Crate overloadf

Overloadf

** Let function overloading possible in rust **

With a single attribute on top of the function, you can overload the function with different parameters. Current implementation still has some flaws and todo items, so use at your own risk.

This library is based on some unstable features. To use this library, please put the following lines in crate root and the beginning of test files:

#![feature(fn_traits, unboxed_closures)]

There are some features that cannot be achieved until now:

• unsafe function overloading
• const function overloading
• different privacy setting on function overloading (will pickup the privacy setting in first function and apply to all)
• function overloading inside traits (for limited cases)

Examples:

simple one:

#![feature(fn_traits, unboxed_closures)]

use overloadf::*;
#[overload]
pub fn xdd(number: i32) -> i32 {
    number * 3
}

#[overload]
pub unsafe fn xdd(number: &u64) -> u64 {
    let n = number as *const u64;
    *n * 4
}

assert_eq!(xdd(3_i32), 9_i32);
let c: &u64 = &6_u64;
assert_eq!(xdd(c), 24_u64); // unsafe function is not supported.

with generic and custom type:

#![feature(fn_traits, unboxed_closures)]

use overloadf::*;
use std::ops::MulAssign;
use std::fmt::Debug;
#[overload]
pub fn xdd<T: Copy + Debug + MulAssign<i32>>(mut number: T) -> T {
    println!("number {:?}", number);
    number *= 3_i32;
    number
}

struct ABC;
impl Debug for ABC {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "xdddd")
    }
}

#[overload]
pub fn xdd(number: ABC) -> () {
    println!("number {:?}", number);
}
let aa = 123;
assert_eq!(xdd(aa), 369);
assert_eq!(xdd(ABC), ());

async / await:

#![feature(fn_traits, unboxed_closures)]
use overloadf::*;

#[overload]
pub async fn xdd(number: i32) -> i32 {
    number + 3
}
#[overload]
pub async fn xdd(number: i64) -> i64 {
    number + 4
}
assert_eq!(futures::executor::block_on(xdd(3_i32)), 6);
assert_eq!(futures::executor::block_on(xdd(3_i64)), 7);

type conflict might happen if generic overlaps with the definition of implemented types:

#![feature(fn_traits, unboxed_closures)]

use overloadf::*;
use std::ops::Mul;
use std::fmt::Debug;
#[overload]
pub fn xdd(number: i32) -> i32 {
    number * 2
}
#[overload]
pub fn xdd<T: Copy + Debug + Mul<i32>>(number: T) -> T {
    number * 3_i32
}

for trait methods:

#![feature(fn_traits, unboxed_closures)]
use overloadf::*;
#[overload]
trait Xdd: Sized {
    fn new(input: i32) -> Self;
    fn new(input :u32) -> Self;
}
struct Haha {
    a: u32,
    b: i32,
}
#[overload]
impl Xdd for Haha {
    fn new(b: i32) -> Self {
        Self {
            a: 1,
            b,
        }
    }
    fn new(a: u32) -> Self {
        Self {
            a,
            b: 2,
        }
    }
}
let haha = Haha::new(12_i32);
assert_eq!(haha.a, 1_u32);
assert_eq!(haha.b, 12_i32);
let haha = Haha::new(9_u32);
assert_eq!(haha.a, 9_u32);
assert_eq!(haha.b, 2_i32);

non-trait impl:

#![feature(fn_traits, unboxed_closures)]
use overloadf::*;
#[derive(Debug)]
pub struct Haha {
    a: u32,
    b: i32,
}
#[overload]
impl Haha {
    pub fn new(b: i32) -> Self {
        Self {
            a: 1,
            b,
        }
    }
    pub fn new(a: u32) -> Self {
        Self {
            a,
            b: 2,
        }
    }
    // will do nothing to functions without overloading
    pub fn normal(&self) -> String {
        format!("{:?}", self)
    }
}
let haha = Haha::new(12_i32);
assert_eq!(haha.a, 1_u32);
assert_eq!(haha.b, 12_i32);
let haha = Haha::new(9_u32);
assert_eq!(haha.a, 9_u32);
assert_eq!(haha.b, 2_i32);
assert_eq!(haha.normal(), "Haha { a: 9, b: 2 }");

Re-exports

pub extern crate overloadf_derive;

Attribute Macros

overload