SI-8582 emit InnerClasses attribute in GenBCode

I removed the `-bcode` test since we have a build that passes
`-Ybackend:GenBCode` to all tests.

Short intro do the [`InnerClass` attribute][1]:

  - A class needs one `InnerClass` attribute for each of its nested
    classes

  - A class needs the `InnerClass` attribute for all (nested) classes
    that are mentioned in its constant pool

The attribute for a nested class `A$B$C` consists of the long name of
the outer class `A$B`, the short name of the inner class `C`, and
an access flag set describig the visibility.

The attribute seems to be used for reflection.

[1]: http://docs.oracle.com/javase/specs/jvms/se7/html/jvms-4.html#jvms-4.7.6

Author: lrytz

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

@@ -116,12 +116,13 @@ abstract class BCodeSkelBuilder extends BCodeHelpers {
       addClassFields()
 
       innerClassBufferASM ++= trackMemberClasses(claszSymbol, Nil)
-
       gen(cd.impl)
+      addInnerClassesASM(cnode, innerClassBufferASM.toList)
 
       if (AsmUtils.traceClassEnabled && cnode.name.contains(AsmUtils.traceClassPattern))
         AsmUtils.traceClass(cnode)
 
+      cnode.innerClasses
       assert(cd.symbol == claszSymbol, "Someone messed up BCodePhase.claszSymbol during genPlainClass().")
 
     } // end of method genPlainClass()

test/files/run/t8582.check

@@ -1,2 +1,44 @@
-class p1.p2.Singleton$Singleton$
-List(class p1.p2.Singleton$Singleton$Singleton$)
+getClass on module gives module class
+ class p1.p2.Singleton$Singleton$
+
+Nested module classes are found through reflection
+ p1.p2.Singleton$Singleton$: List(class p1.p2.Singleton$Singleton$Singleton$)
+
+Reflection can find direct nested classes (A1-B1-C1)
+ A1: List(class A1$B1)
+ A1$B1: List(class A1$B1$C1)
+ A1$B1$C1: List()
+
+Reflection can find direct nested classes (A2-B2-C2)
+ A2: List(class A2$B2)
+ 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
+ className[p1/p2/Singleton$Singleton$] outerClassName[p1/p2/Singleton] innerName[Singleton$] access[9]
+
+An outer class has a InnerClass attribute for direct nested classes
+ className[A1$B1] outerClassName[A1] innerName[B1] access[1]
+A nested class has an InnerClass attribute for itself (and also for its nested classes)
+ className[A1$B1] outerClassName[A1] innerName[B1] access[1]
+ className[A1$B1$C1] outerClassName[A1$B1] innerName[C1] access[1]
+C1 is a nested class, so it has an InnerClass attribute for itself.
+Because that attribute leads to an entry for B1 in the constant pool, C1 needs an InnerClass attribute for B1.
+ className[A1$B1] outerClassName[A1] innerName[B1] access[1]
+ className[A1$B1$C1] outerClassName[A1$B1] innerName[C1] access[1]
+
+The BeanInfo class has the same InnerClass attributes as the corresponding bean
+ className[A1$B1] outerClassName[A1] innerName[B1] access[1]
+ className[A1$B1$C1] outerClassName[A1$B1] innerName[C1] access[1]
+
+Class A2 mentions class C2 in the constant pool (due to method  f), therefore it needs an InnerClass attribute for C1
+ className[A2$B2] outerClassName[A2] innerName[B2] access[1]
+ className[A2$B2$C2] outerClassName[A2$B2] innerName[C2] access[1]
+B2
+ className[A2$B2] outerClassName[A2] innerName[B2] access[1]
+ className[A2$B2$C2] outerClassName[A2$B2] innerName[C2] access[1]
+C2
+ className[A2$B2] outerClassName[A2] innerName[B2] access[1]
+ className[A2$B2$C2] outerClassName[A2$B2] innerName[C2] access[1]

test/files/run/t8582.scala

@@ -1,3 +1,6 @@
+import scala.tools.partest.BytecodeTest
+import scala.collection.JavaConverters._
+
 package p1 {
   package p2 {
     object Singleton {
@@ -8,9 +11,71 @@ package p1 {
   }
 }
 
+class A1 {
+  class B1 {
+    @scala.beans.BeanInfo
+    class C1
+  }
+}
+
+class A2 {
+  class B2 {
+    class C2
+  }
+  def f: B2#C2 = null
+}
+
 
-object Test extends App {
+object Test extends BytecodeTest {
   import p1.p2._
-  println(Singleton.Singleton.getClass)
-  println(Singleton.Singleton.getClass.getDeclaredClasses.toList)
+
+  def nested(c: Class[_]) = s" ${c.getName}: ${c.getDeclaredClasses.toList}"
+
+  def nprintln(s: String) = println("\n"+s)
+  def printInner(cname: String): Unit = {
+    val cnode = loadClassNode(cname)
+    println(cnode.innerClasses.asScala.toList.map(i => s"className[${i.name}] outerClassName[${i.outerName}] innerName[${i.innerName}] access[${i.access}]").mkString(" ", "\n ", ""))
+  }
+
+  def show() {
+
+    println("getClass on module gives module class")
+    println(" " + Singleton.Singleton.getClass)
+
+    nprintln("Nested module classes are found through reflection")
+    println(nested(Singleton.Singleton.getClass))
+
+    nprintln("Reflection can find direct nested classes (A1-B1-C1)")
+    println(nested(classOf[A1]))
+    println(nested(classOf[A1#B1]))
+    println(nested(classOf[A1#B1#C1]))
+
+    nprintln("Reflection can find direct nested classes (A2-B2-C2)")
+    println(nested(classOf[A2]))
+    println(nested(classOf[A2#B2]))
+    println(nested(classOf[A2#B2#C2]))
+
+    nprintln("Mirror classes have the same InnerClass attributes as the corresponding module class:")
+    printInner("p1.p2.Singleton") // mirror class
+    println("Module class")
+    printInner("p1.p2.Singleton$")
+
+    nprintln("An outer class has a InnerClass attribute for direct nested classes")
+    printInner("A1")
+    println("A nested class has an InnerClass attribute for itself (and also for its nested classes)")
+    printInner("A1$B1")
+    println("C1 is a nested class, so it has an InnerClass attribute for itself.\n"+
+            "Because that attribute leads to an entry for B1 in the constant pool, C1 needs an InnerClass attribute for B1.")
+    printInner("A1$B1$C1")
+
+    nprintln("The BeanInfo class has the same InnerClass attributes as the corresponding bean")
+    printInner("A1$B1$C1BeanInfo")
+
+    nprintln("Class A2 mentions class C2 in the constant pool (due to method  f), therefore it needs an InnerClass attribute for C1")
+    printInner("A2")
+    println("B2")
+    printInner("A2$B2")
+    println("C2")
+    printInner("A2$B2$C2")
+  }
 }