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