c7f57d6a0b
This PR improves match compilation: Branch on variables in the order suggested by the first remaining alternative, and do not branch when the first remaining alternative does not require it. This fixes https://github.com/leanprover/lean4/issues/10749. With `set_option backwards.match.rowMajor false` the old behavior can be turned on. (For now this is an experiment to get familiar with the code and the whole problem domain. It is likely overly naive.)
36 lines
870 B
Text
36 lines
870 B
Text
/--
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error: Dependent elimination failed: Type mismatch when solving this alternative: it has type
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motive false
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but is expected to have type
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motive b✝
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-/
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#guard_msgs in
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def test1 b := match b with
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| .(false) => 1
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| true => 2
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/--
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error: Dependent elimination failed: Type mismatch when solving this alternative: it has type
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motive false ⋯
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but is expected to have type
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motive x✝¹ x✝
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-/
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#guard_msgs in
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def test2 : (b : Bool) → (h : b = false) → Nat
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| .(false), .(rfl) => 1
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| true, _ => 2
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-- works
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def test3 : (b : Bool) → (h : b = false) → Nat
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| .(false), rfl => 1
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/--
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@ +3:4...11
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error: Redundant alternative: Any expression matching
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true, x✝
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will match one of the preceding alternatives
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-/
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#guard_msgs (positions := true) in
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def test4 : (b : Bool) → (h : b = false) → Nat
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| .(false), rfl => 1
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| true, _ => 2 -- error here
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