Feature #22137: Change `Symbol#to_s` to return frozen strings

• Status: Open
• Assignee: -
• Target version: -

[byroot (Jean Boussier)]

Since Ruby 3.4 ([Feature #20350]) Symbol#to_s returns a chilled string, meaning mutating it emits a deprecation warning.

I believe it's now time to act on this deprecation, I'd like to request that on Ruby 4.1, Symbol#to_s always return a frozen string.

Several very large codebases include Shopify and GitHub have been running with Symbol.alias_method(:to_s, :name) without any compatibility issues whatsoever.

Making this change would allow to progressively get rid of an annoying pattern in performance sensitive code:

arg.is_a?(Symbol) ? arg.name : arg.to_s

[byroot (Jean Boussier)]

• Related to Feature #20350: Return chilled string from Symbol#to_s added

[headius (Charles Nutter)]

Related discussions in https://bugs.ruby-lang.org/issues/16150 where I proposed a way to request frozen strings from to_s. I've always been +1 for all immediate values that return the same string content every time to return frozen strings.

This has shown up as a problem in performance profiles of JRuby apps for decades.