crypto-mac v0.9

[newpavlov]

• Add FromBlockCipher trait and respective NewMac blanket implementation
• Bump blobby to v0.3
• Remove impl_write! macro, since it's useless for generic types

I couldn't make code generic over From<BlockCipher> trait due to the "unconstrained type parameter" error, so I had to introduce a new non-polymorphic trait instead. Any ideas how this problem can be worked around?

[tarcieri]

I couldn't make code generic over From trait due to the "unconstrained type parameter" error, so I had to introduce a new non-polymorphic trait instead. Any ideas how this problem can be worked around?

What's the concrete error? Do you have a full example?

[newpavlov]

I've tried the following code:

impl<T,C>NewMacforTwhereT:From<C>,C:BlockCipher + NewBlockCipher,{typeKeySize = C::KeySize;fnnew(key:&Key<Self>) -> Self{C::new(key).into()}fnnew_varkey(key:&[u8]) -> Result<Self,InvalidKeyLength>{C::new_varkey(key).map_err(|_| InvalidKeyLength)?.into()}}

And I get this compilation error:

error[E0207]: the type parameter `C` is not constrained by the impl trait, self
type, or predicates
--> crypto-mac/src/lib.rs:124:9
|
124 | impl<T, C> NewMac for T
| ^ unconstrained type parameter
error: aborting due to previous error

Which in hindsight should've been expected. Right now I have no idea how to properly structure code and if it's even possible in principle.

[tarcieri]

@newpavlov aah yeah, that looks similar to what I was running into with signature. I ended up solving it with custom derive.

[newpavlov]

So what do you think? Should we go ahead with the current code for the time being?

[tarcieri]

Seems fine to me