NullPointerException at jdk.nashorn.internal.codegen.LocalVariableTypesCalculator.symbolIsUsed(LocalVariableTypesCalculator.java:224)

I found this while trying Biwascheme ( https://github.com/biwascheme/biwascheme ) on nashorn jdk9-dev tip changeset: 1026:9f8ab1b79632

jjs $biwascheme/release/biwascheme-0.6.2.js

Exception in thread "main" java.lang.NullPointerException
at jdk.nashorn.internal.codegen.LocalVariableTypesCalculator$LvarType.access$100(LocalVariableTypesCalculator.java:119)
at jdk.nashorn.internal.codegen.LocalVariableTypesCalculator.symbolIsUsed(LocalVariableTypesCalculator.java:224)
at jdk.nashorn.internal.codegen.LocalVariableTypesCalculator.symbolIsUsed(LocalVariableTypesCalculator.java:1473)
at jdk.nashorn.internal.codegen.LocalVariableTypesCalculator.enterIdentNode(LocalVariableTypesCalculator.java:618)
at jdk.nashorn.internal.ir.IdentNode.accept(IdentNode.java:136)
at jdk.nashorn.internal.codegen.LocalVariableTypesCalculator.enterReturnNode(LocalVariableTypesCalculator.java:692)
at jdk.nashorn.internal.ir.ReturnNode.accept(ReturnNode.java:91)
at jdk.nashorn.internal.ir.Node.accept(Node.java:249)
at jdk.nashorn.internal.ir.Block.accept(Block.java:152)
at jdk.nashorn.internal.ir.LexicalContextNode$Acceptor.accept(LexicalContextNode.java:57)
at jdk.nashorn.internal.ir.Block.accept(Block.java:399)
at jdk.nashorn.internal.ir.FunctionNode.accept(FunctionNode.java:376)
at jdk.nashorn.internal.ir.LexicalContextNode$Acceptor.accept(LexicalContextNode.java:57)
at jdk.nashorn.internal.ir.LexicalContextExpression.accept(LexicalContextExpression.java:46)
at jdk.nashorn.internal.ir.FunctionNode.accept(FunctionNode.java:58)
at jdk.nashorn.internal.codegen.LocalVariableTypesCalculator$1.leaveFunctionNode(LocalVariableTypesCalculator.java:1238)
at jdk.nashorn.internal.ir.FunctionNode.accept(FunctionNode.java:376)
at jdk.nashorn.internal.ir.LexicalContextNode$Acceptor.accept(LexicalContextNode.java:57)
at jdk.nashorn.internal.ir.LexicalContextExpression.accept(LexicalContextExpression.java:46)
at jdk.nashorn.internal.ir.FunctionNode.accept(FunctionNode.java:58)
at jdk.nashorn.internal.ir.PropertyNode.accept(PropertyNode.java:88)
at jdk.nashorn.internal.ir.Node.accept(Node.java:249)
at jdk.nashorn.internal.ir.ObjectNode.accept(ObjectNode.java:64)
at jdk.nashorn.internal.ir.Node.accept(Node.java:249)
at jdk.nashorn.internal.ir.CallNode.accept(CallNode.java:178)
at jdk.nashorn.internal.ir.LexicalContextNode$Acceptor.accept(LexicalContextNode.java:57)
at jdk.nashorn.internal.ir.LexicalContextExpression.accept(LexicalContextExpression.java:46)
at jdk.nashorn.internal.ir.CallNode.accept(CallNode.java:41)
at jdk.nashorn.internal.ir.BinaryNode.accept(BinaryNode.java:341)
at jdk.nashorn.internal.ir.BinaryNode.accept(BinaryNode.java:341)
at jdk.nashorn.internal.ir.ExpressionStatement.accept(ExpressionStatement.java:62)
at jdk.nashorn.internal.ir.Node.accept(Node.java:249)
at jdk.nashorn.internal.ir.Block.accept(Block.java:152)
at jdk.nashorn.internal.ir.LexicalContextNode$Acceptor.accept(LexicalContextNode.java:57)
at jdk.nashorn.internal.ir.Block.accept(Block.java:399)
at jdk.nashorn.internal.ir.SplitNode.accept(SplitNode.java:94)
at jdk.nashorn.internal.ir.LexicalContextNode$Acceptor.accept(LexicalContextNode.java:57)
at jdk.nashorn.internal.ir.LexicalContextStatement.accept(LexicalContextStatement.java:53)
at jdk.nashorn.internal.ir.SplitNode.accept(SplitNode.java:41)
at jdk.nashorn.internal.ir.Node.accept(Node.java:249)
at jdk.nashorn.internal.ir.Block.accept(Block.java:152)
at jdk.nashorn.internal.ir.LexicalContextNode$Acceptor.accept(LexicalContextNode.java:57)
at jdk.nashorn.internal.ir.Block.accept(Block.java:399)
at jdk.nashorn.internal.codegen.LocalVariableTypesCalculator.leaveFunctionNode(LocalVariableTypesCalculator.java:1294)
at jdk.nashorn.internal.ir.FunctionNode.accept(FunctionNode.java:376)
at jdk.nashorn.internal.ir.LexicalContextNode$Acceptor.accept(LexicalContextNode.java:57)
at jdk.nashorn.internal.ir.LexicalContextExpression.accept(LexicalContextExpression.java:46)
at jdk.nashorn.internal.ir.FunctionNode.accept(FunctionNode.java:58)
at jdk.nashorn.internal.codegen.CompilationPhase$9.transform(CompilationPhase.java:279)
at jdk.nashorn.internal.codegen.CompilationPhase.apply(CompilationPhase.java:703)
at jdk.nashorn.internal.codegen.Compiler.compile(Compiler.java:560)
at jdk.nashorn.internal.runtime.Context.compile(Context.java:1159)
at jdk.nashorn.internal.runtime.Context.compileScript(Context.java:1098)
at jdk.nashorn.internal.runtime.Context.compileScript(Context.java:543)
at jdk.nashorn.tools.Shell.runScripts(Shell.java:317)
at jdk.nashorn.tools.Shell.run(Shell.java:169)
at jdk.nashorn.tools.Shell.main(Shell.java:133)
at jdk.nashorn.tools.Shell.main(Shell.java:112)

Based on some println debugging, I think I managed to reduce this to simple script below:

function func(x, y) {
  while(true) {
     switch (y[0]) {
       case "bar":
           x = 'xxx';
           break;
     }
  }
  return x;
}

If you turn on asserts with -J-ea, we get the following trace:

Exception in thread "main" java.lang.AssertionError
at jdk.nashorn.internal.codegen.LocalVariableTypesCalculator.getLocalVariableType(LocalVariableTypesCalculator.java:998)
at jdk.nashorn.internal.codegen.LocalVariableTypesCalculator.symbolIsUsed(LocalVariableTypesCalculator.java:1473)
at jdk.nashorn.internal.codegen.LocalVariableTypesCalculator.enterIdentNode(LocalVariableTypesCalculator.java:618)
at jdk.nashorn.internal.ir.IdentNode.accept(IdentNode.java:136)
at jdk.nashorn.internal.codegen.LocalVariableTypesCalculator.enterReturnNode(LocalVariableTypesCalculator.java:692)
at jdk.nashorn.internal.ir.ReturnNode.accept(ReturnNode.java:91)
at jdk.nashorn.internal.ir.Node.accept(Node.java:249)
at jdk.nashorn.internal.ir.Block.accept(Block.java:152)
at jdk.nashorn.internal.ir.LexicalContextNode$Acceptor.accept(LexicalContextNode.java:57)
at jdk.nashorn.internal.ir.Block.accept(Block.java:399)
at jdk.nashorn.internal.ir.FunctionNode.accept(FunctionNode.java:376)
at jdk.nashorn.internal.ir.LexicalContextNode$Acceptor.accept(LexicalContextNode.java:57)
at jdk.nashorn.internal.ir.LexicalContextExpression.accept(LexicalContextExpression.java:46)
at jdk.nashorn.internal.ir.FunctionNode.accept(FunctionNode.java:58)
at jdk.nashorn.internal.codegen.LocalVariableTypesCalculator$1.leaveFunctionNode(LocalVariableTypesCalculator.java:1238)
at jdk.nashorn.internal.ir.FunctionNode.accept(FunctionNode.java:376)
at jdk.nashorn.internal.ir.LexicalContextNode$Acceptor.accept(LexicalContextNode.java:57)
at jdk.nashorn.internal.ir.LexicalContextExpression.accept(LexicalContextExpression.java:46)
at jdk.nashorn.internal.ir.FunctionNode.accept(FunctionNode.java:58)
at jdk.nashorn.internal.ir.VarNode.accept(VarNode.java:171)
at jdk.nashorn.internal.ir.Node.accept(Node.java:249)
at jdk.nashorn.internal.ir.Block.accept(Block.java:152)
at jdk.nashorn.internal.ir.LexicalContextNode$Acceptor.accept(LexicalContextNode.java:57)
at jdk.nashorn.internal.ir.Block.accept(Block.java:399)
at jdk.nashorn.internal.codegen.LocalVariableTypesCalculator.leaveFunctionNode
[... more frames...]