Unused trait in Serial?

[hargoniX]

So I was just reading through our UART/USART implementation in serial.rs and there we define the trait pub trait PinCk<USART> {} in line 155. It's only ever used again in the macro that implements it en mass for all the pins that are valid clock pins for USART. However I believe the correct intention should be to implement the Pin trait for a (TX, RX, CK) triple for all USART constructors right? Otherwise the trait doesn't bring any additional safety guarantees as far as I can see (feel free to correct me on that).

[hargoniX]

Pinging @richardeoin as he implemented it

[richardeoin]

You're right, the PinCk trait doesn't do anything here. It's really there for future use, in case we implement one of the synchronous modes in the HAL.

It's also publicly available as a trait bound, which is possibly useful in other crates.