,7 +428,14 @@ object projects:
 
   lazy val catsEffect3 = SbtCommunityProject(
     project        = "cats-effect-3",
-    sbtTestCommand = "ciJVM",
+    sbtTestCommand =
+      List(
+        removeRelease8("core.jvm", "example.jvm", "kernel.jvm", "kernelTestkit.jvm", "laws.jvm", "std.jvm", "testkit.jvm", "tests.jvm", "rootJVM", "ioAppTestsJVM", "benchmarks", "graalVMExample"),
+        // repeats code from `removeRelease8`, but oh well, maybe generalize later
+        """set root/ScalaUnidoc/unidoc/scalacOptions := (root/ScalaUnidoc/unidoc/scalacOptions).value.filterNot(opt => opt == "-release" || opt == "-java-output-version" || opt == "8")""",
+        "set ThisBuild / tlFatalWarnings := false",
+        "ciJVM"
+      ).mkString("; "),
     sbtPublishCommand = "publishLocal",
     sbtDocCommand  = ";coreJVM/doc ;lawsJVM/doc ;kernelJVM/doc",
   )
@@ -762,7 +771,6 @@ def allProjects = List(
   projects.libretto,
   projects.jacksonModuleScala,
   projects.specs2,
-  projects.coop,
   projects.spire,
   projects.http4s,
   projects.parboiled2,

compiler/src/dotty/tools/MainGenericCompiler.scala

@@ -129,6 +129,6 @@ object MainGenericCompiler {
           properArgs
           ++ List("-script", settings.targetScript)
           ++ settings.scriptArgs
-        scripting.Main.main(properArgs.toArray)
+        scripting.Main.main(fullArgs.toArray)
   end main
 }