Change class evaluation for Rationals in cast_value

activerecord/lib/active_record/type/decimal.rb

@@ -14,14 +14,16 @@ def type_cast_for_schema(value)
       private
 
       def cast_value(value)
-        if value.class == Rational
-          BigDecimal.new(value, precision.to_i)
-        elsif value.respond_to?(:to_d)
+        case value
+        when Numeric, String, Rational
+          BigDecimal(value, precision.to_i)
+        when proc { value.respond_to?(:to_d) }
           value.to_d
         else
-          value.to_s.to_d
+          cast_value(value.to_s)
         end
       end
+
     end
   end
 end

activerecord/test/cases/types_test.rb

@@ -103,7 +103,7 @@ def test_type_cast_decimal
       end
 
       def test_type_cast_rational_to_decimal_with_precision
-        type = Type::Decimal.new(:precision => 2)
+        type = Type::Decimal.new(precision: 2)
         assert_equal BigDecimal("0.33"), type.type_cast_from_user(Rational(1, 3))
       end