Re: [PATCH 3/5] rust: list: use consistent type parameter names

[Benno Lossin]

On Tue Mar 25, 2025 at 11:42 AM CET, Tamir Duberstein wrote:
> On Tue, Mar 25, 2025 at 6:37 AM Benno Lossin <benno.lossin@xxxxxxxxx> wrote:
>> On Tue Mar 25, 2025 at 10:52 AM CET, Tamir Duberstein wrote:
>> > On Tue, Mar 25, 2025 at 12:02 AM Boqun Feng <boqun.feng@xxxxxxxxx> wrote:
>> >> On Mon, Mar 24, 2025 at 05:56:57PM -0400, Tamir Duberstein wrote:
>> >> > On Mon, Mar 24, 2025 at 5:51 PM Tamir Duberstein <tamird@xxxxxxxxx> wrote:
>> >> > > On Mon, Mar 24, 2025 at 5:42 PM Boqun Feng <boqun.feng@xxxxxxxxx> wrote:
>> >> > > > On Mon, Mar 24, 2025 at 05:33:45PM -0400, Tamir Duberstein wrote:
>> >> > > > >              #[inline]
>> >> > > > > @@ -81,16 +81,16 @@ pub unsafe trait HasSelfPtr<T: ?Sized, const ID: u64 = 0>
>> >> > > > >  /// Implements the [`HasListLinks`] and [`HasSelfPtr`] traits for the given type.
>> >> > > > >  #[macro_export]
>> >> > > > >  macro_rules! impl_has_list_links_self_ptr {
>> >> > > > > -    ($(impl$({$($implarg:tt)*})?
>> >> > > > > +    ($(impl$({$($generics:tt)*})?
>> >> > > >
>> >> > > > While you're at it, can you also change this to be
>> >> > > >
>> >> > > >         ($(impl$(<$($generics:tt)*>)?
>> >> > > >
>> >> > > > ?
>> >> > > >
>> >> > > > I don't know why we chose <> for impl_has_list_links, but {} for
>> >> > > > impl_has_list_links_self_ptr ;-)
>> >> > >
>> >> > > This doesn't work in all cases:
>> >> > >
>> >> > > error: local ambiguity when calling macro `impl_has_work`: multiple
>> >> > > parsing options: built-in NTs tt ('generics') or 1 other option.
>> >> > >    --> ../rust/kernel/workqueue.rs:522:11
>> >> > >     |
>> >> > > 522 |     impl<T> HasWork<Self> for ClosureWork<T> { self.work }
>> >> > >
>> >> > > The reason that `impl_has_list_links` uses <> and all others use {} is
>> >> > > that `impl_has_list_links` is the only one that captures the generic
>> >> > > parameter as an `ident`, the rest use `tt`. So we could change
>> >>
>> >> Why impl_has_list_links uses generics at `ident` but rest use `tt`? I'm
>> >> a bit curious.
>> >
>> > I think it's because `ident` cannot deal with lifetimes or const
>> > generics - or at least I was not able to make it work with them.
>>
>> If you use `ident`, you can use the normal `<>` as the delimiters of
>> generics. For `tt`, you have to use `{}` (or `()`/`[]`).
>
> Yes I know. But with `ident` you cannot capture lifetimes or const generics.

Why is that required for this macro? I think we could use `tt`.

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Cheers,
Benno