Updated Symbol to record classfile origin.

This change should be transparent to anything using sourceFile,
unless it was drinking from the inheritance well too deeply. Rather
than squander the already allocated field for every ClassSymbol not
being compiled from source, I'm now populating it with the file
representing the class. This will make a broad range of things easier,
like debugging, issuing useful error messages, symbol invalidation,
signature verification, you name it.

  def sourceFile      - still returns only source code files
  def binaryFile      - returns only class files
  def associatedFile  - returns whatever is there, if anything

Performance: I may be mistaken, but I believe this is a zero-impact
change.  No new fields are allocated; fields which were null now hold
a useful reference.  The reference is to a file instance which was
already being allocated and already long-lived.

Compare error messages:

  // Version 1
  % scalac a.scala
  error: type _$1 is defined twice

  // Version 2
  % scalac a.scala
  error: type _$1 is defined twice
    conflicting symbols both originated in file './foo/package.class'
    Note: this may be due to a bug in the compiler involving wildcards in package objects
  one error found

Bonus for people who read commit logs.  Try this in the repl
after starting power mode.

ListClass.info.members groupBy (_.associatedFile) foreach {
  case (k, vs) => println("%s\n  %s\n".format(k, vs map (_.defString) mkString "\n  "))
}

9 files changed, 74 insertions, 33 deletions

diff --git a/src/compiler/scala/reflect/internal/SymbolFlags.scala b/src/compiler/scala/reflect/internal/SymbolFlags.scala
index 7741d700b9..4ce8ac40df 100644
--- a/src/compiler/scala/reflect/internal/SymbolFlags.scala
+++ b/src/compiler/scala/reflect/internal/SymbolFlags.scala
@@ -162,7 +162,7 @@ trait SymbolFlags {
       case _         => abort("setNotFlag on invalid flag: " + flag)
     })
 
-    protected def shortSymbolClass = getClass.getName.split('.').last.stripPrefix("Symbols$")
+    def shortSymbolClass = getClass.getName.split('.').last.stripPrefix("Symbols$")
     def symbolCreationString: String = (
       "%s%25s | %-40s | %s".format(
         if (settings.uniqid.value) "%06d | ".format(id) else "",
diff --git a/src/compiler/scala/reflect/internal/Symbols.scala b/src/compiler/scala/reflect/internal/Symbols.scala
index 78cec02c0a..2a5b759f94 100644
--- a/src/compiler/scala/reflect/internal/Symbols.scala
+++ b/src/compiler/scala/reflect/internal/Symbols.scala
@@ -2036,13 +2036,27 @@ trait Symbols extends api.Symbols { self: SymbolTable =>
 
     def isExpandedModuleClass: Boolean = name(name.length - 1) == '$'
 */
-    def sourceFile: AbstractFileType =
-      if (isModule) moduleClass.sourceFile
-      else enclosingTopLevelClass.sourceFile
 
-    def sourceFile_=(f: AbstractFileType) {
-      abort("sourceFile_= inapplicable for " + this)
-    }
+    /** Desire to re-use the field in ClassSymbol which stores the source
+     *  file to also store the classfile, but without changing the behavior
+     *  of sourceFile (which is expected at least in the IDE only to
+     *  return actual source code.) So sourceFile has classfiles filtered out.
+     */
+    private def sourceFileOnly(file: AbstractFileType): AbstractFileType =
+      if ((file eq null) || (file.path endsWith ".class")) null else file
+
+    private def binaryFileOnly(file: AbstractFileType): AbstractFileType =
+      if ((file eq null) || !(file.path endsWith ".class")) null else file
+
+    final def binaryFile: AbstractFileType = binaryFileOnly(associatedFile)
+    final def sourceFile: AbstractFileType = sourceFileOnly(associatedFile)
+
+    /** Overridden in ModuleSymbols to delegate to the module class. */
+    def associatedFile: AbstractFileType = enclosingTopLevelClass.associatedFile
+    def associatedFile_=(f: AbstractFileType) { abort("associatedFile_= inapplicable for " + this) }
+
+    @deprecated("Use associatedFile_= instead", "2.10.0")
+    def sourceFile_=(f: AbstractFileType): Unit = associatedFile_=(f)
 
     /** If this is a sealed class, its known direct subclasses.
      *  Otherwise, the empty set.
@@ -2423,6 +2437,9 @@ trait Symbols extends api.Symbols { self: SymbolTable =>
     def distinguishingFlag = MODULE
     private var flatname: TermName = null
 
+    override def associatedFile = moduleClass.associatedFile
+    override def associatedFile_=(f: AbstractFileType) { moduleClass.associatedFile = f }
+
     override def isModule = true
     override def moduleClass = referenced
     override def companionClass =
@@ -2718,9 +2735,9 @@ trait Symbols extends api.Symbols { self: SymbolTable =>
   extends TypeSymbol(initOwner, initPos, initName) with ClassSymbolApi {
     type TypeOfClonedSymbol = ClassSymbol
 
-    private[this] var flatname: TypeName       = _
-    private[this] var source: AbstractFileType = _
-    private[this] var thissym: Symbol          = this
+    private[this] var flatname: TypeName                = _
+    private[this] var _associatedFile: AbstractFileType = _
+    private[this] var thissym: Symbol                   = this
 
     private[this] var thisTypeCache: Type      = _
     private[this] var thisTypePeriod           = NoPeriod
@@ -2819,10 +2836,8 @@ trait Symbols extends api.Symbols { self: SymbolTable =>
       if (c.isOverloaded) c.alternatives.head else c
     }
 
-    override def sourceFile =
-      if (owner.isPackageClass) source
-      else super.sourceFile
-    override def sourceFile_=(f: AbstractFileType) { source = f }
+    override def associatedFile = if (owner.isPackageClass) _associatedFile else super.associatedFile
+    override def associatedFile_=(f: AbstractFileType) { _associatedFile = f }
 
     override def reset(completer: Type): this.type = {
       super.reset(completer)
@@ -2867,6 +2882,9 @@ trait Symbols extends api.Symbols { self: SymbolTable =>
         clone.typeOfThis = typeOfThis
         clone.thisSym setName thisSym.name
       }
+      if (_associatedFile ne null)
+        clone.associatedFile = _associatedFile
+
       clone
     }
 
@@ -3021,7 +3039,7 @@ trait Symbols extends api.Symbols { self: SymbolTable =>
     override def enclosingTopLevelClass: Symbol = this
     override def enclosingPackageClass: Symbol = this
     override def enclMethod: Symbol = this
-    override def sourceFile: AbstractFileType = null
+    override def associatedFile = null
     override def ownerChain: List[Symbol] = List()
     override def ownersIterator: Iterator[Symbol] = Iterator.empty
     override def alternatives: List[Symbol] = List()
diff --git a/src/compiler/scala/reflect/runtime/SynchronizedSymbols.scala b/src/compiler/scala/reflect/runtime/SynchronizedSymbols.scala
index 8378f1a892..2322911220 100644
--- a/src/compiler/scala/reflect/runtime/SynchronizedSymbols.scala
+++ b/src/compiler/scala/reflect/runtime/SynchronizedSymbols.scala
@@ -121,8 +121,8 @@ trait SynchronizedSymbols extends internal.Symbols { self: SymbolTable =>
   }
 
   trait SynchronizedClassSymbol extends ClassSymbol with SynchronizedTypeSymbol {
-    override def sourceFile = synchronized { super.sourceFile }
-    override def sourceFile_=(f: AbstractFileType) = synchronized { super.sourceFile_=(f) }
+    override def associatedFile = synchronized { super.associatedFile }
+    override def associatedFile_=(f: AbstractFileType) = synchronized { super.associatedFile_=(f) }
     override def thisSym: Symbol = synchronized { super.thisSym }
     override def thisType: Type = synchronized { super.thisType }
     override def typeOfThis: Type = synchronized { super.typeOfThis }
diff --git a/src/compiler/scala/tools/nsc/io/PlainFile.scala b/src/compiler/scala/tools/nsc/io/PlainFile.scala
index 83b8cc32c4..21276e8740 100644
--- a/src/compiler/scala/tools/nsc/io/PlainFile.scala
+++ b/src/compiler/scala/tools/nsc/io/PlainFile.scala
@@ -51,6 +51,7 @@ class PlainFile(val givenPath: Path) extends AbstractFile {
   override def output = givenPath.toFile.outputStream()
   override def sizeOption = Some(givenPath.length.toInt)
 
+  override def toString = path
   override def hashCode(): Int = fpath.hashCode
   override def equals(that: Any): Boolean = that match {
     case x: PlainFile => fpath == x.fpath
diff --git a/src/compiler/scala/tools/nsc/symtab/SymbolLoaders.scala b/src/compiler/scala/tools/nsc/symtab/SymbolLoaders.scala
index 7eb04eaf40..390b1a5ec6 100644
--- a/src/compiler/scala/tools/nsc/symtab/SymbolLoaders.scala
+++ b/src/compiler/scala/tools/nsc/symtab/SymbolLoaders.scala
@@ -232,6 +232,16 @@ abstract class SymbolLoaders {
     protected def doComplete(root: Symbol) {
       val start = startTimer(classReadNanos)
       classfileParser.parse(classfile, root)
+      if (root.associatedFile eq null) {
+        root match {
+          // In fact, the ModuleSymbol forwards its setter to the module class
+          case _: ClassSymbol | _: ModuleSymbol =>
+            debuglog("ClassfileLoader setting %s.associatedFile = %s".format(root.name, classfile))
+            root.associatedFile = classfile
+          case _ =>
+            debuglog("Not setting associatedFile to %s because %s is a %s".format(classfile, root.name, root.shortSymbolClass))
+        }
+      }
       stopTimer(classReadNanos, start)
     }
     override def sourcefile: Option[AbstractFile] = classfileParser.srcfile
diff --git a/src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala b/src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala
index 0117bfb037..ef73d6db1a 100644
--- a/src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala
+++ b/src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala
@@ -1064,7 +1064,8 @@ abstract class ClassfileParser {
     def className(name: Name): Name =
       name.subName(name.lastPos('.') + 1, name.length)
 
-    def enterClassAndModule(entry: InnerClassEntry, completer: global.loaders.SymbolLoader, jflags: Int) {
+    def enterClassAndModule(entry: InnerClassEntry, file: AbstractFile, jflags: Int) {
+      val completer   = new global.loaders.ClassfileLoader(file)
       val name        = entry.originalName
       var sflags      = toScalaClassFlags(jflags)
       val owner       = getOwner(jflags)
@@ -1073,6 +1074,8 @@ abstract class ClassfileParser {
       val innerModule = owner.newModule(name.toTermName, NoPosition, sflags) setInfo completer
 
       innerModule.moduleClass setInfo global.loaders.moduleClassLoader
+      List(innerClass, innerModule.moduleClass) foreach (_.associatedFile = file)
+
       scope enter innerClass
       scope enter innerModule
 
@@ -1094,7 +1097,7 @@ abstract class ClassfileParser {
         val file = global.classPath.findSourceFile(entry.externalName.toString) getOrElse {
           throw new AssertionError(entry.externalName)
         }
-        enterClassAndModule(entry, new global.loaders.ClassfileLoader(file), entry.jflags)
+        enterClassAndModule(entry, file, entry.jflags)
       }
     }
   }
diff --git a/src/compiler/scala/tools/nsc/typechecker/ContextErrors.scala b/src/compiler/scala/tools/nsc/typechecker/ContextErrors.scala
index 2d1369b11d..6932030fc2 100644
--- a/src/compiler/scala/tools/nsc/typechecker/ContextErrors.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/ContextErrors.scala
@@ -622,19 +622,23 @@ trait ContextErrors {
         setError(tree)
       }
 
-      // checkNoDoubleDefs...
-      // @PP: I hacked the filename in (context0.unit) to work around SI-4893.  It would be
-      // much better if every symbol could offer some idea of where it came from, else
-      // the obviously untrue claim that something has been defined twice can only frustrate.
-      // There's no direct test because partest doesn't work, but to reproduce, separately
-      // compile the next two lines:
-      //    package object foo { val x: Class[_] = null }
-      //    package foo
       def DefDefinedTwiceError(sym0: Symbol, sym1: Symbol) = {
+        // Most of this hard work is associated with SI-4893.
         val isBug = sym0.isAbstractType && sym1.isAbstractType && (sym0.name startsWith "_$")
-        issueSymbolTypeError(sym0, sym1+" is defined twice in " + context0.unit
-          + ( if (isBug) "\n(this error is likely due to a bug in the scala compiler involving wildcards in package objects)" else "" )
+        val addendums = List(
+          if (sym0.associatedFile eq sym1.associatedFile)
+            Some("conflicting symbols both originated in file '%s'".format(sym0.associatedFile.canonicalPath))
+          else if ((sym0.associatedFile ne null) && (sym1.associatedFile ne null))
+            Some("conflicting symbols originated in files '%s' and '%s'".format(sym0.associatedFile.canonicalPath, sym1.associatedFile.canonicalPath))
+          else None ,
+          if (isBug) Some("Note: this may be due to a bug in the compiler involving wildcards in package objects") else None
         )
+        val addendum = addendums.flatten match {
+          case Nil    => ""
+          case xs     => xs.mkString("\n  ", "\n  ", "")
+        }
+
+        issueSymbolTypeError(sym0, sym1+" is defined twice" + addendum)
       }
 
       // cyclic errors
diff --git a/src/library/scala/runtime/ScalaRunTime.scala b/src/library/scala/runtime/ScalaRunTime.scala
index 9d67644d61..0797b65fb0 100644
--- a/src/library/scala/runtime/ScalaRunTime.scala
+++ b/src/library/scala/runtime/ScalaRunTime.scala
@@ -293,8 +293,12 @@ object ScalaRunTime {
    */
   def stringOf(arg: Any): String = stringOf(arg, scala.Int.MaxValue)
   def stringOf(arg: Any, maxElements: Int): String = {
-    def isScalaClass(x: AnyRef) =
-      Option(x.getClass.getPackage) exists (_.getName startsWith "scala.")
+    def packageOf(x: AnyRef) = x.getClass.getPackage match {
+      case null   => ""
+      case p      => p.getName
+    }
+    def isScalaClass(x: AnyRef)         = packageOf(x) startsWith "scala."
+    def isScalaCompilerClass(x: AnyRef) = packageOf(x) startsWith "scala.tools.nsc."
 
     // When doing our own iteration is dangerous
     def useOwnToString(x: Any) = x match {
@@ -310,7 +314,8 @@ object ScalaRunTime {
       case _: TraversableView[_, _] => true
       // Don't want to a) traverse infinity or b) be overly helpful with peoples' custom
       // collections which may have useful toString methods - ticket #3710
-      case x: Traversable[_]  => !x.hasDefiniteSize || !isScalaClass(x)
+      // or c) print AbstractFiles which are somehow also Iterable[AbstractFile]s.
+      case x: Traversable[_] => !x.hasDefiniteSize || !isScalaClass(x) || isScalaCompilerClass(x)
       // Otherwise, nothing could possibly go wrong
       case _ => false
     }
diff --git a/src/partest/scala/tools/partest/nest/Worker.scala b/src/partest/scala/tools/partest/nest/Worker.scala
index c69609ec58..9326a8b232 100644
--- a/src/partest/scala/tools/partest/nest/Worker.scala
+++ b/src/partest/scala/tools/partest/nest/Worker.scala
@@ -357,11 +357,11 @@ class Worker(val fileManager: FileManager, params: TestRunParams) extends Actor
 
   private def compareOutput(dir: File, logFile: File): String = {
     val checkFile = getCheckFilePath(dir, kind)
-    // if check file exists, compare with log file
     val diff =
       if (checkFile.canRead) compareFiles(logFile, checkFile.jfile)
       else file2String(logFile)
 
+    // if check file exists, compare with log file
     if (diff != "" && fileManager.updateCheck) {
       NestUI.verbose("Updating checkfile " + checkFile.jfile)
       val toWrite = if (checkFile.exists) checkFile else getCheckFilePath(dir, "")