ActiveSupport::Concern and Sorbet RBI solution

all_cached_model_concern.rb

# typed: true

module AllCachedModelConcern
  extend ActiveSupport::Concern

  included do
    after_save(:clear_all_cached!)
    after_destroy(:clear_all_cached!)
  end

  def clear_all_cached!
    self.class.all_cached_backend.delete(self.class.all_cached_key) if self.class.all_cached_backend
  end

  class_methods do
    def all_cached_key
      "#{self}:all_cached"
    end

    def cached_find(id)
      cached_find_all([id]).first
    end

    def cached_find!(id)
      cached_find(id) || raise(ActiveRecord::RecordNotFound, "Couldn't find #{self} with ID=#{id}")
    end

    def cached_find_all(ids)
      all_cached.select { |record| ids.map(&:to_i).include?(record.id) }
    end

    def all_cached
      if all_cached_backend.nil?
        order("id ASC").to_a
      else
        all_cached_backend.fetch(all_cached_key, expires_in: 5.minutes) { order("id ASC").to_a }
      end
    end

    def all_cached_backend
      Rails.cache
    end
  end
end

all_cached_model_concern.rbi

# typed: true

module AllCachedModelConcern
  extend ::ActiveSupport::Concern
  extend T::Sig
  extend T::Helpers

  requires_ancestor { T.class_of(ActiveRecord::Base) }
  requires_ancestor { Kernel }

  sig { void }
  def clear_all_cached!; end

  module ClassMethods
    extend T::Sig
    extend T::Helpers
    requires_ancestor { T.class_of(ActiveRecord::Base) }
    requires_ancestor { Kernel }
    TIdParam = T.type_alias { T.any(String, Integer) }
    TSelf = T.type_alias { T.self_type }

    sig { returns(String) }
    def all_cached_key; end

    sig { params(id: TIdParam).returns(T.nilable(TSelf)) }
    def cached_find(id); end

    sig { params(id: TIdParam).returns(TSelf) }
    def cached_find!(id); end

    sig { returns(T::Array[TSelf]) }
    def all_cached; end

    sig { params(ids: T::Array[TIdParam]).returns(T::Array[TSelf]) }
    def cached_find_all(ids); end

    sig { returns(ActiveSupport::Cache::Store) }
    def all_cached_backend; end
  end

  mixes_in_class_methods(ClassMethods)
end

nuts... I was wondering if that was the case (re: T.bind being required, and no RBI solution)

As for the T.self_type, I believe the issue is in returning an T::Array of the T.self_type. Both approaches I tried below failed:

https://sorbet.run/?arg=--enable-experimental-requires-ancestor#%23%20typed%3A%20true%0A%0Amodule%20Foo%0A%20%20%20%20extend%20T%3A%3AHelpers%0A%0A%20%20%20%20module%20ClassMethods%0A%20%20%20%20%20%20%20%20extend%20T%3A%3ASig%0A%0A%20%20%20%20%20%20%20%20TSelf%20%3D%20T.type_alias%20%7B%20T.self_type%20%7D%0A%0A%20%20%20%20%20%20%20%20sig%20%7B%20returns%28T%3A%3AArray%5BT.self_type%5D%29%20%7D%0A%20%20%20%20%20%20%20%20def%20foo%3B%20%5Bself%2C%20self%5D%3B%20end%0A%0A%20%20%20%20%20%20%20%20sig%20%7B%20returns%28T%3A%3AArray%5BTSelf%5D%29%20%7D%0A%20%20%20%20%20%20%20%20def%20bar%3B%20%5Bnew%2C%20new%5D%3B%20end%0A%20%20%20%20end%0A%0A%20%20%20%20mixes_in_class_methods%28ClassMethods%29%0Aend%0A%0Aclass%20Bar%0A%20%20%20%20include%20Foo%0Aend%0A%0A%0AT.reveal_type%20Bar.foo%0AT.reveal_type%20Bar.bar