Initialize instance variables before reading them

lib/parslet/atoms/base.rb

@@ -137,7 +137,7 @@ def self.precedence(prec)
   end
   precedence BASE
   def to_s(outer_prec=OUTER)
-    str = @label || to_s_inner(precedence)
+    str = label || to_s_inner(precedence)
     if outer_prec < precedence
       "(#{str})"
     else

lib/parslet/atoms/entity.rb

@@ -16,6 +16,7 @@ def initialize(name, label=nil, &block)
     @name = name
     @label = label
     @block = block
+    @parslet = nil
   end
 
   def try(source, context, consume_all)

lib/parslet/cause.rb

@@ -5,8 +5,8 @@ module Parslet
   #
   class Cause
     def initialize(message, source, pos, children)
-      @message, @source, @pos, @children = 
-        message, source, pos, children
+      @message, @source, @pos, @children, @context =
+        message, source, pos, children, nil
     end
 
     # @return [String, Array] A string or an array of message pieces that 

lib/parslet/source/line_cache.rb

@@ -10,6 +10,7 @@ def initialize
       # but probably make a scan to that position neccessary.
       @line_ends = []
       @line_ends.extend RangeSearch
+      @last_line_end = nil
     end
 
     # Returns a <line, column> tuple for the given input position. Input

lib/parslet/transform.rb

@@ -131,7 +131,7 @@ def rule(expression, &block)
     # Allows accessing the class' rules
     #
     def rules 
-      @__transform_rules || []
+      @__transform_rules ||= []
     end
 
     def inherited(subclass)