src/librustc_resolve/macros.rs

   1 //! A bunch of methods and structures more or less related to resolving macros and
   2 //! interface provided by `Resolver` to macro expander.
   3
   4 use crate::{AmbiguityError, AmbiguityKind, AmbiguityErrorMisc, Determinacy};
   5 use crate::{CrateLint, Resolver, ResolutionError, Scope, ScopeSet, ParentScope, Weak};
   6 use crate::{ModuleKind, ModuleOrUniformRoot, NameBinding, PathResult, Segment, ToNameBinding};
   7 use crate::Namespace::*;
   8 use crate::resolve_imports::ImportResolver;
   9 use rustc::hir::def::{self, DefKind, NonMacroAttrKind};
  10 use rustc::hir::def_id;
  11 use rustc::middle::stability;
  12 use rustc::session::Session;
  13 use rustc::util::nodemap::FxHashSet;
  14 use rustc::{ty, lint, span_bug};
  15 use syntax::ast::{self, NodeId, Ident};
  16 use syntax::attr::{self, StabilityLevel};
  17 use syntax::edition::Edition;
  18 use syntax::feature_gate::{emit_feature_err, is_builtin_attr_name};
  19 use syntax::feature_gate::GateIssue;
  20 use syntax::print::pprust;
  21 use syntax::symbol::{Symbol, kw, sym};
  22 use syntax_expand::base::{self, InvocationRes, Indeterminate};
  23 use syntax_expand::base::SyntaxExtension;
  24 use syntax_expand::expand::{AstFragment, AstFragmentKind, Invocation, InvocationKind};
  25 use syntax_expand::compile_declarative_macro;
  26 use syntax_pos::hygiene::{self, ExpnId, ExpnData, ExpnKind};
  27 use syntax_pos::{Span, DUMMY_SP};
  28
  29 use std::{mem, ptr};
  30 use rustc_data_structures::sync::Lrc;
  31 use syntax_pos::hygiene::{MacroKind, AstPass};
  32
  33 type Res = def::Res<NodeId>;
  34
  35 /// Binding produced by a `macro_rules` item.
  36 /// Not modularized, can shadow previous legacy bindings, etc.
  37 #[derive(Debug)]
  38 pub struct LegacyBinding<'a> {
  39     crate binding: &'a NameBinding<'a>,
  40     /// Legacy scope into which the `macro_rules` item was planted.
  41     crate parent_legacy_scope: LegacyScope<'a>,
  42     crate ident: Ident,
  43 }
  44
  45 /// The scope introduced by a `macro_rules!` macro.
  46 /// This starts at the macro's definition and ends at the end of the macro's parent
  47 /// module (named or unnamed), or even further if it escapes with `#[macro_use]`.
  48 /// Some macro invocations need to introduce legacy scopes too because they
  49 /// can potentially expand into macro definitions.
  50 #[derive(Copy, Clone, Debug)]
  51 pub enum LegacyScope<'a> {
  52     /// Empty "root" scope at the crate start containing no names.
  53     Empty,
  54     /// The scope introduced by a `macro_rules!` macro definition.
  55     Binding(&'a LegacyBinding<'a>),
  56     /// The scope introduced by a macro invocation that can potentially
  57     /// create a `macro_rules!` macro definition.
  58     Invocation(ExpnId),
  59 }
  60
  61 // Macro namespace is separated into two sub-namespaces, one for bang macros and
  62 // one for attribute-like macros (attributes, derives).
  63 // We ignore resolutions from one sub-namespace when searching names in scope for another.
  64 fn sub_namespace_match(candidate: Option<MacroKind>, requirement: Option<MacroKind>) -> bool {
  65     #[derive(PartialEq)]
  66     enum SubNS { Bang, AttrLike }
  67     let sub_ns = |kind| match kind {
  68         MacroKind::Bang => SubNS::Bang,
  69         MacroKind::Attr | MacroKind::Derive => SubNS::AttrLike,
  70     };
  71     let candidate = candidate.map(sub_ns);
  72     let requirement = requirement.map(sub_ns);
  73     // "No specific sub-namespace" means "matches anything" for both requirements and candidates.
  74     candidate.is_none() || requirement.is_none() || candidate == requirement
  75 }
  76
  77 // We don't want to format a path using pretty-printing,
  78 // `format!("{}", path)`, because that tries to insert
  79 // line-breaks and is slow.
  80 fn fast_print_path(path: &ast::Path) -> Symbol {
  81     if path.segments.len() == 1 {
  82         return path.segments[0].ident.name
  83     } else {
  84         let mut path_str = String::with_capacity(64);
  85         for (i, segment) in path.segments.iter().enumerate() {
  86             if i != 0 {
  87                 path_str.push_str("::");
  88             }
  89             if segment.ident.name != kw::PathRoot {
  90                 path_str.push_str(&segment.ident.as_str())
  91             }
  92         }
  93         Symbol::intern(&path_str)
  94     }
  95 }
  96
  97 fn registered_idents(
  98     sess: &Session,
  99     attrs: &[ast::Attribute],
 100     attr_name: Symbol,
 101     descr: &str,
 102 ) -> FxHashSet<Ident> {
 103     let mut registered = FxHashSet::default();
 104     for attr in attr::filter_by_name(attrs, attr_name) {
 105         for nested_meta in attr.meta_item_list().unwrap_or_default() {
 106             match nested_meta.ident() {
 107                 Some(ident) => if let Some(old_ident) = registered.replace(ident) {
 108                     let msg = format!("{} `{}` was already registered", descr, ident);
 109                     sess.struct_span_err(ident.span, &msg)
 110                         .span_label(old_ident.span, "already registered here").emit();
 111                 }
 112                 None => {
 113                     let msg = format!("`{}` only accepts identifiers", attr_name);
 114                     let span = nested_meta.span();
 115                     sess.struct_span_err(span, &msg).span_label(span, "not an identifier").emit();
 116                 }
 117             }
 118         }
 119     }
 120     registered
 121 }
 122
 123 crate fn registered_attrs_and_tools(
 124     sess: &Session,
 125     attrs: &[ast::Attribute],
 126 ) -> (FxHashSet<Ident>, FxHashSet<Ident>) {
 127     let registered_attrs = registered_idents(sess, attrs, sym::register_attr, "attribute");
 128     let mut registered_tools = registered_idents(sess, attrs, sym::register_tool, "tool");
 129     // We implicitly add `rustfmt` and `clippy` to known tools,
 130     // but it's not an error to register them explicitly.
 131     let predefined_tools = [sym::clippy, sym::rustfmt];
 132     registered_tools.extend(predefined_tools.iter().cloned().map(Ident::with_dummy_span));
 133     (registered_attrs, registered_tools)
 134 }
 135
 136 impl<'a> base::Resolver for Resolver<'a> {
 137     fn next_node_id(&mut self) -> NodeId {
 138         self.session.next_node_id()
 139     }
 140
 141     fn resolve_dollar_crates(&mut self) {
 142         hygiene::update_dollar_crate_names(|ctxt| {
 143             let ident = Ident::new(kw::DollarCrate, DUMMY_SP.with_ctxt(ctxt));
 144             match self.resolve_crate_root(ident).kind {
 145                 ModuleKind::Def(.., name) if name != kw::Invalid => name,
 146                 _ => kw::Crate,
 147             }
 148         });
 149     }
 150
 151     fn visit_ast_fragment_with_placeholders(&mut self, expansion: ExpnId, fragment: &AstFragment) {
 152         // Integrate the new AST fragment into all the definition and module structures.
 153         // We are inside the `expansion` now, but other parent scope components are still the same.
 154         let parent_scope = ParentScope { expansion, ..self.invocation_parent_scopes[&expansion] };
 155         let output_legacy_scope = self.build_reduced_graph(fragment, parent_scope);
 156         self.output_legacy_scopes.insert(expansion, output_legacy_scope);
 157
 158         parent_scope.module.unexpanded_invocations.borrow_mut().remove(&expansion);
 159     }
 160
 161     fn register_builtin_macro(&mut self, ident: ast::Ident, ext: SyntaxExtension) {
 162         if self.builtin_macros.insert(ident.name, ext).is_some() {
 163             self.session.span_err(ident.span,
 164                                   &format!("built-in macro `{}` was already defined", ident));
 165         }
 166     }
 167
 168     // Create a new Expansion with a definition site of the provided module, or
 169     // a fake empty `#[no_implicit_prelude]` module if no module is provided.
 170     fn expansion_for_ast_pass(
 171         &mut self,
 172         call_site: Span,
 173         pass: AstPass,
 174         features: &[Symbol],
 175         parent_module_id: Option<NodeId>,
 176     ) -> ExpnId {
 177         let expn_id = ExpnId::fresh(Some(ExpnData::allow_unstable(
 178             ExpnKind::AstPass(pass),
 179             call_site,
 180             self.session.edition(),
 181             features.into(),
 182         )));
 183
 184         let parent_scope = if let Some(module_id) = parent_module_id {
 185             let parent_def_id = self.definitions.local_def_id(module_id);
 186             self.definitions.add_parent_module_of_macro_def(expn_id, parent_def_id);
 187             self.module_map[&parent_def_id]
 188         } else {
 189             self.definitions.add_parent_module_of_macro_def(
 190                 expn_id,
 191                 def_id::DefId::local(def_id::CRATE_DEF_INDEX),
 192             );
 193             self.empty_module
 194         };
 195         self.ast_transform_scopes.insert(expn_id, parent_scope);
 196         expn_id
 197     }
 198
 199     fn resolve_imports(&mut self) {
 200         ImportResolver { r: self }.resolve_imports()
 201     }
 202
 203     fn resolve_macro_invocation(
 204         &mut self, invoc: &Invocation, eager_expansion_root: ExpnId, force: bool
 205     ) -> Result<InvocationRes, Indeterminate> {
 206         let invoc_id = invoc.expansion_data.id;
 207         let parent_scope = match self.invocation_parent_scopes.get(&invoc_id) {
 208             Some(parent_scope) => *parent_scope,
 209             None => {
 210                 // If there's no entry in the table, then we are resolving an eagerly expanded
 211                 // macro, which should inherit its parent scope from its eager expansion root -
 212                 // the macro that requested this eager expansion.
 213                 let parent_scope = *self.invocation_parent_scopes.get(&eager_expansion_root)
 214                     .expect("non-eager expansion without a parent scope");
 215                 self.invocation_parent_scopes.insert(invoc_id, parent_scope);
 216                 parent_scope
 217             }
 218         };
 219
 220         let (path, kind, derives, after_derive) = match invoc.kind {
 221             InvocationKind::Attr { ref attr, ref derives, after_derive, .. } =>
 222                 (&attr.get_normal_item().path,
 223                  MacroKind::Attr,
 224                  self.arenas.alloc_ast_paths(derives),
 225                  after_derive),
 226             InvocationKind::Bang { ref mac, .. } =>
 227                 (&mac.path, MacroKind::Bang, &[][..], false),
 228             InvocationKind::Derive { ref path, .. } =>
 229                 (path, MacroKind::Derive, &[][..], false),
 230             InvocationKind::DeriveContainer { ref derives, .. } => {
 231                 // Block expansion of the container until we resolve all derives in it.
 232                 // This is required for two reasons:
 233                 // - Derive helper attributes are in scope for the item to which the `#[derive]`
 234                 //   is applied, so they have to be produced by the container's expansion rather
 235                 //   than by individual derives.
 236                 // - Derives in the container need to know whether one of them is a built-in `Copy`.
 237                 // FIXME: Try to avoid repeated resolutions for derives here and in expansion.
 238                 let mut exts = Vec::new();
 239                 for path in derives {
 240                     exts.push(match self.resolve_macro_path(
 241                         path, Some(MacroKind::Derive), &parent_scope, true, force
 242                     ) {
 243                         Ok((Some(ext), _)) => ext,
 244                         Ok(_) | Err(Determinacy::Determined) => self.dummy_ext(MacroKind::Derive),
 245                         Err(Determinacy::Undetermined) => return Err(Indeterminate),
 246                     })
 247                 }
 248                 return Ok(InvocationRes::DeriveContainer(exts));
 249             }
 250         };
 251
 252         // Derives are not included when `invocations` are collected, so we have to add them here.
 253         let parent_scope = &ParentScope { derives, ..parent_scope };
 254         let (ext, res) = self.smart_resolve_macro_path(path, kind, parent_scope, force)?;
 255
 256         let span = invoc.span();
 257         invoc_id.set_expn_data(ext.expn_data(parent_scope.expansion, span, fast_print_path(path)));
 258
 259         if let Res::Def(_, def_id) = res {
 260             if after_derive {
 261                 self.session.span_err(span, "macro attributes must be placed before `#[derive]`");
 262             }
 263             self.macro_defs.insert(invoc_id, def_id);
 264             let normal_module_def_id = self.macro_def_scope(invoc_id).normal_ancestor_id;
 265             self.definitions.add_parent_module_of_macro_def(invoc_id, normal_module_def_id);
 266         }
 267
 268         match invoc.fragment_kind {
 269             AstFragmentKind::Arms
 270                 | AstFragmentKind::Fields
 271                 | AstFragmentKind::FieldPats
 272                 | AstFragmentKind::GenericParams
 273                 | AstFragmentKind::Params
 274                 | AstFragmentKind::StructFields
 275                 | AstFragmentKind::Variants =>
 276             {
 277                 if let Res::Def(..) = res {
 278                     self.session.span_err(
 279                         span,
 280                         &format!("expected an inert attribute, found {} {}",
 281                                  res.article(), res.descr()),
 282                     );
 283                     return Ok(InvocationRes::Single(self.dummy_ext(kind)));
 284                 }
 285             },
 286             _ => {}
 287         }
 288
 289         Ok(InvocationRes::Single(ext))
 290     }
 291
 292     fn check_unused_macros(&mut self) {
 293         for (&node_id, &span) in self.unused_macros.iter() {
 294             self.lint_buffer.buffer_lint(
 295                 lint::builtin::UNUSED_MACROS, node_id, span, "unused macro definition"
 296             );
 297         }
 298     }
 299
 300     fn has_derive_copy(&self, expn_id: ExpnId) -> bool {
 301         self.containers_deriving_copy.contains(&expn_id)
 302     }
 303
 304     fn add_derive_copy(&mut self, expn_id: ExpnId) {
 305         self.containers_deriving_copy.insert(expn_id);
 306     }
 307 }
 308
 309 impl<'a> Resolver<'a> {
 310     /// Resolve macro path with error reporting and recovery.
 311     fn smart_resolve_macro_path(
 312         &mut self,
 313         path: &ast::Path,
 314         kind: MacroKind,
 315         parent_scope: &ParentScope<'a>,
 316         force: bool,
 317     ) -> Result<(Lrc<SyntaxExtension>, Res), Indeterminate> {
 318         let (ext, res) = match self.resolve_macro_path(path, Some(kind), parent_scope,
 319                                                        true, force) {
 320             Ok((Some(ext), res)) => (ext, res),
 321             // Use dummy syntax extensions for unresolved macros for better recovery.
 322             Ok((None, res)) => (self.dummy_ext(kind), res),
 323             Err(Determinacy::Determined) => (self.dummy_ext(kind), Res::Err),
 324             Err(Determinacy::Undetermined) => return Err(Indeterminate),
 325         };
 326
 327         // Report errors and enforce feature gates for the resolved macro.
 328         let features = self.session.features_untracked();
 329         for segment in &path.segments {
 330             if let Some(args) = &segment.args {
 331                 self.session.span_err(args.span(), "generic arguments in macro path");
 332             }
 333             if kind == MacroKind::Attr && !features.rustc_attrs &&
 334                segment.ident.as_str().starts_with("rustc") {
 335                 let msg =
 336                     "attributes starting with `rustc` are reserved for use by the `rustc` compiler";
 337                 emit_feature_err(
 338                     &self.session.parse_sess,
 339                     sym::rustc_attrs,
 340                     segment.ident.span,
 341                     GateIssue::Language,
 342                     msg,
 343                 );
 344             }
 345         }
 346
 347         match res {
 348             Res::Def(DefKind::Macro(_), def_id) => {
 349                 if let Some(node_id) = self.definitions.as_local_node_id(def_id) {
 350                     self.unused_macros.remove(&node_id);
 351                     if self.proc_macro_stubs.contains(&node_id) {
 352                         self.session.span_err(
 353                             path.span,
 354                             "can't use a procedural macro from the same crate that defines it",
 355                         );
 356                     }
 357                 }
 358             }
 359             Res::NonMacroAttr(..) | Res::Err => {}
 360             _ => panic!("expected `DefKind::Macro` or `Res::NonMacroAttr`"),
 361         };
 362
 363         self.check_stability_and_deprecation(&ext, path);
 364
 365         Ok(if ext.macro_kind() != kind {
 366             let expected = kind.descr_expected();
 367             let path_str = pprust::path_to_string(path);
 368             let msg = format!("expected {}, found {} `{}`", expected, res.descr(), path_str);
 369             self.session.struct_span_err(path.span, &msg)
 370                         .span_label(path.span, format!("not {} {}", kind.article(), expected))
 371                         .emit();
 372             // Use dummy syntax extensions for unexpected macro kinds for better recovery.
 373             (self.dummy_ext(kind), Res::Err)
 374         } else {
 375             (ext, res)
 376         })
 377     }
 378
 379     pub fn resolve_macro_path(
 380         &mut self,
 381         path: &ast::Path,
 382         kind: Option<MacroKind>,
 383         parent_scope: &ParentScope<'a>,
 384         trace: bool,
 385         force: bool,
 386     ) -> Result<(Option<Lrc<SyntaxExtension>>, Res), Determinacy> {
 387         let path_span = path.span;
 388         let mut path = Segment::from_path(path);
 389
 390         // Possibly apply the macro helper hack
 391         if kind == Some(MacroKind::Bang) && path.len() == 1 &&
 392            path[0].ident.span.ctxt().outer_expn_data().local_inner_macros {
 393             let root = Ident::new(kw::DollarCrate, path[0].ident.span);
 394             path.insert(0, Segment::from_ident(root));
 395         }
 396
 397         let res = if path.len() > 1 {
 398             let res = match self.resolve_path(&path, Some(MacroNS), parent_scope,
 399                                               false, path_span, CrateLint::No) {
 400                 PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 => {
 401                     Ok(path_res.base_res())
 402                 }
 403                 PathResult::Indeterminate if !force => return Err(Determinacy::Undetermined),
 404                 PathResult::NonModule(..)
 405                 | PathResult::Indeterminate
 406                 | PathResult::Failed { .. } => Err(Determinacy::Determined),
 407                 PathResult::Module(..) => unreachable!(),
 408             };
 409
 410             if trace {
 411                 let kind = kind.expect("macro kind must be specified if tracing is enabled");
 412                 self.multi_segment_macro_resolutions
 413                     .push((path, path_span, kind, *parent_scope, res.ok()));
 414             }
 415
 416             self.prohibit_imported_non_macro_attrs(None, res.ok(), path_span);
 417             res
 418         } else {
 419             let scope_set = kind.map_or(ScopeSet::All(MacroNS, false), ScopeSet::Macro);
 420             let binding = self.early_resolve_ident_in_lexical_scope(
 421                 path[0].ident, scope_set, parent_scope, false, force, path_span
 422             );
 423             if let Err(Determinacy::Undetermined) = binding {
 424                 return Err(Determinacy::Undetermined);
 425             }
 426
 427             if trace {
 428                 let kind = kind.expect("macro kind must be specified if tracing is enabled");
 429                 self.single_segment_macro_resolutions
 430                     .push((path[0].ident, kind, *parent_scope, binding.ok()));
 431             }
 432
 433             let res = binding.map(|binding| binding.res());
 434             self.prohibit_imported_non_macro_attrs(binding.ok(), res.ok(), path_span);
 435             res
 436         };
 437
 438         res.map(|res| (self.get_macro(res), res))
 439     }
 440
 441     // Resolve an identifier in lexical scope.
 442     // This is a variation of `fn resolve_ident_in_lexical_scope` that can be run during
 443     // expansion and import resolution (perhaps they can be merged in the future).
 444     // The function is used for resolving initial segments of macro paths (e.g., `foo` in
 445     // `foo::bar!(); or `foo!();`) and also for import paths on 2018 edition.
 446     crate fn early_resolve_ident_in_lexical_scope(
 447         &mut self,
 448         orig_ident: Ident,
 449         scope_set: ScopeSet,
 450         parent_scope: &ParentScope<'a>,
 451         record_used: bool,
 452         force: bool,
 453         path_span: Span,
 454     ) -> Result<&'a NameBinding<'a>, Determinacy> {
 455         bitflags::bitflags! {
 456             struct Flags: u8 {
 457                 const MACRO_RULES        = 1 << 0;
 458                 const MODULE             = 1 << 1;
 459                 const PRELUDE            = 1 << 2;
 460                 const MISC_SUGGEST_CRATE = 1 << 3;
 461                 const MISC_SUGGEST_SELF  = 1 << 4;
 462                 const MISC_FROM_PRELUDE  = 1 << 5;
 463             }
 464         }
 465
 466         assert!(force || !record_used); // `record_used` implies `force`
 467
 468         // Make sure `self`, `super` etc produce an error when passed to here.
 469         if orig_ident.is_path_segment_keyword() {
 470             return Err(Determinacy::Determined);
 471         }
 472
 473         let (ns, macro_kind, is_import) = match scope_set {
 474             ScopeSet::All(ns, is_import) => (ns, None, is_import),
 475             ScopeSet::AbsolutePath(ns) => (ns, None, false),
 476             ScopeSet::Macro(macro_kind) => (MacroNS, Some(macro_kind), false),
 477         };
 478
 479         // This is *the* result, resolution from the scope closest to the resolved identifier.
 480         // However, sometimes this result is "weak" because it comes from a glob import or
 481         // a macro expansion, and in this case it cannot shadow names from outer scopes, e.g.
 482         // mod m { ... } // solution in outer scope
 483         // {
 484         //     use prefix::*; // imports another `m` - innermost solution
 485         //                    // weak, cannot shadow the outer `m`, need to report ambiguity error
 486         //     m::mac!();
 487         // }
 488         // So we have to save the innermost solution and continue searching in outer scopes
 489         // to detect potential ambiguities.
 490         let mut innermost_result: Option<(&NameBinding<'_>, Flags)> = None;
 491         let mut determinacy = Determinacy::Determined;
 492
 493         // Go through all the scopes and try to resolve the name.
 494         let break_result = self.visit_scopes(scope_set, parent_scope, orig_ident,
 495                                              |this, scope, use_prelude, ident| {
 496             let result = match scope {
 497                 Scope::DeriveHelpers => {
 498                     let mut result = Err(Determinacy::Determined);
 499                     for derive in parent_scope.derives {
 500                         let parent_scope = &ParentScope { derives: &[], ..*parent_scope };
 501                         match this.resolve_macro_path(derive, Some(MacroKind::Derive),
 502                                                       parent_scope, true, force) {
 503                             Ok((Some(ext), _)) => if ext.helper_attrs.contains(&ident.name) {
 504                                 let binding = (Res::NonMacroAttr(NonMacroAttrKind::DeriveHelper),
 505                                                ty::Visibility::Public, derive.span, ExpnId::root())
 506                                                .to_name_binding(this.arenas);
 507                                 result = Ok((binding, Flags::empty()));
 508                                 break;
 509                             }
 510                             Ok(_) | Err(Determinacy::Determined) => {}
 511                             Err(Determinacy::Undetermined) =>
 512                                 result = Err(Determinacy::Undetermined),
 513                         }
 514                     }
 515                     result
 516                 }
 517                 Scope::MacroRules(legacy_scope) => match legacy_scope {
 518                     LegacyScope::Binding(legacy_binding) if ident == legacy_binding.ident =>
 519                         Ok((legacy_binding.binding, Flags::MACRO_RULES)),
 520                     LegacyScope::Invocation(invoc_id)
 521                         if !this.output_legacy_scopes.contains_key(&invoc_id) =>
 522                             Err(Determinacy::Undetermined),
 523                     _ => Err(Determinacy::Determined),
 524                 }
 525                 Scope::CrateRoot => {
 526                     let root_ident = Ident::new(kw::PathRoot, ident.span);
 527                     let root_module = this.resolve_crate_root(root_ident);
 528                     let binding = this.resolve_ident_in_module_ext(
 529                         ModuleOrUniformRoot::Module(root_module),
 530                         ident,
 531                         ns,
 532                         parent_scope,
 533                         record_used,
 534                         path_span,
 535                     );
 536                     match binding {
 537                         Ok(binding) => Ok((binding, Flags::MODULE | Flags::MISC_SUGGEST_CRATE)),
 538                         Err((Determinacy::Undetermined, Weak::No)) =>
 539                             return Some(Err(Determinacy::determined(force))),
 540                         Err((Determinacy::Undetermined, Weak::Yes)) =>
 541                             Err(Determinacy::Undetermined),
 542                         Err((Determinacy::Determined, _)) => Err(Determinacy::Determined),
 543                     }
 544                 }
 545                 Scope::Module(module) => {
 546                     let adjusted_parent_scope = &ParentScope { module, ..*parent_scope };
 547                     let binding = this.resolve_ident_in_module_unadjusted_ext(
 548                         ModuleOrUniformRoot::Module(module),
 549                         ident,
 550                         ns,
 551                         adjusted_parent_scope,
 552                         true,
 553                         record_used,
 554                         path_span,
 555                     );
 556                     match binding {
 557                         Ok(binding) => {
 558                             let misc_flags = if ptr::eq(module, this.graph_root) {
 559                                 Flags::MISC_SUGGEST_CRATE
 560                             } else if module.is_normal() {
 561                                 Flags::MISC_SUGGEST_SELF
 562                             } else {
 563                                 Flags::empty()
 564                             };
 565                             Ok((binding, Flags::MODULE | misc_flags))
 566                         }
 567                         Err((Determinacy::Undetermined, Weak::No)) =>
 568                             return Some(Err(Determinacy::determined(force))),
 569                         Err((Determinacy::Undetermined, Weak::Yes)) =>
 570                             Err(Determinacy::Undetermined),
 571                         Err((Determinacy::Determined, _)) => Err(Determinacy::Determined),
 572                     }
 573                 }
 574                 Scope::RegisteredAttrs => match this.registered_attrs.get(&ident).cloned() {
 575                     Some(ident) => {
 576                         let binding = (Res::NonMacroAttr(NonMacroAttrKind::Registered),
 577                                        ty::Visibility::Public, ident.span, ExpnId::root())
 578                                        .to_name_binding(this.arenas);
 579                         Ok((binding, Flags::PRELUDE))
 580                     }
 581                     None => Err(Determinacy::Determined)
 582                 }
 583                 Scope::MacroUsePrelude => match this.macro_use_prelude.get(&ident.name).cloned() {
 584                     Some(binding) => Ok((binding, Flags::PRELUDE | Flags::MISC_FROM_PRELUDE)),
 585                     None => Err(Determinacy::determined(
 586                         this.graph_root.unexpanded_invocations.borrow().is_empty()
 587                     ))
 588                 }
 589                 Scope::BuiltinAttrs => if is_builtin_attr_name(ident.name) {
 590                     let binding = (Res::NonMacroAttr(NonMacroAttrKind::Builtin),
 591                                    ty::Visibility::Public, DUMMY_SP, ExpnId::root())
 592                                    .to_name_binding(this.arenas);
 593                     Ok((binding, Flags::PRELUDE))
 594                 } else {
 595                     Err(Determinacy::Determined)
 596                 }
 597                 Scope::LegacyPluginHelpers => if this.session.plugin_attributes.borrow().iter()
 598                                                      .any(|(name, _)| ident.name == *name) {
 599                     let binding = (Res::NonMacroAttr(NonMacroAttrKind::LegacyPluginHelper),
 600                                    ty::Visibility::Public, DUMMY_SP, ExpnId::root())
 601                                    .to_name_binding(this.arenas);
 602                     Ok((binding, Flags::PRELUDE))
 603                 } else {
 604                     Err(Determinacy::Determined)
 605                 }
 606                 Scope::ExternPrelude => match this.extern_prelude_get(ident, !record_used) {
 607                     Some(binding) => Ok((binding, Flags::PRELUDE)),
 608                     None => Err(Determinacy::determined(
 609                         this.graph_root.unexpanded_invocations.borrow().is_empty()
 610                     )),
 611                 }
 612                 Scope::ToolPrelude => match this.registered_tools.get(&ident).cloned() {
 613                     Some(ident) => {
 614                         let binding = (Res::ToolMod,
 615                                        ty::Visibility::Public, ident.span, ExpnId::root())
 616                                        .to_name_binding(this.arenas);
 617                         Ok((binding, Flags::PRELUDE))
 618                     }
 619                     None => Err(Determinacy::Determined)
 620                 }
 621                 Scope::StdLibPrelude => {
 622                     let mut result = Err(Determinacy::Determined);
 623                     if let Some(prelude) = this.prelude {
 624                         if let Ok(binding) = this.resolve_ident_in_module_unadjusted(
 625                             ModuleOrUniformRoot::Module(prelude),
 626                             ident,
 627                             ns,
 628                             parent_scope,
 629                             false,
 630                             path_span,
 631                         ) {
 632                             if use_prelude || this.is_builtin_macro(binding.res()) {
 633                                 result = Ok((binding, Flags::PRELUDE | Flags::MISC_FROM_PRELUDE));
 634                             }
 635                         }
 636                     }
 637                     result
 638                 }
 639                 Scope::BuiltinTypes => match this.primitive_type_table.primitive_types
 640                                                  .get(&ident.name).cloned() {
 641                     Some(prim_ty) => {
 642                         let binding = (Res::PrimTy(prim_ty), ty::Visibility::Public,
 643                                        DUMMY_SP, ExpnId::root()).to_name_binding(this.arenas);
 644                         Ok((binding, Flags::PRELUDE))
 645                     }
 646                     None => Err(Determinacy::Determined)
 647                 }
 648             };
 649
 650             match result {
 651                 Ok((binding, flags)) if sub_namespace_match(binding.macro_kind(), macro_kind) => {
 652                     if !record_used {
 653                         return Some(Ok(binding));
 654                     }
 655
 656                     if let Some((innermost_binding, innermost_flags)) = innermost_result {
 657                         // Found another solution, if the first one was "weak", report an error.
 658                         let (res, innermost_res) = (binding.res(), innermost_binding.res());
 659                         if res != innermost_res {
 660                             let builtin = Res::NonMacroAttr(NonMacroAttrKind::Builtin);
 661                             let derive_helper = Res::NonMacroAttr(NonMacroAttrKind::DeriveHelper);
 662                             let legacy_helper =
 663                                 Res::NonMacroAttr(NonMacroAttrKind::LegacyPluginHelper);
 664
 665                             let ambiguity_error_kind = if is_import {
 666                                 Some(AmbiguityKind::Import)
 667                             } else if innermost_res == builtin || res == builtin {
 668                                 Some(AmbiguityKind::BuiltinAttr)
 669                             } else if innermost_res == derive_helper || res == derive_helper {
 670                                 Some(AmbiguityKind::DeriveHelper)
 671                             } else if innermost_res == legacy_helper &&
 672                                       flags.contains(Flags::PRELUDE) ||
 673                                       res == legacy_helper &&
 674                                       innermost_flags.contains(Flags::PRELUDE) {
 675                                 Some(AmbiguityKind::LegacyHelperVsPrelude)
 676                             } else if innermost_flags.contains(Flags::MACRO_RULES) &&
 677                                       flags.contains(Flags::MODULE) &&
 678                                       !this.disambiguate_legacy_vs_modern(innermost_binding,
 679                                                                           binding) ||
 680                                       flags.contains(Flags::MACRO_RULES) &&
 681                                       innermost_flags.contains(Flags::MODULE) &&
 682                                       !this.disambiguate_legacy_vs_modern(binding,
 683                                                                           innermost_binding) {
 684                                 Some(AmbiguityKind::LegacyVsModern)
 685                             } else if innermost_binding.is_glob_import() {
 686                                 Some(AmbiguityKind::GlobVsOuter)
 687                             } else if innermost_binding.may_appear_after(parent_scope.expansion,
 688                                                                          binding) {
 689                                 Some(AmbiguityKind::MoreExpandedVsOuter)
 690                             } else {
 691                                 None
 692                             };
 693                             if let Some(kind) = ambiguity_error_kind {
 694                                 let misc = |f: Flags| if f.contains(Flags::MISC_SUGGEST_CRATE) {
 695                                     AmbiguityErrorMisc::SuggestCrate
 696                                 } else if f.contains(Flags::MISC_SUGGEST_SELF) {
 697                                     AmbiguityErrorMisc::SuggestSelf
 698                                 } else if f.contains(Flags::MISC_FROM_PRELUDE) {
 699                                     AmbiguityErrorMisc::FromPrelude
 700                                 } else {
 701                                     AmbiguityErrorMisc::None
 702                                 };
 703                                 this.ambiguity_errors.push(AmbiguityError {
 704                                     kind,
 705                                     ident: orig_ident,
 706                                     b1: innermost_binding,
 707                                     b2: binding,
 708                                     misc1: misc(innermost_flags),
 709                                     misc2: misc(flags),
 710                                 });
 711                                 return Some(Ok(innermost_binding));
 712                             }
 713                         }
 714                     } else {
 715                         // Found the first solution.
 716                         innermost_result = Some((binding, flags));
 717                     }
 718                 }
 719                 Ok(..) | Err(Determinacy::Determined) => {}
 720                 Err(Determinacy::Undetermined) => determinacy = Determinacy::Undetermined
 721             }
 722
 723             None
 724         });
 725
 726         if let Some(break_result) = break_result {
 727             return break_result;
 728         }
 729
 730         // The first found solution was the only one, return it.
 731         if let Some((binding, _)) = innermost_result {
 732             return Ok(binding);
 733         }
 734
 735         Err(Determinacy::determined(determinacy == Determinacy::Determined || force))
 736     }
 737
 738     crate fn finalize_macro_resolutions(&mut self) {
 739         let check_consistency = |this: &mut Self, path: &[Segment], span, kind: MacroKind,
 740                                  initial_res: Option<Res>, res: Res| {
 741             if let Some(initial_res) = initial_res {
 742                 if res != initial_res && res != Res::Err && this.ambiguity_errors.is_empty() {
 743                     // Make sure compilation does not succeed if preferred macro resolution
 744                     // has changed after the macro had been expanded. In theory all such
 745                     // situations should be reported as ambiguity errors, so this is a bug.
 746                     span_bug!(span, "inconsistent resolution for a macro");
 747                 }
 748             } else {
 749                 // It's possible that the macro was unresolved (indeterminate) and silently
 750                 // expanded into a dummy fragment for recovery during expansion.
 751                 // Now, post-expansion, the resolution may succeed, but we can't change the
 752                 // past and need to report an error.
 753                 // However, non-speculative `resolve_path` can successfully return private items
 754                 // even if speculative `resolve_path` returned nothing previously, so we skip this
 755                 // less informative error if the privacy error is reported elsewhere.
 756                 if this.privacy_errors.is_empty() {
 757                     let msg = format!("cannot determine resolution for the {} `{}`",
 758                                         kind.descr(), Segment::names_to_string(path));
 759                     let msg_note = "import resolution is stuck, try simplifying macro imports";
 760                     this.session.struct_span_err(span, &msg).note(msg_note).emit();
 761                 }
 762             }
 763         };
 764
 765         let macro_resolutions = mem::take(&mut self.multi_segment_macro_resolutions);
 766         for (mut path, path_span, kind, parent_scope, initial_res) in macro_resolutions {
 767             // FIXME: Path resolution will ICE if segment IDs present.
 768             for seg in &mut path { seg.id = None; }
 769             match self.resolve_path(
 770                 &path, Some(MacroNS), &parent_scope, true, path_span, CrateLint::No
 771             ) {
 772                 PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 => {
 773                     let res = path_res.base_res();
 774                     check_consistency(self, &path, path_span, kind, initial_res, res);
 775                 }
 776                 path_res @ PathResult::NonModule(..) | path_res @ PathResult::Failed { .. } => {
 777                     let (span, label) = if let PathResult::Failed { span, label, .. } = path_res {
 778                         (span, label)
 779                     } else {
 780                         (path_span, format!("partially resolved path in {} {}",
 781                                             kind.article(), kind.descr()))
 782                     };
 783                     self.report_error(span, ResolutionError::FailedToResolve {
 784                         label,
 785                         suggestion: None
 786                     });
 787                 }
 788                 PathResult::Module(..) | PathResult::Indeterminate => unreachable!(),
 789             }
 790         }
 791
 792         let macro_resolutions = mem::take(&mut self.single_segment_macro_resolutions);
 793         for (ident, kind, parent_scope, initial_binding) in macro_resolutions {
 794             match self.early_resolve_ident_in_lexical_scope(ident, ScopeSet::Macro(kind),
 795                                                             &parent_scope, true, true, ident.span) {
 796                 Ok(binding) => {
 797                     let initial_res = initial_binding.map(|initial_binding| {
 798                         self.record_use(ident, MacroNS, initial_binding, false);
 799                         initial_binding.res()
 800                     });
 801                     let res = binding.res();
 802                     let seg = Segment::from_ident(ident);
 803                     check_consistency(self, &[seg], ident.span, kind, initial_res, res);
 804                 }
 805                 Err(..) => {
 806                     let expected = kind.descr_expected();
 807                     let msg = format!("cannot find {} `{}` in this scope", expected, ident);
 808                     let mut err = self.session.struct_span_err(ident.span, &msg);
 809                     self.unresolved_macro_suggestions(&mut err, kind, &parent_scope, ident);
 810                     err.emit();
 811                 }
 812             }
 813         }
 814
 815         let builtin_attrs = mem::take(&mut self.builtin_attrs);
 816         for (ident, parent_scope) in builtin_attrs {
 817             let _ = self.early_resolve_ident_in_lexical_scope(
 818                 ident, ScopeSet::Macro(MacroKind::Attr), &parent_scope, true, true, ident.span
 819             );
 820         }
 821     }
 822
 823     fn check_stability_and_deprecation(&mut self, ext: &SyntaxExtension, path: &ast::Path) {
 824         let span = path.span;
 825         if let Some(stability) = &ext.stability {
 826             if let StabilityLevel::Unstable { reason, issue, is_soft } = stability.level {
 827                 let feature = stability.feature;
 828                 if !self.active_features.contains(&feature) && !span.allows_unstable(feature) {
 829                     let node_id = ast::CRATE_NODE_ID;
 830                     let lint_buffer = &mut self.lint_buffer;
 831                     let soft_handler = |lint, span, msg: &_| {
 832                         lint_buffer.buffer_lint(lint, node_id, span, msg)
 833                     };
 834                     stability::report_unstable(
 835                         self.session, feature, reason, issue, is_soft, span, soft_handler
 836                     );
 837                 }
 838             }
 839             if let Some(depr) = &stability.rustc_depr {
 840                 let path = pprust::path_to_string(path);
 841                 let (message, lint) = stability::rustc_deprecation_message(depr, &path);
 842                 stability::early_report_deprecation(
 843                     &mut self.lint_buffer, &message, depr.suggestion, lint, span
 844                 );
 845             }
 846         }
 847         if let Some(depr) = &ext.deprecation {
 848             let path = pprust::path_to_string(&path);
 849             let (message, lint) = stability::deprecation_message(depr, &path);
 850             stability::early_report_deprecation(&mut self.lint_buffer, &message, None, lint, span);
 851         }
 852     }
 853
 854     fn prohibit_imported_non_macro_attrs(&self, binding: Option<&'a NameBinding<'a>>,
 855                                          res: Option<Res>, span: Span) {
 856         if let Some(Res::NonMacroAttr(kind)) = res {
 857             if kind != NonMacroAttrKind::Tool && binding.map_or(true, |b| b.is_import()) {
 858                 let msg = format!("cannot use a {} through an import", kind.descr());
 859                 let mut err = self.session.struct_span_err(span, &msg);
 860                 if let Some(binding) = binding {
 861                     err.span_note(binding.span, &format!("the {} imported here", kind.descr()));
 862                 }
 863                 err.emit();
 864             }
 865         }
 866     }
 867
 868     crate fn check_reserved_macro_name(&mut self, ident: Ident, res: Res) {
 869         // Reserve some names that are not quite covered by the general check
 870         // performed on `Resolver::builtin_attrs`.
 871         if ident.name == sym::cfg || ident.name == sym::cfg_attr || ident.name == sym::derive {
 872             let macro_kind = self.get_macro(res).map(|ext| ext.macro_kind());
 873             if macro_kind.is_some() && sub_namespace_match(macro_kind, Some(MacroKind::Attr)) {
 874                 self.session.span_err(
 875                     ident.span, &format!("name `{}` is reserved in attribute namespace", ident)
 876                 );
 877             }
 878         }
 879     }
 880
 881     /// Compile the macro into a `SyntaxExtension` and possibly replace it with a pre-defined
 882     /// extension partially or entirely for built-in macros and legacy plugin macros.
 883     crate fn compile_macro(&mut self, item: &ast::Item, edition: Edition) -> SyntaxExtension {
 884         let mut result = compile_declarative_macro(
 885             &self.session.parse_sess, self.session.features_untracked(), item, edition
 886         );
 887
 888         if result.is_builtin {
 889             // The macro was marked with `#[rustc_builtin_macro]`.
 890             if let Some(ext) = self.builtin_macros.remove(&item.ident.name) {
 891                 if ext.is_builtin {
 892                     // The macro is a built-in, replace only the expander function.
 893                     result.kind = ext.kind;
 894                 } else {
 895                     // The macro is from a plugin, the in-source definition is dummy,
 896                     // take all the data from the resolver.
 897                     result = ext;
 898                 }
 899             } else {
 900                 let msg = format!("cannot find a built-in macro with name `{}`", item.ident);
 901                 self.session.span_err(item.span, &msg);
 902             }
 903         }
 904
 905         result
 906     }
 907 }