Consts defined in loop blocks retain their values between iterations and after the loop

[michbarsinai]

Given the following code, Rhino and Deno print different outputs. (the out function is just a compatibility layer between the two engines):

function out(x){
    if ( typeof print != "undefined" ) {
        print(x);
    } else {
        console.log(x);
    }
}

let loopCount=3;
while ( loopCount-- ) {
   const i=loopCount;
   out(i);
}

// out(i);

Rhino prints:

$ java -jar rhino-1.7.14.jar  /Users/michael/sandbox/sm1/spec/js-dis/const.js
2
2
2

While Deno prints:

$ deno run /Users/michael/sandbox/sm1/spec/js-dis/const.js
2
1
0

Might be useful to note that when the last line is un-commented, Deno complains that i is not defined at that line, whereas Rhino prints 2. However, if i is defined as let, Rhino behaves like Deno, and complains that i is not defined.

Seems like Rhino defines consts on a parent scope of the correct scope (maybe where vars would have been defined?), but I'm no expert in Rhino's internals.

[p-bakker]

Duplicate of #939