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;
7 use rustc::infer::{self, InferOk};
9 use rustc::ty::adjustment::{Adjust, Adjustment, OverloadedDeref, PointerCast};
10 use rustc::ty::adjustment::{AllowTwoPhase, AutoBorrow, AutoBorrowMutability};
11 use rustc::ty::fold::TypeFoldable;
12 use rustc::ty::subst::{Subst, SubstsRef};
13 use rustc::ty::{self, GenericParamDefKind, Ty};
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: bool,
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 {
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.impl_self_ty(self.span, impl_def_id).substs
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 .filter_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?")
286 "self-type `{}` for ObjectPick never dereferenced to an object",
292 fn instantiate_method_substs(
294 pick: &probe::Pick<'tcx>,
295 seg: &hir::PathSegment<'_>,
296 parent_substs: SubstsRef<'tcx>,
297 ) -> SubstsRef<'tcx> {
298 // Determine the values for the generic parameters of the method.
299 // If they were not explicitly supplied, just construct fresh
301 let generics = self.tcx.generics_of(pick.item.def_id);
302 AstConv::check_generic_arg_count_for_call(
303 self.tcx, self.span, &generics, &seg, true, // `is_method_call`
306 // Create subst for early-bound lifetime parameters, combining
307 // parameters from the type and those from the method.
308 assert_eq!(generics.parent_count, parent_substs.len());
310 AstConv::create_substs_for_generic_args(
316 // Provide the generic args, and whether types should be inferred.
318 // The last argument of the returned tuple here is unimportant.
319 if let Some(ref data) = seg.args { (Some(data), false) } else { (None, false) }
321 // Provide substitutions for parameters for which (valid) arguments have been provided.
322 |param, arg| match (¶m.kind, arg) {
323 (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
324 AstConv::ast_region_to_region(self.fcx, lt, Some(param)).into()
326 (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => self.to_ty(ty).into(),
327 (GenericParamDefKind::Const, GenericArg::Const(ct)) => {
328 self.to_const(&ct.value, self.tcx.type_of(param.def_id)).into()
332 // Provide substitutions for parameters for which arguments are inferred.
333 |_, param, _| self.var_for_def(self.span, param),
337 fn unify_receivers(&mut self, self_ty: Ty<'tcx>, method_self_ty: Ty<'tcx>) {
338 match self.at(&self.misc(self.span), self.param_env).sup(method_self_ty, self_ty) {
339 Ok(InferOk { obligations, value: () }) => {
340 self.register_predicates(obligations);
345 "{} was a subtype of {} but now is not?",
353 // NOTE: this returns the *unnormalized* predicates and method sig. Because of
354 // inference guessing, the predicates and method signature can't be normalized
355 // until we unify the `Self` type.
356 fn instantiate_method_sig(
358 pick: &probe::Pick<'tcx>,
359 all_substs: SubstsRef<'tcx>,
360 ) -> (ty::FnSig<'tcx>, ty::InstantiatedPredicates<'tcx>) {
361 debug!("instantiate_method_sig(pick={:?}, all_substs={:?})", pick, all_substs);
363 // Instantiate the bounds on the method with the
364 // type/early-bound-regions substitutions performed. There can
365 // be no late-bound regions appearing here.
366 let def_id = pick.item.def_id;
367 let method_predicates = self.tcx.predicates_of(def_id).instantiate(self.tcx, all_substs);
369 debug!("method_predicates after subst = {:?}", method_predicates);
371 let sig = self.tcx.fn_sig(def_id);
373 // Instantiate late-bound regions and substitute the trait
374 // parameters into the method type to get the actual method type.
376 // N.B., instantiate late-bound regions first so that
377 // `instantiate_type_scheme` can normalize associated types that
378 // may reference those regions.
379 let method_sig = self.replace_bound_vars_with_fresh_vars(&sig);
380 debug!("late-bound lifetimes from method instantiated, method_sig={:?}", method_sig);
382 let method_sig = method_sig.subst(self.tcx, all_substs);
383 debug!("type scheme substituted, method_sig={:?}", method_sig);
385 (method_sig, method_predicates)
391 all_substs: SubstsRef<'tcx>,
392 method_predicates: &ty::InstantiatedPredicates<'tcx>,
395 "add_obligations: fty={:?} all_substs={:?} method_predicates={:?}",
396 fty, all_substs, method_predicates
399 self.add_obligations_for_parameters(
400 traits::ObligationCause::misc(self.span, self.body_id),
404 // this is a projection from a trait reference, so we have to
405 // make sure that the trait reference inputs are well-formed.
406 self.add_wf_bounds(all_substs, self.call_expr);
408 // the function type must also be well-formed (this is not
409 // implied by the substs being well-formed because of inherent
410 // impls and late-bound regions - see issue #28609).
411 self.register_wf_obligation(fty, self.span, traits::MiscObligation);
414 ///////////////////////////////////////////////////////////////////////////
417 /// When we select a method with a mutable autoref, we have to go convert any
418 /// auto-derefs, indices, etc from `Deref` and `Index` into `DerefMut` and `IndexMut`
420 fn convert_place_derefs_to_mutable(&self) {
421 // Gather up expressions we want to munge.
422 let mut exprs = vec![self.self_expr];
425 match exprs.last().unwrap().kind {
426 hir::ExprKind::Field(ref expr, _)
427 | hir::ExprKind::Index(ref expr, _)
428 | hir::ExprKind::Unary(hir::UnOp::UnDeref, ref expr) => exprs.push(&expr),
433 debug!("convert_place_derefs_to_mutable: exprs={:?}", exprs);
435 // Fix up autoderefs and derefs.
436 for (i, &expr) in exprs.iter().rev().enumerate() {
437 debug!("convert_place_derefs_to_mutable: i={} expr={:?}", i, expr);
439 // Fix up the autoderefs. Autorefs can only occur immediately preceding
440 // overloaded place ops, and will be fixed by them in order to get
441 // the correct region.
442 let mut source = self.node_ty(expr.hir_id);
443 // Do not mutate adjustments in place, but rather take them,
444 // and replace them after mutating them, to avoid having the
445 // tables borrowed during (`deref_mut`) method resolution.
446 let previous_adjustments =
447 self.tables.borrow_mut().adjustments_mut().remove(expr.hir_id);
448 if let Some(mut adjustments) = previous_adjustments {
449 let needs = Needs::MutPlace;
450 for adjustment in &mut adjustments {
451 if let Adjust::Deref(Some(ref mut deref)) = adjustment.kind {
452 if let Some(ok) = self.try_overloaded_deref(expr.span, source, needs) {
453 let method = self.register_infer_ok_obligations(ok);
454 if let ty::Ref(region, _, mutbl) = method.sig.output().kind {
455 *deref = OverloadedDeref { region, mutbl };
459 source = adjustment.target;
461 self.tables.borrow_mut().adjustments_mut().insert(expr.hir_id, adjustments);
465 hir::ExprKind::Index(ref base_expr, ref index_expr) => {
466 let index_expr_ty = self.node_ty(index_expr.hir_id);
467 self.convert_place_op_to_mutable(
474 hir::ExprKind::Unary(hir::UnOp::UnDeref, ref base_expr) => {
475 self.convert_place_op_to_mutable(PlaceOp::Deref, expr, base_expr, &[]);
482 fn convert_place_op_to_mutable(
485 expr: &hir::Expr<'_>,
486 base_expr: &hir::Expr<'_>,
487 arg_tys: &[Ty<'tcx>],
489 debug!("convert_place_op_to_mutable({:?}, {:?}, {:?}, {:?})", op, expr, base_expr, arg_tys);
490 if !self.tables.borrow().is_method_call(expr) {
491 debug!("convert_place_op_to_mutable - builtin, nothing to do");
498 .expr_adjustments(base_expr)
500 .map_or_else(|| self.node_ty(expr.hir_id), |adj| adj.target);
501 let base_ty = self.resolve_vars_if_possible(&base_ty);
503 // Need to deref because overloaded place ops take self by-reference.
505 base_ty.builtin_deref(false).expect("place op takes something that is not a ref").ty;
507 let method = self.try_overloaded_place_op(expr.span, base_ty, arg_tys, Needs::MutPlace, op);
508 let method = match method {
509 Some(ok) => self.register_infer_ok_obligations(ok),
510 None => return self.tcx.sess.delay_span_bug(expr.span, "re-trying op failed"),
512 debug!("convert_place_op_to_mutable: method={:?}", method);
513 self.write_method_call(expr.hir_id, method);
515 let (region, mutbl) = if let ty::Ref(r, _, mutbl) = method.sig.inputs()[0].kind {
518 span_bug!(expr.span, "input to place op is not a ref?");
521 // Convert the autoref in the base expr to mutable with the correct
522 // region and mutability.
523 let base_expr_ty = self.node_ty(base_expr.hir_id);
524 if let Some(adjustments) =
525 self.tables.borrow_mut().adjustments_mut().get_mut(base_expr.hir_id)
527 let mut source = base_expr_ty;
528 for adjustment in &mut adjustments[..] {
529 if let Adjust::Borrow(AutoBorrow::Ref(..)) = adjustment.kind {
530 debug!("convert_place_op_to_mutable: converting autoref {:?}", adjustment);
531 let mutbl = match mutbl {
532 hir::Mutability::Not => AutoBorrowMutability::Not,
533 hir::Mutability::Mut => AutoBorrowMutability::Mut {
534 // For initial two-phase borrow
535 // deployment, conservatively omit
536 // overloaded operators.
537 allow_two_phase_borrow: AllowTwoPhase::No,
540 adjustment.kind = Adjust::Borrow(AutoBorrow::Ref(region, mutbl));
542 self.tcx.mk_ref(region, ty::TypeAndMut { ty: source, mutbl: mutbl.into() });
544 source = adjustment.target;
547 // If we have an autoref followed by unsizing at the end, fix the unsize target.
548 match adjustments[..] {
549 [.., Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(..)), .. }, Adjustment { kind: Adjust::Pointer(PointerCast::Unsize), ref mut target }] =>
551 *target = method.sig.inputs()[0];
558 ///////////////////////////////////////////////////////////////////////////
561 fn predicates_require_illegal_sized_bound(
563 predicates: &ty::InstantiatedPredicates<'tcx>,
565 let sized_def_id = match self.tcx.lang_items().sized_trait() {
566 Some(def_id) => def_id,
567 None => return false,
570 traits::elaborate_predicates(self.tcx, predicates.predicates.clone())
571 .filter_map(|predicate| match predicate {
572 ty::Predicate::Trait(trait_pred, _) if trait_pred.def_id() == sized_def_id => {
577 .any(|trait_pred| match trait_pred.skip_binder().self_ty().kind {
578 ty::Dynamic(..) => true,
583 fn enforce_illegal_method_limitations(&self, pick: &probe::Pick<'_>) {
584 // Disallow calls to the method `drop` defined in the `Drop` trait.
585 match pick.item.container {
586 ty::TraitContainer(trait_def_id) => {
587 callee::check_legal_trait_for_method_call(self.tcx, self.span, trait_def_id)
589 ty::ImplContainer(..) => {}
595 source_trait_ref: ty::PolyTraitRef<'tcx>,
596 target_trait_def_id: DefId,
597 ) -> ty::PolyTraitRef<'tcx> {
598 let upcast_trait_refs =
599 traits::upcast_choices(self.tcx, source_trait_ref.clone(), target_trait_def_id);
601 // must be exactly one trait ref or we'd get an ambig error etc
602 if upcast_trait_refs.len() != 1 {
605 "cannot uniquely upcast `{:?}` to `{:?}`: `{:?}`",
612 upcast_trait_refs.into_iter().next().unwrap()
615 fn replace_bound_vars_with_fresh_vars<T>(&self, value: &ty::Binder<T>) -> T
617 T: TypeFoldable<'tcx>,
619 self.fcx.replace_bound_vars_with_fresh_vars(self.span, infer::FnCall, value).0