[ruby-core:113360] [Ruby master Feature#19520] Support for `Module.new(name)` and `Class.new(superclass, name)`.

Issue #19520 has been updated by Dan0042 (Daniel DeLorme).


ioquatix (Samuel Williams) wrote in #note-33:
> @Dan0042 unfortunately your proposal doesn't really work for nested classes without major performance issues.

I sort of understand what you mean, but I think it's premature to dismiss an idea just based on the fear that it **might** have bad performance. The focus should be on whether the design/API is ok. Then **if** the implementation turns out measurably too slow **and** there is no way to remedy, the idea can be scrapped.

But let's say it really is too slow to do a `rb_funcall` for each nested namespace; I can already think of an easy way to mitigate that: only call #to_s if #name is undefined. That way, performance will be unchanged for regular classes assigned to constants. And that's just the first workaround that came to mind; there may even be other ways.

```ruby
x = Class.new
x.new.inspect #=> #<#<Class:0x00005597d624bd28>:0x00005597d61aa3d8>
def x.to_s; "hey"; end
x.new.inspect #=> #<hey:0x00005597d6860998>
NAMED = x
x.new.inspect #=> #<NAMED:0x00005597d6845968>
```

----------------------------------------
Feature #19520: Support for `Module.new(name)` and `Class.new(superclass, name)`.
https://bugs.ruby-lang.org/issues/19520#change-102923

* Author: ioquatix (Samuel Williams)
* Status: Open
* Priority: Normal
----------------------------------------
See <https://bugs.ruby-lang.org/issues/19450> for previous discussion and motivation.

[This proposal](https://github.com/ruby/ruby/pull/7376) introduces the `name` parameter to `Class.new` and `Module.new`:

```ruby
Class.new(superclass, name)
Module.new(name)
```

As a slight change, we could use keyword arguments instead.

## Example usage

The current Ruby test suite has code which shows the usefulness of this new method:

```ruby
  def labeled_module(name, &block)
    Module.new do
      singleton_class.class_eval {
        define_method(:to_s) {name}
        alias inspect to_s
        alias name to_s
      }
      class_eval(&block) if block
    end
  end
  module_function :labeled_module

  def labeled_class(name, superclass = Object, &block)
    Class.new(superclass) do
      singleton_class.class_eval {
        define_method(:to_s) {name}
        alias inspect to_s
        alias name to_s
      }
      class_eval(&block) if block
    end
  end
  module_function :labeled_class
```

The updated code would look like this:

```ruby
  def labeled_module(name, &block)
    Module.new(name, &block)
  end

  def labeled_class(name, superclass = Object, &block)
    Class.new(superclass, name, &block)
  end
  module_function :labeled_class
```



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