java.lang.InternalError: Malformed class name

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object Test extends App {
  {
    class A
    println(classOf[A].getSimpleName())
  }
}

Exception in thread "main" java.lang.InternalError: Malformed class name
	at java.lang.Class.getSimpleName(Class.java:1133)
	at Test$delayedInit$body.apply(t5256c.scala:4)
	at scala.Function0$class.apply$mcV$sp(Function0.scala:34)
	at scala.runtime.AbstractFunction0.apply$mcV$sp(AbstractFunction0.scala:12)
	at scala.App$$anonfun$main$1.apply(App.scala:61)
	at scala.App$$anonfun$main$1.apply(App.scala:61)
	at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:59)
	at scala.collection.immutable.List.foreach(List.scala:77)
	at scala.collection.generic.TraversableForwarder$class.foreach(TraversableForwarder.scala:31)
	at scala.collection.mutable.ListBuffer.foreach(ListBuffer.scala:45)
	at scala.App$class.main(App.scala:61)
	at Test$.main(t5256c.scala:1)
	at Test.main(t5256c.scala)

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Imported From: https://issues.scala-lang.org/browse/SI-5425?orig=1
Reporter: @xeno-by
Affected Versions: 2.10.0
Duplicates #2034

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@xeno-by said:

    public String getSimpleName() {
	if (isArray())
	    return getComponentType().getSimpleName()+"[]";

	String simpleName = getSimpleBinaryName();
	if (simpleName == null) { // top level class
	    simpleName = getName();
	    return simpleName.substring(simpleName.lastIndexOf(".")+1); // strip the package name
	}
	// According to JLS3 "Binary Compatibility" (13.1) the binary
	// name of non-package classes (not top level) is the binary
	// name of the immediately enclosing class followed by a '$' followed by:
	// (for nested and inner classes): the simple name.
	// (for local classes): 1 or more digits followed by the simple name.
	// (for anonymous classes): 1 or more digits.

	// Since getSimpleBinaryName() will strip the binary name of
	// the immediatly enclosing class, we are now looking at a
	// string that matches the regular expression "\$[0-9]*"
	// followed by a simple name (considering the simple of an
	// anonymous class to be the empty string).

	// Remove leading "\$[0-9]*" from the name
	int length = simpleName.length();
	if (length < 1 || simpleName.charAt(0) != '$')
	    throw new InternalError("Malformed class name");
	int index = 1;
	while (index < length && isAsciiDigit(simpleName.charAt(index)))
	    index++;
	// Eventually, this is the empty string iff this is an anonymous class
	return simpleName.substring(index);
    }

classOf[A].getEnclosingClass().getName => "Test$"
classOf[A].getName => "Test$A$1"

Well, according to the source code of getSimpleName, A should be flattened into Test$$A$1. What's even more interesting, the correct name indeed appears after LambdaLift, but then gets messed by Flatten:

C:\Projects\Kepler\sandbox>scalac -Xprint:lambdalift,flatten t5425.scala
[[syntax trees at end of lambdalift]]// Scala source: t5425.scala
package <empty> {
  final object Test extends Object with App with ScalaObject {
    def <init>(): object Test = {
      Test.super.<init>();
      Test.this.$asInstanceOf[App$class]()./*App$class*/$init$();
      ()
    };
    {
      scala.this.Predef.println(classOf[Test$$A$1].getSimpleName())
    };
    class A$1 extends Object with ScalaObject {
      def <init>(): Test#A$1 = {
        A$1.super.<init>();
        ()
      }
    }
  }
}

[[syntax trees at end of flatten]]// Scala source: t5256c.scala
package <empty> {
  final object Test extends Object with App with ScalaObject {
    def <init>(): object Test = {
      Test.super.<init>();
      Test.this.$asInstanceOf[App$class]()./*App$class*/$init$();
      Test.this.delayedInit(new Test$delayedInit$body(Test.this));
      ()
    }
  };
  class Test$A$1 extends Object with ScalaObject {
    def <init>(): Test$A$1 = {
      Test$A$1.super.<init>();
      ()
    }
  };
  final <synthetic> class Test$delayedInit$body extends scala.runtime.AbstractFunction0 with ScalaObject {
    final def apply(): Object = {
      {
        scala.this.Predef.println(classOf[Test$A$1].getSimpleName())
      };
      scala.runtime.BoxedUnit.UNIT
    };
    def <init>($outer: object Test): Test$delayedInit$body = {
      Test$delayedInit$body.super.<init>();
      ()
    }
  }
}

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@gkossakowski said:
This works:

object Test extends App {
  class A
  println(classOf[A].getSimpleName())
}

But this fails:

object Test extends App {
  object A {
    class B
  }
  println(classOf[A.B].getSimpleName())

for the same reason as Eugene stated. The first example works because we put A into 'Test' class and not 'Test$'. Note that class without dollar sign is generated only for top-level objects as a place where we can put static forwarders to object's method.

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@paulp said:
Be sure to read all the comments in these tickets, there are a lot of them.

https://issues.scala-lang.org/secure/IssueNavigator.jspa?mode=hide&requestId=11004

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@paulp said:
Oh, and keep in mind that the fucking jira conversion turned every '$' into '$$' and nobody ever fixed it.

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@gkossakowski said:
Also, this is useful read: https://groups.google.com/d/topic/scala-internals/5ivpeZCfrW4/discussion

And we would keep the sun shining on this one: https://scala-webapps.epfl.ch/jenkins/view/Misc/job/scala-signatures/

It verifies problems mentioned in original thread do not come back.

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@xeno-by said:
Duplicate of #2034