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

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);
}