compiler/rustc_typeck/src/collect.rs

   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, IsSuggestable, 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().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, |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.replace_late_bound_regions_uncached(
 453                                             poly_trait_ref,
 454                                             |_| {
 455                                                 self.tcx.mk_region(ty::ReEarlyBound(
 456                                                     ty::EarlyBoundRegion {
 457                                                         def_id: item_def_id,
 458                                                         index: 0,
 459                                                         name: Symbol::intern(&lt_name),
 460                                                     },
 461                                                 ))
 462                                             }
 463                                         ),
 464                                     ),
 465                                 ),
 466                             ];
 467                             err.multipart_suggestion(
 468                                 "use a fully qualified path with explicit lifetimes",
 469                                 suggestions,
 470                                 Applicability::MaybeIncorrect,
 471                             );
 472                         }
 473                         _ => {}
 474                     }
 475                 }
 476                 hir::Node::Item(hir::Item {
 477                     kind:
 478                         hir::ItemKind::Struct(..) | hir::ItemKind::Enum(..) | hir::ItemKind::Union(..),
 479                     ..
 480                 }) => {}
 481                 hir::Node::Item(_)
 482                 | hir::Node::ForeignItem(_)
 483                 | hir::Node::TraitItem(_)
 484                 | hir::Node::ImplItem(_) => {
 485                     err.span_suggestion_verbose(
 486                         span.with_hi(item_segment.ident.span.lo()),
 487                         "use a fully qualified path with inferred lifetimes",
 488                         format!(
 489                             "{}::",
 490                             // Erase named lt, we want `<A as B<'_>::C`, not `<A as B<'a>::C`.
 491                             self.tcx.anonymize_late_bound_regions(poly_trait_ref).skip_binder(),
 492                         ),
 493                         Applicability::MaybeIncorrect,
 494                     );
 495                 }
 496                 _ => {}
 497             }
 498             err.emit();
 499             self.tcx().ty_error()
 500         }
 501     }
 502
 503     fn normalize_ty(&self, _span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
 504         // Types in item signatures are not normalized to avoid undue dependencies.
 505         ty
 506     }
 507
 508     fn set_tainted_by_errors(&self) {
 509         // There's no obvious place to track this, so just let it go.
 510     }
 511
 512     fn record_ty(&self, _hir_id: hir::HirId, _ty: Ty<'tcx>, _span: Span) {
 513         // There's no place to record types from signatures?
 514     }
 515 }
 516
 517 /// Synthesize a new lifetime name that doesn't clash with any of the lifetimes already present.
 518 fn get_new_lifetime_name<'tcx>(
 519     tcx: TyCtxt<'tcx>,
 520     poly_trait_ref: ty::PolyTraitRef<'tcx>,
 521     generics: &hir::Generics<'tcx>,
 522 ) -> String {
 523     let existing_lifetimes = tcx
 524         .collect_referenced_late_bound_regions(&poly_trait_ref)
 525         .into_iter()
 526         .filter_map(|lt| {
 527             if let ty::BoundRegionKind::BrNamed(_, name) = lt {
 528                 Some(name.as_str().to_string())
 529             } else {
 530                 None
 531             }
 532         })
 533         .chain(generics.params.iter().filter_map(|param| {
 534             if let hir::GenericParamKind::Lifetime { .. } = &param.kind {
 535                 Some(param.name.ident().as_str().to_string())
 536             } else {
 537                 None
 538             }
 539         }))
 540         .collect::<FxHashSet<String>>();
 541
 542     let a_to_z_repeat_n = |n| {
 543         (b'a'..=b'z').map(move |c| {
 544             let mut s = '\''.to_string();
 545             s.extend(std::iter::repeat(char::from(c)).take(n));
 546             s
 547         })
 548     };
 549
 550     // If all single char lifetime names are present, we wrap around and double the chars.
 551     (1..).flat_map(a_to_z_repeat_n).find(|lt| !existing_lifetimes.contains(lt.as_str())).unwrap()
 552 }
 553
 554 /// Returns the predicates defined on `item_def_id` of the form
 555 /// `X: Foo` where `X` is the type parameter `def_id`.
 556 fn type_param_predicates(
 557     tcx: TyCtxt<'_>,
 558     (item_def_id, def_id, assoc_name): (DefId, LocalDefId, Ident),
 559 ) -> ty::GenericPredicates<'_> {
 560     use rustc_hir::*;
 561
 562     // In the AST, bounds can derive from two places. Either
 563     // written inline like `<T: Foo>` or in a where-clause like
 564     // `where T: Foo`.
 565
 566     let param_id = tcx.hir().local_def_id_to_hir_id(def_id);
 567     let param_owner = tcx.hir().ty_param_owner(def_id);
 568     let generics = tcx.generics_of(param_owner);
 569     let index = generics.param_def_id_to_index[&def_id.to_def_id()];
 570     let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(def_id));
 571
 572     // Don't look for bounds where the type parameter isn't in scope.
 573     let parent = if item_def_id == param_owner.to_def_id() {
 574         None
 575     } else {
 576         tcx.generics_of(item_def_id).parent
 577     };
 578
 579     let mut result = parent
 580         .map(|parent| {
 581             let icx = ItemCtxt::new(tcx, parent);
 582             icx.get_type_parameter_bounds(DUMMY_SP, def_id.to_def_id(), assoc_name)
 583         })
 584         .unwrap_or_default();
 585     let mut extend = None;
 586
 587     let item_hir_id = tcx.hir().local_def_id_to_hir_id(item_def_id.expect_local());
 588     let ast_generics = match tcx.hir().get(item_hir_id) {
 589         Node::TraitItem(item) => &item.generics,
 590
 591         Node::ImplItem(item) => &item.generics,
 592
 593         Node::Item(item) => {
 594             match item.kind {
 595                 ItemKind::Fn(.., ref generics, _)
 596                 | ItemKind::Impl(hir::Impl { ref generics, .. })
 597                 | ItemKind::TyAlias(_, ref generics)
 598                 | ItemKind::OpaqueTy(OpaqueTy {
 599                     ref generics,
 600                     origin: hir::OpaqueTyOrigin::TyAlias,
 601                     ..
 602                 })
 603                 | ItemKind::Enum(_, ref generics)
 604                 | ItemKind::Struct(_, ref generics)
 605                 | ItemKind::Union(_, ref generics) => generics,
 606                 ItemKind::Trait(_, _, ref generics, ..) => {
 607                     // Implied `Self: Trait` and supertrait bounds.
 608                     if param_id == item_hir_id {
 609                         let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id);
 610                         extend =
 611                             Some((identity_trait_ref.without_const().to_predicate(tcx), item.span));
 612                     }
 613                     generics
 614                 }
 615                 _ => return result,
 616             }
 617         }
 618
 619         Node::ForeignItem(item) => match item.kind {
 620             ForeignItemKind::Fn(_, _, ref generics) => generics,
 621             _ => return result,
 622         },
 623
 624         _ => return result,
 625     };
 626
 627     let icx = ItemCtxt::new(tcx, item_def_id);
 628     let extra_predicates = extend.into_iter().chain(
 629         icx.type_parameter_bounds_in_generics(
 630             ast_generics,
 631             param_id,
 632             ty,
 633             OnlySelfBounds(true),
 634             Some(assoc_name),
 635         )
 636         .into_iter()
 637         .filter(|(predicate, _)| match predicate.kind().skip_binder() {
 638             ty::PredicateKind::Trait(data) => data.self_ty().is_param(index),
 639             _ => false,
 640         }),
 641     );
 642     result.predicates =
 643         tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(extra_predicates));
 644     result
 645 }
 646
 647 impl<'tcx> ItemCtxt<'tcx> {
 648     /// Finds bounds from `hir::Generics`. This requires scanning through the
 649     /// AST. We do this to avoid having to convert *all* the bounds, which
 650     /// would create artificial cycles. Instead, we can only convert the
 651     /// bounds for a type parameter `X` if `X::Foo` is used.
 652     #[instrument(level = "trace", skip(self, ast_generics))]
 653     fn type_parameter_bounds_in_generics(
 654         &self,
 655         ast_generics: &'tcx hir::Generics<'tcx>,
 656         param_id: hir::HirId,
 657         ty: Ty<'tcx>,
 658         only_self_bounds: OnlySelfBounds,
 659         assoc_name: Option<Ident>,
 660     ) -> Vec<(ty::Predicate<'tcx>, Span)> {
 661         let param_def_id = self.tcx.hir().local_def_id(param_id).to_def_id();
 662         debug!(?param_def_id);
 663         ast_generics
 664             .predicates
 665             .iter()
 666             .filter_map(|wp| match *wp {
 667                 hir::WherePredicate::BoundPredicate(ref bp) => Some(bp),
 668                 _ => None,
 669             })
 670             .flat_map(|bp| {
 671                 let bt = if bp.is_param_bound(param_def_id) {
 672                     Some(ty)
 673                 } else if !only_self_bounds.0 {
 674                     Some(self.to_ty(bp.bounded_ty))
 675                 } else {
 676                     None
 677                 };
 678                 let bvars = self.tcx.late_bound_vars(bp.bounded_ty.hir_id);
 679
 680                 bp.bounds.iter().filter_map(move |b| bt.map(|bt| (bt, b, bvars))).filter(
 681                     |(_, b, _)| match assoc_name {
 682                         Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
 683                         None => true,
 684                     },
 685                 )
 686             })
 687             .flat_map(|(bt, b, bvars)| predicates_from_bound(self, bt, b, bvars))
 688             .collect()
 689     }
 690
 691     fn bound_defines_assoc_item(&self, b: &hir::GenericBound<'_>, assoc_name: Ident) -> bool {
 692         debug!("bound_defines_assoc_item(b={:?}, assoc_name={:?})", b, assoc_name);
 693
 694         match b {
 695             hir::GenericBound::Trait(poly_trait_ref, _) => {
 696                 let trait_ref = &poly_trait_ref.trait_ref;
 697                 if let Some(trait_did) = trait_ref.trait_def_id() {
 698                     self.tcx.trait_may_define_assoc_type(trait_did, assoc_name)
 699                 } else {
 700                     false
 701                 }
 702             }
 703             _ => false,
 704         }
 705     }
 706 }
 707
 708 fn convert_item(tcx: TyCtxt<'_>, item_id: hir::ItemId) {
 709     let it = tcx.hir().item(item_id);
 710     debug!("convert: item {} with id {}", it.ident, it.hir_id());
 711     let def_id = item_id.def_id;
 712
 713     match it.kind {
 714         // These don't define types.
 715         hir::ItemKind::ExternCrate(_)
 716         | hir::ItemKind::Use(..)
 717         | hir::ItemKind::Macro(..)
 718         | hir::ItemKind::Mod(_)
 719         | hir::ItemKind::GlobalAsm(_) => {}
 720         hir::ItemKind::ForeignMod { items, .. } => {
 721             for item in items {
 722                 let item = tcx.hir().foreign_item(item.id);
 723                 tcx.ensure().generics_of(item.def_id);
 724                 tcx.ensure().type_of(item.def_id);
 725                 tcx.ensure().predicates_of(item.def_id);
 726                 match item.kind {
 727                     hir::ForeignItemKind::Fn(..) => tcx.ensure().fn_sig(item.def_id),
 728                     hir::ForeignItemKind::Static(..) => {
 729                         let mut visitor = HirPlaceholderCollector::default();
 730                         visitor.visit_foreign_item(item);
 731                         placeholder_type_error(
 732                             tcx,
 733                             None,
 734                             visitor.0,
 735                             false,
 736                             None,
 737                             "static variable",
 738                         );
 739                     }
 740                     _ => (),
 741                 }
 742             }
 743         }
 744         hir::ItemKind::Enum(ref enum_definition, _) => {
 745             tcx.ensure().generics_of(def_id);
 746             tcx.ensure().type_of(def_id);
 747             tcx.ensure().predicates_of(def_id);
 748             convert_enum_variant_types(tcx, def_id.to_def_id(), enum_definition.variants);
 749         }
 750         hir::ItemKind::Impl { .. } => {
 751             tcx.ensure().generics_of(def_id);
 752             tcx.ensure().type_of(def_id);
 753             tcx.ensure().impl_trait_ref(def_id);
 754             tcx.ensure().predicates_of(def_id);
 755         }
 756         hir::ItemKind::Trait(..) => {
 757             tcx.ensure().generics_of(def_id);
 758             tcx.ensure().trait_def(def_id);
 759             tcx.at(it.span).super_predicates_of(def_id);
 760             tcx.ensure().predicates_of(def_id);
 761         }
 762         hir::ItemKind::TraitAlias(..) => {
 763             tcx.ensure().generics_of(def_id);
 764             tcx.at(it.span).super_predicates_of(def_id);
 765             tcx.ensure().predicates_of(def_id);
 766         }
 767         hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 768             tcx.ensure().generics_of(def_id);
 769             tcx.ensure().type_of(def_id);
 770             tcx.ensure().predicates_of(def_id);
 771
 772             for f in struct_def.fields() {
 773                 let def_id = tcx.hir().local_def_id(f.hir_id);
 774                 tcx.ensure().generics_of(def_id);
 775                 tcx.ensure().type_of(def_id);
 776                 tcx.ensure().predicates_of(def_id);
 777             }
 778
 779             if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
 780                 convert_variant_ctor(tcx, ctor_hir_id);
 781             }
 782         }
 783
 784         // Desugared from `impl Trait`, so visited by the function's return type.
 785         hir::ItemKind::OpaqueTy(hir::OpaqueTy {
 786             origin: hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..),
 787             ..
 788         }) => {}
 789
 790         // Don't call `type_of` on opaque types, since that depends on type
 791         // checking function bodies. `check_item_type` ensures that it's called
 792         // instead.
 793         hir::ItemKind::OpaqueTy(..) => {
 794             tcx.ensure().generics_of(def_id);
 795             tcx.ensure().predicates_of(def_id);
 796             tcx.ensure().explicit_item_bounds(def_id);
 797         }
 798         hir::ItemKind::TyAlias(..)
 799         | hir::ItemKind::Static(..)
 800         | hir::ItemKind::Const(..)
 801         | hir::ItemKind::Fn(..) => {
 802             tcx.ensure().generics_of(def_id);
 803             tcx.ensure().type_of(def_id);
 804             tcx.ensure().predicates_of(def_id);
 805             match it.kind {
 806                 hir::ItemKind::Fn(..) => tcx.ensure().fn_sig(def_id),
 807                 hir::ItemKind::OpaqueTy(..) => tcx.ensure().item_bounds(def_id),
 808                 hir::ItemKind::Const(ty, ..) | hir::ItemKind::Static(ty, ..) => {
 809                     if !is_suggestable_infer_ty(ty) {
 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         generics: &'tcx hir::Generics<'tcx>,
1368         decl: &'tcx hir::FnDecl<'tcx>,
1369     ) -> Option<Span> {
1370         let mut visitor = LateBoundRegionsDetector {
1371             tcx,
1372             outer_index: ty::INNERMOST,
1373             has_late_bound_regions: None,
1374         };
1375         for param in generics.params {
1376             if let GenericParamKind::Lifetime { .. } = param.kind {
1377                 if tcx.is_late_bound(param.hir_id) {
1378                     return Some(param.span);
1379                 }
1380             }
1381         }
1382         visitor.visit_fn_decl(decl);
1383         visitor.has_late_bound_regions
1384     }
1385
1386     match node {
1387         Node::TraitItem(item) => match item.kind {
1388             hir::TraitItemKind::Fn(ref sig, _) => {
1389                 has_late_bound_regions(tcx, &item.generics, sig.decl)
1390             }
1391             _ => None,
1392         },
1393         Node::ImplItem(item) => match item.kind {
1394             hir::ImplItemKind::Fn(ref sig, _) => {
1395                 has_late_bound_regions(tcx, &item.generics, sig.decl)
1396             }
1397             _ => None,
1398         },
1399         Node::ForeignItem(item) => match item.kind {
1400             hir::ForeignItemKind::Fn(fn_decl, _, ref generics) => {
1401                 has_late_bound_regions(tcx, generics, fn_decl)
1402             }
1403             _ => None,
1404         },
1405         Node::Item(item) => match item.kind {
1406             hir::ItemKind::Fn(ref sig, .., ref generics, _) => {
1407                 has_late_bound_regions(tcx, generics, sig.decl)
1408             }
1409             _ => None,
1410         },
1411         _ => None,
1412     }
1413 }
1414
1415 struct AnonConstInParamTyDetector {
1416     in_param_ty: bool,
1417     found_anon_const_in_param_ty: bool,
1418     ct: HirId,
1419 }
1420
1421 impl<'v> Visitor<'v> for AnonConstInParamTyDetector {
1422     fn visit_generic_param(&mut self, p: &'v hir::GenericParam<'v>) {
1423         if let GenericParamKind::Const { ty, default: _ } = p.kind {
1424             let prev = self.in_param_ty;
1425             self.in_param_ty = true;
1426             self.visit_ty(ty);
1427             self.in_param_ty = prev;
1428         }
1429     }
1430
1431     fn visit_anon_const(&mut self, c: &'v hir::AnonConst) {
1432         if self.in_param_ty && self.ct == c.hir_id {
1433             self.found_anon_const_in_param_ty = true;
1434         } else {
1435             intravisit::walk_anon_const(self, c)
1436         }
1437     }
1438 }
1439
1440 fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::Generics {
1441     use rustc_hir::*;
1442
1443     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1444
1445     let node = tcx.hir().get(hir_id);
1446     let parent_def_id = match node {
1447         Node::ImplItem(_)
1448         | Node::TraitItem(_)
1449         | Node::Variant(_)
1450         | Node::Ctor(..)
1451         | Node::Field(_) => {
1452             let parent_id = tcx.hir().get_parent_item(hir_id);
1453             Some(parent_id.to_def_id())
1454         }
1455         // FIXME(#43408) always enable this once `lazy_normalization` is
1456         // stable enough and does not need a feature gate anymore.
1457         Node::AnonConst(_) => {
1458             let parent_def_id = tcx.hir().get_parent_item(hir_id);
1459
1460             let mut in_param_ty = false;
1461             for (_parent, node) in tcx.hir().parent_iter(hir_id) {
1462                 if let Some(generics) = node.generics() {
1463                     let mut visitor = AnonConstInParamTyDetector {
1464                         in_param_ty: false,
1465                         found_anon_const_in_param_ty: false,
1466                         ct: hir_id,
1467                     };
1468
1469                     visitor.visit_generics(generics);
1470                     in_param_ty = visitor.found_anon_const_in_param_ty;
1471                     break;
1472                 }
1473             }
1474
1475             if in_param_ty {
1476                 // We do not allow generic parameters in anon consts if we are inside
1477                 // of a const parameter type, e.g. `struct Foo<const N: usize, const M: [u8; N]>` is not allowed.
1478                 None
1479             } else if tcx.lazy_normalization() {
1480                 if let Some(param_id) = tcx.hir().opt_const_param_default_param_hir_id(hir_id) {
1481                     // If the def_id we are calling generics_of on is an anon ct default i.e:
1482                     //
1483                     // struct Foo<const N: usize = { .. }>;
1484                     //        ^^^       ^          ^^^^^^ def id of this anon const
1485                     //        ^         ^ param_id
1486                     //        ^ parent_def_id
1487                     //
1488                     // then we only want to return generics for params to the left of `N`. If we don't do that we
1489                     // end up with that const looking like: `ty::ConstKind::Unevaluated(def_id, substs: [N#0])`.
1490                     //
1491                     // This causes ICEs (#86580) when building the substs for Foo in `fn foo() -> Foo { .. }` as
1492                     // we substitute the defaults with the partially built substs when we build the substs. Subst'ing
1493                     // the `N#0` on the unevaluated const indexes into the empty substs we're in the process of building.
1494                     //
1495                     // We fix this by having this function return the parent's generics ourselves and truncating the
1496                     // generics to only include non-forward declared params (with the exception of the `Self` ty)
1497                     //
1498                     // For the above code example that means we want `substs: []`
1499                     // For the following struct def we want `substs: [N#0]` when generics_of is called on
1500                     // the def id of the `{ N + 1 }` anon const
1501                     // struct Foo<const N: usize, const M: usize = { N + 1 }>;
1502                     //
1503                     // This has some implications for how we get the predicates available to the anon const
1504                     // see `explicit_predicates_of` for more information on this
1505                     let generics = tcx.generics_of(parent_def_id.to_def_id());
1506                     let param_def = tcx.hir().local_def_id(param_id).to_def_id();
1507                     let param_def_idx = generics.param_def_id_to_index[&param_def];
1508                     // In the above example this would be .params[..N#0]
1509                     let params = generics.params[..param_def_idx as usize].to_owned();
1510                     let param_def_id_to_index =
1511                         params.iter().map(|param| (param.def_id, param.index)).collect();
1512
1513                     return ty::Generics {
1514                         // we set the parent of these generics to be our parent's parent so that we
1515                         // dont end up with substs: [N, M, N] for the const default on a struct like this:
1516                         // struct Foo<const N: usize, const M: usize = { ... }>;
1517                         parent: generics.parent,
1518                         parent_count: generics.parent_count,
1519                         params,
1520                         param_def_id_to_index,
1521                         has_self: generics.has_self,
1522                         has_late_bound_regions: generics.has_late_bound_regions,
1523                     };
1524                 }
1525
1526                 // HACK(eddyb) this provides the correct generics when
1527                 // `feature(generic_const_expressions)` is enabled, so that const expressions
1528                 // used with const generics, e.g. `Foo<{N+1}>`, can work at all.
1529                 //
1530                 // Note that we do not supply the parent generics when using
1531                 // `min_const_generics`.
1532                 Some(parent_def_id.to_def_id())
1533             } else {
1534                 let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1535                 match parent_node {
1536                     // HACK(eddyb) this provides the correct generics for repeat
1537                     // expressions' count (i.e. `N` in `[x; N]`), and explicit
1538                     // `enum` discriminants (i.e. `D` in `enum Foo { Bar = D }`),
1539                     // as they shouldn't be able to cause query cycle errors.
1540                     Node::Expr(&Expr { kind: ExprKind::Repeat(_, ref constant), .. })
1541                         if constant.hir_id() == hir_id =>
1542                     {
1543                         Some(parent_def_id.to_def_id())
1544                     }
1545                     Node::Variant(Variant { disr_expr: Some(ref constant), .. })
1546                         if constant.hir_id == hir_id =>
1547                     {
1548                         Some(parent_def_id.to_def_id())
1549                     }
1550                     Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) => {
1551                         Some(tcx.typeck_root_def_id(def_id))
1552                     }
1553                     // Exclude `GlobalAsm` here which cannot have generics.
1554                     Node::Expr(&Expr { kind: ExprKind::InlineAsm(asm), .. })
1555                         if asm.operands.iter().any(|(op, _op_sp)| match op {
1556                             hir::InlineAsmOperand::Const { anon_const }
1557                             | hir::InlineAsmOperand::SymFn { anon_const } => {
1558                                 anon_const.hir_id == hir_id
1559                             }
1560                             _ => false,
1561                         }) =>
1562                     {
1563                         Some(parent_def_id.to_def_id())
1564                     }
1565                     _ => None,
1566                 }
1567             }
1568         }
1569         Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure { .. }, .. }) => {
1570             Some(tcx.typeck_root_def_id(def_id))
1571         }
1572         Node::Item(item) => match item.kind {
1573             ItemKind::OpaqueTy(hir::OpaqueTy {
1574                 origin:
1575                     hir::OpaqueTyOrigin::FnReturn(fn_def_id) | hir::OpaqueTyOrigin::AsyncFn(fn_def_id),
1576                 ..
1577             }) => Some(fn_def_id.to_def_id()),
1578             ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::TyAlias, .. }) => {
1579                 let parent_id = tcx.hir().get_parent_item(hir_id);
1580                 assert_ne!(parent_id, CRATE_DEF_ID);
1581                 debug!("generics_of: parent of opaque ty {:?} is {:?}", def_id, parent_id);
1582                 // Opaque types are always nested within another item, and
1583                 // inherit the generics of the item.
1584                 Some(parent_id.to_def_id())
1585             }
1586             _ => None,
1587         },
1588         _ => None,
1589     };
1590
1591     let no_generics = hir::Generics::empty();
1592     let ast_generics = node.generics().unwrap_or(&no_generics);
1593     let (opt_self, allow_defaults) = match node {
1594         Node::Item(item) => {
1595             match item.kind {
1596                 ItemKind::Trait(..) | ItemKind::TraitAlias(..) => {
1597                     // Add in the self type parameter.
1598                     //
1599                     // Something of a hack: use the node id for the trait, also as
1600                     // the node id for the Self type parameter.
1601                     let opt_self = Some(ty::GenericParamDef {
1602                         index: 0,
1603                         name: kw::SelfUpper,
1604                         def_id,
1605                         pure_wrt_drop: false,
1606                         kind: ty::GenericParamDefKind::Type {
1607                             has_default: false,
1608                             object_lifetime_default: rl::Set1::Empty,
1609                             synthetic: false,
1610                         },
1611                     });
1612
1613                     (opt_self, true)
1614                 }
1615                 ItemKind::TyAlias(..)
1616                 | ItemKind::Enum(..)
1617                 | ItemKind::Struct(..)
1618                 | ItemKind::OpaqueTy(..)
1619                 | ItemKind::Union(..) => (None, true),
1620                 _ => (None, false),
1621             }
1622         }
1623         _ => (None, false),
1624     };
1625
1626     let has_self = opt_self.is_some();
1627     let mut parent_has_self = false;
1628     let mut own_start = has_self as u32;
1629     let parent_count = parent_def_id.map_or(0, |def_id| {
1630         let generics = tcx.generics_of(def_id);
1631         assert!(!has_self);
1632         parent_has_self = generics.has_self;
1633         own_start = generics.count() as u32;
1634         generics.parent_count + generics.params.len()
1635     });
1636
1637     let mut params: Vec<_> = Vec::with_capacity(ast_generics.params.len() + has_self as usize);
1638
1639     if let Some(opt_self) = opt_self {
1640         params.push(opt_self);
1641     }
1642
1643     let early_lifetimes = early_bound_lifetimes_from_generics(tcx, ast_generics);
1644     params.extend(early_lifetimes.enumerate().map(|(i, param)| ty::GenericParamDef {
1645         name: param.name.ident().name,
1646         index: own_start + i as u32,
1647         def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1648         pure_wrt_drop: param.pure_wrt_drop,
1649         kind: ty::GenericParamDefKind::Lifetime,
1650     }));
1651
1652     let object_lifetime_defaults = tcx.object_lifetime_defaults(hir_id.owner);
1653
1654     // Now create the real type and const parameters.
1655     let type_start = own_start - has_self as u32 + params.len() as u32;
1656     let mut i = 0;
1657
1658     params.extend(ast_generics.params.iter().filter_map(|param| match param.kind {
1659         GenericParamKind::Lifetime { .. } => None,
1660         GenericParamKind::Type { ref default, synthetic, .. } => {
1661             if !allow_defaults && default.is_some() {
1662                 if !tcx.features().default_type_parameter_fallback {
1663                     tcx.struct_span_lint_hir(
1664                         lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
1665                         param.hir_id,
1666                         param.span,
1667                         |lint| {
1668                             lint.build(
1669                                 "defaults for type parameters are only allowed in \
1670                                  `struct`, `enum`, `type`, or `trait` definitions",
1671                             )
1672                             .emit();
1673                         },
1674                     );
1675                 }
1676             }
1677
1678             let kind = ty::GenericParamDefKind::Type {
1679                 has_default: default.is_some(),
1680                 object_lifetime_default: object_lifetime_defaults
1681                     .as_ref()
1682                     .map_or(rl::Set1::Empty, |o| o[i]),
1683                 synthetic,
1684             };
1685
1686             let param_def = ty::GenericParamDef {
1687                 index: type_start + i as u32,
1688                 name: param.name.ident().name,
1689                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1690                 pure_wrt_drop: param.pure_wrt_drop,
1691                 kind,
1692             };
1693             i += 1;
1694             Some(param_def)
1695         }
1696         GenericParamKind::Const { default, .. } => {
1697             if !allow_defaults && default.is_some() {
1698                 tcx.sess.span_err(
1699                     param.span,
1700                     "defaults for const parameters are only allowed in \
1701                     `struct`, `enum`, `type`, or `trait` definitions",
1702                 );
1703             }
1704
1705             let param_def = ty::GenericParamDef {
1706                 index: type_start + i as u32,
1707                 name: param.name.ident().name,
1708                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1709                 pure_wrt_drop: param.pure_wrt_drop,
1710                 kind: ty::GenericParamDefKind::Const { has_default: default.is_some() },
1711             };
1712             i += 1;
1713             Some(param_def)
1714         }
1715     }));
1716
1717     // provide junk type parameter defs - the only place that
1718     // cares about anything but the length is instantiation,
1719     // and we don't do that for closures.
1720     if let Node::Expr(&hir::Expr {
1721         kind: hir::ExprKind::Closure(hir::Closure { movability: gen, .. }),
1722         ..
1723     }) = node
1724     {
1725         let dummy_args = if gen.is_some() {
1726             &["<resume_ty>", "<yield_ty>", "<return_ty>", "<witness>", "<upvars>"][..]
1727         } else {
1728             &["<closure_kind>", "<closure_signature>", "<upvars>"][..]
1729         };
1730
1731         params.extend(dummy_args.iter().enumerate().map(|(i, &arg)| ty::GenericParamDef {
1732             index: type_start + i as u32,
1733             name: Symbol::intern(arg),
1734             def_id,
1735             pure_wrt_drop: false,
1736             kind: ty::GenericParamDefKind::Type {
1737                 has_default: false,
1738                 object_lifetime_default: rl::Set1::Empty,
1739                 synthetic: false,
1740             },
1741         }));
1742     }
1743
1744     // provide junk type parameter defs for const blocks.
1745     if let Node::AnonConst(_) = node {
1746         let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1747         if let Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) = parent_node {
1748             params.push(ty::GenericParamDef {
1749                 index: type_start,
1750                 name: Symbol::intern("<const_ty>"),
1751                 def_id,
1752                 pure_wrt_drop: false,
1753                 kind: ty::GenericParamDefKind::Type {
1754                     has_default: false,
1755                     object_lifetime_default: rl::Set1::Empty,
1756                     synthetic: false,
1757                 },
1758             });
1759         }
1760     }
1761
1762     let param_def_id_to_index = params.iter().map(|param| (param.def_id, param.index)).collect();
1763
1764     ty::Generics {
1765         parent: parent_def_id,
1766         parent_count,
1767         params,
1768         param_def_id_to_index,
1769         has_self: has_self || parent_has_self,
1770         has_late_bound_regions: has_late_bound_regions(tcx, node),
1771     }
1772 }
1773
1774 fn are_suggestable_generic_args(generic_args: &[hir::GenericArg<'_>]) -> bool {
1775     generic_args.iter().any(|arg| match arg {
1776         hir::GenericArg::Type(ty) => is_suggestable_infer_ty(ty),
1777         hir::GenericArg::Infer(_) => true,
1778         _ => false,
1779     })
1780 }
1781
1782 /// Whether `ty` is a type with `_` placeholders that can be inferred. Used in diagnostics only to
1783 /// use inference to provide suggestions for the appropriate type if possible.
1784 fn is_suggestable_infer_ty(ty: &hir::Ty<'_>) -> bool {
1785     debug!(?ty);
1786     use hir::TyKind::*;
1787     match &ty.kind {
1788         Infer => true,
1789         Slice(ty) => is_suggestable_infer_ty(ty),
1790         Array(ty, length) => {
1791             is_suggestable_infer_ty(ty) || matches!(length, hir::ArrayLen::Infer(_, _))
1792         }
1793         Tup(tys) => tys.iter().any(is_suggestable_infer_ty),
1794         Ptr(mut_ty) | Rptr(_, mut_ty) => is_suggestable_infer_ty(mut_ty.ty),
1795         OpaqueDef(_, generic_args) => are_suggestable_generic_args(generic_args),
1796         Path(hir::QPath::TypeRelative(ty, segment)) => {
1797             is_suggestable_infer_ty(ty) || are_suggestable_generic_args(segment.args().args)
1798         }
1799         Path(hir::QPath::Resolved(ty_opt, hir::Path { segments, .. })) => {
1800             ty_opt.map_or(false, is_suggestable_infer_ty)
1801                 || segments.iter().any(|segment| are_suggestable_generic_args(segment.args().args))
1802         }
1803         _ => false,
1804     }
1805 }
1806
1807 pub fn get_infer_ret_ty<'hir>(output: &'hir hir::FnRetTy<'hir>) -> Option<&'hir hir::Ty<'hir>> {
1808     if let hir::FnRetTy::Return(ty) = output {
1809         if is_suggestable_infer_ty(ty) {
1810             return Some(&*ty);
1811         }
1812     }
1813     None
1814 }
1815
1816 fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
1817     use rustc_hir::Node::*;
1818     use rustc_hir::*;
1819
1820     let def_id = def_id.expect_local();
1821     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1822
1823     let icx = ItemCtxt::new(tcx, def_id.to_def_id());
1824
1825     match tcx.hir().get(hir_id) {
1826         TraitItem(hir::TraitItem {
1827             kind: TraitItemKind::Fn(sig, TraitFn::Provided(_)),
1828             generics,
1829             ..
1830         })
1831         | Item(hir::Item { kind: ItemKind::Fn(sig, generics, _), .. }) => {
1832             infer_return_ty_for_fn_sig(tcx, sig, generics, def_id, &icx)
1833         }
1834
1835         ImplItem(hir::ImplItem { kind: ImplItemKind::Fn(sig, _), generics, .. }) => {
1836             // Do not try to inference the return type for a impl method coming from a trait
1837             if let Item(hir::Item { kind: ItemKind::Impl(i), .. }) =
1838                 tcx.hir().get(tcx.hir().get_parent_node(hir_id))
1839                 && i.of_trait.is_some()
1840             {
1841                 <dyn AstConv<'_>>::ty_of_fn(
1842                     &icx,
1843                     hir_id,
1844                     sig.header.unsafety,
1845                     sig.header.abi,
1846                     sig.decl,
1847                     Some(generics),
1848                     None,
1849                 )
1850             } else {
1851                 infer_return_ty_for_fn_sig(tcx, sig, generics, def_id, &icx)
1852             }
1853         }
1854
1855         TraitItem(hir::TraitItem {
1856             kind: TraitItemKind::Fn(FnSig { header, decl, span: _ }, _),
1857             generics,
1858             ..
1859         }) => <dyn AstConv<'_>>::ty_of_fn(
1860             &icx,
1861             hir_id,
1862             header.unsafety,
1863             header.abi,
1864             decl,
1865             Some(generics),
1866             None,
1867         ),
1868
1869         ForeignItem(&hir::ForeignItem { kind: ForeignItemKind::Fn(fn_decl, _, _), .. }) => {
1870             let abi = tcx.hir().get_foreign_abi(hir_id);
1871             compute_sig_of_foreign_fn_decl(tcx, def_id.to_def_id(), fn_decl, abi)
1872         }
1873
1874         Ctor(data) | Variant(hir::Variant { data, .. }) if data.ctor_hir_id().is_some() => {
1875             let ty = tcx.type_of(tcx.hir().get_parent_item(hir_id));
1876             let inputs =
1877                 data.fields().iter().map(|f| tcx.type_of(tcx.hir().local_def_id(f.hir_id)));
1878             ty::Binder::dummy(tcx.mk_fn_sig(
1879                 inputs,
1880                 ty,
1881                 false,
1882                 hir::Unsafety::Normal,
1883                 abi::Abi::Rust,
1884             ))
1885         }
1886
1887         Expr(&hir::Expr { kind: hir::ExprKind::Closure { .. }, .. }) => {
1888             // Closure signatures are not like other function
1889             // signatures and cannot be accessed through `fn_sig`. For
1890             // example, a closure signature excludes the `self`
1891             // argument. In any case they are embedded within the
1892             // closure type as part of the `ClosureSubsts`.
1893             //
1894             // To get the signature of a closure, you should use the
1895             // `sig` method on the `ClosureSubsts`:
1896             //
1897             //    substs.as_closure().sig(def_id, tcx)
1898             bug!(
1899                 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
1900             );
1901         }
1902
1903         x => {
1904             bug!("unexpected sort of node in fn_sig(): {:?}", x);
1905         }
1906     }
1907 }
1908
1909 fn infer_return_ty_for_fn_sig<'tcx>(
1910     tcx: TyCtxt<'tcx>,
1911     sig: &hir::FnSig<'_>,
1912     generics: &hir::Generics<'_>,
1913     def_id: LocalDefId,
1914     icx: &ItemCtxt<'tcx>,
1915 ) -> ty::PolyFnSig<'tcx> {
1916     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1917
1918     match get_infer_ret_ty(&sig.decl.output) {
1919         Some(ty) => {
1920             let fn_sig = tcx.typeck(def_id).liberated_fn_sigs()[hir_id];
1921             // Typeck doesn't expect erased regions to be returned from `type_of`.
1922             let fn_sig = tcx.fold_regions(fn_sig, |r, _| match *r {
1923                 ty::ReErased => tcx.lifetimes.re_static,
1924                 _ => r,
1925             });
1926             let fn_sig = ty::Binder::dummy(fn_sig);
1927
1928             let mut visitor = HirPlaceholderCollector::default();
1929             visitor.visit_ty(ty);
1930             let mut diag = bad_placeholder(tcx, visitor.0, "return type");
1931             let ret_ty = fn_sig.skip_binder().output();
1932             if ret_ty.is_suggestable(tcx) {
1933                 diag.span_suggestion(
1934                     ty.span,
1935                     "replace with the correct return type",
1936                     ret_ty,
1937                     Applicability::MachineApplicable,
1938                 );
1939             } else if matches!(ret_ty.kind(), ty::FnDef(..)) {
1940                 let fn_sig = ret_ty.fn_sig(tcx);
1941                 if fn_sig.skip_binder().inputs_and_output.iter().all(|t| t.is_suggestable(tcx)) {
1942                     diag.span_suggestion(
1943                         ty.span,
1944                         "replace with the correct return type",
1945                         fn_sig,
1946                         Applicability::MachineApplicable,
1947                     );
1948                 }
1949             } else if ret_ty.is_closure() {
1950                 // We're dealing with a closure, so we should suggest using `impl Fn` or trait bounds
1951                 // to prevent the user from getting a papercut while trying to use the unique closure
1952                 // syntax (e.g. `[closure@src/lib.rs:2:5: 2:9]`).
1953                 diag.help("consider using an `Fn`, `FnMut`, or `FnOnce` trait bound");
1954                 diag.note("for more information on `Fn` traits and closure types, see https://doc.rust-lang.org/book/ch13-01-closures.html");
1955             }
1956             diag.emit();
1957
1958             fn_sig
1959         }
1960         None => <dyn AstConv<'_>>::ty_of_fn(
1961             icx,
1962             hir_id,
1963             sig.header.unsafety,
1964             sig.header.abi,
1965             sig.decl,
1966             Some(generics),
1967             None,
1968         ),
1969     }
1970 }
1971
1972 fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> {
1973     let icx = ItemCtxt::new(tcx, def_id);
1974     match tcx.hir().expect_item(def_id.expect_local()).kind {
1975         hir::ItemKind::Impl(ref impl_) => impl_.of_trait.as_ref().map(|ast_trait_ref| {
1976             let selfty = tcx.type_of(def_id);
1977             <dyn AstConv<'_>>::instantiate_mono_trait_ref(&icx, ast_trait_ref, selfty)
1978         }),
1979         _ => bug!(),
1980     }
1981 }
1982
1983 fn impl_polarity(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ImplPolarity {
1984     let is_rustc_reservation = tcx.has_attr(def_id, sym::rustc_reservation_impl);
1985     let item = tcx.hir().expect_item(def_id.expect_local());
1986     match &item.kind {
1987         hir::ItemKind::Impl(hir::Impl {
1988             polarity: hir::ImplPolarity::Negative(span),
1989             of_trait,
1990             ..
1991         }) => {
1992             if is_rustc_reservation {
1993                 let span = span.to(of_trait.as_ref().map_or(*span, |t| t.path.span));
1994                 tcx.sess.span_err(span, "reservation impls can't be negative");
1995             }
1996             ty::ImplPolarity::Negative
1997         }
1998         hir::ItemKind::Impl(hir::Impl {
1999             polarity: hir::ImplPolarity::Positive,
2000             of_trait: None,
2001             ..
2002         }) => {
2003             if is_rustc_reservation {
2004                 tcx.sess.span_err(item.span, "reservation impls can't be inherent");
2005             }
2006             ty::ImplPolarity::Positive
2007         }
2008         hir::ItemKind::Impl(hir::Impl {
2009             polarity: hir::ImplPolarity::Positive,
2010             of_trait: Some(_),
2011             ..
2012         }) => {
2013             if is_rustc_reservation {
2014                 ty::ImplPolarity::Reservation
2015             } else {
2016                 ty::ImplPolarity::Positive
2017             }
2018         }
2019         item => bug!("impl_polarity: {:?} not an impl", item),
2020     }
2021 }
2022
2023 /// Returns the early-bound lifetimes declared in this generics
2024 /// listing. For anything other than fns/methods, this is just all
2025 /// the lifetimes that are declared. For fns or methods, we have to
2026 /// screen out those that do not appear in any where-clauses etc using
2027 /// `resolve_lifetime::early_bound_lifetimes`.
2028 fn early_bound_lifetimes_from_generics<'a, 'tcx: 'a>(
2029     tcx: TyCtxt<'tcx>,
2030     generics: &'a hir::Generics<'a>,
2031 ) -> impl Iterator<Item = &'a hir::GenericParam<'a>> + Captures<'tcx> {
2032     generics.params.iter().filter(move |param| match param.kind {
2033         GenericParamKind::Lifetime { .. } => !tcx.is_late_bound(param.hir_id),
2034         _ => false,
2035     })
2036 }
2037
2038 /// Returns a list of type predicates for the definition with ID `def_id`, including inferred
2039 /// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus
2040 /// inferred constraints concerning which regions outlive other regions.
2041 fn predicates_defined_on(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2042     debug!("predicates_defined_on({:?})", def_id);
2043     let mut result = tcx.explicit_predicates_of(def_id);
2044     debug!("predicates_defined_on: explicit_predicates_of({:?}) = {:?}", def_id, result,);
2045     let inferred_outlives = tcx.inferred_outlives_of(def_id);
2046     if !inferred_outlives.is_empty() {
2047         debug!(
2048             "predicates_defined_on: inferred_outlives_of({:?}) = {:?}",
2049             def_id, inferred_outlives,
2050         );
2051         if result.predicates.is_empty() {
2052             result.predicates = inferred_outlives;
2053         } else {
2054             result.predicates = tcx
2055                 .arena
2056                 .alloc_from_iter(result.predicates.iter().chain(inferred_outlives).copied());
2057         }
2058     }
2059
2060     debug!("predicates_defined_on({:?}) = {:?}", def_id, result);
2061     result
2062 }
2063
2064 /// Returns a list of all type predicates (explicit and implicit) for the definition with
2065 /// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus
2066 /// `Self: Trait` predicates for traits.
2067 fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2068     let mut result = tcx.predicates_defined_on(def_id);
2069
2070     if tcx.is_trait(def_id) {
2071         // For traits, add `Self: Trait` predicate. This is
2072         // not part of the predicates that a user writes, but it
2073         // is something that one must prove in order to invoke a
2074         // method or project an associated type.
2075         //
2076         // In the chalk setup, this predicate is not part of the
2077         // "predicates" for a trait item. But it is useful in
2078         // rustc because if you directly (e.g.) invoke a trait
2079         // method like `Trait::method(...)`, you must naturally
2080         // prove that the trait applies to the types that were
2081         // used, and adding the predicate into this list ensures
2082         // that this is done.
2083         //
2084         // We use a DUMMY_SP here as a way to signal trait bounds that come
2085         // from the trait itself that *shouldn't* be shown as the source of
2086         // an obligation and instead be skipped. Otherwise we'd use
2087         // `tcx.def_span(def_id);`
2088         let span = rustc_span::DUMMY_SP;
2089         result.predicates =
2090             tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once((
2091                 ty::TraitRef::identity(tcx, def_id).without_const().to_predicate(tcx),
2092                 span,
2093             ))));
2094     }
2095     debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
2096     result
2097 }
2098
2099 /// Returns a list of user-specified type predicates for the definition with ID `def_id`.
2100 /// N.B., this does not include any implied/inferred constraints.
2101 fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2102     use rustc_hir::*;
2103
2104     debug!("explicit_predicates_of(def_id={:?})", def_id);
2105
2106     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2107     let node = tcx.hir().get(hir_id);
2108
2109     let mut is_trait = None;
2110     let mut is_default_impl_trait = None;
2111
2112     let icx = ItemCtxt::new(tcx, def_id);
2113
2114     const NO_GENERICS: &hir::Generics<'_> = hir::Generics::empty();
2115
2116     // We use an `IndexSet` to preserves order of insertion.
2117     // Preserving the order of insertion is important here so as not to break UI tests.
2118     let mut predicates: FxIndexSet<(ty::Predicate<'_>, Span)> = FxIndexSet::default();
2119
2120     let ast_generics = match node {
2121         Node::TraitItem(item) => item.generics,
2122
2123         Node::ImplItem(item) => item.generics,
2124
2125         Node::Item(item) => {
2126             match item.kind {
2127                 ItemKind::Impl(ref impl_) => {
2128                     if impl_.defaultness.is_default() {
2129                         is_default_impl_trait = tcx.impl_trait_ref(def_id).map(ty::Binder::dummy);
2130                     }
2131                     &impl_.generics
2132                 }
2133                 ItemKind::Fn(.., ref generics, _)
2134                 | ItemKind::TyAlias(_, ref generics)
2135                 | ItemKind::Enum(_, ref generics)
2136                 | ItemKind::Struct(_, ref generics)
2137                 | ItemKind::Union(_, ref generics) => *generics,
2138
2139                 ItemKind::Trait(_, _, ref generics, ..) => {
2140                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2141                     *generics
2142                 }
2143                 ItemKind::TraitAlias(ref generics, _) => {
2144                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2145                     *generics
2146                 }
2147                 ItemKind::OpaqueTy(OpaqueTy {
2148                     origin: hir::OpaqueTyOrigin::AsyncFn(..) | hir::OpaqueTyOrigin::FnReturn(..),
2149                     ..
2150                 }) => {
2151                     // return-position impl trait
2152                     //
2153                     // We don't inherit predicates from the parent here:
2154                     // If we have, say `fn f<'a, T: 'a>() -> impl Sized {}`
2155                     // then the return type is `f::<'static, T>::{{opaque}}`.
2156                     //
2157                     // If we inherited the predicates of `f` then we would
2158                     // require that `T: 'static` to show that the return
2159                     // type is well-formed.
2160                     //
2161                     // The only way to have something with this opaque type
2162                     // is from the return type of the containing function,
2163                     // which will ensure that the function's predicates
2164                     // hold.
2165                     return ty::GenericPredicates { parent: None, predicates: &[] };
2166                 }
2167                 ItemKind::OpaqueTy(OpaqueTy {
2168                     ref generics,
2169                     origin: hir::OpaqueTyOrigin::TyAlias,
2170                     ..
2171                 }) => {
2172                     // type-alias impl trait
2173                     generics
2174                 }
2175
2176                 _ => NO_GENERICS,
2177             }
2178         }
2179
2180         Node::ForeignItem(item) => match item.kind {
2181             ForeignItemKind::Static(..) => NO_GENERICS,
2182             ForeignItemKind::Fn(_, _, ref generics) => *generics,
2183             ForeignItemKind::Type => NO_GENERICS,
2184         },
2185
2186         _ => NO_GENERICS,
2187     };
2188
2189     let generics = tcx.generics_of(def_id);
2190     let parent_count = generics.parent_count as u32;
2191     let has_own_self = generics.has_self && parent_count == 0;
2192
2193     // Below we'll consider the bounds on the type parameters (including `Self`)
2194     // and the explicit where-clauses, but to get the full set of predicates
2195     // on a trait we need to add in the supertrait bounds and bounds found on
2196     // associated types.
2197     if let Some(_trait_ref) = is_trait {
2198         predicates.extend(tcx.super_predicates_of(def_id).predicates.iter().cloned());
2199     }
2200
2201     // In default impls, we can assume that the self type implements
2202     // the trait. So in:
2203     //
2204     //     default impl Foo for Bar { .. }
2205     //
2206     // we add a default where clause `Foo: Bar`. We do a similar thing for traits
2207     // (see below). Recall that a default impl is not itself an impl, but rather a
2208     // set of defaults that can be incorporated into another impl.
2209     if let Some(trait_ref) = is_default_impl_trait {
2210         predicates.insert((trait_ref.without_const().to_predicate(tcx), tcx.def_span(def_id)));
2211     }
2212
2213     // Collect the region predicates that were declared inline as
2214     // well. In the case of parameters declared on a fn or method, we
2215     // have to be careful to only iterate over early-bound regions.
2216     let mut index = parent_count
2217         + has_own_self as u32
2218         + early_bound_lifetimes_from_generics(tcx, ast_generics).count() as u32;
2219
2220     // Collect the predicates that were written inline by the user on each
2221     // type parameter (e.g., `<T: Foo>`).
2222     for param in ast_generics.params {
2223         match param.kind {
2224             // We already dealt with early bound lifetimes above.
2225             GenericParamKind::Lifetime { .. } => (),
2226             GenericParamKind::Type { .. } => {
2227                 let name = param.name.ident().name;
2228                 let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
2229                 index += 1;
2230
2231                 let mut bounds = Bounds::default();
2232                 // Params are implicitly sized unless a `?Sized` bound is found
2233                 <dyn AstConv<'_>>::add_implicitly_sized(
2234                     &icx,
2235                     &mut bounds,
2236                     &[],
2237                     Some((param.hir_id, ast_generics.predicates)),
2238                     param.span,
2239                 );
2240                 predicates.extend(bounds.predicates(tcx, param_ty));
2241             }
2242             GenericParamKind::Const { .. } => {
2243                 // Bounds on const parameters are currently not possible.
2244                 index += 1;
2245             }
2246         }
2247     }
2248
2249     // Add in the bounds that appear in the where-clause.
2250     for predicate in ast_generics.predicates {
2251         match predicate {
2252             hir::WherePredicate::BoundPredicate(bound_pred) => {
2253                 let ty = icx.to_ty(bound_pred.bounded_ty);
2254                 let bound_vars = icx.tcx.late_bound_vars(bound_pred.bounded_ty.hir_id);
2255
2256                 // Keep the type around in a dummy predicate, in case of no bounds.
2257                 // That way, `where Ty:` is not a complete noop (see #53696) and `Ty`
2258                 // is still checked for WF.
2259                 if bound_pred.bounds.is_empty() {
2260                     if let ty::Param(_) = ty.kind() {
2261                         // This is a `where T:`, which can be in the HIR from the
2262                         // transformation that moves `?Sized` to `T`'s declaration.
2263                         // We can skip the predicate because type parameters are
2264                         // trivially WF, but also we *should*, to avoid exposing
2265                         // users who never wrote `where Type:,` themselves, to
2266                         // compiler/tooling bugs from not handling WF predicates.
2267                     } else {
2268                         let span = bound_pred.bounded_ty.span;
2269                         let predicate = ty::Binder::bind_with_vars(
2270                             ty::PredicateKind::WellFormed(ty.into()),
2271                             bound_vars,
2272                         );
2273                         predicates.insert((predicate.to_predicate(tcx), span));
2274                     }
2275                 }
2276
2277                 let mut bounds = Bounds::default();
2278                 <dyn AstConv<'_>>::add_bounds(
2279                     &icx,
2280                     ty,
2281                     bound_pred.bounds.iter(),
2282                     &mut bounds,
2283                     bound_vars,
2284                 );
2285                 predicates.extend(bounds.predicates(tcx, ty));
2286             }
2287
2288             hir::WherePredicate::RegionPredicate(region_pred) => {
2289                 let r1 = <dyn AstConv<'_>>::ast_region_to_region(&icx, &region_pred.lifetime, None);
2290                 predicates.extend(region_pred.bounds.iter().map(|bound| {
2291                     let (r2, span) = match bound {
2292                         hir::GenericBound::Outlives(lt) => {
2293                             (<dyn AstConv<'_>>::ast_region_to_region(&icx, lt, None), lt.span)
2294                         }
2295                         _ => bug!(),
2296                     };
2297                     let pred = ty::Binder::dummy(ty::PredicateKind::RegionOutlives(
2298                         ty::OutlivesPredicate(r1, r2),
2299                     ))
2300                     .to_predicate(icx.tcx);
2301
2302                     (pred, span)
2303                 }))
2304             }
2305
2306             hir::WherePredicate::EqPredicate(..) => {
2307                 // FIXME(#20041)
2308             }
2309         }
2310     }
2311
2312     if tcx.features().generic_const_exprs {
2313         predicates.extend(const_evaluatable_predicates_of(tcx, def_id.expect_local()));
2314     }
2315
2316     let mut predicates: Vec<_> = predicates.into_iter().collect();
2317
2318     // Subtle: before we store the predicates into the tcx, we
2319     // sort them so that predicates like `T: Foo<Item=U>` come
2320     // before uses of `U`.  This avoids false ambiguity errors
2321     // in trait checking. See `setup_constraining_predicates`
2322     // for details.
2323     if let Node::Item(&Item { kind: ItemKind::Impl { .. }, .. }) = node {
2324         let self_ty = tcx.type_of(def_id);
2325         let trait_ref = tcx.impl_trait_ref(def_id);
2326         cgp::setup_constraining_predicates(
2327             tcx,
2328             &mut predicates,
2329             trait_ref,
2330             &mut cgp::parameters_for_impl(self_ty, trait_ref),
2331         );
2332     }
2333
2334     let result = ty::GenericPredicates {
2335         parent: generics.parent,
2336         predicates: tcx.arena.alloc_from_iter(predicates),
2337     };
2338     debug!("explicit_predicates_of(def_id={:?}) = {:?}", def_id, result);
2339     result
2340 }
2341
2342 fn const_evaluatable_predicates_of<'tcx>(
2343     tcx: TyCtxt<'tcx>,
2344     def_id: LocalDefId,
2345 ) -> FxIndexSet<(ty::Predicate<'tcx>, Span)> {
2346     struct ConstCollector<'tcx> {
2347         tcx: TyCtxt<'tcx>,
2348         preds: FxIndexSet<(ty::Predicate<'tcx>, Span)>,
2349     }
2350
2351     impl<'tcx> intravisit::Visitor<'tcx> for ConstCollector<'tcx> {
2352         fn visit_anon_const(&mut self, c: &'tcx hir::AnonConst) {
2353             let def_id = self.tcx.hir().local_def_id(c.hir_id);
2354             let ct = ty::Const::from_anon_const(self.tcx, def_id);
2355             if let ty::ConstKind::Unevaluated(uv) = ct.kind() {
2356                 assert_eq!(uv.promoted, None);
2357                 let span = self.tcx.hir().span(c.hir_id);
2358                 self.preds.insert((
2359                     ty::Binder::dummy(ty::PredicateKind::ConstEvaluatable(uv.shrink()))
2360                         .to_predicate(self.tcx),
2361                     span,
2362                 ));
2363             }
2364         }
2365
2366         fn visit_const_param_default(&mut self, _param: HirId, _ct: &'tcx hir::AnonConst) {
2367             // Do not look into const param defaults,
2368             // these get checked when they are actually instantiated.
2369             //
2370             // We do not want the following to error:
2371             //
2372             //     struct Foo<const N: usize, const M: usize = { N + 1 }>;
2373             //     struct Bar<const N: usize>(Foo<N, 3>);
2374         }
2375     }
2376
2377     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
2378     let node = tcx.hir().get(hir_id);
2379
2380     let mut collector = ConstCollector { tcx, preds: FxIndexSet::default() };
2381     if let hir::Node::Item(item) = node && let hir::ItemKind::Impl(ref impl_) = item.kind {
2382         if let Some(of_trait) = &impl_.of_trait {
2383             debug!("const_evaluatable_predicates_of({:?}): visit impl trait_ref", def_id);
2384             collector.visit_trait_ref(of_trait);
2385         }
2386
2387         debug!("const_evaluatable_predicates_of({:?}): visit_self_ty", def_id);
2388         collector.visit_ty(impl_.self_ty);
2389     }
2390
2391     if let Some(generics) = node.generics() {
2392         debug!("const_evaluatable_predicates_of({:?}): visit_generics", def_id);
2393         collector.visit_generics(generics);
2394     }
2395
2396     if let Some(fn_sig) = tcx.hir().fn_sig_by_hir_id(hir_id) {
2397         debug!("const_evaluatable_predicates_of({:?}): visit_fn_decl", def_id);
2398         collector.visit_fn_decl(fn_sig.decl);
2399     }
2400     debug!("const_evaluatable_predicates_of({:?}) = {:?}", def_id, collector.preds);
2401
2402     collector.preds
2403 }
2404
2405 fn trait_explicit_predicates_and_bounds(
2406     tcx: TyCtxt<'_>,
2407     def_id: LocalDefId,
2408 ) -> ty::GenericPredicates<'_> {
2409     assert_eq!(tcx.def_kind(def_id), DefKind::Trait);
2410     gather_explicit_predicates_of(tcx, def_id.to_def_id())
2411 }
2412
2413 fn explicit_predicates_of<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> ty::GenericPredicates<'tcx> {
2414     let def_kind = tcx.def_kind(def_id);
2415     if let DefKind::Trait = def_kind {
2416         // Remove bounds on associated types from the predicates, they will be
2417         // returned by `explicit_item_bounds`.
2418         let predicates_and_bounds = tcx.trait_explicit_predicates_and_bounds(def_id.expect_local());
2419         let trait_identity_substs = InternalSubsts::identity_for_item(tcx, def_id);
2420
2421         let is_assoc_item_ty = |ty: Ty<'tcx>| {
2422             // For a predicate from a where clause to become a bound on an
2423             // associated type:
2424             // * It must use the identity substs of the item.
2425             //     * Since any generic parameters on the item are not in scope,
2426             //       this means that the item is not a GAT, and its identity
2427             //       substs are the same as the trait's.
2428             // * It must be an associated type for this trait (*not* a
2429             //   supertrait).
2430             if let ty::Projection(projection) = ty.kind() {
2431                 projection.substs == trait_identity_substs
2432                     && tcx.associated_item(projection.item_def_id).container.id() == def_id
2433             } else {
2434                 false
2435             }
2436         };
2437
2438         let predicates: Vec<_> = predicates_and_bounds
2439             .predicates
2440             .iter()
2441             .copied()
2442             .filter(|(pred, _)| match pred.kind().skip_binder() {
2443                 ty::PredicateKind::Trait(tr) => !is_assoc_item_ty(tr.self_ty()),
2444                 ty::PredicateKind::Projection(proj) => {
2445                     !is_assoc_item_ty(proj.projection_ty.self_ty())
2446                 }
2447                 ty::PredicateKind::TypeOutlives(outlives) => !is_assoc_item_ty(outlives.0),
2448                 _ => true,
2449             })
2450             .collect();
2451         if predicates.len() == predicates_and_bounds.predicates.len() {
2452             predicates_and_bounds
2453         } else {
2454             ty::GenericPredicates {
2455                 parent: predicates_and_bounds.parent,
2456                 predicates: tcx.arena.alloc_slice(&predicates),
2457             }
2458         }
2459     } else {
2460         if matches!(def_kind, DefKind::AnonConst) && tcx.lazy_normalization() {
2461             let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2462             if tcx.hir().opt_const_param_default_param_hir_id(hir_id).is_some() {
2463                 // In `generics_of` we set the generics' parent to be our parent's parent which means that
2464                 // we lose out on the predicates of our actual parent if we dont return those predicates here.
2465                 // (See comment in `generics_of` for more information on why the parent shenanigans is necessary)
2466                 //
2467                 // struct Foo<T, const N: usize = { <T as Trait>::ASSOC }>(T) where T: Trait;
2468                 //        ^^^                     ^^^^^^^^^^^^^^^^^^^^^^^ the def id we are calling
2469                 //        ^^^                                             explicit_predicates_of on
2470                 //        parent item we dont have set as the
2471                 //        parent of generics returned by `generics_of`
2472                 //
2473                 // In the above code we want the anon const to have predicates in its param env for `T: Trait`
2474                 let item_def_id = tcx.hir().get_parent_item(hir_id);
2475                 // In the above code example we would be calling `explicit_predicates_of(Foo)` here
2476                 return tcx.explicit_predicates_of(item_def_id);
2477             }
2478         }
2479         gather_explicit_predicates_of(tcx, def_id)
2480     }
2481 }
2482
2483 /// Converts a specific `GenericBound` from the AST into a set of
2484 /// predicates that apply to the self type. A vector is returned
2485 /// because this can be anywhere from zero predicates (`T: ?Sized` adds no
2486 /// predicates) to one (`T: Foo`) to many (`T: Bar<X = i32>` adds `T: Bar`
2487 /// and `<T as Bar>::X == i32`).
2488 fn predicates_from_bound<'tcx>(
2489     astconv: &dyn AstConv<'tcx>,
2490     param_ty: Ty<'tcx>,
2491     bound: &'tcx hir::GenericBound<'tcx>,
2492     bound_vars: &'tcx ty::List<ty::BoundVariableKind>,
2493 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2494     let mut bounds = Bounds::default();
2495     astconv.add_bounds(param_ty, [bound].into_iter(), &mut bounds, bound_vars);
2496     bounds.predicates(astconv.tcx(), param_ty).collect()
2497 }
2498
2499 fn compute_sig_of_foreign_fn_decl<'tcx>(
2500     tcx: TyCtxt<'tcx>,
2501     def_id: DefId,
2502     decl: &'tcx hir::FnDecl<'tcx>,
2503     abi: abi::Abi,
2504 ) -> ty::PolyFnSig<'tcx> {
2505     let unsafety = if abi == abi::Abi::RustIntrinsic {
2506         intrinsic_operation_unsafety(tcx.item_name(def_id))
2507     } else {
2508         hir::Unsafety::Unsafe
2509     };
2510     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2511     let fty = <dyn AstConv<'_>>::ty_of_fn(
2512         &ItemCtxt::new(tcx, def_id),
2513         hir_id,
2514         unsafety,
2515         abi,
2516         decl,
2517         None,
2518         None,
2519     );
2520
2521     // Feature gate SIMD types in FFI, since I am not sure that the
2522     // ABIs are handled at all correctly. -huonw
2523     if abi != abi::Abi::RustIntrinsic
2524         && abi != abi::Abi::PlatformIntrinsic
2525         && !tcx.features().simd_ffi
2526     {
2527         let check = |ast_ty: &hir::Ty<'_>, ty: Ty<'_>| {
2528             if ty.is_simd() {
2529                 let snip = tcx
2530                     .sess
2531                     .source_map()
2532                     .span_to_snippet(ast_ty.span)
2533                     .map_or_else(|_| String::new(), |s| format!(" `{}`", s));
2534                 tcx.sess
2535                     .struct_span_err(
2536                         ast_ty.span,
2537                         &format!(
2538                             "use of SIMD type{} in FFI is highly experimental and \
2539                              may result in invalid code",
2540                             snip
2541                         ),
2542                     )
2543                     .help("add `#![feature(simd_ffi)]` to the crate attributes to enable")
2544                     .emit();
2545             }
2546         };
2547         for (input, ty) in iter::zip(decl.inputs, fty.inputs().skip_binder()) {
2548             check(input, *ty)
2549         }
2550         if let hir::FnRetTy::Return(ref ty) = decl.output {
2551             check(ty, fty.output().skip_binder())
2552         }
2553     }
2554
2555     fty
2556 }
2557
2558 fn is_foreign_item(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2559     match tcx.hir().get_if_local(def_id) {
2560         Some(Node::ForeignItem(..)) => true,
2561         Some(_) => false,
2562         _ => bug!("is_foreign_item applied to non-local def-id {:?}", def_id),
2563     }
2564 }
2565
2566 fn generator_kind(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::GeneratorKind> {
2567     match tcx.hir().get_if_local(def_id) {
2568         Some(Node::Expr(&rustc_hir::Expr {
2569             kind: rustc_hir::ExprKind::Closure(&rustc_hir::Closure { body, .. }),
2570             ..
2571         })) => tcx.hir().body(body).generator_kind(),
2572         Some(_) => None,
2573         _ => bug!("generator_kind applied to non-local def-id {:?}", def_id),
2574     }
2575 }
2576
2577 fn from_target_feature(
2578     tcx: TyCtxt<'_>,
2579     attr: &ast::Attribute,
2580     supported_target_features: &FxHashMap<String, Option<Symbol>>,
2581     target_features: &mut Vec<Symbol>,
2582 ) {
2583     let Some(list) = attr.meta_item_list() else { return };
2584     let bad_item = |span| {
2585         let msg = "malformed `target_feature` attribute input";
2586         let code = "enable = \"..\"";
2587         tcx.sess
2588             .struct_span_err(span, msg)
2589             .span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
2590             .emit();
2591     };
2592     let rust_features = tcx.features();
2593     for item in list {
2594         // Only `enable = ...` is accepted in the meta-item list.
2595         if !item.has_name(sym::enable) {
2596             bad_item(item.span());
2597             continue;
2598         }
2599
2600         // Must be of the form `enable = "..."` (a string).
2601         let Some(value) = item.value_str() else {
2602             bad_item(item.span());
2603             continue;
2604         };
2605
2606         // We allow comma separation to enable multiple features.
2607         target_features.extend(value.as_str().split(',').filter_map(|feature| {
2608             let Some(feature_gate) = supported_target_features.get(feature) else {
2609                 let msg =
2610                     format!("the feature named `{}` is not valid for this target", feature);
2611                 let mut err = tcx.sess.struct_span_err(item.span(), &msg);
2612                 err.span_label(
2613                     item.span(),
2614                     format!("`{}` is not valid for this target", feature),
2615                 );
2616                 if let Some(stripped) = feature.strip_prefix('+') {
2617                     let valid = supported_target_features.contains_key(stripped);
2618                     if valid {
2619                         err.help("consider removing the leading `+` in the feature name");
2620                     }
2621                 }
2622                 err.emit();
2623                 return None;
2624             };
2625
2626             // Only allow features whose feature gates have been enabled.
2627             let allowed = match feature_gate.as_ref().copied() {
2628                 Some(sym::arm_target_feature) => rust_features.arm_target_feature,
2629                 Some(sym::hexagon_target_feature) => rust_features.hexagon_target_feature,
2630                 Some(sym::powerpc_target_feature) => rust_features.powerpc_target_feature,
2631                 Some(sym::mips_target_feature) => rust_features.mips_target_feature,
2632                 Some(sym::riscv_target_feature) => rust_features.riscv_target_feature,
2633                 Some(sym::avx512_target_feature) => rust_features.avx512_target_feature,
2634                 Some(sym::sse4a_target_feature) => rust_features.sse4a_target_feature,
2635                 Some(sym::tbm_target_feature) => rust_features.tbm_target_feature,
2636                 Some(sym::wasm_target_feature) => rust_features.wasm_target_feature,
2637                 Some(sym::cmpxchg16b_target_feature) => rust_features.cmpxchg16b_target_feature,
2638                 Some(sym::movbe_target_feature) => rust_features.movbe_target_feature,
2639                 Some(sym::rtm_target_feature) => rust_features.rtm_target_feature,
2640                 Some(sym::f16c_target_feature) => rust_features.f16c_target_feature,
2641                 Some(sym::ermsb_target_feature) => rust_features.ermsb_target_feature,
2642                 Some(sym::bpf_target_feature) => rust_features.bpf_target_feature,
2643                 Some(sym::aarch64_ver_target_feature) => rust_features.aarch64_ver_target_feature,
2644                 Some(name) => bug!("unknown target feature gate {}", name),
2645                 None => true,
2646             };
2647             if !allowed {
2648                 feature_err(
2649                     &tcx.sess.parse_sess,
2650                     feature_gate.unwrap(),
2651                     item.span(),
2652                     &format!("the target feature `{}` is currently unstable", feature),
2653                 )
2654                 .emit();
2655             }
2656             Some(Symbol::intern(feature))
2657         }));
2658     }
2659 }
2660
2661 fn linkage_by_name(tcx: TyCtxt<'_>, def_id: LocalDefId, name: &str) -> Linkage {
2662     use rustc_middle::mir::mono::Linkage::*;
2663
2664     // Use the names from src/llvm/docs/LangRef.rst here. Most types are only
2665     // applicable to variable declarations and may not really make sense for
2666     // Rust code in the first place but allow them anyway and trust that the
2667     // user knows what they're doing. Who knows, unanticipated use cases may pop
2668     // up in the future.
2669     //
2670     // ghost, dllimport, dllexport and linkonce_odr_autohide are not supported
2671     // and don't have to be, LLVM treats them as no-ops.
2672     match name {
2673         "appending" => Appending,
2674         "available_externally" => AvailableExternally,
2675         "common" => Common,
2676         "extern_weak" => ExternalWeak,
2677         "external" => External,
2678         "internal" => Internal,
2679         "linkonce" => LinkOnceAny,
2680         "linkonce_odr" => LinkOnceODR,
2681         "private" => Private,
2682         "weak" => WeakAny,
2683         "weak_odr" => WeakODR,
2684         _ => tcx.sess.span_fatal(tcx.def_span(def_id), "invalid linkage specified"),
2685     }
2686 }
2687
2688 fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: DefId) -> CodegenFnAttrs {
2689     if cfg!(debug_assertions) {
2690         let def_kind = tcx.def_kind(did);
2691         assert!(
2692             def_kind.has_codegen_attrs(),
2693             "unexpected `def_kind` in `codegen_fn_attrs`: {def_kind:?}",
2694         );
2695     }
2696
2697     let did = did.expect_local();
2698     let attrs = tcx.hir().attrs(tcx.hir().local_def_id_to_hir_id(did));
2699     let mut codegen_fn_attrs = CodegenFnAttrs::new();
2700     if tcx.should_inherit_track_caller(did) {
2701         codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2702     }
2703
2704     // The panic_no_unwind function called by TerminatorKind::Abort will never
2705     // unwind. If the panic handler that it invokes unwind then it will simply
2706     // call the panic handler again.
2707     if Some(did.to_def_id()) == tcx.lang_items().panic_no_unwind() {
2708         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2709     }
2710
2711     let supported_target_features = tcx.supported_target_features(LOCAL_CRATE);
2712
2713     let mut inline_span = None;
2714     let mut link_ordinal_span = None;
2715     let mut no_sanitize_span = None;
2716     for attr in attrs.iter() {
2717         if attr.has_name(sym::cold) {
2718             codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD;
2719         } else if attr.has_name(sym::rustc_allocator) {
2720             codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR;
2721         } else if attr.has_name(sym::ffi_returns_twice) {
2722             if tcx.is_foreign_item(did) {
2723                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE;
2724             } else {
2725                 // `#[ffi_returns_twice]` is only allowed `extern fn`s.
2726                 struct_span_err!(
2727                     tcx.sess,
2728                     attr.span,
2729                     E0724,
2730                     "`#[ffi_returns_twice]` may only be used on foreign functions"
2731                 )
2732                 .emit();
2733             }
2734         } else if attr.has_name(sym::ffi_pure) {
2735             if tcx.is_foreign_item(did) {
2736                 if attrs.iter().any(|a| a.has_name(sym::ffi_const)) {
2737                     // `#[ffi_const]` functions cannot be `#[ffi_pure]`
2738                     struct_span_err!(
2739                         tcx.sess,
2740                         attr.span,
2741                         E0757,
2742                         "`#[ffi_const]` function cannot be `#[ffi_pure]`"
2743                     )
2744                     .emit();
2745                 } else {
2746                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_PURE;
2747                 }
2748             } else {
2749                 // `#[ffi_pure]` is only allowed on foreign functions
2750                 struct_span_err!(
2751                     tcx.sess,
2752                     attr.span,
2753                     E0755,
2754                     "`#[ffi_pure]` may only be used on foreign functions"
2755                 )
2756                 .emit();
2757             }
2758         } else if attr.has_name(sym::ffi_const) {
2759             if tcx.is_foreign_item(did) {
2760                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_CONST;
2761             } else {
2762                 // `#[ffi_const]` is only allowed on foreign functions
2763                 struct_span_err!(
2764                     tcx.sess,
2765                     attr.span,
2766                     E0756,
2767                     "`#[ffi_const]` may only be used on foreign functions"
2768                 )
2769                 .emit();
2770             }
2771         } else if attr.has_name(sym::rustc_allocator_nounwind) {
2772             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2773         } else if attr.has_name(sym::naked) {
2774             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
2775         } else if attr.has_name(sym::no_mangle) {
2776             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2777         } else if attr.has_name(sym::no_coverage) {
2778             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_COVERAGE;
2779         } else if attr.has_name(sym::rustc_std_internal_symbol) {
2780             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2781         } else if attr.has_name(sym::used) {
2782             let inner = attr.meta_item_list();
2783             match inner.as_deref() {
2784                 Some([item]) if item.has_name(sym::linker) => {
2785                     if !tcx.features().used_with_arg {
2786                         feature_err(
2787                             &tcx.sess.parse_sess,
2788                             sym::used_with_arg,
2789                             attr.span,
2790                             "`#[used(linker)]` is currently unstable",
2791                         )
2792                         .emit();
2793                     }
2794                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED_LINKER;
2795                 }
2796                 Some([item]) if item.has_name(sym::compiler) => {
2797                     if !tcx.features().used_with_arg {
2798                         feature_err(
2799                             &tcx.sess.parse_sess,
2800                             sym::used_with_arg,
2801                             attr.span,
2802                             "`#[used(compiler)]` is currently unstable",
2803                         )
2804                         .emit();
2805                     }
2806                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
2807                 }
2808                 Some(_) => {
2809                     tcx.sess
2810                         .struct_span_err(
2811                             attr.span,
2812                             "expected `used`, `used(compiler)` or `used(linker)`",
2813                         )
2814                         .emit();
2815                 }
2816                 None => {
2817                     // Unfortunately, unconditionally using `llvm.used` causes
2818                     // issues in handling `.init_array` with the gold linker,
2819                     // but using `llvm.compiler.used` caused a nontrival amount
2820                     // of unintentional ecosystem breakage -- particularly on
2821                     // Mach-O targets.
2822                     //
2823                     // As a result, we emit `llvm.compiler.used` only on ELF
2824                     // targets. This is somewhat ad-hoc, but actually follows
2825                     // our pre-LLVM 13 behavior (prior to the ecosystem
2826                     // breakage), and seems to match `clang`'s behavior as well
2827                     // (both before and after LLVM 13), possibly because they
2828                     // have similar compatibility concerns to us. See
2829                     // https://github.com/rust-lang/rust/issues/47384#issuecomment-1019080146
2830                     // and following comments for some discussion of this, as
2831                     // well as the comments in `rustc_codegen_llvm` where these
2832                     // flags are handled.
2833                     //
2834                     // Anyway, to be clear: this is still up in the air
2835                     // somewhat, and is subject to change in the future (which
2836                     // is a good thing, because this would ideally be a bit
2837                     // more firmed up).
2838                     let is_like_elf = !(tcx.sess.target.is_like_osx
2839                         || tcx.sess.target.is_like_windows
2840                         || tcx.sess.target.is_like_wasm);
2841                     codegen_fn_attrs.flags = if is_like_elf {
2842                         CodegenFnAttrFlags::USED
2843                     } else {
2844                         CodegenFnAttrFlags::USED_LINKER
2845                     };
2846                 }
2847             }
2848         } else if attr.has_name(sym::cmse_nonsecure_entry) {
2849             if !matches!(tcx.fn_sig(did).abi(), abi::Abi::C { .. }) {
2850                 struct_span_err!(
2851                     tcx.sess,
2852                     attr.span,
2853                     E0776,
2854                     "`#[cmse_nonsecure_entry]` requires C ABI"
2855                 )
2856                 .emit();
2857             }
2858             if !tcx.sess.target.llvm_target.contains("thumbv8m") {
2859                 struct_span_err!(tcx.sess, attr.span, E0775, "`#[cmse_nonsecure_entry]` is only valid for targets with the TrustZone-M extension")
2860                     .emit();
2861             }
2862             codegen_fn_attrs.flags |= CodegenFnAttrFlags::CMSE_NONSECURE_ENTRY;
2863         } else if attr.has_name(sym::thread_local) {
2864             codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
2865         } else if attr.has_name(sym::track_caller) {
2866             if !tcx.is_closure(did.to_def_id()) && tcx.fn_sig(did).abi() != abi::Abi::Rust {
2867                 struct_span_err!(tcx.sess, attr.span, E0737, "`#[track_caller]` requires Rust ABI")
2868                     .emit();
2869             }
2870             if tcx.is_closure(did.to_def_id()) && !tcx.features().closure_track_caller {
2871                 feature_err(
2872                     &tcx.sess.parse_sess,
2873                     sym::closure_track_caller,
2874                     attr.span,
2875                     "`#[track_caller]` on closures is currently unstable",
2876                 )
2877                 .emit();
2878             }
2879             codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2880         } else if attr.has_name(sym::export_name) {
2881             if let Some(s) = attr.value_str() {
2882                 if s.as_str().contains('\0') {
2883                     // `#[export_name = ...]` will be converted to a null-terminated string,
2884                     // so it may not contain any null characters.
2885                     struct_span_err!(
2886                         tcx.sess,
2887                         attr.span,
2888                         E0648,
2889                         "`export_name` may not contain null characters"
2890                     )
2891                     .emit();
2892                 }
2893                 codegen_fn_attrs.export_name = Some(s);
2894             }
2895         } else if attr.has_name(sym::target_feature) {
2896             if !tcx.is_closure(did.to_def_id())
2897                 && tcx.fn_sig(did).unsafety() == hir::Unsafety::Normal
2898             {
2899                 if tcx.sess.target.is_like_wasm || tcx.sess.opts.actually_rustdoc {
2900                     // The `#[target_feature]` attribute is allowed on
2901                     // WebAssembly targets on all functions, including safe
2902                     // ones. Other targets require that `#[target_feature]` is
2903                     // only applied to unsafe functions (pending the
2904                     // `target_feature_11` feature) because on most targets
2905                     // execution of instructions that are not supported is
2906                     // considered undefined behavior. For WebAssembly which is a
2907                     // 100% safe target at execution time it's not possible to
2908                     // execute undefined instructions, and even if a future
2909                     // feature was added in some form for this it would be a
2910                     // deterministic trap. There is no undefined behavior when
2911                     // executing WebAssembly so `#[target_feature]` is allowed
2912                     // on safe functions (but again, only for WebAssembly)
2913                     //
2914                     // Note that this is also allowed if `actually_rustdoc` so
2915                     // if a target is documenting some wasm-specific code then
2916                     // it's not spuriously denied.
2917                 } else if !tcx.features().target_feature_11 {
2918                     let mut err = feature_err(
2919                         &tcx.sess.parse_sess,
2920                         sym::target_feature_11,
2921                         attr.span,
2922                         "`#[target_feature(..)]` can only be applied to `unsafe` functions",
2923                     );
2924                     err.span_label(tcx.def_span(did), "not an `unsafe` function");
2925                     err.emit();
2926                 } else {
2927                     check_target_feature_trait_unsafe(tcx, did, attr.span);
2928                 }
2929             }
2930             from_target_feature(
2931                 tcx,
2932                 attr,
2933                 supported_target_features,
2934                 &mut codegen_fn_attrs.target_features,
2935             );
2936         } else if attr.has_name(sym::linkage) {
2937             if let Some(val) = attr.value_str() {
2938                 codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, did, val.as_str()));
2939             }
2940         } else if attr.has_name(sym::link_section) {
2941             if let Some(val) = attr.value_str() {
2942                 if val.as_str().bytes().any(|b| b == 0) {
2943                     let msg = format!(
2944                         "illegal null byte in link_section \
2945                          value: `{}`",
2946                         &val
2947                     );
2948                     tcx.sess.span_err(attr.span, &msg);
2949                 } else {
2950                     codegen_fn_attrs.link_section = Some(val);
2951                 }
2952             }
2953         } else if attr.has_name(sym::link_name) {
2954             codegen_fn_attrs.link_name = attr.value_str();
2955         } else if attr.has_name(sym::link_ordinal) {
2956             link_ordinal_span = Some(attr.span);
2957             if let ordinal @ Some(_) = check_link_ordinal(tcx, attr) {
2958                 codegen_fn_attrs.link_ordinal = ordinal;
2959             }
2960         } else if attr.has_name(sym::no_sanitize) {
2961             no_sanitize_span = Some(attr.span);
2962             if let Some(list) = attr.meta_item_list() {
2963                 for item in list.iter() {
2964                     if item.has_name(sym::address) {
2965                         codegen_fn_attrs.no_sanitize |= SanitizerSet::ADDRESS;
2966                     } else if item.has_name(sym::cfi) {
2967                         codegen_fn_attrs.no_sanitize |= SanitizerSet::CFI;
2968                     } else if item.has_name(sym::memory) {
2969                         codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMORY;
2970                     } else if item.has_name(sym::memtag) {
2971                         codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMTAG;
2972                     } else if item.has_name(sym::thread) {
2973                         codegen_fn_attrs.no_sanitize |= SanitizerSet::THREAD;
2974                     } else if item.has_name(sym::hwaddress) {
2975                         codegen_fn_attrs.no_sanitize |= SanitizerSet::HWADDRESS;
2976                     } else {
2977                         tcx.sess
2978                             .struct_span_err(item.span(), "invalid argument for `no_sanitize`")
2979                             .note("expected one of: `address`, `cfi`, `hwaddress`, `memory`, `memtag`, or `thread`")
2980                             .emit();
2981                     }
2982                 }
2983             }
2984         } else if attr.has_name(sym::instruction_set) {
2985             codegen_fn_attrs.instruction_set = match attr.meta_kind() {
2986                 Some(MetaItemKind::List(ref items)) => match items.as_slice() {
2987                     [NestedMetaItem::MetaItem(set)] => {
2988                         let segments =
2989                             set.path.segments.iter().map(|x| x.ident.name).collect::<Vec<_>>();
2990                         match segments.as_slice() {
2991                             [sym::arm, sym::a32] | [sym::arm, sym::t32] => {
2992                                 if !tcx.sess.target.has_thumb_interworking {
2993                                     struct_span_err!(
2994                                         tcx.sess.diagnostic(),
2995                                         attr.span,
2996                                         E0779,
2997                                         "target does not support `#[instruction_set]`"
2998                                     )
2999                                     .emit();
3000                                     None
3001                                 } else if segments[1] == sym::a32 {
3002                                     Some(InstructionSetAttr::ArmA32)
3003                                 } else if segments[1] == sym::t32 {
3004                                     Some(InstructionSetAttr::ArmT32)
3005                                 } else {
3006                                     unreachable!()
3007                                 }
3008                             }
3009                             _ => {
3010                                 struct_span_err!(
3011                                     tcx.sess.diagnostic(),
3012                                     attr.span,
3013                                     E0779,
3014                                     "invalid instruction set specified",
3015                                 )
3016                                 .emit();
3017                                 None
3018                             }
3019                         }
3020                     }
3021                     [] => {
3022                         struct_span_err!(
3023                             tcx.sess.diagnostic(),
3024                             attr.span,
3025                             E0778,
3026                             "`#[instruction_set]` requires an argument"
3027                         )
3028                         .emit();
3029                         None
3030                     }
3031                     _ => {
3032                         struct_span_err!(
3033                             tcx.sess.diagnostic(),
3034                             attr.span,
3035                             E0779,
3036                             "cannot specify more than one instruction set"
3037                         )
3038                         .emit();
3039                         None
3040                     }
3041                 },
3042                 _ => {
3043                     struct_span_err!(
3044                         tcx.sess.diagnostic(),
3045                         attr.span,
3046                         E0778,
3047                         "must specify an instruction set"
3048                     )
3049                     .emit();
3050                     None
3051                 }
3052             };
3053         } else if attr.has_name(sym::repr) {
3054             codegen_fn_attrs.alignment = match attr.meta_item_list() {
3055                 Some(items) => match items.as_slice() {
3056                     [item] => match item.name_value_literal() {
3057                         Some((sym::align, literal)) => {
3058                             let alignment = rustc_attr::parse_alignment(&literal.kind);
3059
3060                             match alignment {
3061                                 Ok(align) => Some(align),
3062                                 Err(msg) => {
3063                                     struct_span_err!(
3064                                         tcx.sess.diagnostic(),
3065                                         attr.span,
3066                                         E0589,
3067                                         "invalid `repr(align)` attribute: {}",
3068                                         msg
3069                                     )
3070                                     .emit();
3071
3072                                     None
3073                                 }
3074                             }
3075                         }
3076                         _ => None,
3077                     },
3078                     [] => None,
3079                     _ => None,
3080                 },
3081                 None => None,
3082             };
3083         }
3084     }
3085
3086     codegen_fn_attrs.inline = attrs.iter().fold(InlineAttr::None, |ia, attr| {
3087         if !attr.has_name(sym::inline) {
3088             return ia;
3089         }
3090         match attr.meta_kind() {
3091             Some(MetaItemKind::Word) => InlineAttr::Hint,
3092             Some(MetaItemKind::List(ref items)) => {
3093                 inline_span = Some(attr.span);
3094                 if items.len() != 1 {
3095                     struct_span_err!(
3096                         tcx.sess.diagnostic(),
3097                         attr.span,
3098                         E0534,
3099                         "expected one argument"
3100                     )
3101                     .emit();
3102                     InlineAttr::None
3103                 } else if list_contains_name(&items, sym::always) {
3104                     InlineAttr::Always
3105                 } else if list_contains_name(&items, sym::never) {
3106                     InlineAttr::Never
3107                 } else {
3108                     struct_span_err!(
3109                         tcx.sess.diagnostic(),
3110                         items[0].span(),
3111                         E0535,
3112                         "invalid argument"
3113                     )
3114                     .emit();
3115
3116                     InlineAttr::None
3117                 }
3118             }
3119             Some(MetaItemKind::NameValue(_)) => ia,
3120             None => ia,
3121         }
3122     });
3123
3124     codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
3125         if !attr.has_name(sym::optimize) {
3126             return ia;
3127         }
3128         let err = |sp, s| struct_span_err!(tcx.sess.diagnostic(), sp, E0722, "{}", s).emit();
3129         match attr.meta_kind() {
3130             Some(MetaItemKind::Word) => {
3131                 err(attr.span, "expected one argument");
3132                 ia
3133             }
3134             Some(MetaItemKind::List(ref items)) => {
3135                 inline_span = Some(attr.span);
3136                 if items.len() != 1 {
3137                     err(attr.span, "expected one argument");
3138                     OptimizeAttr::None
3139                 } else if list_contains_name(&items, sym::size) {
3140                     OptimizeAttr::Size
3141                 } else if list_contains_name(&items, sym::speed) {
3142                     OptimizeAttr::Speed
3143                 } else {
3144                     err(items[0].span(), "invalid argument");
3145                     OptimizeAttr::None
3146                 }
3147             }
3148             Some(MetaItemKind::NameValue(_)) => ia,
3149             None => ia,
3150         }
3151     });
3152
3153     // #73631: closures inherit `#[target_feature]` annotations
3154     if tcx.features().target_feature_11 && tcx.is_closure(did.to_def_id()) {
3155         let owner_id = tcx.parent(did.to_def_id());
3156         codegen_fn_attrs
3157             .target_features
3158             .extend(tcx.codegen_fn_attrs(owner_id).target_features.iter().copied())
3159     }
3160
3161     // If a function uses #[target_feature] it can't be inlined into general
3162     // purpose functions as they wouldn't have the right target features
3163     // enabled. For that reason we also forbid #[inline(always)] as it can't be
3164     // respected.
3165     if !codegen_fn_attrs.target_features.is_empty() {
3166         if codegen_fn_attrs.inline == InlineAttr::Always {
3167             if let Some(span) = inline_span {
3168                 tcx.sess.span_err(
3169                     span,
3170                     "cannot use `#[inline(always)]` with \
3171                      `#[target_feature]`",
3172                 );
3173             }
3174         }
3175     }
3176
3177     if !codegen_fn_attrs.no_sanitize.is_empty() {
3178         if codegen_fn_attrs.inline == InlineAttr::Always {
3179             if let (Some(no_sanitize_span), Some(inline_span)) = (no_sanitize_span, inline_span) {
3180                 let hir_id = tcx.hir().local_def_id_to_hir_id(did);
3181                 tcx.struct_span_lint_hir(
3182                     lint::builtin::INLINE_NO_SANITIZE,
3183                     hir_id,
3184                     no_sanitize_span,
3185                     |lint| {
3186                         lint.build("`no_sanitize` will have no effect after inlining")
3187                             .span_note(inline_span, "inlining requested here")
3188                             .emit();
3189                     },
3190                 )
3191             }
3192         }
3193     }
3194
3195     // Weak lang items have the same semantics as "std internal" symbols in the
3196     // sense that they're preserved through all our LTO passes and only
3197     // strippable by the linker.
3198     //
3199     // Additionally weak lang items have predetermined symbol names.
3200     if tcx.is_weak_lang_item(did.to_def_id()) {
3201         codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
3202     }
3203     if let Some(name) = weak_lang_items::link_name(attrs) {
3204         codegen_fn_attrs.export_name = Some(name);
3205         codegen_fn_attrs.link_name = Some(name);
3206     }
3207     check_link_name_xor_ordinal(tcx, &codegen_fn_attrs, link_ordinal_span);
3208
3209     // Internal symbols to the standard library all have no_mangle semantics in
3210     // that they have defined symbol names present in the function name. This
3211     // also applies to weak symbols where they all have known symbol names.
3212     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
3213         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
3214     }
3215
3216     // Any linkage to LLVM intrinsics for now forcibly marks them all as never
3217     // unwinds since LLVM sometimes can't handle codegen which `invoke`s
3218     // intrinsic functions.
3219     if let Some(name) = &codegen_fn_attrs.link_name {
3220         if name.as_str().starts_with("llvm.") {
3221             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
3222         }
3223     }
3224
3225     codegen_fn_attrs
3226 }
3227
3228 /// Computes the set of target features used in a function for the purposes of
3229 /// inline assembly.
3230 fn asm_target_features<'tcx>(tcx: TyCtxt<'tcx>, did: DefId) -> &'tcx FxHashSet<Symbol> {
3231     let mut target_features = tcx.sess.unstable_target_features.clone();
3232     if tcx.def_kind(did).has_codegen_attrs() {
3233         let attrs = tcx.codegen_fn_attrs(did);
3234         target_features.extend(&attrs.target_features);
3235         match attrs.instruction_set {
3236             None => {}
3237             Some(InstructionSetAttr::ArmA32) => {
3238                 target_features.remove(&sym::thumb_mode);
3239             }
3240             Some(InstructionSetAttr::ArmT32) => {
3241                 target_features.insert(sym::thumb_mode);
3242             }
3243         }
3244     }
3245
3246     tcx.arena.alloc(target_features)
3247 }
3248
3249 /// Checks if the provided DefId is a method in a trait impl for a trait which has track_caller
3250 /// applied to the method prototype.
3251 fn should_inherit_track_caller(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
3252     if let Some(impl_item) = tcx.opt_associated_item(def_id)
3253         && let ty::AssocItemContainer::ImplContainer(_) = impl_item.container
3254         && let Some(trait_item) = impl_item.trait_item_def_id
3255     {
3256         return tcx
3257             .codegen_fn_attrs(trait_item)
3258             .flags
3259             .intersects(CodegenFnAttrFlags::TRACK_CALLER);
3260     }
3261
3262     false
3263 }
3264
3265 fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<u16> {
3266     use rustc_ast::{Lit, LitIntType, LitKind};
3267     let meta_item_list = attr.meta_item_list();
3268     let meta_item_list: Option<&[ast::NestedMetaItem]> = meta_item_list.as_ref().map(Vec::as_ref);
3269     let sole_meta_list = match meta_item_list {
3270         Some([item]) => item.literal(),
3271         Some(_) => {
3272             tcx.sess
3273                 .struct_span_err(attr.span, "incorrect number of arguments to `#[link_ordinal]`")
3274                 .note("the attribute requires exactly one argument")
3275                 .emit();
3276             return None;
3277         }
3278         _ => None,
3279     };
3280     if let Some(Lit { kind: LitKind::Int(ordinal, LitIntType::Unsuffixed), .. }) = sole_meta_list {
3281         // According to the table at https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#import-header,
3282         // the ordinal must fit into 16 bits.  Similarly, the Ordinal field in COFFShortExport (defined
3283         // in llvm/include/llvm/Object/COFFImportFile.h), which we use to communicate import information
3284         // to LLVM for `#[link(kind = "raw-dylib"_])`, is also defined to be uint16_t.
3285         //
3286         // FIXME: should we allow an ordinal of 0?  The MSVC toolchain has inconsistent support for this:
3287         // both LINK.EXE and LIB.EXE signal errors and abort when given a .DEF file that specifies
3288         // a zero ordinal.  However, llvm-dlltool is perfectly happy to generate an import library
3289         // for such a .DEF file, and MSVC's LINK.EXE is also perfectly happy to consume an import
3290         // library produced by LLVM with an ordinal of 0, and it generates an .EXE.  (I don't know yet
3291         // if the resulting EXE runs, as I haven't yet built the necessary DLL -- see earlier comment
3292         // about LINK.EXE failing.)
3293         if *ordinal <= u16::MAX as u128 {
3294             Some(*ordinal as u16)
3295         } else {
3296             let msg = format!("ordinal value in `link_ordinal` is too large: `{}`", &ordinal);
3297             tcx.sess
3298                 .struct_span_err(attr.span, &msg)
3299                 .note("the value may not exceed `u16::MAX`")
3300                 .emit();
3301             None
3302         }
3303     } else {
3304         tcx.sess
3305             .struct_span_err(attr.span, "illegal ordinal format in `link_ordinal`")
3306             .note("an unsuffixed integer value, e.g., `1`, is expected")
3307             .emit();
3308         None
3309     }
3310 }
3311
3312 fn check_link_name_xor_ordinal(
3313     tcx: TyCtxt<'_>,
3314     codegen_fn_attrs: &CodegenFnAttrs,
3315     inline_span: Option<Span>,
3316 ) {
3317     if codegen_fn_attrs.link_name.is_none() || codegen_fn_attrs.link_ordinal.is_none() {
3318         return;
3319     }
3320     let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
3321     if let Some(span) = inline_span {
3322         tcx.sess.span_err(span, msg);
3323     } else {
3324         tcx.sess.err(msg);
3325     }
3326 }
3327
3328 /// Checks the function annotated with `#[target_feature]` is not a safe
3329 /// trait method implementation, reporting an error if it is.
3330 fn check_target_feature_trait_unsafe(tcx: TyCtxt<'_>, id: LocalDefId, attr_span: Span) {
3331     let hir_id = tcx.hir().local_def_id_to_hir_id(id);
3332     let node = tcx.hir().get(hir_id);
3333     if let Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }) = node {
3334         let parent_id = tcx.hir().get_parent_item(hir_id);
3335         let parent_item = tcx.hir().expect_item(parent_id);
3336         if let hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) = parent_item.kind {
3337             tcx.sess
3338                 .struct_span_err(
3339                     attr_span,
3340                     "`#[target_feature(..)]` cannot be applied to safe trait method",
3341                 )
3342                 .span_label(attr_span, "cannot be applied to safe trait method")
3343                 .span_label(tcx.def_span(id), "not an `unsafe` function")
3344                 .emit();
3345         }
3346     }
3347 }