In ESLint 6, what is the logic behind for loops throwing "no-unused-vars" linter warning?

[GasimGasimzada]

I am using CRA whose new version updates ESLint to v6. Now, I am getting errors in for ... of and for ... in loops. Here is an example:

if (graphQLErrors) {
  for (let err of graphQLErrors) { // this gives me error that "err" is unused
    if (err.extensions && err.extensions.status && err.extensions.status === 401) {
      return fromPromise(performRefresh()).flatMap(() => {
        return forward(operation);
      });
    }
  }
}

What's the logic and what does ESLint expect in this case?

[ooflorent]

I also encounter this warning using the following statements:

const entrypoints = {};
for (const [chunk, entrypoint] of Object.entries(stats.entrypoints)) {
//          ^^^^^  ^^^^^^^^^^
//          flagged as unused
  const js = [];
  const css = [];
  for (const asset of entrypoint.assets) {
//           ^^^^^
//         also here
    if (asset.endsWith(".js")) {
      js.push(PUBLIC_PATH + asset);
    } else if (asset.endsWith(".css")) {
      css.push(PUBLIC_PATH + asset);
    }
  }
  entrypoints[chunk] = { js, css };
}

Works as expected in 6.1.0
Broken in 6.2.0

[g-plane]

Duplicate of #12117 . Please track that issue.