gh-154711: Add tests for comments after escaped quotes in f-strings and t-strings

Main is not affected by this bug after gh-153569, but nothing tested it.
These tests cover a real comment placed after a string that ends with an
escaped quote, in debug f-strings and in t-string interpolations.

Author: ArneshBanerjee

Lib/test/test_fstring.py

@@ -1723,6 +1723,11 @@ def __repr__(self):
 
         self.assertEqual(f'{" # nooo "=}', '" # nooo "=\' # nooo \'')
         self.assertEqual(f'{" \" # nooo \" "=}', '" \\" # nooo \\" "=\' " # nooo " \'')
+
+        # A real comment after a string that ends with an escaped quote must
+        # still be stripped (gh-154711).
+        self.assertEqual(f"{'\'' = # comment
+}", "'\\'' = \n" + repr("'"))
         self.assertEqual(f'{"""a" # inside"""=}',
                          '"""a" # inside"""=\'a" # inside\'')
         self.assertEqual(f"{'''a' # inside'''=}",

Lib/test/test_tstring.py

@@ -257,6 +257,18 @@ def test_interpolation_expression_with_reconstructed_metadata(self):
         self.assertEqual(regular.interpolations[0].expression, expected)
         self.assertEqual(debug.interpolations[0].expression, expected)
 
+    def test_comment_after_escaped_quote(self):
+        # A comment after a string that ends with an escaped quote must be
+        # stripped from the interpolation expression (gh-154711).
+        t = t"{'a\'b' # comment
+}"
+        self.assertEqual(t.interpolations[0].expression, "'a\\'b' \n")
+
+        t = t"{'a\'b' = # comment
+}"
+        self.assertEqual(t.interpolations[0].expression, "'a\\'b' ")
+        self.assertEqual(t.strings, ("'a\\'b' = \n", ""))
+
     def test_raw_tstrings(self):
         path = r"C:\Users"
         t = rt"{path}\Documents"