fix backslash in f-string

Author: LiuYinCarl

coverage/phystokens.py

@@ -69,6 +69,9 @@ def _phys_tokens(toks: TokenInfos) -> TokenInfos:
                         # It's a multi-line string and the first line ends with
                         # a backslash, so we don't need to inject another.
                         inject_backslash = False
+                elif sys.version_info >= (3, 12) and ttype == token.FSTRING_MIDDLE:
+                    if ttext.split("\n", 1)[0][-1] == "\\":
+                        inject_backslash = False
                 if inject_backslash:
                     # Figure out what column the backslash is in.
                     ccol = len(last_line.split("\n")[-2]) - 1