Lean.Compiler.LCNF.Code Lean.Compiler.LCNF.Purity.pure →
  Array (Lean.Compiler.LCNF.LetDecl Lean.Compiler.LCNF.Purity.pure) →
    ℕ →
      Lean.FVarIdSet →
        StateM (Array (Lean.Compiler.LCNF.LetDecl Lean.Compiler.LCNF.Purity.pure))
          (Lean.Compiler.LCNF.Code Lean.Compiler.LCNF.Purity.pure)