Are all attributes in Rust implemented as Macros? Or some native attributes are created specially by the compiler/language and does not use the Macros mechanism?
If there are attributes not created via Macros, how do I identify them?
There are many attributes that are not macros and are treated specifically by the compiler. Examples: #[cfg] (although this one can be considered as a macro, even if not implemented as one), #[repr], #[doc], #[allow(...)]/#[warn(...)]/#[deny(...)]/#[forbid(...)], and many more.
I don't know a way to identify such attributes except to look at the list of builtin macro attributes and see if they're there.