fix incorrect backslash before multi-line string

Author: LiuYinCarl

coverage/phystokens.py

@@ -57,7 +57,15 @@ def _phys_tokens(toks: TokenInfos) -> TokenInfos:
                 if last_ttext.endswith("\\"):
                     inject_backslash = False
                 elif ttype == token.STRING:
-                    if "\n" in ttext and ttext.split("\n", 1)[0][-1] == "\\":
+                    if last_line.endswith(last_ttext+"\\\n"):
+                        # Deal with special cases like such code::
+                        #
+                        #   a = ["aaa",\
+                        #        "bbb \
+                        #        ccc"]
+                        #
+                        pass
+                    elif "\n" in ttext and ttext.split("\n", 1)[0][-1] == "\\":
                         # 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