[autoimpl(Deref, DerefMut using self.animal)]

fn main() { struct Fish; impl Animal for Fish { fn numberoflegs(&self) -> u32 { 0 } }

let my_fish = Named {
    name: "Nemo",
    animal: Box::new(Fish),
};

assert_eq!(
    format!("{my_fish:?} has {} legs!", my_fish.number_of_legs()),
    r#"Named { name: "Nemo", .. } has 0 legs!"#
);

} ```

Impl Default

#[impl_default] implements std::default::Default:

```rust use impltools::{impldefault, impl_scope};

[impl_default(Tree::Ash)]

enum Tree { Ash, Beech, Birch, Willow }

implscope! { #[impldefault] struct Copse { tree_type: Tree, number: u32 = 7, } } ```

Impl Scope

impl_scope! is a function-like macro used to define a type plus its implementations. It supports impl Self syntax:

```rust use impltools::implscope; use std::fmt::Display;

impl_scope! { /// I don't know why this exists pub struct NamedThing { name: T, func: F, }

// Repeats generic parameters of type
impl Self {
    fn format_name(&self) -> String {
        format!("{}", self.name)
    }
}

// Merges generic parameters of type
impl<O> Self where F: Fn(&str) -> O {
    fn invoke(&self) -> O {
        (self.func)(&self.format_name())
    }
}

} ```

Extensibility

Rust's #[derive] macro allows downstream crates to add implementations for their own traits (via a special proc-macro crate). Want to do the same with #[autoimpl] and with attributes in impl_scope!? You can, but the process is a little different:

1. Create a copy of the impl-tools crate (which is just a thin wrapper around impl-tools-lib), and change the name.
2. Add your own implementations of [impl_tools_lib::autoimpl::ImplTrait] and/or [impl_tools_lib::ScopeAttr].
3. Modify the autoimpl / impl_scope attribute definitions to include your implementations.

Supported Rust Versions

The MSRV is 1.56.0 for no particular reason other than that it is the first to support Edition 2021.

Using a nightly compiler allows improved diagnostics, but otherwise stable Rust is fully supported.

no_std is not yet supported (see #7).

Alternatives