[ruby-core:58712] [Backport 200 - Backport #8872] Case statements do not honor a refinement of the '===' method

Issue #8872 has been updated by jballanc (Joshua Ballanco).


To play devil's advocate, I think the opposing question to be asked is "how would you alter the behavior of case evaluation using refinements"?

It may be, as shugo states, that refinements are not meant to be used for altering the behavior of expressions. In this case, the answer to the question I posed is, simply, "you don't."

That said, I think it is fairly well understood in the Ruby community that "===" is related to case. I've even heard the operator described as "case equality". Playing devil's advocate again, what is the use case for refining "===" if it _doesn't_ affect the evaluation of a case...when clause?
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Backport #8872: Case statements do not honor a refinement of the '===' method
https://bugs.ruby-lang.org/issues/8872#change-43283

Author: jconley88 (Jon Conley)
Status: Assigned
Priority: Normal
Assignee: matz (Yukihiro Matsumoto)
Category: 
Target version: 


=begin
Below, I've redefined the ((|===|)) method of symbol to always return true.  In ((|RefineTest#uses_refinement|)), I call ((|===|)) directly and the refined method is called.  In ((|RefineTest#does_not_use_refinement|)), the ((|===|)) method is called indirectly through a case statement.  If the refined ((|===|)) method was called, the result should be ((*'The refinement was used'*)), but this code currently returns ((*'The refinement was not used'*)).

 module RefineSymbol
   refine Symbol do
     def ===(other)
       true
     end
   end
 end
 
 using RefineSymbol
 
 class RefineTest
   def uses_refinement
     :a === :b
   end
 
   def does_not_use_refinement
     case :a
     when :b
       'The refinement was used'
     else
       'The refinement was not used'
     end
   end
 end
 
 rt = RefineTest.new
 rt.uses_refinement   # => true
 rt.does_not_use_refinement  # => expected 'The refinement was used' but got 'The refinement was not used'
=end



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