-- Mathlib/.lake/packages/lean4/src/lean/Std/Tactic/BVDecide/LRAT/Internal/Formula/RatAddResult.lean
theorem formula_performRatCheck {n : Nat} (f : DefaultFormula n)
    (hf : f.ratUnits = #[] ∧ f.assignments.size = n) (p : Literal (PosFin n))
    (ratHint : Nat × Array Nat) :
    (performRatCheck f p ratHint).1 = f

Proof state:
case isFalse
n : Nat
f : DefaultFormula n
hf : f.ratUnits = #[] ∧ f.assignments.size = n
p : Literal (PosFin n)
ratHint : Nat × Array Nat
x✝ : Option (DefaultClause n)
c : DefaultClause n
heq✝ : f.clauses[ratHint.fst]! = some c
h✝ :
  ¬({ clauses := f.clauses, rupUnits := f.rupUnits, ratUnits := f.ratUnits,
              assignments := f.assignments }.insertRatUnits
          (c.delete p).negate).snd =
      true
fc : DefaultFormula n := (f.insertRatUnits (c.delete p).negate).fst
fc_assignments_size : fc.assignments.size = n
insertRatUnits_rw :
  (f.insertRatUnits (c.delete p).negate).fst =
    { clauses := (f.insertRatUnits (c.delete p).negate).fst.clauses,
      rupUnits := (f.insertRatUnits (c.delete p).negate).fst.rupUnits,
      ratUnits := (f.insertRatUnits (c.delete p).negate).fst.ratUnits,
      assignments := (f.insertRatUnits (c.delete p).negate).fst.assignments }
⊢ (if
          (({ clauses := f.clauses, rupUnits := f.rupUnits, ratUnits := f.ratUnits,
                                assignments := f.assignments }.insertRatUnits
                            (c.delete p).negate).fst.performRupCheck
                      ratHint.snd).2.2.snd =
              true ∨
            (({ clauses := f.clauses, rupUnits := f.rupUnits, ratUnits := f.ratUnits,
                                assignments := f.assignments }.insertRatUnits
                            (c.delete p).negate).fst.performRupCheck
                      ratHint.snd).2.2.fst =
              false then
        ({
              clauses :=
                ({ clauses := f.clauses, rupUnits := f.rupUnits, ratUnits := f.ratUnits,
                          assignments := f.assignments }.insertRatUnits
                      (c.delete p).negate).fst.clauses,
              rupUnits :=
                ({ clauses := f.clauses, rupUnits := f.rupUnits, ratUnits := f.ratUnits,
                          assignments := f.assignments }.insertRatUnits
                      (c.delete p).negate).fst.rupUnits,
              ratUnits :=
                ({ clauses := f.clauses, rupUnits := f.rupUnits, ratUnits := f.ratUnits,
                          assignments := f.assignments }.insertRatUnits
                      (c.delete p).negate).fst.ratUnits,
              assignments :=
                restoreAssignments
                  (({ clauses := f.clauses, rupUnits := f.rupUnits, ratUnits := f.ratUnits,
                                  assignments := f.assignments }.insertRatUnits
                              (c.delete p).negate).fst.performRupCheck
                        ratHint.snd).1.assignments
                  (({ clauses := f.clauses, rupUnits := f.rupUnits, ratUnits := f.ratUnits,
                                  assignments := f.assignments }.insertRatUnits
                              (c.delete p).negate).fst.performRupCheck
                        ratHint.snd).2.fst }.clearRatUnits,
          false)
      else
        ({
              clauses :=
                ({ clauses := f.clauses, rupUnits := f.rupUnits, ratUnits := f.ratUnits,
                          assignments := f.assignments }.insertRatUnits
                      (c.delete p).negate).fst.clauses,
              rupUnits :=
                ({ clauses := f.clauses, rupUnits := f.rupUnits, ratUnits := f.ratUnits,
                          assignments := f.assignments }.insertRatUnits
                      (c.delete p).negate).fst.rupUnits,
              ratUnits :=
                ({ clauses := f.clauses, rupUnits := f.rupUnits, ratUnits := f.ratUnits,
                          assignments := f.assignments }.insertRatUnits
                      (c.delete p).negate).fst.ratUnits,
              assignments :=
                restoreAssignments
                  (({ clauses := f.clauses, rupUnits := f.rupUnits, ratUnits := f.ratUnits,
                                  assignments := f.assignments }.insertRatUnits
                              (c.delete p).negate).fst.performRupCheck
                        ratHint.snd).1.assignments
                  (({ clauses := f.clauses, rupUnits := f.rupUnits, ratUnits := f.ratUnits,
                                  assignments := f.assignments }.insertRatUnits
                              (c.delete p).negate).fst.performRupCheck
                        ratHint.snd).2.fst }.clearRatUnits,
          true)).fst =
    f

Tactic:
rw [restoreAssignments_performRupCheck fc fc_assignments_size ratHint.2, ← insertRatUnits_rw,
  clear_insertRat f hf (negate (DefaultClause.delete c p))]

Result:
case isFalse
n : Nat
f : DefaultFormula n
hf : f.ratUnits = #[] ∧ f.assignments.size = n
p : Literal (PosFin n)
ratHint : Nat × Array Nat
x✝ : Option (DefaultClause n)
c : DefaultClause n
heq✝ : f.clauses[ratHint.fst]! = some c
h✝ :
  ¬({ clauses := f.clauses, rupUnits := f.rupUnits, ratUnits := f.ratUnits,
              assignments := f.assignments }.insertRatUnits
          (c.delete p).negate).snd =
      true
fc : DefaultFormula n := (f.insertRatUnits (c.delete p).negate).fst
fc_assignments_size : fc.assignments.size = n
insertRatUnits_rw :
  (f.insertRatUnits (c.delete p).negate).fst =
    { clauses := (f.insertRatUnits (c.delete p).negate).fst.clauses,
      rupUnits := (f.insertRatUnits (c.delete p).negate).fst.rupUnits,
      ratUnits := (f.insertRatUnits (c.delete p).negate).fst.ratUnits,
      assignments := (f.insertRatUnits (c.delete p).negate).fst.assignments }
⊢ (if
          (({ clauses := f.clauses, rupUnits := f.rupUnits, ratUnits := f.ratUnits,
                                assignments := f.assignments }.insertRatUnits
                            (c.delete p).negate).fst.performRupCheck
                      ratHint.snd).2.2.snd =
              true ∨
            (({ clauses := f.clauses, rupUnits := f.rupUnits, ratUnits := f.ratUnits,
                                assignments := f.assignments }.insertRatUnits
                            (c.delete p).negate).fst.performRupCheck
                      ratHint.snd).2.2.fst =
              false then
        (f, false)
      else (f, true)).fst =
    f