Re: [PATCH 07/11] rust: macros: convert `concat_idents!` to use `syn`

Tamir Duberstein
2026-01-04T23:00:13Z

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

Reviewed-by: Tamir Duberstein <tamird@gmail.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
>