CustomAttributes not returning all attributes??

[i00]

I have a class with 2 custom attributes:

But Mono.Cecil is only picking up one:

I know that this is a built in attribute - but surely this should be listed here as well as in the flags?

[SimonCropp]

perhaps share a failing unit test as a Pull Request

[jbevain]

I think [Serializable] is compiled as a flag on the TypeDefinition, not as a Custom Attribute.

[Zastai]

Exactly. Some attributes are intended for and consumed by the compiler without also being retained as an attribute.

Another example would be the [MethodImpl] attribute, which is used to mode some flags that can be specified on a method in IL.
I added 2 attributes on a method in Cecil; [Obsolete] shows up as an attribute in a .custom declaration; the latter merely becomes the noinlining keyword on the method signature. I suppose it's the difference with a CIL attribute and a custom attribute, both of which can be managed via a C# Attribute.