Bug: Excessive variable and shallow copy for leading or middle rest parameter

Input Code

f1 = (a..., b) ->

f2 = (c, d..., e) ->

Expected Behavior

var f1, f2,
  splice = [].splice;

f1 = function(...a) {
  var b;
  [b] = splice.call(a, -1);
};

f2 = function(c, ...d) {
  var e;
  [e] = splice.call(d, -1);
};

Current Behavior

var f1, f2,
  splice = [].splice;

f1 = function(...a) {
  var b, ref;
  ref = a, [...a] = ref, [b] = splice.call(a, -1);
};

f2 = function(c, ...d) {
  var e, ref;
  ref = d, [...d] = ref, [e] = splice.call(d, -1);
};

Environment

• CoffeeScript version: 2.7.0

Reproduce the issue with the f1 and f2 input snippets using CoffeeScript 2.7.0, then trace the compiler path that handles leading and middle rest parameters. Compare the generated JavaScript with the expected output; done means the redundant variable and shallow-copy operations are no longer emitted.