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, *};
  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};
  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)]
  47 pub struct InvocationData<'a> {
  48     def_index: DefIndex,
  49     /// Module in which the macro was invoked.
  50     crate module: Cell<Module<'a>>,
  51     /// Legacy scope in which the macro was invoked.
  52     /// The invocation path is resolved in this scope.
  53     crate parent_legacy_scope: Cell<LegacyScope<'a>>,
  54     /// Legacy scope *produced* by expanding this macro invocation,
  55     /// includes all the macro_rules items, other invocations, etc generated by it.
  56     /// Set to the parent scope if the macro is not expanded yet (as if the macro produced nothing).
  57     crate output_legacy_scope: Cell<LegacyScope<'a>>,
  58 }
  59
  60 impl<'a> InvocationData<'a> {
  61     pub fn root(graph_root: Module<'a>) -> Self {
  62         InvocationData {
  63             module: Cell::new(graph_root),
  64             def_index: CRATE_DEF_INDEX,
  65             parent_legacy_scope: Cell::new(LegacyScope::Empty),
  66             output_legacy_scope: Cell::new(LegacyScope::Empty),
  67         }
  68     }
  69 }
  70
  71 /// Binding produced by a `macro_rules` item.
  72 /// Not modularized, can shadow previous legacy bindings, etc.
  73 pub struct LegacyBinding<'a> {
  74     binding: &'a NameBinding<'a>,
  75     /// Legacy scope into which the `macro_rules` item was planted.
  76     parent_legacy_scope: LegacyScope<'a>,
  77     ident: Ident,
  78 }
  79
  80 /// Scope introduced by a `macro_rules!` macro.
  81 /// Starts at the macro's definition and ends at the end of the macro's parent module
  82 /// (named or unnamed), or even further if it escapes with `#[macro_use]`.
  83 /// Some macro invocations need to introduce legacy scopes too because they
  84 /// potentially can expand into macro definitions.
  85 #[derive(Copy, Clone)]
  86 pub enum LegacyScope<'a> {
  87     /// Created when invocation data is allocated in the arena,
  88     /// must be replaced with a proper scope later.
  89     Uninitialized,
  90     /// Empty "root" scope at the crate start containing no names.
  91     Empty,
  92     /// Scope introduced by a `macro_rules!` macro definition.
  93     Binding(&'a LegacyBinding<'a>),
  94     /// Scope introduced by a macro invocation that can potentially
  95     /// create a `macro_rules!` macro definition.
  96     Invocation(&'a InvocationData<'a>),
  97 }
  98
  99 /// Everything you need to resolve a macro path.
 100 #[derive(Clone)]
 101 pub struct ParentScope<'a> {
 102     crate module: Module<'a>,
 103     crate expansion: Mark,
 104     crate legacy: LegacyScope<'a>,
 105     crate derives: Vec<ast::Path>,
 106 }
 107
 108 // Macro namespace is separated into two sub-namespaces, one for bang macros and
 109 // one for attribute-like macros (attributes, derives).
 110 // We ignore resolutions from one sub-namespace when searching names in scope for another.
 111 fn sub_namespace_mismatch(requirement: Option<MacroKind>, candidate: Option<MacroKind>) -> bool {
 112     #[derive(PartialEq)]
 113     enum SubNS { Bang, AttrLike }
 114     let sub_ns = |kind| match kind {
 115         MacroKind::Bang => Some(SubNS::Bang),
 116         MacroKind::Attr | MacroKind::Derive => Some(SubNS::AttrLike),
 117         MacroKind::ProcMacroStub => None,
 118     };
 119     let requirement = requirement.and_then(|kind| sub_ns(kind));
 120     let candidate = candidate.and_then(|kind| sub_ns(kind));
 121     // "No specific sub-namespace" means "matches anything" for both requirements and candidates.
 122     candidate.is_some() && requirement.is_some() && candidate != requirement
 123 }
 124
 125 impl<'a, 'crateloader: 'a> base::Resolver for Resolver<'a, 'crateloader> {
 126     fn next_node_id(&mut self) -> ast::NodeId {
 127         self.session.next_node_id()
 128     }
 129
 130     fn get_module_scope(&mut self, id: ast::NodeId) -> Mark {
 131         let mark = Mark::fresh(Mark::root());
 132         let module = self.module_map[&self.definitions.local_def_id(id)];
 133         self.invocations.insert(mark, self.arenas.alloc_invocation_data(InvocationData {
 134             module: Cell::new(module),
 135             def_index: module.def_id().unwrap().index,
 136             parent_legacy_scope: Cell::new(LegacyScope::Empty),
 137             output_legacy_scope: Cell::new(LegacyScope::Empty),
 138         }));
 139         mark
 140     }
 141
 142     fn eliminate_crate_var(&mut self, item: P<ast::Item>) -> P<ast::Item> {
 143         struct EliminateCrateVar<'b, 'a: 'b, 'crateloader: 'a>(
 144             &'b mut Resolver<'a, 'crateloader>, Span
 145         );
 146
 147         impl<'a, 'b, 'crateloader> Folder for EliminateCrateVar<'a, 'b, 'crateloader> {
 148             fn fold_path(&mut self, path: ast::Path) -> ast::Path {
 149                 match self.fold_qpath(None, path) {
 150                     (None, path) => path,
 151                     _ => unreachable!(),
 152                 }
 153             }
 154
 155             fn fold_qpath(&mut self, mut qself: Option<ast::QSelf>, mut path: ast::Path)
 156                           -> (Option<ast::QSelf>, ast::Path) {
 157                 qself = qself.map(|ast::QSelf { ty, path_span, position }| {
 158                     ast::QSelf {
 159                         ty: self.fold_ty(ty),
 160                         path_span: self.new_span(path_span),
 161                         position,
 162                     }
 163                 });
 164
 165                 if path.segments[0].ident.name == keywords::DollarCrate.name() {
 166                     let module = self.0.resolve_crate_root(path.segments[0].ident);
 167                     path.segments[0].ident.name = keywords::CrateRoot.name();
 168                     if !module.is_local() {
 169                         let span = path.segments[0].ident.span;
 170                         path.segments.insert(1, match module.kind {
 171                             ModuleKind::Def(_, name) => ast::PathSegment::from_ident(
 172                                 ast::Ident::with_empty_ctxt(name).with_span_pos(span)
 173                             ),
 174                             _ => unreachable!(),
 175                         });
 176                         if let Some(qself) = &mut qself {
 177                             qself.position += 1;
 178                         }
 179                     }
 180                 }
 181                 (qself, path)
 182             }
 183
 184             fn fold_mac(&mut self, mac: ast::Mac) -> ast::Mac {
 185                 fold::noop_fold_mac(mac, self)
 186             }
 187         }
 188
 189         let ret = EliminateCrateVar(self, item.span).fold_item(item);
 190         assert!(ret.len() == 1);
 191         ret.into_iter().next().unwrap()
 192     }
 193
 194     fn is_whitelisted_legacy_custom_derive(&self, name: Name) -> bool {
 195         self.whitelisted_legacy_custom_derives.contains(&name)
 196     }
 197
 198     fn visit_ast_fragment_with_placeholders(&mut self, mark: Mark, fragment: &AstFragment,
 199                                             derives: &[Mark]) {
 200         let invocation = self.invocations[&mark];
 201         self.collect_def_ids(mark, invocation, fragment);
 202
 203         self.current_module = invocation.module.get();
 204         self.current_module.unresolved_invocations.borrow_mut().remove(&mark);
 205         self.current_module.unresolved_invocations.borrow_mut().extend(derives);
 206         self.invocations.extend(derives.iter().map(|&derive| (derive, invocation)));
 207         let mut visitor = BuildReducedGraphVisitor {
 208             resolver: self,
 209             current_legacy_scope: invocation.parent_legacy_scope.get(),
 210             expansion: mark,
 211         };
 212         fragment.visit_with(&mut visitor);
 213         invocation.output_legacy_scope.set(visitor.current_legacy_scope);
 214     }
 215
 216     fn add_builtin(&mut self, ident: ast::Ident, ext: Lrc<SyntaxExtension>) {
 217         let def_id = DefId {
 218             krate: CrateNum::BuiltinMacros,
 219             index: DefIndex::from_array_index(self.macro_map.len(),
 220                                               DefIndexAddressSpace::Low),
 221         };
 222         let kind = ext.kind();
 223         self.macro_map.insert(def_id, ext);
 224         let binding = self.arenas.alloc_name_binding(NameBinding {
 225             kind: NameBindingKind::Def(Def::Macro(def_id, kind), false),
 226             span: DUMMY_SP,
 227             vis: ty::Visibility::Invisible,
 228             expansion: Mark::root(),
 229         });
 230         if self.builtin_macros.insert(ident.name, binding).is_some() {
 231             self.session.span_err(ident.span,
 232                                   &format!("built-in macro `{}` was already defined", ident));
 233         }
 234     }
 235
 236     fn resolve_imports(&mut self) {
 237         ImportResolver { resolver: self }.resolve_imports()
 238     }
 239
 240     // Resolves attribute and derive legacy macros from `#![plugin(..)]`.
 241     fn find_legacy_attr_invoc(&mut self, attrs: &mut Vec<ast::Attribute>, allow_derive: bool)
 242                               -> Option<ast::Attribute> {
 243         if !allow_derive {
 244             return None;
 245         }
 246
 247         // Check for legacy derives
 248         for i in 0..attrs.len() {
 249             let name = attrs[i].name();
 250
 251             if name == "derive" {
 252                 let result = attrs[i].parse_list(&self.session.parse_sess, |parser| {
 253                     parser.parse_path_allowing_meta(PathStyle::Mod)
 254                 });
 255
 256                 let mut traits = match result {
 257                     Ok(traits) => traits,
 258                     Err(mut e) => {
 259                         e.cancel();
 260                         continue
 261                     }
 262                 };
 263
 264                 for j in 0..traits.len() {
 265                     if traits[j].segments.len() > 1 {
 266                         continue
 267                     }
 268                     let trait_name = traits[j].segments[0].ident.name;
 269                     let legacy_name = Symbol::intern(&format!("derive_{}", trait_name));
 270                     if !self.builtin_macros.contains_key(&legacy_name) {
 271                         continue
 272                     }
 273                     let span = traits.remove(j).span;
 274                     self.gate_legacy_custom_derive(legacy_name, span);
 275                     if traits.is_empty() {
 276                         attrs.remove(i);
 277                     } else {
 278                         let mut tokens = Vec::with_capacity(traits.len() - 1);
 279                         for (j, path) in traits.iter().enumerate() {
 280                             if j > 0 {
 281                                 tokens.push(TokenTree::Token(attrs[i].span, Token::Comma).into());
 282                             }
 283                             tokens.reserve((path.segments.len() * 2).saturating_sub(1));
 284                             for (k, segment) in path.segments.iter().enumerate() {
 285                                 if k > 0 {
 286                                     tokens.push(TokenTree::Token(path.span, Token::ModSep).into());
 287                                 }
 288                                 let tok = Token::from_ast_ident(segment.ident);
 289                                 tokens.push(TokenTree::Token(path.span, tok).into());
 290                             }
 291                         }
 292                         let delim_span = DelimSpan::from_single(attrs[i].span);
 293                         attrs[i].tokens = TokenTree::Delimited(delim_span, Delimited {
 294                             delim: token::Paren,
 295                             tts: TokenStream::concat(tokens).into(),
 296                         }).into();
 297                     }
 298                     return Some(ast::Attribute {
 299                         path: ast::Path::from_ident(Ident::new(legacy_name, span)),
 300                         tokens: TokenStream::empty(),
 301                         id: attr::mk_attr_id(),
 302                         style: ast::AttrStyle::Outer,
 303                         is_sugared_doc: false,
 304                         span,
 305                     });
 306                 }
 307             }
 308         }
 309
 310         None
 311     }
 312
 313     fn resolve_macro_invocation(&mut self, invoc: &Invocation, invoc_id: Mark, force: bool)
 314                                 -> Result<Option<Lrc<SyntaxExtension>>, Determinacy> {
 315         let (path, kind, derives_in_scope, after_derive) = match invoc.kind {
 316             InvocationKind::Attr { attr: None, .. } =>
 317                 return Ok(None),
 318             InvocationKind::Attr { attr: Some(ref attr), ref traits, after_derive, .. } =>
 319                 (&attr.path, MacroKind::Attr, traits.clone(), after_derive),
 320             InvocationKind::Bang { ref mac, .. } =>
 321                 (&mac.node.path, MacroKind::Bang, Vec::new(), false),
 322             InvocationKind::Derive { ref path, .. } =>
 323                 (path, MacroKind::Derive, Vec::new(), false),
 324         };
 325
 326         let parent_scope = self.invoc_parent_scope(invoc_id, derives_in_scope);
 327         let (def, ext) = self.resolve_macro_to_def(path, kind, &parent_scope, force)?;
 328
 329         if let Def::Macro(def_id, _) = def {
 330             if after_derive {
 331                 self.session.span_err(invoc.span(),
 332                                       "macro attributes must be placed before `#[derive]`");
 333             }
 334             self.macro_defs.insert(invoc.expansion_data.mark, def_id);
 335             let normal_module_def_id =
 336                 self.macro_def_scope(invoc.expansion_data.mark).normal_ancestor_id;
 337             self.definitions.add_parent_module_of_macro_def(invoc.expansion_data.mark,
 338                                                             normal_module_def_id);
 339             invoc.expansion_data.mark.set_default_transparency(ext.default_transparency());
 340             invoc.expansion_data.mark.set_is_builtin(def_id.krate == CrateNum::BuiltinMacros);
 341         }
 342
 343         Ok(Some(ext))
 344     }
 345
 346     fn resolve_macro_path(&mut self, path: &ast::Path, kind: MacroKind, invoc_id: Mark,
 347                           derives_in_scope: Vec<ast::Path>, force: bool)
 348                           -> Result<Lrc<SyntaxExtension>, Determinacy> {
 349         let parent_scope = self.invoc_parent_scope(invoc_id, derives_in_scope);
 350         Ok(self.resolve_macro_to_def(path, kind, &parent_scope, force)?.1)
 351     }
 352
 353     fn check_unused_macros(&self) {
 354         for did in self.unused_macros.iter() {
 355             let id_span = match *self.macro_map[did] {
 356                 SyntaxExtension::NormalTT { def_info, .. } |
 357                 SyntaxExtension::DeclMacro { def_info, .. } => def_info,
 358                 _ => None,
 359             };
 360             if let Some((id, span)) = id_span {
 361                 let lint = lint::builtin::UNUSED_MACROS;
 362                 let msg = "unused macro definition";
 363                 self.session.buffer_lint(lint, id, span, msg);
 364             } else {
 365                 bug!("attempted to create unused macro error, but span not available");
 366             }
 367         }
 368     }
 369 }
 370
 371 impl<'a, 'cl> Resolver<'a, 'cl> {
 372     pub fn dummy_parent_scope(&mut self) -> ParentScope<'a> {
 373         self.invoc_parent_scope(Mark::root(), Vec::new())
 374     }
 375
 376     fn invoc_parent_scope(&mut self, invoc_id: Mark, derives: Vec<ast::Path>) -> ParentScope<'a> {
 377         let invoc = self.invocations[&invoc_id];
 378         ParentScope {
 379             module: invoc.module.get().nearest_item_scope(),
 380             expansion: invoc_id.parent(),
 381             legacy: invoc.parent_legacy_scope.get(),
 382             derives,
 383         }
 384     }
 385
 386     fn resolve_macro_to_def(
 387         &mut self,
 388         path: &ast::Path,
 389         kind: MacroKind,
 390         parent_scope: &ParentScope<'a>,
 391         force: bool,
 392     ) -> Result<(Def, Lrc<SyntaxExtension>), Determinacy> {
 393         let def = self.resolve_macro_to_def_inner(path, kind, parent_scope, force);
 394
 395         // Report errors and enforce feature gates for the resolved macro.
 396         if def != Err(Determinacy::Undetermined) {
 397             // Do not report duplicated errors on every undetermined resolution.
 398             for segment in &path.segments {
 399                 if let Some(args) = &segment.args {
 400                     self.session.span_err(args.span(), "generic arguments in macro path");
 401                 }
 402             }
 403         }
 404
 405         let def = def?;
 406
 407         match def {
 408             Def::Macro(def_id, macro_kind) => {
 409                 self.unused_macros.remove(&def_id);
 410                 if macro_kind == MacroKind::ProcMacroStub {
 411                     let msg = "can't use a procedural macro from the same crate that defines it";
 412                     self.session.span_err(path.span, msg);
 413                     return Err(Determinacy::Determined);
 414                 }
 415             }
 416             Def::NonMacroAttr(attr_kind) => {
 417                 if kind == MacroKind::Attr {
 418                     let features = self.session.features_untracked();
 419                     if attr_kind == NonMacroAttrKind::Custom {
 420                         assert!(path.segments.len() == 1);
 421                         let name = path.segments[0].ident.name.as_str();
 422                         if name.starts_with("rustc_") {
 423                             if !features.rustc_attrs {
 424                                 let msg = "unless otherwise specified, attributes with the prefix \
 425                                            `rustc_` are reserved for internal compiler diagnostics";
 426                                 feature_err(&self.session.parse_sess, "rustc_attrs", path.span,
 427                                             GateIssue::Language, &msg).emit();
 428                             }
 429                         } else if name.starts_with("derive_") {
 430                             if !features.custom_derive {
 431                                 feature_err(&self.session.parse_sess, "custom_derive", path.span,
 432                                             GateIssue::Language, EXPLAIN_DERIVE_UNDERSCORE).emit();
 433                             }
 434                         } else if !features.custom_attribute {
 435                             let msg = format!("The attribute `{}` is currently unknown to the \
 436                                                compiler and may have meaning added to it in the \
 437                                                future", path);
 438                             feature_err(&self.session.parse_sess, "custom_attribute", path.span,
 439                                         GateIssue::Language, &msg).emit();
 440                         }
 441                     }
 442                 } else {
 443                     // Not only attributes, but anything in macro namespace can result in
 444                     // `Def::NonMacroAttr` definition (e.g. `inline!()`), so we must report
 445                     // an error for those cases.
 446                     let msg = format!("expected a macro, found {}", def.kind_name());
 447                     self.session.span_err(path.span, &msg);
 448                     return Err(Determinacy::Determined);
 449                 }
 450             }
 451             _ => panic!("expected `Def::Macro` or `Def::NonMacroAttr`"),
 452         }
 453
 454         Ok((def, self.get_macro(def)))
 455     }
 456
 457     pub fn resolve_macro_to_def_inner(
 458         &mut self,
 459         path: &ast::Path,
 460         kind: MacroKind,
 461         parent_scope: &ParentScope<'a>,
 462         force: bool,
 463     ) -> Result<Def, Determinacy> {
 464         let ast::Path { ref segments, span } = *path;
 465         let mut path: Vec<_> = segments.iter().map(|seg| seg.ident).collect();
 466
 467         // Possibly apply the macro helper hack
 468         if kind == MacroKind::Bang && path.len() == 1 &&
 469            path[0].span.ctxt().outer().expn_info().map_or(false, |info| info.local_inner_macros) {
 470             let root = Ident::new(keywords::DollarCrate.name(), path[0].span);
 471             path.insert(0, root);
 472         }
 473
 474         if path.len() > 1 {
 475             let def = match self.resolve_path_with_parent_scope(None, &path, Some(MacroNS),
 476                                                                 parent_scope, false, span,
 477                                                                 CrateLint::No) {
 478                 PathResult::NonModule(path_res) => match path_res.base_def() {
 479                     Def::Err => Err(Determinacy::Determined),
 480                     def @ _ => {
 481                         if path_res.unresolved_segments() > 0 {
 482                             self.found_unresolved_macro = true;
 483                             self.session.span_err(span, "fail to resolve non-ident macro path");
 484                             Err(Determinacy::Determined)
 485                         } else {
 486                             Ok(def)
 487                         }
 488                     }
 489                 },
 490                 PathResult::Module(..) => unreachable!(),
 491                 PathResult::Indeterminate if !force => return Err(Determinacy::Undetermined),
 492                 _ => {
 493                     self.found_unresolved_macro = true;
 494                     Err(Determinacy::Determined)
 495                 },
 496             };
 497
 498             parent_scope.module.macro_resolutions.borrow_mut()
 499                 .push((path.into_boxed_slice(), span));
 500
 501             def
 502         } else {
 503             let binding = self.early_resolve_ident_in_lexical_scope(
 504                 path[0], MacroNS, Some(kind), parent_scope, false, force, span
 505             );
 506             match binding {
 507                 Ok(..) => {}
 508                 Err(Determinacy::Determined) => self.found_unresolved_macro = true,
 509                 Err(Determinacy::Undetermined) => return Err(Determinacy::Undetermined),
 510             }
 511
 512             parent_scope.module.legacy_macro_resolutions.borrow_mut()
 513                 .push((path[0], kind, parent_scope.clone(), binding.ok()));
 514
 515             binding.map(|binding| binding.def_ignoring_ambiguity())
 516         }
 517     }
 518
 519     // Resolve an identifier in lexical scope.
 520     // This is a variation of `fn resolve_ident_in_lexical_scope` that can be run during
 521     // expansion and import resolution (perhaps they can be merged in the future).
 522     // The function is used for resolving initial segments of macro paths (e.g. `foo` in
 523     // `foo::bar!(); or `foo!();`) and can be used for "uniform path" imports in the future.
 524     crate fn early_resolve_ident_in_lexical_scope(
 525         &mut self,
 526         mut ident: Ident,
 527         ns: Namespace,
 528         kind: Option<MacroKind>,
 529         parent_scope: &ParentScope<'a>,
 530         record_used: bool,
 531         force: bool,
 532         path_span: Span,
 533     ) -> Result<&'a NameBinding<'a>, Determinacy> {
 534         // General principles:
 535         // 1. Not controlled (user-defined) names should have higher priority than controlled names
 536         //    built into the language or standard library. This way we can add new names into the
 537         //    language or standard library without breaking user code.
 538         // 2. "Closed set" below means new names cannot appear after the current resolution attempt.
 539         // Places to search (in order of decreasing priority):
 540         // (Type NS)
 541         // 1. FIXME: Ribs (type parameters), there's no necessary infrastructure yet
 542         //    (open set, not controlled).
 543         // 2. Names in modules (both normal `mod`ules and blocks), loop through hygienic parents
 544         //    (open, not controlled).
 545         // 3. Extern prelude (closed, not controlled).
 546         // 4. Tool modules (closed, controlled right now, but not in the future).
 547         // 5. Standard library prelude (de-facto closed, controlled).
 548         // 6. Language prelude (closed, controlled).
 549         // (Value NS)
 550         // 1. FIXME: Ribs (local variables), there's no necessary infrastructure yet
 551         //    (open set, not controlled).
 552         // 2. Names in modules (both normal `mod`ules and blocks), loop through hygienic parents
 553         //    (open, not controlled).
 554         // 3. Standard library prelude (de-facto closed, controlled).
 555         // (Macro NS)
 556         // 1-3. Derive helpers (open, not controlled). All ambiguities with other names
 557         //    are currently reported as errors. They should be higher in priority than preludes
 558         //    and probably even names in modules according to the "general principles" above. They
 559         //    also should be subject to restricted shadowing because are effectively produced by
 560         //    derives (you need to resolve the derive first to add helpers into scope), but they
 561         //    should be available before the derive is expanded for compatibility.
 562         //    It's mess in general, so we are being conservative for now.
 563         // 1-3. `macro_rules` (open, not controlled), loop through legacy scopes. Have higher
 564         //    priority than prelude macros, but create ambiguities with macros in modules.
 565         // 1-3. Names in modules (both normal `mod`ules and blocks), loop through hygienic parents
 566         //    (open, not controlled). Have higher priority than prelude macros, but create
 567         //    ambiguities with `macro_rules`.
 568         // 4. `macro_use` prelude (open, the open part is from macro expansions, not controlled).
 569         // 4a. User-defined prelude from macro-use
 570         //    (open, the open part is from macro expansions, not controlled).
 571         // 4b. Standard library prelude is currently implemented as `macro-use` (closed, controlled)
 572         // 5. Language prelude: builtin macros (closed, controlled, except for legacy plugins).
 573         // 6. Language prelude: builtin attributes (closed, controlled).
 574         // 4-6. Legacy plugin helpers (open, not controlled). Similar to derive helpers,
 575         //    but introduced by legacy plugins using `register_attribute`. Priority is somewhere
 576         //    in prelude, not sure where exactly (creates ambiguities with any other prelude names).
 577
 578         enum WhereToResolve<'a> {
 579             DeriveHelpers,
 580             MacroRules(LegacyScope<'a>),
 581             Module(Module<'a>),
 582             MacroUsePrelude,
 583             BuiltinMacros,
 584             BuiltinAttrs,
 585             LegacyPluginHelpers,
 586             ExternPrelude,
 587             ToolPrelude,
 588             StdLibPrelude,
 589             BuiltinTypes,
 590         }
 591
 592         bitflags! {
 593             struct Flags: u8 {
 594                 const DERIVE_HELPERS = 1 << 0;
 595                 const MACRO_RULES    = 1 << 1;
 596                 const MODULE         = 1 << 2;
 597                 const PRELUDE        = 1 << 3;
 598             }
 599         }
 600
 601         assert!(force || !record_used); // `record_used` implies `force`
 602         ident = ident.modern();
 603
 604         // This is *the* result, resolution from the scope closest to the resolved identifier.
 605         // However, sometimes this result is "weak" because it comes from a glob import or
 606         // a macro expansion, and in this case it cannot shadow names from outer scopes, e.g.
 607         // mod m { ... } // solution in outer scope
 608         // {
 609         //     use prefix::*; // imports another `m` - innermost solution
 610         //                    // weak, cannot shadow the outer `m`, need to report ambiguity error
 611         //     m::mac!();
 612         // }
 613         // So we have to save the innermost solution and continue searching in outer scopes
 614         // to detect potential ambiguities.
 615         let mut innermost_result: Option<(&NameBinding, Flags, /* conflicts with */ Flags)> = None;
 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::DeriveHelpers => {
 623                     let mut result = Err(Determinacy::Determined);
 624                     for derive in &parent_scope.derives {
 625                         let parent_scope = ParentScope { derives: Vec::new(), ..*parent_scope };
 626                         if let Ok((_, ext)) = self.resolve_macro_to_def(derive, MacroKind::Derive,
 627                                                                         &parent_scope, force) {
 628                             if let SyntaxExtension::ProcMacroDerive(_, helper_attrs, _) = &*ext {
 629                                 if helper_attrs.contains(&ident.name) {
 630                                     let binding =
 631                                         (Def::NonMacroAttr(NonMacroAttrKind::DeriveHelper),
 632                                         ty::Visibility::Public, derive.span, Mark::root())
 633                                         .to_name_binding(self.arenas);
 634                                     result = Ok((binding, Flags::DERIVE_HELPERS, Flags::all()));
 635                                     break;
 636                                 }
 637                             }
 638                         }
 639                     }
 640                     result
 641                 }
 642                 WhereToResolve::MacroRules(legacy_scope) => match legacy_scope {
 643                     LegacyScope::Binding(legacy_binding) if ident == legacy_binding.ident =>
 644                         Ok((legacy_binding.binding, Flags::MACRO_RULES, Flags::empty())),
 645                     _ => Err(Determinacy::Determined),
 646                 }
 647                 WhereToResolve::Module(module) => {
 648                     let orig_current_module = mem::replace(&mut self.current_module, module);
 649                     let binding = self.resolve_ident_in_module_unadjusted(
 650                         ModuleOrUniformRoot::Module(module),
 651                         ident,
 652                         ns,
 653                         true,
 654                         record_used,
 655                         path_span,
 656                     );
 657                     self.current_module = orig_current_module;
 658                     binding.map(|binding| (binding, Flags::MODULE, Flags::empty()))
 659                 }
 660                 WhereToResolve::MacroUsePrelude => {
 661                     match self.macro_use_prelude.get(&ident.name).cloned() {
 662                         Some(binding) => Ok((binding, Flags::PRELUDE, Flags::empty())),
 663                         None => Err(Determinacy::Determined),
 664                     }
 665                 }
 666                 WhereToResolve::BuiltinMacros => {
 667                     match self.builtin_macros.get(&ident.name).cloned() {
 668                         Some(binding) => Ok((binding, Flags::PRELUDE, Flags::empty())),
 669                         None => Err(Determinacy::Determined),
 670                     }
 671                 }
 672                 WhereToResolve::BuiltinAttrs => {
 673                     if is_builtin_attr_name(ident.name) {
 674                         let binding = (Def::NonMacroAttr(NonMacroAttrKind::Builtin),
 675                                        ty::Visibility::Public, ident.span, Mark::root())
 676                                        .to_name_binding(self.arenas);
 677                         Ok((binding, Flags::PRELUDE, Flags::empty()))
 678                     } else {
 679                         Err(Determinacy::Determined)
 680                     }
 681                 }
 682                 WhereToResolve::LegacyPluginHelpers => {
 683                     if self.session.plugin_attributes.borrow().iter()
 684                                                      .any(|(name, _)| ident.name == &**name) {
 685                         let binding = (Def::NonMacroAttr(NonMacroAttrKind::LegacyPluginHelper),
 686                                        ty::Visibility::Public, ident.span, Mark::root())
 687                                        .to_name_binding(self.arenas);
 688                         Ok((binding, Flags::PRELUDE, Flags::PRELUDE))
 689                     } else {
 690                         Err(Determinacy::Determined)
 691                     }
 692                 }
 693                 WhereToResolve::ExternPrelude => {
 694                     if use_prelude && self.extern_prelude.contains(&ident.name) {
 695                         let crate_id =
 696                             self.crate_loader.process_path_extern(ident.name, ident.span);
 697                         let crate_root =
 698                             self.get_module(DefId { krate: crate_id, index: CRATE_DEF_INDEX });
 699                         self.populate_module_if_necessary(crate_root);
 700
 701                         let binding = (crate_root, ty::Visibility::Public,
 702                                        ident.span, Mark::root()).to_name_binding(self.arenas);
 703                         Ok((binding, Flags::PRELUDE, Flags::empty()))
 704                     } else {
 705                         Err(Determinacy::Determined)
 706                     }
 707                 }
 708                 WhereToResolve::ToolPrelude => {
 709                     if use_prelude && is_known_tool(ident.name) {
 710                         let binding = (Def::ToolMod, ty::Visibility::Public,
 711                                        ident.span, Mark::root()).to_name_binding(self.arenas);
 712                         Ok((binding, Flags::PRELUDE, Flags::empty()))
 713                     } else {
 714                         Err(Determinacy::Determined)
 715                     }
 716                 }
 717                 WhereToResolve::StdLibPrelude => {
 718                     let mut result = Err(Determinacy::Determined);
 719                     if use_prelude {
 720                         if let Some(prelude) = self.prelude {
 721                             if let Ok(binding) = self.resolve_ident_in_module_unadjusted(
 722                                 ModuleOrUniformRoot::Module(prelude),
 723                                 ident,
 724                                 ns,
 725                                 false,
 726                                 false,
 727                                 path_span,
 728                             ) {
 729                                 result = Ok((binding, Flags::PRELUDE, Flags::empty()));
 730                             }
 731                         }
 732                     }
 733                     result
 734                 }
 735                 WhereToResolve::BuiltinTypes => {
 736                     match self.primitive_type_table.primitive_types.get(&ident.name).cloned() {
 737                         Some(prim_ty) => {
 738                             let binding = (Def::PrimTy(prim_ty), ty::Visibility::Public,
 739                                            ident.span, Mark::root()).to_name_binding(self.arenas);
 740                             Ok((binding, Flags::PRELUDE, Flags::empty()))
 741                         }
 742                         None => Err(Determinacy::Determined)
 743                     }
 744                 }
 745             };
 746
 747             macro_rules! continue_search { () => {
 748                 where_to_resolve = match where_to_resolve {
 749                     WhereToResolve::DeriveHelpers =>
 750                         WhereToResolve::MacroRules(parent_scope.legacy),
 751                     WhereToResolve::MacroRules(legacy_scope) => match legacy_scope {
 752                         LegacyScope::Binding(binding) =>
 753                             WhereToResolve::MacroRules(binding.parent_legacy_scope),
 754                         LegacyScope::Invocation(invocation) =>
 755                             WhereToResolve::MacroRules(invocation.output_legacy_scope.get()),
 756                         LegacyScope::Empty => WhereToResolve::Module(parent_scope.module),
 757                         LegacyScope::Uninitialized => unreachable!(),
 758                     }
 759                     WhereToResolve::Module(module) => {
 760                         match self.hygienic_lexical_parent(module, &mut ident.span) {
 761                             Some(parent_module) => WhereToResolve::Module(parent_module),
 762                             None => {
 763                                 use_prelude = !module.no_implicit_prelude;
 764                                 match ns {
 765                                     TypeNS => WhereToResolve::ExternPrelude,
 766                                     ValueNS => WhereToResolve::StdLibPrelude,
 767                                     MacroNS => WhereToResolve::MacroUsePrelude,
 768                                 }
 769                             }
 770                         }
 771                     }
 772                     WhereToResolve::MacroUsePrelude => WhereToResolve::BuiltinMacros,
 773                     WhereToResolve::BuiltinMacros => WhereToResolve::BuiltinAttrs,
 774                     WhereToResolve::BuiltinAttrs => WhereToResolve::LegacyPluginHelpers,
 775                     WhereToResolve::LegacyPluginHelpers => break, // nowhere else to search
 776                     WhereToResolve::ExternPrelude => WhereToResolve::ToolPrelude,
 777                     WhereToResolve::ToolPrelude => WhereToResolve::StdLibPrelude,
 778                     WhereToResolve::StdLibPrelude => match ns {
 779                         TypeNS => WhereToResolve::BuiltinTypes,
 780                         ValueNS => break, // nowhere else to search
 781                         MacroNS => unreachable!(),
 782                     }
 783                     WhereToResolve::BuiltinTypes => break, // nowhere else to search
 784                 };
 785
 786                 continue;
 787             }}
 788
 789             match result {
 790                 Ok((binding, flags, ambig_flags)) => {
 791                     if sub_namespace_mismatch(kind, binding.macro_kind()) {
 792                         continue_search!();
 793                     }
 794
 795                     if !record_used {
 796                         return Ok(binding);
 797                     }
 798
 799                     if let Some((innermost_binding, innermost_flags, innermost_ambig_flags))
 800                             = innermost_result {
 801                         // Found another solution, if the first one was "weak", report an error.
 802                         if binding.def() != innermost_binding.def() &&
 803                            (innermost_binding.is_glob_import() ||
 804                             innermost_binding.may_appear_after(parent_scope.expansion, binding) ||
 805                             innermost_flags.intersects(ambig_flags) ||
 806                             flags.intersects(innermost_ambig_flags) ||
 807                             (innermost_flags.contains(Flags::MACRO_RULES) &&
 808                              flags.contains(Flags::MODULE) &&
 809                              !self.disambiguate_legacy_vs_modern(innermost_binding, binding))) {
 810                             self.ambiguity_errors.push(AmbiguityError {
 811                                 ident,
 812                                 b1: innermost_binding,
 813                                 b2: binding,
 814                             });
 815                             return Ok(innermost_binding);
 816                         }
 817                     } else {
 818                         // Found the first solution.
 819                         innermost_result = Some((binding, flags, ambig_flags));
 820                     }
 821
 822                     continue_search!();
 823                 },
 824                 Err(Determinacy::Determined) => {
 825                     continue_search!();
 826                 }
 827                 Err(Determinacy::Undetermined) => return Err(Determinacy::determined(force)),
 828             }
 829         }
 830
 831         // The first found solution was the only one, return it.
 832         if let Some((binding, ..)) = innermost_result {
 833             return Ok(binding);
 834         }
 835
 836         let determinacy = Determinacy::determined(force);
 837         if determinacy == Determinacy::Determined && kind == Some(MacroKind::Attr) {
 838             // For single-segment attributes interpret determinate "no resolution" as a custom
 839             // attribute. (Lexical resolution implies the first segment and attr kind should imply
 840             // the last segment, so we are certainly working with a single-segment attribute here.)
 841             assert!(ns == MacroNS);
 842             let binding = (Def::NonMacroAttr(NonMacroAttrKind::Custom),
 843                            ty::Visibility::Public, ident.span, Mark::root())
 844                            .to_name_binding(self.arenas);
 845             Ok(binding)
 846         } else {
 847             Err(determinacy)
 848         }
 849     }
 850
 851     pub fn finalize_current_module_macro_resolutions(&mut self) {
 852         let module = self.current_module;
 853         for &(ref path, span) in module.macro_resolutions.borrow().iter() {
 854             match self.resolve_path(None, &path, Some(MacroNS), true, span, CrateLint::No) {
 855                 PathResult::NonModule(_) => {},
 856                 PathResult::Failed(span, msg, _) => {
 857                     resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
 858                 }
 859                 _ => unreachable!(),
 860             }
 861         }
 862
 863         let legacy_macro_resolutions =
 864             mem::replace(&mut *module.legacy_macro_resolutions.borrow_mut(), Vec::new());
 865         for (ident, kind, parent_scope, initial_binding) in legacy_macro_resolutions {
 866             let binding = self.early_resolve_ident_in_lexical_scope(
 867                 ident, MacroNS, Some(kind), &parent_scope, true, true, ident.span
 868             );
 869             match binding {
 870                 Ok(binding) => {
 871                     let def = binding.def_ignoring_ambiguity();
 872                     if let Some(initial_binding) = initial_binding {
 873                         self.record_use(ident, MacroNS, initial_binding);
 874                         let initial_def = initial_binding.def_ignoring_ambiguity();
 875                         if self.ambiguity_errors.is_empty() &&
 876                            def != initial_def && def != Def::Err {
 877                             // Make sure compilation does not succeed if preferred macro resolution
 878                             // has changed after the macro had been expanded. In theory all such
 879                             // situations should be reported as ambiguity errors, so this is a bug.
 880                             span_bug!(ident.span, "inconsistent resolution for a macro");
 881                         }
 882                     } else {
 883                         // It's possible that the macro was unresolved (indeterminate) and silently
 884                         // expanded into a dummy fragment for recovery during expansion.
 885                         // Now, post-expansion, the resolution may succeed, but we can't change the
 886                         // past and need to report an error.
 887                         let msg = format!("cannot determine resolution for the {} `{}`",
 888                                           kind.descr(), ident);
 889                         let msg_note = "import resolution is stuck, try simplifying macro imports";
 890                         self.session.struct_span_err(ident.span, &msg).note(msg_note).emit();
 891                     }
 892                 }
 893                 Err(..) => {
 894                     assert!(initial_binding.is_none());
 895                     let bang = if kind == MacroKind::Bang { "!" } else { "" };
 896                     let msg =
 897                         format!("cannot find {} `{}{}` in this scope", kind.descr(), ident, bang);
 898                     let mut err = self.session.struct_span_err(ident.span, &msg);
 899                     self.suggest_macro_name(&ident.as_str(), kind, &mut err, ident.span);
 900                     err.emit();
 901                 }
 902             }
 903         }
 904
 905         let builtin_attrs = mem::replace(&mut *module.builtin_attrs.borrow_mut(), Vec::new());
 906         for (ident, parent_scope) in builtin_attrs {
 907             let binding = self.early_resolve_ident_in_lexical_scope(
 908                 ident, MacroNS, Some(MacroKind::Attr), &parent_scope, true, true, ident.span
 909             );
 910             if let Ok(binding) = binding {
 911                 if binding.def_ignoring_ambiguity() !=
 912                         Def::NonMacroAttr(NonMacroAttrKind::Builtin) {
 913                     let builtin_binding = (Def::NonMacroAttr(NonMacroAttrKind::Builtin),
 914                                            ty::Visibility::Public, ident.span, Mark::root())
 915                                            .to_name_binding(self.arenas);
 916                     self.report_ambiguity_error(ident, binding, builtin_binding);
 917                 }
 918             }
 919         }
 920     }
 921
 922     fn suggest_macro_name(&mut self, name: &str, kind: MacroKind,
 923                           err: &mut DiagnosticBuilder<'a>, span: Span) {
 924         // First check if this is a locally-defined bang macro.
 925         let suggestion = if let MacroKind::Bang = kind {
 926             find_best_match_for_name(self.macro_names.iter().map(|ident| &ident.name), name, None)
 927         } else {
 928             None
 929         // Then check global macros.
 930         }.or_else(|| {
 931             let names = self.builtin_macros.iter().chain(self.macro_use_prelude.iter())
 932                                                   .filter_map(|(name, binding)| {
 933                 if binding.macro_kind() == Some(kind) { Some(name) } else { None }
 934             });
 935             find_best_match_for_name(names, name, None)
 936         // Then check modules.
 937         }).or_else(|| {
 938             let is_macro = |def| {
 939                 if let Def::Macro(_, def_kind) = def {
 940                     def_kind == kind
 941                 } else {
 942                     false
 943                 }
 944             };
 945             let ident = Ident::new(Symbol::intern(name), span);
 946             self.lookup_typo_candidate(&[ident], MacroNS, is_macro, span)
 947         });
 948
 949         if let Some(suggestion) = suggestion {
 950             if suggestion != name {
 951                 if let MacroKind::Bang = kind {
 952                     err.span_suggestion_with_applicability(
 953                         span,
 954                         "you could try the macro",
 955                         suggestion.to_string(),
 956                         Applicability::MaybeIncorrect
 957                     );
 958                 } else {
 959                     err.span_suggestion_with_applicability(
 960                         span,
 961                         "try",
 962                         suggestion.to_string(),
 963                         Applicability::MaybeIncorrect
 964                     );
 965                 }
 966             } else {
 967                 err.help("have you added the `#[macro_use]` on the module/import?");
 968             }
 969         }
 970     }
 971
 972     fn collect_def_ids(&mut self,
 973                        mark: Mark,
 974                        invocation: &'a InvocationData<'a>,
 975                        fragment: &AstFragment) {
 976         let Resolver { ref mut invocations, arenas, graph_root, .. } = *self;
 977         let InvocationData { def_index, .. } = *invocation;
 978
 979         let visit_macro_invoc = &mut |invoc: map::MacroInvocationData| {
 980             invocations.entry(invoc.mark).or_insert_with(|| {
 981                 arenas.alloc_invocation_data(InvocationData {
 982                     def_index: invoc.def_index,
 983                     module: Cell::new(graph_root),
 984                     parent_legacy_scope: Cell::new(LegacyScope::Uninitialized),
 985                     output_legacy_scope: Cell::new(LegacyScope::Uninitialized),
 986                 })
 987             });
 988         };
 989
 990         let mut def_collector = DefCollector::new(&mut self.definitions, mark);
 991         def_collector.visit_macro_invoc = Some(visit_macro_invoc);
 992         def_collector.with_parent(def_index, |def_collector| {
 993             fragment.visit_with(def_collector)
 994         });
 995     }
 996
 997     pub fn define_macro(&mut self,
 998                         item: &ast::Item,
 999                         expansion: Mark,
1000                         current_legacy_scope: &mut LegacyScope<'a>) {
1001         self.local_macro_def_scopes.insert(item.id, self.current_module);
1002         let ident = item.ident;
1003         if ident.name == "macro_rules" {
1004             self.session.span_err(item.span, "user-defined macros may not be named `macro_rules`");
1005         }
1006
1007         let def_id = self.definitions.local_def_id(item.id);
1008         let ext = Lrc::new(macro_rules::compile(&self.session.parse_sess,
1009                                                &self.session.features_untracked(),
1010                                                item, hygiene::default_edition()));
1011         self.macro_map.insert(def_id, ext);
1012
1013         let def = match item.node { ast::ItemKind::MacroDef(ref def) => def, _ => unreachable!() };
1014         if def.legacy {
1015             let ident = ident.modern();
1016             self.macro_names.insert(ident);
1017             let def = Def::Macro(def_id, MacroKind::Bang);
1018             let vis = ty::Visibility::Invisible; // Doesn't matter for legacy bindings
1019             let binding = (def, vis, item.span, expansion).to_name_binding(self.arenas);
1020             self.set_binding_parent_module(binding, self.current_module);
1021             let legacy_binding = self.arenas.alloc_legacy_binding(LegacyBinding {
1022                 parent_legacy_scope: *current_legacy_scope, binding, ident
1023             });
1024             *current_legacy_scope = LegacyScope::Binding(legacy_binding);
1025             self.all_macros.insert(ident.name, def);
1026             if attr::contains_name(&item.attrs, "macro_export") {
1027                 let module = self.graph_root;
1028                 let vis = ty::Visibility::Public;
1029                 self.define(module, ident, MacroNS,
1030                             (def, vis, item.span, expansion, IsMacroExport));
1031             } else {
1032                 if !attr::contains_name(&item.attrs, "rustc_doc_only_macro") {
1033                     self.check_reserved_macro_name(ident, MacroNS);
1034                 }
1035                 self.unused_macros.insert(def_id);
1036             }
1037         } else {
1038             let module = self.current_module;
1039             let def = Def::Macro(def_id, MacroKind::Bang);
1040             let vis = self.resolve_visibility(&item.vis);
1041             if vis != ty::Visibility::Public {
1042                 self.unused_macros.insert(def_id);
1043             }
1044             self.define(module, ident, MacroNS, (def, vis, item.span, expansion));
1045         }
1046     }
1047
1048     fn gate_legacy_custom_derive(&mut self, name: Symbol, span: Span) {
1049         if !self.session.features_untracked().custom_derive {
1050             let sess = &self.session.parse_sess;
1051             let explain = feature_gate::EXPLAIN_CUSTOM_DERIVE;
1052             emit_feature_err(sess, "custom_derive", span, GateIssue::Language, explain);
1053         } else if !self.is_whitelisted_legacy_custom_derive(name) {
1054             self.session.span_warn(span, feature_gate::EXPLAIN_DEPR_CUSTOM_DERIVE);
1055         }
1056     }
1057 }