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::generics::{
8 check_generic_arg_count_for_call, create_substs_for_generic_args,
10 use rustc_hir_analysis::astconv::{AstConv, CreateSubstsForGenericArgsCtxt, IsMethodCall};
11 use rustc_infer::infer::{self, InferOk};
12 use rustc_middle::traits::{ObligationCauseCode, UnifyReceiverContext};
13 use rustc_middle::ty::adjustment::{Adjust, Adjustment, PointerCast};
14 use rustc_middle::ty::adjustment::{AllowTwoPhase, AutoBorrow, AutoBorrowMutability};
15 use rustc_middle::ty::fold::TypeFoldable;
16 use rustc_middle::ty::subst::{self, SubstsRef};
17 use rustc_middle::ty::{self, GenericParamDefKind, Ty};
18 use rustc_middle::ty::{InternalSubsts, UserSubsts, UserType};
19 use rustc_span::{Span, DUMMY_SP};
20 use rustc_trait_selection::traits;
24 struct ConfirmContext<'a, 'tcx> {
25 fcx: &'a FnCtxt<'a, 'tcx>,
27 self_expr: &'tcx hir::Expr<'tcx>,
28 call_expr: &'tcx hir::Expr<'tcx>,
31 impl<'a, 'tcx> Deref for ConfirmContext<'a, 'tcx> {
32 type Target = FnCtxt<'a, 'tcx>;
33 fn deref(&self) -> &Self::Target {
39 pub struct ConfirmResult<'tcx> {
40 pub callee: MethodCallee<'tcx>,
41 pub illegal_sized_bound: Option<Span>,
44 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
45 pub fn confirm_method(
48 self_expr: &'tcx hir::Expr<'tcx>,
49 call_expr: &'tcx hir::Expr<'tcx>,
50 unadjusted_self_ty: Ty<'tcx>,
51 pick: &probe::Pick<'tcx>,
52 segment: &hir::PathSegment<'_>,
53 ) -> ConfirmResult<'tcx> {
55 "confirm(unadjusted_self_ty={:?}, pick={:?}, generic_args={:?})",
56 unadjusted_self_ty, pick, segment.args,
59 let mut confirm_cx = ConfirmContext::new(self, span, self_expr, call_expr);
60 confirm_cx.confirm(unadjusted_self_ty, pick, segment)
64 impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
66 fcx: &'a FnCtxt<'a, 'tcx>,
68 self_expr: &'tcx hir::Expr<'tcx>,
69 call_expr: &'tcx hir::Expr<'tcx>,
70 ) -> ConfirmContext<'a, 'tcx> {
71 ConfirmContext { fcx, span, self_expr, call_expr }
76 unadjusted_self_ty: Ty<'tcx>,
77 pick: &probe::Pick<'tcx>,
78 segment: &hir::PathSegment<'_>,
79 ) -> ConfirmResult<'tcx> {
80 // Adjust the self expression the user provided and obtain the adjusted type.
81 let self_ty = self.adjust_self_ty(unadjusted_self_ty, &pick);
83 // Create substitutions for the method's type parameters.
84 let rcvr_substs = self.fresh_receiver_substs(self_ty, &pick);
85 let all_substs = self.instantiate_method_substs(&pick, segment, rcvr_substs);
87 debug!("rcvr_substs={rcvr_substs:?}, all_substs={all_substs:?}");
89 // Create the final signature for the method, replacing late-bound regions.
90 let (method_sig, method_predicates) = self.instantiate_method_sig(&pick, all_substs);
92 // If there is a `Self: Sized` bound and `Self` is a trait object, it is possible that
93 // something which derefs to `Self` actually implements the trait and the caller
94 // wanted to make a static dispatch on it but forgot to import the trait.
95 // See test `tests/ui/issue-35976.rs`.
97 // In that case, we'll error anyway, but we'll also re-run the search with all traits
98 // in scope, and if we find another method which can be used, we'll output an
99 // appropriate hint suggesting to import the trait.
100 let filler_substs = rcvr_substs
101 .extend_to(self.tcx, pick.item.def_id, |def, _| self.tcx.mk_param_from_def(def));
102 let illegal_sized_bound = self.predicates_require_illegal_sized_bound(
103 self.tcx.predicates_of(pick.item.def_id).instantiate(self.tcx, filler_substs),
106 // Unify the (adjusted) self type with what the method expects.
108 // SUBTLE: if we want good error messages, because of "guessing" while matching
109 // traits, no trait system method can be called before this point because they
110 // could alter our Self-type, except for normalizing the receiver from the
111 // signature (which is also done during probing).
112 let method_sig_rcvr = self.normalize(self.span, method_sig.inputs()[0]);
114 "confirm: self_ty={:?} method_sig_rcvr={:?} method_sig={:?} method_predicates={:?}",
115 self_ty, method_sig_rcvr, method_sig, method_predicates
117 self.unify_receivers(self_ty, method_sig_rcvr, &pick, all_substs);
119 let (method_sig, method_predicates) =
120 self.normalize(self.span, (method_sig, method_predicates));
121 let method_sig = ty::Binder::dummy(method_sig);
123 // Make sure nobody calls `drop()` explicitly.
124 self.enforce_illegal_method_limitations(&pick);
126 // Add any trait/regions obligations specified on the method's type parameters.
127 // We won't add these if we encountered an illegal sized bound, so that we can use
128 // a custom error in that case.
129 if illegal_sized_bound.is_none() {
130 self.add_obligations(
131 self.tcx.mk_fn_ptr(method_sig),
138 // Create the final `MethodCallee`.
139 let callee = MethodCallee {
140 def_id: pick.item.def_id,
142 sig: method_sig.skip_binder(),
144 ConfirmResult { callee, illegal_sized_bound }
147 ///////////////////////////////////////////////////////////////////////////
152 unadjusted_self_ty: Ty<'tcx>,
153 pick: &probe::Pick<'tcx>,
155 // Commit the autoderefs by calling `autoderef` again, but this
156 // time writing the results into the various typeck results.
157 let mut autoderef = self.autoderef(self.call_expr.span, unadjusted_self_ty);
158 let Some((ty, n)) = autoderef.nth(pick.autoderefs) else {
159 return self.tcx.ty_error_with_message(
160 rustc_span::DUMMY_SP,
161 &format!("failed autoderef {}", pick.autoderefs),
164 assert_eq!(n, pick.autoderefs);
166 let mut adjustments = self.adjust_steps(&autoderef);
167 let mut target = self.structurally_resolved_type(autoderef.span(), ty);
169 match pick.autoref_or_ptr_adjustment {
170 Some(probe::AutorefOrPtrAdjustment::Autoref { mutbl, unsize }) => {
171 let region = self.next_region_var(infer::Autoref(self.span));
172 // Type we're wrapping in a reference, used later for unsizing
173 let base_ty = target;
175 target = self.tcx.mk_ref(region, ty::TypeAndMut { mutbl, ty: target });
177 // Method call receivers are the primary use case
178 // for two-phase borrows.
179 let mutbl = AutoBorrowMutability::new(mutbl, 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!(mutbl.is_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 = 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 self.cfcx.fcx.astconv().ast_region_to_region(lt, Some(param)).into()
376 (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
377 self.cfcx.to_ty(ty).raw.into()
379 (GenericParamDefKind::Const { .. }, GenericArg::Const(ct)) => {
380 self.cfcx.const_arg_to_const(&ct.value, param.def_id).into()
382 (GenericParamDefKind::Type { .. }, GenericArg::Infer(inf)) => {
383 self.cfcx.ty_infer(Some(param), inf.span).into()
385 (GenericParamDefKind::Const { .. }, GenericArg::Infer(inf)) => {
386 let tcx = self.cfcx.tcx();
387 self.cfcx.ct_infer(tcx.type_of(param.def_id), Some(param), inf.span).into()
395 _substs: Option<&[subst::GenericArg<'tcx>]>,
396 param: &ty::GenericParamDef,
398 ) -> subst::GenericArg<'tcx> {
399 self.cfcx.var_for_def(self.cfcx.span, param)
403 let substs = create_substs_for_generic_args(
410 &mut MethodSubstsCtxt { cfcx: self, pick, seg },
413 // When the method is confirmed, the `substs` includes
414 // parameters from not just the method, but also the impl of
415 // the method -- in particular, the `Self` type will be fully
416 // resolved. However, those are not something that the "user
417 // specified" -- i.e., those types come from the inferred type
418 // of the receiver, not something the user wrote. So when we
419 // create the user-substs, we want to replace those earlier
420 // types with just the types that the user actually wrote --
421 // that is, those that appear on the *method itself*.
423 // As an example, if the user wrote something like
424 // `foo.bar::<u32>(...)` -- the `Self` type here will be the
425 // type of `foo` (possibly adjusted), but we don't want to
426 // include that. We want just the `[_, u32]` part.
427 if !substs.is_empty() && !generics.params.is_empty() {
428 let user_type_annotation = self.probe(|_| {
429 let user_substs = UserSubsts {
430 substs: InternalSubsts::for_item(self.tcx, pick.item.def_id, |param, _| {
431 let i = param.index as usize;
432 if i < generics.parent_count {
433 self.fcx.var_for_def(DUMMY_SP, param)
438 user_self_ty: None, // not relevant here
441 self.fcx.canonicalize_user_type_annotation(UserType::TypeOf(
447 debug!("instantiate_method_substs: user_type_annotation={:?}", user_type_annotation);
448 self.fcx.write_user_type_annotation(self.call_expr.hir_id, user_type_annotation);
451 self.normalize(self.span, substs)
457 method_self_ty: Ty<'tcx>,
458 pick: &probe::Pick<'tcx>,
459 substs: SubstsRef<'tcx>,
462 "unify_receivers: self_ty={:?} method_self_ty={:?} span={:?} pick={:?}",
463 self_ty, method_self_ty, self.span, pick
465 let cause = self.cause(
467 ObligationCauseCode::UnifyReceiver(Box::new(UnifyReceiverContext {
468 assoc_item: pick.item,
469 param_env: self.param_env,
473 match self.at(&cause, self.param_env).sup(method_self_ty, self_ty) {
474 Ok(InferOk { obligations, value: () }) => {
475 self.register_predicates(obligations);
480 "{} was a subtype of {} but now is not?",
488 // NOTE: this returns the *unnormalized* predicates and method sig. Because of
489 // inference guessing, the predicates and method signature can't be normalized
490 // until we unify the `Self` type.
491 fn instantiate_method_sig(
493 pick: &probe::Pick<'tcx>,
494 all_substs: SubstsRef<'tcx>,
495 ) -> (ty::FnSig<'tcx>, ty::InstantiatedPredicates<'tcx>) {
496 debug!("instantiate_method_sig(pick={:?}, all_substs={:?})", pick, all_substs);
498 // Instantiate the bounds on the method with the
499 // type/early-bound-regions substitutions performed. There can
500 // be no late-bound regions appearing here.
501 let def_id = pick.item.def_id;
502 let method_predicates = self.tcx.predicates_of(def_id).instantiate(self.tcx, all_substs);
504 debug!("method_predicates after subst = {:?}", method_predicates);
506 let sig = self.tcx.fn_sig(def_id).subst(self.tcx, all_substs);
507 debug!("type scheme substituted, sig={:?}", sig);
509 let sig = self.replace_bound_vars_with_fresh_vars(sig);
510 debug!("late-bound lifetimes from method instantiated, sig={:?}", sig);
512 (sig, method_predicates)
518 all_substs: SubstsRef<'tcx>,
519 method_predicates: ty::InstantiatedPredicates<'tcx>,
523 "add_obligations: fty={:?} all_substs={:?} method_predicates={:?} def_id={:?}",
524 fty, all_substs, method_predicates, def_id
527 // FIXME: could replace with the following, but we already calculated `method_predicates`,
528 // so we just call `predicates_for_generics` directly to avoid redoing work.
529 // `self.add_required_obligations(self.span, def_id, &all_substs);`
530 for obligation in traits::predicates_for_generics(
532 let code = if span.is_dummy() {
533 ObligationCauseCode::ExprItemObligation(def_id, self.call_expr.hir_id, idx)
535 ObligationCauseCode::ExprBindingObligation(
538 self.call_expr.hir_id,
542 traits::ObligationCause::new(self.span, self.body_id, code)
547 self.register_predicate(obligation);
550 // this is a projection from a trait reference, so we have to
551 // make sure that the trait reference inputs are well-formed.
552 self.add_wf_bounds(all_substs, self.call_expr);
554 // the function type must also be well-formed (this is not
555 // implied by the substs being well-formed because of inherent
556 // impls and late-bound regions - see issue #28609).
557 self.register_wf_obligation(fty.into(), self.span, traits::WellFormed(None));
560 ///////////////////////////////////////////////////////////////////////////
563 fn predicates_require_illegal_sized_bound(
565 predicates: ty::InstantiatedPredicates<'tcx>,
567 let sized_def_id = self.tcx.lang_items().sized_trait()?;
569 traits::elaborate_predicates(self.tcx, predicates.predicates.iter().copied())
570 // We don't care about regions here.
571 .filter_map(|obligation| match obligation.predicate.kind().skip_binder() {
572 ty::PredicateKind::Clause(ty::Clause::Trait(trait_pred))
573 if trait_pred.def_id() == sized_def_id =>
575 let span = predicates
579 if p == obligation.predicate { Some(span) } else { None }
582 .unwrap_or(rustc_span::DUMMY_SP);
583 Some((trait_pred, span))
587 .find_map(|(trait_pred, span)| match trait_pred.self_ty().kind() {
588 ty::Dynamic(..) => Some(span),
593 fn enforce_illegal_method_limitations(&self, pick: &probe::Pick<'_>) {
594 // Disallow calls to the method `drop` defined in the `Drop` trait.
595 if let Some(trait_def_id) = pick.item.trait_container(self.tcx) {
596 callee::check_legal_trait_for_method_call(
599 Some(self.self_expr.span),
608 source_trait_ref: ty::PolyTraitRef<'tcx>,
609 target_trait_def_id: DefId,
610 ) -> ty::PolyTraitRef<'tcx> {
611 let upcast_trait_refs =
612 traits::upcast_choices(self.tcx, source_trait_ref, target_trait_def_id);
614 // must be exactly one trait ref or we'd get an ambig error etc
615 if upcast_trait_refs.len() != 1 {
618 "cannot uniquely upcast `{:?}` to `{:?}`: `{:?}`",
625 upcast_trait_refs.into_iter().next().unwrap()
628 fn replace_bound_vars_with_fresh_vars<T>(&self, value: ty::Binder<'tcx, T>) -> T
630 T: TypeFoldable<'tcx> + Copy,
632 self.fcx.replace_bound_vars_with_fresh_vars(self.span, infer::FnCall, value)