crate::rcc::Clocks struct can be created trivially, violating its invariants

[horazont]

The documentation of crate::rcc::Clocks claims:

The existence of this value indicates that the clock configuration can no longer be changed

But the following example code can be used to obtain a value of crate::rcc::Clocks without actually tying the clocks down:

#![no_std]
#![no_main]

use panic_halt as _;

use stm32f1xx_hal as hal;

use cortex_m_rt::entry;

#[entry]
fn main() -> ! {
	let clocks: hal::rcc::Clocks = hal::rcc::Config{
		hse: Some(8000000),
		pllmul: Some(8),
		hpre: hal::rcc::HPre::DIV1,
		ppre1: hal::rcc::PPre::DIV2,
		ppre2: hal::rcc::PPre::DIV1,
		adcpre: hal::rcc::AdcPre::DIV8,
		usbpre: hal::rcc::UsbPre::DIV1,
	}.get_clocks();

	loop{}
}

[burrbull]

https://docs.rs/stm32f1xx-hal/latest/stm32f1xx_hal/rcc/struct.Config.html#method.get_clocks should be private.
Thanks.
Could you make PR?

[horazont]

Yep sure, done -> #438.