Use vcell v0.1.2

[david-sawatzke]

The register.rs file included in the output of svd2rust uses
as_ptr(), which was only added in vcell v0.1.1 (now yanked).

See rust-embedded/svd2rust#484 (maybe wait until it's looked at/merged)

This was found while doing #355 with a very old existing clone & running into weird compile errors:

error[E0599]: no method named `as_ptr` found for struct `VolatileCell<U>` in the current scope
  --> /[..]/atsamd/pac/atsamd21e/src/generic.rs:39:23
   |
39 |         self.register.as_ptr()
   |                       ^^^^^^ method not found in `VolatileCell<U>`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0599`.
error: could not compile `atsamd21e`

To learn more, run the command again with --verbose.

[twitchyliquid64]

Did you try cargo update on your old clone?

[david-sawatzke]

Yes & that worked. But code needing a caro update is a bit broken, so I'd like to fix it. Especially since it could lead to uncompilable code, if some dependency has a hard dependency on v0.1.0.

[twitchyliquid64]

I dont know enough about cargo / rust idioms to know if this is a bug or a feature, so ill leave this to another reviewer.

[sajattack]

I'm happy with it, it just means we'll have to watch a little more closely for the next update because point releases won't go automatically.

[sajattack]

Should we wait for svd2rust to update?

[david-sawatzke]

Should we maybe switch to a caret requirement to avoid that? Is there any reason why tilde requirements are used? Otherwise I'd switch all the pac dependencies to a caret requirement.

I can't think of any way this is wrong, but I have been proven otherwise in the past and will be in the future. This isn't a particularly pressing issue (the offending code is over half a year old and I seem to be the first one with this issue), so I'd rather wait until the svd2rust folks give their verdict.

[sajattack]

Sure caret seems good. I've always been a little confused by this too. What is the difference between caret, tilde, and just "0.1". Docs here but I'm still not certain https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html

[sajattack]

I guess the difference between caret and tilde is caret can only go upwards, but what is the unspecified one? Is it the same as tilde?

[david-sawatzke]

Since this string does not have any operators in it, it is interpreted the same way as if we had specified "^0.1.12", which is called a caret requirement.

Unspecified is the same as caret

[sajattack]

Ok, let's just do unspecified for everything then. I'm not sure why we have tilde, it's only ever caused problems in the past.

[david-sawatzke]

Done, now let's wait for CI

[sajattack]

Maybe should be "^0.1.2", since that one specifies all the digits and we want it to update on patch versions. Sorry I was unclear.

[david-sawatzke]

Wait, I'm confused now. "0.1.2" and "^0.1.2" mean the same, there's no difference

[sajattack]

Oh. I thought "^0.1.2" was the same as "0.1" but "0.1.2" meant exactly 0.1.2 with no updates.

[sajattack]

Haha I should probably know this by now given how many crates I maintain. 😅

[sajattack]

Ping me when svd2rust r+'es

[david-sawatzke]

@sajattack The time has come

[sajattack]

That was quick.