引用内部静态java类时工具箱编译的奇怪行为

Question

假设我有以下java类:

package com.test;
public class Outer {
    public static class Inner { public static final String VAL = "Inner"; }
}

我可以从scala代码中引用VAL常量，就像你期望的那样，但是当我尝试使用scala工具箱编译器编译引用此字段的代码时，它失败了。(stacktrace跟随下面的例子)。

下面的代码演示了我的意思:

import scala.reflect.runtime.universe
import scala.tools.reflect.ToolBox
object Issue extends App {
  val mirror = universe.runtimeMirror(getClass.getClassLoader)
  val toolbox = ToolBox(mirror).mkToolBox()
  println                  (com.test.Outer.Inner.VAL) // prints 'Inner'
  val tree = toolbox.parse("com.test.Outer.Inner.VAL")
  val compiled = toolbox.compile(tree)() // fails to compile
}

这是我得到的异常跟踪:

Exception in thread "main" scala.tools.reflect.ToolBoxError: reflective compilation has failed: 
value Inner is not a member of object com.test.Outer
    at scala.tools.reflect.ToolBoxFactory$ToolBoxImpl$ToolBoxGlobal.throwIfErrors(ToolBoxFactory.scala:319)
    at scala.tools.reflect.ToolBoxFactory$ToolBoxImpl$ToolBoxGlobal.compile(ToolBoxFactory.scala:252)
    at scala.tools.reflect.ToolBoxFactory$ToolBoxImpl.compile(ToolBoxFactory.scala:416)
    at Issue$delayedInit$body.apply(Issue.scala:8)
    at scala.Function0$class.apply$mcV$sp(Function0.scala:40)
    at scala.runtime.AbstractFunction0.apply$mcV$sp(AbstractFunction0.scala:12)
    at scala.App$$anonfun$main$1.apply(App.scala:71)
    at scala.App$$anonfun$main$1.apply(App.scala:71)
    at scala.collection.immutable.List.foreach(List.scala:318)
    at scala.collection.generic.TraversableForwarder$class.foreach(TraversableForwarder.scala:32)
    at scala.App$class.main(App.scala:71)
    at Issue$.main(Issue.scala:3)
    at Issue.main(Issue.scala)

有人遇到过这种情况吗?有什么我可以改变(即编译器选项)，使这项工作?

谢谢。

编辑

这是我使用"-verbose -Yissue-debug"编译时得到的结果:

[reflect-compiler] made Scala package scala
[reflect-compiler] unpickling Scala package package and package scala, owner = package scala
[reflect-compiler] made Scala package java
[reflect-compiler] made Scala package lang
[reflect-compiler] made Scala package runtime
[reflect-compiler] made Scala package annotation
[reflect-compiler] unpickling Scala package package and package runtime, owner = package runtime
[reflect-compiler] made Scala package collection
[reflect-compiler] unpickling Scala package package and package collection, owner = package collection
[reflect-compiler] translating reflection info for Java class java.lang.Object
[reflect-compiler] unpickling Scala class Unit and object Unit, owner = package scala
[reflect-compiler] translating reflection info for Java class java.lang.Throwable
[reflect-compiler] unpickling Scala class Long and object Long, owner = package scala
[reflect-compiler] translating reflection info for Java class java.lang.InterruptedException
[reflect-compiler] unpickling Scala class Int and object Int, owner = package scala
[reflect-compiler] unpickling Scala class Boolean and object Boolean, owner = package scala
[reflect-compiler] translating reflection info for Java class java.lang.String
[reflect-compiler] translating reflection info for Java class java.lang.CloneNotSupportedException
[reflect-compiler] made Scala package io
[reflect-compiler] translating reflection info for Java interface java.io.Serializable
[reflect-compiler] translating reflection info for Java interface java.lang.CharSequence
[reflect-compiler] unpickling Scala class Char and object Char, owner = package scala
[reflect-compiler] translating reflection info for Java class java.io.ObjectStreamField
[reflect-compiler] made Scala package util
[reflect-compiler] unpickling Scala class Float and object Float, owner = package scala
[reflect-compiler] unpickling Scala class Double and object Double, owner = package scala
[reflect-compiler] unpickling Scala class Byte and object Byte, owner = package scala
[reflect-compiler] translating reflection info for Java class java.lang.StringBuffer
[reflect-compiler] translating reflection info for Java class java.util.Locale
[reflect-compiler] translating reflection info for Java class java.io.UnsupportedEncodingException
[reflect-compiler] made Scala package nio
[reflect-compiler] made Scala package charset
[reflect-compiler] translating reflection info for Java class java.nio.charset.Charset
[reflect-compiler] translating reflection info for Java class java.lang.StringBuilder
[reflect-compiler] translating reflection info for Java interface java.lang.Comparable
[reflect-compiler] made Scala package beans
parsing com.test.Outer.Inner.VAL
importing com.test.Outer.Inner.VAL
compiling com.test.Outer.Inner.VAL
[reflect-compiler] unpickling Scala class Predef and object Predef, owner = package scala
[reflect-compiler] unpickling Scala class ClassfileAnnotation and object ClassfileAnnotation, owner = package annotation
[reflect-compiler] unpickling Scala class Annotation and object Annotation, owner = package annotation
[reflect-compiler] unpickling Scala class StaticAnnotation and object StaticAnnotation, owner = package annotation
[reflect-compiler] made Scala package reflect
[reflect-compiler] unpickling Scala package package and package reflect, owner = package reflect
[reflect-compiler] made Scala package api
[reflect-compiler] unpickling Scala package package and package api, owner = package api
[reflect-compiler] unpickling Scala class Universe and object Universe, owner = package api
[reflect-compiler] unpickling Scala class Symbols and object Symbols, owner = package api
[reflect-compiler] unpickling Scala class Types and object Types, owner = package api
[reflect-compiler] unpickling Scala class FlagSets and object FlagSets, owner = package api
[reflect-compiler] unpickling Scala class Scopes and object Scopes, owner = package api
[reflect-compiler] unpickling Scala class Names and object Names, owner = package api
[reflect-compiler] unpickling Scala class Trees and object Trees, owner = package api
[reflect-compiler] unpickling Scala class Constants and object Constants, owner = package api
[reflect-compiler] unpickling Scala class Annotations and object Annotations, owner = package api
[reflect-compiler] unpickling Scala class Positions and object Positions, owner = package api
[reflect-compiler] unpickling Scala class Exprs and object Exprs, owner = package api
[reflect-compiler] unpickling Scala class TypeTags and object TypeTags, owner = package api
[reflect-compiler] unpickling Scala class TagInterop and object TagInterop, owner = package api
[reflect-compiler] unpickling Scala class StandardDefinitions and object StandardDefinitions, owner = package api
[reflect-compiler] unpickling Scala class StandardNames and object StandardNames, owner = package api
[reflect-compiler] unpickling Scala class BuildUtils and object BuildUtils, owner = package api
[reflect-compiler] unpickling Scala class Mirrors and object Mirrors, owner = package api
[reflect-compiler] unpickling Scala class Printers and object Printers, owner = package api
[reflect-compiler] unpickling Scala class Importers and object Importers, owner = package api
[reflect-compiler] made Scala package runtime
[reflect-compiler] unpickling Scala package package and package runtime, owner = package runtime
[reflect-compiler] unpickling Scala class StringContext and object StringContext, owner = package scala
[reflect-compiler] unpickling Scala class Product and object Product, owner = package scala
[reflect-compiler] unpickling Scala class Equals and object Equals, owner = package scala
[reflect-compiler] unpickling Scala class Serializable and object Serializable, owner = package scala
[reflect-compiler] made Scala package immutable
[reflect-compiler] unpickling Scala package package and package immutable, owner = package immutable
[reflect-compiler] unpickling Scala class Array and object Array, owner = package scala
[reflect-compiler] translating reflection info for Java interface java.lang.Cloneable
[reflect-compiler] unpickling Scala class AnyVal and object AnyVal, owner = package scala
[reflect-compiler] unpickling Scala class NotNull and object NotNull, owner = package scala
[reflect-compiler] unpickling Scala class LowPriorityImplicits and object LowPriorityImplicits, owner = package scala
[reflect-compiler] made Scala package com
[reflect-compiler] unpickling Scala class Dynamic and object Dynamic, owner = package scala
[reflect-compiler] made Scala package test
[reflect-compiler] translating reflection info for Java class com.test.Outer
[reflect-compiler] *** missing: Inner/true/object Outer/false/class scala.reflect.runtime.SynchronizedOps$$anon$1
java.lang.Exception
    at scala.tools.nsc.typechecker.Contexts$Context.issue(Contexts.scala:399)
    at scala.tools.nsc.typechecker.ContextErrors$ErrorUtils$.issueTypeError(ContextErrors.scala:84)
    at scala.tools.nsc.typechecker.ContextErrors$ErrorUtils$.issueNormalTypeError(ContextErrors.scala:69)
    at scala.tools.nsc.typechecker.ContextErrors$TyperContextErrors$TyperErrorGen$.NotAMemberError(ContextErrors.scala:331)
    at scala.tools.nsc.typechecker.Typers$Typer.handleMissing$1(Typers.scala:4846)
    at scala.tools.nsc.typechecker.Typers$Typer.scala$tools$nsc$typechecker$Typers$Typer$$typedSelect$1(Typers.scala:4851)
    at scala.tools.nsc.typechecker.Typers$Typer.typedSelectOrSuperCall$1(Typers.scala:4938)
    at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:5551)
    at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:5630)
    at scala.tools.nsc.typechecker.Typers$Typer.typedQualifier(Typers.scala:5710)
    at scala.tools.nsc.typechecker.Typers$Typer.typedQualifier(Typers.scala:5716)
    at scala.tools.nsc.typechecker.Typers$Typer.typedSelectOrSuperCall$1(Typers.scala:4918)
    at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:5551)
    at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:5630)
    at scala.tools.nsc.typechecker.Typers$Typer.transformedOrTyped(Typers.scala:5825)
    at scala.tools.nsc.typechecker.Typers$Typer.typedDefDef(Typers.scala:2250)
    at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:5557)
    at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:5630)
    at scala.tools.nsc.typechecker.Typers$Typer.scala$tools$nsc$typechecker$Typers$Typer$$typedStat$1(Typers.scala:2921)
    at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$62.apply(Typers.scala:3025)
    at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$62.apply(Typers.scala:3025)
    at scala.collection.immutable.List.loop$1(List.scala:170)
    at scala.collection.immutable.List.mapConserve(List.scala:186)
    at scala.tools.nsc.typechecker.Typers$Typer.typedStats(Typers.scala:3025)
    at scala.tools.nsc.typechecker.Typers$Typer.typedTemplate(Typers.scala:1914)
    at scala.tools.nsc.typechecker.Typers$Typer.typedModuleDef(Typers.scala:1794)
    at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:5572)
    at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:5630)
    at scala.tools.nsc.typechecker.Typers$Typer.scala$tools$nsc$typechecker$Typers$Typer$$typedStat$1(Typers.scala:2921)
    at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$62.apply(Typers.scala:3025)
    at scala.tools.nsc.typechecker.Typers$Typer$$anonfun$62.apply(Typers.scala:3025)
    at scala.collection.immutable.List.loop$1(List.scala:170)
    at scala.collection.immutable.List.mapConserve(List.scala:186)
    at scala.tools.nsc.typechecker.Typers$Typer.typedStats(Typers.scala:3025)
    at scala.tools.nsc.typechecker.Typers$Typer.typedPackageDef$1(Typers.scala:5288)
    at scala.tools.nsc.typechecker.Typers$Typer.typed1(Typers.scala:5575)
    at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:5630)
    at scala.tools.nsc.typechecker.Typers$Typer.typed(Typers.scala:5687)
    at scala.tools.nsc.typechecker.Analyzer$typerFactory$$anon$3.apply(Analyzer.scala:99)
    at scala.tools.nsc.Global$GlobalPhase.applyPhase(Global.scala:463)
    at scala.tools.nsc.typechecker.Analyzer$typerFactory$$anon$3$$anonfun$run$1.apply(Analyzer.scala:91)
    at scala.tools.nsc.typechecker.Analyzer$typerFactory$$anon$3$$anonfun$run$1.apply(Analyzer.scala:91)
    at scala.collection.Iterator$class.foreach(Iterator.scala:727)
    at scala.collection.AbstractIterator.foreach(Iterator.scala:1157)
    at scala.tools.nsc.typechecker.Analyzer$typerFactory$$anon$3.run(Analyzer.scala:91)
    at scala.tools.nsc.Global$Run.compileUnitsInternal(Global.scala:1582)
    at scala.tools.nsc.Global$Run.compileUnits(Global.scala:1556)
    at scala.tools.reflect.ToolBoxFactory$ToolBoxImpl$ToolBoxGlobal.compile(ToolBoxFactory.scala:251)
    at scala.tools.reflect.ToolBoxFactory$ToolBoxImpl.compile(ToolBoxFactory.scala:416)
    at Issue$delayedInit$body.apply(Issue.scala:8)
    at scala.Function0$class.apply$mcV$sp(Function0.scala:40)
    at scala.runtime.AbstractFunction0.apply$mcV$sp(AbstractFunction0.scala:12)
    at scala.App$$anonfun$main$1.apply(App.scala:71)
    at scala.App$$anonfun$main$1.apply(App.scala:71)
    at scala.collection.immutable.List.foreach(List.scala:318)
    at scala.collection.generic.TraversableForwarder$class.foreach(TraversableForwarder.scala:32)
    at scala.App$class.main(App.scala:71)
    at Issue$.main(Issue.scala:3)
    at Issue.main(Issue.scala)
Exception in thread "main" scala.tools.reflect.ToolBoxError: reflective compilation has failed: 
[namer in 31ms]
[packageobjects in 0ms]
value Inner is not a member of object com.test.Outer
[typer in 211ms]
[total in 247ms]
[reset] recursing in package <root>
    at scala.tools.reflect.ToolBoxFactory$ToolBoxImpl$ToolBoxGlobal.throwIfErrors(ToolBoxFactory.scala:319)
    at scala.tools.reflect.ToolBoxFactory$ToolBoxImpl$ToolBoxGlobal.compile(ToolBoxFactory.scala:252)
    at scala.tools.reflect.ToolBoxFactory$ToolBoxImpl.compile(ToolBoxFactory.scala:416)
    at Issue$delayedInit$body.apply(Issue.scala:8)
    at scala.Function0$class.apply$mcV$sp(Function0.scala:40)
    at scala.runtime.AbstractFunction0.apply$mcV$sp(AbstractFunction0.scala:12)
    at scala.App$$anonfun$main$1.apply(App.scala:71)
    at scala.App$$anonfun$main$1.apply(App.scala:71)
    at scala.collection.immutable.List.foreach(List.scala:318)
    at scala.collection.generic.TraversableForwarder$class.foreach(TraversableForwarder.scala:32)
    at scala.App$class.main(App.scala:71)
    at Issue$.main(Issue.scala:3)
    at Issue.main(Issue.scala)

编辑2

我认为这是一个错误的反射API，但我不确定。我调试了键入阶段，并得出以下结论:

在给com.test.Outer赋了合适的符号后，我们进入com.test.Outer.Inner的输入阶段。

在那里，它使用scala.reflect.internal.Scopes.Scope#lookupEntry(Name)查找Inner的符号。

检查所查看的作用域，发现它确实包含ScopeEntry的ClassSymbol的Inner，但作用域符号名和方法的name参数之间的相等性测试是使用Object#equals完成的(即equals没有被覆盖)。并且两个name实例不相同。

关于符号名称和传递的名称参数的最后一个注意事项是，我看到它们具有相同的index字段。我不确定这意味着什么，但我得到的印象是，这意味着它们在名称表中引用相同的名称，所以它们是相等的(?)(两者之间有一个区别，一个是TermName，而符号的名称是TypeName)。

无论如何，我可能会打开Scala的bug跟踪器，只是想在这里总结一下。

Answer 1

正确-看起来Scala/JVM反射API无法确定VAR是嵌套内部类的静态成员。