compiler/rustc_typeck/src/collect.rs

   1 // ignore-tidy-filelength
   2 //! "Collection" is the process of determining the type and other external
   3 //! details of each item in Rust. Collection is specifically concerned
   4 //! with *inter-procedural* things -- for example, for a function
   5 //! definition, collection will figure out the type and signature of the
   6 //! function, but it will not visit the *body* of the function in any way,
   7 //! nor examine type annotations on local variables (that's the job of
   8 //! type *checking*).
   9 //!
  10 //! Collecting is ultimately defined by a bundle of queries that
  11 //! inquire after various facts about the items in the crate (e.g.,
  12 //! `type_of`, `generics_of`, `predicates_of`, etc). See the `provide` function
  13 //! for the full set.
  14 //!
  15 //! At present, however, we do run collection across all items in the
  16 //! crate as a kind of pass. This should eventually be factored away.
  17
  18 use crate::astconv::AstConv;
  19 use crate::bounds::Bounds;
  20 use crate::check::intrinsic::intrinsic_operation_unsafety;
  21 use crate::constrained_generic_params as cgp;
  22 use crate::errors;
  23 use crate::middle::resolve_lifetime as rl;
  24 use rustc_ast as ast;
  25 use rustc_ast::{MetaItemKind, NestedMetaItem};
  26 use rustc_attr::{list_contains_name, InlineAttr, InstructionSetAttr, OptimizeAttr};
  27 use rustc_data_structures::captures::Captures;
  28 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
  29 use rustc_errors::{struct_span_err, Applicability};
  30 use rustc_hir as hir;
  31 use rustc_hir::def::{CtorKind, DefKind};
  32 use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_ID, LOCAL_CRATE};
  33 use rustc_hir::intravisit::{self, Visitor};
  34 use rustc_hir::weak_lang_items;
  35 use rustc_hir::{GenericParamKind, HirId, Node};
  36 use rustc_middle::hir::nested_filter;
  37 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
  38 use rustc_middle::mir::mono::Linkage;
  39 use rustc_middle::ty::query::Providers;
  40 use rustc_middle::ty::subst::InternalSubsts;
  41 use rustc_middle::ty::util::Discr;
  42 use rustc_middle::ty::util::IntTypeExt;
  43 use rustc_middle::ty::{self, AdtKind, Const, DefIdTree, Ty, TyCtxt};
  44 use rustc_middle::ty::{ReprOptions, ToPredicate, TypeFoldable};
  45 use rustc_session::lint;
  46 use rustc_session::parse::feature_err;
  47 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  48 use rustc_span::{Span, DUMMY_SP};
  49 use rustc_target::spec::{abi, PanicStrategy, SanitizerSet};
  50 use rustc_trait_selection::traits::error_reporting::suggestions::NextTypeParamName;
  51 use std::iter;
  52
  53 mod item_bounds;
  54 mod type_of;
  55
  56 struct OnlySelfBounds(bool);
  57
  58 ///////////////////////////////////////////////////////////////////////////
  59 // Main entry point
  60
  61 fn collect_mod_item_types(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
  62     tcx.hir().visit_item_likes_in_module(
  63         module_def_id,
  64         &mut CollectItemTypesVisitor { tcx }.as_deep_visitor(),
  65     );
  66 }
  67
  68 pub fn provide(providers: &mut Providers) {
  69     *providers = Providers {
  70         opt_const_param_of: type_of::opt_const_param_of,
  71         type_of: type_of::type_of,
  72         item_bounds: item_bounds::item_bounds,
  73         explicit_item_bounds: item_bounds::explicit_item_bounds,
  74         generics_of,
  75         predicates_of,
  76         predicates_defined_on,
  77         explicit_predicates_of,
  78         super_predicates_of,
  79         super_predicates_that_define_assoc_type,
  80         trait_explicit_predicates_and_bounds,
  81         type_param_predicates,
  82         trait_def,
  83         adt_def,
  84         fn_sig,
  85         impl_trait_ref,
  86         impl_polarity,
  87         is_foreign_item,
  88         static_mutability,
  89         generator_kind,
  90         codegen_fn_attrs,
  91         collect_mod_item_types,
  92         should_inherit_track_caller,
  93         ..*providers
  94     };
  95 }
  96
  97 ///////////////////////////////////////////////////////////////////////////
  98
  99 /// Context specific to some particular item. This is what implements
 100 /// `AstConv`. It has information about the predicates that are defined
 101 /// on the trait. Unfortunately, this predicate information is
 102 /// available in various different forms at various points in the
 103 /// process. So we can't just store a pointer to e.g., the AST or the
 104 /// parsed ty form, we have to be more flexible. To this end, the
 105 /// `ItemCtxt` is parameterized by a `DefId` that it uses to satisfy
 106 /// `get_type_parameter_bounds` requests, drawing the information from
 107 /// the AST (`hir::Generics`), recursively.
 108 pub struct ItemCtxt<'tcx> {
 109     tcx: TyCtxt<'tcx>,
 110     item_def_id: DefId,
 111 }
 112
 113 ///////////////////////////////////////////////////////////////////////////
 114
 115 #[derive(Default)]
 116 crate struct HirPlaceholderCollector(crate Vec<Span>);
 117
 118 impl<'v> Visitor<'v> for HirPlaceholderCollector {
 119     fn visit_ty(&mut self, t: &'v hir::Ty<'v>) {
 120         if let hir::TyKind::Infer = t.kind {
 121             self.0.push(t.span);
 122         }
 123         intravisit::walk_ty(self, t)
 124     }
 125     fn visit_generic_arg(&mut self, generic_arg: &'v hir::GenericArg<'v>) {
 126         match generic_arg {
 127             hir::GenericArg::Infer(inf) => {
 128                 self.0.push(inf.span);
 129                 intravisit::walk_inf(self, inf);
 130             }
 131             hir::GenericArg::Type(t) => self.visit_ty(t),
 132             _ => {}
 133         }
 134     }
 135     fn visit_array_length(&mut self, length: &'v hir::ArrayLen) {
 136         if let &hir::ArrayLen::Infer(_, span) = length {
 137             self.0.push(span);
 138         }
 139         intravisit::walk_array_len(self, length)
 140     }
 141 }
 142
 143 struct CollectItemTypesVisitor<'tcx> {
 144     tcx: TyCtxt<'tcx>,
 145 }
 146
 147 /// If there are any placeholder types (`_`), emit an error explaining that this is not allowed
 148 /// and suggest adding type parameters in the appropriate place, taking into consideration any and
 149 /// all already existing generic type parameters to avoid suggesting a name that is already in use.
 150 crate fn placeholder_type_error<'tcx>(
 151     tcx: TyCtxt<'tcx>,
 152     span: Option<Span>,
 153     generics: &[hir::GenericParam<'_>],
 154     placeholder_types: Vec<Span>,
 155     suggest: bool,
 156     hir_ty: Option<&hir::Ty<'_>>,
 157     kind: &'static str,
 158 ) {
 159     if placeholder_types.is_empty() {
 160         return;
 161     }
 162
 163     let type_name = generics.next_type_param_name(None);
 164     let mut sugg: Vec<_> =
 165         placeholder_types.iter().map(|sp| (*sp, (*type_name).to_string())).collect();
 166
 167     if generics.is_empty() {
 168         if let Some(span) = span {
 169             sugg.push((span, format!("<{}>", type_name)));
 170         }
 171     } else if let Some(arg) = generics
 172         .iter()
 173         .find(|arg| matches!(arg.name, hir::ParamName::Plain(Ident { name: kw::Underscore, .. })))
 174     {
 175         // Account for `_` already present in cases like `struct S<_>(_);` and suggest
 176         // `struct S<T>(T);` instead of `struct S<_, T>(T);`.
 177         sugg.push((arg.span, (*type_name).to_string()));
 178     } else {
 179         let last = generics.iter().last().unwrap();
 180         // Account for bounds, we want `fn foo<T: E, K>(_: K)` not `fn foo<T, K: E>(_: K)`.
 181         let span = last.bounds_span_for_suggestions().unwrap_or(last.span.shrink_to_hi());
 182         sugg.push((span, format!(", {}", type_name)));
 183     }
 184
 185     let mut err = bad_placeholder(tcx, placeholder_types, kind);
 186
 187     // Suggest, but only if it is not a function in const or static
 188     if suggest {
 189         let mut is_fn = false;
 190         let mut is_const_or_static = false;
 191
 192         if let Some(hir_ty) = hir_ty {
 193             if let hir::TyKind::BareFn(_) = hir_ty.kind {
 194                 is_fn = true;
 195
 196                 // Check if parent is const or static
 197                 let parent_id = tcx.hir().get_parent_node(hir_ty.hir_id);
 198                 let parent_node = tcx.hir().get(parent_id);
 199
 200                 is_const_or_static = matches!(
 201                     parent_node,
 202                     Node::Item(&hir::Item {
 203                         kind: hir::ItemKind::Const(..) | hir::ItemKind::Static(..),
 204                         ..
 205                     }) | Node::TraitItem(&hir::TraitItem {
 206                         kind: hir::TraitItemKind::Const(..),
 207                         ..
 208                     }) | Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Const(..), .. })
 209                 );
 210             }
 211         }
 212
 213         // if function is wrapped around a const or static,
 214         // then don't show the suggestion
 215         if !(is_fn && is_const_or_static) {
 216             err.multipart_suggestion(
 217                 "use type parameters instead",
 218                 sugg,
 219                 Applicability::HasPlaceholders,
 220             );
 221         }
 222     }
 223     err.emit();
 224 }
 225
 226 fn reject_placeholder_type_signatures_in_item<'tcx>(
 227     tcx: TyCtxt<'tcx>,
 228     item: &'tcx hir::Item<'tcx>,
 229 ) {
 230     let (generics, suggest) = match &item.kind {
 231         hir::ItemKind::Union(_, generics)
 232         | hir::ItemKind::Enum(_, generics)
 233         | hir::ItemKind::TraitAlias(generics, _)
 234         | hir::ItemKind::Trait(_, _, generics, ..)
 235         | hir::ItemKind::Impl(hir::Impl { generics, .. })
 236         | hir::ItemKind::Struct(_, generics) => (generics, true),
 237         hir::ItemKind::OpaqueTy(hir::OpaqueTy { generics, .. })
 238         | hir::ItemKind::TyAlias(_, generics) => (generics, false),
 239         // `static`, `fn` and `const` are handled elsewhere to suggest appropriate type.
 240         _ => return,
 241     };
 242
 243     let mut visitor = HirPlaceholderCollector::default();
 244     visitor.visit_item(item);
 245
 246     placeholder_type_error(
 247         tcx,
 248         Some(generics.span),
 249         generics.params,
 250         visitor.0,
 251         suggest,
 252         None,
 253         item.kind.descr(),
 254     );
 255 }
 256
 257 impl<'tcx> Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
 258     type NestedFilter = nested_filter::OnlyBodies;
 259
 260     fn nested_visit_map(&mut self) -> Self::Map {
 261         self.tcx.hir()
 262     }
 263
 264     fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
 265         convert_item(self.tcx, item.item_id());
 266         reject_placeholder_type_signatures_in_item(self.tcx, item);
 267         intravisit::walk_item(self, item);
 268     }
 269
 270     fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) {
 271         for param in generics.params {
 272             match param.kind {
 273                 hir::GenericParamKind::Lifetime { .. } => {}
 274                 hir::GenericParamKind::Type { default: Some(_), .. } => {
 275                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 276                     self.tcx.ensure().type_of(def_id);
 277                 }
 278                 hir::GenericParamKind::Type { .. } => {}
 279                 hir::GenericParamKind::Const { default, .. } => {
 280                     let def_id = self.tcx.hir().local_def_id(param.hir_id);
 281                     self.tcx.ensure().type_of(def_id);
 282                     if let Some(default) = default {
 283                         let default_def_id = self.tcx.hir().local_def_id(default.hir_id);
 284                         // need to store default and type of default
 285                         self.tcx.ensure().type_of(default_def_id);
 286                         self.tcx.ensure().const_param_default(def_id);
 287                     }
 288                 }
 289             }
 290         }
 291         intravisit::walk_generics(self, generics);
 292     }
 293
 294     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
 295         if let hir::ExprKind::Closure(..) = expr.kind {
 296             let def_id = self.tcx.hir().local_def_id(expr.hir_id);
 297             self.tcx.ensure().generics_of(def_id);
 298             // We do not call `type_of` for closures here as that
 299             // depends on typecheck and would therefore hide
 300             // any further errors in case one typeck fails.
 301         }
 302         intravisit::walk_expr(self, expr);
 303     }
 304
 305     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
 306         convert_trait_item(self.tcx, trait_item.trait_item_id());
 307         intravisit::walk_trait_item(self, trait_item);
 308     }
 309
 310     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
 311         convert_impl_item(self.tcx, impl_item.impl_item_id());
 312         intravisit::walk_impl_item(self, impl_item);
 313     }
 314 }
 315
 316 ///////////////////////////////////////////////////////////////////////////
 317 // Utility types and common code for the above passes.
 318
 319 fn bad_placeholder<'tcx>(
 320     tcx: TyCtxt<'tcx>,
 321     mut spans: Vec<Span>,
 322     kind: &'static str,
 323 ) -> rustc_errors::DiagnosticBuilder<'tcx> {
 324     let kind = if kind.ends_with('s') { format!("{}es", kind) } else { format!("{}s", kind) };
 325
 326     spans.sort();
 327     let mut err = struct_span_err!(
 328         tcx.sess,
 329         spans.clone(),
 330         E0121,
 331         "the placeholder `_` is not allowed within types on item signatures for {}",
 332         kind
 333     );
 334     for span in spans {
 335         err.span_label(span, "not allowed in type signatures");
 336     }
 337     err
 338 }
 339
 340 impl<'tcx> ItemCtxt<'tcx> {
 341     pub fn new(tcx: TyCtxt<'tcx>, item_def_id: DefId) -> ItemCtxt<'tcx> {
 342         ItemCtxt { tcx, item_def_id }
 343     }
 344
 345     pub fn to_ty(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> {
 346         <dyn AstConv<'_>>::ast_ty_to_ty(self, ast_ty)
 347     }
 348
 349     pub fn hir_id(&self) -> hir::HirId {
 350         self.tcx.hir().local_def_id_to_hir_id(self.item_def_id.expect_local())
 351     }
 352
 353     pub fn node(&self) -> hir::Node<'tcx> {
 354         self.tcx.hir().get(self.hir_id())
 355     }
 356 }
 357
 358 impl<'tcx> AstConv<'tcx> for ItemCtxt<'tcx> {
 359     fn tcx(&self) -> TyCtxt<'tcx> {
 360         self.tcx
 361     }
 362
 363     fn item_def_id(&self) -> Option<DefId> {
 364         Some(self.item_def_id)
 365     }
 366
 367     fn get_type_parameter_bounds(
 368         &self,
 369         span: Span,
 370         def_id: DefId,
 371         assoc_name: Ident,
 372     ) -> ty::GenericPredicates<'tcx> {
 373         self.tcx.at(span).type_param_predicates((
 374             self.item_def_id,
 375             def_id.expect_local(),
 376             assoc_name,
 377         ))
 378     }
 379
 380     fn re_infer(&self, _: Option<&ty::GenericParamDef>, _: Span) -> Option<ty::Region<'tcx>> {
 381         None
 382     }
 383
 384     fn allow_ty_infer(&self) -> bool {
 385         false
 386     }
 387
 388     fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
 389         self.tcx().ty_error_with_message(span, "bad placeholder type")
 390     }
 391
 392     fn ct_infer(&self, ty: Ty<'tcx>, _: Option<&ty::GenericParamDef>, span: Span) -> Const<'tcx> {
 393         let ty = self.tcx.fold_regions(ty, &mut false, |r, _| match *r {
 394             ty::ReErased => self.tcx.lifetimes.re_static,
 395             _ => r,
 396         });
 397         self.tcx().const_error_with_message(ty, span, "bad placeholder constant")
 398     }
 399
 400     fn projected_ty_from_poly_trait_ref(
 401         &self,
 402         span: Span,
 403         item_def_id: DefId,
 404         item_segment: &hir::PathSegment<'_>,
 405         poly_trait_ref: ty::PolyTraitRef<'tcx>,
 406     ) -> Ty<'tcx> {
 407         if let Some(trait_ref) = poly_trait_ref.no_bound_vars() {
 408             let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
 409                 self,
 410                 self.tcx,
 411                 span,
 412                 item_def_id,
 413                 item_segment,
 414                 trait_ref.substs,
 415             );
 416             self.tcx().mk_projection(item_def_id, item_substs)
 417         } else {
 418             // There are no late-bound regions; we can just ignore the binder.
 419             let mut err = struct_span_err!(
 420                 self.tcx().sess,
 421                 span,
 422                 E0212,
 423                 "cannot use the associated type of a trait \
 424                  with uninferred generic parameters"
 425             );
 426
 427             match self.node() {
 428                 hir::Node::Field(_) | hir::Node::Ctor(_) | hir::Node::Variant(_) => {
 429                     let item =
 430                         self.tcx.hir().expect_item(self.tcx.hir().get_parent_item(self.hir_id()));
 431                     match &item.kind {
 432                         hir::ItemKind::Enum(_, generics)
 433                         | hir::ItemKind::Struct(_, generics)
 434                         | hir::ItemKind::Union(_, generics) => {
 435                             let lt_name = get_new_lifetime_name(self.tcx, poly_trait_ref, generics);
 436                             let (lt_sp, sugg) = match generics.params {
 437                                 [] => (generics.span, format!("<{}>", lt_name)),
 438                                 [bound, ..] => {
 439                                     (bound.span.shrink_to_lo(), format!("{}, ", lt_name))
 440                                 }
 441                             };
 442                             let suggestions = vec![
 443                                 (lt_sp, sugg),
 444                                 (
 445                                     span.with_hi(item_segment.ident.span.lo()),
 446                                     format!(
 447                                         "{}::",
 448                                         // Replace the existing lifetimes with a new named lifetime.
 449                                         self.tcx
 450                                             .replace_late_bound_regions(poly_trait_ref, |_| {
 451                                                 self.tcx.mk_region(ty::ReEarlyBound(
 452                                                     ty::EarlyBoundRegion {
 453                                                         def_id: item_def_id,
 454                                                         index: 0,
 455                                                         name: Symbol::intern(&lt_name),
 456                                                     },
 457                                                 ))
 458                                             })
 459                                             .0,
 460                                     ),
 461                                 ),
 462                             ];
 463                             err.multipart_suggestion(
 464                                 "use a fully qualified path with explicit lifetimes",
 465                                 suggestions,
 466                                 Applicability::MaybeIncorrect,
 467                             );
 468                         }
 469                         _ => {}
 470                     }
 471                 }
 472                 hir::Node::Item(hir::Item {
 473                     kind:
 474                         hir::ItemKind::Struct(..) | hir::ItemKind::Enum(..) | hir::ItemKind::Union(..),
 475                     ..
 476                 }) => {}
 477                 hir::Node::Item(_)
 478                 | hir::Node::ForeignItem(_)
 479                 | hir::Node::TraitItem(_)
 480                 | hir::Node::ImplItem(_) => {
 481                     err.span_suggestion_verbose(
 482                         span.with_hi(item_segment.ident.span.lo()),
 483                         "use a fully qualified path with inferred lifetimes",
 484                         format!(
 485                             "{}::",
 486                             // Erase named lt, we want `<A as B<'_>::C`, not `<A as B<'a>::C`.
 487                             self.tcx.anonymize_late_bound_regions(poly_trait_ref).skip_binder(),
 488                         ),
 489                         Applicability::MaybeIncorrect,
 490                     );
 491                 }
 492                 _ => {}
 493             }
 494             err.emit();
 495             self.tcx().ty_error()
 496         }
 497     }
 498
 499     fn normalize_ty(&self, _span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
 500         // Types in item signatures are not normalized to avoid undue dependencies.
 501         ty
 502     }
 503
 504     fn set_tainted_by_errors(&self) {
 505         // There's no obvious place to track this, so just let it go.
 506     }
 507
 508     fn record_ty(&self, _hir_id: hir::HirId, _ty: Ty<'tcx>, _span: Span) {
 509         // There's no place to record types from signatures?
 510     }
 511 }
 512
 513 /// Synthesize a new lifetime name that doesn't clash with any of the lifetimes already present.
 514 fn get_new_lifetime_name<'tcx>(
 515     tcx: TyCtxt<'tcx>,
 516     poly_trait_ref: ty::PolyTraitRef<'tcx>,
 517     generics: &hir::Generics<'tcx>,
 518 ) -> String {
 519     let existing_lifetimes = tcx
 520         .collect_referenced_late_bound_regions(&poly_trait_ref)
 521         .into_iter()
 522         .filter_map(|lt| {
 523             if let ty::BoundRegionKind::BrNamed(_, name) = lt {
 524                 Some(name.as_str().to_string())
 525             } else {
 526                 None
 527             }
 528         })
 529         .chain(generics.params.iter().filter_map(|param| {
 530             if let hir::GenericParamKind::Lifetime { .. } = &param.kind {
 531                 Some(param.name.ident().as_str().to_string())
 532             } else {
 533                 None
 534             }
 535         }))
 536         .collect::<FxHashSet<String>>();
 537
 538     let a_to_z_repeat_n = |n| {
 539         (b'a'..=b'z').map(move |c| {
 540             let mut s = '\''.to_string();
 541             s.extend(std::iter::repeat(char::from(c)).take(n));
 542             s
 543         })
 544     };
 545
 546     // If all single char lifetime names are present, we wrap around and double the chars.
 547     (1..).flat_map(a_to_z_repeat_n).find(|lt| !existing_lifetimes.contains(lt.as_str())).unwrap()
 548 }
 549
 550 /// Returns the predicates defined on `item_def_id` of the form
 551 /// `X: Foo` where `X` is the type parameter `def_id`.
 552 fn type_param_predicates(
 553     tcx: TyCtxt<'_>,
 554     (item_def_id, def_id, assoc_name): (DefId, LocalDefId, Ident),
 555 ) -> ty::GenericPredicates<'_> {
 556     use rustc_hir::*;
 557
 558     // In the AST, bounds can derive from two places. Either
 559     // written inline like `<T: Foo>` or in a where-clause like
 560     // `where T: Foo`.
 561
 562     let param_id = tcx.hir().local_def_id_to_hir_id(def_id);
 563     let param_owner = tcx.hir().ty_param_owner(param_id);
 564     let generics = tcx.generics_of(param_owner);
 565     let index = generics.param_def_id_to_index[&def_id.to_def_id()];
 566     let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(param_id));
 567
 568     // Don't look for bounds where the type parameter isn't in scope.
 569     let parent = if item_def_id == param_owner.to_def_id() {
 570         None
 571     } else {
 572         tcx.generics_of(item_def_id).parent
 573     };
 574
 575     let mut result = parent
 576         .map(|parent| {
 577             let icx = ItemCtxt::new(tcx, parent);
 578             icx.get_type_parameter_bounds(DUMMY_SP, def_id.to_def_id(), assoc_name)
 579         })
 580         .unwrap_or_default();
 581     let mut extend = None;
 582
 583     let item_hir_id = tcx.hir().local_def_id_to_hir_id(item_def_id.expect_local());
 584     let ast_generics = match tcx.hir().get(item_hir_id) {
 585         Node::TraitItem(item) => &item.generics,
 586
 587         Node::ImplItem(item) => &item.generics,
 588
 589         Node::Item(item) => {
 590             match item.kind {
 591                 ItemKind::Fn(.., ref generics, _)
 592                 | ItemKind::Impl(hir::Impl { ref generics, .. })
 593                 | ItemKind::TyAlias(_, ref generics)
 594                 | ItemKind::OpaqueTy(OpaqueTy {
 595                     ref generics,
 596                     origin: hir::OpaqueTyOrigin::TyAlias,
 597                     ..
 598                 })
 599                 | ItemKind::Enum(_, ref generics)
 600                 | ItemKind::Struct(_, ref generics)
 601                 | ItemKind::Union(_, ref generics) => generics,
 602                 ItemKind::Trait(_, _, ref generics, ..) => {
 603                     // Implied `Self: Trait` and supertrait bounds.
 604                     if param_id == item_hir_id {
 605                         let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id);
 606                         extend =
 607                             Some((identity_trait_ref.without_const().to_predicate(tcx), item.span));
 608                     }
 609                     generics
 610                 }
 611                 _ => return result,
 612             }
 613         }
 614
 615         Node::ForeignItem(item) => match item.kind {
 616             ForeignItemKind::Fn(_, _, ref generics) => generics,
 617             _ => return result,
 618         },
 619
 620         _ => return result,
 621     };
 622
 623     let icx = ItemCtxt::new(tcx, item_def_id);
 624     let extra_predicates = extend.into_iter().chain(
 625         icx.type_parameter_bounds_in_generics(
 626             ast_generics,
 627             param_id,
 628             ty,
 629             OnlySelfBounds(true),
 630             Some(assoc_name),
 631         )
 632         .into_iter()
 633         .filter(|(predicate, _)| match predicate.kind().skip_binder() {
 634             ty::PredicateKind::Trait(data) => data.self_ty().is_param(index),
 635             _ => false,
 636         }),
 637     );
 638     result.predicates =
 639         tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(extra_predicates));
 640     result
 641 }
 642
 643 impl<'tcx> ItemCtxt<'tcx> {
 644     /// Finds bounds from `hir::Generics`. This requires scanning through the
 645     /// AST. We do this to avoid having to convert *all* the bounds, which
 646     /// would create artificial cycles. Instead, we can only convert the
 647     /// bounds for a type parameter `X` if `X::Foo` is used.
 648     fn type_parameter_bounds_in_generics(
 649         &self,
 650         ast_generics: &'tcx hir::Generics<'tcx>,
 651         param_id: hir::HirId,
 652         ty: Ty<'tcx>,
 653         only_self_bounds: OnlySelfBounds,
 654         assoc_name: Option<Ident>,
 655     ) -> Vec<(ty::Predicate<'tcx>, Span)> {
 656         let from_ty_params = ast_generics
 657             .params
 658             .iter()
 659             .filter_map(|param| match param.kind {
 660                 GenericParamKind::Type { .. } | GenericParamKind::Const { .. }
 661                     if param.hir_id == param_id =>
 662                 {
 663                     Some(&param.bounds)
 664                 }
 665                 _ => None,
 666             })
 667             .flat_map(|bounds| bounds.iter())
 668             .filter(|b| match assoc_name {
 669                 Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
 670                 None => true,
 671             })
 672             .flat_map(|b| predicates_from_bound(self, ty, b, ty::List::empty()));
 673
 674         let param_def_id = self.tcx.hir().local_def_id(param_id).to_def_id();
 675         let from_where_clauses = ast_generics
 676             .where_clause
 677             .predicates
 678             .iter()
 679             .filter_map(|wp| match *wp {
 680                 hir::WherePredicate::BoundPredicate(ref bp) => Some(bp),
 681                 _ => None,
 682             })
 683             .flat_map(|bp| {
 684                 let bt = if bp.is_param_bound(param_def_id) {
 685                     Some(ty)
 686                 } else if !only_self_bounds.0 {
 687                     Some(self.to_ty(bp.bounded_ty))
 688                 } else {
 689                     None
 690                 };
 691                 let bvars = self.tcx.late_bound_vars(bp.bounded_ty.hir_id);
 692
 693                 bp.bounds
 694                     .iter()
 695                     .filter(|b| match assoc_name {
 696                         Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name),
 697                         None => true,
 698                     })
 699                     .filter_map(move |b| bt.map(|bt| (bt, b, bvars)))
 700             })
 701             .flat_map(|(bt, b, bvars)| predicates_from_bound(self, bt, b, bvars));
 702
 703         from_ty_params.chain(from_where_clauses).collect()
 704     }
 705
 706     fn bound_defines_assoc_item(&self, b: &hir::GenericBound<'_>, assoc_name: Ident) -> bool {
 707         debug!("bound_defines_assoc_item(b={:?}, assoc_name={:?})", b, assoc_name);
 708
 709         match b {
 710             hir::GenericBound::Trait(poly_trait_ref, _) => {
 711                 let trait_ref = &poly_trait_ref.trait_ref;
 712                 if let Some(trait_did) = trait_ref.trait_def_id() {
 713                     self.tcx.trait_may_define_assoc_type(trait_did, assoc_name)
 714                 } else {
 715                     false
 716                 }
 717             }
 718             _ => false,
 719         }
 720     }
 721 }
 722
 723 fn convert_item(tcx: TyCtxt<'_>, item_id: hir::ItemId) {
 724     let it = tcx.hir().item(item_id);
 725     debug!("convert: item {} with id {}", it.ident, it.hir_id());
 726     let def_id = item_id.def_id;
 727
 728     match it.kind {
 729         // These don't define types.
 730         hir::ItemKind::ExternCrate(_)
 731         | hir::ItemKind::Use(..)
 732         | hir::ItemKind::Macro(_)
 733         | hir::ItemKind::Mod(_)
 734         | hir::ItemKind::GlobalAsm(_) => {}
 735         hir::ItemKind::ForeignMod { items, .. } => {
 736             for item in items {
 737                 let item = tcx.hir().foreign_item(item.id);
 738                 tcx.ensure().generics_of(item.def_id);
 739                 tcx.ensure().type_of(item.def_id);
 740                 tcx.ensure().predicates_of(item.def_id);
 741                 match item.kind {
 742                     hir::ForeignItemKind::Fn(..) => tcx.ensure().fn_sig(item.def_id),
 743                     hir::ForeignItemKind::Static(..) => {
 744                         let mut visitor = HirPlaceholderCollector::default();
 745                         visitor.visit_foreign_item(item);
 746                         placeholder_type_error(
 747                             tcx,
 748                             None,
 749                             &[],
 750                             visitor.0,
 751                             false,
 752                             None,
 753                             "static variable",
 754                         );
 755                     }
 756                     _ => (),
 757                 }
 758             }
 759         }
 760         hir::ItemKind::Enum(ref enum_definition, _) => {
 761             tcx.ensure().generics_of(def_id);
 762             tcx.ensure().type_of(def_id);
 763             tcx.ensure().predicates_of(def_id);
 764             convert_enum_variant_types(tcx, def_id.to_def_id(), enum_definition.variants);
 765         }
 766         hir::ItemKind::Impl { .. } => {
 767             tcx.ensure().generics_of(def_id);
 768             tcx.ensure().type_of(def_id);
 769             tcx.ensure().impl_trait_ref(def_id);
 770             tcx.ensure().predicates_of(def_id);
 771         }
 772         hir::ItemKind::Trait(..) => {
 773             tcx.ensure().generics_of(def_id);
 774             tcx.ensure().trait_def(def_id);
 775             tcx.at(it.span).super_predicates_of(def_id);
 776             tcx.ensure().predicates_of(def_id);
 777         }
 778         hir::ItemKind::TraitAlias(..) => {
 779             tcx.ensure().generics_of(def_id);
 780             tcx.at(it.span).super_predicates_of(def_id);
 781             tcx.ensure().predicates_of(def_id);
 782         }
 783         hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
 784             tcx.ensure().generics_of(def_id);
 785             tcx.ensure().type_of(def_id);
 786             tcx.ensure().predicates_of(def_id);
 787
 788             for f in struct_def.fields() {
 789                 let def_id = tcx.hir().local_def_id(f.hir_id);
 790                 tcx.ensure().generics_of(def_id);
 791                 tcx.ensure().type_of(def_id);
 792                 tcx.ensure().predicates_of(def_id);
 793             }
 794
 795             if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
 796                 convert_variant_ctor(tcx, ctor_hir_id);
 797             }
 798         }
 799
 800         // Desugared from `impl Trait`, so visited by the function's return type.
 801         hir::ItemKind::OpaqueTy(hir::OpaqueTy {
 802             origin: hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..),
 803             ..
 804         }) => {}
 805
 806         // Don't call `type_of` on opaque types, since that depends on type
 807         // checking function bodies. `check_item_type` ensures that it's called
 808         // instead.
 809         hir::ItemKind::OpaqueTy(..) => {
 810             tcx.ensure().generics_of(def_id);
 811             tcx.ensure().predicates_of(def_id);
 812             tcx.ensure().explicit_item_bounds(def_id);
 813         }
 814         hir::ItemKind::TyAlias(..)
 815         | hir::ItemKind::Static(..)
 816         | hir::ItemKind::Const(..)
 817         | hir::ItemKind::Fn(..) => {
 818             tcx.ensure().generics_of(def_id);
 819             tcx.ensure().type_of(def_id);
 820             tcx.ensure().predicates_of(def_id);
 821             match it.kind {
 822                 hir::ItemKind::Fn(..) => tcx.ensure().fn_sig(def_id),
 823                 hir::ItemKind::OpaqueTy(..) => tcx.ensure().item_bounds(def_id),
 824                 hir::ItemKind::Const(ty, ..) | hir::ItemKind::Static(ty, ..) => {
 825                     // (#75889): Account for `const C: dyn Fn() -> _ = "";`
 826                     if let hir::TyKind::TraitObject(..) = ty.kind {
 827                         let mut visitor = HirPlaceholderCollector::default();
 828                         visitor.visit_item(it);
 829                         placeholder_type_error(
 830                             tcx,
 831                             None,
 832                             &[],
 833                             visitor.0,
 834                             false,
 835                             None,
 836                             it.kind.descr(),
 837                         );
 838                     }
 839                 }
 840                 _ => (),
 841             }
 842         }
 843     }
 844 }
 845
 846 fn convert_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::TraitItemId) {
 847     let trait_item = tcx.hir().trait_item(trait_item_id);
 848     tcx.ensure().generics_of(trait_item_id.def_id);
 849
 850     match trait_item.kind {
 851         hir::TraitItemKind::Fn(..) => {
 852             tcx.ensure().type_of(trait_item_id.def_id);
 853             tcx.ensure().fn_sig(trait_item_id.def_id);
 854         }
 855
 856         hir::TraitItemKind::Const(.., Some(_)) => {
 857             tcx.ensure().type_of(trait_item_id.def_id);
 858         }
 859
 860         hir::TraitItemKind::Const(..) => {
 861             tcx.ensure().type_of(trait_item_id.def_id);
 862             // Account for `const C: _;`.
 863             let mut visitor = HirPlaceholderCollector::default();
 864             visitor.visit_trait_item(trait_item);
 865             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "constant");
 866         }
 867
 868         hir::TraitItemKind::Type(_, Some(_)) => {
 869             tcx.ensure().item_bounds(trait_item_id.def_id);
 870             tcx.ensure().type_of(trait_item_id.def_id);
 871             // Account for `type T = _;`.
 872             let mut visitor = HirPlaceholderCollector::default();
 873             visitor.visit_trait_item(trait_item);
 874             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 875         }
 876
 877         hir::TraitItemKind::Type(_, None) => {
 878             tcx.ensure().item_bounds(trait_item_id.def_id);
 879             // #74612: Visit and try to find bad placeholders
 880             // even if there is no concrete type.
 881             let mut visitor = HirPlaceholderCollector::default();
 882             visitor.visit_trait_item(trait_item);
 883
 884             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 885         }
 886     };
 887
 888     tcx.ensure().predicates_of(trait_item_id.def_id);
 889 }
 890
 891 fn convert_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::ImplItemId) {
 892     let def_id = impl_item_id.def_id;
 893     tcx.ensure().generics_of(def_id);
 894     tcx.ensure().type_of(def_id);
 895     tcx.ensure().predicates_of(def_id);
 896     let impl_item = tcx.hir().impl_item(impl_item_id);
 897     match impl_item.kind {
 898         hir::ImplItemKind::Fn(..) => {
 899             tcx.ensure().fn_sig(def_id);
 900         }
 901         hir::ImplItemKind::TyAlias(_) => {
 902             // Account for `type T = _;`
 903             let mut visitor = HirPlaceholderCollector::default();
 904             visitor.visit_impl_item(impl_item);
 905
 906             placeholder_type_error(tcx, None, &[], visitor.0, false, None, "associated type");
 907         }
 908         hir::ImplItemKind::Const(..) => {}
 909     }
 910 }
 911
 912 fn convert_variant_ctor(tcx: TyCtxt<'_>, ctor_id: hir::HirId) {
 913     let def_id = tcx.hir().local_def_id(ctor_id);
 914     tcx.ensure().generics_of(def_id);
 915     tcx.ensure().type_of(def_id);
 916     tcx.ensure().predicates_of(def_id);
 917 }
 918
 919 fn convert_enum_variant_types(tcx: TyCtxt<'_>, def_id: DefId, variants: &[hir::Variant<'_>]) {
 920     let def = tcx.adt_def(def_id);
 921     let repr_type = def.repr.discr_type();
 922     let initial = repr_type.initial_discriminant(tcx);
 923     let mut prev_discr = None::<Discr<'_>>;
 924
 925     // fill the discriminant values and field types
 926     for variant in variants {
 927         let wrapped_discr = prev_discr.map_or(initial, |d| d.wrap_incr(tcx));
 928         prev_discr = Some(
 929             if let Some(ref e) = variant.disr_expr {
 930                 let expr_did = tcx.hir().local_def_id(e.hir_id);
 931                 def.eval_explicit_discr(tcx, expr_did.to_def_id())
 932             } else if let Some(discr) = repr_type.disr_incr(tcx, prev_discr) {
 933                 Some(discr)
 934             } else {
 935                 struct_span_err!(tcx.sess, variant.span, E0370, "enum discriminant overflowed")
 936                     .span_label(
 937                         variant.span,
 938                         format!("overflowed on value after {}", prev_discr.unwrap()),
 939                     )
 940                     .note(&format!(
 941                         "explicitly set `{} = {}` if that is desired outcome",
 942                         variant.ident, wrapped_discr
 943                     ))
 944                     .emit();
 945                 None
 946             }
 947             .unwrap_or(wrapped_discr),
 948         );
 949
 950         for f in variant.data.fields() {
 951             let def_id = tcx.hir().local_def_id(f.hir_id);
 952             tcx.ensure().generics_of(def_id);
 953             tcx.ensure().type_of(def_id);
 954             tcx.ensure().predicates_of(def_id);
 955         }
 956
 957         // Convert the ctor, if any. This also registers the variant as
 958         // an item.
 959         if let Some(ctor_hir_id) = variant.data.ctor_hir_id() {
 960             convert_variant_ctor(tcx, ctor_hir_id);
 961         }
 962     }
 963 }
 964
 965 fn convert_variant(
 966     tcx: TyCtxt<'_>,
 967     variant_did: Option<LocalDefId>,
 968     ctor_did: Option<LocalDefId>,
 969     ident: Ident,
 970     discr: ty::VariantDiscr,
 971     def: &hir::VariantData<'_>,
 972     adt_kind: ty::AdtKind,
 973     parent_did: LocalDefId,
 974 ) -> ty::VariantDef {
 975     let mut seen_fields: FxHashMap<Ident, Span> = Default::default();
 976     let fields = def
 977         .fields()
 978         .iter()
 979         .map(|f| {
 980             let fid = tcx.hir().local_def_id(f.hir_id);
 981             let dup_span = seen_fields.get(&f.ident.normalize_to_macros_2_0()).cloned();
 982             if let Some(prev_span) = dup_span {
 983                 tcx.sess.emit_err(errors::FieldAlreadyDeclared {
 984                     field_name: f.ident,
 985                     span: f.span,
 986                     prev_span,
 987                 });
 988             } else {
 989                 seen_fields.insert(f.ident.normalize_to_macros_2_0(), f.span);
 990             }
 991
 992             ty::FieldDef { did: fid.to_def_id(), name: f.ident.name, vis: tcx.visibility(fid) }
 993         })
 994         .collect();
 995     let recovered = match def {
 996         hir::VariantData::Struct(_, r) => *r,
 997         _ => false,
 998     };
 999     ty::VariantDef::new(
1000         ident.name,
1001         variant_did.map(LocalDefId::to_def_id),
1002         ctor_did.map(LocalDefId::to_def_id),
1003         discr,
1004         fields,
1005         CtorKind::from_hir(def),
1006         adt_kind,
1007         parent_did.to_def_id(),
1008         recovered,
1009         adt_kind == AdtKind::Struct && tcx.has_attr(parent_did.to_def_id(), sym::non_exhaustive)
1010             || variant_did.map_or(false, |variant_did| {
1011                 tcx.has_attr(variant_did.to_def_id(), sym::non_exhaustive)
1012             }),
1013     )
1014 }
1015
1016 fn adt_def(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::AdtDef {
1017     use rustc_hir::*;
1018
1019     let def_id = def_id.expect_local();
1020     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1021     let item = match tcx.hir().get(hir_id) {
1022         Node::Item(item) => item,
1023         _ => bug!(),
1024     };
1025
1026     let repr = ReprOptions::new(tcx, def_id.to_def_id());
1027     let (kind, variants) = match item.kind {
1028         ItemKind::Enum(ref def, _) => {
1029             let mut distance_from_explicit = 0;
1030             let variants = def
1031                 .variants
1032                 .iter()
1033                 .map(|v| {
1034                     let variant_did = Some(tcx.hir().local_def_id(v.id));
1035                     let ctor_did =
1036                         v.data.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1037
1038                     let discr = if let Some(ref e) = v.disr_expr {
1039                         distance_from_explicit = 0;
1040                         ty::VariantDiscr::Explicit(tcx.hir().local_def_id(e.hir_id).to_def_id())
1041                     } else {
1042                         ty::VariantDiscr::Relative(distance_from_explicit)
1043                     };
1044                     distance_from_explicit += 1;
1045
1046                     convert_variant(
1047                         tcx,
1048                         variant_did,
1049                         ctor_did,
1050                         v.ident,
1051                         discr,
1052                         &v.data,
1053                         AdtKind::Enum,
1054                         def_id,
1055                     )
1056                 })
1057                 .collect();
1058
1059             (AdtKind::Enum, variants)
1060         }
1061         ItemKind::Struct(ref def, _) => {
1062             let variant_did = None::<LocalDefId>;
1063             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1064
1065             let variants = std::iter::once(convert_variant(
1066                 tcx,
1067                 variant_did,
1068                 ctor_did,
1069                 item.ident,
1070                 ty::VariantDiscr::Relative(0),
1071                 def,
1072                 AdtKind::Struct,
1073                 def_id,
1074             ))
1075             .collect();
1076
1077             (AdtKind::Struct, variants)
1078         }
1079         ItemKind::Union(ref def, _) => {
1080             let variant_did = None;
1081             let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
1082
1083             let variants = std::iter::once(convert_variant(
1084                 tcx,
1085                 variant_did,
1086                 ctor_did,
1087                 item.ident,
1088                 ty::VariantDiscr::Relative(0),
1089                 def,
1090                 AdtKind::Union,
1091                 def_id,
1092             ))
1093             .collect();
1094
1095             (AdtKind::Union, variants)
1096         }
1097         _ => bug!(),
1098     };
1099     tcx.alloc_adt_def(def_id.to_def_id(), kind, variants, repr)
1100 }
1101
1102 /// Ensures that the super-predicates of the trait with a `DefId`
1103 /// of `trait_def_id` are converted and stored. This also ensures that
1104 /// the transitive super-predicates are converted.
1105 fn super_predicates_of(tcx: TyCtxt<'_>, trait_def_id: DefId) -> ty::GenericPredicates<'_> {
1106     debug!("super_predicates(trait_def_id={:?})", trait_def_id);
1107     tcx.super_predicates_that_define_assoc_type((trait_def_id, None))
1108 }
1109
1110 /// Ensures that the super-predicates of the trait with a `DefId`
1111 /// of `trait_def_id` are converted and stored. This also ensures that
1112 /// the transitive super-predicates are converted.
1113 fn super_predicates_that_define_assoc_type(
1114     tcx: TyCtxt<'_>,
1115     (trait_def_id, assoc_name): (DefId, Option<Ident>),
1116 ) -> ty::GenericPredicates<'_> {
1117     debug!(
1118         "super_predicates_that_define_assoc_type(trait_def_id={:?}, assoc_name={:?})",
1119         trait_def_id, assoc_name
1120     );
1121     if trait_def_id.is_local() {
1122         debug!("super_predicates_that_define_assoc_type: local trait_def_id={:?}", trait_def_id);
1123         let trait_hir_id = tcx.hir().local_def_id_to_hir_id(trait_def_id.expect_local());
1124
1125         let item = match tcx.hir().get(trait_hir_id) {
1126             Node::Item(item) => item,
1127             _ => bug!("trait_node_id {} is not an item", trait_hir_id),
1128         };
1129
1130         let (generics, bounds) = match item.kind {
1131             hir::ItemKind::Trait(.., ref generics, ref supertraits, _) => (generics, supertraits),
1132             hir::ItemKind::TraitAlias(ref generics, ref supertraits) => (generics, supertraits),
1133             _ => span_bug!(item.span, "super_predicates invoked on non-trait"),
1134         };
1135
1136         let icx = ItemCtxt::new(tcx, trait_def_id);
1137
1138         // Convert the bounds that follow the colon, e.g., `Bar + Zed` in `trait Foo: Bar + Zed`.
1139         let self_param_ty = tcx.types.self_param;
1140         let superbounds1 = if let Some(assoc_name) = assoc_name {
1141             <dyn AstConv<'_>>::compute_bounds_that_match_assoc_type(
1142                 &icx,
1143                 self_param_ty,
1144                 bounds,
1145                 assoc_name,
1146             )
1147         } else {
1148             <dyn AstConv<'_>>::compute_bounds(&icx, self_param_ty, bounds)
1149         };
1150
1151         let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
1152
1153         // Convert any explicit superbounds in the where-clause,
1154         // e.g., `trait Foo where Self: Bar`.
1155         // In the case of trait aliases, however, we include all bounds in the where-clause,
1156         // so e.g., `trait Foo = where u32: PartialEq<Self>` would include `u32: PartialEq<Self>`
1157         // as one of its "superpredicates".
1158         let is_trait_alias = tcx.is_trait_alias(trait_def_id);
1159         let superbounds2 = icx.type_parameter_bounds_in_generics(
1160             generics,
1161             item.hir_id(),
1162             self_param_ty,
1163             OnlySelfBounds(!is_trait_alias),
1164             assoc_name,
1165         );
1166
1167         // Combine the two lists to form the complete set of superbounds:
1168         let superbounds = &*tcx.arena.alloc_from_iter(superbounds1.into_iter().chain(superbounds2));
1169
1170         // Now require that immediate supertraits are converted,
1171         // which will, in turn, reach indirect supertraits.
1172         if assoc_name.is_none() {
1173             // Now require that immediate supertraits are converted,
1174             // which will, in turn, reach indirect supertraits.
1175             for &(pred, span) in superbounds {
1176                 debug!("superbound: {:?}", pred);
1177                 if let ty::PredicateKind::Trait(bound) = pred.kind().skip_binder() {
1178                     tcx.at(span).super_predicates_of(bound.def_id());
1179                 }
1180             }
1181         }
1182
1183         ty::GenericPredicates { parent: None, predicates: superbounds }
1184     } else {
1185         // if `assoc_name` is None, then the query should've been redirected to an
1186         // external provider
1187         assert!(assoc_name.is_some());
1188         tcx.super_predicates_of(trait_def_id)
1189     }
1190 }
1191
1192 fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> ty::TraitDef {
1193     let item = tcx.hir().expect_item(def_id.expect_local());
1194
1195     let (is_auto, unsafety, items) = match item.kind {
1196         hir::ItemKind::Trait(is_auto, unsafety, .., items) => {
1197             (is_auto == hir::IsAuto::Yes, unsafety, items)
1198         }
1199         hir::ItemKind::TraitAlias(..) => (false, hir::Unsafety::Normal, &[][..]),
1200         _ => span_bug!(item.span, "trait_def_of_item invoked on non-trait"),
1201     };
1202
1203     let paren_sugar = tcx.has_attr(def_id, sym::rustc_paren_sugar);
1204     if paren_sugar && !tcx.features().unboxed_closures {
1205         tcx.sess
1206             .struct_span_err(
1207                 item.span,
1208                 "the `#[rustc_paren_sugar]` attribute is a temporary means of controlling \
1209                  which traits can use parenthetical notation",
1210             )
1211             .help("add `#![feature(unboxed_closures)]` to the crate attributes to use it")
1212             .emit();
1213     }
1214
1215     let is_marker = tcx.has_attr(def_id, sym::marker);
1216     let skip_array_during_method_dispatch =
1217         tcx.has_attr(def_id, sym::rustc_skip_array_during_method_dispatch);
1218     let spec_kind = if tcx.has_attr(def_id, sym::rustc_unsafe_specialization_marker) {
1219         ty::trait_def::TraitSpecializationKind::Marker
1220     } else if tcx.has_attr(def_id, sym::rustc_specialization_trait) {
1221         ty::trait_def::TraitSpecializationKind::AlwaysApplicable
1222     } else {
1223         ty::trait_def::TraitSpecializationKind::None
1224     };
1225     let def_path_hash = tcx.def_path_hash(def_id);
1226
1227     let must_implement_one_of = tcx
1228         .get_attrs(def_id)
1229         .iter()
1230         .find(|attr| attr.has_name(sym::rustc_must_implement_one_of))
1231         // Check that there are at least 2 arguments of `#[rustc_must_implement_one_of]`
1232         // and that they are all identifiers
1233         .and_then(|attr| match attr.meta_item_list() {
1234             Some(items) if items.len() < 2 => {
1235                 tcx.sess
1236                     .struct_span_err(
1237                         attr.span,
1238                         "the `#[rustc_must_implement_one_of]` attribute must be \
1239                         used with at least 2 args",
1240                     )
1241                     .emit();
1242
1243                 None
1244             }
1245             Some(items) => items
1246                 .into_iter()
1247                 .map(|item| item.ident().ok_or(item.span()))
1248                 .collect::<Result<Box<[_]>, _>>()
1249                 .map_err(|span| {
1250                     tcx.sess
1251                         .struct_span_err(span, "must be a name of an associated function")
1252                         .emit();
1253                 })
1254                 .ok()
1255                 .zip(Some(attr.span)),
1256             // Error is reported by `rustc_attr!`
1257             None => None,
1258         })
1259         // Check that all arguments of `#[rustc_must_implement_one_of]` reference
1260         // functions in the trait with default implementations
1261         .and_then(|(list, attr_span)| {
1262             let errors = list.iter().filter_map(|ident| {
1263                 let item = items.iter().find(|item| item.ident == *ident);
1264
1265                 match item {
1266                     Some(item) if matches!(item.kind, hir::AssocItemKind::Fn { .. }) => {
1267                         if !item.defaultness.has_value() {
1268                             tcx.sess
1269                                 .struct_span_err(
1270                                     item.span,
1271                                     "This function doesn't have a default implementation",
1272                                 )
1273                                 .span_note(attr_span, "required by this annotation")
1274                                 .emit();
1275
1276                             return Some(());
1277                         }
1278
1279                         return None;
1280                     }
1281                     Some(item) => tcx
1282                         .sess
1283                         .struct_span_err(item.span, "Not a function")
1284                         .span_note(attr_span, "required by this annotation")
1285                         .note(
1286                             "All `#[rustc_must_implement_one_of]` arguments \
1287                             must be associated function names",
1288                         )
1289                         .emit(),
1290                     None => tcx
1291                         .sess
1292                         .struct_span_err(ident.span, "Function not found in this trait")
1293                         .emit(),
1294                 }
1295
1296                 Some(())
1297             });
1298
1299             (errors.count() == 0).then_some(list)
1300         })
1301         // Check for duplicates
1302         .and_then(|list| {
1303             let mut set: FxHashMap<Symbol, Span> = FxHashMap::default();
1304             let mut no_dups = true;
1305
1306             for ident in &*list {
1307                 if let Some(dup) = set.insert(ident.name, ident.span) {
1308                     tcx.sess
1309                         .struct_span_err(vec![dup, ident.span], "Functions names are duplicated")
1310                         .note(
1311                             "All `#[rustc_must_implement_one_of]` arguments \
1312                             must be unique",
1313                         )
1314                         .emit();
1315
1316                     no_dups = false;
1317                 }
1318             }
1319
1320             no_dups.then_some(list)
1321         });
1322
1323     ty::TraitDef::new(
1324         def_id,
1325         unsafety,
1326         paren_sugar,
1327         is_auto,
1328         is_marker,
1329         skip_array_during_method_dispatch,
1330         spec_kind,
1331         def_path_hash,
1332         must_implement_one_of,
1333     )
1334 }
1335
1336 fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option<Span> {
1337     struct LateBoundRegionsDetector<'tcx> {
1338         tcx: TyCtxt<'tcx>,
1339         outer_index: ty::DebruijnIndex,
1340         has_late_bound_regions: Option<Span>,
1341     }
1342
1343     impl<'tcx> Visitor<'tcx> for LateBoundRegionsDetector<'tcx> {
1344         fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
1345             if self.has_late_bound_regions.is_some() {
1346                 return;
1347             }
1348             match ty.kind {
1349                 hir::TyKind::BareFn(..) => {
1350                     self.outer_index.shift_in(1);
1351                     intravisit::walk_ty(self, ty);
1352                     self.outer_index.shift_out(1);
1353                 }
1354                 _ => intravisit::walk_ty(self, ty),
1355             }
1356         }
1357
1358         fn visit_poly_trait_ref(
1359             &mut self,
1360             tr: &'tcx hir::PolyTraitRef<'tcx>,
1361             m: hir::TraitBoundModifier,
1362         ) {
1363             if self.has_late_bound_regions.is_some() {
1364                 return;
1365             }
1366             self.outer_index.shift_in(1);
1367             intravisit::walk_poly_trait_ref(self, tr, m);
1368             self.outer_index.shift_out(1);
1369         }
1370
1371         fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
1372             if self.has_late_bound_regions.is_some() {
1373                 return;
1374             }
1375
1376             match self.tcx.named_region(lt.hir_id) {
1377                 Some(rl::Region::Static | rl::Region::EarlyBound(..)) => {}
1378                 Some(
1379                     rl::Region::LateBound(debruijn, _, _, _)
1380                     | rl::Region::LateBoundAnon(debruijn, _, _),
1381                 ) if debruijn < self.outer_index => {}
1382                 Some(
1383                     rl::Region::LateBound(..)
1384                     | rl::Region::LateBoundAnon(..)
1385                     | rl::Region::Free(..),
1386                 )
1387                 | None => {
1388                     self.has_late_bound_regions = Some(lt.span);
1389                 }
1390             }
1391         }
1392     }
1393
1394     fn has_late_bound_regions<'tcx>(
1395         tcx: TyCtxt<'tcx>,
1396         generics: &'tcx hir::Generics<'tcx>,
1397         decl: &'tcx hir::FnDecl<'tcx>,
1398     ) -> Option<Span> {
1399         let mut visitor = LateBoundRegionsDetector {
1400             tcx,
1401             outer_index: ty::INNERMOST,
1402             has_late_bound_regions: None,
1403         };
1404         for param in generics.params {
1405             if let GenericParamKind::Lifetime { .. } = param.kind {
1406                 if tcx.is_late_bound(param.hir_id) {
1407                     return Some(param.span);
1408                 }
1409             }
1410         }
1411         visitor.visit_fn_decl(decl);
1412         visitor.has_late_bound_regions
1413     }
1414
1415     match node {
1416         Node::TraitItem(item) => match item.kind {
1417             hir::TraitItemKind::Fn(ref sig, _) => {
1418                 has_late_bound_regions(tcx, &item.generics, sig.decl)
1419             }
1420             _ => None,
1421         },
1422         Node::ImplItem(item) => match item.kind {
1423             hir::ImplItemKind::Fn(ref sig, _) => {
1424                 has_late_bound_regions(tcx, &item.generics, sig.decl)
1425             }
1426             _ => None,
1427         },
1428         Node::ForeignItem(item) => match item.kind {
1429             hir::ForeignItemKind::Fn(fn_decl, _, ref generics) => {
1430                 has_late_bound_regions(tcx, generics, fn_decl)
1431             }
1432             _ => None,
1433         },
1434         Node::Item(item) => match item.kind {
1435             hir::ItemKind::Fn(ref sig, .., ref generics, _) => {
1436                 has_late_bound_regions(tcx, generics, sig.decl)
1437             }
1438             _ => None,
1439         },
1440         _ => None,
1441     }
1442 }
1443
1444 struct AnonConstInParamTyDetector {
1445     in_param_ty: bool,
1446     found_anon_const_in_param_ty: bool,
1447     ct: HirId,
1448 }
1449
1450 impl<'v> Visitor<'v> for AnonConstInParamTyDetector {
1451     fn visit_generic_param(&mut self, p: &'v hir::GenericParam<'v>) {
1452         if let GenericParamKind::Const { ty, default: _ } = p.kind {
1453             let prev = self.in_param_ty;
1454             self.in_param_ty = true;
1455             self.visit_ty(ty);
1456             self.in_param_ty = prev;
1457         }
1458     }
1459
1460     fn visit_anon_const(&mut self, c: &'v hir::AnonConst) {
1461         if self.in_param_ty && self.ct == c.hir_id {
1462             self.found_anon_const_in_param_ty = true;
1463         } else {
1464             intravisit::walk_anon_const(self, c)
1465         }
1466     }
1467 }
1468
1469 fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::Generics {
1470     use rustc_hir::*;
1471
1472     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1473
1474     let node = tcx.hir().get(hir_id);
1475     let parent_def_id = match node {
1476         Node::ImplItem(_)
1477         | Node::TraitItem(_)
1478         | Node::Variant(_)
1479         | Node::Ctor(..)
1480         | Node::Field(_) => {
1481             let parent_id = tcx.hir().get_parent_item(hir_id);
1482             Some(parent_id.to_def_id())
1483         }
1484         // FIXME(#43408) always enable this once `lazy_normalization` is
1485         // stable enough and does not need a feature gate anymore.
1486         Node::AnonConst(_) => {
1487             let parent_def_id = tcx.hir().get_parent_item(hir_id);
1488
1489             let mut in_param_ty = false;
1490             for (_parent, node) in tcx.hir().parent_iter(hir_id) {
1491                 if let Some(generics) = node.generics() {
1492                     let mut visitor = AnonConstInParamTyDetector {
1493                         in_param_ty: false,
1494                         found_anon_const_in_param_ty: false,
1495                         ct: hir_id,
1496                     };
1497
1498                     visitor.visit_generics(generics);
1499                     in_param_ty = visitor.found_anon_const_in_param_ty;
1500                     break;
1501                 }
1502             }
1503
1504             if in_param_ty {
1505                 // We do not allow generic parameters in anon consts if we are inside
1506                 // of a const parameter type, e.g. `struct Foo<const N: usize, const M: [u8; N]>` is not allowed.
1507                 None
1508             } else if tcx.lazy_normalization() {
1509                 if let Some(param_id) = tcx.hir().opt_const_param_default_param_hir_id(hir_id) {
1510                     // If the def_id we are calling generics_of on is an anon ct default i.e:
1511                     //
1512                     // struct Foo<const N: usize = { .. }>;
1513                     //        ^^^       ^          ^^^^^^ def id of this anon const
1514                     //        ^         ^ param_id
1515                     //        ^ parent_def_id
1516                     //
1517                     // then we only want to return generics for params to the left of `N`. If we don't do that we
1518                     // end up with that const looking like: `ty::ConstKind::Unevaluated(def_id, substs: [N#0])`.
1519                     //
1520                     // This causes ICEs (#86580) when building the substs for Foo in `fn foo() -> Foo { .. }` as
1521                     // we substitute the defaults with the partially built substs when we build the substs. Subst'ing
1522                     // the `N#0` on the unevaluated const indexes into the empty substs we're in the process of building.
1523                     //
1524                     // We fix this by having this function return the parent's generics ourselves and truncating the
1525                     // generics to only include non-forward declared params (with the exception of the `Self` ty)
1526                     //
1527                     // For the above code example that means we want `substs: []`
1528                     // For the following struct def we want `substs: [N#0]` when generics_of is called on
1529                     // the def id of the `{ N + 1 }` anon const
1530                     // struct Foo<const N: usize, const M: usize = { N + 1 }>;
1531                     //
1532                     // This has some implications for how we get the predicates available to the anon const
1533                     // see `explicit_predicates_of` for more information on this
1534                     let generics = tcx.generics_of(parent_def_id.to_def_id());
1535                     let param_def = tcx.hir().local_def_id(param_id).to_def_id();
1536                     let param_def_idx = generics.param_def_id_to_index[&param_def];
1537                     // In the above example this would be .params[..N#0]
1538                     let params = generics.params[..param_def_idx as usize].to_owned();
1539                     let param_def_id_to_index =
1540                         params.iter().map(|param| (param.def_id, param.index)).collect();
1541
1542                     return ty::Generics {
1543                         // we set the parent of these generics to be our parent's parent so that we
1544                         // dont end up with substs: [N, M, N] for the const default on a struct like this:
1545                         // struct Foo<const N: usize, const M: usize = { ... }>;
1546                         parent: generics.parent,
1547                         parent_count: generics.parent_count,
1548                         params,
1549                         param_def_id_to_index,
1550                         has_self: generics.has_self,
1551                         has_late_bound_regions: generics.has_late_bound_regions,
1552                     };
1553                 }
1554
1555                 // HACK(eddyb) this provides the correct generics when
1556                 // `feature(generic_const_expressions)` is enabled, so that const expressions
1557                 // used with const generics, e.g. `Foo<{N+1}>`, can work at all.
1558                 //
1559                 // Note that we do not supply the parent generics when using
1560                 // `min_const_generics`.
1561                 Some(parent_def_id.to_def_id())
1562             } else {
1563                 let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1564                 match parent_node {
1565                     // HACK(eddyb) this provides the correct generics for repeat
1566                     // expressions' count (i.e. `N` in `[x; N]`), and explicit
1567                     // `enum` discriminants (i.e. `D` in `enum Foo { Bar = D }`),
1568                     // as they shouldn't be able to cause query cycle errors.
1569                     Node::Expr(&Expr { kind: ExprKind::Repeat(_, ref constant), .. })
1570                         if constant.hir_id() == hir_id =>
1571                     {
1572                         Some(parent_def_id.to_def_id())
1573                     }
1574                     Node::Variant(Variant { disr_expr: Some(ref constant), .. })
1575                         if constant.hir_id == hir_id =>
1576                     {
1577                         Some(parent_def_id.to_def_id())
1578                     }
1579                     Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) => {
1580                         Some(tcx.typeck_root_def_id(def_id))
1581                     }
1582                     _ => None,
1583                 }
1584             }
1585         }
1586         Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1587             Some(tcx.typeck_root_def_id(def_id))
1588         }
1589         Node::Item(item) => match item.kind {
1590             ItemKind::OpaqueTy(hir::OpaqueTy {
1591                 origin:
1592                     hir::OpaqueTyOrigin::FnReturn(fn_def_id) | hir::OpaqueTyOrigin::AsyncFn(fn_def_id),
1593                 ..
1594             }) => Some(fn_def_id.to_def_id()),
1595             ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::TyAlias, .. }) => {
1596                 let parent_id = tcx.hir().get_parent_item(hir_id);
1597                 assert_ne!(parent_id, CRATE_DEF_ID);
1598                 debug!("generics_of: parent of opaque ty {:?} is {:?}", def_id, parent_id);
1599                 // Opaque types are always nested within another item, and
1600                 // inherit the generics of the item.
1601                 Some(parent_id.to_def_id())
1602             }
1603             _ => None,
1604         },
1605         _ => None,
1606     };
1607
1608     let mut opt_self = None;
1609     let mut allow_defaults = false;
1610
1611     let no_generics = hir::Generics::empty();
1612     let ast_generics = match node {
1613         Node::TraitItem(item) => &item.generics,
1614
1615         Node::ImplItem(item) => &item.generics,
1616
1617         Node::Item(item) => {
1618             match item.kind {
1619                 ItemKind::Fn(.., ref generics, _)
1620                 | ItemKind::Impl(hir::Impl { ref generics, .. }) => generics,
1621
1622                 ItemKind::TyAlias(_, ref generics)
1623                 | ItemKind::Enum(_, ref generics)
1624                 | ItemKind::Struct(_, ref generics)
1625                 | ItemKind::OpaqueTy(hir::OpaqueTy { ref generics, .. })
1626                 | ItemKind::Union(_, ref generics) => {
1627                     allow_defaults = true;
1628                     generics
1629                 }
1630
1631                 ItemKind::Trait(_, _, ref generics, ..)
1632                 | ItemKind::TraitAlias(ref generics, ..) => {
1633                     // Add in the self type parameter.
1634                     //
1635                     // Something of a hack: use the node id for the trait, also as
1636                     // the node id for the Self type parameter.
1637                     let param_id = item.def_id;
1638
1639                     opt_self = Some(ty::GenericParamDef {
1640                         index: 0,
1641                         name: kw::SelfUpper,
1642                         def_id: param_id.to_def_id(),
1643                         pure_wrt_drop: false,
1644                         kind: ty::GenericParamDefKind::Type {
1645                             has_default: false,
1646                             object_lifetime_default: rl::Set1::Empty,
1647                             synthetic: false,
1648                         },
1649                     });
1650
1651                     allow_defaults = true;
1652                     generics
1653                 }
1654
1655                 _ => &no_generics,
1656             }
1657         }
1658
1659         Node::ForeignItem(item) => match item.kind {
1660             ForeignItemKind::Static(..) => &no_generics,
1661             ForeignItemKind::Fn(_, _, ref generics) => generics,
1662             ForeignItemKind::Type => &no_generics,
1663         },
1664
1665         _ => &no_generics,
1666     };
1667
1668     let has_self = opt_self.is_some();
1669     let mut parent_has_self = false;
1670     let mut own_start = has_self as u32;
1671     let parent_count = parent_def_id.map_or(0, |def_id| {
1672         let generics = tcx.generics_of(def_id);
1673         assert!(!has_self);
1674         parent_has_self = generics.has_self;
1675         own_start = generics.count() as u32;
1676         generics.parent_count + generics.params.len()
1677     });
1678
1679     let mut params: Vec<_> = Vec::with_capacity(ast_generics.params.len() + has_self as usize);
1680
1681     if let Some(opt_self) = opt_self {
1682         params.push(opt_self);
1683     }
1684
1685     let early_lifetimes = early_bound_lifetimes_from_generics(tcx, ast_generics);
1686     params.extend(early_lifetimes.enumerate().map(|(i, param)| ty::GenericParamDef {
1687         name: param.name.ident().name,
1688         index: own_start + i as u32,
1689         def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1690         pure_wrt_drop: param.pure_wrt_drop,
1691         kind: ty::GenericParamDefKind::Lifetime,
1692     }));
1693
1694     let object_lifetime_defaults = tcx.object_lifetime_defaults(hir_id.owner);
1695
1696     // Now create the real type and const parameters.
1697     let type_start = own_start - has_self as u32 + params.len() as u32;
1698     let mut i = 0;
1699
1700     params.extend(ast_generics.params.iter().filter_map(|param| match param.kind {
1701         GenericParamKind::Lifetime { .. } => None,
1702         GenericParamKind::Type { ref default, synthetic, .. } => {
1703             if !allow_defaults && default.is_some() {
1704                 if !tcx.features().default_type_parameter_fallback {
1705                     tcx.struct_span_lint_hir(
1706                         lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
1707                         param.hir_id,
1708                         param.span,
1709                         |lint| {
1710                             lint.build(
1711                                 "defaults for type parameters are only allowed in \
1712                                  `struct`, `enum`, `type`, or `trait` definitions",
1713                             )
1714                             .emit();
1715                         },
1716                     );
1717                 }
1718             }
1719
1720             let kind = ty::GenericParamDefKind::Type {
1721                 has_default: default.is_some(),
1722                 object_lifetime_default: object_lifetime_defaults
1723                     .as_ref()
1724                     .map_or(rl::Set1::Empty, |o| o[i]),
1725                 synthetic,
1726             };
1727
1728             let param_def = ty::GenericParamDef {
1729                 index: type_start + i as u32,
1730                 name: param.name.ident().name,
1731                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1732                 pure_wrt_drop: param.pure_wrt_drop,
1733                 kind,
1734             };
1735             i += 1;
1736             Some(param_def)
1737         }
1738         GenericParamKind::Const { default, .. } => {
1739             if !allow_defaults && default.is_some() {
1740                 tcx.sess.span_err(
1741                     param.span,
1742                     "defaults for const parameters are only allowed in \
1743                     `struct`, `enum`, `type`, or `trait` definitions",
1744                 );
1745             }
1746
1747             let param_def = ty::GenericParamDef {
1748                 index: type_start + i as u32,
1749                 name: param.name.ident().name,
1750                 def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
1751                 pure_wrt_drop: param.pure_wrt_drop,
1752                 kind: ty::GenericParamDefKind::Const { has_default: default.is_some() },
1753             };
1754             i += 1;
1755             Some(param_def)
1756         }
1757     }));
1758
1759     // provide junk type parameter defs - the only place that
1760     // cares about anything but the length is instantiation,
1761     // and we don't do that for closures.
1762     if let Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(.., gen), .. }) = node {
1763         let dummy_args = if gen.is_some() {
1764             &["<resume_ty>", "<yield_ty>", "<return_ty>", "<witness>", "<upvars>"][..]
1765         } else {
1766             &["<closure_kind>", "<closure_signature>", "<upvars>"][..]
1767         };
1768
1769         params.extend(dummy_args.iter().enumerate().map(|(i, &arg)| ty::GenericParamDef {
1770             index: type_start + i as u32,
1771             name: Symbol::intern(arg),
1772             def_id,
1773             pure_wrt_drop: false,
1774             kind: ty::GenericParamDefKind::Type {
1775                 has_default: false,
1776                 object_lifetime_default: rl::Set1::Empty,
1777                 synthetic: false,
1778             },
1779         }));
1780     }
1781
1782     // provide junk type parameter defs for const blocks.
1783     if let Node::AnonConst(_) = node {
1784         let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
1785         if let Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) = parent_node {
1786             params.push(ty::GenericParamDef {
1787                 index: type_start,
1788                 name: Symbol::intern("<const_ty>"),
1789                 def_id,
1790                 pure_wrt_drop: false,
1791                 kind: ty::GenericParamDefKind::Type {
1792                     has_default: false,
1793                     object_lifetime_default: rl::Set1::Empty,
1794                     synthetic: false,
1795                 },
1796             });
1797         }
1798     }
1799
1800     let param_def_id_to_index = params.iter().map(|param| (param.def_id, param.index)).collect();
1801
1802     ty::Generics {
1803         parent: parent_def_id,
1804         parent_count,
1805         params,
1806         param_def_id_to_index,
1807         has_self: has_self || parent_has_self,
1808         has_late_bound_regions: has_late_bound_regions(tcx, node),
1809     }
1810 }
1811
1812 fn are_suggestable_generic_args(generic_args: &[hir::GenericArg<'_>]) -> bool {
1813     generic_args.iter().any(|arg| match arg {
1814         hir::GenericArg::Type(ty) => is_suggestable_infer_ty(ty),
1815         hir::GenericArg::Infer(_) => true,
1816         _ => false,
1817     })
1818 }
1819
1820 /// Whether `ty` is a type with `_` placeholders that can be inferred. Used in diagnostics only to
1821 /// use inference to provide suggestions for the appropriate type if possible.
1822 fn is_suggestable_infer_ty(ty: &hir::Ty<'_>) -> bool {
1823     debug!(?ty);
1824     use hir::TyKind::*;
1825     match &ty.kind {
1826         Infer => true,
1827         Slice(ty) => is_suggestable_infer_ty(ty),
1828         Array(ty, length) => {
1829             is_suggestable_infer_ty(ty) || matches!(length, hir::ArrayLen::Infer(_, _))
1830         }
1831         Tup(tys) => tys.iter().any(is_suggestable_infer_ty),
1832         Ptr(mut_ty) | Rptr(_, mut_ty) => is_suggestable_infer_ty(mut_ty.ty),
1833         OpaqueDef(_, generic_args) => are_suggestable_generic_args(generic_args),
1834         Path(hir::QPath::TypeRelative(ty, segment)) => {
1835             is_suggestable_infer_ty(ty) || are_suggestable_generic_args(segment.args().args)
1836         }
1837         Path(hir::QPath::Resolved(ty_opt, hir::Path { segments, .. })) => {
1838             ty_opt.map_or(false, is_suggestable_infer_ty)
1839                 || segments.iter().any(|segment| are_suggestable_generic_args(segment.args().args))
1840         }
1841         _ => false,
1842     }
1843 }
1844
1845 pub fn get_infer_ret_ty<'hir>(output: &'hir hir::FnRetTy<'hir>) -> Option<&'hir hir::Ty<'hir>> {
1846     if let hir::FnRetTy::Return(ty) = output {
1847         if is_suggestable_infer_ty(ty) {
1848             return Some(&*ty);
1849         }
1850     }
1851     None
1852 }
1853
1854 fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
1855     use rustc_hir::Node::*;
1856     use rustc_hir::*;
1857
1858     let def_id = def_id.expect_local();
1859     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1860
1861     let icx = ItemCtxt::new(tcx, def_id.to_def_id());
1862
1863     match tcx.hir().get(hir_id) {
1864         TraitItem(hir::TraitItem {
1865             kind: TraitItemKind::Fn(sig, TraitFn::Provided(_)),
1866             ident,
1867             generics,
1868             ..
1869         })
1870         | ImplItem(hir::ImplItem { kind: ImplItemKind::Fn(sig, _), ident, generics, .. })
1871         | Item(hir::Item { kind: ItemKind::Fn(sig, generics, _), ident, .. }) => {
1872             match get_infer_ret_ty(&sig.decl.output) {
1873                 Some(ty) => {
1874                     let fn_sig = tcx.typeck(def_id).liberated_fn_sigs()[hir_id];
1875                     // Typeck doesn't expect erased regions to be returned from `type_of`.
1876                     let fn_sig = tcx.fold_regions(fn_sig, &mut false, |r, _| match *r {
1877                         ty::ReErased => tcx.lifetimes.re_static,
1878                         _ => r,
1879                     });
1880                     let fn_sig = ty::Binder::dummy(fn_sig);
1881
1882                     let mut visitor = HirPlaceholderCollector::default();
1883                     visitor.visit_ty(ty);
1884                     let mut diag = bad_placeholder(tcx, visitor.0, "return type");
1885                     let ret_ty = fn_sig.skip_binder().output();
1886                     if !ret_ty.references_error() {
1887                         if !ret_ty.is_closure() {
1888                             let ret_ty_str = match ret_ty.kind() {
1889                                 // Suggest a function pointer return type instead of a unique function definition
1890                                 // (e.g. `fn() -> i32` instead of `fn() -> i32 { f }`, the latter of which is invalid
1891                                 // syntax)
1892                                 ty::FnDef(..) => ret_ty.fn_sig(tcx).to_string(),
1893                                 _ => ret_ty.to_string(),
1894                             };
1895                             diag.span_suggestion(
1896                                 ty.span,
1897                                 "replace with the correct return type",
1898                                 ret_ty_str,
1899                                 Applicability::MaybeIncorrect,
1900                             );
1901                         } else {
1902                             // We're dealing with a closure, so we should suggest using `impl Fn` or trait bounds
1903                             // to prevent the user from getting a papercut while trying to use the unique closure
1904                             // syntax (e.g. `[closure@src/lib.rs:2:5: 2:9]`).
1905                             diag.help("consider using an `Fn`, `FnMut`, or `FnOnce` trait bound");
1906                             diag.note("for more information on `Fn` traits and closure types, see https://doc.rust-lang.org/book/ch13-01-closures.html");
1907                         }
1908                     }
1909                     diag.emit();
1910
1911                     fn_sig
1912                 }
1913                 None => <dyn AstConv<'_>>::ty_of_fn(
1914                     &icx,
1915                     hir_id,
1916                     sig.header.unsafety,
1917                     sig.header.abi,
1918                     sig.decl,
1919                     generics,
1920                     Some(ident.span),
1921                     None,
1922                 ),
1923             }
1924         }
1925
1926         TraitItem(hir::TraitItem {
1927             kind: TraitItemKind::Fn(FnSig { header, decl, span: _ }, _),
1928             ident,
1929             generics,
1930             ..
1931         }) => <dyn AstConv<'_>>::ty_of_fn(
1932             &icx,
1933             hir_id,
1934             header.unsafety,
1935             header.abi,
1936             decl,
1937             generics,
1938             Some(ident.span),
1939             None,
1940         ),
1941
1942         ForeignItem(&hir::ForeignItem {
1943             kind: ForeignItemKind::Fn(fn_decl, _, _), ident, ..
1944         }) => {
1945             let abi = tcx.hir().get_foreign_abi(hir_id);
1946             compute_sig_of_foreign_fn_decl(tcx, def_id.to_def_id(), fn_decl, abi, ident)
1947         }
1948
1949         Ctor(data) | Variant(hir::Variant { data, .. }) if data.ctor_hir_id().is_some() => {
1950             let ty = tcx.type_of(tcx.hir().get_parent_item(hir_id));
1951             let inputs =
1952                 data.fields().iter().map(|f| tcx.type_of(tcx.hir().local_def_id(f.hir_id)));
1953             ty::Binder::dummy(tcx.mk_fn_sig(
1954                 inputs,
1955                 ty,
1956                 false,
1957                 hir::Unsafety::Normal,
1958                 abi::Abi::Rust,
1959             ))
1960         }
1961
1962         Expr(&hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => {
1963             // Closure signatures are not like other function
1964             // signatures and cannot be accessed through `fn_sig`. For
1965             // example, a closure signature excludes the `self`
1966             // argument. In any case they are embedded within the
1967             // closure type as part of the `ClosureSubsts`.
1968             //
1969             // To get the signature of a closure, you should use the
1970             // `sig` method on the `ClosureSubsts`:
1971             //
1972             //    substs.as_closure().sig(def_id, tcx)
1973             bug!(
1974                 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
1975             );
1976         }
1977
1978         x => {
1979             bug!("unexpected sort of node in fn_sig(): {:?}", x);
1980         }
1981     }
1982 }
1983
1984 fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> {
1985     let icx = ItemCtxt::new(tcx, def_id);
1986     match tcx.hir().expect_item(def_id.expect_local()).kind {
1987         hir::ItemKind::Impl(ref impl_) => impl_.of_trait.as_ref().map(|ast_trait_ref| {
1988             let selfty = tcx.type_of(def_id);
1989             <dyn AstConv<'_>>::instantiate_mono_trait_ref(&icx, ast_trait_ref, selfty)
1990         }),
1991         _ => bug!(),
1992     }
1993 }
1994
1995 fn impl_polarity(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ImplPolarity {
1996     let is_rustc_reservation = tcx.has_attr(def_id, sym::rustc_reservation_impl);
1997     let item = tcx.hir().expect_item(def_id.expect_local());
1998     match &item.kind {
1999         hir::ItemKind::Impl(hir::Impl {
2000             polarity: hir::ImplPolarity::Negative(span),
2001             of_trait,
2002             ..
2003         }) => {
2004             if is_rustc_reservation {
2005                 let span = span.to(of_trait.as_ref().map_or(*span, |t| t.path.span));
2006                 tcx.sess.span_err(span, "reservation impls can't be negative");
2007             }
2008             ty::ImplPolarity::Negative
2009         }
2010         hir::ItemKind::Impl(hir::Impl {
2011             polarity: hir::ImplPolarity::Positive,
2012             of_trait: None,
2013             ..
2014         }) => {
2015             if is_rustc_reservation {
2016                 tcx.sess.span_err(item.span, "reservation impls can't be inherent");
2017             }
2018             ty::ImplPolarity::Positive
2019         }
2020         hir::ItemKind::Impl(hir::Impl {
2021             polarity: hir::ImplPolarity::Positive,
2022             of_trait: Some(_),
2023             ..
2024         }) => {
2025             if is_rustc_reservation {
2026                 ty::ImplPolarity::Reservation
2027             } else {
2028                 ty::ImplPolarity::Positive
2029             }
2030         }
2031         item => bug!("impl_polarity: {:?} not an impl", item),
2032     }
2033 }
2034
2035 /// Returns the early-bound lifetimes declared in this generics
2036 /// listing. For anything other than fns/methods, this is just all
2037 /// the lifetimes that are declared. For fns or methods, we have to
2038 /// screen out those that do not appear in any where-clauses etc using
2039 /// `resolve_lifetime::early_bound_lifetimes`.
2040 fn early_bound_lifetimes_from_generics<'a, 'tcx: 'a>(
2041     tcx: TyCtxt<'tcx>,
2042     generics: &'a hir::Generics<'a>,
2043 ) -> impl Iterator<Item = &'a hir::GenericParam<'a>> + Captures<'tcx> {
2044     generics.params.iter().filter(move |param| match param.kind {
2045         GenericParamKind::Lifetime { .. } => !tcx.is_late_bound(param.hir_id),
2046         _ => false,
2047     })
2048 }
2049
2050 /// Returns a list of type predicates for the definition with ID `def_id`, including inferred
2051 /// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus
2052 /// inferred constraints concerning which regions outlive other regions.
2053 fn predicates_defined_on(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2054     debug!("predicates_defined_on({:?})", def_id);
2055     let mut result = tcx.explicit_predicates_of(def_id);
2056     debug!("predicates_defined_on: explicit_predicates_of({:?}) = {:?}", def_id, result,);
2057     let inferred_outlives = tcx.inferred_outlives_of(def_id);
2058     if !inferred_outlives.is_empty() {
2059         debug!(
2060             "predicates_defined_on: inferred_outlives_of({:?}) = {:?}",
2061             def_id, inferred_outlives,
2062         );
2063         if result.predicates.is_empty() {
2064             result.predicates = inferred_outlives;
2065         } else {
2066             result.predicates = tcx
2067                 .arena
2068                 .alloc_from_iter(result.predicates.iter().chain(inferred_outlives).copied());
2069         }
2070     }
2071
2072     debug!("predicates_defined_on({:?}) = {:?}", def_id, result);
2073     result
2074 }
2075
2076 /// Returns a list of all type predicates (explicit and implicit) for the definition with
2077 /// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus
2078 /// `Self: Trait` predicates for traits.
2079 fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2080     let mut result = tcx.predicates_defined_on(def_id);
2081
2082     if tcx.is_trait(def_id) {
2083         // For traits, add `Self: Trait` predicate. This is
2084         // not part of the predicates that a user writes, but it
2085         // is something that one must prove in order to invoke a
2086         // method or project an associated type.
2087         //
2088         // In the chalk setup, this predicate is not part of the
2089         // "predicates" for a trait item. But it is useful in
2090         // rustc because if you directly (e.g.) invoke a trait
2091         // method like `Trait::method(...)`, you must naturally
2092         // prove that the trait applies to the types that were
2093         // used, and adding the predicate into this list ensures
2094         // that this is done.
2095         //
2096         // We use a DUMMY_SP here as a way to signal trait bounds that come
2097         // from the trait itself that *shouldn't* be shown as the source of
2098         // an obligation and instead be skipped. Otherwise we'd use
2099         // `tcx.def_span(def_id);`
2100         let span = rustc_span::DUMMY_SP;
2101         result.predicates =
2102             tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once((
2103                 ty::TraitRef::identity(tcx, def_id).without_const().to_predicate(tcx),
2104                 span,
2105             ))));
2106     }
2107     debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
2108     result
2109 }
2110
2111 /// Returns a list of user-specified type predicates for the definition with ID `def_id`.
2112 /// N.B., this does not include any implied/inferred constraints.
2113 fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2114     use rustc_hir::*;
2115
2116     debug!("explicit_predicates_of(def_id={:?})", def_id);
2117
2118     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2119     let node = tcx.hir().get(hir_id);
2120
2121     let mut is_trait = None;
2122     let mut is_default_impl_trait = None;
2123
2124     let icx = ItemCtxt::new(tcx, def_id);
2125
2126     const NO_GENERICS: &hir::Generics<'_> = &hir::Generics::empty();
2127
2128     // We use an `IndexSet` to preserves order of insertion.
2129     // Preserving the order of insertion is important here so as not to break UI tests.
2130     let mut predicates: FxIndexSet<(ty::Predicate<'_>, Span)> = FxIndexSet::default();
2131
2132     let ast_generics = match node {
2133         Node::TraitItem(item) => &item.generics,
2134
2135         Node::ImplItem(item) => &item.generics,
2136
2137         Node::Item(item) => {
2138             match item.kind {
2139                 ItemKind::Impl(ref impl_) => {
2140                     if impl_.defaultness.is_default() {
2141                         is_default_impl_trait = tcx.impl_trait_ref(def_id).map(ty::Binder::dummy);
2142                     }
2143                     &impl_.generics
2144                 }
2145                 ItemKind::Fn(.., ref generics, _)
2146                 | ItemKind::TyAlias(_, ref generics)
2147                 | ItemKind::Enum(_, ref generics)
2148                 | ItemKind::Struct(_, ref generics)
2149                 | ItemKind::Union(_, ref generics) => generics,
2150
2151                 ItemKind::Trait(_, _, ref generics, ..) => {
2152                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2153                     generics
2154                 }
2155                 ItemKind::TraitAlias(ref generics, _) => {
2156                     is_trait = Some(ty::TraitRef::identity(tcx, def_id));
2157                     generics
2158                 }
2159                 ItemKind::OpaqueTy(OpaqueTy {
2160                     origin: hir::OpaqueTyOrigin::FnReturn(..), ..
2161                 }) => {
2162                     // return-position impl trait
2163                     //
2164                     // We don't inherit predicates from the parent here:
2165                     // If we have, say `fn f<'a, T: 'a>() -> impl Sized {}`
2166                     // then the return type is `f::<'static, T>::{{opaque}}`.
2167                     //
2168                     // If we inherited the predicates of `f` then we would
2169                     // require that `T: 'static` to show that the return
2170                     // type is well-formed.
2171                     //
2172                     // The only way to have something with this opaque type
2173                     // is from the return type of the containing function,
2174                     // which will ensure that the function's predicates
2175                     // hold.
2176                     return ty::GenericPredicates { parent: None, predicates: &[] };
2177                 }
2178                 ItemKind::OpaqueTy(OpaqueTy {
2179                     ref generics,
2180                     origin: hir::OpaqueTyOrigin::AsyncFn(..) | hir::OpaqueTyOrigin::TyAlias,
2181                     ..
2182                 }) => {
2183                     // type-alias impl trait
2184                     generics
2185                 }
2186
2187                 _ => NO_GENERICS,
2188             }
2189         }
2190
2191         Node::ForeignItem(item) => match item.kind {
2192             ForeignItemKind::Static(..) => NO_GENERICS,
2193             ForeignItemKind::Fn(_, _, ref generics) => generics,
2194             ForeignItemKind::Type => NO_GENERICS,
2195         },
2196
2197         _ => NO_GENERICS,
2198     };
2199
2200     let generics = tcx.generics_of(def_id);
2201     let parent_count = generics.parent_count as u32;
2202     let has_own_self = generics.has_self && parent_count == 0;
2203
2204     // Below we'll consider the bounds on the type parameters (including `Self`)
2205     // and the explicit where-clauses, but to get the full set of predicates
2206     // on a trait we need to add in the supertrait bounds and bounds found on
2207     // associated types.
2208     if let Some(_trait_ref) = is_trait {
2209         predicates.extend(tcx.super_predicates_of(def_id).predicates.iter().cloned());
2210     }
2211
2212     // In default impls, we can assume that the self type implements
2213     // the trait. So in:
2214     //
2215     //     default impl Foo for Bar { .. }
2216     //
2217     // we add a default where clause `Foo: Bar`. We do a similar thing for traits
2218     // (see below). Recall that a default impl is not itself an impl, but rather a
2219     // set of defaults that can be incorporated into another impl.
2220     if let Some(trait_ref) = is_default_impl_trait {
2221         predicates.insert((trait_ref.without_const().to_predicate(tcx), tcx.def_span(def_id)));
2222     }
2223
2224     // Collect the region predicates that were declared inline as
2225     // well. In the case of parameters declared on a fn or method, we
2226     // have to be careful to only iterate over early-bound regions.
2227     let mut index = parent_count + has_own_self as u32;
2228     for param in early_bound_lifetimes_from_generics(tcx, ast_generics) {
2229         let region = tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
2230             def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(),
2231             index,
2232             name: param.name.ident().name,
2233         }));
2234         index += 1;
2235
2236         match param.kind {
2237             GenericParamKind::Lifetime { .. } => {
2238                 param.bounds.iter().for_each(|bound| match bound {
2239                     hir::GenericBound::Outlives(lt) => {
2240                         let bound = <dyn AstConv<'_>>::ast_region_to_region(&icx, lt, None);
2241                         let outlives = ty::Binder::dummy(ty::OutlivesPredicate(region, bound));
2242                         predicates.insert((outlives.to_predicate(tcx), lt.span));
2243                     }
2244                     _ => bug!(),
2245                 });
2246             }
2247             _ => bug!(),
2248         }
2249     }
2250
2251     // Collect the predicates that were written inline by the user on each
2252     // type parameter (e.g., `<T: Foo>`).
2253     for param in ast_generics.params {
2254         match param.kind {
2255             // We already dealt with early bound lifetimes above.
2256             GenericParamKind::Lifetime { .. } => (),
2257             GenericParamKind::Type { .. } => {
2258                 let name = param.name.ident().name;
2259                 let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
2260                 index += 1;
2261
2262                 let mut bounds = <dyn AstConv<'_>>::compute_bounds(&icx, param_ty, param.bounds);
2263                 // Params are implicitly sized unless a `?Sized` bound is found
2264                 <dyn AstConv<'_>>::add_implicitly_sized(
2265                     &icx,
2266                     &mut bounds,
2267                     param.bounds,
2268                     Some((param.hir_id, ast_generics.where_clause.predicates)),
2269                     param.span,
2270                 );
2271                 predicates.extend(bounds.predicates(tcx, param_ty));
2272             }
2273             GenericParamKind::Const { .. } => {
2274                 // Bounds on const parameters are currently not possible.
2275                 debug_assert!(param.bounds.is_empty());
2276                 index += 1;
2277             }
2278         }
2279     }
2280
2281     // Add in the bounds that appear in the where-clause.
2282     let where_clause = &ast_generics.where_clause;
2283     for predicate in where_clause.predicates {
2284         match predicate {
2285             hir::WherePredicate::BoundPredicate(bound_pred) => {
2286                 let ty = icx.to_ty(bound_pred.bounded_ty);
2287                 let bound_vars = icx.tcx.late_bound_vars(bound_pred.bounded_ty.hir_id);
2288
2289                 // Keep the type around in a dummy predicate, in case of no bounds.
2290                 // That way, `where Ty:` is not a complete noop (see #53696) and `Ty`
2291                 // is still checked for WF.
2292                 if bound_pred.bounds.is_empty() {
2293                     if let ty::Param(_) = ty.kind() {
2294                         // This is a `where T:`, which can be in the HIR from the
2295                         // transformation that moves `?Sized` to `T`'s declaration.
2296                         // We can skip the predicate because type parameters are
2297                         // trivially WF, but also we *should*, to avoid exposing
2298                         // users who never wrote `where Type:,` themselves, to
2299                         // compiler/tooling bugs from not handling WF predicates.
2300                     } else {
2301                         let span = bound_pred.bounded_ty.span;
2302                         let re_root_empty = tcx.lifetimes.re_root_empty;
2303                         let predicate = ty::Binder::bind_with_vars(
2304                             ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(
2305                                 ty,
2306                                 re_root_empty,
2307                             )),
2308                             bound_vars,
2309                         );
2310                         predicates.insert((predicate.to_predicate(tcx), span));
2311                     }
2312                 }
2313
2314                 let mut bounds = Bounds::default();
2315                 <dyn AstConv<'_>>::add_bounds(
2316                     &icx,
2317                     ty,
2318                     bound_pred.bounds.iter(),
2319                     &mut bounds,
2320                     bound_vars,
2321                 );
2322                 predicates.extend(bounds.predicates(tcx, ty));
2323             }
2324
2325             hir::WherePredicate::RegionPredicate(region_pred) => {
2326                 let r1 = <dyn AstConv<'_>>::ast_region_to_region(&icx, &region_pred.lifetime, None);
2327                 predicates.extend(region_pred.bounds.iter().map(|bound| {
2328                     let (r2, span) = match bound {
2329                         hir::GenericBound::Outlives(lt) => {
2330                             (<dyn AstConv<'_>>::ast_region_to_region(&icx, lt, None), lt.span)
2331                         }
2332                         _ => bug!(),
2333                     };
2334                     let pred = ty::Binder::dummy(ty::PredicateKind::RegionOutlives(
2335                         ty::OutlivesPredicate(r1, r2),
2336                     ))
2337                     .to_predicate(icx.tcx);
2338
2339                     (pred, span)
2340                 }))
2341             }
2342
2343             hir::WherePredicate::EqPredicate(..) => {
2344                 // FIXME(#20041)
2345             }
2346         }
2347     }
2348
2349     if tcx.features().generic_const_exprs {
2350         predicates.extend(const_evaluatable_predicates_of(tcx, def_id.expect_local()));
2351     }
2352
2353     let mut predicates: Vec<_> = predicates.into_iter().collect();
2354
2355     // Subtle: before we store the predicates into the tcx, we
2356     // sort them so that predicates like `T: Foo<Item=U>` come
2357     // before uses of `U`.  This avoids false ambiguity errors
2358     // in trait checking. See `setup_constraining_predicates`
2359     // for details.
2360     if let Node::Item(&Item { kind: ItemKind::Impl { .. }, .. }) = node {
2361         let self_ty = tcx.type_of(def_id);
2362         let trait_ref = tcx.impl_trait_ref(def_id);
2363         cgp::setup_constraining_predicates(
2364             tcx,
2365             &mut predicates,
2366             trait_ref,
2367             &mut cgp::parameters_for_impl(self_ty, trait_ref),
2368         );
2369     }
2370
2371     let result = ty::GenericPredicates {
2372         parent: generics.parent,
2373         predicates: tcx.arena.alloc_from_iter(predicates),
2374     };
2375     debug!("explicit_predicates_of(def_id={:?}) = {:?}", def_id, result);
2376     result
2377 }
2378
2379 fn const_evaluatable_predicates_of<'tcx>(
2380     tcx: TyCtxt<'tcx>,
2381     def_id: LocalDefId,
2382 ) -> FxIndexSet<(ty::Predicate<'tcx>, Span)> {
2383     struct ConstCollector<'tcx> {
2384         tcx: TyCtxt<'tcx>,
2385         preds: FxIndexSet<(ty::Predicate<'tcx>, Span)>,
2386     }
2387
2388     impl<'tcx> intravisit::Visitor<'tcx> for ConstCollector<'tcx> {
2389         fn visit_anon_const(&mut self, c: &'tcx hir::AnonConst) {
2390             let def_id = self.tcx.hir().local_def_id(c.hir_id);
2391             let ct = ty::Const::from_anon_const(self.tcx, def_id);
2392             if let ty::ConstKind::Unevaluated(uv) = ct.val() {
2393                 assert_eq!(uv.promoted, None);
2394                 let span = self.tcx.hir().span(c.hir_id);
2395                 self.preds.insert((
2396                     ty::Binder::dummy(ty::PredicateKind::ConstEvaluatable(uv.shrink()))
2397                         .to_predicate(self.tcx),
2398                     span,
2399                 ));
2400             }
2401         }
2402
2403         fn visit_const_param_default(&mut self, _param: HirId, _ct: &'tcx hir::AnonConst) {
2404             // Do not look into const param defaults,
2405             // these get checked when they are actually instantiated.
2406             //
2407             // We do not want the following to error:
2408             //
2409             //     struct Foo<const N: usize, const M: usize = { N + 1 }>;
2410             //     struct Bar<const N: usize>(Foo<N, 3>);
2411         }
2412     }
2413
2414     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
2415     let node = tcx.hir().get(hir_id);
2416
2417     let mut collector = ConstCollector { tcx, preds: FxIndexSet::default() };
2418     if let hir::Node::Item(item) = node {
2419         if let hir::ItemKind::Impl(ref impl_) = item.kind {
2420             if let Some(of_trait) = &impl_.of_trait {
2421                 debug!("const_evaluatable_predicates_of({:?}): visit impl trait_ref", def_id);
2422                 collector.visit_trait_ref(of_trait);
2423             }
2424
2425             debug!("const_evaluatable_predicates_of({:?}): visit_self_ty", def_id);
2426             collector.visit_ty(impl_.self_ty);
2427         }
2428     }
2429
2430     if let Some(generics) = node.generics() {
2431         debug!("const_evaluatable_predicates_of({:?}): visit_generics", def_id);
2432         collector.visit_generics(generics);
2433     }
2434
2435     if let Some(fn_sig) = tcx.hir().fn_sig_by_hir_id(hir_id) {
2436         debug!("const_evaluatable_predicates_of({:?}): visit_fn_decl", def_id);
2437         collector.visit_fn_decl(fn_sig.decl);
2438     }
2439     debug!("const_evaluatable_predicates_of({:?}) = {:?}", def_id, collector.preds);
2440
2441     collector.preds
2442 }
2443
2444 fn trait_explicit_predicates_and_bounds(
2445     tcx: TyCtxt<'_>,
2446     def_id: LocalDefId,
2447 ) -> ty::GenericPredicates<'_> {
2448     assert_eq!(tcx.def_kind(def_id), DefKind::Trait);
2449     gather_explicit_predicates_of(tcx, def_id.to_def_id())
2450 }
2451
2452 fn explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
2453     let def_kind = tcx.def_kind(def_id);
2454     if let DefKind::Trait = def_kind {
2455         // Remove bounds on associated types from the predicates, they will be
2456         // returned by `explicit_item_bounds`.
2457         let predicates_and_bounds = tcx.trait_explicit_predicates_and_bounds(def_id.expect_local());
2458         let trait_identity_substs = InternalSubsts::identity_for_item(tcx, def_id);
2459
2460         let is_assoc_item_ty = |ty: Ty<'_>| {
2461             // For a predicate from a where clause to become a bound on an
2462             // associated type:
2463             // * It must use the identity substs of the item.
2464             //     * Since any generic parameters on the item are not in scope,
2465             //       this means that the item is not a GAT, and its identity
2466             //       substs are the same as the trait's.
2467             // * It must be an associated type for this trait (*not* a
2468             //   supertrait).
2469             if let ty::Projection(projection) = ty.kind() {
2470                 projection.substs == trait_identity_substs
2471                     && tcx.associated_item(projection.item_def_id).container.id() == def_id
2472             } else {
2473                 false
2474             }
2475         };
2476
2477         let predicates: Vec<_> = predicates_and_bounds
2478             .predicates
2479             .iter()
2480             .copied()
2481             .filter(|(pred, _)| match pred.kind().skip_binder() {
2482                 ty::PredicateKind::Trait(tr) => !is_assoc_item_ty(tr.self_ty()),
2483                 ty::PredicateKind::Projection(proj) => {
2484                     !is_assoc_item_ty(proj.projection_ty.self_ty())
2485                 }
2486                 ty::PredicateKind::TypeOutlives(outlives) => !is_assoc_item_ty(outlives.0),
2487                 _ => true,
2488             })
2489             .collect();
2490         if predicates.len() == predicates_and_bounds.predicates.len() {
2491             predicates_and_bounds
2492         } else {
2493             ty::GenericPredicates {
2494                 parent: predicates_and_bounds.parent,
2495                 predicates: tcx.arena.alloc_slice(&predicates),
2496             }
2497         }
2498     } else {
2499         if matches!(def_kind, DefKind::AnonConst) && tcx.lazy_normalization() {
2500             let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2501             if tcx.hir().opt_const_param_default_param_hir_id(hir_id).is_some() {
2502                 // In `generics_of` we set the generics' parent to be our parent's parent which means that
2503                 // we lose out on the predicates of our actual parent if we dont return those predicates here.
2504                 // (See comment in `generics_of` for more information on why the parent shenanigans is necessary)
2505                 //
2506                 // struct Foo<T, const N: usize = { <T as Trait>::ASSOC }>(T) where T: Trait;
2507                 //        ^^^                     ^^^^^^^^^^^^^^^^^^^^^^^ the def id we are calling
2508                 //        ^^^                                             explicit_predicates_of on
2509                 //        parent item we dont have set as the
2510                 //        parent of generics returned by `generics_of`
2511                 //
2512                 // In the above code we want the anon const to have predicates in its param env for `T: Trait`
2513                 let item_def_id = tcx.hir().get_parent_item(hir_id);
2514                 // In the above code example we would be calling `explicit_predicates_of(Foo)` here
2515                 return tcx.explicit_predicates_of(item_def_id);
2516             }
2517         }
2518         gather_explicit_predicates_of(tcx, def_id)
2519     }
2520 }
2521
2522 /// Converts a specific `GenericBound` from the AST into a set of
2523 /// predicates that apply to the self type. A vector is returned
2524 /// because this can be anywhere from zero predicates (`T: ?Sized` adds no
2525 /// predicates) to one (`T: Foo`) to many (`T: Bar<X = i32>` adds `T: Bar`
2526 /// and `<T as Bar>::X == i32`).
2527 fn predicates_from_bound<'tcx>(
2528     astconv: &dyn AstConv<'tcx>,
2529     param_ty: Ty<'tcx>,
2530     bound: &'tcx hir::GenericBound<'tcx>,
2531     bound_vars: &'tcx ty::List<ty::BoundVariableKind>,
2532 ) -> Vec<(ty::Predicate<'tcx>, Span)> {
2533     let mut bounds = Bounds::default();
2534     astconv.add_bounds(param_ty, [bound].into_iter(), &mut bounds, bound_vars);
2535     bounds.predicates(astconv.tcx(), param_ty).collect()
2536 }
2537
2538 fn compute_sig_of_foreign_fn_decl<'tcx>(
2539     tcx: TyCtxt<'tcx>,
2540     def_id: DefId,
2541     decl: &'tcx hir::FnDecl<'tcx>,
2542     abi: abi::Abi,
2543     ident: Ident,
2544 ) -> ty::PolyFnSig<'tcx> {
2545     let unsafety = if abi == abi::Abi::RustIntrinsic {
2546         intrinsic_operation_unsafety(tcx.item_name(def_id))
2547     } else {
2548         hir::Unsafety::Unsafe
2549     };
2550     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2551     let fty = <dyn AstConv<'_>>::ty_of_fn(
2552         &ItemCtxt::new(tcx, def_id),
2553         hir_id,
2554         unsafety,
2555         abi,
2556         decl,
2557         &hir::Generics::empty(),
2558         Some(ident.span),
2559         None,
2560     );
2561
2562     // Feature gate SIMD types in FFI, since I am not sure that the
2563     // ABIs are handled at all correctly. -huonw
2564     if abi != abi::Abi::RustIntrinsic
2565         && abi != abi::Abi::PlatformIntrinsic
2566         && !tcx.features().simd_ffi
2567     {
2568         let check = |ast_ty: &hir::Ty<'_>, ty: Ty<'_>| {
2569             if ty.is_simd() {
2570                 let snip = tcx
2571                     .sess
2572                     .source_map()
2573                     .span_to_snippet(ast_ty.span)
2574                     .map_or_else(|_| String::new(), |s| format!(" `{}`", s));
2575                 tcx.sess
2576                     .struct_span_err(
2577                         ast_ty.span,
2578                         &format!(
2579                             "use of SIMD type{} in FFI is highly experimental and \
2580                              may result in invalid code",
2581                             snip
2582                         ),
2583                     )
2584                     .help("add `#![feature(simd_ffi)]` to the crate attributes to enable")
2585                     .emit();
2586             }
2587         };
2588         for (input, ty) in iter::zip(decl.inputs, fty.inputs().skip_binder()) {
2589             check(input, *ty)
2590         }
2591         if let hir::FnRetTy::Return(ref ty) = decl.output {
2592             check(ty, fty.output().skip_binder())
2593         }
2594     }
2595
2596     fty
2597 }
2598
2599 fn is_foreign_item(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2600     match tcx.hir().get_if_local(def_id) {
2601         Some(Node::ForeignItem(..)) => true,
2602         Some(_) => false,
2603         _ => bug!("is_foreign_item applied to non-local def-id {:?}", def_id),
2604     }
2605 }
2606
2607 fn static_mutability(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::Mutability> {
2608     match tcx.hir().get_if_local(def_id) {
2609         Some(
2610             Node::Item(&hir::Item { kind: hir::ItemKind::Static(_, mutbl, _), .. })
2611             | Node::ForeignItem(&hir::ForeignItem {
2612                 kind: hir::ForeignItemKind::Static(_, mutbl),
2613                 ..
2614             }),
2615         ) => Some(mutbl),
2616         Some(_) => None,
2617         _ => bug!("static_mutability applied to non-local def-id {:?}", def_id),
2618     }
2619 }
2620
2621 fn generator_kind(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::GeneratorKind> {
2622     match tcx.hir().get_if_local(def_id) {
2623         Some(Node::Expr(&rustc_hir::Expr {
2624             kind: rustc_hir::ExprKind::Closure(_, _, body_id, _, _),
2625             ..
2626         })) => tcx.hir().body(body_id).generator_kind(),
2627         Some(_) => None,
2628         _ => bug!("generator_kind applied to non-local def-id {:?}", def_id),
2629     }
2630 }
2631
2632 fn from_target_feature(
2633     tcx: TyCtxt<'_>,
2634     id: DefId,
2635     attr: &ast::Attribute,
2636     supported_target_features: &FxHashMap<String, Option<Symbol>>,
2637     target_features: &mut Vec<Symbol>,
2638 ) {
2639     let list = match attr.meta_item_list() {
2640         Some(list) => list,
2641         None => return,
2642     };
2643     let bad_item = |span| {
2644         let msg = "malformed `target_feature` attribute input";
2645         let code = "enable = \"..\"".to_owned();
2646         tcx.sess
2647             .struct_span_err(span, msg)
2648             .span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
2649             .emit();
2650     };
2651     let rust_features = tcx.features();
2652     for item in list {
2653         // Only `enable = ...` is accepted in the meta-item list.
2654         if !item.has_name(sym::enable) {
2655             bad_item(item.span());
2656             continue;
2657         }
2658
2659         // Must be of the form `enable = "..."` (a string).
2660         let value = match item.value_str() {
2661             Some(value) => value,
2662             None => {
2663                 bad_item(item.span());
2664                 continue;
2665             }
2666         };
2667
2668         // We allow comma separation to enable multiple features.
2669         target_features.extend(value.as_str().split(',').filter_map(|feature| {
2670             let feature_gate = match supported_target_features.get(feature) {
2671                 Some(g) => g,
2672                 None => {
2673                     let msg =
2674                         format!("the feature named `{}` is not valid for this target", feature);
2675                     let mut err = tcx.sess.struct_span_err(item.span(), &msg);
2676                     err.span_label(
2677                         item.span(),
2678                         format!("`{}` is not valid for this target", feature),
2679                     );
2680                     if let Some(stripped) = feature.strip_prefix('+') {
2681                         let valid = supported_target_features.contains_key(stripped);
2682                         if valid {
2683                             err.help("consider removing the leading `+` in the feature name");
2684                         }
2685                     }
2686                     err.emit();
2687                     return None;
2688                 }
2689             };
2690
2691             // Only allow features whose feature gates have been enabled.
2692             let allowed = match feature_gate.as_ref().copied() {
2693                 Some(sym::arm_target_feature) => rust_features.arm_target_feature,
2694                 Some(sym::aarch64_target_feature) => rust_features.aarch64_target_feature,
2695                 Some(sym::hexagon_target_feature) => rust_features.hexagon_target_feature,
2696                 Some(sym::powerpc_target_feature) => rust_features.powerpc_target_feature,
2697                 Some(sym::mips_target_feature) => rust_features.mips_target_feature,
2698                 Some(sym::riscv_target_feature) => rust_features.riscv_target_feature,
2699                 Some(sym::avx512_target_feature) => rust_features.avx512_target_feature,
2700                 Some(sym::sse4a_target_feature) => rust_features.sse4a_target_feature,
2701                 Some(sym::tbm_target_feature) => rust_features.tbm_target_feature,
2702                 Some(sym::wasm_target_feature) => rust_features.wasm_target_feature,
2703                 Some(sym::cmpxchg16b_target_feature) => rust_features.cmpxchg16b_target_feature,
2704                 Some(sym::adx_target_feature) => rust_features.adx_target_feature,
2705                 Some(sym::movbe_target_feature) => rust_features.movbe_target_feature,
2706                 Some(sym::rtm_target_feature) => rust_features.rtm_target_feature,
2707                 Some(sym::f16c_target_feature) => rust_features.f16c_target_feature,
2708                 Some(sym::ermsb_target_feature) => rust_features.ermsb_target_feature,
2709                 Some(sym::bpf_target_feature) => rust_features.bpf_target_feature,
2710                 Some(name) => bug!("unknown target feature gate {}", name),
2711                 None => true,
2712             };
2713             if !allowed && id.is_local() {
2714                 feature_err(
2715                     &tcx.sess.parse_sess,
2716                     feature_gate.unwrap(),
2717                     item.span(),
2718                     &format!("the target feature `{}` is currently unstable", feature),
2719                 )
2720                 .emit();
2721             }
2722             Some(Symbol::intern(feature))
2723         }));
2724     }
2725 }
2726
2727 fn linkage_by_name(tcx: TyCtxt<'_>, def_id: DefId, name: &str) -> Linkage {
2728     use rustc_middle::mir::mono::Linkage::*;
2729
2730     // Use the names from src/llvm/docs/LangRef.rst here. Most types are only
2731     // applicable to variable declarations and may not really make sense for
2732     // Rust code in the first place but allow them anyway and trust that the
2733     // user knows what s/he's doing. Who knows, unanticipated use cases may pop
2734     // up in the future.
2735     //
2736     // ghost, dllimport, dllexport and linkonce_odr_autohide are not supported
2737     // and don't have to be, LLVM treats them as no-ops.
2738     match name {
2739         "appending" => Appending,
2740         "available_externally" => AvailableExternally,
2741         "common" => Common,
2742         "extern_weak" => ExternalWeak,
2743         "external" => External,
2744         "internal" => Internal,
2745         "linkonce" => LinkOnceAny,
2746         "linkonce_odr" => LinkOnceODR,
2747         "private" => Private,
2748         "weak" => WeakAny,
2749         "weak_odr" => WeakODR,
2750         _ => {
2751             let span = tcx.hir().span_if_local(def_id);
2752             if let Some(span) = span {
2753                 tcx.sess.span_fatal(span, "invalid linkage specified")
2754             } else {
2755                 tcx.sess.fatal(&format!("invalid linkage specified: {}", name))
2756             }
2757         }
2758     }
2759 }
2760
2761 fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
2762     let attrs = tcx.get_attrs(id);
2763
2764     let mut codegen_fn_attrs = CodegenFnAttrs::new();
2765     if tcx.should_inherit_track_caller(id) {
2766         codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2767     }
2768
2769     // With -Z panic-in-drop=abort, drop_in_place never unwinds.
2770     if tcx.sess.opts.debugging_opts.panic_in_drop == PanicStrategy::Abort {
2771         if Some(id) == tcx.lang_items().drop_in_place_fn() {
2772             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2773         }
2774     }
2775
2776     // The panic_no_unwind function called by TerminatorKind::Abort will never
2777     // unwind. If the panic handler that it invokes unwind then it will simply
2778     // call the panic handler again.
2779     if Some(id) == tcx.lang_items().panic_no_unwind() {
2780         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2781     }
2782
2783     let supported_target_features = tcx.supported_target_features(LOCAL_CRATE);
2784
2785     let mut inline_span = None;
2786     let mut link_ordinal_span = None;
2787     let mut no_sanitize_span = None;
2788     for attr in attrs.iter() {
2789         if attr.has_name(sym::cold) {
2790             codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD;
2791         } else if attr.has_name(sym::rustc_allocator) {
2792             codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR;
2793         } else if attr.has_name(sym::ffi_returns_twice) {
2794             if tcx.is_foreign_item(id) {
2795                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE;
2796             } else {
2797                 // `#[ffi_returns_twice]` is only allowed `extern fn`s.
2798                 struct_span_err!(
2799                     tcx.sess,
2800                     attr.span,
2801                     E0724,
2802                     "`#[ffi_returns_twice]` may only be used on foreign functions"
2803                 )
2804                 .emit();
2805             }
2806         } else if attr.has_name(sym::ffi_pure) {
2807             if tcx.is_foreign_item(id) {
2808                 if attrs.iter().any(|a| a.has_name(sym::ffi_const)) {
2809                     // `#[ffi_const]` functions cannot be `#[ffi_pure]`
2810                     struct_span_err!(
2811                         tcx.sess,
2812                         attr.span,
2813                         E0757,
2814                         "`#[ffi_const]` function cannot be `#[ffi_pure]`"
2815                     )
2816                     .emit();
2817                 } else {
2818                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_PURE;
2819                 }
2820             } else {
2821                 // `#[ffi_pure]` is only allowed on foreign functions
2822                 struct_span_err!(
2823                     tcx.sess,
2824                     attr.span,
2825                     E0755,
2826                     "`#[ffi_pure]` may only be used on foreign functions"
2827                 )
2828                 .emit();
2829             }
2830         } else if attr.has_name(sym::ffi_const) {
2831             if tcx.is_foreign_item(id) {
2832                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_CONST;
2833             } else {
2834                 // `#[ffi_const]` is only allowed on foreign functions
2835                 struct_span_err!(
2836                     tcx.sess,
2837                     attr.span,
2838                     E0756,
2839                     "`#[ffi_const]` may only be used on foreign functions"
2840                 )
2841                 .emit();
2842             }
2843         } else if attr.has_name(sym::rustc_allocator_nounwind) {
2844             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2845         } else if attr.has_name(sym::naked) {
2846             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
2847         } else if attr.has_name(sym::no_mangle) {
2848             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2849         } else if attr.has_name(sym::no_coverage) {
2850             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_COVERAGE;
2851         } else if attr.has_name(sym::rustc_std_internal_symbol) {
2852             codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2853         } else if attr.has_name(sym::used) {
2854             let inner = attr.meta_item_list();
2855             match inner.as_deref() {
2856                 Some([item]) if item.has_name(sym::linker) => {
2857                     if !tcx.features().used_with_arg {
2858                         feature_err(
2859                             &tcx.sess.parse_sess,
2860                             sym::used_with_arg,
2861                             attr.span,
2862                             "`#[used(linker)]` is currently unstable",
2863                         )
2864                         .emit();
2865                     }
2866                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED_LINKER;
2867                 }
2868                 Some([item]) if item.has_name(sym::compiler) => {
2869                     if !tcx.features().used_with_arg {
2870                         feature_err(
2871                             &tcx.sess.parse_sess,
2872                             sym::used_with_arg,
2873                             attr.span,
2874                             "`#[used(compiler)]` is currently unstable",
2875                         )
2876                         .emit();
2877                     }
2878                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
2879                 }
2880                 Some(_) => {
2881                     tcx.sess
2882                         .struct_span_err(
2883                             attr.span,
2884                             "expected `used`, `used(compiler)` or `used(linker)`",
2885                         )
2886                         .emit();
2887                 }
2888                 None => codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED,
2889             }
2890         } else if attr.has_name(sym::cmse_nonsecure_entry) {
2891             if !matches!(tcx.fn_sig(id).abi(), abi::Abi::C { .. }) {
2892                 struct_span_err!(
2893                     tcx.sess,
2894                     attr.span,
2895                     E0776,
2896                     "`#[cmse_nonsecure_entry]` requires C ABI"
2897                 )
2898                 .emit();
2899             }
2900             if !tcx.sess.target.llvm_target.contains("thumbv8m") {
2901                 struct_span_err!(tcx.sess, attr.span, E0775, "`#[cmse_nonsecure_entry]` is only valid for targets with the TrustZone-M extension")
2902                     .emit();
2903             }
2904             codegen_fn_attrs.flags |= CodegenFnAttrFlags::CMSE_NONSECURE_ENTRY;
2905         } else if attr.has_name(sym::thread_local) {
2906             codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
2907         } else if attr.has_name(sym::track_caller) {
2908             if !tcx.is_closure(id) && tcx.fn_sig(id).abi() != abi::Abi::Rust {
2909                 struct_span_err!(tcx.sess, attr.span, E0737, "`#[track_caller]` requires Rust ABI")
2910                     .emit();
2911             }
2912             if tcx.is_closure(id) && !tcx.features().closure_track_caller {
2913                 feature_err(
2914                     &tcx.sess.parse_sess,
2915                     sym::closure_track_caller,
2916                     attr.span,
2917                     "`#[track_caller]` on closures is currently unstable",
2918                 )
2919                 .emit();
2920             }
2921             codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
2922         } else if attr.has_name(sym::export_name) {
2923             if let Some(s) = attr.value_str() {
2924                 if s.as_str().contains('\0') {
2925                     // `#[export_name = ...]` will be converted to a null-terminated string,
2926                     // so it may not contain any null characters.
2927                     struct_span_err!(
2928                         tcx.sess,
2929                         attr.span,
2930                         E0648,
2931                         "`export_name` may not contain null characters"
2932                     )
2933                     .emit();
2934                 }
2935                 codegen_fn_attrs.export_name = Some(s);
2936             }
2937         } else if attr.has_name(sym::target_feature) {
2938             if !tcx.is_closure(id) && tcx.fn_sig(id).unsafety() == hir::Unsafety::Normal {
2939                 if tcx.sess.target.is_like_wasm || tcx.sess.opts.actually_rustdoc {
2940                     // The `#[target_feature]` attribute is allowed on
2941                     // WebAssembly targets on all functions, including safe
2942                     // ones. Other targets require that `#[target_feature]` is
2943                     // only applied to unsafe funtions (pending the
2944                     // `target_feature_11` feature) because on most targets
2945                     // execution of instructions that are not supported is
2946                     // considered undefined behavior. For WebAssembly which is a
2947                     // 100% safe target at execution time it's not possible to
2948                     // execute undefined instructions, and even if a future
2949                     // feature was added in some form for this it would be a
2950                     // deterministic trap. There is no undefined behavior when
2951                     // executing WebAssembly so `#[target_feature]` is allowed
2952                     // on safe functions (but again, only for WebAssembly)
2953                     //
2954                     // Note that this is also allowed if `actually_rustdoc` so
2955                     // if a target is documenting some wasm-specific code then
2956                     // it's not spuriously denied.
2957                 } else if !tcx.features().target_feature_11 {
2958                     let mut err = feature_err(
2959                         &tcx.sess.parse_sess,
2960                         sym::target_feature_11,
2961                         attr.span,
2962                         "`#[target_feature(..)]` can only be applied to `unsafe` functions",
2963                     );
2964                     err.span_label(tcx.def_span(id), "not an `unsafe` function");
2965                     err.emit();
2966                 } else if let Some(local_id) = id.as_local() {
2967                     check_target_feature_trait_unsafe(tcx, local_id, attr.span);
2968                 }
2969             }
2970             from_target_feature(
2971                 tcx,
2972                 id,
2973                 attr,
2974                 supported_target_features,
2975                 &mut codegen_fn_attrs.target_features,
2976             );
2977         } else if attr.has_name(sym::linkage) {
2978             if let Some(val) = attr.value_str() {
2979                 codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, id, val.as_str()));
2980             }
2981         } else if attr.has_name(sym::link_section) {
2982             if let Some(val) = attr.value_str() {
2983                 if val.as_str().bytes().any(|b| b == 0) {
2984                     let msg = format!(
2985                         "illegal null byte in link_section \
2986                          value: `{}`",
2987                         &val
2988                     );
2989                     tcx.sess.span_err(attr.span, &msg);
2990                 } else {
2991                     codegen_fn_attrs.link_section = Some(val);
2992                 }
2993             }
2994         } else if attr.has_name(sym::link_name) {
2995             codegen_fn_attrs.link_name = attr.value_str();
2996         } else if attr.has_name(sym::link_ordinal) {
2997             link_ordinal_span = Some(attr.span);
2998             if let ordinal @ Some(_) = check_link_ordinal(tcx, attr) {
2999                 codegen_fn_attrs.link_ordinal = ordinal;
3000             }
3001         } else if attr.has_name(sym::no_sanitize) {
3002             no_sanitize_span = Some(attr.span);
3003             if let Some(list) = attr.meta_item_list() {
3004                 for item in list.iter() {
3005                     if item.has_name(sym::address) {
3006                         codegen_fn_attrs.no_sanitize |= SanitizerSet::ADDRESS;
3007                     } else if item.has_name(sym::cfi) {
3008                         codegen_fn_attrs.no_sanitize |= SanitizerSet::CFI;
3009                     } else if item.has_name(sym::memory) {
3010                         codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMORY;
3011                     } else if item.has_name(sym::thread) {
3012                         codegen_fn_attrs.no_sanitize |= SanitizerSet::THREAD;
3013                     } else if item.has_name(sym::hwaddress) {
3014                         codegen_fn_attrs.no_sanitize |= SanitizerSet::HWADDRESS;
3015                     } else {
3016                         tcx.sess
3017                             .struct_span_err(item.span(), "invalid argument for `no_sanitize`")
3018                             .note("expected one of: `address`, `hwaddress`, `memory` or `thread`")
3019                             .emit();
3020                     }
3021                 }
3022             }
3023         } else if attr.has_name(sym::instruction_set) {
3024             codegen_fn_attrs.instruction_set = match attr.meta_kind() {
3025                 Some(MetaItemKind::List(ref items)) => match items.as_slice() {
3026                     [NestedMetaItem::MetaItem(set)] => {
3027                         let segments =
3028                             set.path.segments.iter().map(|x| x.ident.name).collect::<Vec<_>>();
3029                         match segments.as_slice() {
3030                             [sym::arm, sym::a32] | [sym::arm, sym::t32] => {
3031                                 if !tcx.sess.target.has_thumb_interworking {
3032                                     struct_span_err!(
3033                                         tcx.sess.diagnostic(),
3034                                         attr.span,
3035                                         E0779,
3036                                         "target does not support `#[instruction_set]`"
3037                                     )
3038                                     .emit();
3039                                     None
3040                                 } else if segments[1] == sym::a32 {
3041                                     Some(InstructionSetAttr::ArmA32)
3042                                 } else if segments[1] == sym::t32 {
3043                                     Some(InstructionSetAttr::ArmT32)
3044                                 } else {
3045                                     unreachable!()
3046                                 }
3047                             }
3048                             _ => {
3049                                 struct_span_err!(
3050                                     tcx.sess.diagnostic(),
3051                                     attr.span,
3052                                     E0779,
3053                                     "invalid instruction set specified",
3054                                 )
3055                                 .emit();
3056                                 None
3057                             }
3058                         }
3059                     }
3060                     [] => {
3061                         struct_span_err!(
3062                             tcx.sess.diagnostic(),
3063                             attr.span,
3064                             E0778,
3065                             "`#[instruction_set]` requires an argument"
3066                         )
3067                         .emit();
3068                         None
3069                     }
3070                     _ => {
3071                         struct_span_err!(
3072                             tcx.sess.diagnostic(),
3073                             attr.span,
3074                             E0779,
3075                             "cannot specify more than one instruction set"
3076                         )
3077                         .emit();
3078                         None
3079                     }
3080                 },
3081                 _ => {
3082                     struct_span_err!(
3083                         tcx.sess.diagnostic(),
3084                         attr.span,
3085                         E0778,
3086                         "must specify an instruction set"
3087                     )
3088                     .emit();
3089                     None
3090                 }
3091             };
3092         } else if attr.has_name(sym::repr) {
3093             codegen_fn_attrs.alignment = match attr.meta_item_list() {
3094                 Some(items) => match items.as_slice() {
3095                     [item] => match item.name_value_literal() {
3096                         Some((sym::align, literal)) => {
3097                             let alignment = rustc_attr::parse_alignment(&literal.kind);
3098
3099                             match alignment {
3100                                 Ok(align) => Some(align),
3101                                 Err(msg) => {
3102                                     struct_span_err!(
3103                                         tcx.sess.diagnostic(),
3104                                         attr.span,
3105                                         E0589,
3106                                         "invalid `repr(align)` attribute: {}",
3107                                         msg
3108                                     )
3109                                     .emit();
3110
3111                                     None
3112                                 }
3113                             }
3114                         }
3115                         _ => None,
3116                     },
3117                     [] => None,
3118                     _ => None,
3119                 },
3120                 None => None,
3121             };
3122         }
3123     }
3124
3125     codegen_fn_attrs.inline = attrs.iter().fold(InlineAttr::None, |ia, attr| {
3126         if !attr.has_name(sym::inline) {
3127             return ia;
3128         }
3129         match attr.meta_kind() {
3130             Some(MetaItemKind::Word) => InlineAttr::Hint,
3131             Some(MetaItemKind::List(ref items)) => {
3132                 inline_span = Some(attr.span);
3133                 if items.len() != 1 {
3134                     struct_span_err!(
3135                         tcx.sess.diagnostic(),
3136                         attr.span,
3137                         E0534,
3138                         "expected one argument"
3139                     )
3140                     .emit();
3141                     InlineAttr::None
3142                 } else if list_contains_name(&items, sym::always) {
3143                     InlineAttr::Always
3144                 } else if list_contains_name(&items, sym::never) {
3145                     InlineAttr::Never
3146                 } else {
3147                     struct_span_err!(
3148                         tcx.sess.diagnostic(),
3149                         items[0].span(),
3150                         E0535,
3151                         "invalid argument"
3152                     )
3153                     .emit();
3154
3155                     InlineAttr::None
3156                 }
3157             }
3158             Some(MetaItemKind::NameValue(_)) => ia,
3159             None => ia,
3160         }
3161     });
3162
3163     codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
3164         if !attr.has_name(sym::optimize) {
3165             return ia;
3166         }
3167         let err = |sp, s| struct_span_err!(tcx.sess.diagnostic(), sp, E0722, "{}", s).emit();
3168         match attr.meta_kind() {
3169             Some(MetaItemKind::Word) => {
3170                 err(attr.span, "expected one argument");
3171                 ia
3172             }
3173             Some(MetaItemKind::List(ref items)) => {
3174                 inline_span = Some(attr.span);
3175                 if items.len() != 1 {
3176                     err(attr.span, "expected one argument");
3177                     OptimizeAttr::None
3178                 } else if list_contains_name(&items, sym::size) {
3179                     OptimizeAttr::Size
3180                 } else if list_contains_name(&items, sym::speed) {
3181                     OptimizeAttr::Speed
3182                 } else {
3183                     err(items[0].span(), "invalid argument");
3184                     OptimizeAttr::None
3185                 }
3186             }
3187             Some(MetaItemKind::NameValue(_)) => ia,
3188             None => ia,
3189         }
3190     });
3191
3192     // #73631: closures inherit `#[target_feature]` annotations
3193     if tcx.features().target_feature_11 && tcx.is_closure(id) {
3194         let owner_id = tcx.parent(id).expect("closure should have a parent");
3195         codegen_fn_attrs
3196             .target_features
3197             .extend(tcx.codegen_fn_attrs(owner_id).target_features.iter().copied())
3198     }
3199
3200     // If a function uses #[target_feature] it can't be inlined into general
3201     // purpose functions as they wouldn't have the right target features
3202     // enabled. For that reason we also forbid #[inline(always)] as it can't be
3203     // respected.
3204     if !codegen_fn_attrs.target_features.is_empty() {
3205         if codegen_fn_attrs.inline == InlineAttr::Always {
3206             if let Some(span) = inline_span {
3207                 tcx.sess.span_err(
3208                     span,
3209                     "cannot use `#[inline(always)]` with \
3210                      `#[target_feature]`",
3211                 );
3212             }
3213         }
3214     }
3215
3216     if !codegen_fn_attrs.no_sanitize.is_empty() {
3217         if codegen_fn_attrs.inline == InlineAttr::Always {
3218             if let (Some(no_sanitize_span), Some(inline_span)) = (no_sanitize_span, inline_span) {
3219                 let hir_id = tcx.hir().local_def_id_to_hir_id(id.expect_local());
3220                 tcx.struct_span_lint_hir(
3221                     lint::builtin::INLINE_NO_SANITIZE,
3222                     hir_id,
3223                     no_sanitize_span,
3224                     |lint| {
3225                         lint.build("`no_sanitize` will have no effect after inlining")
3226                             .span_note(inline_span, "inlining requested here")
3227                             .emit();
3228                     },
3229                 )
3230             }
3231         }
3232     }
3233
3234     // Weak lang items have the same semantics as "std internal" symbols in the
3235     // sense that they're preserved through all our LTO passes and only
3236     // strippable by the linker.
3237     //
3238     // Additionally weak lang items have predetermined symbol names.
3239     if tcx.is_weak_lang_item(id) {
3240         codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
3241     }
3242     if let Some(name) = weak_lang_items::link_name(attrs) {
3243         codegen_fn_attrs.export_name = Some(name);
3244         codegen_fn_attrs.link_name = Some(name);
3245     }
3246     check_link_name_xor_ordinal(tcx, &codegen_fn_attrs, link_ordinal_span);
3247
3248     // Internal symbols to the standard library all have no_mangle semantics in
3249     // that they have defined symbol names present in the function name. This
3250     // also applies to weak symbols where they all have known symbol names.
3251     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
3252         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
3253     }
3254
3255     // Any linkage to LLVM intrinsics for now forcibly marks them all as never
3256     // unwinds since LLVM sometimes can't handle codegen which `invoke`s
3257     // intrinsic functions.
3258     if let Some(name) = &codegen_fn_attrs.link_name {
3259         if name.as_str().starts_with("llvm.") {
3260             codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
3261         }
3262     }
3263
3264     codegen_fn_attrs
3265 }
3266
3267 /// Checks if the provided DefId is a method in a trait impl for a trait which has track_caller
3268 /// applied to the method prototype.
3269 fn should_inherit_track_caller(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
3270     if let Some(impl_item) = tcx.opt_associated_item(def_id) {
3271         if let ty::AssocItemContainer::ImplContainer(_) = impl_item.container {
3272             if let Some(trait_item) = impl_item.trait_item_def_id {
3273                 return tcx
3274                     .codegen_fn_attrs(trait_item)
3275                     .flags
3276                     .intersects(CodegenFnAttrFlags::TRACK_CALLER);
3277             }
3278         }
3279     }
3280
3281     false
3282 }
3283
3284 fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<u16> {
3285     use rustc_ast::{Lit, LitIntType, LitKind};
3286     let meta_item_list = attr.meta_item_list();
3287     let meta_item_list: Option<&[ast::NestedMetaItem]> = meta_item_list.as_ref().map(Vec::as_ref);
3288     let sole_meta_list = match meta_item_list {
3289         Some([item]) => item.literal(),
3290         Some(_) => {
3291             tcx.sess
3292                 .struct_span_err(attr.span, "incorrect number of arguments to `#[link_ordinal]`")
3293                 .note("the attribute requires exactly one argument")
3294                 .emit();
3295             return None;
3296         }
3297         _ => None,
3298     };
3299     if let Some(Lit { kind: LitKind::Int(ordinal, LitIntType::Unsuffixed), .. }) = sole_meta_list {
3300         // According to the table at https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#import-header,
3301         // the ordinal must fit into 16 bits.  Similarly, the Ordinal field in COFFShortExport (defined
3302         // in llvm/include/llvm/Object/COFFImportFile.h), which we use to communicate import information
3303         // to LLVM for `#[link(kind = "raw-dylib"_])`, is also defined to be uint16_t.
3304         //
3305         // FIXME: should we allow an ordinal of 0?  The MSVC toolchain has inconsistent support for this:
3306         // both LINK.EXE and LIB.EXE signal errors and abort when given a .DEF file that specifies
3307         // a zero ordinal.  However, llvm-dlltool is perfectly happy to generate an import library
3308         // for such a .DEF file, and MSVC's LINK.EXE is also perfectly happy to consume an import
3309         // library produced by LLVM with an ordinal of 0, and it generates an .EXE.  (I don't know yet
3310         // if the resulting EXE runs, as I haven't yet built the necessary DLL -- see earlier comment
3311         // about LINK.EXE failing.)
3312         if *ordinal <= u16::MAX as u128 {
3313             Some(*ordinal as u16)
3314         } else {
3315             let msg = format!("ordinal value in `link_ordinal` is too large: `{}`", &ordinal);
3316             tcx.sess
3317                 .struct_span_err(attr.span, &msg)
3318                 .note("the value may not exceed `u16::MAX`")
3319                 .emit();
3320             None
3321         }
3322     } else {
3323         tcx.sess
3324             .struct_span_err(attr.span, "illegal ordinal format in `link_ordinal`")
3325             .note("an unsuffixed integer value, e.g., `1`, is expected")
3326             .emit();
3327         None
3328     }
3329 }
3330
3331 fn check_link_name_xor_ordinal(
3332     tcx: TyCtxt<'_>,
3333     codegen_fn_attrs: &CodegenFnAttrs,
3334     inline_span: Option<Span>,
3335 ) {
3336     if codegen_fn_attrs.link_name.is_none() || codegen_fn_attrs.link_ordinal.is_none() {
3337         return;
3338     }
3339     let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
3340     if let Some(span) = inline_span {
3341         tcx.sess.span_err(span, msg);
3342     } else {
3343         tcx.sess.err(msg);
3344     }
3345 }
3346
3347 /// Checks the function annotated with `#[target_feature]` is not a safe
3348 /// trait method implementation, reporting an error if it is.
3349 fn check_target_feature_trait_unsafe(tcx: TyCtxt<'_>, id: LocalDefId, attr_span: Span) {
3350     let hir_id = tcx.hir().local_def_id_to_hir_id(id);
3351     let node = tcx.hir().get(hir_id);
3352     if let Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }) = node {
3353         let parent_id = tcx.hir().get_parent_item(hir_id);
3354         let parent_item = tcx.hir().expect_item(parent_id);
3355         if let hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) = parent_item.kind {
3356             tcx.sess
3357                 .struct_span_err(
3358                     attr_span,
3359                     "`#[target_feature(..)]` cannot be applied to safe trait method",
3360                 )
3361                 .span_label(attr_span, "cannot be applied to safe trait method")
3362                 .span_label(tcx.def_span(id), "not an `unsafe` function")
3363                 .emit();
3364         }
3365     }
3366 }