binread 2.2.0

A Rust crate for helping read structs from binary data using ✨macro magic✨
Documentation 
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use crate::{io, BinRead, BinResult, Error, ReadOptions};
#[cfg(not(feature = "std"))]
use alloc::{boxed::Box, string::String};

pub enum AssertErrorFn<M, E> {
    Message(M),
    Error(E),
}

pub fn assert<MsgFn, Msg, ErrorFn, Err>(
    test: bool,
    pos: u64,
    error_fn: AssertErrorFn<MsgFn, ErrorFn>,
) -> BinResult<()>
where
    MsgFn: Fn() -> Msg,
    Msg: Into<String> + Sized,
    ErrorFn: Fn() -> Err,
    Err: core::any::Any + Sync + Send + 'static,
{
    if test {
        Ok(())
    } else {
        Err(match error_fn {
            AssertErrorFn::Message(error_fn) => Error::AssertFail {
                pos,
                message: error_fn().into(),
            },
            AssertErrorFn::Error(error_fn) => Error::Custom {
                pos,
                err: Box::new(error_fn()),
            },
        })
    }
}

// This validates the map function return value by trying to coerce it into
// a function with the expected return type. If this is not done, the
// compiler will emit the diagnostic on the `#[derive(BinRead)]` attribute
// instead of the return statement of the map function. The simpler approach
// of assigning the map function to a variable with a function pointer type
// does not work for capturing closures since they are not compatible with
// that type.
pub fn coerce_fn<R, T, F>(f: F) -> F
where
    F: Fn(T) -> R,
{
    f
}

pub fn try_after_parse<Reader, ValueType, ArgType>(
    item: &mut Option<ValueType>,
    reader: &mut Reader,
    ro: &ReadOptions,
    args: ArgType,
) -> BinResult<()>
where
    Reader: io::Read + io::Seek,
    ValueType: BinRead<Args = ArgType>,
    ArgType: Copy + 'static,
{
    if let Some(value) = item.as_mut() {
        value.after_parse(reader, ro, args)?;
    }

    Ok(())
}