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.
47 lines
1.4 KiB
Text
47 lines
1.4 KiB
Text
set_option linter.unusedVariables false
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/-! A variety of matches that failed at some point during the development of the sparse match features. -/
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inductive Finn : Nat → Type where
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| fzero : {n : Nat} → Finn n
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| fsucc : {n : Nat} → Finn n → Finn (n+1)
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def Finn.min (x : Bool) {n : Nat} (m : Nat) : Finn n → (f : Finn n) → Unit
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| fzero, _ => ()
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| _, fzero => ()
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| fsucc i, fsucc j => ()
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def boo (x : Fin 3) : Nat :=
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match x with
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| 0 => 1
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| 1 => 2
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| 2 => 4
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-- This only works if we do not use the sparse cases on when there are no alternatives left
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def List.nth : (as : List α) → (i : Fin as.length) → α
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| a::as, ⟨0, _⟩ => a
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| a::as, ⟨i+1, h⟩ => nth as ⟨i, Nat.lt_of_succ_lt_succ h⟩
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-- set_option trace.Meta.Match.match true
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-- This, taken from the standard library, used to work, but it was
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-- fragile and broke with sparse matching and refacotrings in #11695
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-- and the error message is rather helpful actually
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/--
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error: Missing cases:
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_, (Int.negSucc _), _
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-/
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#guard_msgs in
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example : (a b : Int) → (h : a * b = 0) → a = 0 ∨ b = 0
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| .ofNat 0, _, _ => by simp
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| _, .ofNat 0, _ => by simp
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| .ofNat (a+1), .negSucc b, h => by cases h
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-- We can fix it this way:
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example : (a b : Int) → (h : a * b = 0) → a = 0 ∨ b = 0
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| .ofNat 0, _, _ => by simp
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| _, .ofNat 0, _ => by simp
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| .ofNat (a+1), .negSucc b, h => by cases h
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| .negSucc _, .negSucc _, h => by cases h
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