[bug] immediately invoked function and variable-name collision

[freund17]

Bug report

My second attempt on reproducing this bug... (first attempt: #352).
I think I got it this time around...
No idea what to title this issue though...

Version (complete output of terser -V or specific git commit)
terser 4.0.0

Complete CLI command or minify() options used
terser --compress

terser input

(function(callback) {
  callback();
})(function() {
  window.used = function() {
    var A = window.foo,
      B = window.bar,
      C = window.foobar;

    return (function(A, c) {
      if (-1 === c) return A;
      return $(A, c);
    })(B, C);
  }.call(this);
});

terser output

window.used = (function() {
  window.foo;
  var B = window.bar,
    C = window.foobar;
  return (function(A, c) {
    return $(A, c);
  })(B, C);
})();

(Prettified)

Notice the missing if.

Expected result

window.used = (function() {
  window.foo;
  var B = window.bar,
    C = window.foobar;
  return -1 === C ? B : $(B, C);
})();

(Prettified)

[freund17]

With the outer function dropped - works:

terser input

(function() {
  window.used = (function() {
    var A = window.foo,
      B = window.bar,
      C = window.foobar;

    return (function(A, c) {
      if (-1 === c) return A;
      return $(A, c);
    })(B, C);
  })();
})();

terser output

window.used = (function() {
  window.foo;
  var B = window.bar,
    C = window.foobar;
  return -1 === C ? B : $(B, C);
})();

(Prettified)

[freund17]

With the unused variable, A, renamed to X - works:

terser input

(function(callback) {
  callback();
})(function() {
  window.used = (function() {
    var X = window.foo,
      B = window.bar,
      C = window.foobar;

    return (function(A, c) {
      if (-1 === c) return A;
      return $(A, c);
    })(B, C);
  })();
});

terser output

window.used = (function() {
  window.foo;
  var A,
    c,
    B = window.bar,
    C = window.foobar;
  return (A = B), -1 === (c = C) ? A : $(A, c);
})();

(Prettified)

[fabiosantoscode]

Oh my, this looks like a tough and serious one. Thanks for the repro :)

[roblan]

@fabiosantoscode looks a little like #294 and #308

and there is already MR for that: #320

[L2jLiga]

@roblan, #320 did not fix issue. I've just checked it, output same to master for given input

[fabiosantoscode]

Damn, I got my hopes up :(

[L2jLiga]

Hey, dont give it up!

[roblan]

Sorry :(

[L2jLiga]

PR created