Merge pull request scala#5082 from lrytz/inlineImplClassCleanup

Cleanups related to the removal of trait impl classes

Author: lrytz

src/compiler/scala/tools/nsc/backend/jvm/BCodeHelpers.scala

@@ -30,8 +30,7 @@ abstract class BCodeHelpers extends BCodeIdiomatic with BytecodeWriters {
    * True for classes generated by the Scala compiler that are considered top-level in terms of
    * the InnerClass / EnclosingMethod classfile attributes. See comment in BTypes.
    */
-  def considerAsTopLevelImplementationArtifact(classSym: Symbol) =
-    classSym.isSpecialized
+  def considerAsTopLevelImplementationArtifact(classSym: Symbol) = classSym.isSpecialized
 
   /**
    * Cache the value of delambdafy == "inline" for each run. We need to query this value many
@@ -146,10 +145,10 @@ abstract class BCodeHelpers extends BCodeIdiomatic with BytecodeWriters {
     assert(classSym.isClass, classSym)
 
     def doesNotExist(method: Symbol) = {
-      //     Value classes. Member methods of value classes exist in the generated box class. However,
-      //     nested methods lifted into a value class are moved to the companion object and don't exist
-      //     in the value class itself. We can identify such nested methods: the initial enclosing class
-      //     is a value class, but the current owner is some other class (the module class).
+      // Value classes. Member methods of value classes exist in the generated box class. However,
+      // nested methods lifted into a value class are moved to the companion object and don't exist
+      // in the value class itself. We can identify such nested methods: the initial enclosing class
+      // is a value class, but the current owner is some other class (the module class).
       val enclCls = nextEnclosingClass(method)
       exitingPickler(enclCls.isDerivedValueClass) && method.owner != enclCls
     }
@@ -171,8 +170,6 @@ abstract class BCodeHelpers extends BCodeIdiomatic with BytecodeWriters {
   private def enclosingClassForEnclosingMethodAttribute(classSym: Symbol): Symbol = {
     assert(classSym.isClass, classSym)
     val r = nextEnclosingClass(nextEnclosing(classSym))
-    // this should be an assertion, but we are more cautious for now as it was introduced before the 2.11.6 minor release
-    if (considerAsTopLevelImplementationArtifact(r)) devWarning(s"enclosing class of $classSym should not be an implementation artifact class: $r")
     r
   }
 
@@ -187,20 +184,11 @@ abstract class BCodeHelpers extends BCodeIdiomatic with BytecodeWriters {
    * on the implementation of GenASM / GenBCode, so they need to be passed in.
    */
   def enclosingMethodAttribute(classSym: Symbol, classDesc: Symbol => String, methodDesc: Symbol => String): Option[EnclosingMethodEntry] = {
-    // trait impl classes are always top-level, see comment in BTypes
+    // specialized classes are always top-level, see comment in BTypes
     if (isAnonymousOrLocalClass(classSym) && !considerAsTopLevelImplementationArtifact(classSym)) {
       val enclosingClass = enclosingClassForEnclosingMethodAttribute(classSym)
-      val methodOpt = enclosingMethodForEnclosingMethodAttribute(classSym) match {
-        case some @ Some(m) =>
-          if (m.owner != enclosingClass) {
-            // This should never happen. In case it does, it prevents emitting an invalid
-            // EnclosingMethod attribute: if the attribute specifies an enclosing method,
-            // it needs to exist in the specified enclosing class.
-            devWarning(s"the owner of the enclosing method ${m.locationString} should be the same as the enclosing class $enclosingClass")
-            None
-          } else some
-        case none => none
-      }
+      val methodOpt = enclosingMethodForEnclosingMethodAttribute(classSym)
+      for (m <- methodOpt) assert(m.owner == enclosingClass, s"the owner of the enclosing method ${m.locationString} should be the same as the enclosing class $enclosingClass")
       Some(EnclosingMethodEntry(
         classDesc(enclosingClass),
         methodOpt.map(_.javaSimpleName.toString).orNull,
@@ -246,14 +234,6 @@ abstract class BCodeHelpers extends BCodeIdiomatic with BytecodeWriters {
    * Build the [[InlineInfo]] for a class symbol.
    */
   def buildInlineInfoFromClassSymbol(classSym: Symbol, classSymToInternalName: Symbol => InternalName, methodSymToDescriptor: Symbol => String): InlineInfo = {
-    val traitSelfType = if (classSym.isTrait) {
-      // The mixin phase uses typeOfThis for the self parameter in implementation class methods.
-      val selfSym = classSym.typeOfThis.typeSymbol
-      if (selfSym != classSym) Some(classSymToInternalName(selfSym)) else None
-    } else {
-      None
-    }
-
     val isEffectivelyFinal = classSym.isEffectivelyFinal
 
     val sam = {
@@ -282,23 +262,24 @@ abstract class BCodeHelpers extends BCodeIdiomatic with BytecodeWriters {
           val name      = methodSym.javaSimpleName.toString // same as in genDefDef
           val signature = name + methodSymToDescriptor(methodSym)
 
-          // Some detours are required here because of changing flags (lateDEFERRED):
-          // 1. Why the phase travel? Concrete trait methods obtain the lateDEFERRED flag in Mixin.
-          //    This makes isEffectivelyFinalOrNotOverridden false, which would prevent non-final
-          //    but non-overridden methods of sealed traits from being inlined.
-          val effectivelyFinal = exitingPickler(methodSym.isEffectivelyFinalOrNotOverridden) && !(methodSym.owner.isTrait && methodSym.isModule)
+          // In `trait T { object O }`, `oSym.isEffectivelyFinalOrNotOverridden` is true, but the
+          // method is abstract in bytecode, `defDef.rhs.isEmpty`. Abstract methods are excluded
+          // so they are not marked final in the InlineInfo attribute.
+          //
+          // However, due to https://github.com/scala/scala-dev/issues/126, this currently does not
+          // work, the abstract accessor for O will be marked effectivelyFinal.
+          val effectivelyFinal = methodSym.isEffectivelyFinalOrNotOverridden && !methodSym.isDeferred
 
           val info = MethodInlineInfo(
             effectivelyFinal                    = effectivelyFinal,
-            traitMethodWithStaticImplementation = false,
             annotatedInline                     = methodSym.hasAnnotation(ScalaInlineClass),
             annotatedNoInline                   = methodSym.hasAnnotation(ScalaNoInlineClass)
           )
           Some((signature, info))
         }
     }).toMap
 
-    InlineInfo(traitSelfType, isEffectivelyFinal, sam, methodInlineInfos, warning)
+    InlineInfo(isEffectivelyFinal, sam, methodInlineInfos, warning)
   }
 
   /*

src/compiler/scala/tools/nsc/backend/jvm/BCodeSkelBuilder.scala

@@ -232,13 +232,6 @@ abstract class BCodeSkelBuilder extends BCodeHelpers {
     }
 
     def addClassFields() {
-      /*  Non-method term members are fields, except for module members. Module
-       *  members can only happen on .NET (no flatten) for inner traits. There,
-       *  a module symbol is generated (transformInfo in mixin) which is used
-       *  as owner for the members of the implementation class (so that the
-       *  backend emits them as static).
-       *  No code is needed for this module symbol.
-       */
       for (f <- fieldSymbols(claszSymbol)) {
         val javagensig = getGenericSignature(f, claszSymbol)
         val flags = javaFieldFlags(f)

src/compiler/scala/tools/nsc/backend/jvm/BTypes.scala

@@ -255,13 +255,11 @@ abstract class BTypes {
       val methodInfos = classNode.methods.asScala.map(methodNode => {
         val info = MethodInlineInfo(
           effectivelyFinal                    = BytecodeUtils.isFinalMethod(methodNode),
-          traitMethodWithStaticImplementation = false,
           annotatedInline                     = false,
           annotatedNoInline                   = false)
         (methodNode.name + methodNode.desc, info)
       }).toMap
       InlineInfo(
-        traitImplClassSelfType = None,
         isEffectivelyFinal = BytecodeUtils.isFinalClass(classNode),
         sam = inlinerHeuristics.javaSam(classNode.name),
         methodInfos = methodInfos,
@@ -792,26 +790,17 @@ abstract class BTypes {
    *   }
    *
    *
-   * Traits Members
-   * --------------
-   *
-   * Some trait methods don't exist in the generated interface, but only in the implementation class
-   * (private methods in traits for example). Since EnclosingMethod expresses a source-level property,
-   * but the source-level enclosing method doesn't exist in the classfile, we the enclosing method
-   * is null (the enclosing class is still emitted).
-   * See BCodeAsmCommon.considerAsTopLevelImplementationArtifact
-   *
-   *
-   * Implementation Classes, Specialized Classes, Delambdafy:method closure classes
-   * ------------------------------------------------------------------------------
+   * Specialized Classes, Delambdafy:method closure classes
+   * ------------------------------------------------------
    *
-   * Trait implementation classes and specialized classes are always considered top-level. Again,
-   * the InnerClass / EnclosingMethod attributes describe a source-level properties. The impl
-   * classes are compilation artifacts.
+   * Specialized classes are always considered top-level, as the InnerClass / EnclosingMethod
+   * attributes describe a source-level properties.
    *
    * The same is true for delambdafy:method closure classes. These classes are generated at
    * top-level in the delambdafy phase, no special support is required in the backend.
    *
+   * See also BCodeHelpers.considerAsTopLevelImplementationArtifact.
+   *
    *
    * Mirror Classes
    * --------------
@@ -1139,22 +1128,8 @@ object BTypes {
    * Note that this class should contain information that can only be obtained from the ClassSymbol.
    * Information that can be computed from the ClassNode should be added to the call graph instead.
    *
-   * @param traitImplClassSelfType `Some(tp)` if this InlineInfo describes a trait, and the `self`
-   *                               parameter type of the methods in the implementation class is not
-   *                               the trait itself. Example:
-   *                                 trait T { self: U => def f = 1 }
-   *                               Generates something like:
-   *                                 class T$class { static def f(self: U) = 1 }
-   *
-   *                               In order to inline a trat method call, the INVOKEINTERFACE is
-   *                               rewritten to an INVOKESTATIC of the impl class, so we need the
-   *                               self type (U) to get the right signature.
-   *
-   *                               `None` if the self type is the interface type, or if this
-   *                               InlineInfo does not describe a trait.
-   *
    * @param isEffectivelyFinal     True if the class cannot have subclasses: final classes, module
-   *                               classes, trait impl classes.
+   *                               classes.
    *
    * @param sam                    If this class is a SAM type, the SAM's "$name$descriptor".
    *
@@ -1166,26 +1141,21 @@ object BTypes {
    *                               InlineInfo, for example if some classfile could not be found on
    *                               the classpath. This warning can be reported later by the inliner.
    */
-  final case class InlineInfo(traitImplClassSelfType: Option[InternalName],
-                              isEffectivelyFinal: Boolean,
+  final case class InlineInfo(isEffectivelyFinal: Boolean,
                               sam: Option[String],
                               methodInfos: Map[String, MethodInlineInfo],
                               warning: Option[ClassInlineInfoWarning])
 
-  val EmptyInlineInfo = InlineInfo(None, false, None, Map.empty, None)
+  val EmptyInlineInfo = InlineInfo(false, None, Map.empty, None)
 
   /**
    * Metadata about a method, used by the inliner.
    *
    * @param effectivelyFinal                    True if the method cannot be overridden (in Scala)
-   * @param traitMethodWithStaticImplementation True if the method is an interface method method of
-   *                                            a trait method and has a static counterpart in the
-   *                                            implementation class.
    * @param annotatedInline                     True if the method is annotated `@inline`
    * @param annotatedNoInline                   True if the method is annotated `@noinline`
    */
   final case class MethodInlineInfo(effectivelyFinal: Boolean,
-                                    traitMethodWithStaticImplementation: Boolean,
                                     annotatedInline: Boolean,
                                     annotatedNoInline: Boolean)
 

src/compiler/scala/tools/nsc/backend/jvm/BTypesFromSymbols.scala

@@ -96,11 +96,6 @@ class BTypesFromSymbols[G <: Global](val global: G) extends BTypes {
    * scala.Null is mapped to scala.runtime.Null$. This is because there exist no class files
    * for the Nothing / Null. If used for example as a parameter type, we use the runtime classes
    * in the classfile method signature.
-   *
-   * Note that the referenced class symbol may be an implementation class. For example when
-   * compiling a mixed-in method that forwards to the static method in the implementation class,
-   * the class descriptor of the receiver (the implementation class) is obtained by creating the
-   * ClassBType.
    */
   final def classBTypeFromSymbol(classSym: Symbol): ClassBType = {
     assert(classSym != NoSymbol, "Cannot create ClassBType from NoSymbol")
@@ -159,9 +154,6 @@ class BTypesFromSymbols[G <: Global](val global: G) extends BTypes {
 
   /**
    * This method returns the BType for a type reference, for example a parameter type.
-   *
-   * If `t` references a class, typeToBType ensures that the class is not an implementation class.
-   * See also comment on classBTypeFromSymbol, which is invoked for implementation classes.
    */
   final def typeToBType(t: Type): BType = {
     import definitions.ArrayClass
@@ -264,12 +256,12 @@ class BTypesFromSymbols[G <: Global](val global: G) extends BTypes {
    * current phase, for example, after lambdalift, all local classes become member of the enclosing
    * class.
    *
-   * Impl classes are always considered top-level, see comment in BTypes.
+   * Specialized classes are always considered top-level, see comment in BTypes.
    */
   private def memberClassesForInnerClassTable(classSymbol: Symbol): List[Symbol] = classSymbol.info.decls.collect({
     case sym if sym.isClass && !considerAsTopLevelImplementationArtifact(sym) =>
       sym
-    case sym if sym.isModule && !considerAsTopLevelImplementationArtifact(sym) => // impl classes get the lateMODULE flag in mixin
+    case sym if sym.isModule && !considerAsTopLevelImplementationArtifact(sym) =>
       val r = exitingPickler(sym.moduleClass)
       assert(r != NoSymbol, sym.fullLocationString)
       r
@@ -317,7 +309,6 @@ class BTypesFromSymbols[G <: Global](val global: G) extends BTypes {
       )
     }
 
-    // Check for isImplClass: trait implementation classes have NoSymbol as superClass
     // Check for hasAnnotationFlag for SI-9393: the classfile / java source parsers add
     // scala.annotation.Annotation as superclass to java annotations. In reality, java
     // annotation classfiles have superclass Object (like any interface classfile).
@@ -380,8 +371,8 @@ class BTypesFromSymbols[G <: Global](val global: G) extends BTypes {
       }
 
       val companionModuleMembers = if (considerAsTopLevelImplementationArtifact(classSym)) Nil else {
-        // If this is a top-level non-impl (*) class, the member classes of the companion object are
-        // added as members of the class. For example:
+        // If this is a top-level class, the member classes of the companion object are added as
+        // members of the class. For example:
         //   class C { }
         //   object C {
         //     class D
@@ -392,11 +383,6 @@ class BTypesFromSymbols[G <: Global](val global: G) extends BTypes {
         // (done by buildNestedInfo). See comment in BTypes.
         // For consistency, the InnerClass entry for D needs to be present in C - to Java it looks
         // like D is a member of C, not C$.
-        //
-        // (*) We exclude impl classes: if the classfile for the impl class exists on the classpath,
-        // a linkedClass symbol is found for which isTopLevelModule is true, so we end up searching
-        // members of that weird impl-class-module-class-symbol. that search probably cannot return
-        // any classes, but it's better to exclude it.
         val javaCompatMembers = {
           if (linkedClass != NoSymbol && isTopLevelModuleClass(linkedClass))
           // phase travel to exitingPickler: this makes sure that memberClassesForInnerClassTable only sees member
@@ -454,7 +440,7 @@ class BTypesFromSymbols[G <: Global](val global: G) extends BTypes {
     assert(innerClassSym.isClass, s"Cannot build NestedInfo for non-class symbol $innerClassSym")
 
     val isTopLevel = innerClassSym.rawowner.isPackageClass
-    // impl classes are considered top-level, see comment in BTypes
+    // specialized classes are considered top-level, see comment in BTypes
     if (isTopLevel || considerAsTopLevelImplementationArtifact(innerClassSym)) None
     else if (innerClassSym.rawowner.isTerm) {
       // This case should never be reached: the lambdalift phase mutates the rawowner field of all
@@ -592,17 +578,11 @@ class BTypesFromSymbols[G <: Global](val global: G) extends BTypes {
 
   /**
    * True for module classes of modules that are top-level or owned only by objects. Module classes
-   * for such objects will get a MODULE$ flag and a corresponding static initializer.
+   * for such objects will get a MODULE$ field and a corresponding static initializer.
    */
   final def isStaticModuleClass(sym: Symbol): Boolean = {
-    /* (1) Phase travel to to pickler is required to exclude implementation classes; they have the
-     * lateMODULEs after mixin, so isModuleClass would be true.
-     * (2) isStaticModuleClass is a source-level property. See comment on isOriginallyStaticOwner.
-     */
-    exitingPickler { // (1)
-      sym.isModuleClass &&
-      isOriginallyStaticOwner(sym.originalOwner) // (2)
-    }
+    sym.isModuleClass &&
+    isOriginallyStaticOwner(sym.originalOwner) // isStaticModuleClass is a source-level property, see comment on isOriginallyStaticOwner
   }
 
   // legacy, to be removed when the @remote annotation gets removed

src/compiler/scala/tools/nsc/backend/jvm/BackendReporting.scala

@@ -170,9 +170,6 @@ object BackendReporting {
 
       case MethodInlineInfoError(_, _, _, cause) =>
         s"Error while computing the inline information for method $warningMessageSignature:\n" + cause
-
-      case RewriteTraitCallToStaticImplMethodFailed(_, _, _, cause) =>
-        cause.toString
     }
 
     def emitWarning(settings: ScalaSettings): Boolean = this match {
@@ -182,15 +179,12 @@ object BackendReporting {
       case MethodInlineInfoMissing(_, _, _, None)                   => settings.YoptWarningNoInlineMissingBytecode
 
       case MethodInlineInfoError(_, _, _, cause)                    => cause.emitWarning(settings)
-
-      case RewriteTraitCallToStaticImplMethodFailed(_, _, _, cause) => cause.emitWarning(settings)
     }
   }
 
   case class MethodInlineInfoIncomplete(declarationClass: InternalName, name: String, descriptor: String, cause: ClassInlineInfoWarning) extends CalleeInfoWarning
   case class MethodInlineInfoMissing(declarationClass: InternalName, name: String, descriptor: String, cause: Option[ClassInlineInfoWarning]) extends CalleeInfoWarning
   case class MethodInlineInfoError(declarationClass: InternalName, name: String, descriptor: String, cause: NoClassBTypeInfo) extends CalleeInfoWarning
-  case class RewriteTraitCallToStaticImplMethodFailed(declarationClass: InternalName, name: String, descriptor: String, cause: OptimizerWarning) extends CalleeInfoWarning
 
   sealed trait CannotInlineWarning extends OptimizerWarning {
     def calleeDeclarationClass: InternalName