From: Logan Capaldo <logancapaldo@...>
Date: 2007-05-27T23:44:23+09:00
Subject: Re: local variables vs. methods

On Sat, May 26, 2007 at 10:35:03PM +0900, Henrik Schmidt wrote:
> As seen above, there are several ways of getting around this, but this 
> is the question: Why is this behaviour useful? As I see it, it's bad 
> practice to give a method and a local variable the same name. At least I 
> can't think of an example where it would make sense. Why not simply 
> disallow this or at least have the interpreter issue a warning?
> 
Just to throw out another reason, that I don't think has been mentioned
yet, it would be expensive. For the interpreter to issue a warning about
local variables shadowing method names, it would require the interpreter
to do a method lookup on _every_ variable assignment. And it couldn't
even be at parse time, it would have to be every time. Eg:

class A
  def bar
    foo = 1 # the interpreter doesn't yet know that there will be a foo
            # method
    foo
  end
  
  def foo
    "foo"
  end
end

# Therefore, it has to do at least 2 method lookups everytime I call
# bar below, one for bar itself, and one to make sure foo isn't a method

v = A.new
v.bar
v.bar
v.bar

It also can't cache the need to warn, because I can remove_method :foo,
making the warning incorrect.

Method lookup on every assign would not be a cheap operation. (I know we
don't usually like to talk about speed here, but this would be _really_
bad).

> Best regards,
>   Henrik Schmidt