linux-kernel - Re: [PATCH v1 1/3] rust: macros: add `quote!` macro

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Date:   Mon, 13 Mar 2023 08:30:05 -0700
From:   Boqun Feng <boqun.feng@...il.com>
To:     y86-dev <y86-dev@...tonmail.com>
Cc:     "ojeda@...nel.org" <ojeda@...nel.org>,
        "alex.gaynor@...il.com" <alex.gaynor@...il.com>,
        "wedsonaf@...il.com" <wedsonaf@...il.com>,
        Gary Guo <gary@...yguo.net>,
        "bjorn3_gh@...tonmail.com" <bjorn3_gh@...tonmail.com>,
        "rust-for-linux@...r.kernel.org" <rust-for-linux@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "patches@...ts.linux.dev" <patches@...ts.linux.dev>
Subject: Re: [PATCH v1 1/3] rust: macros: add `quote!` macro

On Mon, Mar 13, 2023 at 01:23:18AM +0000, y86-dev wrote:
> From: Gary Guo <gary@...yguo.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@...yguo.net>
> Signed-off-by: Benno Lossin <y86-dev@...tonmail.com>

Not sure whether I missed any sutble details, but the macros look
straight-forward. One thing could be improved is having a doc describing
what `quote!` does, a link to the quote crate will do the trick.

Anyway, the code looks good to me.

Acked-by: Boqun Feng <boqun.feng@...il.com>

Regards,
Boqun

> ---
>  rust/macros/lib.rs   |   2 +
>  rust/macros/quote.rs | 125 +++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 127 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..55b663d665ec
> --- /dev/null
> +++ b/rust/macros/quote.rs
> @@ -0,0 +1,125 @@
> +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());
> +    }
> +}
> +
> +macro_rules! quote_spanned {
> +    ($span:expr => $($tt:tt)*) => {{
> +        let mut tokens = Vec::new();
> +        let span = $span;
> +        quote_spanned!(@proc tokens span $($tt)*);
> +        proc_macro::TokenStream::from_iter(tokens)
> +    }};
> +    (@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());
> +        }
> +        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)*);
> +    };
> +}
> +
> +macro_rules! quote {
> +    ($($tt:tt)*) => {
> +        quote_spanned!(proc_macro::Span::mixed_site() => $($tt)*)
> +    }
> +}
> -- 
> 2.39.2