src/librustc_resolve/macros.rs

   1 use crate::{AmbiguityError, AmbiguityKind, AmbiguityErrorMisc};
   2 use crate::{CrateLint, Resolver, ResolutionError, ScopeSet, Weak};
   3 use crate::{Module, ModuleKind, NameBinding, NameBindingKind, PathResult, Segment, ToNameBinding};
   4 use crate::{is_known_tool, resolve_error};
   5 use crate::ModuleOrUniformRoot;
   6 use crate::Namespace::*;
   7 use crate::build_reduced_graph::{BuildReducedGraphVisitor, IsMacroExport};
   8 use crate::resolve_imports::ImportResolver;
   9 use rustc::hir::def_id::{DefId, CRATE_DEF_INDEX, DefIndex,
  10                          CrateNum, DefIndexAddressSpace};
  11 use rustc::hir::def::{Def, NonMacroAttrKind};
  12 use rustc::hir::map::{self, DefCollector};
  13 use rustc::{ty, lint};
  14 use rustc::{bug, span_bug};
  15 use syntax::ast::{self, Ident};
  16 use syntax::attr;
  17 use syntax::errors::DiagnosticBuilder;
  18 use syntax::ext::base::{self, Determinacy};
  19 use syntax::ext::base::{MacroKind, SyntaxExtension};
  20 use syntax::ext::expand::{AstFragment, Invocation, InvocationKind};
  21 use syntax::ext::hygiene::{self, Mark};
  22 use syntax::ext::tt::macro_rules;
  23 use syntax::feature_gate::{
  24     feature_err, is_builtin_attr_name, AttributeGate, GateIssue, Stability, BUILTIN_ATTRIBUTES,
  25 };
  26 use syntax::symbol::{Symbol, keywords};
  27 use syntax::visit::Visitor;
  28 use syntax::util::lev_distance::find_best_match_for_name;
  29 use syntax_pos::{Span, DUMMY_SP};
  30 use crate::errors::Applicability;
  31
  32 use std::cell::Cell;
  33 use std::{mem, ptr};
  34 use rustc_data_structures::sync::Lrc;
  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 impl<'a> base::Resolver for Resolver<'a> {
 117     fn next_node_id(&mut self) -> ast::NodeId {
 118         self.session.next_node_id()
 119     }
 120
 121     fn get_module_scope(&mut self, id: ast::NodeId) -> Mark {
 122         let mark = Mark::fresh(Mark::root());
 123         let module = self.module_map[&self.definitions.local_def_id(id)];
 124         self.invocations.insert(mark, self.arenas.alloc_invocation_data(InvocationData {
 125             module: Cell::new(module),
 126             def_index: module.def_id().unwrap().index,
 127             parent_legacy_scope: Cell::new(LegacyScope::Empty),
 128             output_legacy_scope: Cell::new(Some(LegacyScope::Empty)),
 129         }));
 130         mark
 131     }
 132
 133     fn resolve_dollar_crates(&mut self, fragment: &AstFragment) {
 134         struct ResolveDollarCrates<'a, 'b: 'a> {
 135             resolver: &'a mut Resolver<'b>
 136         }
 137         impl<'a> Visitor<'a> for ResolveDollarCrates<'a, '_> {
 138             fn visit_ident(&mut self, ident: Ident) {
 139                 if ident.name == keywords::DollarCrate.name() {
 140                     let name = match self.resolver.resolve_crate_root(ident).kind {
 141                         ModuleKind::Def(_, name) if name != keywords::Invalid.name() => name,
 142                         _ => keywords::Crate.name(),
 143                     };
 144                     ident.span.ctxt().set_dollar_crate_name(name);
 145                 }
 146             }
 147             fn visit_mac(&mut self, _: &ast::Mac) {}
 148         }
 149
 150         fragment.visit_with(&mut ResolveDollarCrates { resolver: self });
 151     }
 152
 153     fn visit_ast_fragment_with_placeholders(&mut self, mark: Mark, fragment: &AstFragment,
 154                                             derives: &[Mark]) {
 155         let invocation = self.invocations[&mark];
 156         self.collect_def_ids(mark, invocation, fragment);
 157
 158         self.current_module = invocation.module.get();
 159         self.current_module.unresolved_invocations.borrow_mut().remove(&mark);
 160         self.current_module.unresolved_invocations.borrow_mut().extend(derives);
 161         self.invocations.extend(derives.iter().map(|&derive| (derive, invocation)));
 162         let mut visitor = BuildReducedGraphVisitor {
 163             resolver: self,
 164             current_legacy_scope: invocation.parent_legacy_scope.get(),
 165             expansion: mark,
 166         };
 167         fragment.visit_with(&mut visitor);
 168         invocation.output_legacy_scope.set(Some(visitor.current_legacy_scope));
 169     }
 170
 171     fn add_builtin(&mut self, ident: ast::Ident, ext: Lrc<SyntaxExtension>) {
 172         let def_id = DefId {
 173             krate: CrateNum::BuiltinMacros,
 174             index: DefIndex::from_array_index(self.macro_map.len(),
 175                                               DefIndexAddressSpace::Low),
 176         };
 177         let kind = ext.kind();
 178         self.macro_map.insert(def_id, ext);
 179         let binding = self.arenas.alloc_name_binding(NameBinding {
 180             kind: NameBindingKind::Def(Def::Macro(def_id, kind), false),
 181             ambiguity: None,
 182             span: DUMMY_SP,
 183             vis: ty::Visibility::Public,
 184             expansion: Mark::root(),
 185         });
 186         if self.builtin_macros.insert(ident.name, binding).is_some() {
 187             self.session.span_err(ident.span,
 188                                   &format!("built-in macro `{}` was already defined", ident));
 189         }
 190     }
 191
 192     fn resolve_imports(&mut self) {
 193         ImportResolver { resolver: self }.resolve_imports()
 194     }
 195
 196     fn resolve_macro_invocation(&mut self, invoc: &Invocation, invoc_id: Mark, force: bool)
 197                                 -> Result<Option<Lrc<SyntaxExtension>>, Determinacy> {
 198         let (path, kind, derives_in_scope, after_derive) = match invoc.kind {
 199             InvocationKind::Attr { attr: None, .. } =>
 200                 return Ok(None),
 201             InvocationKind::Attr { attr: Some(ref attr), ref traits, after_derive, .. } =>
 202                 (&attr.path, MacroKind::Attr, traits.clone(), after_derive),
 203             InvocationKind::Bang { ref mac, .. } =>
 204                 (&mac.node.path, MacroKind::Bang, Vec::new(), false),
 205             InvocationKind::Derive { ref path, .. } =>
 206                 (path, MacroKind::Derive, Vec::new(), false),
 207         };
 208
 209         let parent_scope = self.invoc_parent_scope(invoc_id, derives_in_scope);
 210         let (def, ext) = match self.resolve_macro_to_def(path, kind, &parent_scope, true, force) {
 211             Ok((def, ext)) => (def, ext),
 212             Err(Determinacy::Determined) if kind == MacroKind::Attr => {
 213                 // Replace unresolved attributes with used inert attributes for better recovery.
 214                 return Ok(Some(Lrc::new(SyntaxExtension::NonMacroAttr { mark_used: true })));
 215             }
 216             Err(determinacy) => return Err(determinacy),
 217         };
 218
 219         if let Def::Macro(def_id, _) = def {
 220             if after_derive {
 221                 self.session.span_err(invoc.span(),
 222                                       "macro attributes must be placed before `#[derive]`");
 223             }
 224             self.macro_defs.insert(invoc.expansion_data.mark, def_id);
 225             let normal_module_def_id =
 226                 self.macro_def_scope(invoc.expansion_data.mark).normal_ancestor_id;
 227             self.definitions.add_parent_module_of_macro_def(invoc.expansion_data.mark,
 228                                                             normal_module_def_id);
 229             invoc.expansion_data.mark.set_default_transparency(ext.default_transparency());
 230         }
 231
 232         Ok(Some(ext))
 233     }
 234
 235     fn resolve_macro_path(&mut self, path: &ast::Path, kind: MacroKind, invoc_id: Mark,
 236                           derives_in_scope: Vec<ast::Path>, force: bool)
 237                           -> Result<Lrc<SyntaxExtension>, Determinacy> {
 238         let parent_scope = self.invoc_parent_scope(invoc_id, derives_in_scope);
 239         Ok(self.resolve_macro_to_def(path, kind, &parent_scope, false, force)?.1)
 240     }
 241
 242     fn check_unused_macros(&self) {
 243         for did in self.unused_macros.iter() {
 244             let id_span = match *self.macro_map[did] {
 245                 SyntaxExtension::NormalTT { def_info, .. } |
 246                 SyntaxExtension::DeclMacro { def_info, .. } => def_info,
 247                 _ => None,
 248             };
 249             if let Some((id, span)) = id_span {
 250                 let lint = lint::builtin::UNUSED_MACROS;
 251                 let msg = "unused macro definition";
 252                 self.session.buffer_lint(lint, id, span, msg);
 253             } else {
 254                 bug!("attempted to create unused macro error, but span not available");
 255             }
 256         }
 257     }
 258 }
 259
 260 impl<'a> Resolver<'a> {
 261     pub fn dummy_parent_scope(&self) -> ParentScope<'a> {
 262         self.invoc_parent_scope(Mark::root(), Vec::new())
 263     }
 264
 265     fn invoc_parent_scope(&self, invoc_id: Mark, derives: Vec<ast::Path>) -> ParentScope<'a> {
 266         let invoc = self.invocations[&invoc_id];
 267         ParentScope {
 268             module: invoc.module.get().nearest_item_scope(),
 269             expansion: invoc_id.parent(),
 270             legacy: invoc.parent_legacy_scope.get(),
 271             derives,
 272         }
 273     }
 274
 275     fn resolve_macro_to_def(
 276         &mut self,
 277         path: &ast::Path,
 278         kind: MacroKind,
 279         parent_scope: &ParentScope<'a>,
 280         trace: bool,
 281         force: bool,
 282     ) -> Result<(Def, Lrc<SyntaxExtension>), Determinacy> {
 283         let def = self.resolve_macro_to_def_inner(path, kind, parent_scope, trace, force);
 284
 285         // Report errors and enforce feature gates for the resolved macro.
 286         if def != Err(Determinacy::Undetermined) {
 287             // Do not report duplicated errors on every undetermined resolution.
 288             for segment in &path.segments {
 289                 if let Some(args) = &segment.args {
 290                     self.session.span_err(args.span(), "generic arguments in macro path");
 291                 }
 292             }
 293         }
 294
 295         let def = def?;
 296
 297         match def {
 298             Def::Macro(def_id, macro_kind) => {
 299                 self.unused_macros.remove(&def_id);
 300                 if macro_kind == MacroKind::ProcMacroStub {
 301                     let msg = "can't use a procedural macro from the same crate that defines it";
 302                     self.session.span_err(path.span, msg);
 303                     return Err(Determinacy::Determined);
 304                 }
 305             }
 306             Def::NonMacroAttr(attr_kind) => {
 307                 if kind == MacroKind::Attr {
 308                     let features = self.session.features_untracked();
 309                     if attr_kind == NonMacroAttrKind::Custom {
 310                         assert!(path.segments.len() == 1);
 311                         let name = path.segments[0].ident.as_str();
 312                         if name.starts_with("rustc_") {
 313                             if !features.rustc_attrs {
 314                                 let msg = "unless otherwise specified, attributes with the prefix \
 315                                            `rustc_` are reserved for internal compiler diagnostics";
 316                                 self.report_unknown_attribute(path.span, &name, msg, "rustc_attrs");
 317                             }
 318                         } else if !features.custom_attribute {
 319                             let msg = format!("The attribute `{}` is currently unknown to the \
 320                                                compiler and may have meaning added to it in the \
 321                                                future", path);
 322                             self.report_unknown_attribute(
 323                                 path.span,
 324                                 &name,
 325                                 &msg,
 326                                 "custom_attribute",
 327                             );
 328                         }
 329                     }
 330                 } else {
 331                     // Not only attributes, but anything in macro namespace can result in
 332                     // `Def::NonMacroAttr` definition (e.g., `inline!()`), so we must report
 333                     // an error for those cases.
 334                     let msg = format!("expected a macro, found {}", def.kind_name());
 335                     self.session.span_err(path.span, &msg);
 336                     return Err(Determinacy::Determined);
 337                 }
 338             }
 339             Def::Err => {
 340                 return Err(Determinacy::Determined);
 341             }
 342             _ => panic!("expected `Def::Macro` or `Def::NonMacroAttr`"),
 343         }
 344
 345         Ok((def, self.get_macro(def)))
 346     }
 347
 348     fn report_unknown_attribute(&self, span: Span, name: &str, msg: &str, feature: &str) {
 349         let mut err = feature_err(
 350             &self.session.parse_sess,
 351             feature,
 352             span,
 353             GateIssue::Language,
 354             &msg,
 355         );
 356
 357         let features = self.session.features_untracked();
 358
 359         let attr_candidates = BUILTIN_ATTRIBUTES
 360             .iter()
 361             .filter_map(|(name, _, _, gate)| {
 362                 if name.starts_with("rustc_") && !features.rustc_attrs {
 363                     return None;
 364                 }
 365
 366                 match gate {
 367                     AttributeGate::Gated(Stability::Unstable, ..)
 368                         if self.session.opts.unstable_features.is_nightly_build() =>
 369                     {
 370                         Some(name)
 371                     }
 372                     AttributeGate::Gated(Stability::Deprecated(..), ..) => Some(name),
 373                     AttributeGate::Ungated => Some(name),
 374                     _ => None,
 375                 }
 376             })
 377             .map(|name| Symbol::intern(name))
 378             .chain(
 379                 // Add built-in macro attributes as well.
 380                 self.builtin_macros.iter().filter_map(|(name, binding)| {
 381                     match binding.macro_kind() {
 382                         Some(MacroKind::Attr) => Some(*name),
 383                         _ => None,
 384                     }
 385                 }),
 386             )
 387             .collect::<Vec<_>>();
 388
 389         let lev_suggestion = find_best_match_for_name(attr_candidates.iter(), &name, None);
 390
 391         if let Some(suggestion) = lev_suggestion {
 392             err.span_suggestion(
 393                 span,
 394                 "a built-in attribute with a similar name exists",
 395                 suggestion.to_string(),
 396                 Applicability::MaybeIncorrect,
 397             );
 398         }
 399
 400         err.emit();
 401     }
 402
 403     pub fn resolve_macro_to_def_inner(
 404         &mut self,
 405         path: &ast::Path,
 406         kind: MacroKind,
 407         parent_scope: &ParentScope<'a>,
 408         trace: bool,
 409         force: bool,
 410     ) -> Result<Def, Determinacy> {
 411         let path_span = path.span;
 412         let mut path = Segment::from_path(path);
 413
 414         // Possibly apply the macro helper hack
 415         if kind == MacroKind::Bang && path.len() == 1 &&
 416            path[0].ident.span.ctxt().outer().expn_info()
 417                .map_or(false, |info| info.local_inner_macros) {
 418             let root = Ident::new(keywords::DollarCrate.name(), path[0].ident.span);
 419             path.insert(0, Segment::from_ident(root));
 420         }
 421
 422         if path.len() > 1 {
 423             let def = match self.resolve_path(&path, Some(MacroNS), parent_scope,
 424                                               false, path_span, CrateLint::No) {
 425                 PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 => {
 426                     Ok(path_res.base_def())
 427                 }
 428                 PathResult::Indeterminate if !force => return Err(Determinacy::Undetermined),
 429                 PathResult::NonModule(..) | PathResult::Indeterminate | PathResult::Failed(..) => {
 430                     Err(Determinacy::Determined)
 431                 }
 432                 PathResult::Module(..) => unreachable!(),
 433             };
 434
 435             if trace {
 436                 parent_scope.module.multi_segment_macro_resolutions.borrow_mut()
 437                     .push((path, path_span, kind, parent_scope.clone(), def.ok()));
 438             }
 439
 440             self.prohibit_imported_non_macro_attrs(None, def.ok(), path_span);
 441             def
 442         } else {
 443             let binding = self.early_resolve_ident_in_lexical_scope(
 444                 path[0].ident, ScopeSet::Macro(kind), parent_scope, false, force, path_span
 445             );
 446             if let Err(Determinacy::Undetermined) = binding {
 447                 return Err(Determinacy::Undetermined);
 448             }
 449
 450             if trace {
 451                 parent_scope.module.single_segment_macro_resolutions.borrow_mut()
 452                     .push((path[0].ident, kind, parent_scope.clone(), binding.ok()));
 453             }
 454
 455             let def = binding.map(|binding| binding.def());
 456             self.prohibit_imported_non_macro_attrs(binding.ok(), def.ok(), path_span);
 457             def
 458         }
 459     }
 460
 461     // Resolve an identifier in lexical scope.
 462     // This is a variation of `fn resolve_ident_in_lexical_scope` that can be run during
 463     // expansion and import resolution (perhaps they can be merged in the future).
 464     // The function is used for resolving initial segments of macro paths (e.g., `foo` in
 465     // `foo::bar!(); or `foo!();`) and also for import paths on 2018 edition.
 466     crate fn early_resolve_ident_in_lexical_scope(
 467         &mut self,
 468         orig_ident: Ident,
 469         scope_set: ScopeSet,
 470         parent_scope: &ParentScope<'a>,
 471         record_used: bool,
 472         force: bool,
 473         path_span: Span,
 474     ) -> Result<&'a NameBinding<'a>, Determinacy> {
 475         // General principles:
 476         // 1. Not controlled (user-defined) names should have higher priority than controlled names
 477         //    built into the language or standard library. This way we can add new names into the
 478         //    language or standard library without breaking user code.
 479         // 2. "Closed set" below means new names cannot appear after the current resolution attempt.
 480         // Places to search (in order of decreasing priority):
 481         // (Type NS)
 482         // 1. FIXME: Ribs (type parameters), there's no necessary infrastructure yet
 483         //    (open set, not controlled).
 484         // 2. Names in modules (both normal `mod`ules and blocks), loop through hygienic parents
 485         //    (open, not controlled).
 486         // 3. Extern prelude (closed, not controlled).
 487         // 4. Tool modules (closed, controlled right now, but not in the future).
 488         // 5. Standard library prelude (de-facto closed, controlled).
 489         // 6. Language prelude (closed, controlled).
 490         // (Value NS)
 491         // 1. FIXME: Ribs (local variables), there's no necessary infrastructure yet
 492         //    (open set, not controlled).
 493         // 2. Names in modules (both normal `mod`ules and blocks), loop through hygienic parents
 494         //    (open, not controlled).
 495         // 3. Standard library prelude (de-facto closed, controlled).
 496         // (Macro NS)
 497         // 1-3. Derive helpers (open, not controlled). All ambiguities with other names
 498         //    are currently reported as errors. They should be higher in priority than preludes
 499         //    and probably even names in modules according to the "general principles" above. They
 500         //    also should be subject to restricted shadowing because are effectively produced by
 501         //    derives (you need to resolve the derive first to add helpers into scope), but they
 502         //    should be available before the derive is expanded for compatibility.
 503         //    It's mess in general, so we are being conservative for now.
 504         // 1-3. `macro_rules` (open, not controlled), loop through legacy scopes. Have higher
 505         //    priority than prelude macros, but create ambiguities with macros in modules.
 506         // 1-3. Names in modules (both normal `mod`ules and blocks), loop through hygienic parents
 507         //    (open, not controlled). Have higher priority than prelude macros, but create
 508         //    ambiguities with `macro_rules`.
 509         // 4. `macro_use` prelude (open, the open part is from macro expansions, not controlled).
 510         // 4a. User-defined prelude from macro-use
 511         //    (open, the open part is from macro expansions, not controlled).
 512         // 4b. Standard library prelude is currently implemented as `macro-use` (closed, controlled)
 513         // 5. Language prelude: builtin macros (closed, controlled, except for legacy plugins).
 514         // 6. Language prelude: builtin attributes (closed, controlled).
 515         // 4-6. Legacy plugin helpers (open, not controlled). Similar to derive helpers,
 516         //    but introduced by legacy plugins using `register_attribute`. Priority is somewhere
 517         //    in prelude, not sure where exactly (creates ambiguities with any other prelude names).
 518
 519         enum WhereToResolve<'a> {
 520             DeriveHelpers,
 521             MacroRules(LegacyScope<'a>),
 522             CrateRoot,
 523             Module(Module<'a>),
 524             MacroUsePrelude,
 525             BuiltinMacros,
 526             BuiltinAttrs,
 527             LegacyPluginHelpers,
 528             ExternPrelude,
 529             ToolPrelude,
 530             StdLibPrelude,
 531             BuiltinTypes,
 532         }
 533
 534         bitflags::bitflags! {
 535             struct Flags: u8 {
 536                 const MACRO_RULES        = 1 << 0;
 537                 const MODULE             = 1 << 1;
 538                 const PRELUDE            = 1 << 2;
 539                 const MISC_SUGGEST_CRATE = 1 << 3;
 540                 const MISC_SUGGEST_SELF  = 1 << 4;
 541                 const MISC_FROM_PRELUDE  = 1 << 5;
 542             }
 543         }
 544
 545         assert!(force || !record_used); // `record_used` implies `force`
 546         let mut ident = orig_ident.modern();
 547
 548         // Make sure `self`, `super` etc produce an error when passed to here.
 549         if ident.is_path_segment_keyword() {
 550             return Err(Determinacy::Determined);
 551         }
 552
 553         // This is *the* result, resolution from the scope closest to the resolved identifier.
 554         // However, sometimes this result is "weak" because it comes from a glob import or
 555         // a macro expansion, and in this case it cannot shadow names from outer scopes, e.g.
 556         // mod m { ... } // solution in outer scope
 557         // {
 558         //     use prefix::*; // imports another `m` - innermost solution
 559         //                    // weak, cannot shadow the outer `m`, need to report ambiguity error
 560         //     m::mac!();
 561         // }
 562         // So we have to save the innermost solution and continue searching in outer scopes
 563         // to detect potential ambiguities.
 564         let mut innermost_result: Option<(&NameBinding<'_>, Flags)> = None;
 565
 566         // Go through all the scopes and try to resolve the name.
 567         let rust_2015 = orig_ident.span.rust_2015();
 568         let (ns, macro_kind, is_import, is_absolute_path) = match scope_set {
 569             ScopeSet::Import(ns) => (ns, None, true, false),
 570             ScopeSet::AbsolutePath(ns) => (ns, None, false, true),
 571             ScopeSet::Macro(macro_kind) => (MacroNS, Some(macro_kind), false, false),
 572             ScopeSet::Module => (TypeNS, None, false, false),
 573         };
 574         let mut where_to_resolve = match ns {
 575             _ if is_absolute_path || is_import && rust_2015 => WhereToResolve::CrateRoot,
 576             TypeNS | ValueNS => WhereToResolve::Module(parent_scope.module),
 577             MacroNS => WhereToResolve::DeriveHelpers,
 578         };
 579         let mut use_prelude = !parent_scope.module.no_implicit_prelude;
 580         let mut determinacy = Determinacy::Determined;
 581         loop {
 582             let result = match where_to_resolve {
 583                 WhereToResolve::DeriveHelpers => {
 584                     let mut result = Err(Determinacy::Determined);
 585                     for derive in &parent_scope.derives {
 586                         let parent_scope = ParentScope { derives: Vec::new(), ..*parent_scope };
 587                         match self.resolve_macro_to_def(derive, MacroKind::Derive,
 588                                                         &parent_scope, true, force) {
 589                             Ok((_, ext)) => {
 590                                 if let SyntaxExtension::ProcMacroDerive(_, helpers, _) = &*ext {
 591                                     if helpers.contains(&ident.name) {
 592                                         let binding =
 593                                             (Def::NonMacroAttr(NonMacroAttrKind::DeriveHelper),
 594                                             ty::Visibility::Public, derive.span, Mark::root())
 595                                             .to_name_binding(self.arenas);
 596                                         result = Ok((binding, Flags::empty()));
 597                                         break;
 598                                     }
 599                                 }
 600                             }
 601                             Err(Determinacy::Determined) => {}
 602                             Err(Determinacy::Undetermined) =>
 603                                 result = Err(Determinacy::Undetermined),
 604                         }
 605                     }
 606                     result
 607                 }
 608                 WhereToResolve::MacroRules(legacy_scope) => match legacy_scope {
 609                     LegacyScope::Binding(legacy_binding) if ident == legacy_binding.ident =>
 610                         Ok((legacy_binding.binding, Flags::MACRO_RULES)),
 611                     LegacyScope::Invocation(invoc) if invoc.output_legacy_scope.get().is_none() =>
 612                         Err(Determinacy::Undetermined),
 613                     _ => Err(Determinacy::Determined),
 614                 }
 615                 WhereToResolve::CrateRoot => {
 616                     let root_ident = Ident::new(keywords::PathRoot.name(), orig_ident.span);
 617                     let root_module = self.resolve_crate_root(root_ident);
 618                     let binding = self.resolve_ident_in_module_ext(
 619                         ModuleOrUniformRoot::Module(root_module),
 620                         orig_ident,
 621                         ns,
 622                         None,
 623                         record_used,
 624                         path_span,
 625                     );
 626                     match binding {
 627                         Ok(binding) => Ok((binding, Flags::MODULE | Flags::MISC_SUGGEST_CRATE)),
 628                         Err((Determinacy::Undetermined, Weak::No)) =>
 629                             return Err(Determinacy::determined(force)),
 630                         Err((Determinacy::Undetermined, Weak::Yes)) =>
 631                             Err(Determinacy::Undetermined),
 632                         Err((Determinacy::Determined, _)) => Err(Determinacy::Determined),
 633                     }
 634                 }
 635                 WhereToResolve::Module(module) => {
 636                     let orig_current_module = mem::replace(&mut self.current_module, module);
 637                     let binding = self.resolve_ident_in_module_unadjusted_ext(
 638                         ModuleOrUniformRoot::Module(module),
 639                         ident,
 640                         ns,
 641                         None,
 642                         true,
 643                         record_used,
 644                         path_span,
 645                     );
 646                     self.current_module = orig_current_module;
 647                     match binding {
 648                         Ok(binding) => {
 649                             let misc_flags = if ptr::eq(module, self.graph_root) {
 650                                 Flags::MISC_SUGGEST_CRATE
 651                             } else if module.is_normal() {
 652                                 Flags::MISC_SUGGEST_SELF
 653                             } else {
 654                                 Flags::empty()
 655                             };
 656                             Ok((binding, Flags::MODULE | misc_flags))
 657                         }
 658                         Err((Determinacy::Undetermined, Weak::No)) =>
 659                             return Err(Determinacy::determined(force)),
 660                         Err((Determinacy::Undetermined, Weak::Yes)) =>
 661                             Err(Determinacy::Undetermined),
 662                         Err((Determinacy::Determined, _)) => Err(Determinacy::Determined),
 663                     }
 664                 }
 665                 WhereToResolve::MacroUsePrelude => {
 666                     if use_prelude || rust_2015 {
 667                         match self.macro_use_prelude.get(&ident.name).cloned() {
 668                             Some(binding) =>
 669                                 Ok((binding, Flags::PRELUDE | Flags::MISC_FROM_PRELUDE)),
 670                             None => Err(Determinacy::determined(
 671                                 self.graph_root.unresolved_invocations.borrow().is_empty()
 672                             ))
 673                         }
 674                     } else {
 675                         Err(Determinacy::Determined)
 676                     }
 677                 }
 678                 WhereToResolve::BuiltinMacros => {
 679                     match self.builtin_macros.get(&ident.name).cloned() {
 680                         Some(binding) => Ok((binding, Flags::PRELUDE)),
 681                         None => Err(Determinacy::Determined),
 682                     }
 683                 }
 684                 WhereToResolve::BuiltinAttrs => {
 685                     if is_builtin_attr_name(ident.name) {
 686                         let binding = (Def::NonMacroAttr(NonMacroAttrKind::Builtin),
 687                                        ty::Visibility::Public, DUMMY_SP, Mark::root())
 688                                        .to_name_binding(self.arenas);
 689                         Ok((binding, Flags::PRELUDE))
 690                     } else {
 691                         Err(Determinacy::Determined)
 692                     }
 693                 }
 694                 WhereToResolve::LegacyPluginHelpers => {
 695                     if (use_prelude || rust_2015) &&
 696                        self.session.plugin_attributes.borrow().iter()
 697                                                      .any(|(name, _)| ident.name == &**name) {
 698                         let binding = (Def::NonMacroAttr(NonMacroAttrKind::LegacyPluginHelper),
 699                                        ty::Visibility::Public, DUMMY_SP, Mark::root())
 700                                        .to_name_binding(self.arenas);
 701                         Ok((binding, Flags::PRELUDE))
 702                     } else {
 703                         Err(Determinacy::Determined)
 704                     }
 705                 }
 706                 WhereToResolve::ExternPrelude => {
 707                     if use_prelude || is_absolute_path {
 708                         match self.extern_prelude_get(ident, !record_used) {
 709                             Some(binding) => Ok((binding, Flags::PRELUDE)),
 710                             None => Err(Determinacy::determined(
 711                                 self.graph_root.unresolved_invocations.borrow().is_empty()
 712                             )),
 713                         }
 714                     } else {
 715                         Err(Determinacy::Determined)
 716                     }
 717                 }
 718                 WhereToResolve::ToolPrelude => {
 719                     if use_prelude && is_known_tool(ident.name) {
 720                         let binding = (Def::ToolMod, ty::Visibility::Public,
 721                                        DUMMY_SP, Mark::root()).to_name_binding(self.arenas);
 722                         Ok((binding, Flags::PRELUDE))
 723                     } else {
 724                         Err(Determinacy::Determined)
 725                     }
 726                 }
 727                 WhereToResolve::StdLibPrelude => {
 728                     let mut result = Err(Determinacy::Determined);
 729                     if use_prelude {
 730                         if let Some(prelude) = self.prelude {
 731                             if let Ok(binding) = self.resolve_ident_in_module_unadjusted(
 732                                 ModuleOrUniformRoot::Module(prelude),
 733                                 ident,
 734                                 ns,
 735                                 false,
 736                                 path_span,
 737                             ) {
 738                                 result = Ok((binding, Flags::PRELUDE | Flags::MISC_FROM_PRELUDE));
 739                             }
 740                         }
 741                     }
 742                     result
 743                 }
 744                 WhereToResolve::BuiltinTypes => {
 745                     match self.primitive_type_table.primitive_types.get(&ident.name).cloned() {
 746                         Some(prim_ty) => {
 747                             let binding = (Def::PrimTy(prim_ty), ty::Visibility::Public,
 748                                            DUMMY_SP, Mark::root()).to_name_binding(self.arenas);
 749                             Ok((binding, Flags::PRELUDE))
 750                         }
 751                         None => Err(Determinacy::Determined)
 752                     }
 753                 }
 754             };
 755
 756             match result {
 757                 Ok((binding, flags)) if sub_namespace_match(binding.macro_kind(), macro_kind) => {
 758                     if !record_used {
 759                         return Ok(binding);
 760                     }
 761
 762                     if let Some((innermost_binding, innermost_flags)) = innermost_result {
 763                         // Found another solution, if the first one was "weak", report an error.
 764                         let (def, innermost_def) = (binding.def(), innermost_binding.def());
 765                         if def != innermost_def {
 766                             let builtin = Def::NonMacroAttr(NonMacroAttrKind::Builtin);
 767                             let derive_helper = Def::NonMacroAttr(NonMacroAttrKind::DeriveHelper);
 768                             let legacy_helper =
 769                                 Def::NonMacroAttr(NonMacroAttrKind::LegacyPluginHelper);
 770
 771                             let ambiguity_error_kind = if is_import {
 772                                 Some(AmbiguityKind::Import)
 773                             } else if is_absolute_path {
 774                                 Some(AmbiguityKind::AbsolutePath)
 775                             } else if innermost_def == builtin || def == builtin {
 776                                 Some(AmbiguityKind::BuiltinAttr)
 777                             } else if innermost_def == derive_helper || def == derive_helper {
 778                                 Some(AmbiguityKind::DeriveHelper)
 779                             } else if innermost_def == legacy_helper &&
 780                                       flags.contains(Flags::PRELUDE) ||
 781                                       def == legacy_helper &&
 782                                       innermost_flags.contains(Flags::PRELUDE) {
 783                                 Some(AmbiguityKind::LegacyHelperVsPrelude)
 784                             } else if innermost_flags.contains(Flags::MACRO_RULES) &&
 785                                       flags.contains(Flags::MODULE) &&
 786                                       !self.disambiguate_legacy_vs_modern(innermost_binding,
 787                                                                           binding) ||
 788                                       flags.contains(Flags::MACRO_RULES) &&
 789                                       innermost_flags.contains(Flags::MODULE) &&
 790                                       !self.disambiguate_legacy_vs_modern(binding,
 791                                                                           innermost_binding) {
 792                                 Some(AmbiguityKind::LegacyVsModern)
 793                             } else if innermost_binding.is_glob_import() {
 794                                 Some(AmbiguityKind::GlobVsOuter)
 795                             } else if innermost_binding.may_appear_after(parent_scope.expansion,
 796                                                                          binding) {
 797                                 Some(AmbiguityKind::MoreExpandedVsOuter)
 798                             } else {
 799                                 None
 800                             };
 801                             if let Some(kind) = ambiguity_error_kind {
 802                                 let misc = |f: Flags| if f.contains(Flags::MISC_SUGGEST_CRATE) {
 803                                     AmbiguityErrorMisc::SuggestCrate
 804                                 } else if f.contains(Flags::MISC_SUGGEST_SELF) {
 805                                     AmbiguityErrorMisc::SuggestSelf
 806                                 } else if f.contains(Flags::MISC_FROM_PRELUDE) {
 807                                     AmbiguityErrorMisc::FromPrelude
 808                                 } else {
 809                                     AmbiguityErrorMisc::None
 810                                 };
 811                                 self.ambiguity_errors.push(AmbiguityError {
 812                                     kind,
 813                                     ident: orig_ident,
 814                                     b1: innermost_binding,
 815                                     b2: binding,
 816                                     misc1: misc(innermost_flags),
 817                                     misc2: misc(flags),
 818                                 });
 819                                 return Ok(innermost_binding);
 820                             }
 821                         }
 822                     } else {
 823                         // Found the first solution.
 824                         innermost_result = Some((binding, flags));
 825                     }
 826                 }
 827                 Ok(..) | Err(Determinacy::Determined) => {}
 828                 Err(Determinacy::Undetermined) => determinacy = Determinacy::Undetermined
 829             }
 830
 831             where_to_resolve = match where_to_resolve {
 832                 WhereToResolve::DeriveHelpers =>
 833                     WhereToResolve::MacroRules(parent_scope.legacy),
 834                 WhereToResolve::MacroRules(legacy_scope) => match legacy_scope {
 835                     LegacyScope::Binding(binding) => WhereToResolve::MacroRules(
 836                         binding.parent_legacy_scope
 837                     ),
 838                     LegacyScope::Invocation(invoc) => WhereToResolve::MacroRules(
 839                         invoc.output_legacy_scope.get().unwrap_or(invoc.parent_legacy_scope.get())
 840                     ),
 841                     LegacyScope::Empty => WhereToResolve::Module(parent_scope.module),
 842                     LegacyScope::Uninitialized => unreachable!(),
 843                 }
 844                 WhereToResolve::CrateRoot if is_import => match ns {
 845                     TypeNS | ValueNS => WhereToResolve::Module(parent_scope.module),
 846                     MacroNS => WhereToResolve::DeriveHelpers,
 847                 }
 848                 WhereToResolve::CrateRoot if is_absolute_path => match ns {
 849                     TypeNS => {
 850                         ident.span.adjust(Mark::root());
 851                         WhereToResolve::ExternPrelude
 852                     }
 853                     ValueNS | MacroNS => break,
 854                 }
 855                 WhereToResolve::CrateRoot => unreachable!(),
 856                 WhereToResolve::Module(module) => {
 857                     match self.hygienic_lexical_parent(module, &mut ident.span) {
 858                         Some(parent_module) => WhereToResolve::Module(parent_module),
 859                         None => {
 860                             use_prelude = !module.no_implicit_prelude;
 861                             match ns {
 862                                 TypeNS => WhereToResolve::ExternPrelude,
 863                                 ValueNS => WhereToResolve::StdLibPrelude,
 864                                 MacroNS => WhereToResolve::MacroUsePrelude,
 865                             }
 866                         }
 867                     }
 868                 }
 869                 WhereToResolve::MacroUsePrelude => WhereToResolve::BuiltinMacros,
 870                 WhereToResolve::BuiltinMacros => WhereToResolve::BuiltinAttrs,
 871                 WhereToResolve::BuiltinAttrs => WhereToResolve::LegacyPluginHelpers,
 872                 WhereToResolve::LegacyPluginHelpers => break, // nowhere else to search
 873                 WhereToResolve::ExternPrelude if is_absolute_path => break,
 874                 WhereToResolve::ExternPrelude => WhereToResolve::ToolPrelude,
 875                 WhereToResolve::ToolPrelude => WhereToResolve::StdLibPrelude,
 876                 WhereToResolve::StdLibPrelude => match ns {
 877                     TypeNS => WhereToResolve::BuiltinTypes,
 878                     ValueNS => break, // nowhere else to search
 879                     MacroNS => unreachable!(),
 880                 }
 881                 WhereToResolve::BuiltinTypes => break, // nowhere else to search
 882             };
 883
 884             continue;
 885         }
 886
 887         // The first found solution was the only one, return it.
 888         if let Some((binding, flags)) = innermost_result {
 889             // We get to here only if there's no ambiguity, in ambiguous cases an error will
 890             // be reported anyway, so there's no reason to report an additional feature error.
 891             // The `binding` can actually be introduced by something other than `--extern`,
 892             // but its `Def` should coincide with a crate passed with `--extern`
 893             // (otherwise there would be ambiguity) and we can skip feature error in this case.
 894             'ok: {
 895                 if !is_import || !rust_2015 {
 896                     break 'ok;
 897                 }
 898                 if ns == TypeNS && use_prelude && self.extern_prelude_get(ident, true).is_some() {
 899                     break 'ok;
 900                 }
 901                 let root_ident = Ident::new(keywords::PathRoot.name(), orig_ident.span);
 902                 let root_module = self.resolve_crate_root(root_ident);
 903                 if self.resolve_ident_in_module_ext(ModuleOrUniformRoot::Module(root_module),
 904                                                     orig_ident, ns, None, false, path_span)
 905                                                     .is_ok() {
 906                     break 'ok;
 907                 }
 908
 909                 let msg = "imports can only refer to extern crate names passed with \
 910                            `--extern` in macros originating from 2015 edition";
 911                 let mut err = self.session.struct_span_err(ident.span, msg);
 912                 let what = self.binding_description(binding, ident,
 913                                                     flags.contains(Flags::MISC_FROM_PRELUDE));
 914                 let note_msg = format!("this import refers to {what}", what = what);
 915                 let label_span = if binding.span.is_dummy() {
 916                     err.note(&note_msg);
 917                     ident.span
 918                 } else {
 919                     err.span_note(binding.span, &note_msg);
 920                     binding.span
 921                 };
 922                 err.span_label(label_span, "not an extern crate passed with `--extern`");
 923                 err.emit();
 924             }
 925
 926             return Ok(binding);
 927         }
 928
 929         let determinacy = Determinacy::determined(determinacy == Determinacy::Determined || force);
 930         if determinacy == Determinacy::Determined && macro_kind == Some(MacroKind::Attr) {
 931             // For single-segment attributes interpret determinate "no resolution" as a custom
 932             // attribute. (Lexical resolution implies the first segment and attr kind should imply
 933             // the last segment, so we are certainly working with a single-segment attribute here.)
 934             assert!(ns == MacroNS);
 935             let binding = (Def::NonMacroAttr(NonMacroAttrKind::Custom),
 936                            ty::Visibility::Public, ident.span, Mark::root())
 937                            .to_name_binding(self.arenas);
 938             Ok(binding)
 939         } else {
 940             Err(determinacy)
 941         }
 942     }
 943
 944     pub fn finalize_current_module_macro_resolutions(&mut self) {
 945         let module = self.current_module;
 946
 947         let check_consistency = |this: &mut Self, path: &[Segment], span, kind: MacroKind,
 948                                  initial_def: Option<Def>, def: Def| {
 949             if let Some(initial_def) = initial_def {
 950                 if def != initial_def && def != Def::Err && this.ambiguity_errors.is_empty() {
 951                     // Make sure compilation does not succeed if preferred macro resolution
 952                     // has changed after the macro had been expanded. In theory all such
 953                     // situations should be reported as ambiguity errors, so this is a bug.
 954                     if initial_def == Def::NonMacroAttr(NonMacroAttrKind::Custom) {
 955                         // Yeah, legacy custom attributes are implemented using forced resolution
 956                         // (which is a best effort error recovery tool, basically), so we can't
 957                         // promise their resolution won't change later.
 958                         let msg = format!("inconsistent resolution for a macro: first {}, then {}",
 959                                           initial_def.kind_name(), def.kind_name());
 960                         this.session.span_err(span, &msg);
 961                     } else {
 962                         span_bug!(span, "inconsistent resolution for a macro");
 963                     }
 964                 }
 965             } else {
 966                 // It's possible that the macro was unresolved (indeterminate) and silently
 967                 // expanded into a dummy fragment for recovery during expansion.
 968                 // Now, post-expansion, the resolution may succeed, but we can't change the
 969                 // past and need to report an error.
 970                 // However, non-speculative `resolve_path` can successfully return private items
 971                 // even if speculative `resolve_path` returned nothing previously, so we skip this
 972                 // less informative error if the privacy error is reported elsewhere.
 973                 if this.privacy_errors.is_empty() {
 974                     let msg = format!("cannot determine resolution for the {} `{}`",
 975                                         kind.descr(), Segment::names_to_string(path));
 976                     let msg_note = "import resolution is stuck, try simplifying macro imports";
 977                     this.session.struct_span_err(span, &msg).note(msg_note).emit();
 978                 }
 979             }
 980         };
 981
 982         let macro_resolutions =
 983             mem::replace(&mut *module.multi_segment_macro_resolutions.borrow_mut(), Vec::new());
 984         for (mut path, path_span, kind, parent_scope, initial_def) in macro_resolutions {
 985             // FIXME: Path resolution will ICE if segment IDs present.
 986             for seg in &mut path { seg.id = None; }
 987             match self.resolve_path(&path, Some(MacroNS), &parent_scope,
 988                                     true, path_span, CrateLint::No) {
 989                 PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 => {
 990                     let def = path_res.base_def();
 991                     check_consistency(self, &path, path_span, kind, initial_def, def);
 992                 }
 993                 path_res @ PathResult::NonModule(..) | path_res @ PathResult::Failed(..) => {
 994                     let (span, msg) = if let PathResult::Failed(span, msg, ..) = path_res {
 995                         (span, msg)
 996                     } else {
 997                         (path_span, format!("partially resolved path in {} {}",
 998                                             kind.article(), kind.descr()))
 999                     };
1000                     resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
1001                 }
1002                 PathResult::Module(..) | PathResult::Indeterminate => unreachable!(),
1003             }
1004         }
1005
1006         let macro_resolutions =
1007             mem::replace(&mut *module.single_segment_macro_resolutions.borrow_mut(), Vec::new());
1008         for (ident, kind, parent_scope, initial_binding) in macro_resolutions {
1009             match self.early_resolve_ident_in_lexical_scope(ident, ScopeSet::Macro(kind),
1010                                                             &parent_scope, true, true, ident.span) {
1011                 Ok(binding) => {
1012                     let initial_def = initial_binding.map(|initial_binding| {
1013                         self.record_use(ident, MacroNS, initial_binding, false);
1014                         initial_binding.def()
1015                     });
1016                     let def = binding.def();
1017                     let seg = Segment::from_ident(ident);
1018                     check_consistency(self, &[seg], ident.span, kind, initial_def, def);
1019                 }
1020                 Err(..) => {
1021                     assert!(initial_binding.is_none());
1022                     let bang = if kind == MacroKind::Bang { "!" } else { "" };
1023                     let msg =
1024                         format!("cannot find {} `{}{}` in this scope", kind.descr(), ident, bang);
1025                     let mut err = self.session.struct_span_err(ident.span, &msg);
1026                     self.suggest_macro_name(&ident.as_str(), kind, &mut err, ident.span);
1027                     err.emit();
1028                 }
1029             }
1030         }
1031
1032         let builtin_attrs = mem::replace(&mut *module.builtin_attrs.borrow_mut(), Vec::new());
1033         for (ident, parent_scope) in builtin_attrs {
1034             let _ = self.early_resolve_ident_in_lexical_scope(
1035                 ident, ScopeSet::Macro(MacroKind::Attr), &parent_scope, true, true, ident.span
1036             );
1037         }
1038     }
1039
1040     fn prohibit_imported_non_macro_attrs(&self, binding: Option<&'a NameBinding<'a>>,
1041                                          def: Option<Def>, span: Span) {
1042         if let Some(Def::NonMacroAttr(kind)) = def {
1043             if kind != NonMacroAttrKind::Tool && binding.map_or(true, |b| b.is_import()) {
1044                 let msg = format!("cannot use a {} through an import", kind.descr());
1045                 let mut err = self.session.struct_span_err(span, &msg);
1046                 if let Some(binding) = binding {
1047                     err.span_note(binding.span, &format!("the {} imported here", kind.descr()));
1048                 }
1049                 err.emit();
1050             }
1051         }
1052     }
1053
1054     fn suggest_macro_name(&mut self, name: &str, kind: MacroKind,
1055                           err: &mut DiagnosticBuilder<'a>, span: Span) {
1056         // First check if this is a locally-defined bang macro.
1057         let suggestion = if let MacroKind::Bang = kind {
1058             find_best_match_for_name(self.macro_names.iter().map(|ident| &ident.name), name, None)
1059         } else {
1060             None
1061         // Then check global macros.
1062         }.or_else(|| {
1063             let names = self.builtin_macros.iter().chain(self.macro_use_prelude.iter())
1064                                                   .filter_map(|(name, binding)| {
1065                 if binding.macro_kind() == Some(kind) { Some(name) } else { None }
1066             });
1067             find_best_match_for_name(names, name, None)
1068         // Then check modules.
1069         }).or_else(|| {
1070             let is_macro = |def| {
1071                 if let Def::Macro(_, def_kind) = def {
1072                     def_kind == kind
1073                 } else {
1074                     false
1075                 }
1076             };
1077             let ident = Ident::new(Symbol::intern(name), span);
1078             self.lookup_typo_candidate(&[Segment::from_ident(ident)], MacroNS, is_macro, span)
1079                 .map(|suggestion| suggestion.candidate)
1080         });
1081
1082         if let Some(suggestion) = suggestion {
1083             if suggestion != name {
1084                 if let MacroKind::Bang = kind {
1085                     err.span_suggestion(
1086                         span,
1087                         "you could try the macro",
1088                         suggestion.to_string(),
1089                         Applicability::MaybeIncorrect
1090                     );
1091                 } else {
1092                     err.span_suggestion(
1093                         span,
1094                         "try",
1095                         suggestion.to_string(),
1096                         Applicability::MaybeIncorrect
1097                     );
1098                 }
1099             } else {
1100                 err.help("have you added the `#[macro_use]` on the module/import?");
1101             }
1102         }
1103     }
1104
1105     fn collect_def_ids(&mut self,
1106                        mark: Mark,
1107                        invocation: &'a InvocationData<'a>,
1108                        fragment: &AstFragment) {
1109         let Resolver { ref mut invocations, arenas, graph_root, .. } = *self;
1110         let InvocationData { def_index, .. } = *invocation;
1111
1112         let visit_macro_invoc = &mut |invoc: map::MacroInvocationData| {
1113             invocations.entry(invoc.mark).or_insert_with(|| {
1114                 arenas.alloc_invocation_data(InvocationData {
1115                     def_index: invoc.def_index,
1116                     module: Cell::new(graph_root),
1117                     parent_legacy_scope: Cell::new(LegacyScope::Uninitialized),
1118                     output_legacy_scope: Cell::new(None),
1119                 })
1120             });
1121         };
1122
1123         let mut def_collector = DefCollector::new(&mut self.definitions, mark);
1124         def_collector.visit_macro_invoc = Some(visit_macro_invoc);
1125         def_collector.with_parent(def_index, |def_collector| {
1126             fragment.visit_with(def_collector)
1127         });
1128     }
1129
1130     pub fn define_macro(&mut self,
1131                         item: &ast::Item,
1132                         expansion: Mark,
1133                         current_legacy_scope: &mut LegacyScope<'a>) {
1134         self.local_macro_def_scopes.insert(item.id, self.current_module);
1135         let ident = item.ident;
1136         if ident.name == "macro_rules" {
1137             self.session.span_err(item.span, "user-defined macros may not be named `macro_rules`");
1138         }
1139
1140         let def_id = self.definitions.local_def_id(item.id);
1141         let ext = Lrc::new(macro_rules::compile(&self.session.parse_sess,
1142                                                &self.session.features_untracked(),
1143                                                item, hygiene::default_edition()));
1144         self.macro_map.insert(def_id, ext);
1145
1146         let def = match item.node { ast::ItemKind::MacroDef(ref def) => def, _ => unreachable!() };
1147         if def.legacy {
1148             let ident = ident.modern();
1149             self.macro_names.insert(ident);
1150             let def = Def::Macro(def_id, MacroKind::Bang);
1151             let is_macro_export = attr::contains_name(&item.attrs, "macro_export");
1152             let vis = if is_macro_export {
1153                 ty::Visibility::Public
1154             } else {
1155                 ty::Visibility::Restricted(DefId::local(CRATE_DEF_INDEX))
1156             };
1157             let binding = (def, vis, item.span, expansion).to_name_binding(self.arenas);
1158             self.set_binding_parent_module(binding, self.current_module);
1159             let legacy_binding = self.arenas.alloc_legacy_binding(LegacyBinding {
1160                 parent_legacy_scope: *current_legacy_scope, binding, ident
1161             });
1162             *current_legacy_scope = LegacyScope::Binding(legacy_binding);
1163             self.all_macros.insert(ident.name, def);
1164             if is_macro_export {
1165                 let module = self.graph_root;
1166                 self.define(module, ident, MacroNS,
1167                             (def, vis, item.span, expansion, IsMacroExport));
1168             } else {
1169                 if !attr::contains_name(&item.attrs, "rustc_doc_only_macro") {
1170                     self.check_reserved_macro_name(ident, MacroNS);
1171                 }
1172                 self.unused_macros.insert(def_id);
1173             }
1174         } else {
1175             let module = self.current_module;
1176             let def = Def::Macro(def_id, MacroKind::Bang);
1177             let vis = self.resolve_visibility(&item.vis);
1178             if vis != ty::Visibility::Public {
1179                 self.unused_macros.insert(def_id);
1180             }
1181             self.define(module, ident, MacroNS, (def, vis, item.span, expansion));
1182         }
1183     }
1184 }