Inlined function reassigns const variable

[bhollis]

Bug report or feature request?

Bug report.

ES5 or ES6+ input?

ES6

Uglify version (uglifyjs -V)
uglify-es 3.3.8

JavaScript input

function makeService() {
  function load() {
    return Promise.resolve(null)
      .then((data) => {
        const version = data;

        return Promise.resolve(null)
          .catch((e) => log(version));
      });
  }

  function log(version) {
    console.log(version);
  }

  return load;
}

The uglifyjs CLI command executed or minify() options used.
uglify-es --ecma 6 -b -c -m --harmony -- uglify-bug.js

JavaScript output or error produced.

function makeService() {
    return function() {
        return Promise.resolve(null).then(e => {
            const n = e;
            return Promise.resolve(null).catch(e => (n = n, void console.log(n)));
        });
        var e;
    };
}

I believe this is the same (or related to) #2842 but I wanted to contribute another test case. This is the smallest test case I could make - it didn't repro without the nested promise, or the function returned from a function.

The error is in the assignment n = n in the inlined catch handler - it fails with "Assignment to constant variable."

[kzc]

This is a dup of #2842 and can be closed.
Just use -c inline=1 as a workaround.

[bhollis]

Yup, just hoping to offer a different repro.

[alexlamsl]

@bhollis thanks for providing the details.

In the future please leave this as a comment on #2842 so it is easier for others to follow, and for me to manage this issue tracker.

[kzc]

An ideal uglify test case is a small standalone program that prints out something with console.log that when minified has different behavior. Rather than reasoning the minified code is correct we'd rather just run it and compare results with the original code run.

Promises/async/await currently don't play well with the uglify test sandbox because their actions run asynchronously in the event loop.