CS9192 Argument 1 should be passed with 'ref' or 'in' keyword - In generated code for struct

[RandallFlagg]

Hi Is it possible to fix the generated code so in the output code the CS9192 warning won't show up?

This is the file that it happens in:

C:\MyProj\MemoryPack.Generator\MemoryPack.Generator.MemoryPackGenerator\MyProj.StructFile.MemoryPackFormatter.g.cs

[vcampoy]

I have a similar issue, when I find the solution, I'll post it here.

[rayfung]

The following code can reproduce the warning in .NET 8:

[MemoryPackable]
public partial class Foo
{
    public List<Bar> Bars1; // Warning CS9192
    public List<Bar> Bars2 { get; set; } // Warning CS9193
}

[MemoryPackable]
public partial class Bar
{
    public int Id { get; set; }
}

Look at the generated code, it seems that we should add ref before the parameter of Unsafe.AsRef (eg: Unsafe.AsRef(ref value.@Bars1)) ?

[global::MemoryPack.Internal.Preserve]
static void IMemoryPackable<Foo>.Serialize<TBufferWriter>(ref MemoryPackWriter<TBufferWriter> writer, scoped ref Foo? value) 
{
    if (value == null)
    {
        writer.WriteNullObjectHeader();
        goto END;
    }

    writer.WriteObjectHeader(2);
    global::MemoryPack.Formatters.ListFormatter.SerializePackable(ref writer,
        ref System.Runtime.CompilerServices.Unsafe.AsRef(value.@Bars1));
    global::MemoryPack.Formatters.ListFormatter.SerializePackable(ref writer,
        ref System.Runtime.CompilerServices.Unsafe.AsRef(value.@Bars2));

END:
    return;
}

[maboroshinokiseki]

I think it's not too hard to fix, just add two more checks to the generator, one for checking if it's a property, and the other for checking if it's a class type. Or maybe we can just remove the ref, since it seems like that SerializePackable does not modify the variable itself.

[rayfung]

The following code can reproduce the warning in .NET 8:

[MemoryPackable]
public partial class Foo
{
    public List<Bar> Bars1; // Warning CS9192
    public List<Bar> Bars2 { get; set; } // Warning CS9193
}

[MemoryPackable]
public partial class Bar
{
    public int Id { get; set; }
}

Look at the generated code, it seems that we should add ref before the parameter of Unsafe.AsRef (eg: Unsafe.AsRef(ref value.@Bars1)) ?

[global::MemoryPack.Internal.Preserve]
static void IMemoryPackable<Foo>.Serialize<TBufferWriter>(ref MemoryPackWriter<TBufferWriter> writer, scoped ref Foo? value) 
{
    if (value == null)
    {
        writer.WriteNullObjectHeader();
        goto END;
    }

    writer.WriteObjectHeader(2);
    global::MemoryPack.Formatters.ListFormatter.SerializePackable(ref writer,
        ref System.Runtime.CompilerServices.Unsafe.AsRef(value.@Bars1));
    global::MemoryPack.Formatters.ListFormatter.SerializePackable(ref writer,
        ref System.Runtime.CompilerServices.Unsafe.AsRef(value.@Bars2));

END:
    return;
}

I found the above code compiles without warnings in .NET 7 because the signature of Unsafe.AsRef is: public static ref T AsRef<T> (scoped in T source); while in .NET 8 it is: public static ref T AsRef<T> (scoped ref T source);

So there is a breaking change in .NET 8.

[rayfung]

There is no need for ref in ListFormatter.SerializePackable while serialization will not (and should not) change the list reference.

I suggest changing void SerializePackable<T, TBufferWriter>(ref MemoryPackWriter<TBufferWriter> writer, scoped ref List<T?>? value) to void SerializePackable<T, TBufferWriter>(ref MemoryPackWriter<TBufferWriter> writer, List<T?>? value)

[hadashiA]

Hi. Thanks for the suggestions. I fixed in #232.