functional_trait 0.1.1

A macro that impls trait for Fns
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# Functional trait


## Description


A simple macro that inspired by java's functional interface.

the macro impls a trait for `Fn`, `FnMut` or `FnOnce` when the trait:

- contains one and only one method

- the method has a receiver, and the receiver is `&self`, `&mut self` or `self`

- has no generic types in the trait or the method (may change in the future versions)

- has no generic lifetime in the trait (may change in the future versions)

- has no super trait (may change in the future versions)

- is not unsafe

- have no unsafe method (may change in the future versions)

## Example


```rust
use functional_trait::functional_trait;

#[functional_trait]

trait A {
    fn a(&self, i: i32, j: i32) -> i32;
}

#[functional_trait]

trait B {
    fn b(&mut self, i: i32, j: i32) -> i32;
}

#[functional_trait]

trait C {
    fn c(self, i: i32, j: i32) -> i32;
}

#[functional_trait]

trait D {
    fn d<'c>(&self, b: &'c i32) -> &'c i32;
}

fn main() {
    let f = |a, b| a + b + 10;
    dbg!(f.a(1, 2));

    let mut i = 0;
    let mut f = |a, b| {
        i += 1;
        a + b + i
    };
    dbg!(f.b(1, 2));

    let s = String::new();
    let f = |a, b| {
        drop(s);
        a + b + i
    };
    dbg!(f.c(1, 2));

    let f = {
        fn f(a: &i32) -> &i32 {
            a
        }
        f
    };
    f.d(&1);
}

```