通过IMain在scala repl中获取类型信息

时间：2013-03-28 09:48:14

标签： scala reflection scala-2.10

意图

我trying to add支持:kind命令 repl。感谢Eugene Burmako，我得到了working prototype。虽然它只适用于完全限定名称，但无法解析导入的名称。

我现在正在尝试使用IMain.exprTyper来完成这项工作，因为它知道导入到repl中的类型。但有一个问题。我尝试过的所有内容都会返回ClassInfoType，如下所示（显示为showRaw）：

ClassInfoType(List(TypeRef(TypeRef(TypeRef(TypeRef(NoPrefix(), package <root>, List()), package java, List()), package lang, List()), class Object, List()), TypeRef(TypeRef(TypeRef(NoPrefix(), package <root>, List()), package scala, List()), trait Serializable, List())), Scope{
  def <init>(): Option.type;
  implicit def option2Iterable(xo: Option): Iterable;
  def apply(x: Object): Option;
  def empty(): Option;
  private def readResolve(): Object
}, object Option)

虽然工作实现返回特定的Type：

PolyType(List(TypeName("A")), ClassInfoType(List(TypeRef(ThisType(scala), TypeName("AnyRef"), List()), TypeRef(ThisType(scala), scala.Product, List()), TypeRef(ThisType(scala), scala.Serializable, List())), Scope(nme.CONSTRUCTOR, TermName("isEmpty"), TermName("isDefined"), TermName("get"), TermName("getOrElse"), TermName("orNull"), TermName("map"), TermName("fold"), TermName("flatMap"), TermName("flatten"), TermName("filter"), TermName("filterNot"), TermName("nonEmpty"), TermName("withFilter"), TypeName("WithFilter"), TermName("contains"), TermName("exists"), TermName("forall"), TermName("foreach"), TermName("collect"), TermName("orElse"), TermName("iterator"), TermName("toList"), TermName("toRight"), TermName("toLeft")), scala.Option))

问题

我觉得我很亲密。这是一个游乐场，您可以自己尝试一切：

Welcome to Scala version 2.11.0-20130328-093148-47645c7e7e (OpenJDK 64-Bit Server VM, Java 1.7.0_17).
Type in expressions to have them evaluated.
Type :help for more information.

scala> import scala.reflect.runtime.universe._
import scala.reflect.runtime.universe._

scala> import scala.tools.nsc.interpreter.IMain
import scala.tools.nsc.interpreter.IMain

scala> val mirror = runtimeMirror(getClass.getClassLoader) // Working approach
mirror: reflect.runtime.universe.Mirror = JavaMirror with scala.tools.nsc.interpreter.IMain$TranslatingClassLoader@3d34ec98 of type class scala.tools.nsc.interpreter.IMain$TranslatingClassLoader with classpath [<unknown>] and parent being scala.tools.nsc.util.ScalaClassLoader$URLClassLoader@5d990e8c of type class scala.tools.nsc.util.ScalaClassLoader$URLClassLoader with classpath [file:/usr/lib/jvm/java-7-openjdk/jre/lib/resources.jar,file:/usr/lib/jvm/java-7-openjdk/jre/lib/rt.jar,file:/usr/lib/jvm/java-7-openjdk/jre/lib/jsse.jar,file:/usr/lib/jvm/java-7-openjdk/jre/lib/jce.jar,file:/usr/lib/jvm/java-7-openjdk/jre/lib/charsets.jar,file:/usr/lib/jvm/java-7-openjdk/jre/lib/rhino.jar,file:/home/folone/workspace/scala-myfork/build/pack/lib/jline.jar,file:/home/folone/workspace/scala-myfork...

scala> val typer = new IMain().exprTyper // Not working approach
typer: scala.tools.nsc.interpreter.IMain#exprTyper.type = scala.tools.nsc.interpreter.IMain$exprTyper$@68c181f0

scala> val expr = "scala.Option"
expr: String = scala.Option

scala> showRaw(mirror.staticClass(expr).toType.typeSymbol.typeSignature) // Correct signature
res6: String = PolyType(List(TypeName("A")), ClassInfoType(List(TypeRef(ThisType(scala), TypeName("AnyRef"), List()), TypeRef(ThisType(scala), scala.Product, List()), TypeRef(ThisType(scala), scala.Serializable, List())), Scope(nme.CONSTRUCTOR, TermName("isEmpty"), TermName("isDefined"), TermName("get"), TermName("getOrElse"), TermName("orNull"), TermName("map"), TermName("fold"), TermName("flatMap"), TermName("flatten"), TermName("filter"), TermName("filterNot"), TermName("nonEmpty"), TermName("withFilter"), TypeName("WithFilter"), TermName("contains"), TermName("exists"), TermName("forall"), TermName("foreach"), TermName("collect"), TermName("orElse"), TermName("iterator"), TermName("toList"), TermName("toRight"), TermName("toLeft")), scala.Option))

scala> showRaw(typer.typeOfExpression(expr).typeSymbol.typeSignature) // Wrong signature
res7: String = 
ClassInfoType(List(TypeRef(TypeRef(TypeRef(TypeRef(NoPrefix(), package <root>, List()), package java, List()), package lang, List()), class Object, List()), TypeRef(TypeRef(TypeRef(NoPrefix(), package <root>, List()), package scala, List()), trait Serializable, List())), Scope{
  def <init>(): Option.type;
  implicit def option2Iterable(xo: Option): Iterable;
  def apply(x: Object): Option;
  def empty(): Option;
  private def readResolve(): Object
}, object Option)

如何将ClassInfoType转换为包含所需信息的有效Type？或者，如何首先使用Type获取IMain？

2 个答案:

答案 0 :(得分：3)

这个怎么样？我正在使用电源模式，它允许您从当前运行的REPL访问全局，这比创建新的IMain更方便。

scala> :power
Already in power mode.

scala> val g = global
g: $r.intp.global.type = <global>

scala> val context = g.analyzer.rootContext(NoCompilationUnit)
context: g.analyzer.Context = Context(<root>@EmptyTree unit=NoCompilationUnit scope=997093283 errors=false, reportErrors=true, throwErrors=false)

// aware imports of scala._, etc.
scala> val sym = context.lookupSymbol("Option": TypeName, _ => true).symbol
sym: g.analyzer.global.Symbol = class Option

scala> sym.tpeHK.typeParams
res21: List[g.analyzer.global.Symbol] = List(type A)

另见：

scala> intp.symbolOfType("Foo")
res26: $r.intp.global.Symbol = class Foo

但我不确定如何获得以前导入的符号：

scala> object Bar { class Bop }
defined object Bar

scala> import Bar.Bop
import Bar.Bop

scala> intp.symbolOfType("Bop")
res27: $r.intp.global.Symbol = <none>

修改

OP获得ClassInfoType而非PolyType的原因是相位原因。要获得与电源模式global相同的结果，必须将相位设置为typer。从REPL: intp.global vs "global" available in :power mode引用@ retronym的解释：

scala> :power
** Power User mode enabled - BEEP WHIR GYVE **
** :phase has been set to 'typer'.          **
    ^
    `----  this part is relevant
  

符号有一个类型列表（又名info - s），由编译器阶段索引。 （又名TypeHistory）。许多编译器阶段安装InfoTransformer来变形类型。有关一些文档，请参阅src / compiler / scala / tools / nsc / transform / InfoTransform.scala。

     

要在特定阶段检查类型，您可以使用'exitingTyper`等方法。

scala> exitingPostErasure($intp.global.rootMirror.staticClass("scala.Option").typeSignature).getClass
res6: Class[_ <: $intp.global.Type] = class scala.reflect.internal.Types$ClassInfoType

scala> exitingTyper($intp.global.rootMirror.staticClass("scala.Option").typeSignature).getClass
res7: Class[_ <: $intp.global.Type] = class scala.reflect.internal.Types$PolyType
  

或者，更方便一点：电源模式：

scala> :phase typer
Active phase is now: Typer

scala> global.rootMirror.staticClass("scala.Option").typeSignature.getClass
res16: Class[_ <: $r.global.Type] = class scala.reflect.internal.Types$PolyType

scala> :phase cleanup
Active phase is now: Cleanup

scala> global.rootMirror.staticClass("scala.Option").typeSignature.getClass
res17: Class[_ <: $r.global.Type] = class scala.reflect.internal.Types$ClassInfoType

答案 1 :(得分：1)

你应该使用IMain全局的镜像：

scala> val imain = new IMain()
imain: scala.tools.nsc.interpreter.IMain = scala

scala> val mirror = imain.global.rootMirror
mirror: imain.global.Mirror = compiler mirror
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