After updating from 3.0.15 to 3.1.0 I am now having validation issues when using Symbol fields. If you set a field to a string value then it gets properly converted to a symbol, however validation_inclusion_of fails.

For example:

class Example
include Mongoid::Document
field :name, type: Symbol
validates_inclusion_of :name, in: [:foo]
end

example = Example.new

1. this works
   example.name = :foo
   example.valid? # => true

1. but this fails
   example.name = "foo"
   example.name == :foo #=> true - string properly gets auto-converted to a symbol
   example.valid? #=> false - string version seems to be getting compared on validation