[GeneratedComInterface] Generates incorrect code if base interface has unsafe method

[jevansaks]

Description

If a base type has an unsafe method then GeneratedComInterface generates methods for the derived class that need unsafe but are missing the keyword:

    public partial interface IDerivedInterface
    {
        [global::System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.Interop.ComInterfaceGenerator", "9.0.12.41916")]
        [global::System.Runtime.CompilerServices.SkipLocalsInitAttribute]
        new void BaseMethod(void* pBuffer) => ((global::Repro.IBaseInterface)this).BaseMethod(pBuffer);
    }

Error: Pointers and fixed size buffers may only be used in an unsafe context

Practical scenario where this comes up: ISequentialStream defines Read/Write that take pointers and IStream derives from it.

I also tried net10.0 (10.0.100-rc.1.25451.107 ) and it still reproed.

Reproduction Steps

Put this code in a new console app (I also put the repro here: https://github.com/jevansaks/GeneratedComInterfaceRepro/blob/master/Program.cs)

    [Guid("00000000-0000-0000-0000-000000000011"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown), GeneratedComInterface]
    public partial interface IBaseInterface
    {
        unsafe void BaseMethod(void* pBuffer);
    }

    [Guid("00000000-0000-0000-0000-000000000012"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown), GeneratedComInterface]
    public partial interface IDerivedInterface : IBaseInterface
    {
        void DerivedMethod();
    }

Expected behavior

GeneratedComInterface needs to add unsafe

Actual behavior

No unsafe keyword.

Regression?

No response

Known Workarounds

No response

Configuration

No response

Other information

No response

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[jevansaks]

Thankfully I found a workaround, I can put "unsafe" on the managed interface declaration and that carries over to the GeneratedComInterface-generated methods to allow them to be unsafe without explicitly being so.

I cannot explain why this workaround works, though. "unsafe" is not explicitly emitted on the partial class from the source generator and if I try this manually, it does not work. Perhaps there's some affordance for source-generated classes to pick up attributes from the manually authored partial class?