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[Merged by Bors] - fix: prevent Int.ofNat being used instead of Nat.cast #2878

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[Merged by Bors] - fix: prevent Int.ofNat being used instead of Nat.cast #2878

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d82ec2a
fix: prevent `Int.ofNat` being used instead of `Nat.cast`
eric-wieser Mar 14, 2023
45d1ed3
fix the CanLift instance
eric-wieser Mar 14, 2023
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3 changes: 3 additions & 0 deletions Mathlib/Data/Nat/Cast/Defs.lean
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Expand Up @@ -45,6 +45,9 @@ instance [NatCast R] : CoeTail ℕ R where coe := Nat.cast
-- see note [coercion into rings]
instance [NatCast R] : CoeHTCT ℕ R where coe := Nat.cast
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These two are in std4 now. ^^


/-- This instance is needed to ensure that `instCoeNatInt` is not used. -/
instance : Coe ℕ ℤ where coe := Nat.cast

-- the following four declarations are not in mathlib3 and are relevant to the way numeric
-- literals are handled in Lean 4.

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3 changes: 2 additions & 1 deletion Mathlib/Data/PNat/Defs.lean
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Expand Up @@ -10,6 +10,7 @@ Authors: Mario Carneiro, Neil Strickland
-/

import Mathlib.Algebra.NeZero
import Mathlib.Data.Nat.Cast.Defs
import Mathlib.Order.Basic
import Mathlib.Tactic.Coe
import Mathlib.Tactic.Lift
Expand Down Expand Up @@ -299,7 +300,7 @@ instance Nat.canLiftPNat : CanLift ℕ ℕ+ (↑) (fun n => 0 < n) :=
instance Int.canLiftPNat : CanLift ℤ ℕ+ (↑) ((0 < ·)) :=
⟨fun n hn =>
⟨Nat.toPNat' (Int.natAbs n), by
rw [Nat.toPNat'_coe, if_pos (Int.natAbs_pos.2 hn.ne'), Int.ofNat_eq_coe,
rw [Nat.toPNat'_coe, if_pos (Int.natAbs_pos.2 hn.ne'),
Int.natAbs_of_nonneg hn.le]⟩⟩
#align int.can_lift_pnat Int.canLiftPNat

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