1 use super::{probe, MethodCallee};
3 use crate::{callee, FnCtxt};
5 use rustc_hir::def_id::DefId;
6 use rustc_hir::GenericArg;
7 use rustc_hir_analysis::astconv::{AstConv, CreateSubstsForGenericArgsCtxt, IsMethodCall};
8 use rustc_infer::infer::{self, InferOk};
9 use rustc_middle::traits::{ObligationCauseCode, UnifyReceiverContext};
10 use rustc_middle::ty::adjustment::{Adjust, Adjustment, PointerCast};
11 use rustc_middle::ty::adjustment::{AllowTwoPhase, AutoBorrow, AutoBorrowMutability};
12 use rustc_middle::ty::fold::TypeFoldable;
13 use rustc_middle::ty::subst::{self, SubstsRef};
14 use rustc_middle::ty::{self, GenericParamDefKind, Ty};
16 use rustc_trait_selection::traits;
21 struct ConfirmContext<'a, 'tcx> {
22 fcx: &'a FnCtxt<'a, 'tcx>,
24 self_expr: &'tcx hir::Expr<'tcx>,
25 call_expr: &'tcx hir::Expr<'tcx>,
28 impl<'a, 'tcx> Deref for ConfirmContext<'a, 'tcx> {
29 type Target = FnCtxt<'a, 'tcx>;
30 fn deref(&self) -> &Self::Target {
36 pub struct ConfirmResult<'tcx> {
37 pub callee: MethodCallee<'tcx>,
38 pub illegal_sized_bound: Option<Span>,
41 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
42 pub fn confirm_method(
45 self_expr: &'tcx hir::Expr<'tcx>,
46 call_expr: &'tcx hir::Expr<'tcx>,
47 unadjusted_self_ty: Ty<'tcx>,
48 pick: probe::Pick<'tcx>,
49 segment: &hir::PathSegment<'_>,
50 ) -> ConfirmResult<'tcx> {
52 "confirm(unadjusted_self_ty={:?}, pick={:?}, generic_args={:?})",
53 unadjusted_self_ty, pick, segment.args,
56 let mut confirm_cx = ConfirmContext::new(self, span, self_expr, call_expr);
57 confirm_cx.confirm(unadjusted_self_ty, pick, segment)
61 impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
63 fcx: &'a FnCtxt<'a, 'tcx>,
65 self_expr: &'tcx hir::Expr<'tcx>,
66 call_expr: &'tcx hir::Expr<'tcx>,
67 ) -> ConfirmContext<'a, 'tcx> {
68 ConfirmContext { fcx, span, self_expr, call_expr }
73 unadjusted_self_ty: Ty<'tcx>,
74 pick: probe::Pick<'tcx>,
75 segment: &hir::PathSegment<'_>,
76 ) -> ConfirmResult<'tcx> {
77 // Adjust the self expression the user provided and obtain the adjusted type.
78 let self_ty = self.adjust_self_ty(unadjusted_self_ty, &pick);
80 // Create substitutions for the method's type parameters.
81 let rcvr_substs = self.fresh_receiver_substs(self_ty, &pick);
82 let all_substs = self.instantiate_method_substs(&pick, segment, rcvr_substs);
84 debug!("rcvr_substs={rcvr_substs:?}, all_substs={all_substs:?}");
86 // Create the final signature for the method, replacing late-bound regions.
87 let (method_sig, method_predicates) = self.instantiate_method_sig(&pick, all_substs);
89 // If there is a `Self: Sized` bound and `Self` is a trait object, it is possible that
90 // something which derefs to `Self` actually implements the trait and the caller
91 // wanted to make a static dispatch on it but forgot to import the trait.
92 // See test `src/test/ui/issue-35976.rs`.
94 // In that case, we'll error anyway, but we'll also re-run the search with all traits
95 // in scope, and if we find another method which can be used, we'll output an
96 // appropriate hint suggesting to import the trait.
97 let filler_substs = rcvr_substs
98 .extend_to(self.tcx, pick.item.def_id, |def, _| self.tcx.mk_param_from_def(def));
99 let illegal_sized_bound = self.predicates_require_illegal_sized_bound(
100 &self.tcx.predicates_of(pick.item.def_id).instantiate(self.tcx, filler_substs),
103 // Unify the (adjusted) self type with what the method expects.
105 // SUBTLE: if we want good error messages, because of "guessing" while matching
106 // traits, no trait system method can be called before this point because they
107 // could alter our Self-type, except for normalizing the receiver from the
108 // signature (which is also done during probing).
109 let method_sig_rcvr = self.normalize_associated_types_in(self.span, method_sig.inputs()[0]);
111 "confirm: self_ty={:?} method_sig_rcvr={:?} method_sig={:?} method_predicates={:?}",
112 self_ty, method_sig_rcvr, method_sig, method_predicates
114 self.unify_receivers(self_ty, method_sig_rcvr, &pick, all_substs);
116 let (method_sig, method_predicates) =
117 self.normalize_associated_types_in(self.span, (method_sig, method_predicates));
118 let method_sig = ty::Binder::dummy(method_sig);
120 // Make sure nobody calls `drop()` explicitly.
121 self.enforce_illegal_method_limitations(&pick);
123 // Add any trait/regions obligations specified on the method's type parameters.
124 // We won't add these if we encountered an illegal sized bound, so that we can use
125 // a custom error in that case.
126 if illegal_sized_bound.is_none() {
127 self.add_obligations(
128 self.tcx.mk_fn_ptr(method_sig),
135 // Create the final `MethodCallee`.
136 let callee = MethodCallee {
137 def_id: pick.item.def_id,
139 sig: method_sig.skip_binder(),
141 ConfirmResult { callee, illegal_sized_bound }
144 ///////////////////////////////////////////////////////////////////////////
149 unadjusted_self_ty: Ty<'tcx>,
150 pick: &probe::Pick<'tcx>,
152 // Commit the autoderefs by calling `autoderef` again, but this
153 // time writing the results into the various typeck results.
154 let mut autoderef = self.autoderef(self.call_expr.span, unadjusted_self_ty);
155 let Some((ty, n)) = autoderef.nth(pick.autoderefs) else {
156 return self.tcx.ty_error_with_message(
157 rustc_span::DUMMY_SP,
158 &format!("failed autoderef {}", pick.autoderefs),
161 assert_eq!(n, pick.autoderefs);
163 let mut adjustments = self.adjust_steps(&autoderef);
164 let mut target = self.structurally_resolved_type(autoderef.span(), ty);
166 match pick.autoref_or_ptr_adjustment {
167 Some(probe::AutorefOrPtrAdjustment::Autoref { mutbl, unsize }) => {
168 let region = self.next_region_var(infer::Autoref(self.span));
169 // Type we're wrapping in a reference, used later for unsizing
170 let base_ty = target;
172 target = self.tcx.mk_ref(region, ty::TypeAndMut { mutbl, ty: target });
173 let mutbl = match mutbl {
174 hir::Mutability::Not => AutoBorrowMutability::Not,
175 hir::Mutability::Mut => AutoBorrowMutability::Mut {
176 // Method call receivers are the primary use case
177 // for two-phase borrows.
178 allow_two_phase_borrow: AllowTwoPhase::Yes,
181 adjustments.push(Adjustment {
182 kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
187 let unsized_ty = if let ty::Array(elem_ty, _) = base_ty.kind() {
188 self.tcx.mk_slice(*elem_ty)
191 "AutorefOrPtrAdjustment's unsize flag should only be set for array ty, found {}",
197 .mk_ref(region, ty::TypeAndMut { mutbl: mutbl.into(), ty: unsized_ty });
199 .push(Adjustment { kind: Adjust::Pointer(PointerCast::Unsize), target });
202 Some(probe::AutorefOrPtrAdjustment::ToConstPtr) => {
203 target = match target.kind() {
204 &ty::RawPtr(ty::TypeAndMut { ty, mutbl }) => {
205 assert_eq!(mutbl, hir::Mutability::Mut);
206 self.tcx.mk_ptr(ty::TypeAndMut { mutbl: hir::Mutability::Not, ty })
208 other => panic!("Cannot adjust receiver type {:?} to const ptr", other),
211 adjustments.push(Adjustment {
212 kind: Adjust::Pointer(PointerCast::MutToConstPointer),
219 self.register_predicates(autoderef.into_obligations());
221 // Write out the final adjustments.
222 self.apply_adjustments(self.self_expr, adjustments);
227 /// Returns a set of substitutions for the method *receiver* where all type and region
228 /// parameters are instantiated with fresh variables. This substitution does not include any
229 /// parameters declared on the method itself.
231 /// Note that this substitution may include late-bound regions from the impl level. If so,
232 /// these are instantiated later in the `instantiate_method_sig` routine.
233 fn fresh_receiver_substs(
236 pick: &probe::Pick<'tcx>,
237 ) -> SubstsRef<'tcx> {
239 probe::InherentImplPick => {
240 let impl_def_id = pick.item.container_id(self.tcx);
242 self.tcx.impl_trait_ref(impl_def_id).is_none(),
243 "impl {:?} is not an inherent impl",
246 self.fresh_substs_for_item(self.span, impl_def_id)
249 probe::ObjectPick => {
250 let trait_def_id = pick.item.container_id(self.tcx);
251 self.extract_existential_trait_ref(self_ty, |this, object_ty, principal| {
252 // The object data has no entry for the Self
253 // Type. For the purposes of this method call, we
254 // substitute the object type itself. This
255 // wouldn't be a sound substitution in all cases,
256 // since each instance of the object type is a
257 // different existential and hence could match
258 // distinct types (e.g., if `Self` appeared as an
259 // argument type), but those cases have already
260 // been ruled out when we deemed the trait to be
262 let original_poly_trait_ref = principal.with_self_ty(this.tcx, object_ty);
263 let upcast_poly_trait_ref = this.upcast(original_poly_trait_ref, trait_def_id);
264 let upcast_trait_ref =
265 this.replace_bound_vars_with_fresh_vars(upcast_poly_trait_ref);
267 "original_poly_trait_ref={:?} upcast_trait_ref={:?} target_trait={:?}",
268 original_poly_trait_ref, upcast_trait_ref, trait_def_id
270 upcast_trait_ref.substs
274 probe::TraitPick => {
275 let trait_def_id = pick.item.container_id(self.tcx);
277 // Make a trait reference `$0 : Trait<$1...$n>`
278 // consisting entirely of type variables. Later on in
279 // the process we will unify the transformed-self-type
280 // of the method with the actual type in order to
281 // unify some of these variables.
282 self.fresh_substs_for_item(self.span, trait_def_id)
285 probe::WhereClausePick(poly_trait_ref) => {
286 // Where clauses can have bound regions in them. We need to instantiate
287 // those to convert from a poly-trait-ref to a trait-ref.
288 self.replace_bound_vars_with_fresh_vars(poly_trait_ref).substs
293 fn extract_existential_trait_ref<R, F>(&mut self, self_ty: Ty<'tcx>, mut closure: F) -> R
295 F: FnMut(&mut ConfirmContext<'a, 'tcx>, Ty<'tcx>, ty::PolyExistentialTraitRef<'tcx>) -> R,
297 // If we specified that this is an object method, then the
298 // self-type ought to be something that can be dereferenced to
299 // yield an object-type (e.g., `&Object` or `Box<Object>`
302 // FIXME: this feels, like, super dubious
304 .autoderef(self.span, self_ty)
305 .include_raw_pointers()
306 .find_map(|(ty, _)| match ty.kind() {
307 ty::Dynamic(data, ..) => Some(closure(
310 data.principal().unwrap_or_else(|| {
311 span_bug!(self.span, "calling trait method on empty object?")
319 "self-type `{}` for ObjectPick never dereferenced to an object",
325 fn instantiate_method_substs(
327 pick: &probe::Pick<'tcx>,
328 seg: &hir::PathSegment<'_>,
329 parent_substs: SubstsRef<'tcx>,
330 ) -> SubstsRef<'tcx> {
331 // Determine the values for the generic parameters of the method.
332 // If they were not explicitly supplied, just construct fresh
334 let generics = self.tcx.generics_of(pick.item.def_id);
336 let arg_count_correct = <dyn AstConv<'_>>::check_generic_arg_count_for_call(
345 // Create subst for early-bound lifetime parameters, combining
346 // parameters from the type and those from the method.
347 assert_eq!(generics.parent_count, parent_substs.len());
349 struct MethodSubstsCtxt<'a, 'tcx> {
350 cfcx: &'a ConfirmContext<'a, 'tcx>,
351 pick: &'a probe::Pick<'tcx>,
352 seg: &'a hir::PathSegment<'a>,
354 impl<'a, 'tcx> CreateSubstsForGenericArgsCtxt<'a, 'tcx> for MethodSubstsCtxt<'a, 'tcx> {
358 ) -> (Option<&'a hir::GenericArgs<'a>>, bool) {
359 if def_id == self.pick.item.def_id {
360 if let Some(data) = self.seg.args {
361 return (Some(data), false);
369 param: &ty::GenericParamDef,
370 arg: &GenericArg<'_>,
371 ) -> subst::GenericArg<'tcx> {
372 match (¶m.kind, arg) {
373 (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
374 <dyn AstConv<'_>>::ast_region_to_region(self.cfcx.fcx, lt, Some(param))
377 (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
378 self.cfcx.to_ty(ty).into()
380 (GenericParamDefKind::Const { .. }, GenericArg::Const(ct)) => {
381 self.cfcx.const_arg_to_const(&ct.value, param.def_id).into()
383 (GenericParamDefKind::Type { .. }, GenericArg::Infer(inf)) => {
384 self.cfcx.ty_infer(Some(param), inf.span).into()
386 (GenericParamDefKind::Const { .. }, GenericArg::Infer(inf)) => {
387 let tcx = self.cfcx.tcx();
388 self.cfcx.ct_infer(tcx.type_of(param.def_id), Some(param), inf.span).into()
396 _substs: Option<&[subst::GenericArg<'tcx>]>,
397 param: &ty::GenericParamDef,
399 ) -> subst::GenericArg<'tcx> {
400 self.cfcx.var_for_def(self.cfcx.span, param)
403 <dyn AstConv<'_>>::create_substs_for_generic_args(
410 &mut MethodSubstsCtxt { cfcx: self, pick, seg },
417 method_self_ty: Ty<'tcx>,
418 pick: &probe::Pick<'tcx>,
419 substs: SubstsRef<'tcx>,
422 "unify_receivers: self_ty={:?} method_self_ty={:?} span={:?} pick={:?}",
423 self_ty, method_self_ty, self.span, pick
425 let cause = self.cause(
427 ObligationCauseCode::UnifyReceiver(Box::new(UnifyReceiverContext {
428 assoc_item: pick.item,
429 param_env: self.param_env,
433 match self.at(&cause, self.param_env).sup(method_self_ty, self_ty) {
434 Ok(InferOk { obligations, value: () }) => {
435 self.register_predicates(obligations);
440 "{} was a subtype of {} but now is not?",
448 // NOTE: this returns the *unnormalized* predicates and method sig. Because of
449 // inference guessing, the predicates and method signature can't be normalized
450 // until we unify the `Self` type.
451 fn instantiate_method_sig(
453 pick: &probe::Pick<'tcx>,
454 all_substs: SubstsRef<'tcx>,
455 ) -> (ty::FnSig<'tcx>, ty::InstantiatedPredicates<'tcx>) {
456 debug!("instantiate_method_sig(pick={:?}, all_substs={:?})", pick, all_substs);
458 // Instantiate the bounds on the method with the
459 // type/early-bound-regions substitutions performed. There can
460 // be no late-bound regions appearing here.
461 let def_id = pick.item.def_id;
462 let method_predicates = self.tcx.predicates_of(def_id).instantiate(self.tcx, all_substs);
464 debug!("method_predicates after subst = {:?}", method_predicates);
466 let sig = self.tcx.bound_fn_sig(def_id);
468 let sig = sig.subst(self.tcx, all_substs);
469 debug!("type scheme substituted, sig={:?}", sig);
471 let sig = self.replace_bound_vars_with_fresh_vars(sig);
472 debug!("late-bound lifetimes from method instantiated, sig={:?}", sig);
474 (sig, method_predicates)
480 all_substs: SubstsRef<'tcx>,
481 method_predicates: ty::InstantiatedPredicates<'tcx>,
485 "add_obligations: fty={:?} all_substs={:?} method_predicates={:?} def_id={:?}",
486 fty, all_substs, method_predicates, def_id
489 // FIXME: could replace with the following, but we already calculated `method_predicates`,
490 // so we just call `predicates_for_generics` directly to avoid redoing work.
491 // `self.add_required_obligations(self.span, def_id, &all_substs);`
492 for obligation in traits::predicates_for_generics(
494 let code = if span.is_dummy() {
495 ObligationCauseCode::ExprItemObligation(def_id, self.call_expr.hir_id, idx)
497 ObligationCauseCode::ExprBindingObligation(
500 self.call_expr.hir_id,
504 traits::ObligationCause::new(self.span, self.body_id, code)
509 self.register_predicate(obligation);
512 // this is a projection from a trait reference, so we have to
513 // make sure that the trait reference inputs are well-formed.
514 self.add_wf_bounds(all_substs, self.call_expr);
516 // the function type must also be well-formed (this is not
517 // implied by the substs being well-formed because of inherent
518 // impls and late-bound regions - see issue #28609).
519 self.register_wf_obligation(fty.into(), self.span, traits::WellFormed(None));
522 ///////////////////////////////////////////////////////////////////////////
525 fn predicates_require_illegal_sized_bound(
527 predicates: &ty::InstantiatedPredicates<'tcx>,
529 let sized_def_id = self.tcx.lang_items().sized_trait()?;
531 traits::elaborate_predicates(self.tcx, predicates.predicates.iter().copied())
532 // We don't care about regions here.
533 .filter_map(|obligation| match obligation.predicate.kind().skip_binder() {
534 ty::PredicateKind::Trait(trait_pred) if trait_pred.def_id() == sized_def_id => {
535 let span = iter::zip(&predicates.predicates, &predicates.spans)
538 if *p == obligation.predicate { Some(*span) } else { None }
541 .unwrap_or(rustc_span::DUMMY_SP);
542 Some((trait_pred, span))
546 .find_map(|(trait_pred, span)| match trait_pred.self_ty().kind() {
547 ty::Dynamic(..) => Some(span),
552 fn enforce_illegal_method_limitations(&self, pick: &probe::Pick<'_>) {
553 // Disallow calls to the method `drop` defined in the `Drop` trait.
554 if let Some(trait_def_id) = pick.item.trait_container(self.tcx) {
555 callee::check_legal_trait_for_method_call(
558 Some(self.self_expr.span),
567 source_trait_ref: ty::PolyTraitRef<'tcx>,
568 target_trait_def_id: DefId,
569 ) -> ty::PolyTraitRef<'tcx> {
570 let upcast_trait_refs =
571 traits::upcast_choices(self.tcx, source_trait_ref, target_trait_def_id);
573 // must be exactly one trait ref or we'd get an ambig error etc
574 if upcast_trait_refs.len() != 1 {
577 "cannot uniquely upcast `{:?}` to `{:?}`: `{:?}`",
584 upcast_trait_refs.into_iter().next().unwrap()
587 fn replace_bound_vars_with_fresh_vars<T>(&self, value: ty::Binder<'tcx, T>) -> T
589 T: TypeFoldable<'tcx> + Copy,
591 self.fcx.replace_bound_vars_with_fresh_vars(self.span, infer::FnCall, value)