qualifier_attr

[][qualifier_attr] [][qualifier_attr] [][qualifier_attr/docs] [][qualifier_attr/license] [][qualifier_attr/depstatus]

Procedural macro attributes for adding "qualifiers" to various items.

At the moment, the crate supports the following "qualifiers":

• pub, pub(crate), etc. - visibility and restriction
• default - default implementations (a feature of specialization)
• async - asynchronous code, e.g. async fn
• unsafe - unsafe code, e.g. unsafe fn, unsafe trait
• const - code that may run at compile time, e.g. const fn
• extern "ABI" - specifying an ABI, e.g. extern "C" fn

Limitations

• It seems that rust-analyzer will sometimes complain when the attribute is used with modules.

Examples

```rust

[macro_use]

extern crate qualifier_attr;

// We can add a qualifier to a function // with an attribute.

[qualifiers(const)]

fn const_fn() -> u32 { 42 }

const CONSTRES: u32 = constfn();

// It's not so impressive on its own, // but with cfg_attr, it can be conditional.

[cfgattr(feature = "externc", no_mangle, qualifiers(pub, extern "C"))]

fn externcfn() -> u32 { 42 }

// It even works with types, imports, and more! mod foo { #[qualifiers(pub)] struct Foo { x: i32, y: i32, } }

[qualifiers(pub)]

use foo::Foo;

// Traits and implementations too!?

[cfgattr(feature = "unsafequux", qualifiers(unsafe))]

trait Quux { fn quuxthething(); }

[cfgattr(feature = "unsafequux", qualifiers(unsafe))]

impl Quux for Foo { fn quuxthething() { println!("The thing was quuxed."); } }

// You can add qualifiers to the fields of a // struct as well with this special attribute.

[field_qualifiers(x(pub), y(pub))]

struct Point2 { x: i32, y: i32, }

[fieldqualifiers(0(pub), _1(pub), _2(pub))]

struct Point3(i32, i32, i32); ```

Learn more about cfg_attr here.

Note on legacy attributes

Before version 0.2.0, this crate provided a separate attribute for each kind of item. While this should generally be a small win for compile times, it is generally not justified by the additional complexity. The legacy attributes are still available behind the default legacy_attrs feature flag, but their use is currently discouraged. In order to disable the legacy attributes, add the following to your Cargo.toml:

toml [dependencies] qualifier_attr = { version = "0.2", default-features = false }

Similar crates

• const_fn.

License

<sup>Licensed under either of Apache License, Version 2.0 or MIT license at your option.</sup>

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