This code with a struct generic type parameter <div class="highlight highlight-sou

Using Traits within `ctx` and `endian` fails for some cases about deku HOT 3 CLOSED

wcampbell0x2a commented on June 9, 2024

Using Traits within `ctx` and `endian` fails for some cases

from deku.

Comments (3)

wcampbell0x2a commented on June 9, 2024

Actually not sure how to solve this. Looks like the impl<N: Nice> is required at the beginning, but deku has no way of knowing that bound.

from deku.

wcampbell0x2a commented on June 9, 2024

Nevermind, struct Test<N : Nice> { fixes this.

from deku.

wcampbell0x2a commented on June 9, 2024

This isn't an issue with deku, just noting you need to use PhantomData for this to work:

use std::marker::PhantomData;

use deku::prelude::*;

trait Nice {}

struct Kind<N: Nice> {
    n: N,
    endian: deku::ctx::Endian,
}

#[derive(DekuRead)]
#[deku(ctx = "kind: Kind<N>")]
#[deku(endian = "kind.endian ")]
struct Test<N: Nice> {
    whatever: u8,
    #[deku(skip)]
    phantom: PhantomData<N>,
}

fn main() {
}

Otherwise you get this error!:

error[E0392]: parameter `N` is never used
  --> src/main.rs:13:13
   |
13 | struct Test<N: Nice> {
   |             ^ unused parameter
   |
   = help: consider removing `N`, referring to it in a field, or using a marker such as `PhantomData`

For more information about this error, try `rustc --explain E0392`.
error: could not compile `testing` due to previous error