I saw one phrase:
He will have eaten it until it made him sick.
Why don't we say ...until it makes him sick?
I saw this rule under Time words with no future forms: by the time, until, as soon as, when (except for questions), etc) in Round Up 5.
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The future perfect simple is a funny tense, and since it is a future tense, I can see why you might expect to use the word will.
However, it's not quite that simple. We use the perfective will have when we are looking back from a point in time when something will have already happened. Therefore, what follows is in the past tense.
By the time he gets home, he will have played for six hours hours in the park.
I would love to go out for dessert with you after the feast, but I will have had too much to eat by then. I'm afraid I wouldn't have room in my tummy for any more food!