Use the correct values for int max and min

We had accidentally gone one power of two too far. In addition, we need
to handle minimum values as well as the maximum.

1 files changed, 13 insertions, 9 deletions

diff --git a/activerecord/lib/active_record/type/integer.rb b/activerecord/lib/active_record/type/integer.rb
index 2b0f0b2734..d69e5b3f28 100644
--- a/activerecord/lib/active_record/type/integer.rb
+++ b/activerecord/lib/active_record/type/integer.rb
@@ -3,12 +3,21 @@ module ActiveRecord
     class Integer < Value # :nodoc:
       include Numeric
 
+      def initialize(*)
+        super
+        @range = -max_value...max_value
+      end
+
       def type
         :integer
       end
 
       alias type_cast_for_database type_cast
 
+      protected
+
+      attr_reader :range
+
       private
 
       def cast_value(value)
@@ -17,25 +26,20 @@ module ActiveRecord
         when false then 0
         else
           result = value.to_i rescue nil
-          ensure_below_max(result) if result
+          ensure_in_range(result) if result
           result
         end
       end
 
-      def ensure_below_max(value)
-        if value > max_value
+      def ensure_in_range(value)
+        unless range.cover?(value)
           raise RangeError, "#{value} is too large for #{self.class} with limit #{limit || 4}"
         end
       end
 
       def max_value
-        @max_value = determine_max_value unless defined?(@max_value)
-        @max_value
-      end
-
-      def determine_max_value
         limit = self.limit || 4
-        2 << (limit * 8 - 1) # 8 bits per byte with one bit for sign
+        1 << (limit * 8 - 1) # 8 bits per byte with one bit for sign
       end
     end
   end