Change Into<Hertz> to TryInto<Hertz> in rcc.rs

[rfuest]

In contrast to my suggestion in #136 I decided to change Into<Hertz> to TryInto<Hertz> in rcc.rs. All methods that take a frequency argument already contained assertions that would cause a panic if the value is out of range. The same assertions can also catch if TryInto<Hertz> fails.

I've also added some docs to make the user aware that these methods might panic and under which conditions.

[hannobraun]

Thank you, @rfuest. I agree with your reasoning regarding TryInto.

I see you're a following the school of "first lines of documentation need to end with a period, even though that doesn't make sense because they're titles and not sentences". I won't hold that against you 😁

[rfuest]

I see you're a following the school of "first lines of documentation need to end with a period, even though that doesn't make sense because they're titles and not sentences". I won't hold that against you grin

😁 I try to follow the precedence set by the std library docs, the API guidelines and RFC 1574. It might not make sense, but at least it's consistent 😉

[hannobraun]

Ah, I didn't know this was the officially recommended style. Oh well, looks like I'm on the wrong side of history, yet again 😁

[hellow554]

I really would like to see a point release, because without this all builds fail that try to use a function that has a {Try,}Into<Hertz> constraint:

error[E0277]: the trait bound `Hertz: From<Megahertz>` is not satisfied
  --> src/main.rs:14:10
   |
14 |         .sysclk(216_u32.MHz())
   |          ^^^^^^ the trait `From<Megahertz>` is not implemented for `Hertz`
   |
   = help: the following implementations were found:
             <Hertz<u64> as From<Centihertz>>
             <Hertz<u64> as From<Decihertz>>
             <Hertz<u64> as From<Hertz>>
             <Hertz<u64> as From<Kibihertz>>
           and 5 others
   = note: required because of the requirements on the impl of `Into<Hertz>` for `Megahertz`

[hannobraun]

Thanks for the note, @hellow554. I'm busy right now, but I've added releasing a new version to my task list. I hope I'll be able to get to it within the next 1-2 weeks.

[hannobraun]

@hellow554: Version 0.5 has been published.