1use std::iter;
2
3use GenericArgsInfo::*;
4use rustc_errors::codes::*;
5use rustc_errors::{Applicability, Diag, Diagnostic, EmissionGuarantee, MultiSpan, pluralize};
6use rustc_hir as hir;
7use rustc_middle::ty::{self as ty, AssocItems, AssocKind, TyCtxt};
8use rustc_span::def_id::DefId;
9use tracing::debug;
10
11pub(crate) struct WrongNumberOfGenericArgs<'a, 'tcx> {
13 pub(crate) tcx: TyCtxt<'tcx>,
14
15 pub(crate) angle_brackets: AngleBrackets,
16
17 pub(crate) gen_args_info: GenericArgsInfo,
18
19 pub(crate) path_segment: &'a hir::PathSegment<'a>,
21
22 pub(crate) gen_params: &'a ty::Generics,
24
25 pub(crate) params_offset: usize,
29
30 pub(crate) gen_args: &'a hir::GenericArgs<'a>,
32
33 pub(crate) def_id: DefId,
35}
36
37#[derive(Debug)]
40pub(crate) enum AngleBrackets {
41 Implied,
43
44 Missing,
46
47 Available,
49}
50
51#[derive(Debug)]
53pub(crate) enum GenericArgsInfo {
54 MissingLifetimes {
55 num_missing_args: usize,
56 },
57 ExcessLifetimes {
58 num_redundant_args: usize,
59 },
60 MissingTypesOrConsts {
61 num_missing_args: usize,
62
63 num_default_params: usize,
65
66 args_offset: usize,
71 },
72
73 ExcessTypesOrConsts {
74 num_redundant_args: usize,
75
76 num_default_params: usize,
78
79 args_offset: usize,
84
85 synth_provided: bool,
87 },
88}
89
90impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
91 pub(crate) fn new(
92 tcx: TyCtxt<'tcx>,
93 gen_args_info: GenericArgsInfo,
94 path_segment: &'a hir::PathSegment<'_>,
95 gen_params: &'a ty::Generics,
96 params_offset: usize,
97 gen_args: &'a hir::GenericArgs<'a>,
98 def_id: DefId,
99 ) -> Self {
100 let angle_brackets = if gen_args.span_ext().is_none() {
101 if gen_args.is_empty() { AngleBrackets::Missing } else { AngleBrackets::Implied }
102 } else {
103 AngleBrackets::Available
104 };
105
106 Self {
107 tcx,
108 angle_brackets,
109 gen_args_info,
110 path_segment,
111 gen_params,
112 params_offset,
113 gen_args,
114 def_id,
115 }
116 }
117
118 fn missing_lifetimes(&self) -> bool {
119 match self.gen_args_info {
120 MissingLifetimes { .. } | ExcessLifetimes { .. } => true,
121 MissingTypesOrConsts { .. } | ExcessTypesOrConsts { .. } => false,
122 }
123 }
124
125 fn kind(&self) -> &str {
126 if self.missing_lifetimes() { "lifetime" } else { "generic" }
127 }
128
129 fn is_in_trait_impl(&self) -> bool {
132 if self.tcx.is_trait(self.def_id) {
133 let parent = self.tcx.parent_hir_node(self.path_segment.hir_id);
137 let parent_item = self
138 .tcx
139 .hir_node_by_def_id(self.tcx.hir_get_parent_item(self.path_segment.hir_id).def_id);
140
141 let hir::Node::TraitRef(hir::TraitRef { hir_ref_id: trait_ref_id, .. }) = parent else {
143 return false;
144 };
145
146 let hir::Node::Item(hir::Item {
148 kind:
149 hir::ItemKind::Impl(hir::Impl {
150 of_trait: Some(hir::TraitRef { hir_ref_id: id_in_of_trait, .. }),
151 ..
152 }),
153 ..
154 }) = parent_item
155 else {
156 return false;
157 };
158
159 trait_ref_id == id_in_of_trait
161 } else {
162 false
163 }
164 }
165
166 fn num_provided_args(&self) -> usize {
167 if self.missing_lifetimes() {
168 self.num_provided_lifetime_args()
169 } else {
170 self.num_provided_type_or_const_args()
171 }
172 }
173
174 fn num_provided_lifetime_args(&self) -> usize {
175 match self.angle_brackets {
176 AngleBrackets::Missing => 0,
177 AngleBrackets::Implied => self.gen_args.args.len(),
179 AngleBrackets::Available => self.gen_args.num_lifetime_params(),
180 }
181 }
182
183 fn num_provided_type_or_const_args(&self) -> usize {
184 match self.angle_brackets {
185 AngleBrackets::Missing => 0,
186 AngleBrackets::Implied => 0,
188 AngleBrackets::Available => self.gen_args.num_generic_params(),
189 }
190 }
191
192 fn num_expected_lifetime_args(&self) -> usize {
193 let num_provided_args = self.num_provided_lifetime_args();
194 match self.gen_args_info {
195 MissingLifetimes { num_missing_args } => num_provided_args + num_missing_args,
196 ExcessLifetimes { num_redundant_args } => num_provided_args - num_redundant_args,
197 _ => 0,
198 }
199 }
200
201 fn num_expected_type_or_const_args(&self) -> usize {
202 let num_provided_args = self.num_provided_type_or_const_args();
203 match self.gen_args_info {
204 MissingTypesOrConsts { num_missing_args, .. } => num_provided_args + num_missing_args,
205 ExcessTypesOrConsts { num_redundant_args, .. } => {
206 num_provided_args - num_redundant_args
207 }
208 _ => 0,
209 }
210 }
211
212 fn num_expected_type_or_const_args_including_defaults(&self) -> usize {
214 let provided_args = self.num_provided_type_or_const_args();
215 match self.gen_args_info {
216 MissingTypesOrConsts { num_missing_args, num_default_params, .. } => {
217 provided_args + num_missing_args - num_default_params
218 }
219 ExcessTypesOrConsts { num_redundant_args, num_default_params, .. } => {
220 provided_args - num_redundant_args - num_default_params
221 }
222 _ => 0,
223 }
224 }
225
226 fn num_missing_lifetime_args(&self) -> usize {
227 let missing_args = self.num_expected_lifetime_args() - self.num_provided_lifetime_args();
228 assert!(missing_args > 0);
229 missing_args
230 }
231
232 fn num_missing_type_or_const_args(&self) -> usize {
233 let missing_args = self.num_expected_type_or_const_args_including_defaults()
234 - self.num_provided_type_or_const_args();
235 assert!(missing_args > 0);
236 missing_args
237 }
238
239 fn num_excess_lifetime_args(&self) -> usize {
240 match self.gen_args_info {
241 ExcessLifetimes { num_redundant_args } => num_redundant_args,
242 _ => 0,
243 }
244 }
245
246 fn num_excess_type_or_const_args(&self) -> usize {
247 match self.gen_args_info {
248 ExcessTypesOrConsts { num_redundant_args, .. } => num_redundant_args,
249 _ => 0,
250 }
251 }
252
253 fn too_many_args_provided(&self) -> bool {
254 match self.gen_args_info {
255 MissingLifetimes { .. } | MissingTypesOrConsts { .. } => false,
256 ExcessLifetimes { num_redundant_args }
257 | ExcessTypesOrConsts { num_redundant_args, .. } => {
258 assert!(num_redundant_args > 0);
259 true
260 }
261 }
262 }
263
264 fn not_enough_args_provided(&self) -> bool {
265 match self.gen_args_info {
266 MissingLifetimes { num_missing_args }
267 | MissingTypesOrConsts { num_missing_args, .. } => {
268 assert!(num_missing_args > 0);
269 true
270 }
271 ExcessLifetimes { .. } | ExcessTypesOrConsts { .. } => false,
272 }
273 }
274
275 fn get_lifetime_args_offset(&self) -> usize {
278 match self.gen_args_info {
279 MissingLifetimes { .. } | ExcessLifetimes { .. } => 0,
280 MissingTypesOrConsts { args_offset, .. } | ExcessTypesOrConsts { args_offset, .. } => {
281 args_offset
282 }
283 }
284 }
285
286 fn get_num_default_params(&self) -> usize {
287 match self.gen_args_info {
288 MissingTypesOrConsts { num_default_params, .. }
289 | ExcessTypesOrConsts { num_default_params, .. } => num_default_params,
290 _ => 0,
291 }
292 }
293
294 fn is_synth_provided(&self) -> bool {
295 match self.gen_args_info {
296 ExcessTypesOrConsts { synth_provided, .. } => synth_provided,
297 _ => false,
298 }
299 }
300
301 fn get_quantifier_and_bound(&self) -> (&'static str, usize) {
304 if self.get_num_default_params() == 0 {
305 match self.gen_args_info {
306 MissingLifetimes { .. } | ExcessLifetimes { .. } => {
307 ("", self.num_expected_lifetime_args())
308 }
309 MissingTypesOrConsts { .. } | ExcessTypesOrConsts { .. } => {
310 ("", self.num_expected_type_or_const_args())
311 }
312 }
313 } else {
314 match self.gen_args_info {
315 MissingLifetimes { .. } => ("at least ", self.num_expected_lifetime_args()),
316 MissingTypesOrConsts { .. } => {
317 ("at least ", self.num_expected_type_or_const_args_including_defaults())
318 }
319 ExcessLifetimes { .. } => ("at most ", self.num_expected_lifetime_args()),
320 ExcessTypesOrConsts { .. } => ("at most ", self.num_expected_type_or_const_args()),
321 }
322 }
323 }
324
325 fn get_lifetime_args_suggestions_from_param_names(
327 &self,
328 path_hir_id: hir::HirId,
329 num_params_to_take: usize,
330 ) -> String {
331 debug!(?path_hir_id);
332
333 if let Some(lt) = self.gen_args.args.iter().find_map(|arg| match arg {
335 hir::GenericArg::Lifetime(lt) => Some(lt),
336 _ => None,
337 }) {
338 return std::iter::repeat(lt.to_string())
339 .take(num_params_to_take)
340 .collect::<Vec<_>>()
341 .join(", ");
342 }
343
344 let mut ret = Vec::new();
345 let mut ty_id = None;
346 for (id, node) in self.tcx.hir_parent_iter(path_hir_id) {
347 debug!(?id);
348 if let hir::Node::Ty(_) = node {
349 ty_id = Some(id);
350 }
351
352 if let Some(fn_decl) = node.fn_decl()
354 && let Some(ty_id) = ty_id
355 {
356 let in_arg = fn_decl.inputs.iter().any(|t| t.hir_id == ty_id);
357 let in_ret =
358 matches!(fn_decl.output, hir::FnRetTy::Return(ty) if ty.hir_id == ty_id);
359
360 if in_arg || (in_ret && fn_decl.lifetime_elision_allowed) {
361 return std::iter::repeat("'_".to_owned())
362 .take(num_params_to_take)
363 .collect::<Vec<_>>()
364 .join(", ");
365 }
366 }
367
368 if let hir::Node::Item(hir::Item {
370 kind: hir::ItemKind::Static { .. } | hir::ItemKind::Const { .. },
371 ..
372 })
373 | hir::Node::TraitItem(hir::TraitItem {
374 kind: hir::TraitItemKind::Const { .. },
375 ..
376 })
377 | hir::Node::ImplItem(hir::ImplItem {
378 kind: hir::ImplItemKind::Const { .. },
379 ..
380 })
381 | hir::Node::ForeignItem(hir::ForeignItem {
382 kind: hir::ForeignItemKind::Static { .. },
383 ..
384 })
385 | hir::Node::AnonConst(..) = node
386 {
387 return std::iter::repeat("'static".to_owned())
388 .take(num_params_to_take.saturating_sub(ret.len()))
389 .collect::<Vec<_>>()
390 .join(", ");
391 }
392
393 let params = if let Some(generics) = node.generics() {
394 generics.params
395 } else if let hir::Node::Ty(ty) = node
396 && let hir::TyKind::BareFn(bare_fn) = ty.kind
397 {
398 bare_fn.generic_params
399 } else {
400 &[]
401 };
402 ret.extend(params.iter().filter_map(|p| {
403 let hir::GenericParamKind::Lifetime { kind: hir::LifetimeParamKind::Explicit } =
404 p.kind
405 else {
406 return None;
407 };
408 let hir::ParamName::Plain(name) = p.name else { return None };
409 Some(name.to_string())
410 }));
411
412 if ret.len() >= num_params_to_take {
413 return ret[..num_params_to_take].join(", ");
414 }
415 if let hir::Node::Item(_) = node {
417 break;
418 }
419 }
420
421 self.gen_params
424 .own_params
425 .iter()
426 .skip(self.params_offset + self.num_provided_lifetime_args())
427 .take(num_params_to_take)
428 .map(|param| param.name.to_string())
429 .collect::<Vec<_>>()
430 .join(", ")
431 }
432
433 fn get_type_or_const_args_suggestions_from_param_names(
435 &self,
436 num_params_to_take: usize,
437 ) -> String {
438 let is_in_a_method_call = self
439 .tcx
440 .hir_parent_iter(self.path_segment.hir_id)
441 .skip(1)
442 .find_map(|(_, node)| match node {
443 hir::Node::Expr(expr) => Some(expr),
444 _ => None,
445 })
446 .is_some_and(|expr| {
447 matches!(
448 expr.kind,
449 hir::ExprKind::MethodCall(hir::PathSegment { args: Some(_), .. }, ..)
450 )
451 });
452
453 let fn_sig = self.tcx.hir_get_if_local(self.def_id).and_then(hir::Node::fn_sig);
454 let is_used_in_input = |def_id| {
455 fn_sig.is_some_and(|fn_sig| {
456 fn_sig.decl.inputs.iter().any(|ty| match ty.kind {
457 hir::TyKind::Path(hir::QPath::Resolved(
458 None,
459 hir::Path { res: hir::def::Res::Def(_, id), .. },
460 )) => *id == def_id,
461 _ => false,
462 })
463 })
464 };
465 self.gen_params
466 .own_params
467 .iter()
468 .skip(self.params_offset + self.num_provided_type_or_const_args())
469 .take(num_params_to_take)
470 .map(|param| match param.kind {
471 ty::GenericParamDefKind::Type { .. }
474 if is_in_a_method_call || is_used_in_input(param.def_id) =>
475 {
476 "_"
477 }
478 _ => param.name.as_str(),
479 })
480 .intersperse(", ")
481 .collect()
482 }
483
484 fn get_unbound_associated_types(&self) -> Vec<String> {
485 if self.tcx.is_trait(self.def_id) {
486 let items: &AssocItems = self.tcx.associated_items(self.def_id);
487 items
488 .in_definition_order()
489 .filter(|item| item.kind == AssocKind::Type)
490 .filter(|item| {
491 !self
492 .gen_args
493 .constraints
494 .iter()
495 .any(|constraint| constraint.ident.name == item.name)
496 })
497 .filter(|item| !item.is_impl_trait_in_trait())
498 .map(|item| self.tcx.item_ident(item.def_id).to_string())
499 .collect()
500 } else {
501 Vec::default()
502 }
503 }
504
505 fn create_error_message(&self) -> String {
506 let def_path = self.tcx.def_path_str(self.def_id);
507 let def_kind = self.tcx.def_descr(self.def_id);
508 let (quantifier, bound) = self.get_quantifier_and_bound();
509 let kind = self.kind();
510 let provided_lt_args = self.num_provided_lifetime_args();
511 let provided_type_or_const_args = self.num_provided_type_or_const_args();
512
513 let (provided_args_str, verb) = match self.gen_args_info {
514 MissingLifetimes { .. } | ExcessLifetimes { .. } => (
515 format!("{} lifetime argument{}", provided_lt_args, pluralize!(provided_lt_args)),
516 pluralize!("was", provided_lt_args),
517 ),
518 MissingTypesOrConsts { .. } | ExcessTypesOrConsts { .. } => (
519 format!(
520 "{} generic argument{}",
521 provided_type_or_const_args,
522 pluralize!(provided_type_or_const_args)
523 ),
524 pluralize!("was", provided_type_or_const_args),
525 ),
526 };
527
528 if self.gen_args.span_ext().is_some() {
529 format!(
530 "{} takes {}{} {} argument{} but {} {} supplied",
531 def_kind,
532 quantifier,
533 bound,
534 kind,
535 pluralize!(bound),
536 provided_args_str.as_str(),
537 verb
538 )
539 } else {
540 format!("missing generics for {def_kind} `{def_path}`")
541 }
542 }
543
544 fn notify(&self, err: &mut Diag<'_, impl EmissionGuarantee>) {
546 let (quantifier, bound) = self.get_quantifier_and_bound();
547 let provided_args = self.num_provided_args();
548
549 err.span_label(
550 self.path_segment.ident.span,
551 format!(
552 "expected {}{} {} argument{}",
553 quantifier,
554 bound,
555 self.kind(),
556 pluralize!(bound),
557 ),
558 );
559
560 if self.too_many_args_provided() {
569 return;
570 }
571
572 let args = self
573 .gen_args
574 .args
575 .iter()
576 .skip(self.get_lifetime_args_offset())
577 .take(provided_args)
578 .enumerate();
579
580 for (i, arg) in args {
581 err.span_label(
582 arg.span(),
583 if i + 1 == provided_args {
584 format!(
585 "supplied {} {} argument{}",
586 provided_args,
587 self.kind(),
588 pluralize!(provided_args)
589 )
590 } else {
591 String::new()
592 },
593 );
594 }
595 }
596
597 fn suggest(&self, err: &mut Diag<'_, impl EmissionGuarantee>) {
598 debug!(
599 "suggest(self.provided {:?}, self.gen_args.span(): {:?})",
600 self.num_provided_args(),
601 self.gen_args.span(),
602 );
603
604 match self.angle_brackets {
605 AngleBrackets::Missing | AngleBrackets::Implied => self.suggest_adding_args(err),
606 AngleBrackets::Available => {
607 if self.not_enough_args_provided() {
608 self.suggest_adding_args(err);
609 } else if self.too_many_args_provided() {
610 self.suggest_moving_args_from_assoc_fn_to_trait(err);
611 self.suggest_removing_args_or_generics(err);
612 } else {
613 unreachable!();
614 }
615 }
616 }
617 }
618
619 fn suggest_adding_args(&self, err: &mut Diag<'_, impl EmissionGuarantee>) {
626 if self.gen_args.parenthesized != hir::GenericArgsParentheses::No {
627 return;
628 }
629
630 match self.gen_args_info {
631 MissingLifetimes { .. } => {
632 self.suggest_adding_lifetime_args(err);
633 }
634 MissingTypesOrConsts { .. } => {
635 self.suggest_adding_type_and_const_args(err);
636 }
637 ExcessTypesOrConsts { .. } => {
638 }
640 _ => unreachable!(),
641 }
642 }
643
644 fn suggest_adding_lifetime_args(&self, err: &mut Diag<'_, impl EmissionGuarantee>) {
645 debug!("suggest_adding_lifetime_args(path_segment: {:?})", self.path_segment);
646 let num_missing_args = self.num_missing_lifetime_args();
647 let num_params_to_take = num_missing_args;
648 let msg = format!("add missing {} argument{}", self.kind(), pluralize!(num_missing_args));
649
650 let suggested_args = self.get_lifetime_args_suggestions_from_param_names(
651 self.path_segment.hir_id,
652 num_params_to_take,
653 );
654 debug!("suggested_args: {suggested_args:?}");
655
656 match self.angle_brackets {
657 AngleBrackets::Missing => {
658 let span = self.path_segment.ident.span;
659
660 let sugg = format!("<{suggested_args}>");
662 debug!("sugg: {:?}", sugg);
663
664 err.span_suggestion_verbose(
665 span.shrink_to_hi(),
666 msg,
667 sugg,
668 Applicability::HasPlaceholders,
669 );
670 }
671
672 AngleBrackets::Available => {
673 let (sugg_span, is_first) = if self.num_provided_lifetime_args() == 0 {
674 (self.gen_args.span().unwrap().shrink_to_lo(), true)
675 } else {
676 let last_lt = &self.gen_args.args[self.num_provided_lifetime_args() - 1];
677 (last_lt.span().shrink_to_hi(), false)
678 };
679 let has_non_lt_args = self.num_provided_type_or_const_args() != 0;
680 let has_constraints = !self.gen_args.constraints.is_empty();
681
682 let sugg_prefix = if is_first { "" } else { ", " };
683 let sugg_suffix =
684 if is_first && (has_non_lt_args || has_constraints) { ", " } else { "" };
685
686 let sugg = format!("{sugg_prefix}{suggested_args}{sugg_suffix}");
687 debug!("sugg: {:?}", sugg);
688
689 err.span_suggestion_verbose(sugg_span, msg, sugg, Applicability::HasPlaceholders);
690 }
691 AngleBrackets::Implied => {
692 unreachable!();
694 }
695 }
696 }
697
698 fn suggest_adding_type_and_const_args(&self, err: &mut Diag<'_, impl EmissionGuarantee>) {
699 let num_missing_args = self.num_missing_type_or_const_args();
700 let msg = format!("add missing {} argument{}", self.kind(), pluralize!(num_missing_args));
701
702 let suggested_args =
703 self.get_type_or_const_args_suggestions_from_param_names(num_missing_args);
704 debug!("suggested_args: {:?}", suggested_args);
705
706 match self.angle_brackets {
707 AngleBrackets::Missing | AngleBrackets::Implied => {
708 let span = self.path_segment.ident.span;
709
710 let sugg = format!("<{suggested_args}>");
712 debug!("sugg: {:?}", sugg);
713
714 err.span_suggestion_verbose(
715 span.shrink_to_hi(),
716 msg,
717 sugg,
718 Applicability::HasPlaceholders,
719 );
720 }
721 AngleBrackets::Available => {
722 let gen_args_span = self.gen_args.span().unwrap();
723 let sugg_offset =
724 self.get_lifetime_args_offset() + self.num_provided_type_or_const_args();
725
726 let (sugg_span, is_first) = if sugg_offset == 0 {
727 (gen_args_span.shrink_to_lo(), true)
728 } else {
729 let arg_span = self.gen_args.args[sugg_offset - 1].span();
730 (arg_span.shrink_to_hi(), arg_span.hi() <= gen_args_span.lo())
738 };
739
740 let sugg_prefix = if is_first { "" } else { ", " };
741 let sugg_suffix =
742 if is_first && !self.gen_args.constraints.is_empty() { ", " } else { "" };
743
744 let sugg = format!("{sugg_prefix}{suggested_args}{sugg_suffix}");
745 debug!("sugg: {:?}", sugg);
746
747 err.span_suggestion_verbose(sugg_span, msg, sugg, Applicability::HasPlaceholders);
748 }
749 }
750 }
751
752 fn suggest_moving_args_from_assoc_fn_to_trait(
759 &self,
760 err: &mut Diag<'_, impl EmissionGuarantee>,
761 ) {
762 let trait_ = match self.tcx.trait_of_item(self.def_id) {
763 Some(def_id) => def_id,
764 None => return,
765 };
766
767 let num_assoc_fn_expected_args =
771 self.num_expected_type_or_const_args() + self.num_expected_lifetime_args();
772 if num_assoc_fn_expected_args > 0 {
773 return;
774 }
775
776 let num_assoc_fn_excess_args =
777 self.num_excess_type_or_const_args() + self.num_excess_lifetime_args();
778
779 let trait_generics = self.tcx.generics_of(trait_);
780 let num_trait_generics_except_self =
781 trait_generics.count() - if trait_generics.has_self { 1 } else { 0 };
782
783 let msg = format!(
784 "consider moving {these} generic argument{s} to the `{name}` trait, which takes up to {num} argument{s}",
785 these = pluralize!("this", num_assoc_fn_excess_args),
786 s = pluralize!(num_assoc_fn_excess_args),
787 name = self.tcx.item_name(trait_),
788 num = num_trait_generics_except_self,
789 );
790
791 if let hir::Node::Expr(expr) = self.tcx.parent_hir_node(self.path_segment.hir_id) {
792 match &expr.kind {
793 hir::ExprKind::Path(qpath) => self
794 .suggest_moving_args_from_assoc_fn_to_trait_for_qualified_path(
795 err,
796 qpath,
797 msg,
798 num_assoc_fn_excess_args,
799 num_trait_generics_except_self,
800 ),
801 hir::ExprKind::MethodCall(..) => self
802 .suggest_moving_args_from_assoc_fn_to_trait_for_method_call(
803 err,
804 trait_,
805 expr,
806 msg,
807 num_assoc_fn_excess_args,
808 num_trait_generics_except_self,
809 ),
810 _ => return,
811 }
812 }
813 }
814
815 fn suggest_moving_args_from_assoc_fn_to_trait_for_qualified_path(
816 &self,
817 err: &mut Diag<'_, impl EmissionGuarantee>,
818 qpath: &'tcx hir::QPath<'tcx>,
819 msg: String,
820 num_assoc_fn_excess_args: usize,
821 num_trait_generics_except_self: usize,
822 ) {
823 if let hir::QPath::Resolved(_, path) = qpath
824 && let Some(trait_path_segment) = path.segments.get(0)
825 {
826 let num_generic_args_supplied_to_trait = trait_path_segment.args().num_generic_params();
827
828 if num_generic_args_supplied_to_trait + num_assoc_fn_excess_args
829 == num_trait_generics_except_self
830 && let Some(span) = self.gen_args.span_ext()
831 && let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span)
832 {
833 let sugg = vec![
834 (
835 self.path_segment.ident.span,
836 format!("{}::{}", snippet, self.path_segment.ident),
837 ),
838 (span.with_lo(self.path_segment.ident.span.hi()), "".to_owned()),
839 ];
840
841 err.multipart_suggestion(msg, sugg, Applicability::MaybeIncorrect);
842 }
843 }
844 }
845
846 fn suggest_moving_args_from_assoc_fn_to_trait_for_method_call(
847 &self,
848 err: &mut Diag<'_, impl EmissionGuarantee>,
849 trait_def_id: DefId,
850 expr: &'tcx hir::Expr<'tcx>,
851 msg: String,
852 num_assoc_fn_excess_args: usize,
853 num_trait_generics_except_self: usize,
854 ) {
855 let sm = self.tcx.sess.source_map();
856 let hir::ExprKind::MethodCall(_, rcvr, args, _) = expr.kind else {
857 return;
858 };
859 if num_assoc_fn_excess_args != num_trait_generics_except_self {
860 return;
861 }
862 let Some(gen_args) = self.gen_args.span_ext() else {
863 return;
864 };
865 let Ok(generics) = sm.span_to_snippet(gen_args) else {
866 return;
867 };
868 let Ok(rcvr) =
869 sm.span_to_snippet(rcvr.span.find_ancestor_inside(expr.span).unwrap_or(rcvr.span))
870 else {
871 return;
872 };
873 let Ok(rest) = (match args {
874 [] => Ok(String::new()),
875 [arg] => {
876 sm.span_to_snippet(arg.span.find_ancestor_inside(expr.span).unwrap_or(arg.span))
877 }
878 [first, .., last] => {
879 let first_span = first.span.find_ancestor_inside(expr.span).unwrap_or(first.span);
880 let last_span = last.span.find_ancestor_inside(expr.span).unwrap_or(last.span);
881 sm.span_to_snippet(first_span.to(last_span))
882 }
883 }) else {
884 return;
885 };
886 let comma = if args.len() > 0 { ", " } else { "" };
887 let trait_path = self.tcx.def_path_str(trait_def_id);
888 let method_name = self.tcx.item_name(self.def_id);
889 err.span_suggestion_verbose(
890 expr.span,
891 msg,
892 format!("{trait_path}::{generics}::{method_name}({rcvr}{comma}{rest})"),
893 Applicability::MaybeIncorrect,
894 );
895 }
896
897 fn suggest_removing_args_or_generics(&self, err: &mut Diag<'_, impl EmissionGuarantee>) {
903 let num_provided_lt_args = self.num_provided_lifetime_args();
904 let num_provided_type_const_args = self.num_provided_type_or_const_args();
905 let unbound_types = self.get_unbound_associated_types();
906 let num_provided_args = num_provided_lt_args + num_provided_type_const_args;
907 assert!(num_provided_args > 0);
908
909 let num_redundant_lt_args = self.num_excess_lifetime_args();
910 let num_redundant_type_or_const_args = self.num_excess_type_or_const_args();
911 let num_redundant_args = num_redundant_lt_args + num_redundant_type_or_const_args;
912
913 let redundant_lifetime_args = num_redundant_lt_args > 0;
914 let redundant_type_or_const_args = num_redundant_type_or_const_args > 0;
915
916 let remove_entire_generics = num_redundant_args >= self.gen_args.args.len();
917 let provided_args_matches_unbound_traits =
918 unbound_types.len() == num_redundant_type_or_const_args;
919
920 let remove_lifetime_args = |err: &mut Diag<'_, _>| {
921 let mut lt_arg_spans = Vec::new();
922 let mut found_redundant = false;
923 for arg in self.gen_args.args {
924 if let hir::GenericArg::Lifetime(_) = arg {
925 lt_arg_spans.push(arg.span());
926 if lt_arg_spans.len() > self.num_expected_lifetime_args() {
927 found_redundant = true;
928 }
929 } else if found_redundant {
930 break;
937 }
938 }
939
940 let span_lo_redundant_lt_args = if self.num_expected_lifetime_args() == 0 {
941 lt_arg_spans[0]
942 } else {
943 lt_arg_spans[self.num_expected_lifetime_args() - 1]
944 };
945 let span_hi_redundant_lt_args = lt_arg_spans[lt_arg_spans.len() - 1];
946
947 let span_redundant_lt_args =
948 span_lo_redundant_lt_args.shrink_to_hi().to(span_hi_redundant_lt_args);
949 debug!("span_redundant_lt_args: {:?}", span_redundant_lt_args);
950
951 let num_redundant_lt_args = lt_arg_spans.len() - self.num_expected_lifetime_args();
952 let msg_lifetimes =
953 format!("remove the lifetime argument{s}", s = pluralize!(num_redundant_lt_args));
954
955 err.span_suggestion(
956 span_redundant_lt_args,
957 msg_lifetimes,
958 "",
959 Applicability::MaybeIncorrect,
960 );
961 };
962
963 let remove_type_or_const_args = |err: &mut Diag<'_, _>| {
964 let mut gen_arg_spans = Vec::new();
965 let mut found_redundant = false;
966 for arg in self.gen_args.args {
967 match arg {
968 hir::GenericArg::Type(_)
969 | hir::GenericArg::Const(_)
970 | hir::GenericArg::Infer(_) => {
971 gen_arg_spans.push(arg.span());
972 if gen_arg_spans.len() > self.num_expected_type_or_const_args() {
973 found_redundant = true;
974 }
975 }
976 _ if found_redundant => break,
977 _ => {}
978 }
979 }
980
981 let span_lo_redundant_type_or_const_args =
982 if self.num_expected_type_or_const_args() == 0 {
983 gen_arg_spans[0]
984 } else {
985 gen_arg_spans[self.num_expected_type_or_const_args() - 1]
986 };
987 let span_hi_redundant_type_or_const_args = gen_arg_spans[gen_arg_spans.len() - 1];
988 let span_redundant_type_or_const_args = span_lo_redundant_type_or_const_args
989 .shrink_to_hi()
990 .to(span_hi_redundant_type_or_const_args);
991
992 debug!("span_redundant_type_or_const_args: {:?}", span_redundant_type_or_const_args);
993
994 let num_redundant_gen_args =
995 gen_arg_spans.len() - self.num_expected_type_or_const_args();
996 let msg_types_or_consts = format!(
997 "remove the unnecessary generic argument{s}",
998 s = pluralize!(num_redundant_gen_args),
999 );
1000
1001 err.span_suggestion(
1002 span_redundant_type_or_const_args,
1003 msg_types_or_consts,
1004 "",
1005 Applicability::MaybeIncorrect,
1006 );
1007 };
1008
1009 if provided_args_matches_unbound_traits && !unbound_types.is_empty() {
1012 if !self.is_in_trait_impl() {
1015 let unused_generics = &self.gen_args.args[self.num_expected_type_or_const_args()..];
1016 let suggestions = iter::zip(unused_generics, &unbound_types)
1017 .map(|(potential, name)| {
1018 (potential.span().shrink_to_lo(), format!("{name} = "))
1019 })
1020 .collect::<Vec<_>>();
1021
1022 if !suggestions.is_empty() {
1023 err.multipart_suggestion_verbose(
1024 format!(
1025 "replace the generic bound{s} with the associated type{s}",
1026 s = pluralize!(unbound_types.len())
1027 ),
1028 suggestions,
1029 Applicability::MaybeIncorrect,
1030 );
1031 }
1032 }
1033 } else if remove_entire_generics {
1034 let span = self
1035 .path_segment
1036 .args
1037 .unwrap()
1038 .span_ext()
1039 .unwrap()
1040 .with_lo(self.path_segment.ident.span.hi());
1041
1042 let msg = format!(
1043 "remove the unnecessary {}generics",
1044 if self.gen_args.parenthesized == hir::GenericArgsParentheses::ParenSugar {
1045 "parenthetical "
1046 } else {
1047 ""
1048 },
1049 );
1050
1051 if span.is_empty() {
1052 } else {
1061 err.span_suggestion(span, msg, "", Applicability::MaybeIncorrect);
1062 }
1063 } else if redundant_lifetime_args && redundant_type_or_const_args {
1064 remove_lifetime_args(err);
1065 remove_type_or_const_args(err);
1066 } else if redundant_lifetime_args {
1067 remove_lifetime_args(err);
1068 } else {
1069 assert!(redundant_type_or_const_args);
1070 remove_type_or_const_args(err);
1071 }
1072 }
1073
1074 fn show_definition(&self, err: &mut Diag<'_, impl EmissionGuarantee>) {
1076 let mut spans: MultiSpan = if let Some(def_span) = self.tcx.def_ident_span(self.def_id) {
1077 if self.tcx.sess.source_map().is_span_accessible(def_span) {
1078 def_span.into()
1079 } else {
1080 return;
1081 }
1082 } else {
1083 return;
1084 };
1085
1086 let msg = {
1087 let def_kind = self.tcx.def_descr(self.def_id);
1088 let (quantifier, bound) = self.get_quantifier_and_bound();
1089
1090 let params = if bound == 0 {
1091 String::new()
1092 } else {
1093 let params = self
1094 .gen_params
1095 .own_params
1096 .iter()
1097 .skip(self.params_offset)
1098 .take(bound)
1099 .map(|param| {
1100 let span = self.tcx.def_span(param.def_id);
1101 spans.push_span_label(span, "");
1102 param
1103 })
1104 .map(|param| format!("`{}`", param.name))
1105 .collect::<Vec<_>>()
1106 .join(", ");
1107
1108 format!(": {params}")
1109 };
1110
1111 format!(
1112 "{} defined here, with {}{} {} parameter{}{}",
1113 def_kind,
1114 quantifier,
1115 bound,
1116 self.kind(),
1117 pluralize!(bound),
1118 params,
1119 )
1120 };
1121
1122 err.span_note(spans, msg);
1123 }
1124
1125 fn note_synth_provided(&self, err: &mut Diag<'_, impl EmissionGuarantee>) {
1127 if !self.is_synth_provided() {
1128 return;
1129 }
1130
1131 err.note("`impl Trait` cannot be explicitly specified as a generic argument");
1132 }
1133}
1134
1135impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for WrongNumberOfGenericArgs<'_, '_> {
1136 fn into_diag(
1137 self,
1138 dcx: rustc_errors::DiagCtxtHandle<'a>,
1139 level: rustc_errors::Level,
1140 ) -> Diag<'a, G> {
1141 let msg = self.create_error_message();
1142 let mut err = Diag::new(dcx, level, msg);
1143 err.code(E0107);
1144 err.span(self.path_segment.ident.span);
1145
1146 self.notify(&mut err);
1147 self.suggest(&mut err);
1148 self.show_definition(&mut err);
1149 self.note_synth_provided(&mut err);
1150
1151 err
1152 }
1153}