1 //! "Collection" is the process of determining the type and other external
2 //! details of each item in Rust. Collection is specifically concerned
3 //! with *inter-procedural* things -- for example, for a function
4 //! definition, collection will figure out the type and signature of the
5 //! function, but it will not visit the *body* of the function in any way,
6 //! nor examine type annotations on local variables (that's the job of
9 //! Collecting is ultimately defined by a bundle of queries that
10 //! inquire after various facts about the items in the crate (e.g.,
11 //! `type_of`, `generics_of`, `predicates_of`, etc). See the `provide` function
14 //! At present, however, we do run collection across all items in the
15 //! crate as a kind of pass. This should eventually be factored away.
17 use crate::astconv::{AstConv, Bounds, SizedByDefault};
18 use crate::constrained_generic_params as cgp;
19 use crate::check::intrinsic::intrinsic_operation_unsafety;
21 use crate::middle::resolve_lifetime as rl;
22 use crate::middle::weak_lang_items;
23 use rustc::mir::mono::Linkage;
24 use rustc::ty::query::Providers;
25 use rustc::ty::subst::{Subst, InternalSubsts};
26 use rustc::ty::util::Discr;
27 use rustc::ty::util::IntTypeExt;
28 use rustc::ty::subst::GenericArgKind;
29 use rustc::ty::{self, AdtKind, DefIdTree, ToPolyTraitRef, Ty, TyCtxt, Const};
30 use rustc::ty::{ReprOptions, ToPredicate};
31 use rustc::util::captures::Captures;
32 use rustc::util::nodemap::FxHashMap;
33 use rustc_target::spec::abi;
36 use syntax::ast::{Ident, MetaItemKind};
37 use syntax::attr::{InlineAttr, OptimizeAttr, list_contains_name, mark_used};
38 use syntax::feature_gate;
39 use syntax::symbol::{kw, Symbol, sym};
40 use syntax_pos::{Span, DUMMY_SP};
42 use rustc::hir::def::{CtorKind, Res, DefKind};
44 use rustc::hir::def_id::{DefId, LOCAL_CRATE};
45 use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
46 use rustc::hir::GenericParamKind;
47 use rustc::hir::{self, CodegenFnAttrFlags, CodegenFnAttrs, Unsafety};
49 use errors::{Applicability, StashKey};
51 use rustc_error_codes::*;
53 struct OnlySelfBounds(bool);
55 ///////////////////////////////////////////////////////////////////////////
58 fn collect_mod_item_types(tcx: TyCtxt<'_>, module_def_id: DefId) {
59 tcx.hir().visit_item_likes_in_module(
61 &mut CollectItemTypesVisitor { tcx }.as_deep_visitor()
65 pub fn provide(providers: &mut Providers<'_>) {
66 *providers = Providers {
70 predicates_defined_on,
71 explicit_predicates_of,
73 type_param_predicates,
82 collect_mod_item_types,
87 ///////////////////////////////////////////////////////////////////////////
89 /// Context specific to some particular item. This is what implements
90 /// `AstConv`. It has information about the predicates that are defined
91 /// on the trait. Unfortunately, this predicate information is
92 /// available in various different forms at various points in the
93 /// process. So we can't just store a pointer to e.g., the AST or the
94 /// parsed ty form, we have to be more flexible. To this end, the
95 /// `ItemCtxt` is parameterized by a `DefId` that it uses to satisfy
96 /// `get_type_parameter_bounds` requests, drawing the information from
97 /// the AST (`hir::Generics`), recursively.
98 pub struct ItemCtxt<'tcx> {
103 ///////////////////////////////////////////////////////////////////////////
105 struct CollectItemTypesVisitor<'tcx> {
109 impl Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
110 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
111 NestedVisitorMap::OnlyBodies(&self.tcx.hir())
114 fn visit_item(&mut self, item: &'tcx hir::Item) {
115 convert_item(self.tcx, item.hir_id);
116 intravisit::walk_item(self, item);
119 fn visit_generics(&mut self, generics: &'tcx hir::Generics) {
120 for param in &generics.params {
122 hir::GenericParamKind::Lifetime { .. } => {}
123 hir::GenericParamKind::Type {
126 let def_id = self.tcx.hir().local_def_id(param.hir_id);
127 self.tcx.type_of(def_id);
129 hir::GenericParamKind::Type { .. } => {}
130 hir::GenericParamKind::Const { .. } => {
131 let def_id = self.tcx.hir().local_def_id(param.hir_id);
132 self.tcx.type_of(def_id);
136 intravisit::walk_generics(self, generics);
139 fn visit_expr(&mut self, expr: &'tcx hir::Expr) {
140 if let hir::ExprKind::Closure(..) = expr.kind {
141 let def_id = self.tcx.hir().local_def_id(expr.hir_id);
142 self.tcx.generics_of(def_id);
143 self.tcx.type_of(def_id);
145 intravisit::walk_expr(self, expr);
148 fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem) {
149 convert_trait_item(self.tcx, trait_item.hir_id);
150 intravisit::walk_trait_item(self, trait_item);
153 fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem) {
154 convert_impl_item(self.tcx, impl_item.hir_id);
155 intravisit::walk_impl_item(self, impl_item);
159 ///////////////////////////////////////////////////////////////////////////
160 // Utility types and common code for the above passes.
162 fn bad_placeholder_type(tcx: TyCtxt<'tcx>, span: Span) -> errors::DiagnosticBuilder<'tcx> {
163 let mut diag = struct_span_err!(
167 "the type placeholder `_` is not allowed within types on item signatures",
169 diag.span_label(span, "not allowed in type signatures");
173 impl ItemCtxt<'tcx> {
174 pub fn new(tcx: TyCtxt<'tcx>, item_def_id: DefId) -> ItemCtxt<'tcx> {
175 ItemCtxt { tcx, item_def_id }
178 pub fn to_ty(&self, ast_ty: &'tcx hir::Ty) -> Ty<'tcx> {
179 AstConv::ast_ty_to_ty(self, ast_ty)
183 impl AstConv<'tcx> for ItemCtxt<'tcx> {
184 fn tcx(&self) -> TyCtxt<'tcx> {
188 fn item_def_id(&self) -> Option<DefId> {
189 Some(self.item_def_id)
192 fn get_type_parameter_bounds(&self, span: Span, def_id: DefId) -> ty::GenericPredicates<'tcx> {
195 .type_param_predicates((self.item_def_id, def_id))
200 _: Option<&ty::GenericParamDef>,
202 ) -> Option<ty::Region<'tcx>> {
206 fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
207 bad_placeholder_type(self.tcx(), span).emit();
215 _: Option<&ty::GenericParamDef>,
217 ) -> &'tcx Const<'tcx> {
218 bad_placeholder_type(self.tcx(), span).emit();
220 self.tcx().consts.err
223 fn projected_ty_from_poly_trait_ref(
227 poly_trait_ref: ty::PolyTraitRef<'tcx>,
229 if let Some(trait_ref) = poly_trait_ref.no_bound_vars() {
230 self.tcx().mk_projection(item_def_id, trait_ref.substs)
232 // There are no late-bound regions; we can just ignore the binder.
237 "cannot extract an associated type from a higher-ranked trait bound \
244 fn normalize_ty(&self, _span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
245 // Types in item signatures are not normalized to avoid undue dependencies.
249 fn set_tainted_by_errors(&self) {
250 // There's no obvious place to track this, so just let it go.
253 fn record_ty(&self, _hir_id: hir::HirId, _ty: Ty<'tcx>, _span: Span) {
254 // There's no place to record types from signatures?
258 /// Returns the predicates defined on `item_def_id` of the form
259 /// `X: Foo` where `X` is the type parameter `def_id`.
260 fn type_param_predicates(
262 (item_def_id, def_id): (DefId, DefId),
263 ) -> ty::GenericPredicates<'_> {
266 // In the AST, bounds can derive from two places. Either
267 // written inline like `<T: Foo>` or in a where-clause like
270 let param_id = tcx.hir().as_local_hir_id(def_id).unwrap();
271 let param_owner = tcx.hir().ty_param_owner(param_id);
272 let param_owner_def_id = tcx.hir().local_def_id(param_owner);
273 let generics = tcx.generics_of(param_owner_def_id);
274 let index = generics.param_def_id_to_index[&def_id];
275 let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(param_id));
277 // Don't look for bounds where the type parameter isn't in scope.
278 let parent = if item_def_id == param_owner_def_id {
281 tcx.generics_of(item_def_id).parent
284 let mut result = parent.map(|parent| {
285 let icx = ItemCtxt::new(tcx, parent);
286 icx.get_type_parameter_bounds(DUMMY_SP, def_id)
287 }).unwrap_or_default();
288 let mut extend = None;
290 let item_hir_id = tcx.hir().as_local_hir_id(item_def_id).unwrap();
291 let ast_generics = match tcx.hir().get(item_hir_id) {
292 Node::TraitItem(item) => &item.generics,
294 Node::ImplItem(item) => &item.generics,
296 Node::Item(item) => {
298 ItemKind::Fn(.., ref generics, _)
299 | ItemKind::Impl(_, _, _, ref generics, ..)
300 | ItemKind::TyAlias(_, ref generics)
301 | ItemKind::OpaqueTy(OpaqueTy {
306 | ItemKind::Enum(_, ref generics)
307 | ItemKind::Struct(_, ref generics)
308 | ItemKind::Union(_, ref generics) => generics,
309 ItemKind::Trait(_, _, ref generics, ..) => {
310 // Implied `Self: Trait` and supertrait bounds.
311 if param_id == item_hir_id {
312 let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id);
313 extend = Some((identity_trait_ref.to_predicate(), item.span));
321 Node::ForeignItem(item) => match item.kind {
322 ForeignItemKind::Fn(_, _, ref generics) => generics,
329 let icx = ItemCtxt::new(tcx, item_def_id);
330 let extra_predicates = extend.into_iter().chain(
331 icx.type_parameter_bounds_in_generics(ast_generics, param_id, ty, OnlySelfBounds(true))
333 .filter(|(predicate, _)| {
335 ty::Predicate::Trait(ref data) => data.skip_binder().self_ty().is_param(index),
340 result.predicates = tcx.arena.alloc_from_iter(
341 result.predicates.iter().copied().chain(extra_predicates),
346 impl ItemCtxt<'tcx> {
347 /// Finds bounds from `hir::Generics`. This requires scanning through the
348 /// AST. We do this to avoid having to convert *all* the bounds, which
349 /// would create artificial cycles. Instead, we can only convert the
350 /// bounds for a type parameter `X` if `X::Foo` is used.
351 fn type_parameter_bounds_in_generics(
353 ast_generics: &'tcx hir::Generics,
354 param_id: hir::HirId,
356 only_self_bounds: OnlySelfBounds,
357 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
358 let from_ty_params = ast_generics
361 .filter_map(|param| match param.kind {
362 GenericParamKind::Type { .. } if param.hir_id == param_id => Some(¶m.bounds),
365 .flat_map(|bounds| bounds.iter())
366 .flat_map(|b| predicates_from_bound(self, ty, b));
368 let from_where_clauses = ast_generics
372 .filter_map(|wp| match *wp {
373 hir::WherePredicate::BoundPredicate(ref bp) => Some(bp),
377 let bt = if is_param(self.tcx, &bp.bounded_ty, param_id) {
379 } else if !only_self_bounds.0 {
380 Some(self.to_ty(&bp.bounded_ty))
384 bp.bounds.iter().filter_map(move |b| bt.map(|bt| (bt, b)))
386 .flat_map(|(bt, b)| predicates_from_bound(self, bt, b));
388 from_ty_params.chain(from_where_clauses).collect()
392 /// Tests whether this is the AST for a reference to the type
393 /// parameter with ID `param_id`. We use this so as to avoid running
394 /// `ast_ty_to_ty`, because we want to avoid triggering an all-out
395 /// conversion of the type to avoid inducing unnecessary cycles.
396 fn is_param(tcx: TyCtxt<'_>, ast_ty: &hir::Ty, param_id: hir::HirId) -> bool {
397 if let hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) = ast_ty.kind {
399 Res::SelfTy(Some(def_id), None) | Res::Def(DefKind::TyParam, def_id) => {
400 def_id == tcx.hir().local_def_id(param_id)
409 fn convert_item(tcx: TyCtxt<'_>, item_id: hir::HirId) {
410 let it = tcx.hir().expect_item(item_id);
411 debug!("convert: item {} with id {}", it.ident, it.hir_id);
412 let def_id = tcx.hir().local_def_id(item_id);
414 // These don't define types.
415 hir::ItemKind::ExternCrate(_)
416 | hir::ItemKind::Use(..)
417 | hir::ItemKind::Mod(_)
418 | hir::ItemKind::GlobalAsm(_) => {}
419 hir::ItemKind::ForeignMod(ref foreign_mod) => {
420 for item in &foreign_mod.items {
421 let def_id = tcx.hir().local_def_id(item.hir_id);
422 tcx.generics_of(def_id);
424 tcx.predicates_of(def_id);
425 if let hir::ForeignItemKind::Fn(..) = item.kind {
430 hir::ItemKind::Enum(ref enum_definition, _) => {
431 tcx.generics_of(def_id);
433 tcx.predicates_of(def_id);
434 convert_enum_variant_types(tcx, def_id, &enum_definition.variants);
436 hir::ItemKind::Impl(..) => {
437 tcx.generics_of(def_id);
439 tcx.impl_trait_ref(def_id);
440 tcx.predicates_of(def_id);
442 hir::ItemKind::Trait(..) => {
443 tcx.generics_of(def_id);
444 tcx.trait_def(def_id);
445 tcx.at(it.span).super_predicates_of(def_id);
446 tcx.predicates_of(def_id);
448 hir::ItemKind::TraitAlias(..) => {
449 tcx.generics_of(def_id);
450 tcx.at(it.span).super_predicates_of(def_id);
451 tcx.predicates_of(def_id);
453 hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
454 tcx.generics_of(def_id);
456 tcx.predicates_of(def_id);
458 for f in struct_def.fields() {
459 let def_id = tcx.hir().local_def_id(f.hir_id);
460 tcx.generics_of(def_id);
462 tcx.predicates_of(def_id);
465 if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
466 convert_variant_ctor(tcx, ctor_hir_id);
470 // Desugared from `impl Trait`, so visited by the function's return type.
471 hir::ItemKind::OpaqueTy(hir::OpaqueTy {
472 impl_trait_fn: Some(_),
476 hir::ItemKind::OpaqueTy(..)
477 | hir::ItemKind::TyAlias(..)
478 | hir::ItemKind::Static(..)
479 | hir::ItemKind::Const(..)
480 | hir::ItemKind::Fn(..) => {
481 tcx.generics_of(def_id);
483 tcx.predicates_of(def_id);
484 if let hir::ItemKind::Fn(..) = it.kind {
491 fn convert_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::HirId) {
492 let trait_item = tcx.hir().expect_trait_item(trait_item_id);
493 let def_id = tcx.hir().local_def_id(trait_item.hir_id);
494 tcx.generics_of(def_id);
496 match trait_item.kind {
497 hir::TraitItemKind::Const(..)
498 | hir::TraitItemKind::Type(_, Some(_))
499 | hir::TraitItemKind::Method(..) => {
501 if let hir::TraitItemKind::Method(..) = trait_item.kind {
506 hir::TraitItemKind::Type(_, None) => {}
509 tcx.predicates_of(def_id);
512 fn convert_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::HirId) {
513 let def_id = tcx.hir().local_def_id(impl_item_id);
514 tcx.generics_of(def_id);
516 tcx.predicates_of(def_id);
517 if let hir::ImplItemKind::Method(..) = tcx.hir().expect_impl_item(impl_item_id).kind {
522 fn convert_variant_ctor(tcx: TyCtxt<'_>, ctor_id: hir::HirId) {
523 let def_id = tcx.hir().local_def_id(ctor_id);
524 tcx.generics_of(def_id);
526 tcx.predicates_of(def_id);
529 fn convert_enum_variant_types(
532 variants: &[hir::Variant]
534 let def = tcx.adt_def(def_id);
535 let repr_type = def.repr.discr_type();
536 let initial = repr_type.initial_discriminant(tcx);
537 let mut prev_discr = None::<Discr<'_>>;
539 // fill the discriminant values and field types
540 for variant in variants {
541 let wrapped_discr = prev_discr.map_or(initial, |d| d.wrap_incr(tcx));
543 if let Some(ref e) = variant.disr_expr {
544 let expr_did = tcx.hir().local_def_id(e.hir_id);
545 def.eval_explicit_discr(tcx, expr_did)
546 } else if let Some(discr) = repr_type.disr_incr(tcx, prev_discr) {
553 "enum discriminant overflowed"
556 format!("overflowed on value after {}", prev_discr.unwrap()),
558 "explicitly set `{} = {}` if that is desired outcome",
559 variant.ident, wrapped_discr
563 }.unwrap_or(wrapped_discr),
566 for f in variant.data.fields() {
567 let def_id = tcx.hir().local_def_id(f.hir_id);
568 tcx.generics_of(def_id);
570 tcx.predicates_of(def_id);
573 // Convert the ctor, if any. This also registers the variant as
575 if let Some(ctor_hir_id) = variant.data.ctor_hir_id() {
576 convert_variant_ctor(tcx, ctor_hir_id);
583 variant_did: Option<DefId>,
584 ctor_did: Option<DefId>,
586 discr: ty::VariantDiscr,
587 def: &hir::VariantData,
588 adt_kind: ty::AdtKind,
590 ) -> ty::VariantDef {
591 let mut seen_fields: FxHashMap<ast::Ident, Span> = Default::default();
592 let hir_id = tcx.hir().as_local_hir_id(variant_did.unwrap_or(parent_did)).unwrap();
597 let fid = tcx.hir().local_def_id(f.hir_id);
598 let dup_span = seen_fields.get(&f.ident.modern()).cloned();
599 if let Some(prev_span) = dup_span {
604 "field `{}` is already declared",
606 ).span_label(f.span, "field already declared")
607 .span_label(prev_span, format!("`{}` first declared here", f.ident))
610 seen_fields.insert(f.ident.modern(), f.span);
616 vis: ty::Visibility::from_hir(&f.vis, hir_id, tcx),
620 let recovered = match def {
621 hir::VariantData::Struct(_, r) => *r,
631 CtorKind::from_hir(def),
638 fn adt_def(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::AdtDef {
641 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
642 let item = match tcx.hir().get(hir_id) {
643 Node::Item(item) => item,
647 let repr = ReprOptions::new(tcx, def_id);
648 let (kind, variants) = match item.kind {
649 ItemKind::Enum(ref def, _) => {
650 let mut distance_from_explicit = 0;
651 let variants = def.variants
654 let variant_did = Some(tcx.hir().local_def_id(v.id));
655 let ctor_did = v.data.ctor_hir_id()
656 .map(|hir_id| tcx.hir().local_def_id(hir_id));
658 let discr = if let Some(ref e) = v.disr_expr {
659 distance_from_explicit = 0;
660 ty::VariantDiscr::Explicit(tcx.hir().local_def_id(e.hir_id))
662 ty::VariantDiscr::Relative(distance_from_explicit)
664 distance_from_explicit += 1;
666 convert_variant(tcx, variant_did, ctor_did, v.ident, discr,
667 &v.data, AdtKind::Enum, def_id)
671 (AdtKind::Enum, variants)
673 ItemKind::Struct(ref def, _) => {
674 let variant_did = None;
675 let ctor_did = def.ctor_hir_id()
676 .map(|hir_id| tcx.hir().local_def_id(hir_id));
678 let variants = std::iter::once(convert_variant(
679 tcx, variant_did, ctor_did, item.ident, ty::VariantDiscr::Relative(0), def,
680 AdtKind::Struct, def_id,
683 (AdtKind::Struct, variants)
685 ItemKind::Union(ref def, _) => {
686 let variant_did = None;
687 let ctor_did = def.ctor_hir_id()
688 .map(|hir_id| tcx.hir().local_def_id(hir_id));
690 let variants = std::iter::once(convert_variant(
691 tcx, variant_did, ctor_did, item.ident, ty::VariantDiscr::Relative(0), def,
692 AdtKind::Union, def_id,
695 (AdtKind::Union, variants)
699 tcx.alloc_adt_def(def_id, kind, variants, repr)
702 /// Ensures that the super-predicates of the trait with a `DefId`
703 /// of `trait_def_id` are converted and stored. This also ensures that
704 /// the transitive super-predicates are converted.
705 fn super_predicates_of(
708 ) -> ty::GenericPredicates<'_> {
709 debug!("super_predicates(trait_def_id={:?})", trait_def_id);
710 let trait_hir_id = tcx.hir().as_local_hir_id(trait_def_id).unwrap();
712 let item = match tcx.hir().get(trait_hir_id) {
713 Node::Item(item) => item,
714 _ => bug!("trait_node_id {} is not an item", trait_hir_id),
717 let (generics, bounds) = match item.kind {
718 hir::ItemKind::Trait(.., ref generics, ref supertraits, _) => (generics, supertraits),
719 hir::ItemKind::TraitAlias(ref generics, ref supertraits) => (generics, supertraits),
720 _ => span_bug!(item.span, "super_predicates invoked on non-trait"),
723 let icx = ItemCtxt::new(tcx, trait_def_id);
725 // Convert the bounds that follow the colon, e.g., `Bar + Zed` in `trait Foo: Bar + Zed`.
726 let self_param_ty = tcx.types.self_param;
727 let superbounds1 = AstConv::compute_bounds(&icx, self_param_ty, bounds, SizedByDefault::No,
730 let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
732 // Convert any explicit superbounds in the where-clause,
733 // e.g., `trait Foo where Self: Bar`.
734 // In the case of trait aliases, however, we include all bounds in the where-clause,
735 // so e.g., `trait Foo = where u32: PartialEq<Self>` would include `u32: PartialEq<Self>`
736 // as one of its "superpredicates".
737 let is_trait_alias = tcx.is_trait_alias(trait_def_id);
738 let superbounds2 = icx.type_parameter_bounds_in_generics(
739 generics, item.hir_id, self_param_ty, OnlySelfBounds(!is_trait_alias));
741 // Combine the two lists to form the complete set of superbounds:
742 let superbounds = &*tcx.arena.alloc_from_iter(
743 superbounds1.into_iter().chain(superbounds2)
746 // Now require that immediate supertraits are converted,
747 // which will, in turn, reach indirect supertraits.
748 for &(pred, span) in superbounds {
749 debug!("superbound: {:?}", pred);
750 if let ty::Predicate::Trait(bound) = pred {
751 tcx.at(span).super_predicates_of(bound.def_id());
755 ty::GenericPredicates {
757 predicates: superbounds,
761 fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::TraitDef {
762 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
763 let item = tcx.hir().expect_item(hir_id);
765 let (is_auto, unsafety) = match item.kind {
766 hir::ItemKind::Trait(is_auto, unsafety, ..) => (is_auto == hir::IsAuto::Yes, unsafety),
767 hir::ItemKind::TraitAlias(..) => (false, hir::Unsafety::Normal),
768 _ => span_bug!(item.span, "trait_def_of_item invoked on non-trait"),
771 let paren_sugar = tcx.has_attr(def_id, sym::rustc_paren_sugar);
772 if paren_sugar && !tcx.features().unboxed_closures {
773 let mut err = tcx.sess.struct_span_err(
775 "the `#[rustc_paren_sugar]` attribute is a temporary means of controlling \
776 which traits can use parenthetical notation",
780 "add `#![feature(unboxed_closures)]` to \
781 the crate attributes to use it"
786 let is_marker = tcx.has_attr(def_id, sym::marker);
787 let def_path_hash = tcx.def_path_hash(def_id);
788 let def = ty::TraitDef::new(def_id, unsafety, paren_sugar, is_auto, is_marker, def_path_hash);
792 fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<Span> {
793 struct LateBoundRegionsDetector<'tcx> {
795 outer_index: ty::DebruijnIndex,
796 has_late_bound_regions: Option<Span>,
799 impl Visitor<'tcx> for LateBoundRegionsDetector<'tcx> {
800 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
801 NestedVisitorMap::None
804 fn visit_ty(&mut self, ty: &'tcx hir::Ty) {
805 if self.has_late_bound_regions.is_some() {
809 hir::TyKind::BareFn(..) => {
810 self.outer_index.shift_in(1);
811 intravisit::walk_ty(self, ty);
812 self.outer_index.shift_out(1);
814 _ => intravisit::walk_ty(self, ty),
818 fn visit_poly_trait_ref(
820 tr: &'tcx hir::PolyTraitRef,
821 m: hir::TraitBoundModifier,
823 if self.has_late_bound_regions.is_some() {
826 self.outer_index.shift_in(1);
827 intravisit::walk_poly_trait_ref(self, tr, m);
828 self.outer_index.shift_out(1);
831 fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
832 if self.has_late_bound_regions.is_some() {
836 match self.tcx.named_region(lt.hir_id) {
837 Some(rl::Region::Static) | Some(rl::Region::EarlyBound(..)) => {}
838 Some(rl::Region::LateBound(debruijn, _, _))
839 | Some(rl::Region::LateBoundAnon(debruijn, _)) if debruijn < self.outer_index => {}
840 Some(rl::Region::LateBound(..))
841 | Some(rl::Region::LateBoundAnon(..))
842 | Some(rl::Region::Free(..))
844 self.has_late_bound_regions = Some(lt.span);
850 fn has_late_bound_regions<'tcx>(
852 generics: &'tcx hir::Generics,
853 decl: &'tcx hir::FnDecl,
855 let mut visitor = LateBoundRegionsDetector {
857 outer_index: ty::INNERMOST,
858 has_late_bound_regions: None,
860 for param in &generics.params {
861 if let GenericParamKind::Lifetime { .. } = param.kind {
862 if tcx.is_late_bound(param.hir_id) {
863 return Some(param.span);
867 visitor.visit_fn_decl(decl);
868 visitor.has_late_bound_regions
872 Node::TraitItem(item) => match item.kind {
873 hir::TraitItemKind::Method(ref sig, _) => {
874 has_late_bound_regions(tcx, &item.generics, &sig.decl)
878 Node::ImplItem(item) => match item.kind {
879 hir::ImplItemKind::Method(ref sig, _) => {
880 has_late_bound_regions(tcx, &item.generics, &sig.decl)
884 Node::ForeignItem(item) => match item.kind {
885 hir::ForeignItemKind::Fn(ref fn_decl, _, ref generics) => {
886 has_late_bound_regions(tcx, generics, fn_decl)
890 Node::Item(item) => match item.kind {
891 hir::ItemKind::Fn(ref sig, .., ref generics, _) => {
892 has_late_bound_regions(tcx, generics, &sig.decl)
900 fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::Generics {
903 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
905 let node = tcx.hir().get(hir_id);
906 let parent_def_id = match node {
907 Node::ImplItem(_) | Node::TraitItem(_) | Node::Variant(_) |
908 Node::Ctor(..) | Node::Field(_) => {
909 let parent_id = tcx.hir().get_parent_item(hir_id);
910 Some(tcx.hir().local_def_id(parent_id))
912 // FIXME(#43408) enable this in all cases when we get lazy normalization.
913 Node::AnonConst(&anon_const) => {
914 // HACK(eddyb) this provides the correct generics when the workaround
915 // for a const parameter `AnonConst` is being used elsewhere, as then
916 // there won't be the kind of cyclic dependency blocking #43408.
917 let expr = &tcx.hir().body(anon_const.body).value;
918 let icx = ItemCtxt::new(tcx, def_id);
919 if AstConv::const_param_def_id(&icx, expr).is_some() {
920 let parent_id = tcx.hir().get_parent_item(hir_id);
921 Some(tcx.hir().local_def_id(parent_id))
926 Node::Expr(&hir::Expr {
927 kind: hir::ExprKind::Closure(..),
929 }) => Some(tcx.closure_base_def_id(def_id)),
930 Node::Item(item) => match item.kind {
931 ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn, .. }) => impl_trait_fn,
937 let mut opt_self = None;
938 let mut allow_defaults = false;
940 let no_generics = hir::Generics::empty();
941 let ast_generics = match node {
942 Node::TraitItem(item) => &item.generics,
944 Node::ImplItem(item) => &item.generics,
946 Node::Item(item) => {
948 ItemKind::Fn(.., ref generics, _) | ItemKind::Impl(_, _, _, ref generics, ..) => {
952 ItemKind::TyAlias(_, ref generics)
953 | ItemKind::Enum(_, ref generics)
954 | ItemKind::Struct(_, ref generics)
955 | ItemKind::OpaqueTy(hir::OpaqueTy { ref generics, .. })
956 | ItemKind::Union(_, ref generics) => {
957 allow_defaults = true;
961 ItemKind::Trait(_, _, ref generics, ..)
962 | ItemKind::TraitAlias(ref generics, ..) => {
963 // Add in the self type parameter.
965 // Something of a hack: use the node id for the trait, also as
966 // the node id for the Self type parameter.
967 let param_id = item.hir_id;
969 opt_self = Some(ty::GenericParamDef {
972 def_id: tcx.hir().local_def_id(param_id),
973 pure_wrt_drop: false,
974 kind: ty::GenericParamDefKind::Type {
976 object_lifetime_default: rl::Set1::Empty,
981 allow_defaults = true;
989 Node::ForeignItem(item) => match item.kind {
990 ForeignItemKind::Static(..) => &no_generics,
991 ForeignItemKind::Fn(_, _, ref generics) => generics,
992 ForeignItemKind::Type => &no_generics,
998 let has_self = opt_self.is_some();
999 let mut parent_has_self = false;
1000 let mut own_start = has_self as u32;
1001 let parent_count = parent_def_id.map_or(0, |def_id| {
1002 let generics = tcx.generics_of(def_id);
1003 assert_eq!(has_self, false);
1004 parent_has_self = generics.has_self;
1005 own_start = generics.count() as u32;
1006 generics.parent_count + generics.params.len()
1009 let mut params: Vec<_> = opt_self.into_iter().collect();
1011 let early_lifetimes = early_bound_lifetimes_from_generics(tcx, ast_generics);
1015 .map(|(i, param)| ty::GenericParamDef {
1016 name: param.name.ident().name,
1017 index: own_start + i as u32,
1018 def_id: tcx.hir().local_def_id(param.hir_id),
1019 pure_wrt_drop: param.pure_wrt_drop,
1020 kind: ty::GenericParamDefKind::Lifetime,
1024 let object_lifetime_defaults = tcx.object_lifetime_defaults(hir_id);
1026 // Now create the real type parameters.
1027 let type_start = own_start - has_self as u32 + params.len() as u32;
1033 .filter_map(|param| {
1034 let kind = match param.kind {
1035 GenericParamKind::Type {
1040 if !allow_defaults && default.is_some() {
1041 if !tcx.features().default_type_parameter_fallback {
1043 lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
1047 "defaults for type parameters are only allowed in \
1048 `struct`, `enum`, `type`, or `trait` definitions."
1054 ty::GenericParamDefKind::Type {
1055 has_default: default.is_some(),
1056 object_lifetime_default: object_lifetime_defaults
1058 .map_or(rl::Set1::Empty, |o| o[i]),
1062 GenericParamKind::Const { .. } => {
1063 ty::GenericParamDefKind::Const
1068 let param_def = ty::GenericParamDef {
1069 index: type_start + i as u32,
1070 name: param.name.ident().name,
1071 def_id: tcx.hir().local_def_id(param.hir_id),
1072 pure_wrt_drop: param.pure_wrt_drop,
1080 // provide junk type parameter defs - the only place that
1081 // cares about anything but the length is instantiation,
1082 // and we don't do that for closures.
1083 if let Node::Expr(&hir::Expr {
1084 kind: hir::ExprKind::Closure(.., gen),
1088 let dummy_args = if gen.is_some() {
1089 &["<yield_ty>", "<return_ty>", "<witness>"][..]
1091 &["<closure_kind>", "<closure_signature>"][..]
1098 .map(|(i, &arg)| ty::GenericParamDef {
1099 index: type_start + i as u32,
1100 name: Symbol::intern(arg),
1102 pure_wrt_drop: false,
1103 kind: ty::GenericParamDefKind::Type {
1105 object_lifetime_default: rl::Set1::Empty,
1111 if let Some(upvars) = tcx.upvars(def_id) {
1112 params.extend(upvars.iter().zip((dummy_args.len() as u32)..).map(|(_, i)| {
1113 ty::GenericParamDef {
1114 index: type_start + i,
1115 name: Symbol::intern("<upvar>"),
1117 pure_wrt_drop: false,
1118 kind: ty::GenericParamDefKind::Type {
1120 object_lifetime_default: rl::Set1::Empty,
1128 let param_def_id_to_index = params
1130 .map(|param| (param.def_id, param.index))
1133 tcx.arena.alloc(ty::Generics {
1134 parent: parent_def_id,
1137 param_def_id_to_index,
1138 has_self: has_self || parent_has_self,
1139 has_late_bound_regions: has_late_bound_regions(tcx, node),
1143 fn report_assoc_ty_on_inherent_impl(tcx: TyCtxt<'_>, span: Span) {
1148 "associated types are not yet supported in inherent impls (see #8995)"
1152 fn infer_placeholder_type(
1155 body_id: hir::BodyId,
1159 let ty = tcx.typeck_tables_of(def_id).node_type(body_id.hir_id);
1161 // If this came from a free `const` or `static mut?` item,
1162 // then the user may have written e.g. `const A = 42;`.
1163 // In this case, the parser has stashed a diagnostic for
1164 // us to improve in typeck so we do that now.
1165 match tcx.sess.diagnostic().steal_diagnostic(span, StashKey::ItemNoType) {
1167 // The parser provided a sub-optimal `HasPlaceholders` suggestion for the type.
1168 // We are typeck and have the real type, so remove that and suggest the actual type.
1169 err.suggestions.clear();
1170 err.span_suggestion(
1172 "provide a type for the item",
1173 format!("{}: {}", item_ident, ty),
1174 Applicability::MachineApplicable,
1179 let mut diag = bad_placeholder_type(tcx, span);
1180 if ty != tcx.types.err {
1181 diag.span_suggestion(
1183 "replace `_` with the correct type",
1185 Applicability::MaybeIncorrect,
1195 fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
1198 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1200 let icx = ItemCtxt::new(tcx, def_id);
1202 match tcx.hir().get(hir_id) {
1203 Node::TraitItem(item) => match item.kind {
1204 TraitItemKind::Method(..) => {
1205 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1206 tcx.mk_fn_def(def_id, substs)
1208 TraitItemKind::Const(ref ty, body_id) => {
1209 body_id.and_then(|body_id| {
1210 if let hir::TyKind::Infer = ty.kind {
1211 Some(infer_placeholder_type(tcx, def_id, body_id, ty.span, item.ident))
1215 }).unwrap_or_else(|| icx.to_ty(ty))
1217 TraitItemKind::Type(_, Some(ref ty)) => icx.to_ty(ty),
1218 TraitItemKind::Type(_, None) => {
1219 span_bug!(item.span, "associated type missing default");
1223 Node::ImplItem(item) => match item.kind {
1224 ImplItemKind::Method(..) => {
1225 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1226 tcx.mk_fn_def(def_id, substs)
1228 ImplItemKind::Const(ref ty, body_id) => {
1229 if let hir::TyKind::Infer = ty.kind {
1230 infer_placeholder_type(tcx, def_id, body_id, ty.span, item.ident)
1235 ImplItemKind::OpaqueTy(_) => {
1237 .impl_trait_ref(tcx.hir().get_parent_did(hir_id))
1240 report_assoc_ty_on_inherent_impl(tcx, item.span);
1243 find_opaque_ty_constraints(tcx, def_id)
1245 ImplItemKind::TyAlias(ref ty) => {
1247 .impl_trait_ref(tcx.hir().get_parent_did(hir_id))
1250 report_assoc_ty_on_inherent_impl(tcx, item.span);
1257 Node::Item(item) => {
1259 ItemKind::Static(ref ty, .., body_id)
1260 | ItemKind::Const(ref ty, body_id) => {
1261 if let hir::TyKind::Infer = ty.kind {
1262 infer_placeholder_type(tcx, def_id, body_id, ty.span, item.ident)
1267 ItemKind::TyAlias(ref ty, _)
1268 | ItemKind::Impl(.., ref ty, _) => icx.to_ty(ty),
1269 ItemKind::Fn(..) => {
1270 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1271 tcx.mk_fn_def(def_id, substs)
1273 ItemKind::Enum(..) | ItemKind::Struct(..) | ItemKind::Union(..) => {
1274 let def = tcx.adt_def(def_id);
1275 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1276 tcx.mk_adt(def, substs)
1278 ItemKind::OpaqueTy(hir::OpaqueTy {
1279 impl_trait_fn: None,
1281 }) => find_opaque_ty_constraints(tcx, def_id),
1282 // Opaque types desugared from `impl Trait`.
1283 ItemKind::OpaqueTy(hir::OpaqueTy {
1284 impl_trait_fn: Some(owner),
1287 tcx.typeck_tables_of(owner)
1288 .concrete_opaque_types
1290 .map(|opaque| opaque.concrete_type)
1291 .unwrap_or_else(|| {
1292 // This can occur if some error in the
1293 // owner fn prevented us from populating
1294 // the `concrete_opaque_types` table.
1295 tcx.sess.delay_span_bug(
1298 "owner {:?} has no opaque type for {:?} in its tables",
1306 | ItemKind::TraitAlias(..)
1308 | ItemKind::ForeignMod(..)
1309 | ItemKind::GlobalAsm(..)
1310 | ItemKind::ExternCrate(..)
1311 | ItemKind::Use(..) => {
1314 "compute_type_of_item: unexpected item type: {:?}",
1321 Node::ForeignItem(foreign_item) => match foreign_item.kind {
1322 ForeignItemKind::Fn(..) => {
1323 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1324 tcx.mk_fn_def(def_id, substs)
1326 ForeignItemKind::Static(ref t, _) => icx.to_ty(t),
1327 ForeignItemKind::Type => tcx.mk_foreign(def_id),
1330 Node::Ctor(&ref def) | Node::Variant(
1331 hir::Variant { data: ref def, .. }
1333 VariantData::Unit(..) | VariantData::Struct(..) => {
1334 tcx.type_of(tcx.hir().get_parent_did(hir_id))
1336 VariantData::Tuple(..) => {
1337 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1338 tcx.mk_fn_def(def_id, substs)
1342 Node::Field(field) => icx.to_ty(&field.ty),
1344 Node::Expr(&hir::Expr {
1345 kind: hir::ExprKind::Closure(.., gen),
1349 return tcx.typeck_tables_of(def_id).node_type(hir_id);
1352 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1353 tcx.mk_closure(def_id, substs)
1356 Node::AnonConst(_) => {
1357 let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1360 kind: hir::TyKind::Array(_, ref constant),
1363 | Node::Ty(&hir::Ty {
1364 kind: hir::TyKind::Typeof(ref constant),
1367 | Node::Expr(&hir::Expr {
1368 kind: ExprKind::Repeat(_, ref constant),
1370 }) if constant.hir_id == hir_id =>
1375 Node::Variant(Variant {
1376 disr_expr: Some(ref e),
1378 }) if e.hir_id == hir_id =>
1380 tcx.adt_def(tcx.hir().get_parent_did(hir_id))
1386 Node::Ty(&hir::Ty { kind: hir::TyKind::Path(_), .. }) |
1387 Node::Expr(&hir::Expr { kind: ExprKind::Struct(..), .. }) |
1388 Node::Expr(&hir::Expr { kind: ExprKind::Path(_), .. }) |
1389 Node::TraitRef(..) => {
1390 let path = match parent_node {
1392 kind: hir::TyKind::Path(QPath::Resolved(_, ref path)),
1395 | Node::Expr(&hir::Expr {
1396 kind: ExprKind::Path(QPath::Resolved(_, ref path)),
1401 Node::Expr(&hir::Expr { kind: ExprKind::Struct(ref path, ..), .. }) => {
1402 if let QPath::Resolved(_, ref path) = **path {
1408 Node::TraitRef(&hir::TraitRef { ref path, .. }) => Some(&**path),
1412 if let Some(path) = path {
1413 let arg_index = path.segments.iter()
1414 .filter_map(|seg| seg.args.as_ref())
1415 .map(|generic_args| generic_args.args.as_ref())
1418 .filter(|arg| arg.is_const())
1420 .filter(|(_, arg)| arg.id() == hir_id)
1421 .map(|(index, _)| index)
1424 .unwrap_or_else(|| {
1425 bug!("no arg matching AnonConst in path");
1428 // We've encountered an `AnonConst` in some path, so we need to
1429 // figure out which generic parameter it corresponds to and return
1430 // the relevant type.
1431 let generics = match path.res {
1432 Res::Def(DefKind::Ctor(..), def_id) => {
1433 tcx.generics_of(tcx.parent(def_id).unwrap())
1435 Res::Def(_, def_id) => tcx.generics_of(def_id),
1436 Res::Err => return tcx.types.err,
1438 tcx.sess.delay_span_bug(
1441 "unexpected const parent path def {:?}",
1445 return tcx.types.err;
1449 generics.params.iter()
1451 if let ty::GenericParamDefKind::Const = param.kind {
1458 .map(|param| tcx.type_of(param.def_id))
1459 // This is no generic parameter associated with the arg. This is
1460 // probably from an extra arg where one is not needed.
1461 .unwrap_or(tcx.types.err)
1463 tcx.sess.delay_span_bug(
1466 "unexpected const parent path {:?}",
1470 return tcx.types.err;
1475 tcx.sess.delay_span_bug(
1478 "unexpected const parent in type_of_def_id(): {:?}", x
1486 Node::GenericParam(param) => match ¶m.kind {
1487 hir::GenericParamKind::Type { default: Some(ref ty), .. } => icx.to_ty(ty),
1488 hir::GenericParamKind::Const { ty: ref hir_ty, .. } => {
1489 let ty = icx.to_ty(hir_ty);
1490 if !tcx.features().const_compare_raw_pointers {
1491 let err = match ty.peel_refs().kind {
1492 ty::FnPtr(_) => Some("function pointers"),
1493 ty::RawPtr(_) => Some("raw pointers"),
1496 if let Some(unsupported_type) = err {
1497 feature_gate::emit_feature_err(
1498 &tcx.sess.parse_sess,
1499 sym::const_compare_raw_pointers,
1501 feature_gate::GateIssue::Language,
1503 "using {} as const generic parameters is unstable",
1509 if ty::search_for_structural_match_violation(
1510 param.hir_id, param.span, tcx, ty).is_some()
1516 "the types of const generic parameters must derive `PartialEq` and `Eq`",
1519 format!("`{}` doesn't derive both `PartialEq` and `Eq`", ty),
1524 x => bug!("unexpected non-type Node::GenericParam: {:?}", x),
1528 bug!("unexpected sort of node in type_of_def_id(): {:?}", x);
1533 fn find_opaque_ty_constraints(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
1534 use rustc::hir::{ImplItem, Item, TraitItem};
1536 debug!("find_opaque_ty_constraints({:?})", def_id);
1538 struct ConstraintLocator<'tcx> {
1541 // (first found type span, actual type, mapping from the opaque type's generic
1542 // parameters to the concrete type's generic parameters)
1544 // The mapping is an index for each use site of a generic parameter in the concrete type
1546 // The indices index into the generic parameters on the opaque type.
1547 found: Option<(Span, Ty<'tcx>, Vec<usize>)>,
1550 impl ConstraintLocator<'tcx> {
1551 fn check(&mut self, def_id: DefId) {
1552 // Don't try to check items that cannot possibly constrain the type.
1553 if !self.tcx.has_typeck_tables(def_id) {
1555 "find_opaque_ty_constraints: no constraint for `{:?}` at `{:?}`: no tables",
1563 .typeck_tables_of(def_id)
1564 .concrete_opaque_types
1566 if let Some(ty::ResolvedOpaqueTy { concrete_type, substs }) = ty {
1568 "find_opaque_ty_constraints: found constraint for `{:?}` at `{:?}`: {:?}",
1574 // FIXME(oli-obk): trace the actual span from inference to improve errors.
1575 let span = self.tcx.def_span(def_id);
1576 // used to quickly look up the position of a generic parameter
1577 let mut index_map: FxHashMap<ty::ParamTy, usize> = FxHashMap::default();
1578 // Skipping binder is ok, since we only use this to find generic parameters and
1580 for (idx, subst) in substs.iter().enumerate() {
1581 if let GenericArgKind::Type(ty) = subst.unpack() {
1582 if let ty::Param(p) = ty.kind {
1583 if index_map.insert(p, idx).is_some() {
1584 // There was already an entry for `p`, meaning a generic parameter
1586 self.tcx.sess.span_err(
1589 "defining opaque type use restricts opaque \
1590 type by using the generic parameter `{}` twice",
1597 self.tcx.sess.delay_span_bug(
1600 "non-defining opaque ty use in defining scope: {:?}, {:?}",
1601 concrete_type, substs,
1607 // Compute the index within the opaque type for each generic parameter used in
1608 // the concrete type.
1609 let indices = concrete_type
1610 .subst(self.tcx, substs)
1612 .filter_map(|t| match &t.kind {
1613 ty::Param(p) => Some(*index_map.get(p).unwrap()),
1616 let is_param = |ty: Ty<'_>| match ty.kind {
1617 ty::Param(_) => true,
1620 if !substs.types().all(is_param) {
1621 self.tcx.sess.span_err(
1623 "defining opaque type use does not fully define opaque type",
1625 } else if let Some((prev_span, prev_ty, ref prev_indices)) = self.found {
1626 let mut ty = concrete_type.walk().fuse();
1627 let mut p_ty = prev_ty.walk().fuse();
1628 let iter_eq = (&mut ty).zip(&mut p_ty).all(|(t, p)| match (&t.kind, &p.kind) {
1629 // Type parameters are equal to any other type parameter for the purpose of
1630 // concrete type equality, as it is possible to obtain the same type just
1631 // by passing matching parameters to a function.
1632 (ty::Param(_), ty::Param(_)) => true,
1635 if !iter_eq || ty.next().is_some() || p_ty.next().is_some() {
1636 debug!("find_opaque_ty_constraints: span={:?}", span);
1637 // Found different concrete types for the opaque type.
1638 let mut err = self.tcx.sess.struct_span_err(
1640 "concrete type differs from previous defining opaque type use",
1644 format!("expected `{}`, got `{}`", prev_ty, concrete_type),
1646 err.span_note(prev_span, "previous use here");
1648 } else if indices != *prev_indices {
1649 // Found "same" concrete types, but the generic parameter order differs.
1650 let mut err = self.tcx.sess.struct_span_err(
1652 "concrete type's generic parameters differ from previous defining use",
1654 use std::fmt::Write;
1655 let mut s = String::new();
1656 write!(s, "expected [").unwrap();
1657 let list = |s: &mut String, indices: &Vec<usize>| {
1658 let mut indices = indices.iter().cloned();
1659 if let Some(first) = indices.next() {
1660 write!(s, "`{}`", substs[first]).unwrap();
1662 write!(s, ", `{}`", substs[i]).unwrap();
1666 list(&mut s, prev_indices);
1667 write!(s, "], got [").unwrap();
1668 list(&mut s, &indices);
1669 write!(s, "]").unwrap();
1670 err.span_label(span, s);
1671 err.span_note(prev_span, "previous use here");
1675 self.found = Some((span, concrete_type, indices));
1679 "find_opaque_ty_constraints: no constraint for `{:?}` at `{:?}`",
1687 impl<'tcx> intravisit::Visitor<'tcx> for ConstraintLocator<'tcx> {
1688 fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'tcx> {
1689 intravisit::NestedVisitorMap::All(&self.tcx.hir())
1691 fn visit_item(&mut self, it: &'tcx Item) {
1692 debug!("find_existential_constraints: visiting {:?}", it);
1693 let def_id = self.tcx.hir().local_def_id(it.hir_id);
1694 // The opaque type itself or its children are not within its reveal scope.
1695 if def_id != self.def_id {
1697 intravisit::walk_item(self, it);
1700 fn visit_impl_item(&mut self, it: &'tcx ImplItem) {
1701 debug!("find_existential_constraints: visiting {:?}", it);
1702 let def_id = self.tcx.hir().local_def_id(it.hir_id);
1703 // The opaque type itself or its children are not within its reveal scope.
1704 if def_id != self.def_id {
1706 intravisit::walk_impl_item(self, it);
1709 fn visit_trait_item(&mut self, it: &'tcx TraitItem) {
1710 debug!("find_existential_constraints: visiting {:?}", it);
1711 let def_id = self.tcx.hir().local_def_id(it.hir_id);
1713 intravisit::walk_trait_item(self, it);
1717 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1718 let scope = tcx.hir().get_defining_scope(hir_id);
1719 let mut locator = ConstraintLocator {
1725 debug!("find_opaque_ty_constraints: scope={:?}", scope);
1727 if scope == hir::CRATE_HIR_ID {
1728 intravisit::walk_crate(&mut locator, tcx.hir().krate());
1730 debug!("find_opaque_ty_constraints: scope={:?}", tcx.hir().get(scope));
1731 match tcx.hir().get(scope) {
1732 // We explicitly call `visit_*` methods, instead of using `intravisit::walk_*` methods
1733 // This allows our visitor to process the defining item itself, causing
1734 // it to pick up any 'sibling' defining uses.
1736 // For example, this code:
1739 // type Blah = impl Debug;
1740 // let my_closure = || -> Blah { true };
1744 // requires us to explicitly process `foo()` in order
1745 // to notice the defining usage of `Blah`.
1746 Node::Item(ref it) => locator.visit_item(it),
1747 Node::ImplItem(ref it) => locator.visit_impl_item(it),
1748 Node::TraitItem(ref it) => locator.visit_trait_item(it),
1750 "{:?} is not a valid scope for an opaque type item",
1756 match locator.found {
1757 Some((_, ty, _)) => ty,
1759 let span = tcx.def_span(def_id);
1760 tcx.sess.span_err(span, "could not find defining uses");
1766 pub fn get_infer_ret_ty(output: &'_ hir::FunctionRetTy) -> Option<&hir::Ty> {
1767 if let hir::FunctionRetTy::Return(ref ty) = output {
1768 if let hir::TyKind::Infer = ty.kind {
1775 fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
1777 use rustc::hir::Node::*;
1779 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1781 let icx = ItemCtxt::new(tcx, def_id);
1783 match tcx.hir().get(hir_id) {
1784 TraitItem(hir::TraitItem {
1785 kind: TraitItemKind::Method(sig, TraitMethod::Provided(_)),
1788 | ImplItem(hir::ImplItem {
1789 kind: ImplItemKind::Method(sig, _),
1793 kind: ItemKind::Fn(sig, _, _),
1795 }) => match get_infer_ret_ty(&sig.decl.output) {
1797 let fn_sig = tcx.typeck_tables_of(def_id).liberated_fn_sigs()[hir_id];
1798 let mut diag = bad_placeholder_type(tcx, ty.span);
1799 let ret_ty = fn_sig.output();
1800 if ret_ty != tcx.types.err {
1801 diag.span_suggestion(
1803 "replace `_` with the correct return type",
1805 Applicability::MaybeIncorrect,
1809 ty::Binder::bind(fn_sig)
1811 None => AstConv::ty_of_fn(&icx, sig.header.unsafety, sig.header.abi, &sig.decl)
1814 TraitItem(hir::TraitItem {
1815 kind: TraitItemKind::Method(FnSig { header, decl }, _),
1818 AstConv::ty_of_fn(&icx, header.unsafety, header.abi, decl)
1821 ForeignItem(&hir::ForeignItem {
1822 kind: ForeignItemKind::Fn(ref fn_decl, _, _),
1825 let abi = tcx.hir().get_foreign_abi(hir_id);
1826 compute_sig_of_foreign_fn_decl(tcx, def_id, fn_decl, abi)
1829 Ctor(data) | Variant(
1830 hir::Variant { data, .. }
1831 ) if data.ctor_hir_id().is_some() => {
1832 let ty = tcx.type_of(tcx.hir().get_parent_did(hir_id));
1833 let inputs = data.fields()
1835 .map(|f| tcx.type_of(tcx.hir().local_def_id(f.hir_id)));
1836 ty::Binder::bind(tcx.mk_fn_sig(
1840 hir::Unsafety::Normal,
1846 kind: hir::ExprKind::Closure(..),
1849 // Closure signatures are not like other function
1850 // signatures and cannot be accessed through `fn_sig`. For
1851 // example, a closure signature excludes the `self`
1852 // argument. In any case they are embedded within the
1853 // closure type as part of the `ClosureSubsts`.
1856 // the signature of a closure, you should use the
1857 // `closure_sig` method on the `ClosureSubsts`:
1859 // closure_substs.sig(def_id, tcx)
1861 // or, inside of an inference context, you can use
1863 // infcx.closure_sig(def_id, closure_substs)
1864 bug!("to get the signature of a closure, use `closure_sig()` not `fn_sig()`");
1868 bug!("unexpected sort of node in fn_sig(): {:?}", x);
1873 fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> {
1874 let icx = ItemCtxt::new(tcx, def_id);
1876 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1877 match tcx.hir().expect_item(hir_id).kind {
1878 hir::ItemKind::Impl(.., ref opt_trait_ref, _, _) => {
1879 opt_trait_ref.as_ref().map(|ast_trait_ref| {
1880 let selfty = tcx.type_of(def_id);
1881 AstConv::instantiate_mono_trait_ref(&icx, ast_trait_ref, selfty)
1888 fn impl_polarity(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ImplPolarity {
1889 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1890 let is_rustc_reservation = tcx.has_attr(def_id, sym::rustc_reservation_impl);
1891 let item = tcx.hir().expect_item(hir_id);
1893 hir::ItemKind::Impl(_, hir::ImplPolarity::Negative, ..) => {
1894 if is_rustc_reservation {
1895 tcx.sess.span_err(item.span, "reservation impls can't be negative");
1897 ty::ImplPolarity::Negative
1899 hir::ItemKind::Impl(_, hir::ImplPolarity::Positive, _, _, None, _, _) => {
1900 if is_rustc_reservation {
1901 tcx.sess.span_err(item.span, "reservation impls can't be inherent");
1903 ty::ImplPolarity::Positive
1905 hir::ItemKind::Impl(_, hir::ImplPolarity::Positive, _, _, Some(_tr), _, _) => {
1906 if is_rustc_reservation {
1907 ty::ImplPolarity::Reservation
1909 ty::ImplPolarity::Positive
1912 ref item => bug!("impl_polarity: {:?} not an impl", item),
1916 /// Returns the early-bound lifetimes declared in this generics
1917 /// listing. For anything other than fns/methods, this is just all
1918 /// the lifetimes that are declared. For fns or methods, we have to
1919 /// screen out those that do not appear in any where-clauses etc using
1920 /// `resolve_lifetime::early_bound_lifetimes`.
1921 fn early_bound_lifetimes_from_generics<'a, 'tcx: 'a>(
1923 generics: &'a hir::Generics,
1924 ) -> impl Iterator<Item = &'a hir::GenericParam> + Captures<'tcx> {
1928 .filter(move |param| match param.kind {
1929 GenericParamKind::Lifetime { .. } => {
1930 !tcx.is_late_bound(param.hir_id)
1936 /// Returns a list of type predicates for the definition with ID `def_id`, including inferred
1937 /// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus
1938 /// inferred constraints concerning which regions outlive other regions.
1939 fn predicates_defined_on(
1942 ) -> ty::GenericPredicates<'_> {
1943 debug!("predicates_defined_on({:?})", def_id);
1944 let mut result = tcx.explicit_predicates_of(def_id);
1946 "predicates_defined_on: explicit_predicates_of({:?}) = {:?}",
1950 let inferred_outlives = tcx.inferred_outlives_of(def_id);
1951 if !inferred_outlives.is_empty() {
1953 "predicates_defined_on: inferred_outlives_of({:?}) = {:?}",
1957 if result.predicates.is_empty() {
1958 result.predicates = inferred_outlives;
1960 result.predicates = tcx.arena.alloc_from_iter(
1961 result.predicates.iter().chain(inferred_outlives).copied(),
1965 debug!("predicates_defined_on({:?}) = {:?}", def_id, result);
1969 /// Returns a list of all type predicates (explicit and implicit) for the definition with
1970 /// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus
1971 /// `Self: Trait` predicates for traits.
1972 fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
1973 let mut result = tcx.predicates_defined_on(def_id);
1975 if tcx.is_trait(def_id) {
1976 // For traits, add `Self: Trait` predicate. This is
1977 // not part of the predicates that a user writes, but it
1978 // is something that one must prove in order to invoke a
1979 // method or project an associated type.
1981 // In the chalk setup, this predicate is not part of the
1982 // "predicates" for a trait item. But it is useful in
1983 // rustc because if you directly (e.g.) invoke a trait
1984 // method like `Trait::method(...)`, you must naturally
1985 // prove that the trait applies to the types that were
1986 // used, and adding the predicate into this list ensures
1987 // that this is done.
1988 let span = tcx.def_span(def_id);
1989 result.predicates = tcx.arena.alloc_from_iter(
1990 result.predicates.iter().copied().chain(
1991 std::iter::once((ty::TraitRef::identity(tcx, def_id).to_predicate(), span))
1995 debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
1999 /// Returns a list of user-specified type predicates for the definition with ID `def_id`.
2000 /// N.B., this does not include any implied/inferred constraints.
2001 fn explicit_predicates_of(
2004 ) -> ty::GenericPredicates<'_> {
2006 use rustc_data_structures::fx::FxHashSet;
2008 debug!("explicit_predicates_of(def_id={:?})", def_id);
2010 /// A data structure with unique elements, which preserves order of insertion.
2011 /// Preserving the order of insertion is important here so as not to break
2012 /// compile-fail UI tests.
2013 // FIXME(eddyb) just use `IndexSet` from `indexmap`.
2014 struct UniquePredicates<'tcx> {
2015 predicates: Vec<(ty::Predicate<'tcx>, Span)>,
2016 uniques: FxHashSet<(ty::Predicate<'tcx>, Span)>,
2019 impl<'tcx> UniquePredicates<'tcx> {
2023 uniques: FxHashSet::default(),
2027 fn push(&mut self, value: (ty::Predicate<'tcx>, Span)) {
2028 if self.uniques.insert(value) {
2029 self.predicates.push(value);
2033 fn extend<I: IntoIterator<Item = (ty::Predicate<'tcx>, Span)>>(&mut self, iter: I) {
2040 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
2041 let node = tcx.hir().get(hir_id);
2043 let mut is_trait = None;
2044 let mut is_default_impl_trait = None;
2046 let icx = ItemCtxt::new(tcx, def_id);
2048 const NO_GENERICS: &hir::Generics = &hir::Generics::empty();
2050 let empty_trait_items = HirVec::new();
2052 let mut predicates = UniquePredicates::new();
2054 let ast_generics = match node {
2055 Node::TraitItem(item) => &item.generics,
2057 Node::ImplItem(item) => match item.kind {
2058 ImplItemKind::OpaqueTy(ref bounds) => {
2059 ty::print::with_no_queries(|| {
2060 let substs = InternalSubsts::identity_for_item(tcx, def_id);
2061 let opaque_ty = tcx.mk_opaque(def_id, substs);
2063 // Collect the bounds, i.e., the `A + B + 'c` in `impl A + B + 'c`.
2064 let bounds = AstConv::compute_bounds(
2068 SizedByDefault::Yes,
2069 tcx.def_span(def_id),
2072 predicates.extend(bounds.predicates(tcx, opaque_ty));
2076 _ => &item.generics,
2079 Node::Item(item) => {
2081 ItemKind::Impl(_, _, defaultness, ref generics, ..) => {
2082 if defaultness.is_default() {
2083 is_default_impl_trait = tcx.impl_trait_ref(def_id);
2087 ItemKind::Fn(.., ref generics, _)
2088 | ItemKind::TyAlias(_, ref generics)
2089 | ItemKind::Enum(_, ref generics)
2090 | ItemKind::Struct(_, ref generics)
2091 | ItemKind::Union(_, ref generics) => generics,
2093 ItemKind::Trait(_, _, ref generics, .., ref items) => {
2094 is_trait = Some((ty::TraitRef::identity(tcx, def_id), items));
2097 ItemKind::TraitAlias(ref generics, _) => {
2098 is_trait = Some((ty::TraitRef::identity(tcx, def_id), &empty_trait_items));
2101 ItemKind::OpaqueTy(OpaqueTy {
2107 let bounds_predicates = ty::print::with_no_queries(|| {
2108 let substs = InternalSubsts::identity_for_item(tcx, def_id);
2109 let opaque_ty = tcx.mk_opaque(def_id, substs);
2111 // Collect the bounds, i.e., the `A + B + 'c` in `impl A + B + 'c`.
2112 let bounds = AstConv::compute_bounds(
2116 SizedByDefault::Yes,
2117 tcx.def_span(def_id),
2120 bounds.predicates(tcx, opaque_ty)
2122 if impl_trait_fn.is_some() {
2124 return ty::GenericPredicates {
2126 predicates: tcx.arena.alloc_from_iter(bounds_predicates),
2129 // named opaque types
2130 predicates.extend(bounds_predicates);
2139 Node::ForeignItem(item) => match item.kind {
2140 ForeignItemKind::Static(..) => NO_GENERICS,
2141 ForeignItemKind::Fn(_, _, ref generics) => generics,
2142 ForeignItemKind::Type => NO_GENERICS,
2148 let generics = tcx.generics_of(def_id);
2149 let parent_count = generics.parent_count as u32;
2150 let has_own_self = generics.has_self && parent_count == 0;
2152 // Below we'll consider the bounds on the type parameters (including `Self`)
2153 // and the explicit where-clauses, but to get the full set of predicates
2154 // on a trait we need to add in the supertrait bounds and bounds found on
2155 // associated types.
2156 if let Some((_trait_ref, _)) = is_trait {
2157 predicates.extend(tcx.super_predicates_of(def_id).predicates.iter().cloned());
2160 // In default impls, we can assume that the self type implements
2161 // the trait. So in:
2163 // default impl Foo for Bar { .. }
2165 // we add a default where clause `Foo: Bar`. We do a similar thing for traits
2166 // (see below). Recall that a default impl is not itself an impl, but rather a
2167 // set of defaults that can be incorporated into another impl.
2168 if let Some(trait_ref) = is_default_impl_trait {
2169 predicates.push((trait_ref.to_poly_trait_ref().to_predicate(), tcx.def_span(def_id)));
2172 // Collect the region predicates that were declared inline as
2173 // well. In the case of parameters declared on a fn or method, we
2174 // have to be careful to only iterate over early-bound regions.
2175 let mut index = parent_count + has_own_self as u32;
2176 for param in early_bound_lifetimes_from_generics(tcx, ast_generics) {
2177 let region = tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
2178 def_id: tcx.hir().local_def_id(param.hir_id),
2180 name: param.name.ident().name,
2185 GenericParamKind::Lifetime { .. } => {
2186 param.bounds.iter().for_each(|bound| match bound {
2187 hir::GenericBound::Outlives(lt) => {
2188 let bound = AstConv::ast_region_to_region(&icx, <, None);
2189 let outlives = ty::Binder::bind(ty::OutlivesPredicate(region, bound));
2190 predicates.push((outlives.to_predicate(), lt.span));
2199 // Collect the predicates that were written inline by the user on each
2200 // type parameter (e.g., `<T: Foo>`).
2201 for param in &ast_generics.params {
2202 if let GenericParamKind::Type { .. } = param.kind {
2203 let name = param.name.ident().name;
2204 let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
2207 let sized = SizedByDefault::Yes;
2208 let bounds = AstConv::compute_bounds(&icx, param_ty, ¶m.bounds, sized, param.span);
2209 predicates.extend(bounds.predicates(tcx, param_ty));
2213 // Add in the bounds that appear in the where-clause.
2214 let where_clause = &ast_generics.where_clause;
2215 for predicate in &where_clause.predicates {
2217 &hir::WherePredicate::BoundPredicate(ref bound_pred) => {
2218 let ty = icx.to_ty(&bound_pred.bounded_ty);
2220 // Keep the type around in a dummy predicate, in case of no bounds.
2221 // That way, `where Ty:` is not a complete noop (see #53696) and `Ty`
2222 // is still checked for WF.
2223 if bound_pred.bounds.is_empty() {
2224 if let ty::Param(_) = ty.kind {
2225 // This is a `where T:`, which can be in the HIR from the
2226 // transformation that moves `?Sized` to `T`'s declaration.
2227 // We can skip the predicate because type parameters are
2228 // trivially WF, but also we *should*, to avoid exposing
2229 // users who never wrote `where Type:,` themselves, to
2230 // compiler/tooling bugs from not handling WF predicates.
2232 let span = bound_pred.bounded_ty.span;
2233 let predicate = ty::OutlivesPredicate(ty, tcx.mk_region(ty::ReEmpty));
2235 (ty::Predicate::TypeOutlives(ty::Binder::dummy(predicate)), span)
2240 for bound in bound_pred.bounds.iter() {
2242 &hir::GenericBound::Trait(ref poly_trait_ref, _) => {
2243 let mut bounds = Bounds::default();
2244 let _ = AstConv::instantiate_poly_trait_ref(
2250 predicates.extend(bounds.predicates(tcx, ty));
2253 &hir::GenericBound::Outlives(ref lifetime) => {
2254 let region = AstConv::ast_region_to_region(&icx, lifetime, None);
2255 let pred = ty::Binder::bind(ty::OutlivesPredicate(ty, region));
2256 predicates.push((ty::Predicate::TypeOutlives(pred), lifetime.span))
2262 &hir::WherePredicate::RegionPredicate(ref region_pred) => {
2263 let r1 = AstConv::ast_region_to_region(&icx, ®ion_pred.lifetime, None);
2264 predicates.extend(region_pred.bounds.iter().map(|bound| {
2265 let (r2, span) = match bound {
2266 hir::GenericBound::Outlives(lt) => {
2267 (AstConv::ast_region_to_region(&icx, lt, None), lt.span)
2271 let pred = ty::Binder::bind(ty::OutlivesPredicate(r1, r2));
2273 (ty::Predicate::RegionOutlives(pred), span)
2277 &hir::WherePredicate::EqPredicate(..) => {
2283 // Add predicates from associated type bounds.
2284 if let Some((self_trait_ref, trait_items)) = is_trait {
2285 predicates.extend(trait_items.iter().flat_map(|trait_item_ref| {
2286 let trait_item = tcx.hir().trait_item(trait_item_ref.id);
2287 let bounds = match trait_item.kind {
2288 hir::TraitItemKind::Type(ref bounds, _) => bounds,
2289 _ => return Vec::new().into_iter()
2293 tcx.mk_projection(tcx.hir().local_def_id(trait_item.hir_id),
2294 self_trait_ref.substs);
2296 let bounds = AstConv::compute_bounds(
2297 &ItemCtxt::new(tcx, def_id),
2300 SizedByDefault::Yes,
2304 bounds.predicates(tcx, assoc_ty).into_iter()
2308 let mut predicates = predicates.predicates;
2310 // Subtle: before we store the predicates into the tcx, we
2311 // sort them so that predicates like `T: Foo<Item=U>` come
2312 // before uses of `U`. This avoids false ambiguity errors
2313 // in trait checking. See `setup_constraining_predicates`
2315 if let Node::Item(&Item {
2316 kind: ItemKind::Impl(..),
2320 let self_ty = tcx.type_of(def_id);
2321 let trait_ref = tcx.impl_trait_ref(def_id);
2322 cgp::setup_constraining_predicates(
2326 &mut cgp::parameters_for_impl(self_ty, trait_ref),
2330 let result = ty::GenericPredicates {
2331 parent: generics.parent,
2332 predicates: tcx.arena.alloc_from_iter(predicates),
2334 debug!("explicit_predicates_of(def_id={:?}) = {:?}", def_id, result);
2338 /// Converts a specific `GenericBound` from the AST into a set of
2339 /// predicates that apply to the self type. A vector is returned
2340 /// because this can be anywhere from zero predicates (`T: ?Sized` adds no
2341 /// predicates) to one (`T: Foo`) to many (`T: Bar<X = i32>` adds `T: Bar`
2342 /// and `<T as Bar>::X == i32`).
2343 fn predicates_from_bound<'tcx>(
2344 astconv: &dyn AstConv<'tcx>,
2346 bound: &'tcx hir::GenericBound,
2347 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2349 hir::GenericBound::Trait(ref tr, hir::TraitBoundModifier::None) => {
2350 let mut bounds = Bounds::default();
2351 let _ = astconv.instantiate_poly_trait_ref(
2356 bounds.predicates(astconv.tcx(), param_ty)
2358 hir::GenericBound::Outlives(ref lifetime) => {
2359 let region = astconv.ast_region_to_region(lifetime, None);
2360 let pred = ty::Binder::bind(ty::OutlivesPredicate(param_ty, region));
2361 vec![(ty::Predicate::TypeOutlives(pred), lifetime.span)]
2363 hir::GenericBound::Trait(_, hir::TraitBoundModifier::Maybe) => vec![],
2367 fn compute_sig_of_foreign_fn_decl<'tcx>(
2370 decl: &'tcx hir::FnDecl,
2372 ) -> ty::PolyFnSig<'tcx> {
2373 let unsafety = if abi == abi::Abi::RustIntrinsic {
2374 intrinsic_operation_unsafety(&tcx.item_name(def_id).as_str())
2376 hir::Unsafety::Unsafe
2378 let fty = AstConv::ty_of_fn(&ItemCtxt::new(tcx, def_id), unsafety, abi, decl);
2380 // Feature gate SIMD types in FFI, since I am not sure that the
2381 // ABIs are handled at all correctly. -huonw
2382 if abi != abi::Abi::RustIntrinsic
2383 && abi != abi::Abi::PlatformIntrinsic
2384 && !tcx.features().simd_ffi
2386 let check = |ast_ty: &hir::Ty, ty: Ty<'_>| {
2392 "use of SIMD type `{}` in FFI is highly experimental and \
2393 may result in invalid code",
2394 tcx.hir().hir_to_pretty_string(ast_ty.hir_id)
2397 .help("add `#![feature(simd_ffi)]` to the crate attributes to enable")
2401 for (input, ty) in decl.inputs.iter().zip(*fty.inputs().skip_binder()) {
2404 if let hir::Return(ref ty) = decl.output {
2405 check(&ty, *fty.output().skip_binder())
2412 fn is_foreign_item(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2413 match tcx.hir().get_if_local(def_id) {
2414 Some(Node::ForeignItem(..)) => true,
2416 _ => bug!("is_foreign_item applied to non-local def-id {:?}", def_id),
2420 fn static_mutability(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::Mutability> {
2421 match tcx.hir().get_if_local(def_id) {
2422 Some(Node::Item(&hir::Item {
2423 kind: hir::ItemKind::Static(_, mutbl, _), ..
2425 Some(Node::ForeignItem( &hir::ForeignItem {
2426 kind: hir::ForeignItemKind::Static(_, mutbl), ..
2429 _ => bug!("static_mutability applied to non-local def-id {:?}", def_id),
2433 fn from_target_feature(
2436 attr: &ast::Attribute,
2437 whitelist: &FxHashMap<String, Option<Symbol>>,
2438 target_features: &mut Vec<Symbol>,
2440 let list = match attr.meta_item_list() {
2444 let bad_item = |span| {
2445 let msg = "malformed `target_feature` attribute input";
2446 let code = "enable = \"..\"".to_owned();
2447 tcx.sess.struct_span_err(span, &msg)
2448 .span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
2451 let rust_features = tcx.features();
2453 // Only `enable = ...` is accepted in the meta-item list.
2454 if !item.check_name(sym::enable) {
2455 bad_item(item.span());
2459 // Must be of the form `enable = "..."` (a string).
2460 let value = match item.value_str() {
2461 Some(value) => value,
2463 bad_item(item.span());
2468 // We allow comma separation to enable multiple features.
2469 target_features.extend(value.as_str().split(',').filter_map(|feature| {
2470 // Only allow whitelisted features per platform.
2471 let feature_gate = match whitelist.get(feature) {
2475 "the feature named `{}` is not valid for this target",
2478 let mut err = tcx.sess.struct_span_err(item.span(), &msg);
2481 format!("`{}` is not valid for this target", feature),
2483 if feature.starts_with("+") {
2484 let valid = whitelist.contains_key(&feature[1..]);
2486 err.help("consider removing the leading `+` in the feature name");
2494 // Only allow features whose feature gates have been enabled.
2495 let allowed = match feature_gate.as_ref().map(|s| *s) {
2496 Some(sym::arm_target_feature) => rust_features.arm_target_feature,
2497 Some(sym::aarch64_target_feature) => rust_features.aarch64_target_feature,
2498 Some(sym::hexagon_target_feature) => rust_features.hexagon_target_feature,
2499 Some(sym::powerpc_target_feature) => rust_features.powerpc_target_feature,
2500 Some(sym::mips_target_feature) => rust_features.mips_target_feature,
2501 Some(sym::avx512_target_feature) => rust_features.avx512_target_feature,
2502 Some(sym::mmx_target_feature) => rust_features.mmx_target_feature,
2503 Some(sym::sse4a_target_feature) => rust_features.sse4a_target_feature,
2504 Some(sym::tbm_target_feature) => rust_features.tbm_target_feature,
2505 Some(sym::wasm_target_feature) => rust_features.wasm_target_feature,
2506 Some(sym::cmpxchg16b_target_feature) => rust_features.cmpxchg16b_target_feature,
2507 Some(sym::adx_target_feature) => rust_features.adx_target_feature,
2508 Some(sym::movbe_target_feature) => rust_features.movbe_target_feature,
2509 Some(sym::rtm_target_feature) => rust_features.rtm_target_feature,
2510 Some(sym::f16c_target_feature) => rust_features.f16c_target_feature,
2511 Some(name) => bug!("unknown target feature gate {}", name),
2514 if !allowed && id.is_local() {
2515 feature_gate::emit_feature_err(
2516 &tcx.sess.parse_sess,
2517 feature_gate.unwrap(),
2519 feature_gate::GateIssue::Language,
2520 &format!("the target feature `{}` is currently unstable", feature),
2523 Some(Symbol::intern(feature))
2528 fn linkage_by_name(tcx: TyCtxt<'_>, def_id: DefId, name: &str) -> Linkage {
2529 use rustc::mir::mono::Linkage::*;
2531 // Use the names from src/llvm/docs/LangRef.rst here. Most types are only
2532 // applicable to variable declarations and may not really make sense for
2533 // Rust code in the first place but whitelist them anyway and trust that
2534 // the user knows what s/he's doing. Who knows, unanticipated use cases
2535 // may pop up in the future.
2537 // ghost, dllimport, dllexport and linkonce_odr_autohide are not supported
2538 // and don't have to be, LLVM treats them as no-ops.
2540 "appending" => Appending,
2541 "available_externally" => AvailableExternally,
2543 "extern_weak" => ExternalWeak,
2544 "external" => External,
2545 "internal" => Internal,
2546 "linkonce" => LinkOnceAny,
2547 "linkonce_odr" => LinkOnceODR,
2548 "private" => Private,
2550 "weak_odr" => WeakODR,
2552 let span = tcx.hir().span_if_local(def_id);
2553 if let Some(span) = span {
2554 tcx.sess.span_fatal(span, "invalid linkage specified")
2557 .fatal(&format!("invalid linkage specified: {}", name))
2563 fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
2564 let attrs = tcx.get_attrs(id);
2566 let mut codegen_fn_attrs = CodegenFnAttrs::new();
2568 let whitelist = tcx.target_features_whitelist(LOCAL_CRATE);
2570 let mut inline_span = None;
2571 let mut link_ordinal_span = None;
2572 for attr in attrs.iter() {
2573 if attr.check_name(sym::cold) {
2574 codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD;
2575 } else if attr.check_name(sym::rustc_allocator) {
2576 codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR;
2577 } else if attr.check_name(sym::unwind) {
2578 codegen_fn_attrs.flags |= CodegenFnAttrFlags::UNWIND;
2579 } else if attr.check_name(sym::ffi_returns_twice) {
2580 if tcx.is_foreign_item(id) {
2581 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE;
2583 // `#[ffi_returns_twice]` is only allowed `extern fn`s.
2588 "`#[ffi_returns_twice]` may only be used on foreign functions"
2591 } else if attr.check_name(sym::rustc_allocator_nounwind) {
2592 codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_ALLOCATOR_NOUNWIND;
2593 } else if attr.check_name(sym::naked) {
2594 codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
2595 } else if attr.check_name(sym::no_mangle) {
2596 codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2597 } else if attr.check_name(sym::rustc_std_internal_symbol) {
2598 codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2599 } else if attr.check_name(sym::no_debug) {
2600 codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_DEBUG;
2601 } else if attr.check_name(sym::used) {
2602 codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
2603 } else if attr.check_name(sym::thread_local) {
2604 codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
2605 } else if attr.check_name(sym::track_caller) {
2606 if tcx.fn_sig(id).abi() != abi::Abi::Rust {
2611 "Rust ABI is required to use `#[track_caller]`"
2614 codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2615 } else if attr.check_name(sym::export_name) {
2616 if let Some(s) = attr.value_str() {
2617 if s.as_str().contains("\0") {
2618 // `#[export_name = ...]` will be converted to a null-terminated string,
2619 // so it may not contain any null characters.
2624 "`export_name` may not contain null characters"
2627 codegen_fn_attrs.export_name = Some(s);
2629 } else if attr.check_name(sym::target_feature) {
2630 if tcx.fn_sig(id).unsafety() == Unsafety::Normal {
2631 let msg = "`#[target_feature(..)]` can only be applied to `unsafe` functions";
2632 tcx.sess.struct_span_err(attr.span, msg)
2633 .span_label(attr.span, "can only be applied to `unsafe` functions")
2634 .span_label(tcx.def_span(id), "not an `unsafe` function")
2637 from_target_feature(
2642 &mut codegen_fn_attrs.target_features,
2644 } else if attr.check_name(sym::linkage) {
2645 if let Some(val) = attr.value_str() {
2646 codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, id, &val.as_str()));
2648 } else if attr.check_name(sym::link_section) {
2649 if let Some(val) = attr.value_str() {
2650 if val.as_str().bytes().any(|b| b == 0) {
2652 "illegal null byte in link_section \
2656 tcx.sess.span_err(attr.span, &msg);
2658 codegen_fn_attrs.link_section = Some(val);
2661 } else if attr.check_name(sym::link_name) {
2662 codegen_fn_attrs.link_name = attr.value_str();
2663 } else if attr.check_name(sym::link_ordinal) {
2664 link_ordinal_span = Some(attr.span);
2665 if let ordinal @ Some(_) = check_link_ordinal(tcx, attr) {
2666 codegen_fn_attrs.link_ordinal = ordinal;
2671 codegen_fn_attrs.inline = attrs.iter().fold(InlineAttr::None, |ia, attr| {
2672 if !attr.has_name(sym::inline) {
2675 match attr.meta().map(|i| i.kind) {
2676 Some(MetaItemKind::Word) => {
2680 Some(MetaItemKind::List(ref items)) => {
2682 inline_span = Some(attr.span);
2683 if items.len() != 1 {
2685 tcx.sess.diagnostic(),
2688 "expected one argument"
2691 } else if list_contains_name(&items[..], sym::always) {
2693 } else if list_contains_name(&items[..], sym::never) {
2697 tcx.sess.diagnostic(),
2706 Some(MetaItemKind::NameValue(_)) => ia,
2711 codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
2712 if !attr.has_name(sym::optimize) {
2715 let err = |sp, s| span_err!(tcx.sess.diagnostic(), sp, E0722, "{}", s);
2716 match attr.meta().map(|i| i.kind) {
2717 Some(MetaItemKind::Word) => {
2718 err(attr.span, "expected one argument");
2721 Some(MetaItemKind::List(ref items)) => {
2723 inline_span = Some(attr.span);
2724 if items.len() != 1 {
2725 err(attr.span, "expected one argument");
2727 } else if list_contains_name(&items[..], sym::size) {
2729 } else if list_contains_name(&items[..], sym::speed) {
2732 err(items[0].span(), "invalid argument");
2736 Some(MetaItemKind::NameValue(_)) => ia,
2741 // If a function uses #[target_feature] it can't be inlined into general
2742 // purpose functions as they wouldn't have the right target features
2743 // enabled. For that reason we also forbid #[inline(always)] as it can't be
2746 if codegen_fn_attrs.target_features.len() > 0 {
2747 if codegen_fn_attrs.inline == InlineAttr::Always {
2748 if let Some(span) = inline_span {
2751 "cannot use `#[inline(always)]` with \
2752 `#[target_feature]`",
2758 // Weak lang items have the same semantics as "std internal" symbols in the
2759 // sense that they're preserved through all our LTO passes and only
2760 // strippable by the linker.
2762 // Additionally weak lang items have predetermined symbol names.
2763 if tcx.is_weak_lang_item(id) {
2764 codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2766 if let Some(name) = weak_lang_items::link_name(&attrs) {
2767 codegen_fn_attrs.export_name = Some(name);
2768 codegen_fn_attrs.link_name = Some(name);
2770 check_link_name_xor_ordinal(tcx, &codegen_fn_attrs, link_ordinal_span);
2772 // Internal symbols to the standard library all have no_mangle semantics in
2773 // that they have defined symbol names present in the function name. This
2774 // also applies to weak symbols where they all have known symbol names.
2775 if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
2776 codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2782 fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<usize> {
2783 use syntax::ast::{Lit, LitIntType, LitKind};
2784 let meta_item_list = attr.meta_item_list();
2785 let meta_item_list: Option<&[ast::NestedMetaItem]> = meta_item_list.as_ref().map(Vec::as_ref);
2786 let sole_meta_list = match meta_item_list {
2787 Some([item]) => item.literal(),
2790 if let Some(Lit { kind: LitKind::Int(ordinal, LitIntType::Unsuffixed), .. }) = sole_meta_list {
2791 if *ordinal <= std::usize::MAX as u128 {
2792 Some(*ordinal as usize)
2795 "ordinal value in `link_ordinal` is too large: `{}`",
2798 tcx.sess.struct_span_err(attr.span, &msg)
2799 .note("the value may not exceed `std::usize::MAX`")
2804 tcx.sess.struct_span_err(attr.span, "illegal ordinal format in `link_ordinal`")
2805 .note("an unsuffixed integer value, e.g., `1`, is expected")
2811 fn check_link_name_xor_ordinal(
2813 codegen_fn_attrs: &CodegenFnAttrs,
2814 inline_span: Option<Span>,
2816 if codegen_fn_attrs.link_name.is_none() || codegen_fn_attrs.link_ordinal.is_none() {
2819 let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
2820 if let Some(span) = inline_span {
2821 tcx.sess.span_err(span, msg);