Decrease string allocations in apply_inflections

In `apply_inflections` a string is down cased and some whitespace stripped in the front (which allocate strings). This would normally be fine, however `uncountables` is a fairly small array (10 elements out of the box) and this method gets called a TON. Instead we can keep an array of valid regexes for each uncountable so we don't have to allocate new strings.

This change buys us 325,106 bytes of memory and 3,251 fewer objects per request.

activesupport/lib/active_support/inflector/inflections.rb

@@ -27,14 +27,45 @@ module Inflector
     class Inflections
       @__instance__ = ThreadSafe::Cache.new
 
+      class Uncountables < Array
+        def initialize
+          @regex_array = []
+          super
+        end
+
+        def delete(entry)
+          super entry
+          @regex_array.delete(to_regex(entry))
+        end
+
+        def <<(*word)
+          add(word)
+        end
+
+        def add(words)
+          self.concat(words.flatten.map(&:downcase))
+          @regex_array += self.map {|word|  to_regex(word) }
+          self
+        end
+
+        def uncountable?(str)
+          @regex_array.detect {|regex| regex.match(str) }
+        end
+
+        private
+          def to_regex(string)
+            /\b#{::Regexp.escape(string)}\Z/i
+          end
+      end
+
       def self.instance(locale = :en)
         @__instance__[locale] ||= new
       end
 
       attr_reader :plurals, :singulars, :uncountables, :humans, :acronyms, :acronym_regex
 
       def initialize
-        @plurals, @singulars, @uncountables, @humans, @acronyms, @acronym_regex = [], [], [], [], {}, /(?=a)b/
+        @plurals, @singulars, @uncountables, @humans, @acronyms, @acronym_regex = [], [], Uncountables.new, [], {}, /(?=a)b/
       end
 
       # Private, for the test suite.
@@ -160,7 +191,7 @@ def irregular(singular, plural)
       #   uncountable 'money', 'information'
       #   uncountable %w( money information rice )
       def uncountable(*words)
-        @uncountables += words.flatten.map(&:downcase)
+        @uncountables.add(words)
       end
 
       # Specifies a humanized form of a string by a regular expression rule or
@@ -185,7 +216,7 @@ def human(rule, replacement)
       def clear(scope = :all)
         case scope
           when :all
-            @plurals, @singulars, @uncountables, @humans = [], [], [], []
+            @plurals, @singulars, @uncountables, @humans = [], [], Uncountables.new, []
           else
             instance_variable_set "@#{scope}", []
         end

activesupport/lib/active_support/inflector/methods.rb

@@ -354,7 +354,7 @@ def ordinalize(number)
     #   const_regexp("Foo::Bar::Baz") # => "Foo(::Bar(::Baz)?)?"
     #   const_regexp("::")            # => "::"
     def const_regexp(camel_cased_word) #:nodoc:
-      parts = camel_cased_word.split("::")
+      parts = camel_cased_word.split("::".freeze)
 
       return Regexp.escape(camel_cased_word) if parts.blank?
 
@@ -372,7 +372,7 @@ def const_regexp(camel_cased_word) #:nodoc:
     def apply_inflections(word, rules)
       result = word.to_s.dup
 
-      if word.empty? || inflections.uncountables.include?(result.downcase[/\b\w+\Z/])
+      if word.empty? || inflections.uncountables.uncountable?(result)
         result
       else
         rules.each { |(rule, replacement)| break if result.sub!(rule, replacement) }