1 use crate::errors::LifetimesOrBoundsMismatchOnTrait;
2 use rustc_data_structures::stable_set::FxHashSet;
3 use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticId, ErrorGuaranteed};
5 use rustc_hir::def::{DefKind, Res};
6 use rustc_hir::intravisit;
7 use rustc_hir::{GenericParamKind, ImplItemKind, TraitItemKind};
8 use rustc_infer::infer::{self, InferOk, TyCtxtInferExt};
9 use rustc_infer::traits::util;
10 use rustc_middle::ty::error::{ExpectedFound, TypeError};
11 use rustc_middle::ty::subst::{InternalSubsts, Subst};
12 use rustc_middle::ty::util::ExplicitSelf;
13 use rustc_middle::ty::{self, DefIdTree};
14 use rustc_middle::ty::{GenericParamDefKind, ToPredicate, TyCtxt};
16 use rustc_trait_selection::traits::error_reporting::InferCtxtExt;
17 use rustc_trait_selection::traits::{self, ObligationCause, ObligationCauseCode, Reveal};
20 use super::{potentially_plural_count, FnCtxt, Inherited};
22 /// Checks that a method from an impl conforms to the signature of
23 /// the same method as declared in the trait.
27 /// - `impl_m`: type of the method we are checking
28 /// - `impl_m_span`: span to use for reporting errors
29 /// - `trait_m`: the method in the trait
30 /// - `impl_trait_ref`: the TraitRef corresponding to the trait implementation
31 crate fn compare_impl_method<'tcx>(
33 impl_m: &ty::AssocItem,
35 trait_m: &ty::AssocItem,
36 impl_trait_ref: ty::TraitRef<'tcx>,
37 trait_item_span: Option<Span>,
39 debug!("compare_impl_method(impl_trait_ref={:?})", impl_trait_ref);
41 let impl_m_span = tcx.sess.source_map().guess_head_span(impl_m_span);
43 if let Err(_) = compare_self_type(tcx, impl_m, impl_m_span, trait_m, impl_trait_ref) {
47 if let Err(_) = compare_number_of_generics(tcx, impl_m, impl_m_span, trait_m, trait_item_span) {
51 if let Err(_) = compare_generic_param_kinds(tcx, impl_m, trait_m) {
56 compare_number_of_method_arguments(tcx, impl_m, impl_m_span, trait_m, trait_item_span)
61 if let Err(_) = compare_synthetic_generics(tcx, impl_m, trait_m) {
65 if let Err(_) = compare_predicate_entailment(tcx, impl_m, impl_m_span, trait_m, impl_trait_ref)
71 fn compare_predicate_entailment<'tcx>(
73 impl_m: &ty::AssocItem,
75 trait_m: &ty::AssocItem,
76 impl_trait_ref: ty::TraitRef<'tcx>,
77 ) -> Result<(), ErrorGuaranteed> {
78 let trait_to_impl_substs = impl_trait_ref.substs;
80 // This node-id should be used for the `body_id` field on each
81 // `ObligationCause` (and the `FnCtxt`). This is what
82 // `regionck_item` expects.
83 let impl_m_hir_id = tcx.hir().local_def_id_to_hir_id(impl_m.def_id.expect_local());
85 // We sometimes modify the span further down.
86 let mut cause = ObligationCause::new(
89 ObligationCauseCode::CompareImplMethodObligation {
90 impl_item_def_id: impl_m.def_id.expect_local(),
91 trait_item_def_id: trait_m.def_id,
95 // This code is best explained by example. Consider a trait:
97 // trait Trait<'t, T> {
98 // fn method<'a, M>(t: &'t T, m: &'a M) -> Self;
103 // impl<'i, 'j, U> Trait<'j, &'i U> for Foo {
104 // fn method<'b, N>(t: &'j &'i U, m: &'b N) -> Foo;
107 // We wish to decide if those two method types are compatible.
109 // We start out with trait_to_impl_substs, that maps the trait
110 // type parameters to impl type parameters. This is taken from the
111 // impl trait reference:
113 // trait_to_impl_substs = {'t => 'j, T => &'i U, Self => Foo}
115 // We create a mapping `dummy_substs` that maps from the impl type
116 // parameters to fresh types and regions. For type parameters,
117 // this is the identity transform, but we could as well use any
118 // placeholder types. For regions, we convert from bound to free
119 // regions (Note: but only early-bound regions, i.e., those
120 // declared on the impl or used in type parameter bounds).
122 // impl_to_placeholder_substs = {'i => 'i0, U => U0, N => N0 }
124 // Now we can apply placeholder_substs to the type of the impl method
125 // to yield a new function type in terms of our fresh, placeholder
128 // <'b> fn(t: &'i0 U0, m: &'b) -> Foo
130 // We now want to extract and substitute the type of the *trait*
131 // method and compare it. To do so, we must create a compound
132 // substitution by combining trait_to_impl_substs and
133 // impl_to_placeholder_substs, and also adding a mapping for the method
134 // type parameters. We extend the mapping to also include
135 // the method parameters.
137 // trait_to_placeholder_substs = { T => &'i0 U0, Self => Foo, M => N0 }
139 // Applying this to the trait method type yields:
141 // <'a> fn(t: &'i0 U0, m: &'a) -> Foo
143 // This type is also the same but the name of the bound region ('a
144 // vs 'b). However, the normal subtyping rules on fn types handle
145 // this kind of equivalency just fine.
147 // We now use these substitutions to ensure that all declared bounds are
148 // satisfied by the implementation's method.
150 // We do this by creating a parameter environment which contains a
151 // substitution corresponding to impl_to_placeholder_substs. We then build
152 // trait_to_placeholder_substs and use it to convert the predicates contained
153 // in the trait_m.generics to the placeholder form.
155 // Finally we register each of these predicates as an obligation in
156 // a fresh FulfillmentCtxt, and invoke select_all_or_error.
158 // Create mapping from impl to placeholder.
159 let impl_to_placeholder_substs = InternalSubsts::identity_for_item(tcx, impl_m.def_id);
161 // Create mapping from trait to placeholder.
162 let trait_to_placeholder_substs =
163 impl_to_placeholder_substs.rebase_onto(tcx, impl_m.container.id(), trait_to_impl_substs);
164 debug!("compare_impl_method: trait_to_placeholder_substs={:?}", trait_to_placeholder_substs);
166 let impl_m_generics = tcx.generics_of(impl_m.def_id);
167 let trait_m_generics = tcx.generics_of(trait_m.def_id);
168 let impl_m_predicates = tcx.predicates_of(impl_m.def_id);
169 let trait_m_predicates = tcx.predicates_of(trait_m.def_id);
171 // Check region bounds.
172 check_region_bounds_on_impl_item(
181 // Create obligations for each predicate declared by the impl
182 // definition in the context of the trait's parameter
183 // environment. We can't just use `impl_env.caller_bounds`,
184 // however, because we want to replace all late-bound regions with
186 let impl_predicates = tcx.predicates_of(impl_m_predicates.parent.unwrap());
187 let mut hybrid_preds = impl_predicates.instantiate_identity(tcx);
189 debug!("compare_impl_method: impl_bounds={:?}", hybrid_preds);
191 // This is the only tricky bit of the new way we check implementation methods
192 // We need to build a set of predicates where only the method-level bounds
193 // are from the trait and we assume all other bounds from the implementation
194 // to be previously satisfied.
196 // We then register the obligations from the impl_m and check to see
197 // if all constraints hold.
200 .extend(trait_m_predicates.instantiate_own(tcx, trait_to_placeholder_substs).predicates);
202 // Construct trait parameter environment and then shift it into the placeholder viewpoint.
203 // The key step here is to update the caller_bounds's predicates to be
204 // the new hybrid bounds we computed.
205 let normalize_cause = traits::ObligationCause::misc(impl_m_span, impl_m_hir_id);
206 let param_env = ty::ParamEnv::new(
207 tcx.intern_predicates(&hybrid_preds.predicates),
209 hir::Constness::NotConst,
212 traits::normalize_param_env_or_error(tcx, impl_m.def_id, param_env, normalize_cause);
214 tcx.infer_ctxt().enter(|infcx| {
215 let inh = Inherited::new(infcx, impl_m.def_id.expect_local());
216 let infcx = &inh.infcx;
218 debug!("compare_impl_method: caller_bounds={:?}", param_env.caller_bounds());
220 let mut selcx = traits::SelectionContext::new(&infcx);
222 let impl_m_own_bounds = impl_m_predicates.instantiate_own(tcx, impl_to_placeholder_substs);
223 for (predicate, span) in iter::zip(impl_m_own_bounds.predicates, impl_m_own_bounds.spans) {
224 let normalize_cause = traits::ObligationCause::misc(span, impl_m_hir_id);
225 let traits::Normalized { value: predicate, obligations } =
226 traits::normalize(&mut selcx, param_env, normalize_cause, predicate);
228 inh.register_predicates(obligations);
229 let cause = ObligationCause::new(
232 ObligationCauseCode::CompareImplMethodObligation {
233 impl_item_def_id: impl_m.def_id.expect_local(),
234 trait_item_def_id: trait_m.def_id,
237 inh.register_predicate(traits::Obligation::new(cause, param_env, predicate));
240 // We now need to check that the signature of the impl method is
241 // compatible with that of the trait method. We do this by
242 // checking that `impl_fty <: trait_fty`.
244 // FIXME. Unfortunately, this doesn't quite work right now because
245 // associated type normalization is not integrated into subtype
246 // checks. For the comparison to be valid, we need to
247 // normalize the associated types in the impl/trait methods
248 // first. However, because function types bind regions, just
249 // calling `normalize_associated_types_in` would have no effect on
250 // any associated types appearing in the fn arguments or return
253 // Compute placeholder form of impl and trait method tys.
256 let mut wf_tys = FxHashSet::default();
258 let (impl_sig, _) = infcx.replace_bound_vars_with_fresh_vars(
260 infer::HigherRankedType,
261 tcx.fn_sig(impl_m.def_id),
264 inh.normalize_associated_types_in(impl_m_span, impl_m_hir_id, param_env, impl_sig);
265 let impl_fty = tcx.mk_fn_ptr(ty::Binder::dummy(impl_sig));
266 debug!("compare_impl_method: impl_fty={:?}", impl_fty);
268 let trait_sig = tcx.bound_fn_sig(trait_m.def_id).subst(tcx, trait_to_placeholder_substs);
269 let trait_sig = tcx.liberate_late_bound_regions(impl_m.def_id, trait_sig);
271 inh.normalize_associated_types_in(impl_m_span, impl_m_hir_id, param_env, trait_sig);
272 // Add the resulting inputs and output as well-formed.
273 wf_tys.extend(trait_sig.inputs_and_output.iter());
274 let trait_fty = tcx.mk_fn_ptr(ty::Binder::dummy(trait_sig));
276 debug!("compare_impl_method: trait_fty={:?}", trait_fty);
278 let sub_result = infcx.at(&cause, param_env).sup(trait_fty, impl_fty).map(
279 |InferOk { obligations, .. }| {
280 // FIXME: We'd want to keep more accurate spans than "the method signature" when
281 // processing the comparison between the trait and impl fn, but we sadly lose them
282 // and point at the whole signature when a trait bound or specific input or output
283 // type would be more appropriate. In other places we have a `Vec<Span>`
284 // corresponding to their `Vec<Predicate>`, but we don't have that here.
285 // Fixing this would improve the output of test `issue-83765.rs`.
286 inh.register_predicates(obligations);
290 if let Err(terr) = sub_result {
291 debug!("sub_types failed: impl ty {:?}, trait ty {:?}", impl_fty, trait_fty);
293 let (impl_err_span, trait_err_span) =
294 extract_spans_for_error_reporting(&infcx, &terr, &cause, impl_m, trait_m);
296 cause.span = impl_err_span;
298 let mut diag = struct_span_err!(
302 "method `{}` has an incompatible type for trait",
306 TypeError::ArgumentMutability(0) | TypeError::ArgumentSorts(_, 0)
307 if trait_m.fn_has_self_parameter =>
309 let ty = trait_sig.inputs()[0];
310 let sugg = match ExplicitSelf::determine(ty, |_| ty == impl_trait_ref.self_ty())
312 ExplicitSelf::ByValue => "self".to_owned(),
313 ExplicitSelf::ByReference(_, hir::Mutability::Not) => "&self".to_owned(),
314 ExplicitSelf::ByReference(_, hir::Mutability::Mut) => {
315 "&mut self".to_owned()
317 _ => format!("self: {ty}"),
320 // When the `impl` receiver is an arbitrary self type, like `self: Box<Self>`, the
321 // span points only at the type `Box<Self`>, but we want to cover the whole
322 // argument pattern and type.
323 let span = match tcx.hir().expect_impl_item(impl_m.def_id.expect_local()).kind {
324 ImplItemKind::Fn(ref sig, body) => tcx
326 .body_param_names(body)
327 .zip(sig.decl.inputs.iter())
328 .map(|(param, ty)| param.span.to(ty.span))
330 .unwrap_or(impl_err_span),
331 _ => bug!("{:?} is not a method", impl_m),
334 diag.span_suggestion(
336 "change the self-receiver type to match the trait",
338 Applicability::MachineApplicable,
341 TypeError::ArgumentMutability(i) | TypeError::ArgumentSorts(_, i) => {
342 if trait_sig.inputs().len() == *i {
343 // Suggestion to change output type. We do not suggest in `async` functions
344 // to avoid complex logic or incorrect output.
345 match tcx.hir().expect_impl_item(impl_m.def_id.expect_local()).kind {
346 ImplItemKind::Fn(ref sig, _)
347 if sig.header.asyncness == hir::IsAsync::NotAsync =>
349 let msg = "change the output type to match the trait";
350 let ap = Applicability::MachineApplicable;
351 match sig.decl.output {
352 hir::FnRetTy::DefaultReturn(sp) => {
353 let sugg = format!("-> {} ", trait_sig.output());
354 diag.span_suggestion_verbose(sp, msg, sugg, ap);
356 hir::FnRetTy::Return(hir_ty) => {
357 let sugg = trait_sig.output().to_string();
358 diag.span_suggestion(hir_ty.span, msg, sugg, ap);
364 } else if let Some(trait_ty) = trait_sig.inputs().get(*i) {
365 diag.span_suggestion(
367 "change the parameter type to match the trait",
368 trait_ty.to_string(),
369 Applicability::MachineApplicable,
379 trait_err_span.map(|sp| (sp, "type in trait".to_owned())),
380 Some(infer::ValuePairs::Terms(ExpectedFound {
381 expected: trait_fty.into(),
382 found: impl_fty.into(),
389 return Err(diag.emit());
392 // Check that all obligations are satisfied by the implementation's
394 let errors = inh.fulfillment_cx.borrow_mut().select_all_or_error(&infcx);
395 if !errors.is_empty() {
396 let reported = infcx.report_fulfillment_errors(&errors, None, false);
397 return Err(reported);
400 // Finally, resolve all regions. This catches wily misuses of
401 // lifetime parameters.
402 let fcx = FnCtxt::new(&inh, param_env, impl_m_hir_id);
403 fcx.regionck_item(impl_m_hir_id, impl_m_span, wf_tys);
409 fn check_region_bounds_on_impl_item<'tcx>(
412 impl_m: &ty::AssocItem,
413 trait_m: &ty::AssocItem,
414 trait_generics: &ty::Generics,
415 impl_generics: &ty::Generics,
416 ) -> Result<(), ErrorGuaranteed> {
417 let trait_params = trait_generics.own_counts().lifetimes;
418 let impl_params = impl_generics.own_counts().lifetimes;
421 "check_region_bounds_on_impl_item: \
422 trait_generics={:?} \
424 trait_generics, impl_generics
427 // Must have same number of early-bound lifetime parameters.
428 // Unfortunately, if the user screws up the bounds, then this
429 // will change classification between early and late. E.g.,
430 // if in trait we have `<'a,'b:'a>`, and in impl we just have
431 // `<'a,'b>`, then we have 2 early-bound lifetime parameters
432 // in trait but 0 in the impl. But if we report "expected 2
433 // but found 0" it's confusing, because it looks like there
434 // are zero. Since I don't quite know how to phrase things at
435 // the moment, give a kind of vague error message.
436 if trait_params != impl_params {
437 let item_kind = assoc_item_kind_str(impl_m);
438 let def_span = tcx.sess.source_map().guess_head_span(span);
442 .and_then(|did| tcx.hir().get_generics(did))
443 .map_or(def_span, |g| g.span);
444 let generics_span = tcx.hir().span_if_local(trait_m.def_id).map(|sp| {
445 let def_sp = tcx.sess.source_map().guess_head_span(sp);
449 .and_then(|did| tcx.hir().get_generics(did))
450 .map_or(def_sp, |g| g.span)
453 let reported = tcx.sess.emit_err(LifetimesOrBoundsMismatchOnTrait {
456 ident: impl_m.ident(tcx),
459 return Err(reported);
465 #[instrument(level = "debug", skip(infcx))]
466 fn extract_spans_for_error_reporting<'a, 'tcx>(
467 infcx: &infer::InferCtxt<'a, 'tcx>,
468 terr: &TypeError<'_>,
469 cause: &ObligationCause<'tcx>,
470 impl_m: &ty::AssocItem,
471 trait_m: &ty::AssocItem,
472 ) -> (Span, Option<Span>) {
474 let mut impl_args = match tcx.hir().expect_impl_item(impl_m.def_id.expect_local()).kind {
475 ImplItemKind::Fn(ref sig, _) => {
476 sig.decl.inputs.iter().map(|t| t.span).chain(iter::once(sig.decl.output.span()))
478 _ => bug!("{:?} is not a method", impl_m),
481 trait_m.def_id.as_local().map(|def_id| match tcx.hir().expect_trait_item(def_id).kind {
482 TraitItemKind::Fn(ref sig, _) => {
483 sig.decl.inputs.iter().map(|t| t.span).chain(iter::once(sig.decl.output.span()))
485 _ => bug!("{:?} is not a TraitItemKind::Fn", trait_m),
489 TypeError::ArgumentMutability(i) => {
490 (impl_args.nth(i).unwrap(), trait_args.and_then(|mut args| args.nth(i)))
492 TypeError::ArgumentSorts(ExpectedFound { .. }, i) => {
493 (impl_args.nth(i).unwrap(), trait_args.and_then(|mut args| args.nth(i)))
495 _ => (cause.span(tcx), tcx.hir().span_if_local(trait_m.def_id)),
499 fn compare_self_type<'tcx>(
501 impl_m: &ty::AssocItem,
503 trait_m: &ty::AssocItem,
504 impl_trait_ref: ty::TraitRef<'tcx>,
505 ) -> Result<(), ErrorGuaranteed> {
506 // Try to give more informative error messages about self typing
507 // mismatches. Note that any mismatch will also be detected
508 // below, where we construct a canonical function type that
509 // includes the self parameter as a normal parameter. It's just
510 // that the error messages you get out of this code are a bit more
511 // inscrutable, particularly for cases where one method has no
514 let self_string = |method: &ty::AssocItem| {
515 let untransformed_self_ty = match method.container {
516 ty::ImplContainer(_) => impl_trait_ref.self_ty(),
517 ty::TraitContainer(_) => tcx.types.self_param,
519 let self_arg_ty = tcx.fn_sig(method.def_id).input(0);
520 let param_env = ty::ParamEnv::reveal_all();
522 tcx.infer_ctxt().enter(|infcx| {
523 let self_arg_ty = tcx.liberate_late_bound_regions(method.def_id, self_arg_ty);
524 let can_eq_self = |ty| infcx.can_eq(param_env, untransformed_self_ty, ty).is_ok();
525 match ExplicitSelf::determine(self_arg_ty, can_eq_self) {
526 ExplicitSelf::ByValue => "self".to_owned(),
527 ExplicitSelf::ByReference(_, hir::Mutability::Not) => "&self".to_owned(),
528 ExplicitSelf::ByReference(_, hir::Mutability::Mut) => "&mut self".to_owned(),
529 _ => format!("self: {self_arg_ty}"),
534 match (trait_m.fn_has_self_parameter, impl_m.fn_has_self_parameter) {
535 (false, false) | (true, true) => {}
538 let self_descr = self_string(impl_m);
539 let mut err = struct_span_err!(
543 "method `{}` has a `{}` declaration in the impl, but not in the trait",
547 err.span_label(impl_m_span, format!("`{self_descr}` used in impl"));
548 if let Some(span) = tcx.hir().span_if_local(trait_m.def_id) {
549 err.span_label(span, format!("trait method declared without `{self_descr}`"));
551 err.note_trait_signature(trait_m.name.to_string(), trait_m.signature(tcx));
553 let reported = err.emit();
554 return Err(reported);
558 let self_descr = self_string(trait_m);
559 let mut err = struct_span_err!(
563 "method `{}` has a `{}` declaration in the trait, but not in the impl",
567 err.span_label(impl_m_span, format!("expected `{self_descr}` in impl"));
568 if let Some(span) = tcx.hir().span_if_local(trait_m.def_id) {
569 err.span_label(span, format!("`{self_descr}` used in trait"));
571 err.note_trait_signature(trait_m.name.to_string(), trait_m.signature(tcx));
573 let reported = err.emit();
574 return Err(reported);
581 /// Checks that the number of generics on a given assoc item in a trait impl is the same
582 /// as the number of generics on the respective assoc item in the trait definition.
584 /// For example this code emits the errors in the following code:
591 /// impl Trait for () {
594 /// type Assoc = u32;
599 /// Notably this does not error on `foo<T>` implemented as `foo<const N: u8>` or
600 /// `foo<const N: u8>` implemented as `foo<const N: u32>`. This is handled in
601 /// [`compare_generic_param_kinds`]. This function also does not handle lifetime parameters
602 fn compare_number_of_generics<'tcx>(
604 impl_: &ty::AssocItem,
606 trait_: &ty::AssocItem,
607 trait_span: Option<Span>,
608 ) -> Result<(), ErrorGuaranteed> {
609 let trait_own_counts = tcx.generics_of(trait_.def_id).own_counts();
610 let impl_own_counts = tcx.generics_of(impl_.def_id).own_counts();
612 // This avoids us erroring on `foo<T>` implemented as `foo<const N: u8>` as this is implemented
613 // in `compare_generic_param_kinds` which will give a nicer error message than something like:
614 // "expected 1 type parameter, found 0 type parameters"
615 if (trait_own_counts.types + trait_own_counts.consts)
616 == (impl_own_counts.types + impl_own_counts.consts)
622 ("type", trait_own_counts.types, impl_own_counts.types),
623 ("const", trait_own_counts.consts, impl_own_counts.consts),
626 let item_kind = assoc_item_kind_str(impl_);
628 let mut err_occurred = None;
629 for (kind, trait_count, impl_count) in matchings {
630 if impl_count != trait_count {
631 let (trait_spans, impl_trait_spans) = if let Some(def_id) = trait_.def_id.as_local() {
632 let trait_item = tcx.hir().expect_trait_item(def_id);
633 if trait_item.generics.params.is_empty() {
634 (Some(vec![trait_item.generics.span]), vec![])
636 let arg_spans: Vec<Span> =
637 trait_item.generics.params.iter().map(|p| p.span).collect();
638 let impl_trait_spans: Vec<Span> = trait_item
642 .filter_map(|p| match p.kind {
643 GenericParamKind::Type { synthetic: true, .. } => Some(p.span),
647 (Some(arg_spans), impl_trait_spans)
650 (trait_span.map(|s| vec![s]), vec![])
653 let impl_item = tcx.hir().expect_impl_item(impl_.def_id.expect_local());
654 let impl_item_impl_trait_spans: Vec<Span> = impl_item
658 .filter_map(|p| match p.kind {
659 GenericParamKind::Type { synthetic: true, .. } => Some(p.span),
663 let spans = impl_item.generics.spans();
664 let span = spans.primary_span();
666 let mut err = tcx.sess.struct_span_err_with_code(
669 "{} `{}` has {} {kind} parameter{} but its trait \
670 declaration has {} {kind} parameter{}",
674 pluralize!(impl_count),
676 pluralize!(trait_count),
679 DiagnosticId::Error("E0049".into()),
682 let mut suffix = None;
684 if let Some(spans) = trait_spans {
685 let mut spans = spans.iter();
686 if let Some(span) = spans.next() {
690 "expected {} {} parameter{}",
693 pluralize!(trait_count),
698 err.span_label(*span, "");
701 suffix = Some(format!(", expected {trait_count}"));
704 if let Some(span) = span {
708 "found {} {} parameter{}{}",
711 pluralize!(impl_count),
712 suffix.unwrap_or_else(String::new),
717 for span in impl_trait_spans.iter().chain(impl_item_impl_trait_spans.iter()) {
718 err.span_label(*span, "`impl Trait` introduces an implicit type parameter");
721 let reported = err.emit();
722 err_occurred = Some(reported);
726 if let Some(reported) = err_occurred { Err(reported) } else { Ok(()) }
729 fn compare_number_of_method_arguments<'tcx>(
731 impl_m: &ty::AssocItem,
733 trait_m: &ty::AssocItem,
734 trait_item_span: Option<Span>,
735 ) -> Result<(), ErrorGuaranteed> {
736 let impl_m_fty = tcx.fn_sig(impl_m.def_id);
737 let trait_m_fty = tcx.fn_sig(trait_m.def_id);
738 let trait_number_args = trait_m_fty.inputs().skip_binder().len();
739 let impl_number_args = impl_m_fty.inputs().skip_binder().len();
740 if trait_number_args != impl_number_args {
741 let trait_span = if let Some(def_id) = trait_m.def_id.as_local() {
742 match tcx.hir().expect_trait_item(def_id).kind {
743 TraitItemKind::Fn(ref trait_m_sig, _) => {
744 let pos = if trait_number_args > 0 { trait_number_args - 1 } else { 0 };
745 if let Some(arg) = trait_m_sig.decl.inputs.get(pos) {
749 arg.span.with_lo(trait_m_sig.decl.inputs[0].span.lo())
755 _ => bug!("{:?} is not a method", impl_m),
760 let impl_span = match tcx.hir().expect_impl_item(impl_m.def_id.expect_local()).kind {
761 ImplItemKind::Fn(ref impl_m_sig, _) => {
762 let pos = if impl_number_args > 0 { impl_number_args - 1 } else { 0 };
763 if let Some(arg) = impl_m_sig.decl.inputs.get(pos) {
767 arg.span.with_lo(impl_m_sig.decl.inputs[0].span.lo())
773 _ => bug!("{:?} is not a method", impl_m),
775 let mut err = struct_span_err!(
779 "method `{}` has {} but the declaration in trait `{}` has {}",
781 potentially_plural_count(impl_number_args, "parameter"),
782 tcx.def_path_str(trait_m.def_id),
785 if let Some(trait_span) = trait_span {
790 potentially_plural_count(trait_number_args, "parameter")
794 err.note_trait_signature(trait_m.name.to_string(), trait_m.signature(tcx));
799 "expected {}, found {}",
800 potentially_plural_count(trait_number_args, "parameter"),
804 let reported = err.emit();
805 return Err(reported);
811 fn compare_synthetic_generics<'tcx>(
813 impl_m: &ty::AssocItem,
814 trait_m: &ty::AssocItem,
815 ) -> Result<(), ErrorGuaranteed> {
816 // FIXME(chrisvittal) Clean up this function, list of FIXME items:
817 // 1. Better messages for the span labels
818 // 2. Explanation as to what is going on
819 // If we get here, we already have the same number of generics, so the zip will
821 let mut error_found = None;
822 let impl_m_generics = tcx.generics_of(impl_m.def_id);
823 let trait_m_generics = tcx.generics_of(trait_m.def_id);
824 let impl_m_type_params = impl_m_generics.params.iter().filter_map(|param| match param.kind {
825 GenericParamDefKind::Type { synthetic, .. } => Some((param.def_id, synthetic)),
826 GenericParamDefKind::Lifetime | GenericParamDefKind::Const { .. } => None,
828 let trait_m_type_params = trait_m_generics.params.iter().filter_map(|param| match param.kind {
829 GenericParamDefKind::Type { synthetic, .. } => Some((param.def_id, synthetic)),
830 GenericParamDefKind::Lifetime | GenericParamDefKind::Const { .. } => None,
832 for ((impl_def_id, impl_synthetic), (trait_def_id, trait_synthetic)) in
833 iter::zip(impl_m_type_params, trait_m_type_params)
835 if impl_synthetic != trait_synthetic {
836 let impl_def_id = impl_def_id.expect_local();
837 let impl_hir_id = tcx.hir().local_def_id_to_hir_id(impl_def_id);
838 let impl_span = tcx.hir().span(impl_hir_id);
839 let trait_span = tcx.def_span(trait_def_id);
840 let mut err = struct_span_err!(
844 "method `{}` has incompatible signature for trait",
847 err.span_label(trait_span, "declaration in trait here");
848 match (impl_synthetic, trait_synthetic) {
849 // The case where the impl method uses `impl Trait` but the trait method uses
852 err.span_label(impl_span, "expected generic parameter, found `impl Trait`");
854 // try taking the name from the trait impl
855 // FIXME: this is obviously suboptimal since the name can already be used
856 // as another generic argument
857 let new_name = tcx.sess.source_map().span_to_snippet(trait_span).ok()?;
858 let trait_m = trait_m.def_id.as_local()?;
859 let trait_m = tcx.hir().trait_item(hir::TraitItemId { def_id: trait_m });
861 let impl_m = impl_m.def_id.as_local()?;
862 let impl_m = tcx.hir().impl_item(hir::ImplItemId { def_id: impl_m });
864 // in case there are no generics, take the spot between the function name
865 // and the opening paren of the argument list
866 let new_generics_span =
867 tcx.sess.source_map().generate_fn_name_span(impl_span)?.shrink_to_hi();
868 // in case there are generics, just replace them
870 impl_m.generics.span.substitute_dummy(new_generics_span);
871 // replace with the generics from the trait
873 tcx.sess.source_map().span_to_snippet(trait_m.generics.span).ok()?;
875 err.multipart_suggestion(
876 "try changing the `impl Trait` argument to a generic parameter",
878 // replace `impl Trait` with `T`
879 (impl_span, new_name),
880 // replace impl method generics with trait method generics
881 // This isn't quite right, as users might have changed the names
882 // of the generics, but it works for the common case
883 (generics_span, new_generics),
885 Applicability::MaybeIncorrect,
890 // The case where the trait method uses `impl Trait`, but the impl method uses
891 // explicit generics.
893 err.span_label(impl_span, "expected `impl Trait`, found generic parameter");
895 let impl_m = impl_m.def_id.as_local()?;
896 let impl_m = tcx.hir().impl_item(hir::ImplItemId { def_id: impl_m });
897 let input_tys = match impl_m.kind {
898 hir::ImplItemKind::Fn(ref sig, _) => sig.decl.inputs,
901 struct Visitor(Option<Span>, hir::def_id::LocalDefId);
902 impl<'v> intravisit::Visitor<'v> for Visitor {
903 fn visit_ty(&mut self, ty: &'v hir::Ty<'v>) {
904 intravisit::walk_ty(self, ty);
905 if let hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) =
907 && let Res::Def(DefKind::TyParam, def_id) = path.res
908 && def_id == self.1.to_def_id()
910 self.0 = Some(ty.span);
914 let mut visitor = Visitor(None, impl_def_id);
915 for ty in input_tys {
916 intravisit::Visitor::visit_ty(&mut visitor, ty);
918 let span = visitor.0?;
920 let bounds = impl_m.generics.bounds_for_param(impl_def_id).next()?.bounds;
921 let bounds = bounds.first()?.span().to(bounds.last()?.span());
922 let bounds = tcx.sess.source_map().span_to_snippet(bounds).ok()?;
924 err.multipart_suggestion(
925 "try removing the generic parameter and using `impl Trait` instead",
927 // delete generic parameters
928 (impl_m.generics.span, String::new()),
929 // replace param usage with `impl Trait`
930 (span, format!("impl {bounds}")),
932 Applicability::MaybeIncorrect,
939 let reported = err.emit();
940 error_found = Some(reported);
943 if let Some(reported) = error_found { Err(reported) } else { Ok(()) }
946 /// Checks that all parameters in the generics of a given assoc item in a trait impl have
947 /// the same kind as the respective generic parameter in the trait def.
949 /// For example all 4 errors in the following code are emitted here:
952 /// fn foo<const N: u8>();
953 /// type bar<const N: u8>;
954 /// fn baz<const N: u32>();
958 /// impl Foo for () {
959 /// fn foo<const N: u64>() {}
961 /// type bar<const N: u64> {}
965 /// type blah<const N: i64> = u32;
970 /// This function does not handle lifetime parameters
971 fn compare_generic_param_kinds<'tcx>(
973 impl_item: &ty::AssocItem,
974 trait_item: &ty::AssocItem,
975 ) -> Result<(), ErrorGuaranteed> {
976 assert_eq!(impl_item.kind, trait_item.kind);
978 let ty_const_params_of = |def_id| {
979 tcx.generics_of(def_id).params.iter().filter(|param| {
982 GenericParamDefKind::Const { .. } | GenericParamDefKind::Type { .. }
987 for (param_impl, param_trait) in
988 iter::zip(ty_const_params_of(impl_item.def_id), ty_const_params_of(trait_item.def_id))
990 use GenericParamDefKind::*;
991 if match (¶m_impl.kind, ¶m_trait.kind) {
992 (Const { .. }, Const { .. })
993 if tcx.type_of(param_impl.def_id) != tcx.type_of(param_trait.def_id) =>
997 (Const { .. }, Type { .. }) | (Type { .. }, Const { .. }) => true,
998 // this is exhaustive so that anyone adding new generic param kinds knows
999 // to make sure this error is reported for them.
1000 (Const { .. }, Const { .. }) | (Type { .. }, Type { .. }) => false,
1001 (Lifetime { .. }, _) | (_, Lifetime { .. }) => unreachable!(),
1003 let param_impl_span = tcx.def_span(param_impl.def_id);
1004 let param_trait_span = tcx.def_span(param_trait.def_id);
1006 let mut err = struct_span_err!(
1010 "{} `{}` has an incompatible generic parameter for trait `{}`",
1011 assoc_item_kind_str(&impl_item),
1013 &tcx.def_path_str(tcx.parent(trait_item.def_id))
1016 let make_param_message = |prefix: &str, param: &ty::GenericParamDef| match param.kind {
1018 format!("{} const parameter of type `{}`", prefix, tcx.type_of(param.def_id))
1020 Type { .. } => format!("{} type parameter", prefix),
1021 Lifetime { .. } => unreachable!(),
1024 let trait_header_span = tcx.def_ident_span(tcx.parent(trait_item.def_id)).unwrap();
1025 err.span_label(trait_header_span, "");
1026 err.span_label(param_trait_span, make_param_message("expected", param_trait));
1028 let impl_header_span =
1029 tcx.sess.source_map().guess_head_span(tcx.def_span(tcx.parent(impl_item.def_id)));
1030 err.span_label(impl_header_span, "");
1031 err.span_label(param_impl_span, make_param_message("found", param_impl));
1033 let reported = err.emit();
1034 return Err(reported);
1041 crate fn compare_const_impl<'tcx>(
1043 impl_c: &ty::AssocItem,
1045 trait_c: &ty::AssocItem,
1046 impl_trait_ref: ty::TraitRef<'tcx>,
1048 debug!("compare_const_impl(impl_trait_ref={:?})", impl_trait_ref);
1050 tcx.infer_ctxt().enter(|infcx| {
1051 let param_env = tcx.param_env(impl_c.def_id);
1052 let inh = Inherited::new(infcx, impl_c.def_id.expect_local());
1053 let infcx = &inh.infcx;
1055 // The below is for the most part highly similar to the procedure
1056 // for methods above. It is simpler in many respects, especially
1057 // because we shouldn't really have to deal with lifetimes or
1058 // predicates. In fact some of this should probably be put into
1059 // shared functions because of DRY violations...
1060 let trait_to_impl_substs = impl_trait_ref.substs;
1062 // Create a parameter environment that represents the implementation's
1064 let impl_c_hir_id = tcx.hir().local_def_id_to_hir_id(impl_c.def_id.expect_local());
1066 // Compute placeholder form of impl and trait const tys.
1067 let impl_ty = tcx.type_of(impl_c.def_id);
1068 let trait_ty = tcx.bound_type_of(trait_c.def_id).subst(tcx, trait_to_impl_substs);
1069 let mut cause = ObligationCause::new(
1072 ObligationCauseCode::CompareImplConstObligation,
1075 // There is no "body" here, so just pass dummy id.
1077 inh.normalize_associated_types_in(impl_c_span, impl_c_hir_id, param_env, impl_ty);
1079 debug!("compare_const_impl: impl_ty={:?}", impl_ty);
1082 inh.normalize_associated_types_in(impl_c_span, impl_c_hir_id, param_env, trait_ty);
1084 debug!("compare_const_impl: trait_ty={:?}", trait_ty);
1087 .at(&cause, param_env)
1088 .sup(trait_ty, impl_ty)
1089 .map(|ok| inh.register_infer_ok_obligations(ok));
1091 if let Err(terr) = err {
1093 "checking associated const for compatibility: impl ty {:?}, trait ty {:?}",
1097 // Locate the Span containing just the type of the offending impl
1098 match tcx.hir().expect_impl_item(impl_c.def_id.expect_local()).kind {
1099 ImplItemKind::Const(ref ty, _) => cause.span = ty.span,
1100 _ => bug!("{:?} is not a impl const", impl_c),
1103 let mut diag = struct_span_err!(
1107 "implemented const `{}` has an incompatible type for trait",
1111 let trait_c_span = trait_c.def_id.as_local().map(|trait_c_def_id| {
1112 // Add a label to the Span containing just the type of the const
1113 match tcx.hir().expect_trait_item(trait_c_def_id).kind {
1114 TraitItemKind::Const(ref ty, _) => ty.span,
1115 _ => bug!("{:?} is not a trait const", trait_c),
1119 infcx.note_type_err(
1122 trait_c_span.map(|span| (span, "type in trait".to_owned())),
1123 Some(infer::ValuePairs::Terms(ExpectedFound {
1124 expected: trait_ty.into(),
1125 found: impl_ty.into(),
1134 // Check that all obligations are satisfied by the implementation's
1136 let errors = inh.fulfillment_cx.borrow_mut().select_all_or_error(&infcx);
1137 if !errors.is_empty() {
1138 infcx.report_fulfillment_errors(&errors, None, false);
1142 let fcx = FnCtxt::new(&inh, param_env, impl_c_hir_id);
1143 fcx.regionck_item(impl_c_hir_id, impl_c_span, FxHashSet::default());
1147 crate fn compare_ty_impl<'tcx>(
1149 impl_ty: &ty::AssocItem,
1151 trait_ty: &ty::AssocItem,
1152 impl_trait_ref: ty::TraitRef<'tcx>,
1153 trait_item_span: Option<Span>,
1155 debug!("compare_impl_type(impl_trait_ref={:?})", impl_trait_ref);
1157 let _: Result<(), ErrorGuaranteed> = (|| {
1158 compare_number_of_generics(tcx, impl_ty, impl_ty_span, trait_ty, trait_item_span)?;
1160 compare_generic_param_kinds(tcx, impl_ty, trait_ty)?;
1162 let sp = tcx.def_span(impl_ty.def_id);
1163 compare_type_predicate_entailment(tcx, impl_ty, sp, trait_ty, impl_trait_ref)?;
1165 check_type_bounds(tcx, trait_ty, impl_ty, impl_ty_span, impl_trait_ref)
1169 /// The equivalent of [compare_predicate_entailment], but for associated types
1170 /// instead of associated functions.
1171 fn compare_type_predicate_entailment<'tcx>(
1173 impl_ty: &ty::AssocItem,
1175 trait_ty: &ty::AssocItem,
1176 impl_trait_ref: ty::TraitRef<'tcx>,
1177 ) -> Result<(), ErrorGuaranteed> {
1178 let impl_substs = InternalSubsts::identity_for_item(tcx, impl_ty.def_id);
1179 let trait_to_impl_substs =
1180 impl_substs.rebase_onto(tcx, impl_ty.container.id(), impl_trait_ref.substs);
1182 let impl_ty_generics = tcx.generics_of(impl_ty.def_id);
1183 let trait_ty_generics = tcx.generics_of(trait_ty.def_id);
1184 let impl_ty_predicates = tcx.predicates_of(impl_ty.def_id);
1185 let trait_ty_predicates = tcx.predicates_of(trait_ty.def_id);
1187 check_region_bounds_on_impl_item(
1196 let impl_ty_own_bounds = impl_ty_predicates.instantiate_own(tcx, impl_substs);
1198 if impl_ty_own_bounds.is_empty() {
1199 // Nothing to check.
1203 // This `HirId` should be used for the `body_id` field on each
1204 // `ObligationCause` (and the `FnCtxt`). This is what
1205 // `regionck_item` expects.
1206 let impl_ty_hir_id = tcx.hir().local_def_id_to_hir_id(impl_ty.def_id.expect_local());
1207 let cause = ObligationCause::new(
1210 ObligationCauseCode::CompareImplTypeObligation {
1211 impl_item_def_id: impl_ty.def_id.expect_local(),
1212 trait_item_def_id: trait_ty.def_id,
1216 debug!("compare_type_predicate_entailment: trait_to_impl_substs={:?}", trait_to_impl_substs);
1218 // The predicates declared by the impl definition, the trait and the
1219 // associated type in the trait are assumed.
1220 let impl_predicates = tcx.predicates_of(impl_ty_predicates.parent.unwrap());
1221 let mut hybrid_preds = impl_predicates.instantiate_identity(tcx);
1224 .extend(trait_ty_predicates.instantiate_own(tcx, trait_to_impl_substs).predicates);
1226 debug!("compare_type_predicate_entailment: bounds={:?}", hybrid_preds);
1228 let normalize_cause = traits::ObligationCause::misc(impl_ty_span, impl_ty_hir_id);
1229 let param_env = ty::ParamEnv::new(
1230 tcx.intern_predicates(&hybrid_preds.predicates),
1232 hir::Constness::NotConst,
1234 let param_env = traits::normalize_param_env_or_error(
1238 normalize_cause.clone(),
1240 tcx.infer_ctxt().enter(|infcx| {
1241 let inh = Inherited::new(infcx, impl_ty.def_id.expect_local());
1242 let infcx = &inh.infcx;
1244 debug!("compare_type_predicate_entailment: caller_bounds={:?}", param_env.caller_bounds());
1246 let mut selcx = traits::SelectionContext::new(&infcx);
1248 for predicate in impl_ty_own_bounds.predicates {
1249 let traits::Normalized { value: predicate, obligations } =
1250 traits::normalize(&mut selcx, param_env, normalize_cause.clone(), predicate);
1252 inh.register_predicates(obligations);
1253 inh.register_predicate(traits::Obligation::new(cause.clone(), param_env, predicate));
1256 // Check that all obligations are satisfied by the implementation's
1258 let errors = inh.fulfillment_cx.borrow_mut().select_all_or_error(&infcx);
1259 if !errors.is_empty() {
1260 let reported = infcx.report_fulfillment_errors(&errors, None, false);
1261 return Err(reported);
1264 // Finally, resolve all regions. This catches wily misuses of
1265 // lifetime parameters.
1266 let fcx = FnCtxt::new(&inh, param_env, impl_ty_hir_id);
1267 fcx.regionck_item(impl_ty_hir_id, impl_ty_span, FxHashSet::default());
1273 /// Validate that `ProjectionCandidate`s created for this associated type will
1278 /// trait X { type Y: Copy } impl X for T { type Y = S; }
1280 /// We are able to normalize `<T as X>::U` to `S`, and so when we check the
1281 /// impl is well-formed we have to prove `S: Copy`.
1283 /// For default associated types the normalization is not possible (the value
1284 /// from the impl could be overridden). We also can't normalize generic
1285 /// associated types (yet) because they contain bound parameters.
1286 #[tracing::instrument(level = "debug", skip(tcx))]
1287 pub fn check_type_bounds<'tcx>(
1289 trait_ty: &ty::AssocItem,
1290 impl_ty: &ty::AssocItem,
1292 impl_trait_ref: ty::TraitRef<'tcx>,
1293 ) -> Result<(), ErrorGuaranteed> {
1296 // impl<A, B> Foo<u32> for (A, B) {
1300 // - `impl_trait_ref` would be `<(A, B) as Foo<u32>>
1301 // - `impl_ty_substs` would be `[A, B, ^0.0]` (`^0.0` here is the bound var with db 0 and index 0)
1302 // - `rebased_substs` would be `[(A, B), u32, ^0.0]`, combining the substs from
1303 // the *trait* with the generic associated type parameters (as bound vars).
1305 // A note regarding the use of bound vars here:
1306 // Imagine as an example
1309 // type Member<C: Eq>;
1312 // impl Family for VecFamily {
1313 // type Member<C: Eq> = i32;
1316 // Here, we would generate
1318 // forall<C> { Normalize(<VecFamily as Family>::Member<C> => i32) }
1320 // when we really would like to generate
1322 // forall<C> { Normalize(<VecFamily as Family>::Member<C> => i32) :- Implemented(C: Eq) }
1324 // But, this is probably fine, because although the first clause can be used with types C that
1325 // do not implement Eq, for it to cause some kind of problem, there would have to be a
1326 // VecFamily::Member<X> for some type X where !(X: Eq), that appears in the value of type
1327 // Member<C: Eq> = .... That type would fail a well-formedness check that we ought to be doing
1328 // elsewhere, which would check that any <T as Family>::Member<X> meets the bounds declared in
1329 // the trait (notably, that X: Eq and T: Family).
1330 let defs: &ty::Generics = tcx.generics_of(impl_ty.def_id);
1331 let mut substs = smallvec::SmallVec::with_capacity(defs.count());
1332 if let Some(def_id) = defs.parent {
1333 let parent_defs = tcx.generics_of(def_id);
1334 InternalSubsts::fill_item(&mut substs, tcx, parent_defs, &mut |param, _| {
1335 tcx.mk_param_from_def(param)
1338 let mut bound_vars: smallvec::SmallVec<[ty::BoundVariableKind; 8]> =
1339 smallvec::SmallVec::with_capacity(defs.count());
1340 InternalSubsts::fill_single(&mut substs, defs, &mut |param, _| match param.kind {
1341 GenericParamDefKind::Type { .. } => {
1342 let kind = ty::BoundTyKind::Param(param.name);
1343 let bound_var = ty::BoundVariableKind::Ty(kind);
1344 bound_vars.push(bound_var);
1345 tcx.mk_ty(ty::Bound(
1347 ty::BoundTy { var: ty::BoundVar::from_usize(bound_vars.len() - 1), kind },
1351 GenericParamDefKind::Lifetime => {
1352 let kind = ty::BoundRegionKind::BrNamed(param.def_id, param.name);
1353 let bound_var = ty::BoundVariableKind::Region(kind);
1354 bound_vars.push(bound_var);
1355 tcx.mk_region(ty::ReLateBound(
1357 ty::BoundRegion { var: ty::BoundVar::from_usize(bound_vars.len() - 1), kind },
1361 GenericParamDefKind::Const { .. } => {
1362 let bound_var = ty::BoundVariableKind::Const;
1363 bound_vars.push(bound_var);
1364 tcx.mk_const(ty::ConstS {
1365 ty: tcx.type_of(param.def_id),
1366 val: ty::ConstKind::Bound(
1368 ty::BoundVar::from_usize(bound_vars.len() - 1),
1374 let bound_vars = tcx.mk_bound_variable_kinds(bound_vars.into_iter());
1375 let impl_ty_substs = tcx.intern_substs(&substs);
1377 let rebased_substs =
1378 impl_ty_substs.rebase_onto(tcx, impl_ty.container.id(), impl_trait_ref.substs);
1379 let impl_ty_value = tcx.type_of(impl_ty.def_id);
1381 let param_env = tcx.param_env(impl_ty.def_id);
1383 // When checking something like
1385 // trait X { type Y: PartialEq<<Self as X>::Y> }
1386 // impl X for T { default type Y = S; }
1388 // We will have to prove the bound S: PartialEq<<T as X>::Y>. In this case
1389 // we want <T as X>::Y to normalize to S. This is valid because we are
1390 // checking the default value specifically here. Add this equality to the
1391 // ParamEnv for normalization specifically.
1392 let normalize_param_env = {
1393 let mut predicates = param_env.caller_bounds().iter().collect::<Vec<_>>();
1394 match impl_ty_value.kind() {
1395 ty::Projection(proj)
1396 if proj.item_def_id == trait_ty.def_id && proj.substs == rebased_substs =>
1398 // Don't include this predicate if the projected type is
1399 // exactly the same as the projection. This can occur in
1400 // (somewhat dubious) code like this:
1402 // impl<T> X for T where T: X { type Y = <T as X>::Y; }
1404 _ => predicates.push(
1405 ty::Binder::bind_with_vars(
1406 ty::ProjectionPredicate {
1407 projection_ty: ty::ProjectionTy {
1408 item_def_id: trait_ty.def_id,
1409 substs: rebased_substs,
1411 term: impl_ty_value.into(),
1419 tcx.intern_predicates(&predicates),
1421 param_env.constness(),
1424 debug!(?normalize_param_env);
1426 let impl_ty_substs = InternalSubsts::identity_for_item(tcx, impl_ty.def_id);
1427 let rebased_substs =
1428 impl_ty_substs.rebase_onto(tcx, impl_ty.container.id(), impl_trait_ref.substs);
1430 tcx.infer_ctxt().enter(move |infcx| {
1431 let inh = Inherited::new(infcx, impl_ty.def_id.expect_local());
1432 let infcx = &inh.infcx;
1433 let mut selcx = traits::SelectionContext::new(&infcx);
1435 let impl_ty_hir_id = tcx.hir().local_def_id_to_hir_id(impl_ty.def_id.expect_local());
1436 let normalize_cause = ObligationCause::new(
1439 ObligationCauseCode::CheckAssociatedTypeBounds {
1440 impl_item_def_id: impl_ty.def_id.expect_local(),
1441 trait_item_def_id: trait_ty.def_id,
1444 let mk_cause = |span: Span| {
1445 let code = if span.is_dummy() {
1446 traits::MiscObligation
1448 traits::BindingObligation(trait_ty.def_id, span)
1450 ObligationCause::new(impl_ty_span, impl_ty_hir_id, code)
1453 let obligations = tcx
1454 .bound_explicit_item_bounds(trait_ty.def_id)
1456 .map(|e| e.map_bound(|e| *e).transpose_tuple2())
1457 .map(|(bound, span)| {
1459 let concrete_ty_bound = bound.subst(tcx, rebased_substs);
1460 debug!("check_type_bounds: concrete_ty_bound = {:?}", concrete_ty_bound);
1462 traits::Obligation::new(mk_cause(span.0), param_env, concrete_ty_bound)
1465 debug!("check_type_bounds: item_bounds={:?}", obligations);
1467 for mut obligation in util::elaborate_obligations(tcx, obligations) {
1468 let traits::Normalized { value: normalized_predicate, obligations } = traits::normalize(
1470 normalize_param_env,
1471 normalize_cause.clone(),
1472 obligation.predicate,
1474 debug!("compare_projection_bounds: normalized predicate = {:?}", normalized_predicate);
1475 obligation.predicate = normalized_predicate;
1477 inh.register_predicates(obligations);
1478 inh.register_predicate(obligation);
1481 // Check that all obligations are satisfied by the implementation's
1483 let errors = inh.fulfillment_cx.borrow_mut().select_all_or_error(&infcx);
1484 if !errors.is_empty() {
1485 let reported = infcx.report_fulfillment_errors(&errors, None, false);
1486 return Err(reported);
1489 // Finally, resolve all regions. This catches wily misuses of
1490 // lifetime parameters.
1491 let fcx = FnCtxt::new(&inh, param_env, impl_ty_hir_id);
1492 let implied_bounds = match impl_ty.container {
1493 ty::TraitContainer(_) => FxHashSet::default(),
1494 ty::ImplContainer(def_id) => fcx.impl_implied_bounds(def_id, impl_ty_span),
1496 fcx.regionck_item(impl_ty_hir_id, impl_ty_span, implied_bounds);
1502 fn assoc_item_kind_str(impl_item: &ty::AssocItem) -> &'static str {
1503 match impl_item.kind {
1504 ty::AssocKind::Const => "const",
1505 ty::AssocKind::Fn => "method",
1506 ty::AssocKind::Type => "type",