metatype's Introduction

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!(Type::meta_type(&*a), MetaType::Concrete);
let a: Box<dyn any::Any> = a;
assert_eq!(Type::meta_type(&*a), MetaType::TraitObject);

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

let a: Box<dyn any::Any> = Box::new(123);
let meta: TraitObject = type_coerce(Type::meta(&*a));
println!("vtable: {:?}", meta.vtable);

Note

This currently requires Rust nightly for the ptr_metadata, specialization and arbitrary_self_types features.

License

Licensed under either of

Apache License, Version 2.0, (LICENSE-APACHE.txt or http://www.apache.org/licenses/LICENSE-2.0)
MIT license (LICENSE-MIT.txt or http://opensource.org/licenses/MIT)

at your option.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

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metatype's Issues

Can't compile?

I'm definitely on nightly, but for some reason I can't compile metatype. I'm told:

error[E0432]: unresolved import `std::raw`
  --> src/lib.rs:56:190
   |
56 | ...smute_copy}, ptr::{slice_from_raw_parts_mut, NonNull}, raw
   |                                                           ^^^ no `raw` in the root

Any idea what's going on here?

Thank you 🙏

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