summaryrefslogtreecommitdiffstats
path: root/sources/shiboken2/shibokenmodule/files.dir/shibokensupport/typing27.py
blob: 786a84ecb02652a43a2c963dd7d76b8b362e0e5c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
# This Python file uses the following encoding: utf-8
# It has been edited by fix-complaints.py .

#############################################################################
##
## Copyright (C) 2019 The Qt Company Ltd.
## Contact: https://www.qt.io/licensing/
##
## This file is part of Qt for Python.
##
## $QT_BEGIN_LICENSE:LGPL$
## Commercial License Usage
## Licensees holding valid commercial Qt licenses may use this file in
## accordance with the commercial license agreement provided with the
## Software or, alternatively, in accordance with the terms contained in
## a written agreement between you and The Qt Company. For licensing terms
## and conditions see https://www.qt.io/terms-conditions. For further
## information use the contact form at https://www.qt.io/contact-us.
##
## GNU Lesser General Public License Usage
## Alternatively, this file may be used under the terms of the GNU Lesser
## General Public License version 3 as published by the Free Software
## Foundation and appearing in the file LICENSE.LGPL3 included in the
## packaging of this file. Please review the following information to
## ensure the GNU Lesser General Public License version 3 requirements
## will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
##
## GNU General Public License Usage
## Alternatively, this file may be used under the terms of the GNU
## General Public License version 2.0 or (at your option) the GNU General
## Public license version 3 or any later version approved by the KDE Free
## Qt Foundation. The licenses are as published by the Free Software
## Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
## included in the packaging of this file. Please review the following
## information to ensure the GNU General Public License requirements will
## be met: https://www.gnu.org/licenses/gpl-2.0.html and
## https://www.gnu.org/licenses/gpl-3.0.html.
##
## $QT_END_LICENSE$
##
#############################################################################

"""
PSF LICENSE AGREEMENT FOR PYTHON 3.7.0

1. This LICENSE AGREEMENT is between the Python Software Foundation ("PSF"), and
   the Individual or Organization ("Licensee") accessing and otherwise using Python
   3.7.0 software in source or binary form and its associated documentation.

2. Subject to the terms and conditions of this License Agreement, PSF hereby
   grants Licensee a nonexclusive, royalty-free, world-wide license to reproduce,
   analyze, test, perform and/or display publicly, prepare derivative works,
   distribute, and otherwise use Python 3.7.0 alone or in any derivative
   version, provided, however, that PSF's License Agreement and PSF's notice of
   copyright, i.e., "Copyright © 2001-2018 Python Software Foundation; All Rights
   Reserved" are retained in Python 3.7.0 alone or in any derivative version
   prepared by Licensee.

3. In the event Licensee prepares a derivative work that is based on or
   incorporates Python 3.7.0 or any part thereof, and wants to make the
   derivative work available to others as provided herein, then Licensee hereby
   agrees to include in any such work a brief summary of the changes made to Python
   3.7.0.

4. PSF is making Python 3.7.0 available to Licensee on an "AS IS" basis.
   PSF MAKES NO REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED.  BY WAY OF
   EXAMPLE, BUT NOT LIMITATION, PSF MAKES NO AND DISCLAIMS ANY REPRESENTATION OR
   WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE OR THAT THE
   USE OF PYTHON 3.7.0 WILL NOT INFRINGE ANY THIRD PARTY RIGHTS.

5. PSF SHALL NOT BE LIABLE TO LICENSEE OR ANY OTHER USERS OF PYTHON 3.7.0
   FOR ANY INCIDENTAL, SPECIAL, OR CONSEQUENTIAL DAMAGES OR LOSS AS A RESULT OF
   MODIFYING, DISTRIBUTING, OR OTHERWISE USING PYTHON 3.7.0, OR ANY DERIVATIVE
   THEREOF, EVEN IF ADVISED OF THE POSSIBILITY THEREOF.

6. This License Agreement will automatically terminate upon a material breach of
   its terms and conditions.

7. Nothing in this License Agreement shall be deemed to create any relationship
   of agency, partnership, or joint venture between PSF and Licensee.  This License
   Agreement does not grant permission to use PSF trademarks or trade name in a
   trademark sense to endorse or promote products or services of Licensee, or any
   third party.

8. By copying, installing or otherwise using Python 3.7.0, Licensee agrees
   to be bound by the terms and conditions of this License Agreement.
"""

from __future__ import absolute_import, unicode_literals

import abc
from abc import abstractmethod, abstractproperty
import collections
import functools
import re as stdlib_re  # Avoid confusion with the re we export.
import sys
import types
import copy
try:
    import collections.abc as collections_abc
except ImportError:
    import collections as collections_abc  # Fallback for PY3.2.


# Please keep __all__ alphabetized within each category.
__all__ = [
    # Super-special typing primitives.
    'Any',
    'Callable',
    'ClassVar',
    'Generic',
    'Optional',
    'Tuple',
    'Type',
    'TypeVar',
    'Union',

    # ABCs (from collections.abc).
    'AbstractSet',  # collections.abc.Set.
    'GenericMeta',  # subclass of abc.ABCMeta and a metaclass
                    # for 'Generic' and ABCs below.
    'ByteString',
    'Container',
    'ContextManager',
    'Hashable',
    'ItemsView',
    'Iterable',
    'Iterator',
    'KeysView',
    'Mapping',
    'MappingView',
    'MutableMapping',
    'MutableSequence',
    'MutableSet',
    'Sequence',
    'Sized',
    'ValuesView',

    # Structural checks, a.k.a. protocols.
    'Reversible',
    'SupportsAbs',
    'SupportsComplex',
    'SupportsFloat',
    'SupportsInt',

    # Concrete collection types.
    'Counter',
    'Deque',
    'Dict',
    'DefaultDict',
    'List',
    'Set',
    'FrozenSet',
    'NamedTuple',  # Not really a type.
    'Generator',

    # One-off things.
    'AnyStr',
    'cast',
    'get_type_hints',
    'NewType',
    'no_type_check',
    'no_type_check_decorator',
    'NoReturn',
    'overload',
    'Text',
    'TYPE_CHECKING',
]

# The pseudo-submodules 're' and 'io' are part of the public
# namespace, but excluded from __all__ because they might stomp on
# legitimate imports of those modules.


def _qualname(x):
    if sys.version_info[:2] >= (3, 3):
        return x.__qualname__
    else:
        # Fall back to just name.
        return x.__name__


def _trim_name(nm):
    whitelist = ('_TypeAlias', '_ForwardRef', '_TypingBase', '_FinalTypingBase')
    if nm.startswith('_') and nm not in whitelist:
        nm = nm[1:]
    return nm


class TypingMeta(type):
    """Metaclass for most types defined in typing module
    (not a part of public API).

    This also defines a dummy constructor (all the work for most typing
    constructs is done in __new__) and a nicer repr().
    """

    _is_protocol = False

    def __new__(cls, name, bases, namespace):
        return super(TypingMeta, cls).__new__(cls, str(name), bases, namespace)

    @classmethod
    def assert_no_subclassing(cls, bases):
        for base in bases:
            if isinstance(base, cls):
                raise TypeError("Cannot subclass %s" %
                                (', '.join(map(_type_repr, bases)) or '()'))

    def __init__(self, *args, **kwds):
        pass

    def _eval_type(self, globalns, localns):
        """Override this in subclasses to interpret forward references.

        For example, List['C'] is internally stored as
        List[_ForwardRef('C')], which should evaluate to List[C],
        where C is an object found in globalns or localns (searching
        localns first, of course).
        """
        return self

    def _get_type_vars(self, tvars):
        pass

    def __repr__(self):
        qname = _trim_name(_qualname(self))
        return '%s.%s' % (self.__module__, qname)


class _TypingBase(object):
    """Internal indicator of special typing constructs."""
    __metaclass__ = TypingMeta
    __slots__ = ('__weakref__',)

    def __init__(self, *args, **kwds):
        pass

    def __new__(cls, *args, **kwds):
        """Constructor.

        This only exists to give a better error message in case
        someone tries to subclass a special typing object (not a good idea).
        """
        if (len(args) == 3 and
                isinstance(args[0], str) and
                isinstance(args[1], tuple)):
            # Close enough.
            raise TypeError("Cannot subclass %r" % cls)
        return super(_TypingBase, cls).__new__(cls)

    # Things that are not classes also need these.
    def _eval_type(self, globalns, localns):
        return self

    def _get_type_vars(self, tvars):
        pass

    def __repr__(self):
        cls = type(self)
        qname = _trim_name(_qualname(cls))
        return '%s.%s' % (cls.__module__, qname)

    def __call__(self, *args, **kwds):
        raise TypeError("Cannot instantiate %r" % type(self))


class _FinalTypingBase(_TypingBase):
    """Internal mix-in class to prevent instantiation.

    Prevents instantiation unless _root=True is given in class call.
    It is used to create pseudo-singleton instances Any, Union, Optional, etc.
    """

    __slots__ = ()

    def __new__(cls, *args, **kwds):
        self = super(_FinalTypingBase, cls).__new__(cls, *args, **kwds)
        if '_root' in kwds and kwds['_root'] is True:
            return self
        raise TypeError("Cannot instantiate %r" % cls)

    def __reduce__(self):
        return _trim_name(type(self).__name__)


class _ForwardRef(_TypingBase):
    """Internal wrapper to hold a forward reference."""

    __slots__ = ('__forward_arg__', '__forward_code__',
                 '__forward_evaluated__', '__forward_value__')

    def __init__(self, arg):
        super(_ForwardRef, self).__init__(arg)
        if not isinstance(arg, basestring):
            raise TypeError('Forward reference must be a string -- got %r' % (arg,))
        try:
            code = compile(arg, '<string>', 'eval')
        except SyntaxError:
            raise SyntaxError('Forward reference must be an expression -- got %r' %
                              (arg,))
        self.__forward_arg__ = arg
        self.__forward_code__ = code
        self.__forward_evaluated__ = False
        self.__forward_value__ = None

    def _eval_type(self, globalns, localns):
        if not self.__forward_evaluated__ or localns is not globalns:
            if globalns is None and localns is None:
                globalns = localns = {}
            elif globalns is None:
                globalns = localns
            elif localns is None:
                localns = globalns
            self.__forward_value__ = _type_check(
                eval(self.__forward_code__, globalns, localns),
                "Forward references must evaluate to types.")
            self.__forward_evaluated__ = True
        return self.__forward_value__

    def __eq__(self, other):
        if not isinstance(other, _ForwardRef):
            return NotImplemented
        return (self.__forward_arg__ == other.__forward_arg__ and
                self.__forward_value__ == other.__forward_value__)

    def __hash__(self):
        return hash((self.__forward_arg__, self.__forward_value__))

    def __instancecheck__(self, obj):
        raise TypeError("Forward references cannot be used with isinstance().")

    def __subclasscheck__(self, cls):
        raise TypeError("Forward references cannot be used with issubclass().")

    def __repr__(self):
        return '_ForwardRef(%r)' % (self.__forward_arg__,)


class _TypeAlias(_TypingBase):
    """Internal helper class for defining generic variants of concrete types.

    Note that this is not a type; let's call it a pseudo-type.  It cannot
    be used in instance and subclass checks in parameterized form, i.e.
    ``isinstance(42, Match[str])`` raises ``TypeError`` instead of returning
    ``False``.
    """

    __slots__ = ('name', 'type_var', 'impl_type', 'type_checker')

    def __init__(self, name, type_var, impl_type, type_checker):
        """Initializer.

        Args:
            name: The name, e.g. 'Pattern'.
            type_var: The type parameter, e.g. AnyStr, or the
                specific type, e.g. str.
            impl_type: The implementation type.
            type_checker: Function that takes an impl_type instance.
                and returns a value that should be a type_var instance.
        """
        assert isinstance(name, basestring), repr(name)
        assert isinstance(impl_type, type), repr(impl_type)
        assert not isinstance(impl_type, TypingMeta), repr(impl_type)
        assert isinstance(type_var, (type, _TypingBase)), repr(type_var)
        self.name = name
        self.type_var = type_var
        self.impl_type = impl_type
        self.type_checker = type_checker

    def __repr__(self):
        return "%s[%s]" % (self.name, _type_repr(self.type_var))

    def __getitem__(self, parameter):
        if not isinstance(self.type_var, TypeVar):
            raise TypeError("%s cannot be further parameterized." % self)
        if self.type_var.__constraints__ and isinstance(parameter, type):
            if not issubclass(parameter, self.type_var.__constraints__):
                raise TypeError("%s is not a valid substitution for %s." %
                                (parameter, self.type_var))
        if isinstance(parameter, TypeVar) and parameter is not self.type_var:
            raise TypeError("%s cannot be re-parameterized." % self)
        return self.__class__(self.name, parameter,
                              self.impl_type, self.type_checker)

    def __eq__(self, other):
        if not isinstance(other, _TypeAlias):
            return NotImplemented
        return self.name == other.name and self.type_var == other.type_var

    def __hash__(self):
        return hash((self.name, self.type_var))

    def __instancecheck__(self, obj):
        if not isinstance(self.type_var, TypeVar):
            raise TypeError("Parameterized type aliases cannot be used "
                            "with isinstance().")
        return isinstance(obj, self.impl_type)

    def __subclasscheck__(self, cls):
        if not isinstance(self.type_var, TypeVar):
            raise TypeError("Parameterized type aliases cannot be used "
                            "with issubclass().")
        return issubclass(cls, self.impl_type)


def _get_type_vars(types, tvars):
    for t in types:
        if isinstance(t, TypingMeta) or isinstance(t, _TypingBase):
            t._get_type_vars(tvars)


def _type_vars(types):
    tvars = []
    _get_type_vars(types, tvars)
    return tuple(tvars)


def _eval_type(t, globalns, localns):
    if isinstance(t, TypingMeta) or isinstance(t, _TypingBase):
        return t._eval_type(globalns, localns)
    return t


def _type_check(arg, msg):
    """Check that the argument is a type, and return it (internal helper).

    As a special case, accept None and return type(None) instead.
    Also, _TypeAlias instances (e.g. Match, Pattern) are acceptable.

    The msg argument is a human-readable error message, e.g.

        "Union[arg, ...]: arg should be a type."

    We append the repr() of the actual value (truncated to 100 chars).
    """
    if arg is None:
        return type(None)
    if isinstance(arg, basestring):
        arg = _ForwardRef(arg)
    if (
        isinstance(arg, _TypingBase) and type(arg).__name__ == '_ClassVar' or
        not isinstance(arg, (type, _TypingBase)) and not callable(arg)
    ):
        raise TypeError(msg + " Got %.100r." % (arg,))
    # Bare Union etc. are not valid as type arguments
    if (
        type(arg).__name__ in ('_Union', '_Optional') and
        not getattr(arg, '__origin__', None) or
        isinstance(arg, TypingMeta) and arg._gorg in (Generic, _Protocol)
    ):
        raise TypeError("Plain %s is not valid as type argument" % arg)
    return arg


def _type_repr(obj):
    """Return the repr() of an object, special-casing types (internal helper).

    If obj is a type, we return a shorter version than the default
    type.__repr__, based on the module and qualified name, which is
    typically enough to uniquely identify a type.  For everything
    else, we fall back on repr(obj).
    """
    if isinstance(obj, type) and not isinstance(obj, TypingMeta):
        if obj.__module__ == '__builtin__':
            return _qualname(obj)
        return '%s.%s' % (obj.__module__, _qualname(obj))
    if obj is Ellipsis:
        return('...')
    if isinstance(obj, types.FunctionType):
        return obj.__name__
    return repr(obj)


class ClassVarMeta(TypingMeta):
    """Metaclass for _ClassVar"""

    def __new__(cls, name, bases, namespace):
        cls.assert_no_subclassing(bases)
        self = super(ClassVarMeta, cls).__new__(cls, name, bases, namespace)
        return self


class _ClassVar(_FinalTypingBase):
    """Special type construct to mark class variables.

    An annotation wrapped in ClassVar indicates that a given
    attribute is intended to be used as a class variable and
    should not be set on instances of that class. Usage::

      class Starship:
          stats = {}  # type: ClassVar[Dict[str, int]] # class variable
          damage = 10 # type: int                      # instance variable

    ClassVar accepts only types and cannot be further subscribed.

    Note that ClassVar is not a class itself, and should not
    be used with isinstance() or issubclass().
    """

    __metaclass__ = ClassVarMeta
    __slots__ = ('__type__',)

    def __init__(self, tp=None, _root=False):
        self.__type__ = tp

    def __getitem__(self, item):
        cls = type(self)
        if self.__type__ is None:
            return cls(_type_check(item,
                       '{} accepts only types.'.format(cls.__name__[1:])),
                       _root=True)
        raise TypeError('{} cannot be further subscripted'
                        .format(cls.__name__[1:]))

    def _eval_type(self, globalns, localns):
        return type(self)(_eval_type(self.__type__, globalns, localns),
                          _root=True)

    def __repr__(self):
        r = super(_ClassVar, self).__repr__()
        if self.__type__ is not None:
            r += '[{}]'.format(_type_repr(self.__type__))
        return r

    def __hash__(self):
        return hash((type(self).__name__, self.__type__))

    def __eq__(self, other):
        if not isinstance(other, _ClassVar):
            return NotImplemented
        if self.__type__ is not None:
            return self.__type__ == other.__type__
        return self is other


ClassVar = _ClassVar(_root=True)


class AnyMeta(TypingMeta):
    """Metaclass for Any."""

    def __new__(cls, name, bases, namespace):
        cls.assert_no_subclassing(bases)
        self = super(AnyMeta, cls).__new__(cls, name, bases, namespace)
        return self


class _Any(_FinalTypingBase):
    """Special type indicating an unconstrained type.

    - Any is compatible with every type.
    - Any assumed to have all methods.
    - All values assumed to be instances of Any.

    Note that all the above statements are true from the point of view of
    static type checkers. At runtime, Any should not be used with instance
    or class checks.
    """
    __metaclass__ = AnyMeta
    __slots__ = ()

    def __instancecheck__(self, obj):
        raise TypeError("Any cannot be used with isinstance().")

    def __subclasscheck__(self, cls):
        raise TypeError("Any cannot be used with issubclass().")


Any = _Any(_root=True)


class NoReturnMeta(TypingMeta):
    """Metaclass for NoReturn."""

    def __new__(cls, name, bases, namespace):
        cls.assert_no_subclassing(bases)
        self = super(NoReturnMeta, cls).__new__(cls, name, bases, namespace)
        return self


class _NoReturn(_FinalTypingBase):
    """Special type indicating functions that never return.
    Example::

      from typing import NoReturn

      def stop() -> NoReturn:
          raise Exception('no way')

    This type is invalid in other positions, e.g., ``List[NoReturn]``
    will fail in static type checkers.
    """
    __metaclass__ = NoReturnMeta
    __slots__ = ()

    def __instancecheck__(self, obj):
        raise TypeError("NoReturn cannot be used with isinstance().")

    def __subclasscheck__(self, cls):
        raise TypeError("NoReturn cannot be used with issubclass().")


NoReturn = _NoReturn(_root=True)


class TypeVarMeta(TypingMeta):
    def __new__(cls, name, bases, namespace):
        cls.assert_no_subclassing(bases)
        return super(TypeVarMeta, cls).__new__(cls, name, bases, namespace)


class TypeVar(_TypingBase):
    """Type variable.

    Usage::

      T = TypeVar('T')  # Can be anything
      A = TypeVar('A', str, bytes)  # Must be str or bytes

    Type variables exist primarily for the benefit of static type
    checkers.  They serve as the parameters for generic types as well
    as for generic function definitions.  See class Generic for more
    information on generic types.  Generic functions work as follows:

      def repeat(x: T, n: int) -> List[T]:
          '''Return a list containing n references to x.'''
          return [x]*n

      def longest(x: A, y: A) -> A:
          '''Return the longest of two strings.'''
          return x if len(x) >= len(y) else y

    The latter example's signature is essentially the overloading
    of (str, str) -> str and (bytes, bytes) -> bytes.  Also note
    that if the arguments are instances of some subclass of str,
    the return type is still plain str.

    At runtime, isinstance(x, T) and issubclass(C, T) will raise TypeError.

    Type variables defined with covariant=True or contravariant=True
    can be used do declare covariant or contravariant generic types.
    See PEP 484 for more details. By default generic types are invariant
    in all type variables.

    Type variables can be introspected. e.g.:

      T.__name__ == 'T'
      T.__constraints__ == ()
      T.__covariant__ == False
      T.__contravariant__ = False
      A.__constraints__ == (str, bytes)
    """

    __metaclass__ = TypeVarMeta
    __slots__ = ('__name__', '__bound__', '__constraints__',
                 '__covariant__', '__contravariant__')

    def __init__(self, name, *constraints, **kwargs):
        super(TypeVar, self).__init__(name, *constraints, **kwargs)
        bound = kwargs.get('bound', None)
        covariant = kwargs.get('covariant', False)
        contravariant = kwargs.get('contravariant', False)
        self.__name__ = name
        if covariant and contravariant:
            raise ValueError("Bivariant types are not supported.")
        self.__covariant__ = bool(covariant)
        self.__contravariant__ = bool(contravariant)
        if constraints and bound is not None:
            raise TypeError("Constraints cannot be combined with bound=...")
        if constraints and len(constraints) == 1:
            raise TypeError("A single constraint is not allowed")
        msg = "TypeVar(name, constraint, ...): constraints must be types."
        self.__constraints__ = tuple(_type_check(t, msg) for t in constraints)
        if bound:
            self.__bound__ = _type_check(bound, "Bound must be a type.")
        else:
            self.__bound__ = None

    def _get_type_vars(self, tvars):
        if self not in tvars:
            tvars.append(self)

    def __repr__(self):
        if self.__covariant__:
            prefix = '+'
        elif self.__contravariant__:
            prefix = '-'
        else:
            prefix = '~'
        return prefix + self.__name__

    def __instancecheck__(self, instance):
        raise TypeError("Type variables cannot be used with isinstance().")

    def __subclasscheck__(self, cls):
        raise TypeError("Type variables cannot be used with issubclass().")


# Some unconstrained type variables.  These are used by the container types.
# (These are not for export.)
T = TypeVar('T')  # Any type.
KT = TypeVar('KT')  # Key type.
VT = TypeVar('VT')  # Value type.
T_co = TypeVar('T_co', covariant=True)  # Any type covariant containers.
V_co = TypeVar('V_co', covariant=True)  # Any type covariant containers.
VT_co = TypeVar('VT_co', covariant=True)  # Value type covariant containers.
T_contra = TypeVar('T_contra', contravariant=True)  # Ditto contravariant.

# A useful type variable with constraints.  This represents string types.
# (This one *is* for export!)
AnyStr = TypeVar('AnyStr', bytes, unicode)


def _replace_arg(arg, tvars, args):
    """An internal helper function: replace arg if it is a type variable
    found in tvars with corresponding substitution from args or
    with corresponding substitution sub-tree if arg is a generic type.
    """

    if tvars is None:
        tvars = []
    if hasattr(arg, '_subs_tree') and isinstance(arg, (GenericMeta, _TypingBase)):
        return arg._subs_tree(tvars, args)
    if isinstance(arg, TypeVar):
        for i, tvar in enumerate(tvars):
            if arg == tvar:
                return args[i]
    return arg


# Special typing constructs Union, Optional, Generic, Callable and Tuple
# use three special attributes for internal bookkeeping of generic types:
# * __parameters__ is a tuple of unique free type parameters of a generic
#   type, for example, Dict[T, T].__parameters__ == (T,);
# * __origin__ keeps a reference to a type that was subscripted,
#   e.g., Union[T, int].__origin__ == Union;
# * __args__ is a tuple of all arguments used in subscripting,
#   e.g., Dict[T, int].__args__ == (T, int).


def _subs_tree(cls, tvars=None, args=None):
    """An internal helper function: calculate substitution tree
    for generic cls after replacing its type parameters with
    substitutions in tvars -> args (if any).
    Repeat the same following __origin__'s.

    Return a list of arguments with all possible substitutions
    performed. Arguments that are generic classes themselves are represented
    as tuples (so that no new classes are created by this function).
    For example: _subs_tree(List[Tuple[int, T]][str]) == [(Tuple, int, str)]
    """

    if cls.__origin__ is None:
        return cls
    # Make of chain of origins (i.e. cls -> cls.__origin__)
    current = cls.__origin__
    orig_chain = []
    while current.__origin__ is not None:
        orig_chain.append(current)
        current = current.__origin__
    # Replace type variables in __args__ if asked ...
    tree_args = []
    for arg in cls.__args__:
        tree_args.append(_replace_arg(arg, tvars, args))
    # ... then continue replacing down the origin chain.
    for ocls in orig_chain:
        new_tree_args = []
        for arg in ocls.__args__:
            new_tree_args.append(_replace_arg(arg, ocls.__parameters__, tree_args))
        tree_args = new_tree_args
    return tree_args


def _remove_dups_flatten(parameters):
    """An internal helper for Union creation and substitution: flatten Union's
    among parameters, then remove duplicates and strict subclasses.
    """

    # Flatten out Union[Union[...], ...].
    params = []
    for p in parameters:
        if isinstance(p, _Union) and p.__origin__ is Union:
            params.extend(p.__args__)
        elif isinstance(p, tuple) and len(p) > 0 and p[0] is Union:
            params.extend(p[1:])
        else:
            params.append(p)
    # Weed out strict duplicates, preserving the first of each occurrence.
    all_params = set(params)
    if len(all_params) < len(params):
        new_params = []
        for t in params:
            if t in all_params:
                new_params.append(t)
                all_params.remove(t)
        params = new_params
        assert not all_params, all_params
    # Weed out subclasses.
    # E.g. Union[int, Employee, Manager] == Union[int, Employee].
    # If object is present it will be sole survivor among proper classes.
    # Never discard type variables.
    # (In particular, Union[str, AnyStr] != AnyStr.)
    all_params = set(params)
    for t1 in params:
        if not isinstance(t1, type):
            continue
        if any(isinstance(t2, type) and issubclass(t1, t2)
               for t2 in all_params - {t1}
               if not (isinstance(t2, GenericMeta) and
                       t2.__origin__ is not None)):
            all_params.remove(t1)
    return tuple(t for t in params if t in all_params)


def _check_generic(cls, parameters):
    # Check correct count for parameters of a generic cls (internal helper).
    if not cls.__parameters__:
        raise TypeError("%s is not a generic class" % repr(cls))
    alen = len(parameters)
    elen = len(cls.__parameters__)
    if alen != elen:
        raise TypeError("Too %s parameters for %s; actual %s, expected %s" %
                        ("many" if alen > elen else "few", repr(cls), alen, elen))


_cleanups = []


def _tp_cache(func):
    maxsize = 128
    cache = {}
    _cleanups.append(cache.clear)

    @functools.wraps(func)
    def inner(*args):
        key = args
        try:
            return cache[key]
        except TypeError:
            # Assume it's an unhashable argument.
            return func(*args)
        except KeyError:
            value = func(*args)
            if len(cache) >= maxsize:
                # If the cache grows too much, just start over.
                cache.clear()
            cache[key] = value
            return value

    return inner


class UnionMeta(TypingMeta):
    """Metaclass for Union."""

    def __new__(cls, name, bases, namespace):
        cls.assert_no_subclassing(bases)
        return super(UnionMeta, cls).__new__(cls, name, bases, namespace)


class _Union(_FinalTypingBase):
    """Union type; Union[X, Y] means either X or Y.

    To define a union, use e.g. Union[int, str].  Details:

    - The arguments must be types and there must be at least one.

    - None as an argument is a special case and is replaced by
      type(None).

    - Unions of unions are flattened, e.g.::

        Union[Union[int, str], float] == Union[int, str, float]

    - Unions of a single argument vanish, e.g.::

        Union[int] == int  # The constructor actually returns int

    - Redundant arguments are skipped, e.g.::

        Union[int, str, int] == Union[int, str]

    - When comparing unions, the argument order is ignored, e.g.::

        Union[int, str] == Union[str, int]

    - When two arguments have a subclass relationship, the least
      derived argument is kept, e.g.::

        class Employee: pass
        class Manager(Employee): pass
        Union[int, Employee, Manager] == Union[int, Employee]
        Union[Manager, int, Employee] == Union[int, Employee]
        Union[Employee, Manager] == Employee

    - Similar for object::

        Union[int, object] == object

    - You cannot subclass or instantiate a union.

    - You can use Optional[X] as a shorthand for Union[X, None].
    """

    __metaclass__ = UnionMeta
    __slots__ = ('__parameters__', '__args__', '__origin__', '__tree_hash__')

    def __new__(cls, parameters=None, origin=None, *args, **kwds):
        self = super(_Union, cls).__new__(cls, parameters, origin, *args, **kwds)
        if origin is None:
            self.__parameters__ = None
            self.__args__ = None
            self.__origin__ = None
            self.__tree_hash__ = hash(frozenset(('Union',)))
            return self
        if not isinstance(parameters, tuple):
            raise TypeError("Expected parameters=<tuple>")
        if origin is Union:
            parameters = _remove_dups_flatten(parameters)
            # It's not a union if there's only one type left.
            if len(parameters) == 1:
                return parameters[0]
        self.__parameters__ = _type_vars(parameters)
        self.__args__ = parameters
        self.__origin__ = origin
        # Pre-calculate the __hash__ on instantiation.
        # This improves speed for complex substitutions.
        subs_tree = self._subs_tree()
        if isinstance(subs_tree, tuple):
            self.__tree_hash__ = hash(frozenset(subs_tree))
        else:
            self.__tree_hash__ = hash(subs_tree)
        return self

    def _eval_type(self, globalns, localns):
        if self.__args__ is None:
            return self
        ev_args = tuple(_eval_type(t, globalns, localns) for t in self.__args__)
        ev_origin = _eval_type(self.__origin__, globalns, localns)
        if ev_args == self.__args__ and ev_origin == self.__origin__:
            # Everything is already evaluated.
            return self
        return self.__class__(ev_args, ev_origin, _root=True)

    def _get_type_vars(self, tvars):
        if self.__origin__ and self.__parameters__:
            _get_type_vars(self.__parameters__, tvars)

    def __repr__(self):
        if self.__origin__ is None:
            return super(_Union, self).__repr__()
        tree = self._subs_tree()
        if not isinstance(tree, tuple):
            return repr(tree)
        return tree[0]._tree_repr(tree)

    def _tree_repr(self, tree):
        arg_list = []
        for arg in tree[1:]:
            if not isinstance(arg, tuple):
                arg_list.append(_type_repr(arg))
            else:
                arg_list.append(arg[0]._tree_repr(arg))
        return super(_Union, self).__repr__() + '[%s]' % ', '.join(arg_list)

    @_tp_cache
    def __getitem__(self, parameters):
        if parameters == ():
            raise TypeError("Cannot take a Union of no types.")
        if not isinstance(parameters, tuple):
            parameters = (parameters,)
        if self.__origin__ is None:
            msg = "Union[arg, ...]: each arg must be a type."
        else:
            msg = "Parameters to generic types must be types."
        parameters = tuple(_type_check(p, msg) for p in parameters)
        if self is not Union:
            _check_generic(self, parameters)
        return self.__class__(parameters, origin=self, _root=True)

    def _subs_tree(self, tvars=None, args=None):
        if self is Union:
            return Union  # Nothing to substitute
        tree_args = _subs_tree(self, tvars, args)
        tree_args = _remove_dups_flatten(tree_args)
        if len(tree_args) == 1:
            return tree_args[0]  # Union of a single type is that type
        return (Union,) + tree_args

    def __eq__(self, other):
        if isinstance(other, _Union):
            return self.__tree_hash__ == other.__tree_hash__
        elif self is not Union:
            return self._subs_tree() == other
        else:
            return self is other

    def __hash__(self):
        return self.__tree_hash__

    def __instancecheck__(self, obj):
        raise TypeError("Unions cannot be used with isinstance().")

    def __subclasscheck__(self, cls):
        raise TypeError("Unions cannot be used with issubclass().")


Union = _Union(_root=True)


class OptionalMeta(TypingMeta):
    """Metaclass for Optional."""

    def __new__(cls, name, bases, namespace):
        cls.assert_no_subclassing(bases)
        return super(OptionalMeta, cls).__new__(cls, name, bases, namespace)


class _Optional(_FinalTypingBase):
    """Optional type.

    Optional[X] is equivalent to Union[X, None].
    """

    __metaclass__ = OptionalMeta
    __slots__ = ()

    @_tp_cache
    def __getitem__(self, arg):
        arg = _type_check(arg, "Optional[t] requires a single type.")
        return Union[arg, type(None)]


Optional = _Optional(_root=True)


def _next_in_mro(cls):
    """Helper for Generic.__new__.

    Returns the class after the last occurrence of Generic or
    Generic[...] in cls.__mro__.
    """
    next_in_mro = object
    # Look for the last occurrence of Generic or Generic[...].
    for i, c in enumerate(cls.__mro__[:-1]):
        if isinstance(c, GenericMeta) and c._gorg is Generic:
            next_in_mro = cls.__mro__[i + 1]
    return next_in_mro


def _make_subclasshook(cls):
    """Construct a __subclasshook__ callable that incorporates
    the associated __extra__ class in subclass checks performed
    against cls.
    """
    if isinstance(cls.__extra__, abc.ABCMeta):
        # The logic mirrors that of ABCMeta.__subclasscheck__.
        # Registered classes need not be checked here because
        # cls and its extra share the same _abc_registry.
        def __extrahook__(cls, subclass):
            res = cls.__extra__.__subclasshook__(subclass)
            if res is not NotImplemented:
                return res
            if cls.__extra__ in getattr(subclass, '__mro__', ()):
                return True
            for scls in cls.__extra__.__subclasses__():
                if isinstance(scls, GenericMeta):
                    continue
                if issubclass(subclass, scls):
                    return True
            return NotImplemented
    else:
        # For non-ABC extras we'll just call issubclass().
        def __extrahook__(cls, subclass):
            if cls.__extra__ and issubclass(subclass, cls.__extra__):
                return True
            return NotImplemented
    return classmethod(__extrahook__)


class GenericMeta(TypingMeta, abc.ABCMeta):
    """Metaclass for generic types.

    This is a metaclass for typing.Generic and generic ABCs defined in
    typing module. User defined subclasses of GenericMeta can override
    __new__ and invoke super().__new__. Note that GenericMeta.__new__
    has strict rules on what is allowed in its bases argument:
    * plain Generic is disallowed in bases;
    * Generic[...] should appear in bases at most once;
    * if Generic[...] is present, then it should list all type variables
      that appear in other bases.
    In addition, type of all generic bases is erased, e.g., C[int] is
    stripped to plain C.
    """

    def __new__(cls, name, bases, namespace,
                tvars=None, args=None, origin=None, extra=None, orig_bases=None):
        """Create a new generic class. GenericMeta.__new__ accepts
        keyword arguments that are used for internal bookkeeping, therefore
        an override should pass unused keyword arguments to super().
        """
        if tvars is not None:
            # Called from __getitem__() below.
            assert origin is not None
            assert all(isinstance(t, TypeVar) for t in tvars), tvars
        else:
            # Called from class statement.
            assert tvars is None, tvars
            assert args is None, args
            assert origin is None, origin

            # Get the full set of tvars from the bases.
            tvars = _type_vars(bases)
            # Look for Generic[T1, ..., Tn].
            # If found, tvars must be a subset of it.
            # If not found, tvars is it.
            # Also check for and reject plain Generic,
            # and reject multiple Generic[...].
            gvars = None
            for base in bases:
                if base is Generic:
                    raise TypeError("Cannot inherit from plain Generic")
                if (isinstance(base, GenericMeta) and
                        base.__origin__ is Generic):
                    if gvars is not None:
                        raise TypeError(
                            "Cannot inherit from Generic[...] multiple types.")
                    gvars = base.__parameters__
            if gvars is None:
                gvars = tvars
            else:
                tvarset = set(tvars)
                gvarset = set(gvars)
                if not tvarset <= gvarset:
                    raise TypeError(
                        "Some type variables (%s) "
                        "are not listed in Generic[%s]" %
                        (", ".join(str(t) for t in tvars if t not in gvarset),
                         ", ".join(str(g) for g in gvars)))
                tvars = gvars

        initial_bases = bases
        if extra is None:
            extra = namespace.get('__extra__')
        if extra is not None and type(extra) is abc.ABCMeta and extra not in bases:
            bases = (extra,) + bases
        bases = tuple(b._gorg if isinstance(b, GenericMeta) else b for b in bases)

        # remove bare Generic from bases if there are other generic bases
        if any(isinstance(b, GenericMeta) and b is not Generic for b in bases):
            bases = tuple(b for b in bases if b is not Generic)
        namespace.update({'__origin__': origin, '__extra__': extra})
        self = super(GenericMeta, cls).__new__(cls, name, bases, namespace)
        super(GenericMeta, self).__setattr__('_gorg',
                                             self if not origin else origin._gorg)

        self.__parameters__ = tvars
        # Be prepared that GenericMeta will be subclassed by TupleMeta
        # and CallableMeta, those two allow ..., (), or [] in __args___.
        self.__args__ = tuple(Ellipsis if a is _TypingEllipsis else
                              () if a is _TypingEmpty else
                              a for a in args) if args else None
        # Speed hack (https://github.com/python/typing/issues/196).
        self.__next_in_mro__ = _next_in_mro(self)
        # Preserve base classes on subclassing (__bases__ are type erased now).
        if orig_bases is None:
            self.__orig_bases__ = initial_bases

        # This allows unparameterized generic collections to be used
        # with issubclass() and isinstance() in the same way as their
        # collections.abc counterparts (e.g., isinstance([], Iterable)).
        if (
            '__subclasshook__' not in namespace and extra or
            # allow overriding
            getattr(self.__subclasshook__, '__name__', '') == '__extrahook__'
        ):
            self.__subclasshook__ = _make_subclasshook(self)

        if origin and hasattr(origin, '__qualname__'):  # Fix for Python 3.2.
            self.__qualname__ = origin.__qualname__
        self.__tree_hash__ = (hash(self._subs_tree()) if origin else
                              super(GenericMeta, self).__hash__())
        return self

    def __init__(self, *args, **kwargs):
        super(GenericMeta, self).__init__(*args, **kwargs)
        if isinstance(self.__extra__, abc.ABCMeta):
            self._abc_registry = self.__extra__._abc_registry
            self._abc_cache = self.__extra__._abc_cache
        elif self.__origin__ is not None:
            self._abc_registry = self.__origin__._abc_registry
            self._abc_cache = self.__origin__._abc_cache

    # _abc_negative_cache and _abc_negative_cache_version
    # realized as descriptors, since GenClass[t1, t2, ...] always
    # share subclass info with GenClass.
    # This is an important memory optimization.
    @property
    def _abc_negative_cache(self):
        if isinstance(self.__extra__, abc.ABCMeta):
            return self.__extra__._abc_negative_cache
        return self._gorg._abc_generic_negative_cache

    @_abc_negative_cache.setter
    def _abc_negative_cache(self, value):
        if self.__origin__ is None:
            if isinstance(self.__extra__, abc.ABCMeta):
                self.__extra__._abc_negative_cache = value
            else:
                self._abc_generic_negative_cache = value

    @property
    def _abc_negative_cache_version(self):
        if isinstance(self.__extra__, abc.ABCMeta):
            return self.__extra__._abc_negative_cache_version
        return self._gorg._abc_generic_negative_cache_version

    @_abc_negative_cache_version.setter
    def _abc_negative_cache_version(self, value):
        if self.__origin__ is None:
            if isinstance(self.__extra__, abc.ABCMeta):
                self.__extra__._abc_negative_cache_version = value
            else:
                self._abc_generic_negative_cache_version = value

    def _get_type_vars(self, tvars):
        if self.__origin__ and self.__parameters__:
            _get_type_vars(self.__parameters__, tvars)

    def _eval_type(self, globalns, localns):
        ev_origin = (self.__origin__._eval_type(globalns, localns)
                     if self.__origin__ else None)
        ev_args = tuple(_eval_type(a, globalns, localns) for a
                        in self.__args__) if self.__args__ else None
        if ev_origin == self.__origin__ and ev_args == self.__args__:
            return self
        return self.__class__(self.__name__,
                              self.__bases__,
                              dict(self.__dict__),
                              tvars=_type_vars(ev_args) if ev_args else None,
                              args=ev_args,
                              origin=ev_origin,
                              extra=self.__extra__,
                              orig_bases=self.__orig_bases__)

    def __repr__(self):
        if self.__origin__ is None:
            return super(GenericMeta, self).__repr__()
        return self._tree_repr(self._subs_tree())

    def _tree_repr(self, tree):
        arg_list = []
        for arg in tree[1:]:
            if arg == ():
                arg_list.append('()')
            elif not isinstance(arg, tuple):
                arg_list.append(_type_repr(arg))
            else:
                arg_list.append(arg[0]._tree_repr(arg))
        return super(GenericMeta, self).__repr__() + '[%s]' % ', '.join(arg_list)

    def _subs_tree(self, tvars=None, args=None):
        if self.__origin__ is None:
            return self
        tree_args = _subs_tree(self, tvars, args)
        return (self._gorg,) + tuple(tree_args)

    def __eq__(self, other):
        if not isinstance(other, GenericMeta):
            return NotImplemented
        if self.__origin__ is None or other.__origin__ is None:
            return self is other
        return self.__tree_hash__ == other.__tree_hash__

    def __hash__(self):
        return self.__tree_hash__

    @_tp_cache
    def __getitem__(self, params):
        if not isinstance(params, tuple):
            params = (params,)
        if not params and self._gorg is not Tuple:
            raise TypeError(
                "Parameter list to %s[...] cannot be empty" % _qualname(self))
        msg = "Parameters to generic types must be types."
        params = tuple(_type_check(p, msg) for p in params)
        if self is Generic:
            # Generic can only be subscripted with unique type variables.
            if not all(isinstance(p, TypeVar) for p in params):
                raise TypeError(
                    "Parameters to Generic[...] must all be type variables")
            if len(set(params)) != len(params):
                raise TypeError(
                    "Parameters to Generic[...] must all be unique")
            tvars = params
            args = params
        elif self in (Tuple, Callable):
            tvars = _type_vars(params)
            args = params
        elif self is _Protocol:
            # _Protocol is internal, don't check anything.
            tvars = params
            args = params
        elif self.__origin__ in (Generic, _Protocol):
            # Can't subscript Generic[...] or _Protocol[...].
            raise TypeError("Cannot subscript already-subscripted %s" %
                            repr(self))
        else:
            # Subscripting a regular Generic subclass.
            _check_generic(self, params)
            tvars = _type_vars(params)
            args = params

        prepend = (self,) if self.__origin__ is None else ()
        return self.__class__(self.__name__,
                              prepend + self.__bases__,
                              dict(self.__dict__),
                              tvars=tvars,
                              args=args,
                              origin=self,
                              extra=self.__extra__,
                              orig_bases=self.__orig_bases__)

    def __subclasscheck__(self, cls):
        if self.__origin__ is not None:
            # This should only be modules within the standard
            # library. singledispatch is the only exception, because
            # it's a Python 2 backport of functools.singledispatch.
            if sys._getframe(1).f_globals['__name__'] not in ['abc', 'functools',
                                                              'singledispatch']:
                raise TypeError("Parameterized generics cannot be used with class "
                                "or instance checks")
            return False
        if self is Generic:
            raise TypeError("Class %r cannot be used with class "
                            "or instance checks" % self)
        return super(GenericMeta, self).__subclasscheck__(cls)

    def __instancecheck__(self, instance):
        # Since we extend ABC.__subclasscheck__ and
        # ABC.__instancecheck__ inlines the cache checking done by the
        # latter, we must extend __instancecheck__ too. For simplicity
        # we just skip the cache check -- instance checks for generic
        # classes are supposed to be rare anyways.
        if not isinstance(instance, type):
            return issubclass(instance.__class__, self)
        return False

    def __setattr__(self, attr, value):
        # We consider all the subscripted genrics as proxies for original class
        if (
            attr.startswith('__') and attr.endswith('__') or
            attr.startswith('_abc_')
        ):
            super(GenericMeta, self).__setattr__(attr, value)
        else:
            super(GenericMeta, self._gorg).__setattr__(attr, value)


def _copy_generic(self):
    """Hack to work around https://bugs.python.org/issue11480 on Python 2"""
    return self.__class__(self.__name__, self.__bases__, dict(self.__dict__),
                          self.__parameters__, self.__args__, self.__origin__,
                          self.__extra__, self.__orig_bases__)


copy._copy_dispatch[GenericMeta] = _copy_generic


# Prevent checks for Generic to crash when defining Generic.
Generic = None


def _generic_new(base_cls, cls, *args, **kwds):
    # Assure type is erased on instantiation,
    # but attempt to store it in __orig_class__
    if cls.__origin__ is None:
        if (base_cls.__new__ is object.__new__ and
                cls.__init__ is not object.__init__):
            return base_cls.__new__(cls)
        else:
            return base_cls.__new__(cls, *args, **kwds)
    else:
        origin = cls._gorg
        if (base_cls.__new__ is object.__new__ and
                cls.__init__ is not object.__init__):
            obj = base_cls.__new__(origin)
        else:
            obj = base_cls.__new__(origin, *args, **kwds)
        try:
            obj.__orig_class__ = cls
        except AttributeError:
            pass
        obj.__init__(*args, **kwds)
        return obj


class Generic(object):
    """Abstract base class for generic types.

    A generic type is typically declared by inheriting from
    this class parameterized with one or more type variables.
    For example, a generic mapping type might be defined as::

      class Mapping(Generic[KT, VT]):
          def __getitem__(self, key: KT) -> VT:
              ...
          # Etc.

    This class can then be used as follows::

      def lookup_name(mapping: Mapping[KT, VT], key: KT, default: VT) -> VT:
          try:
              return mapping[key]
          except KeyError:
              return default
    """

    __metaclass__ = GenericMeta
    __slots__ = ()

    def __new__(cls, *args, **kwds):
        if cls._gorg is Generic:
            raise TypeError("Type Generic cannot be instantiated; "
                            "it can be used only as a base class")
        return _generic_new(cls.__next_in_mro__, cls, *args, **kwds)


class _TypingEmpty(object):
    """Internal placeholder for () or []. Used by TupleMeta and CallableMeta
    to allow empty list/tuple in specific places, without allowing them
    to sneak in where prohibited.
    """


class _TypingEllipsis(object):
    """Internal placeholder for ... (ellipsis)."""


class TupleMeta(GenericMeta):
    """Metaclass for Tuple (internal)."""

    @_tp_cache
    def __getitem__(self, parameters):
        if self.__origin__ is not None or self._gorg is not Tuple:
            # Normal generic rules apply if this is not the first subscription
            # or a subscription of a subclass.
            return super(TupleMeta, self).__getitem__(parameters)
        if parameters == ():
            return super(TupleMeta, self).__getitem__((_TypingEmpty,))
        if not isinstance(parameters, tuple):
            parameters = (parameters,)
        if len(parameters) == 2 and parameters[1] is Ellipsis:
            msg = "Tuple[t, ...]: t must be a type."
            p = _type_check(parameters[0], msg)
            return super(TupleMeta, self).__getitem__((p, _TypingEllipsis))
        msg = "Tuple[t0, t1, ...]: each t must be a type."
        parameters = tuple(_type_check(p, msg) for p in parameters)
        return super(TupleMeta, self).__getitem__(parameters)

    def __instancecheck__(self, obj):
        if self.__args__ is None:
            return isinstance(obj, tuple)
        raise TypeError("Parameterized Tuple cannot be used "
                        "with isinstance().")

    def __subclasscheck__(self, cls):
        if self.__args__ is None:
            return issubclass(cls, tuple)
        raise TypeError("Parameterized Tuple cannot be used "
                        "with issubclass().")


copy._copy_dispatch[TupleMeta] = _copy_generic


class Tuple(tuple):
    """Tuple type; Tuple[X, Y] is the cross-product type of X and Y.

    Example: Tuple[T1, T2] is a tuple of two elements corresponding
    to type variables T1 and T2.  Tuple[int, float, str] is a tuple
    of an int, a float and a string.

    To specify a variable-length tuple of homogeneous type, use Tuple[T, ...].
    """

    __metaclass__ = TupleMeta
    __extra__ = tuple
    __slots__ = ()

    def __new__(cls, *args, **kwds):
        if cls._gorg is Tuple:
            raise TypeError("Type Tuple cannot be instantiated; "
                            "use tuple() instead")
        return _generic_new(tuple, cls, *args, **kwds)


class CallableMeta(GenericMeta):
    """ Metaclass for Callable."""

    def __repr__(self):
        if self.__origin__ is None:
            return super(CallableMeta, self).__repr__()
        return self._tree_repr(self._subs_tree())

    def _tree_repr(self, tree):
        if self._gorg is not Callable:
            return super(CallableMeta, self)._tree_repr(tree)
        # For actual Callable (not its subclass) we override
        # super(CallableMeta, self)._tree_repr() for nice formatting.
        arg_list = []
        for arg in tree[1:]:
            if not isinstance(arg, tuple):
                arg_list.append(_type_repr(arg))
            else:
                arg_list.append(arg[0]._tree_repr(arg))
        if arg_list[0] == '...':
            return repr(tree[0]) + '[..., %s]' % arg_list[1]
        return (repr(tree[0]) +
                '[[%s], %s]' % (', '.join(arg_list[:-1]), arg_list[-1]))

    def __getitem__(self, parameters):
        """A thin wrapper around __getitem_inner__ to provide the latter
        with hashable arguments to improve speed.
        """

        if self.__origin__ is not None or self._gorg is not Callable:
            return super(CallableMeta, self).__getitem__(parameters)
        if not isinstance(parameters, tuple) or len(parameters) != 2:
            raise TypeError("Callable must be used as "
                            "Callable[[arg, ...], result].")
        args, result = parameters
        if args is Ellipsis:
            parameters = (Ellipsis, result)
        else:
            if not isinstance(args, list):
                raise TypeError("Callable[args, result]: args must be a list."
                                " Got %.100r." % (args,))
            parameters = (tuple(args), result)
        return self.__getitem_inner__(parameters)

    @_tp_cache
    def __getitem_inner__(self, parameters):
        args, result = parameters
        msg = "Callable[args, result]: result must be a type."
        result = _type_check(result, msg)
        if args is Ellipsis:
            return super(CallableMeta, self).__getitem__((_TypingEllipsis, result))
        msg = "Callable[[arg, ...], result]: each arg must be a type."
        args = tuple(_type_check(arg, msg) for arg in args)
        parameters = args + (result,)
        return super(CallableMeta, self).__getitem__(parameters)


copy._copy_dispatch[CallableMeta] = _copy_generic


class Callable(object):
    """Callable type; Callable[[int], str] is a function of (int) -> str.

    The subscription syntax must always be used with exactly two
    values: the argument list and the return type.  The argument list
    must be a list of types or ellipsis; the return type must be a single type.

    There is no syntax to indicate optional or keyword arguments,
    such function types are rarely used as callback types.
    """

    __metaclass__ = CallableMeta
    __extra__ = collections_abc.Callable
    __slots__ = ()

    def __new__(cls, *args, **kwds):
        if cls._gorg is Callable:
            raise TypeError("Type Callable cannot be instantiated; "
                            "use a non-abstract subclass instead")
        return _generic_new(cls.__next_in_mro__, cls, *args, **kwds)


def cast(typ, val):
    """Cast a value to a type.

    This returns the value unchanged.  To the type checker this
    signals that the return value has the designated type, but at
    runtime we intentionally don't check anything (we want this
    to be as fast as possible).
    """
    return val


def _get_defaults(func):
    """Internal helper to extract the default arguments, by name."""
    code = func.__code__
    pos_count = code.co_argcount
    arg_names = code.co_varnames
    arg_names = arg_names[:pos_count]
    defaults = func.__defaults__ or ()
    kwdefaults = func.__kwdefaults__
    res = dict(kwdefaults) if kwdefaults else {}
    pos_offset = pos_count - len(defaults)
    for name, value in zip(arg_names[pos_offset:], defaults):
        assert name not in res
        res[name] = value
    return res


def get_type_hints(obj, globalns=None, localns=None):
    """In Python 2 this is not supported and always returns None."""
    return None


def no_type_check(arg):
    """Decorator to indicate that annotations are not type hints.

    The argument must be a class or function; if it is a class, it
    applies recursively to all methods and classes defined in that class
    (but not to methods defined in its superclasses or subclasses).

    This mutates the function(s) or class(es) in place.
    """
    if isinstance(arg, type):
        arg_attrs = arg.__dict__.copy()
        for attr, val in arg.__dict__.items():
            if val in arg.__bases__ + (arg,):
                arg_attrs.pop(attr)
        for obj in arg_attrs.values():
            if isinstance(obj, types.FunctionType):
                obj.__no_type_check__ = True
            if isinstance(obj, type):
                no_type_check(obj)
    try:
        arg.__no_type_check__ = True
    except TypeError:  # built-in classes
        pass
    return arg


def no_type_check_decorator(decorator):
    """Decorator to give another decorator the @no_type_check effect.

    This wraps the decorator with something that wraps the decorated
    function in @no_type_check.
    """

    @functools.wraps(decorator)
    def wrapped_decorator(*args, **kwds):
        func = decorator(*args, **kwds)
        func = no_type_check(func)
        return func

    return wrapped_decorator


def _overload_dummy(*args, **kwds):
    """Helper for @overload to raise when called."""
    raise NotImplementedError(
        "You should not call an overloaded function. "
        "A series of @overload-decorated functions "
        "outside a stub module should always be followed "
        "by an implementation that is not @overload-ed.")


def overload(func):
    """Decorator for overloaded functions/methods.

    In a stub file, place two or more stub definitions for the same
    function in a row, each decorated with @overload.  For example:

      @overload
      def utf8(value: None) -> None: ...
      @overload
      def utf8(value: bytes) -> bytes: ...
      @overload
      def utf8(value: str) -> bytes: ...

    In a non-stub file (i.e. a regular .py file), do the same but
    follow it with an implementation.  The implementation should *not*
    be decorated with @overload.  For example:

      @overload
      def utf8(value: None) -> None: ...
      @overload
      def utf8(value: bytes) -> bytes: ...
      @overload
      def utf8(value: str) -> bytes: ...
      def utf8(value):
          # implementation goes here
    """
    return _overload_dummy


class _ProtocolMeta(GenericMeta):
    """Internal metaclass for _Protocol.

    This exists so _Protocol classes can be generic without deriving
    from Generic.
    """

    def __instancecheck__(self, obj):
        if _Protocol not in self.__bases__:
            return super(_ProtocolMeta, self).__instancecheck__(obj)
        raise TypeError("Protocols cannot be used with isinstance().")

    def __subclasscheck__(self, cls):
        if not self._is_protocol:
            # No structural checks since this isn't a protocol.
            return NotImplemented

        if self is _Protocol:
            # Every class is a subclass of the empty protocol.
            return True

        # Find all attributes defined in the protocol.
        attrs = self._get_protocol_attrs()

        for attr in attrs:
            if not any(attr in d.__dict__ for d in cls.__mro__):
                return False
        return True

    def _get_protocol_attrs(self):
        # Get all Protocol base classes.
        protocol_bases = []
        for c in self.__mro__:
            if getattr(c, '_is_protocol', False) and c.__name__ != '_Protocol':
                protocol_bases.append(c)

        # Get attributes included in protocol.
        attrs = set()
        for base in protocol_bases:
            for attr in base.__dict__.keys():
                # Include attributes not defined in any non-protocol bases.
                for c in self.__mro__:
                    if (c is not base and attr in c.__dict__ and
                            not getattr(c, '_is_protocol', False)):
                        break
                else:
                    if (not attr.startswith('_abc_') and
                            attr != '__abstractmethods__' and
                            attr != '_is_protocol' and
                            attr != '_gorg' and
                            attr != '__dict__' and
                            attr != '__args__' and
                            attr != '__slots__' and
                            attr != '_get_protocol_attrs' and
                            attr != '__next_in_mro__' and
                            attr != '__parameters__' and
                            attr != '__origin__' and
                            attr != '__orig_bases__' and
                            attr != '__extra__' and
                            attr != '__tree_hash__' and
                            attr != '__module__'):
                        attrs.add(attr)

        return attrs


class _Protocol(object):
    """Internal base class for protocol classes.

    This implements a simple-minded structural issubclass check
    (similar but more general than the one-offs in collections.abc
    such as Hashable).
    """

    __metaclass__ = _ProtocolMeta
    __slots__ = ()

    _is_protocol = True


# Various ABCs mimicking those in collections.abc.
# A few are simply re-exported for completeness.

Hashable = collections_abc.Hashable  # Not generic.


class Iterable(Generic[T_co]):
    __slots__ = ()
    __extra__ = collections_abc.Iterable


class Iterator(Iterable[T_co]):
    __slots__ = ()
    __extra__ = collections_abc.Iterator


class SupportsInt(_Protocol):
    __slots__ = ()

    @abstractmethod
    def __int__(self):
        pass


class SupportsFloat(_Protocol):
    __slots__ = ()

    @abstractmethod
    def __float__(self):
        pass


class SupportsComplex(_Protocol):
    __slots__ = ()

    @abstractmethod
    def __complex__(self):
        pass


class SupportsAbs(_Protocol[T_co]):
    __slots__ = ()

    @abstractmethod
    def __abs__(self):
        pass


if hasattr(collections_abc, 'Reversible'):
    class Reversible(Iterable[T_co]):
        __slots__ = ()
        __extra__ = collections_abc.Reversible
else:
    class Reversible(_Protocol[T_co]):
        __slots__ = ()

        @abstractmethod
        def __reversed__(self):
            pass


Sized = collections_abc.Sized  # Not generic.


class Container(Generic[T_co]):
    __slots__ = ()
    __extra__ = collections_abc.Container


# Callable was defined earlier.


class AbstractSet(Sized, Iterable[T_co], Container[T_co]):
    __slots__ = ()
    __extra__ = collections_abc.Set


class MutableSet(AbstractSet[T]):
    __slots__ = ()
    __extra__ = collections_abc.MutableSet


# NOTE: It is only covariant in the value type.
class Mapping(Sized, Iterable[KT], Container[KT], Generic[KT, VT_co]):
    __slots__ = ()
    __extra__ = collections_abc.Mapping


class MutableMapping(Mapping[KT, VT]):
    __slots__ = ()
    __extra__ = collections_abc.MutableMapping


if hasattr(collections_abc, 'Reversible'):
    class Sequence(Sized, Reversible[T_co], Container[T_co]):
        __slots__ = ()
        __extra__ = collections_abc.Sequence
else:
    class Sequence(Sized, Iterable[T_co], Container[T_co]):
        __slots__ = ()
        __extra__ = collections_abc.Sequence


class MutableSequence(Sequence[T]):
    __slots__ = ()
    __extra__ = collections_abc.MutableSequence


class ByteString(Sequence[int]):
    pass


ByteString.register(str)
ByteString.register(bytearray)


class List(list, MutableSequence[T]):
    __slots__ = ()
    __extra__ = list

    def __new__(cls, *args, **kwds):
        if cls._gorg is List:
            raise TypeError("Type List cannot be instantiated; "
                            "use list() instead")
        return _generic_new(list, cls, *args, **kwds)


class Deque(collections.deque, MutableSequence[T]):
    __slots__ = ()
    __extra__ = collections.deque

    def __new__(cls, *args, **kwds):
        if cls._gorg is Deque:
            return collections.deque(*args, **kwds)
        return _generic_new(collections.deque, cls, *args, **kwds)


class Set(set, MutableSet[T]):
    __slots__ = ()
    __extra__ = set

    def __new__(cls, *args, **kwds):
        if cls._gorg is Set:
            raise TypeError("Type Set cannot be instantiated; "
                            "use set() instead")
        return _generic_new(set, cls, *args, **kwds)


class FrozenSet(frozenset, AbstractSet[T_co]):
    __slots__ = ()
    __extra__ = frozenset

    def __new__(cls, *args, **kwds):
        if cls._gorg is FrozenSet:
            raise TypeError("Type FrozenSet cannot be instantiated; "
                            "use frozenset() instead")
        return _generic_new(frozenset, cls, *args, **kwds)


class MappingView(Sized, Iterable[T_co]):
    __slots__ = ()
    __extra__ = collections_abc.MappingView


class KeysView(MappingView[KT], AbstractSet[KT]):
    __slots__ = ()
    __extra__ = collections_abc.KeysView


class ItemsView(MappingView[Tuple[KT, VT_co]],
                AbstractSet[Tuple[KT, VT_co]],
                Generic[KT, VT_co]):
    __slots__ = ()
    __extra__ = collections_abc.ItemsView


class ValuesView(MappingView[VT_co]):
    __slots__ = ()
    __extra__ = collections_abc.ValuesView


class ContextManager(Generic[T_co]):
    __slots__ = ()

    def __enter__(self):
        return self

    @abc.abstractmethod
    def __exit__(self, exc_type, exc_value, traceback):
        return None

    @classmethod
    def __subclasshook__(cls, C):
        if cls is ContextManager:
            # In Python 3.6+, it is possible to set a method to None to
            # explicitly indicate that the class does not implement an ABC
            # (https://bugs.python.org/issue25958), but we do not support
            # that pattern here because this fallback class is only used
            # in Python 3.5 and earlier.
            if (any("__enter__" in B.__dict__ for B in C.__mro__) and
                any("__exit__" in B.__dict__ for B in C.__mro__)):
                return True
        return NotImplemented


class Dict(dict, MutableMapping[KT, VT]):
    __slots__ = ()
    __extra__ = dict

    def __new__(cls, *args, **kwds):
        if cls._gorg is Dict:
            raise TypeError("Type Dict cannot be instantiated; "
                            "use dict() instead")
        return _generic_new(dict, cls, *args, **kwds)


class DefaultDict(collections.defaultdict, MutableMapping[KT, VT]):
    __slots__ = ()
    __extra__ = collections.defaultdict

    def __new__(cls, *args, **kwds):
        if cls._gorg is DefaultDict:
            return collections.defaultdict(*args, **kwds)
        return _generic_new(collections.defaultdict, cls, *args, **kwds)


############################
# Insertion by CT 2019-02-21
#
class OrderedDict(collections.OrderedDict, MutableMapping[KT, VT]):
    __slots__ = ()
    __extra__ = collections.OrderedDict

    def __new__(cls, *args, **kwds):
        if cls._gorg is OrderedDict:
            return collections.OrderedDict(*args, **kwds)
        return _generic_new(collections.OrderedDict, cls, *args, **kwds)
#
############################


class Counter(collections.Counter, Dict[T, int]):
    __slots__ = ()
    __extra__ = collections.Counter

    def __new__(cls, *args, **kwds):
        if cls._gorg is Counter:
            return collections.Counter(*args, **kwds)
        return _generic_new(collections.Counter, cls, *args, **kwds)


# Determine what base class to use for Generator.
if hasattr(collections_abc, 'Generator'):
    # Sufficiently recent versions of 3.5 have a Generator ABC.
    _G_base = collections_abc.Generator
else:
    # Fall back on the exact type.
    _G_base = types.GeneratorType


class Generator(Iterator[T_co], Generic[T_co, T_contra, V_co]):
    __slots__ = ()
    __extra__ = _G_base

    def __new__(cls, *args, **kwds):
        if cls._gorg is Generator:
            raise TypeError("Type Generator cannot be instantiated; "
                            "create a subclass instead")
        return _generic_new(_G_base, cls, *args, **kwds)


# Internal type variable used for Type[].
CT_co = TypeVar('CT_co', covariant=True, bound=type)


# This is not a real generic class.  Don't use outside annotations.
class Type(Generic[CT_co]):
    """A special construct usable to annotate class objects.

    For example, suppose we have the following classes::

      class User: ...  # Abstract base for User classes
      class BasicUser(User): ...
      class ProUser(User): ...
      class TeamUser(User): ...

    And a function that takes a class argument that's a subclass of
    User and returns an instance of the corresponding class::

      U = TypeVar('U', bound=User)
      def new_user(user_class: Type[U]) -> U:
          user = user_class()
          # (Here we could write the user object to a database)
          return user

      joe = new_user(BasicUser)

    At this point the type checker knows that joe has type BasicUser.
    """
    __slots__ = ()
    __extra__ = type


def NamedTuple(typename, fields):
    """Typed version of namedtuple.

    Usage::

        Employee = typing.NamedTuple('Employee', [('name', str), ('id', int)])

    This is equivalent to::

        Employee = collections.namedtuple('Employee', ['name', 'id'])

    The resulting class has one extra attribute: _field_types,
    giving a dict mapping field names to types.  (The field names
    are in the _fields attribute, which is part of the namedtuple
    API.)
    """
    fields = [(n, t) for n, t in fields]
    cls = collections.namedtuple(typename, [n for n, t in fields])
    cls._field_types = dict(fields)
    # Set the module to the caller's module (otherwise it'd be 'typing').
    try:
        cls.__module__ = sys._getframe(1).f_globals.get('__name__', '__main__')
    except (AttributeError, ValueError):
        pass
    return cls


def NewType(name, tp):
    """NewType creates simple unique types with almost zero
    runtime overhead. NewType(name, tp) is considered a subtype of tp
    by static type checkers. At runtime, NewType(name, tp) returns
    a dummy function that simply returns its argument. Usage::

        UserId = NewType('UserId', int)

        def name_by_id(user_id):
            # type: (UserId) -> str
            ...

        UserId('user')          # Fails type check

        name_by_id(42)          # Fails type check
        name_by_id(UserId(42))  # OK

        num = UserId(5) + 1     # type: int
    """

    def new_type(x):
        return x

    # Some versions of Python 2 complain because of making all strings unicode
    new_type.__name__ = str(name)
    new_type.__supertype__ = tp
    return new_type


# Python-version-specific alias (Python 2: unicode; Python 3: str)
Text = unicode


# Constant that's True when type checking, but False here.
TYPE_CHECKING = False


class IO(Generic[AnyStr]):
    """Generic base class for TextIO and BinaryIO.

    This is an abstract, generic version of the return of open().

    NOTE: This does not distinguish between the different possible
    classes (text vs. binary, read vs. write vs. read/write,
    append-only, unbuffered).  The TextIO and BinaryIO subclasses
    below capture the distinctions between text vs. binary, which is
    pervasive in the interface; however we currently do not offer a
    way to track the other distinctions in the type system.
    """

    __slots__ = ()

    @abstractproperty
    def mode(self):
        pass

    @abstractproperty
    def name(self):
        pass

    @abstractmethod
    def close(self):
        pass

    @abstractproperty
    def closed(self):
        pass

    @abstractmethod
    def fileno(self):
        pass

    @abstractmethod
    def flush(self):
        pass

    @abstractmethod
    def isatty(self):
        pass

    @abstractmethod
    def read(self, n=-1):
        pass

    @abstractmethod
    def readable(self):
        pass

    @abstractmethod
    def readline(self, limit=-1):
        pass

    @abstractmethod
    def readlines(self, hint=-1):
        pass

    @abstractmethod
    def seek(self, offset, whence=0):
        pass

    @abstractmethod
    def seekable(self):
        pass

    @abstractmethod
    def tell(self):
        pass

    @abstractmethod
    def truncate(self, size=None):
        pass

    @abstractmethod
    def writable(self):
        pass

    @abstractmethod
    def write(self, s):
        pass

    @abstractmethod
    def writelines(self, lines):
        pass

    @abstractmethod
    def __enter__(self):
        pass

    @abstractmethod
    def __exit__(self, type, value, traceback):
        pass


class BinaryIO(IO[bytes]):
    """Typed version of the return of open() in binary mode."""

    __slots__ = ()

    @abstractmethod
    def write(self, s):
        pass

    @abstractmethod
    def __enter__(self):
        pass


class TextIO(IO[unicode]):
    """Typed version of the return of open() in text mode."""

    __slots__ = ()

    @abstractproperty
    def buffer(self):
        pass

    @abstractproperty
    def encoding(self):
        pass

    @abstractproperty
    def errors(self):
        pass

    @abstractproperty
    def line_buffering(self):
        pass

    @abstractproperty
    def newlines(self):
        pass

    @abstractmethod
    def __enter__(self):
        pass


class io(object):
    """Wrapper namespace for IO generic classes."""

    __all__ = ['IO', 'TextIO', 'BinaryIO']
    IO = IO
    TextIO = TextIO
    BinaryIO = BinaryIO


io.__name__ = __name__ + b'.io'
sys.modules[io.__name__] = io


Pattern = _TypeAlias('Pattern', AnyStr, type(stdlib_re.compile('')),
                     lambda p: p.pattern)
Match = _TypeAlias('Match', AnyStr, type(stdlib_re.match('', '')),
                   lambda m: m.re.pattern)


class re(object):
    """Wrapper namespace for re type aliases."""

    __all__ = ['Pattern', 'Match']
    Pattern = Pattern
    Match = Match


re.__name__ = __name__ + b'.re'
sys.modules[re.__name__] = re