use super::potentially_plural_count; use crate::check::regionck::OutlivesEnvironmentExt; use crate::check::wfcheck; use crate::errors::LifetimesOrBoundsMismatchOnTrait; use rustc_data_structures::fx::FxHashSet; use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticId, ErrorGuaranteed}; use rustc_hir as hir; use rustc_hir::def::{DefKind, Res}; use rustc_hir::intravisit; use rustc_hir::{GenericParamKind, ImplItemKind, TraitItemKind}; use rustc_infer::infer::outlives::env::OutlivesEnvironment; use rustc_infer::infer::{self, TyCtxtInferExt}; use rustc_infer::traits::util; use rustc_middle::ty::error::{ExpectedFound, TypeError}; use rustc_middle::ty::subst::{InternalSubsts, Subst}; use rustc_middle::ty::util::ExplicitSelf; use rustc_middle::ty::{self, DefIdTree}; use rustc_middle::ty::{GenericParamDefKind, ToPredicate, TyCtxt}; use rustc_span::Span; use rustc_trait_selection::traits::error_reporting::InferCtxtExt; use rustc_trait_selection::traits::{ self, ObligationCause, ObligationCauseCode, ObligationCtxt, Reveal, }; use std::iter; /// Checks that a method from an impl conforms to the signature of /// the same method as declared in the trait. /// /// # Parameters /// /// - `impl_m`: type of the method we are checking /// - `impl_m_span`: span to use for reporting errors /// - `trait_m`: the method in the trait /// - `impl_trait_ref`: the TraitRef corresponding to the trait implementation pub(crate) fn compare_impl_method<'tcx>( tcx: TyCtxt<'tcx>, impl_m: &ty::AssocItem, trait_m: &ty::AssocItem, impl_trait_ref: ty::TraitRef<'tcx>, trait_item_span: Option, ) { debug!("compare_impl_method(impl_trait_ref={:?})", impl_trait_ref); let impl_m_span = tcx.def_span(impl_m.def_id); if let Err(_) = compare_self_type(tcx, impl_m, impl_m_span, trait_m, impl_trait_ref) { return; } if let Err(_) = compare_number_of_generics(tcx, impl_m, impl_m_span, trait_m, trait_item_span) { return; } if let Err(_) = compare_generic_param_kinds(tcx, impl_m, trait_m) { return; } if let Err(_) = compare_number_of_method_arguments(tcx, impl_m, impl_m_span, trait_m, trait_item_span) { return; } if let Err(_) = compare_synthetic_generics(tcx, impl_m, trait_m) { return; } if let Err(_) = compare_predicate_entailment(tcx, impl_m, impl_m_span, trait_m, impl_trait_ref) { return; } } fn compare_predicate_entailment<'tcx>( tcx: TyCtxt<'tcx>, impl_m: &ty::AssocItem, impl_m_span: Span, trait_m: &ty::AssocItem, impl_trait_ref: ty::TraitRef<'tcx>, ) -> Result<(), ErrorGuaranteed> { let trait_to_impl_substs = impl_trait_ref.substs; // This node-id should be used for the `body_id` field on each // `ObligationCause` (and the `FnCtxt`). // // FIXME(@lcnr): remove that after removing `cause.body_id` from // obligations. let impl_m_hir_id = tcx.hir().local_def_id_to_hir_id(impl_m.def_id.expect_local()); // We sometimes modify the span further down. let mut cause = ObligationCause::new( impl_m_span, impl_m_hir_id, ObligationCauseCode::CompareImplItemObligation { impl_item_def_id: impl_m.def_id.expect_local(), trait_item_def_id: trait_m.def_id, kind: impl_m.kind, }, ); // This code is best explained by example. Consider a trait: // // trait Trait<'t, T> { // fn method<'a, M>(t: &'t T, m: &'a M) -> Self; // } // // And an impl: // // impl<'i, 'j, U> Trait<'j, &'i U> for Foo { // fn method<'b, N>(t: &'j &'i U, m: &'b N) -> Foo; // } // // We wish to decide if those two method types are compatible. // // We start out with trait_to_impl_substs, that maps the trait // type parameters to impl type parameters. This is taken from the // impl trait reference: // // trait_to_impl_substs = {'t => 'j, T => &'i U, Self => Foo} // // We create a mapping `dummy_substs` that maps from the impl type // parameters to fresh types and regions. For type parameters, // this is the identity transform, but we could as well use any // placeholder types. For regions, we convert from bound to free // regions (Note: but only early-bound regions, i.e., those // declared on the impl or used in type parameter bounds). // // impl_to_placeholder_substs = {'i => 'i0, U => U0, N => N0 } // // Now we can apply placeholder_substs to the type of the impl method // to yield a new function type in terms of our fresh, placeholder // types: // // <'b> fn(t: &'i0 U0, m: &'b) -> Foo // // We now want to extract and substitute the type of the *trait* // method and compare it. To do so, we must create a compound // substitution by combining trait_to_impl_substs and // impl_to_placeholder_substs, and also adding a mapping for the method // type parameters. We extend the mapping to also include // the method parameters. // // trait_to_placeholder_substs = { T => &'i0 U0, Self => Foo, M => N0 } // // Applying this to the trait method type yields: // // <'a> fn(t: &'i0 U0, m: &'a) -> Foo // // This type is also the same but the name of the bound region ('a // vs 'b). However, the normal subtyping rules on fn types handle // this kind of equivalency just fine. // // We now use these substitutions to ensure that all declared bounds are // satisfied by the implementation's method. // // We do this by creating a parameter environment which contains a // substitution corresponding to impl_to_placeholder_substs. We then build // trait_to_placeholder_substs and use it to convert the predicates contained // in the trait_m.generics to the placeholder form. // // Finally we register each of these predicates as an obligation in // a fresh FulfillmentCtxt, and invoke select_all_or_error. // Create mapping from impl to placeholder. let impl_to_placeholder_substs = InternalSubsts::identity_for_item(tcx, impl_m.def_id); // Create mapping from trait to placeholder. let trait_to_placeholder_substs = impl_to_placeholder_substs.rebase_onto(tcx, impl_m.container_id(tcx), trait_to_impl_substs); debug!("compare_impl_method: trait_to_placeholder_substs={:?}", trait_to_placeholder_substs); let impl_m_generics = tcx.generics_of(impl_m.def_id); let trait_m_generics = tcx.generics_of(trait_m.def_id); let impl_m_predicates = tcx.predicates_of(impl_m.def_id); let trait_m_predicates = tcx.predicates_of(trait_m.def_id); // Check region bounds. check_region_bounds_on_impl_item(tcx, impl_m, trait_m, &trait_m_generics, &impl_m_generics)?; // Create obligations for each predicate declared by the impl // definition in the context of the trait's parameter // environment. We can't just use `impl_env.caller_bounds`, // however, because we want to replace all late-bound regions with // region variables. let impl_predicates = tcx.predicates_of(impl_m_predicates.parent.unwrap()); let mut hybrid_preds = impl_predicates.instantiate_identity(tcx); debug!("compare_impl_method: impl_bounds={:?}", hybrid_preds); // This is the only tricky bit of the new way we check implementation methods // We need to build a set of predicates where only the method-level bounds // are from the trait and we assume all other bounds from the implementation // to be previously satisfied. // // We then register the obligations from the impl_m and check to see // if all constraints hold. hybrid_preds .predicates .extend(trait_m_predicates.instantiate_own(tcx, trait_to_placeholder_substs).predicates); // Construct trait parameter environment and then shift it into the placeholder viewpoint. // The key step here is to update the caller_bounds's predicates to be // the new hybrid bounds we computed. let normalize_cause = traits::ObligationCause::misc(impl_m_span, impl_m_hir_id); let param_env = ty::ParamEnv::new( tcx.intern_predicates(&hybrid_preds.predicates), Reveal::UserFacing, hir::Constness::NotConst, ); let param_env = traits::normalize_param_env_or_error(tcx, param_env, normalize_cause); tcx.infer_ctxt().enter(|ref infcx| { let ocx = ObligationCtxt::new(infcx); debug!("compare_impl_method: caller_bounds={:?}", param_env.caller_bounds()); let mut selcx = traits::SelectionContext::new(&infcx); let impl_m_own_bounds = impl_m_predicates.instantiate_own(tcx, impl_to_placeholder_substs); for (predicate, span) in iter::zip(impl_m_own_bounds.predicates, impl_m_own_bounds.spans) { let normalize_cause = traits::ObligationCause::misc(span, impl_m_hir_id); let traits::Normalized { value: predicate, obligations } = traits::normalize(&mut selcx, param_env, normalize_cause, predicate); ocx.register_obligations(obligations); let cause = ObligationCause::new( span, impl_m_hir_id, ObligationCauseCode::CompareImplItemObligation { impl_item_def_id: impl_m.def_id.expect_local(), trait_item_def_id: trait_m.def_id, kind: impl_m.kind, }, ); ocx.register_obligation(traits::Obligation::new(cause, param_env, predicate)); } // We now need to check that the signature of the impl method is // compatible with that of the trait method. We do this by // checking that `impl_fty <: trait_fty`. // // FIXME. Unfortunately, this doesn't quite work right now because // associated type normalization is not integrated into subtype // checks. For the comparison to be valid, we need to // normalize the associated types in the impl/trait methods // first. However, because function types bind regions, just // calling `normalize_associated_types_in` would have no effect on // any associated types appearing in the fn arguments or return // type. // Compute placeholder form of impl and trait method tys. let tcx = infcx.tcx; let mut wf_tys = FxHashSet::default(); let impl_sig = infcx.replace_bound_vars_with_fresh_vars( impl_m_span, infer::HigherRankedType, tcx.fn_sig(impl_m.def_id), ); let norm_cause = ObligationCause::misc(impl_m_span, impl_m_hir_id); let impl_sig = ocx.normalize(norm_cause.clone(), param_env, impl_sig); let impl_fty = tcx.mk_fn_ptr(ty::Binder::dummy(impl_sig)); debug!("compare_impl_method: impl_fty={:?}", impl_fty); let trait_sig = tcx.bound_fn_sig(trait_m.def_id).subst(tcx, trait_to_placeholder_substs); let trait_sig = tcx.liberate_late_bound_regions(impl_m.def_id, trait_sig); let trait_sig = ocx.normalize(norm_cause, param_env, trait_sig); // Add the resulting inputs and output as well-formed. wf_tys.extend(trait_sig.inputs_and_output.iter()); let trait_fty = tcx.mk_fn_ptr(ty::Binder::dummy(trait_sig)); debug!("compare_impl_method: trait_fty={:?}", trait_fty); // FIXME: We'd want to keep more accurate spans than "the method signature" when // processing the comparison between the trait and impl fn, but we sadly lose them // and point at the whole signature when a trait bound or specific input or output // type would be more appropriate. In other places we have a `Vec` // corresponding to their `Vec`, but we don't have that here. // Fixing this would improve the output of test `issue-83765.rs`. let sub_result = infcx .at(&cause, param_env) .sup(trait_fty, impl_fty) .map(|infer_ok| ocx.register_infer_ok_obligations(infer_ok)); if let Err(terr) = sub_result { debug!("sub_types failed: impl ty {:?}, trait ty {:?}", impl_fty, trait_fty); let (impl_err_span, trait_err_span) = extract_spans_for_error_reporting(&infcx, &terr, &cause, impl_m, trait_m); cause.span = impl_err_span; let mut diag = struct_span_err!( tcx.sess, cause.span(), E0053, "method `{}` has an incompatible type for trait", trait_m.name ); match &terr { TypeError::ArgumentMutability(0) | TypeError::ArgumentSorts(_, 0) if trait_m.fn_has_self_parameter => { let ty = trait_sig.inputs()[0]; let sugg = match ExplicitSelf::determine(ty, |_| ty == impl_trait_ref.self_ty()) { ExplicitSelf::ByValue => "self".to_owned(), ExplicitSelf::ByReference(_, hir::Mutability::Not) => "&self".to_owned(), ExplicitSelf::ByReference(_, hir::Mutability::Mut) => { "&mut self".to_owned() } _ => format!("self: {ty}"), }; // When the `impl` receiver is an arbitrary self type, like `self: Box`, the // span points only at the type `Box, but we want to cover the whole // argument pattern and type. let span = match tcx.hir().expect_impl_item(impl_m.def_id.expect_local()).kind { ImplItemKind::Fn(ref sig, body) => tcx .hir() .body_param_names(body) .zip(sig.decl.inputs.iter()) .map(|(param, ty)| param.span.to(ty.span)) .next() .unwrap_or(impl_err_span), _ => bug!("{:?} is not a method", impl_m), }; diag.span_suggestion( span, "change the self-receiver type to match the trait", sugg, Applicability::MachineApplicable, ); } TypeError::ArgumentMutability(i) | TypeError::ArgumentSorts(_, i) => { if trait_sig.inputs().len() == *i { // Suggestion to change output type. We do not suggest in `async` functions // to avoid complex logic or incorrect output. match tcx.hir().expect_impl_item(impl_m.def_id.expect_local()).kind { ImplItemKind::Fn(ref sig, _) if sig.header.asyncness == hir::IsAsync::NotAsync => { let msg = "change the output type to match the trait"; let ap = Applicability::MachineApplicable; match sig.decl.output { hir::FnRetTy::DefaultReturn(sp) => { let sugg = format!("-> {} ", trait_sig.output()); diag.span_suggestion_verbose(sp, msg, sugg, ap); } hir::FnRetTy::Return(hir_ty) => { let sugg = trait_sig.output(); diag.span_suggestion(hir_ty.span, msg, sugg, ap); } }; } _ => {} }; } else if let Some(trait_ty) = trait_sig.inputs().get(*i) { diag.span_suggestion( impl_err_span, "change the parameter type to match the trait", trait_ty, Applicability::MachineApplicable, ); } } _ => {} } infcx.note_type_err( &mut diag, &cause, trait_err_span.map(|sp| (sp, "type in trait".to_owned())), Some(infer::ValuePairs::Terms(ExpectedFound { expected: trait_fty.into(), found: impl_fty.into(), })), &terr, false, false, ); return Err(diag.emit()); } // Check that all obligations are satisfied by the implementation's // version. let errors = ocx.select_all_or_error(); if !errors.is_empty() { let reported = infcx.report_fulfillment_errors(&errors, None, false); return Err(reported); } // Finally, resolve all regions. This catches wily misuses of // lifetime parameters. let mut outlives_environment = OutlivesEnvironment::new(param_env); outlives_environment.add_implied_bounds(infcx, wf_tys, impl_m_hir_id); infcx.check_region_obligations_and_report_errors( impl_m.def_id.expect_local(), &outlives_environment, ); Ok(()) }) } fn check_region_bounds_on_impl_item<'tcx>( tcx: TyCtxt<'tcx>, impl_m: &ty::AssocItem, trait_m: &ty::AssocItem, trait_generics: &ty::Generics, impl_generics: &ty::Generics, ) -> Result<(), ErrorGuaranteed> { let trait_params = trait_generics.own_counts().lifetimes; let impl_params = impl_generics.own_counts().lifetimes; debug!( "check_region_bounds_on_impl_item: \ trait_generics={:?} \ impl_generics={:?}", trait_generics, impl_generics ); // Must have same number of early-bound lifetime parameters. // Unfortunately, if the user screws up the bounds, then this // will change classification between early and late. E.g., // if in trait we have `<'a,'b:'a>`, and in impl we just have // `<'a,'b>`, then we have 2 early-bound lifetime parameters // in trait but 0 in the impl. But if we report "expected 2 // but found 0" it's confusing, because it looks like there // are zero. Since I don't quite know how to phrase things at // the moment, give a kind of vague error message. if trait_params != impl_params { let span = tcx .hir() .get_generics(impl_m.def_id.expect_local()) .expect("expected impl item to have generics or else we can't compare them") .span; let generics_span = if let Some(local_def_id) = trait_m.def_id.as_local() { Some( tcx.hir() .get_generics(local_def_id) .expect("expected trait item to have generics or else we can't compare them") .span, ) } else { None }; let reported = tcx.sess.emit_err(LifetimesOrBoundsMismatchOnTrait { span, item_kind: assoc_item_kind_str(impl_m), ident: impl_m.ident(tcx), generics_span, }); return Err(reported); } Ok(()) } #[instrument(level = "debug", skip(infcx))] fn extract_spans_for_error_reporting<'a, 'tcx>( infcx: &infer::InferCtxt<'a, 'tcx>, terr: &TypeError<'_>, cause: &ObligationCause<'tcx>, impl_m: &ty::AssocItem, trait_m: &ty::AssocItem, ) -> (Span, Option) { let tcx = infcx.tcx; let mut impl_args = match tcx.hir().expect_impl_item(impl_m.def_id.expect_local()).kind { ImplItemKind::Fn(ref sig, _) => { sig.decl.inputs.iter().map(|t| t.span).chain(iter::once(sig.decl.output.span())) } _ => bug!("{:?} is not a method", impl_m), }; let trait_args = trait_m.def_id.as_local().map(|def_id| match tcx.hir().expect_trait_item(def_id).kind { TraitItemKind::Fn(ref sig, _) => { sig.decl.inputs.iter().map(|t| t.span).chain(iter::once(sig.decl.output.span())) } _ => bug!("{:?} is not a TraitItemKind::Fn", trait_m), }); match *terr { TypeError::ArgumentMutability(i) => { (impl_args.nth(i).unwrap(), trait_args.and_then(|mut args| args.nth(i))) } TypeError::ArgumentSorts(ExpectedFound { .. }, i) => { (impl_args.nth(i).unwrap(), trait_args.and_then(|mut args| args.nth(i))) } _ => (cause.span(), tcx.hir().span_if_local(trait_m.def_id)), } } fn compare_self_type<'tcx>( tcx: TyCtxt<'tcx>, impl_m: &ty::AssocItem, impl_m_span: Span, trait_m: &ty::AssocItem, impl_trait_ref: ty::TraitRef<'tcx>, ) -> Result<(), ErrorGuaranteed> { // Try to give more informative error messages about self typing // mismatches. Note that any mismatch will also be detected // below, where we construct a canonical function type that // includes the self parameter as a normal parameter. It's just // that the error messages you get out of this code are a bit more // inscrutable, particularly for cases where one method has no // self. let self_string = |method: &ty::AssocItem| { let untransformed_self_ty = match method.container { ty::ImplContainer => impl_trait_ref.self_ty(), ty::TraitContainer => tcx.types.self_param, }; let self_arg_ty = tcx.fn_sig(method.def_id).input(0); let param_env = ty::ParamEnv::reveal_all(); tcx.infer_ctxt().enter(|infcx| { let self_arg_ty = tcx.liberate_late_bound_regions(method.def_id, self_arg_ty); let can_eq_self = |ty| infcx.can_eq(param_env, untransformed_self_ty, ty).is_ok(); match ExplicitSelf::determine(self_arg_ty, can_eq_self) { ExplicitSelf::ByValue => "self".to_owned(), ExplicitSelf::ByReference(_, hir::Mutability::Not) => "&self".to_owned(), ExplicitSelf::ByReference(_, hir::Mutability::Mut) => "&mut self".to_owned(), _ => format!("self: {self_arg_ty}"), } }) }; match (trait_m.fn_has_self_parameter, impl_m.fn_has_self_parameter) { (false, false) | (true, true) => {} (false, true) => { let self_descr = self_string(impl_m); let mut err = struct_span_err!( tcx.sess, impl_m_span, E0185, "method `{}` has a `{}` declaration in the impl, but not in the trait", trait_m.name, self_descr ); err.span_label(impl_m_span, format!("`{self_descr}` used in impl")); if let Some(span) = tcx.hir().span_if_local(trait_m.def_id) { err.span_label(span, format!("trait method declared without `{self_descr}`")); } else { err.note_trait_signature(trait_m.name, trait_m.signature(tcx)); } let reported = err.emit(); return Err(reported); } (true, false) => { let self_descr = self_string(trait_m); let mut err = struct_span_err!( tcx.sess, impl_m_span, E0186, "method `{}` has a `{}` declaration in the trait, but not in the impl", trait_m.name, self_descr ); err.span_label(impl_m_span, format!("expected `{self_descr}` in impl")); if let Some(span) = tcx.hir().span_if_local(trait_m.def_id) { err.span_label(span, format!("`{self_descr}` used in trait")); } else { err.note_trait_signature(trait_m.name, trait_m.signature(tcx)); } let reported = err.emit(); return Err(reported); } } Ok(()) } /// Checks that the number of generics on a given assoc item in a trait impl is the same /// as the number of generics on the respective assoc item in the trait definition. /// /// For example this code emits the errors in the following code: /// ``` /// trait Trait { /// fn foo(); /// type Assoc; /// } /// /// impl Trait for () { /// fn foo() {} /// //~^ error /// type Assoc = u32; /// //~^ error /// } /// ``` /// /// Notably this does not error on `foo` implemented as `foo` or /// `foo` implemented as `foo`. This is handled in /// [`compare_generic_param_kinds`]. This function also does not handle lifetime parameters fn compare_number_of_generics<'tcx>( tcx: TyCtxt<'tcx>, impl_: &ty::AssocItem, _impl_span: Span, trait_: &ty::AssocItem, trait_span: Option, ) -> Result<(), ErrorGuaranteed> { let trait_own_counts = tcx.generics_of(trait_.def_id).own_counts(); let impl_own_counts = tcx.generics_of(impl_.def_id).own_counts(); // This avoids us erroring on `foo` implemented as `foo` as this is implemented // in `compare_generic_param_kinds` which will give a nicer error message than something like: // "expected 1 type parameter, found 0 type parameters" if (trait_own_counts.types + trait_own_counts.consts) == (impl_own_counts.types + impl_own_counts.consts) { return Ok(()); } let matchings = [ ("type", trait_own_counts.types, impl_own_counts.types), ("const", trait_own_counts.consts, impl_own_counts.consts), ]; let item_kind = assoc_item_kind_str(impl_); let mut err_occurred = None; for (kind, trait_count, impl_count) in matchings { if impl_count != trait_count { let arg_spans = |kind: ty::AssocKind, generics: &hir::Generics<'_>| { let mut spans = generics .params .iter() .filter(|p| match p.kind { hir::GenericParamKind::Lifetime { kind: hir::LifetimeParamKind::Elided, } => { // A fn can have an arbitrary number of extra elided lifetimes for the // same signature. !matches!(kind, ty::AssocKind::Fn) } _ => true, }) .map(|p| p.span) .collect::>(); if spans.is_empty() { spans = vec![generics.span] } spans }; let (trait_spans, impl_trait_spans) = if let Some(def_id) = trait_.def_id.as_local() { let trait_item = tcx.hir().expect_trait_item(def_id); let arg_spans: Vec = arg_spans(trait_.kind, trait_item.generics); let impl_trait_spans: Vec = trait_item .generics .params .iter() .filter_map(|p| match p.kind { GenericParamKind::Type { synthetic: true, .. } => Some(p.span), _ => None, }) .collect(); (Some(arg_spans), impl_trait_spans) } else { (trait_span.map(|s| vec![s]), vec![]) }; let impl_item = tcx.hir().expect_impl_item(impl_.def_id.expect_local()); let impl_item_impl_trait_spans: Vec = impl_item .generics .params .iter() .filter_map(|p| match p.kind { GenericParamKind::Type { synthetic: true, .. } => Some(p.span), _ => None, }) .collect(); let spans = arg_spans(impl_.kind, impl_item.generics); let span = spans.first().copied(); let mut err = tcx.sess.struct_span_err_with_code( spans, &format!( "{} `{}` has {} {kind} parameter{} but its trait \ declaration has {} {kind} parameter{}", item_kind, trait_.name, impl_count, pluralize!(impl_count), trait_count, pluralize!(trait_count), kind = kind, ), DiagnosticId::Error("E0049".into()), ); let mut suffix = None; if let Some(spans) = trait_spans { let mut spans = spans.iter(); if let Some(span) = spans.next() { err.span_label( *span, format!( "expected {} {} parameter{}", trait_count, kind, pluralize!(trait_count), ), ); } for span in spans { err.span_label(*span, ""); } } else { suffix = Some(format!(", expected {trait_count}")); } if let Some(span) = span { err.span_label( span, format!( "found {} {} parameter{}{}", impl_count, kind, pluralize!(impl_count), suffix.unwrap_or_else(String::new), ), ); } for span in impl_trait_spans.iter().chain(impl_item_impl_trait_spans.iter()) { err.span_label(*span, "`impl Trait` introduces an implicit type parameter"); } let reported = err.emit(); err_occurred = Some(reported); } } if let Some(reported) = err_occurred { Err(reported) } else { Ok(()) } } fn compare_number_of_method_arguments<'tcx>( tcx: TyCtxt<'tcx>, impl_m: &ty::AssocItem, impl_m_span: Span, trait_m: &ty::AssocItem, trait_item_span: Option, ) -> Result<(), ErrorGuaranteed> { let impl_m_fty = tcx.fn_sig(impl_m.def_id); let trait_m_fty = tcx.fn_sig(trait_m.def_id); let trait_number_args = trait_m_fty.inputs().skip_binder().len(); let impl_number_args = impl_m_fty.inputs().skip_binder().len(); if trait_number_args != impl_number_args { let trait_span = if let Some(def_id) = trait_m.def_id.as_local() { match tcx.hir().expect_trait_item(def_id).kind { TraitItemKind::Fn(ref trait_m_sig, _) => { let pos = if trait_number_args > 0 { trait_number_args - 1 } else { 0 }; if let Some(arg) = trait_m_sig.decl.inputs.get(pos) { Some(if pos == 0 { arg.span } else { arg.span.with_lo(trait_m_sig.decl.inputs[0].span.lo()) }) } else { trait_item_span } } _ => bug!("{:?} is not a method", impl_m), } } else { trait_item_span }; let impl_span = match tcx.hir().expect_impl_item(impl_m.def_id.expect_local()).kind { ImplItemKind::Fn(ref impl_m_sig, _) => { let pos = if impl_number_args > 0 { impl_number_args - 1 } else { 0 }; if let Some(arg) = impl_m_sig.decl.inputs.get(pos) { if pos == 0 { arg.span } else { arg.span.with_lo(impl_m_sig.decl.inputs[0].span.lo()) } } else { impl_m_span } } _ => bug!("{:?} is not a method", impl_m), }; let mut err = struct_span_err!( tcx.sess, impl_span, E0050, "method `{}` has {} but the declaration in trait `{}` has {}", trait_m.name, potentially_plural_count(impl_number_args, "parameter"), tcx.def_path_str(trait_m.def_id), trait_number_args ); if let Some(trait_span) = trait_span { err.span_label( trait_span, format!( "trait requires {}", potentially_plural_count(trait_number_args, "parameter") ), ); } else { err.note_trait_signature(trait_m.name, trait_m.signature(tcx)); } err.span_label( impl_span, format!( "expected {}, found {}", potentially_plural_count(trait_number_args, "parameter"), impl_number_args ), ); let reported = err.emit(); return Err(reported); } Ok(()) } fn compare_synthetic_generics<'tcx>( tcx: TyCtxt<'tcx>, impl_m: &ty::AssocItem, trait_m: &ty::AssocItem, ) -> Result<(), ErrorGuaranteed> { // FIXME(chrisvittal) Clean up this function, list of FIXME items: // 1. Better messages for the span labels // 2. Explanation as to what is going on // If we get here, we already have the same number of generics, so the zip will // be okay. let mut error_found = None; let impl_m_generics = tcx.generics_of(impl_m.def_id); let trait_m_generics = tcx.generics_of(trait_m.def_id); let impl_m_type_params = impl_m_generics.params.iter().filter_map(|param| match param.kind { GenericParamDefKind::Type { synthetic, .. } => Some((param.def_id, synthetic)), GenericParamDefKind::Lifetime | GenericParamDefKind::Const { .. } => None, }); let trait_m_type_params = trait_m_generics.params.iter().filter_map(|param| match param.kind { GenericParamDefKind::Type { synthetic, .. } => Some((param.def_id, synthetic)), GenericParamDefKind::Lifetime | GenericParamDefKind::Const { .. } => None, }); for ((impl_def_id, impl_synthetic), (trait_def_id, trait_synthetic)) in iter::zip(impl_m_type_params, trait_m_type_params) { if impl_synthetic != trait_synthetic { let impl_def_id = impl_def_id.expect_local(); let impl_hir_id = tcx.hir().local_def_id_to_hir_id(impl_def_id); let impl_span = tcx.hir().span(impl_hir_id); let trait_span = tcx.def_span(trait_def_id); let mut err = struct_span_err!( tcx.sess, impl_span, E0643, "method `{}` has incompatible signature for trait", trait_m.name ); err.span_label(trait_span, "declaration in trait here"); match (impl_synthetic, trait_synthetic) { // The case where the impl method uses `impl Trait` but the trait method uses // explicit generics (true, false) => { err.span_label(impl_span, "expected generic parameter, found `impl Trait`"); (|| { // try taking the name from the trait impl // FIXME: this is obviously suboptimal since the name can already be used // as another generic argument let new_name = tcx.sess.source_map().span_to_snippet(trait_span).ok()?; let trait_m = trait_m.def_id.as_local()?; let trait_m = tcx.hir().trait_item(hir::TraitItemId { def_id: trait_m }); let impl_m = impl_m.def_id.as_local()?; let impl_m = tcx.hir().impl_item(hir::ImplItemId { def_id: impl_m }); // in case there are no generics, take the spot between the function name // and the opening paren of the argument list let new_generics_span = tcx.sess.source_map().generate_fn_name_span(impl_span)?.shrink_to_hi(); // in case there are generics, just replace them let generics_span = impl_m.generics.span.substitute_dummy(new_generics_span); // replace with the generics from the trait let new_generics = tcx.sess.source_map().span_to_snippet(trait_m.generics.span).ok()?; err.multipart_suggestion( "try changing the `impl Trait` argument to a generic parameter", vec![ // replace `impl Trait` with `T` (impl_span, new_name), // replace impl method generics with trait method generics // This isn't quite right, as users might have changed the names // of the generics, but it works for the common case (generics_span, new_generics), ], Applicability::MaybeIncorrect, ); Some(()) })(); } // The case where the trait method uses `impl Trait`, but the impl method uses // explicit generics. (false, true) => { err.span_label(impl_span, "expected `impl Trait`, found generic parameter"); (|| { let impl_m = impl_m.def_id.as_local()?; let impl_m = tcx.hir().impl_item(hir::ImplItemId { def_id: impl_m }); let input_tys = match impl_m.kind { hir::ImplItemKind::Fn(ref sig, _) => sig.decl.inputs, _ => unreachable!(), }; struct Visitor(Option, hir::def_id::LocalDefId); impl<'v> intravisit::Visitor<'v> for Visitor { fn visit_ty(&mut self, ty: &'v hir::Ty<'v>) { intravisit::walk_ty(self, ty); if let hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) = ty.kind && let Res::Def(DefKind::TyParam, def_id) = path.res && def_id == self.1.to_def_id() { self.0 = Some(ty.span); } } } let mut visitor = Visitor(None, impl_def_id); for ty in input_tys { intravisit::Visitor::visit_ty(&mut visitor, ty); } let span = visitor.0?; let bounds = impl_m.generics.bounds_for_param(impl_def_id).next()?.bounds; let bounds = bounds.first()?.span().to(bounds.last()?.span()); let bounds = tcx.sess.source_map().span_to_snippet(bounds).ok()?; err.multipart_suggestion( "try removing the generic parameter and using `impl Trait` instead", vec![ // delete generic parameters (impl_m.generics.span, String::new()), // replace param usage with `impl Trait` (span, format!("impl {bounds}")), ], Applicability::MaybeIncorrect, ); Some(()) })(); } _ => unreachable!(), } let reported = err.emit(); error_found = Some(reported); } } if let Some(reported) = error_found { Err(reported) } else { Ok(()) } } /// Checks that all parameters in the generics of a given assoc item in a trait impl have /// the same kind as the respective generic parameter in the trait def. /// /// For example all 4 errors in the following code are emitted here: /// ``` /// trait Foo { /// fn foo(); /// type bar; /// fn baz(); /// type blah; /// } /// /// impl Foo for () { /// fn foo() {} /// //~^ error /// type bar {} /// //~^ error /// fn baz() {} /// //~^ error /// type blah = u32; /// //~^ error /// } /// ``` /// /// This function does not handle lifetime parameters fn compare_generic_param_kinds<'tcx>( tcx: TyCtxt<'tcx>, impl_item: &ty::AssocItem, trait_item: &ty::AssocItem, ) -> Result<(), ErrorGuaranteed> { assert_eq!(impl_item.kind, trait_item.kind); let ty_const_params_of = |def_id| { tcx.generics_of(def_id).params.iter().filter(|param| { matches!( param.kind, GenericParamDefKind::Const { .. } | GenericParamDefKind::Type { .. } ) }) }; for (param_impl, param_trait) in iter::zip(ty_const_params_of(impl_item.def_id), ty_const_params_of(trait_item.def_id)) { use GenericParamDefKind::*; if match (¶m_impl.kind, ¶m_trait.kind) { (Const { .. }, Const { .. }) if tcx.type_of(param_impl.def_id) != tcx.type_of(param_trait.def_id) => { true } (Const { .. }, Type { .. }) | (Type { .. }, Const { .. }) => true, // this is exhaustive so that anyone adding new generic param kinds knows // to make sure this error is reported for them. (Const { .. }, Const { .. }) | (Type { .. }, Type { .. }) => false, (Lifetime { .. }, _) | (_, Lifetime { .. }) => unreachable!(), } { let param_impl_span = tcx.def_span(param_impl.def_id); let param_trait_span = tcx.def_span(param_trait.def_id); let mut err = struct_span_err!( tcx.sess, param_impl_span, E0053, "{} `{}` has an incompatible generic parameter for trait `{}`", assoc_item_kind_str(&impl_item), trait_item.name, &tcx.def_path_str(tcx.parent(trait_item.def_id)) ); let make_param_message = |prefix: &str, param: &ty::GenericParamDef| match param.kind { Const { .. } => { format!("{} const parameter of type `{}`", prefix, tcx.type_of(param.def_id)) } Type { .. } => format!("{} type parameter", prefix), Lifetime { .. } => unreachable!(), }; let trait_header_span = tcx.def_ident_span(tcx.parent(trait_item.def_id)).unwrap(); err.span_label(trait_header_span, ""); err.span_label(param_trait_span, make_param_message("expected", param_trait)); let impl_header_span = tcx.def_span(tcx.parent(impl_item.def_id)); err.span_label(impl_header_span, ""); err.span_label(param_impl_span, make_param_message("found", param_impl)); let reported = err.emit(); return Err(reported); } } Ok(()) } pub(crate) fn compare_const_impl<'tcx>( tcx: TyCtxt<'tcx>, impl_c: &ty::AssocItem, impl_c_span: Span, trait_c: &ty::AssocItem, impl_trait_ref: ty::TraitRef<'tcx>, ) { debug!("compare_const_impl(impl_trait_ref={:?})", impl_trait_ref); tcx.infer_ctxt().enter(|infcx| { let param_env = tcx.param_env(impl_c.def_id); let ocx = ObligationCtxt::new(&infcx); // The below is for the most part highly similar to the procedure // for methods above. It is simpler in many respects, especially // because we shouldn't really have to deal with lifetimes or // predicates. In fact some of this should probably be put into // shared functions because of DRY violations... let trait_to_impl_substs = impl_trait_ref.substs; // Create a parameter environment that represents the implementation's // method. let impl_c_hir_id = tcx.hir().local_def_id_to_hir_id(impl_c.def_id.expect_local()); // Compute placeholder form of impl and trait const tys. let impl_ty = tcx.type_of(impl_c.def_id); let trait_ty = tcx.bound_type_of(trait_c.def_id).subst(tcx, trait_to_impl_substs); let mut cause = ObligationCause::new( impl_c_span, impl_c_hir_id, ObligationCauseCode::CompareImplItemObligation { impl_item_def_id: impl_c.def_id.expect_local(), trait_item_def_id: trait_c.def_id, kind: impl_c.kind, }, ); // There is no "body" here, so just pass dummy id. let impl_ty = ocx.normalize(cause.clone(), param_env, impl_ty); debug!("compare_const_impl: impl_ty={:?}", impl_ty); let trait_ty = ocx.normalize(cause.clone(), param_env, trait_ty); debug!("compare_const_impl: trait_ty={:?}", trait_ty); let err = infcx .at(&cause, param_env) .sup(trait_ty, impl_ty) .map(|ok| ocx.register_infer_ok_obligations(ok)); if let Err(terr) = err { debug!( "checking associated const for compatibility: impl ty {:?}, trait ty {:?}", impl_ty, trait_ty ); // Locate the Span containing just the type of the offending impl match tcx.hir().expect_impl_item(impl_c.def_id.expect_local()).kind { ImplItemKind::Const(ref ty, _) => cause.span = ty.span, _ => bug!("{:?} is not a impl const", impl_c), } let mut diag = struct_span_err!( tcx.sess, cause.span, E0326, "implemented const `{}` has an incompatible type for trait", trait_c.name ); let trait_c_span = trait_c.def_id.as_local().map(|trait_c_def_id| { // Add a label to the Span containing just the type of the const match tcx.hir().expect_trait_item(trait_c_def_id).kind { TraitItemKind::Const(ref ty, _) => ty.span, _ => bug!("{:?} is not a trait const", trait_c), } }); infcx.note_type_err( &mut diag, &cause, trait_c_span.map(|span| (span, "type in trait".to_owned())), Some(infer::ValuePairs::Terms(ExpectedFound { expected: trait_ty.into(), found: impl_ty.into(), })), &terr, false, false, ); diag.emit(); } // Check that all obligations are satisfied by the implementation's // version. let errors = ocx.select_all_or_error(); if !errors.is_empty() { infcx.report_fulfillment_errors(&errors, None, false); return; } let outlives_environment = OutlivesEnvironment::new(param_env); infcx.check_region_obligations_and_report_errors( impl_c.def_id.expect_local(), &outlives_environment, ); }); } pub(crate) fn compare_ty_impl<'tcx>( tcx: TyCtxt<'tcx>, impl_ty: &ty::AssocItem, impl_ty_span: Span, trait_ty: &ty::AssocItem, impl_trait_ref: ty::TraitRef<'tcx>, trait_item_span: Option, ) { debug!("compare_impl_type(impl_trait_ref={:?})", impl_trait_ref); let _: Result<(), ErrorGuaranteed> = (|| { compare_number_of_generics(tcx, impl_ty, impl_ty_span, trait_ty, trait_item_span)?; compare_generic_param_kinds(tcx, impl_ty, trait_ty)?; let sp = tcx.def_span(impl_ty.def_id); compare_type_predicate_entailment(tcx, impl_ty, sp, trait_ty, impl_trait_ref)?; check_type_bounds(tcx, trait_ty, impl_ty, impl_ty_span, impl_trait_ref) })(); } /// The equivalent of [compare_predicate_entailment], but for associated types /// instead of associated functions. fn compare_type_predicate_entailment<'tcx>( tcx: TyCtxt<'tcx>, impl_ty: &ty::AssocItem, impl_ty_span: Span, trait_ty: &ty::AssocItem, impl_trait_ref: ty::TraitRef<'tcx>, ) -> Result<(), ErrorGuaranteed> { let impl_substs = InternalSubsts::identity_for_item(tcx, impl_ty.def_id); let trait_to_impl_substs = impl_substs.rebase_onto(tcx, impl_ty.container_id(tcx), impl_trait_ref.substs); let impl_ty_generics = tcx.generics_of(impl_ty.def_id); let trait_ty_generics = tcx.generics_of(trait_ty.def_id); let impl_ty_predicates = tcx.predicates_of(impl_ty.def_id); let trait_ty_predicates = tcx.predicates_of(trait_ty.def_id); check_region_bounds_on_impl_item( tcx, impl_ty, trait_ty, &trait_ty_generics, &impl_ty_generics, )?; let impl_ty_own_bounds = impl_ty_predicates.instantiate_own(tcx, impl_substs); if impl_ty_own_bounds.is_empty() { // Nothing to check. return Ok(()); } // This `HirId` should be used for the `body_id` field on each // `ObligationCause` (and the `FnCtxt`). This is what // `regionck_item` expects. let impl_ty_hir_id = tcx.hir().local_def_id_to_hir_id(impl_ty.def_id.expect_local()); debug!("compare_type_predicate_entailment: trait_to_impl_substs={:?}", trait_to_impl_substs); // The predicates declared by the impl definition, the trait and the // associated type in the trait are assumed. let impl_predicates = tcx.predicates_of(impl_ty_predicates.parent.unwrap()); let mut hybrid_preds = impl_predicates.instantiate_identity(tcx); hybrid_preds .predicates .extend(trait_ty_predicates.instantiate_own(tcx, trait_to_impl_substs).predicates); debug!("compare_type_predicate_entailment: bounds={:?}", hybrid_preds); let normalize_cause = traits::ObligationCause::misc(impl_ty_span, impl_ty_hir_id); let param_env = ty::ParamEnv::new( tcx.intern_predicates(&hybrid_preds.predicates), Reveal::UserFacing, hir::Constness::NotConst, ); let param_env = traits::normalize_param_env_or_error(tcx, param_env, normalize_cause); tcx.infer_ctxt().enter(|infcx| { let ocx = ObligationCtxt::new(&infcx); debug!("compare_type_predicate_entailment: caller_bounds={:?}", param_env.caller_bounds()); let mut selcx = traits::SelectionContext::new(&infcx); assert_eq!(impl_ty_own_bounds.predicates.len(), impl_ty_own_bounds.spans.len()); for (span, predicate) in std::iter::zip(impl_ty_own_bounds.spans, impl_ty_own_bounds.predicates) { let cause = ObligationCause::misc(span, impl_ty_hir_id); let traits::Normalized { value: predicate, obligations } = traits::normalize(&mut selcx, param_env, cause, predicate); let cause = ObligationCause::new( span, impl_ty_hir_id, ObligationCauseCode::CompareImplItemObligation { impl_item_def_id: impl_ty.def_id.expect_local(), trait_item_def_id: trait_ty.def_id, kind: impl_ty.kind, }, ); ocx.register_obligations(obligations); ocx.register_obligation(traits::Obligation::new(cause, param_env, predicate)); } // Check that all obligations are satisfied by the implementation's // version. let errors = ocx.select_all_or_error(); if !errors.is_empty() { let reported = infcx.report_fulfillment_errors(&errors, None, false); return Err(reported); } // Finally, resolve all regions. This catches wily misuses of // lifetime parameters. let outlives_environment = OutlivesEnvironment::new(param_env); infcx.check_region_obligations_and_report_errors( impl_ty.def_id.expect_local(), &outlives_environment, ); Ok(()) }) } /// Validate that `ProjectionCandidate`s created for this associated type will /// be valid. /// /// Usually given /// /// trait X { type Y: Copy } impl X for T { type Y = S; } /// /// We are able to normalize `::U` to `S`, and so when we check the /// impl is well-formed we have to prove `S: Copy`. /// /// For default associated types the normalization is not possible (the value /// from the impl could be overridden). We also can't normalize generic /// associated types (yet) because they contain bound parameters. #[tracing::instrument(level = "debug", skip(tcx))] pub fn check_type_bounds<'tcx>( tcx: TyCtxt<'tcx>, trait_ty: &ty::AssocItem, impl_ty: &ty::AssocItem, impl_ty_span: Span, impl_trait_ref: ty::TraitRef<'tcx>, ) -> Result<(), ErrorGuaranteed> { // Given // // impl Foo for (A, B) { // type Bar =... // } // // - `impl_trait_ref` would be `<(A, B) as Foo> // - `impl_ty_substs` would be `[A, B, ^0.0]` (`^0.0` here is the bound var with db 0 and index 0) // - `rebased_substs` would be `[(A, B), u32, ^0.0]`, combining the substs from // the *trait* with the generic associated type parameters (as bound vars). // // A note regarding the use of bound vars here: // Imagine as an example // ``` // trait Family { // type Member; // } // // impl Family for VecFamily { // type Member = i32; // } // ``` // Here, we would generate // ```notrust // forall { Normalize(::Member => i32) } // ``` // when we really would like to generate // ```notrust // forall { Normalize(::Member => i32) :- Implemented(C: Eq) } // ``` // But, this is probably fine, because although the first clause can be used with types C that // do not implement Eq, for it to cause some kind of problem, there would have to be a // VecFamily::Member for some type X where !(X: Eq), that appears in the value of type // Member = .... That type would fail a well-formedness check that we ought to be doing // elsewhere, which would check that any ::Member meets the bounds declared in // the trait (notably, that X: Eq and T: Family). let defs: &ty::Generics = tcx.generics_of(impl_ty.def_id); let mut substs = smallvec::SmallVec::with_capacity(defs.count()); if let Some(def_id) = defs.parent { let parent_defs = tcx.generics_of(def_id); InternalSubsts::fill_item(&mut substs, tcx, parent_defs, &mut |param, _| { tcx.mk_param_from_def(param) }); } let mut bound_vars: smallvec::SmallVec<[ty::BoundVariableKind; 8]> = smallvec::SmallVec::with_capacity(defs.count()); InternalSubsts::fill_single(&mut substs, defs, &mut |param, _| match param.kind { GenericParamDefKind::Type { .. } => { let kind = ty::BoundTyKind::Param(param.name); let bound_var = ty::BoundVariableKind::Ty(kind); bound_vars.push(bound_var); tcx.mk_ty(ty::Bound( ty::INNERMOST, ty::BoundTy { var: ty::BoundVar::from_usize(bound_vars.len() - 1), kind }, )) .into() } GenericParamDefKind::Lifetime => { let kind = ty::BoundRegionKind::BrNamed(param.def_id, param.name); let bound_var = ty::BoundVariableKind::Region(kind); bound_vars.push(bound_var); tcx.mk_region(ty::ReLateBound( ty::INNERMOST, ty::BoundRegion { var: ty::BoundVar::from_usize(bound_vars.len() - 1), kind }, )) .into() } GenericParamDefKind::Const { .. } => { let bound_var = ty::BoundVariableKind::Const; bound_vars.push(bound_var); tcx.mk_const(ty::ConstS { ty: tcx.type_of(param.def_id), kind: ty::ConstKind::Bound( ty::INNERMOST, ty::BoundVar::from_usize(bound_vars.len() - 1), ), }) .into() } }); let bound_vars = tcx.mk_bound_variable_kinds(bound_vars.into_iter()); let impl_ty_substs = tcx.intern_substs(&substs); let container_id = impl_ty.container_id(tcx); let rebased_substs = impl_ty_substs.rebase_onto(tcx, container_id, impl_trait_ref.substs); let impl_ty_value = tcx.type_of(impl_ty.def_id); let param_env = tcx.param_env(impl_ty.def_id); // When checking something like // // trait X { type Y: PartialEq<::Y> } // impl X for T { default type Y = S; } // // We will have to prove the bound S: PartialEq<::Y>. In this case // we want ::Y to normalize to S. This is valid because we are // checking the default value specifically here. Add this equality to the // ParamEnv for normalization specifically. let normalize_param_env = { let mut predicates = param_env.caller_bounds().iter().collect::>(); match impl_ty_value.kind() { ty::Projection(proj) if proj.item_def_id == trait_ty.def_id && proj.substs == rebased_substs => { // Don't include this predicate if the projected type is // exactly the same as the projection. This can occur in // (somewhat dubious) code like this: // // impl X for T where T: X { type Y = ::Y; } } _ => predicates.push( ty::Binder::bind_with_vars( ty::ProjectionPredicate { projection_ty: ty::ProjectionTy { item_def_id: trait_ty.def_id, substs: rebased_substs, }, term: impl_ty_value.into(), }, bound_vars, ) .to_predicate(tcx), ), }; ty::ParamEnv::new( tcx.intern_predicates(&predicates), Reveal::UserFacing, param_env.constness(), ) }; debug!(?normalize_param_env); let impl_ty_substs = InternalSubsts::identity_for_item(tcx, impl_ty.def_id); let rebased_substs = impl_ty_substs.rebase_onto(tcx, container_id, impl_trait_ref.substs); tcx.infer_ctxt().enter(move |infcx| { let ocx = ObligationCtxt::new(&infcx); let mut selcx = traits::SelectionContext::new(&infcx); let impl_ty_hir_id = tcx.hir().local_def_id_to_hir_id(impl_ty.def_id.expect_local()); let normalize_cause = ObligationCause::new( impl_ty_span, impl_ty_hir_id, ObligationCauseCode::CheckAssociatedTypeBounds { impl_item_def_id: impl_ty.def_id.expect_local(), trait_item_def_id: trait_ty.def_id, }, ); let mk_cause = |span: Span| { let code = if span.is_dummy() { traits::MiscObligation } else { traits::BindingObligation(trait_ty.def_id, span) }; ObligationCause::new(impl_ty_span, impl_ty_hir_id, code) }; let obligations = tcx .bound_explicit_item_bounds(trait_ty.def_id) .transpose_iter() .map(|e| e.map_bound(|e| *e).transpose_tuple2()) .map(|(bound, span)| { debug!(?bound); // this is where opaque type is found let concrete_ty_bound = bound.subst(tcx, rebased_substs); debug!("check_type_bounds: concrete_ty_bound = {:?}", concrete_ty_bound); traits::Obligation::new(mk_cause(span.0), param_env, concrete_ty_bound) }) .collect(); debug!("check_type_bounds: item_bounds={:?}", obligations); for mut obligation in util::elaborate_obligations(tcx, obligations) { let traits::Normalized { value: normalized_predicate, obligations } = traits::normalize( &mut selcx, normalize_param_env, normalize_cause.clone(), obligation.predicate, ); debug!("compare_projection_bounds: normalized predicate = {:?}", normalized_predicate); obligation.predicate = normalized_predicate; ocx.register_obligations(obligations); ocx.register_obligation(obligation); } // Check that all obligations are satisfied by the implementation's // version. let errors = ocx.select_all_or_error(); if !errors.is_empty() { let reported = infcx.report_fulfillment_errors(&errors, None, false); return Err(reported); } // Finally, resolve all regions. This catches wily misuses of // lifetime parameters. let implied_bounds = match impl_ty.container { ty::TraitContainer => FxHashSet::default(), ty::ImplContainer => wfcheck::impl_implied_bounds( tcx, param_env, container_id.expect_local(), impl_ty_span, ), }; let mut outlives_environment = OutlivesEnvironment::new(param_env); outlives_environment.add_implied_bounds(&infcx, implied_bounds, impl_ty_hir_id); infcx.check_region_obligations_and_report_errors( impl_ty.def_id.expect_local(), &outlives_environment, ); let constraints = infcx.inner.borrow_mut().opaque_type_storage.take_opaque_types(); for (key, value) in constraints { infcx .report_mismatched_types( &ObligationCause::misc( value.hidden_type.span, tcx.hir().local_def_id_to_hir_id(impl_ty.def_id.expect_local()), ), tcx.mk_opaque(key.def_id.to_def_id(), key.substs), value.hidden_type.ty, TypeError::Mismatch, ) .emit(); } Ok(()) }) } fn assoc_item_kind_str(impl_item: &ty::AssocItem) -> &'static str { match impl_item.kind { ty::AssocKind::Const => "const", ty::AssocKind::Fn => "method", ty::AssocKind::Type => "type", } }