linux-kernel - [PATCH 2/3] rust: macros: concat_idents: Allow

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Message-Id: <20230224-rust-macros-v1-2-b39fae46e102@asahilina.net>
Date:   Fri, 24 Feb 2023 16:25:56 +0900
From:   Asahi Lina <lina@...hilina.net>
To:     Miguel Ojeda <ojeda@...nel.org>,
        Alex Gaynor <alex.gaynor@...il.com>,
        Wedson Almeida Filho <wedsonaf@...il.com>,
        Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
        Björn Roy Baron <bjorn3_gh@...tonmail.com>
Cc:     rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
        asahi@...ts.linux.dev, Asahi Lina <lina@...hilina.net>
Subject: [PATCH 2/3] rust: macros: concat_idents: Allow :: paths in the
 first argument

This makes things like concat_idents!(bindings::foo, bar) work.
Otherwise, there is no way to concatenate two idents and then use the
result as part of a type path.

Signed-off-by: Asahi Lina <lina@...hilina.net>
---
 rust/macros/concat_idents.rs | 24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/rust/macros/concat_idents.rs b/rust/macros/concat_idents.rs
index 6d955d65016e..d6614b900aa2 100644
--- a/rust/macros/concat_idents.rs
+++ b/rust/macros/concat_idents.rs
@@ -14,10 +14,28 @@ fn expect_ident(it: &mut token_stream::IntoIter) -> Ident {
 
 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).as_char(), ',');
+    let mut out = TokenStream::new();
+    let a = loop {
+        let ident = expect_ident(&mut it);
+        let punct = expect_punct(&mut it);
+        match punct.as_char() {
+            ',' => break ident,
+            ':' => {
+                let punct2 = expect_punct(&mut it);
+                assert_eq!(punct2.as_char(), ':');
+                out.extend([
+                    TokenTree::Ident(ident),
+                    TokenTree::Punct(punct),
+                    TokenTree::Punct(punct2),
+                ]);
+            }
+            _ => panic!("Expected , or ::"),
+        }
+    };
+
     let b = expect_ident(&mut it);
     assert!(it.next().is_none(), "only two idents can be concatenated");
     let res = Ident::new(&format!("{a}{b}"), b.span());
-    TokenStream::from_iter([TokenTree::Ident(res)])
+    out.extend([TokenTree::Ident(res)]);
+    out
 }

-- 
2.35.1