Whitespace not handled consistently on + operator

[burlesona]

If you leave a space before a + operator but not after it, the compiler will interpret the + and the string behind it as being passed to as arguments to a function call. Here's an example:

test.coffee

test = "abc"
result = test+"def"
result = test + "def"
result = test+ "def"
result = test +"def"

test.js

// Generated by CoffeeScript 1.4.0
(function() {
  var result, test;

  test = "abc";

  result = test + "def";

  result = test + "def";

  result = test + "def";

  result = test(+"def");

}).call(this);

My first thought was that this must be just a consequence of CS optional parenthesis, but even when adding some parenthesis to try and separate the arguments, if the plus is adjacent to the string the result is the same:

test = "abc"
result = (test) +"def"
result = test +("def")

// Generated by CoffeeScript 1.4.0
(function() {
  var result, test;

  test = "abc";

  result = test(+"def");

  result = test(+"def");

}).call(this);

I think the fact that test +("def") is parsed into test(+"def"); seems especially odd.

Anyway, I wanted to share this since it really surprised me. Lastly, I realize this is not "typical" coding style so it's probably not encountered very often, however I discovered it because I accidentally left out the space after a + in some code today, and the result was TypeError: string is not a function, which was surprising.

Interested to hear whether this is considered a bug, and if not, why not. Thanks!

[vendethiel]

Why is that odd? CoffeeScript is a white-space significant language, and a b is a(b) (implicit call), nothing inconsistent.
#2595 #2469 #2210 and others

[jashkenas]

Interested to hear whether this is considered a bug, and if not, why not. Thanks!

Not. If you expect:

return -x

To return -x, then you should expect the following to pass -x to the callback in CoffeeScript.

callback -x