When whoever vs. whomever fails the he/him test [duplicate]

The following example fails the he/him test for whoever/whomever:

Please give the key to whoever needs to open that cabinet.

Give the key to him or he? Give the key to him.

However, when asking who opened that cabinet, he works instead.

So the question, then, is which part of the sentence do we perform the trick on? The predicate is "open that cabinet," which would mean whoever does take on the subject and is correct here. But why isn't "give the key" the predicate?

Solution 1:

The he/him test is much overrated, especially when it comes
without instructions for use in complex sentences.

Let's parse it as a statement, not an order, ok?

• He'll give the key to whoever needs to open that cabinet

is indeed correct. Whomever would be ungrammatical. That follows the actual rule.

The reason why the he/him test doesn't work here is that the wh-ever word is
not only
- after the preposition to (where him would work),
but also
- before the tensed verb needs (where he would work).

So the question is whether the wh-ever word is (respectively)
- the object of the preposition to
or
- the subject of the verb needs.

Elimination gives the answer. It has to be one or the other.

• On the one hand, if it's the object of the preposition, it can't be the subject; but then what is the subject of needs? This is a tensed clause, and they require a subject. That's a problem.

• On the other hand, if it's the subject of needs, then that requirement is filled, but what's the object of to? Well, it's the whole Wh-complement clause (which is in fact a noun phrase and can be an object or a subject) whoever needs to open that cabinet. That clause describes and refers to the indefinite person who is the legitimate receiver of the key, the one who needs it. So that's no problem.

By elimination, then, it's whoever.