gecko-dev/third_party/rust/inherent/README.md

#[inherent]

This crate provides an attribute macro to make trait methods callable without the trait in scope.

[dependencies]
inherent = "0.1"

Example

mod types {
    use inherent::inherent;

    trait Trait {
        fn f(self);
    }

    pub struct Struct;

    #[inherent(pub)]
    impl Trait for Struct {
        fn f(self) {}
    }
}

fn main() {
    // types::Trait is not in scope, but method can be called.
    types::Struct.f();
}

Without the inherent macro on the trait impl, this would have failed with the following error:

error[E0599]: no method named `f` found for type `types::Struct` in the current scope
  --> src/main.rs:18:19
   |
8  |     pub struct Struct;
   |     ------------------ method `f` not found for this
...
18 |     types::Struct.f();
   |                   ^
   |
   = help: items from traits can only be used if the trait is implemented and in scope
   = note: the following trait defines an item `f`, perhaps you need to implement it:
           candidate #1: `types::Trait`

The inherent macro expands to inherent methods on the Self type of the trait impl that forward to the trait methods. In the case above, the generated code would be:

impl Struct {
    pub fn f(self) {
        <Self as Trait>::f(self)
    }
}

Visibility

Ordinary trait methods have the same visibility as the trait or the Self type, whichever's is smaller. Neither of these visibilities is knowable to the inherent macro, so we simply emit all inherent methods as private by default. A different visibility may be specified explicitly in the inherent macro invocation.

#[inherent]  // private inherent methods are the default

#[inherent(pub)]  // all methods pub

#[inherent(crate)]  // all methods pub(crate)

#[inherent(in path::to)]  // all methods pub(in path::to)

License

^{Licensed under either of Apache License, Version 2.0 or MIT license at your option.}
_{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.}