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Rollup merge of #97190 - SylvainDe:master, r=Dylan-DPC
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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
7 //! type *checking*).
8 //!
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
12 //! for the full set.
13 //!
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.
16
17 use crate::astconv::AstConv;
18 use crate::bounds::Bounds;
19 use crate::check::intrinsic::intrinsic_operation_unsafety;
20 use crate::constrained_generic_params as cgp;
21 use crate::errors;
22 use crate::middle::resolve_lifetime as rl;
23 use rustc_ast as ast;
24 use rustc_ast::{MetaItemKind, NestedMetaItem};
25 use rustc_attr::{list_contains_name, InlineAttr, InstructionSetAttr, OptimizeAttr};
26 use rustc_data_structures::captures::Captures;
27 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
28 use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder, ErrorGuaranteed};
29 use rustc_hir as hir;
30 use rustc_hir::def::{CtorKind, DefKind};
31 use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_ID, LOCAL_CRATE};
32 use rustc_hir::intravisit::{self, Visitor};
33 use rustc_hir::weak_lang_items;
34 use rustc_hir::{GenericParamKind, HirId, Node};
35 use rustc_middle::hir::nested_filter;
36 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
37 use rustc_middle::mir::mono::Linkage;
38 use rustc_middle::ty::query::Providers;
39 use rustc_middle::ty::subst::InternalSubsts;
40 use rustc_middle::ty::util::Discr;
41 use rustc_middle::ty::util::IntTypeExt;
42 use rustc_middle::ty::{self, AdtKind, Const, DefIdTree, Ty, TyCtxt};
43 use rustc_middle::ty::{ReprOptions, ToPredicate};
44 use rustc_session::lint;
45 use rustc_session::parse::feature_err;
46 use rustc_span::symbol::{kw, sym, Ident, Symbol};
47 use rustc_span::{Span, DUMMY_SP};
48 use rustc_target::spec::{abi, SanitizerSet};
49 use rustc_trait_selection::traits::error_reporting::suggestions::NextTypeParamName;
50 use std::iter;
51
52 mod item_bounds;
53 mod type_of;
54
55 #[derive(Debug)]
56 struct OnlySelfBounds(bool);
57
58 ///////////////////////////////////////////////////////////////////////////
59 // Main entry point
60
61 fn collect_mod_item_types(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
62     tcx.hir().deep_visit_item_likes_in_module(module_def_id, &mut CollectItemTypesVisitor { tcx });
63 }
64
65 pub fn provide(providers: &mut Providers) {
66     *providers = Providers {
67         opt_const_param_of: type_of::opt_const_param_of,
68         type_of: type_of::type_of,
69         item_bounds: item_bounds::item_bounds,
70         explicit_item_bounds: item_bounds::explicit_item_bounds,
71         generics_of,
72         predicates_of,
73         predicates_defined_on,
74         explicit_predicates_of,
75         super_predicates_of,
76         super_predicates_that_define_assoc_type,
77         trait_explicit_predicates_and_bounds,
78         type_param_predicates,
79         trait_def,
80         adt_def,
81         fn_sig,
82         impl_trait_ref,
83         impl_polarity,
84         is_foreign_item,
85         generator_kind,
86         codegen_fn_attrs,
87         asm_target_features,
88         collect_mod_item_types,
89         should_inherit_track_caller,
90         ..*providers
91     };
92 }
93
94 ///////////////////////////////////////////////////////////////////////////
95
96 /// Context specific to some particular item. This is what implements
97 /// `AstConv`. It has information about the predicates that are defined
98 /// on the trait. Unfortunately, this predicate information is
99 /// available in various different forms at various points in the
100 /// process. So we can't just store a pointer to e.g., the AST or the
101 /// parsed ty form, we have to be more flexible. To this end, the
102 /// `ItemCtxt` is parameterized by a `DefId` that it uses to satisfy
103 /// `get_type_parameter_bounds` requests, drawing the information from
104 /// the AST (`hir::Generics`), recursively.
105 pub struct ItemCtxt<'tcx> {
106     tcx: TyCtxt<'tcx>,
107     item_def_id: DefId,
108 }
109
110 ///////////////////////////////////////////////////////////////////////////
111
112 #[derive(Default)]
113 pub(crate) struct HirPlaceholderCollector(pub(crate) Vec<Span>);
114
115 impl<'v> Visitor<'v> for HirPlaceholderCollector {
116     fn visit_ty(&mut self, t: &'v hir::Ty<'v>) {
117         if let hir::TyKind::Infer = t.kind {
118             self.0.push(t.span);
119         }
120         intravisit::walk_ty(self, t)
121     }
122     fn visit_generic_arg(&mut self, generic_arg: &'v hir::GenericArg<'v>) {
123         match generic_arg {
124             hir::GenericArg::Infer(inf) => {
125                 self.0.push(inf.span);
126                 intravisit::walk_inf(self, inf);
127             }
128             hir::GenericArg::Type(t) => self.visit_ty(t),
129             _ => {}
130         }
131     }
132     fn visit_array_length(&mut self, length: &'v hir::ArrayLen) {
133         if let &hir::ArrayLen::Infer(_, span) = length {
134             self.0.push(span);
135         }
136         intravisit::walk_array_len(self, length)
137     }
138 }
139
140 struct CollectItemTypesVisitor<'tcx> {
141     tcx: TyCtxt<'tcx>,
142 }
143
144 /// If there are any placeholder types (`_`), emit an error explaining that this is not allowed
145 /// and suggest adding type parameters in the appropriate place, taking into consideration any and
146 /// all already existing generic type parameters to avoid suggesting a name that is already in use.
147 pub(crate) fn placeholder_type_error<'tcx>(
148     tcx: TyCtxt<'tcx>,
149     generics: Option<&hir::Generics<'_>>,
150     placeholder_types: Vec<Span>,
151     suggest: bool,
152     hir_ty: Option<&hir::Ty<'_>>,
153     kind: &'static str,
154 ) {
155     if placeholder_types.is_empty() {
156         return;
157     }
158
159     placeholder_type_error_diag(tcx, generics, placeholder_types, vec![], suggest, hir_ty, kind)
160         .emit();
161 }
162
163 pub(crate) fn placeholder_type_error_diag<'tcx>(
164     tcx: TyCtxt<'tcx>,
165     generics: Option<&hir::Generics<'_>>,
166     placeholder_types: Vec<Span>,
167     additional_spans: Vec<Span>,
168     suggest: bool,
169     hir_ty: Option<&hir::Ty<'_>>,
170     kind: &'static str,
171 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
172     if placeholder_types.is_empty() {
173         return bad_placeholder(tcx, additional_spans, kind);
174     }
175
176     let params = generics.map(|g| g.params).unwrap_or_default();
177     let type_name = params.next_type_param_name(None);
178     let mut sugg: Vec<_> =
179         placeholder_types.iter().map(|sp| (*sp, (*type_name).to_string())).collect();
180
181     if let Some(generics) = generics {
182         if let Some(arg) = params.iter().find(|arg| {
183             matches!(arg.name, hir::ParamName::Plain(Ident { name: kw::Underscore, .. }))
184         }) {
185             // Account for `_` already present in cases like `struct S<_>(_);` and suggest
186             // `struct S<T>(T);` instead of `struct S<_, T>(T);`.
187             sugg.push((arg.span, (*type_name).to_string()));
188         } else if let Some(span) = generics.span_for_param_suggestion() {
189             // Account for bounds, we want `fn foo<T: E, K>(_: K)` not `fn foo<T, K: E>(_: K)`.
190             sugg.push((span, format!(", {}", type_name)));
191         } else {
192             sugg.push((generics.span, format!("<{}>", type_name)));
193         }
194     }
195
196     let mut err =
197         bad_placeholder(tcx, placeholder_types.into_iter().chain(additional_spans).collect(), kind);
198
199     // Suggest, but only if it is not a function in const or static
200     if suggest {
201         let mut is_fn = false;
202         let mut is_const_or_static = false;
203
204         if let Some(hir_ty) = hir_ty && let hir::TyKind::BareFn(_) = hir_ty.kind {
205             is_fn = true;
206
207             // Check if parent is const or static
208             let parent_id = tcx.hir().get_parent_node(hir_ty.hir_id);
209             let parent_node = tcx.hir().get(parent_id);
210
211             is_const_or_static = matches!(
212                 parent_node,
213                 Node::Item(&hir::Item {
214                     kind: hir::ItemKind::Const(..) | hir::ItemKind::Static(..),
215                     ..
216                 }) | Node::TraitItem(&hir::TraitItem {
217                     kind: hir::TraitItemKind::Const(..),
218                     ..
219                 }) | Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Const(..), .. })
220             );
221         }
222
223         // if function is wrapped around a const or static,
224         // then don't show the suggestion
225         if !(is_fn && is_const_or_static) {
226             err.multipart_suggestion(
227                 "use type parameters instead",
228                 sugg,
229                 Applicability::HasPlaceholders,
230             );
231         }
232     }
233
234     err
235 }
236
237 fn reject_placeholder_type_signatures_in_item<'tcx>(
238     tcx: TyCtxt<'tcx>,
239     item: &'tcx hir::Item<'tcx>,
240 ) {
241     let (generics, suggest) = match &item.kind {
242         hir::ItemKind::Union(_, generics)
243         | hir::ItemKind::Enum(_, generics)
244         | hir::ItemKind::TraitAlias(generics, _)
245         | hir::ItemKind::Trait(_, _, generics, ..)
246         | hir::ItemKind::Impl(hir::Impl { generics, .. })
247         | hir::ItemKind::Struct(_, generics) => (generics, true),
248         hir::ItemKind::OpaqueTy(hir::OpaqueTy { generics, .. })
249         | hir::ItemKind::TyAlias(_, generics) => (generics, false),
250         // `static`, `fn` and `const` are handled elsewhere to suggest appropriate type.
251         _ => return,
252     };
253
254     let mut visitor = HirPlaceholderCollector::default();
255     visitor.visit_item(item);
256
257     placeholder_type_error(tcx, Some(generics), visitor.0, suggest, None, item.kind.descr());
258 }
259
260 impl<'tcx> Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
261     type NestedFilter = nested_filter::OnlyBodies;
262
263     fn nested_visit_map(&mut self) -> Self::Map {
264         self.tcx.hir()
265     }
266
267     fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
268         convert_item(self.tcx, item.item_id());
269         reject_placeholder_type_signatures_in_item(self.tcx, item);
270         intravisit::walk_item(self, item);
271     }
272
273     fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) {
274         for param in generics.params {
275             match param.kind {
276                 hir::GenericParamKind::Lifetime { .. } => {}
277                 hir::GenericParamKind::Type { default: Some(_), .. } => {
278                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
279                     self.tcx.ensure().type_of(def_id);
280                 }
281                 hir::GenericParamKind::Type { .. } => {}
282                 hir::GenericParamKind::Const { default, .. } => {
283                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
284                     self.tcx.ensure().type_of(def_id);
285                     if let Some(default) = default {
286                         let default_def_id = self.tcx.hir().local_def_id(default.hir_id);
287                         // need to store default and type of default
288                         self.tcx.ensure().type_of(default_def_id);
289                         self.tcx.ensure().const_param_default(def_id);
290                     }
291                 }
292             }
293         }
294         intravisit::walk_generics(self, generics);
295     }
296
297     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
298         if let hir::ExprKind::Closure(..) = expr.kind {
299             let def_id = self.tcx.hir().local_def_id(expr.hir_id);
300             self.tcx.ensure().generics_of(def_id);
301             // We do not call `type_of` for closures here as that
302             // depends on typecheck and would therefore hide
303             // any further errors in case one typeck fails.
304         }
305         intravisit::walk_expr(self, expr);
306     }
307
308     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
309         convert_trait_item(self.tcx, trait_item.trait_item_id());
310         intravisit::walk_trait_item(self, trait_item);
311     }
312
313     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
314         convert_impl_item(self.tcx, impl_item.impl_item_id());
315         intravisit::walk_impl_item(self, impl_item);
316     }
317 }
318
319 ///////////////////////////////////////////////////////////////////////////
320 // Utility types and common code for the above passes.
321
322 fn bad_placeholder<'tcx>(
323     tcx: TyCtxt<'tcx>,
324     mut spans: Vec<Span>,
325     kind: &'static str,
326 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
327     let kind = if kind.ends_with('s') { format!("{}es", kind) } else { format!("{}s", kind) };
328
329     spans.sort();
330     let mut err = struct_span_err!(
331         tcx.sess,
332         spans.clone(),
333         E0121,
334         "the placeholder `_` is not allowed within types on item signatures for {}",
335         kind
336     );
337     for span in spans {
338         err.span_label(span, "not allowed in type signatures");
339     }
340     err
341 }
342
343 impl<'tcx> ItemCtxt<'tcx> {
344     pub fn new(tcx: TyCtxt<'tcx>, item_def_id: DefId) -> ItemCtxt<'tcx> {
345         ItemCtxt { tcx, item_def_id }
346     }
347
348     pub fn to_ty(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> {
349         <dyn AstConv<'_>>::ast_ty_to_ty(self, ast_ty)
350     }
351
352     pub fn hir_id(&self) -> hir::HirId {
353         self.tcx.hir().local_def_id_to_hir_id(self.item_def_id.expect_local())
354     }
355
356     pub fn node(&self) -> hir::Node<'tcx> {
357         self.tcx.hir().get(self.hir_id())
358     }
359 }
360
361 impl<'tcx> AstConv<'tcx> for ItemCtxt<'tcx> {
362     fn tcx(&self) -> TyCtxt<'tcx> {
363         self.tcx
364     }
365
366     fn item_def_id(&self) -> Option<DefId> {
367         Some(self.item_def_id)
368     }
369
370     fn get_type_parameter_bounds(
371         &self,
372         span: Span,
373         def_id: DefId,
374         assoc_name: Ident,
375     ) -> ty::GenericPredicates<'tcx> {
376         self.tcx.at(span).type_param_predicates((
377             self.item_def_id,
378             def_id.expect_local(),
379             assoc_name,
380         ))
381     }
382
383     fn re_infer(&self, _: Option<&ty::GenericParamDef>, _: Span) -> Option<ty::Region<'tcx>> {
384         None
385     }
386
387     fn allow_ty_infer(&self) -> bool {
388         false
389     }
390
391     fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
392         self.tcx().ty_error_with_message(span, "bad placeholder type")
393     }
394
395     fn ct_infer(&self, ty: Ty<'tcx>, _: Option<&ty::GenericParamDef>, span: Span) -> Const<'tcx> {
396         let ty = self.tcx.fold_regions(ty, &mut false, |r, _| match *r {
397             ty::ReErased => self.tcx.lifetimes.re_static,
398             _ => r,
399         });
400         self.tcx().const_error_with_message(ty, span, "bad placeholder constant")
401     }
402
403     fn projected_ty_from_poly_trait_ref(
404         &self,
405         span: Span,
406         item_def_id: DefId,
407         item_segment: &hir::PathSegment<'_>,
408         poly_trait_ref: ty::PolyTraitRef<'tcx>,
409     ) -> Ty<'tcx> {
410         if let Some(trait_ref) = poly_trait_ref.no_bound_vars() {
411             let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
412                 self,
413                 self.tcx,
414                 span,
415                 item_def_id,
416                 item_segment,
417                 trait_ref.substs,
418             );
419             self.tcx().mk_projection(item_def_id, item_substs)
420         } else {
421             // There are no late-bound regions; we can just ignore the binder.
422             let mut err = struct_span_err!(
423                 self.tcx().sess,
424                 span,
425                 E0212,
426                 "cannot use the associated type of a trait \
427                  with uninferred generic parameters"
428             );
429
430             match self.node() {
431                 hir::Node::Field(_) | hir::Node::Ctor(_) | hir::Node::Variant(_) => {
432                     let item =
433                         self.tcx.hir().expect_item(self.tcx.hir().get_parent_item(self.hir_id()));
434                     match &item.kind {
435                         hir::ItemKind::Enum(_, generics)
436                         | hir::ItemKind::Struct(_, generics)
437                         | hir::ItemKind::Union(_, generics) => {
438                             let lt_name = get_new_lifetime_name(self.tcx, poly_trait_ref, generics);
439                             let (lt_sp, sugg) = match generics.params {
440                                 [] => (generics.span, format!("<{}>", lt_name)),
441                                 [bound, ..] => {
442                                     (bound.span.shrink_to_lo(), format!("{}, ", lt_name))
443                                 }
444                             };
445                             let suggestions = vec![
446                                 (lt_sp, sugg),
447                                 (
448                                     span.with_hi(item_segment.ident.span.lo()),
449                                     format!(
450                                         "{}::",
451                                         // Replace the existing lifetimes with a new named lifetime.
452                                         self.tcx
453                                             .replace_late_bound_regions(poly_trait_ref, |_| {
454                                                 self.tcx.mk_region(ty::ReEarlyBound(
455                                                     ty::EarlyBoundRegion {
456                                                         def_id: item_def_id,
457                                                         index: 0,
458                                                         name: Symbol::intern(&lt_name),
459                                                     },
460                                                 ))
461                                             })
462                                             .0,
463                                     ),
464                                 ),
465                             ];
466                             err.multipart_suggestion(
467                                 "use a fully qualified path with explicit lifetimes",
468                                 suggestions,
469                                 Applicability::MaybeIncorrect,
470                             );
471                         }
472                         _ => {}
473                     }
474                 }
475                 hir::Node::Item(hir::Item {
476                     kind:
477                         hir::ItemKind::Struct(..) | hir::ItemKind::Enum(..) | hir::ItemKind::Union(..),
478                     ..
479                 }) => {}
480                 hir::Node::Item(_)
481                 | hir::Node::ForeignItem(_)
482                 | hir::Node::TraitItem(_)
483                 | hir::Node::ImplItem(_) => {
484                     err.span_suggestion_verbose(
485                         span.with_hi(item_segment.ident.span.lo()),
486                         "use a fully qualified path with inferred lifetimes",
487                         format!(
488                             "{}::",
489                             // Erase named lt, we want `<A as B<'_>::C`, not `<A as B<'a>::C`.
490                             self.tcx.anonymize_late_bound_regions(poly_trait_ref).skip_binder(),
491                         ),
492                         Applicability::MaybeIncorrect,
493                     );
494                 }
495                 _ => {}
496             }
497             err.emit();
498             self.tcx().ty_error()
499         }
500     }
501
502     fn normalize_ty(&self, _span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
503         // Types in item signatures are not normalized to avoid undue dependencies.
504         ty
505     }
506
507     fn set_tainted_by_errors(&self) {
508         // There's no obvious place to track this, so just let it go.
509     }
510
511     fn record_ty(&self, _hir_id: hir::HirId, _ty: Ty<'tcx>, _span: Span) {
512         // There's no place to record types from signatures?
513     }
514 }
515
516 /// Synthesize a new lifetime name that doesn't clash with any of the lifetimes already present.
517 fn get_new_lifetime_name<'tcx>(
518     tcx: TyCtxt<'tcx>,
519     poly_trait_ref: ty::PolyTraitRef<'tcx>,
520     generics: &hir::Generics<'tcx>,
521 ) -> String {
522     let existing_lifetimes = tcx
523         .collect_referenced_late_bound_regions(&poly_trait_ref)
524         .into_iter()
525         .filter_map(|lt| {
526             if let ty::BoundRegionKind::BrNamed(_, name) = lt {
527                 Some(name.as_str().to_string())
528             } else {
529                 None
530             }
531         })
532         .chain(generics.params.iter().filter_map(|param| {
533             if let hir::GenericParamKind::Lifetime { .. } = &param.kind {
534                 Some(param.name.ident().as_str().to_string())
535             } else {
536                 None
537             }
538         }))
539         .collect::<FxHashSet<String>>();
540
541     let a_to_z_repeat_n = |n| {
542         (b'a'..=b'z').map(move |c| {
543             let mut s = '\''.to_string();
544             s.extend(std::iter::repeat(char::from(c)).take(n));
545             s
546         })
547     };
548
549     // If all single char lifetime names are present, we wrap around and double the chars.
550     (1..).flat_map(a_to_z_repeat_n).find(|lt| !existing_lifetimes.contains(lt.as_str())).unwrap()
551 }
552
553 /// Returns the predicates defined on `item_def_id` of the form
554 /// `X: Foo` where `X` is the type parameter `def_id`.
555 fn type_param_predicates(
556     tcx: TyCtxt<'_>,
557     (item_def_id, def_id, assoc_name): (DefId, LocalDefId, Ident),
558 ) -> ty::GenericPredicates<'_> {
559     use rustc_hir::*;
560
561     // In the AST, bounds can derive from two places. Either
562     // written inline like `<T: Foo>` or in a where-clause like
563     // `where T: Foo`.
564
565     let param_id = tcx.hir().local_def_id_to_hir_id(def_id);
566     let param_owner = tcx.hir().ty_param_owner(def_id);
567     let generics = tcx.generics_of(param_owner);
568     let index = generics.param_def_id_to_index[&def_id.to_def_id()];
569     let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(def_id));
570
571     // Don't look for bounds where the type parameter isn't in scope.
572     let parent = if item_def_id == param_owner.to_def_id() {
573         None
574     } else {
575         tcx.generics_of(item_def_id).parent
576     };
577
578     let mut result = parent
579         .map(|parent| {
580             let icx = ItemCtxt::new(tcx, parent);
581             icx.get_type_parameter_bounds(DUMMY_SP, def_id.to_def_id(), assoc_name)
582         })
583         .unwrap_or_default();
584     let mut extend = None;
585
586     let item_hir_id = tcx.hir().local_def_id_to_hir_id(item_def_id.expect_local());
587     let ast_generics = match tcx.hir().get(item_hir_id) {
588         Node::TraitItem(item) => &item.generics,
589
590         Node::ImplItem(item) => &item.generics,
591
592         Node::Item(item) => {
593             match item.kind {
594                 ItemKind::Fn(.., ref generics, _)
595                 | ItemKind::Impl(hir::Impl { ref generics, .. })
596                 | ItemKind::TyAlias(_, ref generics)
597                 | ItemKind::OpaqueTy(OpaqueTy {
598                     ref generics,
599                     origin: hir::OpaqueTyOrigin::TyAlias,
600                     ..
601                 })
602                 | ItemKind::Enum(_, ref generics)
603                 | ItemKind::Struct(_, ref generics)
604                 | ItemKind::Union(_, ref generics) => generics,
605                 ItemKind::Trait(_, _, ref generics, ..) => {
606                     // Implied `Self: Trait` and supertrait bounds.
607                     if param_id == item_hir_id {
608                         let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id);
609                         extend =
610                             Some((identity_trait_ref.without_const().to_predicate(tcx), item.span));
611                     }
612                     generics
613                 }
614                 _ => return result,
615             }
616         }
617
618         Node::ForeignItem(item) => match item.kind {
619             ForeignItemKind::Fn(_, _, ref generics) => generics,
620             _ => return result,
621         },
622
623         _ => return result,
624     };
625
626     let icx = ItemCtxt::new(tcx, item_def_id);
627     let extra_predicates = extend.into_iter().chain(
628         icx.type_parameter_bounds_in_generics(
629             ast_generics,
630             param_id,
631             ty,
632             OnlySelfBounds(true),
633             Some(assoc_name),
634         )
635         .into_iter()
636         .filter(|(predicate, _)| match predicate.kind().skip_binder() {
637             ty::PredicateKind::Trait(data) => data.self_ty().is_param(index),
638             _ => false,
639         }),
640     );
641     result.predicates =
642         tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(extra_predicates));
643     result
644 }
645
646 impl<'tcx> ItemCtxt<'tcx> {
647     /// Finds bounds from `hir::Generics`. This requires scanning through the
648     /// AST. We do this to avoid having to convert *all* the bounds, which
649     /// would create artificial cycles. Instead, we can only convert the
650     /// bounds for a type parameter `X` if `X::Foo` is used.
651     #[instrument(level = "trace", skip(self, ast_generics))]
652     fn type_parameter_bounds_in_generics(
653         &self,
654         ast_generics: &'tcx hir::Generics<'tcx>,
655         param_id: hir::HirId,
656         ty: Ty<'tcx>,
657         only_self_bounds: OnlySelfBounds,
658         assoc_name: Option<Ident>,
659     ) -> Vec<(ty::Predicate<'tcx>, Span)> {
660         let param_def_id = self.tcx.hir().local_def_id(param_id).to_def_id();
661         debug!(?param_def_id);
662         ast_generics
663             .predicates
664             .iter()
665             .filter_map(|wp| match *wp {
666                 hir::WherePredicate::BoundPredicate(ref bp) => Some(bp),
667                 _ => None,
668             })
669             .flat_map(|bp| {
670                 let bt = if bp.is_param_bound(param_def_id) {
671                     Some(ty)
672                 } else if !only_self_bounds.0 {
673                     Some(self.to_ty(bp.bounded_ty))
674                 } else {
675                     None
676                 };
677                 let bvars = self.tcx.late_bound_vars(bp.bounded_ty.hir_id);
678
679                 bp.bounds.iter().filter_map(move |b| bt.map(|bt| (bt, b, bvars))).filter(
680                     |(_, b, _)| match assoc_name {
681                         Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
682                         None => true,
683                     },
684                 )
685             })
686             .flat_map(|(bt, b, bvars)| predicates_from_bound(self, bt, b, bvars))
687             .collect()
688     }
689
690     fn bound_defines_assoc_item(&self, b: &hir::GenericBound<'_>, assoc_name: Ident) -> bool {
691         debug!("bound_defines_assoc_item(b={:?}, assoc_name={:?})", b, assoc_name);
692
693         match b {
694             hir::GenericBound::Trait(poly_trait_ref, _) => {
695                 let trait_ref = &poly_trait_ref.trait_ref;
696                 if let Some(trait_did) = trait_ref.trait_def_id() {
697                     self.tcx.trait_may_define_assoc_type(trait_did, assoc_name)
698                 } else {
699                     false
700                 }
701             }
702             _ => false,
703         }
704     }
705 }
706
707 fn convert_item(tcx: TyCtxt<'_>, item_id: hir::ItemId) {
708     let it = tcx.hir().item(item_id);
709     debug!("convert: item {} with id {}", it.ident, it.hir_id());
710     let def_id = item_id.def_id;
711
712     match it.kind {
713         // These don't define types.
714         hir::ItemKind::ExternCrate(_)
715         | hir::ItemKind::Use(..)
716         | hir::ItemKind::Macro(..)
717         | hir::ItemKind::Mod(_)
718         | hir::ItemKind::GlobalAsm(_) => {}
719         hir::ItemKind::ForeignMod { items, .. } => {
720             for item in items {
721                 let item = tcx.hir().foreign_item(item.id);
722                 tcx.ensure().generics_of(item.def_id);
723                 tcx.ensure().type_of(item.def_id);
724                 tcx.ensure().predicates_of(item.def_id);
725                 match item.kind {
726                     hir::ForeignItemKind::Fn(..) => tcx.ensure().fn_sig(item.def_id),
727                     hir::ForeignItemKind::Static(..) => {
728                         let mut visitor = HirPlaceholderCollector::default();
729                         visitor.visit_foreign_item(item);
730                         placeholder_type_error(
731                             tcx,
732                             None,
733                             visitor.0,
734                             false,
735                             None,
736                             "static variable",
737                         );
738                     }
739                     _ => (),
740                 }
741             }
742         }
743         hir::ItemKind::Enum(ref enum_definition, _) => {
744             tcx.ensure().generics_of(def_id);
745             tcx.ensure().type_of(def_id);
746             tcx.ensure().predicates_of(def_id);
747             convert_enum_variant_types(tcx, def_id.to_def_id(), enum_definition.variants);
748         }
749         hir::ItemKind::Impl { .. } => {
750             tcx.ensure().generics_of(def_id);
751             tcx.ensure().type_of(def_id);
752             tcx.ensure().impl_trait_ref(def_id);
753             tcx.ensure().predicates_of(def_id);
754         }
755         hir::ItemKind::Trait(..) => {
756             tcx.ensure().generics_of(def_id);
757             tcx.ensure().trait_def(def_id);
758             tcx.at(it.span).super_predicates_of(def_id);
759             tcx.ensure().predicates_of(def_id);
760         }
761         hir::ItemKind::TraitAlias(..) => {
762             tcx.ensure().generics_of(def_id);
763             tcx.at(it.span).super_predicates_of(def_id);
764             tcx.ensure().predicates_of(def_id);
765         }
766         hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
767             tcx.ensure().generics_of(def_id);
768             tcx.ensure().type_of(def_id);
769             tcx.ensure().predicates_of(def_id);
770
771             for f in struct_def.fields() {
772                 let def_id = tcx.hir().local_def_id(f.hir_id);
773                 tcx.ensure().generics_of(def_id);
774                 tcx.ensure().type_of(def_id);
775                 tcx.ensure().predicates_of(def_id);
776             }
777
778             if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
779                 convert_variant_ctor(tcx, ctor_hir_id);
780             }
781         }
782
783         // Desugared from `impl Trait`, so visited by the function's return type.
784         hir::ItemKind::OpaqueTy(hir::OpaqueTy {
785             origin: hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..),
786             ..
787         }) => {}
788
789         // Don't call `type_of` on opaque types, since that depends on type
790         // checking function bodies. `check_item_type` ensures that it's called
791         // instead.
792         hir::ItemKind::OpaqueTy(..) => {
793             tcx.ensure().generics_of(def_id);
794             tcx.ensure().predicates_of(def_id);
795             tcx.ensure().explicit_item_bounds(def_id);
796         }
797         hir::ItemKind::TyAlias(..)
798         | hir::ItemKind::Static(..)
799         | hir::ItemKind::Const(..)
800         | hir::ItemKind::Fn(..) => {
801             tcx.ensure().generics_of(def_id);
802             tcx.ensure().type_of(def_id);
803             tcx.ensure().predicates_of(def_id);
804             match it.kind {
805                 hir::ItemKind::Fn(..) => tcx.ensure().fn_sig(def_id),
806                 hir::ItemKind::OpaqueTy(..) => tcx.ensure().item_bounds(def_id),
807                 hir::ItemKind::Const(ty, ..) | hir::ItemKind::Static(ty, ..) => {
808                     // (#75889): Account for `const C: dyn Fn() -> _ = "";`
809                     if let hir::TyKind::TraitObject(..) = ty.kind {
810                         let mut visitor = HirPlaceholderCollector::default();
811                         visitor.visit_item(it);
812                         placeholder_type_error(tcx, None, visitor.0, false, None, it.kind.descr());
813                     }
814                 }
815                 _ => (),
816             }
817         }
818     }
819 }
820
821 fn convert_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::TraitItemId) {
822     let trait_item = tcx.hir().trait_item(trait_item_id);
823     tcx.ensure().generics_of(trait_item_id.def_id);
824
825     match trait_item.kind {
826         hir::TraitItemKind::Fn(..) => {
827             tcx.ensure().type_of(trait_item_id.def_id);
828             tcx.ensure().fn_sig(trait_item_id.def_id);
829         }
830
831         hir::TraitItemKind::Const(.., Some(_)) => {
832             tcx.ensure().type_of(trait_item_id.def_id);
833         }
834
835         hir::TraitItemKind::Const(..) => {
836             tcx.ensure().type_of(trait_item_id.def_id);
837             // Account for `const C: _;`.
838             let mut visitor = HirPlaceholderCollector::default();
839             visitor.visit_trait_item(trait_item);
840             placeholder_type_error(tcx, None, visitor.0, false, None, "constant");
841         }
842
843         hir::TraitItemKind::Type(_, Some(_)) => {
844             tcx.ensure().item_bounds(trait_item_id.def_id);
845             tcx.ensure().type_of(trait_item_id.def_id);
846             // Account for `type T = _;`.
847             let mut visitor = HirPlaceholderCollector::default();
848             visitor.visit_trait_item(trait_item);
849             placeholder_type_error(tcx, None, visitor.0, false, None, "associated type");
850         }
851
852         hir::TraitItemKind::Type(_, None) => {
853             tcx.ensure().item_bounds(trait_item_id.def_id);
854             // #74612: Visit and try to find bad placeholders
855             // even if there is no concrete type.
856             let mut visitor = HirPlaceholderCollector::default();
857             visitor.visit_trait_item(trait_item);
858
859             placeholder_type_error(tcx, None, visitor.0, false, None, "associated type");
860         }
861     };
862
863     tcx.ensure().predicates_of(trait_item_id.def_id);
864 }
865
866 fn convert_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::ImplItemId) {
867     let def_id = impl_item_id.def_id;
868     tcx.ensure().generics_of(def_id);
869     tcx.ensure().type_of(def_id);
870     tcx.ensure().predicates_of(def_id);
871     let impl_item = tcx.hir().impl_item(impl_item_id);
872     match impl_item.kind {
873         hir::ImplItemKind::Fn(..) => {
874             tcx.ensure().fn_sig(def_id);
875         }
876         hir::ImplItemKind::TyAlias(_) => {
877             // Account for `type T = _;`
878             let mut visitor = HirPlaceholderCollector::default();
879             visitor.visit_impl_item(impl_item);
880
881             placeholder_type_error(tcx, None, visitor.0, false, None, "associated type");
882         }
883         hir::ImplItemKind::Const(..) => {}
884     }
885 }
886
887 fn convert_variant_ctor(tcx: TyCtxt<'_>, ctor_id: hir::HirId) {
888     let def_id = tcx.hir().local_def_id(ctor_id);
889     tcx.ensure().generics_of(def_id);
890     tcx.ensure().type_of(def_id);
891     tcx.ensure().predicates_of(def_id);
892 }
893
894 fn convert_enum_variant_types(tcx: TyCtxt<'_>, def_id: DefId, variants: &[hir::Variant<'_>]) {
895     let def = tcx.adt_def(def_id);
896     let repr_type = def.repr().discr_type();
897     let initial = repr_type.initial_discriminant(tcx);
898     let mut prev_discr = None::<Discr<'_>>;
899
900     // fill the discriminant values and field types
901     for variant in variants {
902         let wrapped_discr = prev_discr.map_or(initial, |d| d.wrap_incr(tcx));
903         prev_discr = Some(
904             if let Some(ref e) = variant.disr_expr {
905                 let expr_did = tcx.hir().local_def_id(e.hir_id);
906                 def.eval_explicit_discr(tcx, expr_did.to_def_id())
907             } else if let Some(discr) = repr_type.disr_incr(tcx, prev_discr) {
908                 Some(discr)
909             } else {
910                 struct_span_err!(tcx.sess, variant.span, E0370, "enum discriminant overflowed")
911                     .span_label(
912                         variant.span,
913                         format!("overflowed on value after {}", prev_discr.unwrap()),
914                     )
915                     .note(&format!(
916                         "explicitly set `{} = {}` if that is desired outcome",
917                         variant.ident, wrapped_discr
918                     ))
919                     .emit();
920                 None
921             }
922             .unwrap_or(wrapped_discr),
923         );
924
925         for f in variant.data.fields() {
926             let def_id = tcx.hir().local_def_id(f.hir_id);
927             tcx.ensure().generics_of(def_id);
928             tcx.ensure().type_of(def_id);
929             tcx.ensure().predicates_of(def_id);
930         }
931
932         // Convert the ctor, if any. This also registers the variant as
933         // an item.
934         if let Some(ctor_hir_id) = variant.data.ctor_hir_id() {
935             convert_variant_ctor(tcx, ctor_hir_id);
936         }
937     }
938 }
939
940 fn convert_variant(
941     tcx: TyCtxt<'_>,
942     variant_did: Option<LocalDefId>,
943     ctor_did: Option<LocalDefId>,
944     ident: Ident,
945     discr: ty::VariantDiscr,
946     def: &hir::VariantData<'_>,
947     adt_kind: ty::AdtKind,
948     parent_did: LocalDefId,
949 ) -> ty::VariantDef {
950     let mut seen_fields: FxHashMap<Ident, Span> = Default::default();
951     let fields = def
952         .fields()
953         .iter()
954         .map(|f| {
955             let fid = tcx.hir().local_def_id(f.hir_id);
956             let dup_span = seen_fields.get(&f.ident.normalize_to_macros_2_0()).cloned();
957             if let Some(prev_span) = dup_span {
958                 tcx.sess.emit_err(errors::FieldAlreadyDeclared {
959                     field_name: f.ident,
960                     span: f.span,
961                     prev_span,
962                 });
963             } else {
964                 seen_fields.insert(f.ident.normalize_to_macros_2_0(), f.span);
965             }
966
967             ty::FieldDef { did: fid.to_def_id(), name: f.ident.name, vis: tcx.visibility(fid) }
968         })
969         .collect();
970     let recovered = match def {
971         hir::VariantData::Struct(_, r) => *r,
972         _ => false,
973     };
974     ty::VariantDef::new(
975         ident.name,
976         variant_did.map(LocalDefId::to_def_id),
977         ctor_did.map(LocalDefId::to_def_id),
978         discr,
979         fields,
980         CtorKind::from_hir(def),
981         adt_kind,
982         parent_did.to_def_id(),
983         recovered,
984         adt_kind == AdtKind::Struct && tcx.has_attr(parent_did.to_def_id(), sym::non_exhaustive)
985             || variant_did.map_or(false, |variant_did| {
986                 tcx.has_attr(variant_did.to_def_id(), sym::non_exhaustive)
987             }),
988     )
989 }
990
991 fn adt_def<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> ty::AdtDef<'tcx> {
992     use rustc_hir::*;
993
994     let def_id = def_id.expect_local();
995     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
996     let Node::Item(item) = tcx.hir().get(hir_id) else {
997         bug!();
998     };
999
1000     let repr = ReprOptions::new(tcx, def_id.to_def_id());
1001     let (kind, variants) = match item.kind {
1002         ItemKind::Enum(ref def, _) => {
1003             let mut distance_from_explicit = 0;
1004             let variants = def
1005                 .variants
1006                 .iter()
1007                 .map(|v| {
1008                     let variant_did = Some(tcx.hir().local_def_id(v.id));
1009                     let ctor_did =
1010                         v.data.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1011
1012                     let discr = if let Some(ref e) = v.disr_expr {
1013                         distance_from_explicit = 0;
1014                         ty::VariantDiscr::Explicit(tcx.hir().local_def_id(e.hir_id).to_def_id())
1015                     } else {
1016                         ty::VariantDiscr::Relative(distance_from_explicit)
1017                     };
1018                     distance_from_explicit += 1;
1019
1020                     convert_variant(
1021                         tcx,
1022                         variant_did,
1023                         ctor_did,
1024                         v.ident,
1025                         discr,
1026                         &v.data,
1027                         AdtKind::Enum,
1028                         def_id,
1029                     )
1030                 })
1031                 .collect();
1032
1033             (AdtKind::Enum, variants)
1034         }
1035         ItemKind::Struct(ref def, _) => {
1036             let variant_did = None::<LocalDefId>;
1037             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1038
1039             let variants = std::iter::once(convert_variant(
1040                 tcx,
1041                 variant_did,
1042                 ctor_did,
1043                 item.ident,
1044                 ty::VariantDiscr::Relative(0),
1045                 def,
1046                 AdtKind::Struct,
1047                 def_id,
1048             ))
1049             .collect();
1050
1051             (AdtKind::Struct, variants)
1052         }
1053         ItemKind::Union(ref def, _) => {
1054             let variant_did = None;
1055             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1056
1057             let variants = std::iter::once(convert_variant(
1058                 tcx,
1059                 variant_did,
1060                 ctor_did,
1061                 item.ident,
1062                 ty::VariantDiscr::Relative(0),
1063                 def,
1064                 AdtKind::Union,
1065                 def_id,
1066             ))
1067             .collect();
1068
1069             (AdtKind::Union, variants)
1070         }
1071         _ => bug!(),
1072     };
1073     tcx.alloc_adt_def(def_id.to_def_id(), kind, variants, repr)
1074 }
1075
1076 /// Ensures that the super-predicates of the trait with a `DefId`
1077 /// of `trait_def_id` are converted and stored. This also ensures that
1078 /// the transitive super-predicates are converted.
1079 fn super_predicates_of(tcx: TyCtxt<'_>, trait_def_id: DefId) -> ty::GenericPredicates<'_> {
1080     debug!("super_predicates(trait_def_id={:?})", trait_def_id);
1081     tcx.super_predicates_that_define_assoc_type((trait_def_id, None))
1082 }
1083
1084 /// Ensures that the super-predicates of the trait with a `DefId`
1085 /// of `trait_def_id` are converted and stored. This also ensures that
1086 /// the transitive super-predicates are converted.
1087 fn super_predicates_that_define_assoc_type(
1088     tcx: TyCtxt<'_>,
1089     (trait_def_id, assoc_name): (DefId, Option<Ident>),
1090 ) -> ty::GenericPredicates<'_> {
1091     debug!(
1092         "super_predicates_that_define_assoc_type(trait_def_id={:?}, assoc_name={:?})",
1093         trait_def_id, assoc_name
1094     );
1095     if trait_def_id.is_local() {
1096         debug!("super_predicates_that_define_assoc_type: local trait_def_id={:?}", trait_def_id);
1097         let trait_hir_id = tcx.hir().local_def_id_to_hir_id(trait_def_id.expect_local());
1098
1099         let Node::Item(item) = tcx.hir().get(trait_hir_id) else {
1100             bug!("trait_node_id {} is not an item", trait_hir_id);
1101         };
1102
1103         let (generics, bounds) = match item.kind {
1104             hir::ItemKind::Trait(.., ref generics, ref supertraits, _) => (generics, supertraits),
1105             hir::ItemKind::TraitAlias(ref generics, ref supertraits) => (generics, supertraits),
1106             _ => span_bug!(item.span, "super_predicates invoked on non-trait"),
1107         };
1108
1109         let icx = ItemCtxt::new(tcx, trait_def_id);
1110
1111         // Convert the bounds that follow the colon, e.g., `Bar + Zed` in `trait Foo: Bar + Zed`.
1112         let self_param_ty = tcx.types.self_param;
1113         let superbounds1 = if let Some(assoc_name) = assoc_name {
1114             <dyn AstConv<'_>>::compute_bounds_that_match_assoc_type(
1115                 &icx,
1116                 self_param_ty,
1117                 bounds,
1118                 assoc_name,
1119             )
1120         } else {
1121             <dyn AstConv<'_>>::compute_bounds(&icx, self_param_ty, bounds)
1122         };
1123
1124         let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
1125
1126         // Convert any explicit superbounds in the where-clause,
1127         // e.g., `trait Foo where Self: Bar`.
1128         // In the case of trait aliases, however, we include all bounds in the where-clause,
1129         // so e.g., `trait Foo = where u32: PartialEq<Self>` would include `u32: PartialEq<Self>`
1130         // as one of its "superpredicates".
1131         let is_trait_alias = tcx.is_trait_alias(trait_def_id);
1132         let superbounds2 = icx.type_parameter_bounds_in_generics(
1133             generics,
1134             item.hir_id(),
1135             self_param_ty,
1136             OnlySelfBounds(!is_trait_alias),
1137             assoc_name,
1138         );
1139
1140         // Combine the two lists to form the complete set of superbounds:
1141         let superbounds = &*tcx.arena.alloc_from_iter(superbounds1.into_iter().chain(superbounds2));
1142         debug!(?superbounds);
1143
1144         // Now require that immediate supertraits are converted,
1145         // which will, in turn, reach indirect supertraits.
1146         if assoc_name.is_none() {
1147             // Now require that immediate supertraits are converted,
1148             // which will, in turn, reach indirect supertraits.
1149             for &(pred, span) in superbounds {
1150                 debug!("superbound: {:?}", pred);
1151                 if let ty::PredicateKind::Trait(bound) = pred.kind().skip_binder() {
1152                     tcx.at(span).super_predicates_of(bound.def_id());
1153                 }
1154             }
1155         }
1156
1157         ty::GenericPredicates { parent: None, predicates: superbounds }
1158     } else {
1159         // if `assoc_name` is None, then the query should've been redirected to an
1160         // external provider
1161         assert!(assoc_name.is_some());
1162         tcx.super_predicates_of(trait_def_id)
1163     }
1164 }
1165
1166 fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> ty::TraitDef {
1167     let item = tcx.hir().expect_item(def_id.expect_local());
1168
1169     let (is_auto, unsafety, items) = match item.kind {
1170         hir::ItemKind::Trait(is_auto, unsafety, .., items) => {
1171             (is_auto == hir::IsAuto::Yes, unsafety, items)
1172         }
1173         hir::ItemKind::TraitAlias(..) => (false, hir::Unsafety::Normal, &[][..]),
1174         _ => span_bug!(item.span, "trait_def_of_item invoked on non-trait"),
1175     };
1176
1177     let paren_sugar = tcx.has_attr(def_id, sym::rustc_paren_sugar);
1178     if paren_sugar && !tcx.features().unboxed_closures {
1179         tcx.sess
1180             .struct_span_err(
1181                 item.span,
1182                 "the `#[rustc_paren_sugar]` attribute is a temporary means of controlling \
1183                  which traits can use parenthetical notation",
1184             )
1185             .help("add `#![feature(unboxed_closures)]` to the crate attributes to use it")
1186             .emit();
1187     }
1188
1189     let is_marker = tcx.has_attr(def_id, sym::marker);
1190     let skip_array_during_method_dispatch =
1191         tcx.has_attr(def_id, sym::rustc_skip_array_during_method_dispatch);
1192     let spec_kind = if tcx.has_attr(def_id, sym::rustc_unsafe_specialization_marker) {
1193         ty::trait_def::TraitSpecializationKind::Marker
1194     } else if tcx.has_attr(def_id, sym::rustc_specialization_trait) {
1195         ty::trait_def::TraitSpecializationKind::AlwaysApplicable
1196     } else {
1197         ty::trait_def::TraitSpecializationKind::None
1198     };
1199     let must_implement_one_of = tcx
1200         .get_attr(def_id, sym::rustc_must_implement_one_of)
1201         // Check that there are at least 2 arguments of `#[rustc_must_implement_one_of]`
1202         // and that they are all identifiers
1203         .and_then(|attr| match attr.meta_item_list() {
1204             Some(items) if items.len() < 2 => {
1205                 tcx.sess
1206                     .struct_span_err(
1207                         attr.span,
1208                         "the `#[rustc_must_implement_one_of]` attribute must be \
1209                         used with at least 2 args",
1210                     )
1211                     .emit();
1212
1213                 None
1214             }
1215             Some(items) => items
1216                 .into_iter()
1217                 .map(|item| item.ident().ok_or(item.span()))
1218                 .collect::<Result<Box<[_]>, _>>()
1219                 .map_err(|span| {
1220                     tcx.sess
1221                         .struct_span_err(span, "must be a name of an associated function")
1222                         .emit();
1223                 })
1224                 .ok()
1225                 .zip(Some(attr.span)),
1226             // Error is reported by `rustc_attr!`
1227             None => None,
1228         })
1229         // Check that all arguments of `#[rustc_must_implement_one_of]` reference
1230         // functions in the trait with default implementations
1231         .and_then(|(list, attr_span)| {
1232             let errors = list.iter().filter_map(|ident| {
1233                 let item = items.iter().find(|item| item.ident == *ident);
1234
1235                 match item {
1236                     Some(item) if matches!(item.kind, hir::AssocItemKind::Fn { .. }) => {
1237                         if !item.defaultness.has_value() {
1238                             tcx.sess
1239                                 .struct_span_err(
1240                                     item.span,
1241                                     "This function doesn't have a default implementation",
1242                                 )
1243                                 .span_note(attr_span, "required by this annotation")
1244                                 .emit();
1245
1246                             return Some(());
1247                         }
1248
1249                         return None;
1250                     }
1251                     Some(item) => {
1252                         tcx.sess
1253                             .struct_span_err(item.span, "Not a function")
1254                             .span_note(attr_span, "required by this annotation")
1255                             .note(
1256                                 "All `#[rustc_must_implement_one_of]` arguments \
1257                             must be associated function names",
1258                             )
1259                             .emit();
1260                     }
1261                     None => {
1262                         tcx.sess
1263                             .struct_span_err(ident.span, "Function not found in this trait")
1264                             .emit();
1265                     }
1266                 }
1267
1268                 Some(())
1269             });
1270
1271             (errors.count() == 0).then_some(list)
1272         })
1273         // Check for duplicates
1274         .and_then(|list| {
1275             let mut set: FxHashMap<Symbol, Span> = FxHashMap::default();
1276             let mut no_dups = true;
1277
1278             for ident in &*list {
1279                 if let Some(dup) = set.insert(ident.name, ident.span) {
1280                     tcx.sess
1281                         .struct_span_err(vec![dup, ident.span], "Functions names are duplicated")
1282                         .note(
1283                             "All `#[rustc_must_implement_one_of]` arguments \
1284                             must be unique",
1285                         )
1286                         .emit();
1287
1288                     no_dups = false;
1289                 }
1290             }
1291
1292             no_dups.then_some(list)
1293         });
1294
1295     ty::TraitDef::new(
1296         def_id,
1297         unsafety,
1298         paren_sugar,
1299         is_auto,
1300         is_marker,
1301         skip_array_during_method_dispatch,
1302         spec_kind,
1303         must_implement_one_of,
1304     )
1305 }
1306
1307 fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<Span> {
1308     struct LateBoundRegionsDetector<'tcx> {
1309         tcx: TyCtxt<'tcx>,
1310         outer_index: ty::DebruijnIndex,
1311         has_late_bound_regions: Option<Span>,
1312     }
1313
1314     impl<'tcx> Visitor<'tcx> for LateBoundRegionsDetector<'tcx> {
1315         fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
1316             if self.has_late_bound_regions.is_some() {
1317                 return;
1318             }
1319             match ty.kind {
1320                 hir::TyKind::BareFn(..) => {
1321                     self.outer_index.shift_in(1);
1322                     intravisit::walk_ty(self, ty);
1323                     self.outer_index.shift_out(1);
1324                 }
1325                 _ => intravisit::walk_ty(self, ty),
1326             }
1327         }
1328
1329         fn visit_poly_trait_ref(
1330             &mut self,
1331             tr: &'tcx hir::PolyTraitRef<'tcx>,
1332             m: hir::TraitBoundModifier,
1333         ) {
1334             if self.has_late_bound_regions.is_some() {
1335                 return;
1336             }
1337             self.outer_index.shift_in(1);
1338             intravisit::walk_poly_trait_ref(self, tr, m);
1339             self.outer_index.shift_out(1);
1340         }
1341
1342         fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
1343             if self.has_late_bound_regions.is_some() {
1344                 return;
1345             }
1346
1347             match self.tcx.named_region(lt.hir_id) {
1348                 Some(rl::Region::Static | rl::Region::EarlyBound(..)) => {}
1349                 Some(
1350                     rl::Region::LateBound(debruijn, _, _)
1351                     | rl::Region::LateBoundAnon(debruijn, _, _),
1352                 ) if debruijn < self.outer_index => {}
1353                 Some(
1354                     rl::Region::LateBound(..)
1355                     | rl::Region::LateBoundAnon(..)
1356                     | rl::Region::Free(..),
1357                 )
1358                 | None => {
1359                     self.has_late_bound_regions = Some(lt.span);
1360                 }
1361             }
1362         }
1363     }
1364
1365     fn has_late_bound_regions<'tcx>(
1366         tcx: TyCtxt<'tcx>,
1367         def_id: LocalDefId,
1368         generics: &'tcx hir::Generics<'tcx>,
1369         decl: &'tcx hir::FnDecl<'tcx>,
1370     ) -> Option<Span> {
1371         let mut visitor = LateBoundRegionsDetector {
1372             tcx,
1373             outer_index: ty::INNERMOST,
1374             has_late_bound_regions: None,
1375         };
1376         let late_bound_map = tcx.is_late_bound_map(def_id);
1377         let is_late_bound = |id| {
1378             let id = tcx.hir().local_def_id(id);
1379             late_bound_map.map_or(false, |(_, set)| set.contains(&id))
1380         };
1381         for param in generics.params {
1382             if let GenericParamKind::Lifetime { .. } = param.kind {
1383                 if is_late_bound(param.hir_id) {
1384                     return Some(param.span);
1385                 }
1386             }
1387         }
1388         visitor.visit_fn_decl(decl);
1389         visitor.has_late_bound_regions
1390     }
1391
1392     match node {
1393         Node::TraitItem(item) => match item.kind {
1394             hir::TraitItemKind::Fn(ref sig, _) => {
1395                 has_late_bound_regions(tcx, item.def_id, &item.generics, sig.decl)
1396             }
1397             _ => None,
1398         },
1399         Node::ImplItem(item) => match item.kind {
1400             hir::ImplItemKind::Fn(ref sig, _) => {
1401                 has_late_bound_regions(tcx, item.def_id, &item.generics, sig.decl)
1402             }
1403             _ => None,
1404         },
1405         Node::ForeignItem(item) => match item.kind {
1406             hir::ForeignItemKind::Fn(fn_decl, _, ref generics) => {
1407                 has_late_bound_regions(tcx, item.def_id, generics, fn_decl)
1408             }
1409             _ => None,
1410         },
1411         Node::Item(item) => match item.kind {
1412             hir::ItemKind::Fn(ref sig, .., ref generics, _) => {
1413                 has_late_bound_regions(tcx, item.def_id, generics, sig.decl)
1414             }
1415             _ => None,
1416         },
1417         _ => None,
1418     }
1419 }
1420
1421 struct AnonConstInParamTyDetector {
1422     in_param_ty: bool,
1423     found_anon_const_in_param_ty: bool,
1424     ct: HirId,
1425 }
1426
1427 impl<'v> Visitor<'v> for AnonConstInParamTyDetector {
1428     fn visit_generic_param(&mut self, p: &'v hir::GenericParam<'v>) {
1429         if let GenericParamKind::Const { ty, default: _ } = p.kind {
1430             let prev = self.in_param_ty;
1431             self.in_param_ty = true;
1432             self.visit_ty(ty);
1433             self.in_param_ty = prev;
1434         }
1435     }
1436
1437     fn visit_anon_const(&mut self, c: &'v hir::AnonConst) {
1438         if self.in_param_ty && self.ct == c.hir_id {
1439             self.found_anon_const_in_param_ty = true;
1440         } else {
1441             intravisit::walk_anon_const(self, c)
1442         }
1443     }
1444 }
1445
1446 fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::Generics {
1447     use rustc_hir::*;
1448
1449     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1450
1451     let node = tcx.hir().get(hir_id);
1452     let parent_def_id = match node {
1453         Node::ImplItem(_)
1454         | Node::TraitItem(_)
1455         | Node::Variant(_)
1456         | Node::Ctor(..)
1457         | Node::Field(_) => {
1458             let parent_id = tcx.hir().get_parent_item(hir_id);
1459             Some(parent_id.to_def_id())
1460         }
1461         // FIXME(#43408) always enable this once `lazy_normalization` is
1462         // stable enough and does not need a feature gate anymore.
1463         Node::AnonConst(_) => {
1464             let parent_def_id = tcx.hir().get_parent_item(hir_id);
1465
1466             let mut in_param_ty = false;
1467             for (_parent, node) in tcx.hir().parent_iter(hir_id) {
1468                 if let Some(generics) = node.generics() {
1469                     let mut visitor = AnonConstInParamTyDetector {
1470                         in_param_ty: false,
1471                         found_anon_const_in_param_ty: false,
1472                         ct: hir_id,
1473                     };
1474
1475                     visitor.visit_generics(generics);
1476                     in_param_ty = visitor.found_anon_const_in_param_ty;
1477                     break;
1478                 }
1479             }
1480
1481             if in_param_ty {
1482                 // We do not allow generic parameters in anon consts if we are inside
1483                 // of a const parameter type, e.g. `struct Foo<const N: usize, const M: [u8; N]>` is not allowed.
1484                 None
1485             } else if tcx.lazy_normalization() {
1486                 if let Some(param_id) = tcx.hir().opt_const_param_default_param_hir_id(hir_id) {
1487                     // If the def_id we are calling generics_of on is an anon ct default i.e:
1488                     //
1489                     // struct Foo<const N: usize = { .. }>;
1490                     //        ^^^       ^          ^^^^^^ def id of this anon const
1491                     //        ^         ^ param_id
1492                     //        ^ parent_def_id
1493                     //
1494                     // then we only want to return generics for params to the left of `N`. If we don't do that we
1495                     // end up with that const looking like: `ty::ConstKind::Unevaluated(def_id, substs: [N#0])`.
1496                     //
1497                     // This causes ICEs (#86580) when building the substs for Foo in `fn foo() -> Foo { .. }` as
1498                     // we substitute the defaults with the partially built substs when we build the substs. Subst'ing
1499                     // the `N#0` on the unevaluated const indexes into the empty substs we're in the process of building.
1500                     //
1501                     // We fix this by having this function return the parent's generics ourselves and truncating the
1502                     // generics to only include non-forward declared params (with the exception of the `Self` ty)
1503                     //
1504                     // For the above code example that means we want `substs: []`
1505                     // For the following struct def we want `substs: [N#0]` when generics_of is called on
1506                     // the def id of the `{ N + 1 }` anon const
1507                     // struct Foo<const N: usize, const M: usize = { N + 1 }>;
1508                     //
1509                     // This has some implications for how we get the predicates available to the anon const
1510                     // see `explicit_predicates_of` for more information on this
1511                     let generics = tcx.generics_of(parent_def_id.to_def_id());
1512                     let param_def = tcx.hir().local_def_id(param_id).to_def_id();
1513                     let param_def_idx = generics.param_def_id_to_index[&param_def];
1514                     // In the above example this would be .params[..N#0]
1515                     let params = generics.params[..param_def_idx as usize].to_owned();
1516                     let param_def_id_to_index =
1517                         params.iter().map(|param| (param.def_id, param.index)).collect();
1518
1519                     return ty::Generics {
1520                         // we set the parent of these generics to be our parent's parent so that we
1521                         // dont end up with substs: [N, M, N] for the const default on a struct like this:
1522                         // struct Foo<const N: usize, const M: usize = { ... }>;
1523                         parent: generics.parent,
1524                         parent_count: generics.parent_count,
1525                         params,
1526                         param_def_id_to_index,
1527                         has_self: generics.has_self,
1528                         has_late_bound_regions: generics.has_late_bound_regions,
1529                     };
1530                 }
1531
1532                 // HACK(eddyb) this provides the correct generics when
1533                 // `feature(generic_const_expressions)` is enabled, so that const expressions
1534                 // used with const generics, e.g. `Foo<{N+1}>`, can work at all.
1535                 //
1536                 // Note that we do not supply the parent generics when using
1537                 // `min_const_generics`.
1538                 Some(parent_def_id.to_def_id())
1539             } else {
1540                 let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1541                 match parent_node {
1542                     // HACK(eddyb) this provides the correct generics for repeat
1543                     // expressions' count (i.e. `N` in `[x; N]`), and explicit
1544                     // `enum` discriminants (i.e. `D` in `enum Foo { Bar = D }`),
1545                     // as they shouldn't be able to cause query cycle errors.
1546                     Node::Expr(&Expr { kind: ExprKind::Repeat(_, ref constant), .. })
1547                         if constant.hir_id() == hir_id =>
1548                     {
1549                         Some(parent_def_id.to_def_id())
1550                     }
1551                     Node::Variant(Variant { disr_expr: Some(ref constant), .. })
1552                         if constant.hir_id == hir_id =>
1553                     {
1554                         Some(parent_def_id.to_def_id())
1555                     }
1556                     Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) => {
1557                         Some(tcx.typeck_root_def_id(def_id))
1558                     }
1559                     // Exclude `GlobalAsm` here which cannot have generics.
1560                     Node::Expr(&Expr { kind: ExprKind::InlineAsm(asm), .. })
1561                         if asm.operands.iter().any(|(op, _op_sp)| match op {
1562                             hir::InlineAsmOperand::Const { anon_const }
1563                             | hir::InlineAsmOperand::SymFn { anon_const } => {
1564                                 anon_const.hir_id == hir_id
1565                             }
1566                             _ => false,
1567                         }) =>
1568                     {
1569                         Some(parent_def_id.to_def_id())
1570                     }
1571                     _ => None,
1572                 }
1573             }
1574         }
1575         Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1576             Some(tcx.typeck_root_def_id(def_id))
1577         }
1578         Node::Item(item) => match item.kind {
1579             ItemKind::OpaqueTy(hir::OpaqueTy {
1580                 origin:
1581                     hir::OpaqueTyOrigin::FnReturn(fn_def_id) | hir::OpaqueTyOrigin::AsyncFn(fn_def_id),
1582                 ..
1583             }) => Some(fn_def_id.to_def_id()),
1584             ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::TyAlias, .. }) => {
1585                 let parent_id = tcx.hir().get_parent_item(hir_id);
1586                 assert_ne!(parent_id, CRATE_DEF_ID);
1587                 debug!("generics_of: parent of opaque ty {:?} is {:?}", def_id, parent_id);
1588                 // Opaque types are always nested within another item, and
1589                 // inherit the generics of the item.
1590                 Some(parent_id.to_def_id())
1591             }
1592             _ => None,
1593         },
1594         _ => None,
1595     };
1596
1597     let mut opt_self = None;
1598     let mut allow_defaults = false;
1599
1600     let no_generics = hir::Generics::empty();
1601     let ast_generics = match node {
1602         Node::TraitItem(item) => &item.generics,
1603
1604         Node::ImplItem(item) => &item.generics,
1605
1606         Node::Item(item) => {
1607             match item.kind {
1608                 ItemKind::Fn(.., ref generics, _)
1609                 | ItemKind::Impl(hir::Impl { ref generics, .. }) => generics,
1610
1611                 ItemKind::TyAlias(_, ref generics)
1612                 | ItemKind::Enum(_, ref generics)
1613                 | ItemKind::Struct(_, ref generics)
1614                 | ItemKind::OpaqueTy(hir::OpaqueTy { ref generics, .. })
1615                 | ItemKind::Union(_, ref generics) => {
1616                     allow_defaults = true;
1617                     generics
1618                 }
1619
1620                 ItemKind::Trait(_, _, ref generics, ..)
1621                 | ItemKind::TraitAlias(ref generics, ..) => {
1622                     // Add in the self type parameter.
1623                     //
1624                     // Something of a hack: use the node id for the trait, also as
1625                     // the node id for the Self type parameter.
1626                     let param_id = item.def_id;
1627
1628                     opt_self = Some(ty::GenericParamDef {
1629                         index: 0,
1630                         name: kw::SelfUpper,
1631                         def_id: param_id.to_def_id(),
1632                         pure_wrt_drop: false,
1633                         kind: ty::GenericParamDefKind::Type {
1634                             has_default: false,
1635                             object_lifetime_default: rl::Set1::Empty,
1636                             synthetic: false,
1637                         },
1638                     });
1639
1640                     allow_defaults = true;
1641                     generics
1642                 }
1643
1644                 _ => &no_generics,
1645             }
1646         }
1647
1648         Node::ForeignItem(item) => match item.kind {
1649             ForeignItemKind::Static(..) => &no_generics,
1650             ForeignItemKind::Fn(_, _, ref generics) => generics,
1651             ForeignItemKind::Type => &no_generics,
1652         },
1653
1654         _ => &no_generics,
1655     };
1656
1657     let has_self = opt_self.is_some();
1658     let mut parent_has_self = false;
1659     let mut own_start = has_self as u32;
1660     let parent_count = parent_def_id.map_or(0, |def_id| {
1661         let generics = tcx.generics_of(def_id);
1662         assert!(!has_self);
1663         parent_has_self = generics.has_self;
1664         own_start = generics.count() as u32;
1665         generics.parent_count + generics.params.len()
1666     });
1667
1668     let mut params: Vec<_> = Vec::with_capacity(ast_generics.params.len() + has_self as usize);
1669
1670     if let Some(opt_self) = opt_self {
1671         params.push(opt_self);
1672     }
1673
1674     let early_lifetimes = early_bound_lifetimes_from_generics(tcx, hir_id.owner, ast_generics);
1675     params.extend(early_lifetimes.enumerate().map(|(i, param)| ty::GenericParamDef {
1676         name: param.name.ident().name,
1677         index: own_start + i as u32,
1678         def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1679         pure_wrt_drop: param.pure_wrt_drop,
1680         kind: ty::GenericParamDefKind::Lifetime,
1681     }));
1682
1683     let object_lifetime_defaults = tcx.object_lifetime_defaults(hir_id.owner);
1684
1685     // Now create the real type and const parameters.
1686     let type_start = own_start - has_self as u32 + params.len() as u32;
1687     let mut i = 0;
1688
1689     params.extend(ast_generics.params.iter().filter_map(|param| match param.kind {
1690         GenericParamKind::Lifetime { .. } => None,
1691         GenericParamKind::Type { ref default, synthetic, .. } => {
1692             if !allow_defaults && default.is_some() {
1693                 if !tcx.features().default_type_parameter_fallback {
1694                     tcx.struct_span_lint_hir(
1695                         lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
1696                         param.hir_id,
1697                         param.span,
1698                         |lint| {
1699                             lint.build(
1700                                 "defaults for type parameters are only allowed in \
1701                                  `struct`, `enum`, `type`, or `trait` definitions",
1702                             )
1703                             .emit();
1704                         },
1705                     );
1706                 }
1707             }
1708
1709             let kind = ty::GenericParamDefKind::Type {
1710                 has_default: default.is_some(),
1711                 object_lifetime_default: object_lifetime_defaults
1712                     .as_ref()
1713                     .map_or(rl::Set1::Empty, |o| o[i]),
1714                 synthetic,
1715             };
1716
1717             let param_def = ty::GenericParamDef {
1718                 index: type_start + i as u32,
1719                 name: param.name.ident().name,
1720                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1721                 pure_wrt_drop: param.pure_wrt_drop,
1722                 kind,
1723             };
1724             i += 1;
1725             Some(param_def)
1726         }
1727         GenericParamKind::Const { default, .. } => {
1728             if !allow_defaults && default.is_some() {
1729                 tcx.sess.span_err(
1730                     param.span,
1731                     "defaults for const parameters are only allowed in \
1732                     `struct`, `enum`, `type`, or `trait` definitions",
1733                 );
1734             }
1735
1736             let param_def = ty::GenericParamDef {
1737                 index: type_start + i as u32,
1738                 name: param.name.ident().name,
1739                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1740                 pure_wrt_drop: param.pure_wrt_drop,
1741                 kind: ty::GenericParamDefKind::Const { has_default: default.is_some() },
1742             };
1743             i += 1;
1744             Some(param_def)
1745         }
1746     }));
1747
1748     // provide junk type parameter defs - the only place that
1749     // cares about anything but the length is instantiation,
1750     // and we don't do that for closures.
1751     if let Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(.., gen), .. }) = node {
1752         let dummy_args = if gen.is_some() {
1753             &["<resume_ty>", "<yield_ty>", "<return_ty>", "<witness>", "<upvars>"][..]
1754         } else {
1755             &["<closure_kind>", "<closure_signature>", "<upvars>"][..]
1756         };
1757
1758         params.extend(dummy_args.iter().enumerate().map(|(i, &arg)| ty::GenericParamDef {
1759             index: type_start + i as u32,
1760             name: Symbol::intern(arg),
1761             def_id,
1762             pure_wrt_drop: false,
1763             kind: ty::GenericParamDefKind::Type {
1764                 has_default: false,
1765                 object_lifetime_default: rl::Set1::Empty,
1766                 synthetic: false,
1767             },
1768         }));
1769     }
1770
1771     // provide junk type parameter defs for const blocks.
1772     if let Node::AnonConst(_) = node {
1773         let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1774         if let Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) = parent_node {
1775             params.push(ty::GenericParamDef {
1776                 index: type_start,
1777                 name: Symbol::intern("<const_ty>"),
1778                 def_id,
1779                 pure_wrt_drop: false,
1780                 kind: ty::GenericParamDefKind::Type {
1781                     has_default: false,
1782                     object_lifetime_default: rl::Set1::Empty,
1783                     synthetic: false,
1784                 },
1785             });
1786         }
1787     }
1788
1789     let param_def_id_to_index = params.iter().map(|param| (param.def_id, param.index)).collect();
1790
1791     ty::Generics {
1792         parent: parent_def_id,
1793         parent_count,
1794         params,
1795         param_def_id_to_index,
1796         has_self: has_self || parent_has_self,
1797         has_late_bound_regions: has_late_bound_regions(tcx, node),
1798     }
1799 }
1800
1801 fn are_suggestable_generic_args(generic_args: &[hir::GenericArg<'_>]) -> bool {
1802     generic_args.iter().any(|arg| match arg {
1803         hir::GenericArg::Type(ty) => is_suggestable_infer_ty(ty),
1804         hir::GenericArg::Infer(_) => true,
1805         _ => false,
1806     })
1807 }
1808
1809 /// Whether `ty` is a type with `_` placeholders that can be inferred. Used in diagnostics only to
1810 /// use inference to provide suggestions for the appropriate type if possible.
1811 fn is_suggestable_infer_ty(ty: &hir::Ty<'_>) -> bool {
1812     debug!(?ty);
1813     use hir::TyKind::*;
1814     match &ty.kind {
1815         Infer => true,
1816         Slice(ty) => is_suggestable_infer_ty(ty),
1817         Array(ty, length) => {
1818             is_suggestable_infer_ty(ty) || matches!(length, hir::ArrayLen::Infer(_, _))
1819         }
1820         Tup(tys) => tys.iter().any(is_suggestable_infer_ty),
1821         Ptr(mut_ty) | Rptr(_, mut_ty) => is_suggestable_infer_ty(mut_ty.ty),
1822         OpaqueDef(_, generic_args) => are_suggestable_generic_args(generic_args),
1823         Path(hir::QPath::TypeRelative(ty, segment)) => {
1824             is_suggestable_infer_ty(ty) || are_suggestable_generic_args(segment.args().args)
1825         }
1826         Path(hir::QPath::Resolved(ty_opt, hir::Path { segments, .. })) => {
1827             ty_opt.map_or(false, is_suggestable_infer_ty)
1828                 || segments.iter().any(|segment| are_suggestable_generic_args(segment.args().args))
1829         }
1830         _ => false,
1831     }
1832 }
1833
1834 pub fn get_infer_ret_ty<'hir>(output: &'hir hir::FnRetTy<'hir>) -> Option<&'hir hir::Ty<'hir>> {
1835     if let hir::FnRetTy::Return(ty) = output {
1836         if is_suggestable_infer_ty(ty) {
1837             return Some(&*ty);
1838         }
1839     }
1840     None
1841 }
1842
1843 fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
1844     use rustc_hir::Node::*;
1845     use rustc_hir::*;
1846
1847     let def_id = def_id.expect_local();
1848     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1849
1850     let icx = ItemCtxt::new(tcx, def_id.to_def_id());
1851
1852     match tcx.hir().get(hir_id) {
1853         TraitItem(hir::TraitItem {
1854             kind: TraitItemKind::Fn(sig, TraitFn::Provided(_)),
1855             generics,
1856             ..
1857         })
1858         | Item(hir::Item { kind: ItemKind::Fn(sig, generics, _), .. }) => {
1859             infer_return_ty_for_fn_sig(tcx, sig, generics, def_id, &icx)
1860         }
1861
1862         ImplItem(hir::ImplItem { kind: ImplItemKind::Fn(sig, _), generics, .. }) => {
1863             // Do not try to inference the return type for a impl method coming from a trait
1864             if let Item(hir::Item { kind: ItemKind::Impl(i), .. }) =
1865                 tcx.hir().get(tcx.hir().get_parent_node(hir_id))
1866                 && i.of_trait.is_some()
1867             {
1868                 <dyn AstConv<'_>>::ty_of_fn(
1869                     &icx,
1870                     hir_id,
1871                     sig.header.unsafety,
1872                     sig.header.abi,
1873                     sig.decl,
1874                     Some(generics),
1875                     None,
1876                 )
1877             } else {
1878                 infer_return_ty_for_fn_sig(tcx, sig, generics, def_id, &icx)
1879             }
1880         }
1881
1882         TraitItem(hir::TraitItem {
1883             kind: TraitItemKind::Fn(FnSig { header, decl, span: _ }, _),
1884             generics,
1885             ..
1886         }) => <dyn AstConv<'_>>::ty_of_fn(
1887             &icx,
1888             hir_id,
1889             header.unsafety,
1890             header.abi,
1891             decl,
1892             Some(generics),
1893             None,
1894         ),
1895
1896         ForeignItem(&hir::ForeignItem { kind: ForeignItemKind::Fn(fn_decl, _, _), .. }) => {
1897             let abi = tcx.hir().get_foreign_abi(hir_id);
1898             compute_sig_of_foreign_fn_decl(tcx, def_id.to_def_id(), fn_decl, abi)
1899         }
1900
1901         Ctor(data) | Variant(hir::Variant { data, .. }) if data.ctor_hir_id().is_some() => {
1902             let ty = tcx.type_of(tcx.hir().get_parent_item(hir_id));
1903             let inputs =
1904                 data.fields().iter().map(|f| tcx.type_of(tcx.hir().local_def_id(f.hir_id)));
1905             ty::Binder::dummy(tcx.mk_fn_sig(
1906                 inputs,
1907                 ty,
1908                 false,
1909                 hir::Unsafety::Normal,
1910                 abi::Abi::Rust,
1911             ))
1912         }
1913
1914         Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1915             // Closure signatures are not like other function
1916             // signatures and cannot be accessed through `fn_sig`. For
1917             // example, a closure signature excludes the `self`
1918             // argument. In any case they are embedded within the
1919             // closure type as part of the `ClosureSubsts`.
1920             //
1921             // To get the signature of a closure, you should use the
1922             // `sig` method on the `ClosureSubsts`:
1923             //
1924             //    substs.as_closure().sig(def_id, tcx)
1925             bug!(
1926                 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
1927             );
1928         }
1929
1930         x => {
1931             bug!("unexpected sort of node in fn_sig(): {:?}", x);
1932         }
1933     }
1934 }
1935
1936 fn infer_return_ty_for_fn_sig<'tcx>(
1937     tcx: TyCtxt<'tcx>,
1938     sig: &hir::FnSig<'_>,
1939     generics: &hir::Generics<'_>,
1940     def_id: LocalDefId,
1941     icx: &ItemCtxt<'tcx>,
1942 ) -> ty::PolyFnSig<'tcx> {
1943     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1944
1945     match get_infer_ret_ty(&sig.decl.output) {
1946         Some(ty) => {
1947             let fn_sig = tcx.typeck(def_id).liberated_fn_sigs()[hir_id];
1948             // Typeck doesn't expect erased regions to be returned from `type_of`.
1949             let fn_sig = tcx.fold_regions(fn_sig, &mut false, |r, _| match *r {
1950                 ty::ReErased => tcx.lifetimes.re_static,
1951                 _ => r,
1952             });
1953             let fn_sig = ty::Binder::dummy(fn_sig);
1954
1955             let mut visitor = HirPlaceholderCollector::default();
1956             visitor.visit_ty(ty);
1957             let mut diag = bad_placeholder(tcx, visitor.0, "return type");
1958             let ret_ty = fn_sig.skip_binder().output();
1959             if ret_ty.is_suggestable(tcx) {
1960                 diag.span_suggestion(
1961                     ty.span,
1962                     "replace with the correct return type",
1963                     ret_ty.to_string(),
1964                     Applicability::MachineApplicable,
1965                 );
1966             } else if matches!(ret_ty.kind(), ty::FnDef(..)) {
1967                 let fn_sig = ret_ty.fn_sig(tcx);
1968                 if fn_sig.skip_binder().inputs_and_output.iter().all(|t| t.is_suggestable(tcx)) {
1969                     diag.span_suggestion(
1970                         ty.span,
1971                         "replace with the correct return type",
1972                         fn_sig.to_string(),
1973                         Applicability::MachineApplicable,
1974                     );
1975                 }
1976             } else if ret_ty.is_closure() {
1977                 // We're dealing with a closure, so we should suggest using `impl Fn` or trait bounds
1978                 // to prevent the user from getting a papercut while trying to use the unique closure
1979                 // syntax (e.g. `[closure@src/lib.rs:2:5: 2:9]`).
1980                 diag.help("consider using an `Fn`, `FnMut`, or `FnOnce` trait bound");
1981                 diag.note("for more information on `Fn` traits and closure types, see https://doc.rust-lang.org/book/ch13-01-closures.html");
1982             }
1983             diag.emit();
1984
1985             fn_sig
1986         }
1987         None => <dyn AstConv<'_>>::ty_of_fn(
1988             icx,
1989             hir_id,
1990             sig.header.unsafety,
1991             sig.header.abi,
1992             sig.decl,
1993             Some(generics),
1994             None,
1995         ),
1996     }
1997 }
1998
1999 fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> {
2000     let icx = ItemCtxt::new(tcx, def_id);
2001     match tcx.hir().expect_item(def_id.expect_local()).kind {
2002         hir::ItemKind::Impl(ref impl_) => impl_.of_trait.as_ref().map(|ast_trait_ref| {
2003             let selfty = tcx.type_of(def_id);
2004             <dyn AstConv<'_>>::instantiate_mono_trait_ref(&icx, ast_trait_ref, selfty)
2005         }),
2006         _ => bug!(),
2007     }
2008 }
2009
2010 fn impl_polarity(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ImplPolarity {
2011     let is_rustc_reservation = tcx.has_attr(def_id, sym::rustc_reservation_impl);
2012     let item = tcx.hir().expect_item(def_id.expect_local());
2013     match &item.kind {
2014         hir::ItemKind::Impl(hir::Impl {
2015             polarity: hir::ImplPolarity::Negative(span),
2016             of_trait,
2017             ..
2018         }) => {
2019             if is_rustc_reservation {
2020                 let span = span.to(of_trait.as_ref().map_or(*span, |t| t.path.span));
2021                 tcx.sess.span_err(span, "reservation impls can't be negative");
2022             }
2023             ty::ImplPolarity::Negative
2024         }
2025         hir::ItemKind::Impl(hir::Impl {
2026             polarity: hir::ImplPolarity::Positive,
2027             of_trait: None,
2028             ..
2029         }) => {
2030             if is_rustc_reservation {
2031                 tcx.sess.span_err(item.span, "reservation impls can't be inherent");
2032             }
2033             ty::ImplPolarity::Positive
2034         }
2035         hir::ItemKind::Impl(hir::Impl {
2036             polarity: hir::ImplPolarity::Positive,
2037             of_trait: Some(_),
2038             ..
2039         }) => {
2040             if is_rustc_reservation {
2041                 ty::ImplPolarity::Reservation
2042             } else {
2043                 ty::ImplPolarity::Positive
2044             }
2045         }
2046         item => bug!("impl_polarity: {:?} not an impl", item),
2047     }
2048 }
2049
2050 /// Returns the early-bound lifetimes declared in this generics
2051 /// listing. For anything other than fns/methods, this is just all
2052 /// the lifetimes that are declared. For fns or methods, we have to
2053 /// screen out those that do not appear in any where-clauses etc using
2054 /// `resolve_lifetime::early_bound_lifetimes`.
2055 fn early_bound_lifetimes_from_generics<'a, 'tcx: 'a>(
2056     tcx: TyCtxt<'tcx>,
2057     def_id: LocalDefId,
2058     generics: &'a hir::Generics<'a>,
2059 ) -> impl Iterator<Item = &'a hir::GenericParam<'a>> + Captures<'tcx> {
2060     let late_bound_map = if generics.params.is_empty() {
2061         // This function may be called on `def_id == CRATE_DEF_ID`,
2062         // which makes `is_late_bound_map` ICE.  Don't even try if there
2063         // is no generic parameter.
2064         None
2065     } else {
2066         tcx.is_late_bound_map(def_id)
2067     };
2068     let is_late_bound = move |hir_id| {
2069         let id = tcx.hir().local_def_id(hir_id);
2070         late_bound_map.map_or(false, |(_, set)| set.contains(&id))
2071     };
2072     generics.params.iter().filter(move |param| match param.kind {
2073         GenericParamKind::Lifetime { .. } => !is_late_bound(param.hir_id),
2074         _ => false,
2075     })
2076 }
2077
2078 /// Returns a list of type predicates for the definition with ID `def_id`, including inferred
2079 /// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus
2080 /// inferred constraints concerning which regions outlive other regions.
2081 fn predicates_defined_on(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2082     debug!("predicates_defined_on({:?})", def_id);
2083     let mut result = tcx.explicit_predicates_of(def_id);
2084     debug!("predicates_defined_on: explicit_predicates_of({:?}) = {:?}", def_id, result,);
2085     let inferred_outlives = tcx.inferred_outlives_of(def_id);
2086     if !inferred_outlives.is_empty() {
2087         debug!(
2088             "predicates_defined_on: inferred_outlives_of({:?}) = {:?}",
2089             def_id, inferred_outlives,
2090         );
2091         if result.predicates.is_empty() {
2092             result.predicates = inferred_outlives;
2093         } else {
2094             result.predicates = tcx
2095                 .arena
2096                 .alloc_from_iter(result.predicates.iter().chain(inferred_outlives).copied());
2097         }
2098     }
2099
2100     debug!("predicates_defined_on({:?}) = {:?}", def_id, result);
2101     result
2102 }
2103
2104 /// Returns a list of all type predicates (explicit and implicit) for the definition with
2105 /// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus
2106 /// `Self: Trait` predicates for traits.
2107 fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2108     let mut result = tcx.predicates_defined_on(def_id);
2109
2110     if tcx.is_trait(def_id) {
2111         // For traits, add `Self: Trait` predicate. This is
2112         // not part of the predicates that a user writes, but it
2113         // is something that one must prove in order to invoke a
2114         // method or project an associated type.
2115         //
2116         // In the chalk setup, this predicate is not part of the
2117         // "predicates" for a trait item. But it is useful in
2118         // rustc because if you directly (e.g.) invoke a trait
2119         // method like `Trait::method(...)`, you must naturally
2120         // prove that the trait applies to the types that were
2121         // used, and adding the predicate into this list ensures
2122         // that this is done.
2123         //
2124         // We use a DUMMY_SP here as a way to signal trait bounds that come
2125         // from the trait itself that *shouldn't* be shown as the source of
2126         // an obligation and instead be skipped. Otherwise we'd use
2127         // `tcx.def_span(def_id);`
2128         let span = rustc_span::DUMMY_SP;
2129         result.predicates =
2130             tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once((
2131                 ty::TraitRef::identity(tcx, def_id).without_const().to_predicate(tcx),
2132                 span,
2133             ))));
2134     }
2135     debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
2136     result
2137 }
2138
2139 /// Returns a list of user-specified type predicates for the definition with ID `def_id`.
2140 /// N.B., this does not include any implied/inferred constraints.
2141 fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2142     use rustc_hir::*;
2143
2144     debug!("explicit_predicates_of(def_id={:?})", def_id);
2145
2146     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2147     let node = tcx.hir().get(hir_id);
2148
2149     let mut is_trait = None;
2150     let mut is_default_impl_trait = None;
2151
2152     let icx = ItemCtxt::new(tcx, def_id);
2153
2154     const NO_GENERICS: &hir::Generics<'_> = hir::Generics::empty();
2155
2156     // We use an `IndexSet` to preserves order of insertion.
2157     // Preserving the order of insertion is important here so as not to break UI tests.
2158     let mut predicates: FxIndexSet<(ty::Predicate<'_>, Span)> = FxIndexSet::default();
2159
2160     let ast_generics = match node {
2161         Node::TraitItem(item) => item.generics,
2162
2163         Node::ImplItem(item) => item.generics,
2164
2165         Node::Item(item) => {
2166             match item.kind {
2167                 ItemKind::Impl(ref impl_) => {
2168                     if impl_.defaultness.is_default() {
2169                         is_default_impl_trait = tcx.impl_trait_ref(def_id).map(ty::Binder::dummy);
2170                     }
2171                     &impl_.generics
2172                 }
2173                 ItemKind::Fn(.., ref generics, _)
2174                 | ItemKind::TyAlias(_, ref generics)
2175                 | ItemKind::Enum(_, ref generics)
2176                 | ItemKind::Struct(_, ref generics)
2177                 | ItemKind::Union(_, ref generics) => *generics,
2178
2179                 ItemKind::Trait(_, _, ref generics, ..) => {
2180                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2181                     *generics
2182                 }
2183                 ItemKind::TraitAlias(ref generics, _) => {
2184                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2185                     *generics
2186                 }
2187                 ItemKind::OpaqueTy(OpaqueTy {
2188                     origin: hir::OpaqueTyOrigin::AsyncFn(..) | hir::OpaqueTyOrigin::FnReturn(..),
2189                     ..
2190                 }) => {
2191                     // return-position impl trait
2192                     //
2193                     // We don't inherit predicates from the parent here:
2194                     // If we have, say `fn f<'a, T: 'a>() -> impl Sized {}`
2195                     // then the return type is `f::<'static, T>::{{opaque}}`.
2196                     //
2197                     // If we inherited the predicates of `f` then we would
2198                     // require that `T: 'static` to show that the return
2199                     // type is well-formed.
2200                     //
2201                     // The only way to have something with this opaque type
2202                     // is from the return type of the containing function,
2203                     // which will ensure that the function's predicates
2204                     // hold.
2205                     return ty::GenericPredicates { parent: None, predicates: &[] };
2206                 }
2207                 ItemKind::OpaqueTy(OpaqueTy {
2208                     ref generics,
2209                     origin: hir::OpaqueTyOrigin::TyAlias,
2210                     ..
2211                 }) => {
2212                     // type-alias impl trait
2213                     generics
2214                 }
2215
2216                 _ => NO_GENERICS,
2217             }
2218         }
2219
2220         Node::ForeignItem(item) => match item.kind {
2221             ForeignItemKind::Static(..) => NO_GENERICS,
2222             ForeignItemKind::Fn(_, _, ref generics) => *generics,
2223             ForeignItemKind::Type => NO_GENERICS,
2224         },
2225
2226         _ => NO_GENERICS,
2227     };
2228
2229     let generics = tcx.generics_of(def_id);
2230     let parent_count = generics.parent_count as u32;
2231     let has_own_self = generics.has_self && parent_count == 0;
2232
2233     // Below we'll consider the bounds on the type parameters (including `Self`)
2234     // and the explicit where-clauses, but to get the full set of predicates
2235     // on a trait we need to add in the supertrait bounds and bounds found on
2236     // associated types.
2237     if let Some(_trait_ref) = is_trait {
2238         predicates.extend(tcx.super_predicates_of(def_id).predicates.iter().cloned());
2239     }
2240
2241     // In default impls, we can assume that the self type implements
2242     // the trait. So in:
2243     //
2244     //     default impl Foo for Bar { .. }
2245     //
2246     // we add a default where clause `Foo: Bar`. We do a similar thing for traits
2247     // (see below). Recall that a default impl is not itself an impl, but rather a
2248     // set of defaults that can be incorporated into another impl.
2249     if let Some(trait_ref) = is_default_impl_trait {
2250         predicates.insert((trait_ref.without_const().to_predicate(tcx), tcx.def_span(def_id)));
2251     }
2252
2253     // Collect the region predicates that were declared inline as
2254     // well. In the case of parameters declared on a fn or method, we
2255     // have to be careful to only iterate over early-bound regions.
2256     let mut index = parent_count
2257         + has_own_self as u32
2258         + early_bound_lifetimes_from_generics(tcx, hir_id.owner, ast_generics).count() as u32;
2259
2260     // Collect the predicates that were written inline by the user on each
2261     // type parameter (e.g., `<T: Foo>`).
2262     for param in ast_generics.params {
2263         match param.kind {
2264             // We already dealt with early bound lifetimes above.
2265             GenericParamKind::Lifetime { .. } => (),
2266             GenericParamKind::Type { .. } => {
2267                 let name = param.name.ident().name;
2268                 let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
2269                 index += 1;
2270
2271                 let mut bounds = Bounds::default();
2272                 // Params are implicitly sized unless a `?Sized` bound is found
2273                 <dyn AstConv<'_>>::add_implicitly_sized(
2274                     &icx,
2275                     &mut bounds,
2276                     &[],
2277                     Some((param.hir_id, ast_generics.predicates)),
2278                     param.span,
2279                 );
2280                 predicates.extend(bounds.predicates(tcx, param_ty));
2281             }
2282             GenericParamKind::Const { .. } => {
2283                 // Bounds on const parameters are currently not possible.
2284                 index += 1;
2285             }
2286         }
2287     }
2288
2289     // Add in the bounds that appear in the where-clause.
2290     for predicate in ast_generics.predicates {
2291         match predicate {
2292             hir::WherePredicate::BoundPredicate(bound_pred) => {
2293                 let ty = icx.to_ty(bound_pred.bounded_ty);
2294                 let bound_vars = icx.tcx.late_bound_vars(bound_pred.bounded_ty.hir_id);
2295
2296                 // Keep the type around in a dummy predicate, in case of no bounds.
2297                 // That way, `where Ty:` is not a complete noop (see #53696) and `Ty`
2298                 // is still checked for WF.
2299                 if bound_pred.bounds.is_empty() {
2300                     if let ty::Param(_) = ty.kind() {
2301                         // This is a `where T:`, which can be in the HIR from the
2302                         // transformation that moves `?Sized` to `T`'s declaration.
2303                         // We can skip the predicate because type parameters are
2304                         // trivially WF, but also we *should*, to avoid exposing
2305                         // users who never wrote `where Type:,` themselves, to
2306                         // compiler/tooling bugs from not handling WF predicates.
2307                     } else {
2308                         let span = bound_pred.bounded_ty.span;
2309                         let re_root_empty = tcx.lifetimes.re_root_empty;
2310                         let predicate = ty::Binder::bind_with_vars(
2311                             ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(
2312                                 ty,
2313                                 re_root_empty,
2314                             )),
2315                             bound_vars,
2316                         );
2317                         predicates.insert((predicate.to_predicate(tcx), span));
2318                     }
2319                 }
2320
2321                 let mut bounds = Bounds::default();
2322                 <dyn AstConv<'_>>::add_bounds(
2323                     &icx,
2324                     ty,
2325                     bound_pred.bounds.iter(),
2326                     &mut bounds,
2327                     bound_vars,
2328                 );
2329                 predicates.extend(bounds.predicates(tcx, ty));
2330             }
2331
2332             hir::WherePredicate::RegionPredicate(region_pred) => {
2333                 let r1 = <dyn AstConv<'_>>::ast_region_to_region(&icx, &region_pred.lifetime, None);
2334                 predicates.extend(region_pred.bounds.iter().map(|bound| {
2335                     let (r2, span) = match bound {
2336                         hir::GenericBound::Outlives(lt) => {
2337                             (<dyn AstConv<'_>>::ast_region_to_region(&icx, lt, None), lt.span)
2338                         }
2339                         _ => bug!(),
2340                     };
2341                     let pred = ty::Binder::dummy(ty::PredicateKind::RegionOutlives(
2342                         ty::OutlivesPredicate(r1, r2),
2343                     ))
2344                     .to_predicate(icx.tcx);
2345
2346                     (pred, span)
2347                 }))
2348             }
2349
2350             hir::WherePredicate::EqPredicate(..) => {
2351                 // FIXME(#20041)
2352             }
2353         }
2354     }
2355
2356     if tcx.features().generic_const_exprs {
2357         predicates.extend(const_evaluatable_predicates_of(tcx, def_id.expect_local()));
2358     }
2359
2360     let mut predicates: Vec<_> = predicates.into_iter().collect();
2361
2362     // Subtle: before we store the predicates into the tcx, we
2363     // sort them so that predicates like `T: Foo<Item=U>` come
2364     // before uses of `U`.  This avoids false ambiguity errors
2365     // in trait checking. See `setup_constraining_predicates`
2366     // for details.
2367     if let Node::Item(&Item { kind: ItemKind::Impl { .. }, .. }) = node {
2368         let self_ty = tcx.type_of(def_id);
2369         let trait_ref = tcx.impl_trait_ref(def_id);
2370         cgp::setup_constraining_predicates(
2371             tcx,
2372             &mut predicates,
2373             trait_ref,
2374             &mut cgp::parameters_for_impl(self_ty, trait_ref),
2375         );
2376     }
2377
2378     let result = ty::GenericPredicates {
2379         parent: generics.parent,
2380         predicates: tcx.arena.alloc_from_iter(predicates),
2381     };
2382     debug!("explicit_predicates_of(def_id={:?}) = {:?}", def_id, result);
2383     result
2384 }
2385
2386 fn const_evaluatable_predicates_of<'tcx>(
2387     tcx: TyCtxt<'tcx>,
2388     def_id: LocalDefId,
2389 ) -> FxIndexSet<(ty::Predicate<'tcx>, Span)> {
2390     struct ConstCollector<'tcx> {
2391         tcx: TyCtxt<'tcx>,
2392         preds: FxIndexSet<(ty::Predicate<'tcx>, Span)>,
2393     }
2394
2395     impl<'tcx> intravisit::Visitor<'tcx> for ConstCollector<'tcx> {
2396         fn visit_anon_const(&mut self, c: &'tcx hir::AnonConst) {
2397             let def_id = self.tcx.hir().local_def_id(c.hir_id);
2398             let ct = ty::Const::from_anon_const(self.tcx, def_id);
2399             if let ty::ConstKind::Unevaluated(uv) = ct.val() {
2400                 assert_eq!(uv.promoted, None);
2401                 let span = self.tcx.hir().span(c.hir_id);
2402                 self.preds.insert((
2403                     ty::Binder::dummy(ty::PredicateKind::ConstEvaluatable(uv.shrink()))
2404                         .to_predicate(self.tcx),
2405                     span,
2406                 ));
2407             }
2408         }
2409
2410         fn visit_const_param_default(&mut self, _param: HirId, _ct: &'tcx hir::AnonConst) {
2411             // Do not look into const param defaults,
2412             // these get checked when they are actually instantiated.
2413             //
2414             // We do not want the following to error:
2415             //
2416             //     struct Foo<const N: usize, const M: usize = { N + 1 }>;
2417             //     struct Bar<const N: usize>(Foo<N, 3>);
2418         }
2419     }
2420
2421     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
2422     let node = tcx.hir().get(hir_id);
2423
2424     let mut collector = ConstCollector { tcx, preds: FxIndexSet::default() };
2425     if let hir::Node::Item(item) = node && let hir::ItemKind::Impl(ref impl_) = item.kind {
2426         if let Some(of_trait) = &impl_.of_trait {
2427             debug!("const_evaluatable_predicates_of({:?}): visit impl trait_ref", def_id);
2428             collector.visit_trait_ref(of_trait);
2429         }
2430
2431         debug!("const_evaluatable_predicates_of({:?}): visit_self_ty", def_id);
2432         collector.visit_ty(impl_.self_ty);
2433     }
2434
2435     if let Some(generics) = node.generics() {
2436         debug!("const_evaluatable_predicates_of({:?}): visit_generics", def_id);
2437         collector.visit_generics(generics);
2438     }
2439
2440     if let Some(fn_sig) = tcx.hir().fn_sig_by_hir_id(hir_id) {
2441         debug!("const_evaluatable_predicates_of({:?}): visit_fn_decl", def_id);
2442         collector.visit_fn_decl(fn_sig.decl);
2443     }
2444     debug!("const_evaluatable_predicates_of({:?}) = {:?}", def_id, collector.preds);
2445
2446     collector.preds
2447 }
2448
2449 fn trait_explicit_predicates_and_bounds(
2450     tcx: TyCtxt<'_>,
2451     def_id: LocalDefId,
2452 ) -> ty::GenericPredicates<'_> {
2453     assert_eq!(tcx.def_kind(def_id), DefKind::Trait);
2454     gather_explicit_predicates_of(tcx, def_id.to_def_id())
2455 }
2456
2457 fn explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2458     let def_kind = tcx.def_kind(def_id);
2459     if let DefKind::Trait = def_kind {
2460         // Remove bounds on associated types from the predicates, they will be
2461         // returned by `explicit_item_bounds`.
2462         let predicates_and_bounds = tcx.trait_explicit_predicates_and_bounds(def_id.expect_local());
2463         let trait_identity_substs = InternalSubsts::identity_for_item(tcx, def_id);
2464
2465         let is_assoc_item_ty = |ty: Ty<'_>| {
2466             // For a predicate from a where clause to become a bound on an
2467             // associated type:
2468             // * It must use the identity substs of the item.
2469             //     * Since any generic parameters on the item are not in scope,
2470             //       this means that the item is not a GAT, and its identity
2471             //       substs are the same as the trait's.
2472             // * It must be an associated type for this trait (*not* a
2473             //   supertrait).
2474             if let ty::Projection(projection) = ty.kind() {
2475                 projection.substs == trait_identity_substs
2476                     && tcx.associated_item(projection.item_def_id).container.id() == def_id
2477             } else {
2478                 false
2479             }
2480         };
2481
2482         let predicates: Vec<_> = predicates_and_bounds
2483             .predicates
2484             .iter()
2485             .copied()
2486             .filter(|(pred, _)| match pred.kind().skip_binder() {
2487                 ty::PredicateKind::Trait(tr) => !is_assoc_item_ty(tr.self_ty()),
2488                 ty::PredicateKind::Projection(proj) => {
2489                     !is_assoc_item_ty(proj.projection_ty.self_ty())
2490                 }
2491                 ty::PredicateKind::TypeOutlives(outlives) => !is_assoc_item_ty(outlives.0),
2492                 _ => true,
2493             })
2494             .collect();
2495         if predicates.len() == predicates_and_bounds.predicates.len() {
2496             predicates_and_bounds
2497         } else {
2498             ty::GenericPredicates {
2499                 parent: predicates_and_bounds.parent,
2500                 predicates: tcx.arena.alloc_slice(&predicates),
2501             }
2502         }
2503     } else {
2504         if matches!(def_kind, DefKind::AnonConst) && tcx.lazy_normalization() {
2505             let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2506             if tcx.hir().opt_const_param_default_param_hir_id(hir_id).is_some() {
2507                 // In `generics_of` we set the generics' parent to be our parent's parent which means that
2508                 // we lose out on the predicates of our actual parent if we dont return those predicates here.
2509                 // (See comment in `generics_of` for more information on why the parent shenanigans is necessary)
2510                 //
2511                 // struct Foo<T, const N: usize = { <T as Trait>::ASSOC }>(T) where T: Trait;
2512                 //        ^^^                     ^^^^^^^^^^^^^^^^^^^^^^^ the def id we are calling
2513                 //        ^^^                                             explicit_predicates_of on
2514                 //        parent item we dont have set as the
2515                 //        parent of generics returned by `generics_of`
2516                 //
2517                 // In the above code we want the anon const to have predicates in its param env for `T: Trait`
2518                 let item_def_id = tcx.hir().get_parent_item(hir_id);
2519                 // In the above code example we would be calling `explicit_predicates_of(Foo)` here
2520                 return tcx.explicit_predicates_of(item_def_id);
2521             }
2522         }
2523         gather_explicit_predicates_of(tcx, def_id)
2524     }
2525 }
2526
2527 /// Converts a specific `GenericBound` from the AST into a set of
2528 /// predicates that apply to the self type. A vector is returned
2529 /// because this can be anywhere from zero predicates (`T: ?Sized` adds no
2530 /// predicates) to one (`T: Foo`) to many (`T: Bar<X = i32>` adds `T: Bar`
2531 /// and `<T as Bar>::X == i32`).
2532 fn predicates_from_bound<'tcx>(
2533     astconv: &dyn AstConv<'tcx>,
2534     param_ty: Ty<'tcx>,
2535     bound: &'tcx hir::GenericBound<'tcx>,
2536     bound_vars: &'tcx ty::List<ty::BoundVariableKind>,
2537 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2538     let mut bounds = Bounds::default();
2539     astconv.add_bounds(param_ty, [bound].into_iter(), &mut bounds, bound_vars);
2540     bounds.predicates(astconv.tcx(), param_ty).collect()
2541 }
2542
2543 fn compute_sig_of_foreign_fn_decl<'tcx>(
2544     tcx: TyCtxt<'tcx>,
2545     def_id: DefId,
2546     decl: &'tcx hir::FnDecl<'tcx>,
2547     abi: abi::Abi,
2548 ) -> ty::PolyFnSig<'tcx> {
2549     let unsafety = if abi == abi::Abi::RustIntrinsic {
2550         intrinsic_operation_unsafety(tcx.item_name(def_id))
2551     } else {
2552         hir::Unsafety::Unsafe
2553     };
2554     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2555     let fty = <dyn AstConv<'_>>::ty_of_fn(
2556         &ItemCtxt::new(tcx, def_id),
2557         hir_id,
2558         unsafety,
2559         abi,
2560         decl,
2561         None,
2562         None,
2563     );
2564
2565     // Feature gate SIMD types in FFI, since I am not sure that the
2566     // ABIs are handled at all correctly. -huonw
2567     if abi != abi::Abi::RustIntrinsic
2568         && abi != abi::Abi::PlatformIntrinsic
2569         && !tcx.features().simd_ffi
2570     {
2571         let check = |ast_ty: &hir::Ty<'_>, ty: Ty<'_>| {
2572             if ty.is_simd() {
2573                 let snip = tcx
2574                     .sess
2575                     .source_map()
2576                     .span_to_snippet(ast_ty.span)
2577                     .map_or_else(|_| String::new(), |s| format!(" `{}`", s));
2578                 tcx.sess
2579                     .struct_span_err(
2580                         ast_ty.span,
2581                         &format!(
2582                             "use of SIMD type{} in FFI is highly experimental and \
2583                              may result in invalid code",
2584                             snip
2585                         ),
2586                     )
2587                     .help("add `#![feature(simd_ffi)]` to the crate attributes to enable")
2588                     .emit();
2589             }
2590         };
2591         for (input, ty) in iter::zip(decl.inputs, fty.inputs().skip_binder()) {
2592             check(input, *ty)
2593         }
2594         if let hir::FnRetTy::Return(ref ty) = decl.output {
2595             check(ty, fty.output().skip_binder())
2596         }
2597     }
2598
2599     fty
2600 }
2601
2602 fn is_foreign_item(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2603     match tcx.hir().get_if_local(def_id) {
2604         Some(Node::ForeignItem(..)) => true,
2605         Some(_) => false,
2606         _ => bug!("is_foreign_item applied to non-local def-id {:?}", def_id),
2607     }
2608 }
2609
2610 fn generator_kind(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::GeneratorKind> {
2611     match tcx.hir().get_if_local(def_id) {
2612         Some(Node::Expr(&rustc_hir::Expr {
2613             kind: rustc_hir::ExprKind::Closure(_, _, body_id, _, _),
2614             ..
2615         })) => tcx.hir().body(body_id).generator_kind(),
2616         Some(_) => None,
2617         _ => bug!("generator_kind applied to non-local def-id {:?}", def_id),
2618     }
2619 }
2620
2621 fn from_target_feature(
2622     tcx: TyCtxt<'_>,
2623     attr: &ast::Attribute,
2624     supported_target_features: &FxHashMap<String, Option<Symbol>>,
2625     target_features: &mut Vec<Symbol>,
2626 ) {
2627     let Some(list) = attr.meta_item_list() else { return };
2628     let bad_item = |span| {
2629         let msg = "malformed `target_feature` attribute input";
2630         let code = "enable = \"..\"".to_owned();
2631         tcx.sess
2632             .struct_span_err(span, msg)
2633             .span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
2634             .emit();
2635     };
2636     let rust_features = tcx.features();
2637     for item in list {
2638         // Only `enable = ...` is accepted in the meta-item list.
2639         if !item.has_name(sym::enable) {
2640             bad_item(item.span());
2641             continue;
2642         }
2643
2644         // Must be of the form `enable = "..."` (a string).
2645         let Some(value) = item.value_str() else {
2646             bad_item(item.span());
2647             continue;
2648         };
2649
2650         // We allow comma separation to enable multiple features.
2651         target_features.extend(value.as_str().split(',').filter_map(|feature| {
2652             let Some(feature_gate) = supported_target_features.get(feature) else {
2653                 let msg =
2654                     format!("the feature named `{}` is not valid for this target", feature);
2655                 let mut err = tcx.sess.struct_span_err(item.span(), &msg);
2656                 err.span_label(
2657                     item.span(),
2658                     format!("`{}` is not valid for this target", feature),
2659                 );
2660                 if let Some(stripped) = feature.strip_prefix('+') {
2661                     let valid = supported_target_features.contains_key(stripped);
2662                     if valid {
2663                         err.help("consider removing the leading `+` in the feature name");
2664                     }
2665                 }
2666                 err.emit();
2667                 return None;
2668             };
2669
2670             // Only allow features whose feature gates have been enabled.
2671             let allowed = match feature_gate.as_ref().copied() {
2672                 Some(sym::arm_target_feature) => rust_features.arm_target_feature,
2673                 Some(sym::hexagon_target_feature) => rust_features.hexagon_target_feature,
2674                 Some(sym::powerpc_target_feature) => rust_features.powerpc_target_feature,
2675                 Some(sym::mips_target_feature) => rust_features.mips_target_feature,
2676                 Some(sym::riscv_target_feature) => rust_features.riscv_target_feature,
2677                 Some(sym::avx512_target_feature) => rust_features.avx512_target_feature,
2678                 Some(sym::sse4a_target_feature) => rust_features.sse4a_target_feature,
2679                 Some(sym::tbm_target_feature) => rust_features.tbm_target_feature,
2680                 Some(sym::wasm_target_feature) => rust_features.wasm_target_feature,
2681                 Some(sym::cmpxchg16b_target_feature) => rust_features.cmpxchg16b_target_feature,
2682                 Some(sym::movbe_target_feature) => rust_features.movbe_target_feature,
2683                 Some(sym::rtm_target_feature) => rust_features.rtm_target_feature,
2684                 Some(sym::f16c_target_feature) => rust_features.f16c_target_feature,
2685                 Some(sym::ermsb_target_feature) => rust_features.ermsb_target_feature,
2686                 Some(sym::bpf_target_feature) => rust_features.bpf_target_feature,
2687                 Some(sym::aarch64_ver_target_feature) => rust_features.aarch64_ver_target_feature,
2688                 Some(name) => bug!("unknown target feature gate {}", name),
2689                 None => true,
2690             };
2691             if !allowed {
2692                 feature_err(
2693                     &tcx.sess.parse_sess,
2694                     feature_gate.unwrap(),
2695                     item.span(),
2696                     &format!("the target feature `{}` is currently unstable", feature),
2697                 )
2698                 .emit();
2699             }
2700             Some(Symbol::intern(feature))
2701         }));
2702     }
2703 }
2704
2705 fn linkage_by_name(tcx: TyCtxt<'_>, def_id: LocalDefId, name: &str) -> Linkage {
2706     use rustc_middle::mir::mono::Linkage::*;
2707
2708     // Use the names from src/llvm/docs/LangRef.rst here. Most types are only
2709     // applicable to variable declarations and may not really make sense for
2710     // Rust code in the first place but allow them anyway and trust that the
2711     // user knows what they're doing. Who knows, unanticipated use cases may pop
2712     // up in the future.
2713     //
2714     // ghost, dllimport, dllexport and linkonce_odr_autohide are not supported
2715     // and don't have to be, LLVM treats them as no-ops.
2716     match name {
2717         "appending" => Appending,
2718         "available_externally" => AvailableExternally,
2719         "common" => Common,
2720         "extern_weak" => ExternalWeak,
2721         "external" => External,
2722         "internal" => Internal,
2723         "linkonce" => LinkOnceAny,
2724         "linkonce_odr" => LinkOnceODR,
2725         "private" => Private,
2726         "weak" => WeakAny,
2727         "weak_odr" => WeakODR,
2728         _ => tcx.sess.span_fatal(tcx.def_span(def_id), "invalid linkage specified"),
2729     }
2730 }
2731
2732 fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: DefId) -> CodegenFnAttrs {
2733     if cfg!(debug_assertions) {
2734         let def_kind = tcx.def_kind(did);
2735         assert!(
2736             def_kind.has_codegen_attrs(),
2737             "unexpected `def_kind` in `codegen_fn_attrs`: {def_kind:?}",
2738         );
2739     }
2740
2741     let did = did.expect_local();
2742     let attrs = tcx.hir().attrs(tcx.hir().local_def_id_to_hir_id(did));
2743     let mut codegen_fn_attrs = CodegenFnAttrs::new();
2744     if tcx.should_inherit_track_caller(did) {
2745         codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2746     }
2747
2748     // The panic_no_unwind function called by TerminatorKind::Abort will never
2749     // unwind. If the panic handler that it invokes unwind then it will simply
2750     // call the panic handler again.
2751     if Some(did.to_def_id()) == tcx.lang_items().panic_no_unwind() {
2752         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2753     }
2754
2755     let supported_target_features = tcx.supported_target_features(LOCAL_CRATE);
2756
2757     let mut inline_span = None;
2758     let mut link_ordinal_span = None;
2759     let mut no_sanitize_span = None;
2760     for attr in attrs.iter() {
2761         if attr.has_name(sym::cold) {
2762             codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD;
2763         } else if attr.has_name(sym::rustc_allocator) {
2764             codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR;
2765         } else if attr.has_name(sym::ffi_returns_twice) {
2766             if tcx.is_foreign_item(did) {
2767                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE;
2768             } else {
2769                 // `#[ffi_returns_twice]` is only allowed `extern fn`s.
2770                 struct_span_err!(
2771                     tcx.sess,
2772                     attr.span,
2773                     E0724,
2774                     "`#[ffi_returns_twice]` may only be used on foreign functions"
2775                 )
2776                 .emit();
2777             }
2778         } else if attr.has_name(sym::ffi_pure) {
2779             if tcx.is_foreign_item(did) {
2780                 if attrs.iter().any(|a| a.has_name(sym::ffi_const)) {
2781                     // `#[ffi_const]` functions cannot be `#[ffi_pure]`
2782                     struct_span_err!(
2783                         tcx.sess,
2784                         attr.span,
2785                         E0757,
2786                         "`#[ffi_const]` function cannot be `#[ffi_pure]`"
2787                     )
2788                     .emit();
2789                 } else {
2790                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_PURE;
2791                 }
2792             } else {
2793                 // `#[ffi_pure]` is only allowed on foreign functions
2794                 struct_span_err!(
2795                     tcx.sess,
2796                     attr.span,
2797                     E0755,
2798                     "`#[ffi_pure]` may only be used on foreign functions"
2799                 )
2800                 .emit();
2801             }
2802         } else if attr.has_name(sym::ffi_const) {
2803             if tcx.is_foreign_item(did) {
2804                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_CONST;
2805             } else {
2806                 // `#[ffi_const]` is only allowed on foreign functions
2807                 struct_span_err!(
2808                     tcx.sess,
2809                     attr.span,
2810                     E0756,
2811                     "`#[ffi_const]` may only be used on foreign functions"
2812                 )
2813                 .emit();
2814             }
2815         } else if attr.has_name(sym::rustc_allocator_nounwind) {
2816             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2817         } else if attr.has_name(sym::naked) {
2818             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
2819         } else if attr.has_name(sym::no_mangle) {
2820             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2821         } else if attr.has_name(sym::no_coverage) {
2822             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_COVERAGE;
2823         } else if attr.has_name(sym::rustc_std_internal_symbol) {
2824             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2825         } else if attr.has_name(sym::used) {
2826             let inner = attr.meta_item_list();
2827             match inner.as_deref() {
2828                 Some([item]) if item.has_name(sym::linker) => {
2829                     if !tcx.features().used_with_arg {
2830                         feature_err(
2831                             &tcx.sess.parse_sess,
2832                             sym::used_with_arg,
2833                             attr.span,
2834                             "`#[used(linker)]` is currently unstable",
2835                         )
2836                         .emit();
2837                     }
2838                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED_LINKER;
2839                 }
2840                 Some([item]) if item.has_name(sym::compiler) => {
2841                     if !tcx.features().used_with_arg {
2842                         feature_err(
2843                             &tcx.sess.parse_sess,
2844                             sym::used_with_arg,
2845                             attr.span,
2846                             "`#[used(compiler)]` is currently unstable",
2847                         )
2848                         .emit();
2849                     }
2850                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
2851                 }
2852                 Some(_) => {
2853                     tcx.sess
2854                         .struct_span_err(
2855                             attr.span,
2856                             "expected `used`, `used(compiler)` or `used(linker)`",
2857                         )
2858                         .emit();
2859                 }
2860                 None => codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED,
2861             }
2862         } else if attr.has_name(sym::cmse_nonsecure_entry) {
2863             if !matches!(tcx.fn_sig(did).abi(), abi::Abi::C { .. }) {
2864                 struct_span_err!(
2865                     tcx.sess,
2866                     attr.span,
2867                     E0776,
2868                     "`#[cmse_nonsecure_entry]` requires C ABI"
2869                 )
2870                 .emit();
2871             }
2872             if !tcx.sess.target.llvm_target.contains("thumbv8m") {
2873                 struct_span_err!(tcx.sess, attr.span, E0775, "`#[cmse_nonsecure_entry]` is only valid for targets with the TrustZone-M extension")
2874                     .emit();
2875             }
2876             codegen_fn_attrs.flags |= CodegenFnAttrFlags::CMSE_NONSECURE_ENTRY;
2877         } else if attr.has_name(sym::thread_local) {
2878             codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
2879         } else if attr.has_name(sym::track_caller) {
2880             if !tcx.is_closure(did.to_def_id()) && tcx.fn_sig(did).abi() != abi::Abi::Rust {
2881                 struct_span_err!(tcx.sess, attr.span, E0737, "`#[track_caller]` requires Rust ABI")
2882                     .emit();
2883             }
2884             if tcx.is_closure(did.to_def_id()) && !tcx.features().closure_track_caller {
2885                 feature_err(
2886                     &tcx.sess.parse_sess,
2887                     sym::closure_track_caller,
2888                     attr.span,
2889                     "`#[track_caller]` on closures is currently unstable",
2890                 )
2891                 .emit();
2892             }
2893             codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2894         } else if attr.has_name(sym::export_name) {
2895             if let Some(s) = attr.value_str() {
2896                 if s.as_str().contains('\0') {
2897                     // `#[export_name = ...]` will be converted to a null-terminated string,
2898                     // so it may not contain any null characters.
2899                     struct_span_err!(
2900                         tcx.sess,
2901                         attr.span,
2902                         E0648,
2903                         "`export_name` may not contain null characters"
2904                     )
2905                     .emit();
2906                 }
2907                 codegen_fn_attrs.export_name = Some(s);
2908             }
2909         } else if attr.has_name(sym::target_feature) {
2910             if !tcx.is_closure(did.to_def_id())
2911                 && tcx.fn_sig(did).unsafety() == hir::Unsafety::Normal
2912             {
2913                 if tcx.sess.target.is_like_wasm || tcx.sess.opts.actually_rustdoc {
2914                     // The `#[target_feature]` attribute is allowed on
2915                     // WebAssembly targets on all functions, including safe
2916                     // ones. Other targets require that `#[target_feature]` is
2917                     // only applied to unsafe functions (pending the
2918                     // `target_feature_11` feature) because on most targets
2919                     // execution of instructions that are not supported is
2920                     // considered undefined behavior. For WebAssembly which is a
2921                     // 100% safe target at execution time it's not possible to
2922                     // execute undefined instructions, and even if a future
2923                     // feature was added in some form for this it would be a
2924                     // deterministic trap. There is no undefined behavior when
2925                     // executing WebAssembly so `#[target_feature]` is allowed
2926                     // on safe functions (but again, only for WebAssembly)
2927                     //
2928                     // Note that this is also allowed if `actually_rustdoc` so
2929                     // if a target is documenting some wasm-specific code then
2930                     // it's not spuriously denied.
2931                 } else if !tcx.features().target_feature_11 {
2932                     let mut err = feature_err(
2933                         &tcx.sess.parse_sess,
2934                         sym::target_feature_11,
2935                         attr.span,
2936                         "`#[target_feature(..)]` can only be applied to `unsafe` functions",
2937                     );
2938                     err.span_label(tcx.def_span(did), "not an `unsafe` function");
2939                     err.emit();
2940                 } else {
2941                     check_target_feature_trait_unsafe(tcx, did, attr.span);
2942                 }
2943             }
2944             from_target_feature(
2945                 tcx,
2946                 attr,
2947                 supported_target_features,
2948                 &mut codegen_fn_attrs.target_features,
2949             );
2950         } else if attr.has_name(sym::linkage) {
2951             if let Some(val) = attr.value_str() {
2952                 codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, did, val.as_str()));
2953             }
2954         } else if attr.has_name(sym::link_section) {
2955             if let Some(val) = attr.value_str() {
2956                 if val.as_str().bytes().any(|b| b == 0) {
2957                     let msg = format!(
2958                         "illegal null byte in link_section \
2959                          value: `{}`",
2960                         &val
2961                     );
2962                     tcx.sess.span_err(attr.span, &msg);
2963                 } else {
2964                     codegen_fn_attrs.link_section = Some(val);
2965                 }
2966             }
2967         } else if attr.has_name(sym::link_name) {
2968             codegen_fn_attrs.link_name = attr.value_str();
2969         } else if attr.has_name(sym::link_ordinal) {
2970             link_ordinal_span = Some(attr.span);
2971             if let ordinal @ Some(_) = check_link_ordinal(tcx, attr) {
2972                 codegen_fn_attrs.link_ordinal = ordinal;
2973             }
2974         } else if attr.has_name(sym::no_sanitize) {
2975             no_sanitize_span = Some(attr.span);
2976             if let Some(list) = attr.meta_item_list() {
2977                 for item in list.iter() {
2978                     if item.has_name(sym::address) {
2979                         codegen_fn_attrs.no_sanitize |= SanitizerSet::ADDRESS;
2980                     } else if item.has_name(sym::cfi) {
2981                         codegen_fn_attrs.no_sanitize |= SanitizerSet::CFI;
2982                     } else if item.has_name(sym::memory) {
2983                         codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMORY;
2984                     } else if item.has_name(sym::memtag) {
2985                         codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMTAG;
2986                     } else if item.has_name(sym::thread) {
2987                         codegen_fn_attrs.no_sanitize |= SanitizerSet::THREAD;
2988                     } else if item.has_name(sym::hwaddress) {
2989                         codegen_fn_attrs.no_sanitize |= SanitizerSet::HWADDRESS;
2990                     } else {
2991                         tcx.sess
2992                             .struct_span_err(item.span(), "invalid argument for `no_sanitize`")
2993                             .note("expected one of: `address`, `cfi`, `hwaddress`, `memory`, `memtag`, or `thread`")
2994                             .emit();
2995                     }
2996                 }
2997             }
2998         } else if attr.has_name(sym::instruction_set) {
2999             codegen_fn_attrs.instruction_set = match attr.meta_kind() {
3000                 Some(MetaItemKind::List(ref items)) => match items.as_slice() {
3001                     [NestedMetaItem::MetaItem(set)] => {
3002                         let segments =
3003                             set.path.segments.iter().map(|x| x.ident.name).collect::<Vec<_>>();
3004                         match segments.as_slice() {
3005                             [sym::arm, sym::a32] | [sym::arm, sym::t32] => {
3006                                 if !tcx.sess.target.has_thumb_interworking {
3007                                     struct_span_err!(
3008                                         tcx.sess.diagnostic(),
3009                                         attr.span,
3010                                         E0779,
3011                                         "target does not support `#[instruction_set]`"
3012                                     )
3013                                     .emit();
3014                                     None
3015                                 } else if segments[1] == sym::a32 {
3016                                     Some(InstructionSetAttr::ArmA32)
3017                                 } else if segments[1] == sym::t32 {
3018                                     Some(InstructionSetAttr::ArmT32)
3019                                 } else {
3020                                     unreachable!()
3021                                 }
3022                             }
3023                             _ => {
3024                                 struct_span_err!(
3025                                     tcx.sess.diagnostic(),
3026                                     attr.span,
3027                                     E0779,
3028                                     "invalid instruction set specified",
3029                                 )
3030                                 .emit();
3031                                 None
3032                             }
3033                         }
3034                     }
3035                     [] => {
3036                         struct_span_err!(
3037                             tcx.sess.diagnostic(),
3038                             attr.span,
3039                             E0778,
3040                             "`#[instruction_set]` requires an argument"
3041                         )
3042                         .emit();
3043                         None
3044                     }
3045                     _ => {
3046                         struct_span_err!(
3047                             tcx.sess.diagnostic(),
3048                             attr.span,
3049                             E0779,
3050                             "cannot specify more than one instruction set"
3051                         )
3052                         .emit();
3053                         None
3054                     }
3055                 },
3056                 _ => {
3057                     struct_span_err!(
3058                         tcx.sess.diagnostic(),
3059                         attr.span,
3060                         E0778,
3061                         "must specify an instruction set"
3062                     )
3063                     .emit();
3064                     None
3065                 }
3066             };
3067         } else if attr.has_name(sym::repr) {
3068             codegen_fn_attrs.alignment = match attr.meta_item_list() {
3069                 Some(items) => match items.as_slice() {
3070                     [item] => match item.name_value_literal() {
3071                         Some((sym::align, literal)) => {
3072                             let alignment = rustc_attr::parse_alignment(&literal.kind);
3073
3074                             match alignment {
3075                                 Ok(align) => Some(align),
3076                                 Err(msg) => {
3077                                     struct_span_err!(
3078                                         tcx.sess.diagnostic(),
3079                                         attr.span,
3080                                         E0589,
3081                                         "invalid `repr(align)` attribute: {}",
3082                                         msg
3083                                     )
3084                                     .emit();
3085
3086                                     None
3087                                 }
3088                             }
3089                         }
3090                         _ => None,
3091                     },
3092                     [] => None,
3093                     _ => None,
3094                 },
3095                 None => None,
3096             };
3097         }
3098     }
3099
3100     codegen_fn_attrs.inline = attrs.iter().fold(InlineAttr::None, |ia, attr| {
3101         if !attr.has_name(sym::inline) {
3102             return ia;
3103         }
3104         match attr.meta_kind() {
3105             Some(MetaItemKind::Word) => InlineAttr::Hint,
3106             Some(MetaItemKind::List(ref items)) => {
3107                 inline_span = Some(attr.span);
3108                 if items.len() != 1 {
3109                     struct_span_err!(
3110                         tcx.sess.diagnostic(),
3111                         attr.span,
3112                         E0534,
3113                         "expected one argument"
3114                     )
3115                     .emit();
3116                     InlineAttr::None
3117                 } else if list_contains_name(&items, sym::always) {
3118                     InlineAttr::Always
3119                 } else if list_contains_name(&items, sym::never) {
3120                     InlineAttr::Never
3121                 } else {
3122                     struct_span_err!(
3123                         tcx.sess.diagnostic(),
3124                         items[0].span(),
3125                         E0535,
3126                         "invalid argument"
3127                     )
3128                     .emit();
3129
3130                     InlineAttr::None
3131                 }
3132             }
3133             Some(MetaItemKind::NameValue(_)) => ia,
3134             None => ia,
3135         }
3136     });
3137
3138     codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
3139         if !attr.has_name(sym::optimize) {
3140             return ia;
3141         }
3142         let err = |sp, s| struct_span_err!(tcx.sess.diagnostic(), sp, E0722, "{}", s).emit();
3143         match attr.meta_kind() {
3144             Some(MetaItemKind::Word) => {
3145                 err(attr.span, "expected one argument");
3146                 ia
3147             }
3148             Some(MetaItemKind::List(ref items)) => {
3149                 inline_span = Some(attr.span);
3150                 if items.len() != 1 {
3151                     err(attr.span, "expected one argument");
3152                     OptimizeAttr::None
3153                 } else if list_contains_name(&items, sym::size) {
3154                     OptimizeAttr::Size
3155                 } else if list_contains_name(&items, sym::speed) {
3156                     OptimizeAttr::Speed
3157                 } else {
3158                     err(items[0].span(), "invalid argument");
3159                     OptimizeAttr::None
3160                 }
3161             }
3162             Some(MetaItemKind::NameValue(_)) => ia,
3163             None => ia,
3164         }
3165     });
3166
3167     // #73631: closures inherit `#[target_feature]` annotations
3168     if tcx.features().target_feature_11 && tcx.is_closure(did.to_def_id()) {
3169         let owner_id = tcx.parent(did.to_def_id());
3170         codegen_fn_attrs
3171             .target_features
3172             .extend(tcx.codegen_fn_attrs(owner_id).target_features.iter().copied())
3173     }
3174
3175     // If a function uses #[target_feature] it can't be inlined into general
3176     // purpose functions as they wouldn't have the right target features
3177     // enabled. For that reason we also forbid #[inline(always)] as it can't be
3178     // respected.
3179     if !codegen_fn_attrs.target_features.is_empty() {
3180         if codegen_fn_attrs.inline == InlineAttr::Always {
3181             if let Some(span) = inline_span {
3182                 tcx.sess.span_err(
3183                     span,
3184                     "cannot use `#[inline(always)]` with \
3185                      `#[target_feature]`",
3186                 );
3187             }
3188         }
3189     }
3190
3191     if !codegen_fn_attrs.no_sanitize.is_empty() {
3192         if codegen_fn_attrs.inline == InlineAttr::Always {
3193             if let (Some(no_sanitize_span), Some(inline_span)) = (no_sanitize_span, inline_span) {
3194                 let hir_id = tcx.hir().local_def_id_to_hir_id(did);
3195                 tcx.struct_span_lint_hir(
3196                     lint::builtin::INLINE_NO_SANITIZE,
3197                     hir_id,
3198                     no_sanitize_span,
3199                     |lint| {
3200                         lint.build("`no_sanitize` will have no effect after inlining")
3201                             .span_note(inline_span, "inlining requested here")
3202                             .emit();
3203                     },
3204                 )
3205             }
3206         }
3207     }
3208
3209     // Weak lang items have the same semantics as "std internal" symbols in the
3210     // sense that they're preserved through all our LTO passes and only
3211     // strippable by the linker.
3212     //
3213     // Additionally weak lang items have predetermined symbol names.
3214     if tcx.is_weak_lang_item(did.to_def_id()) {
3215         codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
3216     }
3217     if let Some(name) = weak_lang_items::link_name(attrs) {
3218         codegen_fn_attrs.export_name = Some(name);
3219         codegen_fn_attrs.link_name = Some(name);
3220     }
3221     check_link_name_xor_ordinal(tcx, &codegen_fn_attrs, link_ordinal_span);
3222
3223     // Internal symbols to the standard library all have no_mangle semantics in
3224     // that they have defined symbol names present in the function name. This
3225     // also applies to weak symbols where they all have known symbol names.
3226     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
3227         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
3228     }
3229
3230     // Any linkage to LLVM intrinsics for now forcibly marks them all as never
3231     // unwinds since LLVM sometimes can't handle codegen which `invoke`s
3232     // intrinsic functions.
3233     if let Some(name) = &codegen_fn_attrs.link_name {
3234         if name.as_str().starts_with("llvm.") {
3235             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
3236         }
3237     }
3238
3239     codegen_fn_attrs
3240 }
3241
3242 /// Computes the set of target features used in a function for the purposes of
3243 /// inline assembly.
3244 fn asm_target_features<'tcx>(tcx: TyCtxt<'tcx>, did: DefId) -> &'tcx FxHashSet<Symbol> {
3245     let mut target_features = tcx.sess.target_features.clone();
3246     if tcx.def_kind(did).has_codegen_attrs() {
3247         let attrs = tcx.codegen_fn_attrs(did);
3248         target_features.extend(&attrs.target_features);
3249         match attrs.instruction_set {
3250             None => {}
3251             Some(InstructionSetAttr::ArmA32) => {
3252                 target_features.remove(&sym::thumb_mode);
3253             }
3254             Some(InstructionSetAttr::ArmT32) => {
3255                 target_features.insert(sym::thumb_mode);
3256             }
3257         }
3258     }
3259
3260     tcx.arena.alloc(target_features)
3261 }
3262
3263 /// Checks if the provided DefId is a method in a trait impl for a trait which has track_caller
3264 /// applied to the method prototype.
3265 fn should_inherit_track_caller(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
3266     if let Some(impl_item) = tcx.opt_associated_item(def_id)
3267         && let ty::AssocItemContainer::ImplContainer(_) = impl_item.container
3268         && let Some(trait_item) = impl_item.trait_item_def_id
3269     {
3270         return tcx
3271             .codegen_fn_attrs(trait_item)
3272             .flags
3273             .intersects(CodegenFnAttrFlags::TRACK_CALLER);
3274     }
3275
3276     false
3277 }
3278
3279 fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<u16> {
3280     use rustc_ast::{Lit, LitIntType, LitKind};
3281     let meta_item_list = attr.meta_item_list();
3282     let meta_item_list: Option<&[ast::NestedMetaItem]> = meta_item_list.as_ref().map(Vec::as_ref);
3283     let sole_meta_list = match meta_item_list {
3284         Some([item]) => item.literal(),
3285         Some(_) => {
3286             tcx.sess
3287                 .struct_span_err(attr.span, "incorrect number of arguments to `#[link_ordinal]`")
3288                 .note("the attribute requires exactly one argument")
3289                 .emit();
3290             return None;
3291         }
3292         _ => None,
3293     };
3294     if let Some(Lit { kind: LitKind::Int(ordinal, LitIntType::Unsuffixed), .. }) = sole_meta_list {
3295         // According to the table at https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#import-header,
3296         // the ordinal must fit into 16 bits.  Similarly, the Ordinal field in COFFShortExport (defined
3297         // in llvm/include/llvm/Object/COFFImportFile.h), which we use to communicate import information
3298         // to LLVM for `#[link(kind = "raw-dylib"_])`, is also defined to be uint16_t.
3299         //
3300         // FIXME: should we allow an ordinal of 0?  The MSVC toolchain has inconsistent support for this:
3301         // both LINK.EXE and LIB.EXE signal errors and abort when given a .DEF file that specifies
3302         // a zero ordinal.  However, llvm-dlltool is perfectly happy to generate an import library
3303         // for such a .DEF file, and MSVC's LINK.EXE is also perfectly happy to consume an import
3304         // library produced by LLVM with an ordinal of 0, and it generates an .EXE.  (I don't know yet
3305         // if the resulting EXE runs, as I haven't yet built the necessary DLL -- see earlier comment
3306         // about LINK.EXE failing.)
3307         if *ordinal <= u16::MAX as u128 {
3308             Some(*ordinal as u16)
3309         } else {
3310             let msg = format!("ordinal value in `link_ordinal` is too large: `{}`", &ordinal);
3311             tcx.sess
3312                 .struct_span_err(attr.span, &msg)
3313                 .note("the value may not exceed `u16::MAX`")
3314                 .emit();
3315             None
3316         }
3317     } else {
3318         tcx.sess
3319             .struct_span_err(attr.span, "illegal ordinal format in `link_ordinal`")
3320             .note("an unsuffixed integer value, e.g., `1`, is expected")
3321             .emit();
3322         None
3323     }
3324 }
3325
3326 fn check_link_name_xor_ordinal(
3327     tcx: TyCtxt<'_>,
3328     codegen_fn_attrs: &CodegenFnAttrs,
3329     inline_span: Option<Span>,
3330 ) {
3331     if codegen_fn_attrs.link_name.is_none() || codegen_fn_attrs.link_ordinal.is_none() {
3332         return;
3333     }
3334     let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
3335     if let Some(span) = inline_span {
3336         tcx.sess.span_err(span, msg);
3337     } else {
3338         tcx.sess.err(msg);
3339     }
3340 }
3341
3342 /// Checks the function annotated with `#[target_feature]` is not a safe
3343 /// trait method implementation, reporting an error if it is.
3344 fn check_target_feature_trait_unsafe(tcx: TyCtxt<'_>, id: LocalDefId, attr_span: Span) {
3345     let hir_id = tcx.hir().local_def_id_to_hir_id(id);
3346     let node = tcx.hir().get(hir_id);
3347     if let Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }) = node {
3348         let parent_id = tcx.hir().get_parent_item(hir_id);
3349         let parent_item = tcx.hir().expect_item(parent_id);
3350         if let hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) = parent_item.kind {
3351             tcx.sess
3352                 .struct_span_err(
3353                     attr_span,
3354                     "`#[target_feature(..)]` cannot be applied to safe trait method",
3355                 )
3356                 .span_label(attr_span, "cannot be applied to safe trait method")
3357                 .span_label(tcx.def_span(id), "not an `unsafe` function")
3358                 .emit();
3359         }
3360     }
3361 }