THIS IS A GENERAL ERRORS QUESTION, WHICH SHOULDN'T BE AFFECTED BY THE FACT THAT ITS AN EMBEDDED RUST PROJECT.

Hi im a beginner rustacean, I just finished THE BOOK, and am doing some embedded rust on the pico2. I was modifying the tmc2209-uart crate on crates.io to use the rp235x-hal uart functions/methods, when bam out of nowhere I get hit with this trait cyclical dependency error, that doesn't even make sense. I can't understand what the compiler is trying to tell me, and I don't find these links:- "note: see Overview of the compiler - Rust Compiler Development Guide and Queries: demand-driven compilation - Rust Compiler Development Guide for more information" very helpful.

the traits bit that is causing the error is this bit:

pub struct Tmc2209<D, P>
where
    D: uart::UartDevice,
    P: uart::ValidUartPinout<D>,
{
    /// UART peripheral.
    uart: uart::UartPeripheral<uart::Enabled, D, P>,
}

I'll post the full code in a separate post below

I am downright confused I would be grateful if the community could enlighten me.

the output of cargo check has been given below

Thank You

error[E0391]: cycle detected when computing the variances for items in this crate
    |
note: ...which requires computing function signature of `driver::<impl at src/driver.rs:125:1: 128:33>::read_register`...
   --> src/driver.rs:141:5
    |
141 |     pub fn read_register<R: ReadableRegister>(&mut self) -> Result<R, Error<_>> {
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires type-checking `driver::<impl at src/driver.rs:125:1: 128:33>::read_register`...
   --> src/driver.rs:141:5
    |
141 |     pub fn read_register<R: ReadableRegister>(&mut self) -> Result<R, Error<_>> {
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires computing function signature of `driver::<impl at src/driver.rs:125:1: 128:33>::read_echo`...
   --> src/driver.rs:222:5
    |
222 |     fn read_echo(&mut self, buf: &mut [u8]) -> Result<(), Error<_>> {
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires type-checking `driver::<impl at src/driver.rs:125:1: 128:33>::read_echo`...
   --> src/driver.rs:222:5
    |
222 |     fn read_echo(&mut self, buf: &mut [u8]) -> Result<(), Error<_>> {
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires computing the variances of `error::Error::Echo`...
   --> src/error.rs:33:5
    |
 33 |     Echo(E),
    |     ^^^^
    = note: ...which again requires computing the variances for items in this crate, completing the cycle
note: cycle used when computing the variances of `driver::Tmc2209`
   --> src/driver.rs:42:1
    |
 42 | pub struct Tmc2209<D, P>
    | ^^^^^^^^^^^^^^^^^^^^^^^^
    = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information

For more information about this error, try `rustc --explain E0391`.
error: could not compile `tmc2209-pi` (lib) due to 1 previous error

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