auto_impl

A simple compiler plugin for automatically implementing a trait for some common smart pointers and closures.

Usage

This library requires the nightly channel.

Add auto_impl to your Cargo.toml:

auto_impl = "*"

Reference in your crate root:

```rust

![feature(proc_macro)]

extern crate auto_impl;

use autoimpl::autoimpl; ```

Add an auto_impl attribute to traits you want to automatically implement for wrapper types:

```rust

[auto_impl(&, Arc)]

pub trait OrderStoreFilter { fn filter(&self, predicate: F) -> Result where F: Fn(&OrderData) -> bool; } ```

Now anywhere that requires a T: OrderStoreFilter will also accept an &T or Arc<T> where T implements OrderStoreFilter.

Specifics

The following types are supported and can be freely combined:

• Arc
• Rc
• Box

The following types are also supported, but require a blanket implementation (you can only have one of these per trait):

• Fn
• FnMut
• FnOnce
• &
• &mut

Implement a trait for Box

```rust

[auto_impl(Box)]

trait MyTrait<'a, T> where T: AsRef { type Type1; type Type2;

fn execute1<'b>(&'a self, arg1: &'b T) -> Result<Self::Type1, String>;
fn execute2(&self) -> Self::Type2;
fn execute3(self) -> Self::Type1;
fn execute4() -> &'static str;

} ```

Will expand to:

```rust impl<'a, T, TAutoImpl> MyTrait<'a, T> for ::std::boxed::Box where TAutoImpl: MyTrait<'a, T>, T: AsRef { type Type1 = TAutoImpl::Type1; type Type2 = TAutoImpl::Type2;

fn execute1<'b>(&'a self, arg1: &'b T) -> Result<Self::Type1, String> {
    (**self).execute1(arg1)
}

fn execute2(&self) -> Self::Type2 {
    (**self).execute2()
}

fn execute3(self) -> Self::Type1 {
    (*self).execute3()
}

fn execute4() -> &'static str {
    TAutoImpl::execute4()
}

} ```

There are no restrictions on auto_impl for Box.

Implement a trait for a smart pointer

Add the #[auto_impl] attribute to traits to automatically implement them for wrapper types:

```rust

[auto_impl(Arc, Rc)]

trait MyTrait<'a, T> where T: AsRef { type Type1; type Type2;

fn execute1<'b>(&'a self, arg1: &'b T) -> Result<Self::Type1, String>;
fn execute2(&self) -> Self::Type2;

} ```

Will expand to:

```rust impl<'a, T, TAutoImpl> MyTrait<'a, T> for ::std::sync::Arc where TAutoImpl: MyTrait<'a, T>, T: AsRef { type Type1 = TAutoImpl::Type1; type Type2 = TAutoImpl::Type2;

fn execute1<'b>(&'a self, arg1: &'b T) -> Result<Self::Type1, String> {
    (**self).execute1(arg1)
}

fn execute2(&self) -> Self::Type2 {
    (**self).execute2()
}

}

impl<'a, T, TAutoImpl> MyTrait<'a, T> for ::std::rc::Rc where TAutoImpl: MyTrait<'a, T>, T: AsRef { type Type1 = TAutoImpl::Type1; type Type2 = TAutoImpl::Type2;

fn execute1<'b>(&'a self, arg1: &'b T) -> Result<Self::Type1, String> {
    (**self).execute1(arg1)
}

fn execute2(&self) -> Self::Type2 {
    (**self).execute2()
}

} ```

There are a few restrictions on #[auto_impl] for smart pointers. The trait must:

• Only have methods that take &self or have no receiver (static)

Implement a trait for a closure

```rust

[auto_impl(Fn)]

trait MyTrait<'a, T> { fn execute<'b>(&'a self, arg1: &'b T, arg2: &'static str) -> Result<(), String>; } ```

Will expand to:

rust impl<'a, T, TAutoImpl> MyTrait<'a, T> for TAutoImpl where TAutoImpl: ::std::ops::Fn(&T, &'static str) -> Result<(), String> { fn execute<'b>(&'a self, arg1: &'b T, arg1: &'static str) -> Result<(), String> { self(arg1, arg2) } }

There are a few restrictions on #[auto_impl] for closures. The trait must:

• Have a single method
• Have no associated types
• Have no non-static lifetimes in the return type

Implement a trait for a borrowed reference

```rust

[auto_impl(&, &mut)]

trait MyTrait<'a, T> { fn execute<'b>(&'a self, arg1: &'b T, arg2: &'static str) -> Result<(), String>; } ```

Will expand to:

```rust impl<'auto, 'a, T, TAutoImpl> MyTrait<'a, T> for &'auto TAutoImpl { fn execute<'b>(&'a self, arg1: &'b T, arg1: &'static str) -> Result<(), String> { (**self).execute(arg1, arg2) } }

impl<'auto, 'a, T, TAutoImpl> MyTrait<'a, T> for &'auto mut TAutoImpl { fn execute<'b>(&'a self, arg1: &'b T, arg1: &'static str) -> Result<(), String> { (**self).execute(arg1, arg2) } } ```

There are a few restrictions on #[auto_impl] for immutably borrowed references. The trait must:

• Only have methods that take &self or have no receiver (static)

There are a few restrictions on #[auto_impl] for mutably borrowed references. The trait must:

• Only have methods that take &self, &mut self or have no receiver (static)