84f15ac93a
This PR fixes a bug in `simp` where it was not resetting the set of zeta-delta reduced let definitions between `simp` calls. It also fixes a bug where `simp` would report zeta-delta reduced let definitions that weren't given as simp arguments (these extraneous let definitions appear due to certain processes temporarily setting `zetaDelta := true`). This PR also modifies the metaprogramming interface for the zeta-delta tracking functions to be re-entrant and to prevent this kind of no-reset bug from occurring again. Closes #6655. Re-entrance of this metaprogramming interface is not needed to fix #6655, but it is needed for some future PRs. The `tests/lean/run/6655.lean` file has an example of a deficiency of `simp?`, where `simp?` still over-reports unfolded let declarations. This is likely due to `withInferTypeConfig` setting `zetaDelta := true` from within `isDefEq`, but I did not verify this. This PR supersedes #7539. The difference is that this PR has `withResetZetaDeltaFVarIds` save and restore `zetaDeltaFVarIds`, but that PR saves and then extends `zetaDeltaFVarIds` to persist unfolded fvars. The behavior in this PR lets metaprograms control whether they want to persist any of the unfolded fvars in this context themselves. In practice, metaprograms that use `withResetZetaDeltaFVarIds` are creating many temporary fvars and are doing dependence computations. These temporary fvars shouldn't be persisted, and also dependence shouldn't be inferred from the fact that a dependence calculation was done. (Concrete example: the let-to-have transformation in an upcoming PR can be run from within simp. Just because let-to-have unfolds an fvar while calculating dependencies of lets doesn't mean that this fvar should be included by `simp?`.)
109 lines
2.3 KiB
Text
109 lines
2.3 KiB
Text
/-!
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# Improve zeta-delta tracking for `simp?`
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https://github.com/leanprover/lean4/issues/6655 reports issues with `simp?` where
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it would over-report local variables. This comes down to two kinds of issues:
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- zeta-delta tracking wasn't being reset, so previous `simp?`s would contribute variables
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- `simp?` would report variables that weren't explicitly mentioned,
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because `whnf` would be run with different configurations during the tracking.
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(e.g. `withInferTypeConfig` enables `zetaDelta`.)
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This file tests that it resets the tracking and filters the list.
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-/
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/-!
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Example from #6655. This used to suggest `simp only [e, d]`.
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-/
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/--
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info: Try this: simp only [e]
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---
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trace: α : Type
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c : α → α
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x : α
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d : α → α := c
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e : α → α := d
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⊢ d x = x
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---
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warning: declaration uses 'sorry'
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-/
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#guard_msgs in
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example {α : Type} (c : α → α) (x : α) : c x = x := by
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let d := c
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let e := d
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change e x = x
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simp? [e]
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trace_state
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sorry
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/-!
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Example from #6655. This used to suggest `simp only [d]`.
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-/
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/--
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info: Try this: simp only
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---
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warning: declaration uses 'sorry'
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-/
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#guard_msgs in
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example {α : Type} (c : α → α) (x : α) : c x = x := by
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let d := c
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change d x = x
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simp [d]
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have : x = x := by
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simp?
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sorry
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/-!
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Example from comments of #6655. This used to suggest `simp only [Int.add_sub_cancel, p]`.
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(N.B. the goal at that point does not have `p` in it!)
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-/
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/-- info: Try this: simp only [Int.add_sub_cancel] -/
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#guard_msgs in
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example (a b : Int) : a + b - b = a := by
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let p := 1
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have h : p = 1 := by
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simp only [p]
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simp?
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/-!
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Example from https://github.com/leanprover/lean4/pull/7539 by JovanGerb.
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This used to suggest `simp only [a, b] ` and `simp only [a, b]`
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-/
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/--
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info: Try this: simp only [a]
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---
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info: Try this: simp only
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-/
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#guard_msgs in
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example : True := by
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let a := 1
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let b := 2
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have : b = 2 := by simp [a,b]
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have : a = 1 := by simp? [a]
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have : 1 = 1 := by simp?
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trivial
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/-!
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Test that there is still a deficiency. This should say `simp only [e]`.
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-/
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/--
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info: Try this: simp only [e, c]
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---
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trace: α : Type
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b : α → α
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x : α
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c : α → α := b
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d : α → α := c
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e : α → α := d
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⊢ d x = x
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---
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warning: declaration uses 'sorry'
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-/
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#guard_msgs in
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example {α : Type} (b : α → α) (x : α) : b x = x := by
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let c := b
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let d := c
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let e := d
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change e x = x
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simp? [e, c]
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trace_state
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sorry
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