Construct ClassBTypes from parsed classfiles

This infrastructure is required for the inliner: when inlining code
from a classfile, the corresponding ClassBType is needed for various
things (eg access checks, InnerClass attribute).

The test creates two ClassBTypes for the same class: once using the
(unpickled) Symbol, once using the parsed ASM ClassNode, and verifies
that the two are the same.

There's a cleanup to the InnerClass attribute:

    object T { class Member; def foo = { class Local } }
    class T

For Java compatibility the InnerClass entry for Member says the class
is nested in T (not in the module class T$). We now make sure to add
that entry only to T, not to T$ (unless Member is actually referenced
in the classfile T$, in that case it will be added, as required).

13 files changed, 421 insertions, 101 deletions

diff --git a/src/compiler/scala/tools/nsc/backend/jvm/BCodeHelpers.scala b/src/compiler/scala/tools/nsc/backend/jvm/BCodeHelpers.scala
index 806d4b277c..8d1c37532e 100644
--- a/src/compiler/scala/tools/nsc/backend/jvm/BCodeHelpers.scala
+++ b/src/compiler/scala/tools/nsc/backend/jvm/BCodeHelpers.scala
@@ -791,32 +791,28 @@ abstract class BCodeHelpers extends BCodeIdiomatic with BytecodeWriters {
       assert(moduleClass.companionClass == NoSymbol, moduleClass)
       innerClassBufferASM.clear()
       this.cunit = cunit
-      val moduleName = internalName(moduleClass) // + "$"
-      val mirrorName = moduleName.substring(0, moduleName.length() - 1)
 
-      val flags = (asm.Opcodes.ACC_SUPER | asm.Opcodes.ACC_PUBLIC | asm.Opcodes.ACC_FINAL)
+      val bType = mirrorClassClassBType(moduleClass)
       val mirrorClass = new asm.tree.ClassNode
       mirrorClass.visit(
         classfileVersion,
-        flags,
-        mirrorName,
+        bType.info.flags,
+        bType.internalName,
         null /* no java-generic-signature */,
         ObjectReference.internalName,
         EMPTY_STRING_ARRAY
       )
 
-      if (emitSource) {
-        mirrorClass.visitSource("" + cunit.source,
-                                null /* SourceDebugExtension */)
-      }
+      if (emitSource)
+        mirrorClass.visitSource("" + cunit.source, null /* SourceDebugExtension */)
 
-      val ssa = getAnnotPickle(mirrorName, moduleClass.companionSymbol)
+      val ssa = getAnnotPickle(bType.internalName, moduleClass.companionSymbol)
       mirrorClass.visitAttribute(if (ssa.isDefined) pickleMarkerLocal else pickleMarkerForeign)
       emitAnnotations(mirrorClass, moduleClass.annotations ++ ssa)
 
-      addForwarders(isRemote(moduleClass), mirrorClass, mirrorName, moduleClass)
+      addForwarders(isRemote(moduleClass), mirrorClass, bType.internalName, moduleClass)
 
-      innerClassBufferASM ++= classBTypeFromSymbol(moduleClass).info.memberClasses
+      innerClassBufferASM ++= bType.info.nestedClasses
       addInnerClassesASM(mirrorClass, innerClassBufferASM.toList)
 
       mirrorClass.visitEnd()
@@ -932,7 +928,7 @@ abstract class BCodeHelpers extends BCodeIdiomatic with BytecodeWriters {
       constructor.visitMaxs(0, 0) // just to follow protocol, dummy arguments
       constructor.visitEnd()
 
-      innerClassBufferASM ++= classBTypeFromSymbol(cls).info.memberClasses
+      innerClassBufferASM ++= classBTypeFromSymbol(cls).info.nestedClasses
       addInnerClassesASM(beanInfoClass, innerClassBufferASM.toList)
 
       beanInfoClass.visitEnd()
diff --git a/src/compiler/scala/tools/nsc/backend/jvm/BCodeSkelBuilder.scala b/src/compiler/scala/tools/nsc/backend/jvm/BCodeSkelBuilder.scala
index 03bc32061b..142c901c21 100644
--- a/src/compiler/scala/tools/nsc/backend/jvm/BCodeSkelBuilder.scala
+++ b/src/compiler/scala/tools/nsc/backend/jvm/BCodeSkelBuilder.scala
@@ -118,7 +118,7 @@ abstract class BCodeSkelBuilder extends BCodeHelpers {
 
       addClassFields()
 
-      innerClassBufferASM ++= classBTypeFromSymbol(claszSymbol).info.memberClasses
+      innerClassBufferASM ++= classBTypeFromSymbol(claszSymbol).info.nestedClasses
       gen(cd.impl)
       addInnerClassesASM(cnode, innerClassBufferASM.toList)
 
diff --git a/src/compiler/scala/tools/nsc/backend/jvm/BTypes.scala b/src/compiler/scala/tools/nsc/backend/jvm/BTypes.scala
index e1ca13cba9..11ee0d127b 100644
--- a/src/compiler/scala/tools/nsc/backend/jvm/BTypes.scala
+++ b/src/compiler/scala/tools/nsc/backend/jvm/BTypes.scala
@@ -8,6 +8,9 @@ package backend.jvm
 
 import scala.tools.asm
 import asm.Opcodes
+import scala.tools.asm.tree.{InnerClassNode, ClassNode}
+import opt.CodeRepository
+import scala.collection.convert.decorateAsScala._
 
 /**
  * The BTypes component defines The BType class hierarchy. BTypes encapsulate all type information
@@ -20,6 +23,17 @@ import asm.Opcodes
 abstract class BTypes {
   import BTypes.InternalName
 
+  // Some core BTypes are required here, in class BType, where no Global instance is available.
+  // The Global is only available in the subclass BTypesFromSymbols. We cannot depend on the actual
+  // implementation (CoreBTypesProxy) here because it has members that refer to global.Symbol.
+  val coreBTypes: CoreBTypesProxyGlobalIndependent[this.type]
+  import coreBTypes._
+
+  /**
+   * Tools for parsing classfiles, used by the inliner.
+   */
+  val codeRepository: CodeRepository
+
   /**
    * A map from internal names to ClassBTypes. Every ClassBType is added to this map on its
    * construction.
@@ -31,18 +45,77 @@ abstract class BTypes {
    * Concurrent because stack map frames are computed when in the class writer, which might run
    * on multiple classes concurrently.
    */
-  protected val classBTypeFromInternalNameMap: collection.concurrent.Map[InternalName, ClassBType]
+  val classBTypeFromInternalName: collection.concurrent.Map[InternalName, ClassBType]
 
   /**
-   * Obtain a previously constructed ClassBType for a given internal name.
+   * Parse the classfile for `internalName` and construct the [[ClassBType]].
    */
-  def classBTypeFromInternalName(internalName: InternalName) = classBTypeFromInternalNameMap(internalName)
+  def classBTypeFromParsedClassfile(internalName: InternalName): ClassBType = {
+    classBTypeFromClassNode(codeRepository.classNode(internalName))
+  }
 
-  // Some core BTypes are required here, in class BType, where no Global instance is available.
-  // The Global is only available in the subclass BTypesFromSymbols. We cannot depend on the actual
-  // implementation (CoreBTypesProxy) here because it has members that refer to global.Symbol.
-  val coreBTypes: CoreBTypesProxyGlobalIndependent[this.type]
-  import coreBTypes._
+  /**
+   * Construct the [[ClassBType]] for a parsed classfile.
+   */
+  def classBTypeFromClassNode(classNode: ClassNode): ClassBType = {
+    classBTypeFromInternalName.getOrElse(classNode.name, {
+      setClassInfo(classNode, ClassBType(classNode.name))
+    })
+  }
+
+  private def setClassInfo(classNode: ClassNode, classBType: ClassBType): ClassBType = {
+    val superClass = classNode.superName match {
+      case null =>
+        assert(classNode.name == ObjectReference.internalName, s"class with missing super type: ${classNode.name}")
+        None
+      case superName =>
+        Some(classBTypeFromParsedClassfile(superName))
+    }
+
+    val interfaces: List[ClassBType] = classNode.interfaces.asScala.map(classBTypeFromParsedClassfile)(collection.breakOut)
+
+    val flags = classNode.access
+
+    /**
+     * Find all nested classes of classNode. The innerClasses attribute contains all nested classes
+     * that are declared inside classNode or used in the bytecode of classNode. So some of them are
+     * nested in some other class than classNode, and we need to filter them.
+     *
+     * For member classes, innerClassNode.outerName is defined, so we compare that to classNode.name.
+     *
+     * For local and anonymous classes, innerClassNode.outerName is null. Such classes are required
+     * to have an EnclosingMethod attribute declaring the outer class. So we keep those local and
+     * anonymous classes whose outerClass is classNode.name.
+     *
+     */
+    def nestedInCurrentClass(innerClassNode: InnerClassNode): Boolean = {
+      (innerClassNode.outerName != null && innerClassNode.outerName == classNode.name) ||
+      (innerClassNode.outerName == null && codeRepository.classNode(innerClassNode.name).outerClass == classNode.name)
+    }
+
+    val nestedClasses: List[ClassBType] = classNode.innerClasses.asScala.collect({
+      case i if nestedInCurrentClass(i) => classBTypeFromParsedClassfile(i.name)
+    })(collection.breakOut)
+
+    // if classNode is a nested class, it has an innerClass attribute for itself. in this
+    // case we build the NestedInfo.
+    val nestedInfo = classNode.innerClasses.asScala.find(_.name == classNode.name) map {
+      case innerEntry =>
+        val enclosingClass =
+          if (innerEntry.outerName != null) {
+            // if classNode is a member class, the outerName is non-null
+            classBTypeFromParsedClassfile(innerEntry.outerName)
+          } else {
+            // for anonymous or local classes, the outerName is null, but the enclosing class is
+            // stored in the EnclosingMethod attribute (which ASM encodes in classNode.outerClass).
+            classBTypeFromParsedClassfile(classNode.outerClass)
+          }
+        val staticFlag = (innerEntry.access & Opcodes.ACC_STATIC) != 0
+        NestedInfo(enclosingClass, Option(innerEntry.outerName), Option(innerEntry.innerName), staticFlag)
+    }
+    classBType.info = ClassInfo(superClass, interfaces, flags, nestedClasses, nestedInfo)
+    classBType
+  }
 
   /**
    * A BType is either a primitive type, a ClassBType, an ArrayBType of one of these, or a MethodType
@@ -574,7 +647,7 @@ abstract class BTypes {
      * nested classes. Example: for the definition `class A { class B }` we have
      *
      *   B.info.nestedInfo.outerClass == A
-     *   A.info.memberClasses contains B
+     *   A.info.nestedClasses contains B
      */
     private var _info: ClassInfo = null
 
@@ -589,7 +662,7 @@ abstract class BTypes {
       checkInfoConsistency()
     }
 
-    classBTypeFromInternalNameMap(internalName) = this
+    classBTypeFromInternalName(internalName) = this
 
     private def checkInfoConsistency(): Unit = {
       // we assert some properties. however, some of the linked ClassBType (members, superClass,
@@ -597,7 +670,7 @@ abstract class BTypes {
       // best-effort verification.
       def ifInit(c: ClassBType)(p: ClassBType => Boolean): Boolean = c._info == null || p(c)
 
-      def isJLO(t: ClassBType) = t.internalName == "java/lang/Object"
+      def isJLO(t: ClassBType) = t.internalName == ObjectReference.internalName
 
       assert(!ClassBType.isInternalPhantomType(internalName), s"Cannot create ClassBType for phantom type $this")
 
@@ -612,7 +685,7 @@ abstract class BTypes {
         s"Invalid interfaces in $this: ${info.interfaces}"
       )
 
-      assert(info.memberClasses.forall(c => ifInit(c)(_.isNestedClass)), info.memberClasses)
+      assert(info.nestedClasses.forall(c => ifInit(c)(_.isNestedClass)), info.nestedClasses)
     }
 
     /**
@@ -640,8 +713,9 @@ abstract class BTypes {
           outerName.orNull,
           innerName.orNull,
           GenBCode.mkFlags(
-            info.flags,
-            if (isStaticNestedClass) asm.Opcodes.ACC_STATIC else 0
+            // the static flag in the InnerClass table has a special meaning, see InnerClass comment
+            info.flags & ~Opcodes.ACC_STATIC,
+            if (isStaticNestedClass) Opcodes.ACC_STATIC else 0
           ) & ClassBType.INNER_CLASSES_FLAGS
         )
     }
@@ -757,12 +831,12 @@ abstract class BTypes {
    *                      through the superclass.
    * @param flags         The java flags, obtained through `javaFlags`. Used also to derive
    *                      the flags for InnerClass entries.
-   * @param memberClasses Classes nested in this class. Those need to be added to the
+   * @param nestedClasses Classes nested in this class. Those need to be added to the
    *                      InnerClass table, see the InnerClass spec summary above.
    * @param nestedInfo    If this describes a nested class, information for the InnerClass table.
    */
-  case class ClassInfo(superClass: Option[ClassBType], interfaces: List[ClassBType], flags: Int,
-                       memberClasses: List[ClassBType], nestedInfo: Option[NestedInfo])
+  final case class ClassInfo(superClass: Option[ClassBType], interfaces: List[ClassBType], flags: Int,
+                             nestedClasses: List[ClassBType], nestedInfo: Option[NestedInfo])
 
   /**
    * Information required to add a class to an InnerClass table.
@@ -779,10 +853,10 @@ abstract class BTypes {
    * a source-level property: if the class is in a static context (does not have an outer pointer).
    * This is checked when building the NestedInfo.
    */
-  case class NestedInfo(enclosingClass: ClassBType,
-                        outerName: Option[String],
-                        innerName: Option[String],
-                        isStaticNestedClass: Boolean)
+  final case class NestedInfo(enclosingClass: ClassBType,
+                              outerName: Option[String],
+                              innerName: Option[String],
+                              isStaticNestedClass: Boolean)
 
   /**
    * This class holds the data for an entry in the InnerClass table. See the InnerClass summary
diff --git a/src/compiler/scala/tools/nsc/backend/jvm/BTypesFromSymbols.scala b/src/compiler/scala/tools/nsc/backend/jvm/BTypesFromSymbols.scala
index 0582088710..9b8ac82340 100644
--- a/src/compiler/scala/tools/nsc/backend/jvm/BTypesFromSymbols.scala
+++ b/src/compiler/scala/tools/nsc/backend/jvm/BTypesFromSymbols.scala
@@ -7,6 +7,7 @@ package scala.tools.nsc
 package backend.jvm
 
 import scala.tools.asm
+import opt.CodeRepository
 import BTypes.InternalName
 
 /**
@@ -33,11 +34,13 @@ class BTypesFromSymbols[G <: Global](val global: G) extends BTypes {
   val coreBTypes = new CoreBTypesProxy[this.type](this)
   import coreBTypes._
 
-  final def intializeCoreBTypes(): Unit = {
+  val codeRepository = new CodeRepository(global.classPath)
+
+  final def initializeCoreBTypes(): Unit = {
     coreBTypes.setBTypes(new CoreBTypes[this.type](this))
   }
 
-  protected val classBTypeFromInternalNameMap = {
+  val classBTypeFromInternalName = {
     global.perRunCaches.recordCache(collection.concurrent.TrieMap.empty[InternalName, ClassBType])
   }
 
@@ -84,7 +87,7 @@ class BTypesFromSymbols[G <: Global](val global: G) extends BTypes {
       s"Cannot create ClassBType for special class symbol ${classSym.fullName}")
 
     val internalName = classSym.javaBinaryName.toString
-    classBTypeFromInternalNameMap.getOrElse(internalName, {
+    classBTypeFromInternalName.getOrElse(internalName, {
       // The new ClassBType is added to the map in its constructor, before we set its info. This
       // allows initializing cyclic dependencies, see the comment on variable ClassBType._info.
       setClassInfo(classSym, ClassBType(internalName))
@@ -118,25 +121,35 @@ class BTypesFromSymbols[G <: Global](val global: G) extends BTypes {
      * code generation, but those duplicates will be eliminated when emitting the InnerClass
      * attribute.
      *
-     * Why doe we need to collect classes into innerClassBufferASM at all? To collect references to
+     * Why do we need to collect classes into innerClassBufferASM at all? To collect references to
      * nested classes, but NOT nested in C, that are used within C.
      */
     val nestedClassSymbols = {
       // The lambdalift phase lifts all nested classes to the enclosing class, so if we collect
       // member classes right after lambdalift, we obtain all nested classes, including local and
       // anonymous ones.
-      val nestedClasses = exitingPhase(currentRun.lambdaliftPhase)(memberClassesOf(classSym))
+      val nestedClasses = {
+        val nested = exitingPhase(currentRun.lambdaliftPhase)(memberClassesOf(classSym))
+        if (isTopLevelModuleClass(classSym)) {
+          // For Java compatibility, member classes of top-level objects are treated as members of
+          // the top-level companion class, see comment below.
+          val members = exitingPickler(memberClassesOf(classSym))
+          nested diff members
+        } else {
+          nested
+        }
+      }
 
-      // If this is a top-level class, and it has a companion object, the member classes of the
-      // companion 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
       //     def f = { class E }
       //   }
-      // The class D is added as a member of class C. The reason is that the InnerClass attribute
-      // for D will containt class "C" and NOT the module class "C$" as the outer class of D.
-      // This is done by buildNestedInfo, the reason is Java compatibility, see comment in BTypes.
+      // The class D is added as a member of class C. The reason is: for Java compatibility, the
+      // InnerClass attribute for D has "C" (NOT the module class "C$") as the outer class of D
+      // (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$.
       val linkedClass = exitingPickler(classSym.linkedClassOfClass) // linkedCoC does not work properly in late phases
@@ -166,53 +179,51 @@ class BTypesFromSymbols[G <: Global](val global: G) extends BTypes {
       } else true
     })
 
-    val memberClasses = nestedClassSymbolsNoJavaModuleClasses.map(classBTypeFromSymbol)
+    val nestedClasses = nestedClassSymbolsNoJavaModuleClasses.map(classBTypeFromSymbol)
 
     val nestedInfo = buildNestedInfo(classSym)
 
-    classBType.info = ClassInfo(superClass, interfaces, flags, memberClasses, nestedInfo)
+    classBType.info = ClassInfo(superClass, interfaces, flags, nestedClasses, nestedInfo)
     classBType
   }
 
   private def buildNestedInfo(innerClassSym: Symbol): Option[NestedInfo] = {
     assert(innerClassSym.isClass, s"Cannot build NestedInfo for non-class symbol $innerClassSym")
 
-    val isNested = !innerClassSym.rawowner.isPackageClass
-    if (!isNested) None
+    val isTopLevel = innerClassSym.rawowner.isPackageClass
+    if (isTopLevel) None
     else {
       // See comment in BTypes, when is a class marked static in the InnerClass table.
       val isStaticNestedClass = isOriginallyStaticOwner(innerClassSym.originalOwner)
 
       // After lambdalift (which is where we are), the rawowoner field contains the enclosing class.
-      val enclosingClassSym = {
-        if (innerClassSym.isJavaDefined && innerClassSym.rawowner.isModuleClass) {
-          // Example java source: class C { static class D { } }
-          // The Scala compiler creates a class and a module symbol for C. Because D is a static
-          // nested class, the symbol for D is nested in the module class C (not in the class C).
-          // For the InnerClass attribute, we use the class symbol C, which represents the situation
-          // in the source code.
-
-          // Cannot use innerClassSym.isStatic: this method looks at the owner, which is a package
-          // at this pahse (after lambdalift, flatten).
-          assert(isOriginallyStaticOwner(innerClassSym.originalOwner), innerClassSym.originalOwner)
-
+      val enclosingClass = {
+        // (1) Example java source: class C { static class D { } }
+        // The Scala compiler creates a class and a module symbol for C. Because D is a static
+        // nested class, the symbol for D is nested in the module class C (not in the class C).
+        // For the InnerClass attribute, we use the class symbol C, which represents the situation
+        // in the source code.
+
+        // (2) Java compatibility. See the big comment in BTypes that summarizes the InnerClass spec.
+        if ((innerClassSym.isJavaDefined && innerClassSym.rawowner.isModuleClass) ||                      // (1)
+            (!isAnonymousOrLocalClass(innerClassSym) && isTopLevelModuleClass(innerClassSym.rawowner))) { // (2)
           // phase travel for linkedCoC - does not always work in late phases
-          exitingPickler(innerClassSym.rawowner.linkedClassOfClass)
+          exitingPickler(innerClassSym.rawowner.linkedClassOfClass) match {
+            case NoSymbol =>
+              // For top-level modules without a companion class, see doc of mirrorClassClassBType.
+              mirrorClassClassBType(exitingPickler(innerClassSym.rawowner))
+
+            case companionClass =>
+              classBTypeFromSymbol(companionClass)
+          }
+        } else {
+          classBTypeFromSymbol(innerClassSym.rawowner)
         }
-        else innerClassSym.rawowner
       }
-      val enclosingClass: ClassBType = classBTypeFromSymbol(enclosingClassSym)
 
       val outerName: Option[String] = {
-        if (isAnonymousOrLocalClass(innerClassSym)) {
-          None
-        } else {
-          val outerName = innerClassSym.rawowner.javaBinaryName
-          // Java compatibility. See the big comment in BTypes that summarizes the InnerClass spec.
-          val outerNameModule = if (isTopLevelModuleClass(innerClassSym.rawowner)) outerName.dropModule
-          else outerName
-          Some(outerNameModule.toString)
-        }
+        if (isAnonymousOrLocalClass(innerClassSym)) None
+        else Some(enclosingClass.internalName)
       }
 
       val innerName: Option[String] = {
@@ -225,6 +236,29 @@ class BTypesFromSymbols[G <: Global](val global: G) extends BTypes {
   }
 
   /**
+   * For top-level objects without a companion class, the compilere generates a mirror class with
+   * static forwarders (Java compat). There's no symbol for the mirror class, but we still need a
+   * ClassBType (its info.nestedClasses will hold the InnerClass entries, see comment in BTypes).
+   */
+  def mirrorClassClassBType(moduleClassSym: Symbol): ClassBType = {
+    assert(isTopLevelModuleClass(moduleClassSym), s"not a top-level module class: $moduleClassSym")
+    val internalName = moduleClassSym.javaBinaryName.dropModule.toString
+    classBTypeFromInternalName.getOrElse(internalName, {
+      val c = ClassBType(internalName)
+      // class info consistent with BCodeHelpers.genMirrorClass
+      val nested = exitingPickler(memberClassesOf(moduleClassSym)) map classBTypeFromSymbol
+      c.info = ClassInfo(
+        superClass = Some(ObjectReference),
+        interfaces = Nil,
+        flags = asm.Opcodes.ACC_SUPER | asm.Opcodes.ACC_PUBLIC | asm.Opcodes.ACC_FINAL,
+        nestedClasses = nested,
+        nestedInfo = None
+      )
+      c
+    })
+  }
+
+  /**
    * True for module classes of package level objects. The backend will generate a mirror class for
    * such objects.
    */
diff --git a/src/compiler/scala/tools/nsc/backend/jvm/GenASM.scala b/src/compiler/scala/tools/nsc/backend/jvm/GenASM.scala
index de468c0a6d..abe3bc512c 100644
--- a/src/compiler/scala/tools/nsc/backend/jvm/GenASM.scala
+++ b/src/compiler/scala/tools/nsc/backend/jvm/GenASM.scala
@@ -677,7 +677,7 @@ abstract class GenASM extends SubComponent with BytecodeWriters { self =>
 
     def isDeprecated(sym: Symbol): Boolean = { sym.annotations exists (_ matches definitions.DeprecatedAttr) }
 
-    def addInnerClasses(csym: Symbol, jclass: asm.ClassVisitor) {
+    def addInnerClasses(csym: Symbol, jclass: asm.ClassVisitor, isMirror: Boolean = false) {
       /* The outer name for this inner class. Note that it returns null
        * when the inner class should not get an index in the constant pool.
        * That means non-member classes (anonymous). See Section 4.7.5 in the JVMS.
@@ -698,11 +698,19 @@ abstract class GenASM extends SubComponent with BytecodeWriters { self =>
         else
           innerSym.rawname + innerSym.moduleSuffix
 
-      // This collects all inner classes of csym, including local and anonymous: lambdalift makes
-      // them members of their enclosing class.
-      innerClassBuffer ++= exitingPhase(currentRun.lambdaliftPhase)(memberClassesOf(csym))
+      innerClassBuffer ++= {
+        val members = exitingPickler(memberClassesOf(csym))
+        // lambdalift makes all classes (also local, anonymous) members of their enclosing class
+        val allNested = exitingPhase(currentRun.lambdaliftPhase)(memberClassesOf(csym))
 
-      // Add members of the companion object (if top-level). why, see comment in BTypes.scala.
+        // for the mirror class, we take the members of the companion module class (Java compat,
+        // see doc in BTypes.scala). for module classes, we filter out those members.
+        if (isMirror)  members
+        else if (isTopLevelModule(csym)) allNested diff members
+        else allNested
+      }
+
+      // If this is a top-level class, add members of the companion object.
       val linkedClass = exitingPickler(csym.linkedClassOfClass) // linkedCoC does not work properly in late phases
       if (isTopLevelModule(linkedClass)) {
         // phase travel to exitingPickler: this makes sure that memberClassesOf only sees member classes,
@@ -2796,7 +2804,7 @@ abstract class GenASM extends SubComponent with BytecodeWriters { self =>
 
       addForwarders(isRemote(modsym), mirrorClass, mirrorName, modsym)
 
-      addInnerClasses(modsym, mirrorClass)
+      addInnerClasses(modsym, mirrorClass, isMirror = true)
       mirrorClass.visitEnd()
       writeIfNotTooBig("" + modsym.name, mirrorName, mirrorClass, modsym)
     }
diff --git a/src/compiler/scala/tools/nsc/backend/jvm/GenBCode.scala b/src/compiler/scala/tools/nsc/backend/jvm/GenBCode.scala
index a45f586666..d5e95c47cf 100644
--- a/src/compiler/scala/tools/nsc/backend/jvm/GenBCode.scala
+++ b/src/compiler/scala/tools/nsc/backend/jvm/GenBCode.scala
@@ -286,7 +286,7 @@ abstract class GenBCode extends BCodeSyncAndTry {
       val initStart = Statistics.startTimer(BackendStats.bcodeInitTimer)
       arrivalPos = 0 // just in case
       scalaPrimitives.init()
-      bTypes.intializeCoreBTypes()
+      bTypes.initializeCoreBTypes()
       Statistics.stopTimer(BackendStats.bcodeInitTimer, initStart)
 
       // initBytecodeWriter invokes fullName, thus we have to run it before the typer-dependent thread is activated.
diff --git a/src/compiler/scala/tools/nsc/backend/jvm/opt/CodeRepository.scala b/src/compiler/scala/tools/nsc/backend/jvm/opt/CodeRepository.scala
new file mode 100644
index 0000000000..285855d083
--- /dev/null
+++ b/src/compiler/scala/tools/nsc/backend/jvm/opt/CodeRepository.scala
@@ -0,0 +1,93 @@
+/* NSC -- new Scala compiler
+ * Copyright 2005-2014 LAMP/EPFL
+ * @author  Martin Odersky
+ */
+
+package scala.tools.nsc
+package backend.jvm
+package opt
+
+import scala.tools.asm
+import asm.tree._
+import scala.collection.convert.decorateAsScala._
+import scala.tools.nsc.io.AbstractFile
+import scala.tools.nsc.util.ClassFileLookup
+import OptimizerReporting._
+
+class CodeRepository(val classPath: ClassFileLookup[AbstractFile]) {
+  import BTypes.InternalName
+
+  /**
+   * Cache for parsed ClassNodes.
+   */
+  val classes: collection.concurrent.Map[InternalName, ClassNode] = collection.concurrent.TrieMap.empty[InternalName, ClassNode]
+
+  /**
+   * The class node for an internal name. If the class node is not yet available, it is parsed from
+   * the classfile on the compile classpath.
+   */
+  def classNode(internalName: InternalName): ClassNode = {
+    classes.getOrElseUpdate(internalName, parseClass(internalName))
+  }
+
+  /**
+   * The field node for a field matching `name` and `descriptor`, accessed in class `classInternalName`.
+   * The declaration of the field may be in one of the superclasses.
+   *
+   * @return The [[FieldNode]] of the requested field and the [[InternalName]] of its declaring class.
+   */
+  def fieldNode(classInternalName: InternalName, name: String, descriptor: String): Option[(FieldNode, InternalName)] = {
+    val c = classNode(classInternalName)
+    c.fields.asScala.find(f => f.name == name && f.desc == descriptor).map((_, classInternalName)) orElse {
+      Option(c.superName).flatMap(n => fieldNode(n, name, descriptor))
+    }
+  }
+
+  /**
+   * The method node for a method matching `name` and `descriptor`, accessed in class `classInternalName`.
+   * The declaration of the method may be in one of the parents.
+   *
+   * @return The [[MethodNode]] of the requested method and the [[InternalName]] of its declaring class.
+   */
+  def methodNode(classInternalName: InternalName, name: String, descriptor: String): Option[(MethodNode, InternalName)] = {
+    val c = classNode(classInternalName)
+    c.methods.asScala.find(m => m.name == name && m.desc == descriptor).map((_, classInternalName)) orElse {
+      val parents = Option(c.superName) ++ c.interfaces.asScala
+      // `view` to stop at the first result
+      parents.view.flatMap(methodNode(_, name, descriptor)).headOption
+    }
+  }
+
+  private def parseClass(internalName: InternalName): ClassNode = {
+    val fullName = internalName.replace('/', '.')
+    classPath.findClassFile(fullName) map { classFile =>
+      val classNode = new asm.tree.ClassNode()
+      val classReader = new asm.ClassReader(classFile.toByteArray)
+      // We don't need frames when inlining, but we want to keep the local variable table, so we
+      // don't use SKIP_DEBUG.
+      classReader.accept(classNode, asm.ClassReader.SKIP_FRAMES)
+      // SKIP_FRAMES leaves line number nodes. Remove them because they are not correct after
+      // inlining.
+      // TODO: we need to remove them also for classes that are not parsed from classfiles, why not simplify and do it once when inlining?
+      // OR: instead of skipping line numbers for inlined code, use write a SourceDebugExtension
+      // attribute that contains JSR-45 data that encodes debugging info.
+      //   http://docs.oracle.com/javase/specs/jvms/se7/html/jvms-4.html#jvms-4.7.11
+      //   https://jcp.org/aboutJava/communityprocess/final/jsr045/index.html
+      removeLineNumberNodes(classNode)
+      classes(internalName) = classNode
+      classNode
+    } getOrElse {
+      inlineFailure(s"Class file for class $fullName not found.")
+    }
+  }
+
+  private def removeLineNumberNodes(classNode: ClassNode): Unit = {
+    for (method <- classNode.methods.asScala) {
+      val iter = method.instructions.iterator()
+      while (iter.hasNext) iter.next() match {
+        case _: LineNumberNode => iter.remove()
+        case _ =>
+      }
+    }
+  }
+}
diff --git a/src/compiler/scala/tools/nsc/backend/jvm/opt/OptimizerReporting.scala b/src/compiler/scala/tools/nsc/backend/jvm/opt/OptimizerReporting.scala
new file mode 100644
index 0000000000..c07fda2bc5
--- /dev/null
+++ b/src/compiler/scala/tools/nsc/backend/jvm/opt/OptimizerReporting.scala
@@ -0,0 +1,21 @@
+/* NSC -- new Scala compiler
+ * Copyright 2005-2014 LAMP/EPFL
+ * @author  Martin Odersky
+ */
+
+package scala.tools.nsc
+package backend.jvm
+
+import scala.tools.asm
+import asm.tree._
+
+object OptimizerReporting {
+  def methodSignature(className: String, methodName: String, methodDescriptor: String): String = {
+    className + "::" + methodName + methodDescriptor
+  }
+
+  def methodSignature(className: String, method: MethodNode): String = methodSignature(className, method.name, method.desc)
+
+  def inlineFailure(reason: String): Nothing = MissingRequirementError.signal(reason)
+  def assertionError(message: String): Nothing = throw new AssertionError(message)
+}
diff --git a/test/files/jvm/innerClassAttribute/Test.scala b/test/files/jvm/innerClassAttribute/Test.scala
index 1c1a0522e4..3820048cb4 100644
--- a/test/files/jvm/innerClassAttribute/Test.scala
+++ b/test/files/jvm/innerClassAttribute/Test.scala
@@ -84,17 +84,15 @@ object Test extends BytecodeTest {
   }
 
   def testA3() = {
-    def t(c: String) = {
-      val List(b1, b2) = innerClassNodes(c)
-      // the outer class for classes nested inside top-level modules is not the module class, but the mirror class.
-      // this is a hack for java interop, handled in the backend. see BTypes.scala, comment on "Java Compatibility".
-      assertMember(b1, "A3", "B1", flags = publicStatic)
-      assertMember(b2, "A3", "B2$", flags = publicStatic)
-    }
-    t("A3$")
-    // the mirror class has the same inner class attributes as the module
-    // class (added when the mirror is created in the backend)
-    t("A3")
+    // the inner class entries for top-level object members are in the companion class, so nothing in the module class
+    val List() = innerClassNodes("A3$")
+
+    // inner class entries in the companion class (a backend-generated mirror class in this case)
+    val List(b1, b2) = innerClassNodes("A3")
+    // the outer class for classes nested inside top-level modules is not the module class, but the mirror class.
+    // this is a hack for java interop, handled in the backend. see BTypes.scala, comment on "Java Compatibility".
+    assertMember(b1, "A3", "B1", flags = publicStatic)
+    assertMember(b2, "A3", "B2$", flags = publicStatic)
   }
 
   def testA4() = {
@@ -164,7 +162,10 @@ object Test extends BytecodeTest {
   }
 
   def testA15() = {
-    val List(b) = innerClassNodes("A15")
+    // no member classes, only anonymous / local. these are nested in the module class, not the companion.
+    val List() = innerClassNodes("A15")
+
+    val List(b) = innerClassNodes("A15$")
     assertLocal(b, "A15$B$3", "B$3")
 
     val List(_, c) = innerClassNodes("A15$B$3")
@@ -283,9 +284,7 @@ object Test extends BytecodeTest {
     assertMember(i3c, "A21", "I3$", flags = publicStatic)
     assertLocal(j1, "A21$J1$1", "J1$1")
 
-    val List(i2m, i3m, j3, j4, j5) = innerClassNodes("A21$")
-    assertMember(i2m, "A21", "I2", flags = publicStatic)
-    assertMember(i3m, "A21", "I3$", flags = publicStatic)
+    val List(j3, j4, j5) = innerClassNodes("A21$")
     assertLocal(j3, "A21$J3$1", "J3$1")
     assertLocal(j4, "A21$J4$1", "J4$1")
     assertLocal(j5, "A21$J5$1", "J5$1") // non-static!
diff --git a/test/files/jvm/t8582.check b/test/files/jvm/t8582.check
index 564f482ff8..e388366270 100644
--- a/test/files/jvm/t8582.check
+++ b/test/files/jvm/t8582.check
@@ -14,10 +14,10 @@ Reflection can find direct nested classes (A2-B2-C2)
  A2$B2: List(class A2$B2$C2)
  A2$B2$C2: List()
 
-Mirror classes have the same InnerClass attributes as the corresponding module class:
- className[p1/p2/Singleton$Singleton$] outerClassName[p1/p2/Singleton] innerName[Singleton$] access[9]
-Module class
+The InnerClass attribute of a mirror class contains the members of the module class:
  className[p1/p2/Singleton$Singleton$] outerClassName[p1/p2/Singleton] innerName[Singleton$] access[9]
+The module members are not in the InnerClass table of the module class (unless referenced):
+ 
 
 An outer class has a InnerClass attribute for direct nested classes
  className[A1$B1] outerClassName[A1] innerName[B1] access[1]
diff --git a/test/files/jvm/t8582.scala b/test/files/jvm/t8582.scala
index 8a57ef7952..e9a01f9016 100644
--- a/test/files/jvm/t8582.scala
+++ b/test/files/jvm/t8582.scala
@@ -55,9 +55,9 @@ object Test extends BytecodeTest {
     println(nested(classOf[A2#B2]))
     println(nested(classOf[A2#B2#C2]))
 
-    nprintln("Mirror classes have the same InnerClass attributes as the corresponding module class:")
+    nprintln("The InnerClass attribute of a mirror class contains the members of the module class:")
     printInner("p1.p2.Singleton") // mirror class
-    println("Module class")
+    println("The module members are not in the InnerClass table of the module class (unless referenced):")
     printInner("p1.p2.Singleton$")
 
     nprintln("An outer class has a InnerClass attribute for direct nested classes")
diff --git a/test/junit/scala/tools/nsc/backend/jvm/BTypesTest.scala b/test/junit/scala/tools/nsc/backend/jvm/BTypesTest.scala
index 221aad6536..2347e8288e 100644
--- a/test/junit/scala/tools/nsc/backend/jvm/BTypesTest.scala
+++ b/test/junit/scala/tools/nsc/backend/jvm/BTypesTest.scala
@@ -19,7 +19,7 @@ class BTypesTest {
 
   val btypes = new BTypesFromSymbols[g.type](g)
   import btypes._
-  duringBackend(btypes.intializeCoreBTypes())
+  duringBackend(btypes.initializeCoreBTypes())
 
   def classBTypeFromSymbol(sym: Symbol) = duringBackend(btypes.classBTypeFromSymbol(sym))
 
diff --git a/test/junit/scala/tools/nsc/backend/jvm/opt/BTypesFromClassfileTest.scala b/test/junit/scala/tools/nsc/backend/jvm/opt/BTypesFromClassfileTest.scala
new file mode 100644
index 0000000000..2975bd060d
--- /dev/null
+++ b/test/junit/scala/tools/nsc/backend/jvm/opt/BTypesFromClassfileTest.scala
@@ -0,0 +1,95 @@
+package scala.tools.nsc
+package backend.jvm
+package opt
+
+import org.junit.runner.RunWith
+import org.junit.runners.JUnit4
+import org.junit.Test
+import scala.tools.asm.Opcodes._
+import org.junit.Assert._
+
+import scala.tools.nsc.backend.jvm.BTypes.InternalName
+import scala.tools.testing.AssertUtil._
+
+import CodeGenTools._
+import scala.tools.partest.ASMConverters
+import ASMConverters._
+
+import scala.collection.convert.decorateAsScala._
+
+@RunWith(classOf[JUnit4])
+class BTypesFromClassfileTest {
+  val compiler = newCompiler(extraArgs = "-Ybackend:GenBCode")
+
+  import compiler._
+  import definitions._
+  import genBCode.bTypes
+  import bTypes._
+
+  def duringBackend[T](f: => T) = compiler.exitingDelambdafy(f)
+
+  val run = new compiler.Run() // initializes some of the compiler
+  duringBackend(bTypes.initializeCoreBTypes())
+
+  def clearCache() = bTypes.classBTypeFromInternalName.clear()
+
+  def sameBType(fromSym: ClassBType, fromClassfile: ClassBType, checked: Set[InternalName] = Set.empty): Set[InternalName] = {
+    if (checked(fromSym.internalName)) checked
+    else {
+      assert(fromSym == fromClassfile, s"$fromSym != $fromClassfile")
+      sameInfo(fromSym.info, fromClassfile.info, checked + fromSym.internalName)
+    }
+  }
+
+  def sameBTypes(fromSyms: Iterable[ClassBType], fromClassfiles: Iterable[ClassBType], checked: Set[InternalName]): Set[InternalName] = {
+    assert(fromSyms.size == fromClassfiles.size, s"\n$fromSyms\n$fromClassfiles")
+    (fromSyms, fromClassfiles).zipped.foldLeft(checked) {
+      case (chk, (fromSym, fromClassfile)) => sameBType(fromSym, fromClassfile, chk)
+    }
+  }
+
+  def sameInfo(fromSym: ClassInfo, fromClassfile: ClassInfo, checked: Set[InternalName]): Set[InternalName] = {
+    assert({
+      // Nested class symbols can undergo makeNotPrivate (ExplicitOuter). But this is only applied
+      // for symbols of class symbols that are being compiled, not those read from a pickle.
+      // So a class may be public in bytecode, but the symbol still says private.
+      if (fromSym.nestedInfo.isEmpty) fromSym.flags == fromClassfile.flags
+      else (fromSym.flags | ACC_PRIVATE | ACC_PUBLIC) == (fromClassfile.flags | ACC_PRIVATE | ACC_PUBLIC)
+    }, s"class flags differ\n$fromSym\n$fromClassfile")
+
+    val chk1 = sameBTypes(fromSym.superClass, fromClassfile.superClass, checked)
+
+    val chk2 = sameBTypes(fromSym.interfaces, fromClassfile.interfaces, chk1)
+
+    // The fromSym info has only member classes, no local or anonymous. The symbol is read from the
+    // Scala pickle data and only member classes are created / entered.
+    //  (This is different for symbols that are being compiled, there flatten will enter all local
+    //   and anonymous classes as members of the outer class. But not for unpickled symbols).
+    // The fromClassfile info has all nested classes, including anonymous and local. So we filter
+    // them out: member classes are identified by having the `outerName` defined.
+    val memberClassesFromClassfile = fromClassfile.nestedClasses.filter(_.info.nestedInfo.get.outerName.isDefined)
+    // Sorting is required: the backend sorts all InnerClass entries by internalName before writing
+    // them to the classfile (to make it deterministic: the entries are collected in a Set during
+    // code generation).
+    val chk3 = sameBTypes(fromSym.nestedClasses.sortBy(_.internalName), memberClassesFromClassfile.sortBy(_.internalName), chk2)
+    sameBTypes(fromSym.nestedInfo.map(_.enclosingClass), fromClassfile.nestedInfo.map(_.enclosingClass), chk3)
+  }
+
+  def check(classSym: Symbol): Unit = duringBackend {
+    clearCache()
+    val fromSymbol = classBTypeFromSymbol(classSym)
+    clearCache()
+    val fromClassfile = bTypes.classBTypeFromParsedClassfile(fromSymbol.internalName)
+    sameBType(fromSymbol, fromClassfile)
+  }
+
+  @Test
+  def compareClassBTypes(): Unit = {
+    // Note that not only these classes are tested, but also all their parents and all nested
+    // classes in their InnerClass attributes.
+    check(ObjectClass)
+    check(JavaNumberClass)
+    check(ConsClass)
+    check(ListModule.moduleClass)
+  }
+}