1 files changed, 19 insertions, 1 deletions
diff --git a/vendor/syn/src/verbatim.rs b/vendor/syn/src/verbatim.rs
index 0686352f7..58cf68d17 100644
--- a/vendor/syn/src/verbatim.rs
+++ b/vendor/syn/src/verbatim.rs
@@ -1,13 +1,31 @@
 use crate::parse::{ParseBuffer, ParseStream};
-use proc_macro2::TokenStream;
+use proc_macro2::{Delimiter, TokenStream};
+use std::cmp::Ordering;
 use std::iter;
 
 pub fn between<'a>(begin: ParseBuffer<'a>, end: ParseStream<'a>) -> TokenStream {
     let end = end.cursor();
     let mut cursor = begin.cursor();
+    assert!(crate::buffer::same_buffer(end, cursor));
+
     let mut tokens = TokenStream::new();
     while cursor != end {
         let (tt, next) = cursor.token_tree().unwrap();
+
+        if crate::buffer::cmp_assuming_same_buffer(end, next) == Ordering::Less {
+            // A syntax node can cross the boundary of a None-delimited group
+            // due to such groups being transparent to the parser in most cases.
+            // Any time this occurs the group is known to be semantically
+            // irrelevant. https://github.com/dtolnay/syn/issues/1235
+            if let Some((inside, _span, after)) = cursor.group(Delimiter::None) {
+                assert!(next == after);
+                cursor = inside;
+                continue;
+            } else {
+                panic!("verbatim end must not be inside a delimited group");
+            }
+        }
+
         tokens.extend(iter::once(tt));
         cursor = next;
     }