Macro derive_storage 

macro_rules! derive_storage {
    ($( $tokens:tt )*) => { ... };
}

Prepares a struct for use as the type parameter of World.

The struct’s fields must be of type ComponentVec. It implements RemoveAll, as well as AsRef and AsMut for each field.

This macro can be used as an alternative to the custom derive Storage, e.g. because the feature proc is not enabled.