compiler/rustc_resolve/src/late.rs

   1 //! "Late resolution" is the pass that resolves most of names in a crate beside imports and macros.
   2 //! It runs when the crate is fully expanded and its module structure is fully built.
   3 //! So it just walks through the crate and resolves all the expressions, types, etc.
   4 //!
   5 //! If you wonder why there's no `early.rs`, that's because it's split into three files -
   6 //! `build_reduced_graph.rs`, `macros.rs` and `imports.rs`.
   7
   8 use RibKind::*;
   9
  10 use crate::{path_names_to_string, BindingError, Finalize, LexicalScopeBinding};
  11 use crate::{Module, ModuleOrUniformRoot, NameBinding, ParentScope, PathResult};
  12 use crate::{ResolutionError, Resolver, Segment, UseError};
  13
  14 use rustc_ast::ptr::P;
  15 use rustc_ast::visit::{self, AssocCtxt, BoundKind, FnCtxt, FnKind, Visitor};
  16 use rustc_ast::*;
  17 use rustc_ast_lowering::{LifetimeRes, ResolverAstLowering};
  18 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap};
  19 use rustc_errors::DiagnosticId;
  20 use rustc_hir::def::Namespace::{self, *};
  21 use rustc_hir::def::{self, CtorKind, DefKind, PartialRes, PerNS};
  22 use rustc_hir::def_id::{DefId, CRATE_DEF_ID};
  23 use rustc_hir::definitions::DefPathData;
  24 use rustc_hir::{PrimTy, TraitCandidate};
  25 use rustc_index::vec::Idx;
  26 use rustc_middle::ty::DefIdTree;
  27 use rustc_middle::{bug, span_bug};
  28 use rustc_session::lint;
  29 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  30 use rustc_span::{BytePos, Span};
  31 use smallvec::{smallvec, SmallVec};
  32
  33 use rustc_span::source_map::{respan, Spanned};
  34 use std::collections::{hash_map::Entry, BTreeSet};
  35 use std::mem::{replace, take};
  36 use tracing::debug;
  37
  38 mod diagnostics;
  39 crate mod lifetimes;
  40
  41 type Res = def::Res<NodeId>;
  42
  43 type IdentMap<T> = FxHashMap<Ident, T>;
  44
  45 /// Map from the name in a pattern to its binding mode.
  46 type BindingMap = IdentMap<BindingInfo>;
  47
  48 #[derive(Copy, Clone, Debug)]
  49 struct BindingInfo {
  50     span: Span,
  51     binding_mode: BindingMode,
  52 }
  53
  54 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
  55 enum PatternSource {
  56     Match,
  57     Let,
  58     For,
  59     FnParam,
  60 }
  61
  62 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
  63 enum IsRepeatExpr {
  64     No,
  65     Yes,
  66 }
  67
  68 impl PatternSource {
  69     fn descr(self) -> &'static str {
  70         match self {
  71             PatternSource::Match => "match binding",
  72             PatternSource::Let => "let binding",
  73             PatternSource::For => "for binding",
  74             PatternSource::FnParam => "function parameter",
  75         }
  76     }
  77 }
  78
  79 /// Denotes whether the context for the set of already bound bindings is a `Product`
  80 /// or `Or` context. This is used in e.g., `fresh_binding` and `resolve_pattern_inner`.
  81 /// See those functions for more information.
  82 #[derive(PartialEq)]
  83 enum PatBoundCtx {
  84     /// A product pattern context, e.g., `Variant(a, b)`.
  85     Product,
  86     /// An or-pattern context, e.g., `p_0 | ... | p_n`.
  87     Or,
  88 }
  89
  90 /// Does this the item (from the item rib scope) allow generic parameters?
  91 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
  92 crate enum HasGenericParams {
  93     Yes,
  94     No,
  95 }
  96
  97 impl HasGenericParams {
  98     fn force_yes_if(self, b: bool) -> Self {
  99         if b { Self::Yes } else { self }
 100     }
 101 }
 102
 103 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
 104 crate enum ConstantItemKind {
 105     Const,
 106     Static,
 107 }
 108
 109 /// The rib kind restricts certain accesses,
 110 /// e.g. to a `Res::Local` of an outer item.
 111 #[derive(Copy, Clone, Debug)]
 112 crate enum RibKind<'a> {
 113     /// No restriction needs to be applied.
 114     NormalRibKind,
 115
 116     /// We passed through an impl or trait and are now in one of its
 117     /// methods or associated types. Allow references to ty params that impl or trait
 118     /// binds. Disallow any other upvars (including other ty params that are
 119     /// upvars).
 120     AssocItemRibKind,
 121
 122     /// We passed through a closure. Disallow labels.
 123     ClosureOrAsyncRibKind,
 124
 125     /// We passed through a function definition. Disallow upvars.
 126     /// Permit only those const parameters that are specified in the function's generics.
 127     FnItemRibKind,
 128
 129     /// We passed through an item scope. Disallow upvars.
 130     ItemRibKind(HasGenericParams),
 131
 132     /// We're in a constant item. Can't refer to dynamic stuff.
 133     ///
 134     /// The item may reference generic parameters in trivial constant expressions.
 135     /// All other constants aren't allowed to use generic params at all.
 136     ConstantItemRibKind(HasGenericParams, Option<(Ident, ConstantItemKind)>),
 137
 138     /// We passed through a module.
 139     ModuleRibKind(Module<'a>),
 140
 141     /// We passed through a `macro_rules!` statement
 142     MacroDefinition(DefId),
 143
 144     /// All bindings in this rib are generic parameters that can't be used
 145     /// from the default of a generic parameter because they're not declared
 146     /// before said generic parameter. Also see the `visit_generics` override.
 147     ForwardGenericParamBanRibKind,
 148
 149     /// We are inside of the type of a const parameter. Can't refer to any
 150     /// parameters.
 151     ConstParamTyRibKind,
 152
 153     /// We are inside a `sym` inline assembly operand. Can only refer to
 154     /// globals.
 155     InlineAsmSymRibKind,
 156 }
 157
 158 impl RibKind<'_> {
 159     /// Whether this rib kind contains generic parameters, as opposed to local
 160     /// variables.
 161     crate fn contains_params(&self) -> bool {
 162         match self {
 163             NormalRibKind
 164             | ClosureOrAsyncRibKind
 165             | FnItemRibKind
 166             | ConstantItemRibKind(..)
 167             | ModuleRibKind(_)
 168             | MacroDefinition(_)
 169             | ConstParamTyRibKind
 170             | InlineAsmSymRibKind => false,
 171             AssocItemRibKind | ItemRibKind(_) | ForwardGenericParamBanRibKind => true,
 172         }
 173     }
 174 }
 175
 176 /// A single local scope.
 177 ///
 178 /// A rib represents a scope names can live in. Note that these appear in many places, not just
 179 /// around braces. At any place where the list of accessible names (of the given namespace)
 180 /// changes or a new restrictions on the name accessibility are introduced, a new rib is put onto a
 181 /// stack. This may be, for example, a `let` statement (because it introduces variables), a macro,
 182 /// etc.
 183 ///
 184 /// Different [rib kinds](enum.RibKind) are transparent for different names.
 185 ///
 186 /// The resolution keeps a separate stack of ribs as it traverses the AST for each namespace. When
 187 /// resolving, the name is looked up from inside out.
 188 #[derive(Debug)]
 189 crate struct Rib<'a, R = Res> {
 190     pub bindings: IdentMap<R>,
 191     pub kind: RibKind<'a>,
 192 }
 193
 194 impl<'a, R> Rib<'a, R> {
 195     fn new(kind: RibKind<'a>) -> Rib<'a, R> {
 196         Rib { bindings: Default::default(), kind }
 197     }
 198 }
 199
 200 #[derive(Copy, Clone, Debug)]
 201 enum LifetimeRibKind {
 202     /// This rib acts as a barrier to forbid reference to lifetimes of a parent item.
 203     Item,
 204
 205     /// This rib declares generic parameters.
 206     Generics { parent: NodeId, span: Span, kind: LifetimeBinderKind },
 207
 208     /// FIXME(const_generics): This patches over an ICE caused by non-'static lifetimes in const
 209     /// generics. We are disallowing this until we can decide on how we want to handle non-'static
 210     /// lifetimes in const generics. See issue #74052 for discussion.
 211     ConstGeneric,
 212
 213     /// Non-static lifetimes are prohibited in anonymous constants under `min_const_generics`.
 214     /// This function will emit an error if `generic_const_exprs` is not enabled, the body identified by
 215     /// `body_id` is an anonymous constant and `lifetime_ref` is non-static.
 216     AnonConst,
 217
 218     /// For **Modern** cases, create a new anonymous region parameter
 219     /// and reference that.
 220     ///
 221     /// For **Dyn Bound** cases, pass responsibility to
 222     /// `resolve_lifetime` code.
 223     ///
 224     /// For **Deprecated** cases, report an error.
 225     AnonymousCreateParameter(NodeId),
 226
 227     /// Give a hard error when either `&` or `'_` is written. Used to
 228     /// rule out things like `where T: Foo<'_>`. Does not imply an
 229     /// error on default object bounds (e.g., `Box<dyn Foo>`).
 230     AnonymousReportError,
 231
 232     /// Pass responsibility to `resolve_lifetime` code for all cases.
 233     AnonymousPassThrough(NodeId),
 234 }
 235
 236 #[derive(Copy, Clone, Debug)]
 237 enum LifetimeBinderKind {
 238     BareFnType,
 239     PolyTrait,
 240     WhereBound,
 241     Item,
 242     Function,
 243     ImplBlock,
 244 }
 245
 246 impl LifetimeBinderKind {
 247     fn descr(self) -> &'static str {
 248         use LifetimeBinderKind::*;
 249         match self {
 250             BareFnType => "type",
 251             PolyTrait => "bound",
 252             WhereBound => "bound",
 253             Item => "item",
 254             ImplBlock => "impl block",
 255             Function => "function",
 256         }
 257     }
 258 }
 259
 260 #[derive(Debug)]
 261 struct LifetimeRib {
 262     kind: LifetimeRibKind,
 263     // We need to preserve insertion order for async fns.
 264     bindings: FxIndexMap<Ident, (NodeId, LifetimeRes)>,
 265 }
 266
 267 impl LifetimeRib {
 268     fn new(kind: LifetimeRibKind) -> LifetimeRib {
 269         LifetimeRib { bindings: Default::default(), kind }
 270     }
 271 }
 272
 273 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 274 crate enum AliasPossibility {
 275     No,
 276     Maybe,
 277 }
 278
 279 #[derive(Copy, Clone, Debug)]
 280 crate enum PathSource<'a> {
 281     // Type paths `Path`.
 282     Type,
 283     // Trait paths in bounds or impls.
 284     Trait(AliasPossibility),
 285     // Expression paths `path`, with optional parent context.
 286     Expr(Option<&'a Expr>),
 287     // Paths in path patterns `Path`.
 288     Pat,
 289     // Paths in struct expressions and patterns `Path { .. }`.
 290     Struct,
 291     // Paths in tuple struct patterns `Path(..)`.
 292     TupleStruct(Span, &'a [Span]),
 293     // `m::A::B` in `<T as m::A>::B::C`.
 294     TraitItem(Namespace),
 295 }
 296
 297 impl<'a> PathSource<'a> {
 298     fn namespace(self) -> Namespace {
 299         match self {
 300             PathSource::Type | PathSource::Trait(_) | PathSource::Struct => TypeNS,
 301             PathSource::Expr(..) | PathSource::Pat | PathSource::TupleStruct(..) => ValueNS,
 302             PathSource::TraitItem(ns) => ns,
 303         }
 304     }
 305
 306     fn defer_to_typeck(self) -> bool {
 307         match self {
 308             PathSource::Type
 309             | PathSource::Expr(..)
 310             | PathSource::Pat
 311             | PathSource::Struct
 312             | PathSource::TupleStruct(..) => true,
 313             PathSource::Trait(_) | PathSource::TraitItem(..) => false,
 314         }
 315     }
 316
 317     fn descr_expected(self) -> &'static str {
 318         match &self {
 319             PathSource::Type => "type",
 320             PathSource::Trait(_) => "trait",
 321             PathSource::Pat => "unit struct, unit variant or constant",
 322             PathSource::Struct => "struct, variant or union type",
 323             PathSource::TupleStruct(..) => "tuple struct or tuple variant",
 324             PathSource::TraitItem(ns) => match ns {
 325                 TypeNS => "associated type",
 326                 ValueNS => "method or associated constant",
 327                 MacroNS => bug!("associated macro"),
 328             },
 329             PathSource::Expr(parent) => match parent.as_ref().map(|p| &p.kind) {
 330                 // "function" here means "anything callable" rather than `DefKind::Fn`,
 331                 // this is not precise but usually more helpful than just "value".
 332                 Some(ExprKind::Call(call_expr, _)) => match &call_expr.kind {
 333                     // the case of `::some_crate()`
 334                     ExprKind::Path(_, path)
 335                         if path.segments.len() == 2
 336                             && path.segments[0].ident.name == kw::PathRoot =>
 337                     {
 338                         "external crate"
 339                     }
 340                     ExprKind::Path(_, path) => {
 341                         let mut msg = "function";
 342                         if let Some(segment) = path.segments.iter().last() {
 343                             if let Some(c) = segment.ident.to_string().chars().next() {
 344                                 if c.is_uppercase() {
 345                                     msg = "function, tuple struct or tuple variant";
 346                                 }
 347                             }
 348                         }
 349                         msg
 350                     }
 351                     _ => "function",
 352                 },
 353                 _ => "value",
 354             },
 355         }
 356     }
 357
 358     fn is_call(self) -> bool {
 359         matches!(self, PathSource::Expr(Some(&Expr { kind: ExprKind::Call(..), .. })))
 360     }
 361
 362     crate fn is_expected(self, res: Res) -> bool {
 363         match self {
 364             PathSource::Type => matches!(
 365                 res,
 366                 Res::Def(
 367                     DefKind::Struct
 368                         | DefKind::Union
 369                         | DefKind::Enum
 370                         | DefKind::Trait
 371                         | DefKind::TraitAlias
 372                         | DefKind::TyAlias
 373                         | DefKind::AssocTy
 374                         | DefKind::TyParam
 375                         | DefKind::OpaqueTy
 376                         | DefKind::ForeignTy,
 377                     _,
 378                 ) | Res::PrimTy(..)
 379                     | Res::SelfTy { .. }
 380             ),
 381             PathSource::Trait(AliasPossibility::No) => matches!(res, Res::Def(DefKind::Trait, _)),
 382             PathSource::Trait(AliasPossibility::Maybe) => {
 383                 matches!(res, Res::Def(DefKind::Trait | DefKind::TraitAlias, _))
 384             }
 385             PathSource::Expr(..) => matches!(
 386                 res,
 387                 Res::Def(
 388                     DefKind::Ctor(_, CtorKind::Const | CtorKind::Fn)
 389                         | DefKind::Const
 390                         | DefKind::Static(_)
 391                         | DefKind::Fn
 392                         | DefKind::AssocFn
 393                         | DefKind::AssocConst
 394                         | DefKind::ConstParam,
 395                     _,
 396                 ) | Res::Local(..)
 397                     | Res::SelfCtor(..)
 398             ),
 399             PathSource::Pat => {
 400                 res.expected_in_unit_struct_pat()
 401                     || matches!(res, Res::Def(DefKind::Const | DefKind::AssocConst, _))
 402             }
 403             PathSource::TupleStruct(..) => res.expected_in_tuple_struct_pat(),
 404             PathSource::Struct => matches!(
 405                 res,
 406                 Res::Def(
 407                     DefKind::Struct
 408                         | DefKind::Union
 409                         | DefKind::Variant
 410                         | DefKind::TyAlias
 411                         | DefKind::AssocTy,
 412                     _,
 413                 ) | Res::SelfTy { .. }
 414             ),
 415             PathSource::TraitItem(ns) => match res {
 416                 Res::Def(DefKind::AssocConst | DefKind::AssocFn, _) if ns == ValueNS => true,
 417                 Res::Def(DefKind::AssocTy, _) if ns == TypeNS => true,
 418                 _ => false,
 419             },
 420         }
 421     }
 422
 423     fn error_code(self, has_unexpected_resolution: bool) -> DiagnosticId {
 424         use rustc_errors::error_code;
 425         match (self, has_unexpected_resolution) {
 426             (PathSource::Trait(_), true) => error_code!(E0404),
 427             (PathSource::Trait(_), false) => error_code!(E0405),
 428             (PathSource::Type, true) => error_code!(E0573),
 429             (PathSource::Type, false) => error_code!(E0412),
 430             (PathSource::Struct, true) => error_code!(E0574),
 431             (PathSource::Struct, false) => error_code!(E0422),
 432             (PathSource::Expr(..), true) => error_code!(E0423),
 433             (PathSource::Expr(..), false) => error_code!(E0425),
 434             (PathSource::Pat | PathSource::TupleStruct(..), true) => error_code!(E0532),
 435             (PathSource::Pat | PathSource::TupleStruct(..), false) => error_code!(E0531),
 436             (PathSource::TraitItem(..), true) => error_code!(E0575),
 437             (PathSource::TraitItem(..), false) => error_code!(E0576),
 438         }
 439     }
 440 }
 441
 442 #[derive(Default)]
 443 struct DiagnosticMetadata<'ast> {
 444     /// The current trait's associated items' ident, used for diagnostic suggestions.
 445     current_trait_assoc_items: Option<&'ast [P<AssocItem>]>,
 446
 447     /// The current self type if inside an impl (used for better errors).
 448     current_self_type: Option<Ty>,
 449
 450     /// The current self item if inside an ADT (used for better errors).
 451     current_self_item: Option<NodeId>,
 452
 453     /// The current trait (used to suggest).
 454     current_item: Option<&'ast Item>,
 455
 456     /// When processing generics and encountering a type not found, suggest introducing a type
 457     /// param.
 458     currently_processing_generics: bool,
 459
 460     /// The current enclosing (non-closure) function (used for better errors).
 461     current_function: Option<(FnKind<'ast>, Span)>,
 462
 463     /// A list of labels as of yet unused. Labels will be removed from this map when
 464     /// they are used (in a `break` or `continue` statement)
 465     unused_labels: FxHashMap<NodeId, Span>,
 466
 467     /// Only used for better errors on `fn(): fn()`.
 468     current_type_ascription: Vec<Span>,
 469
 470     /// Only used for better errors on `let x = { foo: bar };`.
 471     /// In the case of a parse error with `let x = { foo: bar, };`, this isn't needed, it's only
 472     /// needed for cases where this parses as a correct type ascription.
 473     current_block_could_be_bare_struct_literal: Option<Span>,
 474
 475     /// Only used for better errors on `let <pat>: <expr, not type>;`.
 476     current_let_binding: Option<(Span, Option<Span>, Option<Span>)>,
 477
 478     /// Used to detect possible `if let` written without `let` and to provide structured suggestion.
 479     in_if_condition: Option<&'ast Expr>,
 480
 481     /// If we are currently in a trait object definition. Used to point at the bounds when
 482     /// encountering a struct or enum.
 483     current_trait_object: Option<&'ast [ast::GenericBound]>,
 484
 485     /// Given `where <T as Bar>::Baz: String`, suggest `where T: Bar<Baz = String>`.
 486     current_where_predicate: Option<&'ast WherePredicate>,
 487
 488     current_type_path: Option<&'ast Ty>,
 489
 490     /// The current impl items (used to suggest).
 491     current_impl_items: Option<&'ast [P<AssocItem>]>,
 492 }
 493
 494 struct LateResolutionVisitor<'a, 'b, 'ast> {
 495     r: &'b mut Resolver<'a>,
 496
 497     /// The module that represents the current item scope.
 498     parent_scope: ParentScope<'a>,
 499
 500     /// The current set of local scopes for types and values.
 501     /// FIXME #4948: Reuse ribs to avoid allocation.
 502     ribs: PerNS<Vec<Rib<'a>>>,
 503
 504     /// The current set of local scopes, for labels.
 505     label_ribs: Vec<Rib<'a, NodeId>>,
 506
 507     /// The current set of local scopes for lifetimes.
 508     lifetime_ribs: Vec<LifetimeRib>,
 509
 510     /// The trait that the current context can refer to.
 511     current_trait_ref: Option<(Module<'a>, TraitRef)>,
 512
 513     /// Fields used to add information to diagnostic errors.
 514     diagnostic_metadata: DiagnosticMetadata<'ast>,
 515
 516     /// State used to know whether to ignore resolution errors for function bodies.
 517     ///
 518     /// In particular, rustdoc uses this to avoid giving errors for `cfg()` items.
 519     /// In most cases this will be `None`, in which case errors will always be reported.
 520     /// If it is `true`, then it will be updated when entering a nested function or trait body.
 521     in_func_body: bool,
 522 }
 523
 524 /// Walks the whole crate in DFS order, visiting each item, resolving names as it goes.
 525 impl<'a: 'ast, 'ast> Visitor<'ast> for LateResolutionVisitor<'a, '_, 'ast> {
 526     fn visit_attribute(&mut self, _: &'ast Attribute) {
 527         // We do not want to resolve expressions that appear in attributes,
 528         // as they do not correspond to actual code.
 529     }
 530     fn visit_item(&mut self, item: &'ast Item) {
 531         let prev = replace(&mut self.diagnostic_metadata.current_item, Some(item));
 532         // Always report errors in items we just entered.
 533         let old_ignore = replace(&mut self.in_func_body, false);
 534         self.with_lifetime_rib(LifetimeRibKind::Item, |this| this.resolve_item(item));
 535         self.in_func_body = old_ignore;
 536         self.diagnostic_metadata.current_item = prev;
 537     }
 538     fn visit_arm(&mut self, arm: &'ast Arm) {
 539         self.resolve_arm(arm);
 540     }
 541     fn visit_block(&mut self, block: &'ast Block) {
 542         self.resolve_block(block);
 543     }
 544     fn visit_anon_const(&mut self, constant: &'ast AnonConst) {
 545         // We deal with repeat expressions explicitly in `resolve_expr`.
 546         self.with_lifetime_rib(LifetimeRibKind::AnonConst, |this| {
 547             this.resolve_anon_const(constant, IsRepeatExpr::No);
 548         })
 549     }
 550     fn visit_expr(&mut self, expr: &'ast Expr) {
 551         self.resolve_expr(expr, None);
 552     }
 553     fn visit_local(&mut self, local: &'ast Local) {
 554         let local_spans = match local.pat.kind {
 555             // We check for this to avoid tuple struct fields.
 556             PatKind::Wild => None,
 557             _ => Some((
 558                 local.pat.span,
 559                 local.ty.as_ref().map(|ty| ty.span),
 560                 local.kind.init().map(|init| init.span),
 561             )),
 562         };
 563         let original = replace(&mut self.diagnostic_metadata.current_let_binding, local_spans);
 564         self.resolve_local(local);
 565         self.diagnostic_metadata.current_let_binding = original;
 566     }
 567     fn visit_ty(&mut self, ty: &'ast Ty) {
 568         let prev = self.diagnostic_metadata.current_trait_object;
 569         let prev_ty = self.diagnostic_metadata.current_type_path;
 570         match ty.kind {
 571             TyKind::Rptr(None, _) => {
 572                 // Elided lifetime in reference: we resolve as if there was some lifetime `'_` with
 573                 // NodeId `ty.id`.
 574                 let span = self.r.session.source_map().next_point(ty.span.shrink_to_lo());
 575                 self.resolve_elided_lifetime(ty.id, span);
 576             }
 577             TyKind::Path(ref qself, ref path) => {
 578                 self.diagnostic_metadata.current_type_path = Some(ty);
 579                 self.smart_resolve_path(ty.id, qself.as_ref(), path, PathSource::Type);
 580             }
 581             TyKind::ImplicitSelf => {
 582                 let self_ty = Ident::with_dummy_span(kw::SelfUpper);
 583                 let res = self
 584                     .resolve_ident_in_lexical_scope(
 585                         self_ty,
 586                         TypeNS,
 587                         Some(Finalize::new(ty.id, ty.span)),
 588                         None,
 589                     )
 590                     .map_or(Res::Err, |d| d.res());
 591                 self.r.record_partial_res(ty.id, PartialRes::new(res));
 592             }
 593             TyKind::TraitObject(ref bounds, ..) => {
 594                 self.diagnostic_metadata.current_trait_object = Some(&bounds[..]);
 595             }
 596             TyKind::BareFn(ref bare_fn) => {
 597                 let span = if bare_fn.generic_params.is_empty() {
 598                     ty.span.shrink_to_lo()
 599                 } else {
 600                     ty.span
 601                 };
 602                 self.with_generic_param_rib(
 603                     &bare_fn.generic_params,
 604                     NormalRibKind,
 605                     LifetimeRibKind::Generics {
 606                         parent: ty.id,
 607                         kind: LifetimeBinderKind::BareFnType,
 608                         span,
 609                     },
 610                     |this| {
 611                         this.with_lifetime_rib(
 612                             LifetimeRibKind::AnonymousPassThrough(ty.id),
 613                             |this| {
 614                                 this.visit_generic_param_vec(&bare_fn.generic_params, false);
 615                                 visit::walk_fn_decl(this, &bare_fn.decl);
 616                             },
 617                         );
 618                     },
 619                 );
 620                 self.diagnostic_metadata.current_trait_object = prev;
 621                 return;
 622             }
 623             _ => (),
 624         }
 625         visit::walk_ty(self, ty);
 626         self.diagnostic_metadata.current_trait_object = prev;
 627         self.diagnostic_metadata.current_type_path = prev_ty;
 628     }
 629     fn visit_poly_trait_ref(&mut self, tref: &'ast PolyTraitRef, _: &'ast TraitBoundModifier) {
 630         let span =
 631             if tref.bound_generic_params.is_empty() { tref.span.shrink_to_lo() } else { tref.span };
 632         self.with_generic_param_rib(
 633             &tref.bound_generic_params,
 634             NormalRibKind,
 635             LifetimeRibKind::Generics {
 636                 parent: tref.trait_ref.ref_id,
 637                 kind: LifetimeBinderKind::PolyTrait,
 638                 span,
 639             },
 640             |this| {
 641                 this.visit_generic_param_vec(&tref.bound_generic_params, false);
 642                 this.smart_resolve_path(
 643                     tref.trait_ref.ref_id,
 644                     None,
 645                     &tref.trait_ref.path,
 646                     PathSource::Trait(AliasPossibility::Maybe),
 647                 );
 648                 this.visit_trait_ref(&tref.trait_ref);
 649             },
 650         );
 651     }
 652     fn visit_foreign_item(&mut self, foreign_item: &'ast ForeignItem) {
 653         match foreign_item.kind {
 654             ForeignItemKind::TyAlias(box TyAlias { ref generics, .. }) => {
 655                 self.with_lifetime_rib(LifetimeRibKind::Item, |this| {
 656                     this.with_generic_param_rib(
 657                         &generics.params,
 658                         ItemRibKind(HasGenericParams::Yes),
 659                         LifetimeRibKind::Generics {
 660                             parent: foreign_item.id,
 661                             kind: LifetimeBinderKind::Item,
 662                             span: generics.span,
 663                         },
 664                         |this| visit::walk_foreign_item(this, foreign_item),
 665                     )
 666                 });
 667             }
 668             ForeignItemKind::Fn(box Fn { ref generics, .. }) => {
 669                 self.with_lifetime_rib(LifetimeRibKind::Item, |this| {
 670                     this.with_generic_param_rib(
 671                         &generics.params,
 672                         ItemRibKind(HasGenericParams::Yes),
 673                         LifetimeRibKind::Generics {
 674                             parent: foreign_item.id,
 675                             kind: LifetimeBinderKind::Function,
 676                             span: generics.span,
 677                         },
 678                         |this| visit::walk_foreign_item(this, foreign_item),
 679                     )
 680                 });
 681             }
 682             ForeignItemKind::Static(..) => {
 683                 self.with_item_rib(|this| {
 684                     visit::walk_foreign_item(this, foreign_item);
 685                 });
 686             }
 687             ForeignItemKind::MacCall(..) => {
 688                 panic!("unexpanded macro in resolve!")
 689             }
 690         }
 691     }
 692     fn visit_fn(&mut self, fn_kind: FnKind<'ast>, sp: Span, fn_id: NodeId) {
 693         let rib_kind = match fn_kind {
 694             // Bail if the function is foreign, and thus cannot validly have
 695             // a body, or if there's no body for some other reason.
 696             FnKind::Fn(FnCtxt::Foreign, _, sig, _, generics, _)
 697             | FnKind::Fn(_, _, sig, _, generics, None) => {
 698                 self.with_lifetime_rib(LifetimeRibKind::AnonymousPassThrough(fn_id), |this| {
 699                     // We don't need to deal with patterns in parameters, because
 700                     // they are not possible for foreign or bodiless functions.
 701                     this.visit_fn_header(&sig.header);
 702                     this.visit_generics(generics);
 703                     visit::walk_fn_decl(this, &sig.decl);
 704                 });
 705                 return;
 706             }
 707             FnKind::Fn(FnCtxt::Free, ..) => FnItemRibKind,
 708             FnKind::Fn(FnCtxt::Assoc(_), ..) => NormalRibKind,
 709             FnKind::Closure(..) => ClosureOrAsyncRibKind,
 710         };
 711         let previous_value = self.diagnostic_metadata.current_function;
 712         if matches!(fn_kind, FnKind::Fn(..)) {
 713             self.diagnostic_metadata.current_function = Some((fn_kind, sp));
 714         }
 715         debug!("(resolving function) entering function");
 716         let declaration = fn_kind.decl();
 717
 718         // Create a value rib for the function.
 719         self.with_rib(ValueNS, rib_kind, |this| {
 720             // Create a label rib for the function.
 721             this.with_label_rib(rib_kind, |this| {
 722                 let async_node_id = fn_kind.header().and_then(|h| h.asyncness.opt_return_id());
 723
 724                 if let FnKind::Fn(_, _, _, _, generics, _) = fn_kind {
 725                     this.visit_generics(generics);
 726                 }
 727
 728                 if let Some(async_node_id) = async_node_id {
 729                     // In `async fn`, argument-position elided lifetimes
 730                     // must be transformed into fresh generic parameters so that
 731                     // they can be applied to the opaque `impl Trait` return type.
 732                     this.with_lifetime_rib(
 733                         LifetimeRibKind::AnonymousCreateParameter(fn_id),
 734                         |this| {
 735                             // Add each argument to the rib.
 736                             this.resolve_params(&declaration.inputs)
 737                         },
 738                     );
 739
 740                     // Construct the list of in-scope lifetime parameters for async lowering.
 741                     // We include all lifetime parameters, either named or "Fresh".
 742                     // The order of those parameters does not matter, as long as it is
 743                     // deterministic.
 744                     let mut extra_lifetime_params =
 745                         this.r.extra_lifetime_params_map.get(&fn_id).cloned().unwrap_or_default();
 746                     for rib in this.lifetime_ribs.iter().rev() {
 747                         extra_lifetime_params.extend(
 748                             rib.bindings
 749                                 .iter()
 750                                 .map(|(&ident, &(node_id, res))| (ident, node_id, res)),
 751                         );
 752                         match rib.kind {
 753                             LifetimeRibKind::Item => break,
 754                             LifetimeRibKind::AnonymousCreateParameter(id) => {
 755                                 if let Some(earlier_fresh) =
 756                                     this.r.extra_lifetime_params_map.get(&id)
 757                                 {
 758                                     extra_lifetime_params.extend(earlier_fresh);
 759                                 }
 760                             }
 761                             _ => {}
 762                         }
 763                     }
 764                     this.r.extra_lifetime_params_map.insert(async_node_id, extra_lifetime_params);
 765
 766                     this.with_lifetime_rib(
 767                         LifetimeRibKind::AnonymousPassThrough(async_node_id),
 768                         |this| visit::walk_fn_ret_ty(this, &declaration.output),
 769                     );
 770                 } else {
 771                     this.with_lifetime_rib(LifetimeRibKind::AnonymousPassThrough(fn_id), |this| {
 772                         // Add each argument to the rib.
 773                         this.resolve_params(&declaration.inputs);
 774
 775                         visit::walk_fn_ret_ty(this, &declaration.output);
 776                     });
 777                 };
 778
 779                 // Ignore errors in function bodies if this is rustdoc
 780                 // Be sure not to set this until the function signature has been resolved.
 781                 let previous_state = replace(&mut this.in_func_body, true);
 782                 // Resolve the function body, potentially inside the body of an async closure
 783                 this.with_lifetime_rib(LifetimeRibKind::AnonymousPassThrough(fn_id), |this| {
 784                     match fn_kind {
 785                         FnKind::Fn(.., body) => walk_list!(this, visit_block, body),
 786                         FnKind::Closure(_, body) => this.visit_expr(body),
 787                     }
 788                 });
 789
 790                 debug!("(resolving function) leaving function");
 791                 this.in_func_body = previous_state;
 792             })
 793         });
 794         self.diagnostic_metadata.current_function = previous_value;
 795     }
 796     fn visit_lifetime(&mut self, lifetime: &'ast Lifetime) {
 797         self.resolve_lifetime(lifetime)
 798     }
 799
 800     fn visit_generics(&mut self, generics: &'ast Generics) {
 801         self.visit_generic_param_vec(
 802             &generics.params,
 803             self.diagnostic_metadata.current_self_item.is_some(),
 804         );
 805         for p in &generics.where_clause.predicates {
 806             self.visit_where_predicate(p);
 807         }
 808     }
 809
 810     fn visit_generic_arg(&mut self, arg: &'ast GenericArg) {
 811         debug!("visit_generic_arg({:?})", arg);
 812         let prev = replace(&mut self.diagnostic_metadata.currently_processing_generics, true);
 813         match arg {
 814             GenericArg::Type(ref ty) => {
 815                 // We parse const arguments as path types as we cannot distinguish them during
 816                 // parsing. We try to resolve that ambiguity by attempting resolution the type
 817                 // namespace first, and if that fails we try again in the value namespace. If
 818                 // resolution in the value namespace succeeds, we have an generic const argument on
 819                 // our hands.
 820                 if let TyKind::Path(ref qself, ref path) = ty.kind {
 821                     // We cannot disambiguate multi-segment paths right now as that requires type
 822                     // checking.
 823                     if path.segments.len() == 1 && path.segments[0].args.is_none() {
 824                         let mut check_ns = |ns| {
 825                             self.maybe_resolve_ident_in_lexical_scope(path.segments[0].ident, ns)
 826                                 .is_some()
 827                         };
 828                         if !check_ns(TypeNS) && check_ns(ValueNS) {
 829                             // This must be equivalent to `visit_anon_const`, but we cannot call it
 830                             // directly due to visitor lifetimes so we have to copy-paste some code.
 831                             //
 832                             // Note that we might not be inside of an repeat expression here,
 833                             // but considering that `IsRepeatExpr` is only relevant for
 834                             // non-trivial constants this is doesn't matter.
 835                             self.with_constant_rib(
 836                                 IsRepeatExpr::No,
 837                                 HasGenericParams::Yes,
 838                                 None,
 839                                 |this| {
 840                                     this.smart_resolve_path(
 841                                         ty.id,
 842                                         qself.as_ref(),
 843                                         path,
 844                                         PathSource::Expr(None),
 845                                     );
 846
 847                                     if let Some(ref qself) = *qself {
 848                                         this.visit_ty(&qself.ty);
 849                                     }
 850                                     this.visit_path(path, ty.id);
 851                                 },
 852                             );
 853
 854                             self.diagnostic_metadata.currently_processing_generics = prev;
 855                             return;
 856                         }
 857                     }
 858                 }
 859
 860                 self.visit_ty(ty);
 861             }
 862             GenericArg::Lifetime(lt) => self.visit_lifetime(lt),
 863             GenericArg::Const(ct) => self.visit_anon_const(ct),
 864         }
 865         self.diagnostic_metadata.currently_processing_generics = prev;
 866     }
 867
 868     fn visit_path_segment(&mut self, path_span: Span, path_segment: &'ast PathSegment) {
 869         if let Some(ref args) = path_segment.args {
 870             match &**args {
 871                 GenericArgs::AngleBracketed(..) => visit::walk_generic_args(self, path_span, args),
 872                 GenericArgs::Parenthesized(..) => self.with_lifetime_rib(
 873                     LifetimeRibKind::AnonymousPassThrough(path_segment.id),
 874                     |this| visit::walk_generic_args(this, path_span, args),
 875                 ),
 876             }
 877         }
 878     }
 879
 880     fn visit_where_predicate(&mut self, p: &'ast WherePredicate) {
 881         debug!("visit_where_predicate {:?}", p);
 882         let previous_value =
 883             replace(&mut self.diagnostic_metadata.current_where_predicate, Some(p));
 884         self.with_lifetime_rib(LifetimeRibKind::AnonymousReportError, |this| {
 885             if let WherePredicate::BoundPredicate(WhereBoundPredicate {
 886                 ref bounded_ty,
 887                 ref bounds,
 888                 ref bound_generic_params,
 889                 span: predicate_span,
 890                 ..
 891             }) = p
 892             {
 893                 let span = if bound_generic_params.is_empty() {
 894                     predicate_span.shrink_to_lo()
 895                 } else {
 896                     *predicate_span
 897                 };
 898                 this.with_generic_param_rib(
 899                     &bound_generic_params,
 900                     NormalRibKind,
 901                     LifetimeRibKind::Generics {
 902                         parent: bounded_ty.id,
 903                         kind: LifetimeBinderKind::WhereBound,
 904                         span,
 905                     },
 906                     |this| {
 907                         this.visit_generic_param_vec(&bound_generic_params, false);
 908                         this.visit_ty(bounded_ty);
 909                         for bound in bounds {
 910                             this.visit_param_bound(bound, BoundKind::Bound)
 911                         }
 912                     },
 913                 );
 914             } else {
 915                 visit::walk_where_predicate(this, p);
 916             }
 917         });
 918         self.diagnostic_metadata.current_where_predicate = previous_value;
 919     }
 920
 921     fn visit_inline_asm_sym(&mut self, sym: &'ast InlineAsmSym) {
 922         // This is similar to the code for AnonConst.
 923         self.with_rib(ValueNS, InlineAsmSymRibKind, |this| {
 924             this.with_rib(TypeNS, InlineAsmSymRibKind, |this| {
 925                 this.with_label_rib(InlineAsmSymRibKind, |this| {
 926                     this.smart_resolve_path(
 927                         sym.id,
 928                         sym.qself.as_ref(),
 929                         &sym.path,
 930                         PathSource::Expr(None),
 931                     );
 932                     visit::walk_inline_asm_sym(this, sym);
 933                 });
 934             })
 935         });
 936     }
 937 }
 938
 939 impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
 940     fn new(resolver: &'b mut Resolver<'a>) -> LateResolutionVisitor<'a, 'b, 'ast> {
 941         // During late resolution we only track the module component of the parent scope,
 942         // although it may be useful to track other components as well for diagnostics.
 943         let graph_root = resolver.graph_root;
 944         let parent_scope = ParentScope::module(graph_root, resolver);
 945         let start_rib_kind = ModuleRibKind(graph_root);
 946         LateResolutionVisitor {
 947             r: resolver,
 948             parent_scope,
 949             ribs: PerNS {
 950                 value_ns: vec![Rib::new(start_rib_kind)],
 951                 type_ns: vec![Rib::new(start_rib_kind)],
 952                 macro_ns: vec![Rib::new(start_rib_kind)],
 953             },
 954             label_ribs: Vec::new(),
 955             lifetime_ribs: Vec::new(),
 956             current_trait_ref: None,
 957             diagnostic_metadata: DiagnosticMetadata::default(),
 958             // errors at module scope should always be reported
 959             in_func_body: false,
 960         }
 961     }
 962
 963     fn maybe_resolve_ident_in_lexical_scope(
 964         &mut self,
 965         ident: Ident,
 966         ns: Namespace,
 967     ) -> Option<LexicalScopeBinding<'a>> {
 968         self.r.resolve_ident_in_lexical_scope(
 969             ident,
 970             ns,
 971             &self.parent_scope,
 972             None,
 973             &self.ribs[ns],
 974             None,
 975         )
 976     }
 977
 978     fn resolve_ident_in_lexical_scope(
 979         &mut self,
 980         ident: Ident,
 981         ns: Namespace,
 982         finalize: Option<Finalize>,
 983         ignore_binding: Option<&'a NameBinding<'a>>,
 984     ) -> Option<LexicalScopeBinding<'a>> {
 985         self.r.resolve_ident_in_lexical_scope(
 986             ident,
 987             ns,
 988             &self.parent_scope,
 989             finalize,
 990             &self.ribs[ns],
 991             ignore_binding,
 992         )
 993     }
 994
 995     fn resolve_path(
 996         &mut self,
 997         path: &[Segment],
 998         opt_ns: Option<Namespace>, // `None` indicates a module path in import
 999         finalize: Option<Finalize>,
1000     ) -> PathResult<'a> {
1001         self.r.resolve_path_with_ribs(
1002             path,
1003             opt_ns,
1004             &self.parent_scope,
1005             finalize,
1006             Some(&self.ribs),
1007             None,
1008         )
1009     }
1010
1011     // AST resolution
1012     //
1013     // We maintain a list of value ribs and type ribs.
1014     //
1015     // Simultaneously, we keep track of the current position in the module
1016     // graph in the `parent_scope.module` pointer. When we go to resolve a name in
1017     // the value or type namespaces, we first look through all the ribs and
1018     // then query the module graph. When we resolve a name in the module
1019     // namespace, we can skip all the ribs (since nested modules are not
1020     // allowed within blocks in Rust) and jump straight to the current module
1021     // graph node.
1022     //
1023     // Named implementations are handled separately. When we find a method
1024     // call, we consult the module node to find all of the implementations in
1025     // scope. This information is lazily cached in the module node. We then
1026     // generate a fake "implementation scope" containing all the
1027     // implementations thus found, for compatibility with old resolve pass.
1028
1029     /// Do some `work` within a new innermost rib of the given `kind` in the given namespace (`ns`).
1030     fn with_rib<T>(
1031         &mut self,
1032         ns: Namespace,
1033         kind: RibKind<'a>,
1034         work: impl FnOnce(&mut Self) -> T,
1035     ) -> T {
1036         self.ribs[ns].push(Rib::new(kind));
1037         let ret = work(self);
1038         self.ribs[ns].pop();
1039         ret
1040     }
1041
1042     fn with_scope<T>(&mut self, id: NodeId, f: impl FnOnce(&mut Self) -> T) -> T {
1043         if let Some(module) = self.r.get_module(self.r.local_def_id(id).to_def_id()) {
1044             // Move down in the graph.
1045             let orig_module = replace(&mut self.parent_scope.module, module);
1046             self.with_rib(ValueNS, ModuleRibKind(module), |this| {
1047                 this.with_rib(TypeNS, ModuleRibKind(module), |this| {
1048                     let ret = f(this);
1049                     this.parent_scope.module = orig_module;
1050                     ret
1051                 })
1052             })
1053         } else {
1054             f(self)
1055         }
1056     }
1057
1058     fn visit_generic_param_vec(&mut self, params: &'ast Vec<GenericParam>, add_self_upper: bool) {
1059         // For type parameter defaults, we have to ban access
1060         // to following type parameters, as the InternalSubsts can only
1061         // provide previous type parameters as they're built. We
1062         // put all the parameters on the ban list and then remove
1063         // them one by one as they are processed and become available.
1064         let mut forward_ty_ban_rib = Rib::new(ForwardGenericParamBanRibKind);
1065         let mut forward_const_ban_rib = Rib::new(ForwardGenericParamBanRibKind);
1066         for param in params.iter() {
1067             match param.kind {
1068                 GenericParamKind::Type { .. } => {
1069                     forward_ty_ban_rib
1070                         .bindings
1071                         .insert(Ident::with_dummy_span(param.ident.name), Res::Err);
1072                 }
1073                 GenericParamKind::Const { .. } => {
1074                     forward_const_ban_rib
1075                         .bindings
1076                         .insert(Ident::with_dummy_span(param.ident.name), Res::Err);
1077                 }
1078                 GenericParamKind::Lifetime => {}
1079             }
1080         }
1081
1082         // rust-lang/rust#61631: The type `Self` is essentially
1083         // another type parameter. For ADTs, we consider it
1084         // well-defined only after all of the ADT type parameters have
1085         // been provided. Therefore, we do not allow use of `Self`
1086         // anywhere in ADT type parameter defaults.
1087         //
1088         // (We however cannot ban `Self` for defaults on *all* generic
1089         // lists; e.g. trait generics can usefully refer to `Self`,
1090         // such as in the case of `trait Add<Rhs = Self>`.)
1091         if add_self_upper {
1092             // (`Some` if + only if we are in ADT's generics.)
1093             forward_ty_ban_rib.bindings.insert(Ident::with_dummy_span(kw::SelfUpper), Res::Err);
1094         }
1095
1096         self.with_lifetime_rib(LifetimeRibKind::AnonymousReportError, |this| {
1097             for param in params {
1098                 match param.kind {
1099                     GenericParamKind::Lifetime => {
1100                         for bound in &param.bounds {
1101                             this.visit_param_bound(bound, BoundKind::Bound);
1102                         }
1103                     }
1104                     GenericParamKind::Type { ref default } => {
1105                         for bound in &param.bounds {
1106                             this.visit_param_bound(bound, BoundKind::Bound);
1107                         }
1108
1109                         if let Some(ref ty) = default {
1110                             this.ribs[TypeNS].push(forward_ty_ban_rib);
1111                             this.ribs[ValueNS].push(forward_const_ban_rib);
1112                             this.visit_ty(ty);
1113                             forward_const_ban_rib = this.ribs[ValueNS].pop().unwrap();
1114                             forward_ty_ban_rib = this.ribs[TypeNS].pop().unwrap();
1115                         }
1116
1117                         // Allow all following defaults to refer to this type parameter.
1118                         forward_ty_ban_rib
1119                             .bindings
1120                             .remove(&Ident::with_dummy_span(param.ident.name));
1121                     }
1122                     GenericParamKind::Const { ref ty, kw_span: _, ref default } => {
1123                         // Const parameters can't have param bounds.
1124                         assert!(param.bounds.is_empty());
1125
1126                         this.ribs[TypeNS].push(Rib::new(ConstParamTyRibKind));
1127                         this.ribs[ValueNS].push(Rib::new(ConstParamTyRibKind));
1128                         this.with_lifetime_rib(LifetimeRibKind::ConstGeneric, |this| {
1129                             this.visit_ty(ty)
1130                         });
1131                         this.ribs[TypeNS].pop().unwrap();
1132                         this.ribs[ValueNS].pop().unwrap();
1133
1134                         if let Some(ref expr) = default {
1135                             this.ribs[TypeNS].push(forward_ty_ban_rib);
1136                             this.ribs[ValueNS].push(forward_const_ban_rib);
1137                             this.with_lifetime_rib(LifetimeRibKind::ConstGeneric, |this| {
1138                                 this.resolve_anon_const(expr, IsRepeatExpr::No)
1139                             });
1140                             forward_const_ban_rib = this.ribs[ValueNS].pop().unwrap();
1141                             forward_ty_ban_rib = this.ribs[TypeNS].pop().unwrap();
1142                         }
1143
1144                         // Allow all following defaults to refer to this const parameter.
1145                         forward_const_ban_rib
1146                             .bindings
1147                             .remove(&Ident::with_dummy_span(param.ident.name));
1148                     }
1149                 }
1150             }
1151         })
1152     }
1153
1154     #[tracing::instrument(level = "debug", skip(self, work))]
1155     fn with_lifetime_rib<T>(
1156         &mut self,
1157         kind: LifetimeRibKind,
1158         work: impl FnOnce(&mut Self) -> T,
1159     ) -> T {
1160         self.lifetime_ribs.push(LifetimeRib::new(kind));
1161         let ret = work(self);
1162         self.lifetime_ribs.pop();
1163         ret
1164     }
1165
1166     #[tracing::instrument(level = "debug", skip(self))]
1167     fn resolve_lifetime(&mut self, lifetime: &'ast Lifetime) {
1168         let ident = lifetime.ident;
1169
1170         if ident.name == kw::StaticLifetime {
1171             self.record_lifetime_res(lifetime.id, LifetimeRes::Static);
1172             return;
1173         }
1174
1175         if ident.name == kw::UnderscoreLifetime {
1176             return self.resolve_anonymous_lifetime(lifetime, false);
1177         }
1178
1179         let mut indices = (0..self.lifetime_ribs.len()).rev();
1180         for i in &mut indices {
1181             let rib = &self.lifetime_ribs[i];
1182             let normalized_ident = ident.normalize_to_macros_2_0();
1183             if let Some(&(_, region)) = rib.bindings.get(&normalized_ident) {
1184                 self.record_lifetime_res(lifetime.id, region);
1185                 return;
1186             }
1187
1188             match rib.kind {
1189                 LifetimeRibKind::Item => break,
1190                 LifetimeRibKind::ConstGeneric => {
1191                     self.emit_non_static_lt_in_const_generic_error(lifetime);
1192                     self.r.lifetimes_res_map.insert(lifetime.id, LifetimeRes::Error);
1193                     return;
1194                 }
1195                 LifetimeRibKind::AnonConst => {
1196                     self.maybe_emit_forbidden_non_static_lifetime_error(lifetime);
1197                     self.r.lifetimes_res_map.insert(lifetime.id, LifetimeRes::Error);
1198                     return;
1199                 }
1200                 _ => {}
1201             }
1202         }
1203
1204         let mut outer_res = None;
1205         for i in indices {
1206             let rib = &self.lifetime_ribs[i];
1207             let normalized_ident = ident.normalize_to_macros_2_0();
1208             if let Some((&outer, _)) = rib.bindings.get_key_value(&normalized_ident) {
1209                 outer_res = Some(outer);
1210                 break;
1211             }
1212         }
1213
1214         self.emit_undeclared_lifetime_error(lifetime, outer_res);
1215         self.record_lifetime_res(lifetime.id, LifetimeRes::Error);
1216     }
1217
1218     #[tracing::instrument(level = "debug", skip(self))]
1219     fn resolve_anonymous_lifetime(&mut self, lifetime: &Lifetime, elided: bool) {
1220         debug_assert_eq!(lifetime.ident.name, kw::UnderscoreLifetime);
1221
1222         for i in (0..self.lifetime_ribs.len()).rev() {
1223             let rib = &mut self.lifetime_ribs[i];
1224             match rib.kind {
1225                 LifetimeRibKind::AnonymousCreateParameter(item_node_id) => {
1226                     self.create_fresh_lifetime(lifetime.id, lifetime.ident, item_node_id);
1227                     return;
1228                 }
1229                 LifetimeRibKind::AnonymousReportError => {
1230                     let (msg, note) = if elided {
1231                         (
1232                             "`&` without an explicit lifetime name cannot be used here",
1233                             "explicit lifetime name needed here",
1234                         )
1235                     } else {
1236                         ("`'_` cannot be used here", "`'_` is a reserved lifetime name")
1237                     };
1238                     rustc_errors::struct_span_err!(
1239                         self.r.session,
1240                         lifetime.ident.span,
1241                         E0637,
1242                         "{}",
1243                         msg,
1244                     )
1245                     .span_label(lifetime.ident.span, note)
1246                     .emit();
1247
1248                     self.record_lifetime_res(lifetime.id, LifetimeRes::Error);
1249                     return;
1250                 }
1251                 LifetimeRibKind::AnonymousPassThrough(node_id) => {
1252                     self.record_lifetime_res(
1253                         lifetime.id,
1254                         LifetimeRes::Anonymous { binder: node_id, elided },
1255                     );
1256                     return;
1257                 }
1258                 LifetimeRibKind::Item => break,
1259                 _ => {}
1260             }
1261         }
1262         // This resolution is wrong, it passes the work to HIR lifetime resolution.
1263         // We cannot use `LifetimeRes::Error` because we do not emit a diagnostic.
1264         self.record_lifetime_res(
1265             lifetime.id,
1266             LifetimeRes::Anonymous { binder: DUMMY_NODE_ID, elided },
1267         );
1268     }
1269
1270     #[tracing::instrument(level = "debug", skip(self))]
1271     fn resolve_elided_lifetime(&mut self, anchor_id: NodeId, span: Span) {
1272         let id = self.r.next_node_id();
1273         self.record_lifetime_res(
1274             anchor_id,
1275             LifetimeRes::ElidedAnchor { start: id, end: NodeId::from_u32(id.as_u32() + 1) },
1276         );
1277
1278         let lt = Lifetime { id, ident: Ident::new(kw::UnderscoreLifetime, span) };
1279         self.resolve_anonymous_lifetime(&lt, true);
1280     }
1281
1282     #[tracing::instrument(level = "debug", skip(self))]
1283     fn create_fresh_lifetime(&mut self, id: NodeId, ident: Ident, item_node_id: NodeId) {
1284         debug_assert_eq!(ident.name, kw::UnderscoreLifetime);
1285         debug!(?ident.span);
1286         let item_def_id = self.r.local_def_id(item_node_id);
1287         let def_node_id = self.r.next_node_id();
1288         let def_id = self.r.create_def(
1289             item_def_id,
1290             def_node_id,
1291             DefPathData::LifetimeNs(kw::UnderscoreLifetime),
1292             self.parent_scope.expansion.to_expn_id(),
1293             ident.span,
1294         );
1295         debug!(?def_id);
1296
1297         let region = LifetimeRes::Fresh { param: def_id, binder: item_node_id };
1298         self.record_lifetime_res(id, region);
1299         self.r.extra_lifetime_params_map.entry(item_node_id).or_insert_with(Vec::new).push((
1300             ident,
1301             def_node_id,
1302             region,
1303         ));
1304     }
1305
1306     #[tracing::instrument(level = "debug", skip(self))]
1307     fn resolve_elided_lifetimes_in_path(
1308         &mut self,
1309         path_id: NodeId,
1310         partial_res: PartialRes,
1311         path: &[Segment],
1312         source: PathSource<'_>,
1313         path_span: Span,
1314     ) {
1315         let proj_start = path.len() - partial_res.unresolved_segments();
1316         for (i, segment) in path.iter().enumerate() {
1317             if segment.has_lifetime_args {
1318                 continue;
1319             }
1320             let Some(segment_id) = segment.id else {
1321                 continue;
1322             };
1323
1324             // Figure out if this is a type/trait segment,
1325             // which may need lifetime elision performed.
1326             let type_def_id = match partial_res.base_res() {
1327                 Res::Def(DefKind::AssocTy, def_id) if i + 2 == proj_start => self.r.parent(def_id),
1328                 Res::Def(DefKind::Variant, def_id) if i + 1 == proj_start => self.r.parent(def_id),
1329                 Res::Def(DefKind::Struct, def_id)
1330                 | Res::Def(DefKind::Union, def_id)
1331                 | Res::Def(DefKind::Enum, def_id)
1332                 | Res::Def(DefKind::TyAlias, def_id)
1333                 | Res::Def(DefKind::Trait, def_id)
1334                     if i + 1 == proj_start =>
1335                 {
1336                     def_id
1337                 }
1338                 _ => continue,
1339             };
1340
1341             let expected_lifetimes = self.r.item_generics_num_lifetimes(type_def_id);
1342             if expected_lifetimes == 0 {
1343                 continue;
1344             }
1345
1346             let missing = match source {
1347                 PathSource::Trait(..) | PathSource::TraitItem(..) | PathSource::Type => true,
1348                 PathSource::Expr(..)
1349                 | PathSource::Pat
1350                 | PathSource::Struct
1351                 | PathSource::TupleStruct(..) => false,
1352             };
1353             let mut res = LifetimeRes::Error;
1354             for rib in self.lifetime_ribs.iter().rev() {
1355                 match rib.kind {
1356                     // In create-parameter mode we error here because we don't want to support
1357                     // deprecated impl elision in new features like impl elision and `async fn`,
1358                     // both of which work using the `CreateParameter` mode:
1359                     //
1360                     //     impl Foo for std::cell::Ref<u32> // note lack of '_
1361                     //     async fn foo(_: std::cell::Ref<u32>) { ... }
1362                     LifetimeRibKind::AnonymousCreateParameter(_) => {
1363                         break;
1364                     }
1365                     // `PassThrough` is the normal case.
1366                     // `new_error_lifetime`, which would usually be used in the case of `ReportError`,
1367                     // is unsuitable here, as these can occur from missing lifetime parameters in a
1368                     // `PathSegment`, for which there is no associated `'_` or `&T` with no explicit
1369                     // lifetime. Instead, we simply create an implicit lifetime, which will be checked
1370                     // later, at which point a suitable error will be emitted.
1371                     LifetimeRibKind::AnonymousPassThrough(binder) => {
1372                         res = LifetimeRes::Anonymous { binder, elided: true };
1373                         break;
1374                     }
1375                     LifetimeRibKind::AnonymousReportError | LifetimeRibKind::Item => {
1376                         // FIXME(cjgillot) This resolution is wrong, but this does not matter
1377                         // since these cases are erroneous anyway.  Lifetime resolution should
1378                         // emit a "missing lifetime specifier" diagnostic.
1379                         res = LifetimeRes::Anonymous { binder: DUMMY_NODE_ID, elided: true };
1380                         break;
1381                     }
1382                     _ => {}
1383                 }
1384             }
1385
1386             let node_ids = self.r.next_node_ids(expected_lifetimes);
1387             self.record_lifetime_res(
1388                 segment_id,
1389                 LifetimeRes::ElidedAnchor { start: node_ids.start, end: node_ids.end },
1390             );
1391             for i in 0..expected_lifetimes {
1392                 let id = node_ids.start.plus(i);
1393                 self.record_lifetime_res(id, res);
1394             }
1395
1396             if !missing {
1397                 continue;
1398             }
1399
1400             let elided_lifetime_span = if segment.has_generic_args {
1401                 // If there are brackets, but not generic arguments, then use the opening bracket
1402                 segment.args_span.with_hi(segment.args_span.lo() + BytePos(1))
1403             } else {
1404                 // If there are no brackets, use the identifier span.
1405                 // HACK: we use find_ancestor_inside to properly suggest elided spans in paths
1406                 // originating from macros, since the segment's span might be from a macro arg.
1407                 segment.ident.span.find_ancestor_inside(path_span).unwrap_or(path_span)
1408             };
1409             if let LifetimeRes::Error = res {
1410                 let sess = self.r.session;
1411                 let mut err = rustc_errors::struct_span_err!(
1412                     sess,
1413                     path_span,
1414                     E0726,
1415                     "implicit elided lifetime not allowed here"
1416                 );
1417                 rustc_errors::add_elided_lifetime_in_path_suggestion(
1418                     sess.source_map(),
1419                     &mut err,
1420                     expected_lifetimes,
1421                     path_span,
1422                     !segment.has_generic_args,
1423                     elided_lifetime_span,
1424                 );
1425                 err.note("assuming a `'static` lifetime...");
1426                 err.emit();
1427             } else {
1428                 self.r.lint_buffer.buffer_lint_with_diagnostic(
1429                     lint::builtin::ELIDED_LIFETIMES_IN_PATHS,
1430                     segment_id,
1431                     elided_lifetime_span,
1432                     "hidden lifetime parameters in types are deprecated",
1433                     lint::BuiltinLintDiagnostics::ElidedLifetimesInPaths(
1434                         expected_lifetimes,
1435                         path_span,
1436                         !segment.has_generic_args,
1437                         elided_lifetime_span,
1438                     ),
1439                 );
1440             }
1441         }
1442     }
1443
1444     #[tracing::instrument(level = "debug", skip(self))]
1445     fn record_lifetime_res(&mut self, id: NodeId, res: LifetimeRes) {
1446         if let Some(prev_res) = self.r.lifetimes_res_map.insert(id, res) {
1447             panic!(
1448                 "lifetime {:?} resolved multiple times ({:?} before, {:?} now)",
1449                 id, prev_res, res
1450             )
1451         }
1452     }
1453
1454     /// Searches the current set of local scopes for labels. Returns the `NodeId` of the resolved
1455     /// label and reports an error if the label is not found or is unreachable.
1456     fn resolve_label(&mut self, mut label: Ident) -> Option<NodeId> {
1457         let mut suggestion = None;
1458
1459         // Preserve the original span so that errors contain "in this macro invocation"
1460         // information.
1461         let original_span = label.span;
1462
1463         for i in (0..self.label_ribs.len()).rev() {
1464             let rib = &self.label_ribs[i];
1465
1466             if let MacroDefinition(def) = rib.kind {
1467                 // If an invocation of this macro created `ident`, give up on `ident`
1468                 // and switch to `ident`'s source from the macro definition.
1469                 if def == self.r.macro_def(label.span.ctxt()) {
1470                     label.span.remove_mark();
1471                 }
1472             }
1473
1474             let ident = label.normalize_to_macro_rules();
1475             if let Some((ident, id)) = rib.bindings.get_key_value(&ident) {
1476                 let definition_span = ident.span;
1477                 return if self.is_label_valid_from_rib(i) {
1478                     Some(*id)
1479                 } else {
1480                     self.report_error(
1481                         original_span,
1482                         ResolutionError::UnreachableLabel {
1483                             name: label.name,
1484                             definition_span,
1485                             suggestion,
1486                         },
1487                     );
1488
1489                     None
1490                 };
1491             }
1492
1493             // Diagnostics: Check if this rib contains a label with a similar name, keep track of
1494             // the first such label that is encountered.
1495             suggestion = suggestion.or_else(|| self.suggestion_for_label_in_rib(i, label));
1496         }
1497
1498         self.report_error(
1499             original_span,
1500             ResolutionError::UndeclaredLabel { name: label.name, suggestion },
1501         );
1502         None
1503     }
1504
1505     /// Determine whether or not a label from the `rib_index`th label rib is reachable.
1506     fn is_label_valid_from_rib(&self, rib_index: usize) -> bool {
1507         let ribs = &self.label_ribs[rib_index + 1..];
1508
1509         for rib in ribs {
1510             match rib.kind {
1511                 NormalRibKind | MacroDefinition(..) => {
1512                     // Nothing to do. Continue.
1513                 }
1514
1515                 AssocItemRibKind
1516                 | ClosureOrAsyncRibKind
1517                 | FnItemRibKind
1518                 | ItemRibKind(..)
1519                 | ConstantItemRibKind(..)
1520                 | ModuleRibKind(..)
1521                 | ForwardGenericParamBanRibKind
1522                 | ConstParamTyRibKind
1523                 | InlineAsmSymRibKind => {
1524                     return false;
1525                 }
1526             }
1527         }
1528
1529         true
1530     }
1531
1532     fn resolve_adt(&mut self, item: &'ast Item, generics: &'ast Generics) {
1533         debug!("resolve_adt");
1534         self.with_current_self_item(item, |this| {
1535             this.with_generic_param_rib(
1536                 &generics.params,
1537                 ItemRibKind(HasGenericParams::Yes),
1538                 LifetimeRibKind::Generics {
1539                     parent: item.id,
1540                     kind: LifetimeBinderKind::Item,
1541                     span: generics.span,
1542                 },
1543                 |this| {
1544                     let item_def_id = this.r.local_def_id(item.id).to_def_id();
1545                     this.with_self_rib(
1546                         Res::SelfTy { trait_: None, alias_to: Some((item_def_id, false)) },
1547                         |this| {
1548                             visit::walk_item(this, item);
1549                         },
1550                     );
1551                 },
1552             );
1553         });
1554     }
1555
1556     fn future_proof_import(&mut self, use_tree: &UseTree) {
1557         let segments = &use_tree.prefix.segments;
1558         if !segments.is_empty() {
1559             let ident = segments[0].ident;
1560             if ident.is_path_segment_keyword() || ident.span.rust_2015() {
1561                 return;
1562             }
1563
1564             let nss = match use_tree.kind {
1565                 UseTreeKind::Simple(..) if segments.len() == 1 => &[TypeNS, ValueNS][..],
1566                 _ => &[TypeNS],
1567             };
1568             let report_error = |this: &Self, ns| {
1569                 let what = if ns == TypeNS { "type parameters" } else { "local variables" };
1570                 if this.should_report_errs() {
1571                     this.r
1572                         .session
1573                         .span_err(ident.span, &format!("imports cannot refer to {}", what));
1574                 }
1575             };
1576
1577             for &ns in nss {
1578                 match self.maybe_resolve_ident_in_lexical_scope(ident, ns) {
1579                     Some(LexicalScopeBinding::Res(..)) => {
1580                         report_error(self, ns);
1581                     }
1582                     Some(LexicalScopeBinding::Item(binding)) => {
1583                         if let Some(LexicalScopeBinding::Res(..)) =
1584                             self.resolve_ident_in_lexical_scope(ident, ns, None, Some(binding))
1585                         {
1586                             report_error(self, ns);
1587                         }
1588                     }
1589                     None => {}
1590                 }
1591             }
1592         } else if let UseTreeKind::Nested(use_trees) = &use_tree.kind {
1593             for (use_tree, _) in use_trees {
1594                 self.future_proof_import(use_tree);
1595             }
1596         }
1597     }
1598
1599     fn resolve_item(&mut self, item: &'ast Item) {
1600         let name = item.ident.name;
1601         debug!("(resolving item) resolving {} ({:?})", name, item.kind);
1602
1603         match item.kind {
1604             ItemKind::TyAlias(box TyAlias { ref generics, .. }) => {
1605                 self.with_generic_param_rib(
1606                     &generics.params,
1607                     ItemRibKind(HasGenericParams::Yes),
1608                     LifetimeRibKind::Generics {
1609                         parent: item.id,
1610                         kind: LifetimeBinderKind::Item,
1611                         span: generics.span,
1612                     },
1613                     |this| visit::walk_item(this, item),
1614                 );
1615             }
1616
1617             ItemKind::Fn(box Fn { ref generics, .. }) => {
1618                 self.with_generic_param_rib(
1619                     &generics.params,
1620                     ItemRibKind(HasGenericParams::Yes),
1621                     LifetimeRibKind::Generics {
1622                         parent: item.id,
1623                         kind: LifetimeBinderKind::Function,
1624                         span: generics.span,
1625                     },
1626                     |this| visit::walk_item(this, item),
1627                 );
1628             }
1629
1630             ItemKind::Enum(_, ref generics)
1631             | ItemKind::Struct(_, ref generics)
1632             | ItemKind::Union(_, ref generics) => {
1633                 self.resolve_adt(item, generics);
1634             }
1635
1636             ItemKind::Impl(box Impl {
1637                 ref generics,
1638                 ref of_trait,
1639                 ref self_ty,
1640                 items: ref impl_items,
1641                 ..
1642             }) => {
1643                 self.diagnostic_metadata.current_impl_items = Some(impl_items);
1644                 self.resolve_implementation(generics, of_trait, &self_ty, item.id, impl_items);
1645                 self.diagnostic_metadata.current_impl_items = None;
1646             }
1647
1648             ItemKind::Trait(box Trait { ref generics, ref bounds, ref items, .. }) => {
1649                 // Create a new rib for the trait-wide type parameters.
1650                 self.with_generic_param_rib(
1651                     &generics.params,
1652                     ItemRibKind(HasGenericParams::Yes),
1653                     LifetimeRibKind::Generics {
1654                         parent: item.id,
1655                         kind: LifetimeBinderKind::Item,
1656                         span: generics.span,
1657                     },
1658                     |this| {
1659                         let local_def_id = this.r.local_def_id(item.id).to_def_id();
1660                         this.with_self_rib(
1661                             Res::SelfTy { trait_: Some(local_def_id), alias_to: None },
1662                             |this| {
1663                                 this.visit_generics(generics);
1664                                 walk_list!(this, visit_param_bound, bounds, BoundKind::SuperTraits);
1665
1666                                 let walk_assoc_item =
1667                                     |this: &mut Self,
1668                                      generics: &Generics,
1669                                      kind,
1670                                      item: &'ast AssocItem| {
1671                                         this.with_generic_param_rib(
1672                                             &generics.params,
1673                                             AssocItemRibKind,
1674                                             LifetimeRibKind::Generics {
1675                                                 parent: item.id,
1676                                                 span: generics.span,
1677                                                 kind,
1678                                             },
1679                                             |this| {
1680                                                 visit::walk_assoc_item(this, item, AssocCtxt::Trait)
1681                                             },
1682                                         );
1683                                     };
1684
1685                                 this.with_trait_items(items, |this| {
1686                                     for item in items {
1687                                         match &item.kind {
1688                                             AssocItemKind::Const(_, ty, default) => {
1689                                                 this.visit_ty(ty);
1690                                                 // Only impose the restrictions of `ConstRibKind` for an
1691                                                 // actual constant expression in a provided default.
1692                                                 if let Some(expr) = default {
1693                                                     // We allow arbitrary const expressions inside of associated consts,
1694                                                     // even if they are potentially not const evaluatable.
1695                                                     //
1696                                                     // Type parameters can already be used and as associated consts are
1697                                                     // not used as part of the type system, this is far less surprising.
1698                                                     this.with_constant_rib(
1699                                                         IsRepeatExpr::No,
1700                                                         HasGenericParams::Yes,
1701                                                         None,
1702                                                         |this| this.visit_expr(expr),
1703                                                     );
1704                                                 }
1705                                             }
1706                                             AssocItemKind::Fn(box Fn { generics, .. }) => {
1707                                                 walk_assoc_item(
1708                                                     this,
1709                                                     generics,
1710                                                     LifetimeBinderKind::Function,
1711                                                     item,
1712                                                 );
1713                                             }
1714                                             AssocItemKind::TyAlias(box TyAlias {
1715                                                 generics,
1716                                                 ..
1717                                             }) => {
1718                                                 walk_assoc_item(
1719                                                     this,
1720                                                     generics,
1721                                                     LifetimeBinderKind::Item,
1722                                                     item,
1723                                                 );
1724                                             }
1725                                             AssocItemKind::MacCall(_) => {
1726                                                 panic!("unexpanded macro in resolve!")
1727                                             }
1728                                         };
1729                                     }
1730                                 });
1731                             },
1732                         );
1733                     },
1734                 );
1735             }
1736
1737             ItemKind::TraitAlias(ref generics, ref bounds) => {
1738                 // Create a new rib for the trait-wide type parameters.
1739                 self.with_generic_param_rib(
1740                     &generics.params,
1741                     ItemRibKind(HasGenericParams::Yes),
1742                     LifetimeRibKind::Generics {
1743                         parent: item.id,
1744                         kind: LifetimeBinderKind::Item,
1745                         span: generics.span,
1746                     },
1747                     |this| {
1748                         let local_def_id = this.r.local_def_id(item.id).to_def_id();
1749                         this.with_self_rib(
1750                             Res::SelfTy { trait_: Some(local_def_id), alias_to: None },
1751                             |this| {
1752                                 this.visit_generics(generics);
1753                                 walk_list!(this, visit_param_bound, bounds, BoundKind::Bound);
1754                             },
1755                         );
1756                     },
1757                 );
1758             }
1759
1760             ItemKind::Mod(..) | ItemKind::ForeignMod(_) => {
1761                 self.with_scope(item.id, |this| {
1762                     visit::walk_item(this, item);
1763                 });
1764             }
1765
1766             ItemKind::Static(ref ty, _, ref expr) | ItemKind::Const(_, ref ty, ref expr) => {
1767                 self.with_item_rib(|this| {
1768                     this.visit_ty(ty);
1769                     if let Some(expr) = expr {
1770                         let constant_item_kind = match item.kind {
1771                             ItemKind::Const(..) => ConstantItemKind::Const,
1772                             ItemKind::Static(..) => ConstantItemKind::Static,
1773                             _ => unreachable!(),
1774                         };
1775                         // We already forbid generic params because of the above item rib,
1776                         // so it doesn't matter whether this is a trivial constant.
1777                         this.with_constant_rib(
1778                             IsRepeatExpr::No,
1779                             HasGenericParams::Yes,
1780                             Some((item.ident, constant_item_kind)),
1781                             |this| this.visit_expr(expr),
1782                         );
1783                     }
1784                 });
1785             }
1786
1787             ItemKind::Use(ref use_tree) => {
1788                 self.future_proof_import(use_tree);
1789             }
1790
1791             ItemKind::ExternCrate(..) | ItemKind::MacroDef(..) => {
1792                 // do nothing, these are just around to be encoded
1793             }
1794
1795             ItemKind::GlobalAsm(_) => {
1796                 visit::walk_item(self, item);
1797             }
1798
1799             ItemKind::MacCall(_) => panic!("unexpanded macro in resolve!"),
1800         }
1801     }
1802
1803     fn with_generic_param_rib<'c, F>(
1804         &'c mut self,
1805         params: &'c Vec<GenericParam>,
1806         kind: RibKind<'a>,
1807         lifetime_kind: LifetimeRibKind,
1808         f: F,
1809     ) where
1810         F: FnOnce(&mut Self),
1811     {
1812         debug!("with_generic_param_rib");
1813         let mut function_type_rib = Rib::new(kind);
1814         let mut function_value_rib = Rib::new(kind);
1815         let mut function_lifetime_rib = LifetimeRib::new(lifetime_kind);
1816         let mut seen_bindings = FxHashMap::default();
1817
1818         // We also can't shadow bindings from the parent item
1819         if let AssocItemRibKind = kind {
1820             let mut add_bindings_for_ns = |ns| {
1821                 let parent_rib = self.ribs[ns]
1822                     .iter()
1823                     .rfind(|r| matches!(r.kind, ItemRibKind(_)))
1824                     .expect("associated item outside of an item");
1825                 seen_bindings
1826                     .extend(parent_rib.bindings.iter().map(|(ident, _)| (*ident, ident.span)));
1827             };
1828             add_bindings_for_ns(ValueNS);
1829             add_bindings_for_ns(TypeNS);
1830         }
1831
1832         for param in params {
1833             let ident = param.ident.normalize_to_macros_2_0();
1834             debug!("with_generic_param_rib: {}", param.id);
1835
1836             match seen_bindings.entry(ident) {
1837                 Entry::Occupied(entry) => {
1838                     let span = *entry.get();
1839                     let err = ResolutionError::NameAlreadyUsedInParameterList(ident.name, span);
1840                     if !matches!(param.kind, GenericParamKind::Lifetime) {
1841                         self.report_error(param.ident.span, err);
1842                     }
1843                 }
1844                 Entry::Vacant(entry) => {
1845                     entry.insert(param.ident.span);
1846                 }
1847             }
1848
1849             if param.ident.name == kw::UnderscoreLifetime {
1850                 rustc_errors::struct_span_err!(
1851                     self.r.session,
1852                     param.ident.span,
1853                     E0637,
1854                     "`'_` cannot be used here"
1855                 )
1856                 .span_label(param.ident.span, "`'_` is a reserved lifetime name")
1857                 .emit();
1858                 continue;
1859             }
1860
1861             if param.ident.name == kw::StaticLifetime {
1862                 rustc_errors::struct_span_err!(
1863                     self.r.session,
1864                     param.ident.span,
1865                     E0262,
1866                     "invalid lifetime parameter name: `{}`",
1867                     param.ident,
1868                 )
1869                 .span_label(param.ident.span, "'static is a reserved lifetime name")
1870                 .emit();
1871                 continue;
1872             }
1873
1874             let def_id = self.r.local_def_id(param.id);
1875
1876             // Plain insert (no renaming).
1877             let (rib, def_kind) = match param.kind {
1878                 GenericParamKind::Type { .. } => (&mut function_type_rib, DefKind::TyParam),
1879                 GenericParamKind::Const { .. } => (&mut function_value_rib, DefKind::ConstParam),
1880                 GenericParamKind::Lifetime => {
1881                     let LifetimeRibKind::Generics { parent, .. } = lifetime_kind else { panic!() };
1882                     let res = LifetimeRes::Param { param: def_id, binder: parent };
1883                     self.record_lifetime_res(param.id, res);
1884                     function_lifetime_rib.bindings.insert(ident, (param.id, res));
1885                     continue;
1886                 }
1887             };
1888             let res = Res::Def(def_kind, def_id.to_def_id());
1889             self.r.record_partial_res(param.id, PartialRes::new(res));
1890             rib.bindings.insert(ident, res);
1891         }
1892
1893         self.lifetime_ribs.push(function_lifetime_rib);
1894         self.ribs[ValueNS].push(function_value_rib);
1895         self.ribs[TypeNS].push(function_type_rib);
1896
1897         f(self);
1898
1899         self.ribs[TypeNS].pop();
1900         self.ribs[ValueNS].pop();
1901         self.lifetime_ribs.pop();
1902     }
1903
1904     fn with_label_rib(&mut self, kind: RibKind<'a>, f: impl FnOnce(&mut Self)) {
1905         self.label_ribs.push(Rib::new(kind));
1906         f(self);
1907         self.label_ribs.pop();
1908     }
1909
1910     fn with_item_rib(&mut self, f: impl FnOnce(&mut Self)) {
1911         let kind = ItemRibKind(HasGenericParams::No);
1912         self.with_lifetime_rib(LifetimeRibKind::Item, |this| {
1913             this.with_rib(ValueNS, kind, |this| this.with_rib(TypeNS, kind, f))
1914         })
1915     }
1916
1917     // HACK(min_const_generics,const_evaluatable_unchecked): We
1918     // want to keep allowing `[0; std::mem::size_of::<*mut T>()]`
1919     // with a future compat lint for now. We do this by adding an
1920     // additional special case for repeat expressions.
1921     //
1922     // Note that we intentionally still forbid `[0; N + 1]` during
1923     // name resolution so that we don't extend the future
1924     // compat lint to new cases.
1925     #[instrument(level = "debug", skip(self, f))]
1926     fn with_constant_rib(
1927         &mut self,
1928         is_repeat: IsRepeatExpr,
1929         may_use_generics: HasGenericParams,
1930         item: Option<(Ident, ConstantItemKind)>,
1931         f: impl FnOnce(&mut Self),
1932     ) {
1933         self.with_rib(ValueNS, ConstantItemRibKind(may_use_generics, item), |this| {
1934             this.with_rib(
1935                 TypeNS,
1936                 ConstantItemRibKind(
1937                     may_use_generics.force_yes_if(is_repeat == IsRepeatExpr::Yes),
1938                     item,
1939                 ),
1940                 |this| {
1941                     this.with_label_rib(ConstantItemRibKind(may_use_generics, item), f);
1942                 },
1943             )
1944         });
1945     }
1946
1947     fn with_current_self_type<T>(&mut self, self_type: &Ty, f: impl FnOnce(&mut Self) -> T) -> T {
1948         // Handle nested impls (inside fn bodies)
1949         let previous_value =
1950             replace(&mut self.diagnostic_metadata.current_self_type, Some(self_type.clone()));
1951         let result = f(self);
1952         self.diagnostic_metadata.current_self_type = previous_value;
1953         result
1954     }
1955
1956     fn with_current_self_item<T>(&mut self, self_item: &Item, f: impl FnOnce(&mut Self) -> T) -> T {
1957         let previous_value =
1958             replace(&mut self.diagnostic_metadata.current_self_item, Some(self_item.id));
1959         let result = f(self);
1960         self.diagnostic_metadata.current_self_item = previous_value;
1961         result
1962     }
1963
1964     /// When evaluating a `trait` use its associated types' idents for suggestions in E0412.
1965     fn with_trait_items<T>(
1966         &mut self,
1967         trait_items: &'ast [P<AssocItem>],
1968         f: impl FnOnce(&mut Self) -> T,
1969     ) -> T {
1970         let trait_assoc_items =
1971             replace(&mut self.diagnostic_metadata.current_trait_assoc_items, Some(&trait_items));
1972         let result = f(self);
1973         self.diagnostic_metadata.current_trait_assoc_items = trait_assoc_items;
1974         result
1975     }
1976
1977     /// This is called to resolve a trait reference from an `impl` (i.e., `impl Trait for Foo`).
1978     fn with_optional_trait_ref<T>(
1979         &mut self,
1980         opt_trait_ref: Option<&TraitRef>,
1981         f: impl FnOnce(&mut Self, Option<DefId>) -> T,
1982     ) -> T {
1983         let mut new_val = None;
1984         let mut new_id = None;
1985         if let Some(trait_ref) = opt_trait_ref {
1986             let path: Vec<_> = Segment::from_path(&trait_ref.path);
1987             let res = self.smart_resolve_path_fragment(
1988                 None,
1989                 &path,
1990                 PathSource::Trait(AliasPossibility::No),
1991                 Finalize::new(trait_ref.ref_id, trait_ref.path.span),
1992             );
1993             if let Some(def_id) = res.base_res().opt_def_id() {
1994                 new_id = Some(def_id);
1995                 new_val = Some((self.r.expect_module(def_id), trait_ref.clone()));
1996             }
1997         }
1998         let original_trait_ref = replace(&mut self.current_trait_ref, new_val);
1999         let result = f(self, new_id);
2000         self.current_trait_ref = original_trait_ref;
2001         result
2002     }
2003
2004     fn with_self_rib_ns(&mut self, ns: Namespace, self_res: Res, f: impl FnOnce(&mut Self)) {
2005         let mut self_type_rib = Rib::new(NormalRibKind);
2006
2007         // Plain insert (no renaming, since types are not currently hygienic)
2008         self_type_rib.bindings.insert(Ident::with_dummy_span(kw::SelfUpper), self_res);
2009         self.ribs[ns].push(self_type_rib);
2010         f(self);
2011         self.ribs[ns].pop();
2012     }
2013
2014     fn with_self_rib(&mut self, self_res: Res, f: impl FnOnce(&mut Self)) {
2015         self.with_self_rib_ns(TypeNS, self_res, f)
2016     }
2017
2018     fn resolve_implementation(
2019         &mut self,
2020         generics: &'ast Generics,
2021         opt_trait_reference: &'ast Option<TraitRef>,
2022         self_type: &'ast Ty,
2023         item_id: NodeId,
2024         impl_items: &'ast [P<AssocItem>],
2025     ) {
2026         debug!("resolve_implementation");
2027         // If applicable, create a rib for the type parameters.
2028         self.with_generic_param_rib(&generics.params, ItemRibKind(HasGenericParams::Yes), LifetimeRibKind::Generics { span: generics.span, parent: item_id, kind: LifetimeBinderKind::ImplBlock }, |this| {
2029             // Dummy self type for better errors if `Self` is used in the trait path.
2030             this.with_self_rib(Res::SelfTy { trait_: None, alias_to: None }, |this| {
2031                 this.with_lifetime_rib(LifetimeRibKind::AnonymousCreateParameter(item_id), |this| {
2032                     // Resolve the trait reference, if necessary.
2033                     this.with_optional_trait_ref(opt_trait_reference.as_ref(), |this, trait_id| {
2034                         let item_def_id = this.r.local_def_id(item_id);
2035
2036                         // Register the trait definitions from here.
2037                         if let Some(trait_id) = trait_id {
2038                             this.r.trait_impls.entry(trait_id).or_default().push(item_def_id);
2039                         }
2040
2041                         let item_def_id = item_def_id.to_def_id();
2042                         let res =
2043                             Res::SelfTy { trait_: trait_id, alias_to: Some((item_def_id, false)) };
2044                         this.with_self_rib(res, |this| {
2045                             if let Some(trait_ref) = opt_trait_reference.as_ref() {
2046                                 // Resolve type arguments in the trait path.
2047                                 visit::walk_trait_ref(this, trait_ref);
2048                             }
2049                             // Resolve the self type.
2050                             this.visit_ty(self_type);
2051                             // Resolve the generic parameters.
2052                             this.visit_generics(generics);
2053
2054                             // Resolve the items within the impl.
2055                             this.with_lifetime_rib(LifetimeRibKind::AnonymousPassThrough(item_id),
2056                                 |this| {
2057                                     this.with_current_self_type(self_type, |this| {
2058                                         this.with_self_rib_ns(ValueNS, Res::SelfCtor(item_def_id), |this| {
2059                                             debug!("resolve_implementation with_self_rib_ns(ValueNS, ...)");
2060                                             for item in impl_items {
2061                                                 use crate::ResolutionError::*;
2062                                                 match &item.kind {
2063                                                     AssocItemKind::Const(_default, _ty, _expr) => {
2064                                                         debug!("resolve_implementation AssocItemKind::Const");
2065                                                         // If this is a trait impl, ensure the const
2066                                                         // exists in trait
2067                                                         this.check_trait_item(
2068                                                             item.id,
2069                                                             item.ident,
2070                                                             &item.kind,
2071                                                             ValueNS,
2072                                                             item.span,
2073                                                             |i, s, c| ConstNotMemberOfTrait(i, s, c),
2074                                                         );
2075
2076                                                         // We allow arbitrary const expressions inside of associated consts,
2077                                                         // even if they are potentially not const evaluatable.
2078                                                         //
2079                                                         // Type parameters can already be used and as associated consts are
2080                                                         // not used as part of the type system, this is far less surprising.
2081                                                         this.with_constant_rib(
2082                                                             IsRepeatExpr::No,
2083                                                             HasGenericParams::Yes,
2084                                                             None,
2085                                                             |this| {
2086                                                                 visit::walk_assoc_item(
2087                                                                     this,
2088                                                                     item,
2089                                                                     AssocCtxt::Impl,
2090                                                                 )
2091                                                             },
2092                                                         );
2093                                                     }
2094                                                     AssocItemKind::Fn(box Fn { generics, .. }) => {
2095                                                         debug!("resolve_implementation AssocItemKind::Fn");
2096                                                         // We also need a new scope for the impl item type parameters.
2097                                                         this.with_generic_param_rib(
2098                                                             &generics.params,
2099                                                             AssocItemRibKind,
2100                                                             LifetimeRibKind::Generics { parent: item.id, span: generics.span, kind: LifetimeBinderKind::Function },
2101                                                             |this| {
2102                                                                 // If this is a trait impl, ensure the method
2103                                                                 // exists in trait
2104                                                                 this.check_trait_item(
2105                                                                     item.id,
2106                                                                     item.ident,
2107                                                                     &item.kind,
2108                                                                     ValueNS,
2109                                                                     item.span,
2110                                                                     |i, s, c| MethodNotMemberOfTrait(i, s, c),
2111                                                                 );
2112
2113                                                                 visit::walk_assoc_item(
2114                                                                     this,
2115                                                                     item,
2116                                                                     AssocCtxt::Impl,
2117                                                                 )
2118                                                             },
2119                                                         );
2120                                                     }
2121                                                     AssocItemKind::TyAlias(box TyAlias {
2122                                                         generics, ..
2123                                                     }) => {
2124                                                         debug!("resolve_implementation AssocItemKind::TyAlias");
2125                                                         // We also need a new scope for the impl item type parameters.
2126                                                         this.with_generic_param_rib(
2127                                                             &generics.params,
2128                                                             AssocItemRibKind,
2129                                                             LifetimeRibKind::Generics { parent: item.id, span: generics.span, kind: LifetimeBinderKind::Item },
2130                                                             |this| {
2131                                                                 // If this is a trait impl, ensure the type
2132                                                                 // exists in trait
2133                                                                 this.check_trait_item(
2134                                                                     item.id,
2135                                                                     item.ident,
2136                                                                     &item.kind,
2137                                                                     TypeNS,
2138                                                                     item.span,
2139                                                                     |i, s, c| TypeNotMemberOfTrait(i, s, c),
2140                                                                 );
2141
2142                                                                 visit::walk_assoc_item(
2143                                                                     this,
2144                                                                     item,
2145                                                                     AssocCtxt::Impl,
2146                                                                 )
2147                                                             },
2148                                                         );
2149                                                     }
2150                                                     AssocItemKind::MacCall(_) => {
2151                                                         panic!("unexpanded macro in resolve!")
2152                                                     }
2153                                                 }
2154                                             }
2155                                         });
2156                                     });
2157                                 },
2158                             );
2159                         });
2160                     });
2161                 });
2162             });
2163         });
2164     }
2165
2166     fn check_trait_item<F>(
2167         &mut self,
2168         id: NodeId,
2169         mut ident: Ident,
2170         kind: &AssocItemKind,
2171         ns: Namespace,
2172         span: Span,
2173         err: F,
2174     ) where
2175         F: FnOnce(Ident, String, Option<Symbol>) -> ResolutionError<'a>,
2176     {
2177         // If there is a TraitRef in scope for an impl, then the method must be in the trait.
2178         let Some((module, _)) = &self.current_trait_ref else { return; };
2179         ident.span.normalize_to_macros_2_0_and_adjust(module.expansion);
2180         let key = self.r.new_key(ident, ns);
2181         let mut binding = self.r.resolution(module, key).try_borrow().ok().and_then(|r| r.binding);
2182         debug!(?binding);
2183         if binding.is_none() {
2184             // We could not find the trait item in the correct namespace.
2185             // Check the other namespace to report an error.
2186             let ns = match ns {
2187                 ValueNS => TypeNS,
2188                 TypeNS => ValueNS,
2189                 _ => ns,
2190             };
2191             let key = self.r.new_key(ident, ns);
2192             binding = self.r.resolution(module, key).try_borrow().ok().and_then(|r| r.binding);
2193             debug!(?binding);
2194         }
2195         let Some(binding) = binding else {
2196             // We could not find the method: report an error.
2197             let candidate = self.find_similarly_named_assoc_item(ident.name, kind);
2198             let path = &self.current_trait_ref.as_ref().unwrap().1.path;
2199             let path_names = path_names_to_string(path);
2200             self.report_error(span, err(ident, path_names, candidate));
2201             return;
2202         };
2203
2204         let res = binding.res();
2205         let Res::Def(def_kind, _) = res else { bug!() };
2206         match (def_kind, kind) {
2207             (DefKind::AssocTy, AssocItemKind::TyAlias(..))
2208             | (DefKind::AssocFn, AssocItemKind::Fn(..))
2209             | (DefKind::AssocConst, AssocItemKind::Const(..)) => {
2210                 self.r.record_partial_res(id, PartialRes::new(res));
2211                 return;
2212             }
2213             _ => {}
2214         }
2215
2216         // The method kind does not correspond to what appeared in the trait, report.
2217         let path = &self.current_trait_ref.as_ref().unwrap().1.path;
2218         let (code, kind) = match kind {
2219             AssocItemKind::Const(..) => (rustc_errors::error_code!(E0323), "const"),
2220             AssocItemKind::Fn(..) => (rustc_errors::error_code!(E0324), "method"),
2221             AssocItemKind::TyAlias(..) => (rustc_errors::error_code!(E0325), "type"),
2222             AssocItemKind::MacCall(..) => span_bug!(span, "unexpanded macro"),
2223         };
2224         let trait_path = path_names_to_string(path);
2225         self.report_error(
2226             span,
2227             ResolutionError::TraitImplMismatch {
2228                 name: ident.name,
2229                 kind,
2230                 code,
2231                 trait_path,
2232                 trait_item_span: binding.span,
2233             },
2234         );
2235     }
2236
2237     fn resolve_params(&mut self, params: &'ast [Param]) {
2238         let mut bindings = smallvec![(PatBoundCtx::Product, Default::default())];
2239         for Param { pat, ty, .. } in params {
2240             self.resolve_pattern(pat, PatternSource::FnParam, &mut bindings);
2241             self.visit_ty(ty);
2242             debug!("(resolving function / closure) recorded parameter");
2243         }
2244     }
2245
2246     fn resolve_local(&mut self, local: &'ast Local) {
2247         debug!("resolving local ({:?})", local);
2248         // Resolve the type.
2249         walk_list!(self, visit_ty, &local.ty);
2250
2251         // Resolve the initializer.
2252         if let Some((init, els)) = local.kind.init_else_opt() {
2253             self.visit_expr(init);
2254
2255             // Resolve the `else` block
2256             if let Some(els) = els {
2257                 self.visit_block(els);
2258             }
2259         }
2260
2261         // Resolve the pattern.
2262         self.resolve_pattern_top(&local.pat, PatternSource::Let);
2263     }
2264
2265     /// build a map from pattern identifiers to binding-info's.
2266     /// this is done hygienically. This could arise for a macro
2267     /// that expands into an or-pattern where one 'x' was from the
2268     /// user and one 'x' came from the macro.
2269     fn binding_mode_map(&mut self, pat: &Pat) -> BindingMap {
2270         let mut binding_map = FxHashMap::default();
2271
2272         pat.walk(&mut |pat| {
2273             match pat.kind {
2274                 PatKind::Ident(binding_mode, ident, ref sub_pat)
2275                     if sub_pat.is_some() || self.is_base_res_local(pat.id) =>
2276                 {
2277                     binding_map.insert(ident, BindingInfo { span: ident.span, binding_mode });
2278                 }
2279                 PatKind::Or(ref ps) => {
2280                     // Check the consistency of this or-pattern and
2281                     // then add all bindings to the larger map.
2282                     for bm in self.check_consistent_bindings(ps) {
2283                         binding_map.extend(bm);
2284                     }
2285                     return false;
2286                 }
2287                 _ => {}
2288             }
2289
2290             true
2291         });
2292
2293         binding_map
2294     }
2295
2296     fn is_base_res_local(&self, nid: NodeId) -> bool {
2297         matches!(self.r.partial_res_map.get(&nid).map(|res| res.base_res()), Some(Res::Local(..)))
2298     }
2299
2300     /// Checks that all of the arms in an or-pattern have exactly the
2301     /// same set of bindings, with the same binding modes for each.
2302     fn check_consistent_bindings(&mut self, pats: &[P<Pat>]) -> Vec<BindingMap> {
2303         let mut missing_vars = FxHashMap::default();
2304         let mut inconsistent_vars = FxHashMap::default();
2305
2306         // 1) Compute the binding maps of all arms.
2307         let maps = pats.iter().map(|pat| self.binding_mode_map(pat)).collect::<Vec<_>>();
2308
2309         // 2) Record any missing bindings or binding mode inconsistencies.
2310         for (map_outer, pat_outer) in pats.iter().enumerate().map(|(idx, pat)| (&maps[idx], pat)) {
2311             // Check against all arms except for the same pattern which is always self-consistent.
2312             let inners = pats
2313                 .iter()
2314                 .enumerate()
2315                 .filter(|(_, pat)| pat.id != pat_outer.id)
2316                 .flat_map(|(idx, _)| maps[idx].iter())
2317                 .map(|(key, binding)| (key.name, map_outer.get(&key), binding));
2318
2319             for (name, info, &binding_inner) in inners {
2320                 match info {
2321                     None => {
2322                         // The inner binding is missing in the outer.
2323                         let binding_error =
2324                             missing_vars.entry(name).or_insert_with(|| BindingError {
2325                                 name,
2326                                 origin: BTreeSet::new(),
2327                                 target: BTreeSet::new(),
2328                                 could_be_path: name.as_str().starts_with(char::is_uppercase),
2329                             });
2330                         binding_error.origin.insert(binding_inner.span);
2331                         binding_error.target.insert(pat_outer.span);
2332                     }
2333                     Some(binding_outer) => {
2334                         if binding_outer.binding_mode != binding_inner.binding_mode {
2335                             // The binding modes in the outer and inner bindings differ.
2336                             inconsistent_vars
2337                                 .entry(name)
2338                                 .or_insert((binding_inner.span, binding_outer.span));
2339                         }
2340                     }
2341                 }
2342             }
2343         }
2344
2345         // 3) Report all missing variables we found.
2346         let mut missing_vars = missing_vars.into_iter().collect::<Vec<_>>();
2347         missing_vars.sort_by_key(|&(sym, ref _err)| sym);
2348
2349         for (name, mut v) in missing_vars.into_iter() {
2350             if inconsistent_vars.contains_key(&name) {
2351                 v.could_be_path = false;
2352             }
2353             self.report_error(
2354                 *v.origin.iter().next().unwrap(),
2355                 ResolutionError::VariableNotBoundInPattern(v, self.parent_scope),
2356             );
2357         }
2358
2359         // 4) Report all inconsistencies in binding modes we found.
2360         let mut inconsistent_vars = inconsistent_vars.iter().collect::<Vec<_>>();
2361         inconsistent_vars.sort();
2362         for (name, v) in inconsistent_vars {
2363             self.report_error(v.0, ResolutionError::VariableBoundWithDifferentMode(*name, v.1));
2364         }
2365
2366         // 5) Finally bubble up all the binding maps.
2367         maps
2368     }
2369
2370     /// Check the consistency of the outermost or-patterns.
2371     fn check_consistent_bindings_top(&mut self, pat: &'ast Pat) {
2372         pat.walk(&mut |pat| match pat.kind {
2373             PatKind::Or(ref ps) => {
2374                 self.check_consistent_bindings(ps);
2375                 false
2376             }
2377             _ => true,
2378         })
2379     }
2380
2381     fn resolve_arm(&mut self, arm: &'ast Arm) {
2382         self.with_rib(ValueNS, NormalRibKind, |this| {
2383             this.resolve_pattern_top(&arm.pat, PatternSource::Match);
2384             walk_list!(this, visit_expr, &arm.guard);
2385             this.visit_expr(&arm.body);
2386         });
2387     }
2388
2389     /// Arising from `source`, resolve a top level pattern.
2390     fn resolve_pattern_top(&mut self, pat: &'ast Pat, pat_src: PatternSource) {
2391         let mut bindings = smallvec![(PatBoundCtx::Product, Default::default())];
2392         self.resolve_pattern(pat, pat_src, &mut bindings);
2393     }
2394
2395     fn resolve_pattern(
2396         &mut self,
2397         pat: &'ast Pat,
2398         pat_src: PatternSource,
2399         bindings: &mut SmallVec<[(PatBoundCtx, FxHashSet<Ident>); 1]>,
2400     ) {
2401         // We walk the pattern before declaring the pattern's inner bindings,
2402         // so that we avoid resolving a literal expression to a binding defined
2403         // by the pattern.
2404         visit::walk_pat(self, pat);
2405         self.resolve_pattern_inner(pat, pat_src, bindings);
2406         // This has to happen *after* we determine which pat_idents are variants:
2407         self.check_consistent_bindings_top(pat);
2408     }
2409
2410     /// Resolve bindings in a pattern. This is a helper to `resolve_pattern`.
2411     ///
2412     /// ### `bindings`
2413     ///
2414     /// A stack of sets of bindings accumulated.
2415     ///
2416     /// In each set, `PatBoundCtx::Product` denotes that a found binding in it should
2417     /// be interpreted as re-binding an already bound binding. This results in an error.
2418     /// Meanwhile, `PatBound::Or` denotes that a found binding in the set should result
2419     /// in reusing this binding rather than creating a fresh one.
2420     ///
2421     /// When called at the top level, the stack must have a single element
2422     /// with `PatBound::Product`. Otherwise, pushing to the stack happens as
2423     /// or-patterns (`p_0 | ... | p_n`) are encountered and the context needs
2424     /// to be switched to `PatBoundCtx::Or` and then `PatBoundCtx::Product` for each `p_i`.
2425     /// When each `p_i` has been dealt with, the top set is merged with its parent.
2426     /// When a whole or-pattern has been dealt with, the thing happens.
2427     ///
2428     /// See the implementation and `fresh_binding` for more details.
2429     fn resolve_pattern_inner(
2430         &mut self,
2431         pat: &Pat,
2432         pat_src: PatternSource,
2433         bindings: &mut SmallVec<[(PatBoundCtx, FxHashSet<Ident>); 1]>,
2434     ) {
2435         // Visit all direct subpatterns of this pattern.
2436         pat.walk(&mut |pat| {
2437             debug!("resolve_pattern pat={:?} node={:?}", pat, pat.kind);
2438             match pat.kind {
2439                 PatKind::Ident(bmode, ident, ref sub) => {
2440                     // First try to resolve the identifier as some existing entity,
2441                     // then fall back to a fresh binding.
2442                     let has_sub = sub.is_some();
2443                     let res = self
2444                         .try_resolve_as_non_binding(pat_src, bmode, ident, has_sub)
2445                         .unwrap_or_else(|| self.fresh_binding(ident, pat.id, pat_src, bindings));
2446                     self.r.record_partial_res(pat.id, PartialRes::new(res));
2447                     self.r.record_pat_span(pat.id, pat.span);
2448                 }
2449                 PatKind::TupleStruct(ref qself, ref path, ref sub_patterns) => {
2450                     self.smart_resolve_path(
2451                         pat.id,
2452                         qself.as_ref(),
2453                         path,
2454                         PathSource::TupleStruct(
2455                             pat.span,
2456                             self.r.arenas.alloc_pattern_spans(sub_patterns.iter().map(|p| p.span)),
2457                         ),
2458                     );
2459                 }
2460                 PatKind::Path(ref qself, ref path) => {
2461                     self.smart_resolve_path(pat.id, qself.as_ref(), path, PathSource::Pat);
2462                 }
2463                 PatKind::Struct(ref qself, ref path, ..) => {
2464                     self.smart_resolve_path(pat.id, qself.as_ref(), path, PathSource::Struct);
2465                 }
2466                 PatKind::Or(ref ps) => {
2467                     // Add a new set of bindings to the stack. `Or` here records that when a
2468                     // binding already exists in this set, it should not result in an error because
2469                     // `V1(a) | V2(a)` must be allowed and are checked for consistency later.
2470                     bindings.push((PatBoundCtx::Or, Default::default()));
2471                     for p in ps {
2472                         // Now we need to switch back to a product context so that each
2473                         // part of the or-pattern internally rejects already bound names.
2474                         // For example, `V1(a) | V2(a, a)` and `V1(a, a) | V2(a)` are bad.
2475                         bindings.push((PatBoundCtx::Product, Default::default()));
2476                         self.resolve_pattern_inner(p, pat_src, bindings);
2477                         // Move up the non-overlapping bindings to the or-pattern.
2478                         // Existing bindings just get "merged".
2479                         let collected = bindings.pop().unwrap().1;
2480                         bindings.last_mut().unwrap().1.extend(collected);
2481                     }
2482                     // This or-pattern itself can itself be part of a product,
2483                     // e.g. `(V1(a) | V2(a), a)` or `(a, V1(a) | V2(a))`.
2484                     // Both cases bind `a` again in a product pattern and must be rejected.
2485                     let collected = bindings.pop().unwrap().1;
2486                     bindings.last_mut().unwrap().1.extend(collected);
2487
2488                     // Prevent visiting `ps` as we've already done so above.
2489                     return false;
2490                 }
2491                 _ => {}
2492             }
2493             true
2494         });
2495     }
2496
2497     fn fresh_binding(
2498         &mut self,
2499         ident: Ident,
2500         pat_id: NodeId,
2501         pat_src: PatternSource,
2502         bindings: &mut SmallVec<[(PatBoundCtx, FxHashSet<Ident>); 1]>,
2503     ) -> Res {
2504         // Add the binding to the local ribs, if it doesn't already exist in the bindings map.
2505         // (We must not add it if it's in the bindings map because that breaks the assumptions
2506         // later passes make about or-patterns.)
2507         let ident = ident.normalize_to_macro_rules();
2508
2509         let mut bound_iter = bindings.iter().filter(|(_, set)| set.contains(&ident));
2510         // Already bound in a product pattern? e.g. `(a, a)` which is not allowed.
2511         let already_bound_and = bound_iter.clone().any(|(ctx, _)| *ctx == PatBoundCtx::Product);
2512         // Already bound in an or-pattern? e.g. `V1(a) | V2(a)`.
2513         // This is *required* for consistency which is checked later.
2514         let already_bound_or = bound_iter.any(|(ctx, _)| *ctx == PatBoundCtx::Or);
2515
2516         if already_bound_and {
2517             // Overlap in a product pattern somewhere; report an error.
2518             use ResolutionError::*;
2519             let error = match pat_src {
2520                 // `fn f(a: u8, a: u8)`:
2521                 PatternSource::FnParam => IdentifierBoundMoreThanOnceInParameterList,
2522                 // `Variant(a, a)`:
2523                 _ => IdentifierBoundMoreThanOnceInSamePattern,
2524             };
2525             self.report_error(ident.span, error(ident.name));
2526         }
2527
2528         // Record as bound if it's valid:
2529         let ident_valid = ident.name != kw::Empty;
2530         if ident_valid {
2531             bindings.last_mut().unwrap().1.insert(ident);
2532         }
2533
2534         if already_bound_or {
2535             // `Variant1(a) | Variant2(a)`, ok
2536             // Reuse definition from the first `a`.
2537             self.innermost_rib_bindings(ValueNS)[&ident]
2538         } else {
2539             let res = Res::Local(pat_id);
2540             if ident_valid {
2541                 // A completely fresh binding add to the set if it's valid.
2542                 self.innermost_rib_bindings(ValueNS).insert(ident, res);
2543             }
2544             res
2545         }
2546     }
2547
2548     fn innermost_rib_bindings(&mut self, ns: Namespace) -> &mut IdentMap<Res> {
2549         &mut self.ribs[ns].last_mut().unwrap().bindings
2550     }
2551
2552     fn try_resolve_as_non_binding(
2553         &mut self,
2554         pat_src: PatternSource,
2555         bm: BindingMode,
2556         ident: Ident,
2557         has_sub: bool,
2558     ) -> Option<Res> {
2559         // An immutable (no `mut`) by-value (no `ref`) binding pattern without
2560         // a sub pattern (no `@ $pat`) is syntactically ambiguous as it could
2561         // also be interpreted as a path to e.g. a constant, variant, etc.
2562         let is_syntactic_ambiguity = !has_sub && bm == BindingMode::ByValue(Mutability::Not);
2563
2564         let ls_binding = self.maybe_resolve_ident_in_lexical_scope(ident, ValueNS)?;
2565         let (res, binding) = match ls_binding {
2566             LexicalScopeBinding::Item(binding)
2567                 if is_syntactic_ambiguity && binding.is_ambiguity() =>
2568             {
2569                 // For ambiguous bindings we don't know all their definitions and cannot check
2570                 // whether they can be shadowed by fresh bindings or not, so force an error.
2571                 // issues/33118#issuecomment-233962221 (see below) still applies here,
2572                 // but we have to ignore it for backward compatibility.
2573                 self.r.record_use(ident, binding, false);
2574                 return None;
2575             }
2576             LexicalScopeBinding::Item(binding) => (binding.res(), Some(binding)),
2577             LexicalScopeBinding::Res(res) => (res, None),
2578         };
2579
2580         match res {
2581             Res::SelfCtor(_) // See #70549.
2582             | Res::Def(
2583                 DefKind::Ctor(_, CtorKind::Const) | DefKind::Const | DefKind::ConstParam,
2584                 _,
2585             ) if is_syntactic_ambiguity => {
2586                 // Disambiguate in favor of a unit struct/variant or constant pattern.
2587                 if let Some(binding) = binding {
2588                     self.r.record_use(ident, binding, false);
2589                 }
2590                 Some(res)
2591             }
2592             Res::Def(DefKind::Ctor(..) | DefKind::Const | DefKind::Static(_), _) => {
2593                 // This is unambiguously a fresh binding, either syntactically
2594                 // (e.g., `IDENT @ PAT` or `ref IDENT`) or because `IDENT` resolves
2595                 // to something unusable as a pattern (e.g., constructor function),
2596                 // but we still conservatively report an error, see
2597                 // issues/33118#issuecomment-233962221 for one reason why.
2598                 let binding = binding.expect("no binding for a ctor or static");
2599                 self.report_error(
2600                     ident.span,
2601                     ResolutionError::BindingShadowsSomethingUnacceptable {
2602                         shadowing_binding_descr: pat_src.descr(),
2603                         name: ident.name,
2604                         participle: if binding.is_import() { "imported" } else { "defined" },
2605                         article: binding.res().article(),
2606                         shadowed_binding_descr: binding.res().descr(),
2607                         shadowed_binding_span: binding.span,
2608                     },
2609                 );
2610                 None
2611             }
2612             Res::Def(DefKind::ConstParam, def_id) => {
2613                 // Same as for DefKind::Const above, but here, `binding` is `None`, so we
2614                 // have to construct the error differently
2615                 self.report_error(
2616                     ident.span,
2617                     ResolutionError::BindingShadowsSomethingUnacceptable {
2618                         shadowing_binding_descr: pat_src.descr(),
2619                         name: ident.name,
2620                         participle: "defined",
2621                         article: res.article(),
2622                         shadowed_binding_descr: res.descr(),
2623                         shadowed_binding_span: self.r.opt_span(def_id).expect("const parameter defined outside of local crate"),
2624                     }
2625                 );
2626                 None
2627             }
2628             Res::Def(DefKind::Fn, _) | Res::Local(..) | Res::Err => {
2629                 // These entities are explicitly allowed to be shadowed by fresh bindings.
2630                 None
2631             }
2632             Res::SelfCtor(_) => {
2633                 // We resolve `Self` in pattern position as an ident sometimes during recovery,
2634                 // so delay a bug instead of ICEing.
2635                 self.r.session.delay_span_bug(
2636                     ident.span,
2637                     "unexpected `SelfCtor` in pattern, expected identifier"
2638                 );
2639                 None
2640             }
2641             _ => span_bug!(
2642                 ident.span,
2643                 "unexpected resolution for an identifier in pattern: {:?}",
2644                 res,
2645             ),
2646         }
2647     }
2648
2649     // High-level and context dependent path resolution routine.
2650     // Resolves the path and records the resolution into definition map.
2651     // If resolution fails tries several techniques to find likely
2652     // resolution candidates, suggest imports or other help, and report
2653     // errors in user friendly way.
2654     fn smart_resolve_path(
2655         &mut self,
2656         id: NodeId,
2657         qself: Option<&QSelf>,
2658         path: &Path,
2659         source: PathSource<'ast>,
2660     ) {
2661         self.smart_resolve_path_fragment(
2662             qself,
2663             &Segment::from_path(path),
2664             source,
2665             Finalize::new(id, path.span),
2666         );
2667     }
2668
2669     fn smart_resolve_path_fragment(
2670         &mut self,
2671         qself: Option<&QSelf>,
2672         path: &[Segment],
2673         source: PathSource<'ast>,
2674         finalize: Finalize,
2675     ) -> PartialRes {
2676         tracing::debug!(
2677             "smart_resolve_path_fragment(qself={:?}, path={:?}, finalize={:?})",
2678             qself,
2679             path,
2680             finalize,
2681         );
2682         let ns = source.namespace();
2683
2684         let Finalize { node_id, path_span, .. } = finalize;
2685         let report_errors = |this: &mut Self, res: Option<Res>| {
2686             if this.should_report_errs() {
2687                 let (err, candidates) =
2688                     this.smart_resolve_report_errors(path, path_span, source, res);
2689
2690                 let def_id = this.parent_scope.module.nearest_parent_mod();
2691                 let instead = res.is_some();
2692                 let suggestion =
2693                     if res.is_none() { this.report_missing_type_error(path) } else { None };
2694
2695                 this.r.use_injections.push(UseError {
2696                     err,
2697                     candidates,
2698                     def_id,
2699                     instead,
2700                     suggestion,
2701                     path: path.into(),
2702                 });
2703             }
2704
2705             PartialRes::new(Res::Err)
2706         };
2707
2708         // For paths originating from calls (like in `HashMap::new()`), tries
2709         // to enrich the plain `failed to resolve: ...` message with hints
2710         // about possible missing imports.
2711         //
2712         // Similar thing, for types, happens in `report_errors` above.
2713         let report_errors_for_call = |this: &mut Self, parent_err: Spanned<ResolutionError<'a>>| {
2714             if !source.is_call() {
2715                 return Some(parent_err);
2716             }
2717
2718             // Before we start looking for candidates, we have to get our hands
2719             // on the type user is trying to perform invocation on; basically:
2720             // we're transforming `HashMap::new` into just `HashMap`.
2721             let path = match path.split_last() {
2722                 Some((_, path)) if !path.is_empty() => path,
2723                 _ => return Some(parent_err),
2724             };
2725
2726             let (mut err, candidates) =
2727                 this.smart_resolve_report_errors(path, path_span, PathSource::Type, None);
2728
2729             if candidates.is_empty() {
2730                 err.cancel();
2731                 return Some(parent_err);
2732             }
2733
2734             // There are two different error messages user might receive at
2735             // this point:
2736             // - E0412 cannot find type `{}` in this scope
2737             // - E0433 failed to resolve: use of undeclared type or module `{}`
2738             //
2739             // The first one is emitted for paths in type-position, and the
2740             // latter one - for paths in expression-position.
2741             //
2742             // Thus (since we're in expression-position at this point), not to
2743             // confuse the user, we want to keep the *message* from E0432 (so
2744             // `parent_err`), but we want *hints* from E0412 (so `err`).
2745             //
2746             // And that's what happens below - we're just mixing both messages
2747             // into a single one.
2748             let mut parent_err = this.r.into_struct_error(parent_err.span, parent_err.node);
2749
2750             err.message = take(&mut parent_err.message);
2751             err.code = take(&mut parent_err.code);
2752             err.children = take(&mut parent_err.children);
2753
2754             parent_err.cancel();
2755
2756             let def_id = this.parent_scope.module.nearest_parent_mod();
2757
2758             if this.should_report_errs() {
2759                 this.r.use_injections.push(UseError {
2760                     err,
2761                     candidates,
2762                     def_id,
2763                     instead: false,
2764                     suggestion: None,
2765                     path: path.into(),
2766                 });
2767             } else {
2768                 err.cancel();
2769             }
2770
2771             // We don't return `Some(parent_err)` here, because the error will
2772             // be already printed as part of the `use` injections
2773             None
2774         };
2775
2776         let partial_res = match self.resolve_qpath_anywhere(
2777             qself,
2778             path,
2779             ns,
2780             path_span,
2781             source.defer_to_typeck(),
2782             finalize,
2783         ) {
2784             Ok(Some(partial_res)) if partial_res.unresolved_segments() == 0 => {
2785                 if source.is_expected(partial_res.base_res()) || partial_res.base_res() == Res::Err
2786                 {
2787                     partial_res
2788                 } else {
2789                     report_errors(self, Some(partial_res.base_res()))
2790                 }
2791             }
2792
2793             Ok(Some(partial_res)) if source.defer_to_typeck() => {
2794                 // Not fully resolved associated item `T::A::B` or `<T as Tr>::A::B`
2795                 // or `<T>::A::B`. If `B` should be resolved in value namespace then
2796                 // it needs to be added to the trait map.
2797                 if ns == ValueNS {
2798                     let item_name = path.last().unwrap().ident;
2799                     let traits = self.traits_in_scope(item_name, ns);
2800                     self.r.trait_map.insert(node_id, traits);
2801                 }
2802
2803                 if PrimTy::from_name(path[0].ident.name).is_some() {
2804                     let mut std_path = Vec::with_capacity(1 + path.len());
2805
2806                     std_path.push(Segment::from_ident(Ident::with_dummy_span(sym::std)));
2807                     std_path.extend(path);
2808                     if let PathResult::Module(_) | PathResult::NonModule(_) =
2809                         self.resolve_path(&std_path, Some(ns), None)
2810                     {
2811                         // Check if we wrote `str::from_utf8` instead of `std::str::from_utf8`
2812                         let item_span =
2813                             path.iter().last().map_or(path_span, |segment| segment.ident.span);
2814
2815                         self.r.confused_type_with_std_module.insert(item_span, path_span);
2816                         self.r.confused_type_with_std_module.insert(path_span, path_span);
2817                     }
2818                 }
2819
2820                 partial_res
2821             }
2822
2823             Err(err) => {
2824                 if let Some(err) = report_errors_for_call(self, err) {
2825                     self.report_error(err.span, err.node);
2826                 }
2827
2828                 PartialRes::new(Res::Err)
2829             }
2830
2831             _ => report_errors(self, None),
2832         };
2833
2834         if !matches!(source, PathSource::TraitItem(..)) {
2835             // Avoid recording definition of `A::B` in `<T as A>::B::C`.
2836             self.r.record_partial_res(node_id, partial_res);
2837             self.resolve_elided_lifetimes_in_path(node_id, partial_res, path, source, path_span);
2838         }
2839
2840         partial_res
2841     }
2842
2843     fn self_type_is_available(&mut self) -> bool {
2844         let binding = self
2845             .maybe_resolve_ident_in_lexical_scope(Ident::with_dummy_span(kw::SelfUpper), TypeNS);
2846         if let Some(LexicalScopeBinding::Res(res)) = binding { res != Res::Err } else { false }
2847     }
2848
2849     fn self_value_is_available(&mut self, self_span: Span) -> bool {
2850         let ident = Ident::new(kw::SelfLower, self_span);
2851         let binding = self.maybe_resolve_ident_in_lexical_scope(ident, ValueNS);
2852         if let Some(LexicalScopeBinding::Res(res)) = binding { res != Res::Err } else { false }
2853     }
2854
2855     /// A wrapper around [`Resolver::report_error`].
2856     ///
2857     /// This doesn't emit errors for function bodies if this is rustdoc.
2858     fn report_error(&mut self, span: Span, resolution_error: ResolutionError<'a>) {
2859         if self.should_report_errs() {
2860             self.r.report_error(span, resolution_error);
2861         }
2862     }
2863
2864     #[inline]
2865     /// If we're actually rustdoc then avoid giving a name resolution error for `cfg()` items.
2866     fn should_report_errs(&self) -> bool {
2867         !(self.r.session.opts.actually_rustdoc && self.in_func_body)
2868     }
2869
2870     // Resolve in alternative namespaces if resolution in the primary namespace fails.
2871     fn resolve_qpath_anywhere(
2872         &mut self,
2873         qself: Option<&QSelf>,
2874         path: &[Segment],
2875         primary_ns: Namespace,
2876         span: Span,
2877         defer_to_typeck: bool,
2878         finalize: Finalize,
2879     ) -> Result<Option<PartialRes>, Spanned<ResolutionError<'a>>> {
2880         let mut fin_res = None;
2881
2882         for (i, &ns) in [primary_ns, TypeNS, ValueNS].iter().enumerate() {
2883             if i == 0 || ns != primary_ns {
2884                 match self.resolve_qpath(qself, path, ns, finalize)? {
2885                     Some(partial_res)
2886                         if partial_res.unresolved_segments() == 0 || defer_to_typeck =>
2887                     {
2888                         return Ok(Some(partial_res));
2889                     }
2890                     partial_res => {
2891                         if fin_res.is_none() {
2892                             fin_res = partial_res;
2893                         }
2894                     }
2895                 }
2896             }
2897         }
2898
2899         assert!(primary_ns != MacroNS);
2900
2901         if qself.is_none() {
2902             let path_seg = |seg: &Segment| PathSegment::from_ident(seg.ident);
2903             let path = Path { segments: path.iter().map(path_seg).collect(), span, tokens: None };
2904             if let Ok((_, res)) =
2905                 self.r.resolve_macro_path(&path, None, &self.parent_scope, false, false)
2906             {
2907                 return Ok(Some(PartialRes::new(res)));
2908             }
2909         }
2910
2911         Ok(fin_res)
2912     }
2913
2914     /// Handles paths that may refer to associated items.
2915     fn resolve_qpath(
2916         &mut self,
2917         qself: Option<&QSelf>,
2918         path: &[Segment],
2919         ns: Namespace,
2920         finalize: Finalize,
2921     ) -> Result<Option<PartialRes>, Spanned<ResolutionError<'a>>> {
2922         debug!(
2923             "resolve_qpath(qself={:?}, path={:?}, ns={:?}, finalize={:?})",
2924             qself, path, ns, finalize,
2925         );
2926
2927         if let Some(qself) = qself {
2928             if qself.position == 0 {
2929                 // This is a case like `<T>::B`, where there is no
2930                 // trait to resolve.  In that case, we leave the `B`
2931                 // segment to be resolved by type-check.
2932                 return Ok(Some(PartialRes::with_unresolved_segments(
2933                     Res::Def(DefKind::Mod, CRATE_DEF_ID.to_def_id()),
2934                     path.len(),
2935                 )));
2936             }
2937
2938             // Make sure `A::B` in `<T as A::B>::C` is a trait item.
2939             //
2940             // Currently, `path` names the full item (`A::B::C`, in
2941             // our example).  so we extract the prefix of that that is
2942             // the trait (the slice upto and including
2943             // `qself.position`). And then we recursively resolve that,
2944             // but with `qself` set to `None`.
2945             let ns = if qself.position + 1 == path.len() { ns } else { TypeNS };
2946             let partial_res = self.smart_resolve_path_fragment(
2947                 None,
2948                 &path[..=qself.position],
2949                 PathSource::TraitItem(ns),
2950                 Finalize::with_root_span(finalize.node_id, finalize.path_span, qself.path_span),
2951             );
2952
2953             // The remaining segments (the `C` in our example) will
2954             // have to be resolved by type-check, since that requires doing
2955             // trait resolution.
2956             return Ok(Some(PartialRes::with_unresolved_segments(
2957                 partial_res.base_res(),
2958                 partial_res.unresolved_segments() + path.len() - qself.position - 1,
2959             )));
2960         }
2961
2962         let result = match self.resolve_path(&path, Some(ns), Some(finalize)) {
2963             PathResult::NonModule(path_res) => path_res,
2964             PathResult::Module(ModuleOrUniformRoot::Module(module)) if !module.is_normal() => {
2965                 PartialRes::new(module.res().unwrap())
2966             }
2967             // In `a(::assoc_item)*` `a` cannot be a module. If `a` does resolve to a module we
2968             // don't report an error right away, but try to fallback to a primitive type.
2969             // So, we are still able to successfully resolve something like
2970             //
2971             // use std::u8; // bring module u8 in scope
2972             // fn f() -> u8 { // OK, resolves to primitive u8, not to std::u8
2973             //     u8::max_value() // OK, resolves to associated function <u8>::max_value,
2974             //                     // not to non-existent std::u8::max_value
2975             // }
2976             //
2977             // Such behavior is required for backward compatibility.
2978             // The same fallback is used when `a` resolves to nothing.
2979             PathResult::Module(ModuleOrUniformRoot::Module(_)) | PathResult::Failed { .. }
2980                 if (ns == TypeNS || path.len() > 1)
2981                     && PrimTy::from_name(path[0].ident.name).is_some() =>
2982             {
2983                 let prim = PrimTy::from_name(path[0].ident.name).unwrap();
2984                 PartialRes::with_unresolved_segments(Res::PrimTy(prim), path.len() - 1)
2985             }
2986             PathResult::Module(ModuleOrUniformRoot::Module(module)) => {
2987                 PartialRes::new(module.res().unwrap())
2988             }
2989             PathResult::Failed { is_error_from_last_segment: false, span, label, suggestion } => {
2990                 return Err(respan(span, ResolutionError::FailedToResolve { label, suggestion }));
2991             }
2992             PathResult::Module(..) | PathResult::Failed { .. } => return Ok(None),
2993             PathResult::Indeterminate => bug!("indeterminate path result in resolve_qpath"),
2994         };
2995
2996         if path.len() > 1
2997             && result.base_res() != Res::Err
2998             && path[0].ident.name != kw::PathRoot
2999             && path[0].ident.name != kw::DollarCrate
3000         {
3001             let unqualified_result = {
3002                 match self.resolve_path(&[*path.last().unwrap()], Some(ns), None) {
3003                     PathResult::NonModule(path_res) => path_res.base_res(),
3004                     PathResult::Module(ModuleOrUniformRoot::Module(module)) => {
3005                         module.res().unwrap()
3006                     }
3007                     _ => return Ok(Some(result)),
3008                 }
3009             };
3010             if result.base_res() == unqualified_result {
3011                 let lint = lint::builtin::UNUSED_QUALIFICATIONS;
3012                 self.r.lint_buffer.buffer_lint(
3013                     lint,
3014                     finalize.node_id,
3015                     finalize.path_span,
3016                     "unnecessary qualification",
3017                 )
3018             }
3019         }
3020
3021         Ok(Some(result))
3022     }
3023
3024     fn with_resolved_label(&mut self, label: Option<Label>, id: NodeId, f: impl FnOnce(&mut Self)) {
3025         if let Some(label) = label {
3026             if label.ident.as_str().as_bytes()[1] != b'_' {
3027                 self.diagnostic_metadata.unused_labels.insert(id, label.ident.span);
3028             }
3029             self.with_label_rib(NormalRibKind, |this| {
3030                 let ident = label.ident.normalize_to_macro_rules();
3031                 this.label_ribs.last_mut().unwrap().bindings.insert(ident, id);
3032                 f(this);
3033             });
3034         } else {
3035             f(self);
3036         }
3037     }
3038
3039     fn resolve_labeled_block(&mut self, label: Option<Label>, id: NodeId, block: &'ast Block) {
3040         self.with_resolved_label(label, id, |this| this.visit_block(block));
3041     }
3042
3043     fn resolve_block(&mut self, block: &'ast Block) {
3044         debug!("(resolving block) entering block");
3045         // Move down in the graph, if there's an anonymous module rooted here.
3046         let orig_module = self.parent_scope.module;
3047         let anonymous_module = self.r.block_map.get(&block.id).cloned(); // clones a reference
3048
3049         let mut num_macro_definition_ribs = 0;
3050         if let Some(anonymous_module) = anonymous_module {
3051             debug!("(resolving block) found anonymous module, moving down");
3052             self.ribs[ValueNS].push(Rib::new(ModuleRibKind(anonymous_module)));
3053             self.ribs[TypeNS].push(Rib::new(ModuleRibKind(anonymous_module)));
3054             self.parent_scope.module = anonymous_module;
3055         } else {
3056             self.ribs[ValueNS].push(Rib::new(NormalRibKind));
3057         }
3058
3059         let prev = self.diagnostic_metadata.current_block_could_be_bare_struct_literal.take();
3060         if let (true, [Stmt { kind: StmtKind::Expr(expr), .. }]) =
3061             (block.could_be_bare_literal, &block.stmts[..])
3062             && let ExprKind::Type(..) = expr.kind
3063         {
3064             self.diagnostic_metadata.current_block_could_be_bare_struct_literal =
3065             Some(block.span);
3066         }
3067         // Descend into the block.
3068         for stmt in &block.stmts {
3069             if let StmtKind::Item(ref item) = stmt.kind
3070                 && let ItemKind::MacroDef(..) = item.kind {
3071                 num_macro_definition_ribs += 1;
3072                 let res = self.r.local_def_id(item.id).to_def_id();
3073                 self.ribs[ValueNS].push(Rib::new(MacroDefinition(res)));
3074                 self.label_ribs.push(Rib::new(MacroDefinition(res)));
3075             }
3076
3077             self.visit_stmt(stmt);
3078         }
3079         self.diagnostic_metadata.current_block_could_be_bare_struct_literal = prev;
3080
3081         // Move back up.
3082         self.parent_scope.module = orig_module;
3083         for _ in 0..num_macro_definition_ribs {
3084             self.ribs[ValueNS].pop();
3085             self.label_ribs.pop();
3086         }
3087         self.ribs[ValueNS].pop();
3088         if anonymous_module.is_some() {
3089             self.ribs[TypeNS].pop();
3090         }
3091         debug!("(resolving block) leaving block");
3092     }
3093
3094     fn resolve_anon_const(&mut self, constant: &'ast AnonConst, is_repeat: IsRepeatExpr) {
3095         debug!("resolve_anon_const {:?} is_repeat: {:?}", constant, is_repeat);
3096         self.with_constant_rib(
3097             is_repeat,
3098             if constant.value.is_potential_trivial_const_param() {
3099                 HasGenericParams::Yes
3100             } else {
3101                 HasGenericParams::No
3102             },
3103             None,
3104             |this| visit::walk_anon_const(this, constant),
3105         );
3106     }
3107
3108     fn resolve_inline_const(&mut self, constant: &'ast AnonConst) {
3109         debug!("resolve_anon_const {constant:?}");
3110         self.with_constant_rib(IsRepeatExpr::No, HasGenericParams::Yes, None, |this| {
3111             visit::walk_anon_const(this, constant);
3112         });
3113     }
3114
3115     fn resolve_expr(&mut self, expr: &'ast Expr, parent: Option<&'ast Expr>) {
3116         // First, record candidate traits for this expression if it could
3117         // result in the invocation of a method call.
3118
3119         self.record_candidate_traits_for_expr_if_necessary(expr);
3120
3121         // Next, resolve the node.
3122         match expr.kind {
3123             ExprKind::Path(ref qself, ref path) => {
3124                 self.smart_resolve_path(expr.id, qself.as_ref(), path, PathSource::Expr(parent));
3125                 visit::walk_expr(self, expr);
3126             }
3127
3128             ExprKind::Struct(ref se) => {
3129                 self.smart_resolve_path(expr.id, se.qself.as_ref(), &se.path, PathSource::Struct);
3130                 visit::walk_expr(self, expr);
3131             }
3132
3133             ExprKind::Break(Some(label), _) | ExprKind::Continue(Some(label)) => {
3134                 if let Some(node_id) = self.resolve_label(label.ident) {
3135                     // Since this res is a label, it is never read.
3136                     self.r.label_res_map.insert(expr.id, node_id);
3137                     self.diagnostic_metadata.unused_labels.remove(&node_id);
3138                 }
3139
3140                 // visit `break` argument if any
3141                 visit::walk_expr(self, expr);
3142             }
3143
3144             ExprKind::Break(None, Some(ref e)) => {
3145                 // We use this instead of `visit::walk_expr` to keep the parent expr around for
3146                 // better diagnostics.
3147                 self.resolve_expr(e, Some(&expr));
3148             }
3149
3150             ExprKind::Let(ref pat, ref scrutinee, _) => {
3151                 self.visit_expr(scrutinee);
3152                 self.resolve_pattern_top(pat, PatternSource::Let);
3153             }
3154
3155             ExprKind::If(ref cond, ref then, ref opt_else) => {
3156                 self.with_rib(ValueNS, NormalRibKind, |this| {
3157                     let old = this.diagnostic_metadata.in_if_condition.replace(cond);
3158                     this.visit_expr(cond);
3159                     this.diagnostic_metadata.in_if_condition = old;
3160                     this.visit_block(then);
3161                 });
3162                 if let Some(expr) = opt_else {
3163                     self.visit_expr(expr);
3164                 }
3165             }
3166
3167             ExprKind::Loop(ref block, label) => self.resolve_labeled_block(label, expr.id, &block),
3168
3169             ExprKind::While(ref cond, ref block, label) => {
3170                 self.with_resolved_label(label, expr.id, |this| {
3171                     this.with_rib(ValueNS, NormalRibKind, |this| {
3172                         let old = this.diagnostic_metadata.in_if_condition.replace(cond);
3173                         this.visit_expr(cond);
3174                         this.diagnostic_metadata.in_if_condition = old;
3175                         this.visit_block(block);
3176                     })
3177                 });
3178             }
3179
3180             ExprKind::ForLoop(ref pat, ref iter_expr, ref block, label) => {
3181                 self.visit_expr(iter_expr);
3182                 self.with_rib(ValueNS, NormalRibKind, |this| {
3183                     this.resolve_pattern_top(pat, PatternSource::For);
3184                     this.resolve_labeled_block(label, expr.id, block);
3185                 });
3186             }
3187
3188             ExprKind::Block(ref block, label) => self.resolve_labeled_block(label, block.id, block),
3189
3190             // Equivalent to `visit::walk_expr` + passing some context to children.
3191             ExprKind::Field(ref subexpression, _) => {
3192                 self.resolve_expr(subexpression, Some(expr));
3193             }
3194             ExprKind::MethodCall(ref segment, ref arguments, _) => {
3195                 let mut arguments = arguments.iter();
3196                 self.resolve_expr(arguments.next().unwrap(), Some(expr));
3197                 for argument in arguments {
3198                     self.resolve_expr(argument, None);
3199                 }
3200                 self.visit_path_segment(expr.span, segment);
3201             }
3202
3203             ExprKind::Call(ref callee, ref arguments) => {
3204                 self.resolve_expr(callee, Some(expr));
3205                 let const_args = self.r.legacy_const_generic_args(callee).unwrap_or_default();
3206                 for (idx, argument) in arguments.iter().enumerate() {
3207                     // Constant arguments need to be treated as AnonConst since
3208                     // that is how they will be later lowered to HIR.
3209                     if const_args.contains(&idx) {
3210                         self.with_constant_rib(
3211                             IsRepeatExpr::No,
3212                             if argument.is_potential_trivial_const_param() {
3213                                 HasGenericParams::Yes
3214                             } else {
3215                                 HasGenericParams::No
3216                             },
3217                             None,
3218                             |this| {
3219                                 this.resolve_expr(argument, None);
3220                             },
3221                         );
3222                     } else {
3223                         self.resolve_expr(argument, None);
3224                     }
3225                 }
3226             }
3227             ExprKind::Type(ref type_expr, ref ty) => {
3228                 // `ParseSess::type_ascription_path_suggestions` keeps spans of colon tokens in
3229                 // type ascription. Here we are trying to retrieve the span of the colon token as
3230                 // well, but only if it's written without spaces `expr:Ty` and therefore confusable
3231                 // with `expr::Ty`, only in this case it will match the span from
3232                 // `type_ascription_path_suggestions`.
3233                 self.diagnostic_metadata
3234                     .current_type_ascription
3235                     .push(type_expr.span.between(ty.span));
3236                 visit::walk_expr(self, expr);
3237                 self.diagnostic_metadata.current_type_ascription.pop();
3238             }
3239             // `async |x| ...` gets desugared to `|x| future_from_generator(|| ...)`, so we need to
3240             // resolve the arguments within the proper scopes so that usages of them inside the
3241             // closure are detected as upvars rather than normal closure arg usages.
3242             ExprKind::Closure(_, Async::Yes { .. }, _, ref fn_decl, ref body, _span) => {
3243                 self.with_rib(ValueNS, NormalRibKind, |this| {
3244                     this.with_label_rib(ClosureOrAsyncRibKind, |this| {
3245                         // Resolve arguments:
3246                         this.resolve_params(&fn_decl.inputs);
3247                         // No need to resolve return type --
3248                         // the outer closure return type is `FnRetTy::Default`.
3249
3250                         // Now resolve the inner closure
3251                         {
3252                             // No need to resolve arguments: the inner closure has none.
3253                             // Resolve the return type:
3254                             visit::walk_fn_ret_ty(this, &fn_decl.output);
3255                             // Resolve the body
3256                             this.visit_expr(body);
3257                         }
3258                     })
3259                 });
3260             }
3261             ExprKind::Async(..) | ExprKind::Closure(..) => {
3262                 self.with_label_rib(ClosureOrAsyncRibKind, |this| visit::walk_expr(this, expr));
3263             }
3264             ExprKind::Repeat(ref elem, ref ct) => {
3265                 self.visit_expr(elem);
3266                 self.with_lifetime_rib(LifetimeRibKind::AnonConst, |this| {
3267                     this.resolve_anon_const(ct, IsRepeatExpr::Yes)
3268                 });
3269             }
3270             ExprKind::ConstBlock(ref ct) => {
3271                 self.resolve_inline_const(ct);
3272             }
3273             ExprKind::Index(ref elem, ref idx) => {
3274                 self.resolve_expr(elem, Some(expr));
3275                 self.visit_expr(idx);
3276             }
3277             _ => {
3278                 visit::walk_expr(self, expr);
3279             }
3280         }
3281     }
3282
3283     fn record_candidate_traits_for_expr_if_necessary(&mut self, expr: &'ast Expr) {
3284         match expr.kind {
3285             ExprKind::Field(_, ident) => {
3286                 // FIXME(#6890): Even though you can't treat a method like a
3287                 // field, we need to add any trait methods we find that match
3288                 // the field name so that we can do some nice error reporting
3289                 // later on in typeck.
3290                 let traits = self.traits_in_scope(ident, ValueNS);
3291                 self.r.trait_map.insert(expr.id, traits);
3292             }
3293             ExprKind::MethodCall(ref segment, ..) => {
3294                 debug!("(recording candidate traits for expr) recording traits for {}", expr.id);
3295                 let traits = self.traits_in_scope(segment.ident, ValueNS);
3296                 self.r.trait_map.insert(expr.id, traits);
3297             }
3298             _ => {
3299                 // Nothing to do.
3300             }
3301         }
3302     }
3303
3304     fn traits_in_scope(&mut self, ident: Ident, ns: Namespace) -> Vec<TraitCandidate> {
3305         self.r.traits_in_scope(
3306             self.current_trait_ref.as_ref().map(|(module, _)| *module),
3307             &self.parent_scope,
3308             ident.span.ctxt(),
3309             Some((ident.name, ns)),
3310         )
3311     }
3312 }
3313
3314 struct LifetimeCountVisitor<'a, 'b> {
3315     r: &'b mut Resolver<'a>,
3316 }
3317
3318 /// Walks the whole crate in DFS order, visiting each item, counting the declared number of
3319 /// lifetime generic parameters.
3320 impl<'ast> Visitor<'ast> for LifetimeCountVisitor<'_, '_> {
3321     fn visit_item(&mut self, item: &'ast Item) {
3322         match &item.kind {
3323             ItemKind::TyAlias(box TyAlias { ref generics, .. })
3324             | ItemKind::Fn(box Fn { ref generics, .. })
3325             | ItemKind::Enum(_, ref generics)
3326             | ItemKind::Struct(_, ref generics)
3327             | ItemKind::Union(_, ref generics)
3328             | ItemKind::Impl(box Impl { ref generics, .. })
3329             | ItemKind::Trait(box Trait { ref generics, .. })
3330             | ItemKind::TraitAlias(ref generics, _) => {
3331                 let def_id = self.r.local_def_id(item.id);
3332                 let count = generics
3333                     .params
3334                     .iter()
3335                     .filter(|param| matches!(param.kind, ast::GenericParamKind::Lifetime { .. }))
3336                     .count();
3337                 self.r.item_generics_num_lifetimes.insert(def_id, count);
3338             }
3339
3340             ItemKind::Mod(..)
3341             | ItemKind::ForeignMod(..)
3342             | ItemKind::Static(..)
3343             | ItemKind::Const(..)
3344             | ItemKind::Use(..)
3345             | ItemKind::ExternCrate(..)
3346             | ItemKind::MacroDef(..)
3347             | ItemKind::GlobalAsm(..)
3348             | ItemKind::MacCall(..) => {}
3349         }
3350         visit::walk_item(self, item)
3351     }
3352 }
3353
3354 impl<'a> Resolver<'a> {
3355     pub(crate) fn late_resolve_crate(&mut self, krate: &Crate) {
3356         visit::walk_crate(&mut LifetimeCountVisitor { r: self }, krate);
3357         let mut late_resolution_visitor = LateResolutionVisitor::new(self);
3358         visit::walk_crate(&mut late_resolution_visitor, krate);
3359         for (id, span) in late_resolution_visitor.diagnostic_metadata.unused_labels.iter() {
3360             self.lint_buffer.buffer_lint(lint::builtin::UNUSED_LABELS, *id, *span, "unused label");
3361         }
3362     }
3363 }