Crate metatype

Helper methods to determine whether a type is TraitObject, Slice or Concrete, and work with them respectively.

Examples

assert_eq!(usize::METATYPE, MetaType::Concrete);
assert_eq!(any::Any::METATYPE, MetaType::TraitObject);
assert_eq!(<[u8]>::METATYPE, MetaType::Slice);

let a: Box<usize> = Box::new(123);
assert_eq!((&*a).meta_type(), MetaType::Concrete);
let a: Box<any::Any> = a;
assert_eq!((&*a).meta_type(), MetaType::TraitObject);

let a = [123,456];
assert_eq!(a.meta_type(), MetaType::Concrete);
let a: &[i32] = &a;
assert_eq!(a.meta_type(), MetaType::Slice);

let a: Box<any::Any> = Box::new(123);
// https://github.com/rust-lang/rust/issues/50318
// let meta: TraitObject = (&*a).meta();
// println!("vtable: {:?}", meta.vtable);

Note

This currently requires Rust nightly for the raw and specialization features.

Structs

Concrete	Meta data for a concrete, sized type
Slice	Meta data for a slice
TraitObject	Meta data for a trait object

Enums

MetaType

Meta type of a type

Traits

Type	Implemented on all types, it provides helper methods to determine whether a type is TraitObject, Slice or Concrete, and work with them respectively.