[ruby-core:84824] [Ruby trunk Feature#14336] Create new method String#symbol? and deprecate Symbol class

Issue #14336 has been updated by rosenfeld (Rodrigo Rosenfeld Rosas).


Thank you for confirming, Daniel. Indeed it seems the confusion would be about the same except that it seems symbols are seldom used in Smalltalk from what I've read in this thread. But it's good to know that Ruby and Smalltalk symbols vs strings comparison are pretty similar to each other, even if symbols are inherited from strings in Smalltalk while they are not in Ruby. It doesn't make much difference in practice, since many string operations don't make much sense for symbols in my opinion and since symbols wouldn't compare to strings in Smalltalk either. Thank you for your research and explanations :)

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Feature #14336: Create new method String#symbol? and deprecate Symbol class
https://bugs.ruby-lang.org/issues/14336#change-69537

* Author: dsferreira (Daniel Ferreira)
* Status: Rejected
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
From  the discussions on the three previous issues related to the String vs Symbol subject ([5964](https://bugs.ruby-lang.org/issues/5964), [7792](https://bugs.ruby-lang.org/issues/7792), [14277](https://bugs.ruby-lang.org/issues/14277)) there are some conclusions we can assume:
* Current String vs Symbol is not the ideal scenario. See: Matz and Koichi comments.
* Current philosophy is to use Symbols as identifiers and Strings when strings are needed.
* Current situation is that Symbols are being used in many code bases as strings except for strings that really need the String methods.
* Current situation is that we are designing APIs to handle both String and Symbol inputs forcing an overhead of API development.

I propose the deprecation of `Symbol` class and the introduction of `String#symbol?`.

```ruby
foo = :foo
foo.class # => String
foo.symbol? # => true
bar = "bar"
bar.class # => String
bar.symbol? # => false
```

For backwards compatibility transition path I propose:

```ruby
class Symbol
  def self.===(var)
    warn ("Warning message regarding deprecated class")
    if var.class == Symbol
      true
    elsif var.class == String && var.symbol?
      true
    else
      false
    end
  end
end

class String
  def is_a?(klass)
    case klass
    when String
      true
    when Symbol
      self.symbol?
    else
      false
    end
  end
end
```



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