const-block-item-macro-codegen.rs

//@ run-pass
#![allow(dead_code)]
// General test that function items in static blocks
// can be generated with a macro.


struct MyType {
    desc: &'static str,
    data: usize,
    code: fn(usize, usize) -> usize
}

impl MyType {
    fn eval(&self, a: usize) -> usize {
        (self.code)(self.data, a)
    }
}

macro_rules! codegen {
    ($e:expr, $v:expr) => {
        {
            fn generated(a: usize, b: usize) -> usize {
                a - ($e * b)
            }
            MyType {
                desc: "test",
                data: $v,
                code: generated
            }
        }
    }
}

static GENERATED_CODE_1: MyType = codegen!(2, 100);
static GENERATED_CODE_2: MyType = codegen!(5, 1000);

pub fn main() {
    assert_eq!(GENERATED_CODE_1.eval(10), 80);
    assert_eq!(GENERATED_CODE_2.eval(100), 500);
}