Bug in Kernel#method objects that call super?

[Charles Oliver Nutter]

I posted this to ruby-core and got a somewhat mixed response. I'm
curious what the rest of you might think of this behavior.

-------- Original Message --------
Subject: Bug in Kernel#method objects that call super?
Date: Sat, 07 Jul 2007 05:57:13 +0900
From: Charles Oliver Nutter <[email protected]>
Reply-To: (e-mail address removed)
To: (e-mail address removed)

This seems very wrong to me. Calling through a method object should
behave the same for super as calling directly or calling through an alias:


class Foo
def a; puts 'Foo a'; end
def b; puts 'Foo b'; end
end

class Bar < Foo
def a; puts 'Bar a'; super; end
alias b a
end

Bar.new.a # => "Bar a\nFoo a"
Bar.new.b # => "Bar a\nFoo a"
Bar.new.methodb).call # => "Bar a\nFoo b"


It seems incorrect for method objects to change the behavior of super.
If I super in 'a', I want super's 'a' to be called, without exception.

Can someone confirm this is a bug? In JRuby we always super up the
same-named chain, so this represents an incompatibility.

- Charlie

 

[dblack]

HI --

This seems very wrong to me. Calling through a method object should
behave the same for super as calling directly or calling through an alias:


class Foo
def a; puts 'Foo a'; end
def b; puts 'Foo b'; end
end

class Bar < Foo
def a; puts 'Bar a'; super; end
alias b a
end

Bar.new.a # => "Bar a\nFoo a"
Bar.new.b # => "Bar a\nFoo a"
Bar.new.methodb).call # => "Bar a\nFoo b"


It seems incorrect for method objects to change the behavior of super.
If I super in 'a', I want super's 'a' to be called, without exception.

I agree that it's very odd that the two ways of calling behave
differently. A secondary question is whether the #method behavior --
the dynamic calculation of what method super should look for -- has
any useful application. I can't think of any. Maybe we need "super!"



David

--
* Books:
RAILS ROUTING (new! http://www.awprofessional.com/title/0321509242)
RUBY FOR RAILS (http://www.manning.com/black)
* Ruby/Rails training
& consulting: Ruby Power and Light, LLC (http://www.rubypal.com)

 

[Charles Oliver Nutter]

I agree that it's very odd that the two ways of calling behave
differently. A secondary question is whether the #method behavior --
the dynamic calculation of what method super should look for -- has
any useful application. I can't think of any. Maybe we need "super!"

I can't really think of any either; if you want that sort of
polymorphism on a superclass, you shouldn't use super.

- Charlie

 

[ara.t.howard]

This seems very wrong to me

me too.

-a

 

[Tim Pease]

I posted this to ruby-core and got a somewhat mixed response. I'm
curious what the rest of you might think of this behavior.

-------- Original Message --------
Subject: Bug in Kernel#method objects that call super?
Date: Sat, 07 Jul 2007 05:57:13 +0900
From: Charles Oliver Nutter <[email protected]>
Reply-To: (e-mail address removed)
To: (e-mail address removed)

This seems very wrong to me. Calling through a method object should
behave the same for super as calling directly or calling through an alias:


class Foo
def a; puts 'Foo a'; end
def b; puts 'Foo b'; end
end

class Bar < Foo
def a; puts 'Bar a'; super; end
alias b a
end

Bar.new.a # => "Bar a\nFoo a"
Bar.new.b # => "Bar a\nFoo a"
Bar.new.methodb).call # => "Bar a\nFoo b"


It seems incorrect for method objects to change the behavior of super.
If I super in 'a', I want super's 'a' to be called, without exception.

Can someone confirm this is a bug? In JRuby we always super up the
same-named chain, so this represents an incompatibility.

I think the bug is in alias and not in #method ....

Or at least the bug is brought about by some odd interaction between
alias and #method. My WAG at the problem is that alias creates a copy
of the method :a and renames it method :b in Bar. There is some hint
in the lookup table in class Bar that tells the Ruby interpreter --
"hey, this is really method :a, so super should redirect to method :a
in the superclass".

When #method generates the Proc object, this hinting is not preserved.
So, when super is called, it redirects to method :b in Foo.

Again, just my WAG -- I have not looked at the source code on this one.

Blessings,
TwP