xuwei-k

compiler/src/dotty/tools/dotc/config/CommandLineParser.scala:    end loop
compiler/src/dotty/tools/dotc/config/CommandLineParser.scala:  end tokenize
compiler/src/dotty/tools/dotc/core/ConstraintHandling.scala:  end addOneBound
compiler/src/dotty/tools/dotc/core/ConstraintHandling.scala:  end addBoundTransitively
compiler/src/dotty/tools/dotc/core/ConstraintHandling.scala:    end dropSuperTraits
compiler/src/dotty/tools/dotc/core/ConstraintHandling.scala:  end widenInferred
compiler/src/dotty/tools/dotc/core/ConstraintHandling.scala:  end addConstraint
compiler/src/dotty/tools/dotc/core/Contexts.scala:  end ops
compiler/src/dotty/tools/dotc/core/Contexts.scala:  end comparing
compiler/src/dotty/tools/dotc/core/Decorators.scala:  end extension

xuwei-k

Principled Meta Programming for Scala

This note outlines a principled way to meta-programming in Scala. It tries to combine the best ideas from LMS and Scala macros in a minimalistic design.

• LMS: Types matter. Inputs, outputs and transformations should all be statically typed.

• Macros: Quotations are ultimately more easy to deal with than implicit-based type-lifting

• LMS: Some of the most interesting and powerful applications of meta-programming

xuwei-k

import scalafix.v1._
import scala.meta._

class ThrowableToNonFatal extends SemanticRule("ThrowableToNonFatal") {
  override def fix(implicit doc: SemanticDocument): Patch = {
    doc.tree.collect {
      case c @ Case(Pat.Typed(v, Type.Name("Throwable")), _, _) =>
        List(
          Patch.addGlobalImport(importer"scala.util.control.NonFatal"),
          Patch.replaceTree(

xuwei-k

xuwei-k

$ scala -version
Scala code runner version 2.13.2 -- Copyright 2002-2020, LAMP/EPFL and Lightbend, Inc.
$ scala -Xprint:jvm -e 'if (util.Random.nextInt == 1) 2 else "3"'
[[syntax trees at end of                       jvm]] // scalacmd6816512509873541389.scala
package <empty> {
  object Main extends Object {
    def main(args: Array[String]): Unit = {
      new <$anon: Object>();
      ()
    };

xuwei-k

package scalaz

import scalafix.v1.{Patch, SemanticDocument, SemanticRule}
import scala.meta._
import scalafix.v1._

class ScalazEitherInfix extends SemanticRule("ScalazEitherInfix") {

  override def fix(implicit doc: SemanticDocument): Patch = {
    doc.tree.collect {

xuwei-k

echo 'addSbtPlugin("ch.epfl.scala" % "sbt-scalafix" % "0.9.15")' > project/scalafix.sbt

sbt scalafixEnable "scalafix https://raw.githubusercontent.com/scalaz/scalazfix/master/rules/src/main/scala/scalaz/ScalazFix.scala" "test:scalafix https://raw.githubusercontent.com/scalaz/scalazfix/master/rules/src/main/scala/scalaz/ScalazFix.scala"

rm project/scalafix.sbt

xuwei-k

[info] running foo.Main 
2.12.11
class foo.A

xuwei-k

import scalafix.v1.{Patch, SyntacticDocument, SyntacticRule}
import scala.meta.{Name, Term, Transformer, Tree, Type, XtensionQuasiquoteType}

class ExpandPolymorphicLambdas extends SyntacticRule("ExpandPolymorphicLambdas") {
  override def description: String = "Expand kind-projector's syntax for polymorphic lambda values"
  override def isLinter: Boolean = false

  private def replacePlaceholder(tree: Term, param: Term.Name): Option[Term] = tree match {
    case Term.Select(Term.Placeholder(), method) => Some(Term.Select(param, method))
    case Term.Select(select @ Term.Select(_, _), method) =>

xuwei-k

$ cat A.java 
record A(int x, int y) { }
$ javac A.java 
A.java:1: エラー: レコードはプレビュー機能であり、デフォルトで無効になっています。
record A(int x, int y) { }
^
  (レコードを有効にするには--enable-previewを使用します)
エラー1個
$ javac --enable-preview A.java 
エラー: --enable-previewは-sourceまたは--releaseとともに使用する必要があります