Harmonious developer tools

I’m trying out Rust for a project of mine, alongside Embassy.

I’ve found the compiler errors for Rust to be very straight forward, especially compared to the cryptic stream you get from C++. ¹

One thing that quite blew my mind though, was when I was trying to use the ADC on the Pico W. (RP2040) I didn’t have anything connected (I didn’t even have the hardware), I just wanted to get the code compiling so I took a pin on random and tried to use that as input.

    let lvl_channel = Channel::new_pin(peripherals.PIN_23, Pull::None);

Pin 23, as it happens, is not an ADC input on the RP2040.

I would expect that this would compile just fine and when you tried to run in you would get some unexpected behaviour.

But since Rust has pretty nice error messages, and the Embassy developers clearly thought of this, I was instead presented with the following when I tried to compile.

error[E0277]: the trait bound `PIN_23: AdcPin` is not satisfied
  --> src/main.rs:42:23
   |
42 |     let lvl_channel = Channel::new_pin(peripherals.PIN_23, Pull::None);
   |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `AdcPin` is not implemented for `PIN_23`
   |
   = help: the following other types implement trait `AdcPin`:
             PIN_26
             PIN_27
             PIN_28
             PIN_29

Isn’t it great when you not only get a compile time error when a feature isn’t available on a specific pin, but you also get a list of which pins do implement that feature?

All this, and not because the Rust compiler has specific support for the RP2040, but because the compiler has good error messages and the framework good design.

That is harmony.