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, Resolver, ResolutionError, resolve_error};
  12 use {Module, ModuleKind, NameBinding, NameBindingKind, PathResult};
  13 use Namespace::{self, MacroNS};
  14 use build_reduced_graph::BuildReducedGraphVisitor;
  15 use resolve_imports::ImportResolver;
  16 use rustc::hir::def_id::{DefId, BUILTIN_MACROS_CRATE, CRATE_DEF_INDEX, DefIndex};
  17 use rustc::hir::def::{Def, Export};
  18 use rustc::hir::map::{self, DefCollector};
  19 use rustc::{ty, lint};
  20 use syntax::ast::{self, Name, Ident};
  21 use syntax::attr::{self, HasAttrs};
  22 use syntax::errors::DiagnosticBuilder;
  23 use syntax::ext::base::{self, Annotatable, Determinacy, MultiModifier, MultiDecorator};
  24 use syntax::ext::base::{MacroKind, SyntaxExtension, Resolver as SyntaxResolver};
  25 use syntax::ext::expand::{Expansion, ExpansionKind, Invocation, InvocationKind, find_attr_invoc};
  26 use syntax::ext::hygiene::Mark;
  27 use syntax::ext::placeholders::placeholder;
  28 use syntax::ext::tt::macro_rules;
  29 use syntax::feature_gate::{self, emit_feature_err, GateIssue};
  30 use syntax::fold::{self, Folder};
  31 use syntax::parse::parser::PathStyle;
  32 use syntax::parse::token::{self, Token};
  33 use syntax::ptr::P;
  34 use syntax::symbol::{Symbol, keywords};
  35 use syntax::tokenstream::{TokenStream, TokenTree, Delimited};
  36 use syntax::util::lev_distance::find_best_match_for_name;
  37 use syntax_pos::{Span, DUMMY_SP};
  38
  39 use std::cell::Cell;
  40 use std::mem;
  41 use std::rc::Rc;
  42
  43 #[derive(Clone)]
  44 pub struct InvocationData<'a> {
  45     pub module: Cell<Module<'a>>,
  46     pub def_index: DefIndex,
  47     // True if this expansion is in a `const_expr` position, for example `[u32; m!()]`.
  48     // c.f. `DefCollector::visit_const_expr`.
  49     pub const_expr: bool,
  50     // The scope in which the invocation path is resolved.
  51     pub legacy_scope: Cell<LegacyScope<'a>>,
  52     // The smallest scope that includes this invocation's expansion,
  53     // or `Empty` if this invocation has not been expanded yet.
  54     pub expansion: Cell<LegacyScope<'a>>,
  55 }
  56
  57 impl<'a> InvocationData<'a> {
  58     pub fn root(graph_root: Module<'a>) -> Self {
  59         InvocationData {
  60             module: Cell::new(graph_root),
  61             def_index: CRATE_DEF_INDEX,
  62             const_expr: false,
  63             legacy_scope: Cell::new(LegacyScope::Empty),
  64             expansion: Cell::new(LegacyScope::Empty),
  65         }
  66     }
  67 }
  68
  69 #[derive(Copy, Clone)]
  70 pub enum LegacyScope<'a> {
  71     Empty,
  72     Invocation(&'a InvocationData<'a>), // The scope of the invocation, not including its expansion
  73     Expansion(&'a InvocationData<'a>), // The scope of the invocation, including its expansion
  74     Binding(&'a LegacyBinding<'a>),
  75 }
  76
  77 pub struct LegacyBinding<'a> {
  78     pub parent: Cell<LegacyScope<'a>>,
  79     pub name: ast::Name,
  80     def_id: DefId,
  81     pub span: Span,
  82 }
  83
  84 #[derive(Copy, Clone)]
  85 pub enum MacroBinding<'a> {
  86     Legacy(&'a LegacyBinding<'a>),
  87     Global(&'a NameBinding<'a>),
  88     Modern(&'a NameBinding<'a>),
  89 }
  90
  91 impl<'a> MacroBinding<'a> {
  92     pub fn span(self) -> Span {
  93         match self {
  94             MacroBinding::Legacy(binding) => binding.span,
  95             MacroBinding::Global(binding) | MacroBinding::Modern(binding) => binding.span,
  96         }
  97     }
  98
  99     pub fn binding(self) -> &'a NameBinding<'a> {
 100         match self {
 101             MacroBinding::Global(binding) | MacroBinding::Modern(binding) => binding,
 102             MacroBinding::Legacy(_) => panic!("unexpected MacroBinding::Legacy"),
 103         }
 104     }
 105 }
 106
 107 impl<'a> base::Resolver for Resolver<'a> {
 108     fn next_node_id(&mut self) -> ast::NodeId {
 109         self.session.next_node_id()
 110     }
 111
 112     fn get_module_scope(&mut self, id: ast::NodeId) -> Mark {
 113         let mark = Mark::fresh();
 114         let module = self.module_map[&self.definitions.local_def_id(id)];
 115         self.invocations.insert(mark, self.arenas.alloc_invocation_data(InvocationData {
 116             module: Cell::new(module),
 117             def_index: module.def_id().unwrap().index,
 118             const_expr: false,
 119             legacy_scope: Cell::new(LegacyScope::Empty),
 120             expansion: Cell::new(LegacyScope::Empty),
 121         }));
 122         mark
 123     }
 124
 125     fn eliminate_crate_var(&mut self, item: P<ast::Item>) -> P<ast::Item> {
 126         struct EliminateCrateVar<'b, 'a: 'b>(&'b mut Resolver<'a>, Span);
 127
 128         impl<'a, 'b> Folder for EliminateCrateVar<'a, 'b> {
 129             fn fold_path(&mut self, mut path: ast::Path) -> ast::Path {
 130                 let ident = path.segments[0].identifier;
 131                 if ident.name == "$crate" {
 132                     path.segments[0].identifier.name = keywords::CrateRoot.name();
 133                     let module = self.0.resolve_crate_var(ident.ctxt, self.1);
 134                     if !module.is_local() {
 135                         let span = path.segments[0].span;
 136                         path.segments.insert(1, match module.kind {
 137                             ModuleKind::Def(_, name) => ast::PathSegment::from_ident(
 138                                 ast::Ident::with_empty_ctxt(name), span
 139                             ),
 140                             _ => unreachable!(),
 141                         })
 142                     }
 143                 }
 144                 path
 145             }
 146
 147             fn fold_mac(&mut self, mac: ast::Mac) -> ast::Mac {
 148                 fold::noop_fold_mac(mac, self)
 149             }
 150         }
 151
 152         EliminateCrateVar(self, item.span).fold_item(item).expect_one("")
 153     }
 154
 155     fn is_whitelisted_legacy_custom_derive(&self, name: Name) -> bool {
 156         self.whitelisted_legacy_custom_derives.contains(&name)
 157     }
 158
 159     fn visit_expansion(&mut self, mark: Mark, expansion: &Expansion, derives: &[Mark]) {
 160         let invocation = self.invocations[&mark];
 161         self.collect_def_ids(invocation, expansion);
 162
 163         self.current_module = invocation.module.get();
 164         self.current_module.unresolved_invocations.borrow_mut().remove(&mark);
 165         self.current_module.unresolved_invocations.borrow_mut().extend(derives);
 166         for &derive in derives {
 167             self.invocations.insert(derive, invocation);
 168         }
 169         let mut visitor = BuildReducedGraphVisitor {
 170             resolver: self,
 171             legacy_scope: LegacyScope::Invocation(invocation),
 172             expansion: mark,
 173         };
 174         expansion.visit_with(&mut visitor);
 175         invocation.expansion.set(visitor.legacy_scope);
 176     }
 177
 178     fn add_builtin(&mut self, ident: ast::Ident, ext: Rc<SyntaxExtension>) {
 179         let def_id = DefId {
 180             krate: BUILTIN_MACROS_CRATE,
 181             index: DefIndex::new(self.macro_map.len()),
 182         };
 183         let kind = ext.kind();
 184         self.macro_map.insert(def_id, ext);
 185         let binding = self.arenas.alloc_name_binding(NameBinding {
 186             kind: NameBindingKind::Def(Def::Macro(def_id, kind)),
 187             span: DUMMY_SP,
 188             vis: ty::Visibility::Invisible,
 189             expansion: Mark::root(),
 190         });
 191         self.global_macros.insert(ident.name, binding);
 192     }
 193
 194     fn resolve_imports(&mut self) {
 195         ImportResolver { resolver: self }.resolve_imports()
 196     }
 197
 198     // Resolves attribute and derive legacy macros from `#![plugin(..)]`.
 199     fn find_legacy_attr_invoc(&mut self, attrs: &mut Vec<ast::Attribute>)
 200                               -> Option<ast::Attribute> {
 201         for i in 0..attrs.len() {
 202             let name = unwrap_or!(attrs[i].name(), continue);
 203
 204             if self.session.plugin_attributes.borrow().iter()
 205                     .any(|&(ref attr_nm, _)| name == &**attr_nm) {
 206                 attr::mark_known(&attrs[i]);
 207             }
 208
 209             match self.global_macros.get(&name).cloned() {
 210                 Some(binding) => match *binding.get_macro(self) {
 211                     MultiModifier(..) | MultiDecorator(..) | SyntaxExtension::AttrProcMacro(..) => {
 212                         return Some(attrs.remove(i))
 213                     }
 214                     _ => {}
 215                 },
 216                 None => {}
 217             }
 218         }
 219
 220         // Check for legacy derives
 221         for i in 0..attrs.len() {
 222             let name = unwrap_or!(attrs[i].name(), continue);
 223
 224             if name == "derive" {
 225                 let result = attrs[i].parse_list(&self.session.parse_sess, |parser| {
 226                     parser.parse_path_allowing_meta(PathStyle::Mod)
 227                 });
 228
 229                 let mut traits = match result {
 230                     Ok(traits) => traits,
 231                     Err(mut e) => {
 232                         e.cancel();
 233                         continue
 234                     }
 235                 };
 236
 237                 for j in 0..traits.len() {
 238                     if traits[j].segments.len() > 1 {
 239                         continue
 240                     }
 241                     let trait_name = traits[j].segments[0].identifier.name;
 242                     let legacy_name = Symbol::intern(&format!("derive_{}", trait_name));
 243                     if !self.global_macros.contains_key(&legacy_name) {
 244                         continue
 245                     }
 246                     let span = traits.remove(j).span;
 247                     self.gate_legacy_custom_derive(legacy_name, span);
 248                     if traits.is_empty() {
 249                         attrs.remove(i);
 250                     } else {
 251                         let mut tokens = Vec::new();
 252                         for (j, path) in traits.iter().enumerate() {
 253                             if j > 0 {
 254                                 tokens.push(TokenTree::Token(attrs[i].span, Token::Comma).into());
 255                             }
 256                             for (k, segment) in path.segments.iter().enumerate() {
 257                                 if k > 0 {
 258                                     tokens.push(TokenTree::Token(path.span, Token::ModSep).into());
 259                                 }
 260                                 let tok = Token::Ident(segment.identifier);
 261                                 tokens.push(TokenTree::Token(path.span, tok).into());
 262                             }
 263                         }
 264                         attrs[i].tokens = TokenTree::Delimited(attrs[i].span, Delimited {
 265                             delim: token::Paren,
 266                             tts: TokenStream::concat(tokens).into(),
 267                         }).into();
 268                     }
 269                     return Some(ast::Attribute {
 270                         path: ast::Path::from_ident(span, Ident::with_empty_ctxt(legacy_name)),
 271                         tokens: TokenStream::empty(),
 272                         id: attr::mk_attr_id(),
 273                         style: ast::AttrStyle::Outer,
 274                         is_sugared_doc: false,
 275                         span: span,
 276                     });
 277                 }
 278             }
 279         }
 280
 281         None
 282     }
 283
 284     fn resolve_invoc(&mut self, invoc: &mut Invocation, scope: Mark, force: bool)
 285                      -> Result<Option<Rc<SyntaxExtension>>, Determinacy> {
 286         let def = match invoc.kind {
 287             InvocationKind::Attr { attr: None, .. } => return Ok(None),
 288             _ => match self.resolve_invoc_to_def(invoc, scope, force) {
 289                 Ok(def) => def,
 290                 Err(determinacy) => return Err(determinacy),
 291             },
 292         };
 293         self.macro_defs.insert(invoc.expansion_data.mark, def.def_id());
 294         self.unused_macros.remove(&def.def_id());
 295         Ok(Some(self.get_macro(def)))
 296     }
 297
 298     fn resolve_macro(&mut self, scope: Mark, path: &ast::Path, kind: MacroKind, force: bool)
 299                      -> Result<Rc<SyntaxExtension>, Determinacy> {
 300         self.resolve_macro_to_def(scope, path, kind, force).map(|def| {
 301             self.unused_macros.remove(&def.def_id());
 302             self.get_macro(def)
 303         })
 304     }
 305
 306     fn check_unused_macros(&self) {
 307         for did in self.unused_macros.iter() {
 308             let id_span = match *self.macro_map[did] {
 309                 SyntaxExtension::NormalTT(_, isp, _) => isp,
 310                 _ => None,
 311             };
 312             if let Some((id, span)) = id_span {
 313                 let lint = lint::builtin::UNUSED_MACROS;
 314                 let msg = "unused macro definition".to_string();
 315                 self.session.add_lint(lint, id, span, msg);
 316             } else {
 317                 bug!("attempted to create unused macro error, but span not available");
 318             }
 319         }
 320     }
 321 }
 322
 323 impl<'a> Resolver<'a> {
 324     fn resolve_invoc_to_def(&mut self, invoc: &mut Invocation, scope: Mark, force: bool)
 325                             -> Result<Def, Determinacy> {
 326         let (attr, traits, item) = match invoc.kind {
 327             InvocationKind::Attr { ref mut attr, ref traits, ref mut item } => (attr, traits, item),
 328             InvocationKind::Bang { ref mac, .. } => {
 329                 return self.resolve_macro_to_def(scope, &mac.node.path, MacroKind::Bang, force);
 330             }
 331             InvocationKind::Derive { ref path, .. } => {
 332                 return self.resolve_macro_to_def(scope, path, MacroKind::Derive, force);
 333             }
 334         };
 335
 336
 337         let path = attr.as_ref().unwrap().path.clone();
 338         let mut determinacy = Determinacy::Determined;
 339         match self.resolve_macro_to_def(scope, &path, MacroKind::Attr, force) {
 340             Ok(def) => return Ok(def),
 341             Err(Determinacy::Undetermined) => determinacy = Determinacy::Undetermined,
 342             Err(Determinacy::Determined) if force => return Err(Determinacy::Determined),
 343             Err(Determinacy::Determined) => {}
 344         }
 345
 346         let attr_name = match path.segments.len() {
 347             1 => path.segments[0].identifier.name,
 348             _ => return Err(determinacy),
 349         };
 350         for path in traits {
 351             match self.resolve_macro(scope, path, MacroKind::Derive, force) {
 352                 Ok(ext) => if let SyntaxExtension::ProcMacroDerive(_, ref inert_attrs) = *ext {
 353                     if inert_attrs.contains(&attr_name) {
 354                         // FIXME(jseyfried) Avoid `mem::replace` here.
 355                         let dummy_item = placeholder(ExpansionKind::Items, ast::DUMMY_NODE_ID)
 356                             .make_items().pop().unwrap();
 357                         let dummy_item = Annotatable::Item(dummy_item);
 358                         *item = mem::replace(item, dummy_item).map_attrs(|mut attrs| {
 359                             let inert_attr = attr.take().unwrap();
 360                             attr::mark_known(&inert_attr);
 361                             if self.proc_macro_enabled {
 362                                 *attr = find_attr_invoc(&mut attrs);
 363                             }
 364                             attrs.push(inert_attr);
 365                             attrs
 366                         });
 367                     }
 368                     return Err(Determinacy::Undetermined);
 369                 },
 370                 Err(Determinacy::Undetermined) => determinacy = Determinacy::Undetermined,
 371                 Err(Determinacy::Determined) => {}
 372             }
 373         }
 374
 375         Err(determinacy)
 376     }
 377
 378     fn resolve_macro_to_def(&mut self, scope: Mark, path: &ast::Path, kind: MacroKind, force: bool)
 379                             -> Result<Def, Determinacy> {
 380         let ast::Path { ref segments, span } = *path;
 381         if segments.iter().any(|segment| segment.parameters.is_some()) {
 382             let kind =
 383                 if segments.last().unwrap().parameters.is_some() { "macro" } else { "module" };
 384             let msg = format!("type parameters are not allowed on {}s", kind);
 385             self.session.span_err(path.span, &msg);
 386             return Err(Determinacy::Determined);
 387         }
 388
 389         let path: Vec<_> = segments.iter().map(|seg| seg.identifier).collect();
 390         let invocation = self.invocations[&scope];
 391         self.current_module = invocation.module.get();
 392
 393         if path.len() > 1 {
 394             if !self.use_extern_macros && self.gated_errors.insert(span) {
 395                 let msg = "non-ident macro paths are experimental";
 396                 let feature = "use_extern_macros";
 397                 emit_feature_err(&self.session.parse_sess, feature, span, GateIssue::Language, msg);
 398                 self.found_unresolved_macro = true;
 399                 return Err(Determinacy::Determined);
 400             }
 401
 402             let def = match self.resolve_path(&path, Some(MacroNS), false, span) {
 403                 PathResult::NonModule(path_res) => match path_res.base_def() {
 404                     Def::Err => Err(Determinacy::Determined),
 405                     def @ _ => Ok(def),
 406                 },
 407                 PathResult::Module(..) => unreachable!(),
 408                 PathResult::Indeterminate if !force => return Err(Determinacy::Undetermined),
 409                 _ => {
 410                     self.found_unresolved_macro = true;
 411                     Err(Determinacy::Determined)
 412                 },
 413             };
 414             self.current_module.nearest_item_scope().macro_resolutions.borrow_mut()
 415                 .push((path.into_boxed_slice(), span));
 416             return def;
 417         }
 418
 419         let name = path[0].name;
 420         let legacy_resolution = self.resolve_legacy_scope(&invocation.legacy_scope, name, false);
 421         let result = if let Some(MacroBinding::Legacy(binding)) = legacy_resolution {
 422             Ok(Def::Macro(binding.def_id, MacroKind::Bang))
 423         } else {
 424             match self.resolve_lexical_macro_path_segment(path[0], MacroNS, false, span) {
 425                 Ok(binding) => Ok(binding.binding().def_ignoring_ambiguity()),
 426                 Err(Determinacy::Undetermined) if !force => return Err(Determinacy::Undetermined),
 427                 Err(_) => {
 428                     self.found_unresolved_macro = true;
 429                     Err(Determinacy::Determined)
 430                 }
 431             }
 432         };
 433
 434         self.current_module.nearest_item_scope().legacy_macro_resolutions.borrow_mut()
 435             .push((scope, path[0], span, kind));
 436
 437         result
 438     }
 439
 440     // Resolve the initial segment of a non-global macro path (e.g. `foo` in `foo::bar!();`)
 441     pub fn resolve_lexical_macro_path_segment(&mut self,
 442                                               ident: Ident,
 443                                               ns: Namespace,
 444                                               record_used: bool,
 445                                               path_span: Span)
 446                                               -> Result<MacroBinding<'a>, Determinacy> {
 447         let mut module = Some(self.current_module);
 448         let mut potential_illegal_shadower = Err(Determinacy::Determined);
 449         let determinacy =
 450             if record_used { Determinacy::Determined } else { Determinacy::Undetermined };
 451         loop {
 452             let result = if let Some(module) = module {
 453                 // Since expanded macros may not shadow the lexical scope and
 454                 // globs may not shadow global macros (both enforced below),
 455                 // we resolve with restricted shadowing (indicated by the penultimate argument).
 456                 self.resolve_ident_in_module(module, ident, ns, true, record_used, path_span)
 457                     .map(MacroBinding::Modern)
 458             } else {
 459                 self.global_macros.get(&ident.name).cloned().ok_or(determinacy)
 460                     .map(MacroBinding::Global)
 461             };
 462
 463             match result.map(MacroBinding::binding) {
 464                 Ok(binding) => {
 465                     if !record_used {
 466                         return result;
 467                     }
 468                     if let Ok(MacroBinding::Modern(shadower)) = potential_illegal_shadower {
 469                         if shadower.def() != binding.def() {
 470                             let name = ident.name;
 471                             self.ambiguity_errors.push(AmbiguityError {
 472                                 span: path_span,
 473                                 name: name,
 474                                 b1: shadower,
 475                                 b2: binding,
 476                                 lexical: true,
 477                                 legacy: false,
 478                             });
 479                             return potential_illegal_shadower;
 480                         }
 481                     }
 482                     if binding.expansion != Mark::root() ||
 483                        (binding.is_glob_import() && module.unwrap().def().is_some()) {
 484                         potential_illegal_shadower = result;
 485                     } else {
 486                         return result;
 487                     }
 488                 },
 489                 Err(Determinacy::Undetermined) => return Err(Determinacy::Undetermined),
 490                 Err(Determinacy::Determined) => {}
 491             }
 492
 493             module = match module {
 494                 Some(module) => match module.kind {
 495                     ModuleKind::Block(..) => module.parent,
 496                     ModuleKind::Def(..) => None,
 497                 },
 498                 None => return potential_illegal_shadower,
 499             }
 500         }
 501     }
 502
 503     pub fn resolve_legacy_scope(&mut self,
 504                                 mut scope: &'a Cell<LegacyScope<'a>>,
 505                                 name: Name,
 506                                 record_used: bool)
 507                                 -> Option<MacroBinding<'a>> {
 508         let mut possible_time_travel = None;
 509         let mut relative_depth: u32 = 0;
 510         let mut binding = None;
 511         loop {
 512             match scope.get() {
 513                 LegacyScope::Empty => break,
 514                 LegacyScope::Expansion(invocation) => {
 515                     match invocation.expansion.get() {
 516                         LegacyScope::Invocation(_) => scope.set(invocation.legacy_scope.get()),
 517                         LegacyScope::Empty => {
 518                             if possible_time_travel.is_none() {
 519                                 possible_time_travel = Some(scope);
 520                             }
 521                             scope = &invocation.legacy_scope;
 522                         }
 523                         _ => {
 524                             relative_depth += 1;
 525                             scope = &invocation.expansion;
 526                         }
 527                     }
 528                 }
 529                 LegacyScope::Invocation(invocation) => {
 530                     relative_depth = relative_depth.saturating_sub(1);
 531                     scope = &invocation.legacy_scope;
 532                 }
 533                 LegacyScope::Binding(potential_binding) => {
 534                     if potential_binding.name == name {
 535                         if (!self.use_extern_macros || record_used) && relative_depth > 0 {
 536                             self.disallowed_shadowing.push(potential_binding);
 537                         }
 538                         binding = Some(potential_binding);
 539                         break
 540                     }
 541                     scope = &potential_binding.parent;
 542                 }
 543             };
 544         }
 545
 546         let binding = if let Some(binding) = binding {
 547             MacroBinding::Legacy(binding)
 548         } else if let Some(binding) = self.global_macros.get(&name).cloned() {
 549             if !self.use_extern_macros {
 550                 self.record_use(Ident::with_empty_ctxt(name), MacroNS, binding, DUMMY_SP);
 551             }
 552             MacroBinding::Global(binding)
 553         } else {
 554             return None;
 555         };
 556
 557         if !self.use_extern_macros {
 558             if let Some(scope) = possible_time_travel {
 559                 // Check for disallowed shadowing later
 560                 self.lexical_macro_resolutions.push((name, scope));
 561             }
 562         }
 563
 564         Some(binding)
 565     }
 566
 567     pub fn finalize_current_module_macro_resolutions(&mut self) {
 568         let module = self.current_module;
 569         for &(ref path, span) in module.macro_resolutions.borrow().iter() {
 570             match self.resolve_path(path, Some(MacroNS), true, span) {
 571                 PathResult::NonModule(_) => {},
 572                 PathResult::Failed(msg, _) => {
 573                     resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
 574                 }
 575                 _ => unreachable!(),
 576             }
 577         }
 578
 579         for &(mark, ident, span, kind) in module.legacy_macro_resolutions.borrow().iter() {
 580             let legacy_scope = &self.invocations[&mark].legacy_scope;
 581             let legacy_resolution = self.resolve_legacy_scope(legacy_scope, ident.name, true);
 582             let resolution = self.resolve_lexical_macro_path_segment(ident, MacroNS, true, span);
 583             match (legacy_resolution, resolution) {
 584                 (Some(MacroBinding::Legacy(legacy_binding)), Ok(MacroBinding::Modern(binding))) => {
 585                     let msg1 = format!("`{}` could refer to the macro defined here", ident);
 586                     let msg2 = format!("`{}` could also refer to the macro imported here", ident);
 587                     self.session.struct_span_err(span, &format!("`{}` is ambiguous", ident))
 588                         .span_note(legacy_binding.span, &msg1)
 589                         .span_note(binding.span, &msg2)
 590                         .emit();
 591                 },
 592                 (Some(MacroBinding::Global(binding)), Ok(MacroBinding::Global(_))) => {
 593                     self.record_use(ident, MacroNS, binding, span);
 594                     self.err_if_macro_use_proc_macro(ident.name, span, binding);
 595                 },
 596                 (None, Err(_)) => {
 597                     let msg = match kind {
 598                         MacroKind::Bang =>
 599                             format!("cannot find macro `{}!` in this scope", ident),
 600                         MacroKind::Attr =>
 601                             format!("cannot find attribute macro `{}` in this scope", ident),
 602                         MacroKind::Derive =>
 603                             format!("cannot find derive macro `{}` in this scope", ident),
 604                     };
 605                     let mut err = self.session.struct_span_err(span, &msg);
 606                     self.suggest_macro_name(&ident.name.as_str(), kind, &mut err, span);
 607                     err.emit();
 608                 },
 609                 _ => {},
 610             };
 611         }
 612     }
 613
 614     fn suggest_macro_name(&mut self, name: &str, kind: MacroKind,
 615                           err: &mut DiagnosticBuilder<'a>, span: Span) {
 616         // First check if this is a locally-defined bang macro.
 617         let suggestion = if let MacroKind::Bang = kind {
 618             find_best_match_for_name(self.macro_names.iter(), name, None)
 619         } else {
 620             None
 621         // Then check global macros.
 622         }.or_else(|| {
 623             // FIXME: get_macro needs an &mut Resolver, can we do it without cloning?
 624             let global_macros = self.global_macros.clone();
 625             let names = global_macros.iter().filter_map(|(name, binding)| {
 626                 if binding.get_macro(self).kind() == kind {
 627                     Some(name)
 628                 } else {
 629                     None
 630                 }
 631             });
 632             find_best_match_for_name(names, name, None)
 633         // Then check modules.
 634         }).or_else(|| {
 635             if !self.use_extern_macros {
 636                 return None;
 637             }
 638             let is_macro = |def| {
 639                 if let Def::Macro(_, def_kind) = def {
 640                     def_kind == kind
 641                 } else {
 642                     false
 643                 }
 644             };
 645             let ident = Ident::from_str(name);
 646             self.lookup_typo_candidate(&vec![ident], MacroNS, is_macro, span)
 647         });
 648
 649         if let Some(suggestion) = suggestion {
 650             if suggestion != name {
 651                 if let MacroKind::Bang = kind {
 652                     err.help(&format!("did you mean `{}!`?", suggestion));
 653                 } else {
 654                     err.help(&format!("did you mean `{}`?", suggestion));
 655                 }
 656             } else {
 657                 err.help("have you added the `#[macro_use]` on the module/import?");
 658             }
 659         }
 660     }
 661
 662     fn collect_def_ids(&mut self, invocation: &'a InvocationData<'a>, expansion: &Expansion) {
 663         let Resolver { ref mut invocations, arenas, graph_root, .. } = *self;
 664         let InvocationData { def_index, const_expr, .. } = *invocation;
 665
 666         let visit_macro_invoc = &mut |invoc: map::MacroInvocationData| {
 667             invocations.entry(invoc.mark).or_insert_with(|| {
 668                 arenas.alloc_invocation_data(InvocationData {
 669                     def_index: invoc.def_index,
 670                     const_expr: invoc.const_expr,
 671                     module: Cell::new(graph_root),
 672                     expansion: Cell::new(LegacyScope::Empty),
 673                     legacy_scope: Cell::new(LegacyScope::Empty),
 674                 })
 675             });
 676         };
 677
 678         let mut def_collector = DefCollector::new(&mut self.definitions);
 679         def_collector.visit_macro_invoc = Some(visit_macro_invoc);
 680         def_collector.with_parent(def_index, |def_collector| {
 681             if const_expr {
 682                 if let Expansion::Expr(ref expr) = *expansion {
 683                     def_collector.visit_const_expr(expr);
 684                 }
 685             }
 686             expansion.visit_with(def_collector)
 687         });
 688     }
 689
 690     pub fn define_macro(&mut self,
 691                         item: &ast::Item,
 692                         expansion: Mark,
 693                         legacy_scope: &mut LegacyScope<'a>) {
 694         self.local_macro_def_scopes.insert(item.id, self.current_module);
 695         let ident = item.ident;
 696         if ident.name == "macro_rules" {
 697             self.session.span_err(item.span, "user-defined macros may not be named `macro_rules`");
 698         }
 699
 700         let def_id = self.definitions.local_def_id(item.id);
 701         let ext = Rc::new(macro_rules::compile(&self.session.parse_sess,
 702                                                &self.session.features,
 703                                                item));
 704         self.macro_map.insert(def_id, ext);
 705
 706         let def = match item.node { ast::ItemKind::MacroDef(ref def) => def, _ => unreachable!() };
 707         if def.legacy {
 708             self.macro_names.insert(ident.name);
 709             *legacy_scope = LegacyScope::Binding(self.arenas.alloc_legacy_binding(LegacyBinding {
 710                 parent: Cell::new(*legacy_scope), name: ident.name, def_id: def_id, span: item.span,
 711             }));
 712             if attr::contains_name(&item.attrs, "macro_export") {
 713                 let def = Def::Macro(def_id, MacroKind::Bang);
 714                 self.macro_exports.push(Export { name: ident.name, def: def, span: item.span });
 715             } else {
 716                 self.unused_macros.insert(def_id);
 717             }
 718         } else {
 719             let module = self.current_module;
 720             let def = Def::Macro(def_id, MacroKind::Bang);
 721             let vis = self.resolve_visibility(&item.vis);
 722             self.define(module, ident, MacroNS, (def, vis, item.span, expansion));
 723         }
 724     }
 725
 726     /// Error if `ext` is a Macros 1.1 procedural macro being imported by `#[macro_use]`
 727     fn err_if_macro_use_proc_macro(&mut self, name: Name, use_span: Span,
 728                                    binding: &NameBinding<'a>) {
 729         use self::SyntaxExtension::*;
 730
 731         let krate = binding.def().def_id().krate;
 732
 733         // Plugin-based syntax extensions are exempt from this check
 734         if krate == BUILTIN_MACROS_CRATE { return; }
 735
 736         let ext = binding.get_macro(self);
 737
 738         match *ext {
 739             // If `ext` is a procedural macro, check if we've already warned about it
 740             AttrProcMacro(_) | ProcMacro(_) => if !self.warned_proc_macros.insert(name) { return; },
 741             _ => return,
 742         }
 743
 744         let warn_msg = match *ext {
 745             AttrProcMacro(_) => "attribute procedural macros cannot be \
 746                                  imported with `#[macro_use]`",
 747             ProcMacro(_) => "procedural macros cannot be imported with `#[macro_use]`",
 748             _ => return,
 749         };
 750
 751         let crate_name = self.session.cstore.crate_name(krate);
 752
 753         self.session.struct_span_err(use_span, warn_msg)
 754             .help(&format!("instead, import the procedural macro like any other item: \
 755                              `use {}::{};`", crate_name, name))
 756             .emit();
 757     }
 758
 759     fn gate_legacy_custom_derive(&mut self, name: Symbol, span: Span) {
 760         if !self.session.features.borrow().custom_derive {
 761             let sess = &self.session.parse_sess;
 762             let explain = feature_gate::EXPLAIN_CUSTOM_DERIVE;
 763             emit_feature_err(sess, "custom_derive", span, GateIssue::Language, explain);
 764         } else if !self.is_whitelisted_legacy_custom_derive(name) {
 765             self.session.span_warn(span, feature_gate::EXPLAIN_DEPR_CUSTOM_DERIVE);
 766         }
 767     }
 768 }