Blittability check doesn't account for generic structs

[jtschuster]

MarshallingRequired check does not have a case for generic value types and will report them as requiring marshalling at runtime and throw an invalid program exception.

A minimal repro is below:

public static unsafe class Program
{
    public static unsafe void Main()
    {
        unsafe {
            void* m = (void*)(delegate* unmanaged[MemberFunction]<void*, MyStruct<nint>, int, int> )&ABI_Method;
            var i = ((delegate* unmanaged[MemberFunction]<MyStruct<int>, int, int>)m)(new MyStruct<int>(), 1);
        }
    }
    [global::System.Runtime.InteropServices.UnmanagedCallersOnlyAttribute(CallConvs = new[] { typeof(global::System.Runtime.CompilerServices.CallConvMemberFunction) })]
    internal static int ABI_Method(void* __this_native, MyStruct<nint> __p_native, int size)
    { return 0;}

}

struct MyStruct<T> where T: unmanaged {}

[ghost]

Tagging subscribers to this area: @dotnet/interop-contrib
See info in area-owners.md if you want to be subscribed.

Issue Details

---

MarshallingRequired check does not have a case for generic value types and will report them as requiring marshalling at runtime and throw an invalid program exception.

A minimal repro is below:

public static unsafe class Program
{
    public static unsafe void Main()
    {
        unsafe {
            void* m = (void*)(delegate* unmanaged[MemberFunction]<void*, MyStruct<nint>, int, int> )&ABI_Method;
            var i = ((delegate* unmanaged[MemberFunction]<MyStruct<int>, int, int>)m)(new MyStruct<int>(), 1);
        }
    }
    [global::System.Runtime.InteropServices.UnmanagedCallersOnlyAttribute(CallConvs = new[] { typeof(global::System.Runtime.CompilerServices.CallConvMemberFunction) })]
    internal static int ABI_Method(void* __this_native, MyStruct<nint> __p_native, int size)
    { return 0;}

}

struct MyStruct<T> where T: unmanaged {}

Author:	jtschuster
Assignees:	jtschuster
Labels:	area-System.Runtime.InteropServices
Milestone:	9.0.0