use errors::{pluralize, struct_span_err, Applicability, DiagnosticId}; use rustc::hir::intravisit; use rustc::infer::{self, InferOk}; use rustc::traits::{self, ObligationCause, ObligationCauseCode, Reveal}; use rustc::ty::error::{ExpectedFound, TypeError}; use rustc::ty::subst::{InternalSubsts, Subst}; use rustc::ty::util::ExplicitSelf; use rustc::ty::{self, GenericParamDefKind, TyCtxt}; use rustc::util::common::ErrorReported; use rustc_hir as hir; use rustc_hir::def::{DefKind, Res}; use rustc_hir::{GenericParamKind, ImplItemKind, TraitItemKind}; use rustc_span::Span; use super::{potentially_plural_count, FnCtxt, Inherited}; use rustc_error_codes::*; /// 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 crate fn compare_impl_method<'tcx>( tcx: TyCtxt<'tcx>, impl_m: &ty::AssocItem, impl_m_span: Span, 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.sess.source_map().def_span(impl_m_span); if let Err(ErrorReported) = compare_self_type(tcx, impl_m, impl_m_span, trait_m, impl_trait_ref) { return; } if let Err(ErrorReported) = compare_number_of_generics(tcx, impl_m, impl_m_span, trait_m, trait_item_span) { return; } if let Err(ErrorReported) = compare_number_of_method_arguments(tcx, impl_m, impl_m_span, trait_m, trait_item_span) { return; } if let Err(ErrorReported) = compare_synthetic_generics(tcx, impl_m, trait_m) { return; } if let Err(ErrorReported) = 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<(), ErrorReported> { 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`). This is what // `regionck_item` expects. let impl_m_hir_id = tcx.hir().as_local_hir_id(impl_m.def_id).unwrap(); let cause = ObligationCause { span: impl_m_span, body_id: impl_m_hir_id, code: ObligationCauseCode::CompareImplMethodObligation { item_name: impl_m.ident.name, impl_item_def_id: impl_m.def_id, trait_item_def_id: trait_m.def_id, }, }; // 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_skol_substs = {'i => 'i0, U => U0, N => N0 } // // Now we can apply skol_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_skol_substs, and also adding a mapping for the method // type parameters. We extend the mapping to also include // the method parameters. // // trait_to_skol_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_skol_substs. We then build // trait_to_skol_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_skol_substs = InternalSubsts::identity_for_item(tcx, impl_m.def_id); // Create mapping from trait to placeholder. let trait_to_skol_substs = impl_to_skol_substs.rebase_onto(tcx, impl_m.container.id(), trait_to_impl_substs); debug!("compare_impl_method: trait_to_skol_substs={:?}", trait_to_skol_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_span, 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_skol_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, None, ); let param_env = traits::normalize_param_env_or_error( tcx, impl_m.def_id, param_env, normalize_cause.clone(), ); tcx.infer_ctxt().enter(|infcx| { let inh = Inherited::new(infcx, impl_m.def_id); let infcx = &inh.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_skol_substs); let (impl_m_own_bounds, _) = infcx.replace_bound_vars_with_fresh_vars( impl_m_span, infer::HigherRankedType, &ty::Binder::bind(impl_m_own_bounds.predicates), ); for predicate in impl_m_own_bounds { let traits::Normalized { value: predicate, obligations } = traits::normalize(&mut selcx, param_env, normalize_cause.clone(), &predicate); inh.register_predicates(obligations); inh.register_predicate(traits::Obligation::new(cause.clone(), 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 (impl_sig, _) = infcx.replace_bound_vars_with_fresh_vars( impl_m_span, infer::HigherRankedType, &tcx.fn_sig(impl_m.def_id), ); let impl_sig = inh.normalize_associated_types_in(impl_m_span, impl_m_hir_id, param_env, &impl_sig); let impl_fty = tcx.mk_fn_ptr(ty::Binder::bind(impl_sig)); debug!("compare_impl_method: impl_fty={:?}", impl_fty); let trait_sig = tcx.liberate_late_bound_regions(impl_m.def_id, &tcx.fn_sig(trait_m.def_id)); let trait_sig = trait_sig.subst(tcx, trait_to_skol_substs); let trait_sig = inh.normalize_associated_types_in(impl_m_span, impl_m_hir_id, param_env, &trait_sig); let trait_fty = tcx.mk_fn_ptr(ty::Binder::bind(trait_sig)); debug!("compare_impl_method: trait_fty={:?}", trait_fty); let sub_result = infcx.at(&cause, param_env).sup(trait_fty, impl_fty).map( |InferOk { obligations, .. }| { inh.register_predicates(obligations); }, ); 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, param_env, &terr, &cause, impl_m, impl_sig, trait_m, trait_sig, ); let cause = ObligationCause { span: impl_err_span, ..cause }; let mut diag = struct_span_err!( tcx.sess, cause.span(tcx), E0053, "method `{}` has an incompatible type for trait", trait_m.ident ); if let TypeError::Mutability = terr { if let Some(trait_err_span) = trait_err_span { if let Ok(trait_err_str) = tcx.sess.source_map().span_to_snippet(trait_err_span) { diag.span_suggestion( impl_err_span, "consider change the type to match the mutability in trait", trait_err_str, Applicability::MachineApplicable, ); } } } infcx.note_type_err( &mut diag, &cause, trait_err_span.map(|sp| (sp, "type in trait".to_owned())), Some(infer::ValuePairs::Types(ExpectedFound { expected: trait_fty, found: impl_fty, })), &terr, ); diag.emit(); return Err(ErrorReported); } // Check that all obligations are satisfied by the implementation's // version. if let Err(ref errors) = inh.fulfillment_cx.borrow_mut().select_all_or_error(&infcx) { infcx.report_fulfillment_errors(errors, None, false); return Err(ErrorReported); } // Finally, resolve all regions. This catches wily misuses of // lifetime parameters. let fcx = FnCtxt::new(&inh, param_env, impl_m_hir_id); fcx.regionck_item(impl_m_hir_id, impl_m_span, &[]); Ok(()) }) } fn check_region_bounds_on_impl_item<'tcx>( tcx: TyCtxt<'tcx>, span: Span, impl_m: &ty::AssocItem, trait_m: &ty::AssocItem, trait_generics: &ty::Generics, impl_generics: &ty::Generics, ) -> Result<(), ErrorReported> { 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 item_kind = assoc_item_kind_str(impl_m); let def_span = tcx.sess.source_map().def_span(span); let span = tcx.hir().get_generics(impl_m.def_id).map(|g| g.span).unwrap_or(def_span); let mut err = struct_span_err!( tcx.sess, span, E0195, "lifetime parameters or bounds on {} `{}` do not match the trait declaration", item_kind, impl_m.ident, ); err.span_label(span, &format!("lifetimes do not match {} in trait", item_kind)); if let Some(sp) = tcx.hir().span_if_local(trait_m.def_id) { let def_sp = tcx.sess.source_map().def_span(sp); let sp = tcx.hir().get_generics(trait_m.def_id).map(|g| g.span).unwrap_or(def_sp); err.span_label( sp, &format!("lifetimes in impl do not match this {} in trait", item_kind), ); } err.emit(); return Err(ErrorReported); } Ok(()) } fn extract_spans_for_error_reporting<'a, 'tcx>( infcx: &infer::InferCtxt<'a, 'tcx>, param_env: ty::ParamEnv<'tcx>, terr: &TypeError<'_>, cause: &ObligationCause<'tcx>, impl_m: &ty::AssocItem, impl_sig: ty::FnSig<'tcx>, trait_m: &ty::AssocItem, trait_sig: ty::FnSig<'tcx>, ) -> (Span, Option) { let tcx = infcx.tcx; let impl_m_hir_id = tcx.hir().as_local_hir_id(impl_m.def_id).unwrap(); let (impl_m_output, impl_m_iter) = match tcx.hir().expect_impl_item(impl_m_hir_id).kind { ImplItemKind::Method(ref impl_m_sig, _) => { (&impl_m_sig.decl.output, impl_m_sig.decl.inputs.iter()) } _ => bug!("{:?} is not a method", impl_m), }; match *terr { TypeError::Mutability => { if let Some(trait_m_hir_id) = tcx.hir().as_local_hir_id(trait_m.def_id) { let trait_m_iter = match tcx.hir().expect_trait_item(trait_m_hir_id).kind { TraitItemKind::Method(ref trait_m_sig, _) => trait_m_sig.decl.inputs.iter(), _ => bug!("{:?} is not a TraitItemKind::Method", trait_m), }; impl_m_iter .zip(trait_m_iter) .find(|&(ref impl_arg, ref trait_arg)| { match (&impl_arg.kind, &trait_arg.kind) { ( &hir::TyKind::Rptr(_, ref impl_mt), &hir::TyKind::Rptr(_, ref trait_mt), ) | (&hir::TyKind::Ptr(ref impl_mt), &hir::TyKind::Ptr(ref trait_mt)) => { impl_mt.mutbl != trait_mt.mutbl } _ => false, } }) .map(|(ref impl_arg, ref trait_arg)| (impl_arg.span, Some(trait_arg.span))) .unwrap_or_else(|| (cause.span(tcx), tcx.hir().span_if_local(trait_m.def_id))) } else { (cause.span(tcx), tcx.hir().span_if_local(trait_m.def_id)) } } TypeError::Sorts(ExpectedFound { .. }) => { if let Some(trait_m_hir_id) = tcx.hir().as_local_hir_id(trait_m.def_id) { let (trait_m_output, trait_m_iter) = match tcx.hir().expect_trait_item(trait_m_hir_id).kind { TraitItemKind::Method(ref trait_m_sig, _) => { (&trait_m_sig.decl.output, trait_m_sig.decl.inputs.iter()) } _ => bug!("{:?} is not a TraitItemKind::Method", trait_m), }; let impl_iter = impl_sig.inputs().iter(); let trait_iter = trait_sig.inputs().iter(); impl_iter .zip(trait_iter) .zip(impl_m_iter) .zip(trait_m_iter) .filter_map( |(((&impl_arg_ty, &trait_arg_ty), impl_arg), trait_arg)| match infcx .at(&cause, param_env) .sub(trait_arg_ty, impl_arg_ty) { Ok(_) => None, Err(_) => Some((impl_arg.span, Some(trait_arg.span))), }, ) .next() .unwrap_or_else(|| { if infcx .at(&cause, param_env) .sup(trait_sig.output(), impl_sig.output()) .is_err() { (impl_m_output.span(), Some(trait_m_output.span())) } else { (cause.span(tcx), tcx.hir().span_if_local(trait_m.def_id)) } }) } else { (cause.span(tcx), tcx.hir().span_if_local(trait_m.def_id)) } } _ => (cause.span(tcx), 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<(), ErrorReported> { // 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).skip_binder(); let param_env = ty::ParamEnv::reveal_all(); tcx.infer_ctxt().enter(|infcx| { let self_arg_ty = tcx.liberate_late_bound_regions(method.def_id, &ty::Binder::bind(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.method_has_self_argument, impl_m.method_has_self_argument) { (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.ident, self_descr ); err.span_label(impl_m_span, format!("`{}` used in impl", self_descr)); 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.ident.to_string(), trait_m.signature(tcx)); } err.emit(); return Err(ErrorReported); } (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.ident, self_descr ); err.span_label(impl_m_span, format!("expected `{}` in impl", self_descr)); if let Some(span) = tcx.hir().span_if_local(trait_m.def_id) { err.span_label(span, format!("`{}` used in trait", self_descr)); } else { err.note_trait_signature(trait_m.ident.to_string(), trait_m.signature(tcx)); } err.emit(); return Err(ErrorReported); } } Ok(()) } fn compare_number_of_generics<'tcx>( tcx: TyCtxt<'tcx>, impl_: &ty::AssocItem, _impl_span: Span, trait_: &ty::AssocItem, trait_span: Option, ) -> Result<(), ErrorReported> { let trait_own_counts = tcx.generics_of(trait_.def_id).own_counts(); let impl_own_counts = tcx.generics_of(impl_.def_id).own_counts(); 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 = false; for &(kind, trait_count, impl_count) in &matchings { if impl_count != trait_count { err_occurred = true; let (trait_spans, impl_trait_spans) = if let Some(trait_hir_id) = tcx.hir().as_local_hir_id(trait_.def_id) { let trait_item = tcx.hir().expect_trait_item(trait_hir_id); if trait_item.generics.params.is_empty() { (Some(vec![trait_item.generics.span]), vec![]) } else { let arg_spans: Vec = trait_item.generics.params.iter().map(|p| p.span).collect(); let impl_trait_spans: Vec = trait_item .generics .params .iter() .filter_map(|p| match p.kind { GenericParamKind::Type { synthetic: Some(hir::SyntheticTyParamKind::ImplTrait), .. } => Some(p.span), _ => None, }) .collect(); (Some(arg_spans), impl_trait_spans) } } else { (trait_span.map(|s| vec![s]), vec![]) }; let impl_hir_id = tcx.hir().as_local_hir_id(impl_.def_id).unwrap(); let impl_item = tcx.hir().expect_impl_item(impl_hir_id); let impl_item_impl_trait_spans: Vec = impl_item .generics .params .iter() .filter_map(|p| match p.kind { GenericParamKind::Type { synthetic: Some(hir::SyntheticTyParamKind::ImplTrait), .. } => Some(p.span), _ => None, }) .collect(); let spans = impl_item.generics.spans(); let span = spans.primary_span(); 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_.ident, 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"); } err.emit(); } } if err_occurred { Err(ErrorReported) } 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<(), ErrorReported> { 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_m_hir_id = tcx.hir().as_local_hir_id(trait_m.def_id); let trait_span = if let Some(trait_id) = trait_m_hir_id { match tcx.hir().expect_trait_item(trait_id).kind { TraitItemKind::Method(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 { Span::new( trait_m_sig.decl.inputs[0].span.lo(), arg.span.hi(), arg.span.ctxt(), ) }) } else { trait_item_span } } _ => bug!("{:?} is not a method", impl_m), } } else { trait_item_span }; let impl_m_hir_id = tcx.hir().as_local_hir_id(impl_m.def_id).unwrap(); let impl_span = match tcx.hir().expect_impl_item(impl_m_hir_id).kind { ImplItemKind::Method(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 { Span::new( impl_m_sig.decl.inputs[0].span.lo(), arg.span.hi(), arg.span.ctxt(), ) } } 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.ident, 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.ident.to_string(), trait_m.signature(tcx)); } err.span_label( impl_span, format!( "expected {}, found {}", potentially_plural_count(trait_number_args, "parameter"), impl_number_args ), ); err.emit(); return Err(ErrorReported); } Ok(()) } fn compare_synthetic_generics<'tcx>( tcx: TyCtxt<'tcx>, impl_m: &ty::AssocItem, trait_m: &ty::AssocItem, ) -> Result<(), ErrorReported> { // 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 = false; 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 impl_m_type_params.zip(trait_m_type_params) { if impl_synthetic != trait_synthetic { let impl_hir_id = tcx.hir().as_local_hir_id(impl_def_id).unwrap(); 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.ident ); 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 (Some(hir::SyntheticTyParamKind::ImplTrait), None) => { 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 = tcx.hir().as_local_hir_id(trait_m.def_id)?; let trait_m = tcx.hir().trait_item(hir::TraitItemId { hir_id: trait_m }); let impl_m = tcx.hir().as_local_hir_id(impl_m.def_id)?; let impl_m = tcx.hir().impl_item(hir::ImplItemId { hir_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. (None, Some(hir::SyntheticTyParamKind::ImplTrait)) => { err.span_label(impl_span, "expected `impl Trait`, found generic parameter"); (|| { let impl_m = tcx.hir().as_local_hir_id(impl_m.def_id)?; let impl_m = tcx.hir().impl_item(hir::ImplItemId { hir_id: impl_m }); let input_tys = match impl_m.kind { hir::ImplItemKind::Method(ref sig, _) => sig.decl.inputs, _ => unreachable!(), }; struct Visitor(Option, hir::def_id::DefId); 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 { if let Res::Def(DefKind::TyParam, def_id) = path.res { if def_id == self.1 { self.0 = Some(ty.span); } } } } fn nested_visit_map<'this>( &'this mut self, ) -> intravisit::NestedVisitorMap<'this, 'v> { intravisit::NestedVisitorMap::None } } 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.params.iter().find_map(|param| match param.kind { GenericParamKind::Lifetime { .. } => None, GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => { if param.hir_id == impl_hir_id { Some(¶m.bounds) } else { None } } })?; 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!(), } err.emit(); error_found = true; } } if error_found { Err(ErrorReported) } else { Ok(()) } } 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 inh = Inherited::new(infcx, impl_c.def_id); let infcx = &inh.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().as_local_hir_id(impl_c.def_id).unwrap(); // Compute placeholder form of impl and trait const tys. let impl_ty = tcx.type_of(impl_c.def_id); let trait_ty = tcx.type_of(trait_c.def_id).subst(tcx, trait_to_impl_substs); let mut cause = ObligationCause::misc(impl_c_span, impl_c_hir_id); // There is no "body" here, so just pass dummy id. let impl_ty = inh.normalize_associated_types_in(impl_c_span, impl_c_hir_id, param_env, &impl_ty); debug!("compare_const_impl: impl_ty={:?}", impl_ty); let trait_ty = inh.normalize_associated_types_in(impl_c_span, impl_c_hir_id, 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| inh.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_hir_id).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.ident ); let trait_c_hir_id = tcx.hir().as_local_hir_id(trait_c.def_id); let trait_c_span = trait_c_hir_id.map(|trait_c_hir_id| { // Add a label to the Span containing just the type of the const match tcx.hir().expect_trait_item(trait_c_hir_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::Types(ExpectedFound { expected: trait_ty, found: impl_ty, })), &terr, ); diag.emit(); } // Check that all obligations are satisfied by the implementation's // version. if let Err(ref errors) = inh.fulfillment_cx.borrow_mut().select_all_or_error(&infcx) { infcx.report_fulfillment_errors(errors, None, false); return; } let fcx = FnCtxt::new(&inh, param_env, impl_c_hir_id); fcx.regionck_item(impl_c_hir_id, impl_c_span, &[]); }); } 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<(), ErrorReported> = (|| { compare_number_of_generics(tcx, impl_ty, impl_ty_span, trait_ty, trait_item_span)?; compare_type_predicate_entailment(tcx, impl_ty, impl_ty_span, trait_ty, impl_trait_ref) })(); } /// The equivalent of [compare_predicate_entailment], but for associated types /// instead of associated functions. fn compare_type_predicate_entailment( tcx: TyCtxt<'tcx>, impl_ty: &ty::AssocItem, impl_ty_span: Span, trait_ty: &ty::AssocItem, impl_trait_ref: ty::TraitRef<'tcx>, ) -> Result<(), ErrorReported> { 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(), 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_span, 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().as_local_hir_id(impl_ty.def_id).unwrap(); let cause = ObligationCause { span: impl_ty_span, body_id: impl_ty_hir_id, code: ObligationCauseCode::CompareImplTypeObligation { item_name: impl_ty.ident.name, impl_item_def_id: impl_ty.def_id, trait_item_def_id: trait_ty.def_id, }, }; 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, None, ); let param_env = traits::normalize_param_env_or_error( tcx, impl_ty.def_id, param_env, normalize_cause.clone(), ); tcx.infer_ctxt().enter(|infcx| { let inh = Inherited::new(infcx, impl_ty.def_id); let infcx = &inh.infcx; debug!("compare_type_predicate_entailment: caller_bounds={:?}", param_env.caller_bounds); let mut selcx = traits::SelectionContext::new(&infcx); for predicate in impl_ty_own_bounds.predicates { let traits::Normalized { value: predicate, obligations } = traits::normalize(&mut selcx, param_env, normalize_cause.clone(), &predicate); inh.register_predicates(obligations); inh.register_predicate(traits::Obligation::new(cause.clone(), param_env, predicate)); } // Check that all obligations are satisfied by the implementation's // version. if let Err(ref errors) = inh.fulfillment_cx.borrow_mut().select_all_or_error(&infcx) { infcx.report_fulfillment_errors(errors, None, false); return Err(ErrorReported); } // Finally, resolve all regions. This catches wily misuses of // lifetime parameters. let fcx = FnCtxt::new(&inh, param_env, impl_ty_hir_id); fcx.regionck_item(impl_ty_hir_id, impl_ty_span, &[]); Ok(()) }) } fn assoc_item_kind_str(impl_item: &ty::AssocItem) -> &'static str { match impl_item.kind { ty::AssocKind::Const => "const", ty::AssocKind::Method => "method", ty::AssocKind::Type | ty::AssocKind::OpaqueTy => "type", } }