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, _, _, ref gate)| {
 364                 if name.as_str().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             .chain(
 380                 // Add built-in macro attributes as well.
 381                 self.builtin_macros.iter().filter_map(|(name, binding)| {
 382                     match binding.macro_kind() {
 383                         Some(MacroKind::Attr) => Some(*name),
 384                         _ => None,
 385                     }
 386                 }),
 387             )
 388             .collect::<Vec<_>>();
 389
 390         let lev_suggestion = find_best_match_for_name(attr_candidates.iter(), &name, None);
 391
 392         if let Some(suggestion) = lev_suggestion {
 393             err.span_suggestion(
 394                 span,
 395                 "a built-in attribute with a similar name exists",
 396                 suggestion.to_string(),
 397                 Applicability::MaybeIncorrect,
 398             );
 399         }
 400
 401         err.emit();
 402     }
 403
 404     pub fn resolve_macro_to_def_inner(
 405         &mut self,
 406         path: &ast::Path,
 407         kind: MacroKind,
 408         parent_scope: &ParentScope<'a>,
 409         trace: bool,
 410         force: bool,
 411     ) -> Result<Def, Determinacy> {
 412         let path_span = path.span;
 413         let mut path = Segment::from_path(path);
 414
 415         // Possibly apply the macro helper hack
 416         if kind == MacroKind::Bang && path.len() == 1 &&
 417            path[0].ident.span.ctxt().outer().expn_info()
 418                .map_or(false, |info| info.local_inner_macros) {
 419             let root = Ident::new(keywords::DollarCrate.name(), path[0].ident.span);
 420             path.insert(0, Segment::from_ident(root));
 421         }
 422
 423         if path.len() > 1 {
 424             let def = match self.resolve_path(&path, Some(MacroNS), parent_scope,
 425                                               false, path_span, CrateLint::No) {
 426                 PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 => {
 427                     Ok(path_res.base_def())
 428                 }
 429                 PathResult::Indeterminate if !force => return Err(Determinacy::Undetermined),
 430                 PathResult::NonModule(..)
 431                 | PathResult::Indeterminate
 432                 | PathResult::Failed { .. } => Err(Determinacy::Determined),
 433                 PathResult::Module(..) => unreachable!(),
 434             };
 435
 436             if trace {
 437                 parent_scope.module.multi_segment_macro_resolutions.borrow_mut()
 438                     .push((path, path_span, kind, parent_scope.clone(), def.ok()));
 439             }
 440
 441             self.prohibit_imported_non_macro_attrs(None, def.ok(), path_span);
 442             def
 443         } else {
 444             let binding = self.early_resolve_ident_in_lexical_scope(
 445                 path[0].ident, ScopeSet::Macro(kind), parent_scope, false, force, path_span
 446             );
 447             if let Err(Determinacy::Undetermined) = binding {
 448                 return Err(Determinacy::Undetermined);
 449             }
 450
 451             if trace {
 452                 parent_scope.module.single_segment_macro_resolutions.borrow_mut()
 453                     .push((path[0].ident, kind, parent_scope.clone(), binding.ok()));
 454             }
 455
 456             let def = binding.map(|binding| binding.def());
 457             self.prohibit_imported_non_macro_attrs(binding.ok(), def.ok(), path_span);
 458             def
 459         }
 460     }
 461
 462     // Resolve an identifier in lexical scope.
 463     // This is a variation of `fn resolve_ident_in_lexical_scope` that can be run during
 464     // expansion and import resolution (perhaps they can be merged in the future).
 465     // The function is used for resolving initial segments of macro paths (e.g., `foo` in
 466     // `foo::bar!(); or `foo!();`) and also for import paths on 2018 edition.
 467     crate fn early_resolve_ident_in_lexical_scope(
 468         &mut self,
 469         orig_ident: Ident,
 470         scope_set: ScopeSet,
 471         parent_scope: &ParentScope<'a>,
 472         record_used: bool,
 473         force: bool,
 474         path_span: Span,
 475     ) -> Result<&'a NameBinding<'a>, Determinacy> {
 476         // General principles:
 477         // 1. Not controlled (user-defined) names should have higher priority than controlled names
 478         //    built into the language or standard library. This way we can add new names into the
 479         //    language or standard library without breaking user code.
 480         // 2. "Closed set" below means new names cannot appear after the current resolution attempt.
 481         // Places to search (in order of decreasing priority):
 482         // (Type NS)
 483         // 1. FIXME: Ribs (type parameters), there's no necessary infrastructure yet
 484         //    (open set, not controlled).
 485         // 2. Names in modules (both normal `mod`ules and blocks), loop through hygienic parents
 486         //    (open, not controlled).
 487         // 3. Extern prelude (closed, not controlled).
 488         // 4. Tool modules (closed, controlled right now, but not in the future).
 489         // 5. Standard library prelude (de-facto closed, controlled).
 490         // 6. Language prelude (closed, controlled).
 491         // (Value NS)
 492         // 1. FIXME: Ribs (local variables), there's no necessary infrastructure yet
 493         //    (open set, not controlled).
 494         // 2. Names in modules (both normal `mod`ules and blocks), loop through hygienic parents
 495         //    (open, not controlled).
 496         // 3. Standard library prelude (de-facto closed, controlled).
 497         // (Macro NS)
 498         // 1-3. Derive helpers (open, not controlled). All ambiguities with other names
 499         //    are currently reported as errors. They should be higher in priority than preludes
 500         //    and probably even names in modules according to the "general principles" above. They
 501         //    also should be subject to restricted shadowing because are effectively produced by
 502         //    derives (you need to resolve the derive first to add helpers into scope), but they
 503         //    should be available before the derive is expanded for compatibility.
 504         //    It's mess in general, so we are being conservative for now.
 505         // 1-3. `macro_rules` (open, not controlled), loop through legacy scopes. Have higher
 506         //    priority than prelude macros, but create ambiguities with macros in modules.
 507         // 1-3. Names in modules (both normal `mod`ules and blocks), loop through hygienic parents
 508         //    (open, not controlled). Have higher priority than prelude macros, but create
 509         //    ambiguities with `macro_rules`.
 510         // 4. `macro_use` prelude (open, the open part is from macro expansions, not controlled).
 511         // 4a. User-defined prelude from macro-use
 512         //    (open, the open part is from macro expansions, not controlled).
 513         // 4b. Standard library prelude is currently implemented as `macro-use` (closed, controlled)
 514         // 5. Language prelude: builtin macros (closed, controlled, except for legacy plugins).
 515         // 6. Language prelude: builtin attributes (closed, controlled).
 516         // 4-6. Legacy plugin helpers (open, not controlled). Similar to derive helpers,
 517         //    but introduced by legacy plugins using `register_attribute`. Priority is somewhere
 518         //    in prelude, not sure where exactly (creates ambiguities with any other prelude names).
 519
 520         enum WhereToResolve<'a> {
 521             DeriveHelpers,
 522             MacroRules(LegacyScope<'a>),
 523             CrateRoot,
 524             Module(Module<'a>),
 525             MacroUsePrelude,
 526             BuiltinMacros,
 527             BuiltinAttrs,
 528             LegacyPluginHelpers,
 529             ExternPrelude,
 530             ToolPrelude,
 531             StdLibPrelude,
 532             BuiltinTypes,
 533         }
 534
 535         bitflags::bitflags! {
 536             struct Flags: u8 {
 537                 const MACRO_RULES        = 1 << 0;
 538                 const MODULE             = 1 << 1;
 539                 const PRELUDE            = 1 << 2;
 540                 const MISC_SUGGEST_CRATE = 1 << 3;
 541                 const MISC_SUGGEST_SELF  = 1 << 4;
 542                 const MISC_FROM_PRELUDE  = 1 << 5;
 543             }
 544         }
 545
 546         assert!(force || !record_used); // `record_used` implies `force`
 547         let mut ident = orig_ident.modern();
 548
 549         // Make sure `self`, `super` etc produce an error when passed to here.
 550         if ident.is_path_segment_keyword() {
 551             return Err(Determinacy::Determined);
 552         }
 553
 554         // This is *the* result, resolution from the scope closest to the resolved identifier.
 555         // However, sometimes this result is "weak" because it comes from a glob import or
 556         // a macro expansion, and in this case it cannot shadow names from outer scopes, e.g.
 557         // mod m { ... } // solution in outer scope
 558         // {
 559         //     use prefix::*; // imports another `m` - innermost solution
 560         //                    // weak, cannot shadow the outer `m`, need to report ambiguity error
 561         //     m::mac!();
 562         // }
 563         // So we have to save the innermost solution and continue searching in outer scopes
 564         // to detect potential ambiguities.
 565         let mut innermost_result: Option<(&NameBinding<'_>, Flags)> = None;
 566
 567         // Go through all the scopes and try to resolve the name.
 568         let rust_2015 = orig_ident.span.rust_2015();
 569         let (ns, macro_kind, is_import, is_absolute_path) = match scope_set {
 570             ScopeSet::Import(ns) => (ns, None, true, false),
 571             ScopeSet::AbsolutePath(ns) => (ns, None, false, true),
 572             ScopeSet::Macro(macro_kind) => (MacroNS, Some(macro_kind), false, false),
 573             ScopeSet::Module => (TypeNS, None, false, false),
 574         };
 575         let mut where_to_resolve = match ns {
 576             _ if is_absolute_path => WhereToResolve::CrateRoot,
 577             TypeNS | ValueNS => WhereToResolve::Module(parent_scope.module),
 578             MacroNS => WhereToResolve::DeriveHelpers,
 579         };
 580         let mut use_prelude = !parent_scope.module.no_implicit_prelude;
 581         let mut determinacy = Determinacy::Determined;
 582         loop {
 583             let result = match where_to_resolve {
 584                 WhereToResolve::DeriveHelpers => {
 585                     let mut result = Err(Determinacy::Determined);
 586                     for derive in &parent_scope.derives {
 587                         let parent_scope = ParentScope { derives: Vec::new(), ..*parent_scope };
 588                         match self.resolve_macro_to_def(derive, MacroKind::Derive,
 589                                                         &parent_scope, true, force) {
 590                             Ok((_, ext)) => {
 591                                 if let SyntaxExtension::ProcMacroDerive(_, helpers, _) = &*ext {
 592                                     if helpers.contains(&ident.name) {
 593                                         let binding =
 594                                             (Def::NonMacroAttr(NonMacroAttrKind::DeriveHelper),
 595                                             ty::Visibility::Public, derive.span, Mark::root())
 596                                             .to_name_binding(self.arenas);
 597                                         result = Ok((binding, Flags::empty()));
 598                                         break;
 599                                     }
 600                                 }
 601                             }
 602                             Err(Determinacy::Determined) => {}
 603                             Err(Determinacy::Undetermined) =>
 604                                 result = Err(Determinacy::Undetermined),
 605                         }
 606                     }
 607                     result
 608                 }
 609                 WhereToResolve::MacroRules(legacy_scope) => match legacy_scope {
 610                     LegacyScope::Binding(legacy_binding) if ident == legacy_binding.ident =>
 611                         Ok((legacy_binding.binding, Flags::MACRO_RULES)),
 612                     LegacyScope::Invocation(invoc) if invoc.output_legacy_scope.get().is_none() =>
 613                         Err(Determinacy::Undetermined),
 614                     _ => Err(Determinacy::Determined),
 615                 }
 616                 WhereToResolve::CrateRoot => {
 617                     let root_ident = Ident::new(keywords::PathRoot.name(), orig_ident.span);
 618                     let root_module = self.resolve_crate_root(root_ident);
 619                     let binding = self.resolve_ident_in_module_ext(
 620                         ModuleOrUniformRoot::Module(root_module),
 621                         orig_ident,
 622                         ns,
 623                         None,
 624                         record_used,
 625                         path_span,
 626                     );
 627                     match binding {
 628                         Ok(binding) => Ok((binding, Flags::MODULE | Flags::MISC_SUGGEST_CRATE)),
 629                         Err((Determinacy::Undetermined, Weak::No)) =>
 630                             return Err(Determinacy::determined(force)),
 631                         Err((Determinacy::Undetermined, Weak::Yes)) =>
 632                             Err(Determinacy::Undetermined),
 633                         Err((Determinacy::Determined, _)) => Err(Determinacy::Determined),
 634                     }
 635                 }
 636                 WhereToResolve::Module(module) => {
 637                     let orig_current_module = mem::replace(&mut self.current_module, module);
 638                     let binding = self.resolve_ident_in_module_unadjusted_ext(
 639                         ModuleOrUniformRoot::Module(module),
 640                         ident,
 641                         ns,
 642                         None,
 643                         true,
 644                         record_used,
 645                         path_span,
 646                     );
 647                     self.current_module = orig_current_module;
 648                     match binding {
 649                         Ok(binding) => {
 650                             let misc_flags = if ptr::eq(module, self.graph_root) {
 651                                 Flags::MISC_SUGGEST_CRATE
 652                             } else if module.is_normal() {
 653                                 Flags::MISC_SUGGEST_SELF
 654                             } else {
 655                                 Flags::empty()
 656                             };
 657                             Ok((binding, Flags::MODULE | misc_flags))
 658                         }
 659                         Err((Determinacy::Undetermined, Weak::No)) =>
 660                             return Err(Determinacy::determined(force)),
 661                         Err((Determinacy::Undetermined, Weak::Yes)) =>
 662                             Err(Determinacy::Undetermined),
 663                         Err((Determinacy::Determined, _)) => Err(Determinacy::Determined),
 664                     }
 665                 }
 666                 WhereToResolve::MacroUsePrelude => {
 667                     if use_prelude || rust_2015 {
 668                         match self.macro_use_prelude.get(&ident.name).cloned() {
 669                             Some(binding) =>
 670                                 Ok((binding, Flags::PRELUDE | Flags::MISC_FROM_PRELUDE)),
 671                             None => Err(Determinacy::determined(
 672                                 self.graph_root.unresolved_invocations.borrow().is_empty()
 673                             ))
 674                         }
 675                     } else {
 676                         Err(Determinacy::Determined)
 677                     }
 678                 }
 679                 WhereToResolve::BuiltinMacros => {
 680                     match self.builtin_macros.get(&ident.name).cloned() {
 681                         Some(binding) => Ok((binding, Flags::PRELUDE)),
 682                         None => Err(Determinacy::Determined),
 683                     }
 684                 }
 685                 WhereToResolve::BuiltinAttrs => {
 686                     if is_builtin_attr_name(ident.name) {
 687                         let binding = (Def::NonMacroAttr(NonMacroAttrKind::Builtin),
 688                                        ty::Visibility::Public, DUMMY_SP, Mark::root())
 689                                        .to_name_binding(self.arenas);
 690                         Ok((binding, Flags::PRELUDE))
 691                     } else {
 692                         Err(Determinacy::Determined)
 693                     }
 694                 }
 695                 WhereToResolve::LegacyPluginHelpers => {
 696                     if (use_prelude || rust_2015) &&
 697                        self.session.plugin_attributes.borrow().iter()
 698                                                      .any(|(name, _)| ident.name == &**name) {
 699                         let binding = (Def::NonMacroAttr(NonMacroAttrKind::LegacyPluginHelper),
 700                                        ty::Visibility::Public, DUMMY_SP, Mark::root())
 701                                        .to_name_binding(self.arenas);
 702                         Ok((binding, Flags::PRELUDE))
 703                     } else {
 704                         Err(Determinacy::Determined)
 705                     }
 706                 }
 707                 WhereToResolve::ExternPrelude => {
 708                     if use_prelude || is_absolute_path {
 709                         match self.extern_prelude_get(ident, !record_used) {
 710                             Some(binding) => Ok((binding, Flags::PRELUDE)),
 711                             None => Err(Determinacy::determined(
 712                                 self.graph_root.unresolved_invocations.borrow().is_empty()
 713                             )),
 714                         }
 715                     } else {
 716                         Err(Determinacy::Determined)
 717                     }
 718                 }
 719                 WhereToResolve::ToolPrelude => {
 720                     if use_prelude && is_known_tool(ident.name) {
 721                         let binding = (Def::ToolMod, ty::Visibility::Public,
 722                                        DUMMY_SP, Mark::root()).to_name_binding(self.arenas);
 723                         Ok((binding, Flags::PRELUDE))
 724                     } else {
 725                         Err(Determinacy::Determined)
 726                     }
 727                 }
 728                 WhereToResolve::StdLibPrelude => {
 729                     let mut result = Err(Determinacy::Determined);
 730                     if use_prelude {
 731                         if let Some(prelude) = self.prelude {
 732                             if let Ok(binding) = self.resolve_ident_in_module_unadjusted(
 733                                 ModuleOrUniformRoot::Module(prelude),
 734                                 ident,
 735                                 ns,
 736                                 false,
 737                                 path_span,
 738                             ) {
 739                                 result = Ok((binding, Flags::PRELUDE | Flags::MISC_FROM_PRELUDE));
 740                             }
 741                         }
 742                     }
 743                     result
 744                 }
 745                 WhereToResolve::BuiltinTypes => {
 746                     match self.primitive_type_table.primitive_types.get(&ident.name).cloned() {
 747                         Some(prim_ty) => {
 748                             let binding = (Def::PrimTy(prim_ty), ty::Visibility::Public,
 749                                            DUMMY_SP, Mark::root()).to_name_binding(self.arenas);
 750                             Ok((binding, Flags::PRELUDE))
 751                         }
 752                         None => Err(Determinacy::Determined)
 753                     }
 754                 }
 755             };
 756
 757             match result {
 758                 Ok((binding, flags)) if sub_namespace_match(binding.macro_kind(), macro_kind) => {
 759                     if !record_used {
 760                         return Ok(binding);
 761                     }
 762
 763                     if let Some((innermost_binding, innermost_flags)) = innermost_result {
 764                         // Found another solution, if the first one was "weak", report an error.
 765                         let (def, innermost_def) = (binding.def(), innermost_binding.def());
 766                         if def != innermost_def {
 767                             let builtin = Def::NonMacroAttr(NonMacroAttrKind::Builtin);
 768                             let derive_helper = Def::NonMacroAttr(NonMacroAttrKind::DeriveHelper);
 769                             let legacy_helper =
 770                                 Def::NonMacroAttr(NonMacroAttrKind::LegacyPluginHelper);
 771
 772                             let ambiguity_error_kind = if is_import {
 773                                 Some(AmbiguityKind::Import)
 774                             } else if innermost_def == builtin || def == builtin {
 775                                 Some(AmbiguityKind::BuiltinAttr)
 776                             } else if innermost_def == derive_helper || def == derive_helper {
 777                                 Some(AmbiguityKind::DeriveHelper)
 778                             } else if innermost_def == legacy_helper &&
 779                                       flags.contains(Flags::PRELUDE) ||
 780                                       def == legacy_helper &&
 781                                       innermost_flags.contains(Flags::PRELUDE) {
 782                                 Some(AmbiguityKind::LegacyHelperVsPrelude)
 783                             } else if innermost_flags.contains(Flags::MACRO_RULES) &&
 784                                       flags.contains(Flags::MODULE) &&
 785                                       !self.disambiguate_legacy_vs_modern(innermost_binding,
 786                                                                           binding) ||
 787                                       flags.contains(Flags::MACRO_RULES) &&
 788                                       innermost_flags.contains(Flags::MODULE) &&
 789                                       !self.disambiguate_legacy_vs_modern(binding,
 790                                                                           innermost_binding) {
 791                                 Some(AmbiguityKind::LegacyVsModern)
 792                             } else if innermost_binding.is_glob_import() {
 793                                 Some(AmbiguityKind::GlobVsOuter)
 794                             } else if innermost_binding.may_appear_after(parent_scope.expansion,
 795                                                                          binding) {
 796                                 Some(AmbiguityKind::MoreExpandedVsOuter)
 797                             } else {
 798                                 None
 799                             };
 800                             if let Some(kind) = ambiguity_error_kind {
 801                                 let misc = |f: Flags| if f.contains(Flags::MISC_SUGGEST_CRATE) {
 802                                     AmbiguityErrorMisc::SuggestCrate
 803                                 } else if f.contains(Flags::MISC_SUGGEST_SELF) {
 804                                     AmbiguityErrorMisc::SuggestSelf
 805                                 } else if f.contains(Flags::MISC_FROM_PRELUDE) {
 806                                     AmbiguityErrorMisc::FromPrelude
 807                                 } else {
 808                                     AmbiguityErrorMisc::None
 809                                 };
 810                                 self.ambiguity_errors.push(AmbiguityError {
 811                                     kind,
 812                                     ident: orig_ident,
 813                                     b1: innermost_binding,
 814                                     b2: binding,
 815                                     misc1: misc(innermost_flags),
 816                                     misc2: misc(flags),
 817                                 });
 818                                 return Ok(innermost_binding);
 819                             }
 820                         }
 821                     } else {
 822                         // Found the first solution.
 823                         innermost_result = Some((binding, flags));
 824                     }
 825                 }
 826                 Ok(..) | Err(Determinacy::Determined) => {}
 827                 Err(Determinacy::Undetermined) => determinacy = Determinacy::Undetermined
 828             }
 829
 830             where_to_resolve = match where_to_resolve {
 831                 WhereToResolve::DeriveHelpers =>
 832                     WhereToResolve::MacroRules(parent_scope.legacy),
 833                 WhereToResolve::MacroRules(legacy_scope) => match legacy_scope {
 834                     LegacyScope::Binding(binding) => WhereToResolve::MacroRules(
 835                         binding.parent_legacy_scope
 836                     ),
 837                     LegacyScope::Invocation(invoc) => WhereToResolve::MacroRules(
 838                         invoc.output_legacy_scope.get().unwrap_or(invoc.parent_legacy_scope.get())
 839                     ),
 840                     LegacyScope::Empty => WhereToResolve::Module(parent_scope.module),
 841                     LegacyScope::Uninitialized => unreachable!(),
 842                 }
 843                 WhereToResolve::CrateRoot => match ns {
 844                     TypeNS => {
 845                         ident.span.adjust(Mark::root());
 846                         WhereToResolve::ExternPrelude
 847                     }
 848                     ValueNS | MacroNS => break,
 849                 }
 850                 WhereToResolve::Module(module) => {
 851                     match self.hygienic_lexical_parent(module, &mut ident.span) {
 852                         Some(parent_module) => WhereToResolve::Module(parent_module),
 853                         None => {
 854                             use_prelude = !module.no_implicit_prelude;
 855                             match ns {
 856                                 TypeNS => WhereToResolve::ExternPrelude,
 857                                 ValueNS => WhereToResolve::StdLibPrelude,
 858                                 MacroNS => WhereToResolve::MacroUsePrelude,
 859                             }
 860                         }
 861                     }
 862                 }
 863                 WhereToResolve::MacroUsePrelude => WhereToResolve::BuiltinMacros,
 864                 WhereToResolve::BuiltinMacros => WhereToResolve::BuiltinAttrs,
 865                 WhereToResolve::BuiltinAttrs => WhereToResolve::LegacyPluginHelpers,
 866                 WhereToResolve::LegacyPluginHelpers => break, // nowhere else to search
 867                 WhereToResolve::ExternPrelude if is_absolute_path => break,
 868                 WhereToResolve::ExternPrelude => WhereToResolve::ToolPrelude,
 869                 WhereToResolve::ToolPrelude => WhereToResolve::StdLibPrelude,
 870                 WhereToResolve::StdLibPrelude => match ns {
 871                     TypeNS => WhereToResolve::BuiltinTypes,
 872                     ValueNS => break, // nowhere else to search
 873                     MacroNS => unreachable!(),
 874                 }
 875                 WhereToResolve::BuiltinTypes => break, // nowhere else to search
 876             };
 877
 878             continue;
 879         }
 880
 881         // The first found solution was the only one, return it.
 882         if let Some((binding, _)) = innermost_result {
 883             return Ok(binding);
 884         }
 885
 886         let determinacy = Determinacy::determined(determinacy == Determinacy::Determined || force);
 887         if determinacy == Determinacy::Determined && macro_kind == Some(MacroKind::Attr) {
 888             // For single-segment attributes interpret determinate "no resolution" as a custom
 889             // attribute. (Lexical resolution implies the first segment and attr kind should imply
 890             // the last segment, so we are certainly working with a single-segment attribute here.)
 891             assert!(ns == MacroNS);
 892             let binding = (Def::NonMacroAttr(NonMacroAttrKind::Custom),
 893                            ty::Visibility::Public, ident.span, Mark::root())
 894                            .to_name_binding(self.arenas);
 895             Ok(binding)
 896         } else {
 897             Err(determinacy)
 898         }
 899     }
 900
 901     pub fn finalize_current_module_macro_resolutions(&mut self) {
 902         let module = self.current_module;
 903
 904         let check_consistency = |this: &mut Self, path: &[Segment], span, kind: MacroKind,
 905                                  initial_def: Option<Def>, def: Def| {
 906             if let Some(initial_def) = initial_def {
 907                 if def != initial_def && def != Def::Err && this.ambiguity_errors.is_empty() {
 908                     // Make sure compilation does not succeed if preferred macro resolution
 909                     // has changed after the macro had been expanded. In theory all such
 910                     // situations should be reported as ambiguity errors, so this is a bug.
 911                     if initial_def == Def::NonMacroAttr(NonMacroAttrKind::Custom) {
 912                         // Yeah, legacy custom attributes are implemented using forced resolution
 913                         // (which is a best effort error recovery tool, basically), so we can't
 914                         // promise their resolution won't change later.
 915                         let msg = format!("inconsistent resolution for a macro: first {}, then {}",
 916                                           initial_def.kind_name(), def.kind_name());
 917                         this.session.span_err(span, &msg);
 918                     } else {
 919                         span_bug!(span, "inconsistent resolution for a macro");
 920                     }
 921                 }
 922             } else {
 923                 // It's possible that the macro was unresolved (indeterminate) and silently
 924                 // expanded into a dummy fragment for recovery during expansion.
 925                 // Now, post-expansion, the resolution may succeed, but we can't change the
 926                 // past and need to report an error.
 927                 // However, non-speculative `resolve_path` can successfully return private items
 928                 // even if speculative `resolve_path` returned nothing previously, so we skip this
 929                 // less informative error if the privacy error is reported elsewhere.
 930                 if this.privacy_errors.is_empty() {
 931                     let msg = format!("cannot determine resolution for the {} `{}`",
 932                                         kind.descr(), Segment::names_to_string(path));
 933                     let msg_note = "import resolution is stuck, try simplifying macro imports";
 934                     this.session.struct_span_err(span, &msg).note(msg_note).emit();
 935                 }
 936             }
 937         };
 938
 939         let macro_resolutions =
 940             mem::replace(&mut *module.multi_segment_macro_resolutions.borrow_mut(), Vec::new());
 941         for (mut path, path_span, kind, parent_scope, initial_def) in macro_resolutions {
 942             // FIXME: Path resolution will ICE if segment IDs present.
 943             for seg in &mut path { seg.id = None; }
 944             match self.resolve_path(&path, Some(MacroNS), &parent_scope,
 945                                     true, path_span, CrateLint::No) {
 946                 PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 => {
 947                     let def = path_res.base_def();
 948                     check_consistency(self, &path, path_span, kind, initial_def, def);
 949                 }
 950                 path_res @ PathResult::NonModule(..) | path_res @ PathResult::Failed { .. } => {
 951                     let (span, label) = if let PathResult::Failed { span, label, .. } = path_res {
 952                         (span, label)
 953                     } else {
 954                         (path_span, format!("partially resolved path in {} {}",
 955                                             kind.article(), kind.descr()))
 956                     };
 957                     resolve_error(self, span, ResolutionError::FailedToResolve {
 958                         label,
 959                         suggestion: None
 960                     });
 961                 }
 962                 PathResult::Module(..) | PathResult::Indeterminate => unreachable!(),
 963             }
 964         }
 965
 966         let macro_resolutions =
 967             mem::replace(&mut *module.single_segment_macro_resolutions.borrow_mut(), Vec::new());
 968         for (ident, kind, parent_scope, initial_binding) in macro_resolutions {
 969             match self.early_resolve_ident_in_lexical_scope(ident, ScopeSet::Macro(kind),
 970                                                             &parent_scope, true, true, ident.span) {
 971                 Ok(binding) => {
 972                     let initial_def = initial_binding.map(|initial_binding| {
 973                         self.record_use(ident, MacroNS, initial_binding, false);
 974                         initial_binding.def()
 975                     });
 976                     let def = binding.def();
 977                     let seg = Segment::from_ident(ident);
 978                     check_consistency(self, &[seg], ident.span, kind, initial_def, def);
 979                 }
 980                 Err(..) => {
 981                     assert!(initial_binding.is_none());
 982                     let bang = if kind == MacroKind::Bang { "!" } else { "" };
 983                     let msg =
 984                         format!("cannot find {} `{}{}` in this scope", kind.descr(), ident, bang);
 985                     let mut err = self.session.struct_span_err(ident.span, &msg);
 986                     self.suggest_macro_name(&ident.as_str(), kind, &mut err, ident.span);
 987                     err.emit();
 988                 }
 989             }
 990         }
 991
 992         let builtin_attrs = mem::replace(&mut *module.builtin_attrs.borrow_mut(), Vec::new());
 993         for (ident, parent_scope) in builtin_attrs {
 994             let _ = self.early_resolve_ident_in_lexical_scope(
 995                 ident, ScopeSet::Macro(MacroKind::Attr), &parent_scope, true, true, ident.span
 996             );
 997         }
 998     }
 999
1000     fn prohibit_imported_non_macro_attrs(&self, binding: Option<&'a NameBinding<'a>>,
1001                                          def: Option<Def>, span: Span) {
1002         if let Some(Def::NonMacroAttr(kind)) = def {
1003             if kind != NonMacroAttrKind::Tool && binding.map_or(true, |b| b.is_import()) {
1004                 let msg = format!("cannot use a {} through an import", kind.descr());
1005                 let mut err = self.session.struct_span_err(span, &msg);
1006                 if let Some(binding) = binding {
1007                     err.span_note(binding.span, &format!("the {} imported here", kind.descr()));
1008                 }
1009                 err.emit();
1010             }
1011         }
1012     }
1013
1014     fn suggest_macro_name(&mut self, name: &str, kind: MacroKind,
1015                           err: &mut DiagnosticBuilder<'a>, span: Span) {
1016         // First check if this is a locally-defined bang macro.
1017         let suggestion = if let MacroKind::Bang = kind {
1018             find_best_match_for_name(self.macro_names.iter().map(|ident| &ident.name), name, None)
1019         } else {
1020             None
1021         // Then check global macros.
1022         }.or_else(|| {
1023             let names = self.builtin_macros.iter().chain(self.macro_use_prelude.iter())
1024                                                   .filter_map(|(name, binding)| {
1025                 if binding.macro_kind() == Some(kind) { Some(name) } else { None }
1026             });
1027             find_best_match_for_name(names, name, None)
1028         // Then check modules.
1029         }).or_else(|| {
1030             let is_macro = |def| {
1031                 if let Def::Macro(_, def_kind) = def {
1032                     def_kind == kind
1033                 } else {
1034                     false
1035                 }
1036             };
1037             let ident = Ident::new(Symbol::intern(name), span);
1038             self.lookup_typo_candidate(&[Segment::from_ident(ident)], MacroNS, is_macro, span)
1039                 .map(|suggestion| suggestion.candidate)
1040         });
1041
1042         if let Some(suggestion) = suggestion {
1043             if suggestion != name {
1044                 if let MacroKind::Bang = kind {
1045                     err.span_suggestion(
1046                         span,
1047                         "you could try the macro",
1048                         suggestion.to_string(),
1049                         Applicability::MaybeIncorrect
1050                     );
1051                 } else {
1052                     err.span_suggestion(
1053                         span,
1054                         "try",
1055                         suggestion.to_string(),
1056                         Applicability::MaybeIncorrect
1057                     );
1058                 }
1059             } else {
1060                 err.help("have you added the `#[macro_use]` on the module/import?");
1061             }
1062         }
1063     }
1064
1065     fn collect_def_ids(&mut self,
1066                        mark: Mark,
1067                        invocation: &'a InvocationData<'a>,
1068                        fragment: &AstFragment) {
1069         let Resolver { ref mut invocations, arenas, graph_root, .. } = *self;
1070         let InvocationData { def_index, .. } = *invocation;
1071
1072         let visit_macro_invoc = &mut |invoc: map::MacroInvocationData| {
1073             invocations.entry(invoc.mark).or_insert_with(|| {
1074                 arenas.alloc_invocation_data(InvocationData {
1075                     def_index: invoc.def_index,
1076                     module: Cell::new(graph_root),
1077                     parent_legacy_scope: Cell::new(LegacyScope::Uninitialized),
1078                     output_legacy_scope: Cell::new(None),
1079                 })
1080             });
1081         };
1082
1083         let mut def_collector = DefCollector::new(&mut self.definitions, mark);
1084         def_collector.visit_macro_invoc = Some(visit_macro_invoc);
1085         def_collector.with_parent(def_index, |def_collector| {
1086             fragment.visit_with(def_collector)
1087         });
1088     }
1089
1090     pub fn define_macro(&mut self,
1091                         item: &ast::Item,
1092                         expansion: Mark,
1093                         current_legacy_scope: &mut LegacyScope<'a>) {
1094         self.local_macro_def_scopes.insert(item.id, self.current_module);
1095         let ident = item.ident;
1096         if ident.name == "macro_rules" {
1097             self.session.span_err(item.span, "user-defined macros may not be named `macro_rules`");
1098         }
1099
1100         let def_id = self.definitions.local_def_id(item.id);
1101         let ext = Lrc::new(macro_rules::compile(&self.session.parse_sess,
1102                                                &self.session.features_untracked(),
1103                                                item, hygiene::default_edition()));
1104         self.macro_map.insert(def_id, ext);
1105
1106         let def = match item.node { ast::ItemKind::MacroDef(ref def) => def, _ => unreachable!() };
1107         if def.legacy {
1108             let ident = ident.modern();
1109             self.macro_names.insert(ident);
1110             let def = Def::Macro(def_id, MacroKind::Bang);
1111             let is_macro_export = attr::contains_name(&item.attrs, "macro_export");
1112             let vis = if is_macro_export {
1113                 ty::Visibility::Public
1114             } else {
1115                 ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX))
1116             };
1117             let binding = (def, vis, item.span, expansion).to_name_binding(self.arenas);
1118             self.set_binding_parent_module(binding, self.current_module);
1119             let legacy_binding = self.arenas.alloc_legacy_binding(LegacyBinding {
1120                 parent_legacy_scope: *current_legacy_scope, binding, ident
1121             });
1122             *current_legacy_scope = LegacyScope::Binding(legacy_binding);
1123             self.all_macros.insert(ident.name, def);
1124             if is_macro_export {
1125                 let module = self.graph_root;
1126                 self.define(module, ident, MacroNS,
1127                             (def, vis, item.span, expansion, IsMacroExport));
1128             } else {
1129                 if !attr::contains_name(&item.attrs, "rustc_doc_only_macro") {
1130                     self.check_reserved_macro_name(ident, MacroNS);
1131                 }
1132                 self.unused_macros.insert(def_id);
1133             }
1134         } else {
1135             let module = self.current_module;
1136             let def = Def::Macro(def_id, MacroKind::Bang);
1137             let vis = self.resolve_visibility(&item.vis);
1138             if vis != ty::Visibility::Public {
1139                 self.unused_macros.insert(def_id);
1140             }
1141             self.define(module, ident, MacroNS, (def, vis, item.span, expansion));
1142         }
1143     }
1144 }