[Bug]: plugin-transform-object-super incorrect output where object created in a loop

[overlookmotel]

💻

• Would you like to work on a fix?

How are you using Babel?

Programmatic API (babel.transform, babel.parse)

Input code

const objects = [];
for (const proto of [{x: 0}, {x: 1}]) {
  objects.push({
    __proto__: proto,
    foo() {
      return super.x
    }
  });
}
assert(objects[0].foo() === 0);
assert(objects[1].foo() === 1);

REPL

Configuration file name

No response

Configuration

No response

Current and expected behavior

In the original code, the assertions pass. When transformed with @babel/plugin-transform-object-super, the first assertion fails.

The transformed output is:

const objects = [];
for (const proto of [{x: 0}, {x: 1}]) {
  var _obj;
  objects.push(
    (_obj = {
      __proto__: proto,
      foo() {
        return _get(_getPrototypeOf(_obj), "x", this);
      }
    })
  );
}
assert(objects[0].foo() === 0);
assert(objects[1].foo() === 1);

Environment

REPL

Possible solution

The problem is that _obj for the 1st turn of the loop is over-written in 2nd turn, because _obj is not block scoped. Could be solved by changing var _obj to let _obj.

Please see REPL.

Additional context

No response

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