simp only [removePosAssignment, hasPosAssignment, Bool.not_eq_true]
assignment : Assignment
⊢ ¬assignment.removePosAssignment.hasPosAssignment = true
assignment : Assignment
⊢ (match
      match assignment with
      | pos => unassigned
      | neg => neg
      | both => neg
      | unassigned => unassigned with
    | pos => true
    | neg => false
    | both => true
    | unassigned => false) =
    false