Show the crate…
1 unstable release
0.1.0 | Mar 16, 2021 |
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#13 in #metaprogramming
8KB
136 lines
ay
This experimental crate provides an attribute macro to implement Fn
traits for any struct/enum,
essentially enabling you to use it as a regular function/pass it like a closure or use it like an overloaded function.
Why shouldn't I use this?
If the fact that you have to enable unstable features still doesn't convince you, here's why you should stay away from this (or any other simillar patterns) in any real project:
- It introduces ambiguity - What does this code do? Where do I find the implementation? Why am I calling a struct?
- It promotes rust anti-patterns - Rust doesn't allow you to, for example, overload functions in classical sense for a reason. You shouldn't try to do it.
If you're still positive about using this in your project - I'm trurly sorry. And I hope you won't try to implement this in the real-world.
Any more reasons not to use this are welcome.
Example
#![feature(unboxed_closures, fn_traits, type_alias_impl_trait)]
use ay::ay;
#[derive(Debug)]
struct MyFunc {
state: i32,
}
#[ay]
impl MyFunc {
fn get_state(&self) -> i32 {
self.state
}
fn update(&mut self, new: i32) {
self.state += new;
}
}
fn main() {
let mut my_func = MyFunc { state: 5 };
println!("{}", my_func()); // 5
my_func(3);
println!("{}", my_func()); // 8
my_func(-8);
println!("{}", my_func()); // 0
}
Firstly, we need to enable both unboxed_closures
and fn_traits
features.
Once we have those, we can use #[ay]
on an impl
block with methods (it's important for all the methods to have self
, &mut self
or &self
argument).
Warning
Generics are only supported on impl
level so if you try to make a method generic expect stuff to break.
Async methods are not supported at all (yet).
Dependencies
~1.5MB
~35K SLoC