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