compiler/rustc_typeck/src/collect.rs

   1 // ignore-tidy-filelength
   2 //! "Collection" is the process of determining the type and other external
   3 //! details of each item in Rust. Collection is specifically concerned
   4 //! with *inter-procedural* things -- for example, for a function
   5 //! definition, collection will figure out the type and signature of the
   6 //! function, but it will not visit the *body* of the function in any way,
   7 //! nor examine type annotations on local variables (that's the job of
   8 //! type *checking*).
   9 //!
  10 //! Collecting is ultimately defined by a bundle of queries that
  11 //! inquire after various facts about the items in the crate (e.g.,
  12 //! `type_of`, `generics_of`, `predicates_of`, etc). See the `provide` function
  13 //! for the full set.
  14 //!
  15 //! At present, however, we do run collection across all items in the
  16 //! crate as a kind of pass. This should eventually be factored away.
  17
  18 use crate::astconv::AstConv;
  19 use crate::bounds::Bounds;
  20 use crate::check::intrinsic::intrinsic_operation_unsafety;
  21 use crate::constrained_generic_params as cgp;
  22 use crate::errors;
  23 use crate::middle::resolve_lifetime as rl;
  24 use rustc_ast as ast;
  25 use rustc_ast::{MetaItemKind, NestedMetaItem};
  26 use rustc_attr::{list_contains_name, InlineAttr, InstructionSetAttr, OptimizeAttr};
  27 use rustc_data_structures::captures::Captures;
  28 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
  29 use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder, ErrorGuaranteed};
  30 use rustc_hir as hir;
  31 use rustc_hir::def::{CtorKind, DefKind};
  32 use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_ID, LOCAL_CRATE};
  33 use rustc_hir::intravisit::{self, Visitor};
  34 use rustc_hir::weak_lang_items;
  35 use rustc_hir::{GenericParamKind, HirId, Node};
  36 use rustc_middle::hir::nested_filter;
  37 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
  38 use rustc_middle::mir::mono::Linkage;
  39 use rustc_middle::ty::query::Providers;
  40 use rustc_middle::ty::subst::InternalSubsts;
  41 use rustc_middle::ty::util::Discr;
  42 use rustc_middle::ty::util::IntTypeExt;
  43 use rustc_middle::ty::{self, AdtKind, Const, DefIdTree, Ty, TyCtxt};
  44 use rustc_middle::ty::{ReprOptions, ToPredicate};
  45 use rustc_session::lint;
  46 use rustc_session::parse::feature_err;
  47 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  48 use rustc_span::{Span, DUMMY_SP};
  49 use rustc_target::spec::{abi, PanicStrategy, SanitizerSet};
  50 use rustc_trait_selection::traits::error_reporting::suggestions::NextTypeParamName;
  51 use std::iter;
  52
  53 mod item_bounds;
  54 mod type_of;
  55
  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(
  63         module_def_id,
  64         &mut CollectItemTypesVisitor { tcx }.as_deep_visitor(),
  65     );
  66 }
  67
  68 pub fn provide(providers: &mut Providers) {
  69     *providers = Providers {
  70         opt_const_param_of: type_of::opt_const_param_of,
  71         type_of: type_of::type_of,
  72         item_bounds: item_bounds::item_bounds,
  73         explicit_item_bounds: item_bounds::explicit_item_bounds,
  74         generics_of,
  75         predicates_of,
  76         predicates_defined_on,
  77         explicit_predicates_of,
  78         super_predicates_of,
  79         super_predicates_that_define_assoc_type,
  80         trait_explicit_predicates_and_bounds,
  81         type_param_predicates,
  82         trait_def,
  83         adt_def,
  84         fn_sig,
  85         impl_trait_ref,
  86         impl_polarity,
  87         is_foreign_item,
  88         generator_kind,
  89         codegen_fn_attrs,
  90         asm_target_features,
  91         collect_mod_item_types,
  92         should_inherit_track_caller,
  93         ..*providers
  94     };
  95 }
  96
  97 ///////////////////////////////////////////////////////////////////////////
  98
  99 /// Context specific to some particular item. This is what implements
 100 /// `AstConv`. It has information about the predicates that are defined
 101 /// on the trait. Unfortunately, this predicate information is
 102 /// available in various different forms at various points in the
 103 /// process. So we can't just store a pointer to e.g., the AST or the
 104 /// parsed ty form, we have to be more flexible. To this end, the
 105 /// `ItemCtxt` is parameterized by a `DefId` that it uses to satisfy
 106 /// `get_type_parameter_bounds` requests, drawing the information from
 107 /// the AST (`hir::Generics`), recursively.
 108 pub struct ItemCtxt<'tcx> {
 109     tcx: TyCtxt<'tcx>,
 110     item_def_id: DefId,
 111 }
 112
 113 ///////////////////////////////////////////////////////////////////////////
 114
 115 #[derive(Default)]
 116 crate struct HirPlaceholderCollector(crate Vec<Span>);
 117
 118 impl<'v> Visitor<'v> for HirPlaceholderCollector {
 119     fn visit_ty(&mut self, t: &'v hir::Ty<'v>) {
 120         if let hir::TyKind::Infer = t.kind {
 121             self.0.push(t.span);
 122         }
 123         intravisit::walk_ty(self, t)
 124     }
 125     fn visit_generic_arg(&mut self, generic_arg: &'v hir::GenericArg<'v>) {
 126         match generic_arg {
 127             hir::GenericArg::Infer(inf) => {
 128                 self.0.push(inf.span);
 129                 intravisit::walk_inf(self, inf);
 130             }
 131             hir::GenericArg::Type(t) => self.visit_ty(t),
 132             _ => {}
 133         }
 134     }
 135     fn visit_array_length(&mut self, length: &'v hir::ArrayLen) {
 136         if let &hir::ArrayLen::Infer(_, span) = length {
 137             self.0.push(span);
 138         }
 139         intravisit::walk_array_len(self, length)
 140     }
 141 }
 142
 143 struct CollectItemTypesVisitor<'tcx> {
 144     tcx: TyCtxt<'tcx>,
 145 }
 146
 147 /// If there are any placeholder types (`_`), emit an error explaining that this is not allowed
 148 /// and suggest adding type parameters in the appropriate place, taking into consideration any and
 149 /// all already existing generic type parameters to avoid suggesting a name that is already in use.
 150 crate fn placeholder_type_error<'tcx>(
 151     tcx: TyCtxt<'tcx>,
 152     span: Option<Span>,
 153     generics: &[hir::GenericParam<'_>],
 154     placeholder_types: Vec<Span>,
 155     suggest: bool,
 156     hir_ty: Option<&hir::Ty<'_>>,
 157     kind: &'static str,
 158 ) {
 159     if placeholder_types.is_empty() {
 160         return;
 161     }
 162
 163     placeholder_type_error_diag(
 164         tcx,
 165         span,
 166         generics,
 167         placeholder_types,
 168         vec![],
 169         suggest,
 170         hir_ty,
 171         kind,
 172     )
 173     .emit();
 174 }
 175
 176 crate fn placeholder_type_error_diag<'tcx>(
 177     tcx: TyCtxt<'tcx>,
 178     span: Option<Span>,
 179     generics: &[hir::GenericParam<'_>],
 180     placeholder_types: Vec<Span>,
 181     additional_spans: Vec<Span>,
 182     suggest: bool,
 183     hir_ty: Option<&hir::Ty<'_>>,
 184     kind: &'static str,
 185 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
 186     if placeholder_types.is_empty() {
 187         return bad_placeholder(tcx, additional_spans, kind);
 188     }
 189
 190     let type_name = generics.next_type_param_name(None);
 191     let mut sugg: Vec<_> =
 192         placeholder_types.iter().map(|sp| (*sp, (*type_name).to_string())).collect();
 193
 194     if generics.is_empty() {
 195         if let Some(span) = span {
 196             sugg.push((span, format!("<{}>", type_name)));
 197         }
 198     } else if let Some(arg) = generics
 199         .iter()
 200         .find(|arg| matches!(arg.name, hir::ParamName::Plain(Ident { name: kw::Underscore, .. })))
 201     {
 202         // Account for `_` already present in cases like `struct S<_>(_);` and suggest
 203         // `struct S<T>(T);` instead of `struct S<_, T>(T);`.
 204         sugg.push((arg.span, (*type_name).to_string()));
 205     } else {
 206         let last = generics.iter().last().unwrap();
 207         // Account for bounds, we want `fn foo<T: E, K>(_: K)` not `fn foo<T, K: E>(_: K)`.
 208         let span = last.bounds_span_for_suggestions().unwrap_or(last.span.shrink_to_hi());
 209         sugg.push((span, format!(", {}", type_name)));
 210     }
 211
 212     let mut err =
 213         bad_placeholder(tcx, placeholder_types.into_iter().chain(additional_spans).collect(), kind);
 214
 215     // Suggest, but only if it is not a function in const or static
 216     if suggest {
 217         let mut is_fn = false;
 218         let mut is_const_or_static = false;
 219
 220         if let Some(hir_ty) = hir_ty && let hir::TyKind::BareFn(_) = hir_ty.kind {
 221             is_fn = true;
 222
 223             // Check if parent is const or static
 224             let parent_id = tcx.hir().get_parent_node(hir_ty.hir_id);
 225             let parent_node = tcx.hir().get(parent_id);
 226
 227             is_const_or_static = matches!(
 228                 parent_node,
 229                 Node::Item(&hir::Item {
 230                     kind: hir::ItemKind::Const(..) | hir::ItemKind::Static(..),
 231                     ..
 232                 }) | Node::TraitItem(&hir::TraitItem {
 233                     kind: hir::TraitItemKind::Const(..),
 234                     ..
 235                 }) | Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Const(..), .. })
 236             );
 237         }
 238
 239         // if function is wrapped around a const or static,
 240         // then don't show the suggestion
 241         if !(is_fn && is_const_or_static) {
 242             err.multipart_suggestion(
 243                 "use type parameters instead",
 244                 sugg,
 245                 Applicability::HasPlaceholders,
 246             );
 247         }
 248     }
 249
 250     err
 251 }
 252
 253 fn reject_placeholder_type_signatures_in_item<'tcx>(
 254     tcx: TyCtxt<'tcx>,
 255     item: &'tcx hir::Item<'tcx>,
 256 ) {
 257     let (generics, suggest) = match &item.kind {
 258         hir::ItemKind::Union(_, generics)
 259         | hir::ItemKind::Enum(_, generics)
 260         | hir::ItemKind::TraitAlias(generics, _)
 261         | hir::ItemKind::Trait(_, _, generics, ..)
 262         | hir::ItemKind::Impl(hir::Impl { generics, .. })
 263         | hir::ItemKind::Struct(_, generics) => (generics, true),
 264         hir::ItemKind::OpaqueTy(hir::OpaqueTy { generics, .. })
 265         | hir::ItemKind::TyAlias(_, generics) => (generics, false),
 266         // `static`, `fn` and `const` are handled elsewhere to suggest appropriate type.
 267         _ => return,
 268     };
 269
 270     let mut visitor = HirPlaceholderCollector::default();
 271     visitor.visit_item(item);
 272
 273     placeholder_type_error(
 274         tcx,
 275         Some(generics.span),
 276         generics.params,
 277         visitor.0,
 278         suggest,
 279         None,
 280         item.kind.descr(),
 281     );
 282 }
 283
 284 impl<'tcx> Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
 285     type NestedFilter = nested_filter::OnlyBodies;
 286
 287     fn nested_visit_map(&mut self) -> Self::Map {
 288         self.tcx.hir()
 289     }
 290
 291     fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
 292         convert_item(self.tcx, item.item_id());
 293         reject_placeholder_type_signatures_in_item(self.tcx, item);
 294         intravisit::walk_item(self, item);
 295     }
 296
 297     fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) {
 298         for param in generics.params {
 299             match param.kind {
 300                 hir::GenericParamKind::Lifetime { .. } => {}
 301                 hir::GenericParamKind::Type { default: Some(_), .. } => {
 302                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 303                     self.tcx.ensure().type_of(def_id);
 304                 }
 305                 hir::GenericParamKind::Type { .. } => {}
 306                 hir::GenericParamKind::Const { default, .. } => {
 307                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 308                     self.tcx.ensure().type_of(def_id);
 309                     if let Some(default) = default {
 310                         let default_def_id = self.tcx.hir().local_def_id(default.hir_id);
 311                         // need to store default and type of default
 312                         self.tcx.ensure().type_of(default_def_id);
 313                         self.tcx.ensure().const_param_default(def_id);
 314                     }
 315                 }
 316             }
 317         }
 318         intravisit::walk_generics(self, generics);
 319     }
 320
 321     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
 322         if let hir::ExprKind::Closure(..) = expr.kind {
 323             let def_id = self.tcx.hir().local_def_id(expr.hir_id);
 324             self.tcx.ensure().generics_of(def_id);
 325             // We do not call `type_of` for closures here as that
 326             // depends on typecheck and would therefore hide
 327             // any further errors in case one typeck fails.
 328         }
 329         intravisit::walk_expr(self, expr);
 330     }
 331
 332     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
 333         convert_trait_item(self.tcx, trait_item.trait_item_id());
 334         intravisit::walk_trait_item(self, trait_item);
 335     }
 336
 337     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
 338         convert_impl_item(self.tcx, impl_item.impl_item_id());
 339         intravisit::walk_impl_item(self, impl_item);
 340     }
 341 }
 342
 343 ///////////////////////////////////////////////////////////////////////////
 344 // Utility types and common code for the above passes.
 345
 346 fn bad_placeholder<'tcx>(
 347     tcx: TyCtxt<'tcx>,
 348     mut spans: Vec<Span>,
 349     kind: &'static str,
 350 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
 351     let kind = if kind.ends_with('s') { format!("{}es", kind) } else { format!("{}s", kind) };
 352
 353     spans.sort();
 354     let mut err = struct_span_err!(
 355         tcx.sess,
 356         spans.clone(),
 357         E0121,
 358         "the placeholder `_` is not allowed within types on item signatures for {}",
 359         kind
 360     );
 361     for span in spans {
 362         err.span_label(span, "not allowed in type signatures");
 363     }
 364     err
 365 }
 366
 367 impl<'tcx> ItemCtxt<'tcx> {
 368     pub fn new(tcx: TyCtxt<'tcx>, item_def_id: DefId) -> ItemCtxt<'tcx> {
 369         ItemCtxt { tcx, item_def_id }
 370     }
 371
 372     pub fn to_ty(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> {
 373         <dyn AstConv<'_>>::ast_ty_to_ty(self, ast_ty)
 374     }
 375
 376     pub fn hir_id(&self) -> hir::HirId {
 377         self.tcx.hir().local_def_id_to_hir_id(self.item_def_id.expect_local())
 378     }
 379
 380     pub fn node(&self) -> hir::Node<'tcx> {
 381         self.tcx.hir().get(self.hir_id())
 382     }
 383 }
 384
 385 impl<'tcx> AstConv<'tcx> for ItemCtxt<'tcx> {
 386     fn tcx(&self) -> TyCtxt<'tcx> {
 387         self.tcx
 388     }
 389
 390     fn item_def_id(&self) -> Option<DefId> {
 391         Some(self.item_def_id)
 392     }
 393
 394     fn get_type_parameter_bounds(
 395         &self,
 396         span: Span,
 397         def_id: DefId,
 398         assoc_name: Ident,
 399     ) -> ty::GenericPredicates<'tcx> {
 400         self.tcx.at(span).type_param_predicates((
 401             self.item_def_id,
 402             def_id.expect_local(),
 403             assoc_name,
 404         ))
 405     }
 406
 407     fn re_infer(&self, _: Option<&ty::GenericParamDef>, _: Span) -> Option<ty::Region<'tcx>> {
 408         None
 409     }
 410
 411     fn allow_ty_infer(&self) -> bool {
 412         false
 413     }
 414
 415     fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
 416         self.tcx().ty_error_with_message(span, "bad placeholder type")
 417     }
 418
 419     fn ct_infer(&self, ty: Ty<'tcx>, _: Option<&ty::GenericParamDef>, span: Span) -> Const<'tcx> {
 420         let ty = self.tcx.fold_regions(ty, &mut false, |r, _| match *r {
 421             ty::ReErased => self.tcx.lifetimes.re_static,
 422             _ => r,
 423         });
 424         self.tcx().const_error_with_message(ty, span, "bad placeholder constant")
 425     }
 426
 427     fn projected_ty_from_poly_trait_ref(
 428         &self,
 429         span: Span,
 430         item_def_id: DefId,
 431         item_segment: &hir::PathSegment<'_>,
 432         poly_trait_ref: ty::PolyTraitRef<'tcx>,
 433     ) -> Ty<'tcx> {
 434         if let Some(trait_ref) = poly_trait_ref.no_bound_vars() {
 435             let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
 436                 self,
 437                 self.tcx,
 438                 span,
 439                 item_def_id,
 440                 item_segment,
 441                 trait_ref.substs,
 442             );
 443             self.tcx().mk_projection(item_def_id, item_substs)
 444         } else {
 445             // There are no late-bound regions; we can just ignore the binder.
 446             let mut err = struct_span_err!(
 447                 self.tcx().sess,
 448                 span,
 449                 E0212,
 450                 "cannot use the associated type of a trait \
 451                  with uninferred generic parameters"
 452             );
 453
 454             match self.node() {
 455                 hir::Node::Field(_) | hir::Node::Ctor(_) | hir::Node::Variant(_) => {
 456                     let item =
 457                         self.tcx.hir().expect_item(self.tcx.hir().get_parent_item(self.hir_id()));
 458                     match &item.kind {
 459                         hir::ItemKind::Enum(_, generics)
 460                         | hir::ItemKind::Struct(_, generics)
 461                         | hir::ItemKind::Union(_, generics) => {
 462                             let lt_name = get_new_lifetime_name(self.tcx, poly_trait_ref, generics);
 463                             let (lt_sp, sugg) = match generics.params {
 464                                 [] => (generics.span, format!("<{}>", lt_name)),
 465                                 [bound, ..] => {
 466                                     (bound.span.shrink_to_lo(), format!("{}, ", lt_name))
 467                                 }
 468                             };
 469                             let suggestions = vec![
 470                                 (lt_sp, sugg),
 471                                 (
 472                                     span.with_hi(item_segment.ident.span.lo()),
 473                                     format!(
 474                                         "{}::",
 475                                         // Replace the existing lifetimes with a new named lifetime.
 476                                         self.tcx
 477                                             .replace_late_bound_regions(poly_trait_ref, |_| {
 478                                                 self.tcx.mk_region(ty::ReEarlyBound(
 479                                                     ty::EarlyBoundRegion {
 480                                                         def_id: item_def_id,
 481                                                         index: 0,
 482                                                         name: Symbol::intern(&lt_name),
 483                                                     },
 484                                                 ))
 485                                             })
 486                                             .0,
 487                                     ),
 488                                 ),
 489                             ];
 490                             err.multipart_suggestion(
 491                                 "use a fully qualified path with explicit lifetimes",
 492                                 suggestions,
 493                                 Applicability::MaybeIncorrect,
 494                             );
 495                         }
 496                         _ => {}
 497                     }
 498                 }
 499                 hir::Node::Item(hir::Item {
 500                     kind:
 501                         hir::ItemKind::Struct(..) | hir::ItemKind::Enum(..) | hir::ItemKind::Union(..),
 502                     ..
 503                 }) => {}
 504                 hir::Node::Item(_)
 505                 | hir::Node::ForeignItem(_)
 506                 | hir::Node::TraitItem(_)
 507                 | hir::Node::ImplItem(_) => {
 508                     err.span_suggestion_verbose(
 509                         span.with_hi(item_segment.ident.span.lo()),
 510                         "use a fully qualified path with inferred lifetimes",
 511                         format!(
 512                             "{}::",
 513                             // Erase named lt, we want `<A as B<'_>::C`, not `<A as B<'a>::C`.
 514                             self.tcx.anonymize_late_bound_regions(poly_trait_ref).skip_binder(),
 515                         ),
 516                         Applicability::MaybeIncorrect,
 517                     );
 518                 }
 519                 _ => {}
 520             }
 521             err.emit();
 522             self.tcx().ty_error()
 523         }
 524     }
 525
 526     fn normalize_ty(&self, _span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
 527         // Types in item signatures are not normalized to avoid undue dependencies.
 528         ty
 529     }
 530
 531     fn set_tainted_by_errors(&self) {
 532         // There's no obvious place to track this, so just let it go.
 533     }
 534
 535     fn record_ty(&self, _hir_id: hir::HirId, _ty: Ty<'tcx>, _span: Span) {
 536         // There's no place to record types from signatures?
 537     }
 538 }
 539
 540 /// Synthesize a new lifetime name that doesn't clash with any of the lifetimes already present.
 541 fn get_new_lifetime_name<'tcx>(
 542     tcx: TyCtxt<'tcx>,
 543     poly_trait_ref: ty::PolyTraitRef<'tcx>,
 544     generics: &hir::Generics<'tcx>,
 545 ) -> String {
 546     let existing_lifetimes = tcx
 547         .collect_referenced_late_bound_regions(&poly_trait_ref)
 548         .into_iter()
 549         .filter_map(|lt| {
 550             if let ty::BoundRegionKind::BrNamed(_, name) = lt {
 551                 Some(name.as_str().to_string())
 552             } else {
 553                 None
 554             }
 555         })
 556         .chain(generics.params.iter().filter_map(|param| {
 557             if let hir::GenericParamKind::Lifetime { .. } = &param.kind {
 558                 Some(param.name.ident().as_str().to_string())
 559             } else {
 560                 None
 561             }
 562         }))
 563         .collect::<FxHashSet<String>>();
 564
 565     let a_to_z_repeat_n = |n| {
 566         (b'a'..=b'z').map(move |c| {
 567             let mut s = '\''.to_string();
 568             s.extend(std::iter::repeat(char::from(c)).take(n));
 569             s
 570         })
 571     };
 572
 573     // If all single char lifetime names are present, we wrap around and double the chars.
 574     (1..).flat_map(a_to_z_repeat_n).find(|lt| !existing_lifetimes.contains(lt.as_str())).unwrap()
 575 }
 576
 577 /// Returns the predicates defined on `item_def_id` of the form
 578 /// `X: Foo` where `X` is the type parameter `def_id`.
 579 fn type_param_predicates(
 580     tcx: TyCtxt<'_>,
 581     (item_def_id, def_id, assoc_name): (DefId, LocalDefId, Ident),
 582 ) -> ty::GenericPredicates<'_> {
 583     use rustc_hir::*;
 584
 585     // In the AST, bounds can derive from two places. Either
 586     // written inline like `<T: Foo>` or in a where-clause like
 587     // `where T: Foo`.
 588
 589     let param_id = tcx.hir().local_def_id_to_hir_id(def_id);
 590     let param_owner = tcx.hir().ty_param_owner(def_id);
 591     let generics = tcx.generics_of(param_owner);
 592     let index = generics.param_def_id_to_index[&def_id.to_def_id()];
 593     let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(def_id));
 594
 595     // Don't look for bounds where the type parameter isn't in scope.
 596     let parent = if item_def_id == param_owner.to_def_id() {
 597         None
 598     } else {
 599         tcx.generics_of(item_def_id).parent
 600     };
 601
 602     let mut result = parent
 603         .map(|parent| {
 604             let icx = ItemCtxt::new(tcx, parent);
 605             icx.get_type_parameter_bounds(DUMMY_SP, def_id.to_def_id(), assoc_name)
 606         })
 607         .unwrap_or_default();
 608     let mut extend = None;
 609
 610     let item_hir_id = tcx.hir().local_def_id_to_hir_id(item_def_id.expect_local());
 611     let ast_generics = match tcx.hir().get(item_hir_id) {
 612         Node::TraitItem(item) => &item.generics,
 613
 614         Node::ImplItem(item) => &item.generics,
 615
 616         Node::Item(item) => {
 617             match item.kind {
 618                 ItemKind::Fn(.., ref generics, _)
 619                 | ItemKind::Impl(hir::Impl { ref generics, .. })
 620                 | ItemKind::TyAlias(_, ref generics)
 621                 | ItemKind::OpaqueTy(OpaqueTy {
 622                     ref generics,
 623                     origin: hir::OpaqueTyOrigin::TyAlias,
 624                     ..
 625                 })
 626                 | ItemKind::Enum(_, ref generics)
 627                 | ItemKind::Struct(_, ref generics)
 628                 | ItemKind::Union(_, ref generics) => generics,
 629                 ItemKind::Trait(_, _, ref generics, ..) => {
 630                     // Implied `Self: Trait` and supertrait bounds.
 631                     if param_id == item_hir_id {
 632                         let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id);
 633                         extend =
 634                             Some((identity_trait_ref.without_const().to_predicate(tcx), item.span));
 635                     }
 636                     generics
 637                 }
 638                 _ => return result,
 639             }
 640         }
 641
 642         Node::ForeignItem(item) => match item.kind {
 643             ForeignItemKind::Fn(_, _, ref generics) => generics,
 644             _ => return result,
 645         },
 646
 647         _ => return result,
 648     };
 649
 650     let icx = ItemCtxt::new(tcx, item_def_id);
 651     let extra_predicates = extend.into_iter().chain(
 652         icx.type_parameter_bounds_in_generics(
 653             ast_generics,
 654             param_id,
 655             ty,
 656             OnlySelfBounds(true),
 657             Some(assoc_name),
 658         )
 659         .into_iter()
 660         .filter(|(predicate, _)| match predicate.kind().skip_binder() {
 661             ty::PredicateKind::Trait(data) => data.self_ty().is_param(index),
 662             _ => false,
 663         }),
 664     );
 665     result.predicates =
 666         tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(extra_predicates));
 667     result
 668 }
 669
 670 impl<'tcx> ItemCtxt<'tcx> {
 671     /// Finds bounds from `hir::Generics`. This requires scanning through the
 672     /// AST. We do this to avoid having to convert *all* the bounds, which
 673     /// would create artificial cycles. Instead, we can only convert the
 674     /// bounds for a type parameter `X` if `X::Foo` is used.
 675     fn type_parameter_bounds_in_generics(
 676         &self,
 677         ast_generics: &'tcx hir::Generics<'tcx>,
 678         param_id: hir::HirId,
 679         ty: Ty<'tcx>,
 680         only_self_bounds: OnlySelfBounds,
 681         assoc_name: Option<Ident>,
 682     ) -> Vec<(ty::Predicate<'tcx>, Span)> {
 683         let from_ty_params = ast_generics
 684             .params
 685             .iter()
 686             .filter_map(|param| match param.kind {
 687                 GenericParamKind::Type { .. } | GenericParamKind::Const { .. }
 688                     if param.hir_id == param_id =>
 689                 {
 690                     Some(&param.bounds)
 691                 }
 692                 _ => None,
 693             })
 694             .flat_map(|bounds| bounds.iter())
 695             .filter(|b| match assoc_name {
 696                 Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
 697                 None => true,
 698             })
 699             .flat_map(|b| predicates_from_bound(self, ty, b, ty::List::empty()));
 700
 701         let param_def_id = self.tcx.hir().local_def_id(param_id).to_def_id();
 702         let from_where_clauses = ast_generics
 703             .predicates
 704             .iter()
 705             .filter_map(|wp| match *wp {
 706                 hir::WherePredicate::BoundPredicate(ref bp) => Some(bp),
 707                 _ => None,
 708             })
 709             .flat_map(|bp| {
 710                 let bt = if bp.is_param_bound(param_def_id) {
 711                     Some(ty)
 712                 } else if !only_self_bounds.0 {
 713                     Some(self.to_ty(bp.bounded_ty))
 714                 } else {
 715                     None
 716                 };
 717                 let bvars = self.tcx.late_bound_vars(bp.bounded_ty.hir_id);
 718
 719                 bp.bounds
 720                     .iter()
 721                     .filter(|b| match assoc_name {
 722                         Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
 723                         None => true,
 724                     })
 725                     .filter_map(move |b| bt.map(|bt| (bt, b, bvars)))
 726             })
 727             .flat_map(|(bt, b, bvars)| predicates_from_bound(self, bt, b, bvars));
 728
 729         from_ty_params.chain(from_where_clauses).collect()
 730     }
 731
 732     fn bound_defines_assoc_item(&self, b: &hir::GenericBound<'_>, assoc_name: Ident) -> bool {
 733         debug!("bound_defines_assoc_item(b={:?}, assoc_name={:?})", b, assoc_name);
 734
 735         match b {
 736             hir::GenericBound::Trait(poly_trait_ref, _) => {
 737                 let trait_ref = &poly_trait_ref.trait_ref;
 738                 if let Some(trait_did) = trait_ref.trait_def_id() {
 739                     self.tcx.trait_may_define_assoc_type(trait_did, assoc_name)
 740                 } else {
 741                     false
 742                 }
 743             }
 744             _ => false,
 745         }
 746     }
 747 }
 748
 749 fn convert_item(tcx: TyCtxt<'_>, item_id: hir::ItemId) {
 750     let it = tcx.hir().item(item_id);
 751     debug!("convert: item {} with id {}", it.ident, it.hir_id());
 752     let def_id = item_id.def_id;
 753
 754     match it.kind {
 755         // These don't define types.
 756         hir::ItemKind::ExternCrate(_)
 757         | hir::ItemKind::Use(..)
 758         | hir::ItemKind::Macro(..)
 759         | hir::ItemKind::Mod(_)
 760         | hir::ItemKind::GlobalAsm(_) => {}
 761         hir::ItemKind::ForeignMod { items, .. } => {
 762             for item in items {
 763                 let item = tcx.hir().foreign_item(item.id);
 764                 tcx.ensure().generics_of(item.def_id);
 765                 tcx.ensure().type_of(item.def_id);
 766                 tcx.ensure().predicates_of(item.def_id);
 767                 match item.kind {
 768                     hir::ForeignItemKind::Fn(..) => tcx.ensure().fn_sig(item.def_id),
 769                     hir::ForeignItemKind::Static(..) => {
 770                         let mut visitor = HirPlaceholderCollector::default();
 771                         visitor.visit_foreign_item(item);
 772                         placeholder_type_error(
 773                             tcx,
 774                             None,
 775                             &[],
 776                             visitor.0,
 777                             false,
 778                             None,
 779                             "static variable",
 780                         );
 781                     }
 782                     _ => (),
 783                 }
 784             }
 785         }
 786         hir::ItemKind::Enum(ref enum_definition, _) => {
 787             tcx.ensure().generics_of(def_id);
 788             tcx.ensure().type_of(def_id);
 789             tcx.ensure().predicates_of(def_id);
 790             convert_enum_variant_types(tcx, def_id.to_def_id(), enum_definition.variants);
 791         }
 792         hir::ItemKind::Impl { .. } => {
 793             tcx.ensure().generics_of(def_id);
 794             tcx.ensure().type_of(def_id);
 795             tcx.ensure().impl_trait_ref(def_id);
 796             tcx.ensure().predicates_of(def_id);
 797         }
 798         hir::ItemKind::Trait(..) => {
 799             tcx.ensure().generics_of(def_id);
 800             tcx.ensure().trait_def(def_id);
 801             tcx.at(it.span).super_predicates_of(def_id);
 802             tcx.ensure().predicates_of(def_id);
 803         }
 804         hir::ItemKind::TraitAlias(..) => {
 805             tcx.ensure().generics_of(def_id);
 806             tcx.at(it.span).super_predicates_of(def_id);
 807             tcx.ensure().predicates_of(def_id);
 808         }
 809         hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 810             tcx.ensure().generics_of(def_id);
 811             tcx.ensure().type_of(def_id);
 812             tcx.ensure().predicates_of(def_id);
 813
 814             for f in struct_def.fields() {
 815                 let def_id = tcx.hir().local_def_id(f.hir_id);
 816                 tcx.ensure().generics_of(def_id);
 817                 tcx.ensure().type_of(def_id);
 818                 tcx.ensure().predicates_of(def_id);
 819             }
 820
 821             if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
 822                 convert_variant_ctor(tcx, ctor_hir_id);
 823             }
 824         }
 825
 826         // Desugared from `impl Trait`, so visited by the function's return type.
 827         hir::ItemKind::OpaqueTy(hir::OpaqueTy {
 828             origin: hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..),
 829             ..
 830         }) => {}
 831
 832         // Don't call `type_of` on opaque types, since that depends on type
 833         // checking function bodies. `check_item_type` ensures that it's called
 834         // instead.
 835         hir::ItemKind::OpaqueTy(..) => {
 836             tcx.ensure().generics_of(def_id);
 837             tcx.ensure().predicates_of(def_id);
 838             tcx.ensure().explicit_item_bounds(def_id);
 839         }
 840         hir::ItemKind::TyAlias(..)
 841         | hir::ItemKind::Static(..)
 842         | hir::ItemKind::Const(..)
 843         | hir::ItemKind::Fn(..) => {
 844             tcx.ensure().generics_of(def_id);
 845             tcx.ensure().type_of(def_id);
 846             tcx.ensure().predicates_of(def_id);
 847             match it.kind {
 848                 hir::ItemKind::Fn(..) => tcx.ensure().fn_sig(def_id),
 849                 hir::ItemKind::OpaqueTy(..) => tcx.ensure().item_bounds(def_id),
 850                 hir::ItemKind::Const(ty, ..) | hir::ItemKind::Static(ty, ..) => {
 851                     // (#75889): Account for `const C: dyn Fn() -> _ = "";`
 852                     if let hir::TyKind::TraitObject(..) = ty.kind {
 853                         let mut visitor = HirPlaceholderCollector::default();
 854                         visitor.visit_item(it);
 855                         placeholder_type_error(
 856                             tcx,
 857                             None,
 858                             &[],
 859                             visitor.0,
 860                             false,
 861                             None,
 862                             it.kind.descr(),
 863                         );
 864                     }
 865                 }
 866                 _ => (),
 867             }
 868         }
 869     }
 870 }
 871
 872 fn convert_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::TraitItemId) {
 873     let trait_item = tcx.hir().trait_item(trait_item_id);
 874     tcx.ensure().generics_of(trait_item_id.def_id);
 875
 876     match trait_item.kind {
 877         hir::TraitItemKind::Fn(..) => {
 878             tcx.ensure().type_of(trait_item_id.def_id);
 879             tcx.ensure().fn_sig(trait_item_id.def_id);
 880         }
 881
 882         hir::TraitItemKind::Const(.., Some(_)) => {
 883             tcx.ensure().type_of(trait_item_id.def_id);
 884         }
 885
 886         hir::TraitItemKind::Const(..) => {
 887             tcx.ensure().type_of(trait_item_id.def_id);
 888             // Account for `const C: _;`.
 889             let mut visitor = HirPlaceholderCollector::default();
 890             visitor.visit_trait_item(trait_item);
 891             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "constant");
 892         }
 893
 894         hir::TraitItemKind::Type(_, Some(_)) => {
 895             tcx.ensure().item_bounds(trait_item_id.def_id);
 896             tcx.ensure().type_of(trait_item_id.def_id);
 897             // Account for `type T = _;`.
 898             let mut visitor = HirPlaceholderCollector::default();
 899             visitor.visit_trait_item(trait_item);
 900             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 901         }
 902
 903         hir::TraitItemKind::Type(_, None) => {
 904             tcx.ensure().item_bounds(trait_item_id.def_id);
 905             // #74612: Visit and try to find bad placeholders
 906             // even if there is no concrete type.
 907             let mut visitor = HirPlaceholderCollector::default();
 908             visitor.visit_trait_item(trait_item);
 909
 910             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 911         }
 912     };
 913
 914     tcx.ensure().predicates_of(trait_item_id.def_id);
 915 }
 916
 917 fn convert_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::ImplItemId) {
 918     let def_id = impl_item_id.def_id;
 919     tcx.ensure().generics_of(def_id);
 920     tcx.ensure().type_of(def_id);
 921     tcx.ensure().predicates_of(def_id);
 922     let impl_item = tcx.hir().impl_item(impl_item_id);
 923     match impl_item.kind {
 924         hir::ImplItemKind::Fn(..) => {
 925             tcx.ensure().fn_sig(def_id);
 926         }
 927         hir::ImplItemKind::TyAlias(_) => {
 928             // Account for `type T = _;`
 929             let mut visitor = HirPlaceholderCollector::default();
 930             visitor.visit_impl_item(impl_item);
 931
 932             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 933         }
 934         hir::ImplItemKind::Const(..) => {}
 935     }
 936 }
 937
 938 fn convert_variant_ctor(tcx: TyCtxt<'_>, ctor_id: hir::HirId) {
 939     let def_id = tcx.hir().local_def_id(ctor_id);
 940     tcx.ensure().generics_of(def_id);
 941     tcx.ensure().type_of(def_id);
 942     tcx.ensure().predicates_of(def_id);
 943 }
 944
 945 fn convert_enum_variant_types(tcx: TyCtxt<'_>, def_id: DefId, variants: &[hir::Variant<'_>]) {
 946     let def = tcx.adt_def(def_id);
 947     let repr_type = def.repr().discr_type();
 948     let initial = repr_type.initial_discriminant(tcx);
 949     let mut prev_discr = None::<Discr<'_>>;
 950
 951     // fill the discriminant values and field types
 952     for variant in variants {
 953         let wrapped_discr = prev_discr.map_or(initial, |d| d.wrap_incr(tcx));
 954         prev_discr = Some(
 955             if let Some(ref e) = variant.disr_expr {
 956                 let expr_did = tcx.hir().local_def_id(e.hir_id);
 957                 def.eval_explicit_discr(tcx, expr_did.to_def_id())
 958             } else if let Some(discr) = repr_type.disr_incr(tcx, prev_discr) {
 959                 Some(discr)
 960             } else {
 961                 struct_span_err!(tcx.sess, variant.span, E0370, "enum discriminant overflowed")
 962                     .span_label(
 963                         variant.span,
 964                         format!("overflowed on value after {}", prev_discr.unwrap()),
 965                     )
 966                     .note(&format!(
 967                         "explicitly set `{} = {}` if that is desired outcome",
 968                         variant.ident, wrapped_discr
 969                     ))
 970                     .emit();
 971                 None
 972             }
 973             .unwrap_or(wrapped_discr),
 974         );
 975
 976         for f in variant.data.fields() {
 977             let def_id = tcx.hir().local_def_id(f.hir_id);
 978             tcx.ensure().generics_of(def_id);
 979             tcx.ensure().type_of(def_id);
 980             tcx.ensure().predicates_of(def_id);
 981         }
 982
 983         // Convert the ctor, if any. This also registers the variant as
 984         // an item.
 985         if let Some(ctor_hir_id) = variant.data.ctor_hir_id() {
 986             convert_variant_ctor(tcx, ctor_hir_id);
 987         }
 988     }
 989 }
 990
 991 fn convert_variant(
 992     tcx: TyCtxt<'_>,
 993     variant_did: Option<LocalDefId>,
 994     ctor_did: Option<LocalDefId>,
 995     ident: Ident,
 996     discr: ty::VariantDiscr,
 997     def: &hir::VariantData<'_>,
 998     adt_kind: ty::AdtKind,
 999     parent_did: LocalDefId,
1000 ) -> ty::VariantDef {
1001     let mut seen_fields: FxHashMap<Ident, Span> = Default::default();
1002     let fields = def
1003         .fields()
1004         .iter()
1005         .map(|f| {
1006             let fid = tcx.hir().local_def_id(f.hir_id);
1007             let dup_span = seen_fields.get(&f.ident.normalize_to_macros_2_0()).cloned();
1008             if let Some(prev_span) = dup_span {
1009                 tcx.sess.emit_err(errors::FieldAlreadyDeclared {
1010                     field_name: f.ident,
1011                     span: f.span,
1012                     prev_span,
1013                 });
1014             } else {
1015                 seen_fields.insert(f.ident.normalize_to_macros_2_0(), f.span);
1016             }
1017
1018             ty::FieldDef { did: fid.to_def_id(), name: f.ident.name, vis: tcx.visibility(fid) }
1019         })
1020         .collect();
1021     let recovered = match def {
1022         hir::VariantData::Struct(_, r) => *r,
1023         _ => false,
1024     };
1025     ty::VariantDef::new(
1026         ident.name,
1027         variant_did.map(LocalDefId::to_def_id),
1028         ctor_did.map(LocalDefId::to_def_id),
1029         discr,
1030         fields,
1031         CtorKind::from_hir(def),
1032         adt_kind,
1033         parent_did.to_def_id(),
1034         recovered,
1035         adt_kind == AdtKind::Struct && tcx.has_attr(parent_did.to_def_id(), sym::non_exhaustive)
1036             || variant_did.map_or(false, |variant_did| {
1037                 tcx.has_attr(variant_did.to_def_id(), sym::non_exhaustive)
1038             }),
1039     )
1040 }
1041
1042 fn adt_def<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> ty::AdtDef<'tcx> {
1043     use rustc_hir::*;
1044
1045     let def_id = def_id.expect_local();
1046     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1047     let Node::Item(item) = tcx.hir().get(hir_id) else {
1048         bug!();
1049     };
1050
1051     let repr = ReprOptions::new(tcx, def_id.to_def_id());
1052     let (kind, variants) = match item.kind {
1053         ItemKind::Enum(ref def, _) => {
1054             let mut distance_from_explicit = 0;
1055             let variants = def
1056                 .variants
1057                 .iter()
1058                 .map(|v| {
1059                     let variant_did = Some(tcx.hir().local_def_id(v.id));
1060                     let ctor_did =
1061                         v.data.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1062
1063                     let discr = if let Some(ref e) = v.disr_expr {
1064                         distance_from_explicit = 0;
1065                         ty::VariantDiscr::Explicit(tcx.hir().local_def_id(e.hir_id).to_def_id())
1066                     } else {
1067                         ty::VariantDiscr::Relative(distance_from_explicit)
1068                     };
1069                     distance_from_explicit += 1;
1070
1071                     convert_variant(
1072                         tcx,
1073                         variant_did,
1074                         ctor_did,
1075                         v.ident,
1076                         discr,
1077                         &v.data,
1078                         AdtKind::Enum,
1079                         def_id,
1080                     )
1081                 })
1082                 .collect();
1083
1084             (AdtKind::Enum, variants)
1085         }
1086         ItemKind::Struct(ref def, _) => {
1087             let variant_did = None::<LocalDefId>;
1088             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1089
1090             let variants = std::iter::once(convert_variant(
1091                 tcx,
1092                 variant_did,
1093                 ctor_did,
1094                 item.ident,
1095                 ty::VariantDiscr::Relative(0),
1096                 def,
1097                 AdtKind::Struct,
1098                 def_id,
1099             ))
1100             .collect();
1101
1102             (AdtKind::Struct, variants)
1103         }
1104         ItemKind::Union(ref def, _) => {
1105             let variant_did = None;
1106             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1107
1108             let variants = std::iter::once(convert_variant(
1109                 tcx,
1110                 variant_did,
1111                 ctor_did,
1112                 item.ident,
1113                 ty::VariantDiscr::Relative(0),
1114                 def,
1115                 AdtKind::Union,
1116                 def_id,
1117             ))
1118             .collect();
1119
1120             (AdtKind::Union, variants)
1121         }
1122         _ => bug!(),
1123     };
1124     tcx.alloc_adt_def(def_id.to_def_id(), kind, variants, repr)
1125 }
1126
1127 /// Ensures that the super-predicates of the trait with a `DefId`
1128 /// of `trait_def_id` are converted and stored. This also ensures that
1129 /// the transitive super-predicates are converted.
1130 fn super_predicates_of(tcx: TyCtxt<'_>, trait_def_id: DefId) -> ty::GenericPredicates<'_> {
1131     debug!("super_predicates(trait_def_id={:?})", trait_def_id);
1132     tcx.super_predicates_that_define_assoc_type((trait_def_id, None))
1133 }
1134
1135 /// Ensures that the super-predicates of the trait with a `DefId`
1136 /// of `trait_def_id` are converted and stored. This also ensures that
1137 /// the transitive super-predicates are converted.
1138 fn super_predicates_that_define_assoc_type(
1139     tcx: TyCtxt<'_>,
1140     (trait_def_id, assoc_name): (DefId, Option<Ident>),
1141 ) -> ty::GenericPredicates<'_> {
1142     debug!(
1143         "super_predicates_that_define_assoc_type(trait_def_id={:?}, assoc_name={:?})",
1144         trait_def_id, assoc_name
1145     );
1146     if trait_def_id.is_local() {
1147         debug!("super_predicates_that_define_assoc_type: local trait_def_id={:?}", trait_def_id);
1148         let trait_hir_id = tcx.hir().local_def_id_to_hir_id(trait_def_id.expect_local());
1149
1150         let Node::Item(item) = tcx.hir().get(trait_hir_id) else {
1151             bug!("trait_node_id {} is not an item", trait_hir_id);
1152         };
1153
1154         let (generics, bounds) = match item.kind {
1155             hir::ItemKind::Trait(.., ref generics, ref supertraits, _) => (generics, supertraits),
1156             hir::ItemKind::TraitAlias(ref generics, ref supertraits) => (generics, supertraits),
1157             _ => span_bug!(item.span, "super_predicates invoked on non-trait"),
1158         };
1159
1160         let icx = ItemCtxt::new(tcx, trait_def_id);
1161
1162         // Convert the bounds that follow the colon, e.g., `Bar + Zed` in `trait Foo: Bar + Zed`.
1163         let self_param_ty = tcx.types.self_param;
1164         let superbounds1 = if let Some(assoc_name) = assoc_name {
1165             <dyn AstConv<'_>>::compute_bounds_that_match_assoc_type(
1166                 &icx,
1167                 self_param_ty,
1168                 bounds,
1169                 assoc_name,
1170             )
1171         } else {
1172             <dyn AstConv<'_>>::compute_bounds(&icx, self_param_ty, bounds)
1173         };
1174
1175         let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
1176
1177         // Convert any explicit superbounds in the where-clause,
1178         // e.g., `trait Foo where Self: Bar`.
1179         // In the case of trait aliases, however, we include all bounds in the where-clause,
1180         // so e.g., `trait Foo = where u32: PartialEq<Self>` would include `u32: PartialEq<Self>`
1181         // as one of its "superpredicates".
1182         let is_trait_alias = tcx.is_trait_alias(trait_def_id);
1183         let superbounds2 = icx.type_parameter_bounds_in_generics(
1184             generics,
1185             item.hir_id(),
1186             self_param_ty,
1187             OnlySelfBounds(!is_trait_alias),
1188             assoc_name,
1189         );
1190
1191         // Combine the two lists to form the complete set of superbounds:
1192         let superbounds = &*tcx.arena.alloc_from_iter(superbounds1.into_iter().chain(superbounds2));
1193
1194         // Now require that immediate supertraits are converted,
1195         // which will, in turn, reach indirect supertraits.
1196         if assoc_name.is_none() {
1197             // Now require that immediate supertraits are converted,
1198             // which will, in turn, reach indirect supertraits.
1199             for &(pred, span) in superbounds {
1200                 debug!("superbound: {:?}", pred);
1201                 if let ty::PredicateKind::Trait(bound) = pred.kind().skip_binder() {
1202                     tcx.at(span).super_predicates_of(bound.def_id());
1203                 }
1204             }
1205         }
1206
1207         ty::GenericPredicates { parent: None, predicates: superbounds }
1208     } else {
1209         // if `assoc_name` is None, then the query should've been redirected to an
1210         // external provider
1211         assert!(assoc_name.is_some());
1212         tcx.super_predicates_of(trait_def_id)
1213     }
1214 }
1215
1216 fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> ty::TraitDef {
1217     let item = tcx.hir().expect_item(def_id.expect_local());
1218
1219     let (is_auto, unsafety, items) = match item.kind {
1220         hir::ItemKind::Trait(is_auto, unsafety, .., items) => {
1221             (is_auto == hir::IsAuto::Yes, unsafety, items)
1222         }
1223         hir::ItemKind::TraitAlias(..) => (false, hir::Unsafety::Normal, &[][..]),
1224         _ => span_bug!(item.span, "trait_def_of_item invoked on non-trait"),
1225     };
1226
1227     let paren_sugar = tcx.has_attr(def_id, sym::rustc_paren_sugar);
1228     if paren_sugar && !tcx.features().unboxed_closures {
1229         tcx.sess
1230             .struct_span_err(
1231                 item.span,
1232                 "the `#[rustc_paren_sugar]` attribute is a temporary means of controlling \
1233                  which traits can use parenthetical notation",
1234             )
1235             .help("add `#![feature(unboxed_closures)]` to the crate attributes to use it")
1236             .emit();
1237     }
1238
1239     let is_marker = tcx.has_attr(def_id, sym::marker);
1240     let skip_array_during_method_dispatch =
1241         tcx.has_attr(def_id, sym::rustc_skip_array_during_method_dispatch);
1242     let spec_kind = if tcx.has_attr(def_id, sym::rustc_unsafe_specialization_marker) {
1243         ty::trait_def::TraitSpecializationKind::Marker
1244     } else if tcx.has_attr(def_id, sym::rustc_specialization_trait) {
1245         ty::trait_def::TraitSpecializationKind::AlwaysApplicable
1246     } else {
1247         ty::trait_def::TraitSpecializationKind::None
1248     };
1249     let must_implement_one_of = tcx
1250         .get_attrs(def_id)
1251         .iter()
1252         .find(|attr| attr.has_name(sym::rustc_must_implement_one_of))
1253         // Check that there are at least 2 arguments of `#[rustc_must_implement_one_of]`
1254         // and that they are all identifiers
1255         .and_then(|attr| match attr.meta_item_list() {
1256             Some(items) if items.len() < 2 => {
1257                 tcx.sess
1258                     .struct_span_err(
1259                         attr.span,
1260                         "the `#[rustc_must_implement_one_of]` attribute must be \
1261                         used with at least 2 args",
1262                     )
1263                     .emit();
1264
1265                 None
1266             }
1267             Some(items) => items
1268                 .into_iter()
1269                 .map(|item| item.ident().ok_or(item.span()))
1270                 .collect::<Result<Box<[_]>, _>>()
1271                 .map_err(|span| {
1272                     tcx.sess
1273                         .struct_span_err(span, "must be a name of an associated function")
1274                         .emit();
1275                 })
1276                 .ok()
1277                 .zip(Some(attr.span)),
1278             // Error is reported by `rustc_attr!`
1279             None => None,
1280         })
1281         // Check that all arguments of `#[rustc_must_implement_one_of]` reference
1282         // functions in the trait with default implementations
1283         .and_then(|(list, attr_span)| {
1284             let errors = list.iter().filter_map(|ident| {
1285                 let item = items.iter().find(|item| item.ident == *ident);
1286
1287                 match item {
1288                     Some(item) if matches!(item.kind, hir::AssocItemKind::Fn { .. }) => {
1289                         if !item.defaultness.has_value() {
1290                             tcx.sess
1291                                 .struct_span_err(
1292                                     item.span,
1293                                     "This function doesn't have a default implementation",
1294                                 )
1295                                 .span_note(attr_span, "required by this annotation")
1296                                 .emit();
1297
1298                             return Some(());
1299                         }
1300
1301                         return None;
1302                     }
1303                     Some(item) => {
1304                         tcx.sess
1305                             .struct_span_err(item.span, "Not a function")
1306                             .span_note(attr_span, "required by this annotation")
1307                             .note(
1308                                 "All `#[rustc_must_implement_one_of]` arguments \
1309                             must be associated function names",
1310                             )
1311                             .emit();
1312                     }
1313                     None => {
1314                         tcx.sess
1315                             .struct_span_err(ident.span, "Function not found in this trait")
1316                             .emit();
1317                     }
1318                 }
1319
1320                 Some(())
1321             });
1322
1323             (errors.count() == 0).then_some(list)
1324         })
1325         // Check for duplicates
1326         .and_then(|list| {
1327             let mut set: FxHashMap<Symbol, Span> = FxHashMap::default();
1328             let mut no_dups = true;
1329
1330             for ident in &*list {
1331                 if let Some(dup) = set.insert(ident.name, ident.span) {
1332                     tcx.sess
1333                         .struct_span_err(vec![dup, ident.span], "Functions names are duplicated")
1334                         .note(
1335                             "All `#[rustc_must_implement_one_of]` arguments \
1336                             must be unique",
1337                         )
1338                         .emit();
1339
1340                     no_dups = false;
1341                 }
1342             }
1343
1344             no_dups.then_some(list)
1345         });
1346
1347     ty::TraitDef::new(
1348         def_id,
1349         unsafety,
1350         paren_sugar,
1351         is_auto,
1352         is_marker,
1353         skip_array_during_method_dispatch,
1354         spec_kind,
1355         must_implement_one_of,
1356     )
1357 }
1358
1359 fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<Span> {
1360     struct LateBoundRegionsDetector<'tcx> {
1361         tcx: TyCtxt<'tcx>,
1362         outer_index: ty::DebruijnIndex,
1363         has_late_bound_regions: Option<Span>,
1364     }
1365
1366     impl<'tcx> Visitor<'tcx> for LateBoundRegionsDetector<'tcx> {
1367         fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
1368             if self.has_late_bound_regions.is_some() {
1369                 return;
1370             }
1371             match ty.kind {
1372                 hir::TyKind::BareFn(..) => {
1373                     self.outer_index.shift_in(1);
1374                     intravisit::walk_ty(self, ty);
1375                     self.outer_index.shift_out(1);
1376                 }
1377                 _ => intravisit::walk_ty(self, ty),
1378             }
1379         }
1380
1381         fn visit_poly_trait_ref(
1382             &mut self,
1383             tr: &'tcx hir::PolyTraitRef<'tcx>,
1384             m: hir::TraitBoundModifier,
1385         ) {
1386             if self.has_late_bound_regions.is_some() {
1387                 return;
1388             }
1389             self.outer_index.shift_in(1);
1390             intravisit::walk_poly_trait_ref(self, tr, m);
1391             self.outer_index.shift_out(1);
1392         }
1393
1394         fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
1395             if self.has_late_bound_regions.is_some() {
1396                 return;
1397             }
1398
1399             match self.tcx.named_region(lt.hir_id) {
1400                 Some(rl::Region::Static | rl::Region::EarlyBound(..)) => {}
1401                 Some(
1402                     rl::Region::LateBound(debruijn, _, _)
1403                     | rl::Region::LateBoundAnon(debruijn, _, _),
1404                 ) if debruijn < self.outer_index => {}
1405                 Some(
1406                     rl::Region::LateBound(..)
1407                     | rl::Region::LateBoundAnon(..)
1408                     | rl::Region::Free(..),
1409                 )
1410                 | None => {
1411                     self.has_late_bound_regions = Some(lt.span);
1412                 }
1413             }
1414         }
1415     }
1416
1417     fn has_late_bound_regions<'tcx>(
1418         tcx: TyCtxt<'tcx>,
1419         def_id: LocalDefId,
1420         generics: &'tcx hir::Generics<'tcx>,
1421         decl: &'tcx hir::FnDecl<'tcx>,
1422     ) -> Option<Span> {
1423         let mut visitor = LateBoundRegionsDetector {
1424             tcx,
1425             outer_index: ty::INNERMOST,
1426             has_late_bound_regions: None,
1427         };
1428         let late_bound_map = tcx.is_late_bound_map(def_id);
1429         let is_late_bound = |id| {
1430             let id = tcx.hir().local_def_id(id);
1431             late_bound_map.map_or(false, |(_, set)| set.contains(&id))
1432         };
1433         for param in generics.params {
1434             if let GenericParamKind::Lifetime { .. } = param.kind {
1435                 if is_late_bound(param.hir_id) {
1436                     return Some(param.span);
1437                 }
1438             }
1439         }
1440         visitor.visit_fn_decl(decl);
1441         visitor.has_late_bound_regions
1442     }
1443
1444     match node {
1445         Node::TraitItem(item) => match item.kind {
1446             hir::TraitItemKind::Fn(ref sig, _) => {
1447                 has_late_bound_regions(tcx, item.def_id, &item.generics, sig.decl)
1448             }
1449             _ => None,
1450         },
1451         Node::ImplItem(item) => match item.kind {
1452             hir::ImplItemKind::Fn(ref sig, _) => {
1453                 has_late_bound_regions(tcx, item.def_id, &item.generics, sig.decl)
1454             }
1455             _ => None,
1456         },
1457         Node::ForeignItem(item) => match item.kind {
1458             hir::ForeignItemKind::Fn(fn_decl, _, ref generics) => {
1459                 has_late_bound_regions(tcx, item.def_id, generics, fn_decl)
1460             }
1461             _ => None,
1462         },
1463         Node::Item(item) => match item.kind {
1464             hir::ItemKind::Fn(ref sig, .., ref generics, _) => {
1465                 has_late_bound_regions(tcx, item.def_id, generics, sig.decl)
1466             }
1467             _ => None,
1468         },
1469         _ => None,
1470     }
1471 }
1472
1473 struct AnonConstInParamTyDetector {
1474     in_param_ty: bool,
1475     found_anon_const_in_param_ty: bool,
1476     ct: HirId,
1477 }
1478
1479 impl<'v> Visitor<'v> for AnonConstInParamTyDetector {
1480     fn visit_generic_param(&mut self, p: &'v hir::GenericParam<'v>) {
1481         if let GenericParamKind::Const { ty, default: _ } = p.kind {
1482             let prev = self.in_param_ty;
1483             self.in_param_ty = true;
1484             self.visit_ty(ty);
1485             self.in_param_ty = prev;
1486         }
1487     }
1488
1489     fn visit_anon_const(&mut self, c: &'v hir::AnonConst) {
1490         if self.in_param_ty && self.ct == c.hir_id {
1491             self.found_anon_const_in_param_ty = true;
1492         } else {
1493             intravisit::walk_anon_const(self, c)
1494         }
1495     }
1496 }
1497
1498 fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::Generics {
1499     use rustc_hir::*;
1500
1501     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1502
1503     let node = tcx.hir().get(hir_id);
1504     let parent_def_id = match node {
1505         Node::ImplItem(_)
1506         | Node::TraitItem(_)
1507         | Node::Variant(_)
1508         | Node::Ctor(..)
1509         | Node::Field(_) => {
1510             let parent_id = tcx.hir().get_parent_item(hir_id);
1511             Some(parent_id.to_def_id())
1512         }
1513         // FIXME(#43408) always enable this once `lazy_normalization` is
1514         // stable enough and does not need a feature gate anymore.
1515         Node::AnonConst(_) => {
1516             let parent_def_id = tcx.hir().get_parent_item(hir_id);
1517
1518             let mut in_param_ty = false;
1519             for (_parent, node) in tcx.hir().parent_iter(hir_id) {
1520                 if let Some(generics) = node.generics() {
1521                     let mut visitor = AnonConstInParamTyDetector {
1522                         in_param_ty: false,
1523                         found_anon_const_in_param_ty: false,
1524                         ct: hir_id,
1525                     };
1526
1527                     visitor.visit_generics(generics);
1528                     in_param_ty = visitor.found_anon_const_in_param_ty;
1529                     break;
1530                 }
1531             }
1532
1533             if in_param_ty {
1534                 // We do not allow generic parameters in anon consts if we are inside
1535                 // of a const parameter type, e.g. `struct Foo<const N: usize, const M: [u8; N]>` is not allowed.
1536                 None
1537             } else if tcx.lazy_normalization() {
1538                 if let Some(param_id) = tcx.hir().opt_const_param_default_param_hir_id(hir_id) {
1539                     // If the def_id we are calling generics_of on is an anon ct default i.e:
1540                     //
1541                     // struct Foo<const N: usize = { .. }>;
1542                     //        ^^^       ^          ^^^^^^ def id of this anon const
1543                     //        ^         ^ param_id
1544                     //        ^ parent_def_id
1545                     //
1546                     // then we only want to return generics for params to the left of `N`. If we don't do that we
1547                     // end up with that const looking like: `ty::ConstKind::Unevaluated(def_id, substs: [N#0])`.
1548                     //
1549                     // This causes ICEs (#86580) when building the substs for Foo in `fn foo() -> Foo { .. }` as
1550                     // we substitute the defaults with the partially built substs when we build the substs. Subst'ing
1551                     // the `N#0` on the unevaluated const indexes into the empty substs we're in the process of building.
1552                     //
1553                     // We fix this by having this function return the parent's generics ourselves and truncating the
1554                     // generics to only include non-forward declared params (with the exception of the `Self` ty)
1555                     //
1556                     // For the above code example that means we want `substs: []`
1557                     // For the following struct def we want `substs: [N#0]` when generics_of is called on
1558                     // the def id of the `{ N + 1 }` anon const
1559                     // struct Foo<const N: usize, const M: usize = { N + 1 }>;
1560                     //
1561                     // This has some implications for how we get the predicates available to the anon const
1562                     // see `explicit_predicates_of` for more information on this
1563                     let generics = tcx.generics_of(parent_def_id.to_def_id());
1564                     let param_def = tcx.hir().local_def_id(param_id).to_def_id();
1565                     let param_def_idx = generics.param_def_id_to_index[&param_def];
1566                     // In the above example this would be .params[..N#0]
1567                     let params = generics.params[..param_def_idx as usize].to_owned();
1568                     let param_def_id_to_index =
1569                         params.iter().map(|param| (param.def_id, param.index)).collect();
1570
1571                     return ty::Generics {
1572                         // we set the parent of these generics to be our parent's parent so that we
1573                         // dont end up with substs: [N, M, N] for the const default on a struct like this:
1574                         // struct Foo<const N: usize, const M: usize = { ... }>;
1575                         parent: generics.parent,
1576                         parent_count: generics.parent_count,
1577                         params,
1578                         param_def_id_to_index,
1579                         has_self: generics.has_self,
1580                         has_late_bound_regions: generics.has_late_bound_regions,
1581                     };
1582                 }
1583
1584                 // HACK(eddyb) this provides the correct generics when
1585                 // `feature(generic_const_expressions)` is enabled, so that const expressions
1586                 // used with const generics, e.g. `Foo<{N+1}>`, can work at all.
1587                 //
1588                 // Note that we do not supply the parent generics when using
1589                 // `min_const_generics`.
1590                 Some(parent_def_id.to_def_id())
1591             } else {
1592                 let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1593                 match parent_node {
1594                     // HACK(eddyb) this provides the correct generics for repeat
1595                     // expressions' count (i.e. `N` in `[x; N]`), and explicit
1596                     // `enum` discriminants (i.e. `D` in `enum Foo { Bar = D }`),
1597                     // as they shouldn't be able to cause query cycle errors.
1598                     Node::Expr(&Expr { kind: ExprKind::Repeat(_, ref constant), .. })
1599                         if constant.hir_id() == hir_id =>
1600                     {
1601                         Some(parent_def_id.to_def_id())
1602                     }
1603                     Node::Variant(Variant { disr_expr: Some(ref constant), .. })
1604                         if constant.hir_id == hir_id =>
1605                     {
1606                         Some(parent_def_id.to_def_id())
1607                     }
1608                     Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) => {
1609                         Some(tcx.typeck_root_def_id(def_id))
1610                     }
1611                     _ => None,
1612                 }
1613             }
1614         }
1615         Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1616             Some(tcx.typeck_root_def_id(def_id))
1617         }
1618         Node::Item(item) => match item.kind {
1619             ItemKind::OpaqueTy(hir::OpaqueTy {
1620                 origin:
1621                     hir::OpaqueTyOrigin::FnReturn(fn_def_id) | hir::OpaqueTyOrigin::AsyncFn(fn_def_id),
1622                 ..
1623             }) => Some(fn_def_id.to_def_id()),
1624             ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::TyAlias, .. }) => {
1625                 let parent_id = tcx.hir().get_parent_item(hir_id);
1626                 assert_ne!(parent_id, CRATE_DEF_ID);
1627                 debug!("generics_of: parent of opaque ty {:?} is {:?}", def_id, parent_id);
1628                 // Opaque types are always nested within another item, and
1629                 // inherit the generics of the item.
1630                 Some(parent_id.to_def_id())
1631             }
1632             _ => None,
1633         },
1634         _ => None,
1635     };
1636
1637     let mut opt_self = None;
1638     let mut allow_defaults = false;
1639
1640     let no_generics = hir::Generics::empty();
1641     let ast_generics = match node {
1642         Node::TraitItem(item) => &item.generics,
1643
1644         Node::ImplItem(item) => &item.generics,
1645
1646         Node::Item(item) => {
1647             match item.kind {
1648                 ItemKind::Fn(.., ref generics, _)
1649                 | ItemKind::Impl(hir::Impl { ref generics, .. }) => generics,
1650
1651                 ItemKind::TyAlias(_, ref generics)
1652                 | ItemKind::Enum(_, ref generics)
1653                 | ItemKind::Struct(_, ref generics)
1654                 | ItemKind::OpaqueTy(hir::OpaqueTy { ref generics, .. })
1655                 | ItemKind::Union(_, ref generics) => {
1656                     allow_defaults = true;
1657                     generics
1658                 }
1659
1660                 ItemKind::Trait(_, _, ref generics, ..)
1661                 | ItemKind::TraitAlias(ref generics, ..) => {
1662                     // Add in the self type parameter.
1663                     //
1664                     // Something of a hack: use the node id for the trait, also as
1665                     // the node id for the Self type parameter.
1666                     let param_id = item.def_id;
1667
1668                     opt_self = Some(ty::GenericParamDef {
1669                         index: 0,
1670                         name: kw::SelfUpper,
1671                         def_id: param_id.to_def_id(),
1672                         pure_wrt_drop: false,
1673                         kind: ty::GenericParamDefKind::Type {
1674                             has_default: false,
1675                             object_lifetime_default: rl::Set1::Empty,
1676                             synthetic: false,
1677                         },
1678                     });
1679
1680                     allow_defaults = true;
1681                     generics
1682                 }
1683
1684                 _ => &no_generics,
1685             }
1686         }
1687
1688         Node::ForeignItem(item) => match item.kind {
1689             ForeignItemKind::Static(..) => &no_generics,
1690             ForeignItemKind::Fn(_, _, ref generics) => generics,
1691             ForeignItemKind::Type => &no_generics,
1692         },
1693
1694         _ => &no_generics,
1695     };
1696
1697     let has_self = opt_self.is_some();
1698     let mut parent_has_self = false;
1699     let mut own_start = has_self as u32;
1700     let parent_count = parent_def_id.map_or(0, |def_id| {
1701         let generics = tcx.generics_of(def_id);
1702         assert!(!has_self);
1703         parent_has_self = generics.has_self;
1704         own_start = generics.count() as u32;
1705         generics.parent_count + generics.params.len()
1706     });
1707
1708     let mut params: Vec<_> = Vec::with_capacity(ast_generics.params.len() + has_self as usize);
1709
1710     if let Some(opt_self) = opt_self {
1711         params.push(opt_self);
1712     }
1713
1714     let early_lifetimes = early_bound_lifetimes_from_generics(tcx, hir_id.owner, ast_generics);
1715     params.extend(early_lifetimes.enumerate().map(|(i, param)| ty::GenericParamDef {
1716         name: param.name.ident().name,
1717         index: own_start + i as u32,
1718         def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1719         pure_wrt_drop: param.pure_wrt_drop,
1720         kind: ty::GenericParamDefKind::Lifetime,
1721     }));
1722
1723     let object_lifetime_defaults = tcx.object_lifetime_defaults(hir_id.owner);
1724
1725     // Now create the real type and const parameters.
1726     let type_start = own_start - has_self as u32 + params.len() as u32;
1727     let mut i = 0;
1728
1729     params.extend(ast_generics.params.iter().filter_map(|param| match param.kind {
1730         GenericParamKind::Lifetime { .. } => None,
1731         GenericParamKind::Type { ref default, synthetic, .. } => {
1732             if !allow_defaults && default.is_some() {
1733                 if !tcx.features().default_type_parameter_fallback {
1734                     tcx.struct_span_lint_hir(
1735                         lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
1736                         param.hir_id,
1737                         param.span,
1738                         |lint| {
1739                             lint.build(
1740                                 "defaults for type parameters are only allowed in \
1741                                  `struct`, `enum`, `type`, or `trait` definitions",
1742                             )
1743                             .emit();
1744                         },
1745                     );
1746                 }
1747             }
1748
1749             let kind = ty::GenericParamDefKind::Type {
1750                 has_default: default.is_some(),
1751                 object_lifetime_default: object_lifetime_defaults
1752                     .as_ref()
1753                     .map_or(rl::Set1::Empty, |o| o[i]),
1754                 synthetic,
1755             };
1756
1757             let param_def = ty::GenericParamDef {
1758                 index: type_start + i as u32,
1759                 name: param.name.ident().name,
1760                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1761                 pure_wrt_drop: param.pure_wrt_drop,
1762                 kind,
1763             };
1764             i += 1;
1765             Some(param_def)
1766         }
1767         GenericParamKind::Const { default, .. } => {
1768             if !allow_defaults && default.is_some() {
1769                 tcx.sess.span_err(
1770                     param.span,
1771                     "defaults for const parameters are only allowed in \
1772                     `struct`, `enum`, `type`, or `trait` definitions",
1773                 );
1774             }
1775
1776             let param_def = ty::GenericParamDef {
1777                 index: type_start + i as u32,
1778                 name: param.name.ident().name,
1779                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1780                 pure_wrt_drop: param.pure_wrt_drop,
1781                 kind: ty::GenericParamDefKind::Const { has_default: default.is_some() },
1782             };
1783             i += 1;
1784             Some(param_def)
1785         }
1786     }));
1787
1788     // provide junk type parameter defs - the only place that
1789     // cares about anything but the length is instantiation,
1790     // and we don't do that for closures.
1791     if let Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(.., gen), .. }) = node {
1792         let dummy_args = if gen.is_some() {
1793             &["<resume_ty>", "<yield_ty>", "<return_ty>", "<witness>", "<upvars>"][..]
1794         } else {
1795             &["<closure_kind>", "<closure_signature>", "<upvars>"][..]
1796         };
1797
1798         params.extend(dummy_args.iter().enumerate().map(|(i, &arg)| ty::GenericParamDef {
1799             index: type_start + i as u32,
1800             name: Symbol::intern(arg),
1801             def_id,
1802             pure_wrt_drop: false,
1803             kind: ty::GenericParamDefKind::Type {
1804                 has_default: false,
1805                 object_lifetime_default: rl::Set1::Empty,
1806                 synthetic: false,
1807             },
1808         }));
1809     }
1810
1811     // provide junk type parameter defs for const blocks.
1812     if let Node::AnonConst(_) = node {
1813         let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1814         if let Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) = parent_node {
1815             params.push(ty::GenericParamDef {
1816                 index: type_start,
1817                 name: Symbol::intern("<const_ty>"),
1818                 def_id,
1819                 pure_wrt_drop: false,
1820                 kind: ty::GenericParamDefKind::Type {
1821                     has_default: false,
1822                     object_lifetime_default: rl::Set1::Empty,
1823                     synthetic: false,
1824                 },
1825             });
1826         }
1827     }
1828
1829     let param_def_id_to_index = params.iter().map(|param| (param.def_id, param.index)).collect();
1830
1831     ty::Generics {
1832         parent: parent_def_id,
1833         parent_count,
1834         params,
1835         param_def_id_to_index,
1836         has_self: has_self || parent_has_self,
1837         has_late_bound_regions: has_late_bound_regions(tcx, node),
1838     }
1839 }
1840
1841 fn are_suggestable_generic_args(generic_args: &[hir::GenericArg<'_>]) -> bool {
1842     generic_args.iter().any(|arg| match arg {
1843         hir::GenericArg::Type(ty) => is_suggestable_infer_ty(ty),
1844         hir::GenericArg::Infer(_) => true,
1845         _ => false,
1846     })
1847 }
1848
1849 /// Whether `ty` is a type with `_` placeholders that can be inferred. Used in diagnostics only to
1850 /// use inference to provide suggestions for the appropriate type if possible.
1851 fn is_suggestable_infer_ty(ty: &hir::Ty<'_>) -> bool {
1852     debug!(?ty);
1853     use hir::TyKind::*;
1854     match &ty.kind {
1855         Infer => true,
1856         Slice(ty) => is_suggestable_infer_ty(ty),
1857         Array(ty, length) => {
1858             is_suggestable_infer_ty(ty) || matches!(length, hir::ArrayLen::Infer(_, _))
1859         }
1860         Tup(tys) => tys.iter().any(is_suggestable_infer_ty),
1861         Ptr(mut_ty) | Rptr(_, mut_ty) => is_suggestable_infer_ty(mut_ty.ty),
1862         OpaqueDef(_, generic_args) => are_suggestable_generic_args(generic_args),
1863         Path(hir::QPath::TypeRelative(ty, segment)) => {
1864             is_suggestable_infer_ty(ty) || are_suggestable_generic_args(segment.args().args)
1865         }
1866         Path(hir::QPath::Resolved(ty_opt, hir::Path { segments, .. })) => {
1867             ty_opt.map_or(false, is_suggestable_infer_ty)
1868                 || segments.iter().any(|segment| are_suggestable_generic_args(segment.args().args))
1869         }
1870         _ => false,
1871     }
1872 }
1873
1874 pub fn get_infer_ret_ty<'hir>(output: &'hir hir::FnRetTy<'hir>) -> Option<&'hir hir::Ty<'hir>> {
1875     if let hir::FnRetTy::Return(ty) = output {
1876         if is_suggestable_infer_ty(ty) {
1877             return Some(&*ty);
1878         }
1879     }
1880     None
1881 }
1882
1883 fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
1884     use rustc_hir::Node::*;
1885     use rustc_hir::*;
1886
1887     let def_id = def_id.expect_local();
1888     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1889
1890     let icx = ItemCtxt::new(tcx, def_id.to_def_id());
1891
1892     match tcx.hir().get(hir_id) {
1893         TraitItem(hir::TraitItem {
1894             kind: TraitItemKind::Fn(sig, TraitFn::Provided(_)),
1895             ident,
1896             generics,
1897             ..
1898         })
1899         | Item(hir::Item { kind: ItemKind::Fn(sig, generics, _), ident, .. }) => {
1900             infer_return_ty_for_fn_sig(tcx, sig, *ident, generics, def_id, &icx)
1901         }
1902
1903         ImplItem(hir::ImplItem { kind: ImplItemKind::Fn(sig, _), ident, generics, .. }) => {
1904             // Do not try to inference the return type for a impl method coming from a trait
1905             if let Item(hir::Item { kind: ItemKind::Impl(i), .. }) =
1906                 tcx.hir().get(tcx.hir().get_parent_node(hir_id))
1907                 && i.of_trait.is_some()
1908             {
1909                 <dyn AstConv<'_>>::ty_of_fn(
1910                     &icx,
1911                     hir_id,
1912                     sig.header.unsafety,
1913                     sig.header.abi,
1914                     sig.decl,
1915                     generics,
1916                     Some(ident.span),
1917                     None,
1918                 )
1919             } else {
1920                 infer_return_ty_for_fn_sig(tcx, sig, *ident, generics, def_id, &icx)
1921             }
1922         }
1923
1924         TraitItem(hir::TraitItem {
1925             kind: TraitItemKind::Fn(FnSig { header, decl, span: _ }, _),
1926             ident,
1927             generics,
1928             ..
1929         }) => <dyn AstConv<'_>>::ty_of_fn(
1930             &icx,
1931             hir_id,
1932             header.unsafety,
1933             header.abi,
1934             decl,
1935             generics,
1936             Some(ident.span),
1937             None,
1938         ),
1939
1940         ForeignItem(&hir::ForeignItem {
1941             kind: ForeignItemKind::Fn(fn_decl, _, _), ident, ..
1942         }) => {
1943             let abi = tcx.hir().get_foreign_abi(hir_id);
1944             compute_sig_of_foreign_fn_decl(tcx, def_id.to_def_id(), fn_decl, abi, ident)
1945         }
1946
1947         Ctor(data) | Variant(hir::Variant { data, .. }) if data.ctor_hir_id().is_some() => {
1948             let ty = tcx.type_of(tcx.hir().get_parent_item(hir_id));
1949             let inputs =
1950                 data.fields().iter().map(|f| tcx.type_of(tcx.hir().local_def_id(f.hir_id)));
1951             ty::Binder::dummy(tcx.mk_fn_sig(
1952                 inputs,
1953                 ty,
1954                 false,
1955                 hir::Unsafety::Normal,
1956                 abi::Abi::Rust,
1957             ))
1958         }
1959
1960         Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1961             // Closure signatures are not like other function
1962             // signatures and cannot be accessed through `fn_sig`. For
1963             // example, a closure signature excludes the `self`
1964             // argument. In any case they are embedded within the
1965             // closure type as part of the `ClosureSubsts`.
1966             //
1967             // To get the signature of a closure, you should use the
1968             // `sig` method on the `ClosureSubsts`:
1969             //
1970             //    substs.as_closure().sig(def_id, tcx)
1971             bug!(
1972                 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
1973             );
1974         }
1975
1976         x => {
1977             bug!("unexpected sort of node in fn_sig(): {:?}", x);
1978         }
1979     }
1980 }
1981
1982 fn infer_return_ty_for_fn_sig<'tcx>(
1983     tcx: TyCtxt<'tcx>,
1984     sig: &hir::FnSig<'_>,
1985     ident: Ident,
1986     generics: &hir::Generics<'_>,
1987     def_id: LocalDefId,
1988     icx: &ItemCtxt<'tcx>,
1989 ) -> ty::PolyFnSig<'tcx> {
1990     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1991
1992     match get_infer_ret_ty(&sig.decl.output) {
1993         Some(ty) => {
1994             let fn_sig = tcx.typeck(def_id).liberated_fn_sigs()[hir_id];
1995             // Typeck doesn't expect erased regions to be returned from `type_of`.
1996             let fn_sig = tcx.fold_regions(fn_sig, &mut false, |r, _| match *r {
1997                 ty::ReErased => tcx.lifetimes.re_static,
1998                 _ => r,
1999             });
2000             let fn_sig = ty::Binder::dummy(fn_sig);
2001
2002             let mut visitor = HirPlaceholderCollector::default();
2003             visitor.visit_ty(ty);
2004             let mut diag = bad_placeholder(tcx, visitor.0, "return type");
2005             let ret_ty = fn_sig.skip_binder().output();
2006             if ret_ty.is_suggestable(tcx) {
2007                 diag.span_suggestion(
2008                     ty.span,
2009                     "replace with the correct return type",
2010                     ret_ty.to_string(),
2011                     Applicability::MachineApplicable,
2012                 );
2013             } else if matches!(ret_ty.kind(), ty::FnDef(..)) {
2014                 let fn_sig = ret_ty.fn_sig(tcx);
2015                 if fn_sig.skip_binder().inputs_and_output.iter().all(|t| t.is_suggestable(tcx)) {
2016                     diag.span_suggestion(
2017                         ty.span,
2018                         "replace with the correct return type",
2019                         fn_sig.to_string(),
2020                         Applicability::MachineApplicable,
2021                     );
2022                 }
2023             } else if ret_ty.is_closure() {
2024                 // We're dealing with a closure, so we should suggest using `impl Fn` or trait bounds
2025                 // to prevent the user from getting a papercut while trying to use the unique closure
2026                 // syntax (e.g. `[closure@src/lib.rs:2:5: 2:9]`).
2027                 diag.help("consider using an `Fn`, `FnMut`, or `FnOnce` trait bound");
2028                 diag.note("for more information on `Fn` traits and closure types, see https://doc.rust-lang.org/book/ch13-01-closures.html");
2029             }
2030             diag.emit();
2031
2032             fn_sig
2033         }
2034         None => <dyn AstConv<'_>>::ty_of_fn(
2035             icx,
2036             hir_id,
2037             sig.header.unsafety,
2038             sig.header.abi,
2039             sig.decl,
2040             generics,
2041             Some(ident.span),
2042             None,
2043         ),
2044     }
2045 }
2046
2047 fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> {
2048     let icx = ItemCtxt::new(tcx, def_id);
2049     match tcx.hir().expect_item(def_id.expect_local()).kind {
2050         hir::ItemKind::Impl(ref impl_) => impl_.of_trait.as_ref().map(|ast_trait_ref| {
2051             let selfty = tcx.type_of(def_id);
2052             <dyn AstConv<'_>>::instantiate_mono_trait_ref(&icx, ast_trait_ref, selfty)
2053         }),
2054         _ => bug!(),
2055     }
2056 }
2057
2058 fn impl_polarity(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ImplPolarity {
2059     let is_rustc_reservation = tcx.has_attr(def_id, sym::rustc_reservation_impl);
2060     let item = tcx.hir().expect_item(def_id.expect_local());
2061     match &item.kind {
2062         hir::ItemKind::Impl(hir::Impl {
2063             polarity: hir::ImplPolarity::Negative(span),
2064             of_trait,
2065             ..
2066         }) => {
2067             if is_rustc_reservation {
2068                 let span = span.to(of_trait.as_ref().map_or(*span, |t| t.path.span));
2069                 tcx.sess.span_err(span, "reservation impls can't be negative");
2070             }
2071             ty::ImplPolarity::Negative
2072         }
2073         hir::ItemKind::Impl(hir::Impl {
2074             polarity: hir::ImplPolarity::Positive,
2075             of_trait: None,
2076             ..
2077         }) => {
2078             if is_rustc_reservation {
2079                 tcx.sess.span_err(item.span, "reservation impls can't be inherent");
2080             }
2081             ty::ImplPolarity::Positive
2082         }
2083         hir::ItemKind::Impl(hir::Impl {
2084             polarity: hir::ImplPolarity::Positive,
2085             of_trait: Some(_),
2086             ..
2087         }) => {
2088             if is_rustc_reservation {
2089                 ty::ImplPolarity::Reservation
2090             } else {
2091                 ty::ImplPolarity::Positive
2092             }
2093         }
2094         item => bug!("impl_polarity: {:?} not an impl", item),
2095     }
2096 }
2097
2098 /// Returns the early-bound lifetimes declared in this generics
2099 /// listing. For anything other than fns/methods, this is just all
2100 /// the lifetimes that are declared. For fns or methods, we have to
2101 /// screen out those that do not appear in any where-clauses etc using
2102 /// `resolve_lifetime::early_bound_lifetimes`.
2103 fn early_bound_lifetimes_from_generics<'a, 'tcx: 'a>(
2104     tcx: TyCtxt<'tcx>,
2105     def_id: LocalDefId,
2106     generics: &'a hir::Generics<'a>,
2107 ) -> impl Iterator<Item = &'a hir::GenericParam<'a>> + Captures<'tcx> {
2108     let late_bound_map = if generics.params.is_empty() {
2109         // This function may be called on `def_id == CRATE_DEF_ID`,
2110         // which makes `is_late_bound_map` ICE.  Don't even try if there
2111         // is no generic parameter.
2112         None
2113     } else {
2114         tcx.is_late_bound_map(def_id)
2115     };
2116     let is_late_bound = move |hir_id| {
2117         let id = tcx.hir().local_def_id(hir_id);
2118         late_bound_map.map_or(false, |(_, set)| set.contains(&id))
2119     };
2120     generics.params.iter().filter(move |param| match param.kind {
2121         GenericParamKind::Lifetime { .. } => !is_late_bound(param.hir_id),
2122         _ => false,
2123     })
2124 }
2125
2126 /// Returns a list of type predicates for the definition with ID `def_id`, including inferred
2127 /// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus
2128 /// inferred constraints concerning which regions outlive other regions.
2129 fn predicates_defined_on(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2130     debug!("predicates_defined_on({:?})", def_id);
2131     let mut result = tcx.explicit_predicates_of(def_id);
2132     debug!("predicates_defined_on: explicit_predicates_of({:?}) = {:?}", def_id, result,);
2133     let inferred_outlives = tcx.inferred_outlives_of(def_id);
2134     if !inferred_outlives.is_empty() {
2135         debug!(
2136             "predicates_defined_on: inferred_outlives_of({:?}) = {:?}",
2137             def_id, inferred_outlives,
2138         );
2139         if result.predicates.is_empty() {
2140             result.predicates = inferred_outlives;
2141         } else {
2142             result.predicates = tcx
2143                 .arena
2144                 .alloc_from_iter(result.predicates.iter().chain(inferred_outlives).copied());
2145         }
2146     }
2147
2148     debug!("predicates_defined_on({:?}) = {:?}", def_id, result);
2149     result
2150 }
2151
2152 /// Returns a list of all type predicates (explicit and implicit) for the definition with
2153 /// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus
2154 /// `Self: Trait` predicates for traits.
2155 fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2156     let mut result = tcx.predicates_defined_on(def_id);
2157
2158     if tcx.is_trait(def_id) {
2159         // For traits, add `Self: Trait` predicate. This is
2160         // not part of the predicates that a user writes, but it
2161         // is something that one must prove in order to invoke a
2162         // method or project an associated type.
2163         //
2164         // In the chalk setup, this predicate is not part of the
2165         // "predicates" for a trait item. But it is useful in
2166         // rustc because if you directly (e.g.) invoke a trait
2167         // method like `Trait::method(...)`, you must naturally
2168         // prove that the trait applies to the types that were
2169         // used, and adding the predicate into this list ensures
2170         // that this is done.
2171         //
2172         // We use a DUMMY_SP here as a way to signal trait bounds that come
2173         // from the trait itself that *shouldn't* be shown as the source of
2174         // an obligation and instead be skipped. Otherwise we'd use
2175         // `tcx.def_span(def_id);`
2176         let span = rustc_span::DUMMY_SP;
2177         result.predicates =
2178             tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once((
2179                 ty::TraitRef::identity(tcx, def_id).without_const().to_predicate(tcx),
2180                 span,
2181             ))));
2182     }
2183     debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
2184     result
2185 }
2186
2187 /// Returns a list of user-specified type predicates for the definition with ID `def_id`.
2188 /// N.B., this does not include any implied/inferred constraints.
2189 fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2190     use rustc_hir::*;
2191
2192     debug!("explicit_predicates_of(def_id={:?})", def_id);
2193
2194     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2195     let node = tcx.hir().get(hir_id);
2196
2197     let mut is_trait = None;
2198     let mut is_default_impl_trait = None;
2199
2200     let icx = ItemCtxt::new(tcx, def_id);
2201
2202     const NO_GENERICS: &hir::Generics<'_> = hir::Generics::empty();
2203
2204     // We use an `IndexSet` to preserves order of insertion.
2205     // Preserving the order of insertion is important here so as not to break UI tests.
2206     let mut predicates: FxIndexSet<(ty::Predicate<'_>, Span)> = FxIndexSet::default();
2207
2208     let ast_generics = match node {
2209         Node::TraitItem(item) => item.generics,
2210
2211         Node::ImplItem(item) => item.generics,
2212
2213         Node::Item(item) => {
2214             match item.kind {
2215                 ItemKind::Impl(ref impl_) => {
2216                     if impl_.defaultness.is_default() {
2217                         is_default_impl_trait = tcx.impl_trait_ref(def_id).map(ty::Binder::dummy);
2218                     }
2219                     &impl_.generics
2220                 }
2221                 ItemKind::Fn(.., ref generics, _)
2222                 | ItemKind::TyAlias(_, ref generics)
2223                 | ItemKind::Enum(_, ref generics)
2224                 | ItemKind::Struct(_, ref generics)
2225                 | ItemKind::Union(_, ref generics) => *generics,
2226
2227                 ItemKind::Trait(_, _, ref generics, ..) => {
2228                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2229                     *generics
2230                 }
2231                 ItemKind::TraitAlias(ref generics, _) => {
2232                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2233                     *generics
2234                 }
2235                 ItemKind::OpaqueTy(OpaqueTy {
2236                     origin: hir::OpaqueTyOrigin::AsyncFn(..) | hir::OpaqueTyOrigin::FnReturn(..),
2237                     ..
2238                 }) => {
2239                     // return-position impl trait
2240                     //
2241                     // We don't inherit predicates from the parent here:
2242                     // If we have, say `fn f<'a, T: 'a>() -> impl Sized {}`
2243                     // then the return type is `f::<'static, T>::{{opaque}}`.
2244                     //
2245                     // If we inherited the predicates of `f` then we would
2246                     // require that `T: 'static` to show that the return
2247                     // type is well-formed.
2248                     //
2249                     // The only way to have something with this opaque type
2250                     // is from the return type of the containing function,
2251                     // which will ensure that the function's predicates
2252                     // hold.
2253                     return ty::GenericPredicates { parent: None, predicates: &[] };
2254                 }
2255                 ItemKind::OpaqueTy(OpaqueTy {
2256                     ref generics,
2257                     origin: hir::OpaqueTyOrigin::TyAlias,
2258                     ..
2259                 }) => {
2260                     // type-alias impl trait
2261                     generics
2262                 }
2263
2264                 _ => NO_GENERICS,
2265             }
2266         }
2267
2268         Node::ForeignItem(item) => match item.kind {
2269             ForeignItemKind::Static(..) => NO_GENERICS,
2270             ForeignItemKind::Fn(_, _, ref generics) => *generics,
2271             ForeignItemKind::Type => NO_GENERICS,
2272         },
2273
2274         _ => NO_GENERICS,
2275     };
2276
2277     let generics = tcx.generics_of(def_id);
2278     let parent_count = generics.parent_count as u32;
2279     let has_own_self = generics.has_self && parent_count == 0;
2280
2281     // Below we'll consider the bounds on the type parameters (including `Self`)
2282     // and the explicit where-clauses, but to get the full set of predicates
2283     // on a trait we need to add in the supertrait bounds and bounds found on
2284     // associated types.
2285     if let Some(_trait_ref) = is_trait {
2286         predicates.extend(tcx.super_predicates_of(def_id).predicates.iter().cloned());
2287     }
2288
2289     // In default impls, we can assume that the self type implements
2290     // the trait. So in:
2291     //
2292     //     default impl Foo for Bar { .. }
2293     //
2294     // we add a default where clause `Foo: Bar`. We do a similar thing for traits
2295     // (see below). Recall that a default impl is not itself an impl, but rather a
2296     // set of defaults that can be incorporated into another impl.
2297     if let Some(trait_ref) = is_default_impl_trait {
2298         predicates.insert((trait_ref.without_const().to_predicate(tcx), tcx.def_span(def_id)));
2299     }
2300
2301     // Collect the region predicates that were declared inline as
2302     // well. In the case of parameters declared on a fn or method, we
2303     // have to be careful to only iterate over early-bound regions.
2304     let mut index = parent_count + has_own_self as u32;
2305     for param in early_bound_lifetimes_from_generics(tcx, hir_id.owner, ast_generics) {
2306         let region = tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
2307             def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
2308             index,
2309             name: param.name.ident().name,
2310         }));
2311         index += 1;
2312
2313         match param.kind {
2314             GenericParamKind::Lifetime { .. } => {
2315                 param.bounds.iter().for_each(|bound| match bound {
2316                     hir::GenericBound::Outlives(lt) => {
2317                         let bound = <dyn AstConv<'_>>::ast_region_to_region(&icx, lt, None);
2318                         let outlives = ty::Binder::dummy(ty::OutlivesPredicate(region, bound));
2319                         predicates.insert((outlives.to_predicate(tcx), lt.span));
2320                     }
2321                     _ => bug!(),
2322                 });
2323             }
2324             _ => bug!(),
2325         }
2326     }
2327
2328     // Collect the predicates that were written inline by the user on each
2329     // type parameter (e.g., `<T: Foo>`).
2330     for param in ast_generics.params {
2331         match param.kind {
2332             // We already dealt with early bound lifetimes above.
2333             GenericParamKind::Lifetime { .. } => (),
2334             GenericParamKind::Type { .. } => {
2335                 let name = param.name.ident().name;
2336                 let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
2337                 index += 1;
2338
2339                 let mut bounds = <dyn AstConv<'_>>::compute_bounds(&icx, param_ty, param.bounds);
2340                 // Params are implicitly sized unless a `?Sized` bound is found
2341                 <dyn AstConv<'_>>::add_implicitly_sized(
2342                     &icx,
2343                     &mut bounds,
2344                     param.bounds,
2345                     Some((param.hir_id, ast_generics.predicates)),
2346                     param.span,
2347                 );
2348                 predicates.extend(bounds.predicates(tcx, param_ty));
2349             }
2350             GenericParamKind::Const { .. } => {
2351                 // Bounds on const parameters are currently not possible.
2352                 debug_assert!(param.bounds.is_empty());
2353                 index += 1;
2354             }
2355         }
2356     }
2357
2358     // Add in the bounds that appear in the where-clause.
2359     for predicate in ast_generics.predicates {
2360         match predicate {
2361             hir::WherePredicate::BoundPredicate(bound_pred) => {
2362                 let ty = icx.to_ty(bound_pred.bounded_ty);
2363                 let bound_vars = icx.tcx.late_bound_vars(bound_pred.bounded_ty.hir_id);
2364
2365                 // Keep the type around in a dummy predicate, in case of no bounds.
2366                 // That way, `where Ty:` is not a complete noop (see #53696) and `Ty`
2367                 // is still checked for WF.
2368                 if bound_pred.bounds.is_empty() {
2369                     if let ty::Param(_) = ty.kind() {
2370                         // This is a `where T:`, which can be in the HIR from the
2371                         // transformation that moves `?Sized` to `T`'s declaration.
2372                         // We can skip the predicate because type parameters are
2373                         // trivially WF, but also we *should*, to avoid exposing
2374                         // users who never wrote `where Type:,` themselves, to
2375                         // compiler/tooling bugs from not handling WF predicates.
2376                     } else {
2377                         let span = bound_pred.bounded_ty.span;
2378                         let re_root_empty = tcx.lifetimes.re_root_empty;
2379                         let predicate = ty::Binder::bind_with_vars(
2380                             ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(
2381                                 ty,
2382                                 re_root_empty,
2383                             )),
2384                             bound_vars,
2385                         );
2386                         predicates.insert((predicate.to_predicate(tcx), span));
2387                     }
2388                 }
2389
2390                 let mut bounds = Bounds::default();
2391                 <dyn AstConv<'_>>::add_bounds(
2392                     &icx,
2393                     ty,
2394                     bound_pred.bounds.iter(),
2395                     &mut bounds,
2396                     bound_vars,
2397                 );
2398                 predicates.extend(bounds.predicates(tcx, ty));
2399             }
2400
2401             hir::WherePredicate::RegionPredicate(region_pred) => {
2402                 let r1 = <dyn AstConv<'_>>::ast_region_to_region(&icx, &region_pred.lifetime, None);
2403                 predicates.extend(region_pred.bounds.iter().map(|bound| {
2404                     let (r2, span) = match bound {
2405                         hir::GenericBound::Outlives(lt) => {
2406                             (<dyn AstConv<'_>>::ast_region_to_region(&icx, lt, None), lt.span)
2407                         }
2408                         _ => bug!(),
2409                     };
2410                     let pred = ty::Binder::dummy(ty::PredicateKind::RegionOutlives(
2411                         ty::OutlivesPredicate(r1, r2),
2412                     ))
2413                     .to_predicate(icx.tcx);
2414
2415                     (pred, span)
2416                 }))
2417             }
2418
2419             hir::WherePredicate::EqPredicate(..) => {
2420                 // FIXME(#20041)
2421             }
2422         }
2423     }
2424
2425     if tcx.features().generic_const_exprs {
2426         predicates.extend(const_evaluatable_predicates_of(tcx, def_id.expect_local()));
2427     }
2428
2429     let mut predicates: Vec<_> = predicates.into_iter().collect();
2430
2431     // Subtle: before we store the predicates into the tcx, we
2432     // sort them so that predicates like `T: Foo<Item=U>` come
2433     // before uses of `U`.  This avoids false ambiguity errors
2434     // in trait checking. See `setup_constraining_predicates`
2435     // for details.
2436     if let Node::Item(&Item { kind: ItemKind::Impl { .. }, .. }) = node {
2437         let self_ty = tcx.type_of(def_id);
2438         let trait_ref = tcx.impl_trait_ref(def_id);
2439         cgp::setup_constraining_predicates(
2440             tcx,
2441             &mut predicates,
2442             trait_ref,
2443             &mut cgp::parameters_for_impl(self_ty, trait_ref),
2444         );
2445     }
2446
2447     let result = ty::GenericPredicates {
2448         parent: generics.parent,
2449         predicates: tcx.arena.alloc_from_iter(predicates),
2450     };
2451     debug!("explicit_predicates_of(def_id={:?}) = {:?}", def_id, result);
2452     result
2453 }
2454
2455 fn const_evaluatable_predicates_of<'tcx>(
2456     tcx: TyCtxt<'tcx>,
2457     def_id: LocalDefId,
2458 ) -> FxIndexSet<(ty::Predicate<'tcx>, Span)> {
2459     struct ConstCollector<'tcx> {
2460         tcx: TyCtxt<'tcx>,
2461         preds: FxIndexSet<(ty::Predicate<'tcx>, Span)>,
2462     }
2463
2464     impl<'tcx> intravisit::Visitor<'tcx> for ConstCollector<'tcx> {
2465         fn visit_anon_const(&mut self, c: &'tcx hir::AnonConst) {
2466             let def_id = self.tcx.hir().local_def_id(c.hir_id);
2467             let ct = ty::Const::from_anon_const(self.tcx, def_id);
2468             if let ty::ConstKind::Unevaluated(uv) = ct.val() {
2469                 assert_eq!(uv.promoted, None);
2470                 let span = self.tcx.hir().span(c.hir_id);
2471                 self.preds.insert((
2472                     ty::Binder::dummy(ty::PredicateKind::ConstEvaluatable(uv.shrink()))
2473                         .to_predicate(self.tcx),
2474                     span,
2475                 ));
2476             }
2477         }
2478
2479         fn visit_const_param_default(&mut self, _param: HirId, _ct: &'tcx hir::AnonConst) {
2480             // Do not look into const param defaults,
2481             // these get checked when they are actually instantiated.
2482             //
2483             // We do not want the following to error:
2484             //
2485             //     struct Foo<const N: usize, const M: usize = { N + 1 }>;
2486             //     struct Bar<const N: usize>(Foo<N, 3>);
2487         }
2488     }
2489
2490     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
2491     let node = tcx.hir().get(hir_id);
2492
2493     let mut collector = ConstCollector { tcx, preds: FxIndexSet::default() };
2494     if let hir::Node::Item(item) = node && let hir::ItemKind::Impl(ref impl_) = item.kind {
2495         if let Some(of_trait) = &impl_.of_trait {
2496             debug!("const_evaluatable_predicates_of({:?}): visit impl trait_ref", def_id);
2497             collector.visit_trait_ref(of_trait);
2498         }
2499
2500         debug!("const_evaluatable_predicates_of({:?}): visit_self_ty", def_id);
2501         collector.visit_ty(impl_.self_ty);
2502     }
2503
2504     if let Some(generics) = node.generics() {
2505         debug!("const_evaluatable_predicates_of({:?}): visit_generics", def_id);
2506         collector.visit_generics(generics);
2507     }
2508
2509     if let Some(fn_sig) = tcx.hir().fn_sig_by_hir_id(hir_id) {
2510         debug!("const_evaluatable_predicates_of({:?}): visit_fn_decl", def_id);
2511         collector.visit_fn_decl(fn_sig.decl);
2512     }
2513     debug!("const_evaluatable_predicates_of({:?}) = {:?}", def_id, collector.preds);
2514
2515     collector.preds
2516 }
2517
2518 fn trait_explicit_predicates_and_bounds(
2519     tcx: TyCtxt<'_>,
2520     def_id: LocalDefId,
2521 ) -> ty::GenericPredicates<'_> {
2522     assert_eq!(tcx.def_kind(def_id), DefKind::Trait);
2523     gather_explicit_predicates_of(tcx, def_id.to_def_id())
2524 }
2525
2526 fn explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2527     let def_kind = tcx.def_kind(def_id);
2528     if let DefKind::Trait = def_kind {
2529         // Remove bounds on associated types from the predicates, they will be
2530         // returned by `explicit_item_bounds`.
2531         let predicates_and_bounds = tcx.trait_explicit_predicates_and_bounds(def_id.expect_local());
2532         let trait_identity_substs = InternalSubsts::identity_for_item(tcx, def_id);
2533
2534         let is_assoc_item_ty = |ty: Ty<'_>| {
2535             // For a predicate from a where clause to become a bound on an
2536             // associated type:
2537             // * It must use the identity substs of the item.
2538             //     * Since any generic parameters on the item are not in scope,
2539             //       this means that the item is not a GAT, and its identity
2540             //       substs are the same as the trait's.
2541             // * It must be an associated type for this trait (*not* a
2542             //   supertrait).
2543             if let ty::Projection(projection) = ty.kind() {
2544                 projection.substs == trait_identity_substs
2545                     && tcx.associated_item(projection.item_def_id).container.id() == def_id
2546             } else {
2547                 false
2548             }
2549         };
2550
2551         let predicates: Vec<_> = predicates_and_bounds
2552             .predicates
2553             .iter()
2554             .copied()
2555             .filter(|(pred, _)| match pred.kind().skip_binder() {
2556                 ty::PredicateKind::Trait(tr) => !is_assoc_item_ty(tr.self_ty()),
2557                 ty::PredicateKind::Projection(proj) => {
2558                     !is_assoc_item_ty(proj.projection_ty.self_ty())
2559                 }
2560                 ty::PredicateKind::TypeOutlives(outlives) => !is_assoc_item_ty(outlives.0),
2561                 _ => true,
2562             })
2563             .collect();
2564         if predicates.len() == predicates_and_bounds.predicates.len() {
2565             predicates_and_bounds
2566         } else {
2567             ty::GenericPredicates {
2568                 parent: predicates_and_bounds.parent,
2569                 predicates: tcx.arena.alloc_slice(&predicates),
2570             }
2571         }
2572     } else {
2573         if matches!(def_kind, DefKind::AnonConst) && tcx.lazy_normalization() {
2574             let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2575             if tcx.hir().opt_const_param_default_param_hir_id(hir_id).is_some() {
2576                 // In `generics_of` we set the generics' parent to be our parent's parent which means that
2577                 // we lose out on the predicates of our actual parent if we dont return those predicates here.
2578                 // (See comment in `generics_of` for more information on why the parent shenanigans is necessary)
2579                 //
2580                 // struct Foo<T, const N: usize = { <T as Trait>::ASSOC }>(T) where T: Trait;
2581                 //        ^^^                     ^^^^^^^^^^^^^^^^^^^^^^^ the def id we are calling
2582                 //        ^^^                                             explicit_predicates_of on
2583                 //        parent item we dont have set as the
2584                 //        parent of generics returned by `generics_of`
2585                 //
2586                 // In the above code we want the anon const to have predicates in its param env for `T: Trait`
2587                 let item_def_id = tcx.hir().get_parent_item(hir_id);
2588                 // In the above code example we would be calling `explicit_predicates_of(Foo)` here
2589                 return tcx.explicit_predicates_of(item_def_id);
2590             }
2591         }
2592         gather_explicit_predicates_of(tcx, def_id)
2593     }
2594 }
2595
2596 /// Converts a specific `GenericBound` from the AST into a set of
2597 /// predicates that apply to the self type. A vector is returned
2598 /// because this can be anywhere from zero predicates (`T: ?Sized` adds no
2599 /// predicates) to one (`T: Foo`) to many (`T: Bar<X = i32>` adds `T: Bar`
2600 /// and `<T as Bar>::X == i32`).
2601 fn predicates_from_bound<'tcx>(
2602     astconv: &dyn AstConv<'tcx>,
2603     param_ty: Ty<'tcx>,
2604     bound: &'tcx hir::GenericBound<'tcx>,
2605     bound_vars: &'tcx ty::List<ty::BoundVariableKind>,
2606 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2607     let mut bounds = Bounds::default();
2608     astconv.add_bounds(param_ty, [bound].into_iter(), &mut bounds, bound_vars);
2609     bounds.predicates(astconv.tcx(), param_ty).collect()
2610 }
2611
2612 fn compute_sig_of_foreign_fn_decl<'tcx>(
2613     tcx: TyCtxt<'tcx>,
2614     def_id: DefId,
2615     decl: &'tcx hir::FnDecl<'tcx>,
2616     abi: abi::Abi,
2617     ident: Ident,
2618 ) -> ty::PolyFnSig<'tcx> {
2619     let unsafety = if abi == abi::Abi::RustIntrinsic {
2620         intrinsic_operation_unsafety(tcx.item_name(def_id))
2621     } else {
2622         hir::Unsafety::Unsafe
2623     };
2624     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2625     let fty = <dyn AstConv<'_>>::ty_of_fn(
2626         &ItemCtxt::new(tcx, def_id),
2627         hir_id,
2628         unsafety,
2629         abi,
2630         decl,
2631         &hir::Generics::empty(),
2632         Some(ident.span),
2633         None,
2634     );
2635
2636     // Feature gate SIMD types in FFI, since I am not sure that the
2637     // ABIs are handled at all correctly. -huonw
2638     if abi != abi::Abi::RustIntrinsic
2639         && abi != abi::Abi::PlatformIntrinsic
2640         && !tcx.features().simd_ffi
2641     {
2642         let check = |ast_ty: &hir::Ty<'_>, ty: Ty<'_>| {
2643             if ty.is_simd() {
2644                 let snip = tcx
2645                     .sess
2646                     .source_map()
2647                     .span_to_snippet(ast_ty.span)
2648                     .map_or_else(|_| String::new(), |s| format!(" `{}`", s));
2649                 tcx.sess
2650                     .struct_span_err(
2651                         ast_ty.span,
2652                         &format!(
2653                             "use of SIMD type{} in FFI is highly experimental and \
2654                              may result in invalid code",
2655                             snip
2656                         ),
2657                     )
2658                     .help("add `#![feature(simd_ffi)]` to the crate attributes to enable")
2659                     .emit();
2660             }
2661         };
2662         for (input, ty) in iter::zip(decl.inputs, fty.inputs().skip_binder()) {
2663             check(input, *ty)
2664         }
2665         if let hir::FnRetTy::Return(ref ty) = decl.output {
2666             check(ty, fty.output().skip_binder())
2667         }
2668     }
2669
2670     fty
2671 }
2672
2673 fn is_foreign_item(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2674     match tcx.hir().get_if_local(def_id) {
2675         Some(Node::ForeignItem(..)) => true,
2676         Some(_) => false,
2677         _ => bug!("is_foreign_item applied to non-local def-id {:?}", def_id),
2678     }
2679 }
2680
2681 fn generator_kind(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::GeneratorKind> {
2682     match tcx.hir().get_if_local(def_id) {
2683         Some(Node::Expr(&rustc_hir::Expr {
2684             kind: rustc_hir::ExprKind::Closure(_, _, body_id, _, _),
2685             ..
2686         })) => tcx.hir().body(body_id).generator_kind(),
2687         Some(_) => None,
2688         _ => bug!("generator_kind applied to non-local def-id {:?}", def_id),
2689     }
2690 }
2691
2692 fn from_target_feature(
2693     tcx: TyCtxt<'_>,
2694     id: DefId,
2695     attr: &ast::Attribute,
2696     supported_target_features: &FxHashMap<String, Option<Symbol>>,
2697     target_features: &mut Vec<Symbol>,
2698 ) {
2699     let Some(list) = attr.meta_item_list() else { return };
2700     let bad_item = |span| {
2701         let msg = "malformed `target_feature` attribute input";
2702         let code = "enable = \"..\"".to_owned();
2703         tcx.sess
2704             .struct_span_err(span, msg)
2705             .span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
2706             .emit();
2707     };
2708     let rust_features = tcx.features();
2709     for item in list {
2710         // Only `enable = ...` is accepted in the meta-item list.
2711         if !item.has_name(sym::enable) {
2712             bad_item(item.span());
2713             continue;
2714         }
2715
2716         // Must be of the form `enable = "..."` (a string).
2717         let Some(value) = item.value_str() else {
2718             bad_item(item.span());
2719             continue;
2720         };
2721
2722         // We allow comma separation to enable multiple features.
2723         target_features.extend(value.as_str().split(',').filter_map(|feature| {
2724             let Some(feature_gate) = supported_target_features.get(feature) else {
2725                 let msg =
2726                     format!("the feature named `{}` is not valid for this target", feature);
2727                 let mut err = tcx.sess.struct_span_err(item.span(), &msg);
2728                 err.span_label(
2729                     item.span(),
2730                     format!("`{}` is not valid for this target", feature),
2731                 );
2732                 if let Some(stripped) = feature.strip_prefix('+') {
2733                     let valid = supported_target_features.contains_key(stripped);
2734                     if valid {
2735                         err.help("consider removing the leading `+` in the feature name");
2736                     }
2737                 }
2738                 err.emit();
2739                 return None;
2740             };
2741
2742             // Only allow features whose feature gates have been enabled.
2743             let allowed = match feature_gate.as_ref().copied() {
2744                 Some(sym::arm_target_feature) => rust_features.arm_target_feature,
2745                 Some(sym::hexagon_target_feature) => rust_features.hexagon_target_feature,
2746                 Some(sym::powerpc_target_feature) => rust_features.powerpc_target_feature,
2747                 Some(sym::mips_target_feature) => rust_features.mips_target_feature,
2748                 Some(sym::riscv_target_feature) => rust_features.riscv_target_feature,
2749                 Some(sym::avx512_target_feature) => rust_features.avx512_target_feature,
2750                 Some(sym::sse4a_target_feature) => rust_features.sse4a_target_feature,
2751                 Some(sym::tbm_target_feature) => rust_features.tbm_target_feature,
2752                 Some(sym::wasm_target_feature) => rust_features.wasm_target_feature,
2753                 Some(sym::cmpxchg16b_target_feature) => rust_features.cmpxchg16b_target_feature,
2754                 Some(sym::movbe_target_feature) => rust_features.movbe_target_feature,
2755                 Some(sym::rtm_target_feature) => rust_features.rtm_target_feature,
2756                 Some(sym::f16c_target_feature) => rust_features.f16c_target_feature,
2757                 Some(sym::ermsb_target_feature) => rust_features.ermsb_target_feature,
2758                 Some(sym::bpf_target_feature) => rust_features.bpf_target_feature,
2759                 Some(sym::aarch64_ver_target_feature) => rust_features.aarch64_ver_target_feature,
2760                 Some(name) => bug!("unknown target feature gate {}", name),
2761                 None => true,
2762             };
2763             if !allowed && id.is_local() {
2764                 feature_err(
2765                     &tcx.sess.parse_sess,
2766                     feature_gate.unwrap(),
2767                     item.span(),
2768                     &format!("the target feature `{}` is currently unstable", feature),
2769                 )
2770                 .emit();
2771             }
2772             Some(Symbol::intern(feature))
2773         }));
2774     }
2775 }
2776
2777 fn linkage_by_name(tcx: TyCtxt<'_>, def_id: DefId, name: &str) -> Linkage {
2778     use rustc_middle::mir::mono::Linkage::*;
2779
2780     // Use the names from src/llvm/docs/LangRef.rst here. Most types are only
2781     // applicable to variable declarations and may not really make sense for
2782     // Rust code in the first place but allow them anyway and trust that the
2783     // user knows what they're doing. Who knows, unanticipated use cases may pop
2784     // up in the future.
2785     //
2786     // ghost, dllimport, dllexport and linkonce_odr_autohide are not supported
2787     // and don't have to be, LLVM treats them as no-ops.
2788     match name {
2789         "appending" => Appending,
2790         "available_externally" => AvailableExternally,
2791         "common" => Common,
2792         "extern_weak" => ExternalWeak,
2793         "external" => External,
2794         "internal" => Internal,
2795         "linkonce" => LinkOnceAny,
2796         "linkonce_odr" => LinkOnceODR,
2797         "private" => Private,
2798         "weak" => WeakAny,
2799         "weak_odr" => WeakODR,
2800         _ => {
2801             let span = tcx.hir().span_if_local(def_id);
2802             if let Some(span) = span {
2803                 tcx.sess.span_fatal(span, "invalid linkage specified")
2804             } else {
2805                 tcx.sess.fatal(&format!("invalid linkage specified: {}", name))
2806             }
2807         }
2808     }
2809 }
2810
2811 fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
2812     let attrs = tcx.get_attrs(id);
2813
2814     let mut codegen_fn_attrs = CodegenFnAttrs::new();
2815     if tcx.should_inherit_track_caller(id) {
2816         codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2817     }
2818
2819     // With -Z panic-in-drop=abort, drop_in_place never unwinds.
2820     if tcx.sess.opts.debugging_opts.panic_in_drop == PanicStrategy::Abort {
2821         if Some(id) == tcx.lang_items().drop_in_place_fn() {
2822             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2823         }
2824     }
2825
2826     // The panic_no_unwind function called by TerminatorKind::Abort will never
2827     // unwind. If the panic handler that it invokes unwind then it will simply
2828     // call the panic handler again.
2829     if Some(id) == tcx.lang_items().panic_no_unwind() {
2830         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2831     }
2832
2833     let supported_target_features = tcx.supported_target_features(LOCAL_CRATE);
2834
2835     let mut inline_span = None;
2836     let mut link_ordinal_span = None;
2837     let mut no_sanitize_span = None;
2838     for attr in attrs.iter() {
2839         if attr.has_name(sym::cold) {
2840             codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD;
2841         } else if attr.has_name(sym::rustc_allocator) {
2842             codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR;
2843         } else if attr.has_name(sym::ffi_returns_twice) {
2844             if tcx.is_foreign_item(id) {
2845                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE;
2846             } else {
2847                 // `#[ffi_returns_twice]` is only allowed `extern fn`s.
2848                 struct_span_err!(
2849                     tcx.sess,
2850                     attr.span,
2851                     E0724,
2852                     "`#[ffi_returns_twice]` may only be used on foreign functions"
2853                 )
2854                 .emit();
2855             }
2856         } else if attr.has_name(sym::ffi_pure) {
2857             if tcx.is_foreign_item(id) {
2858                 if attrs.iter().any(|a| a.has_name(sym::ffi_const)) {
2859                     // `#[ffi_const]` functions cannot be `#[ffi_pure]`
2860                     struct_span_err!(
2861                         tcx.sess,
2862                         attr.span,
2863                         E0757,
2864                         "`#[ffi_const]` function cannot be `#[ffi_pure]`"
2865                     )
2866                     .emit();
2867                 } else {
2868                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_PURE;
2869                 }
2870             } else {
2871                 // `#[ffi_pure]` is only allowed on foreign functions
2872                 struct_span_err!(
2873                     tcx.sess,
2874                     attr.span,
2875                     E0755,
2876                     "`#[ffi_pure]` may only be used on foreign functions"
2877                 )
2878                 .emit();
2879             }
2880         } else if attr.has_name(sym::ffi_const) {
2881             if tcx.is_foreign_item(id) {
2882                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_CONST;
2883             } else {
2884                 // `#[ffi_const]` is only allowed on foreign functions
2885                 struct_span_err!(
2886                     tcx.sess,
2887                     attr.span,
2888                     E0756,
2889                     "`#[ffi_const]` may only be used on foreign functions"
2890                 )
2891                 .emit();
2892             }
2893         } else if attr.has_name(sym::rustc_allocator_nounwind) {
2894             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2895         } else if attr.has_name(sym::naked) {
2896             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
2897         } else if attr.has_name(sym::no_mangle) {
2898             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2899         } else if attr.has_name(sym::no_coverage) {
2900             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_COVERAGE;
2901         } else if attr.has_name(sym::rustc_std_internal_symbol) {
2902             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2903         } else if attr.has_name(sym::used) {
2904             let inner = attr.meta_item_list();
2905             match inner.as_deref() {
2906                 Some([item]) if item.has_name(sym::linker) => {
2907                     if !tcx.features().used_with_arg {
2908                         feature_err(
2909                             &tcx.sess.parse_sess,
2910                             sym::used_with_arg,
2911                             attr.span,
2912                             "`#[used(linker)]` is currently unstable",
2913                         )
2914                         .emit();
2915                     }
2916                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED_LINKER;
2917                 }
2918                 Some([item]) if item.has_name(sym::compiler) => {
2919                     if !tcx.features().used_with_arg {
2920                         feature_err(
2921                             &tcx.sess.parse_sess,
2922                             sym::used_with_arg,
2923                             attr.span,
2924                             "`#[used(compiler)]` is currently unstable",
2925                         )
2926                         .emit();
2927                     }
2928                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
2929                 }
2930                 Some(_) => {
2931                     tcx.sess
2932                         .struct_span_err(
2933                             attr.span,
2934                             "expected `used`, `used(compiler)` or `used(linker)`",
2935                         )
2936                         .emit();
2937                 }
2938                 None => codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED,
2939             }
2940         } else if attr.has_name(sym::cmse_nonsecure_entry) {
2941             if !matches!(tcx.fn_sig(id).abi(), abi::Abi::C { .. }) {
2942                 struct_span_err!(
2943                     tcx.sess,
2944                     attr.span,
2945                     E0776,
2946                     "`#[cmse_nonsecure_entry]` requires C ABI"
2947                 )
2948                 .emit();
2949             }
2950             if !tcx.sess.target.llvm_target.contains("thumbv8m") {
2951                 struct_span_err!(tcx.sess, attr.span, E0775, "`#[cmse_nonsecure_entry]` is only valid for targets with the TrustZone-M extension")
2952                     .emit();
2953             }
2954             codegen_fn_attrs.flags |= CodegenFnAttrFlags::CMSE_NONSECURE_ENTRY;
2955         } else if attr.has_name(sym::thread_local) {
2956             codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
2957         } else if attr.has_name(sym::track_caller) {
2958             if !tcx.is_closure(id) && tcx.fn_sig(id).abi() != abi::Abi::Rust {
2959                 struct_span_err!(tcx.sess, attr.span, E0737, "`#[track_caller]` requires Rust ABI")
2960                     .emit();
2961             }
2962             if tcx.is_closure(id) && !tcx.features().closure_track_caller {
2963                 feature_err(
2964                     &tcx.sess.parse_sess,
2965                     sym::closure_track_caller,
2966                     attr.span,
2967                     "`#[track_caller]` on closures is currently unstable",
2968                 )
2969                 .emit();
2970             }
2971             codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2972         } else if attr.has_name(sym::export_name) {
2973             if let Some(s) = attr.value_str() {
2974                 if s.as_str().contains('\0') {
2975                     // `#[export_name = ...]` will be converted to a null-terminated string,
2976                     // so it may not contain any null characters.
2977                     struct_span_err!(
2978                         tcx.sess,
2979                         attr.span,
2980                         E0648,
2981                         "`export_name` may not contain null characters"
2982                     )
2983                     .emit();
2984                 }
2985                 codegen_fn_attrs.export_name = Some(s);
2986             }
2987         } else if attr.has_name(sym::target_feature) {
2988             if !tcx.is_closure(id) && tcx.fn_sig(id).unsafety() == hir::Unsafety::Normal {
2989                 if tcx.sess.target.is_like_wasm || tcx.sess.opts.actually_rustdoc {
2990                     // The `#[target_feature]` attribute is allowed on
2991                     // WebAssembly targets on all functions, including safe
2992                     // ones. Other targets require that `#[target_feature]` is
2993                     // only applied to unsafe functions (pending the
2994                     // `target_feature_11` feature) because on most targets
2995                     // execution of instructions that are not supported is
2996                     // considered undefined behavior. For WebAssembly which is a
2997                     // 100% safe target at execution time it's not possible to
2998                     // execute undefined instructions, and even if a future
2999                     // feature was added in some form for this it would be a
3000                     // deterministic trap. There is no undefined behavior when
3001                     // executing WebAssembly so `#[target_feature]` is allowed
3002                     // on safe functions (but again, only for WebAssembly)
3003                     //
3004                     // Note that this is also allowed if `actually_rustdoc` so
3005                     // if a target is documenting some wasm-specific code then
3006                     // it's not spuriously denied.
3007                 } else if !tcx.features().target_feature_11 {
3008                     let mut err = feature_err(
3009                         &tcx.sess.parse_sess,
3010                         sym::target_feature_11,
3011                         attr.span,
3012                         "`#[target_feature(..)]` can only be applied to `unsafe` functions",
3013                     );
3014                     err.span_label(tcx.def_span(id), "not an `unsafe` function");
3015                     err.emit();
3016                 } else if let Some(local_id) = id.as_local() {
3017                     check_target_feature_trait_unsafe(tcx, local_id, attr.span);
3018                 }
3019             }
3020             from_target_feature(
3021                 tcx,
3022                 id,
3023                 attr,
3024                 supported_target_features,
3025                 &mut codegen_fn_attrs.target_features,
3026             );
3027         } else if attr.has_name(sym::linkage) {
3028             if let Some(val) = attr.value_str() {
3029                 codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, id, val.as_str()));
3030             }
3031         } else if attr.has_name(sym::link_section) {
3032             if let Some(val) = attr.value_str() {
3033                 if val.as_str().bytes().any(|b| b == 0) {
3034                     let msg = format!(
3035                         "illegal null byte in link_section \
3036                          value: `{}`",
3037                         &val
3038                     );
3039                     tcx.sess.span_err(attr.span, &msg);
3040                 } else {
3041                     codegen_fn_attrs.link_section = Some(val);
3042                 }
3043             }
3044         } else if attr.has_name(sym::link_name) {
3045             codegen_fn_attrs.link_name = attr.value_str();
3046         } else if attr.has_name(sym::link_ordinal) {
3047             link_ordinal_span = Some(attr.span);
3048             if let ordinal @ Some(_) = check_link_ordinal(tcx, attr) {
3049                 codegen_fn_attrs.link_ordinal = ordinal;
3050             }
3051         } else if attr.has_name(sym::no_sanitize) {
3052             no_sanitize_span = Some(attr.span);
3053             if let Some(list) = attr.meta_item_list() {
3054                 for item in list.iter() {
3055                     if item.has_name(sym::address) {
3056                         codegen_fn_attrs.no_sanitize |= SanitizerSet::ADDRESS;
3057                     } else if item.has_name(sym::cfi) {
3058                         codegen_fn_attrs.no_sanitize |= SanitizerSet::CFI;
3059                     } else if item.has_name(sym::memory) {
3060                         codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMORY;
3061                     } else if item.has_name(sym::memtag) {
3062                         codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMTAG;
3063                     } else if item.has_name(sym::thread) {
3064                         codegen_fn_attrs.no_sanitize |= SanitizerSet::THREAD;
3065                     } else if item.has_name(sym::hwaddress) {
3066                         codegen_fn_attrs.no_sanitize |= SanitizerSet::HWADDRESS;
3067                     } else {
3068                         tcx.sess
3069                             .struct_span_err(item.span(), "invalid argument for `no_sanitize`")
3070                             .note("expected one of: `address`, `cfi`, `hwaddress`, `memory`, `memtag`, or `thread`")
3071                             .emit();
3072                     }
3073                 }
3074             }
3075         } else if attr.has_name(sym::instruction_set) {
3076             codegen_fn_attrs.instruction_set = match attr.meta_kind() {
3077                 Some(MetaItemKind::List(ref items)) => match items.as_slice() {
3078                     [NestedMetaItem::MetaItem(set)] => {
3079                         let segments =
3080                             set.path.segments.iter().map(|x| x.ident.name).collect::<Vec<_>>();
3081                         match segments.as_slice() {
3082                             [sym::arm, sym::a32] | [sym::arm, sym::t32] => {
3083                                 if !tcx.sess.target.has_thumb_interworking {
3084                                     struct_span_err!(
3085                                         tcx.sess.diagnostic(),
3086                                         attr.span,
3087                                         E0779,
3088                                         "target does not support `#[instruction_set]`"
3089                                     )
3090                                     .emit();
3091                                     None
3092                                 } else if segments[1] == sym::a32 {
3093                                     Some(InstructionSetAttr::ArmA32)
3094                                 } else if segments[1] == sym::t32 {
3095                                     Some(InstructionSetAttr::ArmT32)
3096                                 } else {
3097                                     unreachable!()
3098                                 }
3099                             }
3100                             _ => {
3101                                 struct_span_err!(
3102                                     tcx.sess.diagnostic(),
3103                                     attr.span,
3104                                     E0779,
3105                                     "invalid instruction set specified",
3106                                 )
3107                                 .emit();
3108                                 None
3109                             }
3110                         }
3111                     }
3112                     [] => {
3113                         struct_span_err!(
3114                             tcx.sess.diagnostic(),
3115                             attr.span,
3116                             E0778,
3117                             "`#[instruction_set]` requires an argument"
3118                         )
3119                         .emit();
3120                         None
3121                     }
3122                     _ => {
3123                         struct_span_err!(
3124                             tcx.sess.diagnostic(),
3125                             attr.span,
3126                             E0779,
3127                             "cannot specify more than one instruction set"
3128                         )
3129                         .emit();
3130                         None
3131                     }
3132                 },
3133                 _ => {
3134                     struct_span_err!(
3135                         tcx.sess.diagnostic(),
3136                         attr.span,
3137                         E0778,
3138                         "must specify an instruction set"
3139                     )
3140                     .emit();
3141                     None
3142                 }
3143             };
3144         } else if attr.has_name(sym::repr) {
3145             codegen_fn_attrs.alignment = match attr.meta_item_list() {
3146                 Some(items) => match items.as_slice() {
3147                     [item] => match item.name_value_literal() {
3148                         Some((sym::align, literal)) => {
3149                             let alignment = rustc_attr::parse_alignment(&literal.kind);
3150
3151                             match alignment {
3152                                 Ok(align) => Some(align),
3153                                 Err(msg) => {
3154                                     struct_span_err!(
3155                                         tcx.sess.diagnostic(),
3156                                         attr.span,
3157                                         E0589,
3158                                         "invalid `repr(align)` attribute: {}",
3159                                         msg
3160                                     )
3161                                     .emit();
3162
3163                                     None
3164                                 }
3165                             }
3166                         }
3167                         _ => None,
3168                     },
3169                     [] => None,
3170                     _ => None,
3171                 },
3172                 None => None,
3173             };
3174         }
3175     }
3176
3177     codegen_fn_attrs.inline = attrs.iter().fold(InlineAttr::None, |ia, attr| {
3178         if !attr.has_name(sym::inline) {
3179             return ia;
3180         }
3181         match attr.meta_kind() {
3182             Some(MetaItemKind::Word) => InlineAttr::Hint,
3183             Some(MetaItemKind::List(ref items)) => {
3184                 inline_span = Some(attr.span);
3185                 if items.len() != 1 {
3186                     struct_span_err!(
3187                         tcx.sess.diagnostic(),
3188                         attr.span,
3189                         E0534,
3190                         "expected one argument"
3191                     )
3192                     .emit();
3193                     InlineAttr::None
3194                 } else if list_contains_name(&items, sym::always) {
3195                     InlineAttr::Always
3196                 } else if list_contains_name(&items, sym::never) {
3197                     InlineAttr::Never
3198                 } else {
3199                     struct_span_err!(
3200                         tcx.sess.diagnostic(),
3201                         items[0].span(),
3202                         E0535,
3203                         "invalid argument"
3204                     )
3205                     .emit();
3206
3207                     InlineAttr::None
3208                 }
3209             }
3210             Some(MetaItemKind::NameValue(_)) => ia,
3211             None => ia,
3212         }
3213     });
3214
3215     codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
3216         if !attr.has_name(sym::optimize) {
3217             return ia;
3218         }
3219         let err = |sp, s| struct_span_err!(tcx.sess.diagnostic(), sp, E0722, "{}", s).emit();
3220         match attr.meta_kind() {
3221             Some(MetaItemKind::Word) => {
3222                 err(attr.span, "expected one argument");
3223                 ia
3224             }
3225             Some(MetaItemKind::List(ref items)) => {
3226                 inline_span = Some(attr.span);
3227                 if items.len() != 1 {
3228                     err(attr.span, "expected one argument");
3229                     OptimizeAttr::None
3230                 } else if list_contains_name(&items, sym::size) {
3231                     OptimizeAttr::Size
3232                 } else if list_contains_name(&items, sym::speed) {
3233                     OptimizeAttr::Speed
3234                 } else {
3235                     err(items[0].span(), "invalid argument");
3236                     OptimizeAttr::None
3237                 }
3238             }
3239             Some(MetaItemKind::NameValue(_)) => ia,
3240             None => ia,
3241         }
3242     });
3243
3244     // #73631: closures inherit `#[target_feature]` annotations
3245     if tcx.features().target_feature_11 && tcx.is_closure(id) {
3246         let owner_id = tcx.parent(id).expect("closure should have a parent");
3247         codegen_fn_attrs
3248             .target_features
3249             .extend(tcx.codegen_fn_attrs(owner_id).target_features.iter().copied())
3250     }
3251
3252     // If a function uses #[target_feature] it can't be inlined into general
3253     // purpose functions as they wouldn't have the right target features
3254     // enabled. For that reason we also forbid #[inline(always)] as it can't be
3255     // respected.
3256     if !codegen_fn_attrs.target_features.is_empty() {
3257         if codegen_fn_attrs.inline == InlineAttr::Always {
3258             if let Some(span) = inline_span {
3259                 tcx.sess.span_err(
3260                     span,
3261                     "cannot use `#[inline(always)]` with \
3262                      `#[target_feature]`",
3263                 );
3264             }
3265         }
3266     }
3267
3268     if !codegen_fn_attrs.no_sanitize.is_empty() {
3269         if codegen_fn_attrs.inline == InlineAttr::Always {
3270             if let (Some(no_sanitize_span), Some(inline_span)) = (no_sanitize_span, inline_span) {
3271                 let hir_id = tcx.hir().local_def_id_to_hir_id(id.expect_local());
3272                 tcx.struct_span_lint_hir(
3273                     lint::builtin::INLINE_NO_SANITIZE,
3274                     hir_id,
3275                     no_sanitize_span,
3276                     |lint| {
3277                         lint.build("`no_sanitize` will have no effect after inlining")
3278                             .span_note(inline_span, "inlining requested here")
3279                             .emit();
3280                     },
3281                 )
3282             }
3283         }
3284     }
3285
3286     // Weak lang items have the same semantics as "std internal" symbols in the
3287     // sense that they're preserved through all our LTO passes and only
3288     // strippable by the linker.
3289     //
3290     // Additionally weak lang items have predetermined symbol names.
3291     if tcx.is_weak_lang_item(id) {
3292         codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
3293     }
3294     if let Some(name) = weak_lang_items::link_name(attrs) {
3295         codegen_fn_attrs.export_name = Some(name);
3296         codegen_fn_attrs.link_name = Some(name);
3297     }
3298     check_link_name_xor_ordinal(tcx, &codegen_fn_attrs, link_ordinal_span);
3299
3300     // Internal symbols to the standard library all have no_mangle semantics in
3301     // that they have defined symbol names present in the function name. This
3302     // also applies to weak symbols where they all have known symbol names.
3303     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
3304         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
3305     }
3306
3307     // Any linkage to LLVM intrinsics for now forcibly marks them all as never
3308     // unwinds since LLVM sometimes can't handle codegen which `invoke`s
3309     // intrinsic functions.
3310     if let Some(name) = &codegen_fn_attrs.link_name {
3311         if name.as_str().starts_with("llvm.") {
3312             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
3313         }
3314     }
3315
3316     codegen_fn_attrs
3317 }
3318
3319 /// Computes the set of target features used in a function for the purposes of
3320 /// inline assembly.
3321 fn asm_target_features<'tcx>(tcx: TyCtxt<'tcx>, id: DefId) -> &'tcx FxHashSet<Symbol> {
3322     let mut target_features = tcx.sess.target_features.clone();
3323     let attrs = tcx.codegen_fn_attrs(id);
3324     target_features.extend(&attrs.target_features);
3325     match attrs.instruction_set {
3326         None => {}
3327         Some(InstructionSetAttr::ArmA32) => {
3328             target_features.remove(&sym::thumb_mode);
3329         }
3330         Some(InstructionSetAttr::ArmT32) => {
3331             target_features.insert(sym::thumb_mode);
3332         }
3333     }
3334     tcx.arena.alloc(target_features)
3335 }
3336
3337 /// Checks if the provided DefId is a method in a trait impl for a trait which has track_caller
3338 /// applied to the method prototype.
3339 fn should_inherit_track_caller(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
3340     if let Some(impl_item) = tcx.opt_associated_item(def_id)
3341         && let ty::AssocItemContainer::ImplContainer(_) = impl_item.container
3342         && let Some(trait_item) = impl_item.trait_item_def_id
3343     {
3344         return tcx
3345             .codegen_fn_attrs(trait_item)
3346             .flags
3347             .intersects(CodegenFnAttrFlags::TRACK_CALLER);
3348     }
3349
3350     false
3351 }
3352
3353 fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<u16> {
3354     use rustc_ast::{Lit, LitIntType, LitKind};
3355     let meta_item_list = attr.meta_item_list();
3356     let meta_item_list: Option<&[ast::NestedMetaItem]> = meta_item_list.as_ref().map(Vec::as_ref);
3357     let sole_meta_list = match meta_item_list {
3358         Some([item]) => item.literal(),
3359         Some(_) => {
3360             tcx.sess
3361                 .struct_span_err(attr.span, "incorrect number of arguments to `#[link_ordinal]`")
3362                 .note("the attribute requires exactly one argument")
3363                 .emit();
3364             return None;
3365         }
3366         _ => None,
3367     };
3368     if let Some(Lit { kind: LitKind::Int(ordinal, LitIntType::Unsuffixed), .. }) = sole_meta_list {
3369         // According to the table at https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#import-header,
3370         // the ordinal must fit into 16 bits.  Similarly, the Ordinal field in COFFShortExport (defined
3371         // in llvm/include/llvm/Object/COFFImportFile.h), which we use to communicate import information
3372         // to LLVM for `#[link(kind = "raw-dylib"_])`, is also defined to be uint16_t.
3373         //
3374         // FIXME: should we allow an ordinal of 0?  The MSVC toolchain has inconsistent support for this:
3375         // both LINK.EXE and LIB.EXE signal errors and abort when given a .DEF file that specifies
3376         // a zero ordinal.  However, llvm-dlltool is perfectly happy to generate an import library
3377         // for such a .DEF file, and MSVC's LINK.EXE is also perfectly happy to consume an import
3378         // library produced by LLVM with an ordinal of 0, and it generates an .EXE.  (I don't know yet
3379         // if the resulting EXE runs, as I haven't yet built the necessary DLL -- see earlier comment
3380         // about LINK.EXE failing.)
3381         if *ordinal <= u16::MAX as u128 {
3382             Some(*ordinal as u16)
3383         } else {
3384             let msg = format!("ordinal value in `link_ordinal` is too large: `{}`", &ordinal);
3385             tcx.sess
3386                 .struct_span_err(attr.span, &msg)
3387                 .note("the value may not exceed `u16::MAX`")
3388                 .emit();
3389             None
3390         }
3391     } else {
3392         tcx.sess
3393             .struct_span_err(attr.span, "illegal ordinal format in `link_ordinal`")
3394             .note("an unsuffixed integer value, e.g., `1`, is expected")
3395             .emit();
3396         None
3397     }
3398 }
3399
3400 fn check_link_name_xor_ordinal(
3401     tcx: TyCtxt<'_>,
3402     codegen_fn_attrs: &CodegenFnAttrs,
3403     inline_span: Option<Span>,
3404 ) {
3405     if codegen_fn_attrs.link_name.is_none() || codegen_fn_attrs.link_ordinal.is_none() {
3406         return;
3407     }
3408     let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
3409     if let Some(span) = inline_span {
3410         tcx.sess.span_err(span, msg);
3411     } else {
3412         tcx.sess.err(msg);
3413     }
3414 }
3415
3416 /// Checks the function annotated with `#[target_feature]` is not a safe
3417 /// trait method implementation, reporting an error if it is.
3418 fn check_target_feature_trait_unsafe(tcx: TyCtxt<'_>, id: LocalDefId, attr_span: Span) {
3419     let hir_id = tcx.hir().local_def_id_to_hir_id(id);
3420     let node = tcx.hir().get(hir_id);
3421     if let Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }) = node {
3422         let parent_id = tcx.hir().get_parent_item(hir_id);
3423         let parent_item = tcx.hir().expect_item(parent_id);
3424         if let hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) = parent_item.kind {
3425             tcx.sess
3426                 .struct_span_err(
3427                     attr_span,
3428                     "`#[target_feature(..)]` cannot be applied to safe trait method",
3429                 )
3430                 .span_label(attr_span, "cannot be applied to safe trait method")
3431                 .span_label(tcx.def_span(id), "not an `unsafe` function")
3432                 .emit();
3433         }
3434     }
3435 }