Bug #10103

Unable to refine class with CONSTANT

Added by Kyle Decot 8 months ago. Updated 8 months ago.

[ruby-core:<unknown>]
Status:Feedback
Priority:Normal
Assignee:-
ruby -v:2.1.1 Backport:2.0.0: UNKNOWN, 2.1: UNKNOWN

Description

When refining a class (such as String in the following example) it is impossible to assign a constant. The constant will get attached to the module containing the refinement instead of the refined class. When inside of a refine block constants should get assigned to that class.

module Foobar
  refine String do
    FOO = "BAR"

    def foobar
      "foobar"
    end
  end
end

using Foobar

puts "".class::FOO # => uninitialized constant String::FOO (NameError)
puts "".foobar # => "foobar"

History

#1 Updated by Mike Hein 8 months ago

I would like to also mention that this impacts class_variables as well

   module Foobar
     @@baz = "boom"
     refine String do 
       @@foo = "bar"
       def foobar
         @@foo
       end
       def bazical
         @@baz
       end
     end
   end

   using Foobar

   Foobar.class_variables #=> [:@@baz, :@@foo]
   "".bazical #=> "boom"
   "".foobar #=> "bar"

The first one I understand since the block can utilize variables and methods outside of itself. The second one really confuses me as I didn't expect it to skip over String and end up in Foobar. It also does not raise any warning about warning: class variable access from toplevel. Just as I would have expected constants to raise a SyntaxError for dynamic assignment. Instance variables seem to be ignored all together from what I can see.

#2 Updated by Yukihiro Matsumoto 8 months ago

  • Status changed from Open to Feedback

Constants (and class variables) are not included in refinement modification. Constants still belong to outer class.
If we change this, we have to make incompatible change to constant scoping rules.
I don't think its wise.

But maybe above class variables case should be warned, probably.

Matz.

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