Fix python#153

Author: isidentical

Lib/test/test_fstring.py

@@ -589,6 +589,7 @@ def test_format_specifier_expressions(self):
         self.assertEqual(f'{-10:-{"#"}1{0}x}', '      -0xa')
         self.assertEqual(f'{-10:{"-"}#{1}0{"x"}}', '      -0xa')
         self.assertEqual(f'{10:#{3 != {4:5} and width}x}', '       0xa')
+        self.assertEqual(f'result: {value:{width:{0}}.{precision:1}}', 'result:      12.35')
 
         self.assertAllRaise(SyntaxError, "f-string: expecting '}'",
                             ["""f'{"s"!r{":10"}}'""",
@@ -601,11 +602,6 @@ def test_format_specifier_expressions(self):
                              "f'{4:{/5}}'",
                              ])
 
-        self.assertAllRaise(SyntaxError, "f-string: expressions nested too deeply",
-                            [# Can't nest format specifiers.
-                             "f'result: {value:{width:{0}}.{precision:1}}'",
-                             ])
-
         self.assertAllRaise(SyntaxError, 'f-string: invalid conversion character',
                             [# No expansion inside conversion or for
                              #  the : or ! itself.