forked from rust-lang/rust
/
mod.rs
2863 lines (2648 loc) · 124 KB
/
mod.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
mod ambiguity;
pub mod method_chain;
pub mod on_unimplemented;
pub mod suggestions;
use super::{
FulfillmentError, FulfillmentErrorCode, MismatchedProjectionTypes, Obligation, ObligationCause,
ObligationCauseCode, ObligationCtxt, OutputTypeParameterMismatch, Overflow,
PredicateObligation, SelectionContext, SelectionError, TraitNotObjectSafe,
};
use crate::infer::error_reporting::{TyCategory, TypeAnnotationNeeded as ErrorCode};
use crate::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
use crate::infer::{self, InferCtxt};
use crate::traits::query::evaluate_obligation::InferCtxtExt as _;
use crate::traits::query::normalize::QueryNormalizeExt as _;
use crate::traits::specialize::to_pretty_impl_header;
use crate::traits::NormalizeExt;
use on_unimplemented::OnUnimplementedNote;
use on_unimplemented::TypeErrCtxtExt as _;
use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
use rustc_errors::{
pluralize, struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed,
MultiSpan, Style,
};
use rustc_hir as hir;
use rustc_hir::def::Namespace;
use rustc_hir::def_id::DefId;
use rustc_hir::intravisit::Visitor;
use rustc_hir::GenericParam;
use rustc_hir::Item;
use rustc_hir::Node;
use rustc_infer::infer::error_reporting::TypeErrCtxt;
use rustc_infer::infer::{InferOk, TypeTrace};
use rustc_middle::traits::select::OverflowError;
use rustc_middle::ty::abstract_const::NotConstEvaluatable;
use rustc_middle::ty::error::{ExpectedFound, TypeError};
use rustc_middle::ty::fold::{TypeFolder, TypeSuperFoldable};
use rustc_middle::ty::print::{with_forced_trimmed_paths, FmtPrinter, Print};
use rustc_middle::ty::{
self, SubtypePredicate, ToPolyTraitRef, ToPredicate, TraitRef, Ty, TyCtxt, TypeFoldable,
TypeVisitable,
};
use rustc_session::Limit;
use rustc_span::def_id::LOCAL_CRATE;
use rustc_span::symbol::sym;
use rustc_span::{ExpnKind, Span, DUMMY_SP};
use std::fmt;
use std::iter;
use std::ops::ControlFlow;
use suggestions::TypeErrCtxtExt as _;
pub use rustc_infer::traits::error_reporting::*;
// When outputting impl candidates, prefer showing those that are more similar.
//
// We also compare candidates after skipping lifetimes, which has a lower
// priority than exact matches.
#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
pub enum CandidateSimilarity {
Exact { ignoring_lifetimes: bool },
Fuzzy { ignoring_lifetimes: bool },
}
#[derive(Debug, Clone, Copy)]
pub struct ImplCandidate<'tcx> {
pub trait_ref: ty::TraitRef<'tcx>,
pub similarity: CandidateSimilarity,
}
pub trait InferCtxtExt<'tcx> {
/// Given some node representing a fn-like thing in the HIR map,
/// returns a span and `ArgKind` information that describes the
/// arguments it expects. This can be supplied to
/// `report_arg_count_mismatch`.
fn get_fn_like_arguments(&self, node: Node<'_>) -> Option<(Span, Option<Span>, Vec<ArgKind>)>;
/// Reports an error when the number of arguments needed by a
/// trait match doesn't match the number that the expression
/// provides.
fn report_arg_count_mismatch(
&self,
span: Span,
found_span: Option<Span>,
expected_args: Vec<ArgKind>,
found_args: Vec<ArgKind>,
is_closure: bool,
closure_pipe_span: Option<Span>,
) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>;
/// Checks if the type implements one of `Fn`, `FnMut`, or `FnOnce`
/// in that order, and returns the generic type corresponding to the
/// argument of that trait (corresponding to the closure arguments).
fn type_implements_fn_trait(
&self,
param_env: ty::ParamEnv<'tcx>,
ty: ty::Binder<'tcx, Ty<'tcx>>,
constness: ty::BoundConstness,
polarity: ty::ImplPolarity,
) -> Result<(ty::ClosureKind, ty::Binder<'tcx, Ty<'tcx>>), ()>;
}
pub trait TypeErrCtxtExt<'tcx> {
fn report_overflow_error<T>(
&self,
predicate: &T,
span: Span,
suggest_increasing_limit: bool,
mutate: impl FnOnce(&mut Diagnostic),
) -> !
where
T: fmt::Display
+ TypeFoldable<'tcx>
+ Print<'tcx, FmtPrinter<'tcx, 'tcx>, Output = FmtPrinter<'tcx, 'tcx>>,
<T as Print<'tcx, FmtPrinter<'tcx, 'tcx>>>::Error: std::fmt::Debug;
fn report_fulfillment_errors(
&self,
errors: &[FulfillmentError<'tcx>],
body_id: Option<hir::BodyId>,
) -> ErrorGuaranteed;
fn report_overflow_obligation<T>(
&self,
obligation: &Obligation<'tcx, T>,
suggest_increasing_limit: bool,
) -> !
where
T: ToPredicate<'tcx> + Clone;
fn suggest_new_overflow_limit(&self, err: &mut Diagnostic);
fn report_overflow_obligation_cycle(&self, cycle: &[PredicateObligation<'tcx>]) -> !;
/// The `root_obligation` parameter should be the `root_obligation` field
/// from a `FulfillmentError`. If no `FulfillmentError` is available,
/// then it should be the same as `obligation`.
fn report_selection_error(
&self,
obligation: PredicateObligation<'tcx>,
root_obligation: &PredicateObligation<'tcx>,
error: &SelectionError<'tcx>,
);
}
impl<'tcx> InferCtxtExt<'tcx> for InferCtxt<'tcx> {
/// Given some node representing a fn-like thing in the HIR map,
/// returns a span and `ArgKind` information that describes the
/// arguments it expects. This can be supplied to
/// `report_arg_count_mismatch`.
fn get_fn_like_arguments(&self, node: Node<'_>) -> Option<(Span, Option<Span>, Vec<ArgKind>)> {
let sm = self.tcx.sess.source_map();
let hir = self.tcx.hir();
Some(match node {
Node::Expr(&hir::Expr {
kind: hir::ExprKind::Closure(&hir::Closure { body, fn_decl_span, fn_arg_span, .. }),
..
}) => (
fn_decl_span,
fn_arg_span,
hir.body(body)
.params
.iter()
.map(|arg| {
if let hir::Pat { kind: hir::PatKind::Tuple(ref args, _), span, .. } =
*arg.pat
{
Some(ArgKind::Tuple(
Some(span),
args.iter()
.map(|pat| {
sm.span_to_snippet(pat.span)
.ok()
.map(|snippet| (snippet, "_".to_owned()))
})
.collect::<Option<Vec<_>>>()?,
))
} else {
let name = sm.span_to_snippet(arg.pat.span).ok()?;
Some(ArgKind::Arg(name, "_".to_owned()))
}
})
.collect::<Option<Vec<ArgKind>>>()?,
),
Node::Item(&hir::Item { kind: hir::ItemKind::Fn(ref sig, ..), .. })
| Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Fn(ref sig, _), .. })
| Node::TraitItem(&hir::TraitItem {
kind: hir::TraitItemKind::Fn(ref sig, _), ..
}) => (
sig.span,
None,
sig.decl
.inputs
.iter()
.map(|arg| match arg.kind {
hir::TyKind::Tup(ref tys) => ArgKind::Tuple(
Some(arg.span),
vec![("_".to_owned(), "_".to_owned()); tys.len()],
),
_ => ArgKind::empty(),
})
.collect::<Vec<ArgKind>>(),
),
Node::Ctor(ref variant_data) => {
let span = variant_data.ctor_hir_id().map_or(DUMMY_SP, |id| hir.span(id));
(span, None, vec![ArgKind::empty(); variant_data.fields().len()])
}
_ => panic!("non-FnLike node found: {:?}", node),
})
}
/// Reports an error when the number of arguments needed by a
/// trait match doesn't match the number that the expression
/// provides.
fn report_arg_count_mismatch(
&self,
span: Span,
found_span: Option<Span>,
expected_args: Vec<ArgKind>,
found_args: Vec<ArgKind>,
is_closure: bool,
closure_arg_span: Option<Span>,
) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
let kind = if is_closure { "closure" } else { "function" };
let args_str = |arguments: &[ArgKind], other: &[ArgKind]| {
let arg_length = arguments.len();
let distinct = matches!(other, &[ArgKind::Tuple(..)]);
match (arg_length, arguments.get(0)) {
(1, Some(ArgKind::Tuple(_, fields))) => {
format!("a single {}-tuple as argument", fields.len())
}
_ => format!(
"{} {}argument{}",
arg_length,
if distinct && arg_length > 1 { "distinct " } else { "" },
pluralize!(arg_length)
),
}
};
let expected_str = args_str(&expected_args, &found_args);
let found_str = args_str(&found_args, &expected_args);
let mut err = struct_span_err!(
self.tcx.sess,
span,
E0593,
"{} is expected to take {}, but it takes {}",
kind,
expected_str,
found_str,
);
err.span_label(span, format!("expected {} that takes {}", kind, expected_str));
if let Some(found_span) = found_span {
err.span_label(found_span, format!("takes {}", found_str));
// Suggest to take and ignore the arguments with expected_args_length `_`s if
// found arguments is empty (assume the user just wants to ignore args in this case).
// For example, if `expected_args_length` is 2, suggest `|_, _|`.
if found_args.is_empty() && is_closure {
let underscores = vec!["_"; expected_args.len()].join(", ");
err.span_suggestion_verbose(
closure_arg_span.unwrap_or(found_span),
&format!(
"consider changing the closure to take and ignore the expected argument{}",
pluralize!(expected_args.len())
),
format!("|{}|", underscores),
Applicability::MachineApplicable,
);
}
if let &[ArgKind::Tuple(_, ref fields)] = &found_args[..] {
if fields.len() == expected_args.len() {
let sugg = fields
.iter()
.map(|(name, _)| name.to_owned())
.collect::<Vec<String>>()
.join(", ");
err.span_suggestion_verbose(
found_span,
"change the closure to take multiple arguments instead of a single tuple",
format!("|{}|", sugg),
Applicability::MachineApplicable,
);
}
}
if let &[ArgKind::Tuple(_, ref fields)] = &expected_args[..]
&& fields.len() == found_args.len()
&& is_closure
{
let sugg = format!(
"|({}){}|",
found_args
.iter()
.map(|arg| match arg {
ArgKind::Arg(name, _) => name.to_owned(),
_ => "_".to_owned(),
})
.collect::<Vec<String>>()
.join(", "),
// add type annotations if available
if found_args.iter().any(|arg| match arg {
ArgKind::Arg(_, ty) => ty != "_",
_ => false,
}) {
format!(
": ({})",
fields
.iter()
.map(|(_, ty)| ty.to_owned())
.collect::<Vec<String>>()
.join(", ")
)
} else {
String::new()
},
);
err.span_suggestion_verbose(
found_span,
"change the closure to accept a tuple instead of individual arguments",
sugg,
Applicability::MachineApplicable,
);
}
}
err
}
fn type_implements_fn_trait(
&self,
param_env: ty::ParamEnv<'tcx>,
ty: ty::Binder<'tcx, Ty<'tcx>>,
constness: ty::BoundConstness,
polarity: ty::ImplPolarity,
) -> Result<(ty::ClosureKind, ty::Binder<'tcx, Ty<'tcx>>), ()> {
self.commit_if_ok(|_| {
for trait_def_id in [
self.tcx.lang_items().fn_trait(),
self.tcx.lang_items().fn_mut_trait(),
self.tcx.lang_items().fn_once_trait(),
] {
let Some(trait_def_id) = trait_def_id else { continue };
// Make a fresh inference variable so we can determine what the substitutions
// of the trait are.
let var = self.next_ty_var(TypeVariableOrigin {
span: DUMMY_SP,
kind: TypeVariableOriginKind::MiscVariable,
});
let trait_ref = self.tcx.mk_trait_ref(trait_def_id, [ty.skip_binder(), var]);
let obligation = Obligation::new(
self.tcx,
ObligationCause::dummy(),
param_env,
ty.rebind(ty::TraitPredicate { trait_ref, constness, polarity }),
);
let ocx = ObligationCtxt::new_in_snapshot(self);
ocx.register_obligation(obligation);
if ocx.select_all_or_error().is_empty() {
return Ok((
self.tcx
.fn_trait_kind_from_def_id(trait_def_id)
.expect("expected to map DefId to ClosureKind"),
ty.rebind(self.resolve_vars_if_possible(var)),
));
}
}
Err(())
})
}
}
impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
fn report_fulfillment_errors(
&self,
errors: &[FulfillmentError<'tcx>],
body_id: Option<hir::BodyId>,
) -> ErrorGuaranteed {
#[derive(Debug)]
struct ErrorDescriptor<'tcx> {
predicate: ty::Predicate<'tcx>,
index: Option<usize>, // None if this is an old error
}
let mut error_map: FxIndexMap<_, Vec<_>> = self
.reported_trait_errors
.borrow()
.iter()
.map(|(&span, predicates)| {
(
span,
predicates
.iter()
.map(|&predicate| ErrorDescriptor { predicate, index: None })
.collect(),
)
})
.collect();
for (index, error) in errors.iter().enumerate() {
// We want to ignore desugarings here: spans are equivalent even
// if one is the result of a desugaring and the other is not.
let mut span = error.obligation.cause.span;
let expn_data = span.ctxt().outer_expn_data();
if let ExpnKind::Desugaring(_) = expn_data.kind {
span = expn_data.call_site;
}
error_map.entry(span).or_default().push(ErrorDescriptor {
predicate: error.obligation.predicate,
index: Some(index),
});
self.reported_trait_errors
.borrow_mut()
.entry(span)
.or_default()
.push(error.obligation.predicate);
}
// We do this in 2 passes because we want to display errors in order, though
// maybe it *is* better to sort errors by span or something.
let mut is_suppressed = vec![false; errors.len()];
for (_, error_set) in error_map.iter() {
// We want to suppress "duplicate" errors with the same span.
for error in error_set {
if let Some(index) = error.index {
// Suppress errors that are either:
// 1) strictly implied by another error.
// 2) implied by an error with a smaller index.
for error2 in error_set {
if error2.index.map_or(false, |index2| is_suppressed[index2]) {
// Avoid errors being suppressed by already-suppressed
// errors, to prevent all errors from being suppressed
// at once.
continue;
}
if self.error_implies(error2.predicate, error.predicate)
&& !(error2.index >= error.index
&& self.error_implies(error.predicate, error2.predicate))
{
info!("skipping {:?} (implied by {:?})", error, error2);
is_suppressed[index] = true;
break;
}
}
}
}
}
for (error, suppressed) in iter::zip(errors, is_suppressed) {
if !suppressed {
self.report_fulfillment_error(error, body_id);
}
}
self.tcx.sess.delay_span_bug(DUMMY_SP, "expected fullfillment errors")
}
/// Reports that an overflow has occurred and halts compilation. We
/// halt compilation unconditionally because it is important that
/// overflows never be masked -- they basically represent computations
/// whose result could not be truly determined and thus we can't say
/// if the program type checks or not -- and they are unusual
/// occurrences in any case.
fn report_overflow_error<T>(
&self,
predicate: &T,
span: Span,
suggest_increasing_limit: bool,
mutate: impl FnOnce(&mut Diagnostic),
) -> !
where
T: fmt::Display
+ TypeFoldable<'tcx>
+ Print<'tcx, FmtPrinter<'tcx, 'tcx>, Output = FmtPrinter<'tcx, 'tcx>>,
<T as Print<'tcx, FmtPrinter<'tcx, 'tcx>>>::Error: std::fmt::Debug,
{
let predicate = self.resolve_vars_if_possible(predicate.clone());
let mut pred_str = predicate.to_string();
if pred_str.len() > 50 {
// We don't need to save the type to a file, we will be talking about this type already
// in a separate note when we explain the obligation, so it will be available that way.
pred_str = predicate
.print(FmtPrinter::new_with_limit(
self.tcx,
Namespace::TypeNS,
rustc_session::Limit(6),
))
.unwrap()
.into_buffer();
}
let mut err = struct_span_err!(
self.tcx.sess,
span,
E0275,
"overflow evaluating the requirement `{}`",
pred_str,
);
if suggest_increasing_limit {
self.suggest_new_overflow_limit(&mut err);
}
mutate(&mut err);
err.emit();
self.tcx.sess.abort_if_errors();
bug!();
}
/// Reports that an overflow has occurred and halts compilation. We
/// halt compilation unconditionally because it is important that
/// overflows never be masked -- they basically represent computations
/// whose result could not be truly determined and thus we can't say
/// if the program type checks or not -- and they are unusual
/// occurrences in any case.
fn report_overflow_obligation<T>(
&self,
obligation: &Obligation<'tcx, T>,
suggest_increasing_limit: bool,
) -> !
where
T: ToPredicate<'tcx> + Clone,
{
let predicate = obligation.predicate.clone().to_predicate(self.tcx);
let predicate = self.resolve_vars_if_possible(predicate);
self.report_overflow_error(
&predicate,
obligation.cause.span,
suggest_increasing_limit,
|err| {
self.note_obligation_cause_code(
err,
predicate,
obligation.param_env,
obligation.cause.code(),
&mut vec![],
&mut Default::default(),
);
},
);
}
fn suggest_new_overflow_limit(&self, err: &mut Diagnostic) {
let suggested_limit = match self.tcx.recursion_limit() {
Limit(0) => Limit(2),
limit => limit * 2,
};
err.help(&format!(
"consider increasing the recursion limit by adding a \
`#![recursion_limit = \"{}\"]` attribute to your crate (`{}`)",
suggested_limit,
self.tcx.crate_name(LOCAL_CRATE),
));
}
/// Reports that a cycle was detected which led to overflow and halts
/// compilation. This is equivalent to `report_overflow_obligation` except
/// that we can give a more helpful error message (and, in particular,
/// we do not suggest increasing the overflow limit, which is not
/// going to help).
fn report_overflow_obligation_cycle(&self, cycle: &[PredicateObligation<'tcx>]) -> ! {
let cycle = self.resolve_vars_if_possible(cycle.to_owned());
assert!(!cycle.is_empty());
debug!(?cycle, "report_overflow_error_cycle");
// The 'deepest' obligation is most likely to have a useful
// cause 'backtrace'
self.report_overflow_obligation(
cycle.iter().max_by_key(|p| p.recursion_depth).unwrap(),
false,
);
}
fn report_selection_error(
&self,
mut obligation: PredicateObligation<'tcx>,
root_obligation: &PredicateObligation<'tcx>,
error: &SelectionError<'tcx>,
) {
let tcx = self.tcx;
let mut span = obligation.cause.span;
// FIXME: statically guarantee this by tainting after the diagnostic is emitted
self.set_tainted_by_errors(
tcx.sess.delay_span_bug(span, "`report_selection_error` did not emit an error"),
);
let mut err = match *error {
SelectionError::Unimplemented => {
// If this obligation was generated as a result of well-formedness checking, see if we
// can get a better error message by performing HIR-based well-formedness checking.
if let ObligationCauseCode::WellFormed(Some(wf_loc)) =
root_obligation.cause.code().peel_derives()
&& !obligation.predicate.has_non_region_infer()
{
if let Some(cause) = self
.tcx
.diagnostic_hir_wf_check((tcx.erase_regions(obligation.predicate), *wf_loc))
{
obligation.cause = cause.clone();
span = obligation.cause.span;
}
}
if let ObligationCauseCode::CompareImplItemObligation {
impl_item_def_id,
trait_item_def_id,
kind: _,
} = *obligation.cause.code()
{
self.report_extra_impl_obligation(
span,
impl_item_def_id,
trait_item_def_id,
&format!("`{}`", obligation.predicate),
)
.emit();
return;
}
let bound_predicate = obligation.predicate.kind();
match bound_predicate.skip_binder() {
ty::PredicateKind::Clause(ty::Clause::Trait(trait_predicate)) => {
let trait_predicate = bound_predicate.rebind(trait_predicate);
let mut trait_predicate = self.resolve_vars_if_possible(trait_predicate);
trait_predicate.remap_constness_diag(obligation.param_env);
let predicate_is_const = ty::BoundConstness::ConstIfConst
== trait_predicate.skip_binder().constness;
if self.tcx.sess.has_errors().is_some()
&& trait_predicate.references_error()
{
return;
}
let trait_ref = trait_predicate.to_poly_trait_ref();
let (post_message, pre_message, type_def) = self
.get_parent_trait_ref(obligation.cause.code())
.map(|(t, s)| {
(
format!(" in `{}`", t),
format!("within `{}`, ", t),
s.map(|s| (format!("within this `{}`", t), s)),
)
})
.unwrap_or_default();
let OnUnimplementedNote {
message,
label,
note,
parent_label,
append_const_msg,
} = self.on_unimplemented_note(trait_ref, &obligation);
let have_alt_message = message.is_some() || label.is_some();
let is_try_conversion = self.is_try_conversion(span, trait_ref.def_id());
let is_unsize =
Some(trait_ref.def_id()) == self.tcx.lang_items().unsize_trait();
let (message, note, append_const_msg) = if is_try_conversion {
(
Some(format!(
"`?` couldn't convert the error to `{}`",
trait_ref.skip_binder().self_ty(),
)),
Some(
"the question mark operation (`?`) implicitly performs a \
conversion on the error value using the `From` trait"
.to_owned(),
),
Some(None),
)
} else {
(message, note, append_const_msg)
};
let mut err = struct_span_err!(
self.tcx.sess,
span,
E0277,
"{}",
message
.and_then(|cannot_do_this| {
match (predicate_is_const, append_const_msg) {
// do nothing if predicate is not const
(false, _) => Some(cannot_do_this),
// suggested using default post message
(true, Some(None)) => {
Some(format!("{cannot_do_this} in const contexts"))
}
// overridden post message
(true, Some(Some(post_message))) => {
Some(format!("{cannot_do_this}{post_message}"))
}
// fallback to generic message
(true, None) => None,
}
})
.unwrap_or_else(|| format!(
"the trait bound `{}` is not satisfied{}",
trait_predicate, post_message,
))
);
if is_try_conversion && let Some(ret_span) = self.return_type_span(&obligation) {
err.span_label(
ret_span,
&format!(
"expected `{}` because of this",
trait_ref.skip_binder().self_ty()
),
);
}
if Some(trait_ref.def_id()) == tcx.lang_items().tuple_trait() {
match obligation.cause.code().peel_derives() {
ObligationCauseCode::RustCall => {
err.set_primary_message("functions with the \"rust-call\" ABI must take a single non-self tuple argument");
}
ObligationCauseCode::BindingObligation(def_id, _)
| ObligationCauseCode::ItemObligation(def_id)
if tcx.is_fn_trait(*def_id) =>
{
err.code(rustc_errors::error_code!(E0059));
err.set_primary_message(format!(
"type parameter to bare `{}` trait must be a tuple",
tcx.def_path_str(*def_id)
));
}
_ => {}
}
}
if Some(trait_ref.def_id()) == tcx.lang_items().drop_trait()
&& predicate_is_const
{
err.note("`~const Drop` was renamed to `~const Destruct`");
err.note("See <https://github.com/rust-lang/rust/pull/94901> for more details");
}
let explanation = if let ObligationCauseCode::MainFunctionType =
obligation.cause.code()
{
"consider using `()`, or a `Result`".to_owned()
} else {
let ty_desc = match trait_ref.skip_binder().self_ty().kind() {
ty::FnDef(_, _) => Some("fn item"),
ty::Closure(_, _) => Some("closure"),
_ => None,
};
match ty_desc {
Some(desc) => format!(
"{}the trait `{}` is not implemented for {} `{}`",
pre_message,
trait_predicate.print_modifiers_and_trait_path(),
desc,
trait_ref.skip_binder().self_ty(),
),
None => format!(
"{}the trait `{}` is not implemented for `{}`",
pre_message,
trait_predicate.print_modifiers_and_trait_path(),
trait_ref.skip_binder().self_ty(),
),
}
};
if self.suggest_add_reference_to_arg(
&obligation,
&mut err,
trait_predicate,
have_alt_message,
) {
self.note_obligation_cause(&mut err, &obligation);
err.emit();
return;
}
if let Some(ref s) = label {
// If it has a custom `#[rustc_on_unimplemented]`
// error message, let's display it as the label!
err.span_label(span, s);
if !matches!(trait_ref.skip_binder().self_ty().kind(), ty::Param(_)) {
// When the self type is a type param We don't need to "the trait
// `std::marker::Sized` is not implemented for `T`" as we will point
// at the type param with a label to suggest constraining it.
err.help(&explanation);
}
} else {
err.span_label(span, explanation);
}
if let ObligationCauseCode::ObjectCastObligation(concrete_ty, obj_ty) = obligation.cause.code().peel_derives() &&
Some(trait_ref.def_id()) == self.tcx.lang_items().sized_trait() {
self.suggest_borrowing_for_object_cast(&mut err, &root_obligation, *concrete_ty, *obj_ty);
}
let mut unsatisfied_const = false;
if trait_predicate.is_const_if_const() && obligation.param_env.is_const() {
let non_const_predicate = trait_ref.without_const();
let non_const_obligation = Obligation {
cause: obligation.cause.clone(),
param_env: obligation.param_env.without_const(),
predicate: non_const_predicate.to_predicate(tcx),
recursion_depth: obligation.recursion_depth,
};
if self.predicate_may_hold(&non_const_obligation) {
unsatisfied_const = true;
err.span_note(
span,
&format!(
"the trait `{}` is implemented for `{}`, \
but that implementation is not `const`",
non_const_predicate.print_modifiers_and_trait_path(),
trait_ref.skip_binder().self_ty(),
),
);
}
}
if let Some((msg, span)) = type_def {
err.span_label(span, &msg);
}
if let Some(ref s) = note {
// If it has a custom `#[rustc_on_unimplemented]` note, let's display it
err.note(s.as_str());
}
if let Some(ref s) = parent_label {
let body = tcx
.hir()
.opt_local_def_id(obligation.cause.body_id)
.unwrap_or_else(|| {
tcx.hir().body_owner_def_id(hir::BodyId {
hir_id: obligation.cause.body_id,
})
});
err.span_label(tcx.def_span(body), s);
}
self.suggest_floating_point_literal(&obligation, &mut err, &trait_ref);
self.suggest_dereferencing_index(&obligation, &mut err, trait_predicate);
let mut suggested =
self.suggest_dereferences(&obligation, &mut err, trait_predicate);
suggested |= self.suggest_fn_call(&obligation, &mut err, trait_predicate);
suggested |=
self.suggest_remove_reference(&obligation, &mut err, trait_predicate);
suggested |= self.suggest_semicolon_removal(
&obligation,
&mut err,
span,
trait_predicate,
);
self.note_version_mismatch(&mut err, &trait_ref);
self.suggest_remove_await(&obligation, &mut err);
self.suggest_derive(&obligation, &mut err, trait_predicate);
if Some(trait_ref.def_id()) == tcx.lang_items().try_trait() {
self.suggest_await_before_try(
&mut err,
&obligation,
trait_predicate,
span,
);
}
if self.suggest_impl_trait(&mut err, span, &obligation, trait_predicate) {
err.emit();
return;
}
if is_unsize {
// If the obligation failed due to a missing implementation of the
// `Unsize` trait, give a pointer to why that might be the case
err.note(
"all implementations of `Unsize` are provided \
automatically by the compiler, see \
<https://doc.rust-lang.org/stable/std/marker/trait.Unsize.html> \
for more information",
);
}
let is_fn_trait = tcx.is_fn_trait(trait_ref.def_id());
let is_target_feature_fn = if let ty::FnDef(def_id, _) =
*trait_ref.skip_binder().self_ty().kind()
{
!self.tcx.codegen_fn_attrs(def_id).target_features.is_empty()
} else {
false
};
if is_fn_trait && is_target_feature_fn {
err.note(
"`#[target_feature]` functions do not implement the `Fn` traits",
);
}
// Try to report a help message
if is_fn_trait
&& let Ok((implemented_kind, params)) = self.type_implements_fn_trait(
obligation.param_env,
trait_ref.self_ty(),
trait_predicate.skip_binder().constness,
trait_predicate.skip_binder().polarity,
)
{
// If the type implements `Fn`, `FnMut`, or `FnOnce`, suppress the following
// suggestion to add trait bounds for the type, since we only typically implement
// these traits once.
// Note if the `FnMut` or `FnOnce` is less general than the trait we're trying
// to implement.
let selected_kind =
self.tcx.fn_trait_kind_from_def_id(trait_ref.def_id())
.expect("expected to map DefId to ClosureKind");
if !implemented_kind.extends(selected_kind) {
err.note(
&format!(
"`{}` implements `{}`, but it must implement `{}`, which is more general",
trait_ref.skip_binder().self_ty(),
implemented_kind,
selected_kind
)
);
}
// Note any argument mismatches
let given_ty = params.skip_binder();
let expected_ty = trait_ref.skip_binder().substs.type_at(1);
if let ty::Tuple(given) = given_ty.kind()
&& let ty::Tuple(expected) = expected_ty.kind()
{
if expected.len() != given.len() {
// Note number of types that were expected and given
err.note(
&format!(
"expected a closure taking {} argument{}, but one taking {} argument{} was given",
given.len(),
pluralize!(given.len()),
expected.len(),
pluralize!(expected.len()),
)
);
} else if !self.same_type_modulo_infer(given_ty, expected_ty) {
// Print type mismatch
let (expected_args, given_args) =
self.cmp(given_ty, expected_ty);
err.note_expected_found(
&"a closure with arguments",
expected_args,
&"a closure with arguments",
given_args,
);
}
}
} else if !trait_ref.has_non_region_infer()
&& self.predicate_can_apply(obligation.param_env, trait_predicate)
{
// If a where-clause may be useful, remind the
// user that they can add it.
//
// don't display an on-unimplemented note, as
// these notes will often be of the form
// "the type `T` can't be frobnicated"
// which is somewhat confusing.
self.suggest_restricting_param_bound(
&mut err,
trait_predicate,
None,
obligation.cause.body_id,
);
} else if !suggested && !unsatisfied_const {
// Can't show anything else useful, try to find similar impls.
let impl_candidates = self.find_similar_impl_candidates(trait_predicate);
if !self.report_similar_impl_candidates(
impl_candidates,
trait_ref,
obligation.cause.body_id,
&mut err,
true,
) {
// This is *almost* equivalent to
// `obligation.cause.code().peel_derives()`, but it gives us the
// trait predicate for that corresponding root obligation. This
// lets us get a derived obligation from a type parameter, like
// when calling `string.strip_suffix(p)` where `p` is *not* an
// implementer of `Pattern<'_>`.
let mut code = obligation.cause.code();
let mut trait_pred = trait_predicate;
let mut peeled = false;
while let Some((parent_code, parent_trait_pred)) = code.parent() {
code = parent_code;
if let Some(parent_trait_pred) = parent_trait_pred {
trait_pred = parent_trait_pred;
peeled = true;
}
}