Crate easy_ext

An attribute macro for easily writing extension trait pattern.

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)
      }
  }

• The visibility of all the items in the original impl must be identical.

Supertraits

If you want the extension trait to be a subtrait of another trait, add Self: SubTrait bound to the where clause.

use easy_ext::ext;

#[ext(Ext)]
impl<T> T
where
    Self: Default,
{
    fn method(&self) {}
}

Supported items

• Methods

use easy_ext::ext;

#[ext(Ext)]
impl<T> T {
    fn method(&self) {}
}

• Associated constants

use easy_ext::ext;

#[ext(Ext)]
impl<T> T {
    const MSG: &'static str = "Hello!";
}

Attribute Macros

ext	An attribute macro for easily writing extension trait pattern. See crate level documentation for details.