Cache stuff in method matcher => ~20% speedup

lib/mutant/matcher/method.rb

@@ -59,6 +59,14 @@ module Mutant
       #
       attr_reader :method_name
 
+      def self.cache
+        @cache ||= {}
+      end
+
+      def self.ast(file)
+        cache[file] ||= File.read(file).to_ast
+      end
+
     private
 
       # Initialize method filter
@@ -90,7 +98,7 @@ module Mutant
       # @api private
       #
       def ast
-        File.read(source_path).to_ast
+        self.class.ast(source_path)
       end
 
       # Return path to source
@@ -112,6 +120,7 @@ module Mutant
       def source_line
         source_location.last
       end
+      memoize :source_line
 
       # Return source location
       #
@@ -122,6 +131,7 @@ module Mutant
       def source_location
         method.source_location
       end
+      memoize :source_location
 
       # Return matched node
       #