Nullable constraints not validated on tuple types inside method bodies

[jaredpar]

Consider the following code:

#nullable enable

namespace System
{
    // struct with two values
    public struct ValueTuple<T1, T2>
        where T1 : object
        where T2 : object
    {
        public T1 Item1;
        public T2 Item2;

        public ValueTuple(T1 item1, T2 item2)
        {
            this.Item1 = item1;
            this.Item2 = item2;
        }

        public override string ToString()
        {
            return "";
        }
    }

}

class C {
    void M((string?, string) a) {
        string? s = null;
        var x = ("", s);
    }
}

The compiler will issue a warning for the tuple inside the method signature but not inside the method body.