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
55 lines
1.6 KiB
Text
55 lines
1.6 KiB
Text
def step (state: Nat): Option Nat :=
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if state = 0 then none else some (state - 1)
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set_option linter.unusedVariables false
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def countdown (state: Nat) :=
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match h: step state with
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| none => [state]
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| some newState => state :: countdown newState
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termination_by state
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decreasing_by sorry
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/--
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error: Tactic `split` failed: Could not split an `if` or `match` expression in the goal
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state : Nat
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p :
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(match h : step state with
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| none => [state]
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| some newState => state :: countdown newState) ≠
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[]
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⊢ (match h : step state with
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| none => [state]
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| some newState => state :: countdown newState).head
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p =
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state
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---
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trace: [split.failure] `split` tactic failed to generalize discriminant(s) at
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match h : step state with
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| none => [state]
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| some newState => state :: countdown newState
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resulting expression was not type correct
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possible solution: generalize discriminant(s) manually before using `split`
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-/
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#guard_msgs in
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example (state: Nat) (p : (match h : step state with
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| none => [state]
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| some newState => state :: countdown newState) ≠
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[]): (match h : step state with
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| none => [state]
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| some newState => state :: countdown newState).head
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p =
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state := by
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set_option trace.split.failure true in
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split
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example (state: Nat) (p : (match h : step state with
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| none => [state]
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| some newState => state :: countdown newState) ≠
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[]): (match h : step state with
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| none => [state]
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| some newState => state :: countdown newState).head
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p =
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state := by
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split at p <;> simp
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