∀ (typeBackDeps valueBackDeps : Std.HashSet ℕ) (decl : Lean.LocalDecl) (level : Lean.Level),
  sizeOf { typeBackDeps := typeBackDeps, valueBackDeps := valueBackDeps, decl := decl, level := level } =
    1 + sizeOf typeBackDeps + sizeOf valueBackDeps + sizeOf decl + sizeOf level