Code example doesn't compile

[diondokter]

@hdoordt

https://github.com/tweedegolf/rust-workshop/blob/eb901ff9b2984177e5baea397abd335be52f1df7/slides/A-intro-to-rust.md#L1995

All these a,b,c,d have to be cast to u32. But that doesn't look nice...
So... Should we change it?

[squell]

During the last training I did, this was a nice moment to re-inforce the point that Rust is quite strict on integer conversions (although I'd prefer these kind of safe upcasts were allowed). I.e.

• Either we fix this error, but that would require finding a 'nicer' example; I'm pretty sure those exists.
• Or we own up to it (we could even add a slide after this one that goes "woops, it didnd't compile, here's how to fix it")