6514385bb9
This adds the ability to add the converse direction of a rewrite rule not just in simp arguments `simp [← thm]`, but also as a global attribute ```lean attribute [simp ←] thm ``` This fixes #5828. This can be undone with `attribute [-simp]`, although note that `[-simp]` wins and cannot be undone at the moment (#5868). Like `simp [← thm]` (see #4290), this will do an implicit `attribute [-simp] thm` if the other direction is already defined.
97 lines
1.8 KiB
Text
97 lines
1.8 KiB
Text
axiom a : Nat
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axiom b : Nat
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axiom a_eq_b : a = b
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axiom P : Nat → Nat → Prop
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-- Warm-up: rewriting in the forward direction
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/-- error: simp made no progress -/
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#guard_msgs in example : P a b := by simp
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attribute [simp] a_eq_b
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/--
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error: unsolved goals
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⊢ P b b
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-/
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#guard_msgs in example : P a b := by simp
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attribute [-simp] a_eq_b
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/-- error: simp made no progress -/
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#guard_msgs in example : P a b := by simp
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-- Re-adding an attribute after [-simp] does not work, see
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-- https://github.com/leanprover/lean4/issues/5868
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attribute [simp] a_eq_b
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/-- error: simp made no progress -/
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#guard_msgs in example : P a b := by simp
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-- so this test use new copies of `a_eq_b` for now
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axiom a_eq_b_2 : a = b
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attribute [simp ←] a_eq_b_2
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/--
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error: unsolved goals
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⊢ P a a
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-/
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#guard_msgs in example : P a b := by simp
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-- Removing the attribute works, no matter the direction
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attribute [-simp] a_eq_b_2
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/-- error: simp made no progress -/
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#guard_msgs in example : P a b := by simp
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-- Setting one should erase the other
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axiom a_eq_b_3 : a = b
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attribute [simp ←] a_eq_b_3
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attribute [simp] a_eq_b_3
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/--
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error: unsolved goals
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⊢ P b b
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-/
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#guard_msgs in example : P a b := by simp
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-- The erasure is sticky:
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attribute [simp ←] a_eq_b_3
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/-- error: simp made no progress -/
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#guard_msgs in example : P a b := by simp
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axiom a_eq_b_4 : a = b
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attribute [simp] a_eq_b_4
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attribute [simp ←] a_eq_b_4
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/--
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error: unsolved goals
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⊢ P a a
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-/
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#guard_msgs in example : P a b := by simp
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-- Some more error conditions
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axiom P_a : P a a
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/-- error: invalid '←' modifier in rewrite rule to 'True' -/
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#guard_msgs in
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attribute [simp ←] P_a
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/-- error: invalid 'simp', it is not a proposition nor a definition (to unfold) -/
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#guard_msgs in
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attribute [simp ←] P
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/-- error: invalid '←' modifier, 'id' is a declaration name to be unfolded -/
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#guard_msgs in
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attribute [simp ←] id
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