NET 9 Regression: Razor Source Generator False IL2111 Warning with DynamicComponent

[ScarletKuro]

The DynamicComponent has the following signature:

public class DynamicComponent : IComponent
{
    ...
    [Parameter]
    [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.All)]
    [EditorRequired]
    public Type Type { get; set; }
    ...
}

Now, if you have a class that uses the DynamicComponent:

internal class SnackbarMessage
{
    [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.All)]
    internal Type ComponentType { get; }
    internal Dictionary<string, object>? ComponentParameters { get; }
    internal string? Key { get; }

    internal SnackbarMessage(
        [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.All)] Type componentType, 
        Dictionary<string, object>? componentParameters = null, 
        string? key = null)
    {
        ComponentType = componentType;
        ComponentParameters = componentParameters;
        Key = key;
    }

    internal string? Text { get; init; }
}

And you use it like this:

<DynamicComponent Type="Message.ComponentType" Parameters="Message.ComponentParameters" />

This will always result in an error / warning:

C:\Users\KuroPC\source\repos\MudBlazor\src\MudBlazor\obj\Debug\net9.0\generated\Microsoft.CodeAnalysis.Razor.Compiler\Microsoft.NET.Sdk.Razor.SourceGenerators.RazorSourceGenerator\Components_Snackbar_MudSnackbarElement_razor.g.cs(236,13,236,98): 
error IL2111: Method 'Microsoft.AspNetCore.Components.DynamicComponent.Type.set' with parameters or return value with `DynamicallyAccessedMembersAttribute` is accessed via reflection. Trimmer can't guarantee availability of the requirements of the method.

However, since both the DynamicComponent and the ComponentType property in SnackbarMessage have the same DAM annotation, why does this result in an error? There are no RequiresUnreferencedCode attributes on DynamicComponent, so I would expect that if the annotations match, there shouldn't be any issues.

Here’s the generated Razor code lines that it complains on:

#nullable restore
#line (37,10)-(39,1) "C:\Users\KuroPC\source\repos\MudBlazor\src\MudBlazor\Components\Snackbar\MudSnackbarElement.razor"
if (Message?.ComponentType != null)
        {

#line default
#line hidden
#nullable disable

            __builder.OpenComponent<global::Microsoft.AspNetCore.Components.DynamicComponent>(22);
            __builder.AddComponentParameter(23, nameof(global::Microsoft.AspNetCore.Components.DynamicComponent.
#nullable restore
#line (39,31)-(39,35) "C:\Users\KuroPC\source\repos\MudBlazor\src\MudBlazor\Components\Snackbar\MudSnackbarElement.razor"
Type

#line default
#line hidden
#nullable disable
            ), global::Microsoft.AspNetCore.Components.CompilerServices.RuntimeHelpers.TypeCheck<global::System.Type>(
#nullable restore
#line (39,37)-(39,58) "C:\Users\KuroPC\source\repos\MudBlazor\src\MudBlazor\Components\Snackbar\MudSnackbarElement.razor"
Message.ComponentType

#line default
#line hidden
#nullable disable
            ));

NB! This was not an issue with the .NET 8 SDK and it had the same DAM annotation like in NET9.

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