2.9 regression: can't use scala.collection.mutable.HashMap from Java

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  ~/nl> java -version
java version "1.6.0_22"
Java(TM) SE Runtime Environment (build 1.6.0_22-b04-307-10M3261)
Java HotSpot(TM) 64-Bit Server VM (build 17.1-b03-307, mixed mode)
  ~/nl> bin/scala -version                                                             
Scala code runner version 2.9.0.r24265-b20110211020037 -- Copyright 2002-2011, LAMP/EPFL
  ~/nl> cat J.java                                                                     
class J {
	scala.collection.mutable.HashMap<String, String> x =
		new scala.collection.mutable.HashMap<String, String>() ;
}
  ~/nl> javac -classpath project/boot/scala-2.9.0-SNAPSHOT/lib/scala-library.jar J.java
J.java:2: cannot access scala.collection.mutable.HashMap
bad class file: scala/collection/mutable/HashMap.class(scala/collection/mutable:HashMap.class)
undeclared type variable: Entry
Please remove or make sure it appears in the correct subdirectory of the classpath.
	scala.collection.mutable.HashMap<String, String> x =
	                        ^

possibly related: #3249

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Imported From: https://issues.scala-lang.org/browse/SI-4238?orig=1
Reporter: @SethTisue

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@SethTisue said:
(it worked in 2.8.1)

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@odersky said:
I verified that the regression occurs somewhere between 23500 and 23507, so the fix to
#3249 seems to be the culprit. Bumped to high, because it is a blocker for 2.9

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@dragos said:
This has been fixed in r24319.

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@dragos said:
I reopen this as the commit that fixed it was reverted in r23344.

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@paulp said:
Here's the difference from recently working variation to now.
These signatures should not be in there.

  < signature: TE;
  < signature: ()Lscala/collection/mutable/DefaultEntry<TA;TB;>;
  < signature: (Lscala/collection/mutable/DefaultEntry<TA;TB;>;)V

The type variable E is the clunker. It is defined here:

trait HashEntry [A, E] {
  val key: A
  var next: E = _
}

Then DefaultEntry extends that.

final class DefaultEntry[A, B](val key: A, var value: B)
  extends HashEntry[A, DefaultEntry[A, B]] with Serializable

But DefaultEntry#next's signature refers to E instead of DefaultEntry<TA;TB;>.

This is perhaps related to next being a var (having a getter.)

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@paulp said:
I've just about got this wrapped up.

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@paulp said:
(In r24369) Seem to have made a breakthrough with signature correctness.
Most of the remaining troubles were due to inherited members
and their foreign identifiers, but I think I found a simple way
to make everyone happy. Closes #4238, review by moors.

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@SethTisue said:
as of r24372:

BUILD FAILED
/Users/tisue/scala/build.xml:48: The following error occurred while executing this line:
/Users/tisue/scala/build.xml:1555: java.lang.RuntimeException: Test suite finished with 1 case failing:
/Users/tisue/scala/test/files/run/bug4238 [FAILED]
	at scala.sys.package$$.error(package.scala:27)
	at scala.tools.partest.PartestTask$$$$anonfun$$f$$1$$1.apply(PartestTask.scala:291)
	at scala.tools.partest.PartestTask$$$$anonfun$$f$$1$$1.apply(PartestTask.scala:291)
	at scala.tools.partest.PartestTask.execute(PartestTask.scala:300)
	at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:291)
	at sun.reflect.GeneratedMethodAccessor4.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at org.apache.tools.ant.dispatch.DispatchUtils.execute(DispatchUtils.java:106)
	at org.apache.tools.ant.Task.perform(Task.java:348)
	at org.apache.tools.ant.Target.execute(Target.java:390)
	at org.apache.tools.ant.Target.performTasks(Target.java:411)
	at org.apache.tools.ant.Project.executeSortedTargets(Project.java:1399)
	at org.apache.tools.ant.helper.SingleCheckExecutor.executeTargets(SingleCheckExecutor.java:38)
	at org.apache.tools.ant.Project.executeTargets(Project.java:1251)
	at org.apache.tools.ant.taskdefs.Ant.execute(Ant.java:442)
	at org.apache.tools.ant.taskdefs.CallTarget.execute(CallTarget.java:105)
	at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:291)
	at sun.reflect.GeneratedMethodAccessor4.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at org.apache.tools.ant.dispatch.DispatchUtils.execute(DispatchUtils.java:106)
	at org.apache.tools.ant.Task.perform(Task.java:348)
	at org.apache.tools.ant.Target.execute(Target.java:390)
	at org.apache.tools.ant.Target.performTasks(Target.java:411)
	at org.apache.tools.ant.Project.executeSortedTargets(Project.java:1399)
	at org.apache.tools.ant.Project.executeTarget(Project.java:1368)
	at org.apache.tools.ant.helper.DefaultExecutor.executeTargets(DefaultExecutor.java:41)
	at org.apache.tools.ant.Project.executeTargets(Project.java:1251)
	at org.apache.tools.ant.Main.runBuild(Main.java:809)
	at org.apache.tools.ant.Main.startAnt(Main.java:217)
	at org.apache.tools.ant.launch.Launcher.run(Launcher.java:280)
	at org.apache.tools.ant.launch.Launcher.main(Launcher.java:109)

this is after ant all.clean; ant dist

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@paulp said:
Yeah, I know. It was working the commit before that one, and fixing the other broken test apparently broke this one. I say apparently because 4238 passes on my machine. At least the tests are doing something useful.

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@dragos said:
Paul, I believe you're on this anyway, so I reassign it to you.

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@paulp said:
(In r24390) Re-enabling the disabled signature test along with changes which
allow it to pass. Closes #4238 again, no review. (But would anyone
like to expand the signature tests? Great idea, extempore!)