| // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT |
| // file at the top-level directory of this distribution and at |
| // http://rust-lang.org/COPYRIGHT. |
| // |
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your |
| // option. This file may not be copied, modified, or distributed |
| // except according to those terms. |
| |
| use middle::free_region::FreeRegionMap; |
| use rustc::infer::{self, InferOk, TypeOrigin}; |
| use rustc::ty; |
| use rustc::traits::{self, ProjectionMode}; |
| use rustc::ty::error::ExpectedFound; |
| use rustc::ty::subst::{self, Subst, Substs, VecPerParamSpace}; |
| |
| use syntax::ast; |
| use syntax_pos::Span; |
| |
| use CrateCtxt; |
| use super::assoc; |
| |
| /// 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 |
| /// - impl_m_body_id: id of the method body |
| /// - trait_m: the method in the trait |
| /// - impl_trait_ref: the TraitRef corresponding to the trait implementation |
| |
| pub fn compare_impl_method<'a, 'tcx>(ccx: &CrateCtxt<'a, 'tcx>, |
| impl_m: &ty::Method<'tcx>, |
| impl_m_span: Span, |
| impl_m_body_id: ast::NodeId, |
| trait_m: &ty::Method<'tcx>, |
| impl_trait_ref: &ty::TraitRef<'tcx>) { |
| debug!("compare_impl_method(impl_trait_ref={:?})", |
| impl_trait_ref); |
| |
| debug!("compare_impl_method: impl_trait_ref (liberated) = {:?}", |
| impl_trait_ref); |
| |
| let tcx = ccx.tcx; |
| |
| let trait_to_impl_substs = &impl_trait_ref.substs; |
| |
| // 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. |
| match (&trait_m.explicit_self, &impl_m.explicit_self) { |
| (&ty::ExplicitSelfCategory::Static, |
| &ty::ExplicitSelfCategory::Static) => {} |
| (&ty::ExplicitSelfCategory::Static, _) => { |
| span_err!(tcx.sess, impl_m_span, E0185, |
| "method `{}` has a `{}` declaration in the impl, \ |
| but not in the trait", |
| trait_m.name, |
| impl_m.explicit_self); |
| return; |
| } |
| (_, &ty::ExplicitSelfCategory::Static) => { |
| span_err!(tcx.sess, impl_m_span, E0186, |
| "method `{}` has a `{}` declaration in the trait, \ |
| but not in the impl", |
| trait_m.name, |
| trait_m.explicit_self); |
| return; |
| } |
| _ => { |
| // Let the type checker catch other errors below |
| } |
| } |
| |
| let num_impl_m_type_params = impl_m.generics.types.len(subst::FnSpace); |
| let num_trait_m_type_params = trait_m.generics.types.len(subst::FnSpace); |
| if num_impl_m_type_params != num_trait_m_type_params { |
| span_err!(tcx.sess, impl_m_span, E0049, |
| "method `{}` has {} type parameter{} \ |
| but its trait declaration has {} type parameter{}", |
| trait_m.name, |
| num_impl_m_type_params, |
| if num_impl_m_type_params == 1 {""} else {"s"}, |
| num_trait_m_type_params, |
| if num_trait_m_type_params == 1 {""} else {"s"}); |
| return; |
| } |
| |
| if impl_m.fty.sig.0.inputs.len() != trait_m.fty.sig.0.inputs.len() { |
| span_err!(tcx.sess, impl_m_span, E0050, |
| "method `{}` has {} parameter{} \ |
| but the declaration in trait `{}` has {}", |
| trait_m.name, |
| impl_m.fty.sig.0.inputs.len(), |
| if impl_m.fty.sig.0.inputs.len() == 1 {""} else {"s"}, |
| tcx.item_path_str(trait_m.def_id), |
| trait_m.fty.sig.0.inputs.len()); |
| return; |
| } |
| |
| // 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 |
| // skolemized 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, skolemized |
| // 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 skolemized form. |
| // |
| // Finally we register each of these predicates as an obligation in |
| // a fresh FulfillmentCtxt, and invoke select_all_or_error. |
| |
| // Create a parameter environment that represents the implementation's |
| // method. |
| let impl_m_node_id = tcx.map.as_local_node_id(impl_m.def_id).unwrap(); |
| let impl_param_env = ty::ParameterEnvironment::for_item(tcx, impl_m_node_id); |
| |
| // Create mapping from impl to skolemized. |
| let impl_to_skol_substs = &impl_param_env.free_substs; |
| |
| // Create mapping from trait to skolemized. |
| let trait_to_skol_substs = |
| trait_to_impl_substs |
| .subst(tcx, impl_to_skol_substs).clone() |
| .with_method(impl_to_skol_substs.types.get_slice(subst::FnSpace).to_vec(), |
| impl_to_skol_substs.regions.get_slice(subst::FnSpace).to_vec()); |
| debug!("compare_impl_method: trait_to_skol_substs={:?}", |
| trait_to_skol_substs); |
| |
| // Check region bounds. FIXME(@jroesch) refactor this away when removing |
| // ParamBounds. |
| if !check_region_bounds_on_impl_method(ccx, |
| impl_m_span, |
| impl_m, |
| &trait_m.generics, |
| &impl_m.generics, |
| &trait_to_skol_substs, |
| impl_to_skol_substs) { |
| return; |
| } |
| |
| tcx.infer_ctxt(None, None, ProjectionMode::AnyFinal).enter(|mut infcx| { |
| let mut fulfillment_cx = traits::FulfillmentContext::new(); |
| |
| // Normalize the associated types in the trait_bounds. |
| let trait_bounds = trait_m.predicates.instantiate(tcx, &trait_to_skol_substs); |
| |
| // 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_bounds = |
| impl_m.predicates.instantiate(tcx, impl_to_skol_substs); |
| |
| debug!("compare_impl_method: impl_bounds={:?}", impl_bounds); |
| |
| // Obtain the predicate split predicate sets for each. |
| let trait_pred = trait_bounds.predicates.split(); |
| let impl_pred = impl_bounds.predicates.split(); |
| |
| // 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 FnSpace 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. |
| let hybrid_preds = VecPerParamSpace::new( |
| impl_pred.types, |
| impl_pred.selfs, |
| trait_pred.fns |
| ); |
| |
| // Construct trait parameter environment and then shift it into the skolemized 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_body_id); |
| let trait_param_env = impl_param_env.with_caller_bounds(hybrid_preds.into_vec()); |
| let trait_param_env = traits::normalize_param_env_or_error(tcx, |
| trait_param_env, |
| normalize_cause.clone()); |
| // FIXME(@jroesch) this seems ugly, but is a temporary change |
| infcx.parameter_environment = trait_param_env; |
| |
| debug!("compare_impl_method: trait_bounds={:?}", |
| infcx.parameter_environment.caller_bounds); |
| |
| let mut selcx = traits::SelectionContext::new(&infcx); |
| |
| let (impl_pred_fns, _) = |
| infcx.replace_late_bound_regions_with_fresh_var( |
| impl_m_span, |
| infer::HigherRankedType, |
| &ty::Binder(impl_pred.fns)); |
| for predicate in impl_pred_fns { |
| let traits::Normalized { value: predicate, .. } = |
| traits::normalize(&mut selcx, normalize_cause.clone(), &predicate); |
| |
| let cause = traits::ObligationCause { |
| span: impl_m_span, |
| body_id: impl_m_body_id, |
| code: traits::ObligationCauseCode::CompareImplMethodObligation |
| }; |
| |
| fulfillment_cx.register_predicate_obligation( |
| &infcx, |
| traits::Obligation::new(cause, 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 skolemized form of impl and trait method tys. |
| let tcx = infcx.tcx; |
| let origin = TypeOrigin::MethodCompatCheck(impl_m_span); |
| |
| let (impl_sig, _) = |
| infcx.replace_late_bound_regions_with_fresh_var(impl_m_span, |
| infer::HigherRankedType, |
| &impl_m.fty.sig); |
| let impl_sig = |
| impl_sig.subst(tcx, impl_to_skol_substs); |
| let impl_sig = |
| assoc::normalize_associated_types_in(&infcx, |
| &mut fulfillment_cx, |
| impl_m_span, |
| impl_m_body_id, |
| &impl_sig); |
| let impl_fty = tcx.mk_fn_ptr(tcx.mk_bare_fn(ty::BareFnTy { |
| unsafety: impl_m.fty.unsafety, |
| abi: impl_m.fty.abi, |
| sig: ty::Binder(impl_sig) |
| })); |
| debug!("compare_impl_method: impl_fty={:?}", impl_fty); |
| |
| let trait_sig = tcx.liberate_late_bound_regions( |
| infcx.parameter_environment.free_id_outlive, |
| &trait_m.fty.sig); |
| let trait_sig = |
| trait_sig.subst(tcx, &trait_to_skol_substs); |
| let trait_sig = |
| assoc::normalize_associated_types_in(&infcx, |
| &mut fulfillment_cx, |
| impl_m_span, |
| impl_m_body_id, |
| &trait_sig); |
| let trait_fty = tcx.mk_fn_ptr(tcx.mk_bare_fn(ty::BareFnTy { |
| unsafety: trait_m.fty.unsafety, |
| abi: trait_m.fty.abi, |
| sig: ty::Binder(trait_sig) |
| })); |
| |
| debug!("compare_impl_method: trait_fty={:?}", trait_fty); |
| |
| if let Err(terr) = infcx.sub_types(false, origin, impl_fty, trait_fty) { |
| debug!("sub_types failed: impl ty {:?}, trait ty {:?}", |
| impl_fty, |
| trait_fty); |
| |
| let mut diag = struct_span_err!( |
| tcx.sess, origin.span(), E0053, |
| "method `{}` has an incompatible type for trait", trait_m.name |
| ); |
| infcx.note_type_err( |
| &mut diag, origin, |
| Some(infer::ValuePairs::Types(ExpectedFound { |
| expected: trait_fty, |
| found: impl_fty |
| })), &terr |
| ); |
| diag.emit(); |
| return |
| } |
| |
| // Check that all obligations are satisfied by the implementation's |
| // version. |
| if let Err(ref errors) = fulfillment_cx.select_all_or_error(&infcx) { |
| infcx.report_fulfillment_errors(errors); |
| return |
| } |
| |
| // Finally, resolve all regions. This catches wily misuses of |
| // lifetime parameters. We have to build up a plausible lifetime |
| // environment based on what we find in the trait. We could also |
| // include the obligations derived from the method argument types, |
| // but I don't think it's necessary -- after all, those are still |
| // in effect when type-checking the body, and all the |
| // where-clauses in the header etc should be implied by the trait |
| // anyway, so it shouldn't be needed there either. Anyway, we can |
| // always add more relations later (it's backwards compat). |
| let mut free_regions = FreeRegionMap::new(); |
| free_regions.relate_free_regions_from_predicates( |
| &infcx.parameter_environment.caller_bounds); |
| |
| infcx.resolve_regions_and_report_errors(&free_regions, impl_m_body_id); |
| }); |
| |
| fn check_region_bounds_on_impl_method<'a, 'tcx>(ccx: &CrateCtxt<'a, 'tcx>, |
| span: Span, |
| impl_m: &ty::Method<'tcx>, |
| trait_generics: &ty::Generics<'tcx>, |
| impl_generics: &ty::Generics<'tcx>, |
| trait_to_skol_substs: &Substs<'tcx>, |
| impl_to_skol_substs: &Substs<'tcx>) |
| -> bool |
| { |
| |
| let trait_params = trait_generics.regions.get_slice(subst::FnSpace); |
| let impl_params = impl_generics.regions.get_slice(subst::FnSpace); |
| |
| debug!("check_region_bounds_on_impl_method: \ |
| trait_generics={:?} \ |
| impl_generics={:?} \ |
| trait_to_skol_substs={:?} \ |
| impl_to_skol_substs={:?}", |
| trait_generics, |
| impl_generics, |
| trait_to_skol_substs, |
| impl_to_skol_substs); |
| |
| // 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.len() != impl_params.len() { |
| span_err!(ccx.tcx.sess, span, E0195, |
| "lifetime parameters or bounds on method `{}` do \ |
| not match the trait declaration", |
| impl_m.name); |
| return false; |
| } |
| |
| return true; |
| } |
| } |
| |
| pub fn compare_const_impl<'a, 'tcx>(ccx: &CrateCtxt<'a, 'tcx>, |
| impl_c: &ty::AssociatedConst<'tcx>, |
| impl_c_span: Span, |
| trait_c: &ty::AssociatedConst<'tcx>, |
| impl_trait_ref: &ty::TraitRef<'tcx>) { |
| debug!("compare_const_impl(impl_trait_ref={:?})", |
| impl_trait_ref); |
| |
| let tcx = ccx.tcx; |
| tcx.infer_ctxt(None, None, ProjectionMode::AnyFinal).enter(|infcx| { |
| let mut fulfillment_cx = traits::FulfillmentContext::new(); |
| |
| // 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_node_id = tcx.map.as_local_node_id(impl_c.def_id).unwrap(); |
| let impl_param_env = ty::ParameterEnvironment::for_item(tcx, impl_c_node_id); |
| |
| // Create mapping from impl to skolemized. |
| let impl_to_skol_substs = &impl_param_env.free_substs; |
| |
| // Create mapping from trait to skolemized. |
| let trait_to_skol_substs = |
| trait_to_impl_substs |
| .subst(tcx, impl_to_skol_substs).clone() |
| .with_method(impl_to_skol_substs.types.get_slice(subst::FnSpace).to_vec(), |
| impl_to_skol_substs.regions.get_slice(subst::FnSpace).to_vec()); |
| debug!("compare_const_impl: trait_to_skol_substs={:?}", |
| trait_to_skol_substs); |
| |
| // Compute skolemized form of impl and trait const tys. |
| let impl_ty = impl_c.ty.subst(tcx, impl_to_skol_substs); |
| let trait_ty = trait_c.ty.subst(tcx, &trait_to_skol_substs); |
| let origin = TypeOrigin::Misc(impl_c_span); |
| |
| let err = infcx.commit_if_ok(|_| { |
| // There is no "body" here, so just pass dummy id. |
| let impl_ty = |
| assoc::normalize_associated_types_in(&infcx, |
| &mut fulfillment_cx, |
| impl_c_span, |
| 0, |
| &impl_ty); |
| |
| debug!("compare_const_impl: impl_ty={:?}", |
| impl_ty); |
| |
| let trait_ty = |
| assoc::normalize_associated_types_in(&infcx, |
| &mut fulfillment_cx, |
| impl_c_span, |
| 0, |
| &trait_ty); |
| |
| debug!("compare_const_impl: trait_ty={:?}", |
| trait_ty); |
| |
| infcx.sub_types(false, origin, impl_ty, trait_ty) |
| .map(|InferOk { obligations, .. }| { |
| // FIXME(#32730) propagate obligations |
| assert!(obligations.is_empty()) |
| }) |
| }); |
| |
| if let Err(terr) = err { |
| debug!("checking associated const for compatibility: impl ty {:?}, trait ty {:?}", |
| impl_ty, |
| trait_ty); |
| let mut diag = struct_span_err!( |
| tcx.sess, origin.span(), E0326, |
| "implemented const `{}` has an incompatible type for trait", |
| trait_c.name |
| ); |
| infcx.note_type_err( |
| &mut diag, origin, |
| Some(infer::ValuePairs::Types(ExpectedFound { |
| expected: trait_ty, |
| found: impl_ty |
| })), &terr |
| ); |
| diag.emit(); |
| } |
| }); |
| } |
