linux-kernel - Re: [PATCH] rust: macros: update 'paste!' macro to accept string literals

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Date:   Tue, 24 Oct 2023 09:51:10 -0700
From:   Boqun Feng <boqun.feng@...il.com>
To:     Trevor Gross <tmgross@...ch.edu>
Cc:     Miguel Ojeda <ojeda@...nel.org>,
        Alex Gaynor <alex.gaynor@...il.com>,
        Wedson Almeida Filho <wedsonaf@...il.com>,
        Gary Guo <gary@...yguo.net>,
        Björn Roy Baron <bjorn3_gh@...tonmail.com>,
        Benno Lossin <benno.lossin@...ton.me>,
        Andreas Hindborg <a.hindborg@...sung.com>,
        Alice Ryhl <aliceryhl@...gle.com>,
        Martin Rodriguez Reboredo <yakoyoku@...il.com>,
        rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
        FUJITA Tomonori <fujita.tomonori@...il.com>
Subject: Re: [PATCH] rust: macros: update 'paste!' macro to accept string
 literals

On Sun, Oct 08, 2023 at 05:48:18AM -0400, Trevor Gross wrote:
> Enable combining identifiers with string literals in the 'paste!' macro.
> This allows combining user-specified strings with affixes to create
> namespaced identifiers.
> 
> This sample code:
> 
>     macro_rules! m {
>         ($name:lit) => {
>             paste!(struct [<_some_ $name _struct_>];)
>         }
>     }
> 
>     m!("foo_bar");
> 
> Would previously cause a compilation error. It will now generate:
> 
>     struct _some_foo_bar_struct_;
> 
> Reported-by: FUJITA Tomonori <fujita.tomonori@...il.com>
> Signed-off-by: Trevor Gross <tmgross@...ch.edu>

This looks good to me, but could you (in a follow-up patch mabye) add an
example demonstrating the usage, which could also serve as a test if we
can run doctest for macro doc. Thanks!

Regards,
Boqun

> ---
> 
> Original mention of this problem in [1]
> 
> [1]: https://lore.kernel.org/rust-for-linux/20231008.164906.1151622782836568538.fujita.tomonori@gmail.com/
> 
>  rust/macros/paste.rs | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/rust/macros/paste.rs b/rust/macros/paste.rs
> index 385a78434224..f40d42b35b58 100644
> --- a/rust/macros/paste.rs
> +++ b/rust/macros/paste.rs
> @@ -9,7 +9,15 @@ fn concat(tokens: &[TokenTree], group_span: Span) -> TokenTree {
>      loop {
>          match tokens.next() {
>              None => break,
> -            Some(TokenTree::Literal(lit)) => segments.push((lit.to_string(), lit.span())),
> +            Some(TokenTree::Literal(lit)) => {
> +                // Allow us to concat string literals by stripping quotes
> +                let mut value = lit.to_string();
> +                if value.starts_with('"') && value.ends_with('"') {
> +                    value.remove(0);
> +                    value.pop();
> +                }
> +                segments.push((value, lit.span()));
> +            }
>              Some(TokenTree::Ident(ident)) => {
>                  let mut value = ident.to_string();
>                  if value.starts_with("r#") {
> -- 
> 2.34.1
> 
>