| use crate::errors::LifetimesOrBoundsMismatchOnTrait; |
| use rustc_data_structures::stable_set::FxHashSet; |
| use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticId, ErrorReported}; |
| 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::{self, InferOk, TyCtxtInferExt}; |
| use rustc_infer::traits::util; |
| use rustc_middle::ty; |
| use rustc_middle::ty::error::{ExpectedFound, TypeError}; |
| use rustc_middle::ty::subst::{InternalSubsts, Subst}; |
| use rustc_middle::ty::util::ExplicitSelf; |
| 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, Reveal}; |
| use std::iter; |
| |
| use super::{potentially_plural_count, FnCtxt, Inherited}; |
| |
| /// 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<Span>, |
| ) { |
| debug!("compare_impl_method(impl_trait_ref={:?})", impl_trait_ref); |
| |
| let impl_m_span = tcx.sess.source_map().guess_head_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; |
| } |
| |
| if let Err(ErrorReported) = compare_const_param_types(tcx, impl_m, trait_m, trait_item_span) { |
| 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().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::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_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(), 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_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_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); |
| 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.expect_local()); |
| 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_placeholder_substs); |
| for predicate in impl_m_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)); |
| } |
| |
| // 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 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::dummy(impl_sig)); |
| debug!("compare_impl_method: impl_fty={:?}", impl_fty); |
| |
| // First liberate late bound regions and subst placeholders |
| 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_placeholder_substs); |
| // Next, add all inputs and output as well-formed tys. Importantly, |
| // we have to do this before normalization, since the normalized ty may |
| // not contain the input parameters. See issue #87748. |
| wf_tys.extend(trait_sig.inputs_and_output.iter()); |
| let trait_sig = |
| inh.normalize_associated_types_in(impl_m_span, impl_m_hir_id, param_env, trait_sig); |
| // Also add the resulting inputs and output as well-formed. |
| // This probably isn't strictly necessary. |
| 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); |
| |
| 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, &terr, &cause, impl_m, trait_m); |
| |
| cause.make_mut().span = impl_err_span; |
| |
| let mut diag = struct_span_err!( |
| tcx.sess, |
| cause.span(tcx), |
| E0053, |
| "method `{}` has an incompatible type for trait", |
| trait_m.ident |
| ); |
| 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<Self>`, the |
| // span points only at the type `Box<Self`>, but we want to cover the whole |
| // argument pattern and type. |
| let impl_m_hir_id = |
| tcx.hir().local_def_id_to_hir_id(impl_m.def_id.expect_local()); |
| let span = match tcx.hir().expect_impl_item(impl_m_hir_id).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. |
| let impl_m_hir_id = |
| tcx.hir().local_def_id_to_hir_id(impl_m.def_id.expect_local()); |
| match tcx.hir().expect_impl_item(impl_m_hir_id).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().to_string(); |
| 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.to_string(), |
| 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, wf_tys); |
| |
| 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().guess_head_span(span); |
| let span = tcx.hir().get_generics(impl_m.def_id).map_or(def_span, |g| g.span); |
| let generics_span = tcx.hir().span_if_local(trait_m.def_id).map(|sp| { |
| let def_sp = tcx.sess.source_map().guess_head_span(sp); |
| tcx.hir().get_generics(trait_m.def_id).map_or(def_sp, |g| g.span) |
| }); |
| |
| tcx.sess.emit_err(LifetimesOrBoundsMismatchOnTrait { |
| span, |
| item_kind, |
| ident: impl_m.ident, |
| generics_span, |
| }); |
| return Err(ErrorReported); |
| } |
| |
| Ok(()) |
| } |
| |
| 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<Span>) { |
| let tcx = infcx.tcx; |
| let impl_m_hir_id = tcx.hir().local_def_id_to_hir_id(impl_m.def_id.expect_local()); |
| let mut impl_args = match tcx.hir().expect_impl_item(impl_m_hir_id).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| { |
| let trait_m_hir_id = tcx.hir().local_def_id_to_hir_id(def_id); |
| match tcx.hir().expect_trait_item(trait_m_hir_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), 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); |
| 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.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<Span>, |
| ) -> 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(def_id) = trait_.def_id.as_local() { |
| let trait_hir_id = tcx.hir().local_def_id_to_hir_id(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<Span> = |
| trait_item.generics.params.iter().map(|p| p.span).collect(); |
| let impl_trait_spans: Vec<Span> = 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().local_def_id_to_hir_id(impl_.def_id.expect_local()); |
| let impl_item = tcx.hir().expect_impl_item(impl_hir_id); |
| let impl_item_impl_trait_spans: Vec<Span> = 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<Span>, |
| ) -> 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_span = if let Some(def_id) = trait_m.def_id.as_local() { |
| let trait_id = tcx.hir().local_def_id_to_hir_id(def_id); |
| match tcx.hir().expect_trait_item(trait_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_m_hir_id = tcx.hir().local_def_id_to_hir_id(impl_m.def_id.expect_local()); |
| let impl_span = match tcx.hir().expect_impl_item(impl_m_hir_id).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.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 |
| iter::zip(impl_m_type_params, trait_m_type_params) |
| { |
| if impl_synthetic != trait_synthetic { |
| let impl_hir_id = tcx.hir().local_def_id_to_hir_id(impl_def_id.expect_local()); |
| 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 = 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. |
| (None, Some(hir::SyntheticTyParamKind::ImplTrait)) => { |
| 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<Span>, 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); |
| } |
| } |
| } |
| } |
| type Map = intravisit::ErasedMap<'v>; |
| fn nested_visit_map( |
| &mut self, |
| ) -> intravisit::NestedVisitorMap<Self::Map> |
| { |
| 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(()) } |
| } |
| |
| fn compare_const_param_types<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| impl_m: &ty::AssocItem, |
| trait_m: &ty::AssocItem, |
| trait_item_span: Option<Span>, |
| ) -> Result<(), ErrorReported> { |
| let const_params_of = |def_id| { |
| tcx.generics_of(def_id).params.iter().filter_map(|param| match param.kind { |
| GenericParamDefKind::Const { .. } => Some(param.def_id), |
| _ => None, |
| }) |
| }; |
| let const_params_impl = const_params_of(impl_m.def_id); |
| let const_params_trait = const_params_of(trait_m.def_id); |
| |
| for (const_param_impl, const_param_trait) in iter::zip(const_params_impl, const_params_trait) { |
| let impl_ty = tcx.type_of(const_param_impl); |
| let trait_ty = tcx.type_of(const_param_trait); |
| if impl_ty != trait_ty { |
| let (impl_span, impl_ident) = match tcx.hir().get_if_local(const_param_impl) { |
| Some(hir::Node::GenericParam(hir::GenericParam { span, name, .. })) => ( |
| span, |
| match name { |
| hir::ParamName::Plain(ident) => Some(ident), |
| _ => None, |
| }, |
| ), |
| other => bug!( |
| "expected GenericParam, found {:?}", |
| other.map_or_else(|| "nothing".to_string(), |n| format!("{:?}", n)) |
| ), |
| }; |
| let trait_span = match tcx.hir().get_if_local(const_param_trait) { |
| Some(hir::Node::GenericParam(hir::GenericParam { span, .. })) => Some(span), |
| _ => None, |
| }; |
| let mut err = struct_span_err!( |
| tcx.sess, |
| *impl_span, |
| E0053, |
| "method `{}` has an incompatible const parameter type for trait", |
| trait_m.ident |
| ); |
| err.span_note( |
| trait_span.map_or_else(|| trait_item_span.unwrap_or(*impl_span), |span| *span), |
| &format!( |
| "the const parameter{} has type `{}`, but the declaration \ |
| in trait `{}` has type `{}`", |
| &impl_ident.map_or_else(|| "".to_string(), |ident| format!(" `{}`", ident)), |
| impl_ty, |
| tcx.def_path_str(trait_m.def_id), |
| trait_ty |
| ), |
| ); |
| err.emit(); |
| return Err(ErrorReported); |
| } |
| } |
| |
| 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.expect_local()); |
| 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().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.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::CompareImplConstObligation, |
| ); |
| |
| // 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.make_mut().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 = |
| trait_c.def_id.as_local().map(|def_id| tcx.hir().local_def_id_to_hir_id(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, FxHashSet::default()); |
| }); |
| } |
| |
| 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<Span>, |
| ) { |
| 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)?; |
| |
| 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<(), 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().local_def_id_to_hir_id(impl_ty.def_id.expect_local()); |
| let cause = ObligationCause::new( |
| impl_ty_span, |
| impl_ty_hir_id, |
| 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); |
| 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.expect_local()); |
| 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, FxHashSet::default()); |
| |
| 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 `<T as X>::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<(), ErrorReported> { |
| // Given |
| // |
| // impl<A, B> Foo<u32> for (A, B) { |
| // type Bar<C> =... |
| // } |
| // |
| // - `impl_trait_ref` would be `<(A, B) as Foo<u32>> |
| // - `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<C: Eq>; |
| // } |
| // |
| // impl Family for VecFamily { |
| // type Member<C: Eq> = i32; |
| // } |
| // ``` |
| // Here, we would generate |
| // ```notrust |
| // forall<C> { Normalize(<VecFamily as Family>::Member<C> => i32) } |
| // ``` |
| // when we really would like to generate |
| // ```notrust |
| // forall<C> { Normalize(<VecFamily as Family>::Member<C> => 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<X> for some type X where !(X: Eq), that appears in the value of type |
| // Member<C: Eq> = .... That type would fail a well-formedness check that we ought to be doing |
| // elsewhere, which would check that any <T as Family>::Member<X> 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::Const { |
| ty: tcx.type_of(param.def_id), |
| val: 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 rebased_substs = |
| impl_ty_substs.rebase_onto(tcx, impl_ty.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<<Self as X>::Y> } |
| // impl X for T { default type Y = S; } |
| // |
| // We will have to prove the bound S: PartialEq<<T as X>::Y>. In this case |
| // we want <T as X>::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::<Vec<_>>(); |
| 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<T> X for T where T: X { type Y = <T as X>::Y; } |
| } |
| _ => predicates.push( |
| ty::Binder::bind_with_vars( |
| ty::ProjectionPredicate { |
| projection_ty: ty::ProjectionTy { |
| item_def_id: trait_ty.def_id, |
| substs: rebased_substs, |
| }, |
| ty: impl_ty_value, |
| }, |
| bound_vars, |
| ) |
| .to_predicate(tcx), |
| ), |
| }; |
| ty::ParamEnv::new(tcx.intern_predicates(&predicates), Reveal::UserFacing) |
| }; |
| 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, impl_ty.container.id(), impl_trait_ref.substs); |
| |
| tcx.infer_ctxt().enter(move |infcx| { |
| let constness = impl_ty |
| .container |
| .impl_def_id() |
| .map(|did| tcx.impl_constness(did)) |
| .unwrap_or(hir::Constness::NotConst); |
| |
| let inh = Inherited::with_constness(infcx, impl_ty.def_id.expect_local(), constness); |
| let infcx = &inh.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 = traits::ObligationCause::misc(impl_ty_span, impl_ty_hir_id); |
| let mk_cause = |span| { |
| ObligationCause::new( |
| impl_ty_span, |
| impl_ty_hir_id, |
| ObligationCauseCode::BindingObligation(trait_ty.def_id, span), |
| ) |
| }; |
| |
| let obligations = tcx |
| .explicit_item_bounds(trait_ty.def_id) |
| .iter() |
| .map(|&(bound, span)| { |
| debug!(?bound); |
| 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), 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; |
| |
| inh.register_predicates(obligations); |
| inh.register_predicate(obligation); |
| } |
| |
| // Check that all obligations are satisfied by the implementation's |
| // version. |
| if let Err(ref errors) = |
| inh.fulfillment_cx.borrow_mut().select_all_with_constness_or_error(&infcx, constness) |
| { |
| 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); |
| let implied_bounds = match impl_ty.container { |
| ty::TraitContainer(_) => FxHashSet::default(), |
| ty::ImplContainer(def_id) => fcx.impl_implied_bounds(def_id, impl_ty_span), |
| }; |
| fcx.regionck_item(impl_ty_hir_id, impl_ty_span, implied_bounds); |
| |
| 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", |
| } |
| } |
