linux-kernel - Re: [PATCH 07/11] rust: macros: convert `concat

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Message-ID: <CAJ-ks9=525PETbRGuZn=rv=H9AC=Sjgn47DSGxrKLi=0HxBmfQ@mail.gmail.com>
Date: Sun, 4 Jan 2026 17:59:35 -0500
From: Tamir Duberstein <tamird@...il.com>
To: Gary Guo <gary@...yguo.net>
Cc: Miguel Ojeda <ojeda@...nel.org>, Boqun Feng <boqun.feng@...il.com>, 
	Björn Roy Baron <bjorn3_gh@...tonmail.com>, 
	Benno Lossin <lossin@...nel.org>, Andreas Hindborg <a.hindborg@...nel.org>, 
	Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>, 
	Danilo Krummrich <dakr@...nel.org>, Fiona Behrens <me@...enk.dev>, 
	Guilherme Giacomo Simoes <trintaeoitogc@...il.com>, José Expósito <jose.exposito89@...il.com>, 
	rust-for-linux@...r.kernel.org, David Gow <davidgow@...gle.com>, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 07/11] rust: macros: convert `concat_idents!` to use `syn`

On Thu, Dec 11, 2025 at 2:30 PM Gary Guo <gary@...nel.org> wrote:
>
> From: Gary Guo <gary@...yguo.net>
>
> This eliminates the need for `expect_punct` helper.
>
> Signed-off-by: Gary Guo <gary@...yguo.net>

Reviewed-by: Tamir Duberstein <tamird@...il.com>

> ---
>  rust/macros/concat_idents.rs | 39 ++++++++++++++++++++++++------------
>  rust/macros/helpers.rs       | 14 +------------
>  rust/macros/lib.rs           |  4 ++--
>  3 files changed, 29 insertions(+), 28 deletions(-)
>
> diff --git a/rust/macros/concat_idents.rs b/rust/macros/concat_idents.rs
> index 12cb231c3d715..47b6add378d2c 100644
> --- a/rust/macros/concat_idents.rs
> +++ b/rust/macros/concat_idents.rs
> @@ -1,23 +1,36 @@
>  // SPDX-License-Identifier: GPL-2.0
>
> -use proc_macro2::{token_stream, Ident, TokenStream, TokenTree};
> +use proc_macro2::{
> +    Ident,
> +    TokenStream,
> +    TokenTree, //
> +};
> +use syn::{
> +    parse::{
> +        Parse,
> +        ParseStream, //
> +    },
> +    Result,
> +    Token, //
> +};
>
> -use crate::helpers::expect_punct;
> +pub(crate) struct Input {
> +    a: Ident,
> +    _comma: Token![,],
> +    b: Ident,
> +}
>
> -fn expect_ident(it: &mut token_stream::IntoIter) -> Ident {
> -    if let Some(TokenTree::Ident(ident)) = it.next() {
> -        ident
> -    } else {
> -        panic!("Expected Ident")
> +impl Parse for Input {
> +    fn parse(input: ParseStream<'_>) -> Result<Self> {
> +        Ok(Self {
> +            a: input.parse()?,
> +            _comma: input.parse()?,
> +            b: input.parse()?,
> +        })
>      }
>  }
>
> -pub(crate) fn concat_idents(ts: TokenStream) -> TokenStream {
> -    let mut it = ts.into_iter();
> -    let a = expect_ident(&mut it);
> -    assert_eq!(expect_punct(&mut it), ',');
> -    let b = expect_ident(&mut it);
> -    assert!(it.next().is_none(), "only two idents can be concatenated");
> +pub(crate) fn concat_idents(Input { a, b, .. }: Input) -> TokenStream {
>      let res = Ident::new(&format!("{a}{b}"), b.span());
>      TokenStream::from_iter([TokenTree::Ident(res)])
>  }
> diff --git a/rust/macros/helpers.rs b/rust/macros/helpers.rs
> index 754c827cc21e1..adfa60d8f42d8 100644
> --- a/rust/macros/helpers.rs
> +++ b/rust/macros/helpers.rs
> @@ -1,10 +1,6 @@
>  // SPDX-License-Identifier: GPL-2.0
>
> -use proc_macro2::{
> -    token_stream,
> -    TokenStream,
> -    TokenTree, //
> -};
> +use proc_macro2::TokenStream;
>  use quote::ToTokens;
>  use syn::{
>      parse::{
> @@ -16,14 +12,6 @@
>      Result, //
>  };
>
> -pub(crate) fn expect_punct(it: &mut token_stream::IntoIter) -> char {
> -    if let TokenTree::Punct(punct) = it.next().expect("Reached end of token stream for Punct") {
> -        punct.as_char()
> -    } else {
> -        panic!("Expected Punct");
> -    }
> -}
> -
>  /// A string literal that is required to have ASCII value only.
>  pub(crate) struct AsciiLitStr(LitStr);
>
> diff --git a/rust/macros/lib.rs b/rust/macros/lib.rs
> index 870a42d41ac91..bb2dfd4a4dafc 100644
> --- a/rust/macros/lib.rs
> +++ b/rust/macros/lib.rs
> @@ -283,8 +283,8 @@ pub fn fmt(input: TokenStream) -> TokenStream {
>  /// assert_eq!(BR_OK, binder_driver_return_protocol_BR_OK);
>  /// ```
>  #[proc_macro]
> -pub fn concat_idents(ts: TokenStream) -> TokenStream {
> -    concat_idents::concat_idents(ts.into()).into()
> +pub fn concat_idents(input: TokenStream) -> TokenStream {
> +    concat_idents::concat_idents(parse_macro_input!(input)).into()
>  }
>
>  /// Paste identifiers together.
> --
> 2.51.2
>