I still don’t agree. In the sentence we are referencing, “to code” is not the verb. “to rest” is the verb.

It’s like the sentence “Give the recipe to whomever has to cook the meal.” In this sentence “to give” is the verb and “to whomever has to cook the meal” is the prepositional phrase, not the subject. So you would not use the subjective case.

I think it is actually whomever in this case. “Whom” is the objective case and in this sentence it serves as the object of the preposition “to.”