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"; }
}

我可以像您期望的那样从scala代码引用VAL常量，但是当我尝试使用scala工具箱编译器编译引用该字段的代码时，它会失败。（stacktrace遵循以下示例）。

这段代码证明了我的意思：

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
}

这是我得到的异常追踪：

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)

之前有没有遇到过这个？有什么我可以改变（即编译器选项）来使这个工作吗？

感谢。

修改

这是我用“-verbose -Yissue-debug”编译时得到的：

[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

我认为这是反射API中的一个错误，但我不确定。我已经调试了打字阶段，并提出了以下内容：

在为com.test.Outer分配了适当的符号后，我们会到达com.test.Outer.Inner的输入阶段。

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

检查所查看的范围会发现它确实包含ScopeEntry ClassSymbol Inner，但范围符号名称和方法name参数之间的相等测试是使用Object#equals完成（即equals未被覆盖），并且两个名称实例不一样。

关于符号名称和传递的名称参数的最后一个注释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他们在名称表中引用相同的名称，所以它们是相同的（？）（两者之间有一个区别，一个是TermName，符号的名称是TypeName。）

无论如何，我可能会打开一个错误Scala的bug追踪器，只是想在这里得出结论。

Answer 1

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

引用内部静态java类时工具箱编译的奇怪行为

1 个答案: