False negative: eval(params[:code]).to_s is not detected

[Becojo]

Background

Brakeman version: 5.0.1
Rails version: 6.1.3.2
Ruby version: 2.7.2

Link to Rails application code: https://github.com/Becojo/rails-eval-to-s

Issue

Brakeman should report both eval in this code as dangerous but doesn't:

class ApplicationController < ActionController::Base
  def dangerous_eval
    # reported by Brakeman
    eval(params[:code])
  end

  def also_dangerous_eval
    # not reported by Brakeman
    eval(params[:code]).to_s
  end
end

https://github.com/Becojo/rails-eval-to-s/blob/e983dd26f19ec14bedc1c22eb3afd377e098433e/app/controllers/application_controller.rb#L1-L11