The `proc-macro2` crate depends on the `unicode-ident` crate to determine
whether characters have the XID_Start or XID_Continue properties according
to Unicode Standard Annex #31.

However, we only need ASCII identifiers in the kernel, thus we can
simplify the check and remove completely that dependency.

Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Tested-by: Gary Guo <gary@garyguo.net>
Tested-by: Jesung Yang <y.j3ms.n@gmail.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
 rust/proc-macro2/fallback.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/rust/proc-macro2/fallback.rs b/rust/proc-macro2/fallback.rs
index 9e005d67f7f5..9b43c97df97a 100644
--- a/rust/proc-macro2/fallback.rs
+++ b/rust/proc-macro2/fallback.rs
@@ -818,11 +818,11 @@ pub(crate) fn set_span(&mut self, span: Span) {
 }
 
 pub(crate) fn is_ident_start(c: char) -> bool {
-    c == '_' || unicode_ident::is_xid_start(c)
+    c == '_' || c.is_ascii_alphabetic()
 }
 
 pub(crate) fn is_ident_continue(c: char) -> bool {
-    unicode_ident::is_xid_continue(c)
+    c == '_' || c.is_ascii_alphanumeric()
 }
 
 #[track_caller]
-- 
2.52.0