src/librustc_resolve/macros.rs

   1 // Copyright 2016 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use {AmbiguityError, AmbiguityKind, AmbiguityErrorMisc};
  12 use {CrateLint, Resolver, ResolutionError, ScopeSet, Weak};
  13 use {Module, NameBinding, NameBindingKind, PathResult, Segment, ToNameBinding};
  14 use {is_known_tool, resolve_error};
  15 use ModuleOrUniformRoot;
  16 use Namespace::*;
  17 use build_reduced_graph::{BuildReducedGraphVisitor, IsMacroExport};
  18 use resolve_imports::ImportResolver;
  19 use rustc::hir::def_id::{DefId, CRATE_DEF_INDEX, DefIndex,
  20                          CrateNum, DefIndexAddressSpace};
  21 use rustc::hir::def::{Def, NonMacroAttrKind};
  22 use rustc::hir::map::{self, DefCollector};
  23 use rustc::{ty, lint};
  24 use syntax::ast::{self, Ident};
  25 use syntax::attr;
  26 use syntax::errors::DiagnosticBuilder;
  27 use syntax::ext::base::{self, Determinacy};
  28 use syntax::ext::base::{MacroKind, SyntaxExtension};
  29 use syntax::ext::expand::{AstFragment, Invocation, InvocationKind};
  30 use syntax::ext::hygiene::{self, Mark};
  31 use syntax::ext::tt::macro_rules;
  32 use syntax::feature_gate::{feature_err, is_builtin_attr_name, GateIssue};
  33 use syntax::symbol::{Symbol, keywords};
  34 use syntax::util::lev_distance::find_best_match_for_name;
  35 use syntax_pos::{Span, DUMMY_SP};
  36 use errors::Applicability;
  37
  38 use std::cell::Cell;
  39 use std::{mem, ptr};
  40 use rustc_data_structures::sync::Lrc;
  41
  42 #[derive(Clone, Debug)]
  43 pub struct InvocationData<'a> {
  44     def_index: DefIndex,
  45     /// Module in which the macro was invoked.
  46     crate module: Cell<Module<'a>>,
  47     /// Legacy scope in which the macro was invoked.
  48     /// The invocation path is resolved in this scope.
  49     crate parent_legacy_scope: Cell<LegacyScope<'a>>,
  50     /// Legacy scope *produced* by expanding this macro invocation,
  51     /// includes all the macro_rules items, other invocations, etc generated by it.
  52     /// `None` if the macro is not expanded yet.
  53     crate output_legacy_scope: Cell<Option<LegacyScope<'a>>>,
  54 }
  55
  56 impl<'a> InvocationData<'a> {
  57     pub fn root(graph_root: Module<'a>) -> Self {
  58         InvocationData {
  59             module: Cell::new(graph_root),
  60             def_index: CRATE_DEF_INDEX,
  61             parent_legacy_scope: Cell::new(LegacyScope::Empty),
  62             output_legacy_scope: Cell::new(Some(LegacyScope::Empty)),
  63         }
  64     }
  65 }
  66
  67 /// Binding produced by a `macro_rules` item.
  68 /// Not modularized, can shadow previous legacy bindings, etc.
  69 #[derive(Debug)]
  70 pub struct LegacyBinding<'a> {
  71     binding: &'a NameBinding<'a>,
  72     /// Legacy scope into which the `macro_rules` item was planted.
  73     parent_legacy_scope: LegacyScope<'a>,
  74     ident: Ident,
  75 }
  76
  77 /// Scope introduced by a `macro_rules!` macro.
  78 /// Starts at the macro's definition and ends at the end of the macro's parent module
  79 /// (named or unnamed), or even further if it escapes with `#[macro_use]`.
  80 /// Some macro invocations need to introduce legacy scopes too because they
  81 /// potentially can expand into macro definitions.
  82 #[derive(Copy, Clone, Debug)]
  83 pub enum LegacyScope<'a> {
  84     /// Created when invocation data is allocated in the arena,
  85     /// must be replaced with a proper scope later.
  86     Uninitialized,
  87     /// Empty "root" scope at the crate start containing no names.
  88     Empty,
  89     /// Scope introduced by a `macro_rules!` macro definition.
  90     Binding(&'a LegacyBinding<'a>),
  91     /// Scope introduced by a macro invocation that can potentially
  92     /// create a `macro_rules!` macro definition.
  93     Invocation(&'a InvocationData<'a>),
  94 }
  95
  96 /// Everything you need to resolve a macro or import path.
  97 #[derive(Clone, Debug)]
  98 pub struct ParentScope<'a> {
  99     crate module: Module<'a>,
 100     crate expansion: Mark,
 101     crate legacy: LegacyScope<'a>,
 102     crate derives: Vec<ast::Path>,
 103 }
 104
 105 // Macro namespace is separated into two sub-namespaces, one for bang macros and
 106 // one for attribute-like macros (attributes, derives).
 107 // We ignore resolutions from one sub-namespace when searching names in scope for another.
 108 fn sub_namespace_match(candidate: Option<MacroKind>, requirement: Option<MacroKind>) -> bool {
 109     #[derive(PartialEq)]
 110     enum SubNS { Bang, AttrLike }
 111     let sub_ns = |kind| match kind {
 112         MacroKind::Bang => Some(SubNS::Bang),
 113         MacroKind::Attr | MacroKind::Derive => Some(SubNS::AttrLike),
 114         MacroKind::ProcMacroStub => None,
 115     };
 116     let requirement = requirement.and_then(|kind| sub_ns(kind));
 117     let candidate = candidate.and_then(|kind| sub_ns(kind));
 118     // "No specific sub-namespace" means "matches anything" for both requirements and candidates.
 119     candidate.is_none() || requirement.is_none() || candidate == requirement
 120 }
 121
 122 impl<'a> base::Resolver for Resolver<'a> {
 123     fn next_node_id(&mut self) -> ast::NodeId {
 124         self.session.next_node_id()
 125     }
 126
 127     fn get_module_scope(&mut self, id: ast::NodeId) -> Mark {
 128         let mark = Mark::fresh(Mark::root());
 129         let module = self.module_map[&self.definitions.local_def_id(id)];
 130         self.invocations.insert(mark, self.arenas.alloc_invocation_data(InvocationData {
 131             module: Cell::new(module),
 132             def_index: module.def_id().unwrap().index,
 133             parent_legacy_scope: Cell::new(LegacyScope::Empty),
 134             output_legacy_scope: Cell::new(Some(LegacyScope::Empty)),
 135         }));
 136         mark
 137     }
 138
 139     fn visit_ast_fragment_with_placeholders(&mut self, mark: Mark, fragment: &AstFragment,
 140                                             derives: &[Mark]) {
 141         let invocation = self.invocations[&mark];
 142         self.collect_def_ids(mark, invocation, fragment);
 143
 144         self.current_module = invocation.module.get();
 145         self.current_module.unresolved_invocations.borrow_mut().remove(&mark);
 146         self.current_module.unresolved_invocations.borrow_mut().extend(derives);
 147         self.invocations.extend(derives.iter().map(|&derive| (derive, invocation)));
 148         let mut visitor = BuildReducedGraphVisitor {
 149             resolver: self,
 150             current_legacy_scope: invocation.parent_legacy_scope.get(),
 151             expansion: mark,
 152         };
 153         fragment.visit_with(&mut visitor);
 154         invocation.output_legacy_scope.set(Some(visitor.current_legacy_scope));
 155     }
 156
 157     fn add_builtin(&mut self, ident: ast::Ident, ext: Lrc<SyntaxExtension>) {
 158         let def_id = DefId {
 159             krate: CrateNum::BuiltinMacros,
 160             index: DefIndex::from_array_index(self.macro_map.len(),
 161                                               DefIndexAddressSpace::Low),
 162         };
 163         let kind = ext.kind();
 164         self.macro_map.insert(def_id, ext);
 165         let binding = self.arenas.alloc_name_binding(NameBinding {
 166             kind: NameBindingKind::Def(Def::Macro(def_id, kind), false),
 167             span: DUMMY_SP,
 168             vis: ty::Visibility::Public,
 169             expansion: Mark::root(),
 170         });
 171         if self.builtin_macros.insert(ident.name, binding).is_some() {
 172             self.session.span_err(ident.span,
 173                                   &format!("built-in macro `{}` was already defined", ident));
 174         }
 175     }
 176
 177     fn resolve_imports(&mut self) {
 178         ImportResolver { resolver: self }.resolve_imports()
 179     }
 180
 181     fn resolve_macro_invocation(&mut self, invoc: &Invocation, invoc_id: Mark, force: bool)
 182                                 -> Result<Option<Lrc<SyntaxExtension>>, Determinacy> {
 183         let (path, kind, derives_in_scope, after_derive) = match invoc.kind {
 184             InvocationKind::Attr { attr: None, .. } =>
 185                 return Ok(None),
 186             InvocationKind::Attr { attr: Some(ref attr), ref traits, after_derive, .. } =>
 187                 (&attr.path, MacroKind::Attr, traits.clone(), after_derive),
 188             InvocationKind::Bang { ref mac, .. } =>
 189                 (&mac.node.path, MacroKind::Bang, Vec::new(), false),
 190             InvocationKind::Derive { ref path, .. } =>
 191                 (path, MacroKind::Derive, Vec::new(), false),
 192         };
 193
 194         let parent_scope = self.invoc_parent_scope(invoc_id, derives_in_scope);
 195         let (def, ext) = self.resolve_macro_to_def(path, kind, &parent_scope, true, force)?;
 196
 197         if let Def::Macro(def_id, _) = def {
 198             if after_derive {
 199                 self.session.span_err(invoc.span(),
 200                                       "macro attributes must be placed before `#[derive]`");
 201             }
 202             self.macro_defs.insert(invoc.expansion_data.mark, def_id);
 203             let normal_module_def_id =
 204                 self.macro_def_scope(invoc.expansion_data.mark).normal_ancestor_id;
 205             self.definitions.add_parent_module_of_macro_def(invoc.expansion_data.mark,
 206                                                             normal_module_def_id);
 207             invoc.expansion_data.mark.set_default_transparency(ext.default_transparency());
 208         }
 209
 210         Ok(Some(ext))
 211     }
 212
 213     fn resolve_macro_path(&mut self, path: &ast::Path, kind: MacroKind, invoc_id: Mark,
 214                           derives_in_scope: Vec<ast::Path>, force: bool)
 215                           -> Result<Lrc<SyntaxExtension>, Determinacy> {
 216         let parent_scope = self.invoc_parent_scope(invoc_id, derives_in_scope);
 217         Ok(self.resolve_macro_to_def(path, kind, &parent_scope, false, force)?.1)
 218     }
 219
 220     fn check_unused_macros(&self) {
 221         for did in self.unused_macros.iter() {
 222             let id_span = match *self.macro_map[did] {
 223                 SyntaxExtension::NormalTT { def_info, .. } |
 224                 SyntaxExtension::DeclMacro { def_info, .. } => def_info,
 225                 _ => None,
 226             };
 227             if let Some((id, span)) = id_span {
 228                 let lint = lint::builtin::UNUSED_MACROS;
 229                 let msg = "unused macro definition";
 230                 self.session.buffer_lint(lint, id, span, msg);
 231             } else {
 232                 bug!("attempted to create unused macro error, but span not available");
 233             }
 234         }
 235     }
 236 }
 237
 238 impl<'a> Resolver<'a> {
 239     pub fn dummy_parent_scope(&self) -> ParentScope<'a> {
 240         self.invoc_parent_scope(Mark::root(), Vec::new())
 241     }
 242
 243     fn invoc_parent_scope(&self, invoc_id: Mark, derives: Vec<ast::Path>) -> ParentScope<'a> {
 244         let invoc = self.invocations[&invoc_id];
 245         ParentScope {
 246             module: invoc.module.get().nearest_item_scope(),
 247             expansion: invoc_id.parent(),
 248             legacy: invoc.parent_legacy_scope.get(),
 249             derives,
 250         }
 251     }
 252
 253     fn resolve_macro_to_def(
 254         &mut self,
 255         path: &ast::Path,
 256         kind: MacroKind,
 257         parent_scope: &ParentScope<'a>,
 258         trace: bool,
 259         force: bool,
 260     ) -> Result<(Def, Lrc<SyntaxExtension>), Determinacy> {
 261         let def = self.resolve_macro_to_def_inner(path, kind, parent_scope, trace, force);
 262
 263         // Report errors and enforce feature gates for the resolved macro.
 264         if def != Err(Determinacy::Undetermined) {
 265             // Do not report duplicated errors on every undetermined resolution.
 266             for segment in &path.segments {
 267                 if let Some(args) = &segment.args {
 268                     self.session.span_err(args.span(), "generic arguments in macro path");
 269                 }
 270             }
 271         }
 272
 273         let def = def?;
 274
 275         match def {
 276             Def::Macro(def_id, macro_kind) => {
 277                 self.unused_macros.remove(&def_id);
 278                 if macro_kind == MacroKind::ProcMacroStub {
 279                     let msg = "can't use a procedural macro from the same crate that defines it";
 280                     self.session.span_err(path.span, msg);
 281                     return Err(Determinacy::Determined);
 282                 }
 283             }
 284             Def::NonMacroAttr(attr_kind) => {
 285                 if kind == MacroKind::Attr {
 286                     let features = self.session.features_untracked();
 287                     if attr_kind == NonMacroAttrKind::Custom {
 288                         assert!(path.segments.len() == 1);
 289                         let name = path.segments[0].ident.name.as_str();
 290                         if name.starts_with("rustc_") {
 291                             if !features.rustc_attrs {
 292                                 let msg = "unless otherwise specified, attributes with the prefix \
 293                                            `rustc_` are reserved for internal compiler diagnostics";
 294                                 feature_err(&self.session.parse_sess, "rustc_attrs", path.span,
 295                                             GateIssue::Language, &msg).emit();
 296                             }
 297                         } else if !features.custom_attribute {
 298                             let msg = format!("The attribute `{}` is currently unknown to the \
 299                                                compiler and may have meaning added to it in the \
 300                                                future", path);
 301                             feature_err(&self.session.parse_sess, "custom_attribute", path.span,
 302                                         GateIssue::Language, &msg).emit();
 303                         }
 304                     }
 305                 } else {
 306                     // Not only attributes, but anything in macro namespace can result in
 307                     // `Def::NonMacroAttr` definition (e.g., `inline!()`), so we must report
 308                     // an error for those cases.
 309                     let msg = format!("expected a macro, found {}", def.kind_name());
 310                     self.session.span_err(path.span, &msg);
 311                     return Err(Determinacy::Determined);
 312                 }
 313             }
 314             Def::Err => {
 315                 return Err(Determinacy::Determined);
 316             }
 317             _ => panic!("expected `Def::Macro` or `Def::NonMacroAttr`"),
 318         }
 319
 320         Ok((def, self.get_macro(def)))
 321     }
 322
 323     pub fn resolve_macro_to_def_inner(
 324         &mut self,
 325         path: &ast::Path,
 326         kind: MacroKind,
 327         parent_scope: &ParentScope<'a>,
 328         trace: bool,
 329         force: bool,
 330     ) -> Result<Def, Determinacy> {
 331         let path_span = path.span;
 332         let mut path = Segment::from_path(path);
 333
 334         // Possibly apply the macro helper hack
 335         if kind == MacroKind::Bang && path.len() == 1 &&
 336            path[0].ident.span.ctxt().outer().expn_info()
 337                .map_or(false, |info| info.local_inner_macros) {
 338             let root = Ident::new(keywords::DollarCrate.name(), path[0].ident.span);
 339             path.insert(0, Segment::from_ident(root));
 340         }
 341
 342         if path.len() > 1 {
 343             let def = match self.resolve_path(&path, Some(MacroNS), parent_scope,
 344                                               false, path_span, CrateLint::No) {
 345                 PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 => {
 346                     Ok(path_res.base_def())
 347                 }
 348                 PathResult::Indeterminate if !force => return Err(Determinacy::Undetermined),
 349                 PathResult::NonModule(..) | PathResult::Indeterminate | PathResult::Failed(..) => {
 350                     self.found_unresolved_macro = true;
 351                     Err(Determinacy::Determined)
 352                 }
 353                 PathResult::Module(..) => unreachable!(),
 354             };
 355
 356             if trace {
 357                 parent_scope.module.multi_segment_macro_resolutions.borrow_mut()
 358                     .push((path, path_span, kind, parent_scope.clone(), def.ok()));
 359             }
 360
 361             def
 362         } else {
 363             let binding = self.early_resolve_ident_in_lexical_scope(
 364                 path[0].ident, ScopeSet::Macro(kind), parent_scope, false, force, path_span
 365             );
 366             match binding {
 367                 Ok(..) => {}
 368                 Err(Determinacy::Determined) => self.found_unresolved_macro = true,
 369                 Err(Determinacy::Undetermined) => return Err(Determinacy::Undetermined),
 370             }
 371
 372             if trace {
 373                 parent_scope.module.single_segment_macro_resolutions.borrow_mut()
 374                     .push((path[0].ident, kind, parent_scope.clone(), binding.ok()));
 375             }
 376
 377             binding.map(|binding| binding.def_ignoring_ambiguity())
 378         }
 379     }
 380
 381     // Resolve an identifier in lexical scope.
 382     // This is a variation of `fn resolve_ident_in_lexical_scope` that can be run during
 383     // expansion and import resolution (perhaps they can be merged in the future).
 384     // The function is used for resolving initial segments of macro paths (e.g., `foo` in
 385     // `foo::bar!(); or `foo!();`) and also for import paths on 2018 edition.
 386     crate fn early_resolve_ident_in_lexical_scope(
 387         &mut self,
 388         orig_ident: Ident,
 389         scope_set: ScopeSet,
 390         parent_scope: &ParentScope<'a>,
 391         record_used: bool,
 392         force: bool,
 393         path_span: Span,
 394     ) -> Result<&'a NameBinding<'a>, Determinacy> {
 395         // General principles:
 396         // 1. Not controlled (user-defined) names should have higher priority than controlled names
 397         //    built into the language or standard library. This way we can add new names into the
 398         //    language or standard library without breaking user code.
 399         // 2. "Closed set" below means new names cannot appear after the current resolution attempt.
 400         // Places to search (in order of decreasing priority):
 401         // (Type NS)
 402         // 1. FIXME: Ribs (type parameters), there's no necessary infrastructure yet
 403         //    (open set, not controlled).
 404         // 2. Names in modules (both normal `mod`ules and blocks), loop through hygienic parents
 405         //    (open, not controlled).
 406         // 3. Extern prelude (closed, not controlled).
 407         // 4. Tool modules (closed, controlled right now, but not in the future).
 408         // 5. Standard library prelude (de-facto closed, controlled).
 409         // 6. Language prelude (closed, controlled).
 410         // (Value NS)
 411         // 1. FIXME: Ribs (local variables), there's no necessary infrastructure yet
 412         //    (open set, not controlled).
 413         // 2. Names in modules (both normal `mod`ules and blocks), loop through hygienic parents
 414         //    (open, not controlled).
 415         // 3. Standard library prelude (de-facto closed, controlled).
 416         // (Macro NS)
 417         // 1-3. Derive helpers (open, not controlled). All ambiguities with other names
 418         //    are currently reported as errors. They should be higher in priority than preludes
 419         //    and probably even names in modules according to the "general principles" above. They
 420         //    also should be subject to restricted shadowing because are effectively produced by
 421         //    derives (you need to resolve the derive first to add helpers into scope), but they
 422         //    should be available before the derive is expanded for compatibility.
 423         //    It's mess in general, so we are being conservative for now.
 424         // 1-3. `macro_rules` (open, not controlled), loop through legacy scopes. Have higher
 425         //    priority than prelude macros, but create ambiguities with macros in modules.
 426         // 1-3. Names in modules (both normal `mod`ules and blocks), loop through hygienic parents
 427         //    (open, not controlled). Have higher priority than prelude macros, but create
 428         //    ambiguities with `macro_rules`.
 429         // 4. `macro_use` prelude (open, the open part is from macro expansions, not controlled).
 430         // 4a. User-defined prelude from macro-use
 431         //    (open, the open part is from macro expansions, not controlled).
 432         // 4b. Standard library prelude is currently implemented as `macro-use` (closed, controlled)
 433         // 5. Language prelude: builtin macros (closed, controlled, except for legacy plugins).
 434         // 6. Language prelude: builtin attributes (closed, controlled).
 435         // 4-6. Legacy plugin helpers (open, not controlled). Similar to derive helpers,
 436         //    but introduced by legacy plugins using `register_attribute`. Priority is somewhere
 437         //    in prelude, not sure where exactly (creates ambiguities with any other prelude names).
 438
 439         enum WhereToResolve<'a> {
 440             DeriveHelpers,
 441             MacroRules(LegacyScope<'a>),
 442             CrateRoot,
 443             Module(Module<'a>),
 444             MacroUsePrelude,
 445             BuiltinMacros,
 446             BuiltinAttrs,
 447             LegacyPluginHelpers,
 448             ExternPrelude,
 449             ToolPrelude,
 450             StdLibPrelude,
 451             BuiltinTypes,
 452         }
 453
 454         bitflags! {
 455             struct Flags: u8 {
 456                 const MACRO_RULES        = 1 << 0;
 457                 const MODULE             = 1 << 1;
 458                 const PRELUDE            = 1 << 2;
 459                 const MISC_SUGGEST_CRATE = 1 << 3;
 460                 const MISC_SUGGEST_SELF  = 1 << 4;
 461                 const MISC_FROM_PRELUDE  = 1 << 5;
 462             }
 463         }
 464
 465         assert!(force || !record_used); // `record_used` implies `force`
 466         let mut ident = orig_ident.modern();
 467
 468         // Make sure `self`, `super` etc produce an error when passed to here.
 469         if ident.is_path_segment_keyword() {
 470             return Err(Determinacy::Determined);
 471         }
 472
 473         // This is *the* result, resolution from the scope closest to the resolved identifier.
 474         // However, sometimes this result is "weak" because it comes from a glob import or
 475         // a macro expansion, and in this case it cannot shadow names from outer scopes, e.g.
 476         // mod m { ... } // solution in outer scope
 477         // {
 478         //     use prefix::*; // imports another `m` - innermost solution
 479         //                    // weak, cannot shadow the outer `m`, need to report ambiguity error
 480         //     m::mac!();
 481         // }
 482         // So we have to save the innermost solution and continue searching in outer scopes
 483         // to detect potential ambiguities.
 484         let mut innermost_result: Option<(&NameBinding, Flags)> = None;
 485
 486         // Go through all the scopes and try to resolve the name.
 487         let rust_2015 = orig_ident.span.rust_2015();
 488         let (ns, macro_kind, is_import, is_absolute_path) = match scope_set {
 489             ScopeSet::Import(ns) => (ns, None, true, false),
 490             ScopeSet::AbsolutePath(ns) => (ns, None, false, true),
 491             ScopeSet::Macro(macro_kind) => (MacroNS, Some(macro_kind), false, false),
 492             ScopeSet::Module => (TypeNS, None, false, false),
 493         };
 494         let mut where_to_resolve = match ns {
 495             _ if is_absolute_path || is_import && rust_2015 => WhereToResolve::CrateRoot,
 496             TypeNS | ValueNS => WhereToResolve::Module(parent_scope.module),
 497             MacroNS => WhereToResolve::DeriveHelpers,
 498         };
 499         let mut use_prelude = !parent_scope.module.no_implicit_prelude;
 500         let mut determinacy = Determinacy::Determined;
 501         loop {
 502             let result = match where_to_resolve {
 503                 WhereToResolve::DeriveHelpers => {
 504                     let mut result = Err(Determinacy::Determined);
 505                     for derive in &parent_scope.derives {
 506                         let parent_scope = ParentScope { derives: Vec::new(), ..*parent_scope };
 507                         match self.resolve_macro_to_def(derive, MacroKind::Derive,
 508                                                         &parent_scope, true, force) {
 509                             Ok((_, ext)) => {
 510                                 if let SyntaxExtension::ProcMacroDerive(_, helpers, _) = &*ext {
 511                                     if helpers.contains(&ident.name) {
 512                                         let binding =
 513                                             (Def::NonMacroAttr(NonMacroAttrKind::DeriveHelper),
 514                                             ty::Visibility::Public, derive.span, Mark::root())
 515                                             .to_name_binding(self.arenas);
 516                                         result = Ok((binding, Flags::empty()));
 517                                         break;
 518                                     }
 519                                 }
 520                             }
 521                             Err(Determinacy::Determined) => {}
 522                             Err(Determinacy::Undetermined) =>
 523                                 result = Err(Determinacy::Undetermined),
 524                         }
 525                     }
 526                     result
 527                 }
 528                 WhereToResolve::MacroRules(legacy_scope) => match legacy_scope {
 529                     LegacyScope::Binding(legacy_binding) if ident == legacy_binding.ident =>
 530                         Ok((legacy_binding.binding, Flags::MACRO_RULES)),
 531                     LegacyScope::Invocation(invoc) if invoc.output_legacy_scope.get().is_none() =>
 532                         Err(Determinacy::Undetermined),
 533                     _ => Err(Determinacy::Determined),
 534                 }
 535                 WhereToResolve::CrateRoot => {
 536                     let root_ident = Ident::new(keywords::PathRoot.name(), orig_ident.span);
 537                     let root_module = self.resolve_crate_root(root_ident);
 538                     let binding = self.resolve_ident_in_module_ext(
 539                         ModuleOrUniformRoot::Module(root_module),
 540                         orig_ident,
 541                         ns,
 542                         None,
 543                         record_used,
 544                         path_span,
 545                     );
 546                     match binding {
 547                         Ok(binding) => Ok((binding, Flags::MODULE | Flags::MISC_SUGGEST_CRATE)),
 548                         Err((Determinacy::Undetermined, Weak::No)) =>
 549                             return Err(Determinacy::determined(force)),
 550                         Err((Determinacy::Undetermined, Weak::Yes)) =>
 551                             Err(Determinacy::Undetermined),
 552                         Err((Determinacy::Determined, _)) => Err(Determinacy::Determined),
 553                     }
 554                 }
 555                 WhereToResolve::Module(module) => {
 556                     let orig_current_module = mem::replace(&mut self.current_module, module);
 557                     let binding = self.resolve_ident_in_module_unadjusted_ext(
 558                         ModuleOrUniformRoot::Module(module),
 559                         ident,
 560                         ns,
 561                         None,
 562                         true,
 563                         record_used,
 564                         path_span,
 565                     );
 566                     self.current_module = orig_current_module;
 567                     match binding {
 568                         Ok(binding) => {
 569                             let misc_flags = if ptr::eq(module, self.graph_root) {
 570                                 Flags::MISC_SUGGEST_CRATE
 571                             } else if module.is_normal() {
 572                                 Flags::MISC_SUGGEST_SELF
 573                             } else {
 574                                 Flags::empty()
 575                             };
 576                             Ok((binding, Flags::MODULE | misc_flags))
 577                         }
 578                         Err((Determinacy::Undetermined, Weak::No)) =>
 579                             return Err(Determinacy::determined(force)),
 580                         Err((Determinacy::Undetermined, Weak::Yes)) =>
 581                             Err(Determinacy::Undetermined),
 582                         Err((Determinacy::Determined, _)) => Err(Determinacy::Determined),
 583                     }
 584                 }
 585                 WhereToResolve::MacroUsePrelude => {
 586                     if use_prelude || rust_2015 {
 587                         match self.macro_use_prelude.get(&ident.name).cloned() {
 588                             Some(binding) =>
 589                                 Ok((binding, Flags::PRELUDE | Flags::MISC_FROM_PRELUDE)),
 590                             None => Err(Determinacy::determined(
 591                                 self.graph_root.unresolved_invocations.borrow().is_empty()
 592                             ))
 593                         }
 594                     } else {
 595                         Err(Determinacy::Determined)
 596                     }
 597                 }
 598                 WhereToResolve::BuiltinMacros => {
 599                     match self.builtin_macros.get(&ident.name).cloned() {
 600                         Some(binding) => Ok((binding, Flags::PRELUDE)),
 601                         None => Err(Determinacy::Determined),
 602                     }
 603                 }
 604                 WhereToResolve::BuiltinAttrs => {
 605                     if is_builtin_attr_name(ident.name) {
 606                         let binding = (Def::NonMacroAttr(NonMacroAttrKind::Builtin),
 607                                        ty::Visibility::Public, DUMMY_SP, Mark::root())
 608                                        .to_name_binding(self.arenas);
 609                         Ok((binding, Flags::PRELUDE))
 610                     } else {
 611                         Err(Determinacy::Determined)
 612                     }
 613                 }
 614                 WhereToResolve::LegacyPluginHelpers => {
 615                     if (use_prelude || rust_2015) &&
 616                        self.session.plugin_attributes.borrow().iter()
 617                                                      .any(|(name, _)| ident.name == &**name) {
 618                         let binding = (Def::NonMacroAttr(NonMacroAttrKind::LegacyPluginHelper),
 619                                        ty::Visibility::Public, DUMMY_SP, Mark::root())
 620                                        .to_name_binding(self.arenas);
 621                         Ok((binding, Flags::PRELUDE))
 622                     } else {
 623                         Err(Determinacy::Determined)
 624                     }
 625                 }
 626                 WhereToResolve::ExternPrelude => {
 627                     if use_prelude || is_absolute_path {
 628                         match self.extern_prelude_get(ident, !record_used) {
 629                             Some(binding) => Ok((binding, Flags::PRELUDE)),
 630                             None => Err(Determinacy::determined(
 631                                 self.graph_root.unresolved_invocations.borrow().is_empty()
 632                             )),
 633                         }
 634                     } else {
 635                         Err(Determinacy::Determined)
 636                     }
 637                 }
 638                 WhereToResolve::ToolPrelude => {
 639                     if use_prelude && is_known_tool(ident.name) {
 640                         let binding = (Def::ToolMod, ty::Visibility::Public,
 641                                        DUMMY_SP, Mark::root()).to_name_binding(self.arenas);
 642                         Ok((binding, Flags::PRELUDE))
 643                     } else {
 644                         Err(Determinacy::Determined)
 645                     }
 646                 }
 647                 WhereToResolve::StdLibPrelude => {
 648                     let mut result = Err(Determinacy::Determined);
 649                     if use_prelude {
 650                         if let Some(prelude) = self.prelude {
 651                             if let Ok(binding) = self.resolve_ident_in_module_unadjusted(
 652                                 ModuleOrUniformRoot::Module(prelude),
 653                                 ident,
 654                                 ns,
 655                                 false,
 656                                 path_span,
 657                             ) {
 658                                 result = Ok((binding, Flags::PRELUDE | Flags::MISC_FROM_PRELUDE));
 659                             }
 660                         }
 661                     }
 662                     result
 663                 }
 664                 WhereToResolve::BuiltinTypes => {
 665                     match self.primitive_type_table.primitive_types.get(&ident.name).cloned() {
 666                         Some(prim_ty) => {
 667                             let binding = (Def::PrimTy(prim_ty), ty::Visibility::Public,
 668                                            DUMMY_SP, Mark::root()).to_name_binding(self.arenas);
 669                             Ok((binding, Flags::PRELUDE))
 670                         }
 671                         None => Err(Determinacy::Determined)
 672                     }
 673                 }
 674             };
 675
 676             match result {
 677                 Ok((binding, flags)) if sub_namespace_match(binding.macro_kind(), macro_kind) => {
 678                     if !record_used {
 679                         return Ok(binding);
 680                     }
 681
 682                     if let Some((innermost_binding, innermost_flags)) = innermost_result {
 683                         // Found another solution, if the first one was "weak", report an error.
 684                         let (def, innermost_def) = (binding.def(), innermost_binding.def());
 685                         if def != innermost_def {
 686                             let builtin = Def::NonMacroAttr(NonMacroAttrKind::Builtin);
 687                             let derive_helper = Def::NonMacroAttr(NonMacroAttrKind::DeriveHelper);
 688                             let legacy_helper =
 689                                 Def::NonMacroAttr(NonMacroAttrKind::LegacyPluginHelper);
 690
 691                             let ambiguity_error_kind = if is_import {
 692                                 Some(AmbiguityKind::Import)
 693                             } else if is_absolute_path {
 694                                 Some(AmbiguityKind::AbsolutePath)
 695                             } else if innermost_def == builtin || def == builtin {
 696                                 Some(AmbiguityKind::BuiltinAttr)
 697                             } else if innermost_def == derive_helper || def == derive_helper {
 698                                 Some(AmbiguityKind::DeriveHelper)
 699                             } else if innermost_def == legacy_helper &&
 700                                       flags.contains(Flags::PRELUDE) ||
 701                                       def == legacy_helper &&
 702                                       innermost_flags.contains(Flags::PRELUDE) {
 703                                 Some(AmbiguityKind::LegacyHelperVsPrelude)
 704                             } else if innermost_flags.contains(Flags::MACRO_RULES) &&
 705                                       flags.contains(Flags::MODULE) &&
 706                                       !self.disambiguate_legacy_vs_modern(innermost_binding,
 707                                                                           binding) ||
 708                                       flags.contains(Flags::MACRO_RULES) &&
 709                                       innermost_flags.contains(Flags::MODULE) &&
 710                                       !self.disambiguate_legacy_vs_modern(binding,
 711                                                                           innermost_binding) {
 712                                 Some(AmbiguityKind::LegacyVsModern)
 713                             } else if innermost_binding.is_glob_import() {
 714                                 Some(AmbiguityKind::GlobVsOuter)
 715                             } else if innermost_binding.may_appear_after(parent_scope.expansion,
 716                                                                          binding) {
 717                                 Some(AmbiguityKind::MoreExpandedVsOuter)
 718                             } else {
 719                                 None
 720                             };
 721                             if let Some(kind) = ambiguity_error_kind {
 722                                 let misc = |f: Flags| if f.contains(Flags::MISC_SUGGEST_CRATE) {
 723                                     AmbiguityErrorMisc::SuggestCrate
 724                                 } else if f.contains(Flags::MISC_SUGGEST_SELF) {
 725                                     AmbiguityErrorMisc::SuggestSelf
 726                                 } else if f.contains(Flags::MISC_FROM_PRELUDE) {
 727                                     AmbiguityErrorMisc::FromPrelude
 728                                 } else {
 729                                     AmbiguityErrorMisc::None
 730                                 };
 731                                 self.ambiguity_errors.push(AmbiguityError {
 732                                     kind,
 733                                     ident: orig_ident,
 734                                     b1: innermost_binding,
 735                                     b2: binding,
 736                                     misc1: misc(innermost_flags),
 737                                     misc2: misc(flags),
 738                                 });
 739                                 return Ok(innermost_binding);
 740                             }
 741                         }
 742                     } else {
 743                         // Found the first solution.
 744                         innermost_result = Some((binding, flags));
 745                     }
 746                 }
 747                 Ok(..) | Err(Determinacy::Determined) => {}
 748                 Err(Determinacy::Undetermined) => determinacy = Determinacy::Undetermined
 749             }
 750
 751             where_to_resolve = match where_to_resolve {
 752                 WhereToResolve::DeriveHelpers =>
 753                     WhereToResolve::MacroRules(parent_scope.legacy),
 754                 WhereToResolve::MacroRules(legacy_scope) => match legacy_scope {
 755                     LegacyScope::Binding(binding) => WhereToResolve::MacroRules(
 756                         binding.parent_legacy_scope
 757                     ),
 758                     LegacyScope::Invocation(invoc) => WhereToResolve::MacroRules(
 759                         invoc.output_legacy_scope.get().unwrap_or(invoc.parent_legacy_scope.get())
 760                     ),
 761                     LegacyScope::Empty => WhereToResolve::Module(parent_scope.module),
 762                     LegacyScope::Uninitialized => unreachable!(),
 763                 }
 764                 WhereToResolve::CrateRoot if is_import => match ns {
 765                     TypeNS | ValueNS => WhereToResolve::Module(parent_scope.module),
 766                     MacroNS => WhereToResolve::DeriveHelpers,
 767                 }
 768                 WhereToResolve::CrateRoot if is_absolute_path => match ns {
 769                     TypeNS => {
 770                         ident.span.adjust(Mark::root());
 771                         WhereToResolve::ExternPrelude
 772                     }
 773                     ValueNS | MacroNS => break,
 774                 }
 775                 WhereToResolve::CrateRoot => unreachable!(),
 776                 WhereToResolve::Module(module) => {
 777                     match self.hygienic_lexical_parent(module, &mut ident.span) {
 778                         Some(parent_module) => WhereToResolve::Module(parent_module),
 779                         None => {
 780                             use_prelude = !module.no_implicit_prelude;
 781                             match ns {
 782                                 TypeNS => WhereToResolve::ExternPrelude,
 783                                 ValueNS => WhereToResolve::StdLibPrelude,
 784                                 MacroNS => WhereToResolve::MacroUsePrelude,
 785                             }
 786                         }
 787                     }
 788                 }
 789                 WhereToResolve::MacroUsePrelude => WhereToResolve::BuiltinMacros,
 790                 WhereToResolve::BuiltinMacros => WhereToResolve::BuiltinAttrs,
 791                 WhereToResolve::BuiltinAttrs => WhereToResolve::LegacyPluginHelpers,
 792                 WhereToResolve::LegacyPluginHelpers => break, // nowhere else to search
 793                 WhereToResolve::ExternPrelude if is_absolute_path => break,
 794                 WhereToResolve::ExternPrelude => WhereToResolve::ToolPrelude,
 795                 WhereToResolve::ToolPrelude => WhereToResolve::StdLibPrelude,
 796                 WhereToResolve::StdLibPrelude => match ns {
 797                     TypeNS => WhereToResolve::BuiltinTypes,
 798                     ValueNS => break, // nowhere else to search
 799                     MacroNS => unreachable!(),
 800                 }
 801                 WhereToResolve::BuiltinTypes => break, // nowhere else to search
 802             };
 803
 804             continue;
 805         }
 806
 807         // The first found solution was the only one, return it.
 808         if let Some((binding, flags)) = innermost_result {
 809             // We get to here only if there's no ambiguity, in ambiguous cases an error will
 810             // be reported anyway, so there's no reason to report an additional feature error.
 811             // The `binding` can actually be introduced by something other than `--extern`,
 812             // but its `Def` should coincide with a crate passed with `--extern`
 813             // (otherwise there would be ambiguity) and we can skip feature error in this case.
 814             'ok: {
 815                 if !is_import || self.session.features_untracked().uniform_paths {
 816                     break 'ok;
 817                 }
 818                 if ns == TypeNS && use_prelude && self.extern_prelude_get(ident, true).is_some() {
 819                     break 'ok;
 820                 }
 821                 if rust_2015 {
 822                     let root_ident = Ident::new(keywords::PathRoot.name(), orig_ident.span);
 823                     let root_module = self.resolve_crate_root(root_ident);
 824                     if self.resolve_ident_in_module_ext(ModuleOrUniformRoot::Module(root_module),
 825                                                         orig_ident, ns, None, false, path_span)
 826                                                         .is_ok() {
 827                         break 'ok;
 828                     }
 829                 }
 830
 831                 let msg = "imports can only refer to extern crate names \
 832                            passed with `--extern` on stable channel";
 833                 let mut err = feature_err(&self.session.parse_sess, "uniform_paths",
 834                                           ident.span, GateIssue::Language, msg);
 835
 836                 let what = self.binding_description(binding, ident,
 837                                                     flags.contains(Flags::MISC_FROM_PRELUDE));
 838                 let note_msg = format!("this import refers to {what}", what = what);
 839                 let label_span = if binding.span.is_dummy() {
 840                     err.note(&note_msg);
 841                     ident.span
 842                 } else {
 843                     err.span_note(binding.span, &note_msg);
 844                     binding.span
 845                 };
 846                 err.span_label(label_span, "not an extern crate passed with `--extern`");
 847                 err.emit();
 848             }
 849
 850             return Ok(binding);
 851         }
 852
 853         let determinacy = Determinacy::determined(determinacy == Determinacy::Determined || force);
 854         if determinacy == Determinacy::Determined && macro_kind == Some(MacroKind::Attr) {
 855             // For single-segment attributes interpret determinate "no resolution" as a custom
 856             // attribute. (Lexical resolution implies the first segment and attr kind should imply
 857             // the last segment, so we are certainly working with a single-segment attribute here.)
 858             assert!(ns == MacroNS);
 859             let binding = (Def::NonMacroAttr(NonMacroAttrKind::Custom),
 860                            ty::Visibility::Public, ident.span, Mark::root())
 861                            .to_name_binding(self.arenas);
 862             Ok(binding)
 863         } else {
 864             Err(determinacy)
 865         }
 866     }
 867
 868     pub fn finalize_current_module_macro_resolutions(&mut self) {
 869         let module = self.current_module;
 870
 871         let check_consistency = |this: &mut Self, path: &[Segment], span,
 872                                  kind: MacroKind, initial_def, def| {
 873             if let Some(initial_def) = initial_def {
 874                 if def != initial_def && def != Def::Err && this.ambiguity_errors.is_empty() {
 875                     // Make sure compilation does not succeed if preferred macro resolution
 876                     // has changed after the macro had been expanded. In theory all such
 877                     // situations should be reported as ambiguity errors, so this is a bug.
 878                     span_bug!(span, "inconsistent resolution for a macro");
 879                 }
 880             } else {
 881                 // It's possible that the macro was unresolved (indeterminate) and silently
 882                 // expanded into a dummy fragment for recovery during expansion.
 883                 // Now, post-expansion, the resolution may succeed, but we can't change the
 884                 // past and need to report an error.
 885                 // However, non-speculative `resolve_path` can successfully return private items
 886                 // even if speculative `resolve_path` returned nothing previously, so we skip this
 887                 // less informative error if the privacy error is reported elsewhere.
 888                 if this.privacy_errors.is_empty() {
 889                     let msg = format!("cannot determine resolution for the {} `{}`",
 890                                         kind.descr(), Segment::names_to_string(path));
 891                     let msg_note = "import resolution is stuck, try simplifying macro imports";
 892                     this.session.struct_span_err(span, &msg).note(msg_note).emit();
 893                 }
 894             }
 895         };
 896
 897         let macro_resolutions =
 898             mem::replace(&mut *module.multi_segment_macro_resolutions.borrow_mut(), Vec::new());
 899         for (mut path, path_span, kind, parent_scope, initial_def) in macro_resolutions {
 900             // FIXME: Path resolution will ICE if segment IDs present.
 901             for seg in &mut path { seg.id = None; }
 902             match self.resolve_path(&path, Some(MacroNS), &parent_scope,
 903                                     true, path_span, CrateLint::No) {
 904                 PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 => {
 905                     let def = path_res.base_def();
 906                     check_consistency(self, &path, path_span, kind, initial_def, def);
 907                 }
 908                 path_res @ PathResult::NonModule(..) | path_res @  PathResult::Failed(..) => {
 909                     let (span, msg) = if let PathResult::Failed(span, msg, ..) = path_res {
 910                         (span, msg)
 911                     } else {
 912                         (path_span, format!("partially resolved path in {} {}",
 913                                             kind.article(), kind.descr()))
 914                     };
 915                     resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
 916                 }
 917                 PathResult::Module(..) | PathResult::Indeterminate => unreachable!(),
 918             }
 919         }
 920
 921         let macro_resolutions =
 922             mem::replace(&mut *module.single_segment_macro_resolutions.borrow_mut(), Vec::new());
 923         for (ident, kind, parent_scope, initial_binding) in macro_resolutions {
 924             match self.early_resolve_ident_in_lexical_scope(ident, ScopeSet::Macro(kind),
 925                                                             &parent_scope, true, true, ident.span) {
 926                 Ok(binding) => {
 927                     let initial_def = initial_binding.map(|initial_binding| {
 928                         self.record_use(ident, MacroNS, initial_binding, false);
 929                         initial_binding.def_ignoring_ambiguity()
 930                     });
 931                     let def = binding.def_ignoring_ambiguity();
 932                     let seg = Segment::from_ident(ident);
 933                     check_consistency(self, &[seg], ident.span, kind, initial_def, def);
 934                 }
 935                 Err(..) => {
 936                     assert!(initial_binding.is_none());
 937                     let bang = if kind == MacroKind::Bang { "!" } else { "" };
 938                     let msg =
 939                         format!("cannot find {} `{}{}` in this scope", kind.descr(), ident, bang);
 940                     let mut err = self.session.struct_span_err(ident.span, &msg);
 941                     self.suggest_macro_name(&ident.as_str(), kind, &mut err, ident.span);
 942                     err.emit();
 943                 }
 944             }
 945         }
 946
 947         let builtin_attrs = mem::replace(&mut *module.builtin_attrs.borrow_mut(), Vec::new());
 948         for (ident, parent_scope) in builtin_attrs {
 949             let _ = self.early_resolve_ident_in_lexical_scope(
 950                 ident, ScopeSet::Macro(MacroKind::Attr), &parent_scope, true, true, ident.span
 951             );
 952         }
 953     }
 954
 955     fn suggest_macro_name(&mut self, name: &str, kind: MacroKind,
 956                           err: &mut DiagnosticBuilder<'a>, span: Span) {
 957         // First check if this is a locally-defined bang macro.
 958         let suggestion = if let MacroKind::Bang = kind {
 959             find_best_match_for_name(self.macro_names.iter().map(|ident| &ident.name), name, None)
 960         } else {
 961             None
 962         // Then check global macros.
 963         }.or_else(|| {
 964             let names = self.builtin_macros.iter().chain(self.macro_use_prelude.iter())
 965                                                   .filter_map(|(name, binding)| {
 966                 if binding.macro_kind() == Some(kind) { Some(name) } else { None }
 967             });
 968             find_best_match_for_name(names, name, None)
 969         // Then check modules.
 970         }).or_else(|| {
 971             let is_macro = |def| {
 972                 if let Def::Macro(_, def_kind) = def {
 973                     def_kind == kind
 974                 } else {
 975                     false
 976                 }
 977             };
 978             let ident = Ident::new(Symbol::intern(name), span);
 979             self.lookup_typo_candidate(&[Segment::from_ident(ident)], MacroNS, is_macro, span)
 980         });
 981
 982         if let Some(suggestion) = suggestion {
 983             if suggestion != name {
 984                 if let MacroKind::Bang = kind {
 985                     err.span_suggestion_with_applicability(
 986                         span,
 987                         "you could try the macro",
 988                         suggestion.to_string(),
 989                         Applicability::MaybeIncorrect
 990                     );
 991                 } else {
 992                     err.span_suggestion_with_applicability(
 993                         span,
 994                         "try",
 995                         suggestion.to_string(),
 996                         Applicability::MaybeIncorrect
 997                     );
 998                 }
 999             } else {
1000                 err.help("have you added the `#[macro_use]` on the module/import?");
1001             }
1002         }
1003     }
1004
1005     fn collect_def_ids(&mut self,
1006                        mark: Mark,
1007                        invocation: &'a InvocationData<'a>,
1008                        fragment: &AstFragment) {
1009         let Resolver { ref mut invocations, arenas, graph_root, .. } = *self;
1010         let InvocationData { def_index, .. } = *invocation;
1011
1012         let visit_macro_invoc = &mut |invoc: map::MacroInvocationData| {
1013             invocations.entry(invoc.mark).or_insert_with(|| {
1014                 arenas.alloc_invocation_data(InvocationData {
1015                     def_index: invoc.def_index,
1016                     module: Cell::new(graph_root),
1017                     parent_legacy_scope: Cell::new(LegacyScope::Uninitialized),
1018                     output_legacy_scope: Cell::new(None),
1019                 })
1020             });
1021         };
1022
1023         let mut def_collector = DefCollector::new(&mut self.definitions, mark);
1024         def_collector.visit_macro_invoc = Some(visit_macro_invoc);
1025         def_collector.with_parent(def_index, |def_collector| {
1026             fragment.visit_with(def_collector)
1027         });
1028     }
1029
1030     pub fn define_macro(&mut self,
1031                         item: &ast::Item,
1032                         expansion: Mark,
1033                         current_legacy_scope: &mut LegacyScope<'a>) {
1034         self.local_macro_def_scopes.insert(item.id, self.current_module);
1035         let ident = item.ident;
1036         if ident.name == "macro_rules" {
1037             self.session.span_err(item.span, "user-defined macros may not be named `macro_rules`");
1038         }
1039
1040         let def_id = self.definitions.local_def_id(item.id);
1041         let ext = Lrc::new(macro_rules::compile(&self.session.parse_sess,
1042                                                &self.session.features_untracked(),
1043                                                item, hygiene::default_edition()));
1044         self.macro_map.insert(def_id, ext);
1045
1046         let def = match item.node { ast::ItemKind::MacroDef(ref def) => def, _ => unreachable!() };
1047         if def.legacy {
1048             let ident = ident.modern();
1049             self.macro_names.insert(ident);
1050             let def = Def::Macro(def_id, MacroKind::Bang);
1051             let vis = ty::Visibility::Invisible; // Doesn't matter for legacy bindings
1052             let binding = (def, vis, item.span, expansion).to_name_binding(self.arenas);
1053             self.set_binding_parent_module(binding, self.current_module);
1054             let legacy_binding = self.arenas.alloc_legacy_binding(LegacyBinding {
1055                 parent_legacy_scope: *current_legacy_scope, binding, ident
1056             });
1057             *current_legacy_scope = LegacyScope::Binding(legacy_binding);
1058             self.all_macros.insert(ident.name, def);
1059             if attr::contains_name(&item.attrs, "macro_export") {
1060                 let module = self.graph_root;
1061                 let vis = ty::Visibility::Public;
1062                 self.define(module, ident, MacroNS,
1063                             (def, vis, item.span, expansion, IsMacroExport));
1064             } else {
1065                 if !attr::contains_name(&item.attrs, "rustc_doc_only_macro") {
1066                     self.check_reserved_macro_name(ident, MacroNS);
1067                 }
1068                 self.unused_macros.insert(def_id);
1069             }
1070         } else {
1071             let module = self.current_module;
1072             let def = Def::Macro(def_id, MacroKind::Bang);
1073             let vis = self.resolve_visibility(&item.vis);
1074             if vis != ty::Visibility::Public {
1075                 self.unused_macros.insert(def_id);
1076             }
1077             self.define(module, ident, MacroNS, (def, vis, item.span, expansion));
1078         }
1079     }
1080 }