kernel hangs on ac_nf expression

Prerequisites

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Description

The following test case hangs in the kernel

axiom foo {p : Prop} {x : BitVec 32} (h : (!x == x + 0#32) = true) : p

theorem add_eq_sub_not_sub_one (x : BitVec 32) (h : (!x == x + (1#32 + 4294967295#32)) = true) : False := by
  simp only [BitVec.reduceAdd] at h
  exact foo h -- this works

theorem add_eq_sub_not_sub_one' (x : BitVec 32) (h : (!x == x + 1#32 + 4294967295#32) = true) : False := by
  ac_nf0 at h
  simp only [BitVec.reduceAdd] at h
  exact foo h -- this hangs here

Context

This issue arose when testing bv_decide with ac_nf enabled.

Steps to Reproduce

Copy into Lean
Wait for it to run
Observe yellow line next to exact foo h not disappearing

Expected behavior: Proof should be confirmed by kernel

Actual behavior: Kernel is hanging

Versions

"4.12.0, commit 225e08965d644715e8961cd205ffedf1cf7d24c2"

Impact

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leanprover / lean4

kernel hangs on ac_nf expression #5699