summaryrefslogtreecommitdiff
path: root/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala
blob: ba1659d274720cec3c263047e5b9a531f5e62792 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
2731
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
2748
2749
2750
2751
2752
2753
2754
2755
2756
2757
2758
2759
2760
2761
2762
2763
2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775
2776
2777
2778
2779
2780
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802
2803
2804
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
2820
2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
2844
2845
2846
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
2857
2858
2859
2860
2861
2862
2863
2864
2865
2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
2877
2878
2879
2880
2881
2882
2883
2884
2885
2886
2887
2888
2889
2890
2891
2892
2893
2894
2895
2896
2897
2898
2899
2900
2901
2902
2903
2904
2905
2906
2907
2908
2909
2910
2911
2912
2913
2914
2915
2916
2917
2918
2919
2920
2921
2922
2923
2924
2925
2926
2927
2928
2929
2930
2931
2932
2933
2934
2935
2936
2937
2938
2939
2940
2941
2942
2943
2944
2945
2946
2947
2948
2949
2950
2951
2952
2953
2954
2955
2956
2957
2958
2959
2960
2961
2962
2963
2964
2965
2966
2967
2968
2969
2970
2971
2972
2973
2974
2975
2976
2977
2978
2979
2980
2981
2982
2983
2984
2985
2986
2987
2988
2989
2990
2991
2992
2993
2994
2995
2996
2997
2998
2999
3000
3001
3002
3003
3004
3005
3006
3007
3008
3009
3010
3011
3012
3013
3014
3015
3016
3017
3018
3019
3020
3021
3022
3023
3024
3025
3026
3027
3028
3029
3030
3031
3032
3033
3034
3035
3036
3037
3038
3039
3040
3041
3042
3043
3044
3045
3046
3047
3048
3049
3050
3051
3052
3053
3054
3055
3056
3057
3058
3059
3060
3061
3062
3063
3064
3065
3066
3067
3068
3069
3070
3071
3072
3073
3074
3075
3076
3077
3078
3079
3080
3081
3082
3083
3084
3085
3086
3087
3088
3089
3090
3091
3092
3093
3094
3095
3096
3097
3098
3099
3100
3101
3102
3103
3104
3105
3106
3107
3108
3109
3110
3111
3112
3113
3114
3115
3116
3117
3118
3119
3120
3121
3122
3123
3124
3125
3126
3127
3128
3129
3130
3131
3132
3133
3134
3135
3136
3137
3138
3139
3140
3141
3142
3143
3144
3145
3146
3147
3148
3149
3150
3151
3152
3153
3154
3155
3156
3157
3158
3159
3160
3161
3162
3163
3164
3165
3166
3167
3168
3169
3170
3171
3172
3173
3174
3175
3176
3177
3178
3179
3180
3181
3182
3183
3184
3185
3186
3187
3188
3189
3190
3191
3192
3193
3194
3195
3196
3197
3198
3199
3200
3201
3202
3203
3204
3205
3206
3207
3208
3209
3210
3211
3212
3213
3214
3215
3216
3217
3218
3219
3220
3221
3222
3223
3224
3225
3226
3227
3228
3229
3230
3231
3232
3233
3234
3235
3236
3237
3238
3239
3240
3241
3242
3243
3244
3245
3246
3247
3248
3249
3250
3251
3252
3253
3254
3255
3256
3257
3258
3259
3260
3261
3262
3263
3264
3265
3266
3267
3268
3269
3270
3271
3272
3273
3274
3275
3276
3277
3278
3279
3280
3281
3282
3283
3284
3285
3286
3287
3288
3289
3290
3291
3292
3293
3294
3295
3296
3297
3298
3299
3300
3301
3302
3303
3304
/* NSC -- new Scala compiler
 * Copyright 2005-2013 LAMP/EPFL
 * @author  Martin Odersky
 */

//todo: allow infix type patterns
//todo verify when stableId's should be just plain qualified type ids

package scala.tools.nsc
package ast.parser

import scala.collection.mutable
import mutable.ListBuffer
import scala.reflect.internal.{ Precedence, ModifierFlags => Flags }
import scala.reflect.internal.util.{ SourceFile, Position, FreshNameCreator, ListOfNil }
import Tokens._

/** Historical note: JavaParsers started life as a direct copy of Parsers
 *  but at a time when that Parsers had been replaced by a different one.
 *  Later it was dropped and the original Parsers reinstated, leaving us with
 *  massive duplication between Parsers and JavaParsers.
 *
 *  This trait and the similar one for Scanners/JavaScanners represents
 *  the beginnings of a campaign against this latest incursion by Cutty
 *  McPastington and his army of very similar soldiers.
 */
trait ParsersCommon extends ScannersCommon { self =>
  val global : Global
  // the use of currentUnit in the parser should be avoided as it might
  // cause unexpected behaviour when you work with two units at the
  // same time; use Parser.unit instead
  import global.{currentUnit => _, _}

  def newLiteral(const: Any) = Literal(Constant(const))
  def literalUnit            = gen.mkSyntheticUnit()

  /** This is now an abstract class, only to work around the optimizer:
   *  methods in traits are never inlined.
   */
  abstract class ParserCommon {
    val in: ScannerCommon
    def deprecationWarning(off: Offset, msg: String, since: String): Unit
    def accept(token: Token): Int

    /** Methods inParensOrError and similar take a second argument which, should
     *  the next token not be the expected opener (e.g. LPAREN) will be returned
     *  instead of the contents of the groupers.  However in all cases accept(LPAREN)
     *  will be called, so a parse error will still result.  If the grouping is
     *  optional, in.token should be tested before calling these methods.
     */
    @inline final def inParens[T](body: => T): T = {
      accept(LPAREN)
      val ret = body
      accept(RPAREN)
      ret
    }
    @inline final def inParensOrError[T](body: => T, alt: T): T =
      if (in.token == LPAREN) inParens(body)
      else { accept(LPAREN) ; alt }

    @inline final def inParensOrUnit[T](body: => Tree): Tree = inParensOrError(body, literalUnit)
    @inline final def inParensOrNil[T](body: => List[T]): List[T] = inParensOrError(body, Nil)

    @inline final def inBraces[T](body: => T): T = {
      accept(LBRACE)
      val ret = body
      accept(RBRACE)
      ret
    }
    @inline final def inBracesOrError[T](body: => T, alt: T): T =
      if (in.token == LBRACE) inBraces(body)
      else { accept(LBRACE) ; alt }

    @inline final def inBracesOrNil[T](body: => List[T]): List[T] = inBracesOrError(body, Nil)
    @inline final def inBracesOrUnit[T](body: => Tree): Tree = inBracesOrError(body, literalUnit)
    @inline final def dropAnyBraces[T](body: => T): T =
      if (in.token == LBRACE) inBraces(body)
      else body

    @inline final def inBrackets[T](body: => T): T = {
      accept(LBRACKET)
      val ret = body
      accept(RBRACKET)
      ret
    }

    /** Creates an actual Parens node (only used during parsing.)
     */
    @inline final def makeParens(body: => List[Tree]): Parens =
      Parens(inParens(if (in.token == RPAREN) Nil else body))
  }
}

/** Performs the following context-free rewritings:
 *
 *  <ol>
 *    <li>
 *      Places all pattern variables in Bind nodes. In a pattern, for
 *      identifiers `x`:<pre>
 *                 x  => x @ _
 *               x:T  => x @ (_ : T)</pre>
 *    </li>
 *    <li>Removes pattern definitions (PatDef's) as follows:
 *      If pattern is a simple (typed) identifier:<pre>
 *        <b>val</b> x = e     ==>  <b>val</b> x = e
 *        <b>val</b> x: T = e  ==>  <b>val</b> x: T = e</pre>
 *
 *      if there are no variables in pattern<pre>
 *        <b>val</b> p = e  ==>  e match (case p => ())</pre>
 *
 *      if there is exactly one variable in pattern<pre>
 *        <b>val</b> x_1 = e <b>match</b> (case p => (x_1))</pre>
 *
 *      if there is more than one variable in pattern<pre>
 *        <b>val</b> p = e  ==>  <b>private synthetic val</b> t$ = e <b>match</b> (case p => (x_1, ..., x_N))
 *                        <b>val</b> x_1 = t$._1
 *                        ...
 *                        <b>val</b> x_N = t$._N</pre>
 *    </li>
 *    <li>
 *       Removes function types as follows:<pre>
 *        (argtpes) => restpe   ==>   scala.Function_n[argtpes, restpe]</pre>
 *    </li>
 *    <li>
 *      Wraps naked case definitions in a match as follows:<pre>
 *        { cases }   ==>   (x => x.match {cases})<span style="font-family:normal;">, except when already argument to match</span></pre>
 *    </li>
 *  </ol>
 */
trait Parsers extends Scanners with MarkupParsers with ParsersCommon {
self =>
  val global: Global
  import global._

  case class OpInfo(lhs: Tree, operator: TermName, targs: List[Tree], offset: Offset) {
    def precedence = Precedence(operator.toString)
  }

  class SourceFileParser(val source: SourceFile) extends Parser {

    /** The parse starting point depends on whether the source file is self-contained:
     *  if not, the AST will be supplemented.
     */
    def parseStartRule =
      if (source.isSelfContained) () => compilationUnit()
      else () => scriptBody()

    def newScanner(): Scanner = new SourceFileScanner(source)

    val in = newScanner()
    in.init()

    def unit = global.currentUnit

    // suppress warnings; silent abort on errors
    def warning(offset: Offset, msg: String): Unit = ()
    def deprecationWarning(offset: Offset, msg: String, since: String): Unit = ()

    def syntaxError(offset: Offset, msg: String): Unit = throw new MalformedInput(offset, msg)
    def incompleteInputError(msg: String): Unit = throw new MalformedInput(source.content.length - 1, msg)

    object symbXMLBuilder extends SymbolicXMLBuilder(this, preserveWS = true) { // DEBUG choices
      val global: self.global.type = self.global
    }

    /** the markup parser
     * The first time this lazy val is accessed, we assume we were trying to parse an xml literal.
     * The current position is recorded for later error reporting if it turns out
     * that we don't have the xml library on the compilation classpath.
     */
    private[this] lazy val xmlp = {
      unit.encounteredXml(o2p(in.offset))
      new MarkupParser(this, preserveWS = true)
    }

    def xmlLiteral() : Tree = xmlp.xLiteral
    def xmlLiteralPattern() : Tree = xmlp.xLiteralPattern
  }

  class OutlineParser(source: SourceFile) extends SourceFileParser(source) {

    def skipBraces[T](body: T): T = {
      accept(LBRACE)
      var openBraces = 1
      while (in.token != EOF && openBraces > 0) {
        if (in.token == XMLSTART) xmlLiteral()
        else {
          if (in.token == LBRACE) openBraces += 1
          else if (in.token == RBRACE) openBraces -= 1
          in.nextToken()
        }
      }
      body
    }

    override def blockExpr(): Tree = skipBraces(EmptyTree)

    override def templateBody(isPre: Boolean) = skipBraces((noSelfType, EmptyTree.asList))
  }

  class UnitParser(override val unit: global.CompilationUnit, patches: List[BracePatch]) extends SourceFileParser(unit.source) { uself =>
    def this(unit: global.CompilationUnit) = this(unit, Nil)

    override def newScanner() = new UnitScanner(unit, patches)

    override def warning(offset: Offset, msg: String): Unit =
      reporter.warning(o2p(offset), msg)

    override def deprecationWarning(offset: Offset, msg: String, since: String): Unit =
      currentRun.reporting.deprecationWarning(o2p(offset), msg, since)

    private var smartParsing = false
    @inline private def withSmartParsing[T](body: => T): T = {
      val saved = smartParsing
      smartParsing = true
      try body
      finally smartParsing = saved
    }
    def withPatches(patches: List[BracePatch]): UnitParser = new UnitParser(unit, patches)

    val syntaxErrors = new ListBuffer[(Int, String)]
    def showSyntaxErrors() =
      for ((offset, msg) <- syntaxErrors)
        reporter.error(o2p(offset), msg)

    override def syntaxError(offset: Offset, msg: String): Unit = {
      if (smartParsing) syntaxErrors += ((offset, msg))
      else reporter.error(o2p(offset), msg)
    }

    override def incompleteInputError(msg: String): Unit = {
      val offset = source.content.length - 1
      if (smartParsing) syntaxErrors += ((offset, msg))
      else currentRun.parsing.incompleteInputError(o2p(offset), msg)
    }

    /** parse unit. If there are inbalanced braces,
     *  try to correct them and reparse.
     */
    def smartParse(): Tree = withSmartParsing {
      val firstTry = parse()
      if (syntaxErrors.isEmpty) firstTry
      else in.healBraces() match {
        case Nil      => showSyntaxErrors() ; firstTry
        case patches  => (this withPatches patches).parse()
      }
    }
  }

  type Location = Int
  final val Local: Location = 0
  final val InBlock: Location = 1
  final val InTemplate: Location = 2

  // These symbols may not yet be loaded (e.g. in the ide) so don't go
  // through definitions to obtain the names.
  lazy val ScalaValueClassNames = Seq(tpnme.AnyVal,
      tpnme.Unit,
      tpnme.Boolean,
      tpnme.Byte,
      tpnme.Short,
      tpnme.Char,
      tpnme.Int,
      tpnme.Long,
      tpnme.Float,
      tpnme.Double)

  import nme.raw

  abstract class Parser extends ParserCommon { parser =>
    val in: Scanner
    def unit: CompilationUnit
    def source: SourceFile

    /** Scoping operator used to temporarily look into the future.
     *  Backs up scanner data before evaluating a block and restores it after.
     */
    @inline final def lookingAhead[T](body: => T): T = {
      val saved = new ScannerData {} copyFrom in
      in.nextToken()
      try body finally in copyFrom saved
    }

    /** Perform an operation while peeking ahead.
     *  Pushback if the operation yields an empty tree or blows to pieces.
     */
    @inline def peekingAhead(tree: =>Tree): Tree = {
      @inline def peekahead() = {
        in.prev copyFrom in
        in.nextToken()
      }
      @inline def pushback() = {
        in.next copyFrom in
        in copyFrom in.prev
      }
      peekahead()
      // try it, in case it is recoverable
      val res = try tree catch { case e: Exception => pushback() ; throw e }
      if (res.isEmpty) pushback()
      res
    }

    class ParserTreeBuilder extends TreeBuilder {
      val global: self.global.type = self.global
      def unit = parser.unit
      def source = parser.source
    }
    val treeBuilder = new ParserTreeBuilder
    import treeBuilder.{global => _, unit => _, source => _, fresh => _, _}

    implicit def fresh: FreshNameCreator = unit.fresh

    def o2p(offset: Offset): Position                          = Position.offset(source, offset)
    def r2p(start: Offset, mid: Offset, end: Offset): Position = rangePos(source, start, mid, end)
    def r2p(start: Offset, mid: Offset): Position              = r2p(start, mid, in.lastOffset max start)
    def r2p(offset: Offset): Position                          = r2p(offset, offset)

    /** whether a non-continuable syntax error has been seen */
    private var lastErrorOffset : Int = -1

    /** The types of the context bounds of type parameters of the surrounding class
     */
    private var classContextBounds: List[Tree] = Nil
    @inline private def savingClassContextBounds[T](op: => T): T = {
      val saved = classContextBounds
      try op
      finally classContextBounds = saved
    }


    /** Are we inside the Scala package? Set for files that start with package scala
     */
    private var inScalaPackage = false
    private var currentPackage = ""
    def resetPackage(): Unit = {
      inScalaPackage = false
      currentPackage = ""
    }
    private def inScalaRootPackage = inScalaPackage && currentPackage == "scala"

    def parseStartRule: () => Tree

    def parseRule[T](rule: this.type => T): T = {
      val t = rule(this)
      accept(EOF)
      t
    }

    /** This is the general parse entry point.
     */
    def parse(): Tree = parseRule(_.parseStartRule())

    /** These are alternative entry points for repl, script runner, toolbox and parsing in macros.
     */
    def parseStats(): List[Tree] = parseRule(_.templateStats())
    def parseStatsOrPackages(): List[Tree] = parseRule(_.templateOrTopStatSeq())

    /** This is the parse entry point for code which is not self-contained, e.g.
     *  a script which is a series of template statements.  They will be
     *  swaddled in Trees until the AST is equivalent to the one returned
     *  by compilationUnit().
     */
    def scriptBody(): Tree = {
      val stmts = parseStats()

      def mainModuleName = newTermName(settings.script.value)

      /* If there is only a single object template in the file and it has a
       * suitable main method, we will use it rather than building another object
       * around it.  Since objects are loaded lazily the whole script would have
       * been a no-op, so we're not taking much liberty.
       */
      def searchForMain(): Tree = {
        import PartialFunction.cond

        /* Have to be fairly liberal about what constitutes a main method since
         * nothing has been typed yet - for instance we can't assume the parameter
         * type will look exactly like "Array[String]" as it could have been renamed
         * via import, etc.
         */
        def isMainMethod(t: Tree) = t match {
          case DefDef(_, nme.main, Nil, List(_), _, _)  => true
          case _                                        => false
        }
        def isApp(t: Tree) = t match {
          case Template(parents, _, _) => parents.exists(cond(_) { case Ident(tpnme.App) => true })
          case _ => false
        }
        /* We allow only one main module. */
        var seenModule = false
        var disallowed = EmptyTree: Tree
        val newStmts = stmts.map {
          case md @ ModuleDef(mods, name, template) if !seenModule && (isApp(template) || md.exists(isMainMethod)) =>
            seenModule = true
            /* This slightly hacky situation arises because we have no way to communicate
             * back to the scriptrunner what the name of the program is.  Even if we were
             * willing to take the sketchy route of settings.script.value = progName, that
             * does not work when using fsc.  And to find out in advance would impose a
             * whole additional parse.  So instead, if the actual object's name differs from
             * what the script is expecting, we transform it to match.
             */
            if (name == mainModuleName) md
            else treeCopy.ModuleDef(md, mods, mainModuleName, template)
          case md @ ModuleDef(_, _, _)   => md
          case cd @ ClassDef(_, _, _, _) => cd
          case t  @ Import(_, _)         => t
          case t =>
            /* If we see anything but the above, fail. */
            if (disallowed.isEmpty) disallowed = t
            EmptyTree
        }
        if (disallowed.isEmpty) makeEmptyPackage(0, newStmts)
        else {
          if (seenModule)
            warning(disallowed.pos.point, "Script has a main object but statement is disallowed")
          EmptyTree
        }
      }

      def mainModule: Tree =
        if (mainModuleName == newTermName(ScriptRunner.defaultScriptMain)) searchForMain() else EmptyTree

      def repackaged: Tree = {
        /*  Here we are building an AST representing the following source fiction,
         *  where `moduleName` is from -Xscript (defaults to "Main") and <stmts> are
         *  the result of parsing the script file.
         *
         *  {{{
         *  object moduleName {
         *    def main(args: Array[String]): Unit =
         *      new AnyRef {
         *        stmts
         *      }
         *  }
         *  }}}
         */
        def emptyInit   = DefDef(
          NoMods,
          nme.CONSTRUCTOR,
          Nil,
          ListOfNil,
          TypeTree(),
          Block(List(Apply(gen.mkSuperInitCall, Nil)), literalUnit)
        )

        // def main
        def mainParamType = AppliedTypeTree(Ident(tpnme.Array), List(Ident(tpnme.String)))
        def mainParameter = List(ValDef(Modifiers(Flags.PARAM), nme.args, mainParamType, EmptyTree))
        def mainDef       = DefDef(NoMods, nme.main, Nil, List(mainParameter), scalaDot(tpnme.Unit), gen.mkAnonymousNew(stmts))

        // object Main
        def moduleName  = newTermName(ScriptRunner scriptMain settings)
        def moduleBody  = Template(atInPos(scalaAnyRefConstr) :: Nil, noSelfType, List(emptyInit, mainDef))
        def moduleDef   = ModuleDef(NoMods, moduleName, moduleBody)

        // package <empty> { ... }
        makeEmptyPackage(0, moduleDef :: Nil)
      }

      mainModule orElse repackaged
    }

/* --------------- PLACEHOLDERS ------------------------------------------- */

    /** The implicit parameters introduced by `_` in the current expression.
     *  Parameters appear in reverse order.
     */
    var placeholderParams: List[ValDef] = Nil

    /** The placeholderTypes introduced by `_` in the current type.
     *  Parameters appear in reverse order.
     */
    var placeholderTypes: List[TypeDef] = Nil

    def checkNoEscapingPlaceholders[T](op: => T): T = {
      val savedPlaceholderParams = placeholderParams
      val savedPlaceholderTypes = placeholderTypes
      placeholderParams = List()
      placeholderTypes = List()

      val res = op

      placeholderParams match {
        case vd :: _ =>
          syntaxError(vd.pos, "unbound placeholder parameter", skipIt = false)
          placeholderParams = List()
        case _ =>
      }
      placeholderTypes match {
        case td :: _ =>
          syntaxError(td.pos, "unbound wildcard type", skipIt = false)
          placeholderTypes = List()
        case _ =>
      }
      placeholderParams = savedPlaceholderParams
      placeholderTypes = savedPlaceholderTypes

      res
    }

    def placeholderTypeBoundary(op: => Tree): Tree = {
      val savedPlaceholderTypes = placeholderTypes
      placeholderTypes = List()
      var t = op
      if (!placeholderTypes.isEmpty && t.isInstanceOf[AppliedTypeTree]) {
        val expos = t.pos
        ensureNonOverlapping(t, placeholderTypes)
        t = atPos(expos) { ExistentialTypeTree(t, placeholderTypes.reverse) }
        placeholderTypes = List()
      }
      placeholderTypes = placeholderTypes ::: savedPlaceholderTypes
      t
    }

    def isWildcard(t: Tree): Boolean = t match {
      case Ident(name1) => !placeholderParams.isEmpty && name1 == placeholderParams.head.name
      case Typed(t1, _) => isWildcard(t1)
      case Annotated(t1, _) => isWildcard(t1)
      case _ => false
    }

/* ------------- ERROR HANDLING ------------------------------------------- */

    val assumedClosingParens = mutable.Map(RPAREN -> 0, RBRACKET -> 0, RBRACE -> 0)

    private var inFunReturnType = false
    @inline private def fromWithinReturnType[T](body: => T): T = {
      val saved = inFunReturnType
      inFunReturnType = true
      try body
      finally inFunReturnType = saved
    }

    protected def skip(targetToken: Token): Unit = {
      var nparens = 0
      var nbraces = 0
      while (true) {
        in.token match {
          case EOF =>
            return
          case SEMI =>
            if (nparens == 0 && nbraces == 0) return
          case NEWLINE =>
            if (nparens == 0 && nbraces == 0) return
          case NEWLINES =>
            if (nparens == 0 && nbraces == 0) return
          case RPAREN =>
            nparens -= 1
          case RBRACE =>
            if (nbraces == 0) return
            nbraces -= 1
          case LPAREN =>
            nparens += 1
          case LBRACE =>
            nbraces += 1
          case _ =>
        }
        if (targetToken == in.token && nparens == 0 && nbraces == 0) return
        in.nextToken()
      }
    }
    def warning(offset: Offset, msg: String): Unit
    def incompleteInputError(msg: String): Unit
    def syntaxError(offset: Offset, msg: String): Unit

    private def syntaxError(pos: Position, msg: String, skipIt: Boolean): Unit =
      syntaxError(pos pointOrElse in.offset, msg, skipIt)
    def syntaxError(msg: String, skipIt: Boolean): Unit =
      syntaxError(in.offset, msg, skipIt)

    def syntaxError(offset: Offset, msg: String, skipIt: Boolean): Unit = {
      if (offset > lastErrorOffset) {
        syntaxError(offset, msg)
        lastErrorOffset = in.offset         // no more errors on this token.
      }
      if (skipIt)
        skip(UNDEF)
    }

    def warning(msg: String): Unit = warning(in.offset, msg)

    def syntaxErrorOrIncomplete(msg: String, skipIt: Boolean): Unit = {
      if (in.token == EOF)
        incompleteInputError(msg)
      else
        syntaxError(in.offset, msg, skipIt)
    }
    def syntaxErrorOrIncompleteAnd[T](msg: String, skipIt: Boolean)(and: T): T = {
      syntaxErrorOrIncomplete(msg, skipIt)
      and
    }

    def expectedMsgTemplate(exp: String, fnd: String) = s"$exp expected but $fnd found."
    def expectedMsg(token: Token): String = expectedMsgTemplate(token2string(token), token2string(in.token))

    /** Consume one token of the specified type, or signal an error if it is not there. */
    def accept(token: Token): Offset = {
      val offset = in.offset
      if (in.token != token) {
        syntaxErrorOrIncomplete(expectedMsg(token), skipIt = false)
        if ((token == RPAREN || token == RBRACE || token == RBRACKET))
          if (in.parenBalance(token) + assumedClosingParens(token) < 0)
            assumedClosingParens(token) += 1
          else
            skip(token)
        else
          skip(UNDEF)
      }
      if (in.token == token) in.nextToken()
      offset
    }

    /** {{{
     *  semi = nl {nl} | `;`
     *  nl  = `\n' // where allowed
     *  }}}
     */
    def acceptStatSep(): Unit = in.token match {
      case NEWLINE | NEWLINES => in.nextToken()
      case _                  => accept(SEMI)
    }
    def acceptStatSepOpt() =
      if (!isStatSeqEnd)
        acceptStatSep()

    def errorTypeTree    = setInPos(TypeTree() setType ErrorType)
    def errorTermTree    = setInPos(newLiteral(null))
    def errorPatternTree = setInPos(Ident(nme.WILDCARD))

    /** Check that type parameter is not by name or repeated. */
    def checkNotByNameOrVarargs(tpt: Tree) = {
      if (treeInfo isByNameParamType tpt)
        syntaxError(tpt.pos, "no by-name parameter type allowed here", skipIt = false)
      else if (treeInfo isRepeatedParamType tpt)
        syntaxError(tpt.pos, "no * parameter type allowed here", skipIt = false)
    }

/* -------------- TOKEN CLASSES ------------------------------------------- */

    def isModifier: Boolean = in.token match {
      case ABSTRACT | FINAL | SEALED | PRIVATE |
           PROTECTED | OVERRIDE | IMPLICIT | LAZY => true
      case _ => false
    }

    def isAnnotation: Boolean = in.token == AT

    def isLocalModifier: Boolean = in.token match {
      case ABSTRACT | FINAL | SEALED | IMPLICIT | LAZY => true
      case _ => false
    }

    def isTemplateIntro: Boolean = in.token match {
      case OBJECT | CASEOBJECT | CLASS | CASECLASS | TRAIT  => true
      case _                                                => false
    }
    def isDclIntro: Boolean = in.token match {
      case VAL | VAR | DEF | TYPE => true
      case _ => false
    }

    def isDefIntro = isTemplateIntro || isDclIntro

    def isNumericLit: Boolean = in.token match {
      case INTLIT | LONGLIT | FLOATLIT | DOUBLELIT => true
      case _ => false
    }

    def isIdentExcept(except: Name) = isIdent && in.name != except
    def isIdentOf(name: Name)       = isIdent && in.name == name

    def isUnaryOp  = isIdent && raw.isUnary(in.name)
    def isRawStar  = isRawIdent && in.name == raw.STAR
    def isRawBar   = isRawIdent && in.name == raw.BAR
    def isRawIdent = in.token == IDENTIFIER

    def isIdent = in.token == IDENTIFIER || in.token == BACKQUOTED_IDENT
    def isMacro = in.token == IDENTIFIER && in.name == nme.MACROkw

    def isLiteralToken(token: Token) = token match {
      case CHARLIT | INTLIT | LONGLIT | FLOATLIT | DOUBLELIT |
           STRINGLIT | INTERPOLATIONID | SYMBOLLIT | TRUE | FALSE | NULL => true
      case _                                                        => false
    }
    def isLiteral = isLiteralToken(in.token)

    def isSimpleExprIntroToken(token: Token): Boolean = isLiteralToken(token) || (token match {
      case IDENTIFIER | BACKQUOTED_IDENT |
           THIS | SUPER | NEW | USCORE |
           LPAREN | LBRACE | XMLSTART => true
      case _ => false
    })

    def isSimpleExprIntro: Boolean = isExprIntroToken(in.token)

    def isExprIntroToken(token: Token): Boolean = isLiteralToken(token) || (token match {
      case IDENTIFIER | BACKQUOTED_IDENT |
           THIS | SUPER | IF | FOR | NEW | USCORE | TRY | WHILE |
           DO | RETURN | THROW | LPAREN | LBRACE | XMLSTART => true
      case _ => false
    })

    def isExprIntro: Boolean = isExprIntroToken(in.token)

    def isTypeIntroToken(token: Token): Boolean = token match {
      case IDENTIFIER | BACKQUOTED_IDENT | THIS |
           SUPER | USCORE | LPAREN | AT => true
      case _ => false
    }

    def isStatSeqEnd = in.token == RBRACE || in.token == EOF

    def isCaseDefEnd = in.token == RBRACE || in.token == CASE || in.token == EOF

    def isStatSep(token: Token): Boolean =
      token == NEWLINE || token == NEWLINES || token == SEMI

    def isStatSep: Boolean = isStatSep(in.token)


/* --------- COMMENT AND ATTRIBUTE COLLECTION ----------------------------- */

    /** A hook for joining the comment associated with a definition.
     *  Overridden by scaladoc.
     */
    def joinComment(trees: => List[Tree]): List[Tree] = trees

/* ---------- TREE CONSTRUCTION ------------------------------------------- */

    def atPos[T <: Tree](offset: Offset)(t: T): T                            = atPos(r2p(offset))(t)
    def atPos[T <: Tree](start: Offset, point: Offset)(t: T): T              = atPos(r2p(start, point))(t)
    def atPos[T <: Tree](start: Offset, point: Offset, end: Offset)(t: T): T = atPos(r2p(start, point, end))(t)
    def atPos[T <: Tree](pos: Position)(t: T): T                             = global.atPos(pos)(t)

    def atInPos[T <: Tree](t: T): T  = atPos(o2p(in.offset))(t)
    def setInPos[T <: Tree](t: T): T = t setPos o2p(in.offset)

    /** Convert tree to formal parameter list. */
    def convertToParams(tree: Tree): List[ValDef] = tree match {
      case Parens(ts) => ts map convertToParam
      case _          => List(convertToParam(tree))
    }

    /** Convert tree to formal parameter. */
    def convertToParam(tree: Tree): ValDef = atPos(tree.pos) {
      def removeAsPlaceholder(name: Name): Unit = {
        placeholderParams = placeholderParams filter (_.name != name)
      }
      def errorParam = makeParam(nme.ERROR, errorTypeTree setPos o2p(tree.pos.end))
      tree match {
        case Ident(name) =>
          removeAsPlaceholder(name)
          makeParam(name.toTermName, TypeTree() setPos o2p(tree.pos.end))
        case Typed(Ident(name), tpe) if tpe.isType => // get the ident!
          removeAsPlaceholder(name)
          makeParam(name.toTermName, tpe)
        case build.SyntacticTuple(as) =>
          val arity = as.length
          val example = analyzer.exampleTuplePattern(as map { case Ident(name) => name; case _ => nme.EMPTY })
          val msg =
            sm"""|not a legal formal parameter.
                 |Note: Tuples cannot be directly destructured in method or function parameters.
                 |      Either create a single parameter accepting the Tuple${arity},
                 |      or consider a pattern matching anonymous function: `{ case $example => ... }"""
          syntaxError(tree.pos, msg, skipIt = false)
          errorParam
        case _ =>
          syntaxError(tree.pos, "not a legal formal parameter", skipIt = false)
          errorParam
      }
    }

    /** Convert (qual)ident to type identifier. */
    def convertToTypeId(tree: Tree): Tree = atPos(tree.pos) {
      convertToTypeName(tree) getOrElse {
        syntaxError(tree.pos, "identifier expected", skipIt = false)
        errorTypeTree
      }
    }

    /** {{{ part { `sep` part } }}},or if sepFirst is true, {{{ { `sep` part } }}}. */
    final def tokenSeparated[T](separator: Token, sepFirst: Boolean, part: => T): List[T] = {
      val ts = new ListBuffer[T]
      if (!sepFirst)
        ts += part

      while (in.token == separator) {
        in.nextToken()
        ts += part
      }
      ts.toList
    }
    @inline final def commaSeparated[T](part: => T): List[T] = tokenSeparated(COMMA, sepFirst = false, part)
    @inline final def caseSeparated[T](part: => T): List[T] = tokenSeparated(CASE, sepFirst = true, part)
    def readAnnots(part: => Tree): List[Tree] = tokenSeparated(AT, sepFirst = true, part)

    /** Create a tuple type Tree. If the arity is not supported, a syntax error is emitted. */
    def makeSafeTupleType(elems: List[Tree], offset: Offset) = {
      if (checkTupleSize(elems, offset)) makeTupleType(elems)
      else makeTupleType(Nil) // create a dummy node; makeTupleType(elems) would fail
    }

    /** Create a tuple term Tree. If the arity is not supported, a syntax error is emitted. */
    def makeSafeTupleTerm(elems: List[Tree], offset: Offset) = {
      checkTupleSize(elems, offset)
      makeTupleTerm(elems)
    }

    private[this] def checkTupleSize(elems: List[Tree], offset: Offset): Boolean =
      if (elems.lengthCompare(definitions.MaxTupleArity) > 0) {
        syntaxError(offset, "too many elements for tuple: "+elems.length+", allowed: "+definitions.MaxTupleArity, skipIt = false)
        false
      } else true

    /** Strip the artifitial `Parens` node to create a tuple term Tree. */
    def stripParens(t: Tree) = t match {
      case Parens(ts) => atPos(t.pos) { makeSafeTupleTerm(ts, t.pos.point) }
      case _ => t
    }

    /** Create tree representing (unencoded) binary operation expression or pattern. */
    def makeBinop(isExpr: Boolean, left: Tree, op: TermName, right: Tree, opPos: Position, targs: List[Tree] = Nil): Tree = {
      require(isExpr || targs.isEmpty || targs.exists(_.isErroneous), s"Incompatible args to makeBinop: !isExpr but targs=$targs")

      def mkSelection(t: Tree) = {
        def sel = atPos(opPos union t.pos)(Select(stripParens(t), op.encode))
        if (targs.isEmpty) sel else atPos(left.pos)(TypeApply(sel, targs))
      }
      def mkNamed(args: List[Tree]) = if (isExpr) args map treeInfo.assignmentToMaybeNamedArg else args
      val arguments = right match {
        case Parens(args) => mkNamed(args)
        case _            => List(right)
      }
      if (isExpr) {
        if (treeInfo.isLeftAssoc(op)) {
          Apply(mkSelection(left), arguments)
        } else {
          val x = freshTermName()
          Block(
            List(ValDef(Modifiers(symtab.Flags.SYNTHETIC | symtab.Flags.ARTIFACT), x, TypeTree(), stripParens(left))),
            Apply(mkSelection(right), List(Ident(x))))
        }
      } else {
        Apply(Ident(op.encode), stripParens(left) :: arguments)
      }
    }

    /* --------- OPERAND/OPERATOR STACK --------------------------------------- */

    /** Modes for infix types. */
    object InfixMode extends Enumeration {
      val FirstOp, LeftOp, RightOp = Value
    }

    var opstack: List[OpInfo] = Nil

    @deprecated("Use `scala.reflect.internal.Precedence`", "2.11.0")
    def precedence(operator: Name): Int = Precedence(operator.toString).level

    private def opHead = opstack.head
    private def headPrecedence = opHead.precedence
    private def popOpInfo(): OpInfo = try opHead finally opstack = opstack.tail
    private def pushOpInfo(top: Tree): Unit = {
      val name   = in.name
      val offset = in.offset
      ident()
      val targs = if (in.token == LBRACKET) exprTypeArgs() else Nil
      val opinfo = OpInfo(top, name, targs, offset)
      opstack ::= opinfo
    }

    def checkHeadAssoc(leftAssoc: Boolean) = checkAssoc(opHead.offset, opHead.operator, leftAssoc)
    def checkAssoc(offset: Offset, op: Name, leftAssoc: Boolean) = (
      if (treeInfo.isLeftAssoc(op) != leftAssoc)
        syntaxError(offset, "left- and right-associative operators with same precedence may not be mixed", skipIt = false)
    )

    def finishPostfixOp(start: Int, base: List[OpInfo], opinfo: OpInfo): Tree = {
      if (opinfo.targs.nonEmpty)
        syntaxError(opinfo.offset, "type application is not allowed for postfix operators")

      val od = stripParens(reduceExprStack(base, opinfo.lhs))
      makePostfixSelect(start, opinfo.offset, od, opinfo.operator)
    }

    def finishBinaryOp(isExpr: Boolean, opinfo: OpInfo, rhs: Tree): Tree = {
      import opinfo._
      val operatorPos: Position = Position.range(rhs.pos.source, offset, offset, offset + operator.length)
      val pos                   = lhs.pos union rhs.pos union operatorPos withPoint offset

      atPos(pos)(makeBinop(isExpr, lhs, operator, rhs, operatorPos, opinfo.targs))
    }

    def reduceExprStack(base: List[OpInfo], top: Tree): Tree    = reduceStack(isExpr = true, base, top)
    def reducePatternStack(base: List[OpInfo], top: Tree): Tree = reduceStack(isExpr = false, base, top)

    def reduceStack(isExpr: Boolean, base: List[OpInfo], top: Tree): Tree = {
      val opPrecedence = if (isIdent) Precedence(in.name.toString) else Precedence(0)
      val leftAssoc    = !isIdent || (treeInfo isLeftAssoc in.name)

      reduceStack(isExpr, base, top, opPrecedence, leftAssoc)
    }

    def reduceStack(isExpr: Boolean, base: List[OpInfo], top: Tree, opPrecedence: Precedence, leftAssoc: Boolean): Tree = {
      def isDone          = opstack == base
      def lowerPrecedence = !isDone && (opPrecedence < headPrecedence)
      def samePrecedence  = !isDone && (opPrecedence == headPrecedence)
      def canReduce       = lowerPrecedence || leftAssoc && samePrecedence

      if (samePrecedence)
        checkHeadAssoc(leftAssoc)

      def loop(top: Tree): Tree = if (canReduce) {
        val info = popOpInfo()
        if (!isExpr && info.targs.nonEmpty) {
          syntaxError(info.offset, "type application is not allowed in pattern")
          info.targs.foreach(_.setType(ErrorType))
        }
        loop(finishBinaryOp(isExpr, info, top))
      } else top

      loop(top)
    }

/* -------- IDENTIFIERS AND LITERALS ------------------------------------------- */

    /** Methods which implicitly propagate the context in which they were
     *  called: either in a pattern context or not.  Formerly, this was
     *  threaded through numerous methods as boolean isPattern.
     */
    trait PatternContextSensitive {
      /** {{{
       *  ArgType       ::=  Type
       *  }}}
       */
      def argType(): Tree
      def functionArgType(): Tree

      private def tupleInfixType(start: Offset) = {
        in.nextToken()
        if (in.token == RPAREN) {
          in.nextToken()
          atPos(start, accept(ARROW)) { makeFunctionTypeTree(Nil, typ()) }
        }
        else {
          val ts = functionTypes()
          accept(RPAREN)
          if (in.token == ARROW)
            atPos(start, in.skipToken()) { makeFunctionTypeTree(ts, typ()) }
          else {
            ts foreach checkNotByNameOrVarargs
            val tuple = atPos(start) { makeSafeTupleType(ts, start) }
            infixTypeRest(
              compoundTypeRest(
                annotTypeRest(
                  simpleTypeRest(
                    tuple))),
              InfixMode.FirstOp
            )
          }
        }
      }
      private def makeExistentialTypeTree(t: Tree) = {
        // EmptyTrees in the result of refinement() stand for parse errors
        // so it's okay for us to filter them out here
        ExistentialTypeTree(t, refinement() flatMap {
          case t @ TypeDef(_, _, _, TypeBoundsTree(_, _)) => Some(t)
          case t @ ValDef(_, _, _, EmptyTree) => Some(t)
          case EmptyTree => None
          case _ => syntaxError(t.pos, "not a legal existential clause", skipIt = false); None
        })
      }

      /** {{{
       *  Type ::= InfixType `=>' Type
       *         | `(' [`=>' Type] `)' `=>' Type
       *         | InfixType [ExistentialClause]
       *  ExistentialClause ::= forSome `{' ExistentialDcl {semi ExistentialDcl}} `}'
       *  ExistentialDcl    ::= type TypeDcl | val ValDcl
       *  }}}
       */
      def typ(): Tree = placeholderTypeBoundary {
        val start = in.offset
        val t =
          if (in.token == LPAREN) tupleInfixType(start)
          else infixType(InfixMode.FirstOp)

        in.token match {
          case ARROW    => atPos(start, in.skipToken()) { makeFunctionTypeTree(List(t), typ()) }
          case FORSOME  => atPos(start, in.skipToken()) { makeExistentialTypeTree(t) }
          case _        => t
        }
      }

      /** {{{
       *  TypeArgs    ::= `[' ArgType {`,' ArgType} `]'
       *  }}}
       */
      def typeArgs(): List[Tree] = inBrackets(types())

      /** {{{
       *  AnnotType        ::=  SimpleType {Annotation}
       *  }}}
       */
      def annotType(): Tree = placeholderTypeBoundary { annotTypeRest(simpleType()) }

      /** {{{
       *  SimpleType       ::=  SimpleType TypeArgs
       *                     |  SimpleType `#' Id
       *                     |  StableId
       *                     |  Path `.' type
       *                     |  `(' Types `)'
       *                     |  WildcardType
       *  }}}
       */
      def simpleType(): Tree = {
        val start = in.offset
        simpleTypeRest(in.token match {
          case LPAREN   => atPos(start)(makeSafeTupleType(inParens(types()), start))
          case USCORE   => wildcardType(in.skipToken())
          case _        =>
            path(thisOK = false, typeOK = true) match {
              case r @ SingletonTypeTree(_) => r
              case r => convertToTypeId(r)
            }
        })
      }

      private def typeProjection(t: Tree): Tree = {
        val hashOffset = in.skipToken()
        val nameOffset = in.offset
        val name       = identForType(skipIt = false)
        val point      = if (name == tpnme.ERROR) hashOffset else nameOffset
        atPos(t.pos.start, point)(SelectFromTypeTree(t, name))
      }
      def simpleTypeRest(t: Tree): Tree = in.token match {
        case HASH     => simpleTypeRest(typeProjection(t))
        case LBRACKET => simpleTypeRest(atPos(t.pos.start, t.pos.point)(AppliedTypeTree(t, typeArgs())))
        case _        => t
      }

      /** {{{
       *  CompoundType ::= AnnotType {with AnnotType} [Refinement]
       *                |  Refinement
       *  }}}
       */
      def compoundType(): Tree = compoundTypeRest(
        if (in.token == LBRACE) atInPos(scalaAnyRefConstr)
        else annotType()
      )

      def compoundTypeRest(t: Tree): Tree = {
        val ts = new ListBuffer[Tree] += t
        while (in.token == WITH) {
          in.nextToken()
          ts += annotType()
        }
        newLineOptWhenFollowedBy(LBRACE)
        val types         = ts.toList
        val braceOffset   = in.offset
        val hasRefinement = in.token == LBRACE
        val refinements   = if (hasRefinement) refinement() else Nil
        // Warn if they are attempting to refine Unit; we can't be certain it's
        // scala.Unit they're refining because at this point all we have is an
        // identifier, but at a later stage we lose the ability to tell an empty
        // refinement from no refinement at all.  See bug #284.
        if (hasRefinement) types match {
          case Ident(name) :: Nil if name endsWith "Unit" => warning(braceOffset, "Detected apparent refinement of Unit; are you missing an '=' sign?")
          case _                                          =>
        }
        // The second case includes an empty refinement - refinements is empty, but
        // it still gets a CompoundTypeTree.
        ts.toList match {
          case tp :: Nil if !hasRefinement => tp  // single type, no refinement, already positioned
          case tps                         => atPos(t.pos.start)(CompoundTypeTree(Template(tps, noSelfType, refinements)))
        }
      }

      def infixTypeRest(t: Tree, mode: InfixMode.Value): Tree = {
        // Detect postfix star for repeated args.
        // Only RPAREN can follow, but accept COMMA and EQUALS for error's sake.
        // Take RBRACE as a paren typo.
        def checkRepeatedParam = if (isRawStar) {
          lookingAhead (in.token match {
            case RPAREN | COMMA | EQUALS | RBRACE => t
            case _                                => EmptyTree
          })
        } else EmptyTree
        def asInfix = {
          val opOffset  = in.offset
          val leftAssoc = treeInfo.isLeftAssoc(in.name)
          if (mode != InfixMode.FirstOp)
            checkAssoc(opOffset, in.name, leftAssoc = mode == InfixMode.LeftOp)
          val tycon = atPos(opOffset) { Ident(identForType()) }
          newLineOptWhenFollowing(isTypeIntroToken)
          def mkOp(t1: Tree) = atPos(t.pos.start, opOffset) { AppliedTypeTree(tycon, List(t, t1)) }
          if (leftAssoc)
            infixTypeRest(mkOp(compoundType()), InfixMode.LeftOp)
          else
            mkOp(infixType(InfixMode.RightOp))
        }
        if (isIdent) checkRepeatedParam orElse asInfix
        else t
      }

      /** {{{
       *  InfixType ::= CompoundType {id [nl] CompoundType}
       *  }}}
       */
      def infixType(mode: InfixMode.Value): Tree =
        placeholderTypeBoundary { infixTypeRest(compoundType(), mode) }

      /** {{{
       *  Types ::= Type {`,' Type}
       *  }}}
       */
      def types(): List[Tree] = commaSeparated(argType())
      def functionTypes(): List[Tree] = commaSeparated(functionArgType())
    }

    /** Assumed (provisionally) to be TermNames. */
    def ident(skipIt: Boolean): Name = (
      if (isIdent) {
        val name = in.name.encode
        in.nextToken()
        name
      }
      else syntaxErrorOrIncompleteAnd(expectedMsg(IDENTIFIER), skipIt)(nme.ERROR)
    )

    def ident(): Name = ident(skipIt = true)
    def rawIdent(): Name = try in.name finally in.nextToken()

    /** For when it's known already to be a type name. */
    def identForType(): TypeName = ident().toTypeName
    def identForType(skipIt: Boolean): TypeName = ident(skipIt).toTypeName

    def identOrMacro(): Name = if (isMacro) rawIdent() else ident()

    def selector(t: Tree): Tree = {
      val point = if(isIdent) in.offset else in.lastOffset //SI-8459
      //assert(t.pos.isDefined, t)
      if (t != EmptyTree)
        Select(t, ident(skipIt = false)) setPos r2p(t.pos.start, point, in.lastOffset)
      else
        errorTermTree // has already been reported
    }

    /** {{{
     *  Path       ::= StableId
     *              |  [Ident `.'] this
     *  AnnotType ::= Path [`.' type]
     *  }}}
     */
    def path(thisOK: Boolean, typeOK: Boolean): Tree = {
      val start = in.offset
      var t: Tree = null
      if (in.token == THIS) {
        in.nextToken()
        t = atPos(start) { This(tpnme.EMPTY) }
        if (!thisOK || in.token == DOT) {
          t = selectors(t, typeOK, accept(DOT))
        }
      } else if (in.token == SUPER) {
        in.nextToken()
        t = atPos(start) { Super(This(tpnme.EMPTY), mixinQualifierOpt()) }
        accept(DOT)
        t = selector(t)
        if (in.token == DOT) t = selectors(t, typeOK, in.skipToken())
      } else {
        val tok = in.token
        val name = ident()
        t = atPos(start) {
          if (tok == BACKQUOTED_IDENT) Ident(name) updateAttachment BackquotedIdentifierAttachment
          else Ident(name)
        }
        if (in.token == DOT) {
          val dotOffset = in.skipToken()
          if (in.token == THIS) {
            in.nextToken()
            t = atPos(start) { This(name.toTypeName) }
            if (!thisOK || in.token == DOT)
              t = selectors(t, typeOK, accept(DOT))
          } else if (in.token == SUPER) {
            in.nextToken()
            t = atPos(start) { Super(This(name.toTypeName), mixinQualifierOpt()) }
            accept(DOT)
            t = selector(t)
            if (in.token == DOT) t = selectors(t, typeOK, in.skipToken())
          } else {
            t = selectors(t, typeOK, dotOffset)
          }
        }
      }
      t
    }

    def selectors(t: Tree, typeOK: Boolean, dotOffset: Offset): Tree =
      if (typeOK && in.token == TYPE) {
        in.nextToken()
        atPos(t.pos.start, dotOffset) { SingletonTypeTree(t) }
      }
      else {
        val t1 = selector(t)
        if (in.token == DOT) { selectors(t1, typeOK, in.skipToken()) }
        else t1
      }

    /** {{{
    *   MixinQualifier ::= `[' Id `]'
    *   }}}
    */
    def mixinQualifierOpt(): TypeName =
      if (in.token == LBRACKET) inBrackets(identForType())
      else tpnme.EMPTY

    /** {{{
     *  StableId ::= Id
     *            |  Path `.' Id
     *            |  [id `.'] super [`[' id `]']`.' id
     *  }}}
     */
    def stableId(): Tree =
      path(thisOK = false, typeOK = false)

    /** {{{
    *   QualId ::= Id {`.' Id}
    *   }}}
    */
    def qualId(): Tree = {
      val start = in.offset
      val id = atPos(start) { Ident(ident()) }
      if (in.token == DOT) { selectors(id, typeOK = false, in.skipToken()) }
      else id
    }
    /** Calls `qualId()` and manages some package state. */
    private def pkgQualId() = {
      if (in.token == IDENTIFIER && in.name.encode == nme.scala_)
        inScalaPackage = true

      val pkg = qualId()
      newLineOptWhenFollowedBy(LBRACE)

      if (currentPackage == "") currentPackage = pkg.toString
      else currentPackage = currentPackage + "." + pkg

      pkg
    }

    /** {{{
     *  SimpleExpr    ::= literal
     *                  | symbol
     *                  | null
     *  }}}
     */
    def literal(isNegated: Boolean = false, inPattern: Boolean = false, start: Offset = in.offset): Tree = atPos(start) {
      def finish(value: Any): Tree = try newLiteral(value) finally in.nextToken()
      if (in.token == SYMBOLLIT)
        Apply(scalaDot(nme.Symbol), List(finish(in.strVal)))
      else if (in.token == INTERPOLATIONID)
        interpolatedString(inPattern = inPattern)
      else finish(in.token match {
        case CHARLIT                => in.charVal
        case INTLIT                 => in.intVal(isNegated).toInt
        case LONGLIT                => in.intVal(isNegated)
        case FLOATLIT               => in.floatVal(isNegated)
        case DOUBLELIT              => in.doubleVal(isNegated)
        case STRINGLIT | STRINGPART => in.strVal.intern()
        case TRUE                   => true
        case FALSE                  => false
        case NULL                   => null
        case _                      => syntaxErrorOrIncompleteAnd("illegal literal", skipIt = true)(null)
      })
    }

    /** Handle placeholder syntax.
     *  If evaluating the tree produces placeholders, then make it a function.
     */
    private def withPlaceholders(tree: =>Tree, isAny: Boolean): Tree = {
      val savedPlaceholderParams = placeholderParams
      placeholderParams = List()
      var res = tree
      if (placeholderParams.nonEmpty && !isWildcard(res)) {
        res = atPos(res.pos)(Function(placeholderParams.reverse, res))
        if (isAny) placeholderParams foreach (_.tpt match {
          case tpt @ TypeTree() => tpt setType definitions.AnyTpe
          case _                => // some ascription
        })
        placeholderParams = List()
      }
      placeholderParams = placeholderParams ::: savedPlaceholderParams
      res
    }

    /** Consume a USCORE and create a fresh synthetic placeholder param. */
    private def freshPlaceholder(): Tree = {
      val start = in.offset
      val pname = freshTermName()
      in.nextToken()
      val id = atPos(start)(Ident(pname))
      val param = atPos(id.pos.focus)(gen.mkSyntheticParam(pname.toTermName))
      placeholderParams = param :: placeholderParams
      id
    }

    private def interpolatedString(inPattern: Boolean): Tree = {
      def errpolation() = syntaxErrorOrIncompleteAnd("error in interpolated string: identifier or block expected",
                                                     skipIt = true)(EmptyTree)
      // Like Swiss cheese, with holes
      def stringCheese: Tree = atPos(in.offset) {
        val start        = in.offset
        val interpolator = in.name.encoded // ident() for INTERPOLATIONID

        val partsBuf = new ListBuffer[Tree]
        val exprsBuf = new ListBuffer[Tree]
        in.nextToken()
        while (in.token == STRINGPART) {
          partsBuf += literal()
          exprsBuf += (
            if (inPattern) dropAnyBraces(pattern())
            else in.token match {
              case IDENTIFIER => atPos(in.offset)(Ident(ident()))
              //case USCORE   => freshPlaceholder()  // ifonly etapolation
              case LBRACE     => expr()              // dropAnyBraces(expr0(Local))
              case THIS       => in.nextToken(); atPos(in.offset)(This(tpnme.EMPTY))
              case _          => errpolation()
            }
          )
        }
        if (in.token == STRINGLIT) partsBuf += literal()

      // Documenting that it is intentional that the ident is not rooted for purposes of virtualization
      //val t1 = atPos(o2p(start)) { Select(Select (Ident(nme.ROOTPKG), nme.scala_), nme.StringContext) }
        val t1 = atPos(o2p(start)) { Ident(nme.StringContext) }
        val t2 = atPos(start) { Apply(t1, partsBuf.toList) }
        t2 setPos t2.pos.makeTransparent
        val t3 = Select(t2, interpolator) setPos t2.pos
        atPos(start) { Apply(t3, exprsBuf.toList) }
      }
      if (inPattern) stringCheese
      else withPlaceholders(stringCheese, isAny = true) // string interpolator params are Any* by definition
    }

/* ------------- NEW LINES ------------------------------------------------- */

    def newLineOpt(): Unit = {
      if (in.token == NEWLINE) in.nextToken()
    }

    def newLinesOpt(): Unit = {
      if (in.token == NEWLINE || in.token == NEWLINES)
        in.nextToken()
    }

    def newLineOptWhenFollowedBy(token: Offset): Unit = {
      // note: next is defined here because current == NEWLINE
      if (in.token == NEWLINE && in.next.token == token) newLineOpt()
    }

    def newLineOptWhenFollowing(p: Token => Boolean): Unit = {
      // note: next is defined here because current == NEWLINE
      if (in.token == NEWLINE && p(in.next.token)) newLineOpt()
    }

/* ------------- TYPES ---------------------------------------------------- */

    /** {{{
     *  TypedOpt ::= [`:' Type]
     *  }}}
     */
    def typedOpt(): Tree =
      if (in.token == COLON) { in.nextToken(); typ() }
      else TypeTree()

    def typeOrInfixType(location: Location): Tree =
      if (location == Local) typ()
      else startInfixType()

    def annotTypeRest(t: Tree): Tree =
      (t /: annotations(skipNewLines = false)) (makeAnnotated)

    /** {{{
     *  WildcardType ::= `_' TypeBounds
     *  }}}
     */
    def wildcardType(start: Offset) = {
      val pname = freshTypeName("_$")
      val t = atPos(start)(Ident(pname))
      val bounds = typeBounds()
      val param = atPos(t.pos union bounds.pos) { makeSyntheticTypeParam(pname, bounds) }
      placeholderTypes = param :: placeholderTypes
      t
    }

/* ----------- EXPRESSIONS ------------------------------------------------ */

    def condExpr(): Tree = {
      if (in.token == LPAREN) {
        in.nextToken()
        val r = expr()
        accept(RPAREN)
        r
      } else {
        accept(LPAREN)
        newLiteral(true)
      }
    }

    /* hook for IDE, unlike expression can be stubbed
     * don't use for any tree that can be inspected in the parser!
     */
    def statement(location: Location): Tree = expr(location) // !!! still needed?

    /** {{{
     *  Expr       ::= (Bindings | [`implicit'] Id | `_')  `=>' Expr
     *               | Expr1
     *  ResultExpr ::= (Bindings | Id `:' CompoundType) `=>' Block
     *               | Expr1
     *  Expr1      ::= if `(' Expr `)' {nl} Expr [[semi] else Expr]
     *               | try (`{' Block `}' | Expr) [catch `{' CaseClauses `}'] [finally Expr]
     *               | while `(' Expr `)' {nl} Expr
     *               | do Expr [semi] while `(' Expr `)'
     *               | for (`(' Enumerators `)' | `{' Enumerators `}') {nl} [yield] Expr
     *               | throw Expr
     *               | return [Expr]
     *               | [SimpleExpr `.'] Id `=' Expr
     *               | SimpleExpr1 ArgumentExprs `=' Expr
     *               | PostfixExpr Ascription
     *               | PostfixExpr match `{' CaseClauses `}'
     *  Bindings   ::= `(' [Binding {`,' Binding}] `)'
     *  Binding    ::= (Id | `_') [`:' Type]
     *  Ascription ::= `:' CompoundType
     *               | `:' Annotation {Annotation}
     *               | `:' `_' `*'
     *  }}}
     */
    def expr(): Tree = expr(Local)

    def expr(location: Location): Tree = withPlaceholders(expr0(location), isAny = false)

    def expr0(location: Location): Tree = (in.token: @scala.annotation.switch) match {
      case IF =>
        def parseIf = atPos(in.skipToken()) {
          val cond = condExpr()
          newLinesOpt()
          val thenp = expr()
          val elsep = if (in.token == ELSE) { in.nextToken(); expr() }
          else literalUnit
          If(cond, thenp, elsep)
        }
        parseIf
      case TRY =>
        def parseTry = atPos(in.skipToken()) {
          val body = in.token match {
            case LBRACE => inBracesOrUnit(block())
            case LPAREN => inParensOrUnit(expr())
            case _ => expr()
          }
          def catchFromExpr() = List(makeCatchFromExpr(expr()))
          val catches: List[CaseDef] =
            if (in.token != CATCH) Nil
            else {
              in.nextToken()
              if (in.token != LBRACE) catchFromExpr()
              else inBracesOrNil {
                if (in.token == CASE) caseClauses()
                else catchFromExpr()
              }
            }
          val finalizer = in.token match {
            case FINALLY => in.nextToken(); expr()
            case _ => EmptyTree
          }
          Try(body, catches, finalizer)
        }
        parseTry
      case WHILE =>
        def parseWhile = {
          val start = in.offset
          atPos(in.skipToken()) {
            val cond = condExpr()
            newLinesOpt()
            val body = expr()
            makeWhile(start, cond, body)
          }
        }
        parseWhile
      case DO =>
        def parseDo = {
          atPos(in.skipToken()) {
            val lname: Name = freshTermName(nme.DO_WHILE_PREFIX)
            val body = expr()
            if (isStatSep) in.nextToken()
            accept(WHILE)
            val cond = condExpr()
            makeDoWhile(lname.toTermName, body, cond)
          }
        }
        parseDo
      case FOR =>
        val start = in.skipToken()
        def parseFor = atPos(start) {
          val enums =
            if (in.token == LBRACE) inBracesOrNil(enumerators())
            else inParensOrNil(enumerators())
          newLinesOpt()
          if (in.token == YIELD) {
            in.nextToken()
            gen.mkFor(enums, gen.Yield(expr()))
          } else {
            gen.mkFor(enums, expr())
          }
        }
        def adjustStart(tree: Tree) =
          if (tree.pos.isRange && start < tree.pos.start)
            tree setPos tree.pos.withStart(start)
          else tree
        adjustStart(parseFor)
      case RETURN =>
        def parseReturn =
          atPos(in.skipToken()) {
            Return(if (isExprIntro) expr() else literalUnit)
          }
        parseReturn
      case THROW =>
        def parseThrow =
          atPos(in.skipToken()) {
            Throw(expr())
          }
        parseThrow
      case IMPLICIT =>
        implicitClosure(in.skipToken(), location)
      case _ =>
        def parseOther = {
          var t = postfixExpr()
          if (in.token == EQUALS) {
            t match {
              case Ident(_) | Select(_, _) | Apply(_, _) =>
                t = atPos(t.pos.start, in.skipToken()) { gen.mkAssign(t, expr()) }
              case _ =>
            }
          } else if (in.token == COLON) {
            t = stripParens(t)
            val colonPos = in.skipToken()
            if (in.token == USCORE) {
              //todo: need to handle case where USCORE is a wildcard in a type
              val uscorePos = in.skipToken()
              if (isIdent && in.name == nme.STAR) {
                in.nextToken()
                t = atPos(t.pos.start, colonPos) {
                  Typed(t, atPos(uscorePos) { Ident(tpnme.WILDCARD_STAR) })
                }
              } else {
                syntaxErrorOrIncomplete("`*' expected", skipIt = true)
              }
            } else if (isAnnotation) {
              t = (t /: annotations(skipNewLines = false))(makeAnnotated)
            } else {
              t = atPos(t.pos.start, colonPos) {
                val tpt = typeOrInfixType(location)
                if (isWildcard(t))
                  (placeholderParams: @unchecked) match {
                    case (vd @ ValDef(mods, name, _, _)) :: rest =>
                      placeholderParams = treeCopy.ValDef(vd, mods, name, tpt.duplicate, EmptyTree) :: rest
                  }
                // this does not correspond to syntax, but is necessary to
                // accept closures. We might restrict closures to be between {...} only.
                Typed(t, tpt)
              }
            }
          } else if (in.token == MATCH) {
            t = atPos(t.pos.start, in.skipToken())(Match(stripParens(t), inBracesOrNil(caseClauses())))
          }
          // in order to allow anonymous functions as statements (as opposed to expressions) inside
          // templates, we have to disambiguate them from self type declarations - bug #1565
          // The case still missed is unparenthesized single argument, like "x: Int => x + 1", which
          // may be impossible to distinguish from a self-type and so remains an error.  (See #1564)
          def lhsIsTypedParamList() = t match {
            case Parens(xs) if xs.forall(isTypedParam) => true
            case _ => false
          }
          if (in.token == ARROW && (location != InTemplate || lhsIsTypedParamList)) {
            t = atPos(t.pos.start, in.skipToken()) {
              Function(convertToParams(t), if (location != InBlock) expr() else block())
            }
          }
          stripParens(t)
        }
        parseOther
    }

    def isTypedParam(t: Tree) = t.isInstanceOf[Typed]

    /** {{{
     *  Expr ::= implicit Id => Expr
     *  }}}
     */

    def implicitClosure(start: Offset, location: Location): Tree = {
      val param0 = convertToParam {
        atPos(in.offset) {
          Ident(ident()) match {
            case expr if in.token == COLON  =>
              in.nextToken() ; Typed(expr, typeOrInfixType(location))
            case expr => expr
          }
        }
      }
      val param = copyValDef(param0)(mods = param0.mods | Flags.IMPLICIT)
      atPos(start, in.offset) {
        accept(ARROW)
        Function(List(param), if (location != InBlock) expr() else block())
      }
    }

    /** {{{
     *  PostfixExpr   ::= InfixExpr [Id [nl]]
     *  InfixExpr     ::= PrefixExpr
     *                  | InfixExpr Id [nl] InfixExpr
     *  }}}
     */
    def postfixExpr(): Tree = {
      val start = in.offset
      val base  = opstack

      def loop(top: Tree): Tree = if (!isIdent) top else {
        pushOpInfo(reduceExprStack(base, top))
        newLineOptWhenFollowing(isExprIntroToken)
        if (isExprIntro)
          prefixExpr() match {
            case EmptyTree => reduceExprStack(base, top)
            case next      => loop(next)
          }
        else finishPostfixOp(start, base, popOpInfo())
      }

      reduceExprStack(base, loop(prefixExpr()))
    }

    /** {{{
     *  PrefixExpr   ::= [`-' | `+' | `~' | `!'] SimpleExpr
     *  }}}
     */
    def prefixExpr(): Tree = {
      if (isUnaryOp) {
        atPos(in.offset) {
          if (lookingAhead(isSimpleExprIntro)) {
            val uname = nme.toUnaryName(rawIdent().toTermName)
            if (uname == nme.UNARY_- && isNumericLit)
              simpleExprRest(literal(isNegated = true), canApply = true)
            else
              Select(stripParens(simpleExpr()), uname)
          }
          else simpleExpr()
        }
      }
      else simpleExpr()
    }
    def xmlLiteral(): Tree

    /** {{{
     *  SimpleExpr    ::= new (ClassTemplate | TemplateBody)
     *                  |  BlockExpr
     *                  |  SimpleExpr1 [`_']
     *  SimpleExpr1   ::= literal
     *                  |  xLiteral
     *                  |  Path
     *                  |  `(' [Exprs] `)'
     *                  |  SimpleExpr `.' Id
     *                  |  SimpleExpr TypeArgs
     *                  |  SimpleExpr1 ArgumentExprs
     *  }}}
     */
    def simpleExpr(): Tree = {
      var canApply = true
      val t =
        if (isLiteral) literal()
        else in.token match {
          case XMLSTART =>
            xmlLiteral()
          case IDENTIFIER | BACKQUOTED_IDENT | THIS | SUPER =>
            path(thisOK = true, typeOK = false)
          case USCORE =>
            freshPlaceholder()
          case LPAREN =>
            atPos(in.offset)(makeParens(commaSeparated(expr())))
          case LBRACE =>
            canApply = false
            blockExpr()
          case NEW =>
            canApply = false
            val nstart = in.skipToken()
            val npos = r2p(nstart, nstart, in.lastOffset)
            val tstart = in.offset
            val (parents, self, stats) = template()
            val cpos = r2p(tstart, tstart, in.lastOffset max tstart)
            gen.mkNew(parents, self, stats, npos, cpos)
          case _ =>
            syntaxErrorOrIncompleteAnd("illegal start of simple expression", skipIt = true)(errorTermTree)
        }
      simpleExprRest(t, canApply = canApply)
    }

    def simpleExprRest(t: Tree, canApply: Boolean): Tree = {
      if (canApply) newLineOptWhenFollowedBy(LBRACE)
      in.token match {
        case DOT =>
          in.nextToken()
          simpleExprRest(selector(stripParens(t)), canApply = true)
        case LBRACKET =>
          val t1 = stripParens(t)
          t1 match {
            case Ident(_) | Select(_, _) | Apply(_, _) =>
              var app: Tree = t1
              while (in.token == LBRACKET)
                app = atPos(app.pos.start, in.offset)(TypeApply(app, exprTypeArgs()))

              simpleExprRest(app, canApply = true)
            case _ =>
              t1
          }
        case LPAREN | LBRACE if (canApply) =>
          val app = atPos(t.pos.start, in.offset) {
            // look for anonymous function application like (f _)(x) and
            // translate to (f _).apply(x), bug #460
            val sel = t match {
              case Parens(List(Typed(_, _: Function))) =>
                Select(stripParens(t), nme.apply)
              case _ =>
                stripParens(t)
            }
            Apply(sel, argumentExprs())
          }
          simpleExprRest(app, canApply = true)
        case USCORE =>
          atPos(t.pos.start, in.skipToken()) { makeMethodValue(stripParens(t)) }
        case _ =>
          t
      }
    }

    /** {{{
     *  ArgumentExprs ::= `(' [Exprs] `)'
     *                  | [nl] BlockExpr
     *  }}}
     */
    def argumentExprs(): List[Tree] = {
      def args(): List[Tree] = commaSeparated(
        if (isIdent) treeInfo.assignmentToMaybeNamedArg(expr()) else expr()
      )
      in.token match {
        case LBRACE   => List(blockExpr())
        case LPAREN   => inParens(if (in.token == RPAREN) Nil else args())
        case _        => Nil
      }
    }
    /** A succession of argument lists. */
    def multipleArgumentExprs(): List[List[Tree]] = {
      if (in.token != LPAREN) Nil
      else argumentExprs() :: multipleArgumentExprs()
    }

    /** {{{
     *  BlockExpr ::= `{' (CaseClauses | Block) `}'
     *  }}}
     */
    def blockExpr(): Tree = atPos(in.offset) {
      inBraces {
        if (in.token == CASE) Match(EmptyTree, caseClauses())
        else block()
      }
    }

    /** {{{
     *  Block ::= BlockStatSeq
     *  }}}
     *  @note  Return tree does not carry position.
     */
    def block(): Tree = makeBlock(blockStatSeq())

    def caseClause(): CaseDef =
      atPos(in.offset)(makeCaseDef(pattern(), guard(), caseBlock()))

    /** {{{
     *  CaseClauses ::= CaseClause {CaseClause}
     *  CaseClause  ::= case Pattern [Guard] `=>' Block
     *  }}}
     */
    def caseClauses(): List[CaseDef] = {
      val cases = caseSeparated { caseClause() }
      if (cases.isEmpty)  // trigger error if there are no cases
        accept(CASE)

      cases
    }

    // IDE HOOK (so we can memoize case blocks) // needed?
    def caseBlock(): Tree =
      atPos(accept(ARROW))(block())

    /** {{{
     *  Guard ::= if PostfixExpr
     *  }}}
     */
    def guard(): Tree =
      if (in.token == IF) { in.nextToken(); stripParens(postfixExpr()) }
      else EmptyTree

    /** {{{
     *  Enumerators ::= Generator {semi Enumerator}
     *  Enumerator  ::=  Generator
     *                |  Guard
     *                |  val Pattern1 `=' Expr
     *  }}}
     */
    def enumerators(): List[Tree] = {
      val enums = new ListBuffer[Tree]
      enums ++= enumerator(isFirst = true)
      while (isStatSep) {
        in.nextToken()
        enums ++= enumerator(isFirst = false)
      }
      enums.toList
    }

    def enumerator(isFirst: Boolean, allowNestedIf: Boolean = true): List[Tree] =
      if (in.token == IF && !isFirst) makeFilter(in.offset, guard()) :: Nil
      else generator(!isFirst, allowNestedIf)

    /** {{{
     *  Generator ::= Pattern1 (`<-' | `=') Expr [Guard]
     *  }}}
     */
    def generator(eqOK: Boolean, allowNestedIf: Boolean = true): List[Tree] = {
      val start  = in.offset
      val hasVal = in.token == VAL
      if (hasVal)
        in.nextToken()

      val pat   = noSeq.pattern1()
      val point = in.offset
      val hasEq = in.token == EQUALS

      if (hasVal) {
        if (hasEq) deprecationWarning(in.offset, "val keyword in for comprehension is deprecated", "2.10.0")
        else syntaxError(in.offset, "val in for comprehension must be followed by assignment")
      }

      if (hasEq && eqOK) in.nextToken()
      else accept(LARROW)
      val rhs = expr()

      def loop(): List[Tree] =
        if (in.token != IF) Nil
        else makeFilter(in.offset, guard()) :: loop()

      val tail =
        if (allowNestedIf) loop()
        else Nil

      // why max? IDE stress tests have shown that lastOffset could be less than start,
      // I guess this happens if instead if a for-expression we sit on a closing paren.
      val genPos = r2p(start, point, in.lastOffset max start)
      gen.mkGenerator(genPos, pat, hasEq, rhs) :: tail
    }

    def makeFilter(start: Offset, tree: Tree) = gen.Filter(tree).setPos(r2p(start, tree.pos.point, tree.pos.end))

/* -------- PATTERNS ------------------------------------------- */

    /** Methods which implicitly propagate whether the initial call took
     *  place in a context where sequences are allowed.  Formerly, this
     *  was threaded through methods as boolean seqOK.
     */
    trait SeqContextSensitive extends PatternContextSensitive {
      // is a sequence pattern _* allowed?
      def isSequenceOK: Boolean

      // are we in an XML pattern?
      def isXML: Boolean = false

      def functionArgType(): Tree = argType()
      def argType(): Tree = {
        val start = in.offset
        in.token match {
          case USCORE =>
            in.nextToken()
            if (in.token == SUBTYPE || in.token == SUPERTYPE) wildcardType(start)
            else atPos(start) { Bind(tpnme.WILDCARD, EmptyTree) }
          case _ =>
            typ() match {
              case Ident(name: TypeName) if nme.isVariableName(name) =>
                atPos(start) { Bind(name, EmptyTree) }
              case t => t
            }
        }
      }

      /** {{{
       *  Patterns ::= Pattern { `,' Pattern }
       *  SeqPatterns ::= SeqPattern { `,' SeqPattern }
       *  }}}
       */
      def patterns(): List[Tree] = commaSeparated(pattern())

      /** {{{
       *  Pattern  ::=  Pattern1 { `|' Pattern1 }
       *  SeqPattern ::= SeqPattern1 { `|' SeqPattern1 }
       *  }}}
       */
      def pattern(): Tree = {
        val start = in.offset
        def loop(): List[Tree] = pattern1() :: {
          if (isRawBar) { in.nextToken() ; loop() }
          else Nil
        }
        loop() match {
          case pat :: Nil => pat
          case xs         => atPos(start)(makeAlternative(xs))
        }
      }

      /** {{{
       *  Pattern1    ::= boundvarid `:' TypePat
       *                |  `_' `:' TypePat
       *                |  Pattern2
       *  SeqPattern1 ::= boundvarid `:' TypePat
       *                |  `_' `:' TypePat
       *                |  [SeqPattern2]
       *  }}}
       */
      def pattern1(): Tree = pattern2() match {
        case p @ Ident(name) if in.token == COLON =>
          if (nme.isVariableName(name)) {
            p.removeAttachment[BackquotedIdentifierAttachment.type]
            atPos(p.pos.start, in.skipToken())(Typed(p, compoundType()))
          } else {
            syntaxError(in.offset, "Pattern variables must start with a lower-case letter. (SLS 8.1.1.)")
            p
          }
        case p => p
      }

      /** {{{
       *  Pattern2    ::=  id  @ Pattern3
       *                |  `_' @ Pattern3
       *                |   Pattern3
       *  }}}
       */
      def pattern2(): Tree = {
        val p = pattern3()

        if (in.token != AT) p
        else p match {
          case Ident(nme.WILDCARD) =>
            in.nextToken()
            pattern3()
          case Ident(name) =>
            in.nextToken()
            val body = pattern3()
            atPos(p.pos.start, p.pos.start, body.pos.end) {
              val t = Bind(name, body)
              body match {
                case Ident(nme.WILDCARD) => t updateAttachment AtBoundIdentifierAttachment
                case _ => t
              }
            }
          case _ => p
        }
      }

      /** {{{
       *  Pattern3    ::= SimplePattern
       *                |  SimplePattern {Id [nl] SimplePattern}
       *  }}}
       */
      def pattern3(): Tree = {
        val top = simplePattern(badPattern3)
        val base = opstack
        // See SI-3189, SI-4832 for motivation. Cf SI-3480 for counter-motivation.
        def isCloseDelim = in.token match {
          case RBRACE => isXML
          case RPAREN => !isXML
          case _      => false
        }
        def checkWildStar: Tree = top match {
          case Ident(nme.WILDCARD) if isSequenceOK && isRawStar => peekingAhead (
            if (isCloseDelim) atPos(top.pos.start, in.prev.offset)(Star(stripParens(top)))
            else EmptyTree
          )
          case _ => EmptyTree
        }
        def loop(top: Tree): Tree = reducePatternStack(base, top) match {
          case next if isIdent && !isRawBar => pushOpInfo(next) ; loop(simplePattern(badPattern3))
          case next                         => next
        }
        checkWildStar orElse stripParens(loop(top))
      }

      def badPattern3(): Tree = {
        def isComma                = in.token == COMMA
        def isDelimiter            = in.token == RPAREN || in.token == RBRACE
        def isCommaOrDelimiter     = isComma || isDelimiter
        val (isUnderscore, isStar) = opstack match {
          case OpInfo(Ident(nme.WILDCARD), nme.STAR, _, _) :: _ => (true,   true)
          case OpInfo(_, nme.STAR, _, _) :: _                   => (false,  true)
          case _                                                => (false, false)
        }
        def isSeqPatternClose = isUnderscore && isStar && isSequenceOK && isDelimiter
        val preamble = "bad simple pattern:"
        val subtext = (isUnderscore, isStar, isSequenceOK) match {
          case (true,  true, true)  if isComma            => "bad use of _* (a sequence pattern must be the last pattern)"
          case (true,  true, true)  if isDelimiter        => "bad brace or paren after _*"
          case (true,  true, false) if isDelimiter        => "bad use of _* (sequence pattern not allowed)"
          case (false, true, true)  if isDelimiter        => "use _* to match a sequence"
          case (false, true, _)     if isCommaOrDelimiter => "trailing * is not a valid pattern"
          case _                                          => null
        }
        val msg = if (subtext != null) s"$preamble $subtext" else "illegal start of simple pattern"
        // better recovery if don't skip delims of patterns
        val skip = !isCommaOrDelimiter || isSeqPatternClose
        syntaxErrorOrIncompleteAnd(msg, skip)(errorPatternTree)
      }

      /** {{{
       *  SimplePattern    ::= varid
       *                    |  `_'
       *                    |  literal
       *                    |  XmlPattern
       *                    |  StableId  /[TypeArgs]/ [`(' [Patterns] `)']
       *                    |  StableId  [`(' [Patterns] `)']
       *                    |  StableId  [`(' [Patterns] `,' [varid `@'] `_' `*' `)']
       *                    |  `(' [Patterns] `)'
       *  }}}
       *
       * XXX: Hook for IDE
       */
      def simplePattern(): Tree = (
        // simple diagnostics for this entry point
        simplePattern(() => syntaxErrorOrIncompleteAnd("illegal start of simple pattern", skipIt = true)(errorPatternTree))
      )
      def simplePattern(onError: () => Tree): Tree = {
        val start = in.offset
        in.token match {
          case IDENTIFIER | BACKQUOTED_IDENT | THIS =>
            val t = stableId()
            in.token match {
              case INTLIT | LONGLIT | FLOATLIT | DOUBLELIT =>
                t match {
                  case Ident(nme.MINUS) =>
                    return literal(isNegated = true, inPattern = true, start = start)
                  case _ =>
                }
              case _ =>
            }
            val typeAppliedTree = in.token match {
              case LBRACKET   => atPos(start, in.offset)(AppliedTypeTree(convertToTypeId(t), typeArgs()))
              case _          => t
            }
            in.token match {
              case LPAREN   => atPos(start, in.offset)(Apply(typeAppliedTree, argumentPatterns()))
              case _        => typeAppliedTree
            }
          case USCORE =>
            in.nextToken()
            atPos(start, start) { Ident(nme.WILDCARD) }
          case CHARLIT | INTLIT | LONGLIT | FLOATLIT | DOUBLELIT |
               STRINGLIT | INTERPOLATIONID | SYMBOLLIT | TRUE | FALSE | NULL =>
            literal(inPattern = true)
          case LPAREN =>
            atPos(start)(makeParens(noSeq.patterns()))
          case XMLSTART =>
            xmlLiteralPattern()
          case _ =>
            onError()
        }
      }
    }
    /** The implementation of the context sensitive methods for parsing outside of patterns. */
    object outPattern extends PatternContextSensitive {
      def argType(): Tree = typ()
      def functionArgType(): Tree = paramType(useStartAsPosition = true)
    }
    /** The implementation for parsing inside of patterns at points where sequences are allowed. */
    object seqOK extends SeqContextSensitive {
      val isSequenceOK = true
    }
    /** The implementation for parsing inside of patterns at points where sequences are disallowed. */
    object noSeq extends SeqContextSensitive {
      val isSequenceOK = false
    }
    /** For use from xml pattern, where sequence is allowed and encouraged. */
    object xmlSeqOK extends SeqContextSensitive {
      val isSequenceOK = true
      override val isXML = true
    }
    /** These are default entry points into the pattern context sensitive methods:
     *  they are all initiated from non-pattern context.
     */
    def typ(): Tree      = outPattern.typ()
    def startInfixType() = outPattern.infixType(InfixMode.FirstOp)
    def startAnnotType() = outPattern.annotType()
    def exprTypeArgs()   = outPattern.typeArgs()
    def exprSimpleType() = outPattern.simpleType()

    /** Default entry points into some pattern contexts. */
    def pattern(): Tree = noSeq.pattern()
    def seqPatterns(): List[Tree] = seqOK.patterns()
    def xmlSeqPatterns(): List[Tree] = xmlSeqOK.patterns() // Called from xml parser
    def argumentPatterns(): List[Tree] = inParens {
      if (in.token == RPAREN) Nil
      else seqPatterns()
    }
    def xmlLiteralPattern(): Tree

/* -------- MODIFIERS and ANNOTATIONS ------------------------------------------- */

    /** Drop `private` modifier when followed by a qualifier.
     *  Contract `abstract` and `override` to ABSOVERRIDE
     */
    private def normalizeModifiers(mods: Modifiers): Modifiers =
      if (mods.isPrivate && mods.hasAccessBoundary)
        normalizeModifiers(mods &~ Flags.PRIVATE)
      else if (mods hasAllFlags (Flags.ABSTRACT | Flags.OVERRIDE))
        normalizeModifiers(mods &~ (Flags.ABSTRACT | Flags.OVERRIDE) | Flags.ABSOVERRIDE)
      else
        mods

    private def addMod(mods: Modifiers, mod: Long, pos: Position): Modifiers = {
      if (mods hasFlag mod) syntaxError(in.offset, "repeated modifier", skipIt = false)
      in.nextToken()
      (mods | mod) withPosition (mod, pos)
    }

    private def tokenRange(token: TokenData) =
      r2p(token.offset, token.offset, token.offset + token.name.length - 1)

    /** {{{
     *  AccessQualifier ::= `[' (Id | this) `]'
     *  }}}
     */
    def accessQualifierOpt(mods: Modifiers): Modifiers = {
      var result = mods
      if (in.token == LBRACKET) {
        in.nextToken()
        if (mods.hasAccessBoundary)
          syntaxError("duplicate private/protected qualifier", skipIt = false)
        result = if (in.token == THIS) { in.nextToken(); mods | Flags.LOCAL }
                 else Modifiers(mods.flags, identForType())
        accept(RBRACKET)
      }
      result
    }

    private val flagTokens: Map[Int, Long] = Map(
      ABSTRACT  -> Flags.ABSTRACT,
      FINAL     -> Flags.FINAL,
      IMPLICIT  -> Flags.IMPLICIT,
      LAZY      -> Flags.LAZY,
      OVERRIDE  -> Flags.OVERRIDE,
      PRIVATE   -> Flags.PRIVATE,
      PROTECTED -> Flags.PROTECTED,
      SEALED    -> Flags.SEALED
    )

    /** {{{
     *  AccessModifier ::= (private | protected) [AccessQualifier]
     *  }}}
     */
    def accessModifierOpt(): Modifiers = normalizeModifiers {
      in.token match {
        case m @ (PRIVATE | PROTECTED)  => in.nextToken() ; accessQualifierOpt(Modifiers(flagTokens(m)))
        case _                          => NoMods
      }
    }

    /** {{{
     *  Modifiers ::= {Modifier}
     *  Modifier  ::= LocalModifier
     *              |  AccessModifier
     *              |  override
     *  }}}
     */
    def modifiers(): Modifiers = normalizeModifiers {
      def loop(mods: Modifiers): Modifiers = in.token match {
        case PRIVATE | PROTECTED =>
          loop(accessQualifierOpt(addMod(mods, flagTokens(in.token), tokenRange(in))))
        case ABSTRACT | FINAL | SEALED | OVERRIDE | IMPLICIT | LAZY =>
          loop(addMod(mods, flagTokens(in.token), tokenRange(in)))
        case NEWLINE =>
          in.nextToken()
          loop(mods)
        case _ =>
          mods
      }
      loop(NoMods)
    }

    /** {{{
     *  LocalModifiers ::= {LocalModifier}
     *  LocalModifier  ::= abstract | final | sealed | implicit | lazy
     *  }}}
     */
    def localModifiers(): Modifiers = {
      def loop(mods: Modifiers): Modifiers =
        if (isLocalModifier) loop(addMod(mods, flagTokens(in.token), tokenRange(in)))
        else mods

      loop(NoMods)
    }

    /** {{{
     *  Annotations      ::= {`@' SimpleType {ArgumentExprs}}
     *  ConsrAnnotations ::= {`@' SimpleType ArgumentExprs}
     *  }}}
     */
    def annotations(skipNewLines: Boolean): List[Tree] = readAnnots {
      val t = annotationExpr()
      if (skipNewLines) newLineOpt()
      t
    }
    def constructorAnnotations(): List[Tree] = readAnnots {
      atPos(in.offset)(New(exprSimpleType(), List(argumentExprs())))
    }

    def annotationExpr(): Tree = atPos(in.offset) {
      val t = exprSimpleType()
      if (in.token == LPAREN) New(t, multipleArgumentExprs())
      else New(t, Nil)
    }

/* -------- PARAMETERS ------------------------------------------- */

    /** {{{
     *  ParamClauses      ::= {ParamClause} [[nl] `(' implicit Params `)']
     *  ParamClause       ::= [nl] `(' [Params] `)'
     *  Params            ::= Param {`,' Param}
     *  Param             ::= {Annotation} Id [`:' ParamType] [`=' Expr]
     *  ClassParamClauses ::= {ClassParamClause} [[nl] `(' implicit ClassParams `)']
     *  ClassParamClause  ::= [nl] `(' [ClassParams] `)'
     *  ClassParams       ::= ClassParam {`,' ClassParam}
     *  ClassParam        ::= {Annotation}  [{Modifier} (`val' | `var')] Id [`:' ParamType] [`=' Expr]
     *  }}}
     */
    def paramClauses(owner: Name, contextBounds: List[Tree], ofCaseClass: Boolean): List[List[ValDef]] = {
      var implicitSection = -1
      var implicitOffset  = -1
      var warnAt          = -1
      var caseParam       = ofCaseClass
      val vds   = new ListBuffer[List[ValDef]]
      val start = in.offset
      def paramClause(): List[ValDef] = if (in.token == RPAREN) Nil else {
        val implicitmod = 
          if (in.token == IMPLICIT) {
            if (implicitOffset == -1) { implicitOffset = in.offset ; implicitSection = vds.length }
            else if (warnAt == -1) warnAt = in.offset
            in.nextToken()
            Flags.IMPLICIT
          } else 0
        commaSeparated(param(owner, implicitmod, caseParam))
      }
      newLineOptWhenFollowedBy(LPAREN)
      while (in.token == LPAREN) {
        in.nextToken()
        vds += paramClause()
        accept(RPAREN)
        caseParam = false
        newLineOptWhenFollowedBy(LPAREN)
      }
      if (ofCaseClass) {
        if (vds.isEmpty)
          syntaxError(start, s"case classes must have a parameter list; try 'case class ${owner.encoded
                                         }()' or 'case object ${owner.encoded}'")
        else if (vds.head.nonEmpty && vds.head.head.mods.isImplicit) {
          if (settings.isScala213)
            syntaxError(start, s"case classes must have a non-implicit parameter list; try 'case class ${
                                         owner.encoded}()${ vds.map(vs => "(...)").mkString }'")
          else {
            deprecationWarning(start, s"case classes should have a non-implicit parameter list; adapting to 'case class ${
                                         owner.encoded}()${ vds.map(vs => "(...)").mkString }'", "2.12.2")
            vds.insert(0, List.empty[ValDef])
            vds(1) = vds(1).map(vd => copyValDef(vd)(mods = vd.mods & ~Flags.CASEACCESSOR))
            if (implicitSection != -1) implicitSection += 1
          }
        }
      }
      if (implicitSection != -1 && implicitSection != vds.length - 1)
        syntaxError(implicitOffset, "an implicit parameter section must be last")
      if (warnAt != -1)
        syntaxError(warnAt, "multiple implicit parameter sections are not allowed")
      else if (settings.warnExtraImplicit) {
        // guard against anomalous class C(private implicit val x: Int)(implicit s: String)
        val ttl = vds.count { case ValDef(mods, _, _, _) :: _ => mods.isImplicit ; case _ => false }
        if (ttl > 1)
          warning(in.offset, s"$ttl parameter sections are effectively implicit")
      }
      val result = vds.toList
      if (owner == nme.CONSTRUCTOR && (result.isEmpty || (result.head take 1 exists (_.mods.isImplicit)))) {
        in.token match {
          case LBRACKET   => syntaxError(in.offset, "no type parameters allowed here", skipIt = false)
          case EOF        => incompleteInputError("auxiliary constructor needs non-implicit parameter list")
          case _          => syntaxError(start, "auxiliary constructor needs non-implicit parameter list", skipIt = false)
        }
      }
      addEvidenceParams(owner, result, contextBounds)
    }

    /** {{{
     *  ParamType ::= Type | `=>' Type | Type `*'
     *  }}}
     */
    def paramType(): Tree = paramType(useStartAsPosition = false)
    def paramType(useStartAsPosition: Boolean): Tree = {
      val start = in.offset
      in.token match {
        case ARROW  =>
          in.nextToken()
          atPos(start)(byNameApplication(typ()))
        case _      =>
          val t = typ()
          if (isRawStar) {
            in.nextToken()
            if (useStartAsPosition) atPos(start)(repeatedApplication(t))
            else atPos(t.pos.start, t.pos.point)(repeatedApplication(t))
          }
          else t
      }
    }

    def param(owner: Name, implicitmod: Int, caseParam: Boolean): ValDef = {
      val start = in.offset
      val annots = annotations(skipNewLines = false)
      var mods = Modifiers(Flags.PARAM)
      if (owner.isTypeName) {
        mods = modifiers() | Flags.PARAMACCESSOR
        if (mods.isLazy) syntaxError("lazy modifier not allowed here. Use call-by-name parameters instead", skipIt = false)
        in.token match {
          case v @ (VAL | VAR) =>
            mods = mods withPosition (in.token.toLong, tokenRange(in))
            if (v == VAR) mods |= Flags.MUTABLE
            in.nextToken()
          case _ =>
            if (mods.flags != Flags.PARAMACCESSOR) accept(VAL)
            if (!caseParam) mods |= Flags.PrivateLocal
        }
        if (caseParam) mods |= Flags.CASEACCESSOR
      }
      val nameOffset = in.offset
      val name = ident()
      var bynamemod = 0
      val tpt =
        if ((settings.YmethodInfer && !owner.isTypeName) && in.token != COLON) {
          TypeTree()
        } else { // XX-METHOD-INFER
          accept(COLON)
          if (in.token == ARROW) {
            if (owner.isTypeName && !mods.isLocalToThis)
              syntaxError(
                in.offset,
                (if (mods.isMutable) "`var'" else "`val'") +
                " parameters may not be call-by-name", skipIt = false)
            else if (implicitmod != 0)
              syntaxError(
                in.offset,
                "implicit parameters may not be call-by-name", skipIt = false)
            else bynamemod = Flags.BYNAMEPARAM
          }
          paramType()
        }
      val default =
        if (in.token == EQUALS) {
          in.nextToken()
          mods |= Flags.DEFAULTPARAM
          expr()
        } else EmptyTree
      atPos(start, if (name == nme.ERROR) start else nameOffset) {
        ValDef((mods | implicitmod.toLong | bynamemod) withAnnotations annots, name.toTermName, tpt, default)
      }
    }

    /** {{{
     *  TypeParamClauseOpt    ::= [TypeParamClause]
     *  TypeParamClause       ::= `[' VariantTypeParam {`,' VariantTypeParam} `]']
     *  VariantTypeParam      ::= {Annotation} [`+' | `-'] TypeParam
     *  FunTypeParamClauseOpt ::= [FunTypeParamClause]
     *  FunTypeParamClause    ::= `[' TypeParam {`,' TypeParam} `]']
     *  TypeParam             ::= Id TypeParamClauseOpt TypeBounds {<% Type} {":" Type}
     *  }}}
     */
    def typeParamClauseOpt(owner: Name, contextBoundBuf: ListBuffer[Tree]): List[TypeDef] = {
      def typeParam(ms: Modifiers): TypeDef = {
        var mods = ms | Flags.PARAM
        val start = in.offset
        if (owner.isTypeName && isIdent) {
          if (in.name == raw.PLUS) {
            in.nextToken()
            mods |= Flags.COVARIANT
          } else if (in.name == raw.MINUS) {
            in.nextToken()
            mods |= Flags.CONTRAVARIANT
          }
        }
        val nameOffset = in.offset
        // TODO AM: freshTermName(o2p(in.skipToken()), "_$$"), will need to update test suite
        val pname: TypeName = wildcardOrIdent().toTypeName
        val param = atPos(start, nameOffset) {
          val tparams = typeParamClauseOpt(pname, null) // @M TODO null --> no higher-order context bounds for now
          TypeDef(mods, pname, tparams, typeBounds())
        }
        if (contextBoundBuf ne null) {
          while (in.token == VIEWBOUND) {
            val msg = "Use an implicit parameter instead.\nExample: Instead of `def f[A <% Int](a: A)` use `def f[A](a: A)(implicit ev: A => Int)`."
            if (settings.future)
              deprecationWarning(in.offset, s"View bounds are deprecated. $msg", "2.12.0")
            contextBoundBuf += atPos(in.skipToken())(makeFunctionTypeTree(List(Ident(pname)), typ()))
          }
          while (in.token == COLON) {
            contextBoundBuf += atPos(in.skipToken()) {
              AppliedTypeTree(typ(), List(Ident(pname)))
            }
          }
        }
        param
      }
      newLineOptWhenFollowedBy(LBRACKET)
      if (in.token == LBRACKET) inBrackets(commaSeparated(typeParam(NoMods withAnnotations annotations(skipNewLines = true))))
      else Nil
    }

    /** {{{
     *  TypeBounds ::= [`>:' Type] [`<:' Type]
     *  }}}
     */
    def typeBounds(): TypeBoundsTree = {
      val lo      = bound(SUPERTYPE)
      val hi      = bound(SUBTYPE)
      val t       = TypeBoundsTree(lo, hi)
      val defined = List(t.hi, t.lo) filter (_.pos.isDefined)

      if (defined.nonEmpty)
        t setPos wrappingPos(defined)
      else
        t setPos o2p(in.offset)
    }

    def bound(tok: Token): Tree = if (in.token == tok) { in.nextToken(); typ() } else EmptyTree

/* -------- DEFS ------------------------------------------- */


    /** {{{
     *  Import  ::= import ImportExpr {`,' ImportExpr}
     *  }}}
     */
    def importClause(): List[Tree] = {
      val offset = accept(IMPORT)
      commaSeparated(importExpr()) match {
        case Nil => Nil
        case t :: rest =>
          // The first import should start at the position of the keyword.
          t.setPos(t.pos.withStart(offset))
          t :: rest
      }
    }

    /** {{{
     *  ImportExpr ::= StableId `.' (Id | `_' | ImportSelectors)
     *  }}}
     */
    def importExpr(): Tree = {
      val start = in.offset
      def thisDotted(name: TypeName) = {
        in.nextToken()
        val t = atPos(start)(This(name))
        accept(DOT)
        val result = selector(t)
        accept(DOT)
        result
      }
      /* Walks down import `foo.bar.baz.{ ... }` until it ends at a
       * an underscore, a left brace, or an undotted identifier.
       */
      def loop(expr: Tree): Tree = {
        expr setPos expr.pos.makeTransparent
        val selectors: List[ImportSelector] = in.token match {
          case USCORE   => List(importSelector()) // import foo.bar._;
          case LBRACE   => importSelectors()      // import foo.bar.{ x, y, z }
          case _        =>
            val nameOffset = in.offset
            val name = ident()
            if (in.token == DOT) {
              // import foo.bar.ident.<unknown> and so create a select node and recurse.
              val t = atPos(start, if (name == nme.ERROR) in.offset else nameOffset)(Select(expr, name))
              in.nextToken()
              return loop(t)
            }
            // import foo.bar.Baz;
            else List(makeImportSelector(name, nameOffset))
        }
        // reaching here means we're done walking.
        atPos(start)(Import(expr, selectors))
      }

      loop(in.token match {
        case THIS   => thisDotted(tpnme.EMPTY)
        case _      =>
          val id = atPos(start)(Ident(ident()))
          accept(DOT)
          if (in.token == THIS) thisDotted(id.name.toTypeName)
          else id
      })
    }

    /** {{{
     *  ImportSelectors ::= `{' {ImportSelector `,'} (ImportSelector | `_') `}'
     *  }}}
     */
    def importSelectors(): List[ImportSelector] = {
      val selectors = inBracesOrNil(commaSeparated(importSelector()))
      selectors.init foreach {
        case ImportSelector(nme.WILDCARD, pos, _, _)  => syntaxError(pos, "Wildcard import must be in last position")
        case _                                        => ()
      }
      selectors
    }

    def wildcardOrIdent() = {
      if (in.token == USCORE) { in.nextToken() ; nme.WILDCARD }
      else ident()
    }

    /** {{{
     *  ImportSelector ::= Id [`=>' Id | `=>' `_']
     *  }}}
     */
    def importSelector(): ImportSelector = {
      val start        = in.offset
      val name         = wildcardOrIdent()
      var renameOffset = -1
      val rename       = in.token match {
        case ARROW    =>
          in.nextToken()
          renameOffset = in.offset
          wildcardOrIdent()
        case _ if name == nme.WILDCARD  => null
        case _ =>
          renameOffset = start
          name
      }
      ImportSelector(name, start, rename, renameOffset)
    }

    /** {{{
     *  Def    ::= val PatDef
     *           | var PatDef
     *           | def FunDef
     *           | type [nl] TypeDef
     *           | TmplDef
     *  Dcl    ::= val PatDcl
     *           | var PatDcl
     *           | def FunDcl
     *           | type [nl] TypeDcl
     *  }}}
     */
    def defOrDcl(pos: Offset, mods: Modifiers): List[Tree] = {
      if (mods.isLazy && in.token != VAL)
        syntaxError("lazy not allowed here. Only vals can be lazy", skipIt = false)
      in.token match {
        case VAL =>
          patDefOrDcl(pos, mods withPosition(VAL, tokenRange(in)))
        case VAR =>
          patDefOrDcl(pos, (mods | Flags.MUTABLE) withPosition (VAR, tokenRange(in)))
        case DEF =>
          List(funDefOrDcl(pos, mods withPosition(DEF, tokenRange(in))))
        case TYPE =>
          List(typeDefOrDcl(pos, mods withPosition(TYPE, tokenRange(in))))
        case _ =>
          List(tmplDef(pos, mods))
      }
    }

    private def caseAwareTokenOffset = if (in.token == CASECLASS || in.token == CASEOBJECT) in.prev.offset else in.offset

    def nonLocalDefOrDcl : List[Tree] = {
      val annots = annotations(skipNewLines = true)
      defOrDcl(caseAwareTokenOffset, modifiers() withAnnotations annots)
    }

    /** {{{
     *  PatDef ::= Pattern2 {`,' Pattern2} [`:' Type] `=' Expr
     *  ValDcl ::= Id {`,' Id} `:' Type
     *  VarDef ::= PatDef | Id {`,' Id} `:' Type `=' `_'
     *  }}}
     */
    def patDefOrDcl(pos : Int, mods: Modifiers): List[Tree] = {
      var newmods = mods
      in.nextToken()
      val lhs = commaSeparated(stripParens(noSeq.pattern2()))
      val tp = typedOpt()
      val rhs =
        if (tp.isEmpty || in.token == EQUALS) {
          accept(EQUALS)
          if (!tp.isEmpty && newmods.isMutable &&
              (lhs.toList forall (_.isInstanceOf[Ident])) && in.token == USCORE) {
            in.nextToken()
            newmods = newmods | Flags.DEFAULTINIT
            EmptyTree
          } else {
            expr()
          }
        } else {
          newmods = newmods | Flags.DEFERRED
          EmptyTree
        }
      def mkDefs(p: Tree, tp: Tree, rhs: Tree): List[Tree] = {
        val trees = {
          val pat = if (tp.isEmpty) p else Typed(p, tp) setPos (p.pos union tp.pos)
          makePatDef(newmods, pat, rhs)
        }
        if (newmods.isDeferred) {
          trees match {
            case List(ValDef(_, _, _, EmptyTree)) =>
              if (mods.isLazy) syntaxError(p.pos, "lazy values may not be abstract", skipIt = false)
            case _ => syntaxError(p.pos, "pattern definition may not be abstract", skipIt = false)
          }
        }
        trees
      }
      val trees = (lhs.toList.init flatMap (mkDefs(_, tp.duplicate, rhs.duplicate))) ::: mkDefs(lhs.last, tp, rhs)
      val hd = trees.head
      hd setPos hd.pos.withStart(pos)
      ensureNonOverlapping(hd, trees.tail)
      trees
    }

    /** {{{
     *  VarDef ::= PatDef
     *           | Id {`,' Id} `:' Type `=' `_'
     *  VarDcl ::= Id {`,' Id} `:' Type
     *  }}}
    def varDefOrDcl(mods: Modifiers): List[Tree] = {
      var newmods = mods | Flags.MUTABLE
      val lhs = new ListBuffer[(Int, Name)]
      do {
        in.nextToken()
        lhs += (in.offset, ident())
      } while (in.token == COMMA)
      val tp = typedOpt()
      val rhs = if (tp.isEmpty || in.token == EQUALS) {
        accept(EQUALS)
        if (!tp.isEmpty && in.token == USCORE) {
          in.nextToken()
          EmptyTree
        } else {
          expr()
        }
      } else {
        newmods = newmods | Flags.DEFERRED
        EmptyTree
      }
    }
     */

    /** {{{
     *  FunDef ::= FunSig [`:' Type] `=' [`macro'] Expr
     *          |  FunSig [nl] `{' Block `}'
     *          |  `this' ParamClause ParamClauses
     *                 (`=' ConstrExpr | [nl] ConstrBlock)
     *  FunDcl ::= FunSig [`:' Type]
     *  FunSig ::= id [FunTypeParamClause] ParamClauses
     *  }}}
     */
    def funDefOrDcl(start : Int, mods: Modifiers): Tree = {
      in.nextToken()
      if (in.token == THIS) {
        atPos(start, in.skipToken()) {
          val vparamss = paramClauses(nme.CONSTRUCTOR, classContextBounds map (_.duplicate), ofCaseClass = false)
          newLineOptWhenFollowedBy(LBRACE)
          val rhs = in.token match {
            case LBRACE   => atPos(in.offset) { constrBlock(vparamss) }
            case _        => accept(EQUALS) ; atPos(in.offset) { constrExpr(vparamss) }
          }
          DefDef(mods, nme.CONSTRUCTOR, List(), vparamss, TypeTree(), rhs)
        }
      }
      else {
        val nameOffset = in.offset
        val name = identOrMacro()
        funDefRest(start, nameOffset, mods, name)
      }
    }

    def funDefRest(start: Offset, nameOffset: Offset, mods: Modifiers, name: Name): Tree = {
      val result = atPos(start, if (name.toTermName == nme.ERROR) start else nameOffset) {
        var newmods = mods
        // contextBoundBuf is for context bounded type parameters of the form
        // [T : B] or [T : => B]; it contains the equivalent implicit parameter type,
        // i.e. (B[T] or T => B)
        val contextBoundBuf = new ListBuffer[Tree]
        val tparams = typeParamClauseOpt(name, contextBoundBuf)
        val vparamss = paramClauses(name, contextBoundBuf.toList, ofCaseClass = false)
        newLineOptWhenFollowedBy(LBRACE)
        var restype = fromWithinReturnType(typedOpt())
        val rhs =
          if (isStatSep || in.token == RBRACE) {
            if (restype.isEmpty) {
              if (settings.future)
                deprecationWarning(in.lastOffset, s"Procedure syntax is deprecated. Convert procedure `$name` to method by adding `: Unit`.", "2.12.0")
              restype = scalaUnitConstr
            }
            newmods |= Flags.DEFERRED
            EmptyTree
          } else if (restype.isEmpty && in.token == LBRACE) {
            if (settings.future)
              deprecationWarning(in.offset, s"Procedure syntax is deprecated. Convert procedure `$name` to method by adding `: Unit =`.", "2.12.0")
            restype = scalaUnitConstr
            blockExpr()
          } else {
            if (in.token == EQUALS) {
              in.nextTokenAllow(nme.MACROkw)
              if (isMacro) {
                in.nextToken()
                newmods |= Flags.MACRO
              }
            } else {
              accept(EQUALS)
            }
            expr()
          }
        DefDef(newmods, name.toTermName, tparams, vparamss, restype, rhs)
      }
      signalParseProgress(result.pos)
      result
    }

    /** {{{
     *  ConstrExpr      ::=  SelfInvocation
     *                    |  ConstrBlock
     *  }}}
     */
    def constrExpr(vparamss: List[List[ValDef]]): Tree =
      if (in.token == LBRACE) constrBlock(vparamss)
      else Block(selfInvocation(vparamss) :: Nil, literalUnit)

    /** {{{
     *  SelfInvocation  ::= this ArgumentExprs {ArgumentExprs}
     *  }}}
     */
    def selfInvocation(vparamss: List[List[ValDef]]): Tree =
      atPos(accept(THIS)) {
        newLineOptWhenFollowedBy(LBRACE)
        var t = Apply(Ident(nme.CONSTRUCTOR), argumentExprs())
        newLineOptWhenFollowedBy(LBRACE)
        while (in.token == LPAREN || in.token == LBRACE) {
          t = Apply(t, argumentExprs())
          newLineOptWhenFollowedBy(LBRACE)
        }
        if (classContextBounds.isEmpty) t
        else Apply(t, vparamss.last.map(vp => Ident(vp.name)))
      }

    /** {{{
     *  ConstrBlock    ::=  `{' SelfInvocation {semi BlockStat} `}'
     *  }}}
     */
    def constrBlock(vparamss: List[List[ValDef]]): Tree =
      atPos(in.skipToken()) {
        val stats = selfInvocation(vparamss) :: {
          if (isStatSep) { in.nextToken(); blockStatSeq() }
          else Nil
        }
        accept(RBRACE)
        Block(stats, literalUnit)
      }

    /** {{{
     *  TypeDef ::= type Id [TypeParamClause] `=' Type
     *            | FunSig `=' Expr
     *  TypeDcl ::= type Id [TypeParamClause] TypeBounds
     *  }}}
     */
    def typeDefOrDcl(start: Offset, mods: Modifiers): Tree = {
      in.nextToken()
      newLinesOpt()
      atPos(start, in.offset) {
        val name = identForType()
        // @M! a type alias as well as an abstract type may declare type parameters
        val tparams = typeParamClauseOpt(name, null)
        in.token match {
          case EQUALS =>
            in.nextToken()
            TypeDef(mods, name, tparams, typ())
          case t if t == SUPERTYPE || t == SUBTYPE || t == COMMA || t == RBRACE || isStatSep(t) =>
            TypeDef(mods | Flags.DEFERRED, name, tparams, typeBounds())
          case _ =>
            syntaxErrorOrIncompleteAnd("`=', `>:', or `<:' expected", skipIt = true)(
              // assume a dummy type def so as to have somewhere to stash the annotations
              TypeDef(mods, tpnme.ERROR, Nil, EmptyTree)
            )
        }
      }
    }

    /** Hook for IDE, for top-level classes/objects. */
    def topLevelTmplDef: Tree = {
      val annots = annotations(skipNewLines = true)
      val pos    = caseAwareTokenOffset
      val mods   = modifiers() withAnnotations annots
      tmplDef(pos, mods)
    }

    /** {{{
     *  TmplDef ::= [case] class ClassDef
     *            |  [case] object ObjectDef
     *            |  [override] trait TraitDef
     *  }}}
     */
    def tmplDef(pos: Offset, mods: Modifiers): Tree = {
      if (mods.isLazy) syntaxError("classes cannot be lazy", skipIt = false)
      in.token match {
        case TRAIT =>
          classDef(pos, (mods | Flags.TRAIT | Flags.ABSTRACT) withPosition (Flags.TRAIT, tokenRange(in)))
        case CLASS =>
          classDef(pos, mods)
        case CASECLASS =>
          classDef(pos, (mods | Flags.CASE) withPosition (Flags.CASE, tokenRange(in.prev /*scanner skips on 'case' to 'class', thus take prev*/)))
        case OBJECT =>
          objectDef(pos, mods)
        case CASEOBJECT =>
          objectDef(pos, (mods | Flags.CASE) withPosition (Flags.CASE, tokenRange(in.prev /*scanner skips on 'case' to 'object', thus take prev*/)))
        case _ =>
          syntaxErrorOrIncompleteAnd("expected start of definition", skipIt = true)(
            // assume a class definition so as to have somewhere to stash the annotations
            atPos(pos)(gen.mkClassDef(mods, tpnme.ERROR, Nil, Template(Nil, noSelfType, Nil)))
          )
      }
    }

    /** {{{
     *  ClassDef ::= Id [TypeParamClause] {Annotation}
     *               [AccessModifier] ClassParamClauses RequiresTypeOpt ClassTemplateOpt
     *  TraitDef ::= Id [TypeParamClause] RequiresTypeOpt TraitTemplateOpt
     *  }}}
     */
    def classDef(start: Offset, mods: Modifiers): ClassDef = {
      in.nextToken()
      val nameOffset = in.offset
      val name = identForType()
      atPos(start, if (name == tpnme.ERROR) start else nameOffset) {
        savingClassContextBounds {
          val contextBoundBuf = new ListBuffer[Tree]
          val tparams = typeParamClauseOpt(name, contextBoundBuf)
          classContextBounds = contextBoundBuf.toList
          val tstart = (in.offset :: classContextBounds.map(_.pos.start)).min
          if (!classContextBounds.isEmpty && mods.isTrait) {
            val viewBoundsExist = if (settings.future) "" else " nor view bounds `<% ...'"
              syntaxError(s"traits cannot have type parameters with context bounds `: ...'$viewBoundsExist", skipIt = false)
            classContextBounds = List()
          }
          val constrAnnots = if (!mods.isTrait) constructorAnnotations() else Nil
          val (constrMods, vparamss) =
            if (mods.isTrait) (Modifiers(Flags.TRAIT), List())
            else (accessModifierOpt(), paramClauses(name, classContextBounds, ofCaseClass = mods.isCase))
          val template = templateOpt(mods, name, constrMods withAnnotations constrAnnots, vparamss, tstart)
          val result = gen.mkClassDef(mods, name, tparams, template)
          // Context bounds generate implicit parameters (part of the template) with types
          // from tparams: we need to ensure these don't overlap
          if (!classContextBounds.isEmpty)
            ensureNonOverlapping(template, tparams)
          result
        }
      }
    }

    /** {{{
     *  ObjectDef       ::= Id ClassTemplateOpt
     *  }}}
     */
    def objectDef(start: Offset, mods: Modifiers): ModuleDef = {
      in.nextToken()
      val nameOffset = in.offset
      val name = ident()
      val tstart = in.offset
      atPos(start, if (name == nme.ERROR) start else nameOffset) {
        val mods1 = if (in.token == SUBTYPE) mods | Flags.DEFERRED else mods
        val template = templateOpt(mods1, name, NoMods, Nil, tstart)
        ModuleDef(mods1, name.toTermName, template)
      }
    }

    /** Create a tree representing a package object, converting
     *  {{{
     *    package object foo { ... }
     *  }}}
     *  to
     *  {{{
     *    package foo {
     *      object `package` { ... }
     *    }
     *  }}}
     */
    def packageObjectDef(start: Offset): PackageDef = {
      val defn   = objectDef(in.offset, NoMods)
      val pidPos = o2p(defn.pos.start)
      val pkgPos = r2p(start, pidPos.point)
      gen.mkPackageObject(defn, pidPos, pkgPos)
    }
    def packageOrPackageObject(start: Offset): Tree = (
      if (in.token == OBJECT)
        joinComment(packageObjectDef(start) :: Nil).head
      else {
        in.flushDoc
        makePackaging(start, pkgQualId(), inBracesOrNil(topStatSeq()))
      }
    )
    // TODO - eliminate this and use "def packageObjectDef" (see call site of this
    // method for small elaboration.)
    def makePackageObject(start: Offset, objDef: ModuleDef): PackageDef = objDef match {
      case ModuleDef(mods, name, impl) =>
        makePackaging(
          start, atPos(o2p(objDef.pos.start)){ Ident(name) }, List(ModuleDef(mods, nme.PACKAGEkw, impl)))
    }

    /** {{{
     *  ClassParents       ::= AnnotType {`(' [Exprs] `)'} {with AnnotType}
     *  TraitParents       ::= AnnotType {with AnnotType}
     *  }}}
     */
    def templateParents(): List[Tree] = {
      val parents = new ListBuffer[Tree]
      def readAppliedParent() = {
        val start = in.offset
        val parent = startAnnotType()
        parents += (in.token match {
          case LPAREN => atPos(start)((parent /: multipleArgumentExprs())(Apply.apply))
          case _      => parent
        })
      }
      readAppliedParent()
      while (in.token == WITH) { in.nextToken(); readAppliedParent() }
      parents.toList
    }

    /** {{{
     *  ClassTemplate ::= [EarlyDefs with] ClassParents [TemplateBody]
     *  TraitTemplate ::= [EarlyDefs with] TraitParents [TemplateBody]
     *  EarlyDefs     ::= `{' [EarlyDef {semi EarlyDef}] `}'
     *  EarlyDef      ::= Annotations Modifiers PatDef
     *  }}}
     */
    def template(): (List[Tree], ValDef, List[Tree]) = {
      newLineOptWhenFollowedBy(LBRACE)
      if (in.token == LBRACE) {
        // @S: pre template body cannot stub like post body can!
        val (self, body) = templateBody(isPre = true)
        if (in.token == WITH && (self eq noSelfType)) {
          val earlyDefs: List[Tree] = body.map(ensureEarlyDef).filter(_.nonEmpty)
          in.nextToken()
          val parents = templateParents()
          val (self1, body1) = templateBodyOpt(parenMeansSyntaxError = false)
          (parents, self1, earlyDefs ::: body1)
        } else {
          (List(), self, body)
        }
      } else {
        val parents = templateParents()
        val (self, body) = templateBodyOpt(parenMeansSyntaxError = false)
        (parents, self, body)
      }
    }

    def ensureEarlyDef(tree: Tree): Tree = tree match {
      case vdef @ ValDef(mods, _, _, _) if !mods.isDeferred =>
        copyValDef(vdef)(mods = mods | Flags.PRESUPER)
      case tdef @ TypeDef(mods, name, tparams, rhs) =>
        deprecationWarning(tdef.pos.point, "early type members are deprecated. Move them to the regular body: the semantics are the same.", "2.11.0")
        treeCopy.TypeDef(tdef, mods | Flags.PRESUPER, name, tparams, rhs)
      case docdef @ DocDef(comm, rhs) =>
        treeCopy.DocDef(docdef, comm, rhs)
      case stat if !stat.isEmpty =>
        syntaxError(stat.pos, "only concrete field definitions allowed in early object initialization section", skipIt = false)
        EmptyTree
      case _ =>
        EmptyTree
    }

    /** {{{
     *  ClassTemplateOpt ::= `extends' ClassTemplate | [[`extends'] TemplateBody]
     *  TraitTemplateOpt ::= TraitExtends TraitTemplate | [[`extends'] TemplateBody] | `<:' TemplateBody
     *  TraitExtends     ::= `extends' | `<:'
     *  }}}
     */
    def templateOpt(mods: Modifiers, name: Name, constrMods: Modifiers, vparamss: List[List[ValDef]], tstart: Offset): Template = {
      val (parents, self, body) = (
        if (in.token == EXTENDS || in.token == SUBTYPE && mods.isTrait) {
          in.nextToken()
          template()
        }
        else {
          newLineOptWhenFollowedBy(LBRACE)
          val (self, body) = templateBodyOpt(parenMeansSyntaxError = mods.isTrait || name.isTermName)
          (List(), self, body)
        }
      )
      def anyvalConstructor() = (
        // Not a well-formed constructor, has to be finished later - see note
        // regarding AnyVal constructor in AddInterfaces.
        DefDef(NoMods, nme.CONSTRUCTOR, Nil, ListOfNil, TypeTree(), Block(Nil, literalUnit))
      )
      val parentPos = o2p(in.offset)
      val tstart1 = if (body.isEmpty && in.lastOffset < tstart) in.lastOffset else tstart

      atPos(tstart1) {
        // Exclude only the 9 primitives plus AnyVal.
        if (inScalaRootPackage && ScalaValueClassNames.contains(name))
          Template(parents, self, anyvalConstructor :: body)
        else
          gen.mkTemplate(gen.mkParents(mods, parents, parentPos),
                         self, constrMods, vparamss, body, o2p(tstart))
      }
    }

/* -------- TEMPLATES ------------------------------------------- */

    /** {{{
     *  TemplateBody ::= [nl] `{' TemplateStatSeq `}'
     *  }}}
     * @param isPre specifies whether in early initializer (true) or not (false)
     */
    def templateBody(isPre: Boolean) = inBraces(templateStatSeq(isPre = isPre)) match {
      case (self, Nil)  => (self, EmptyTree.asList)
      case result       => result
    }
    def templateBodyOpt(parenMeansSyntaxError: Boolean): (ValDef, List[Tree]) = {
      newLineOptWhenFollowedBy(LBRACE)
      if (in.token == LBRACE) {
        templateBody(isPre = false)
      } else {
        if (in.token == LPAREN) {
          if (parenMeansSyntaxError) syntaxError(s"traits or objects may not have parameters", skipIt = true)
          else abort("unexpected opening parenthesis")
        }
        (noSelfType, List())
      }
    }

    /** {{{
     *  Refinement ::= [nl] `{' RefineStat {semi RefineStat} `}'
     *  }}}
     */
    def refinement(): List[Tree] = inBraces(refineStatSeq())

/* -------- STATSEQS ------------------------------------------- */

  /** Create a tree representing a packaging. */
    def makePackaging(start: Offset, pkg: Tree, stats: List[Tree]): PackageDef = pkg match {
      case x: RefTree => atPos(start, pkg.pos.point)(PackageDef(x, stats))
    }

    def makeEmptyPackage(start: Offset, stats: List[Tree]): PackageDef = (
      makePackaging(start, atPos(start, start, start)(Ident(nme.EMPTY_PACKAGE_NAME)), stats)
    )

    def statSeq(stat: PartialFunction[Token, List[Tree]], errorMsg: String = "illegal start of definition"): List[Tree] = {
      val stats = new ListBuffer[Tree]
      def default(tok: Token) =
        if (isStatSep) Nil
        else syntaxErrorOrIncompleteAnd(errorMsg, skipIt = true)(Nil)
      while (!isStatSeqEnd) {
        stats ++= stat.applyOrElse(in.token, default)
        acceptStatSepOpt()
      }
      stats.toList
    }

    /** {{{
     *  TopStatSeq ::= TopStat {semi TopStat}
     *  TopStat ::= Annotations Modifiers TmplDef
     *            | Packaging
     *            | package object objectDef
     *            | Import
     *            |
     *  }}}
     */
    def topStatSeq(): List[Tree] = statSeq(topStat, errorMsg = "expected class or object definition")
    def topStat: PartialFunction[Token, List[Tree]] = {
      case PACKAGE  =>
        packageOrPackageObject(in.skipToken()) :: Nil
      case IMPORT =>
        in.flushDoc
        importClause()
      case _ if isAnnotation || isTemplateIntro || isModifier =>
        joinComment(topLevelTmplDef :: Nil)
    }

    /** {{{
     *  TemplateStatSeq  ::= [id [`:' Type] `=>'] TemplateStats
     *  }}}
     * @param isPre specifies whether in early initializer (true) or not (false)
     */
    def templateStatSeq(isPre : Boolean): (ValDef, List[Tree]) = checkNoEscapingPlaceholders {
      var self: ValDef = noSelfType
      var firstOpt: Option[Tree] = None
      if (isExprIntro) {
        in.flushDoc
        val first = expr(InTemplate) // @S: first statement is potentially converted so cannot be stubbed.
        if (in.token == ARROW) {
          first match {
            case Typed(tree @ This(tpnme.EMPTY), tpt) =>
              self = atPos(tree.pos union tpt.pos) { makeSelfDef(nme.WILDCARD, tpt) }
            case _ =>
              convertToParam(first) match {
                case tree @ ValDef(_, name, tpt, EmptyTree) if (name != nme.ERROR) =>
                  self = atPos(tree.pos union tpt.pos) { makeSelfDef(name, tpt) }
                case _ =>
              }
          }
          in.nextToken()
        } else {
          firstOpt = Some(first)
          acceptStatSepOpt()
        }
      }
      (self, firstOpt ++: templateStats())
    }

    /** {{{
     *  TemplateStats    ::= TemplateStat {semi TemplateStat}
     *  TemplateStat     ::= Import
     *                     | Annotations Modifiers Def
     *                     | Annotations Modifiers Dcl
     *                     | Expr1
     *                     | super ArgumentExprs {ArgumentExprs}
     *                     |
     *  }}}
     */
    def templateStats(): List[Tree] = statSeq(templateStat)
    def templateStat: PartialFunction[Token, List[Tree]] = {
      case IMPORT =>
        in.flushDoc
        importClause()
      case _ if isDefIntro || isModifier || isAnnotation =>
        joinComment(nonLocalDefOrDcl)
      case _ if isExprIntro =>
        in.flushDoc
        statement(InTemplate) :: Nil
    }

    def templateOrTopStatSeq(): List[Tree] = statSeq(templateStat.orElse(topStat))

    /** {{{
     *  RefineStatSeq    ::= RefineStat {semi RefineStat}
     *  RefineStat       ::= Dcl
     *                     | type TypeDef
     *                     |
     *  }}}
     */
    def refineStatSeq(): List[Tree] = checkNoEscapingPlaceholders {
      val stats = new ListBuffer[Tree]
      while (!isStatSeqEnd) {
        stats ++= refineStat()
        if (in.token != RBRACE) acceptStatSep()
      }
      stats.toList
    }

    def refineStat(): List[Tree] =
      if (isDclIntro) { // don't IDE hook
        joinComment(defOrDcl(in.offset, NoMods))
      } else if (!isStatSep) {
        syntaxErrorOrIncomplete(
          "illegal start of declaration"+
          (if (inFunReturnType) " (possible cause: missing `=' in front of current method body)"
           else ""), skipIt = true)
        Nil
      } else Nil

    /** overridable IDE hook for local definitions of blockStatSeq
     *  Here's an idea how to fill in start and end positions.
    def localDef : List[Tree] = {
      atEndPos {
        atStartPos(in.offset) {
          val annots = annotations(skipNewLines = true)
          val mods = localModifiers() withAnnotations annots
          if (!(mods hasFlag ~(Flags.IMPLICIT | Flags.LAZY))) defOrDcl(mods)
          else List(tmplDef(mods))
        }
      } (in.offset)
    }
    */

    def localDef(implicitMod: Int): List[Tree] = {
      val annots = annotations(skipNewLines = true)
      val pos = in.offset
      val mods = (localModifiers() | implicitMod.toLong) withAnnotations annots
      val defs =
        if (!(mods hasFlag ~(Flags.IMPLICIT | Flags.LAZY))) defOrDcl(pos, mods)
        else List(tmplDef(pos, mods))

      in.token match {
        case RBRACE | CASE  => defs :+ setInPos(literalUnit)
        case _              => defs
      }
    }

    /** {{{
     *  BlockStatSeq ::= { BlockStat semi } [ResultExpr]
     *  BlockStat    ::= Import
     *                 | Annotations [implicit] [lazy] Def
     *                 | Annotations LocalModifiers TmplDef
     *                 | Expr1
     *                 |
     *  }}}
     */
    def blockStatSeq(): List[Tree] = checkNoEscapingPlaceholders {
      val stats = new ListBuffer[Tree]
      while (!isStatSeqEnd && !isCaseDefEnd) {
        if (in.token == IMPORT) {
          stats ++= importClause()
          acceptStatSepOpt()
        }
        else if (isDefIntro || isLocalModifier || isAnnotation) {
          if (in.token == IMPLICIT) {
            val start = in.skipToken()
            if (isIdent) stats += implicitClosure(start, InBlock)
            else stats ++= localDef(Flags.IMPLICIT)
          } else {
            stats ++= localDef(0)
          }
          acceptStatSepOpt()
        }
        else if (isExprIntro) {
          stats += statement(InBlock)
          if (!isCaseDefEnd) acceptStatSep()
        }
        else if (isStatSep) {
          in.nextToken()
        }
        else {
          val addendum = if (isModifier) " (no modifiers allowed here)" else ""
          syntaxErrorOrIncomplete("illegal start of statement" + addendum, skipIt = true)
        }
      }
      stats.toList
    }

    /** {{{
     *  CompilationUnit ::= {package QualId semi} TopStatSeq
     *  }}}
     */
    def compilationUnit(): PackageDef = checkNoEscapingPlaceholders {
      def topstats(): List[Tree] = {
        val ts = new ListBuffer[Tree]
        while (in.token == SEMI) in.nextToken()
        val start = in.offset
        if (in.token == PACKAGE) {
          in.nextToken()
          if (in.token == OBJECT) {
            // TODO - this next line is supposed to be
            //    ts += packageObjectDef(start)
            // but this broke a scaladoc test (run/diagrams-filtering.scala) somehow.
            ts ++= joinComment(List(makePackageObject(start, objectDef(in.offset, NoMods))))
            if (in.token != EOF) {
              acceptStatSep()
              ts ++= topStatSeq()
            }
          } else {
            in.flushDoc
            val pkg = pkgQualId()

            if (in.token == EOF) {
              ts += makePackaging(start, pkg, List())
            } else if (isStatSep) {
              in.nextToken()
              ts += makePackaging(start, pkg, topstats())
            } else {
              ts += inBraces(makePackaging(start, pkg, topStatSeq()))
              acceptStatSepOpt()
              ts ++= topStatSeq()
            }
          }
        } else {
          ts ++= topStatSeq()
        }
        ts.toList
      }

      resetPackage()
      topstats() match {
        case (stat @ PackageDef(_, _)) :: Nil => stat
        case stats                            =>
          val start =
            if (stats forall (_ == EmptyTree)) 0
            else {
              val wpos = wrappingPos(stats)
              if (wpos.isDefined) wpos.start
              else 0
            }

          makeEmptyPackage(start, stats)
      }
    }
  }
}