27e5e21bfe
This PR changes how sparse case expressions represent the none-of-the-above information. Instead of of many `x.ctorIdx ≠ i` hypotheses, it introduces a single `Nat.hasNotBit mask x.ctorIdx` hypothesis which compresses that information into a bitmask. This avoids a quadratic overhead during splitter generation, where all n assumptions would be refined through `.subst` and `.cases` constructions for all n assumption of the splitter alternative. The definition of `Nat.hasNotBit` uses `Nat.rightShift` which is fiddly to get to reduce well, especially on open terms and with `Meta.whnf`. Some experimentation was needed to find proof terms that work, these are all put together in the `Lean.Meta.HasNotBit` module. Fixes #11183 --------- Co-authored-by: Rob23oba <152706811+Rob23oba@users.noreply.github.com>
45 lines
1.3 KiB
Text
45 lines
1.3 KiB
Text
import Lean
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/-- info: test._sparseCasesOn_1 -/
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#guard_msgs in
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run_meta
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Lean.withDeclNameForAuxNaming `test do
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let name ← Lean.Meta.mkSparseCasesOn ``Lean.Expr #[``Lean.Expr.fvar, ``Lean.Expr.sort]
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Lean.logInfo m!"{name}"
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/--
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info: test._sparseCasesOn_1.{u} {motive : Lean.Expr → Sort u} (t : Lean.Expr)
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(fvar : (fvarId : Lean.FVarId) → motive (Lean.Expr.fvar fvarId))
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(sort : (u : Lean.Level) → motive (Lean.Expr.sort u)) : (Nat.hasNotBit 10 t.ctorIdx → motive t) → motive t
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-/
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#guard_msgs in
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#check test._sparseCasesOn_1
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/-- error: mkSparseCasesOn: unexpected number of universe parameters in `Or.casesOn` -/
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#guard_msgs in
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run_meta
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Lean.withDeclNameForAuxNaming `test do
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let name ← Lean.Meta.mkSparseCasesOn ``Or #[``Or.inl]
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Lean.logInfo m!"{name}"
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/- Check that the compiler is producin good code -/
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set_option trace.Compiler.saveBase true
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/--
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trace: [Compiler.saveBase] size: 7
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def testDecl motive t fvar sort x.1 : motive lcAny :=
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cases t : motive lcAny
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| Lean.Expr.fvar fvarId =>
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let _x.2 := fvar fvarId;
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return _x.2
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| Lean.Expr.sort u =>
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let _x.3 := sort u;
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return _x.3
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| _ =>
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let _x.4 := x.1 _;
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return _x.4
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-/
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#guard_msgs in
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def testDecl := @test._sparseCasesOn_1
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