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
//! [![github]](https://github.com/dtolnay/syn) [![crates-io]](https://crates.io/crates/syn) [![docs-rs]](crate)
//!
//! [github]: https://img.shields.io/badge/github-8da0cb?style=for-the-badge&labelColor=555555&logo=github
//! [crates-io]: https://img.shields.io/badge/crates.io-fc8d62?style=for-the-badge&labelColor=555555&logo=rust
//! [docs-rs]: https://img.shields.io/badge/docs.rs-66c2a5?style=for-the-badge&labelColor=555555&logo=docs.rs
//!
//! <br>
//!
//! Syn is a parsing library for parsing a stream of Rust tokens into a syntax
//! tree of Rust source code.
//!
//! Currently this library is geared toward use in Rust procedural macros, but
//! contains some APIs that may be useful more generally.
//!
//! - **Data structures** — Syn provides a complete syntax tree that can
//!   represent any valid Rust source code. The syntax tree is rooted at
//!   [`syn::File`] which represents a full source file, but there are other
//!   entry points that may be useful to procedural macros including
//!   [`syn::Item`], [`syn::Expr`] and [`syn::Type`].
//!
//! - **Derives** — Of particular interest to derive macros is
//!   [`syn::DeriveInput`] which is any of the three legal input items to a
//!   derive macro. An example below shows using this type in a library that can
//!   derive implementations of a user-defined trait.
//!
//! - **Parsing** — Parsing in Syn is built around [parser functions] with the
//!   signature `fn(ParseStream) -> Result<T>`. Every syntax tree node defined
//!   by Syn is individually parsable and may be used as a building block for
//!   custom syntaxes, or you may dream up your own brand new syntax without
//!   involving any of our syntax tree types.
//!
//! - **Location information** — Every token parsed by Syn is associated with a
//!   `Span` that tracks line and column information back to the source of that
//!   token. These spans allow a procedural macro to display detailed error
//!   messages pointing to all the right places in the user's code. There is an
//!   example of this below.
//!
//! - **Feature flags** — Functionality is aggressively feature gated so your
//!   procedural macros enable only what they need, and do not pay in compile
//!   time for all the rest.
//!
//! [`syn::File`]: File
//! [`syn::Item`]: Item
//! [`syn::Expr`]: Expr
//! [`syn::Type`]: Type
//! [`syn::DeriveInput`]: DeriveInput
//! [parser functions]: mod@parse
//!
//! <br>
//!
//! # Example of a derive macro
//!
//! The canonical derive macro using Syn looks like this. We write an ordinary
//! Rust function tagged with a `proc_macro_derive` attribute and the name of
//! the trait we are deriving. Any time that derive appears in the user's code,
//! the Rust compiler passes their data structure as tokens into our macro. We
//! get to execute arbitrary Rust code to figure out what to do with those
//! tokens, then hand some tokens back to the compiler to compile into the
//! user's crate.
//!
//! [`TokenStream`]: proc_macro::TokenStream
//!
//! ```toml
//! [dependencies]
//! syn = "2.0"
//! quote = "1.0"
//!
//! [lib]
//! proc-macro = true
//! ```
//!
//! ```
//! # extern crate proc_macro;
//! #
//! use proc_macro::TokenStream;
//! use quote::quote;
//! use syn::{parse_macro_input, DeriveInput};
//!
//! # const IGNORE_TOKENS: &str = stringify! {
//! #[proc_macro_derive(MyMacro)]
//! # };
//! pub fn my_macro(input: TokenStream) -> TokenStream {
//!     // Parse the input tokens into a syntax tree
//!     let input = parse_macro_input!(input as DeriveInput);
//!
//!     // Build the output, possibly using quasi-quotation
//!     let expanded = quote! {
//!         // ...
//!     };
//!
//!     // Hand the output tokens back to the compiler
//!     TokenStream::from(expanded)
//! }
//! ```
//!
//! The [`heapsize`] example directory shows a complete working implementation
//! of a derive macro. The example derives a `HeapSize` trait which computes an
//! estimate of the amount of heap memory owned by a value.
//!
//! [`heapsize`]: https://github.com/dtolnay/syn/tree/master/examples/heapsize
//!
//! ```
//! pub trait HeapSize {
//!     /// Total number of bytes of heap memory owned by `self`.
//!     fn heap_size_of_children(&self) -> usize;
//! }
//! ```
//!
//! The derive macro allows users to write `#[derive(HeapSize)]` on data
//! structures in their program.
//!
//! ```
//! # const IGNORE_TOKENS: &str = stringify! {
//! #[derive(HeapSize)]
//! # };
//! struct Demo<'a, T: ?Sized> {
//!     a: Box<T>,
//!     b: u8,
//!     c: &'a str,
//!     d: String,
//! }
//! ```
//!
//! <p><br></p>
//!
//! # Spans and error reporting
//!
//! The token-based procedural macro API provides great control over where the
//! compiler's error messages are displayed in user code. Consider the error the
//! user sees if one of their field types does not implement `HeapSize`.
//!
//! ```
//! # const IGNORE_TOKENS: &str = stringify! {
//! #[derive(HeapSize)]
//! # };
//! struct Broken {
//!     ok: String,
//!     bad: std::thread::Thread,
//! }
//! ```
//!
//! By tracking span information all the way through the expansion of a
//! procedural macro as shown in the `heapsize` example, token-based macros in
//! Syn are able to trigger errors that directly pinpoint the source of the
//! problem.
//!
//! ```text
//! error[E0277]: the trait bound `std::thread::Thread: HeapSize` is not satisfied
//!  --> src/main.rs:7:5
//!   |
//! 7 |     bad: std::thread::Thread,
//!   |     ^^^^^^^^^^^^^^^^^^^^^^^^ the trait `HeapSize` is not implemented for `Thread`
//! ```
//!
//! <br>
//!
//! # Parsing a custom syntax
//!
//! The [`lazy-static`] example directory shows the implementation of a
//! `functionlike!(...)` procedural macro in which the input tokens are parsed
//! using Syn's parsing API.
//!
//! [`lazy-static`]: https://github.com/dtolnay/syn/tree/master/examples/lazy-static
//!
//! The example reimplements the popular `lazy_static` crate from crates.io as a
//! procedural macro.
//!
//! ```
//! # macro_rules! lazy_static {
//! #     ($($tt:tt)*) => {}
//! # }
//! #
//! lazy_static! {
//!     static ref USERNAME: Regex = Regex::new("^[a-z0-9_-]{3,16}$").unwrap();
//! }
//! ```
//!
//! The implementation shows how to trigger custom warnings and error messages
//! on the macro input.
//!
//! ```text
//! warning: come on, pick a more creative name
//!   --> src/main.rs:10:16
//!    |
//! 10 |     static ref FOO: String = "lazy_static".to_owned();
//!    |                ^^^
//! ```
//!
//! <br>
//!
//! # Testing
//!
//! When testing macros, we often care not just that the macro can be used
//! successfully but also that when the macro is provided with invalid input it
//! produces maximally helpful error messages. Consider using the [`trybuild`]
//! crate to write tests for errors that are emitted by your macro or errors
//! detected by the Rust compiler in the expanded code following misuse of the
//! macro. Such tests help avoid regressions from later refactors that
//! mistakenly make an error no longer trigger or be less helpful than it used
//! to be.
//!
//! [`trybuild`]: https://github.com/dtolnay/trybuild
//!
//! <br>
//!
//! # Debugging
//!
//! When developing a procedural macro it can be helpful to look at what the
//! generated code looks like. Use `cargo rustc -- -Zunstable-options
//! --pretty=expanded` or the [`cargo expand`] subcommand.
//!
//! [`cargo expand`]: https://github.com/dtolnay/cargo-expand
//!
//! To show the expanded code for some crate that uses your procedural macro,
//! run `cargo expand` from that crate. To show the expanded code for one of
//! your own test cases, run `cargo expand --test the_test_case` where the last
//! argument is the name of the test file without the `.rs` extension.
//!
//! This write-up by Brandon W Maister discusses debugging in more detail:
//! [Debugging Rust's new Custom Derive system][debugging].
//!
//! [debugging]: https://quodlibetor.github.io/posts/debugging-rusts-new-custom-derive-system/
//!
//! <br>
//!
//! # Optional features
//!
//! Syn puts a lot of functionality behind optional features in order to
//! optimize compile time for the most common use cases. The following features
//! are available.
//!
//! - **`derive`** *(enabled by default)* — Data structures for representing the
//!   possible input to a derive macro, including structs and enums and types.
//! - **`full`** — Data structures for representing the syntax tree of all valid
//!   Rust source code, including items and expressions.
//! - **`parsing`** *(enabled by default)* — Ability to parse input tokens into
//!   a syntax tree node of a chosen type.
//! - **`printing`** *(enabled by default)* — Ability to print a syntax tree
//!   node as tokens of Rust source code.
//! - **`visit`** — Trait for traversing a syntax tree.
//! - **`visit-mut`** — Trait for traversing and mutating in place a syntax
//!   tree.
//! - **`fold`** — Trait for transforming an owned syntax tree.
//! - **`clone-impls`** *(enabled by default)* — Clone impls for all syntax tree
//!   types.
//! - **`extra-traits`** — Debug, Eq, PartialEq, Hash impls for all syntax tree
//!   types.
//! - **`proc-macro`** *(enabled by default)* — Runtime dependency on the
//!   dynamic library libproc_macro from rustc toolchain.

// Syn types in rustdoc of other crates get linked to here.
#![doc(html_root_url = "https://docs.rs/syn/2.0.89")]
#![cfg_attr(docsrs, feature(doc_cfg))]
#![deny(unsafe_op_in_unsafe_fn)]
#![allow(non_camel_case_types)]
#![cfg_attr(not(check_cfg), allow(unexpected_cfgs))]
#![allow(
    clippy::bool_to_int_with_if,
    clippy::cast_lossless,
    clippy::cast_possible_truncation,
    clippy::cast_possible_wrap,
    clippy::cast_ptr_alignment,
    clippy::default_trait_access,
    clippy::derivable_impls,
    clippy::diverging_sub_expression,
    clippy::doc_markdown,
    clippy::enum_glob_use,
    clippy::expl_impl_clone_on_copy,
    clippy::explicit_auto_deref,
    clippy::if_not_else,
    clippy::inherent_to_string,
    clippy::into_iter_without_iter,
    clippy::items_after_statements,
    clippy::large_enum_variant,
    clippy::let_underscore_untyped, // https://github.com/rust-lang/rust-clippy/issues/10410
    clippy::manual_assert,
    clippy::manual_let_else,
    clippy::manual_map,
    clippy::match_like_matches_macro,
    clippy::match_on_vec_items,
    clippy::match_same_arms,
    clippy::match_wildcard_for_single_variants, // clippy bug: https://github.com/rust-lang/rust-clippy/issues/6984
    clippy::missing_errors_doc,
    clippy::missing_panics_doc,
    clippy::module_name_repetitions,
    clippy::must_use_candidate,
    clippy::needless_doctest_main,
    clippy::needless_lifetimes,
    clippy::needless_pass_by_value,
    clippy::needless_update,
    clippy::never_loop,
    clippy::range_plus_one,
    clippy::redundant_else,
    clippy::ref_option,
    clippy::return_self_not_must_use,
    clippy::similar_names,
    clippy::single_match_else,
    clippy::struct_excessive_bools,
    clippy::too_many_arguments,
    clippy::too_many_lines,
    clippy::trivially_copy_pass_by_ref,
    clippy::unconditional_recursion, // https://github.com/rust-lang/rust-clippy/issues/12133
    clippy::uninhabited_references,
    clippy::uninlined_format_args,
    clippy::unnecessary_box_returns,
    clippy::unnecessary_unwrap,
    clippy::used_underscore_binding,
    clippy::wildcard_imports,
)]

extern crate self as syn;

#[cfg(feature = "proc-macro")]
extern crate proc_macro;

#[macro_use]
mod macros;

#[cfg(feature = "parsing")]
#[macro_use]
mod group;

#[macro_use]
pub mod token;

#[cfg(any(feature = "full", feature = "derive"))]
mod attr;
#[cfg(any(feature = "full", feature = "derive"))]
#[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
pub use crate::attr::{AttrStyle, Attribute, Meta, MetaList, MetaNameValue};

mod bigint;

#[cfg(feature = "parsing")]
#[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
pub mod buffer;

#[cfg(any(
    all(feature = "parsing", feature = "full"),
    all(feature = "printing", any(feature = "full", feature = "derive")),
))]
mod classify;

mod custom_keyword;

mod custom_punctuation;

#[cfg(any(feature = "full", feature = "derive"))]
mod data;
#[cfg(any(feature = "full", feature = "derive"))]
#[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
pub use crate::data::{Field, Fields, FieldsNamed, FieldsUnnamed, Variant};

#[cfg(any(feature = "full", feature = "derive"))]
mod derive;
#[cfg(feature = "derive")]
#[cfg_attr(docsrs, doc(cfg(feature = "derive")))]
pub use crate::derive::{Data, DataEnum, DataStruct, DataUnion, DeriveInput};

mod drops;

mod error;
pub use crate::error::{Error, Result};

#[cfg(any(feature = "full", feature = "derive"))]
mod expr;
#[cfg(feature = "full")]
#[cfg_attr(docsrs, doc(cfg(feature = "full")))]
pub use crate::expr::{Arm, Label, PointerMutability, RangeLimits};
#[cfg(any(feature = "full", feature = "derive"))]
#[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
pub use crate::expr::{
    Expr, ExprBinary, ExprCall, ExprCast, ExprField, ExprIndex, ExprLit, ExprMacro, ExprMethodCall,
    ExprParen, ExprPath, ExprReference, ExprStruct, ExprUnary, FieldValue, Index, Member,
};
#[cfg(any(feature = "full", feature = "derive"))]
#[cfg_attr(docsrs, doc(cfg(feature = "full")))]
pub use crate::expr::{
    ExprArray, ExprAssign, ExprAsync, ExprAwait, ExprBlock, ExprBreak, ExprClosure, ExprConst,
    ExprContinue, ExprForLoop, ExprGroup, ExprIf, ExprInfer, ExprLet, ExprLoop, ExprMatch,
    ExprRange, ExprRawAddr, ExprRepeat, ExprReturn, ExprTry, ExprTryBlock, ExprTuple, ExprUnsafe,
    ExprWhile, ExprYield,
};

#[cfg(feature = "parsing")]
#[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
pub mod ext;

#[cfg(feature = "full")]
mod file;
#[cfg(feature = "full")]
#[cfg_attr(docsrs, doc(cfg(feature = "full")))]
pub use crate::file::File;

#[cfg(all(any(feature = "full", feature = "derive"), feature = "printing"))]
mod fixup;

#[cfg(any(feature = "full", feature = "derive"))]
mod generics;
#[cfg(any(feature = "full", feature = "derive"))]
#[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
pub use crate::generics::{
    BoundLifetimes, ConstParam, GenericParam, Generics, LifetimeParam, PredicateLifetime,
    PredicateType, TraitBound, TraitBoundModifier, TypeParam, TypeParamBound, WhereClause,
    WherePredicate,
};
#[cfg(feature = "full")]
#[cfg_attr(docsrs, doc(cfg(feature = "full")))]
pub use crate::generics::{CapturedParam, PreciseCapture};
#[cfg(all(any(feature = "full", feature = "derive"), feature = "printing"))]
#[cfg_attr(
    docsrs,
    doc(cfg(all(any(feature = "full", feature = "derive"), feature = "printing")))
)]
pub use crate::generics::{ImplGenerics, Turbofish, TypeGenerics};

mod ident;
#[doc(inline)]
pub use crate::ident::Ident;

#[cfg(feature = "full")]
mod item;
#[cfg(feature = "full")]
#[cfg_attr(docsrs, doc(cfg(feature = "full")))]
pub use crate::item::{
    FnArg, ForeignItem, ForeignItemFn, ForeignItemMacro, ForeignItemStatic, ForeignItemType,
    ImplItem, ImplItemConst, ImplItemFn, ImplItemMacro, ImplItemType, ImplRestriction, Item,
    ItemConst, ItemEnum, ItemExternCrate, ItemFn, ItemForeignMod, ItemImpl, ItemMacro, ItemMod,
    ItemStatic, ItemStruct, ItemTrait, ItemTraitAlias, ItemType, ItemUnion, ItemUse, Receiver,
    Signature, StaticMutability, TraitItem, TraitItemConst, TraitItemFn, TraitItemMacro,
    TraitItemType, UseGlob, UseGroup, UseName, UsePath, UseRename, UseTree, Variadic,
};

mod lifetime;
#[doc(inline)]
pub use crate::lifetime::Lifetime;

mod lit;
#[doc(hidden)] // https://github.com/dtolnay/syn/issues/1566
pub use crate::lit::StrStyle;
#[doc(inline)]
pub use crate::lit::{
    Lit, LitBool, LitByte, LitByteStr, LitCStr, LitChar, LitFloat, LitInt, LitStr,
};

#[cfg(feature = "parsing")]
mod lookahead;

#[cfg(any(feature = "full", feature = "derive"))]
mod mac;
#[cfg(any(feature = "full", feature = "derive"))]
#[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
pub use crate::mac::{Macro, MacroDelimiter};

#[cfg(all(feature = "parsing", any(feature = "full", feature = "derive")))]
#[cfg_attr(
    docsrs,
    doc(cfg(all(feature = "parsing", any(feature = "full", feature = "derive"))))
)]
pub mod meta;

#[cfg(any(feature = "full", feature = "derive"))]
mod op;
#[cfg(any(feature = "full", feature = "derive"))]
#[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
pub use crate::op::{BinOp, UnOp};

#[cfg(feature = "parsing")]
#[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
pub mod parse;

#[cfg(all(feature = "parsing", feature = "proc-macro"))]
mod parse_macro_input;

#[cfg(all(feature = "parsing", feature = "printing"))]
mod parse_quote;

#[cfg(feature = "full")]
mod pat;
#[cfg(feature = "full")]
#[cfg_attr(docsrs, doc(cfg(feature = "full")))]
pub use crate::pat::{
    FieldPat, Pat, PatConst, PatIdent, PatLit, PatMacro, PatOr, PatParen, PatPath, PatRange,
    PatReference, PatRest, PatSlice, PatStruct, PatTuple, PatTupleStruct, PatType, PatWild,
};

#[cfg(any(feature = "full", feature = "derive"))]
mod path;
#[cfg(any(feature = "full", feature = "derive"))]
#[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
pub use crate::path::{
    AngleBracketedGenericArguments, AssocConst, AssocType, Constraint, GenericArgument,
    ParenthesizedGenericArguments, Path, PathArguments, PathSegment, QSelf,
};

#[cfg(all(
    any(feature = "full", feature = "derive"),
    any(feature = "parsing", feature = "printing")
))]
mod precedence;

#[cfg(all(any(feature = "full", feature = "derive"), feature = "printing"))]
mod print;

pub mod punctuated;

#[cfg(any(feature = "full", feature = "derive"))]
mod restriction;
#[cfg(any(feature = "full", feature = "derive"))]
#[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
pub use crate::restriction::{FieldMutability, VisRestricted, Visibility};

mod sealed;

#[cfg(all(feature = "parsing", feature = "derive", not(feature = "full")))]
mod scan_expr;

mod span;

#[cfg(all(feature = "parsing", feature = "printing"))]
#[cfg_attr(docsrs, doc(cfg(all(feature = "parsing", feature = "printing"))))]
pub mod spanned;

#[cfg(feature = "full")]
mod stmt;
#[cfg(feature = "full")]
#[cfg_attr(docsrs, doc(cfg(feature = "full")))]
pub use crate::stmt::{Block, Local, LocalInit, Stmt, StmtMacro};

mod thread;

#[cfg(all(any(feature = "full", feature = "derive"), feature = "extra-traits"))]
mod tt;

#[cfg(any(feature = "full", feature = "derive"))]
mod ty;
#[cfg(any(feature = "full", feature = "derive"))]
#[cfg_attr(docsrs, doc(cfg(any(feature = "full", feature = "derive"))))]
pub use crate::ty::{
    Abi, BareFnArg, BareVariadic, ReturnType, Type, TypeArray, TypeBareFn, TypeGroup,
    TypeImplTrait, TypeInfer, TypeMacro, TypeNever, TypeParen, TypePath, TypePtr, TypeReference,
    TypeSlice, TypeTraitObject, TypeTuple,
};

#[cfg(all(any(feature = "full", feature = "derive"), feature = "parsing"))]
mod verbatim;

#[cfg(all(feature = "parsing", feature = "full"))]
mod whitespace;

#[rustfmt::skip] // https://github.com/rust-lang/rustfmt/issues/6176
mod gen {
    /// Syntax tree traversal to transform the nodes of an owned syntax tree.
    ///
    /// Each method of the [`Fold`] trait is a hook that can be overridden to
    /// customize the behavior when transforming the corresponding type of node.
    /// By default, every method recursively visits the substructure of the
    /// input by invoking the right visitor method of each of its fields.
    ///
    /// [`Fold`]: fold::Fold
    ///
    /// ```
    /// # use syn::{Attribute, BinOp, Expr, ExprBinary};
    /// #
    /// pub trait Fold {
    ///     /* ... */
    ///
    ///     fn fold_expr_binary(&mut self, node: ExprBinary) -> ExprBinary {
    ///         fold_expr_binary(self, node)
    ///     }
    ///
    ///     /* ... */
    ///     # fn fold_attribute(&mut self, node: Attribute) -> Attribute;
    ///     # fn fold_expr(&mut self, node: Expr) -> Expr;
    ///     # fn fold_bin_op(&mut self, node: BinOp) -> BinOp;
    /// }
    ///
    /// pub fn fold_expr_binary<V>(v: &mut V, node: ExprBinary) -> ExprBinary
    /// where
    ///     V: Fold + ?Sized,
    /// {
    ///     ExprBinary {
    ///         attrs: node
    ///             .attrs
    ///             .into_iter()
    ///             .map(|attr| v.fold_attribute(attr))
    ///             .collect(),
    ///         left: Box::new(v.fold_expr(*node.left)),
    ///         op: v.fold_bin_op(node.op),
    ///         right: Box::new(v.fold_expr(*node.right)),
    ///     }
    /// }
    ///
    /// /* ... */
    /// ```
    ///
    /// <br>
    ///
    /// # Example
    ///
    /// This fold inserts parentheses to fully parenthesizes any expression.
    ///
    /// ```
    /// // [dependencies]
    /// // quote = "1.0"
    /// // syn = { version = "2.0", features = ["fold", "full"] }
    ///
    /// use quote::quote;
    /// use syn::fold::{fold_expr, Fold};
    /// use syn::{token, Expr, ExprParen};
    ///
    /// struct ParenthesizeEveryExpr;
    ///
    /// impl Fold for ParenthesizeEveryExpr {
    ///     fn fold_expr(&mut self, expr: Expr) -> Expr {
    ///         Expr::Paren(ExprParen {
    ///             attrs: Vec::new(),
    ///             expr: Box::new(fold_expr(self, expr)),
    ///             paren_token: token::Paren::default(),
    ///         })
    ///     }
    /// }
    ///
    /// fn main() {
    ///     let code = quote! { a() + b(1) * c.d };
    ///     let expr: Expr = syn::parse2(code).unwrap();
    ///     let parenthesized = ParenthesizeEveryExpr.fold_expr(expr);
    ///     println!("{}", quote!(#parenthesized));
    ///
    ///     // Output: (((a)()) + (((b)((1))) * ((c).d)))
    /// }
    /// ```
    #[cfg(feature = "fold")]
    #[cfg_attr(docsrs, doc(cfg(feature = "fold")))]
    #[rustfmt::skip]
    pub mod fold;

    /// Syntax tree traversal to walk a shared borrow of a syntax tree.
    ///
    /// Each method of the [`Visit`] trait is a hook that can be overridden to
    /// customize the behavior when visiting the corresponding type of node. By
    /// default, every method recursively visits the substructure of the input
    /// by invoking the right visitor method of each of its fields.
    ///
    /// [`Visit`]: visit::Visit
    ///
    /// ```
    /// # use syn::{Attribute, BinOp, Expr, ExprBinary};
    /// #
    /// pub trait Visit<'ast> {
    ///     /* ... */
    ///
    ///     fn visit_expr_binary(&mut self, node: &'ast ExprBinary) {
    ///         visit_expr_binary(self, node);
    ///     }
    ///
    ///     /* ... */
    ///     # fn visit_attribute(&mut self, node: &'ast Attribute);
    ///     # fn visit_expr(&mut self, node: &'ast Expr);
    ///     # fn visit_bin_op(&mut self, node: &'ast BinOp);
    /// }
    ///
    /// pub fn visit_expr_binary<'ast, V>(v: &mut V, node: &'ast ExprBinary)
    /// where
    ///     V: Visit<'ast> + ?Sized,
    /// {
    ///     for attr in &node.attrs {
    ///         v.visit_attribute(attr);
    ///     }
    ///     v.visit_expr(&*node.left);
    ///     v.visit_bin_op(&node.op);
    ///     v.visit_expr(&*node.right);
    /// }
    ///
    /// /* ... */
    /// ```
    ///
    /// <br>
    ///
    /// # Example
    ///
    /// This visitor will print the name of every freestanding function in the
    /// syntax tree, including nested functions.
    ///
    /// ```
    /// // [dependencies]
    /// // quote = "1.0"
    /// // syn = { version = "2.0", features = ["full", "visit"] }
    ///
    /// use quote::quote;
    /// use syn::visit::{self, Visit};
    /// use syn::{File, ItemFn};
    ///
    /// struct FnVisitor;
    ///
    /// impl<'ast> Visit<'ast> for FnVisitor {
    ///     fn visit_item_fn(&mut self, node: &'ast ItemFn) {
    ///         println!("Function with name={}", node.sig.ident);
    ///
    ///         // Delegate to the default impl to visit any nested functions.
    ///         visit::visit_item_fn(self, node);
    ///     }
    /// }
    ///
    /// fn main() {
    ///     let code = quote! {
    ///         pub fn f() {
    ///             fn g() {}
    ///         }
    ///     };
    ///
    ///     let syntax_tree: File = syn::parse2(code).unwrap();
    ///     FnVisitor.visit_file(&syntax_tree);
    /// }
    /// ```
    ///
    /// The `'ast` lifetime on the input references means that the syntax tree
    /// outlives the complete recursive visit call, so the visitor is allowed to
    /// hold on to references into the syntax tree.
    ///
    /// ```
    /// use quote::quote;
    /// use syn::visit::{self, Visit};
    /// use syn::{File, ItemFn};
    ///
    /// struct FnVisitor<'ast> {
    ///     functions: Vec<&'ast ItemFn>,
    /// }
    ///
    /// impl<'ast> Visit<'ast> for FnVisitor<'ast> {
    ///     fn visit_item_fn(&mut self, node: &'ast ItemFn) {
    ///         self.functions.push(node);
    ///         visit::visit_item_fn(self, node);
    ///     }
    /// }
    ///
    /// fn main() {
    ///     let code = quote! {
    ///         pub fn f() {
    ///             fn g() {}
    ///         }
    ///     };
    ///
    ///     let syntax_tree: File = syn::parse2(code).unwrap();
    ///     let mut visitor = FnVisitor { functions: Vec::new() };
    ///     visitor.visit_file(&syntax_tree);
    ///     for f in visitor.functions {
    ///         println!("Function with name={}", f.sig.ident);
    ///     }
    /// }
    /// ```
    #[cfg(feature = "visit")]
    #[cfg_attr(docsrs, doc(cfg(feature = "visit")))]
    #[rustfmt::skip]
    pub mod visit;

    /// Syntax tree traversal to mutate an exclusive borrow of a syntax tree in
    /// place.
    ///
    /// Each method of the [`VisitMut`] trait is a hook that can be overridden
    /// to customize the behavior when mutating the corresponding type of node.
    /// By default, every method recursively visits the substructure of the
    /// input by invoking the right visitor method of each of its fields.
    ///
    /// [`VisitMut`]: visit_mut::VisitMut
    ///
    /// ```
    /// # use syn::{Attribute, BinOp, Expr, ExprBinary};
    /// #
    /// pub trait VisitMut {
    ///     /* ... */
    ///
    ///     fn visit_expr_binary_mut(&mut self, node: &mut ExprBinary) {
    ///         visit_expr_binary_mut(self, node);
    ///     }
    ///
    ///     /* ... */
    ///     # fn visit_attribute_mut(&mut self, node: &mut Attribute);
    ///     # fn visit_expr_mut(&mut self, node: &mut Expr);
    ///     # fn visit_bin_op_mut(&mut self, node: &mut BinOp);
    /// }
    ///
    /// pub fn visit_expr_binary_mut<V>(v: &mut V, node: &mut ExprBinary)
    /// where
    ///     V: VisitMut + ?Sized,
    /// {
    ///     for attr in &mut node.attrs {
    ///         v.visit_attribute_mut(attr);
    ///     }
    ///     v.visit_expr_mut(&mut *node.left);
    ///     v.visit_bin_op_mut(&mut node.op);
    ///     v.visit_expr_mut(&mut *node.right);
    /// }
    ///
    /// /* ... */
    /// ```
    ///
    /// <br>
    ///
    /// # Example
    ///
    /// This mut visitor replace occurrences of u256 suffixed integer literals
    /// like `999u256` with a macro invocation `bigint::u256!(999)`.
    ///
    /// ```
    /// // [dependencies]
    /// // quote = "1.0"
    /// // syn = { version = "2.0", features = ["full", "visit-mut"] }
    ///
    /// use quote::quote;
    /// use syn::visit_mut::{self, VisitMut};
    /// use syn::{parse_quote, Expr, File, Lit, LitInt};
    ///
    /// struct BigintReplace;
    ///
    /// impl VisitMut for BigintReplace {
    ///     fn visit_expr_mut(&mut self, node: &mut Expr) {
    ///         if let Expr::Lit(expr) = &node {
    ///             if let Lit::Int(int) = &expr.lit {
    ///                 if int.suffix() == "u256" {
    ///                     let digits = int.base10_digits();
    ///                     let unsuffixed: LitInt = syn::parse_str(digits).unwrap();
    ///                     *node = parse_quote!(bigint::u256!(#unsuffixed));
    ///                     return;
    ///                 }
    ///             }
    ///         }
    ///
    ///         // Delegate to the default impl to visit nested expressions.
    ///         visit_mut::visit_expr_mut(self, node);
    ///     }
    /// }
    ///
    /// fn main() {
    ///     let code = quote! {
    ///         fn main() {
    ///             let _ = 999u256;
    ///         }
    ///     };
    ///
    ///     let mut syntax_tree: File = syn::parse2(code).unwrap();
    ///     BigintReplace.visit_file_mut(&mut syntax_tree);
    ///     println!("{}", quote!(#syntax_tree));
    /// }
    /// ```
    #[cfg(feature = "visit-mut")]
    #[cfg_attr(docsrs, doc(cfg(feature = "visit-mut")))]
    #[rustfmt::skip]
    pub mod visit_mut;

    #[cfg(feature = "clone-impls")]
    #[rustfmt::skip]
    mod clone;

    #[cfg(feature = "extra-traits")]
    #[rustfmt::skip]
    mod debug;

    #[cfg(feature = "extra-traits")]
    #[rustfmt::skip]
    mod eq;

    #[cfg(feature = "extra-traits")]
    #[rustfmt::skip]
    mod hash;
}

#[cfg(feature = "fold")]
#[cfg_attr(docsrs, doc(cfg(feature = "fold")))]
pub use crate::gen::fold;

#[cfg(feature = "visit")]
#[cfg_attr(docsrs, doc(cfg(feature = "visit")))]
pub use crate::gen::visit;

#[cfg(feature = "visit-mut")]
#[cfg_attr(docsrs, doc(cfg(feature = "visit-mut")))]
pub use crate::gen::visit_mut;

// Not public API.
#[doc(hidden)]
#[path = "export.rs"]
pub mod __private;

/// Parse tokens of source code into the chosen syntax tree node.
///
/// This is preferred over parsing a string because tokens are able to preserve
/// information about where in the user's code they were originally written (the
/// "span" of the token), possibly allowing the compiler to produce better error
/// messages.
///
/// This function parses a `proc_macro::TokenStream` which is the type used for
/// interop with the compiler in a procedural macro. To parse a
/// `proc_macro2::TokenStream`, use [`syn::parse2`] instead.
///
/// [`syn::parse2`]: parse2
///
/// This function enforces that the input is fully parsed. If there are any
/// unparsed tokens at the end of the stream, an error is returned.
#[cfg(all(feature = "parsing", feature = "proc-macro"))]
#[cfg_attr(docsrs, doc(cfg(all(feature = "parsing", feature = "proc-macro"))))]
pub fn parse<T: parse::Parse>(tokens: proc_macro::TokenStream) -> Result<T> {
    parse::Parser::parse(T::parse, tokens)
}

/// Parse a proc-macro2 token stream into the chosen syntax tree node.
///
/// This function parses a `proc_macro2::TokenStream` which is commonly useful
/// when the input comes from a node of the Syn syntax tree, for example the
/// body tokens of a [`Macro`] node. When in a procedural macro parsing the
/// `proc_macro::TokenStream` provided by the compiler, use [`syn::parse`]
/// instead.
///
/// [`syn::parse`]: parse()
///
/// This function enforces that the input is fully parsed. If there are any
/// unparsed tokens at the end of the stream, an error is returned.
#[cfg(feature = "parsing")]
#[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
pub fn parse2<T: parse::Parse>(tokens: proc_macro2::TokenStream) -> Result<T> {
    parse::Parser::parse2(T::parse, tokens)
}

/// Parse a string of Rust code into the chosen syntax tree node.
///
/// This function enforces that the input is fully parsed. If there are any
/// unparsed tokens at the end of the stream, an error is returned.
///
/// # Hygiene
///
/// Every span in the resulting syntax tree will be set to resolve at the macro
/// call site.
///
/// # Examples
///
/// ```
/// use syn::{Expr, Result};
///
/// fn run() -> Result<()> {
///     let code = "assert_eq!(u8::max_value(), 255)";
///     let expr = syn::parse_str::<Expr>(code)?;
///     println!("{:#?}", expr);
///     Ok(())
/// }
/// #
/// # run().unwrap();
/// ```
#[cfg(feature = "parsing")]
#[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
pub fn parse_str<T: parse::Parse>(s: &str) -> Result<T> {
    parse::Parser::parse_str(T::parse, s)
}

/// Parse the content of a file of Rust code.
///
/// This is different from `syn::parse_str::<File>(content)` in two ways:
///
/// - It discards a leading byte order mark `\u{FEFF}` if the file has one.
/// - It preserves the shebang line of the file, such as `#!/usr/bin/env rustx`.
///
/// If present, either of these would be an error using `from_str`.
///
/// # Examples
///
/// ```no_run
/// use std::error::Error;
/// use std::fs;
/// use std::io::Read;
///
/// fn run() -> Result<(), Box<dyn Error>> {
///     let content = fs::read_to_string("path/to/code.rs")?;
///     let ast = syn::parse_file(&content)?;
///     if let Some(shebang) = ast.shebang {
///         println!("{}", shebang);
///     }
///     println!("{} items", ast.items.len());
///
///     Ok(())
/// }
/// #
/// # run().unwrap();
/// ```
#[cfg(all(feature = "parsing", feature = "full"))]
#[cfg_attr(docsrs, doc(cfg(all(feature = "parsing", feature = "full"))))]
pub fn parse_file(mut content: &str) -> Result<File> {
    // Strip the BOM if it is present
    const BOM: &str = "\u{feff}";
    if content.starts_with(BOM) {
        content = &content[BOM.len()..];
    }

    let mut shebang = None;
    if content.starts_with("#!") {
        let rest = whitespace::skip(&content[2..]);
        if !rest.starts_with('[') {
            if let Some(idx) = content.find('\n') {
                shebang = Some(content[..idx].to_string());
                content = &content[idx..];
            } else {
                shebang = Some(content.to_string());
                content = "";
            }
        }
    }

    let mut file: File = parse_str(content)?;
    file.shebang = shebang;
    Ok(file)
}