∀ {pat s : String.Slice} {stackPos needlePos : String.Pos.Raw}
  (h : String.Slice.Pattern.Model.ForwardSliceSearcher.Invariants✝ pat s needlePos stackPos)
  (h' : needlePos = pat.rawEndPos),
  String.Slice.Pattern.Model.IsLongestMatchAt pat (String.Slice.Pattern.Model.ForwardSliceSearcher.Invariants.base✝ h)
    (String.Slice.Pattern.Model.ForwardSliceSearcher.Invariants.base✝ ⋯)