meta programming Scala

Metaprogramming Scala using scala.meta.
performed presentation as Scala-Kansai Summit 2017.

Transcript

1. メタプログラミング
   Scala
   Hiroki Komurasaki
   @petitviolet
   
   

   View Slide

2. 自己紹介
   • 小紫 弘貴(Hiroki Komurasaki)
   • インターネットだと@petitviolet
   • Scala歴2年くらい
   • でScalaとかGo書いてます
   • https://www.facebook.com/fringeneer/
   • http://fringeneer.hatenablog.com/
   
   

   View Slide

3. 今日話すこと
   • メタプログラミングってなに？
   • Scalaで出来るメタプログラミング
   • scala.meta
   • 使い方イメージ
   • ユースケース・実装例
   • 実装方法
   • scalametaの内部的な話
   • ロードマップ
   
   

   View Slide

4. 目指すゴール
   • メタプログラミング怖くなくなる
   • コード読んでみようかなと思う
   • ちょっとやってみようかなって思う
   • scalametaやってみようかなって思う
   
   

   View Slide

5. メタプログラミングってなに？
   
   

   View Slide

6. メタ
   > メタ（meta-）とは、「高次な－」「超－」
   「－間の」「－を含んだ」「－の後ろの」等の
   意味の接頭語。ギリシア語から。
   https://ja.wikipedia.org/wiki/メタ
   
   

   View Slide

7. メタプログラミングって何
   > プログラミング技法の一種で、ロジックを直
   接コーディングするのではなく、あるパターン
   をもったロジックを生成する高位ロジックに
   よってプログラミングを行う方法、またその高
   位ロジックを定義する方法のこと。
   https://ja.wikipedia.org/wiki/メタプログラミング
   
   

   View Slide

8. メタプログラミングって何
   ざっくり言うと、プログラムを引数としてプロ
   グラムを出力とする関数みたいなもの。
   ボイラープレートを削減できる！
   
   

   View Slide

9. 身近な例？
   • getter/setterの自動生成
   • マクロで`log.debug()`を削除
   • case class→classへの変換
   • コンパイラがよしなにやってくれている
   • for式をflatMapとmapとwithFilterに展開
   • desugar的な処理
   
   

   View Slide

10. Scalaで出来る
    メタプログラミング
    
    

    View Slide

11. 
    http://docs.scala-lang.org/ja/overviews/
    

    View Slide

12. 
    

    View Slide

13. よく使われるリフレクションもメタプログラミ
    ングの一種。
    実行時/コンパイル時のオブジェクトにアクセス
    出来る。
    
    try {
    Class> cl = Class.forName("Foo");
    Method method = cl.getMethod("hello");
    method.invoke(cl.newInstance());
    } catch (Exception e) {
    e.printStackTrace();
    }
    

    View Slide

14. よく使われるリフレクションもメタプログラミ
    ングの一種。
    実行時/コンパイル時のオブジェクトにアクセス
    出来る。
    
    import scala.reflect.runtime.{universe => ru}
    def getTypeTag[T: ru.TypeTag](obj: T) = ru.typeTag[T]
    val l = List(1, 2, 3)
    val head: ru.Symbol = getTypeTag(l).tpe.decl(ru.TermName("head"))
    val lMirror: ru.InstanceMirror =
    ru.runtimeMirror(getClass.getClassLoader).reflect(l)
    lMirror.reflectMethod(head.asMethod).apply() // 1
    

    View Slide

15. よく使われるリフレクションもメタプログラミ
    ングの一種。
    実行時/コンパイル時のオブジェクトにアクセス
    出来る。
    
    import scala.reflect.runtime.{universe => ru}
    def getTypeTag[T: ru.TypeTag](obj: T) = ru.typeTag[T]
    val l = List(1, 2, 3)
    val head: ru.Symbol = getTypeTag(l).tpe.decl(ru.TermName("head"))
    val lMirror: ru.InstanceMirror =
    ru.runtimeMirror(getClass.getClassLoader).reflect(l)
    lMirror.reflectMethod(head.asMethod).apply() // 1
    

    View Slide

16. 
    

    View Slide

17. • def macro
    • 引数等のメタ情報を利用できる
    • macro annotation
    • annotationをつけたクラスやメソッドのメタ情報、例
    えば型情報が利用できる
    • implicit macro
    • implicit parameterの自動生成
    • type provider
    • 型そのものを自動生成
    • 構造的部分型
    • 他にもいろいろ
    • マクロバンドルとか抽出子マクロとか
    
    http://docs.scala-lang.org/ja/overviews/macros/usecases.html
    

    View Slide

18. • def macro
    • 引数等のメタ情報を利用できる
    • macro annotation
    • annotationをつけたクラスやメソッドのメタ情報、例
    えば型情報が利用できる
    • implicit macro
    • implicit parameterの自動生成
    • type provider
    • 型そのものを自動生成
    • 構造的部分型
    • 他にもいろいろ
    • マクロバンドルとか抽出子マクロとか
    
    http://docs.scala-lang.org/ja/overviews/macros/usecases.html
    

    View Slide

19. def macro
    • Scalaマクロの代表格(要出典
    
    object DefMacro {
    def show[A](value: A): String = macro DefMacroImpl.showImpl[A]
    }
    

    View Slide

20. def macro
    • Scalaマクロの代表格(要出典
    
    object DefMacro {
    def show[A](value: A): String = macro DefMacroImpl.showImpl[A]
    }
    

    View Slide

21. def macro
    • Scalaマクロの代表格(要出典
    
    object DefMacro {
    def show[A](value: A): String = macro DefMacroImpl.showImpl[A]
    }
    object DefMacroImpl {
    def showImpl[A: c.WeakTypeTag](c: blackbox.Context)
    (value: c.Expr[A]): c.Expr[String] = {
    import c.universe._
    val typeName = c.weakTypeTag[A].tpe.typeSymbol.fullName
    val tree = value.tree
    c.Expr[String](Literal(Constant(s"type: $typeName, value: $tree")))
    }
    }
    

    View Slide

22. def macro
    • Scalaマクロの代表格(要出典
    
    object DefMacro {
    def show[A](value: A): String = macro DefMacroImpl.showImpl[A]
    }
    object DefMacroImpl {
    def showImpl[A: c.WeakTypeTag](c: blackbox.Context)
    (value: c.Expr[A]): c.Expr[String] = {
    import c.universe._
    val typeName = c.weakTypeTag[A].tpe.typeSymbol.fullName
    val tree = value.tree
    c.Expr[String](Literal(Constant(s"type: $typeName, value: $tree")))
    }
    }
    

    View Slide

23. def macro
    • Scalaマクロの代表格(要出典
    
    object DefMacro {
    def show[A](value: A): String = macro DefMacroImpl.showImpl[A]
    }
    object DefMacroImpl {
    def showImpl[A: c.WeakTypeTag](c: blackbox.Context)
    (value: c.Expr[A]): c.Expr[String] = {
    import c.universe._
    val typeName = c.weakTypeTag[A].tpe.typeSymbol.fullName
    val tree = value.tree
    c.Expr[String](Literal(Constant(s"type: $typeName, value: $tree")))
    }
    }
    

    View Slide

24. 
    object DefMacro {
    def show[A](value: A): String = macro DefMacroImpl.showImpl[A]
    }
    object DefMacroImpl {
    def showImpl[A: c.WeakTypeTag](c: blackbox.Context)
    (value: c.Expr[A]): c.Expr[String] = {
    import c.universe._
    val typeName = c.weakTypeTag[A].tpe.typeSymbol.fullName
    val tree = value.tree
    c.Expr[String](Literal(Constant(s"type: $typeName, value: $tree")))
    }
    }
    println(DefMacro.show[Int](100))
    // type: scala.Int, value: 100
    println(DefMacro.show[Long](100L))
    // type: scala.Long, value: 100L
    println(DefMacro.show(new java.lang.String("hello")))
    // type: java.lang.String, value: new java.lang.String("hello")
    

    View Slide

25. 
    def log(foo: String)(implicit line: sourcecode.Line,
    file: sourcecode.File) = {
    println(s"${file.value}:${line.value} $foo")
    }
    log("Foooooo")
    // sourcecode/shared/src/test/scala/sourcecode/Tests.scala:86 Foooooo
    lihaoyi/sourcecode
    • ソースコードの行番号やファイル名を取得
    • プログラムをメタに扱っている
    • 内部実装はdef macroを使用
    

    View Slide

26. 
    

    View Slide

27. 
    

    View Slide

28. scalameta
    
    

    View Slide

29. scalameta?
    > Scalameta is a clean-room implementation
    of a metaprogramming toolkit for Scala,
    designed to be simple, robust and portable.
    > We are striving for scalameta to become a
    successor of scala.reflect, the current de
    facto standard in the Scala ecosystem.
    http://scalameta.org/
    
    

    View Slide

30. scalameta?
    > Scalameta is a clean-room implementation
    of a metaprogramming toolkit for Scala,
    designed to be simple, robust and portable.
    > We are striving for scalameta to become a
    successor of scala.reflect, the current de
    facto standard in the Scala ecosystem.
    http://scalameta.org/
    
    

    View Slide

31. scalameta?
    > Scalameta is a clean-room implementation
    of a metaprogramming toolkit for Scala,
    designed to be simple, robust and portable.
    > We are striving for scalameta to become a
    successor of scala.reflect, the current de
    facto standard in the Scala ecosystem.
    http://scalameta.org/
    
    

    View Slide

32. scalameta?
    > Scalameta is a clean-room implementation
    of a metaprogramming toolkit for Scala,
    designed to be simple, robust and portable.
    > We are striving for scalameta to become a
    successor of scala.reflect, the current de
    facto standard in the Scala ecosystem.
    http://scalameta.org/
    
    

    View Slide

33. scalameta?
    > Scalameta is a modern metaprogramming
    library for Scala that supports a wide range of
    language versions and execution platforms.
    > Originally, Scalameta was founded to
    become a better macro system for Scala, but
    over time we shifted focus to developer tools
    and spun off the new macro system into a
    separate project.
    http://scalameta.org/
    
    

    View Slide

34. scalameta?
    • 現在Scalaのメタプログラミング関連で実装が
    進んでいるモダンなライブラリ
    • Scalaのバージョンや実行環境を幅広くサポー
    トする
    
    

    View Slide

35. 今のうちに
    やっておくしかない
    
    

    View Slide

36. なにができる？
    • macro annotation
    • `@Foo class MyClass()`
    • Java-erには馴染みのあるやつ
    
    

    View Slide

37. マクロアノテーション
    • ちなみに現行のScalaマクロでも可能
    
    

    View Slide

38. scalametaの
    使い方
    
    

    View Slide

39. scalametaの
    使い方
    (v1.8.0)
    
    

    View Slide

40. どんな感じで使えるか
    
    

    View Slide

41. 
    

    View Slide

42. 
    QuasiQuotes(ޙͰ
    

    View Slide

43. 
    

    View Slide

44. 
    

    View Slide

45. 
    

    View Slide

46. 
    

    View Slide

47. 
    

    View Slide

48. 
    hello
    world
    @hello
    def say() = {
    println("world")
    }
    say()
    

    View Slide

49. @hello?
    
    

    View Slide

50. 
    import scala.annotation.{StaticAnnotation, compileTimeOnly}
    import scala.meta._
    @compileTimeOnly("hello")
    class hello extends StaticAnnotation {
    inline def apply(defn: Any): Any = meta {
    defn match {
    case d: Defn.Def =>
    val newBody = q"""{
    println("hello")
    ${d.body}
    }"""
    d.copy(body = newBody)
    case _ =>
    abort("annotate only def")
    }
    }
    }
    

    View Slide

51. 
    import scala.annotation.{StaticAnnotation, compileTimeOnly}
    import scala.meta._
    @compileTimeOnly("hello")
    class hello extends StaticAnnotation {
    inline def apply(defn: Any): Any = meta {
    defn match {
    case d: Defn.Def =>
    val newBody = q"""{
    println("hello")
    ${d.body}
    }"""
    d.copy(body = newBody)
    case _ =>
    abort("annotate only def")
    }
    }
    }
    scala.metaͷimport
    

    View Slide

52. 
    import scala.annotation.{StaticAnnotation, compileTimeOnly}
    import scala.meta._
    @compileTimeOnly("hello")
    class hello extends StaticAnnotation {
    inline def apply(defn: Any): Any = meta {
    defn match {
    case d: Defn.Def =>
    val newBody = q"""{
    println("hello")
    ${d.body}
    }"""
    d.copy(body = newBody)
    case _ =>
    abort("annotate only def")
    }
    }
    }
    annotation༻ͷclassͰ͢Αએݴ
    

    View Slide

53. 
    import scala.annotation.{StaticAnnotation, compileTimeOnly}
    import scala.meta._
    @compileTimeOnly("hello")
    class hello extends StaticAnnotation {
    inline def apply(defn: Any): Any = meta {
    defn match {
    case d: Defn.Def =>
    val newBody = q"""{
    println("hello")
    ${d.body}
    }"""
    d.copy(body = newBody)
    case _ =>
    abort("annotate only def")
    }
    }
    }
    ࣮ߦ͞ΕΔapplyؔ਺
    

    View Slide

54. 
    import scala.annotation.{StaticAnnotation, compileTimeOnly}
    import scala.meta._
    @compileTimeOnly("hello")
    class hello extends StaticAnnotation {
    inline def apply(defn: Any): Any = meta {
    defn match {
    case d: Defn.Def =>
    val newBody = q"""{
    println("hello")
    ${d.body}
    }"""
    d.copy(body = newBody)
    case _ =>
    abort("annotate only def")
    }
    }
    }
    annotationͨ͠ର৅
    

    View Slide

55. 
    import scala.annotation.{StaticAnnotation, compileTimeOnly}
    import scala.meta._
    @compileTimeOnly("hello")
    class hello extends StaticAnnotation {
    inline def apply(defn: Any): Any = meta {
    defn match {
    case d: Defn.Def =>
    val newBody = q"""{
    println("hello")
    ${d.body}
    }"""
    d.copy(body = newBody)
    case _ =>
    abort("annotate only def")
    }
    }
    }
    ASTͷॻ͖׵͑
    

    View Slide

56. 
    import scala.annotation.{StaticAnnotation, compileTimeOnly}
    import scala.meta._
    @compileTimeOnly("hello")
    class hello extends StaticAnnotation {
    inline def apply(defn: Any): Any = meta {
    defn match {
    case d: Defn.Def =>
    val newBody = q"""{
    println("hello")
    ${d.body}
    }"""
    d.copy(body = newBody)
    case _ =>
    abort("annotate only def")
    }
    }
    }
    ৽͍͠AST
    

    View Slide

57. 
    import scala.annotation.{StaticAnnotation, compileTimeOnly}
    import scala.meta._
    @compileTimeOnly("hello")
    class hello extends StaticAnnotation {
    inline def apply(defn: Any): Any = meta {
    defn match {
    case d: Defn.Def =>
    val newBody = q"""{
    println("hello")
    ${d.body}
    }"""
    d.copy(body = newBody)
    case _ =>
    abort("annotate only def")
    }
    }
    }
    def͡Όͳ͚Ε͹ࣦഊ
    

    View Slide

58. 
    @hello
    def say() = {
    println("world")
    }
    class hello extends StaticAnnotation {
    inline def apply(defn: Any): Any = meta {
    defn match {
    case d: Defn.Def =>
    val newBody = q"""{
    println("hello")
    ${d.body}
    }"""
    d.copy(body = newBody)
    case _ =>
    abort("annotate only def")
    }
    }
    }
    

    View Slide

59. 
    @hello
    def say() = {
    println("world")
    }
    class hello extends StaticAnnotation {
    inline def apply(defn: Any): Any = meta {
    defn match {
    case d: Defn.Def =>
    val newBody = q"""{
    println("hello")
    ${d.body}
    }"""
    d.copy(body = newBody)
    case _ =>
    abort("annotate only def")
    }
    }
    }
    

    View Slide

60. 
    • IntelliJは展開してくれる
    Before
    

    View Slide

61. 
    • IntelliJは展開してくれる
    Before
    After
    

    View Slide

62. 
    • IntelliJは展開してくれる
    Before
    After
    

    View Slide

63. • (展開しなければ)ちゃんと動く
    
    hello
    world
    @hello
    def say() = {
    println("world")
    }
    say()
    

    View Slide

64. 
    • 別のBlockとして認識されているので動く
    

    View Slide

65. 要するに
    
    

    View Slide

66. annotationした対象の
    ASTを書き換えられる
    
    

    View Slide

67. ユースケース
    
    

    View Slide

68. scalametaを使うと
    例えば何が出来るのか
    
    

    View Slide

69. メソッドの実行時間を計測
    
    

    View Slide

70. 
    object TimeLoggingApp extends App {
    def heavy(n: Long): Long = {
    Thread.sleep(n)
    n
    }
    println(heavy(100))
    }
    

    View Slide

71. 
    object TimeLoggingApp extends App {
    @TimeLogging
    def heavy(n: Long): Long = {
    Thread.sleep(n)
    n
    }
    println(heavy(100))
    }
    

    View Slide

72. 
    [heavy]tracking time:101 ms
    100
    object TimeLoggingApp extends App {
    @TimeLogging
    def heavy(n: Long): Long = {
    Thread.sleep(n)
    n
    }
    println(heavy(100))
    }
    

    View Slide

73. 
    class TimeLogging extends StaticAnnotation {
    inline def apply(defn: Any): Any = meta {
    defn match {
    case d @ Defn.Def(_, name, _, _, _, body) =>
    def s = Lit.String.apply _
    val newBody =
    q"""
    val start = System.nanoTime()
    val result = $body
    val end = System.nanoTime()
    println(${s(s"[${name.value}]tracking time:")} +
    ((end - start) / ${Lit.Long(1000000)}) + ${s(" ms")})
    result
    """
    d.copy(body = newBody)
    case _ =>
    abort("annotate only function!")
    }
    }
    }
    

    View Slide

74. 
    class TimeLogging extends StaticAnnotation {
    inline def apply(defn: Any): Any = meta {
    defn match {
    case d @ Defn.Def(_, name, _, _, _, body) =>
    def s = Lit.String.apply _
    val newBody =
    q"""
    val start = System.nanoTime()
    val result = $body
    val end = System.nanoTime()
    println(${s(s"[${name.value}]tracking time:")} +
    ((end - start) / ${Lit.Long(1000000)}) + ${s(" ms")})
    result
    """
    d.copy(body = newBody)
    case _ =>
    abort("annotate only function!")
    }
    }
    }
    લޙͰ࣌ؒऔಘ
    

    View Slide

75. 
    class TimeLogging extends StaticAnnotation {
    inline def apply(defn: Any): Any = meta {
    defn match {
    case d @ Defn.Def(_, name, _, _, _, body) =>
    def s = Lit.String.apply _
    val newBody =
    q"""
    val start = System.nanoTime()
    val result = $body
    val end = System.nanoTime()
    println(${s(s"[${name.value}]tracking time:")} +
    ((end - start) / ${Lit.Long(1000000)}) + ${s(" ms")})
    result
    """
    d.copy(body = newBody)
    case _ =>
    abort("annotate only function!")
    }
    }
    }
    ग़ྗ͍ͯ͠Δ͚ͩ
    

    View Slide

76. annotationでValidation
    
    

    View Slide

77. 
    val ok = 1 to 10
    val ng = 1 to 10
    

    View Slide

78. 
    @Length(min = 1, max = 10)
    val ok = 1 to 10
    @Length(min = 100)
    val ng = 1 to 10
    

    View Slide

79. 
    requirement failed: ng size is
    invalid. actual: 10, min: 100
    @Length(min = 1, max = 10)
    val ok = 1 to 10 // OK
    @Length(min = 100)
    val ng = 1 to 10 // NG
    

    View Slide

80. 
    q"""
    def msg(min: Int, max: Int, resultSize: Int): String = {
    val minCond = { if (min <= 0) "" else "min: " + min }
    val maxCond = { if (max <= 0) "" else "max: " + max }
    val res = ${s(name.syntax)} + " size is invalid. " +
    "actual: " + resultSize + ", " + minCond + maxCond
    res
    }
    def minValid(min: Int, resultSize: Int): Boolean =
    if (min <= 0) true else min <= resultSize
    def maxValid(max: Int, resultSize: Int): Boolean =
    if (max <= 0) true else max >= resultSize
    val result = $term
    val size: Int = result.size
    require(minValid(${i(min)}, size) && maxValid(${i(max)}, size),
    msg(${i(min)}, ${i(max)}, size))
    result
    """
    

    View Slide

81. 
    q"""
    def msg(min: Int, max: Int, resultSize: Int): String = {
    val minCond = { if (min <= 0) "" else "min: " + min }
    val maxCond = { if (max <= 0) "" else "max: " + max }
    val res = ${s(name.syntax)} + " size is invalid. " +
    "actual: " + resultSize + ", " + minCond + maxCond
    res
    }
    def minValid(min: Int, resultSize: Int): Boolean =
    if (min <= 0) true else min <= resultSize
    def maxValid(max: Int, resultSize: Int): Boolean =
    if (max <= 0) true else max >= resultSize
    val result = $term
    val size: Int = result.size
    require(minValid(${i(min)}, size) && maxValid(${i(max)}, size),
    msg(${i(min)}, ${i(max)}, size))
    result
    """
    ৚݅൑ఆΛࠩ͠ࠐΜͰ͍Δ
    requireͳͷͰ࣮ߦ࣌ྫ֎
    

    View Slide

82. コンパニオンオブジェクトを
    自動で生成
    
    

    View Slide

83. 
    class MyClass(val n: Int, val s: String)
    object UnapplyApp extends App {
    val target = new MyClass(n = 100, s = "hoge")
    }
    

    View Slide

84. 
    @Unapply
    class MyClass(val n: Int, val s: String)
    object UnapplyApp extends App {
    val target = new MyClass(n = 100, s = "hoge")
    }
    

    View Slide

85. 
    @Unapply
    class MyClass(val n: Int, val s: String)
    object UnapplyApp extends App {
    val target = new MyClass(n = 100, s = "hoge")
    target match {
    case MyClass(n, s) => println(s"$n, $s")
    case _ => sys.error("out!")
    }
    }
    

    View Slide

86. 
    100, hoge
    @Unapply
    class MyClass(val n: Int, val s: String)
    object UnapplyApp extends App {
    val target = new MyClass(n = 100, s = "hoge")
    target match {
    case MyClass(n, s) => println(s"$n, $s")
    case _ => sys.error("out!")
    }
    }
    

    View Slide

87. 
    @compileTimeOnly("not expanded")
    class Unapply extends scala.annotation.StaticAnnotation {
    inline def apply(defn: Any): Any = meta {
    defn match {
    // companion object exists
    case Term.Block(
    Seq(cls @ Defn.Class(_, name, _, ctor, _),
    companion: Defn.Object)) =>
    val newCompanion = Unapply.insert(cls)(Some(companion))
    Term.Block(Seq(cls, newCompanion))
    // companion object does not exists
    case cls @ Defn.Class(_, name, _, ctor, _) =>
    val newCompanion = Unapply.insert(cls)(None)
    Term.Block(Seq(cls, newCompanion))
    case _ =>
    println(defn.structure)
    abort("@Unapply must annotate a class.")
    }
    }
    }
    object Unapply extends CompanionMethodHelper {
    override protected val METHOD_NAME: String = "unapply"
    override protected def create(cls: Defn.Class)(companionOpt: Option[Defn.Object]): Defn.Def = {
    val (name, paramss) = (cls.name, cls.ctor.paramss)
    val argName = Term.Name("arg")
    val inputParam: Seq[Seq[Term.Param]] = {
    val param: Term.Param = Term.Param(Nil, argName, Some(name), None)
    (param :: Nil) :: Nil
    }
    val resultParam: Type = {
    val types: Seq[Type] = paramss.flatMap { _.collect {
    case Term.Param(_ :: Mod.ValParam() :: Nil, _, Some(typeArg), _) =>
    // private val n: Int
    Type.Name(typeArg.syntax)
    case Term.Param(_ :: Mod.VarParam() :: Nil, _, Some(typeArg), _) =>
    // private var n: Int
    Type.Name(typeArg.syntax)
    case Term.Param(Mod.ValParam() :: Nil, _, Some(typeArg), _) =>
    // val n: Int
    Type.Name(typeArg.syntax)
    case Term.Param(Mod.VarParam() :: Nil, _, Some(typeArg), _) =>
    // var n: Int
    Type.Name(typeArg.syntax)
    case x =>
    println(s"invalid paramss: $paramss")
    abort(s"non-accessible constructor exists. `unapply` always returns None. cause => $x")
    }}
    val tupled = Type.Tuple(types)
    Type.Apply(Type.Name("Option"), tupled :: Nil)
    }
    val body: Term = {
    val select: Seq[Term.Select] = paramss.flatMap { _.map { param =>
    Term.Select(argName, Term.Name(param.name.value))
    } }
    Term.Block(q"Some((..$select))" :: Nil)
    }
    Defn.Def(Nil, Term.Name("unapply"), Nil, inputParam, Some(resultParam), body)
    }
    }
    private[petitviolet] trait CompanionMethodHelper {
    protected val METHOD_NAME: String
    protected def create(cls: Defn.Class)(companionOpt: Option[Defn.Object]): Defn.Def
    def insert(cls: Defn.Class)(companionOpt: Option[Defn.Object]): Defn.Object = {
    def method = create(cls)(companionOpt)
    companionOpt map { companion =>
    val stats = companion.templ.stats getOrElse Nil
    if (alreadyDefined(stats)) companion
    else companion.copy(templ = companion.templ.copy(stats = Some(method +: stats)))
    } getOrElse {
    q"object ${Term.Name(cls.name.value)} { $method }"
    }
    }
    private def alreadyDefined(stats: Seq[Stat]): Boolean =
    stats.exists { _.syntax.contains(s"def $METHOD_NAME") }
    }
    

    View Slide

88. 
    class Unapply extends scala.annotation.StaticAnnotation {
    inline def apply(defn: Any): Any = meta {
    defn match {
    // companion object exists
    case Term.Block(
    Seq(cls @ Defn.Class(_, name, _, ctor, _),
    companion: Defn.Object)) =>
    val newCompanion = Unapply.insert(cls)(Some(companion))
    Term.Block(Seq(cls, newCompanion))
    // companion object does not exists
    case cls @ Defn.Class(_, name, _, ctor, _) =>
    val newCompanion = Unapply.insert(cls)(None)
    Term.Block(Seq(cls, newCompanion))
    case _ =>
    println(defn.structure)
    abort("@Unapply must annotate a class.")
    }
    }
    }
    

    View Slide

89. 
    class Unapply extends scala.annotation.StaticAnnotation {
    inline def apply(defn: Any): Any = meta {
    defn match {
    // companion object exists
    case Term.Block(
    Seq(cls @ Defn.Class(_, name, _, ctor, _),
    companion: Defn.Object)) =>
    val newCompanion = Unapply.insert(cls)(Some(companion))
    Term.Block(Seq(cls, newCompanion))
    // companion object does not exists
    case cls @ Defn.Class(_, name, _, ctor, _) =>
    val newCompanion = Unapply.insert(cls)(None)
    Term.Block(Seq(cls, newCompanion))
    case _ =>
    println(defn.structure)
    abort("@Unapply must annotate a class.")
    }
    }
    }
    ίϯύχΦϯΦϒδΣΫτ͕͋Ε͹
    Classఆ͕ٛTerm.BlockʹͳΔ
    ίϯύχΦϯΦϒδΣΫτ͕ͳ͚Ε͹
    ClassఆٛͷΈ
    

    View Slide

90. 
    @compileTimeOnly("not expanded")
    class Unapply extends scala.annotation.StaticAnnotation {
    inline def apply(defn: Any): Any = meta {
    defn match {
    // companion object exists
    case Term.Block(
    Seq(cls @ Defn.Class(_, name, _, ctor, _),
    companion: Defn.Object)) =>
    val newCompanion = Unapply.insert(cls)(Some(companion))
    Term.Block(Seq(cls, newCompanion))
    // companion object does not exists
    case cls @ Defn.Class(_, name, _, ctor, _) =>
    val newCompanion = Unapply.insert(cls)(None)
    Term.Block(Seq(cls, newCompanion))
    case _ =>
    println(defn.structure)
    abort("@Unapply must annotate a class.")
    }
    }
    }
    object Unapply extends CompanionMethodHelper {
    override protected val METHOD_NAME: String = "unapply"
    override protected def create(cls: Defn.Class)(companionOpt: Option[Defn.Object]): Defn.Def = {
    val (name, paramss) = (cls.name, cls.ctor.paramss)
    val argName = Term.Name("arg")
    val inputParam: Seq[Seq[Term.Param]] = {
    val param: Term.Param = Term.Param(Nil, argName, Some(name), None)
    (param :: Nil) :: Nil
    }
    val resultParam: Type = {
    val types: Seq[Type] = paramss.flatMap { _.collect {
    case Term.Param(_ :: Mod.ValParam() :: Nil, _, Some(typeArg), _) =>
    // private val n: Int
    Type.Name(typeArg.syntax)
    case Term.Param(_ :: Mod.VarParam() :: Nil, _, Some(typeArg), _) =>
    // private var n: Int
    Type.Name(typeArg.syntax)
    case Term.Param(Mod.ValParam() :: Nil, _, Some(typeArg), _) =>
    // val n: Int
    Type.Name(typeArg.syntax)
    case Term.Param(Mod.VarParam() :: Nil, _, Some(typeArg), _) =>
    // var n: Int
    Type.Name(typeArg.syntax)
    case x =>
    println(s"invalid paramss: $paramss")
    abort(s"non-accessible constructor exists. `unapply` always returns None. cause => $x")
    }}
    val tupled = Type.Tuple(types)
    Type.Apply(Type.Name("Option"), tupled :: Nil)
    }
    val body: Term = {
    val select: Seq[Term.Select] = paramss.flatMap { _.map { param =>
    Term.Select(argName, Term.Name(param.name.value))
    } }
    Term.Block(q"Some((..$select))" :: Nil)
    }
    Defn.Def(Nil, Term.Name("unapply"), Nil, inputParam, Some(resultParam), body)
    }
    }
    private[petitviolet] trait CompanionMethodHelper {
    protected val METHOD_NAME: String
    protected def create(cls: Defn.Class)(companionOpt: Option[Defn.Object]): Defn.Def
    def insert(cls: Defn.Class)(companionOpt: Option[Defn.Object]): Defn.Object = {
    def method = create(cls)(companionOpt)
    companionOpt map { companion =>
    val stats = companion.templ.stats getOrElse Nil
    if (alreadyDefined(stats)) companion
    else companion.copy(templ = companion.templ.copy(stats = Some(method +: stats)))
    } getOrElse {
    q"object ${Term.Name(cls.name.value)} { $method }"
    }
    }
    private def alreadyDefined(stats: Seq[Stat]): Boolean =
    stats.exists { _.syntax.contains(s"def $METHOD_NAME") }
    }
    • ίϯετϥΫλ͔ΒϑΟʔϧυ໊Λऔಘ
    • unapplyͷ࣮૷Ͱඞཁ
    • ίϯύχΦϯΦϒδΣΫτ͕ఆٛࡁΈ͔Ͳ͏͔
    ΛνΣοΫ
    • ͋Ε͹unapplyͷ௥Ճ
    • ͳ͚Ε͹unapplyΛ࣋ͭίϯύχΦϯΦϒ
    δΣΫτΛఆٛ
    • annotationͨ͠ΫϥεΛίϯύχΦϯΦϒδΣ
    ΫτΛ࣋ͭΫϥεͰஔ͖׵͑Δ
    

    View Slide

91. フィールドをinjection
    
    

    View Slide

92. 
    trait MyService {
    def double(i: Int): Int = i * 2
    }
    object MyServiceApp extends App {
    }
    

    View Slide

93. 
    trait MyService {
    def double(i: Int): Int = i * 2
    }
    @MixIn[MyService](new MyService {})
    object MyServiceApp extends App {
    println(myService.double(100))
    }
    

    View Slide

94. 
    trait MyService {
    def double(i: Int): Int = i * 2
    }
    @MixIn[MyService](new MyService {})
    object MyServiceApp extends App {
    println(myService.double(100))
    }
    

    View Slide

95. 
    trait MyService {
    def double(i: Int): Int = i * 2
    }
    @MixIn[MyService](new MyService {})
    object MyServiceApp extends App {
    println(myService.double(100))
    }
    

    View Slide

96. 
    200
    trait MyService {
    def double(i: Int): Int = i * 2
    }
    @MixIn[MyService](new MyService {})
    object MyServiceApp extends App {
    println(myService.double(100))
    }
    

    View Slide

97. 
    @compileTimeOnly("@MixIn not expanded")
    class MixIn[T](impl: T) extends scala.annotation.StaticAnnotation {
    inline def apply(defn: Any): Any = meta {
    val (injectionType: Type.Name, impl: Term) =
    this match {
    case Term.New(Template(_, Seq(
    Term.Apply(
    Term.ApplyType(_, Seq(typeName)),
    Seq(implArg: Term.Arg)
    )), _, _)) =>
    (typeName, implArg)
    case _ =>
    println(this.structure)
    abort("invalid parameters")
    }
    // to inject a field has implementation
    val addField = MixIn.implementationToAdd(injectionType, impl)
    defn match {
    case cls@Defn.Class(_, _, _, _, template) =>
    val templateStats: Seq[Stat] = addField +: template.stats.getOrElse(Nil)
    cls.copy(templ = template.copy(stats = Some(templateStats)))
    case obj@Defn.Object(_, _, template) =>
    val templateStats: Seq[Stat] = addField +: template.stats.getOrElse(Nil)
    obj.copy(templ = template.copy(stats = Some(templateStats)))
    case trt@Defn.Trait(_, _, _, _, template) =>
    val templateStats: Seq[Stat] = addField +: template.stats.getOrElse(Nil)
    trt.copy(templ = template.copy(stats = Some(templateStats)))
    case _ =>
    println(this.structure)
    abort("invalid annotating")
    }
    }
    }
    object MixIn {
    private[metas] def implementationToAdd(typeName: Type.Name, impl: Term): Defn.Val = {
    val fieldName = {
    val _tpeName = typeName.value
    val valName = _tpeName.head.toLower + _tpeName.tail
    Pat.Var.Term(Term.Name(valName))
    }
    q"val $fieldName: $typeName = $impl"
    }
    }
    

    View Slide

98. 
    @compileTimeOnly("@MixIn not expanded")
    class MixIn[T](impl: T) extends scala.annotation.StaticAnnotation {
    inline def apply(defn: Any): Any = meta {
    val (injectionType: Type.Name, impl: Term) =
    this match {
    case Term.New(Template(_, Seq(
    Term.Apply(
    Term.ApplyType(_, Seq(typeName)),
    Seq(implArg: Term.Arg)
    )), _, _)) =>
    (typeName, implArg)
    case _ =>
    println(this.structure)
    abort("invalid parameters")
    }
    // to inject a field has implementation
    val addField = MixIn.implementationToAdd(injectionType, impl)
    defn match {
    case cls@Defn.Class(_, _, _, _, template) =>
    val templateStats: Seq[Stat] = addField +: template.stats.getOrElse(Nil)
    cls.copy(templ = template.copy(stats = Some(templateStats)))
    case obj@Defn.Object(_, _, template) =>
    val templateStats: Seq[Stat] = addField +: template.stats.getOrElse(Nil)
    obj.copy(templ = template.copy(stats = Some(templateStats)))
    case trt@Defn.Trait(_, _, _, _, template) =>
    val templateStats: Seq[Stat] = addField +: template.stats.getOrElse(Nil)
    trt.copy(templ = template.copy(stats = Some(templateStats)))
    case _ =>
    println(this.structure)
    abort("invalid annotating")
    }
    }
    }
    object MixIn {
    private[metas] def implementationToAdd(typeName: Type.Name, impl: Term): Defn.Val = {
    val fieldName = {
    val _tpeName = typeName.value
    val valName = _tpeName.head.toLower + _tpeName.tail
    Pat.Var.Term(Term.Name(valName))
    }
    q"val $fieldName: $typeName = $impl"
    }
    }
    • annotationʹର͢ΔܕύϥϝʔλͱίϯετϥΫ
    λͷtreeΛऔಘ
    • annotationͨ͠Ϋϥεʹରͯ͠ϑΟʔϧυΛ௥Ճ
    • ϑΟʔϧυͷܕͱbodyʹલड़ͷ஋Λ༩͑Δ
    

    View Slide

99. どうやるか
    
    

    View Slide

100. QuasiQuotes
     
     

     View Slide

101. だいたい
     QuasiQuotes
     でイケる
     
     

     View Slide

102. • QuasiQuotes(準クォート)
     
     

     View Slide

103. • QuasiQuotes(準クォート)
     
     

     View Slide

104. • unapplyも可能
     
     

     View Slide

105. • unapplyも可能
     
     

     View Slide

106. • 変数として埋め込める
     
     

     View Slide

107. • 変数として埋め込める
     
     

     View Slide

108. • 変数として埋め込める
     
     

     View Slide

109. • 頑張ってくれる
     
     

     View Slide

110. • 頑張ってくれる
     
     

     View Slide

111. 
     

     View Slide

112. • 優しい…？
     
     

     View Slide

113. • 超えちゃいけないライン
     
     

     View Slide

114. • QuasiQuotesは`q`だけじゃない
     • mod, param, t, tparam, etc.
     
     https://github.com/scalameta/scalameta/blob/master/notes/quasiquotes.md
     

     View Slide

115. コンストラクタ/型パラメータ
     
     

     View Slide

116. 
     200
     trait MyService {
     def double(i: Int): Int = i * 2
     }
     @MixIn[MyService](new MyService {})
     object MyServiceApp extends App {
     println(myService.double(100))
     }
     

     View Slide

117. 
     trait MyService {
     def double(i: Int): Int = i * 2
     }
     @MixIn[MyService](new MyService {})
     object MyServiceApp extends App {
     println(myService.double(100))
     }
     

     View Slide

118. 
     class MixIn[T](impl: T) extends StaticAnnotation {
     inline def apply(defn: Any): Any = meta {
     println(impl)
     defn
     }
     }
     

     View Slide

119. 
     class MixIn[T](impl: T) extends StaticAnnotation {
     inline def apply(defn: Any): Any = meta {
     println(impl)
     defn
     }
     }
     

     View Slide

120. コンストラクタの値は
     直接とれない
     
     

     View Slide

121. 
     class MixIn[T](impl: T) extends StaticAnnotation {
     inline def apply(defn: Any): Any = meta {
     println(s"structure: ${this.structure}")
     defn
     }
     }
     @MixIn[MyService](new MyService {})
     object MyServiceApp extends App {
     println(myService.double(100))
     }
     

     View Slide

122. 
     class MixIn[T](impl: T) extends StaticAnnotation {
     inline def apply(defn: Any): Any = meta {
     println(s"structure: ${this.structure}")
     defn
     }
     }
     @MixIn[MyService](new MyService {})
     object MyServiceApp extends App {
     println(myService.double(100))
     }
     

     View Slide

123. 
     

     View Slide

124. 
     Tͷܕ໊
     ίϯετϥΫλ΁ͷҾ਺
     

     View Slide

125. 
     @compileTimeOnly("@MixIn not expanded")
     class MixIn[T](impl: T) extends
     scala.annotation.StaticAnnotation {
     inline def apply(defn: Any): Any = meta {
     val (injectionType: Type.Name, impl: Term) =
     this match {
     case Term.New(Template(_, Seq(
     Term.Apply(
     Term.ApplyType(_, Seq(typeName)),
     Seq(implArg: Term.Arg)
     )), _, _)) =>
     (typeName, implArg)
     case _ =>
     println(this.structure)
     abort("invalid parameters")
     }
     …
     

     View Slide

126. 
     @compileTimeOnly("@MixIn not expanded")
     class MixIn[T](impl: T) extends
     scala.annotation.StaticAnnotation {
     inline def apply(defn: Any): Any = meta {
     val (injectionType: Type.Name, impl: Term) =
     this match {
     case Term.New(Template(_, Seq(
     Term.Apply(
     Term.ApplyType(_, Seq(typeName)),
     Seq(implArg: Term.Arg)
     )), _, _)) =>
     (typeName, implArg)
     case _ =>
     println(this.structure)
     abort("invalid parameters")
     }
     …
     thisʹର͢ΔύλʔϯϚον
     ίϯετϥΫλͷ`impl`͸௚઀औΕͳ͍
     

     View Slide

127. 
     @compileTimeOnly("@MixIn not expanded")
     class MixIn[T](impl: T) extends
     scala.annotation.StaticAnnotation {
     inline def apply(defn: Any): Any = meta {
     val (injectionType: Type.Name, impl: Term) =
     this match {
     case Term.New(Template(_, Seq(
     Term.Apply(
     Term.ApplyType(_, Seq(typeName)),
     Seq(implArg: Term.Arg)
     )), _, _)) =>
     (typeName, implArg)
     case _ =>
     println(this.structure)
     abort("invalid parameters")
     }
     …
     ܕύϥϝʔλɾίϯετϥΫλΛऔಘ
     

     View Slide

128. 
     @compileTimeOnly("@MixIn not expanded")
     class MixIn[T](impl: T) extends
     scala.annotation.StaticAnnotation {
     inline def apply(defn: Any): Any = meta {
     val (injectionType: Type.Name, impl: Term) =
     this match {
     case Term.New(Template(_, Seq(
     Term.Apply(
     Term.ApplyType(_, Seq(typeName)),
     Seq(implArg: Term.Arg)
     )), _, _)) =>
     (typeName, implArg)
     case _ =>
     println(this.structure)
     abort("invalid parameters")
     }
     …
     ͏·͍͔͘ͳ͍࣌͸
     println(this.structure)͢Δͱྑ͍
     ίϯύΠϧ࣌ͷϝοηʔδͱͯ͠දࣔ͞ΕΔ
     

     View Slide

129. 辛いところ
     • QuasiQuotes補完効かない
     • 人間が頑張る
     • 知らないといけないことは多い
     • Tokenの種類とか一杯
     • メタプログラムとしては正しいが、適用する
     と壊れるパターンに弱い
     
     

     View Slide

130. scalametaの
     内部的な話
     
     

     View Slide

131. そういえば
     
     

     View Slide

132. scalameta
     何がいいの？
     
     

     View Slide

133. 今のマクロじゃだめなの？
     
     

     View Slide

134. 既存のマクロの問題点
     • macro実装/コンパイラ内部の知識が必要になる
     • macroの実装を知っていないと名前解決に失敗したりする
     • 英数字でない名前をmangleしている、とか
     • シグネチャ
     • macroのための実装を別に用意する
     • 同じ仮引数名にしないといけない
     • エコシステム
     • ツールのサポートが弱い
     
     http://docs.scala-lang.org/sips/pending/inline-meta.html
     

     View Slide

135. ダメらしい
     
     

     View Slide

136. scalameta
     • 同じインタフェースでより良くする
     • ぱっと見はおまじない的な記述が減った程度
     だが、内部のメカニズムは改善されている
     
     

     View Slide

137. scalameta
     • 同じインタフェースでより良くする
     • ぱっと見はおまじない的な記述が減った程度
     だが、内部のメカニズムは改善されている
     • inline化
     • metaキーワード
     
     

     View Slide

138. inline化
     
     class hello extends StaticAnnotation {
     inline def apply(defn: Any): Any = meta {
     defn match {
     case d: Defn.Def =>
     val newBody = q"""{
     println("hello")
     ${d.body}
     }"""
     d.copy(body = newBody)
     case _ =>
     abort("annotate only def")
     }
     }
     }
     

     View Slide

139. inlineキーワード
     • インライン化
     • コンパイル時に定数化
     • 関数呼び出しを削除
     • ちゃんと型チェックしていて推論も可能
     
     

     View Slide

140. inlineキーワード
     • インライン化
     • コンパイル時に定数化
     • 関数呼び出しを削除
     • ちゃんと型チェックしていて推論も可能
     • `@inline`アノテーションは保証しない
     • ベストエフォート的なやつ
     • deprecatedになる予定(?)
     
     

     View Slide

141. metaキーワード
     
     class hello extends StaticAnnotation {
     inline def apply(defn: Any): Any = meta {
     defn match {
     case d: Defn.Def =>
     val newBody = q"""{
     println("hello")
     ${d.body}
     }"""
     d.copy(body = newBody)
     case _ =>
     abort("annotate only def")
     }
     }
     }
     

     View Slide

142. metaキーワード
     • コンパイル時に実行するコードを決定
     • スコープ内にscala.metaの機能を提供
     • コンパイラが実行してASTを生成、置換
     
     

     View Slide

143. scalametaは
     どういう造りになっているか
     
     

     View Slide

144. アーキテクチャ
     • 分割されたAPI
     • stateless
     • syntactic
     • semantic
     • 操作と必要な状態に応じて分割されている
     
     

     View Slide

145. Stateless API
     • 状態に依存しないAPI
     • コンパイル時でもランタイムでも関係なく使
     用可能なもの
     
     

     View Slide

146. Stateless API
     • 状態に依存しないAPI
     • コンパイル時でもランタイムでも関係なく使
     用可能なもの
     
     object MetaApp extends App {
     import scala.meta._
     println(Term.Name("x"))
     }
     

     View Slide

147. Syntactic API
     • 構文に関するAPI
     • QuasiQuotesやpretty print
     • 例えばScalaのバージョンが状態となる
     
     

     View Slide

148. Syntactic API
     • 構文に関するAPI
     • QuasiQuotesやpretty print
     • 例えばScalaのバージョンが状態となる
     
     import scala.meta._
     {
     import scala.meta.dialects.Scala211
     "".parse[Term].get
     }
     {
     import scala.meta.dialects.Dotty
     "".parse[Term].get
     }
     

     View Slide

149. Syntactic API
     • 構文に関するAPI
     • QuasiQuotesやpretty print
     • 例えばScalaのバージョンが状態となる
     
     import scala.meta._
     {
     import scala.meta.dialects.Scala211
     "".parse[Term].get
     }
     {
     import scala.meta.dialects.Dotty
     "".parse[Term].get
     }
     ੒ޭ
     ྫ֎ൃੜ
     

     View Slide

150. Semantic API
     • 意味情報に関するAPI
     • 名前解決、型チェック、メンバの列挙など
     • `Mirror`を状態として受け取る
     • プログラム内で使用可能な定義/依存関係の
     indexにあたるものをカプセル化したtrait
     • “semantic”な操作に必要となる
     
     

     View Slide

151. 
     object mirror {
     def show(str: String) = println(str)
     }
     

     View Slide

152. 
     object mirror {
     def show(str: String) = println(str)
     }
     object mirrorApp extends App {
     implicit val m = Mirror()
     m.sources.foreach { _.collect {
     case ref @ Term.Name("println") =>
     println(s"symbol: ${ref.symbol}")
     }}
     }
     

     View Slide

153. 
     object mirror {
     def show(str: String) = println(str)
     }
     object mirrorApp extends App {
     implicit val m = Mirror()
     m.sources.foreach { _.collect {
     case ref @ Term.Name("println") =>
     println(s"symbol: ${ref.symbol}")
     }}
     }
     

     View Slide

154. 
     object mirror {
     def show(str: String) = println(str)
     }
     object mirrorApp extends App {
     implicit val m = Mirror()
     m.sources.foreach { _.collect {
     case ref @ Term.Name("println") =>
     println(s"symbol: ${ref.symbol}")
     }}
     }
     [info] symbol: _root_.scala.Predef.println(Ljava/lang/Object;)V.
     γϯϘϧ৘ใͷऔಘ
     

     View Slide

155. 3種類のAPI
     • stateless
     • いつでも使える
     • syntactic
     • 例えばコードフォーマッタ
     • semantic
     • 例えばlinter
     
     

     View Slide

156. 今後の話
     
     

     View Slide

157. その前に現状
     • v1.8.0まではmacro annotationのみ
     • 色々とツールが作られている
     • http://scalameta.org/#BuiltwithScalameta
     • scalafmt: コードフォーマッタ
     • syntacticな操作
     • scalafix: scalaの自動変換ツール(dotty化とか)
     • semanticな操作
     
     

     View Slide

158. 
     http://docs.scala-lang.org/ja/overviews/
     

     View Slide

159. new-style macro
     
     

     View Slide

160. new-style macro
     
     v1.8.0時点までの話
     

     View Slide

161. 
     

     View Slide

162. 
     

     View Slide

163. 
     

     View Slide

164. 
     scalaマクロの後釜を
     狙っていたが方向性を変えた
     

     View Slide

165. scalamacros/scalamacros
     • scalametaとは別プロジェクトとして進行
     • scalametaをベースとしている
     • new-style macro
     • 絶賛実装中/Dotty対応中
     
     

     View Slide

166. サンプルコード置き場
     • petitviolet/scalameta-prac
     • petitviolet/scala-logging
     • petitviolet/scala-acase
     
     

     View Slide

167. 目指すゴール
     • メタプログラミング怖くなくなる
     • コード読んでみようかなと思う
     • ちょっとやってみようかなって思う
     • scalametaやってみようかなって思う
     
     

     View Slide

168. 今後に期待しつつ
     scalametaを予習！
     
     

     View Slide

169. 
     @petitviolet
     

     View Slide