Correctly enforcing abstract!

[marcandre]

It seems that sorbet enforces abstract classes not being instantiated by defining an initialize that raises an error

This initialize apparently does not check what is the class being instantiated, is there a good reason for this?

Moreover, why not define a class method new that raises instead (only if the receiver is the current abstract class)?

The reasons to go this way are:

1. There are valid reasons to have an abstract class that need initialization and/or initial parameters. sorbet shouldn't mess with initialize

2. There are valid cases of an abstract class that does not require special initialization and/or additional parameters. sorbet shouldn't force having a trivial initialize method

3. Calling super from initialize is considered by many a good practice. sorbet should not break this.

Example:

class Foo
  def self.new(*)
    return super unless self == Foo

    raise 'Can not instantiate abstract class'
  end

  def initialize
    @registry = {}
    puts "initialized, ok"
  end
end

class Bar < Foo
end

Foo.new rescue puts 'raised, ok'
Bar.new and puts 'ok'
# prints "ok" 3 times...