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
//! Conversion from AST representation of types to the `ty.rs` representation.
//! The main routine here is `ast_ty_to_ty()`; each use is parameterized by an
//! instance of `AstConv`.
mod bounds;
mod errors;
pub mod generics;
mod lint;
mod object_safety;
use crate::astconv::errors::prohibit_assoc_ty_binding;
use crate::astconv::generics::{check_generic_arg_count, create_args_for_parent_generic_args};
use crate::bounds::Bounds;
use crate::collect::HirPlaceholderCollector;
use crate::errors::{AmbiguousLifetimeBound, TypeofReservedKeywordUsed};
use crate::middle::resolve_bound_vars as rbv;
use crate::require_c_abi_if_c_variadic;
use rustc_ast::TraitObjectSyntax;
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
use rustc_errors::{
struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, FatalError,
MultiSpan,
};
use rustc_hir as hir;
use rustc_hir::def::{CtorOf, DefKind, Namespace, Res};
use rustc_hir::def_id::{DefId, LocalDefId};
use rustc_hir::intravisit::{walk_generics, Visitor as _};
use rustc_hir::{GenericArg, GenericArgs, OpaqueTyOrigin};
use rustc_infer::infer::{InferCtxt, InferOk, TyCtxtInferExt};
use rustc_infer::traits::ObligationCause;
use rustc_middle::middle::stability::AllowUnstable;
use rustc_middle::ty::GenericParamDefKind;
use rustc_middle::ty::{
self, Const, GenericArgKind, GenericArgsRef, IsSuggestable, Ty, TyCtxt, TypeVisitableExt,
};
use rustc_session::lint::builtin::AMBIGUOUS_ASSOCIATED_ITEMS;
use rustc_span::edit_distance::find_best_match_for_name;
use rustc_span::symbol::{kw, Ident, Symbol};
use rustc_span::{sym, Span, DUMMY_SP};
use rustc_target::spec::abi;
use rustc_trait_selection::traits::wf::object_region_bounds;
use rustc_trait_selection::traits::{self, NormalizeExt, ObligationCtxt};
use rustc_type_ir::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
use std::fmt::Display;
use std::slice;
#[derive(Debug)]
pub struct PathSeg(pub DefId, pub usize);
#[derive(Copy, Clone, Debug)]
pub struct OnlySelfBounds(pub bool);
#[derive(Copy, Clone, Debug)]
pub enum PredicateFilter {
/// All predicates may be implied by the trait.
All,
/// Only traits that reference `Self: ..` are implied by the trait.
SelfOnly,
/// Only traits that reference `Self: ..` and define an associated type
/// with the given ident are implied by the trait.
SelfThatDefines(Ident),
/// Only traits that reference `Self: ..` and their associated type bounds.
/// For example, given `Self: Tr<A: B>`, this would expand to `Self: Tr`
/// and `<Self as Tr>::A: B`.
SelfAndAssociatedTypeBounds,
}
pub trait AstConv<'tcx> {
fn tcx(&self) -> TyCtxt<'tcx>;
fn item_def_id(&self) -> DefId;
/// Returns predicates in scope of the form `X: Foo<T>`, where `X`
/// is a type parameter `X` with the given id `def_id` and T
/// matches `assoc_name`. This is a subset of the full set of
/// predicates.
///
/// This is used for one specific purpose: resolving "short-hand"
/// associated type references like `T::Item`. In principle, we
/// would do that by first getting the full set of predicates in
/// scope and then filtering down to find those that apply to `T`,
/// but this can lead to cycle errors. The problem is that we have
/// to do this resolution *in order to create the predicates in
/// the first place*. Hence, we have this "special pass".
fn get_type_parameter_bounds(
&self,
span: Span,
def_id: LocalDefId,
assoc_name: Ident,
) -> ty::GenericPredicates<'tcx>;
/// Returns the lifetime to use when a lifetime is omitted (and not elided).
fn re_infer(&self, param: Option<&ty::GenericParamDef>, span: Span)
-> Option<ty::Region<'tcx>>;
/// Returns the type to use when a type is omitted.
fn ty_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx>;
/// Returns `true` if `_` is allowed in type signatures in the current context.
fn allow_ty_infer(&self) -> bool;
/// Returns the const to use when a const is omitted.
fn ct_infer(
&self,
ty: Ty<'tcx>,
param: Option<&ty::GenericParamDef>,
span: Span,
) -> Const<'tcx>;
/// Projecting an associated type from a (potentially)
/// higher-ranked trait reference is more complicated, because of
/// the possibility of late-bound regions appearing in the
/// associated type binding. This is not legal in function
/// signatures for that reason. In a function body, we can always
/// handle it because we can use inference variables to remove the
/// late-bound regions.
fn projected_ty_from_poly_trait_ref(
&self,
span: Span,
item_def_id: DefId,
item_segment: &hir::PathSegment<'_>,
poly_trait_ref: ty::PolyTraitRef<'tcx>,
) -> Ty<'tcx>;
/// Returns `AdtDef` if `ty` is an ADT.
/// Note that `ty` might be a projection type that needs normalization.
/// This used to get the enum variants in scope of the type.
/// For example, `Self::A` could refer to an associated type
/// or to an enum variant depending on the result of this function.
fn probe_adt(&self, span: Span, ty: Ty<'tcx>) -> Option<ty::AdtDef<'tcx>>;
/// Invoked when we encounter an error from some prior pass
/// (e.g., resolve) that is translated into a ty-error. This is
/// used to help suppress derived errors typeck might otherwise
/// report.
fn set_tainted_by_errors(&self, e: ErrorGuaranteed);
fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, span: Span);
fn astconv(&self) -> &dyn AstConv<'tcx>
where
Self: Sized,
{
self
}
fn infcx(&self) -> Option<&InferCtxt<'tcx>>;
}
#[derive(Debug)]
struct ConvertedBinding<'a, 'tcx> {
hir_id: hir::HirId,
item_name: Ident,
kind: ConvertedBindingKind<'a, 'tcx>,
gen_args: &'a GenericArgs<'a>,
span: Span,
}
#[derive(Debug)]
enum ConvertedBindingKind<'a, 'tcx> {
Equality(ty::Term<'tcx>),
Constraint(&'a [hir::GenericBound<'a>]),
}
/// New-typed boolean indicating whether explicit late-bound lifetimes
/// are present in a set of generic arguments.
///
/// For example if we have some method `fn f<'a>(&'a self)` implemented
/// for some type `T`, although `f` is generic in the lifetime `'a`, `'a`
/// is late-bound so should not be provided explicitly. Thus, if `f` is
/// instantiated with some generic arguments providing `'a` explicitly,
/// we taint those arguments with `ExplicitLateBound::Yes` so that we
/// can provide an appropriate diagnostic later.
#[derive(Copy, Clone, PartialEq, Debug)]
pub enum ExplicitLateBound {
Yes,
No,
}
#[derive(Copy, Clone, PartialEq)]
pub enum IsMethodCall {
Yes,
No,
}
/// Denotes the "position" of a generic argument, indicating if it is a generic type,
/// generic function or generic method call.
#[derive(Copy, Clone, PartialEq)]
pub(crate) enum GenericArgPosition {
Type,
Value, // e.g., functions
MethodCall,
}
/// A marker denoting that the generic arguments that were
/// provided did not match the respective generic parameters.
#[derive(Clone, Default, Debug)]
pub struct GenericArgCountMismatch {
/// Indicates whether a fatal error was reported (`Some`), or just a lint (`None`).
pub reported: Option<ErrorGuaranteed>,
/// A list of spans of arguments provided that were not valid.
pub invalid_args: Vec<Span>,
}
/// Decorates the result of a generic argument count mismatch
/// check with whether explicit late bounds were provided.
#[derive(Clone, Debug)]
pub struct GenericArgCountResult {
pub explicit_late_bound: ExplicitLateBound,
pub correct: Result<(), GenericArgCountMismatch>,
}
pub trait CreateSubstsForGenericArgsCtxt<'a, 'tcx> {
fn args_for_def_id(&mut self, def_id: DefId) -> (Option<&'a GenericArgs<'a>>, bool);
fn provided_kind(
&mut self,
param: &ty::GenericParamDef,
arg: &GenericArg<'_>,
) -> ty::GenericArg<'tcx>;
fn inferred_kind(
&mut self,
args: Option<&[ty::GenericArg<'tcx>]>,
param: &ty::GenericParamDef,
infer_args: bool,
) -> ty::GenericArg<'tcx>;
}
impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
#[instrument(level = "debug", skip(self), ret)]
pub fn ast_region_to_region(
&self,
lifetime: &hir::Lifetime,
def: Option<&ty::GenericParamDef>,
) -> ty::Region<'tcx> {
let tcx = self.tcx();
let lifetime_name = |def_id| tcx.hir().name(tcx.hir().local_def_id_to_hir_id(def_id));
match tcx.named_bound_var(lifetime.hir_id) {
Some(rbv::ResolvedArg::StaticLifetime) => tcx.lifetimes.re_static,
Some(rbv::ResolvedArg::LateBound(debruijn, index, def_id)) => {
let name = lifetime_name(def_id.expect_local());
let br = ty::BoundRegion {
var: ty::BoundVar::from_u32(index),
kind: ty::BrNamed(def_id, name),
};
ty::Region::new_late_bound(tcx, debruijn, br)
}
Some(rbv::ResolvedArg::EarlyBound(def_id)) => {
let name = tcx.hir().ty_param_name(def_id.expect_local());
let item_def_id = tcx.hir().ty_param_owner(def_id.expect_local());
let generics = tcx.generics_of(item_def_id);
let index = generics.param_def_id_to_index[&def_id];
ty::Region::new_early_bound(tcx, ty::EarlyBoundRegion { def_id, index, name })
}
Some(rbv::ResolvedArg::Free(scope, id)) => {
let name = lifetime_name(id.expect_local());
ty::Region::new_free(tcx, scope, ty::BrNamed(id, name))
// (*) -- not late-bound, won't change
}
Some(rbv::ResolvedArg::Error(guar)) => ty::Region::new_error(tcx, guar),
None => {
self.re_infer(def, lifetime.ident.span).unwrap_or_else(|| {
debug!(?lifetime, "unelided lifetime in signature");
// This indicates an illegal lifetime
// elision. `resolve_lifetime` should have
// reported an error in this case -- but if
// not, let's error out.
ty::Region::new_error_with_message(
tcx,
lifetime.ident.span,
"unelided lifetime in signature",
)
})
}
}
}
/// Given a path `path` that refers to an item `I` with the declared generics `decl_generics`,
/// returns an appropriate set of generic arguments for this particular reference to `I`.
pub fn ast_path_args_for_ty(
&self,
span: Span,
def_id: DefId,
item_segment: &hir::PathSegment<'_>,
) -> GenericArgsRef<'tcx> {
let (args, _) = self.create_args_for_ast_path(
span,
def_id,
&[],
item_segment,
item_segment.args(),
item_segment.infer_args,
None,
ty::BoundConstness::NotConst,
);
if let Some(b) = item_segment.args().bindings.first() {
prohibit_assoc_ty_binding(self.tcx(), b.span, Some((item_segment, span)));
}
args
}
/// Given the type/lifetime/const arguments provided to some path (along with
/// an implicit `Self`, if this is a trait reference), returns the complete
/// set of generic arguments. This may involve applying defaulted type parameters.
/// Constraints on associated types are created from `create_assoc_bindings_for_generic_args`.
///
/// Example:
///
/// ```ignore (illustrative)
/// T: std::ops::Index<usize, Output = u32>
/// // ^1 ^^^^^^^^^^^^^^2 ^^^^3 ^^^^^^^^^^^4
/// ```
///
/// 1. The `self_ty` here would refer to the type `T`.
/// 2. The path in question is the path to the trait `std::ops::Index`,
/// which will have been resolved to a `def_id`
/// 3. The `generic_args` contains info on the `<...>` contents. The `usize` type
/// parameters are returned in the `GenericArgsRef`, the associated type bindings like
/// `Output = u32` are returned from `create_assoc_bindings_for_generic_args`.
///
/// Note that the type listing given here is *exactly* what the user provided.
///
/// For (generic) associated types
///
/// ```ignore (illustrative)
/// <Vec<u8> as Iterable<u8>>::Iter::<'a>
/// ```
///
/// We have the parent args are the args for the parent trait:
/// `[Vec<u8>, u8]` and `generic_args` are the arguments for the associated
/// type itself: `['a]`. The returned `GenericArgsRef` concatenates these two
/// lists: `[Vec<u8>, u8, 'a]`.
#[instrument(level = "debug", skip(self, span), ret)]
fn create_args_for_ast_path<'a>(
&self,
span: Span,
def_id: DefId,
parent_args: &[ty::GenericArg<'tcx>],
seg: &hir::PathSegment<'_>,
generic_args: &'a hir::GenericArgs<'_>,
infer_args: bool,
self_ty: Option<Ty<'tcx>>,
constness: ty::BoundConstness,
) -> (GenericArgsRef<'tcx>, GenericArgCountResult) {
// If the type is parameterized by this region, then replace this
// region with the current anon region binding (in other words,
// whatever & would get replaced with).
let tcx = self.tcx();
let generics = tcx.generics_of(def_id);
debug!("generics: {:?}", generics);
if generics.has_self {
if generics.parent.is_some() {
// The parent is a trait so it should have at least one subst
// for the `Self` type.
assert!(!parent_args.is_empty())
} else {
// This item (presumably a trait) needs a self-type.
assert!(self_ty.is_some());
}
} else {
assert!(self_ty.is_none());
}
let arg_count = check_generic_arg_count(
tcx,
span,
def_id,
seg,
generics,
generic_args,
GenericArgPosition::Type,
self_ty.is_some(),
infer_args,
);
// Skip processing if type has no generic parameters.
// Traits always have `Self` as a generic parameter, which means they will not return early
// here and so associated type bindings will be handled regardless of whether there are any
// non-`Self` generic parameters.
if generics.params.is_empty() {
return (tcx.mk_args(parent_args), arg_count);
}
struct SubstsForAstPathCtxt<'a, 'tcx> {
astconv: &'a (dyn AstConv<'tcx> + 'a),
def_id: DefId,
generic_args: &'a GenericArgs<'a>,
span: Span,
inferred_params: Vec<Span>,
infer_args: bool,
}
impl<'a, 'tcx> CreateSubstsForGenericArgsCtxt<'a, 'tcx> for SubstsForAstPathCtxt<'a, 'tcx> {
fn args_for_def_id(&mut self, did: DefId) -> (Option<&'a GenericArgs<'a>>, bool) {
if did == self.def_id {
(Some(self.generic_args), self.infer_args)
} else {
// The last component of this tuple is unimportant.
(None, false)
}
}
fn provided_kind(
&mut self,
param: &ty::GenericParamDef,
arg: &GenericArg<'_>,
) -> ty::GenericArg<'tcx> {
let tcx = self.astconv.tcx();
let mut handle_ty_args = |has_default, ty: &hir::Ty<'_>| {
if has_default {
tcx.check_optional_stability(
param.def_id,
Some(arg.hir_id()),
arg.span(),
None,
AllowUnstable::No,
|_, _| {
// Default generic parameters may not be marked
// with stability attributes, i.e. when the
// default parameter was defined at the same time
// as the rest of the type. As such, we ignore missing
// stability attributes.
},
);
}
if let (hir::TyKind::Infer, false) = (&ty.kind, self.astconv.allow_ty_infer()) {
self.inferred_params.push(ty.span);
Ty::new_misc_error(tcx).into()
} else {
self.astconv.ast_ty_to_ty(ty).into()
}
};
match (¶m.kind, arg) {
(GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
self.astconv.ast_region_to_region(lt, Some(param)).into()
}
(&GenericParamDefKind::Type { has_default, .. }, GenericArg::Type(ty)) => {
handle_ty_args(has_default, ty)
}
(&GenericParamDefKind::Type { has_default, .. }, GenericArg::Infer(inf)) => {
handle_ty_args(has_default, &inf.to_ty())
}
(GenericParamDefKind::Const { .. }, GenericArg::Const(ct)) => {
let did = ct.value.def_id;
tcx.feed_anon_const_type(did, tcx.type_of(param.def_id));
ty::Const::from_anon_const(tcx, did).into()
}
(&GenericParamDefKind::Const { .. }, hir::GenericArg::Infer(inf)) => {
let ty = tcx
.at(self.span)
.type_of(param.def_id)
.no_bound_vars()
.expect("const parameter types cannot be generic");
if self.astconv.allow_ty_infer() {
self.astconv.ct_infer(ty, Some(param), inf.span).into()
} else {
self.inferred_params.push(inf.span);
ty::Const::new_misc_error(tcx, ty).into()
}
}
_ => unreachable!(),
}
}
fn inferred_kind(
&mut self,
args: Option<&[ty::GenericArg<'tcx>]>,
param: &ty::GenericParamDef,
infer_args: bool,
) -> ty::GenericArg<'tcx> {
let tcx = self.astconv.tcx();
match param.kind {
GenericParamDefKind::Lifetime => self
.astconv
.re_infer(Some(param), self.span)
.unwrap_or_else(|| {
debug!(?param, "unelided lifetime in signature");
// This indicates an illegal lifetime in a non-assoc-trait position
ty::Region::new_error_with_message(
tcx,
self.span,
"unelided lifetime in signature",
)
})
.into(),
GenericParamDefKind::Type { has_default, .. } => {
if !infer_args && has_default {
// No type parameter provided, but a default exists.
let args = args.unwrap();
if args.iter().any(|arg| match arg.unpack() {
GenericArgKind::Type(ty) => ty.references_error(),
_ => false,
}) {
// Avoid ICE #86756 when type error recovery goes awry.
return Ty::new_misc_error(tcx).into();
}
tcx.at(self.span).type_of(param.def_id).instantiate(tcx, args).into()
} else if infer_args {
self.astconv.ty_infer(Some(param), self.span).into()
} else {
// We've already errored above about the mismatch.
Ty::new_misc_error(tcx).into()
}
}
GenericParamDefKind::Const { has_default, .. } => {
let ty = tcx
.at(self.span)
.type_of(param.def_id)
.no_bound_vars()
.expect("const parameter types cannot be generic");
if let Err(guar) = ty.error_reported() {
return ty::Const::new_error(tcx, guar, ty).into();
}
// FIXME(effects) see if we should special case effect params here
if !infer_args && has_default {
tcx.const_param_default(param.def_id)
.instantiate(tcx, args.unwrap())
.into()
} else {
if infer_args {
self.astconv.ct_infer(ty, Some(param), self.span).into()
} else {
// We've already errored above about the mismatch.
ty::Const::new_misc_error(tcx, ty).into()
}
}
}
}
}
}
let mut args_ctx = SubstsForAstPathCtxt {
astconv: self,
def_id,
span,
generic_args,
inferred_params: vec![],
infer_args,
};
let args = create_args_for_parent_generic_args(
tcx,
def_id,
parent_args,
self_ty.is_some(),
self_ty,
&arg_count,
&mut args_ctx,
);
if let ty::BoundConstness::ConstIfConst = constness
&& generics.has_self && !tcx.has_attr(def_id, sym::const_trait)
{
tcx.sess.emit_err(crate::errors::ConstBoundForNonConstTrait { span } );
}
(args, arg_count)
}
fn create_assoc_bindings_for_generic_args<'a>(
&self,
generic_args: &'a hir::GenericArgs<'_>,
) -> Vec<ConvertedBinding<'a, 'tcx>> {
// Convert associated-type bindings or constraints into a separate vector.
// Example: Given this:
//
// T: Iterator<Item = u32>
//
// The `T` is passed in as a self-type; the `Item = u32` is
// not a "type parameter" of the `Iterator` trait, but rather
// a restriction on `<T as Iterator>::Item`, so it is passed
// back separately.
let assoc_bindings = generic_args
.bindings
.iter()
.map(|binding| {
let kind = match &binding.kind {
hir::TypeBindingKind::Equality { term } => match term {
hir::Term::Ty(ty) => {
ConvertedBindingKind::Equality(self.ast_ty_to_ty(ty).into())
}
hir::Term::Const(c) => {
let c = Const::from_anon_const(self.tcx(), c.def_id);
ConvertedBindingKind::Equality(c.into())
}
},
hir::TypeBindingKind::Constraint { bounds } => {
ConvertedBindingKind::Constraint(bounds)
}
};
ConvertedBinding {
hir_id: binding.hir_id,
item_name: binding.ident,
kind,
gen_args: binding.gen_args,
span: binding.span,
}
})
.collect();
assoc_bindings
}
pub fn create_args_for_associated_item(
&self,
span: Span,
item_def_id: DefId,
item_segment: &hir::PathSegment<'_>,
parent_args: GenericArgsRef<'tcx>,
) -> GenericArgsRef<'tcx> {
debug!(
"create_args_for_associated_item(span: {:?}, item_def_id: {:?}, item_segment: {:?}",
span, item_def_id, item_segment
);
let (args, _) = self.create_args_for_ast_path(
span,
item_def_id,
parent_args,
item_segment,
item_segment.args(),
item_segment.infer_args,
None,
ty::BoundConstness::NotConst,
);
if let Some(b) = item_segment.args().bindings.first() {
prohibit_assoc_ty_binding(self.tcx(), b.span, Some((item_segment, span)));
}
args
}
/// Instantiates the path for the given trait reference, assuming that it's
/// bound to a valid trait type. Returns the `DefId` of the defining trait.
/// The type _cannot_ be a type other than a trait type.
///
/// If the `projections` argument is `None`, then assoc type bindings like `Foo<T = X>`
/// are disallowed. Otherwise, they are pushed onto the vector given.
pub fn instantiate_mono_trait_ref(
&self,
trait_ref: &hir::TraitRef<'_>,
self_ty: Ty<'tcx>,
) -> ty::TraitRef<'tcx> {
self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1.iter(), |_| {});
self.ast_path_to_mono_trait_ref(
trait_ref.path.span,
trait_ref.trait_def_id().unwrap_or_else(|| FatalError.raise()),
self_ty,
trait_ref.path.segments.last().unwrap(),
true,
ty::BoundConstness::NotConst,
)
}
fn instantiate_poly_trait_ref_inner(
&self,
hir_id: hir::HirId,
span: Span,
binding_span: Option<Span>,
constness: ty::BoundConstness,
polarity: ty::ImplPolarity,
bounds: &mut Bounds<'tcx>,
speculative: bool,
trait_ref_span: Span,
trait_def_id: DefId,
trait_segment: &hir::PathSegment<'_>,
args: &GenericArgs<'_>,
infer_args: bool,
self_ty: Ty<'tcx>,
only_self_bounds: OnlySelfBounds,
) -> GenericArgCountResult {
let (generic_args, arg_count) = self.create_args_for_ast_path(
trait_ref_span,
trait_def_id,
&[],
trait_segment,
args,
infer_args,
Some(self_ty),
constness,
);
let tcx = self.tcx();
let bound_vars = tcx.late_bound_vars(hir_id);
debug!(?bound_vars);
let assoc_bindings = self.create_assoc_bindings_for_generic_args(args);
let poly_trait_ref = ty::Binder::bind_with_vars(
ty::TraitRef::new(tcx, trait_def_id, generic_args),
bound_vars,
);
debug!(?poly_trait_ref, ?assoc_bindings);
bounds.push_trait_bound(tcx, poly_trait_ref, span, polarity);
let mut dup_bindings = FxHashMap::default();
for binding in &assoc_bindings {
// Don't register additional associated type bounds for negative bounds,
// since we should have emitten an error for them earlier, and they will
// not be well-formed!
if polarity == ty::ImplPolarity::Negative {
self.tcx()
.sess
.delay_span_bug(binding.span, "negative trait bounds should not have bindings");
continue;
}
// Specify type to assert that error was already reported in `Err` case.
let _: Result<_, ErrorGuaranteed> = self.add_predicates_for_ast_type_binding(
hir_id,
poly_trait_ref,
binding,
bounds,
speculative,
&mut dup_bindings,
binding_span.unwrap_or(binding.span),
constness,
only_self_bounds,
polarity,
);
// Okay to ignore `Err` because of `ErrorGuaranteed` (see above).
}
arg_count
}
/// Given a trait bound like `Debug`, applies that trait bound the given self-type to construct
/// a full trait reference. The resulting trait reference is returned. This may also generate
/// auxiliary bounds, which are added to `bounds`.
///
/// Example:
///
/// ```ignore (illustrative)
/// poly_trait_ref = Iterator<Item = u32>
/// self_ty = Foo
/// ```
///
/// this would return `Foo: Iterator` and add `<Foo as Iterator>::Item = u32` into `bounds`.
///
/// **A note on binders:** against our usual convention, there is an implied bounder around
/// the `self_ty` and `poly_trait_ref` parameters here. So they may reference bound regions.
/// If for example you had `for<'a> Foo<'a>: Bar<'a>`, then the `self_ty` would be `Foo<'a>`
/// where `'a` is a bound region at depth 0. Similarly, the `poly_trait_ref` would be
/// `Bar<'a>`. The returned poly-trait-ref will have this binder instantiated explicitly,
/// however.
#[instrument(level = "debug", skip(self, span, constness, bounds, speculative))]
pub(crate) fn instantiate_poly_trait_ref(
&self,
trait_ref: &hir::TraitRef<'_>,
span: Span,
constness: ty::BoundConstness,
polarity: ty::ImplPolarity,
self_ty: Ty<'tcx>,
bounds: &mut Bounds<'tcx>,
speculative: bool,
only_self_bounds: OnlySelfBounds,
) -> GenericArgCountResult {
let hir_id = trait_ref.hir_ref_id;
let binding_span = None;
let trait_ref_span = trait_ref.path.span;
let trait_def_id = trait_ref.trait_def_id().unwrap_or_else(|| FatalError.raise());
let trait_segment = trait_ref.path.segments.last().unwrap();
let args = trait_segment.args();
let infer_args = trait_segment.infer_args;
self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1.iter(), |_| {});
self.complain_about_internal_fn_trait(span, trait_def_id, trait_segment, false);
self.instantiate_poly_trait_ref_inner(
hir_id,
span,
binding_span,
constness,
polarity,
bounds,
speculative,
trait_ref_span,
trait_def_id,
trait_segment,
args,
infer_args,
self_ty,
only_self_bounds,
)
}
pub(crate) fn instantiate_lang_item_trait_ref(
&self,
lang_item: hir::LangItem,
span: Span,
hir_id: hir::HirId,
args: &GenericArgs<'_>,
self_ty: Ty<'tcx>,
bounds: &mut Bounds<'tcx>,
only_self_bounds: OnlySelfBounds,
) {
let binding_span = Some(span);
let constness = ty::BoundConstness::NotConst;
let speculative = false;
let trait_ref_span = span;
let trait_def_id = self.tcx().require_lang_item(lang_item, Some(span));
let trait_segment = &hir::PathSegment::invalid();
let infer_args = false;
self.instantiate_poly_trait_ref_inner(
hir_id,
span,
binding_span,
constness,
ty::ImplPolarity::Positive,
bounds,
speculative,
trait_ref_span,
trait_def_id,
trait_segment,
args,
infer_args,
self_ty,
only_self_bounds,
);
}
fn ast_path_to_mono_trait_ref(
&self,
span: Span,
trait_def_id: DefId,
self_ty: Ty<'tcx>,
trait_segment: &hir::PathSegment<'_>,
is_impl: bool,
// FIXME(effects) move all host param things in astconv to hir lowering
constness: ty::BoundConstness,
) -> ty::TraitRef<'tcx> {
let (generic_args, _) = self.create_args_for_ast_trait_ref(
span,
trait_def_id,
self_ty,
trait_segment,
is_impl,
constness,
);
if let Some(b) = trait_segment.args().bindings.first() {
prohibit_assoc_ty_binding(self.tcx(), b.span, Some((trait_segment, span)));
}
ty::TraitRef::new(self.tcx(), trait_def_id, generic_args)
}
#[instrument(level = "debug", skip(self, span))]
fn create_args_for_ast_trait_ref<'a>(
&self,
span: Span,
trait_def_id: DefId,
self_ty: Ty<'tcx>,
trait_segment: &'a hir::PathSegment<'a>,
is_impl: bool,
constness: ty::BoundConstness,
) -> (GenericArgsRef<'tcx>, GenericArgCountResult) {
self.complain_about_internal_fn_trait(span, trait_def_id, trait_segment, is_impl);
self.create_args_for_ast_path(
span,
trait_def_id,
&[],
trait_segment,
trait_segment.args(),
trait_segment.infer_args,
Some(self_ty),
constness,
)
}
fn trait_defines_associated_item_named(
&self,
trait_def_id: DefId,
assoc_kind: ty::AssocKind,
assoc_name: Ident,
) -> bool {
self.tcx()
.associated_items(trait_def_id)
.find_by_name_and_kind(self.tcx(), assoc_name, assoc_kind, trait_def_id)
.is_some()
}
fn ast_path_to_ty(
&self,
span: Span,
did: DefId,
item_segment: &hir::PathSegment<'_>,
) -> Ty<'tcx> {
let tcx = self.tcx();
let args = self.ast_path_args_for_ty(span, did, item_segment);
if let DefKind::TyAlias = tcx.def_kind(did)
&& tcx.type_alias_is_lazy(did)
{
// Type aliases defined in crates that have the
// feature `lazy_type_alias` enabled get encoded as a type alias that normalization will
// then actually instantiate the where bounds of.
let alias_ty = tcx.mk_alias_ty(did, args);
Ty::new_alias(tcx, ty::Weak, alias_ty)
} else {
tcx.at(span).type_of(did).instantiate(tcx, args)
}
}
fn report_ambiguous_associated_type(
&self,
span: Span,
types: &[String],
traits: &[String],
name: Symbol,
) -> ErrorGuaranteed {
let mut err = struct_span_err!(self.tcx().sess, span, E0223, "ambiguous associated type");
if self
.tcx()
.resolutions(())
.confused_type_with_std_module
.keys()
.any(|full_span| full_span.contains(span))
{
err.span_suggestion_verbose(
span.shrink_to_lo(),
"you are looking for the module in `std`, not the primitive type",
"std::",
Applicability::MachineApplicable,
);
} else {
match (types, traits) {
([], []) => {
err.span_suggestion_verbose(
span,
format!(
"if there were a type named `Type` that implements a trait named \
`Trait` with associated type `{name}`, you could use the \
fully-qualified path",
),
format!("<Type as Trait>::{name}"),
Applicability::HasPlaceholders,
);
}
([], [trait_str]) => {
err.span_suggestion_verbose(
span,
format!(
"if there were a type named `Example` that implemented `{trait_str}`, \
you could use the fully-qualified path",
),
format!("<Example as {trait_str}>::{name}"),
Applicability::HasPlaceholders,
);
}
([], traits) => {
err.span_suggestions(
span,
format!(
"if there were a type named `Example` that implemented one of the \
traits with associated type `{name}`, you could use the \
fully-qualified path",
),
traits
.iter()
.map(|trait_str| format!("<Example as {trait_str}>::{name}"))
.collect::<Vec<_>>(),
Applicability::HasPlaceholders,
);
}
([type_str], []) => {
err.span_suggestion_verbose(
span,
format!(
"if there were a trait named `Example` with associated type `{name}` \
implemented for `{type_str}`, you could use the fully-qualified path",
),
format!("<{type_str} as Example>::{name}"),
Applicability::HasPlaceholders,
);
}
(types, []) => {
err.span_suggestions(
span,
format!(
"if there were a trait named `Example` with associated type `{name}` \
implemented for one of the types, you could use the fully-qualified \
path",
),
types
.into_iter()
.map(|type_str| format!("<{type_str} as Example>::{name}")),
Applicability::HasPlaceholders,
);
}
(types, traits) => {
let mut suggestions = vec![];
for type_str in types {
for trait_str in traits {
suggestions.push(format!("<{type_str} as {trait_str}>::{name}"));
}
}
err.span_suggestions(
span,
"use the fully-qualified path",
suggestions,
Applicability::MachineApplicable,
);
}
}
}
err.emit()
}
// Search for a bound on a type parameter which includes the associated item
// given by `assoc_name`. `ty_param_def_id` is the `DefId` of the type parameter
// This function will fail if there are no suitable bounds or there is
// any ambiguity.
fn find_bound_for_assoc_item(
&self,
ty_param_def_id: LocalDefId,
assoc_name: Ident,
span: Span,
) -> Result<ty::PolyTraitRef<'tcx>, ErrorGuaranteed> {
let tcx = self.tcx();
debug!(
"find_bound_for_assoc_item(ty_param_def_id={:?}, assoc_name={:?}, span={:?})",
ty_param_def_id, assoc_name, span,
);
let predicates =
&self.get_type_parameter_bounds(span, ty_param_def_id, assoc_name).predicates;
debug!("find_bound_for_assoc_item: predicates={:#?}", predicates);
let param_name = tcx.hir().ty_param_name(ty_param_def_id);
self.one_bound_for_assoc_type(
|| {
traits::transitive_bounds_that_define_assoc_item(
tcx,
predicates
.iter()
.filter_map(|(p, _)| Some(p.as_trait_clause()?.map_bound(|t| t.trait_ref))),
assoc_name,
)
},
param_name,
assoc_name,
span,
None,
)
}
// Checks that `bounds` contains exactly one element and reports appropriate
// errors otherwise.
#[instrument(level = "debug", skip(self, all_candidates, ty_param_name, is_equality), ret)]
fn one_bound_for_assoc_type<I>(
&self,
all_candidates: impl Fn() -> I,
ty_param_name: impl Display,
assoc_name: Ident,
span: Span,
is_equality: Option<ty::Term<'tcx>>,
) -> Result<ty::PolyTraitRef<'tcx>, ErrorGuaranteed>
where
I: Iterator<Item = ty::PolyTraitRef<'tcx>>,
{
let mut matching_candidates = all_candidates().filter(|r| {
self.trait_defines_associated_item_named(r.def_id(), ty::AssocKind::Type, assoc_name)
});
let mut const_candidates = all_candidates().filter(|r| {
self.trait_defines_associated_item_named(r.def_id(), ty::AssocKind::Const, assoc_name)
});
let (bound, next_cand) = match (matching_candidates.next(), const_candidates.next()) {
(Some(bound), _) => (bound, matching_candidates.next()),
(None, Some(bound)) => (bound, const_candidates.next()),
(None, None) => {
let reported = self.complain_about_assoc_type_not_found(
all_candidates,
&ty_param_name.to_string(),
assoc_name,
span,
);
return Err(reported);
}
};
debug!(?bound);
if let Some(bound2) = next_cand {
debug!(?bound2);
let bounds = IntoIterator::into_iter([bound, bound2]).chain(matching_candidates);
let mut err = if is_equality.is_some() {
// More specific Error Index entry.
struct_span_err!(
self.tcx().sess,
span,
E0222,
"ambiguous associated type `{}` in bounds of `{}`",
assoc_name,
ty_param_name
)
} else {
struct_span_err!(
self.tcx().sess,
span,
E0221,
"ambiguous associated type `{}` in bounds of `{}`",
assoc_name,
ty_param_name
)
};
err.span_label(span, format!("ambiguous associated type `{assoc_name}`"));
let mut where_bounds = vec![];
for bound in bounds {
let bound_id = bound.def_id();
let bound_span = self
.tcx()
.associated_items(bound_id)
.find_by_name_and_kind(self.tcx(), assoc_name, ty::AssocKind::Type, bound_id)
.and_then(|item| self.tcx().hir().span_if_local(item.def_id));
if let Some(bound_span) = bound_span {
err.span_label(
bound_span,
format!(
"ambiguous `{}` from `{}`",
assoc_name,
bound.print_only_trait_path(),
),
);
if let Some(constraint) = &is_equality {
where_bounds.push(format!(
" T: {trait}::{assoc} = {constraint}",
trait=bound.print_only_trait_path(),
assoc=assoc_name,
constraint=constraint,
));
} else {
err.span_suggestion_verbose(
span.with_hi(assoc_name.span.lo()),
"use fully qualified syntax to disambiguate",
format!("<{} as {}>::", ty_param_name, bound.print_only_trait_path()),
Applicability::MaybeIncorrect,
);
}
} else {
err.note(format!(
"associated type `{}` could derive from `{}`",
ty_param_name,
bound.print_only_trait_path(),
));
}
}
if !where_bounds.is_empty() {
err.help(format!(
"consider introducing a new type parameter `T` and adding `where` constraints:\
\n where\n T: {},\n{}",
ty_param_name,
where_bounds.join(",\n"),
));
}
let reported = err.emit();
if !where_bounds.is_empty() {
return Err(reported);
}
}
Ok(bound)
}
#[instrument(level = "debug", skip(self, all_candidates, ty_name), ret)]
fn one_bound_for_assoc_method(
&self,
all_candidates: impl Iterator<Item = ty::PolyTraitRef<'tcx>>,
ty_name: impl Display,
assoc_name: Ident,
span: Span,
) -> Result<ty::PolyTraitRef<'tcx>, ErrorGuaranteed> {
let mut matching_candidates = all_candidates.filter(|r| {
self.trait_defines_associated_item_named(r.def_id(), ty::AssocKind::Fn, assoc_name)
});
let candidate = match matching_candidates.next() {
Some(candidate) => candidate,
None => {
return Err(self.tcx().sess.emit_err(
crate::errors::ReturnTypeNotationMissingMethod {
span,
ty_name: ty_name.to_string(),
assoc_name: assoc_name.name,
},
));
}
};
if let Some(conflicting_candidate) = matching_candidates.next() {
return Err(self.tcx().sess.emit_err(
crate::errors::ReturnTypeNotationConflictingBound {
span,
ty_name: ty_name.to_string(),
assoc_name: assoc_name.name,
first_bound: candidate.print_only_trait_path(),
second_bound: conflicting_candidate.print_only_trait_path(),
},
));
}
Ok(candidate)
}
// Create a type from a path to an associated type or to an enum variant.
// For a path `A::B::C::D`, `qself_ty` and `qself_def` are the type and def for `A::B::C`
// and item_segment is the path segment for `D`. We return a type and a def for
// the whole path.
// Will fail except for `T::A` and `Self::A`; i.e., if `qself_ty`/`qself_def` are not a type
// parameter or `Self`.
// NOTE: When this function starts resolving `Trait::AssocTy` successfully
// it should also start reporting the `BARE_TRAIT_OBJECTS` lint.
#[instrument(level = "debug", skip(self, hir_ref_id, span, qself, assoc_segment), fields(assoc_ident=?assoc_segment.ident), ret)]
pub fn associated_path_to_ty(
&self,
hir_ref_id: hir::HirId,
span: Span,
qself_ty: Ty<'tcx>,
qself: &hir::Ty<'_>,
assoc_segment: &hir::PathSegment<'_>,
permit_variants: bool,
) -> Result<(Ty<'tcx>, DefKind, DefId), ErrorGuaranteed> {
let tcx = self.tcx();
let assoc_ident = assoc_segment.ident;
let qself_res = if let hir::TyKind::Path(hir::QPath::Resolved(_, path)) = &qself.kind {
path.res
} else {
Res::Err
};
// Check if we have an enum variant or an inherent associated type.
let mut variant_resolution = None;
if let Some(adt_def) = self.probe_adt(span, qself_ty) {
if adt_def.is_enum() {
let variant_def = adt_def
.variants()
.iter()
.find(|vd| tcx.hygienic_eq(assoc_ident, vd.ident(tcx), adt_def.did()));
if let Some(variant_def) = variant_def {
if permit_variants {
tcx.check_stability(variant_def.def_id, Some(hir_ref_id), span, None);
self.prohibit_generics(slice::from_ref(assoc_segment).iter(), |err| {
err.note("enum variants can't have type parameters");
let type_name = tcx.item_name(adt_def.did());
let msg = format!(
"you might have meant to specify type parameters on enum \
`{type_name}`"
);
let Some(args) = assoc_segment.args else {
return;
};
// Get the span of the generics args *including* the leading `::`.
let args_span =
assoc_segment.ident.span.shrink_to_hi().to(args.span_ext);
if tcx.generics_of(adt_def.did()).count() == 0 {
// FIXME(estebank): we could also verify that the arguments being
// work for the `enum`, instead of just looking if it takes *any*.
err.span_suggestion_verbose(
args_span,
format!("{type_name} doesn't have generic parameters"),
"",
Applicability::MachineApplicable,
);
return;
}
let Ok(snippet) = tcx.sess.source_map().span_to_snippet(args_span)
else {
err.note(msg);
return;
};
let (qself_sugg_span, is_self) =
if let hir::TyKind::Path(hir::QPath::Resolved(_, path)) =
&qself.kind
{
// If the path segment already has type params, we want to overwrite
// them.
match &path.segments {
// `segment` is the previous to last element on the path,
// which would normally be the `enum` itself, while the last
// `_` `PathSegment` corresponds to the variant.
[
..,
hir::PathSegment {
ident,
args,
res: Res::Def(DefKind::Enum, _),
..
},
_,
] => (
// We need to include the `::` in `Type::Variant::<Args>`
// to point the span to `::<Args>`, not just `<Args>`.
ident.span.shrink_to_hi().to(args
.map_or(ident.span.shrink_to_hi(), |a| a.span_ext)),
false,
),
[segment] => (
// We need to include the `::` in `Type::Variant::<Args>`
// to point the span to `::<Args>`, not just `<Args>`.
segment.ident.span.shrink_to_hi().to(segment
.args
.map_or(segment.ident.span.shrink_to_hi(), |a| {
a.span_ext
})),
kw::SelfUpper == segment.ident.name,
),
_ => {
err.note(msg);
return;
}
}
} else {
err.note(msg);
return;
};
let suggestion = vec![
if is_self {
// Account for people writing `Self::Variant::<Args>`, where
// `Self` is the enum, and suggest replacing `Self` with the
// appropriate type: `Type::<Args>::Variant`.
(qself.span, format!("{type_name}{snippet}"))
} else {
(qself_sugg_span, snippet)
},
(args_span, String::new()),
];
err.multipart_suggestion_verbose(
msg,
suggestion,
Applicability::MaybeIncorrect,
);
});
return Ok((qself_ty, DefKind::Variant, variant_def.def_id));
} else {
variant_resolution = Some(variant_def.def_id);
}
}
}
if let Some((ty, did)) = self.lookup_inherent_assoc_ty(
assoc_ident,
assoc_segment,
adt_def.did(),
qself_ty,
hir_ref_id,
span,
)? {
return Ok((ty, DefKind::AssocTy, did));
}
}
// Find the type of the associated item, and the trait where the associated
// item is declared.
let bound = match (&qself_ty.kind(), qself_res) {
(_, Res::SelfTyAlias { alias_to: impl_def_id, is_trait_impl: true, .. }) => {
// `Self` in an impl of a trait -- we have a concrete self type and a
// trait reference.
let Some(trait_ref) = tcx.impl_trait_ref(impl_def_id) else {
// A cycle error occurred, most likely.
let guar = tcx.sess.delay_span_bug(span, "expected cycle error");
return Err(guar);
};
self.one_bound_for_assoc_type(
|| {
traits::supertraits(
tcx,
ty::Binder::dummy(trait_ref.instantiate_identity()),
)
},
kw::SelfUpper,
assoc_ident,
span,
None,
)?
}
(
&ty::Param(_),
Res::SelfTyParam { trait_: param_did } | Res::Def(DefKind::TyParam, param_did),
) => self.find_bound_for_assoc_item(param_did.expect_local(), assoc_ident, span)?,
_ => {
let reported = if variant_resolution.is_some() {
// Variant in type position
let msg = format!("expected type, found variant `{assoc_ident}`");
tcx.sess.span_err(span, msg)
} else if qself_ty.is_enum() {
let mut err = struct_span_err!(
tcx.sess,
assoc_ident.span,
E0599,
"no variant named `{}` found for enum `{}`",
assoc_ident,
qself_ty,
);
let adt_def = qself_ty.ty_adt_def().expect("enum is not an ADT");
if let Some(suggested_name) = find_best_match_for_name(
&adt_def
.variants()
.iter()
.map(|variant| variant.name)
.collect::<Vec<Symbol>>(),
assoc_ident.name,
None,
) {
err.span_suggestion(
assoc_ident.span,
"there is a variant with a similar name",
suggested_name,
Applicability::MaybeIncorrect,
);
} else {
err.span_label(
assoc_ident.span,
format!("variant not found in `{qself_ty}`"),
);
}
if let Some(sp) = tcx.hir().span_if_local(adt_def.did()) {
err.span_label(sp, format!("variant `{assoc_ident}` not found here"));
}
err.emit()
} else if let Err(reported) = qself_ty.error_reported() {
reported
} else if let ty::Alias(ty::Opaque, alias_ty) = qself_ty.kind() {
// `<impl Trait as OtherTrait>::Assoc` makes no sense.
struct_span_err!(
tcx.sess,
tcx.def_span(alias_ty.def_id),
E0667,
"`impl Trait` is not allowed in path parameters"
)
.emit() // Already reported in an earlier stage.
} else {
let traits: Vec<_> =
self.probe_traits_that_match_assoc_ty(qself_ty, assoc_ident);
// Don't print `ty::Error` to the user.
self.report_ambiguous_associated_type(
span,
&[qself_ty.to_string()],
&traits,
assoc_ident.name,
)
};
return Err(reported);
}
};
let trait_did = bound.def_id();
let Some(assoc_ty_did) = self.lookup_assoc_ty(assoc_ident, hir_ref_id, span, trait_did)
else {
// Assume that if it's not matched, there must be a const defined with the same name
// but it was used in a type position.
let msg = format!("found associated const `{assoc_ident}` when type was expected");
let guar = tcx.sess.struct_span_err(span, msg).emit();
return Err(guar);
};
let ty = self.projected_ty_from_poly_trait_ref(span, assoc_ty_did, assoc_segment, bound);
if let Some(variant_def_id) = variant_resolution {
tcx.struct_span_lint_hir(
AMBIGUOUS_ASSOCIATED_ITEMS,
hir_ref_id,
span,
"ambiguous associated item",
|lint| {
let mut could_refer_to = |kind: DefKind, def_id, also| {
let note_msg = format!(
"`{}` could{} refer to the {} defined here",
assoc_ident,
also,
tcx.def_kind_descr(kind, def_id)
);
lint.span_note(tcx.def_span(def_id), note_msg);
};
could_refer_to(DefKind::Variant, variant_def_id, "");
could_refer_to(DefKind::AssocTy, assoc_ty_did, " also");
lint.span_suggestion(
span,
"use fully-qualified syntax",
format!("<{} as {}>::{}", qself_ty, tcx.item_name(trait_did), assoc_ident),
Applicability::MachineApplicable,
);
lint
},
);
}
Ok((ty, DefKind::AssocTy, assoc_ty_did))
}
fn lookup_inherent_assoc_ty(
&self,
name: Ident,
segment: &hir::PathSegment<'_>,
adt_did: DefId,
self_ty: Ty<'tcx>,
block: hir::HirId,
span: Span,
) -> Result<Option<(Ty<'tcx>, DefId)>, ErrorGuaranteed> {
let tcx = self.tcx();
// Don't attempt to look up inherent associated types when the feature is not enabled.
// Theoretically it'd be fine to do so since we feature-gate their definition site.
// However, due to current limitations of the implementation (caused by us performing
// selection in AstConv), IATs can lead to cycle errors (#108491, #110106) which mask the
// feature-gate error, needlessly confusing users that use IATs by accident (#113265).
if !tcx.features().inherent_associated_types {
return Ok(None);
}
let candidates: Vec<_> = tcx
.inherent_impls(adt_did)
.iter()
.filter_map(|&impl_| Some((impl_, self.lookup_assoc_ty_unchecked(name, block, impl_)?)))
.collect();
if candidates.is_empty() {
return Ok(None);
}
//
// Select applicable inherent associated type candidates modulo regions.
//
// In contexts that have no inference context, just make a new one.
// We do need a local variable to store it, though.
let infcx_;
let infcx = match self.infcx() {
Some(infcx) => infcx,
None => {
assert!(!self_ty.has_infer());
infcx_ = tcx.infer_ctxt().ignoring_regions().build();
&infcx_
}
};
// FIXME(inherent_associated_types): Acquiring the ParamEnv this early leads to cycle errors
// when inside of an ADT (#108491) or where clause.
let param_env = tcx.param_env(block.owner);
let cause = ObligationCause::misc(span, block.owner.def_id);
let mut fulfillment_errors = Vec::new();
let mut applicable_candidates: Vec<_> = infcx.probe(|_| {
// Regions are not considered during selection.
let self_ty = self_ty
.fold_with(&mut BoundVarEraser { tcx, universe: infcx.create_next_universe() });
struct BoundVarEraser<'tcx> {
tcx: TyCtxt<'tcx>,
universe: ty::UniverseIndex,
}
// FIXME(non_lifetime_binders): Don't assign the same universe to each placeholder.
impl<'tcx> TypeFolder<TyCtxt<'tcx>> for BoundVarEraser<'tcx> {
fn interner(&self) -> TyCtxt<'tcx> {
self.tcx
}
fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
if r.is_late_bound() { self.tcx.lifetimes.re_erased } else { r }
}
fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
match *ty.kind() {
ty::Bound(_, bv) => Ty::new_placeholder(
self.tcx,
ty::PlaceholderType { universe: self.universe, bound: bv },
),
_ => ty.super_fold_with(self),
}
}
fn fold_const(
&mut self,
ct: ty::Const<'tcx>,
) -> <TyCtxt<'tcx> as rustc_type_ir::Interner>::Const {
assert!(!ct.ty().has_escaping_bound_vars());
match ct.kind() {
ty::ConstKind::Bound(_, bv) => ty::Const::new_placeholder(
self.tcx,
ty::PlaceholderConst { universe: self.universe, bound: bv },
ct.ty(),
),
_ => ct.super_fold_with(self),
}
}
}
let InferOk { value: self_ty, obligations } =
infcx.at(&cause, param_env).normalize(self_ty);
candidates
.iter()
.copied()
.filter(|&(impl_, _)| {
infcx.probe(|_| {
let ocx = ObligationCtxt::new(&infcx);
ocx.register_obligations(obligations.clone());
let impl_args = infcx.fresh_args_for_item(span, impl_);
let impl_ty = tcx.type_of(impl_).instantiate(tcx, impl_args);
let impl_ty = ocx.normalize(&cause, param_env, impl_ty);
// Check that the self types can be related.
// FIXME(inherent_associated_types): Should we use `eq` here? Method probing uses
// `sup` for this situtation, too. What for? To constrain inference variables?
if ocx.sup(&ObligationCause::dummy(), param_env, impl_ty, self_ty).is_err()
{
return false;
}
// Check whether the impl imposes obligations we have to worry about.
let impl_bounds = tcx.predicates_of(impl_).instantiate(tcx, impl_args);
let impl_bounds = ocx.normalize(&cause, param_env, impl_bounds);
let impl_obligations = traits::predicates_for_generics(
|_, _| cause.clone(),
param_env,
impl_bounds,
);
ocx.register_obligations(impl_obligations);
let mut errors = ocx.select_where_possible();
if !errors.is_empty() {
fulfillment_errors.append(&mut errors);
return false;
}
true
})
})
.collect()
});
if applicable_candidates.len() > 1 {
return Err(self.complain_about_ambiguous_inherent_assoc_type(
name,
applicable_candidates.into_iter().map(|(_, (candidate, _))| candidate).collect(),
span,
));
}
if let Some((impl_, (assoc_item, def_scope))) = applicable_candidates.pop() {
self.check_assoc_ty(assoc_item, name, def_scope, block, span);
// FIXME(fmease): Currently creating throwaway `parent_args` to please
// `create_args_for_associated_item`. Modify the latter instead (or sth. similar) to
// not require the parent args logic.
let parent_args = ty::GenericArgs::identity_for_item(tcx, impl_);
let args = self.create_args_for_associated_item(span, assoc_item, segment, parent_args);
let args = tcx.mk_args_from_iter(
std::iter::once(ty::GenericArg::from(self_ty))
.chain(args.into_iter().skip(parent_args.len())),
);
let ty = Ty::new_alias(tcx, ty::Inherent, tcx.mk_alias_ty(assoc_item, args));
return Ok(Some((ty, assoc_item)));
}
Err(self.complain_about_inherent_assoc_type_not_found(
name,
self_ty,
candidates,
fulfillment_errors,
span,
))
}
fn lookup_assoc_ty(
&self,
name: Ident,
block: hir::HirId,
span: Span,
scope: DefId,
) -> Option<DefId> {
let (item, def_scope) = self.lookup_assoc_ty_unchecked(name, block, scope)?;
self.check_assoc_ty(item, name, def_scope, block, span);
Some(item)
}
fn lookup_assoc_ty_unchecked(
&self,
name: Ident,
block: hir::HirId,
scope: DefId,
) -> Option<(DefId, DefId)> {
let tcx = self.tcx();
let (ident, def_scope) = tcx.adjust_ident_and_get_scope(name, scope, block);
// We have already adjusted the item name above, so compare with `ident.normalize_to_macros_2_0()` instead
// of calling `find_by_name_and_kind`.
let item = tcx.associated_items(scope).in_definition_order().find(|i| {
i.kind.namespace() == Namespace::TypeNS
&& i.ident(tcx).normalize_to_macros_2_0() == ident
})?;
Some((item.def_id, def_scope))
}
fn check_assoc_ty(
&self,
item: DefId,
name: Ident,
def_scope: DefId,
block: hir::HirId,
span: Span,
) {
let tcx = self.tcx();
let kind = DefKind::AssocTy;
if !tcx.visibility(item).is_accessible_from(def_scope, tcx) {
let kind = tcx.def_kind_descr(kind, item);
let msg = format!("{kind} `{name}` is private");
let def_span = tcx.def_span(item);
tcx.sess
.struct_span_err_with_code(span, msg, rustc_errors::error_code!(E0624))
.span_label(span, format!("private {kind}"))
.span_label(def_span, format!("{kind} defined here"))
.emit();
}
tcx.check_stability(item, Some(block), span, None);
}
fn probe_traits_that_match_assoc_ty(
&self,
qself_ty: Ty<'tcx>,
assoc_ident: Ident,
) -> Vec<String> {
let tcx = self.tcx();
// In contexts that have no inference context, just make a new one.
// We do need a local variable to store it, though.
let infcx_;
let infcx = if let Some(infcx) = self.infcx() {
infcx
} else {
assert!(!qself_ty.has_infer());
infcx_ = tcx.infer_ctxt().build();
&infcx_
};
tcx.all_traits()
.filter(|trait_def_id| {
// Consider only traits with the associated type
tcx.associated_items(*trait_def_id)
.in_definition_order()
.any(|i| {
i.kind.namespace() == Namespace::TypeNS
&& i.ident(tcx).normalize_to_macros_2_0() == assoc_ident
&& matches!(i.kind, ty::AssocKind::Type)
})
// Consider only accessible traits
&& tcx.visibility(*trait_def_id)
.is_accessible_from(self.item_def_id(), tcx)
&& tcx.all_impls(*trait_def_id)
.any(|impl_def_id| {
let trait_ref = tcx.impl_trait_ref(impl_def_id);
trait_ref.is_some_and(|trait_ref| {
let impl_ = trait_ref.instantiate(
tcx,
infcx.fresh_args_for_item(DUMMY_SP, impl_def_id),
);
let value = tcx.fold_regions(qself_ty, |_, _| tcx.lifetimes.re_erased);
// FIXME: Don't bother dealing with non-lifetime binders here...
if value.has_escaping_bound_vars() {
return false;
}
infcx
.can_eq(
ty::ParamEnv::empty(),
impl_.self_ty(),
value,
)
})
&& tcx.impl_polarity(impl_def_id) != ty::ImplPolarity::Negative
})
})
.map(|trait_def_id| tcx.def_path_str(trait_def_id))
.collect()
}
fn qpath_to_ty(
&self,
span: Span,
opt_self_ty: Option<Ty<'tcx>>,
item_def_id: DefId,
trait_segment: &hir::PathSegment<'_>,
item_segment: &hir::PathSegment<'_>,
constness: ty::BoundConstness,
) -> Ty<'tcx> {
let tcx = self.tcx();
let trait_def_id = tcx.parent(item_def_id);
debug!("qpath_to_ty: trait_def_id={:?}", trait_def_id);
let Some(self_ty) = opt_self_ty else {
let path_str = tcx.def_path_str(trait_def_id);
let def_id = self.item_def_id();
debug!("qpath_to_ty: self.item_def_id()={:?}", def_id);
let parent_def_id = def_id
.as_local()
.map(|def_id| tcx.hir().local_def_id_to_hir_id(def_id))
.map(|hir_id| tcx.hir().get_parent_item(hir_id).to_def_id());
debug!("qpath_to_ty: parent_def_id={:?}", parent_def_id);
// If the trait in segment is the same as the trait defining the item,
// use the `<Self as ..>` syntax in the error.
let is_part_of_self_trait_constraints = def_id == trait_def_id;
let is_part_of_fn_in_self_trait = parent_def_id == Some(trait_def_id);
let type_names = if is_part_of_self_trait_constraints || is_part_of_fn_in_self_trait {
vec!["Self".to_string()]
} else {
// Find all the types that have an `impl` for the trait.
tcx.all_impls(trait_def_id)
.filter(|impl_def_id| {
// Consider only accessible traits
tcx.visibility(trait_def_id).is_accessible_from(self.item_def_id(), tcx)
&& tcx.impl_polarity(impl_def_id) != ty::ImplPolarity::Negative
})
.filter_map(|impl_def_id| tcx.impl_trait_ref(impl_def_id))
.map(|impl_| impl_.instantiate_identity().self_ty())
// We don't care about blanket impls.
.filter(|self_ty| !self_ty.has_non_region_param())
.map(|self_ty| tcx.erase_regions(self_ty).to_string())
.collect()
};
// FIXME: also look at `tcx.generics_of(self.item_def_id()).params` any that
// references the trait. Relevant for the first case in
// `src/test/ui/associated-types/associated-types-in-ambiguous-context.rs`
let reported = self.report_ambiguous_associated_type(
span,
&type_names,
&[path_str],
item_segment.ident.name,
);
return Ty::new_error(tcx, reported);
};
debug!("qpath_to_ty: self_type={:?}", self_ty);
let trait_ref = self.ast_path_to_mono_trait_ref(
span,
trait_def_id,
self_ty,
trait_segment,
false,
constness,
);
let item_args =
self.create_args_for_associated_item(span, item_def_id, item_segment, trait_ref.args);
debug!("qpath_to_ty: trait_ref={:?}", trait_ref);
Ty::new_projection(tcx, item_def_id, item_args)
}
pub fn prohibit_generics<'a>(
&self,
segments: impl Iterator<Item = &'a hir::PathSegment<'a>> + Clone,
extend: impl Fn(&mut Diagnostic),
) -> bool {
let args = segments.clone().flat_map(|segment| segment.args().args);
let (lt, ty, ct, inf) =
args.clone().fold((false, false, false, false), |(lt, ty, ct, inf), arg| match arg {
hir::GenericArg::Lifetime(_) => (true, ty, ct, inf),
hir::GenericArg::Type(_) => (lt, true, ct, inf),
hir::GenericArg::Const(_) => (lt, ty, true, inf),
hir::GenericArg::Infer(_) => (lt, ty, ct, true),
});
let mut emitted = false;
if lt || ty || ct || inf {
let types_and_spans: Vec<_> = segments
.clone()
.flat_map(|segment| {
if segment.args().args.is_empty() {
None
} else {
Some((
match segment.res {
Res::PrimTy(ty) => format!("{} `{}`", segment.res.descr(), ty.name()),
Res::Def(_, def_id)
if let Some(name) = self.tcx().opt_item_name(def_id) => {
format!("{} `{name}`", segment.res.descr())
}
Res::Err => "this type".to_string(),
_ => segment.res.descr().to_string(),
},
segment.ident.span,
))
}
})
.collect();
let this_type = match &types_and_spans[..] {
[.., _, (last, _)] => format!(
"{} and {last}",
types_and_spans[..types_and_spans.len() - 1]
.iter()
.map(|(x, _)| x.as_str())
.intersperse(&", ")
.collect::<String>()
),
[(only, _)] => only.to_string(),
[] => "this type".to_string(),
};
let arg_spans: Vec<Span> = args.map(|arg| arg.span()).collect();
let mut kinds = Vec::with_capacity(4);
if lt {
kinds.push("lifetime");
}
if ty {
kinds.push("type");
}
if ct {
kinds.push("const");
}
if inf {
kinds.push("generic");
}
let (kind, s) = match kinds[..] {
[.., _, last] => (
format!(
"{} and {last}",
kinds[..kinds.len() - 1]
.iter()
.map(|&x| x)
.intersperse(", ")
.collect::<String>()
),
"s",
),
[only] => (only.to_string(), ""),
[] => unreachable!(),
};
let last_span = *arg_spans.last().unwrap();
let span: MultiSpan = arg_spans.into();
let mut err = struct_span_err!(
self.tcx().sess,
span,
E0109,
"{kind} arguments are not allowed on {this_type}",
);
err.span_label(last_span, format!("{kind} argument{s} not allowed"));
for (what, span) in types_and_spans {
err.span_label(span, format!("not allowed on {what}"));
}
extend(&mut err);
err.emit();
emitted = true;
}
for segment in segments {
// Only emit the first error to avoid overloading the user with error messages.
if let Some(b) = segment.args().bindings.first() {
prohibit_assoc_ty_binding(self.tcx(), b.span, None);
return true;
}
}
emitted
}
// FIXME(eddyb, varkor) handle type paths here too, not just value ones.
pub fn def_ids_for_value_path_segments(
&self,
segments: &[hir::PathSegment<'_>],
self_ty: Option<Ty<'tcx>>,
kind: DefKind,
def_id: DefId,
span: Span,
) -> Vec<PathSeg> {
// We need to extract the type parameters supplied by the user in
// the path `path`. Due to the current setup, this is a bit of a
// tricky-process; the problem is that resolve only tells us the
// end-point of the path resolution, and not the intermediate steps.
// Luckily, we can (at least for now) deduce the intermediate steps
// just from the end-point.
//
// There are basically five cases to consider:
//
// 1. Reference to a constructor of a struct:
//
// struct Foo<T>(...)
//
// In this case, the parameters are declared in the type space.
//
// 2. Reference to a constructor of an enum variant:
//
// enum E<T> { Foo(...) }
//
// In this case, the parameters are defined in the type space,
// but may be specified either on the type or the variant.
//
// 3. Reference to a fn item or a free constant:
//
// fn foo<T>() { }
//
// In this case, the path will again always have the form
// `a::b::foo::<T>` where only the final segment should have
// type parameters. However, in this case, those parameters are
// declared on a value, and hence are in the `FnSpace`.
//
// 4. Reference to a method or an associated constant:
//
// impl<A> SomeStruct<A> {
// fn foo<B>(...)
// }
//
// Here we can have a path like
// `a::b::SomeStruct::<A>::foo::<B>`, in which case parameters
// may appear in two places. The penultimate segment,
// `SomeStruct::<A>`, contains parameters in TypeSpace, and the
// final segment, `foo::<B>` contains parameters in fn space.
//
// The first step then is to categorize the segments appropriately.
let tcx = self.tcx();
assert!(!segments.is_empty());
let last = segments.len() - 1;
let mut path_segs = vec![];
match kind {
// Case 1. Reference to a struct constructor.
DefKind::Ctor(CtorOf::Struct, ..) => {
// Everything but the final segment should have no
// parameters at all.
let generics = tcx.generics_of(def_id);
// Variant and struct constructors use the
// generics of their parent type definition.
let generics_def_id = generics.parent.unwrap_or(def_id);
path_segs.push(PathSeg(generics_def_id, last));
}
// Case 2. Reference to a variant constructor.
DefKind::Ctor(CtorOf::Variant, ..) | DefKind::Variant => {
let (generics_def_id, index) = if let Some(self_ty) = self_ty {
let adt_def = self.probe_adt(span, self_ty).unwrap();
debug_assert!(adt_def.is_enum());
(adt_def.did(), last)
} else if last >= 1 && segments[last - 1].args.is_some() {
// Everything but the penultimate segment should have no
// parameters at all.
let mut def_id = def_id;
// `DefKind::Ctor` -> `DefKind::Variant`
if let DefKind::Ctor(..) = kind {
def_id = tcx.parent(def_id);
}
// `DefKind::Variant` -> `DefKind::Enum`
let enum_def_id = tcx.parent(def_id);
(enum_def_id, last - 1)
} else {
// FIXME: lint here recommending `Enum::<...>::Variant` form
// instead of `Enum::Variant::<...>` form.
// Everything but the final segment should have no
// parameters at all.
let generics = tcx.generics_of(def_id);
// Variant and struct constructors use the
// generics of their parent type definition.
(generics.parent.unwrap_or(def_id), last)
};
path_segs.push(PathSeg(generics_def_id, index));
}
// Case 3. Reference to a top-level value.
DefKind::Fn | DefKind::Const | DefKind::ConstParam | DefKind::Static(_) => {
path_segs.push(PathSeg(def_id, last));
}
// Case 4. Reference to a method or associated const.
DefKind::AssocFn | DefKind::AssocConst => {
if segments.len() >= 2 {
let generics = tcx.generics_of(def_id);
path_segs.push(PathSeg(generics.parent.unwrap(), last - 1));
}
path_segs.push(PathSeg(def_id, last));
}
kind => bug!("unexpected definition kind {:?} for {:?}", kind, def_id),
}
debug!("path_segs = {:?}", path_segs);
path_segs
}
/// Check a type `Path` and convert it to a `Ty`.
pub fn res_to_ty(
&self,
opt_self_ty: Option<Ty<'tcx>>,
path: &hir::Path<'_>,
hir_id: hir::HirId,
permit_variants: bool,
) -> Ty<'tcx> {
let tcx = self.tcx();
debug!(
"res_to_ty(res={:?}, opt_self_ty={:?}, path_segments={:?})",
path.res, opt_self_ty, path.segments
);
let span = path.span;
match path.res {
Res::Def(DefKind::OpaqueTy, did) => {
// Check for desugared `impl Trait`.
assert!(tcx.is_type_alias_impl_trait(did));
let item_segment = path.segments.split_last().unwrap();
self.prohibit_generics(item_segment.1.iter(), |err| {
err.note("`impl Trait` types can't have type parameters");
});
let args = self.ast_path_args_for_ty(span, did, item_segment.0);
Ty::new_opaque(tcx, did, args)
}
Res::Def(
DefKind::Enum
| DefKind::TyAlias
| DefKind::Struct
| DefKind::Union
| DefKind::ForeignTy,
did,
) => {
assert_eq!(opt_self_ty, None);
self.prohibit_generics(path.segments.split_last().unwrap().1.iter(), |_| {});
self.ast_path_to_ty(span, did, path.segments.last().unwrap())
}
Res::Def(kind @ DefKind::Variant, def_id) if permit_variants => {
// Convert "variant type" as if it were a real type.
// The resulting `Ty` is type of the variant's enum for now.
assert_eq!(opt_self_ty, None);
let path_segs =
self.def_ids_for_value_path_segments(path.segments, None, kind, def_id, span);
let generic_segs: FxHashSet<_> =
path_segs.iter().map(|PathSeg(_, index)| index).collect();
self.prohibit_generics(
path.segments.iter().enumerate().filter_map(|(index, seg)| {
if !generic_segs.contains(&index) { Some(seg) } else { None }
}),
|err| {
err.note("enum variants can't have type parameters");
},
);
let PathSeg(def_id, index) = path_segs.last().unwrap();
self.ast_path_to_ty(span, *def_id, &path.segments[*index])
}
Res::Def(DefKind::TyParam, def_id) => {
assert_eq!(opt_self_ty, None);
self.prohibit_generics(path.segments.iter(), |err| {
if let Some(span) = tcx.def_ident_span(def_id) {
let name = tcx.item_name(def_id);
err.span_note(span, format!("type parameter `{name}` defined here"));
}
});
self.hir_id_to_bound_ty(hir_id)
}
Res::SelfTyParam { .. } => {
// `Self` in trait or type alias.
assert_eq!(opt_self_ty, None);
self.prohibit_generics(path.segments.iter(), |err| {
if let [hir::PathSegment { args: Some(args), ident, .. }] = &path.segments {
err.span_suggestion_verbose(
ident.span.shrink_to_hi().to(args.span_ext),
"the `Self` type doesn't accept type parameters",
"",
Applicability::MaybeIncorrect,
);
}
});
tcx.types.self_param
}
Res::SelfTyAlias { alias_to: def_id, forbid_generic, .. } => {
// `Self` in impl (we know the concrete type).
assert_eq!(opt_self_ty, None);
// Try to evaluate any array length constants.
let ty = tcx.at(span).type_of(def_id).instantiate_identity();
let span_of_impl = tcx.span_of_impl(def_id);
self.prohibit_generics(path.segments.iter(), |err| {
let def_id = match *ty.kind() {
ty::Adt(self_def, _) => self_def.did(),
_ => return,
};
let type_name = tcx.item_name(def_id);
let span_of_ty = tcx.def_ident_span(def_id);
let generics = tcx.generics_of(def_id).count();
let msg = format!("`Self` is of type `{ty}`");
if let (Ok(i_sp), Some(t_sp)) = (span_of_impl, span_of_ty) {
let mut span: MultiSpan = vec![t_sp].into();
span.push_span_label(
i_sp,
format!("`Self` is on type `{type_name}` in this `impl`"),
);
let mut postfix = "";
if generics == 0 {
postfix = ", which doesn't have generic parameters";
}
span.push_span_label(
t_sp,
format!("`Self` corresponds to this type{postfix}"),
);
err.span_note(span, msg);
} else {
err.note(msg);
}
for segment in path.segments {
if let Some(args) = segment.args && segment.ident.name == kw::SelfUpper {
if generics == 0 {
// FIXME(estebank): we could also verify that the arguments being
// work for the `enum`, instead of just looking if it takes *any*.
err.span_suggestion_verbose(
segment.ident.span.shrink_to_hi().to(args.span_ext),
"the `Self` type doesn't accept type parameters",
"",
Applicability::MachineApplicable,
);
return;
} else {
err.span_suggestion_verbose(
segment.ident.span,
format!(
"the `Self` type doesn't accept type parameters, use the \
concrete type's name `{type_name}` instead if you want to \
specify its type parameters"
),
type_name,
Applicability::MaybeIncorrect,
);
}
}
}
});
// HACK(min_const_generics): Forbid generic `Self` types
// here as we can't easily do that during nameres.
//
// We do this before normalization as we otherwise allow
// ```rust
// trait AlwaysApplicable { type Assoc; }
// impl<T: ?Sized> AlwaysApplicable for T { type Assoc = usize; }
//
// trait BindsParam<T> {
// type ArrayTy;
// }
// impl<T> BindsParam<T> for <T as AlwaysApplicable>::Assoc {
// type ArrayTy = [u8; Self::MAX];
// }
// ```
// Note that the normalization happens in the param env of
// the anon const, which is empty. This is why the
// `AlwaysApplicable` impl needs a `T: ?Sized` bound for
// this to compile if we were to normalize here.
if forbid_generic && ty.has_param() {
let mut err = tcx.sess.struct_span_err(
path.span,
"generic `Self` types are currently not permitted in anonymous constants",
);
if let Some(hir::Node::Item(&hir::Item {
kind: hir::ItemKind::Impl(impl_),
..
})) = tcx.hir().get_if_local(def_id)
{
err.span_note(impl_.self_ty.span, "not a concrete type");
}
Ty::new_error(tcx, err.emit())
} else {
ty
}
}
Res::Def(DefKind::AssocTy, def_id) => {
debug_assert!(path.segments.len() >= 2);
self.prohibit_generics(path.segments[..path.segments.len() - 2].iter(), |_| {});
// HACK: until we support `<Type as ~const Trait>`, assume all of them are.
let constness = if tcx.has_attr(tcx.parent(def_id), sym::const_trait) {
ty::BoundConstness::ConstIfConst
} else {
ty::BoundConstness::NotConst
};
self.qpath_to_ty(
span,
opt_self_ty,
def_id,
&path.segments[path.segments.len() - 2],
path.segments.last().unwrap(),
constness,
)
}
Res::PrimTy(prim_ty) => {
assert_eq!(opt_self_ty, None);
self.prohibit_generics(path.segments.iter(), |err| {
let name = prim_ty.name_str();
for segment in path.segments {
if let Some(args) = segment.args {
err.span_suggestion_verbose(
segment.ident.span.shrink_to_hi().to(args.span_ext),
format!("primitive type `{name}` doesn't have generic parameters"),
"",
Applicability::MaybeIncorrect,
);
}
}
});
match prim_ty {
hir::PrimTy::Bool => tcx.types.bool,
hir::PrimTy::Char => tcx.types.char,
hir::PrimTy::Int(it) => Ty::new_int(tcx, ty::int_ty(it)),
hir::PrimTy::Uint(uit) => Ty::new_uint(tcx, ty::uint_ty(uit)),
hir::PrimTy::Float(ft) => Ty::new_float(tcx, ty::float_ty(ft)),
hir::PrimTy::Str => tcx.types.str_,
}
}
Res::Err => {
let e = self
.tcx()
.sess
.delay_span_bug(path.span, "path with `Res::Err` but no error emitted");
self.set_tainted_by_errors(e);
Ty::new_error(self.tcx(), e)
}
_ => span_bug!(span, "unexpected resolution: {:?}", path.res),
}
}
// Converts a hir id corresponding to a type parameter to
// a early-bound `ty::Param` or late-bound `ty::Bound`.
pub(crate) fn hir_id_to_bound_ty(&self, hir_id: hir::HirId) -> Ty<'tcx> {
let tcx = self.tcx();
match tcx.named_bound_var(hir_id) {
Some(rbv::ResolvedArg::LateBound(debruijn, index, def_id)) => {
let name = tcx.item_name(def_id);
let br = ty::BoundTy {
var: ty::BoundVar::from_u32(index),
kind: ty::BoundTyKind::Param(def_id, name),
};
Ty::new_bound(tcx, debruijn, br)
}
Some(rbv::ResolvedArg::EarlyBound(def_id)) => {
let def_id = def_id.expect_local();
let item_def_id = tcx.hir().ty_param_owner(def_id);
let generics = tcx.generics_of(item_def_id);
let index = generics.param_def_id_to_index[&def_id.to_def_id()];
Ty::new_param(tcx, index, tcx.hir().ty_param_name(def_id))
}
Some(rbv::ResolvedArg::Error(guar)) => Ty::new_error(tcx, guar),
arg => bug!("unexpected bound var resolution for {hir_id:?}: {arg:?}"),
}
}
// Converts a hir id corresponding to a const parameter to
// a early-bound `ConstKind::Param` or late-bound `ConstKind::Bound`.
pub(crate) fn hir_id_to_bound_const(
&self,
hir_id: hir::HirId,
param_ty: Ty<'tcx>,
) -> Const<'tcx> {
let tcx = self.tcx();
match tcx.named_bound_var(hir_id) {
Some(rbv::ResolvedArg::EarlyBound(def_id)) => {
// Find the name and index of the const parameter by indexing the generics of
// the parent item and construct a `ParamConst`.
let item_def_id = tcx.parent(def_id);
let generics = tcx.generics_of(item_def_id);
let index = generics.param_def_id_to_index[&def_id];
let name = tcx.item_name(def_id);
ty::Const::new_param(tcx, ty::ParamConst::new(index, name), param_ty)
}
Some(rbv::ResolvedArg::LateBound(debruijn, index, _)) => {
ty::Const::new_bound(tcx, debruijn, ty::BoundVar::from_u32(index), param_ty)
}
Some(rbv::ResolvedArg::Error(guar)) => ty::Const::new_error(tcx, guar, param_ty),
arg => bug!("unexpected bound var resolution for {:?}: {arg:?}", hir_id),
}
}
/// Parses the programmer's textual representation of a type into our
/// internal notion of a type.
pub fn ast_ty_to_ty(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> {
self.ast_ty_to_ty_inner(ast_ty, false, false)
}
/// Parses the programmer's textual representation of a type into our
/// internal notion of a type. This is meant to be used within a path.
pub fn ast_ty_to_ty_in_path(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> {
self.ast_ty_to_ty_inner(ast_ty, false, true)
}
/// Turns a `hir::Ty` into a `Ty`. For diagnostics' purposes we keep track of whether trait
/// objects are borrowed like `&dyn Trait` to avoid emitting redundant errors.
#[instrument(level = "debug", skip(self), ret)]
fn ast_ty_to_ty_inner(&self, ast_ty: &hir::Ty<'_>, borrowed: bool, in_path: bool) -> Ty<'tcx> {
let tcx = self.tcx();
let result_ty = match &ast_ty.kind {
hir::TyKind::Slice(ty) => Ty::new_slice(tcx, self.ast_ty_to_ty(ty)),
hir::TyKind::Ptr(mt) => {
Ty::new_ptr(tcx, ty::TypeAndMut { ty: self.ast_ty_to_ty(mt.ty), mutbl: mt.mutbl })
}
hir::TyKind::Ref(region, mt) => {
let r = self.ast_region_to_region(region, None);
debug!(?r);
let t = self.ast_ty_to_ty_inner(mt.ty, true, false);
Ty::new_ref(tcx, r, ty::TypeAndMut { ty: t, mutbl: mt.mutbl })
}
hir::TyKind::Never => tcx.types.never,
hir::TyKind::Tup(fields) => {
Ty::new_tup_from_iter(tcx, fields.iter().map(|t| self.ast_ty_to_ty(t)))
}
hir::TyKind::BareFn(bf) => {
require_c_abi_if_c_variadic(tcx, bf.decl, bf.abi, ast_ty.span);
Ty::new_fn_ptr(
tcx,
self.ty_of_fn(ast_ty.hir_id, bf.unsafety, bf.abi, bf.decl, None, Some(ast_ty)),
)
}
hir::TyKind::TraitObject(bounds, lifetime, repr) => {
self.maybe_lint_bare_trait(ast_ty, in_path);
let repr = match repr {
TraitObjectSyntax::Dyn | TraitObjectSyntax::None => ty::Dyn,
TraitObjectSyntax::DynStar => ty::DynStar,
};
self.conv_object_ty_poly_trait_ref(
ast_ty.span,
ast_ty.hir_id,
bounds,
lifetime,
borrowed,
repr,
)
}
hir::TyKind::Path(hir::QPath::Resolved(maybe_qself, path)) => {
debug!(?maybe_qself, ?path);
let opt_self_ty = maybe_qself.as_ref().map(|qself| self.ast_ty_to_ty(qself));
self.res_to_ty(opt_self_ty, path, ast_ty.hir_id, false)
}
&hir::TyKind::OpaqueDef(item_id, lifetimes, in_trait) => {
let opaque_ty = tcx.hir().item(item_id);
match opaque_ty.kind {
hir::ItemKind::OpaqueTy(&hir::OpaqueTy { origin, .. }) => {
let local_def_id = item_id.owner_id.def_id;
// If this is an RPITIT and we are using the new RPITIT lowering scheme, we
// generate the def_id of an associated type for the trait and return as
// type a projection.
let def_id = if in_trait {
tcx.associated_type_for_impl_trait_in_trait(local_def_id).to_def_id()
} else {
local_def_id.to_def_id()
};
self.impl_trait_ty_to_ty(def_id, lifetimes, origin, in_trait)
}
ref i => bug!("`impl Trait` pointed to non-opaque type?? {:#?}", i),
}
}
hir::TyKind::Path(hir::QPath::TypeRelative(qself, segment)) => {
debug!(?qself, ?segment);
let ty = self.ast_ty_to_ty_inner(qself, false, true);
self.associated_path_to_ty(ast_ty.hir_id, ast_ty.span, ty, qself, segment, false)
.map(|(ty, _, _)| ty)
.unwrap_or_else(|guar| Ty::new_error(tcx, guar))
}
&hir::TyKind::Path(hir::QPath::LangItem(lang_item, span, _)) => {
let def_id = tcx.require_lang_item(lang_item, Some(span));
let (args, _) = self.create_args_for_ast_path(
span,
def_id,
&[],
&hir::PathSegment::invalid(),
&GenericArgs::none(),
true,
None,
ty::BoundConstness::NotConst,
);
tcx.at(span).type_of(def_id).instantiate(tcx, args)
}
hir::TyKind::Array(ty, length) => {
let length = match length {
&hir::ArrayLen::Infer(_, span) => self.ct_infer(tcx.types.usize, None, span),
hir::ArrayLen::Body(constant) => {
ty::Const::from_anon_const(tcx, constant.def_id)
}
};
Ty::new_array_with_const_len(tcx, self.ast_ty_to_ty(ty), length)
}
hir::TyKind::Typeof(e) => {
let ty_erased = tcx.type_of(e.def_id).instantiate_identity();
let ty = tcx.fold_regions(ty_erased, |r, _| {
if r.is_erased() { tcx.lifetimes.re_static } else { r }
});
let span = ast_ty.span;
let (ty, opt_sugg) = if let Some(ty) = ty.make_suggestable(tcx, false) {
(ty, Some((span, Applicability::MachineApplicable)))
} else {
(ty, None)
};
tcx.sess.emit_err(TypeofReservedKeywordUsed { span, ty, opt_sugg });
ty
}
hir::TyKind::Infer => {
// Infer also appears as the type of arguments or return
// values in an ExprKind::Closure, or as
// the type of local variables. Both of these cases are
// handled specially and will not descend into this routine.
self.ty_infer(None, ast_ty.span)
}
hir::TyKind::Err(guar) => Ty::new_error(tcx, *guar),
};
self.record_ty(ast_ty.hir_id, result_ty, ast_ty.span);
result_ty
}
#[instrument(level = "debug", skip(self), ret)]
fn impl_trait_ty_to_ty(
&self,
def_id: DefId,
lifetimes: &[hir::GenericArg<'_>],
origin: OpaqueTyOrigin,
in_trait: bool,
) -> Ty<'tcx> {
debug!("impl_trait_ty_to_ty(def_id={:?}, lifetimes={:?})", def_id, lifetimes);
let tcx = self.tcx();
let generics = tcx.generics_of(def_id);
debug!("impl_trait_ty_to_ty: generics={:?}", generics);
let args = ty::GenericArgs::for_item(tcx, def_id, |param, _| {
// We use `generics.count() - lifetimes.len()` here instead of `generics.parent_count`
// since return-position impl trait in trait squashes all of the generics from its source fn
// into its own generics, so the opaque's "own" params isn't always just lifetimes.
if let Some(i) = (param.index as usize).checked_sub(generics.count() - lifetimes.len())
{
// Resolve our own lifetime parameters.
let GenericParamDefKind::Lifetime { .. } = param.kind else { bug!() };
let hir::GenericArg::Lifetime(lifetime) = &lifetimes[i] else { bug!() };
self.ast_region_to_region(lifetime, None).into()
} else {
tcx.mk_param_from_def(param)
}
});
debug!("impl_trait_ty_to_ty: args={:?}", args);
if in_trait {
Ty::new_projection(tcx, def_id, args)
} else {
Ty::new_opaque(tcx, def_id, args)
}
}
pub fn ty_of_arg(&self, ty: &hir::Ty<'_>, expected_ty: Option<Ty<'tcx>>) -> Ty<'tcx> {
match ty.kind {
hir::TyKind::Infer if expected_ty.is_some() => {
self.record_ty(ty.hir_id, expected_ty.unwrap(), ty.span);
expected_ty.unwrap()
}
_ => self.ast_ty_to_ty(ty),
}
}
#[instrument(level = "debug", skip(self, hir_id, unsafety, abi, decl, generics, hir_ty), ret)]
pub fn ty_of_fn(
&self,
hir_id: hir::HirId,
unsafety: hir::Unsafety,
abi: abi::Abi,
decl: &hir::FnDecl<'_>,
generics: Option<&hir::Generics<'_>>,
hir_ty: Option<&hir::Ty<'_>>,
) -> ty::PolyFnSig<'tcx> {
let tcx = self.tcx();
let bound_vars = tcx.late_bound_vars(hir_id);
debug!(?bound_vars);
// We proactively collect all the inferred type params to emit a single error per fn def.
let mut visitor = HirPlaceholderCollector::default();
let mut infer_replacements = vec![];
if let Some(generics) = generics {
walk_generics(&mut visitor, generics);
}
let input_tys: Vec<_> = decl
.inputs
.iter()
.enumerate()
.map(|(i, a)| {
if let hir::TyKind::Infer = a.kind && !self.allow_ty_infer() {
if let Some(suggested_ty) =
self.suggest_trait_fn_ty_for_impl_fn_infer(hir_id, Some(i))
{
infer_replacements.push((a.span, suggested_ty.to_string()));
return suggested_ty;
}
}
// Only visit the type looking for `_` if we didn't fix the type above
visitor.visit_ty(a);
self.ty_of_arg(a, None)
})
.collect();
let output_ty = match decl.output {
hir::FnRetTy::Return(output) => {
if let hir::TyKind::Infer = output.kind
&& !self.allow_ty_infer()
&& let Some(suggested_ty) =
self.suggest_trait_fn_ty_for_impl_fn_infer(hir_id, None)
{
infer_replacements.push((output.span, suggested_ty.to_string()));
suggested_ty
} else {
visitor.visit_ty(output);
self.ast_ty_to_ty(output)
}
}
hir::FnRetTy::DefaultReturn(..) => Ty::new_unit(tcx,),
};
debug!(?output_ty);
let fn_ty = tcx.mk_fn_sig(input_tys, output_ty, decl.c_variadic, unsafety, abi);
let bare_fn_ty = ty::Binder::bind_with_vars(fn_ty, bound_vars);
if !self.allow_ty_infer() && !(visitor.0.is_empty() && infer_replacements.is_empty()) {
// We always collect the spans for placeholder types when evaluating `fn`s, but we
// only want to emit an error complaining about them if infer types (`_`) are not
// allowed. `allow_ty_infer` gates this behavior. We check for the presence of
// `ident_span` to not emit an error twice when we have `fn foo(_: fn() -> _)`.
let mut diag = crate::collect::placeholder_type_error_diag(
tcx,
generics,
visitor.0,
infer_replacements.iter().map(|(s, _)| *s).collect(),
true,
hir_ty,
"function",
);
if !infer_replacements.is_empty() {
diag.multipart_suggestion(
format!(
"try replacing `_` with the type{} in the corresponding trait method signature",
rustc_errors::pluralize!(infer_replacements.len()),
),
infer_replacements,
Applicability::MachineApplicable,
);
}
diag.emit();
}
// Find any late-bound regions declared in return type that do
// not appear in the arguments. These are not well-formed.
//
// Example:
// for<'a> fn() -> &'a str <-- 'a is bad
// for<'a> fn(&'a String) -> &'a str <-- 'a is ok
let inputs = bare_fn_ty.inputs();
let late_bound_in_args =
tcx.collect_constrained_late_bound_regions(&inputs.map_bound(|i| i.to_owned()));
let output = bare_fn_ty.output();
let late_bound_in_ret = tcx.collect_referenced_late_bound_regions(&output);
self.validate_late_bound_regions(late_bound_in_args, late_bound_in_ret, |br_name| {
struct_span_err!(
tcx.sess,
decl.output.span(),
E0581,
"return type references {}, which is not constrained by the fn input types",
br_name
)
});
bare_fn_ty
}
/// Given a fn_hir_id for a impl function, suggest the type that is found on the
/// corresponding function in the trait that the impl implements, if it exists.
/// If arg_idx is Some, then it corresponds to an input type index, otherwise it
/// corresponds to the return type.
fn suggest_trait_fn_ty_for_impl_fn_infer(
&self,
fn_hir_id: hir::HirId,
arg_idx: Option<usize>,
) -> Option<Ty<'tcx>> {
let tcx = self.tcx();
let hir = tcx.hir();
let hir::Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(..), ident, .. }) =
hir.get(fn_hir_id)
else {
return None;
};
let i = hir.get_parent(fn_hir_id).expect_item().expect_impl();
let trait_ref =
self.instantiate_mono_trait_ref(i.of_trait.as_ref()?, self.ast_ty_to_ty(i.self_ty));
let assoc = tcx.associated_items(trait_ref.def_id).find_by_name_and_kind(
tcx,
*ident,
ty::AssocKind::Fn,
trait_ref.def_id,
)?;
let fn_sig = tcx.fn_sig(assoc.def_id).instantiate(
tcx,
trait_ref.args.extend_to(tcx, assoc.def_id, |param, _| tcx.mk_param_from_def(param)),
);
let fn_sig = tcx.liberate_late_bound_regions(fn_hir_id.expect_owner().to_def_id(), fn_sig);
Some(if let Some(arg_idx) = arg_idx {
*fn_sig.inputs().get(arg_idx)?
} else {
fn_sig.output()
})
}
#[instrument(level = "trace", skip(self, generate_err))]
fn validate_late_bound_regions(
&self,
constrained_regions: FxHashSet<ty::BoundRegionKind>,
referenced_regions: FxHashSet<ty::BoundRegionKind>,
generate_err: impl Fn(&str) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>,
) {
for br in referenced_regions.difference(&constrained_regions) {
let br_name = match *br {
ty::BrNamed(_, kw::UnderscoreLifetime) | ty::BrAnon | ty::BrEnv => {
"an anonymous lifetime".to_string()
}
ty::BrNamed(_, name) => format!("lifetime `{name}`"),
};
let mut err = generate_err(&br_name);
if let ty::BrNamed(_, kw::UnderscoreLifetime) | ty::BrAnon = *br {
// The only way for an anonymous lifetime to wind up
// in the return type but **also** be unconstrained is
// if it only appears in "associated types" in the
// input. See #47511 and #62200 for examples. In this case,
// though we can easily give a hint that ought to be
// relevant.
err.note(
"lifetimes appearing in an associated or opaque type are not considered constrained",
);
err.note("consider introducing a named lifetime parameter");
}
err.emit();
}
}
/// Given the bounds on an object, determines what single region bound (if any) we can
/// use to summarize this type. The basic idea is that we will use the bound the user
/// provided, if they provided one, and otherwise search the supertypes of trait bounds
/// for region bounds. It may be that we can derive no bound at all, in which case
/// we return `None`.
fn compute_object_lifetime_bound(
&self,
span: Span,
existential_predicates: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
) -> Option<ty::Region<'tcx>> // if None, use the default
{
let tcx = self.tcx();
debug!("compute_opt_region_bound(existential_predicates={:?})", existential_predicates);
// No explicit region bound specified. Therefore, examine trait
// bounds and see if we can derive region bounds from those.
let derived_region_bounds = object_region_bounds(tcx, existential_predicates);
// If there are no derived region bounds, then report back that we
// can find no region bound. The caller will use the default.
if derived_region_bounds.is_empty() {
return None;
}
// If any of the derived region bounds are 'static, that is always
// the best choice.
if derived_region_bounds.iter().any(|r| r.is_static()) {
return Some(tcx.lifetimes.re_static);
}
// Determine whether there is exactly one unique region in the set
// of derived region bounds. If so, use that. Otherwise, report an
// error.
let r = derived_region_bounds[0];
if derived_region_bounds[1..].iter().any(|r1| r != *r1) {
tcx.sess.emit_err(AmbiguousLifetimeBound { span });
}
Some(r)
}
}