Bug with "let" variable in for loop: ReferenceError: "obj" is not defined

[Anton Mitrofanov]

Hi.

We have some code like this:

let System = Java.type('java.lang.System');
let ArrayList = Java.type('java.util.ArrayList');

function test(array) {
    let list = new ArrayList();
    for each (let obj in array) {
        let found = list.stream().filter(function(o) {
            return o == obj;
        }).findFirst().orElse(null);
        if (found) continue;
        list.add(obj);
    }
    return list;
}

let res = test(['test1', 'test2', 'test1', 'test3']);
System.out.println(res.size());

The expected result of which is: 3
But with Java 17 and Nashorn 15.4 the result is an exception:

<eval>:8 ReferenceError: "obj" is not defined
Caused by: <eval>:8 ReferenceError: "obj" is not defined
	at org.openjdk.nashorn.internal.runtime.ECMAErrors.error(ECMAErrors.java:57)
	at org.openjdk.nashorn.internal.runtime.ECMAErrors.referenceError(ECMAErrors.java:318)
	at org.openjdk.nashorn.internal.runtime.ECMAErrors.referenceError(ECMAErrors.java:290)
	at org.openjdk.nashorn.internal.runtime.ECMAErrors.referenceError(ECMAErrors.java:277)
	at org.openjdk.nashorn.internal.runtime.AccessorProperty.checkUndeclared(AccessorProperty.java:570)
	at org.openjdk.nashorn.internal.runtime.AccessorProperty.getGetter(AccessorProperty.java:505)
	at org.openjdk.nashorn.internal.runtime.FindProperty.getGetter(FindProperty.java:91)
	at org.openjdk.nashorn.internal.runtime.ScriptObject.findGetMethod(ScriptObject.java:1997)
	at org.openjdk.nashorn.internal.runtime.ScriptObject.lookup(ScriptObject.java:1867)

If you change the "let" declaration to "var", then everything is fine.

If you leave "let" in the code and change "if (found)" to "if (true)", then the exception becomes different:

Caused by: java.lang.NullPointerException: Cannot invoke "org.openjdk.nashorn.internal.codegen.Label$Stack.push(org.openjdk.nashorn.internal.codegen.types.Type)" because "this.stack" is null
	at org.openjdk.nashorn.internal.codegen.MethodEmitter.pushType(MethodEmitter.java:250)
	at org.openjdk.nashorn.internal.codegen.MethodEmitter._new(MethodEmitter.java:359)
	at org.openjdk.nashorn.internal.codegen.MethodEmitter._new(MethodEmitter.java:372)
	at org.openjdk.nashorn.internal.codegen.FieldObjectCreator.createForInIterationScope(FieldObjectCreator.java:133)
	at org.openjdk.nashorn.internal.codegen.CodeGenerator.enterForIn(CodeGenerator.java:1817)

But the expected result is the same as with "var": 0

P.S. I apologize for writing directly to ML and not to the issue tracker, but I couldn’t find my bug there and create a new one.