Re: [PATCH 3/4] rust: macros: Enable use from macro_rules!

[Alice Ryhl <aliceryhl@google.com>]

Ethan D. Twardy <ethan.twardy@gmail.com> writes:
> According to the rustdoc for the proc_macro crate[1], tokens captured
> from a "macro variable" (e.g. from within macro_rules!) may be delimited
> by invisible tokens and be contained within a proc_macro::Group.
> Previously, this scenario was not handled by macros::paste, which caused
> a proc-macro panic when the corresponding tests are enabled. Enable the
> tests, and handle this case by making macros::paste::concat recursive.

The actual change looks good to me.

Reviewed-by: Alice Ryhl <aliceryhl@google.com>

However, I have a bunch of formatting nits:

> [1]: https://doc.rust-lang.org/stable/proc_macro/enum.Delimiter.html
> 
> Signed-off-by: Ethan D. Twardy <ethan.twardy@gmail.com>

Normally this would be formatted as:

Link: https://doc.rust-lang.org/stable/proc_macro/enum.Delimiter.html [1]
Signed-off-by: Ethan D. Twardy <ethan.twardy@gmail.com>

> diff --git a/rust/macros/lib.rs b/rust/macros/lib.rs
> index d8bd34c0ba89..8afed8facb21 100644
> --- a/rust/macros/lib.rs
> +++ b/rust/macros/lib.rs
> @@ -269,12 +269,26 @@ pub fn pinned_drop(args: TokenStream, input: TokenStream) -> TokenStream {
>  ///
>  /// # Example
>  ///
> -/// ```ignore
> -/// use kernel::macro::paste;
> +/// ```
> +/// # const binder_driver_return_protocol_BR_OK: u32 = 0;
> +/// # const binder_driver_return_protocol_BR_ERROR: u32 = 1;
> +/// # const binder_driver_return_protocol_BR_TRANSACTION: u32 = 2;
> +/// # const binder_driver_return_protocol_BR_REPLY: u32 = 3;
> +/// # const binder_driver_return_protocol_BR_DEAD_REPLY: u32 = 4;
> +/// # const binder_driver_return_protocol_BR_TRANSACTION_COMPLETE: u32 = 5;
> +/// # const binder_driver_return_protocol_BR_INCREFS: u32 = 6;
> +/// # const binder_driver_return_protocol_BR_ACQUIRE: u32 = 7;
> +/// # const binder_driver_return_protocol_BR_RELEASE: u32 = 8;
> +/// # const binder_driver_return_protocol_BR_DECREFS: u32 = 9;
> +/// # const binder_driver_return_protocol_BR_NOOP: u32 = 10;
> +/// # const binder_driver_return_protocol_BR_SPAWN_LOOPER: u32 = 11;
> +/// # const binder_driver_return_protocol_BR_DEAD_BINDER: u32 = 12;
> +/// # const binder_driver_return_protocol_BR_CLEAR_DEATH_NOTIFICATION_DONE: u32 = 13;
> +/// # const binder_driver_return_protocol_BR_FAILED_REPLY: u32 = 14;
>  ///
>  /// macro_rules! pub_no_prefix {
>  ///     ($prefix:ident, $($newname:ident),+) => {

There's a non-hidden empty line between the last constant and
`macro_rules! pub_no_prefix`. You should either hide the empty line or
get rid of it, because it will look weird when the example is rendered.

> -///         paste! {
> +///         kernel::macros::paste! {

Another option would be to keep the import so that the empty line
separates the import from the macro declaration.

>  ///             $(pub(crate) const $newname: u32 = [<$prefix $newname>];)+
>  ///         }
>  ///     };
> @@ -313,13 +327,29 @@ pub fn pinned_drop(args: TokenStream, input: TokenStream) -> TokenStream {
>  /// * `lower`: change the identifier to lower case.
>  /// * `upper`: change the identifier to upper case.
>  ///
> -/// ```ignore
> -/// use kernel::macro::paste;
> +/// ```rust
> +/// # const binder_driver_return_protocol_BR_OK: u32 = 0;
> +/// # const binder_driver_return_protocol_BR_ERROR: u32 = 1;
> +/// # const binder_driver_return_protocol_BR_TRANSACTION: u32 = 2;
> +/// # const binder_driver_return_protocol_BR_REPLY: u32 = 3;
> +/// # const binder_driver_return_protocol_BR_DEAD_REPLY: u32 = 4;
> +/// # const binder_driver_return_protocol_BR_TRANSACTION_COMPLETE: u32 = 5;
> +/// # const binder_driver_return_protocol_BR_INCREFS: u32 = 6;
> +/// # const binder_driver_return_protocol_BR_ACQUIRE: u32 = 7;
> +/// # const binder_driver_return_protocol_BR_RELEASE: u32 = 8;
> +/// # const binder_driver_return_protocol_BR_DECREFS: u32 = 9;
> +/// # const binder_driver_return_protocol_BR_NOOP: u32 = 10;
> +/// # const binder_driver_return_protocol_BR_SPAWN_LOOPER: u32 = 11;
> +/// # const binder_driver_return_protocol_BR_DEAD_BINDER: u32 = 12;
> +/// # const binder_driver_return_protocol_BR_CLEAR_DEATH_NOTIFICATION_DONE: u32 = 13;
> +/// # const binder_driver_return_protocol_BR_FAILED_REPLY: u32 = 14;
>  ///
>  /// macro_rules! pub_no_prefix {
>  ///     ($prefix:ident, $($newname:ident),+) => {

Same here.

>  ///         kernel::macros::paste! {
> -///             $(pub(crate) const fn [<$newname:lower:span>]: u32 = [<$prefix $newname:span>];)+
> +///             $(pub(crate) const fn [<$newname:lower:span>]() -> u32 {
> +///             [<$prefix $newname:span>]
> +///             })+

I would probably indent [<$prefix $newname:span>] one more time.

Alice