src/librustc_resolve/macros.rs

   1 use crate::{AmbiguityError, AmbiguityKind, AmbiguityErrorMisc, Determinacy};
   2 use crate::{CrateLint, Resolver, ResolutionError, Scope, ScopeSet, ParentScope, Weak};
   3 use crate::{Module, ModuleKind, NameBinding, PathResult, Segment, ToNameBinding};
   4 use crate::{ModuleOrUniformRoot, KNOWN_TOOLS};
   5 use crate::Namespace::*;
   6 use crate::build_reduced_graph::BuildReducedGraphVisitor;
   7 use crate::resolve_imports::ImportResolver;
   8 use rustc::hir::def::{self, DefKind, NonMacroAttrKind};
   9 use rustc::hir::map::DefCollector;
  10 use rustc::middle::stability;
  11 use rustc::{ty, lint, span_bug};
  12 use syntax::ast::{self, Ident};
  13 use syntax::attr::StabilityLevel;
  14 use syntax::edition::Edition;
  15 use syntax::ext::base::{self, Indeterminate, SpecialDerives};
  16 use syntax::ext::base::{MacroKind, SyntaxExtension};
  17 use syntax::ext::expand::{AstFragment, Invocation, InvocationKind};
  18 use syntax::ext::hygiene::{self, ExpnId, ExpnInfo, ExpnKind};
  19 use syntax::ext::tt::macro_rules;
  20 use syntax::feature_gate::{emit_feature_err, is_builtin_attr_name};
  21 use syntax::feature_gate::GateIssue;
  22 use syntax::symbol::{Symbol, kw, sym};
  23 use syntax_pos::{Span, DUMMY_SP};
  24
  25 use std::cell::Cell;
  26 use std::{mem, ptr};
  27 use rustc_data_structures::sync::Lrc;
  28
  29 type Res = def::Res<ast::NodeId>;
  30
  31 // FIXME: Merge this with `ParentScope`.
  32 #[derive(Clone, Debug)]
  33 pub struct InvocationData<'a> {
  34     /// The module in which the macro was invoked.
  35     crate module: Module<'a>,
  36     /// The legacy scope in which the macro was invoked.
  37     /// The invocation path is resolved in this scope.
  38     crate parent_legacy_scope: LegacyScope<'a>,
  39     /// The legacy scope *produced* by expanding this macro invocation,
  40     /// includes all the macro_rules items, other invocations, etc generated by it.
  41     /// `None` if the macro is not expanded yet.
  42     crate output_legacy_scope: Cell<Option<LegacyScope<'a>>>,
  43 }
  44
  45 impl<'a> InvocationData<'a> {
  46     pub fn root(graph_root: Module<'a>) -> Self {
  47         InvocationData {
  48             module: graph_root,
  49             parent_legacy_scope: LegacyScope::Empty,
  50             output_legacy_scope: Cell::new(None),
  51         }
  52     }
  53 }
  54
  55 /// Binding produced by a `macro_rules` item.
  56 /// Not modularized, can shadow previous legacy bindings, etc.
  57 #[derive(Debug)]
  58 pub struct LegacyBinding<'a> {
  59     crate binding: &'a NameBinding<'a>,
  60     /// Legacy scope into which the `macro_rules` item was planted.
  61     crate parent_legacy_scope: LegacyScope<'a>,
  62     crate ident: Ident,
  63 }
  64
  65 /// The scope introduced by a `macro_rules!` macro.
  66 /// This starts at the macro's definition and ends at the end of the macro's parent
  67 /// module (named or unnamed), or even further if it escapes with `#[macro_use]`.
  68 /// Some macro invocations need to introduce legacy scopes too because they
  69 /// can potentially expand into macro definitions.
  70 #[derive(Copy, Clone, Debug)]
  71 pub enum LegacyScope<'a> {
  72     /// Empty "root" scope at the crate start containing no names.
  73     Empty,
  74     /// The scope introduced by a `macro_rules!` macro definition.
  75     Binding(&'a LegacyBinding<'a>),
  76     /// The scope introduced by a macro invocation that can potentially
  77     /// create a `macro_rules!` macro definition.
  78     Invocation(&'a InvocationData<'a>),
  79 }
  80
  81 // Macro namespace is separated into two sub-namespaces, one for bang macros and
  82 // one for attribute-like macros (attributes, derives).
  83 // We ignore resolutions from one sub-namespace when searching names in scope for another.
  84 fn sub_namespace_match(candidate: Option<MacroKind>, requirement: Option<MacroKind>) -> bool {
  85     #[derive(PartialEq)]
  86     enum SubNS { Bang, AttrLike }
  87     let sub_ns = |kind| match kind {
  88         MacroKind::Bang => SubNS::Bang,
  89         MacroKind::Attr | MacroKind::Derive => SubNS::AttrLike,
  90     };
  91     let candidate = candidate.map(sub_ns);
  92     let requirement = requirement.map(sub_ns);
  93     // "No specific sub-namespace" means "matches anything" for both requirements and candidates.
  94     candidate.is_none() || requirement.is_none() || candidate == requirement
  95 }
  96
  97 // We don't want to format a path using pretty-printing,
  98 // `format!("{}", path)`, because that tries to insert
  99 // line-breaks and is slow.
 100 fn fast_print_path(path: &ast::Path) -> Symbol {
 101     if path.segments.len() == 1 {
 102         return path.segments[0].ident.name
 103     } else {
 104         let mut path_str = String::with_capacity(64);
 105         for (i, segment) in path.segments.iter().enumerate() {
 106             if i != 0 {
 107                 path_str.push_str("::");
 108             }
 109             if segment.ident.name != kw::PathRoot {
 110                 path_str.push_str(&segment.ident.as_str())
 111             }
 112         }
 113         Symbol::intern(&path_str)
 114     }
 115 }
 116
 117 impl<'a> base::Resolver for Resolver<'a> {
 118     fn next_node_id(&mut self) -> ast::NodeId {
 119         self.session.next_node_id()
 120     }
 121
 122     fn get_module_scope(&mut self, id: ast::NodeId) -> ExpnId {
 123         let span = DUMMY_SP.fresh_expansion(ExpnId::root(), ExpnInfo::default(
 124             ExpnKind::Macro(MacroKind::Attr, sym::test_case), DUMMY_SP, self.session.edition()
 125         ));
 126         let expn_id = span.ctxt().outer_expn();
 127         let module = self.module_map[&self.definitions.local_def_id(id)];
 128         self.definitions.set_invocation_parent(expn_id, module.def_id().unwrap().index);
 129         self.invocations.insert(expn_id, self.arenas.alloc_invocation_data(InvocationData {
 130             module,
 131             parent_legacy_scope: LegacyScope::Empty,
 132             output_legacy_scope: Cell::new(None),
 133         }));
 134         expn_id
 135     }
 136
 137     fn resolve_dollar_crates(&mut self) {
 138         hygiene::update_dollar_crate_names(|ctxt| {
 139             let ident = Ident::new(kw::DollarCrate, DUMMY_SP.with_ctxt(ctxt));
 140             match self.resolve_crate_root(ident).kind {
 141                 ModuleKind::Def(.., name) if name != kw::Invalid => name,
 142                 _ => kw::Crate,
 143             }
 144         });
 145     }
 146
 147     fn visit_ast_fragment_with_placeholders(&mut self, expn_id: ExpnId, fragment: &AstFragment,
 148                                             derives: &[ExpnId]) {
 149         fragment.visit_with(&mut DefCollector::new(&mut self.definitions, expn_id));
 150
 151         let invocation = self.invocations[&expn_id];
 152         invocation.module.unresolved_invocations.borrow_mut().remove(&expn_id);
 153         invocation.module.unresolved_invocations.borrow_mut().extend(derives);
 154         let parent_def = self.definitions.invocation_parent(expn_id);
 155         for &derive_invoc_id in derives {
 156             self.definitions.set_invocation_parent(derive_invoc_id, parent_def);
 157         }
 158         self.invocations.extend(derives.iter().map(|&derive| (derive, invocation)));
 159         let mut visitor = BuildReducedGraphVisitor {
 160             r: self,
 161             parent_scope: ParentScope {
 162                 module: invocation.module,
 163                 expansion: expn_id,
 164                 legacy: invocation.parent_legacy_scope,
 165                 derives: Vec::new(),
 166             },
 167         };
 168         fragment.visit_with(&mut visitor);
 169         invocation.output_legacy_scope.set(Some(visitor.parent_scope.legacy));
 170     }
 171
 172     fn register_builtin_macro(&mut self, ident: ast::Ident, ext: SyntaxExtension) {
 173         if self.builtin_macros.insert(ident.name, ext).is_some() {
 174             self.session.span_err(ident.span,
 175                                   &format!("built-in macro `{}` was already defined", ident));
 176         }
 177     }
 178
 179     fn resolve_imports(&mut self) {
 180         ImportResolver { r: self }.resolve_imports()
 181     }
 182
 183     fn resolve_macro_invocation(&mut self, invoc: &Invocation, invoc_id: ExpnId, force: bool)
 184                                 -> Result<Option<Lrc<SyntaxExtension>>, Indeterminate> {
 185         let (path, kind, derives_in_scope, after_derive) = match invoc.kind {
 186             InvocationKind::Attr { ref attr, ref derives, after_derive, .. } =>
 187                 (&attr.path, MacroKind::Attr, derives.clone(), after_derive),
 188             InvocationKind::Bang { ref mac, .. } =>
 189                 (&mac.node.path, MacroKind::Bang, Vec::new(), false),
 190             InvocationKind::Derive { ref path, .. } =>
 191                 (path, MacroKind::Derive, Vec::new(), false),
 192             InvocationKind::DeriveContainer { ref derives, .. } => {
 193                 // Block expansion of derives in the container until we know whether one of them
 194                 // is a built-in `Copy`. Skip the resolution if there's only one derive - either
 195                 // it's not a `Copy` and we don't need to do anything, or it's a `Copy` and it
 196                 // will automatically knows about itself.
 197                 let mut result = Ok(None);
 198                 if derives.len() > 1 {
 199                     let parent_scope = &self.invoc_parent_scope(invoc_id, Vec::new());
 200                     for path in derives {
 201                         match self.resolve_macro_path(path, Some(MacroKind::Derive),
 202                                                       parent_scope, true, force) {
 203                             Ok((Some(ref ext), _)) if ext.is_derive_copy => {
 204                                 self.add_derives(invoc.expansion_data.id, SpecialDerives::COPY);
 205                                 return Ok(None);
 206                             }
 207                             Err(Determinacy::Undetermined) => result = Err(Indeterminate),
 208                             _ => {}
 209                         }
 210                     }
 211                 }
 212                 return result;
 213             }
 214         };
 215
 216         let parent_scope = &self.invoc_parent_scope(invoc_id, derives_in_scope);
 217         let (ext, res) = self.smart_resolve_macro_path(path, kind, parent_scope, force)?;
 218
 219         let span = invoc.span();
 220         invoc.expansion_data.id.set_expn_info(ext.expn_info(span, fast_print_path(path)));
 221
 222         if let Res::Def(_, def_id) = res {
 223             if after_derive {
 224                 self.session.span_err(span, "macro attributes must be placed before `#[derive]`");
 225             }
 226             self.macro_defs.insert(invoc.expansion_data.id, def_id);
 227             let normal_module_def_id =
 228                 self.macro_def_scope(invoc.expansion_data.id).normal_ancestor_id;
 229             self.definitions.add_parent_module_of_macro_def(invoc.expansion_data.id,
 230                                                             normal_module_def_id);
 231         }
 232
 233         Ok(Some(ext))
 234     }
 235
 236     fn check_unused_macros(&self) {
 237         for (&node_id, &span) in self.unused_macros.iter() {
 238             self.session.buffer_lint(
 239                 lint::builtin::UNUSED_MACROS, node_id, span, "unused macro definition"
 240             );
 241         }
 242     }
 243
 244     fn has_derives(&self, expn_id: ExpnId, derives: SpecialDerives) -> bool {
 245         self.has_derives(expn_id, derives)
 246     }
 247
 248     fn add_derives(&mut self, expn_id: ExpnId, derives: SpecialDerives) {
 249         *self.special_derives.entry(expn_id).or_default() |= derives;
 250     }
 251 }
 252
 253 impl<'a> Resolver<'a> {
 254     pub fn dummy_parent_scope(&self) -> ParentScope<'a> {
 255         self.invoc_parent_scope(ExpnId::root(), Vec::new())
 256     }
 257
 258     fn invoc_parent_scope(&self, invoc_id: ExpnId, derives: Vec<ast::Path>) -> ParentScope<'a> {
 259         let invoc = self.invocations[&invoc_id];
 260         ParentScope {
 261             module: invoc.module.nearest_item_scope(),
 262             expansion: invoc_id.parent(),
 263             legacy: invoc.parent_legacy_scope,
 264             derives,
 265         }
 266     }
 267
 268     /// Resolve macro path with error reporting and recovery.
 269     fn smart_resolve_macro_path(
 270         &mut self,
 271         path: &ast::Path,
 272         kind: MacroKind,
 273         parent_scope: &ParentScope<'a>,
 274         force: bool,
 275     ) -> Result<(Lrc<SyntaxExtension>, Res), Indeterminate> {
 276         let (ext, res) = match self.resolve_macro_path(path, Some(kind), parent_scope,
 277                                                        true, force) {
 278             Ok((Some(ext), res)) => (ext, res),
 279             // Use dummy syntax extensions for unresolved macros for better recovery.
 280             Ok((None, res)) => (self.dummy_ext(kind), res),
 281             Err(Determinacy::Determined) => (self.dummy_ext(kind), Res::Err),
 282             Err(Determinacy::Undetermined) => return Err(Indeterminate),
 283         };
 284
 285         // Report errors and enforce feature gates for the resolved macro.
 286         let features = self.session.features_untracked();
 287         for segment in &path.segments {
 288             if let Some(args) = &segment.args {
 289                 self.session.span_err(args.span(), "generic arguments in macro path");
 290             }
 291             if kind == MacroKind::Attr && !features.rustc_attrs &&
 292                segment.ident.as_str().starts_with("rustc") {
 293                 let msg =
 294                     "attributes starting with `rustc` are reserved for use by the `rustc` compiler";
 295                 emit_feature_err(
 296                     &self.session.parse_sess,
 297                     sym::rustc_attrs,
 298                     segment.ident.span,
 299                     GateIssue::Language,
 300                     msg,
 301                 );
 302             }
 303         }
 304
 305         match res {
 306             Res::Def(DefKind::Macro(_), def_id) => {
 307                 if let Some(node_id) = self.definitions.as_local_node_id(def_id) {
 308                     self.unused_macros.remove(&node_id);
 309                     if self.proc_macro_stubs.contains(&node_id) {
 310                         self.session.span_err(
 311                             path.span,
 312                             "can't use a procedural macro from the same crate that defines it",
 313                         );
 314                     }
 315                 }
 316             }
 317             Res::NonMacroAttr(..) | Res::Err => {}
 318             _ => panic!("expected `DefKind::Macro` or `Res::NonMacroAttr`"),
 319         };
 320
 321         self.check_stability_and_deprecation(&ext, path);
 322
 323         Ok(if ext.macro_kind() != kind {
 324             let expected = if kind == MacroKind::Attr { "attribute" } else  { kind.descr() };
 325             let msg = format!("expected {}, found {} `{}`", expected, res.descr(), path);
 326             self.session.struct_span_err(path.span, &msg)
 327                         .span_label(path.span, format!("not {} {}", kind.article(), expected))
 328                         .emit();
 329             // Use dummy syntax extensions for unexpected macro kinds for better recovery.
 330             (self.dummy_ext(kind), Res::Err)
 331         } else {
 332             (ext, res)
 333         })
 334     }
 335
 336     pub fn resolve_macro_path(
 337         &mut self,
 338         path: &ast::Path,
 339         kind: Option<MacroKind>,
 340         parent_scope: &ParentScope<'a>,
 341         trace: bool,
 342         force: bool,
 343     ) -> Result<(Option<Lrc<SyntaxExtension>>, Res), Determinacy> {
 344         let path_span = path.span;
 345         let mut path = Segment::from_path(path);
 346
 347         // Possibly apply the macro helper hack
 348         if kind == Some(MacroKind::Bang) && path.len() == 1 &&
 349            path[0].ident.span.ctxt().outer_expn_info()
 350                .map_or(false, |info| info.local_inner_macros) {
 351             let root = Ident::new(kw::DollarCrate, path[0].ident.span);
 352             path.insert(0, Segment::from_ident(root));
 353         }
 354
 355         let res = if path.len() > 1 {
 356             let res = match self.resolve_path(&path, Some(MacroNS), parent_scope,
 357                                               false, path_span, CrateLint::No) {
 358                 PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 => {
 359                     Ok(path_res.base_res())
 360                 }
 361                 PathResult::Indeterminate if !force => return Err(Determinacy::Undetermined),
 362                 PathResult::NonModule(..)
 363                 | PathResult::Indeterminate
 364                 | PathResult::Failed { .. } => Err(Determinacy::Determined),
 365                 PathResult::Module(..) => unreachable!(),
 366             };
 367
 368             if trace {
 369                 let kind = kind.expect("macro kind must be specified if tracing is enabled");
 370                 parent_scope.module.multi_segment_macro_resolutions.borrow_mut()
 371                     .push((path, path_span, kind, parent_scope.clone(), res.ok()));
 372             }
 373
 374             self.prohibit_imported_non_macro_attrs(None, res.ok(), path_span);
 375             res
 376         } else {
 377             let scope_set = kind.map_or(ScopeSet::All(MacroNS, false), ScopeSet::Macro);
 378             let binding = self.early_resolve_ident_in_lexical_scope(
 379                 path[0].ident, scope_set, parent_scope, false, force, path_span
 380             );
 381             if let Err(Determinacy::Undetermined) = binding {
 382                 return Err(Determinacy::Undetermined);
 383             }
 384
 385             if trace {
 386                 let kind = kind.expect("macro kind must be specified if tracing is enabled");
 387                 parent_scope.module.single_segment_macro_resolutions.borrow_mut()
 388                     .push((path[0].ident, kind, parent_scope.clone(), binding.ok()));
 389             }
 390
 391             let res = binding.map(|binding| binding.res());
 392             self.prohibit_imported_non_macro_attrs(binding.ok(), res.ok(), path_span);
 393             res
 394         };
 395
 396         res.map(|res| (self.get_macro(res), res))
 397     }
 398
 399     // Resolve an identifier in lexical scope.
 400     // This is a variation of `fn resolve_ident_in_lexical_scope` that can be run during
 401     // expansion and import resolution (perhaps they can be merged in the future).
 402     // The function is used for resolving initial segments of macro paths (e.g., `foo` in
 403     // `foo::bar!(); or `foo!();`) and also for import paths on 2018 edition.
 404     crate fn early_resolve_ident_in_lexical_scope(
 405         &mut self,
 406         orig_ident: Ident,
 407         scope_set: ScopeSet,
 408         parent_scope: &ParentScope<'a>,
 409         record_used: bool,
 410         force: bool,
 411         path_span: Span,
 412     ) -> Result<&'a NameBinding<'a>, Determinacy> {
 413         bitflags::bitflags! {
 414             struct Flags: u8 {
 415                 const MACRO_RULES        = 1 << 0;
 416                 const MODULE             = 1 << 1;
 417                 const PRELUDE            = 1 << 2;
 418                 const MISC_SUGGEST_CRATE = 1 << 3;
 419                 const MISC_SUGGEST_SELF  = 1 << 4;
 420                 const MISC_FROM_PRELUDE  = 1 << 5;
 421             }
 422         }
 423
 424         assert!(force || !record_used); // `record_used` implies `force`
 425
 426         // Make sure `self`, `super` etc produce an error when passed to here.
 427         if orig_ident.is_path_segment_keyword() {
 428             return Err(Determinacy::Determined);
 429         }
 430
 431         let (ns, macro_kind, is_import) = match scope_set {
 432             ScopeSet::All(ns, is_import) => (ns, None, is_import),
 433             ScopeSet::AbsolutePath(ns) => (ns, None, false),
 434             ScopeSet::Macro(macro_kind) => (MacroNS, Some(macro_kind), false),
 435         };
 436
 437         // This is *the* result, resolution from the scope closest to the resolved identifier.
 438         // However, sometimes this result is "weak" because it comes from a glob import or
 439         // a macro expansion, and in this case it cannot shadow names from outer scopes, e.g.
 440         // mod m { ... } // solution in outer scope
 441         // {
 442         //     use prefix::*; // imports another `m` - innermost solution
 443         //                    // weak, cannot shadow the outer `m`, need to report ambiguity error
 444         //     m::mac!();
 445         // }
 446         // So we have to save the innermost solution and continue searching in outer scopes
 447         // to detect potential ambiguities.
 448         let mut innermost_result: Option<(&NameBinding<'_>, Flags)> = None;
 449         let mut determinacy = Determinacy::Determined;
 450
 451         // Go through all the scopes and try to resolve the name.
 452         let break_result = self.visit_scopes(scope_set, parent_scope, orig_ident,
 453                                              |this, scope, use_prelude, ident| {
 454             let result = match scope {
 455                 Scope::DeriveHelpers => {
 456                     let mut result = Err(Determinacy::Determined);
 457                     for derive in &parent_scope.derives {
 458                         let parent_scope = &ParentScope { derives: Vec::new(), ..*parent_scope };
 459                         match this.resolve_macro_path(derive, Some(MacroKind::Derive),
 460                                                       parent_scope, true, force) {
 461                             Ok((Some(ext), _)) => if ext.helper_attrs.contains(&ident.name) {
 462                                 let binding = (Res::NonMacroAttr(NonMacroAttrKind::DeriveHelper),
 463                                                ty::Visibility::Public, derive.span, ExpnId::root())
 464                                                .to_name_binding(this.arenas);
 465                                 result = Ok((binding, Flags::empty()));
 466                                 break;
 467                             }
 468                             Ok(_) | Err(Determinacy::Determined) => {}
 469                             Err(Determinacy::Undetermined) =>
 470                                 result = Err(Determinacy::Undetermined),
 471                         }
 472                     }
 473                     result
 474                 }
 475                 Scope::MacroRules(legacy_scope) => match legacy_scope {
 476                     LegacyScope::Binding(legacy_binding) if ident == legacy_binding.ident =>
 477                         Ok((legacy_binding.binding, Flags::MACRO_RULES)),
 478                     LegacyScope::Invocation(invoc) if invoc.output_legacy_scope.get().is_none() =>
 479                         Err(Determinacy::Undetermined),
 480                     _ => Err(Determinacy::Determined),
 481                 }
 482                 Scope::CrateRoot => {
 483                     let root_ident = Ident::new(kw::PathRoot, ident.span);
 484                     let root_module = this.resolve_crate_root(root_ident);
 485                     let binding = this.resolve_ident_in_module_ext(
 486                         ModuleOrUniformRoot::Module(root_module),
 487                         ident,
 488                         ns,
 489                         parent_scope,
 490                         record_used,
 491                         path_span,
 492                     );
 493                     match binding {
 494                         Ok(binding) => Ok((binding, Flags::MODULE | Flags::MISC_SUGGEST_CRATE)),
 495                         Err((Determinacy::Undetermined, Weak::No)) =>
 496                             return Some(Err(Determinacy::determined(force))),
 497                         Err((Determinacy::Undetermined, Weak::Yes)) =>
 498                             Err(Determinacy::Undetermined),
 499                         Err((Determinacy::Determined, _)) => Err(Determinacy::Determined),
 500                     }
 501                 }
 502                 Scope::Module(module) => {
 503                     let adjusted_parent_scope = &ParentScope { module, ..parent_scope.clone() };
 504                     let binding = this.resolve_ident_in_module_unadjusted_ext(
 505                         ModuleOrUniformRoot::Module(module),
 506                         ident,
 507                         ns,
 508                         adjusted_parent_scope,
 509                         true,
 510                         record_used,
 511                         path_span,
 512                     );
 513                     match binding {
 514                         Ok(binding) => {
 515                             let misc_flags = if ptr::eq(module, this.graph_root) {
 516                                 Flags::MISC_SUGGEST_CRATE
 517                             } else if module.is_normal() {
 518                                 Flags::MISC_SUGGEST_SELF
 519                             } else {
 520                                 Flags::empty()
 521                             };
 522                             Ok((binding, Flags::MODULE | misc_flags))
 523                         }
 524                         Err((Determinacy::Undetermined, Weak::No)) =>
 525                             return Some(Err(Determinacy::determined(force))),
 526                         Err((Determinacy::Undetermined, Weak::Yes)) =>
 527                             Err(Determinacy::Undetermined),
 528                         Err((Determinacy::Determined, _)) => Err(Determinacy::Determined),
 529                     }
 530                 }
 531                 Scope::MacroUsePrelude => match this.macro_use_prelude.get(&ident.name).cloned() {
 532                     Some(binding) => Ok((binding, Flags::PRELUDE | Flags::MISC_FROM_PRELUDE)),
 533                     None => Err(Determinacy::determined(
 534                         this.graph_root.unresolved_invocations.borrow().is_empty()
 535                     ))
 536                 }
 537                 Scope::BuiltinAttrs => if is_builtin_attr_name(ident.name) {
 538                     let binding = (Res::NonMacroAttr(NonMacroAttrKind::Builtin),
 539                                    ty::Visibility::Public, DUMMY_SP, ExpnId::root())
 540                                    .to_name_binding(this.arenas);
 541                     Ok((binding, Flags::PRELUDE))
 542                 } else {
 543                     Err(Determinacy::Determined)
 544                 }
 545                 Scope::LegacyPluginHelpers => if this.session.plugin_attributes.borrow().iter()
 546                                                      .any(|(name, _)| ident.name == *name) {
 547                     let binding = (Res::NonMacroAttr(NonMacroAttrKind::LegacyPluginHelper),
 548                                    ty::Visibility::Public, DUMMY_SP, ExpnId::root())
 549                                    .to_name_binding(this.arenas);
 550                     Ok((binding, Flags::PRELUDE))
 551                 } else {
 552                     Err(Determinacy::Determined)
 553                 }
 554                 Scope::ExternPrelude => match this.extern_prelude_get(ident, !record_used) {
 555                     Some(binding) => Ok((binding, Flags::PRELUDE)),
 556                     None => Err(Determinacy::determined(
 557                         this.graph_root.unresolved_invocations.borrow().is_empty()
 558                     )),
 559                 }
 560                 Scope::ToolPrelude => if KNOWN_TOOLS.contains(&ident.name) {
 561                     let binding = (Res::ToolMod, ty::Visibility::Public, DUMMY_SP, ExpnId::root())
 562                                    .to_name_binding(this.arenas);
 563                     Ok((binding, Flags::PRELUDE))
 564                 } else {
 565                     Err(Determinacy::Determined)
 566                 }
 567                 Scope::StdLibPrelude => {
 568                     let mut result = Err(Determinacy::Determined);
 569                     if let Some(prelude) = this.prelude {
 570                         if let Ok(binding) = this.resolve_ident_in_module_unadjusted(
 571                             ModuleOrUniformRoot::Module(prelude),
 572                             ident,
 573                             ns,
 574                             parent_scope,
 575                             false,
 576                             path_span,
 577                         ) {
 578                             if use_prelude || this.is_builtin_macro(binding.res().opt_def_id()) {
 579                                 result = Ok((binding, Flags::PRELUDE | Flags::MISC_FROM_PRELUDE));
 580                             }
 581                         }
 582                     }
 583                     result
 584                 }
 585                 Scope::BuiltinTypes => match this.primitive_type_table.primitive_types
 586                                                  .get(&ident.name).cloned() {
 587                     Some(prim_ty) => {
 588                         let binding = (Res::PrimTy(prim_ty), ty::Visibility::Public,
 589                                        DUMMY_SP, ExpnId::root()).to_name_binding(this.arenas);
 590                         Ok((binding, Flags::PRELUDE))
 591                     }
 592                     None => Err(Determinacy::Determined)
 593                 }
 594             };
 595
 596             match result {
 597                 Ok((binding, flags)) if sub_namespace_match(binding.macro_kind(), macro_kind) => {
 598                     if !record_used {
 599                         return Some(Ok(binding));
 600                     }
 601
 602                     if let Some((innermost_binding, innermost_flags)) = innermost_result {
 603                         // Found another solution, if the first one was "weak", report an error.
 604                         let (res, innermost_res) = (binding.res(), innermost_binding.res());
 605                         if res != innermost_res {
 606                             let builtin = Res::NonMacroAttr(NonMacroAttrKind::Builtin);
 607                             let derive_helper = Res::NonMacroAttr(NonMacroAttrKind::DeriveHelper);
 608                             let legacy_helper =
 609                                 Res::NonMacroAttr(NonMacroAttrKind::LegacyPluginHelper);
 610
 611                             let ambiguity_error_kind = if is_import {
 612                                 Some(AmbiguityKind::Import)
 613                             } else if innermost_res == builtin || res == builtin {
 614                                 Some(AmbiguityKind::BuiltinAttr)
 615                             } else if innermost_res == derive_helper || res == derive_helper {
 616                                 Some(AmbiguityKind::DeriveHelper)
 617                             } else if innermost_res == legacy_helper &&
 618                                       flags.contains(Flags::PRELUDE) ||
 619                                       res == legacy_helper &&
 620                                       innermost_flags.contains(Flags::PRELUDE) {
 621                                 Some(AmbiguityKind::LegacyHelperVsPrelude)
 622                             } else if innermost_flags.contains(Flags::MACRO_RULES) &&
 623                                       flags.contains(Flags::MODULE) &&
 624                                       !this.disambiguate_legacy_vs_modern(innermost_binding,
 625                                                                           binding) ||
 626                                       flags.contains(Flags::MACRO_RULES) &&
 627                                       innermost_flags.contains(Flags::MODULE) &&
 628                                       !this.disambiguate_legacy_vs_modern(binding,
 629                                                                           innermost_binding) {
 630                                 Some(AmbiguityKind::LegacyVsModern)
 631                             } else if innermost_binding.is_glob_import() {
 632                                 Some(AmbiguityKind::GlobVsOuter)
 633                             } else if innermost_binding.may_appear_after(parent_scope.expansion,
 634                                                                          binding) {
 635                                 Some(AmbiguityKind::MoreExpandedVsOuter)
 636                             } else {
 637                                 None
 638                             };
 639                             if let Some(kind) = ambiguity_error_kind {
 640                                 let misc = |f: Flags| if f.contains(Flags::MISC_SUGGEST_CRATE) {
 641                                     AmbiguityErrorMisc::SuggestCrate
 642                                 } else if f.contains(Flags::MISC_SUGGEST_SELF) {
 643                                     AmbiguityErrorMisc::SuggestSelf
 644                                 } else if f.contains(Flags::MISC_FROM_PRELUDE) {
 645                                     AmbiguityErrorMisc::FromPrelude
 646                                 } else {
 647                                     AmbiguityErrorMisc::None
 648                                 };
 649                                 this.ambiguity_errors.push(AmbiguityError {
 650                                     kind,
 651                                     ident: orig_ident,
 652                                     b1: innermost_binding,
 653                                     b2: binding,
 654                                     misc1: misc(innermost_flags),
 655                                     misc2: misc(flags),
 656                                 });
 657                                 return Some(Ok(innermost_binding));
 658                             }
 659                         }
 660                     } else {
 661                         // Found the first solution.
 662                         innermost_result = Some((binding, flags));
 663                     }
 664                 }
 665                 Ok(..) | Err(Determinacy::Determined) => {}
 666                 Err(Determinacy::Undetermined) => determinacy = Determinacy::Undetermined
 667             }
 668
 669             None
 670         });
 671
 672         if let Some(break_result) = break_result {
 673             return break_result;
 674         }
 675
 676         // The first found solution was the only one, return it.
 677         if let Some((binding, _)) = innermost_result {
 678             return Ok(binding);
 679         }
 680
 681         let determinacy = Determinacy::determined(determinacy == Determinacy::Determined || force);
 682         if determinacy == Determinacy::Determined && macro_kind == Some(MacroKind::Attr) &&
 683            self.session.features_untracked().custom_attribute {
 684             // For single-segment attributes interpret determinate "no resolution" as a custom
 685             // attribute. (Lexical resolution implies the first segment and attr kind should imply
 686             // the last segment, so we are certainly working with a single-segment attribute here.)
 687             assert!(ns == MacroNS);
 688             let binding = (Res::NonMacroAttr(NonMacroAttrKind::Custom),
 689                            ty::Visibility::Public, orig_ident.span, ExpnId::root())
 690                            .to_name_binding(self.arenas);
 691             Ok(binding)
 692         } else {
 693             Err(determinacy)
 694         }
 695     }
 696
 697     pub fn finalize_current_module_macro_resolutions(&mut self, module: Module<'a>) {
 698         let check_consistency = |this: &mut Self, path: &[Segment], span, kind: MacroKind,
 699                                  initial_res: Option<Res>, res: Res| {
 700             if let Some(initial_res) = initial_res {
 701                 if res != initial_res && res != Res::Err && this.ambiguity_errors.is_empty() {
 702                     // Make sure compilation does not succeed if preferred macro resolution
 703                     // has changed after the macro had been expanded. In theory all such
 704                     // situations should be reported as ambiguity errors, so this is a bug.
 705                     if initial_res == Res::NonMacroAttr(NonMacroAttrKind::Custom) {
 706                         // Yeah, legacy custom attributes are implemented using forced resolution
 707                         // (which is a best effort error recovery tool, basically), so we can't
 708                         // promise their resolution won't change later.
 709                         let msg = format!("inconsistent resolution for a macro: first {}, then {}",
 710                                           initial_res.descr(), res.descr());
 711                         this.session.span_err(span, &msg);
 712                     } else {
 713                         span_bug!(span, "inconsistent resolution for a macro");
 714                     }
 715                 }
 716             } else {
 717                 // It's possible that the macro was unresolved (indeterminate) and silently
 718                 // expanded into a dummy fragment for recovery during expansion.
 719                 // Now, post-expansion, the resolution may succeed, but we can't change the
 720                 // past and need to report an error.
 721                 // However, non-speculative `resolve_path` can successfully return private items
 722                 // even if speculative `resolve_path` returned nothing previously, so we skip this
 723                 // less informative error if the privacy error is reported elsewhere.
 724                 if this.privacy_errors.is_empty() {
 725                     let msg = format!("cannot determine resolution for the {} `{}`",
 726                                         kind.descr(), Segment::names_to_string(path));
 727                     let msg_note = "import resolution is stuck, try simplifying macro imports";
 728                     this.session.struct_span_err(span, &msg).note(msg_note).emit();
 729                 }
 730             }
 731         };
 732
 733         let macro_resolutions =
 734             mem::take(&mut *module.multi_segment_macro_resolutions.borrow_mut());
 735         for (mut path, path_span, kind, parent_scope, initial_res) in macro_resolutions {
 736             // FIXME: Path resolution will ICE if segment IDs present.
 737             for seg in &mut path { seg.id = None; }
 738             match self.resolve_path(
 739                 &path, Some(MacroNS), &parent_scope, true, path_span, CrateLint::No
 740             ) {
 741                 PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 => {
 742                     let res = path_res.base_res();
 743                     check_consistency(self, &path, path_span, kind, initial_res, res);
 744                 }
 745                 path_res @ PathResult::NonModule(..) | path_res @ PathResult::Failed { .. } => {
 746                     let (span, label) = if let PathResult::Failed { span, label, .. } = path_res {
 747                         (span, label)
 748                     } else {
 749                         (path_span, format!("partially resolved path in {} {}",
 750                                             kind.article(), kind.descr()))
 751                     };
 752                     self.report_error(span, ResolutionError::FailedToResolve {
 753                         label,
 754                         suggestion: None
 755                     });
 756                 }
 757                 PathResult::Module(..) | PathResult::Indeterminate => unreachable!(),
 758             }
 759         }
 760
 761         let macro_resolutions =
 762             mem::take(&mut *module.single_segment_macro_resolutions.borrow_mut());
 763         for (ident, kind, parent_scope, initial_binding) in macro_resolutions {
 764             match self.early_resolve_ident_in_lexical_scope(ident, ScopeSet::Macro(kind),
 765                                                             &parent_scope, true, true, ident.span) {
 766                 Ok(binding) => {
 767                     let initial_res = initial_binding.map(|initial_binding| {
 768                         self.record_use(ident, MacroNS, initial_binding, false);
 769                         initial_binding.res()
 770                     });
 771                     let res = binding.res();
 772                     let seg = Segment::from_ident(ident);
 773                     check_consistency(self, &[seg], ident.span, kind, initial_res, res);
 774                 }
 775                 Err(..) => {
 776                     assert!(initial_binding.is_none());
 777                     let bang = if kind == MacroKind::Bang { "!" } else { "" };
 778                     let msg =
 779                         format!("cannot find {} `{}{}` in this scope", kind.descr(), ident, bang);
 780                     let mut err = self.session.struct_span_err(ident.span, &msg);
 781                     self.unresolved_macro_suggestions(&mut err, kind, &parent_scope, ident);
 782                     err.emit();
 783                 }
 784             }
 785         }
 786
 787         let builtin_attrs = mem::take(&mut *module.builtin_attrs.borrow_mut());
 788         for (ident, parent_scope) in builtin_attrs {
 789             let _ = self.early_resolve_ident_in_lexical_scope(
 790                 ident, ScopeSet::Macro(MacroKind::Attr), &parent_scope, true, true, ident.span
 791             );
 792         }
 793     }
 794
 795     fn check_stability_and_deprecation(&self, ext: &SyntaxExtension, path: &ast::Path) {
 796         let span = path.span;
 797         if let Some(stability) = &ext.stability {
 798             if let StabilityLevel::Unstable { reason, issue } = stability.level {
 799                 let feature = stability.feature;
 800                 if !self.active_features.contains(&feature) && !span.allows_unstable(feature) {
 801                     stability::report_unstable(self.session, feature, reason, issue, span);
 802                 }
 803             }
 804             if let Some(depr) = &stability.rustc_depr {
 805                 let (message, lint) = stability::rustc_deprecation_message(depr, &path.to_string());
 806                 stability::early_report_deprecation(
 807                     self.session, &message, depr.suggestion, lint, span
 808                 );
 809             }
 810         }
 811         if let Some(depr) = &ext.deprecation {
 812             let (message, lint) = stability::deprecation_message(depr, &path.to_string());
 813             stability::early_report_deprecation(self.session, &message, None, lint, span);
 814         }
 815     }
 816
 817     fn prohibit_imported_non_macro_attrs(&self, binding: Option<&'a NameBinding<'a>>,
 818                                          res: Option<Res>, span: Span) {
 819         if let Some(Res::NonMacroAttr(kind)) = res {
 820             if kind != NonMacroAttrKind::Tool && binding.map_or(true, |b| b.is_import()) {
 821                 let msg = format!("cannot use a {} through an import", kind.descr());
 822                 let mut err = self.session.struct_span_err(span, &msg);
 823                 if let Some(binding) = binding {
 824                     err.span_note(binding.span, &format!("the {} imported here", kind.descr()));
 825                 }
 826                 err.emit();
 827             }
 828         }
 829     }
 830
 831     crate fn check_reserved_macro_name(&mut self, ident: Ident, res: Res) {
 832         // Reserve some names that are not quite covered by the general check
 833         // performed on `Resolver::builtin_attrs`.
 834         if ident.name == sym::cfg || ident.name == sym::cfg_attr || ident.name == sym::derive {
 835             let macro_kind = self.get_macro(res).map(|ext| ext.macro_kind());
 836             if macro_kind.is_some() && sub_namespace_match(macro_kind, Some(MacroKind::Attr)) {
 837                 self.session.span_err(
 838                     ident.span, &format!("name `{}` is reserved in attribute namespace", ident)
 839                 );
 840             }
 841         }
 842     }
 843
 844     /// Compile the macro into a `SyntaxExtension` and possibly replace it with a pre-defined
 845     /// extension partially or entirely for built-in macros and legacy plugin macros.
 846     crate fn compile_macro(&mut self, item: &ast::Item, edition: Edition) -> Lrc<SyntaxExtension> {
 847         let mut result = macro_rules::compile(
 848             &self.session.parse_sess, self.session.features_untracked(), item, edition
 849         );
 850
 851         if result.is_builtin {
 852             // The macro was marked with `#[rustc_builtin_macro]`.
 853             if let Some(ext) = self.builtin_macros.remove(&item.ident.name) {
 854                 if ext.is_builtin {
 855                     // The macro is a built-in, replace only the expander function.
 856                     result.kind = ext.kind;
 857                 } else {
 858                     // The macro is from a plugin, the in-source definition is dummy,
 859                     // take all the data from the resolver.
 860                     result = ext;
 861                 }
 862             } else {
 863                 let msg = format!("cannot find a built-in macro with name `{}`", item.ident);
 864                 self.session.span_err(item.span, &msg);
 865             }
 866         }
 867
 868         Lrc::new(result)
 869     }
 870 }