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