rustc_errors/
diagnostic.rs

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

use rustc_data_structures::fx::FxIndexMap;
use rustc_error_messages::{FluentValue, fluent_value_from_str_list_sep_by_and};
use rustc_lint_defs::Applicability;
use rustc_macros::{Decodable, Encodable};
use rustc_span::source_map::Spanned;
use rustc_span::symbol::Symbol;
use rustc_span::{DUMMY_SP, Span};
use tracing::debug;

use crate::snippet::Style;
use crate::{
    CodeSuggestion, DiagCtxtHandle, DiagMessage, ErrCode, ErrorGuaranteed, ExplicitBug, Level,
    MultiSpan, StashKey, SubdiagMessage, Substitution, SubstitutionPart, SuggestionStyle,
    Suggestions,
};

/// Simplified version of `FluentArg` that can implement `Encodable` and `Decodable`. Collection of
/// `DiagArg` are converted to `FluentArgs` (consuming the collection) at the start of diagnostic
/// emission.
pub type DiagArg<'iter> = (&'iter DiagArgName, &'iter DiagArgValue);

/// Name of a diagnostic argument.
pub type DiagArgName = Cow<'static, str>;

/// Simplified version of `FluentValue` that can implement `Encodable` and `Decodable`. Converted
/// to a `FluentValue` by the emitter to be used in diagnostic translation.
#[derive(Clone, Debug, PartialEq, Eq, Hash, Encodable, Decodable)]
pub enum DiagArgValue {
    Str(Cow<'static, str>),
    // This gets converted to a `FluentNumber`, which is an `f64`. An `i32`
    // safely fits in an `f64`. Any integers bigger than that will be converted
    // to strings in `into_diag_arg` and stored using the `Str` variant.
    Number(i32),
    StrListSepByAnd(Vec<Cow<'static, str>>),
}

pub type DiagArgMap = FxIndexMap<DiagArgName, DiagArgValue>;

/// Trait for types that `Diag::emit` can return as a "guarantee" (or "proof")
/// token that the emission happened.
pub trait EmissionGuarantee: Sized {
    /// This exists so that bugs and fatal errors can both result in `!` (an
    /// abort) when emitted, but have different aborting behaviour.
    type EmitResult = Self;

    /// Implementation of `Diag::emit`, fully controlled by each `impl` of
    /// `EmissionGuarantee`, to make it impossible to create a value of
    /// `Self::EmitResult` without actually performing the emission.
    #[track_caller]
    fn emit_producing_guarantee(diag: Diag<'_, Self>) -> Self::EmitResult;
}

impl EmissionGuarantee for ErrorGuaranteed {
    fn emit_producing_guarantee(diag: Diag<'_, Self>) -> Self::EmitResult {
        diag.emit_producing_error_guaranteed()
    }
}

impl EmissionGuarantee for () {
    fn emit_producing_guarantee(diag: Diag<'_, Self>) -> Self::EmitResult {
        diag.emit_producing_nothing();
    }
}

/// Marker type which enables implementation of `create_bug` and `emit_bug` functions for
/// bug diagnostics.
#[derive(Copy, Clone)]
pub struct BugAbort;

impl EmissionGuarantee for BugAbort {
    type EmitResult = !;

    fn emit_producing_guarantee(diag: Diag<'_, Self>) -> Self::EmitResult {
        diag.emit_producing_nothing();
        panic::panic_any(ExplicitBug);
    }
}

/// Marker type which enables implementation of `create_fatal` and `emit_fatal` functions for
/// fatal diagnostics.
#[derive(Copy, Clone)]
pub struct FatalAbort;

impl EmissionGuarantee for FatalAbort {
    type EmitResult = !;

    fn emit_producing_guarantee(diag: Diag<'_, Self>) -> Self::EmitResult {
        diag.emit_producing_nothing();
        crate::FatalError.raise()
    }
}

impl EmissionGuarantee for rustc_span::fatal_error::FatalError {
    fn emit_producing_guarantee(diag: Diag<'_, Self>) -> Self::EmitResult {
        diag.emit_producing_nothing();
        rustc_span::fatal_error::FatalError
    }
}

/// Trait implemented by error types. This is rarely implemented manually. Instead, use
/// `#[derive(Diagnostic)]` -- see [rustc_macros::Diagnostic].
///
/// When implemented manually, it should be generic over the emission
/// guarantee, i.e.:
/// ```ignore (fragment)
/// impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for Foo { ... }
/// ```
/// rather than being specific:
/// ```ignore (fragment)
/// impl<'a> Diagnostic<'a> for Bar { ... }  // the default type param is `ErrorGuaranteed`
/// impl<'a> Diagnostic<'a, ()> for Baz { ... }
/// ```
/// There are two reasons for this.
/// - A diagnostic like `Foo` *could* be emitted at any level -- `level` is
///   passed in to `into_diag` from outside. Even if in practice it is
///   always emitted at a single level, we let the diagnostic creation/emission
///   site determine the level (by using `create_err`, `emit_warn`, etc.)
///   rather than the `Diagnostic` impl.
/// - Derived impls are always generic, and it's good for the hand-written
///   impls to be consistent with them.
#[rustc_diagnostic_item = "Diagnostic"]
pub trait Diagnostic<'a, G: EmissionGuarantee = ErrorGuaranteed> {
    /// Write out as a diagnostic out of `DiagCtxt`.
    #[must_use]
    fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'a, G>;
}

impl<'a, T, G> Diagnostic<'a, G> for Spanned<T>
where
    T: Diagnostic<'a, G>,
    G: EmissionGuarantee,
{
    fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'a, G> {
        self.node.into_diag(dcx, level).with_span(self.span)
    }
}

/// Converts a value of a type into a `DiagArg` (typically a field of an `Diag` struct).
/// Implemented as a custom trait rather than `From` so that it is implemented on the type being
/// converted rather than on `DiagArgValue`, which enables types from other `rustc_*` crates to
/// implement this.
pub trait IntoDiagArg {
    fn into_diag_arg(self) -> DiagArgValue;
}

impl IntoDiagArg for DiagArgValue {
    fn into_diag_arg(self) -> DiagArgValue {
        self
    }
}

impl Into<FluentValue<'static>> for DiagArgValue {
    fn into(self) -> FluentValue<'static> {
        match self {
            DiagArgValue::Str(s) => From::from(s),
            DiagArgValue::Number(n) => From::from(n),
            DiagArgValue::StrListSepByAnd(l) => fluent_value_from_str_list_sep_by_and(l),
        }
    }
}

/// Trait implemented by error types. This should not be implemented manually. Instead, use
/// `#[derive(Subdiagnostic)]` -- see [rustc_macros::Subdiagnostic].
#[rustc_diagnostic_item = "Subdiagnostic"]
pub trait Subdiagnostic
where
    Self: Sized,
{
    /// Add a subdiagnostic to an existing diagnostic.
    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
        self.add_to_diag_with(diag, &|_, m| m);
    }

    /// Add a subdiagnostic to an existing diagnostic where `f` is invoked on every message used
    /// (to optionally perform eager translation).
    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
        self,
        diag: &mut Diag<'_, G>,
        f: &F,
    );
}

pub trait SubdiagMessageOp<G: EmissionGuarantee> =
    Fn(&mut Diag<'_, G>, SubdiagMessage) -> SubdiagMessage;

/// Trait implemented by lint types. This should not be implemented manually. Instead, use
/// `#[derive(LintDiagnostic)]` -- see [rustc_macros::LintDiagnostic].
#[rustc_diagnostic_item = "LintDiagnostic"]
pub trait LintDiagnostic<'a, G: EmissionGuarantee> {
    /// Decorate and emit a lint.
    fn decorate_lint<'b>(self, diag: &'b mut Diag<'a, G>);
}

#[derive(Clone, Debug, Encodable, Decodable)]
pub(crate) struct DiagLocation {
    file: Cow<'static, str>,
    line: u32,
    col: u32,
}

impl DiagLocation {
    #[track_caller]
    fn caller() -> Self {
        let loc = panic::Location::caller();
        DiagLocation { file: loc.file().into(), line: loc.line(), col: loc.column() }
    }
}

impl fmt::Display for DiagLocation {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}:{}:{}", self.file, self.line, self.col)
    }
}

#[derive(Clone, Debug, PartialEq, Eq, Hash, Encodable, Decodable)]
pub struct IsLint {
    /// The lint name.
    pub(crate) name: String,
    /// Indicates whether this lint should show up in cargo's future breakage report.
    has_future_breakage: bool,
}

#[derive(Debug, PartialEq, Eq)]
pub struct DiagStyledString(pub Vec<StringPart>);

impl DiagStyledString {
    pub fn new() -> DiagStyledString {
        DiagStyledString(vec![])
    }
    pub fn push_normal<S: Into<String>>(&mut self, t: S) {
        self.0.push(StringPart::normal(t));
    }
    pub fn push_highlighted<S: Into<String>>(&mut self, t: S) {
        self.0.push(StringPart::highlighted(t));
    }
    pub fn push<S: Into<String>>(&mut self, t: S, highlight: bool) {
        if highlight {
            self.push_highlighted(t);
        } else {
            self.push_normal(t);
        }
    }
    pub fn normal<S: Into<String>>(t: S) -> DiagStyledString {
        DiagStyledString(vec![StringPart::normal(t)])
    }

    pub fn highlighted<S: Into<String>>(t: S) -> DiagStyledString {
        DiagStyledString(vec![StringPart::highlighted(t)])
    }

    pub fn content(&self) -> String {
        self.0.iter().map(|x| x.content.as_str()).collect::<String>()
    }
}

#[derive(Debug, PartialEq, Eq)]
pub struct StringPart {
    content: String,
    style: Style,
}

impl StringPart {
    pub fn normal<S: Into<String>>(content: S) -> StringPart {
        StringPart { content: content.into(), style: Style::NoStyle }
    }

    pub fn highlighted<S: Into<String>>(content: S) -> StringPart {
        StringPart { content: content.into(), style: Style::Highlight }
    }
}

/// The main part of a diagnostic. Note that `Diag`, which wraps this type, is
/// used for most operations, and should be used instead whenever possible.
/// This type should only be used when `Diag`'s lifetime causes difficulties,
/// e.g. when storing diagnostics within `DiagCtxt`.
#[must_use]
#[derive(Clone, Debug, Encodable, Decodable)]
pub struct DiagInner {
    // NOTE(eddyb) this is private to disallow arbitrary after-the-fact changes,
    // outside of what methods in this crate themselves allow.
    pub(crate) level: Level,

    pub messages: Vec<(DiagMessage, Style)>,
    pub code: Option<ErrCode>,
    pub span: MultiSpan,
    pub children: Vec<Subdiag>,
    pub suggestions: Suggestions,
    pub args: DiagArgMap,

    /// This is not used for highlighting or rendering any error message. Rather, it can be used
    /// as a sort key to sort a buffer of diagnostics. By default, it is the primary span of
    /// `span` if there is one. Otherwise, it is `DUMMY_SP`.
    pub sort_span: Span,

    pub is_lint: Option<IsLint>,

    /// With `-Ztrack_diagnostics` enabled,
    /// we print where in rustc this error was emitted.
    pub(crate) emitted_at: DiagLocation,
}

impl DiagInner {
    #[track_caller]
    pub fn new<M: Into<DiagMessage>>(level: Level, message: M) -> Self {
        DiagInner::new_with_messages(level, vec![(message.into(), Style::NoStyle)])
    }

    #[track_caller]
    pub fn new_with_messages(level: Level, messages: Vec<(DiagMessage, Style)>) -> Self {
        DiagInner {
            level,
            messages,
            code: None,
            span: MultiSpan::new(),
            children: vec![],
            suggestions: Suggestions::Enabled(vec![]),
            args: Default::default(),
            sort_span: DUMMY_SP,
            is_lint: None,
            emitted_at: DiagLocation::caller(),
        }
    }

    #[inline(always)]
    pub fn level(&self) -> Level {
        self.level
    }

    pub fn is_error(&self) -> bool {
        match self.level {
            Level::Bug | Level::Fatal | Level::Error | Level::DelayedBug => true,

            Level::ForceWarning(_)
            | Level::Warning
            | Level::Note
            | Level::OnceNote
            | Level::Help
            | Level::OnceHelp
            | Level::FailureNote
            | Level::Allow
            | Level::Expect(_) => false,
        }
    }

    /// Indicates whether this diagnostic should show up in cargo's future breakage report.
    pub(crate) fn has_future_breakage(&self) -> bool {
        matches!(self.is_lint, Some(IsLint { has_future_breakage: true, .. }))
    }

    pub(crate) fn is_force_warn(&self) -> bool {
        match self.level {
            Level::ForceWarning(_) => {
                assert!(self.is_lint.is_some());
                true
            }
            _ => false,
        }
    }

    // See comment on `Diag::subdiagnostic_message_to_diagnostic_message`.
    pub(crate) fn subdiagnostic_message_to_diagnostic_message(
        &self,
        attr: impl Into<SubdiagMessage>,
    ) -> DiagMessage {
        let msg =
            self.messages.iter().map(|(msg, _)| msg).next().expect("diagnostic with no messages");
        msg.with_subdiagnostic_message(attr.into())
    }

    pub(crate) fn sub(
        &mut self,
        level: Level,
        message: impl Into<SubdiagMessage>,
        span: MultiSpan,
    ) {
        let sub = Subdiag {
            level,
            messages: vec![(
                self.subdiagnostic_message_to_diagnostic_message(message),
                Style::NoStyle,
            )],
            span,
        };
        self.children.push(sub);
    }

    pub(crate) fn arg(&mut self, name: impl Into<DiagArgName>, arg: impl IntoDiagArg) {
        self.args.insert(name.into(), arg.into_diag_arg());
    }

    /// Fields used for Hash, and PartialEq trait.
    fn keys(
        &self,
    ) -> (
        &Level,
        &[(DiagMessage, Style)],
        &Option<ErrCode>,
        &MultiSpan,
        &[Subdiag],
        &Suggestions,
        Vec<(&DiagArgName, &DiagArgValue)>,
        &Option<IsLint>,
    ) {
        (
            &self.level,
            &self.messages,
            &self.code,
            &self.span,
            &self.children,
            &self.suggestions,
            self.args.iter().collect(),
            // omit self.sort_span
            &self.is_lint,
            // omit self.emitted_at
        )
    }
}

impl Hash for DiagInner {
    fn hash<H>(&self, state: &mut H)
    where
        H: Hasher,
    {
        self.keys().hash(state);
    }
}

impl PartialEq for DiagInner {
    fn eq(&self, other: &Self) -> bool {
        self.keys() == other.keys()
    }
}

/// A "sub"-diagnostic attached to a parent diagnostic.
/// For example, a note attached to an error.
#[derive(Clone, Debug, PartialEq, Hash, Encodable, Decodable)]
pub struct Subdiag {
    pub level: Level,
    pub messages: Vec<(DiagMessage, Style)>,
    pub span: MultiSpan,
}

/// Used for emitting structured error messages and other diagnostic information.
/// Wraps a `DiagInner`, adding some useful things.
/// - The `dcx` field, allowing it to (a) emit itself, and (b) do a drop check
///   that it has been emitted or cancelled.
/// - The `EmissionGuarantee`, which determines the type returned from `emit`.
///
/// Each constructed `Diag` must be consumed by a function such as `emit`,
/// `cancel`, `delay_as_bug`, or `into_diag`. A panic occurs if a `Diag`
/// is dropped without being consumed by one of these functions.
///
/// If there is some state in a downstream crate you would like to access in
/// the methods of `Diag` here, consider extending `DiagCtxtFlags`.
#[must_use]
pub struct Diag<'a, G: EmissionGuarantee = ErrorGuaranteed> {
    pub dcx: DiagCtxtHandle<'a>,

    /// Why the `Option`? It is always `Some` until the `Diag` is consumed via
    /// `emit`, `cancel`, etc. At that point it is consumed and replaced with
    /// `None`. Then `drop` checks that it is `None`; if not, it panics because
    /// a diagnostic was built but not used.
    ///
    /// Why the Box? `DiagInner` is a large type, and `Diag` is often used as a
    /// return value, especially within the frequently-used `PResult` type. In
    /// theory, return value optimization (RVO) should avoid unnecessary
    /// copying. In practice, it does not (at the time of writing).
    diag: Option<Box<DiagInner>>,

    _marker: PhantomData<G>,
}

// Cloning a `Diag` is a recipe for a diagnostic being emitted twice, which
// would be bad.
impl<G> !Clone for Diag<'_, G> {}

rustc_data_structures::static_assert_size!(Diag<'_, ()>, 3 * std::mem::size_of::<usize>());

impl<G: EmissionGuarantee> Deref for Diag<'_, G> {
    type Target = DiagInner;

    fn deref(&self) -> &DiagInner {
        self.diag.as_ref().unwrap()
    }
}

impl<G: EmissionGuarantee> DerefMut for Diag<'_, G> {
    fn deref_mut(&mut self) -> &mut DiagInner {
        self.diag.as_mut().unwrap()
    }
}

impl<G: EmissionGuarantee> Debug for Diag<'_, G> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        self.diag.fmt(f)
    }
}

/// `Diag` impls many `&mut self -> &mut Self` methods. Each one modifies an
/// existing diagnostic, either in a standalone fashion, e.g.
/// `err.code(code);`, or in a chained fashion to make multiple modifications,
/// e.g. `err.code(code).span(span);`.
///
/// This macro creates an equivalent `self -> Self` method, with a `with_`
/// prefix. This can be used in a chained fashion when making a new diagnostic,
/// e.g. `let err = struct_err(msg).with_code(code);`, or emitting a new
/// diagnostic, e.g. `struct_err(msg).with_code(code).emit();`.
///
/// Although the latter method can be used to modify an existing diagnostic,
/// e.g. `err = err.with_code(code);`, this should be avoided because the former
/// method gives shorter code, e.g. `err.code(code);`.
///
/// Note: the `with_` methods are added only when needed. If you want to use
/// one and it's not defined, feel free to add it.
///
/// Note: any doc comments must be within the `with_fn!` call.
macro_rules! with_fn {
    {
        $with_f:ident,
        $(#[$attrs:meta])*
        pub fn $f:ident(&mut $self:ident, $($name:ident: $ty:ty),* $(,)?) -> &mut Self {
            $($body:tt)*
        }
    } => {
        // The original function.
        $(#[$attrs])*
        #[doc = concat!("See [`Diag::", stringify!($f), "()`].")]
        pub fn $f(&mut $self, $($name: $ty),*) -> &mut Self {
            $($body)*
        }

        // The `with_*` variant.
        $(#[$attrs])*
        #[doc = concat!("See [`Diag::", stringify!($f), "()`].")]
        pub fn $with_f(mut $self, $($name: $ty),*) -> Self {
            $self.$f($($name),*);
            $self
        }
    };
}

impl<'a, G: EmissionGuarantee> Diag<'a, G> {
    #[rustc_lint_diagnostics]
    #[track_caller]
    pub fn new(dcx: DiagCtxtHandle<'a>, level: Level, message: impl Into<DiagMessage>) -> Self {
        Self::new_diagnostic(dcx, DiagInner::new(level, message))
    }

    /// Allow moving diagnostics between different error tainting contexts
    pub fn with_dcx(mut self, dcx: DiagCtxtHandle<'_>) -> Diag<'_, G> {
        Diag { dcx, diag: self.diag.take(), _marker: PhantomData }
    }

    /// Creates a new `Diag` with an already constructed diagnostic.
    #[track_caller]
    pub(crate) fn new_diagnostic(dcx: DiagCtxtHandle<'a>, diag: DiagInner) -> Self {
        debug!("Created new diagnostic");
        Self { dcx, diag: Some(Box::new(diag)), _marker: PhantomData }
    }

    /// Delay emission of this diagnostic as a bug.
    ///
    /// This can be useful in contexts where an error indicates a bug but
    /// typically this only happens when other compilation errors have already
    /// happened. In those cases this can be used to defer emission of this
    /// diagnostic as a bug in the compiler only if no other errors have been
    /// emitted.
    ///
    /// In the meantime, though, callsites are required to deal with the "bug"
    /// locally in whichever way makes the most sense.
    #[rustc_lint_diagnostics]
    #[track_caller]
    pub fn downgrade_to_delayed_bug(&mut self) {
        assert!(
            matches!(self.level, Level::Error | Level::DelayedBug),
            "downgrade_to_delayed_bug: cannot downgrade {:?} to DelayedBug: not an error",
            self.level
        );
        self.level = Level::DelayedBug;
    }

    with_fn! { with_span_label,
    /// Appends a labeled span to the diagnostic.
    ///
    /// Labels are used to convey additional context for the diagnostic's primary span. They will
    /// be shown together with the original diagnostic's span, *not* with spans added by
    /// `span_note`, `span_help`, etc. Therefore, if the primary span is not displayable (because
    /// the span is `DUMMY_SP` or the source code isn't found), labels will not be displayed
    /// either.
    ///
    /// Implementation-wise, the label span is pushed onto the [`MultiSpan`] that was created when
    /// the diagnostic was constructed. However, the label span is *not* considered a
    /// ["primary span"][`MultiSpan`]; only the `Span` supplied when creating the diagnostic is
    /// primary.
    #[rustc_lint_diagnostics]
    pub fn span_label(&mut self, span: Span, label: impl Into<SubdiagMessage>) -> &mut Self {
        let msg = self.subdiagnostic_message_to_diagnostic_message(label);
        self.span.push_span_label(span, msg);
        self
    } }

    with_fn! { with_span_labels,
    /// Labels all the given spans with the provided label.
    /// See [`Self::span_label()`] for more information.
    #[rustc_lint_diagnostics]
    pub fn span_labels(&mut self, spans: impl IntoIterator<Item = Span>, label: &str) -> &mut Self {
        for span in spans {
            self.span_label(span, label.to_string());
        }
        self
    } }

    #[rustc_lint_diagnostics]
    pub fn replace_span_with(&mut self, after: Span, keep_label: bool) -> &mut Self {
        let before = self.span.clone();
        self.span(after);
        for span_label in before.span_labels() {
            if let Some(label) = span_label.label {
                if span_label.is_primary && keep_label {
                    self.span.push_span_label(after, label);
                } else {
                    self.span.push_span_label(span_label.span, label);
                }
            }
        }
        self
    }

    #[rustc_lint_diagnostics]
    pub fn note_expected_found(
        &mut self,
        expected_label: &dyn fmt::Display,
        expected: DiagStyledString,
        found_label: &dyn fmt::Display,
        found: DiagStyledString,
    ) -> &mut Self {
        self.note_expected_found_extra(expected_label, expected, found_label, found, &"", &"")
    }

    #[rustc_lint_diagnostics]
    pub fn note_expected_found_extra(
        &mut self,
        expected_label: &dyn fmt::Display,
        expected: DiagStyledString,
        found_label: &dyn fmt::Display,
        found: DiagStyledString,
        expected_extra: &dyn fmt::Display,
        found_extra: &dyn fmt::Display,
    ) -> &mut Self {
        let expected_label = expected_label.to_string();
        let expected_label = if expected_label.is_empty() {
            "expected".to_string()
        } else {
            format!("expected {expected_label}")
        };
        let found_label = found_label.to_string();
        let found_label = if found_label.is_empty() {
            "found".to_string()
        } else {
            format!("found {found_label}")
        };
        let (found_padding, expected_padding) = if expected_label.len() > found_label.len() {
            (expected_label.len() - found_label.len(), 0)
        } else {
            (0, found_label.len() - expected_label.len())
        };
        let mut msg = vec![StringPart::normal(format!(
            "{}{} `",
            " ".repeat(expected_padding),
            expected_label
        ))];
        msg.extend(expected.0);
        msg.push(StringPart::normal(format!("`{expected_extra}\n")));
        msg.push(StringPart::normal(format!("{}{} `", " ".repeat(found_padding), found_label)));
        msg.extend(found.0);
        msg.push(StringPart::normal(format!("`{found_extra}")));

        // For now, just attach these as notes.
        self.highlighted_note(msg);
        self
    }

    #[rustc_lint_diagnostics]
    pub fn note_trait_signature(&mut self, name: Symbol, signature: String) -> &mut Self {
        self.highlighted_note(vec![
            StringPart::normal(format!("`{name}` from trait: `")),
            StringPart::highlighted(signature),
            StringPart::normal("`"),
        ]);
        self
    }

    with_fn! { with_note,
    /// Add a note attached to this diagnostic.
    #[rustc_lint_diagnostics]
    pub fn note(&mut self, msg: impl Into<SubdiagMessage>) -> &mut Self {
        self.sub(Level::Note, msg, MultiSpan::new());
        self
    } }

    #[rustc_lint_diagnostics]
    pub fn highlighted_note(&mut self, msg: Vec<StringPart>) -> &mut Self {
        self.sub_with_highlights(Level::Note, msg, MultiSpan::new());
        self
    }

    #[rustc_lint_diagnostics]
    pub fn highlighted_span_note(
        &mut self,
        span: impl Into<MultiSpan>,
        msg: Vec<StringPart>,
    ) -> &mut Self {
        self.sub_with_highlights(Level::Note, msg, span.into());
        self
    }

    /// This is like [`Diag::note()`], but it's only printed once.
    #[rustc_lint_diagnostics]
    pub fn note_once(&mut self, msg: impl Into<SubdiagMessage>) -> &mut Self {
        self.sub(Level::OnceNote, msg, MultiSpan::new());
        self
    }

    with_fn! { with_span_note,
    /// Prints the span with a note above it.
    /// This is like [`Diag::note()`], but it gets its own span.
    #[rustc_lint_diagnostics]
    pub fn span_note(
        &mut self,
        sp: impl Into<MultiSpan>,
        msg: impl Into<SubdiagMessage>,
    ) -> &mut Self {
        self.sub(Level::Note, msg, sp.into());
        self
    } }

    /// Prints the span with a note above it.
    /// This is like [`Diag::note_once()`], but it gets its own span.
    #[rustc_lint_diagnostics]
    pub fn span_note_once<S: Into<MultiSpan>>(
        &mut self,
        sp: S,
        msg: impl Into<SubdiagMessage>,
    ) -> &mut Self {
        self.sub(Level::OnceNote, msg, sp.into());
        self
    }

    with_fn! { with_warn,
    /// Add a warning attached to this diagnostic.
    #[rustc_lint_diagnostics]
    pub fn warn(&mut self, msg: impl Into<SubdiagMessage>) -> &mut Self {
        self.sub(Level::Warning, msg, MultiSpan::new());
        self
    } }

    /// Prints the span with a warning above it.
    /// This is like [`Diag::warn()`], but it gets its own span.
    #[rustc_lint_diagnostics]
    pub fn span_warn<S: Into<MultiSpan>>(
        &mut self,
        sp: S,
        msg: impl Into<SubdiagMessage>,
    ) -> &mut Self {
        self.sub(Level::Warning, msg, sp.into());
        self
    }

    with_fn! { with_help,
    /// Add a help message attached to this diagnostic.
    #[rustc_lint_diagnostics]
    pub fn help(&mut self, msg: impl Into<SubdiagMessage>) -> &mut Self {
        self.sub(Level::Help, msg, MultiSpan::new());
        self
    } }

    /// This is like [`Diag::help()`], but it's only printed once.
    #[rustc_lint_diagnostics]
    pub fn help_once(&mut self, msg: impl Into<SubdiagMessage>) -> &mut Self {
        self.sub(Level::OnceHelp, msg, MultiSpan::new());
        self
    }

    /// Add a help message attached to this diagnostic with a customizable highlighted message.
    #[rustc_lint_diagnostics]
    pub fn highlighted_help(&mut self, msg: Vec<StringPart>) -> &mut Self {
        self.sub_with_highlights(Level::Help, msg, MultiSpan::new());
        self
    }

    /// Add a help message attached to this diagnostic with a customizable highlighted message.
    #[rustc_lint_diagnostics]
    pub fn highlighted_span_help(
        &mut self,
        span: impl Into<MultiSpan>,
        msg: Vec<StringPart>,
    ) -> &mut Self {
        self.sub_with_highlights(Level::Help, msg, span.into());
        self
    }

    /// Prints the span with some help above it.
    /// This is like [`Diag::help()`], but it gets its own span.
    #[rustc_lint_diagnostics]
    pub fn span_help<S: Into<MultiSpan>>(
        &mut self,
        sp: S,
        msg: impl Into<SubdiagMessage>,
    ) -> &mut Self {
        self.sub(Level::Help, msg, sp.into());
        self
    }

    /// Disallow attaching suggestions to this diagnostic.
    /// Any suggestions attached e.g. with the `span_suggestion_*` methods
    /// (before and after the call to `disable_suggestions`) will be ignored.
    #[rustc_lint_diagnostics]
    pub fn disable_suggestions(&mut self) -> &mut Self {
        self.suggestions = Suggestions::Disabled;
        self
    }

    /// Prevent new suggestions from being added to this diagnostic.
    ///
    /// Suggestions added before the call to `.seal_suggestions()` will be preserved
    /// and new suggestions will be ignored.
    #[rustc_lint_diagnostics]
    pub fn seal_suggestions(&mut self) -> &mut Self {
        if let Suggestions::Enabled(suggestions) = &mut self.suggestions {
            let suggestions_slice = std::mem::take(suggestions).into_boxed_slice();
            self.suggestions = Suggestions::Sealed(suggestions_slice);
        }
        self
    }

    /// Helper for pushing to `self.suggestions`.
    ///
    /// A new suggestion is added if suggestions are enabled for this diagnostic.
    /// Otherwise, they are ignored.
    #[rustc_lint_diagnostics]
    fn push_suggestion(&mut self, suggestion: CodeSuggestion) {
        for subst in &suggestion.substitutions {
            for part in &subst.parts {
                let span = part.span;
                let call_site = span.ctxt().outer_expn_data().call_site;
                if span.in_derive_expansion() && span.overlaps_or_adjacent(call_site) {
                    // Ignore if spans is from derive macro.
                    return;
                }
            }
        }

        if let Suggestions::Enabled(suggestions) = &mut self.suggestions {
            suggestions.push(suggestion);
        }
    }

    with_fn! { with_multipart_suggestion,
    /// Show a suggestion that has multiple parts to it.
    /// In other words, multiple changes need to be applied as part of this suggestion.
    #[rustc_lint_diagnostics]
    pub fn multipart_suggestion(
        &mut self,
        msg: impl Into<SubdiagMessage>,
        suggestion: Vec<(Span, String)>,
        applicability: Applicability,
    ) -> &mut Self {
        self.multipart_suggestion_with_style(
            msg,
            suggestion,
            applicability,
            SuggestionStyle::ShowCode,
        )
    } }

    /// Show a suggestion that has multiple parts to it, always as it's own subdiagnostic.
    /// In other words, multiple changes need to be applied as part of this suggestion.
    #[rustc_lint_diagnostics]
    pub fn multipart_suggestion_verbose(
        &mut self,
        msg: impl Into<SubdiagMessage>,
        suggestion: Vec<(Span, String)>,
        applicability: Applicability,
    ) -> &mut Self {
        self.multipart_suggestion_with_style(
            msg,
            suggestion,
            applicability,
            SuggestionStyle::ShowAlways,
        )
    }

    /// [`Diag::multipart_suggestion()`] but you can set the [`SuggestionStyle`].
    #[rustc_lint_diagnostics]
    pub fn multipart_suggestion_with_style(
        &mut self,
        msg: impl Into<SubdiagMessage>,
        mut suggestion: Vec<(Span, String)>,
        applicability: Applicability,
        style: SuggestionStyle,
    ) -> &mut Self {
        let mut seen = crate::FxHashSet::default();
        suggestion.retain(|(span, msg)| seen.insert((span.lo(), span.hi(), msg.clone())));

        let parts = suggestion
            .into_iter()
            .map(|(span, snippet)| SubstitutionPart { snippet, span })
            .collect::<Vec<_>>();

        assert!(!parts.is_empty());
        debug_assert_eq!(
            parts.iter().find(|part| part.span.is_empty() && part.snippet.is_empty()),
            None,
            "Span must not be empty and have no suggestion",
        );
        debug_assert_eq!(
            parts.array_windows().find(|[a, b]| a.span.overlaps(b.span)),
            None,
            "suggestion must not have overlapping parts",
        );

        self.push_suggestion(CodeSuggestion {
            substitutions: vec![Substitution { parts }],
            msg: self.subdiagnostic_message_to_diagnostic_message(msg),
            style,
            applicability,
        });
        self
    }

    /// Prints out a message with for a multipart suggestion without showing the suggested code.
    ///
    /// This is intended to be used for suggestions that are obvious in what the changes need to
    /// be from the message, showing the span label inline would be visually unpleasant
    /// (marginally overlapping spans or multiline spans) and showing the snippet window wouldn't
    /// improve understandability.
    #[rustc_lint_diagnostics]
    pub fn tool_only_multipart_suggestion(
        &mut self,
        msg: impl Into<SubdiagMessage>,
        suggestion: Vec<(Span, String)>,
        applicability: Applicability,
    ) -> &mut Self {
        self.multipart_suggestion_with_style(
            msg,
            suggestion,
            applicability,
            SuggestionStyle::CompletelyHidden,
        )
    }

    with_fn! { with_span_suggestion,
    /// Prints out a message with a suggested edit of the code.
    ///
    /// In case of short messages and a simple suggestion, rustc displays it as a label:
    ///
    /// ```text
    /// try adding parentheses: `(tup.0).1`
    /// ```
    ///
    /// The message
    ///
    /// * should not end in any punctuation (a `:` is added automatically)
    /// * should not be a question (avoid language like "did you mean")
    /// * should not contain any phrases like "the following", "as shown", etc.
    /// * may look like "to do xyz, use" or "to do xyz, use abc"
    /// * may contain a name of a function, variable, or type, but not whole expressions
    ///
    /// See `CodeSuggestion` for more information.
    #[rustc_lint_diagnostics]
    pub fn span_suggestion(
        &mut self,
        sp: Span,
        msg: impl Into<SubdiagMessage>,
        suggestion: impl ToString,
        applicability: Applicability,
    ) -> &mut Self {
        self.span_suggestion_with_style(
            sp,
            msg,
            suggestion,
            applicability,
            SuggestionStyle::ShowCode,
        );
        self
    } }

    /// [`Diag::span_suggestion()`] but you can set the [`SuggestionStyle`].
    #[rustc_lint_diagnostics]
    pub fn span_suggestion_with_style(
        &mut self,
        sp: Span,
        msg: impl Into<SubdiagMessage>,
        suggestion: impl ToString,
        applicability: Applicability,
        style: SuggestionStyle,
    ) -> &mut Self {
        debug_assert!(
            !(sp.is_empty() && suggestion.to_string().is_empty()),
            "Span must not be empty and have no suggestion"
        );
        self.push_suggestion(CodeSuggestion {
            substitutions: vec![Substitution {
                parts: vec![SubstitutionPart { snippet: suggestion.to_string(), span: sp }],
            }],
            msg: self.subdiagnostic_message_to_diagnostic_message(msg),
            style,
            applicability,
        });
        self
    }

    with_fn! { with_span_suggestion_verbose,
    /// Always show the suggested change.
    #[rustc_lint_diagnostics]
    pub fn span_suggestion_verbose(
        &mut self,
        sp: Span,
        msg: impl Into<SubdiagMessage>,
        suggestion: impl ToString,
        applicability: Applicability,
    ) -> &mut Self {
        self.span_suggestion_with_style(
            sp,
            msg,
            suggestion,
            applicability,
            SuggestionStyle::ShowAlways,
        );
        self
    } }

    with_fn! { with_span_suggestions,
    /// Prints out a message with multiple suggested edits of the code.
    /// See also [`Diag::span_suggestion()`].
    #[rustc_lint_diagnostics]
    pub fn span_suggestions(
        &mut self,
        sp: Span,
        msg: impl Into<SubdiagMessage>,
        suggestions: impl IntoIterator<Item = String>,
        applicability: Applicability,
    ) -> &mut Self {
        self.span_suggestions_with_style(
            sp,
            msg,
            suggestions,
            applicability,
            SuggestionStyle::ShowCode,
        )
    } }

    #[rustc_lint_diagnostics]
    pub fn span_suggestions_with_style(
        &mut self,
        sp: Span,
        msg: impl Into<SubdiagMessage>,
        suggestions: impl IntoIterator<Item = String>,
        applicability: Applicability,
        style: SuggestionStyle,
    ) -> &mut Self {
        let substitutions = suggestions
            .into_iter()
            .map(|snippet| {
                debug_assert!(
                    !(sp.is_empty() && snippet.is_empty()),
                    "Span must not be empty and have no suggestion"
                );
                Substitution { parts: vec![SubstitutionPart { snippet, span: sp }] }
            })
            .collect();
        self.push_suggestion(CodeSuggestion {
            substitutions,
            msg: self.subdiagnostic_message_to_diagnostic_message(msg),
            style,
            applicability,
        });
        self
    }

    /// Prints out a message with multiple suggested edits of the code, where each edit consists of
    /// multiple parts.
    /// See also [`Diag::multipart_suggestion()`].
    #[rustc_lint_diagnostics]
    pub fn multipart_suggestions(
        &mut self,
        msg: impl Into<SubdiagMessage>,
        suggestions: impl IntoIterator<Item = Vec<(Span, String)>>,
        applicability: Applicability,
    ) -> &mut Self {
        let substitutions = suggestions
            .into_iter()
            .map(|sugg| {
                let mut parts = sugg
                    .into_iter()
                    .map(|(span, snippet)| SubstitutionPart { snippet, span })
                    .collect::<Vec<_>>();

                parts.sort_unstable_by_key(|part| part.span);

                assert!(!parts.is_empty());
                debug_assert_eq!(
                    parts.iter().find(|part| part.span.is_empty() && part.snippet.is_empty()),
                    None,
                    "Span must not be empty and have no suggestion",
                );
                debug_assert_eq!(
                    parts.array_windows().find(|[a, b]| a.span.overlaps(b.span)),
                    None,
                    "suggestion must not have overlapping parts",
                );

                Substitution { parts }
            })
            .collect();

        self.push_suggestion(CodeSuggestion {
            substitutions,
            msg: self.subdiagnostic_message_to_diagnostic_message(msg),
            style: SuggestionStyle::ShowCode,
            applicability,
        });
        self
    }

    with_fn! { with_span_suggestion_short,
    /// Prints out a message with a suggested edit of the code. If the suggestion is presented
    /// inline, it will only show the message and not the suggestion.
    ///
    /// See `CodeSuggestion` for more information.
    #[rustc_lint_diagnostics]
    pub fn span_suggestion_short(
        &mut self,
        sp: Span,
        msg: impl Into<SubdiagMessage>,
        suggestion: impl ToString,
        applicability: Applicability,
    ) -> &mut Self {
        self.span_suggestion_with_style(
            sp,
            msg,
            suggestion,
            applicability,
            SuggestionStyle::HideCodeInline,
        );
        self
    } }

    /// Prints out a message for a suggestion without showing the suggested code.
    ///
    /// This is intended to be used for suggestions that are obvious in what the changes need to
    /// be from the message, showing the span label inline would be visually unpleasant
    /// (marginally overlapping spans or multiline spans) and showing the snippet window wouldn't
    /// improve understandability.
    #[rustc_lint_diagnostics]
    pub fn span_suggestion_hidden(
        &mut self,
        sp: Span,
        msg: impl Into<SubdiagMessage>,
        suggestion: impl ToString,
        applicability: Applicability,
    ) -> &mut Self {
        self.span_suggestion_with_style(
            sp,
            msg,
            suggestion,
            applicability,
            SuggestionStyle::HideCodeAlways,
        );
        self
    }

    with_fn! { with_tool_only_span_suggestion,
    /// Adds a suggestion to the JSON output that will not be shown in the CLI.
    ///
    /// This is intended to be used for suggestions that are *very* obvious in what the changes
    /// need to be from the message, but we still want other tools to be able to apply them.
    #[rustc_lint_diagnostics]
    pub fn tool_only_span_suggestion(
        &mut self,
        sp: Span,
        msg: impl Into<SubdiagMessage>,
        suggestion: impl ToString,
        applicability: Applicability,
    ) -> &mut Self {
        self.span_suggestion_with_style(
            sp,
            msg,
            suggestion,
            applicability,
            SuggestionStyle::CompletelyHidden,
        );
        self
    } }

    /// Add a subdiagnostic from a type that implements `Subdiagnostic` (see
    /// [rustc_macros::Subdiagnostic]). Performs eager translation of any translatable messages
    /// used in the subdiagnostic, so suitable for use with repeated messages (i.e. re-use of
    /// interpolated variables).
    #[rustc_lint_diagnostics]
    pub fn subdiagnostic(&mut self, subdiagnostic: impl Subdiagnostic) -> &mut Self {
        let dcx = self.dcx;
        subdiagnostic.add_to_diag_with(self, &|diag, msg| {
            let args = diag.args.iter();
            let msg = diag.subdiagnostic_message_to_diagnostic_message(msg);
            dcx.eagerly_translate(msg, args)
        });
        self
    }

    with_fn! { with_span,
    /// Add a span.
    #[rustc_lint_diagnostics]
    pub fn span(&mut self, sp: impl Into<MultiSpan>) -> &mut Self {
        self.span = sp.into();
        if let Some(span) = self.span.primary_span() {
            self.sort_span = span;
        }
        self
    } }

    #[rustc_lint_diagnostics]
    pub fn is_lint(&mut self, name: String, has_future_breakage: bool) -> &mut Self {
        self.is_lint = Some(IsLint { name, has_future_breakage });
        self
    }

    with_fn! { with_code,
    /// Add an error code.
    #[rustc_lint_diagnostics]
    pub fn code(&mut self, code: ErrCode) -> &mut Self {
        self.code = Some(code);
        self
    } }

    with_fn! { with_primary_message,
    /// Add a primary message.
    #[rustc_lint_diagnostics]
    pub fn primary_message(&mut self, msg: impl Into<DiagMessage>) -> &mut Self {
        self.messages[0] = (msg.into(), Style::NoStyle);
        self
    } }

    with_fn! { with_arg,
    /// Add an argument.
    #[rustc_lint_diagnostics]
    pub fn arg(
        &mut self,
        name: impl Into<DiagArgName>,
        arg: impl IntoDiagArg,
    ) -> &mut Self {
        self.deref_mut().arg(name, arg);
        self
    } }

    /// Helper function that takes a `SubdiagMessage` and returns a `DiagMessage` by
    /// combining it with the primary message of the diagnostic (if translatable, otherwise it just
    /// passes the user's string along).
    pub(crate) fn subdiagnostic_message_to_diagnostic_message(
        &self,
        attr: impl Into<SubdiagMessage>,
    ) -> DiagMessage {
        self.deref().subdiagnostic_message_to_diagnostic_message(attr)
    }

    /// Convenience function for internal use, clients should use one of the
    /// public methods above.
    ///
    /// Used by `proc_macro_server` for implementing `server::Diagnostic`.
    pub fn sub(&mut self, level: Level, message: impl Into<SubdiagMessage>, span: MultiSpan) {
        self.deref_mut().sub(level, message, span);
    }

    /// Convenience function for internal use, clients should use one of the
    /// public methods above.
    fn sub_with_highlights(&mut self, level: Level, messages: Vec<StringPart>, span: MultiSpan) {
        let messages = messages
            .into_iter()
            .map(|m| (self.subdiagnostic_message_to_diagnostic_message(m.content), m.style))
            .collect();
        let sub = Subdiag { level, messages, span };
        self.children.push(sub);
    }

    /// Takes the diagnostic. For use by methods that consume the Diag: `emit`,
    /// `cancel`, etc. Afterwards, `drop` is the only code that will be run on
    /// `self`.
    fn take_diag(&mut self) -> DiagInner {
        Box::into_inner(self.diag.take().unwrap())
    }

    /// Most `emit_producing_guarantee` functions use this as a starting point.
    fn emit_producing_nothing(mut self) {
        let diag = self.take_diag();
        self.dcx.emit_diagnostic(diag);
    }

    /// `ErrorGuaranteed::emit_producing_guarantee` uses this.
    fn emit_producing_error_guaranteed(mut self) -> ErrorGuaranteed {
        let diag = self.take_diag();

        // The only error levels that produce `ErrorGuaranteed` are
        // `Error` and `DelayedBug`. But `DelayedBug` should never occur here
        // because delayed bugs have their level changed to `Bug` when they are
        // actually printed, so they produce an ICE.
        //
        // (Also, even though `level` isn't `pub`, the whole `DiagInner` could
        // be overwritten with a new one thanks to `DerefMut`. So this assert
        // protects against that, too.)
        assert!(
            matches!(diag.level, Level::Error | Level::DelayedBug),
            "invalid diagnostic level ({:?})",
            diag.level,
        );

        let guar = self.dcx.emit_diagnostic(diag);
        guar.unwrap()
    }

    /// Emit and consume the diagnostic.
    #[track_caller]
    pub fn emit(self) -> G::EmitResult {
        G::emit_producing_guarantee(self)
    }

    /// Emit the diagnostic unless `delay` is true,
    /// in which case the emission will be delayed as a bug.
    ///
    /// See `emit` and `delay_as_bug` for details.
    #[track_caller]
    pub fn emit_unless(mut self, delay: bool) -> G::EmitResult {
        if delay {
            self.downgrade_to_delayed_bug();
        }
        self.emit()
    }

    /// Cancel and consume the diagnostic. (A diagnostic must either be emitted or
    /// cancelled or it will panic when dropped).
    pub fn cancel(mut self) {
        self.diag = None;
        drop(self);
    }

    /// See `DiagCtxt::stash_diagnostic` for details.
    pub fn stash(mut self, span: Span, key: StashKey) -> Option<ErrorGuaranteed> {
        let diag = self.take_diag();
        self.dcx.stash_diagnostic(span, key, diag)
    }

    /// Delay emission of this diagnostic as a bug.
    ///
    /// This can be useful in contexts where an error indicates a bug but
    /// typically this only happens when other compilation errors have already
    /// happened. In those cases this can be used to defer emission of this
    /// diagnostic as a bug in the compiler only if no other errors have been
    /// emitted.
    ///
    /// In the meantime, though, callsites are required to deal with the "bug"
    /// locally in whichever way makes the most sense.
    #[track_caller]
    pub fn delay_as_bug(mut self) -> G::EmitResult {
        self.downgrade_to_delayed_bug();
        self.emit()
    }
}

/// Destructor bomb: every `Diag` must be consumed (emitted, cancelled, etc.)
/// or we emit a bug.
impl<G: EmissionGuarantee> Drop for Diag<'_, G> {
    fn drop(&mut self) {
        match self.diag.take() {
            Some(diag) if !panicking() => {
                self.dcx.emit_diagnostic(DiagInner::new(
                    Level::Bug,
                    DiagMessage::from("the following error was constructed but not emitted"),
                ));
                self.dcx.emit_diagnostic(*diag);
                panic!("error was constructed but not emitted");
            }
            _ => {}
        }
    }
}

#[macro_export]
macro_rules! struct_span_code_err {
    ($dcx:expr, $span:expr, $code:expr, $($message:tt)*) => ({
        $dcx.struct_span_err($span, format!($($message)*)).with_code($code)
    })
}