Inherited Class generated code does not match order of execution

[alanning]

Severity Low

Proposal
Move the generated function declaration to the first line of the generated class.

Issue
Coffeescript currently outputs the __extends call prior to the function declaration of generated classes while order of execution is actually the opposite.

//Generated Code
NS.Snake = (function() {
  __extends(Snake, NS.Animal);
  function Snake() {
    Snake.__super__.constructor.apply(this, arguments);
  }
  //...
}

//Actual Execution Order:
NS.Snake = (function() {
  function Snake() {
    Snake.__super__.constructor.apply(this, arguments);
  }
  __extends(Snake, NS.Animal);
  //...
}

Rationale
While this currently causes no errors due to the happy coincidence that function declarations are always executed first, I believe implementing the proposed change avoids confusion for those trying to understand the generated code.

Example
An example of the issue can be found here: http://jsfiddle.net/alanning/yDnxL/

Reference
IRC #coffeescript channel discussion with jaskenas
Snipped for conciseness. Full chat log found here: http://irclogger.com/.coffeescript/2011-06-21#1308678991

<Adrian_>   I've got a couple suggested changes to coffeescript compiler behavior that I would like to get feedback on before I submit...
<Adrian_>   Class Extends behavior -> move "__extends(a,b)" call to after function declaration
<Adrian_>   The goal of the first change is to make it easier for beginners to understand the generated javascript as many tend to think (var func_name = function...) is the same as (function func_name...)
...
<jashkenas_work>    Adrian_: the __extends actually has to happen first, to make executable class bodies work right with static inheritance.
<Adrian_>   __extends can not happen before the function that it is extending is actually created
...
<jashkenas_work>    Adrian_: yes, but executable class bodies preserve the order of their statements.
<Adrian_>   it happens to work in how coffeescript generates it due to function _declarations_ always being executed first
<jashkenas_work>    and __extends has to happen before the first statement.
<jashkenas_work>    right, just so.
<Adrian_>   __extends does not actually happen first
<Adrian_>   if you put a breakpoint you will see it executing after the function declaration
<Adrian_>   i am suggesting changing it to match how the actual execution is occurring to help avoid confusion
...
<Adrian_>   jashkenas, to make what is happening in the class example clearer, add a namespace to the class names in the try coffeescript example
<Adrian_>   NS.Animal, etc
<Adrian_>   jashkenas_work, here is an example where you can see the difference: http://jsfiddle.net/alanning/yDnxL/
<Adrian_>   if you move the __extends call to before the function expression, the example stops working.
<Adrian_>   as you would expect
<Adrian_>   the fact that coffeescript outputs function declarations instead keeps the code working but it doesn't match order of execution
<jashkenas_work>    Adrian_: I understand the proposal.