Can't resolve custom attributes outside of the target assembly

[asklar]

I have a type/method that I've added [deprecated("foo", deprecate, 1)] to.

ca.GetArguments(out var fixedArgs, out var namedArgs);

both argument lists are empty, because it's trying to resolve the custom attribute in the same Assembly where it is applied to.

The code correctly identifies the need to resolve DeprecationType in the Windows.FoundationContract assembly, but this is marked as a fake assembly, so it calls RaiseFakeTypeRequired, but the FakeTypeRequired event handler is null.

Update:
The solution is to do something like:

            context.FakeTypeRequired += (sender, e) => {
                var ctx = sender as MrLoadContext;
                if (e.AssemblyName == "Windows.Foundation.FoundationContract")
                {
                    e.ReplacementType = ctx.GetTypeFromAssembly(e.TypeName, "Windows");
                }
            };

This should probably be a default though, or at least documented :)

[MikeHillberg]

Attributes outside of the target assembly should be OK, but I don't think there's a way to make this work with a fake type. At least when there's an enum involved, it's necessary to know the type information so that the metadata reader understands the binary layout in the file.

(Error shows up here, fallback code for attributes is here).