29298c9f30
This PR allows `simp` to recognize and warn about simp lemmas that are likely looping in the current simp set. It does so automatically whenever simplification fails with the dreaded “max recursion depth” error fails, but it can be made to do it always with `set_option linter.loopingSimpArgs true`. This check is not on by default because it is somewhat costly, and can warn about simp calls that still happen to work. This closes #5111. In the end, this implemented much simpler logic than described there (and tried in the abandoned #8688; see that PR description for more background information), but it didn’t work as well as I thought. The current logic is: “Simplify the RHS of the simp theorem, complain if that fails”. It is a reasonable policy for a Lean project to say that all simp invocation should be so that this linter does not complain. Often it is just a matter of explicitly disabling some simp theorems from the default simp set, to make it clear and robust that in this call, we do not want them to trigger. But given that often such simp call happen to work, it’s too pedantic to impose it on everyone.
399 lines
11 KiB
Text
399 lines
11 KiB
Text
set_option linter.unusedSimpArgs false
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axiom testSorry : α
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opaque a : Nat
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opaque b : Nat
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theorem ab : a = b := testSorry
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theorem ba : b = a := testSorry
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theorem aa : a = id a := testSorry
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/--
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warning: Possibly looping simp theorem: `aa`
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Note: Possibly caused by: `id`
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Hint: You can disable a simp theorem from the default simp set by passing `- theoremName` to `simp`.
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---
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error: tactic 'simp' failed, nested error:
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maximum recursion depth has been reached
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use `set_option maxRecDepth <num>` to increase limit
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use `set_option diagnostics true` to get diagnostic information
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-/
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#guard_msgs in
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example : id a = 23 := by simp -failIfUnchanged only [aa, id]
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-- also simp_all
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/--
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warning: Possibly looping simp theorem: `aa`
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Note: Possibly caused by: `id`
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Hint: You can disable a simp theorem from the default simp set by passing `- theoremName` to `simp`.
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---
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error: tactic 'simp' failed, nested error:
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maximum recursion depth has been reached
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use `set_option maxRecDepth <num>` to increase limit
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use `set_option diagnostics true` to get diagnostic information
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-/
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#guard_msgs in
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example : id a = 23 := by simp_all -failIfUnchanged only [aa, id]
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-- Other exceptions do not trigger the loop check
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/--
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error: unsolved goals
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⊢ b = 23
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-/
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#guard_msgs in
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example : id b = 23 := by simp -failIfUnchanged only [aa, id]
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/--
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warning: Possibly looping simp theorem: `aa`
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Note: Possibly caused by: `id`
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Hint: You can disable a simp theorem from the default simp set by passing `- theoremName` to `simp`.
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note: this linter can be disabled with `set_option linter.loopingSimpArgs false`
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---
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error: unsolved goals
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⊢ b = 23
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-/
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#guard_msgs in
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set_option linter.loopingSimpArgs true in
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example : id b = 23 := by simp -failIfUnchanged only [aa, id]
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/-- error: simp made no progress -/
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#guard_msgs in
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example : b = 23 := by simp only [aa, id]
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/--
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warning: Possibly looping simp theorem: `ab`
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Note: Possibly caused by: `ba`
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Hint: You can disable a simp theorem from the default simp set by passing `- theoremName` to `simp`.
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---
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warning: Possibly looping simp theorem: `ba`
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Note: Possibly caused by: `ab`
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Hint: You can disable a simp theorem from the default simp set by passing `- theoremName` to `simp`.
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---
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error: tactic 'simp' failed, nested error:
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maximum recursion depth has been reached
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use `set_option maxRecDepth <num>` to increase limit
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use `set_option diagnostics true` to get diagnostic information
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-/
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#guard_msgs in
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example : a = 23 := by simp -failIfUnchanged [ab, ba]
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/--
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warning: Possibly looping simp theorem: `ab`
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Note: Possibly caused by: `ba`
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Hint: You can disable a simp theorem from the default simp set by passing `- theoremName` to `simp`.
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---
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warning: Possibly looping simp theorem: `ba`
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Note: Possibly caused by: `ab`
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Hint: You can disable a simp theorem from the default simp set by passing `- theoremName` to `simp`.
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---
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error: tactic 'simp' failed, nested error:
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maximum recursion depth has been reached
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use `set_option maxRecDepth <num>` to increase limit
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use `set_option diagnostics true` to get diagnostic information
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-/
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#guard_msgs in
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example : a = 2*b := by simp -failIfUnchanged [ab, ba]
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/--
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warning: Possibly looping simp theorem: `← ab`
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Note: Possibly caused by: `← ba`
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Hint: You can disable a simp theorem from the default simp set by passing `- theoremName` to `simp`.
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---
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warning: Possibly looping simp theorem: `← ba`
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Note: Possibly caused by: `← ab`
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Hint: You can disable a simp theorem from the default simp set by passing `- theoremName` to `simp`.
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---
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error: tactic 'simp' failed, nested error:
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maximum recursion depth has been reached
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use `set_option maxRecDepth <num>` to increase limit
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use `set_option diagnostics true` to get diagnostic information
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-/
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#guard_msgs in
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example : a = 23 := by simp -failIfUnchanged [← ab, ← ba]
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-- Local theorems are not checked for loops,
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-- but are still applied when checking other rules
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/--
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warning: Possibly looping simp theorem: `ab`
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Note: Possibly caused by: `h`
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Hint: You can disable a simp theorem from the default simp set by passing `- theoremName` to `simp`.
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---
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error: tactic 'simp' failed, nested error:
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maximum recursion depth has been reached
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use `set_option maxRecDepth <num>` to increase limit
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use `set_option diagnostics true` to get diagnostic information
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-/
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#guard_msgs in
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example (h : b = a) : a = 23 := by simp -failIfUnchanged [ab, h]
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/-! Examples from the original RFC -/
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variable (P : Nat → Prop)
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/--
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warning: Possibly looping simp theorem: `Nat.add_assoc`
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Note: Possibly caused by: `(Nat.add_assoc _ _ _).symm`
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Hint: You can disable a simp theorem from the default simp set by passing `- theoremName` to `simp`.
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---
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warning: Possibly looping simp theorem: `(Nat.add_assoc _ _ _).symm`
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Note: Possibly caused by: `Nat.add_assoc`
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Hint: You can disable a simp theorem from the default simp set by passing `- theoremName` to `simp`.
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---
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error: tactic 'simp' failed, nested error:
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maximum recursion depth has been reached
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use `set_option maxRecDepth <num>` to increase limit
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use `set_option diagnostics true` to get diagnostic information
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-/
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#guard_msgs in
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example (a b c : Nat) : P (a + b + c) := by simp [Nat.add_assoc, (Nat.add_assoc _ _ _).symm]
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inductive Tree (α : Type) where | node : α → List (Tree α) → Tree α
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def Tree.children : Tree α → List (Tree α) | .node _ ts => ts
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def Tree.size (t : Tree α) := 1 + List.sum (t.children.attach.map (fun ⟨c,_⟩ => c.size))
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decreasing_by simp_wf; cases t; simp_all [Tree.children]; decreasing_trivial
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/--
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warning: Possibly looping simp theorem: `Tree.size.eq_1`
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Note: Possibly caused by: `Tree.size`
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Hint: You can disable a simp theorem from the default simp set by passing `- theoremName` to `simp`.
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---
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error: tactic 'simp' failed, nested error:
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maximum recursion depth has been reached
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use `set_option maxRecDepth <num>` to increase limit
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use `set_option diagnostics true` to get diagnostic information
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-/
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#guard_msgs in
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example (t : Tree α) : 0 < t.size := by simp [Tree.size]
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/--
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Identifiyng looping theorems by their origin is not enough,
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as the elements of conjunctions would clash, as shown by these:
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(The error message isn't great yet, but it's a corner case)
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-/
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theorem b1ab : b = 1 ∧ a = b := testSorry
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theorem baab : b = a ∧ a = b := testSorry
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/--
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error: unsolved goals
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P : Nat → Prop
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⊢ 1 > 0
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-/
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#guard_msgs in
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example : a > 0 := by simp only [b1ab]
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/--
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warning: Possibly looping simp theorem: `baab`
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Hint: You can disable a simp theorem from the default simp set by passing `- theoremName` to `simp`.
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---
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warning: Possibly looping simp theorem: `baab`
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Hint: You can disable a simp theorem from the default simp set by passing `- theoremName` to `simp`.
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---
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error: tactic 'simp' failed, nested error:
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maximum recursion depth has been reached
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use `set_option maxRecDepth <num>` to increase limit
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use `set_option diagnostics true` to get diagnostic information
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-/
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#guard_msgs in
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example : a > 0 := by simp only [baab]
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-- Same, with local theorems (should we ever support them):
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/--
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error: unsolved goals
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P : Nat → Prop
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a b : Nat
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h1 : b = 1 ∧ a = b
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h2 : 1 > 0
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⊢ True
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-/
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#guard_msgs in
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example
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(a b : Nat)
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(h1 : b = 1 ∧ a = b )
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(h2 : a > 0) : True := by
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simp only [h1] at h2
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/-!
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Unfolding should not confuse it.
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(Error message is not optimal as it does not mention the unfolded definition.)
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-/
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def c := a
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def ac : a = c := rfl
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def ca : c = a := rfl
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def d := c
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def dc : d = c := rfl
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/--
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warning: Possibly looping simp theorem: `c.eq_1`
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Note: Possibly caused by: `ac` and `c`
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Hint: You can disable a simp theorem from the default simp set by passing `- theoremName` to `simp`.
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---
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warning: Possibly looping simp theorem: `ac`
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Note: Possibly caused by: `c`
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Hint: You can disable a simp theorem from the default simp set by passing `- theoremName` to `simp`.
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---
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error: tactic 'simp' failed, nested error:
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maximum recursion depth has been reached
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use `set_option maxRecDepth <num>` to increase limit
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use `set_option diagnostics true` to get diagnostic information
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-/
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#guard_msgs in
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example : c > 0 := by simp only [c, ac]
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/--
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warning: Possibly looping simp theorem: `dc`
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Note: Possibly caused by: `c` and `ac`
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Hint: You can disable a simp theorem from the default simp set by passing `- theoremName` to `simp`.
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---
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warning: Possibly looping simp theorem: `c.eq_1`
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Note: Possibly caused by: `ac` and `c`
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Hint: You can disable a simp theorem from the default simp set by passing `- theoremName` to `simp`.
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---
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warning: Possibly looping simp theorem: `ac`
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Note: Possibly caused by: `c`
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Hint: You can disable a simp theorem from the default simp set by passing `- theoremName` to `simp`.
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---
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error: tactic 'simp' failed, nested error:
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maximum recursion depth has been reached
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use `set_option maxRecDepth <num>` to increase limit
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use `set_option diagnostics true` to get diagnostic information
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-/
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#guard_msgs in
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example : d > 0 := by simp only [dc, c, ac]
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/--
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warning: Possibly looping simp theorem: `c.eq_1`
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Note: Possibly caused by: `ac` and `c`
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Hint: You can disable a simp theorem from the default simp set by passing `- theoremName` to `simp`.
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---
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warning: Possibly looping simp theorem: `ac`
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Note: Possibly caused by: `c`
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Hint: You can disable a simp theorem from the default simp set by passing `- theoremName` to `simp`.
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---
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error: tactic 'simp' failed, nested error:
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maximum recursion depth has been reached
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use `set_option maxRecDepth <num>` to increase limit
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use `set_option diagnostics true` to get diagnostic information
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-/
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#guard_msgs in
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example : a > 0 := by simp only [c, ac]
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example (h : c = 1) : d > 0 := by simp only [dc, h, ca, ac, Nat.one_pos]
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/-!
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Simp? does not print the warnings for now. Let’s see if users find that helpful or confusing.
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-/
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/--
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error: tactic 'simp' failed, nested error:
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maximum recursion depth has been reached
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use `set_option maxRecDepth <num>` to increase limit
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use `set_option diagnostics true` to get diagnostic information
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-/
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#guard_msgs in
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example : d > 0 := by simp? only [dc, ca, ac]; exact testSorry
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/-!
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But we can turn it on:
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-/
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set_option linter.loopingSimpArgs true in
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/--
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error: tactic 'simp' failed, nested error:
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maximum recursion depth has been reached
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use `set_option maxRecDepth <num>` to increase limit
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use `set_option diagnostics true` to get diagnostic information
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-/
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#guard_msgs in
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example : d > 0 := by simp? only [dc, ca, ac]; exact testSorry
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/-- info: Try this: simp only [dc, h, Nat.one_pos] -/
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#guard_msgs in
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example (h : c = 1) : d > 0 := by simp? only [dc, h, ca, ac, Nat.one_pos]
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/-! An example where a second rewrite rules makes the looping rule looping,
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without being itself looping.
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-/
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opaque f : Nat → Nat
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theorem fbfa : f b = f a := testSorry
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theorem fbffa : f b = f (f a) := testSorry
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-- This one doesn't actually trigger because `simpLoop` does not recurse when
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-- the expression is the same after `post`. Also see issue #8864
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/--
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error: unsolved goals
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P : Nat → Prop
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⊢ 0 < f a
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-/
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#guard_msgs in
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example : 0 < f a := by simp -failIfUnchanged [fbfa, ab]
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/--
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warning: Possibly looping simp theorem: `fbffa`
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Note: Possibly caused by: `ab`
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Hint: You can disable a simp theorem from the default simp set by passing `- theoremName` to `simp`.
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---
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error: tactic 'simp' failed, nested error:
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maximum recursion depth has been reached
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use `set_option maxRecDepth <num>` to increase limit
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use `set_option diagnostics true` to get diagnostic information
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-/
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#guard_msgs in
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example : 0 < f a := by simp -failIfUnchanged [fbffa, ab]
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