Clone API docs

[jorgecarleitao]

It would be nice for the missing docs to not complain when compiling multiversion. I.e. we could make following compile by also cloning the docs:

#![deny(missing_docs)]

use multiversion::multiversion;

/// Sums values
#[multiversion]
#[clone(target = "x86_64+aes+sse3+ssse3+avx+avx2")]
/// Sums values
pub fn sum(array: &[i32]) -> i32 {
    let mut sum = 0;
    for i in array {
        sum += i;
    }
    sum
}

fn main() {
    let _ = sum(&[1, 2]);
}

cargo build yields

error: missing documentation for the crate
  --> examples/bla.rs:1:1
   |
1  | / #![deny(missing_docs)]
2  | |
3  | | use multiversion::multiversion;
4  | |
...  |
18 | |     let _ = sum(&[1, 2]);
19 | | }
   | |_^
   |
note: the lint level is defined here
  --> examples/bla.rs:1:9
   |
1  | #![deny(missing_docs)]
   |         ^^^^^^^^^^^^

error: missing documentation for a function
 --> examples/bla.rs:6:1
  |
6 | #[multiversion]
  | ^^^^^^^^^^^^^^^
  |
  = note: this error originates in the attribute macro `multiversion` (in Nightly builds, run with -Z macro-backtrace for more info)

[calebzulawski]

I'm working on a change that should place the clones within the scope of the multiversioned function, which I think should incidentally solve this as well.

[calebzulawski]

More broadly, though, I'm unsure how to handle attributes on the multiversioned function vs on the clones. Copying all attributes doesn't quite make sense, for example:

#[multiversion(...)]
#[export_name = "foo"]
pub fn some_multiversioned_function() { ... }

However sometimes you might want it copied, like the tracing::instrument macro. Maybe the default should be to not copy, and provide a mechanism to copy particular attributes.

[calebzulawski]

On master, the clones are now completely contained within the multiversioned function, which solves this issue. It also helps some more peculiar cases, like multiversioned trait implementations.