How to mutate a boxed value type (primitive or struct) in C#/IL

Question

Related to How to mutate a boxed struct using IL I am trying to change the value of a boxed value type but in a generic way, so trying to implement the following method:

Answer 1

One solution, is by making an Unbox method in IL that calls unbox and returns a ref to the type contained in the object:

.method public hidebysig static !!T&  Unbox(object o) cil managed aggressiveinlining
{
  .maxstack  1
  ldarg.0
  unbox !!T
  ret
}

And then using this like:

public static void MutateValueType(object o, T v)
{
    ref T ub = ref Unsafe.Unbox(o);
    ub = v;
}

This correctly outputs:

        var oi = (object)17;
        MutateValueType(oi, 43);
        Console.WriteLine(oi); // 43

        var od = (object)17.7d;
        MutateValueType(od, 42.3);
        Console.WriteLine(od); // 42.3

NOTE: This requires C# 7 support for ref returns.

This might be added to say https://github.com/DotNetCross/Memory.Unsafe but it must also be possible with il.Emit also, so I am looking for that.