src/librustc_resolve/macros.rs

   1 use crate::{AmbiguityError, AmbiguityKind, AmbiguityErrorMisc};
   2 use crate::{CrateLint, Resolver, ResolutionError, ScopeSet, Weak};
   3 use crate::{Module, ModuleKind, NameBinding, NameBindingKind, PathResult, Segment, ToNameBinding};
   4 use crate::{is_known_tool, resolve_error};
   5 use crate::ModuleOrUniformRoot;
   6 use crate::Namespace::*;
   7 use crate::build_reduced_graph::{BuildReducedGraphVisitor, IsMacroExport};
   8 use crate::resolve_imports::ImportResolver;
   9 use rustc::hir::def_id::{DefId, CRATE_DEF_INDEX, DefIndex,
  10                          CrateNum, DefIndexAddressSpace};
  11 use rustc::hir::def::{self, NonMacroAttrKind};
  12 use rustc::hir::map::{self, DefCollector};
  13 use rustc::{ty, lint};
  14 use rustc::{bug, span_bug};
  15 use syntax::ast::{self, Ident};
  16 use syntax::attr;
  17 use syntax::errors::DiagnosticBuilder;
  18 use syntax::ext::base::{self, Determinacy};
  19 use syntax::ext::base::{MacroKind, SyntaxExtension};
  20 use syntax::ext::expand::{AstFragment, Invocation, InvocationKind};
  21 use syntax::ext::hygiene::{self, Mark};
  22 use syntax::ext::tt::macro_rules;
  23 use syntax::feature_gate::{
  24     feature_err, is_builtin_attr_name, AttributeGate, GateIssue, Stability, BUILTIN_ATTRIBUTES,
  25 };
  26 use syntax::symbol::{Symbol, keywords};
  27 use syntax::visit::Visitor;
  28 use syntax::util::lev_distance::find_best_match_for_name;
  29 use syntax_pos::{Span, DUMMY_SP};
  30 use errors::Applicability;
  31
  32 use std::cell::Cell;
  33 use std::{mem, ptr};
  34 use rustc_data_structures::sync::Lrc;
  35
  36 type Def = def::Def<ast::NodeId>;
  37
  38 #[derive(Clone, Debug)]
  39 pub struct InvocationData<'a> {
  40     def_index: DefIndex,
  41     /// The module in which the macro was invoked.
  42     crate module: Cell<Module<'a>>,
  43     /// The legacy scope in which the macro was invoked.
  44     /// The invocation path is resolved in this scope.
  45     crate parent_legacy_scope: Cell<LegacyScope<'a>>,
  46     /// The legacy scope *produced* by expanding this macro invocation,
  47     /// includes all the macro_rules items, other invocations, etc generated by it.
  48     /// `None` if the macro is not expanded yet.
  49     crate output_legacy_scope: Cell<Option<LegacyScope<'a>>>,
  50 }
  51
  52 impl<'a> InvocationData<'a> {
  53     pub fn root(graph_root: Module<'a>) -> Self {
  54         InvocationData {
  55             module: Cell::new(graph_root),
  56             def_index: CRATE_DEF_INDEX,
  57             parent_legacy_scope: Cell::new(LegacyScope::Empty),
  58             output_legacy_scope: Cell::new(Some(LegacyScope::Empty)),
  59         }
  60     }
  61 }
  62
  63 /// Binding produced by a `macro_rules` item.
  64 /// Not modularized, can shadow previous legacy bindings, etc.
  65 #[derive(Debug)]
  66 pub struct LegacyBinding<'a> {
  67     binding: &'a NameBinding<'a>,
  68     /// Legacy scope into which the `macro_rules` item was planted.
  69     parent_legacy_scope: LegacyScope<'a>,
  70     ident: Ident,
  71 }
  72
  73 /// The scope introduced by a `macro_rules!` macro.
  74 /// This starts at the macro's definition and ends at the end of the macro's parent
  75 /// module (named or unnamed), or even further if it escapes with `#[macro_use]`.
  76 /// Some macro invocations need to introduce legacy scopes too because they
  77 /// can potentially expand into macro definitions.
  78 #[derive(Copy, Clone, Debug)]
  79 pub enum LegacyScope<'a> {
  80     /// Created when invocation data is allocated in the arena;
  81     /// must be replaced with a proper scope later.
  82     Uninitialized,
  83     /// Empty "root" scope at the crate start containing no names.
  84     Empty,
  85     /// The scope introduced by a `macro_rules!` macro definition.
  86     Binding(&'a LegacyBinding<'a>),
  87     /// The scope introduced by a macro invocation that can potentially
  88     /// create a `macro_rules!` macro definition.
  89     Invocation(&'a InvocationData<'a>),
  90 }
  91
  92 /// Everything you need to resolve a macro or import path.
  93 #[derive(Clone, Debug)]
  94 pub struct ParentScope<'a> {
  95     crate module: Module<'a>,
  96     crate expansion: Mark,
  97     crate legacy: LegacyScope<'a>,
  98     crate derives: Vec<ast::Path>,
  99 }
 100
 101 // Macro namespace is separated into two sub-namespaces, one for bang macros and
 102 // one for attribute-like macros (attributes, derives).
 103 // We ignore resolutions from one sub-namespace when searching names in scope for another.
 104 fn sub_namespace_match(candidate: Option<MacroKind>, requirement: Option<MacroKind>) -> bool {
 105     #[derive(PartialEq)]
 106     enum SubNS { Bang, AttrLike }
 107     let sub_ns = |kind| match kind {
 108         MacroKind::Bang => Some(SubNS::Bang),
 109         MacroKind::Attr | MacroKind::Derive => Some(SubNS::AttrLike),
 110         MacroKind::ProcMacroStub => None,
 111     };
 112     let requirement = requirement.and_then(|kind| sub_ns(kind));
 113     let candidate = candidate.and_then(|kind| sub_ns(kind));
 114     // "No specific sub-namespace" means "matches anything" for both requirements and candidates.
 115     candidate.is_none() || requirement.is_none() || candidate == requirement
 116 }
 117
 118 impl<'a> base::Resolver for Resolver<'a> {
 119     fn next_node_id(&mut self) -> ast::NodeId {
 120         self.session.next_node_id()
 121     }
 122
 123     fn get_module_scope(&mut self, id: ast::NodeId) -> Mark {
 124         let mark = Mark::fresh(Mark::root());
 125         let module = self.module_map[&self.definitions.local_def_id(id)];
 126         self.invocations.insert(mark, self.arenas.alloc_invocation_data(InvocationData {
 127             module: Cell::new(module),
 128             def_index: module.def_id().unwrap().index,
 129             parent_legacy_scope: Cell::new(LegacyScope::Empty),
 130             output_legacy_scope: Cell::new(Some(LegacyScope::Empty)),
 131         }));
 132         mark
 133     }
 134
 135     fn resolve_dollar_crates(&mut self, fragment: &AstFragment) {
 136         struct ResolveDollarCrates<'a, 'b: 'a> {
 137             resolver: &'a mut Resolver<'b>
 138         }
 139         impl<'a> Visitor<'a> for ResolveDollarCrates<'a, '_> {
 140             fn visit_ident(&mut self, ident: Ident) {
 141                 if ident.name == keywords::DollarCrate.name() {
 142                     let name = match self.resolver.resolve_crate_root(ident).kind {
 143                         ModuleKind::Def(_, name) if name != keywords::Invalid.name() => name,
 144                         _ => keywords::Crate.name(),
 145                     };
 146                     ident.span.ctxt().set_dollar_crate_name(name);
 147                 }
 148             }
 149             fn visit_mac(&mut self, _: &ast::Mac) {}
 150         }
 151
 152         fragment.visit_with(&mut ResolveDollarCrates { resolver: self });
 153     }
 154
 155     fn visit_ast_fragment_with_placeholders(&mut self, mark: Mark, fragment: &AstFragment,
 156                                             derives: &[Mark]) {
 157         let invocation = self.invocations[&mark];
 158         self.collect_def_ids(mark, invocation, fragment);
 159
 160         self.current_module = invocation.module.get();
 161         self.current_module.unresolved_invocations.borrow_mut().remove(&mark);
 162         self.current_module.unresolved_invocations.borrow_mut().extend(derives);
 163         self.invocations.extend(derives.iter().map(|&derive| (derive, invocation)));
 164         let mut visitor = BuildReducedGraphVisitor {
 165             resolver: self,
 166             current_legacy_scope: invocation.parent_legacy_scope.get(),
 167             expansion: mark,
 168         };
 169         fragment.visit_with(&mut visitor);
 170         invocation.output_legacy_scope.set(Some(visitor.current_legacy_scope));
 171     }
 172
 173     fn add_builtin(&mut self, ident: ast::Ident, ext: Lrc<SyntaxExtension>) {
 174         let def_id = DefId {
 175             krate: CrateNum::BuiltinMacros,
 176             index: DefIndex::from_array_index(self.macro_map.len(),
 177                                               DefIndexAddressSpace::Low),
 178         };
 179         let kind = ext.kind();
 180         self.macro_map.insert(def_id, ext);
 181         let binding = self.arenas.alloc_name_binding(NameBinding {
 182             kind: NameBindingKind::Def(Def::Macro(def_id, kind), false),
 183             ambiguity: None,
 184             span: DUMMY_SP,
 185             vis: ty::Visibility::Public,
 186             expansion: Mark::root(),
 187         });
 188         if self.builtin_macros.insert(ident.name, binding).is_some() {
 189             self.session.span_err(ident.span,
 190                                   &format!("built-in macro `{}` was already defined", ident));
 191         }
 192     }
 193
 194     fn resolve_imports(&mut self) {
 195         ImportResolver { resolver: self }.resolve_imports()
 196     }
 197
 198     fn resolve_macro_invocation(&mut self, invoc: &Invocation, invoc_id: Mark, force: bool)
 199                                 -> Result<Option<Lrc<SyntaxExtension>>, Determinacy> {
 200         let (path, kind, derives_in_scope, after_derive) = match invoc.kind {
 201             InvocationKind::Attr { attr: None, .. } =>
 202                 return Ok(None),
 203             InvocationKind::Attr { attr: Some(ref attr), ref traits, after_derive, .. } =>
 204                 (&attr.path, MacroKind::Attr, traits.clone(), after_derive),
 205             InvocationKind::Bang { ref mac, .. } =>
 206                 (&mac.node.path, MacroKind::Bang, Vec::new(), false),
 207             InvocationKind::Derive { ref path, .. } =>
 208                 (path, MacroKind::Derive, Vec::new(), false),
 209         };
 210
 211         let parent_scope = self.invoc_parent_scope(invoc_id, derives_in_scope);
 212         let (def, ext) = match self.resolve_macro_to_def(path, kind, &parent_scope, true, force) {
 213             Ok((def, ext)) => (def, ext),
 214             Err(Determinacy::Determined) if kind == MacroKind::Attr => {
 215                 // Replace unresolved attributes with used inert attributes for better recovery.
 216                 return Ok(Some(Lrc::new(SyntaxExtension::NonMacroAttr { mark_used: true })));
 217             }
 218             Err(determinacy) => return Err(determinacy),
 219         };
 220
 221         if let Def::Macro(def_id, _) = def {
 222             if after_derive {
 223                 self.session.span_err(invoc.span(),
 224                                       "macro attributes must be placed before `#[derive]`");
 225             }
 226             self.macro_defs.insert(invoc.expansion_data.mark, def_id);
 227             let normal_module_def_id =
 228                 self.macro_def_scope(invoc.expansion_data.mark).normal_ancestor_id;
 229             self.definitions.add_parent_module_of_macro_def(invoc.expansion_data.mark,
 230                                                             normal_module_def_id);
 231             invoc.expansion_data.mark.set_default_transparency(ext.default_transparency());
 232         }
 233
 234         Ok(Some(ext))
 235     }
 236
 237     fn resolve_macro_path(&mut self, path: &ast::Path, kind: MacroKind, invoc_id: Mark,
 238                           derives_in_scope: Vec<ast::Path>, force: bool)
 239                           -> Result<Lrc<SyntaxExtension>, Determinacy> {
 240         let parent_scope = self.invoc_parent_scope(invoc_id, derives_in_scope);
 241         Ok(self.resolve_macro_to_def(path, kind, &parent_scope, false, force)?.1)
 242     }
 243
 244     fn check_unused_macros(&self) {
 245         for did in self.unused_macros.iter() {
 246             let id_span = match *self.macro_map[did] {
 247                 SyntaxExtension::NormalTT { def_info, .. } |
 248                 SyntaxExtension::DeclMacro { def_info, .. } => def_info,
 249                 _ => None,
 250             };
 251             if let Some((id, span)) = id_span {
 252                 let lint = lint::builtin::UNUSED_MACROS;
 253                 let msg = "unused macro definition";
 254                 self.session.buffer_lint(lint, id, span, msg);
 255             } else {
 256                 bug!("attempted to create unused macro error, but span not available");
 257             }
 258         }
 259     }
 260 }
 261
 262 impl<'a> Resolver<'a> {
 263     pub fn dummy_parent_scope(&self) -> ParentScope<'a> {
 264         self.invoc_parent_scope(Mark::root(), Vec::new())
 265     }
 266
 267     fn invoc_parent_scope(&self, invoc_id: Mark, derives: Vec<ast::Path>) -> ParentScope<'a> {
 268         let invoc = self.invocations[&invoc_id];
 269         ParentScope {
 270             module: invoc.module.get().nearest_item_scope(),
 271             expansion: invoc_id.parent(),
 272             legacy: invoc.parent_legacy_scope.get(),
 273             derives,
 274         }
 275     }
 276
 277     fn resolve_macro_to_def(
 278         &mut self,
 279         path: &ast::Path,
 280         kind: MacroKind,
 281         parent_scope: &ParentScope<'a>,
 282         trace: bool,
 283         force: bool,
 284     ) -> Result<(Def, Lrc<SyntaxExtension>), Determinacy> {
 285         let def = self.resolve_macro_to_def_inner(path, kind, parent_scope, trace, force);
 286
 287         // Report errors and enforce feature gates for the resolved macro.
 288         if def != Err(Determinacy::Undetermined) {
 289             // Do not report duplicated errors on every undetermined resolution.
 290             for segment in &path.segments {
 291                 if let Some(args) = &segment.args {
 292                     self.session.span_err(args.span(), "generic arguments in macro path");
 293                 }
 294             }
 295         }
 296
 297         let def = def?;
 298
 299         match def {
 300             Def::Macro(def_id, macro_kind) => {
 301                 self.unused_macros.remove(&def_id);
 302                 if macro_kind == MacroKind::ProcMacroStub {
 303                     let msg = "can't use a procedural macro from the same crate that defines it";
 304                     self.session.span_err(path.span, msg);
 305                     return Err(Determinacy::Determined);
 306                 }
 307             }
 308             Def::NonMacroAttr(attr_kind) => {
 309                 if kind == MacroKind::Attr {
 310                     let features = self.session.features_untracked();
 311                     if attr_kind == NonMacroAttrKind::Custom {
 312                         assert!(path.segments.len() == 1);
 313                         let name = path.segments[0].ident.as_str();
 314                         if name.starts_with("rustc_") {
 315                             if !features.rustc_attrs {
 316                                 let msg = "unless otherwise specified, attributes with the prefix \
 317                                            `rustc_` are reserved for internal compiler diagnostics";
 318                                 self.report_unknown_attribute(path.span, &name, msg, "rustc_attrs");
 319                             }
 320                         } else if !features.custom_attribute {
 321                             let msg = format!("The attribute `{}` is currently unknown to the \
 322                                                compiler and may have meaning added to it in the \
 323                                                future", path);
 324                             self.report_unknown_attribute(
 325                                 path.span,
 326                                 &name,
 327                                 &msg,
 328                                 "custom_attribute",
 329                             );
 330                         }
 331                     }
 332                 } else {
 333                     // Not only attributes, but anything in macro namespace can result in
 334                     // `Def::NonMacroAttr` definition (e.g., `inline!()`), so we must report
 335                     // an error for those cases.
 336                     let msg = format!("expected a macro, found {}", def.kind_name());
 337                     self.session.span_err(path.span, &msg);
 338                     return Err(Determinacy::Determined);
 339                 }
 340             }
 341             Def::Err => {
 342                 return Err(Determinacy::Determined);
 343             }
 344             _ => panic!("expected `Def::Macro` or `Def::NonMacroAttr`"),
 345         }
 346
 347         Ok((def, self.get_macro(def)))
 348     }
 349
 350     fn report_unknown_attribute(&self, span: Span, name: &str, msg: &str, feature: &str) {
 351         let mut err = feature_err(
 352             &self.session.parse_sess,
 353             feature,
 354             span,
 355             GateIssue::Language,
 356             &msg,
 357         );
 358
 359         let features = self.session.features_untracked();
 360
 361         let attr_candidates = BUILTIN_ATTRIBUTES
 362             .iter()
 363             .filter_map(|(name, _, _, gate)| {
 364                 if name.starts_with("rustc_") && !features.rustc_attrs {
 365                     return None;
 366                 }
 367
 368                 match gate {
 369                     AttributeGate::Gated(Stability::Unstable, ..)
 370                         if self.session.opts.unstable_features.is_nightly_build() =>
 371                     {
 372                         Some(name)
 373                     }
 374                     AttributeGate::Gated(Stability::Deprecated(..), ..) => Some(name),
 375                     AttributeGate::Ungated => Some(name),
 376                     _ => None,
 377                 }
 378             })
 379             .map(|name| Symbol::intern(name))
 380             .chain(
 381                 // Add built-in macro attributes as well.
 382                 self.builtin_macros.iter().filter_map(|(name, binding)| {
 383                     match binding.macro_kind() {
 384                         Some(MacroKind::Attr) => Some(*name),
 385                         _ => None,
 386                     }
 387                 }),
 388             )
 389             .collect::<Vec<_>>();
 390
 391         let lev_suggestion = find_best_match_for_name(attr_candidates.iter(), &name, None);
 392
 393         if let Some(suggestion) = lev_suggestion {
 394             err.span_suggestion(
 395                 span,
 396                 "a built-in attribute with a similar name exists",
 397                 suggestion.to_string(),
 398                 Applicability::MaybeIncorrect,
 399             );
 400         }
 401
 402         err.emit();
 403     }
 404
 405     pub fn resolve_macro_to_def_inner(
 406         &mut self,
 407         path: &ast::Path,
 408         kind: MacroKind,
 409         parent_scope: &ParentScope<'a>,
 410         trace: bool,
 411         force: bool,
 412     ) -> Result<Def, Determinacy> {
 413         let path_span = path.span;
 414         let mut path = Segment::from_path(path);
 415
 416         // Possibly apply the macro helper hack
 417         if kind == MacroKind::Bang && path.len() == 1 &&
 418            path[0].ident.span.ctxt().outer().expn_info()
 419                .map_or(false, |info| info.local_inner_macros) {
 420             let root = Ident::new(keywords::DollarCrate.name(), path[0].ident.span);
 421             path.insert(0, Segment::from_ident(root));
 422         }
 423
 424         if path.len() > 1 {
 425             let def = match self.resolve_path(&path, Some(MacroNS), parent_scope,
 426                                               false, path_span, CrateLint::No) {
 427                 PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 => {
 428                     Ok(path_res.base_def())
 429                 }
 430                 PathResult::Indeterminate if !force => return Err(Determinacy::Undetermined),
 431                 PathResult::NonModule(..)
 432                 | PathResult::Indeterminate
 433                 | PathResult::Failed { .. } => Err(Determinacy::Determined),
 434                 PathResult::Module(..) => unreachable!(),
 435             };
 436
 437             if trace {
 438                 parent_scope.module.multi_segment_macro_resolutions.borrow_mut()
 439                     .push((path, path_span, kind, parent_scope.clone(), def.ok()));
 440             }
 441
 442             self.prohibit_imported_non_macro_attrs(None, def.ok(), path_span);
 443             def
 444         } else {
 445             let binding = self.early_resolve_ident_in_lexical_scope(
 446                 path[0].ident, ScopeSet::Macro(kind), parent_scope, false, force, path_span
 447             );
 448             if let Err(Determinacy::Undetermined) = binding {
 449                 return Err(Determinacy::Undetermined);
 450             }
 451
 452             if trace {
 453                 parent_scope.module.single_segment_macro_resolutions.borrow_mut()
 454                     .push((path[0].ident, kind, parent_scope.clone(), binding.ok()));
 455             }
 456
 457             let def = binding.map(|binding| binding.def());
 458             self.prohibit_imported_non_macro_attrs(binding.ok(), def.ok(), path_span);
 459             def
 460         }
 461     }
 462
 463     // Resolve an identifier in lexical scope.
 464     // This is a variation of `fn resolve_ident_in_lexical_scope` that can be run during
 465     // expansion and import resolution (perhaps they can be merged in the future).
 466     // The function is used for resolving initial segments of macro paths (e.g., `foo` in
 467     // `foo::bar!(); or `foo!();`) and also for import paths on 2018 edition.
 468     crate fn early_resolve_ident_in_lexical_scope(
 469         &mut self,
 470         orig_ident: Ident,
 471         scope_set: ScopeSet,
 472         parent_scope: &ParentScope<'a>,
 473         record_used: bool,
 474         force: bool,
 475         path_span: Span,
 476     ) -> Result<&'a NameBinding<'a>, Determinacy> {
 477         // General principles:
 478         // 1. Not controlled (user-defined) names should have higher priority than controlled names
 479         //    built into the language or standard library. This way we can add new names into the
 480         //    language or standard library without breaking user code.
 481         // 2. "Closed set" below means new names cannot appear after the current resolution attempt.
 482         // Places to search (in order of decreasing priority):
 483         // (Type NS)
 484         // 1. FIXME: Ribs (type parameters), there's no necessary infrastructure yet
 485         //    (open set, not controlled).
 486         // 2. Names in modules (both normal `mod`ules and blocks), loop through hygienic parents
 487         //    (open, not controlled).
 488         // 3. Extern prelude (closed, not controlled).
 489         // 4. Tool modules (closed, controlled right now, but not in the future).
 490         // 5. Standard library prelude (de-facto closed, controlled).
 491         // 6. Language prelude (closed, controlled).
 492         // (Value NS)
 493         // 1. FIXME: Ribs (local variables), there's no necessary infrastructure yet
 494         //    (open set, not controlled).
 495         // 2. Names in modules (both normal `mod`ules and blocks), loop through hygienic parents
 496         //    (open, not controlled).
 497         // 3. Standard library prelude (de-facto closed, controlled).
 498         // (Macro NS)
 499         // 1-3. Derive helpers (open, not controlled). All ambiguities with other names
 500         //    are currently reported as errors. They should be higher in priority than preludes
 501         //    and probably even names in modules according to the "general principles" above. They
 502         //    also should be subject to restricted shadowing because are effectively produced by
 503         //    derives (you need to resolve the derive first to add helpers into scope), but they
 504         //    should be available before the derive is expanded for compatibility.
 505         //    It's mess in general, so we are being conservative for now.
 506         // 1-3. `macro_rules` (open, not controlled), loop through legacy scopes. Have higher
 507         //    priority than prelude macros, but create ambiguities with macros in modules.
 508         // 1-3. Names in modules (both normal `mod`ules and blocks), loop through hygienic parents
 509         //    (open, not controlled). Have higher priority than prelude macros, but create
 510         //    ambiguities with `macro_rules`.
 511         // 4. `macro_use` prelude (open, the open part is from macro expansions, not controlled).
 512         // 4a. User-defined prelude from macro-use
 513         //    (open, the open part is from macro expansions, not controlled).
 514         // 4b. Standard library prelude is currently implemented as `macro-use` (closed, controlled)
 515         // 5. Language prelude: builtin macros (closed, controlled, except for legacy plugins).
 516         // 6. Language prelude: builtin attributes (closed, controlled).
 517         // 4-6. Legacy plugin helpers (open, not controlled). Similar to derive helpers,
 518         //    but introduced by legacy plugins using `register_attribute`. Priority is somewhere
 519         //    in prelude, not sure where exactly (creates ambiguities with any other prelude names).
 520
 521         enum WhereToResolve<'a> {
 522             DeriveHelpers,
 523             MacroRules(LegacyScope<'a>),
 524             CrateRoot,
 525             Module(Module<'a>),
 526             MacroUsePrelude,
 527             BuiltinMacros,
 528             BuiltinAttrs,
 529             LegacyPluginHelpers,
 530             ExternPrelude,
 531             ToolPrelude,
 532             StdLibPrelude,
 533             BuiltinTypes,
 534         }
 535
 536         bitflags::bitflags! {
 537             struct Flags: u8 {
 538                 const MACRO_RULES        = 1 << 0;
 539                 const MODULE             = 1 << 1;
 540                 const PRELUDE            = 1 << 2;
 541                 const MISC_SUGGEST_CRATE = 1 << 3;
 542                 const MISC_SUGGEST_SELF  = 1 << 4;
 543                 const MISC_FROM_PRELUDE  = 1 << 5;
 544             }
 545         }
 546
 547         assert!(force || !record_used); // `record_used` implies `force`
 548         let mut ident = orig_ident.modern();
 549
 550         // Make sure `self`, `super` etc produce an error when passed to here.
 551         if ident.is_path_segment_keyword() {
 552             return Err(Determinacy::Determined);
 553         }
 554
 555         // This is *the* result, resolution from the scope closest to the resolved identifier.
 556         // However, sometimes this result is "weak" because it comes from a glob import or
 557         // a macro expansion, and in this case it cannot shadow names from outer scopes, e.g.
 558         // mod m { ... } // solution in outer scope
 559         // {
 560         //     use prefix::*; // imports another `m` - innermost solution
 561         //                    // weak, cannot shadow the outer `m`, need to report ambiguity error
 562         //     m::mac!();
 563         // }
 564         // So we have to save the innermost solution and continue searching in outer scopes
 565         // to detect potential ambiguities.
 566         let mut innermost_result: Option<(&NameBinding<'_>, Flags)> = None;
 567
 568         // Go through all the scopes and try to resolve the name.
 569         let rust_2015 = orig_ident.span.rust_2015();
 570         let (ns, macro_kind, is_import, is_absolute_path) = match scope_set {
 571             ScopeSet::Import(ns) => (ns, None, true, false),
 572             ScopeSet::AbsolutePath(ns) => (ns, None, false, true),
 573             ScopeSet::Macro(macro_kind) => (MacroNS, Some(macro_kind), false, false),
 574             ScopeSet::Module => (TypeNS, None, false, false),
 575         };
 576         let mut where_to_resolve = match ns {
 577             _ if is_absolute_path => WhereToResolve::CrateRoot,
 578             TypeNS | ValueNS => WhereToResolve::Module(parent_scope.module),
 579             MacroNS => WhereToResolve::DeriveHelpers,
 580         };
 581         let mut use_prelude = !parent_scope.module.no_implicit_prelude;
 582         let mut determinacy = Determinacy::Determined;
 583         loop {
 584             let result = match where_to_resolve {
 585                 WhereToResolve::DeriveHelpers => {
 586                     let mut result = Err(Determinacy::Determined);
 587                     for derive in &parent_scope.derives {
 588                         let parent_scope = ParentScope { derives: Vec::new(), ..*parent_scope };
 589                         match self.resolve_macro_to_def(derive, MacroKind::Derive,
 590                                                         &parent_scope, true, force) {
 591                             Ok((_, ext)) => {
 592                                 if let SyntaxExtension::ProcMacroDerive(_, helpers, _) = &*ext {
 593                                     if helpers.contains(&ident.name) {
 594                                         let binding =
 595                                             (Def::NonMacroAttr(NonMacroAttrKind::DeriveHelper),
 596                                             ty::Visibility::Public, derive.span, Mark::root())
 597                                             .to_name_binding(self.arenas);
 598                                         result = Ok((binding, Flags::empty()));
 599                                         break;
 600                                     }
 601                                 }
 602                             }
 603                             Err(Determinacy::Determined) => {}
 604                             Err(Determinacy::Undetermined) =>
 605                                 result = Err(Determinacy::Undetermined),
 606                         }
 607                     }
 608                     result
 609                 }
 610                 WhereToResolve::MacroRules(legacy_scope) => match legacy_scope {
 611                     LegacyScope::Binding(legacy_binding) if ident == legacy_binding.ident =>
 612                         Ok((legacy_binding.binding, Flags::MACRO_RULES)),
 613                     LegacyScope::Invocation(invoc) if invoc.output_legacy_scope.get().is_none() =>
 614                         Err(Determinacy::Undetermined),
 615                     _ => Err(Determinacy::Determined),
 616                 }
 617                 WhereToResolve::CrateRoot => {
 618                     let root_ident = Ident::new(keywords::PathRoot.name(), orig_ident.span);
 619                     let root_module = self.resolve_crate_root(root_ident);
 620                     let binding = self.resolve_ident_in_module_ext(
 621                         ModuleOrUniformRoot::Module(root_module),
 622                         orig_ident,
 623                         ns,
 624                         None,
 625                         record_used,
 626                         path_span,
 627                     );
 628                     match binding {
 629                         Ok(binding) => Ok((binding, Flags::MODULE | Flags::MISC_SUGGEST_CRATE)),
 630                         Err((Determinacy::Undetermined, Weak::No)) =>
 631                             return Err(Determinacy::determined(force)),
 632                         Err((Determinacy::Undetermined, Weak::Yes)) =>
 633                             Err(Determinacy::Undetermined),
 634                         Err((Determinacy::Determined, _)) => Err(Determinacy::Determined),
 635                     }
 636                 }
 637                 WhereToResolve::Module(module) => {
 638                     let orig_current_module = mem::replace(&mut self.current_module, module);
 639                     let binding = self.resolve_ident_in_module_unadjusted_ext(
 640                         ModuleOrUniformRoot::Module(module),
 641                         ident,
 642                         ns,
 643                         None,
 644                         true,
 645                         record_used,
 646                         path_span,
 647                     );
 648                     self.current_module = orig_current_module;
 649                     match binding {
 650                         Ok(binding) => {
 651                             let misc_flags = if ptr::eq(module, self.graph_root) {
 652                                 Flags::MISC_SUGGEST_CRATE
 653                             } else if module.is_normal() {
 654                                 Flags::MISC_SUGGEST_SELF
 655                             } else {
 656                                 Flags::empty()
 657                             };
 658                             Ok((binding, Flags::MODULE | misc_flags))
 659                         }
 660                         Err((Determinacy::Undetermined, Weak::No)) =>
 661                             return Err(Determinacy::determined(force)),
 662                         Err((Determinacy::Undetermined, Weak::Yes)) =>
 663                             Err(Determinacy::Undetermined),
 664                         Err((Determinacy::Determined, _)) => Err(Determinacy::Determined),
 665                     }
 666                 }
 667                 WhereToResolve::MacroUsePrelude => {
 668                     if use_prelude || rust_2015 {
 669                         match self.macro_use_prelude.get(&ident.name).cloned() {
 670                             Some(binding) =>
 671                                 Ok((binding, Flags::PRELUDE | Flags::MISC_FROM_PRELUDE)),
 672                             None => Err(Determinacy::determined(
 673                                 self.graph_root.unresolved_invocations.borrow().is_empty()
 674                             ))
 675                         }
 676                     } else {
 677                         Err(Determinacy::Determined)
 678                     }
 679                 }
 680                 WhereToResolve::BuiltinMacros => {
 681                     match self.builtin_macros.get(&ident.name).cloned() {
 682                         Some(binding) => Ok((binding, Flags::PRELUDE)),
 683                         None => Err(Determinacy::Determined),
 684                     }
 685                 }
 686                 WhereToResolve::BuiltinAttrs => {
 687                     if is_builtin_attr_name(ident.name) {
 688                         let binding = (Def::NonMacroAttr(NonMacroAttrKind::Builtin),
 689                                        ty::Visibility::Public, DUMMY_SP, Mark::root())
 690                                        .to_name_binding(self.arenas);
 691                         Ok((binding, Flags::PRELUDE))
 692                     } else {
 693                         Err(Determinacy::Determined)
 694                     }
 695                 }
 696                 WhereToResolve::LegacyPluginHelpers => {
 697                     if (use_prelude || rust_2015) &&
 698                        self.session.plugin_attributes.borrow().iter()
 699                                                      .any(|(name, _)| ident.name == &**name) {
 700                         let binding = (Def::NonMacroAttr(NonMacroAttrKind::LegacyPluginHelper),
 701                                        ty::Visibility::Public, DUMMY_SP, Mark::root())
 702                                        .to_name_binding(self.arenas);
 703                         Ok((binding, Flags::PRELUDE))
 704                     } else {
 705                         Err(Determinacy::Determined)
 706                     }
 707                 }
 708                 WhereToResolve::ExternPrelude => {
 709                     if use_prelude || is_absolute_path {
 710                         match self.extern_prelude_get(ident, !record_used) {
 711                             Some(binding) => Ok((binding, Flags::PRELUDE)),
 712                             None => Err(Determinacy::determined(
 713                                 self.graph_root.unresolved_invocations.borrow().is_empty()
 714                             )),
 715                         }
 716                     } else {
 717                         Err(Determinacy::Determined)
 718                     }
 719                 }
 720                 WhereToResolve::ToolPrelude => {
 721                     if use_prelude && is_known_tool(ident.name) {
 722                         let binding = (Def::ToolMod, ty::Visibility::Public,
 723                                        DUMMY_SP, Mark::root()).to_name_binding(self.arenas);
 724                         Ok((binding, Flags::PRELUDE))
 725                     } else {
 726                         Err(Determinacy::Determined)
 727                     }
 728                 }
 729                 WhereToResolve::StdLibPrelude => {
 730                     let mut result = Err(Determinacy::Determined);
 731                     if use_prelude {
 732                         if let Some(prelude) = self.prelude {
 733                             if let Ok(binding) = self.resolve_ident_in_module_unadjusted(
 734                                 ModuleOrUniformRoot::Module(prelude),
 735                                 ident,
 736                                 ns,
 737                                 false,
 738                                 path_span,
 739                             ) {
 740                                 result = Ok((binding, Flags::PRELUDE | Flags::MISC_FROM_PRELUDE));
 741                             }
 742                         }
 743                     }
 744                     result
 745                 }
 746                 WhereToResolve::BuiltinTypes => {
 747                     match self.primitive_type_table.primitive_types.get(&ident.name).cloned() {
 748                         Some(prim_ty) => {
 749                             let binding = (Def::PrimTy(prim_ty), ty::Visibility::Public,
 750                                            DUMMY_SP, Mark::root()).to_name_binding(self.arenas);
 751                             Ok((binding, Flags::PRELUDE))
 752                         }
 753                         None => Err(Determinacy::Determined)
 754                     }
 755                 }
 756             };
 757
 758             match result {
 759                 Ok((binding, flags)) if sub_namespace_match(binding.macro_kind(), macro_kind) => {
 760                     if !record_used {
 761                         return Ok(binding);
 762                     }
 763
 764                     if let Some((innermost_binding, innermost_flags)) = innermost_result {
 765                         // Found another solution, if the first one was "weak", report an error.
 766                         let (def, innermost_def) = (binding.def(), innermost_binding.def());
 767                         if def != innermost_def {
 768                             let builtin = Def::NonMacroAttr(NonMacroAttrKind::Builtin);
 769                             let derive_helper = Def::NonMacroAttr(NonMacroAttrKind::DeriveHelper);
 770                             let legacy_helper =
 771                                 Def::NonMacroAttr(NonMacroAttrKind::LegacyPluginHelper);
 772
 773                             let ambiguity_error_kind = if is_import {
 774                                 Some(AmbiguityKind::Import)
 775                             } else if innermost_def == builtin || def == builtin {
 776                                 Some(AmbiguityKind::BuiltinAttr)
 777                             } else if innermost_def == derive_helper || def == derive_helper {
 778                                 Some(AmbiguityKind::DeriveHelper)
 779                             } else if innermost_def == legacy_helper &&
 780                                       flags.contains(Flags::PRELUDE) ||
 781                                       def == legacy_helper &&
 782                                       innermost_flags.contains(Flags::PRELUDE) {
 783                                 Some(AmbiguityKind::LegacyHelperVsPrelude)
 784                             } else if innermost_flags.contains(Flags::MACRO_RULES) &&
 785                                       flags.contains(Flags::MODULE) &&
 786                                       !self.disambiguate_legacy_vs_modern(innermost_binding,
 787                                                                           binding) ||
 788                                       flags.contains(Flags::MACRO_RULES) &&
 789                                       innermost_flags.contains(Flags::MODULE) &&
 790                                       !self.disambiguate_legacy_vs_modern(binding,
 791                                                                           innermost_binding) {
 792                                 Some(AmbiguityKind::LegacyVsModern)
 793                             } else if innermost_binding.is_glob_import() {
 794                                 Some(AmbiguityKind::GlobVsOuter)
 795                             } else if innermost_binding.may_appear_after(parent_scope.expansion,
 796                                                                          binding) {
 797                                 Some(AmbiguityKind::MoreExpandedVsOuter)
 798                             } else {
 799                                 None
 800                             };
 801                             if let Some(kind) = ambiguity_error_kind {
 802                                 let misc = |f: Flags| if f.contains(Flags::MISC_SUGGEST_CRATE) {
 803                                     AmbiguityErrorMisc::SuggestCrate
 804                                 } else if f.contains(Flags::MISC_SUGGEST_SELF) {
 805                                     AmbiguityErrorMisc::SuggestSelf
 806                                 } else if f.contains(Flags::MISC_FROM_PRELUDE) {
 807                                     AmbiguityErrorMisc::FromPrelude
 808                                 } else {
 809                                     AmbiguityErrorMisc::None
 810                                 };
 811                                 self.ambiguity_errors.push(AmbiguityError {
 812                                     kind,
 813                                     ident: orig_ident,
 814                                     b1: innermost_binding,
 815                                     b2: binding,
 816                                     misc1: misc(innermost_flags),
 817                                     misc2: misc(flags),
 818                                 });
 819                                 return Ok(innermost_binding);
 820                             }
 821                         }
 822                     } else {
 823                         // Found the first solution.
 824                         innermost_result = Some((binding, flags));
 825                     }
 826                 }
 827                 Ok(..) | Err(Determinacy::Determined) => {}
 828                 Err(Determinacy::Undetermined) => determinacy = Determinacy::Undetermined
 829             }
 830
 831             where_to_resolve = match where_to_resolve {
 832                 WhereToResolve::DeriveHelpers =>
 833                     WhereToResolve::MacroRules(parent_scope.legacy),
 834                 WhereToResolve::MacroRules(legacy_scope) => match legacy_scope {
 835                     LegacyScope::Binding(binding) => WhereToResolve::MacroRules(
 836                         binding.parent_legacy_scope
 837                     ),
 838                     LegacyScope::Invocation(invoc) => WhereToResolve::MacroRules(
 839                         invoc.output_legacy_scope.get().unwrap_or(invoc.parent_legacy_scope.get())
 840                     ),
 841                     LegacyScope::Empty => WhereToResolve::Module(parent_scope.module),
 842                     LegacyScope::Uninitialized => unreachable!(),
 843                 }
 844                 WhereToResolve::CrateRoot => match ns {
 845                     TypeNS => {
 846                         ident.span.adjust(Mark::root());
 847                         WhereToResolve::ExternPrelude
 848                     }
 849                     ValueNS | MacroNS => break,
 850                 }
 851                 WhereToResolve::Module(module) => {
 852                     match self.hygienic_lexical_parent(module, &mut ident.span) {
 853                         Some(parent_module) => WhereToResolve::Module(parent_module),
 854                         None => {
 855                             use_prelude = !module.no_implicit_prelude;
 856                             match ns {
 857                                 TypeNS => WhereToResolve::ExternPrelude,
 858                                 ValueNS => WhereToResolve::StdLibPrelude,
 859                                 MacroNS => WhereToResolve::MacroUsePrelude,
 860                             }
 861                         }
 862                     }
 863                 }
 864                 WhereToResolve::MacroUsePrelude => WhereToResolve::BuiltinMacros,
 865                 WhereToResolve::BuiltinMacros => WhereToResolve::BuiltinAttrs,
 866                 WhereToResolve::BuiltinAttrs => WhereToResolve::LegacyPluginHelpers,
 867                 WhereToResolve::LegacyPluginHelpers => break, // nowhere else to search
 868                 WhereToResolve::ExternPrelude if is_absolute_path => break,
 869                 WhereToResolve::ExternPrelude => WhereToResolve::ToolPrelude,
 870                 WhereToResolve::ToolPrelude => WhereToResolve::StdLibPrelude,
 871                 WhereToResolve::StdLibPrelude => match ns {
 872                     TypeNS => WhereToResolve::BuiltinTypes,
 873                     ValueNS => break, // nowhere else to search
 874                     MacroNS => unreachable!(),
 875                 }
 876                 WhereToResolve::BuiltinTypes => break, // nowhere else to search
 877             };
 878
 879             continue;
 880         }
 881
 882         // The first found solution was the only one, return it.
 883         if let Some((binding, _)) = innermost_result {
 884             return Ok(binding);
 885         }
 886
 887         let determinacy = Determinacy::determined(determinacy == Determinacy::Determined || force);
 888         if determinacy == Determinacy::Determined && macro_kind == Some(MacroKind::Attr) {
 889             // For single-segment attributes interpret determinate "no resolution" as a custom
 890             // attribute. (Lexical resolution implies the first segment and attr kind should imply
 891             // the last segment, so we are certainly working with a single-segment attribute here.)
 892             assert!(ns == MacroNS);
 893             let binding = (Def::NonMacroAttr(NonMacroAttrKind::Custom),
 894                            ty::Visibility::Public, ident.span, Mark::root())
 895                            .to_name_binding(self.arenas);
 896             Ok(binding)
 897         } else {
 898             Err(determinacy)
 899         }
 900     }
 901
 902     pub fn finalize_current_module_macro_resolutions(&mut self) {
 903         let module = self.current_module;
 904
 905         let check_consistency = |this: &mut Self, path: &[Segment], span, kind: MacroKind,
 906                                  initial_def: Option<Def>, def: Def| {
 907             if let Some(initial_def) = initial_def {
 908                 if def != initial_def && def != Def::Err && this.ambiguity_errors.is_empty() {
 909                     // Make sure compilation does not succeed if preferred macro resolution
 910                     // has changed after the macro had been expanded. In theory all such
 911                     // situations should be reported as ambiguity errors, so this is a bug.
 912                     if initial_def == Def::NonMacroAttr(NonMacroAttrKind::Custom) {
 913                         // Yeah, legacy custom attributes are implemented using forced resolution
 914                         // (which is a best effort error recovery tool, basically), so we can't
 915                         // promise their resolution won't change later.
 916                         let msg = format!("inconsistent resolution for a macro: first {}, then {}",
 917                                           initial_def.kind_name(), def.kind_name());
 918                         this.session.span_err(span, &msg);
 919                     } else {
 920                         span_bug!(span, "inconsistent resolution for a macro");
 921                     }
 922                 }
 923             } else {
 924                 // It's possible that the macro was unresolved (indeterminate) and silently
 925                 // expanded into a dummy fragment for recovery during expansion.
 926                 // Now, post-expansion, the resolution may succeed, but we can't change the
 927                 // past and need to report an error.
 928                 // However, non-speculative `resolve_path` can successfully return private items
 929                 // even if speculative `resolve_path` returned nothing previously, so we skip this
 930                 // less informative error if the privacy error is reported elsewhere.
 931                 if this.privacy_errors.is_empty() {
 932                     let msg = format!("cannot determine resolution for the {} `{}`",
 933                                         kind.descr(), Segment::names_to_string(path));
 934                     let msg_note = "import resolution is stuck, try simplifying macro imports";
 935                     this.session.struct_span_err(span, &msg).note(msg_note).emit();
 936                 }
 937             }
 938         };
 939
 940         let macro_resolutions =
 941             mem::replace(&mut *module.multi_segment_macro_resolutions.borrow_mut(), Vec::new());
 942         for (mut path, path_span, kind, parent_scope, initial_def) in macro_resolutions {
 943             // FIXME: Path resolution will ICE if segment IDs present.
 944             for seg in &mut path { seg.id = None; }
 945             match self.resolve_path(&path, Some(MacroNS), &parent_scope,
 946                                     true, path_span, CrateLint::No) {
 947                 PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 => {
 948                     let def = path_res.base_def();
 949                     check_consistency(self, &path, path_span, kind, initial_def, def);
 950                 }
 951                 path_res @ PathResult::NonModule(..) | path_res @ PathResult::Failed { .. } => {
 952                     let (span, label) = if let PathResult::Failed { span, label, .. } = path_res {
 953                         (span, label)
 954                     } else {
 955                         (path_span, format!("partially resolved path in {} {}",
 956                                             kind.article(), kind.descr()))
 957                     };
 958                     resolve_error(self, span, ResolutionError::FailedToResolve {
 959                         label,
 960                         suggestion: None
 961                     });
 962                 }
 963                 PathResult::Module(..) | PathResult::Indeterminate => unreachable!(),
 964             }
 965         }
 966
 967         let macro_resolutions =
 968             mem::replace(&mut *module.single_segment_macro_resolutions.borrow_mut(), Vec::new());
 969         for (ident, kind, parent_scope, initial_binding) in macro_resolutions {
 970             match self.early_resolve_ident_in_lexical_scope(ident, ScopeSet::Macro(kind),
 971                                                             &parent_scope, true, true, ident.span) {
 972                 Ok(binding) => {
 973                     let initial_def = initial_binding.map(|initial_binding| {
 974                         self.record_use(ident, MacroNS, initial_binding, false);
 975                         initial_binding.def()
 976                     });
 977                     let def = binding.def();
 978                     let seg = Segment::from_ident(ident);
 979                     check_consistency(self, &[seg], ident.span, kind, initial_def, def);
 980                 }
 981                 Err(..) => {
 982                     assert!(initial_binding.is_none());
 983                     let bang = if kind == MacroKind::Bang { "!" } else { "" };
 984                     let msg =
 985                         format!("cannot find {} `{}{}` in this scope", kind.descr(), ident, bang);
 986                     let mut err = self.session.struct_span_err(ident.span, &msg);
 987                     self.suggest_macro_name(&ident.as_str(), kind, &mut err, ident.span);
 988                     err.emit();
 989                 }
 990             }
 991         }
 992
 993         let builtin_attrs = mem::replace(&mut *module.builtin_attrs.borrow_mut(), Vec::new());
 994         for (ident, parent_scope) in builtin_attrs {
 995             let _ = self.early_resolve_ident_in_lexical_scope(
 996                 ident, ScopeSet::Macro(MacroKind::Attr), &parent_scope, true, true, ident.span
 997             );
 998         }
 999     }
1000
1001     fn prohibit_imported_non_macro_attrs(&self, binding: Option<&'a NameBinding<'a>>,
1002                                          def: Option<Def>, span: Span) {
1003         if let Some(Def::NonMacroAttr(kind)) = def {
1004             if kind != NonMacroAttrKind::Tool && binding.map_or(true, |b| b.is_import()) {
1005                 let msg = format!("cannot use a {} through an import", kind.descr());
1006                 let mut err = self.session.struct_span_err(span, &msg);
1007                 if let Some(binding) = binding {
1008                     err.span_note(binding.span, &format!("the {} imported here", kind.descr()));
1009                 }
1010                 err.emit();
1011             }
1012         }
1013     }
1014
1015     fn suggest_macro_name(&mut self, name: &str, kind: MacroKind,
1016                           err: &mut DiagnosticBuilder<'a>, span: Span) {
1017         // First check if this is a locally-defined bang macro.
1018         let suggestion = if let MacroKind::Bang = kind {
1019             find_best_match_for_name(self.macro_names.iter().map(|ident| &ident.name), name, None)
1020         } else {
1021             None
1022         // Then check global macros.
1023         }.or_else(|| {
1024             let names = self.builtin_macros.iter().chain(self.macro_use_prelude.iter())
1025                                                   .filter_map(|(name, binding)| {
1026                 if binding.macro_kind() == Some(kind) { Some(name) } else { None }
1027             });
1028             find_best_match_for_name(names, name, None)
1029         // Then check modules.
1030         }).or_else(|| {
1031             let is_macro = |def| {
1032                 if let Def::Macro(_, def_kind) = def {
1033                     def_kind == kind
1034                 } else {
1035                     false
1036                 }
1037             };
1038             let ident = Ident::new(Symbol::intern(name), span);
1039             self.lookup_typo_candidate(&[Segment::from_ident(ident)], MacroNS, is_macro, span)
1040                 .map(|suggestion| suggestion.candidate)
1041         });
1042
1043         if let Some(suggestion) = suggestion {
1044             if suggestion != name {
1045                 if let MacroKind::Bang = kind {
1046                     err.span_suggestion(
1047                         span,
1048                         "you could try the macro",
1049                         suggestion.to_string(),
1050                         Applicability::MaybeIncorrect
1051                     );
1052                 } else {
1053                     err.span_suggestion(
1054                         span,
1055                         "try",
1056                         suggestion.to_string(),
1057                         Applicability::MaybeIncorrect
1058                     );
1059                 }
1060             } else {
1061                 err.help("have you added the `#[macro_use]` on the module/import?");
1062             }
1063         }
1064     }
1065
1066     fn collect_def_ids(&mut self,
1067                        mark: Mark,
1068                        invocation: &'a InvocationData<'a>,
1069                        fragment: &AstFragment) {
1070         let Resolver { ref mut invocations, arenas, graph_root, .. } = *self;
1071         let InvocationData { def_index, .. } = *invocation;
1072
1073         let visit_macro_invoc = &mut |invoc: map::MacroInvocationData| {
1074             invocations.entry(invoc.mark).or_insert_with(|| {
1075                 arenas.alloc_invocation_data(InvocationData {
1076                     def_index: invoc.def_index,
1077                     module: Cell::new(graph_root),
1078                     parent_legacy_scope: Cell::new(LegacyScope::Uninitialized),
1079                     output_legacy_scope: Cell::new(None),
1080                 })
1081             });
1082         };
1083
1084         let mut def_collector = DefCollector::new(&mut self.definitions, mark);
1085         def_collector.visit_macro_invoc = Some(visit_macro_invoc);
1086         def_collector.with_parent(def_index, |def_collector| {
1087             fragment.visit_with(def_collector)
1088         });
1089     }
1090
1091     pub fn define_macro(&mut self,
1092                         item: &ast::Item,
1093                         expansion: Mark,
1094                         current_legacy_scope: &mut LegacyScope<'a>) {
1095         self.local_macro_def_scopes.insert(item.id, self.current_module);
1096         let ident = item.ident;
1097         if ident.name == "macro_rules" {
1098             self.session.span_err(item.span, "user-defined macros may not be named `macro_rules`");
1099         }
1100
1101         let def_id = self.definitions.local_def_id(item.id);
1102         let ext = Lrc::new(macro_rules::compile(&self.session.parse_sess,
1103                                                &self.session.features_untracked(),
1104                                                item, hygiene::default_edition()));
1105         self.macro_map.insert(def_id, ext);
1106
1107         let def = match item.node { ast::ItemKind::MacroDef(ref def) => def, _ => unreachable!() };
1108         if def.legacy {
1109             let ident = ident.modern();
1110             self.macro_names.insert(ident);
1111             let def = Def::Macro(def_id, MacroKind::Bang);
1112             let is_macro_export = attr::contains_name(&item.attrs, "macro_export");
1113             let vis = if is_macro_export {
1114                 ty::Visibility::Public
1115             } else {
1116                 ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX))
1117             };
1118             let binding = (def, vis, item.span, expansion).to_name_binding(self.arenas);
1119             self.set_binding_parent_module(binding, self.current_module);
1120             let legacy_binding = self.arenas.alloc_legacy_binding(LegacyBinding {
1121                 parent_legacy_scope: *current_legacy_scope, binding, ident
1122             });
1123             *current_legacy_scope = LegacyScope::Binding(legacy_binding);
1124             self.all_macros.insert(ident.name, def);
1125             if is_macro_export {
1126                 let module = self.graph_root;
1127                 self.define(module, ident, MacroNS,
1128                             (def, vis, item.span, expansion, IsMacroExport));
1129             } else {
1130                 if !attr::contains_name(&item.attrs, "rustc_doc_only_macro") {
1131                     self.check_reserved_macro_name(ident, MacroNS);
1132                 }
1133                 self.unused_macros.insert(def_id);
1134             }
1135         } else {
1136             let module = self.current_module;
1137             let def = Def::Macro(def_id, MacroKind::Bang);
1138             let vis = self.resolve_visibility(&item.vis);
1139             if vis != ty::Visibility::Public {
1140                 self.unused_macros.insert(def_id);
1141             }
1142             self.define(module, ident, MacroNS, (def, vis, item.span, expansion));
1143         }
1144     }
1145 }