class RSpec::Matchers::BuiltIn::ThrowSymbol

def matches?(given_proc)
  begin
    if @expected_symbol.nil?
      given_proc.call
    else
      @caught_arg = catch :proc_did_not_throw_anything do
        catch @expected_symbol do
          given_proc.call
          throw :proc_did_not_throw_anything, :nothing_thrown
        end
      end
      if @caught_arg == :nothing_thrown
        @caught_arg = nil
      else
        @caught_symbol = @expected_symbol
      end
    end
    # Ruby 1.8 uses NameError with `symbol'
    # Ruby 1.9 uses ArgumentError with :symbol
  rescue NameError, ArgumentError => e
    unless e.message =~ /uncaught throw (`|\:)([a-zA-Z0-9_]*)(')?/
      other_exception = e
      raise
    end
    @caught_symbol = $2.to_sym
  rescue => other_exception
    raise
  ensure
    unless other_exception
      if @expected_symbol.nil?
        return !@caught_symbol.nil?
      else
        if @expected_arg.nil?
          return @caught_symbol == @expected_symbol
        else
          return (@caught_symbol == @expected_symbol) & (@caught_arg == @expected_arg)
        end
      end
    end
  end
end