summaryrefslogtreecommitdiffstats
path: root/library/proc_macro/src/lib.rs
blob: 495c1c5ae46c155bb0877a3a22dbc5756f3b2a83 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
//! A support library for macro authors when defining new macros.
//!
//! This library, provided by the standard distribution, provides the types
//! consumed in the interfaces of procedurally defined macro definitions such as
//! function-like macros `#[proc_macro]`, macro attributes `#[proc_macro_attribute]` and
//! custom derive attributes`#[proc_macro_derive]`.
//!
//! See [the book] for more.
//!
//! [the book]: ../book/ch19-06-macros.html#procedural-macros-for-generating-code-from-attributes

#![stable(feature = "proc_macro_lib", since = "1.15.0")]
#![deny(missing_docs)]
#![doc(
    html_playground_url = "https://play.rust-lang.org/",
    issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/",
    test(no_crate_inject, attr(deny(warnings))),
    test(attr(allow(dead_code, deprecated, unused_variables, unused_mut)))
)]
// This library is copied into rust-analyzer to allow loading rustc compiled proc macros.
// Please avoid unstable features where possible to minimize the amount of changes necessary
// to make it compile with rust-analyzer on stable.
#![feature(rustc_allow_const_fn_unstable)]
#![feature(staged_api)]
#![feature(allow_internal_unstable)]
#![feature(decl_macro)]
#![feature(local_key_cell_methods)]
#![feature(maybe_uninit_write_slice)]
#![feature(negative_impls)]
#![feature(new_uninit)]
#![feature(restricted_std)]
#![feature(rustc_attrs)]
#![feature(min_specialization)]
#![feature(strict_provenance)]
#![recursion_limit = "256"]

#[unstable(feature = "proc_macro_internals", issue = "27812")]
#[doc(hidden)]
pub mod bridge;

mod diagnostic;

#[unstable(feature = "proc_macro_diagnostic", issue = "54140")]
pub use diagnostic::{Diagnostic, Level, MultiSpan};

use std::cmp::Ordering;
use std::ops::RangeBounds;
use std::path::PathBuf;
use std::str::FromStr;
use std::{error, fmt, iter};

/// Determines whether proc_macro has been made accessible to the currently
/// running program.
///
/// The proc_macro crate is only intended for use inside the implementation of
/// procedural macros. All the functions in this crate panic if invoked from
/// outside of a procedural macro, such as from a build script or unit test or
/// ordinary Rust binary.
///
/// With consideration for Rust libraries that are designed to support both
/// macro and non-macro use cases, `proc_macro::is_available()` provides a
/// non-panicking way to detect whether the infrastructure required to use the
/// API of proc_macro is presently available. Returns true if invoked from
/// inside of a procedural macro, false if invoked from any other binary.
#[stable(feature = "proc_macro_is_available", since = "1.57.0")]
pub fn is_available() -> bool {
    bridge::client::is_available()
}

/// The main type provided by this crate, representing an abstract stream of
/// tokens, or, more specifically, a sequence of token trees.
/// The type provide interfaces for iterating over those token trees and, conversely,
/// collecting a number of token trees into one stream.
///
/// This is both the input and output of `#[proc_macro]`, `#[proc_macro_attribute]`
/// and `#[proc_macro_derive]` definitions.
#[stable(feature = "proc_macro_lib", since = "1.15.0")]
#[derive(Clone)]
pub struct TokenStream(Option<bridge::client::TokenStream>);

#[stable(feature = "proc_macro_lib", since = "1.15.0")]
impl !Send for TokenStream {}
#[stable(feature = "proc_macro_lib", since = "1.15.0")]
impl !Sync for TokenStream {}

/// Error returned from `TokenStream::from_str`.
#[stable(feature = "proc_macro_lib", since = "1.15.0")]
#[non_exhaustive]
#[derive(Debug)]
pub struct LexError;

#[stable(feature = "proc_macro_lexerror_impls", since = "1.44.0")]
impl fmt::Display for LexError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str("cannot parse string into token stream")
    }
}

#[stable(feature = "proc_macro_lexerror_impls", since = "1.44.0")]
impl error::Error for LexError {}

#[stable(feature = "proc_macro_lib", since = "1.15.0")]
impl !Send for LexError {}
#[stable(feature = "proc_macro_lib", since = "1.15.0")]
impl !Sync for LexError {}

/// Error returned from `TokenStream::expand_expr`.
#[unstable(feature = "proc_macro_expand", issue = "90765")]
#[non_exhaustive]
#[derive(Debug)]
pub struct ExpandError;

#[unstable(feature = "proc_macro_expand", issue = "90765")]
impl fmt::Display for ExpandError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str("macro expansion failed")
    }
}

#[unstable(feature = "proc_macro_expand", issue = "90765")]
impl error::Error for ExpandError {}

#[unstable(feature = "proc_macro_expand", issue = "90765")]
impl !Send for ExpandError {}

#[unstable(feature = "proc_macro_expand", issue = "90765")]
impl !Sync for ExpandError {}

impl TokenStream {
    /// Returns an empty `TokenStream` containing no token trees.
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    pub fn new() -> TokenStream {
        TokenStream(None)
    }

    /// Checks if this `TokenStream` is empty.
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    pub fn is_empty(&self) -> bool {
        self.0.as_ref().map(|h| h.is_empty()).unwrap_or(true)
    }

    /// Parses this `TokenStream` as an expression and attempts to expand any
    /// macros within it. Returns the expanded `TokenStream`.
    ///
    /// Currently only expressions expanding to literals will succeed, although
    /// this may be relaxed in the future.
    ///
    /// NOTE: In error conditions, `expand_expr` may leave macros unexpanded,
    /// report an error, failing compilation, and/or return an `Err(..)`. The
    /// specific behavior for any error condition, and what conditions are
    /// considered errors, is unspecified and may change in the future.
    #[unstable(feature = "proc_macro_expand", issue = "90765")]
    pub fn expand_expr(&self) -> Result<TokenStream, ExpandError> {
        let stream = self.0.as_ref().ok_or(ExpandError)?;
        match bridge::client::TokenStream::expand_expr(stream) {
            Ok(stream) => Ok(TokenStream(Some(stream))),
            Err(_) => Err(ExpandError),
        }
    }
}

/// Attempts to break the string into tokens and parse those tokens into a token stream.
/// May fail for a number of reasons, for example, if the string contains unbalanced delimiters
/// or characters not existing in the language.
/// All tokens in the parsed stream get `Span::call_site()` spans.
///
/// NOTE: some errors may cause panics instead of returning `LexError`. We reserve the right to
/// change these errors into `LexError`s later.
#[stable(feature = "proc_macro_lib", since = "1.15.0")]
impl FromStr for TokenStream {
    type Err = LexError;

    fn from_str(src: &str) -> Result<TokenStream, LexError> {
        Ok(TokenStream(Some(bridge::client::TokenStream::from_str(src))))
    }
}

// N.B., the bridge only provides `to_string`, implement `fmt::Display`
// based on it (the reverse of the usual relationship between the two).
#[stable(feature = "proc_macro_lib", since = "1.15.0")]
impl ToString for TokenStream {
    fn to_string(&self) -> String {
        self.0.as_ref().map(|t| t.to_string()).unwrap_or_default()
    }
}

/// Prints the token stream as a string that is supposed to be losslessly convertible back
/// into the same token stream (modulo spans), except for possibly `TokenTree::Group`s
/// with `Delimiter::None` delimiters and negative numeric literals.
#[stable(feature = "proc_macro_lib", since = "1.15.0")]
impl fmt::Display for TokenStream {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str(&self.to_string())
    }
}

/// Prints token in a form convenient for debugging.
#[stable(feature = "proc_macro_lib", since = "1.15.0")]
impl fmt::Debug for TokenStream {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str("TokenStream ")?;
        f.debug_list().entries(self.clone()).finish()
    }
}

#[stable(feature = "proc_macro_token_stream_default", since = "1.45.0")]
impl Default for TokenStream {
    fn default() -> Self {
        TokenStream::new()
    }
}

#[unstable(feature = "proc_macro_quote", issue = "54722")]
pub use quote::{quote, quote_span};

fn tree_to_bridge_tree(
    tree: TokenTree,
) -> bridge::TokenTree<bridge::client::TokenStream, bridge::client::Span, bridge::client::Symbol> {
    match tree {
        TokenTree::Group(tt) => bridge::TokenTree::Group(tt.0),
        TokenTree::Punct(tt) => bridge::TokenTree::Punct(tt.0),
        TokenTree::Ident(tt) => bridge::TokenTree::Ident(tt.0),
        TokenTree::Literal(tt) => bridge::TokenTree::Literal(tt.0),
    }
}

/// Creates a token stream containing a single token tree.
#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
impl From<TokenTree> for TokenStream {
    fn from(tree: TokenTree) -> TokenStream {
        TokenStream(Some(bridge::client::TokenStream::from_token_tree(tree_to_bridge_tree(tree))))
    }
}

/// Non-generic helper for implementing `FromIterator<TokenTree>` and
/// `Extend<TokenTree>` with less monomorphization in calling crates.
struct ConcatTreesHelper {
    trees: Vec<
        bridge::TokenTree<
            bridge::client::TokenStream,
            bridge::client::Span,
            bridge::client::Symbol,
        >,
    >,
}

impl ConcatTreesHelper {
    fn new(capacity: usize) -> Self {
        ConcatTreesHelper { trees: Vec::with_capacity(capacity) }
    }

    fn push(&mut self, tree: TokenTree) {
        self.trees.push(tree_to_bridge_tree(tree));
    }

    fn build(self) -> TokenStream {
        if self.trees.is_empty() {
            TokenStream(None)
        } else {
            TokenStream(Some(bridge::client::TokenStream::concat_trees(None, self.trees)))
        }
    }

    fn append_to(self, stream: &mut TokenStream) {
        if self.trees.is_empty() {
            return;
        }
        stream.0 = Some(bridge::client::TokenStream::concat_trees(stream.0.take(), self.trees))
    }
}

/// Non-generic helper for implementing `FromIterator<TokenStream>` and
/// `Extend<TokenStream>` with less monomorphization in calling crates.
struct ConcatStreamsHelper {
    streams: Vec<bridge::client::TokenStream>,
}

impl ConcatStreamsHelper {
    fn new(capacity: usize) -> Self {
        ConcatStreamsHelper { streams: Vec::with_capacity(capacity) }
    }

    fn push(&mut self, stream: TokenStream) {
        if let Some(stream) = stream.0 {
            self.streams.push(stream);
        }
    }

    fn build(mut self) -> TokenStream {
        if self.streams.len() <= 1 {
            TokenStream(self.streams.pop())
        } else {
            TokenStream(Some(bridge::client::TokenStream::concat_streams(None, self.streams)))
        }
    }

    fn append_to(mut self, stream: &mut TokenStream) {
        if self.streams.is_empty() {
            return;
        }
        let base = stream.0.take();
        if base.is_none() && self.streams.len() == 1 {
            stream.0 = self.streams.pop();
        } else {
            stream.0 = Some(bridge::client::TokenStream::concat_streams(base, self.streams));
        }
    }
}

/// Collects a number of token trees into a single stream.
#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
impl iter::FromIterator<TokenTree> for TokenStream {
    fn from_iter<I: IntoIterator<Item = TokenTree>>(trees: I) -> Self {
        let iter = trees.into_iter();
        let mut builder = ConcatTreesHelper::new(iter.size_hint().0);
        iter.for_each(|tree| builder.push(tree));
        builder.build()
    }
}

/// A "flattening" operation on token streams, collects token trees
/// from multiple token streams into a single stream.
#[stable(feature = "proc_macro_lib", since = "1.15.0")]
impl iter::FromIterator<TokenStream> for TokenStream {
    fn from_iter<I: IntoIterator<Item = TokenStream>>(streams: I) -> Self {
        let iter = streams.into_iter();
        let mut builder = ConcatStreamsHelper::new(iter.size_hint().0);
        iter.for_each(|stream| builder.push(stream));
        builder.build()
    }
}

#[stable(feature = "token_stream_extend", since = "1.30.0")]
impl Extend<TokenTree> for TokenStream {
    fn extend<I: IntoIterator<Item = TokenTree>>(&mut self, trees: I) {
        let iter = trees.into_iter();
        let mut builder = ConcatTreesHelper::new(iter.size_hint().0);
        iter.for_each(|tree| builder.push(tree));
        builder.append_to(self);
    }
}

#[stable(feature = "token_stream_extend", since = "1.30.0")]
impl Extend<TokenStream> for TokenStream {
    fn extend<I: IntoIterator<Item = TokenStream>>(&mut self, streams: I) {
        let iter = streams.into_iter();
        let mut builder = ConcatStreamsHelper::new(iter.size_hint().0);
        iter.for_each(|stream| builder.push(stream));
        builder.append_to(self);
    }
}

/// Public implementation details for the `TokenStream` type, such as iterators.
#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
pub mod token_stream {
    use crate::{bridge, Group, Ident, Literal, Punct, TokenStream, TokenTree};

    /// An iterator over `TokenStream`'s `TokenTree`s.
    /// The iteration is "shallow", e.g., the iterator doesn't recurse into delimited groups,
    /// and returns whole groups as token trees.
    #[derive(Clone)]
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    pub struct IntoIter(
        std::vec::IntoIter<
            bridge::TokenTree<
                bridge::client::TokenStream,
                bridge::client::Span,
                bridge::client::Symbol,
            >,
        >,
    );

    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    impl Iterator for IntoIter {
        type Item = TokenTree;

        fn next(&mut self) -> Option<TokenTree> {
            self.0.next().map(|tree| match tree {
                bridge::TokenTree::Group(tt) => TokenTree::Group(Group(tt)),
                bridge::TokenTree::Punct(tt) => TokenTree::Punct(Punct(tt)),
                bridge::TokenTree::Ident(tt) => TokenTree::Ident(Ident(tt)),
                bridge::TokenTree::Literal(tt) => TokenTree::Literal(Literal(tt)),
            })
        }

        fn size_hint(&self) -> (usize, Option<usize>) {
            self.0.size_hint()
        }

        fn count(self) -> usize {
            self.0.count()
        }
    }

    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    impl IntoIterator for TokenStream {
        type Item = TokenTree;
        type IntoIter = IntoIter;

        fn into_iter(self) -> IntoIter {
            IntoIter(self.0.map(|v| v.into_trees()).unwrap_or_default().into_iter())
        }
    }
}

/// `quote!(..)` accepts arbitrary tokens and expands into a `TokenStream` describing the input.
/// For example, `quote!(a + b)` will produce an expression, that, when evaluated, constructs
/// the `TokenStream` `[Ident("a"), Punct('+', Alone), Ident("b")]`.
///
/// Unquoting is done with `$`, and works by taking the single next ident as the unquoted term.
/// To quote `$` itself, use `$$`.
#[unstable(feature = "proc_macro_quote", issue = "54722")]
#[allow_internal_unstable(proc_macro_def_site, proc_macro_internals)]
#[rustc_builtin_macro]
pub macro quote($($t:tt)*) {
    /* compiler built-in */
}

#[unstable(feature = "proc_macro_internals", issue = "27812")]
#[doc(hidden)]
mod quote;

/// A region of source code, along with macro expansion information.
#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
#[derive(Copy, Clone)]
pub struct Span(bridge::client::Span);

#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
impl !Send for Span {}
#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
impl !Sync for Span {}

macro_rules! diagnostic_method {
    ($name:ident, $level:expr) => {
        /// Creates a new `Diagnostic` with the given `message` at the span
        /// `self`.
        #[unstable(feature = "proc_macro_diagnostic", issue = "54140")]
        pub fn $name<T: Into<String>>(self, message: T) -> Diagnostic {
            Diagnostic::spanned(self, $level, message)
        }
    };
}

impl Span {
    /// A span that resolves at the macro definition site.
    #[unstable(feature = "proc_macro_def_site", issue = "54724")]
    pub fn def_site() -> Span {
        Span(bridge::client::Span::def_site())
    }

    /// The span of the invocation of the current procedural macro.
    /// Identifiers created with this span will be resolved as if they were written
    /// directly at the macro call location (call-site hygiene) and other code
    /// at the macro call site will be able to refer to them as well.
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    pub fn call_site() -> Span {
        Span(bridge::client::Span::call_site())
    }

    /// A span that represents `macro_rules` hygiene, and sometimes resolves at the macro
    /// definition site (local variables, labels, `$crate`) and sometimes at the macro
    /// call site (everything else).
    /// The span location is taken from the call-site.
    #[stable(feature = "proc_macro_mixed_site", since = "1.45.0")]
    pub fn mixed_site() -> Span {
        Span(bridge::client::Span::mixed_site())
    }

    /// The original source file into which this span points.
    #[unstable(feature = "proc_macro_span", issue = "54725")]
    pub fn source_file(&self) -> SourceFile {
        SourceFile(self.0.source_file())
    }

    /// The `Span` for the tokens in the previous macro expansion from which
    /// `self` was generated from, if any.
    #[unstable(feature = "proc_macro_span", issue = "54725")]
    pub fn parent(&self) -> Option<Span> {
        self.0.parent().map(Span)
    }

    /// The span for the origin source code that `self` was generated from. If
    /// this `Span` wasn't generated from other macro expansions then the return
    /// value is the same as `*self`.
    #[unstable(feature = "proc_macro_span", issue = "54725")]
    pub fn source(&self) -> Span {
        Span(self.0.source())
    }

    /// Gets the starting line/column in the source file for this span.
    #[unstable(feature = "proc_macro_span", issue = "54725")]
    pub fn start(&self) -> LineColumn {
        self.0.start().add_1_to_column()
    }

    /// Gets the ending line/column in the source file for this span.
    #[unstable(feature = "proc_macro_span", issue = "54725")]
    pub fn end(&self) -> LineColumn {
        self.0.end().add_1_to_column()
    }

    /// Creates an empty span pointing to directly before this span.
    #[unstable(feature = "proc_macro_span_shrink", issue = "87552")]
    pub fn before(&self) -> Span {
        Span(self.0.before())
    }

    /// Creates an empty span pointing to directly after this span.
    #[unstable(feature = "proc_macro_span_shrink", issue = "87552")]
    pub fn after(&self) -> Span {
        Span(self.0.after())
    }

    /// Creates a new span encompassing `self` and `other`.
    ///
    /// Returns `None` if `self` and `other` are from different files.
    #[unstable(feature = "proc_macro_span", issue = "54725")]
    pub fn join(&self, other: Span) -> Option<Span> {
        self.0.join(other.0).map(Span)
    }

    /// Creates a new span with the same line/column information as `self` but
    /// that resolves symbols as though it were at `other`.
    #[stable(feature = "proc_macro_span_resolved_at", since = "1.45.0")]
    pub fn resolved_at(&self, other: Span) -> Span {
        Span(self.0.resolved_at(other.0))
    }

    /// Creates a new span with the same name resolution behavior as `self` but
    /// with the line/column information of `other`.
    #[stable(feature = "proc_macro_span_located_at", since = "1.45.0")]
    pub fn located_at(&self, other: Span) -> Span {
        other.resolved_at(*self)
    }

    /// Compares to spans to see if they're equal.
    #[unstable(feature = "proc_macro_span", issue = "54725")]
    pub fn eq(&self, other: &Span) -> bool {
        self.0 == other.0
    }

    /// Returns the source text behind a span. This preserves the original source
    /// code, including spaces and comments. It only returns a result if the span
    /// corresponds to real source code.
    ///
    /// Note: The observable result of a macro should only rely on the tokens and
    /// not on this source text. The result of this function is a best effort to
    /// be used for diagnostics only.
    #[unstable(feature = "proc_macro_span", issue = "54725")]
    pub fn source_text(&self) -> Option<String> {
        self.0.source_text()
    }

    // Used by the implementation of `Span::quote`
    #[doc(hidden)]
    #[unstable(feature = "proc_macro_internals", issue = "27812")]
    pub fn save_span(&self) -> usize {
        self.0.save_span()
    }

    // Used by the implementation of `Span::quote`
    #[doc(hidden)]
    #[unstable(feature = "proc_macro_internals", issue = "27812")]
    pub fn recover_proc_macro_span(id: usize) -> Span {
        Span(bridge::client::Span::recover_proc_macro_span(id))
    }

    diagnostic_method!(error, Level::Error);
    diagnostic_method!(warning, Level::Warning);
    diagnostic_method!(note, Level::Note);
    diagnostic_method!(help, Level::Help);
}

/// Prints a span in a form convenient for debugging.
#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
impl fmt::Debug for Span {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        self.0.fmt(f)
    }
}

/// A line-column pair representing the start or end of a `Span`.
#[unstable(feature = "proc_macro_span", issue = "54725")]
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub struct LineColumn {
    /// The 1-indexed line in the source file on which the span starts or ends (inclusive).
    #[unstable(feature = "proc_macro_span", issue = "54725")]
    pub line: usize,
    /// The 1-indexed column (number of bytes in UTF-8 encoding) in the source
    /// file on which the span starts or ends (inclusive).
    #[unstable(feature = "proc_macro_span", issue = "54725")]
    pub column: usize,
}

impl LineColumn {
    fn add_1_to_column(self) -> Self {
        LineColumn { line: self.line, column: self.column + 1 }
    }
}

#[unstable(feature = "proc_macro_span", issue = "54725")]
impl !Send for LineColumn {}
#[unstable(feature = "proc_macro_span", issue = "54725")]
impl !Sync for LineColumn {}

#[unstable(feature = "proc_macro_span", issue = "54725")]
impl Ord for LineColumn {
    fn cmp(&self, other: &Self) -> Ordering {
        self.line.cmp(&other.line).then(self.column.cmp(&other.column))
    }
}

#[unstable(feature = "proc_macro_span", issue = "54725")]
impl PartialOrd for LineColumn {
    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
        Some(self.cmp(other))
    }
}

/// The source file of a given `Span`.
#[unstable(feature = "proc_macro_span", issue = "54725")]
#[derive(Clone)]
pub struct SourceFile(bridge::client::SourceFile);

impl SourceFile {
    /// Gets the path to this source file.
    ///
    /// ### Note
    /// If the code span associated with this `SourceFile` was generated by an external macro, this
    /// macro, this might not be an actual path on the filesystem. Use [`is_real`] to check.
    ///
    /// Also note that even if `is_real` returns `true`, if `--remap-path-prefix` was passed on
    /// the command line, the path as given might not actually be valid.
    ///
    /// [`is_real`]: Self::is_real
    #[unstable(feature = "proc_macro_span", issue = "54725")]
    pub fn path(&self) -> PathBuf {
        PathBuf::from(self.0.path())
    }

    /// Returns `true` if this source file is a real source file, and not generated by an external
    /// macro's expansion.
    #[unstable(feature = "proc_macro_span", issue = "54725")]
    pub fn is_real(&self) -> bool {
        // This is a hack until intercrate spans are implemented and we can have real source files
        // for spans generated in external macros.
        // https://github.com/rust-lang/rust/pull/43604#issuecomment-333334368
        self.0.is_real()
    }
}

#[unstable(feature = "proc_macro_span", issue = "54725")]
impl fmt::Debug for SourceFile {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("SourceFile")
            .field("path", &self.path())
            .field("is_real", &self.is_real())
            .finish()
    }
}

#[unstable(feature = "proc_macro_span", issue = "54725")]
impl PartialEq for SourceFile {
    fn eq(&self, other: &Self) -> bool {
        self.0.eq(&other.0)
    }
}

#[unstable(feature = "proc_macro_span", issue = "54725")]
impl Eq for SourceFile {}

/// A single token or a delimited sequence of token trees (e.g., `[1, (), ..]`).
#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
#[derive(Clone)]
pub enum TokenTree {
    /// A token stream surrounded by bracket delimiters.
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    Group(#[stable(feature = "proc_macro_lib2", since = "1.29.0")] Group),
    /// An identifier.
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    Ident(#[stable(feature = "proc_macro_lib2", since = "1.29.0")] Ident),
    /// A single punctuation character (`+`, `,`, `$`, etc.).
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    Punct(#[stable(feature = "proc_macro_lib2", since = "1.29.0")] Punct),
    /// A literal character (`'a'`), string (`"hello"`), number (`2.3`), etc.
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    Literal(#[stable(feature = "proc_macro_lib2", since = "1.29.0")] Literal),
}

#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
impl !Send for TokenTree {}
#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
impl !Sync for TokenTree {}

impl TokenTree {
    /// Returns the span of this tree, delegating to the `span` method of
    /// the contained token or a delimited stream.
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    pub fn span(&self) -> Span {
        match *self {
            TokenTree::Group(ref t) => t.span(),
            TokenTree::Ident(ref t) => t.span(),
            TokenTree::Punct(ref t) => t.span(),
            TokenTree::Literal(ref t) => t.span(),
        }
    }

    /// Configures the span for *only this token*.
    ///
    /// Note that if this token is a `Group` then this method will not configure
    /// the span of each of the internal tokens, this will simply delegate to
    /// the `set_span` method of each variant.
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    pub fn set_span(&mut self, span: Span) {
        match *self {
            TokenTree::Group(ref mut t) => t.set_span(span),
            TokenTree::Ident(ref mut t) => t.set_span(span),
            TokenTree::Punct(ref mut t) => t.set_span(span),
            TokenTree::Literal(ref mut t) => t.set_span(span),
        }
    }
}

/// Prints token tree in a form convenient for debugging.
#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
impl fmt::Debug for TokenTree {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        // Each of these has the name in the struct type in the derived debug,
        // so don't bother with an extra layer of indirection
        match *self {
            TokenTree::Group(ref tt) => tt.fmt(f),
            TokenTree::Ident(ref tt) => tt.fmt(f),
            TokenTree::Punct(ref tt) => tt.fmt(f),
            TokenTree::Literal(ref tt) => tt.fmt(f),
        }
    }
}

#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
impl From<Group> for TokenTree {
    fn from(g: Group) -> TokenTree {
        TokenTree::Group(g)
    }
}

#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
impl From<Ident> for TokenTree {
    fn from(g: Ident) -> TokenTree {
        TokenTree::Ident(g)
    }
}

#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
impl From<Punct> for TokenTree {
    fn from(g: Punct) -> TokenTree {
        TokenTree::Punct(g)
    }
}

#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
impl From<Literal> for TokenTree {
    fn from(g: Literal) -> TokenTree {
        TokenTree::Literal(g)
    }
}

// N.B., the bridge only provides `to_string`, implement `fmt::Display`
// based on it (the reverse of the usual relationship between the two).
#[stable(feature = "proc_macro_lib", since = "1.15.0")]
impl ToString for TokenTree {
    fn to_string(&self) -> String {
        match *self {
            TokenTree::Group(ref t) => t.to_string(),
            TokenTree::Ident(ref t) => t.to_string(),
            TokenTree::Punct(ref t) => t.to_string(),
            TokenTree::Literal(ref t) => t.to_string(),
        }
    }
}

/// Prints the token tree as a string that is supposed to be losslessly convertible back
/// into the same token tree (modulo spans), except for possibly `TokenTree::Group`s
/// with `Delimiter::None` delimiters and negative numeric literals.
#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
impl fmt::Display for TokenTree {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str(&self.to_string())
    }
}

/// A delimited token stream.
///
/// A `Group` internally contains a `TokenStream` which is surrounded by `Delimiter`s.
#[derive(Clone)]
#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
pub struct Group(bridge::Group<bridge::client::TokenStream, bridge::client::Span>);

#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
impl !Send for Group {}
#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
impl !Sync for Group {}

/// Describes how a sequence of token trees is delimited.
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
pub enum Delimiter {
    /// `( ... )`
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    Parenthesis,
    /// `{ ... }`
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    Brace,
    /// `[ ... ]`
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    Bracket,
    /// `Ø ... Ø`
    /// An invisible delimiter, that may, for example, appear around tokens coming from a
    /// "macro variable" `$var`. It is important to preserve operator priorities in cases like
    /// `$var * 3` where `$var` is `1 + 2`.
    /// Invisible delimiters might not survive roundtrip of a token stream through a string.
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    None,
}

impl Group {
    /// Creates a new `Group` with the given delimiter and token stream.
    ///
    /// This constructor will set the span for this group to
    /// `Span::call_site()`. To change the span you can use the `set_span`
    /// method below.
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    pub fn new(delimiter: Delimiter, stream: TokenStream) -> Group {
        Group(bridge::Group {
            delimiter,
            stream: stream.0,
            span: bridge::DelimSpan::from_single(Span::call_site().0),
        })
    }

    /// Returns the delimiter of this `Group`
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    pub fn delimiter(&self) -> Delimiter {
        self.0.delimiter
    }

    /// Returns the `TokenStream` of tokens that are delimited in this `Group`.
    ///
    /// Note that the returned token stream does not include the delimiter
    /// returned above.
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    pub fn stream(&self) -> TokenStream {
        TokenStream(self.0.stream.clone())
    }

    /// Returns the span for the delimiters of this token stream, spanning the
    /// entire `Group`.
    ///
    /// ```text
    /// pub fn span(&self) -> Span {
    ///            ^^^^^^^
    /// ```
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    pub fn span(&self) -> Span {
        Span(self.0.span.entire)
    }

    /// Returns the span pointing to the opening delimiter of this group.
    ///
    /// ```text
    /// pub fn span_open(&self) -> Span {
    ///                 ^
    /// ```
    #[stable(feature = "proc_macro_group_span", since = "1.55.0")]
    pub fn span_open(&self) -> Span {
        Span(self.0.span.open)
    }

    /// Returns the span pointing to the closing delimiter of this group.
    ///
    /// ```text
    /// pub fn span_close(&self) -> Span {
    ///                        ^
    /// ```
    #[stable(feature = "proc_macro_group_span", since = "1.55.0")]
    pub fn span_close(&self) -> Span {
        Span(self.0.span.close)
    }

    /// Configures the span for this `Group`'s delimiters, but not its internal
    /// tokens.
    ///
    /// This method will **not** set the span of all the internal tokens spanned
    /// by this group, but rather it will only set the span of the delimiter
    /// tokens at the level of the `Group`.
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    pub fn set_span(&mut self, span: Span) {
        self.0.span = bridge::DelimSpan::from_single(span.0);
    }
}

// N.B., the bridge only provides `to_string`, implement `fmt::Display`
// based on it (the reverse of the usual relationship between the two).
#[stable(feature = "proc_macro_lib", since = "1.15.0")]
impl ToString for Group {
    fn to_string(&self) -> String {
        TokenStream::from(TokenTree::from(self.clone())).to_string()
    }
}

/// Prints the group as a string that should be losslessly convertible back
/// into the same group (modulo spans), except for possibly `TokenTree::Group`s
/// with `Delimiter::None` delimiters.
#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
impl fmt::Display for Group {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str(&self.to_string())
    }
}

#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
impl fmt::Debug for Group {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("Group")
            .field("delimiter", &self.delimiter())
            .field("stream", &self.stream())
            .field("span", &self.span())
            .finish()
    }
}

/// A `Punct` is a single punctuation character such as `+`, `-` or `#`.
///
/// Multi-character operators like `+=` are represented as two instances of `Punct` with different
/// forms of `Spacing` returned.
#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
#[derive(Clone)]
pub struct Punct(bridge::Punct<bridge::client::Span>);

#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
impl !Send for Punct {}
#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
impl !Sync for Punct {}

/// Describes whether a `Punct` is followed immediately by another `Punct` ([`Spacing::Joint`]) or
/// by a different token or whitespace ([`Spacing::Alone`]).
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
pub enum Spacing {
    /// A `Punct` is not immediately followed by another `Punct`.
    /// E.g. `+` is `Alone` in `+ =`, `+ident` and `+()`.
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    Alone,
    /// A `Punct` is immediately followed by another `Punct`.
    /// E.g. `+` is `Joint` in `+=` and `++`.
    ///
    /// Additionally, single quote `'` can join with identifiers to form lifetimes: `'ident`.
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    Joint,
}

impl Punct {
    /// Creates a new `Punct` from the given character and spacing.
    /// The `ch` argument must be a valid punctuation character permitted by the language,
    /// otherwise the function will panic.
    ///
    /// The returned `Punct` will have the default span of `Span::call_site()`
    /// which can be further configured with the `set_span` method below.
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    pub fn new(ch: char, spacing: Spacing) -> Punct {
        const LEGAL_CHARS: &[char] = &[
            '=', '<', '>', '!', '~', '+', '-', '*', '/', '%', '^', '&', '|', '@', '.', ',', ';',
            ':', '#', '$', '?', '\'',
        ];
        if !LEGAL_CHARS.contains(&ch) {
            panic!("unsupported character `{:?}`", ch);
        }
        Punct(bridge::Punct {
            ch: ch as u8,
            joint: spacing == Spacing::Joint,
            span: Span::call_site().0,
        })
    }

    /// Returns the value of this punctuation character as `char`.
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    pub fn as_char(&self) -> char {
        self.0.ch as char
    }

    /// Returns the spacing of this punctuation character, indicating whether it's immediately
    /// followed by another `Punct` in the token stream, so they can potentially be combined into
    /// a multi-character operator (`Joint`), or it's followed by some other token or whitespace
    /// (`Alone`) so the operator has certainly ended.
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    pub fn spacing(&self) -> Spacing {
        if self.0.joint { Spacing::Joint } else { Spacing::Alone }
    }

    /// Returns the span for this punctuation character.
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    pub fn span(&self) -> Span {
        Span(self.0.span)
    }

    /// Configure the span for this punctuation character.
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    pub fn set_span(&mut self, span: Span) {
        self.0.span = span.0;
    }
}

#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
impl ToString for Punct {
    fn to_string(&self) -> String {
        self.as_char().to_string()
    }
}

/// Prints the punctuation character as a string that should be losslessly convertible
/// back into the same character.
#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
impl fmt::Display for Punct {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}", self.as_char())
    }
}

#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
impl fmt::Debug for Punct {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("Punct")
            .field("ch", &self.as_char())
            .field("spacing", &self.spacing())
            .field("span", &self.span())
            .finish()
    }
}

#[stable(feature = "proc_macro_punct_eq", since = "1.50.0")]
impl PartialEq<char> for Punct {
    fn eq(&self, rhs: &char) -> bool {
        self.as_char() == *rhs
    }
}

#[stable(feature = "proc_macro_punct_eq_flipped", since = "1.52.0")]
impl PartialEq<Punct> for char {
    fn eq(&self, rhs: &Punct) -> bool {
        *self == rhs.as_char()
    }
}

/// An identifier (`ident`).
#[derive(Clone)]
#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
pub struct Ident(bridge::Ident<bridge::client::Span, bridge::client::Symbol>);

impl Ident {
    /// Creates a new `Ident` with the given `string` as well as the specified
    /// `span`.
    /// The `string` argument must be a valid identifier permitted by the
    /// language (including keywords, e.g. `self` or `fn`). Otherwise, the function will panic.
    ///
    /// Note that `span`, currently in rustc, configures the hygiene information
    /// for this identifier.
    ///
    /// As of this time `Span::call_site()` explicitly opts-in to "call-site" hygiene
    /// meaning that identifiers created with this span will be resolved as if they were written
    /// directly at the location of the macro call, and other code at the macro call site will be
    /// able to refer to them as well.
    ///
    /// Later spans like `Span::def_site()` will allow to opt-in to "definition-site" hygiene
    /// meaning that identifiers created with this span will be resolved at the location of the
    /// macro definition and other code at the macro call site will not be able to refer to them.
    ///
    /// Due to the current importance of hygiene this constructor, unlike other
    /// tokens, requires a `Span` to be specified at construction.
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    pub fn new(string: &str, span: Span) -> Ident {
        Ident(bridge::Ident {
            sym: bridge::client::Symbol::new_ident(string, false),
            is_raw: false,
            span: span.0,
        })
    }

    /// Same as `Ident::new`, but creates a raw identifier (`r#ident`).
    /// The `string` argument be a valid identifier permitted by the language
    /// (including keywords, e.g. `fn`). Keywords which are usable in path segments
    /// (e.g. `self`, `super`) are not supported, and will cause a panic.
    #[stable(feature = "proc_macro_raw_ident", since = "1.47.0")]
    pub fn new_raw(string: &str, span: Span) -> Ident {
        Ident(bridge::Ident {
            sym: bridge::client::Symbol::new_ident(string, true),
            is_raw: true,
            span: span.0,
        })
    }

    /// Returns the span of this `Ident`, encompassing the entire string returned
    /// by [`to_string`](ToString::to_string).
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    pub fn span(&self) -> Span {
        Span(self.0.span)
    }

    /// Configures the span of this `Ident`, possibly changing its hygiene context.
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    pub fn set_span(&mut self, span: Span) {
        self.0.span = span.0;
    }
}

/// Converts the identifier to a string that should be losslessly convertible
/// back into the same identifier.
#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
impl ToString for Ident {
    fn to_string(&self) -> String {
        self.0.sym.with(|sym| if self.0.is_raw { ["r#", sym].concat() } else { sym.to_owned() })
    }
}

/// Prints the identifier as a string that should be losslessly convertible back
/// into the same identifier.
#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
impl fmt::Display for Ident {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        if self.0.is_raw {
            f.write_str("r#")?;
        }
        fmt::Display::fmt(&self.0.sym, f)
    }
}

#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
impl fmt::Debug for Ident {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("Ident")
            .field("ident", &self.to_string())
            .field("span", &self.span())
            .finish()
    }
}

/// A literal string (`"hello"`), byte string (`b"hello"`),
/// character (`'a'`), byte character (`b'a'`), an integer or floating point number
/// with or without a suffix (`1`, `1u8`, `2.3`, `2.3f32`).
/// Boolean literals like `true` and `false` do not belong here, they are `Ident`s.
#[derive(Clone)]
#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
pub struct Literal(bridge::Literal<bridge::client::Span, bridge::client::Symbol>);

macro_rules! suffixed_int_literals {
    ($($name:ident => $kind:ident,)*) => ($(
        /// Creates a new suffixed integer literal with the specified value.
        ///
        /// This function will create an integer like `1u32` where the integer
        /// value specified is the first part of the token and the integral is
        /// also suffixed at the end.
        /// Literals created from negative numbers might not survive round-trips through
        /// `TokenStream` or strings and may be broken into two tokens (`-` and positive literal).
        ///
        /// Literals created through this method have the `Span::call_site()`
        /// span by default, which can be configured with the `set_span` method
        /// below.
        #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
        pub fn $name(n: $kind) -> Literal {
            Literal(bridge::Literal {
                kind: bridge::LitKind::Integer,
                symbol: bridge::client::Symbol::new(&n.to_string()),
                suffix: Some(bridge::client::Symbol::new(stringify!($kind))),
                span: Span::call_site().0,
            })
        }
    )*)
}

macro_rules! unsuffixed_int_literals {
    ($($name:ident => $kind:ident,)*) => ($(
        /// Creates a new unsuffixed integer literal with the specified value.
        ///
        /// This function will create an integer like `1` where the integer
        /// value specified is the first part of the token. No suffix is
        /// specified on this token, meaning that invocations like
        /// `Literal::i8_unsuffixed(1)` are equivalent to
        /// `Literal::u32_unsuffixed(1)`.
        /// Literals created from negative numbers might not survive rountrips through
        /// `TokenStream` or strings and may be broken into two tokens (`-` and positive literal).
        ///
        /// Literals created through this method have the `Span::call_site()`
        /// span by default, which can be configured with the `set_span` method
        /// below.
        #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
        pub fn $name(n: $kind) -> Literal {
            Literal(bridge::Literal {
                kind: bridge::LitKind::Integer,
                symbol: bridge::client::Symbol::new(&n.to_string()),
                suffix: None,
                span: Span::call_site().0,
            })
        }
    )*)
}

impl Literal {
    fn new(kind: bridge::LitKind, value: &str, suffix: Option<&str>) -> Self {
        Literal(bridge::Literal {
            kind,
            symbol: bridge::client::Symbol::new(value),
            suffix: suffix.map(bridge::client::Symbol::new),
            span: Span::call_site().0,
        })
    }

    suffixed_int_literals! {
        u8_suffixed => u8,
        u16_suffixed => u16,
        u32_suffixed => u32,
        u64_suffixed => u64,
        u128_suffixed => u128,
        usize_suffixed => usize,
        i8_suffixed => i8,
        i16_suffixed => i16,
        i32_suffixed => i32,
        i64_suffixed => i64,
        i128_suffixed => i128,
        isize_suffixed => isize,
    }

    unsuffixed_int_literals! {
        u8_unsuffixed => u8,
        u16_unsuffixed => u16,
        u32_unsuffixed => u32,
        u64_unsuffixed => u64,
        u128_unsuffixed => u128,
        usize_unsuffixed => usize,
        i8_unsuffixed => i8,
        i16_unsuffixed => i16,
        i32_unsuffixed => i32,
        i64_unsuffixed => i64,
        i128_unsuffixed => i128,
        isize_unsuffixed => isize,
    }

    /// Creates a new unsuffixed floating-point literal.
    ///
    /// This constructor is similar to those like `Literal::i8_unsuffixed` where
    /// the float's value is emitted directly into the token but no suffix is
    /// used, so it may be inferred to be a `f64` later in the compiler.
    /// Literals created from negative numbers might not survive rountrips through
    /// `TokenStream` or strings and may be broken into two tokens (`-` and positive literal).
    ///
    /// # Panics
    ///
    /// This function requires that the specified float is finite, for
    /// example if it is infinity or NaN this function will panic.
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    pub fn f32_unsuffixed(n: f32) -> Literal {
        if !n.is_finite() {
            panic!("Invalid float literal {n}");
        }
        let mut repr = n.to_string();
        if !repr.contains('.') {
            repr.push_str(".0");
        }
        Literal::new(bridge::LitKind::Float, &repr, None)
    }

    /// Creates a new suffixed floating-point literal.
    ///
    /// This constructor will create a literal like `1.0f32` where the value
    /// specified is the preceding part of the token and `f32` is the suffix of
    /// the token. This token will always be inferred to be an `f32` in the
    /// compiler.
    /// Literals created from negative numbers might not survive rountrips through
    /// `TokenStream` or strings and may be broken into two tokens (`-` and positive literal).
    ///
    /// # Panics
    ///
    /// This function requires that the specified float is finite, for
    /// example if it is infinity or NaN this function will panic.
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    pub fn f32_suffixed(n: f32) -> Literal {
        if !n.is_finite() {
            panic!("Invalid float literal {n}");
        }
        Literal::new(bridge::LitKind::Float, &n.to_string(), Some("f32"))
    }

    /// Creates a new unsuffixed floating-point literal.
    ///
    /// This constructor is similar to those like `Literal::i8_unsuffixed` where
    /// the float's value is emitted directly into the token but no suffix is
    /// used, so it may be inferred to be a `f64` later in the compiler.
    /// Literals created from negative numbers might not survive rountrips through
    /// `TokenStream` or strings and may be broken into two tokens (`-` and positive literal).
    ///
    /// # Panics
    ///
    /// This function requires that the specified float is finite, for
    /// example if it is infinity or NaN this function will panic.
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    pub fn f64_unsuffixed(n: f64) -> Literal {
        if !n.is_finite() {
            panic!("Invalid float literal {n}");
        }
        let mut repr = n.to_string();
        if !repr.contains('.') {
            repr.push_str(".0");
        }
        Literal::new(bridge::LitKind::Float, &repr, None)
    }

    /// Creates a new suffixed floating-point literal.
    ///
    /// This constructor will create a literal like `1.0f64` where the value
    /// specified is the preceding part of the token and `f64` is the suffix of
    /// the token. This token will always be inferred to be an `f64` in the
    /// compiler.
    /// Literals created from negative numbers might not survive rountrips through
    /// `TokenStream` or strings and may be broken into two tokens (`-` and positive literal).
    ///
    /// # Panics
    ///
    /// This function requires that the specified float is finite, for
    /// example if it is infinity or NaN this function will panic.
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    pub fn f64_suffixed(n: f64) -> Literal {
        if !n.is_finite() {
            panic!("Invalid float literal {n}");
        }
        Literal::new(bridge::LitKind::Float, &n.to_string(), Some("f64"))
    }

    /// String literal.
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    pub fn string(string: &str) -> Literal {
        let quoted = format!("{:?}", string);
        assert!(quoted.starts_with('"') && quoted.ends_with('"'));
        let symbol = &quoted[1..quoted.len() - 1];
        Literal::new(bridge::LitKind::Str, symbol, None)
    }

    /// Character literal.
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    pub fn character(ch: char) -> Literal {
        let quoted = format!("{:?}", ch);
        assert!(quoted.starts_with('\'') && quoted.ends_with('\''));
        let symbol = &quoted[1..quoted.len() - 1];
        Literal::new(bridge::LitKind::Char, symbol, None)
    }

    /// Byte string literal.
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    pub fn byte_string(bytes: &[u8]) -> Literal {
        let string = bytes.escape_ascii().to_string();
        Literal::new(bridge::LitKind::ByteStr, &string, None)
    }

    /// Returns the span encompassing this literal.
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    pub fn span(&self) -> Span {
        Span(self.0.span)
    }

    /// Configures the span associated for this literal.
    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
    pub fn set_span(&mut self, span: Span) {
        self.0.span = span.0;
    }

    /// Returns a `Span` that is a subset of `self.span()` containing only the
    /// source bytes in range `range`. Returns `None` if the would-be trimmed
    /// span is outside the bounds of `self`.
    // FIXME(SergioBenitez): check that the byte range starts and ends at a
    // UTF-8 boundary of the source. otherwise, it's likely that a panic will
    // occur elsewhere when the source text is printed.
    // FIXME(SergioBenitez): there is no way for the user to know what
    // `self.span()` actually maps to, so this method can currently only be
    // called blindly. For example, `to_string()` for the character 'c' returns
    // "'\u{63}'"; there is no way for the user to know whether the source text
    // was 'c' or whether it was '\u{63}'.
    #[unstable(feature = "proc_macro_span", issue = "54725")]
    pub fn subspan<R: RangeBounds<usize>>(&self, range: R) -> Option<Span> {
        self.0.span.subspan(range.start_bound().cloned(), range.end_bound().cloned()).map(Span)
    }

    fn with_symbol_and_suffix<R>(&self, f: impl FnOnce(&str, &str) -> R) -> R {
        self.0.symbol.with(|symbol| match self.0.suffix {
            Some(suffix) => suffix.with(|suffix| f(symbol, suffix)),
            None => f(symbol, ""),
        })
    }

    /// Invokes the callback with a `&[&str]` consisting of each part of the
    /// literal's representation. This is done to allow the `ToString` and
    /// `Display` implementations to borrow references to symbol values, and
    /// both be optimized to reduce overhead.
    fn with_stringify_parts<R>(&self, f: impl FnOnce(&[&str]) -> R) -> R {
        /// Returns a string containing exactly `num` '#' characters.
        /// Uses a 256-character source string literal which is always safe to
        /// index with a `u8` index.
        fn get_hashes_str(num: u8) -> &'static str {
            const HASHES: &str = "\
            ################################################################\
            ################################################################\
            ################################################################\
            ################################################################\
            ";
            const _: () = assert!(HASHES.len() == 256);
            &HASHES[..num as usize]
        }

        self.with_symbol_and_suffix(|symbol, suffix| match self.0.kind {
            bridge::LitKind::Byte => f(&["b'", symbol, "'", suffix]),
            bridge::LitKind::Char => f(&["'", symbol, "'", suffix]),
            bridge::LitKind::Str => f(&["\"", symbol, "\"", suffix]),
            bridge::LitKind::StrRaw(n) => {
                let hashes = get_hashes_str(n);
                f(&["r", hashes, "\"", symbol, "\"", hashes, suffix])
            }
            bridge::LitKind::ByteStr => f(&["b\"", symbol, "\"", suffix]),
            bridge::LitKind::ByteStrRaw(n) => {
                let hashes = get_hashes_str(n);
                f(&["br", hashes, "\"", symbol, "\"", hashes, suffix])
            }
            _ => f(&[symbol, suffix]),
        })
    }
}

/// Parse a single literal from its stringified representation.
///
/// In order to parse successfully, the input string must not contain anything
/// but the literal token. Specifically, it must not contain whitespace or
/// comments in addition to the literal.
///
/// The resulting literal token will have a `Span::call_site()` span.
///
/// NOTE: some errors may cause panics instead of returning `LexError`. We
/// reserve the right to change these errors into `LexError`s later.
#[stable(feature = "proc_macro_literal_parse", since = "1.54.0")]
impl FromStr for Literal {
    type Err = LexError;

    fn from_str(src: &str) -> Result<Self, LexError> {
        match bridge::client::FreeFunctions::literal_from_str(src) {
            Ok(literal) => Ok(Literal(literal)),
            Err(()) => Err(LexError),
        }
    }
}

#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
impl ToString for Literal {
    fn to_string(&self) -> String {
        self.with_stringify_parts(|parts| parts.concat())
    }
}

/// Prints the literal as a string that should be losslessly convertible
/// back into the same literal (except for possible rounding for floating point literals).
#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
impl fmt::Display for Literal {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        self.with_stringify_parts(|parts| {
            for part in parts {
                fmt::Display::fmt(part, f)?;
            }
            Ok(())
        })
    }
}

#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
impl fmt::Debug for Literal {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("Literal")
            // format the kind on one line even in {:#?} mode
            .field("kind", &format_args!("{:?}", &self.0.kind))
            .field("symbol", &self.0.symbol)
            // format `Some("...")` on one line even in {:#?} mode
            .field("suffix", &format_args!("{:?}", &self.0.suffix))
            .field("span", &self.0.span)
            .finish()
    }
}

/// Tracked access to environment variables.
#[unstable(feature = "proc_macro_tracked_env", issue = "99515")]
pub mod tracked_env {
    use std::env::{self, VarError};
    use std::ffi::OsStr;

    /// Retrieve an environment variable and add it to build dependency info.
    /// Build system executing the compiler will know that the variable was accessed during
    /// compilation, and will be able to rerun the build when the value of that variable changes.
    /// Besides the dependency tracking this function should be equivalent to `env::var` from the
    /// standard library, except that the argument must be UTF-8.
    #[unstable(feature = "proc_macro_tracked_env", issue = "99515")]
    pub fn var<K: AsRef<OsStr> + AsRef<str>>(key: K) -> Result<String, VarError> {
        let key: &str = key.as_ref();
        let value = env::var(key);
        crate::bridge::client::FreeFunctions::track_env_var(key, value.as_deref().ok());
        value
    }
}

/// Tracked access to additional files.
#[unstable(feature = "track_path", issue = "99515")]
pub mod tracked_path {

    /// Track a file explicitly.
    ///
    /// Commonly used for tracking asset preprocessing.
    #[unstable(feature = "track_path", issue = "99515")]
    pub fn path<P: AsRef<str>>(path: P) {
        let path: &str = path.as_ref();
        crate::bridge::client::FreeFunctions::track_path(path);
    }
}