[PATCH 2/3] rust: macros: concat_idents: Allow :: paths in the first argument

[Asahi Lina]

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@xxxxxxxxxxxxx>
---
 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