dsimp at hgo
case isTrue
w : Nat
aig : AIG BVBit
a curr : Nat
hcurr : curr ≤ w
s : aig.RefStream curr
idx : Nat
hidx : idx < curr
res : RefStreamEntry BVBit w
h✝ : curr < w
hgo :
  (let res := aig.mkAtomCached (BVBit.mk a ⟨curr, h✝⟩);
    let aig_1 := res.aig;
    let bitRef := res.ref;
    let s := s.cast ⋯;
    let s := s.pushRef bitRef;
    go w aig_1 (curr + 1) s a ⋯) =
    res
⊢ ∀ (hfoo : aig.decls.size ≤ res.aig.decls.size), res.stream.getRef idx ⋯ = (s.getRef idx hidx).cast hfoo
case isTrue
w : Nat
aig : AIG BVBit
a curr : Nat
hcurr : curr ≤ w
s : aig.RefStream curr
idx : Nat
hidx : idx < curr
res : RefStreamEntry BVBit w
h✝ : curr < w
hgo :
  go w (aig.mkAtomCached (BVBit.mk a ⟨curr, h✝⟩)).aig (curr + 1)
      ((s.cast ⋯).pushRef (aig.mkAtomCached (BVBit.mk a ⟨curr, h✝⟩)).ref) a ⋯ =
    res
⊢ ∀ (hfoo : aig.decls.size ≤ res.aig.decls.size), res.stream.getRef idx ⋯ = (s.getRef idx hidx).cast hfoo