compiler/rustc_typeck/src/collect.rs

   1 //! "Collection" is the process of determining the type and other external
   2 //! details of each item in Rust. Collection is specifically concerned
   3 //! with *inter-procedural* things -- for example, for a function
   4 //! definition, collection will figure out the type and signature of the
   5 //! function, but it will not visit the *body* of the function in any way,
   6 //! nor examine type annotations on local variables (that's the job of
   7 //! type *checking*).
   8 //!
   9 //! Collecting is ultimately defined by a bundle of queries that
  10 //! inquire after various facts about the items in the crate (e.g.,
  11 //! `type_of`, `generics_of`, `predicates_of`, etc). See the `provide` function
  12 //! for the full set.
  13 //!
  14 //! At present, however, we do run collection across all items in the
  15 //! crate as a kind of pass. This should eventually be factored away.
  16
  17 use crate::astconv::AstConv;
  18 use crate::bounds::Bounds;
  19 use crate::check::intrinsic::intrinsic_operation_unsafety;
  20 use crate::constrained_generic_params as cgp;
  21 use crate::errors;
  22 use crate::middle::resolve_lifetime as rl;
  23 use rustc_ast as ast;
  24 use rustc_ast::{MetaItemKind, NestedMetaItem};
  25 use rustc_attr::{list_contains_name, InlineAttr, InstructionSetAttr, OptimizeAttr};
  26 use rustc_data_structures::captures::Captures;
  27 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
  28 use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder, ErrorGuaranteed};
  29 use rustc_hir as hir;
  30 use rustc_hir::def::{CtorKind, DefKind};
  31 use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_ID, LOCAL_CRATE};
  32 use rustc_hir::intravisit::{self, Visitor};
  33 use rustc_hir::weak_lang_items;
  34 use rustc_hir::{GenericParamKind, HirId, Node};
  35 use rustc_middle::hir::nested_filter;
  36 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
  37 use rustc_middle::mir::mono::Linkage;
  38 use rustc_middle::ty::query::Providers;
  39 use rustc_middle::ty::subst::InternalSubsts;
  40 use rustc_middle::ty::util::Discr;
  41 use rustc_middle::ty::util::IntTypeExt;
  42 use rustc_middle::ty::{self, AdtKind, Const, DefIdTree, IsSuggestable, Ty, TyCtxt};
  43 use rustc_middle::ty::{ReprOptions, ToPredicate};
  44 use rustc_session::lint;
  45 use rustc_session::parse::feature_err;
  46 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  47 use rustc_span::{Span, DUMMY_SP};
  48 use rustc_target::spec::{abi, SanitizerSet};
  49 use rustc_trait_selection::traits::error_reporting::suggestions::NextTypeParamName;
  50 use std::iter;
  51
  52 mod item_bounds;
  53 mod type_of;
  54
  55 #[derive(Debug)]
  56 struct OnlySelfBounds(bool);
  57
  58 ///////////////////////////////////////////////////////////////////////////
  59 // Main entry point
  60
  61 fn collect_mod_item_types(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
  62     tcx.hir().visit_item_likes_in_module(module_def_id, &mut CollectItemTypesVisitor { tcx });
  63 }
  64
  65 pub fn provide(providers: &mut Providers) {
  66     *providers = Providers {
  67         opt_const_param_of: type_of::opt_const_param_of,
  68         type_of: type_of::type_of,
  69         item_bounds: item_bounds::item_bounds,
  70         explicit_item_bounds: item_bounds::explicit_item_bounds,
  71         generics_of,
  72         predicates_of,
  73         predicates_defined_on,
  74         explicit_predicates_of,
  75         super_predicates_of,
  76         super_predicates_that_define_assoc_type,
  77         trait_explicit_predicates_and_bounds,
  78         type_param_predicates,
  79         trait_def,
  80         adt_def,
  81         fn_sig,
  82         impl_trait_ref,
  83         impl_polarity,
  84         is_foreign_item,
  85         generator_kind,
  86         codegen_fn_attrs,
  87         asm_target_features,
  88         collect_mod_item_types,
  89         should_inherit_track_caller,
  90         ..*providers
  91     };
  92 }
  93
  94 ///////////////////////////////////////////////////////////////////////////
  95
  96 /// Context specific to some particular item. This is what implements
  97 /// [`AstConv`].
  98 ///
  99 /// # `ItemCtxt` vs `FnCtxt`
 100 ///
 101 /// `ItemCtxt` is primarily used to type-check item signatures and lower them
 102 /// from HIR to their [`ty::Ty`] representation, which is exposed using [`AstConv`].
 103 /// It's also used for the bodies of items like structs where the body (the fields)
 104 /// are just signatures.
 105 ///
 106 /// This is in contrast to [`FnCtxt`], which is used to type-check bodies of
 107 /// functions, closures, and `const`s -- anywhere that expressions and statements show up.
 108 ///
 109 /// An important thing to note is that `ItemCtxt` does no inference -- it has no [`InferCtxt`] --
 110 /// while `FnCtxt` does do inference.
 111 ///
 112 /// [`FnCtxt`]: crate::check::FnCtxt
 113 /// [`InferCtxt`]: rustc_infer::infer::InferCtxt
 114 ///
 115 /// # Trait predicates
 116 ///
 117 /// `ItemCtxt` has information about the predicates that are defined
 118 /// on the trait. Unfortunately, this predicate information is
 119 /// available in various different forms at various points in the
 120 /// process. So we can't just store a pointer to e.g., the AST or the
 121 /// parsed ty form, we have to be more flexible. To this end, the
 122 /// `ItemCtxt` is parameterized by a `DefId` that it uses to satisfy
 123 /// `get_type_parameter_bounds` requests, drawing the information from
 124 /// the AST (`hir::Generics`), recursively.
 125 pub struct ItemCtxt<'tcx> {
 126     tcx: TyCtxt<'tcx>,
 127     item_def_id: DefId,
 128 }
 129
 130 ///////////////////////////////////////////////////////////////////////////
 131
 132 #[derive(Default)]
 133 pub(crate) struct HirPlaceholderCollector(pub(crate) Vec<Span>);
 134
 135 impl<'v> Visitor<'v> for HirPlaceholderCollector {
 136     fn visit_ty(&mut self, t: &'v hir::Ty<'v>) {
 137         if let hir::TyKind::Infer = t.kind {
 138             self.0.push(t.span);
 139         }
 140         intravisit::walk_ty(self, t)
 141     }
 142     fn visit_generic_arg(&mut self, generic_arg: &'v hir::GenericArg<'v>) {
 143         match generic_arg {
 144             hir::GenericArg::Infer(inf) => {
 145                 self.0.push(inf.span);
 146                 intravisit::walk_inf(self, inf);
 147             }
 148             hir::GenericArg::Type(t) => self.visit_ty(t),
 149             _ => {}
 150         }
 151     }
 152     fn visit_array_length(&mut self, length: &'v hir::ArrayLen) {
 153         if let &hir::ArrayLen::Infer(_, span) = length {
 154             self.0.push(span);
 155         }
 156         intravisit::walk_array_len(self, length)
 157     }
 158 }
 159
 160 struct CollectItemTypesVisitor<'tcx> {
 161     tcx: TyCtxt<'tcx>,
 162 }
 163
 164 /// If there are any placeholder types (`_`), emit an error explaining that this is not allowed
 165 /// and suggest adding type parameters in the appropriate place, taking into consideration any and
 166 /// all already existing generic type parameters to avoid suggesting a name that is already in use.
 167 pub(crate) fn placeholder_type_error<'tcx>(
 168     tcx: TyCtxt<'tcx>,
 169     generics: Option<&hir::Generics<'_>>,
 170     placeholder_types: Vec<Span>,
 171     suggest: bool,
 172     hir_ty: Option<&hir::Ty<'_>>,
 173     kind: &'static str,
 174 ) {
 175     if placeholder_types.is_empty() {
 176         return;
 177     }
 178
 179     placeholder_type_error_diag(tcx, generics, placeholder_types, vec![], suggest, hir_ty, kind)
 180         .emit();
 181 }
 182
 183 pub(crate) fn placeholder_type_error_diag<'tcx>(
 184     tcx: TyCtxt<'tcx>,
 185     generics: Option<&hir::Generics<'_>>,
 186     placeholder_types: Vec<Span>,
 187     additional_spans: Vec<Span>,
 188     suggest: bool,
 189     hir_ty: Option<&hir::Ty<'_>>,
 190     kind: &'static str,
 191 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
 192     if placeholder_types.is_empty() {
 193         return bad_placeholder(tcx, additional_spans, kind);
 194     }
 195
 196     let params = generics.map(|g| g.params).unwrap_or_default();
 197     let type_name = params.next_type_param_name(None);
 198     let mut sugg: Vec<_> =
 199         placeholder_types.iter().map(|sp| (*sp, (*type_name).to_string())).collect();
 200
 201     if let Some(generics) = generics {
 202         if let Some(arg) = params.iter().find(|arg| {
 203             matches!(arg.name, hir::ParamName::Plain(Ident { name: kw::Underscore, .. }))
 204         }) {
 205             // Account for `_` already present in cases like `struct S<_>(_);` and suggest
 206             // `struct S<T>(T);` instead of `struct S<_, T>(T);`.
 207             sugg.push((arg.span, (*type_name).to_string()));
 208         } else if let Some(span) = generics.span_for_param_suggestion() {
 209             // Account for bounds, we want `fn foo<T: E, K>(_: K)` not `fn foo<T, K: E>(_: K)`.
 210             sugg.push((span, format!(", {}", type_name)));
 211         } else {
 212             sugg.push((generics.span, format!("<{}>", type_name)));
 213         }
 214     }
 215
 216     let mut err =
 217         bad_placeholder(tcx, placeholder_types.into_iter().chain(additional_spans).collect(), kind);
 218
 219     // Suggest, but only if it is not a function in const or static
 220     if suggest {
 221         let mut is_fn = false;
 222         let mut is_const_or_static = false;
 223
 224         if let Some(hir_ty) = hir_ty && let hir::TyKind::BareFn(_) = hir_ty.kind {
 225             is_fn = true;
 226
 227             // Check if parent is const or static
 228             let parent_id = tcx.hir().get_parent_node(hir_ty.hir_id);
 229             let parent_node = tcx.hir().get(parent_id);
 230
 231             is_const_or_static = matches!(
 232                 parent_node,
 233                 Node::Item(&hir::Item {
 234                     kind: hir::ItemKind::Const(..) | hir::ItemKind::Static(..),
 235                     ..
 236                 }) | Node::TraitItem(&hir::TraitItem {
 237                     kind: hir::TraitItemKind::Const(..),
 238                     ..
 239                 }) | Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Const(..), .. })
 240             );
 241         }
 242
 243         // if function is wrapped around a const or static,
 244         // then don't show the suggestion
 245         if !(is_fn && is_const_or_static) {
 246             err.multipart_suggestion(
 247                 "use type parameters instead",
 248                 sugg,
 249                 Applicability::HasPlaceholders,
 250             );
 251         }
 252     }
 253
 254     err
 255 }
 256
 257 fn reject_placeholder_type_signatures_in_item<'tcx>(
 258     tcx: TyCtxt<'tcx>,
 259     item: &'tcx hir::Item<'tcx>,
 260 ) {
 261     let (generics, suggest) = match &item.kind {
 262         hir::ItemKind::Union(_, generics)
 263         | hir::ItemKind::Enum(_, generics)
 264         | hir::ItemKind::TraitAlias(generics, _)
 265         | hir::ItemKind::Trait(_, _, generics, ..)
 266         | hir::ItemKind::Impl(hir::Impl { generics, .. })
 267         | hir::ItemKind::Struct(_, generics) => (generics, true),
 268         hir::ItemKind::OpaqueTy(hir::OpaqueTy { generics, .. })
 269         | hir::ItemKind::TyAlias(_, generics) => (generics, false),
 270         // `static`, `fn` and `const` are handled elsewhere to suggest appropriate type.
 271         _ => return,
 272     };
 273
 274     let mut visitor = HirPlaceholderCollector::default();
 275     visitor.visit_item(item);
 276
 277     placeholder_type_error(tcx, Some(generics), visitor.0, suggest, None, item.kind.descr());
 278 }
 279
 280 impl<'tcx> Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
 281     type NestedFilter = nested_filter::OnlyBodies;
 282
 283     fn nested_visit_map(&mut self) -> Self::Map {
 284         self.tcx.hir()
 285     }
 286
 287     fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
 288         convert_item(self.tcx, item.item_id());
 289         reject_placeholder_type_signatures_in_item(self.tcx, item);
 290         intravisit::walk_item(self, item);
 291     }
 292
 293     fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) {
 294         for param in generics.params {
 295             match param.kind {
 296                 hir::GenericParamKind::Lifetime { .. } => {}
 297                 hir::GenericParamKind::Type { default: Some(_), .. } => {
 298                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 299                     self.tcx.ensure().type_of(def_id);
 300                 }
 301                 hir::GenericParamKind::Type { .. } => {}
 302                 hir::GenericParamKind::Const { default, .. } => {
 303                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 304                     self.tcx.ensure().type_of(def_id);
 305                     if let Some(default) = default {
 306                         let default_def_id = self.tcx.hir().local_def_id(default.hir_id);
 307                         // need to store default and type of default
 308                         self.tcx.ensure().type_of(default_def_id);
 309                         self.tcx.ensure().const_param_default(def_id);
 310                     }
 311                 }
 312             }
 313         }
 314         intravisit::walk_generics(self, generics);
 315     }
 316
 317     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
 318         if let hir::ExprKind::Closure { .. } = expr.kind {
 319             let def_id = self.tcx.hir().local_def_id(expr.hir_id);
 320             self.tcx.ensure().generics_of(def_id);
 321             // We do not call `type_of` for closures here as that
 322             // depends on typecheck and would therefore hide
 323             // any further errors in case one typeck fails.
 324         }
 325         intravisit::walk_expr(self, expr);
 326     }
 327
 328     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
 329         convert_trait_item(self.tcx, trait_item.trait_item_id());
 330         intravisit::walk_trait_item(self, trait_item);
 331     }
 332
 333     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
 334         convert_impl_item(self.tcx, impl_item.impl_item_id());
 335         intravisit::walk_impl_item(self, impl_item);
 336     }
 337 }
 338
 339 ///////////////////////////////////////////////////////////////////////////
 340 // Utility types and common code for the above passes.
 341
 342 fn bad_placeholder<'tcx>(
 343     tcx: TyCtxt<'tcx>,
 344     mut spans: Vec<Span>,
 345     kind: &'static str,
 346 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
 347     let kind = if kind.ends_with('s') { format!("{}es", kind) } else { format!("{}s", kind) };
 348
 349     spans.sort();
 350     let mut err = struct_span_err!(
 351         tcx.sess,
 352         spans.clone(),
 353         E0121,
 354         "the placeholder `_` is not allowed within types on item signatures for {}",
 355         kind
 356     );
 357     for span in spans {
 358         err.span_label(span, "not allowed in type signatures");
 359     }
 360     err
 361 }
 362
 363 impl<'tcx> ItemCtxt<'tcx> {
 364     pub fn new(tcx: TyCtxt<'tcx>, item_def_id: DefId) -> ItemCtxt<'tcx> {
 365         ItemCtxt { tcx, item_def_id }
 366     }
 367
 368     pub fn to_ty(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> {
 369         <dyn AstConv<'_>>::ast_ty_to_ty(self, ast_ty)
 370     }
 371
 372     pub fn hir_id(&self) -> hir::HirId {
 373         self.tcx.hir().local_def_id_to_hir_id(self.item_def_id.expect_local())
 374     }
 375
 376     pub fn node(&self) -> hir::Node<'tcx> {
 377         self.tcx.hir().get(self.hir_id())
 378     }
 379 }
 380
 381 impl<'tcx> AstConv<'tcx> for ItemCtxt<'tcx> {
 382     fn tcx(&self) -> TyCtxt<'tcx> {
 383         self.tcx
 384     }
 385
 386     fn item_def_id(&self) -> Option<DefId> {
 387         Some(self.item_def_id)
 388     }
 389
 390     fn get_type_parameter_bounds(
 391         &self,
 392         span: Span,
 393         def_id: DefId,
 394         assoc_name: Ident,
 395     ) -> ty::GenericPredicates<'tcx> {
 396         self.tcx.at(span).type_param_predicates((
 397             self.item_def_id,
 398             def_id.expect_local(),
 399             assoc_name,
 400         ))
 401     }
 402
 403     fn re_infer(&self, _: Option<&ty::GenericParamDef>, _: Span) -> Option<ty::Region<'tcx>> {
 404         None
 405     }
 406
 407     fn allow_ty_infer(&self) -> bool {
 408         false
 409     }
 410
 411     fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
 412         self.tcx().ty_error_with_message(span, "bad placeholder type")
 413     }
 414
 415     fn ct_infer(&self, ty: Ty<'tcx>, _: Option<&ty::GenericParamDef>, span: Span) -> Const<'tcx> {
 416         let ty = self.tcx.fold_regions(ty, |r, _| match *r {
 417             ty::ReErased => self.tcx.lifetimes.re_static,
 418             _ => r,
 419         });
 420         self.tcx().const_error_with_message(ty, span, "bad placeholder constant")
 421     }
 422
 423     fn projected_ty_from_poly_trait_ref(
 424         &self,
 425         span: Span,
 426         item_def_id: DefId,
 427         item_segment: &hir::PathSegment<'_>,
 428         poly_trait_ref: ty::PolyTraitRef<'tcx>,
 429     ) -> Ty<'tcx> {
 430         if let Some(trait_ref) = poly_trait_ref.no_bound_vars() {
 431             let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
 432                 self,
 433                 self.tcx,
 434                 span,
 435                 item_def_id,
 436                 item_segment,
 437                 trait_ref.substs,
 438             );
 439             self.tcx().mk_projection(item_def_id, item_substs)
 440         } else {
 441             // There are no late-bound regions; we can just ignore the binder.
 442             let mut err = struct_span_err!(
 443                 self.tcx().sess,
 444                 span,
 445                 E0212,
 446                 "cannot use the associated type of a trait \
 447                  with uninferred generic parameters"
 448             );
 449
 450             match self.node() {
 451                 hir::Node::Field(_) | hir::Node::Ctor(_) | hir::Node::Variant(_) => {
 452                     let item =
 453                         self.tcx.hir().expect_item(self.tcx.hir().get_parent_item(self.hir_id()));
 454                     match &item.kind {
 455                         hir::ItemKind::Enum(_, generics)
 456                         | hir::ItemKind::Struct(_, generics)
 457                         | hir::ItemKind::Union(_, generics) => {
 458                             let lt_name = get_new_lifetime_name(self.tcx, poly_trait_ref, generics);
 459                             let (lt_sp, sugg) = match generics.params {
 460                                 [] => (generics.span, format!("<{}>", lt_name)),
 461                                 [bound, ..] => {
 462                                     (bound.span.shrink_to_lo(), format!("{}, ", lt_name))
 463                                 }
 464                             };
 465                             let suggestions = vec![
 466                                 (lt_sp, sugg),
 467                                 (
 468                                     span.with_hi(item_segment.ident.span.lo()),
 469                                     format!(
 470                                         "{}::",
 471                                         // Replace the existing lifetimes with a new named lifetime.
 472                                         self.tcx.replace_late_bound_regions_uncached(
 473                                             poly_trait_ref,
 474                                             |_| {
 475                                                 self.tcx.mk_region(ty::ReEarlyBound(
 476                                                     ty::EarlyBoundRegion {
 477                                                         def_id: item_def_id,
 478                                                         index: 0,
 479                                                         name: Symbol::intern(&lt_name),
 480                                                     },
 481                                                 ))
 482                                             }
 483                                         ),
 484                                     ),
 485                                 ),
 486                             ];
 487                             err.multipart_suggestion(
 488                                 "use a fully qualified path with explicit lifetimes",
 489                                 suggestions,
 490                                 Applicability::MaybeIncorrect,
 491                             );
 492                         }
 493                         _ => {}
 494                     }
 495                 }
 496                 hir::Node::Item(hir::Item {
 497                     kind:
 498                         hir::ItemKind::Struct(..) | hir::ItemKind::Enum(..) | hir::ItemKind::Union(..),
 499                     ..
 500                 }) => {}
 501                 hir::Node::Item(_)
 502                 | hir::Node::ForeignItem(_)
 503                 | hir::Node::TraitItem(_)
 504                 | hir::Node::ImplItem(_) => {
 505                     err.span_suggestion_verbose(
 506                         span.with_hi(item_segment.ident.span.lo()),
 507                         "use a fully qualified path with inferred lifetimes",
 508                         format!(
 509                             "{}::",
 510                             // Erase named lt, we want `<A as B<'_>::C`, not `<A as B<'a>::C`.
 511                             self.tcx.anonymize_late_bound_regions(poly_trait_ref).skip_binder(),
 512                         ),
 513                         Applicability::MaybeIncorrect,
 514                     );
 515                 }
 516                 _ => {}
 517             }
 518             err.emit();
 519             self.tcx().ty_error()
 520         }
 521     }
 522
 523     fn normalize_ty(&self, _span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
 524         // Types in item signatures are not normalized to avoid undue dependencies.
 525         ty
 526     }
 527
 528     fn set_tainted_by_errors(&self) {
 529         // There's no obvious place to track this, so just let it go.
 530     }
 531
 532     fn record_ty(&self, _hir_id: hir::HirId, _ty: Ty<'tcx>, _span: Span) {
 533         // There's no place to record types from signatures?
 534     }
 535 }
 536
 537 /// Synthesize a new lifetime name that doesn't clash with any of the lifetimes already present.
 538 fn get_new_lifetime_name<'tcx>(
 539     tcx: TyCtxt<'tcx>,
 540     poly_trait_ref: ty::PolyTraitRef<'tcx>,
 541     generics: &hir::Generics<'tcx>,
 542 ) -> String {
 543     let existing_lifetimes = tcx
 544         .collect_referenced_late_bound_regions(&poly_trait_ref)
 545         .into_iter()
 546         .filter_map(|lt| {
 547             if let ty::BoundRegionKind::BrNamed(_, name) = lt {
 548                 Some(name.as_str().to_string())
 549             } else {
 550                 None
 551             }
 552         })
 553         .chain(generics.params.iter().filter_map(|param| {
 554             if let hir::GenericParamKind::Lifetime { .. } = &param.kind {
 555                 Some(param.name.ident().as_str().to_string())
 556             } else {
 557                 None
 558             }
 559         }))
 560         .collect::<FxHashSet<String>>();
 561
 562     let a_to_z_repeat_n = |n| {
 563         (b'a'..=b'z').map(move |c| {
 564             let mut s = '\''.to_string();
 565             s.extend(std::iter::repeat(char::from(c)).take(n));
 566             s
 567         })
 568     };
 569
 570     // If all single char lifetime names are present, we wrap around and double the chars.
 571     (1..).flat_map(a_to_z_repeat_n).find(|lt| !existing_lifetimes.contains(lt.as_str())).unwrap()
 572 }
 573
 574 /// Returns the predicates defined on `item_def_id` of the form
 575 /// `X: Foo` where `X` is the type parameter `def_id`.
 576 fn type_param_predicates(
 577     tcx: TyCtxt<'_>,
 578     (item_def_id, def_id, assoc_name): (DefId, LocalDefId, Ident),
 579 ) -> ty::GenericPredicates<'_> {
 580     use rustc_hir::*;
 581
 582     // In the AST, bounds can derive from two places. Either
 583     // written inline like `<T: Foo>` or in a where-clause like
 584     // `where T: Foo`.
 585
 586     let param_id = tcx.hir().local_def_id_to_hir_id(def_id);
 587     let param_owner = tcx.hir().ty_param_owner(def_id);
 588     let generics = tcx.generics_of(param_owner);
 589     let index = generics.param_def_id_to_index[&def_id.to_def_id()];
 590     let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(def_id));
 591
 592     // Don't look for bounds where the type parameter isn't in scope.
 593     let parent = if item_def_id == param_owner.to_def_id() {
 594         None
 595     } else {
 596         tcx.generics_of(item_def_id).parent
 597     };
 598
 599     let mut result = parent
 600         .map(|parent| {
 601             let icx = ItemCtxt::new(tcx, parent);
 602             icx.get_type_parameter_bounds(DUMMY_SP, def_id.to_def_id(), assoc_name)
 603         })
 604         .unwrap_or_default();
 605     let mut extend = None;
 606
 607     let item_hir_id = tcx.hir().local_def_id_to_hir_id(item_def_id.expect_local());
 608     let ast_generics = match tcx.hir().get(item_hir_id) {
 609         Node::TraitItem(item) => &item.generics,
 610
 611         Node::ImplItem(item) => &item.generics,
 612
 613         Node::Item(item) => {
 614             match item.kind {
 615                 ItemKind::Fn(.., ref generics, _)
 616                 | ItemKind::Impl(hir::Impl { ref generics, .. })
 617                 | ItemKind::TyAlias(_, ref generics)
 618                 | ItemKind::OpaqueTy(OpaqueTy {
 619                     ref generics,
 620                     origin: hir::OpaqueTyOrigin::TyAlias,
 621                     ..
 622                 })
 623                 | ItemKind::Enum(_, ref generics)
 624                 | ItemKind::Struct(_, ref generics)
 625                 | ItemKind::Union(_, ref generics) => generics,
 626                 ItemKind::Trait(_, _, ref generics, ..) => {
 627                     // Implied `Self: Trait` and supertrait bounds.
 628                     if param_id == item_hir_id {
 629                         let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id);
 630                         extend =
 631                             Some((identity_trait_ref.without_const().to_predicate(tcx), item.span));
 632                     }
 633                     generics
 634                 }
 635                 _ => return result,
 636             }
 637         }
 638
 639         Node::ForeignItem(item) => match item.kind {
 640             ForeignItemKind::Fn(_, _, ref generics) => generics,
 641             _ => return result,
 642         },
 643
 644         _ => return result,
 645     };
 646
 647     let icx = ItemCtxt::new(tcx, item_def_id);
 648     let extra_predicates = extend.into_iter().chain(
 649         icx.type_parameter_bounds_in_generics(
 650             ast_generics,
 651             param_id,
 652             ty,
 653             OnlySelfBounds(true),
 654             Some(assoc_name),
 655         )
 656         .into_iter()
 657         .filter(|(predicate, _)| match predicate.kind().skip_binder() {
 658             ty::PredicateKind::Trait(data) => data.self_ty().is_param(index),
 659             _ => false,
 660         }),
 661     );
 662     result.predicates =
 663         tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(extra_predicates));
 664     result
 665 }
 666
 667 impl<'tcx> ItemCtxt<'tcx> {
 668     /// Finds bounds from `hir::Generics`. This requires scanning through the
 669     /// AST. We do this to avoid having to convert *all* the bounds, which
 670     /// would create artificial cycles. Instead, we can only convert the
 671     /// bounds for a type parameter `X` if `X::Foo` is used.
 672     #[instrument(level = "trace", skip(self, ast_generics))]
 673     fn type_parameter_bounds_in_generics(
 674         &self,
 675         ast_generics: &'tcx hir::Generics<'tcx>,
 676         param_id: hir::HirId,
 677         ty: Ty<'tcx>,
 678         only_self_bounds: OnlySelfBounds,
 679         assoc_name: Option<Ident>,
 680     ) -> Vec<(ty::Predicate<'tcx>, Span)> {
 681         let param_def_id = self.tcx.hir().local_def_id(param_id).to_def_id();
 682         debug!(?param_def_id);
 683         ast_generics
 684             .predicates
 685             .iter()
 686             .filter_map(|wp| match *wp {
 687                 hir::WherePredicate::BoundPredicate(ref bp) => Some(bp),
 688                 _ => None,
 689             })
 690             .flat_map(|bp| {
 691                 let bt = if bp.is_param_bound(param_def_id) {
 692                     Some(ty)
 693                 } else if !only_self_bounds.0 {
 694                     Some(self.to_ty(bp.bounded_ty))
 695                 } else {
 696                     None
 697                 };
 698                 let bvars = self.tcx.late_bound_vars(bp.bounded_ty.hir_id);
 699
 700                 bp.bounds.iter().filter_map(move |b| bt.map(|bt| (bt, b, bvars))).filter(
 701                     |(_, b, _)| match assoc_name {
 702                         Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
 703                         None => true,
 704                     },
 705                 )
 706             })
 707             .flat_map(|(bt, b, bvars)| predicates_from_bound(self, bt, b, bvars))
 708             .collect()
 709     }
 710
 711     fn bound_defines_assoc_item(&self, b: &hir::GenericBound<'_>, assoc_name: Ident) -> bool {
 712         debug!("bound_defines_assoc_item(b={:?}, assoc_name={:?})", b, assoc_name);
 713
 714         match b {
 715             hir::GenericBound::Trait(poly_trait_ref, _) => {
 716                 let trait_ref = &poly_trait_ref.trait_ref;
 717                 if let Some(trait_did) = trait_ref.trait_def_id() {
 718                     self.tcx.trait_may_define_assoc_type(trait_did, assoc_name)
 719                 } else {
 720                     false
 721                 }
 722             }
 723             _ => false,
 724         }
 725     }
 726 }
 727
 728 fn convert_item(tcx: TyCtxt<'_>, item_id: hir::ItemId) {
 729     let it = tcx.hir().item(item_id);
 730     debug!("convert: item {} with id {}", it.ident, it.hir_id());
 731     let def_id = item_id.def_id;
 732
 733     match it.kind {
 734         // These don't define types.
 735         hir::ItemKind::ExternCrate(_)
 736         | hir::ItemKind::Use(..)
 737         | hir::ItemKind::Macro(..)
 738         | hir::ItemKind::Mod(_)
 739         | hir::ItemKind::GlobalAsm(_) => {}
 740         hir::ItemKind::ForeignMod { items, .. } => {
 741             for item in items {
 742                 let item = tcx.hir().foreign_item(item.id);
 743                 tcx.ensure().generics_of(item.def_id);
 744                 tcx.ensure().type_of(item.def_id);
 745                 tcx.ensure().predicates_of(item.def_id);
 746                 match item.kind {
 747                     hir::ForeignItemKind::Fn(..) => tcx.ensure().fn_sig(item.def_id),
 748                     hir::ForeignItemKind::Static(..) => {
 749                         let mut visitor = HirPlaceholderCollector::default();
 750                         visitor.visit_foreign_item(item);
 751                         placeholder_type_error(
 752                             tcx,
 753                             None,
 754                             visitor.0,
 755                             false,
 756                             None,
 757                             "static variable",
 758                         );
 759                     }
 760                     _ => (),
 761                 }
 762             }
 763         }
 764         hir::ItemKind::Enum(ref enum_definition, _) => {
 765             tcx.ensure().generics_of(def_id);
 766             tcx.ensure().type_of(def_id);
 767             tcx.ensure().predicates_of(def_id);
 768             convert_enum_variant_types(tcx, def_id.to_def_id(), enum_definition.variants);
 769         }
 770         hir::ItemKind::Impl { .. } => {
 771             tcx.ensure().generics_of(def_id);
 772             tcx.ensure().type_of(def_id);
 773             tcx.ensure().impl_trait_ref(def_id);
 774             tcx.ensure().predicates_of(def_id);
 775         }
 776         hir::ItemKind::Trait(..) => {
 777             tcx.ensure().generics_of(def_id);
 778             tcx.ensure().trait_def(def_id);
 779             tcx.at(it.span).super_predicates_of(def_id);
 780             tcx.ensure().predicates_of(def_id);
 781         }
 782         hir::ItemKind::TraitAlias(..) => {
 783             tcx.ensure().generics_of(def_id);
 784             tcx.at(it.span).super_predicates_of(def_id);
 785             tcx.ensure().predicates_of(def_id);
 786         }
 787         hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 788             tcx.ensure().generics_of(def_id);
 789             tcx.ensure().type_of(def_id);
 790             tcx.ensure().predicates_of(def_id);
 791
 792             for f in struct_def.fields() {
 793                 let def_id = tcx.hir().local_def_id(f.hir_id);
 794                 tcx.ensure().generics_of(def_id);
 795                 tcx.ensure().type_of(def_id);
 796                 tcx.ensure().predicates_of(def_id);
 797             }
 798
 799             if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
 800                 convert_variant_ctor(tcx, ctor_hir_id);
 801             }
 802         }
 803
 804         // Desugared from `impl Trait`, so visited by the function's return type.
 805         hir::ItemKind::OpaqueTy(hir::OpaqueTy {
 806             origin: hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..),
 807             ..
 808         }) => {}
 809
 810         // Don't call `type_of` on opaque types, since that depends on type
 811         // checking function bodies. `check_item_type` ensures that it's called
 812         // instead.
 813         hir::ItemKind::OpaqueTy(..) => {
 814             tcx.ensure().generics_of(def_id);
 815             tcx.ensure().predicates_of(def_id);
 816             tcx.ensure().explicit_item_bounds(def_id);
 817         }
 818         hir::ItemKind::TyAlias(..)
 819         | hir::ItemKind::Static(..)
 820         | hir::ItemKind::Const(..)
 821         | hir::ItemKind::Fn(..) => {
 822             tcx.ensure().generics_of(def_id);
 823             tcx.ensure().type_of(def_id);
 824             tcx.ensure().predicates_of(def_id);
 825             match it.kind {
 826                 hir::ItemKind::Fn(..) => tcx.ensure().fn_sig(def_id),
 827                 hir::ItemKind::OpaqueTy(..) => tcx.ensure().item_bounds(def_id),
 828                 hir::ItemKind::Const(ty, ..) | hir::ItemKind::Static(ty, ..) => {
 829                     if !is_suggestable_infer_ty(ty) {
 830                         let mut visitor = HirPlaceholderCollector::default();
 831                         visitor.visit_item(it);
 832                         placeholder_type_error(tcx, None, visitor.0, false, None, it.kind.descr());
 833                     }
 834                 }
 835                 _ => (),
 836             }
 837         }
 838     }
 839 }
 840
 841 fn convert_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::TraitItemId) {
 842     let trait_item = tcx.hir().trait_item(trait_item_id);
 843     tcx.ensure().generics_of(trait_item_id.def_id);
 844
 845     match trait_item.kind {
 846         hir::TraitItemKind::Fn(..) => {
 847             tcx.ensure().type_of(trait_item_id.def_id);
 848             tcx.ensure().fn_sig(trait_item_id.def_id);
 849         }
 850
 851         hir::TraitItemKind::Const(.., Some(_)) => {
 852             tcx.ensure().type_of(trait_item_id.def_id);
 853         }
 854
 855         hir::TraitItemKind::Const(..) => {
 856             tcx.ensure().type_of(trait_item_id.def_id);
 857             // Account for `const C: _;`.
 858             let mut visitor = HirPlaceholderCollector::default();
 859             visitor.visit_trait_item(trait_item);
 860             placeholder_type_error(tcx, None, visitor.0, false, None, "constant");
 861         }
 862
 863         hir::TraitItemKind::Type(_, Some(_)) => {
 864             tcx.ensure().item_bounds(trait_item_id.def_id);
 865             tcx.ensure().type_of(trait_item_id.def_id);
 866             // Account for `type T = _;`.
 867             let mut visitor = HirPlaceholderCollector::default();
 868             visitor.visit_trait_item(trait_item);
 869             placeholder_type_error(tcx, None, visitor.0, false, None, "associated type");
 870         }
 871
 872         hir::TraitItemKind::Type(_, None) => {
 873             tcx.ensure().item_bounds(trait_item_id.def_id);
 874             // #74612: Visit and try to find bad placeholders
 875             // even if there is no concrete type.
 876             let mut visitor = HirPlaceholderCollector::default();
 877             visitor.visit_trait_item(trait_item);
 878
 879             placeholder_type_error(tcx, None, visitor.0, false, None, "associated type");
 880         }
 881     };
 882
 883     tcx.ensure().predicates_of(trait_item_id.def_id);
 884 }
 885
 886 fn convert_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::ImplItemId) {
 887     let def_id = impl_item_id.def_id;
 888     tcx.ensure().generics_of(def_id);
 889     tcx.ensure().type_of(def_id);
 890     tcx.ensure().predicates_of(def_id);
 891     let impl_item = tcx.hir().impl_item(impl_item_id);
 892     match impl_item.kind {
 893         hir::ImplItemKind::Fn(..) => {
 894             tcx.ensure().fn_sig(def_id);
 895         }
 896         hir::ImplItemKind::TyAlias(_) => {
 897             // Account for `type T = _;`
 898             let mut visitor = HirPlaceholderCollector::default();
 899             visitor.visit_impl_item(impl_item);
 900
 901             placeholder_type_error(tcx, None, visitor.0, false, None, "associated type");
 902         }
 903         hir::ImplItemKind::Const(..) => {}
 904     }
 905 }
 906
 907 fn convert_variant_ctor(tcx: TyCtxt<'_>, ctor_id: hir::HirId) {
 908     let def_id = tcx.hir().local_def_id(ctor_id);
 909     tcx.ensure().generics_of(def_id);
 910     tcx.ensure().type_of(def_id);
 911     tcx.ensure().predicates_of(def_id);
 912 }
 913
 914 fn convert_enum_variant_types(tcx: TyCtxt<'_>, def_id: DefId, variants: &[hir::Variant<'_>]) {
 915     let def = tcx.adt_def(def_id);
 916     let repr_type = def.repr().discr_type();
 917     let initial = repr_type.initial_discriminant(tcx);
 918     let mut prev_discr = None::<Discr<'_>>;
 919
 920     // fill the discriminant values and field types
 921     for variant in variants {
 922         let wrapped_discr = prev_discr.map_or(initial, |d| d.wrap_incr(tcx));
 923         prev_discr = Some(
 924             if let Some(ref e) = variant.disr_expr {
 925                 let expr_did = tcx.hir().local_def_id(e.hir_id);
 926                 def.eval_explicit_discr(tcx, expr_did.to_def_id())
 927             } else if let Some(discr) = repr_type.disr_incr(tcx, prev_discr) {
 928                 Some(discr)
 929             } else {
 930                 struct_span_err!(tcx.sess, variant.span, E0370, "enum discriminant overflowed")
 931                     .span_label(
 932                         variant.span,
 933                         format!("overflowed on value after {}", prev_discr.unwrap()),
 934                     )
 935                     .note(&format!(
 936                         "explicitly set `{} = {}` if that is desired outcome",
 937                         variant.ident, wrapped_discr
 938                     ))
 939                     .emit();
 940                 None
 941             }
 942             .unwrap_or(wrapped_discr),
 943         );
 944
 945         for f in variant.data.fields() {
 946             let def_id = tcx.hir().local_def_id(f.hir_id);
 947             tcx.ensure().generics_of(def_id);
 948             tcx.ensure().type_of(def_id);
 949             tcx.ensure().predicates_of(def_id);
 950         }
 951
 952         // Convert the ctor, if any. This also registers the variant as
 953         // an item.
 954         if let Some(ctor_hir_id) = variant.data.ctor_hir_id() {
 955             convert_variant_ctor(tcx, ctor_hir_id);
 956         }
 957     }
 958 }
 959
 960 fn convert_variant(
 961     tcx: TyCtxt<'_>,
 962     variant_did: Option<LocalDefId>,
 963     ctor_did: Option<LocalDefId>,
 964     ident: Ident,
 965     discr: ty::VariantDiscr,
 966     def: &hir::VariantData<'_>,
 967     adt_kind: ty::AdtKind,
 968     parent_did: LocalDefId,
 969 ) -> ty::VariantDef {
 970     let mut seen_fields: FxHashMap<Ident, Span> = Default::default();
 971     let fields = def
 972         .fields()
 973         .iter()
 974         .map(|f| {
 975             let fid = tcx.hir().local_def_id(f.hir_id);
 976             let dup_span = seen_fields.get(&f.ident.normalize_to_macros_2_0()).cloned();
 977             if let Some(prev_span) = dup_span {
 978                 tcx.sess.emit_err(errors::FieldAlreadyDeclared {
 979                     field_name: f.ident,
 980                     span: f.span,
 981                     prev_span,
 982                 });
 983             } else {
 984                 seen_fields.insert(f.ident.normalize_to_macros_2_0(), f.span);
 985             }
 986
 987             ty::FieldDef { did: fid.to_def_id(), name: f.ident.name, vis: tcx.visibility(fid) }
 988         })
 989         .collect();
 990     let recovered = match def {
 991         hir::VariantData::Struct(_, r) => *r,
 992         _ => false,
 993     };
 994     ty::VariantDef::new(
 995         ident.name,
 996         variant_did.map(LocalDefId::to_def_id),
 997         ctor_did.map(LocalDefId::to_def_id),
 998         discr,
 999         fields,
1000         CtorKind::from_hir(def),
1001         adt_kind,
1002         parent_did.to_def_id(),
1003         recovered,
1004         adt_kind == AdtKind::Struct && tcx.has_attr(parent_did.to_def_id(), sym::non_exhaustive)
1005             || variant_did.map_or(false, |variant_did| {
1006                 tcx.has_attr(variant_did.to_def_id(), sym::non_exhaustive)
1007             }),
1008     )
1009 }
1010
1011 fn adt_def<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> ty::AdtDef<'tcx> {
1012     use rustc_hir::*;
1013
1014     let def_id = def_id.expect_local();
1015     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1016     let Node::Item(item) = tcx.hir().get(hir_id) else {
1017         bug!();
1018     };
1019
1020     let repr = ReprOptions::new(tcx, def_id.to_def_id());
1021     let (kind, variants) = match item.kind {
1022         ItemKind::Enum(ref def, _) => {
1023             let mut distance_from_explicit = 0;
1024             let variants = def
1025                 .variants
1026                 .iter()
1027                 .map(|v| {
1028                     let variant_did = Some(tcx.hir().local_def_id(v.id));
1029                     let ctor_did =
1030                         v.data.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1031
1032                     let discr = if let Some(ref e) = v.disr_expr {
1033                         distance_from_explicit = 0;
1034                         ty::VariantDiscr::Explicit(tcx.hir().local_def_id(e.hir_id).to_def_id())
1035                     } else {
1036                         ty::VariantDiscr::Relative(distance_from_explicit)
1037                     };
1038                     distance_from_explicit += 1;
1039
1040                     convert_variant(
1041                         tcx,
1042                         variant_did,
1043                         ctor_did,
1044                         v.ident,
1045                         discr,
1046                         &v.data,
1047                         AdtKind::Enum,
1048                         def_id,
1049                     )
1050                 })
1051                 .collect();
1052
1053             (AdtKind::Enum, variants)
1054         }
1055         ItemKind::Struct(ref def, _) => {
1056             let variant_did = None::<LocalDefId>;
1057             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1058
1059             let variants = std::iter::once(convert_variant(
1060                 tcx,
1061                 variant_did,
1062                 ctor_did,
1063                 item.ident,
1064                 ty::VariantDiscr::Relative(0),
1065                 def,
1066                 AdtKind::Struct,
1067                 def_id,
1068             ))
1069             .collect();
1070
1071             (AdtKind::Struct, variants)
1072         }
1073         ItemKind::Union(ref def, _) => {
1074             let variant_did = None;
1075             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1076
1077             let variants = std::iter::once(convert_variant(
1078                 tcx,
1079                 variant_did,
1080                 ctor_did,
1081                 item.ident,
1082                 ty::VariantDiscr::Relative(0),
1083                 def,
1084                 AdtKind::Union,
1085                 def_id,
1086             ))
1087             .collect();
1088
1089             (AdtKind::Union, variants)
1090         }
1091         _ => bug!(),
1092     };
1093     tcx.alloc_adt_def(def_id.to_def_id(), kind, variants, repr)
1094 }
1095
1096 /// Ensures that the super-predicates of the trait with a `DefId`
1097 /// of `trait_def_id` are converted and stored. This also ensures that
1098 /// the transitive super-predicates are converted.
1099 fn super_predicates_of(tcx: TyCtxt<'_>, trait_def_id: DefId) -> ty::GenericPredicates<'_> {
1100     debug!("super_predicates(trait_def_id={:?})", trait_def_id);
1101     tcx.super_predicates_that_define_assoc_type((trait_def_id, None))
1102 }
1103
1104 /// Ensures that the super-predicates of the trait with a `DefId`
1105 /// of `trait_def_id` are converted and stored. This also ensures that
1106 /// the transitive super-predicates are converted.
1107 fn super_predicates_that_define_assoc_type(
1108     tcx: TyCtxt<'_>,
1109     (trait_def_id, assoc_name): (DefId, Option<Ident>),
1110 ) -> ty::GenericPredicates<'_> {
1111     debug!(
1112         "super_predicates_that_define_assoc_type(trait_def_id={:?}, assoc_name={:?})",
1113         trait_def_id, assoc_name
1114     );
1115     if trait_def_id.is_local() {
1116         debug!("super_predicates_that_define_assoc_type: local trait_def_id={:?}", trait_def_id);
1117         let trait_hir_id = tcx.hir().local_def_id_to_hir_id(trait_def_id.expect_local());
1118
1119         let Node::Item(item) = tcx.hir().get(trait_hir_id) else {
1120             bug!("trait_node_id {} is not an item", trait_hir_id);
1121         };
1122
1123         let (generics, bounds) = match item.kind {
1124             hir::ItemKind::Trait(.., ref generics, ref supertraits, _) => (generics, supertraits),
1125             hir::ItemKind::TraitAlias(ref generics, ref supertraits) => (generics, supertraits),
1126             _ => span_bug!(item.span, "super_predicates invoked on non-trait"),
1127         };
1128
1129         let icx = ItemCtxt::new(tcx, trait_def_id);
1130
1131         // Convert the bounds that follow the colon, e.g., `Bar + Zed` in `trait Foo: Bar + Zed`.
1132         let self_param_ty = tcx.types.self_param;
1133         let superbounds1 = if let Some(assoc_name) = assoc_name {
1134             <dyn AstConv<'_>>::compute_bounds_that_match_assoc_type(
1135                 &icx,
1136                 self_param_ty,
1137                 bounds,
1138                 assoc_name,
1139             )
1140         } else {
1141             <dyn AstConv<'_>>::compute_bounds(&icx, self_param_ty, bounds)
1142         };
1143
1144         let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
1145
1146         // Convert any explicit superbounds in the where-clause,
1147         // e.g., `trait Foo where Self: Bar`.
1148         // In the case of trait aliases, however, we include all bounds in the where-clause,
1149         // so e.g., `trait Foo = where u32: PartialEq<Self>` would include `u32: PartialEq<Self>`
1150         // as one of its "superpredicates".
1151         let is_trait_alias = tcx.is_trait_alias(trait_def_id);
1152         let superbounds2 = icx.type_parameter_bounds_in_generics(
1153             generics,
1154             item.hir_id(),
1155             self_param_ty,
1156             OnlySelfBounds(!is_trait_alias),
1157             assoc_name,
1158         );
1159
1160         // Combine the two lists to form the complete set of superbounds:
1161         let superbounds = &*tcx.arena.alloc_from_iter(superbounds1.into_iter().chain(superbounds2));
1162         debug!(?superbounds);
1163
1164         // Now require that immediate supertraits are converted,
1165         // which will, in turn, reach indirect supertraits.
1166         if assoc_name.is_none() {
1167             // Now require that immediate supertraits are converted,
1168             // which will, in turn, reach indirect supertraits.
1169             for &(pred, span) in superbounds {
1170                 debug!("superbound: {:?}", pred);
1171                 if let ty::PredicateKind::Trait(bound) = pred.kind().skip_binder() {
1172                     tcx.at(span).super_predicates_of(bound.def_id());
1173                 }
1174             }
1175         }
1176
1177         ty::GenericPredicates { parent: None, predicates: superbounds }
1178     } else {
1179         // if `assoc_name` is None, then the query should've been redirected to an
1180         // external provider
1181         assert!(assoc_name.is_some());
1182         tcx.super_predicates_of(trait_def_id)
1183     }
1184 }
1185
1186 fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> ty::TraitDef {
1187     let item = tcx.hir().expect_item(def_id.expect_local());
1188
1189     let (is_auto, unsafety, items) = match item.kind {
1190         hir::ItemKind::Trait(is_auto, unsafety, .., items) => {
1191             (is_auto == hir::IsAuto::Yes, unsafety, items)
1192         }
1193         hir::ItemKind::TraitAlias(..) => (false, hir::Unsafety::Normal, &[][..]),
1194         _ => span_bug!(item.span, "trait_def_of_item invoked on non-trait"),
1195     };
1196
1197     let paren_sugar = tcx.has_attr(def_id, sym::rustc_paren_sugar);
1198     if paren_sugar && !tcx.features().unboxed_closures {
1199         tcx.sess
1200             .struct_span_err(
1201                 item.span,
1202                 "the `#[rustc_paren_sugar]` attribute is a temporary means of controlling \
1203                  which traits can use parenthetical notation",
1204             )
1205             .help("add `#![feature(unboxed_closures)]` to the crate attributes to use it")
1206             .emit();
1207     }
1208
1209     let is_marker = tcx.has_attr(def_id, sym::marker);
1210     let skip_array_during_method_dispatch =
1211         tcx.has_attr(def_id, sym::rustc_skip_array_during_method_dispatch);
1212     let spec_kind = if tcx.has_attr(def_id, sym::rustc_unsafe_specialization_marker) {
1213         ty::trait_def::TraitSpecializationKind::Marker
1214     } else if tcx.has_attr(def_id, sym::rustc_specialization_trait) {
1215         ty::trait_def::TraitSpecializationKind::AlwaysApplicable
1216     } else {
1217         ty::trait_def::TraitSpecializationKind::None
1218     };
1219     let must_implement_one_of = tcx
1220         .get_attr(def_id, sym::rustc_must_implement_one_of)
1221         // Check that there are at least 2 arguments of `#[rustc_must_implement_one_of]`
1222         // and that they are all identifiers
1223         .and_then(|attr| match attr.meta_item_list() {
1224             Some(items) if items.len() < 2 => {
1225                 tcx.sess
1226                     .struct_span_err(
1227                         attr.span,
1228                         "the `#[rustc_must_implement_one_of]` attribute must be \
1229                         used with at least 2 args",
1230                     )
1231                     .emit();
1232
1233                 None
1234             }
1235             Some(items) => items
1236                 .into_iter()
1237                 .map(|item| item.ident().ok_or(item.span()))
1238                 .collect::<Result<Box<[_]>, _>>()
1239                 .map_err(|span| {
1240                     tcx.sess
1241                         .struct_span_err(span, "must be a name of an associated function")
1242                         .emit();
1243                 })
1244                 .ok()
1245                 .zip(Some(attr.span)),
1246             // Error is reported by `rustc_attr!`
1247             None => None,
1248         })
1249         // Check that all arguments of `#[rustc_must_implement_one_of]` reference
1250         // functions in the trait with default implementations
1251         .and_then(|(list, attr_span)| {
1252             let errors = list.iter().filter_map(|ident| {
1253                 let item = items.iter().find(|item| item.ident == *ident);
1254
1255                 match item {
1256                     Some(item) if matches!(item.kind, hir::AssocItemKind::Fn { .. }) => {
1257                         if !tcx.impl_defaultness(item.id.def_id).has_value() {
1258                             tcx.sess
1259                                 .struct_span_err(
1260                                     item.span,
1261                                     "This function doesn't have a default implementation",
1262                                 )
1263                                 .span_note(attr_span, "required by this annotation")
1264                                 .emit();
1265
1266                             return Some(());
1267                         }
1268
1269                         return None;
1270                     }
1271                     Some(item) => {
1272                         tcx.sess
1273                             .struct_span_err(item.span, "Not a function")
1274                             .span_note(attr_span, "required by this annotation")
1275                             .note(
1276                                 "All `#[rustc_must_implement_one_of]` arguments \
1277                             must be associated function names",
1278                             )
1279                             .emit();
1280                     }
1281                     None => {
1282                         tcx.sess
1283                             .struct_span_err(ident.span, "Function not found in this trait")
1284                             .emit();
1285                     }
1286                 }
1287
1288                 Some(())
1289             });
1290
1291             (errors.count() == 0).then_some(list)
1292         })
1293         // Check for duplicates
1294         .and_then(|list| {
1295             let mut set: FxHashMap<Symbol, Span> = FxHashMap::default();
1296             let mut no_dups = true;
1297
1298             for ident in &*list {
1299                 if let Some(dup) = set.insert(ident.name, ident.span) {
1300                     tcx.sess
1301                         .struct_span_err(vec![dup, ident.span], "Functions names are duplicated")
1302                         .note(
1303                             "All `#[rustc_must_implement_one_of]` arguments \
1304                             must be unique",
1305                         )
1306                         .emit();
1307
1308                     no_dups = false;
1309                 }
1310             }
1311
1312             no_dups.then_some(list)
1313         });
1314
1315     ty::TraitDef::new(
1316         def_id,
1317         unsafety,
1318         paren_sugar,
1319         is_auto,
1320         is_marker,
1321         skip_array_during_method_dispatch,
1322         spec_kind,
1323         must_implement_one_of,
1324     )
1325 }
1326
1327 fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<Span> {
1328     struct LateBoundRegionsDetector<'tcx> {
1329         tcx: TyCtxt<'tcx>,
1330         outer_index: ty::DebruijnIndex,
1331         has_late_bound_regions: Option<Span>,
1332     }
1333
1334     impl<'tcx> Visitor<'tcx> for LateBoundRegionsDetector<'tcx> {
1335         fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
1336             if self.has_late_bound_regions.is_some() {
1337                 return;
1338             }
1339             match ty.kind {
1340                 hir::TyKind::BareFn(..) => {
1341                     self.outer_index.shift_in(1);
1342                     intravisit::walk_ty(self, ty);
1343                     self.outer_index.shift_out(1);
1344                 }
1345                 _ => intravisit::walk_ty(self, ty),
1346             }
1347         }
1348
1349         fn visit_poly_trait_ref(
1350             &mut self,
1351             tr: &'tcx hir::PolyTraitRef<'tcx>,
1352             m: hir::TraitBoundModifier,
1353         ) {
1354             if self.has_late_bound_regions.is_some() {
1355                 return;
1356             }
1357             self.outer_index.shift_in(1);
1358             intravisit::walk_poly_trait_ref(self, tr, m);
1359             self.outer_index.shift_out(1);
1360         }
1361
1362         fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
1363             if self.has_late_bound_regions.is_some() {
1364                 return;
1365             }
1366
1367             match self.tcx.named_region(lt.hir_id) {
1368                 Some(rl::Region::Static | rl::Region::EarlyBound(..)) => {}
1369                 Some(rl::Region::LateBound(debruijn, _, _)) if debruijn < self.outer_index => {}
1370                 Some(rl::Region::LateBound(..) | rl::Region::Free(..)) | None => {
1371                     self.has_late_bound_regions = Some(lt.span);
1372                 }
1373             }
1374         }
1375     }
1376
1377     fn has_late_bound_regions<'tcx>(
1378         tcx: TyCtxt<'tcx>,
1379         generics: &'tcx hir::Generics<'tcx>,
1380         decl: &'tcx hir::FnDecl<'tcx>,
1381     ) -> Option<Span> {
1382         let mut visitor = LateBoundRegionsDetector {
1383             tcx,
1384             outer_index: ty::INNERMOST,
1385             has_late_bound_regions: None,
1386         };
1387         for param in generics.params {
1388             if let GenericParamKind::Lifetime { .. } = param.kind {
1389                 if tcx.is_late_bound(param.hir_id) {
1390                     return Some(param.span);
1391                 }
1392             }
1393         }
1394         visitor.visit_fn_decl(decl);
1395         visitor.has_late_bound_regions
1396     }
1397
1398     match node {
1399         Node::TraitItem(item) => match item.kind {
1400             hir::TraitItemKind::Fn(ref sig, _) => {
1401                 has_late_bound_regions(tcx, &item.generics, sig.decl)
1402             }
1403             _ => None,
1404         },
1405         Node::ImplItem(item) => match item.kind {
1406             hir::ImplItemKind::Fn(ref sig, _) => {
1407                 has_late_bound_regions(tcx, &item.generics, sig.decl)
1408             }
1409             _ => None,
1410         },
1411         Node::ForeignItem(item) => match item.kind {
1412             hir::ForeignItemKind::Fn(fn_decl, _, ref generics) => {
1413                 has_late_bound_regions(tcx, generics, fn_decl)
1414             }
1415             _ => None,
1416         },
1417         Node::Item(item) => match item.kind {
1418             hir::ItemKind::Fn(ref sig, .., ref generics, _) => {
1419                 has_late_bound_regions(tcx, generics, sig.decl)
1420             }
1421             _ => None,
1422         },
1423         _ => None,
1424     }
1425 }
1426
1427 struct AnonConstInParamTyDetector {
1428     in_param_ty: bool,
1429     found_anon_const_in_param_ty: bool,
1430     ct: HirId,
1431 }
1432
1433 impl<'v> Visitor<'v> for AnonConstInParamTyDetector {
1434     fn visit_generic_param(&mut self, p: &'v hir::GenericParam<'v>) {
1435         if let GenericParamKind::Const { ty, default: _ } = p.kind {
1436             let prev = self.in_param_ty;
1437             self.in_param_ty = true;
1438             self.visit_ty(ty);
1439             self.in_param_ty = prev;
1440         }
1441     }
1442
1443     fn visit_anon_const(&mut self, c: &'v hir::AnonConst) {
1444         if self.in_param_ty && self.ct == c.hir_id {
1445             self.found_anon_const_in_param_ty = true;
1446         } else {
1447             intravisit::walk_anon_const(self, c)
1448         }
1449     }
1450 }
1451
1452 fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::Generics {
1453     use rustc_hir::*;
1454
1455     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1456
1457     let node = tcx.hir().get(hir_id);
1458     let parent_def_id = match node {
1459         Node::ImplItem(_)
1460         | Node::TraitItem(_)
1461         | Node::Variant(_)
1462         | Node::Ctor(..)
1463         | Node::Field(_) => {
1464             let parent_id = tcx.hir().get_parent_item(hir_id);
1465             Some(parent_id.to_def_id())
1466         }
1467         // FIXME(#43408) always enable this once `lazy_normalization` is
1468         // stable enough and does not need a feature gate anymore.
1469         Node::AnonConst(_) => {
1470             let parent_def_id = tcx.hir().get_parent_item(hir_id);
1471
1472             let mut in_param_ty = false;
1473             for (_parent, node) in tcx.hir().parent_iter(hir_id) {
1474                 if let Some(generics) = node.generics() {
1475                     let mut visitor = AnonConstInParamTyDetector {
1476                         in_param_ty: false,
1477                         found_anon_const_in_param_ty: false,
1478                         ct: hir_id,
1479                     };
1480
1481                     visitor.visit_generics(generics);
1482                     in_param_ty = visitor.found_anon_const_in_param_ty;
1483                     break;
1484                 }
1485             }
1486
1487             if in_param_ty {
1488                 // We do not allow generic parameters in anon consts if we are inside
1489                 // of a const parameter type, e.g. `struct Foo<const N: usize, const M: [u8; N]>` is not allowed.
1490                 None
1491             } else if tcx.lazy_normalization() {
1492                 if let Some(param_id) = tcx.hir().opt_const_param_default_param_hir_id(hir_id) {
1493                     // If the def_id we are calling generics_of on is an anon ct default i.e:
1494                     //
1495                     // struct Foo<const N: usize = { .. }>;
1496                     //        ^^^       ^          ^^^^^^ def id of this anon const
1497                     //        ^         ^ param_id
1498                     //        ^ parent_def_id
1499                     //
1500                     // then we only want to return generics for params to the left of `N`. If we don't do that we
1501                     // end up with that const looking like: `ty::ConstKind::Unevaluated(def_id, substs: [N#0])`.
1502                     //
1503                     // This causes ICEs (#86580) when building the substs for Foo in `fn foo() -> Foo { .. }` as
1504                     // we substitute the defaults with the partially built substs when we build the substs. Subst'ing
1505                     // the `N#0` on the unevaluated const indexes into the empty substs we're in the process of building.
1506                     //
1507                     // We fix this by having this function return the parent's generics ourselves and truncating the
1508                     // generics to only include non-forward declared params (with the exception of the `Self` ty)
1509                     //
1510                     // For the above code example that means we want `substs: []`
1511                     // For the following struct def we want `substs: [N#0]` when generics_of is called on
1512                     // the def id of the `{ N + 1 }` anon const
1513                     // struct Foo<const N: usize, const M: usize = { N + 1 }>;
1514                     //
1515                     // This has some implications for how we get the predicates available to the anon const
1516                     // see `explicit_predicates_of` for more information on this
1517                     let generics = tcx.generics_of(parent_def_id.to_def_id());
1518                     let param_def = tcx.hir().local_def_id(param_id).to_def_id();
1519                     let param_def_idx = generics.param_def_id_to_index[&param_def];
1520                     // In the above example this would be .params[..N#0]
1521                     let params = generics.params[..param_def_idx as usize].to_owned();
1522                     let param_def_id_to_index =
1523                         params.iter().map(|param| (param.def_id, param.index)).collect();
1524
1525                     return ty::Generics {
1526                         // we set the parent of these generics to be our parent's parent so that we
1527                         // dont end up with substs: [N, M, N] for the const default on a struct like this:
1528                         // struct Foo<const N: usize, const M: usize = { ... }>;
1529                         parent: generics.parent,
1530                         parent_count: generics.parent_count,
1531                         params,
1532                         param_def_id_to_index,
1533                         has_self: generics.has_self,
1534                         has_late_bound_regions: generics.has_late_bound_regions,
1535                     };
1536                 }
1537
1538                 // HACK(eddyb) this provides the correct generics when
1539                 // `feature(generic_const_expressions)` is enabled, so that const expressions
1540                 // used with const generics, e.g. `Foo<{N+1}>`, can work at all.
1541                 //
1542                 // Note that we do not supply the parent generics when using
1543                 // `min_const_generics`.
1544                 Some(parent_def_id.to_def_id())
1545             } else {
1546                 let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1547                 match parent_node {
1548                     // HACK(eddyb) this provides the correct generics for repeat
1549                     // expressions' count (i.e. `N` in `[x; N]`), and explicit
1550                     // `enum` discriminants (i.e. `D` in `enum Foo { Bar = D }`),
1551                     // as they shouldn't be able to cause query cycle errors.
1552                     Node::Expr(&Expr { kind: ExprKind::Repeat(_, ref constant), .. })
1553                         if constant.hir_id() == hir_id =>
1554                     {
1555                         Some(parent_def_id.to_def_id())
1556                     }
1557                     Node::Variant(Variant { disr_expr: Some(ref constant), .. })
1558                         if constant.hir_id == hir_id =>
1559                     {
1560                         Some(parent_def_id.to_def_id())
1561                     }
1562                     Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) => {
1563                         Some(tcx.typeck_root_def_id(def_id))
1564                     }
1565                     // Exclude `GlobalAsm` here which cannot have generics.
1566                     Node::Expr(&Expr { kind: ExprKind::InlineAsm(asm), .. })
1567                         if asm.operands.iter().any(|(op, _op_sp)| match op {
1568                             hir::InlineAsmOperand::Const { anon_const }
1569                             | hir::InlineAsmOperand::SymFn { anon_const } => {
1570                                 anon_const.hir_id == hir_id
1571                             }
1572                             _ => false,
1573                         }) =>
1574                     {
1575                         Some(parent_def_id.to_def_id())
1576                     }
1577                     _ => None,
1578                 }
1579             }
1580         }
1581         Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure { .. }, .. }) => {
1582             Some(tcx.typeck_root_def_id(def_id))
1583         }
1584         Node::Item(item) => match item.kind {
1585             ItemKind::OpaqueTy(hir::OpaqueTy {
1586                 origin:
1587                     hir::OpaqueTyOrigin::FnReturn(fn_def_id) | hir::OpaqueTyOrigin::AsyncFn(fn_def_id),
1588                 ..
1589             }) => Some(fn_def_id.to_def_id()),
1590             ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::TyAlias, .. }) => {
1591                 let parent_id = tcx.hir().get_parent_item(hir_id);
1592                 assert_ne!(parent_id, CRATE_DEF_ID);
1593                 debug!("generics_of: parent of opaque ty {:?} is {:?}", def_id, parent_id);
1594                 // Opaque types are always nested within another item, and
1595                 // inherit the generics of the item.
1596                 Some(parent_id.to_def_id())
1597             }
1598             _ => None,
1599         },
1600         _ => None,
1601     };
1602
1603     let no_generics = hir::Generics::empty();
1604     let ast_generics = node.generics().unwrap_or(&no_generics);
1605     let (opt_self, allow_defaults) = match node {
1606         Node::Item(item) => {
1607             match item.kind {
1608                 ItemKind::Trait(..) | ItemKind::TraitAlias(..) => {
1609                     // Add in the self type parameter.
1610                     //
1611                     // Something of a hack: use the node id for the trait, also as
1612                     // the node id for the Self type parameter.
1613                     let opt_self = Some(ty::GenericParamDef {
1614                         index: 0,
1615                         name: kw::SelfUpper,
1616                         def_id,
1617                         pure_wrt_drop: false,
1618                         kind: ty::GenericParamDefKind::Type {
1619                             has_default: false,
1620                             synthetic: false,
1621                         },
1622                     });
1623
1624                     (opt_self, true)
1625                 }
1626                 ItemKind::TyAlias(..)
1627                 | ItemKind::Enum(..)
1628                 | ItemKind::Struct(..)
1629                 | ItemKind::OpaqueTy(..)
1630                 | ItemKind::Union(..) => (None, true),
1631                 _ => (None, false),
1632             }
1633         }
1634         _ => (None, false),
1635     };
1636
1637     let has_self = opt_self.is_some();
1638     let mut parent_has_self = false;
1639     let mut own_start = has_self as u32;
1640     let parent_count = parent_def_id.map_or(0, |def_id| {
1641         let generics = tcx.generics_of(def_id);
1642         assert!(!has_self);
1643         parent_has_self = generics.has_self;
1644         own_start = generics.count() as u32;
1645         generics.parent_count + generics.params.len()
1646     });
1647
1648     let mut params: Vec<_> = Vec::with_capacity(ast_generics.params.len() + has_self as usize);
1649
1650     if let Some(opt_self) = opt_self {
1651         params.push(opt_self);
1652     }
1653
1654     let early_lifetimes = early_bound_lifetimes_from_generics(tcx, ast_generics);
1655     params.extend(early_lifetimes.enumerate().map(|(i, param)| ty::GenericParamDef {
1656         name: param.name.ident().name,
1657         index: own_start + i as u32,
1658         def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1659         pure_wrt_drop: param.pure_wrt_drop,
1660         kind: ty::GenericParamDefKind::Lifetime,
1661     }));
1662
1663     // Now create the real type and const parameters.
1664     let type_start = own_start - has_self as u32 + params.len() as u32;
1665     let mut i = 0;
1666
1667     params.extend(ast_generics.params.iter().filter_map(|param| match param.kind {
1668         GenericParamKind::Lifetime { .. } => None,
1669         GenericParamKind::Type { ref default, synthetic, .. } => {
1670             if !allow_defaults && default.is_some() {
1671                 if !tcx.features().default_type_parameter_fallback {
1672                     tcx.struct_span_lint_hir(
1673                         lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
1674                         param.hir_id,
1675                         param.span,
1676                         |lint| {
1677                             lint.build(
1678                                 "defaults for type parameters are only allowed in \
1679                                  `struct`, `enum`, `type`, or `trait` definitions",
1680                             )
1681                             .emit();
1682                         },
1683                     );
1684                 }
1685             }
1686
1687             let kind = ty::GenericParamDefKind::Type { has_default: default.is_some(), synthetic };
1688
1689             let param_def = ty::GenericParamDef {
1690                 index: type_start + i as u32,
1691                 name: param.name.ident().name,
1692                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1693                 pure_wrt_drop: param.pure_wrt_drop,
1694                 kind,
1695             };
1696             i += 1;
1697             Some(param_def)
1698         }
1699         GenericParamKind::Const { default, .. } => {
1700             if !allow_defaults && default.is_some() {
1701                 tcx.sess.span_err(
1702                     param.span,
1703                     "defaults for const parameters are only allowed in \
1704                     `struct`, `enum`, `type`, or `trait` definitions",
1705                 );
1706             }
1707
1708             let param_def = ty::GenericParamDef {
1709                 index: type_start + i as u32,
1710                 name: param.name.ident().name,
1711                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1712                 pure_wrt_drop: param.pure_wrt_drop,
1713                 kind: ty::GenericParamDefKind::Const { has_default: default.is_some() },
1714             };
1715             i += 1;
1716             Some(param_def)
1717         }
1718     }));
1719
1720     // provide junk type parameter defs - the only place that
1721     // cares about anything but the length is instantiation,
1722     // and we don't do that for closures.
1723     if let Node::Expr(&hir::Expr {
1724         kind: hir::ExprKind::Closure(hir::Closure { movability: gen, .. }),
1725         ..
1726     }) = node
1727     {
1728         let dummy_args = if gen.is_some() {
1729             &["<resume_ty>", "<yield_ty>", "<return_ty>", "<witness>", "<upvars>"][..]
1730         } else {
1731             &["<closure_kind>", "<closure_signature>", "<upvars>"][..]
1732         };
1733
1734         params.extend(dummy_args.iter().enumerate().map(|(i, &arg)| ty::GenericParamDef {
1735             index: type_start + i as u32,
1736             name: Symbol::intern(arg),
1737             def_id,
1738             pure_wrt_drop: false,
1739             kind: ty::GenericParamDefKind::Type { has_default: false, synthetic: false },
1740         }));
1741     }
1742
1743     // provide junk type parameter defs for const blocks.
1744     if let Node::AnonConst(_) = node {
1745         let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1746         if let Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) = parent_node {
1747             params.push(ty::GenericParamDef {
1748                 index: type_start,
1749                 name: Symbol::intern("<const_ty>"),
1750                 def_id,
1751                 pure_wrt_drop: false,
1752                 kind: ty::GenericParamDefKind::Type { has_default: false, synthetic: false },
1753             });
1754         }
1755     }
1756
1757     let param_def_id_to_index = params.iter().map(|param| (param.def_id, param.index)).collect();
1758
1759     ty::Generics {
1760         parent: parent_def_id,
1761         parent_count,
1762         params,
1763         param_def_id_to_index,
1764         has_self: has_self || parent_has_self,
1765         has_late_bound_regions: has_late_bound_regions(tcx, node),
1766     }
1767 }
1768
1769 fn are_suggestable_generic_args(generic_args: &[hir::GenericArg<'_>]) -> bool {
1770     generic_args.iter().any(|arg| match arg {
1771         hir::GenericArg::Type(ty) => is_suggestable_infer_ty(ty),
1772         hir::GenericArg::Infer(_) => true,
1773         _ => false,
1774     })
1775 }
1776
1777 /// Whether `ty` is a type with `_` placeholders that can be inferred. Used in diagnostics only to
1778 /// use inference to provide suggestions for the appropriate type if possible.
1779 fn is_suggestable_infer_ty(ty: &hir::Ty<'_>) -> bool {
1780     debug!(?ty);
1781     use hir::TyKind::*;
1782     match &ty.kind {
1783         Infer => true,
1784         Slice(ty) => is_suggestable_infer_ty(ty),
1785         Array(ty, length) => {
1786             is_suggestable_infer_ty(ty) || matches!(length, hir::ArrayLen::Infer(_, _))
1787         }
1788         Tup(tys) => tys.iter().any(is_suggestable_infer_ty),
1789         Ptr(mut_ty) | Rptr(_, mut_ty) => is_suggestable_infer_ty(mut_ty.ty),
1790         OpaqueDef(_, generic_args) => are_suggestable_generic_args(generic_args),
1791         Path(hir::QPath::TypeRelative(ty, segment)) => {
1792             is_suggestable_infer_ty(ty) || are_suggestable_generic_args(segment.args().args)
1793         }
1794         Path(hir::QPath::Resolved(ty_opt, hir::Path { segments, .. })) => {
1795             ty_opt.map_or(false, is_suggestable_infer_ty)
1796                 || segments.iter().any(|segment| are_suggestable_generic_args(segment.args().args))
1797         }
1798         _ => false,
1799     }
1800 }
1801
1802 pub fn get_infer_ret_ty<'hir>(output: &'hir hir::FnRetTy<'hir>) -> Option<&'hir hir::Ty<'hir>> {
1803     if let hir::FnRetTy::Return(ty) = output {
1804         if is_suggestable_infer_ty(ty) {
1805             return Some(&*ty);
1806         }
1807     }
1808     None
1809 }
1810
1811 fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
1812     use rustc_hir::Node::*;
1813     use rustc_hir::*;
1814
1815     let def_id = def_id.expect_local();
1816     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1817
1818     let icx = ItemCtxt::new(tcx, def_id.to_def_id());
1819
1820     match tcx.hir().get(hir_id) {
1821         TraitItem(hir::TraitItem {
1822             kind: TraitItemKind::Fn(sig, TraitFn::Provided(_)),
1823             generics,
1824             ..
1825         })
1826         | Item(hir::Item { kind: ItemKind::Fn(sig, generics, _), .. }) => {
1827             infer_return_ty_for_fn_sig(tcx, sig, generics, def_id, &icx)
1828         }
1829
1830         ImplItem(hir::ImplItem { kind: ImplItemKind::Fn(sig, _), generics, .. }) => {
1831             // Do not try to inference the return type for a impl method coming from a trait
1832             if let Item(hir::Item { kind: ItemKind::Impl(i), .. }) =
1833                 tcx.hir().get(tcx.hir().get_parent_node(hir_id))
1834                 && i.of_trait.is_some()
1835             {
1836                 <dyn AstConv<'_>>::ty_of_fn(
1837                     &icx,
1838                     hir_id,
1839                     sig.header.unsafety,
1840                     sig.header.abi,
1841                     sig.decl,
1842                     Some(generics),
1843                     None,
1844                 )
1845             } else {
1846                 infer_return_ty_for_fn_sig(tcx, sig, generics, def_id, &icx)
1847             }
1848         }
1849
1850         TraitItem(hir::TraitItem {
1851             kind: TraitItemKind::Fn(FnSig { header, decl, span: _ }, _),
1852             generics,
1853             ..
1854         }) => <dyn AstConv<'_>>::ty_of_fn(
1855             &icx,
1856             hir_id,
1857             header.unsafety,
1858             header.abi,
1859             decl,
1860             Some(generics),
1861             None,
1862         ),
1863
1864         ForeignItem(&hir::ForeignItem { kind: ForeignItemKind::Fn(fn_decl, _, _), .. }) => {
1865             let abi = tcx.hir().get_foreign_abi(hir_id);
1866             compute_sig_of_foreign_fn_decl(tcx, def_id.to_def_id(), fn_decl, abi)
1867         }
1868
1869         Ctor(data) | Variant(hir::Variant { data, .. }) if data.ctor_hir_id().is_some() => {
1870             let ty = tcx.type_of(tcx.hir().get_parent_item(hir_id));
1871             let inputs =
1872                 data.fields().iter().map(|f| tcx.type_of(tcx.hir().local_def_id(f.hir_id)));
1873             ty::Binder::dummy(tcx.mk_fn_sig(
1874                 inputs,
1875                 ty,
1876                 false,
1877                 hir::Unsafety::Normal,
1878                 abi::Abi::Rust,
1879             ))
1880         }
1881
1882         Expr(&hir::Expr { kind: hir::ExprKind::Closure { .. }, .. }) => {
1883             // Closure signatures are not like other function
1884             // signatures and cannot be accessed through `fn_sig`. For
1885             // example, a closure signature excludes the `self`
1886             // argument. In any case they are embedded within the
1887             // closure type as part of the `ClosureSubsts`.
1888             //
1889             // To get the signature of a closure, you should use the
1890             // `sig` method on the `ClosureSubsts`:
1891             //
1892             //    substs.as_closure().sig(def_id, tcx)
1893             bug!(
1894                 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
1895             );
1896         }
1897
1898         x => {
1899             bug!("unexpected sort of node in fn_sig(): {:?}", x);
1900         }
1901     }
1902 }
1903
1904 fn infer_return_ty_for_fn_sig<'tcx>(
1905     tcx: TyCtxt<'tcx>,
1906     sig: &hir::FnSig<'_>,
1907     generics: &hir::Generics<'_>,
1908     def_id: LocalDefId,
1909     icx: &ItemCtxt<'tcx>,
1910 ) -> ty::PolyFnSig<'tcx> {
1911     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1912
1913     match get_infer_ret_ty(&sig.decl.output) {
1914         Some(ty) => {
1915             let fn_sig = tcx.typeck(def_id).liberated_fn_sigs()[hir_id];
1916             // Typeck doesn't expect erased regions to be returned from `type_of`.
1917             let fn_sig = tcx.fold_regions(fn_sig, |r, _| match *r {
1918                 ty::ReErased => tcx.lifetimes.re_static,
1919                 _ => r,
1920             });
1921             let fn_sig = ty::Binder::dummy(fn_sig);
1922
1923             let mut visitor = HirPlaceholderCollector::default();
1924             visitor.visit_ty(ty);
1925             let mut diag = bad_placeholder(tcx, visitor.0, "return type");
1926             let ret_ty = fn_sig.skip_binder().output();
1927             if ret_ty.is_suggestable(tcx, false) {
1928                 diag.span_suggestion(
1929                     ty.span,
1930                     "replace with the correct return type",
1931                     ret_ty,
1932                     Applicability::MachineApplicable,
1933                 );
1934             } else if matches!(ret_ty.kind(), ty::FnDef(..)) {
1935                 let fn_sig = ret_ty.fn_sig(tcx);
1936                 if fn_sig
1937                     .skip_binder()
1938                     .inputs_and_output
1939                     .iter()
1940                     .all(|t| t.is_suggestable(tcx, false))
1941                 {
1942                     diag.span_suggestion(
1943                         ty.span,
1944                         "replace with the correct return type",
1945                         fn_sig,
1946                         Applicability::MachineApplicable,
1947                     );
1948                 }
1949             } else if ret_ty.is_closure() {
1950                 // We're dealing with a closure, so we should suggest using `impl Fn` or trait bounds
1951                 // to prevent the user from getting a papercut while trying to use the unique closure
1952                 // syntax (e.g. `[closure@src/lib.rs:2:5: 2:9]`).
1953                 diag.help("consider using an `Fn`, `FnMut`, or `FnOnce` trait bound");
1954                 diag.note("for more information on `Fn` traits and closure types, see https://doc.rust-lang.org/book/ch13-01-closures.html");
1955             }
1956             diag.emit();
1957
1958             fn_sig
1959         }
1960         None => <dyn AstConv<'_>>::ty_of_fn(
1961             icx,
1962             hir_id,
1963             sig.header.unsafety,
1964             sig.header.abi,
1965             sig.decl,
1966             Some(generics),
1967             None,
1968         ),
1969     }
1970 }
1971
1972 fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> {
1973     let icx = ItemCtxt::new(tcx, def_id);
1974     match tcx.hir().expect_item(def_id.expect_local()).kind {
1975         hir::ItemKind::Impl(ref impl_) => impl_.of_trait.as_ref().map(|ast_trait_ref| {
1976             let selfty = tcx.type_of(def_id);
1977             <dyn AstConv<'_>>::instantiate_mono_trait_ref(&icx, ast_trait_ref, selfty)
1978         }),
1979         _ => bug!(),
1980     }
1981 }
1982
1983 fn impl_polarity(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ImplPolarity {
1984     let is_rustc_reservation = tcx.has_attr(def_id, sym::rustc_reservation_impl);
1985     let item = tcx.hir().expect_item(def_id.expect_local());
1986     match &item.kind {
1987         hir::ItemKind::Impl(hir::Impl {
1988             polarity: hir::ImplPolarity::Negative(span),
1989             of_trait,
1990             ..
1991         }) => {
1992             if is_rustc_reservation {
1993                 let span = span.to(of_trait.as_ref().map_or(*span, |t| t.path.span));
1994                 tcx.sess.span_err(span, "reservation impls can't be negative");
1995             }
1996             ty::ImplPolarity::Negative
1997         }
1998         hir::ItemKind::Impl(hir::Impl {
1999             polarity: hir::ImplPolarity::Positive,
2000             of_trait: None,
2001             ..
2002         }) => {
2003             if is_rustc_reservation {
2004                 tcx.sess.span_err(item.span, "reservation impls can't be inherent");
2005             }
2006             ty::ImplPolarity::Positive
2007         }
2008         hir::ItemKind::Impl(hir::Impl {
2009             polarity: hir::ImplPolarity::Positive,
2010             of_trait: Some(_),
2011             ..
2012         }) => {
2013             if is_rustc_reservation {
2014                 ty::ImplPolarity::Reservation
2015             } else {
2016                 ty::ImplPolarity::Positive
2017             }
2018         }
2019         item => bug!("impl_polarity: {:?} not an impl", item),
2020     }
2021 }
2022
2023 /// Returns the early-bound lifetimes declared in this generics
2024 /// listing. For anything other than fns/methods, this is just all
2025 /// the lifetimes that are declared. For fns or methods, we have to
2026 /// screen out those that do not appear in any where-clauses etc using
2027 /// `resolve_lifetime::early_bound_lifetimes`.
2028 fn early_bound_lifetimes_from_generics<'a, 'tcx: 'a>(
2029     tcx: TyCtxt<'tcx>,
2030     generics: &'a hir::Generics<'a>,
2031 ) -> impl Iterator<Item = &'a hir::GenericParam<'a>> + Captures<'tcx> {
2032     generics.params.iter().filter(move |param| match param.kind {
2033         GenericParamKind::Lifetime { .. } => !tcx.is_late_bound(param.hir_id),
2034         _ => false,
2035     })
2036 }
2037
2038 /// Returns a list of type predicates for the definition with ID `def_id`, including inferred
2039 /// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus
2040 /// inferred constraints concerning which regions outlive other regions.
2041 fn predicates_defined_on(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2042     debug!("predicates_defined_on({:?})", def_id);
2043     let mut result = tcx.explicit_predicates_of(def_id);
2044     debug!("predicates_defined_on: explicit_predicates_of({:?}) = {:?}", def_id, result,);
2045     let inferred_outlives = tcx.inferred_outlives_of(def_id);
2046     if !inferred_outlives.is_empty() {
2047         debug!(
2048             "predicates_defined_on: inferred_outlives_of({:?}) = {:?}",
2049             def_id, inferred_outlives,
2050         );
2051         if result.predicates.is_empty() {
2052             result.predicates = inferred_outlives;
2053         } else {
2054             result.predicates = tcx
2055                 .arena
2056                 .alloc_from_iter(result.predicates.iter().chain(inferred_outlives).copied());
2057         }
2058     }
2059
2060     debug!("predicates_defined_on({:?}) = {:?}", def_id, result);
2061     result
2062 }
2063
2064 /// Returns a list of all type predicates (explicit and implicit) for the definition with
2065 /// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus
2066 /// `Self: Trait` predicates for traits.
2067 fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2068     let mut result = tcx.predicates_defined_on(def_id);
2069
2070     if tcx.is_trait(def_id) {
2071         // For traits, add `Self: Trait` predicate. This is
2072         // not part of the predicates that a user writes, but it
2073         // is something that one must prove in order to invoke a
2074         // method or project an associated type.
2075         //
2076         // In the chalk setup, this predicate is not part of the
2077         // "predicates" for a trait item. But it is useful in
2078         // rustc because if you directly (e.g.) invoke a trait
2079         // method like `Trait::method(...)`, you must naturally
2080         // prove that the trait applies to the types that were
2081         // used, and adding the predicate into this list ensures
2082         // that this is done.
2083         //
2084         // We use a DUMMY_SP here as a way to signal trait bounds that come
2085         // from the trait itself that *shouldn't* be shown as the source of
2086         // an obligation and instead be skipped. Otherwise we'd use
2087         // `tcx.def_span(def_id);`
2088
2089         let constness = if tcx.has_attr(def_id, sym::const_trait) {
2090             ty::BoundConstness::ConstIfConst
2091         } else {
2092             ty::BoundConstness::NotConst
2093         };
2094
2095         let span = rustc_span::DUMMY_SP;
2096         result.predicates =
2097             tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once((
2098                 ty::TraitRef::identity(tcx, def_id).with_constness(constness).to_predicate(tcx),
2099                 span,
2100             ))));
2101     }
2102     debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
2103     result
2104 }
2105
2106 /// Returns a list of user-specified type predicates for the definition with ID `def_id`.
2107 /// N.B., this does not include any implied/inferred constraints.
2108 fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2109     use rustc_hir::*;
2110
2111     debug!("explicit_predicates_of(def_id={:?})", def_id);
2112
2113     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2114     let node = tcx.hir().get(hir_id);
2115
2116     let mut is_trait = None;
2117     let mut is_default_impl_trait = None;
2118
2119     let icx = ItemCtxt::new(tcx, def_id);
2120
2121     const NO_GENERICS: &hir::Generics<'_> = hir::Generics::empty();
2122
2123     // We use an `IndexSet` to preserves order of insertion.
2124     // Preserving the order of insertion is important here so as not to break UI tests.
2125     let mut predicates: FxIndexSet<(ty::Predicate<'_>, Span)> = FxIndexSet::default();
2126
2127     let ast_generics = match node {
2128         Node::TraitItem(item) => item.generics,
2129
2130         Node::ImplItem(item) => item.generics,
2131
2132         Node::Item(item) => {
2133             match item.kind {
2134                 ItemKind::Impl(ref impl_) => {
2135                     if impl_.defaultness.is_default() {
2136                         is_default_impl_trait = tcx.impl_trait_ref(def_id).map(ty::Binder::dummy);
2137                     }
2138                     &impl_.generics
2139                 }
2140                 ItemKind::Fn(.., ref generics, _)
2141                 | ItemKind::TyAlias(_, ref generics)
2142                 | ItemKind::Enum(_, ref generics)
2143                 | ItemKind::Struct(_, ref generics)
2144                 | ItemKind::Union(_, ref generics) => *generics,
2145
2146                 ItemKind::Trait(_, _, ref generics, ..) => {
2147                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2148                     *generics
2149                 }
2150                 ItemKind::TraitAlias(ref generics, _) => {
2151                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2152                     *generics
2153                 }
2154                 ItemKind::OpaqueTy(OpaqueTy {
2155                     origin: hir::OpaqueTyOrigin::AsyncFn(..) | hir::OpaqueTyOrigin::FnReturn(..),
2156                     ..
2157                 }) => {
2158                     // return-position impl trait
2159                     //
2160                     // We don't inherit predicates from the parent here:
2161                     // If we have, say `fn f<'a, T: 'a>() -> impl Sized {}`
2162                     // then the return type is `f::<'static, T>::{{opaque}}`.
2163                     //
2164                     // If we inherited the predicates of `f` then we would
2165                     // require that `T: 'static` to show that the return
2166                     // type is well-formed.
2167                     //
2168                     // The only way to have something with this opaque type
2169                     // is from the return type of the containing function,
2170                     // which will ensure that the function's predicates
2171                     // hold.
2172                     return ty::GenericPredicates { parent: None, predicates: &[] };
2173                 }
2174                 ItemKind::OpaqueTy(OpaqueTy {
2175                     ref generics,
2176                     origin: hir::OpaqueTyOrigin::TyAlias,
2177                     ..
2178                 }) => {
2179                     // type-alias impl trait
2180                     generics
2181                 }
2182
2183                 _ => NO_GENERICS,
2184             }
2185         }
2186
2187         Node::ForeignItem(item) => match item.kind {
2188             ForeignItemKind::Static(..) => NO_GENERICS,
2189             ForeignItemKind::Fn(_, _, ref generics) => *generics,
2190             ForeignItemKind::Type => NO_GENERICS,
2191         },
2192
2193         _ => NO_GENERICS,
2194     };
2195
2196     let generics = tcx.generics_of(def_id);
2197     let parent_count = generics.parent_count as u32;
2198     let has_own_self = generics.has_self && parent_count == 0;
2199
2200     // Below we'll consider the bounds on the type parameters (including `Self`)
2201     // and the explicit where-clauses, but to get the full set of predicates
2202     // on a trait we need to add in the supertrait bounds and bounds found on
2203     // associated types.
2204     if let Some(_trait_ref) = is_trait {
2205         predicates.extend(tcx.super_predicates_of(def_id).predicates.iter().cloned());
2206     }
2207
2208     // In default impls, we can assume that the self type implements
2209     // the trait. So in:
2210     //
2211     //     default impl Foo for Bar { .. }
2212     //
2213     // we add a default where clause `Foo: Bar`. We do a similar thing for traits
2214     // (see below). Recall that a default impl is not itself an impl, but rather a
2215     // set of defaults that can be incorporated into another impl.
2216     if let Some(trait_ref) = is_default_impl_trait {
2217         predicates.insert((trait_ref.without_const().to_predicate(tcx), tcx.def_span(def_id)));
2218     }
2219
2220     // Collect the region predicates that were declared inline as
2221     // well. In the case of parameters declared on a fn or method, we
2222     // have to be careful to only iterate over early-bound regions.
2223     let mut index = parent_count
2224         + has_own_self as u32
2225         + early_bound_lifetimes_from_generics(tcx, ast_generics).count() as u32;
2226
2227     // Collect the predicates that were written inline by the user on each
2228     // type parameter (e.g., `<T: Foo>`).
2229     for param in ast_generics.params {
2230         match param.kind {
2231             // We already dealt with early bound lifetimes above.
2232             GenericParamKind::Lifetime { .. } => (),
2233             GenericParamKind::Type { .. } => {
2234                 let name = param.name.ident().name;
2235                 let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
2236                 index += 1;
2237
2238                 let mut bounds = Bounds::default();
2239                 // Params are implicitly sized unless a `?Sized` bound is found
2240                 <dyn AstConv<'_>>::add_implicitly_sized(
2241                     &icx,
2242                     &mut bounds,
2243                     &[],
2244                     Some((param.hir_id, ast_generics.predicates)),
2245                     param.span,
2246                 );
2247                 predicates.extend(bounds.predicates(tcx, param_ty));
2248             }
2249             GenericParamKind::Const { .. } => {
2250                 // Bounds on const parameters are currently not possible.
2251                 index += 1;
2252             }
2253         }
2254     }
2255
2256     // Add in the bounds that appear in the where-clause.
2257     for predicate in ast_generics.predicates {
2258         match predicate {
2259             hir::WherePredicate::BoundPredicate(bound_pred) => {
2260                 let ty = icx.to_ty(bound_pred.bounded_ty);
2261                 let bound_vars = icx.tcx.late_bound_vars(bound_pred.bounded_ty.hir_id);
2262
2263                 // Keep the type around in a dummy predicate, in case of no bounds.
2264                 // That way, `where Ty:` is not a complete noop (see #53696) and `Ty`
2265                 // is still checked for WF.
2266                 if bound_pred.bounds.is_empty() {
2267                     if let ty::Param(_) = ty.kind() {
2268                         // This is a `where T:`, which can be in the HIR from the
2269                         // transformation that moves `?Sized` to `T`'s declaration.
2270                         // We can skip the predicate because type parameters are
2271                         // trivially WF, but also we *should*, to avoid exposing
2272                         // users who never wrote `where Type:,` themselves, to
2273                         // compiler/tooling bugs from not handling WF predicates.
2274                     } else {
2275                         let span = bound_pred.bounded_ty.span;
2276                         let predicate = ty::Binder::bind_with_vars(
2277                             ty::PredicateKind::WellFormed(ty.into()),
2278                             bound_vars,
2279                         );
2280                         predicates.insert((predicate.to_predicate(tcx), span));
2281                     }
2282                 }
2283
2284                 let mut bounds = Bounds::default();
2285                 <dyn AstConv<'_>>::add_bounds(
2286                     &icx,
2287                     ty,
2288                     bound_pred.bounds.iter(),
2289                     &mut bounds,
2290                     bound_vars,
2291                 );
2292                 predicates.extend(bounds.predicates(tcx, ty));
2293             }
2294
2295             hir::WherePredicate::RegionPredicate(region_pred) => {
2296                 let r1 = <dyn AstConv<'_>>::ast_region_to_region(&icx, &region_pred.lifetime, None);
2297                 predicates.extend(region_pred.bounds.iter().map(|bound| {
2298                     let (r2, span) = match bound {
2299                         hir::GenericBound::Outlives(lt) => {
2300                             (<dyn AstConv<'_>>::ast_region_to_region(&icx, lt, None), lt.span)
2301                         }
2302                         _ => bug!(),
2303                     };
2304                     let pred = ty::Binder::dummy(ty::PredicateKind::RegionOutlives(
2305                         ty::OutlivesPredicate(r1, r2),
2306                     ))
2307                     .to_predicate(icx.tcx);
2308
2309                     (pred, span)
2310                 }))
2311             }
2312
2313             hir::WherePredicate::EqPredicate(..) => {
2314                 // FIXME(#20041)
2315             }
2316         }
2317     }
2318
2319     if tcx.features().generic_const_exprs {
2320         predicates.extend(const_evaluatable_predicates_of(tcx, def_id.expect_local()));
2321     }
2322
2323     let mut predicates: Vec<_> = predicates.into_iter().collect();
2324
2325     // Subtle: before we store the predicates into the tcx, we
2326     // sort them so that predicates like `T: Foo<Item=U>` come
2327     // before uses of `U`.  This avoids false ambiguity errors
2328     // in trait checking. See `setup_constraining_predicates`
2329     // for details.
2330     if let Node::Item(&Item { kind: ItemKind::Impl { .. }, .. }) = node {
2331         let self_ty = tcx.type_of(def_id);
2332         let trait_ref = tcx.impl_trait_ref(def_id);
2333         cgp::setup_constraining_predicates(
2334             tcx,
2335             &mut predicates,
2336             trait_ref,
2337             &mut cgp::parameters_for_impl(self_ty, trait_ref),
2338         );
2339     }
2340
2341     let result = ty::GenericPredicates {
2342         parent: generics.parent,
2343         predicates: tcx.arena.alloc_from_iter(predicates),
2344     };
2345     debug!("explicit_predicates_of(def_id={:?}) = {:?}", def_id, result);
2346     result
2347 }
2348
2349 fn const_evaluatable_predicates_of<'tcx>(
2350     tcx: TyCtxt<'tcx>,
2351     def_id: LocalDefId,
2352 ) -> FxIndexSet<(ty::Predicate<'tcx>, Span)> {
2353     struct ConstCollector<'tcx> {
2354         tcx: TyCtxt<'tcx>,
2355         preds: FxIndexSet<(ty::Predicate<'tcx>, Span)>,
2356     }
2357
2358     impl<'tcx> intravisit::Visitor<'tcx> for ConstCollector<'tcx> {
2359         fn visit_anon_const(&mut self, c: &'tcx hir::AnonConst) {
2360             let def_id = self.tcx.hir().local_def_id(c.hir_id);
2361             let ct = ty::Const::from_anon_const(self.tcx, def_id);
2362             if let ty::ConstKind::Unevaluated(uv) = ct.kind() {
2363                 assert_eq!(uv.promoted, None);
2364                 let span = self.tcx.hir().span(c.hir_id);
2365                 self.preds.insert((
2366                     ty::Binder::dummy(ty::PredicateKind::ConstEvaluatable(uv.shrink()))
2367                         .to_predicate(self.tcx),
2368                     span,
2369                 ));
2370             }
2371         }
2372
2373         fn visit_const_param_default(&mut self, _param: HirId, _ct: &'tcx hir::AnonConst) {
2374             // Do not look into const param defaults,
2375             // these get checked when they are actually instantiated.
2376             //
2377             // We do not want the following to error:
2378             //
2379             //     struct Foo<const N: usize, const M: usize = { N + 1 }>;
2380             //     struct Bar<const N: usize>(Foo<N, 3>);
2381         }
2382     }
2383
2384     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
2385     let node = tcx.hir().get(hir_id);
2386
2387     let mut collector = ConstCollector { tcx, preds: FxIndexSet::default() };
2388     if let hir::Node::Item(item) = node && let hir::ItemKind::Impl(ref impl_) = item.kind {
2389         if let Some(of_trait) = &impl_.of_trait {
2390             debug!("const_evaluatable_predicates_of({:?}): visit impl trait_ref", def_id);
2391             collector.visit_trait_ref(of_trait);
2392         }
2393
2394         debug!("const_evaluatable_predicates_of({:?}): visit_self_ty", def_id);
2395         collector.visit_ty(impl_.self_ty);
2396     }
2397
2398     if let Some(generics) = node.generics() {
2399         debug!("const_evaluatable_predicates_of({:?}): visit_generics", def_id);
2400         collector.visit_generics(generics);
2401     }
2402
2403     if let Some(fn_sig) = tcx.hir().fn_sig_by_hir_id(hir_id) {
2404         debug!("const_evaluatable_predicates_of({:?}): visit_fn_decl", def_id);
2405         collector.visit_fn_decl(fn_sig.decl);
2406     }
2407     debug!("const_evaluatable_predicates_of({:?}) = {:?}", def_id, collector.preds);
2408
2409     collector.preds
2410 }
2411
2412 fn trait_explicit_predicates_and_bounds(
2413     tcx: TyCtxt<'_>,
2414     def_id: LocalDefId,
2415 ) -> ty::GenericPredicates<'_> {
2416     assert_eq!(tcx.def_kind(def_id), DefKind::Trait);
2417     gather_explicit_predicates_of(tcx, def_id.to_def_id())
2418 }
2419
2420 fn explicit_predicates_of<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> ty::GenericPredicates<'tcx> {
2421     let def_kind = tcx.def_kind(def_id);
2422     if let DefKind::Trait = def_kind {
2423         // Remove bounds on associated types from the predicates, they will be
2424         // returned by `explicit_item_bounds`.
2425         let predicates_and_bounds = tcx.trait_explicit_predicates_and_bounds(def_id.expect_local());
2426         let trait_identity_substs = InternalSubsts::identity_for_item(tcx, def_id);
2427
2428         let is_assoc_item_ty = |ty: Ty<'tcx>| {
2429             // For a predicate from a where clause to become a bound on an
2430             // associated type:
2431             // * It must use the identity substs of the item.
2432             //     * Since any generic parameters on the item are not in scope,
2433             //       this means that the item is not a GAT, and its identity
2434             //       substs are the same as the trait's.
2435             // * It must be an associated type for this trait (*not* a
2436             //   supertrait).
2437             if let ty::Projection(projection) = ty.kind() {
2438                 projection.substs == trait_identity_substs
2439                     && tcx.associated_item(projection.item_def_id).container_id(tcx) == def_id
2440             } else {
2441                 false
2442             }
2443         };
2444
2445         let predicates: Vec<_> = predicates_and_bounds
2446             .predicates
2447             .iter()
2448             .copied()
2449             .filter(|(pred, _)| match pred.kind().skip_binder() {
2450                 ty::PredicateKind::Trait(tr) => !is_assoc_item_ty(tr.self_ty()),
2451                 ty::PredicateKind::Projection(proj) => {
2452                     !is_assoc_item_ty(proj.projection_ty.self_ty())
2453                 }
2454                 ty::PredicateKind::TypeOutlives(outlives) => !is_assoc_item_ty(outlives.0),
2455                 _ => true,
2456             })
2457             .collect();
2458         if predicates.len() == predicates_and_bounds.predicates.len() {
2459             predicates_and_bounds
2460         } else {
2461             ty::GenericPredicates {
2462                 parent: predicates_and_bounds.parent,
2463                 predicates: tcx.arena.alloc_slice(&predicates),
2464             }
2465         }
2466     } else {
2467         if matches!(def_kind, DefKind::AnonConst) && tcx.lazy_normalization() {
2468             let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2469             if tcx.hir().opt_const_param_default_param_hir_id(hir_id).is_some() {
2470                 // In `generics_of` we set the generics' parent to be our parent's parent which means that
2471                 // we lose out on the predicates of our actual parent if we dont return those predicates here.
2472                 // (See comment in `generics_of` for more information on why the parent shenanigans is necessary)
2473                 //
2474                 // struct Foo<T, const N: usize = { <T as Trait>::ASSOC }>(T) where T: Trait;
2475                 //        ^^^                     ^^^^^^^^^^^^^^^^^^^^^^^ the def id we are calling
2476                 //        ^^^                                             explicit_predicates_of on
2477                 //        parent item we dont have set as the
2478                 //        parent of generics returned by `generics_of`
2479                 //
2480                 // In the above code we want the anon const to have predicates in its param env for `T: Trait`
2481                 let item_def_id = tcx.hir().get_parent_item(hir_id);
2482                 // In the above code example we would be calling `explicit_predicates_of(Foo)` here
2483                 return tcx.explicit_predicates_of(item_def_id);
2484             }
2485         }
2486         gather_explicit_predicates_of(tcx, def_id)
2487     }
2488 }
2489
2490 /// Converts a specific `GenericBound` from the AST into a set of
2491 /// predicates that apply to the self type. A vector is returned
2492 /// because this can be anywhere from zero predicates (`T: ?Sized` adds no
2493 /// predicates) to one (`T: Foo`) to many (`T: Bar<X = i32>` adds `T: Bar`
2494 /// and `<T as Bar>::X == i32`).
2495 fn predicates_from_bound<'tcx>(
2496     astconv: &dyn AstConv<'tcx>,
2497     param_ty: Ty<'tcx>,
2498     bound: &'tcx hir::GenericBound<'tcx>,
2499     bound_vars: &'tcx ty::List<ty::BoundVariableKind>,
2500 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2501     let mut bounds = Bounds::default();
2502     astconv.add_bounds(param_ty, [bound].into_iter(), &mut bounds, bound_vars);
2503     bounds.predicates(astconv.tcx(), param_ty).collect()
2504 }
2505
2506 fn compute_sig_of_foreign_fn_decl<'tcx>(
2507     tcx: TyCtxt<'tcx>,
2508     def_id: DefId,
2509     decl: &'tcx hir::FnDecl<'tcx>,
2510     abi: abi::Abi,
2511 ) -> ty::PolyFnSig<'tcx> {
2512     let unsafety = if abi == abi::Abi::RustIntrinsic {
2513         intrinsic_operation_unsafety(tcx.item_name(def_id))
2514     } else {
2515         hir::Unsafety::Unsafe
2516     };
2517     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2518     let fty = <dyn AstConv<'_>>::ty_of_fn(
2519         &ItemCtxt::new(tcx, def_id),
2520         hir_id,
2521         unsafety,
2522         abi,
2523         decl,
2524         None,
2525         None,
2526     );
2527
2528     // Feature gate SIMD types in FFI, since I am not sure that the
2529     // ABIs are handled at all correctly. -huonw
2530     if abi != abi::Abi::RustIntrinsic
2531         && abi != abi::Abi::PlatformIntrinsic
2532         && !tcx.features().simd_ffi
2533     {
2534         let check = |ast_ty: &hir::Ty<'_>, ty: Ty<'_>| {
2535             if ty.is_simd() {
2536                 let snip = tcx
2537                     .sess
2538                     .source_map()
2539                     .span_to_snippet(ast_ty.span)
2540                     .map_or_else(|_| String::new(), |s| format!(" `{}`", s));
2541                 tcx.sess
2542                     .struct_span_err(
2543                         ast_ty.span,
2544                         &format!(
2545                             "use of SIMD type{} in FFI is highly experimental and \
2546                              may result in invalid code",
2547                             snip
2548                         ),
2549                     )
2550                     .help("add `#![feature(simd_ffi)]` to the crate attributes to enable")
2551                     .emit();
2552             }
2553         };
2554         for (input, ty) in iter::zip(decl.inputs, fty.inputs().skip_binder()) {
2555             check(input, *ty)
2556         }
2557         if let hir::FnRetTy::Return(ref ty) = decl.output {
2558             check(ty, fty.output().skip_binder())
2559         }
2560     }
2561
2562     fty
2563 }
2564
2565 fn is_foreign_item(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2566     match tcx.hir().get_if_local(def_id) {
2567         Some(Node::ForeignItem(..)) => true,
2568         Some(_) => false,
2569         _ => bug!("is_foreign_item applied to non-local def-id {:?}", def_id),
2570     }
2571 }
2572
2573 fn generator_kind(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::GeneratorKind> {
2574     match tcx.hir().get_if_local(def_id) {
2575         Some(Node::Expr(&rustc_hir::Expr {
2576             kind: rustc_hir::ExprKind::Closure(&rustc_hir::Closure { body, .. }),
2577             ..
2578         })) => tcx.hir().body(body).generator_kind(),
2579         Some(_) => None,
2580         _ => bug!("generator_kind applied to non-local def-id {:?}", def_id),
2581     }
2582 }
2583
2584 fn from_target_feature(
2585     tcx: TyCtxt<'_>,
2586     attr: &ast::Attribute,
2587     supported_target_features: &FxHashMap<String, Option<Symbol>>,
2588     target_features: &mut Vec<Symbol>,
2589 ) {
2590     let Some(list) = attr.meta_item_list() else { return };
2591     let bad_item = |span| {
2592         let msg = "malformed `target_feature` attribute input";
2593         let code = "enable = \"..\"";
2594         tcx.sess
2595             .struct_span_err(span, msg)
2596             .span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
2597             .emit();
2598     };
2599     let rust_features = tcx.features();
2600     for item in list {
2601         // Only `enable = ...` is accepted in the meta-item list.
2602         if !item.has_name(sym::enable) {
2603             bad_item(item.span());
2604             continue;
2605         }
2606
2607         // Must be of the form `enable = "..."` (a string).
2608         let Some(value) = item.value_str() else {
2609             bad_item(item.span());
2610             continue;
2611         };
2612
2613         // We allow comma separation to enable multiple features.
2614         target_features.extend(value.as_str().split(',').filter_map(|feature| {
2615             let Some(feature_gate) = supported_target_features.get(feature) else {
2616                 let msg =
2617                     format!("the feature named `{}` is not valid for this target", feature);
2618                 let mut err = tcx.sess.struct_span_err(item.span(), &msg);
2619                 err.span_label(
2620                     item.span(),
2621                     format!("`{}` is not valid for this target", feature),
2622                 );
2623                 if let Some(stripped) = feature.strip_prefix('+') {
2624                     let valid = supported_target_features.contains_key(stripped);
2625                     if valid {
2626                         err.help("consider removing the leading `+` in the feature name");
2627                     }
2628                 }
2629                 err.emit();
2630                 return None;
2631             };
2632
2633             // Only allow features whose feature gates have been enabled.
2634             let allowed = match feature_gate.as_ref().copied() {
2635                 Some(sym::arm_target_feature) => rust_features.arm_target_feature,
2636                 Some(sym::hexagon_target_feature) => rust_features.hexagon_target_feature,
2637                 Some(sym::powerpc_target_feature) => rust_features.powerpc_target_feature,
2638                 Some(sym::mips_target_feature) => rust_features.mips_target_feature,
2639                 Some(sym::riscv_target_feature) => rust_features.riscv_target_feature,
2640                 Some(sym::avx512_target_feature) => rust_features.avx512_target_feature,
2641                 Some(sym::sse4a_target_feature) => rust_features.sse4a_target_feature,
2642                 Some(sym::tbm_target_feature) => rust_features.tbm_target_feature,
2643                 Some(sym::wasm_target_feature) => rust_features.wasm_target_feature,
2644                 Some(sym::cmpxchg16b_target_feature) => rust_features.cmpxchg16b_target_feature,
2645                 Some(sym::movbe_target_feature) => rust_features.movbe_target_feature,
2646                 Some(sym::rtm_target_feature) => rust_features.rtm_target_feature,
2647                 Some(sym::f16c_target_feature) => rust_features.f16c_target_feature,
2648                 Some(sym::ermsb_target_feature) => rust_features.ermsb_target_feature,
2649                 Some(sym::bpf_target_feature) => rust_features.bpf_target_feature,
2650                 Some(sym::aarch64_ver_target_feature) => rust_features.aarch64_ver_target_feature,
2651                 Some(name) => bug!("unknown target feature gate {}", name),
2652                 None => true,
2653             };
2654             if !allowed {
2655                 feature_err(
2656                     &tcx.sess.parse_sess,
2657                     feature_gate.unwrap(),
2658                     item.span(),
2659                     &format!("the target feature `{}` is currently unstable", feature),
2660                 )
2661                 .emit();
2662             }
2663             Some(Symbol::intern(feature))
2664         }));
2665     }
2666 }
2667
2668 fn linkage_by_name(tcx: TyCtxt<'_>, def_id: LocalDefId, name: &str) -> Linkage {
2669     use rustc_middle::mir::mono::Linkage::*;
2670
2671     // Use the names from src/llvm/docs/LangRef.rst here. Most types are only
2672     // applicable to variable declarations and may not really make sense for
2673     // Rust code in the first place but allow them anyway and trust that the
2674     // user knows what they're doing. Who knows, unanticipated use cases may pop
2675     // up in the future.
2676     //
2677     // ghost, dllimport, dllexport and linkonce_odr_autohide are not supported
2678     // and don't have to be, LLVM treats them as no-ops.
2679     match name {
2680         "appending" => Appending,
2681         "available_externally" => AvailableExternally,
2682         "common" => Common,
2683         "extern_weak" => ExternalWeak,
2684         "external" => External,
2685         "internal" => Internal,
2686         "linkonce" => LinkOnceAny,
2687         "linkonce_odr" => LinkOnceODR,
2688         "private" => Private,
2689         "weak" => WeakAny,
2690         "weak_odr" => WeakODR,
2691         _ => tcx.sess.span_fatal(tcx.def_span(def_id), "invalid linkage specified"),
2692     }
2693 }
2694
2695 fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: DefId) -> CodegenFnAttrs {
2696     if cfg!(debug_assertions) {
2697         let def_kind = tcx.def_kind(did);
2698         assert!(
2699             def_kind.has_codegen_attrs(),
2700             "unexpected `def_kind` in `codegen_fn_attrs`: {def_kind:?}",
2701         );
2702     }
2703
2704     let did = did.expect_local();
2705     let attrs = tcx.hir().attrs(tcx.hir().local_def_id_to_hir_id(did));
2706     let mut codegen_fn_attrs = CodegenFnAttrs::new();
2707     if tcx.should_inherit_track_caller(did) {
2708         codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2709     }
2710
2711     // The panic_no_unwind function called by TerminatorKind::Abort will never
2712     // unwind. If the panic handler that it invokes unwind then it will simply
2713     // call the panic handler again.
2714     if Some(did.to_def_id()) == tcx.lang_items().panic_no_unwind() {
2715         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2716     }
2717
2718     let supported_target_features = tcx.supported_target_features(LOCAL_CRATE);
2719
2720     let mut inline_span = None;
2721     let mut link_ordinal_span = None;
2722     let mut no_sanitize_span = None;
2723     for attr in attrs.iter() {
2724         if attr.has_name(sym::cold) {
2725             codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD;
2726         } else if attr.has_name(sym::rustc_allocator) {
2727             codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR;
2728         } else if attr.has_name(sym::ffi_returns_twice) {
2729             if tcx.is_foreign_item(did) {
2730                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE;
2731             } else {
2732                 // `#[ffi_returns_twice]` is only allowed `extern fn`s.
2733                 struct_span_err!(
2734                     tcx.sess,
2735                     attr.span,
2736                     E0724,
2737                     "`#[ffi_returns_twice]` may only be used on foreign functions"
2738                 )
2739                 .emit();
2740             }
2741         } else if attr.has_name(sym::ffi_pure) {
2742             if tcx.is_foreign_item(did) {
2743                 if attrs.iter().any(|a| a.has_name(sym::ffi_const)) {
2744                     // `#[ffi_const]` functions cannot be `#[ffi_pure]`
2745                     struct_span_err!(
2746                         tcx.sess,
2747                         attr.span,
2748                         E0757,
2749                         "`#[ffi_const]` function cannot be `#[ffi_pure]`"
2750                     )
2751                     .emit();
2752                 } else {
2753                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_PURE;
2754                 }
2755             } else {
2756                 // `#[ffi_pure]` is only allowed on foreign functions
2757                 struct_span_err!(
2758                     tcx.sess,
2759                     attr.span,
2760                     E0755,
2761                     "`#[ffi_pure]` may only be used on foreign functions"
2762                 )
2763                 .emit();
2764             }
2765         } else if attr.has_name(sym::ffi_const) {
2766             if tcx.is_foreign_item(did) {
2767                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_CONST;
2768             } else {
2769                 // `#[ffi_const]` is only allowed on foreign functions
2770                 struct_span_err!(
2771                     tcx.sess,
2772                     attr.span,
2773                     E0756,
2774                     "`#[ffi_const]` may only be used on foreign functions"
2775                 )
2776                 .emit();
2777             }
2778         } else if attr.has_name(sym::rustc_allocator_nounwind) {
2779             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2780         } else if attr.has_name(sym::rustc_reallocator) {
2781             codegen_fn_attrs.flags |= CodegenFnAttrFlags::REALLOCATOR;
2782         } else if attr.has_name(sym::rustc_deallocator) {
2783             codegen_fn_attrs.flags |= CodegenFnAttrFlags::DEALLOCATOR;
2784         } else if attr.has_name(sym::rustc_allocator_zeroed) {
2785             codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR_ZEROED;
2786         } else if attr.has_name(sym::naked) {
2787             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
2788         } else if attr.has_name(sym::no_mangle) {
2789             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2790         } else if attr.has_name(sym::no_coverage) {
2791             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_COVERAGE;
2792         } else if attr.has_name(sym::rustc_std_internal_symbol) {
2793             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2794         } else if attr.has_name(sym::used) {
2795             let inner = attr.meta_item_list();
2796             match inner.as_deref() {
2797                 Some([item]) if item.has_name(sym::linker) => {
2798                     if !tcx.features().used_with_arg {
2799                         feature_err(
2800                             &tcx.sess.parse_sess,
2801                             sym::used_with_arg,
2802                             attr.span,
2803                             "`#[used(linker)]` is currently unstable",
2804                         )
2805                         .emit();
2806                     }
2807                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED_LINKER;
2808                 }
2809                 Some([item]) if item.has_name(sym::compiler) => {
2810                     if !tcx.features().used_with_arg {
2811                         feature_err(
2812                             &tcx.sess.parse_sess,
2813                             sym::used_with_arg,
2814                             attr.span,
2815                             "`#[used(compiler)]` is currently unstable",
2816                         )
2817                         .emit();
2818                     }
2819                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
2820                 }
2821                 Some(_) => {
2822                     tcx.sess.emit_err(errors::ExpectedUsedSymbol { span: attr.span });
2823                 }
2824                 None => {
2825                     // Unfortunately, unconditionally using `llvm.used` causes
2826                     // issues in handling `.init_array` with the gold linker,
2827                     // but using `llvm.compiler.used` caused a nontrival amount
2828                     // of unintentional ecosystem breakage -- particularly on
2829                     // Mach-O targets.
2830                     //
2831                     // As a result, we emit `llvm.compiler.used` only on ELF
2832                     // targets. This is somewhat ad-hoc, but actually follows
2833                     // our pre-LLVM 13 behavior (prior to the ecosystem
2834                     // breakage), and seems to match `clang`'s behavior as well
2835                     // (both before and after LLVM 13), possibly because they
2836                     // have similar compatibility concerns to us. See
2837                     // https://github.com/rust-lang/rust/issues/47384#issuecomment-1019080146
2838                     // and following comments for some discussion of this, as
2839                     // well as the comments in `rustc_codegen_llvm` where these
2840                     // flags are handled.
2841                     //
2842                     // Anyway, to be clear: this is still up in the air
2843                     // somewhat, and is subject to change in the future (which
2844                     // is a good thing, because this would ideally be a bit
2845                     // more firmed up).
2846                     let is_like_elf = !(tcx.sess.target.is_like_osx
2847                         || tcx.sess.target.is_like_windows
2848                         || tcx.sess.target.is_like_wasm);
2849                     codegen_fn_attrs.flags |= if is_like_elf {
2850                         CodegenFnAttrFlags::USED
2851                     } else {
2852                         CodegenFnAttrFlags::USED_LINKER
2853                     };
2854                 }
2855             }
2856         } else if attr.has_name(sym::cmse_nonsecure_entry) {
2857             if !matches!(tcx.fn_sig(did).abi(), abi::Abi::C { .. }) {
2858                 struct_span_err!(
2859                     tcx.sess,
2860                     attr.span,
2861                     E0776,
2862                     "`#[cmse_nonsecure_entry]` requires C ABI"
2863                 )
2864                 .emit();
2865             }
2866             if !tcx.sess.target.llvm_target.contains("thumbv8m") {
2867                 struct_span_err!(tcx.sess, attr.span, E0775, "`#[cmse_nonsecure_entry]` is only valid for targets with the TrustZone-M extension")
2868                     .emit();
2869             }
2870             codegen_fn_attrs.flags |= CodegenFnAttrFlags::CMSE_NONSECURE_ENTRY;
2871         } else if attr.has_name(sym::thread_local) {
2872             codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
2873         } else if attr.has_name(sym::track_caller) {
2874             if !tcx.is_closure(did.to_def_id()) && tcx.fn_sig(did).abi() != abi::Abi::Rust {
2875                 struct_span_err!(tcx.sess, attr.span, E0737, "`#[track_caller]` requires Rust ABI")
2876                     .emit();
2877             }
2878             if tcx.is_closure(did.to_def_id()) && !tcx.features().closure_track_caller {
2879                 feature_err(
2880                     &tcx.sess.parse_sess,
2881                     sym::closure_track_caller,
2882                     attr.span,
2883                     "`#[track_caller]` on closures is currently unstable",
2884                 )
2885                 .emit();
2886             }
2887             codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2888         } else if attr.has_name(sym::export_name) {
2889             if let Some(s) = attr.value_str() {
2890                 if s.as_str().contains('\0') {
2891                     // `#[export_name = ...]` will be converted to a null-terminated string,
2892                     // so it may not contain any null characters.
2893                     struct_span_err!(
2894                         tcx.sess,
2895                         attr.span,
2896                         E0648,
2897                         "`export_name` may not contain null characters"
2898                     )
2899                     .emit();
2900                 }
2901                 codegen_fn_attrs.export_name = Some(s);
2902             }
2903         } else if attr.has_name(sym::target_feature) {
2904             if !tcx.is_closure(did.to_def_id())
2905                 && tcx.fn_sig(did).unsafety() == hir::Unsafety::Normal
2906             {
2907                 if tcx.sess.target.is_like_wasm || tcx.sess.opts.actually_rustdoc {
2908                     // The `#[target_feature]` attribute is allowed on
2909                     // WebAssembly targets on all functions, including safe
2910                     // ones. Other targets require that `#[target_feature]` is
2911                     // only applied to unsafe functions (pending the
2912                     // `target_feature_11` feature) because on most targets
2913                     // execution of instructions that are not supported is
2914                     // considered undefined behavior. For WebAssembly which is a
2915                     // 100% safe target at execution time it's not possible to
2916                     // execute undefined instructions, and even if a future
2917                     // feature was added in some form for this it would be a
2918                     // deterministic trap. There is no undefined behavior when
2919                     // executing WebAssembly so `#[target_feature]` is allowed
2920                     // on safe functions (but again, only for WebAssembly)
2921                     //
2922                     // Note that this is also allowed if `actually_rustdoc` so
2923                     // if a target is documenting some wasm-specific code then
2924                     // it's not spuriously denied.
2925                 } else if !tcx.features().target_feature_11 {
2926                     let mut err = feature_err(
2927                         &tcx.sess.parse_sess,
2928                         sym::target_feature_11,
2929                         attr.span,
2930                         "`#[target_feature(..)]` can only be applied to `unsafe` functions",
2931                     );
2932                     err.span_label(tcx.def_span(did), "not an `unsafe` function");
2933                     err.emit();
2934                 } else {
2935                     check_target_feature_trait_unsafe(tcx, did, attr.span);
2936                 }
2937             }
2938             from_target_feature(
2939                 tcx,
2940                 attr,
2941                 supported_target_features,
2942                 &mut codegen_fn_attrs.target_features,
2943             );
2944         } else if attr.has_name(sym::linkage) {
2945             if let Some(val) = attr.value_str() {
2946                 codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, did, val.as_str()));
2947             }
2948         } else if attr.has_name(sym::link_section) {
2949             if let Some(val) = attr.value_str() {
2950                 if val.as_str().bytes().any(|b| b == 0) {
2951                     let msg = format!(
2952                         "illegal null byte in link_section \
2953                          value: `{}`",
2954                         &val
2955                     );
2956                     tcx.sess.span_err(attr.span, &msg);
2957                 } else {
2958                     codegen_fn_attrs.link_section = Some(val);
2959                 }
2960             }
2961         } else if attr.has_name(sym::link_name) {
2962             codegen_fn_attrs.link_name = attr.value_str();
2963         } else if attr.has_name(sym::link_ordinal) {
2964             link_ordinal_span = Some(attr.span);
2965             if let ordinal @ Some(_) = check_link_ordinal(tcx, attr) {
2966                 codegen_fn_attrs.link_ordinal = ordinal;
2967             }
2968         } else if attr.has_name(sym::no_sanitize) {
2969             no_sanitize_span = Some(attr.span);
2970             if let Some(list) = attr.meta_item_list() {
2971                 for item in list.iter() {
2972                     if item.has_name(sym::address) {
2973                         codegen_fn_attrs.no_sanitize |= SanitizerSet::ADDRESS;
2974                     } else if item.has_name(sym::cfi) {
2975                         codegen_fn_attrs.no_sanitize |= SanitizerSet::CFI;
2976                     } else if item.has_name(sym::memory) {
2977                         codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMORY;
2978                     } else if item.has_name(sym::memtag) {
2979                         codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMTAG;
2980                     } else if item.has_name(sym::shadow_call_stack) {
2981                         codegen_fn_attrs.no_sanitize |= SanitizerSet::SHADOWCALLSTACK;
2982                     } else if item.has_name(sym::thread) {
2983                         codegen_fn_attrs.no_sanitize |= SanitizerSet::THREAD;
2984                     } else if item.has_name(sym::hwaddress) {
2985                         codegen_fn_attrs.no_sanitize |= SanitizerSet::HWADDRESS;
2986                     } else {
2987                         tcx.sess
2988                             .struct_span_err(item.span(), "invalid argument for `no_sanitize`")
2989                             .note("expected one of: `address`, `cfi`, `hwaddress`, `memory`, `memtag`, `shadow-call-stack`, or `thread`")
2990                             .emit();
2991                     }
2992                 }
2993             }
2994         } else if attr.has_name(sym::instruction_set) {
2995             codegen_fn_attrs.instruction_set = match attr.meta_kind() {
2996                 Some(MetaItemKind::List(ref items)) => match items.as_slice() {
2997                     [NestedMetaItem::MetaItem(set)] => {
2998                         let segments =
2999                             set.path.segments.iter().map(|x| x.ident.name).collect::<Vec<_>>();
3000                         match segments.as_slice() {
3001                             [sym::arm, sym::a32] | [sym::arm, sym::t32] => {
3002                                 if !tcx.sess.target.has_thumb_interworking {
3003                                     struct_span_err!(
3004                                         tcx.sess.diagnostic(),
3005                                         attr.span,
3006                                         E0779,
3007                                         "target does not support `#[instruction_set]`"
3008                                     )
3009                                     .emit();
3010                                     None
3011                                 } else if segments[1] == sym::a32 {
3012                                     Some(InstructionSetAttr::ArmA32)
3013                                 } else if segments[1] == sym::t32 {
3014                                     Some(InstructionSetAttr::ArmT32)
3015                                 } else {
3016                                     unreachable!()
3017                                 }
3018                             }
3019                             _ => {
3020                                 struct_span_err!(
3021                                     tcx.sess.diagnostic(),
3022                                     attr.span,
3023                                     E0779,
3024                                     "invalid instruction set specified",
3025                                 )
3026                                 .emit();
3027                                 None
3028                             }
3029                         }
3030                     }
3031                     [] => {
3032                         struct_span_err!(
3033                             tcx.sess.diagnostic(),
3034                             attr.span,
3035                             E0778,
3036                             "`#[instruction_set]` requires an argument"
3037                         )
3038                         .emit();
3039                         None
3040                     }
3041                     _ => {
3042                         struct_span_err!(
3043                             tcx.sess.diagnostic(),
3044                             attr.span,
3045                             E0779,
3046                             "cannot specify more than one instruction set"
3047                         )
3048                         .emit();
3049                         None
3050                     }
3051                 },
3052                 _ => {
3053                     struct_span_err!(
3054                         tcx.sess.diagnostic(),
3055                         attr.span,
3056                         E0778,
3057                         "must specify an instruction set"
3058                     )
3059                     .emit();
3060                     None
3061                 }
3062             };
3063         } else if attr.has_name(sym::repr) {
3064             codegen_fn_attrs.alignment = match attr.meta_item_list() {
3065                 Some(items) => match items.as_slice() {
3066                     [item] => match item.name_value_literal() {
3067                         Some((sym::align, literal)) => {
3068                             let alignment = rustc_attr::parse_alignment(&literal.kind);
3069
3070                             match alignment {
3071                                 Ok(align) => Some(align),
3072                                 Err(msg) => {
3073                                     struct_span_err!(
3074                                         tcx.sess.diagnostic(),
3075                                         attr.span,
3076                                         E0589,
3077                                         "invalid `repr(align)` attribute: {}",
3078                                         msg
3079                                     )
3080                                     .emit();
3081
3082                                     None
3083                                 }
3084                             }
3085                         }
3086                         _ => None,
3087                     },
3088                     [] => None,
3089                     _ => None,
3090                 },
3091                 None => None,
3092             };
3093         }
3094     }
3095
3096     codegen_fn_attrs.inline = attrs.iter().fold(InlineAttr::None, |ia, attr| {
3097         if !attr.has_name(sym::inline) {
3098             return ia;
3099         }
3100         match attr.meta_kind() {
3101             Some(MetaItemKind::Word) => InlineAttr::Hint,
3102             Some(MetaItemKind::List(ref items)) => {
3103                 inline_span = Some(attr.span);
3104                 if items.len() != 1 {
3105                     struct_span_err!(
3106                         tcx.sess.diagnostic(),
3107                         attr.span,
3108                         E0534,
3109                         "expected one argument"
3110                     )
3111                     .emit();
3112                     InlineAttr::None
3113                 } else if list_contains_name(&items, sym::always) {
3114                     InlineAttr::Always
3115                 } else if list_contains_name(&items, sym::never) {
3116                     InlineAttr::Never
3117                 } else {
3118                     struct_span_err!(
3119                         tcx.sess.diagnostic(),
3120                         items[0].span(),
3121                         E0535,
3122                         "invalid argument"
3123                     )
3124                     .emit();
3125
3126                     InlineAttr::None
3127                 }
3128             }
3129             Some(MetaItemKind::NameValue(_)) => ia,
3130             None => ia,
3131         }
3132     });
3133
3134     codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
3135         if !attr.has_name(sym::optimize) {
3136             return ia;
3137         }
3138         let err = |sp, s| struct_span_err!(tcx.sess.diagnostic(), sp, E0722, "{}", s).emit();
3139         match attr.meta_kind() {
3140             Some(MetaItemKind::Word) => {
3141                 err(attr.span, "expected one argument");
3142                 ia
3143             }
3144             Some(MetaItemKind::List(ref items)) => {
3145                 inline_span = Some(attr.span);
3146                 if items.len() != 1 {
3147                     err(attr.span, "expected one argument");
3148                     OptimizeAttr::None
3149                 } else if list_contains_name(&items, sym::size) {
3150                     OptimizeAttr::Size
3151                 } else if list_contains_name(&items, sym::speed) {
3152                     OptimizeAttr::Speed
3153                 } else {
3154                     err(items[0].span(), "invalid argument");
3155                     OptimizeAttr::None
3156                 }
3157             }
3158             Some(MetaItemKind::NameValue(_)) => ia,
3159             None => ia,
3160         }
3161     });
3162
3163     // #73631: closures inherit `#[target_feature]` annotations
3164     if tcx.features().target_feature_11 && tcx.is_closure(did.to_def_id()) {
3165         let owner_id = tcx.parent(did.to_def_id());
3166         if tcx.def_kind(owner_id).has_codegen_attrs() {
3167             codegen_fn_attrs
3168                 .target_features
3169                 .extend(tcx.codegen_fn_attrs(owner_id).target_features.iter().copied());
3170         }
3171     }
3172
3173     // If a function uses #[target_feature] it can't be inlined into general
3174     // purpose functions as they wouldn't have the right target features
3175     // enabled. For that reason we also forbid #[inline(always)] as it can't be
3176     // respected.
3177     if !codegen_fn_attrs.target_features.is_empty() {
3178         if codegen_fn_attrs.inline == InlineAttr::Always {
3179             if let Some(span) = inline_span {
3180                 tcx.sess.span_err(
3181                     span,
3182                     "cannot use `#[inline(always)]` with \
3183                      `#[target_feature]`",
3184                 );
3185             }
3186         }
3187     }
3188
3189     if !codegen_fn_attrs.no_sanitize.is_empty() {
3190         if codegen_fn_attrs.inline == InlineAttr::Always {
3191             if let (Some(no_sanitize_span), Some(inline_span)) = (no_sanitize_span, inline_span) {
3192                 let hir_id = tcx.hir().local_def_id_to_hir_id(did);
3193                 tcx.struct_span_lint_hir(
3194                     lint::builtin::INLINE_NO_SANITIZE,
3195                     hir_id,
3196                     no_sanitize_span,
3197                     |lint| {
3198                         lint.build("`no_sanitize` will have no effect after inlining")
3199                             .span_note(inline_span, "inlining requested here")
3200                             .emit();
3201                     },
3202                 )
3203             }
3204         }
3205     }
3206
3207     // Weak lang items have the same semantics as "std internal" symbols in the
3208     // sense that they're preserved through all our LTO passes and only
3209     // strippable by the linker.
3210     //
3211     // Additionally weak lang items have predetermined symbol names.
3212     if tcx.is_weak_lang_item(did.to_def_id()) {
3213         codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
3214     }
3215     if let Some(name) = weak_lang_items::link_name(attrs) {
3216         codegen_fn_attrs.export_name = Some(name);
3217         codegen_fn_attrs.link_name = Some(name);
3218     }
3219     check_link_name_xor_ordinal(tcx, &codegen_fn_attrs, link_ordinal_span);
3220
3221     // Internal symbols to the standard library all have no_mangle semantics in
3222     // that they have defined symbol names present in the function name. This
3223     // also applies to weak symbols where they all have known symbol names.
3224     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
3225         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
3226     }
3227
3228     // Any linkage to LLVM intrinsics for now forcibly marks them all as never
3229     // unwinds since LLVM sometimes can't handle codegen which `invoke`s
3230     // intrinsic functions.
3231     if let Some(name) = &codegen_fn_attrs.link_name {
3232         if name.as_str().starts_with("llvm.") {
3233             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
3234         }
3235     }
3236
3237     codegen_fn_attrs
3238 }
3239
3240 /// Computes the set of target features used in a function for the purposes of
3241 /// inline assembly.
3242 fn asm_target_features<'tcx>(tcx: TyCtxt<'tcx>, did: DefId) -> &'tcx FxHashSet<Symbol> {
3243     let mut target_features = tcx.sess.unstable_target_features.clone();
3244     if tcx.def_kind(did).has_codegen_attrs() {
3245         let attrs = tcx.codegen_fn_attrs(did);
3246         target_features.extend(&attrs.target_features);
3247         match attrs.instruction_set {
3248             None => {}
3249             Some(InstructionSetAttr::ArmA32) => {
3250                 target_features.remove(&sym::thumb_mode);
3251             }
3252             Some(InstructionSetAttr::ArmT32) => {
3253                 target_features.insert(sym::thumb_mode);
3254             }
3255         }
3256     }
3257
3258     tcx.arena.alloc(target_features)
3259 }
3260
3261 /// Checks if the provided DefId is a method in a trait impl for a trait which has track_caller
3262 /// applied to the method prototype.
3263 fn should_inherit_track_caller(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
3264     if let Some(impl_item) = tcx.opt_associated_item(def_id)
3265         && let ty::AssocItemContainer::ImplContainer = impl_item.container
3266         && let Some(trait_item) = impl_item.trait_item_def_id
3267     {
3268         return tcx
3269             .codegen_fn_attrs(trait_item)
3270             .flags
3271             .intersects(CodegenFnAttrFlags::TRACK_CALLER);
3272     }
3273
3274     false
3275 }
3276
3277 fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<u16> {
3278     use rustc_ast::{Lit, LitIntType, LitKind};
3279     let meta_item_list = attr.meta_item_list();
3280     let meta_item_list: Option<&[ast::NestedMetaItem]> = meta_item_list.as_ref().map(Vec::as_ref);
3281     let sole_meta_list = match meta_item_list {
3282         Some([item]) => item.literal(),
3283         Some(_) => {
3284             tcx.sess
3285                 .struct_span_err(attr.span, "incorrect number of arguments to `#[link_ordinal]`")
3286                 .note("the attribute requires exactly one argument")
3287                 .emit();
3288             return None;
3289         }
3290         _ => None,
3291     };
3292     if let Some(Lit { kind: LitKind::Int(ordinal, LitIntType::Unsuffixed), .. }) = sole_meta_list {
3293         // According to the table at https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#import-header,
3294         // the ordinal must fit into 16 bits.  Similarly, the Ordinal field in COFFShortExport (defined
3295         // in llvm/include/llvm/Object/COFFImportFile.h), which we use to communicate import information
3296         // to LLVM for `#[link(kind = "raw-dylib"_])`, is also defined to be uint16_t.
3297         //
3298         // FIXME: should we allow an ordinal of 0?  The MSVC toolchain has inconsistent support for this:
3299         // both LINK.EXE and LIB.EXE signal errors and abort when given a .DEF file that specifies
3300         // a zero ordinal.  However, llvm-dlltool is perfectly happy to generate an import library
3301         // for such a .DEF file, and MSVC's LINK.EXE is also perfectly happy to consume an import
3302         // library produced by LLVM with an ordinal of 0, and it generates an .EXE.  (I don't know yet
3303         // if the resulting EXE runs, as I haven't yet built the necessary DLL -- see earlier comment
3304         // about LINK.EXE failing.)
3305         if *ordinal <= u16::MAX as u128 {
3306             Some(*ordinal as u16)
3307         } else {
3308             let msg = format!("ordinal value in `link_ordinal` is too large: `{}`", &ordinal);
3309             tcx.sess
3310                 .struct_span_err(attr.span, &msg)
3311                 .note("the value may not exceed `u16::MAX`")
3312                 .emit();
3313             None
3314         }
3315     } else {
3316         tcx.sess
3317             .struct_span_err(attr.span, "illegal ordinal format in `link_ordinal`")
3318             .note("an unsuffixed integer value, e.g., `1`, is expected")
3319             .emit();
3320         None
3321     }
3322 }
3323
3324 fn check_link_name_xor_ordinal(
3325     tcx: TyCtxt<'_>,
3326     codegen_fn_attrs: &CodegenFnAttrs,
3327     inline_span: Option<Span>,
3328 ) {
3329     if codegen_fn_attrs.link_name.is_none() || codegen_fn_attrs.link_ordinal.is_none() {
3330         return;
3331     }
3332     let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
3333     if let Some(span) = inline_span {
3334         tcx.sess.span_err(span, msg);
3335     } else {
3336         tcx.sess.err(msg);
3337     }
3338 }
3339
3340 /// Checks the function annotated with `#[target_feature]` is not a safe
3341 /// trait method implementation, reporting an error if it is.
3342 fn check_target_feature_trait_unsafe(tcx: TyCtxt<'_>, id: LocalDefId, attr_span: Span) {
3343     let hir_id = tcx.hir().local_def_id_to_hir_id(id);
3344     let node = tcx.hir().get(hir_id);
3345     if let Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }) = node {
3346         let parent_id = tcx.hir().get_parent_item(hir_id);
3347         let parent_item = tcx.hir().expect_item(parent_id);
3348         if let hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) = parent_item.kind {
3349             tcx.sess
3350                 .struct_span_err(
3351                     attr_span,
3352                     "`#[target_feature(..)]` cannot be applied to safe trait method",
3353                 )
3354                 .span_label(attr_span, "cannot be applied to safe trait method")
3355                 .span_label(tcx.def_span(id), "not an `unsafe` function")
3356                 .emit();
3357         }
3358     }
3359 }