1 use crate::structured_errors::StructuredDiagnostic;
3 pluralize, Applicability, Diagnostic, DiagnosticBuilder, DiagnosticId, ErrorGuaranteed,
7 use rustc_middle::ty::{self as ty, AssocItems, AssocKind, TyCtxt};
8 use rustc_session::Session;
9 use rustc_span::def_id::DefId;
12 use GenericArgsInfo::*;
14 /// Handles the `wrong number of type / lifetime / ... arguments` family of error messages.
15 pub struct WrongNumberOfGenericArgs<'a, 'tcx> {
16 pub(crate) tcx: TyCtxt<'tcx>,
18 pub(crate) angle_brackets: AngleBrackets,
20 pub(crate) gen_args_info: GenericArgsInfo,
22 /// Offending path segment
23 pub(crate) path_segment: &'a hir::PathSegment<'a>,
25 /// Generic parameters as expected by type or trait
26 pub(crate) gen_params: &'a ty::Generics,
28 /// Index offset into parameters. Depends on whether `Self` is included and on
29 /// number of lifetime parameters in case we're processing missing or redundant
30 /// type or constant arguments.
31 pub(crate) params_offset: usize,
33 /// Generic arguments as provided by user
34 pub(crate) gen_args: &'a hir::GenericArgs<'a>,
36 /// DefId of the generic type
37 pub(crate) def_id: DefId,
40 // Provides information about the kind of arguments that were provided for
41 // the PathSegment, for which missing generic arguments were detected
43 pub(crate) enum AngleBrackets {
44 // No angle brackets were provided, but generic arguments exist in elided form
47 // No angle brackets were provided
50 // Angle brackets are available, but missing some generic arguments
54 // Information about the kind of arguments that are either missing or are unexpected
56 pub enum GenericArgsInfo {
58 num_missing_args: usize,
61 num_redundant_args: usize,
63 MissingTypesOrConsts {
64 num_missing_args: usize,
66 // type or const generic arguments can have default values
67 num_default_params: usize,
69 // lifetime arguments precede type and const parameters, this
70 // field gives the number of generic lifetime arguments to let
71 // us infer the position of type and const generic arguments
72 // in the angle brackets
77 num_redundant_args: usize,
79 // type or const generic arguments can have default values
80 num_default_params: usize,
82 // lifetime arguments precede type and const parameters, this
83 // field gives the number of generic lifetime arguments to let
84 // us infer the position of type and const generic arguments
85 // in the angle brackets
88 // if synthetic type arguments (e.g. `impl Trait`) are specified
93 impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
96 gen_args_info: GenericArgsInfo,
97 path_segment: &'a hir::PathSegment<'_>,
98 gen_params: &'a ty::Generics,
100 gen_args: &'a hir::GenericArgs<'a>,
103 let angle_brackets = if gen_args.span_ext().is_none() {
104 if gen_args.is_empty() { AngleBrackets::Missing } else { AngleBrackets::Implied }
106 AngleBrackets::Available
121 fn missing_lifetimes(&self) -> bool {
122 match self.gen_args_info {
123 MissingLifetimes { .. } | ExcessLifetimes { .. } => true,
124 MissingTypesOrConsts { .. } | ExcessTypesOrConsts { .. } => false,
128 fn kind(&self) -> &str {
129 if self.missing_lifetimes() { "lifetime" } else { "generic" }
132 fn num_provided_args(&self) -> usize {
133 if self.missing_lifetimes() {
134 self.num_provided_lifetime_args()
136 self.num_provided_type_or_const_args()
140 fn num_provided_lifetime_args(&self) -> usize {
141 match self.angle_brackets {
142 AngleBrackets::Missing => 0,
143 // Only lifetime arguments can be implied
144 AngleBrackets::Implied => self.gen_args.args.len(),
145 AngleBrackets::Available => self.gen_args.num_lifetime_params(),
149 fn num_provided_type_or_const_args(&self) -> usize {
150 match self.angle_brackets {
151 AngleBrackets::Missing => 0,
152 // Only lifetime arguments can be implied
153 AngleBrackets::Implied => 0,
154 AngleBrackets::Available => self.gen_args.num_generic_params(),
158 fn num_expected_lifetime_args(&self) -> usize {
159 let num_provided_args = self.num_provided_lifetime_args();
160 match self.gen_args_info {
161 MissingLifetimes { num_missing_args } => num_provided_args + num_missing_args,
162 ExcessLifetimes { num_redundant_args } => num_provided_args - num_redundant_args,
167 fn num_expected_type_or_const_args(&self) -> usize {
168 let num_provided_args = self.num_provided_type_or_const_args();
169 match self.gen_args_info {
170 MissingTypesOrConsts { num_missing_args, .. } => num_provided_args + num_missing_args,
171 ExcessTypesOrConsts { num_redundant_args, .. } => {
172 num_provided_args - num_redundant_args
178 // Gives the number of expected arguments taking into account default arguments
179 fn num_expected_type_or_const_args_including_defaults(&self) -> usize {
180 let provided_args = self.num_provided_type_or_const_args();
181 match self.gen_args_info {
182 MissingTypesOrConsts { num_missing_args, num_default_params, .. } => {
183 provided_args + num_missing_args - num_default_params
185 ExcessTypesOrConsts { num_redundant_args, num_default_params, .. } => {
186 provided_args - num_redundant_args - num_default_params
192 fn num_missing_lifetime_args(&self) -> usize {
193 let missing_args = self.num_expected_lifetime_args() - self.num_provided_lifetime_args();
194 assert!(missing_args > 0);
198 fn num_missing_type_or_const_args(&self) -> usize {
199 let missing_args = self.num_expected_type_or_const_args_including_defaults()
200 - self.num_provided_type_or_const_args();
201 assert!(missing_args > 0);
205 fn num_excess_lifetime_args(&self) -> usize {
206 match self.gen_args_info {
207 ExcessLifetimes { num_redundant_args } => num_redundant_args,
212 fn num_excess_type_or_const_args(&self) -> usize {
213 match self.gen_args_info {
214 ExcessTypesOrConsts { num_redundant_args, .. } => num_redundant_args,
219 fn too_many_args_provided(&self) -> bool {
220 match self.gen_args_info {
221 MissingLifetimes { .. } | MissingTypesOrConsts { .. } => false,
222 ExcessLifetimes { num_redundant_args }
223 | ExcessTypesOrConsts { num_redundant_args, .. } => {
224 assert!(num_redundant_args > 0);
230 fn not_enough_args_provided(&self) -> bool {
231 match self.gen_args_info {
232 MissingLifetimes { num_missing_args }
233 | MissingTypesOrConsts { num_missing_args, .. } => {
234 assert!(num_missing_args > 0);
237 ExcessLifetimes { .. } | ExcessTypesOrConsts { .. } => false,
241 // Helper method to get the index offset in angle brackets, at which type or const arguments
243 fn get_lifetime_args_offset(&self) -> usize {
244 match self.gen_args_info {
245 MissingLifetimes { .. } | ExcessLifetimes { .. } => 0,
246 MissingTypesOrConsts { args_offset, .. } | ExcessTypesOrConsts { args_offset, .. } => {
252 fn get_num_default_params(&self) -> usize {
253 match self.gen_args_info {
254 MissingTypesOrConsts { num_default_params, .. }
255 | ExcessTypesOrConsts { num_default_params, .. } => num_default_params,
260 fn is_synth_provided(&self) -> bool {
261 match self.gen_args_info {
262 ExcessTypesOrConsts { synth_provided, .. } => synth_provided,
267 // Helper function to choose a quantifier word for the number of expected arguments
268 // and to give a bound for the number of expected arguments
269 fn get_quantifier_and_bound(&self) -> (&'static str, usize) {
270 if self.get_num_default_params() == 0 {
271 match self.gen_args_info {
272 MissingLifetimes { .. } | ExcessLifetimes { .. } => {
273 ("", self.num_expected_lifetime_args())
275 MissingTypesOrConsts { .. } | ExcessTypesOrConsts { .. } => {
276 ("", self.num_expected_type_or_const_args())
280 match self.gen_args_info {
281 MissingLifetimes { .. } => ("at least ", self.num_expected_lifetime_args()),
282 MissingTypesOrConsts { .. } => {
283 ("at least ", self.num_expected_type_or_const_args_including_defaults())
285 ExcessLifetimes { .. } => ("at most ", self.num_expected_lifetime_args()),
286 ExcessTypesOrConsts { .. } => ("at most ", self.num_expected_type_or_const_args()),
291 // Creates lifetime name suggestions from the lifetime parameter names
292 fn get_lifetime_args_suggestions_from_param_names(
294 path_hir_id: Option<hir::HirId>,
295 num_params_to_take: usize,
297 debug!(?path_hir_id);
299 if let Some(path_hir_id) = path_hir_id {
300 let mut ret = Vec::new();
301 for (id, node) in self.tcx.hir().parent_iter(path_hir_id) {
303 let params = if let Some(generics) = node.generics() {
305 } else if let hir::Node::Ty(ty) = node
306 && let hir::TyKind::BareFn(bare_fn) = ty.kind
308 bare_fn.generic_params
312 ret.extend(params.iter().filter_map(|p| {
313 let hir::GenericParamKind::Lifetime { kind: hir::LifetimeParamKind::Explicit }
315 else { return None };
316 let hir::ParamName::Plain(name) = p.name else { return None };
317 Some(name.to_string())
319 // Suggest `'static` when in const/static item-like.
320 if let hir::Node::Item(hir::Item {
321 kind: hir::ItemKind::Static { .. } | hir::ItemKind::Const { .. },
324 | hir::Node::TraitItem(hir::TraitItem {
325 kind: hir::TraitItemKind::Const { .. },
328 | hir::Node::ImplItem(hir::ImplItem {
329 kind: hir::ImplItemKind::Const { .. },
332 | hir::Node::ForeignItem(hir::ForeignItem {
333 kind: hir::ForeignItemKind::Static { .. },
336 | hir::Node::AnonConst(..) = node
339 std::iter::repeat("'static".to_owned())
340 .take(num_params_to_take.saturating_sub(ret.len())),
343 if ret.len() >= num_params_to_take {
344 return ret[..num_params_to_take].join(", ");
346 // We cannot refer to lifetimes defined in an outer function.
347 if let hir::Node::Item(_) = node {
353 // We could not gather enough lifetime parameters in the scope.
354 // We use the parameter names from the target type's definition instead.
358 .skip(self.params_offset + self.num_provided_lifetime_args())
359 .take(num_params_to_take)
360 .map(|param| param.name.to_string())
365 // Creates type or constant name suggestions from the provided parameter names
366 fn get_type_or_const_args_suggestions_from_param_names(
368 num_params_to_take: usize,
370 let fn_sig = self.tcx.hir().get_if_local(self.def_id).and_then(hir::Node::fn_sig);
371 let is_used_in_input = |def_id| {
372 fn_sig.map_or(false, |fn_sig| {
373 fn_sig.decl.inputs.iter().any(|ty| match ty.kind {
374 hir::TyKind::Path(hir::QPath::Resolved(
376 hir::Path { res: hir::def::Res::Def(_, id), .. },
385 .skip(self.params_offset + self.num_provided_type_or_const_args())
386 .take(num_params_to_take)
387 .map(|param| match param.kind {
388 // This is being inferred from the item's inputs, no need to set it.
389 ty::GenericParamDefKind::Type { .. } if is_used_in_input(param.def_id) => {
392 _ => param.name.to_string(),
398 fn get_unbound_associated_types(&self) -> Vec<String> {
399 if self.tcx.is_trait(self.def_id) {
400 let items: &AssocItems<'_> = self.tcx.associated_items(self.def_id);
402 .in_definition_order()
403 .filter(|item| item.kind == AssocKind::Type)
405 !self.gen_args.bindings.iter().any(|binding| binding.ident.name == item.name)
407 .map(|item| item.name.to_ident_string())
414 fn create_error_message(&self) -> String {
415 let def_path = self.tcx.def_path_str(self.def_id);
416 let def_kind = self.tcx.def_kind(self.def_id).descr(self.def_id);
417 let (quantifier, bound) = self.get_quantifier_and_bound();
418 let kind = self.kind();
419 let provided_lt_args = self.num_provided_lifetime_args();
420 let provided_type_or_const_args = self.num_provided_type_or_const_args();
422 let (provided_args_str, verb) = match self.gen_args_info {
423 MissingLifetimes { .. } | ExcessLifetimes { .. } => (
424 format!("{} lifetime argument{}", provided_lt_args, pluralize!(provided_lt_args)),
425 pluralize!("was", provided_lt_args),
427 MissingTypesOrConsts { .. } | ExcessTypesOrConsts { .. } => (
429 "{} generic argument{}",
430 provided_type_or_const_args,
431 pluralize!(provided_type_or_const_args)
433 pluralize!("was", provided_type_or_const_args),
437 if self.gen_args.span_ext().is_some() {
439 "this {} takes {}{} {} argument{} but {} {} supplied",
445 provided_args_str.as_str(),
449 format!("missing generics for {} `{}`", def_kind, def_path)
453 fn start_diagnostics(&self) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
454 let span = self.path_segment.ident.span;
455 let msg = self.create_error_message();
457 self.tcx.sess.struct_span_err_with_code(span, &msg, self.code())
460 /// Builds the `expected 1 type argument / supplied 2 type arguments` message.
461 fn notify(&self, err: &mut Diagnostic) {
462 let (quantifier, bound) = self.get_quantifier_and_bound();
463 let provided_args = self.num_provided_args();
466 self.path_segment.ident.span,
468 "expected {}{} {} argument{}",
476 // When too many arguments were provided, we don't highlight each of them, because it
477 // would overlap with the suggestion to remove them:
480 // type Foo = Bar<usize, usize>;
481 // ----- ----- supplied 2 type arguments
482 // ^^^^^^^ remove this type argument
484 if self.too_many_args_provided() {
492 .skip(self.get_lifetime_args_offset())
496 for (i, arg) in args {
499 if i + 1 == provided_args {
501 "supplied {} {} argument{}",
504 pluralize!(provided_args)
513 fn suggest(&self, err: &mut Diagnostic) {
515 "suggest(self.provided {:?}, self.gen_args.span(): {:?})",
516 self.num_provided_args(),
517 self.gen_args.span(),
520 match self.angle_brackets {
521 AngleBrackets::Missing | AngleBrackets::Implied => self.suggest_adding_args(err),
522 AngleBrackets::Available => {
523 if self.not_enough_args_provided() {
524 self.suggest_adding_args(err);
525 } else if self.too_many_args_provided() {
526 self.suggest_moving_args_from_assoc_fn_to_trait(err);
527 self.suggest_removing_args_or_generics(err);
535 /// Suggests to add missing argument(s) when current invocation site already contains some
539 /// type Map = HashMap<String>;
541 fn suggest_adding_args(&self, err: &mut Diagnostic) {
542 if self.gen_args.parenthesized {
546 match self.gen_args_info {
547 MissingLifetimes { .. } => {
548 self.suggest_adding_lifetime_args(err);
550 MissingTypesOrConsts { .. } => {
551 self.suggest_adding_type_and_const_args(err);
557 fn suggest_adding_lifetime_args(&self, err: &mut Diagnostic) {
558 debug!("suggest_adding_lifetime_args(path_segment: {:?})", self.path_segment);
559 let num_missing_args = self.num_missing_lifetime_args();
560 let num_params_to_take = num_missing_args;
561 let msg = format!("add missing {} argument{}", self.kind(), pluralize!(num_missing_args));
563 let suggested_args = self.get_lifetime_args_suggestions_from_param_names(
564 self.path_segment.hir_id,
567 debug!("suggested_args: {:?}", &suggested_args);
569 match self.angle_brackets {
570 AngleBrackets::Missing => {
571 let span = self.path_segment.ident.span;
573 // insert a suggestion of the form "Y<'a, 'b>"
574 let ident = self.path_segment.ident.name.to_ident_string();
575 let sugg = format!("{}<{}>", ident, suggested_args);
576 debug!("sugg: {:?}", sugg);
578 err.span_suggestion_verbose(span, &msg, sugg, Applicability::HasPlaceholders);
581 AngleBrackets::Available => {
582 let (sugg_span, is_first) = if self.num_provided_lifetime_args() == 0 {
583 (self.gen_args.span().unwrap().shrink_to_lo(), true)
585 let last_lt = &self.gen_args.args[self.num_provided_lifetime_args() - 1];
586 (last_lt.span().shrink_to_hi(), false)
588 let has_non_lt_args = self.num_provided_type_or_const_args() != 0;
589 let has_bindings = !self.gen_args.bindings.is_empty();
591 let sugg_prefix = if is_first { "" } else { ", " };
593 if is_first && (has_non_lt_args || has_bindings) { ", " } else { "" };
595 let sugg = format!("{}{}{}", sugg_prefix, suggested_args, sugg_suffix);
596 debug!("sugg: {:?}", sugg);
598 err.span_suggestion_verbose(sugg_span, &msg, sugg, Applicability::HasPlaceholders);
600 AngleBrackets::Implied => {
601 // We never encounter missing lifetimes in situations in which lifetimes are elided
607 fn suggest_adding_type_and_const_args(&self, err: &mut Diagnostic) {
608 let num_missing_args = self.num_missing_type_or_const_args();
609 let msg = format!("add missing {} argument{}", self.kind(), pluralize!(num_missing_args));
612 self.get_type_or_const_args_suggestions_from_param_names(num_missing_args);
613 debug!("suggested_args: {:?}", suggested_args);
615 match self.angle_brackets {
616 AngleBrackets::Missing | AngleBrackets::Implied => {
617 let span = self.path_segment.ident.span;
619 // insert a suggestion of the form "Y<T, U>"
620 let ident = self.path_segment.ident.name.to_ident_string();
621 let sugg = format!("{}<{}>", ident, suggested_args);
622 debug!("sugg: {:?}", sugg);
624 err.span_suggestion_verbose(span, &msg, sugg, Applicability::HasPlaceholders);
626 AngleBrackets::Available => {
627 let gen_args_span = self.gen_args.span().unwrap();
629 self.get_lifetime_args_offset() + self.num_provided_type_or_const_args();
631 let (sugg_span, is_first) = if sugg_offset == 0 {
632 (gen_args_span.shrink_to_lo(), true)
634 let arg_span = self.gen_args.args[sugg_offset - 1].span();
635 // If we came here then inferred lifetime's spans can only point
636 // to either the opening bracket or to the space right after.
637 // Both of these spans have an `hi` lower than or equal to the span
638 // of the generics excluding the brackets.
639 // This allows us to check if `arg_span` is the artificial span of
640 // an inferred lifetime, in which case the generic we're suggesting to
641 // add will be the first visible, even if it isn't the actual first generic.
642 (arg_span.shrink_to_hi(), arg_span.hi() <= gen_args_span.lo())
645 let sugg_prefix = if is_first { "" } else { ", " };
647 if is_first && !self.gen_args.bindings.is_empty() { ", " } else { "" };
649 let sugg = format!("{}{}{}", sugg_prefix, suggested_args, sugg_suffix);
650 debug!("sugg: {:?}", sugg);
652 err.span_suggestion_verbose(sugg_span, &msg, sugg, Applicability::HasPlaceholders);
657 /// Suggests moving redundant argument(s) of an associate function to the
658 /// trait it belongs to.
661 /// Into::into::<Option<_>>(42) // suggests considering `Into::<Option<_>>::into(42)`
663 fn suggest_moving_args_from_assoc_fn_to_trait(&self, err: &mut Diagnostic) {
664 let trait_ = match self.tcx.trait_of_item(self.def_id) {
665 Some(def_id) => def_id,
669 // Skip suggestion when the associated function is itself generic, it is unclear
670 // how to split the provided parameters between those to suggest to the trait and
671 // those to remain on the associated type.
672 let num_assoc_fn_expected_args =
673 self.num_expected_type_or_const_args() + self.num_expected_lifetime_args();
674 if num_assoc_fn_expected_args > 0 {
678 let num_assoc_fn_excess_args =
679 self.num_excess_type_or_const_args() + self.num_excess_lifetime_args();
681 let trait_generics = self.tcx.generics_of(trait_);
682 let num_trait_generics_except_self =
683 trait_generics.count() - if trait_generics.has_self { 1 } else { 0 };
686 "consider moving {these} generic argument{s} to the `{name}` trait, which takes up to {num} argument{s}",
687 these = pluralize!("this", num_assoc_fn_excess_args),
688 s = pluralize!(num_assoc_fn_excess_args),
689 name = self.tcx.item_name(trait_),
690 num = num_trait_generics_except_self,
693 if let Some(hir_id) = self.path_segment.hir_id
694 && let Some(parent_node) = self.tcx.hir().find_parent_node(hir_id)
695 && let Some(parent_node) = self.tcx.hir().find(parent_node)
696 && let hir::Node::Expr(expr) = parent_node {
698 hir::ExprKind::Path(ref qpath) => {
699 self.suggest_moving_args_from_assoc_fn_to_trait_for_qualified_path(
703 num_assoc_fn_excess_args,
704 num_trait_generics_except_self
707 hir::ExprKind::MethodCall(..) => {
708 self.suggest_moving_args_from_assoc_fn_to_trait_for_method_call(
713 num_assoc_fn_excess_args,
714 num_trait_generics_except_self
722 fn suggest_moving_args_from_assoc_fn_to_trait_for_qualified_path(
724 err: &mut Diagnostic,
725 qpath: &'tcx hir::QPath<'tcx>,
727 num_assoc_fn_excess_args: usize,
728 num_trait_generics_except_self: usize,
730 if let hir::QPath::Resolved(_, path) = qpath
731 && let Some(trait_path_segment) = path.segments.get(0) {
732 let num_generic_args_supplied_to_trait = trait_path_segment.args().num_generic_params();
734 if num_assoc_fn_excess_args == num_trait_generics_except_self - num_generic_args_supplied_to_trait {
735 if let Some(span) = self.gen_args.span_ext()
736 && let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
738 (self.path_segment.ident.span, format!("{}::{}", snippet, self.path_segment.ident)),
739 (span.with_lo(self.path_segment.ident.span.hi()), "".to_owned())
742 err.multipart_suggestion(
745 Applicability::MaybeIncorrect
752 fn suggest_moving_args_from_assoc_fn_to_trait_for_method_call(
754 err: &mut Diagnostic,
756 expr: &'tcx hir::Expr<'tcx>,
758 num_assoc_fn_excess_args: usize,
759 num_trait_generics_except_self: usize,
761 if let hir::ExprKind::MethodCall(_, args, _) = expr.kind {
762 assert_eq!(args.len(), 1);
763 if num_assoc_fn_excess_args == num_trait_generics_except_self {
764 if let Some(gen_args) = self.gen_args.span_ext()
765 && let Ok(gen_args) = self.tcx.sess.source_map().span_to_snippet(gen_args)
766 && let Ok(args) = self.tcx.sess.source_map().span_to_snippet(args[0].span) {
767 let sugg = format!("{}::{}::{}({})", self.tcx.item_name(trait_), gen_args, self.tcx.item_name(self.def_id), args);
768 err.span_suggestion(expr.span, msg, sugg, Applicability::MaybeIncorrect);
774 /// Suggests to remove redundant argument(s):
777 /// type Map = HashMap<String, String, String, String>;
779 fn suggest_removing_args_or_generics(&self, err: &mut Diagnostic) {
780 let num_provided_lt_args = self.num_provided_lifetime_args();
781 let num_provided_type_const_args = self.num_provided_type_or_const_args();
782 let unbound_types = self.get_unbound_associated_types();
783 let num_provided_args = num_provided_lt_args + num_provided_type_const_args;
784 assert!(num_provided_args > 0);
786 let num_redundant_lt_args = self.num_excess_lifetime_args();
787 let num_redundant_type_or_const_args = self.num_excess_type_or_const_args();
788 let num_redundant_args = num_redundant_lt_args + num_redundant_type_or_const_args;
790 let redundant_lifetime_args = num_redundant_lt_args > 0;
791 let redundant_type_or_const_args = num_redundant_type_or_const_args > 0;
793 let remove_entire_generics = num_redundant_args >= self.gen_args.args.len();
794 let provided_args_matches_unbound_traits =
795 unbound_types.len() == num_redundant_type_or_const_args;
797 let remove_lifetime_args = |err: &mut Diagnostic| {
798 let mut lt_arg_spans = Vec::new();
799 let mut found_redundant = false;
800 for arg in self.gen_args.args {
801 if let hir::GenericArg::Lifetime(_) = arg {
802 lt_arg_spans.push(arg.span());
803 if lt_arg_spans.len() > self.num_expected_lifetime_args() {
804 found_redundant = true;
806 } else if found_redundant {
807 // Argument which is redundant and separated like this `'c`
808 // is not included to avoid including `Bar` in span.
810 // type Foo<'a, T> = &'a T;
811 // let _: Foo<'a, 'b, Bar, 'c>;
817 let span_lo_redundant_lt_args = lt_arg_spans[self.num_expected_lifetime_args()];
818 let span_hi_redundant_lt_args = lt_arg_spans[lt_arg_spans.len() - 1];
820 let span_redundant_lt_args = span_lo_redundant_lt_args.to(span_hi_redundant_lt_args);
821 debug!("span_redundant_lt_args: {:?}", span_redundant_lt_args);
823 let num_redundant_lt_args = lt_arg_spans.len() - self.num_expected_lifetime_args();
824 let msg_lifetimes = format!(
825 "remove {these} lifetime argument{s}",
826 these = pluralize!("this", num_redundant_lt_args),
827 s = pluralize!(num_redundant_lt_args),
831 span_redundant_lt_args,
834 Applicability::MaybeIncorrect,
838 let remove_type_or_const_args = |err: &mut Diagnostic| {
839 let mut gen_arg_spans = Vec::new();
840 let mut found_redundant = false;
841 for arg in self.gen_args.args {
843 hir::GenericArg::Type(_)
844 | hir::GenericArg::Const(_)
845 | hir::GenericArg::Infer(_) => {
846 gen_arg_spans.push(arg.span());
847 if gen_arg_spans.len() > self.num_expected_type_or_const_args() {
848 found_redundant = true;
851 _ if found_redundant => break,
856 let span_lo_redundant_type_or_const_args =
857 gen_arg_spans[self.num_expected_type_or_const_args()];
858 let span_hi_redundant_type_or_const_args = gen_arg_spans[gen_arg_spans.len() - 1];
860 let span_redundant_type_or_const_args =
861 span_lo_redundant_type_or_const_args.to(span_hi_redundant_type_or_const_args);
862 debug!("span_redundant_type_or_const_args: {:?}", span_redundant_type_or_const_args);
864 let num_redundant_gen_args =
865 gen_arg_spans.len() - self.num_expected_type_or_const_args();
866 let msg_types_or_consts = format!(
867 "remove {these} generic argument{s}",
868 these = pluralize!("this", num_redundant_gen_args),
869 s = pluralize!(num_redundant_gen_args),
873 span_redundant_type_or_const_args,
874 &msg_types_or_consts,
876 Applicability::MaybeIncorrect,
880 // If there is a single unbound associated type and a single excess generic param
881 // suggest replacing the generic param with the associated type bound
882 if provided_args_matches_unbound_traits && !unbound_types.is_empty() {
883 let unused_generics = &self.gen_args.args[self.num_expected_type_or_const_args()..];
884 let suggestions = iter::zip(unused_generics, &unbound_types)
885 .map(|(potential, name)| (potential.span().shrink_to_lo(), format!("{name} = ")))
886 .collect::<Vec<_>>();
888 if !suggestions.is_empty() {
889 err.multipart_suggestion_verbose(
891 "replace the generic bound{s} with the associated type{s}",
892 s = pluralize!(unbound_types.len())
895 Applicability::MaybeIncorrect,
898 } else if remove_entire_generics {
905 .with_lo(self.path_segment.ident.span.hi());
908 "remove these {}generics",
909 if self.gen_args.parenthesized { "parenthetical " } else { "" },
912 err.span_suggestion(span, &msg, "", Applicability::MaybeIncorrect);
913 } else if redundant_lifetime_args && redundant_type_or_const_args {
914 remove_lifetime_args(err);
915 remove_type_or_const_args(err);
916 } else if redundant_lifetime_args {
917 remove_lifetime_args(err);
919 assert!(redundant_type_or_const_args);
920 remove_type_or_const_args(err);
924 /// Builds the `type defined here` message.
925 fn show_definition(&self, err: &mut Diagnostic) {
926 let mut spans: MultiSpan = if let Some(def_span) = self.tcx.def_ident_span(self.def_id) {
927 if self.tcx.sess.source_map().is_span_accessible(def_span) {
937 let def_kind = self.tcx.def_kind(self.def_id).descr(self.def_id);
938 let (quantifier, bound) = self.get_quantifier_and_bound();
940 let params = if bound == 0 {
947 .skip(self.params_offset)
950 let span = self.tcx.def_span(param.def_id);
951 spans.push_span_label(span, "");
954 .map(|param| format!("`{}`", param.name))
958 format!(": {}", params)
962 "{} defined here, with {}{} {} parameter{}{}",
972 err.span_note(spans, &msg);
975 /// Add note if `impl Trait` is explicitly specified.
976 fn note_synth_provided(&self, err: &mut Diagnostic) {
977 if !self.is_synth_provided() {
981 err.note("`impl Trait` cannot be explicitly specified as a generic argument");
985 impl<'tcx> StructuredDiagnostic<'tcx> for WrongNumberOfGenericArgs<'_, 'tcx> {
986 fn session(&self) -> &Session {
990 fn code(&self) -> DiagnosticId {
991 rustc_errors::error_code!(E0107)
994 fn diagnostic_common(&self) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
995 let mut err = self.start_diagnostics();
997 self.notify(&mut err);
998 self.suggest(&mut err);
999 self.show_definition(&mut err);
1000 self.note_synth_provided(&mut err);