gh-94808: Coverage: Test uppercase string literal prefixes (GH-95925)

(cherry picked from commit f00383e)

Co-authored-by: Michael Droettboom <mdboom@gmail.com>

Author: miss-islington

Lib/test/test_string_literals.py

@@ -213,6 +213,13 @@ def test_eval_str_u(self):
         self.assertRaises(SyntaxError, eval, """ bu'' """)
         self.assertRaises(SyntaxError, eval, """ ub'' """)
 
+    def test_uppercase_prefixes(self):
+        self.assertEqual(eval(""" B'x' """), b'x')
+        self.assertEqual(eval(r""" R'\x01' """), r'\x01')
+        self.assertEqual(eval(r""" BR'\x01' """), br'\x01')
+        self.assertEqual(eval(""" F'{1+1}' """), f'{1+1}')
+        self.assertEqual(eval(r""" U'\U0001d120' """), u'\U0001d120')
+
     def check_encoding(self, encoding, extra=""):
         modname = "xx_" + encoding.replace("-", "_")
         fn = os.path.join(self.tmpdir, modname + ".py")