local_detector.rb

require "ripper"

class LocalDetector < ::Ripper
  Ident = Struct.new(:value)

  attr_reader :vcalls, :var_assigns, :var_refs

  def initialize(code)
    @vcalls = Set.new
    @var_assigns = Set.new
    @var_refs = Set.new
    super(code)
  end

  def possible_locals
    @vcalls | @var_assigns | @var_refs
  end

  def on_var_field(name, *args)
    @var_assigns << name.value if Ident === name
    super
  end

  def on_var_ref(name, *args)
    @var_refs << name.value if Ident === name
    super
  end

  def on_vcall(name, *args)
    @vcalls << name.value if Ident === name
    super
  end

  def on_ident(value)
    Ident.new(value)
  end

  def self.call(src)
    parser = new(src)
    parser.parse
    parser
  end
end