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.