`DynamicallyAccessedMembers` annotations do not seem to be working on type delcarations.

[eiriktsarpalis]

Consider the following application:

using System.Diagnostics.CodeAnalysis;

Test(typeof(MyPoco));
static void Test(Type type) => Activator.CreateInstance(type);

[DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicParameterlessConstructor)]
class MyPoco;

I would have expected that this would instruct the linker to preserve the default constructor for MyPoco, however when I publish to AOT I get the error:

Unhandled exception. System.MissingMethodException: No parameterless constructor defined for type 'MyPoco'.
   at System.ActivatorImplementation.CreateInstance(Type, Boolean) + 0x198
   at Program.<Main>$(String[] args) + 0x2c

[dotnet-policy-service]

Tagging subscribers to 'linkable-framework': @eerhardt, @vitek-karas, @LakshanF, @sbomer, @joperezr, @marek-safar
See info in area-owners.md if you want to be subscribed.

[dotnet-policy-service]

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

[MichalStrehovsky]

The purpose of the annotation is to make this pattern work:

// Works no matter what descendants of MyPoco
static void Test(MyPoco p) => Activator.CreateInstance(p.GetType());

We don't have DAM annotations to just keep stuff because that would just encourage suppressing warnings. DAM is always paired with enabling new warningfree scenarios. The example in top post would still produce warnings.

[MichalStrehovsky]

(We delay marking things until we see the GetType call. The annotation is meaningless on it's own)

[agocke]

Closing as by-design. Code with warnings has undefined behavior.