linux-kernel - [PATCH 2/4] rust: macros: extend custom `quote!` macro

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Message-Id: <f75b20619c4269edad12ad826caf83ceeed89dbb.1750689857.git.y.j3ms.n@gmail.com>
Date: Mon, 23 Jun 2025 15:14:28 +0000
From: Jesung Yang <y.j3ms.n@...il.com>
To: Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...il.com>,
	Boqun Feng <boqun.feng@...il.com>,
	Gary Guo <gary@...yguo.net>,
	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>
Cc: linux-kernel@...r.kernel.org,
	rust-for-linux@...r.kernel.org,
	nouveau@...ts.freedesktop.org,
	Jesung Yang <y.j3ms.n@...il.com>
Subject: [PATCH 2/4] rust: macros: extend custom `quote!` macro

Implement the `ToTokens` trait for `&T` where `T` implements `ToTokens`.
This allows users to use the `quote!` macro with references directly,
avoiding the need to clone values.

Implement the `ToTokens` trait for `proc_macro::Literal`. This enables
the direct use of literals in the `quote!` macro, which is useful when
emitting numeric constants.

Extend the `quote_spanned!` macro to support additional punctuation
tokens: `->`, `<`, `>`, and `==`. This symbols are commonly needed when
dealing with functions, generic bounds, and equality comparisons.

Signed-off-by: Jesung Yang <y.j3ms.n@...il.com>
---
 rust/macros/quote.rs | 42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/rust/macros/quote.rs b/rust/macros/quote.rs
index 92cacc4067c9..d05f60f55623 100644
--- a/rust/macros/quote.rs
+++ b/rust/macros/quote.rs
@@ -7,6 +7,12 @@ pub(crate) trait ToTokens {
     fn to_tokens(&self, tokens: &mut TokenStream);
 }
 
+impl<T: ToTokens> ToTokens for &T {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        (*self).to_tokens(tokens);
+    }
+}
+
 impl<T: ToTokens> ToTokens for Option<T> {
     fn to_tokens(&self, tokens: &mut TokenStream) {
         if let Some(v) = self {
@@ -27,6 +33,12 @@ fn to_tokens(&self, tokens: &mut TokenStream) {
     }
 }
 
+impl ToTokens for proc_macro::Literal {
+    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()]);
@@ -144,6 +156,36 @@ macro_rules! quote_spanned {
         ));
         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::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)
-- 
2.39.5