rustc_resolve/
diagnostics.rs

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
use rustc_ast::expand::StrippedCfgItem;
use rustc_ast::ptr::P;
use rustc_ast::visit::{self, Visitor};
use rustc_ast::{
    self as ast, CRATE_NODE_ID, Crate, ItemKind, MetaItemKind, ModKind, NestedMetaItem, NodeId,
    Path,
};
use rustc_ast_pretty::pprust;
use rustc_data_structures::fx::FxHashSet;
use rustc_errors::codes::*;
use rustc_errors::{
    Applicability, Diag, DiagCtxtHandle, ErrorGuaranteed, MultiSpan, SuggestionStyle,
    report_ambiguity_error, struct_span_code_err,
};
use rustc_feature::BUILTIN_ATTRIBUTES;
use rustc_hir::PrimTy;
use rustc_hir::def::Namespace::{self, *};
use rustc_hir::def::{self, CtorKind, CtorOf, DefKind, NonMacroAttrKind, PerNS};
use rustc_hir::def_id::{CRATE_DEF_ID, DefId};
use rustc_middle::bug;
use rustc_middle::ty::TyCtxt;
use rustc_session::Session;
use rustc_session::lint::builtin::{
    ABSOLUTE_PATHS_NOT_STARTING_WITH_CRATE, AMBIGUOUS_GLOB_IMPORTS,
    MACRO_EXPANDED_MACRO_EXPORTS_ACCESSED_BY_ABSOLUTE_PATHS,
};
use rustc_session::lint::{AmbiguityErrorDiag, BuiltinLintDiag};
use rustc_span::edit_distance::find_best_match_for_name;
use rustc_span::edition::Edition;
use rustc_span::hygiene::MacroKind;
use rustc_span::source_map::SourceMap;
use rustc_span::symbol::{Ident, Symbol, kw, sym};
use rustc_span::{BytePos, Span, SyntaxContext};
use thin_vec::{ThinVec, thin_vec};
use tracing::debug;

use crate::errors::{
    self, AddedMacroUse, ChangeImportBinding, ChangeImportBindingSuggestion, ConsiderAddingADerive,
    ExplicitUnsafeTraits, MacroDefinedLater, MacroSuggMovePosition, MaybeMissingMacroRulesName,
};
use crate::imports::{Import, ImportKind};
use crate::late::{PatternSource, Rib};
use crate::{
    AmbiguityError, AmbiguityErrorMisc, AmbiguityKind, BindingError, BindingKey, Finalize,
    HasGenericParams, LexicalScopeBinding, MacroRulesScope, Module, ModuleKind,
    ModuleOrUniformRoot, NameBinding, NameBindingKind, ParentScope, PathResult, PrivacyError,
    ResolutionError, Resolver, Scope, ScopeSet, Segment, UseError, Used, VisResolutionError,
    errors as errs, path_names_to_string,
};

type Res = def::Res<ast::NodeId>;

/// A vector of spans and replacements, a message and applicability.
pub(crate) type Suggestion = (Vec<(Span, String)>, String, Applicability);

/// Potential candidate for an undeclared or out-of-scope label - contains the ident of a
/// similarly named label and whether or not it is reachable.
pub(crate) type LabelSuggestion = (Ident, bool);

#[derive(Debug)]
pub(crate) enum SuggestionTarget {
    /// The target has a similar name as the name used by the programmer (probably a typo)
    SimilarlyNamed,
    /// The target is the only valid item that can be used in the corresponding context
    SingleItem,
}

#[derive(Debug)]
pub(crate) struct TypoSuggestion {
    pub candidate: Symbol,
    /// The source location where the name is defined; None if the name is not defined
    /// in source e.g. primitives
    pub span: Option<Span>,
    pub res: Res,
    pub target: SuggestionTarget,
}

impl TypoSuggestion {
    pub(crate) fn typo_from_ident(ident: Ident, res: Res) -> TypoSuggestion {
        Self {
            candidate: ident.name,
            span: Some(ident.span),
            res,
            target: SuggestionTarget::SimilarlyNamed,
        }
    }
    pub(crate) fn typo_from_name(candidate: Symbol, res: Res) -> TypoSuggestion {
        Self { candidate, span: None, res, target: SuggestionTarget::SimilarlyNamed }
    }
    pub(crate) fn single_item_from_ident(ident: Ident, res: Res) -> TypoSuggestion {
        Self {
            candidate: ident.name,
            span: Some(ident.span),
            res,
            target: SuggestionTarget::SingleItem,
        }
    }
}

/// A free importable items suggested in case of resolution failure.
#[derive(Debug, Clone)]
pub(crate) struct ImportSuggestion {
    pub did: Option<DefId>,
    pub descr: &'static str,
    pub path: Path,
    pub accessible: bool,
    // false if the path traverses a foreign `#[doc(hidden)]` item.
    pub doc_visible: bool,
    pub via_import: bool,
    /// An extra note that should be issued if this item is suggested
    pub note: Option<String>,
}

/// Adjust the impl span so that just the `impl` keyword is taken by removing
/// everything after `<` (`"impl<T> Iterator for A<T> {}" -> "impl"`) and
/// everything after the first whitespace (`"impl Iterator for A" -> "impl"`).
///
/// *Attention*: the method used is very fragile since it essentially duplicates the work of the
/// parser. If you need to use this function or something similar, please consider updating the
/// `source_map` functions and this function to something more robust.
fn reduce_impl_span_to_impl_keyword(sm: &SourceMap, impl_span: Span) -> Span {
    let impl_span = sm.span_until_char(impl_span, '<');
    sm.span_until_whitespace(impl_span)
}

impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
    pub(crate) fn dcx(&self) -> DiagCtxtHandle<'tcx> {
        self.tcx.dcx()
    }

    pub(crate) fn report_errors(&mut self, krate: &Crate) {
        self.report_with_use_injections(krate);

        for &(span_use, span_def) in &self.macro_expanded_macro_export_errors {
            self.lint_buffer.buffer_lint(
                MACRO_EXPANDED_MACRO_EXPORTS_ACCESSED_BY_ABSOLUTE_PATHS,
                CRATE_NODE_ID,
                span_use,
                BuiltinLintDiag::MacroExpandedMacroExportsAccessedByAbsolutePaths(span_def),
            );
        }

        for ambiguity_error in &self.ambiguity_errors {
            let diag = self.ambiguity_diagnostics(ambiguity_error);
            if ambiguity_error.warning {
                let NameBindingKind::Import { import, .. } = ambiguity_error.b1.0.kind else {
                    unreachable!()
                };
                self.lint_buffer.buffer_lint(
                    AMBIGUOUS_GLOB_IMPORTS,
                    import.root_id,
                    ambiguity_error.ident.span,
                    BuiltinLintDiag::AmbiguousGlobImports { diag },
                );
            } else {
                let mut err = struct_span_code_err!(self.dcx(), diag.span, E0659, "{}", diag.msg);
                report_ambiguity_error(&mut err, diag);
                err.emit();
            }
        }

        let mut reported_spans = FxHashSet::default();
        for error in std::mem::take(&mut self.privacy_errors) {
            if reported_spans.insert(error.dedup_span) {
                self.report_privacy_error(&error);
            }
        }
    }

    fn report_with_use_injections(&mut self, krate: &Crate) {
        for UseError { mut err, candidates, def_id, instead, suggestion, path, is_call } in
            self.use_injections.drain(..)
        {
            let (span, found_use) = if let Some(def_id) = def_id.as_local() {
                UsePlacementFinder::check(krate, self.def_id_to_node_id[def_id])
            } else {
                (None, FoundUse::No)
            };

            if !candidates.is_empty() {
                show_candidates(
                    self.tcx,
                    &mut err,
                    span,
                    &candidates,
                    if instead { Instead::Yes } else { Instead::No },
                    found_use,
                    DiagMode::Normal,
                    path,
                    "",
                );
                err.emit();
            } else if let Some((span, msg, sugg, appl)) = suggestion {
                err.span_suggestion_verbose(span, msg, sugg, appl);
                err.emit();
            } else if let [segment] = path.as_slice()
                && is_call
            {
                err.stash(segment.ident.span, rustc_errors::StashKey::CallIntoMethod);
            } else {
                err.emit();
            }
        }
    }

    pub(crate) fn report_conflict(
        &mut self,
        parent: Module<'_>,
        ident: Ident,
        ns: Namespace,
        new_binding: NameBinding<'ra>,
        old_binding: NameBinding<'ra>,
    ) {
        // Error on the second of two conflicting names
        if old_binding.span.lo() > new_binding.span.lo() {
            return self.report_conflict(parent, ident, ns, old_binding, new_binding);
        }

        let container = match parent.kind {
            // Avoid using TyCtxt::def_kind_descr in the resolver, because it
            // indirectly *calls* the resolver, and would cause a query cycle.
            ModuleKind::Def(kind, _, _) => kind.descr(parent.def_id()),
            ModuleKind::Block => "block",
        };

        let (name, span) =
            (ident.name, self.tcx.sess.source_map().guess_head_span(new_binding.span));

        if let Some(s) = self.name_already_seen.get(&name) {
            if s == &span {
                return;
            }
        }

        let old_kind = match (ns, old_binding.module()) {
            (ValueNS, _) => "value",
            (MacroNS, _) => "macro",
            (TypeNS, _) if old_binding.is_extern_crate() => "extern crate",
            (TypeNS, Some(module)) if module.is_normal() => "module",
            (TypeNS, Some(module)) if module.is_trait() => "trait",
            (TypeNS, _) => "type",
        };

        let code = match (old_binding.is_extern_crate(), new_binding.is_extern_crate()) {
            (true, true) => E0259,
            (true, _) | (_, true) => match new_binding.is_import() && old_binding.is_import() {
                true => E0254,
                false => E0260,
            },
            _ => match (old_binding.is_import_user_facing(), new_binding.is_import_user_facing()) {
                (false, false) => E0428,
                (true, true) => E0252,
                _ => E0255,
            },
        };

        let label = match new_binding.is_import_user_facing() {
            true => errors::NameDefinedMultipleTimeLabel::Reimported { span, name },
            false => errors::NameDefinedMultipleTimeLabel::Redefined { span, name },
        };

        let old_binding_label =
            (!old_binding.span.is_dummy() && old_binding.span != span).then(|| {
                let span = self.tcx.sess.source_map().guess_head_span(old_binding.span);
                match old_binding.is_import_user_facing() {
                    true => errors::NameDefinedMultipleTimeOldBindingLabel::Import {
                        span,
                        name,
                        old_kind,
                    },
                    false => errors::NameDefinedMultipleTimeOldBindingLabel::Definition {
                        span,
                        name,
                        old_kind,
                    },
                }
            });

        let mut err = self
            .dcx()
            .create_err(errors::NameDefinedMultipleTime {
                span,
                descr: ns.descr(),
                container,
                label,
                old_binding_label,
            })
            .with_code(code);

        // See https://github.com/rust-lang/rust/issues/32354
        use NameBindingKind::Import;
        let can_suggest = |binding: NameBinding<'_>, import: self::Import<'_>| {
            !binding.span.is_dummy()
                && !matches!(import.kind, ImportKind::MacroUse { .. } | ImportKind::MacroExport)
        };
        let import = match (&new_binding.kind, &old_binding.kind) {
            // If there are two imports where one or both have attributes then prefer removing the
            // import without attributes.
            (Import { import: new, .. }, Import { import: old, .. })
                if {
                    (new.has_attributes || old.has_attributes)
                        && can_suggest(old_binding, *old)
                        && can_suggest(new_binding, *new)
                } =>
            {
                if old.has_attributes {
                    Some((*new, new_binding.span, true))
                } else {
                    Some((*old, old_binding.span, true))
                }
            }
            // Otherwise prioritize the new binding.
            (Import { import, .. }, other) if can_suggest(new_binding, *import) => {
                Some((*import, new_binding.span, other.is_import()))
            }
            (other, Import { import, .. }) if can_suggest(old_binding, *import) => {
                Some((*import, old_binding.span, other.is_import()))
            }
            _ => None,
        };

        // Check if the target of the use for both bindings is the same.
        let duplicate = new_binding.res().opt_def_id() == old_binding.res().opt_def_id();
        let has_dummy_span = new_binding.span.is_dummy() || old_binding.span.is_dummy();
        let from_item =
            self.extern_prelude.get(&ident).map_or(true, |entry| entry.introduced_by_item);
        // Only suggest removing an import if both bindings are to the same def, if both spans
        // aren't dummy spans. Further, if both bindings are imports, then the ident must have
        // been introduced by an item.
        let should_remove_import = duplicate
            && !has_dummy_span
            && ((new_binding.is_extern_crate() || old_binding.is_extern_crate()) || from_item);

        match import {
            Some((import, span, true)) if should_remove_import && import.is_nested() => {
                self.add_suggestion_for_duplicate_nested_use(&mut err, import, span);
            }
            Some((import, _, true)) if should_remove_import && !import.is_glob() => {
                // Simple case - remove the entire import. Due to the above match arm, this can
                // only be a single use so just remove it entirely.
                err.subdiagnostic(errors::ToolOnlyRemoveUnnecessaryImport {
                    span: import.use_span_with_attributes,
                });
            }
            Some((import, span, _)) => {
                self.add_suggestion_for_rename_of_use(&mut err, name, import, span);
            }
            _ => {}
        }

        err.emit();
        self.name_already_seen.insert(name, span);
    }

    /// This function adds a suggestion to change the binding name of a new import that conflicts
    /// with an existing import.
    ///
    /// ```text,ignore (diagnostic)
    /// help: you can use `as` to change the binding name of the import
    ///    |
    /// LL | use foo::bar as other_bar;
    ///    |     ^^^^^^^^^^^^^^^^^^^^^
    /// ```
    fn add_suggestion_for_rename_of_use(
        &self,
        err: &mut Diag<'_>,
        name: Symbol,
        import: Import<'_>,
        binding_span: Span,
    ) {
        let suggested_name = if name.as_str().chars().next().unwrap().is_uppercase() {
            format!("Other{name}")
        } else {
            format!("other_{name}")
        };

        let mut suggestion = None;
        let mut span = binding_span;
        match import.kind {
            ImportKind::Single { type_ns_only: true, .. } => {
                suggestion = Some(format!("self as {suggested_name}"))
            }
            ImportKind::Single { source, .. } => {
                if let Some(pos) =
                    source.span.hi().0.checked_sub(binding_span.lo().0).map(|pos| pos as usize)
                {
                    if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(binding_span) {
                        if pos <= snippet.len() {
                            span = binding_span
                                .with_lo(binding_span.lo() + BytePos(pos as u32))
                                .with_hi(
                                    binding_span.hi()
                                        - BytePos(if snippet.ends_with(';') { 1 } else { 0 }),
                                );
                            suggestion = Some(format!(" as {suggested_name}"));
                        }
                    }
                }
            }
            ImportKind::ExternCrate { source, target, .. } => {
                suggestion = Some(format!(
                    "extern crate {} as {};",
                    source.unwrap_or(target.name),
                    suggested_name,
                ))
            }
            _ => unreachable!(),
        }

        if let Some(suggestion) = suggestion {
            err.subdiagnostic(ChangeImportBindingSuggestion { span, suggestion });
        } else {
            err.subdiagnostic(ChangeImportBinding { span });
        }
    }

    /// This function adds a suggestion to remove an unnecessary binding from an import that is
    /// nested. In the following example, this function will be invoked to remove the `a` binding
    /// in the second use statement:
    ///
    /// ```ignore (diagnostic)
    /// use issue_52891::a;
    /// use issue_52891::{d, a, e};
    /// ```
    ///
    /// The following suggestion will be added:
    ///
    /// ```ignore (diagnostic)
    /// use issue_52891::{d, a, e};
    ///                      ^-- help: remove unnecessary import
    /// ```
    ///
    /// If the nested use contains only one import then the suggestion will remove the entire
    /// line.
    ///
    /// It is expected that the provided import is nested - this isn't checked by the
    /// function. If this invariant is not upheld, this function's behaviour will be unexpected
    /// as characters expected by span manipulations won't be present.
    fn add_suggestion_for_duplicate_nested_use(
        &self,
        err: &mut Diag<'_>,
        import: Import<'_>,
        binding_span: Span,
    ) {
        assert!(import.is_nested());

        // Two examples will be used to illustrate the span manipulations we're doing:
        //
        // - Given `use issue_52891::{d, a, e};` where `a` is a duplicate then `binding_span` is
        //   `a` and `import.use_span` is `issue_52891::{d, a, e};`.
        // - Given `use issue_52891::{d, e, a};` where `a` is a duplicate then `binding_span` is
        //   `a` and `import.use_span` is `issue_52891::{d, e, a};`.

        let (found_closing_brace, span) =
            find_span_of_binding_until_next_binding(self.tcx.sess, binding_span, import.use_span);

        // If there was a closing brace then identify the span to remove any trailing commas from
        // previous imports.
        if found_closing_brace {
            if let Some(span) = extend_span_to_previous_binding(self.tcx.sess, span) {
                err.subdiagnostic(errors::ToolOnlyRemoveUnnecessaryImport { span });
            } else {
                // Remove the entire line if we cannot extend the span back, this indicates an
                // `issue_52891::{self}` case.
                err.subdiagnostic(errors::RemoveUnnecessaryImport {
                    span: import.use_span_with_attributes,
                });
            }

            return;
        }

        err.subdiagnostic(errors::RemoveUnnecessaryImport { span });
    }

    pub(crate) fn lint_if_path_starts_with_module(
        &mut self,
        finalize: Option<Finalize>,
        path: &[Segment],
        second_binding: Option<NameBinding<'_>>,
    ) {
        let Some(Finalize { node_id, root_span, .. }) = finalize else {
            return;
        };

        let first_name = match path.get(0) {
            // In the 2018 edition this lint is a hard error, so nothing to do
            Some(seg) if seg.ident.span.is_rust_2015() && self.tcx.sess.is_rust_2015() => {
                seg.ident.name
            }
            _ => return,
        };

        // We're only interested in `use` paths which should start with
        // `{{root}}` currently.
        if first_name != kw::PathRoot {
            return;
        }

        match path.get(1) {
            // If this import looks like `crate::...` it's already good
            Some(Segment { ident, .. }) if ident.name == kw::Crate => return,
            // Otherwise go below to see if it's an extern crate
            Some(_) => {}
            // If the path has length one (and it's `PathRoot` most likely)
            // then we don't know whether we're gonna be importing a crate or an
            // item in our crate. Defer this lint to elsewhere
            None => return,
        }

        // If the first element of our path was actually resolved to an
        // `ExternCrate` (also used for `crate::...`) then no need to issue a
        // warning, this looks all good!
        if let Some(binding) = second_binding {
            if let NameBindingKind::Import { import, .. } = binding.kind {
                // Careful: we still want to rewrite paths from renamed extern crates.
                if let ImportKind::ExternCrate { source: None, .. } = import.kind {
                    return;
                }
            }
        }

        let diag = BuiltinLintDiag::AbsPathWithModule(root_span);
        self.lint_buffer.buffer_lint(
            ABSOLUTE_PATHS_NOT_STARTING_WITH_CRATE,
            node_id,
            root_span,
            diag,
        );
    }

    pub(crate) fn add_module_candidates(
        &mut self,
        module: Module<'ra>,
        names: &mut Vec<TypoSuggestion>,
        filter_fn: &impl Fn(Res) -> bool,
        ctxt: Option<SyntaxContext>,
    ) {
        for (key, resolution) in self.resolutions(module).borrow().iter() {
            if let Some(binding) = resolution.borrow().binding {
                let res = binding.res();
                if filter_fn(res) && ctxt.map_or(true, |ctxt| ctxt == key.ident.span.ctxt()) {
                    names.push(TypoSuggestion::typo_from_ident(key.ident, res));
                }
            }
        }
    }

    /// Combines an error with provided span and emits it.
    ///
    /// This takes the error provided, combines it with the span and any additional spans inside the
    /// error and emits it.
    pub(crate) fn report_error(
        &mut self,
        span: Span,
        resolution_error: ResolutionError<'ra>,
    ) -> ErrorGuaranteed {
        self.into_struct_error(span, resolution_error).emit()
    }

    pub(crate) fn into_struct_error(
        &mut self,
        span: Span,
        resolution_error: ResolutionError<'ra>,
    ) -> Diag<'_> {
        match resolution_error {
            ResolutionError::GenericParamsFromOuterItem(
                outer_res,
                has_generic_params,
                def_kind,
            ) => {
                use errs::GenericParamsFromOuterItemLabel as Label;
                let static_or_const = match def_kind {
                    DefKind::Static { .. } => {
                        Some(errs::GenericParamsFromOuterItemStaticOrConst::Static)
                    }
                    DefKind::Const => Some(errs::GenericParamsFromOuterItemStaticOrConst::Const),
                    _ => None,
                };
                let is_self =
                    matches!(outer_res, Res::SelfTyParam { .. } | Res::SelfTyAlias { .. });
                let mut err = errs::GenericParamsFromOuterItem {
                    span,
                    label: None,
                    refer_to_type_directly: None,
                    sugg: None,
                    static_or_const,
                    is_self,
                };

                let sm = self.tcx.sess.source_map();
                let def_id = match outer_res {
                    Res::SelfTyParam { .. } => {
                        err.label = Some(Label::SelfTyParam(span));
                        return self.dcx().create_err(err);
                    }
                    Res::SelfTyAlias { alias_to: def_id, .. } => {
                        err.label = Some(Label::SelfTyAlias(reduce_impl_span_to_impl_keyword(
                            sm,
                            self.def_span(def_id),
                        )));
                        err.refer_to_type_directly = Some(span);
                        return self.dcx().create_err(err);
                    }
                    Res::Def(DefKind::TyParam, def_id) => {
                        err.label = Some(Label::TyParam(self.def_span(def_id)));
                        def_id
                    }
                    Res::Def(DefKind::ConstParam, def_id) => {
                        err.label = Some(Label::ConstParam(self.def_span(def_id)));
                        def_id
                    }
                    _ => {
                        bug!(
                            "GenericParamsFromOuterItem should only be used with \
                            Res::SelfTyParam, Res::SelfTyAlias, DefKind::TyParam or \
                            DefKind::ConstParam"
                        );
                    }
                };

                if let HasGenericParams::Yes(span) = has_generic_params {
                    let name = self.tcx.item_name(def_id);
                    let (span, snippet) = if span.is_empty() {
                        let snippet = format!("<{name}>");
                        (span, snippet)
                    } else {
                        let span = sm.span_through_char(span, '<').shrink_to_hi();
                        let snippet = format!("{name}, ");
                        (span, snippet)
                    };
                    err.sugg = Some(errs::GenericParamsFromOuterItemSugg { span, snippet });
                }

                self.dcx().create_err(err)
            }
            ResolutionError::NameAlreadyUsedInParameterList(name, first_use_span) => self
                .dcx()
                .create_err(errs::NameAlreadyUsedInParameterList { span, first_use_span, name }),
            ResolutionError::MethodNotMemberOfTrait(method, trait_, candidate) => {
                self.dcx().create_err(errs::MethodNotMemberOfTrait {
                    span,
                    method,
                    trait_,
                    sub: candidate.map(|c| errs::AssociatedFnWithSimilarNameExists {
                        span: method.span,
                        candidate: c,
                    }),
                })
            }
            ResolutionError::TypeNotMemberOfTrait(type_, trait_, candidate) => {
                self.dcx().create_err(errs::TypeNotMemberOfTrait {
                    span,
                    type_,
                    trait_,
                    sub: candidate.map(|c| errs::AssociatedTypeWithSimilarNameExists {
                        span: type_.span,
                        candidate: c,
                    }),
                })
            }
            ResolutionError::ConstNotMemberOfTrait(const_, trait_, candidate) => {
                self.dcx().create_err(errs::ConstNotMemberOfTrait {
                    span,
                    const_,
                    trait_,
                    sub: candidate.map(|c| errs::AssociatedConstWithSimilarNameExists {
                        span: const_.span,
                        candidate: c,
                    }),
                })
            }
            ResolutionError::VariableNotBoundInPattern(binding_error, parent_scope) => {
                let BindingError { name, target, origin, could_be_path } = binding_error;

                let target_sp = target.iter().copied().collect::<Vec<_>>();
                let origin_sp = origin.iter().copied().collect::<Vec<_>>();

                let msp = MultiSpan::from_spans(target_sp.clone());
                let mut err = self
                    .dcx()
                    .create_err(errors::VariableIsNotBoundInAllPatterns { multispan: msp, name });
                for sp in target_sp {
                    err.subdiagnostic(errors::PatternDoesntBindName { span: sp, name });
                }
                for sp in origin_sp {
                    err.subdiagnostic(errors::VariableNotInAllPatterns { span: sp });
                }
                if could_be_path {
                    let import_suggestions = self.lookup_import_candidates(
                        Ident::with_dummy_span(name),
                        Namespace::ValueNS,
                        &parent_scope,
                        &|res: Res| {
                            matches!(
                                res,
                                Res::Def(
                                    DefKind::Ctor(CtorOf::Variant, CtorKind::Const)
                                        | DefKind::Ctor(CtorOf::Struct, CtorKind::Const)
                                        | DefKind::Const
                                        | DefKind::AssocConst,
                                    _,
                                )
                            )
                        },
                    );

                    if import_suggestions.is_empty() {
                        let help_msg = format!(
                            "if you meant to match on a variant or a `const` item, consider \
                             making the path in the pattern qualified: `path::to::ModOrType::{name}`",
                        );
                        err.span_help(span, help_msg);
                    }
                    show_candidates(
                        self.tcx,
                        &mut err,
                        Some(span),
                        &import_suggestions,
                        Instead::No,
                        FoundUse::Yes,
                        DiagMode::Pattern,
                        vec![],
                        "",
                    );
                }
                err
            }
            ResolutionError::VariableBoundWithDifferentMode(variable_name, first_binding_span) => {
                self.dcx().create_err(errs::VariableBoundWithDifferentMode {
                    span,
                    first_binding_span,
                    variable_name,
                })
            }
            ResolutionError::IdentifierBoundMoreThanOnceInParameterList(identifier) => self
                .dcx()
                .create_err(errs::IdentifierBoundMoreThanOnceInParameterList { span, identifier }),
            ResolutionError::IdentifierBoundMoreThanOnceInSamePattern(identifier) => self
                .dcx()
                .create_err(errs::IdentifierBoundMoreThanOnceInSamePattern { span, identifier }),
            ResolutionError::UndeclaredLabel { name, suggestion } => {
                let ((sub_reachable, sub_reachable_suggestion), sub_unreachable) = match suggestion
                {
                    // A reachable label with a similar name exists.
                    Some((ident, true)) => (
                        (
                            Some(errs::LabelWithSimilarNameReachable(ident.span)),
                            Some(errs::TryUsingSimilarlyNamedLabel {
                                span,
                                ident_name: ident.name,
                            }),
                        ),
                        None,
                    ),
                    // An unreachable label with a similar name exists.
                    Some((ident, false)) => (
                        (None, None),
                        Some(errs::UnreachableLabelWithSimilarNameExists {
                            ident_span: ident.span,
                        }),
                    ),
                    // No similarly-named labels exist.
                    None => ((None, None), None),
                };
                self.dcx().create_err(errs::UndeclaredLabel {
                    span,
                    name,
                    sub_reachable,
                    sub_reachable_suggestion,
                    sub_unreachable,
                })
            }
            ResolutionError::SelfImportsOnlyAllowedWithin { root, span_with_rename } => {
                // None of the suggestions below would help with a case like `use self`.
                let (suggestion, mpart_suggestion) = if root {
                    (None, None)
                } else {
                    // use foo::bar::self        -> foo::bar
                    // use foo::bar::self as abc -> foo::bar as abc
                    let suggestion = errs::SelfImportsOnlyAllowedWithinSuggestion { span };

                    // use foo::bar::self        -> foo::bar::{self}
                    // use foo::bar::self as abc -> foo::bar::{self as abc}
                    let mpart_suggestion = errs::SelfImportsOnlyAllowedWithinMultipartSuggestion {
                        multipart_start: span_with_rename.shrink_to_lo(),
                        multipart_end: span_with_rename.shrink_to_hi(),
                    };
                    (Some(suggestion), Some(mpart_suggestion))
                };
                self.dcx().create_err(errs::SelfImportsOnlyAllowedWithin {
                    span,
                    suggestion,
                    mpart_suggestion,
                })
            }
            ResolutionError::SelfImportCanOnlyAppearOnceInTheList => {
                self.dcx().create_err(errs::SelfImportCanOnlyAppearOnceInTheList { span })
            }
            ResolutionError::SelfImportOnlyInImportListWithNonEmptyPrefix => {
                self.dcx().create_err(errs::SelfImportOnlyInImportListWithNonEmptyPrefix { span })
            }
            ResolutionError::FailedToResolve { segment, label, suggestion, module } => {
                let mut err =
                    struct_span_code_err!(self.dcx(), span, E0433, "failed to resolve: {label}");
                err.span_label(span, label);

                if let Some((suggestions, msg, applicability)) = suggestion {
                    if suggestions.is_empty() {
                        err.help(msg);
                        return err;
                    }
                    err.multipart_suggestion(msg, suggestions, applicability);
                }

                if let Some(ModuleOrUniformRoot::Module(module)) = module
                    && let Some(module) = module.opt_def_id()
                    && let Some(segment) = segment
                {
                    self.find_cfg_stripped(&mut err, &segment, module);
                }

                err
            }
            ResolutionError::CannotCaptureDynamicEnvironmentInFnItem => {
                self.dcx().create_err(errs::CannotCaptureDynamicEnvironmentInFnItem { span })
            }
            ResolutionError::AttemptToUseNonConstantValueInConstant {
                ident,
                suggestion,
                current,
                type_span,
            } => {
                // let foo =...
                //     ^^^ given this Span
                // ------- get this Span to have an applicable suggestion

                // edit:
                // only do this if the const and usage of the non-constant value are on the same line
                // the further the two are apart, the higher the chance of the suggestion being wrong

                let sp = self
                    .tcx
                    .sess
                    .source_map()
                    .span_extend_to_prev_str(ident.span, current, true, false);

                let ((with, with_label), without) = match sp {
                    Some(sp) if !self.tcx.sess.source_map().is_multiline(sp) => {
                        let sp = sp
                            .with_lo(BytePos(sp.lo().0 - (current.len() as u32)))
                            .until(ident.span);
                        (
                        (Some(errs::AttemptToUseNonConstantValueInConstantWithSuggestion {
                                span: sp,
                                suggestion,
                                current,
                                type_span,
                            }), Some(errs::AttemptToUseNonConstantValueInConstantLabelWithSuggestion {span})),
                            None,
                        )
                    }
                    _ => (
                        (None, None),
                        Some(errs::AttemptToUseNonConstantValueInConstantWithoutSuggestion {
                            ident_span: ident.span,
                            suggestion,
                        }),
                    ),
                };

                self.dcx().create_err(errs::AttemptToUseNonConstantValueInConstant {
                    span,
                    with,
                    with_label,
                    without,
                })
            }
            ResolutionError::BindingShadowsSomethingUnacceptable {
                shadowing_binding,
                name,
                participle,
                article,
                shadowed_binding,
                shadowed_binding_span,
            } => self.dcx().create_err(errs::BindingShadowsSomethingUnacceptable {
                span,
                shadowing_binding,
                shadowed_binding,
                article,
                sub_suggestion: match (shadowing_binding, shadowed_binding) {
                    (
                        PatternSource::Match,
                        Res::Def(DefKind::Ctor(CtorOf::Variant | CtorOf::Struct, CtorKind::Fn), _),
                    ) => Some(errs::BindingShadowsSomethingUnacceptableSuggestion { span, name }),
                    _ => None,
                },
                shadowed_binding_span,
                participle,
                name,
            }),
            ResolutionError::ForwardDeclaredGenericParam => {
                self.dcx().create_err(errs::ForwardDeclaredGenericParam { span })
            }
            ResolutionError::ParamInTyOfConstParam { name, param_kind: is_type } => self
                .dcx()
                .create_err(errs::ParamInTyOfConstParam { span, name, param_kind: is_type }),
            ResolutionError::ParamInNonTrivialAnonConst { name, param_kind: is_type } => {
                self.dcx().create_err(errs::ParamInNonTrivialAnonConst {
                    span,
                    name,
                    param_kind: is_type,
                    help: self
                        .tcx
                        .sess
                        .is_nightly_build()
                        .then_some(errs::ParamInNonTrivialAnonConstHelp),
                })
            }
            ResolutionError::ParamInEnumDiscriminant { name, param_kind: is_type } => self
                .dcx()
                .create_err(errs::ParamInEnumDiscriminant { span, name, param_kind: is_type }),
            ResolutionError::SelfInGenericParamDefault => {
                self.dcx().create_err(errs::SelfInGenericParamDefault { span })
            }
            ResolutionError::UnreachableLabel { name, definition_span, suggestion } => {
                let ((sub_suggestion_label, sub_suggestion), sub_unreachable_label) =
                    match suggestion {
                        // A reachable label with a similar name exists.
                        Some((ident, true)) => (
                            (
                                Some(errs::UnreachableLabelSubLabel { ident_span: ident.span }),
                                Some(errs::UnreachableLabelSubSuggestion {
                                    span,
                                    // intentionally taking 'ident.name' instead of 'ident' itself, as this
                                    // could be used in suggestion context
                                    ident_name: ident.name,
                                }),
                            ),
                            None,
                        ),
                        // An unreachable label with a similar name exists.
                        Some((ident, false)) => (
                            (None, None),
                            Some(errs::UnreachableLabelSubLabelUnreachable {
                                ident_span: ident.span,
                            }),
                        ),
                        // No similarly-named labels exist.
                        None => ((None, None), None),
                    };
                self.dcx().create_err(errs::UnreachableLabel {
                    span,
                    name,
                    definition_span,
                    sub_suggestion,
                    sub_suggestion_label,
                    sub_unreachable_label,
                })
            }
            ResolutionError::TraitImplMismatch {
                name,
                kind,
                code,
                trait_item_span,
                trait_path,
            } => self
                .dcx()
                .create_err(errors::TraitImplMismatch {
                    span,
                    name,
                    kind,
                    trait_path,
                    trait_item_span,
                })
                .with_code(code),
            ResolutionError::TraitImplDuplicate { name, trait_item_span, old_span } => self
                .dcx()
                .create_err(errs::TraitImplDuplicate { span, name, trait_item_span, old_span }),
            ResolutionError::InvalidAsmSym => self.dcx().create_err(errs::InvalidAsmSym { span }),
            ResolutionError::LowercaseSelf => self.dcx().create_err(errs::LowercaseSelf { span }),
            ResolutionError::BindingInNeverPattern => {
                self.dcx().create_err(errs::BindingInNeverPattern { span })
            }
        }
    }

    pub(crate) fn report_vis_error(
        &mut self,
        vis_resolution_error: VisResolutionError<'_>,
    ) -> ErrorGuaranteed {
        match vis_resolution_error {
            VisResolutionError::Relative2018(span, path) => {
                self.dcx().create_err(errs::Relative2018 {
                    span,
                    path_span: path.span,
                    // intentionally converting to String, as the text would also be used as
                    // in suggestion context
                    path_str: pprust::path_to_string(path),
                })
            }
            VisResolutionError::AncestorOnly(span) => {
                self.dcx().create_err(errs::AncestorOnly(span))
            }
            VisResolutionError::FailedToResolve(span, label, suggestion) => {
                self.into_struct_error(span, ResolutionError::FailedToResolve {
                    segment: None,
                    label,
                    suggestion,
                    module: None,
                })
            }
            VisResolutionError::ExpectedFound(span, path_str, res) => {
                self.dcx().create_err(errs::ExpectedModuleFound { span, res, path_str })
            }
            VisResolutionError::Indeterminate(span) => {
                self.dcx().create_err(errs::Indeterminate(span))
            }
            VisResolutionError::ModuleOnly(span) => self.dcx().create_err(errs::ModuleOnly(span)),
        }
        .emit()
    }

    /// Lookup typo candidate in scope for a macro or import.
    fn early_lookup_typo_candidate(
        &mut self,
        scope_set: ScopeSet<'ra>,
        parent_scope: &ParentScope<'ra>,
        ident: Ident,
        filter_fn: &impl Fn(Res) -> bool,
    ) -> Option<TypoSuggestion> {
        let mut suggestions = Vec::new();
        let ctxt = ident.span.ctxt();
        self.visit_scopes(scope_set, parent_scope, ctxt, |this, scope, use_prelude, _| {
            match scope {
                Scope::DeriveHelpers(expn_id) => {
                    let res = Res::NonMacroAttr(NonMacroAttrKind::DeriveHelper);
                    if filter_fn(res) {
                        suggestions.extend(
                            this.helper_attrs
                                .get(&expn_id)
                                .into_iter()
                                .flatten()
                                .map(|(ident, _)| TypoSuggestion::typo_from_ident(*ident, res)),
                        );
                    }
                }
                Scope::DeriveHelpersCompat => {
                    let res = Res::NonMacroAttr(NonMacroAttrKind::DeriveHelperCompat);
                    if filter_fn(res) {
                        for derive in parent_scope.derives {
                            let parent_scope = &ParentScope { derives: &[], ..*parent_scope };
                            if let Ok((Some(ext), _)) = this.resolve_macro_path(
                                derive,
                                Some(MacroKind::Derive),
                                parent_scope,
                                false,
                                false,
                                None,
                            ) {
                                suggestions.extend(
                                    ext.helper_attrs
                                        .iter()
                                        .map(|name| TypoSuggestion::typo_from_name(*name, res)),
                                );
                            }
                        }
                    }
                }
                Scope::MacroRules(macro_rules_scope) => {
                    if let MacroRulesScope::Binding(macro_rules_binding) = macro_rules_scope.get() {
                        let res = macro_rules_binding.binding.res();
                        if filter_fn(res) {
                            suggestions.push(TypoSuggestion::typo_from_ident(
                                macro_rules_binding.ident,
                                res,
                            ))
                        }
                    }
                }
                Scope::CrateRoot => {
                    let root_ident = Ident::new(kw::PathRoot, ident.span);
                    let root_module = this.resolve_crate_root(root_ident);
                    this.add_module_candidates(root_module, &mut suggestions, filter_fn, None);
                }
                Scope::Module(module, _) => {
                    this.add_module_candidates(module, &mut suggestions, filter_fn, None);
                }
                Scope::MacroUsePrelude => {
                    suggestions.extend(this.macro_use_prelude.iter().filter_map(
                        |(name, binding)| {
                            let res = binding.res();
                            filter_fn(res).then_some(TypoSuggestion::typo_from_name(*name, res))
                        },
                    ));
                }
                Scope::BuiltinAttrs => {
                    let res = Res::NonMacroAttr(NonMacroAttrKind::Builtin(kw::Empty));
                    if filter_fn(res) {
                        suggestions.extend(
                            BUILTIN_ATTRIBUTES
                                .iter()
                                .map(|attr| TypoSuggestion::typo_from_name(attr.name, res)),
                        );
                    }
                }
                Scope::ExternPrelude => {
                    suggestions.extend(this.extern_prelude.iter().filter_map(|(ident, _)| {
                        let res = Res::Def(DefKind::Mod, CRATE_DEF_ID.to_def_id());
                        filter_fn(res).then_some(TypoSuggestion::typo_from_ident(*ident, res))
                    }));
                }
                Scope::ToolPrelude => {
                    let res = Res::NonMacroAttr(NonMacroAttrKind::Tool);
                    suggestions.extend(
                        this.registered_tools
                            .iter()
                            .map(|ident| TypoSuggestion::typo_from_ident(*ident, res)),
                    );
                }
                Scope::StdLibPrelude => {
                    if let Some(prelude) = this.prelude {
                        let mut tmp_suggestions = Vec::new();
                        this.add_module_candidates(prelude, &mut tmp_suggestions, filter_fn, None);
                        suggestions.extend(
                            tmp_suggestions
                                .into_iter()
                                .filter(|s| use_prelude.into() || this.is_builtin_macro(s.res)),
                        );
                    }
                }
                Scope::BuiltinTypes => {
                    suggestions.extend(PrimTy::ALL.iter().filter_map(|prim_ty| {
                        let res = Res::PrimTy(*prim_ty);
                        filter_fn(res)
                            .then_some(TypoSuggestion::typo_from_name(prim_ty.name(), res))
                    }))
                }
            }

            None::<()>
        });

        // Make sure error reporting is deterministic.
        suggestions.sort_by(|a, b| a.candidate.as_str().partial_cmp(b.candidate.as_str()).unwrap());

        match find_best_match_for_name(
            &suggestions.iter().map(|suggestion| suggestion.candidate).collect::<Vec<Symbol>>(),
            ident.name,
            None,
        ) {
            Some(found) if found != ident.name => {
                suggestions.into_iter().find(|suggestion| suggestion.candidate == found)
            }
            _ => None,
        }
    }

    fn lookup_import_candidates_from_module<FilterFn>(
        &mut self,
        lookup_ident: Ident,
        namespace: Namespace,
        parent_scope: &ParentScope<'ra>,
        start_module: Module<'ra>,
        crate_path: ThinVec<ast::PathSegment>,
        filter_fn: FilterFn,
    ) -> Vec<ImportSuggestion>
    where
        FilterFn: Fn(Res) -> bool,
    {
        let mut candidates = Vec::new();
        let mut seen_modules = FxHashSet::default();
        let start_did = start_module.def_id();
        let mut worklist = vec![(
            start_module,
            ThinVec::<ast::PathSegment>::new(),
            true,
            start_did.is_local() || !self.tcx.is_doc_hidden(start_did),
        )];
        let mut worklist_via_import = vec![];

        while let Some((in_module, path_segments, accessible, doc_visible)) = match worklist.pop() {
            None => worklist_via_import.pop(),
            Some(x) => Some(x),
        } {
            let in_module_is_extern = !in_module.def_id().is_local();
            in_module.for_each_child(self, |this, ident, ns, name_binding| {
                // avoid non-importable candidates
                if !name_binding.is_importable() {
                    return;
                }

                if ident.name == kw::Underscore {
                    return;
                }

                let child_accessible =
                    accessible && this.is_accessible_from(name_binding.vis, parent_scope.module);

                // do not venture inside inaccessible items of other crates
                if in_module_is_extern && !child_accessible {
                    return;
                }

                let via_import = name_binding.is_import() && !name_binding.is_extern_crate();

                // There is an assumption elsewhere that paths of variants are in the enum's
                // declaration and not imported. With this assumption, the variant component is
                // chopped and the rest of the path is assumed to be the enum's own path. For
                // errors where a variant is used as the type instead of the enum, this causes
                // funny looking invalid suggestions, i.e `foo` instead of `foo::MyEnum`.
                if via_import && name_binding.is_possibly_imported_variant() {
                    return;
                }

                // #90113: Do not count an inaccessible reexported item as a candidate.
                if let NameBindingKind::Import { binding, .. } = name_binding.kind {
                    if this.is_accessible_from(binding.vis, parent_scope.module)
                        && !this.is_accessible_from(name_binding.vis, parent_scope.module)
                    {
                        return;
                    }
                }

                let res = name_binding.res();
                let did = match res {
                    Res::Def(DefKind::Ctor(..), did) => this.tcx.opt_parent(did),
                    _ => res.opt_def_id(),
                };
                let child_doc_visible = doc_visible
                    && (did.map_or(true, |did| did.is_local() || !this.tcx.is_doc_hidden(did)));

                // collect results based on the filter function
                // avoid suggesting anything from the same module in which we are resolving
                // avoid suggesting anything with a hygienic name
                if ident.name == lookup_ident.name
                    && ns == namespace
                    && in_module != parent_scope.module
                    && !ident.span.normalize_to_macros_2_0().from_expansion()
                    && filter_fn(res)
                {
                    // create the path
                    let mut segms = if lookup_ident.span.at_least_rust_2018() {
                        // crate-local absolute paths start with `crate::` in edition 2018
                        // FIXME: may also be stabilized for Rust 2015 (Issues #45477, #44660)
                        crate_path.clone()
                    } else {
                        ThinVec::new()
                    };
                    segms.append(&mut path_segments.clone());

                    segms.push(ast::PathSegment::from_ident(ident));
                    let path = Path { span: name_binding.span, segments: segms, tokens: None };

                    if child_accessible {
                        // Remove invisible match if exists
                        if let Some(idx) = candidates
                            .iter()
                            .position(|v: &ImportSuggestion| v.did == did && !v.accessible)
                        {
                            candidates.remove(idx);
                        }
                    }

                    if candidates.iter().all(|v: &ImportSuggestion| v.did != did) {
                        // See if we're recommending TryFrom, TryInto, or FromIterator and add
                        // a note about editions
                        let note = if let Some(did) = did {
                            let requires_note = !did.is_local()
                                && this.tcx.get_attrs(did, sym::rustc_diagnostic_item).any(
                                    |attr| {
                                        [sym::TryInto, sym::TryFrom, sym::FromIterator]
                                            .map(|x| Some(x))
                                            .contains(&attr.value_str())
                                    },
                                );

                            requires_note.then(|| {
                                format!(
                                    "'{}' is included in the prelude starting in Edition 2021",
                                    path_names_to_string(&path)
                                )
                            })
                        } else {
                            None
                        };

                        candidates.push(ImportSuggestion {
                            did,
                            descr: res.descr(),
                            path,
                            accessible: child_accessible,
                            doc_visible: child_doc_visible,
                            note,
                            via_import,
                        });
                    }
                }

                // collect submodules to explore
                if let Some(module) = name_binding.module() {
                    // form the path
                    let mut path_segments = path_segments.clone();
                    path_segments.push(ast::PathSegment::from_ident(ident));

                    let alias_import = if let NameBindingKind::Import { import, .. } =
                        name_binding.kind
                        && let ImportKind::ExternCrate { source: Some(_), .. } = import.kind
                        && import.parent_scope.expansion == parent_scope.expansion
                    {
                        true
                    } else {
                        false
                    };

                    let is_extern_crate_that_also_appears_in_prelude =
                        name_binding.is_extern_crate() && lookup_ident.span.at_least_rust_2018();

                    if !is_extern_crate_that_also_appears_in_prelude || alias_import {
                        // add the module to the lookup
                        if seen_modules.insert(module.def_id()) {
                            if via_import { &mut worklist_via_import } else { &mut worklist }
                                .push((module, path_segments, child_accessible, child_doc_visible));
                        }
                    }
                }
            })
        }

        // If only some candidates are accessible, take just them
        if !candidates.iter().all(|v: &ImportSuggestion| !v.accessible) {
            candidates.retain(|x| x.accessible)
        }

        candidates
    }

    /// When name resolution fails, this method can be used to look up candidate
    /// entities with the expected name. It allows filtering them using the
    /// supplied predicate (which should be used to only accept the types of
    /// definitions expected, e.g., traits). The lookup spans across all crates.
    ///
    /// N.B., the method does not look into imports, but this is not a problem,
    /// since we report the definitions (thus, the de-aliased imports).
    pub(crate) fn lookup_import_candidates<FilterFn>(
        &mut self,
        lookup_ident: Ident,
        namespace: Namespace,
        parent_scope: &ParentScope<'ra>,
        filter_fn: FilterFn,
    ) -> Vec<ImportSuggestion>
    where
        FilterFn: Fn(Res) -> bool,
    {
        let crate_path = thin_vec![ast::PathSegment::from_ident(Ident::with_dummy_span(kw::Crate))];
        let mut suggestions = self.lookup_import_candidates_from_module(
            lookup_ident,
            namespace,
            parent_scope,
            self.graph_root,
            crate_path,
            &filter_fn,
        );

        if lookup_ident.span.at_least_rust_2018() {
            for ident in self.extern_prelude.clone().into_keys() {
                if ident.span.from_expansion() {
                    // Idents are adjusted to the root context before being
                    // resolved in the extern prelude, so reporting this to the
                    // user is no help. This skips the injected
                    // `extern crate std` in the 2018 edition, which would
                    // otherwise cause duplicate suggestions.
                    continue;
                }
                let crate_id = self.crate_loader(|c| c.maybe_process_path_extern(ident.name));
                if let Some(crate_id) = crate_id {
                    let crate_def_id = crate_id.as_def_id();
                    let crate_root = self.expect_module(crate_def_id);

                    // Check if there's already an item in scope with the same name as the crate.
                    // If so, we have to disambiguate the potential import suggestions by making
                    // the paths *global* (i.e., by prefixing them with `::`).
                    let needs_disambiguation =
                        self.resolutions(parent_scope.module).borrow().iter().any(
                            |(key, name_resolution)| {
                                if key.ns == TypeNS
                                    && key.ident == ident
                                    && let Some(binding) = name_resolution.borrow().binding
                                {
                                    match binding.res() {
                                        // No disambiguation needed if the identically named item we
                                        // found in scope actually refers to the crate in question.
                                        Res::Def(_, def_id) => def_id != crate_def_id,
                                        Res::PrimTy(_) => true,
                                        _ => false,
                                    }
                                } else {
                                    false
                                }
                            },
                        );
                    let mut crate_path = ThinVec::new();
                    if needs_disambiguation {
                        crate_path.push(ast::PathSegment::path_root(rustc_span::DUMMY_SP));
                    }
                    crate_path.push(ast::PathSegment::from_ident(ident));

                    suggestions.extend(self.lookup_import_candidates_from_module(
                        lookup_ident,
                        namespace,
                        parent_scope,
                        crate_root,
                        crate_path,
                        &filter_fn,
                    ));
                }
            }
        }

        suggestions
    }

    pub(crate) fn unresolved_macro_suggestions(
        &mut self,
        err: &mut Diag<'_>,
        macro_kind: MacroKind,
        parent_scope: &ParentScope<'ra>,
        ident: Ident,
        krate: &Crate,
    ) {
        let is_expected = &|res: Res| res.macro_kind() == Some(macro_kind);
        let suggestion = self.early_lookup_typo_candidate(
            ScopeSet::Macro(macro_kind),
            parent_scope,
            ident,
            is_expected,
        );
        self.add_typo_suggestion(err, suggestion, ident.span);

        let import_suggestions =
            self.lookup_import_candidates(ident, Namespace::MacroNS, parent_scope, is_expected);
        let (span, found_use) = match parent_scope.module.nearest_parent_mod().as_local() {
            Some(def_id) => UsePlacementFinder::check(krate, self.def_id_to_node_id[def_id]),
            None => (None, FoundUse::No),
        };
        show_candidates(
            self.tcx,
            err,
            span,
            &import_suggestions,
            Instead::No,
            found_use,
            DiagMode::Normal,
            vec![],
            "",
        );

        if macro_kind == MacroKind::Bang && ident.name == sym::macro_rules {
            let label_span = ident.span.shrink_to_hi();
            let mut spans = MultiSpan::from_span(label_span);
            spans.push_span_label(label_span, "put a macro name here");
            err.subdiagnostic(MaybeMissingMacroRulesName { spans });
            return;
        }

        if macro_kind == MacroKind::Derive && (ident.name == sym::Send || ident.name == sym::Sync) {
            err.subdiagnostic(ExplicitUnsafeTraits { span: ident.span, ident });
            return;
        }

        let unused_macro = self.unused_macros.iter().find_map(|(def_id, (_, unused_ident))| {
            if unused_ident.name == ident.name { Some((def_id, unused_ident)) } else { None }
        });

        if let Some((def_id, unused_ident)) = unused_macro {
            let scope = self.local_macro_def_scopes[&def_id];
            let parent_nearest = parent_scope.module.nearest_parent_mod();
            if Some(parent_nearest) == scope.opt_def_id() {
                err.subdiagnostic(MacroDefinedLater { span: unused_ident.span });
                err.subdiagnostic(MacroSuggMovePosition { span: ident.span, ident });
                return;
            }
        }

        if self.macro_names.contains(&ident.normalize_to_macros_2_0()) {
            err.subdiagnostic(AddedMacroUse);
            return;
        }

        if ident.name == kw::Default
            && let ModuleKind::Def(DefKind::Enum, def_id, _) = parent_scope.module.kind
        {
            let span = self.def_span(def_id);
            let source_map = self.tcx.sess.source_map();
            let head_span = source_map.guess_head_span(span);
            err.subdiagnostic(ConsiderAddingADerive {
                span: head_span.shrink_to_lo(),
                suggestion: "#[derive(Default)]\n".to_string(),
            });
        }
        for ns in [Namespace::MacroNS, Namespace::TypeNS, Namespace::ValueNS] {
            if let Ok(binding) = self.early_resolve_ident_in_lexical_scope(
                ident,
                ScopeSet::All(ns),
                parent_scope,
                None,
                false,
                None,
                None,
            ) {
                let desc = match binding.res() {
                    Res::Def(DefKind::Macro(MacroKind::Bang), _) => {
                        "a function-like macro".to_string()
                    }
                    Res::Def(DefKind::Macro(MacroKind::Attr), _) | Res::NonMacroAttr(..) => {
                        format!("an attribute: `#[{ident}]`")
                    }
                    Res::Def(DefKind::Macro(MacroKind::Derive), _) => {
                        format!("a derive macro: `#[derive({ident})]`")
                    }
                    Res::ToolMod => {
                        // Don't confuse the user with tool modules.
                        continue;
                    }
                    Res::Def(DefKind::Trait, _) if macro_kind == MacroKind::Derive => {
                        "only a trait, without a derive macro".to_string()
                    }
                    res => format!(
                        "{} {}, not {} {}",
                        res.article(),
                        res.descr(),
                        macro_kind.article(),
                        macro_kind.descr_expected(),
                    ),
                };
                if let crate::NameBindingKind::Import { import, .. } = binding.kind {
                    if !import.span.is_dummy() {
                        let note = errors::IdentImporterHereButItIsDesc {
                            span: import.span,
                            imported_ident: ident,
                            imported_ident_desc: &desc,
                        };
                        err.subdiagnostic(note);
                        // Silence the 'unused import' warning we might get,
                        // since this diagnostic already covers that import.
                        self.record_use(ident, binding, Used::Other);
                        return;
                    }
                }
                let note = errors::IdentInScopeButItIsDesc {
                    imported_ident: ident,
                    imported_ident_desc: &desc,
                };
                err.subdiagnostic(note);
                return;
            }
        }
    }

    pub(crate) fn add_typo_suggestion(
        &self,
        err: &mut Diag<'_>,
        suggestion: Option<TypoSuggestion>,
        span: Span,
    ) -> bool {
        let suggestion = match suggestion {
            None => return false,
            // We shouldn't suggest underscore.
            Some(suggestion) if suggestion.candidate == kw::Underscore => return false,
            Some(suggestion) => suggestion,
        };

        let mut did_label_def_span = false;

        if let Some(def_span) = suggestion.res.opt_def_id().map(|def_id| self.def_span(def_id)) {
            if span.overlaps(def_span) {
                // Don't suggest typo suggestion for itself like in the following:
                // error[E0423]: expected function, tuple struct or tuple variant, found struct `X`
                //   --> $DIR/issue-64792-bad-unicode-ctor.rs:3:14
                //    |
                // LL | struct X {}
                //    | ----------- `X` defined here
                // LL |
                // LL | const Y: X = X("ö");
                //    | -------------^^^^^^- similarly named constant `Y` defined here
                //    |
                // help: use struct literal syntax instead
                //    |
                // LL | const Y: X = X {};
                //    |              ^^^^
                // help: a constant with a similar name exists
                //    |
                // LL | const Y: X = Y("ö");
                //    |              ^
                return false;
            }
            let span = self.tcx.sess.source_map().guess_head_span(def_span);
            let candidate_descr = suggestion.res.descr();
            let candidate = suggestion.candidate;
            let label = match suggestion.target {
                SuggestionTarget::SimilarlyNamed => {
                    errors::DefinedHere::SimilarlyNamed { span, candidate_descr, candidate }
                }
                SuggestionTarget::SingleItem => {
                    errors::DefinedHere::SingleItem { span, candidate_descr, candidate }
                }
            };
            did_label_def_span = true;
            err.subdiagnostic(label);
        }

        let (span, msg, sugg) = if let SuggestionTarget::SimilarlyNamed = suggestion.target
            && let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span)
            && let Some(span) = suggestion.span
            && let Some(candidate) = suggestion.candidate.as_str().strip_prefix('_')
            && snippet == candidate
        {
            let candidate = suggestion.candidate;
            // When the suggested binding change would be from `x` to `_x`, suggest changing the
            // original binding definition instead. (#60164)
            let msg = format!(
                "the leading underscore in `{candidate}` marks it as unused, consider renaming it to `{snippet}`"
            );
            if !did_label_def_span {
                err.span_label(span, format!("`{candidate}` defined here"));
            }
            (span, msg, snippet)
        } else {
            let msg = match suggestion.target {
                SuggestionTarget::SimilarlyNamed => format!(
                    "{} {} with a similar name exists",
                    suggestion.res.article(),
                    suggestion.res.descr()
                ),
                SuggestionTarget::SingleItem => {
                    format!("maybe you meant this {}", suggestion.res.descr())
                }
            };
            (span, msg, suggestion.candidate.to_ident_string())
        };
        err.span_suggestion(span, msg, sugg, Applicability::MaybeIncorrect);
        true
    }

    fn binding_description(&self, b: NameBinding<'_>, ident: Ident, from_prelude: bool) -> String {
        let res = b.res();
        if b.span.is_dummy() || !self.tcx.sess.source_map().is_span_accessible(b.span) {
            // These already contain the "built-in" prefix or look bad with it.
            let add_built_in =
                !matches!(b.res(), Res::NonMacroAttr(..) | Res::PrimTy(..) | Res::ToolMod);
            let (built_in, from) = if from_prelude {
                ("", " from prelude")
            } else if b.is_extern_crate()
                && !b.is_import()
                && self.tcx.sess.opts.externs.get(ident.as_str()).is_some()
            {
                ("", " passed with `--extern`")
            } else if add_built_in {
                (" built-in", "")
            } else {
                ("", "")
            };

            let a = if built_in.is_empty() { res.article() } else { "a" };
            format!("{a}{built_in} {thing}{from}", thing = res.descr())
        } else {
            let introduced = if b.is_import_user_facing() { "imported" } else { "defined" };
            format!("the {thing} {introduced} here", thing = res.descr())
        }
    }

    fn ambiguity_diagnostics(&self, ambiguity_error: &AmbiguityError<'_>) -> AmbiguityErrorDiag {
        let AmbiguityError { kind, ident, b1, b2, misc1, misc2, .. } = *ambiguity_error;
        let (b1, b2, misc1, misc2, swapped) = if b2.span.is_dummy() && !b1.span.is_dummy() {
            // We have to print the span-less alternative first, otherwise formatting looks bad.
            (b2, b1, misc2, misc1, true)
        } else {
            (b1, b2, misc1, misc2, false)
        };
        let could_refer_to = |b: NameBinding<'_>, misc: AmbiguityErrorMisc, also: &str| {
            let what = self.binding_description(b, ident, misc == AmbiguityErrorMisc::FromPrelude);
            let note_msg = format!("`{ident}` could{also} refer to {what}");

            let thing = b.res().descr();
            let mut help_msgs = Vec::new();
            if b.is_glob_import()
                && (kind == AmbiguityKind::GlobVsGlob
                    || kind == AmbiguityKind::GlobVsExpanded
                    || kind == AmbiguityKind::GlobVsOuter && swapped != also.is_empty())
            {
                help_msgs.push(format!(
                    "consider adding an explicit import of `{ident}` to disambiguate"
                ))
            }
            if b.is_extern_crate() && ident.span.at_least_rust_2018() {
                help_msgs.push(format!("use `::{ident}` to refer to this {thing} unambiguously"))
            }
            match misc {
                AmbiguityErrorMisc::SuggestCrate => help_msgs
                    .push(format!("use `crate::{ident}` to refer to this {thing} unambiguously")),
                AmbiguityErrorMisc::SuggestSelf => help_msgs
                    .push(format!("use `self::{ident}` to refer to this {thing} unambiguously")),
                AmbiguityErrorMisc::FromPrelude | AmbiguityErrorMisc::None => {}
            }

            (
                b.span,
                note_msg,
                help_msgs
                    .iter()
                    .enumerate()
                    .map(|(i, help_msg)| {
                        let or = if i == 0 { "" } else { "or " };
                        format!("{or}{help_msg}")
                    })
                    .collect::<Vec<_>>(),
            )
        };
        let (b1_span, b1_note_msg, b1_help_msgs) = could_refer_to(b1, misc1, "");
        let (b2_span, b2_note_msg, b2_help_msgs) = could_refer_to(b2, misc2, " also");

        AmbiguityErrorDiag {
            msg: format!("`{ident}` is ambiguous"),
            span: ident.span,
            label_span: ident.span,
            label_msg: "ambiguous name".to_string(),
            note_msg: format!("ambiguous because of {}", kind.descr()),
            b1_span,
            b1_note_msg,
            b1_help_msgs,
            b2_span,
            b2_note_msg,
            b2_help_msgs,
        }
    }

    /// If the binding refers to a tuple struct constructor with fields,
    /// returns the span of its fields.
    fn ctor_fields_span(&self, binding: NameBinding<'_>) -> Option<Span> {
        if let NameBindingKind::Res(Res::Def(
            DefKind::Ctor(CtorOf::Struct, CtorKind::Fn),
            ctor_def_id,
        )) = binding.kind
        {
            let def_id = self.tcx.parent(ctor_def_id);
            return self.field_idents(def_id)?.iter().map(|&f| f.span).reduce(Span::to); // None for `struct Foo()`
        }
        None
    }

    fn report_privacy_error(&mut self, privacy_error: &PrivacyError<'ra>) {
        let PrivacyError { ident, binding, outermost_res, parent_scope, single_nested, dedup_span } =
            *privacy_error;

        let res = binding.res();
        let ctor_fields_span = self.ctor_fields_span(binding);
        let plain_descr = res.descr().to_string();
        let nonimport_descr =
            if ctor_fields_span.is_some() { plain_descr + " constructor" } else { plain_descr };
        let import_descr = nonimport_descr.clone() + " import";
        let get_descr =
            |b: NameBinding<'_>| if b.is_import() { &import_descr } else { &nonimport_descr };

        // Print the primary message.
        let ident_descr = get_descr(binding);
        let mut err =
            self.dcx().create_err(errors::IsPrivate { span: ident.span, ident_descr, ident });

        let mut not_publicly_reexported = false;
        if let Some((this_res, outer_ident)) = outermost_res {
            let import_suggestions = self.lookup_import_candidates(
                outer_ident,
                this_res.ns().unwrap_or(Namespace::TypeNS),
                &parent_scope,
                &|res: Res| res == this_res,
            );
            let point_to_def = !show_candidates(
                self.tcx,
                &mut err,
                Some(dedup_span.until(outer_ident.span.shrink_to_hi())),
                &import_suggestions,
                Instead::Yes,
                FoundUse::Yes,
                DiagMode::Import { append: single_nested },
                vec![],
                "",
            );
            // If we suggest importing a public re-export, don't point at the definition.
            if point_to_def && ident.span != outer_ident.span {
                not_publicly_reexported = true;
                let label = errors::OuterIdentIsNotPubliclyReexported {
                    span: outer_ident.span,
                    outer_ident_descr: this_res.descr(),
                    outer_ident,
                };
                err.subdiagnostic(label);
            }
        }

        let mut non_exhaustive = None;
        // If an ADT is foreign and marked as `non_exhaustive`, then that's
        // probably why we have the privacy error.
        // Otherwise, point out if the struct has any private fields.
        if let Some(def_id) = res.opt_def_id()
            && !def_id.is_local()
            && let Some(attr) = self.tcx.get_attr(def_id, sym::non_exhaustive)
        {
            non_exhaustive = Some(attr.span);
        } else if let Some(span) = ctor_fields_span {
            let label = errors::ConstructorPrivateIfAnyFieldPrivate { span };
            err.subdiagnostic(label);
            if let Res::Def(_, d) = res
                && let Some(fields) = self.field_visibility_spans.get(&d)
            {
                let spans = fields.iter().map(|span| *span).collect();
                let sugg =
                    errors::ConsiderMakingTheFieldPublic { spans, number_of_fields: fields.len() };
                err.subdiagnostic(sugg);
            }
        }

        let mut sugg_paths = vec![];
        if let Some(mut def_id) = res.opt_def_id() {
            // We can't use `def_path_str` in resolve.
            let mut path = vec![def_id];
            while let Some(parent) = self.tcx.opt_parent(def_id) {
                def_id = parent;
                if !def_id.is_top_level_module() {
                    path.push(def_id);
                } else {
                    break;
                }
            }
            // We will only suggest importing directly if it is accessible through that path.
            let path_names: Option<Vec<String>> = path
                .iter()
                .rev()
                .map(|def_id| {
                    self.tcx.opt_item_name(*def_id).map(|n| {
                        if def_id.is_top_level_module() {
                            "crate".to_string()
                        } else {
                            n.to_string()
                        }
                    })
                })
                .collect();
            if let Some(def_id) = path.get(0)
                && let Some(path) = path_names
            {
                if let Some(def_id) = def_id.as_local() {
                    if self.effective_visibilities.is_directly_public(def_id) {
                        sugg_paths.push((path, false));
                    }
                } else if self.is_accessible_from(self.tcx.visibility(def_id), parent_scope.module)
                {
                    sugg_paths.push((path, false));
                }
            }
        }

        // Print the whole import chain to make it easier to see what happens.
        let first_binding = binding;
        let mut next_binding = Some(binding);
        let mut next_ident = ident;
        let mut path = vec![];
        while let Some(binding) = next_binding {
            let name = next_ident;
            next_binding = match binding.kind {
                _ if res == Res::Err => None,
                NameBindingKind::Import { binding, import, .. } => match import.kind {
                    _ if binding.span.is_dummy() => None,
                    ImportKind::Single { source, .. } => {
                        next_ident = source;
                        Some(binding)
                    }
                    ImportKind::Glob { .. }
                    | ImportKind::MacroUse { .. }
                    | ImportKind::MacroExport => Some(binding),
                    ImportKind::ExternCrate { .. } => None,
                },
                _ => None,
            };

            match binding.kind {
                NameBindingKind::Import { import, .. } => {
                    for segment in import.module_path.iter().skip(1) {
                        path.push(segment.ident.to_string());
                    }
                    sugg_paths.push((
                        path.iter()
                            .cloned()
                            .chain(vec![ident.to_string()].into_iter())
                            .collect::<Vec<_>>(),
                        true, // re-export
                    ));
                }
                NameBindingKind::Res(_) | NameBindingKind::Module(_) => {}
            }
            let first = binding == first_binding;
            let def_span = self.tcx.sess.source_map().guess_head_span(binding.span);
            let mut note_span = MultiSpan::from_span(def_span);
            if !first && binding.vis.is_public() {
                let desc = match binding.kind {
                    NameBindingKind::Import { .. } => "re-export",
                    _ => "directly",
                };
                note_span.push_span_label(def_span, format!("you could import this {desc}"));
            }
            // Final step in the import chain, point out if the ADT is `non_exhaustive`
            // which is probably why this privacy violation occurred.
            if next_binding.is_none()
                && let Some(span) = non_exhaustive
            {
                note_span.push_span_label(
                    span,
                    "cannot be constructed because it is `#[non_exhaustive]`",
                );
            }
            let note = errors::NoteAndRefersToTheItemDefinedHere {
                span: note_span,
                binding_descr: get_descr(binding),
                binding_name: name,
                first,
                dots: next_binding.is_some(),
            };
            err.subdiagnostic(note);
        }
        // We prioritize shorter paths, non-core imports and direct imports over the alternatives.
        sugg_paths.sort_by_key(|(p, reexport)| (p.len(), p[0] == "core", *reexport));
        for (sugg, reexport) in sugg_paths {
            if not_publicly_reexported {
                break;
            }
            if sugg.len() <= 1 {
                // A single path segment suggestion is wrong. This happens on circular imports.
                // `tests/ui/imports/issue-55884-2.rs`
                continue;
            }
            let path = sugg.join("::");
            let sugg = if reexport {
                errors::ImportIdent::ThroughReExport { span: dedup_span, ident, path }
            } else {
                errors::ImportIdent::Directly { span: dedup_span, ident, path }
            };
            err.subdiagnostic(sugg);
            break;
        }

        err.emit();
    }

    pub(crate) fn find_similarly_named_module_or_crate(
        &mut self,
        ident: Symbol,
        current_module: Module<'ra>,
    ) -> Option<Symbol> {
        let mut candidates = self
            .extern_prelude
            .keys()
            .map(|ident| ident.name)
            .chain(
                self.module_map
                    .iter()
                    .filter(|(_, module)| {
                        current_module.is_ancestor_of(**module) && current_module != **module
                    })
                    .flat_map(|(_, module)| module.kind.name()),
            )
            .filter(|c| !c.to_string().is_empty())
            .collect::<Vec<_>>();
        candidates.sort();
        candidates.dedup();
        match find_best_match_for_name(&candidates, ident, None) {
            Some(sugg) if sugg == ident => None,
            sugg => sugg,
        }
    }

    pub(crate) fn report_path_resolution_error(
        &mut self,
        path: &[Segment],
        opt_ns: Option<Namespace>, // `None` indicates a module path in import
        parent_scope: &ParentScope<'ra>,
        ribs: Option<&PerNS<Vec<Rib<'ra>>>>,
        ignore_binding: Option<NameBinding<'ra>>,
        ignore_import: Option<Import<'ra>>,
        module: Option<ModuleOrUniformRoot<'ra>>,
        failed_segment_idx: usize,
        ident: Ident,
    ) -> (String, Option<Suggestion>) {
        let is_last = failed_segment_idx == path.len() - 1;
        let ns = if is_last { opt_ns.unwrap_or(TypeNS) } else { TypeNS };
        let module_res = match module {
            Some(ModuleOrUniformRoot::Module(module)) => module.res(),
            _ => None,
        };
        if module_res == self.graph_root.res() {
            let is_mod = |res| matches!(res, Res::Def(DefKind::Mod, _));
            let mut candidates = self.lookup_import_candidates(ident, TypeNS, parent_scope, is_mod);
            candidates
                .sort_by_cached_key(|c| (c.path.segments.len(), pprust::path_to_string(&c.path)));
            if let Some(candidate) = candidates.get(0) {
                let path = {
                    // remove the possible common prefix of the path
                    let len = candidate.path.segments.len();
                    let start_index = (0..=failed_segment_idx.min(len - 1))
                        .find(|&i| path[i].ident.name != candidate.path.segments[i].ident.name)
                        .unwrap_or_default();
                    let segments =
                        (start_index..len).map(|s| candidate.path.segments[s].clone()).collect();
                    Path { segments, span: Span::default(), tokens: None }
                };
                (
                    String::from("unresolved import"),
                    Some((
                        vec![(ident.span, pprust::path_to_string(&path))],
                        String::from("a similar path exists"),
                        Applicability::MaybeIncorrect,
                    )),
                )
            } else if ident.name == sym::core {
                (
                    format!("you might be missing crate `{ident}`"),
                    Some((
                        vec![(ident.span, "std".to_string())],
                        "try using `std` instead of `core`".to_string(),
                        Applicability::MaybeIncorrect,
                    )),
                )
            } else if ident.name == kw::Underscore {
                (format!("`_` is not a valid crate or module name"), None)
            } else if self.tcx.sess.is_rust_2015() {
                (
                    format!("you might be missing crate `{ident}`"),
                    Some((
                        vec![(
                            self.current_crate_outer_attr_insert_span,
                            format!("extern crate {ident};\n"),
                        )],
                        format!("consider importing the `{ident}` crate"),
                        Applicability::MaybeIncorrect,
                    )),
                )
            } else {
                (format!("could not find `{ident}` in the crate root"), None)
            }
        } else if failed_segment_idx > 0 {
            let parent = path[failed_segment_idx - 1].ident.name;
            let parent = match parent {
                // ::foo is mounted at the crate root for 2015, and is the extern
                // prelude for 2018+
                kw::PathRoot if self.tcx.sess.edition() > Edition::Edition2015 => {
                    "the list of imported crates".to_owned()
                }
                kw::PathRoot | kw::Crate => "the crate root".to_owned(),
                _ => format!("`{parent}`"),
            };

            let mut msg = format!("could not find `{ident}` in {parent}");
            if ns == TypeNS || ns == ValueNS {
                let ns_to_try = if ns == TypeNS { ValueNS } else { TypeNS };
                let binding = if let Some(module) = module {
                    self.resolve_ident_in_module(
                        module,
                        ident,
                        ns_to_try,
                        parent_scope,
                        None,
                        ignore_binding,
                        ignore_import,
                    )
                    .ok()
                } else if let Some(ribs) = ribs
                    && let Some(TypeNS | ValueNS) = opt_ns
                {
                    assert!(ignore_import.is_none());
                    match self.resolve_ident_in_lexical_scope(
                        ident,
                        ns_to_try,
                        parent_scope,
                        None,
                        &ribs[ns_to_try],
                        ignore_binding,
                    ) {
                        // we found a locally-imported or available item/module
                        Some(LexicalScopeBinding::Item(binding)) => Some(binding),
                        _ => None,
                    }
                } else {
                    self.early_resolve_ident_in_lexical_scope(
                        ident,
                        ScopeSet::All(ns_to_try),
                        parent_scope,
                        None,
                        false,
                        ignore_binding,
                        ignore_import,
                    )
                    .ok()
                };
                if let Some(binding) = binding {
                    let mut found = |what| {
                        msg = format!(
                            "expected {}, found {} `{}` in {}",
                            ns.descr(),
                            what,
                            ident,
                            parent
                        )
                    };
                    if binding.module().is_some() {
                        found("module")
                    } else {
                        match binding.res() {
                            // Avoid using TyCtxt::def_kind_descr in the resolver, because it
                            // indirectly *calls* the resolver, and would cause a query cycle.
                            Res::Def(kind, id) => found(kind.descr(id)),
                            _ => found(ns_to_try.descr()),
                        }
                    }
                };
            }
            (msg, None)
        } else if ident.name == kw::SelfUpper {
            // As mentioned above, `opt_ns` being `None` indicates a module path in import.
            // We can use this to improve a confusing error for, e.g. `use Self::Variant` in an
            // impl
            if opt_ns.is_none() {
                ("`Self` cannot be used in imports".to_string(), None)
            } else {
                (
                    "`Self` is only available in impls, traits, and type definitions".to_string(),
                    None,
                )
            }
        } else if ident.name.as_str().chars().next().is_some_and(|c| c.is_ascii_uppercase()) {
            // Check whether the name refers to an item in the value namespace.
            let binding = if let Some(ribs) = ribs {
                assert!(ignore_import.is_none());
                self.resolve_ident_in_lexical_scope(
                    ident,
                    ValueNS,
                    parent_scope,
                    None,
                    &ribs[ValueNS],
                    ignore_binding,
                )
            } else {
                None
            };
            let match_span = match binding {
                // Name matches a local variable. For example:
                // ```
                // fn f() {
                //     let Foo: &str = "";
                //     println!("{}", Foo::Bar); // Name refers to local
                //                               // variable `Foo`.
                // }
                // ```
                Some(LexicalScopeBinding::Res(Res::Local(id))) => {
                    Some(*self.pat_span_map.get(&id).unwrap())
                }
                // Name matches item from a local name binding
                // created by `use` declaration. For example:
                // ```
                // pub Foo: &str = "";
                //
                // mod submod {
                //     use super::Foo;
                //     println!("{}", Foo::Bar); // Name refers to local
                //                               // binding `Foo`.
                // }
                // ```
                Some(LexicalScopeBinding::Item(name_binding)) => Some(name_binding.span),
                _ => None,
            };
            let suggestion = match_span.map(|span| {
                (
                    vec![(span, String::from(""))],
                    format!("`{ident}` is defined here, but is not a type"),
                    Applicability::MaybeIncorrect,
                )
            });

            (format!("use of undeclared type `{ident}`"), suggestion)
        } else {
            let mut suggestion = None;
            if ident.name == sym::alloc {
                suggestion = Some((
                    vec![],
                    String::from("add `extern crate alloc` to use the `alloc` crate"),
                    Applicability::MaybeIncorrect,
                ))
            }

            suggestion = suggestion.or_else(|| {
                self.find_similarly_named_module_or_crate(ident.name, parent_scope.module).map(
                    |sugg| {
                        (
                            vec![(ident.span, sugg.to_string())],
                            String::from("there is a crate or module with a similar name"),
                            Applicability::MaybeIncorrect,
                        )
                    },
                )
            });
            if let Ok(binding) = self.early_resolve_ident_in_lexical_scope(
                ident,
                ScopeSet::All(ValueNS),
                parent_scope,
                None,
                false,
                ignore_binding,
                ignore_import,
            ) {
                let descr = binding.res().descr();
                (format!("{descr} `{ident}` is not a crate or module"), suggestion)
            } else {
                (format!("use of undeclared crate or module `{ident}`"), suggestion)
            }
        }
    }

    /// Adds suggestions for a path that cannot be resolved.
    pub(crate) fn make_path_suggestion(
        &mut self,
        span: Span,
        mut path: Vec<Segment>,
        parent_scope: &ParentScope<'ra>,
    ) -> Option<(Vec<Segment>, Option<String>)> {
        debug!("make_path_suggestion: span={:?} path={:?}", span, path);

        match (path.get(0), path.get(1)) {
            // `{{root}}::ident::...` on both editions.
            // On 2015 `{{root}}` is usually added implicitly.
            (Some(fst), Some(snd))
                if fst.ident.name == kw::PathRoot && !snd.ident.is_path_segment_keyword() => {}
            // `ident::...` on 2018.
            (Some(fst), _)
                if fst.ident.span.at_least_rust_2018() && !fst.ident.is_path_segment_keyword() =>
            {
                // Insert a placeholder that's later replaced by `self`/`super`/etc.
                path.insert(0, Segment::from_ident(Ident::empty()));
            }
            _ => return None,
        }

        self.make_missing_self_suggestion(path.clone(), parent_scope)
            .or_else(|| self.make_missing_crate_suggestion(path.clone(), parent_scope))
            .or_else(|| self.make_missing_super_suggestion(path.clone(), parent_scope))
            .or_else(|| self.make_external_crate_suggestion(path, parent_scope))
    }

    /// Suggest a missing `self::` if that resolves to an correct module.
    ///
    /// ```text
    ///    |
    /// LL | use foo::Bar;
    ///    |     ^^^ did you mean `self::foo`?
    /// ```
    fn make_missing_self_suggestion(
        &mut self,
        mut path: Vec<Segment>,
        parent_scope: &ParentScope<'ra>,
    ) -> Option<(Vec<Segment>, Option<String>)> {
        // Replace first ident with `self` and check if that is valid.
        path[0].ident.name = kw::SelfLower;
        let result = self.maybe_resolve_path(&path, None, parent_scope, None);
        debug!("make_missing_self_suggestion: path={:?} result={:?}", path, result);
        if let PathResult::Module(..) = result { Some((path, None)) } else { None }
    }

    /// Suggests a missing `crate::` if that resolves to an correct module.
    ///
    /// ```text
    ///    |
    /// LL | use foo::Bar;
    ///    |     ^^^ did you mean `crate::foo`?
    /// ```
    fn make_missing_crate_suggestion(
        &mut self,
        mut path: Vec<Segment>,
        parent_scope: &ParentScope<'ra>,
    ) -> Option<(Vec<Segment>, Option<String>)> {
        // Replace first ident with `crate` and check if that is valid.
        path[0].ident.name = kw::Crate;
        let result = self.maybe_resolve_path(&path, None, parent_scope, None);
        debug!("make_missing_crate_suggestion:  path={:?} result={:?}", path, result);
        if let PathResult::Module(..) = result {
            Some((
                path,
                Some(
                    "`use` statements changed in Rust 2018; read more at \
                     <https://doc.rust-lang.org/edition-guide/rust-2018/module-system/path-\
                     clarity.html>"
                        .to_string(),
                ),
            ))
        } else {
            None
        }
    }

    /// Suggests a missing `super::` if that resolves to an correct module.
    ///
    /// ```text
    ///    |
    /// LL | use foo::Bar;
    ///    |     ^^^ did you mean `super::foo`?
    /// ```
    fn make_missing_super_suggestion(
        &mut self,
        mut path: Vec<Segment>,
        parent_scope: &ParentScope<'ra>,
    ) -> Option<(Vec<Segment>, Option<String>)> {
        // Replace first ident with `crate` and check if that is valid.
        path[0].ident.name = kw::Super;
        let result = self.maybe_resolve_path(&path, None, parent_scope, None);
        debug!("make_missing_super_suggestion:  path={:?} result={:?}", path, result);
        if let PathResult::Module(..) = result { Some((path, None)) } else { None }
    }

    /// Suggests a missing external crate name if that resolves to an correct module.
    ///
    /// ```text
    ///    |
    /// LL | use foobar::Baz;
    ///    |     ^^^^^^ did you mean `baz::foobar`?
    /// ```
    ///
    /// Used when importing a submodule of an external crate but missing that crate's
    /// name as the first part of path.
    fn make_external_crate_suggestion(
        &mut self,
        mut path: Vec<Segment>,
        parent_scope: &ParentScope<'ra>,
    ) -> Option<(Vec<Segment>, Option<String>)> {
        if path[1].ident.span.is_rust_2015() {
            return None;
        }

        // Sort extern crate names in *reverse* order to get
        // 1) some consistent ordering for emitted diagnostics, and
        // 2) `std` suggestions before `core` suggestions.
        let mut extern_crate_names =
            self.extern_prelude.keys().map(|ident| ident.name).collect::<Vec<_>>();
        extern_crate_names.sort_by(|a, b| b.as_str().partial_cmp(a.as_str()).unwrap());

        for name in extern_crate_names.into_iter() {
            // Replace first ident with a crate name and check if that is valid.
            path[0].ident.name = name;
            let result = self.maybe_resolve_path(&path, None, parent_scope, None);
            debug!(
                "make_external_crate_suggestion: name={:?} path={:?} result={:?}",
                name, path, result
            );
            if let PathResult::Module(..) = result {
                return Some((path, None));
            }
        }

        None
    }

    /// Suggests importing a macro from the root of the crate rather than a module within
    /// the crate.
    ///
    /// ```text
    /// help: a macro with this name exists at the root of the crate
    ///    |
    /// LL | use issue_59764::makro;
    ///    |     ^^^^^^^^^^^^^^^^^^
    ///    |
    ///    = note: this could be because a macro annotated with `#[macro_export]` will be exported
    ///            at the root of the crate instead of the module where it is defined
    /// ```
    pub(crate) fn check_for_module_export_macro(
        &mut self,
        import: Import<'ra>,
        module: ModuleOrUniformRoot<'ra>,
        ident: Ident,
    ) -> Option<(Option<Suggestion>, Option<String>)> {
        let ModuleOrUniformRoot::Module(mut crate_module) = module else {
            return None;
        };

        while let Some(parent) = crate_module.parent {
            crate_module = parent;
        }

        if module == ModuleOrUniformRoot::Module(crate_module) {
            // Don't make a suggestion if the import was already from the root of the crate.
            return None;
        }

        let resolutions = self.resolutions(crate_module).borrow();
        let binding_key = BindingKey::new(ident, MacroNS);
        let resolution = resolutions.get(&binding_key)?;
        let binding = resolution.borrow().binding()?;
        if let Res::Def(DefKind::Macro(MacroKind::Bang), _) = binding.res() {
            let module_name = crate_module.kind.name().unwrap();
            let import_snippet = match import.kind {
                ImportKind::Single { source, target, .. } if source != target => {
                    format!("{source} as {target}")
                }
                _ => format!("{ident}"),
            };

            let mut corrections: Vec<(Span, String)> = Vec::new();
            if !import.is_nested() {
                // Assume this is the easy case of `use issue_59764::foo::makro;` and just remove
                // intermediate segments.
                corrections.push((import.span, format!("{module_name}::{import_snippet}")));
            } else {
                // Find the binding span (and any trailing commas and spaces).
                //   ie. `use a::b::{c, d, e};`
                //                      ^^^
                let (found_closing_brace, binding_span) = find_span_of_binding_until_next_binding(
                    self.tcx.sess,
                    import.span,
                    import.use_span,
                );
                debug!(
                    "check_for_module_export_macro: found_closing_brace={:?} binding_span={:?}",
                    found_closing_brace, binding_span
                );

                let mut removal_span = binding_span;
                if found_closing_brace {
                    // If the binding span ended with a closing brace, as in the below example:
                    //   ie. `use a::b::{c, d};`
                    //                      ^
                    // Then expand the span of characters to remove to include the previous
                    // binding's trailing comma.
                    //   ie. `use a::b::{c, d};`
                    //                    ^^^
                    if let Some(previous_span) =
                        extend_span_to_previous_binding(self.tcx.sess, binding_span)
                    {
                        debug!("check_for_module_export_macro: previous_span={:?}", previous_span);
                        removal_span = removal_span.with_lo(previous_span.lo());
                    }
                }
                debug!("check_for_module_export_macro: removal_span={:?}", removal_span);

                // Remove the `removal_span`.
                corrections.push((removal_span, "".to_string()));

                // Find the span after the crate name and if it has nested imports immediately
                // after the crate name already.
                //   ie. `use a::b::{c, d};`
                //               ^^^^^^^^^
                //   or  `use a::{b, c, d}};`
                //               ^^^^^^^^^^^
                let (has_nested, after_crate_name) = find_span_immediately_after_crate_name(
                    self.tcx.sess,
                    module_name,
                    import.use_span,
                );
                debug!(
                    "check_for_module_export_macro: has_nested={:?} after_crate_name={:?}",
                    has_nested, after_crate_name
                );

                let source_map = self.tcx.sess.source_map();

                // Make sure this is actually crate-relative.
                let is_definitely_crate = import
                    .module_path
                    .first()
                    .is_some_and(|f| f.ident.name != kw::SelfLower && f.ident.name != kw::Super);

                // Add the import to the start, with a `{` if required.
                let start_point = source_map.start_point(after_crate_name);
                if is_definitely_crate
                    && let Ok(start_snippet) = source_map.span_to_snippet(start_point)
                {
                    corrections.push((
                        start_point,
                        if has_nested {
                            // In this case, `start_snippet` must equal '{'.
                            format!("{start_snippet}{import_snippet}, ")
                        } else {
                            // In this case, add a `{`, then the moved import, then whatever
                            // was there before.
                            format!("{{{import_snippet}, {start_snippet}")
                        },
                    ));

                    // Add a `};` to the end if nested, matching the `{` added at the start.
                    if !has_nested {
                        corrections
                            .push((source_map.end_point(after_crate_name), "};".to_string()));
                    }
                } else {
                    // If the root import is module-relative, add the import separately
                    corrections.push((
                        import.use_span.shrink_to_lo(),
                        format!("use {module_name}::{import_snippet};\n"),
                    ));
                }
            }

            let suggestion = Some((
                corrections,
                String::from("a macro with this name exists at the root of the crate"),
                Applicability::MaybeIncorrect,
            ));
            Some((suggestion, Some("this could be because a macro annotated with `#[macro_export]` will be exported \
            at the root of the crate instead of the module where it is defined"
               .to_string())))
        } else {
            None
        }
    }

    /// Finds a cfg-ed out item inside `module` with the matching name.
    pub(crate) fn find_cfg_stripped(&self, err: &mut Diag<'_>, segment: &Symbol, module: DefId) {
        let local_items;
        let symbols = if module.is_local() {
            local_items = self
                .stripped_cfg_items
                .iter()
                .filter_map(|item| {
                    let parent_module = self.opt_local_def_id(item.parent_module)?.to_def_id();
                    Some(StrippedCfgItem { parent_module, name: item.name, cfg: item.cfg.clone() })
                })
                .collect::<Vec<_>>();
            local_items.as_slice()
        } else {
            self.tcx.stripped_cfg_items(module.krate)
        };

        for &StrippedCfgItem { parent_module, name, ref cfg } in symbols {
            if parent_module != module || name.name != *segment {
                continue;
            }

            let note = errors::FoundItemConfigureOut { span: name.span };
            err.subdiagnostic(note);

            if let MetaItemKind::List(nested) = &cfg.kind
                && let NestedMetaItem::MetaItem(meta_item) = &nested[0]
                && let MetaItemKind::NameValue(feature_name) = &meta_item.kind
            {
                let note = errors::ItemWasBehindFeature {
                    feature: feature_name.symbol,
                    span: meta_item.span,
                };
                err.subdiagnostic(note);
            } else {
                let note = errors::ItemWasCfgOut { span: cfg.span };
                err.subdiagnostic(note);
            }
        }
    }
}

/// Given a `binding_span` of a binding within a use statement:
///
/// ```ignore (illustrative)
/// use foo::{a, b, c};
/// //           ^
/// ```
///
/// then return the span until the next binding or the end of the statement:
///
/// ```ignore (illustrative)
/// use foo::{a, b, c};
/// //           ^^^
/// ```
fn find_span_of_binding_until_next_binding(
    sess: &Session,
    binding_span: Span,
    use_span: Span,
) -> (bool, Span) {
    let source_map = sess.source_map();

    // Find the span of everything after the binding.
    //   ie. `a, e};` or `a};`
    let binding_until_end = binding_span.with_hi(use_span.hi());

    // Find everything after the binding but not including the binding.
    //   ie. `, e};` or `};`
    let after_binding_until_end = binding_until_end.with_lo(binding_span.hi());

    // Keep characters in the span until we encounter something that isn't a comma or
    // whitespace.
    //   ie. `, ` or ``.
    //
    // Also note whether a closing brace character was encountered. If there
    // was, then later go backwards to remove any trailing commas that are left.
    let mut found_closing_brace = false;
    let after_binding_until_next_binding =
        source_map.span_take_while(after_binding_until_end, |&ch| {
            if ch == '}' {
                found_closing_brace = true;
            }
            ch == ' ' || ch == ','
        });

    // Combine the two spans.
    //   ie. `a, ` or `a`.
    //
    // Removing these would leave `issue_52891::{d, e};` or `issue_52891::{d, e, };`
    let span = binding_span.with_hi(after_binding_until_next_binding.hi());

    (found_closing_brace, span)
}

/// Given a `binding_span`, return the span through to the comma or opening brace of the previous
/// binding.
///
/// ```ignore (illustrative)
/// use foo::a::{a, b, c};
/// //            ^^--- binding span
/// //            |
/// //            returned span
///
/// use foo::{a, b, c};
/// //        --- binding span
/// ```
fn extend_span_to_previous_binding(sess: &Session, binding_span: Span) -> Option<Span> {
    let source_map = sess.source_map();

    // `prev_source` will contain all of the source that came before the span.
    // Then split based on a command and take the first (ie. closest to our span)
    // snippet. In the example, this is a space.
    let prev_source = source_map.span_to_prev_source(binding_span).ok()?;

    let prev_comma = prev_source.rsplit(',').collect::<Vec<_>>();
    let prev_starting_brace = prev_source.rsplit('{').collect::<Vec<_>>();
    if prev_comma.len() <= 1 || prev_starting_brace.len() <= 1 {
        return None;
    }

    let prev_comma = prev_comma.first().unwrap();
    let prev_starting_brace = prev_starting_brace.first().unwrap();

    // If the amount of source code before the comma is greater than
    // the amount of source code before the starting brace then we've only
    // got one item in the nested item (eg. `issue_52891::{self}`).
    if prev_comma.len() > prev_starting_brace.len() {
        return None;
    }

    Some(binding_span.with_lo(BytePos(
        // Take away the number of bytes for the characters we've found and an
        // extra for the comma.
        binding_span.lo().0 - (prev_comma.as_bytes().len() as u32) - 1,
    )))
}

/// Given a `use_span` of a binding within a use statement, returns the highlighted span and if
/// it is a nested use tree.
///
/// ```ignore (illustrative)
/// use foo::a::{b, c};
/// //       ^^^^^^^^^^ -- false
///
/// use foo::{a, b, c};
/// //       ^^^^^^^^^^ -- true
///
/// use foo::{a, b::{c, d}};
/// //       ^^^^^^^^^^^^^^^ -- true
/// ```
fn find_span_immediately_after_crate_name(
    sess: &Session,
    module_name: Symbol,
    use_span: Span,
) -> (bool, Span) {
    debug!(
        "find_span_immediately_after_crate_name: module_name={:?} use_span={:?}",
        module_name, use_span
    );
    let source_map = sess.source_map();

    // Using `use issue_59764::foo::{baz, makro};` as an example throughout..
    let mut num_colons = 0;
    // Find second colon.. `use issue_59764:`
    let until_second_colon = source_map.span_take_while(use_span, |c| {
        if *c == ':' {
            num_colons += 1;
        }
        !matches!(c, ':' if num_colons == 2)
    });
    // Find everything after the second colon.. `foo::{baz, makro};`
    let from_second_colon = use_span.with_lo(until_second_colon.hi() + BytePos(1));

    let mut found_a_non_whitespace_character = false;
    // Find the first non-whitespace character in `from_second_colon`.. `f`
    let after_second_colon = source_map.span_take_while(from_second_colon, |c| {
        if found_a_non_whitespace_character {
            return false;
        }
        if !c.is_whitespace() {
            found_a_non_whitespace_character = true;
        }
        true
    });

    // Find the first `{` in from_second_colon.. `foo::{`
    let next_left_bracket = source_map.span_through_char(from_second_colon, '{');

    (next_left_bracket == after_second_colon, from_second_colon)
}

/// A suggestion has already been emitted, change the wording slightly to clarify that both are
/// independent options.
enum Instead {
    Yes,
    No,
}

/// Whether an existing place with an `use` item was found.
enum FoundUse {
    Yes,
    No,
}

/// Whether a binding is part of a pattern or a use statement. Used for diagnostics.
pub(crate) enum DiagMode {
    Normal,
    /// The binding is part of a pattern
    Pattern,
    /// The binding is part of a use statement
    Import {
        /// `true` mean add the tips afterward for case `use a::{b,c}`,
        /// rather than replacing within.
        append: bool,
    },
}

pub(crate) fn import_candidates(
    tcx: TyCtxt<'_>,
    err: &mut Diag<'_>,
    // This is `None` if all placement locations are inside expansions
    use_placement_span: Option<Span>,
    candidates: &[ImportSuggestion],
    mode: DiagMode,
    append: &str,
) {
    show_candidates(
        tcx,
        err,
        use_placement_span,
        candidates,
        Instead::Yes,
        FoundUse::Yes,
        mode,
        vec![],
        append,
    );
}

type PathString<'a> = (String, &'a str, Option<Span>, &'a Option<String>, bool);

/// When an entity with a given name is not available in scope, we search for
/// entities with that name in all crates. This method allows outputting the
/// results of this search in a programmer-friendly way. If any entities are
/// found and suggested, returns `true`, otherwise returns `false`.
fn show_candidates(
    tcx: TyCtxt<'_>,
    err: &mut Diag<'_>,
    // This is `None` if all placement locations are inside expansions
    use_placement_span: Option<Span>,
    candidates: &[ImportSuggestion],
    instead: Instead,
    found_use: FoundUse,
    mode: DiagMode,
    path: Vec<Segment>,
    append: &str,
) -> bool {
    if candidates.is_empty() {
        return false;
    }

    let mut accessible_path_strings: Vec<PathString<'_>> = Vec::new();
    let mut inaccessible_path_strings: Vec<PathString<'_>> = Vec::new();

    candidates.iter().for_each(|c| {
        if c.accessible {
            // Don't suggest `#[doc(hidden)]` items from other crates
            if c.doc_visible {
                accessible_path_strings.push((
                    pprust::path_to_string(&c.path),
                    c.descr,
                    c.did.and_then(|did| Some(tcx.source_span(did.as_local()?))),
                    &c.note,
                    c.via_import,
                ))
            }
        } else {
            inaccessible_path_strings.push((
                pprust::path_to_string(&c.path),
                c.descr,
                c.did.and_then(|did| Some(tcx.source_span(did.as_local()?))),
                &c.note,
                c.via_import,
            ))
        }
    });

    // we want consistent results across executions, but candidates are produced
    // by iterating through a hash map, so make sure they are ordered:
    for path_strings in [&mut accessible_path_strings, &mut inaccessible_path_strings] {
        path_strings.sort_by(|a, b| a.0.cmp(&b.0));
        path_strings.dedup_by(|a, b| a.0 == b.0);
        let core_path_strings =
            path_strings.extract_if(|p| p.0.starts_with("core::")).collect::<Vec<_>>();
        let std_path_strings =
            path_strings.extract_if(|p| p.0.starts_with("std::")).collect::<Vec<_>>();
        let foreign_crate_path_strings =
            path_strings.extract_if(|p| !p.0.starts_with("crate::")).collect::<Vec<_>>();

        // We list the `crate` local paths first.
        // Then we list the `std`/`core` paths.
        if std_path_strings.len() == core_path_strings.len() {
            // Do not list `core::` paths if we are already listing the `std::` ones.
            path_strings.extend(std_path_strings);
        } else {
            path_strings.extend(std_path_strings);
            path_strings.extend(core_path_strings);
        }
        // List all paths from foreign crates last.
        path_strings.extend(foreign_crate_path_strings);
    }

    if !accessible_path_strings.is_empty() {
        let (determiner, kind, s, name, through) =
            if let [(name, descr, _, _, via_import)] = &accessible_path_strings[..] {
                (
                    "this",
                    *descr,
                    "",
                    format!(" `{name}`"),
                    if *via_import { " through its public re-export" } else { "" },
                )
            } else {
                // Get the unique item kinds and if there's only one, we use the right kind name
                // instead of the more generic "items".
                let mut kinds = accessible_path_strings
                    .iter()
                    .map(|(_, descr, _, _, _)| *descr)
                    .collect::<FxHashSet<&str>>()
                    .into_iter();
                let kind = if let Some(kind) = kinds.next()
                    && let None = kinds.next()
                {
                    kind
                } else {
                    "item"
                };
                let s = if kind.ends_with('s') { "es" } else { "s" };

                ("one of these", kind, s, String::new(), "")
            };

        let instead = if let Instead::Yes = instead { " instead" } else { "" };
        let mut msg = if let DiagMode::Pattern = mode {
            format!(
                "if you meant to match on {kind}{s}{instead}{name}, use the full path in the \
                 pattern",
            )
        } else {
            format!("consider importing {determiner} {kind}{s}{through}{instead}")
        };

        for note in accessible_path_strings.iter().flat_map(|cand| cand.3.as_ref()) {
            err.note(note.clone());
        }

        let append_candidates = |msg: &mut String, accessible_path_strings: Vec<PathString<'_>>| {
            msg.push(':');

            for candidate in accessible_path_strings {
                msg.push('\n');
                msg.push_str(&candidate.0);
            }
        };

        if let Some(span) = use_placement_span {
            let (add_use, trailing) = match mode {
                DiagMode::Pattern => {
                    err.span_suggestions(
                        span,
                        msg,
                        accessible_path_strings.into_iter().map(|a| a.0),
                        Applicability::MaybeIncorrect,
                    );
                    return true;
                }
                DiagMode::Import { .. } => ("", ""),
                DiagMode::Normal => ("use ", ";\n"),
            };
            for candidate in &mut accessible_path_strings {
                // produce an additional newline to separate the new use statement
                // from the directly following item.
                let additional_newline = if let FoundUse::No = found_use
                    && let DiagMode::Normal = mode
                {
                    "\n"
                } else {
                    ""
                };
                candidate.0 =
                    format!("{add_use}{}{append}{trailing}{additional_newline}", candidate.0);
            }

            match mode {
                DiagMode::Import { append: true, .. } => {
                    append_candidates(&mut msg, accessible_path_strings);
                    err.span_help(span, msg);
                }
                _ => {
                    err.span_suggestions_with_style(
                        span,
                        msg,
                        accessible_path_strings.into_iter().map(|a| a.0),
                        Applicability::MaybeIncorrect,
                        SuggestionStyle::ShowAlways,
                    );
                }
            }

            if let [first, .., last] = &path[..] {
                let sp = first.ident.span.until(last.ident.span);
                // Our suggestion is empty, so make sure the span is not empty (or we'd ICE).
                // Can happen for derive-generated spans.
                if sp.can_be_used_for_suggestions() && !sp.is_empty() {
                    err.span_suggestion_verbose(
                        sp,
                        format!("if you import `{}`, refer to it directly", last.ident),
                        "",
                        Applicability::Unspecified,
                    );
                }
            }
        } else {
            append_candidates(&mut msg, accessible_path_strings);
            err.help(msg);
        }
        true
    } else if !(inaccessible_path_strings.is_empty() || matches!(mode, DiagMode::Import { .. })) {
        let prefix =
            if let DiagMode::Pattern = mode { "you might have meant to match on " } else { "" };
        if let [(name, descr, source_span, note, _)] = &inaccessible_path_strings[..] {
            let msg = format!(
                "{prefix}{descr} `{name}`{} exists but is inaccessible",
                if let DiagMode::Pattern = mode { ", which" } else { "" }
            );

            if let Some(source_span) = source_span {
                let span = tcx.sess.source_map().guess_head_span(*source_span);
                let mut multi_span = MultiSpan::from_span(span);
                multi_span.push_span_label(span, "not accessible");
                err.span_note(multi_span, msg);
            } else {
                err.note(msg);
            }
            if let Some(note) = (*note).as_deref() {
                err.note(note.to_string());
            }
        } else {
            let (_, descr_first, _, _, _) = &inaccessible_path_strings[0];
            let descr = if inaccessible_path_strings
                .iter()
                .skip(1)
                .all(|(_, descr, _, _, _)| descr == descr_first)
            {
                descr_first
            } else {
                "item"
            };
            let plural_descr =
                if descr.ends_with('s') { format!("{descr}es") } else { format!("{descr}s") };

            let mut msg = format!("{prefix}these {plural_descr} exist but are inaccessible");
            let mut has_colon = false;

            let mut spans = Vec::new();
            for (name, _, source_span, _, _) in &inaccessible_path_strings {
                if let Some(source_span) = source_span {
                    let span = tcx.sess.source_map().guess_head_span(*source_span);
                    spans.push((name, span));
                } else {
                    if !has_colon {
                        msg.push(':');
                        has_colon = true;
                    }
                    msg.push('\n');
                    msg.push_str(name);
                }
            }

            let mut multi_span = MultiSpan::from_spans(spans.iter().map(|(_, sp)| *sp).collect());
            for (name, span) in spans {
                multi_span.push_span_label(span, format!("`{name}`: not accessible"));
            }

            for note in inaccessible_path_strings.iter().flat_map(|cand| cand.3.as_ref()) {
                err.note(note.clone());
            }

            err.span_note(multi_span, msg);
        }
        true
    } else {
        false
    }
}

#[derive(Debug)]
struct UsePlacementFinder {
    target_module: NodeId,
    first_legal_span: Option<Span>,
    first_use_span: Option<Span>,
}

impl UsePlacementFinder {
    fn check(krate: &Crate, target_module: NodeId) -> (Option<Span>, FoundUse) {
        let mut finder =
            UsePlacementFinder { target_module, first_legal_span: None, first_use_span: None };
        finder.visit_crate(krate);
        if let Some(use_span) = finder.first_use_span {
            (Some(use_span), FoundUse::Yes)
        } else {
            (finder.first_legal_span, FoundUse::No)
        }
    }
}

impl<'tcx> visit::Visitor<'tcx> for UsePlacementFinder {
    fn visit_crate(&mut self, c: &Crate) {
        if self.target_module == CRATE_NODE_ID {
            let inject = c.spans.inject_use_span;
            if is_span_suitable_for_use_injection(inject) {
                self.first_legal_span = Some(inject);
            }
            self.first_use_span = search_for_any_use_in_items(&c.items);
            return;
        } else {
            visit::walk_crate(self, c);
        }
    }

    fn visit_item(&mut self, item: &'tcx ast::Item) {
        if self.target_module == item.id {
            if let ItemKind::Mod(_, ModKind::Loaded(items, _inline, mod_spans)) = &item.kind {
                let inject = mod_spans.inject_use_span;
                if is_span_suitable_for_use_injection(inject) {
                    self.first_legal_span = Some(inject);
                }
                self.first_use_span = search_for_any_use_in_items(items);
                return;
            }
        } else {
            visit::walk_item(self, item);
        }
    }
}

fn search_for_any_use_in_items(items: &[P<ast::Item>]) -> Option<Span> {
    for item in items {
        if let ItemKind::Use(..) = item.kind {
            if is_span_suitable_for_use_injection(item.span) {
                let mut lo = item.span.lo();
                for attr in &item.attrs {
                    if attr.span.eq_ctxt(item.span) {
                        lo = std::cmp::min(lo, attr.span.lo());
                    }
                }
                return Some(Span::new(lo, lo, item.span.ctxt(), item.span.parent()));
            }
        }
    }
    None
}

fn is_span_suitable_for_use_injection(s: Span) -> bool {
    // don't suggest placing a use before the prelude
    // import or other generated ones
    !s.from_expansion()
}