Reduce max hash in raw strings to 255

src/parse.rs

@@ -472,6 +472,10 @@ fn raw_string(input: Cursor) -> Result<Cursor, Reject> {
             _ => return Err(Reject),
         }
     }
+    if n > 255 {
+        // https://github.com/rust-lang/rust/pull/95251
+        return Err(Reject);
+    }
     while let Some((i, ch)) = chars.next() {
         match ch {
             '"' if input.rest[i + 1..].starts_with(&input.rest[..n]) => {

tests/test.rs

@@ -5,6 +5,7 @@
 )]
 
 use proc_macro2::{Ident, Literal, Punct, Spacing, Span, TokenStream, TokenTree};
+use std::iter;
 use std::panic;
 use std::str::{self, FromStr};
 
@@ -118,6 +119,25 @@ fn literal_string() {
 #[test]
 fn literal_raw_string() {
     "r\"\r\n\"".parse::<TokenStream>().unwrap();
+
+    fn raw_string_literal_with_hashes(n: usize) -> String {
+        let mut literal = String::new();
+        literal.push('r');
+        literal.extend(iter::repeat('#').take(n));
+        literal.push('"');
+        literal.push('"');
+        literal.extend(iter::repeat('#').take(n));
+        literal
+    }
+
+    raw_string_literal_with_hashes(255)
+        .parse::<TokenStream>()
+        .unwrap();
+
+    // https://github.com/rust-lang/rust/pull/95251
+    raw_string_literal_with_hashes(256)
+        .parse::<TokenStream>()
+        .unwrap_err();
 }
 
 #[test]