ActiveRecord::Error does not allow values to add errors

(Message from #3147 ActiveRecord::Error#full_message broken when used with I18n and autosave asso... by Chris Hapgood)

Briefly: an error on an attribute cannot be set as the result of an exception computing the value of the attribute.

For example:

def v compute_it rescue errors.add(:v, "Dadgummit") end

When compute_it raise an exception, ActiveRecord::Error#initialize references v, which in turn raises another exception, which adds another error, which in turn proves that my stack is not infinitely deep.

Is it reasonable to assume that ActiveRecord::Error instances can reference its erroneous attribute's value? If so, the above pattern won't work and instead a sentinel value will need to be set (U-G-L-Y).