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fix: add Nat.cast normalizer missing case (#11580)

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This PR adds a missing `Nat.cast` missing normalization rule for
`grind`. Example:
```lean
example (n : Nat) : Nat.cast n = n := by
  grind
```
This commit is contained in:
Leonardo de Moura 2025-12-10 02:56:47 -08:00 • committed by GitHub
parent 088f8b0b9c
commit b9e888df4e
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2 changed files with 8 additions and 1 deletions
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3
src/Init/Grind/Norm.lean
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@ -82,6 +82,7 @@ theorem natCast_mod (a b : Nat) : (NatCast.natCast (a % b) : Int) = (NatCast.nat
theorem natCast_add (a b : Nat) : (NatCast.natCast (a + b : Nat) : Int) = (NatCast.natCast a : Int) + (NatCast.natCast b : Int) := rfl
theorem natCast_mul (a b : Nat) : (NatCast.natCast (a * b : Nat) : Int) = (NatCast.natCast a : Int) * (NatCast.natCast b : Int) := rfl
theorem natCast_pow (a b : Nat) : (NatCast.natCast (a ^ b : Nat) : Int) = (NatCast.natCast a : Int) ^ b := by simp
theorem natCast_id (a : Nat) : NatCast.natCast a = a := rfl
theorem Nat.pow_one (a : Nat) : a ^ 1 = a := by
simp
@ -184,7 +185,7 @@ init_grind_norm
Int.ediv_zero Int.emod_zero
Int.ediv_one Int.emod_one
Int.negSucc_eq
natCast_div natCast_mod
natCast_div natCast_mod natCast_id
natCast_add natCast_mul natCast_pow
Int.one_pow
Int.pow_zero Int.pow_one

6
tests/lean/run/grind_natCast.lean
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@ -5,3 +5,9 @@ example (x : Nat) : NatCast.natCast x ≥ 0 := by grind
example (x : Nat) : x ≥ (-1 : Int) := by grind
example (x : Nat) : Int.ofNat x ≥ (-1 : Int) := by grind
example (x : Nat) : NatCast.natCast x ≥ -1 := by grind
example (n : Nat) : Nat.cast n = n := by
grind
example (n m a : Nat) : n = m → Nat.cast n - a = m - a := by
grind