1 use super::{probe, MethodCallee};
3 use crate::astconv::AstConv;
4 use crate::check::{callee, FnCtxt, Needs, PlaceOp};
5 use crate::hir::def_id::DefId;
6 use crate::hir::GenericArg;
8 use rustc_infer::infer::{self, InferOk};
9 use rustc_middle::ty::adjustment::{Adjust, Adjustment, OverloadedDeref, PointerCast};
10 use rustc_middle::ty::adjustment::{AllowTwoPhase, AutoBorrow, AutoBorrowMutability};
11 use rustc_middle::ty::fold::TypeFoldable;
12 use rustc_middle::ty::subst::{Subst, SubstsRef};
13 use rustc_middle::ty::{self, GenericParamDefKind, Ty};
15 use rustc_trait_selection::traits;
19 struct ConfirmContext<'a, 'tcx> {
20 fcx: &'a FnCtxt<'a, 'tcx>,
22 self_expr: &'tcx hir::Expr<'tcx>,
23 call_expr: &'tcx hir::Expr<'tcx>,
26 impl<'a, 'tcx> Deref for ConfirmContext<'a, 'tcx> {
27 type Target = FnCtxt<'a, 'tcx>;
28 fn deref(&self) -> &Self::Target {
33 pub struct ConfirmResult<'tcx> {
34 pub callee: MethodCallee<'tcx>,
35 pub illegal_sized_bound: Option<Span>,
38 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
39 pub fn confirm_method(
42 self_expr: &'tcx hir::Expr<'tcx>,
43 call_expr: &'tcx hir::Expr<'tcx>,
44 unadjusted_self_ty: Ty<'tcx>,
45 pick: probe::Pick<'tcx>,
46 segment: &hir::PathSegment<'_>,
47 ) -> ConfirmResult<'tcx> {
49 "confirm(unadjusted_self_ty={:?}, pick={:?}, generic_args={:?})",
50 unadjusted_self_ty, pick, segment.args,
53 let mut confirm_cx = ConfirmContext::new(self, span, self_expr, call_expr);
54 confirm_cx.confirm(unadjusted_self_ty, pick, segment)
58 impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
60 fcx: &'a FnCtxt<'a, 'tcx>,
62 self_expr: &'tcx hir::Expr<'tcx>,
63 call_expr: &'tcx hir::Expr<'tcx>,
64 ) -> ConfirmContext<'a, 'tcx> {
65 ConfirmContext { fcx, span, self_expr, call_expr }
70 unadjusted_self_ty: Ty<'tcx>,
71 pick: probe::Pick<'tcx>,
72 segment: &hir::PathSegment<'_>,
73 ) -> ConfirmResult<'tcx> {
74 // Adjust the self expression the user provided and obtain the adjusted type.
75 let self_ty = self.adjust_self_ty(unadjusted_self_ty, &pick);
77 // Create substitutions for the method's type parameters.
78 let rcvr_substs = self.fresh_receiver_substs(self_ty, &pick);
79 let all_substs = self.instantiate_method_substs(&pick, segment, rcvr_substs);
81 debug!("all_substs={:?}", all_substs);
83 // Create the final signature for the method, replacing late-bound regions.
84 let (method_sig, method_predicates) = self.instantiate_method_sig(&pick, all_substs);
86 // Unify the (adjusted) self type with what the method expects.
88 // SUBTLE: if we want good error messages, because of "guessing" while matching
89 // traits, no trait system method can be called before this point because they
90 // could alter our Self-type, except for normalizing the receiver from the
91 // signature (which is also done during probing).
93 self.normalize_associated_types_in(self.span, &method_sig.inputs()[0]);
94 self.unify_receivers(self_ty, method_sig_rcvr);
96 let (method_sig, method_predicates) =
97 self.normalize_associated_types_in(self.span, &(method_sig, method_predicates));
99 // Make sure nobody calls `drop()` explicitly.
100 self.enforce_illegal_method_limitations(&pick);
102 // If there is a `Self: Sized` bound and `Self` is a trait object, it is possible that
103 // something which derefs to `Self` actually implements the trait and the caller
104 // wanted to make a static dispatch on it but forgot to import the trait.
105 // See test `src/test/ui/issue-35976.rs`.
107 // In that case, we'll error anyway, but we'll also re-run the search with all traits
108 // in scope, and if we find another method which can be used, we'll output an
109 // appropriate hint suggesting to import the trait.
110 let illegal_sized_bound = self.predicates_require_illegal_sized_bound(&method_predicates);
112 // Add any trait/regions obligations specified on the method's type parameters.
113 // We won't add these if we encountered an illegal sized bound, so that we can use
114 // a custom error in that case.
115 if illegal_sized_bound.is_none() {
116 let method_ty = self.tcx.mk_fn_ptr(ty::Binder::bind(method_sig));
117 self.add_obligations(method_ty, all_substs, method_predicates);
120 // Create the final `MethodCallee`.
121 let callee = MethodCallee { def_id: pick.item.def_id, substs: all_substs, sig: method_sig };
123 if let Some(hir::Mutability::Mut) = pick.autoref {
124 self.convert_place_derefs_to_mutable();
127 ConfirmResult { callee, illegal_sized_bound }
130 ///////////////////////////////////////////////////////////////////////////
135 unadjusted_self_ty: Ty<'tcx>,
136 pick: &probe::Pick<'tcx>,
138 // Commit the autoderefs by calling `autoderef` again, but this
139 // time writing the results into the various tables.
140 let mut autoderef = self.autoderef(self.span, unadjusted_self_ty);
141 let (_, n) = match autoderef.nth(pick.autoderefs) {
144 self.tcx.sess.delay_span_bug(
145 rustc_span::DUMMY_SP,
146 &format!("failed autoderef {}", pick.autoderefs),
148 return self.tcx.types.err;
151 assert_eq!(n, pick.autoderefs);
153 let mut adjustments = autoderef.adjust_steps(self, Needs::None);
155 let mut target = autoderef.unambiguous_final_ty(self);
157 if let Some(mutbl) = pick.autoref {
158 let region = self.next_region_var(infer::Autoref(self.span));
159 target = self.tcx.mk_ref(region, ty::TypeAndMut { mutbl, ty: target });
160 let mutbl = match mutbl {
161 hir::Mutability::Not => AutoBorrowMutability::Not,
162 hir::Mutability::Mut => AutoBorrowMutability::Mut {
163 // Method call receivers are the primary use case
164 // for two-phase borrows.
165 allow_two_phase_borrow: AllowTwoPhase::Yes,
169 .push(Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)), target });
171 if let Some(unsize_target) = pick.unsize {
174 .mk_ref(region, ty::TypeAndMut { mutbl: mutbl.into(), ty: unsize_target });
175 adjustments.push(Adjustment { kind: Adjust::Pointer(PointerCast::Unsize), target });
178 // No unsizing should be performed without autoref (at
179 // least during method dispach). This is because we
180 // currently only unsize `[T;N]` to `[T]`, and naturally
181 // that must occur being a reference.
182 assert!(pick.unsize.is_none());
185 autoderef.finalize(self);
187 // Write out the final adjustments.
188 self.apply_adjustments(self.self_expr, adjustments);
193 /// Returns a set of substitutions for the method *receiver* where all type and region
194 /// parameters are instantiated with fresh variables. This substitution does not include any
195 /// parameters declared on the method itself.
197 /// Note that this substitution may include late-bound regions from the impl level. If so,
198 /// these are instantiated later in the `instantiate_method_sig` routine.
199 fn fresh_receiver_substs(
202 pick: &probe::Pick<'tcx>,
203 ) -> SubstsRef<'tcx> {
205 probe::InherentImplPick => {
206 let impl_def_id = pick.item.container.id();
208 self.tcx.impl_trait_ref(impl_def_id).is_none(),
209 "impl {:?} is not an inherent impl",
212 self.fresh_substs_for_item(self.span, impl_def_id)
215 probe::ObjectPick => {
216 let trait_def_id = pick.item.container.id();
217 self.extract_existential_trait_ref(self_ty, |this, object_ty, principal| {
218 // The object data has no entry for the Self
219 // Type. For the purposes of this method call, we
220 // substitute the object type itself. This
221 // wouldn't be a sound substitution in all cases,
222 // since each instance of the object type is a
223 // different existential and hence could match
224 // distinct types (e.g., if `Self` appeared as an
225 // argument type), but those cases have already
226 // been ruled out when we deemed the trait to be
228 let original_poly_trait_ref = principal.with_self_ty(this.tcx, object_ty);
229 let upcast_poly_trait_ref = this.upcast(original_poly_trait_ref, trait_def_id);
230 let upcast_trait_ref =
231 this.replace_bound_vars_with_fresh_vars(&upcast_poly_trait_ref);
233 "original_poly_trait_ref={:?} upcast_trait_ref={:?} target_trait={:?}",
234 original_poly_trait_ref, upcast_trait_ref, trait_def_id
236 upcast_trait_ref.substs
240 probe::TraitPick => {
241 let trait_def_id = pick.item.container.id();
243 // Make a trait reference `$0 : Trait<$1...$n>`
244 // consisting entirely of type variables. Later on in
245 // the process we will unify the transformed-self-type
246 // of the method with the actual type in order to
247 // unify some of these variables.
248 self.fresh_substs_for_item(self.span, trait_def_id)
251 probe::WhereClausePick(ref poly_trait_ref) => {
252 // Where clauses can have bound regions in them. We need to instantiate
253 // those to convert from a poly-trait-ref to a trait-ref.
254 self.replace_bound_vars_with_fresh_vars(&poly_trait_ref).substs
259 fn extract_existential_trait_ref<R, F>(&mut self, self_ty: Ty<'tcx>, mut closure: F) -> R
261 F: FnMut(&mut ConfirmContext<'a, 'tcx>, Ty<'tcx>, ty::PolyExistentialTraitRef<'tcx>) -> R,
263 // If we specified that this is an object method, then the
264 // self-type ought to be something that can be dereferenced to
265 // yield an object-type (e.g., `&Object` or `Box<Object>`
268 // FIXME: this feels, like, super dubious
270 .autoderef(self.span, self_ty)
271 .include_raw_pointers()
272 .find_map(|(ty, _)| match ty.kind {
273 ty::Dynamic(ref data, ..) => Some(closure(
276 data.principal().unwrap_or_else(|| {
277 span_bug!(self.span, "calling trait method on empty object?")
285 "self-type `{}` for ObjectPick never dereferenced to an object",
291 fn instantiate_method_substs(
293 pick: &probe::Pick<'tcx>,
294 seg: &hir::PathSegment<'_>,
295 parent_substs: SubstsRef<'tcx>,
296 ) -> SubstsRef<'tcx> {
297 // Determine the values for the generic parameters of the method.
298 // If they were not explicitly supplied, just construct fresh
300 let generics = self.tcx.generics_of(pick.item.def_id);
301 let arg_count_correct = AstConv::check_generic_arg_count_for_call(
302 self.tcx, self.span, &generics, &seg, true, // `is_method_call`
305 // Create subst for early-bound lifetime parameters, combining
306 // parameters from the type and those from the method.
307 assert_eq!(generics.parent_count, parent_substs.len());
309 AstConv::create_substs_for_generic_args(
316 // Provide the generic args, and whether types should be inferred.
318 // The last component of the returned tuple here is unimportant.
319 if def_id == pick.item.def_id {
320 if let Some(ref data) = seg.args {
321 return (Some(data), false);
326 // Provide substitutions for parameters for which (valid) arguments have been provided.
327 |param, arg| match (¶m.kind, arg) {
328 (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
329 AstConv::ast_region_to_region(self.fcx, lt, Some(param)).into()
331 (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => self.to_ty(ty).into(),
332 (GenericParamDefKind::Const, GenericArg::Const(ct)) => {
333 self.to_const(&ct.value).into()
337 // Provide substitutions for parameters for which arguments are inferred.
338 |_, param, _| self.var_for_def(self.span, param),
342 fn unify_receivers(&mut self, self_ty: Ty<'tcx>, method_self_ty: Ty<'tcx>) {
343 match self.at(&self.misc(self.span), self.param_env).sup(method_self_ty, self_ty) {
344 Ok(InferOk { obligations, value: () }) => {
345 self.register_predicates(obligations);
350 "{} was a subtype of {} but now is not?",
358 // NOTE: this returns the *unnormalized* predicates and method sig. Because of
359 // inference guessing, the predicates and method signature can't be normalized
360 // until we unify the `Self` type.
361 fn instantiate_method_sig(
363 pick: &probe::Pick<'tcx>,
364 all_substs: SubstsRef<'tcx>,
365 ) -> (ty::FnSig<'tcx>, ty::InstantiatedPredicates<'tcx>) {
366 debug!("instantiate_method_sig(pick={:?}, all_substs={:?})", pick, all_substs);
368 // Instantiate the bounds on the method with the
369 // type/early-bound-regions substitutions performed. There can
370 // be no late-bound regions appearing here.
371 let def_id = pick.item.def_id;
372 let method_predicates = self.tcx.predicates_of(def_id).instantiate(self.tcx, all_substs);
374 debug!("method_predicates after subst = {:?}", method_predicates);
376 let sig = self.tcx.fn_sig(def_id);
378 // Instantiate late-bound regions and substitute the trait
379 // parameters into the method type to get the actual method type.
381 // N.B., instantiate late-bound regions first so that
382 // `instantiate_type_scheme` can normalize associated types that
383 // may reference those regions.
384 let method_sig = self.replace_bound_vars_with_fresh_vars(&sig);
385 debug!("late-bound lifetimes from method instantiated, method_sig={:?}", method_sig);
387 let method_sig = method_sig.subst(self.tcx, all_substs);
388 debug!("type scheme substituted, method_sig={:?}", method_sig);
390 (method_sig, method_predicates)
396 all_substs: SubstsRef<'tcx>,
397 method_predicates: ty::InstantiatedPredicates<'tcx>,
400 "add_obligations: fty={:?} all_substs={:?} method_predicates={:?}",
401 fty, all_substs, method_predicates
404 self.add_obligations_for_parameters(
405 traits::ObligationCause::misc(self.span, self.body_id),
409 // this is a projection from a trait reference, so we have to
410 // make sure that the trait reference inputs are well-formed.
411 self.add_wf_bounds(all_substs, self.call_expr);
413 // the function type must also be well-formed (this is not
414 // implied by the substs being well-formed because of inherent
415 // impls and late-bound regions - see issue #28609).
416 self.register_wf_obligation(fty.into(), self.span, traits::MiscObligation);
419 ///////////////////////////////////////////////////////////////////////////
422 /// When we select a method with a mutable autoref, we have to go convert any
423 /// auto-derefs, indices, etc from `Deref` and `Index` into `DerefMut` and `IndexMut`
425 fn convert_place_derefs_to_mutable(&self) {
426 // Gather up expressions we want to munge.
427 let mut exprs = vec![self.self_expr];
430 match exprs.last().unwrap().kind {
431 hir::ExprKind::Field(ref expr, _)
432 | hir::ExprKind::Index(ref expr, _)
433 | hir::ExprKind::Unary(hir::UnOp::UnDeref, ref expr) => exprs.push(&expr),
438 debug!("convert_place_derefs_to_mutable: exprs={:?}", exprs);
440 // Fix up autoderefs and derefs.
441 for (i, &expr) in exprs.iter().rev().enumerate() {
442 debug!("convert_place_derefs_to_mutable: i={} expr={:?}", i, expr);
444 // Fix up the autoderefs. Autorefs can only occur immediately preceding
445 // overloaded place ops, and will be fixed by them in order to get
446 // the correct region.
447 let mut source = self.node_ty(expr.hir_id);
448 // Do not mutate adjustments in place, but rather take them,
449 // and replace them after mutating them, to avoid having the
450 // tables borrowed during (`deref_mut`) method resolution.
451 let previous_adjustments =
452 self.tables.borrow_mut().adjustments_mut().remove(expr.hir_id);
453 if let Some(mut adjustments) = previous_adjustments {
454 let needs = Needs::MutPlace;
455 for adjustment in &mut adjustments {
456 if let Adjust::Deref(Some(ref mut deref)) = adjustment.kind {
457 if let Some(ok) = self.try_overloaded_deref(expr.span, source, needs) {
458 let method = self.register_infer_ok_obligations(ok);
459 if let ty::Ref(region, _, mutbl) = method.sig.output().kind {
460 *deref = OverloadedDeref { region, mutbl };
464 source = adjustment.target;
466 self.tables.borrow_mut().adjustments_mut().insert(expr.hir_id, adjustments);
470 hir::ExprKind::Index(ref base_expr, ref index_expr) => {
471 // We need to get the final type in case dereferences were needed for the trait
472 // to apply (#72002).
473 let index_expr_ty = self.tables.borrow().expr_ty_adjusted(index_expr);
474 self.convert_place_op_to_mutable(
481 hir::ExprKind::Unary(hir::UnOp::UnDeref, ref base_expr) => {
482 self.convert_place_op_to_mutable(PlaceOp::Deref, expr, base_expr, &[]);
489 fn convert_place_op_to_mutable(
492 expr: &hir::Expr<'_>,
493 base_expr: &hir::Expr<'_>,
494 arg_tys: &[Ty<'tcx>],
496 debug!("convert_place_op_to_mutable({:?}, {:?}, {:?}, {:?})", op, expr, base_expr, arg_tys);
497 if !self.tables.borrow().is_method_call(expr) {
498 debug!("convert_place_op_to_mutable - builtin, nothing to do");
505 .expr_adjustments(base_expr)
507 .map_or_else(|| self.node_ty(expr.hir_id), |adj| adj.target);
508 let base_ty = self.resolve_vars_if_possible(&base_ty);
510 // Need to deref because overloaded place ops take self by-reference.
512 base_ty.builtin_deref(false).expect("place op takes something that is not a ref").ty;
514 let method = self.try_overloaded_place_op(expr.span, base_ty, arg_tys, Needs::MutPlace, op);
515 let method = match method {
516 Some(ok) => self.register_infer_ok_obligations(ok),
517 None => return self.tcx.sess.delay_span_bug(expr.span, "re-trying op failed"),
519 debug!("convert_place_op_to_mutable: method={:?}", method);
520 self.write_method_call(expr.hir_id, method);
522 let (region, mutbl) = if let ty::Ref(r, _, mutbl) = method.sig.inputs()[0].kind {
525 span_bug!(expr.span, "input to place op is not a ref?");
528 // Convert the autoref in the base expr to mutable with the correct
529 // region and mutability.
530 let base_expr_ty = self.node_ty(base_expr.hir_id);
531 if let Some(adjustments) =
532 self.tables.borrow_mut().adjustments_mut().get_mut(base_expr.hir_id)
534 let mut source = base_expr_ty;
535 for adjustment in &mut adjustments[..] {
536 if let Adjust::Borrow(AutoBorrow::Ref(..)) = adjustment.kind {
537 debug!("convert_place_op_to_mutable: converting autoref {:?}", adjustment);
538 let mutbl = match mutbl {
539 hir::Mutability::Not => AutoBorrowMutability::Not,
540 hir::Mutability::Mut => AutoBorrowMutability::Mut {
541 // For initial two-phase borrow
542 // deployment, conservatively omit
543 // overloaded operators.
544 allow_two_phase_borrow: AllowTwoPhase::No,
547 adjustment.kind = Adjust::Borrow(AutoBorrow::Ref(region, mutbl));
549 self.tcx.mk_ref(region, ty::TypeAndMut { ty: source, mutbl: mutbl.into() });
551 source = adjustment.target;
554 // If we have an autoref followed by unsizing at the end, fix the unsize target.
556 if let [.., Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(..)), .. }, Adjustment { kind: Adjust::Pointer(PointerCast::Unsize), ref mut target }] =
559 *target = method.sig.inputs()[0];
564 ///////////////////////////////////////////////////////////////////////////
567 fn predicates_require_illegal_sized_bound(
569 predicates: &ty::InstantiatedPredicates<'tcx>,
571 let sized_def_id = match self.tcx.lang_items().sized_trait() {
572 Some(def_id) => def_id,
576 traits::elaborate_predicates(self.tcx, predicates.predicates.iter().copied())
577 .filter_map(|obligation| match obligation.predicate.kind() {
578 ty::PredicateKind::Trait(trait_pred, _) if trait_pred.def_id() == sized_def_id => {
579 let span = predicates
582 .zip(predicates.spans.iter())
584 |(p, span)| if *p == obligation.predicate { Some(*span) } else { None },
586 .unwrap_or(rustc_span::DUMMY_SP);
587 Some((trait_pred, span))
591 .find_map(|(trait_pred, span)| match trait_pred.skip_binder().self_ty().kind {
592 ty::Dynamic(..) => Some(span),
597 fn enforce_illegal_method_limitations(&self, pick: &probe::Pick<'_>) {
598 // Disallow calls to the method `drop` defined in the `Drop` trait.
599 match pick.item.container {
600 ty::TraitContainer(trait_def_id) => callee::check_legal_trait_for_method_call(
603 Some(self.self_expr.span),
606 ty::ImplContainer(..) => {}
612 source_trait_ref: ty::PolyTraitRef<'tcx>,
613 target_trait_def_id: DefId,
614 ) -> ty::PolyTraitRef<'tcx> {
615 let upcast_trait_refs =
616 traits::upcast_choices(self.tcx, source_trait_ref, target_trait_def_id);
618 // must be exactly one trait ref or we'd get an ambig error etc
619 if upcast_trait_refs.len() != 1 {
622 "cannot uniquely upcast `{:?}` to `{:?}`: `{:?}`",
629 upcast_trait_refs.into_iter().next().unwrap()
632 fn replace_bound_vars_with_fresh_vars<T>(&self, value: &ty::Binder<T>) -> T
634 T: TypeFoldable<'tcx>,
636 self.fcx.replace_bound_vars_with_fresh_vars(self.span, infer::FnCall, value).0