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