在F#中,如何生成类型为Func <obj>的表达式？

let func = fun () -> box "Hello, world!"

open System.Linq.Expressions

let func = Expression.Lambda(Expression.Convert(Expression.Constant("Hello, world!"), typeof<obj>))

open Microsoft.FSharp.Core.OptimizedClosures

let func = fun () -> "Hello, world!"
let funcObj = func.ToFSharpFunc().Invoke