summaryrefslogtreecommitdiffstats
path: root/compiler/rustc_hir/src/hir.rs
blob: c4e44a6a4e38868b41509acb0ec2e55fa856a860 (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
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
2731
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
2748
2749
2750
2751
2752
2753
2754
2755
2756
2757
2758
2759
2760
2761
2762
2763
2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775
2776
2777
2778
2779
2780
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802
2803
2804
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
2820
2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
2844
2845
2846
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
2857
2858
2859
2860
2861
2862
2863
2864
2865
2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
2877
2878
2879
2880
2881
2882
2883
2884
2885
2886
2887
2888
2889
2890
2891
2892
2893
2894
2895
2896
2897
2898
2899
2900
2901
2902
2903
2904
2905
2906
2907
2908
2909
2910
2911
2912
2913
2914
2915
2916
2917
2918
2919
2920
2921
2922
2923
2924
2925
2926
2927
2928
2929
2930
2931
2932
2933
2934
2935
2936
2937
2938
2939
2940
2941
2942
2943
2944
2945
2946
2947
2948
2949
2950
2951
2952
2953
2954
2955
2956
2957
2958
2959
2960
2961
2962
2963
2964
2965
2966
2967
2968
2969
2970
2971
2972
2973
2974
2975
2976
2977
2978
2979
2980
2981
2982
2983
2984
2985
2986
2987
2988
2989
2990
2991
2992
2993
2994
2995
2996
2997
2998
2999
3000
3001
3002
3003
3004
3005
3006
3007
3008
3009
3010
3011
3012
3013
3014
3015
3016
3017
3018
3019
3020
3021
3022
3023
3024
3025
3026
3027
3028
3029
3030
3031
3032
3033
3034
3035
3036
3037
3038
3039
3040
3041
3042
3043
3044
3045
3046
3047
3048
3049
3050
3051
3052
3053
3054
3055
3056
3057
3058
3059
3060
3061
3062
3063
3064
3065
3066
3067
3068
3069
3070
3071
3072
3073
3074
3075
3076
3077
3078
3079
3080
3081
3082
3083
3084
3085
3086
3087
3088
3089
3090
3091
3092
3093
3094
3095
3096
3097
3098
3099
3100
3101
3102
3103
3104
3105
3106
3107
3108
3109
3110
3111
3112
3113
3114
3115
3116
3117
3118
3119
3120
3121
3122
3123
3124
3125
3126
3127
3128
3129
3130
3131
3132
3133
3134
3135
3136
3137
3138
3139
3140
3141
3142
3143
3144
3145
3146
3147
3148
3149
3150
3151
3152
3153
3154
3155
3156
3157
3158
3159
3160
3161
3162
3163
3164
3165
3166
3167
3168
3169
3170
3171
3172
3173
3174
3175
3176
3177
3178
3179
3180
3181
3182
3183
3184
3185
3186
3187
3188
3189
3190
3191
3192
3193
3194
3195
3196
3197
3198
3199
3200
3201
3202
3203
3204
3205
3206
3207
3208
3209
3210
3211
3212
3213
3214
3215
3216
3217
3218
3219
3220
3221
3222
3223
3224
3225
3226
3227
3228
3229
3230
3231
3232
3233
3234
3235
3236
3237
3238
3239
3240
3241
3242
3243
3244
3245
3246
3247
3248
3249
3250
3251
3252
3253
3254
3255
3256
3257
3258
3259
3260
3261
3262
3263
3264
3265
3266
3267
3268
3269
3270
3271
3272
3273
3274
3275
3276
3277
3278
3279
3280
3281
3282
3283
3284
3285
3286
3287
3288
3289
3290
3291
3292
3293
3294
3295
3296
3297
3298
3299
3300
3301
3302
3303
3304
3305
3306
3307
3308
3309
3310
3311
3312
3313
3314
3315
3316
3317
3318
3319
3320
3321
3322
3323
3324
3325
3326
3327
3328
3329
3330
3331
3332
3333
3334
3335
3336
3337
3338
3339
3340
3341
3342
3343
3344
3345
3346
3347
3348
3349
3350
3351
3352
3353
3354
3355
3356
3357
3358
3359
3360
3361
3362
3363
3364
3365
3366
3367
3368
3369
3370
3371
3372
3373
3374
3375
3376
3377
3378
3379
3380
3381
3382
3383
3384
3385
3386
3387
3388
3389
3390
3391
3392
3393
3394
3395
3396
3397
3398
3399
3400
3401
3402
3403
3404
3405
3406
3407
3408
3409
3410
3411
3412
3413
3414
3415
3416
3417
3418
3419
3420
3421
3422
3423
3424
3425
3426
3427
3428
3429
3430
3431
3432
3433
3434
3435
3436
3437
3438
3439
3440
3441
3442
3443
3444
3445
3446
3447
3448
3449
3450
3451
3452
3453
3454
3455
3456
3457
3458
3459
3460
3461
3462
3463
3464
3465
3466
3467
3468
3469
3470
3471
3472
3473
3474
3475
3476
3477
3478
3479
3480
3481
3482
3483
3484
3485
3486
3487
3488
3489
3490
3491
3492
3493
3494
3495
3496
3497
3498
3499
3500
3501
3502
3503
3504
3505
3506
3507
3508
3509
3510
3511
3512
3513
3514
3515
3516
3517
3518
3519
3520
3521
3522
3523
3524
3525
3526
3527
3528
3529
3530
3531
3532
3533
3534
3535
3536
3537
3538
3539
3540
3541
3542
3543
3544
3545
3546
3547
3548
3549
3550
3551
3552
3553
3554
3555
3556
3557
3558
3559
3560
3561
3562
3563
3564
3565
3566
3567
3568
3569
3570
3571
3572
3573
3574
3575
3576
3577
3578
3579
3580
3581
3582
3583
3584
3585
3586
3587
3588
3589
3590
3591
3592
3593
3594
3595
3596
3597
3598
3599
3600
3601
3602
3603
3604
3605
3606
3607
3608
3609
3610
3611
3612
3613
3614
3615
3616
3617
3618
3619
3620
3621
3622
3623
3624
3625
3626
3627
3628
3629
3630
3631
3632
3633
3634
3635
3636
3637
3638
3639
3640
3641
3642
3643
3644
3645
3646
3647
3648
3649
3650
3651
3652
3653
3654
3655
3656
3657
3658
3659
3660
3661
3662
3663
3664
3665
3666
3667
3668
3669
3670
3671
3672
3673
3674
3675
3676
3677
3678
3679
3680
3681
3682
3683
3684
3685
3686
3687
3688
3689
3690
3691
3692
3693
3694
3695
3696
3697
3698
3699
3700
3701
3702
3703
3704
3705
3706
3707
3708
3709
3710
3711
3712
3713
3714
3715
3716
3717
3718
3719
3720
3721
3722
3723
3724
3725
3726
3727
3728
3729
3730
3731
3732
3733
3734
3735
3736
3737
3738
3739
3740
3741
3742
3743
3744
3745
3746
3747
3748
3749
3750
3751
3752
3753
3754
3755
3756
3757
3758
3759
3760
3761
3762
3763
3764
3765
3766
3767
3768
3769
3770
3771
3772
3773
3774
3775
3776
3777
3778
3779
3780
3781
3782
3783
3784
3785
3786
3787
3788
3789
3790
3791
3792
3793
3794
3795
3796
3797
3798
3799
3800
3801
3802
3803
3804
3805
3806
3807
3808
3809
3810
3811
3812
3813
3814
3815
3816
3817
3818
3819
3820
3821
3822
3823
3824
3825
3826
3827
3828
3829
3830
3831
3832
3833
3834
3835
3836
3837
3838
3839
3840
3841
3842
3843
3844
3845
3846
3847
3848
3849
3850
3851
3852
3853
3854
3855
3856
3857
3858
3859
3860
3861
3862
3863
3864
3865
3866
3867
3868
3869
3870
3871
3872
3873
3874
3875
3876
3877
3878
3879
3880
3881
3882
3883
3884
3885
3886
3887
3888
3889
3890
3891
3892
3893
3894
3895
3896
3897
3898
3899
3900
3901
3902
3903
3904
3905
3906
3907
3908
3909
3910
3911
3912
3913
3914
3915
3916
3917
3918
3919
3920
3921
3922
3923
3924
3925
3926
3927
3928
3929
3930
3931
3932
3933
3934
3935
3936
3937
3938
3939
3940
3941
3942
3943
3944
3945
3946
3947
3948
3949
3950
3951
3952
3953
3954
3955
3956
3957
3958
3959
3960
3961
3962
3963
3964
3965
3966
3967
3968
3969
3970
3971
3972
3973
3974
3975
3976
3977
3978
3979
3980
3981
3982
3983
3984
3985
3986
3987
3988
3989
3990
3991
3992
3993
3994
3995
3996
3997
3998
3999
4000
4001
4002
4003
4004
4005
4006
4007
4008
4009
4010
4011
4012
4013
4014
4015
4016
4017
4018
4019
4020
4021
4022
4023
4024
4025
4026
4027
4028
4029
4030
4031
4032
4033
4034
4035
4036
4037
4038
4039
4040
4041
4042
4043
4044
4045
4046
4047
4048
4049
4050
4051
4052
4053
4054
4055
4056
4057
4058
4059
4060
4061
4062
4063
4064
4065
4066
4067
4068
4069
4070
4071
4072
4073
4074
4075
4076
4077
4078
4079
4080
4081
4082
4083
4084
4085
4086
4087
4088
4089
4090
4091
4092
4093
4094
4095
4096
4097
4098
4099
4100
4101
4102
4103
4104
4105
4106
4107
4108
4109
4110
4111
4112
4113
4114
4115
4116
4117
4118
4119
4120
4121
4122
4123
4124
4125
4126
4127
4128
4129
4130
4131
4132
4133
4134
4135
4136
4137
4138
4139
4140
4141
4142
4143
use crate::def::{CtorKind, DefKind, Res};
use crate::def_id::DefId;
pub(crate) use crate::hir_id::{HirId, ItemLocalId, OwnerId};
use crate::intravisit::FnKind;
use crate::LangItem;

use rustc_ast as ast;
use rustc_ast::util::parser::ExprPrecedence;
use rustc_ast::{Attribute, FloatTy, IntTy, Label, LitKind, TraitObjectSyntax, UintTy};
pub use rustc_ast::{BindingAnnotation, BorrowKind, ByRef, ImplPolarity, IsAuto};
pub use rustc_ast::{CaptureBy, Movability, Mutability};
use rustc_ast::{InlineAsmOptions, InlineAsmTemplatePiece};
use rustc_data_structures::fingerprint::Fingerprint;
use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::sorted_map::SortedMap;
use rustc_error_messages::MultiSpan;
use rustc_index::IndexVec;
use rustc_macros::HashStable_Generic;
use rustc_span::hygiene::MacroKind;
use rustc_span::source_map::Spanned;
use rustc_span::symbol::{kw, sym, Ident, Symbol};
use rustc_span::ErrorGuaranteed;
use rustc_span::{def_id::LocalDefId, BytePos, Span, DUMMY_SP};
use rustc_target::asm::InlineAsmRegOrRegClass;
use rustc_target::spec::abi::Abi;

use smallvec::SmallVec;
use std::fmt;

#[derive(Debug, Copy, Clone, HashStable_Generic)]
pub struct Lifetime {
    pub hir_id: HirId,

    /// Either "`'a`", referring to a named lifetime definition,
    /// `'_` referring to an anonymous lifetime (either explicitly `'_` or `&type`),
    /// or "``" (i.e., `kw::Empty`) when appearing in path.
    ///
    /// See `Lifetime::suggestion_position` for practical use.
    pub ident: Ident,

    /// Semantics of this lifetime.
    pub res: LifetimeName,
}

#[derive(Debug, Copy, Clone, HashStable_Generic)]
pub enum ParamName {
    /// Some user-given name like `T` or `'x`.
    Plain(Ident),

    /// Synthetic name generated when user elided a lifetime in an impl header.
    ///
    /// E.g., the lifetimes in cases like these:
    /// ```ignore (fragment)
    /// impl Foo for &u32
    /// impl Foo<'_> for u32
    /// ```
    /// in that case, we rewrite to
    /// ```ignore (fragment)
    /// impl<'f> Foo for &'f u32
    /// impl<'f> Foo<'f> for u32
    /// ```
    /// where `'f` is something like `Fresh(0)`. The indices are
    /// unique per impl, but not necessarily continuous.
    Fresh,

    /// Indicates an illegal name was given and an error has been
    /// reported (so we should squelch other derived errors). Occurs
    /// when, e.g., `'_` is used in the wrong place.
    Error,
}

impl ParamName {
    pub fn ident(&self) -> Ident {
        match *self {
            ParamName::Plain(ident) => ident,
            ParamName::Fresh | ParamName::Error => Ident::with_dummy_span(kw::UnderscoreLifetime),
        }
    }

    pub fn normalize_to_macros_2_0(&self) -> ParamName {
        match *self {
            ParamName::Plain(ident) => ParamName::Plain(ident.normalize_to_macros_2_0()),
            param_name => param_name,
        }
    }
}

#[derive(Debug, Copy, Clone, PartialEq, Eq, HashStable_Generic)]
pub enum LifetimeName {
    /// User-given names or fresh (synthetic) names.
    Param(LocalDefId),

    /// Implicit lifetime in a context like `dyn Foo`. This is
    /// distinguished from implicit lifetimes elsewhere because the
    /// lifetime that they default to must appear elsewhere within the
    /// enclosing type. This means that, in an `impl Trait` context, we
    /// don't have to create a parameter for them. That is, `impl
    /// Trait<Item = &u32>` expands to an opaque type like `type
    /// Foo<'a> = impl Trait<Item = &'a u32>`, but `impl Trait<item =
    /// dyn Bar>` expands to `type Foo = impl Trait<Item = dyn Bar +
    /// 'static>`. The latter uses `ImplicitObjectLifetimeDefault` so
    /// that surrounding code knows not to create a lifetime
    /// parameter.
    ImplicitObjectLifetimeDefault,

    /// Indicates an error during lowering (usually `'_` in wrong place)
    /// that was already reported.
    Error,

    /// User wrote an anonymous lifetime, either `'_` or nothing.
    /// The semantics of this lifetime should be inferred by typechecking code.
    Infer,

    /// User wrote `'static`.
    Static,
}

impl LifetimeName {
    pub fn is_elided(&self) -> bool {
        match self {
            LifetimeName::ImplicitObjectLifetimeDefault | LifetimeName::Infer => true,

            // It might seem surprising that `Fresh` counts as not *elided*
            // -- but this is because, as far as the code in the compiler is
            // concerned -- `Fresh` variants act equivalently to "some fresh name".
            // They correspond to early-bound regions on an impl, in other words.
            LifetimeName::Error | LifetimeName::Param(..) | LifetimeName::Static => false,
        }
    }
}

impl fmt::Display for Lifetime {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        if self.ident.name != kw::Empty { self.ident.name.fmt(f) } else { "'_".fmt(f) }
    }
}

pub enum LifetimeSuggestionPosition {
    /// The user wrote `'a` or `'_`.
    Normal,
    /// The user wrote `&type` or `&mut type`.
    Ampersand,
    /// The user wrote `Path` and omitted the `<'_>`.
    ElidedPath,
    /// The user wrote `Path<T>`, and omitted the `'_,`.
    ElidedPathArgument,
    /// The user wrote `dyn Trait` and omitted the `+ '_`.
    ObjectDefault,
}

impl Lifetime {
    pub fn is_elided(&self) -> bool {
        self.res.is_elided()
    }

    pub fn is_anonymous(&self) -> bool {
        self.ident.name == kw::Empty || self.ident.name == kw::UnderscoreLifetime
    }

    pub fn suggestion_position(&self) -> (LifetimeSuggestionPosition, Span) {
        if self.ident.name == kw::Empty {
            if self.ident.span.is_empty() {
                (LifetimeSuggestionPosition::ElidedPathArgument, self.ident.span)
            } else {
                (LifetimeSuggestionPosition::ElidedPath, self.ident.span.shrink_to_hi())
            }
        } else if self.res == LifetimeName::ImplicitObjectLifetimeDefault {
            (LifetimeSuggestionPosition::ObjectDefault, self.ident.span)
        } else if self.ident.span.is_empty() {
            (LifetimeSuggestionPosition::Ampersand, self.ident.span)
        } else {
            (LifetimeSuggestionPosition::Normal, self.ident.span)
        }
    }

    pub fn is_static(&self) -> bool {
        self.res == LifetimeName::Static
    }
}

/// A `Path` is essentially Rust's notion of a name; for instance,
/// `std::cmp::PartialEq`. It's represented as a sequence of identifiers,
/// along with a bunch of supporting information.
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct Path<'hir, R = Res> {
    pub span: Span,
    /// The resolution for the path.
    pub res: R,
    /// The segments in the path: the things separated by `::`.
    pub segments: &'hir [PathSegment<'hir>],
}

/// Up to three resolutions for type, value and macro namespaces.
pub type UsePath<'hir> = Path<'hir, SmallVec<[Res; 3]>>;

impl Path<'_> {
    pub fn is_global(&self) -> bool {
        !self.segments.is_empty() && self.segments[0].ident.name == kw::PathRoot
    }
}

/// A segment of a path: an identifier, an optional lifetime, and a set of
/// types.
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct PathSegment<'hir> {
    /// The identifier portion of this path segment.
    pub ident: Ident,
    pub hir_id: HirId,
    pub res: Res,

    /// Type/lifetime parameters attached to this path. They come in
    /// two flavors: `Path<A,B,C>` and `Path(A,B) -> C`. Note that
    /// this is more than just simple syntactic sugar; the use of
    /// parens affects the region binding rules, so we preserve the
    /// distinction.
    pub args: Option<&'hir GenericArgs<'hir>>,

    /// Whether to infer remaining type parameters, if any.
    /// This only applies to expression and pattern paths, and
    /// out of those only the segments with no type parameters
    /// to begin with, e.g., `Vec::new` is `<Vec<..>>::new::<..>`.
    pub infer_args: bool,
}

impl<'hir> PathSegment<'hir> {
    /// Converts an identifier to the corresponding segment.
    pub fn new(ident: Ident, hir_id: HirId, res: Res) -> PathSegment<'hir> {
        PathSegment { ident, hir_id, res, infer_args: true, args: None }
    }

    pub fn invalid() -> Self {
        Self::new(Ident::empty(), HirId::INVALID, Res::Err)
    }

    pub fn args(&self) -> &GenericArgs<'hir> {
        if let Some(ref args) = self.args {
            args
        } else {
            const DUMMY: &GenericArgs<'_> = &GenericArgs::none();
            DUMMY
        }
    }
}

#[derive(Clone, Copy, Debug, HashStable_Generic)]
pub struct ConstArg {
    pub value: AnonConst,
    pub span: Span,
    /// Indicates whether this comes from a `~const` desugaring.
    pub is_desugared_from_effects: bool,
}

#[derive(Clone, Copy, Debug, HashStable_Generic)]
pub struct InferArg {
    pub hir_id: HirId,
    pub span: Span,
}

impl InferArg {
    pub fn to_ty(&self) -> Ty<'_> {
        Ty { kind: TyKind::Infer, span: self.span, hir_id: self.hir_id }
    }
}

#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub enum GenericArg<'hir> {
    Lifetime(&'hir Lifetime),
    Type(&'hir Ty<'hir>),
    Const(ConstArg),
    Infer(InferArg),
}

impl GenericArg<'_> {
    pub fn span(&self) -> Span {
        match self {
            GenericArg::Lifetime(l) => l.ident.span,
            GenericArg::Type(t) => t.span,
            GenericArg::Const(c) => c.span,
            GenericArg::Infer(i) => i.span,
        }
    }

    pub fn hir_id(&self) -> HirId {
        match self {
            GenericArg::Lifetime(l) => l.hir_id,
            GenericArg::Type(t) => t.hir_id,
            GenericArg::Const(c) => c.value.hir_id,
            GenericArg::Infer(i) => i.hir_id,
        }
    }

    pub fn is_synthetic(&self) -> bool {
        matches!(self, GenericArg::Lifetime(lifetime) if lifetime.ident == Ident::empty())
    }

    pub fn descr(&self) -> &'static str {
        match self {
            GenericArg::Lifetime(_) => "lifetime",
            GenericArg::Type(_) => "type",
            GenericArg::Const(_) => "constant",
            GenericArg::Infer(_) => "inferred",
        }
    }

    pub fn to_ord(&self) -> ast::ParamKindOrd {
        match self {
            GenericArg::Lifetime(_) => ast::ParamKindOrd::Lifetime,
            GenericArg::Type(_) | GenericArg::Const(_) | GenericArg::Infer(_) => {
                ast::ParamKindOrd::TypeOrConst
            }
        }
    }

    pub fn is_ty_or_const(&self) -> bool {
        match self {
            GenericArg::Lifetime(_) => false,
            GenericArg::Type(_) | GenericArg::Const(_) | GenericArg::Infer(_) => true,
        }
    }
}

#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct GenericArgs<'hir> {
    /// The generic arguments for this path segment.
    pub args: &'hir [GenericArg<'hir>],
    /// Bindings (equality constraints) on associated types, if present.
    /// E.g., `Foo<A = Bar>`.
    pub bindings: &'hir [TypeBinding<'hir>],
    /// Were arguments written in parenthesized form `Fn(T) -> U`?
    /// This is required mostly for pretty-printing and diagnostics,
    /// but also for changing lifetime elision rules to be "function-like".
    pub parenthesized: GenericArgsParentheses,
    /// The span encompassing arguments and the surrounding brackets `<>` or `()`
    ///       Foo<A, B, AssocTy = D>           Fn(T, U, V) -> W
    ///          ^^^^^^^^^^^^^^^^^^^             ^^^^^^^^^
    /// Note that this may be:
    /// - empty, if there are no generic brackets (but there may be hidden lifetimes)
    /// - dummy, if this was generated while desugaring
    pub span_ext: Span,
}

impl<'hir> GenericArgs<'hir> {
    pub const fn none() -> Self {
        Self {
            args: &[],
            bindings: &[],
            parenthesized: GenericArgsParentheses::No,
            span_ext: DUMMY_SP,
        }
    }

    pub fn inputs(&self) -> &[Ty<'hir>] {
        if self.parenthesized == GenericArgsParentheses::ParenSugar {
            for arg in self.args {
                match arg {
                    GenericArg::Lifetime(_) => {}
                    GenericArg::Type(ref ty) => {
                        if let TyKind::Tup(ref tys) = ty.kind {
                            return tys;
                        }
                        break;
                    }
                    GenericArg::Const(_) => {}
                    GenericArg::Infer(_) => {}
                }
            }
        }
        panic!("GenericArgs::inputs: not a `Fn(T) -> U`");
    }

    #[inline]
    pub fn has_type_params(&self) -> bool {
        self.args.iter().any(|arg| matches!(arg, GenericArg::Type(_)))
    }

    pub fn has_err(&self) -> bool {
        self.args.iter().any(|arg| match arg {
            GenericArg::Type(ty) => matches!(ty.kind, TyKind::Err(_)),
            _ => false,
        }) || self.bindings.iter().any(|arg| match arg.kind {
            TypeBindingKind::Equality { term: Term::Ty(ty) } => matches!(ty.kind, TyKind::Err(_)),
            _ => false,
        })
    }

    #[inline]
    pub fn num_type_params(&self) -> usize {
        self.args.iter().filter(|arg| matches!(arg, GenericArg::Type(_))).count()
    }

    #[inline]
    pub fn num_lifetime_params(&self) -> usize {
        self.args.iter().filter(|arg| matches!(arg, GenericArg::Lifetime(_))).count()
    }

    #[inline]
    pub fn has_lifetime_params(&self) -> bool {
        self.args.iter().any(|arg| matches!(arg, GenericArg::Lifetime(_)))
    }

    #[inline]
    /// This function returns the number of type and const generic params.
    /// It should only be used for diagnostics.
    pub fn num_generic_params(&self) -> usize {
        self.args
            .iter()
            .filter(|arg| match arg {
                GenericArg::Lifetime(_)
                | GenericArg::Const(ConstArg { is_desugared_from_effects: true, .. }) => false,
                _ => true,
            })
            .count()
    }

    /// The span encompassing the text inside the surrounding brackets.
    /// It will also include bindings if they aren't in the form `-> Ret`
    /// Returns `None` if the span is empty (e.g. no brackets) or dummy
    pub fn span(&self) -> Option<Span> {
        let span_ext = self.span_ext()?;
        Some(span_ext.with_lo(span_ext.lo() + BytePos(1)).with_hi(span_ext.hi() - BytePos(1)))
    }

    /// Returns span encompassing arguments and their surrounding `<>` or `()`
    pub fn span_ext(&self) -> Option<Span> {
        Some(self.span_ext).filter(|span| !span.is_empty())
    }

    pub fn is_empty(&self) -> bool {
        self.args.is_empty()
    }
}

#[derive(Copy, Clone, PartialEq, Eq, Debug, HashStable_Generic)]
pub enum GenericArgsParentheses {
    No,
    /// Bounds for `feature(return_type_notation)`, like `T: Trait<method(..): Send>`,
    /// where the args are explicitly elided with `..`
    ReturnTypeNotation,
    /// parenthesized function-family traits, like `T: Fn(u32) -> i32`
    ParenSugar,
}

/// A modifier on a bound, currently this is only used for `?Sized`, where the
/// modifier is `Maybe`. Negative bounds should also be handled here.
#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, HashStable_Generic)]
pub enum TraitBoundModifier {
    None,
    Negative,
    Maybe,
    MaybeConst,
}

/// The AST represents all type param bounds as types.
/// `typeck::collect::compute_bounds` matches these against
/// the "special" built-in traits (see `middle::lang_items`) and
/// detects `Copy`, `Send` and `Sync`.
#[derive(Clone, Copy, Debug, HashStable_Generic)]
pub enum GenericBound<'hir> {
    Trait(PolyTraitRef<'hir>, TraitBoundModifier),
    // FIXME(davidtwco): Introduce `PolyTraitRef::LangItem`
    LangItemTrait(LangItem, Span, HirId, &'hir GenericArgs<'hir>),
    Outlives(&'hir Lifetime),
}

impl GenericBound<'_> {
    pub fn trait_ref(&self) -> Option<&TraitRef<'_>> {
        match self {
            GenericBound::Trait(data, _) => Some(&data.trait_ref),
            _ => None,
        }
    }

    pub fn span(&self) -> Span {
        match self {
            GenericBound::Trait(t, ..) => t.span,
            GenericBound::LangItemTrait(_, span, ..) => *span,
            GenericBound::Outlives(l) => l.ident.span,
        }
    }
}

pub type GenericBounds<'hir> = &'hir [GenericBound<'hir>];

#[derive(Copy, Clone, Debug, HashStable_Generic)]
pub enum LifetimeParamKind {
    // Indicates that the lifetime definition was explicitly declared (e.g., in
    // `fn foo<'a>(x: &'a u8) -> &'a u8 { x }`).
    Explicit,

    // Indication that the lifetime was elided (e.g., in both cases in
    // `fn foo(x: &u8) -> &'_ u8 { x }`).
    Elided,

    // Indication that the lifetime name was somehow in error.
    Error,
}

#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub enum GenericParamKind<'hir> {
    /// A lifetime definition (e.g., `'a: 'b + 'c + 'd`).
    Lifetime {
        kind: LifetimeParamKind,
    },
    Type {
        default: Option<&'hir Ty<'hir>>,
        synthetic: bool,
    },
    Const {
        ty: &'hir Ty<'hir>,
        /// Optional default value for the const generic param
        default: Option<AnonConst>,
    },
}

#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct GenericParam<'hir> {
    pub hir_id: HirId,
    pub def_id: LocalDefId,
    pub name: ParamName,
    pub span: Span,
    pub pure_wrt_drop: bool,
    pub kind: GenericParamKind<'hir>,
    pub colon_span: Option<Span>,
    pub source: GenericParamSource,
}

impl<'hir> GenericParam<'hir> {
    /// Synthetic type-parameters are inserted after normal ones.
    /// In order for normal parameters to be able to refer to synthetic ones,
    /// scans them first.
    pub fn is_impl_trait(&self) -> bool {
        matches!(self.kind, GenericParamKind::Type { synthetic: true, .. })
    }

    /// This can happen for `async fn`, e.g. `async fn f<'_>(&'_ self)`.
    ///
    /// See `lifetime_to_generic_param` in `rustc_ast_lowering` for more information.
    pub fn is_elided_lifetime(&self) -> bool {
        matches!(self.kind, GenericParamKind::Lifetime { kind: LifetimeParamKind::Elided })
    }
}

/// Records where the generic parameter originated from.
///
/// This can either be from an item's generics, in which case it's typically
/// early-bound (but can be a late-bound lifetime in functions, for example),
/// or from a `for<...>` binder, in which case it's late-bound (and notably,
/// does not show up in the parent item's generics).
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub enum GenericParamSource {
    // Early or late-bound parameters defined on an item
    Generics,
    // Late-bound parameters defined via a `for<...>`
    Binder,
}

#[derive(Default)]
pub struct GenericParamCount {
    pub lifetimes: usize,
    pub types: usize,
    pub consts: usize,
    pub infer: usize,
}

/// Represents lifetimes and type parameters attached to a declaration
/// of a function, enum, trait, etc.
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct Generics<'hir> {
    pub params: &'hir [GenericParam<'hir>],
    pub predicates: &'hir [WherePredicate<'hir>],
    pub has_where_clause_predicates: bool,
    pub where_clause_span: Span,
    pub span: Span,
}

impl<'hir> Generics<'hir> {
    pub const fn empty() -> &'hir Generics<'hir> {
        const NOPE: Generics<'_> = Generics {
            params: &[],
            predicates: &[],
            has_where_clause_predicates: false,
            where_clause_span: DUMMY_SP,
            span: DUMMY_SP,
        };
        &NOPE
    }

    pub fn get_named(&self, name: Symbol) -> Option<&GenericParam<'hir>> {
        self.params.iter().find(|&param| name == param.name.ident().name)
    }

    pub fn spans(&self) -> MultiSpan {
        if self.params.is_empty() {
            self.span.into()
        } else {
            self.params.iter().map(|p| p.span).collect::<Vec<Span>>().into()
        }
    }

    /// If there are generic parameters, return where to introduce a new one.
    pub fn span_for_lifetime_suggestion(&self) -> Option<Span> {
        if let Some(first) = self.params.first()
            && self.span.contains(first.span)
        {
            // `fn foo<A>(t: impl Trait)`
            //         ^ suggest `'a, ` here
            Some(first.span.shrink_to_lo())
        } else {
            None
        }
    }

    /// If there are generic parameters, return where to introduce a new one.
    pub fn span_for_param_suggestion(&self) -> Option<Span> {
        self.params.iter().any(|p| self.span.contains(p.span)).then(|| {
            // `fn foo<A>(t: impl Trait)`
            //          ^ suggest `, T: Trait` here
            self.span.with_lo(self.span.hi() - BytePos(1)).shrink_to_lo()
        })
    }

    /// `Span` where further predicates would be suggested, accounting for trailing commas, like
    ///  in `fn foo<T>(t: T) where T: Foo,` so we don't suggest two trailing commas.
    pub fn tail_span_for_predicate_suggestion(&self) -> Span {
        let end = self.where_clause_span.shrink_to_hi();
        if self.has_where_clause_predicates {
            self.predicates
                .iter()
                .rfind(|&p| p.in_where_clause())
                .map_or(end, |p| p.span())
                .shrink_to_hi()
                .to(end)
        } else {
            end
        }
    }

    pub fn add_where_or_trailing_comma(&self) -> &'static str {
        if self.has_where_clause_predicates {
            ","
        } else if self.where_clause_span.is_empty() {
            " where"
        } else {
            // No where clause predicates, but we have `where` token
            ""
        }
    }

    pub fn bounds_for_param(
        &self,
        param_def_id: LocalDefId,
    ) -> impl Iterator<Item = &WhereBoundPredicate<'hir>> {
        self.predicates.iter().filter_map(move |pred| match pred {
            WherePredicate::BoundPredicate(bp) if bp.is_param_bound(param_def_id.to_def_id()) => {
                Some(bp)
            }
            _ => None,
        })
    }

    pub fn outlives_for_param(
        &self,
        param_def_id: LocalDefId,
    ) -> impl Iterator<Item = &WhereRegionPredicate<'_>> {
        self.predicates.iter().filter_map(move |pred| match pred {
            WherePredicate::RegionPredicate(rp) if rp.is_param_bound(param_def_id) => Some(rp),
            _ => None,
        })
    }

    pub fn bounds_span_for_suggestions(&self, param_def_id: LocalDefId) -> Option<Span> {
        self.bounds_for_param(param_def_id).flat_map(|bp| bp.bounds.iter().rev()).find_map(
            |bound| {
                // We include bounds that come from a `#[derive(_)]` but point at the user's code,
                // as we use this method to get a span appropriate for suggestions.
                let bs = bound.span();
                bs.can_be_used_for_suggestions().then(|| bs.shrink_to_hi())
            },
        )
    }

    pub fn span_for_predicate_removal(&self, pos: usize) -> Span {
        let predicate = &self.predicates[pos];
        let span = predicate.span();

        if !predicate.in_where_clause() {
            // <T: ?Sized, U>
            //   ^^^^^^^^
            return span;
        }

        // We need to find out which comma to remove.
        if pos < self.predicates.len() - 1 {
            let next_pred = &self.predicates[pos + 1];
            if next_pred.in_where_clause() {
                // where T: ?Sized, Foo: Bar,
                //       ^^^^^^^^^^^
                return span.until(next_pred.span());
            }
        }

        if pos > 0 {
            let prev_pred = &self.predicates[pos - 1];
            if prev_pred.in_where_clause() {
                // where Foo: Bar, T: ?Sized,
                //               ^^^^^^^^^^^
                return prev_pred.span().shrink_to_hi().to(span);
            }
        }

        // This is the only predicate in the where clause.
        // where T: ?Sized
        // ^^^^^^^^^^^^^^^
        self.where_clause_span
    }

    pub fn span_for_bound_removal(&self, predicate_pos: usize, bound_pos: usize) -> Span {
        let predicate = &self.predicates[predicate_pos];
        let bounds = predicate.bounds();

        if bounds.len() == 1 {
            return self.span_for_predicate_removal(predicate_pos);
        }

        let span = bounds[bound_pos].span();
        if bound_pos == 0 {
            // where T: ?Sized + Bar, Foo: Bar,
            //          ^^^^^^^^^
            span.to(bounds[1].span().shrink_to_lo())
        } else {
            // where T: Bar + ?Sized, Foo: Bar,
            //             ^^^^^^^^^
            bounds[bound_pos - 1].span().shrink_to_hi().to(span)
        }
    }
}

/// A single predicate in a where-clause.
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub enum WherePredicate<'hir> {
    /// A type binding (e.g., `for<'c> Foo: Send + Clone + 'c`).
    BoundPredicate(WhereBoundPredicate<'hir>),
    /// A lifetime predicate (e.g., `'a: 'b + 'c`).
    RegionPredicate(WhereRegionPredicate<'hir>),
    /// An equality predicate (unsupported).
    EqPredicate(WhereEqPredicate<'hir>),
}

impl<'hir> WherePredicate<'hir> {
    pub fn span(&self) -> Span {
        match self {
            WherePredicate::BoundPredicate(p) => p.span,
            WherePredicate::RegionPredicate(p) => p.span,
            WherePredicate::EqPredicate(p) => p.span,
        }
    }

    pub fn in_where_clause(&self) -> bool {
        match self {
            WherePredicate::BoundPredicate(p) => p.origin == PredicateOrigin::WhereClause,
            WherePredicate::RegionPredicate(p) => p.in_where_clause,
            WherePredicate::EqPredicate(_) => false,
        }
    }

    pub fn bounds(&self) -> GenericBounds<'hir> {
        match self {
            WherePredicate::BoundPredicate(p) => p.bounds,
            WherePredicate::RegionPredicate(p) => p.bounds,
            WherePredicate::EqPredicate(_) => &[],
        }
    }
}

#[derive(Copy, Clone, Debug, HashStable_Generic, PartialEq, Eq)]
pub enum PredicateOrigin {
    WhereClause,
    GenericParam,
    ImplTrait,
}

/// A type bound (e.g., `for<'c> Foo: Send + Clone + 'c`).
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct WhereBoundPredicate<'hir> {
    pub hir_id: HirId,
    pub span: Span,
    /// Origin of the predicate.
    pub origin: PredicateOrigin,
    /// Any generics from a `for` binding.
    pub bound_generic_params: &'hir [GenericParam<'hir>],
    /// The type being bounded.
    pub bounded_ty: &'hir Ty<'hir>,
    /// Trait and lifetime bounds (e.g., `Clone + Send + 'static`).
    pub bounds: GenericBounds<'hir>,
}

impl<'hir> WhereBoundPredicate<'hir> {
    /// Returns `true` if `param_def_id` matches the `bounded_ty` of this predicate.
    pub fn is_param_bound(&self, param_def_id: DefId) -> bool {
        self.bounded_ty.as_generic_param().is_some_and(|(def_id, _)| def_id == param_def_id)
    }
}

/// A lifetime predicate (e.g., `'a: 'b + 'c`).
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct WhereRegionPredicate<'hir> {
    pub span: Span,
    pub in_where_clause: bool,
    pub lifetime: &'hir Lifetime,
    pub bounds: GenericBounds<'hir>,
}

impl<'hir> WhereRegionPredicate<'hir> {
    /// Returns `true` if `param_def_id` matches the `lifetime` of this predicate.
    pub fn is_param_bound(&self, param_def_id: LocalDefId) -> bool {
        self.lifetime.res == LifetimeName::Param(param_def_id)
    }
}

/// An equality predicate (e.g., `T = int`); currently unsupported.
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct WhereEqPredicate<'hir> {
    pub span: Span,
    pub lhs_ty: &'hir Ty<'hir>,
    pub rhs_ty: &'hir Ty<'hir>,
}

/// HIR node coupled with its parent's id in the same HIR owner.
///
/// The parent is trash when the node is a HIR owner.
#[derive(Clone, Copy, Debug)]
pub struct ParentedNode<'tcx> {
    pub parent: ItemLocalId,
    pub node: Node<'tcx>,
}

/// Attributes owned by a HIR owner.
#[derive(Debug)]
pub struct AttributeMap<'tcx> {
    pub map: SortedMap<ItemLocalId, &'tcx [Attribute]>,
    // Only present when the crate hash is needed.
    pub opt_hash: Option<Fingerprint>,
}

impl<'tcx> AttributeMap<'tcx> {
    pub const EMPTY: &'static AttributeMap<'static> =
        &AttributeMap { map: SortedMap::new(), opt_hash: Some(Fingerprint::ZERO) };

    #[inline]
    pub fn get(&self, id: ItemLocalId) -> &'tcx [Attribute] {
        self.map.get(&id).copied().unwrap_or(&[])
    }
}

/// Map of all HIR nodes inside the current owner.
/// These nodes are mapped by `ItemLocalId` alongside the index of their parent node.
/// The HIR tree, including bodies, is pre-hashed.
pub struct OwnerNodes<'tcx> {
    /// Pre-computed hash of the full HIR. Used in the crate hash. Only present
    /// when incr. comp. is enabled.
    pub opt_hash_including_bodies: Option<Fingerprint>,
    /// Full HIR for the current owner.
    // The zeroth node's parent should never be accessed: the owner's parent is computed by the
    // hir_owner_parent query. It is set to `ItemLocalId::INVALID` to force an ICE if accidentally
    // used.
    pub nodes: IndexVec<ItemLocalId, Option<ParentedNode<'tcx>>>,
    /// Content of local bodies.
    pub bodies: SortedMap<ItemLocalId, &'tcx Body<'tcx>>,
}

impl<'tcx> OwnerNodes<'tcx> {
    pub fn node(&self) -> OwnerNode<'tcx> {
        use rustc_index::Idx;
        let node = self.nodes[ItemLocalId::new(0)].as_ref().unwrap().node;
        let node = node.as_owner().unwrap(); // Indexing must ensure it is an OwnerNode.
        node
    }
}

impl fmt::Debug for OwnerNodes<'_> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("OwnerNodes")
            // Do not print all the pointers to all the nodes, as it would be unreadable.
            .field("node", &self.nodes[ItemLocalId::from_u32(0)])
            .field(
                "parents",
                &self
                    .nodes
                    .iter_enumerated()
                    .map(|(id, parented_node)| {
                        let parented_node = parented_node.as_ref().map(|node| node.parent);

                        debug_fn(move |f| write!(f, "({id:?}, {parented_node:?})"))
                    })
                    .collect::<Vec<_>>(),
            )
            .field("bodies", &self.bodies)
            .field("opt_hash_including_bodies", &self.opt_hash_including_bodies)
            .finish()
    }
}

/// Full information resulting from lowering an AST node.
#[derive(Debug, HashStable_Generic)]
pub struct OwnerInfo<'hir> {
    /// Contents of the HIR.
    pub nodes: OwnerNodes<'hir>,
    /// Map from each nested owner to its parent's local id.
    pub parenting: FxHashMap<LocalDefId, ItemLocalId>,
    /// Collected attributes of the HIR nodes.
    pub attrs: AttributeMap<'hir>,
    /// Map indicating what traits are in scope for places where this
    /// is relevant; generated by resolve.
    pub trait_map: FxHashMap<ItemLocalId, Box<[TraitCandidate]>>,
}

impl<'tcx> OwnerInfo<'tcx> {
    #[inline]
    pub fn node(&self) -> OwnerNode<'tcx> {
        self.nodes.node()
    }
}

#[derive(Copy, Clone, Debug, HashStable_Generic)]
pub enum MaybeOwner<T> {
    Owner(T),
    NonOwner(HirId),
    /// Used as a placeholder for unused LocalDefId.
    Phantom,
}

impl<T> MaybeOwner<T> {
    pub fn as_owner(self) -> Option<T> {
        match self {
            MaybeOwner::Owner(i) => Some(i),
            MaybeOwner::NonOwner(_) | MaybeOwner::Phantom => None,
        }
    }

    pub fn map<U>(self, f: impl FnOnce(T) -> U) -> MaybeOwner<U> {
        match self {
            MaybeOwner::Owner(i) => MaybeOwner::Owner(f(i)),
            MaybeOwner::NonOwner(hir_id) => MaybeOwner::NonOwner(hir_id),
            MaybeOwner::Phantom => MaybeOwner::Phantom,
        }
    }

    pub fn unwrap(self) -> T {
        match self {
            MaybeOwner::Owner(i) => i,
            MaybeOwner::NonOwner(_) | MaybeOwner::Phantom => panic!("Not a HIR owner"),
        }
    }
}

/// The top-level data structure that stores the entire contents of
/// the crate currently being compiled.
///
/// For more details, see the [rustc dev guide].
///
/// [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/hir.html
#[derive(Debug)]
pub struct Crate<'hir> {
    pub owners: IndexVec<LocalDefId, MaybeOwner<&'hir OwnerInfo<'hir>>>,
    // Only present when incr. comp. is enabled.
    pub opt_hir_hash: Option<Fingerprint>,
}

#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct Closure<'hir> {
    pub def_id: LocalDefId,
    pub binder: ClosureBinder,
    pub constness: Constness,
    pub capture_clause: CaptureBy,
    pub bound_generic_params: &'hir [GenericParam<'hir>],
    pub fn_decl: &'hir FnDecl<'hir>,
    pub body: BodyId,
    /// The span of the declaration block: 'move |...| -> ...'
    pub fn_decl_span: Span,
    /// The span of the argument block `|...|`
    pub fn_arg_span: Option<Span>,
    pub movability: Option<Movability>,
}

/// A block of statements `{ .. }`, which may have a label (in this case the
/// `targeted_by_break` field will be `true`) and may be `unsafe` by means of
/// the `rules` being anything but `DefaultBlock`.
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct Block<'hir> {
    /// Statements in a block.
    pub stmts: &'hir [Stmt<'hir>],
    /// An expression at the end of the block
    /// without a semicolon, if any.
    pub expr: Option<&'hir Expr<'hir>>,
    #[stable_hasher(ignore)]
    pub hir_id: HirId,
    /// Distinguishes between `unsafe { ... }` and `{ ... }`.
    pub rules: BlockCheckMode,
    pub span: Span,
    /// If true, then there may exist `break 'a` values that aim to
    /// break out of this block early.
    /// Used by `'label: {}` blocks and by `try {}` blocks.
    pub targeted_by_break: bool,
}

impl<'hir> Block<'hir> {
    pub fn innermost_block(&self) -> &Block<'hir> {
        let mut block = self;
        while let Some(Expr { kind: ExprKind::Block(inner_block, _), .. }) = block.expr {
            block = inner_block;
        }
        block
    }
}

#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct Pat<'hir> {
    #[stable_hasher(ignore)]
    pub hir_id: HirId,
    pub kind: PatKind<'hir>,
    pub span: Span,
    /// Whether to use default binding modes.
    /// At present, this is false only for destructuring assignment.
    pub default_binding_modes: bool,
}

impl<'hir> Pat<'hir> {
    fn walk_short_(&self, it: &mut impl FnMut(&Pat<'hir>) -> bool) -> bool {
        if !it(self) {
            return false;
        }

        use PatKind::*;
        match self.kind {
            Wild | Lit(_) | Range(..) | Binding(.., None) | Path(_) => true,
            Box(s) | Ref(s, _) | Binding(.., Some(s)) => s.walk_short_(it),
            Struct(_, fields, _) => fields.iter().all(|field| field.pat.walk_short_(it)),
            TupleStruct(_, s, _) | Tuple(s, _) | Or(s) => s.iter().all(|p| p.walk_short_(it)),
            Slice(before, slice, after) => {
                before.iter().chain(slice).chain(after.iter()).all(|p| p.walk_short_(it))
            }
        }
    }

    /// Walk the pattern in left-to-right order,
    /// short circuiting (with `.all(..)`) if `false` is returned.
    ///
    /// Note that when visiting e.g. `Tuple(ps)`,
    /// if visiting `ps[0]` returns `false`,
    /// then `ps[1]` will not be visited.
    pub fn walk_short(&self, mut it: impl FnMut(&Pat<'hir>) -> bool) -> bool {
        self.walk_short_(&mut it)
    }

    fn walk_(&self, it: &mut impl FnMut(&Pat<'hir>) -> bool) {
        if !it(self) {
            return;
        }

        use PatKind::*;
        match self.kind {
            Wild | Lit(_) | Range(..) | Binding(.., None) | Path(_) => {}
            Box(s) | Ref(s, _) | Binding(.., Some(s)) => s.walk_(it),
            Struct(_, fields, _) => fields.iter().for_each(|field| field.pat.walk_(it)),
            TupleStruct(_, s, _) | Tuple(s, _) | Or(s) => s.iter().for_each(|p| p.walk_(it)),
            Slice(before, slice, after) => {
                before.iter().chain(slice).chain(after.iter()).for_each(|p| p.walk_(it))
            }
        }
    }

    /// Walk the pattern in left-to-right order.
    ///
    /// If `it(pat)` returns `false`, the children are not visited.
    pub fn walk(&self, mut it: impl FnMut(&Pat<'hir>) -> bool) {
        self.walk_(&mut it)
    }

    /// Walk the pattern in left-to-right order.
    ///
    /// If you always want to recurse, prefer this method over `walk`.
    pub fn walk_always(&self, mut it: impl FnMut(&Pat<'_>)) {
        self.walk(|p| {
            it(p);
            true
        })
    }
}

/// A single field in a struct pattern.
///
/// Patterns like the fields of Foo `{ x, ref y, ref mut z }`
/// are treated the same as` x: x, y: ref y, z: ref mut z`,
/// except `is_shorthand` is true.
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct PatField<'hir> {
    #[stable_hasher(ignore)]
    pub hir_id: HirId,
    /// The identifier for the field.
    pub ident: Ident,
    /// The pattern the field is destructured to.
    pub pat: &'hir Pat<'hir>,
    pub is_shorthand: bool,
    pub span: Span,
}

#[derive(Copy, Clone, PartialEq, Debug, HashStable_Generic)]
pub enum RangeEnd {
    Included,
    Excluded,
}

impl fmt::Display for RangeEnd {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str(match self {
            RangeEnd::Included => "..=",
            RangeEnd::Excluded => "..",
        })
    }
}

// Equivalent to `Option<usize>`. That type takes up 16 bytes on 64-bit, but
// this type only takes up 4 bytes, at the cost of being restricted to a
// maximum value of `u32::MAX - 1`. In practice, this is more than enough.
#[derive(Clone, Copy, PartialEq, Eq, Hash, HashStable_Generic)]
pub struct DotDotPos(u32);

impl DotDotPos {
    /// Panics if n >= u32::MAX.
    pub fn new(n: Option<usize>) -> Self {
        match n {
            Some(n) => {
                assert!(n < u32::MAX as usize);
                Self(n as u32)
            }
            None => Self(u32::MAX),
        }
    }

    pub fn as_opt_usize(&self) -> Option<usize> {
        if self.0 == u32::MAX { None } else { Some(self.0 as usize) }
    }
}

impl fmt::Debug for DotDotPos {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        self.as_opt_usize().fmt(f)
    }
}

#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub enum PatKind<'hir> {
    /// Represents a wildcard pattern (i.e., `_`).
    Wild,

    /// A fresh binding `ref mut binding @ OPT_SUBPATTERN`.
    /// The `HirId` is the canonical ID for the variable being bound,
    /// (e.g., in `Ok(x) | Err(x)`, both `x` use the same canonical ID),
    /// which is the pattern ID of the first `x`.
    Binding(BindingAnnotation, HirId, Ident, Option<&'hir Pat<'hir>>),

    /// A struct or struct variant pattern (e.g., `Variant {x, y, ..}`).
    /// The `bool` is `true` in the presence of a `..`.
    Struct(QPath<'hir>, &'hir [PatField<'hir>], bool),

    /// A tuple struct/variant pattern `Variant(x, y, .., z)`.
    /// If the `..` pattern fragment is present, then `DotDotPos` denotes its position.
    /// `0 <= position <= subpats.len()`
    TupleStruct(QPath<'hir>, &'hir [Pat<'hir>], DotDotPos),

    /// An or-pattern `A | B | C`.
    /// Invariant: `pats.len() >= 2`.
    Or(&'hir [Pat<'hir>]),

    /// A path pattern for a unit struct/variant or a (maybe-associated) constant.
    Path(QPath<'hir>),

    /// A tuple pattern (e.g., `(a, b)`).
    /// If the `..` pattern fragment is present, then `Option<usize>` denotes its position.
    /// `0 <= position <= subpats.len()`
    Tuple(&'hir [Pat<'hir>], DotDotPos),

    /// A `box` pattern.
    Box(&'hir Pat<'hir>),

    /// A reference pattern (e.g., `&mut (a, b)`).
    Ref(&'hir Pat<'hir>, Mutability),

    /// A literal.
    Lit(&'hir Expr<'hir>),

    /// A range pattern (e.g., `1..=2` or `1..2`).
    Range(Option<&'hir Expr<'hir>>, Option<&'hir Expr<'hir>>, RangeEnd),

    /// A slice pattern, `[before_0, ..., before_n, (slice, after_0, ..., after_n)?]`.
    ///
    /// Here, `slice` is lowered from the syntax `($binding_mode $ident @)? ..`.
    /// If `slice` exists, then `after` can be non-empty.
    ///
    /// The representation for e.g., `[a, b, .., c, d]` is:
    /// ```ignore (illustrative)
    /// PatKind::Slice([Binding(a), Binding(b)], Some(Wild), [Binding(c), Binding(d)])
    /// ```
    Slice(&'hir [Pat<'hir>], Option<&'hir Pat<'hir>>, &'hir [Pat<'hir>]),
}

#[derive(Copy, Clone, PartialEq, Debug, HashStable_Generic)]
pub enum BinOpKind {
    /// The `+` operator (addition).
    Add,
    /// The `-` operator (subtraction).
    Sub,
    /// The `*` operator (multiplication).
    Mul,
    /// The `/` operator (division).
    Div,
    /// The `%` operator (modulus).
    Rem,
    /// The `&&` operator (logical and).
    And,
    /// The `||` operator (logical or).
    Or,
    /// The `^` operator (bitwise xor).
    BitXor,
    /// The `&` operator (bitwise and).
    BitAnd,
    /// The `|` operator (bitwise or).
    BitOr,
    /// The `<<` operator (shift left).
    Shl,
    /// The `>>` operator (shift right).
    Shr,
    /// The `==` operator (equality).
    Eq,
    /// The `<` operator (less than).
    Lt,
    /// The `<=` operator (less than or equal to).
    Le,
    /// The `!=` operator (not equal to).
    Ne,
    /// The `>=` operator (greater than or equal to).
    Ge,
    /// The `>` operator (greater than).
    Gt,
}

impl BinOpKind {
    pub fn as_str(self) -> &'static str {
        match self {
            BinOpKind::Add => "+",
            BinOpKind::Sub => "-",
            BinOpKind::Mul => "*",
            BinOpKind::Div => "/",
            BinOpKind::Rem => "%",
            BinOpKind::And => "&&",
            BinOpKind::Or => "||",
            BinOpKind::BitXor => "^",
            BinOpKind::BitAnd => "&",
            BinOpKind::BitOr => "|",
            BinOpKind::Shl => "<<",
            BinOpKind::Shr => ">>",
            BinOpKind::Eq => "==",
            BinOpKind::Lt => "<",
            BinOpKind::Le => "<=",
            BinOpKind::Ne => "!=",
            BinOpKind::Ge => ">=",
            BinOpKind::Gt => ">",
        }
    }

    pub fn is_lazy(self) -> bool {
        matches!(self, BinOpKind::And | BinOpKind::Or)
    }

    pub fn is_shift(self) -> bool {
        matches!(self, BinOpKind::Shl | BinOpKind::Shr)
    }

    pub fn is_comparison(self) -> bool {
        match self {
            BinOpKind::Eq
            | BinOpKind::Lt
            | BinOpKind::Le
            | BinOpKind::Ne
            | BinOpKind::Gt
            | BinOpKind::Ge => true,
            BinOpKind::And
            | BinOpKind::Or
            | BinOpKind::Add
            | BinOpKind::Sub
            | BinOpKind::Mul
            | BinOpKind::Div
            | BinOpKind::Rem
            | BinOpKind::BitXor
            | BinOpKind::BitAnd
            | BinOpKind::BitOr
            | BinOpKind::Shl
            | BinOpKind::Shr => false,
        }
    }

    /// Returns `true` if the binary operator takes its arguments by value.
    pub fn is_by_value(self) -> bool {
        !self.is_comparison()
    }
}

impl Into<ast::BinOpKind> for BinOpKind {
    fn into(self) -> ast::BinOpKind {
        match self {
            BinOpKind::Add => ast::BinOpKind::Add,
            BinOpKind::Sub => ast::BinOpKind::Sub,
            BinOpKind::Mul => ast::BinOpKind::Mul,
            BinOpKind::Div => ast::BinOpKind::Div,
            BinOpKind::Rem => ast::BinOpKind::Rem,
            BinOpKind::And => ast::BinOpKind::And,
            BinOpKind::Or => ast::BinOpKind::Or,
            BinOpKind::BitXor => ast::BinOpKind::BitXor,
            BinOpKind::BitAnd => ast::BinOpKind::BitAnd,
            BinOpKind::BitOr => ast::BinOpKind::BitOr,
            BinOpKind::Shl => ast::BinOpKind::Shl,
            BinOpKind::Shr => ast::BinOpKind::Shr,
            BinOpKind::Eq => ast::BinOpKind::Eq,
            BinOpKind::Lt => ast::BinOpKind::Lt,
            BinOpKind::Le => ast::BinOpKind::Le,
            BinOpKind::Ne => ast::BinOpKind::Ne,
            BinOpKind::Ge => ast::BinOpKind::Ge,
            BinOpKind::Gt => ast::BinOpKind::Gt,
        }
    }
}

pub type BinOp = Spanned<BinOpKind>;

#[derive(Copy, Clone, PartialEq, Debug, HashStable_Generic)]
pub enum UnOp {
    /// The `*` operator (dereferencing).
    Deref,
    /// The `!` operator (logical negation).
    Not,
    /// The `-` operator (negation).
    Neg,
}

impl UnOp {
    pub fn as_str(self) -> &'static str {
        match self {
            Self::Deref => "*",
            Self::Not => "!",
            Self::Neg => "-",
        }
    }

    /// Returns `true` if the unary operator takes its argument by value.
    pub fn is_by_value(self) -> bool {
        matches!(self, Self::Neg | Self::Not)
    }
}

/// A statement.
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct Stmt<'hir> {
    pub hir_id: HirId,
    pub kind: StmtKind<'hir>,
    pub span: Span,
}

/// The contents of a statement.
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub enum StmtKind<'hir> {
    /// A local (`let`) binding.
    Local(&'hir Local<'hir>),

    /// An item binding.
    Item(ItemId),

    /// An expression without a trailing semi-colon (must have unit type).
    Expr(&'hir Expr<'hir>),

    /// An expression with a trailing semi-colon (may have any type).
    Semi(&'hir Expr<'hir>),
}

/// Represents a `let` statement (i.e., `let <pat>:<ty> = <init>;`).
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct Local<'hir> {
    pub pat: &'hir Pat<'hir>,
    /// Type annotation, if any (otherwise the type will be inferred).
    pub ty: Option<&'hir Ty<'hir>>,
    /// Initializer expression to set the value, if any.
    pub init: Option<&'hir Expr<'hir>>,
    /// Else block for a `let...else` binding.
    pub els: Option<&'hir Block<'hir>>,
    pub hir_id: HirId,
    pub span: Span,
    /// Can be `ForLoopDesugar` if the `let` statement is part of a `for` loop
    /// desugaring. Otherwise will be `Normal`.
    pub source: LocalSource,
}

/// Represents a single arm of a `match` expression, e.g.
/// `<pat> (if <guard>) => <body>`.
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct Arm<'hir> {
    #[stable_hasher(ignore)]
    pub hir_id: HirId,
    pub span: Span,
    /// If this pattern and the optional guard matches, then `body` is evaluated.
    pub pat: &'hir Pat<'hir>,
    /// Optional guard clause.
    pub guard: Option<Guard<'hir>>,
    /// The expression the arm evaluates to if this arm matches.
    pub body: &'hir Expr<'hir>,
}

/// Represents a `let <pat>[: <ty>] = <expr>` expression (not a Local), occurring in an `if-let` or
/// `let-else`, evaluating to a boolean. Typically the pattern is refutable.
///
/// In an if-let, imagine it as `if (let <pat> = <expr>) { ... }`; in a let-else, it is part of the
/// desugaring to if-let. Only let-else supports the type annotation at present.
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct Let<'hir> {
    pub hir_id: HirId,
    pub span: Span,
    pub pat: &'hir Pat<'hir>,
    pub ty: Option<&'hir Ty<'hir>>,
    pub init: &'hir Expr<'hir>,
    /// `Some` when this let expressions is not in a syntanctically valid location.
    /// Used to prevent building MIR in such situations.
    pub is_recovered: Option<ErrorGuaranteed>,
}

#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub enum Guard<'hir> {
    If(&'hir Expr<'hir>),
    IfLet(&'hir Let<'hir>),
}

impl<'hir> Guard<'hir> {
    /// Returns the body of the guard
    ///
    /// In other words, returns the e in either of the following:
    ///
    /// - `if e`
    /// - `if let x = e`
    pub fn body(&self) -> &'hir Expr<'hir> {
        match self {
            Guard::If(e) | Guard::IfLet(Let { init: e, .. }) => e,
        }
    }
}

#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct ExprField<'hir> {
    #[stable_hasher(ignore)]
    pub hir_id: HirId,
    pub ident: Ident,
    pub expr: &'hir Expr<'hir>,
    pub span: Span,
    pub is_shorthand: bool,
}

#[derive(Copy, Clone, PartialEq, Debug, HashStable_Generic)]
pub enum BlockCheckMode {
    DefaultBlock,
    UnsafeBlock(UnsafeSource),
}

#[derive(Copy, Clone, PartialEq, Debug, HashStable_Generic)]
pub enum UnsafeSource {
    CompilerGenerated,
    UserProvided,
}

#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
pub struct BodyId {
    pub hir_id: HirId,
}

/// The body of a function, closure, or constant value. In the case of
/// a function, the body contains not only the function body itself
/// (which is an expression), but also the argument patterns, since
/// those are something that the caller doesn't really care about.
///
/// # Examples
///
/// ```
/// fn foo((x, y): (u32, u32)) -> u32 {
///     x + y
/// }
/// ```
///
/// Here, the `Body` associated with `foo()` would contain:
///
/// - an `params` array containing the `(x, y)` pattern
/// - a `value` containing the `x + y` expression (maybe wrapped in a block)
/// - `coroutine_kind` would be `None`
///
/// All bodies have an **owner**, which can be accessed via the HIR
/// map using `body_owner_def_id()`.
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct Body<'hir> {
    pub params: &'hir [Param<'hir>],
    pub value: &'hir Expr<'hir>,
    pub coroutine_kind: Option<CoroutineKind>,
}

impl<'hir> Body<'hir> {
    pub fn id(&self) -> BodyId {
        BodyId { hir_id: self.value.hir_id }
    }

    pub fn coroutine_kind(&self) -> Option<CoroutineKind> {
        self.coroutine_kind
    }
}

/// The type of source expression that caused this coroutine to be created.
#[derive(Clone, PartialEq, Eq, Debug, Copy, Hash)]
#[derive(HashStable_Generic, Encodable, Decodable)]
pub enum CoroutineKind {
    /// An explicit `async` block or the body of an async function.
    Async(CoroutineSource),

    /// An explicit `gen` block or the body of a `gen` function.
    Gen(CoroutineSource),

    /// A coroutine literal created via a `yield` inside a closure.
    Coroutine,
}

impl fmt::Display for CoroutineKind {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            CoroutineKind::Async(k) => {
                if f.alternate() {
                    f.write_str("`async` ")?;
                } else {
                    f.write_str("async ")?
                }
                k.fmt(f)
            }
            CoroutineKind::Coroutine => f.write_str("coroutine"),
            CoroutineKind::Gen(k) => {
                if f.alternate() {
                    f.write_str("`gen` ")?;
                } else {
                    f.write_str("gen ")?
                }
                k.fmt(f)
            }
        }
    }
}

/// In the case of a coroutine created as part of an async/gen construct,
/// which kind of async/gen construct caused it to be created?
///
/// This helps error messages but is also used to drive coercions in
/// type-checking (see #60424).
#[derive(Clone, PartialEq, Eq, Hash, Debug, Copy)]
#[derive(HashStable_Generic, Encodable, Decodable)]
pub enum CoroutineSource {
    /// An explicit `async`/`gen` block written by the user.
    Block,

    /// An explicit `async`/`gen` closure written by the user.
    Closure,

    /// The `async`/`gen` block generated as the body of an async/gen function.
    Fn,
}

impl fmt::Display for CoroutineSource {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            CoroutineSource::Block => "block",
            CoroutineSource::Closure => "closure body",
            CoroutineSource::Fn => "fn body",
        }
        .fmt(f)
    }
}

#[derive(Copy, Clone, Debug)]
pub enum BodyOwnerKind {
    /// Functions and methods.
    Fn,

    /// Closures
    Closure,

    /// Constants and associated constants, also including inline constants.
    Const { inline: bool },

    /// Initializer of a `static` item.
    Static(Mutability),
}

impl BodyOwnerKind {
    pub fn is_fn_or_closure(self) -> bool {
        match self {
            BodyOwnerKind::Fn | BodyOwnerKind::Closure => true,
            BodyOwnerKind::Const { .. } | BodyOwnerKind::Static(_) => false,
        }
    }
}

/// The kind of an item that requires const-checking.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum ConstContext {
    /// A `const fn`.
    ConstFn,

    /// A `static` or `static mut`.
    Static(Mutability),

    /// A `const`, associated `const`, or other const context.
    ///
    /// Other contexts include:
    /// - Array length expressions
    /// - Enum discriminants
    /// - Const generics
    ///
    /// For the most part, other contexts are treated just like a regular `const`, so they are
    /// lumped into the same category.
    Const { inline: bool },
}

impl ConstContext {
    /// A description of this const context that can appear between backticks in an error message.
    ///
    /// E.g. `const` or `static mut`.
    pub fn keyword_name(self) -> &'static str {
        match self {
            Self::Const { .. } => "const",
            Self::Static(Mutability::Not) => "static",
            Self::Static(Mutability::Mut) => "static mut",
            Self::ConstFn => "const fn",
        }
    }
}

/// A colloquial, trivially pluralizable description of this const context for use in error
/// messages.
impl fmt::Display for ConstContext {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match *self {
            Self::Const { .. } => write!(f, "constant"),
            Self::Static(_) => write!(f, "static"),
            Self::ConstFn => write!(f, "constant function"),
        }
    }
}

// NOTE: `IntoDiagnosticArg` impl for `ConstContext` lives in `rustc_errors`
// due to a cyclical dependency between hir that crate.

/// A literal.
pub type Lit = Spanned<LitKind>;

#[derive(Copy, Clone, Debug, HashStable_Generic)]
pub enum ArrayLen {
    Infer(HirId, Span),
    Body(AnonConst),
}

impl ArrayLen {
    pub fn hir_id(&self) -> HirId {
        match self {
            &ArrayLen::Infer(hir_id, _) | &ArrayLen::Body(AnonConst { hir_id, .. }) => hir_id,
        }
    }
}

/// A constant (expression) that's not an item or associated item,
/// but needs its own `DefId` for type-checking, const-eval, etc.
/// These are usually found nested inside types (e.g., array lengths)
/// or expressions (e.g., repeat counts), and also used to define
/// explicit discriminant values for enum variants.
///
/// You can check if this anon const is a default in a const param
/// `const N: usize = { ... }` with `tcx.hir().opt_const_param_default_param_def_id(..)`
#[derive(Copy, Clone, Debug, HashStable_Generic)]
pub struct AnonConst {
    pub hir_id: HirId,
    pub def_id: LocalDefId,
    pub body: BodyId,
}

/// An inline constant expression `const { something }`.
#[derive(Copy, Clone, Debug, HashStable_Generic)]
pub struct ConstBlock {
    pub hir_id: HirId,
    pub def_id: LocalDefId,
    pub body: BodyId,
}

/// An expression.
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct Expr<'hir> {
    pub hir_id: HirId,
    pub kind: ExprKind<'hir>,
    pub span: Span,
}

impl Expr<'_> {
    pub fn precedence(&self) -> ExprPrecedence {
        match self.kind {
            ExprKind::ConstBlock(_) => ExprPrecedence::ConstBlock,
            ExprKind::Array(_) => ExprPrecedence::Array,
            ExprKind::Call(..) => ExprPrecedence::Call,
            ExprKind::MethodCall(..) => ExprPrecedence::MethodCall,
            ExprKind::Tup(_) => ExprPrecedence::Tup,
            ExprKind::Binary(op, ..) => ExprPrecedence::Binary(op.node.into()),
            ExprKind::Unary(..) => ExprPrecedence::Unary,
            ExprKind::Lit(_) => ExprPrecedence::Lit,
            ExprKind::Type(..) | ExprKind::Cast(..) => ExprPrecedence::Cast,
            ExprKind::DropTemps(ref expr, ..) => expr.precedence(),
            ExprKind::If(..) => ExprPrecedence::If,
            ExprKind::Let(..) => ExprPrecedence::Let,
            ExprKind::Loop(..) => ExprPrecedence::Loop,
            ExprKind::Match(..) => ExprPrecedence::Match,
            ExprKind::Closure { .. } => ExprPrecedence::Closure,
            ExprKind::Block(..) => ExprPrecedence::Block,
            ExprKind::Assign(..) => ExprPrecedence::Assign,
            ExprKind::AssignOp(..) => ExprPrecedence::AssignOp,
            ExprKind::Field(..) => ExprPrecedence::Field,
            ExprKind::Index(..) => ExprPrecedence::Index,
            ExprKind::Path(..) => ExprPrecedence::Path,
            ExprKind::AddrOf(..) => ExprPrecedence::AddrOf,
            ExprKind::Break(..) => ExprPrecedence::Break,
            ExprKind::Continue(..) => ExprPrecedence::Continue,
            ExprKind::Ret(..) => ExprPrecedence::Ret,
            ExprKind::Become(..) => ExprPrecedence::Become,
            ExprKind::InlineAsm(..) => ExprPrecedence::InlineAsm,
            ExprKind::OffsetOf(..) => ExprPrecedence::OffsetOf,
            ExprKind::Struct(..) => ExprPrecedence::Struct,
            ExprKind::Repeat(..) => ExprPrecedence::Repeat,
            ExprKind::Yield(..) => ExprPrecedence::Yield,
            ExprKind::Err(_) => ExprPrecedence::Err,
        }
    }

    /// Whether this looks like a place expr, without checking for deref
    /// adjustments.
    /// This will return `true` in some potentially surprising cases such as
    /// `CONSTANT.field`.
    pub fn is_syntactic_place_expr(&self) -> bool {
        self.is_place_expr(|_| true)
    }

    /// Whether this is a place expression.
    ///
    /// `allow_projections_from` should return `true` if indexing a field or index expression based
    /// on the given expression should be considered a place expression.
    pub fn is_place_expr(&self, mut allow_projections_from: impl FnMut(&Self) -> bool) -> bool {
        match self.kind {
            ExprKind::Path(QPath::Resolved(_, ref path)) => {
                matches!(path.res, Res::Local(..) | Res::Def(DefKind::Static(_), _) | Res::Err)
            }

            // Type ascription inherits its place expression kind from its
            // operand. See:
            // https://github.com/rust-lang/rfcs/blob/master/text/0803-type-ascription.md#type-ascription-and-temporaries
            ExprKind::Type(ref e, _) => e.is_place_expr(allow_projections_from),

            ExprKind::Unary(UnOp::Deref, _) => true,

            ExprKind::Field(ref base, _) | ExprKind::Index(ref base, _, _) => {
                allow_projections_from(base) || base.is_place_expr(allow_projections_from)
            }

            // Lang item paths cannot currently be local variables or statics.
            ExprKind::Path(QPath::LangItem(..)) => false,

            // Partially qualified paths in expressions can only legally
            // refer to associated items which are always rvalues.
            ExprKind::Path(QPath::TypeRelative(..))
            | ExprKind::Call(..)
            | ExprKind::MethodCall(..)
            | ExprKind::Struct(..)
            | ExprKind::Tup(..)
            | ExprKind::If(..)
            | ExprKind::Match(..)
            | ExprKind::Closure { .. }
            | ExprKind::Block(..)
            | ExprKind::Repeat(..)
            | ExprKind::Array(..)
            | ExprKind::Break(..)
            | ExprKind::Continue(..)
            | ExprKind::Ret(..)
            | ExprKind::Become(..)
            | ExprKind::Let(..)
            | ExprKind::Loop(..)
            | ExprKind::Assign(..)
            | ExprKind::InlineAsm(..)
            | ExprKind::OffsetOf(..)
            | ExprKind::AssignOp(..)
            | ExprKind::Lit(_)
            | ExprKind::ConstBlock(..)
            | ExprKind::Unary(..)
            | ExprKind::AddrOf(..)
            | ExprKind::Binary(..)
            | ExprKind::Yield(..)
            | ExprKind::Cast(..)
            | ExprKind::DropTemps(..)
            | ExprKind::Err(_) => false,
        }
    }

    /// If `Self.kind` is `ExprKind::DropTemps(expr)`, drill down until we get a non-`DropTemps`
    /// `Expr`. This is used in suggestions to ignore this `ExprKind` as it is semantically
    /// silent, only signaling the ownership system. By doing this, suggestions that check the
    /// `ExprKind` of any given `Expr` for presentation don't have to care about `DropTemps`
    /// beyond remembering to call this function before doing analysis on it.
    pub fn peel_drop_temps(&self) -> &Self {
        let mut expr = self;
        while let ExprKind::DropTemps(inner) = &expr.kind {
            expr = inner;
        }
        expr
    }

    pub fn peel_blocks(&self) -> &Self {
        let mut expr = self;
        while let ExprKind::Block(Block { expr: Some(inner), .. }, _) = &expr.kind {
            expr = inner;
        }
        expr
    }

    pub fn peel_borrows(&self) -> &Self {
        let mut expr = self;
        while let ExprKind::AddrOf(.., inner) = &expr.kind {
            expr = inner;
        }
        expr
    }

    pub fn can_have_side_effects(&self) -> bool {
        match self.peel_drop_temps().kind {
            ExprKind::Path(_) | ExprKind::Lit(_) | ExprKind::OffsetOf(..) => false,
            ExprKind::Type(base, _)
            | ExprKind::Unary(_, base)
            | ExprKind::Field(base, _)
            | ExprKind::Index(base, _, _)
            | ExprKind::AddrOf(.., base)
            | ExprKind::Cast(base, _) => {
                // This isn't exactly true for `Index` and all `Unary`, but we are using this
                // method exclusively for diagnostics and there's a *cultural* pressure against
                // them being used only for its side-effects.
                base.can_have_side_effects()
            }
            ExprKind::Struct(_, fields, init) => fields
                .iter()
                .map(|field| field.expr)
                .chain(init.into_iter())
                .any(|e| e.can_have_side_effects()),

            ExprKind::Array(args)
            | ExprKind::Tup(args)
            | ExprKind::Call(
                Expr {
                    kind:
                        ExprKind::Path(QPath::Resolved(
                            None,
                            Path { res: Res::Def(DefKind::Ctor(_, CtorKind::Fn), _), .. },
                        )),
                    ..
                },
                args,
            ) => args.iter().any(|arg| arg.can_have_side_effects()),
            ExprKind::If(..)
            | ExprKind::Match(..)
            | ExprKind::MethodCall(..)
            | ExprKind::Call(..)
            | ExprKind::Closure { .. }
            | ExprKind::Block(..)
            | ExprKind::Repeat(..)
            | ExprKind::Break(..)
            | ExprKind::Continue(..)
            | ExprKind::Ret(..)
            | ExprKind::Become(..)
            | ExprKind::Let(..)
            | ExprKind::Loop(..)
            | ExprKind::Assign(..)
            | ExprKind::InlineAsm(..)
            | ExprKind::AssignOp(..)
            | ExprKind::ConstBlock(..)
            | ExprKind::Binary(..)
            | ExprKind::Yield(..)
            | ExprKind::DropTemps(..)
            | ExprKind::Err(_) => true,
        }
    }

    /// To a first-order approximation, is this a pattern?
    pub fn is_approximately_pattern(&self) -> bool {
        match &self.kind {
            ExprKind::Array(_)
            | ExprKind::Call(..)
            | ExprKind::Tup(_)
            | ExprKind::Lit(_)
            | ExprKind::Path(_)
            | ExprKind::Struct(..) => true,
            _ => false,
        }
    }

    pub fn method_ident(&self) -> Option<Ident> {
        match self.kind {
            ExprKind::MethodCall(receiver_method, ..) => Some(receiver_method.ident),
            ExprKind::Unary(_, expr) | ExprKind::AddrOf(.., expr) => expr.method_ident(),
            _ => None,
        }
    }
}

/// Checks if the specified expression is a built-in range literal.
/// (See: `LoweringContext::lower_expr()`).
pub fn is_range_literal(expr: &Expr<'_>) -> bool {
    match expr.kind {
        // All built-in range literals but `..=` and `..` desugar to `Struct`s.
        ExprKind::Struct(ref qpath, _, _) => matches!(
            **qpath,
            QPath::LangItem(
                LangItem::Range
                    | LangItem::RangeTo
                    | LangItem::RangeFrom
                    | LangItem::RangeFull
                    | LangItem::RangeToInclusive,
                ..
            )
        ),

        // `..=` desugars into `::std::ops::RangeInclusive::new(...)`.
        ExprKind::Call(ref func, _) => {
            matches!(func.kind, ExprKind::Path(QPath::LangItem(LangItem::RangeInclusiveNew, ..)))
        }

        _ => false,
    }
}

#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub enum ExprKind<'hir> {
    /// Allow anonymous constants from an inline `const` block
    ConstBlock(ConstBlock),
    /// An array (e.g., `[a, b, c, d]`).
    Array(&'hir [Expr<'hir>]),
    /// A function call.
    ///
    /// The first field resolves to the function itself (usually an `ExprKind::Path`),
    /// and the second field is the list of arguments.
    /// This also represents calling the constructor of
    /// tuple-like ADTs such as tuple structs and enum variants.
    Call(&'hir Expr<'hir>, &'hir [Expr<'hir>]),
    /// A method call (e.g., `x.foo::<'static, Bar, Baz>(a, b, c, d)`).
    ///
    /// The `PathSegment` represents the method name and its generic arguments
    /// (within the angle brackets).
    /// The `&Expr` is the expression that evaluates
    /// to the object on which the method is being called on (the receiver),
    /// and the `&[Expr]` is the rest of the arguments.
    /// Thus, `x.foo::<Bar, Baz>(a, b, c, d)` is represented as
    /// `ExprKind::MethodCall(PathSegment { foo, [Bar, Baz] }, x, [a, b, c, d], span)`.
    /// The final `Span` represents the span of the function and arguments
    /// (e.g. `foo::<Bar, Baz>(a, b, c, d)` in `x.foo::<Bar, Baz>(a, b, c, d)`
    ///
    /// To resolve the called method to a `DefId`, call [`type_dependent_def_id`] with
    /// the `hir_id` of the `MethodCall` node itself.
    ///
    /// [`type_dependent_def_id`]: ../../rustc_middle/ty/struct.TypeckResults.html#method.type_dependent_def_id
    MethodCall(&'hir PathSegment<'hir>, &'hir Expr<'hir>, &'hir [Expr<'hir>], Span),
    /// A tuple (e.g., `(a, b, c, d)`).
    Tup(&'hir [Expr<'hir>]),
    /// A binary operation (e.g., `a + b`, `a * b`).
    Binary(BinOp, &'hir Expr<'hir>, &'hir Expr<'hir>),
    /// A unary operation (e.g., `!x`, `*x`).
    Unary(UnOp, &'hir Expr<'hir>),
    /// A literal (e.g., `1`, `"foo"`).
    Lit(&'hir Lit),
    /// A cast (e.g., `foo as f64`).
    Cast(&'hir Expr<'hir>, &'hir Ty<'hir>),
    /// A type ascription (e.g., `x: Foo`). See RFC 3307.
    Type(&'hir Expr<'hir>, &'hir Ty<'hir>),
    /// Wraps the expression in a terminating scope.
    /// This makes it semantically equivalent to `{ let _t = expr; _t }`.
    ///
    /// This construct only exists to tweak the drop order in HIR lowering.
    /// An example of that is the desugaring of `for` loops.
    DropTemps(&'hir Expr<'hir>),
    /// A `let $pat = $expr` expression.
    ///
    /// These are not `Local` and only occur as expressions.
    /// The `let Some(x) = foo()` in `if let Some(x) = foo()` is an example of `Let(..)`.
    Let(&'hir Let<'hir>),
    /// An `if` block, with an optional else block.
    ///
    /// I.e., `if <expr> { <expr> } else { <expr> }`.
    If(&'hir Expr<'hir>, &'hir Expr<'hir>, Option<&'hir Expr<'hir>>),
    /// A conditionless loop (can be exited with `break`, `continue`, or `return`).
    ///
    /// I.e., `'label: loop { <block> }`.
    ///
    /// The `Span` is the loop header (`for x in y`/`while let pat = expr`).
    Loop(&'hir Block<'hir>, Option<Label>, LoopSource, Span),
    /// A `match` block, with a source that indicates whether or not it is
    /// the result of a desugaring, and if so, which kind.
    Match(&'hir Expr<'hir>, &'hir [Arm<'hir>], MatchSource),
    /// A closure (e.g., `move |a, b, c| {a + b + c}`).
    ///
    /// The `Span` is the argument block `|...|`.
    ///
    /// This may also be a coroutine literal or an `async block` as indicated by the
    /// `Option<Movability>`.
    Closure(&'hir Closure<'hir>),
    /// A block (e.g., `'label: { ... }`).
    Block(&'hir Block<'hir>, Option<Label>),

    /// An assignment (e.g., `a = foo()`).
    Assign(&'hir Expr<'hir>, &'hir Expr<'hir>, Span),
    /// An assignment with an operator.
    ///
    /// E.g., `a += 1`.
    AssignOp(BinOp, &'hir Expr<'hir>, &'hir Expr<'hir>),
    /// Access of a named (e.g., `obj.foo`) or unnamed (e.g., `obj.0`) struct or tuple field.
    Field(&'hir Expr<'hir>, Ident),
    /// An indexing operation (`foo[2]`).
    /// Similar to [`ExprKind::MethodCall`], the final `Span` represents the span of the brackets
    /// and index.
    Index(&'hir Expr<'hir>, &'hir Expr<'hir>, Span),

    /// Path to a definition, possibly containing lifetime or type parameters.
    Path(QPath<'hir>),

    /// A referencing operation (i.e., `&a` or `&mut a`).
    AddrOf(BorrowKind, Mutability, &'hir Expr<'hir>),
    /// A `break`, with an optional label to break.
    Break(Destination, Option<&'hir Expr<'hir>>),
    /// A `continue`, with an optional label.
    Continue(Destination),
    /// A `return`, with an optional value to be returned.
    Ret(Option<&'hir Expr<'hir>>),
    /// A `become`, with the value to be returned.
    Become(&'hir Expr<'hir>),

    /// Inline assembly (from `asm!`), with its outputs and inputs.
    InlineAsm(&'hir InlineAsm<'hir>),

    /// Field offset (`offset_of!`)
    OffsetOf(&'hir Ty<'hir>, &'hir [Ident]),

    /// A struct or struct-like variant literal expression.
    ///
    /// E.g., `Foo {x: 1, y: 2}`, or `Foo {x: 1, .. base}`,
    /// where `base` is the `Option<Expr>`.
    Struct(&'hir QPath<'hir>, &'hir [ExprField<'hir>], Option<&'hir Expr<'hir>>),

    /// An array literal constructed from one repeated element.
    ///
    /// E.g., `[1; 5]`. The first expression is the element
    /// to be repeated; the second is the number of times to repeat it.
    Repeat(&'hir Expr<'hir>, ArrayLen),

    /// A suspension point for coroutines (i.e., `yield <expr>`).
    Yield(&'hir Expr<'hir>, YieldSource),

    /// A placeholder for an expression that wasn't syntactically well formed in some way.
    Err(rustc_span::ErrorGuaranteed),
}

/// Represents an optionally `Self`-qualified value/type path or associated extension.
///
/// To resolve the path to a `DefId`, call [`qpath_res`].
///
/// [`qpath_res`]: ../../rustc_middle/ty/struct.TypeckResults.html#method.qpath_res
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub enum QPath<'hir> {
    /// Path to a definition, optionally "fully-qualified" with a `Self`
    /// type, if the path points to an associated item in a trait.
    ///
    /// E.g., an unqualified path like `Clone::clone` has `None` for `Self`,
    /// while `<Vec<T> as Clone>::clone` has `Some(Vec<T>)` for `Self`,
    /// even though they both have the same two-segment `Clone::clone` `Path`.
    Resolved(Option<&'hir Ty<'hir>>, &'hir Path<'hir>),

    /// Type-related paths (e.g., `<T>::default` or `<T>::Output`).
    /// Will be resolved by type-checking to an associated item.
    ///
    /// UFCS source paths can desugar into this, with `Vec::new` turning into
    /// `<Vec>::new`, and `T::X::Y::method` into `<<<T>::X>::Y>::method`,
    /// the `X` and `Y` nodes each being a `TyKind::Path(QPath::TypeRelative(..))`.
    TypeRelative(&'hir Ty<'hir>, &'hir PathSegment<'hir>),

    /// Reference to a `#[lang = "foo"]` item. `HirId` of the inner expr.
    LangItem(LangItem, Span, Option<HirId>),
}

impl<'hir> QPath<'hir> {
    /// Returns the span of this `QPath`.
    pub fn span(&self) -> Span {
        match *self {
            QPath::Resolved(_, path) => path.span,
            QPath::TypeRelative(qself, ps) => qself.span.to(ps.ident.span),
            QPath::LangItem(_, span, _) => span,
        }
    }

    /// Returns the span of the qself of this `QPath`. For example, `()` in
    /// `<() as Trait>::method`.
    pub fn qself_span(&self) -> Span {
        match *self {
            QPath::Resolved(_, path) => path.span,
            QPath::TypeRelative(qself, _) => qself.span,
            QPath::LangItem(_, span, _) => span,
        }
    }

    /// Returns the span of the last segment of this `QPath`. For example, `method` in
    /// `<() as Trait>::method`.
    pub fn last_segment_span(&self) -> Span {
        match *self {
            QPath::Resolved(_, path) => path.segments.last().unwrap().ident.span,
            QPath::TypeRelative(_, segment) => segment.ident.span,
            QPath::LangItem(_, span, _) => span,
        }
    }
}

/// Hints at the original code for a let statement.
#[derive(Copy, Clone, Debug, HashStable_Generic)]
pub enum LocalSource {
    /// A `match _ { .. }`.
    Normal,
    /// When lowering async functions, we create locals within the `async move` so that
    /// all parameters are dropped after the future is polled.
    ///
    /// ```ignore (pseudo-Rust)
    /// async fn foo(<pattern> @ x: Type) {
    ///     async move {
    ///         let <pattern> = x;
    ///     }
    /// }
    /// ```
    AsyncFn,
    /// A desugared `<expr>.await`.
    AwaitDesugar,
    /// A desugared `expr = expr`, where the LHS is a tuple, struct or array.
    /// The span is that of the `=` sign.
    AssignDesugar(Span),
}

/// Hints at the original code for a `match _ { .. }`.
#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
#[derive(HashStable_Generic, Encodable, Decodable)]
pub enum MatchSource {
    /// A `match _ { .. }`.
    Normal,
    /// A desugared `for _ in _ { .. }` loop.
    ForLoopDesugar,
    /// A desugared `?` operator.
    TryDesugar(HirId),
    /// A desugared `<expr>.await`.
    AwaitDesugar,
    /// A desugared `format_args!()`.
    FormatArgs,
}

impl MatchSource {
    #[inline]
    pub const fn name(self) -> &'static str {
        use MatchSource::*;
        match self {
            Normal => "match",
            ForLoopDesugar => "for",
            TryDesugar(_) => "?",
            AwaitDesugar => ".await",
            FormatArgs => "format_args!()",
        }
    }
}

/// The loop type that yielded an `ExprKind::Loop`.
#[derive(Copy, Clone, PartialEq, Debug, HashStable_Generic)]
pub enum LoopSource {
    /// A `loop { .. }` loop.
    Loop,
    /// A `while _ { .. }` loop.
    While,
    /// A `for _ in _ { .. }` loop.
    ForLoop,
}

impl LoopSource {
    pub fn name(self) -> &'static str {
        match self {
            LoopSource::Loop => "loop",
            LoopSource::While => "while",
            LoopSource::ForLoop => "for",
        }
    }
}

#[derive(Copy, Clone, Debug, HashStable_Generic)]
pub enum LoopIdError {
    OutsideLoopScope,
    UnlabeledCfInWhileCondition,
    UnresolvedLabel,
}

impl fmt::Display for LoopIdError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str(match self {
            LoopIdError::OutsideLoopScope => "not inside loop scope",
            LoopIdError::UnlabeledCfInWhileCondition => {
                "unlabeled control flow (break or continue) in while condition"
            }
            LoopIdError::UnresolvedLabel => "label not found",
        })
    }
}

#[derive(Copy, Clone, Debug, HashStable_Generic)]
pub struct Destination {
    /// This is `Some(_)` iff there is an explicit user-specified 'label
    pub label: Option<Label>,

    /// These errors are caught and then reported during the diagnostics pass in
    /// `librustc_passes/loops.rs`
    pub target_id: Result<HirId, LoopIdError>,
}

/// The yield kind that caused an `ExprKind::Yield`.
#[derive(Copy, Clone, Debug, HashStable_Generic)]
pub enum YieldSource {
    /// An `<expr>.await`.
    Await { expr: Option<HirId> },
    /// A plain `yield`.
    Yield,
}

impl YieldSource {
    pub fn is_await(&self) -> bool {
        matches!(self, YieldSource::Await { .. })
    }
}

impl fmt::Display for YieldSource {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str(match self {
            YieldSource::Await { .. } => "`await`",
            YieldSource::Yield => "`yield`",
        })
    }
}

impl From<CoroutineKind> for YieldSource {
    fn from(kind: CoroutineKind) -> Self {
        match kind {
            // Guess based on the kind of the current coroutine.
            CoroutineKind::Coroutine => Self::Yield,
            CoroutineKind::Async(_) => Self::Await { expr: None },
            CoroutineKind::Gen(_) => Self::Yield,
        }
    }
}

// N.B., if you change this, you'll probably want to change the corresponding
// type structure in middle/ty.rs as well.
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct MutTy<'hir> {
    pub ty: &'hir Ty<'hir>,
    pub mutbl: Mutability,
}

/// Represents a function's signature in a trait declaration,
/// trait implementation, or a free function.
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct FnSig<'hir> {
    pub header: FnHeader,
    pub decl: &'hir FnDecl<'hir>,
    pub span: Span,
}

// The bodies for items are stored "out of line", in a separate
// hashmap in the `Crate`. Here we just record the hir-id of the item
// so it can fetched later.
#[derive(Copy, Clone, PartialEq, Eq, Encodable, Decodable, Debug, HashStable_Generic)]
pub struct TraitItemId {
    pub owner_id: OwnerId,
}

impl TraitItemId {
    #[inline]
    pub fn hir_id(&self) -> HirId {
        // Items are always HIR owners.
        HirId::make_owner(self.owner_id.def_id)
    }
}

/// Represents an item declaration within a trait declaration,
/// possibly including a default implementation. A trait item is
/// either required (meaning it doesn't have an implementation, just a
/// signature) or provided (meaning it has a default implementation).
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct TraitItem<'hir> {
    pub ident: Ident,
    pub owner_id: OwnerId,
    pub generics: &'hir Generics<'hir>,
    pub kind: TraitItemKind<'hir>,
    pub span: Span,
    pub defaultness: Defaultness,
}

impl<'hir> TraitItem<'hir> {
    #[inline]
    pub fn hir_id(&self) -> HirId {
        // Items are always HIR owners.
        HirId::make_owner(self.owner_id.def_id)
    }

    pub fn trait_item_id(&self) -> TraitItemId {
        TraitItemId { owner_id: self.owner_id }
    }

    /// Expect an [`TraitItemKind::Const`] or panic.
    #[track_caller]
    pub fn expect_const(&self) -> (&'hir Ty<'hir>, Option<BodyId>) {
        let TraitItemKind::Const(ty, body) = self.kind else { self.expect_failed("a constant") };
        (ty, body)
    }

    /// Expect an [`TraitItemKind::Fn`] or panic.
    #[track_caller]
    pub fn expect_fn(&self) -> (&FnSig<'hir>, &TraitFn<'hir>) {
        let TraitItemKind::Fn(ty, trfn) = &self.kind else { self.expect_failed("a function") };
        (ty, trfn)
    }

    /// Expect an [`TraitItemKind::Type`] or panic.
    #[track_caller]
    pub fn expect_type(&self) -> (GenericBounds<'hir>, Option<&'hir Ty<'hir>>) {
        let TraitItemKind::Type(bounds, ty) = self.kind else { self.expect_failed("a type") };
        (bounds, ty)
    }

    #[track_caller]
    fn expect_failed(&self, expected: &'static str) -> ! {
        panic!("expected {expected} item, found {self:?}")
    }
}

/// Represents a trait method's body (or just argument names).
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub enum TraitFn<'hir> {
    /// No default body in the trait, just a signature.
    Required(&'hir [Ident]),

    /// Both signature and body are provided in the trait.
    Provided(BodyId),
}

/// Represents a trait method or associated constant or type
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub enum TraitItemKind<'hir> {
    /// An associated constant with an optional value (otherwise `impl`s must contain a value).
    Const(&'hir Ty<'hir>, Option<BodyId>),
    /// An associated function with an optional body.
    Fn(FnSig<'hir>, TraitFn<'hir>),
    /// An associated type with (possibly empty) bounds and optional concrete
    /// type.
    Type(GenericBounds<'hir>, Option<&'hir Ty<'hir>>),
}

// The bodies for items are stored "out of line", in a separate
// hashmap in the `Crate`. Here we just record the hir-id of the item
// so it can fetched later.
#[derive(Copy, Clone, PartialEq, Eq, Encodable, Decodable, Debug, HashStable_Generic)]
pub struct ImplItemId {
    pub owner_id: OwnerId,
}

impl ImplItemId {
    #[inline]
    pub fn hir_id(&self) -> HirId {
        // Items are always HIR owners.
        HirId::make_owner(self.owner_id.def_id)
    }
}

/// Represents anything within an `impl` block.
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct ImplItem<'hir> {
    pub ident: Ident,
    pub owner_id: OwnerId,
    pub generics: &'hir Generics<'hir>,
    pub kind: ImplItemKind<'hir>,
    pub defaultness: Defaultness,
    pub span: Span,
    pub vis_span: Span,
}

impl<'hir> ImplItem<'hir> {
    #[inline]
    pub fn hir_id(&self) -> HirId {
        // Items are always HIR owners.
        HirId::make_owner(self.owner_id.def_id)
    }

    pub fn impl_item_id(&self) -> ImplItemId {
        ImplItemId { owner_id: self.owner_id }
    }

    /// Expect an [`ImplItemKind::Const`] or panic.
    #[track_caller]
    pub fn expect_const(&self) -> (&'hir Ty<'hir>, BodyId) {
        let ImplItemKind::Const(ty, body) = self.kind else { self.expect_failed("a constant") };
        (ty, body)
    }

    /// Expect an [`ImplItemKind::Fn`] or panic.
    #[track_caller]
    pub fn expect_fn(&self) -> (&FnSig<'hir>, BodyId) {
        let ImplItemKind::Fn(ty, body) = &self.kind else { self.expect_failed("a function") };
        (ty, *body)
    }

    /// Expect an [`ImplItemKind::Type`] or panic.
    #[track_caller]
    pub fn expect_type(&self) -> &'hir Ty<'hir> {
        let ImplItemKind::Type(ty) = self.kind else { self.expect_failed("a type") };
        ty
    }

    #[track_caller]
    fn expect_failed(&self, expected: &'static str) -> ! {
        panic!("expected {expected} item, found {self:?}")
    }
}

/// Represents various kinds of content within an `impl`.
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub enum ImplItemKind<'hir> {
    /// An associated constant of the given type, set to the constant result
    /// of the expression.
    Const(&'hir Ty<'hir>, BodyId),
    /// An associated function implementation with the given signature and body.
    Fn(FnSig<'hir>, BodyId),
    /// An associated type.
    Type(&'hir Ty<'hir>),
}

/// The name of the associated type for `Fn` return types.
pub const FN_OUTPUT_NAME: Symbol = sym::Output;

/// Bind a type to an associated type (i.e., `A = Foo`).
///
/// Bindings like `A: Debug` are represented as a special type `A =
/// $::Debug` that is understood by the astconv code.
///
/// FIXME(alexreg): why have a separate type for the binding case,
/// wouldn't it be better to make the `ty` field an enum like the
/// following?
///
/// ```ignore (pseudo-rust)
/// enum TypeBindingKind {
///    Equals(...),
///    Binding(...),
/// }
/// ```
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct TypeBinding<'hir> {
    pub hir_id: HirId,
    pub ident: Ident,
    pub gen_args: &'hir GenericArgs<'hir>,
    pub kind: TypeBindingKind<'hir>,
    pub span: Span,
}

#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub enum Term<'hir> {
    Ty(&'hir Ty<'hir>),
    Const(AnonConst),
}

impl<'hir> From<&'hir Ty<'hir>> for Term<'hir> {
    fn from(ty: &'hir Ty<'hir>) -> Self {
        Term::Ty(ty)
    }
}

impl<'hir> From<AnonConst> for Term<'hir> {
    fn from(c: AnonConst) -> Self {
        Term::Const(c)
    }
}

// Represents the two kinds of type bindings.
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub enum TypeBindingKind<'hir> {
    /// E.g., `Foo<Bar: Send>`.
    Constraint { bounds: &'hir [GenericBound<'hir>] },
    /// E.g., `Foo<Bar = ()>`, `Foo<Bar = ()>`
    Equality { term: Term<'hir> },
}

impl TypeBinding<'_> {
    pub fn ty(&self) -> &Ty<'_> {
        match self.kind {
            TypeBindingKind::Equality { term: Term::Ty(ref ty) } => ty,
            _ => panic!("expected equality type binding for parenthesized generic args"),
        }
    }
    pub fn opt_const(&self) -> Option<&'_ AnonConst> {
        match self.kind {
            TypeBindingKind::Equality { term: Term::Const(ref c) } => Some(c),
            _ => None,
        }
    }
}

#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct Ty<'hir> {
    pub hir_id: HirId,
    pub kind: TyKind<'hir>,
    pub span: Span,
}

impl<'hir> Ty<'hir> {
    /// Returns `true` if `param_def_id` matches the `bounded_ty` of this predicate.
    pub fn as_generic_param(&self) -> Option<(DefId, Ident)> {
        let TyKind::Path(QPath::Resolved(None, path)) = self.kind else {
            return None;
        };
        let [segment] = &path.segments else {
            return None;
        };
        match path.res {
            Res::Def(DefKind::TyParam, def_id) | Res::SelfTyParam { trait_: def_id } => {
                Some((def_id, segment.ident))
            }
            _ => None,
        }
    }

    pub fn peel_refs(&self) -> &Self {
        let mut final_ty = self;
        while let TyKind::Ref(_, MutTy { ty, .. }) = &final_ty.kind {
            final_ty = ty;
        }
        final_ty
    }

    pub fn find_self_aliases(&self) -> Vec<Span> {
        use crate::intravisit::Visitor;
        struct MyVisitor(Vec<Span>);
        impl<'v> Visitor<'v> for MyVisitor {
            fn visit_ty(&mut self, t: &'v Ty<'v>) {
                if matches!(
                    &t.kind,
                    TyKind::Path(QPath::Resolved(
                        _,
                        Path { res: crate::def::Res::SelfTyAlias { .. }, .. },
                    ))
                ) {
                    self.0.push(t.span);
                    return;
                }
                crate::intravisit::walk_ty(self, t);
            }
        }

        let mut my_visitor = MyVisitor(vec![]);
        my_visitor.visit_ty(self);
        my_visitor.0
    }
}

/// Not represented directly in the AST; referred to by name through a `ty_path`.
#[derive(Copy, Clone, PartialEq, Eq, Encodable, Decodable, Hash, Debug)]
#[derive(HashStable_Generic)]
pub enum PrimTy {
    Int(IntTy),
    Uint(UintTy),
    Float(FloatTy),
    Str,
    Bool,
    Char,
}

impl PrimTy {
    /// All of the primitive types
    pub const ALL: [Self; 17] = [
        // any changes here should also be reflected in `PrimTy::from_name`
        Self::Int(IntTy::I8),
        Self::Int(IntTy::I16),
        Self::Int(IntTy::I32),
        Self::Int(IntTy::I64),
        Self::Int(IntTy::I128),
        Self::Int(IntTy::Isize),
        Self::Uint(UintTy::U8),
        Self::Uint(UintTy::U16),
        Self::Uint(UintTy::U32),
        Self::Uint(UintTy::U64),
        Self::Uint(UintTy::U128),
        Self::Uint(UintTy::Usize),
        Self::Float(FloatTy::F32),
        Self::Float(FloatTy::F64),
        Self::Bool,
        Self::Char,
        Self::Str,
    ];

    /// Like [`PrimTy::name`], but returns a &str instead of a symbol.
    ///
    /// Used by clippy.
    pub fn name_str(self) -> &'static str {
        match self {
            PrimTy::Int(i) => i.name_str(),
            PrimTy::Uint(u) => u.name_str(),
            PrimTy::Float(f) => f.name_str(),
            PrimTy::Str => "str",
            PrimTy::Bool => "bool",
            PrimTy::Char => "char",
        }
    }

    pub fn name(self) -> Symbol {
        match self {
            PrimTy::Int(i) => i.name(),
            PrimTy::Uint(u) => u.name(),
            PrimTy::Float(f) => f.name(),
            PrimTy::Str => sym::str,
            PrimTy::Bool => sym::bool,
            PrimTy::Char => sym::char,
        }
    }

    /// Returns the matching `PrimTy` for a `Symbol` such as "str" or "i32".
    /// Returns `None` if no matching type is found.
    pub fn from_name(name: Symbol) -> Option<Self> {
        let ty = match name {
            // any changes here should also be reflected in `PrimTy::ALL`
            sym::i8 => Self::Int(IntTy::I8),
            sym::i16 => Self::Int(IntTy::I16),
            sym::i32 => Self::Int(IntTy::I32),
            sym::i64 => Self::Int(IntTy::I64),
            sym::i128 => Self::Int(IntTy::I128),
            sym::isize => Self::Int(IntTy::Isize),
            sym::u8 => Self::Uint(UintTy::U8),
            sym::u16 => Self::Uint(UintTy::U16),
            sym::u32 => Self::Uint(UintTy::U32),
            sym::u64 => Self::Uint(UintTy::U64),
            sym::u128 => Self::Uint(UintTy::U128),
            sym::usize => Self::Uint(UintTy::Usize),
            sym::f32 => Self::Float(FloatTy::F32),
            sym::f64 => Self::Float(FloatTy::F64),
            sym::bool => Self::Bool,
            sym::char => Self::Char,
            sym::str => Self::Str,
            _ => return None,
        };
        Some(ty)
    }
}

#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct BareFnTy<'hir> {
    pub unsafety: Unsafety,
    pub abi: Abi,
    pub generic_params: &'hir [GenericParam<'hir>],
    pub decl: &'hir FnDecl<'hir>,
    pub param_names: &'hir [Ident],
}

#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct OpaqueTy<'hir> {
    pub generics: &'hir Generics<'hir>,
    pub bounds: GenericBounds<'hir>,
    pub origin: OpaqueTyOrigin,
    /// Return-position impl traits (and async futures) must "reify" any late-bound
    /// lifetimes that are captured from the function signature they originate from.
    ///
    /// This is done by generating a new early-bound lifetime parameter local to the
    /// opaque which is substituted in the function signature with the late-bound
    /// lifetime.
    ///
    /// This mapping associated a captured lifetime (first parameter) with the new
    /// early-bound lifetime that was generated for the opaque.
    pub lifetime_mapping: &'hir [(&'hir Lifetime, LocalDefId)],
    /// Whether the opaque is a return-position impl trait (or async future)
    /// originating from a trait method. This makes it so that the opaque is
    /// lowered as an associated type.
    pub in_trait: bool,
}

/// From whence the opaque type came.
#[derive(Copy, Clone, PartialEq, Eq, Debug, HashStable_Generic)]
pub enum OpaqueTyOrigin {
    /// `-> impl Trait`
    FnReturn(LocalDefId),
    /// `async fn`
    AsyncFn(LocalDefId),
    /// type aliases: `type Foo = impl Trait;`
    TyAlias {
        /// associated types in impl blocks for traits.
        in_assoc_ty: bool,
    },
}

/// The various kinds of types recognized by the compiler.
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub enum TyKind<'hir> {
    /// A variable length slice (i.e., `[T]`).
    Slice(&'hir Ty<'hir>),
    /// A fixed length array (i.e., `[T; n]`).
    Array(&'hir Ty<'hir>, ArrayLen),
    /// A raw pointer (i.e., `*const T` or `*mut T`).
    Ptr(MutTy<'hir>),
    /// A reference (i.e., `&'a T` or `&'a mut T`).
    Ref(&'hir Lifetime, MutTy<'hir>),
    /// A bare function (e.g., `fn(usize) -> bool`).
    BareFn(&'hir BareFnTy<'hir>),
    /// The never type (`!`).
    Never,
    /// A tuple (`(A, B, C, D, ...)`).
    Tup(&'hir [Ty<'hir>]),
    /// A path to a type definition (`module::module::...::Type`), or an
    /// associated type (e.g., `<Vec<T> as Trait>::Type` or `<T>::Target`).
    ///
    /// Type parameters may be stored in each `PathSegment`.
    Path(QPath<'hir>),
    /// An opaque type definition itself. This is only used for `impl Trait`.
    ///
    /// The generic argument list contains the lifetimes (and in the future
    /// possibly parameters) that are actually bound on the `impl Trait`.
    ///
    /// The last parameter specifies whether this opaque appears in a trait definition.
    OpaqueDef(ItemId, &'hir [GenericArg<'hir>], bool),
    /// A trait object type `Bound1 + Bound2 + Bound3`
    /// where `Bound` is a trait or a lifetime.
    TraitObject(&'hir [PolyTraitRef<'hir>], &'hir Lifetime, TraitObjectSyntax),
    /// Unused for now.
    Typeof(AnonConst),
    /// `TyKind::Infer` means the type should be inferred instead of it having been
    /// specified. This can appear anywhere in a type.
    Infer,
    /// Placeholder for a type that has failed to be defined.
    Err(rustc_span::ErrorGuaranteed),
}

#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub enum InlineAsmOperand<'hir> {
    In {
        reg: InlineAsmRegOrRegClass,
        expr: &'hir Expr<'hir>,
    },
    Out {
        reg: InlineAsmRegOrRegClass,
        late: bool,
        expr: Option<&'hir Expr<'hir>>,
    },
    InOut {
        reg: InlineAsmRegOrRegClass,
        late: bool,
        expr: &'hir Expr<'hir>,
    },
    SplitInOut {
        reg: InlineAsmRegOrRegClass,
        late: bool,
        in_expr: &'hir Expr<'hir>,
        out_expr: Option<&'hir Expr<'hir>>,
    },
    Const {
        anon_const: AnonConst,
    },
    SymFn {
        anon_const: AnonConst,
    },
    SymStatic {
        path: QPath<'hir>,
        def_id: DefId,
    },
}

impl<'hir> InlineAsmOperand<'hir> {
    pub fn reg(&self) -> Option<InlineAsmRegOrRegClass> {
        match *self {
            Self::In { reg, .. }
            | Self::Out { reg, .. }
            | Self::InOut { reg, .. }
            | Self::SplitInOut { reg, .. } => Some(reg),
            Self::Const { .. } | Self::SymFn { .. } | Self::SymStatic { .. } => None,
        }
    }

    pub fn is_clobber(&self) -> bool {
        matches!(
            self,
            InlineAsmOperand::Out { reg: InlineAsmRegOrRegClass::Reg(_), late: _, expr: None }
        )
    }
}

#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct InlineAsm<'hir> {
    pub template: &'hir [InlineAsmTemplatePiece],
    pub template_strs: &'hir [(Symbol, Option<Symbol>, Span)],
    pub operands: &'hir [(InlineAsmOperand<'hir>, Span)],
    pub options: InlineAsmOptions,
    pub line_spans: &'hir [Span],
}

/// Represents a parameter in a function header.
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct Param<'hir> {
    pub hir_id: HirId,
    pub pat: &'hir Pat<'hir>,
    pub ty_span: Span,
    pub span: Span,
}

/// Represents the header (not the body) of a function declaration.
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct FnDecl<'hir> {
    /// The types of the function's parameters.
    ///
    /// Additional argument data is stored in the function's [body](Body::params).
    pub inputs: &'hir [Ty<'hir>],
    pub output: FnRetTy<'hir>,
    pub c_variadic: bool,
    /// Does the function have an implicit self?
    pub implicit_self: ImplicitSelfKind,
    /// Is lifetime elision allowed.
    pub lifetime_elision_allowed: bool,
}

/// Represents what type of implicit self a function has, if any.
#[derive(Copy, Clone, PartialEq, Eq, Encodable, Decodable, Debug, HashStable_Generic)]
pub enum ImplicitSelfKind {
    /// Represents a `fn x(self);`.
    Imm,
    /// Represents a `fn x(mut self);`.
    Mut,
    /// Represents a `fn x(&self);`.
    ImmRef,
    /// Represents a `fn x(&mut self);`.
    MutRef,
    /// Represents when a function does not have a self argument or
    /// when a function has a `self: X` argument.
    None,
}

impl ImplicitSelfKind {
    /// Does this represent an implicit self?
    pub fn has_implicit_self(&self) -> bool {
        !matches!(*self, ImplicitSelfKind::None)
    }
}

#[derive(Copy, Clone, PartialEq, Eq, Encodable, Decodable, Debug)]
#[derive(HashStable_Generic)]
pub enum IsAsync {
    Async(Span),
    NotAsync,
}

impl IsAsync {
    pub fn is_async(self) -> bool {
        matches!(self, IsAsync::Async(_))
    }
}

#[derive(Copy, Clone, PartialEq, Eq, Debug, Encodable, Decodable, HashStable_Generic)]
pub enum Defaultness {
    Default { has_value: bool },
    Final,
}

impl Defaultness {
    pub fn has_value(&self) -> bool {
        match *self {
            Defaultness::Default { has_value } => has_value,
            Defaultness::Final => true,
        }
    }

    pub fn is_final(&self) -> bool {
        *self == Defaultness::Final
    }

    pub fn is_default(&self) -> bool {
        matches!(*self, Defaultness::Default { .. })
    }
}

#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub enum FnRetTy<'hir> {
    /// Return type is not specified.
    ///
    /// Functions default to `()` and
    /// closures default to inference. Span points to where return
    /// type would be inserted.
    DefaultReturn(Span),
    /// Everything else.
    Return(&'hir Ty<'hir>),
}

impl FnRetTy<'_> {
    #[inline]
    pub fn span(&self) -> Span {
        match *self {
            Self::DefaultReturn(span) => span,
            Self::Return(ref ty) => ty.span,
        }
    }
}

/// Represents `for<...>` binder before a closure
#[derive(Copy, Clone, Debug, HashStable_Generic)]
pub enum ClosureBinder {
    /// Binder is not specified.
    Default,
    /// Binder is specified.
    ///
    /// Span points to the whole `for<...>`.
    For { span: Span },
}

#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct Mod<'hir> {
    pub spans: ModSpans,
    pub item_ids: &'hir [ItemId],
}

#[derive(Copy, Clone, Debug, HashStable_Generic)]
pub struct ModSpans {
    /// A span from the first token past `{` to the last token until `}`.
    /// For `mod foo;`, the inner span ranges from the first token
    /// to the last token in the external file.
    pub inner_span: Span,
    pub inject_use_span: Span,
}

#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct EnumDef<'hir> {
    pub variants: &'hir [Variant<'hir>],
}

#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct Variant<'hir> {
    /// Name of the variant.
    pub ident: Ident,
    /// Id of the variant (not the constructor, see `VariantData::ctor_hir_id()`).
    pub hir_id: HirId,
    pub def_id: LocalDefId,
    /// Fields and constructor id of the variant.
    pub data: VariantData<'hir>,
    /// Explicit discriminant (e.g., `Foo = 1`).
    pub disr_expr: Option<AnonConst>,
    /// Span
    pub span: Span,
}

#[derive(Copy, Clone, PartialEq, Debug, HashStable_Generic)]
pub enum UseKind {
    /// One import, e.g., `use foo::bar` or `use foo::bar as baz`.
    /// Also produced for each element of a list `use`, e.g.
    /// `use foo::{a, b}` lowers to `use foo::a; use foo::b;`.
    Single,

    /// Glob import, e.g., `use foo::*`.
    Glob,

    /// Degenerate list import, e.g., `use foo::{a, b}` produces
    /// an additional `use foo::{}` for performing checks such as
    /// unstable feature gating. May be removed in the future.
    ListStem,
}

/// References to traits in impls.
///
/// `resolve` maps each `TraitRef`'s `ref_id` to its defining trait; that's all
/// that the `ref_id` is for. Note that `ref_id`'s value is not the `HirId` of the
/// trait being referred to but just a unique `HirId` that serves as a key
/// within the resolution map.
#[derive(Clone, Debug, Copy, HashStable_Generic)]
pub struct TraitRef<'hir> {
    pub path: &'hir Path<'hir>,
    // Don't hash the `ref_id`. It is tracked via the thing it is used to access.
    #[stable_hasher(ignore)]
    pub hir_ref_id: HirId,
}

impl TraitRef<'_> {
    /// Gets the `DefId` of the referenced trait. It _must_ actually be a trait or trait alias.
    pub fn trait_def_id(&self) -> Option<DefId> {
        match self.path.res {
            Res::Def(DefKind::Trait | DefKind::TraitAlias, did) => Some(did),
            Res::Err => None,
            _ => unreachable!(),
        }
    }
}

#[derive(Clone, Debug, Copy, HashStable_Generic)]
pub struct PolyTraitRef<'hir> {
    /// The `'a` in `for<'a> Foo<&'a T>`.
    pub bound_generic_params: &'hir [GenericParam<'hir>],

    /// The `Foo<&'a T>` in `for<'a> Foo<&'a T>`.
    pub trait_ref: TraitRef<'hir>,

    pub span: Span,
}

#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct FieldDef<'hir> {
    pub span: Span,
    pub vis_span: Span,
    pub ident: Ident,
    pub hir_id: HirId,
    pub def_id: LocalDefId,
    pub ty: &'hir Ty<'hir>,
}

impl FieldDef<'_> {
    // Still necessary in couple of places
    pub fn is_positional(&self) -> bool {
        self.ident.as_str().as_bytes()[0].is_ascii_digit()
    }
}

/// Fields and constructor IDs of enum variants and structs.
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub enum VariantData<'hir> {
    /// A struct variant.
    ///
    /// E.g., `Bar { .. }` as in `enum Foo { Bar { .. } }`.
    Struct(&'hir [FieldDef<'hir>], /* recovered */ bool),
    /// A tuple variant.
    ///
    /// E.g., `Bar(..)` as in `enum Foo { Bar(..) }`.
    Tuple(&'hir [FieldDef<'hir>], HirId, LocalDefId),
    /// A unit variant.
    ///
    /// E.g., `Bar = ..` as in `enum Foo { Bar = .. }`.
    Unit(HirId, LocalDefId),
}

impl<'hir> VariantData<'hir> {
    /// Return the fields of this variant.
    pub fn fields(&self) -> &'hir [FieldDef<'hir>] {
        match *self {
            VariantData::Struct(ref fields, ..) | VariantData::Tuple(ref fields, ..) => fields,
            _ => &[],
        }
    }

    pub fn ctor(&self) -> Option<(CtorKind, HirId, LocalDefId)> {
        match *self {
            VariantData::Tuple(_, hir_id, def_id) => Some((CtorKind::Fn, hir_id, def_id)),
            VariantData::Unit(hir_id, def_id) => Some((CtorKind::Const, hir_id, def_id)),
            VariantData::Struct(..) => None,
        }
    }

    #[inline]
    pub fn ctor_kind(&self) -> Option<CtorKind> {
        self.ctor().map(|(kind, ..)| kind)
    }

    /// Return the `HirId` of this variant's constructor, if it has one.
    #[inline]
    pub fn ctor_hir_id(&self) -> Option<HirId> {
        self.ctor().map(|(_, hir_id, _)| hir_id)
    }

    /// Return the `LocalDefId` of this variant's constructor, if it has one.
    #[inline]
    pub fn ctor_def_id(&self) -> Option<LocalDefId> {
        self.ctor().map(|(.., def_id)| def_id)
    }
}

// The bodies for items are stored "out of line", in a separate
// hashmap in the `Crate`. Here we just record the hir-id of the item
// so it can fetched later.
#[derive(Copy, Clone, PartialEq, Eq, Encodable, Decodable, Debug, Hash, HashStable_Generic)]
pub struct ItemId {
    pub owner_id: OwnerId,
}

impl ItemId {
    #[inline]
    pub fn hir_id(&self) -> HirId {
        // Items are always HIR owners.
        HirId::make_owner(self.owner_id.def_id)
    }
}

/// An item
///
/// The name might be a dummy name in case of anonymous items
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct Item<'hir> {
    pub ident: Ident,
    pub owner_id: OwnerId,
    pub kind: ItemKind<'hir>,
    pub span: Span,
    pub vis_span: Span,
}

impl<'hir> Item<'hir> {
    #[inline]
    pub fn hir_id(&self) -> HirId {
        // Items are always HIR owners.
        HirId::make_owner(self.owner_id.def_id)
    }

    pub fn item_id(&self) -> ItemId {
        ItemId { owner_id: self.owner_id }
    }

    /// Expect an [`ItemKind::ExternCrate`] or panic.
    #[track_caller]
    pub fn expect_extern_crate(&self) -> Option<Symbol> {
        let ItemKind::ExternCrate(s) = self.kind else { self.expect_failed("an extern crate") };
        s
    }

    /// Expect an [`ItemKind::Use`] or panic.
    #[track_caller]
    pub fn expect_use(&self) -> (&'hir UsePath<'hir>, UseKind) {
        let ItemKind::Use(p, uk) = self.kind else { self.expect_failed("a use") };
        (p, uk)
    }

    /// Expect an [`ItemKind::Static`] or panic.
    #[track_caller]
    pub fn expect_static(&self) -> (&'hir Ty<'hir>, Mutability, BodyId) {
        let ItemKind::Static(ty, mutbl, body) = self.kind else { self.expect_failed("a static") };
        (ty, mutbl, body)
    }
    /// Expect an [`ItemKind::Const`] or panic.
    #[track_caller]
    pub fn expect_const(&self) -> (&'hir Ty<'hir>, &'hir Generics<'hir>, BodyId) {
        let ItemKind::Const(ty, gen, body) = self.kind else { self.expect_failed("a constant") };
        (ty, gen, body)
    }
    /// Expect an [`ItemKind::Fn`] or panic.
    #[track_caller]
    pub fn expect_fn(&self) -> (&FnSig<'hir>, &'hir Generics<'hir>, BodyId) {
        let ItemKind::Fn(sig, gen, body) = &self.kind else { self.expect_failed("a function") };
        (sig, gen, *body)
    }

    /// Expect an [`ItemKind::Macro`] or panic.
    #[track_caller]
    pub fn expect_macro(&self) -> (&ast::MacroDef, MacroKind) {
        let ItemKind::Macro(def, mk) = &self.kind else { self.expect_failed("a macro") };
        (def, *mk)
    }

    /// Expect an [`ItemKind::Mod`] or panic.
    #[track_caller]
    pub fn expect_mod(&self) -> &'hir Mod<'hir> {
        let ItemKind::Mod(m) = self.kind else { self.expect_failed("a module") };
        m
    }

    /// Expect an [`ItemKind::ForeignMod`] or panic.
    #[track_caller]
    pub fn expect_foreign_mod(&self) -> (Abi, &'hir [ForeignItemRef]) {
        let ItemKind::ForeignMod { abi, items } = self.kind else {
            self.expect_failed("a foreign module")
        };
        (abi, items)
    }

    /// Expect an [`ItemKind::GlobalAsm`] or panic.
    #[track_caller]
    pub fn expect_global_asm(&self) -> &'hir InlineAsm<'hir> {
        let ItemKind::GlobalAsm(asm) = self.kind else { self.expect_failed("a global asm") };
        asm
    }

    /// Expect an [`ItemKind::TyAlias`] or panic.
    #[track_caller]
    pub fn expect_ty_alias(&self) -> (&'hir Ty<'hir>, &'hir Generics<'hir>) {
        let ItemKind::TyAlias(ty, gen) = self.kind else { self.expect_failed("a type alias") };
        (ty, gen)
    }

    /// Expect an [`ItemKind::OpaqueTy`] or panic.
    #[track_caller]
    pub fn expect_opaque_ty(&self) -> &OpaqueTy<'hir> {
        let ItemKind::OpaqueTy(ty) = &self.kind else { self.expect_failed("an opaque type") };
        ty
    }

    /// Expect an [`ItemKind::Enum`] or panic.
    #[track_caller]
    pub fn expect_enum(&self) -> (&EnumDef<'hir>, &'hir Generics<'hir>) {
        let ItemKind::Enum(def, gen) = &self.kind else { self.expect_failed("an enum") };
        (def, gen)
    }

    /// Expect an [`ItemKind::Struct`] or panic.
    #[track_caller]
    pub fn expect_struct(&self) -> (&VariantData<'hir>, &'hir Generics<'hir>) {
        let ItemKind::Struct(data, gen) = &self.kind else { self.expect_failed("a struct") };
        (data, gen)
    }

    /// Expect an [`ItemKind::Union`] or panic.
    #[track_caller]
    pub fn expect_union(&self) -> (&VariantData<'hir>, &'hir Generics<'hir>) {
        let ItemKind::Union(data, gen) = &self.kind else { self.expect_failed("a union") };
        (data, gen)
    }

    /// Expect an [`ItemKind::Trait`] or panic.
    #[track_caller]
    pub fn expect_trait(
        self,
    ) -> (IsAuto, Unsafety, &'hir Generics<'hir>, GenericBounds<'hir>, &'hir [TraitItemRef]) {
        let ItemKind::Trait(is_auto, unsafety, gen, bounds, items) = self.kind else {
            self.expect_failed("a trait")
        };
        (is_auto, unsafety, gen, bounds, items)
    }

    /// Expect an [`ItemKind::TraitAlias`] or panic.
    #[track_caller]
    pub fn expect_trait_alias(&self) -> (&'hir Generics<'hir>, GenericBounds<'hir>) {
        let ItemKind::TraitAlias(gen, bounds) = self.kind else {
            self.expect_failed("a trait alias")
        };
        (gen, bounds)
    }

    /// Expect an [`ItemKind::Impl`] or panic.
    #[track_caller]
    pub fn expect_impl(&self) -> &'hir Impl<'hir> {
        let ItemKind::Impl(imp) = self.kind else { self.expect_failed("an impl") };
        imp
    }

    #[track_caller]
    fn expect_failed(&self, expected: &'static str) -> ! {
        panic!("expected {expected} item, found {self:?}")
    }
}

#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
#[derive(Encodable, Decodable, HashStable_Generic)]
pub enum Unsafety {
    Unsafe,
    Normal,
}

impl Unsafety {
    pub fn prefix_str(&self) -> &'static str {
        match self {
            Self::Unsafe => "unsafe ",
            Self::Normal => "",
        }
    }
}

impl fmt::Display for Unsafety {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str(match *self {
            Self::Unsafe => "unsafe",
            Self::Normal => "normal",
        })
    }
}

#[derive(Copy, Clone, PartialEq, Eq, Debug)]
#[derive(Encodable, Decodable, HashStable_Generic)]
pub enum Constness {
    Const,
    NotConst,
}

impl fmt::Display for Constness {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str(match *self {
            Self::Const => "const",
            Self::NotConst => "non-const",
        })
    }
}

#[derive(Copy, Clone, Debug, HashStable_Generic)]
pub struct FnHeader {
    pub unsafety: Unsafety,
    pub constness: Constness,
    pub asyncness: IsAsync,
    pub abi: Abi,
}

impl FnHeader {
    pub fn is_async(&self) -> bool {
        matches!(&self.asyncness, IsAsync::Async(_))
    }

    pub fn is_const(&self) -> bool {
        matches!(&self.constness, Constness::Const)
    }

    pub fn is_unsafe(&self) -> bool {
        matches!(&self.unsafety, Unsafety::Unsafe)
    }
}

#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub enum ItemKind<'hir> {
    /// An `extern crate` item, with optional *original* crate name if the crate was renamed.
    ///
    /// E.g., `extern crate foo` or `extern crate foo_bar as foo`.
    ExternCrate(Option<Symbol>),

    /// `use foo::bar::*;` or `use foo::bar::baz as quux;`
    ///
    /// or just
    ///
    /// `use foo::bar::baz;` (with `as baz` implicitly on the right).
    Use(&'hir UsePath<'hir>, UseKind),

    /// A `static` item.
    Static(&'hir Ty<'hir>, Mutability, BodyId),
    /// A `const` item.
    Const(&'hir Ty<'hir>, &'hir Generics<'hir>, BodyId),
    /// A function declaration.
    Fn(FnSig<'hir>, &'hir Generics<'hir>, BodyId),
    /// A MBE macro definition (`macro_rules!` or `macro`).
    Macro(&'hir ast::MacroDef, MacroKind),
    /// A module.
    Mod(&'hir Mod<'hir>),
    /// An external module, e.g. `extern { .. }`.
    ForeignMod { abi: Abi, items: &'hir [ForeignItemRef] },
    /// Module-level inline assembly (from `global_asm!`).
    GlobalAsm(&'hir InlineAsm<'hir>),
    /// A type alias, e.g., `type Foo = Bar<u8>`.
    TyAlias(&'hir Ty<'hir>, &'hir Generics<'hir>),
    /// An opaque `impl Trait` type alias, e.g., `type Foo = impl Bar;`.
    OpaqueTy(&'hir OpaqueTy<'hir>),
    /// An enum definition, e.g., `enum Foo<A, B> {C<A>, D<B>}`.
    Enum(EnumDef<'hir>, &'hir Generics<'hir>),
    /// A struct definition, e.g., `struct Foo<A> {x: A}`.
    Struct(VariantData<'hir>, &'hir Generics<'hir>),
    /// A union definition, e.g., `union Foo<A, B> {x: A, y: B}`.
    Union(VariantData<'hir>, &'hir Generics<'hir>),
    /// A trait definition.
    Trait(IsAuto, Unsafety, &'hir Generics<'hir>, GenericBounds<'hir>, &'hir [TraitItemRef]),
    /// A trait alias.
    TraitAlias(&'hir Generics<'hir>, GenericBounds<'hir>),

    /// An implementation, e.g., `impl<A> Trait for Foo { .. }`.
    Impl(&'hir Impl<'hir>),
}

#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct Impl<'hir> {
    pub unsafety: Unsafety,
    pub polarity: ImplPolarity,
    pub defaultness: Defaultness,
    // We do not put a `Span` in `Defaultness` because it breaks foreign crate metadata
    // decoding as `Span`s cannot be decoded when a `Session` is not available.
    pub defaultness_span: Option<Span>,
    pub generics: &'hir Generics<'hir>,

    /// The trait being implemented, if any.
    pub of_trait: Option<TraitRef<'hir>>,

    pub self_ty: &'hir Ty<'hir>,
    pub items: &'hir [ImplItemRef],
}

impl ItemKind<'_> {
    pub fn generics(&self) -> Option<&Generics<'_>> {
        Some(match *self {
            ItemKind::Fn(_, ref generics, _)
            | ItemKind::TyAlias(_, ref generics)
            | ItemKind::Const(_, ref generics, _)
            | ItemKind::OpaqueTy(OpaqueTy { ref generics, .. })
            | ItemKind::Enum(_, ref generics)
            | ItemKind::Struct(_, ref generics)
            | ItemKind::Union(_, ref generics)
            | ItemKind::Trait(_, _, ref generics, _, _)
            | ItemKind::TraitAlias(ref generics, _)
            | ItemKind::Impl(Impl { ref generics, .. }) => generics,
            _ => return None,
        })
    }

    pub fn descr(&self) -> &'static str {
        match self {
            ItemKind::ExternCrate(..) => "extern crate",
            ItemKind::Use(..) => "`use` import",
            ItemKind::Static(..) => "static item",
            ItemKind::Const(..) => "constant item",
            ItemKind::Fn(..) => "function",
            ItemKind::Macro(..) => "macro",
            ItemKind::Mod(..) => "module",
            ItemKind::ForeignMod { .. } => "extern block",
            ItemKind::GlobalAsm(..) => "global asm item",
            ItemKind::TyAlias(..) => "type alias",
            ItemKind::OpaqueTy(..) => "opaque type",
            ItemKind::Enum(..) => "enum",
            ItemKind::Struct(..) => "struct",
            ItemKind::Union(..) => "union",
            ItemKind::Trait(..) => "trait",
            ItemKind::TraitAlias(..) => "trait alias",
            ItemKind::Impl(..) => "implementation",
        }
    }
}

/// A reference from an trait to one of its associated items. This
/// contains the item's id, naturally, but also the item's name and
/// some other high-level details (like whether it is an associated
/// type or method, and whether it is public). This allows other
/// passes to find the impl they want without loading the ID (which
/// means fewer edges in the incremental compilation graph).
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct TraitItemRef {
    pub id: TraitItemId,
    pub ident: Ident,
    pub kind: AssocItemKind,
    pub span: Span,
}

/// A reference from an impl to one of its associated items. This
/// contains the item's ID, naturally, but also the item's name and
/// some other high-level details (like whether it is an associated
/// type or method, and whether it is public). This allows other
/// passes to find the impl they want without loading the ID (which
/// means fewer edges in the incremental compilation graph).
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct ImplItemRef {
    pub id: ImplItemId,
    pub ident: Ident,
    pub kind: AssocItemKind,
    pub span: Span,
    /// When we are in a trait impl, link to the trait-item's id.
    pub trait_item_def_id: Option<DefId>,
}

#[derive(Copy, Clone, PartialEq, Debug, HashStable_Generic)]
pub enum AssocItemKind {
    Const,
    Fn { has_self: bool },
    Type,
}

// The bodies for items are stored "out of line", in a separate
// hashmap in the `Crate`. Here we just record the hir-id of the item
// so it can fetched later.
#[derive(Copy, Clone, PartialEq, Eq, Encodable, Decodable, Debug, HashStable_Generic)]
pub struct ForeignItemId {
    pub owner_id: OwnerId,
}

impl ForeignItemId {
    #[inline]
    pub fn hir_id(&self) -> HirId {
        // Items are always HIR owners.
        HirId::make_owner(self.owner_id.def_id)
    }
}

/// A reference from a foreign block to one of its items. This
/// contains the item's ID, naturally, but also the item's name and
/// some other high-level details (like whether it is an associated
/// type or method, and whether it is public). This allows other
/// passes to find the impl they want without loading the ID (which
/// means fewer edges in the incremental compilation graph).
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct ForeignItemRef {
    pub id: ForeignItemId,
    pub ident: Ident,
    pub span: Span,
}

#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct ForeignItem<'hir> {
    pub ident: Ident,
    pub kind: ForeignItemKind<'hir>,
    pub owner_id: OwnerId,
    pub span: Span,
    pub vis_span: Span,
}

impl ForeignItem<'_> {
    #[inline]
    pub fn hir_id(&self) -> HirId {
        // Items are always HIR owners.
        HirId::make_owner(self.owner_id.def_id)
    }

    pub fn foreign_item_id(&self) -> ForeignItemId {
        ForeignItemId { owner_id: self.owner_id }
    }
}

/// An item within an `extern` block.
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub enum ForeignItemKind<'hir> {
    /// A foreign function.
    Fn(&'hir FnDecl<'hir>, &'hir [Ident], &'hir Generics<'hir>),
    /// A foreign static item (`static ext: u8`).
    Static(&'hir Ty<'hir>, Mutability),
    /// A foreign type.
    Type,
}

/// A variable captured by a closure.
#[derive(Debug, Copy, Clone, HashStable_Generic)]
pub struct Upvar {
    /// First span where it is accessed (there can be multiple).
    pub span: Span,
}

// The TraitCandidate's import_ids is empty if the trait is defined in the same module, and
// has length > 0 if the trait is found through an chain of imports, starting with the
// import/use statement in the scope where the trait is used.
#[derive(Debug, Clone, HashStable_Generic)]
pub struct TraitCandidate {
    pub def_id: DefId,
    pub import_ids: SmallVec<[LocalDefId; 1]>,
}

#[derive(Copy, Clone, Debug, HashStable_Generic)]
pub enum OwnerNode<'hir> {
    Item(&'hir Item<'hir>),
    ForeignItem(&'hir ForeignItem<'hir>),
    TraitItem(&'hir TraitItem<'hir>),
    ImplItem(&'hir ImplItem<'hir>),
    Crate(&'hir Mod<'hir>),
}

impl<'hir> OwnerNode<'hir> {
    pub fn ident(&self) -> Option<Ident> {
        match self {
            OwnerNode::Item(Item { ident, .. })
            | OwnerNode::ForeignItem(ForeignItem { ident, .. })
            | OwnerNode::ImplItem(ImplItem { ident, .. })
            | OwnerNode::TraitItem(TraitItem { ident, .. }) => Some(*ident),
            OwnerNode::Crate(..) => None,
        }
    }

    pub fn span(&self) -> Span {
        match self {
            OwnerNode::Item(Item { span, .. })
            | OwnerNode::ForeignItem(ForeignItem { span, .. })
            | OwnerNode::ImplItem(ImplItem { span, .. })
            | OwnerNode::TraitItem(TraitItem { span, .. }) => *span,
            OwnerNode::Crate(Mod { spans: ModSpans { inner_span, .. }, .. }) => *inner_span,
        }
    }

    pub fn fn_sig(self) -> Option<&'hir FnSig<'hir>> {
        match self {
            OwnerNode::TraitItem(TraitItem { kind: TraitItemKind::Fn(fn_sig, _), .. })
            | OwnerNode::ImplItem(ImplItem { kind: ImplItemKind::Fn(fn_sig, _), .. })
            | OwnerNode::Item(Item { kind: ItemKind::Fn(fn_sig, _, _), .. }) => Some(fn_sig),
            _ => None,
        }
    }

    pub fn fn_decl(self) -> Option<&'hir FnDecl<'hir>> {
        match self {
            OwnerNode::TraitItem(TraitItem { kind: TraitItemKind::Fn(fn_sig, _), .. })
            | OwnerNode::ImplItem(ImplItem { kind: ImplItemKind::Fn(fn_sig, _), .. })
            | OwnerNode::Item(Item { kind: ItemKind::Fn(fn_sig, _, _), .. }) => Some(fn_sig.decl),
            OwnerNode::ForeignItem(ForeignItem {
                kind: ForeignItemKind::Fn(fn_decl, _, _),
                ..
            }) => Some(fn_decl),
            _ => None,
        }
    }

    pub fn body_id(&self) -> Option<BodyId> {
        match self {
            OwnerNode::Item(Item {
                kind:
                    ItemKind::Static(_, _, body)
                    | ItemKind::Const(_, _, body)
                    | ItemKind::Fn(_, _, body),
                ..
            })
            | OwnerNode::TraitItem(TraitItem {
                kind:
                    TraitItemKind::Fn(_, TraitFn::Provided(body)) | TraitItemKind::Const(_, Some(body)),
                ..
            })
            | OwnerNode::ImplItem(ImplItem {
                kind: ImplItemKind::Fn(_, body) | ImplItemKind::Const(_, body),
                ..
            }) => Some(*body),
            _ => None,
        }
    }

    pub fn generics(self) -> Option<&'hir Generics<'hir>> {
        Node::generics(self.into())
    }

    pub fn def_id(self) -> OwnerId {
        match self {
            OwnerNode::Item(Item { owner_id, .. })
            | OwnerNode::TraitItem(TraitItem { owner_id, .. })
            | OwnerNode::ImplItem(ImplItem { owner_id, .. })
            | OwnerNode::ForeignItem(ForeignItem { owner_id, .. }) => *owner_id,
            OwnerNode::Crate(..) => crate::CRATE_HIR_ID.owner,
        }
    }

    pub fn expect_item(self) -> &'hir Item<'hir> {
        match self {
            OwnerNode::Item(n) => n,
            _ => panic!(),
        }
    }

    pub fn expect_foreign_item(self) -> &'hir ForeignItem<'hir> {
        match self {
            OwnerNode::ForeignItem(n) => n,
            _ => panic!(),
        }
    }

    pub fn expect_impl_item(self) -> &'hir ImplItem<'hir> {
        match self {
            OwnerNode::ImplItem(n) => n,
            _ => panic!(),
        }
    }

    pub fn expect_trait_item(self) -> &'hir TraitItem<'hir> {
        match self {
            OwnerNode::TraitItem(n) => n,
            _ => panic!(),
        }
    }
}

impl<'hir> Into<OwnerNode<'hir>> for &'hir Item<'hir> {
    fn into(self) -> OwnerNode<'hir> {
        OwnerNode::Item(self)
    }
}

impl<'hir> Into<OwnerNode<'hir>> for &'hir ForeignItem<'hir> {
    fn into(self) -> OwnerNode<'hir> {
        OwnerNode::ForeignItem(self)
    }
}

impl<'hir> Into<OwnerNode<'hir>> for &'hir ImplItem<'hir> {
    fn into(self) -> OwnerNode<'hir> {
        OwnerNode::ImplItem(self)
    }
}

impl<'hir> Into<OwnerNode<'hir>> for &'hir TraitItem<'hir> {
    fn into(self) -> OwnerNode<'hir> {
        OwnerNode::TraitItem(self)
    }
}

impl<'hir> Into<Node<'hir>> for OwnerNode<'hir> {
    fn into(self) -> Node<'hir> {
        match self {
            OwnerNode::Item(n) => Node::Item(n),
            OwnerNode::ForeignItem(n) => Node::ForeignItem(n),
            OwnerNode::ImplItem(n) => Node::ImplItem(n),
            OwnerNode::TraitItem(n) => Node::TraitItem(n),
            OwnerNode::Crate(n) => Node::Crate(n),
        }
    }
}

#[derive(Copy, Clone, Debug, HashStable_Generic)]
pub enum Node<'hir> {
    Param(&'hir Param<'hir>),
    Item(&'hir Item<'hir>),
    ForeignItem(&'hir ForeignItem<'hir>),
    TraitItem(&'hir TraitItem<'hir>),
    ImplItem(&'hir ImplItem<'hir>),
    Variant(&'hir Variant<'hir>),
    Field(&'hir FieldDef<'hir>),
    AnonConst(&'hir AnonConst),
    ConstBlock(&'hir ConstBlock),
    Expr(&'hir Expr<'hir>),
    ExprField(&'hir ExprField<'hir>),
    Stmt(&'hir Stmt<'hir>),
    PathSegment(&'hir PathSegment<'hir>),
    Ty(&'hir Ty<'hir>),
    TypeBinding(&'hir TypeBinding<'hir>),
    TraitRef(&'hir TraitRef<'hir>),
    Pat(&'hir Pat<'hir>),
    PatField(&'hir PatField<'hir>),
    Arm(&'hir Arm<'hir>),
    Block(&'hir Block<'hir>),
    Local(&'hir Local<'hir>),

    /// `Ctor` refers to the constructor of an enum variant or struct. Only tuple or unit variants
    /// with synthesized constructors.
    Ctor(&'hir VariantData<'hir>),

    Lifetime(&'hir Lifetime),
    GenericParam(&'hir GenericParam<'hir>),

    Crate(&'hir Mod<'hir>),

    Infer(&'hir InferArg),
}

impl<'hir> Node<'hir> {
    /// Get the identifier of this `Node`, if applicable.
    ///
    /// # Edge cases
    ///
    /// Calling `.ident()` on a [`Node::Ctor`] will return `None`
    /// because `Ctor`s do not have identifiers themselves.
    /// Instead, call `.ident()` on the parent struct/variant, like so:
    ///
    /// ```ignore (illustrative)
    /// ctor
    ///     .ctor_hir_id()
    ///     .and_then(|ctor_id| tcx.hir().find_parent(ctor_id))
    ///     .and_then(|parent| parent.ident())
    /// ```
    pub fn ident(&self) -> Option<Ident> {
        match self {
            Node::TraitItem(TraitItem { ident, .. })
            | Node::ImplItem(ImplItem { ident, .. })
            | Node::ForeignItem(ForeignItem { ident, .. })
            | Node::Field(FieldDef { ident, .. })
            | Node::Variant(Variant { ident, .. })
            | Node::Item(Item { ident, .. })
            | Node::PathSegment(PathSegment { ident, .. }) => Some(*ident),
            Node::Lifetime(lt) => Some(lt.ident),
            Node::GenericParam(p) => Some(p.name.ident()),
            Node::TypeBinding(b) => Some(b.ident),
            Node::PatField(f) => Some(f.ident),
            Node::ExprField(f) => Some(f.ident),
            Node::Param(..)
            | Node::AnonConst(..)
            | Node::ConstBlock(..)
            | Node::Expr(..)
            | Node::Stmt(..)
            | Node::Block(..)
            | Node::Ctor(..)
            | Node::Pat(..)
            | Node::Arm(..)
            | Node::Local(..)
            | Node::Crate(..)
            | Node::Ty(..)
            | Node::TraitRef(..)
            | Node::Infer(..) => None,
        }
    }

    pub fn fn_decl(self) -> Option<&'hir FnDecl<'hir>> {
        match self {
            Node::TraitItem(TraitItem { kind: TraitItemKind::Fn(fn_sig, _), .. })
            | Node::ImplItem(ImplItem { kind: ImplItemKind::Fn(fn_sig, _), .. })
            | Node::Item(Item { kind: ItemKind::Fn(fn_sig, _, _), .. }) => Some(fn_sig.decl),
            Node::Expr(Expr { kind: ExprKind::Closure(Closure { fn_decl, .. }), .. })
            | Node::ForeignItem(ForeignItem { kind: ForeignItemKind::Fn(fn_decl, _, _), .. }) => {
                Some(fn_decl)
            }
            _ => None,
        }
    }

    pub fn fn_sig(self) -> Option<&'hir FnSig<'hir>> {
        match self {
            Node::TraitItem(TraitItem { kind: TraitItemKind::Fn(fn_sig, _), .. })
            | Node::ImplItem(ImplItem { kind: ImplItemKind::Fn(fn_sig, _), .. })
            | Node::Item(Item { kind: ItemKind::Fn(fn_sig, _, _), .. }) => Some(fn_sig),
            _ => None,
        }
    }

    /// Get the type for constants, assoc types, type aliases and statics.
    pub fn ty(self) -> Option<&'hir Ty<'hir>> {
        match self {
            Node::Item(it) => match it.kind {
                ItemKind::TyAlias(ty, _)
                | ItemKind::Static(ty, _, _)
                | ItemKind::Const(ty, _, _) => Some(ty),
                ItemKind::Impl(impl_item) => Some(&impl_item.self_ty),
                _ => None,
            },
            Node::TraitItem(it) => match it.kind {
                TraitItemKind::Const(ty, _) => Some(ty),
                TraitItemKind::Type(_, ty) => ty,
                _ => None,
            },
            Node::ImplItem(it) => match it.kind {
                ImplItemKind::Const(ty, _) => Some(ty),
                ImplItemKind::Type(ty) => Some(ty),
                _ => None,
            },
            _ => None,
        }
    }

    pub fn alias_ty(self) -> Option<&'hir Ty<'hir>> {
        match self {
            Node::Item(Item { kind: ItemKind::TyAlias(ty, ..), .. }) => Some(ty),
            _ => None,
        }
    }

    pub fn body_id(&self) -> Option<BodyId> {
        match self {
            Node::Item(Item {
                kind:
                    ItemKind::Static(_, _, body)
                    | ItemKind::Const(_, _, body)
                    | ItemKind::Fn(_, _, body),
                ..
            })
            | Node::TraitItem(TraitItem {
                kind:
                    TraitItemKind::Fn(_, TraitFn::Provided(body)) | TraitItemKind::Const(_, Some(body)),
                ..
            })
            | Node::ImplItem(ImplItem {
                kind: ImplItemKind::Fn(_, body) | ImplItemKind::Const(_, body),
                ..
            })
            | Node::Expr(Expr {
                kind:
                    ExprKind::ConstBlock(ConstBlock { body, .. })
                    | ExprKind::Closure(Closure { body, .. })
                    | ExprKind::Repeat(_, ArrayLen::Body(AnonConst { body, .. })),
                ..
            }) => Some(*body),
            _ => None,
        }
    }

    pub fn generics(self) -> Option<&'hir Generics<'hir>> {
        match self {
            Node::ForeignItem(ForeignItem {
                kind: ForeignItemKind::Fn(_, _, generics), ..
            })
            | Node::TraitItem(TraitItem { generics, .. })
            | Node::ImplItem(ImplItem { generics, .. }) => Some(generics),
            Node::Item(item) => item.kind.generics(),
            _ => None,
        }
    }

    pub fn as_owner(self) -> Option<OwnerNode<'hir>> {
        match self {
            Node::Item(i) => Some(OwnerNode::Item(i)),
            Node::ForeignItem(i) => Some(OwnerNode::ForeignItem(i)),
            Node::TraitItem(i) => Some(OwnerNode::TraitItem(i)),
            Node::ImplItem(i) => Some(OwnerNode::ImplItem(i)),
            Node::Crate(i) => Some(OwnerNode::Crate(i)),
            _ => None,
        }
    }

    pub fn fn_kind(self) -> Option<FnKind<'hir>> {
        match self {
            Node::Item(i) => match i.kind {
                ItemKind::Fn(ref sig, ref generics, _) => {
                    Some(FnKind::ItemFn(i.ident, generics, sig.header))
                }
                _ => None,
            },
            Node::TraitItem(ti) => match ti.kind {
                TraitItemKind::Fn(ref sig, TraitFn::Provided(_)) => {
                    Some(FnKind::Method(ti.ident, sig))
                }
                _ => None,
            },
            Node::ImplItem(ii) => match ii.kind {
                ImplItemKind::Fn(ref sig, _) => Some(FnKind::Method(ii.ident, sig)),
                _ => None,
            },
            Node::Expr(e) => match e.kind {
                ExprKind::Closure { .. } => Some(FnKind::Closure),
                _ => None,
            },
            _ => None,
        }
    }

    /// Get the fields for the tuple-constructor,
    /// if this node is a tuple constructor, otherwise None
    pub fn tuple_fields(&self) -> Option<&'hir [FieldDef<'hir>]> {
        if let Node::Ctor(&VariantData::Tuple(fields, _, _)) = self { Some(fields) } else { None }
    }

    /// Expect a [`Node::Param`] or panic.
    #[track_caller]
    pub fn expect_param(self) -> &'hir Param<'hir> {
        let Node::Param(this) = self else { self.expect_failed("a parameter") };
        this
    }

    /// Expect a [`Node::Item`] or panic.
    #[track_caller]
    pub fn expect_item(self) -> &'hir Item<'hir> {
        let Node::Item(this) = self else { self.expect_failed("a item") };
        this
    }

    /// Expect a [`Node::ForeignItem`] or panic.
    #[track_caller]
    pub fn expect_foreign_item(self) -> &'hir ForeignItem<'hir> {
        let Node::ForeignItem(this) = self else { self.expect_failed("a foreign item") };
        this
    }

    /// Expect a [`Node::TraitItem`] or panic.
    #[track_caller]
    pub fn expect_trait_item(self) -> &'hir TraitItem<'hir> {
        let Node::TraitItem(this) = self else { self.expect_failed("a trait item") };
        this
    }

    /// Expect a [`Node::ImplItem`] or panic.
    #[track_caller]
    pub fn expect_impl_item(self) -> &'hir ImplItem<'hir> {
        let Node::ImplItem(this) = self else { self.expect_failed("an implementation item") };
        this
    }

    /// Expect a [`Node::Variant`] or panic.
    #[track_caller]
    pub fn expect_variant(self) -> &'hir Variant<'hir> {
        let Node::Variant(this) = self else { self.expect_failed("a variant") };
        this
    }

    /// Expect a [`Node::Field`] or panic.
    #[track_caller]
    pub fn expect_field(self) -> &'hir FieldDef<'hir> {
        let Node::Field(this) = self else { self.expect_failed("a field definition") };
        this
    }

    /// Expect a [`Node::AnonConst`] or panic.
    #[track_caller]
    pub fn expect_anon_const(self) -> &'hir AnonConst {
        let Node::AnonConst(this) = self else { self.expect_failed("an anonymous constant") };
        this
    }

    /// Expect a [`Node::ConstBlock`] or panic.
    #[track_caller]
    pub fn expect_inline_const(self) -> &'hir ConstBlock {
        let Node::ConstBlock(this) = self else { self.expect_failed("an inline constant") };
        this
    }

    /// Expect a [`Node::Expr`] or panic.
    #[track_caller]
    pub fn expect_expr(self) -> &'hir Expr<'hir> {
        let Node::Expr(this) = self else { self.expect_failed("an expression") };
        this
    }
    /// Expect a [`Node::ExprField`] or panic.
    #[track_caller]
    pub fn expect_expr_field(self) -> &'hir ExprField<'hir> {
        let Node::ExprField(this) = self else { self.expect_failed("an expression field") };
        this
    }

    /// Expect a [`Node::Stmt`] or panic.
    #[track_caller]
    pub fn expect_stmt(self) -> &'hir Stmt<'hir> {
        let Node::Stmt(this) = self else { self.expect_failed("a statement") };
        this
    }

    /// Expect a [`Node::PathSegment`] or panic.
    #[track_caller]
    pub fn expect_path_segment(self) -> &'hir PathSegment<'hir> {
        let Node::PathSegment(this) = self else { self.expect_failed("a path segment") };
        this
    }

    /// Expect a [`Node::Ty`] or panic.
    #[track_caller]
    pub fn expect_ty(self) -> &'hir Ty<'hir> {
        let Node::Ty(this) = self else { self.expect_failed("a type") };
        this
    }

    /// Expect a [`Node::TypeBinding`] or panic.
    #[track_caller]
    pub fn expect_type_binding(self) -> &'hir TypeBinding<'hir> {
        let Node::TypeBinding(this) = self else { self.expect_failed("a type binding") };
        this
    }

    /// Expect a [`Node::TraitRef`] or panic.
    #[track_caller]
    pub fn expect_trait_ref(self) -> &'hir TraitRef<'hir> {
        let Node::TraitRef(this) = self else { self.expect_failed("a trait reference") };
        this
    }

    /// Expect a [`Node::Pat`] or panic.
    #[track_caller]
    pub fn expect_pat(self) -> &'hir Pat<'hir> {
        let Node::Pat(this) = self else { self.expect_failed("a pattern") };
        this
    }

    /// Expect a [`Node::PatField`] or panic.
    #[track_caller]
    pub fn expect_pat_field(self) -> &'hir PatField<'hir> {
        let Node::PatField(this) = self else { self.expect_failed("a pattern field") };
        this
    }

    /// Expect a [`Node::Arm`] or panic.
    #[track_caller]
    pub fn expect_arm(self) -> &'hir Arm<'hir> {
        let Node::Arm(this) = self else { self.expect_failed("an arm") };
        this
    }

    /// Expect a [`Node::Block`] or panic.
    #[track_caller]
    pub fn expect_block(self) -> &'hir Block<'hir> {
        let Node::Block(this) = self else { self.expect_failed("a block") };
        this
    }

    /// Expect a [`Node::Local`] or panic.
    #[track_caller]
    pub fn expect_local(self) -> &'hir Local<'hir> {
        let Node::Local(this) = self else { self.expect_failed("a local") };
        this
    }

    /// Expect a [`Node::Ctor`] or panic.
    #[track_caller]
    pub fn expect_ctor(self) -> &'hir VariantData<'hir> {
        let Node::Ctor(this) = self else { self.expect_failed("a constructor") };
        this
    }

    /// Expect a [`Node::Lifetime`] or panic.
    #[track_caller]
    pub fn expect_lifetime(self) -> &'hir Lifetime {
        let Node::Lifetime(this) = self else { self.expect_failed("a lifetime") };
        this
    }

    /// Expect a [`Node::GenericParam`] or panic.
    #[track_caller]
    pub fn expect_generic_param(self) -> &'hir GenericParam<'hir> {
        let Node::GenericParam(this) = self else { self.expect_failed("a generic parameter") };
        this
    }

    /// Expect a [`Node::Crate`] or panic.
    #[track_caller]
    pub fn expect_crate(self) -> &'hir Mod<'hir> {
        let Node::Crate(this) = self else { self.expect_failed("a crate") };
        this
    }

    /// Expect a [`Node::Infer`] or panic.
    #[track_caller]
    pub fn expect_infer(self) -> &'hir InferArg {
        let Node::Infer(this) = self else { self.expect_failed("an infer") };
        this
    }

    #[track_caller]
    fn expect_failed(&self, expected: &'static str) -> ! {
        panic!("expected {expected} node, found {self:?}")
    }
}

// Some nodes are used a lot. Make sure they don't unintentionally get bigger.
#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
mod size_asserts {
    use super::*;
    // tidy-alphabetical-start
    static_assert_size!(Block<'_>, 48);
    static_assert_size!(Body<'_>, 32);
    static_assert_size!(Expr<'_>, 64);
    static_assert_size!(ExprKind<'_>, 48);
    static_assert_size!(FnDecl<'_>, 40);
    static_assert_size!(ForeignItem<'_>, 72);
    static_assert_size!(ForeignItemKind<'_>, 40);
    static_assert_size!(GenericArg<'_>, 32);
    static_assert_size!(GenericBound<'_>, 48);
    static_assert_size!(Generics<'_>, 56);
    static_assert_size!(Impl<'_>, 80);
    static_assert_size!(ImplItem<'_>, 88);
    static_assert_size!(ImplItemKind<'_>, 40);
    static_assert_size!(Item<'_>, 88);
    static_assert_size!(ItemKind<'_>, 56);
    static_assert_size!(Local<'_>, 64);
    static_assert_size!(Param<'_>, 32);
    static_assert_size!(Pat<'_>, 72);
    static_assert_size!(Path<'_>, 40);
    static_assert_size!(PathSegment<'_>, 48);
    static_assert_size!(PatKind<'_>, 48);
    static_assert_size!(QPath<'_>, 24);
    static_assert_size!(Res, 12);
    static_assert_size!(Stmt<'_>, 32);
    static_assert_size!(StmtKind<'_>, 16);
    static_assert_size!(TraitItem<'_>, 88);
    static_assert_size!(TraitItemKind<'_>, 48);
    static_assert_size!(Ty<'_>, 48);
    static_assert_size!(TyKind<'_>, 32);
    // tidy-alphabetical-end
}

fn debug_fn(f: impl Fn(&mut fmt::Formatter<'_>) -> fmt::Result) -> impl fmt::Debug {
    struct DebugFn<F>(F);
    impl<F: Fn(&mut fmt::Formatter<'_>) -> fmt::Result> fmt::Debug for DebugFn<F> {
        fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
            (self.0)(fmt)
        }
    }
    DebugFn(f)
}