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From:   Andreas Hindborg <nmi@metaspace.dk>
To:     Andreas Hindborg <nmi@metaspace.dk>
Cc:     y86-dev@protonmail.com, Miguel Ojeda <ojeda@kernel.org>,
        Alex Gaynor <alex.gaynor@gmail.com>,
        Wedson Almeida Filho <wedsonaf@gmail.com>,
        Boqun Feng <boqun.feng@gmail.com>, Gary Guo <gary@garyguo.net>,
        =?utf-8?Q?Bj?= =?utf-8?Q?=C3=B6rn?= Roy Baron 
        <bjorn3_gh@protonmail.com>, Alice Ryhl <alice@ryhl.io>,
        rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org,
        patches@lists.linux.dev
Subject: Re: [PATCH v3 01/13] rust: macros: add `quote!` macro
Date:   Thu, 30 Mar 2023 14:01:21 +0200
In-reply-to: <877cuy5ur2.fsf@metaspace.dk>
Message-ID: <87355m5tvs.fsf@metaspace.dk>
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Andreas Hindborg <nmi@metaspace.dk> writes:

> y86-dev@protonmail.com writes:
>
>> From: Gary Guo <gary@garyguo.net>
>>
>> Add the `quote!` macro for creating `TokenStream`s directly via the
>> given Rust tokens. It also supports repetitions using iterators.
>>
>> It will be used by the pin-init API proc-macros to generate code.
>>
>> Signed-off-by: Gary Guo <gary@garyguo.net>
>> Signed-off-by: Benno Lossin <y86-dev@protonmail.com>
>> ---
>>  rust/macros/lib.rs   |   2 +
>>  rust/macros/quote.rs | 145 +++++++++++++++++++++++++++++++++++++++++++
>>  2 files changed, 147 insertions(+)
>>  create mode 100644 rust/macros/quote.rs
>>
>> diff --git a/rust/macros/lib.rs b/rust/macros/lib.rs
>> index c1d385e345b9..82b520f024dd 100644
>> --- a/rust/macros/lib.rs
>> +++ b/rust/macros/lib.rs
>> @@ -2,6 +2,8 @@
>>
>>  //! Crate for all kernel procedural macros.
>>
>> +#[macro_use]
>> +mod quote;
>>  mod concat_idents;
>>  mod helpers;
>>  mod module;
>> diff --git a/rust/macros/quote.rs b/rust/macros/quote.rs
>> new file mode 100644
>> index 000000000000..7efb009c25a9
>> --- /dev/null
>> +++ b/rust/macros/quote.rs
>> @@ -0,0 +1,145 @@
>> +// SPDX-License-Identifier: Apache-2.0 OR MIT
>> +
>> +use proc_macro::{TokenStream, TokenTree};
>> +
>> +pub(crate) trait ToTokens {
>> +    fn to_tokens(&self, tokens: &mut TokenStream);
>> +}
>> +
>> +impl<T: ToTokens> ToTokens for Option<T> {
>> +    fn to_tokens(&self, tokens: &mut TokenStream) {
>> +        if let Some(v) = self {
>> +            v.to_tokens(tokens);
>> +        }
>> +    }
>> +}
>> +
>> +impl ToTokens for proc_macro::Group {
>> +    fn to_tokens(&self, tokens: &mut TokenStream) {
>> +        tokens.extend([TokenTree::from(self.clone())]);
>> +    }
>> +}
>> +
>> +impl ToTokens for TokenTree {
>> +    fn to_tokens(&self, tokens: &mut TokenStream) {
>> +        tokens.extend([self.clone()]);
>> +    }
>> +}
>> +
>> +impl ToTokens for TokenStream {
>> +    fn to_tokens(&self, tokens: &mut TokenStream) {
>> +        tokens.extend(self.clone());
>> +    }
>> +}
>> +
>> +/// Converts tokens into [`proc_macro::TokenStream`] and performs variable interpolations with
>> +/// the given span.
>> +///
>> +/// This is a similar to the
>> +/// [`quote_spanned!`](https://docs.rs/quote/latest/quote/macro.quote_spanned.html) macro from the
>> +/// `quote` crate but provides only just enough functionality needed by the current `macros` crate.
>> +#[allow(unused_macros)]
>> +macro_rules! quote_spanned {
>> +    ($span:expr => $($tt:tt)*) => {
>> +    #[allow(clippy::vec_init_then_push)]
>> +    {
>> +        let mut tokens = Vec::new();
>> +        let span = $span;
>> +        quote_spanned!(@proc tokens span $($tt)*);
>> +        proc_macro::TokenStream::from_iter(tokens)
>
> Should this be `::alloc::vec::Vec` and
> `::proc_macro::TokenStream::from_iter` ?
>
> Best regards,
> Andreas
>
>> +    }};
>> +    (@proc $v:ident $span:ident) => {};
>> +    (@proc $v:ident $span:ident #$id:ident $($tt:tt)*) => {
>> +        let mut ts = proc_macro::TokenStream::new();
>> +        crate::quote::ToTokens::to_tokens(&$id, &mut ts);
>> +        $v.extend(ts.into_iter());
>> +        quote_spanned!(@proc $v $span $($tt)*);
>> +    };
>> +    (@proc $v:ident $span:ident #(#$id:ident)* $($tt:tt)*) => {
>> +        for token in $id {
>> +            let mut ts = proc_macro::TokenStream::new();
>> +            crate::quote::ToTokens::to_tokens(&token, &mut ts);
>> +            $v.extend(ts.into_iter());

Also, could this be without `into_iter()`: `$v.extend(ts)`?

BR Andreas

>> +        }
>> +        quote_spanned!(@proc $v $span $($tt)*);
>> +    };
>> +    (@proc $v:ident $span:ident ( $($inner:tt)* ) $($tt:tt)*) => {
>> +        let mut tokens = Vec::new();
>> +        quote_spanned!(@proc tokens $span $($inner)*);
>> +        $v.push(proc_macro::TokenTree::Group(proc_macro::Group::new(
>> +            proc_macro::Delimiter::Parenthesis,
>> +            proc_macro::TokenStream::from_iter(tokens)
>> +        )));
>> +        quote_spanned!(@proc $v $span $($tt)*);
>> +    };
>> +    (@proc $v:ident $span:ident [ $($inner:tt)* ] $($tt:tt)*) => {
>> +        let mut tokens = Vec::new();
>> +        quote_spanned!(@proc tokens $span $($inner)*);
>> +        $v.push(proc_macro::TokenTree::Group(proc_macro::Group::new(
>> +            proc_macro::Delimiter::Bracket,
>> +            proc_macro::TokenStream::from_iter(tokens)
>> +        )));
>> +        quote_spanned!(@proc $v $span $($tt)*);
>> +    };
>> +    (@proc $v:ident $span:ident { $($inner:tt)* } $($tt:tt)*) => {
>> +        let mut tokens = Vec::new();
>> +        quote_spanned!(@proc tokens $span $($inner)*);
>> +        $v.push(proc_macro::TokenTree::Group(proc_macro::Group::new(
>> +            proc_macro::Delimiter::Brace,
>> +            proc_macro::TokenStream::from_iter(tokens)
>> +        )));
>> +        quote_spanned!(@proc $v $span $($tt)*);
>> +    };
>> +    (@proc $v:ident $span:ident :: $($tt:tt)*) => {
>> +        $v.push(
>> +            proc_macro::TokenTree::Punct(proc_macro::Punct::new(':', proc_macro::Spacing::Joint))
>> +        );
>> +        $v.push(
>> +            proc_macro::TokenTree::Punct(proc_macro::Punct::new(':', proc_macro::Spacing::Alone))
>> +        );
>> +        quote_spanned!(@proc $v $span $($tt)*);
>> +    };
>> +    (@proc $v:ident $span:ident : $($tt:tt)*) => {
>> +        $v.push(
>> +            proc_macro::TokenTree::Punct(proc_macro::Punct::new(':', proc_macro::Spacing::Alone))
>> +        );
>> +        quote_spanned!(@proc $v $span $($tt)*);
>> +    };
>> +    (@proc $v:ident $span:ident , $($tt:tt)*) => {
>> +        $v.push(
>> +            proc_macro::TokenTree::Punct(proc_macro::Punct::new(',', proc_macro::Spacing::Alone))
>> +        );
>> +        quote_spanned!(@proc $v $span $($tt)*);
>> +    };
>> +    (@proc $v:ident $span:ident @ $($tt:tt)*) => {
>> +        $v.push(
>> +            proc_macro::TokenTree::Punct(proc_macro::Punct::new('@', proc_macro::Spacing::Alone))
>> +        );
>> +        quote_spanned!(@proc $v $span $($tt)*);
>> +    };
>> +    (@proc $v:ident $span:ident ! $($tt:tt)*) => {
>> +        $v.push(
>> +            proc_macro::TokenTree::Punct(proc_macro::Punct::new('!', proc_macro::Spacing::Alone))
>> +        );
>> +        quote_spanned!(@proc $v $span $($tt)*);
>> +    };
>> +    (@proc $v:ident $span:ident $id:ident $($tt:tt)*) => {
>> +        $v.push(proc_macro::TokenTree::Ident(proc_macro::Ident::new(stringify!($id), $span)));
>> +        quote_spanned!(@proc $v $span $($tt)*);
>> +    };
>> +}
>> +
>> +/// Converts tokens into [`proc_macro::TokenStream`] and performs variable interpolations with
>> +/// mixed site span ([`Span::mixed_site()`]).
>> +///
>> +/// This is a similar to the [`quote!`](https://docs.rs/quote/latest/quote/macro.quote.html) macro
>> +/// from the `quote` crate but provides only just enough functionality needed by the current
>> +/// `macros` crate.
>> +///
>> +/// [`Span::mixed_site()`]: https://doc.rust-lang.org/proc_macro/struct.Span.html#method.mixed_site
>> +#[allow(unused_macros)]
>> +macro_rules! quote {
>> +    ($($tt:tt)*) => {
>> +        quote_spanned!(proc_macro::Span::mixed_site() => $($tt)*)
>> +    }
>> +}