Tail call optimization doesn't work when using default values referring to other parameters

[joshuacaron]

Tail call optimization doesn't work properly if you use a function which has a default parameter refering to another parameter, for example:

function test(a, b = a){
  if(a === 0) {
    return b
  } else {
    return test(a - 1, b)
  }
}

compiles to:

"use strict";

function test(a) {
  var b = arguments.length <= 1 || arguments[1] === undefined ? a : arguments[1];
  return (function () {
    if (a === 0) {
      return b;
    } else {
      return test(a - 1, b);
    }
  })();
}

[loganfsmyth]

This is a downside to the current approach to the context injected for default arguments. Definitely something that'll need to be looked at.

[sebmck]

TCO has since been removed from Babel 6 due to issues and will be redeveloped in the future.

[estaub]

@sebmck The status should be updated in http://babeljs.io/docs/learn-es2015/#tail-calls

[sebmck]

Open an issue on the babel.github.io repo.

On Sun, Nov 15, 2015 at 7:17 AM, Ed Staub notifications@github.com wrote:

@sebmck https://github.com/sebmck The status should be updated in
http://babeljs.io/docs/learn-es2015/#tail-calls

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#2547 (comment).

Sebastian McKenzie