1 use crate::callee::{self, DeferredCallResolution};
2 use crate::method::{self, MethodCallee, SelfSource};
3 use crate::rvalue_scopes;
4 use crate::{BreakableCtxt, Diverges, Expectation, FnCtxt, LocalTy};
5 use rustc_data_structures::captures::Captures;
6 use rustc_data_structures::fx::FxHashSet;
7 use rustc_errors::{Applicability, Diagnostic, ErrorGuaranteed, MultiSpan};
9 use rustc_hir::def::{CtorOf, DefKind, Res};
10 use rustc_hir::def_id::DefId;
11 use rustc_hir::lang_items::LangItem;
12 use rustc_hir::{ExprKind, GenericArg, Node, QPath};
13 use rustc_hir_analysis::astconv::{
14 AstConv, CreateSubstsForGenericArgsCtxt, ExplicitLateBound, GenericArgCountMismatch,
15 GenericArgCountResult, IsMethodCall, PathSeg,
17 use rustc_infer::infer::canonical::{Canonical, OriginalQueryValues, QueryResponse};
18 use rustc_infer::infer::error_reporting::TypeAnnotationNeeded::E0282;
19 use rustc_infer::infer::{InferOk, InferResult};
20 use rustc_middle::ty::adjustment::{Adjust, Adjustment, AutoBorrow, AutoBorrowMutability};
21 use rustc_middle::ty::fold::TypeFoldable;
22 use rustc_middle::ty::visit::TypeVisitable;
23 use rustc_middle::ty::{
24 self, AdtKind, CanonicalUserType, DefIdTree, EarlyBinder, GenericParamDefKind, ToPredicate, Ty,
27 use rustc_middle::ty::{GenericArgKind, InternalSubsts, SubstsRef, UserSelfTy, UserSubsts};
28 use rustc_session::lint;
29 use rustc_span::def_id::LocalDefId;
30 use rustc_span::hygiene::DesugaringKind;
31 use rustc_span::symbol::{kw, sym, Ident};
32 use rustc_span::{Span, DUMMY_SP};
33 use rustc_trait_selection::infer::InferCtxtExt as _;
34 use rustc_trait_selection::traits::error_reporting::TypeErrCtxtExt as _;
35 use rustc_trait_selection::traits::{
36 self, ObligationCause, ObligationCauseCode, TraitEngine, TraitEngineExt,
39 use std::collections::hash_map::Entry;
42 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
43 /// Produces warning on the given node, if the current point in the
44 /// function is unreachable, and there hasn't been another warning.
45 pub(in super::super) fn warn_if_unreachable(&self, id: hir::HirId, span: Span, kind: &str) {
46 // FIXME: Combine these two 'if' expressions into one once
47 // let chains are implemented
48 if let Diverges::Always { span: orig_span, custom_note } = self.diverges.get() {
49 // If span arose from a desugaring of `if` or `while`, then it is the condition itself,
50 // which diverges, that we are about to lint on. This gives suboptimal diagnostics.
51 // Instead, stop here so that the `if`- or `while`-expression's block is linted instead.
52 if !span.is_desugaring(DesugaringKind::CondTemporary)
53 && !span.is_desugaring(DesugaringKind::Async)
54 && !orig_span.is_desugaring(DesugaringKind::Await)
56 self.diverges.set(Diverges::WarnedAlways);
58 debug!("warn_if_unreachable: id={:?} span={:?} kind={}", id, span, kind);
60 let msg = format!("unreachable {}", kind);
61 self.tcx().struct_span_lint_hir(
62 lint::builtin::UNREACHABLE_CODE,
67 lint.span_label(span, &msg).span_label(
70 .unwrap_or("any code following this expression is unreachable"),
78 /// Resolves type and const variables in `ty` if possible. Unlike the infcx
79 /// version (resolve_vars_if_possible), this version will
80 /// also select obligations if it seems useful, in an effort
81 /// to get more type information.
82 pub(in super::super) fn resolve_vars_with_obligations(&self, ty: Ty<'tcx>) -> Ty<'tcx> {
83 self.resolve_vars_with_obligations_and_mutate_fulfillment(ty, |_| {})
86 #[instrument(skip(self, mutate_fulfillment_errors), level = "debug", ret)]
87 pub(in super::super) fn resolve_vars_with_obligations_and_mutate_fulfillment(
90 mutate_fulfillment_errors: impl Fn(&mut Vec<traits::FulfillmentError<'tcx>>),
92 // No Infer()? Nothing needs doing.
93 if !ty.has_non_region_infer() {
94 debug!("no inference var, nothing needs doing");
98 // If `ty` is a type variable, see whether we already know what it is.
99 ty = self.resolve_vars_if_possible(ty);
100 if !ty.has_non_region_infer() {
105 // If not, try resolving pending obligations as much as
106 // possible. This can help substantially when there are
107 // indirect dependencies that don't seem worth tracking
109 self.select_obligations_where_possible(mutate_fulfillment_errors);
110 self.resolve_vars_if_possible(ty)
113 pub(in super::super) fn record_deferred_call_resolution(
115 closure_def_id: LocalDefId,
116 r: DeferredCallResolution<'tcx>,
118 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
119 deferred_call_resolutions.entry(closure_def_id).or_default().push(r);
122 pub(in super::super) fn remove_deferred_call_resolutions(
124 closure_def_id: LocalDefId,
125 ) -> Vec<DeferredCallResolution<'tcx>> {
126 let mut deferred_call_resolutions = self.deferred_call_resolutions.borrow_mut();
127 deferred_call_resolutions.remove(&closure_def_id).unwrap_or_default()
130 pub fn tag(&self) -> String {
131 format!("{:p}", self)
134 pub fn local_ty(&self, span: Span, nid: hir::HirId) -> LocalTy<'tcx> {
135 self.locals.borrow().get(&nid).cloned().unwrap_or_else(|| {
136 span_bug!(span, "no type for local variable {}", self.tcx.hir().node_to_string(nid))
141 pub fn write_ty(&self, id: hir::HirId, ty: Ty<'tcx>) {
142 debug!("write_ty({:?}, {:?}) in fcx {}", id, self.resolve_vars_if_possible(ty), self.tag());
143 self.typeck_results.borrow_mut().node_types_mut().insert(id, ty);
145 if ty.references_error() {
146 self.set_tainted_by_errors();
150 pub fn write_field_index(&self, hir_id: hir::HirId, index: usize) {
151 self.typeck_results.borrow_mut().field_indices_mut().insert(hir_id, index);
154 #[instrument(level = "debug", skip(self))]
155 pub(in super::super) fn write_resolution(
158 r: Result<(DefKind, DefId), ErrorGuaranteed>,
160 self.typeck_results.borrow_mut().type_dependent_defs_mut().insert(hir_id, r);
163 #[instrument(level = "debug", skip(self))]
164 pub fn write_method_call(&self, hir_id: hir::HirId, method: MethodCallee<'tcx>) {
165 self.write_resolution(hir_id, Ok((DefKind::AssocFn, method.def_id)));
166 self.write_substs(hir_id, method.substs);
168 // When the method is confirmed, the `method.substs` includes
169 // parameters from not just the method, but also the impl of
170 // the method -- in particular, the `Self` type will be fully
171 // resolved. However, those are not something that the "user
172 // specified" -- i.e., those types come from the inferred type
173 // of the receiver, not something the user wrote. So when we
174 // create the user-substs, we want to replace those earlier
175 // types with just the types that the user actually wrote --
176 // that is, those that appear on the *method itself*.
178 // As an example, if the user wrote something like
179 // `foo.bar::<u32>(...)` -- the `Self` type here will be the
180 // type of `foo` (possibly adjusted), but we don't want to
181 // include that. We want just the `[_, u32]` part.
182 if !method.substs.is_empty() {
183 let method_generics = self.tcx.generics_of(method.def_id);
184 if !method_generics.params.is_empty() {
185 let user_type_annotation = self.probe(|_| {
186 let user_substs = UserSubsts {
187 substs: InternalSubsts::for_item(self.tcx, method.def_id, |param, _| {
188 let i = param.index as usize;
189 if i < method_generics.parent_count {
190 self.var_for_def(DUMMY_SP, param)
195 user_self_ty: None, // not relevant here
198 self.canonicalize_user_type_annotation(UserType::TypeOf(
204 debug!("write_method_call: user_type_annotation={:?}", user_type_annotation);
205 self.write_user_type_annotation(hir_id, user_type_annotation);
210 pub fn write_substs(&self, node_id: hir::HirId, substs: SubstsRef<'tcx>) {
211 if !substs.is_empty() {
212 debug!("write_substs({:?}, {:?}) in fcx {}", node_id, substs, self.tag());
214 self.typeck_results.borrow_mut().node_substs_mut().insert(node_id, substs);
218 /// Given the substs that we just converted from the HIR, try to
219 /// canonicalize them and store them as user-given substitutions
220 /// (i.e., substitutions that must be respected by the NLL check).
222 /// This should be invoked **before any unifications have
223 /// occurred**, so that annotations like `Vec<_>` are preserved
225 #[instrument(skip(self), level = "debug")]
226 pub fn write_user_type_annotation_from_substs(
230 substs: SubstsRef<'tcx>,
231 user_self_ty: Option<UserSelfTy<'tcx>>,
233 debug!("fcx {}", self.tag());
235 if Self::can_contain_user_lifetime_bounds((substs, user_self_ty)) {
236 let canonicalized = self.canonicalize_user_type_annotation(UserType::TypeOf(
238 UserSubsts { substs, user_self_ty },
240 debug!(?canonicalized);
241 self.write_user_type_annotation(hir_id, canonicalized);
245 #[instrument(skip(self), level = "debug")]
246 pub fn write_user_type_annotation(
249 canonical_user_type_annotation: CanonicalUserType<'tcx>,
251 debug!("fcx {}", self.tag());
253 if !canonical_user_type_annotation.is_identity() {
256 .user_provided_types_mut()
257 .insert(hir_id, canonical_user_type_annotation);
259 debug!("skipping identity substs");
263 #[instrument(skip(self, expr), level = "debug")]
264 pub fn apply_adjustments(&self, expr: &hir::Expr<'_>, adj: Vec<Adjustment<'tcx>>) {
265 debug!("expr = {:#?}", expr);
272 if let Adjust::NeverToAny = a.kind {
273 if a.target.is_ty_var() {
274 self.diverging_type_vars.borrow_mut().insert(a.target);
275 debug!("apply_adjustments: adding `{:?}` as diverging type var", a.target);
280 let autoborrow_mut = adj.iter().any(|adj| {
284 kind: Adjust::Borrow(AutoBorrow::Ref(_, AutoBorrowMutability::Mut { .. })),
290 match self.typeck_results.borrow_mut().adjustments_mut().entry(expr.hir_id) {
291 Entry::Vacant(entry) => {
294 Entry::Occupied(mut entry) => {
295 debug!(" - composing on top of {:?}", entry.get());
296 match (&entry.get()[..], &adj[..]) {
297 // Applying any adjustment on top of a NeverToAny
298 // is a valid NeverToAny adjustment, because it can't
300 (&[Adjustment { kind: Adjust::NeverToAny, .. }], _) => return,
303 Adjustment { kind: Adjust::Deref(_), .. },
304 Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(..)), .. },
307 Adjustment { kind: Adjust::Deref(_), .. },
308 .., // Any following adjustments are allowed.
311 // A reborrow has no effect before a dereference.
313 // FIXME: currently we never try to compose autoderefs
314 // and ReifyFnPointer/UnsafeFnPointer, but we could.
316 self.tcx.sess.delay_span_bug(
319 "while adjusting {:?}, can't compose {:?} and {:?}",
327 *entry.get_mut() = adj;
331 // If there is an mutable auto-borrow, it is equivalent to `&mut <expr>`.
332 // In this case implicit use of `Deref` and `Index` within `<expr>` should
333 // instead be `DerefMut` and `IndexMut`, so fix those up.
335 self.convert_place_derefs_to_mutable(expr);
339 /// Basically whenever we are converting from a type scheme into
340 /// the fn body space, we always want to normalize associated
341 /// types as well. This function combines the two.
342 fn instantiate_type_scheme<T>(&self, span: Span, substs: SubstsRef<'tcx>, value: T) -> T
344 T: TypeFoldable<'tcx>,
346 debug!("instantiate_type_scheme(value={:?}, substs={:?})", value, substs);
347 let value = EarlyBinder(value).subst(self.tcx, substs);
348 let result = self.normalize_associated_types_in(span, value);
349 debug!("instantiate_type_scheme = {:?}", result);
353 /// As `instantiate_type_scheme`, but for the bounds found in a
354 /// generic type scheme.
355 pub(in super::super) fn instantiate_bounds(
359 substs: SubstsRef<'tcx>,
360 ) -> (ty::InstantiatedPredicates<'tcx>, Vec<Span>) {
361 let bounds = self.tcx.predicates_of(def_id);
362 let spans: Vec<Span> = bounds.predicates.iter().map(|(_, span)| *span).collect();
363 let result = bounds.instantiate(self.tcx, substs);
364 let result = self.normalize_associated_types_in(span, result);
366 "instantiate_bounds(bounds={:?}, substs={:?}) = {:?}, {:?}",
367 bounds, substs, result, spans,
372 pub(in super::super) fn normalize_associated_types_in<T>(&self, span: Span, value: T) -> T
374 T: TypeFoldable<'tcx>,
376 self.inh.normalize_associated_types_in(span, self.body_id, self.param_env, value)
379 pub(in super::super) fn normalize_associated_types_in_as_infer_ok<T>(
383 ) -> InferOk<'tcx, T>
385 T: TypeFoldable<'tcx>,
387 self.inh.partially_normalize_associated_types_in(
388 ObligationCause::misc(span, self.body_id),
394 pub(in super::super) fn normalize_op_associated_types_in_as_infer_ok<T>(
398 opt_input_expr: Option<&hir::Expr<'_>>,
399 ) -> InferOk<'tcx, T>
401 T: TypeFoldable<'tcx>,
403 self.inh.partially_normalize_associated_types_in(
404 ObligationCause::new(
408 rhs_span: opt_input_expr.map(|expr| expr.span),
409 is_lit: opt_input_expr
410 .map_or(false, |expr| matches!(expr.kind, ExprKind::Lit(_))),
419 pub fn require_type_meets(
423 code: traits::ObligationCauseCode<'tcx>,
426 self.register_bound(ty, def_id, traits::ObligationCause::new(span, self.body_id, code));
429 pub fn require_type_is_sized(
433 code: traits::ObligationCauseCode<'tcx>,
435 if !ty.references_error() {
436 let lang_item = self.tcx.require_lang_item(LangItem::Sized, None);
437 self.require_type_meets(ty, span, code, lang_item);
441 pub fn require_type_is_sized_deferred(
445 code: traits::ObligationCauseCode<'tcx>,
447 if !ty.references_error() {
448 self.deferred_sized_obligations.borrow_mut().push((ty, span, code));
452 pub fn register_bound(
456 cause: traits::ObligationCause<'tcx>,
458 if !ty.references_error() {
459 self.fulfillment_cx.borrow_mut().register_bound(
469 pub fn to_ty(&self, ast_t: &hir::Ty<'_>) -> Ty<'tcx> {
470 let t = <dyn AstConv<'_>>::ast_ty_to_ty(self, ast_t);
471 self.register_wf_obligation(t.into(), ast_t.span, traits::WellFormed(None));
475 pub fn to_ty_saving_user_provided_ty(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> {
476 let ty = self.to_ty(ast_ty);
477 debug!("to_ty_saving_user_provided_ty: ty={:?}", ty);
479 if Self::can_contain_user_lifetime_bounds(ty) {
480 let c_ty = self.canonicalize_response(UserType::Ty(ty));
481 debug!("to_ty_saving_user_provided_ty: c_ty={:?}", c_ty);
482 self.typeck_results.borrow_mut().user_provided_types_mut().insert(ast_ty.hir_id, c_ty);
488 pub fn array_length_to_const(&self, length: &hir::ArrayLen) -> ty::Const<'tcx> {
490 &hir::ArrayLen::Infer(_, span) => self.ct_infer(self.tcx.types.usize, None, span),
491 hir::ArrayLen::Body(anon_const) => {
492 let const_def_id = self.tcx.hir().local_def_id(anon_const.hir_id);
493 let span = self.tcx.hir().span(anon_const.hir_id);
494 let c = ty::Const::from_anon_const(self.tcx, const_def_id);
495 self.register_wf_obligation(c.into(), span, ObligationCauseCode::WellFormed(None));
496 self.normalize_associated_types_in(span, c)
501 pub fn const_arg_to_const(
503 ast_c: &hir::AnonConst,
505 ) -> ty::Const<'tcx> {
506 let const_def = ty::WithOptConstParam {
507 did: self.tcx.hir().local_def_id(ast_c.hir_id),
508 const_param_did: Some(param_def_id),
510 let c = ty::Const::from_opt_const_arg_anon_const(self.tcx, const_def);
511 self.register_wf_obligation(
513 self.tcx.hir().span(ast_c.hir_id),
514 ObligationCauseCode::WellFormed(None),
519 // If the type given by the user has free regions, save it for later, since
520 // NLL would like to enforce those. Also pass in types that involve
521 // projections, since those can resolve to `'static` bounds (modulo #54940,
522 // which hopefully will be fixed by the time you see this comment, dear
523 // reader, although I have my doubts). Also pass in types with inference
524 // types, because they may be repeated. Other sorts of things are already
525 // sufficiently enforced with erased regions. =)
526 fn can_contain_user_lifetime_bounds<T>(t: T) -> bool
528 T: TypeVisitable<'tcx>,
530 t.has_free_regions() || t.has_projections() || t.has_infer_types()
533 pub fn node_ty(&self, id: hir::HirId) -> Ty<'tcx> {
534 match self.typeck_results.borrow().node_types().get(id) {
536 None if self.is_tainted_by_errors() => self.tcx.ty_error(),
539 "no type for node {}: {} in fcx {}",
541 self.tcx.hir().node_to_string(id),
548 pub fn node_ty_opt(&self, id: hir::HirId) -> Option<Ty<'tcx>> {
549 match self.typeck_results.borrow().node_types().get(id) {
551 None if self.is_tainted_by_errors() => Some(self.tcx.ty_error()),
556 /// Registers an obligation for checking later, during regionck, that `arg` is well-formed.
557 pub fn register_wf_obligation(
559 arg: ty::GenericArg<'tcx>,
561 code: traits::ObligationCauseCode<'tcx>,
563 // WF obligations never themselves fail, so no real need to give a detailed cause:
564 let cause = traits::ObligationCause::new(span, self.body_id, code);
565 self.register_predicate(traits::Obligation::new(
568 ty::Binder::dummy(ty::PredicateKind::WellFormed(arg)).to_predicate(self.tcx),
572 /// Registers obligations that all `substs` are well-formed.
573 pub fn add_wf_bounds(&self, substs: SubstsRef<'tcx>, expr: &hir::Expr<'_>) {
574 for arg in substs.iter().filter(|arg| {
575 matches!(arg.unpack(), GenericArgKind::Type(..) | GenericArgKind::Const(..))
577 self.register_wf_obligation(arg, expr.span, traits::WellFormed(None));
581 // FIXME(arielb1): use this instead of field.ty everywhere
582 // Only for fields! Returns <none> for methods>
583 // Indifferent to privacy flags
587 field: &'tcx ty::FieldDef,
588 substs: SubstsRef<'tcx>,
590 self.normalize_associated_types_in(span, field.ty(self.tcx, substs))
593 pub(in super::super) fn resolve_rvalue_scopes(&self, def_id: DefId) {
594 let scope_tree = self.tcx.region_scope_tree(def_id);
595 let rvalue_scopes = { rvalue_scopes::resolve_rvalue_scopes(self, &scope_tree, def_id) };
596 let mut typeck_results = self.inh.typeck_results.borrow_mut();
597 typeck_results.rvalue_scopes = rvalue_scopes;
600 pub(in super::super) fn resolve_generator_interiors(&self, def_id: DefId) {
601 let mut generators = self.deferred_generator_interiors.borrow_mut();
602 for (body_id, interior, kind) in generators.drain(..) {
603 self.select_obligations_where_possible(|_| {});
604 crate::generator_interior::resolve_interior(self, def_id, body_id, interior, kind);
608 #[instrument(skip(self), level = "debug")]
609 pub(in super::super) fn select_all_obligations_or_error(&self) {
610 let mut errors = self.fulfillment_cx.borrow_mut().select_all_or_error(&self);
612 if !errors.is_empty() {
613 self.adjust_fulfillment_errors_for_expr_obligation(&mut errors);
614 self.err_ctxt().report_fulfillment_errors(&errors, self.inh.body_id);
618 /// Select as many obligations as we can at present.
619 pub(in super::super) fn select_obligations_where_possible(
621 mutate_fulfillment_errors: impl Fn(&mut Vec<traits::FulfillmentError<'tcx>>),
623 let mut result = self.fulfillment_cx.borrow_mut().select_where_possible(self);
624 if !result.is_empty() {
625 mutate_fulfillment_errors(&mut result);
626 self.adjust_fulfillment_errors_for_expr_obligation(&mut result);
627 self.err_ctxt().report_fulfillment_errors(&result, self.inh.body_id);
631 /// For the overloaded place expressions (`*x`, `x[3]`), the trait
632 /// returns a type of `&T`, but the actual type we assign to the
633 /// *expression* is `T`. So this function just peels off the return
634 /// type by one layer to yield `T`.
635 pub(in super::super) fn make_overloaded_place_return_type(
637 method: MethodCallee<'tcx>,
638 ) -> ty::TypeAndMut<'tcx> {
639 // extract method return type, which will be &T;
640 let ret_ty = method.sig.output();
642 // method returns &T, but the type as visible to user is T, so deref
643 ret_ty.builtin_deref(true).unwrap()
646 #[instrument(skip(self), level = "debug")]
647 fn self_type_matches_expected_vid(&self, self_ty: Ty<'tcx>, expected_vid: ty::TyVid) -> bool {
648 let self_ty = self.shallow_resolve(self_ty);
651 match *self_ty.kind() {
652 ty::Infer(ty::TyVar(found_vid)) => {
653 // FIXME: consider using `sub_root_var` here so we
654 // can see through subtyping.
655 let found_vid = self.root_var(found_vid);
656 debug!("self_type_matches_expected_vid - found_vid={:?}", found_vid);
657 expected_vid == found_vid
663 #[instrument(skip(self), level = "debug")]
664 pub(in super::super) fn obligations_for_self_ty<'b>(
667 ) -> impl DoubleEndedIterator<Item = traits::PredicateObligation<'tcx>> + Captures<'tcx> + 'b
669 // FIXME: consider using `sub_root_var` here so we
670 // can see through subtyping.
671 let ty_var_root = self.root_var(self_ty);
672 trace!("pending_obligations = {:#?}", self.fulfillment_cx.borrow().pending_obligations());
674 self.fulfillment_cx.borrow().pending_obligations().into_iter().filter_map(
675 move |obligation| match &obligation.predicate.kind().skip_binder() {
676 ty::PredicateKind::Projection(data)
677 if self.self_type_matches_expected_vid(
678 data.projection_ty.self_ty(),
684 ty::PredicateKind::Trait(data)
685 if self.self_type_matches_expected_vid(data.self_ty(), ty_var_root) =>
690 ty::PredicateKind::Trait(..)
691 | ty::PredicateKind::Projection(..)
692 | ty::PredicateKind::Subtype(..)
693 | ty::PredicateKind::Coerce(..)
694 | ty::PredicateKind::RegionOutlives(..)
695 | ty::PredicateKind::TypeOutlives(..)
696 | ty::PredicateKind::WellFormed(..)
697 | ty::PredicateKind::ObjectSafe(..)
698 | ty::PredicateKind::ConstEvaluatable(..)
699 | ty::PredicateKind::ConstEquate(..)
700 // N.B., this predicate is created by breaking down a
701 // `ClosureType: FnFoo()` predicate, where
702 // `ClosureType` represents some `Closure`. It can't
703 // possibly be referring to the current closure,
704 // because we haven't produced the `Closure` for
705 // this closure yet; this is exactly why the other
706 // code is looking for a self type of an unresolved
707 // inference variable.
708 | ty::PredicateKind::ClosureKind(..)
709 | ty::PredicateKind::TypeWellFormedFromEnv(..) => None,
714 pub(in super::super) fn type_var_is_sized(&self, self_ty: ty::TyVid) -> bool {
715 let sized_did = self.tcx.lang_items().sized_trait();
716 self.obligations_for_self_ty(self_ty).any(|obligation| {
717 match obligation.predicate.kind().skip_binder() {
718 ty::PredicateKind::Trait(data) => Some(data.def_id()) == sized_did,
724 pub(in super::super) fn err_args(&self, len: usize) -> Vec<Ty<'tcx>> {
725 vec![self.tcx.ty_error(); len]
728 /// Unifies the output type with the expected type early, for more coercions
729 /// and forward type information on the input expressions.
730 #[instrument(skip(self, call_span), level = "debug")]
731 pub(in super::super) fn expected_inputs_for_expected_output(
734 expected_ret: Expectation<'tcx>,
735 formal_ret: Ty<'tcx>,
736 formal_args: &[Ty<'tcx>],
737 ) -> Option<Vec<Ty<'tcx>>> {
738 let formal_ret = self.resolve_vars_with_obligations(formal_ret);
739 let ret_ty = expected_ret.only_has_type(self)?;
741 // HACK(oli-obk): This is a hack to keep RPIT and TAIT in sync wrt their behaviour.
742 // Without it, the inference
743 // variable will get instantiated with the opaque type. The inference variable often
744 // has various helpful obligations registered for it that help closures figure out their
745 // signature. If we infer the inference var to the opaque type, the closure won't be able
746 // to find those obligations anymore, and it can't necessarily find them from the opaque
747 // type itself. We could be more powerful with inference if we *combined* the obligations
748 // so that we got both the obligations from the opaque type and the ones from the inference
749 // variable. That will accept more code than we do right now, so we need to carefully consider
751 // Note: this check is pessimistic, as the inference type could be matched with something other
752 // than the opaque type, but then we need a new `TypeRelation` just for this specific case and
753 // can't re-use `sup` below.
754 // See src/test/ui/impl-trait/hidden-type-is-opaque.rs and
755 // src/test/ui/impl-trait/hidden-type-is-opaque-2.rs for examples that hit this path.
756 if formal_ret.has_infer_types() {
757 for ty in ret_ty.walk() {
758 if let ty::subst::GenericArgKind::Type(ty) = ty.unpack()
759 && let ty::Opaque(def_id, _) = *ty.kind()
760 && let Some(def_id) = def_id.as_local()
761 && self.opaque_type_origin(def_id, DUMMY_SP).is_some() {
767 let expect_args = self
768 .fudge_inference_if_ok(|| {
769 // Attempt to apply a subtyping relationship between the formal
770 // return type (likely containing type variables if the function
771 // is polymorphic) and the expected return type.
772 // No argument expectations are produced if unification fails.
773 let origin = self.misc(call_span);
774 let ures = self.at(&origin, self.param_env).sup(ret_ty, formal_ret);
776 // FIXME(#27336) can't use ? here, Try::from_error doesn't default
777 // to identity so the resulting type is not constrained.
780 // Process any obligations locally as much as
781 // we can. We don't care if some things turn
782 // out unconstrained or ambiguous, as we're
783 // just trying to get hints here.
784 let errors = self.save_and_restore_in_snapshot_flag(|_| {
785 let mut fulfill = <dyn TraitEngine<'_>>::new(self.tcx);
786 for obligation in ok.obligations {
787 fulfill.register_predicate_obligation(self, obligation);
789 fulfill.select_where_possible(self)
792 if !errors.is_empty() {
796 Err(_) => return Err(()),
799 // Record all the argument types, with the substitutions
800 // produced from the above subtyping unification.
801 Ok(Some(formal_args.iter().map(|&ty| self.resolve_vars_if_possible(ty)).collect()))
803 .unwrap_or_default();
804 debug!(?formal_args, ?formal_ret, ?expect_args, ?expected_ret);
808 pub(in super::super) fn resolve_lang_item_path(
810 lang_item: hir::LangItem,
813 expr_hir_id: Option<hir::HirId>,
814 ) -> (Res, Ty<'tcx>) {
815 let def_id = self.tcx.require_lang_item(lang_item, Some(span));
816 let def_kind = self.tcx.def_kind(def_id);
818 let item_ty = if let DefKind::Variant = def_kind {
819 self.tcx.bound_type_of(self.tcx.parent(def_id))
821 self.tcx.bound_type_of(def_id)
823 let substs = self.fresh_substs_for_item(span, def_id);
824 let ty = item_ty.subst(self.tcx, substs);
826 self.write_resolution(hir_id, Ok((def_kind, def_id)));
828 let code = match lang_item {
829 hir::LangItem::IntoFutureIntoFuture => {
830 Some(ObligationCauseCode::AwaitableExpr(expr_hir_id))
832 hir::LangItem::IteratorNext | hir::LangItem::IntoIterIntoIter => {
833 Some(ObligationCauseCode::ForLoopIterator)
835 hir::LangItem::TryTraitFromOutput
836 | hir::LangItem::TryTraitFromResidual
837 | hir::LangItem::TryTraitBranch => Some(ObligationCauseCode::QuestionMark),
840 if let Some(code) = code {
841 self.add_required_obligations_with_code(span, def_id, substs, move |_, _| code.clone());
843 self.add_required_obligations_for_hir(span, def_id, substs, hir_id);
846 (Res::Def(def_kind, def_id), ty)
849 /// Resolves an associated value path into a base type and associated constant, or method
850 /// resolution. The newly resolved definition is written into `type_dependent_defs`.
851 pub fn resolve_ty_and_res_fully_qualified_call(
853 qpath: &'tcx QPath<'tcx>,
856 ) -> (Res, Option<Ty<'tcx>>, &'tcx [hir::PathSegment<'tcx>]) {
858 "resolve_ty_and_res_fully_qualified_call: qpath={:?} hir_id={:?} span={:?}",
861 let (ty, qself, item_segment) = match *qpath {
862 QPath::Resolved(ref opt_qself, ref path) => {
865 opt_qself.as_ref().map(|qself| self.to_ty(qself)),
869 QPath::TypeRelative(ref qself, ref segment) => {
870 // Don't use `self.to_ty`, since this will register a WF obligation.
871 // If we're trying to call a non-existent method on a trait
872 // (e.g. `MyTrait::missing_method`), then resolution will
873 // give us a `QPath::TypeRelative` with a trait object as
874 // `qself`. In that case, we want to avoid registering a WF obligation
875 // for `dyn MyTrait`, since we don't actually need the trait
876 // to be object-safe.
877 // We manually call `register_wf_obligation` in the success path
879 (<dyn AstConv<'_>>::ast_ty_to_ty_in_path(self, qself), qself, segment)
881 QPath::LangItem(..) => {
882 bug!("`resolve_ty_and_res_fully_qualified_call` called on `LangItem`")
885 if let Some(&cached_result) = self.typeck_results.borrow().type_dependent_defs().get(hir_id)
887 self.register_wf_obligation(ty.into(), qself.span, traits::WellFormed(None));
888 // Return directly on cache hit. This is useful to avoid doubly reporting
889 // errors with default match binding modes. See #44614.
890 let def = cached_result.map_or(Res::Err, |(kind, def_id)| Res::Def(kind, def_id));
891 return (def, Some(ty), slice::from_ref(&**item_segment));
893 let item_name = item_segment.ident;
895 .resolve_fully_qualified_call(span, item_name, ty, qself.span, hir_id)
897 let result = match error {
898 method::MethodError::PrivateMatch(kind, def_id, _) => Ok((kind, def_id)),
899 _ => Err(ErrorGuaranteed::unchecked_claim_error_was_emitted()),
902 // If we have a path like `MyTrait::missing_method`, then don't register
903 // a WF obligation for `dyn MyTrait` when method lookup fails. Otherwise,
904 // register a WF obligation so that we can detect any additional
905 // errors in the self type.
906 if !(matches!(error, method::MethodError::NoMatch(_)) && ty.is_trait()) {
907 self.register_wf_obligation(ty.into(), qself.span, traits::WellFormed(None));
909 if item_name.name != kw::Empty {
910 if let Some(mut e) = self.report_method_error(
914 SelfSource::QPath(qself),
925 self.register_wf_obligation(ty.into(), qself.span, traits::WellFormed(None));
928 // Write back the new resolution.
929 self.write_resolution(hir_id, result);
931 result.map_or(Res::Err, |(kind, def_id)| Res::Def(kind, def_id)),
933 slice::from_ref(&**item_segment),
937 /// Given a function `Node`, return its `FnDecl` if it exists, or `None` otherwise.
938 pub(in super::super) fn get_node_fn_decl(
941 ) -> Option<(&'tcx hir::FnDecl<'tcx>, Ident, bool)> {
943 Node::Item(&hir::Item { ident, kind: hir::ItemKind::Fn(ref sig, ..), .. }) => {
944 // This is less than ideal, it will not suggest a return type span on any
945 // method called `main`, regardless of whether it is actually the entry point,
946 // but it will still present it as the reason for the expected type.
947 Some((&sig.decl, ident, ident.name != sym::main))
949 Node::TraitItem(&hir::TraitItem {
951 kind: hir::TraitItemKind::Fn(ref sig, ..),
953 }) => Some((&sig.decl, ident, true)),
954 Node::ImplItem(&hir::ImplItem {
956 kind: hir::ImplItemKind::Fn(ref sig, ..),
958 }) => Some((&sig.decl, ident, false)),
963 /// Given a `HirId`, return the `FnDecl` of the method it is enclosed by and whether a
964 /// suggestion can be made, `None` otherwise.
965 pub fn get_fn_decl(&self, blk_id: hir::HirId) -> Option<(&'tcx hir::FnDecl<'tcx>, bool)> {
966 // Get enclosing Fn, if it is a function or a trait method, unless there's a `loop` or
967 // `while` before reaching it, as block tail returns are not available in them.
968 self.tcx.hir().get_return_block(blk_id).and_then(|blk_id| {
969 let parent = self.tcx.hir().get(blk_id);
970 self.get_node_fn_decl(parent).map(|(fn_decl, _, is_main)| (fn_decl, is_main))
974 pub(in super::super) fn note_internal_mutation_in_method(
976 err: &mut Diagnostic,
977 expr: &hir::Expr<'_>,
981 if found != self.tcx.types.unit {
984 if let ExprKind::MethodCall(path_segment, rcvr, ..) = expr.kind {
988 .expr_ty_adjusted_opt(rcvr)
989 .map_or(true, |ty| expected.peel_refs() != ty.peel_refs())
993 let mut sp = MultiSpan::from_span(path_segment.ident.span);
995 path_segment.ident.span,
997 "this call modifies {} in-place",
999 ExprKind::Path(QPath::Resolved(
1001 hir::Path { segments: [segment], .. },
1002 )) => format!("`{}`", segment.ident),
1003 _ => "its receiver".to_string(),
1009 "you probably want to use this value after calling the method...",
1013 &format!("method `{}` modifies its receiver in-place", path_segment.ident),
1015 err.note(&format!("...instead of the `()` output of method `{}`", path_segment.ident));
1019 pub(in super::super) fn note_need_for_fn_pointer(
1021 err: &mut Diagnostic,
1025 let (sig, did, substs) = match (&expected.kind(), &found.kind()) {
1026 (ty::FnDef(did1, substs1), ty::FnDef(did2, substs2)) => {
1027 let sig1 = self.tcx.bound_fn_sig(*did1).subst(self.tcx, substs1);
1028 let sig2 = self.tcx.bound_fn_sig(*did2).subst(self.tcx, substs2);
1033 "different `fn` items always have unique types, even if their signatures are \
1036 (sig1, *did1, substs1)
1038 (ty::FnDef(did, substs), ty::FnPtr(sig2)) => {
1039 let sig1 = self.tcx.bound_fn_sig(*did).subst(self.tcx, substs);
1043 (sig1, *did, substs)
1047 err.help(&format!("change the expected type to be function pointer `{}`", sig));
1049 "if the expected type is due to type inference, cast the expected `fn` to a function \
1050 pointer: `{} as {}`",
1051 self.tcx.def_path_str_with_substs(did, substs),
1056 // Instantiates the given path, which must refer to an item with the given
1057 // number of type parameters and type.
1058 #[instrument(skip(self, span), level = "debug")]
1059 pub fn instantiate_value_path(
1061 segments: &[hir::PathSegment<'_>],
1062 self_ty: Option<Ty<'tcx>>,
1066 ) -> (Ty<'tcx>, Res) {
1069 let path_segs = match res {
1070 Res::Local(_) | Res::SelfCtor(_) => vec![],
1071 Res::Def(kind, def_id) => <dyn AstConv<'_>>::def_ids_for_value_path_segments(
1072 self, segments, self_ty, kind, def_id,
1074 _ => bug!("instantiate_value_path on {:?}", res),
1077 let mut user_self_ty = None;
1078 let mut is_alias_variant_ctor = false;
1080 Res::Def(DefKind::Ctor(CtorOf::Variant, _), _)
1081 if let Some(self_ty) = self_ty =>
1083 let adt_def = self_ty.ty_adt_def().unwrap();
1084 user_self_ty = Some(UserSelfTy { impl_def_id: adt_def.did(), self_ty });
1085 is_alias_variant_ctor = true;
1087 Res::Def(DefKind::AssocFn | DefKind::AssocConst, def_id) => {
1088 let assoc_item = tcx.associated_item(def_id);
1089 let container = assoc_item.container;
1090 let container_id = assoc_item.container_id(tcx);
1091 debug!(?def_id, ?container, ?container_id);
1093 ty::TraitContainer => {
1094 callee::check_legal_trait_for_method_call(tcx, span, None, span, container_id)
1096 ty::ImplContainer => {
1097 if segments.len() == 1 {
1098 // `<T>::assoc` will end up here, and so
1099 // can `T::assoc`. It this came from an
1100 // inherent impl, we need to record the
1101 // `T` for posterity (see `UserSelfTy` for
1103 let self_ty = self_ty.expect("UFCS sugared assoc missing Self");
1104 user_self_ty = Some(UserSelfTy { impl_def_id: container_id, self_ty });
1112 // Now that we have categorized what space the parameters for each
1113 // segment belong to, let's sort out the parameters that the user
1114 // provided (if any) into their appropriate spaces. We'll also report
1115 // errors if type parameters are provided in an inappropriate place.
1117 let generic_segs: FxHashSet<_> = path_segs.iter().map(|PathSeg(_, index)| index).collect();
1118 let generics_has_err = <dyn AstConv<'_>>::prohibit_generics(
1120 segments.iter().enumerate().filter_map(|(index, seg)| {
1121 if !generic_segs.contains(&index) || is_alias_variant_ctor {
1130 if let Res::Local(hid) = res {
1131 let ty = self.local_ty(span, hid).decl_ty;
1132 let ty = self.normalize_associated_types_in(span, ty);
1133 self.write_ty(hir_id, ty);
1137 if generics_has_err {
1138 // Don't try to infer type parameters when prohibited generic arguments were given.
1139 user_self_ty = None;
1142 // Now we have to compare the types that the user *actually*
1143 // provided against the types that were *expected*. If the user
1144 // did not provide any types, then we want to substitute inference
1145 // variables. If the user provided some types, we may still need
1146 // to add defaults. If the user provided *too many* types, that's
1149 let mut infer_args_for_err = FxHashSet::default();
1151 let mut explicit_late_bound = ExplicitLateBound::No;
1152 for &PathSeg(def_id, index) in &path_segs {
1153 let seg = &segments[index];
1154 let generics = tcx.generics_of(def_id);
1156 // Argument-position `impl Trait` is treated as a normal generic
1157 // parameter internally, but we don't allow users to specify the
1158 // parameter's value explicitly, so we have to do some error-
1160 let arg_count = <dyn AstConv<'_>>::check_generic_arg_count_for_call(
1169 if let ExplicitLateBound::Yes = arg_count.explicit_late_bound {
1170 explicit_late_bound = ExplicitLateBound::Yes;
1173 if let Err(GenericArgCountMismatch { reported: Some(_), .. }) = arg_count.correct {
1174 infer_args_for_err.insert(index);
1175 self.set_tainted_by_errors(); // See issue #53251.
1179 let has_self = path_segs
1181 .map(|PathSeg(def_id, _)| tcx.generics_of(*def_id).has_self)
1184 let (res, self_ctor_substs) = if let Res::SelfCtor(impl_def_id) = res {
1185 let ty = self.normalize_ty(span, tcx.at(span).type_of(impl_def_id));
1187 ty::Adt(adt_def, substs) if adt_def.has_ctor() => {
1188 let variant = adt_def.non_enum_variant();
1189 let ctor_def_id = variant.ctor_def_id.unwrap();
1191 Res::Def(DefKind::Ctor(CtorOf::Struct, variant.ctor_kind), ctor_def_id),
1196 let mut err = tcx.sess.struct_span_err(
1198 "the `Self` constructor can only be used with tuple or unit structs",
1200 if let Some(adt_def) = ty.ty_adt_def() {
1201 match adt_def.adt_kind() {
1203 err.help("did you mean to use one of the enum's variants?");
1205 AdtKind::Struct | AdtKind::Union => {
1206 err.span_suggestion(
1208 "use curly brackets",
1209 "Self { /* fields */ }",
1210 Applicability::HasPlaceholders,
1215 let reported = err.emit();
1216 return (tcx.ty_error_with_guaranteed(reported), res);
1222 let def_id = res.def_id();
1224 // The things we are substituting into the type should not contain
1225 // escaping late-bound regions, and nor should the base type scheme.
1226 let ty = tcx.type_of(def_id);
1228 let arg_count = GenericArgCountResult {
1229 explicit_late_bound,
1230 correct: if infer_args_for_err.is_empty() {
1233 Err(GenericArgCountMismatch::default())
1237 struct CreateCtorSubstsContext<'a, 'tcx> {
1238 fcx: &'a FnCtxt<'a, 'tcx>,
1240 path_segs: &'a [PathSeg],
1241 infer_args_for_err: &'a FxHashSet<usize>,
1242 segments: &'a [hir::PathSegment<'a>],
1244 impl<'tcx, 'a> CreateSubstsForGenericArgsCtxt<'a, 'tcx> for CreateCtorSubstsContext<'a, 'tcx> {
1248 ) -> (Option<&'a hir::GenericArgs<'a>>, bool) {
1249 if let Some(&PathSeg(_, index)) =
1250 self.path_segs.iter().find(|&PathSeg(did, _)| *did == def_id)
1252 // If we've encountered an `impl Trait`-related error, we're just
1253 // going to infer the arguments for better error messages.
1254 if !self.infer_args_for_err.contains(&index) {
1255 // Check whether the user has provided generic arguments.
1256 if let Some(ref data) = self.segments[index].args {
1257 return (Some(data), self.segments[index].infer_args);
1260 return (None, self.segments[index].infer_args);
1268 param: &ty::GenericParamDef,
1269 arg: &GenericArg<'_>,
1270 ) -> ty::GenericArg<'tcx> {
1271 match (¶m.kind, arg) {
1272 (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
1273 <dyn AstConv<'_>>::ast_region_to_region(self.fcx, lt, Some(param)).into()
1275 (GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
1276 self.fcx.to_ty(ty).into()
1278 (GenericParamDefKind::Const { .. }, GenericArg::Const(ct)) => {
1279 self.fcx.const_arg_to_const(&ct.value, param.def_id).into()
1281 (GenericParamDefKind::Type { .. }, GenericArg::Infer(inf)) => {
1282 self.fcx.ty_infer(Some(param), inf.span).into()
1284 (GenericParamDefKind::Const { .. }, GenericArg::Infer(inf)) => {
1285 let tcx = self.fcx.tcx();
1286 self.fcx.ct_infer(tcx.type_of(param.def_id), Some(param), inf.span).into()
1288 _ => unreachable!(),
1294 substs: Option<&[ty::GenericArg<'tcx>]>,
1295 param: &ty::GenericParamDef,
1297 ) -> ty::GenericArg<'tcx> {
1298 let tcx = self.fcx.tcx();
1300 GenericParamDefKind::Lifetime => {
1301 self.fcx.re_infer(Some(param), self.span).unwrap().into()
1303 GenericParamDefKind::Type { has_default, .. } => {
1304 if !infer_args && has_default {
1305 // If we have a default, then we it doesn't matter that we're not
1306 // inferring the type arguments: we provide the default where any
1308 let default = tcx.bound_type_of(param.def_id);
1310 .normalize_ty(self.span, default.subst(tcx, substs.unwrap()))
1313 // If no type arguments were provided, we have to infer them.
1314 // This case also occurs as a result of some malformed input, e.g.
1315 // a lifetime argument being given instead of a type parameter.
1316 // Using inference instead of `Error` gives better error messages.
1317 self.fcx.var_for_def(self.span, param)
1320 GenericParamDefKind::Const { has_default } => {
1321 if !infer_args && has_default {
1322 tcx.bound_const_param_default(param.def_id)
1323 .subst(tcx, substs.unwrap())
1326 self.fcx.var_for_def(self.span, param)
1333 let substs = self_ctor_substs.unwrap_or_else(|| {
1334 <dyn AstConv<'_>>::create_substs_for_generic_args(
1341 &mut CreateCtorSubstsContext {
1344 path_segs: &path_segs,
1345 infer_args_for_err: &infer_args_for_err,
1350 assert!(!substs.has_escaping_bound_vars());
1351 assert!(!ty.has_escaping_bound_vars());
1353 // First, store the "user substs" for later.
1354 self.write_user_type_annotation_from_substs(hir_id, def_id, substs, user_self_ty);
1356 self.add_required_obligations_for_hir(span, def_id, &substs, hir_id);
1358 // Substitute the values for the type parameters into the type of
1359 // the referenced item.
1360 let ty_substituted = self.instantiate_type_scheme(span, &substs, ty);
1362 if let Some(UserSelfTy { impl_def_id, self_ty }) = user_self_ty {
1363 // In the case of `Foo<T>::method` and `<Foo<T>>::method`, if `method`
1364 // is inherent, there is no `Self` parameter; instead, the impl needs
1365 // type parameters, which we can infer by unifying the provided `Self`
1366 // with the substituted impl type.
1367 // This also occurs for an enum variant on a type alias.
1368 let ty = tcx.type_of(impl_def_id);
1370 let impl_ty = self.instantiate_type_scheme(span, &substs, ty);
1371 match self.at(&self.misc(span), self.param_env).eq(impl_ty, self_ty) {
1372 Ok(ok) => self.register_infer_ok_obligations(ok),
1374 self.tcx.sess.delay_span_bug(
1377 "instantiate_value_path: (UFCS) {:?} was a subtype of {:?} but now is not?",
1386 debug!("instantiate_value_path: type of {:?} is {:?}", hir_id, ty_substituted);
1387 self.write_substs(hir_id, substs);
1389 (ty_substituted, res)
1392 /// Add all the obligations that are required, substituting and normalized appropriately.
1393 pub(crate) fn add_required_obligations_for_hir(
1397 substs: SubstsRef<'tcx>,
1400 self.add_required_obligations_with_code(span, def_id, substs, |idx, span| {
1401 if span.is_dummy() {
1402 ObligationCauseCode::ExprItemObligation(def_id, hir_id, idx)
1404 ObligationCauseCode::ExprBindingObligation(def_id, span, hir_id, idx)
1409 #[instrument(level = "debug", skip(self, code, span, substs))]
1410 fn add_required_obligations_with_code(
1414 substs: SubstsRef<'tcx>,
1415 code: impl Fn(usize, Span) -> ObligationCauseCode<'tcx>,
1417 let param_env = self.param_env;
1419 let remap = match self.tcx.def_kind(def_id) {
1420 // Associated consts have `Self: ~const Trait` bounds that should be satisfiable when
1421 // `Self: Trait` is satisfied because it does not matter whether the impl is `const`.
1422 // Therefore we have to remap the param env here to be non-const.
1423 hir::def::DefKind::AssocConst => true,
1424 hir::def::DefKind::AssocFn
1425 if self.tcx.def_kind(self.tcx.parent(def_id)) == hir::def::DefKind::Trait =>
1427 // N.B.: All callsites to this function involve checking a path expression.
1429 // When instantiating a trait method as a function item, it does not actually matter whether
1430 // the trait is `const` or not, or whether `where T: ~const Tr` needs to be satisfied as
1431 // `const`. If we were to introduce instantiating trait methods as `const fn`s, we would
1432 // check that after this, either via a bound `where F: ~const FnOnce` or when coercing to a
1433 // `const fn` pointer.
1435 // FIXME(fee1-dead) FIXME(const_trait_impl): update this doc when trait methods can satisfy
1436 // `~const FnOnce` or can be coerced to `const fn` pointer.
1441 let (bounds, _) = self.instantiate_bounds(span, def_id, &substs);
1443 for mut obligation in traits::predicates_for_generics(
1444 |idx, predicate_span| {
1445 traits::ObligationCause::new(span, self.body_id, code(idx, predicate_span))
1451 obligation = obligation.without_const(self.tcx);
1453 self.register_predicate(obligation);
1457 /// Resolves `typ` by a single level if `typ` is a type variable.
1458 /// If no resolution is possible, then an error is reported.
1459 /// Numeric inference variables may be left unresolved.
1460 pub fn structurally_resolved_type(&self, sp: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
1461 let ty = self.resolve_vars_with_obligations(ty);
1462 if !ty.is_ty_var() {
1465 if !self.is_tainted_by_errors() {
1467 .emit_inference_failure_err((**self).body_id, sp, ty.into(), E0282, true)
1470 let err = self.tcx.ty_error();
1471 self.demand_suptype(sp, err, ty);
1476 pub(in super::super) fn with_breakable_ctxt<F: FnOnce() -> R, R>(
1479 ctxt: BreakableCtxt<'tcx>,
1481 ) -> (BreakableCtxt<'tcx>, R) {
1484 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
1485 index = enclosing_breakables.stack.len();
1486 enclosing_breakables.by_id.insert(id, index);
1487 enclosing_breakables.stack.push(ctxt);
1491 let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
1492 debug_assert!(enclosing_breakables.stack.len() == index + 1);
1493 enclosing_breakables.by_id.remove(&id).expect("missing breakable context");
1494 enclosing_breakables.stack.pop().expect("missing breakable context")
1499 /// Instantiate a QueryResponse in a probe context, without a
1500 /// good ObligationCause.
1501 pub(in super::super) fn probe_instantiate_query_response(
1504 original_values: &OriginalQueryValues<'tcx>,
1505 query_result: &Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>,
1506 ) -> InferResult<'tcx, Ty<'tcx>> {
1507 self.instantiate_query_response_and_region_obligations(
1508 &traits::ObligationCause::misc(span, self.body_id),
1515 /// Returns `true` if an expression is contained inside the LHS of an assignment expression.
1516 pub(in super::super) fn expr_in_place(&self, mut expr_id: hir::HirId) -> bool {
1517 let mut contained_in_place = false;
1519 while let hir::Node::Expr(parent_expr) =
1520 self.tcx.hir().get(self.tcx.hir().get_parent_node(expr_id))
1522 match &parent_expr.kind {
1523 hir::ExprKind::Assign(lhs, ..) | hir::ExprKind::AssignOp(_, lhs, ..) => {
1524 if lhs.hir_id == expr_id {
1525 contained_in_place = true;
1531 expr_id = parent_expr.hir_id;