Unicode-width dependent optimization leads to non-portable pyc file

Lib/test/test_peepholer.py

 import dis
 import re
 import sys
 from io import StringIO
 import unittest
 from math import copysign
 
 def disassemble(func):
     f = StringIO()
     tmp = sys.stdout
@@ skipping 186 matching lines @@
             self.assertNotIn('BINARY_', asm)
 
         # Verify that unfoldables are skipped
         asm = dis_single('a=2+"b"')
         self.assertIn('(2)', asm)
         self.assertIn("('b')", asm)
 
         # Verify that large sequences do not result from folding
         asm = dis_single('a="x"*1000')
         self.assertIn('(1000)', asm)
+
+    def test_binary_subscr_on_unicode(self):
+        # valid code get optimized
+        asm = dis_single('"foo"[0]')
+        self.assertIn("('f')", asm)
+        self.assertNotIn('BINARY_SUBSCR', asm)
+        asm = dis_single('"\u0061\uffff"[1]')
+        self.assertIn("('\\uffff')", asm)
+        self.assertNotIn('BINARY_SUBSCR', asm)
+
+        # invalid code doesn't get optimized
+        # out of range
+        asm = dis_single('"fuu"[10]')
+        self.assertIn('BINARY_SUBSCR', asm)
+        # non-BMP char (see #5057)
+        asm = dis_single('"\U00012345"[0]')
+        self.assertIn('BINARY_SUBSCR', asm)
+
 
     def test_folding_of_unaryops_on_constants(self):
         for line, elem in (
             ('-0.5', '(-0.5)'),                     # unary negative
             ('-0.0', '(-0.0)'),                     # -0.0
             ('-(1.0-1.0)','(-0.0)'),                # -0.0 after folding
             ('-0', '(0)'),                          # -0
             ('~-2', '(1)'),                         # unary invert
             ('+1', '(1)'),                          # unary positive
         ):
@@ skipping 113 matching lines @@
         import gc
         counts = [None] * 5
         for i in range(len(counts)):
             support.run_unittest(*test_classes)
             gc.collect()
             counts[i] = sys.gettotalrefcount()
         print(counts)
 
 if __name__ == "__main__":
     test_main(verbose=True)