1 use rustc_errors::{Applicability, StashKey};
3 use rustc_hir::def_id::{DefId, LocalDefId};
4 use rustc_hir::intravisit;
5 use rustc_hir::intravisit::Visitor;
6 use rustc_hir::{HirId, Node};
7 use rustc_middle::hir::nested_filter;
8 use rustc_middle::ty::print::with_forced_trimmed_paths;
9 use rustc_middle::ty::subst::InternalSubsts;
10 use rustc_middle::ty::util::IntTypeExt;
11 use rustc_middle::ty::{self, DefIdTree, Ty, TyCtxt, TypeFolder, TypeSuperFoldable, TypeVisitable};
12 use rustc_span::symbol::Ident;
13 use rustc_span::{Span, DUMMY_SP};
16 use super::{bad_placeholder, is_suggestable_infer_ty};
17 use crate::errors::UnconstrainedOpaqueType;
19 /// Computes the relevant generic parameter for a potential generic const argument.
21 /// This should be called using the query `tcx.opt_const_param_of`.
22 pub(super) fn opt_const_param_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<DefId> {
24 let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
26 match tcx.hir().get(hir_id) {
27 Node::AnonConst(_) => (),
31 let parent_node_id = tcx.hir().get_parent_node(hir_id);
32 let parent_node = tcx.hir().get(parent_node_id);
34 let (generics, arg_idx) = match parent_node {
35 // This match arm is for when the def_id appears in a GAT whose
36 // path can't be resolved without typechecking e.g.
39 // type Assoc<const N: usize>;
40 // fn foo() -> Self::Assoc<3>;
43 // In the above code we would call this query with the def_id of 3 and
44 // the parent_node we match on would be the hir node for Self::Assoc<3>
46 // `Self::Assoc<3>` cant be resolved without typechecking here as we
47 // didnt write <Self as Foo>::Assoc<3>. If we did then another match
48 // arm would handle this.
50 // I believe this match arm is only needed for GAT but I am not 100% sure - BoxyUwU
51 Node::Ty(hir_ty @ Ty { kind: TyKind::Path(QPath::TypeRelative(_, segment)), .. }) => {
52 // Find the Item containing the associated type so we can create an ItemCtxt.
53 // Using the ItemCtxt convert the HIR for the unresolved assoc type into a
54 // ty which is a fully resolved projection.
55 // For the code example above, this would mean converting Self::Assoc<3>
56 // into a ty::Alias(ty::Projection, <Self as Foo>::Assoc<3>)
60 .filter(|(_, node)| matches!(node, Node::Item(_)))
64 let item_did = tcx.hir().local_def_id(item_hir_id).to_def_id();
65 let item_ctxt = &ItemCtxt::new(tcx, item_did) as &dyn crate::astconv::AstConv<'_>;
66 let ty = item_ctxt.ast_ty_to_ty(hir_ty);
68 // Iterate through the generics of the projection to find the one that corresponds to
69 // the def_id that this query was called with. We filter to only type and const args here
70 // as a precaution for if it's ever allowed to elide lifetimes in GAT's. It currently isn't
71 // but it can't hurt to be safe ^^
72 if let ty::Alias(ty::Projection, projection) = ty.kind() {
73 let generics = tcx.generics_of(projection.def_id);
75 let arg_index = segment
80 .filter(|arg| arg.is_ty_or_const())
81 .position(|arg| arg.hir_id() == hir_id)
84 bug!("no arg matching AnonConst in segment");
89 // I dont think it's possible to reach this but I'm not 100% sure - BoxyUwU
90 tcx.sess.delay_span_bug(
92 "unexpected non-GAT usage of an anon const",
99 ExprKind::MethodCall(segment, ..) | ExprKind::Path(QPath::TypeRelative(_, segment)),
102 let body_owner = tcx.hir().enclosing_body_owner(hir_id);
103 let tables = tcx.typeck(body_owner);
104 // This may fail in case the method/path does not actually exist.
105 // As there is no relevant param for `def_id`, we simply return
107 let type_dependent_def = tables.type_dependent_def_id(parent_node_id)?;
113 .filter(|arg| arg.is_ty_or_const())
114 .position(|arg| arg.hir_id() == hir_id)
117 bug!("no arg matching AnonConst in segment");
120 (tcx.generics_of(type_dependent_def), idx)
123 Node::Ty(&Ty { kind: TyKind::Path(_), .. })
124 | Node::Expr(&Expr { kind: ExprKind::Path(_) | ExprKind::Struct(..), .. })
127 let path = match parent_node {
128 Node::Ty(&Ty { kind: TyKind::Path(QPath::Resolved(_, path)), .. })
129 | Node::TraitRef(&TraitRef { path, .. }) => &*path,
132 ExprKind::Path(QPath::Resolved(_, path))
133 | ExprKind::Struct(&QPath::Resolved(_, path), ..),
136 let body_owner = tcx.hir().enclosing_body_owner(hir_id);
137 let _tables = tcx.typeck(body_owner);
141 if let Some(path) = get_path_containing_arg_in_pat(pat, hir_id) {
144 tcx.sess.delay_span_bug(
145 tcx.def_span(def_id),
146 &format!("unable to find const parent for {} in pat {:?}", hir_id, pat),
152 tcx.sess.delay_span_bug(
153 tcx.def_span(def_id),
154 &format!("unexpected const parent path {:?}", parent_node),
160 // We've encountered an `AnonConst` in some path, so we need to
161 // figure out which generic parameter it corresponds to and return
162 // the relevant type.
163 let Some((arg_index, segment)) = path.segments.iter().find_map(|seg| {
164 let args = seg.args?;
167 .filter(|arg| arg.is_ty_or_const())
168 .position(|arg| arg.hir_id() == hir_id)
169 .map(|index| (index, seg)).or_else(|| args.bindings
171 .filter_map(TypeBinding::opt_const)
172 .position(|ct| ct.hir_id == hir_id)
173 .map(|idx| (idx, seg)))
175 tcx.sess.delay_span_bug(
176 tcx.def_span(def_id),
177 "no arg matching AnonConst in path",
182 let generics = match tcx.res_generics_def_id(segment.res) {
183 Some(def_id) => tcx.generics_of(def_id),
185 tcx.sess.delay_span_bug(
186 tcx.def_span(def_id),
187 &format!("unexpected anon const res {:?} in path: {:?}", segment.res, path),
193 (generics, arg_index)
198 debug!(?parent_node);
199 debug!(?generics, ?arg_idx);
203 .filter(|param| param.kind.is_ty_or_const())
204 .nth(match generics.has_self && generics.parent.is_none() {
208 .and_then(|param| match param.kind {
209 ty::GenericParamDefKind::Const { .. } => {
217 fn get_path_containing_arg_in_pat<'hir>(
218 pat: &'hir hir::Pat<'hir>,
220 ) -> Option<&'hir hir::Path<'hir>> {
223 let is_arg_in_path = |p: &hir::Path<'_>| {
226 .filter_map(|seg| seg.args)
227 .flat_map(|args| args.args)
228 .any(|arg| arg.hir_id() == arg_id)
230 let mut arg_path = None;
231 pat.walk(|pat| match pat.kind {
232 PatKind::Struct(QPath::Resolved(_, path), _, _)
233 | PatKind::TupleStruct(QPath::Resolved(_, path), _, _)
234 | PatKind::Path(QPath::Resolved(_, path))
235 if is_arg_in_path(path) =>
237 arg_path = Some(path);
245 pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
246 let def_id = def_id.expect_local();
249 let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
251 let icx = ItemCtxt::new(tcx, def_id.to_def_id());
253 match tcx.hir().get(hir_id) {
254 Node::TraitItem(item) => match item.kind {
255 TraitItemKind::Fn(..) => {
256 let substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id());
257 tcx.mk_fn_def(def_id.to_def_id(), substs)
259 TraitItemKind::Const(ty, body_id) => body_id
260 .and_then(|body_id| {
261 if is_suggestable_infer_ty(ty) {
262 Some(infer_placeholder_type(
263 tcx, def_id, body_id, ty.span, item.ident, "constant",
269 .unwrap_or_else(|| icx.to_ty(ty)),
270 TraitItemKind::Type(_, Some(ty)) => icx.to_ty(ty),
271 TraitItemKind::Type(_, None) => {
272 span_bug!(item.span, "associated type missing default");
276 Node::ImplItem(item) => match item.kind {
277 ImplItemKind::Fn(..) => {
278 let substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id());
279 tcx.mk_fn_def(def_id.to_def_id(), substs)
281 ImplItemKind::Const(ty, body_id) => {
282 if is_suggestable_infer_ty(ty) {
283 infer_placeholder_type(tcx, def_id, body_id, ty.span, item.ident, "constant")
288 ImplItemKind::Type(ty) => {
289 if tcx.impl_trait_ref(tcx.hir().get_parent_item(hir_id)).is_none() {
290 check_feature_inherent_assoc_ty(tcx, item.span);
297 Node::Item(item) => {
299 ItemKind::Static(ty, .., body_id) => {
300 if is_suggestable_infer_ty(ty) {
301 infer_placeholder_type(
313 ItemKind::Const(ty, body_id) => {
314 if is_suggestable_infer_ty(ty) {
315 infer_placeholder_type(
316 tcx, def_id, body_id, ty.span, item.ident, "constant",
322 ItemKind::TyAlias(self_ty, _) => icx.to_ty(self_ty),
323 ItemKind::Impl(hir::Impl { self_ty, .. }) => {
324 match self_ty.find_self_aliases() {
325 spans if spans.len() > 0 => {
326 tcx.sess.emit_err(crate::errors::SelfInImplSelf { span: spans.into(), note: (), });
329 _ => icx.to_ty(*self_ty),
332 ItemKind::Fn(..) => {
333 let substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id());
334 tcx.mk_fn_def(def_id.to_def_id(), substs)
336 ItemKind::Enum(..) | ItemKind::Struct(..) | ItemKind::Union(..) => {
337 let def = tcx.adt_def(def_id);
338 let substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id());
339 tcx.mk_adt(def, substs)
341 ItemKind::OpaqueTy(OpaqueTy { origin: hir::OpaqueTyOrigin::TyAlias, .. }) => {
342 find_opaque_ty_constraints_for_tait(tcx, def_id)
344 // Opaque types desugared from `impl Trait`.
345 ItemKind::OpaqueTy(OpaqueTy {
347 hir::OpaqueTyOrigin::FnReturn(owner) | hir::OpaqueTyOrigin::AsyncFn(owner),
352 assert!(tcx.impl_defaultness(owner).has_value());
354 find_opaque_ty_constraints_for_rpit(tcx, def_id, owner)
357 | ItemKind::TraitAlias(..)
358 | ItemKind::Macro(..)
360 | ItemKind::ForeignMod { .. }
361 | ItemKind::GlobalAsm(..)
362 | ItemKind::ExternCrate(..)
363 | ItemKind::Use(..) => {
366 "compute_type_of_item: unexpected item type: {:?}",
373 Node::ForeignItem(foreign_item) => match foreign_item.kind {
374 ForeignItemKind::Fn(..) => {
375 let substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id());
376 tcx.mk_fn_def(def_id.to_def_id(), substs)
378 ForeignItemKind::Static(t, _) => icx.to_ty(t),
379 ForeignItemKind::Type => tcx.mk_foreign(def_id.to_def_id()),
382 Node::Ctor(&ref def) | Node::Variant(Variant { data: ref def, .. }) => match *def {
383 VariantData::Unit(..) | VariantData::Struct(..) => {
384 tcx.type_of(tcx.hir().get_parent_item(hir_id))
386 VariantData::Tuple(..) => {
387 let substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id());
388 tcx.mk_fn_def(def_id.to_def_id(), substs)
392 Node::Field(field) => icx.to_ty(field.ty),
394 Node::Expr(&Expr { kind: ExprKind::Closure { .. }, .. }) => {
395 tcx.typeck(def_id).node_type(hir_id)
398 Node::AnonConst(_) if let Some(param) = tcx.opt_const_param_of(def_id) => {
399 // We defer to `type_of` of the corresponding parameter
400 // for generic arguments.
404 Node::AnonConst(_) => {
405 let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
407 Node::Ty(&Ty { kind: TyKind::Array(_, ref constant), .. })
408 | Node::Expr(&Expr { kind: ExprKind::Repeat(_, ref constant), .. })
409 if constant.hir_id() == hir_id =>
413 Node::Ty(&Ty { kind: TyKind::Typeof(ref e), .. }) if e.hir_id == hir_id => {
414 tcx.typeck(def_id).node_type(e.hir_id)
417 Node::Expr(&Expr { kind: ExprKind::ConstBlock(ref anon_const), .. })
418 if anon_const.hir_id == hir_id =>
420 let substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id());
421 substs.as_inline_const().ty()
424 Node::Expr(&Expr { kind: ExprKind::InlineAsm(asm), .. })
425 | Node::Item(&Item { kind: ItemKind::GlobalAsm(asm), .. })
426 if asm.operands.iter().any(|(op, _op_sp)| match op {
427 hir::InlineAsmOperand::Const { anon_const }
428 | hir::InlineAsmOperand::SymFn { anon_const } => {
429 anon_const.hir_id == hir_id
434 tcx.typeck(def_id).node_type(hir_id)
437 Node::Variant(Variant { disr_expr: Some(ref e), .. }) if e.hir_id == hir_id => {
438 tcx.adt_def(tcx.hir().get_parent_item(hir_id)).repr().discr_type().to_ty(tcx)
442 binding @ &TypeBinding {
444 kind: TypeBindingKind::Equality { term: Term::Const(ref e) },
447 ) if let Node::TraitRef(trait_ref) =
448 tcx.hir().get(tcx.hir().get_parent_node(binding_id))
449 && e.hir_id == hir_id =>
451 let Some(trait_def_id) = trait_ref.trait_def_id() else {
452 return tcx.ty_error_with_message(DUMMY_SP, "Could not find trait");
454 let assoc_items = tcx.associated_items(trait_def_id);
455 let assoc_item = assoc_items.find_by_name_and_kind(
458 ty::AssocKind::Const,
461 if let Some(assoc_item) = assoc_item {
462 tcx.type_of(assoc_item.def_id)
464 // FIXME(associated_const_equality): add a useful error message here.
465 tcx.ty_error_with_message(
467 "Could not find associated const on trait",
473 binding @ &TypeBinding { hir_id: binding_id, gen_args, ref kind, .. },
474 ) if let Node::TraitRef(trait_ref) =
475 tcx.hir().get(tcx.hir().get_parent_node(binding_id))
476 && let Some((idx, _)) =
477 gen_args.args.iter().enumerate().find(|(_, arg)| {
478 if let GenericArg::Const(ct) = arg {
479 ct.value.hir_id == hir_id
485 let Some(trait_def_id) = trait_ref.trait_def_id() else {
486 return tcx.ty_error_with_message(DUMMY_SP, "Could not find trait");
488 let assoc_items = tcx.associated_items(trait_def_id);
489 let assoc_item = assoc_items.find_by_name_and_kind(
493 // I think `<A: T>` type bindings requires that `A` is a type
494 TypeBindingKind::Constraint { .. }
495 | TypeBindingKind::Equality { term: Term::Ty(..) } => {
498 TypeBindingKind::Equality { term: Term::Const(..) } => {
505 = assoc_item.map(|item| &tcx.generics_of(item.def_id).params[idx]).filter(|param| param.kind.is_ty_or_const())
507 tcx.type_of(param.def_id)
509 // FIXME(associated_const_equality): add a useful error message here.
510 tcx.ty_error_with_message(
512 "Could not find associated const on trait",
517 Node::GenericParam(&GenericParam {
518 def_id: param_def_id,
519 kind: GenericParamKind::Const { default: Some(ct), .. },
521 }) if ct.hir_id == hir_id => tcx.type_of(param_def_id),
523 x => tcx.ty_error_with_message(
525 &format!("unexpected const parent in type_of(): {x:?}"),
530 Node::GenericParam(param) => match ¶m.kind {
531 GenericParamKind::Type { default: Some(ty), .. }
532 | GenericParamKind::Const { ty, .. } => icx.to_ty(ty),
533 x => bug!("unexpected non-type Node::GenericParam: {:?}", x),
537 bug!("unexpected sort of node in type_of(): {:?}", x);
542 #[instrument(skip(tcx), level = "debug")]
543 /// Checks "defining uses" of opaque `impl Trait` types to ensure that they meet the restrictions
544 /// laid for "higher-order pattern unification".
545 /// This ensures that inference is tractable.
546 /// In particular, definitions of opaque types can only use other generics as arguments,
547 /// and they cannot repeat an argument. Example:
549 /// ```ignore (illustrative)
550 /// type Foo<A, B> = impl Bar<A, B>;
552 /// // Okay -- `Foo` is applied to two distinct, generic types.
553 /// fn a<T, U>() -> Foo<T, U> { .. }
555 /// // Not okay -- `Foo` is applied to `T` twice.
556 /// fn b<T>() -> Foo<T, T> { .. }
558 /// // Not okay -- `Foo` is applied to a non-generic type.
559 /// fn b<T>() -> Foo<T, u32> { .. }
562 fn find_opaque_ty_constraints_for_tait(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Ty<'_> {
563 use rustc_hir::{Expr, ImplItem, Item, TraitItem};
565 struct ConstraintLocator<'tcx> {
568 /// def_id of the opaque type whose defining uses are being checked
571 /// as we walk the defining uses, we are checking that all of them
572 /// define the same hidden type. This variable is set to `Some`
573 /// with the first type that we find, and then later types are
574 /// checked against it (we also carry the span of that first
576 found: Option<ty::OpaqueHiddenType<'tcx>>,
578 /// In the presence of dead code, typeck may figure out a hidden type
579 /// while borrowck will now. We collect these cases here and check at
580 /// the end that we actually found a type that matches (modulo regions).
581 typeck_types: Vec<ty::OpaqueHiddenType<'tcx>>,
584 impl ConstraintLocator<'_> {
585 #[instrument(skip(self), level = "debug")]
586 fn check(&mut self, item_def_id: LocalDefId) {
587 // Don't try to check items that cannot possibly constrain the type.
588 if !self.tcx.has_typeck_results(item_def_id) {
589 debug!("no constraint: no typeck results");
592 // Calling `mir_borrowck` can lead to cycle errors through
593 // const-checking, avoid calling it if we don't have to.
595 // type Foo = impl Fn() -> usize; // when computing type for this
596 // const fn bar() -> Foo {
599 // const BAZR: Foo = bar(); // we would mir-borrowck this, causing cycles
600 // // because we again need to reveal `Foo` so we can check whether the
601 // // constant does not contain interior mutability.
603 let tables = self.tcx.typeck(item_def_id);
604 if let Some(_) = tables.tainted_by_errors {
605 self.found = Some(ty::OpaqueHiddenType { span: DUMMY_SP, ty: self.tcx.ty_error() });
608 let Some(&typeck_hidden_ty) = tables.concrete_opaque_types.get(&self.def_id) else {
609 debug!("no constraints in typeck results");
612 if self.typeck_types.iter().all(|prev| prev.ty != typeck_hidden_ty.ty) {
613 self.typeck_types.push(typeck_hidden_ty);
616 // Use borrowck to get the type with unerased regions.
617 let concrete_opaque_types = &self.tcx.mir_borrowck(item_def_id).concrete_opaque_types;
618 debug!(?concrete_opaque_types);
619 if let Some(&concrete_type) = concrete_opaque_types.get(&self.def_id) {
620 debug!(?concrete_type, "found constraint");
621 if let Some(prev) = &mut self.found {
622 if concrete_type.ty != prev.ty && !(concrete_type, prev.ty).references_error() {
623 prev.report_mismatch(&concrete_type, self.tcx);
624 prev.ty = self.tcx.ty_error();
627 self.found = Some(concrete_type);
633 impl<'tcx> intravisit::Visitor<'tcx> for ConstraintLocator<'tcx> {
634 type NestedFilter = nested_filter::All;
636 fn nested_visit_map(&mut self) -> Self::Map {
639 fn visit_expr(&mut self, ex: &'tcx Expr<'tcx>) {
640 if let hir::ExprKind::Closure(closure) = ex.kind {
641 self.check(closure.def_id);
643 intravisit::walk_expr(self, ex);
645 fn visit_item(&mut self, it: &'tcx Item<'tcx>) {
646 trace!(?it.owner_id);
647 // The opaque type itself or its children are not within its reveal scope.
648 if it.owner_id.def_id != self.def_id {
649 self.check(it.owner_id.def_id);
650 intravisit::walk_item(self, it);
653 fn visit_impl_item(&mut self, it: &'tcx ImplItem<'tcx>) {
654 trace!(?it.owner_id);
655 // The opaque type itself or its children are not within its reveal scope.
656 if it.owner_id.def_id != self.def_id {
657 self.check(it.owner_id.def_id);
658 intravisit::walk_impl_item(self, it);
661 fn visit_trait_item(&mut self, it: &'tcx TraitItem<'tcx>) {
662 trace!(?it.owner_id);
663 self.check(it.owner_id.def_id);
664 intravisit::walk_trait_item(self, it);
668 let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
669 let scope = tcx.hir().get_defining_scope(hir_id);
670 let mut locator = ConstraintLocator { def_id, tcx, found: None, typeck_types: vec![] };
674 if scope == hir::CRATE_HIR_ID {
675 tcx.hir().walk_toplevel_module(&mut locator);
677 trace!("scope={:#?}", tcx.hir().get(scope));
678 match tcx.hir().get(scope) {
679 // We explicitly call `visit_*` methods, instead of using `intravisit::walk_*` methods
680 // This allows our visitor to process the defining item itself, causing
681 // it to pick up any 'sibling' defining uses.
683 // For example, this code:
686 // type Blah = impl Debug;
687 // let my_closure = || -> Blah { true };
691 // requires us to explicitly process `foo()` in order
692 // to notice the defining usage of `Blah`.
693 Node::Item(it) => locator.visit_item(it),
694 Node::ImplItem(it) => locator.visit_impl_item(it),
695 Node::TraitItem(it) => locator.visit_trait_item(it),
696 other => bug!("{:?} is not a valid scope for an opaque type item", other),
700 let Some(hidden) = locator.found else {
701 let reported = tcx.sess.emit_err(UnconstrainedOpaqueType {
702 span: tcx.def_span(def_id),
703 name: tcx.item_name(tcx.local_parent(def_id).to_def_id()),
704 what: match tcx.hir().get(scope) {
705 _ if scope == hir::CRATE_HIR_ID => "module",
706 Node::Item(hir::Item { kind: hir::ItemKind::Mod(_), .. }) => "module",
707 Node::Item(hir::Item { kind: hir::ItemKind::Impl(_), .. }) => "impl",
711 return tcx.ty_error_with_guaranteed(reported);
714 // Only check against typeck if we didn't already error
715 if !hidden.ty.references_error() {
716 for concrete_type in locator.typeck_types {
717 if tcx.erase_regions(concrete_type.ty) != tcx.erase_regions(hidden.ty)
718 && !(concrete_type, hidden).references_error()
720 hidden.report_mismatch(&concrete_type, tcx);
728 fn find_opaque_ty_constraints_for_rpit(
731 owner_def_id: LocalDefId,
733 use rustc_hir::{Expr, ImplItem, Item, TraitItem};
735 struct ConstraintChecker<'tcx> {
738 /// def_id of the opaque type whose defining uses are being checked
741 found: ty::OpaqueHiddenType<'tcx>,
744 impl ConstraintChecker<'_> {
745 #[instrument(skip(self), level = "debug")]
746 fn check(&self, def_id: LocalDefId) {
747 // Use borrowck to get the type with unerased regions.
748 let concrete_opaque_types = &self.tcx.mir_borrowck(def_id).concrete_opaque_types;
749 debug!(?concrete_opaque_types);
750 for &(def_id, concrete_type) in concrete_opaque_types {
751 if def_id != self.def_id {
752 // Ignore constraints for other opaque types.
756 debug!(?concrete_type, "found constraint");
758 if concrete_type.ty != self.found.ty
759 && !(concrete_type, self.found).references_error()
761 self.found.report_mismatch(&concrete_type, self.tcx);
767 impl<'tcx> intravisit::Visitor<'tcx> for ConstraintChecker<'tcx> {
768 type NestedFilter = nested_filter::OnlyBodies;
770 fn nested_visit_map(&mut self) -> Self::Map {
773 fn visit_expr(&mut self, ex: &'tcx Expr<'tcx>) {
774 if let hir::ExprKind::Closure(closure) = ex.kind {
775 self.check(closure.def_id);
777 intravisit::walk_expr(self, ex);
779 fn visit_item(&mut self, it: &'tcx Item<'tcx>) {
780 trace!(?it.owner_id);
781 // The opaque type itself or its children are not within its reveal scope.
782 if it.owner_id.def_id != self.def_id {
783 self.check(it.owner_id.def_id);
784 intravisit::walk_item(self, it);
787 fn visit_impl_item(&mut self, it: &'tcx ImplItem<'tcx>) {
788 trace!(?it.owner_id);
789 // The opaque type itself or its children are not within its reveal scope.
790 if it.owner_id.def_id != self.def_id {
791 self.check(it.owner_id.def_id);
792 intravisit::walk_impl_item(self, it);
795 fn visit_trait_item(&mut self, it: &'tcx TraitItem<'tcx>) {
796 trace!(?it.owner_id);
797 self.check(it.owner_id.def_id);
798 intravisit::walk_trait_item(self, it);
802 let concrete = tcx.mir_borrowck(owner_def_id).concrete_opaque_types.get(&def_id).copied();
804 if let Some(concrete) = concrete {
805 let scope = tcx.hir().local_def_id_to_hir_id(owner_def_id);
807 let mut locator = ConstraintChecker { def_id, tcx, found: concrete };
809 match tcx.hir().get(scope) {
810 Node::Item(it) => intravisit::walk_item(&mut locator, it),
811 Node::ImplItem(it) => intravisit::walk_impl_item(&mut locator, it),
812 Node::TraitItem(it) => intravisit::walk_trait_item(&mut locator, it),
813 other => bug!("{:?} is not a valid scope for an opaque type item", other),
817 concrete.map(|concrete| concrete.ty).unwrap_or_else(|| {
818 let table = tcx.typeck(owner_def_id);
819 if let Some(_) = table.tainted_by_errors {
821 // owner fn prevented us from populating
822 // the `concrete_opaque_types` table.
825 table.concrete_opaque_types.get(&def_id).map(|ty| ty.ty).unwrap_or_else(|| {
826 // We failed to resolve the opaque type or it
827 // resolves to itself. We interpret this as the
828 // no values of the hidden type ever being constructed,
829 // so we can just make the hidden type be `!`.
830 // For backwards compatibility reasons, we fall back to
831 // `()` until we the diverging default is changed.
832 tcx.mk_diverging_default()
838 fn infer_placeholder_type<'a>(
841 body_id: hir::BodyId,
846 // Attempts to make the type nameable by turning FnDefs into FnPtrs.
847 struct MakeNameable<'tcx> {
852 impl<'tcx> MakeNameable<'tcx> {
853 fn new(tcx: TyCtxt<'tcx>) -> Self {
854 MakeNameable { success: true, tcx }
858 impl<'tcx> TypeFolder<'tcx> for MakeNameable<'tcx> {
859 fn tcx(&self) -> TyCtxt<'tcx> {
863 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
869 ty::FnDef(def_id, _) => self.tcx.mk_fn_ptr(self.tcx.fn_sig(*def_id)),
870 // FIXME: non-capturing closures should also suggest a function pointer
871 ty::Closure(..) | ty::Generator(..) => {
872 self.success = false;
875 _ => ty.super_fold_with(self),
880 let ty = tcx.diagnostic_only_typeck(def_id).node_type(body_id.hir_id);
882 // If this came from a free `const` or `static mut?` item,
883 // then the user may have written e.g. `const A = 42;`.
884 // In this case, the parser has stashed a diagnostic for
885 // us to improve in typeck so we do that now.
886 match tcx.sess.diagnostic().steal_diagnostic(span, StashKey::ItemNoType) {
888 if !ty.references_error() {
889 // Only suggest adding `:` if it was missing (and suggested by parsing diagnostic)
890 let colon = if span == item_ident.span.shrink_to_hi() { ":" } else { "" };
892 // The parser provided a sub-optimal `HasPlaceholders` suggestion for the type.
893 // We are typeck and have the real type, so remove that and suggest the actual type.
894 // FIXME(eddyb) this looks like it should be functionality on `Diagnostic`.
895 if let Ok(suggestions) = &mut err.suggestions {
899 // Suggesting unnameable types won't help.
900 let mut mk_nameable = MakeNameable::new(tcx);
901 let ty = mk_nameable.fold_ty(ty);
902 let sugg_ty = if mk_nameable.success { Some(ty) } else { None };
903 if let Some(sugg_ty) = sugg_ty {
906 &format!("provide a type for the {item}", item = kind),
907 format!("{colon} {sugg_ty}"),
908 Applicability::MachineApplicable,
911 with_forced_trimmed_paths!(err.span_note(
912 tcx.hir().body(body_id).value.span,
913 &format!("however, the inferred type `{ty}` cannot be named"),
921 let mut diag = bad_placeholder(tcx, vec![span], kind);
923 if !ty.references_error() {
924 let mut mk_nameable = MakeNameable::new(tcx);
925 let ty = mk_nameable.fold_ty(ty);
926 let sugg_ty = if mk_nameable.success { Some(ty) } else { None };
927 if let Some(sugg_ty) = sugg_ty {
928 diag.span_suggestion(
930 "replace with the correct type",
932 Applicability::MaybeIncorrect,
935 with_forced_trimmed_paths!(diag.span_note(
936 tcx.hir().body(body_id).value.span,
937 &format!("however, the inferred type `{ty}` cannot be named"),
946 // Typeck doesn't expect erased regions to be returned from `type_of`.
947 tcx.fold_regions(ty, |r, _| match *r {
948 ty::ReErased => tcx.lifetimes.re_static,
953 fn check_feature_inherent_assoc_ty(tcx: TyCtxt<'_>, span: Span) {
954 if !tcx.features().inherent_associated_types {
955 use rustc_session::parse::feature_err;
956 use rustc_span::symbol::sym;
958 &tcx.sess.parse_sess,
959 sym::inherent_associated_types,
961 "inherent associated types are unstable",