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 ident: Ident,
  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(Mark::root());
 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_root(ident.ctxt);
 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(mark, 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             _ => self.resolve_invoc_to_def(invoc, scope, force)?,
 289         };
 290
 291         self.macro_defs.insert(invoc.expansion_data.mark, def.def_id());
 292         let normal_module_def_id =
 293             self.macro_def_scope(invoc.expansion_data.mark).normal_ancestor_id;
 294         self.definitions.add_macro_def_scope(invoc.expansion_data.mark, normal_module_def_id);
 295
 296         self.unused_macros.remove(&def.def_id());
 297         let ext = self.get_macro(def);
 298         if ext.is_modern() {
 299             invoc.expansion_data.mark.set_modern();
 300         }
 301         Ok(Some(ext))
 302     }
 303
 304     fn resolve_macro(&mut self, scope: Mark, path: &ast::Path, kind: MacroKind, force: bool)
 305                      -> Result<Rc<SyntaxExtension>, Determinacy> {
 306         self.resolve_macro_to_def(scope, path, kind, force).map(|def| {
 307             self.unused_macros.remove(&def.def_id());
 308             self.get_macro(def)
 309         })
 310     }
 311
 312     fn check_unused_macros(&self) {
 313         for did in self.unused_macros.iter() {
 314             let id_span = match *self.macro_map[did] {
 315                 SyntaxExtension::NormalTT(_, isp, _) => isp,
 316                 SyntaxExtension::DeclMacro(.., osp) => osp,
 317                 _ => None,
 318             };
 319             if let Some((id, span)) = id_span {
 320                 let lint = lint::builtin::UNUSED_MACROS;
 321                 let msg = "unused macro definition".to_string();
 322                 self.session.add_lint(lint, id, span, msg);
 323             } else {
 324                 bug!("attempted to create unused macro error, but span not available");
 325             }
 326         }
 327     }
 328 }
 329
 330 impl<'a> Resolver<'a> {
 331     fn resolve_invoc_to_def(&mut self, invoc: &mut Invocation, scope: Mark, force: bool)
 332                             -> Result<Def, Determinacy> {
 333         let (attr, traits, item) = match invoc.kind {
 334             InvocationKind::Attr { ref mut attr, ref traits, ref mut item } => (attr, traits, item),
 335             InvocationKind::Bang { ref mac, .. } => {
 336                 return self.resolve_macro_to_def(scope, &mac.node.path, MacroKind::Bang, force);
 337             }
 338             InvocationKind::Derive { ref path, .. } => {
 339                 return self.resolve_macro_to_def(scope, path, MacroKind::Derive, force);
 340             }
 341         };
 342
 343
 344         let path = attr.as_ref().unwrap().path.clone();
 345         let mut determinacy = Determinacy::Determined;
 346         match self.resolve_macro_to_def(scope, &path, MacroKind::Attr, force) {
 347             Ok(def) => return Ok(def),
 348             Err(Determinacy::Undetermined) => determinacy = Determinacy::Undetermined,
 349             Err(Determinacy::Determined) if force => return Err(Determinacy::Determined),
 350             Err(Determinacy::Determined) => {}
 351         }
 352
 353         let attr_name = match path.segments.len() {
 354             1 => path.segments[0].identifier.name,
 355             _ => return Err(determinacy),
 356         };
 357         for path in traits {
 358             match self.resolve_macro(scope, path, MacroKind::Derive, force) {
 359                 Ok(ext) => if let SyntaxExtension::ProcMacroDerive(_, ref inert_attrs) = *ext {
 360                     if inert_attrs.contains(&attr_name) {
 361                         // FIXME(jseyfried) Avoid `mem::replace` here.
 362                         let dummy_item = placeholder(ExpansionKind::Items, ast::DUMMY_NODE_ID)
 363                             .make_items().pop().unwrap();
 364                         let dummy_item = Annotatable::Item(dummy_item);
 365                         *item = mem::replace(item, dummy_item).map_attrs(|mut attrs| {
 366                             let inert_attr = attr.take().unwrap();
 367                             attr::mark_known(&inert_attr);
 368                             if self.proc_macro_enabled {
 369                                 *attr = find_attr_invoc(&mut attrs);
 370                             }
 371                             attrs.push(inert_attr);
 372                             attrs
 373                         });
 374                     }
 375                     return Err(Determinacy::Undetermined);
 376                 },
 377                 Err(Determinacy::Undetermined) => determinacy = Determinacy::Undetermined,
 378                 Err(Determinacy::Determined) => {}
 379             }
 380         }
 381
 382         Err(determinacy)
 383     }
 384
 385     fn resolve_macro_to_def(&mut self, scope: Mark, path: &ast::Path, kind: MacroKind, force: bool)
 386                             -> Result<Def, Determinacy> {
 387         let ast::Path { ref segments, span } = *path;
 388         if segments.iter().any(|segment| segment.parameters.is_some()) {
 389             let kind =
 390                 if segments.last().unwrap().parameters.is_some() { "macro" } else { "module" };
 391             let msg = format!("type parameters are not allowed on {}s", kind);
 392             self.session.span_err(path.span, &msg);
 393             return Err(Determinacy::Determined);
 394         }
 395
 396         let path: Vec<_> = segments.iter().map(|seg| seg.identifier).collect();
 397         let invocation = self.invocations[&scope];
 398         self.current_module = invocation.module.get();
 399
 400         if path.len() > 1 {
 401             if !self.use_extern_macros && self.gated_errors.insert(span) {
 402                 let msg = "non-ident macro paths are experimental";
 403                 let feature = "use_extern_macros";
 404                 emit_feature_err(&self.session.parse_sess, feature, span, GateIssue::Language, msg);
 405                 self.found_unresolved_macro = true;
 406                 return Err(Determinacy::Determined);
 407             }
 408
 409             let def = match self.resolve_path(&path, Some(MacroNS), false, span) {
 410                 PathResult::NonModule(path_res) => match path_res.base_def() {
 411                     Def::Err => Err(Determinacy::Determined),
 412                     def @ _ => Ok(def),
 413                 },
 414                 PathResult::Module(..) => unreachable!(),
 415                 PathResult::Indeterminate if !force => return Err(Determinacy::Undetermined),
 416                 _ => {
 417                     self.found_unresolved_macro = true;
 418                     Err(Determinacy::Determined)
 419                 },
 420             };
 421             self.current_module.nearest_item_scope().macro_resolutions.borrow_mut()
 422                 .push((path.into_boxed_slice(), span));
 423             return def;
 424         }
 425
 426         let legacy_resolution = self.resolve_legacy_scope(&invocation.legacy_scope, path[0], false);
 427         let result = if let Some(MacroBinding::Legacy(binding)) = legacy_resolution {
 428             Ok(Def::Macro(binding.def_id, MacroKind::Bang))
 429         } else {
 430             match self.resolve_lexical_macro_path_segment(path[0], MacroNS, false, span) {
 431                 Ok(binding) => Ok(binding.binding().def_ignoring_ambiguity()),
 432                 Err(Determinacy::Undetermined) if !force => return Err(Determinacy::Undetermined),
 433                 Err(_) => {
 434                     self.found_unresolved_macro = true;
 435                     Err(Determinacy::Determined)
 436                 }
 437             }
 438         };
 439
 440         self.current_module.nearest_item_scope().legacy_macro_resolutions.borrow_mut()
 441             .push((scope, path[0], span, kind));
 442
 443         result
 444     }
 445
 446     // Resolve the initial segment of a non-global macro path (e.g. `foo` in `foo::bar!();`)
 447     pub fn resolve_lexical_macro_path_segment(&mut self,
 448                                               mut ident: Ident,
 449                                               ns: Namespace,
 450                                               record_used: bool,
 451                                               path_span: Span)
 452                                               -> Result<MacroBinding<'a>, Determinacy> {
 453         ident = ident.modern();
 454         let mut module = Some(self.current_module);
 455         let mut potential_illegal_shadower = Err(Determinacy::Determined);
 456         let determinacy =
 457             if record_used { Determinacy::Determined } else { Determinacy::Undetermined };
 458         loop {
 459             let orig_current_module = self.current_module;
 460             let result = if let Some(module) = module {
 461                 self.current_module = module; // Lexical resolutions can never be a privacy error.
 462                 // Since expanded macros may not shadow the lexical scope and
 463                 // globs may not shadow global macros (both enforced below),
 464                 // we resolve with restricted shadowing (indicated by the penultimate argument).
 465                 self.resolve_ident_in_module_unadjusted(
 466                     module, ident, ns, true, record_used, path_span,
 467                 ).map(MacroBinding::Modern)
 468             } else {
 469                 self.global_macros.get(&ident.name).cloned().ok_or(determinacy)
 470                     .map(MacroBinding::Global)
 471             };
 472             self.current_module = orig_current_module;
 473
 474             match result.map(MacroBinding::binding) {
 475                 Ok(binding) => {
 476                     if !record_used {
 477                         return result;
 478                     }
 479                     if let Ok(MacroBinding::Modern(shadower)) = potential_illegal_shadower {
 480                         if shadower.def() != binding.def() {
 481                             let name = ident.name;
 482                             self.ambiguity_errors.push(AmbiguityError {
 483                                 span: path_span,
 484                                 name: name,
 485                                 b1: shadower,
 486                                 b2: binding,
 487                                 lexical: true,
 488                                 legacy: false,
 489                             });
 490                             return potential_illegal_shadower;
 491                         }
 492                     }
 493                     if binding.expansion != Mark::root() ||
 494                        (binding.is_glob_import() && module.unwrap().def().is_some()) {
 495                         potential_illegal_shadower = result;
 496                     } else {
 497                         return result;
 498                     }
 499                 },
 500                 Err(Determinacy::Undetermined) => return Err(Determinacy::Undetermined),
 501                 Err(Determinacy::Determined) => {}
 502             }
 503
 504             module = match module {
 505                 Some(module) => self.hygienic_lexical_parent(module, &mut ident.ctxt),
 506                 None => return potential_illegal_shadower,
 507             }
 508         }
 509     }
 510
 511     pub fn resolve_legacy_scope(&mut self,
 512                                 mut scope: &'a Cell<LegacyScope<'a>>,
 513                                 ident: Ident,
 514                                 record_used: bool)
 515                                 -> Option<MacroBinding<'a>> {
 516         let ident = ident.modern();
 517         let mut possible_time_travel = None;
 518         let mut relative_depth: u32 = 0;
 519         let mut binding = None;
 520         loop {
 521             match scope.get() {
 522                 LegacyScope::Empty => break,
 523                 LegacyScope::Expansion(invocation) => {
 524                     match invocation.expansion.get() {
 525                         LegacyScope::Invocation(_) => scope.set(invocation.legacy_scope.get()),
 526                         LegacyScope::Empty => {
 527                             if possible_time_travel.is_none() {
 528                                 possible_time_travel = Some(scope);
 529                             }
 530                             scope = &invocation.legacy_scope;
 531                         }
 532                         _ => {
 533                             relative_depth += 1;
 534                             scope = &invocation.expansion;
 535                         }
 536                     }
 537                 }
 538                 LegacyScope::Invocation(invocation) => {
 539                     relative_depth = relative_depth.saturating_sub(1);
 540                     scope = &invocation.legacy_scope;
 541                 }
 542                 LegacyScope::Binding(potential_binding) => {
 543                     if potential_binding.ident == ident {
 544                         if (!self.use_extern_macros || record_used) && relative_depth > 0 {
 545                             self.disallowed_shadowing.push(potential_binding);
 546                         }
 547                         binding = Some(potential_binding);
 548                         break
 549                     }
 550                     scope = &potential_binding.parent;
 551                 }
 552             };
 553         }
 554
 555         let binding = if let Some(binding) = binding {
 556             MacroBinding::Legacy(binding)
 557         } else if let Some(binding) = self.global_macros.get(&ident.name).cloned() {
 558             if !self.use_extern_macros {
 559                 self.record_use(ident, MacroNS, binding, DUMMY_SP);
 560             }
 561             MacroBinding::Global(binding)
 562         } else {
 563             return None;
 564         };
 565
 566         if !self.use_extern_macros {
 567             if let Some(scope) = possible_time_travel {
 568                 // Check for disallowed shadowing later
 569                 self.lexical_macro_resolutions.push((ident, scope));
 570             }
 571         }
 572
 573         Some(binding)
 574     }
 575
 576     pub fn finalize_current_module_macro_resolutions(&mut self) {
 577         let module = self.current_module;
 578         for &(ref path, span) in module.macro_resolutions.borrow().iter() {
 579             match self.resolve_path(path, Some(MacroNS), true, span) {
 580                 PathResult::NonModule(_) => {},
 581                 PathResult::Failed(msg, _) => {
 582                     resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
 583                 }
 584                 _ => unreachable!(),
 585             }
 586         }
 587
 588         for &(mark, ident, span, kind) in module.legacy_macro_resolutions.borrow().iter() {
 589             let legacy_scope = &self.invocations[&mark].legacy_scope;
 590             let legacy_resolution = self.resolve_legacy_scope(legacy_scope, ident, true);
 591             let resolution = self.resolve_lexical_macro_path_segment(ident, MacroNS, true, span);
 592             match (legacy_resolution, resolution) {
 593                 (Some(MacroBinding::Legacy(legacy_binding)), Ok(MacroBinding::Modern(binding))) => {
 594                     let msg1 = format!("`{}` could refer to the macro defined here", ident);
 595                     let msg2 = format!("`{}` could also refer to the macro imported here", ident);
 596                     self.session.struct_span_err(span, &format!("`{}` is ambiguous", ident))
 597                         .span_note(legacy_binding.span, &msg1)
 598                         .span_note(binding.span, &msg2)
 599                         .emit();
 600                 },
 601                 (Some(MacroBinding::Global(binding)), Ok(MacroBinding::Global(_))) => {
 602                     self.record_use(ident, MacroNS, binding, span);
 603                     self.err_if_macro_use_proc_macro(ident.name, span, binding);
 604                 },
 605                 (None, Err(_)) => {
 606                     let msg = match kind {
 607                         MacroKind::Bang =>
 608                             format!("cannot find macro `{}!` in this scope", ident),
 609                         MacroKind::Attr =>
 610                             format!("cannot find attribute macro `{}` in this scope", ident),
 611                         MacroKind::Derive =>
 612                             format!("cannot find derive macro `{}` in this scope", ident),
 613                     };
 614                     let mut err = self.session.struct_span_err(span, &msg);
 615                     self.suggest_macro_name(&ident.name.as_str(), kind, &mut err, span);
 616                     err.emit();
 617                 },
 618                 _ => {},
 619             };
 620         }
 621     }
 622
 623     fn suggest_macro_name(&mut self, name: &str, kind: MacroKind,
 624                           err: &mut DiagnosticBuilder<'a>, span: Span) {
 625         // First check if this is a locally-defined bang macro.
 626         let suggestion = if let MacroKind::Bang = kind {
 627             find_best_match_for_name(self.macro_names.iter().map(|ident| &ident.name), name, None)
 628         } else {
 629             None
 630         // Then check global macros.
 631         }.or_else(|| {
 632             // FIXME: get_macro needs an &mut Resolver, can we do it without cloning?
 633             let global_macros = self.global_macros.clone();
 634             let names = global_macros.iter().filter_map(|(name, binding)| {
 635                 if binding.get_macro(self).kind() == kind {
 636                     Some(name)
 637                 } else {
 638                     None
 639                 }
 640             });
 641             find_best_match_for_name(names, name, None)
 642         // Then check modules.
 643         }).or_else(|| {
 644             if !self.use_extern_macros {
 645                 return None;
 646             }
 647             let is_macro = |def| {
 648                 if let Def::Macro(_, def_kind) = def {
 649                     def_kind == kind
 650                 } else {
 651                     false
 652                 }
 653             };
 654             let ident = Ident::from_str(name);
 655             self.lookup_typo_candidate(&vec![ident], MacroNS, is_macro, span)
 656         });
 657
 658         if let Some(suggestion) = suggestion {
 659             if suggestion != name {
 660                 if let MacroKind::Bang = kind {
 661                     err.help(&format!("did you mean `{}!`?", suggestion));
 662                 } else {
 663                     err.help(&format!("did you mean `{}`?", suggestion));
 664                 }
 665             } else {
 666                 err.help("have you added the `#[macro_use]` on the module/import?");
 667             }
 668         }
 669     }
 670
 671     fn collect_def_ids(&mut self,
 672                        mark: Mark,
 673                        invocation: &'a InvocationData<'a>,
 674                        expansion: &Expansion) {
 675         let Resolver { ref mut invocations, arenas, graph_root, .. } = *self;
 676         let InvocationData { def_index, const_expr, .. } = *invocation;
 677
 678         let visit_macro_invoc = &mut |invoc: map::MacroInvocationData| {
 679             invocations.entry(invoc.mark).or_insert_with(|| {
 680                 arenas.alloc_invocation_data(InvocationData {
 681                     def_index: invoc.def_index,
 682                     const_expr: invoc.const_expr,
 683                     module: Cell::new(graph_root),
 684                     expansion: Cell::new(LegacyScope::Empty),
 685                     legacy_scope: Cell::new(LegacyScope::Empty),
 686                 })
 687             });
 688         };
 689
 690         let mut def_collector = DefCollector::new(&mut self.definitions, mark);
 691         def_collector.visit_macro_invoc = Some(visit_macro_invoc);
 692         def_collector.with_parent(def_index, |def_collector| {
 693             if const_expr {
 694                 if let Expansion::Expr(ref expr) = *expansion {
 695                     def_collector.visit_const_expr(expr);
 696                 }
 697             }
 698             expansion.visit_with(def_collector)
 699         });
 700     }
 701
 702     pub fn define_macro(&mut self,
 703                         item: &ast::Item,
 704                         expansion: Mark,
 705                         legacy_scope: &mut LegacyScope<'a>) {
 706         self.local_macro_def_scopes.insert(item.id, self.current_module);
 707         let ident = item.ident;
 708         if ident.name == "macro_rules" {
 709             self.session.span_err(item.span, "user-defined macros may not be named `macro_rules`");
 710         }
 711
 712         let def_id = self.definitions.local_def_id(item.id);
 713         let ext = Rc::new(macro_rules::compile(&self.session.parse_sess,
 714                                                &self.session.features,
 715                                                item));
 716         self.macro_map.insert(def_id, ext);
 717
 718         let def = match item.node { ast::ItemKind::MacroDef(ref def) => def, _ => unreachable!() };
 719         if def.legacy {
 720             let ident = ident.modern();
 721             self.macro_names.insert(ident);
 722             *legacy_scope = LegacyScope::Binding(self.arenas.alloc_legacy_binding(LegacyBinding {
 723                 parent: Cell::new(*legacy_scope), ident: ident, def_id: def_id, span: item.span,
 724             }));
 725             if attr::contains_name(&item.attrs, "macro_export") {
 726                 let def = Def::Macro(def_id, MacroKind::Bang);
 727                 self.macro_exports
 728                     .push(Export { ident: ident.modern(), def: def, span: item.span });
 729             } else {
 730                 self.unused_macros.insert(def_id);
 731             }
 732         } else {
 733             let module = self.current_module;
 734             let def = Def::Macro(def_id, MacroKind::Bang);
 735             let vis = self.resolve_visibility(&item.vis);
 736             if vis != ty::Visibility::Public {
 737                 self.unused_macros.insert(def_id);
 738             }
 739             self.define(module, ident, MacroNS, (def, vis, item.span, expansion));
 740         }
 741     }
 742
 743     /// Error if `ext` is a Macros 1.1 procedural macro being imported by `#[macro_use]`
 744     fn err_if_macro_use_proc_macro(&mut self, name: Name, use_span: Span,
 745                                    binding: &NameBinding<'a>) {
 746         use self::SyntaxExtension::*;
 747
 748         let krate = binding.def().def_id().krate;
 749
 750         // Plugin-based syntax extensions are exempt from this check
 751         if krate == BUILTIN_MACROS_CRATE { return; }
 752
 753         let ext = binding.get_macro(self);
 754
 755         match *ext {
 756             // If `ext` is a procedural macro, check if we've already warned about it
 757             AttrProcMacro(_) | ProcMacro(_) => if !self.warned_proc_macros.insert(name) { return; },
 758             _ => return,
 759         }
 760
 761         let warn_msg = match *ext {
 762             AttrProcMacro(_) => "attribute procedural macros cannot be \
 763                                  imported with `#[macro_use]`",
 764             ProcMacro(_) => "procedural macros cannot be imported with `#[macro_use]`",
 765             _ => return,
 766         };
 767
 768         let crate_name = self.session.cstore.crate_name(krate);
 769
 770         self.session.struct_span_err(use_span, warn_msg)
 771             .help(&format!("instead, import the procedural macro like any other item: \
 772                              `use {}::{};`", crate_name, name))
 773             .emit();
 774     }
 775
 776     fn gate_legacy_custom_derive(&mut self, name: Symbol, span: Span) {
 777         if !self.session.features.borrow().custom_derive {
 778             let sess = &self.session.parse_sess;
 779             let explain = feature_gate::EXPLAIN_CUSTOM_DERIVE;
 780             emit_feature_err(sess, "custom_derive", span, GateIssue::Language, explain);
 781         } else if !self.is_whitelisted_legacy_custom_derive(name) {
 782             self.session.span_warn(span, feature_gate::EXPLAIN_DEPR_CUSTOM_DERIVE);
 783         }
 784     }
 785 }