Issue #14336 has been updated by dsferreira (Daniel Ferreira).


There is also one important thing here that deserves consideration: We are doing a great effort to improve the performance of strings and everything associated to them.

Symbols are not taking advantage of those improvements.

If we keep saying that everything is a Symbol except user input we will be constraining ourselves to use less performant code. Correct me if I”Ēm wrong but if I”Ēm not mistaken immutable strings can be more performant then symbols, not to mention the memory consumption. 

By merging symbols into strings we can focus all our efforts in improving string”Ēs performance leaving symbols out of the equation.

I only see positive things here.

The transition path that I present will make sure that no code will be broken.




----------------------------------------
Bug #14336: Create new method String#symbol? and deprecate Symbol class
https://bugs.ruby-lang.org/issues/14336#change-69444

* Author: dsferreira (Daniel Ferreira)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: 
* Backport: 2.3: UNKNOWN, 2.4: UNKNOWN, 2.5: UNKNOWN
----------------------------------------
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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