compiler/rustc_resolve/src/ident.rs

   1 use rustc_ast::{self as ast, NodeId};
   2 use rustc_feature::is_builtin_attr_name;
   3 use rustc_hir::def::{DefKind, Namespace, NonMacroAttrKind, PartialRes, PerNS};
   4 use rustc_hir::PrimTy;
   5 use rustc_middle::bug;
   6 use rustc_middle::ty;
   7 use rustc_session::lint::builtin::PROC_MACRO_DERIVE_RESOLUTION_FALLBACK;
   8 use rustc_session::lint::BuiltinLintDiagnostics;
   9 use rustc_span::edition::Edition;
  10 use rustc_span::hygiene::{ExpnId, ExpnKind, LocalExpnId, MacroKind, SyntaxContext};
  11 use rustc_span::symbol::{kw, Ident};
  12 use rustc_span::{Span, DUMMY_SP};
  13
  14 use std::ptr;
  15
  16 use crate::late::{ConstantItemKind, HasGenericParams, PathSource, Rib, RibKind};
  17 use crate::macros::{sub_namespace_match, MacroRulesScope};
  18 use crate::{AmbiguityError, AmbiguityErrorMisc, AmbiguityKind, Determinacy, Finalize};
  19 use crate::{ImportKind, LexicalScopeBinding, Module, ModuleKind, ModuleOrUniformRoot};
  20 use crate::{NameBinding, NameBindingKind, ParentScope, PathResult, PrivacyError, Res};
  21 use crate::{ResolutionError, Resolver, Scope, ScopeSet, Segment, ToNameBinding, Weak};
  22
  23 use Determinacy::*;
  24 use Namespace::*;
  25 use RibKind::*;
  26
  27 impl<'a> Resolver<'a> {
  28     /// A generic scope visitor.
  29     /// Visits scopes in order to resolve some identifier in them or perform other actions.
  30     /// If the callback returns `Some` result, we stop visiting scopes and return it.
  31     crate fn visit_scopes<T>(
  32         &mut self,
  33         scope_set: ScopeSet<'a>,
  34         parent_scope: &ParentScope<'a>,
  35         ctxt: SyntaxContext,
  36         mut visitor: impl FnMut(
  37             &mut Self,
  38             Scope<'a>,
  39             /*use_prelude*/ bool,
  40             SyntaxContext,
  41         ) -> Option<T>,
  42     ) -> Option<T> {
  43         // General principles:
  44         // 1. Not controlled (user-defined) names should have higher priority than controlled names
  45         //    built into the language or standard library. This way we can add new names into the
  46         //    language or standard library without breaking user code.
  47         // 2. "Closed set" below means new names cannot appear after the current resolution attempt.
  48         // Places to search (in order of decreasing priority):
  49         // (Type NS)
  50         // 1. FIXME: Ribs (type parameters), there's no necessary infrastructure yet
  51         //    (open set, not controlled).
  52         // 2. Names in modules (both normal `mod`ules and blocks), loop through hygienic parents
  53         //    (open, not controlled).
  54         // 3. Extern prelude (open, the open part is from macro expansions, not controlled).
  55         // 4. Tool modules (closed, controlled right now, but not in the future).
  56         // 5. Standard library prelude (de-facto closed, controlled).
  57         // 6. Language prelude (closed, controlled).
  58         // (Value NS)
  59         // 1. FIXME: Ribs (local variables), there's no necessary infrastructure yet
  60         //    (open set, not controlled).
  61         // 2. Names in modules (both normal `mod`ules and blocks), loop through hygienic parents
  62         //    (open, not controlled).
  63         // 3. Standard library prelude (de-facto closed, controlled).
  64         // (Macro NS)
  65         // 1-3. Derive helpers (open, not controlled). All ambiguities with other names
  66         //    are currently reported as errors. They should be higher in priority than preludes
  67         //    and probably even names in modules according to the "general principles" above. They
  68         //    also should be subject to restricted shadowing because are effectively produced by
  69         //    derives (you need to resolve the derive first to add helpers into scope), but they
  70         //    should be available before the derive is expanded for compatibility.
  71         //    It's mess in general, so we are being conservative for now.
  72         // 1-3. `macro_rules` (open, not controlled), loop through `macro_rules` scopes. Have higher
  73         //    priority than prelude macros, but create ambiguities with macros in modules.
  74         // 1-3. Names in modules (both normal `mod`ules and blocks), loop through hygienic parents
  75         //    (open, not controlled). Have higher priority than prelude macros, but create
  76         //    ambiguities with `macro_rules`.
  77         // 4. `macro_use` prelude (open, the open part is from macro expansions, not controlled).
  78         // 4a. User-defined prelude from macro-use
  79         //    (open, the open part is from macro expansions, not controlled).
  80         // 4b. "Standard library prelude" part implemented through `macro-use` (closed, controlled).
  81         // 4c. Standard library prelude (de-facto closed, controlled).
  82         // 6. Language prelude: builtin attributes (closed, controlled).
  83
  84         let rust_2015 = ctxt.edition() == Edition::Edition2015;
  85         let (ns, macro_kind, is_absolute_path) = match scope_set {
  86             ScopeSet::All(ns, _) => (ns, None, false),
  87             ScopeSet::AbsolutePath(ns) => (ns, None, true),
  88             ScopeSet::Macro(macro_kind) => (MacroNS, Some(macro_kind), false),
  89             ScopeSet::Late(ns, ..) => (ns, None, false),
  90         };
  91         let module = match scope_set {
  92             // Start with the specified module.
  93             ScopeSet::Late(_, module, _) => module,
  94             // Jump out of trait or enum modules, they do not act as scopes.
  95             _ => parent_scope.module.nearest_item_scope(),
  96         };
  97         let mut scope = match ns {
  98             _ if is_absolute_path => Scope::CrateRoot,
  99             TypeNS | ValueNS => Scope::Module(module, None),
 100             MacroNS => Scope::DeriveHelpers(parent_scope.expansion),
 101         };
 102         let mut ctxt = ctxt.normalize_to_macros_2_0();
 103         let mut use_prelude = !module.no_implicit_prelude;
 104
 105         loop {
 106             let visit = match scope {
 107                 // Derive helpers are not in scope when resolving derives in the same container.
 108                 Scope::DeriveHelpers(expn_id) => {
 109                     !(expn_id == parent_scope.expansion && macro_kind == Some(MacroKind::Derive))
 110                 }
 111                 Scope::DeriveHelpersCompat => true,
 112                 Scope::MacroRules(macro_rules_scope) => {
 113                     // Use "path compression" on `macro_rules` scope chains. This is an optimization
 114                     // used to avoid long scope chains, see the comments on `MacroRulesScopeRef`.
 115                     // As another consequence of this optimization visitors never observe invocation
 116                     // scopes for macros that were already expanded.
 117                     while let MacroRulesScope::Invocation(invoc_id) = macro_rules_scope.get() {
 118                         if let Some(next_scope) = self.output_macro_rules_scopes.get(&invoc_id) {
 119                             macro_rules_scope.set(next_scope.get());
 120                         } else {
 121                             break;
 122                         }
 123                     }
 124                     true
 125                 }
 126                 Scope::CrateRoot => true,
 127                 Scope::Module(..) => true,
 128                 Scope::RegisteredAttrs => use_prelude,
 129                 Scope::MacroUsePrelude => use_prelude || rust_2015,
 130                 Scope::BuiltinAttrs => true,
 131                 Scope::ExternPrelude => use_prelude || is_absolute_path,
 132                 Scope::ToolPrelude => use_prelude,
 133                 Scope::StdLibPrelude => use_prelude || ns == MacroNS,
 134                 Scope::BuiltinTypes => true,
 135             };
 136
 137             if visit {
 138                 if let break_result @ Some(..) = visitor(self, scope, use_prelude, ctxt) {
 139                     return break_result;
 140                 }
 141             }
 142
 143             scope = match scope {
 144                 Scope::DeriveHelpers(LocalExpnId::ROOT) => Scope::DeriveHelpersCompat,
 145                 Scope::DeriveHelpers(expn_id) => {
 146                     // Derive helpers are not visible to code generated by bang or derive macros.
 147                     let expn_data = expn_id.expn_data();
 148                     match expn_data.kind {
 149                         ExpnKind::Root
 150                         | ExpnKind::Macro(MacroKind::Bang | MacroKind::Derive, _) => {
 151                             Scope::DeriveHelpersCompat
 152                         }
 153                         _ => Scope::DeriveHelpers(expn_data.parent.expect_local()),
 154                     }
 155                 }
 156                 Scope::DeriveHelpersCompat => Scope::MacroRules(parent_scope.macro_rules),
 157                 Scope::MacroRules(macro_rules_scope) => match macro_rules_scope.get() {
 158                     MacroRulesScope::Binding(binding) => {
 159                         Scope::MacroRules(binding.parent_macro_rules_scope)
 160                     }
 161                     MacroRulesScope::Invocation(invoc_id) => {
 162                         Scope::MacroRules(self.invocation_parent_scopes[&invoc_id].macro_rules)
 163                     }
 164                     MacroRulesScope::Empty => Scope::Module(module, None),
 165                 },
 166                 Scope::CrateRoot => match ns {
 167                     TypeNS => {
 168                         ctxt.adjust(ExpnId::root());
 169                         Scope::ExternPrelude
 170                     }
 171                     ValueNS | MacroNS => break,
 172                 },
 173                 Scope::Module(module, prev_lint_id) => {
 174                     use_prelude = !module.no_implicit_prelude;
 175                     let derive_fallback_lint_id = match scope_set {
 176                         ScopeSet::Late(.., lint_id) => lint_id,
 177                         _ => None,
 178                     };
 179                     match self.hygienic_lexical_parent(module, &mut ctxt, derive_fallback_lint_id) {
 180                         Some((parent_module, lint_id)) => {
 181                             Scope::Module(parent_module, lint_id.or(prev_lint_id))
 182                         }
 183                         None => {
 184                             ctxt.adjust(ExpnId::root());
 185                             match ns {
 186                                 TypeNS => Scope::ExternPrelude,
 187                                 ValueNS => Scope::StdLibPrelude,
 188                                 MacroNS => Scope::RegisteredAttrs,
 189                             }
 190                         }
 191                     }
 192                 }
 193                 Scope::RegisteredAttrs => Scope::MacroUsePrelude,
 194                 Scope::MacroUsePrelude => Scope::StdLibPrelude,
 195                 Scope::BuiltinAttrs => break, // nowhere else to search
 196                 Scope::ExternPrelude if is_absolute_path => break,
 197                 Scope::ExternPrelude => Scope::ToolPrelude,
 198                 Scope::ToolPrelude => Scope::StdLibPrelude,
 199                 Scope::StdLibPrelude => match ns {
 200                     TypeNS => Scope::BuiltinTypes,
 201                     ValueNS => break, // nowhere else to search
 202                     MacroNS => Scope::BuiltinAttrs,
 203                 },
 204                 Scope::BuiltinTypes => break, // nowhere else to search
 205             };
 206         }
 207
 208         None
 209     }
 210
 211     fn hygienic_lexical_parent(
 212         &mut self,
 213         module: Module<'a>,
 214         ctxt: &mut SyntaxContext,
 215         derive_fallback_lint_id: Option<NodeId>,
 216     ) -> Option<(Module<'a>, Option<NodeId>)> {
 217         if !module.expansion.outer_expn_is_descendant_of(*ctxt) {
 218             return Some((self.expn_def_scope(ctxt.remove_mark()), None));
 219         }
 220
 221         if let ModuleKind::Block(..) = module.kind {
 222             return Some((module.parent.unwrap().nearest_item_scope(), None));
 223         }
 224
 225         // We need to support the next case under a deprecation warning
 226         // ```
 227         // struct MyStruct;
 228         // ---- begin: this comes from a proc macro derive
 229         // mod implementation_details {
 230         //     // Note that `MyStruct` is not in scope here.
 231         //     impl SomeTrait for MyStruct { ... }
 232         // }
 233         // ---- end
 234         // ```
 235         // So we have to fall back to the module's parent during lexical resolution in this case.
 236         if derive_fallback_lint_id.is_some() {
 237             if let Some(parent) = module.parent {
 238                 // Inner module is inside the macro, parent module is outside of the macro.
 239                 if module.expansion != parent.expansion
 240                     && module.expansion.is_descendant_of(parent.expansion)
 241                 {
 242                     // The macro is a proc macro derive
 243                     if let Some(def_id) = module.expansion.expn_data().macro_def_id {
 244                         let ext = self.get_macro_by_def_id(def_id);
 245                         if ext.builtin_name.is_none()
 246                             && ext.macro_kind() == MacroKind::Derive
 247                             && parent.expansion.outer_expn_is_descendant_of(*ctxt)
 248                         {
 249                             return Some((parent, derive_fallback_lint_id));
 250                         }
 251                     }
 252                 }
 253             }
 254         }
 255
 256         None
 257     }
 258
 259     /// This resolves the identifier `ident` in the namespace `ns` in the current lexical scope.
 260     /// More specifically, we proceed up the hierarchy of scopes and return the binding for
 261     /// `ident` in the first scope that defines it (or None if no scopes define it).
 262     ///
 263     /// A block's items are above its local variables in the scope hierarchy, regardless of where
 264     /// the items are defined in the block. For example,
 265     /// ```rust
 266     /// fn f() {
 267     ///    g(); // Since there are no local variables in scope yet, this resolves to the item.
 268     ///    let g = || {};
 269     ///    fn g() {}
 270     ///    g(); // This resolves to the local variable `g` since it shadows the item.
 271     /// }
 272     /// ```
 273     ///
 274     /// Invariant: This must only be called during main resolution, not during
 275     /// import resolution.
 276     #[tracing::instrument(level = "debug", skip(self, ribs))]
 277     crate fn resolve_ident_in_lexical_scope(
 278         &mut self,
 279         mut ident: Ident,
 280         ns: Namespace,
 281         parent_scope: &ParentScope<'a>,
 282         finalize: Option<Finalize>,
 283         ribs: &[Rib<'a>],
 284         ignore_binding: Option<&'a NameBinding<'a>>,
 285     ) -> Option<LexicalScopeBinding<'a>> {
 286         assert!(ns == TypeNS || ns == ValueNS);
 287         let orig_ident = ident;
 288         if ident.name == kw::Empty {
 289             return Some(LexicalScopeBinding::Res(Res::Err));
 290         }
 291         let (general_span, normalized_span) = if ident.name == kw::SelfUpper {
 292             // FIXME(jseyfried) improve `Self` hygiene
 293             let empty_span = ident.span.with_ctxt(SyntaxContext::root());
 294             (empty_span, empty_span)
 295         } else if ns == TypeNS {
 296             let normalized_span = ident.span.normalize_to_macros_2_0();
 297             (normalized_span, normalized_span)
 298         } else {
 299             (ident.span.normalize_to_macro_rules(), ident.span.normalize_to_macros_2_0())
 300         };
 301         ident.span = general_span;
 302         let normalized_ident = Ident { span: normalized_span, ..ident };
 303
 304         // Walk backwards up the ribs in scope.
 305         let mut module = self.graph_root;
 306         for i in (0..ribs.len()).rev() {
 307             debug!("walk rib\n{:?}", ribs[i].bindings);
 308             // Use the rib kind to determine whether we are resolving parameters
 309             // (macro 2.0 hygiene) or local variables (`macro_rules` hygiene).
 310             let rib_ident = if ribs[i].kind.contains_params() { normalized_ident } else { ident };
 311             if let Some((original_rib_ident_def, res)) = ribs[i].bindings.get_key_value(&rib_ident)
 312             {
 313                 // The ident resolves to a type parameter or local variable.
 314                 return Some(LexicalScopeBinding::Res(self.validate_res_from_ribs(
 315                     i,
 316                     rib_ident,
 317                     *res,
 318                     finalize.map(|finalize| finalize.path_span),
 319                     *original_rib_ident_def,
 320                     ribs,
 321                 )));
 322             }
 323
 324             module = match ribs[i].kind {
 325                 ModuleRibKind(module) => module,
 326                 MacroDefinition(def) if def == self.macro_def(ident.span.ctxt()) => {
 327                     // If an invocation of this macro created `ident`, give up on `ident`
 328                     // and switch to `ident`'s source from the macro definition.
 329                     ident.span.remove_mark();
 330                     continue;
 331                 }
 332                 _ => continue,
 333             };
 334
 335             match module.kind {
 336                 ModuleKind::Block(..) => {} // We can see through blocks
 337                 _ => break,
 338             }
 339
 340             let item = self.resolve_ident_in_module_unadjusted(
 341                 ModuleOrUniformRoot::Module(module),
 342                 ident,
 343                 ns,
 344                 parent_scope,
 345                 finalize,
 346                 ignore_binding,
 347             );
 348             if let Ok(binding) = item {
 349                 // The ident resolves to an item.
 350                 return Some(LexicalScopeBinding::Item(binding));
 351             }
 352         }
 353         self.early_resolve_ident_in_lexical_scope(
 354             orig_ident,
 355             ScopeSet::Late(ns, module, finalize.map(|finalize| finalize.node_id)),
 356             parent_scope,
 357             finalize,
 358             finalize.is_some(),
 359             ignore_binding,
 360         )
 361         .ok()
 362         .map(LexicalScopeBinding::Item)
 363     }
 364
 365     /// Resolve an identifier in lexical scope.
 366     /// This is a variation of `fn resolve_ident_in_lexical_scope` that can be run during
 367     /// expansion and import resolution (perhaps they can be merged in the future).
 368     /// The function is used for resolving initial segments of macro paths (e.g., `foo` in
 369     /// `foo::bar!(); or `foo!();`) and also for import paths on 2018 edition.
 370     #[tracing::instrument(level = "debug", skip(self, scope_set))]
 371     crate fn early_resolve_ident_in_lexical_scope(
 372         &mut self,
 373         orig_ident: Ident,
 374         scope_set: ScopeSet<'a>,
 375         parent_scope: &ParentScope<'a>,
 376         finalize: Option<Finalize>,
 377         force: bool,
 378         ignore_binding: Option<&'a NameBinding<'a>>,
 379     ) -> Result<&'a NameBinding<'a>, Determinacy> {
 380         bitflags::bitflags! {
 381             struct Flags: u8 {
 382                 const MACRO_RULES          = 1 << 0;
 383                 const MODULE               = 1 << 1;
 384                 const MISC_SUGGEST_CRATE   = 1 << 2;
 385                 const MISC_SUGGEST_SELF    = 1 << 3;
 386                 const MISC_FROM_PRELUDE    = 1 << 4;
 387             }
 388         }
 389
 390         assert!(force || !finalize.is_some()); // `finalize` implies `force`
 391
 392         // Make sure `self`, `super` etc produce an error when passed to here.
 393         if orig_ident.is_path_segment_keyword() {
 394             return Err(Determinacy::Determined);
 395         }
 396
 397         let (ns, macro_kind, is_import) = match scope_set {
 398             ScopeSet::All(ns, is_import) => (ns, None, is_import),
 399             ScopeSet::AbsolutePath(ns) => (ns, None, false),
 400             ScopeSet::Macro(macro_kind) => (MacroNS, Some(macro_kind), false),
 401             ScopeSet::Late(ns, ..) => (ns, None, false),
 402         };
 403
 404         // This is *the* result, resolution from the scope closest to the resolved identifier.
 405         // However, sometimes this result is "weak" because it comes from a glob import or
 406         // a macro expansion, and in this case it cannot shadow names from outer scopes, e.g.
 407         // mod m { ... } // solution in outer scope
 408         // {
 409         //     use prefix::*; // imports another `m` - innermost solution
 410         //                    // weak, cannot shadow the outer `m`, need to report ambiguity error
 411         //     m::mac!();
 412         // }
 413         // So we have to save the innermost solution and continue searching in outer scopes
 414         // to detect potential ambiguities.
 415         let mut innermost_result: Option<(&NameBinding<'_>, Flags)> = None;
 416         let mut determinacy = Determinacy::Determined;
 417
 418         // Go through all the scopes and try to resolve the name.
 419         let break_result = self.visit_scopes(
 420             scope_set,
 421             parent_scope,
 422             orig_ident.span.ctxt(),
 423             |this, scope, use_prelude, ctxt| {
 424                 let ident = Ident::new(orig_ident.name, orig_ident.span.with_ctxt(ctxt));
 425                 let ok = |res, span, arenas| {
 426                     Ok((
 427                         (res, ty::Visibility::Public, span, LocalExpnId::ROOT)
 428                             .to_name_binding(arenas),
 429                         Flags::empty(),
 430                     ))
 431                 };
 432                 let result = match scope {
 433                     Scope::DeriveHelpers(expn_id) => {
 434                         if let Some(attr) = this
 435                             .helper_attrs
 436                             .get(&expn_id)
 437                             .and_then(|attrs| attrs.iter().rfind(|i| ident == **i))
 438                         {
 439                             let binding = (
 440                                 Res::NonMacroAttr(NonMacroAttrKind::DeriveHelper),
 441                                 ty::Visibility::Public,
 442                                 attr.span,
 443                                 expn_id,
 444                             )
 445                                 .to_name_binding(this.arenas);
 446                             Ok((binding, Flags::empty()))
 447                         } else {
 448                             Err(Determinacy::Determined)
 449                         }
 450                     }
 451                     Scope::DeriveHelpersCompat => {
 452                         let mut result = Err(Determinacy::Determined);
 453                         for derive in parent_scope.derives {
 454                             let parent_scope = &ParentScope { derives: &[], ..*parent_scope };
 455                             match this.resolve_macro_path(
 456                                 derive,
 457                                 Some(MacroKind::Derive),
 458                                 parent_scope,
 459                                 true,
 460                                 force,
 461                             ) {
 462                                 Ok((Some(ext), _)) => {
 463                                     if ext.helper_attrs.contains(&ident.name) {
 464                                         result = ok(
 465                                             Res::NonMacroAttr(NonMacroAttrKind::DeriveHelperCompat),
 466                                             derive.span,
 467                                             this.arenas,
 468                                         );
 469                                         break;
 470                                     }
 471                                 }
 472                                 Ok(_) | Err(Determinacy::Determined) => {}
 473                                 Err(Determinacy::Undetermined) => {
 474                                     result = Err(Determinacy::Undetermined)
 475                                 }
 476                             }
 477                         }
 478                         result
 479                     }
 480                     Scope::MacroRules(macro_rules_scope) => match macro_rules_scope.get() {
 481                         MacroRulesScope::Binding(macro_rules_binding)
 482                             if ident == macro_rules_binding.ident =>
 483                         {
 484                             Ok((macro_rules_binding.binding, Flags::MACRO_RULES))
 485                         }
 486                         MacroRulesScope::Invocation(_) => Err(Determinacy::Undetermined),
 487                         _ => Err(Determinacy::Determined),
 488                     },
 489                     Scope::CrateRoot => {
 490                         let root_ident = Ident::new(kw::PathRoot, ident.span);
 491                         let root_module = this.resolve_crate_root(root_ident);
 492                         let binding = this.resolve_ident_in_module_ext(
 493                             ModuleOrUniformRoot::Module(root_module),
 494                             ident,
 495                             ns,
 496                             parent_scope,
 497                             finalize,
 498                             ignore_binding,
 499                         );
 500                         match binding {
 501                             Ok(binding) => Ok((binding, Flags::MODULE | Flags::MISC_SUGGEST_CRATE)),
 502                             Err((Determinacy::Undetermined, Weak::No)) => {
 503                                 return Some(Err(Determinacy::determined(force)));
 504                             }
 505                             Err((Determinacy::Undetermined, Weak::Yes)) => {
 506                                 Err(Determinacy::Undetermined)
 507                             }
 508                             Err((Determinacy::Determined, _)) => Err(Determinacy::Determined),
 509                         }
 510                     }
 511                     Scope::Module(module, derive_fallback_lint_id) => {
 512                         let adjusted_parent_scope = &ParentScope { module, ..*parent_scope };
 513                         let binding = this.resolve_ident_in_module_unadjusted_ext(
 514                             ModuleOrUniformRoot::Module(module),
 515                             ident,
 516                             ns,
 517                             adjusted_parent_scope,
 518                             !matches!(scope_set, ScopeSet::Late(..)),
 519                             finalize,
 520                             ignore_binding,
 521                         );
 522                         match binding {
 523                             Ok(binding) => {
 524                                 if let Some(lint_id) = derive_fallback_lint_id {
 525                                     this.lint_buffer.buffer_lint_with_diagnostic(
 526                                         PROC_MACRO_DERIVE_RESOLUTION_FALLBACK,
 527                                         lint_id,
 528                                         orig_ident.span,
 529                                         &format!(
 530                                             "cannot find {} `{}` in this scope",
 531                                             ns.descr(),
 532                                             ident
 533                                         ),
 534                                         BuiltinLintDiagnostics::ProcMacroDeriveResolutionFallback(
 535                                             orig_ident.span,
 536                                         ),
 537                                     );
 538                                 }
 539                                 let misc_flags = if ptr::eq(module, this.graph_root) {
 540                                     Flags::MISC_SUGGEST_CRATE
 541                                 } else if module.is_normal() {
 542                                     Flags::MISC_SUGGEST_SELF
 543                                 } else {
 544                                     Flags::empty()
 545                                 };
 546                                 Ok((binding, Flags::MODULE | misc_flags))
 547                             }
 548                             Err((Determinacy::Undetermined, Weak::No)) => {
 549                                 return Some(Err(Determinacy::determined(force)));
 550                             }
 551                             Err((Determinacy::Undetermined, Weak::Yes)) => {
 552                                 Err(Determinacy::Undetermined)
 553                             }
 554                             Err((Determinacy::Determined, _)) => Err(Determinacy::Determined),
 555                         }
 556                     }
 557                     Scope::RegisteredAttrs => match this.registered_attrs.get(&ident).cloned() {
 558                         Some(ident) => ok(
 559                             Res::NonMacroAttr(NonMacroAttrKind::Registered),
 560                             ident.span,
 561                             this.arenas,
 562                         ),
 563                         None => Err(Determinacy::Determined),
 564                     },
 565                     Scope::MacroUsePrelude => {
 566                         match this.macro_use_prelude.get(&ident.name).cloned() {
 567                             Some(binding) => Ok((binding, Flags::MISC_FROM_PRELUDE)),
 568                             None => Err(Determinacy::determined(
 569                                 this.graph_root.unexpanded_invocations.borrow().is_empty(),
 570                             )),
 571                         }
 572                     }
 573                     Scope::BuiltinAttrs => {
 574                         if is_builtin_attr_name(ident.name) {
 575                             ok(
 576                                 Res::NonMacroAttr(NonMacroAttrKind::Builtin(ident.name)),
 577                                 DUMMY_SP,
 578                                 this.arenas,
 579                             )
 580                         } else {
 581                             Err(Determinacy::Determined)
 582                         }
 583                     }
 584                     Scope::ExternPrelude => {
 585                         match this.extern_prelude_get(ident, finalize.is_some()) {
 586                             Some(binding) => Ok((binding, Flags::empty())),
 587                             None => Err(Determinacy::determined(
 588                                 this.graph_root.unexpanded_invocations.borrow().is_empty(),
 589                             )),
 590                         }
 591                     }
 592                     Scope::ToolPrelude => match this.registered_tools.get(&ident).cloned() {
 593                         Some(ident) => ok(Res::ToolMod, ident.span, this.arenas),
 594                         None => Err(Determinacy::Determined),
 595                     },
 596                     Scope::StdLibPrelude => {
 597                         let mut result = Err(Determinacy::Determined);
 598                         if let Some(prelude) = this.prelude {
 599                             if let Ok(binding) = this.resolve_ident_in_module_unadjusted(
 600                                 ModuleOrUniformRoot::Module(prelude),
 601                                 ident,
 602                                 ns,
 603                                 parent_scope,
 604                                 None,
 605                                 ignore_binding,
 606                             ) {
 607                                 if use_prelude || this.is_builtin_macro(binding.res()) {
 608                                     result = Ok((binding, Flags::MISC_FROM_PRELUDE));
 609                                 }
 610                             }
 611                         }
 612                         result
 613                     }
 614                     Scope::BuiltinTypes => match PrimTy::from_name(ident.name) {
 615                         Some(prim_ty) => ok(Res::PrimTy(prim_ty), DUMMY_SP, this.arenas),
 616                         None => Err(Determinacy::Determined),
 617                     },
 618                 };
 619
 620                 match result {
 621                     Ok((binding, flags))
 622                         if sub_namespace_match(binding.macro_kind(), macro_kind) =>
 623                     {
 624                         if finalize.is_none() || matches!(scope_set, ScopeSet::Late(..)) {
 625                             return Some(Ok(binding));
 626                         }
 627
 628                         if let Some((innermost_binding, innermost_flags)) = innermost_result {
 629                             // Found another solution, if the first one was "weak", report an error.
 630                             let (res, innermost_res) = (binding.res(), innermost_binding.res());
 631                             if res != innermost_res {
 632                                 let is_builtin = |res| {
 633                                     matches!(res, Res::NonMacroAttr(NonMacroAttrKind::Builtin(..)))
 634                                 };
 635                                 let derive_helper =
 636                                     Res::NonMacroAttr(NonMacroAttrKind::DeriveHelper);
 637                                 let derive_helper_compat =
 638                                     Res::NonMacroAttr(NonMacroAttrKind::DeriveHelperCompat);
 639
 640                                 let ambiguity_error_kind = if is_import {
 641                                     Some(AmbiguityKind::Import)
 642                                 } else if is_builtin(innermost_res) || is_builtin(res) {
 643                                     Some(AmbiguityKind::BuiltinAttr)
 644                                 } else if innermost_res == derive_helper_compat
 645                                     || res == derive_helper_compat && innermost_res != derive_helper
 646                                 {
 647                                     Some(AmbiguityKind::DeriveHelper)
 648                                 } else if innermost_flags.contains(Flags::MACRO_RULES)
 649                                     && flags.contains(Flags::MODULE)
 650                                     && !this.disambiguate_macro_rules_vs_modularized(
 651                                         innermost_binding,
 652                                         binding,
 653                                     )
 654                                     || flags.contains(Flags::MACRO_RULES)
 655                                         && innermost_flags.contains(Flags::MODULE)
 656                                         && !this.disambiguate_macro_rules_vs_modularized(
 657                                             binding,
 658                                             innermost_binding,
 659                                         )
 660                                 {
 661                                     Some(AmbiguityKind::MacroRulesVsModularized)
 662                                 } else if innermost_binding.is_glob_import() {
 663                                     Some(AmbiguityKind::GlobVsOuter)
 664                                 } else if innermost_binding
 665                                     .may_appear_after(parent_scope.expansion, binding)
 666                                 {
 667                                     Some(AmbiguityKind::MoreExpandedVsOuter)
 668                                 } else {
 669                                     None
 670                                 };
 671                                 if let Some(kind) = ambiguity_error_kind {
 672                                     let misc = |f: Flags| {
 673                                         if f.contains(Flags::MISC_SUGGEST_CRATE) {
 674                                             AmbiguityErrorMisc::SuggestCrate
 675                                         } else if f.contains(Flags::MISC_SUGGEST_SELF) {
 676                                             AmbiguityErrorMisc::SuggestSelf
 677                                         } else if f.contains(Flags::MISC_FROM_PRELUDE) {
 678                                             AmbiguityErrorMisc::FromPrelude
 679                                         } else {
 680                                             AmbiguityErrorMisc::None
 681                                         }
 682                                     };
 683                                     this.ambiguity_errors.push(AmbiguityError {
 684                                         kind,
 685                                         ident: orig_ident,
 686                                         b1: innermost_binding,
 687                                         b2: binding,
 688                                         misc1: misc(innermost_flags),
 689                                         misc2: misc(flags),
 690                                     });
 691                                     return Some(Ok(innermost_binding));
 692                                 }
 693                             }
 694                         } else {
 695                             // Found the first solution.
 696                             innermost_result = Some((binding, flags));
 697                         }
 698                     }
 699                     Ok(..) | Err(Determinacy::Determined) => {}
 700                     Err(Determinacy::Undetermined) => determinacy = Determinacy::Undetermined,
 701                 }
 702
 703                 None
 704             },
 705         );
 706
 707         if let Some(break_result) = break_result {
 708             return break_result;
 709         }
 710
 711         // The first found solution was the only one, return it.
 712         if let Some((binding, _)) = innermost_result {
 713             return Ok(binding);
 714         }
 715
 716         Err(Determinacy::determined(determinacy == Determinacy::Determined || force))
 717     }
 718
 719     #[tracing::instrument(level = "debug", skip(self))]
 720     crate fn maybe_resolve_ident_in_module(
 721         &mut self,
 722         module: ModuleOrUniformRoot<'a>,
 723         ident: Ident,
 724         ns: Namespace,
 725         parent_scope: &ParentScope<'a>,
 726     ) -> Result<&'a NameBinding<'a>, Determinacy> {
 727         self.resolve_ident_in_module_ext(module, ident, ns, parent_scope, None, None)
 728             .map_err(|(determinacy, _)| determinacy)
 729     }
 730
 731     #[tracing::instrument(level = "debug", skip(self))]
 732     crate fn resolve_ident_in_module(
 733         &mut self,
 734         module: ModuleOrUniformRoot<'a>,
 735         ident: Ident,
 736         ns: Namespace,
 737         parent_scope: &ParentScope<'a>,
 738         finalize: Option<Finalize>,
 739         ignore_binding: Option<&'a NameBinding<'a>>,
 740     ) -> Result<&'a NameBinding<'a>, Determinacy> {
 741         self.resolve_ident_in_module_ext(module, ident, ns, parent_scope, finalize, ignore_binding)
 742             .map_err(|(determinacy, _)| determinacy)
 743     }
 744
 745     #[tracing::instrument(level = "debug", skip(self))]
 746     fn resolve_ident_in_module_ext(
 747         &mut self,
 748         module: ModuleOrUniformRoot<'a>,
 749         mut ident: Ident,
 750         ns: Namespace,
 751         parent_scope: &ParentScope<'a>,
 752         finalize: Option<Finalize>,
 753         ignore_binding: Option<&'a NameBinding<'a>>,
 754     ) -> Result<&'a NameBinding<'a>, (Determinacy, Weak)> {
 755         let tmp_parent_scope;
 756         let mut adjusted_parent_scope = parent_scope;
 757         match module {
 758             ModuleOrUniformRoot::Module(m) => {
 759                 if let Some(def) = ident.span.normalize_to_macros_2_0_and_adjust(m.expansion) {
 760                     tmp_parent_scope =
 761                         ParentScope { module: self.expn_def_scope(def), ..*parent_scope };
 762                     adjusted_parent_scope = &tmp_parent_scope;
 763                 }
 764             }
 765             ModuleOrUniformRoot::ExternPrelude => {
 766                 ident.span.normalize_to_macros_2_0_and_adjust(ExpnId::root());
 767             }
 768             ModuleOrUniformRoot::CrateRootAndExternPrelude | ModuleOrUniformRoot::CurrentScope => {
 769                 // No adjustments
 770             }
 771         }
 772         self.resolve_ident_in_module_unadjusted_ext(
 773             module,
 774             ident,
 775             ns,
 776             adjusted_parent_scope,
 777             false,
 778             finalize,
 779             ignore_binding,
 780         )
 781     }
 782
 783     #[tracing::instrument(level = "debug", skip(self))]
 784     fn resolve_ident_in_module_unadjusted(
 785         &mut self,
 786         module: ModuleOrUniformRoot<'a>,
 787         ident: Ident,
 788         ns: Namespace,
 789         parent_scope: &ParentScope<'a>,
 790         finalize: Option<Finalize>,
 791         ignore_binding: Option<&'a NameBinding<'a>>,
 792     ) -> Result<&'a NameBinding<'a>, Determinacy> {
 793         self.resolve_ident_in_module_unadjusted_ext(
 794             module,
 795             ident,
 796             ns,
 797             parent_scope,
 798             false,
 799             finalize,
 800             ignore_binding,
 801         )
 802         .map_err(|(determinacy, _)| determinacy)
 803     }
 804
 805     /// Attempts to resolve `ident` in namespaces `ns` of `module`.
 806     /// Invariant: if `finalize` is `Some`, expansion and import resolution must be complete.
 807     #[tracing::instrument(level = "debug", skip(self))]
 808     fn resolve_ident_in_module_unadjusted_ext(
 809         &mut self,
 810         module: ModuleOrUniformRoot<'a>,
 811         ident: Ident,
 812         ns: Namespace,
 813         parent_scope: &ParentScope<'a>,
 814         restricted_shadowing: bool,
 815         finalize: Option<Finalize>,
 816         // This binding should be ignored during in-module resolution, so that we don't get
 817         // "self-confirming" import resolutions during import validation and checking.
 818         ignore_binding: Option<&'a NameBinding<'a>>,
 819     ) -> Result<&'a NameBinding<'a>, (Determinacy, Weak)> {
 820         let module = match module {
 821             ModuleOrUniformRoot::Module(module) => module,
 822             ModuleOrUniformRoot::CrateRootAndExternPrelude => {
 823                 assert!(!restricted_shadowing);
 824                 let binding = self.early_resolve_ident_in_lexical_scope(
 825                     ident,
 826                     ScopeSet::AbsolutePath(ns),
 827                     parent_scope,
 828                     finalize,
 829                     finalize.is_some(),
 830                     ignore_binding,
 831                 );
 832                 return binding.map_err(|determinacy| (determinacy, Weak::No));
 833             }
 834             ModuleOrUniformRoot::ExternPrelude => {
 835                 assert!(!restricted_shadowing);
 836                 return if ns != TypeNS {
 837                     Err((Determined, Weak::No))
 838                 } else if let Some(binding) = self.extern_prelude_get(ident, finalize.is_some()) {
 839                     Ok(binding)
 840                 } else if !self.graph_root.unexpanded_invocations.borrow().is_empty() {
 841                     // Macro-expanded `extern crate` items can add names to extern prelude.
 842                     Err((Undetermined, Weak::No))
 843                 } else {
 844                     Err((Determined, Weak::No))
 845                 };
 846             }
 847             ModuleOrUniformRoot::CurrentScope => {
 848                 assert!(!restricted_shadowing);
 849                 if ns == TypeNS {
 850                     if ident.name == kw::Crate || ident.name == kw::DollarCrate {
 851                         let module = self.resolve_crate_root(ident);
 852                         let binding =
 853                             (module, ty::Visibility::Public, module.span, LocalExpnId::ROOT)
 854                                 .to_name_binding(self.arenas);
 855                         return Ok(binding);
 856                     } else if ident.name == kw::Super || ident.name == kw::SelfLower {
 857                         // FIXME: Implement these with renaming requirements so that e.g.
 858                         // `use super;` doesn't work, but `use super as name;` does.
 859                         // Fall through here to get an error from `early_resolve_...`.
 860                     }
 861                 }
 862
 863                 let scopes = ScopeSet::All(ns, true);
 864                 let binding = self.early_resolve_ident_in_lexical_scope(
 865                     ident,
 866                     scopes,
 867                     parent_scope,
 868                     finalize,
 869                     finalize.is_some(),
 870                     ignore_binding,
 871                 );
 872                 return binding.map_err(|determinacy| (determinacy, Weak::No));
 873             }
 874         };
 875
 876         let key = self.new_key(ident, ns);
 877         let resolution =
 878             self.resolution(module, key).try_borrow_mut().map_err(|_| (Determined, Weak::No))?; // This happens when there is a cycle of imports.
 879
 880         if let Some(Finalize { path_span, report_private, .. }) = finalize {
 881             // If the primary binding is unusable, search further and return the shadowed glob
 882             // binding if it exists. What we really want here is having two separate scopes in
 883             // a module - one for non-globs and one for globs, but until that's done use this
 884             // hack to avoid inconsistent resolution ICEs during import validation.
 885             let binding = [resolution.binding, resolution.shadowed_glob]
 886                 .into_iter()
 887                 .filter_map(|binding| match (binding, ignore_binding) {
 888                     (Some(binding), Some(ignored)) if ptr::eq(binding, ignored) => None,
 889                     _ => binding,
 890                 })
 891                 .next();
 892             let Some(binding) = binding else {
 893                 return Err((Determined, Weak::No));
 894             };
 895
 896             if !self.is_accessible_from(binding.vis, parent_scope.module) {
 897                 if report_private {
 898                     self.privacy_errors.push(PrivacyError {
 899                         ident,
 900                         binding,
 901                         dedup_span: path_span,
 902                     });
 903                 } else {
 904                     return Err((Determined, Weak::No));
 905                 }
 906             }
 907
 908             // Forbid expanded shadowing to avoid time travel.
 909             if let Some(shadowed_glob) = resolution.shadowed_glob
 910                 && restricted_shadowing
 911                 && binding.expansion != LocalExpnId::ROOT
 912                 && binding.res() != shadowed_glob.res()
 913             {
 914                 self.ambiguity_errors.push(AmbiguityError {
 915                     kind: AmbiguityKind::GlobVsExpanded,
 916                     ident,
 917                     b1: binding,
 918                     b2: shadowed_glob,
 919                     misc1: AmbiguityErrorMisc::None,
 920                     misc2: AmbiguityErrorMisc::None,
 921                 });
 922             }
 923
 924             if !restricted_shadowing && binding.expansion != LocalExpnId::ROOT {
 925                 if let NameBindingKind::Res(_, true) = binding.kind {
 926                     self.macro_expanded_macro_export_errors.insert((path_span, binding.span));
 927                 }
 928             }
 929
 930             self.record_use(ident, binding, restricted_shadowing);
 931             return Ok(binding);
 932         }
 933
 934         let check_usable = |this: &mut Self, binding: &'a NameBinding<'a>| {
 935             if let Some(ignored) = ignore_binding && ptr::eq(binding, ignored) {
 936                 return Err((Determined, Weak::No));
 937             }
 938             let usable = this.is_accessible_from(binding.vis, parent_scope.module);
 939             if usable { Ok(binding) } else { Err((Determined, Weak::No)) }
 940         };
 941
 942         // Items and single imports are not shadowable, if we have one, then it's determined.
 943         if let Some(binding) = resolution.binding {
 944             if !binding.is_glob_import() {
 945                 return check_usable(self, binding);
 946             }
 947         }
 948
 949         // --- From now on we either have a glob resolution or no resolution. ---
 950
 951         // Check if one of single imports can still define the name,
 952         // if it can then our result is not determined and can be invalidated.
 953         for single_import in &resolution.single_imports {
 954             if !self.is_accessible_from(single_import.vis.get(), parent_scope.module) {
 955                 continue;
 956             }
 957             let Some(module) = single_import.imported_module.get() else {
 958                 return Err((Undetermined, Weak::No));
 959             };
 960             let ImportKind::Single { source: ident, .. } = single_import.kind else {
 961                 unreachable!();
 962             };
 963             match self.resolve_ident_in_module(
 964                 module,
 965                 ident,
 966                 ns,
 967                 &single_import.parent_scope,
 968                 None,
 969                 ignore_binding,
 970             ) {
 971                 Err(Determined) => continue,
 972                 Ok(binding)
 973                     if !self.is_accessible_from(binding.vis, single_import.parent_scope.module) =>
 974                 {
 975                     continue;
 976                 }
 977                 Ok(_) | Err(Undetermined) => return Err((Undetermined, Weak::No)),
 978             }
 979         }
 980
 981         // So we have a resolution that's from a glob import. This resolution is determined
 982         // if it cannot be shadowed by some new item/import expanded from a macro.
 983         // This happens either if there are no unexpanded macros, or expanded names cannot
 984         // shadow globs (that happens in macro namespace or with restricted shadowing).
 985         //
 986         // Additionally, any macro in any module can plant names in the root module if it creates
 987         // `macro_export` macros, so the root module effectively has unresolved invocations if any
 988         // module has unresolved invocations.
 989         // However, it causes resolution/expansion to stuck too often (#53144), so, to make
 990         // progress, we have to ignore those potential unresolved invocations from other modules
 991         // and prohibit access to macro-expanded `macro_export` macros instead (unless restricted
 992         // shadowing is enabled, see `macro_expanded_macro_export_errors`).
 993         let unexpanded_macros = !module.unexpanded_invocations.borrow().is_empty();
 994         if let Some(binding) = resolution.binding {
 995             if !unexpanded_macros || ns == MacroNS || restricted_shadowing {
 996                 return check_usable(self, binding);
 997             } else {
 998                 return Err((Undetermined, Weak::No));
 999             }
1000         }
1001
1002         // --- From now on we have no resolution. ---
1003
1004         // Now we are in situation when new item/import can appear only from a glob or a macro
1005         // expansion. With restricted shadowing names from globs and macro expansions cannot
1006         // shadow names from outer scopes, so we can freely fallback from module search to search
1007         // in outer scopes. For `early_resolve_ident_in_lexical_scope` to continue search in outer
1008         // scopes we return `Undetermined` with `Weak::Yes`.
1009
1010         // Check if one of unexpanded macros can still define the name,
1011         // if it can then our "no resolution" result is not determined and can be invalidated.
1012         if unexpanded_macros {
1013             return Err((Undetermined, Weak::Yes));
1014         }
1015
1016         // Check if one of glob imports can still define the name,
1017         // if it can then our "no resolution" result is not determined and can be invalidated.
1018         for glob_import in module.globs.borrow().iter() {
1019             if !self.is_accessible_from(glob_import.vis.get(), parent_scope.module) {
1020                 continue;
1021             }
1022             let module = match glob_import.imported_module.get() {
1023                 Some(ModuleOrUniformRoot::Module(module)) => module,
1024                 Some(_) => continue,
1025                 None => return Err((Undetermined, Weak::Yes)),
1026             };
1027             let tmp_parent_scope;
1028             let (mut adjusted_parent_scope, mut ident) =
1029                 (parent_scope, ident.normalize_to_macros_2_0());
1030             match ident.span.glob_adjust(module.expansion, glob_import.span) {
1031                 Some(Some(def)) => {
1032                     tmp_parent_scope =
1033                         ParentScope { module: self.expn_def_scope(def), ..*parent_scope };
1034                     adjusted_parent_scope = &tmp_parent_scope;
1035                 }
1036                 Some(None) => {}
1037                 None => continue,
1038             };
1039             let result = self.resolve_ident_in_module_unadjusted(
1040                 ModuleOrUniformRoot::Module(module),
1041                 ident,
1042                 ns,
1043                 adjusted_parent_scope,
1044                 None,
1045                 ignore_binding,
1046             );
1047
1048             match result {
1049                 Err(Determined) => continue,
1050                 Ok(binding)
1051                     if !self.is_accessible_from(binding.vis, glob_import.parent_scope.module) =>
1052                 {
1053                     continue;
1054                 }
1055                 Ok(_) | Err(Undetermined) => return Err((Undetermined, Weak::Yes)),
1056             }
1057         }
1058
1059         // No resolution and no one else can define the name - determinate error.
1060         Err((Determined, Weak::No))
1061     }
1062
1063     /// Validate a local resolution (from ribs).
1064     #[tracing::instrument(level = "debug", skip(self, all_ribs))]
1065     fn validate_res_from_ribs(
1066         &mut self,
1067         rib_index: usize,
1068         rib_ident: Ident,
1069         mut res: Res,
1070         finalize: Option<Span>,
1071         original_rib_ident_def: Ident,
1072         all_ribs: &[Rib<'a>],
1073     ) -> Res {
1074         const CG_BUG_STR: &str = "min_const_generics resolve check didn't stop compilation";
1075         debug!("validate_res_from_ribs({:?})", res);
1076         let ribs = &all_ribs[rib_index + 1..];
1077
1078         // An invalid forward use of a generic parameter from a previous default.
1079         if let ForwardGenericParamBanRibKind = all_ribs[rib_index].kind {
1080             if let Some(span) = finalize {
1081                 let res_error = if rib_ident.name == kw::SelfUpper {
1082                     ResolutionError::SelfInGenericParamDefault
1083                 } else {
1084                     ResolutionError::ForwardDeclaredGenericParam
1085                 };
1086                 self.report_error(span, res_error);
1087             }
1088             assert_eq!(res, Res::Err);
1089             return Res::Err;
1090         }
1091
1092         match res {
1093             Res::Local(_) => {
1094                 use ResolutionError::*;
1095                 let mut res_err = None;
1096
1097                 for rib in ribs {
1098                     match rib.kind {
1099                         NormalRibKind
1100                         | ClosureOrAsyncRibKind
1101                         | ModuleRibKind(..)
1102                         | MacroDefinition(..)
1103                         | ForwardGenericParamBanRibKind => {
1104                             // Nothing to do. Continue.
1105                         }
1106                         ItemRibKind(_) | FnItemRibKind | AssocItemRibKind => {
1107                             // This was an attempt to access an upvar inside a
1108                             // named function item. This is not allowed, so we
1109                             // report an error.
1110                             if let Some(span) = finalize {
1111                                 // We don't immediately trigger a resolve error, because
1112                                 // we want certain other resolution errors (namely those
1113                                 // emitted for `ConstantItemRibKind` below) to take
1114                                 // precedence.
1115                                 res_err = Some((span, CannotCaptureDynamicEnvironmentInFnItem));
1116                             }
1117                         }
1118                         ConstantItemRibKind(_, item) => {
1119                             // Still doesn't deal with upvars
1120                             if let Some(span) = finalize {
1121                                 let (span, resolution_error) =
1122                                     if let Some((ident, constant_item_kind)) = item {
1123                                         let kind_str = match constant_item_kind {
1124                                             ConstantItemKind::Const => "const",
1125                                             ConstantItemKind::Static => "static",
1126                                         };
1127                                         (
1128                                             span,
1129                                             AttemptToUseNonConstantValueInConstant(
1130                                                 ident, "let", kind_str,
1131                                             ),
1132                                         )
1133                                     } else {
1134                                         (
1135                                             rib_ident.span,
1136                                             AttemptToUseNonConstantValueInConstant(
1137                                                 original_rib_ident_def,
1138                                                 "const",
1139                                                 "let",
1140                                             ),
1141                                         )
1142                                     };
1143                                 self.report_error(span, resolution_error);
1144                             }
1145                             return Res::Err;
1146                         }
1147                         ConstParamTyRibKind => {
1148                             if let Some(span) = finalize {
1149                                 self.report_error(span, ParamInTyOfConstParam(rib_ident.name));
1150                             }
1151                             return Res::Err;
1152                         }
1153                         InlineAsmSymRibKind => {
1154                             if let Some(span) = finalize {
1155                                 self.report_error(span, InvalidAsmSym);
1156                             }
1157                             return Res::Err;
1158                         }
1159                     }
1160                 }
1161                 if let Some((span, res_err)) = res_err {
1162                     self.report_error(span, res_err);
1163                     return Res::Err;
1164                 }
1165             }
1166             Res::Def(DefKind::TyParam, _) | Res::SelfTy { .. } => {
1167                 for rib in ribs {
1168                     let has_generic_params: HasGenericParams = match rib.kind {
1169                         NormalRibKind
1170                         | ClosureOrAsyncRibKind
1171                         | AssocItemRibKind
1172                         | ModuleRibKind(..)
1173                         | MacroDefinition(..)
1174                         | ForwardGenericParamBanRibKind => {
1175                             // Nothing to do. Continue.
1176                             continue;
1177                         }
1178
1179                         ConstantItemRibKind(trivial, _) => {
1180                             let features = self.session.features_untracked();
1181                             // HACK(min_const_generics): We currently only allow `N` or `{ N }`.
1182                             if !(trivial == HasGenericParams::Yes || features.generic_const_exprs) {
1183                                 // HACK(min_const_generics): If we encounter `Self` in an anonymous constant
1184                                 // we can't easily tell if it's generic at this stage, so we instead remember
1185                                 // this and then enforce the self type to be concrete later on.
1186                                 if let Res::SelfTy { trait_, alias_to: Some((def, _)) } = res {
1187                                     res = Res::SelfTy { trait_, alias_to: Some((def, true)) }
1188                                 } else {
1189                                     if let Some(span) = finalize {
1190                                         self.report_error(
1191                                             span,
1192                                             ResolutionError::ParamInNonTrivialAnonConst {
1193                                                 name: rib_ident.name,
1194                                                 is_type: true,
1195                                             },
1196                                         );
1197                                         self.session.delay_span_bug(span, CG_BUG_STR);
1198                                     }
1199
1200                                     return Res::Err;
1201                                 }
1202                             }
1203
1204                             continue;
1205                         }
1206
1207                         // This was an attempt to use a type parameter outside its scope.
1208                         ItemRibKind(has_generic_params) => has_generic_params,
1209                         FnItemRibKind => HasGenericParams::Yes,
1210                         ConstParamTyRibKind => {
1211                             if let Some(span) = finalize {
1212                                 self.report_error(
1213                                     span,
1214                                     ResolutionError::ParamInTyOfConstParam(rib_ident.name),
1215                                 );
1216                             }
1217                             return Res::Err;
1218                         }
1219                         InlineAsmSymRibKind => {
1220                             let features = self.session.features_untracked();
1221                             if !features.generic_const_exprs {
1222                                 if let Some(span) = finalize {
1223                                     self.report_error(
1224                                         span,
1225                                         ResolutionError::ParamInNonTrivialAnonConst {
1226                                             name: rib_ident.name,
1227                                             is_type: true,
1228                                         },
1229                                     );
1230                                 }
1231                                 return Res::Err;
1232                             }
1233                             continue;
1234                         }
1235                     };
1236
1237                     if let Some(span) = finalize {
1238                         self.report_error(
1239                             span,
1240                             ResolutionError::GenericParamsFromOuterFunction(
1241                                 res,
1242                                 has_generic_params,
1243                             ),
1244                         );
1245                     }
1246                     return Res::Err;
1247                 }
1248             }
1249             Res::Def(DefKind::ConstParam, _) => {
1250                 let mut ribs = ribs.iter().peekable();
1251                 if let Some(Rib { kind: FnItemRibKind, .. }) = ribs.peek() {
1252                     // When declaring const parameters inside function signatures, the first rib
1253                     // is always a `FnItemRibKind`. In this case, we can skip it, to avoid it
1254                     // (spuriously) conflicting with the const param.
1255                     ribs.next();
1256                 }
1257
1258                 for rib in ribs {
1259                     let has_generic_params = match rib.kind {
1260                         NormalRibKind
1261                         | ClosureOrAsyncRibKind
1262                         | AssocItemRibKind
1263                         | ModuleRibKind(..)
1264                         | MacroDefinition(..)
1265                         | ForwardGenericParamBanRibKind => continue,
1266
1267                         ConstantItemRibKind(trivial, _) => {
1268                             let features = self.session.features_untracked();
1269                             // HACK(min_const_generics): We currently only allow `N` or `{ N }`.
1270                             if !(trivial == HasGenericParams::Yes || features.generic_const_exprs) {
1271                                 if let Some(span) = finalize {
1272                                     self.report_error(
1273                                         span,
1274                                         ResolutionError::ParamInNonTrivialAnonConst {
1275                                             name: rib_ident.name,
1276                                             is_type: false,
1277                                         },
1278                                     );
1279                                     self.session.delay_span_bug(span, CG_BUG_STR);
1280                                 }
1281
1282                                 return Res::Err;
1283                             }
1284
1285                             continue;
1286                         }
1287
1288                         ItemRibKind(has_generic_params) => has_generic_params,
1289                         FnItemRibKind => HasGenericParams::Yes,
1290                         ConstParamTyRibKind => {
1291                             if let Some(span) = finalize {
1292                                 self.report_error(
1293                                     span,
1294                                     ResolutionError::ParamInTyOfConstParam(rib_ident.name),
1295                                 );
1296                             }
1297                             return Res::Err;
1298                         }
1299                         InlineAsmSymRibKind => {
1300                             let features = self.session.features_untracked();
1301                             if !features.generic_const_exprs {
1302                                 if let Some(span) = finalize {
1303                                     self.report_error(
1304                                         span,
1305                                         ResolutionError::ParamInNonTrivialAnonConst {
1306                                             name: rib_ident.name,
1307                                             is_type: false,
1308                                         },
1309                                     );
1310                                 }
1311                                 return Res::Err;
1312                             }
1313                             continue;
1314                         }
1315                     };
1316
1317                     // This was an attempt to use a const parameter outside its scope.
1318                     if let Some(span) = finalize {
1319                         self.report_error(
1320                             span,
1321                             ResolutionError::GenericParamsFromOuterFunction(
1322                                 res,
1323                                 has_generic_params,
1324                             ),
1325                         );
1326                     }
1327                     return Res::Err;
1328                 }
1329             }
1330             _ => {}
1331         }
1332         res
1333     }
1334
1335     #[tracing::instrument(level = "debug", skip(self))]
1336     crate fn maybe_resolve_path(
1337         &mut self,
1338         path: &[Segment],
1339         opt_ns: Option<Namespace>, // `None` indicates a module path in import
1340         parent_scope: &ParentScope<'a>,
1341     ) -> PathResult<'a> {
1342         self.resolve_path_with_ribs(path, opt_ns, parent_scope, None, None, None)
1343     }
1344
1345     #[tracing::instrument(level = "debug", skip(self))]
1346     crate fn resolve_path(
1347         &mut self,
1348         path: &[Segment],
1349         opt_ns: Option<Namespace>, // `None` indicates a module path in import
1350         parent_scope: &ParentScope<'a>,
1351         finalize: Option<Finalize>,
1352         ignore_binding: Option<&'a NameBinding<'a>>,
1353     ) -> PathResult<'a> {
1354         self.resolve_path_with_ribs(path, opt_ns, parent_scope, finalize, None, ignore_binding)
1355     }
1356
1357     crate fn resolve_path_with_ribs(
1358         &mut self,
1359         path: &[Segment],
1360         opt_ns: Option<Namespace>, // `None` indicates a module path in import
1361         parent_scope: &ParentScope<'a>,
1362         finalize: Option<Finalize>,
1363         ribs: Option<&PerNS<Vec<Rib<'a>>>>,
1364         ignore_binding: Option<&'a NameBinding<'a>>,
1365     ) -> PathResult<'a> {
1366         debug!("resolve_path(path={:?}, opt_ns={:?}, finalize={:?})", path, opt_ns, finalize);
1367
1368         let mut module = None;
1369         let mut allow_super = true;
1370         let mut second_binding = None;
1371
1372         for (i, &Segment { ident, id, .. }) in path.iter().enumerate() {
1373             debug!("resolve_path ident {} {:?} {:?}", i, ident, id);
1374             let record_segment_res = |this: &mut Self, res| {
1375                 if finalize.is_some() {
1376                     if let Some(id) = id {
1377                         if !this.partial_res_map.contains_key(&id) {
1378                             assert!(id != ast::DUMMY_NODE_ID, "Trying to resolve dummy id");
1379                             this.record_partial_res(id, PartialRes::new(res));
1380                         }
1381                     }
1382                 }
1383             };
1384
1385             let is_last = i == path.len() - 1;
1386             let ns = if is_last { opt_ns.unwrap_or(TypeNS) } else { TypeNS };
1387             let name = ident.name;
1388
1389             allow_super &= ns == TypeNS && (name == kw::SelfLower || name == kw::Super);
1390
1391             if ns == TypeNS {
1392                 if allow_super && name == kw::Super {
1393                     let mut ctxt = ident.span.ctxt().normalize_to_macros_2_0();
1394                     let self_module = match i {
1395                         0 => Some(self.resolve_self(&mut ctxt, parent_scope.module)),
1396                         _ => match module {
1397                             Some(ModuleOrUniformRoot::Module(module)) => Some(module),
1398                             _ => None,
1399                         },
1400                     };
1401                     if let Some(self_module) = self_module {
1402                         if let Some(parent) = self_module.parent {
1403                             module = Some(ModuleOrUniformRoot::Module(
1404                                 self.resolve_self(&mut ctxt, parent),
1405                             ));
1406                             continue;
1407                         }
1408                     }
1409                     return PathResult::failed(ident.span, false, finalize.is_some(), || {
1410                         ("there are too many leading `super` keywords".to_string(), None)
1411                     });
1412                 }
1413                 if i == 0 {
1414                     if name == kw::SelfLower {
1415                         let mut ctxt = ident.span.ctxt().normalize_to_macros_2_0();
1416                         module = Some(ModuleOrUniformRoot::Module(
1417                             self.resolve_self(&mut ctxt, parent_scope.module),
1418                         ));
1419                         continue;
1420                     }
1421                     if name == kw::PathRoot && ident.span.rust_2018() {
1422                         module = Some(ModuleOrUniformRoot::ExternPrelude);
1423                         continue;
1424                     }
1425                     if name == kw::PathRoot && ident.span.rust_2015() && self.session.rust_2018() {
1426                         // `::a::b` from 2015 macro on 2018 global edition
1427                         module = Some(ModuleOrUniformRoot::CrateRootAndExternPrelude);
1428                         continue;
1429                     }
1430                     if name == kw::PathRoot || name == kw::Crate || name == kw::DollarCrate {
1431                         // `::a::b`, `crate::a::b` or `$crate::a::b`
1432                         module = Some(ModuleOrUniformRoot::Module(self.resolve_crate_root(ident)));
1433                         continue;
1434                     }
1435                 }
1436             }
1437
1438             // Report special messages for path segment keywords in wrong positions.
1439             if ident.is_path_segment_keyword() && i != 0 {
1440                 return PathResult::failed(ident.span, false, finalize.is_some(), || {
1441                     let name_str = if name == kw::PathRoot {
1442                         "crate root".to_string()
1443                     } else {
1444                         format!("`{}`", name)
1445                     };
1446                     let label = if i == 1 && path[0].ident.name == kw::PathRoot {
1447                         format!("global paths cannot start with {}", name_str)
1448                     } else {
1449                         format!("{} in paths can only be used in start position", name_str)
1450                     };
1451                     (label, None)
1452                 });
1453             }
1454
1455             enum FindBindingResult<'a> {
1456                 Binding(Result<&'a NameBinding<'a>, Determinacy>),
1457                 Res(Res),
1458             }
1459             let find_binding_in_ns = |this: &mut Self, ns| {
1460                 let binding = if let Some(module) = module {
1461                     this.resolve_ident_in_module(
1462                         module,
1463                         ident,
1464                         ns,
1465                         parent_scope,
1466                         finalize,
1467                         ignore_binding,
1468                     )
1469                 } else if let Some(ribs) = ribs
1470                     && let Some(TypeNS | ValueNS) = opt_ns
1471                 {
1472                     match this.resolve_ident_in_lexical_scope(
1473                         ident,
1474                         ns,
1475                         parent_scope,
1476                         finalize,
1477                         &ribs[ns],
1478                         ignore_binding,
1479                     ) {
1480                         // we found a locally-imported or available item/module
1481                         Some(LexicalScopeBinding::Item(binding)) => Ok(binding),
1482                         // we found a local variable or type param
1483                         Some(LexicalScopeBinding::Res(res)) => return FindBindingResult::Res(res),
1484                         _ => Err(Determinacy::determined(finalize.is_some())),
1485                     }
1486                 } else {
1487                     let scopes = ScopeSet::All(ns, opt_ns.is_none());
1488                     this.early_resolve_ident_in_lexical_scope(
1489                         ident,
1490                         scopes,
1491                         parent_scope,
1492                         finalize,
1493                         finalize.is_some(),
1494                         ignore_binding,
1495                     )
1496                 };
1497                 FindBindingResult::Binding(binding)
1498             };
1499             let binding = match find_binding_in_ns(self, ns) {
1500                 FindBindingResult::Res(res) => {
1501                     record_segment_res(self, res);
1502                     return PathResult::NonModule(PartialRes::with_unresolved_segments(
1503                         res,
1504                         path.len() - 1,
1505                     ));
1506                 }
1507                 FindBindingResult::Binding(binding) => binding,
1508             };
1509             match binding {
1510                 Ok(binding) => {
1511                     if i == 1 {
1512                         second_binding = Some(binding);
1513                     }
1514                     let res = binding.res();
1515                     let maybe_assoc = opt_ns != Some(MacroNS) && PathSource::Type.is_expected(res);
1516                     if let Some(next_module) = binding.module() {
1517                         module = Some(ModuleOrUniformRoot::Module(next_module));
1518                         record_segment_res(self, res);
1519                     } else if res == Res::ToolMod && i + 1 != path.len() {
1520                         if binding.is_import() {
1521                             self.session
1522                                 .struct_span_err(
1523                                     ident.span,
1524                                     "cannot use a tool module through an import",
1525                                 )
1526                                 .span_note(binding.span, "the tool module imported here")
1527                                 .emit();
1528                         }
1529                         let res = Res::NonMacroAttr(NonMacroAttrKind::Tool);
1530                         return PathResult::NonModule(PartialRes::new(res));
1531                     } else if res == Res::Err {
1532                         return PathResult::NonModule(PartialRes::new(Res::Err));
1533                     } else if opt_ns.is_some() && (is_last || maybe_assoc) {
1534                         self.lint_if_path_starts_with_module(finalize, path, second_binding);
1535                         return PathResult::NonModule(PartialRes::with_unresolved_segments(
1536                             res,
1537                             path.len() - i - 1,
1538                         ));
1539                     } else {
1540                         return PathResult::failed(ident.span, is_last, finalize.is_some(), || {
1541                             let label = format!(
1542                                 "`{ident}` is {} {}, not a module",
1543                                 res.article(),
1544                                 res.descr()
1545                             );
1546                             (label, None)
1547                         });
1548                     }
1549                 }
1550                 Err(Undetermined) => return PathResult::Indeterminate,
1551                 Err(Determined) => {
1552                     if let Some(ModuleOrUniformRoot::Module(module)) = module {
1553                         if opt_ns.is_some() && !module.is_normal() {
1554                             return PathResult::NonModule(PartialRes::with_unresolved_segments(
1555                                 module.res().unwrap(),
1556                                 path.len() - i,
1557                             ));
1558                         }
1559                     }
1560
1561                     return PathResult::failed(ident.span, is_last, finalize.is_some(), || {
1562                         self.report_path_resolution_error(
1563                             path,
1564                             opt_ns,
1565                             parent_scope,
1566                             ribs,
1567                             ignore_binding,
1568                             module,
1569                             i,
1570                             ident,
1571                         )
1572                     });
1573                 }
1574             }
1575         }
1576
1577         self.lint_if_path_starts_with_module(finalize, path, second_binding);
1578
1579         PathResult::Module(match module {
1580             Some(module) => module,
1581             None if path.is_empty() => ModuleOrUniformRoot::CurrentScope,
1582             _ => bug!("resolve_path: non-empty path `{:?}` has no module", path),
1583         })
1584     }
1585 }