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                 for path in derives {
 241                     exts.push(match self.resolve_macro_path(
 242                         path, Some(MacroKind::Derive), &parent_scope, true, force
 243                     ) {
 244                         Ok((Some(ext), _)) => ext,
 245                         Ok(_) | Err(Determinacy::Determined) => self.dummy_ext(MacroKind::Derive),
 246                         Err(Determinacy::Undetermined) => return Err(Indeterminate),
 247                     })
 248                 }
 249                 return Ok(InvocationRes::DeriveContainer(exts));
 250             }
 251         };
 252
 253         // Derives are not included when `invocations` are collected, so we have to add them here.
 254         let parent_scope = &ParentScope { derives, ..parent_scope };
 255         let (ext, res) = self.smart_resolve_macro_path(path, kind, parent_scope, force)?;
 256
 257         let span = invoc.span();
 258         invoc_id.set_expn_data(ext.expn_data(parent_scope.expansion, span, fast_print_path(path)));
 259
 260         if let Res::Def(_, def_id) = res {
 261             if after_derive {
 262                 self.session.span_err(span, "macro attributes must be placed before `#[derive]`");
 263             }
 264             self.macro_defs.insert(invoc_id, def_id);
 265             let normal_module_def_id = self.macro_def_scope(invoc_id).normal_ancestor_id;
 266             self.definitions.add_parent_module_of_macro_def(invoc_id, normal_module_def_id);
 267         }
 268
 269         match invoc.fragment_kind {
 270             AstFragmentKind::Arms
 271                 | AstFragmentKind::Fields
 272                 | AstFragmentKind::FieldPats
 273                 | AstFragmentKind::GenericParams
 274                 | AstFragmentKind::Params
 275                 | AstFragmentKind::StructFields
 276                 | AstFragmentKind::Variants =>
 277             {
 278                 if let Res::Def(..) = res {
 279                     self.session.span_err(
 280                         span,
 281                         &format!("expected an inert attribute, found {} {}",
 282                                  res.article(), res.descr()),
 283                     );
 284                     return Ok(InvocationRes::Single(self.dummy_ext(kind)));
 285                 }
 286             },
 287             _ => {}
 288         }
 289
 290         Ok(InvocationRes::Single(ext))
 291     }
 292
 293     fn check_unused_macros(&mut self) {
 294         for (&node_id, &span) in self.unused_macros.iter() {
 295             self.lint_buffer.buffer_lint(
 296                 lint::builtin::UNUSED_MACROS, node_id, span, "unused macro definition"
 297             );
 298         }
 299     }
 300
 301     fn has_derive_copy(&self, expn_id: ExpnId) -> bool {
 302         self.containers_deriving_copy.contains(&expn_id)
 303     }
 304
 305     fn add_derive_copy(&mut self, expn_id: ExpnId) {
 306         self.containers_deriving_copy.insert(expn_id);
 307     }
 308 }
 309
 310 impl<'a> Resolver<'a> {
 311     /// Resolve macro path with error reporting and recovery.
 312     fn smart_resolve_macro_path(
 313         &mut self,
 314         path: &ast::Path,
 315         kind: MacroKind,
 316         parent_scope: &ParentScope<'a>,
 317         force: bool,
 318     ) -> Result<(Lrc<SyntaxExtension>, Res), Indeterminate> {
 319         let (ext, res) = match self.resolve_macro_path(path, Some(kind), parent_scope,
 320                                                        true, force) {
 321             Ok((Some(ext), res)) => (ext, res),
 322             // Use dummy syntax extensions for unresolved macros for better recovery.
 323             Ok((None, res)) => (self.dummy_ext(kind), res),
 324             Err(Determinacy::Determined) => (self.dummy_ext(kind), Res::Err),
 325             Err(Determinacy::Undetermined) => return Err(Indeterminate),
 326         };
 327
 328         // Report errors and enforce feature gates for the resolved macro.
 329         let features = self.session.features_untracked();
 330         for segment in &path.segments {
 331             if let Some(args) = &segment.args {
 332                 self.session.span_err(args.span(), "generic arguments in macro path");
 333             }
 334             if kind == MacroKind::Attr && !features.rustc_attrs &&
 335                segment.ident.as_str().starts_with("rustc") {
 336                 let msg =
 337                     "attributes starting with `rustc` are reserved for use by the `rustc` compiler";
 338                 emit_feature_err(
 339                     &self.session.parse_sess,
 340                     sym::rustc_attrs,
 341                     segment.ident.span,
 342                     GateIssue::Language,
 343                     msg,
 344                 );
 345             }
 346         }
 347
 348         match res {
 349             Res::Def(DefKind::Macro(_), def_id) => {
 350                 if let Some(node_id) = self.definitions.as_local_node_id(def_id) {
 351                     self.unused_macros.remove(&node_id);
 352                     if self.proc_macro_stubs.contains(&node_id) {
 353                         self.session.span_err(
 354                             path.span,
 355                             "can't use a procedural macro from the same crate that defines it",
 356                         );
 357                     }
 358                 }
 359             }
 360             Res::NonMacroAttr(..) | Res::Err => {}
 361             _ => panic!("expected `DefKind::Macro` or `Res::NonMacroAttr`"),
 362         };
 363
 364         self.check_stability_and_deprecation(&ext, path);
 365
 366         Ok(if ext.macro_kind() != kind {
 367             let expected = kind.descr_expected();
 368             let path_str = pprust::path_to_string(path);
 369             let msg = format!("expected {}, found {} `{}`", expected, res.descr(), path_str);
 370             self.session.struct_span_err(path.span, &msg)
 371                         .span_label(path.span, format!("not {} {}", kind.article(), expected))
 372                         .emit();
 373             // Use dummy syntax extensions for unexpected macro kinds for better recovery.
 374             (self.dummy_ext(kind), Res::Err)
 375         } else {
 376             (ext, res)
 377         })
 378     }
 379
 380     pub fn resolve_macro_path(
 381         &mut self,
 382         path: &ast::Path,
 383         kind: Option<MacroKind>,
 384         parent_scope: &ParentScope<'a>,
 385         trace: bool,
 386         force: bool,
 387     ) -> Result<(Option<Lrc<SyntaxExtension>>, Res), Determinacy> {
 388         let path_span = path.span;
 389         let mut path = Segment::from_path(path);
 390
 391         // Possibly apply the macro helper hack
 392         if kind == Some(MacroKind::Bang) && path.len() == 1 &&
 393            path[0].ident.span.ctxt().outer_expn_data().local_inner_macros {
 394             let root = Ident::new(kw::DollarCrate, path[0].ident.span);
 395             path.insert(0, Segment::from_ident(root));
 396         }
 397
 398         let res = if path.len() > 1 {
 399             let res = match self.resolve_path(&path, Some(MacroNS), parent_scope,
 400                                               false, path_span, CrateLint::No) {
 401                 PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 => {
 402                     Ok(path_res.base_res())
 403                 }
 404                 PathResult::Indeterminate if !force => return Err(Determinacy::Undetermined),
 405                 PathResult::NonModule(..)
 406                 | PathResult::Indeterminate
 407                 | PathResult::Failed { .. } => Err(Determinacy::Determined),
 408                 PathResult::Module(..) => unreachable!(),
 409             };
 410
 411             if trace {
 412                 let kind = kind.expect("macro kind must be specified if tracing is enabled");
 413                 self.multi_segment_macro_resolutions
 414                     .push((path, path_span, kind, *parent_scope, res.ok()));
 415             }
 416
 417             self.prohibit_imported_non_macro_attrs(None, res.ok(), path_span);
 418             res
 419         } else {
 420             let scope_set = kind.map_or(ScopeSet::All(MacroNS, false), ScopeSet::Macro);
 421             let binding = self.early_resolve_ident_in_lexical_scope(
 422                 path[0].ident, scope_set, parent_scope, false, force, path_span
 423             );
 424             if let Err(Determinacy::Undetermined) = binding {
 425                 return Err(Determinacy::Undetermined);
 426             }
 427
 428             if trace {
 429                 let kind = kind.expect("macro kind must be specified if tracing is enabled");
 430                 self.single_segment_macro_resolutions
 431                     .push((path[0].ident, kind, *parent_scope, binding.ok()));
 432             }
 433
 434             let res = binding.map(|binding| binding.res());
 435             self.prohibit_imported_non_macro_attrs(binding.ok(), res.ok(), path_span);
 436             res
 437         };
 438
 439         res.map(|res| (self.get_macro(res), res))
 440     }
 441
 442     // Resolve an identifier in lexical scope.
 443     // This is a variation of `fn resolve_ident_in_lexical_scope` that can be run during
 444     // expansion and import resolution (perhaps they can be merged in the future).
 445     // The function is used for resolving initial segments of macro paths (e.g., `foo` in
 446     // `foo::bar!(); or `foo!();`) and also for import paths on 2018 edition.
 447     crate fn early_resolve_ident_in_lexical_scope(
 448         &mut self,
 449         orig_ident: Ident,
 450         scope_set: ScopeSet,
 451         parent_scope: &ParentScope<'a>,
 452         record_used: bool,
 453         force: bool,
 454         path_span: Span,
 455     ) -> Result<&'a NameBinding<'a>, Determinacy> {
 456         bitflags::bitflags! {
 457             struct Flags: u8 {
 458                 const MACRO_RULES        = 1 << 0;
 459                 const MODULE             = 1 << 1;
 460                 const MISC_SUGGEST_CRATE = 1 << 2;
 461                 const MISC_SUGGEST_SELF  = 1 << 3;
 462                 const MISC_FROM_PRELUDE  = 1 << 4;
 463             }
 464         }
 465
 466         assert!(force || !record_used); // `record_used` implies `force`
 467
 468         // Make sure `self`, `super` etc produce an error when passed to here.
 469         if orig_ident.is_path_segment_keyword() {
 470             return Err(Determinacy::Determined);
 471         }
 472
 473         let (ns, macro_kind, is_import) = match scope_set {
 474             ScopeSet::All(ns, is_import) => (ns, None, is_import),
 475             ScopeSet::AbsolutePath(ns) => (ns, None, false),
 476             ScopeSet::Macro(macro_kind) => (MacroNS, Some(macro_kind), false),
 477         };
 478
 479         // This is *the* result, resolution from the scope closest to the resolved identifier.
 480         // However, sometimes this result is "weak" because it comes from a glob import or
 481         // a macro expansion, and in this case it cannot shadow names from outer scopes, e.g.
 482         // mod m { ... } // solution in outer scope
 483         // {
 484         //     use prefix::*; // imports another `m` - innermost solution
 485         //                    // weak, cannot shadow the outer `m`, need to report ambiguity error
 486         //     m::mac!();
 487         // }
 488         // So we have to save the innermost solution and continue searching in outer scopes
 489         // to detect potential ambiguities.
 490         let mut innermost_result: Option<(&NameBinding<'_>, Flags)> = None;
 491         let mut determinacy = Determinacy::Determined;
 492
 493         // Go through all the scopes and try to resolve the name.
 494         let break_result = self.visit_scopes(scope_set, parent_scope, orig_ident,
 495                                              |this, scope, use_prelude, ident| {
 496             let ok = |res, span, arenas| Ok((
 497                 (res, ty::Visibility::Public, span, ExpnId::root()).to_name_binding(arenas),
 498                 Flags::empty(),
 499             ));
 500             let result = match scope {
 501                 Scope::DeriveHelpersCompat => {
 502                     let mut result = Err(Determinacy::Determined);
 503                     for derive in parent_scope.derives {
 504                         let parent_scope = &ParentScope { derives: &[], ..*parent_scope };
 505                         match this.resolve_macro_path(derive, Some(MacroKind::Derive),
 506                                                       parent_scope, true, force) {
 507                             Ok((Some(ext), _)) => if ext.helper_attrs.contains(&ident.name) {
 508                                 let res = Res::NonMacroAttr(NonMacroAttrKind::DeriveHelper);
 509                                 result = ok(res, derive.span, this.arenas);
 510                                 break;
 511                             }
 512                             Ok(_) | Err(Determinacy::Determined) => {}
 513                             Err(Determinacy::Undetermined) =>
 514                                 result = Err(Determinacy::Undetermined),
 515                         }
 516                     }
 517                     result
 518                 }
 519                 Scope::MacroRules(legacy_scope) => match legacy_scope {
 520                     LegacyScope::Binding(legacy_binding) if ident == legacy_binding.ident =>
 521                         Ok((legacy_binding.binding, Flags::MACRO_RULES)),
 522                     LegacyScope::Invocation(invoc_id)
 523                         if !this.output_legacy_scopes.contains_key(&invoc_id) =>
 524                             Err(Determinacy::Undetermined),
 525                     _ => Err(Determinacy::Determined),
 526                 }
 527                 Scope::CrateRoot => {
 528                     let root_ident = Ident::new(kw::PathRoot, ident.span);
 529                     let root_module = this.resolve_crate_root(root_ident);
 530                     let binding = this.resolve_ident_in_module_ext(
 531                         ModuleOrUniformRoot::Module(root_module),
 532                         ident,
 533                         ns,
 534                         parent_scope,
 535                         record_used,
 536                         path_span,
 537                     );
 538                     match binding {
 539                         Ok(binding) => Ok((binding, Flags::MODULE | Flags::MISC_SUGGEST_CRATE)),
 540                         Err((Determinacy::Undetermined, Weak::No)) =>
 541                             return Some(Err(Determinacy::determined(force))),
 542                         Err((Determinacy::Undetermined, Weak::Yes)) =>
 543                             Err(Determinacy::Undetermined),
 544                         Err((Determinacy::Determined, _)) => Err(Determinacy::Determined),
 545                     }
 546                 }
 547                 Scope::Module(module) => {
 548                     let adjusted_parent_scope = &ParentScope { module, ..*parent_scope };
 549                     let binding = this.resolve_ident_in_module_unadjusted_ext(
 550                         ModuleOrUniformRoot::Module(module),
 551                         ident,
 552                         ns,
 553                         adjusted_parent_scope,
 554                         true,
 555                         record_used,
 556                         path_span,
 557                     );
 558                     match binding {
 559                         Ok(binding) => {
 560                             let misc_flags = if ptr::eq(module, this.graph_root) {
 561                                 Flags::MISC_SUGGEST_CRATE
 562                             } else if module.is_normal() {
 563                                 Flags::MISC_SUGGEST_SELF
 564                             } else {
 565                                 Flags::empty()
 566                             };
 567                             Ok((binding, Flags::MODULE | misc_flags))
 568                         }
 569                         Err((Determinacy::Undetermined, Weak::No)) =>
 570                             return Some(Err(Determinacy::determined(force))),
 571                         Err((Determinacy::Undetermined, Weak::Yes)) =>
 572                             Err(Determinacy::Undetermined),
 573                         Err((Determinacy::Determined, _)) => Err(Determinacy::Determined),
 574                     }
 575                 }
 576                 Scope::RegisteredAttrs => match this.registered_attrs.get(&ident).cloned() {
 577                     Some(ident) => ok(
 578                         Res::NonMacroAttr(NonMacroAttrKind::Registered), ident.span, this.arenas
 579                     ),
 580                     None => Err(Determinacy::Determined)
 581                 }
 582                 Scope::MacroUsePrelude => match this.macro_use_prelude.get(&ident.name).cloned() {
 583                     Some(binding) => Ok((binding, Flags::MISC_FROM_PRELUDE)),
 584                     None => Err(Determinacy::determined(
 585                         this.graph_root.unexpanded_invocations.borrow().is_empty()
 586                     ))
 587                 }
 588                 Scope::BuiltinAttrs => if is_builtin_attr_name(ident.name) {
 589                     ok(Res::NonMacroAttr(NonMacroAttrKind::Builtin), DUMMY_SP, this.arenas)
 590                 } else {
 591                     Err(Determinacy::Determined)
 592                 }
 593                 Scope::LegacyPluginHelpers => if this.session.plugin_attributes.borrow().iter()
 594                                                      .any(|(name, _)| ident.name == *name) {
 595                     let res = Res::NonMacroAttr(NonMacroAttrKind::LegacyPluginHelper);
 596                     ok(res, DUMMY_SP, this.arenas)
 597                 } else {
 598                     Err(Determinacy::Determined)
 599                 }
 600                 Scope::ExternPrelude => match this.extern_prelude_get(ident, !record_used) {
 601                     Some(binding) => Ok((binding, Flags::empty())),
 602                     None => Err(Determinacy::determined(
 603                         this.graph_root.unexpanded_invocations.borrow().is_empty()
 604                     )),
 605                 }
 606                 Scope::ToolPrelude => match this.registered_tools.get(&ident).cloned() {
 607                     Some(ident) => ok(Res::ToolMod, ident.span, this.arenas),
 608                     None => Err(Determinacy::Determined)
 609                 }
 610                 Scope::StdLibPrelude => {
 611                     let mut result = Err(Determinacy::Determined);
 612                     if let Some(prelude) = this.prelude {
 613                         if let Ok(binding) = this.resolve_ident_in_module_unadjusted(
 614                             ModuleOrUniformRoot::Module(prelude),
 615                             ident,
 616                             ns,
 617                             parent_scope,
 618                             false,
 619                             path_span,
 620                         ) {
 621                             if use_prelude || this.is_builtin_macro(binding.res()) {
 622                                 result = Ok((binding, Flags::MISC_FROM_PRELUDE));
 623                             }
 624                         }
 625                     }
 626                     result
 627                 }
 628                 Scope::BuiltinTypes => match this.primitive_type_table.primitive_types
 629                                                  .get(&ident.name).cloned() {
 630                     Some(prim_ty) => ok(Res::PrimTy(prim_ty), DUMMY_SP, this.arenas),
 631                     None => Err(Determinacy::Determined)
 632                 }
 633             };
 634
 635             match result {
 636                 Ok((binding, flags)) if sub_namespace_match(binding.macro_kind(), macro_kind) => {
 637                     if !record_used {
 638                         return Some(Ok(binding));
 639                     }
 640
 641                     if let Some((innermost_binding, innermost_flags)) = innermost_result {
 642                         // Found another solution, if the first one was "weak", report an error.
 643                         let (res, innermost_res) = (binding.res(), innermost_binding.res());
 644                         if res != innermost_res {
 645                             let builtin = Res::NonMacroAttr(NonMacroAttrKind::Builtin);
 646                             let derive_helper = Res::NonMacroAttr(NonMacroAttrKind::DeriveHelper);
 647
 648                             let ambiguity_error_kind = if is_import {
 649                                 Some(AmbiguityKind::Import)
 650                             } else if innermost_res == builtin || res == builtin {
 651                                 Some(AmbiguityKind::BuiltinAttr)
 652                             } else if innermost_res == derive_helper || res == derive_helper {
 653                                 Some(AmbiguityKind::DeriveHelper)
 654                             } else if innermost_flags.contains(Flags::MACRO_RULES) &&
 655                                       flags.contains(Flags::MODULE) &&
 656                                       !this.disambiguate_legacy_vs_modern(innermost_binding,
 657                                                                           binding) ||
 658                                       flags.contains(Flags::MACRO_RULES) &&
 659                                       innermost_flags.contains(Flags::MODULE) &&
 660                                       !this.disambiguate_legacy_vs_modern(binding,
 661                                                                           innermost_binding) {
 662                                 Some(AmbiguityKind::LegacyVsModern)
 663                             } else if innermost_binding.is_glob_import() {
 664                                 Some(AmbiguityKind::GlobVsOuter)
 665                             } else if innermost_binding.may_appear_after(parent_scope.expansion,
 666                                                                          binding) {
 667                                 Some(AmbiguityKind::MoreExpandedVsOuter)
 668                             } else {
 669                                 None
 670                             };
 671                             if let Some(kind) = ambiguity_error_kind {
 672                                 let misc = |f: Flags| if f.contains(Flags::MISC_SUGGEST_CRATE) {
 673                                     AmbiguityErrorMisc::SuggestCrate
 674                                 } else if f.contains(Flags::MISC_SUGGEST_SELF) {
 675                                     AmbiguityErrorMisc::SuggestSelf
 676                                 } else if f.contains(Flags::MISC_FROM_PRELUDE) {
 677                                     AmbiguityErrorMisc::FromPrelude
 678                                 } else {
 679                                     AmbiguityErrorMisc::None
 680                                 };
 681                                 this.ambiguity_errors.push(AmbiguityError {
 682                                     kind,
 683                                     ident: orig_ident,
 684                                     b1: innermost_binding,
 685                                     b2: binding,
 686                                     misc1: misc(innermost_flags),
 687                                     misc2: misc(flags),
 688                                 });
 689                                 return Some(Ok(innermost_binding));
 690                             }
 691                         }
 692                     } else {
 693                         // Found the first solution.
 694                         innermost_result = Some((binding, flags));
 695                     }
 696                 }
 697                 Ok(..) | Err(Determinacy::Determined) => {}
 698                 Err(Determinacy::Undetermined) => determinacy = Determinacy::Undetermined
 699             }
 700
 701             None
 702         });
 703
 704         if let Some(break_result) = break_result {
 705             return break_result;
 706         }
 707
 708         // The first found solution was the only one, return it.
 709         if let Some((binding, _)) = innermost_result {
 710             return Ok(binding);
 711         }
 712
 713         Err(Determinacy::determined(determinacy == Determinacy::Determined || force))
 714     }
 715
 716     crate fn finalize_macro_resolutions(&mut self) {
 717         let check_consistency = |this: &mut Self, path: &[Segment], span, kind: MacroKind,
 718                                  initial_res: Option<Res>, res: Res| {
 719             if let Some(initial_res) = initial_res {
 720                 if res != initial_res && res != Res::Err && this.ambiguity_errors.is_empty() {
 721                     // Make sure compilation does not succeed if preferred macro resolution
 722                     // has changed after the macro had been expanded. In theory all such
 723                     // situations should be reported as ambiguity errors, so this is a bug.
 724                     span_bug!(span, "inconsistent resolution for a macro");
 725                 }
 726             } else {
 727                 // It's possible that the macro was unresolved (indeterminate) and silently
 728                 // expanded into a dummy fragment for recovery during expansion.
 729                 // Now, post-expansion, the resolution may succeed, but we can't change the
 730                 // past and need to report an error.
 731                 // However, non-speculative `resolve_path` can successfully return private items
 732                 // even if speculative `resolve_path` returned nothing previously, so we skip this
 733                 // less informative error if the privacy error is reported elsewhere.
 734                 if this.privacy_errors.is_empty() {
 735                     let msg = format!("cannot determine resolution for the {} `{}`",
 736                                         kind.descr(), Segment::names_to_string(path));
 737                     let msg_note = "import resolution is stuck, try simplifying macro imports";
 738                     this.session.struct_span_err(span, &msg).note(msg_note).emit();
 739                 }
 740             }
 741         };
 742
 743         let macro_resolutions = mem::take(&mut self.multi_segment_macro_resolutions);
 744         for (mut path, path_span, kind, parent_scope, initial_res) in macro_resolutions {
 745             // FIXME: Path resolution will ICE if segment IDs present.
 746             for seg in &mut path { seg.id = None; }
 747             match self.resolve_path(
 748                 &path, Some(MacroNS), &parent_scope, true, path_span, CrateLint::No
 749             ) {
 750                 PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 => {
 751                     let res = path_res.base_res();
 752                     check_consistency(self, &path, path_span, kind, initial_res, res);
 753                 }
 754                 path_res @ PathResult::NonModule(..) | path_res @ PathResult::Failed { .. } => {
 755                     let (span, label) = if let PathResult::Failed { span, label, .. } = path_res {
 756                         (span, label)
 757                     } else {
 758                         (path_span, format!("partially resolved path in {} {}",
 759                                             kind.article(), kind.descr()))
 760                     };
 761                     self.report_error(span, ResolutionError::FailedToResolve {
 762                         label,
 763                         suggestion: None
 764                     });
 765                 }
 766                 PathResult::Module(..) | PathResult::Indeterminate => unreachable!(),
 767             }
 768         }
 769
 770         let macro_resolutions = mem::take(&mut self.single_segment_macro_resolutions);
 771         for (ident, kind, parent_scope, initial_binding) in macro_resolutions {
 772             match self.early_resolve_ident_in_lexical_scope(ident, ScopeSet::Macro(kind),
 773                                                             &parent_scope, true, true, ident.span) {
 774                 Ok(binding) => {
 775                     let initial_res = initial_binding.map(|initial_binding| {
 776                         self.record_use(ident, MacroNS, initial_binding, false);
 777                         initial_binding.res()
 778                     });
 779                     let res = binding.res();
 780                     let seg = Segment::from_ident(ident);
 781                     check_consistency(self, &[seg], ident.span, kind, initial_res, res);
 782                 }
 783                 Err(..) => {
 784                     let expected = kind.descr_expected();
 785                     let msg = format!("cannot find {} `{}` in this scope", expected, ident);
 786                     let mut err = self.session.struct_span_err(ident.span, &msg);
 787                     self.unresolved_macro_suggestions(&mut err, kind, &parent_scope, ident);
 788                     err.emit();
 789                 }
 790             }
 791         }
 792
 793         let builtin_attrs = mem::take(&mut self.builtin_attrs);
 794         for (ident, parent_scope) in builtin_attrs {
 795             let _ = self.early_resolve_ident_in_lexical_scope(
 796                 ident, ScopeSet::Macro(MacroKind::Attr), &parent_scope, true, true, ident.span
 797             );
 798         }
 799     }
 800
 801     fn check_stability_and_deprecation(&mut self, ext: &SyntaxExtension, path: &ast::Path) {
 802         let span = path.span;
 803         if let Some(stability) = &ext.stability {
 804             if let StabilityLevel::Unstable { reason, issue, is_soft } = stability.level {
 805                 let feature = stability.feature;
 806                 if !self.active_features.contains(&feature) && !span.allows_unstable(feature) {
 807                     let node_id = ast::CRATE_NODE_ID;
 808                     let lint_buffer = &mut self.lint_buffer;
 809                     let soft_handler = |lint, span, msg: &_| {
 810                         lint_buffer.buffer_lint(lint, node_id, span, msg)
 811                     };
 812                     stability::report_unstable(
 813                         self.session, feature, reason, issue, is_soft, span, soft_handler
 814                     );
 815                 }
 816             }
 817             if let Some(depr) = &stability.rustc_depr {
 818                 let path = pprust::path_to_string(path);
 819                 let (message, lint) = stability::rustc_deprecation_message(depr, &path);
 820                 stability::early_report_deprecation(
 821                     &mut self.lint_buffer, &message, depr.suggestion, lint, span
 822                 );
 823             }
 824         }
 825         if let Some(depr) = &ext.deprecation {
 826             let path = pprust::path_to_string(&path);
 827             let (message, lint) = stability::deprecation_message(depr, &path);
 828             stability::early_report_deprecation(&mut self.lint_buffer, &message, None, lint, span);
 829         }
 830     }
 831
 832     fn prohibit_imported_non_macro_attrs(&self, binding: Option<&'a NameBinding<'a>>,
 833                                          res: Option<Res>, span: Span) {
 834         if let Some(Res::NonMacroAttr(kind)) = res {
 835             if kind != NonMacroAttrKind::Tool && binding.map_or(true, |b| b.is_import()) {
 836                 let msg =
 837                     format!("cannot use {} {} through an import", kind.article(), kind.descr());
 838                 let mut err = self.session.struct_span_err(span, &msg);
 839                 if let Some(binding) = binding {
 840                     err.span_note(binding.span, &format!("the {} imported here", kind.descr()));
 841                 }
 842                 err.emit();
 843             }
 844         }
 845     }
 846
 847     crate fn check_reserved_macro_name(&mut self, ident: Ident, res: Res) {
 848         // Reserve some names that are not quite covered by the general check
 849         // performed on `Resolver::builtin_attrs`.
 850         if ident.name == sym::cfg || ident.name == sym::cfg_attr || ident.name == sym::derive {
 851             let macro_kind = self.get_macro(res).map(|ext| ext.macro_kind());
 852             if macro_kind.is_some() && sub_namespace_match(macro_kind, Some(MacroKind::Attr)) {
 853                 self.session.span_err(
 854                     ident.span, &format!("name `{}` is reserved in attribute namespace", ident)
 855                 );
 856             }
 857         }
 858     }
 859
 860     /// Compile the macro into a `SyntaxExtension` and possibly replace it with a pre-defined
 861     /// extension partially or entirely for built-in macros and legacy plugin macros.
 862     crate fn compile_macro(&mut self, item: &ast::Item, edition: Edition) -> SyntaxExtension {
 863         let mut result = compile_declarative_macro(
 864             &self.session.parse_sess, self.session.features_untracked(), item, edition
 865         );
 866
 867         if result.is_builtin {
 868             // The macro was marked with `#[rustc_builtin_macro]`.
 869             if let Some(ext) = self.builtin_macros.remove(&item.ident.name) {
 870                 if ext.is_builtin {
 871                     // The macro is a built-in, replace only the expander function.
 872                     result.kind = ext.kind;
 873                 } else {
 874                     // The macro is from a plugin, the in-source definition is dummy,
 875                     // take all the data from the resolver.
 876                     result = ext;
 877                 }
 878             } else {
 879                 let msg = format!("cannot find a built-in macro with name `{}`", item.ident);
 880                 self.session.span_err(item.span, &msg);
 881             }
 882         }
 883
 884         result
 885     }
 886 }