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                          DefIndexAddressSpace};
  18 use rustc::hir::def::{Def, Export};
  19 use rustc::hir::map::{self, DefCollector};
  20 use rustc::{ty, lint};
  21 use syntax::ast::{self, Name, Ident};
  22 use syntax::attr::{self, HasAttrs};
  23 use syntax::codemap::respan;
  24 use syntax::errors::DiagnosticBuilder;
  25 use syntax::ext::base::{self, Annotatable, Determinacy, MultiModifier, MultiDecorator};
  26 use syntax::ext::base::{MacroKind, SyntaxExtension, Resolver as SyntaxResolver};
  27 use syntax::ext::expand::{Expansion, ExpansionKind, Invocation, InvocationKind, find_attr_invoc};
  28 use syntax::ext::hygiene::{Mark, MarkKind};
  29 use syntax::ext::placeholders::placeholder;
  30 use syntax::ext::tt::macro_rules;
  31 use syntax::feature_gate::{self, emit_feature_err, GateIssue};
  32 use syntax::fold::{self, Folder};
  33 use syntax::parse::parser::PathStyle;
  34 use syntax::parse::token::{self, Token};
  35 use syntax::ptr::P;
  36 use syntax::symbol::{Symbol, keywords};
  37 use syntax::tokenstream::{TokenStream, TokenTree, Delimited};
  38 use syntax::util::lev_distance::find_best_match_for_name;
  39 use syntax_pos::{Span, DUMMY_SP};
  40
  41 use std::cell::Cell;
  42 use std::mem;
  43 use rustc_data_structures::sync::Lrc;
  44
  45 #[derive(Clone)]
  46 pub struct InvocationData<'a> {
  47     pub module: Cell<Module<'a>>,
  48     pub def_index: DefIndex,
  49     // True if this expansion is in a `const_expr` position, for example `[u32; m!()]`.
  50     // c.f. `DefCollector::visit_const_expr`.
  51     pub const_expr: bool,
  52     // The scope in which the invocation path is resolved.
  53     pub legacy_scope: Cell<LegacyScope<'a>>,
  54     // The smallest scope that includes this invocation's expansion,
  55     // or `Empty` if this invocation has not been expanded yet.
  56     pub expansion: Cell<LegacyScope<'a>>,
  57 }
  58
  59 impl<'a> InvocationData<'a> {
  60     pub fn root(graph_root: Module<'a>) -> Self {
  61         InvocationData {
  62             module: Cell::new(graph_root),
  63             def_index: CRATE_DEF_INDEX,
  64             const_expr: false,
  65             legacy_scope: Cell::new(LegacyScope::Empty),
  66             expansion: Cell::new(LegacyScope::Empty),
  67         }
  68     }
  69 }
  70
  71 #[derive(Copy, Clone)]
  72 pub enum LegacyScope<'a> {
  73     Empty,
  74     Invocation(&'a InvocationData<'a>), // The scope of the invocation, not including its expansion
  75     Expansion(&'a InvocationData<'a>), // The scope of the invocation, including its expansion
  76     Binding(&'a LegacyBinding<'a>),
  77 }
  78
  79 pub struct LegacyBinding<'a> {
  80     pub parent: Cell<LegacyScope<'a>>,
  81     pub ident: Ident,
  82     def_id: DefId,
  83     pub span: Span,
  84 }
  85
  86 pub struct ProcMacError {
  87     crate_name: Symbol,
  88     name: Symbol,
  89     module: ast::NodeId,
  90     use_span: Span,
  91     warn_msg: &'static str,
  92 }
  93
  94 #[derive(Copy, Clone)]
  95 pub enum MacroBinding<'a> {
  96     Legacy(&'a LegacyBinding<'a>),
  97     Global(&'a NameBinding<'a>),
  98     Modern(&'a NameBinding<'a>),
  99 }
 100
 101 impl<'a> MacroBinding<'a> {
 102     pub fn span(self) -> Span {
 103         match self {
 104             MacroBinding::Legacy(binding) => binding.span,
 105             MacroBinding::Global(binding) | MacroBinding::Modern(binding) => binding.span,
 106         }
 107     }
 108
 109     pub fn binding(self) -> &'a NameBinding<'a> {
 110         match self {
 111             MacroBinding::Global(binding) | MacroBinding::Modern(binding) => binding,
 112             MacroBinding::Legacy(_) => panic!("unexpected MacroBinding::Legacy"),
 113         }
 114     }
 115 }
 116
 117 impl<'a> base::Resolver for Resolver<'a> {
 118     fn next_node_id(&mut self) -> ast::NodeId {
 119         self.session.next_node_id()
 120     }
 121
 122     fn get_module_scope(&mut self, id: ast::NodeId) -> Mark {
 123         let mark = Mark::fresh(Mark::root());
 124         let module = self.module_map[&self.definitions.local_def_id(id)];
 125         self.invocations.insert(mark, self.arenas.alloc_invocation_data(InvocationData {
 126             module: Cell::new(module),
 127             def_index: module.def_id().unwrap().index,
 128             const_expr: false,
 129             legacy_scope: Cell::new(LegacyScope::Empty),
 130             expansion: Cell::new(LegacyScope::Empty),
 131         }));
 132         mark
 133     }
 134
 135     fn eliminate_crate_var(&mut self, item: P<ast::Item>) -> P<ast::Item> {
 136         struct EliminateCrateVar<'b, 'a: 'b>(&'b mut Resolver<'a>, Span);
 137
 138         impl<'a, 'b> Folder for EliminateCrateVar<'a, 'b> {
 139             fn fold_path(&mut self, mut path: ast::Path) -> ast::Path {
 140                 let ident = path.segments[0].identifier;
 141                 if ident.name == keywords::DollarCrate.name() {
 142                     path.segments[0].identifier.name = keywords::CrateRoot.name();
 143                     let module = self.0.resolve_crate_root(ident.ctxt, true);
 144                     if !module.is_local() {
 145                         let span = path.segments[0].span;
 146                         path.segments.insert(1, match module.kind {
 147                             ModuleKind::Def(_, name) => ast::PathSegment::from_ident(
 148                                 ast::Ident::with_empty_ctxt(name), span
 149                             ),
 150                             _ => unreachable!(),
 151                         })
 152                     }
 153                 }
 154                 path
 155             }
 156
 157             fn fold_mac(&mut self, mac: ast::Mac) -> ast::Mac {
 158                 fold::noop_fold_mac(mac, self)
 159             }
 160         }
 161
 162         EliminateCrateVar(self, item.span).fold_item(item).expect_one("")
 163     }
 164
 165     fn is_whitelisted_legacy_custom_derive(&self, name: Name) -> bool {
 166         self.whitelisted_legacy_custom_derives.contains(&name)
 167     }
 168
 169     fn visit_expansion(&mut self, mark: Mark, expansion: &Expansion, derives: &[Mark]) {
 170         let invocation = self.invocations[&mark];
 171         self.collect_def_ids(mark, invocation, expansion);
 172
 173         self.current_module = invocation.module.get();
 174         self.current_module.unresolved_invocations.borrow_mut().remove(&mark);
 175         self.current_module.unresolved_invocations.borrow_mut().extend(derives);
 176         for &derive in derives {
 177             self.invocations.insert(derive, invocation);
 178         }
 179         let mut visitor = BuildReducedGraphVisitor {
 180             resolver: self,
 181             legacy_scope: LegacyScope::Invocation(invocation),
 182             expansion: mark,
 183         };
 184         expansion.visit_with(&mut visitor);
 185         invocation.expansion.set(visitor.legacy_scope);
 186     }
 187
 188     fn add_builtin(&mut self, ident: ast::Ident, ext: Lrc<SyntaxExtension>) {
 189         let def_id = DefId {
 190             krate: BUILTIN_MACROS_CRATE,
 191             index: DefIndex::from_array_index(self.macro_map.len(),
 192                                               DefIndexAddressSpace::Low),
 193         };
 194         let kind = ext.kind();
 195         self.macro_map.insert(def_id, ext);
 196         let binding = self.arenas.alloc_name_binding(NameBinding {
 197             kind: NameBindingKind::Def(Def::Macro(def_id, kind)),
 198             span: DUMMY_SP,
 199             vis: ty::Visibility::Invisible,
 200             expansion: Mark::root(),
 201         });
 202         self.global_macros.insert(ident.name, binding);
 203     }
 204
 205     fn resolve_imports(&mut self) {
 206         ImportResolver { resolver: self }.resolve_imports()
 207     }
 208
 209     // Resolves attribute and derive legacy macros from `#![plugin(..)]`.
 210     fn find_legacy_attr_invoc(&mut self, attrs: &mut Vec<ast::Attribute>)
 211                               -> Option<ast::Attribute> {
 212         for i in 0..attrs.len() {
 213             let name = unwrap_or!(attrs[i].name(), continue);
 214
 215             if self.session.plugin_attributes.borrow().iter()
 216                     .any(|&(ref attr_nm, _)| name == &**attr_nm) {
 217                 attr::mark_known(&attrs[i]);
 218             }
 219
 220             match self.global_macros.get(&name).cloned() {
 221                 Some(binding) => match *binding.get_macro(self) {
 222                     MultiModifier(..) | MultiDecorator(..) | SyntaxExtension::AttrProcMacro(..) => {
 223                         return Some(attrs.remove(i))
 224                     }
 225                     _ => {}
 226                 },
 227                 None => {}
 228             }
 229         }
 230
 231         // Check for legacy derives
 232         for i in 0..attrs.len() {
 233             let name = unwrap_or!(attrs[i].name(), continue);
 234
 235             if name == "derive" {
 236                 let result = attrs[i].parse_list(&self.session.parse_sess, |parser| {
 237                     parser.parse_path_allowing_meta(PathStyle::Mod)
 238                 });
 239
 240                 let mut traits = match result {
 241                     Ok(traits) => traits,
 242                     Err(mut e) => {
 243                         e.cancel();
 244                         continue
 245                     }
 246                 };
 247
 248                 for j in 0..traits.len() {
 249                     if traits[j].segments.len() > 1 {
 250                         continue
 251                     }
 252                     let trait_name = traits[j].segments[0].identifier.name;
 253                     let legacy_name = Symbol::intern(&format!("derive_{}", trait_name));
 254                     if !self.global_macros.contains_key(&legacy_name) {
 255                         continue
 256                     }
 257                     let span = traits.remove(j).span;
 258                     self.gate_legacy_custom_derive(legacy_name, span);
 259                     if traits.is_empty() {
 260                         attrs.remove(i);
 261                     } else {
 262                         let mut tokens = Vec::new();
 263                         for (j, path) in traits.iter().enumerate() {
 264                             if j > 0 {
 265                                 tokens.push(TokenTree::Token(attrs[i].span, Token::Comma).into());
 266                             }
 267                             for (k, segment) in path.segments.iter().enumerate() {
 268                                 if k > 0 {
 269                                     tokens.push(TokenTree::Token(path.span, Token::ModSep).into());
 270                                 }
 271                                 let tok = Token::Ident(segment.identifier);
 272                                 tokens.push(TokenTree::Token(path.span, tok).into());
 273                             }
 274                         }
 275                         attrs[i].tokens = TokenTree::Delimited(attrs[i].span, Delimited {
 276                             delim: token::Paren,
 277                             tts: TokenStream::concat(tokens).into(),
 278                         }).into();
 279                     }
 280                     return Some(ast::Attribute {
 281                         path: ast::Path::from_ident(span, Ident::with_empty_ctxt(legacy_name)),
 282                         tokens: TokenStream::empty(),
 283                         id: attr::mk_attr_id(),
 284                         style: ast::AttrStyle::Outer,
 285                         is_sugared_doc: false,
 286                         span,
 287                     });
 288                 }
 289             }
 290         }
 291
 292         None
 293     }
 294
 295     fn resolve_invoc(&mut self, invoc: &mut Invocation, scope: Mark, force: bool)
 296                      -> Result<Option<Lrc<SyntaxExtension>>, Determinacy> {
 297         let def = match invoc.kind {
 298             InvocationKind::Attr { attr: None, .. } => return Ok(None),
 299             _ => self.resolve_invoc_to_def(invoc, scope, force)?,
 300         };
 301         let def_id = def.def_id();
 302
 303         self.macro_defs.insert(invoc.expansion_data.mark, def_id);
 304         let normal_module_def_id =
 305             self.macro_def_scope(invoc.expansion_data.mark).normal_ancestor_id;
 306         self.definitions.add_macro_def_scope(invoc.expansion_data.mark, normal_module_def_id);
 307
 308         self.unused_macros.remove(&def_id);
 309         let ext = self.get_macro(def);
 310         if ext.is_modern() {
 311             invoc.expansion_data.mark.set_kind(MarkKind::Modern);
 312         } else if def_id.krate == BUILTIN_MACROS_CRATE {
 313             invoc.expansion_data.mark.set_kind(MarkKind::Builtin);
 314         }
 315         Ok(Some(ext))
 316     }
 317
 318     fn resolve_macro(&mut self, scope: Mark, path: &ast::Path, kind: MacroKind, force: bool)
 319                      -> Result<Lrc<SyntaxExtension>, Determinacy> {
 320         self.resolve_macro_to_def(scope, path, kind, force).map(|def| {
 321             self.unused_macros.remove(&def.def_id());
 322             self.get_macro(def)
 323         })
 324     }
 325
 326     fn check_unused_macros(&self) {
 327         for did in self.unused_macros.iter() {
 328             let id_span = match *self.macro_map[did] {
 329                 SyntaxExtension::NormalTT { def_info, .. } => def_info,
 330                 SyntaxExtension::DeclMacro(.., osp) => osp,
 331                 _ => None,
 332             };
 333             if let Some((id, span)) = id_span {
 334                 let lint = lint::builtin::UNUSED_MACROS;
 335                 let msg = "unused macro definition";
 336                 self.session.buffer_lint(lint, id, span, msg);
 337             } else {
 338                 bug!("attempted to create unused macro error, but span not available");
 339             }
 340         }
 341     }
 342 }
 343
 344 impl<'a> Resolver<'a> {
 345     fn resolve_invoc_to_def(&mut self, invoc: &mut Invocation, scope: Mark, force: bool)
 346                             -> Result<Def, Determinacy> {
 347         let (attr, traits, item) = match invoc.kind {
 348             InvocationKind::Attr { ref mut attr, ref traits, ref mut item } => (attr, traits, item),
 349             InvocationKind::Bang { ref mac, .. } => {
 350                 return self.resolve_macro_to_def(scope, &mac.node.path, MacroKind::Bang, force);
 351             }
 352             InvocationKind::Derive { ref path, .. } => {
 353                 return self.resolve_macro_to_def(scope, path, MacroKind::Derive, force);
 354             }
 355         };
 356
 357
 358         let path = attr.as_ref().unwrap().path.clone();
 359         let mut determinacy = Determinacy::Determined;
 360         match self.resolve_macro_to_def(scope, &path, MacroKind::Attr, force) {
 361             Ok(def) => return Ok(def),
 362             Err(Determinacy::Undetermined) => determinacy = Determinacy::Undetermined,
 363             Err(Determinacy::Determined) if force => return Err(Determinacy::Determined),
 364             Err(Determinacy::Determined) => {}
 365         }
 366
 367         let attr_name = match path.segments.len() {
 368             1 => path.segments[0].identifier.name,
 369             _ => return Err(determinacy),
 370         };
 371         for path in traits {
 372             match self.resolve_macro(scope, path, MacroKind::Derive, force) {
 373                 Ok(ext) => if let SyntaxExtension::ProcMacroDerive(_, ref inert_attrs) = *ext {
 374                     if inert_attrs.contains(&attr_name) {
 375                         // FIXME(jseyfried) Avoid `mem::replace` here.
 376                         let dummy_item = placeholder(ExpansionKind::Items, ast::DUMMY_NODE_ID)
 377                             .make_items().pop().unwrap();
 378                         let dummy_item = Annotatable::Item(dummy_item);
 379                         *item = mem::replace(item, dummy_item).map_attrs(|mut attrs| {
 380                             let inert_attr = attr.take().unwrap();
 381                             attr::mark_known(&inert_attr);
 382                             if self.proc_macro_enabled {
 383                                 *attr = find_attr_invoc(&mut attrs);
 384                             }
 385                             attrs.push(inert_attr);
 386                             attrs
 387                         });
 388                     }
 389                     return Err(Determinacy::Undetermined);
 390                 },
 391                 Err(Determinacy::Undetermined) => determinacy = Determinacy::Undetermined,
 392                 Err(Determinacy::Determined) => {}
 393             }
 394         }
 395
 396         Err(determinacy)
 397     }
 398
 399     fn resolve_macro_to_def(&mut self, scope: Mark, path: &ast::Path, kind: MacroKind, force: bool)
 400                             -> Result<Def, Determinacy> {
 401         let def = self.resolve_macro_to_def_inner(scope, path, kind, force);
 402         if def != Err(Determinacy::Undetermined) {
 403             // Do not report duplicated errors on every undetermined resolution.
 404             path.segments.iter().find(|segment| segment.parameters.is_some()).map(|segment| {
 405                 self.session.span_err(segment.parameters.as_ref().unwrap().span(),
 406                                       "generic arguments in macro path");
 407             });
 408         }
 409         def
 410     }
 411
 412     pub fn resolve_macro_to_def_inner(&mut self, scope: Mark, path: &ast::Path,
 413                                   kind: MacroKind, force: bool)
 414                                   -> Result<Def, Determinacy> {
 415         let ast::Path { ref segments, span } = *path;
 416         let path: Vec<_> = segments.iter().map(|seg| respan(seg.span, seg.identifier)).collect();
 417         let invocation = self.invocations[&scope];
 418         let module = invocation.module.get();
 419         self.current_module = if module.is_trait() { module.parent.unwrap() } else { module };
 420
 421         if path.len() > 1 {
 422             if !self.use_extern_macros && self.gated_errors.insert(span) {
 423                 let msg = "non-ident macro paths are experimental";
 424                 let feature = "use_extern_macros";
 425                 emit_feature_err(&self.session.parse_sess, feature, span, GateIssue::Language, msg);
 426                 self.found_unresolved_macro = true;
 427                 return Err(Determinacy::Determined);
 428             }
 429
 430             let def = match self.resolve_path(&path, Some(MacroNS), false, span) {
 431                 PathResult::NonModule(path_res) => match path_res.base_def() {
 432                     Def::Err => Err(Determinacy::Determined),
 433                     def @ _ => {
 434                         if path_res.unresolved_segments() > 0 {
 435                             self.found_unresolved_macro = true;
 436                             self.session.span_err(span, "fail to resolve non-ident macro path");
 437                             Err(Determinacy::Determined)
 438                         } else {
 439                             Ok(def)
 440                         }
 441                     }
 442                 },
 443                 PathResult::Module(..) => unreachable!(),
 444                 PathResult::Indeterminate if !force => return Err(Determinacy::Undetermined),
 445                 _ => {
 446                     self.found_unresolved_macro = true;
 447                     Err(Determinacy::Determined)
 448                 },
 449             };
 450             let path = path.iter().map(|p| p.node).collect::<Vec<_>>();
 451             self.current_module.nearest_item_scope().macro_resolutions.borrow_mut()
 452                 .push((path.into_boxed_slice(), span));
 453             return def;
 454         }
 455
 456         let legacy_resolution = self.resolve_legacy_scope(&invocation.legacy_scope,
 457                                                           path[0].node,
 458                                                           false);
 459         let result = if let Some(MacroBinding::Legacy(binding)) = legacy_resolution {
 460             Ok(Def::Macro(binding.def_id, MacroKind::Bang))
 461         } else {
 462             match self.resolve_lexical_macro_path_segment(path[0].node, MacroNS, false, span) {
 463                 Ok(binding) => Ok(binding.binding().def_ignoring_ambiguity()),
 464                 Err(Determinacy::Undetermined) if !force => return Err(Determinacy::Undetermined),
 465                 Err(_) => {
 466                     self.found_unresolved_macro = true;
 467                     Err(Determinacy::Determined)
 468                 }
 469             }
 470         };
 471
 472         self.current_module.nearest_item_scope().legacy_macro_resolutions.borrow_mut()
 473             .push((scope, path[0].node, span, kind));
 474
 475         result
 476     }
 477
 478     // Resolve the initial segment of a non-global macro path (e.g. `foo` in `foo::bar!();`)
 479     pub fn resolve_lexical_macro_path_segment(&mut self,
 480                                               mut ident: Ident,
 481                                               ns: Namespace,
 482                                               record_used: bool,
 483                                               path_span: Span)
 484                                               -> Result<MacroBinding<'a>, Determinacy> {
 485         ident = ident.modern();
 486         let mut module = Some(self.current_module);
 487         let mut potential_illegal_shadower = Err(Determinacy::Determined);
 488         let determinacy =
 489             if record_used { Determinacy::Determined } else { Determinacy::Undetermined };
 490         loop {
 491             let orig_current_module = self.current_module;
 492             let result = if let Some(module) = module {
 493                 self.current_module = module; // Lexical resolutions can never be a privacy error.
 494                 // Since expanded macros may not shadow the lexical scope and
 495                 // globs may not shadow global macros (both enforced below),
 496                 // we resolve with restricted shadowing (indicated by the penultimate argument).
 497                 self.resolve_ident_in_module_unadjusted(
 498                     module, ident, ns, true, record_used, path_span,
 499                 ).map(MacroBinding::Modern)
 500             } else {
 501                 self.global_macros.get(&ident.name).cloned().ok_or(determinacy)
 502                     .map(MacroBinding::Global)
 503             };
 504             self.current_module = orig_current_module;
 505
 506             match result.map(MacroBinding::binding) {
 507                 Ok(binding) => {
 508                     if !record_used {
 509                         return result;
 510                     }
 511                     if let Ok(MacroBinding::Modern(shadower)) = potential_illegal_shadower {
 512                         if shadower.def() != binding.def() {
 513                             let name = ident.name;
 514                             self.ambiguity_errors.push(AmbiguityError {
 515                                 span: path_span,
 516                                 name,
 517                                 b1: shadower,
 518                                 b2: binding,
 519                                 lexical: true,
 520                                 legacy: false,
 521                             });
 522                             return potential_illegal_shadower;
 523                         }
 524                     }
 525                     if binding.expansion != Mark::root() ||
 526                        (binding.is_glob_import() && module.unwrap().def().is_some()) {
 527                         potential_illegal_shadower = result;
 528                     } else {
 529                         return result;
 530                     }
 531                 },
 532                 Err(Determinacy::Undetermined) => return Err(Determinacy::Undetermined),
 533                 Err(Determinacy::Determined) => {}
 534             }
 535
 536             module = match module {
 537                 Some(module) => self.hygienic_lexical_parent(module, &mut ident.ctxt),
 538                 None => return potential_illegal_shadower,
 539             }
 540         }
 541     }
 542
 543     pub fn resolve_legacy_scope(&mut self,
 544                                 mut scope: &'a Cell<LegacyScope<'a>>,
 545                                 ident: Ident,
 546                                 record_used: bool)
 547                                 -> Option<MacroBinding<'a>> {
 548         let ident = ident.modern();
 549         let mut possible_time_travel = None;
 550         let mut relative_depth: u32 = 0;
 551         let mut binding = None;
 552         loop {
 553             match scope.get() {
 554                 LegacyScope::Empty => break,
 555                 LegacyScope::Expansion(invocation) => {
 556                     match invocation.expansion.get() {
 557                         LegacyScope::Invocation(_) => scope.set(invocation.legacy_scope.get()),
 558                         LegacyScope::Empty => {
 559                             if possible_time_travel.is_none() {
 560                                 possible_time_travel = Some(scope);
 561                             }
 562                             scope = &invocation.legacy_scope;
 563                         }
 564                         _ => {
 565                             relative_depth += 1;
 566                             scope = &invocation.expansion;
 567                         }
 568                     }
 569                 }
 570                 LegacyScope::Invocation(invocation) => {
 571                     relative_depth = relative_depth.saturating_sub(1);
 572                     scope = &invocation.legacy_scope;
 573                 }
 574                 LegacyScope::Binding(potential_binding) => {
 575                     if potential_binding.ident == ident {
 576                         if (!self.use_extern_macros || record_used) && relative_depth > 0 {
 577                             self.disallowed_shadowing.push(potential_binding);
 578                         }
 579                         binding = Some(potential_binding);
 580                         break
 581                     }
 582                     scope = &potential_binding.parent;
 583                 }
 584             };
 585         }
 586
 587         let binding = if let Some(binding) = binding {
 588             MacroBinding::Legacy(binding)
 589         } else if let Some(binding) = self.global_macros.get(&ident.name).cloned() {
 590             if !self.use_extern_macros {
 591                 self.record_use(ident, MacroNS, binding, DUMMY_SP);
 592             }
 593             MacroBinding::Global(binding)
 594         } else {
 595             return None;
 596         };
 597
 598         if !self.use_extern_macros {
 599             if let Some(scope) = possible_time_travel {
 600                 // Check for disallowed shadowing later
 601                 self.lexical_macro_resolutions.push((ident, scope));
 602             }
 603         }
 604
 605         Some(binding)
 606     }
 607
 608     pub fn finalize_current_module_macro_resolutions(&mut self) {
 609         let module = self.current_module;
 610         for &(ref path, span) in module.macro_resolutions.borrow().iter() {
 611             let path = path.iter().map(|p| respan(span, *p)).collect::<Vec<_>>();
 612             match self.resolve_path(&path, Some(MacroNS), true, span) {
 613                 PathResult::NonModule(_) => {},
 614                 PathResult::Failed(span, msg, _) => {
 615                     resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
 616                 }
 617                 _ => unreachable!(),
 618             }
 619         }
 620
 621         for &(mark, ident, span, kind) in module.legacy_macro_resolutions.borrow().iter() {
 622             let legacy_scope = &self.invocations[&mark].legacy_scope;
 623             let legacy_resolution = self.resolve_legacy_scope(legacy_scope, ident, true);
 624             let resolution = self.resolve_lexical_macro_path_segment(ident, MacroNS, true, span);
 625             match (legacy_resolution, resolution) {
 626                 (Some(MacroBinding::Legacy(legacy_binding)), Ok(MacroBinding::Modern(binding))) => {
 627                     let msg1 = format!("`{}` could refer to the macro defined here", ident);
 628                     let msg2 = format!("`{}` could also refer to the macro imported here", ident);
 629                     self.session.struct_span_err(span, &format!("`{}` is ambiguous", ident))
 630                         .span_note(legacy_binding.span, &msg1)
 631                         .span_note(binding.span, &msg2)
 632                         .emit();
 633                 },
 634                 (Some(MacroBinding::Global(binding)), Ok(MacroBinding::Global(_))) => {
 635                     self.record_use(ident, MacroNS, binding, span);
 636                     self.err_if_macro_use_proc_macro(ident.name, span, binding);
 637                 },
 638                 (None, Err(_)) => {
 639                     let msg = match kind {
 640                         MacroKind::Bang =>
 641                             format!("cannot find macro `{}!` in this scope", ident),
 642                         MacroKind::Attr =>
 643                             format!("cannot find attribute macro `{}` in this scope", ident),
 644                         MacroKind::Derive =>
 645                             format!("cannot find derive macro `{}` in this scope", ident),
 646                     };
 647                     let mut err = self.session.struct_span_err(span, &msg);
 648                     self.suggest_macro_name(&ident.name.as_str(), kind, &mut err, span);
 649                     err.emit();
 650                 },
 651                 _ => {},
 652             };
 653         }
 654     }
 655
 656     fn suggest_macro_name(&mut self, name: &str, kind: MacroKind,
 657                           err: &mut DiagnosticBuilder<'a>, span: Span) {
 658         // First check if this is a locally-defined bang macro.
 659         let suggestion = if let MacroKind::Bang = kind {
 660             find_best_match_for_name(self.macro_names.iter().map(|ident| &ident.name), name, None)
 661         } else {
 662             None
 663         // Then check global macros.
 664         }.or_else(|| {
 665             // FIXME: get_macro needs an &mut Resolver, can we do it without cloning?
 666             let global_macros = self.global_macros.clone();
 667             let names = global_macros.iter().filter_map(|(name, binding)| {
 668                 if binding.get_macro(self).kind() == kind {
 669                     Some(name)
 670                 } else {
 671                     None
 672                 }
 673             });
 674             find_best_match_for_name(names, name, None)
 675         // Then check modules.
 676         }).or_else(|| {
 677             if !self.use_extern_macros {
 678                 return None;
 679             }
 680             let is_macro = |def| {
 681                 if let Def::Macro(_, def_kind) = def {
 682                     def_kind == kind
 683                 } else {
 684                     false
 685                 }
 686             };
 687             let ident = Ident::from_str(name);
 688             self.lookup_typo_candidate(&vec![respan(span, ident)], MacroNS, is_macro, span)
 689         });
 690
 691         if let Some(suggestion) = suggestion {
 692             if suggestion != name {
 693                 if let MacroKind::Bang = kind {
 694                     err.span_suggestion(span, "you could try the macro", suggestion.to_string());
 695                 } else {
 696                     err.span_suggestion(span, "try", suggestion.to_string());
 697                 }
 698             } else {
 699                 err.help("have you added the `#[macro_use]` on the module/import?");
 700             }
 701         }
 702     }
 703
 704     fn collect_def_ids(&mut self,
 705                        mark: Mark,
 706                        invocation: &'a InvocationData<'a>,
 707                        expansion: &Expansion) {
 708         let Resolver { ref mut invocations, arenas, graph_root, .. } = *self;
 709         let InvocationData { def_index, const_expr, .. } = *invocation;
 710
 711         let visit_macro_invoc = &mut |invoc: map::MacroInvocationData| {
 712             invocations.entry(invoc.mark).or_insert_with(|| {
 713                 arenas.alloc_invocation_data(InvocationData {
 714                     def_index: invoc.def_index,
 715                     const_expr: invoc.const_expr,
 716                     module: Cell::new(graph_root),
 717                     expansion: Cell::new(LegacyScope::Empty),
 718                     legacy_scope: Cell::new(LegacyScope::Empty),
 719                 })
 720             });
 721         };
 722
 723         let mut def_collector = DefCollector::new(&mut self.definitions, mark);
 724         def_collector.visit_macro_invoc = Some(visit_macro_invoc);
 725         def_collector.with_parent(def_index, |def_collector| {
 726             if const_expr {
 727                 if let Expansion::Expr(ref expr) = *expansion {
 728                     def_collector.visit_const_expr(expr);
 729                 }
 730             }
 731             expansion.visit_with(def_collector)
 732         });
 733     }
 734
 735     pub fn define_macro(&mut self,
 736                         item: &ast::Item,
 737                         expansion: Mark,
 738                         legacy_scope: &mut LegacyScope<'a>) {
 739         self.local_macro_def_scopes.insert(item.id, self.current_module);
 740         let ident = item.ident;
 741         if ident.name == "macro_rules" {
 742             self.session.span_err(item.span, "user-defined macros may not be named `macro_rules`");
 743         }
 744
 745         let def_id = self.definitions.local_def_id(item.id);
 746         let ext = Lrc::new(macro_rules::compile(&self.session.parse_sess,
 747                                                &self.session.features,
 748                                                item));
 749         self.macro_map.insert(def_id, ext);
 750
 751         let def = match item.node { ast::ItemKind::MacroDef(ref def) => def, _ => unreachable!() };
 752         if def.legacy {
 753             let ident = ident.modern();
 754             self.macro_names.insert(ident);
 755             *legacy_scope = LegacyScope::Binding(self.arenas.alloc_legacy_binding(LegacyBinding {
 756                 parent: Cell::new(*legacy_scope), ident: ident, def_id: def_id, span: item.span,
 757             }));
 758             let def = Def::Macro(def_id, MacroKind::Bang);
 759             self.all_macros.insert(ident.name, def);
 760             if attr::contains_name(&item.attrs, "macro_export") {
 761                 self.macro_exports.push(Export {
 762                     ident: ident.modern(),
 763                     def: def,
 764                     vis: ty::Visibility::Public,
 765                     span: item.span,
 766                     is_import: false,
 767                 });
 768             } else {
 769                 self.unused_macros.insert(def_id);
 770             }
 771         } else {
 772             let module = self.current_module;
 773             let def = Def::Macro(def_id, MacroKind::Bang);
 774             let vis = self.resolve_visibility(&item.vis);
 775             if vis != ty::Visibility::Public {
 776                 self.unused_macros.insert(def_id);
 777             }
 778             self.define(module, ident, MacroNS, (def, vis, item.span, expansion));
 779         }
 780     }
 781
 782     /// Error if `ext` is a Macros 1.1 procedural macro being imported by `#[macro_use]`
 783     fn err_if_macro_use_proc_macro(&mut self, name: Name, use_span: Span,
 784                                    binding: &NameBinding<'a>) {
 785         use self::SyntaxExtension::*;
 786
 787         let krate = binding.def().def_id().krate;
 788
 789         // Plugin-based syntax extensions are exempt from this check
 790         if krate == BUILTIN_MACROS_CRATE { return; }
 791
 792         let ext = binding.get_macro(self);
 793
 794         match *ext {
 795             // If `ext` is a procedural macro, check if we've already warned about it
 796             AttrProcMacro(_) | ProcMacro(_) => if !self.warned_proc_macros.insert(name) { return; },
 797             _ => return,
 798         }
 799
 800         let warn_msg = match *ext {
 801             AttrProcMacro(_) => "attribute procedural macros cannot be \
 802                                  imported with `#[macro_use]`",
 803             ProcMacro(_) => "procedural macros cannot be imported with `#[macro_use]`",
 804             _ => return,
 805         };
 806
 807         let def_id = self.current_module.normal_ancestor_id;
 808         let node_id = self.definitions.as_local_node_id(def_id).unwrap();
 809
 810         self.proc_mac_errors.push(ProcMacError {
 811             crate_name: self.cstore.crate_name_untracked(krate),
 812             name,
 813             module: node_id,
 814             use_span,
 815             warn_msg,
 816         });
 817     }
 818
 819     pub fn report_proc_macro_import(&mut self, krate: &ast::Crate) {
 820         for err in self.proc_mac_errors.drain(..) {
 821             let (span, found_use) = ::UsePlacementFinder::check(krate, err.module);
 822
 823             if let Some(span) = span {
 824                 let found_use = if found_use { "" } else { "\n" };
 825                 self.session.struct_span_err(err.use_span, err.warn_msg)
 826                     .span_suggestion(
 827                         span,
 828                         "instead, import the procedural macro like any other item",
 829                         format!("use {}::{};{}", err.crate_name, err.name, found_use),
 830                     ).emit();
 831             } else {
 832                 self.session.struct_span_err(err.use_span, err.warn_msg)
 833                     .help(&format!("instead, import the procedural macro like any other item: \
 834                                     `use {}::{};`", err.crate_name, err.name))
 835                     .emit();
 836             }
 837         }
 838     }
 839
 840     fn gate_legacy_custom_derive(&mut self, name: Symbol, span: Span) {
 841         if !self.session.features.borrow().custom_derive {
 842             let sess = &self.session.parse_sess;
 843             let explain = feature_gate::EXPLAIN_CUSTOM_DERIVE;
 844             emit_feature_err(sess, "custom_derive", span, GateIssue::Language, explain);
 845         } else if !self.is_whitelisted_legacy_custom_derive(name) {
 846             self.session.span_warn(span, feature_gate::EXPLAIN_DEPR_CUSTOM_DERIVE);
 847         }
 848     }
 849 }