"I wish I could stay" vs "I wish I stayed"

Question

I have to work tomorrow but I would like to stay in bed. I wish I ...

1. stayed in bed tomorrow
2. could stay in bed tomorrow

This is a test and the answer is number 2 but why is number 1 wrong?

It implies: unfortunately I won't stay in bed tomorrow so I'm unhappy about it.

Answer 1

The correct answer is indeed #2. The sentence "I have to work tomorrow but I would like to stay in bed." implies that you would rather stay in bed instead of having to work tomorrow but you 'can't'.

Cambridge Grammar says that we use past tense modals would and could to talk about wishes for the future:

• I don’t like my work. I wish I could get a better job.

Sticking to this rule we indeed get:

• I wish I could stay in bed tomorrow.

As a counterexample with "not having to want to work" we get:

• I wish I didn't have to work tomorrow.

The first is incorrect because:

We use past tense forms to talk about wishes for the present:

• I don’t like this place. I wish I lived in somewhere more interesting.
• I wish it wasn’t so cold.

Answer 2

Well, you're talking about the future here, aren't you? I don't know how to explain this properly, but if you were to say "I wish I stayed in bed" and left out "tomorrow", as soon as I heard it, it would sound like a past-tense action. But when you tack "tomorrow" on the end, it really does throw you for a loop. Now, your brain just can't reconcile the the idea that you thought you were talking about something that happened in the past and the fact, as it now turns out, that you're speaking about something that should happen in the near future. In principle, this sounds similar to "I didn't do my homework tomorrow". You've got a huge semantic problem there.

Think semantics, not grammar. For example:

I wish I wasn't there tomorrow.

sounds completely wrong. Past and future things don't go together.

However:

I wish I didn't have to be there tomorrow.

sounds very natural. Here you're expressing something that will happen in the future by means of past-tense grammar.

I think that's enough of that. Anyway, to express actions that might happen in the future, we often use modals like could.

Example:

I wish I could go to France with you guys next year.

Though I think I hope would sound better in my example as well as in yours.

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PS: Your problem is that you're trying to follow grammar prescribed in grammar books to a tee. But as it often the case, things are much subtler when it comes to natural speech. You need listening and as well as speaking experience to be able to recognize what sounds right and what sounds wrong.