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::{CrateNum, DefId, DefIndex, CRATE_DEF_INDEX};
  10 use rustc::hir::def::{self, DefKind, NonMacroAttrKind};
  11 use rustc::hir::map::{self, DefCollector};
  12 use rustc::{ty, lint};
  13 use rustc::{bug, span_bug};
  14 use syntax::ast::{self, Ident};
  15 use syntax::attr;
  16 use syntax::errors::DiagnosticBuilder;
  17 use syntax::ext::base::{self, Determinacy};
  18 use syntax::ext::base::{MacroKind, SyntaxExtension};
  19 use syntax::ext::expand::{AstFragment, Invocation, InvocationKind};
  20 use syntax::ext::hygiene::Mark;
  21 use syntax::ext::tt::macro_rules;
  22 use syntax::feature_gate::{feature_err, emit_feature_err, is_builtin_attr_name};
  23 use syntax::feature_gate::{AttributeGate, GateIssue, Stability, BUILTIN_ATTRIBUTES};
  24 use syntax::symbol::{Symbol, kw, sym};
  25 use syntax::visit::Visitor;
  26 use syntax::util::lev_distance::find_best_match_for_name;
  27 use syntax_pos::{Span, DUMMY_SP};
  28 use errors::Applicability;
  29
  30 use std::cell::Cell;
  31 use std::{mem, ptr};
  32 use rustc_data_structures::sync::Lrc;
  33
  34 type Res = def::Res<ast::NodeId>;
  35
  36 #[derive(Clone, Debug)]
  37 pub struct InvocationData<'a> {
  38     def_index: DefIndex,
  39     /// The module in which the macro was invoked.
  40     crate module: Cell<Module<'a>>,
  41     /// The legacy scope in which the macro was invoked.
  42     /// The invocation path is resolved in this scope.
  43     crate parent_legacy_scope: Cell<LegacyScope<'a>>,
  44     /// The legacy scope *produced* by expanding this macro invocation,
  45     /// includes all the macro_rules items, other invocations, etc generated by it.
  46     /// `None` if the macro is not expanded yet.
  47     crate output_legacy_scope: Cell<Option<LegacyScope<'a>>>,
  48 }
  49
  50 impl<'a> InvocationData<'a> {
  51     pub fn root(graph_root: Module<'a>) -> Self {
  52         InvocationData {
  53             module: Cell::new(graph_root),
  54             def_index: CRATE_DEF_INDEX,
  55             parent_legacy_scope: Cell::new(LegacyScope::Empty),
  56             output_legacy_scope: Cell::new(Some(LegacyScope::Empty)),
  57         }
  58     }
  59 }
  60
  61 /// Binding produced by a `macro_rules` item.
  62 /// Not modularized, can shadow previous legacy bindings, etc.
  63 #[derive(Debug)]
  64 pub struct LegacyBinding<'a> {
  65     binding: &'a NameBinding<'a>,
  66     /// Legacy scope into which the `macro_rules` item was planted.
  67     parent_legacy_scope: LegacyScope<'a>,
  68     ident: Ident,
  69 }
  70
  71 /// The scope introduced by a `macro_rules!` macro.
  72 /// This starts at the macro's definition and ends at the end of the macro's parent
  73 /// module (named or unnamed), or even further if it escapes with `#[macro_use]`.
  74 /// Some macro invocations need to introduce legacy scopes too because they
  75 /// can potentially expand into macro definitions.
  76 #[derive(Copy, Clone, Debug)]
  77 pub enum LegacyScope<'a> {
  78     /// Created when invocation data is allocated in the arena;
  79     /// must be replaced with a proper scope later.
  80     Uninitialized,
  81     /// Empty "root" scope at the crate start containing no names.
  82     Empty,
  83     /// The scope introduced by a `macro_rules!` macro definition.
  84     Binding(&'a LegacyBinding<'a>),
  85     /// The scope introduced by a macro invocation that can potentially
  86     /// create a `macro_rules!` macro definition.
  87     Invocation(&'a InvocationData<'a>),
  88 }
  89
  90 /// Everything you need to resolve a macro or import path.
  91 #[derive(Clone, Debug)]
  92 pub struct ParentScope<'a> {
  93     crate module: Module<'a>,
  94     crate expansion: Mark,
  95     crate legacy: LegacyScope<'a>,
  96     crate derives: Vec<ast::Path>,
  97 }
  98
  99 // Macro namespace is separated into two sub-namespaces, one for bang macros and
 100 // one for attribute-like macros (attributes, derives).
 101 // We ignore resolutions from one sub-namespace when searching names in scope for another.
 102 fn sub_namespace_match(candidate: Option<MacroKind>, requirement: Option<MacroKind>) -> bool {
 103     #[derive(PartialEq)]
 104     enum SubNS { Bang, AttrLike }
 105     let sub_ns = |kind| match kind {
 106         MacroKind::Bang => Some(SubNS::Bang),
 107         MacroKind::Attr | MacroKind::Derive => Some(SubNS::AttrLike),
 108         MacroKind::ProcMacroStub => None,
 109     };
 110     let requirement = requirement.and_then(|kind| sub_ns(kind));
 111     let candidate = candidate.and_then(|kind| sub_ns(kind));
 112     // "No specific sub-namespace" means "matches anything" for both requirements and candidates.
 113     candidate.is_none() || requirement.is_none() || candidate == requirement
 114 }
 115
 116 // We don't want to format a path using pretty-printing,
 117 // `format!("{}", path)`, because that tries to insert
 118 // line-breaks and is slow.
 119 fn fast_print_path(path: &ast::Path) -> String {
 120     let mut path_str = String::with_capacity(64);
 121     for (i, segment) in path.segments.iter().enumerate() {
 122         if i != 0 {
 123             path_str.push_str("::");
 124         }
 125         if segment.ident.name != kw::PathRoot {
 126             path_str.push_str(&segment.ident.as_str())
 127         }
 128     }
 129     path_str
 130 }
 131
 132 impl<'a> base::Resolver for Resolver<'a> {
 133     fn next_node_id(&mut self) -> ast::NodeId {
 134         self.session.next_node_id()
 135     }
 136
 137     fn get_module_scope(&mut self, id: ast::NodeId) -> Mark {
 138         let mark = Mark::fresh(Mark::root());
 139         let module = self.module_map[&self.definitions.local_def_id(id)];
 140         self.invocations.insert(mark, self.arenas.alloc_invocation_data(InvocationData {
 141             module: Cell::new(module),
 142             def_index: module.def_id().unwrap().index,
 143             parent_legacy_scope: Cell::new(LegacyScope::Empty),
 144             output_legacy_scope: Cell::new(Some(LegacyScope::Empty)),
 145         }));
 146         mark
 147     }
 148
 149     fn resolve_dollar_crates(&mut self, fragment: &AstFragment) {
 150         struct ResolveDollarCrates<'a, 'b> {
 151             resolver: &'a mut Resolver<'b>
 152         }
 153         impl<'a> Visitor<'a> for ResolveDollarCrates<'a, '_> {
 154             fn visit_ident(&mut self, ident: Ident) {
 155                 if ident.name == kw::DollarCrate {
 156                     let name = match self.resolver.resolve_crate_root(ident).kind {
 157                         ModuleKind::Def(.., name) if name != kw::Invalid => name,
 158                         _ => kw::Crate,
 159                     };
 160                     ident.span.ctxt().set_dollar_crate_name(name);
 161                 }
 162             }
 163             fn visit_mac(&mut self, _: &ast::Mac) {}
 164         }
 165
 166         fragment.visit_with(&mut ResolveDollarCrates { resolver: self });
 167     }
 168
 169     fn visit_ast_fragment_with_placeholders(&mut self, mark: Mark, fragment: &AstFragment,
 170                                             derives: &[Mark]) {
 171         let invocation = self.invocations[&mark];
 172         self.collect_def_ids(mark, invocation, fragment);
 173
 174         self.current_module = invocation.module.get();
 175         self.current_module.unresolved_invocations.borrow_mut().remove(&mark);
 176         self.current_module.unresolved_invocations.borrow_mut().extend(derives);
 177         self.invocations.extend(derives.iter().map(|&derive| (derive, invocation)));
 178         let mut visitor = BuildReducedGraphVisitor {
 179             resolver: self,
 180             current_legacy_scope: invocation.parent_legacy_scope.get(),
 181             expansion: mark,
 182         };
 183         fragment.visit_with(&mut visitor);
 184         invocation.output_legacy_scope.set(Some(visitor.current_legacy_scope));
 185     }
 186
 187     fn add_builtin(&mut self, ident: ast::Ident, ext: Lrc<SyntaxExtension>) {
 188         let def_id = DefId {
 189             krate: CrateNum::BuiltinMacros,
 190             index: DefIndex::from(self.macro_map.len()),
 191         };
 192         let kind = ext.macro_kind();
 193         self.macro_map.insert(def_id, ext);
 194         let binding = self.arenas.alloc_name_binding(NameBinding {
 195             kind: NameBindingKind::Res(Res::Def(DefKind::Macro(kind), def_id), false),
 196             ambiguity: None,
 197             span: DUMMY_SP,
 198             vis: ty::Visibility::Public,
 199             expansion: Mark::root(),
 200         });
 201         if self.builtin_macros.insert(ident.name, binding).is_some() {
 202             self.session.span_err(ident.span,
 203                                   &format!("built-in macro `{}` was already defined", ident));
 204         }
 205     }
 206
 207     fn resolve_imports(&mut self) {
 208         ImportResolver { resolver: self }.resolve_imports()
 209     }
 210
 211     fn resolve_macro_invocation(&mut self, invoc: &Invocation, invoc_id: Mark, force: bool)
 212                                 -> Result<Option<Lrc<SyntaxExtension>>, Determinacy> {
 213         let (path, kind, derives_in_scope, after_derive) = match invoc.kind {
 214             InvocationKind::Attr { attr: None, .. } =>
 215                 return Ok(None),
 216             InvocationKind::Attr { attr: Some(ref attr), ref traits, after_derive, .. } =>
 217                 (&attr.path, MacroKind::Attr, traits.clone(), after_derive),
 218             InvocationKind::Bang { ref mac, .. } =>
 219                 (&mac.node.path, MacroKind::Bang, Vec::new(), false),
 220             InvocationKind::Derive { ref path, .. } =>
 221                 (path, MacroKind::Derive, Vec::new(), false),
 222         };
 223
 224         let parent_scope = self.invoc_parent_scope(invoc_id, derives_in_scope);
 225         let (res, ext) = match self.resolve_macro_to_res(path, kind, &parent_scope, true, force) {
 226             Ok((res, ext)) => (res, ext),
 227             // Replace unresolved attributes with used inert attributes for better recovery.
 228             Err(Determinacy::Determined) if kind == MacroKind::Attr =>
 229                 (Res::Err, self.non_macro_attr(true)),
 230             Err(determinacy) => return Err(determinacy),
 231         };
 232
 233         let format = match kind {
 234             MacroKind::Derive => format!("derive({})", fast_print_path(path)),
 235             _ => fast_print_path(path),
 236         };
 237         invoc.expansion_data.mark.set_expn_info(ext.expn_info(invoc.span(), &format));
 238
 239         if let Res::Def(_, def_id) = res {
 240             if after_derive {
 241                 self.session.span_err(invoc.span(),
 242                                       "macro attributes must be placed before `#[derive]`");
 243             }
 244             self.macro_defs.insert(invoc.expansion_data.mark, def_id);
 245             let normal_module_def_id =
 246                 self.macro_def_scope(invoc.expansion_data.mark).normal_ancestor_id;
 247             self.definitions.add_parent_module_of_macro_def(invoc.expansion_data.mark,
 248                                                             normal_module_def_id);
 249         }
 250
 251         Ok(Some(ext))
 252     }
 253
 254     fn resolve_macro_path(&mut self, path: &ast::Path, kind: MacroKind, invoc_id: Mark,
 255                           derives_in_scope: Vec<ast::Path>, force: bool)
 256                           -> Result<Lrc<SyntaxExtension>, Determinacy> {
 257         let parent_scope = self.invoc_parent_scope(invoc_id, derives_in_scope);
 258         Ok(self.resolve_macro_to_res(path, kind, &parent_scope, false, force)?.1)
 259     }
 260
 261     fn check_unused_macros(&self) {
 262         for did in self.unused_macros.iter() {
 263             if let Some((id, span)) = self.macro_map[did].def_info {
 264                 let lint = lint::builtin::UNUSED_MACROS;
 265                 let msg = "unused macro definition";
 266                 self.session.buffer_lint(lint, id, span, msg);
 267             } else {
 268                 bug!("attempted to create unused macro error, but span not available");
 269             }
 270         }
 271     }
 272 }
 273
 274 impl<'a> Resolver<'a> {
 275     pub fn dummy_parent_scope(&self) -> ParentScope<'a> {
 276         self.invoc_parent_scope(Mark::root(), Vec::new())
 277     }
 278
 279     fn invoc_parent_scope(&self, invoc_id: Mark, derives: Vec<ast::Path>) -> ParentScope<'a> {
 280         let invoc = self.invocations[&invoc_id];
 281         ParentScope {
 282             module: invoc.module.get().nearest_item_scope(),
 283             expansion: invoc_id.parent(),
 284             legacy: invoc.parent_legacy_scope.get(),
 285             derives,
 286         }
 287     }
 288
 289     fn resolve_macro_to_res(
 290         &mut self,
 291         path: &ast::Path,
 292         kind: MacroKind,
 293         parent_scope: &ParentScope<'a>,
 294         trace: bool,
 295         force: bool,
 296     ) -> Result<(Res, Lrc<SyntaxExtension>), Determinacy> {
 297         let res = self.resolve_macro_to_res_inner(path, kind, parent_scope, trace, force);
 298
 299         // Report errors and enforce feature gates for the resolved macro.
 300         let features = self.session.features_untracked();
 301         if res != Err(Determinacy::Undetermined) {
 302             // Do not report duplicated errors on every undetermined resolution.
 303             for segment in &path.segments {
 304                 if let Some(args) = &segment.args {
 305                     self.session.span_err(args.span(), "generic arguments in macro path");
 306                 }
 307                 if kind == MacroKind::Attr && !features.rustc_attrs &&
 308                    segment.ident.as_str().starts_with("rustc") {
 309                     let msg = "attributes starting with `rustc` are \
 310                                reserved for use by the `rustc` compiler";
 311                     emit_feature_err(
 312                         &self.session.parse_sess,
 313                         sym::rustc_attrs,
 314                         segment.ident.span,
 315                         GateIssue::Language,
 316                         msg,
 317                     );
 318                 }
 319             }
 320         }
 321
 322         let res = res?;
 323
 324         match res {
 325             Res::Def(DefKind::Macro(macro_kind), def_id) => {
 326                 self.unused_macros.remove(&def_id);
 327                 if macro_kind == MacroKind::ProcMacroStub {
 328                     let msg = "can't use a procedural macro from the same crate that defines it";
 329                     self.session.span_err(path.span, msg);
 330                     return Err(Determinacy::Determined);
 331                 }
 332             }
 333             Res::NonMacroAttr(attr_kind) => {
 334                 if kind == MacroKind::Attr {
 335                     if attr_kind == NonMacroAttrKind::Custom {
 336                         assert!(path.segments.len() == 1);
 337                         if !features.custom_attribute {
 338                             let msg = format!("The attribute `{}` is currently unknown to the \
 339                                                compiler and may have meaning added to it in the \
 340                                                future", path);
 341                             self.report_unknown_attribute(
 342                                 path.span,
 343                                 &path.segments[0].ident.as_str(),
 344                                 &msg,
 345                                 sym::custom_attribute,
 346                             );
 347                         }
 348                     }
 349                 } else {
 350                     // Not only attributes, but anything in macro namespace can result in
 351                     // `Res::NonMacroAttr` definition (e.g., `inline!()`), so we must report
 352                     // an error for those cases.
 353                     let msg = format!("expected a macro, found {}", res.descr());
 354                     self.session.span_err(path.span, &msg);
 355                     return Err(Determinacy::Determined);
 356                 }
 357             }
 358             Res::Err => {
 359                 return Err(Determinacy::Determined);
 360             }
 361             _ => panic!("expected `DefKind::Macro` or `Res::NonMacroAttr`"),
 362         }
 363
 364         Ok((res, self.get_macro(res)))
 365     }
 366
 367     fn report_unknown_attribute(&self, span: Span, name: &str, msg: &str, feature: Symbol) {
 368         let mut err = feature_err(
 369             &self.session.parse_sess,
 370             feature,
 371             span,
 372             GateIssue::Language,
 373             &msg,
 374         );
 375
 376         let features = self.session.features_untracked();
 377
 378         let attr_candidates = BUILTIN_ATTRIBUTES
 379             .iter()
 380             .filter_map(|&(name, _, _, ref gate)| {
 381                 if name.as_str().starts_with("rustc_") && !features.rustc_attrs {
 382                     return None;
 383                 }
 384
 385                 match gate {
 386                     AttributeGate::Gated(Stability::Unstable, ..)
 387                         if self.session.opts.unstable_features.is_nightly_build() =>
 388                     {
 389                         Some(name)
 390                     }
 391                     AttributeGate::Gated(Stability::Deprecated(..), ..) => Some(name),
 392                     AttributeGate::Ungated => Some(name),
 393                     _ => None,
 394                 }
 395             })
 396             .chain(
 397                 // Add built-in macro attributes as well.
 398                 self.builtin_macros.iter().filter_map(|(name, binding)| {
 399                     match binding.macro_kind() {
 400                         Some(MacroKind::Attr) => Some(*name),
 401                         _ => None,
 402                     }
 403                 }),
 404             )
 405             .collect::<Vec<_>>();
 406
 407         let lev_suggestion = find_best_match_for_name(attr_candidates.iter(), &name, None);
 408
 409         if let Some(suggestion) = lev_suggestion {
 410             err.span_suggestion(
 411                 span,
 412                 "a built-in attribute with a similar name exists",
 413                 suggestion.to_string(),
 414                 Applicability::MaybeIncorrect,
 415             );
 416         }
 417
 418         err.emit();
 419     }
 420
 421     pub fn resolve_macro_to_res_inner(
 422         &mut self,
 423         path: &ast::Path,
 424         kind: MacroKind,
 425         parent_scope: &ParentScope<'a>,
 426         trace: bool,
 427         force: bool,
 428     ) -> Result<Res, Determinacy> {
 429         let path_span = path.span;
 430         let mut path = Segment::from_path(path);
 431
 432         // Possibly apply the macro helper hack
 433         if kind == MacroKind::Bang && path.len() == 1 &&
 434            path[0].ident.span.ctxt().outer_expn_info()
 435                .map_or(false, |info| info.local_inner_macros) {
 436             let root = Ident::new(kw::DollarCrate, path[0].ident.span);
 437             path.insert(0, Segment::from_ident(root));
 438         }
 439
 440         if path.len() > 1 {
 441             let res = match self.resolve_path(&path, Some(MacroNS), parent_scope,
 442                                               false, path_span, CrateLint::No) {
 443                 PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 => {
 444                     Ok(path_res.base_res())
 445                 }
 446                 PathResult::Indeterminate if !force => return Err(Determinacy::Undetermined),
 447                 PathResult::NonModule(..)
 448                 | PathResult::Indeterminate
 449                 | PathResult::Failed { .. } => Err(Determinacy::Determined),
 450                 PathResult::Module(..) => unreachable!(),
 451             };
 452
 453             if trace {
 454                 parent_scope.module.multi_segment_macro_resolutions.borrow_mut()
 455                     .push((path, path_span, kind, parent_scope.clone(), res.ok()));
 456             }
 457
 458             self.prohibit_imported_non_macro_attrs(None, res.ok(), path_span);
 459             res
 460         } else {
 461             let binding = self.early_resolve_ident_in_lexical_scope(
 462                 path[0].ident, ScopeSet::Macro(kind), parent_scope, false, force, path_span
 463             );
 464             if let Err(Determinacy::Undetermined) = binding {
 465                 return Err(Determinacy::Undetermined);
 466             }
 467
 468             if trace {
 469                 parent_scope.module.single_segment_macro_resolutions.borrow_mut()
 470                     .push((path[0].ident, kind, parent_scope.clone(), binding.ok()));
 471             }
 472
 473             let res = binding.map(|binding| binding.res());
 474             self.prohibit_imported_non_macro_attrs(binding.ok(), res.ok(), path_span);
 475             res
 476         }
 477     }
 478
 479     // Resolve an identifier in lexical scope.
 480     // This is a variation of `fn resolve_ident_in_lexical_scope` that can be run during
 481     // expansion and import resolution (perhaps they can be merged in the future).
 482     // The function is used for resolving initial segments of macro paths (e.g., `foo` in
 483     // `foo::bar!(); or `foo!();`) and also for import paths on 2018 edition.
 484     crate fn early_resolve_ident_in_lexical_scope(
 485         &mut self,
 486         orig_ident: Ident,
 487         scope_set: ScopeSet,
 488         parent_scope: &ParentScope<'a>,
 489         record_used: bool,
 490         force: bool,
 491         path_span: Span,
 492     ) -> Result<&'a NameBinding<'a>, Determinacy> {
 493         // General principles:
 494         // 1. Not controlled (user-defined) names should have higher priority than controlled names
 495         //    built into the language or standard library. This way we can add new names into the
 496         //    language or standard library without breaking user code.
 497         // 2. "Closed set" below means new names cannot appear after the current resolution attempt.
 498         // Places to search (in order of decreasing priority):
 499         // (Type NS)
 500         // 1. FIXME: Ribs (type parameters), there's no necessary infrastructure yet
 501         //    (open set, not controlled).
 502         // 2. Names in modules (both normal `mod`ules and blocks), loop through hygienic parents
 503         //    (open, not controlled).
 504         // 3. Extern prelude (closed, not controlled).
 505         // 4. Tool modules (closed, controlled right now, but not in the future).
 506         // 5. Standard library prelude (de-facto closed, controlled).
 507         // 6. Language prelude (closed, controlled).
 508         // (Value NS)
 509         // 1. FIXME: Ribs (local variables), there's no necessary infrastructure yet
 510         //    (open set, not controlled).
 511         // 2. Names in modules (both normal `mod`ules and blocks), loop through hygienic parents
 512         //    (open, not controlled).
 513         // 3. Standard library prelude (de-facto closed, controlled).
 514         // (Macro NS)
 515         // 1-3. Derive helpers (open, not controlled). All ambiguities with other names
 516         //    are currently reported as errors. They should be higher in priority than preludes
 517         //    and probably even names in modules according to the "general principles" above. They
 518         //    also should be subject to restricted shadowing because are effectively produced by
 519         //    derives (you need to resolve the derive first to add helpers into scope), but they
 520         //    should be available before the derive is expanded for compatibility.
 521         //    It's mess in general, so we are being conservative for now.
 522         // 1-3. `macro_rules` (open, not controlled), loop through legacy scopes. Have higher
 523         //    priority than prelude macros, but create ambiguities with macros in modules.
 524         // 1-3. Names in modules (both normal `mod`ules and blocks), loop through hygienic parents
 525         //    (open, not controlled). Have higher priority than prelude macros, but create
 526         //    ambiguities with `macro_rules`.
 527         // 4. `macro_use` prelude (open, the open part is from macro expansions, not controlled).
 528         // 4a. User-defined prelude from macro-use
 529         //    (open, the open part is from macro expansions, not controlled).
 530         // 4b. Standard library prelude is currently implemented as `macro-use` (closed, controlled)
 531         // 5. Language prelude: builtin macros (closed, controlled, except for legacy plugins).
 532         // 6. Language prelude: builtin attributes (closed, controlled).
 533         // 4-6. Legacy plugin helpers (open, not controlled). Similar to derive helpers,
 534         //    but introduced by legacy plugins using `register_attribute`. Priority is somewhere
 535         //    in prelude, not sure where exactly (creates ambiguities with any other prelude names).
 536
 537         enum WhereToResolve<'a> {
 538             DeriveHelpers,
 539             MacroRules(LegacyScope<'a>),
 540             CrateRoot,
 541             Module(Module<'a>),
 542             MacroUsePrelude,
 543             BuiltinMacros,
 544             BuiltinAttrs,
 545             LegacyPluginHelpers,
 546             ExternPrelude,
 547             ToolPrelude,
 548             StdLibPrelude,
 549             BuiltinTypes,
 550         }
 551
 552         bitflags::bitflags! {
 553             struct Flags: u8 {
 554                 const MACRO_RULES        = 1 << 0;
 555                 const MODULE             = 1 << 1;
 556                 const PRELUDE            = 1 << 2;
 557                 const MISC_SUGGEST_CRATE = 1 << 3;
 558                 const MISC_SUGGEST_SELF  = 1 << 4;
 559                 const MISC_FROM_PRELUDE  = 1 << 5;
 560             }
 561         }
 562
 563         assert!(force || !record_used); // `record_used` implies `force`
 564         let mut ident = orig_ident.modern();
 565
 566         // Make sure `self`, `super` etc produce an error when passed to here.
 567         if ident.is_path_segment_keyword() {
 568             return Err(Determinacy::Determined);
 569         }
 570
 571         // This is *the* result, resolution from the scope closest to the resolved identifier.
 572         // However, sometimes this result is "weak" because it comes from a glob import or
 573         // a macro expansion, and in this case it cannot shadow names from outer scopes, e.g.
 574         // mod m { ... } // solution in outer scope
 575         // {
 576         //     use prefix::*; // imports another `m` - innermost solution
 577         //                    // weak, cannot shadow the outer `m`, need to report ambiguity error
 578         //     m::mac!();
 579         // }
 580         // So we have to save the innermost solution and continue searching in outer scopes
 581         // to detect potential ambiguities.
 582         let mut innermost_result: Option<(&NameBinding<'_>, Flags)> = None;
 583
 584         // Go through all the scopes and try to resolve the name.
 585         let rust_2015 = orig_ident.span.rust_2015();
 586         let (ns, macro_kind, is_import, is_absolute_path) = match scope_set {
 587             ScopeSet::Import(ns) => (ns, None, true, false),
 588             ScopeSet::AbsolutePath(ns) => (ns, None, false, true),
 589             ScopeSet::Macro(macro_kind) => (MacroNS, Some(macro_kind), false, false),
 590             ScopeSet::Module => (TypeNS, None, false, false),
 591         };
 592         let mut where_to_resolve = match ns {
 593             _ if is_absolute_path => WhereToResolve::CrateRoot,
 594             TypeNS | ValueNS => WhereToResolve::Module(parent_scope.module),
 595             MacroNS => WhereToResolve::DeriveHelpers,
 596         };
 597         let mut use_prelude = !parent_scope.module.no_implicit_prelude;
 598         let mut determinacy = Determinacy::Determined;
 599         loop {
 600             let result = match where_to_resolve {
 601                 WhereToResolve::DeriveHelpers => {
 602                     let mut result = Err(Determinacy::Determined);
 603                     for derive in &parent_scope.derives {
 604                         let parent_scope = ParentScope { derives: Vec::new(), ..*parent_scope };
 605                         match self.resolve_macro_to_res(derive, MacroKind::Derive,
 606                                                         &parent_scope, true, force) {
 607                             Ok((_, ext)) => if ext.helper_attrs.contains(&ident.name) {
 608                                 let binding = (Res::NonMacroAttr(NonMacroAttrKind::DeriveHelper),
 609                                                ty::Visibility::Public, derive.span, Mark::root())
 610                                                .to_name_binding(self.arenas);
 611                                 result = Ok((binding, Flags::empty()));
 612                                 break;
 613                             }
 614                             Err(Determinacy::Determined) => {}
 615                             Err(Determinacy::Undetermined) =>
 616                                 result = Err(Determinacy::Undetermined),
 617                         }
 618                     }
 619                     result
 620                 }
 621                 WhereToResolve::MacroRules(legacy_scope) => match legacy_scope {
 622                     LegacyScope::Binding(legacy_binding) if ident == legacy_binding.ident =>
 623                         Ok((legacy_binding.binding, Flags::MACRO_RULES)),
 624                     LegacyScope::Invocation(invoc) if invoc.output_legacy_scope.get().is_none() =>
 625                         Err(Determinacy::Undetermined),
 626                     _ => Err(Determinacy::Determined),
 627                 }
 628                 WhereToResolve::CrateRoot => {
 629                     let root_ident = Ident::new(kw::PathRoot, orig_ident.span);
 630                     let root_module = self.resolve_crate_root(root_ident);
 631                     let binding = self.resolve_ident_in_module_ext(
 632                         ModuleOrUniformRoot::Module(root_module),
 633                         orig_ident,
 634                         ns,
 635                         None,
 636                         record_used,
 637                         path_span,
 638                     );
 639                     match binding {
 640                         Ok(binding) => Ok((binding, Flags::MODULE | Flags::MISC_SUGGEST_CRATE)),
 641                         Err((Determinacy::Undetermined, Weak::No)) =>
 642                             return Err(Determinacy::determined(force)),
 643                         Err((Determinacy::Undetermined, Weak::Yes)) =>
 644                             Err(Determinacy::Undetermined),
 645                         Err((Determinacy::Determined, _)) => Err(Determinacy::Determined),
 646                     }
 647                 }
 648                 WhereToResolve::Module(module) => {
 649                     let orig_current_module = mem::replace(&mut self.current_module, module);
 650                     let binding = self.resolve_ident_in_module_unadjusted_ext(
 651                         ModuleOrUniformRoot::Module(module),
 652                         ident,
 653                         ns,
 654                         None,
 655                         true,
 656                         record_used,
 657                         path_span,
 658                     );
 659                     self.current_module = orig_current_module;
 660                     match binding {
 661                         Ok(binding) => {
 662                             let misc_flags = if ptr::eq(module, self.graph_root) {
 663                                 Flags::MISC_SUGGEST_CRATE
 664                             } else if module.is_normal() {
 665                                 Flags::MISC_SUGGEST_SELF
 666                             } else {
 667                                 Flags::empty()
 668                             };
 669                             Ok((binding, Flags::MODULE | misc_flags))
 670                         }
 671                         Err((Determinacy::Undetermined, Weak::No)) =>
 672                             return Err(Determinacy::determined(force)),
 673                         Err((Determinacy::Undetermined, Weak::Yes)) =>
 674                             Err(Determinacy::Undetermined),
 675                         Err((Determinacy::Determined, _)) => Err(Determinacy::Determined),
 676                     }
 677                 }
 678                 WhereToResolve::MacroUsePrelude => {
 679                     if use_prelude || rust_2015 {
 680                         match self.macro_use_prelude.get(&ident.name).cloned() {
 681                             Some(binding) =>
 682                                 Ok((binding, Flags::PRELUDE | Flags::MISC_FROM_PRELUDE)),
 683                             None => Err(Determinacy::determined(
 684                                 self.graph_root.unresolved_invocations.borrow().is_empty()
 685                             ))
 686                         }
 687                     } else {
 688                         Err(Determinacy::Determined)
 689                     }
 690                 }
 691                 WhereToResolve::BuiltinMacros => {
 692                     match self.builtin_macros.get(&ident.name).cloned() {
 693                         Some(binding) => Ok((binding, Flags::PRELUDE)),
 694                         None => Err(Determinacy::Determined),
 695                     }
 696                 }
 697                 WhereToResolve::BuiltinAttrs => {
 698                     if is_builtin_attr_name(ident.name) {
 699                         let binding = (Res::NonMacroAttr(NonMacroAttrKind::Builtin),
 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::LegacyPluginHelpers => {
 708                     if (use_prelude || rust_2015) &&
 709                        self.session.plugin_attributes.borrow().iter()
 710                                                      .any(|(name, _)| ident.name == *name) {
 711                         let binding = (Res::NonMacroAttr(NonMacroAttrKind::LegacyPluginHelper),
 712                                        ty::Visibility::Public, DUMMY_SP, Mark::root())
 713                                        .to_name_binding(self.arenas);
 714                         Ok((binding, Flags::PRELUDE))
 715                     } else {
 716                         Err(Determinacy::Determined)
 717                     }
 718                 }
 719                 WhereToResolve::ExternPrelude => {
 720                     if use_prelude || is_absolute_path {
 721                         match self.extern_prelude_get(ident, !record_used) {
 722                             Some(binding) => Ok((binding, Flags::PRELUDE)),
 723                             None => Err(Determinacy::determined(
 724                                 self.graph_root.unresolved_invocations.borrow().is_empty()
 725                             )),
 726                         }
 727                     } else {
 728                         Err(Determinacy::Determined)
 729                     }
 730                 }
 731                 WhereToResolve::ToolPrelude => {
 732                     if use_prelude && is_known_tool(ident.name) {
 733                         let binding = (Res::ToolMod, ty::Visibility::Public,
 734                                        DUMMY_SP, Mark::root()).to_name_binding(self.arenas);
 735                         Ok((binding, Flags::PRELUDE))
 736                     } else {
 737                         Err(Determinacy::Determined)
 738                     }
 739                 }
 740                 WhereToResolve::StdLibPrelude => {
 741                     let mut result = Err(Determinacy::Determined);
 742                     if use_prelude {
 743                         if let Some(prelude) = self.prelude {
 744                             if let Ok(binding) = self.resolve_ident_in_module_unadjusted(
 745                                 ModuleOrUniformRoot::Module(prelude),
 746                                 ident,
 747                                 ns,
 748                                 false,
 749                                 path_span,
 750                             ) {
 751                                 result = Ok((binding, Flags::PRELUDE | Flags::MISC_FROM_PRELUDE));
 752                             }
 753                         }
 754                     }
 755                     result
 756                 }
 757                 WhereToResolve::BuiltinTypes => {
 758                     match self.primitive_type_table.primitive_types.get(&ident.name).cloned() {
 759                         Some(prim_ty) => {
 760                             let binding = (Res::PrimTy(prim_ty), ty::Visibility::Public,
 761                                            DUMMY_SP, Mark::root()).to_name_binding(self.arenas);
 762                             Ok((binding, Flags::PRELUDE))
 763                         }
 764                         None => Err(Determinacy::Determined)
 765                     }
 766                 }
 767             };
 768
 769             match result {
 770                 Ok((binding, flags)) if sub_namespace_match(binding.macro_kind(), macro_kind) => {
 771                     if !record_used {
 772                         return Ok(binding);
 773                     }
 774
 775                     if let Some((innermost_binding, innermost_flags)) = innermost_result {
 776                         // Found another solution, if the first one was "weak", report an error.
 777                         let (res, innermost_res) = (binding.res(), innermost_binding.res());
 778                         if res != innermost_res {
 779                             let builtin = Res::NonMacroAttr(NonMacroAttrKind::Builtin);
 780                             let derive_helper = Res::NonMacroAttr(NonMacroAttrKind::DeriveHelper);
 781                             let legacy_helper =
 782                                 Res::NonMacroAttr(NonMacroAttrKind::LegacyPluginHelper);
 783
 784                             let ambiguity_error_kind = if is_import {
 785                                 Some(AmbiguityKind::Import)
 786                             } else if innermost_res == builtin || res == builtin {
 787                                 Some(AmbiguityKind::BuiltinAttr)
 788                             } else if innermost_res == derive_helper || res == derive_helper {
 789                                 Some(AmbiguityKind::DeriveHelper)
 790                             } else if innermost_res == legacy_helper &&
 791                                       flags.contains(Flags::PRELUDE) ||
 792                                       res == legacy_helper &&
 793                                       innermost_flags.contains(Flags::PRELUDE) {
 794                                 Some(AmbiguityKind::LegacyHelperVsPrelude)
 795                             } else if innermost_flags.contains(Flags::MACRO_RULES) &&
 796                                       flags.contains(Flags::MODULE) &&
 797                                       !self.disambiguate_legacy_vs_modern(innermost_binding,
 798                                                                           binding) ||
 799                                       flags.contains(Flags::MACRO_RULES) &&
 800                                       innermost_flags.contains(Flags::MODULE) &&
 801                                       !self.disambiguate_legacy_vs_modern(binding,
 802                                                                           innermost_binding) {
 803                                 Some(AmbiguityKind::LegacyVsModern)
 804                             } else if innermost_binding.is_glob_import() {
 805                                 Some(AmbiguityKind::GlobVsOuter)
 806                             } else if innermost_binding.may_appear_after(parent_scope.expansion,
 807                                                                          binding) {
 808                                 Some(AmbiguityKind::MoreExpandedVsOuter)
 809                             } else {
 810                                 None
 811                             };
 812                             if let Some(kind) = ambiguity_error_kind {
 813                                 let misc = |f: Flags| if f.contains(Flags::MISC_SUGGEST_CRATE) {
 814                                     AmbiguityErrorMisc::SuggestCrate
 815                                 } else if f.contains(Flags::MISC_SUGGEST_SELF) {
 816                                     AmbiguityErrorMisc::SuggestSelf
 817                                 } else if f.contains(Flags::MISC_FROM_PRELUDE) {
 818                                     AmbiguityErrorMisc::FromPrelude
 819                                 } else {
 820                                     AmbiguityErrorMisc::None
 821                                 };
 822                                 self.ambiguity_errors.push(AmbiguityError {
 823                                     kind,
 824                                     ident: orig_ident,
 825                                     b1: innermost_binding,
 826                                     b2: binding,
 827                                     misc1: misc(innermost_flags),
 828                                     misc2: misc(flags),
 829                                 });
 830                                 return Ok(innermost_binding);
 831                             }
 832                         }
 833                     } else {
 834                         // Found the first solution.
 835                         innermost_result = Some((binding, flags));
 836                     }
 837                 }
 838                 Ok(..) | Err(Determinacy::Determined) => {}
 839                 Err(Determinacy::Undetermined) => determinacy = Determinacy::Undetermined
 840             }
 841
 842             where_to_resolve = match where_to_resolve {
 843                 WhereToResolve::DeriveHelpers =>
 844                     WhereToResolve::MacroRules(parent_scope.legacy),
 845                 WhereToResolve::MacroRules(legacy_scope) => match legacy_scope {
 846                     LegacyScope::Binding(binding) => WhereToResolve::MacroRules(
 847                         binding.parent_legacy_scope
 848                     ),
 849                     LegacyScope::Invocation(invoc) => WhereToResolve::MacroRules(
 850                         invoc.output_legacy_scope.get().unwrap_or(invoc.parent_legacy_scope.get())
 851                     ),
 852                     LegacyScope::Empty => WhereToResolve::Module(parent_scope.module),
 853                     LegacyScope::Uninitialized => unreachable!(),
 854                 }
 855                 WhereToResolve::CrateRoot => match ns {
 856                     TypeNS => {
 857                         ident.span.adjust(Mark::root());
 858                         WhereToResolve::ExternPrelude
 859                     }
 860                     ValueNS | MacroNS => break,
 861                 }
 862                 WhereToResolve::Module(module) => {
 863                     match self.hygienic_lexical_parent(module, &mut ident.span) {
 864                         Some(parent_module) => WhereToResolve::Module(parent_module),
 865                         None => {
 866                             use_prelude = !module.no_implicit_prelude;
 867                             match ns {
 868                                 TypeNS => WhereToResolve::ExternPrelude,
 869                                 ValueNS => WhereToResolve::StdLibPrelude,
 870                                 MacroNS => WhereToResolve::MacroUsePrelude,
 871                             }
 872                         }
 873                     }
 874                 }
 875                 WhereToResolve::MacroUsePrelude => WhereToResolve::BuiltinMacros,
 876                 WhereToResolve::BuiltinMacros => WhereToResolve::BuiltinAttrs,
 877                 WhereToResolve::BuiltinAttrs => WhereToResolve::LegacyPluginHelpers,
 878                 WhereToResolve::LegacyPluginHelpers => break, // nowhere else to search
 879                 WhereToResolve::ExternPrelude if is_absolute_path => break,
 880                 WhereToResolve::ExternPrelude => WhereToResolve::ToolPrelude,
 881                 WhereToResolve::ToolPrelude => WhereToResolve::StdLibPrelude,
 882                 WhereToResolve::StdLibPrelude => match ns {
 883                     TypeNS => WhereToResolve::BuiltinTypes,
 884                     ValueNS => break, // nowhere else to search
 885                     MacroNS => unreachable!(),
 886                 }
 887                 WhereToResolve::BuiltinTypes => break, // nowhere else to search
 888             };
 889
 890             continue;
 891         }
 892
 893         // The first found solution was the only one, return it.
 894         if let Some((binding, _)) = innermost_result {
 895             return Ok(binding);
 896         }
 897
 898         let determinacy = Determinacy::determined(determinacy == Determinacy::Determined || force);
 899         if determinacy == Determinacy::Determined && macro_kind == Some(MacroKind::Attr) {
 900             // For single-segment attributes interpret determinate "no resolution" as a custom
 901             // attribute. (Lexical resolution implies the first segment and attr kind should imply
 902             // the last segment, so we are certainly working with a single-segment attribute here.)
 903             assert!(ns == MacroNS);
 904             let binding = (Res::NonMacroAttr(NonMacroAttrKind::Custom),
 905                            ty::Visibility::Public, ident.span, Mark::root())
 906                            .to_name_binding(self.arenas);
 907             Ok(binding)
 908         } else {
 909             Err(determinacy)
 910         }
 911     }
 912
 913     pub fn finalize_current_module_macro_resolutions(&mut self) {
 914         let module = self.current_module;
 915
 916         let check_consistency = |this: &mut Self, path: &[Segment], span, kind: MacroKind,
 917                                  initial_res: Option<Res>, res: Res| {
 918             if let Some(initial_res) = initial_res {
 919                 if res != initial_res && res != Res::Err && this.ambiguity_errors.is_empty() {
 920                     // Make sure compilation does not succeed if preferred macro resolution
 921                     // has changed after the macro had been expanded. In theory all such
 922                     // situations should be reported as ambiguity errors, so this is a bug.
 923                     if initial_res == Res::NonMacroAttr(NonMacroAttrKind::Custom) {
 924                         // Yeah, legacy custom attributes are implemented using forced resolution
 925                         // (which is a best effort error recovery tool, basically), so we can't
 926                         // promise their resolution won't change later.
 927                         let msg = format!("inconsistent resolution for a macro: first {}, then {}",
 928                                           initial_res.descr(), res.descr());
 929                         this.session.span_err(span, &msg);
 930                     } else {
 931                         span_bug!(span, "inconsistent resolution for a macro");
 932                     }
 933                 }
 934             } else {
 935                 // It's possible that the macro was unresolved (indeterminate) and silently
 936                 // expanded into a dummy fragment for recovery during expansion.
 937                 // Now, post-expansion, the resolution may succeed, but we can't change the
 938                 // past and need to report an error.
 939                 // However, non-speculative `resolve_path` can successfully return private items
 940                 // even if speculative `resolve_path` returned nothing previously, so we skip this
 941                 // less informative error if the privacy error is reported elsewhere.
 942                 if this.privacy_errors.is_empty() {
 943                     let msg = format!("cannot determine resolution for the {} `{}`",
 944                                         kind.descr(), Segment::names_to_string(path));
 945                     let msg_note = "import resolution is stuck, try simplifying macro imports";
 946                     this.session.struct_span_err(span, &msg).note(msg_note).emit();
 947                 }
 948             }
 949         };
 950
 951         let macro_resolutions =
 952             mem::take(&mut *module.multi_segment_macro_resolutions.borrow_mut());
 953         for (mut path, path_span, kind, parent_scope, initial_res) in macro_resolutions {
 954             // FIXME: Path resolution will ICE if segment IDs present.
 955             for seg in &mut path { seg.id = None; }
 956             match self.resolve_path(&path, Some(MacroNS), &parent_scope,
 957                                     true, path_span, CrateLint::No) {
 958                 PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 => {
 959                     let res = path_res.base_res();
 960                     check_consistency(self, &path, path_span, kind, initial_res, res);
 961                 }
 962                 path_res @ PathResult::NonModule(..) | path_res @ PathResult::Failed { .. } => {
 963                     let (span, label) = if let PathResult::Failed { span, label, .. } = path_res {
 964                         (span, label)
 965                     } else {
 966                         (path_span, format!("partially resolved path in {} {}",
 967                                             kind.article(), kind.descr()))
 968                     };
 969                     resolve_error(self, span, ResolutionError::FailedToResolve {
 970                         label,
 971                         suggestion: None
 972                     });
 973                 }
 974                 PathResult::Module(..) | PathResult::Indeterminate => unreachable!(),
 975             }
 976         }
 977
 978         let macro_resolutions =
 979             mem::take(&mut *module.single_segment_macro_resolutions.borrow_mut());
 980         for (ident, kind, parent_scope, initial_binding) in macro_resolutions {
 981             match self.early_resolve_ident_in_lexical_scope(ident, ScopeSet::Macro(kind),
 982                                                             &parent_scope, true, true, ident.span) {
 983                 Ok(binding) => {
 984                     let initial_res = initial_binding.map(|initial_binding| {
 985                         self.record_use(ident, MacroNS, initial_binding, false);
 986                         initial_binding.res()
 987                     });
 988                     let res = binding.res();
 989                     let seg = Segment::from_ident(ident);
 990                     check_consistency(self, &[seg], ident.span, kind, initial_res, res);
 991                 }
 992                 Err(..) => {
 993                     assert!(initial_binding.is_none());
 994                     let bang = if kind == MacroKind::Bang { "!" } else { "" };
 995                     let msg =
 996                         format!("cannot find {} `{}{}` in this scope", kind.descr(), ident, bang);
 997                     let mut err = self.session.struct_span_err(ident.span, &msg);
 998                     self.suggest_macro_name(ident.name, kind, &mut err, ident.span);
 999                     err.emit();
1000                 }
1001             }
1002         }
1003
1004         let builtin_attrs = mem::take(&mut *module.builtin_attrs.borrow_mut());
1005         for (ident, parent_scope) in builtin_attrs {
1006             let _ = self.early_resolve_ident_in_lexical_scope(
1007                 ident, ScopeSet::Macro(MacroKind::Attr), &parent_scope, true, true, ident.span
1008             );
1009         }
1010     }
1011
1012     fn prohibit_imported_non_macro_attrs(&self, binding: Option<&'a NameBinding<'a>>,
1013                                          res: Option<Res>, span: Span) {
1014         if let Some(Res::NonMacroAttr(kind)) = res {
1015             if kind != NonMacroAttrKind::Tool && binding.map_or(true, |b| b.is_import()) {
1016                 let msg = format!("cannot use a {} through an import", kind.descr());
1017                 let mut err = self.session.struct_span_err(span, &msg);
1018                 if let Some(binding) = binding {
1019                     err.span_note(binding.span, &format!("the {} imported here", kind.descr()));
1020                 }
1021                 err.emit();
1022             }
1023         }
1024     }
1025
1026     fn suggest_macro_name(&mut self, name: Symbol, kind: MacroKind,
1027                           err: &mut DiagnosticBuilder<'a>, span: Span) {
1028         if kind == MacroKind::Derive && (name.as_str() == "Send" || name.as_str() == "Sync") {
1029             let msg = format!("unsafe traits like `{}` should be implemented explicitly", name);
1030             err.span_note(span, &msg);
1031             return;
1032         }
1033
1034         // First check if this is a locally-defined bang macro.
1035         let suggestion = if let MacroKind::Bang = kind {
1036             find_best_match_for_name(
1037                 self.macro_names.iter().map(|ident| &ident.name), &name.as_str(), None)
1038         } else {
1039             None
1040         // Then check global macros.
1041         }.or_else(|| {
1042             let names = self.builtin_macros.iter().chain(self.macro_use_prelude.iter())
1043                                                   .filter_map(|(name, binding)| {
1044                 if binding.macro_kind() == Some(kind) { Some(name) } else { None }
1045             });
1046             find_best_match_for_name(names, &name.as_str(), None)
1047         // Then check modules.
1048         }).or_else(|| {
1049             let is_macro = |res| {
1050                 if let Res::Def(DefKind::Macro(def_kind), _) = res {
1051                     def_kind == kind
1052                 } else {
1053                     false
1054                 }
1055             };
1056             let ident = Ident::new(name, span);
1057             self.lookup_typo_candidate(&[Segment::from_ident(ident)], MacroNS, is_macro, span)
1058                 .map(|suggestion| suggestion.candidate)
1059         });
1060
1061         if let Some(suggestion) = suggestion {
1062             if suggestion != name {
1063                 if let MacroKind::Bang = kind {
1064                     err.span_suggestion(
1065                         span,
1066                         "you could try the macro",
1067                         suggestion.to_string(),
1068                         Applicability::MaybeIncorrect
1069                     );
1070                 } else {
1071                     err.span_suggestion(
1072                         span,
1073                         "try",
1074                         suggestion.to_string(),
1075                         Applicability::MaybeIncorrect
1076                     );
1077                 }
1078             } else {
1079                 err.help("have you added the `#[macro_use]` on the module/import?");
1080             }
1081         }
1082     }
1083
1084     fn collect_def_ids(&mut self,
1085                        mark: Mark,
1086                        invocation: &'a InvocationData<'a>,
1087                        fragment: &AstFragment) {
1088         let Resolver { ref mut invocations, arenas, graph_root, .. } = *self;
1089         let InvocationData { def_index, .. } = *invocation;
1090
1091         let visit_macro_invoc = &mut |invoc: map::MacroInvocationData| {
1092             invocations.entry(invoc.mark).or_insert_with(|| {
1093                 arenas.alloc_invocation_data(InvocationData {
1094                     def_index: invoc.def_index,
1095                     module: Cell::new(graph_root),
1096                     parent_legacy_scope: Cell::new(LegacyScope::Uninitialized),
1097                     output_legacy_scope: Cell::new(None),
1098                 })
1099             });
1100         };
1101
1102         let mut def_collector = DefCollector::new(&mut self.definitions, mark);
1103         def_collector.visit_macro_invoc = Some(visit_macro_invoc);
1104         def_collector.with_parent(def_index, |def_collector| {
1105             fragment.visit_with(def_collector)
1106         });
1107     }
1108
1109     pub fn define_macro(&mut self,
1110                         item: &ast::Item,
1111                         expansion: Mark,
1112                         current_legacy_scope: &mut LegacyScope<'a>) {
1113         self.local_macro_def_scopes.insert(item.id, self.current_module);
1114         let ident = item.ident;
1115
1116         let def_id = self.definitions.local_def_id(item.id);
1117         let ext = Lrc::new(macro_rules::compile(&self.session.parse_sess,
1118                                                &self.session.features_untracked(),
1119                                                item, self.session.edition()));
1120         self.macro_map.insert(def_id, ext);
1121
1122         let def = match item.node { ast::ItemKind::MacroDef(ref def) => def, _ => unreachable!() };
1123         if def.legacy {
1124             let ident = ident.modern();
1125             self.macro_names.insert(ident);
1126             let res = Res::Def(DefKind::Macro(MacroKind::Bang), def_id);
1127             let is_macro_export = attr::contains_name(&item.attrs, sym::macro_export);
1128             let vis = if is_macro_export {
1129                 ty::Visibility::Public
1130             } else {
1131                 ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX))
1132             };
1133             let binding = (res, vis, item.span, expansion).to_name_binding(self.arenas);
1134             self.set_binding_parent_module(binding, self.current_module);
1135             let legacy_binding = self.arenas.alloc_legacy_binding(LegacyBinding {
1136                 parent_legacy_scope: *current_legacy_scope, binding, ident
1137             });
1138             *current_legacy_scope = LegacyScope::Binding(legacy_binding);
1139             self.all_macros.insert(ident.name, res);
1140             if is_macro_export {
1141                 let module = self.graph_root;
1142                 self.define(module, ident, MacroNS,
1143                             (res, vis, item.span, expansion, IsMacroExport));
1144             } else {
1145                 if !attr::contains_name(&item.attrs, sym::rustc_builtin_macro) {
1146                     self.check_reserved_macro_name(ident, MacroNS);
1147                 }
1148                 self.unused_macros.insert(def_id);
1149             }
1150         } else {
1151             let module = self.current_module;
1152             let res = Res::Def(DefKind::Macro(MacroKind::Bang), def_id);
1153             let vis = self.resolve_visibility(&item.vis);
1154             if vis != ty::Visibility::Public {
1155                 self.unused_macros.insert(def_id);
1156             }
1157             self.define(module, ident, MacroNS, (res, vis, item.span, expansion));
1158         }
1159     }
1160 }