61186629d6
This PR implements the option `revert`, which is set to `false` by default. To recover the old `grind` behavior, you should use `grind +revert`. Previously, `grind` used the `RevSimpIntro` idiom, i.e., it would revert all hypotheses and then re-introduce them while simplifying and applying eager `cases`. This idiom created several problems: * Users reported that `grind` would include unnecessary parameters. See [here](https://leanprover.zulipchat.com/#narrow/channel/270676-lean4/topic/Grind.20aggressively.20includes.20local.20hypotheses.2E/near/554887715). * Unnecessary section variables were also being introduced. See the new test contributed by Sebastian Graf. * Finally, it prevented us from supporting arbitrary parameters as we do in `simp`. In `simp`, I implemented a mechanism that simulates local universe-polymorphic theorems, but this approach could not be used in `grind` because there is no mechanism for reverting (and re-introducing) local universe-polymorphic theorems. Adding such a mechanism would require substantial work: I would need to modify the local context object. I considered maintaining a substitution from the original variables to the new ones, but this is also tricky, because the mapping would have to be stored in the `grind` goal objects, and it is not just a simple mapping. After reverting everything, I would need to keep a sequence of original variables that must be added to the mapping as we re-introduce them, but eager case splits complicate this quite a bit. The whole approach felt overly messy. The new behavior `grind -revert` addresses all these issues. None of the `grind` proofs in our test suite broke after we fixed the bugs exposed by the new feature. That said, the traces and counterexamples produced by `grind` are different. The new proof terms are also different.
23 lines
662 B
Text
23 lines
662 B
Text
module
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/--
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trace: [grind.eqResolution] ∀ (x : Nat), p x a → ∀ (y : Nat), p y b → ¬x = y, ∀ (y : Nat), p y a → p y b → False
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[grind.ematch.instance] h: p c a → p c b → c ≠ c
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[grind.ematch.instance] local_0: p c a → ¬p c b
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-/
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#guard_msgs (trace) in
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example
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(p : Nat → Nat → Prop)
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(a b c : Nat)
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(h : ∀ x, p x a → ∀ y, p y b → x ≠ y)
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(h₁ : p c a)
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(h₂ : p c b)
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: False := by
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set_option trace.grind.eqResolution true in
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set_option trace.grind.ematch.instance true in
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grind
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example
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(f : Nat → Nat)
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(h : ∀ x y, f x = f y → x = y)
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: f (f a) = f (f b) → a = b := by
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grind only
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