From: "David A. Black" <dblack@...>
Date: 2008-10-04T23:16:27+09:00
Subject: Re: No warning for redefine

Hi --

On Sat, 4 Oct 2008, Daniel DeLorme wrote:

> David A. Black wrote:
>> 
>> On Fri, 3 Oct 2008, Han Holl wrote:
>>> 
>>> Shouldn't the following:
> [snip]
>>> produce something like:
>>> 
>>> demo.rb:9: warning: method redefined; discarding old function
>>> 
>>> Behaviour now is to discard the mixed-in method silently.
>> 
>> It's not discarded; it's still there (in the module) and you can use
>> it with other classes, or reach it through 'super' in the override.
>
> But since the override doesn't use super, in effect it has the same effect as 
> discarding the included 'function', at least as far as the main object is 
> concerned. I wish ruby would output a warning for cases like this, i.e. 
> "warning: method `foo' ignores method defined in /path/to/file.rb:123"

Yikes. Be careful what you wish for :-) That would put a damper on a
lot of code, as well as slowing things down (the 'super' determination
could only be made at runtime) and spewing endless errors. For
example:

   {}.select ...

would give you a warning, because the Hash override of
Enumerable#select does not call super.

There's absolutely nothing fishy or wrong with not calling super, so
there's nothing to warn about. The whole object/class model of Ruby is
based on the idea of a method search-path, to which you can prepend
classes and modules precisely to prevent the execution of earlier
definitions of methods.  Any issues with name clashing and such (of
which there shouldn't be many, if any, since you'd presumably be
familiar with the class you're inheriting from) would be exposed by
tests.


David

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