easy-ext

An attribute macro for easily writing extension trait pattern.

Usage

Add this to your Cargo.toml:

[dependencies]
easy-ext = "0.2"

Compiler support: requires rustc 1.31+

Examples

use easy_ext::ext;

#[ext(ResultExt)]
impl<T, E> Result<T, E> {
    pub fn err_into<U>(self) -> Result<T, U>
    where
        E: Into<U>,
    {
        self.map_err(Into::into)
    }
}

Code like this will be generated:

pub trait ResultExt<T, E> {
    fn err_into<U>(self) -> Result<T, U>
    where
        E: Into<U>;
}

impl<T, E> ResultExt<T, E> for Result<T, E> {
    fn err_into<U>(self) -> Result<T, U>
    where
        E: Into<U>,
    {
        self.map_err(Into::into)
    }
}

You can elide the trait name. Note that in this case, #[ext] assigns a random name, so you cannot import/export the generated trait.

use easy_ext::ext;

#[ext]
impl<T, E> Result<T, E> {
    fn err_into<U>(self) -> Result<T, U>
    where
        E: Into<U>,
    {
        self.map_err(Into::into)
    }
}

Visibility

The visibility of the generated extension trait inherits the visibility of the item in the original impl.

For example, if the method is pub then the trait will also be pub:

use easy_ext::ext;

#[ext(ResultExt)] // generate `pub trait ResultExt`
impl<T, E> Result<T, E> {
    pub fn err_into<U>(self) -> Result<T, U>
    where
        E: Into<U>,
    {
        self.map_err(Into::into)
    }
}

See documentation for more details.

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 the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.