Lean 4 fork for HoTT-compatible kernel extensions (Path types, transport, HITs). Maintained against upstream leanprover/lean4.
f6e19f1f93
This PR adds normalizers for nonstandard arithmetic instances. The types
`Nat` and `Int` have built-in support in `grind`, which uses the
standard instances for these types and assumes they are the ones in use.
However, users may define their own alternative instances that are
definitionally equal to the standard ones. This PR normalizes such
instances using simprocs. This situation actually occurs in Mathlib.
Example:
```lean
class Distrib (R : Type _) extends Mul R where
namespace Nat
instance instDistrib : Distrib Nat where
mul := (· * ·)
theorem odd_iff.extracted_1_4 {n : Nat} (m : Nat)
(hm : n =
@HMul.hMul _ _ _ (@instHMul Nat instDistrib.toMul)
2 m + 1) :
n % 2 = 1 := by
grind
end Nat
```
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