Error if Start rule not found

lib/imbecile/generator.rb

@@ -22,6 +22,9 @@ module Imbecile
         rule_names[rule.name] ||= []
         rule_names[rule.name] << rule
       end
+      unless rule_names["Start"]
+        raise Error.new("Start rule not found")
+      end
       lexer_dfa = LexerDFA.new(@grammar.tokens)
       classname = @grammar.classname || output_file.sub(%r{[^a-zA-Z0-9].*}, "").capitalize
       erb = ERB.new(File.read(File.join(File.dirname(File.expand_path(__FILE__)), "../../assets/parser.d.erb")), nil, "<>")

lib/imbecile/grammar/rule.rb

@@ -3,6 +3,8 @@ module Imbecile
 
     class Rule
 
+      attr_reader :components
+
       def initialize(name, rule, code)
         @name = name
         rule_components = rule.split(/\s+/)