| use super::{probe, MethodCallee}; |
| |
| use crate::astconv::AstConv; |
| use crate::check::{callee, FnCtxt}; |
| use crate::hir::def_id::DefId; |
| use crate::hir::GenericArg; |
| use rustc_hir as hir; |
| use rustc_infer::infer::{self, InferOk}; |
| use rustc_middle::ty::adjustment::{Adjust, Adjustment, PointerCast}; |
| use rustc_middle::ty::adjustment::{AllowTwoPhase, AutoBorrow, AutoBorrowMutability}; |
| use rustc_middle::ty::fold::TypeFoldable; |
| use rustc_middle::ty::subst::{Subst, SubstsRef}; |
| use rustc_middle::ty::{self, GenericParamDefKind, Ty}; |
| use rustc_span::Span; |
| use rustc_trait_selection::traits; |
| |
| use std::ops::Deref; |
| |
| struct ConfirmContext<'a, 'tcx> { |
| fcx: &'a FnCtxt<'a, 'tcx>, |
| span: Span, |
| self_expr: &'tcx hir::Expr<'tcx>, |
| call_expr: &'tcx hir::Expr<'tcx>, |
| } |
| |
| impl<'a, 'tcx> Deref for ConfirmContext<'a, 'tcx> { |
| type Target = FnCtxt<'a, 'tcx>; |
| fn deref(&self) -> &Self::Target { |
| &self.fcx |
| } |
| } |
| |
| pub struct ConfirmResult<'tcx> { |
| pub callee: MethodCallee<'tcx>, |
| pub illegal_sized_bound: Option<Span>, |
| } |
| |
| impl<'a, 'tcx> FnCtxt<'a, 'tcx> { |
| pub fn confirm_method( |
| &self, |
| span: Span, |
| self_expr: &'tcx hir::Expr<'tcx>, |
| call_expr: &'tcx hir::Expr<'tcx>, |
| unadjusted_self_ty: Ty<'tcx>, |
| pick: probe::Pick<'tcx>, |
| segment: &hir::PathSegment<'_>, |
| ) -> ConfirmResult<'tcx> { |
| debug!( |
| "confirm(unadjusted_self_ty={:?}, pick={:?}, generic_args={:?})", |
| unadjusted_self_ty, pick, segment.args, |
| ); |
| |
| let mut confirm_cx = ConfirmContext::new(self, span, self_expr, call_expr); |
| confirm_cx.confirm(unadjusted_self_ty, pick, segment) |
| } |
| } |
| |
| impl<'a, 'tcx> ConfirmContext<'a, 'tcx> { |
| fn new( |
| fcx: &'a FnCtxt<'a, 'tcx>, |
| span: Span, |
| self_expr: &'tcx hir::Expr<'tcx>, |
| call_expr: &'tcx hir::Expr<'tcx>, |
| ) -> ConfirmContext<'a, 'tcx> { |
| ConfirmContext { fcx, span, self_expr, call_expr } |
| } |
| |
| fn confirm( |
| &mut self, |
| unadjusted_self_ty: Ty<'tcx>, |
| pick: probe::Pick<'tcx>, |
| segment: &hir::PathSegment<'_>, |
| ) -> ConfirmResult<'tcx> { |
| // Adjust the self expression the user provided and obtain the adjusted type. |
| let self_ty = self.adjust_self_ty(unadjusted_self_ty, &pick); |
| |
| // Create substitutions for the method's type parameters. |
| let rcvr_substs = self.fresh_receiver_substs(self_ty, &pick); |
| let all_substs = self.instantiate_method_substs(&pick, segment, rcvr_substs); |
| |
| debug!("all_substs={:?}", all_substs); |
| |
| // Create the final signature for the method, replacing late-bound regions. |
| let (method_sig, method_predicates) = self.instantiate_method_sig(&pick, all_substs); |
| |
| // Unify the (adjusted) self type with what the method expects. |
| // |
| // SUBTLE: if we want good error messages, because of "guessing" while matching |
| // traits, no trait system method can be called before this point because they |
| // could alter our Self-type, except for normalizing the receiver from the |
| // signature (which is also done during probing). |
| let method_sig_rcvr = |
| self.normalize_associated_types_in(self.span, &method_sig.inputs()[0]); |
| self.unify_receivers(self_ty, method_sig_rcvr); |
| |
| let (method_sig, method_predicates) = |
| self.normalize_associated_types_in(self.span, &(method_sig, method_predicates)); |
| |
| // Make sure nobody calls `drop()` explicitly. |
| self.enforce_illegal_method_limitations(&pick); |
| |
| // If there is a `Self: Sized` bound and `Self` is a trait object, it is possible that |
| // something which derefs to `Self` actually implements the trait and the caller |
| // wanted to make a static dispatch on it but forgot to import the trait. |
| // See test `src/test/ui/issue-35976.rs`. |
| // |
| // In that case, we'll error anyway, but we'll also re-run the search with all traits |
| // in scope, and if we find another method which can be used, we'll output an |
| // appropriate hint suggesting to import the trait. |
| let illegal_sized_bound = self.predicates_require_illegal_sized_bound(&method_predicates); |
| |
| // Add any trait/regions obligations specified on the method's type parameters. |
| // We won't add these if we encountered an illegal sized bound, so that we can use |
| // a custom error in that case. |
| if illegal_sized_bound.is_none() { |
| let method_ty = self.tcx.mk_fn_ptr(ty::Binder::bind(method_sig)); |
| self.add_obligations(method_ty, all_substs, method_predicates); |
| } |
| |
| // Create the final `MethodCallee`. |
| let callee = MethodCallee { def_id: pick.item.def_id, substs: all_substs, sig: method_sig }; |
| ConfirmResult { callee, illegal_sized_bound } |
| } |
| |
| /////////////////////////////////////////////////////////////////////////// |
| // ADJUSTMENTS |
| |
| fn adjust_self_ty( |
| &mut self, |
| unadjusted_self_ty: Ty<'tcx>, |
| pick: &probe::Pick<'tcx>, |
| ) -> Ty<'tcx> { |
| // Commit the autoderefs by calling `autoderef` again, but this |
| // time writing the results into the various tables. |
| let mut autoderef = self.autoderef(self.span, unadjusted_self_ty); |
| let (_, n) = match autoderef.nth(pick.autoderefs) { |
| Some(n) => n, |
| None => { |
| return self.tcx.ty_error_with_message( |
| rustc_span::DUMMY_SP, |
| &format!("failed autoderef {}", pick.autoderefs), |
| ); |
| } |
| }; |
| assert_eq!(n, pick.autoderefs); |
| |
| let mut adjustments = self.adjust_steps(&autoderef); |
| |
| let mut target = |
| self.structurally_resolved_type(autoderef.span(), autoderef.final_ty(false)); |
| |
| if let Some(mutbl) = pick.autoref { |
| let region = self.next_region_var(infer::Autoref(self.span)); |
| target = self.tcx.mk_ref(region, ty::TypeAndMut { mutbl, ty: target }); |
| let mutbl = match mutbl { |
| hir::Mutability::Not => AutoBorrowMutability::Not, |
| hir::Mutability::Mut => AutoBorrowMutability::Mut { |
| // Method call receivers are the primary use case |
| // for two-phase borrows. |
| allow_two_phase_borrow: AllowTwoPhase::Yes, |
| }, |
| }; |
| adjustments |
| .push(Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)), target }); |
| |
| if let Some(unsize_target) = pick.unsize { |
| target = self |
| .tcx |
| .mk_ref(region, ty::TypeAndMut { mutbl: mutbl.into(), ty: unsize_target }); |
| adjustments.push(Adjustment { kind: Adjust::Pointer(PointerCast::Unsize), target }); |
| } |
| } else { |
| // No unsizing should be performed without autoref (at |
| // least during method dispach). This is because we |
| // currently only unsize `[T;N]` to `[T]`, and naturally |
| // that must occur being a reference. |
| assert!(pick.unsize.is_none()); |
| } |
| |
| self.register_predicates(autoderef.into_obligations()); |
| |
| // Write out the final adjustments. |
| self.apply_adjustments(self.self_expr, adjustments); |
| |
| target |
| } |
| |
| /// Returns a set of substitutions for the method *receiver* where all type and region |
| /// parameters are instantiated with fresh variables. This substitution does not include any |
| /// parameters declared on the method itself. |
| /// |
| /// Note that this substitution may include late-bound regions from the impl level. If so, |
| /// these are instantiated later in the `instantiate_method_sig` routine. |
| fn fresh_receiver_substs( |
| &mut self, |
| self_ty: Ty<'tcx>, |
| pick: &probe::Pick<'tcx>, |
| ) -> SubstsRef<'tcx> { |
| match pick.kind { |
| probe::InherentImplPick => { |
| let impl_def_id = pick.item.container.id(); |
| assert!( |
| self.tcx.impl_trait_ref(impl_def_id).is_none(), |
| "impl {:?} is not an inherent impl", |
| impl_def_id |
| ); |
| self.fresh_substs_for_item(self.span, impl_def_id) |
| } |
| |
| probe::ObjectPick => { |
| let trait_def_id = pick.item.container.id(); |
| self.extract_existential_trait_ref(self_ty, |this, object_ty, principal| { |
| // The object data has no entry for the Self |
| // Type. For the purposes of this method call, we |
| // substitute the object type itself. This |
| // wouldn't be a sound substitution in all cases, |
| // since each instance of the object type is a |
| // different existential and hence could match |
| // distinct types (e.g., if `Self` appeared as an |
| // argument type), but those cases have already |
| // been ruled out when we deemed the trait to be |
| // "object safe". |
| let original_poly_trait_ref = principal.with_self_ty(this.tcx, object_ty); |
| let upcast_poly_trait_ref = this.upcast(original_poly_trait_ref, trait_def_id); |
| let upcast_trait_ref = |
| this.replace_bound_vars_with_fresh_vars(&upcast_poly_trait_ref); |
| debug!( |
| "original_poly_trait_ref={:?} upcast_trait_ref={:?} target_trait={:?}", |
| original_poly_trait_ref, upcast_trait_ref, trait_def_id |
| ); |
| upcast_trait_ref.substs |
| }) |
| } |
| |
| probe::TraitPick => { |
| let trait_def_id = pick.item.container.id(); |
| |
| // Make a trait reference `$0 : Trait<$1...$n>` |
| // consisting entirely of type variables. Later on in |
| // the process we will unify the transformed-self-type |
| // of the method with the actual type in order to |
| // unify some of these variables. |
| self.fresh_substs_for_item(self.span, trait_def_id) |
| } |
| |
| probe::WhereClausePick(ref poly_trait_ref) => { |
| // Where clauses can have bound regions in them. We need to instantiate |
| // those to convert from a poly-trait-ref to a trait-ref. |
| self.replace_bound_vars_with_fresh_vars(&poly_trait_ref).substs |
| } |
| } |
| } |
| |
| fn extract_existential_trait_ref<R, F>(&mut self, self_ty: Ty<'tcx>, mut closure: F) -> R |
| where |
| F: FnMut(&mut ConfirmContext<'a, 'tcx>, Ty<'tcx>, ty::PolyExistentialTraitRef<'tcx>) -> R, |
| { |
| // If we specified that this is an object method, then the |
| // self-type ought to be something that can be dereferenced to |
| // yield an object-type (e.g., `&Object` or `Box<Object>` |
| // etc). |
| |
| // FIXME: this feels, like, super dubious |
| self.fcx |
| .autoderef(self.span, self_ty) |
| .include_raw_pointers() |
| .find_map(|(ty, _)| match ty.kind { |
| ty::Dynamic(ref data, ..) => Some(closure( |
| self, |
| ty, |
| data.principal().unwrap_or_else(|| { |
| span_bug!(self.span, "calling trait method on empty object?") |
| }), |
| )), |
| _ => None, |
| }) |
| .unwrap_or_else(|| { |
| span_bug!( |
| self.span, |
| "self-type `{}` for ObjectPick never dereferenced to an object", |
| self_ty |
| ) |
| }) |
| } |
| |
| fn instantiate_method_substs( |
| &mut self, |
| pick: &probe::Pick<'tcx>, |
| seg: &hir::PathSegment<'_>, |
| parent_substs: SubstsRef<'tcx>, |
| ) -> SubstsRef<'tcx> { |
| // Determine the values for the generic parameters of the method. |
| // If they were not explicitly supplied, just construct fresh |
| // variables. |
| let generics = self.tcx.generics_of(pick.item.def_id); |
| let arg_count_correct = AstConv::check_generic_arg_count_for_call( |
| self.tcx, self.span, &generics, &seg, true, // `is_method_call` |
| ); |
| |
| // Create subst for early-bound lifetime parameters, combining |
| // parameters from the type and those from the method. |
| assert_eq!(generics.parent_count, parent_substs.len()); |
| |
| AstConv::create_substs_for_generic_args( |
| self.tcx, |
| pick.item.def_id, |
| parent_substs, |
| false, |
| None, |
| arg_count_correct, |
| // Provide the generic args, and whether types should be inferred. |
| |def_id| { |
| // The last component of the returned tuple here is unimportant. |
| if def_id == pick.item.def_id { |
| if let Some(ref data) = seg.args { |
| return (Some(data), false); |
| } |
| } |
| (None, false) |
| }, |
| // Provide substitutions for parameters for which (valid) arguments have been provided. |
| |param, arg| match (¶m.kind, arg) { |
| (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => { |
| AstConv::ast_region_to_region(self.fcx, lt, Some(param)).into() |
| } |
| (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => self.to_ty(ty).into(), |
| (GenericParamDefKind::Const, GenericArg::Const(ct)) => { |
| self.to_const(&ct.value).into() |
| } |
| _ => unreachable!(), |
| }, |
| // Provide substitutions for parameters for which arguments are inferred. |
| |_, param, _| self.var_for_def(self.span, param), |
| ) |
| } |
| |
| fn unify_receivers(&mut self, self_ty: Ty<'tcx>, method_self_ty: Ty<'tcx>) { |
| match self.at(&self.misc(self.span), self.param_env).sup(method_self_ty, self_ty) { |
| Ok(InferOk { obligations, value: () }) => { |
| self.register_predicates(obligations); |
| } |
| Err(_) => { |
| span_bug!( |
| self.span, |
| "{} was a subtype of {} but now is not?", |
| self_ty, |
| method_self_ty |
| ); |
| } |
| } |
| } |
| |
| // NOTE: this returns the *unnormalized* predicates and method sig. Because of |
| // inference guessing, the predicates and method signature can't be normalized |
| // until we unify the `Self` type. |
| fn instantiate_method_sig( |
| &mut self, |
| pick: &probe::Pick<'tcx>, |
| all_substs: SubstsRef<'tcx>, |
| ) -> (ty::FnSig<'tcx>, ty::InstantiatedPredicates<'tcx>) { |
| debug!("instantiate_method_sig(pick={:?}, all_substs={:?})", pick, all_substs); |
| |
| // Instantiate the bounds on the method with the |
| // type/early-bound-regions substitutions performed. There can |
| // be no late-bound regions appearing here. |
| let def_id = pick.item.def_id; |
| let method_predicates = self.tcx.predicates_of(def_id).instantiate(self.tcx, all_substs); |
| |
| debug!("method_predicates after subst = {:?}", method_predicates); |
| |
| let sig = self.tcx.fn_sig(def_id); |
| |
| // Instantiate late-bound regions and substitute the trait |
| // parameters into the method type to get the actual method type. |
| // |
| // N.B., instantiate late-bound regions first so that |
| // `instantiate_type_scheme` can normalize associated types that |
| // may reference those regions. |
| let method_sig = self.replace_bound_vars_with_fresh_vars(&sig); |
| debug!("late-bound lifetimes from method instantiated, method_sig={:?}", method_sig); |
| |
| let method_sig = method_sig.subst(self.tcx, all_substs); |
| debug!("type scheme substituted, method_sig={:?}", method_sig); |
| |
| (method_sig, method_predicates) |
| } |
| |
| fn add_obligations( |
| &mut self, |
| fty: Ty<'tcx>, |
| all_substs: SubstsRef<'tcx>, |
| method_predicates: ty::InstantiatedPredicates<'tcx>, |
| ) { |
| debug!( |
| "add_obligations: fty={:?} all_substs={:?} method_predicates={:?}", |
| fty, all_substs, method_predicates |
| ); |
| |
| self.add_obligations_for_parameters( |
| traits::ObligationCause::misc(self.span, self.body_id), |
| method_predicates, |
| ); |
| |
| // this is a projection from a trait reference, so we have to |
| // make sure that the trait reference inputs are well-formed. |
| self.add_wf_bounds(all_substs, self.call_expr); |
| |
| // the function type must also be well-formed (this is not |
| // implied by the substs being well-formed because of inherent |
| // impls and late-bound regions - see issue #28609). |
| self.register_wf_obligation(fty.into(), self.span, traits::MiscObligation); |
| } |
| |
| /////////////////////////////////////////////////////////////////////////// |
| // MISCELLANY |
| |
| fn predicates_require_illegal_sized_bound( |
| &self, |
| predicates: &ty::InstantiatedPredicates<'tcx>, |
| ) -> Option<Span> { |
| let sized_def_id = match self.tcx.lang_items().sized_trait() { |
| Some(def_id) => def_id, |
| None => return None, |
| }; |
| |
| traits::elaborate_predicates(self.tcx, predicates.predicates.iter().copied()) |
| .filter_map(|obligation| match obligation.predicate.kind() { |
| ty::PredicateKind::Trait(trait_pred, _) if trait_pred.def_id() == sized_def_id => { |
| let span = predicates |
| .predicates |
| .iter() |
| .zip(predicates.spans.iter()) |
| .find_map( |
| |(p, span)| if *p == obligation.predicate { Some(*span) } else { None }, |
| ) |
| .unwrap_or(rustc_span::DUMMY_SP); |
| Some((trait_pred, span)) |
| } |
| _ => None, |
| }) |
| .find_map(|(trait_pred, span)| match trait_pred.skip_binder().self_ty().kind { |
| ty::Dynamic(..) => Some(span), |
| _ => None, |
| }) |
| } |
| |
| fn enforce_illegal_method_limitations(&self, pick: &probe::Pick<'_>) { |
| // Disallow calls to the method `drop` defined in the `Drop` trait. |
| match pick.item.container { |
| ty::TraitContainer(trait_def_id) => callee::check_legal_trait_for_method_call( |
| self.tcx, |
| self.span, |
| Some(self.self_expr.span), |
| trait_def_id, |
| ), |
| ty::ImplContainer(..) => {} |
| } |
| } |
| |
| fn upcast( |
| &mut self, |
| source_trait_ref: ty::PolyTraitRef<'tcx>, |
| target_trait_def_id: DefId, |
| ) -> ty::PolyTraitRef<'tcx> { |
| let upcast_trait_refs = |
| traits::upcast_choices(self.tcx, source_trait_ref, target_trait_def_id); |
| |
| // must be exactly one trait ref or we'd get an ambig error etc |
| if upcast_trait_refs.len() != 1 { |
| span_bug!( |
| self.span, |
| "cannot uniquely upcast `{:?}` to `{:?}`: `{:?}`", |
| source_trait_ref, |
| target_trait_def_id, |
| upcast_trait_refs |
| ); |
| } |
| |
| upcast_trait_refs.into_iter().next().unwrap() |
| } |
| |
| fn replace_bound_vars_with_fresh_vars<T>(&self, value: &ty::Binder<T>) -> T |
| where |
| T: TypeFoldable<'tcx>, |
| { |
| self.fcx.replace_bound_vars_with_fresh_vars(self.span, infer::FnCall, value).0 |
| } |
| } |
