118160bf07
This PR refactors match compilation, to handle “side-effect free” patterns (`.var`, `.inaccessible`, `.as`) eagerly and for each alternative separately. The idea is that there should be less interplay between different alternatives, and prepares the ground for #11105. This may cause some corner case match statements to compiler or fail compile that behaved differently before. For example, it can now use a sparse case where previously was using a full case, and pattern completeness may not be clear to lean now. On the other hand, using a sparse case can mean that match statements mixing matching in indicies with matching on the indexed datatype can work.
36 lines
1.1 KiB
Text
36 lines
1.1 KiB
Text
set_option pp.mvars false
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inductive N : Type where
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| zero : N
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| succ (n : N) : N
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opaque double (n : N) : N := .zero
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inductive Parity : N -> Type
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| even (n) : Parity (double n)
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| odd (n) : Parity (N.succ (double n))
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-- set_option trace.Meta.Match.matchEqs true
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partial def natToBin3 : (n : N) → Parity n → List Bool
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| .zero, _ => []
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| _, Parity.even j => [false, false]
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| _, Parity.odd j => [true, true]
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/--
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error: Tactic `cases` failed with a nested error:
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Dependent elimination failed: Failed to solve equation
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n✝¹.succ = double n✝
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at case `Parity.even` after processing
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(N.succ _), _
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the dependent pattern matcher can solve the following kinds of equations
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- <var> = <term> and <term> = <var>
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- <term> = <term> where the terms are definitionally equal
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- <constructor> = <constructor>, examples: List.cons x xs = List.cons y ys, and List.cons x xs = List.nil
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-/
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#guard_msgs in
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partial def natToBin4 : (n : N) → Parity n → List Bool
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| .zero, _ => []
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| .succ .zero, _ => []
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| _, Parity.even j => [false, false]
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| _, Parity.odd j => [true, true]
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