Ignore a type when registered

[BenjaminBrienen]

There should be a way of saying to ignore a whole type when you register it. For example, marker types such as PhantomData.

#15313 (comment)

Related: #5144

[pablo-lua]

Is this a suggestion to add a new attribute like #[reflect(skip_register)], or something along the line of "always ignore phantom data when registering types"?
If the solution is to implement a new attribute like this, why not ignore PhantomData with #[reflect(ignore)]?

[BenjaminBrienen]

Is this a suggestion to add a new attribute like #[reflect(skip_register)], or something along the line of "always ignore phantom data when registering types"?
If the solution is to implement a new attribute like this, why not ignore PhantomData with #[reflect(ignore)]?

The idea is that bevy knows some types will always be #[reflect(ignore)] and it would be convenient if users don't have to annotate it every time. If we can have bevy handle this for std types and enable users to do this for their own types, we can lessen the verboseness of bevy programs. Maybe we could add a derive trait such as ReflectIgnore.