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, CrateLint, Resolver, ResolutionError, is_known_tool, resolve_error};
  12 use {Module, ModuleKind, NameBinding, NameBindingKind, PathResult, ToNameBinding};
  13 use ModuleOrUniformRoot;
  14 use Namespace::{self, TypeNS, MacroNS};
  15 use build_reduced_graph::{BuildReducedGraphVisitor, IsMacroExport};
  16 use resolve_imports::ImportResolver;
  17 use rustc::hir::def_id::{DefId, CRATE_DEF_INDEX, DefIndex,
  18                          CrateNum, DefIndexAddressSpace};
  19 use rustc::hir::def::{Def, NonMacroAttrKind};
  20 use rustc::hir::map::{self, DefCollector};
  21 use rustc::{ty, lint};
  22 use syntax::ast::{self, Name, Ident};
  23 use syntax::attr;
  24 use syntax::errors::DiagnosticBuilder;
  25 use syntax::ext::base::{self, Determinacy};
  26 use syntax::ext::base::{MacroKind, SyntaxExtension, Resolver as SyntaxResolver};
  27 use syntax::ext::expand::{AstFragment, Invocation, InvocationKind, TogetherWith};
  28 use syntax::ext::hygiene::{self, Mark};
  29 use syntax::ext::tt::macro_rules;
  30 use syntax::feature_gate::{self, feature_err, emit_feature_err, is_builtin_attr_name, GateIssue};
  31 use syntax::feature_gate::EXPLAIN_DERIVE_UNDERSCORE;
  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, DelimSpan};
  38 use syntax::util::lev_distance::find_best_match_for_name;
  39 use syntax_pos::{Span, DUMMY_SP};
  40 use errors::Applicability;
  41
  42 use std::cell::Cell;
  43 use std::mem;
  44 use rustc_data_structures::sync::Lrc;
  45
  46 #[derive(Clone, Copy)]
  47 crate struct FromPrelude(bool);
  48
  49 #[derive(Clone)]
  50 pub struct InvocationData<'a> {
  51     def_index: DefIndex,
  52     /// Module in which the macro was invoked.
  53     crate module: Cell<Module<'a>>,
  54     /// Legacy scope in which the macro was invoked.
  55     /// The invocation path is resolved in this scope.
  56     crate parent_legacy_scope: Cell<LegacyScope<'a>>,
  57     /// Legacy scope *produced* by expanding this macro invocation,
  58     /// includes all the macro_rules items, other invocations, etc generated by it.
  59     /// Set to the parent scope if the macro is not expanded yet (as if the macro produced nothing).
  60     crate output_legacy_scope: Cell<LegacyScope<'a>>,
  61 }
  62
  63 impl<'a> InvocationData<'a> {
  64     pub fn root(graph_root: Module<'a>) -> Self {
  65         InvocationData {
  66             module: Cell::new(graph_root),
  67             def_index: CRATE_DEF_INDEX,
  68             parent_legacy_scope: Cell::new(LegacyScope::Empty),
  69             output_legacy_scope: Cell::new(LegacyScope::Empty),
  70         }
  71     }
  72 }
  73
  74 /// Binding produced by a `macro_rules` item.
  75 /// Not modularized, can shadow previous legacy bindings, etc.
  76 pub struct LegacyBinding<'a> {
  77     binding: &'a NameBinding<'a>,
  78     /// Legacy scope into which the `macro_rules` item was planted.
  79     parent_legacy_scope: LegacyScope<'a>,
  80     ident: Ident,
  81 }
  82
  83 /// Scope introduced by a `macro_rules!` macro.
  84 /// Starts at the macro's definition and ends at the end of the macro's parent module
  85 /// (named or unnamed), or even further if it escapes with `#[macro_use]`.
  86 /// Some macro invocations need to introduce legacy scopes too because they
  87 /// potentially can expand into macro definitions.
  88 #[derive(Copy, Clone)]
  89 pub enum LegacyScope<'a> {
  90     /// Created when invocation data is allocated in the arena,
  91     /// must be replaced with a proper scope later.
  92     Uninitialized,
  93     /// Empty "root" scope at the crate start containing no names.
  94     Empty,
  95     /// Scope introduced by a `macro_rules!` macro definition.
  96     Binding(&'a LegacyBinding<'a>),
  97     /// Scope introduced by a macro invocation that can potentially
  98     /// create a `macro_rules!` macro definition.
  99     Invocation(&'a InvocationData<'a>),
 100 }
 101
 102 /// Everything you need to resolve a macro path.
 103 #[derive(Clone)]
 104 pub struct ParentScope<'a> {
 105     crate module: Module<'a>,
 106     crate expansion: Mark,
 107     crate legacy: LegacyScope<'a>,
 108     crate derives: Vec<ast::Path>,
 109 }
 110
 111 // Macro namespace is separated into two sub-namespaces, one for bang macros and
 112 // one for attribute-like macros (attributes, derives).
 113 // We ignore resolutions from one sub-namespace when searching names in scope for another.
 114 fn sub_namespace_mismatch(requirement: Option<MacroKind>, candidate: Option<MacroKind>) -> bool {
 115     #[derive(PartialEq)]
 116     enum SubNS { Bang, AttrLike }
 117     let sub_ns = |kind| match kind {
 118         MacroKind::Bang => Some(SubNS::Bang),
 119         MacroKind::Attr | MacroKind::Derive => Some(SubNS::AttrLike),
 120         MacroKind::ProcMacroStub => None,
 121     };
 122     let requirement = requirement.and_then(|kind| sub_ns(kind));
 123     let candidate = candidate.and_then(|kind| sub_ns(kind));
 124     // "No specific sub-namespace" means "matches anything" for both requirements and candidates.
 125     candidate.is_some() && requirement.is_some() && candidate != requirement
 126 }
 127
 128 impl<'a, 'crateloader: 'a> base::Resolver for Resolver<'a, 'crateloader> {
 129     fn next_node_id(&mut self) -> ast::NodeId {
 130         self.session.next_node_id()
 131     }
 132
 133     fn get_module_scope(&mut self, id: ast::NodeId) -> Mark {
 134         let mark = Mark::fresh(Mark::root());
 135         let module = self.module_map[&self.definitions.local_def_id(id)];
 136         self.invocations.insert(mark, self.arenas.alloc_invocation_data(InvocationData {
 137             module: Cell::new(module),
 138             def_index: module.def_id().unwrap().index,
 139             parent_legacy_scope: Cell::new(LegacyScope::Empty),
 140             output_legacy_scope: Cell::new(LegacyScope::Empty),
 141         }));
 142         mark
 143     }
 144
 145     fn eliminate_crate_var(&mut self, item: P<ast::Item>) -> P<ast::Item> {
 146         struct EliminateCrateVar<'b, 'a: 'b, 'crateloader: 'a>(
 147             &'b mut Resolver<'a, 'crateloader>, Span
 148         );
 149
 150         impl<'a, 'b, 'crateloader> Folder for EliminateCrateVar<'a, 'b, 'crateloader> {
 151             fn fold_path(&mut self, path: ast::Path) -> ast::Path {
 152                 match self.fold_qpath(None, path) {
 153                     (None, path) => path,
 154                     _ => unreachable!(),
 155                 }
 156             }
 157
 158             fn fold_qpath(&mut self, mut qself: Option<ast::QSelf>, mut path: ast::Path)
 159                           -> (Option<ast::QSelf>, ast::Path) {
 160                 qself = qself.map(|ast::QSelf { ty, path_span, position }| {
 161                     ast::QSelf {
 162                         ty: self.fold_ty(ty),
 163                         path_span: self.new_span(path_span),
 164                         position,
 165                     }
 166                 });
 167
 168                 if path.segments[0].ident.name == keywords::DollarCrate.name() {
 169                     let module = self.0.resolve_crate_root(path.segments[0].ident);
 170                     path.segments[0].ident.name = keywords::CrateRoot.name();
 171                     if !module.is_local() {
 172                         let span = path.segments[0].ident.span;
 173                         path.segments.insert(1, match module.kind {
 174                             ModuleKind::Def(_, name) => ast::PathSegment::from_ident(
 175                                 ast::Ident::with_empty_ctxt(name).with_span_pos(span)
 176                             ),
 177                             _ => unreachable!(),
 178                         });
 179                         if let Some(qself) = &mut qself {
 180                             qself.position += 1;
 181                         }
 182                     }
 183                 }
 184                 (qself, path)
 185             }
 186
 187             fn fold_mac(&mut self, mac: ast::Mac) -> ast::Mac {
 188                 fold::noop_fold_mac(mac, self)
 189             }
 190         }
 191
 192         let ret = EliminateCrateVar(self, item.span).fold_item(item);
 193         assert!(ret.len() == 1);
 194         ret.into_iter().next().unwrap()
 195     }
 196
 197     fn is_whitelisted_legacy_custom_derive(&self, name: Name) -> bool {
 198         self.whitelisted_legacy_custom_derives.contains(&name)
 199     }
 200
 201     fn visit_ast_fragment_with_placeholders(&mut self, mark: Mark, fragment: &AstFragment,
 202                                             derives: &[Mark]) {
 203         let invocation = self.invocations[&mark];
 204         self.collect_def_ids(mark, invocation, fragment);
 205
 206         self.current_module = invocation.module.get();
 207         self.current_module.unresolved_invocations.borrow_mut().remove(&mark);
 208         self.current_module.unresolved_invocations.borrow_mut().extend(derives);
 209         for &derive in derives {
 210             self.invocations.insert(derive, invocation);
 211         }
 212         let mut visitor = BuildReducedGraphVisitor {
 213             resolver: self,
 214             current_legacy_scope: invocation.parent_legacy_scope.get(),
 215             expansion: mark,
 216         };
 217         fragment.visit_with(&mut visitor);
 218         invocation.output_legacy_scope.set(visitor.current_legacy_scope);
 219     }
 220
 221     fn add_builtin(&mut self, ident: ast::Ident, ext: Lrc<SyntaxExtension>) {
 222         let def_id = DefId {
 223             krate: CrateNum::BuiltinMacros,
 224             index: DefIndex::from_array_index(self.macro_map.len(),
 225                                               DefIndexAddressSpace::Low),
 226         };
 227         let kind = ext.kind();
 228         self.macro_map.insert(def_id, ext);
 229         let binding = self.arenas.alloc_name_binding(NameBinding {
 230             kind: NameBindingKind::Def(Def::Macro(def_id, kind), false),
 231             span: DUMMY_SP,
 232             vis: ty::Visibility::Invisible,
 233             expansion: Mark::root(),
 234         });
 235         if self.builtin_macros.insert(ident.name, binding).is_some() {
 236             self.session.span_err(ident.span,
 237                                   &format!("built-in macro `{}` was already defined", ident));
 238         }
 239     }
 240
 241     fn resolve_imports(&mut self) {
 242         ImportResolver { resolver: self }.resolve_imports()
 243     }
 244
 245     // Resolves attribute and derive legacy macros from `#![plugin(..)]`.
 246     fn find_legacy_attr_invoc(&mut self, attrs: &mut Vec<ast::Attribute>, allow_derive: bool)
 247                               -> Option<ast::Attribute> {
 248         if !allow_derive {
 249             return None;
 250         }
 251
 252         // Check for legacy derives
 253         for i in 0..attrs.len() {
 254             let name = attrs[i].name();
 255
 256             if name == "derive" {
 257                 let result = attrs[i].parse_list(&self.session.parse_sess, |parser| {
 258                     parser.parse_path_allowing_meta(PathStyle::Mod)
 259                 });
 260
 261                 let mut traits = match result {
 262                     Ok(traits) => traits,
 263                     Err(mut e) => {
 264                         e.cancel();
 265                         continue
 266                     }
 267                 };
 268
 269                 for j in 0..traits.len() {
 270                     if traits[j].segments.len() > 1 {
 271                         continue
 272                     }
 273                     let trait_name = traits[j].segments[0].ident.name;
 274                     let legacy_name = Symbol::intern(&format!("derive_{}", trait_name));
 275                     if !self.builtin_macros.contains_key(&legacy_name) {
 276                         continue
 277                     }
 278                     let span = traits.remove(j).span;
 279                     self.gate_legacy_custom_derive(legacy_name, span);
 280                     if traits.is_empty() {
 281                         attrs.remove(i);
 282                     } else {
 283                         let mut tokens = Vec::new();
 284                         for (j, path) in traits.iter().enumerate() {
 285                             if j > 0 {
 286                                 tokens.push(TokenTree::Token(attrs[i].span, Token::Comma).into());
 287                             }
 288                             for (k, segment) in path.segments.iter().enumerate() {
 289                                 if k > 0 {
 290                                     tokens.push(TokenTree::Token(path.span, Token::ModSep).into());
 291                                 }
 292                                 let tok = Token::from_ast_ident(segment.ident);
 293                                 tokens.push(TokenTree::Token(path.span, tok).into());
 294                             }
 295                         }
 296                         let delim_span = DelimSpan::from_single(attrs[i].span);
 297                         attrs[i].tokens = TokenTree::Delimited(delim_span, Delimited {
 298                             delim: token::Paren,
 299                             tts: TokenStream::concat(tokens).into(),
 300                         }).into();
 301                     }
 302                     return Some(ast::Attribute {
 303                         path: ast::Path::from_ident(Ident::new(legacy_name, span)),
 304                         tokens: TokenStream::empty(),
 305                         id: attr::mk_attr_id(),
 306                         style: ast::AttrStyle::Outer,
 307                         is_sugared_doc: false,
 308                         span,
 309                     });
 310                 }
 311             }
 312         }
 313
 314         None
 315     }
 316
 317     fn resolve_macro_invocation(&mut self, invoc: &Invocation, invoc_id: Mark, force: bool)
 318                                 -> Result<Option<Lrc<SyntaxExtension>>, Determinacy> {
 319         let (path, kind, derives_in_scope, together_with) = match invoc.kind {
 320             InvocationKind::Attr { attr: None, .. } =>
 321                 return Ok(None),
 322             InvocationKind::Attr { attr: Some(ref attr), ref traits, together_with, .. } =>
 323                 (&attr.path, MacroKind::Attr, traits.clone(), together_with),
 324             InvocationKind::Bang { ref mac, .. } =>
 325                 (&mac.node.path, MacroKind::Bang, Vec::new(), TogetherWith::None),
 326             InvocationKind::Derive { ref path, .. } =>
 327                 (path, MacroKind::Derive, Vec::new(), TogetherWith::None),
 328         };
 329
 330         let parent_scope = self.invoc_parent_scope(invoc_id, derives_in_scope);
 331         let (def, ext) = self.resolve_macro_to_def(path, kind, &parent_scope, force)?;
 332
 333         if let Def::Macro(def_id, _) = def {
 334             match together_with {
 335                 TogetherWith::Derive =>
 336                     self.session.span_err(invoc.span(),
 337                         "macro attributes must be placed before `#[derive]`"),
 338                 TogetherWith::TestBench if !self.session.features_untracked().plugin =>
 339                     self.session.span_err(invoc.span(),
 340                         "macro attributes cannot be used together with `#[test]` or `#[bench]`"),
 341                 _ => {}
 342             }
 343             self.macro_defs.insert(invoc.expansion_data.mark, def_id);
 344             let normal_module_def_id =
 345                 self.macro_def_scope(invoc.expansion_data.mark).normal_ancestor_id;
 346             self.definitions.add_parent_module_of_macro_def(invoc.expansion_data.mark,
 347                                                             normal_module_def_id);
 348             invoc.expansion_data.mark.set_default_transparency(ext.default_transparency());
 349             invoc.expansion_data.mark.set_is_builtin(def_id.krate == CrateNum::BuiltinMacros);
 350         }
 351
 352         Ok(Some(ext))
 353     }
 354
 355     fn resolve_macro_path(&mut self, path: &ast::Path, kind: MacroKind, invoc_id: Mark,
 356                           derives_in_scope: Vec<ast::Path>, force: bool)
 357                           -> Result<Lrc<SyntaxExtension>, Determinacy> {
 358         let parent_scope = self.invoc_parent_scope(invoc_id, derives_in_scope);
 359         Ok(self.resolve_macro_to_def(path, kind, &parent_scope, force)?.1)
 360     }
 361
 362     fn check_unused_macros(&self) {
 363         for did in self.unused_macros.iter() {
 364             let id_span = match *self.macro_map[did] {
 365                 SyntaxExtension::NormalTT { def_info, .. } |
 366                 SyntaxExtension::DeclMacro { def_info, .. } => def_info,
 367                 _ => None,
 368             };
 369             if let Some((id, span)) = id_span {
 370                 let lint = lint::builtin::UNUSED_MACROS;
 371                 let msg = "unused macro definition";
 372                 self.session.buffer_lint(lint, id, span, msg);
 373             } else {
 374                 bug!("attempted to create unused macro error, but span not available");
 375             }
 376         }
 377     }
 378 }
 379
 380 impl<'a, 'cl> Resolver<'a, 'cl> {
 381     pub fn dummy_parent_scope(&mut self) -> ParentScope<'a> {
 382         self.invoc_parent_scope(Mark::root(), Vec::new())
 383     }
 384
 385     fn invoc_parent_scope(&mut self, invoc_id: Mark, derives: Vec<ast::Path>) -> ParentScope<'a> {
 386         let invoc = self.invocations[&invoc_id];
 387         ParentScope {
 388             module: invoc.module.get().nearest_item_scope(),
 389             expansion: invoc_id.parent(),
 390             legacy: invoc.parent_legacy_scope.get(),
 391             derives,
 392         }
 393     }
 394
 395     fn resolve_macro_to_def(
 396         &mut self,
 397         path: &ast::Path,
 398         kind: MacroKind,
 399         parent_scope: &ParentScope<'a>,
 400         force: bool,
 401     ) -> Result<(Def, Lrc<SyntaxExtension>), Determinacy> {
 402         let def = self.resolve_macro_to_def_inner(path, kind, parent_scope, force);
 403
 404         // Report errors and enforce feature gates for the resolved macro.
 405         if def != Err(Determinacy::Undetermined) {
 406             // Do not report duplicated errors on every undetermined resolution.
 407             for segment in &path.segments {
 408                 if let Some(args) = &segment.args {
 409                     self.session.span_err(args.span(), "generic arguments in macro path");
 410                 }
 411             }
 412         }
 413
 414         let def = def?;
 415
 416         match def {
 417             Def::Macro(def_id, macro_kind) => {
 418                 self.unused_macros.remove(&def_id);
 419                 if macro_kind == MacroKind::ProcMacroStub {
 420                     let msg = "can't use a procedural macro from the same crate that defines it";
 421                     self.session.span_err(path.span, msg);
 422                     return Err(Determinacy::Determined);
 423                 }
 424             }
 425             Def::NonMacroAttr(attr_kind) => {
 426                 if kind == MacroKind::Attr {
 427                     let features = self.session.features_untracked();
 428                     if attr_kind == NonMacroAttrKind::Custom {
 429                         assert!(path.segments.len() == 1);
 430                         let name = path.segments[0].ident.name.as_str();
 431                         if name.starts_with("rustc_") {
 432                             if !features.rustc_attrs {
 433                                 let msg = "unless otherwise specified, attributes with the prefix \
 434                                            `rustc_` are reserved for internal compiler diagnostics";
 435                                 feature_err(&self.session.parse_sess, "rustc_attrs", path.span,
 436                                             GateIssue::Language, &msg).emit();
 437                             }
 438                         } else if name.starts_with("derive_") {
 439                             if !features.custom_derive {
 440                                 feature_err(&self.session.parse_sess, "custom_derive", path.span,
 441                                             GateIssue::Language, EXPLAIN_DERIVE_UNDERSCORE).emit();
 442                             }
 443                         } else if !features.custom_attribute {
 444                             let msg = format!("The attribute `{}` is currently unknown to the \
 445                                                compiler and may have meaning added to it in the \
 446                                                future", path);
 447                             feature_err(&self.session.parse_sess, "custom_attribute", path.span,
 448                                         GateIssue::Language, &msg).emit();
 449                         }
 450                     }
 451                 } else {
 452                     // Not only attributes, but anything in macro namespace can result in
 453                     // `Def::NonMacroAttr` definition (e.g. `inline!()`), so we must report
 454                     // an error for those cases.
 455                     let msg = format!("expected a macro, found {}", def.kind_name());
 456                     self.session.span_err(path.span, &msg);
 457                     return Err(Determinacy::Determined);
 458                 }
 459             }
 460             _ => panic!("expected `Def::Macro` or `Def::NonMacroAttr`"),
 461         }
 462
 463         Ok((def, self.get_macro(def)))
 464     }
 465
 466     pub fn resolve_macro_to_def_inner(
 467         &mut self,
 468         path: &ast::Path,
 469         kind: MacroKind,
 470         parent_scope: &ParentScope<'a>,
 471         force: bool,
 472     ) -> Result<Def, Determinacy> {
 473         let ast::Path { ref segments, span } = *path;
 474         let mut path: Vec<_> = segments.iter().map(|seg| seg.ident).collect();
 475
 476         // Possibly apply the macro helper hack
 477         if kind == MacroKind::Bang && path.len() == 1 &&
 478            path[0].span.ctxt().outer().expn_info().map_or(false, |info| info.local_inner_macros) {
 479             let root = Ident::new(keywords::DollarCrate.name(), path[0].span);
 480             path.insert(0, root);
 481         }
 482
 483         if path.len() > 1 {
 484             let def = match self.resolve_path_with_parent_scope(None, &path, Some(MacroNS),
 485                                                                 parent_scope, false, span,
 486                                                                 CrateLint::No) {
 487                 PathResult::NonModule(path_res) => match path_res.base_def() {
 488                     Def::Err => Err(Determinacy::Determined),
 489                     def @ _ => {
 490                         if path_res.unresolved_segments() > 0 {
 491                             self.found_unresolved_macro = true;
 492                             self.session.span_err(span, "fail to resolve non-ident macro path");
 493                             Err(Determinacy::Determined)
 494                         } else {
 495                             Ok(def)
 496                         }
 497                     }
 498                 },
 499                 PathResult::Module(..) => unreachable!(),
 500                 PathResult::Indeterminate if !force => return Err(Determinacy::Undetermined),
 501                 _ => {
 502                     self.found_unresolved_macro = true;
 503                     Err(Determinacy::Determined)
 504                 },
 505             };
 506             parent_scope.module.macro_resolutions.borrow_mut()
 507                 .push((path.into_boxed_slice(), span));
 508             return def;
 509         }
 510
 511         let result = if let Some(legacy_binding) = self.resolve_legacy_scope(path[0], Some(kind),
 512                                                                              parent_scope, false) {
 513             Ok(legacy_binding.def())
 514         } else {
 515             match self.resolve_lexical_macro_path_segment(path[0], MacroNS, Some(kind),
 516                                                           parent_scope, false, force, span) {
 517                 Ok((binding, _)) => Ok(binding.def_ignoring_ambiguity()),
 518                 Err(Determinacy::Undetermined) => return Err(Determinacy::Undetermined),
 519                 Err(Determinacy::Determined) => {
 520                     self.found_unresolved_macro = true;
 521                     Err(Determinacy::Determined)
 522                 }
 523             }
 524         };
 525
 526         parent_scope.module.legacy_macro_resolutions.borrow_mut()
 527             .push((path[0], kind, parent_scope.clone(), result.ok()));
 528
 529         result
 530     }
 531
 532     // Resolve the initial segment of a non-global macro path
 533     // (e.g. `foo` in `foo::bar!(); or `foo!();`).
 534     // This is a variation of `fn resolve_ident_in_lexical_scope` that can be run during
 535     // expansion and import resolution (perhaps they can be merged in the future).
 536     crate fn resolve_lexical_macro_path_segment(
 537         &mut self,
 538         mut ident: Ident,
 539         ns: Namespace,
 540         kind: Option<MacroKind>,
 541         parent_scope: &ParentScope<'a>,
 542         record_used: bool,
 543         force: bool,
 544         path_span: Span,
 545     ) -> Result<(&'a NameBinding<'a>, FromPrelude), Determinacy> {
 546         // General principles:
 547         // 1. Not controlled (user-defined) names should have higher priority than controlled names
 548         //    built into the language or standard library. This way we can add new names into the
 549         //    language or standard library without breaking user code.
 550         // 2. "Closed set" below means new names can appear after the current resolution attempt.
 551         // Places to search (in order of decreasing priority):
 552         // (Type NS)
 553         // 1. FIXME: Ribs (type parameters), there's no necessary infrastructure yet
 554         //    (open set, not controlled).
 555         // 2. Names in modules (both normal `mod`ules and blocks), loop through hygienic parents
 556         //    (open, not controlled).
 557         // 3. Extern prelude (closed, not controlled).
 558         // 4. Tool modules (closed, controlled right now, but not in the future).
 559         // 5. Standard library prelude (de-facto closed, controlled).
 560         // 6. Language prelude (closed, controlled).
 561         // (Macro NS)
 562         // 0. Derive helpers (open, not controlled). All ambiguities with other names
 563         //    are currently reported as errors. They should be higher in priority than preludes
 564         //    and probably even names in modules according to the "general principles" above. They
 565         //    also should be subject to restricted shadowing because are effectively produced by
 566         //    derives (you need to resolve the derive first to add helpers into scope), but they
 567         //    should be available before the derive is expanded for compatibility.
 568         //    It's mess in general, so we are being conservative for now.
 569         // 1. Names in modules (both normal `mod`ules and blocks), loop through hygienic parents
 570         //    (open, not controlled).
 571         // 2. `macro_use` prelude (open, the open part is from macro expansions, not controlled).
 572         // 2a. User-defined prelude from macro-use
 573         //    (open, the open part is from macro expansions, not controlled).
 574         // 2b. Standard library prelude is currently implemented as `macro-use` (closed, controlled)
 575         // 3. Language prelude: builtin macros (closed, controlled, except for legacy plugins).
 576         // 4. Language prelude: builtin attributes (closed, controlled).
 577         // N (unordered). Derive helpers (open, not controlled). All ambiguities with other names
 578         //    are currently reported as errors. They should be higher in priority than preludes
 579         //    and maybe even names in modules according to the "general principles" above. They
 580         //    also should be subject to restricted shadowing because are effectively produced by
 581         //    derives (you need to resolve the derive first to add helpers into scope), but they
 582         //    should be available before the derive is expanded for compatibility.
 583         //    It's mess in general, so we are being conservative for now.
 584         // N (unordered). Legacy plugin helpers (open, not controlled). Similar to derive helpers,
 585         //    but introduced by legacy plugins using `register_attribute`.
 586
 587         assert!(ns == TypeNS  || ns == MacroNS);
 588         assert!(force || !record_used); // `record_used` implies `force`
 589         ident = ident.modern();
 590
 591         // This is *the* result, resolution from the scope closest to the resolved identifier.
 592         // However, sometimes this result is "weak" because it comes from a glob import or
 593         // a macro expansion, and in this case it cannot shadow names from outer scopes, e.g.
 594         // mod m { ... } // solution in outer scope
 595         // {
 596         //     use prefix::*; // imports another `m` - innermost solution
 597         //                    // weak, cannot shadow the outer `m`, need to report ambiguity error
 598         //     m::mac!();
 599         // }
 600         // So we have to save the innermost solution and continue searching in outer scopes
 601         // to detect potential ambiguities.
 602         let mut innermost_result: Option<(&NameBinding, FromPrelude)> = None;
 603
 604         enum WhereToResolve<'a> {
 605             Module(Module<'a>),
 606             MacroUsePrelude,
 607             BuiltinMacros,
 608             BuiltinAttrs,
 609             DeriveHelpers,
 610             LegacyPluginHelpers,
 611             ExternPrelude,
 612             ToolPrelude,
 613             StdLibPrelude,
 614             BuiltinTypes,
 615         }
 616
 617         // Go through all the scopes and try to resolve the name.
 618         let mut where_to_resolve = WhereToResolve::DeriveHelpers;
 619         let mut use_prelude = !parent_scope.module.no_implicit_prelude;
 620         loop {
 621             let result = match where_to_resolve {
 622                 WhereToResolve::Module(module) => {
 623                     let orig_current_module = mem::replace(&mut self.current_module, module);
 624                     let binding = self.resolve_ident_in_module_unadjusted(
 625                         ModuleOrUniformRoot::Module(module),
 626                         ident,
 627                         ns,
 628                         true,
 629                         record_used,
 630                         path_span,
 631                     );
 632                     self.current_module = orig_current_module;
 633                     binding.map(|binding| (binding, FromPrelude(false)))
 634                 }
 635                 WhereToResolve::MacroUsePrelude => {
 636                     match self.macro_use_prelude.get(&ident.name).cloned() {
 637                         Some(binding) => Ok((binding, FromPrelude(true))),
 638                         None => Err(Determinacy::Determined),
 639                     }
 640                 }
 641                 WhereToResolve::BuiltinMacros => {
 642                     match self.builtin_macros.get(&ident.name).cloned() {
 643                         Some(binding) => Ok((binding, FromPrelude(true))),
 644                         None => Err(Determinacy::Determined),
 645                     }
 646                 }
 647                 WhereToResolve::BuiltinAttrs => {
 648                     if is_builtin_attr_name(ident.name) {
 649                         let binding = (Def::NonMacroAttr(NonMacroAttrKind::Builtin),
 650                                        ty::Visibility::Public, ident.span, Mark::root())
 651                                        .to_name_binding(self.arenas);
 652                         Ok((binding, FromPrelude(true)))
 653                     } else {
 654                         Err(Determinacy::Determined)
 655                     }
 656                 }
 657                 WhereToResolve::DeriveHelpers => {
 658                     let mut result = Err(Determinacy::Determined);
 659                     for derive in &parent_scope.derives {
 660                         let parent_scope = ParentScope { derives: Vec::new(), ..*parent_scope };
 661                         if let Ok((_, ext)) = self.resolve_macro_to_def(derive, MacroKind::Derive,
 662                                                                         &parent_scope, force) {
 663                             if let SyntaxExtension::ProcMacroDerive(_, helper_attrs, _) = &*ext {
 664                                 if helper_attrs.contains(&ident.name) {
 665                                     let binding =
 666                                         (Def::NonMacroAttr(NonMacroAttrKind::DeriveHelper),
 667                                         ty::Visibility::Public, derive.span, Mark::root())
 668                                         .to_name_binding(self.arenas);
 669                                     result = Ok((binding, FromPrelude(false)));
 670                                     break;
 671                                 }
 672                             }
 673                         }
 674                     }
 675                     result
 676                 }
 677                 WhereToResolve::LegacyPluginHelpers => {
 678                     if self.session.plugin_attributes.borrow().iter()
 679                                                      .any(|(name, _)| ident.name == &**name) {
 680                         let binding = (Def::NonMacroAttr(NonMacroAttrKind::LegacyPluginHelper),
 681                                        ty::Visibility::Public, ident.span, Mark::root())
 682                                        .to_name_binding(self.arenas);
 683                         Ok((binding, FromPrelude(false)))
 684                     } else {
 685                         Err(Determinacy::Determined)
 686                     }
 687                 }
 688                 WhereToResolve::ExternPrelude => {
 689                     if use_prelude && self.session.extern_prelude.contains(&ident.name) {
 690                         let crate_id =
 691                             self.crate_loader.process_path_extern(ident.name, ident.span);
 692                         let crate_root =
 693                             self.get_module(DefId { krate: crate_id, index: CRATE_DEF_INDEX });
 694                         self.populate_module_if_necessary(crate_root);
 695
 696                         let binding = (crate_root, ty::Visibility::Public,
 697                                        ident.span, Mark::root()).to_name_binding(self.arenas);
 698                         Ok((binding, FromPrelude(true)))
 699                     } else {
 700                         Err(Determinacy::Determined)
 701                     }
 702                 }
 703                 WhereToResolve::ToolPrelude => {
 704                     if use_prelude && is_known_tool(ident.name) {
 705                         let binding = (Def::ToolMod, ty::Visibility::Public,
 706                                        ident.span, Mark::root()).to_name_binding(self.arenas);
 707                         Ok((binding, FromPrelude(true)))
 708                     } else {
 709                         Err(Determinacy::Determined)
 710                     }
 711                 }
 712                 WhereToResolve::StdLibPrelude => {
 713                     let mut result = Err(Determinacy::Determined);
 714                     if use_prelude {
 715                         if let Some(prelude) = self.prelude {
 716                             if let Ok(binding) = self.resolve_ident_in_module_unadjusted(
 717                                 ModuleOrUniformRoot::Module(prelude),
 718                                 ident,
 719                                 ns,
 720                                 false,
 721                                 false,
 722                                 path_span,
 723                             ) {
 724                                 result = Ok((binding, FromPrelude(true)));
 725                             }
 726                         }
 727                     }
 728                     result
 729                 }
 730                 WhereToResolve::BuiltinTypes => {
 731                     if let Some(prim_ty) =
 732                             self.primitive_type_table.primitive_types.get(&ident.name).cloned() {
 733                         let binding = (Def::PrimTy(prim_ty), ty::Visibility::Public,
 734                                        ident.span, Mark::root()).to_name_binding(self.arenas);
 735                         Ok((binding, FromPrelude(true)))
 736                     } else {
 737                         Err(Determinacy::Determined)
 738                     }
 739                 }
 740             };
 741
 742             macro_rules! continue_search { () => {
 743                 where_to_resolve = match where_to_resolve {
 744                     WhereToResolve::Module(module) => {
 745                         match self.hygienic_lexical_parent(module, &mut ident.span) {
 746                             Some(parent_module) => WhereToResolve::Module(parent_module),
 747                             None => {
 748                                 use_prelude = !module.no_implicit_prelude;
 749                                 if ns == MacroNS {
 750                                     WhereToResolve::MacroUsePrelude
 751                                 } else {
 752                                     WhereToResolve::ExternPrelude
 753                                 }
 754                             }
 755                         }
 756                     }
 757                     WhereToResolve::MacroUsePrelude => WhereToResolve::BuiltinMacros,
 758                     WhereToResolve::BuiltinMacros => WhereToResolve::BuiltinAttrs,
 759                     WhereToResolve::BuiltinAttrs => WhereToResolve::DeriveHelpers,
 760                     WhereToResolve::DeriveHelpers => WhereToResolve::LegacyPluginHelpers,
 761                     WhereToResolve::LegacyPluginHelpers => break, // nowhere else to search
 762                     WhereToResolve::ExternPrelude => WhereToResolve::ToolPrelude,
 763                     WhereToResolve::ToolPrelude => WhereToResolve::StdLibPrelude,
 764                     WhereToResolve::StdLibPrelude => WhereToResolve::BuiltinTypes,
 765                     WhereToResolve::BuiltinTypes => break, // nowhere else to search
 766                 };
 767
 768                 continue;
 769             }}
 770
 771             match result {
 772                 Ok(result) => {
 773                     if sub_namespace_mismatch(kind, result.0.macro_kind()) {
 774                         continue_search!();
 775                     }
 776
 777                     if !record_used {
 778                         return Ok(result);
 779                     }
 780
 781                     if let Some(innermost_result) = innermost_result {
 782                         // Found another solution, if the first one was "weak", report an error.
 783                         let prohibit_ambiguities = |def| {
 784                             def == Def::NonMacroAttr(NonMacroAttrKind::DeriveHelper) ||
 785                             def == Def::NonMacroAttr(NonMacroAttrKind::LegacyPluginHelper)
 786                         };
 787                         if result.0.def() != innermost_result.0.def() &&
 788                            (innermost_result.0.is_glob_import() ||
 789                             innermost_result.0.may_appear_after(parent_scope.expansion, result.0) ||
 790                             prohibit_ambiguities(innermost_result.0.def()) ||
 791                             prohibit_ambiguities(result.0.def())) {
 792                             self.ambiguity_errors.push(AmbiguityError {
 793                                 ident,
 794                                 b1: innermost_result.0,
 795                                 b2: result.0,
 796                             });
 797                             return Ok(innermost_result);
 798                         }
 799                     } else {
 800                         // Found the first solution.
 801                         innermost_result = Some(result);
 802                     }
 803
 804                     continue_search!();
 805                 },
 806                 Err(Determinacy::Determined) => {
 807                     continue_search!();
 808                 }
 809                 Err(Determinacy::Undetermined) => return Err(Determinacy::determined(force)),
 810             }
 811         }
 812
 813         // The first found solution was the only one, return it.
 814         if let Some(innermost_result) = innermost_result {
 815             return Ok(innermost_result);
 816         }
 817
 818         let determinacy = Determinacy::determined(force);
 819         if determinacy == Determinacy::Determined && kind == Some(MacroKind::Attr) {
 820             // For single-segment attributes interpret determinate "no resolution" as a custom
 821             // attribute. (Lexical resolution implies the first segment and attr kind should imply
 822             // the last segment, so we are certainly working with a single-segment attribute here.)
 823             assert!(ns == MacroNS);
 824             let binding = (Def::NonMacroAttr(NonMacroAttrKind::Custom),
 825                            ty::Visibility::Public, ident.span, Mark::root())
 826                            .to_name_binding(self.arenas);
 827             Ok((binding, FromPrelude(true)))
 828         } else {
 829             Err(determinacy)
 830         }
 831     }
 832
 833     fn resolve_legacy_scope(
 834         &mut self,
 835         ident: Ident,
 836         kind: Option<MacroKind>,
 837         parent_scope: &ParentScope<'a>,
 838         record_used: bool,
 839     ) -> Option<&'a NameBinding<'a>> {
 840         if sub_namespace_mismatch(kind, Some(MacroKind::Bang)) {
 841             return None;
 842         }
 843
 844         let ident = ident.modern();
 845
 846         // This is *the* result, resolution from the scope closest to the resolved identifier.
 847         // However, sometimes this result is "weak" because it comes from a macro expansion,
 848         // and in this case it cannot shadow names from outer scopes, e.g.
 849         // macro_rules! m { ... } // solution in outer scope
 850         // {
 851         //     define_m!(); // generates another `macro_rules! m` - innermost solution
 852         //                  // weak, cannot shadow the outer `m`, need to report ambiguity error
 853         //     m!();
 854         // }
 855         // So we have to save the innermost solution and continue searching in outer scopes
 856         // to detect potential ambiguities.
 857         let mut innermost_result: Option<&NameBinding> = None;
 858
 859         // Go through all the scopes and try to resolve the name.
 860         let mut where_to_resolve = parent_scope.legacy;
 861         loop {
 862             let result = match where_to_resolve {
 863                 LegacyScope::Binding(legacy_binding) if ident == legacy_binding.ident =>
 864                     Some(legacy_binding.binding),
 865                 _ => None,
 866             };
 867
 868             macro_rules! continue_search { () => {
 869                 where_to_resolve = match where_to_resolve {
 870                     LegacyScope::Empty => break, // nowhere else to search
 871                     LegacyScope::Binding(binding) => binding.parent_legacy_scope,
 872                     LegacyScope::Invocation(invocation) => invocation.output_legacy_scope.get(),
 873                     LegacyScope::Uninitialized => unreachable!(),
 874                 };
 875
 876                 continue;
 877             }}
 878
 879             match result {
 880                 Some(result) => {
 881                     if !record_used {
 882                         return Some(result);
 883                     }
 884
 885                     if let Some(innermost_result) = innermost_result {
 886                         // Found another solution, if the first one was "weak", report an error.
 887                         if result.def() != innermost_result.def() &&
 888                            innermost_result.may_appear_after(parent_scope.expansion, result) {
 889                             self.ambiguity_errors.push(AmbiguityError {
 890                                 ident,
 891                                 b1: innermost_result,
 892                                 b2: result,
 893                             });
 894                             return Some(innermost_result);
 895                         }
 896                     } else {
 897                         // Found the first solution.
 898                         innermost_result = Some(result);
 899                     }
 900
 901                     continue_search!();
 902                 }
 903                 None => {
 904                     continue_search!();
 905                 }
 906             }
 907         }
 908
 909         // The first found solution was the only one (or there was no solution at all), return it.
 910         innermost_result
 911     }
 912
 913     pub fn finalize_current_module_macro_resolutions(&mut self) {
 914         let module = self.current_module;
 915         for &(ref path, span) in module.macro_resolutions.borrow().iter() {
 916             match self.resolve_path(None, &path, Some(MacroNS), true, span, CrateLint::No) {
 917                 PathResult::NonModule(_) => {},
 918                 PathResult::Failed(span, msg, _) => {
 919                     resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
 920                 }
 921                 _ => unreachable!(),
 922             }
 923         }
 924
 925         let legacy_macro_resolutions =
 926             mem::replace(&mut *module.legacy_macro_resolutions.borrow_mut(), Vec::new());
 927         for (ident, kind, parent_scope, def) in legacy_macro_resolutions {
 928             let span = ident.span;
 929             let legacy_resolution = self.resolve_legacy_scope(
 930                 ident, Some(kind), &parent_scope, true
 931             );
 932             let resolution = self.resolve_lexical_macro_path_segment(
 933                 ident, MacroNS, Some(kind), &parent_scope, true, true, span
 934             );
 935
 936             let check_consistency = |this: &Self, new_def: Def| {
 937                 if let Some(def) = def {
 938                     if this.ambiguity_errors.is_empty() && new_def != def && new_def != Def::Err {
 939                         // Make sure compilation does not succeed if preferred macro resolution
 940                         // has changed after the macro had been expanded. In theory all such
 941                         // situations should be reported as ambiguity errors, so this is span-bug.
 942                         span_bug!(span, "inconsistent resolution for a macro");
 943                     }
 944                 } else {
 945                     // It's possible that the macro was unresolved (indeterminate) and silently
 946                     // expanded into a dummy fragment for recovery during expansion.
 947                     // Now, post-expansion, the resolution may succeed, but we can't change the
 948                     // past and need to report an error.
 949                     let msg =
 950                         format!("cannot determine resolution for the {} `{}`", kind.descr(), ident);
 951                     let msg_note = "import resolution is stuck, try simplifying macro imports";
 952                     this.session.struct_span_err(span, &msg).note(msg_note).emit();
 953                 }
 954             };
 955
 956             match (legacy_resolution, resolution) {
 957                 (None, Err(_)) => {
 958                     assert!(def.is_none());
 959                     let bang = if kind == MacroKind::Bang { "!" } else { "" };
 960                     let msg =
 961                         format!("cannot find {} `{}{}` in this scope", kind.descr(), ident, bang);
 962                     let mut err = self.session.struct_span_err(span, &msg);
 963                     self.suggest_macro_name(&ident.as_str(), kind, &mut err, span);
 964                     err.emit();
 965                 },
 966                 (Some(legacy_binding), Ok((binding, FromPrelude(from_prelude))))
 967                         if legacy_binding.def() != binding.def_ignoring_ambiguity() &&
 968                            (!from_prelude &&
 969                             !self.disambiguate_legacy_vs_modern(legacy_binding, binding) ||
 970                             legacy_binding.may_appear_after(parent_scope.expansion, binding)) => {
 971                     self.report_ambiguity_error(ident, legacy_binding, binding);
 972                 },
 973                 // OK, non-macro-expanded legacy wins over prelude even if defs are different
 974                 // Also, non-macro-expanded legacy wins over modern from the same module
 975                 // Also, legacy and modern can co-exist if their defs are same
 976                 (Some(legacy_binding), Ok(_)) |
 977                 // OK, unambiguous resolution
 978                 (Some(legacy_binding), Err(_)) => {
 979                     check_consistency(self, legacy_binding.def());
 980                 }
 981                 // OK, unambiguous resolution
 982                 (None, Ok((binding, FromPrelude(from_prelude)))) => {
 983                     check_consistency(self, binding.def_ignoring_ambiguity());
 984                     if from_prelude {
 985                         self.record_use(ident, MacroNS, binding);
 986                     }
 987                 }
 988             };
 989         }
 990
 991         let builtin_attrs = mem::replace(&mut *module.builtin_attrs.borrow_mut(), Vec::new());
 992         for (ident, parent_scope) in builtin_attrs {
 993             let resolve_legacy = |this: &mut Self| this.resolve_legacy_scope(
 994                 ident, Some(MacroKind::Attr), &parent_scope, true
 995             );
 996             let resolve_modern = |this: &mut Self| this.resolve_lexical_macro_path_segment(
 997                 ident, MacroNS, Some(MacroKind::Attr), &parent_scope, true, true, ident.span
 998             ).map(|(binding, _)| binding).ok();
 999
1000             if let Some(binding) = resolve_legacy(self).or_else(|| resolve_modern(self)) {
1001                 if binding.def_ignoring_ambiguity() !=
1002                         Def::NonMacroAttr(NonMacroAttrKind::Builtin) {
1003                     let builtin_binding = (Def::NonMacroAttr(NonMacroAttrKind::Builtin),
1004                                            ty::Visibility::Public, ident.span, Mark::root())
1005                                            .to_name_binding(self.arenas);
1006                     self.report_ambiguity_error(ident, binding, builtin_binding);
1007                 }
1008             }
1009         }
1010     }
1011
1012     fn suggest_macro_name(&mut self, name: &str, kind: MacroKind,
1013                           err: &mut DiagnosticBuilder<'a>, span: Span) {
1014         // First check if this is a locally-defined bang macro.
1015         let suggestion = if let MacroKind::Bang = kind {
1016             find_best_match_for_name(self.macro_names.iter().map(|ident| &ident.name), name, None)
1017         } else {
1018             None
1019         // Then check global macros.
1020         }.or_else(|| {
1021             let names = self.builtin_macros.iter().chain(self.macro_use_prelude.iter())
1022                                                   .filter_map(|(name, binding)| {
1023                 if binding.macro_kind() == Some(kind) { Some(name) } else { None }
1024             });
1025             find_best_match_for_name(names, name, None)
1026         // Then check modules.
1027         }).or_else(|| {
1028             let is_macro = |def| {
1029                 if let Def::Macro(_, def_kind) = def {
1030                     def_kind == kind
1031                 } else {
1032                     false
1033                 }
1034             };
1035             let ident = Ident::new(Symbol::intern(name), span);
1036             self.lookup_typo_candidate(&[ident], MacroNS, is_macro, span)
1037         });
1038
1039         if let Some(suggestion) = suggestion {
1040             if suggestion != name {
1041                 if let MacroKind::Bang = kind {
1042                     err.span_suggestion_with_applicability(
1043                         span,
1044                         "you could try the macro",
1045                         suggestion.to_string(),
1046                         Applicability::MaybeIncorrect
1047                     );
1048                 } else {
1049                     err.span_suggestion_with_applicability(
1050                         span,
1051                         "try",
1052                         suggestion.to_string(),
1053                         Applicability::MaybeIncorrect
1054                     );
1055                 }
1056             } else {
1057                 err.help("have you added the `#[macro_use]` on the module/import?");
1058             }
1059         }
1060     }
1061
1062     fn collect_def_ids(&mut self,
1063                        mark: Mark,
1064                        invocation: &'a InvocationData<'a>,
1065                        fragment: &AstFragment) {
1066         let Resolver { ref mut invocations, arenas, graph_root, .. } = *self;
1067         let InvocationData { def_index, .. } = *invocation;
1068
1069         let visit_macro_invoc = &mut |invoc: map::MacroInvocationData| {
1070             invocations.entry(invoc.mark).or_insert_with(|| {
1071                 arenas.alloc_invocation_data(InvocationData {
1072                     def_index: invoc.def_index,
1073                     module: Cell::new(graph_root),
1074                     parent_legacy_scope: Cell::new(LegacyScope::Uninitialized),
1075                     output_legacy_scope: Cell::new(LegacyScope::Uninitialized),
1076                 })
1077             });
1078         };
1079
1080         let mut def_collector = DefCollector::new(&mut self.definitions, mark);
1081         def_collector.visit_macro_invoc = Some(visit_macro_invoc);
1082         def_collector.with_parent(def_index, |def_collector| {
1083             fragment.visit_with(def_collector)
1084         });
1085     }
1086
1087     pub fn define_macro(&mut self,
1088                         item: &ast::Item,
1089                         expansion: Mark,
1090                         current_legacy_scope: &mut LegacyScope<'a>) {
1091         self.local_macro_def_scopes.insert(item.id, self.current_module);
1092         let ident = item.ident;
1093         if ident.name == "macro_rules" {
1094             self.session.span_err(item.span, "user-defined macros may not be named `macro_rules`");
1095         }
1096
1097         let def_id = self.definitions.local_def_id(item.id);
1098         let ext = Lrc::new(macro_rules::compile(&self.session.parse_sess,
1099                                                &self.session.features_untracked(),
1100                                                item, hygiene::default_edition()));
1101         self.macro_map.insert(def_id, ext);
1102
1103         let def = match item.node { ast::ItemKind::MacroDef(ref def) => def, _ => unreachable!() };
1104         if def.legacy {
1105             let ident = ident.modern();
1106             self.macro_names.insert(ident);
1107             let def = Def::Macro(def_id, MacroKind::Bang);
1108             let vis = ty::Visibility::Invisible; // Doesn't matter for legacy bindings
1109             let binding = (def, vis, item.span, expansion).to_name_binding(self.arenas);
1110             self.set_binding_parent_module(binding, self.current_module);
1111             let legacy_binding = self.arenas.alloc_legacy_binding(LegacyBinding {
1112                 parent_legacy_scope: *current_legacy_scope, binding, ident
1113             });
1114             *current_legacy_scope = LegacyScope::Binding(legacy_binding);
1115             self.all_macros.insert(ident.name, def);
1116             if attr::contains_name(&item.attrs, "macro_export") {
1117                 let module = self.graph_root;
1118                 let vis = ty::Visibility::Public;
1119                 self.define(module, ident, MacroNS,
1120                             (def, vis, item.span, expansion, IsMacroExport));
1121             } else {
1122                 if !attr::contains_name(&item.attrs, "rustc_doc_only_macro") {
1123                     self.check_reserved_macro_name(ident, MacroNS);
1124                 }
1125                 self.unused_macros.insert(def_id);
1126             }
1127         } else {
1128             let module = self.current_module;
1129             let def = Def::Macro(def_id, MacroKind::Bang);
1130             let vis = self.resolve_visibility(&item.vis);
1131             if vis != ty::Visibility::Public {
1132                 self.unused_macros.insert(def_id);
1133             }
1134             self.define(module, ident, MacroNS, (def, vis, item.span, expansion));
1135         }
1136     }
1137
1138     fn gate_legacy_custom_derive(&mut self, name: Symbol, span: Span) {
1139         if !self.session.features_untracked().custom_derive {
1140             let sess = &self.session.parse_sess;
1141             let explain = feature_gate::EXPLAIN_CUSTOM_DERIVE;
1142             emit_feature_err(sess, "custom_derive", span, GateIssue::Language, explain);
1143         } else if !self.is_whitelisted_legacy_custom_derive(name) {
1144             self.session.span_warn(span, feature_gate::EXPLAIN_DEPR_CUSTOM_DERIVE);
1145         }
1146     }
1147 }