Embedded Rust Discovery Book example fails to compile - rust

Question

I am new to rust and embedded systems. I was reading and going along "The Discovery Book" and I can't seem to figure out the errors below.
I have placed this in my main.rs:
#![deny(unsafe_code)]
#![no_main]
#![no_std]
use aux5::{entry, prelude::*, Delay, Leds};
#[entry]
fn main() -> ! {
let (mut delay, mut leds): (Delay, Leds) = aux5::init();
let half_period = 500_u16;
loop {
leds[0].on();
delay.delay_ms(half_period);
leds[0].off();
delay.delay_ms(half_period);
}
}
My auxiliary lib.rs contains:
pub use stm32f3_discovery::{leds::Leds, stm32f3xx_hal, switch_hal};
pub use switch_hal::{ActiveHigh, OutputSwitch, Switch, ToggleableOutputSwitch};
use stm32f3xx_hal::prelude::*;
pub use stm32f3xx_hal::{
delay::Delay,
gpio::{gpioe, Output, PushPull},
hal::blocking::delay::DelayMs,
stm32,
};
pub type LedArray = [Switch<gpioe::PEx<Output<PushPull>>, ActiveHigh>; 8];
pub fn init() -> (Delay, LedArray) {
let device_periphs = stm32::Peripherals::take().unwrap();
let mut reset_and_clock_control = device_periphs.RCC.constrain();
let core_periphs = cortex_m::Peripherals::take().unwrap();
let mut flash = device_periphs.FLASH.constrain();
let clocks = reset_and_clock_control.cfgr.freeze(&mut flash.acr);
let delay = Delay::new(core_periphs.SYST, clocks);
// initialize user leds
let mut gpioe = device_periphs.GPIOE.split(&mut reset_and_clock_control.ahb);
let leds = Leds::new(
gpioe.pe8,
gpioe.pe9,
gpioe.pe10,
gpioe.pe11,
gpioe.pe12,
gpioe.pe13,
gpioe.pe14,
gpioe.pe15,
&mut gpioe.moder,
&mut gpioe.otyper,
);
(delay, leds.into_array())
}
I have not changed anything in lib.rs and I am following the instructions from the book, along with the source code.
Running the code results in the following errors when building for the target:
error[E0432]: unresolved import `aux5::prelude`
--> src\05-led-roulette\src\main.rs:5:19
|
5 | use aux5::{entry, prelude::*, Delay, Leds};
| ^^^^^^^ could not find `prelude` in `aux5`
error[E0308]: mismatched types
--> src\05-led-roulette\src\main.rs:9:48
|
9 | let (mut delay, mut leds): (Delay, Leds) = aux5::init();
| ------------- ^^^^^^^^^^^^ expected struct `Leds`, found array of 8 elements
| |
| expected due to this
|
= note: expected tuple `(Delay, Leds)`
found tuple `(Delay, [Switch<PEx<Output<PushPull>>, ActiveHigh>; 8])`
error[E0608]: cannot index into a value of type `Leds`
--> src\05-led-roulette\src\main.rs:14:9
|
14 | leds[0].on();
| ^^^^^^^
error[E0599]: no method named `delay_ms` found for struct `Delay` in the current scope
--> src\05-led-roulette\src\main.rs:15:15
|
15 | delay.delay_ms(half_period);
| ^^^^^^^^ method not found in `Delay`
|
= help: items from traits can only be used if the trait is in scope
help: the following trait is implemented but not in scope; perhaps add a `use` for it:
|
5 | use aux5::DelayMs;
|
error[E0608]: cannot index into a value of type `Leds`
--> src\05-led-roulette\src\main.rs:17:9
|
17 | leds[0].off();
| ^^^^^^^
error[E0599]: no method named `delay_ms` found for struct `Delay` in the current scope
--> src\05-led-roulette\src\main.rs:18:15
|
18 | delay.delay_ms(half_period);
| ^^^^^^^^ method not found in `Delay`
|
= help: items from traits can only be used if the trait is in scope
help: the following trait is implemented but not in scope; perhaps add a `use` for it:
|
5 | use aux5::DelayMs;
|
error: aborting due to 6 previous errors
Some errors have detailed explanations: E0308, E0432, E0599, E0608.
For more information about an error, try `rustc --explain E0308`.
error: could not compile `led-roulette`
To learn more, run the command again with --verbose.

Answer 1

From the following page, "The Led and Delay abstractions", it looks like this is the set of imports that you need.
use aux5::{entry, Delay, DelayMs, LedArray, OutputSwitch};
In the above abstraction, compared to your main.rs, note the:
Addition of DelayMs trait, making .delay_ms() available.
Removal of a prelude as it is not being used.
Change from Leds to the expected LedArray.
Also see:
Stack Overflow, "Why do I need to import a trait to use the methods it defines for a type?"