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use core::marker::PhantomData;
pub struct FnMutant<In, Extra, Out, F: for<'a> Fn(In, Extra) -> Out> {
pub f: F,
phantom_in: PhantomData<In>,
phantom_extra: PhantomData<Extra>,
phantom_out: PhantomData<Out>,
}
impl<In, Extra, Out, F: for<'a> Fn(In, Extra) -> Out> FnMutant<In, Extra, Out, F> {
pub fn new(f: F) -> Self {
Self {
f,
phantom_in: PhantomData,
phantom_extra: PhantomData,
phantom_out: PhantomData,
}
}
}
pub fn mutant<In, Extra, Out, F: for<'a> Fn(In, Extra) -> Out>(
f: F,
) -> FnMutant<In, Extra, Out, F> {
FnMutant::new(f)
}
#[cfg(test)]
mod tests {
use std::iter::FromIterator;
use crate::FnMutant;
fn incr(x: &mut i32, amount: i32) {
*x += amount
}
fn decr(x: &mut i32, amount: i32) {
*x -= amount
}
fn helper(fps: &[FnMutant<&mut i32, i32, (), &dyn for<'b> Fn(&mut i32, i32)>],
xs: &mut [i32], expect: Vec<i32>) {
let len = xs.len();
for i in 0..len * 5 {
for fp in fps {
(fp.f)(xs.get_mut(i % len).unwrap(), 1);
}
}
assert_eq!(xs, expect.as_slice());
}
#[test]
fn it_works() {
use super::*;
let fps: [FnMutant<&mut i32, i32, (), &dyn for<'b> Fn(&mut i32, i32)>; 3] =
[mutant(&incr), mutant(&decr), mutant(&incr)];
{
let mut xs = [0, 1, 2, 3, 4, 5];
let expect = Vec::from_iter(xs.iter().map(|x| x + 5));
helper(&fps, &mut xs, expect.clone());
assert_eq!(xs, expect.as_slice());
drop(xs);
}
{
let mut xs = [0, 1, 2, 3, 4, 5];
let expect = Vec::from_iter(xs.iter().map(|x| x + 5));
helper(&fps, &mut xs, expect.clone());
assert_eq!(xs, expect.as_slice());
drop(xs);
}
}
}