34bd6e8bfd
This PR improves the error messages produced by the `split` tactic, including suggesting syntax fixes and related tactics with which it might be confused. Note that, to avoid clashing with the new error message styling conventions used in these messages, this PR also updates the formatting of the message produced by `throwTacticEx`. Closes #6224
50 lines
1.7 KiB
Text
50 lines
1.7 KiB
Text
@[semireducible]
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def sorted_from_var [x: LE α] [DecidableRel x.le] (a: Array α) (i: Nat): Bool :=
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if h: i + 1 < a.size then
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have : i < a.size := Nat.lt_of_succ_lt h
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a[i] ≤ a[i+1] && sorted_from_var a (i + 1)
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else
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true
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termination_by a.size - i
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attribute [irreducible] sorted_from_var
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def check_sorted [x: LE α] [DecidableRel x.le] (a: Array α): Bool :=
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sorted_from_var a 0
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/--
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error: Tactic `rfl` failed: the left-hand side
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check_sorted #[0, 3, 3, 5, 8, 10, 10, 10]
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is not definitionally equal to the right-hand side
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true
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⊢ check_sorted #[0, 3, 3, 5, 8, 10, 10, 10] = true
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-/
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#guard_msgs in
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example: check_sorted #[0, 3, 3, 5, 8, 10, 10, 10] = true := by
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rfl -- fails because `rfl` uses `.default` transparency, and `sorted_from_var` is marked as irreducible
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/--
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error: tactic 'decide' failed for proposition
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check_sorted #[0, 3, 3, 5, 8, 10, 10, 10] = true
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since its 'Decidable' instance
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instDecidableEqBool (check_sorted #[0, 3, 3, 5, 8, 10, 10, 10]) true
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did not reduce to 'isTrue' or 'isFalse'.
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After unfolding the instances 'instDecidableEqBool' and 'Bool.decEq', reduction got stuck at the 'Decidable' instance
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match check_sorted #[0, 3, 3, 5, 8, 10, 10, 10], true with
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| false, false => isTrue ⋯
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| false, true => isFalse ⋯
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| true, false => isFalse ⋯
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| true, true => isTrue ⋯
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-/
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#guard_msgs in
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example: check_sorted #[0, 3, 3, 5, 8, 10, 10, 10] := by
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decide -- fails because `decide` uses `.default` transparency, and `sorted_from_var` is marked as irreducible
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unseal sorted_from_var in
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example: check_sorted #[0, 3, 3, 5, 8, 10, 10, 10] := by
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decide -- works
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example: check_sorted #[0, 3, 3, 5, 8, 10, 10, 10] := by
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with_unfolding_all decide -- should work
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