compiler/rustc_resolve/src/late.rs

   1 // ignore-tidy-filelength
   2 //! "Late resolution" is the pass that resolves most of names in a crate beside imports and macros.
   3 //! It runs when the crate is fully expanded and its module structure is fully built.
   4 //! So it just walks through the crate and resolves all the expressions, types, etc.
   5 //!
   6 //! If you wonder why there's no `early.rs`, that's because it's split into three files -
   7 //! `build_reduced_graph.rs`, `macros.rs` and `imports.rs`.
   8
   9 use RibKind::*;
  10
  11 use crate::{path_names_to_string, BindingError, Finalize, LexicalScopeBinding};
  12 use crate::{Module, ModuleOrUniformRoot, NameBinding, ParentScope, PathResult};
  13 use crate::{ResolutionError, Resolver, Segment, UseError};
  14
  15 use rustc_ast::ptr::P;
  16 use rustc_ast::visit::{self, AssocCtxt, BoundKind, FnCtxt, FnKind, Visitor};
  17 use rustc_ast::*;
  18 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap};
  19 use rustc_errors::{Applicability, DiagnosticArgValue, DiagnosticId, IntoDiagnosticArg};
  20 use rustc_hir::def::Namespace::{self, *};
  21 use rustc_hir::def::{self, CtorKind, DefKind, LifetimeRes, PartialRes, PerNS};
  22 use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_ID, LOCAL_CRATE};
  23 use rustc_hir::{BindingAnnotation, PrimTy, TraitCandidate};
  24 use rustc_middle::middle::resolve_lifetime::Set1;
  25 use rustc_middle::ty::DefIdTree;
  26 use rustc_middle::{bug, span_bug};
  27 use rustc_session::lint;
  28 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  29 use rustc_span::{BytePos, Span};
  30 use smallvec::{smallvec, SmallVec};
  31
  32 use rustc_span::source_map::{respan, Spanned};
  33 use std::assert_matches::debug_assert_matches;
  34 use std::borrow::Cow;
  35 use std::collections::{hash_map::Entry, BTreeSet};
  36 use std::mem::{replace, swap, take};
  37
  38 mod diagnostics;
  39
  40 type Res = def::Res<NodeId>;
  41
  42 type IdentMap<T> = FxHashMap<Ident, T>;
  43
  44 /// Map from the name in a pattern to its binding mode.
  45 type BindingMap = IdentMap<BindingInfo>;
  46
  47 use diagnostics::{
  48     ElisionFnParameter, LifetimeElisionCandidate, MissingLifetime, MissingLifetimeKind,
  49 };
  50
  51 #[derive(Copy, Clone, Debug)]
  52 struct BindingInfo {
  53     span: Span,
  54     annotation: BindingAnnotation,
  55 }
  56
  57 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
  58 pub enum PatternSource {
  59     Match,
  60     Let,
  61     For,
  62     FnParam,
  63 }
  64
  65 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
  66 enum IsRepeatExpr {
  67     No,
  68     Yes,
  69 }
  70
  71 impl PatternSource {
  72     pub fn descr(self) -> &'static str {
  73         match self {
  74             PatternSource::Match => "match binding",
  75             PatternSource::Let => "let binding",
  76             PatternSource::For => "for binding",
  77             PatternSource::FnParam => "function parameter",
  78         }
  79     }
  80 }
  81
  82 impl IntoDiagnosticArg for PatternSource {
  83     fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
  84         DiagnosticArgValue::Str(Cow::Borrowed(self.descr()))
  85     }
  86 }
  87
  88 /// Denotes whether the context for the set of already bound bindings is a `Product`
  89 /// or `Or` context. This is used in e.g., `fresh_binding` and `resolve_pattern_inner`.
  90 /// See those functions for more information.
  91 #[derive(PartialEq)]
  92 enum PatBoundCtx {
  93     /// A product pattern context, e.g., `Variant(a, b)`.
  94     Product,
  95     /// An or-pattern context, e.g., `p_0 | ... | p_n`.
  96     Or,
  97 }
  98
  99 /// Does this the item (from the item rib scope) allow generic parameters?
 100 #[derive(Copy, Clone, Debug)]
 101 pub(crate) enum HasGenericParams {
 102     Yes(Span),
 103     No,
 104 }
 105
 106 /// May this constant have generics?
 107 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
 108 pub(crate) enum ConstantHasGenerics {
 109     Yes,
 110     No,
 111 }
 112
 113 impl ConstantHasGenerics {
 114     fn force_yes_if(self, b: bool) -> Self {
 115         if b { Self::Yes } else { self }
 116     }
 117 }
 118
 119 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
 120 pub(crate) enum ConstantItemKind {
 121     Const,
 122     Static,
 123 }
 124
 125 /// The rib kind restricts certain accesses,
 126 /// e.g. to a `Res::Local` of an outer item.
 127 #[derive(Copy, Clone, Debug)]
 128 pub(crate) enum RibKind<'a> {
 129     /// No restriction needs to be applied.
 130     NormalRibKind,
 131
 132     /// We passed through an impl or trait and are now in one of its
 133     /// methods or associated types. Allow references to ty params that impl or trait
 134     /// binds. Disallow any other upvars (including other ty params that are
 135     /// upvars).
 136     AssocItemRibKind,
 137
 138     /// We passed through a closure. Disallow labels.
 139     ClosureOrAsyncRibKind,
 140
 141     /// We passed through an item scope. Disallow upvars.
 142     ItemRibKind(HasGenericParams),
 143
 144     /// We're in a constant item. Can't refer to dynamic stuff.
 145     ///
 146     /// The item may reference generic parameters in trivial constant expressions.
 147     /// All other constants aren't allowed to use generic params at all.
 148     ConstantItemRibKind(ConstantHasGenerics, Option<(Ident, ConstantItemKind)>),
 149
 150     /// We passed through a module.
 151     ModuleRibKind(Module<'a>),
 152
 153     /// We passed through a `macro_rules!` statement
 154     MacroDefinition(DefId),
 155
 156     /// All bindings in this rib are generic parameters that can't be used
 157     /// from the default of a generic parameter because they're not declared
 158     /// before said generic parameter. Also see the `visit_generics` override.
 159     ForwardGenericParamBanRibKind,
 160
 161     /// We are inside of the type of a const parameter. Can't refer to any
 162     /// parameters.
 163     ConstParamTyRibKind,
 164
 165     /// We are inside a `sym` inline assembly operand. Can only refer to
 166     /// globals.
 167     InlineAsmSymRibKind,
 168 }
 169
 170 impl RibKind<'_> {
 171     /// Whether this rib kind contains generic parameters, as opposed to local
 172     /// variables.
 173     pub(crate) fn contains_params(&self) -> bool {
 174         match self {
 175             NormalRibKind
 176             | ClosureOrAsyncRibKind
 177             | ConstantItemRibKind(..)
 178             | ModuleRibKind(_)
 179             | MacroDefinition(_)
 180             | ConstParamTyRibKind
 181             | InlineAsmSymRibKind => false,
 182             AssocItemRibKind | ItemRibKind(_) | ForwardGenericParamBanRibKind => true,
 183         }
 184     }
 185
 186     /// This rib forbids referring to labels defined in upwards ribs.
 187     fn is_label_barrier(self) -> bool {
 188         match self {
 189             NormalRibKind | MacroDefinition(..) => false,
 190
 191             AssocItemRibKind
 192             | ClosureOrAsyncRibKind
 193             | ItemRibKind(..)
 194             | ConstantItemRibKind(..)
 195             | ModuleRibKind(..)
 196             | ForwardGenericParamBanRibKind
 197             | ConstParamTyRibKind
 198             | InlineAsmSymRibKind => true,
 199         }
 200     }
 201 }
 202
 203 /// A single local scope.
 204 ///
 205 /// A rib represents a scope names can live in. Note that these appear in many places, not just
 206 /// around braces. At any place where the list of accessible names (of the given namespace)
 207 /// changes or a new restrictions on the name accessibility are introduced, a new rib is put onto a
 208 /// stack. This may be, for example, a `let` statement (because it introduces variables), a macro,
 209 /// etc.
 210 ///
 211 /// Different [rib kinds](enum@RibKind) are transparent for different names.
 212 ///
 213 /// The resolution keeps a separate stack of ribs as it traverses the AST for each namespace. When
 214 /// resolving, the name is looked up from inside out.
 215 #[derive(Debug)]
 216 pub(crate) struct Rib<'a, R = Res> {
 217     pub bindings: IdentMap<R>,
 218     pub kind: RibKind<'a>,
 219 }
 220
 221 impl<'a, R> Rib<'a, R> {
 222     fn new(kind: RibKind<'a>) -> Rib<'a, R> {
 223         Rib { bindings: Default::default(), kind }
 224     }
 225 }
 226
 227 #[derive(Clone, Copy, Debug)]
 228 enum LifetimeUseSet {
 229     One { use_span: Span, use_ctxt: visit::LifetimeCtxt },
 230     Many,
 231 }
 232
 233 #[derive(Copy, Clone, Debug)]
 234 enum LifetimeRibKind {
 235     // -- Ribs introducing named lifetimes
 236     //
 237     /// This rib declares generic parameters.
 238     /// Only for this kind the `LifetimeRib::bindings` field can be non-empty.
 239     Generics { binder: NodeId, span: Span, kind: LifetimeBinderKind },
 240
 241     // -- Ribs introducing unnamed lifetimes
 242     //
 243     /// Create a new anonymous lifetime parameter and reference it.
 244     ///
 245     /// If `report_in_path`, report an error when encountering lifetime elision in a path:
 246     /// ```compile_fail
 247     /// struct Foo<'a> { x: &'a () }
 248     /// async fn foo(x: Foo) {}
 249     /// ```
 250     ///
 251     /// Note: the error should not trigger when the elided lifetime is in a pattern or
 252     /// expression-position path:
 253     /// ```
 254     /// struct Foo<'a> { x: &'a () }
 255     /// async fn foo(Foo { x: _ }: Foo<'_>) {}
 256     /// ```
 257     AnonymousCreateParameter { binder: NodeId, report_in_path: bool },
 258
 259     /// Replace all anonymous lifetimes by provided lifetime.
 260     Elided(LifetimeRes),
 261
 262     // -- Barrier ribs that stop lifetime lookup, or continue it but produce an error later.
 263     //
 264     /// Give a hard error when either `&` or `'_` is written. Used to
 265     /// rule out things like `where T: Foo<'_>`. Does not imply an
 266     /// error on default object bounds (e.g., `Box<dyn Foo>`).
 267     AnonymousReportError,
 268
 269     /// Signal we cannot find which should be the anonymous lifetime.
 270     ElisionFailure,
 271
 272     /// FIXME(const_generics): This patches over an ICE caused by non-'static lifetimes in const
 273     /// generics. We are disallowing this until we can decide on how we want to handle non-'static
 274     /// lifetimes in const generics. See issue #74052 for discussion.
 275     ConstGeneric,
 276
 277     /// Non-static lifetimes are prohibited in anonymous constants under `min_const_generics`.
 278     /// This function will emit an error if `generic_const_exprs` is not enabled, the body
 279     /// identified by `body_id` is an anonymous constant and `lifetime_ref` is non-static.
 280     AnonConst,
 281
 282     /// This rib acts as a barrier to forbid reference to lifetimes of a parent item.
 283     Item,
 284 }
 285
 286 #[derive(Copy, Clone, Debug)]
 287 enum LifetimeBinderKind {
 288     BareFnType,
 289     PolyTrait,
 290     WhereBound,
 291     Item,
 292     Function,
 293     Closure,
 294     ImplBlock,
 295 }
 296
 297 impl LifetimeBinderKind {
 298     fn descr(self) -> &'static str {
 299         use LifetimeBinderKind::*;
 300         match self {
 301             BareFnType => "type",
 302             PolyTrait => "bound",
 303             WhereBound => "bound",
 304             Item => "item",
 305             ImplBlock => "impl block",
 306             Function => "function",
 307             Closure => "closure",
 308         }
 309     }
 310 }
 311
 312 #[derive(Debug)]
 313 struct LifetimeRib {
 314     kind: LifetimeRibKind,
 315     // We need to preserve insertion order for async fns.
 316     bindings: FxIndexMap<Ident, (NodeId, LifetimeRes)>,
 317 }
 318
 319 impl LifetimeRib {
 320     fn new(kind: LifetimeRibKind) -> LifetimeRib {
 321         LifetimeRib { bindings: Default::default(), kind }
 322     }
 323 }
 324
 325 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 326 pub(crate) enum AliasPossibility {
 327     No,
 328     Maybe,
 329 }
 330
 331 #[derive(Copy, Clone, Debug)]
 332 pub(crate) enum PathSource<'a> {
 333     // Type paths `Path`.
 334     Type,
 335     // Trait paths in bounds or impls.
 336     Trait(AliasPossibility),
 337     // Expression paths `path`, with optional parent context.
 338     Expr(Option<&'a Expr>),
 339     // Paths in path patterns `Path`.
 340     Pat,
 341     // Paths in struct expressions and patterns `Path { .. }`.
 342     Struct,
 343     // Paths in tuple struct patterns `Path(..)`.
 344     TupleStruct(Span, &'a [Span]),
 345     // `m::A::B` in `<T as m::A>::B::C`.
 346     TraitItem(Namespace),
 347 }
 348
 349 impl<'a> PathSource<'a> {
 350     fn namespace(self) -> Namespace {
 351         match self {
 352             PathSource::Type | PathSource::Trait(_) | PathSource::Struct => TypeNS,
 353             PathSource::Expr(..) | PathSource::Pat | PathSource::TupleStruct(..) => ValueNS,
 354             PathSource::TraitItem(ns) => ns,
 355         }
 356     }
 357
 358     fn defer_to_typeck(self) -> bool {
 359         match self {
 360             PathSource::Type
 361             | PathSource::Expr(..)
 362             | PathSource::Pat
 363             | PathSource::Struct
 364             | PathSource::TupleStruct(..) => true,
 365             PathSource::Trait(_) | PathSource::TraitItem(..) => false,
 366         }
 367     }
 368
 369     fn descr_expected(self) -> &'static str {
 370         match &self {
 371             PathSource::Type => "type",
 372             PathSource::Trait(_) => "trait",
 373             PathSource::Pat => "unit struct, unit variant or constant",
 374             PathSource::Struct => "struct, variant or union type",
 375             PathSource::TupleStruct(..) => "tuple struct or tuple variant",
 376             PathSource::TraitItem(ns) => match ns {
 377                 TypeNS => "associated type",
 378                 ValueNS => "method or associated constant",
 379                 MacroNS => bug!("associated macro"),
 380             },
 381             PathSource::Expr(parent) => match parent.as_ref().map(|p| &p.kind) {
 382                 // "function" here means "anything callable" rather than `DefKind::Fn`,
 383                 // this is not precise but usually more helpful than just "value".
 384                 Some(ExprKind::Call(call_expr, _)) => match &call_expr.kind {
 385                     // the case of `::some_crate()`
 386                     ExprKind::Path(_, path)
 387                         if path.segments.len() == 2
 388                             && path.segments[0].ident.name == kw::PathRoot =>
 389                     {
 390                         "external crate"
 391                     }
 392                     ExprKind::Path(_, path) => {
 393                         let mut msg = "function";
 394                         if let Some(segment) = path.segments.iter().last() {
 395                             if let Some(c) = segment.ident.to_string().chars().next() {
 396                                 if c.is_uppercase() {
 397                                     msg = "function, tuple struct or tuple variant";
 398                                 }
 399                             }
 400                         }
 401                         msg
 402                     }
 403                     _ => "function",
 404                 },
 405                 _ => "value",
 406             },
 407         }
 408     }
 409
 410     fn is_call(self) -> bool {
 411         matches!(self, PathSource::Expr(Some(&Expr { kind: ExprKind::Call(..), .. })))
 412     }
 413
 414     pub(crate) fn is_expected(self, res: Res) -> bool {
 415         match self {
 416             PathSource::Type => matches!(
 417                 res,
 418                 Res::Def(
 419                     DefKind::Struct
 420                         | DefKind::Union
 421                         | DefKind::Enum
 422                         | DefKind::Trait
 423                         | DefKind::TraitAlias
 424                         | DefKind::TyAlias
 425                         | DefKind::AssocTy
 426                         | DefKind::TyParam
 427                         | DefKind::OpaqueTy
 428                         | DefKind::ForeignTy,
 429                     _,
 430                 ) | Res::PrimTy(..)
 431                     | Res::SelfTyParam { .. }
 432                     | Res::SelfTyAlias { .. }
 433             ),
 434             PathSource::Trait(AliasPossibility::No) => matches!(res, Res::Def(DefKind::Trait, _)),
 435             PathSource::Trait(AliasPossibility::Maybe) => {
 436                 matches!(res, Res::Def(DefKind::Trait | DefKind::TraitAlias, _))
 437             }
 438             PathSource::Expr(..) => matches!(
 439                 res,
 440                 Res::Def(
 441                     DefKind::Ctor(_, CtorKind::Const | CtorKind::Fn)
 442                         | DefKind::Const
 443                         | DefKind::Static(_)
 444                         | DefKind::Fn
 445                         | DefKind::AssocFn
 446                         | DefKind::AssocConst
 447                         | DefKind::ConstParam,
 448                     _,
 449                 ) | Res::Local(..)
 450                     | Res::SelfCtor(..)
 451             ),
 452             PathSource::Pat => {
 453                 res.expected_in_unit_struct_pat()
 454                     || matches!(res, Res::Def(DefKind::Const | DefKind::AssocConst, _))
 455             }
 456             PathSource::TupleStruct(..) => res.expected_in_tuple_struct_pat(),
 457             PathSource::Struct => matches!(
 458                 res,
 459                 Res::Def(
 460                     DefKind::Struct
 461                         | DefKind::Union
 462                         | DefKind::Variant
 463                         | DefKind::TyAlias
 464                         | DefKind::AssocTy,
 465                     _,
 466                 ) | Res::SelfTyParam { .. }
 467                     | Res::SelfTyAlias { .. }
 468             ),
 469             PathSource::TraitItem(ns) => match res {
 470                 Res::Def(DefKind::AssocConst | DefKind::AssocFn, _) if ns == ValueNS => true,
 471                 Res::Def(DefKind::AssocTy, _) if ns == TypeNS => true,
 472                 _ => false,
 473             },
 474         }
 475     }
 476
 477     fn error_code(self, has_unexpected_resolution: bool) -> DiagnosticId {
 478         use rustc_errors::error_code;
 479         match (self, has_unexpected_resolution) {
 480             (PathSource::Trait(_), true) => error_code!(E0404),
 481             (PathSource::Trait(_), false) => error_code!(E0405),
 482             (PathSource::Type, true) => error_code!(E0573),
 483             (PathSource::Type, false) => error_code!(E0412),
 484             (PathSource::Struct, true) => error_code!(E0574),
 485             (PathSource::Struct, false) => error_code!(E0422),
 486             (PathSource::Expr(..), true) => error_code!(E0423),
 487             (PathSource::Expr(..), false) => error_code!(E0425),
 488             (PathSource::Pat | PathSource::TupleStruct(..), true) => error_code!(E0532),
 489             (PathSource::Pat | PathSource::TupleStruct(..), false) => error_code!(E0531),
 490             (PathSource::TraitItem(..), true) => error_code!(E0575),
 491             (PathSource::TraitItem(..), false) => error_code!(E0576),
 492         }
 493     }
 494 }
 495
 496 #[derive(Default)]
 497 struct DiagnosticMetadata<'ast> {
 498     /// The current trait's associated items' ident, used for diagnostic suggestions.
 499     current_trait_assoc_items: Option<&'ast [P<AssocItem>]>,
 500
 501     /// The current self type if inside an impl (used for better errors).
 502     current_self_type: Option<Ty>,
 503
 504     /// The current self item if inside an ADT (used for better errors).
 505     current_self_item: Option<NodeId>,
 506
 507     /// The current trait (used to suggest).
 508     current_item: Option<&'ast Item>,
 509
 510     /// When processing generics and encountering a type not found, suggest introducing a type
 511     /// param.
 512     currently_processing_generics: bool,
 513
 514     /// The current enclosing (non-closure) function (used for better errors).
 515     current_function: Option<(FnKind<'ast>, Span)>,
 516
 517     /// A list of labels as of yet unused. Labels will be removed from this map when
 518     /// they are used (in a `break` or `continue` statement)
 519     unused_labels: FxHashMap<NodeId, Span>,
 520
 521     /// Only used for better errors on `fn(): fn()`.
 522     current_type_ascription: Vec<Span>,
 523
 524     /// Only used for better errors on `let x = { foo: bar };`.
 525     /// In the case of a parse error with `let x = { foo: bar, };`, this isn't needed, it's only
 526     /// needed for cases where this parses as a correct type ascription.
 527     current_block_could_be_bare_struct_literal: Option<Span>,
 528
 529     /// Only used for better errors on `let <pat>: <expr, not type>;`.
 530     current_let_binding: Option<(Span, Option<Span>, Option<Span>)>,
 531
 532     /// Used to detect possible `if let` written without `let` and to provide structured suggestion.
 533     in_if_condition: Option<&'ast Expr>,
 534
 535     /// Used to detect possible new binding written without `let` and to provide structured suggestion.
 536     in_assignment: Option<&'ast Expr>,
 537     is_assign_rhs: bool,
 538
 539     /// Used to detect possible `.` -> `..` typo when calling methods.
 540     in_range: Option<(&'ast Expr, &'ast Expr)>,
 541
 542     /// If we are currently in a trait object definition. Used to point at the bounds when
 543     /// encountering a struct or enum.
 544     current_trait_object: Option<&'ast [ast::GenericBound]>,
 545
 546     /// Given `where <T as Bar>::Baz: String`, suggest `where T: Bar<Baz = String>`.
 547     current_where_predicate: Option<&'ast WherePredicate>,
 548
 549     current_type_path: Option<&'ast Ty>,
 550
 551     /// The current impl items (used to suggest).
 552     current_impl_items: Option<&'ast [P<AssocItem>]>,
 553
 554     /// When processing impl trait
 555     currently_processing_impl_trait: Option<(TraitRef, Ty)>,
 556
 557     /// Accumulate the errors due to missed lifetime elision,
 558     /// and report them all at once for each function.
 559     current_elision_failures: Vec<MissingLifetime>,
 560 }
 561
 562 struct LateResolutionVisitor<'a, 'b, 'ast> {
 563     r: &'b mut Resolver<'a>,
 564
 565     /// The module that represents the current item scope.
 566     parent_scope: ParentScope<'a>,
 567
 568     /// The current set of local scopes for types and values.
 569     /// FIXME #4948: Reuse ribs to avoid allocation.
 570     ribs: PerNS<Vec<Rib<'a>>>,
 571
 572     /// Previous poped `rib`, only used for diagnostic.
 573     last_block_rib: Option<Rib<'a>>,
 574
 575     /// The current set of local scopes, for labels.
 576     label_ribs: Vec<Rib<'a, NodeId>>,
 577
 578     /// The current set of local scopes for lifetimes.
 579     lifetime_ribs: Vec<LifetimeRib>,
 580
 581     /// We are looking for lifetimes in an elision context.
 582     /// The set contains all the resolutions that we encountered so far.
 583     /// They will be used to determine the correct lifetime for the fn return type.
 584     /// The `LifetimeElisionCandidate` is used for diagnostics, to suggest introducing named
 585     /// lifetimes.
 586     lifetime_elision_candidates: Option<Vec<(LifetimeRes, LifetimeElisionCandidate)>>,
 587
 588     /// The trait that the current context can refer to.
 589     current_trait_ref: Option<(Module<'a>, TraitRef)>,
 590
 591     /// Fields used to add information to diagnostic errors.
 592     diagnostic_metadata: Box<DiagnosticMetadata<'ast>>,
 593
 594     /// State used to know whether to ignore resolution errors for function bodies.
 595     ///
 596     /// In particular, rustdoc uses this to avoid giving errors for `cfg()` items.
 597     /// In most cases this will be `None`, in which case errors will always be reported.
 598     /// If it is `true`, then it will be updated when entering a nested function or trait body.
 599     in_func_body: bool,
 600
 601     /// Count the number of places a lifetime is used.
 602     lifetime_uses: FxHashMap<LocalDefId, LifetimeUseSet>,
 603 }
 604
 605 /// Walks the whole crate in DFS order, visiting each item, resolving names as it goes.
 606 impl<'a: 'ast, 'ast> Visitor<'ast> for LateResolutionVisitor<'a, '_, 'ast> {
 607     fn visit_attribute(&mut self, _: &'ast Attribute) {
 608         // We do not want to resolve expressions that appear in attributes,
 609         // as they do not correspond to actual code.
 610     }
 611     fn visit_item(&mut self, item: &'ast Item) {
 612         let prev = replace(&mut self.diagnostic_metadata.current_item, Some(item));
 613         // Always report errors in items we just entered.
 614         let old_ignore = replace(&mut self.in_func_body, false);
 615         self.with_lifetime_rib(LifetimeRibKind::Item, |this| this.resolve_item(item));
 616         self.in_func_body = old_ignore;
 617         self.diagnostic_metadata.current_item = prev;
 618     }
 619     fn visit_arm(&mut self, arm: &'ast Arm) {
 620         self.resolve_arm(arm);
 621     }
 622     fn visit_block(&mut self, block: &'ast Block) {
 623         self.resolve_block(block);
 624     }
 625     fn visit_anon_const(&mut self, constant: &'ast AnonConst) {
 626         // We deal with repeat expressions explicitly in `resolve_expr`.
 627         self.with_lifetime_rib(LifetimeRibKind::AnonConst, |this| {
 628             this.with_lifetime_rib(LifetimeRibKind::Elided(LifetimeRes::Static), |this| {
 629                 this.resolve_anon_const(constant, IsRepeatExpr::No);
 630             })
 631         })
 632     }
 633     fn visit_expr(&mut self, expr: &'ast Expr) {
 634         self.resolve_expr(expr, None);
 635     }
 636     fn visit_local(&mut self, local: &'ast Local) {
 637         let local_spans = match local.pat.kind {
 638             // We check for this to avoid tuple struct fields.
 639             PatKind::Wild => None,
 640             _ => Some((
 641                 local.pat.span,
 642                 local.ty.as_ref().map(|ty| ty.span),
 643                 local.kind.init().map(|init| init.span),
 644             )),
 645         };
 646         let original = replace(&mut self.diagnostic_metadata.current_let_binding, local_spans);
 647         self.resolve_local(local);
 648         self.diagnostic_metadata.current_let_binding = original;
 649     }
 650     fn visit_ty(&mut self, ty: &'ast Ty) {
 651         let prev = self.diagnostic_metadata.current_trait_object;
 652         let prev_ty = self.diagnostic_metadata.current_type_path;
 653         match ty.kind {
 654             TyKind::Ref(None, _) => {
 655                 // Elided lifetime in reference: we resolve as if there was some lifetime `'_` with
 656                 // NodeId `ty.id`.
 657                 // This span will be used in case of elision failure.
 658                 let span = self.r.session.source_map().start_point(ty.span);
 659                 self.resolve_elided_lifetime(ty.id, span);
 660                 visit::walk_ty(self, ty);
 661             }
 662             TyKind::Path(ref qself, ref path) => {
 663                 self.diagnostic_metadata.current_type_path = Some(ty);
 664                 self.smart_resolve_path(ty.id, &qself, path, PathSource::Type);
 665
 666                 // Check whether we should interpret this as a bare trait object.
 667                 if qself.is_none()
 668                     && let Some(partial_res) = self.r.partial_res_map.get(&ty.id)
 669                     && let Some(Res::Def(DefKind::Trait | DefKind::TraitAlias, _)) = partial_res.full_res()
 670                 {
 671                     // This path is actually a bare trait object.  In case of a bare `Fn`-trait
 672                     // object with anonymous lifetimes, we need this rib to correctly place the
 673                     // synthetic lifetimes.
 674                     let span = ty.span.shrink_to_lo().to(path.span.shrink_to_lo());
 675                     self.with_generic_param_rib(
 676                         &[],
 677                         NormalRibKind,
 678                         LifetimeRibKind::Generics {
 679                             binder: ty.id,
 680                             kind: LifetimeBinderKind::PolyTrait,
 681                             span,
 682                         },
 683                         |this| this.visit_path(&path, ty.id),
 684                     );
 685                 } else {
 686                     visit::walk_ty(self, ty)
 687                 }
 688             }
 689             TyKind::ImplicitSelf => {
 690                 let self_ty = Ident::with_dummy_span(kw::SelfUpper);
 691                 let res = self
 692                     .resolve_ident_in_lexical_scope(
 693                         self_ty,
 694                         TypeNS,
 695                         Some(Finalize::new(ty.id, ty.span)),
 696                         None,
 697                     )
 698                     .map_or(Res::Err, |d| d.res());
 699                 self.r.record_partial_res(ty.id, PartialRes::new(res));
 700                 visit::walk_ty(self, ty)
 701             }
 702             TyKind::ImplTrait(..) => {
 703                 let candidates = self.lifetime_elision_candidates.take();
 704                 visit::walk_ty(self, ty);
 705                 self.lifetime_elision_candidates = candidates;
 706             }
 707             TyKind::TraitObject(ref bounds, ..) => {
 708                 self.diagnostic_metadata.current_trait_object = Some(&bounds[..]);
 709                 visit::walk_ty(self, ty)
 710             }
 711             TyKind::BareFn(ref bare_fn) => {
 712                 let span = ty.span.shrink_to_lo().to(bare_fn.decl_span.shrink_to_lo());
 713                 self.with_generic_param_rib(
 714                     &bare_fn.generic_params,
 715                     NormalRibKind,
 716                     LifetimeRibKind::Generics {
 717                         binder: ty.id,
 718                         kind: LifetimeBinderKind::BareFnType,
 719                         span,
 720                     },
 721                     |this| {
 722                         this.visit_generic_params(&bare_fn.generic_params, false);
 723                         this.with_lifetime_rib(
 724                             LifetimeRibKind::AnonymousCreateParameter {
 725                                 binder: ty.id,
 726                                 report_in_path: false,
 727                             },
 728                             |this| {
 729                                 this.resolve_fn_signature(
 730                                     ty.id,
 731                                     false,
 732                                     // We don't need to deal with patterns in parameters, because
 733                                     // they are not possible for foreign or bodiless functions.
 734                                     bare_fn
 735                                         .decl
 736                                         .inputs
 737                                         .iter()
 738                                         .map(|Param { ty, .. }| (None, &**ty)),
 739                                     &bare_fn.decl.output,
 740                                 )
 741                             },
 742                         );
 743                     },
 744                 )
 745             }
 746             _ => visit::walk_ty(self, ty),
 747         }
 748         self.diagnostic_metadata.current_trait_object = prev;
 749         self.diagnostic_metadata.current_type_path = prev_ty;
 750     }
 751     fn visit_poly_trait_ref(&mut self, tref: &'ast PolyTraitRef) {
 752         let span = tref.span.shrink_to_lo().to(tref.trait_ref.path.span.shrink_to_lo());
 753         self.with_generic_param_rib(
 754             &tref.bound_generic_params,
 755             NormalRibKind,
 756             LifetimeRibKind::Generics {
 757                 binder: tref.trait_ref.ref_id,
 758                 kind: LifetimeBinderKind::PolyTrait,
 759                 span,
 760             },
 761             |this| {
 762                 this.visit_generic_params(&tref.bound_generic_params, false);
 763                 this.smart_resolve_path(
 764                     tref.trait_ref.ref_id,
 765                     &None,
 766                     &tref.trait_ref.path,
 767                     PathSource::Trait(AliasPossibility::Maybe),
 768                 );
 769                 this.visit_trait_ref(&tref.trait_ref);
 770             },
 771         );
 772     }
 773     fn visit_foreign_item(&mut self, foreign_item: &'ast ForeignItem) {
 774         match foreign_item.kind {
 775             ForeignItemKind::TyAlias(box TyAlias { ref generics, .. }) => {
 776                 self.with_generic_param_rib(
 777                     &generics.params,
 778                     ItemRibKind(HasGenericParams::Yes(generics.span)),
 779                     LifetimeRibKind::Generics {
 780                         binder: foreign_item.id,
 781                         kind: LifetimeBinderKind::Item,
 782                         span: generics.span,
 783                     },
 784                     |this| visit::walk_foreign_item(this, foreign_item),
 785                 );
 786             }
 787             ForeignItemKind::Fn(box Fn { ref generics, .. }) => {
 788                 self.with_generic_param_rib(
 789                     &generics.params,
 790                     ItemRibKind(HasGenericParams::Yes(generics.span)),
 791                     LifetimeRibKind::Generics {
 792                         binder: foreign_item.id,
 793                         kind: LifetimeBinderKind::Function,
 794                         span: generics.span,
 795                     },
 796                     |this| visit::walk_foreign_item(this, foreign_item),
 797                 );
 798             }
 799             ForeignItemKind::Static(..) => {
 800                 self.with_static_rib(|this| {
 801                     visit::walk_foreign_item(this, foreign_item);
 802                 });
 803             }
 804             ForeignItemKind::MacCall(..) => {
 805                 panic!("unexpanded macro in resolve!")
 806             }
 807         }
 808     }
 809     fn visit_fn(&mut self, fn_kind: FnKind<'ast>, sp: Span, fn_id: NodeId) {
 810         let previous_value = self.diagnostic_metadata.current_function;
 811         match fn_kind {
 812             // Bail if the function is foreign, and thus cannot validly have
 813             // a body, or if there's no body for some other reason.
 814             FnKind::Fn(FnCtxt::Foreign, _, sig, _, generics, _)
 815             | FnKind::Fn(_, _, sig, _, generics, None) => {
 816                 self.visit_fn_header(&sig.header);
 817                 self.visit_generics(generics);
 818                 self.with_lifetime_rib(
 819                     LifetimeRibKind::AnonymousCreateParameter {
 820                         binder: fn_id,
 821                         report_in_path: false,
 822                     },
 823                     |this| {
 824                         this.resolve_fn_signature(
 825                             fn_id,
 826                             sig.decl.has_self(),
 827                             sig.decl.inputs.iter().map(|Param { ty, .. }| (None, &**ty)),
 828                             &sig.decl.output,
 829                         );
 830
 831                         this.record_lifetime_params_for_async(
 832                             fn_id,
 833                             sig.header.asyncness.opt_return_id(),
 834                         );
 835                     },
 836                 );
 837                 return;
 838             }
 839             FnKind::Fn(..) => {
 840                 self.diagnostic_metadata.current_function = Some((fn_kind, sp));
 841             }
 842             // Do not update `current_function` for closures: it suggests `self` parameters.
 843             FnKind::Closure(..) => {}
 844         };
 845         debug!("(resolving function) entering function");
 846
 847         // Create a value rib for the function.
 848         self.with_rib(ValueNS, ClosureOrAsyncRibKind, |this| {
 849             // Create a label rib for the function.
 850             this.with_label_rib(ClosureOrAsyncRibKind, |this| {
 851                 match fn_kind {
 852                     FnKind::Fn(_, _, sig, _, generics, body) => {
 853                         this.visit_generics(generics);
 854
 855                         let declaration = &sig.decl;
 856                         let async_node_id = sig.header.asyncness.opt_return_id();
 857
 858                         this.with_lifetime_rib(
 859                             LifetimeRibKind::AnonymousCreateParameter {
 860                                 binder: fn_id,
 861                                 report_in_path: async_node_id.is_some(),
 862                             },
 863                             |this| {
 864                                 this.resolve_fn_signature(
 865                                     fn_id,
 866                                     declaration.has_self(),
 867                                     declaration
 868                                         .inputs
 869                                         .iter()
 870                                         .map(|Param { pat, ty, .. }| (Some(&**pat), &**ty)),
 871                                     &declaration.output,
 872                                 )
 873                             },
 874                         );
 875
 876                         this.record_lifetime_params_for_async(fn_id, async_node_id);
 877
 878                         if let Some(body) = body {
 879                             // Ignore errors in function bodies if this is rustdoc
 880                             // Be sure not to set this until the function signature has been resolved.
 881                             let previous_state = replace(&mut this.in_func_body, true);
 882                             // We only care block in the same function
 883                             this.last_block_rib = None;
 884                             // Resolve the function body, potentially inside the body of an async closure
 885                             this.with_lifetime_rib(
 886                                 LifetimeRibKind::Elided(LifetimeRes::Infer),
 887                                 |this| this.visit_block(body),
 888                             );
 889
 890                             debug!("(resolving function) leaving function");
 891                             this.in_func_body = previous_state;
 892                         }
 893                     }
 894                     FnKind::Closure(binder, declaration, body) => {
 895                         this.visit_closure_binder(binder);
 896
 897                         this.with_lifetime_rib(
 898                             match binder {
 899                                 // We do not have any explicit generic lifetime parameter.
 900                                 ClosureBinder::NotPresent => {
 901                                     LifetimeRibKind::AnonymousCreateParameter {
 902                                         binder: fn_id,
 903                                         report_in_path: false,
 904                                     }
 905                                 }
 906                                 ClosureBinder::For { .. } => LifetimeRibKind::AnonymousReportError,
 907                             },
 908                             // Add each argument to the rib.
 909                             |this| this.resolve_params(&declaration.inputs),
 910                         );
 911                         this.with_lifetime_rib(
 912                             match binder {
 913                                 ClosureBinder::NotPresent => {
 914                                     LifetimeRibKind::Elided(LifetimeRes::Infer)
 915                                 }
 916                                 ClosureBinder::For { .. } => LifetimeRibKind::AnonymousReportError,
 917                             },
 918                             |this| visit::walk_fn_ret_ty(this, &declaration.output),
 919                         );
 920
 921                         // Ignore errors in function bodies if this is rustdoc
 922                         // Be sure not to set this until the function signature has been resolved.
 923                         let previous_state = replace(&mut this.in_func_body, true);
 924                         // Resolve the function body, potentially inside the body of an async closure
 925                         this.with_lifetime_rib(
 926                             LifetimeRibKind::Elided(LifetimeRes::Infer),
 927                             |this| this.visit_expr(body),
 928                         );
 929
 930                         debug!("(resolving function) leaving function");
 931                         this.in_func_body = previous_state;
 932                     }
 933                 }
 934             })
 935         });
 936         self.diagnostic_metadata.current_function = previous_value;
 937     }
 938     fn visit_lifetime(&mut self, lifetime: &'ast Lifetime, use_ctxt: visit::LifetimeCtxt) {
 939         self.resolve_lifetime(lifetime, use_ctxt)
 940     }
 941
 942     fn visit_generics(&mut self, generics: &'ast Generics) {
 943         self.visit_generic_params(
 944             &generics.params,
 945             self.diagnostic_metadata.current_self_item.is_some(),
 946         );
 947         for p in &generics.where_clause.predicates {
 948             self.visit_where_predicate(p);
 949         }
 950     }
 951
 952     fn visit_closure_binder(&mut self, b: &'ast ClosureBinder) {
 953         match b {
 954             ClosureBinder::NotPresent => {}
 955             ClosureBinder::For { generic_params, .. } => {
 956                 self.visit_generic_params(
 957                     &generic_params,
 958                     self.diagnostic_metadata.current_self_item.is_some(),
 959                 );
 960             }
 961         }
 962     }
 963
 964     fn visit_generic_arg(&mut self, arg: &'ast GenericArg) {
 965         debug!("visit_generic_arg({:?})", arg);
 966         let prev = replace(&mut self.diagnostic_metadata.currently_processing_generics, true);
 967         match arg {
 968             GenericArg::Type(ref ty) => {
 969                 // We parse const arguments as path types as we cannot distinguish them during
 970                 // parsing. We try to resolve that ambiguity by attempting resolution the type
 971                 // namespace first, and if that fails we try again in the value namespace. If
 972                 // resolution in the value namespace succeeds, we have an generic const argument on
 973                 // our hands.
 974                 if let TyKind::Path(ref qself, ref path) = ty.kind {
 975                     // We cannot disambiguate multi-segment paths right now as that requires type
 976                     // checking.
 977                     if path.segments.len() == 1 && path.segments[0].args.is_none() {
 978                         let mut check_ns = |ns| {
 979                             self.maybe_resolve_ident_in_lexical_scope(path.segments[0].ident, ns)
 980                                 .is_some()
 981                         };
 982                         if !check_ns(TypeNS) && check_ns(ValueNS) {
 983                             // This must be equivalent to `visit_anon_const`, but we cannot call it
 984                             // directly due to visitor lifetimes so we have to copy-paste some code.
 985                             //
 986                             // Note that we might not be inside of an repeat expression here,
 987                             // but considering that `IsRepeatExpr` is only relevant for
 988                             // non-trivial constants this is doesn't matter.
 989                             self.with_constant_rib(
 990                                 IsRepeatExpr::No,
 991                                 ConstantHasGenerics::Yes,
 992                                 None,
 993                                 |this| {
 994                                     this.smart_resolve_path(
 995                                         ty.id,
 996                                         qself,
 997                                         path,
 998                                         PathSource::Expr(None),
 999                                     );
1000
1001                                     if let Some(ref qself) = *qself {
1002                                         this.visit_ty(&qself.ty);
1003                                     }
1004                                     this.visit_path(path, ty.id);
1005                                 },
1006                             );
1007
1008                             self.diagnostic_metadata.currently_processing_generics = prev;
1009                             return;
1010                         }
1011                     }
1012                 }
1013
1014                 self.visit_ty(ty);
1015             }
1016             GenericArg::Lifetime(lt) => self.visit_lifetime(lt, visit::LifetimeCtxt::GenericArg),
1017             GenericArg::Const(ct) => self.visit_anon_const(ct),
1018         }
1019         self.diagnostic_metadata.currently_processing_generics = prev;
1020     }
1021
1022     fn visit_assoc_constraint(&mut self, constraint: &'ast AssocConstraint) {
1023         self.visit_ident(constraint.ident);
1024         if let Some(ref gen_args) = constraint.gen_args {
1025             // Forbid anonymous lifetimes in GAT parameters until proper semantics are decided.
1026             self.with_lifetime_rib(LifetimeRibKind::AnonymousReportError, |this| {
1027                 this.visit_generic_args(gen_args)
1028             });
1029         }
1030         match constraint.kind {
1031             AssocConstraintKind::Equality { ref term } => match term {
1032                 Term::Ty(ty) => self.visit_ty(ty),
1033                 Term::Const(c) => self.visit_anon_const(c),
1034             },
1035             AssocConstraintKind::Bound { ref bounds } => {
1036                 walk_list!(self, visit_param_bound, bounds, BoundKind::Bound);
1037             }
1038         }
1039     }
1040
1041     fn visit_path_segment(&mut self, path_segment: &'ast PathSegment) {
1042         if let Some(ref args) = path_segment.args {
1043             match &**args {
1044                 GenericArgs::AngleBracketed(..) => visit::walk_generic_args(self, args),
1045                 GenericArgs::Parenthesized(p_args) => {
1046                     // Probe the lifetime ribs to know how to behave.
1047                     for rib in self.lifetime_ribs.iter().rev() {
1048                         match rib.kind {
1049                             // We are inside a `PolyTraitRef`.  The lifetimes are
1050                             // to be intoduced in that (maybe implicit) `for<>` binder.
1051                             LifetimeRibKind::Generics {
1052                                 binder,
1053                                 kind: LifetimeBinderKind::PolyTrait,
1054                                 ..
1055                             } => {
1056                                 self.with_lifetime_rib(
1057                                     LifetimeRibKind::AnonymousCreateParameter {
1058                                         binder,
1059                                         report_in_path: false,
1060                                     },
1061                                     |this| {
1062                                         this.resolve_fn_signature(
1063                                             binder,
1064                                             false,
1065                                             p_args.inputs.iter().map(|ty| (None, &**ty)),
1066                                             &p_args.output,
1067                                         )
1068                                     },
1069                                 );
1070                                 break;
1071                             }
1072                             // We have nowhere to introduce generics.  Code is malformed,
1073                             // so use regular lifetime resolution to avoid spurious errors.
1074                             LifetimeRibKind::Item | LifetimeRibKind::Generics { .. } => {
1075                                 visit::walk_generic_args(self, args);
1076                                 break;
1077                             }
1078                             LifetimeRibKind::AnonymousCreateParameter { .. }
1079                             | LifetimeRibKind::AnonymousReportError
1080                             | LifetimeRibKind::Elided(_)
1081                             | LifetimeRibKind::ElisionFailure
1082                             | LifetimeRibKind::AnonConst
1083                             | LifetimeRibKind::ConstGeneric => {}
1084                         }
1085                     }
1086                 }
1087             }
1088         }
1089     }
1090
1091     fn visit_where_predicate(&mut self, p: &'ast WherePredicate) {
1092         debug!("visit_where_predicate {:?}", p);
1093         let previous_value =
1094             replace(&mut self.diagnostic_metadata.current_where_predicate, Some(p));
1095         self.with_lifetime_rib(LifetimeRibKind::AnonymousReportError, |this| {
1096             if let WherePredicate::BoundPredicate(WhereBoundPredicate {
1097                 ref bounded_ty,
1098                 ref bounds,
1099                 ref bound_generic_params,
1100                 span: predicate_span,
1101                 ..
1102             }) = p
1103             {
1104                 let span = predicate_span.shrink_to_lo().to(bounded_ty.span.shrink_to_lo());
1105                 this.with_generic_param_rib(
1106                     &bound_generic_params,
1107                     NormalRibKind,
1108                     LifetimeRibKind::Generics {
1109                         binder: bounded_ty.id,
1110                         kind: LifetimeBinderKind::WhereBound,
1111                         span,
1112                     },
1113                     |this| {
1114                         this.visit_generic_params(&bound_generic_params, false);
1115                         this.visit_ty(bounded_ty);
1116                         for bound in bounds {
1117                             this.visit_param_bound(bound, BoundKind::Bound)
1118                         }
1119                     },
1120                 );
1121             } else {
1122                 visit::walk_where_predicate(this, p);
1123             }
1124         });
1125         self.diagnostic_metadata.current_where_predicate = previous_value;
1126     }
1127
1128     fn visit_inline_asm(&mut self, asm: &'ast InlineAsm) {
1129         for (op, _) in &asm.operands {
1130             match op {
1131                 InlineAsmOperand::In { expr, .. }
1132                 | InlineAsmOperand::Out { expr: Some(expr), .. }
1133                 | InlineAsmOperand::InOut { expr, .. } => self.visit_expr(expr),
1134                 InlineAsmOperand::Out { expr: None, .. } => {}
1135                 InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
1136                     self.visit_expr(in_expr);
1137                     if let Some(out_expr) = out_expr {
1138                         self.visit_expr(out_expr);
1139                     }
1140                 }
1141                 InlineAsmOperand::Const { anon_const, .. } => {
1142                     // Although this is `DefKind::AnonConst`, it is allowed to reference outer
1143                     // generic parameters like an inline const.
1144                     self.resolve_inline_const(anon_const);
1145                 }
1146                 InlineAsmOperand::Sym { sym } => self.visit_inline_asm_sym(sym),
1147             }
1148         }
1149     }
1150
1151     fn visit_inline_asm_sym(&mut self, sym: &'ast InlineAsmSym) {
1152         // This is similar to the code for AnonConst.
1153         self.with_rib(ValueNS, InlineAsmSymRibKind, |this| {
1154             this.with_rib(TypeNS, InlineAsmSymRibKind, |this| {
1155                 this.with_label_rib(InlineAsmSymRibKind, |this| {
1156                     this.smart_resolve_path(sym.id, &sym.qself, &sym.path, PathSource::Expr(None));
1157                     visit::walk_inline_asm_sym(this, sym);
1158                 });
1159             })
1160         });
1161     }
1162 }
1163
1164 impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
1165     fn new(resolver: &'b mut Resolver<'a>) -> LateResolutionVisitor<'a, 'b, 'ast> {
1166         // During late resolution we only track the module component of the parent scope,
1167         // although it may be useful to track other components as well for diagnostics.
1168         let graph_root = resolver.graph_root;
1169         let parent_scope = ParentScope::module(graph_root, resolver);
1170         let start_rib_kind = ModuleRibKind(graph_root);
1171         LateResolutionVisitor {
1172             r: resolver,
1173             parent_scope,
1174             ribs: PerNS {
1175                 value_ns: vec![Rib::new(start_rib_kind)],
1176                 type_ns: vec![Rib::new(start_rib_kind)],
1177                 macro_ns: vec![Rib::new(start_rib_kind)],
1178             },
1179             last_block_rib: None,
1180             label_ribs: Vec::new(),
1181             lifetime_ribs: Vec::new(),
1182             lifetime_elision_candidates: None,
1183             current_trait_ref: None,
1184             diagnostic_metadata: Box::new(DiagnosticMetadata::default()),
1185             // errors at module scope should always be reported
1186             in_func_body: false,
1187             lifetime_uses: Default::default(),
1188         }
1189     }
1190
1191     fn maybe_resolve_ident_in_lexical_scope(
1192         &mut self,
1193         ident: Ident,
1194         ns: Namespace,
1195     ) -> Option<LexicalScopeBinding<'a>> {
1196         self.r.resolve_ident_in_lexical_scope(
1197             ident,
1198             ns,
1199             &self.parent_scope,
1200             None,
1201             &self.ribs[ns],
1202             None,
1203         )
1204     }
1205
1206     fn resolve_ident_in_lexical_scope(
1207         &mut self,
1208         ident: Ident,
1209         ns: Namespace,
1210         finalize: Option<Finalize>,
1211         ignore_binding: Option<&'a NameBinding<'a>>,
1212     ) -> Option<LexicalScopeBinding<'a>> {
1213         self.r.resolve_ident_in_lexical_scope(
1214             ident,
1215             ns,
1216             &self.parent_scope,
1217             finalize,
1218             &self.ribs[ns],
1219             ignore_binding,
1220         )
1221     }
1222
1223     fn resolve_path(
1224         &mut self,
1225         path: &[Segment],
1226         opt_ns: Option<Namespace>, // `None` indicates a module path in import
1227         finalize: Option<Finalize>,
1228     ) -> PathResult<'a> {
1229         self.r.resolve_path_with_ribs(
1230             path,
1231             opt_ns,
1232             &self.parent_scope,
1233             finalize,
1234             Some(&self.ribs),
1235             None,
1236         )
1237     }
1238
1239     // AST resolution
1240     //
1241     // We maintain a list of value ribs and type ribs.
1242     //
1243     // Simultaneously, we keep track of the current position in the module
1244     // graph in the `parent_scope.module` pointer. When we go to resolve a name in
1245     // the value or type namespaces, we first look through all the ribs and
1246     // then query the module graph. When we resolve a name in the module
1247     // namespace, we can skip all the ribs (since nested modules are not
1248     // allowed within blocks in Rust) and jump straight to the current module
1249     // graph node.
1250     //
1251     // Named implementations are handled separately. When we find a method
1252     // call, we consult the module node to find all of the implementations in
1253     // scope. This information is lazily cached in the module node. We then
1254     // generate a fake "implementation scope" containing all the
1255     // implementations thus found, for compatibility with old resolve pass.
1256
1257     /// Do some `work` within a new innermost rib of the given `kind` in the given namespace (`ns`).
1258     fn with_rib<T>(
1259         &mut self,
1260         ns: Namespace,
1261         kind: RibKind<'a>,
1262         work: impl FnOnce(&mut Self) -> T,
1263     ) -> T {
1264         self.ribs[ns].push(Rib::new(kind));
1265         let ret = work(self);
1266         self.ribs[ns].pop();
1267         ret
1268     }
1269
1270     fn with_scope<T>(&mut self, id: NodeId, f: impl FnOnce(&mut Self) -> T) -> T {
1271         if let Some(module) = self.r.get_module(self.r.local_def_id(id).to_def_id()) {
1272             // Move down in the graph.
1273             let orig_module = replace(&mut self.parent_scope.module, module);
1274             self.with_rib(ValueNS, ModuleRibKind(module), |this| {
1275                 this.with_rib(TypeNS, ModuleRibKind(module), |this| {
1276                     let ret = f(this);
1277                     this.parent_scope.module = orig_module;
1278                     ret
1279                 })
1280             })
1281         } else {
1282             f(self)
1283         }
1284     }
1285
1286     fn visit_generic_params(&mut self, params: &'ast [GenericParam], add_self_upper: bool) {
1287         // For type parameter defaults, we have to ban access
1288         // to following type parameters, as the InternalSubsts can only
1289         // provide previous type parameters as they're built. We
1290         // put all the parameters on the ban list and then remove
1291         // them one by one as they are processed and become available.
1292         let mut forward_ty_ban_rib = Rib::new(ForwardGenericParamBanRibKind);
1293         let mut forward_const_ban_rib = Rib::new(ForwardGenericParamBanRibKind);
1294         for param in params.iter() {
1295             match param.kind {
1296                 GenericParamKind::Type { .. } => {
1297                     forward_ty_ban_rib
1298                         .bindings
1299                         .insert(Ident::with_dummy_span(param.ident.name), Res::Err);
1300                 }
1301                 GenericParamKind::Const { .. } => {
1302                     forward_const_ban_rib
1303                         .bindings
1304                         .insert(Ident::with_dummy_span(param.ident.name), Res::Err);
1305                 }
1306                 GenericParamKind::Lifetime => {}
1307             }
1308         }
1309
1310         // rust-lang/rust#61631: The type `Self` is essentially
1311         // another type parameter. For ADTs, we consider it
1312         // well-defined only after all of the ADT type parameters have
1313         // been provided. Therefore, we do not allow use of `Self`
1314         // anywhere in ADT type parameter defaults.
1315         //
1316         // (We however cannot ban `Self` for defaults on *all* generic
1317         // lists; e.g. trait generics can usefully refer to `Self`,
1318         // such as in the case of `trait Add<Rhs = Self>`.)
1319         if add_self_upper {
1320             // (`Some` if + only if we are in ADT's generics.)
1321             forward_ty_ban_rib.bindings.insert(Ident::with_dummy_span(kw::SelfUpper), Res::Err);
1322         }
1323
1324         self.with_lifetime_rib(LifetimeRibKind::AnonymousReportError, |this| {
1325             for param in params {
1326                 match param.kind {
1327                     GenericParamKind::Lifetime => {
1328                         for bound in &param.bounds {
1329                             this.visit_param_bound(bound, BoundKind::Bound);
1330                         }
1331                     }
1332                     GenericParamKind::Type { ref default } => {
1333                         for bound in &param.bounds {
1334                             this.visit_param_bound(bound, BoundKind::Bound);
1335                         }
1336
1337                         if let Some(ref ty) = default {
1338                             this.ribs[TypeNS].push(forward_ty_ban_rib);
1339                             this.ribs[ValueNS].push(forward_const_ban_rib);
1340                             this.visit_ty(ty);
1341                             forward_const_ban_rib = this.ribs[ValueNS].pop().unwrap();
1342                             forward_ty_ban_rib = this.ribs[TypeNS].pop().unwrap();
1343                         }
1344
1345                         // Allow all following defaults to refer to this type parameter.
1346                         forward_ty_ban_rib
1347                             .bindings
1348                             .remove(&Ident::with_dummy_span(param.ident.name));
1349                     }
1350                     GenericParamKind::Const { ref ty, kw_span: _, ref default } => {
1351                         // Const parameters can't have param bounds.
1352                         assert!(param.bounds.is_empty());
1353
1354                         this.ribs[TypeNS].push(Rib::new(ConstParamTyRibKind));
1355                         this.ribs[ValueNS].push(Rib::new(ConstParamTyRibKind));
1356                         this.with_lifetime_rib(LifetimeRibKind::ConstGeneric, |this| {
1357                             this.visit_ty(ty)
1358                         });
1359                         this.ribs[TypeNS].pop().unwrap();
1360                         this.ribs[ValueNS].pop().unwrap();
1361
1362                         if let Some(ref expr) = default {
1363                             this.ribs[TypeNS].push(forward_ty_ban_rib);
1364                             this.ribs[ValueNS].push(forward_const_ban_rib);
1365                             this.with_lifetime_rib(LifetimeRibKind::ConstGeneric, |this| {
1366                                 this.resolve_anon_const(expr, IsRepeatExpr::No)
1367                             });
1368                             forward_const_ban_rib = this.ribs[ValueNS].pop().unwrap();
1369                             forward_ty_ban_rib = this.ribs[TypeNS].pop().unwrap();
1370                         }
1371
1372                         // Allow all following defaults to refer to this const parameter.
1373                         forward_const_ban_rib
1374                             .bindings
1375                             .remove(&Ident::with_dummy_span(param.ident.name));
1376                     }
1377                 }
1378             }
1379         })
1380     }
1381
1382     #[instrument(level = "debug", skip(self, work))]
1383     fn with_lifetime_rib<T>(
1384         &mut self,
1385         kind: LifetimeRibKind,
1386         work: impl FnOnce(&mut Self) -> T,
1387     ) -> T {
1388         self.lifetime_ribs.push(LifetimeRib::new(kind));
1389         let outer_elision_candidates = self.lifetime_elision_candidates.take();
1390         let ret = work(self);
1391         self.lifetime_elision_candidates = outer_elision_candidates;
1392         self.lifetime_ribs.pop();
1393         ret
1394     }
1395
1396     #[instrument(level = "debug", skip(self))]
1397     fn resolve_lifetime(&mut self, lifetime: &'ast Lifetime, use_ctxt: visit::LifetimeCtxt) {
1398         let ident = lifetime.ident;
1399
1400         if ident.name == kw::StaticLifetime {
1401             self.record_lifetime_res(
1402                 lifetime.id,
1403                 LifetimeRes::Static,
1404                 LifetimeElisionCandidate::Named,
1405             );
1406             return;
1407         }
1408
1409         if ident.name == kw::UnderscoreLifetime {
1410             return self.resolve_anonymous_lifetime(lifetime, false);
1411         }
1412
1413         let mut lifetime_rib_iter = self.lifetime_ribs.iter().rev();
1414         while let Some(rib) = lifetime_rib_iter.next() {
1415             let normalized_ident = ident.normalize_to_macros_2_0();
1416             if let Some(&(_, res)) = rib.bindings.get(&normalized_ident) {
1417                 self.record_lifetime_res(lifetime.id, res, LifetimeElisionCandidate::Named);
1418
1419                 if let LifetimeRes::Param { param, .. } = res {
1420                     match self.lifetime_uses.entry(param) {
1421                         Entry::Vacant(v) => {
1422                             debug!("First use of {:?} at {:?}", res, ident.span);
1423                             let use_set = self
1424                                 .lifetime_ribs
1425                                 .iter()
1426                                 .rev()
1427                                 .find_map(|rib| match rib.kind {
1428                                     // Do not suggest eliding a lifetime where an anonymous
1429                                     // lifetime would be illegal.
1430                                     LifetimeRibKind::Item
1431                                     | LifetimeRibKind::AnonymousReportError
1432                                     | LifetimeRibKind::ElisionFailure => Some(LifetimeUseSet::Many),
1433                                     // An anonymous lifetime is legal here, go ahead.
1434                                     LifetimeRibKind::AnonymousCreateParameter { .. } => {
1435                                         Some(LifetimeUseSet::One { use_span: ident.span, use_ctxt })
1436                                     }
1437                                     // Only report if eliding the lifetime would have the same
1438                                     // semantics.
1439                                     LifetimeRibKind::Elided(r) => Some(if res == r {
1440                                         LifetimeUseSet::One { use_span: ident.span, use_ctxt }
1441                                     } else {
1442                                         LifetimeUseSet::Many
1443                                     }),
1444                                     LifetimeRibKind::Generics { .. } => None,
1445                                     LifetimeRibKind::ConstGeneric | LifetimeRibKind::AnonConst => {
1446                                         span_bug!(ident.span, "unexpected rib kind: {:?}", rib.kind)
1447                                     }
1448                                 })
1449                                 .unwrap_or(LifetimeUseSet::Many);
1450                             debug!(?use_ctxt, ?use_set);
1451                             v.insert(use_set);
1452                         }
1453                         Entry::Occupied(mut o) => {
1454                             debug!("Many uses of {:?} at {:?}", res, ident.span);
1455                             *o.get_mut() = LifetimeUseSet::Many;
1456                         }
1457                     }
1458                 }
1459                 return;
1460             }
1461
1462             match rib.kind {
1463                 LifetimeRibKind::Item => break,
1464                 LifetimeRibKind::ConstGeneric => {
1465                     self.emit_non_static_lt_in_const_generic_error(lifetime);
1466                     self.record_lifetime_res(
1467                         lifetime.id,
1468                         LifetimeRes::Error,
1469                         LifetimeElisionCandidate::Ignore,
1470                     );
1471                     return;
1472                 }
1473                 LifetimeRibKind::AnonConst => {
1474                     self.maybe_emit_forbidden_non_static_lifetime_error(lifetime);
1475                     self.record_lifetime_res(
1476                         lifetime.id,
1477                         LifetimeRes::Error,
1478                         LifetimeElisionCandidate::Ignore,
1479                     );
1480                     return;
1481                 }
1482                 LifetimeRibKind::AnonymousCreateParameter { .. }
1483                 | LifetimeRibKind::Elided(_)
1484                 | LifetimeRibKind::Generics { .. }
1485                 | LifetimeRibKind::ElisionFailure
1486                 | LifetimeRibKind::AnonymousReportError => {}
1487             }
1488         }
1489
1490         let mut outer_res = None;
1491         for rib in lifetime_rib_iter {
1492             let normalized_ident = ident.normalize_to_macros_2_0();
1493             if let Some((&outer, _)) = rib.bindings.get_key_value(&normalized_ident) {
1494                 outer_res = Some(outer);
1495                 break;
1496             }
1497         }
1498
1499         self.emit_undeclared_lifetime_error(lifetime, outer_res);
1500         self.record_lifetime_res(lifetime.id, LifetimeRes::Error, LifetimeElisionCandidate::Named);
1501     }
1502
1503     #[instrument(level = "debug", skip(self))]
1504     fn resolve_anonymous_lifetime(&mut self, lifetime: &Lifetime, elided: bool) {
1505         debug_assert_eq!(lifetime.ident.name, kw::UnderscoreLifetime);
1506
1507         let missing_lifetime = MissingLifetime {
1508             id: lifetime.id,
1509             span: lifetime.ident.span,
1510             kind: if elided {
1511                 MissingLifetimeKind::Ampersand
1512             } else {
1513                 MissingLifetimeKind::Underscore
1514             },
1515             count: 1,
1516         };
1517         let elision_candidate = LifetimeElisionCandidate::Missing(missing_lifetime);
1518         for rib in self.lifetime_ribs.iter().rev() {
1519             debug!(?rib.kind);
1520             match rib.kind {
1521                 LifetimeRibKind::AnonymousCreateParameter { binder, .. } => {
1522                     let res = self.create_fresh_lifetime(lifetime.id, lifetime.ident, binder);
1523                     self.record_lifetime_res(lifetime.id, res, elision_candidate);
1524                     return;
1525                 }
1526                 LifetimeRibKind::AnonymousReportError => {
1527                     let (msg, note) = if elided {
1528                         (
1529                             "`&` without an explicit lifetime name cannot be used here",
1530                             "explicit lifetime name needed here",
1531                         )
1532                     } else {
1533                         ("`'_` cannot be used here", "`'_` is a reserved lifetime name")
1534                     };
1535                     rustc_errors::struct_span_err!(
1536                         self.r.session,
1537                         lifetime.ident.span,
1538                         E0637,
1539                         "{}",
1540                         msg,
1541                     )
1542                     .span_label(lifetime.ident.span, note)
1543                     .emit();
1544
1545                     self.record_lifetime_res(lifetime.id, LifetimeRes::Error, elision_candidate);
1546                     return;
1547                 }
1548                 LifetimeRibKind::Elided(res) => {
1549                     self.record_lifetime_res(lifetime.id, res, elision_candidate);
1550                     return;
1551                 }
1552                 LifetimeRibKind::ElisionFailure => {
1553                     self.diagnostic_metadata.current_elision_failures.push(missing_lifetime);
1554                     self.record_lifetime_res(lifetime.id, LifetimeRes::Error, elision_candidate);
1555                     return;
1556                 }
1557                 LifetimeRibKind::Item => break,
1558                 LifetimeRibKind::Generics { .. } | LifetimeRibKind::ConstGeneric => {}
1559                 LifetimeRibKind::AnonConst => {
1560                     // There is always an `Elided(LifetimeRes::Static)` inside an `AnonConst`.
1561                     span_bug!(lifetime.ident.span, "unexpected rib kind: {:?}", rib.kind)
1562                 }
1563             }
1564         }
1565         self.record_lifetime_res(lifetime.id, LifetimeRes::Error, elision_candidate);
1566         self.report_missing_lifetime_specifiers(vec![missing_lifetime], None);
1567     }
1568
1569     #[instrument(level = "debug", skip(self))]
1570     fn resolve_elided_lifetime(&mut self, anchor_id: NodeId, span: Span) {
1571         let id = self.r.next_node_id();
1572         let lt = Lifetime { id, ident: Ident::new(kw::UnderscoreLifetime, span) };
1573
1574         self.record_lifetime_res(
1575             anchor_id,
1576             LifetimeRes::ElidedAnchor { start: id, end: NodeId::from_u32(id.as_u32() + 1) },
1577             LifetimeElisionCandidate::Ignore,
1578         );
1579         self.resolve_anonymous_lifetime(&lt, true);
1580     }
1581
1582     #[instrument(level = "debug", skip(self))]
1583     fn create_fresh_lifetime(&mut self, id: NodeId, ident: Ident, binder: NodeId) -> LifetimeRes {
1584         debug_assert_eq!(ident.name, kw::UnderscoreLifetime);
1585         debug!(?ident.span);
1586
1587         // Leave the responsibility to create the `LocalDefId` to lowering.
1588         let param = self.r.next_node_id();
1589         let res = LifetimeRes::Fresh { param, binder };
1590
1591         // Record the created lifetime parameter so lowering can pick it up and add it to HIR.
1592         self.r
1593             .extra_lifetime_params_map
1594             .entry(binder)
1595             .or_insert_with(Vec::new)
1596             .push((ident, param, res));
1597         res
1598     }
1599
1600     #[instrument(level = "debug", skip(self))]
1601     fn resolve_elided_lifetimes_in_path(
1602         &mut self,
1603         path_id: NodeId,
1604         partial_res: PartialRes,
1605         path: &[Segment],
1606         source: PathSource<'_>,
1607         path_span: Span,
1608     ) {
1609         let proj_start = path.len() - partial_res.unresolved_segments();
1610         for (i, segment) in path.iter().enumerate() {
1611             if segment.has_lifetime_args {
1612                 continue;
1613             }
1614             let Some(segment_id) = segment.id else {
1615                 continue;
1616             };
1617
1618             // Figure out if this is a type/trait segment,
1619             // which may need lifetime elision performed.
1620             let type_def_id = match partial_res.base_res() {
1621                 Res::Def(DefKind::AssocTy, def_id) if i + 2 == proj_start => self.r.parent(def_id),
1622                 Res::Def(DefKind::Variant, def_id) if i + 1 == proj_start => self.r.parent(def_id),
1623                 Res::Def(DefKind::Struct, def_id)
1624                 | Res::Def(DefKind::Union, def_id)
1625                 | Res::Def(DefKind::Enum, def_id)
1626                 | Res::Def(DefKind::TyAlias, def_id)
1627                 | Res::Def(DefKind::Trait, def_id)
1628                     if i + 1 == proj_start =>
1629                 {
1630                     def_id
1631                 }
1632                 _ => continue,
1633             };
1634
1635             let expected_lifetimes = self.r.item_generics_num_lifetimes(type_def_id);
1636             if expected_lifetimes == 0 {
1637                 continue;
1638             }
1639
1640             let node_ids = self.r.next_node_ids(expected_lifetimes);
1641             self.record_lifetime_res(
1642                 segment_id,
1643                 LifetimeRes::ElidedAnchor { start: node_ids.start, end: node_ids.end },
1644                 LifetimeElisionCandidate::Ignore,
1645             );
1646
1647             let inferred = match source {
1648                 PathSource::Trait(..) | PathSource::TraitItem(..) | PathSource::Type => false,
1649                 PathSource::Expr(..)
1650                 | PathSource::Pat
1651                 | PathSource::Struct
1652                 | PathSource::TupleStruct(..) => true,
1653             };
1654             if inferred {
1655                 // Do not create a parameter for patterns and expressions: type checking can infer
1656                 // the appropriate lifetime for us.
1657                 for id in node_ids {
1658                     self.record_lifetime_res(
1659                         id,
1660                         LifetimeRes::Infer,
1661                         LifetimeElisionCandidate::Named,
1662                     );
1663                 }
1664                 continue;
1665             }
1666
1667             let elided_lifetime_span = if segment.has_generic_args {
1668                 // If there are brackets, but not generic arguments, then use the opening bracket
1669                 segment.args_span.with_hi(segment.args_span.lo() + BytePos(1))
1670             } else {
1671                 // If there are no brackets, use the identifier span.
1672                 // HACK: we use find_ancestor_inside to properly suggest elided spans in paths
1673                 // originating from macros, since the segment's span might be from a macro arg.
1674                 segment.ident.span.find_ancestor_inside(path_span).unwrap_or(path_span)
1675             };
1676             let ident = Ident::new(kw::UnderscoreLifetime, elided_lifetime_span);
1677
1678             let missing_lifetime = MissingLifetime {
1679                 id: node_ids.start,
1680                 span: elided_lifetime_span,
1681                 kind: if segment.has_generic_args {
1682                     MissingLifetimeKind::Comma
1683                 } else {
1684                     MissingLifetimeKind::Brackets
1685                 },
1686                 count: expected_lifetimes,
1687             };
1688             let mut should_lint = true;
1689             for rib in self.lifetime_ribs.iter().rev() {
1690                 match rib.kind {
1691                     // In create-parameter mode we error here because we don't want to support
1692                     // deprecated impl elision in new features like impl elision and `async fn`,
1693                     // both of which work using the `CreateParameter` mode:
1694                     //
1695                     //     impl Foo for std::cell::Ref<u32> // note lack of '_
1696                     //     async fn foo(_: std::cell::Ref<u32>) { ... }
1697                     LifetimeRibKind::AnonymousCreateParameter { report_in_path: true, .. } => {
1698                         let sess = self.r.session;
1699                         let mut err = rustc_errors::struct_span_err!(
1700                             sess,
1701                             path_span,
1702                             E0726,
1703                             "implicit elided lifetime not allowed here"
1704                         );
1705                         rustc_errors::add_elided_lifetime_in_path_suggestion(
1706                             sess.source_map(),
1707                             &mut err,
1708                             expected_lifetimes,
1709                             path_span,
1710                             !segment.has_generic_args,
1711                             elided_lifetime_span,
1712                         );
1713                         err.note("assuming a `'static` lifetime...");
1714                         err.emit();
1715                         should_lint = false;
1716
1717                         for id in node_ids {
1718                             self.record_lifetime_res(
1719                                 id,
1720                                 LifetimeRes::Error,
1721                                 LifetimeElisionCandidate::Named,
1722                             );
1723                         }
1724                         break;
1725                     }
1726                     // Do not create a parameter for patterns and expressions.
1727                     LifetimeRibKind::AnonymousCreateParameter { binder, .. } => {
1728                         // Group all suggestions into the first record.
1729                         let mut candidate = LifetimeElisionCandidate::Missing(missing_lifetime);
1730                         for id in node_ids {
1731                             let res = self.create_fresh_lifetime(id, ident, binder);
1732                             self.record_lifetime_res(
1733                                 id,
1734                                 res,
1735                                 replace(&mut candidate, LifetimeElisionCandidate::Named),
1736                             );
1737                         }
1738                         break;
1739                     }
1740                     LifetimeRibKind::Elided(res) => {
1741                         let mut candidate = LifetimeElisionCandidate::Missing(missing_lifetime);
1742                         for id in node_ids {
1743                             self.record_lifetime_res(
1744                                 id,
1745                                 res,
1746                                 replace(&mut candidate, LifetimeElisionCandidate::Ignore),
1747                             );
1748                         }
1749                         break;
1750                     }
1751                     LifetimeRibKind::ElisionFailure => {
1752                         self.diagnostic_metadata.current_elision_failures.push(missing_lifetime);
1753                         for id in node_ids {
1754                             self.record_lifetime_res(
1755                                 id,
1756                                 LifetimeRes::Error,
1757                                 LifetimeElisionCandidate::Ignore,
1758                             );
1759                         }
1760                         break;
1761                     }
1762                     // `LifetimeRes::Error`, which would usually be used in the case of
1763                     // `ReportError`, is unsuitable here, as we don't emit an error yet.  Instead,
1764                     // we simply resolve to an implicit lifetime, which will be checked later, at
1765                     // which point a suitable error will be emitted.
1766                     LifetimeRibKind::AnonymousReportError | LifetimeRibKind::Item => {
1767                         for id in node_ids {
1768                             self.record_lifetime_res(
1769                                 id,
1770                                 LifetimeRes::Error,
1771                                 LifetimeElisionCandidate::Ignore,
1772                             );
1773                         }
1774                         self.report_missing_lifetime_specifiers(vec![missing_lifetime], None);
1775                         break;
1776                     }
1777                     LifetimeRibKind::Generics { .. } | LifetimeRibKind::ConstGeneric => {}
1778                     LifetimeRibKind::AnonConst => {
1779                         // There is always an `Elided(LifetimeRes::Static)` inside an `AnonConst`.
1780                         span_bug!(elided_lifetime_span, "unexpected rib kind: {:?}", rib.kind)
1781                     }
1782                 }
1783             }
1784
1785             if should_lint {
1786                 self.r.lint_buffer.buffer_lint_with_diagnostic(
1787                     lint::builtin::ELIDED_LIFETIMES_IN_PATHS,
1788                     segment_id,
1789                     elided_lifetime_span,
1790                     "hidden lifetime parameters in types are deprecated",
1791                     lint::BuiltinLintDiagnostics::ElidedLifetimesInPaths(
1792                         expected_lifetimes,
1793                         path_span,
1794                         !segment.has_generic_args,
1795                         elided_lifetime_span,
1796                     ),
1797                 );
1798             }
1799         }
1800     }
1801
1802     #[instrument(level = "debug", skip(self))]
1803     fn record_lifetime_res(
1804         &mut self,
1805         id: NodeId,
1806         res: LifetimeRes,
1807         candidate: LifetimeElisionCandidate,
1808     ) {
1809         if let Some(prev_res) = self.r.lifetimes_res_map.insert(id, res) {
1810             panic!(
1811                 "lifetime {:?} resolved multiple times ({:?} before, {:?} now)",
1812                 id, prev_res, res
1813             )
1814         }
1815         match res {
1816             LifetimeRes::Param { .. } | LifetimeRes::Fresh { .. } | LifetimeRes::Static => {
1817                 if let Some(ref mut candidates) = self.lifetime_elision_candidates {
1818                     candidates.push((res, candidate));
1819                 }
1820             }
1821             LifetimeRes::Infer | LifetimeRes::Error | LifetimeRes::ElidedAnchor { .. } => {}
1822         }
1823     }
1824
1825     #[instrument(level = "debug", skip(self))]
1826     fn record_lifetime_param(&mut self, id: NodeId, res: LifetimeRes) {
1827         if let Some(prev_res) = self.r.lifetimes_res_map.insert(id, res) {
1828             panic!(
1829                 "lifetime parameter {:?} resolved multiple times ({:?} before, {:?} now)",
1830                 id, prev_res, res
1831             )
1832         }
1833     }
1834
1835     /// Perform resolution of a function signature, accounting for lifetime elision.
1836     #[instrument(level = "debug", skip(self, inputs))]
1837     fn resolve_fn_signature(
1838         &mut self,
1839         fn_id: NodeId,
1840         has_self: bool,
1841         inputs: impl Iterator<Item = (Option<&'ast Pat>, &'ast Ty)> + Clone,
1842         output_ty: &'ast FnRetTy,
1843     ) {
1844         // Add each argument to the rib.
1845         let elision_lifetime = self.resolve_fn_params(has_self, inputs);
1846         debug!(?elision_lifetime);
1847
1848         let outer_failures = take(&mut self.diagnostic_metadata.current_elision_failures);
1849         let output_rib = if let Ok(res) = elision_lifetime.as_ref() {
1850             self.r.lifetime_elision_allowed.insert(fn_id);
1851             LifetimeRibKind::Elided(*res)
1852         } else {
1853             LifetimeRibKind::ElisionFailure
1854         };
1855         self.with_lifetime_rib(output_rib, |this| visit::walk_fn_ret_ty(this, &output_ty));
1856         let elision_failures =
1857             replace(&mut self.diagnostic_metadata.current_elision_failures, outer_failures);
1858         if !elision_failures.is_empty() {
1859             let Err(failure_info) = elision_lifetime else { bug!() };
1860             self.report_missing_lifetime_specifiers(elision_failures, Some(failure_info));
1861         }
1862     }
1863
1864     /// Resolve inside function parameters and parameter types.
1865     /// Returns the lifetime for elision in fn return type,
1866     /// or diagnostic information in case of elision failure.
1867     fn resolve_fn_params(
1868         &mut self,
1869         has_self: bool,
1870         inputs: impl Iterator<Item = (Option<&'ast Pat>, &'ast Ty)>,
1871     ) -> Result<LifetimeRes, (Vec<MissingLifetime>, Vec<ElisionFnParameter>)> {
1872         enum Elision {
1873             /// We have not found any candidate.
1874             None,
1875             /// We have a candidate bound to `self`.
1876             Self_(LifetimeRes),
1877             /// We have a candidate bound to a parameter.
1878             Param(LifetimeRes),
1879             /// We failed elision.
1880             Err,
1881         }
1882
1883         // Save elision state to reinstate it later.
1884         let outer_candidates = self.lifetime_elision_candidates.take();
1885
1886         // Result of elision.
1887         let mut elision_lifetime = Elision::None;
1888         // Information for diagnostics.
1889         let mut parameter_info = Vec::new();
1890         let mut all_candidates = Vec::new();
1891
1892         let mut bindings = smallvec![(PatBoundCtx::Product, Default::default())];
1893         for (index, (pat, ty)) in inputs.enumerate() {
1894             debug!(?pat, ?ty);
1895             self.with_lifetime_rib(LifetimeRibKind::Elided(LifetimeRes::Infer), |this| {
1896                 if let Some(pat) = pat {
1897                     this.resolve_pattern(pat, PatternSource::FnParam, &mut bindings);
1898                 }
1899             });
1900
1901             // Record elision candidates only for this parameter.
1902             debug_assert_matches!(self.lifetime_elision_candidates, None);
1903             self.lifetime_elision_candidates = Some(Default::default());
1904             self.visit_ty(ty);
1905             let local_candidates = self.lifetime_elision_candidates.take();
1906
1907             if let Some(candidates) = local_candidates {
1908                 let distinct: FxHashSet<_> = candidates.iter().map(|(res, _)| *res).collect();
1909                 let lifetime_count = distinct.len();
1910                 if lifetime_count != 0 {
1911                     parameter_info.push(ElisionFnParameter {
1912                         index,
1913                         ident: if let Some(pat) = pat && let PatKind::Ident(_, ident, _) = pat.kind {
1914                             Some(ident)
1915                         } else {
1916                             None
1917                         },
1918                         lifetime_count,
1919                         span: ty.span,
1920                     });
1921                     all_candidates.extend(candidates.into_iter().filter_map(|(_, candidate)| {
1922                         match candidate {
1923                             LifetimeElisionCandidate::Ignore | LifetimeElisionCandidate::Named => {
1924                                 None
1925                             }
1926                             LifetimeElisionCandidate::Missing(missing) => Some(missing),
1927                         }
1928                     }));
1929                 }
1930                 let mut distinct_iter = distinct.into_iter();
1931                 if let Some(res) = distinct_iter.next() {
1932                     match elision_lifetime {
1933                         // We are the first parameter to bind lifetimes.
1934                         Elision::None => {
1935                             if distinct_iter.next().is_none() {
1936                                 // We have a single lifetime => success.
1937                                 elision_lifetime = Elision::Param(res)
1938                             } else {
1939                                 // We have multiple lifetimes => error.
1940                                 elision_lifetime = Elision::Err;
1941                             }
1942                         }
1943                         // We have 2 parameters that bind lifetimes => error.
1944                         Elision::Param(_) => elision_lifetime = Elision::Err,
1945                         // `self` elision takes precedence over everything else.
1946                         Elision::Self_(_) | Elision::Err => {}
1947                     }
1948                 }
1949             }
1950
1951             // Handle `self` specially.
1952             if index == 0 && has_self {
1953                 let self_lifetime = self.find_lifetime_for_self(ty);
1954                 if let Set1::One(lifetime) = self_lifetime {
1955                     // We found `self` elision.
1956                     elision_lifetime = Elision::Self_(lifetime);
1957                 } else {
1958                     // We do not have `self` elision: disregard the `Elision::Param` that we may
1959                     // have found.
1960                     elision_lifetime = Elision::None;
1961                 }
1962             }
1963             debug!("(resolving function / closure) recorded parameter");
1964         }
1965
1966         // Reinstate elision state.
1967         debug_assert_matches!(self.lifetime_elision_candidates, None);
1968         self.lifetime_elision_candidates = outer_candidates;
1969
1970         if let Elision::Param(res) | Elision::Self_(res) = elision_lifetime {
1971             return Ok(res);
1972         }
1973
1974         // We do not have a candidate.
1975         Err((all_candidates, parameter_info))
1976     }
1977
1978     /// List all the lifetimes that appear in the provided type.
1979     fn find_lifetime_for_self(&self, ty: &'ast Ty) -> Set1<LifetimeRes> {
1980         struct SelfVisitor<'r, 'a> {
1981             r: &'r Resolver<'a>,
1982             impl_self: Option<Res>,
1983             lifetime: Set1<LifetimeRes>,
1984         }
1985
1986         impl SelfVisitor<'_, '_> {
1987             // Look for `self: &'a Self` - also desugared from `&'a self`,
1988             // and if that matches, use it for elision and return early.
1989             fn is_self_ty(&self, ty: &Ty) -> bool {
1990                 match ty.kind {
1991                     TyKind::ImplicitSelf => true,
1992                     TyKind::Path(None, _) => {
1993                         let path_res = self.r.partial_res_map[&ty.id].full_res();
1994                         if let Some(Res::SelfTyParam { .. } | Res::SelfTyAlias { .. }) = path_res {
1995                             return true;
1996                         }
1997                         self.impl_self.is_some() && path_res == self.impl_self
1998                     }
1999                     _ => false,
2000                 }
2001             }
2002         }
2003
2004         impl<'a> Visitor<'a> for SelfVisitor<'_, '_> {
2005             fn visit_ty(&mut self, ty: &'a Ty) {
2006                 trace!("SelfVisitor considering ty={:?}", ty);
2007                 if let TyKind::Ref(lt, ref mt) = ty.kind && self.is_self_ty(&mt.ty) {
2008                     let lt_id = if let Some(lt) = lt {
2009                         lt.id
2010                     } else {
2011                         let res = self.r.lifetimes_res_map[&ty.id];
2012                         let LifetimeRes::ElidedAnchor { start, .. } = res else { bug!() };
2013                         start
2014                     };
2015                     let lt_res = self.r.lifetimes_res_map[&lt_id];
2016                     trace!("SelfVisitor inserting res={:?}", lt_res);
2017                     self.lifetime.insert(lt_res);
2018                 }
2019                 visit::walk_ty(self, ty)
2020             }
2021         }
2022
2023         let impl_self = self
2024             .diagnostic_metadata
2025             .current_self_type
2026             .as_ref()
2027             .and_then(|ty| {
2028                 if let TyKind::Path(None, _) = ty.kind {
2029                     self.r.partial_res_map.get(&ty.id)
2030                 } else {
2031                     None
2032                 }
2033             })
2034             .and_then(|res| res.full_res())
2035             .filter(|res| {
2036                 // Permit the types that unambiguously always
2037                 // result in the same type constructor being used
2038                 // (it can't differ between `Self` and `self`).
2039                 matches!(
2040                     res,
2041                     Res::Def(DefKind::Struct | DefKind::Union | DefKind::Enum, _,) | Res::PrimTy(_)
2042                 )
2043             });
2044         let mut visitor = SelfVisitor { r: self.r, impl_self, lifetime: Set1::Empty };
2045         visitor.visit_ty(ty);
2046         trace!("SelfVisitor found={:?}", visitor.lifetime);
2047         visitor.lifetime
2048     }
2049
2050     /// Searches the current set of local scopes for labels. Returns the `NodeId` of the resolved
2051     /// label and reports an error if the label is not found or is unreachable.
2052     fn resolve_label(&mut self, mut label: Ident) -> Result<(NodeId, Span), ResolutionError<'a>> {
2053         let mut suggestion = None;
2054
2055         for i in (0..self.label_ribs.len()).rev() {
2056             let rib = &self.label_ribs[i];
2057
2058             if let MacroDefinition(def) = rib.kind {
2059                 // If an invocation of this macro created `ident`, give up on `ident`
2060                 // and switch to `ident`'s source from the macro definition.
2061                 if def == self.r.macro_def(label.span.ctxt()) {
2062                     label.span.remove_mark();
2063                 }
2064             }
2065
2066             let ident = label.normalize_to_macro_rules();
2067             if let Some((ident, id)) = rib.bindings.get_key_value(&ident) {
2068                 let definition_span = ident.span;
2069                 return if self.is_label_valid_from_rib(i) {
2070                     Ok((*id, definition_span))
2071                 } else {
2072                     Err(ResolutionError::UnreachableLabel {
2073                         name: label.name,
2074                         definition_span,
2075                         suggestion,
2076                     })
2077                 };
2078             }
2079
2080             // Diagnostics: Check if this rib contains a label with a similar name, keep track of
2081             // the first such label that is encountered.
2082             suggestion = suggestion.or_else(|| self.suggestion_for_label_in_rib(i, label));
2083         }
2084
2085         Err(ResolutionError::UndeclaredLabel { name: label.name, suggestion })
2086     }
2087
2088     /// Determine whether or not a label from the `rib_index`th label rib is reachable.
2089     fn is_label_valid_from_rib(&self, rib_index: usize) -> bool {
2090         let ribs = &self.label_ribs[rib_index + 1..];
2091
2092         for rib in ribs {
2093             if rib.kind.is_label_barrier() {
2094                 return false;
2095             }
2096         }
2097
2098         true
2099     }
2100
2101     fn resolve_adt(&mut self, item: &'ast Item, generics: &'ast Generics) {
2102         debug!("resolve_adt");
2103         self.with_current_self_item(item, |this| {
2104             this.with_generic_param_rib(
2105                 &generics.params,
2106                 ItemRibKind(HasGenericParams::Yes(generics.span)),
2107                 LifetimeRibKind::Generics {
2108                     binder: item.id,
2109                     kind: LifetimeBinderKind::Item,
2110                     span: generics.span,
2111                 },
2112                 |this| {
2113                     let item_def_id = this.r.local_def_id(item.id).to_def_id();
2114                     this.with_self_rib(
2115                         Res::SelfTyAlias {
2116                             alias_to: item_def_id,
2117                             forbid_generic: false,
2118                             is_trait_impl: false,
2119                         },
2120                         |this| {
2121                             visit::walk_item(this, item);
2122                         },
2123                     );
2124                 },
2125             );
2126         });
2127     }
2128
2129     fn future_proof_import(&mut self, use_tree: &UseTree) {
2130         let segments = &use_tree.prefix.segments;
2131         if !segments.is_empty() {
2132             let ident = segments[0].ident;
2133             if ident.is_path_segment_keyword() || ident.span.rust_2015() {
2134                 return;
2135             }
2136
2137             let nss = match use_tree.kind {
2138                 UseTreeKind::Simple(..) if segments.len() == 1 => &[TypeNS, ValueNS][..],
2139                 _ => &[TypeNS],
2140             };
2141             let report_error = |this: &Self, ns| {
2142                 let what = if ns == TypeNS { "type parameters" } else { "local variables" };
2143                 if this.should_report_errs() {
2144                     this.r
2145                         .session
2146                         .span_err(ident.span, &format!("imports cannot refer to {}", what));
2147                 }
2148             };
2149
2150             for &ns in nss {
2151                 match self.maybe_resolve_ident_in_lexical_scope(ident, ns) {
2152                     Some(LexicalScopeBinding::Res(..)) => {
2153                         report_error(self, ns);
2154                     }
2155                     Some(LexicalScopeBinding::Item(binding)) => {
2156                         if let Some(LexicalScopeBinding::Res(..)) =
2157                             self.resolve_ident_in_lexical_scope(ident, ns, None, Some(binding))
2158                         {
2159                             report_error(self, ns);
2160                         }
2161                     }
2162                     None => {}
2163                 }
2164             }
2165         } else if let UseTreeKind::Nested(use_trees) = &use_tree.kind {
2166             for (use_tree, _) in use_trees {
2167                 self.future_proof_import(use_tree);
2168             }
2169         }
2170     }
2171
2172     fn resolve_item(&mut self, item: &'ast Item) {
2173         let name = item.ident.name;
2174         debug!("(resolving item) resolving {} ({:?})", name, item.kind);
2175
2176         match item.kind {
2177             ItemKind::TyAlias(box TyAlias { ref generics, .. }) => {
2178                 self.with_generic_param_rib(
2179                     &generics.params,
2180                     ItemRibKind(HasGenericParams::Yes(generics.span)),
2181                     LifetimeRibKind::Generics {
2182                         binder: item.id,
2183                         kind: LifetimeBinderKind::Item,
2184                         span: generics.span,
2185                     },
2186                     |this| visit::walk_item(this, item),
2187                 );
2188             }
2189
2190             ItemKind::Fn(box Fn { ref generics, .. }) => {
2191                 self.with_generic_param_rib(
2192                     &generics.params,
2193                     ItemRibKind(HasGenericParams::Yes(generics.span)),
2194                     LifetimeRibKind::Generics {
2195                         binder: item.id,
2196                         kind: LifetimeBinderKind::Function,
2197                         span: generics.span,
2198                     },
2199                     |this| visit::walk_item(this, item),
2200                 );
2201             }
2202
2203             ItemKind::Enum(_, ref generics)
2204             | ItemKind::Struct(_, ref generics)
2205             | ItemKind::Union(_, ref generics) => {
2206                 self.resolve_adt(item, generics);
2207             }
2208
2209             ItemKind::Impl(box Impl {
2210                 ref generics,
2211                 ref of_trait,
2212                 ref self_ty,
2213                 items: ref impl_items,
2214                 ..
2215             }) => {
2216                 self.diagnostic_metadata.current_impl_items = Some(impl_items);
2217                 self.resolve_implementation(generics, of_trait, &self_ty, item.id, impl_items);
2218                 self.diagnostic_metadata.current_impl_items = None;
2219             }
2220
2221             ItemKind::Trait(box Trait { ref generics, ref bounds, ref items, .. }) => {
2222                 // Create a new rib for the trait-wide type parameters.
2223                 self.with_generic_param_rib(
2224                     &generics.params,
2225                     ItemRibKind(HasGenericParams::Yes(generics.span)),
2226                     LifetimeRibKind::Generics {
2227                         binder: item.id,
2228                         kind: LifetimeBinderKind::Item,
2229                         span: generics.span,
2230                     },
2231                     |this| {
2232                         let local_def_id = this.r.local_def_id(item.id).to_def_id();
2233                         this.with_self_rib(Res::SelfTyParam { trait_: local_def_id }, |this| {
2234                             this.visit_generics(generics);
2235                             walk_list!(this, visit_param_bound, bounds, BoundKind::SuperTraits);
2236                             this.resolve_trait_items(items);
2237                         });
2238                     },
2239                 );
2240             }
2241
2242             ItemKind::TraitAlias(ref generics, ref bounds) => {
2243                 // Create a new rib for the trait-wide type parameters.
2244                 self.with_generic_param_rib(
2245                     &generics.params,
2246                     ItemRibKind(HasGenericParams::Yes(generics.span)),
2247                     LifetimeRibKind::Generics {
2248                         binder: item.id,
2249                         kind: LifetimeBinderKind::Item,
2250                         span: generics.span,
2251                     },
2252                     |this| {
2253                         let local_def_id = this.r.local_def_id(item.id).to_def_id();
2254                         this.with_self_rib(Res::SelfTyParam { trait_: local_def_id }, |this| {
2255                             this.visit_generics(generics);
2256                             walk_list!(this, visit_param_bound, bounds, BoundKind::Bound);
2257                         });
2258                     },
2259                 );
2260             }
2261
2262             ItemKind::Mod(..) | ItemKind::ForeignMod(_) => {
2263                 self.with_scope(item.id, |this| {
2264                     visit::walk_item(this, item);
2265                 });
2266             }
2267
2268             ItemKind::Static(ref ty, _, ref expr) | ItemKind::Const(_, ref ty, ref expr) => {
2269                 self.with_static_rib(|this| {
2270                     this.with_lifetime_rib(LifetimeRibKind::Elided(LifetimeRes::Static), |this| {
2271                         this.visit_ty(ty);
2272                     });
2273                     this.with_lifetime_rib(LifetimeRibKind::Elided(LifetimeRes::Infer), |this| {
2274                         if let Some(expr) = expr {
2275                             let constant_item_kind = match item.kind {
2276                                 ItemKind::Const(..) => ConstantItemKind::Const,
2277                                 ItemKind::Static(..) => ConstantItemKind::Static,
2278                                 _ => unreachable!(),
2279                             };
2280                             // We already forbid generic params because of the above item rib,
2281                             // so it doesn't matter whether this is a trivial constant.
2282                             this.with_constant_rib(
2283                                 IsRepeatExpr::No,
2284                                 ConstantHasGenerics::Yes,
2285                                 Some((item.ident, constant_item_kind)),
2286                                 |this| this.visit_expr(expr),
2287                             );
2288                         }
2289                     });
2290                 });
2291             }
2292
2293             ItemKind::Use(ref use_tree) => {
2294                 self.future_proof_import(use_tree);
2295             }
2296
2297             ItemKind::ExternCrate(..) | ItemKind::MacroDef(..) => {
2298                 // do nothing, these are just around to be encoded
2299             }
2300
2301             ItemKind::GlobalAsm(_) => {
2302                 visit::walk_item(self, item);
2303             }
2304
2305             ItemKind::MacCall(_) => panic!("unexpanded macro in resolve!"),
2306         }
2307     }
2308
2309     fn with_generic_param_rib<'c, F>(
2310         &'c mut self,
2311         params: &'c [GenericParam],
2312         kind: RibKind<'a>,
2313         lifetime_kind: LifetimeRibKind,
2314         f: F,
2315     ) where
2316         F: FnOnce(&mut Self),
2317     {
2318         debug!("with_generic_param_rib");
2319         let LifetimeRibKind::Generics { binder, span: generics_span, kind: generics_kind, .. }
2320             = lifetime_kind else { panic!() };
2321
2322         let mut function_type_rib = Rib::new(kind);
2323         let mut function_value_rib = Rib::new(kind);
2324         let mut function_lifetime_rib = LifetimeRib::new(lifetime_kind);
2325         let mut seen_bindings = FxHashMap::default();
2326         // Store all seen lifetimes names from outer scopes.
2327         let mut seen_lifetimes = FxHashSet::default();
2328
2329         // We also can't shadow bindings from the parent item
2330         if let AssocItemRibKind = kind {
2331             let mut add_bindings_for_ns = |ns| {
2332                 let parent_rib = self.ribs[ns]
2333                     .iter()
2334                     .rfind(|r| matches!(r.kind, ItemRibKind(_)))
2335                     .expect("associated item outside of an item");
2336                 seen_bindings
2337                     .extend(parent_rib.bindings.iter().map(|(ident, _)| (*ident, ident.span)));
2338             };
2339             add_bindings_for_ns(ValueNS);
2340             add_bindings_for_ns(TypeNS);
2341         }
2342
2343         // Forbid shadowing lifetime bindings
2344         for rib in self.lifetime_ribs.iter().rev() {
2345             seen_lifetimes.extend(rib.bindings.iter().map(|(ident, _)| *ident));
2346             if let LifetimeRibKind::Item = rib.kind {
2347                 break;
2348             }
2349         }
2350
2351         for param in params {
2352             let ident = param.ident.normalize_to_macros_2_0();
2353             debug!("with_generic_param_rib: {}", param.id);
2354
2355             if let GenericParamKind::Lifetime = param.kind
2356                 && let Some(&original) = seen_lifetimes.get(&ident)
2357             {
2358                 diagnostics::signal_lifetime_shadowing(self.r.session, original, param.ident);
2359                 // Record lifetime res, so lowering knows there is something fishy.
2360                 self.record_lifetime_param(param.id, LifetimeRes::Error);
2361                 continue;
2362             }
2363
2364             match seen_bindings.entry(ident) {
2365                 Entry::Occupied(entry) => {
2366                     let span = *entry.get();
2367                     let err = ResolutionError::NameAlreadyUsedInParameterList(ident.name, span);
2368                     self.report_error(param.ident.span, err);
2369                     if let GenericParamKind::Lifetime = param.kind {
2370                         // Record lifetime res, so lowering knows there is something fishy.
2371                         self.record_lifetime_param(param.id, LifetimeRes::Error);
2372                     }
2373                     continue;
2374                 }
2375                 Entry::Vacant(entry) => {
2376                     entry.insert(param.ident.span);
2377                 }
2378             }
2379
2380             if param.ident.name == kw::UnderscoreLifetime {
2381                 rustc_errors::struct_span_err!(
2382                     self.r.session,
2383                     param.ident.span,
2384                     E0637,
2385                     "`'_` cannot be used here"
2386                 )
2387                 .span_label(param.ident.span, "`'_` is a reserved lifetime name")
2388                 .emit();
2389                 // Record lifetime res, so lowering knows there is something fishy.
2390                 self.record_lifetime_param(param.id, LifetimeRes::Error);
2391                 continue;
2392             }
2393
2394             if param.ident.name == kw::StaticLifetime {
2395                 rustc_errors::struct_span_err!(
2396                     self.r.session,
2397                     param.ident.span,
2398                     E0262,
2399                     "invalid lifetime parameter name: `{}`",
2400                     param.ident,
2401                 )
2402                 .span_label(param.ident.span, "'static is a reserved lifetime name")
2403                 .emit();
2404                 // Record lifetime res, so lowering knows there is something fishy.
2405                 self.record_lifetime_param(param.id, LifetimeRes::Error);
2406                 continue;
2407             }
2408
2409             let def_id = self.r.local_def_id(param.id);
2410
2411             // Plain insert (no renaming).
2412             let (rib, def_kind) = match param.kind {
2413                 GenericParamKind::Type { .. } => (&mut function_type_rib, DefKind::TyParam),
2414                 GenericParamKind::Const { .. } => (&mut function_value_rib, DefKind::ConstParam),
2415                 GenericParamKind::Lifetime => {
2416                     let res = LifetimeRes::Param { param: def_id, binder };
2417                     self.record_lifetime_param(param.id, res);
2418                     function_lifetime_rib.bindings.insert(ident, (param.id, res));
2419                     continue;
2420                 }
2421             };
2422
2423             let res = match kind {
2424                 ItemRibKind(..) | AssocItemRibKind => Res::Def(def_kind, def_id.to_def_id()),
2425                 NormalRibKind => Res::Err,
2426                 _ => span_bug!(param.ident.span, "Unexpected rib kind {:?}", kind),
2427             };
2428             self.r.record_partial_res(param.id, PartialRes::new(res));
2429             rib.bindings.insert(ident, res);
2430         }
2431
2432         self.lifetime_ribs.push(function_lifetime_rib);
2433         self.ribs[ValueNS].push(function_value_rib);
2434         self.ribs[TypeNS].push(function_type_rib);
2435
2436         f(self);
2437
2438         self.ribs[TypeNS].pop();
2439         self.ribs[ValueNS].pop();
2440         let function_lifetime_rib = self.lifetime_ribs.pop().unwrap();
2441
2442         // Do not account for the parameters we just bound for function lifetime elision.
2443         if let Some(ref mut candidates) = self.lifetime_elision_candidates {
2444             for (_, res) in function_lifetime_rib.bindings.values() {
2445                 candidates.retain(|(r, _)| r != res);
2446             }
2447         }
2448
2449         if let LifetimeBinderKind::BareFnType
2450         | LifetimeBinderKind::WhereBound
2451         | LifetimeBinderKind::Function
2452         | LifetimeBinderKind::ImplBlock = generics_kind
2453         {
2454             self.maybe_report_lifetime_uses(generics_span, params)
2455         }
2456     }
2457
2458     fn with_label_rib(&mut self, kind: RibKind<'a>, f: impl FnOnce(&mut Self)) {
2459         self.label_ribs.push(Rib::new(kind));
2460         f(self);
2461         self.label_ribs.pop();
2462     }
2463
2464     fn with_static_rib(&mut self, f: impl FnOnce(&mut Self)) {
2465         let kind = ItemRibKind(HasGenericParams::No);
2466         self.with_rib(ValueNS, kind, |this| this.with_rib(TypeNS, kind, f))
2467     }
2468
2469     // HACK(min_const_generics,const_evaluatable_unchecked): We
2470     // want to keep allowing `[0; std::mem::size_of::<*mut T>()]`
2471     // with a future compat lint for now. We do this by adding an
2472     // additional special case for repeat expressions.
2473     //
2474     // Note that we intentionally still forbid `[0; N + 1]` during
2475     // name resolution so that we don't extend the future
2476     // compat lint to new cases.
2477     #[instrument(level = "debug", skip(self, f))]
2478     fn with_constant_rib(
2479         &mut self,
2480         is_repeat: IsRepeatExpr,
2481         may_use_generics: ConstantHasGenerics,
2482         item: Option<(Ident, ConstantItemKind)>,
2483         f: impl FnOnce(&mut Self),
2484     ) {
2485         self.with_rib(ValueNS, ConstantItemRibKind(may_use_generics, item), |this| {
2486             this.with_rib(
2487                 TypeNS,
2488                 ConstantItemRibKind(
2489                     may_use_generics.force_yes_if(is_repeat == IsRepeatExpr::Yes),
2490                     item,
2491                 ),
2492                 |this| {
2493                     this.with_label_rib(ConstantItemRibKind(may_use_generics, item), f);
2494                 },
2495             )
2496         });
2497     }
2498
2499     fn with_current_self_type<T>(&mut self, self_type: &Ty, f: impl FnOnce(&mut Self) -> T) -> T {
2500         // Handle nested impls (inside fn bodies)
2501         let previous_value =
2502             replace(&mut self.diagnostic_metadata.current_self_type, Some(self_type.clone()));
2503         let result = f(self);
2504         self.diagnostic_metadata.current_self_type = previous_value;
2505         result
2506     }
2507
2508     fn with_current_self_item<T>(&mut self, self_item: &Item, f: impl FnOnce(&mut Self) -> T) -> T {
2509         let previous_value =
2510             replace(&mut self.diagnostic_metadata.current_self_item, Some(self_item.id));
2511         let result = f(self);
2512         self.diagnostic_metadata.current_self_item = previous_value;
2513         result
2514     }
2515
2516     /// When evaluating a `trait` use its associated types' idents for suggestions in E0412.
2517     fn resolve_trait_items(&mut self, trait_items: &'ast [P<AssocItem>]) {
2518         let trait_assoc_items =
2519             replace(&mut self.diagnostic_metadata.current_trait_assoc_items, Some(&trait_items));
2520
2521         let walk_assoc_item =
2522             |this: &mut Self, generics: &Generics, kind, item: &'ast AssocItem| {
2523                 this.with_generic_param_rib(
2524                     &generics.params,
2525                     AssocItemRibKind,
2526                     LifetimeRibKind::Generics { binder: item.id, span: generics.span, kind },
2527                     |this| visit::walk_assoc_item(this, item, AssocCtxt::Trait),
2528                 );
2529             };
2530
2531         for item in trait_items {
2532             match &item.kind {
2533                 AssocItemKind::Const(_, ty, default) => {
2534                     self.visit_ty(ty);
2535                     // Only impose the restrictions of `ConstRibKind` for an
2536                     // actual constant expression in a provided default.
2537                     if let Some(expr) = default {
2538                         // We allow arbitrary const expressions inside of associated consts,
2539                         // even if they are potentially not const evaluatable.
2540                         //
2541                         // Type parameters can already be used and as associated consts are
2542                         // not used as part of the type system, this is far less surprising.
2543                         self.with_lifetime_rib(
2544                             LifetimeRibKind::Elided(LifetimeRes::Infer),
2545                             |this| {
2546                                 this.with_constant_rib(
2547                                     IsRepeatExpr::No,
2548                                     ConstantHasGenerics::Yes,
2549                                     None,
2550                                     |this| this.visit_expr(expr),
2551                                 )
2552                             },
2553                         );
2554                     }
2555                 }
2556                 AssocItemKind::Fn(box Fn { generics, .. }) => {
2557                     walk_assoc_item(self, generics, LifetimeBinderKind::Function, item);
2558                 }
2559                 AssocItemKind::Type(box TyAlias { generics, .. }) => self
2560                     .with_lifetime_rib(LifetimeRibKind::AnonymousReportError, |this| {
2561                         walk_assoc_item(this, generics, LifetimeBinderKind::Item, item)
2562                     }),
2563                 AssocItemKind::MacCall(_) => {
2564                     panic!("unexpanded macro in resolve!")
2565                 }
2566             };
2567         }
2568
2569         self.diagnostic_metadata.current_trait_assoc_items = trait_assoc_items;
2570     }
2571
2572     /// This is called to resolve a trait reference from an `impl` (i.e., `impl Trait for Foo`).
2573     fn with_optional_trait_ref<T>(
2574         &mut self,
2575         opt_trait_ref: Option<&TraitRef>,
2576         self_type: &'ast Ty,
2577         f: impl FnOnce(&mut Self, Option<DefId>) -> T,
2578     ) -> T {
2579         let mut new_val = None;
2580         let mut new_id = None;
2581         if let Some(trait_ref) = opt_trait_ref {
2582             let path: Vec<_> = Segment::from_path(&trait_ref.path);
2583             self.diagnostic_metadata.currently_processing_impl_trait =
2584                 Some((trait_ref.clone(), self_type.clone()));
2585             let res = self.smart_resolve_path_fragment(
2586                 &None,
2587                 &path,
2588                 PathSource::Trait(AliasPossibility::No),
2589                 Finalize::new(trait_ref.ref_id, trait_ref.path.span),
2590             );
2591             self.diagnostic_metadata.currently_processing_impl_trait = None;
2592             if let Some(def_id) = res.expect_full_res().opt_def_id() {
2593                 new_id = Some(def_id);
2594                 new_val = Some((self.r.expect_module(def_id), trait_ref.clone()));
2595             }
2596         }
2597         let original_trait_ref = replace(&mut self.current_trait_ref, new_val);
2598         let result = f(self, new_id);
2599         self.current_trait_ref = original_trait_ref;
2600         result
2601     }
2602
2603     fn with_self_rib_ns(&mut self, ns: Namespace, self_res: Res, f: impl FnOnce(&mut Self)) {
2604         let mut self_type_rib = Rib::new(NormalRibKind);
2605
2606         // Plain insert (no renaming, since types are not currently hygienic)
2607         self_type_rib.bindings.insert(Ident::with_dummy_span(kw::SelfUpper), self_res);
2608         self.ribs[ns].push(self_type_rib);
2609         f(self);
2610         self.ribs[ns].pop();
2611     }
2612
2613     fn with_self_rib(&mut self, self_res: Res, f: impl FnOnce(&mut Self)) {
2614         self.with_self_rib_ns(TypeNS, self_res, f)
2615     }
2616
2617     fn resolve_implementation(
2618         &mut self,
2619         generics: &'ast Generics,
2620         opt_trait_reference: &'ast Option<TraitRef>,
2621         self_type: &'ast Ty,
2622         item_id: NodeId,
2623         impl_items: &'ast [P<AssocItem>],
2624     ) {
2625         debug!("resolve_implementation");
2626         // If applicable, create a rib for the type parameters.
2627         self.with_generic_param_rib(
2628             &generics.params,
2629             ItemRibKind(HasGenericParams::Yes(generics.span)),
2630             LifetimeRibKind::Generics {
2631                 span: generics.span,
2632                 binder: item_id,
2633                 kind: LifetimeBinderKind::ImplBlock,
2634             },
2635             |this| {
2636                 // Dummy self type for better errors if `Self` is used in the trait path.
2637                 this.with_self_rib(Res::SelfTyParam { trait_: LOCAL_CRATE.as_def_id() }, |this| {
2638                     this.with_lifetime_rib(
2639                         LifetimeRibKind::AnonymousCreateParameter {
2640                             binder: item_id,
2641                             report_in_path: true
2642                         },
2643                         |this| {
2644                             // Resolve the trait reference, if necessary.
2645                             this.with_optional_trait_ref(
2646                                 opt_trait_reference.as_ref(),
2647                                 self_type,
2648                                 |this, trait_id| {
2649                                     let item_def_id = this.r.local_def_id(item_id);
2650
2651                                     // Register the trait definitions from here.
2652                                     if let Some(trait_id) = trait_id {
2653                                         this.r
2654                                             .trait_impls
2655                                             .entry(trait_id)
2656                                             .or_default()
2657                                             .push(item_def_id);
2658                                     }
2659
2660                                     let item_def_id = item_def_id.to_def_id();
2661                                     let res = Res::SelfTyAlias {
2662                                         alias_to: item_def_id,
2663                                         forbid_generic: false,
2664                                         is_trait_impl: trait_id.is_some()
2665                                     };
2666                                     this.with_self_rib(res, |this| {
2667                                         if let Some(trait_ref) = opt_trait_reference.as_ref() {
2668                                             // Resolve type arguments in the trait path.
2669                                             visit::walk_trait_ref(this, trait_ref);
2670                                         }
2671                                         // Resolve the self type.
2672                                         this.visit_ty(self_type);
2673                                         // Resolve the generic parameters.
2674                                         this.visit_generics(generics);
2675
2676                                         // Resolve the items within the impl.
2677                                         this.with_current_self_type(self_type, |this| {
2678                                             this.with_self_rib_ns(ValueNS, Res::SelfCtor(item_def_id), |this| {
2679                                                 debug!("resolve_implementation with_self_rib_ns(ValueNS, ...)");
2680                                                 let mut seen_trait_items = Default::default();
2681                                                 for item in impl_items {
2682                                                     this.resolve_impl_item(&**item, &mut seen_trait_items);
2683                                                 }
2684                                             });
2685                                         });
2686                                     });
2687                                 },
2688                             )
2689                         },
2690                     );
2691                 });
2692             },
2693         );
2694     }
2695
2696     fn resolve_impl_item(
2697         &mut self,
2698         item: &'ast AssocItem,
2699         seen_trait_items: &mut FxHashMap<DefId, Span>,
2700     ) {
2701         use crate::ResolutionError::*;
2702         match &item.kind {
2703             AssocItemKind::Const(_, ty, default) => {
2704                 debug!("resolve_implementation AssocItemKind::Const");
2705                 // If this is a trait impl, ensure the const
2706                 // exists in trait
2707                 self.check_trait_item(
2708                     item.id,
2709                     item.ident,
2710                     &item.kind,
2711                     ValueNS,
2712                     item.span,
2713                     seen_trait_items,
2714                     |i, s, c| ConstNotMemberOfTrait(i, s, c),
2715                 );
2716
2717                 self.visit_ty(ty);
2718                 if let Some(expr) = default {
2719                     // We allow arbitrary const expressions inside of associated consts,
2720                     // even if they are potentially not const evaluatable.
2721                     //
2722                     // Type parameters can already be used and as associated consts are
2723                     // not used as part of the type system, this is far less surprising.
2724                     self.with_lifetime_rib(LifetimeRibKind::Elided(LifetimeRes::Infer), |this| {
2725                         this.with_constant_rib(
2726                             IsRepeatExpr::No,
2727                             ConstantHasGenerics::Yes,
2728                             None,
2729                             |this| this.visit_expr(expr),
2730                         )
2731                     });
2732                 }
2733             }
2734             AssocItemKind::Fn(box Fn { generics, .. }) => {
2735                 debug!("resolve_implementation AssocItemKind::Fn");
2736                 // We also need a new scope for the impl item type parameters.
2737                 self.with_generic_param_rib(
2738                     &generics.params,
2739                     AssocItemRibKind,
2740                     LifetimeRibKind::Generics {
2741                         binder: item.id,
2742                         span: generics.span,
2743                         kind: LifetimeBinderKind::Function,
2744                     },
2745                     |this| {
2746                         // If this is a trait impl, ensure the method
2747                         // exists in trait
2748                         this.check_trait_item(
2749                             item.id,
2750                             item.ident,
2751                             &item.kind,
2752                             ValueNS,
2753                             item.span,
2754                             seen_trait_items,
2755                             |i, s, c| MethodNotMemberOfTrait(i, s, c),
2756                         );
2757
2758                         visit::walk_assoc_item(this, item, AssocCtxt::Impl)
2759                     },
2760                 );
2761             }
2762             AssocItemKind::Type(box TyAlias { generics, .. }) => {
2763                 debug!("resolve_implementation AssocItemKind::Type");
2764                 // We also need a new scope for the impl item type parameters.
2765                 self.with_generic_param_rib(
2766                     &generics.params,
2767                     AssocItemRibKind,
2768                     LifetimeRibKind::Generics {
2769                         binder: item.id,
2770                         span: generics.span,
2771                         kind: LifetimeBinderKind::Item,
2772                     },
2773                     |this| {
2774                         this.with_lifetime_rib(LifetimeRibKind::AnonymousReportError, |this| {
2775                             // If this is a trait impl, ensure the type
2776                             // exists in trait
2777                             this.check_trait_item(
2778                                 item.id,
2779                                 item.ident,
2780                                 &item.kind,
2781                                 TypeNS,
2782                                 item.span,
2783                                 seen_trait_items,
2784                                 |i, s, c| TypeNotMemberOfTrait(i, s, c),
2785                             );
2786
2787                             visit::walk_assoc_item(this, item, AssocCtxt::Impl)
2788                         });
2789                     },
2790                 );
2791             }
2792             AssocItemKind::MacCall(_) => {
2793                 panic!("unexpanded macro in resolve!")
2794             }
2795         }
2796     }
2797
2798     fn check_trait_item<F>(
2799         &mut self,
2800         id: NodeId,
2801         mut ident: Ident,
2802         kind: &AssocItemKind,
2803         ns: Namespace,
2804         span: Span,
2805         seen_trait_items: &mut FxHashMap<DefId, Span>,
2806         err: F,
2807     ) where
2808         F: FnOnce(Ident, String, Option<Symbol>) -> ResolutionError<'a>,
2809     {
2810         // If there is a TraitRef in scope for an impl, then the method must be in the trait.
2811         let Some((module, _)) = &self.current_trait_ref else { return; };
2812         ident.span.normalize_to_macros_2_0_and_adjust(module.expansion);
2813         let key = self.r.new_key(ident, ns);
2814         let mut binding = self.r.resolution(module, key).try_borrow().ok().and_then(|r| r.binding);
2815         debug!(?binding);
2816         if binding.is_none() {
2817             // We could not find the trait item in the correct namespace.
2818             // Check the other namespace to report an error.
2819             let ns = match ns {
2820                 ValueNS => TypeNS,
2821                 TypeNS => ValueNS,
2822                 _ => ns,
2823             };
2824             let key = self.r.new_key(ident, ns);
2825             binding = self.r.resolution(module, key).try_borrow().ok().and_then(|r| r.binding);
2826             debug!(?binding);
2827         }
2828         let Some(binding) = binding else {
2829             // We could not find the method: report an error.
2830             let candidate = self.find_similarly_named_assoc_item(ident.name, kind);
2831             let path = &self.current_trait_ref.as_ref().unwrap().1.path;
2832             let path_names = path_names_to_string(path);
2833             self.report_error(span, err(ident, path_names, candidate));
2834             return;
2835         };
2836
2837         let res = binding.res();
2838         let Res::Def(def_kind, id_in_trait) = res else { bug!() };
2839
2840         match seen_trait_items.entry(id_in_trait) {
2841             Entry::Occupied(entry) => {
2842                 self.report_error(
2843                     span,
2844                     ResolutionError::TraitImplDuplicate {
2845                         name: ident.name,
2846                         old_span: *entry.get(),
2847                         trait_item_span: binding.span,
2848                     },
2849                 );
2850                 return;
2851             }
2852             Entry::Vacant(entry) => {
2853                 entry.insert(span);
2854             }
2855         };
2856
2857         match (def_kind, kind) {
2858             (DefKind::AssocTy, AssocItemKind::Type(..))
2859             | (DefKind::AssocFn, AssocItemKind::Fn(..))
2860             | (DefKind::AssocConst, AssocItemKind::Const(..)) => {
2861                 self.r.record_partial_res(id, PartialRes::new(res));
2862                 return;
2863             }
2864             _ => {}
2865         }
2866
2867         // The method kind does not correspond to what appeared in the trait, report.
2868         let path = &self.current_trait_ref.as_ref().unwrap().1.path;
2869         let (code, kind) = match kind {
2870             AssocItemKind::Const(..) => (rustc_errors::error_code!(E0323), "const"),
2871             AssocItemKind::Fn(..) => (rustc_errors::error_code!(E0324), "method"),
2872             AssocItemKind::Type(..) => (rustc_errors::error_code!(E0325), "type"),
2873             AssocItemKind::MacCall(..) => span_bug!(span, "unexpanded macro"),
2874         };
2875         let trait_path = path_names_to_string(path);
2876         self.report_error(
2877             span,
2878             ResolutionError::TraitImplMismatch {
2879                 name: ident.name,
2880                 kind,
2881                 code,
2882                 trait_path,
2883                 trait_item_span: binding.span,
2884             },
2885         );
2886     }
2887
2888     fn resolve_params(&mut self, params: &'ast [Param]) {
2889         let mut bindings = smallvec![(PatBoundCtx::Product, Default::default())];
2890         self.with_lifetime_rib(LifetimeRibKind::Elided(LifetimeRes::Infer), |this| {
2891             for Param { pat, .. } in params {
2892                 this.resolve_pattern(pat, PatternSource::FnParam, &mut bindings);
2893             }
2894         });
2895         for Param { ty, .. } in params {
2896             self.visit_ty(ty);
2897         }
2898     }
2899
2900     fn resolve_local(&mut self, local: &'ast Local) {
2901         debug!("resolving local ({:?})", local);
2902         // Resolve the type.
2903         walk_list!(self, visit_ty, &local.ty);
2904
2905         // Resolve the initializer.
2906         if let Some((init, els)) = local.kind.init_else_opt() {
2907             self.visit_expr(init);
2908
2909             // Resolve the `else` block
2910             if let Some(els) = els {
2911                 self.visit_block(els);
2912             }
2913         }
2914
2915         // Resolve the pattern.
2916         self.resolve_pattern_top(&local.pat, PatternSource::Let);
2917     }
2918
2919     /// build a map from pattern identifiers to binding-info's.
2920     /// this is done hygienically. This could arise for a macro
2921     /// that expands into an or-pattern where one 'x' was from the
2922     /// user and one 'x' came from the macro.
2923     fn binding_mode_map(&mut self, pat: &Pat) -> BindingMap {
2924         let mut binding_map = FxHashMap::default();
2925
2926         pat.walk(&mut |pat| {
2927             match pat.kind {
2928                 PatKind::Ident(annotation, ident, ref sub_pat)
2929                     if sub_pat.is_some() || self.is_base_res_local(pat.id) =>
2930                 {
2931                     binding_map.insert(ident, BindingInfo { span: ident.span, annotation });
2932                 }
2933                 PatKind::Or(ref ps) => {
2934                     // Check the consistency of this or-pattern and
2935                     // then add all bindings to the larger map.
2936                     for bm in self.check_consistent_bindings(ps) {
2937                         binding_map.extend(bm);
2938                     }
2939                     return false;
2940                 }
2941                 _ => {}
2942             }
2943
2944             true
2945         });
2946
2947         binding_map
2948     }
2949
2950     fn is_base_res_local(&self, nid: NodeId) -> bool {
2951         matches!(
2952             self.r.partial_res_map.get(&nid).map(|res| res.expect_full_res()),
2953             Some(Res::Local(..))
2954         )
2955     }
2956
2957     /// Checks that all of the arms in an or-pattern have exactly the
2958     /// same set of bindings, with the same binding modes for each.
2959     fn check_consistent_bindings(&mut self, pats: &[P<Pat>]) -> Vec<BindingMap> {
2960         let mut missing_vars = FxHashMap::default();
2961         let mut inconsistent_vars = FxHashMap::default();
2962
2963         // 1) Compute the binding maps of all arms.
2964         let maps = pats.iter().map(|pat| self.binding_mode_map(pat)).collect::<Vec<_>>();
2965
2966         // 2) Record any missing bindings or binding mode inconsistencies.
2967         for (map_outer, pat_outer) in pats.iter().enumerate().map(|(idx, pat)| (&maps[idx], pat)) {
2968             // Check against all arms except for the same pattern which is always self-consistent.
2969             let inners = pats
2970                 .iter()
2971                 .enumerate()
2972                 .filter(|(_, pat)| pat.id != pat_outer.id)
2973                 .flat_map(|(idx, _)| maps[idx].iter())
2974                 .map(|(key, binding)| (key.name, map_outer.get(&key), binding));
2975
2976             for (name, info, &binding_inner) in inners {
2977                 match info {
2978                     None => {
2979                         // The inner binding is missing in the outer.
2980                         let binding_error =
2981                             missing_vars.entry(name).or_insert_with(|| BindingError {
2982                                 name,
2983                                 origin: BTreeSet::new(),
2984                                 target: BTreeSet::new(),
2985                                 could_be_path: name.as_str().starts_with(char::is_uppercase),
2986                             });
2987                         binding_error.origin.insert(binding_inner.span);
2988                         binding_error.target.insert(pat_outer.span);
2989                     }
2990                     Some(binding_outer) => {
2991                         if binding_outer.annotation != binding_inner.annotation {
2992                             // The binding modes in the outer and inner bindings differ.
2993                             inconsistent_vars
2994                                 .entry(name)
2995                                 .or_insert((binding_inner.span, binding_outer.span));
2996                         }
2997                     }
2998                 }
2999             }
3000         }
3001
3002         // 3) Report all missing variables we found.
3003         let mut missing_vars = missing_vars.into_iter().collect::<Vec<_>>();
3004         missing_vars.sort_by_key(|&(sym, ref _err)| sym);
3005
3006         for (name, mut v) in missing_vars.into_iter() {
3007             if inconsistent_vars.contains_key(&name) {
3008                 v.could_be_path = false;
3009             }
3010             self.report_error(
3011                 *v.origin.iter().next().unwrap(),
3012                 ResolutionError::VariableNotBoundInPattern(v, self.parent_scope),
3013             );
3014         }
3015
3016         // 4) Report all inconsistencies in binding modes we found.
3017         let mut inconsistent_vars = inconsistent_vars.iter().collect::<Vec<_>>();
3018         inconsistent_vars.sort();
3019         for (name, v) in inconsistent_vars {
3020             self.report_error(v.0, ResolutionError::VariableBoundWithDifferentMode(*name, v.1));
3021         }
3022
3023         // 5) Finally bubble up all the binding maps.
3024         maps
3025     }
3026
3027     /// Check the consistency of the outermost or-patterns.
3028     fn check_consistent_bindings_top(&mut self, pat: &'ast Pat) {
3029         pat.walk(&mut |pat| match pat.kind {
3030             PatKind::Or(ref ps) => {
3031                 self.check_consistent_bindings(ps);
3032                 false
3033             }
3034             _ => true,
3035         })
3036     }
3037
3038     fn resolve_arm(&mut self, arm: &'ast Arm) {
3039         self.with_rib(ValueNS, NormalRibKind, |this| {
3040             this.resolve_pattern_top(&arm.pat, PatternSource::Match);
3041             walk_list!(this, visit_expr, &arm.guard);
3042             this.visit_expr(&arm.body);
3043         });
3044     }
3045
3046     /// Arising from `source`, resolve a top level pattern.
3047     fn resolve_pattern_top(&mut self, pat: &'ast Pat, pat_src: PatternSource) {
3048         let mut bindings = smallvec![(PatBoundCtx::Product, Default::default())];
3049         self.resolve_pattern(pat, pat_src, &mut bindings);
3050     }
3051
3052     fn resolve_pattern(
3053         &mut self,
3054         pat: &'ast Pat,
3055         pat_src: PatternSource,
3056         bindings: &mut SmallVec<[(PatBoundCtx, FxHashSet<Ident>); 1]>,
3057     ) {
3058         // We walk the pattern before declaring the pattern's inner bindings,
3059         // so that we avoid resolving a literal expression to a binding defined
3060         // by the pattern.
3061         visit::walk_pat(self, pat);
3062         self.resolve_pattern_inner(pat, pat_src, bindings);
3063         // This has to happen *after* we determine which pat_idents are variants:
3064         self.check_consistent_bindings_top(pat);
3065     }
3066
3067     /// Resolve bindings in a pattern. This is a helper to `resolve_pattern`.
3068     ///
3069     /// ### `bindings`
3070     ///
3071     /// A stack of sets of bindings accumulated.
3072     ///
3073     /// In each set, `PatBoundCtx::Product` denotes that a found binding in it should
3074     /// be interpreted as re-binding an already bound binding. This results in an error.
3075     /// Meanwhile, `PatBound::Or` denotes that a found binding in the set should result
3076     /// in reusing this binding rather than creating a fresh one.
3077     ///
3078     /// When called at the top level, the stack must have a single element
3079     /// with `PatBound::Product`. Otherwise, pushing to the stack happens as
3080     /// or-patterns (`p_0 | ... | p_n`) are encountered and the context needs
3081     /// to be switched to `PatBoundCtx::Or` and then `PatBoundCtx::Product` for each `p_i`.
3082     /// When each `p_i` has been dealt with, the top set is merged with its parent.
3083     /// When a whole or-pattern has been dealt with, the thing happens.
3084     ///
3085     /// See the implementation and `fresh_binding` for more details.
3086     fn resolve_pattern_inner(
3087         &mut self,
3088         pat: &Pat,
3089         pat_src: PatternSource,
3090         bindings: &mut SmallVec<[(PatBoundCtx, FxHashSet<Ident>); 1]>,
3091     ) {
3092         // Visit all direct subpatterns of this pattern.
3093         pat.walk(&mut |pat| {
3094             debug!("resolve_pattern pat={:?} node={:?}", pat, pat.kind);
3095             match pat.kind {
3096                 PatKind::Ident(bmode, ident, ref sub) => {
3097                     // First try to resolve the identifier as some existing entity,
3098                     // then fall back to a fresh binding.
3099                     let has_sub = sub.is_some();
3100                     let res = self
3101                         .try_resolve_as_non_binding(pat_src, bmode, ident, has_sub)
3102                         .unwrap_or_else(|| self.fresh_binding(ident, pat.id, pat_src, bindings));
3103                     self.r.record_partial_res(pat.id, PartialRes::new(res));
3104                     self.r.record_pat_span(pat.id, pat.span);
3105                 }
3106                 PatKind::TupleStruct(ref qself, ref path, ref sub_patterns) => {
3107                     self.smart_resolve_path(
3108                         pat.id,
3109                         qself,
3110                         path,
3111                         PathSource::TupleStruct(
3112                             pat.span,
3113                             self.r.arenas.alloc_pattern_spans(sub_patterns.iter().map(|p| p.span)),
3114                         ),
3115                     );
3116                 }
3117                 PatKind::Path(ref qself, ref path) => {
3118                     self.smart_resolve_path(pat.id, qself, path, PathSource::Pat);
3119                 }
3120                 PatKind::Struct(ref qself, ref path, ..) => {
3121                     self.smart_resolve_path(pat.id, qself, path, PathSource::Struct);
3122                 }
3123                 PatKind::Or(ref ps) => {
3124                     // Add a new set of bindings to the stack. `Or` here records that when a
3125                     // binding already exists in this set, it should not result in an error because
3126                     // `V1(a) | V2(a)` must be allowed and are checked for consistency later.
3127                     bindings.push((PatBoundCtx::Or, Default::default()));
3128                     for p in ps {
3129                         // Now we need to switch back to a product context so that each
3130                         // part of the or-pattern internally rejects already bound names.
3131                         // For example, `V1(a) | V2(a, a)` and `V1(a, a) | V2(a)` are bad.
3132                         bindings.push((PatBoundCtx::Product, Default::default()));
3133                         self.resolve_pattern_inner(p, pat_src, bindings);
3134                         // Move up the non-overlapping bindings to the or-pattern.
3135                         // Existing bindings just get "merged".
3136                         let collected = bindings.pop().unwrap().1;
3137                         bindings.last_mut().unwrap().1.extend(collected);
3138                     }
3139                     // This or-pattern itself can itself be part of a product,
3140                     // e.g. `(V1(a) | V2(a), a)` or `(a, V1(a) | V2(a))`.
3141                     // Both cases bind `a` again in a product pattern and must be rejected.
3142                     let collected = bindings.pop().unwrap().1;
3143                     bindings.last_mut().unwrap().1.extend(collected);
3144
3145                     // Prevent visiting `ps` as we've already done so above.
3146                     return false;
3147                 }
3148                 _ => {}
3149             }
3150             true
3151         });
3152     }
3153
3154     fn fresh_binding(
3155         &mut self,
3156         ident: Ident,
3157         pat_id: NodeId,
3158         pat_src: PatternSource,
3159         bindings: &mut SmallVec<[(PatBoundCtx, FxHashSet<Ident>); 1]>,
3160     ) -> Res {
3161         // Add the binding to the local ribs, if it doesn't already exist in the bindings map.
3162         // (We must not add it if it's in the bindings map because that breaks the assumptions
3163         // later passes make about or-patterns.)
3164         let ident = ident.normalize_to_macro_rules();
3165
3166         let mut bound_iter = bindings.iter().filter(|(_, set)| set.contains(&ident));
3167         // Already bound in a product pattern? e.g. `(a, a)` which is not allowed.
3168         let already_bound_and = bound_iter.clone().any(|(ctx, _)| *ctx == PatBoundCtx::Product);
3169         // Already bound in an or-pattern? e.g. `V1(a) | V2(a)`.
3170         // This is *required* for consistency which is checked later.
3171         let already_bound_or = bound_iter.any(|(ctx, _)| *ctx == PatBoundCtx::Or);
3172
3173         if already_bound_and {
3174             // Overlap in a product pattern somewhere; report an error.
3175             use ResolutionError::*;
3176             let error = match pat_src {
3177                 // `fn f(a: u8, a: u8)`:
3178                 PatternSource::FnParam => IdentifierBoundMoreThanOnceInParameterList,
3179                 // `Variant(a, a)`:
3180                 _ => IdentifierBoundMoreThanOnceInSamePattern,
3181             };
3182             self.report_error(ident.span, error(ident.name));
3183         }
3184
3185         // Record as bound if it's valid:
3186         let ident_valid = ident.name != kw::Empty;
3187         if ident_valid {
3188             bindings.last_mut().unwrap().1.insert(ident);
3189         }
3190
3191         if already_bound_or {
3192             // `Variant1(a) | Variant2(a)`, ok
3193             // Reuse definition from the first `a`.
3194             self.innermost_rib_bindings(ValueNS)[&ident]
3195         } else {
3196             let res = Res::Local(pat_id);
3197             if ident_valid {
3198                 // A completely fresh binding add to the set if it's valid.
3199                 self.innermost_rib_bindings(ValueNS).insert(ident, res);
3200             }
3201             res
3202         }
3203     }
3204
3205     fn innermost_rib_bindings(&mut self, ns: Namespace) -> &mut IdentMap<Res> {
3206         &mut self.ribs[ns].last_mut().unwrap().bindings
3207     }
3208
3209     fn try_resolve_as_non_binding(
3210         &mut self,
3211         pat_src: PatternSource,
3212         ann: BindingAnnotation,
3213         ident: Ident,
3214         has_sub: bool,
3215     ) -> Option<Res> {
3216         // An immutable (no `mut`) by-value (no `ref`) binding pattern without
3217         // a sub pattern (no `@ $pat`) is syntactically ambiguous as it could
3218         // also be interpreted as a path to e.g. a constant, variant, etc.
3219         let is_syntactic_ambiguity = !has_sub && ann == BindingAnnotation::NONE;
3220
3221         let ls_binding = self.maybe_resolve_ident_in_lexical_scope(ident, ValueNS)?;
3222         let (res, binding) = match ls_binding {
3223             LexicalScopeBinding::Item(binding)
3224                 if is_syntactic_ambiguity && binding.is_ambiguity() =>
3225             {
3226                 // For ambiguous bindings we don't know all their definitions and cannot check
3227                 // whether they can be shadowed by fresh bindings or not, so force an error.
3228                 // issues/33118#issuecomment-233962221 (see below) still applies here,
3229                 // but we have to ignore it for backward compatibility.
3230                 self.r.record_use(ident, binding, false);
3231                 return None;
3232             }
3233             LexicalScopeBinding::Item(binding) => (binding.res(), Some(binding)),
3234             LexicalScopeBinding::Res(res) => (res, None),
3235         };
3236
3237         match res {
3238             Res::SelfCtor(_) // See #70549.
3239             | Res::Def(
3240                 DefKind::Ctor(_, CtorKind::Const) | DefKind::Const | DefKind::ConstParam,
3241                 _,
3242             ) if is_syntactic_ambiguity => {
3243                 // Disambiguate in favor of a unit struct/variant or constant pattern.
3244                 if let Some(binding) = binding {
3245                     self.r.record_use(ident, binding, false);
3246                 }
3247                 Some(res)
3248             }
3249             Res::Def(DefKind::Ctor(..) | DefKind::Const | DefKind::Static(_), _) => {
3250                 // This is unambiguously a fresh binding, either syntactically
3251                 // (e.g., `IDENT @ PAT` or `ref IDENT`) or because `IDENT` resolves
3252                 // to something unusable as a pattern (e.g., constructor function),
3253                 // but we still conservatively report an error, see
3254                 // issues/33118#issuecomment-233962221 for one reason why.
3255                 let binding = binding.expect("no binding for a ctor or static");
3256                 self.report_error(
3257                     ident.span,
3258                     ResolutionError::BindingShadowsSomethingUnacceptable {
3259                         shadowing_binding: pat_src,
3260                         name: ident.name,
3261                         participle: if binding.is_import() { "imported" } else { "defined" },
3262                         article: binding.res().article(),
3263                         shadowed_binding: binding.res(),
3264                         shadowed_binding_span: binding.span,
3265                     },
3266                 );
3267                 None
3268             }
3269             Res::Def(DefKind::ConstParam, def_id) => {
3270                 // Same as for DefKind::Const above, but here, `binding` is `None`, so we
3271                 // have to construct the error differently
3272                 self.report_error(
3273                     ident.span,
3274                     ResolutionError::BindingShadowsSomethingUnacceptable {
3275                         shadowing_binding: pat_src,
3276                         name: ident.name,
3277                         participle: "defined",
3278                         article: res.article(),
3279                         shadowed_binding: res,
3280                         shadowed_binding_span: self.r.opt_span(def_id).expect("const parameter defined outside of local crate"),
3281                     }
3282                 );
3283                 None
3284             }
3285             Res::Def(DefKind::Fn, _) | Res::Local(..) | Res::Err => {
3286                 // These entities are explicitly allowed to be shadowed by fresh bindings.
3287                 None
3288             }
3289             Res::SelfCtor(_) => {
3290                 // We resolve `Self` in pattern position as an ident sometimes during recovery,
3291                 // so delay a bug instead of ICEing.
3292                 self.r.session.delay_span_bug(
3293                     ident.span,
3294                     "unexpected `SelfCtor` in pattern, expected identifier"
3295                 );
3296                 None
3297             }
3298             _ => span_bug!(
3299                 ident.span,
3300                 "unexpected resolution for an identifier in pattern: {:?}",
3301                 res,
3302             ),
3303         }
3304     }
3305
3306     // High-level and context dependent path resolution routine.
3307     // Resolves the path and records the resolution into definition map.
3308     // If resolution fails tries several techniques to find likely
3309     // resolution candidates, suggest imports or other help, and report
3310     // errors in user friendly way.
3311     fn smart_resolve_path(
3312         &mut self,
3313         id: NodeId,
3314         qself: &Option<P<QSelf>>,
3315         path: &Path,
3316         source: PathSource<'ast>,
3317     ) {
3318         self.smart_resolve_path_fragment(
3319             qself,
3320             &Segment::from_path(path),
3321             source,
3322             Finalize::new(id, path.span),
3323         );
3324     }
3325
3326     #[instrument(level = "debug", skip(self))]
3327     fn smart_resolve_path_fragment(
3328         &mut self,
3329         qself: &Option<P<QSelf>>,
3330         path: &[Segment],
3331         source: PathSource<'ast>,
3332         finalize: Finalize,
3333     ) -> PartialRes {
3334         let ns = source.namespace();
3335
3336         let Finalize { node_id, path_span, .. } = finalize;
3337         let report_errors = |this: &mut Self, res: Option<Res>| {
3338             if this.should_report_errs() {
3339                 let (err, candidates) =
3340                     this.smart_resolve_report_errors(path, path_span, source, res);
3341
3342                 let def_id = this.parent_scope.module.nearest_parent_mod();
3343                 let instead = res.is_some();
3344                 let suggestion = if let Some((start, end)) = this.diagnostic_metadata.in_range
3345                     && path[0].ident.span.lo() == end.span.lo()
3346                 {
3347                     let mut sugg = ".";
3348                     let mut span = start.span.between(end.span);
3349                     if span.lo() + BytePos(2) == span.hi() {
3350                         // There's no space between the start, the range op and the end, suggest
3351                         // removal which will look better.
3352                         span = span.with_lo(span.lo() + BytePos(1));
3353                         sugg = "";
3354                     }
3355                     Some((
3356                         span,
3357                         "you might have meant to write `.` instead of `..`",
3358                         sugg.to_string(),
3359                         Applicability::MaybeIncorrect,
3360                     ))
3361                 } else if res.is_none() {
3362                     this.report_missing_type_error(path)
3363                 } else {
3364                     None
3365                 };
3366
3367                 this.r.use_injections.push(UseError {
3368                     err,
3369                     candidates,
3370                     def_id,
3371                     instead,
3372                     suggestion,
3373                     path: path.into(),
3374                     is_call: source.is_call(),
3375                 });
3376             }
3377
3378             PartialRes::new(Res::Err)
3379         };
3380
3381         // For paths originating from calls (like in `HashMap::new()`), tries
3382         // to enrich the plain `failed to resolve: ...` message with hints
3383         // about possible missing imports.
3384         //
3385         // Similar thing, for types, happens in `report_errors` above.
3386         let report_errors_for_call = |this: &mut Self, parent_err: Spanned<ResolutionError<'a>>| {
3387             if !source.is_call() {
3388                 return Some(parent_err);
3389             }
3390
3391             // Before we start looking for candidates, we have to get our hands
3392             // on the type user is trying to perform invocation on; basically:
3393             // we're transforming `HashMap::new` into just `HashMap`.
3394             let prefix_path = match path.split_last() {
3395                 Some((_, path)) if !path.is_empty() => path,
3396                 _ => return Some(parent_err),
3397             };
3398
3399             let (mut err, candidates) =
3400                 this.smart_resolve_report_errors(prefix_path, path_span, PathSource::Type, None);
3401
3402             // There are two different error messages user might receive at
3403             // this point:
3404             // - E0412 cannot find type `{}` in this scope
3405             // - E0433 failed to resolve: use of undeclared type or module `{}`
3406             //
3407             // The first one is emitted for paths in type-position, and the
3408             // latter one - for paths in expression-position.
3409             //
3410             // Thus (since we're in expression-position at this point), not to
3411             // confuse the user, we want to keep the *message* from E0433 (so
3412             // `parent_err`), but we want *hints* from E0412 (so `err`).
3413             //
3414             // And that's what happens below - we're just mixing both messages
3415             // into a single one.
3416             let mut parent_err = this.r.into_struct_error(parent_err.span, parent_err.node);
3417
3418             // overwrite all properties with the parent's error message
3419             err.message = take(&mut parent_err.message);
3420             err.code = take(&mut parent_err.code);
3421             swap(&mut err.span, &mut parent_err.span);
3422             err.children = take(&mut parent_err.children);
3423             err.sort_span = parent_err.sort_span;
3424             err.is_lint = parent_err.is_lint;
3425
3426             // merge the parent's suggestions with the typo suggestions
3427             fn append_result<T, E>(res1: &mut Result<Vec<T>, E>, res2: Result<Vec<T>, E>) {
3428                 match res1 {
3429                     Ok(vec1) => match res2 {
3430                         Ok(mut vec2) => vec1.append(&mut vec2),
3431                         Err(e) => *res1 = Err(e),
3432                     },
3433                     Err(_) => (),
3434                 };
3435             }
3436             append_result(&mut err.suggestions, parent_err.suggestions.clone());
3437
3438             parent_err.cancel();
3439
3440             let def_id = this.parent_scope.module.nearest_parent_mod();
3441
3442             if this.should_report_errs() {
3443                 if candidates.is_empty() {
3444                     if path.len() == 2 && prefix_path.len() == 1 {
3445                         // Delay to check whether methond name is an associated function or not
3446                         // ```
3447                         // let foo = Foo {};
3448                         // foo::bar(); // possibly suggest to foo.bar();
3449                         //```
3450                         err.stash(
3451                             prefix_path[0].ident.span,
3452                             rustc_errors::StashKey::CallAssocMethod,
3453                         );
3454                     } else {
3455                         // When there is no suggested imports, we can just emit the error
3456                         // and suggestions immediately. Note that we bypass the usually error
3457                         // reporting routine (ie via `self.r.report_error`) because we need
3458                         // to post-process the `ResolutionError` above.
3459                         err.emit();
3460                     }
3461                 } else {
3462                     // If there are suggested imports, the error reporting is delayed
3463                     this.r.use_injections.push(UseError {
3464                         err,
3465                         candidates,
3466                         def_id,
3467                         instead: false,
3468                         suggestion: None,
3469                         path: prefix_path.into(),
3470                         is_call: source.is_call(),
3471                     });
3472                 }
3473             } else {
3474                 err.cancel();
3475             }
3476
3477             // We don't return `Some(parent_err)` here, because the error will
3478             // be already printed either immediately or as part of the `use` injections
3479             None
3480         };
3481
3482         let partial_res = match self.resolve_qpath_anywhere(
3483             qself,
3484             path,
3485             ns,
3486             path_span,
3487             source.defer_to_typeck(),
3488             finalize,
3489         ) {
3490             Ok(Some(partial_res)) if let Some(res) = partial_res.full_res() => {
3491                 if source.is_expected(res) || res == Res::Err {
3492                     partial_res
3493                 } else {
3494                     report_errors(self, Some(res))
3495                 }
3496             }
3497
3498             Ok(Some(partial_res)) if source.defer_to_typeck() => {
3499                 // Not fully resolved associated item `T::A::B` or `<T as Tr>::A::B`
3500                 // or `<T>::A::B`. If `B` should be resolved in value namespace then
3501                 // it needs to be added to the trait map.
3502                 if ns == ValueNS {
3503                     let item_name = path.last().unwrap().ident;
3504                     let traits = self.traits_in_scope(item_name, ns);
3505                     self.r.trait_map.insert(node_id, traits);
3506                 }
3507
3508                 if PrimTy::from_name(path[0].ident.name).is_some() {
3509                     let mut std_path = Vec::with_capacity(1 + path.len());
3510
3511                     std_path.push(Segment::from_ident(Ident::with_dummy_span(sym::std)));
3512                     std_path.extend(path);
3513                     if let PathResult::Module(_) | PathResult::NonModule(_) =
3514                         self.resolve_path(&std_path, Some(ns), None)
3515                     {
3516                         // Check if we wrote `str::from_utf8` instead of `std::str::from_utf8`
3517                         let item_span =
3518                             path.iter().last().map_or(path_span, |segment| segment.ident.span);
3519
3520                         self.r.confused_type_with_std_module.insert(item_span, path_span);
3521                         self.r.confused_type_with_std_module.insert(path_span, path_span);
3522                     }
3523                 }
3524
3525                 partial_res
3526             }
3527
3528             Err(err) => {
3529                 if let Some(err) = report_errors_for_call(self, err) {
3530                     self.report_error(err.span, err.node);
3531                 }
3532
3533                 PartialRes::new(Res::Err)
3534             }
3535
3536             _ => report_errors(self, None),
3537         };
3538
3539         if !matches!(source, PathSource::TraitItem(..)) {
3540             // Avoid recording definition of `A::B` in `<T as A>::B::C`.
3541             self.r.record_partial_res(node_id, partial_res);
3542             self.resolve_elided_lifetimes_in_path(node_id, partial_res, path, source, path_span);
3543         }
3544
3545         partial_res
3546     }
3547
3548     fn self_type_is_available(&mut self) -> bool {
3549         let binding = self
3550             .maybe_resolve_ident_in_lexical_scope(Ident::with_dummy_span(kw::SelfUpper), TypeNS);
3551         if let Some(LexicalScopeBinding::Res(res)) = binding { res != Res::Err } else { false }
3552     }
3553
3554     fn self_value_is_available(&mut self, self_span: Span) -> bool {
3555         let ident = Ident::new(kw::SelfLower, self_span);
3556         let binding = self.maybe_resolve_ident_in_lexical_scope(ident, ValueNS);
3557         if let Some(LexicalScopeBinding::Res(res)) = binding { res != Res::Err } else { false }
3558     }
3559
3560     /// A wrapper around [`Resolver::report_error`].
3561     ///
3562     /// This doesn't emit errors for function bodies if this is rustdoc.
3563     fn report_error(&mut self, span: Span, resolution_error: ResolutionError<'a>) {
3564         if self.should_report_errs() {
3565             self.r.report_error(span, resolution_error);
3566         }
3567     }
3568
3569     #[inline]
3570     /// If we're actually rustdoc then avoid giving a name resolution error for `cfg()` items.
3571     fn should_report_errs(&self) -> bool {
3572         !(self.r.session.opts.actually_rustdoc && self.in_func_body)
3573     }
3574
3575     // Resolve in alternative namespaces if resolution in the primary namespace fails.
3576     fn resolve_qpath_anywhere(
3577         &mut self,
3578         qself: &Option<P<QSelf>>,
3579         path: &[Segment],
3580         primary_ns: Namespace,
3581         span: Span,
3582         defer_to_typeck: bool,
3583         finalize: Finalize,
3584     ) -> Result<Option<PartialRes>, Spanned<ResolutionError<'a>>> {
3585         let mut fin_res = None;
3586
3587         for (i, &ns) in [primary_ns, TypeNS, ValueNS].iter().enumerate() {
3588             if i == 0 || ns != primary_ns {
3589                 match self.resolve_qpath(qself, path, ns, finalize)? {
3590                     Some(partial_res)
3591                         if partial_res.unresolved_segments() == 0 || defer_to_typeck =>
3592                     {
3593                         return Ok(Some(partial_res));
3594                     }
3595                     partial_res => {
3596                         if fin_res.is_none() {
3597                             fin_res = partial_res;
3598                         }
3599                     }
3600                 }
3601             }
3602         }
3603
3604         assert!(primary_ns != MacroNS);
3605
3606         if qself.is_none() {
3607             let path_seg = |seg: &Segment| PathSegment::from_ident(seg.ident);
3608             let path = Path { segments: path.iter().map(path_seg).collect(), span, tokens: None };
3609             if let Ok((_, res)) =
3610                 self.r.resolve_macro_path(&path, None, &self.parent_scope, false, false)
3611             {
3612                 return Ok(Some(PartialRes::new(res)));
3613             }
3614         }
3615
3616         Ok(fin_res)
3617     }
3618
3619     /// Handles paths that may refer to associated items.
3620     fn resolve_qpath(
3621         &mut self,
3622         qself: &Option<P<QSelf>>,
3623         path: &[Segment],
3624         ns: Namespace,
3625         finalize: Finalize,
3626     ) -> Result<Option<PartialRes>, Spanned<ResolutionError<'a>>> {
3627         debug!(
3628             "resolve_qpath(qself={:?}, path={:?}, ns={:?}, finalize={:?})",
3629             qself, path, ns, finalize,
3630         );
3631
3632         if let Some(qself) = qself {
3633             if qself.position == 0 {
3634                 // This is a case like `<T>::B`, where there is no
3635                 // trait to resolve.  In that case, we leave the `B`
3636                 // segment to be resolved by type-check.
3637                 return Ok(Some(PartialRes::with_unresolved_segments(
3638                     Res::Def(DefKind::Mod, CRATE_DEF_ID.to_def_id()),
3639                     path.len(),
3640                 )));
3641             }
3642
3643             // Make sure `A::B` in `<T as A::B>::C` is a trait item.
3644             //
3645             // Currently, `path` names the full item (`A::B::C`, in
3646             // our example).  so we extract the prefix of that that is
3647             // the trait (the slice upto and including
3648             // `qself.position`). And then we recursively resolve that,
3649             // but with `qself` set to `None`.
3650             let ns = if qself.position + 1 == path.len() { ns } else { TypeNS };
3651             let partial_res = self.smart_resolve_path_fragment(
3652                 &None,
3653                 &path[..=qself.position],
3654                 PathSource::TraitItem(ns),
3655                 Finalize::with_root_span(finalize.node_id, finalize.path_span, qself.path_span),
3656             );
3657
3658             // The remaining segments (the `C` in our example) will
3659             // have to be resolved by type-check, since that requires doing
3660             // trait resolution.
3661             return Ok(Some(PartialRes::with_unresolved_segments(
3662                 partial_res.base_res(),
3663                 partial_res.unresolved_segments() + path.len() - qself.position - 1,
3664             )));
3665         }
3666
3667         let result = match self.resolve_path(&path, Some(ns), Some(finalize)) {
3668             PathResult::NonModule(path_res) => path_res,
3669             PathResult::Module(ModuleOrUniformRoot::Module(module)) if !module.is_normal() => {
3670                 PartialRes::new(module.res().unwrap())
3671             }
3672             // In `a(::assoc_item)*` `a` cannot be a module. If `a` does resolve to a module we
3673             // don't report an error right away, but try to fallback to a primitive type.
3674             // So, we are still able to successfully resolve something like
3675             //
3676             // use std::u8; // bring module u8 in scope
3677             // fn f() -> u8 { // OK, resolves to primitive u8, not to std::u8
3678             //     u8::max_value() // OK, resolves to associated function <u8>::max_value,
3679             //                     // not to non-existent std::u8::max_value
3680             // }
3681             //
3682             // Such behavior is required for backward compatibility.
3683             // The same fallback is used when `a` resolves to nothing.
3684             PathResult::Module(ModuleOrUniformRoot::Module(_)) | PathResult::Failed { .. }
3685                 if (ns == TypeNS || path.len() > 1)
3686                     && PrimTy::from_name(path[0].ident.name).is_some() =>
3687             {
3688                 let prim = PrimTy::from_name(path[0].ident.name).unwrap();
3689                 PartialRes::with_unresolved_segments(Res::PrimTy(prim), path.len() - 1)
3690             }
3691             PathResult::Module(ModuleOrUniformRoot::Module(module)) => {
3692                 PartialRes::new(module.res().unwrap())
3693             }
3694             PathResult::Failed { is_error_from_last_segment: false, span, label, suggestion } => {
3695                 return Err(respan(span, ResolutionError::FailedToResolve { label, suggestion }));
3696             }
3697             PathResult::Module(..) | PathResult::Failed { .. } => return Ok(None),
3698             PathResult::Indeterminate => bug!("indeterminate path result in resolve_qpath"),
3699         };
3700
3701         if path.len() > 1
3702             && let Some(res) = result.full_res()
3703             && res != Res::Err
3704             && path[0].ident.name != kw::PathRoot
3705             && path[0].ident.name != kw::DollarCrate
3706         {
3707             let unqualified_result = {
3708                 match self.resolve_path(&[*path.last().unwrap()], Some(ns), None) {
3709                     PathResult::NonModule(path_res) => path_res.expect_full_res(),
3710                     PathResult::Module(ModuleOrUniformRoot::Module(module)) => {
3711                         module.res().unwrap()
3712                     }
3713                     _ => return Ok(Some(result)),
3714                 }
3715             };
3716             if res == unqualified_result {
3717                 let lint = lint::builtin::UNUSED_QUALIFICATIONS;
3718                 self.r.lint_buffer.buffer_lint(
3719                     lint,
3720                     finalize.node_id,
3721                     finalize.path_span,
3722                     "unnecessary qualification",
3723                 )
3724             }
3725         }
3726
3727         Ok(Some(result))
3728     }
3729
3730     fn with_resolved_label(&mut self, label: Option<Label>, id: NodeId, f: impl FnOnce(&mut Self)) {
3731         if let Some(label) = label {
3732             if label.ident.as_str().as_bytes()[1] != b'_' {
3733                 self.diagnostic_metadata.unused_labels.insert(id, label.ident.span);
3734             }
3735
3736             if let Ok((_, orig_span)) = self.resolve_label(label.ident) {
3737                 diagnostics::signal_label_shadowing(self.r.session, orig_span, label.ident)
3738             }
3739
3740             self.with_label_rib(NormalRibKind, |this| {
3741                 let ident = label.ident.normalize_to_macro_rules();
3742                 this.label_ribs.last_mut().unwrap().bindings.insert(ident, id);
3743                 f(this);
3744             });
3745         } else {
3746             f(self);
3747         }
3748     }
3749
3750     fn resolve_labeled_block(&mut self, label: Option<Label>, id: NodeId, block: &'ast Block) {
3751         self.with_resolved_label(label, id, |this| this.visit_block(block));
3752     }
3753
3754     fn resolve_block(&mut self, block: &'ast Block) {
3755         debug!("(resolving block) entering block");
3756         // Move down in the graph, if there's an anonymous module rooted here.
3757         let orig_module = self.parent_scope.module;
3758         let anonymous_module = self.r.block_map.get(&block.id).cloned(); // clones a reference
3759
3760         let mut num_macro_definition_ribs = 0;
3761         if let Some(anonymous_module) = anonymous_module {
3762             debug!("(resolving block) found anonymous module, moving down");
3763             self.ribs[ValueNS].push(Rib::new(ModuleRibKind(anonymous_module)));
3764             self.ribs[TypeNS].push(Rib::new(ModuleRibKind(anonymous_module)));
3765             self.parent_scope.module = anonymous_module;
3766         } else {
3767             self.ribs[ValueNS].push(Rib::new(NormalRibKind));
3768         }
3769
3770         let prev = self.diagnostic_metadata.current_block_could_be_bare_struct_literal.take();
3771         if let (true, [Stmt { kind: StmtKind::Expr(expr), .. }]) =
3772             (block.could_be_bare_literal, &block.stmts[..])
3773             && let ExprKind::Type(..) = expr.kind
3774         {
3775             self.diagnostic_metadata.current_block_could_be_bare_struct_literal =
3776             Some(block.span);
3777         }
3778         // Descend into the block.
3779         for stmt in &block.stmts {
3780             if let StmtKind::Item(ref item) = stmt.kind
3781                 && let ItemKind::MacroDef(..) = item.kind {
3782                 num_macro_definition_ribs += 1;
3783                 let res = self.r.local_def_id(item.id).to_def_id();
3784                 self.ribs[ValueNS].push(Rib::new(MacroDefinition(res)));
3785                 self.label_ribs.push(Rib::new(MacroDefinition(res)));
3786             }
3787
3788             self.visit_stmt(stmt);
3789         }
3790         self.diagnostic_metadata.current_block_could_be_bare_struct_literal = prev;
3791
3792         // Move back up.
3793         self.parent_scope.module = orig_module;
3794         for _ in 0..num_macro_definition_ribs {
3795             self.ribs[ValueNS].pop();
3796             self.label_ribs.pop();
3797         }
3798         self.last_block_rib = self.ribs[ValueNS].pop();
3799         if anonymous_module.is_some() {
3800             self.ribs[TypeNS].pop();
3801         }
3802         debug!("(resolving block) leaving block");
3803     }
3804
3805     fn resolve_anon_const(&mut self, constant: &'ast AnonConst, is_repeat: IsRepeatExpr) {
3806         debug!("resolve_anon_const {:?} is_repeat: {:?}", constant, is_repeat);
3807         self.with_constant_rib(
3808             is_repeat,
3809             if constant.value.is_potential_trivial_const_param() {
3810                 ConstantHasGenerics::Yes
3811             } else {
3812                 ConstantHasGenerics::No
3813             },
3814             None,
3815             |this| visit::walk_anon_const(this, constant),
3816         );
3817     }
3818
3819     fn resolve_inline_const(&mut self, constant: &'ast AnonConst) {
3820         debug!("resolve_anon_const {constant:?}");
3821         self.with_constant_rib(IsRepeatExpr::No, ConstantHasGenerics::Yes, None, |this| {
3822             visit::walk_anon_const(this, constant)
3823         });
3824     }
3825
3826     fn resolve_expr(&mut self, expr: &'ast Expr, parent: Option<&'ast Expr>) {
3827         // First, record candidate traits for this expression if it could
3828         // result in the invocation of a method call.
3829
3830         self.record_candidate_traits_for_expr_if_necessary(expr);
3831
3832         // Next, resolve the node.
3833         match expr.kind {
3834             ExprKind::Path(ref qself, ref path) => {
3835                 self.smart_resolve_path(expr.id, qself, path, PathSource::Expr(parent));
3836                 visit::walk_expr(self, expr);
3837             }
3838
3839             ExprKind::Struct(ref se) => {
3840                 self.smart_resolve_path(expr.id, &se.qself, &se.path, PathSource::Struct);
3841                 visit::walk_expr(self, expr);
3842             }
3843
3844             ExprKind::Break(Some(label), _) | ExprKind::Continue(Some(label)) => {
3845                 match self.resolve_label(label.ident) {
3846                     Ok((node_id, _)) => {
3847                         // Since this res is a label, it is never read.
3848                         self.r.label_res_map.insert(expr.id, node_id);
3849                         self.diagnostic_metadata.unused_labels.remove(&node_id);
3850                     }
3851                     Err(error) => {
3852                         self.report_error(label.ident.span, error);
3853                     }
3854                 }
3855
3856                 // visit `break` argument if any
3857                 visit::walk_expr(self, expr);
3858             }
3859
3860             ExprKind::Break(None, Some(ref e)) => {
3861                 // We use this instead of `visit::walk_expr` to keep the parent expr around for
3862                 // better diagnostics.
3863                 self.resolve_expr(e, Some(&expr));
3864             }
3865
3866             ExprKind::Let(ref pat, ref scrutinee, _) => {
3867                 self.visit_expr(scrutinee);
3868                 self.resolve_pattern_top(pat, PatternSource::Let);
3869             }
3870
3871             ExprKind::If(ref cond, ref then, ref opt_else) => {
3872                 self.with_rib(ValueNS, NormalRibKind, |this| {
3873                     let old = this.diagnostic_metadata.in_if_condition.replace(cond);
3874                     this.visit_expr(cond);
3875                     this.diagnostic_metadata.in_if_condition = old;
3876                     this.visit_block(then);
3877                 });
3878                 if let Some(expr) = opt_else {
3879                     self.visit_expr(expr);
3880                 }
3881             }
3882
3883             ExprKind::Loop(ref block, label, _) => {
3884                 self.resolve_labeled_block(label, expr.id, &block)
3885             }
3886
3887             ExprKind::While(ref cond, ref block, label) => {
3888                 self.with_resolved_label(label, expr.id, |this| {
3889                     this.with_rib(ValueNS, NormalRibKind, |this| {
3890                         let old = this.diagnostic_metadata.in_if_condition.replace(cond);
3891                         this.visit_expr(cond);
3892                         this.diagnostic_metadata.in_if_condition = old;
3893                         this.visit_block(block);
3894                     })
3895                 });
3896             }
3897
3898             ExprKind::ForLoop(ref pat, ref iter_expr, ref block, label) => {
3899                 self.visit_expr(iter_expr);
3900                 self.with_rib(ValueNS, NormalRibKind, |this| {
3901                     this.resolve_pattern_top(pat, PatternSource::For);
3902                     this.resolve_labeled_block(label, expr.id, block);
3903                 });
3904             }
3905
3906             ExprKind::Block(ref block, label) => self.resolve_labeled_block(label, block.id, block),
3907
3908             // Equivalent to `visit::walk_expr` + passing some context to children.
3909             ExprKind::Field(ref subexpression, _) => {
3910                 self.resolve_expr(subexpression, Some(expr));
3911             }
3912             ExprKind::MethodCall(box MethodCall { ref seg, ref receiver, ref args, .. }) => {
3913                 self.resolve_expr(receiver, Some(expr));
3914                 for arg in args {
3915                     self.resolve_expr(arg, None);
3916                 }
3917                 self.visit_path_segment(seg);
3918             }
3919
3920             ExprKind::Call(ref callee, ref arguments) => {
3921                 self.resolve_expr(callee, Some(expr));
3922                 let const_args = self.r.legacy_const_generic_args(callee).unwrap_or_default();
3923                 for (idx, argument) in arguments.iter().enumerate() {
3924                     // Constant arguments need to be treated as AnonConst since
3925                     // that is how they will be later lowered to HIR.
3926                     if const_args.contains(&idx) {
3927                         self.with_constant_rib(
3928                             IsRepeatExpr::No,
3929                             if argument.is_potential_trivial_const_param() {
3930                                 ConstantHasGenerics::Yes
3931                             } else {
3932                                 ConstantHasGenerics::No
3933                             },
3934                             None,
3935                             |this| {
3936                                 this.resolve_expr(argument, None);
3937                             },
3938                         );
3939                     } else {
3940                         self.resolve_expr(argument, None);
3941                     }
3942                 }
3943             }
3944             ExprKind::Type(ref type_expr, ref ty) => {
3945                 // `ParseSess::type_ascription_path_suggestions` keeps spans of colon tokens in
3946                 // type ascription. Here we are trying to retrieve the span of the colon token as
3947                 // well, but only if it's written without spaces `expr:Ty` and therefore confusable
3948                 // with `expr::Ty`, only in this case it will match the span from
3949                 // `type_ascription_path_suggestions`.
3950                 self.diagnostic_metadata
3951                     .current_type_ascription
3952                     .push(type_expr.span.between(ty.span));
3953                 visit::walk_expr(self, expr);
3954                 self.diagnostic_metadata.current_type_ascription.pop();
3955             }
3956             // `async |x| ...` gets desugared to `|x| async {...}`, so we need to
3957             // resolve the arguments within the proper scopes so that usages of them inside the
3958             // closure are detected as upvars rather than normal closure arg usages.
3959             ExprKind::Closure(box ast::Closure {
3960                 asyncness: Async::Yes { .. },
3961                 ref fn_decl,
3962                 ref body,
3963                 ..
3964             }) => {
3965                 self.with_rib(ValueNS, NormalRibKind, |this| {
3966                     this.with_label_rib(ClosureOrAsyncRibKind, |this| {
3967                         // Resolve arguments:
3968                         this.resolve_params(&fn_decl.inputs);
3969                         // No need to resolve return type --
3970                         // the outer closure return type is `FnRetTy::Default`.
3971
3972                         // Now resolve the inner closure
3973                         {
3974                             // No need to resolve arguments: the inner closure has none.
3975                             // Resolve the return type:
3976                             visit::walk_fn_ret_ty(this, &fn_decl.output);
3977                             // Resolve the body
3978                             this.visit_expr(body);
3979                         }
3980                     })
3981                 });
3982             }
3983             // For closures, ClosureOrAsyncRibKind is added in visit_fn
3984             ExprKind::Closure(box ast::Closure {
3985                 binder: ClosureBinder::For { ref generic_params, span },
3986                 ..
3987             }) => {
3988                 self.with_generic_param_rib(
3989                     &generic_params,
3990                     NormalRibKind,
3991                     LifetimeRibKind::Generics {
3992                         binder: expr.id,
3993                         kind: LifetimeBinderKind::Closure,
3994                         span,
3995                     },
3996                     |this| visit::walk_expr(this, expr),
3997                 );
3998             }
3999             ExprKind::Closure(..) => visit::walk_expr(self, expr),
4000             ExprKind::Async(..) => {
4001                 self.with_label_rib(ClosureOrAsyncRibKind, |this| visit::walk_expr(this, expr));
4002             }
4003             ExprKind::Repeat(ref elem, ref ct) => {
4004                 self.visit_expr(elem);
4005                 self.with_lifetime_rib(LifetimeRibKind::AnonConst, |this| {
4006                     this.with_lifetime_rib(LifetimeRibKind::Elided(LifetimeRes::Static), |this| {
4007                         this.resolve_anon_const(ct, IsRepeatExpr::Yes)
4008                     })
4009                 });
4010             }
4011             ExprKind::ConstBlock(ref ct) => {
4012                 self.resolve_inline_const(ct);
4013             }
4014             ExprKind::Index(ref elem, ref idx) => {
4015                 self.resolve_expr(elem, Some(expr));
4016                 self.visit_expr(idx);
4017             }
4018             ExprKind::Assign(ref lhs, ref rhs, _) => {
4019                 if !self.diagnostic_metadata.is_assign_rhs {
4020                     self.diagnostic_metadata.in_assignment = Some(expr);
4021                 }
4022                 self.visit_expr(lhs);
4023                 self.diagnostic_metadata.is_assign_rhs = true;
4024                 self.diagnostic_metadata.in_assignment = None;
4025                 self.visit_expr(rhs);
4026                 self.diagnostic_metadata.is_assign_rhs = false;
4027             }
4028             ExprKind::Range(Some(ref start), Some(ref end), RangeLimits::HalfOpen) => {
4029                 self.diagnostic_metadata.in_range = Some((start, end));
4030                 self.resolve_expr(start, Some(expr));
4031                 self.resolve_expr(end, Some(expr));
4032                 self.diagnostic_metadata.in_range = None;
4033             }
4034             _ => {
4035                 visit::walk_expr(self, expr);
4036             }
4037         }
4038     }
4039
4040     fn record_candidate_traits_for_expr_if_necessary(&mut self, expr: &'ast Expr) {
4041         match expr.kind {
4042             ExprKind::Field(_, ident) => {
4043                 // FIXME(#6890): Even though you can't treat a method like a
4044                 // field, we need to add any trait methods we find that match
4045                 // the field name so that we can do some nice error reporting
4046                 // later on in typeck.
4047                 let traits = self.traits_in_scope(ident, ValueNS);
4048                 self.r.trait_map.insert(expr.id, traits);
4049             }
4050             ExprKind::MethodCall(ref call) => {
4051                 debug!("(recording candidate traits for expr) recording traits for {}", expr.id);
4052                 let traits = self.traits_in_scope(call.seg.ident, ValueNS);
4053                 self.r.trait_map.insert(expr.id, traits);
4054             }
4055             _ => {
4056                 // Nothing to do.
4057             }
4058         }
4059     }
4060
4061     fn traits_in_scope(&mut self, ident: Ident, ns: Namespace) -> Vec<TraitCandidate> {
4062         self.r.traits_in_scope(
4063             self.current_trait_ref.as_ref().map(|(module, _)| *module),
4064             &self.parent_scope,
4065             ident.span.ctxt(),
4066             Some((ident.name, ns)),
4067         )
4068     }
4069
4070     /// Construct the list of in-scope lifetime parameters for async lowering.
4071     /// We include all lifetime parameters, either named or "Fresh".
4072     /// The order of those parameters does not matter, as long as it is
4073     /// deterministic.
4074     fn record_lifetime_params_for_async(
4075         &mut self,
4076         fn_id: NodeId,
4077         async_node_id: Option<(NodeId, Span)>,
4078     ) {
4079         if let Some((async_node_id, span)) = async_node_id {
4080             let mut extra_lifetime_params =
4081                 self.r.extra_lifetime_params_map.get(&fn_id).cloned().unwrap_or_default();
4082             for rib in self.lifetime_ribs.iter().rev() {
4083                 extra_lifetime_params.extend(
4084                     rib.bindings.iter().map(|(&ident, &(node_id, res))| (ident, node_id, res)),
4085                 );
4086                 match rib.kind {
4087                     LifetimeRibKind::Item => break,
4088                     LifetimeRibKind::AnonymousCreateParameter { binder, .. } => {
4089                         if let Some(earlier_fresh) = self.r.extra_lifetime_params_map.get(&binder) {
4090                             extra_lifetime_params.extend(earlier_fresh);
4091                         }
4092                     }
4093                     LifetimeRibKind::Generics { .. } => {}
4094                     _ => {
4095                         // We are in a function definition. We should only find `Generics`
4096                         // and `AnonymousCreateParameter` inside the innermost `Item`.
4097                         span_bug!(span, "unexpected rib kind: {:?}", rib.kind)
4098                     }
4099                 }
4100             }
4101             self.r.extra_lifetime_params_map.insert(async_node_id, extra_lifetime_params);
4102         }
4103     }
4104 }
4105
4106 struct LifetimeCountVisitor<'a, 'b> {
4107     r: &'b mut Resolver<'a>,
4108 }
4109
4110 /// Walks the whole crate in DFS order, visiting each item, counting the declared number of
4111 /// lifetime generic parameters.
4112 impl<'ast> Visitor<'ast> for LifetimeCountVisitor<'_, '_> {
4113     fn visit_item(&mut self, item: &'ast Item) {
4114         match &item.kind {
4115             ItemKind::TyAlias(box TyAlias { ref generics, .. })
4116             | ItemKind::Fn(box Fn { ref generics, .. })
4117             | ItemKind::Enum(_, ref generics)
4118             | ItemKind::Struct(_, ref generics)
4119             | ItemKind::Union(_, ref generics)
4120             | ItemKind::Impl(box Impl { ref generics, .. })
4121             | ItemKind::Trait(box Trait { ref generics, .. })
4122             | ItemKind::TraitAlias(ref generics, _) => {
4123                 let def_id = self.r.local_def_id(item.id);
4124                 let count = generics
4125                     .params
4126                     .iter()
4127                     .filter(|param| matches!(param.kind, ast::GenericParamKind::Lifetime { .. }))
4128                     .count();
4129                 self.r.item_generics_num_lifetimes.insert(def_id, count);
4130             }
4131
4132             ItemKind::Mod(..)
4133             | ItemKind::ForeignMod(..)
4134             | ItemKind::Static(..)
4135             | ItemKind::Const(..)
4136             | ItemKind::Use(..)
4137             | ItemKind::ExternCrate(..)
4138             | ItemKind::MacroDef(..)
4139             | ItemKind::GlobalAsm(..)
4140             | ItemKind::MacCall(..) => {}
4141         }
4142         visit::walk_item(self, item)
4143     }
4144 }
4145
4146 impl<'a> Resolver<'a> {
4147     pub(crate) fn late_resolve_crate(&mut self, krate: &Crate) {
4148         visit::walk_crate(&mut LifetimeCountVisitor { r: self }, krate);
4149         let mut late_resolution_visitor = LateResolutionVisitor::new(self);
4150         visit::walk_crate(&mut late_resolution_visitor, krate);
4151         for (id, span) in late_resolution_visitor.diagnostic_metadata.unused_labels.iter() {
4152             self.lint_buffer.buffer_lint(lint::builtin::UNUSED_LABELS, *id, *span, "unused label");
4153         }
4154     }
4155 }