Assertion in Attr

jjs> Function("return (void ({ set each (x2)y }));");
Compiling threw: java.lang.AssertionError
java.lang.AssertionError
    at jdk.nashorn.internal.codegen.Attr.enterFunctionBody(Attr.java:276)
    at jdk.nashorn.internal.codegen.Attr.enterBlock(Attr.java:297)
    at jdk.nashorn.internal.ir.Block.accept(Block.java:135)
    at jdk.nashorn.internal.ir.LexicalContextNode.accept(LexicalContextNode.java:69)
    at jdk.nashorn.internal.ir.FunctionNode.accept(FunctionNode.java:285)
    at jdk.nashorn.internal.ir.LexicalContextNode.accept(LexicalContextNode.java:69)
    at jdk.nashorn.internal.ir.PropertyNode.accept(PropertyNode.java:90)
    at jdk.nashorn.internal.ir.Node.accept(Node.java:346)
    at jdk.nashorn.internal.ir.ObjectNode.accept(ObjectNode.java:62)
    at jdk.nashorn.internal.ir.RuntimeNode.accept(RuntimeNode.java:415)
    at ...