Combining bitfields and subtypes leads to `expected (), found Endian` error

[byteit101]

I was following the tutorial at https://docs.rs/deku/latest/deku/index.html and, after 2 successes, I merged the two examples together, getting a strange compilation error.

src/main.rs:

use deku::prelude::*; 

#[derive(Debug, PartialEq, DekuRead, DekuWrite)]
#[deku(endian = "big")]
struct DekuTest {
    #[deku(bits = 4)]
    field_a: u8,
    #[deku(bits = 4)]
    field_b: u8,
    field_c: DekuHeader,
}

#[derive(Debug, PartialEq, DekuRead, DekuWrite)]
struct DekuHeader(u8);

fn main() {
    println!("Hello, world!");
}

cargo.toml:

[package]
name = "test"
version = "0.1.0"
edition = "2021"

[dependencies]
deku = "0.19.1"

Result:

error[E0308]: mismatched types
   --> src/main.rs:3:28
    |
3   | #[derive(Debug, PartialEq, DekuRead, DekuWrite)]
    |                            ^^^^^^^^
    |                            |
    |                            expected `()`, found `Endian`
    |                            arguments to this function are incorrect
    |
note: associated function defined here
   --> /cargo/registry/src/index.crates.io-6f17d22bba15001f/deku-0.19.1/src/lib.rs:423:8
    |
423 |     fn from_reader_with_ctx<R: no_std_io::Read + no_std_io::Seek>(
    |        ^^^^^^^^^^^^^^^^^^^^
    = note: this error originates in the derive macro `DekuRead` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0308]: mismatched types
   --> src/main.rs:3:38
    |
3   | #[derive(Debug, PartialEq, DekuRead, DekuWrite)]
    |                                      ^^^^^^^^^
    |                                      |
    |                                      expected `()`, found `Endian`
    |                                      arguments to this function are incorrect
    |
note: method defined here
   --> /cargo/registry/src/index.crates.io-6f17d22bba15001f/deku-0.19.1/src/lib.rs:489:8
    |
489 |     fn to_writer<W: no_std_io::Write + no_std_io::Seek>(
    |        ^^^^^^^^^
    = note: this error originates in the derive macro `DekuWrite` (in Nightly builds, run with -Z macro-backtrace for more info)

For more information about this error, try `rustc --explain E0308`.
error: could not compile `test` (bin "test") due to 2 previous errors

[sharksforarms]

👋 @byteit101 you're hitting the second example in https://docs.rs/deku/latest/deku/attributes/index.html#endian

DekuHeader, since it's a sub-field of DekuTest, needs knowledge of the endian since it's specified on the top-level

[byteit101]

Ah! Should the first example on https://docs.rs/deku/latest/deku/index.html then either not use endian, or more directly call out that requirement? I'm happy to make a doc PR either way

[sharksforarms]

Ah! Should the first example on docs.rs/deku/latest/deku/index.html then either not use endian, or more directly call out that requirement? I'm happy to make a doc PR either way

I think expanding the existing example to include an owned type (like you're trying to do and what the second example in the endian docs do) would be helpful!