switch from char_indices back to while-loop for check_raw_*

Author: hkBst

src/lib.rs

@@ -126,16 +126,28 @@ trait CheckRaw {
         src: &str,
         mut callback: impl FnMut(Range<usize>, Result<Self::RawUnit, EscapeError>),
     ) {
-        src.char_indices().for_each(|(pos, c)| {
-            callback(
-                pos..pos + c.len_utf8(),
-                if c == '\r' {
-                    Err(EscapeError::BareCarriageReturnInRawString)
-                } else {
-                    Self::char2raw_unit(c)
-                },
-            );
-        });
+        let mut chars = src.chars();
+        while let Some(c) = chars.next() {
+            let start = src.len() - chars.as_str().len() - c.len_utf8();
+            let res = match c {
+                '\r' => Err(EscapeError::BareCarriageReturn),
+                _ => Self::char2raw_unit(c),
+            };
+            let end = src.len() - chars.as_str().len();
+            callback(start..end, res);
+        }
+
+        // Unfortunately, it is a bit unclear whether the following equivalent code is slower or faster: bug 141855
+        // src.char_indices().for_each(|(pos, c)| {
+        //     callback(
+        //         pos..pos + c.len_utf8(),
+        //         if c == '\r' {
+        //             Err(EscapeError::BareCarriageReturnInRawString)
+        //         } else {
+        //             Self::char2raw_unit(c)
+        //         },
+        //     );
+        // });
     }
 }