varargs: javac crashes during overload resolution with generic varargs

The following program crashes javac:

class B {
    public <X extends Number> void m(X... args) { }
    public void m(Object... args) { }

    { m(null, null); }
}


Here's the stack trace:

An exception has occurred in the compiler (1.7.0-ea). Please file a bug at the Java Developer Connection (http://java.sun.com/webapps/bugreport) after checking the Bug Parade for duplicates. Include your program and the following diagnostic in your report. Thank you.
java.lang.NullPointerException
        at com.sun.tools.javac.code.Types$UnaryVisitor.visit(Types.java:3624)
        at com.sun.tools.javac.code.Types$Subst.subst(Types.java:2171)
        at com.sun.tools.javac.code.Types.subst(Types.java:2145)
        at com.sun.tools.javac.comp.Infer.instantiateMethod(Infer.java:401)
        at com.sun.tools.javac.comp.Resolve.rawInstantiate(Resolve.java:378)
        at com.sun.tools.javac.comp.Resolve.instantiate(Resolve.java:405)
        at com.sun.tools.javac.comp.Resolve.signatureMoreSpecific(Resolve.java:811)
        at com.sun.tools.javac.comp.Resolve.mostSpecific(Resolve.java:720)
        at com.sun.tools.javac.comp.Resolve.selectBest(Resolve.java:694)
        at com.sun.tools.javac.comp.Resolve.findMethod(Resolve.java:914)
        at com.sun.tools.javac.comp.Resolve.findMethod(Resolve.java:878)
        at com.sun.tools.javac.comp.Resolve.findFun(Resolve.java:962)
        at com.sun.tools.javac.comp.Resolve.resolveMethod(Resolve.java:1359)
        at com.sun.tools.javac.comp.Attr.visitIdent(Attr.java:2105)
        at com.sun.tools.javac.tree.JCTree$JCIdent.accept(JCTree.java:1704)
        at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:436)
        at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:423)
        at com.sun.tools.javac.comp.Attr.attribExpr(Attr.java:454)
        at com.sun.tools.javac.comp.Attr.visitApply(Attr.java:1434)
        at com.sun.tools.javac.tree.JCTree$JCMethodInvocation.accept(JCTree.java:1320)
        at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:436)
        at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:423)
        at com.sun.tools.javac.comp.Attr.attribExpr(Attr.java:465)
        at com.sun.tools.javac.comp.Attr.visitExec(Attr.java:1207)
        at com.sun.tools.javac.tree.JCTree$JCExpressionStatement.accept(JCTree.java:1166)
        at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:436)
        at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:423)
        at com.sun.tools.javac.comp.Attr.attribStat(Attr.java:485)
        at com.sun.tools.javac.comp.Attr.attribStats(Attr.java:501)
        at com.sun.tools.javac.comp.Attr.visitBlock(Attr.java:862)
        at com.sun.tools.javac.tree.JCTree$JCBlock.accept(JCTree.java:780)
        at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:436)
        at com.sun.tools.javac.comp.Attr.attribTree(Attr.java:423)
        at com.sun.tools.javac.comp.Attr.attribStat(Attr.java:485)
        at com.sun.tools.javac.comp.Attr.attribClassBody(Attr.java:3137)
        at com.sun.tools.javac.comp.Attr.attribClass(Attr.java:3063)
        at com.sun.tools.javac.comp.Attr.attribClass(Attr.java:2999)
        at com.sun.tools.javac.main.JavaCompiler.attribute(JavaCompiler.java:1157)
        at com.sun.tools.javac.main.JavaCompiler.compile2(JavaCompiler.java:847)
        at com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:806)
        at com.sun.tools.javac.main.Main.compile(Main.java:411)
        at com.sun.tools.javac.main.Main.compile(Main.java:329)
        at com.sun.tools.javac.main.Main.compile(Main.java:320)
        at com.sun.tools.javac.Main.compile(Main.java:76)
        at com.sun.tools.javac.Main.main(Main.java:61)