Fix backslash carriage return comments

CHANGES.md

@@ -16,6 +16,7 @@
 - Fix crash when a tuple appears in the `as` clause of a `with` statement
   (#4634)
 - Fix crash when tuple is used as a context manager inside a `with` statement (#4646)
+- Fix crash when formatting a `\` followed by a `\r` followed by a comment (#4663)
 
 ### Preview style
 

src/black/comments.py

@@ -88,7 +88,7 @@ def list_comments(prefix: str, *, is_endmarker: bool) -> list[ProtoComment]:
     nlines = 0
     ignored_lines = 0
     form_feed = False
-    for index, full_line in enumerate(re.split("\r?\n", prefix)):
+    for index, full_line in enumerate(re.split("\r?\n|\r", prefix)):
         consumed += len(full_line) + 1  # adding the length of the split '\n'
         match = re.match(r"^(\s*)(\S.*|)$", full_line)
         assert match

tests/test_black.py

@@ -2064,6 +2064,20 @@ def test_lines_with_leading_tabs_expanded(self) -> None:
         assert lines_with_leading_tabs_expanded("\t\tx") == [f"{tab}{tab}x"]
         assert lines_with_leading_tabs_expanded("\tx\n  y") == [f"{tab}x", "  y"]
 
+    def test_carriage_return_edge_cases(self) -> None:
+        # These tests are here instead of in the normal cases because
+        # of git's newline normalization and because it's hard to
+        # get `\r` vs `\r\n` vs `\n` to display properly
+        assert (
+            black.format_str(
+                "try:\\\r# type: ignore\n pass\nfinally:\n pass\n",
+                mode=black.FileMode(),
+            )
+            == "try:  # type: ignore\n    pass\nfinally:\n    pass\n"
+        )
+        assert black.format_str("{\r}", mode=black.FileMode()) == "{}\n"
+        assert black.format_str("pass #\r#\n", mode=black.FileMode()) == "pass  #\n#\n"
+
 
 class TestCaching:
     def test_get_cache_dir(