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::imports::ImportResolver;
   5 use crate::Namespace::*;
   6 use crate::{AmbiguityError, AmbiguityErrorMisc, AmbiguityKind, Determinacy};
   7 use crate::{CrateLint, ParentScope, ResolutionError, Resolver, Scope, ScopeSet, Weak};
   8 use crate::{ModuleKind, ModuleOrUniformRoot, NameBinding, PathResult, Segment, ToNameBinding};
   9 use rustc::middle::stability;
  10 use rustc::{span_bug, ty};
  11 use rustc_ast::ast::{self, Ident, NodeId};
  12 use rustc_ast_pretty::pprust;
  13 use rustc_attr::{self as attr, StabilityLevel};
  14 use rustc_data_structures::fx::FxHashSet;
  15 use rustc_expand::base::SyntaxExtension;
  16 use rustc_expand::base::{self, Indeterminate, InvocationRes};
  17 use rustc_expand::compile_declarative_macro;
  18 use rustc_expand::expand::{AstFragment, AstFragmentKind, Invocation, InvocationKind};
  19 use rustc_feature::is_builtin_attr_name;
  20 use rustc_hir::def::{self, DefKind, NonMacroAttrKind};
  21 use rustc_hir::def_id;
  22 use rustc_session::lint::builtin::UNUSED_MACROS;
  23 use rustc_session::parse::feature_err;
  24 use rustc_session::Session;
  25 use rustc_span::edition::Edition;
  26 use rustc_span::hygiene::{self, ExpnData, ExpnId, ExpnKind};
  27 use rustc_span::symbol::{kw, sym, Symbol};
  28 use rustc_span::{Span, DUMMY_SP};
  29
  30 use rustc_data_structures::sync::Lrc;
  31 use rustc_span::hygiene::{AstPass, MacroKind};
  32 use std::{mem, ptr};
  33
  34 type Res = def::Res<NodeId>;
  35
  36 /// Binding produced by a `macro_rules` item.
  37 /// Not modularized, can shadow previous legacy bindings, etc.
  38 #[derive(Debug)]
  39 pub struct LegacyBinding<'a> {
  40     crate binding: &'a NameBinding<'a>,
  41     /// Legacy scope into which the `macro_rules` item was planted.
  42     crate parent_legacy_scope: LegacyScope<'a>,
  43     crate ident: Ident,
  44 }
  45
  46 /// The scope introduced by a `macro_rules!` macro.
  47 /// This starts at the macro's definition and ends at the end of the macro's parent
  48 /// module (named or unnamed), or even further if it escapes with `#[macro_use]`.
  49 /// Some macro invocations need to introduce legacy scopes too because they
  50 /// can potentially expand into macro definitions.
  51 #[derive(Copy, Clone, Debug)]
  52 pub enum LegacyScope<'a> {
  53     /// Empty "root" scope at the crate start containing no names.
  54     Empty,
  55     /// The scope introduced by a `macro_rules!` macro definition.
  56     Binding(&'a LegacyBinding<'a>),
  57     /// The scope introduced by a macro invocation that can potentially
  58     /// create a `macro_rules!` macro definition.
  59     Invocation(ExpnId),
  60 }
  61
  62 // Macro namespace is separated into two sub-namespaces, one for bang macros and
  63 // one for attribute-like macros (attributes, derives).
  64 // We ignore resolutions from one sub-namespace when searching names in scope for another.
  65 fn sub_namespace_match(candidate: Option<MacroKind>, requirement: Option<MacroKind>) -> bool {
  66     #[derive(PartialEq)]
  67     enum SubNS {
  68         Bang,
  69         AttrLike,
  70     }
  71     let sub_ns = |kind| match kind {
  72         MacroKind::Bang => SubNS::Bang,
  73         MacroKind::Attr | MacroKind::Derive => SubNS::AttrLike,
  74     };
  75     let candidate = candidate.map(sub_ns);
  76     let requirement = requirement.map(sub_ns);
  77     // "No specific sub-namespace" means "matches anything" for both requirements and candidates.
  78     candidate.is_none() || requirement.is_none() || candidate == requirement
  79 }
  80
  81 // We don't want to format a path using pretty-printing,
  82 // `format!("{}", path)`, because that tries to insert
  83 // line-breaks and is slow.
  84 fn fast_print_path(path: &ast::Path) -> Symbol {
  85     if path.segments.len() == 1 {
  86         return path.segments[0].ident.name;
  87     } else {
  88         let mut path_str = String::with_capacity(64);
  89         for (i, segment) in path.segments.iter().enumerate() {
  90             if i != 0 {
  91                 path_str.push_str("::");
  92             }
  93             if segment.ident.name != kw::PathRoot {
  94                 path_str.push_str(&segment.ident.as_str())
  95             }
  96         }
  97         Symbol::intern(&path_str)
  98     }
  99 }
 100
 101 /// The code common between processing `#![register_tool]` and `#![register_attr]`.
 102 fn registered_idents(
 103     sess: &Session,
 104     attrs: &[ast::Attribute],
 105     attr_name: Symbol,
 106     descr: &str,
 107 ) -> FxHashSet<Ident> {
 108     let mut registered = FxHashSet::default();
 109     for attr in attr::filter_by_name(attrs, attr_name) {
 110         for nested_meta in attr.meta_item_list().unwrap_or_default() {
 111             match nested_meta.ident() {
 112                 Some(ident) => {
 113                     if let Some(old_ident) = registered.replace(ident) {
 114                         let msg = format!("{} `{}` was already registered", descr, ident);
 115                         sess.struct_span_err(ident.span, &msg)
 116                             .span_label(old_ident.span, "already registered here")
 117                             .emit();
 118                     }
 119                 }
 120                 None => {
 121                     let msg = format!("`{}` only accepts identifiers", attr_name);
 122                     let span = nested_meta.span();
 123                     sess.struct_span_err(span, &msg).span_label(span, "not an identifier").emit();
 124                 }
 125             }
 126         }
 127     }
 128     registered
 129 }
 130
 131 crate fn registered_attrs_and_tools(
 132     sess: &Session,
 133     attrs: &[ast::Attribute],
 134 ) -> (FxHashSet<Ident>, FxHashSet<Ident>) {
 135     let registered_attrs = registered_idents(sess, attrs, sym::register_attr, "attribute");
 136     let mut registered_tools = registered_idents(sess, attrs, sym::register_tool, "tool");
 137     // We implicitly add `rustfmt` and `clippy` to known tools,
 138     // but it's not an error to register them explicitly.
 139     let predefined_tools = [sym::clippy, sym::rustfmt];
 140     registered_tools.extend(predefined_tools.iter().cloned().map(Ident::with_dummy_span));
 141     (registered_attrs, registered_tools)
 142 }
 143
 144 impl<'a> base::Resolver for Resolver<'a> {
 145     fn next_node_id(&mut self) -> NodeId {
 146         self.next_node_id()
 147     }
 148
 149     fn resolve_dollar_crates(&mut self) {
 150         hygiene::update_dollar_crate_names(|ctxt| {
 151             let ident = Ident::new(kw::DollarCrate, DUMMY_SP.with_ctxt(ctxt));
 152             match self.resolve_crate_root(ident).kind {
 153                 ModuleKind::Def(.., name) if name != kw::Invalid => name,
 154                 _ => kw::Crate,
 155             }
 156         });
 157     }
 158
 159     fn visit_ast_fragment_with_placeholders(&mut self, expansion: ExpnId, fragment: &AstFragment) {
 160         // Integrate the new AST fragment into all the definition and module structures.
 161         // We are inside the `expansion` now, but other parent scope components are still the same.
 162         let parent_scope = ParentScope { expansion, ..self.invocation_parent_scopes[&expansion] };
 163         let output_legacy_scope = self.build_reduced_graph(fragment, parent_scope);
 164         self.output_legacy_scopes.insert(expansion, output_legacy_scope);
 165
 166         parent_scope.module.unexpanded_invocations.borrow_mut().remove(&expansion);
 167     }
 168
 169     fn register_builtin_macro(&mut self, ident: ast::Ident, ext: SyntaxExtension) {
 170         if self.builtin_macros.insert(ident.name, ext).is_some() {
 171             self.session
 172                 .span_err(ident.span, &format!("built-in macro `{}` was already defined", ident));
 173         }
 174     }
 175
 176     // Create a new Expansion with a definition site of the provided module, or
 177     // a fake empty `#[no_implicit_prelude]` module if no module is provided.
 178     fn expansion_for_ast_pass(
 179         &mut self,
 180         call_site: Span,
 181         pass: AstPass,
 182         features: &[Symbol],
 183         parent_module_id: Option<NodeId>,
 184     ) -> ExpnId {
 185         let expn_id = ExpnId::fresh(Some(ExpnData::allow_unstable(
 186             ExpnKind::AstPass(pass),
 187             call_site,
 188             self.session.edition(),
 189             features.into(),
 190         )));
 191
 192         let parent_scope = if let Some(module_id) = parent_module_id {
 193             let parent_def_id = self.definitions.local_def_id(module_id);
 194             self.definitions.add_parent_module_of_macro_def(expn_id, parent_def_id);
 195             self.module_map[&parent_def_id]
 196         } else {
 197             self.definitions.add_parent_module_of_macro_def(
 198                 expn_id,
 199                 def_id::DefId::local(def_id::CRATE_DEF_INDEX),
 200             );
 201             self.empty_module
 202         };
 203         self.ast_transform_scopes.insert(expn_id, parent_scope);
 204         expn_id
 205     }
 206
 207     fn resolve_imports(&mut self) {
 208         ImportResolver { r: self }.resolve_imports()
 209     }
 210
 211     fn resolve_macro_invocation(
 212         &mut self,
 213         invoc: &Invocation,
 214         eager_expansion_root: ExpnId,
 215         force: bool,
 216     ) -> Result<InvocationRes, Indeterminate> {
 217         let invoc_id = invoc.expansion_data.id;
 218         let parent_scope = match self.invocation_parent_scopes.get(&invoc_id) {
 219             Some(parent_scope) => *parent_scope,
 220             None => {
 221                 // If there's no entry in the table, then we are resolving an eagerly expanded
 222                 // macro, which should inherit its parent scope from its eager expansion root -
 223                 // the macro that requested this eager expansion.
 224                 let parent_scope = *self
 225                     .invocation_parent_scopes
 226                     .get(&eager_expansion_root)
 227                     .expect("non-eager expansion without a parent scope");
 228                 self.invocation_parent_scopes.insert(invoc_id, parent_scope);
 229                 parent_scope
 230             }
 231         };
 232
 233         let (path, kind, derives, after_derive) = match invoc.kind {
 234             InvocationKind::Attr { ref attr, ref derives, after_derive, .. } => (
 235                 &attr.get_normal_item().path,
 236                 MacroKind::Attr,
 237                 self.arenas.alloc_ast_paths(derives),
 238                 after_derive,
 239             ),
 240             InvocationKind::Bang { ref mac, .. } => (&mac.path, MacroKind::Bang, &[][..], false),
 241             InvocationKind::Derive { ref path, .. } => (path, MacroKind::Derive, &[][..], false),
 242             InvocationKind::DeriveContainer { ref derives, .. } => {
 243                 // Block expansion of the container until we resolve all derives in it.
 244                 // This is required for two reasons:
 245                 // - Derive helper attributes are in scope for the item to which the `#[derive]`
 246                 //   is applied, so they have to be produced by the container's expansion rather
 247                 //   than by individual derives.
 248                 // - Derives in the container need to know whether one of them is a built-in `Copy`.
 249                 // FIXME: Try to avoid repeated resolutions for derives here and in expansion.
 250                 let mut exts = Vec::new();
 251                 let mut helper_attrs = Vec::new();
 252                 for path in derives {
 253                     exts.push(
 254                         match self.resolve_macro_path(
 255                             path,
 256                             Some(MacroKind::Derive),
 257                             &parent_scope,
 258                             true,
 259                             force,
 260                         ) {
 261                             Ok((Some(ext), _)) => {
 262                                 let span = path.segments.last().unwrap().ident.span.modern();
 263                                 helper_attrs.extend(
 264                                     ext.helper_attrs.iter().map(|name| Ident::new(*name, span)),
 265                                 );
 266                                 if ext.is_derive_copy {
 267                                     self.add_derive_copy(invoc_id);
 268                                 }
 269                                 ext
 270                             }
 271                             Ok(_) | Err(Determinacy::Determined) => {
 272                                 self.dummy_ext(MacroKind::Derive)
 273                             }
 274                             Err(Determinacy::Undetermined) => return Err(Indeterminate),
 275                         },
 276                     )
 277                 }
 278                 self.helper_attrs.insert(invoc_id, helper_attrs);
 279                 return Ok(InvocationRes::DeriveContainer(exts));
 280             }
 281         };
 282
 283         // Derives are not included when `invocations` are collected, so we have to add them here.
 284         let parent_scope = &ParentScope { derives, ..parent_scope };
 285         let (ext, res) = self.smart_resolve_macro_path(path, kind, parent_scope, force)?;
 286
 287         let span = invoc.span();
 288         invoc_id.set_expn_data(ext.expn_data(parent_scope.expansion, span, fast_print_path(path)));
 289
 290         if let Res::Def(_, def_id) = res {
 291             if after_derive {
 292                 self.session.span_err(span, "macro attributes must be placed before `#[derive]`");
 293             }
 294             self.macro_defs.insert(invoc_id, def_id);
 295             let normal_module_def_id = self.macro_def_scope(invoc_id).normal_ancestor_id;
 296             self.definitions.add_parent_module_of_macro_def(invoc_id, normal_module_def_id);
 297         }
 298
 299         match invoc.fragment_kind {
 300             AstFragmentKind::Arms
 301             | AstFragmentKind::Fields
 302             | AstFragmentKind::FieldPats
 303             | AstFragmentKind::GenericParams
 304             | AstFragmentKind::Params
 305             | AstFragmentKind::StructFields
 306             | AstFragmentKind::Variants => {
 307                 if let Res::Def(..) = res {
 308                     self.session.span_err(
 309                         span,
 310                         &format!(
 311                             "expected an inert attribute, found {} {}",
 312                             res.article(),
 313                             res.descr()
 314                         ),
 315                     );
 316                     return Ok(InvocationRes::Single(self.dummy_ext(kind)));
 317                 }
 318             }
 319             _ => {}
 320         }
 321
 322         Ok(InvocationRes::Single(ext))
 323     }
 324
 325     fn check_unused_macros(&mut self) {
 326         for (&node_id, &span) in self.unused_macros.iter() {
 327             self.lint_buffer.buffer_lint(UNUSED_MACROS, node_id, span, "unused macro definition");
 328         }
 329     }
 330
 331     fn has_derive_copy(&self, expn_id: ExpnId) -> bool {
 332         self.containers_deriving_copy.contains(&expn_id)
 333     }
 334
 335     fn add_derive_copy(&mut self, expn_id: ExpnId) {
 336         self.containers_deriving_copy.insert(expn_id);
 337     }
 338 }
 339
 340 impl<'a> Resolver<'a> {
 341     /// Resolve macro path with error reporting and recovery.
 342     fn smart_resolve_macro_path(
 343         &mut self,
 344         path: &ast::Path,
 345         kind: MacroKind,
 346         parent_scope: &ParentScope<'a>,
 347         force: bool,
 348     ) -> Result<(Lrc<SyntaxExtension>, Res), Indeterminate> {
 349         let (ext, res) = match self.resolve_macro_path(path, Some(kind), parent_scope, true, force)
 350         {
 351             Ok((Some(ext), res)) => (ext, res),
 352             // Use dummy syntax extensions for unresolved macros for better recovery.
 353             Ok((None, res)) => (self.dummy_ext(kind), res),
 354             Err(Determinacy::Determined) => (self.dummy_ext(kind), Res::Err),
 355             Err(Determinacy::Undetermined) => return Err(Indeterminate),
 356         };
 357
 358         // Report errors and enforce feature gates for the resolved macro.
 359         let features = self.session.features_untracked();
 360         for segment in &path.segments {
 361             if let Some(args) = &segment.args {
 362                 self.session.span_err(args.span(), "generic arguments in macro path");
 363             }
 364             if kind == MacroKind::Attr
 365                 && !features.rustc_attrs
 366                 && segment.ident.as_str().starts_with("rustc")
 367             {
 368                 let msg =
 369                     "attributes starting with `rustc` are reserved for use by the `rustc` compiler";
 370                 feature_err(&self.session.parse_sess, sym::rustc_attrs, segment.ident.span, msg)
 371                     .emit();
 372             }
 373         }
 374
 375         match res {
 376             Res::Def(DefKind::Macro(_), def_id) => {
 377                 if let Some(node_id) = self.definitions.as_local_node_id(def_id) {
 378                     self.unused_macros.remove(&node_id);
 379                     if self.proc_macro_stubs.contains(&node_id) {
 380                         self.session.span_err(
 381                             path.span,
 382                             "can't use a procedural macro from the same crate that defines it",
 383                         );
 384                     }
 385                 }
 386             }
 387             Res::NonMacroAttr(..) | Res::Err => {}
 388             _ => panic!("expected `DefKind::Macro` or `Res::NonMacroAttr`"),
 389         };
 390
 391         self.check_stability_and_deprecation(&ext, path);
 392
 393         Ok(if ext.macro_kind() != kind {
 394             let expected = kind.descr_expected();
 395             let path_str = pprust::path_to_string(path);
 396             let msg = format!("expected {}, found {} `{}`", expected, res.descr(), path_str);
 397             self.session
 398                 .struct_span_err(path.span, &msg)
 399                 .span_label(path.span, format!("not {} {}", kind.article(), expected))
 400                 .emit();
 401             // Use dummy syntax extensions for unexpected macro kinds for better recovery.
 402             (self.dummy_ext(kind), Res::Err)
 403         } else {
 404             (ext, res)
 405         })
 406     }
 407
 408     pub fn resolve_macro_path(
 409         &mut self,
 410         path: &ast::Path,
 411         kind: Option<MacroKind>,
 412         parent_scope: &ParentScope<'a>,
 413         trace: bool,
 414         force: bool,
 415     ) -> Result<(Option<Lrc<SyntaxExtension>>, Res), Determinacy> {
 416         let path_span = path.span;
 417         let mut path = Segment::from_path(path);
 418
 419         // Possibly apply the macro helper hack
 420         if kind == Some(MacroKind::Bang)
 421             && path.len() == 1
 422             && path[0].ident.span.ctxt().outer_expn_data().local_inner_macros
 423         {
 424             let root = Ident::new(kw::DollarCrate, path[0].ident.span);
 425             path.insert(0, Segment::from_ident(root));
 426         }
 427
 428         let res = if path.len() > 1 {
 429             let res = match self.resolve_path(
 430                 &path,
 431                 Some(MacroNS),
 432                 parent_scope,
 433                 false,
 434                 path_span,
 435                 CrateLint::No,
 436             ) {
 437                 PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 => {
 438                     Ok(path_res.base_res())
 439                 }
 440                 PathResult::Indeterminate if !force => return Err(Determinacy::Undetermined),
 441                 PathResult::NonModule(..)
 442                 | PathResult::Indeterminate
 443                 | PathResult::Failed { .. } => Err(Determinacy::Determined),
 444                 PathResult::Module(..) => unreachable!(),
 445             };
 446
 447             if trace {
 448                 let kind = kind.expect("macro kind must be specified if tracing is enabled");
 449                 self.multi_segment_macro_resolutions.push((
 450                     path,
 451                     path_span,
 452                     kind,
 453                     *parent_scope,
 454                     res.ok(),
 455                 ));
 456             }
 457
 458             self.prohibit_imported_non_macro_attrs(None, res.ok(), path_span);
 459             res
 460         } else {
 461             let scope_set = kind.map_or(ScopeSet::All(MacroNS, false), ScopeSet::Macro);
 462             let binding = self.early_resolve_ident_in_lexical_scope(
 463                 path[0].ident,
 464                 scope_set,
 465                 parent_scope,
 466                 false,
 467                 force,
 468                 path_span,
 469             );
 470             if let Err(Determinacy::Undetermined) = binding {
 471                 return Err(Determinacy::Undetermined);
 472             }
 473
 474             if trace {
 475                 let kind = kind.expect("macro kind must be specified if tracing is enabled");
 476                 self.single_segment_macro_resolutions.push((
 477                     path[0].ident,
 478                     kind,
 479                     *parent_scope,
 480                     binding.ok(),
 481                 ));
 482             }
 483
 484             let res = binding.map(|binding| binding.res());
 485             self.prohibit_imported_non_macro_attrs(binding.ok(), res.ok(), path_span);
 486             res
 487         };
 488
 489         res.map(|res| (self.get_macro(res), res))
 490     }
 491
 492     // Resolve an identifier in lexical scope.
 493     // This is a variation of `fn resolve_ident_in_lexical_scope` that can be run during
 494     // expansion and import resolution (perhaps they can be merged in the future).
 495     // The function is used for resolving initial segments of macro paths (e.g., `foo` in
 496     // `foo::bar!(); or `foo!();`) and also for import paths on 2018 edition.
 497     crate fn early_resolve_ident_in_lexical_scope(
 498         &mut self,
 499         orig_ident: Ident,
 500         scope_set: ScopeSet,
 501         parent_scope: &ParentScope<'a>,
 502         record_used: bool,
 503         force: bool,
 504         path_span: Span,
 505     ) -> Result<&'a NameBinding<'a>, Determinacy> {
 506         bitflags::bitflags! {
 507             struct Flags: u8 {
 508                 const MACRO_RULES          = 1 << 0;
 509                 const MODULE               = 1 << 1;
 510                 const DERIVE_HELPER_COMPAT = 1 << 2;
 511                 const MISC_SUGGEST_CRATE   = 1 << 3;
 512                 const MISC_SUGGEST_SELF    = 1 << 4;
 513                 const MISC_FROM_PRELUDE    = 1 << 5;
 514             }
 515         }
 516
 517         assert!(force || !record_used); // `record_used` implies `force`
 518
 519         // Make sure `self`, `super` etc produce an error when passed to here.
 520         if orig_ident.is_path_segment_keyword() {
 521             return Err(Determinacy::Determined);
 522         }
 523
 524         let (ns, macro_kind, is_import) = match scope_set {
 525             ScopeSet::All(ns, is_import) => (ns, None, is_import),
 526             ScopeSet::AbsolutePath(ns) => (ns, None, false),
 527             ScopeSet::Macro(macro_kind) => (MacroNS, Some(macro_kind), false),
 528         };
 529
 530         // This is *the* result, resolution from the scope closest to the resolved identifier.
 531         // However, sometimes this result is "weak" because it comes from a glob import or
 532         // a macro expansion, and in this case it cannot shadow names from outer scopes, e.g.
 533         // mod m { ... } // solution in outer scope
 534         // {
 535         //     use prefix::*; // imports another `m` - innermost solution
 536         //                    // weak, cannot shadow the outer `m`, need to report ambiguity error
 537         //     m::mac!();
 538         // }
 539         // So we have to save the innermost solution and continue searching in outer scopes
 540         // to detect potential ambiguities.
 541         let mut innermost_result: Option<(&NameBinding<'_>, Flags)> = None;
 542         let mut determinacy = Determinacy::Determined;
 543
 544         // Go through all the scopes and try to resolve the name.
 545         let break_result = self.visit_scopes(
 546             scope_set,
 547             parent_scope,
 548             orig_ident,
 549             |this, scope, use_prelude, ident| {
 550                 let ok = |res, span, arenas| {
 551                     Ok((
 552                         (res, ty::Visibility::Public, span, ExpnId::root()).to_name_binding(arenas),
 553                         Flags::empty(),
 554                     ))
 555                 };
 556                 let result = match scope {
 557                     Scope::DeriveHelpers(expn_id) => {
 558                         if let Some(attr) = this
 559                             .helper_attrs
 560                             .get(&expn_id)
 561                             .and_then(|attrs| attrs.iter().rfind(|i| ident == **i))
 562                         {
 563                             let binding = (
 564                                 Res::NonMacroAttr(NonMacroAttrKind::DeriveHelper),
 565                                 ty::Visibility::Public,
 566                                 attr.span,
 567                                 expn_id,
 568                             )
 569                                 .to_name_binding(this.arenas);
 570                             Ok((binding, Flags::empty()))
 571                         } else {
 572                             Err(Determinacy::Determined)
 573                         }
 574                     }
 575                     Scope::DeriveHelpersCompat => {
 576                         let mut result = Err(Determinacy::Determined);
 577                         for derive in parent_scope.derives {
 578                             let parent_scope = &ParentScope { derives: &[], ..*parent_scope };
 579                             match this.resolve_macro_path(
 580                                 derive,
 581                                 Some(MacroKind::Derive),
 582                                 parent_scope,
 583                                 true,
 584                                 force,
 585                             ) {
 586                                 Ok((Some(ext), _)) => {
 587                                     if ext.helper_attrs.contains(&ident.name) {
 588                                         let binding = (
 589                                             Res::NonMacroAttr(NonMacroAttrKind::DeriveHelper),
 590                                             ty::Visibility::Public,
 591                                             derive.span,
 592                                             ExpnId::root(),
 593                                         )
 594                                             .to_name_binding(this.arenas);
 595                                         result = Ok((binding, Flags::DERIVE_HELPER_COMPAT));
 596                                         break;
 597                                     }
 598                                 }
 599                                 Ok(_) | Err(Determinacy::Determined) => {}
 600                                 Err(Determinacy::Undetermined) => {
 601                                     result = Err(Determinacy::Undetermined)
 602                                 }
 603                             }
 604                         }
 605                         result
 606                     }
 607                     Scope::MacroRules(legacy_scope) => match legacy_scope {
 608                         LegacyScope::Binding(legacy_binding) if ident == legacy_binding.ident => {
 609                             Ok((legacy_binding.binding, Flags::MACRO_RULES))
 610                         }
 611                         LegacyScope::Invocation(invoc_id)
 612                             if !this.output_legacy_scopes.contains_key(&invoc_id) =>
 613                         {
 614                             Err(Determinacy::Undetermined)
 615                         }
 616                         _ => Err(Determinacy::Determined),
 617                     },
 618                     Scope::CrateRoot => {
 619                         let root_ident = Ident::new(kw::PathRoot, ident.span);
 620                         let root_module = this.resolve_crate_root(root_ident);
 621                         let binding = this.resolve_ident_in_module_ext(
 622                             ModuleOrUniformRoot::Module(root_module),
 623                             ident,
 624                             ns,
 625                             parent_scope,
 626                             record_used,
 627                             path_span,
 628                         );
 629                         match binding {
 630                             Ok(binding) => Ok((binding, Flags::MODULE | Flags::MISC_SUGGEST_CRATE)),
 631                             Err((Determinacy::Undetermined, Weak::No)) => {
 632                                 return Some(Err(Determinacy::determined(force)));
 633                             }
 634                             Err((Determinacy::Undetermined, Weak::Yes)) => {
 635                                 Err(Determinacy::Undetermined)
 636                             }
 637                             Err((Determinacy::Determined, _)) => Err(Determinacy::Determined),
 638                         }
 639                     }
 640                     Scope::Module(module) => {
 641                         let adjusted_parent_scope = &ParentScope { module, ..*parent_scope };
 642                         let binding = this.resolve_ident_in_module_unadjusted_ext(
 643                             ModuleOrUniformRoot::Module(module),
 644                             ident,
 645                             ns,
 646                             adjusted_parent_scope,
 647                             true,
 648                             record_used,
 649                             path_span,
 650                         );
 651                         match binding {
 652                             Ok(binding) => {
 653                                 let misc_flags = if ptr::eq(module, this.graph_root) {
 654                                     Flags::MISC_SUGGEST_CRATE
 655                                 } else if module.is_normal() {
 656                                     Flags::MISC_SUGGEST_SELF
 657                                 } else {
 658                                     Flags::empty()
 659                                 };
 660                                 Ok((binding, Flags::MODULE | misc_flags))
 661                             }
 662                             Err((Determinacy::Undetermined, Weak::No)) => {
 663                                 return Some(Err(Determinacy::determined(force)));
 664                             }
 665                             Err((Determinacy::Undetermined, Weak::Yes)) => {
 666                                 Err(Determinacy::Undetermined)
 667                             }
 668                             Err((Determinacy::Determined, _)) => Err(Determinacy::Determined),
 669                         }
 670                     }
 671                     Scope::RegisteredAttrs => match this.registered_attrs.get(&ident).cloned() {
 672                         Some(ident) => ok(
 673                             Res::NonMacroAttr(NonMacroAttrKind::Registered),
 674                             ident.span,
 675                             this.arenas,
 676                         ),
 677                         None => Err(Determinacy::Determined),
 678                     },
 679                     Scope::MacroUsePrelude => {
 680                         match this.macro_use_prelude.get(&ident.name).cloned() {
 681                             Some(binding) => Ok((binding, Flags::MISC_FROM_PRELUDE)),
 682                             None => Err(Determinacy::determined(
 683                                 this.graph_root.unexpanded_invocations.borrow().is_empty(),
 684                             )),
 685                         }
 686                     }
 687                     Scope::BuiltinAttrs => {
 688                         if is_builtin_attr_name(ident.name) {
 689                             ok(Res::NonMacroAttr(NonMacroAttrKind::Builtin), DUMMY_SP, this.arenas)
 690                         } else {
 691                             Err(Determinacy::Determined)
 692                         }
 693                     }
 694                     Scope::ExternPrelude => match this.extern_prelude_get(ident, !record_used) {
 695                         Some(binding) => Ok((binding, Flags::empty())),
 696                         None => Err(Determinacy::determined(
 697                             this.graph_root.unexpanded_invocations.borrow().is_empty(),
 698                         )),
 699                     },
 700                     Scope::ToolPrelude => match this.registered_tools.get(&ident).cloned() {
 701                         Some(ident) => ok(Res::ToolMod, ident.span, this.arenas),
 702                         None => Err(Determinacy::Determined),
 703                     },
 704                     Scope::StdLibPrelude => {
 705                         let mut result = Err(Determinacy::Determined);
 706                         if let Some(prelude) = this.prelude {
 707                             if let Ok(binding) = this.resolve_ident_in_module_unadjusted(
 708                                 ModuleOrUniformRoot::Module(prelude),
 709                                 ident,
 710                                 ns,
 711                                 parent_scope,
 712                                 false,
 713                                 path_span,
 714                             ) {
 715                                 if use_prelude || this.is_builtin_macro(binding.res()) {
 716                                     result = Ok((binding, Flags::MISC_FROM_PRELUDE));
 717                                 }
 718                             }
 719                         }
 720                         result
 721                     }
 722                     Scope::BuiltinTypes => {
 723                         match this.primitive_type_table.primitive_types.get(&ident.name).cloned() {
 724                             Some(prim_ty) => ok(Res::PrimTy(prim_ty), DUMMY_SP, this.arenas),
 725                             None => Err(Determinacy::Determined),
 726                         }
 727                     }
 728                 };
 729
 730                 match result {
 731                     Ok((binding, flags))
 732                         if sub_namespace_match(binding.macro_kind(), macro_kind) =>
 733                     {
 734                         if !record_used {
 735                             return Some(Ok(binding));
 736                         }
 737
 738                         if let Some((innermost_binding, innermost_flags)) = innermost_result {
 739                             // Found another solution, if the first one was "weak", report an error.
 740                             let (res, innermost_res) = (binding.res(), innermost_binding.res());
 741                             if res != innermost_res {
 742                                 let builtin = Res::NonMacroAttr(NonMacroAttrKind::Builtin);
 743                                 let is_derive_helper_compat = |res, flags: Flags| {
 744                                     res == Res::NonMacroAttr(NonMacroAttrKind::DeriveHelper)
 745                                         && flags.contains(Flags::DERIVE_HELPER_COMPAT)
 746                                 };
 747
 748                                 let ambiguity_error_kind = if is_import {
 749                                     Some(AmbiguityKind::Import)
 750                                 } else if innermost_res == builtin || res == builtin {
 751                                     Some(AmbiguityKind::BuiltinAttr)
 752                                 } else if is_derive_helper_compat(innermost_res, innermost_flags)
 753                                     || is_derive_helper_compat(res, flags)
 754                                 {
 755                                     Some(AmbiguityKind::DeriveHelper)
 756                                 } else if innermost_flags.contains(Flags::MACRO_RULES)
 757                                     && flags.contains(Flags::MODULE)
 758                                     && !this
 759                                         .disambiguate_legacy_vs_modern(innermost_binding, binding)
 760                                     || flags.contains(Flags::MACRO_RULES)
 761                                         && innermost_flags.contains(Flags::MODULE)
 762                                         && !this.disambiguate_legacy_vs_modern(
 763                                             binding,
 764                                             innermost_binding,
 765                                         )
 766                                 {
 767                                     Some(AmbiguityKind::LegacyVsModern)
 768                                 } else if innermost_binding.is_glob_import() {
 769                                     Some(AmbiguityKind::GlobVsOuter)
 770                                 } else if innermost_binding
 771                                     .may_appear_after(parent_scope.expansion, binding)
 772                                 {
 773                                     Some(AmbiguityKind::MoreExpandedVsOuter)
 774                                 } else {
 775                                     None
 776                                 };
 777                                 if let Some(kind) = ambiguity_error_kind {
 778                                     let misc = |f: Flags| {
 779                                         if f.contains(Flags::MISC_SUGGEST_CRATE) {
 780                                             AmbiguityErrorMisc::SuggestCrate
 781                                         } else if f.contains(Flags::MISC_SUGGEST_SELF) {
 782                                             AmbiguityErrorMisc::SuggestSelf
 783                                         } else if f.contains(Flags::MISC_FROM_PRELUDE) {
 784                                             AmbiguityErrorMisc::FromPrelude
 785                                         } else {
 786                                             AmbiguityErrorMisc::None
 787                                         }
 788                                     };
 789                                     this.ambiguity_errors.push(AmbiguityError {
 790                                         kind,
 791                                         ident: orig_ident,
 792                                         b1: innermost_binding,
 793                                         b2: binding,
 794                                         misc1: misc(innermost_flags),
 795                                         misc2: misc(flags),
 796                                     });
 797                                     return Some(Ok(innermost_binding));
 798                                 }
 799                             }
 800                         } else {
 801                             // Found the first solution.
 802                             innermost_result = Some((binding, flags));
 803                         }
 804                     }
 805                     Ok(..) | Err(Determinacy::Determined) => {}
 806                     Err(Determinacy::Undetermined) => determinacy = Determinacy::Undetermined,
 807                 }
 808
 809                 None
 810             },
 811         );
 812
 813         if let Some(break_result) = break_result {
 814             return break_result;
 815         }
 816
 817         // The first found solution was the only one, return it.
 818         if let Some((binding, _)) = innermost_result {
 819             return Ok(binding);
 820         }
 821
 822         Err(Determinacy::determined(determinacy == Determinacy::Determined || force))
 823     }
 824
 825     crate fn finalize_macro_resolutions(&mut self) {
 826         let check_consistency = |this: &mut Self,
 827                                  path: &[Segment],
 828                                  span,
 829                                  kind: MacroKind,
 830                                  initial_res: Option<Res>,
 831                                  res: Res| {
 832             if let Some(initial_res) = initial_res {
 833                 if res != initial_res && res != Res::Err && this.ambiguity_errors.is_empty() {
 834                     // Make sure compilation does not succeed if preferred macro resolution
 835                     // has changed after the macro had been expanded. In theory all such
 836                     // situations should be reported as ambiguity errors, so this is a bug.
 837                     span_bug!(span, "inconsistent resolution for a macro");
 838                 }
 839             } else {
 840                 // It's possible that the macro was unresolved (indeterminate) and silently
 841                 // expanded into a dummy fragment for recovery during expansion.
 842                 // Now, post-expansion, the resolution may succeed, but we can't change the
 843                 // past and need to report an error.
 844                 // However, non-speculative `resolve_path` can successfully return private items
 845                 // even if speculative `resolve_path` returned nothing previously, so we skip this
 846                 // less informative error if the privacy error is reported elsewhere.
 847                 if this.privacy_errors.is_empty() {
 848                     let msg = format!(
 849                         "cannot determine resolution for the {} `{}`",
 850                         kind.descr(),
 851                         Segment::names_to_string(path)
 852                     );
 853                     let msg_note = "import resolution is stuck, try simplifying macro imports";
 854                     this.session.struct_span_err(span, &msg).note(msg_note).emit();
 855                 }
 856             }
 857         };
 858
 859         let macro_resolutions = mem::take(&mut self.multi_segment_macro_resolutions);
 860         for (mut path, path_span, kind, parent_scope, initial_res) in macro_resolutions {
 861             // FIXME: Path resolution will ICE if segment IDs present.
 862             for seg in &mut path {
 863                 seg.id = None;
 864             }
 865             match self.resolve_path(
 866                 &path,
 867                 Some(MacroNS),
 868                 &parent_scope,
 869                 true,
 870                 path_span,
 871                 CrateLint::No,
 872             ) {
 873                 PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 => {
 874                     let res = path_res.base_res();
 875                     check_consistency(self, &path, path_span, kind, initial_res, res);
 876                 }
 877                 path_res @ PathResult::NonModule(..) | path_res @ PathResult::Failed { .. } => {
 878                     let (span, label) = if let PathResult::Failed { span, label, .. } = path_res {
 879                         (span, label)
 880                     } else {
 881                         (
 882                             path_span,
 883                             format!(
 884                                 "partially resolved path in {} {}",
 885                                 kind.article(),
 886                                 kind.descr()
 887                             ),
 888                         )
 889                     };
 890                     self.report_error(
 891                         span,
 892                         ResolutionError::FailedToResolve { label, suggestion: None },
 893                     );
 894                 }
 895                 PathResult::Module(..) | PathResult::Indeterminate => unreachable!(),
 896             }
 897         }
 898
 899         let macro_resolutions = mem::take(&mut self.single_segment_macro_resolutions);
 900         for (ident, kind, parent_scope, initial_binding) in macro_resolutions {
 901             match self.early_resolve_ident_in_lexical_scope(
 902                 ident,
 903                 ScopeSet::Macro(kind),
 904                 &parent_scope,
 905                 true,
 906                 true,
 907                 ident.span,
 908             ) {
 909                 Ok(binding) => {
 910                     let initial_res = initial_binding.map(|initial_binding| {
 911                         self.record_use(ident, MacroNS, initial_binding, false);
 912                         initial_binding.res()
 913                     });
 914                     let res = binding.res();
 915                     let seg = Segment::from_ident(ident);
 916                     check_consistency(self, &[seg], ident.span, kind, initial_res, res);
 917                 }
 918                 Err(..) => {
 919                     let expected = kind.descr_expected();
 920                     let msg = format!("cannot find {} `{}` in this scope", expected, ident);
 921                     let mut err = self.session.struct_span_err(ident.span, &msg);
 922                     self.unresolved_macro_suggestions(&mut err, kind, &parent_scope, ident);
 923                     err.emit();
 924                 }
 925             }
 926         }
 927
 928         let builtin_attrs = mem::take(&mut self.builtin_attrs);
 929         for (ident, parent_scope) in builtin_attrs {
 930             let _ = self.early_resolve_ident_in_lexical_scope(
 931                 ident,
 932                 ScopeSet::Macro(MacroKind::Attr),
 933                 &parent_scope,
 934                 true,
 935                 true,
 936                 ident.span,
 937             );
 938         }
 939     }
 940
 941     fn check_stability_and_deprecation(&mut self, ext: &SyntaxExtension, path: &ast::Path) {
 942         let span = path.span;
 943         if let Some(stability) = &ext.stability {
 944             if let StabilityLevel::Unstable { reason, issue, is_soft } = stability.level {
 945                 let feature = stability.feature;
 946                 if !self.active_features.contains(&feature) && !span.allows_unstable(feature) {
 947                     let node_id = ast::CRATE_NODE_ID;
 948                     let lint_buffer = &mut self.lint_buffer;
 949                     let soft_handler =
 950                         |lint, span, msg: &_| lint_buffer.buffer_lint(lint, node_id, span, msg);
 951                     stability::report_unstable(
 952                         self.session,
 953                         feature,
 954                         reason,
 955                         issue,
 956                         is_soft,
 957                         span,
 958                         soft_handler,
 959                     );
 960                 }
 961             }
 962             if let Some(depr) = &stability.rustc_depr {
 963                 let path = pprust::path_to_string(path);
 964                 let (message, lint) = stability::rustc_deprecation_message(depr, &path);
 965                 stability::early_report_deprecation(
 966                     &mut self.lint_buffer,
 967                     &message,
 968                     depr.suggestion,
 969                     lint,
 970                     span,
 971                 );
 972             }
 973         }
 974         if let Some(depr) = &ext.deprecation {
 975             let path = pprust::path_to_string(&path);
 976             let (message, lint) = stability::deprecation_message(depr, &path);
 977             stability::early_report_deprecation(&mut self.lint_buffer, &message, None, lint, span);
 978         }
 979     }
 980
 981     fn prohibit_imported_non_macro_attrs(
 982         &self,
 983         binding: Option<&'a NameBinding<'a>>,
 984         res: Option<Res>,
 985         span: Span,
 986     ) {
 987         if let Some(Res::NonMacroAttr(kind)) = res {
 988             if kind != NonMacroAttrKind::Tool && binding.map_or(true, |b| b.is_import()) {
 989                 let msg =
 990                     format!("cannot use {} {} through an import", kind.article(), kind.descr());
 991                 let mut err = self.session.struct_span_err(span, &msg);
 992                 if let Some(binding) = binding {
 993                     err.span_note(binding.span, &format!("the {} imported here", kind.descr()));
 994                 }
 995                 err.emit();
 996             }
 997         }
 998     }
 999
1000     crate fn check_reserved_macro_name(&mut self, ident: Ident, res: Res) {
1001         // Reserve some names that are not quite covered by the general check
1002         // performed on `Resolver::builtin_attrs`.
1003         if ident.name == sym::cfg || ident.name == sym::cfg_attr || ident.name == sym::derive {
1004             let macro_kind = self.get_macro(res).map(|ext| ext.macro_kind());
1005             if macro_kind.is_some() && sub_namespace_match(macro_kind, Some(MacroKind::Attr)) {
1006                 self.session.span_err(
1007                     ident.span,
1008                     &format!("name `{}` is reserved in attribute namespace", ident),
1009                 );
1010             }
1011         }
1012     }
1013
1014     /// Compile the macro into a `SyntaxExtension` and possibly replace
1015     /// its expander to a pre-defined one for built-in macros.
1016     crate fn compile_macro(&mut self, item: &ast::Item, edition: Edition) -> SyntaxExtension {
1017         let mut result = compile_declarative_macro(
1018             &self.session.parse_sess,
1019             self.session.features_untracked(),
1020             item,
1021             edition,
1022         );
1023
1024         if result.is_builtin {
1025             // The macro was marked with `#[rustc_builtin_macro]`.
1026             if let Some(ext) = self.builtin_macros.remove(&item.ident.name) {
1027                 // The macro is a built-in, replace its expander function
1028                 // while still taking everything else from the source code.
1029                 result.kind = ext.kind;
1030             } else {
1031                 let msg = format!("cannot find a built-in macro with name `{}`", item.ident);
1032                 self.session.span_err(item.span, &msg);
1033             }
1034         }
1035
1036         result
1037     }
1038 }