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, DiagnosticId, StashKey};
51 struct OnlySelfBounds(bool);
53 ///////////////////////////////////////////////////////////////////////////
56 fn collect_mod_item_types(tcx: TyCtxt<'_>, module_def_id: DefId) {
57 tcx.hir().visit_item_likes_in_module(
59 &mut CollectItemTypesVisitor { tcx }.as_deep_visitor()
63 pub fn provide(providers: &mut Providers<'_>) {
64 *providers = Providers {
68 predicates_defined_on,
69 explicit_predicates_of,
71 type_param_predicates,
80 collect_mod_item_types,
85 ///////////////////////////////////////////////////////////////////////////
87 /// Context specific to some particular item. This is what implements
88 /// `AstConv`. It has information about the predicates that are defined
89 /// on the trait. Unfortunately, this predicate information is
90 /// available in various different forms at various points in the
91 /// process. So we can't just store a pointer to e.g., the AST or the
92 /// parsed ty form, we have to be more flexible. To this end, the
93 /// `ItemCtxt` is parameterized by a `DefId` that it uses to satisfy
94 /// `get_type_parameter_bounds` requests, drawing the information from
95 /// the AST (`hir::Generics`), recursively.
96 pub struct ItemCtxt<'tcx> {
101 ///////////////////////////////////////////////////////////////////////////
103 struct CollectItemTypesVisitor<'tcx> {
107 impl Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
108 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
109 NestedVisitorMap::OnlyBodies(&self.tcx.hir())
112 fn visit_item(&mut self, item: &'tcx hir::Item) {
113 convert_item(self.tcx, item.hir_id);
114 intravisit::walk_item(self, item);
117 fn visit_generics(&mut self, generics: &'tcx hir::Generics) {
118 for param in &generics.params {
120 hir::GenericParamKind::Lifetime { .. } => {}
121 hir::GenericParamKind::Type {
124 let def_id = self.tcx.hir().local_def_id(param.hir_id);
125 self.tcx.type_of(def_id);
127 hir::GenericParamKind::Type { .. } => {}
128 hir::GenericParamKind::Const { .. } => {
129 let def_id = self.tcx.hir().local_def_id(param.hir_id);
130 self.tcx.type_of(def_id);
134 intravisit::walk_generics(self, generics);
137 fn visit_expr(&mut self, expr: &'tcx hir::Expr) {
138 if let hir::ExprKind::Closure(..) = expr.kind {
139 let def_id = self.tcx.hir().local_def_id(expr.hir_id);
140 self.tcx.generics_of(def_id);
141 self.tcx.type_of(def_id);
143 intravisit::walk_expr(self, expr);
146 fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem) {
147 convert_trait_item(self.tcx, trait_item.hir_id);
148 intravisit::walk_trait_item(self, trait_item);
151 fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem) {
152 convert_impl_item(self.tcx, impl_item.hir_id);
153 intravisit::walk_impl_item(self, impl_item);
157 ///////////////////////////////////////////////////////////////////////////
158 // Utility types and common code for the above passes.
160 fn bad_placeholder_type(tcx: TyCtxt<'tcx>, span: Span) -> errors::DiagnosticBuilder<'tcx> {
161 let mut diag = tcx.sess.struct_span_err_with_code(
163 "the type placeholder `_` is not allowed within types on item signatures",
164 DiagnosticId::Error("E0121".into()),
166 diag.span_label(span, "not allowed in type signatures");
170 impl ItemCtxt<'tcx> {
171 pub fn new(tcx: TyCtxt<'tcx>, item_def_id: DefId) -> ItemCtxt<'tcx> {
172 ItemCtxt { tcx, item_def_id }
175 pub fn to_ty(&self, ast_ty: &'tcx hir::Ty) -> Ty<'tcx> {
176 AstConv::ast_ty_to_ty(self, ast_ty)
180 impl AstConv<'tcx> for ItemCtxt<'tcx> {
181 fn tcx(&self) -> TyCtxt<'tcx> {
185 fn item_def_id(&self) -> Option<DefId> {
186 Some(self.item_def_id)
189 fn get_type_parameter_bounds(&self, span: Span, def_id: DefId) -> ty::GenericPredicates<'tcx> {
192 .type_param_predicates((self.item_def_id, def_id))
197 _: Option<&ty::GenericParamDef>,
199 ) -> Option<ty::Region<'tcx>> {
203 fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
204 bad_placeholder_type(self.tcx(), span).emit();
212 _: Option<&ty::GenericParamDef>,
214 ) -> &'tcx Const<'tcx> {
215 bad_placeholder_type(self.tcx(), span).emit();
217 self.tcx().consts.err
220 fn projected_ty_from_poly_trait_ref(
224 poly_trait_ref: ty::PolyTraitRef<'tcx>,
226 if let Some(trait_ref) = poly_trait_ref.no_bound_vars() {
227 self.tcx().mk_projection(item_def_id, trait_ref.substs)
229 // There are no late-bound regions; we can just ignore the binder.
234 "cannot extract an associated type from a higher-ranked trait bound \
241 fn normalize_ty(&self, _span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
242 // Types in item signatures are not normalized to avoid undue dependencies.
246 fn set_tainted_by_errors(&self) {
247 // There's no obvious place to track this, so just let it go.
250 fn record_ty(&self, _hir_id: hir::HirId, _ty: Ty<'tcx>, _span: Span) {
251 // There's no place to record types from signatures?
255 /// Returns the predicates defined on `item_def_id` of the form
256 /// `X: Foo` where `X` is the type parameter `def_id`.
257 fn type_param_predicates(
259 (item_def_id, def_id): (DefId, DefId),
260 ) -> ty::GenericPredicates<'_> {
263 // In the AST, bounds can derive from two places. Either
264 // written inline like `<T: Foo>` or in a where-clause like
267 let param_id = tcx.hir().as_local_hir_id(def_id).unwrap();
268 let param_owner = tcx.hir().ty_param_owner(param_id);
269 let param_owner_def_id = tcx.hir().local_def_id(param_owner);
270 let generics = tcx.generics_of(param_owner_def_id);
271 let index = generics.param_def_id_to_index[&def_id];
272 let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(param_id));
274 // Don't look for bounds where the type parameter isn't in scope.
275 let parent = if item_def_id == param_owner_def_id {
278 tcx.generics_of(item_def_id).parent
281 let mut result = parent.map(|parent| {
282 let icx = ItemCtxt::new(tcx, parent);
283 icx.get_type_parameter_bounds(DUMMY_SP, def_id)
284 }).unwrap_or_default();
285 let mut extend = None;
287 let item_hir_id = tcx.hir().as_local_hir_id(item_def_id).unwrap();
288 let ast_generics = match tcx.hir().get(item_hir_id) {
289 Node::TraitItem(item) => &item.generics,
291 Node::ImplItem(item) => &item.generics,
293 Node::Item(item) => {
295 ItemKind::Fn(.., ref generics, _)
296 | ItemKind::Impl(_, _, _, ref generics, ..)
297 | ItemKind::TyAlias(_, ref generics)
298 | ItemKind::OpaqueTy(OpaqueTy {
303 | ItemKind::Enum(_, ref generics)
304 | ItemKind::Struct(_, ref generics)
305 | ItemKind::Union(_, ref generics) => generics,
306 ItemKind::Trait(_, _, ref generics, ..) => {
307 // Implied `Self: Trait` and supertrait bounds.
308 if param_id == item_hir_id {
309 let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id);
310 extend = Some((identity_trait_ref.to_predicate(), item.span));
318 Node::ForeignItem(item) => match item.kind {
319 ForeignItemKind::Fn(_, _, ref generics) => generics,
326 let icx = ItemCtxt::new(tcx, item_def_id);
327 let extra_predicates = extend.into_iter().chain(
328 icx.type_parameter_bounds_in_generics(ast_generics, param_id, ty, OnlySelfBounds(true))
330 .filter(|(predicate, _)| {
332 ty::Predicate::Trait(ref data) => data.skip_binder().self_ty().is_param(index),
337 result.predicates = tcx.arena.alloc_from_iter(
338 result.predicates.iter().copied().chain(extra_predicates),
343 impl ItemCtxt<'tcx> {
344 /// Finds bounds from `hir::Generics`. This requires scanning through the
345 /// AST. We do this to avoid having to convert *all* the bounds, which
346 /// would create artificial cycles. Instead, we can only convert the
347 /// bounds for a type parameter `X` if `X::Foo` is used.
348 fn type_parameter_bounds_in_generics(
350 ast_generics: &'tcx hir::Generics,
351 param_id: hir::HirId,
353 only_self_bounds: OnlySelfBounds,
354 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
355 let from_ty_params = ast_generics
358 .filter_map(|param| match param.kind {
359 GenericParamKind::Type { .. } if param.hir_id == param_id => Some(¶m.bounds),
362 .flat_map(|bounds| bounds.iter())
363 .flat_map(|b| predicates_from_bound(self, ty, b));
365 let from_where_clauses = ast_generics
369 .filter_map(|wp| match *wp {
370 hir::WherePredicate::BoundPredicate(ref bp) => Some(bp),
374 let bt = if is_param(self.tcx, &bp.bounded_ty, param_id) {
376 } else if !only_self_bounds.0 {
377 Some(self.to_ty(&bp.bounded_ty))
381 bp.bounds.iter().filter_map(move |b| bt.map(|bt| (bt, b)))
383 .flat_map(|(bt, b)| predicates_from_bound(self, bt, b));
385 from_ty_params.chain(from_where_clauses).collect()
389 /// Tests whether this is the AST for a reference to the type
390 /// parameter with ID `param_id`. We use this so as to avoid running
391 /// `ast_ty_to_ty`, because we want to avoid triggering an all-out
392 /// conversion of the type to avoid inducing unnecessary cycles.
393 fn is_param(tcx: TyCtxt<'_>, ast_ty: &hir::Ty, param_id: hir::HirId) -> bool {
394 if let hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) = ast_ty.kind {
396 Res::SelfTy(Some(def_id), None) | Res::Def(DefKind::TyParam, def_id) => {
397 def_id == tcx.hir().local_def_id(param_id)
406 fn convert_item(tcx: TyCtxt<'_>, item_id: hir::HirId) {
407 let it = tcx.hir().expect_item(item_id);
408 debug!("convert: item {} with id {}", it.ident, it.hir_id);
409 let def_id = tcx.hir().local_def_id(item_id);
411 // These don't define types.
412 hir::ItemKind::ExternCrate(_)
413 | hir::ItemKind::Use(..)
414 | hir::ItemKind::Mod(_)
415 | hir::ItemKind::GlobalAsm(_) => {}
416 hir::ItemKind::ForeignMod(ref foreign_mod) => {
417 for item in &foreign_mod.items {
418 let def_id = tcx.hir().local_def_id(item.hir_id);
419 tcx.generics_of(def_id);
421 tcx.predicates_of(def_id);
422 if let hir::ForeignItemKind::Fn(..) = item.kind {
427 hir::ItemKind::Enum(ref enum_definition, _) => {
428 tcx.generics_of(def_id);
430 tcx.predicates_of(def_id);
431 convert_enum_variant_types(tcx, def_id, &enum_definition.variants);
433 hir::ItemKind::Impl(..) => {
434 tcx.generics_of(def_id);
436 tcx.impl_trait_ref(def_id);
437 tcx.predicates_of(def_id);
439 hir::ItemKind::Trait(..) => {
440 tcx.generics_of(def_id);
441 tcx.trait_def(def_id);
442 tcx.at(it.span).super_predicates_of(def_id);
443 tcx.predicates_of(def_id);
445 hir::ItemKind::TraitAlias(..) => {
446 tcx.generics_of(def_id);
447 tcx.at(it.span).super_predicates_of(def_id);
448 tcx.predicates_of(def_id);
450 hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
451 tcx.generics_of(def_id);
453 tcx.predicates_of(def_id);
455 for f in struct_def.fields() {
456 let def_id = tcx.hir().local_def_id(f.hir_id);
457 tcx.generics_of(def_id);
459 tcx.predicates_of(def_id);
462 if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
463 convert_variant_ctor(tcx, ctor_hir_id);
467 // Desugared from `impl Trait`, so visited by the function's return type.
468 hir::ItemKind::OpaqueTy(hir::OpaqueTy {
469 impl_trait_fn: Some(_),
473 hir::ItemKind::OpaqueTy(..)
474 | hir::ItemKind::TyAlias(..)
475 | hir::ItemKind::Static(..)
476 | hir::ItemKind::Const(..)
477 | hir::ItemKind::Fn(..) => {
478 tcx.generics_of(def_id);
480 tcx.predicates_of(def_id);
481 if let hir::ItemKind::Fn(..) = it.kind {
488 fn convert_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::HirId) {
489 let trait_item = tcx.hir().expect_trait_item(trait_item_id);
490 let def_id = tcx.hir().local_def_id(trait_item.hir_id);
491 tcx.generics_of(def_id);
493 match trait_item.kind {
494 hir::TraitItemKind::Const(..)
495 | hir::TraitItemKind::Type(_, Some(_))
496 | hir::TraitItemKind::Method(..) => {
498 if let hir::TraitItemKind::Method(..) = trait_item.kind {
503 hir::TraitItemKind::Type(_, None) => {}
506 tcx.predicates_of(def_id);
509 fn convert_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::HirId) {
510 let def_id = tcx.hir().local_def_id(impl_item_id);
511 tcx.generics_of(def_id);
513 tcx.predicates_of(def_id);
514 if let hir::ImplItemKind::Method(..) = tcx.hir().expect_impl_item(impl_item_id).kind {
519 fn convert_variant_ctor(tcx: TyCtxt<'_>, ctor_id: hir::HirId) {
520 let def_id = tcx.hir().local_def_id(ctor_id);
521 tcx.generics_of(def_id);
523 tcx.predicates_of(def_id);
526 fn convert_enum_variant_types(
529 variants: &[hir::Variant]
531 let def = tcx.adt_def(def_id);
532 let repr_type = def.repr.discr_type();
533 let initial = repr_type.initial_discriminant(tcx);
534 let mut prev_discr = None::<Discr<'_>>;
536 // fill the discriminant values and field types
537 for variant in variants {
538 let wrapped_discr = prev_discr.map_or(initial, |d| d.wrap_incr(tcx));
540 if let Some(ref e) = variant.disr_expr {
541 let expr_did = tcx.hir().local_def_id(e.hir_id);
542 def.eval_explicit_discr(tcx, expr_did)
543 } else if let Some(discr) = repr_type.disr_incr(tcx, prev_discr) {
550 "enum discriminant overflowed"
553 format!("overflowed on value after {}", prev_discr.unwrap()),
555 "explicitly set `{} = {}` if that is desired outcome",
556 variant.ident, wrapped_discr
560 }.unwrap_or(wrapped_discr),
563 for f in variant.data.fields() {
564 let def_id = tcx.hir().local_def_id(f.hir_id);
565 tcx.generics_of(def_id);
567 tcx.predicates_of(def_id);
570 // Convert the ctor, if any. This also registers the variant as
572 if let Some(ctor_hir_id) = variant.data.ctor_hir_id() {
573 convert_variant_ctor(tcx, ctor_hir_id);
580 variant_did: Option<DefId>,
581 ctor_did: Option<DefId>,
583 discr: ty::VariantDiscr,
584 def: &hir::VariantData,
585 adt_kind: ty::AdtKind,
587 ) -> ty::VariantDef {
588 let mut seen_fields: FxHashMap<ast::Ident, Span> = Default::default();
589 let hir_id = tcx.hir().as_local_hir_id(variant_did.unwrap_or(parent_did)).unwrap();
594 let fid = tcx.hir().local_def_id(f.hir_id);
595 let dup_span = seen_fields.get(&f.ident.modern()).cloned();
596 if let Some(prev_span) = dup_span {
601 "field `{}` is already declared",
603 ).span_label(f.span, "field already declared")
604 .span_label(prev_span, format!("`{}` first declared here", f.ident))
607 seen_fields.insert(f.ident.modern(), f.span);
613 vis: ty::Visibility::from_hir(&f.vis, hir_id, tcx),
617 let recovered = match def {
618 hir::VariantData::Struct(_, r) => *r,
628 CtorKind::from_hir(def),
635 fn adt_def(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::AdtDef {
638 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
639 let item = match tcx.hir().get(hir_id) {
640 Node::Item(item) => item,
644 let repr = ReprOptions::new(tcx, def_id);
645 let (kind, variants) = match item.kind {
646 ItemKind::Enum(ref def, _) => {
647 let mut distance_from_explicit = 0;
648 let variants = def.variants
651 let variant_did = Some(tcx.hir().local_def_id(v.id));
652 let ctor_did = v.data.ctor_hir_id()
653 .map(|hir_id| tcx.hir().local_def_id(hir_id));
655 let discr = if let Some(ref e) = v.disr_expr {
656 distance_from_explicit = 0;
657 ty::VariantDiscr::Explicit(tcx.hir().local_def_id(e.hir_id))
659 ty::VariantDiscr::Relative(distance_from_explicit)
661 distance_from_explicit += 1;
663 convert_variant(tcx, variant_did, ctor_did, v.ident, discr,
664 &v.data, AdtKind::Enum, def_id)
668 (AdtKind::Enum, variants)
670 ItemKind::Struct(ref def, _) => {
671 let variant_did = None;
672 let ctor_did = def.ctor_hir_id()
673 .map(|hir_id| tcx.hir().local_def_id(hir_id));
675 let variants = std::iter::once(convert_variant(
676 tcx, variant_did, ctor_did, item.ident, ty::VariantDiscr::Relative(0), def,
677 AdtKind::Struct, def_id,
680 (AdtKind::Struct, variants)
682 ItemKind::Union(ref def, _) => {
683 let variant_did = None;
684 let ctor_did = def.ctor_hir_id()
685 .map(|hir_id| tcx.hir().local_def_id(hir_id));
687 let variants = std::iter::once(convert_variant(
688 tcx, variant_did, ctor_did, item.ident, ty::VariantDiscr::Relative(0), def,
689 AdtKind::Union, def_id,
692 (AdtKind::Union, variants)
696 tcx.alloc_adt_def(def_id, kind, variants, repr)
699 /// Ensures that the super-predicates of the trait with a `DefId`
700 /// of `trait_def_id` are converted and stored. This also ensures that
701 /// the transitive super-predicates are converted.
702 fn super_predicates_of(
705 ) -> ty::GenericPredicates<'_> {
706 debug!("super_predicates(trait_def_id={:?})", trait_def_id);
707 let trait_hir_id = tcx.hir().as_local_hir_id(trait_def_id).unwrap();
709 let item = match tcx.hir().get(trait_hir_id) {
710 Node::Item(item) => item,
711 _ => bug!("trait_node_id {} is not an item", trait_hir_id),
714 let (generics, bounds) = match item.kind {
715 hir::ItemKind::Trait(.., ref generics, ref supertraits, _) => (generics, supertraits),
716 hir::ItemKind::TraitAlias(ref generics, ref supertraits) => (generics, supertraits),
717 _ => span_bug!(item.span, "super_predicates invoked on non-trait"),
720 let icx = ItemCtxt::new(tcx, trait_def_id);
722 // Convert the bounds that follow the colon, e.g., `Bar + Zed` in `trait Foo: Bar + Zed`.
723 let self_param_ty = tcx.types.self_param;
724 let superbounds1 = AstConv::compute_bounds(&icx, self_param_ty, bounds, SizedByDefault::No,
727 let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
729 // Convert any explicit superbounds in the where-clause,
730 // e.g., `trait Foo where Self: Bar`.
731 // In the case of trait aliases, however, we include all bounds in the where-clause,
732 // so e.g., `trait Foo = where u32: PartialEq<Self>` would include `u32: PartialEq<Self>`
733 // as one of its "superpredicates".
734 let is_trait_alias = tcx.is_trait_alias(trait_def_id);
735 let superbounds2 = icx.type_parameter_bounds_in_generics(
736 generics, item.hir_id, self_param_ty, OnlySelfBounds(!is_trait_alias));
738 // Combine the two lists to form the complete set of superbounds:
739 let superbounds = &*tcx.arena.alloc_from_iter(
740 superbounds1.into_iter().chain(superbounds2)
743 // Now require that immediate supertraits are converted,
744 // which will, in turn, reach indirect supertraits.
745 for &(pred, span) in superbounds {
746 debug!("superbound: {:?}", pred);
747 if let ty::Predicate::Trait(bound) = pred {
748 tcx.at(span).super_predicates_of(bound.def_id());
752 ty::GenericPredicates {
754 predicates: superbounds,
758 fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::TraitDef {
759 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
760 let item = tcx.hir().expect_item(hir_id);
762 let (is_auto, unsafety) = match item.kind {
763 hir::ItemKind::Trait(is_auto, unsafety, ..) => (is_auto == hir::IsAuto::Yes, unsafety),
764 hir::ItemKind::TraitAlias(..) => (false, hir::Unsafety::Normal),
765 _ => span_bug!(item.span, "trait_def_of_item invoked on non-trait"),
768 let paren_sugar = tcx.has_attr(def_id, sym::rustc_paren_sugar);
769 if paren_sugar && !tcx.features().unboxed_closures {
770 let mut err = tcx.sess.struct_span_err(
772 "the `#[rustc_paren_sugar]` attribute is a temporary means of controlling \
773 which traits can use parenthetical notation",
777 "add `#![feature(unboxed_closures)]` to \
778 the crate attributes to use it"
783 let is_marker = tcx.has_attr(def_id, sym::marker);
784 let def_path_hash = tcx.def_path_hash(def_id);
785 let def = ty::TraitDef::new(def_id, unsafety, paren_sugar, is_auto, is_marker, def_path_hash);
789 fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<Span> {
790 struct LateBoundRegionsDetector<'tcx> {
792 outer_index: ty::DebruijnIndex,
793 has_late_bound_regions: Option<Span>,
796 impl Visitor<'tcx> for LateBoundRegionsDetector<'tcx> {
797 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
798 NestedVisitorMap::None
801 fn visit_ty(&mut self, ty: &'tcx hir::Ty) {
802 if self.has_late_bound_regions.is_some() {
806 hir::TyKind::BareFn(..) => {
807 self.outer_index.shift_in(1);
808 intravisit::walk_ty(self, ty);
809 self.outer_index.shift_out(1);
811 _ => intravisit::walk_ty(self, ty),
815 fn visit_poly_trait_ref(
817 tr: &'tcx hir::PolyTraitRef,
818 m: hir::TraitBoundModifier,
820 if self.has_late_bound_regions.is_some() {
823 self.outer_index.shift_in(1);
824 intravisit::walk_poly_trait_ref(self, tr, m);
825 self.outer_index.shift_out(1);
828 fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
829 if self.has_late_bound_regions.is_some() {
833 match self.tcx.named_region(lt.hir_id) {
834 Some(rl::Region::Static) | Some(rl::Region::EarlyBound(..)) => {}
835 Some(rl::Region::LateBound(debruijn, _, _))
836 | Some(rl::Region::LateBoundAnon(debruijn, _)) if debruijn < self.outer_index => {}
837 Some(rl::Region::LateBound(..))
838 | Some(rl::Region::LateBoundAnon(..))
839 | Some(rl::Region::Free(..))
841 self.has_late_bound_regions = Some(lt.span);
847 fn has_late_bound_regions<'tcx>(
849 generics: &'tcx hir::Generics,
850 decl: &'tcx hir::FnDecl,
852 let mut visitor = LateBoundRegionsDetector {
854 outer_index: ty::INNERMOST,
855 has_late_bound_regions: None,
857 for param in &generics.params {
858 if let GenericParamKind::Lifetime { .. } = param.kind {
859 if tcx.is_late_bound(param.hir_id) {
860 return Some(param.span);
864 visitor.visit_fn_decl(decl);
865 visitor.has_late_bound_regions
869 Node::TraitItem(item) => match item.kind {
870 hir::TraitItemKind::Method(ref sig, _) => {
871 has_late_bound_regions(tcx, &item.generics, &sig.decl)
875 Node::ImplItem(item) => match item.kind {
876 hir::ImplItemKind::Method(ref sig, _) => {
877 has_late_bound_regions(tcx, &item.generics, &sig.decl)
881 Node::ForeignItem(item) => match item.kind {
882 hir::ForeignItemKind::Fn(ref fn_decl, _, ref generics) => {
883 has_late_bound_regions(tcx, generics, fn_decl)
887 Node::Item(item) => match item.kind {
888 hir::ItemKind::Fn(ref sig, .., ref generics, _) => {
889 has_late_bound_regions(tcx, generics, &sig.decl)
897 fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::Generics {
900 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
902 let node = tcx.hir().get(hir_id);
903 let parent_def_id = match node {
904 Node::ImplItem(_) | Node::TraitItem(_) | Node::Variant(_) |
905 Node::Ctor(..) | Node::Field(_) => {
906 let parent_id = tcx.hir().get_parent_item(hir_id);
907 Some(tcx.hir().local_def_id(parent_id))
909 // FIXME(#43408) enable this in all cases when we get lazy normalization.
910 Node::AnonConst(&anon_const) => {
911 // HACK(eddyb) this provides the correct generics when the workaround
912 // for a const parameter `AnonConst` is being used elsewhere, as then
913 // there won't be the kind of cyclic dependency blocking #43408.
914 let expr = &tcx.hir().body(anon_const.body).value;
915 let icx = ItemCtxt::new(tcx, def_id);
916 if AstConv::const_param_def_id(&icx, expr).is_some() {
917 let parent_id = tcx.hir().get_parent_item(hir_id);
918 Some(tcx.hir().local_def_id(parent_id))
923 Node::Expr(&hir::Expr {
924 kind: hir::ExprKind::Closure(..),
926 }) => Some(tcx.closure_base_def_id(def_id)),
927 Node::Item(item) => match item.kind {
928 ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn, .. }) => impl_trait_fn,
934 let mut opt_self = None;
935 let mut allow_defaults = false;
937 let no_generics = hir::Generics::empty();
938 let ast_generics = match node {
939 Node::TraitItem(item) => &item.generics,
941 Node::ImplItem(item) => &item.generics,
943 Node::Item(item) => {
945 ItemKind::Fn(.., ref generics, _) | ItemKind::Impl(_, _, _, ref generics, ..) => {
949 ItemKind::TyAlias(_, ref generics)
950 | ItemKind::Enum(_, ref generics)
951 | ItemKind::Struct(_, ref generics)
952 | ItemKind::OpaqueTy(hir::OpaqueTy { ref generics, .. })
953 | ItemKind::Union(_, ref generics) => {
954 allow_defaults = true;
958 ItemKind::Trait(_, _, ref generics, ..)
959 | ItemKind::TraitAlias(ref generics, ..) => {
960 // Add in the self type parameter.
962 // Something of a hack: use the node id for the trait, also as
963 // the node id for the Self type parameter.
964 let param_id = item.hir_id;
966 opt_self = Some(ty::GenericParamDef {
969 def_id: tcx.hir().local_def_id(param_id),
970 pure_wrt_drop: false,
971 kind: ty::GenericParamDefKind::Type {
973 object_lifetime_default: rl::Set1::Empty,
978 allow_defaults = true;
986 Node::ForeignItem(item) => match item.kind {
987 ForeignItemKind::Static(..) => &no_generics,
988 ForeignItemKind::Fn(_, _, ref generics) => generics,
989 ForeignItemKind::Type => &no_generics,
995 let has_self = opt_self.is_some();
996 let mut parent_has_self = false;
997 let mut own_start = has_self as u32;
998 let parent_count = parent_def_id.map_or(0, |def_id| {
999 let generics = tcx.generics_of(def_id);
1000 assert_eq!(has_self, false);
1001 parent_has_self = generics.has_self;
1002 own_start = generics.count() as u32;
1003 generics.parent_count + generics.params.len()
1006 let mut params: Vec<_> = opt_self.into_iter().collect();
1008 let early_lifetimes = early_bound_lifetimes_from_generics(tcx, ast_generics);
1012 .map(|(i, param)| ty::GenericParamDef {
1013 name: param.name.ident().name,
1014 index: own_start + i as u32,
1015 def_id: tcx.hir().local_def_id(param.hir_id),
1016 pure_wrt_drop: param.pure_wrt_drop,
1017 kind: ty::GenericParamDefKind::Lifetime,
1021 let object_lifetime_defaults = tcx.object_lifetime_defaults(hir_id);
1023 // Now create the real type parameters.
1024 let type_start = own_start - has_self as u32 + params.len() as u32;
1030 .filter_map(|param| {
1031 let kind = match param.kind {
1032 GenericParamKind::Type {
1037 if !allow_defaults && default.is_some() {
1038 if !tcx.features().default_type_parameter_fallback {
1040 lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
1044 "defaults for type parameters are only allowed in \
1045 `struct`, `enum`, `type`, or `trait` definitions."
1051 ty::GenericParamDefKind::Type {
1052 has_default: default.is_some(),
1053 object_lifetime_default: object_lifetime_defaults
1055 .map_or(rl::Set1::Empty, |o| o[i]),
1059 GenericParamKind::Const { .. } => {
1060 ty::GenericParamDefKind::Const
1065 let param_def = ty::GenericParamDef {
1066 index: type_start + i as u32,
1067 name: param.name.ident().name,
1068 def_id: tcx.hir().local_def_id(param.hir_id),
1069 pure_wrt_drop: param.pure_wrt_drop,
1077 // provide junk type parameter defs - the only place that
1078 // cares about anything but the length is instantiation,
1079 // and we don't do that for closures.
1080 if let Node::Expr(&hir::Expr {
1081 kind: hir::ExprKind::Closure(.., gen),
1085 let dummy_args = if gen.is_some() {
1086 &["<yield_ty>", "<return_ty>", "<witness>"][..]
1088 &["<closure_kind>", "<closure_signature>"][..]
1095 .map(|(i, &arg)| ty::GenericParamDef {
1096 index: type_start + i as u32,
1097 name: Symbol::intern(arg),
1099 pure_wrt_drop: false,
1100 kind: ty::GenericParamDefKind::Type {
1102 object_lifetime_default: rl::Set1::Empty,
1108 if let Some(upvars) = tcx.upvars(def_id) {
1109 params.extend(upvars.iter().zip((dummy_args.len() as u32)..).map(|(_, i)| {
1110 ty::GenericParamDef {
1111 index: type_start + i,
1112 name: Symbol::intern("<upvar>"),
1114 pure_wrt_drop: false,
1115 kind: ty::GenericParamDefKind::Type {
1117 object_lifetime_default: rl::Set1::Empty,
1125 let param_def_id_to_index = params
1127 .map(|param| (param.def_id, param.index))
1130 tcx.arena.alloc(ty::Generics {
1131 parent: parent_def_id,
1134 param_def_id_to_index,
1135 has_self: has_self || parent_has_self,
1136 has_late_bound_regions: has_late_bound_regions(tcx, node),
1140 fn report_assoc_ty_on_inherent_impl(tcx: TyCtxt<'_>, span: Span) {
1145 "associated types are not yet supported in inherent impls (see #8995)"
1149 fn infer_placeholder_type(
1152 body_id: hir::BodyId,
1156 let ty = tcx.typeck_tables_of(def_id).node_type(body_id.hir_id);
1158 // If this came from a free `const` or `static mut?` item,
1159 // then the user may have written e.g. `const A = 42;`.
1160 // In this case, the parser has stashed a diagnostic for
1161 // us to improve in typeck so we do that now.
1162 match tcx.sess.diagnostic().steal_diagnostic(span, StashKey::ItemNoType) {
1164 // The parser provided a sub-optimal `HasPlaceholders` suggestion for the type.
1165 // We are typeck and have the real type, so remove that and suggest the actual type.
1166 err.suggestions.clear();
1167 err.span_suggestion(
1169 "provide a type for the item",
1170 format!("{}: {}", item_ident, ty),
1171 Applicability::MachineApplicable,
1176 let mut diag = bad_placeholder_type(tcx, span);
1177 if ty != tcx.types.err {
1178 diag.span_suggestion(
1180 "replace `_` with the correct type",
1182 Applicability::MaybeIncorrect,
1192 fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
1195 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1197 let icx = ItemCtxt::new(tcx, def_id);
1199 match tcx.hir().get(hir_id) {
1200 Node::TraitItem(item) => match item.kind {
1201 TraitItemKind::Method(..) => {
1202 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1203 tcx.mk_fn_def(def_id, substs)
1205 TraitItemKind::Const(ref ty, body_id) => {
1206 body_id.and_then(|body_id| {
1207 if let hir::TyKind::Infer = ty.kind {
1208 Some(infer_placeholder_type(tcx, def_id, body_id, ty.span, item.ident))
1212 }).unwrap_or_else(|| icx.to_ty(ty))
1214 TraitItemKind::Type(_, Some(ref ty)) => icx.to_ty(ty),
1215 TraitItemKind::Type(_, None) => {
1216 span_bug!(item.span, "associated type missing default");
1220 Node::ImplItem(item) => match item.kind {
1221 ImplItemKind::Method(..) => {
1222 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1223 tcx.mk_fn_def(def_id, substs)
1225 ImplItemKind::Const(ref ty, body_id) => {
1226 if let hir::TyKind::Infer = ty.kind {
1227 infer_placeholder_type(tcx, def_id, body_id, ty.span, item.ident)
1232 ImplItemKind::OpaqueTy(_) => {
1234 .impl_trait_ref(tcx.hir().get_parent_did(hir_id))
1237 report_assoc_ty_on_inherent_impl(tcx, item.span);
1240 find_opaque_ty_constraints(tcx, def_id)
1242 ImplItemKind::TyAlias(ref ty) => {
1244 .impl_trait_ref(tcx.hir().get_parent_did(hir_id))
1247 report_assoc_ty_on_inherent_impl(tcx, item.span);
1254 Node::Item(item) => {
1256 ItemKind::Static(ref ty, .., body_id)
1257 | ItemKind::Const(ref ty, body_id) => {
1258 if let hir::TyKind::Infer = ty.kind {
1259 infer_placeholder_type(tcx, def_id, body_id, ty.span, item.ident)
1264 ItemKind::TyAlias(ref ty, _)
1265 | ItemKind::Impl(.., ref ty, _) => icx.to_ty(ty),
1266 ItemKind::Fn(..) => {
1267 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1268 tcx.mk_fn_def(def_id, substs)
1270 ItemKind::Enum(..) | ItemKind::Struct(..) | ItemKind::Union(..) => {
1271 let def = tcx.adt_def(def_id);
1272 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1273 tcx.mk_adt(def, substs)
1275 ItemKind::OpaqueTy(hir::OpaqueTy {
1276 impl_trait_fn: None,
1278 }) => find_opaque_ty_constraints(tcx, def_id),
1279 // Opaque types desugared from `impl Trait`.
1280 ItemKind::OpaqueTy(hir::OpaqueTy {
1281 impl_trait_fn: Some(owner),
1284 tcx.typeck_tables_of(owner)
1285 .concrete_opaque_types
1287 .map(|opaque| opaque.concrete_type)
1288 .unwrap_or_else(|| {
1289 // This can occur if some error in the
1290 // owner fn prevented us from populating
1291 // the `concrete_opaque_types` table.
1292 tcx.sess.delay_span_bug(
1295 "owner {:?} has no opaque type for {:?} in its tables",
1303 | ItemKind::TraitAlias(..)
1305 | ItemKind::ForeignMod(..)
1306 | ItemKind::GlobalAsm(..)
1307 | ItemKind::ExternCrate(..)
1308 | ItemKind::Use(..) => {
1311 "compute_type_of_item: unexpected item type: {:?}",
1318 Node::ForeignItem(foreign_item) => match foreign_item.kind {
1319 ForeignItemKind::Fn(..) => {
1320 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1321 tcx.mk_fn_def(def_id, substs)
1323 ForeignItemKind::Static(ref t, _) => icx.to_ty(t),
1324 ForeignItemKind::Type => tcx.mk_foreign(def_id),
1327 Node::Ctor(&ref def) | Node::Variant(
1328 hir::Variant { data: ref def, .. }
1330 VariantData::Unit(..) | VariantData::Struct(..) => {
1331 tcx.type_of(tcx.hir().get_parent_did(hir_id))
1333 VariantData::Tuple(..) => {
1334 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1335 tcx.mk_fn_def(def_id, substs)
1339 Node::Field(field) => icx.to_ty(&field.ty),
1341 Node::Expr(&hir::Expr {
1342 kind: hir::ExprKind::Closure(.., gen),
1346 return tcx.typeck_tables_of(def_id).node_type(hir_id);
1349 let substs = InternalSubsts::identity_for_item(tcx, def_id);
1350 tcx.mk_closure(def_id, substs)
1353 Node::AnonConst(_) => {
1354 let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1357 kind: hir::TyKind::Array(_, ref constant),
1360 | Node::Ty(&hir::Ty {
1361 kind: hir::TyKind::Typeof(ref constant),
1364 | Node::Expr(&hir::Expr {
1365 kind: ExprKind::Repeat(_, ref constant),
1367 }) if constant.hir_id == hir_id =>
1372 Node::Variant(Variant {
1373 disr_expr: Some(ref e),
1375 }) if e.hir_id == hir_id =>
1377 tcx.adt_def(tcx.hir().get_parent_did(hir_id))
1383 Node::Ty(&hir::Ty { kind: hir::TyKind::Path(_), .. }) |
1384 Node::Expr(&hir::Expr { kind: ExprKind::Struct(..), .. }) |
1385 Node::Expr(&hir::Expr { kind: ExprKind::Path(_), .. }) |
1386 Node::TraitRef(..) => {
1387 let path = match parent_node {
1389 kind: hir::TyKind::Path(QPath::Resolved(_, ref path)),
1392 | Node::Expr(&hir::Expr {
1393 kind: ExprKind::Path(QPath::Resolved(_, ref path)),
1398 Node::Expr(&hir::Expr { kind: ExprKind::Struct(ref path, ..), .. }) => {
1399 if let QPath::Resolved(_, ref path) = **path {
1405 Node::TraitRef(&hir::TraitRef { ref path, .. }) => Some(&**path),
1409 if let Some(path) = path {
1410 let arg_index = path.segments.iter()
1411 .filter_map(|seg| seg.args.as_ref())
1412 .map(|generic_args| generic_args.args.as_ref())
1415 .filter(|arg| arg.is_const())
1417 .filter(|(_, arg)| arg.id() == hir_id)
1418 .map(|(index, _)| index)
1421 .unwrap_or_else(|| {
1422 bug!("no arg matching AnonConst in path");
1425 // We've encountered an `AnonConst` in some path, so we need to
1426 // figure out which generic parameter it corresponds to and return
1427 // the relevant type.
1428 let generics = match path.res {
1429 Res::Def(DefKind::Ctor(..), def_id) => {
1430 tcx.generics_of(tcx.parent(def_id).unwrap())
1432 Res::Def(_, def_id) => tcx.generics_of(def_id),
1433 Res::Err => return tcx.types.err,
1435 tcx.sess.delay_span_bug(
1438 "unexpected const parent path def {:?}",
1442 return tcx.types.err;
1446 generics.params.iter()
1448 if let ty::GenericParamDefKind::Const = param.kind {
1455 .map(|param| tcx.type_of(param.def_id))
1456 // This is no generic parameter associated with the arg. This is
1457 // probably from an extra arg where one is not needed.
1458 .unwrap_or(tcx.types.err)
1460 tcx.sess.delay_span_bug(
1463 "unexpected const parent path {:?}",
1467 return tcx.types.err;
1472 tcx.sess.delay_span_bug(
1475 "unexpected const parent in type_of_def_id(): {:?}", x
1483 Node::GenericParam(param) => match ¶m.kind {
1484 hir::GenericParamKind::Type { default: Some(ref ty), .. } => icx.to_ty(ty),
1485 hir::GenericParamKind::Const { ty: ref hir_ty, .. } => {
1486 let ty = icx.to_ty(hir_ty);
1487 if !tcx.features().const_compare_raw_pointers {
1488 let err = match ty.peel_refs().kind {
1489 ty::FnPtr(_) => Some("function pointers"),
1490 ty::RawPtr(_) => Some("raw pointers"),
1493 if let Some(unsupported_type) = err {
1494 feature_gate::emit_feature_err(
1495 &tcx.sess.parse_sess,
1496 sym::const_compare_raw_pointers,
1498 feature_gate::GateIssue::Language,
1500 "using {} as const generic parameters is unstable",
1506 if ty::search_for_structural_match_violation(
1507 param.hir_id, param.span, tcx, ty).is_some()
1513 "the types of const generic parameters must derive `PartialEq` and `Eq`",
1516 format!("`{}` doesn't derive both `PartialEq` and `Eq`", ty),
1521 x => bug!("unexpected non-type Node::GenericParam: {:?}", x),
1525 bug!("unexpected sort of node in type_of_def_id(): {:?}", x);
1530 fn find_opaque_ty_constraints(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
1531 use rustc::hir::{ImplItem, Item, TraitItem};
1533 debug!("find_opaque_ty_constraints({:?})", def_id);
1535 struct ConstraintLocator<'tcx> {
1538 // (first found type span, actual type, mapping from the opaque type's generic
1539 // parameters to the concrete type's generic parameters)
1541 // The mapping is an index for each use site of a generic parameter in the concrete type
1543 // The indices index into the generic parameters on the opaque type.
1544 found: Option<(Span, Ty<'tcx>, Vec<usize>)>,
1547 impl ConstraintLocator<'tcx> {
1548 fn check(&mut self, def_id: DefId) {
1549 // Don't try to check items that cannot possibly constrain the type.
1550 if !self.tcx.has_typeck_tables(def_id) {
1552 "find_opaque_ty_constraints: no constraint for `{:?}` at `{:?}`: no tables",
1560 .typeck_tables_of(def_id)
1561 .concrete_opaque_types
1563 if let Some(ty::ResolvedOpaqueTy { concrete_type, substs }) = ty {
1565 "find_opaque_ty_constraints: found constraint for `{:?}` at `{:?}`: {:?}",
1571 // FIXME(oli-obk): trace the actual span from inference to improve errors.
1572 let span = self.tcx.def_span(def_id);
1573 // used to quickly look up the position of a generic parameter
1574 let mut index_map: FxHashMap<ty::ParamTy, usize> = FxHashMap::default();
1575 // Skipping binder is ok, since we only use this to find generic parameters and
1577 for (idx, subst) in substs.iter().enumerate() {
1578 if let GenericArgKind::Type(ty) = subst.unpack() {
1579 if let ty::Param(p) = ty.kind {
1580 if index_map.insert(p, idx).is_some() {
1581 // There was already an entry for `p`, meaning a generic parameter
1583 self.tcx.sess.span_err(
1586 "defining opaque type use restricts opaque \
1587 type by using the generic parameter `{}` twice",
1594 self.tcx.sess.delay_span_bug(
1597 "non-defining opaque ty use in defining scope: {:?}, {:?}",
1598 concrete_type, substs,
1604 // Compute the index within the opaque type for each generic parameter used in
1605 // the concrete type.
1606 let indices = concrete_type
1607 .subst(self.tcx, substs)
1609 .filter_map(|t| match &t.kind {
1610 ty::Param(p) => Some(*index_map.get(p).unwrap()),
1613 let is_param = |ty: Ty<'_>| match ty.kind {
1614 ty::Param(_) => true,
1617 if !substs.types().all(is_param) {
1618 self.tcx.sess.span_err(
1620 "defining opaque type use does not fully define opaque type",
1622 } else if let Some((prev_span, prev_ty, ref prev_indices)) = self.found {
1623 let mut ty = concrete_type.walk().fuse();
1624 let mut p_ty = prev_ty.walk().fuse();
1625 let iter_eq = (&mut ty).zip(&mut p_ty).all(|(t, p)| match (&t.kind, &p.kind) {
1626 // Type parameters are equal to any other type parameter for the purpose of
1627 // concrete type equality, as it is possible to obtain the same type just
1628 // by passing matching parameters to a function.
1629 (ty::Param(_), ty::Param(_)) => true,
1632 if !iter_eq || ty.next().is_some() || p_ty.next().is_some() {
1633 debug!("find_opaque_ty_constraints: span={:?}", span);
1634 // Found different concrete types for the opaque type.
1635 let mut err = self.tcx.sess.struct_span_err(
1637 "concrete type differs from previous defining opaque type use",
1641 format!("expected `{}`, got `{}`", prev_ty, concrete_type),
1643 err.span_note(prev_span, "previous use here");
1645 } else if indices != *prev_indices {
1646 // Found "same" concrete types, but the generic parameter order differs.
1647 let mut err = self.tcx.sess.struct_span_err(
1649 "concrete type's generic parameters differ from previous defining use",
1651 use std::fmt::Write;
1652 let mut s = String::new();
1653 write!(s, "expected [").unwrap();
1654 let list = |s: &mut String, indices: &Vec<usize>| {
1655 let mut indices = indices.iter().cloned();
1656 if let Some(first) = indices.next() {
1657 write!(s, "`{}`", substs[first]).unwrap();
1659 write!(s, ", `{}`", substs[i]).unwrap();
1663 list(&mut s, prev_indices);
1664 write!(s, "], got [").unwrap();
1665 list(&mut s, &indices);
1666 write!(s, "]").unwrap();
1667 err.span_label(span, s);
1668 err.span_note(prev_span, "previous use here");
1672 self.found = Some((span, concrete_type, indices));
1676 "find_opaque_ty_constraints: no constraint for `{:?}` at `{:?}`",
1684 impl<'tcx> intravisit::Visitor<'tcx> for ConstraintLocator<'tcx> {
1685 fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'tcx> {
1686 intravisit::NestedVisitorMap::All(&self.tcx.hir())
1688 fn visit_item(&mut self, it: &'tcx Item) {
1689 debug!("find_existential_constraints: visiting {:?}", it);
1690 let def_id = self.tcx.hir().local_def_id(it.hir_id);
1691 // The opaque type itself or its children are not within its reveal scope.
1692 if def_id != self.def_id {
1694 intravisit::walk_item(self, it);
1697 fn visit_impl_item(&mut self, it: &'tcx ImplItem) {
1698 debug!("find_existential_constraints: visiting {:?}", it);
1699 let def_id = self.tcx.hir().local_def_id(it.hir_id);
1700 // The opaque type itself or its children are not within its reveal scope.
1701 if def_id != self.def_id {
1703 intravisit::walk_impl_item(self, it);
1706 fn visit_trait_item(&mut self, it: &'tcx TraitItem) {
1707 debug!("find_existential_constraints: visiting {:?}", it);
1708 let def_id = self.tcx.hir().local_def_id(it.hir_id);
1710 intravisit::walk_trait_item(self, it);
1714 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1715 let scope = tcx.hir().get_defining_scope(hir_id);
1716 let mut locator = ConstraintLocator {
1722 debug!("find_opaque_ty_constraints: scope={:?}", scope);
1724 if scope == hir::CRATE_HIR_ID {
1725 intravisit::walk_crate(&mut locator, tcx.hir().krate());
1727 debug!("find_opaque_ty_constraints: scope={:?}", tcx.hir().get(scope));
1728 match tcx.hir().get(scope) {
1729 // We explicitly call `visit_*` methods, instead of using `intravisit::walk_*` methods
1730 // This allows our visitor to process the defining item itself, causing
1731 // it to pick up any 'sibling' defining uses.
1733 // For example, this code:
1736 // type Blah = impl Debug;
1737 // let my_closure = || -> Blah { true };
1741 // requires us to explicitly process `foo()` in order
1742 // to notice the defining usage of `Blah`.
1743 Node::Item(ref it) => locator.visit_item(it),
1744 Node::ImplItem(ref it) => locator.visit_impl_item(it),
1745 Node::TraitItem(ref it) => locator.visit_trait_item(it),
1747 "{:?} is not a valid scope for an opaque type item",
1753 match locator.found {
1754 Some((_, ty, _)) => ty,
1756 let span = tcx.def_span(def_id);
1757 tcx.sess.span_err(span, "could not find defining uses");
1763 pub fn get_infer_ret_ty(output: &'_ hir::FunctionRetTy) -> Option<&hir::Ty> {
1764 if let hir::FunctionRetTy::Return(ref ty) = output {
1765 if let hir::TyKind::Infer = ty.kind {
1772 fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
1774 use rustc::hir::Node::*;
1776 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1778 let icx = ItemCtxt::new(tcx, def_id);
1780 match tcx.hir().get(hir_id) {
1781 TraitItem(hir::TraitItem {
1782 kind: TraitItemKind::Method(sig, TraitMethod::Provided(_)),
1785 | ImplItem(hir::ImplItem {
1786 kind: ImplItemKind::Method(sig, _),
1790 kind: ItemKind::Fn(sig, _, _),
1792 }) => match get_infer_ret_ty(&sig.decl.output) {
1794 let fn_sig = tcx.typeck_tables_of(def_id).liberated_fn_sigs()[hir_id];
1795 let mut diag = bad_placeholder_type(tcx, ty.span);
1796 let ret_ty = fn_sig.output();
1797 if ret_ty != tcx.types.err {
1798 diag.span_suggestion(
1800 "replace `_` with the correct return type",
1802 Applicability::MaybeIncorrect,
1806 ty::Binder::bind(fn_sig)
1808 None => AstConv::ty_of_fn(&icx, sig.header.unsafety, sig.header.abi, &sig.decl)
1811 TraitItem(hir::TraitItem {
1812 kind: TraitItemKind::Method(FnSig { header, decl }, _),
1815 AstConv::ty_of_fn(&icx, header.unsafety, header.abi, decl)
1818 ForeignItem(&hir::ForeignItem {
1819 kind: ForeignItemKind::Fn(ref fn_decl, _, _),
1822 let abi = tcx.hir().get_foreign_abi(hir_id);
1823 compute_sig_of_foreign_fn_decl(tcx, def_id, fn_decl, abi)
1826 Ctor(data) | Variant(
1827 hir::Variant { data, .. }
1828 ) if data.ctor_hir_id().is_some() => {
1829 let ty = tcx.type_of(tcx.hir().get_parent_did(hir_id));
1830 let inputs = data.fields()
1832 .map(|f| tcx.type_of(tcx.hir().local_def_id(f.hir_id)));
1833 ty::Binder::bind(tcx.mk_fn_sig(
1837 hir::Unsafety::Normal,
1843 kind: hir::ExprKind::Closure(..),
1846 // Closure signatures are not like other function
1847 // signatures and cannot be accessed through `fn_sig`. For
1848 // example, a closure signature excludes the `self`
1849 // argument. In any case they are embedded within the
1850 // closure type as part of the `ClosureSubsts`.
1853 // the signature of a closure, you should use the
1854 // `closure_sig` method on the `ClosureSubsts`:
1856 // closure_substs.sig(def_id, tcx)
1858 // or, inside of an inference context, you can use
1860 // infcx.closure_sig(def_id, closure_substs)
1861 bug!("to get the signature of a closure, use `closure_sig()` not `fn_sig()`");
1865 bug!("unexpected sort of node in fn_sig(): {:?}", x);
1870 fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> {
1871 let icx = ItemCtxt::new(tcx, def_id);
1873 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1874 match tcx.hir().expect_item(hir_id).kind {
1875 hir::ItemKind::Impl(.., ref opt_trait_ref, _, _) => {
1876 opt_trait_ref.as_ref().map(|ast_trait_ref| {
1877 let selfty = tcx.type_of(def_id);
1878 AstConv::instantiate_mono_trait_ref(&icx, ast_trait_ref, selfty)
1885 fn impl_polarity(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ImplPolarity {
1886 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
1887 let is_rustc_reservation = tcx.has_attr(def_id, sym::rustc_reservation_impl);
1888 let item = tcx.hir().expect_item(hir_id);
1890 hir::ItemKind::Impl(_, hir::ImplPolarity::Negative, ..) => {
1891 if is_rustc_reservation {
1892 tcx.sess.span_err(item.span, "reservation impls can't be negative");
1894 ty::ImplPolarity::Negative
1896 hir::ItemKind::Impl(_, hir::ImplPolarity::Positive, _, _, None, _, _) => {
1897 if is_rustc_reservation {
1898 tcx.sess.span_err(item.span, "reservation impls can't be inherent");
1900 ty::ImplPolarity::Positive
1902 hir::ItemKind::Impl(_, hir::ImplPolarity::Positive, _, _, Some(_tr), _, _) => {
1903 if is_rustc_reservation {
1904 ty::ImplPolarity::Reservation
1906 ty::ImplPolarity::Positive
1909 ref item => bug!("impl_polarity: {:?} not an impl", item),
1913 /// Returns the early-bound lifetimes declared in this generics
1914 /// listing. For anything other than fns/methods, this is just all
1915 /// the lifetimes that are declared. For fns or methods, we have to
1916 /// screen out those that do not appear in any where-clauses etc using
1917 /// `resolve_lifetime::early_bound_lifetimes`.
1918 fn early_bound_lifetimes_from_generics<'a, 'tcx: 'a>(
1920 generics: &'a hir::Generics,
1921 ) -> impl Iterator<Item = &'a hir::GenericParam> + Captures<'tcx> {
1925 .filter(move |param| match param.kind {
1926 GenericParamKind::Lifetime { .. } => {
1927 !tcx.is_late_bound(param.hir_id)
1933 /// Returns a list of type predicates for the definition with ID `def_id`, including inferred
1934 /// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus
1935 /// inferred constraints concerning which regions outlive other regions.
1936 fn predicates_defined_on(
1939 ) -> ty::GenericPredicates<'_> {
1940 debug!("predicates_defined_on({:?})", def_id);
1941 let mut result = tcx.explicit_predicates_of(def_id);
1943 "predicates_defined_on: explicit_predicates_of({:?}) = {:?}",
1947 let inferred_outlives = tcx.inferred_outlives_of(def_id);
1948 if !inferred_outlives.is_empty() {
1950 "predicates_defined_on: inferred_outlives_of({:?}) = {:?}",
1954 if result.predicates.is_empty() {
1955 result.predicates = inferred_outlives;
1957 result.predicates = tcx.arena.alloc_from_iter(
1958 result.predicates.iter().chain(inferred_outlives).copied(),
1962 debug!("predicates_defined_on({:?}) = {:?}", def_id, result);
1966 /// Returns a list of all type predicates (explicit and implicit) for the definition with
1967 /// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus
1968 /// `Self: Trait` predicates for traits.
1969 fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
1970 let mut result = tcx.predicates_defined_on(def_id);
1972 if tcx.is_trait(def_id) {
1973 // For traits, add `Self: Trait` predicate. This is
1974 // not part of the predicates that a user writes, but it
1975 // is something that one must prove in order to invoke a
1976 // method or project an associated type.
1978 // In the chalk setup, this predicate is not part of the
1979 // "predicates" for a trait item. But it is useful in
1980 // rustc because if you directly (e.g.) invoke a trait
1981 // method like `Trait::method(...)`, you must naturally
1982 // prove that the trait applies to the types that were
1983 // used, and adding the predicate into this list ensures
1984 // that this is done.
1985 let span = tcx.def_span(def_id);
1986 result.predicates = tcx.arena.alloc_from_iter(
1987 result.predicates.iter().copied().chain(
1988 std::iter::once((ty::TraitRef::identity(tcx, def_id).to_predicate(), span))
1992 debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
1996 /// Returns a list of user-specified type predicates for the definition with ID `def_id`.
1997 /// N.B., this does not include any implied/inferred constraints.
1998 fn explicit_predicates_of(
2001 ) -> ty::GenericPredicates<'_> {
2003 use rustc_data_structures::fx::FxHashSet;
2005 debug!("explicit_predicates_of(def_id={:?})", def_id);
2007 /// A data structure with unique elements, which preserves order of insertion.
2008 /// Preserving the order of insertion is important here so as not to break
2009 /// compile-fail UI tests.
2010 // FIXME(eddyb) just use `IndexSet` from `indexmap`.
2011 struct UniquePredicates<'tcx> {
2012 predicates: Vec<(ty::Predicate<'tcx>, Span)>,
2013 uniques: FxHashSet<(ty::Predicate<'tcx>, Span)>,
2016 impl<'tcx> UniquePredicates<'tcx> {
2020 uniques: FxHashSet::default(),
2024 fn push(&mut self, value: (ty::Predicate<'tcx>, Span)) {
2025 if self.uniques.insert(value) {
2026 self.predicates.push(value);
2030 fn extend<I: IntoIterator<Item = (ty::Predicate<'tcx>, Span)>>(&mut self, iter: I) {
2037 let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
2038 let node = tcx.hir().get(hir_id);
2040 let mut is_trait = None;
2041 let mut is_default_impl_trait = None;
2043 let icx = ItemCtxt::new(tcx, def_id);
2045 const NO_GENERICS: &hir::Generics = &hir::Generics::empty();
2047 let empty_trait_items = HirVec::new();
2049 let mut predicates = UniquePredicates::new();
2051 let ast_generics = match node {
2052 Node::TraitItem(item) => &item.generics,
2054 Node::ImplItem(item) => match item.kind {
2055 ImplItemKind::OpaqueTy(ref bounds) => {
2056 let substs = InternalSubsts::identity_for_item(tcx, def_id);
2057 let opaque_ty = tcx.mk_opaque(def_id, substs);
2059 // Collect the bounds, i.e., the `A + B + 'c` in `impl A + B + 'c`.
2060 let bounds = AstConv::compute_bounds(
2064 SizedByDefault::Yes,
2065 tcx.def_span(def_id),
2068 predicates.extend(bounds.predicates(tcx, opaque_ty));
2071 _ => &item.generics,
2074 Node::Item(item) => {
2076 ItemKind::Impl(_, _, defaultness, ref generics, ..) => {
2077 if defaultness.is_default() {
2078 is_default_impl_trait = tcx.impl_trait_ref(def_id);
2082 ItemKind::Fn(.., ref generics, _)
2083 | ItemKind::TyAlias(_, ref generics)
2084 | ItemKind::Enum(_, ref generics)
2085 | ItemKind::Struct(_, ref generics)
2086 | ItemKind::Union(_, ref generics) => generics,
2088 ItemKind::Trait(_, _, ref generics, .., ref items) => {
2089 is_trait = Some((ty::TraitRef::identity(tcx, def_id), items));
2092 ItemKind::TraitAlias(ref generics, _) => {
2093 is_trait = Some((ty::TraitRef::identity(tcx, def_id), &empty_trait_items));
2096 ItemKind::OpaqueTy(OpaqueTy {
2102 let substs = InternalSubsts::identity_for_item(tcx, def_id);
2103 let opaque_ty = tcx.mk_opaque(def_id, substs);
2105 // Collect the bounds, i.e., the `A + B + 'c` in `impl A + B + 'c`.
2106 let bounds = AstConv::compute_bounds(
2110 SizedByDefault::Yes,
2111 tcx.def_span(def_id),
2114 let bounds_predicates = bounds.predicates(tcx, opaque_ty);
2115 if impl_trait_fn.is_some() {
2117 return ty::GenericPredicates {
2119 predicates: tcx.arena.alloc_from_iter(bounds_predicates),
2122 // named opaque types
2123 predicates.extend(bounds_predicates);
2132 Node::ForeignItem(item) => match item.kind {
2133 ForeignItemKind::Static(..) => NO_GENERICS,
2134 ForeignItemKind::Fn(_, _, ref generics) => generics,
2135 ForeignItemKind::Type => NO_GENERICS,
2141 let generics = tcx.generics_of(def_id);
2142 let parent_count = generics.parent_count as u32;
2143 let has_own_self = generics.has_self && parent_count == 0;
2145 // Below we'll consider the bounds on the type parameters (including `Self`)
2146 // and the explicit where-clauses, but to get the full set of predicates
2147 // on a trait we need to add in the supertrait bounds and bounds found on
2148 // associated types.
2149 if let Some((_trait_ref, _)) = is_trait {
2150 predicates.extend(tcx.super_predicates_of(def_id).predicates.iter().cloned());
2153 // In default impls, we can assume that the self type implements
2154 // the trait. So in:
2156 // default impl Foo for Bar { .. }
2158 // we add a default where clause `Foo: Bar`. We do a similar thing for traits
2159 // (see below). Recall that a default impl is not itself an impl, but rather a
2160 // set of defaults that can be incorporated into another impl.
2161 if let Some(trait_ref) = is_default_impl_trait {
2162 predicates.push((trait_ref.to_poly_trait_ref().to_predicate(), tcx.def_span(def_id)));
2165 // Collect the region predicates that were declared inline as
2166 // well. In the case of parameters declared on a fn or method, we
2167 // have to be careful to only iterate over early-bound regions.
2168 let mut index = parent_count + has_own_self as u32;
2169 for param in early_bound_lifetimes_from_generics(tcx, ast_generics) {
2170 let region = tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
2171 def_id: tcx.hir().local_def_id(param.hir_id),
2173 name: param.name.ident().name,
2178 GenericParamKind::Lifetime { .. } => {
2179 param.bounds.iter().for_each(|bound| match bound {
2180 hir::GenericBound::Outlives(lt) => {
2181 let bound = AstConv::ast_region_to_region(&icx, <, None);
2182 let outlives = ty::Binder::bind(ty::OutlivesPredicate(region, bound));
2183 predicates.push((outlives.to_predicate(), lt.span));
2192 // Collect the predicates that were written inline by the user on each
2193 // type parameter (e.g., `<T: Foo>`).
2194 for param in &ast_generics.params {
2195 if let GenericParamKind::Type { .. } = param.kind {
2196 let name = param.name.ident().name;
2197 let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
2200 let sized = SizedByDefault::Yes;
2201 let bounds = AstConv::compute_bounds(&icx, param_ty, ¶m.bounds, sized, param.span);
2202 predicates.extend(bounds.predicates(tcx, param_ty));
2206 // Add in the bounds that appear in the where-clause.
2207 let where_clause = &ast_generics.where_clause;
2208 for predicate in &where_clause.predicates {
2210 &hir::WherePredicate::BoundPredicate(ref bound_pred) => {
2211 let ty = icx.to_ty(&bound_pred.bounded_ty);
2213 // Keep the type around in a dummy predicate, in case of no bounds.
2214 // That way, `where Ty:` is not a complete noop (see #53696) and `Ty`
2215 // is still checked for WF.
2216 if bound_pred.bounds.is_empty() {
2217 if let ty::Param(_) = ty.kind {
2218 // This is a `where T:`, which can be in the HIR from the
2219 // transformation that moves `?Sized` to `T`'s declaration.
2220 // We can skip the predicate because type parameters are
2221 // trivially WF, but also we *should*, to avoid exposing
2222 // users who never wrote `where Type:,` themselves, to
2223 // compiler/tooling bugs from not handling WF predicates.
2225 let span = bound_pred.bounded_ty.span;
2226 let predicate = ty::OutlivesPredicate(ty, tcx.mk_region(ty::ReEmpty));
2228 (ty::Predicate::TypeOutlives(ty::Binder::dummy(predicate)), span)
2233 for bound in bound_pred.bounds.iter() {
2235 &hir::GenericBound::Trait(ref poly_trait_ref, _) => {
2236 let mut bounds = Bounds::default();
2237 let _ = AstConv::instantiate_poly_trait_ref(
2243 predicates.extend(bounds.predicates(tcx, ty));
2246 &hir::GenericBound::Outlives(ref lifetime) => {
2247 let region = AstConv::ast_region_to_region(&icx, lifetime, None);
2248 let pred = ty::Binder::bind(ty::OutlivesPredicate(ty, region));
2249 predicates.push((ty::Predicate::TypeOutlives(pred), lifetime.span))
2255 &hir::WherePredicate::RegionPredicate(ref region_pred) => {
2256 let r1 = AstConv::ast_region_to_region(&icx, ®ion_pred.lifetime, None);
2257 predicates.extend(region_pred.bounds.iter().map(|bound| {
2258 let (r2, span) = match bound {
2259 hir::GenericBound::Outlives(lt) => {
2260 (AstConv::ast_region_to_region(&icx, lt, None), lt.span)
2264 let pred = ty::Binder::bind(ty::OutlivesPredicate(r1, r2));
2266 (ty::Predicate::RegionOutlives(pred), span)
2270 &hir::WherePredicate::EqPredicate(..) => {
2276 // Add predicates from associated type bounds.
2277 if let Some((self_trait_ref, trait_items)) = is_trait {
2278 predicates.extend(trait_items.iter().flat_map(|trait_item_ref| {
2279 let trait_item = tcx.hir().trait_item(trait_item_ref.id);
2280 let bounds = match trait_item.kind {
2281 hir::TraitItemKind::Type(ref bounds, _) => bounds,
2282 _ => return Vec::new().into_iter()
2286 tcx.mk_projection(tcx.hir().local_def_id(trait_item.hir_id),
2287 self_trait_ref.substs);
2289 let bounds = AstConv::compute_bounds(
2290 &ItemCtxt::new(tcx, def_id),
2293 SizedByDefault::Yes,
2297 bounds.predicates(tcx, assoc_ty).into_iter()
2301 let mut predicates = predicates.predicates;
2303 // Subtle: before we store the predicates into the tcx, we
2304 // sort them so that predicates like `T: Foo<Item=U>` come
2305 // before uses of `U`. This avoids false ambiguity errors
2306 // in trait checking. See `setup_constraining_predicates`
2308 if let Node::Item(&Item {
2309 kind: ItemKind::Impl(..),
2313 let self_ty = tcx.type_of(def_id);
2314 let trait_ref = tcx.impl_trait_ref(def_id);
2315 cgp::setup_constraining_predicates(
2319 &mut cgp::parameters_for_impl(self_ty, trait_ref),
2323 let result = ty::GenericPredicates {
2324 parent: generics.parent,
2325 predicates: tcx.arena.alloc_from_iter(predicates),
2327 debug!("explicit_predicates_of(def_id={:?}) = {:?}", def_id, result);
2331 /// Converts a specific `GenericBound` from the AST into a set of
2332 /// predicates that apply to the self type. A vector is returned
2333 /// because this can be anywhere from zero predicates (`T: ?Sized` adds no
2334 /// predicates) to one (`T: Foo`) to many (`T: Bar<X = i32>` adds `T: Bar`
2335 /// and `<T as Bar>::X == i32`).
2336 fn predicates_from_bound<'tcx>(
2337 astconv: &dyn AstConv<'tcx>,
2339 bound: &'tcx hir::GenericBound,
2340 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2342 hir::GenericBound::Trait(ref tr, hir::TraitBoundModifier::None) => {
2343 let mut bounds = Bounds::default();
2344 let _ = astconv.instantiate_poly_trait_ref(
2349 bounds.predicates(astconv.tcx(), param_ty)
2351 hir::GenericBound::Outlives(ref lifetime) => {
2352 let region = astconv.ast_region_to_region(lifetime, None);
2353 let pred = ty::Binder::bind(ty::OutlivesPredicate(param_ty, region));
2354 vec![(ty::Predicate::TypeOutlives(pred), lifetime.span)]
2356 hir::GenericBound::Trait(_, hir::TraitBoundModifier::Maybe) => vec![],
2360 fn compute_sig_of_foreign_fn_decl<'tcx>(
2363 decl: &'tcx hir::FnDecl,
2365 ) -> ty::PolyFnSig<'tcx> {
2366 let unsafety = if abi == abi::Abi::RustIntrinsic {
2367 intrinsic_operation_unsafety(&tcx.item_name(def_id).as_str())
2369 hir::Unsafety::Unsafe
2371 let fty = AstConv::ty_of_fn(&ItemCtxt::new(tcx, def_id), unsafety, abi, decl);
2373 // Feature gate SIMD types in FFI, since I am not sure that the
2374 // ABIs are handled at all correctly. -huonw
2375 if abi != abi::Abi::RustIntrinsic
2376 && abi != abi::Abi::PlatformIntrinsic
2377 && !tcx.features().simd_ffi
2379 let check = |ast_ty: &hir::Ty, ty: Ty<'_>| {
2385 "use of SIMD type `{}` in FFI is highly experimental and \
2386 may result in invalid code",
2387 tcx.hir().hir_to_pretty_string(ast_ty.hir_id)
2390 .help("add `#![feature(simd_ffi)]` to the crate attributes to enable")
2394 for (input, ty) in decl.inputs.iter().zip(*fty.inputs().skip_binder()) {
2397 if let hir::Return(ref ty) = decl.output {
2398 check(&ty, *fty.output().skip_binder())
2405 fn is_foreign_item(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2406 match tcx.hir().get_if_local(def_id) {
2407 Some(Node::ForeignItem(..)) => true,
2409 _ => bug!("is_foreign_item applied to non-local def-id {:?}", def_id),
2413 fn static_mutability(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::Mutability> {
2414 match tcx.hir().get_if_local(def_id) {
2415 Some(Node::Item(&hir::Item {
2416 kind: hir::ItemKind::Static(_, mutbl, _), ..
2418 Some(Node::ForeignItem( &hir::ForeignItem {
2419 kind: hir::ForeignItemKind::Static(_, mutbl), ..
2422 _ => bug!("static_mutability applied to non-local def-id {:?}", def_id),
2426 fn from_target_feature(
2429 attr: &ast::Attribute,
2430 whitelist: &FxHashMap<String, Option<Symbol>>,
2431 target_features: &mut Vec<Symbol>,
2433 let list = match attr.meta_item_list() {
2437 let bad_item = |span| {
2438 let msg = "malformed `target_feature` attribute input";
2439 let code = "enable = \"..\"".to_owned();
2440 tcx.sess.struct_span_err(span, &msg)
2441 .span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
2444 let rust_features = tcx.features();
2446 // Only `enable = ...` is accepted in the meta-item list.
2447 if !item.check_name(sym::enable) {
2448 bad_item(item.span());
2452 // Must be of the form `enable = "..."` (a string).
2453 let value = match item.value_str() {
2454 Some(value) => value,
2456 bad_item(item.span());
2461 // We allow comma separation to enable multiple features.
2462 target_features.extend(value.as_str().split(',').filter_map(|feature| {
2463 // Only allow whitelisted features per platform.
2464 let feature_gate = match whitelist.get(feature) {
2468 "the feature named `{}` is not valid for this target",
2471 let mut err = tcx.sess.struct_span_err(item.span(), &msg);
2474 format!("`{}` is not valid for this target", feature),
2476 if feature.starts_with("+") {
2477 let valid = whitelist.contains_key(&feature[1..]);
2479 err.help("consider removing the leading `+` in the feature name");
2487 // Only allow features whose feature gates have been enabled.
2488 let allowed = match feature_gate.as_ref().map(|s| *s) {
2489 Some(sym::arm_target_feature) => rust_features.arm_target_feature,
2490 Some(sym::aarch64_target_feature) => rust_features.aarch64_target_feature,
2491 Some(sym::hexagon_target_feature) => rust_features.hexagon_target_feature,
2492 Some(sym::powerpc_target_feature) => rust_features.powerpc_target_feature,
2493 Some(sym::mips_target_feature) => rust_features.mips_target_feature,
2494 Some(sym::avx512_target_feature) => rust_features.avx512_target_feature,
2495 Some(sym::mmx_target_feature) => rust_features.mmx_target_feature,
2496 Some(sym::sse4a_target_feature) => rust_features.sse4a_target_feature,
2497 Some(sym::tbm_target_feature) => rust_features.tbm_target_feature,
2498 Some(sym::wasm_target_feature) => rust_features.wasm_target_feature,
2499 Some(sym::cmpxchg16b_target_feature) => rust_features.cmpxchg16b_target_feature,
2500 Some(sym::adx_target_feature) => rust_features.adx_target_feature,
2501 Some(sym::movbe_target_feature) => rust_features.movbe_target_feature,
2502 Some(sym::rtm_target_feature) => rust_features.rtm_target_feature,
2503 Some(sym::f16c_target_feature) => rust_features.f16c_target_feature,
2504 Some(name) => bug!("unknown target feature gate {}", name),
2507 if !allowed && id.is_local() {
2508 feature_gate::emit_feature_err(
2509 &tcx.sess.parse_sess,
2510 feature_gate.unwrap(),
2512 feature_gate::GateIssue::Language,
2513 &format!("the target feature `{}` is currently unstable", feature),
2516 Some(Symbol::intern(feature))
2521 fn linkage_by_name(tcx: TyCtxt<'_>, def_id: DefId, name: &str) -> Linkage {
2522 use rustc::mir::mono::Linkage::*;
2524 // Use the names from src/llvm/docs/LangRef.rst here. Most types are only
2525 // applicable to variable declarations and may not really make sense for
2526 // Rust code in the first place but whitelist them anyway and trust that
2527 // the user knows what s/he's doing. Who knows, unanticipated use cases
2528 // may pop up in the future.
2530 // ghost, dllimport, dllexport and linkonce_odr_autohide are not supported
2531 // and don't have to be, LLVM treats them as no-ops.
2533 "appending" => Appending,
2534 "available_externally" => AvailableExternally,
2536 "extern_weak" => ExternalWeak,
2537 "external" => External,
2538 "internal" => Internal,
2539 "linkonce" => LinkOnceAny,
2540 "linkonce_odr" => LinkOnceODR,
2541 "private" => Private,
2543 "weak_odr" => WeakODR,
2545 let span = tcx.hir().span_if_local(def_id);
2546 if let Some(span) = span {
2547 tcx.sess.span_fatal(span, "invalid linkage specified")
2550 .fatal(&format!("invalid linkage specified: {}", name))
2556 fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
2557 let attrs = tcx.get_attrs(id);
2559 let mut codegen_fn_attrs = CodegenFnAttrs::new();
2561 let whitelist = tcx.target_features_whitelist(LOCAL_CRATE);
2563 let mut inline_span = None;
2564 let mut link_ordinal_span = None;
2565 for attr in attrs.iter() {
2566 if attr.check_name(sym::cold) {
2567 codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD;
2568 } else if attr.check_name(sym::rustc_allocator) {
2569 codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR;
2570 } else if attr.check_name(sym::unwind) {
2571 codegen_fn_attrs.flags |= CodegenFnAttrFlags::UNWIND;
2572 } else if attr.check_name(sym::ffi_returns_twice) {
2573 if tcx.is_foreign_item(id) {
2574 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE;
2576 // `#[ffi_returns_twice]` is only allowed `extern fn`s.
2581 "`#[ffi_returns_twice]` may only be used on foreign functions"
2584 } else if attr.check_name(sym::rustc_allocator_nounwind) {
2585 codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_ALLOCATOR_NOUNWIND;
2586 } else if attr.check_name(sym::naked) {
2587 codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
2588 } else if attr.check_name(sym::no_mangle) {
2589 codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2590 } else if attr.check_name(sym::rustc_std_internal_symbol) {
2591 codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2592 } else if attr.check_name(sym::no_debug) {
2593 codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_DEBUG;
2594 } else if attr.check_name(sym::used) {
2595 codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
2596 } else if attr.check_name(sym::thread_local) {
2597 codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
2598 } else if attr.check_name(sym::track_caller) {
2599 if tcx.fn_sig(id).abi() != abi::Abi::Rust {
2604 "Rust ABI is required to use `#[track_caller]`"
2607 codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2608 } else if attr.check_name(sym::export_name) {
2609 if let Some(s) = attr.value_str() {
2610 if s.as_str().contains("\0") {
2611 // `#[export_name = ...]` will be converted to a null-terminated string,
2612 // so it may not contain any null characters.
2617 "`export_name` may not contain null characters"
2620 codegen_fn_attrs.export_name = Some(s);
2622 } else if attr.check_name(sym::target_feature) {
2623 if tcx.fn_sig(id).unsafety() == Unsafety::Normal {
2624 let msg = "`#[target_feature(..)]` can only be applied to `unsafe` functions";
2625 tcx.sess.struct_span_err(attr.span, msg)
2626 .span_label(attr.span, "can only be applied to `unsafe` functions")
2627 .span_label(tcx.def_span(id), "not an `unsafe` function")
2630 from_target_feature(
2635 &mut codegen_fn_attrs.target_features,
2637 } else if attr.check_name(sym::linkage) {
2638 if let Some(val) = attr.value_str() {
2639 codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, id, &val.as_str()));
2641 } else if attr.check_name(sym::link_section) {
2642 if let Some(val) = attr.value_str() {
2643 if val.as_str().bytes().any(|b| b == 0) {
2645 "illegal null byte in link_section \
2649 tcx.sess.span_err(attr.span, &msg);
2651 codegen_fn_attrs.link_section = Some(val);
2654 } else if attr.check_name(sym::link_name) {
2655 codegen_fn_attrs.link_name = attr.value_str();
2656 } else if attr.check_name(sym::link_ordinal) {
2657 link_ordinal_span = Some(attr.span);
2658 if let ordinal @ Some(_) = check_link_ordinal(tcx, attr) {
2659 codegen_fn_attrs.link_ordinal = ordinal;
2664 codegen_fn_attrs.inline = attrs.iter().fold(InlineAttr::None, |ia, attr| {
2665 if !attr.has_name(sym::inline) {
2668 match attr.meta().map(|i| i.kind) {
2669 Some(MetaItemKind::Word) => {
2673 Some(MetaItemKind::List(ref items)) => {
2675 inline_span = Some(attr.span);
2676 if items.len() != 1 {
2678 tcx.sess.diagnostic(),
2681 "expected one argument"
2684 } else if list_contains_name(&items[..], sym::always) {
2686 } else if list_contains_name(&items[..], sym::never) {
2690 tcx.sess.diagnostic(),
2699 Some(MetaItemKind::NameValue(_)) => ia,
2704 codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
2705 if !attr.has_name(sym::optimize) {
2708 let err = |sp, s| span_err!(tcx.sess.diagnostic(), sp, E0722, "{}", s);
2709 match attr.meta().map(|i| i.kind) {
2710 Some(MetaItemKind::Word) => {
2711 err(attr.span, "expected one argument");
2714 Some(MetaItemKind::List(ref items)) => {
2716 inline_span = Some(attr.span);
2717 if items.len() != 1 {
2718 err(attr.span, "expected one argument");
2720 } else if list_contains_name(&items[..], sym::size) {
2722 } else if list_contains_name(&items[..], sym::speed) {
2725 err(items[0].span(), "invalid argument");
2729 Some(MetaItemKind::NameValue(_)) => ia,
2734 // If a function uses #[target_feature] it can't be inlined into general
2735 // purpose functions as they wouldn't have the right target features
2736 // enabled. For that reason we also forbid #[inline(always)] as it can't be
2739 if codegen_fn_attrs.target_features.len() > 0 {
2740 if codegen_fn_attrs.inline == InlineAttr::Always {
2741 if let Some(span) = inline_span {
2744 "cannot use `#[inline(always)]` with \
2745 `#[target_feature]`",
2751 // Weak lang items have the same semantics as "std internal" symbols in the
2752 // sense that they're preserved through all our LTO passes and only
2753 // strippable by the linker.
2755 // Additionally weak lang items have predetermined symbol names.
2756 if tcx.is_weak_lang_item(id) {
2757 codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2759 if let Some(name) = weak_lang_items::link_name(&attrs) {
2760 codegen_fn_attrs.export_name = Some(name);
2761 codegen_fn_attrs.link_name = Some(name);
2763 check_link_name_xor_ordinal(tcx, &codegen_fn_attrs, link_ordinal_span);
2765 // Internal symbols to the standard library all have no_mangle semantics in
2766 // that they have defined symbol names present in the function name. This
2767 // also applies to weak symbols where they all have known symbol names.
2768 if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
2769 codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2775 fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<usize> {
2776 use syntax::ast::{Lit, LitIntType, LitKind};
2777 let meta_item_list = attr.meta_item_list();
2778 let meta_item_list: Option<&[ast::NestedMetaItem]> = meta_item_list.as_ref().map(Vec::as_ref);
2779 let sole_meta_list = match meta_item_list {
2780 Some([item]) => item.literal(),
2783 if let Some(Lit { kind: LitKind::Int(ordinal, LitIntType::Unsuffixed), .. }) = sole_meta_list {
2784 if *ordinal <= std::usize::MAX as u128 {
2785 Some(*ordinal as usize)
2788 "ordinal value in `link_ordinal` is too large: `{}`",
2791 tcx.sess.struct_span_err(attr.span, &msg)
2792 .note("the value may not exceed `std::usize::MAX`")
2797 tcx.sess.struct_span_err(attr.span, "illegal ordinal format in `link_ordinal`")
2798 .note("an unsuffixed integer value, e.g., `1`, is expected")
2804 fn check_link_name_xor_ordinal(
2806 codegen_fn_attrs: &CodegenFnAttrs,
2807 inline_span: Option<Span>,
2809 if codegen_fn_attrs.link_name.is_none() || codegen_fn_attrs.link_ordinal.is_none() {
2812 let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
2813 if let Some(span) = inline_span {
2814 tcx.sess.span_err(span, msg);