AF4, etc

[pdgilbert]

In updating some example for a recent change committed in the git version
(const generics gpio (from F4) 2f5b395) I have had to change

    type I2cBus = I2c<
        I2C1,
        (
            PA9 <Alternate<AF4, OpenDrain>>,
            PA10<Alternate<AF4, OpenDrain>>,
        ),
    >;

to

    type I2cBus = I2c<
        I2C1,
        (
            PA9 <Alternate<OpenDrain, 4u8>>,   
            PA10<Alternate<OpenDrain, 4u8>>,
        ),
    >;

Is there a simpler/clearer way I should specify this, or is there some reason to not export AF4?

For comparison, with other hals I have

    #[cfg(feature = "stm32f1xx")]
    type I2cBus = BlockingI2c<pac::I2C1, (PB8<Alternate<OpenDrain>>, PB9<Alternate<OpenDrain>>)>;

    #[cfg(feature = "stm32f3xx")]
    type I2cBus = I2c<I2C1, (PB6<AF4<OpenDrain>>, PB7<AF4<OpenDrain>>)>;


    #[cfg(feature = "stm32f4xx")]
    type I2cBus = I2c<pac::I2C1, (PB8<AlternateOD<AF4>>, PB9<AlternateOD<AF4>>)>; //NO BlockingI2c

    #[cfg(feature = "stm32f7xx")]
    type I2cBus = BlockingI2c<pac::I2C1, PB8<AlternateOD<AF4>>, PB9<AlternateOD<AF4>>>;

    #[cfg(feature = "stm32h7xx")]
    type I2cBus = I2c<I2C1>;

    #[cfg(feature = "stm32l0xx")]
    type I2cBus = BlockingI2c<pac::I2C1, (PB8<Alternate<OpenDrain>>, PB9<Alternate<OpenDrain>>)>;

    #[cfg(feature = "stm32l1xx")]
    type I2cBus = I2c<I2C1, (PB8<Output<OpenDrain>>, PB9<Output<OpenDrain>>)>;

and by far the stm32h7xx specification seems to be simplest if that can be made to work.
( CI for the examples is at https://github.com/pdgilbert/rust-integration-testing/actions )