compiler/rustc_resolve/src/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, BuiltinMacroState, Determinacy};
   7 use crate::{CrateLint, ParentScope, ResolutionError, Resolver, Scope, ScopeSet, Weak};
   8 use crate::{ModuleKind, ModuleOrUniformRoot, NameBinding, PathResult, Segment, ToNameBinding};
   9 use rustc_ast::{self as ast, NodeId};
  10 use rustc_ast_lowering::ResolverAstLowering;
  11 use rustc_ast_pretty::pprust;
  12 use rustc_attr::StabilityLevel;
  13 use rustc_data_structures::fx::FxHashSet;
  14 use rustc_errors::struct_span_err;
  15 use rustc_expand::base::{Indeterminate, InvocationRes, ResolverExpand, SyntaxExtension};
  16 use rustc_expand::compile_declarative_macro;
  17 use rustc_expand::expand::{AstFragment, AstFragmentKind, Invocation, InvocationKind};
  18 use rustc_feature::is_builtin_attr_name;
  19 use rustc_hir::def::{self, DefKind, NonMacroAttrKind};
  20 use rustc_hir::def_id;
  21 use rustc_middle::middle::stability;
  22 use rustc_middle::{span_bug, ty};
  23 use rustc_session::lint::builtin::UNUSED_MACROS;
  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, Ident, 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 `macro_rules` bindings, etc.
  38 #[derive(Debug)]
  39 pub struct MacroRulesBinding<'a> {
  40     crate binding: &'a NameBinding<'a>,
  41     /// `macro_rules` scope into which the `macro_rules` item was planted.
  42     crate parent_macro_rules_scope: MacroRulesScope<'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 `macro_rules` scopes too because they
  50 /// can potentially expand into macro definitions.
  51 #[derive(Copy, Clone, Debug)]
  52 pub enum MacroRulesScope<'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 MacroRulesBinding<'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         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 sess.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> ResolverExpand 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_macro_rules_scope = self.build_reduced_graph(fragment, parent_scope);
 164         self.output_macro_rules_scopes.insert(expansion, output_macro_rules_scope);
 165
 166         parent_scope.module.unexpanded_invocations.borrow_mut().remove(&expansion);
 167     }
 168
 169     fn register_builtin_macro(&mut self, ident: Ident, ext: SyntaxExtension) {
 170         if self.builtin_macros.insert(ident.name, BuiltinMacroState::NotYetSeen(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             None,
 191         )));
 192
 193         let parent_scope = if let Some(module_id) = parent_module_id {
 194             let parent_def_id = self.local_def_id(module_id);
 195             self.definitions.add_parent_module_of_macro_def(expn_id, parent_def_id.to_def_id());
 196             self.module_map[&parent_def_id]
 197         } else {
 198             self.definitions.add_parent_module_of_macro_def(
 199                 expn_id,
 200                 def_id::DefId::local(def_id::CRATE_DEF_INDEX),
 201             );
 202             self.empty_module
 203         };
 204         self.ast_transform_scopes.insert(expn_id, parent_scope);
 205         expn_id
 206     }
 207
 208     fn resolve_imports(&mut self) {
 209         ImportResolver { r: self }.resolve_imports()
 210     }
 211
 212     fn resolve_macro_invocation(
 213         &mut self,
 214         invoc: &Invocation,
 215         eager_expansion_root: ExpnId,
 216         force: bool,
 217     ) -> Result<InvocationRes, Indeterminate> {
 218         let invoc_id = invoc.expansion_data.id;
 219         let parent_scope = match self.invocation_parent_scopes.get(&invoc_id) {
 220             Some(parent_scope) => *parent_scope,
 221             None => {
 222                 // If there's no entry in the table, then we are resolving an eagerly expanded
 223                 // macro, which should inherit its parent scope from its eager expansion root -
 224                 // the macro that requested this eager expansion.
 225                 let parent_scope = *self
 226                     .invocation_parent_scopes
 227                     .get(&eager_expansion_root)
 228                     .expect("non-eager expansion without a parent scope");
 229                 self.invocation_parent_scopes.insert(invoc_id, parent_scope);
 230                 parent_scope
 231             }
 232         };
 233
 234         let (path, kind, derives, after_derive) = match invoc.kind {
 235             InvocationKind::Attr { ref attr, ref derives, after_derive, .. } => (
 236                 &attr.get_normal_item().path,
 237                 MacroKind::Attr,
 238                 self.arenas.alloc_ast_paths(derives),
 239                 after_derive,
 240             ),
 241             InvocationKind::Bang { ref mac, .. } => (&mac.path, MacroKind::Bang, &[][..], false),
 242             InvocationKind::Derive { ref path, .. } => (path, MacroKind::Derive, &[][..], false),
 243             InvocationKind::DeriveContainer { ref derives, .. } => {
 244                 // Block expansion of the container until we resolve all derives in it.
 245                 // This is required for two reasons:
 246                 // - Derive helper attributes are in scope for the item to which the `#[derive]`
 247                 //   is applied, so they have to be produced by the container's expansion rather
 248                 //   than by individual derives.
 249                 // - Derives in the container need to know whether one of them is a built-in `Copy`.
 250                 // FIXME: Try to avoid repeated resolutions for derives here and in expansion.
 251                 let mut exts = Vec::new();
 252                 let mut helper_attrs = Vec::new();
 253                 for path in derives {
 254                     exts.push(
 255                         match self.resolve_macro_path(
 256                             path,
 257                             Some(MacroKind::Derive),
 258                             &parent_scope,
 259                             true,
 260                             force,
 261                         ) {
 262                             Ok((Some(ext), _)) => {
 263                                 let span = path
 264                                     .segments
 265                                     .last()
 266                                     .unwrap()
 267                                     .ident
 268                                     .span
 269                                     .normalize_to_macros_2_0();
 270                                 helper_attrs.extend(
 271                                     ext.helper_attrs.iter().map(|name| Ident::new(*name, span)),
 272                                 );
 273                                 if ext.is_derive_copy {
 274                                     self.add_derive_copy(invoc_id);
 275                                 }
 276                                 ext
 277                             }
 278                             Ok(_) | Err(Determinacy::Determined) => {
 279                                 self.dummy_ext(MacroKind::Derive)
 280                             }
 281                             Err(Determinacy::Undetermined) => return Err(Indeterminate),
 282                         },
 283                     )
 284                 }
 285                 self.helper_attrs.insert(invoc_id, helper_attrs);
 286                 return Ok(InvocationRes::DeriveContainer(exts));
 287             }
 288         };
 289
 290         // Derives are not included when `invocations` are collected, so we have to add them here.
 291         let parent_scope = &ParentScope { derives, ..parent_scope };
 292         let node_id = self.lint_node_id(eager_expansion_root);
 293         let (ext, res) = self.smart_resolve_macro_path(path, kind, parent_scope, node_id, force)?;
 294
 295         let span = invoc.span();
 296         invoc_id.set_expn_data(ext.expn_data(
 297             parent_scope.expansion,
 298             span,
 299             fast_print_path(path),
 300             res.opt_def_id(),
 301         ));
 302
 303         if let Res::Def(_, _) = res {
 304             if after_derive {
 305                 self.session.span_err(span, "macro attributes must be placed before `#[derive]`");
 306             }
 307             let normal_module_def_id = self.macro_def_scope(invoc_id).normal_ancestor_id;
 308             self.definitions.add_parent_module_of_macro_def(invoc_id, normal_module_def_id);
 309         }
 310
 311         match invoc.fragment_kind {
 312             AstFragmentKind::Arms
 313             | AstFragmentKind::Fields
 314             | AstFragmentKind::FieldPats
 315             | AstFragmentKind::GenericParams
 316             | AstFragmentKind::Params
 317             | AstFragmentKind::StructFields
 318             | AstFragmentKind::Variants => {
 319                 if let Res::Def(..) = res {
 320                     self.session.span_err(
 321                         span,
 322                         &format!(
 323                             "expected an inert attribute, found {} {}",
 324                             res.article(),
 325                             res.descr()
 326                         ),
 327                     );
 328                     return Ok(InvocationRes::Single(self.dummy_ext(kind)));
 329                 }
 330             }
 331             _ => {}
 332         }
 333
 334         Ok(InvocationRes::Single(ext))
 335     }
 336
 337     fn check_unused_macros(&mut self) {
 338         for (_, &(node_id, span)) in self.unused_macros.iter() {
 339             self.lint_buffer.buffer_lint(UNUSED_MACROS, node_id, span, "unused macro definition");
 340         }
 341     }
 342
 343     fn lint_node_id(&mut self, expn_id: ExpnId) -> NodeId {
 344         self.invocation_parents
 345             .get(&expn_id)
 346             .map_or(ast::CRATE_NODE_ID, |id| self.def_id_to_node_id[*id])
 347     }
 348
 349     fn has_derive_copy(&self, expn_id: ExpnId) -> bool {
 350         self.containers_deriving_copy.contains(&expn_id)
 351     }
 352
 353     fn add_derive_copy(&mut self, expn_id: ExpnId) {
 354         self.containers_deriving_copy.insert(expn_id);
 355     }
 356
 357     // The function that implements the resolution logic of `#[cfg_accessible(path)]`.
 358     // Returns true if the path can certainly be resolved in one of three namespaces,
 359     // returns false if the path certainly cannot be resolved in any of the three namespaces.
 360     // Returns `Indeterminate` if we cannot give a certain answer yet.
 361     fn cfg_accessible(&mut self, expn_id: ExpnId, path: &ast::Path) -> Result<bool, Indeterminate> {
 362         let span = path.span;
 363         let path = &Segment::from_path(path);
 364         let parent_scope = self.invocation_parent_scopes[&expn_id];
 365
 366         let mut indeterminate = false;
 367         for ns in [TypeNS, ValueNS, MacroNS].iter().copied() {
 368             match self.resolve_path(path, Some(ns), &parent_scope, false, span, CrateLint::No) {
 369                 PathResult::Module(ModuleOrUniformRoot::Module(_)) => return Ok(true),
 370                 PathResult::NonModule(partial_res) if partial_res.unresolved_segments() == 0 => {
 371                     return Ok(true);
 372                 }
 373                 PathResult::Indeterminate => indeterminate = true,
 374                 // FIXME: `resolve_path` is not ready to report partially resolved paths
 375                 // correctly, so we just report an error if the path was reported as unresolved.
 376                 // This needs to be fixed for `cfg_accessible` to be useful.
 377                 PathResult::NonModule(..) | PathResult::Failed { .. } => {}
 378                 PathResult::Module(_) => panic!("unexpected path resolution"),
 379             }
 380         }
 381
 382         if indeterminate {
 383             return Err(Indeterminate);
 384         }
 385
 386         self.session
 387             .struct_span_err(span, "not sure whether the path is accessible or not")
 388             .span_note(span, "`cfg_accessible` is not fully implemented")
 389             .emit();
 390         Ok(false)
 391     }
 392 }
 393
 394 impl<'a> Resolver<'a> {
 395     /// Resolve macro path with error reporting and recovery.
 396     fn smart_resolve_macro_path(
 397         &mut self,
 398         path: &ast::Path,
 399         kind: MacroKind,
 400         parent_scope: &ParentScope<'a>,
 401         node_id: NodeId,
 402         force: bool,
 403     ) -> Result<(Lrc<SyntaxExtension>, Res), Indeterminate> {
 404         let (ext, res) = match self.resolve_macro_path(path, Some(kind), parent_scope, true, force)
 405         {
 406             Ok((Some(ext), res)) => (ext, res),
 407             // Use dummy syntax extensions for unresolved macros for better recovery.
 408             Ok((None, res)) => (self.dummy_ext(kind), res),
 409             Err(Determinacy::Determined) => (self.dummy_ext(kind), Res::Err),
 410             Err(Determinacy::Undetermined) => return Err(Indeterminate),
 411         };
 412
 413         // Report errors for the resolved macro.
 414         for segment in &path.segments {
 415             if let Some(args) = &segment.args {
 416                 self.session.span_err(args.span(), "generic arguments in macro path");
 417             }
 418             if kind == MacroKind::Attr && segment.ident.as_str().starts_with("rustc") {
 419                 self.session.span_err(
 420                     segment.ident.span,
 421                     "attributes starting with `rustc` are reserved for use by the `rustc` compiler",
 422                 );
 423             }
 424         }
 425
 426         match res {
 427             Res::Def(DefKind::Macro(_), def_id) => {
 428                 if let Some(def_id) = def_id.as_local() {
 429                     self.unused_macros.remove(&def_id);
 430                     if self.proc_macro_stubs.contains(&def_id) {
 431                         self.session.span_err(
 432                             path.span,
 433                             "can't use a procedural macro from the same crate that defines it",
 434                         );
 435                     }
 436                 }
 437             }
 438             Res::NonMacroAttr(..) | Res::Err => {}
 439             _ => panic!("expected `DefKind::Macro` or `Res::NonMacroAttr`"),
 440         };
 441
 442         self.check_stability_and_deprecation(&ext, path, node_id);
 443
 444         Ok(if ext.macro_kind() != kind {
 445             let expected = kind.descr_expected();
 446             let path_str = pprust::path_to_string(path);
 447             let msg = format!("expected {}, found {} `{}`", expected, res.descr(), path_str);
 448             self.session
 449                 .struct_span_err(path.span, &msg)
 450                 .span_label(path.span, format!("not {} {}", kind.article(), expected))
 451                 .emit();
 452             // Use dummy syntax extensions for unexpected macro kinds for better recovery.
 453             (self.dummy_ext(kind), Res::Err)
 454         } else {
 455             (ext, res)
 456         })
 457     }
 458
 459     pub fn resolve_macro_path(
 460         &mut self,
 461         path: &ast::Path,
 462         kind: Option<MacroKind>,
 463         parent_scope: &ParentScope<'a>,
 464         trace: bool,
 465         force: bool,
 466     ) -> Result<(Option<Lrc<SyntaxExtension>>, Res), Determinacy> {
 467         let path_span = path.span;
 468         let mut path = Segment::from_path(path);
 469
 470         // Possibly apply the macro helper hack
 471         if kind == Some(MacroKind::Bang)
 472             && path.len() == 1
 473             && path[0].ident.span.ctxt().outer_expn_data().local_inner_macros
 474         {
 475             let root = Ident::new(kw::DollarCrate, path[0].ident.span);
 476             path.insert(0, Segment::from_ident(root));
 477         }
 478
 479         let res = if path.len() > 1 {
 480             let res = match self.resolve_path(
 481                 &path,
 482                 Some(MacroNS),
 483                 parent_scope,
 484                 false,
 485                 path_span,
 486                 CrateLint::No,
 487             ) {
 488                 PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 => {
 489                     Ok(path_res.base_res())
 490                 }
 491                 PathResult::Indeterminate if !force => return Err(Determinacy::Undetermined),
 492                 PathResult::NonModule(..)
 493                 | PathResult::Indeterminate
 494                 | PathResult::Failed { .. } => Err(Determinacy::Determined),
 495                 PathResult::Module(..) => unreachable!(),
 496             };
 497
 498             if trace {
 499                 let kind = kind.expect("macro kind must be specified if tracing is enabled");
 500                 self.multi_segment_macro_resolutions.push((
 501                     path,
 502                     path_span,
 503                     kind,
 504                     *parent_scope,
 505                     res.ok(),
 506                 ));
 507             }
 508
 509             self.prohibit_imported_non_macro_attrs(None, res.ok(), path_span);
 510             res
 511         } else {
 512             let scope_set = kind.map_or(ScopeSet::All(MacroNS, false), ScopeSet::Macro);
 513             let binding = self.early_resolve_ident_in_lexical_scope(
 514                 path[0].ident,
 515                 scope_set,
 516                 parent_scope,
 517                 false,
 518                 force,
 519                 path_span,
 520             );
 521             if let Err(Determinacy::Undetermined) = binding {
 522                 return Err(Determinacy::Undetermined);
 523             }
 524
 525             if trace {
 526                 let kind = kind.expect("macro kind must be specified if tracing is enabled");
 527                 self.single_segment_macro_resolutions.push((
 528                     path[0].ident,
 529                     kind,
 530                     *parent_scope,
 531                     binding.ok(),
 532                 ));
 533             }
 534
 535             let res = binding.map(|binding| binding.res());
 536             self.prohibit_imported_non_macro_attrs(binding.ok(), res.ok(), path_span);
 537             res
 538         };
 539
 540         res.map(|res| (self.get_macro(res), res))
 541     }
 542
 543     // Resolve an identifier in lexical scope.
 544     // This is a variation of `fn resolve_ident_in_lexical_scope` that can be run during
 545     // expansion and import resolution (perhaps they can be merged in the future).
 546     // The function is used for resolving initial segments of macro paths (e.g., `foo` in
 547     // `foo::bar!(); or `foo!();`) and also for import paths on 2018 edition.
 548     crate fn early_resolve_ident_in_lexical_scope(
 549         &mut self,
 550         orig_ident: Ident,
 551         scope_set: ScopeSet,
 552         parent_scope: &ParentScope<'a>,
 553         record_used: bool,
 554         force: bool,
 555         path_span: Span,
 556     ) -> Result<&'a NameBinding<'a>, Determinacy> {
 557         bitflags::bitflags! {
 558             struct Flags: u8 {
 559                 const MACRO_RULES          = 1 << 0;
 560                 const MODULE               = 1 << 1;
 561                 const DERIVE_HELPER_COMPAT = 1 << 2;
 562                 const MISC_SUGGEST_CRATE   = 1 << 3;
 563                 const MISC_SUGGEST_SELF    = 1 << 4;
 564                 const MISC_FROM_PRELUDE    = 1 << 5;
 565             }
 566         }
 567
 568         assert!(force || !record_used); // `record_used` implies `force`
 569
 570         // Make sure `self`, `super` etc produce an error when passed to here.
 571         if orig_ident.is_path_segment_keyword() {
 572             return Err(Determinacy::Determined);
 573         }
 574
 575         let (ns, macro_kind, is_import) = match scope_set {
 576             ScopeSet::All(ns, is_import) => (ns, None, is_import),
 577             ScopeSet::AbsolutePath(ns) => (ns, None, false),
 578             ScopeSet::Macro(macro_kind) => (MacroNS, Some(macro_kind), false),
 579         };
 580
 581         // This is *the* result, resolution from the scope closest to the resolved identifier.
 582         // However, sometimes this result is "weak" because it comes from a glob import or
 583         // a macro expansion, and in this case it cannot shadow names from outer scopes, e.g.
 584         // mod m { ... } // solution in outer scope
 585         // {
 586         //     use prefix::*; // imports another `m` - innermost solution
 587         //                    // weak, cannot shadow the outer `m`, need to report ambiguity error
 588         //     m::mac!();
 589         // }
 590         // So we have to save the innermost solution and continue searching in outer scopes
 591         // to detect potential ambiguities.
 592         let mut innermost_result: Option<(&NameBinding<'_>, Flags)> = None;
 593         let mut determinacy = Determinacy::Determined;
 594
 595         // Go through all the scopes and try to resolve the name.
 596         let break_result = self.visit_scopes(
 597             scope_set,
 598             parent_scope,
 599             orig_ident,
 600             |this, scope, use_prelude, ident| {
 601                 let ok = |res, span, arenas| {
 602                     Ok((
 603                         (res, ty::Visibility::Public, span, ExpnId::root()).to_name_binding(arenas),
 604                         Flags::empty(),
 605                     ))
 606                 };
 607                 let result = match scope {
 608                     Scope::DeriveHelpers(expn_id) => {
 609                         if let Some(attr) = this
 610                             .helper_attrs
 611                             .get(&expn_id)
 612                             .and_then(|attrs| attrs.iter().rfind(|i| ident == **i))
 613                         {
 614                             let binding = (
 615                                 Res::NonMacroAttr(NonMacroAttrKind::DeriveHelper),
 616                                 ty::Visibility::Public,
 617                                 attr.span,
 618                                 expn_id,
 619                             )
 620                                 .to_name_binding(this.arenas);
 621                             Ok((binding, Flags::empty()))
 622                         } else {
 623                             Err(Determinacy::Determined)
 624                         }
 625                     }
 626                     Scope::DeriveHelpersCompat => {
 627                         let mut result = Err(Determinacy::Determined);
 628                         for derive in parent_scope.derives {
 629                             let parent_scope = &ParentScope { derives: &[], ..*parent_scope };
 630                             match this.resolve_macro_path(
 631                                 derive,
 632                                 Some(MacroKind::Derive),
 633                                 parent_scope,
 634                                 true,
 635                                 force,
 636                             ) {
 637                                 Ok((Some(ext), _)) => {
 638                                     if ext.helper_attrs.contains(&ident.name) {
 639                                         let binding = (
 640                                             Res::NonMacroAttr(NonMacroAttrKind::DeriveHelper),
 641                                             ty::Visibility::Public,
 642                                             derive.span,
 643                                             ExpnId::root(),
 644                                         )
 645                                             .to_name_binding(this.arenas);
 646                                         result = Ok((binding, Flags::DERIVE_HELPER_COMPAT));
 647                                         break;
 648                                     }
 649                                 }
 650                                 Ok(_) | Err(Determinacy::Determined) => {}
 651                                 Err(Determinacy::Undetermined) => {
 652                                     result = Err(Determinacy::Undetermined)
 653                                 }
 654                             }
 655                         }
 656                         result
 657                     }
 658                     Scope::MacroRules(macro_rules_scope) => match macro_rules_scope {
 659                         MacroRulesScope::Binding(macro_rules_binding)
 660                             if ident == macro_rules_binding.ident =>
 661                         {
 662                             Ok((macro_rules_binding.binding, Flags::MACRO_RULES))
 663                         }
 664                         MacroRulesScope::Invocation(invoc_id)
 665                             if !this.output_macro_rules_scopes.contains_key(&invoc_id) =>
 666                         {
 667                             Err(Determinacy::Undetermined)
 668                         }
 669                         _ => Err(Determinacy::Determined),
 670                     },
 671                     Scope::CrateRoot => {
 672                         let root_ident = Ident::new(kw::PathRoot, ident.span);
 673                         let root_module = this.resolve_crate_root(root_ident);
 674                         let binding = this.resolve_ident_in_module_ext(
 675                             ModuleOrUniformRoot::Module(root_module),
 676                             ident,
 677                             ns,
 678                             parent_scope,
 679                             record_used,
 680                             path_span,
 681                         );
 682                         match binding {
 683                             Ok(binding) => Ok((binding, Flags::MODULE | Flags::MISC_SUGGEST_CRATE)),
 684                             Err((Determinacy::Undetermined, Weak::No)) => {
 685                                 return Some(Err(Determinacy::determined(force)));
 686                             }
 687                             Err((Determinacy::Undetermined, Weak::Yes)) => {
 688                                 Err(Determinacy::Undetermined)
 689                             }
 690                             Err((Determinacy::Determined, _)) => Err(Determinacy::Determined),
 691                         }
 692                     }
 693                     Scope::Module(module) => {
 694                         let adjusted_parent_scope = &ParentScope { module, ..*parent_scope };
 695                         let binding = this.resolve_ident_in_module_unadjusted_ext(
 696                             ModuleOrUniformRoot::Module(module),
 697                             ident,
 698                             ns,
 699                             adjusted_parent_scope,
 700                             true,
 701                             record_used,
 702                             path_span,
 703                         );
 704                         match binding {
 705                             Ok(binding) => {
 706                                 let misc_flags = if ptr::eq(module, this.graph_root) {
 707                                     Flags::MISC_SUGGEST_CRATE
 708                                 } else if module.is_normal() {
 709                                     Flags::MISC_SUGGEST_SELF
 710                                 } else {
 711                                     Flags::empty()
 712                                 };
 713                                 Ok((binding, Flags::MODULE | misc_flags))
 714                             }
 715                             Err((Determinacy::Undetermined, Weak::No)) => {
 716                                 return Some(Err(Determinacy::determined(force)));
 717                             }
 718                             Err((Determinacy::Undetermined, Weak::Yes)) => {
 719                                 Err(Determinacy::Undetermined)
 720                             }
 721                             Err((Determinacy::Determined, _)) => Err(Determinacy::Determined),
 722                         }
 723                     }
 724                     Scope::RegisteredAttrs => match this.registered_attrs.get(&ident).cloned() {
 725                         Some(ident) => ok(
 726                             Res::NonMacroAttr(NonMacroAttrKind::Registered),
 727                             ident.span,
 728                             this.arenas,
 729                         ),
 730                         None => Err(Determinacy::Determined),
 731                     },
 732                     Scope::MacroUsePrelude => {
 733                         match this.macro_use_prelude.get(&ident.name).cloned() {
 734                             Some(binding) => Ok((binding, Flags::MISC_FROM_PRELUDE)),
 735                             None => Err(Determinacy::determined(
 736                                 this.graph_root.unexpanded_invocations.borrow().is_empty(),
 737                             )),
 738                         }
 739                     }
 740                     Scope::BuiltinAttrs => {
 741                         if is_builtin_attr_name(ident.name) {
 742                             ok(Res::NonMacroAttr(NonMacroAttrKind::Builtin), DUMMY_SP, this.arenas)
 743                         } else {
 744                             Err(Determinacy::Determined)
 745                         }
 746                     }
 747                     Scope::ExternPrelude => match this.extern_prelude_get(ident, !record_used) {
 748                         Some(binding) => Ok((binding, Flags::empty())),
 749                         None => Err(Determinacy::determined(
 750                             this.graph_root.unexpanded_invocations.borrow().is_empty(),
 751                         )),
 752                     },
 753                     Scope::ToolPrelude => match this.registered_tools.get(&ident).cloned() {
 754                         Some(ident) => ok(Res::ToolMod, ident.span, this.arenas),
 755                         None => Err(Determinacy::Determined),
 756                     },
 757                     Scope::StdLibPrelude => {
 758                         let mut result = Err(Determinacy::Determined);
 759                         if let Some(prelude) = this.prelude {
 760                             if let Ok(binding) = this.resolve_ident_in_module_unadjusted(
 761                                 ModuleOrUniformRoot::Module(prelude),
 762                                 ident,
 763                                 ns,
 764                                 parent_scope,
 765                                 false,
 766                                 path_span,
 767                             ) {
 768                                 if use_prelude || this.is_builtin_macro(binding.res()) {
 769                                     result = Ok((binding, Flags::MISC_FROM_PRELUDE));
 770                                 }
 771                             }
 772                         }
 773                         result
 774                     }
 775                     Scope::BuiltinTypes => {
 776                         match this.primitive_type_table.primitive_types.get(&ident.name).cloned() {
 777                             Some(prim_ty) => ok(Res::PrimTy(prim_ty), DUMMY_SP, this.arenas),
 778                             None => Err(Determinacy::Determined),
 779                         }
 780                     }
 781                 };
 782
 783                 match result {
 784                     Ok((binding, flags))
 785                         if sub_namespace_match(binding.macro_kind(), macro_kind) =>
 786                     {
 787                         if !record_used {
 788                             return Some(Ok(binding));
 789                         }
 790
 791                         if let Some((innermost_binding, innermost_flags)) = innermost_result {
 792                             // Found another solution, if the first one was "weak", report an error.
 793                             let (res, innermost_res) = (binding.res(), innermost_binding.res());
 794                             if res != innermost_res {
 795                                 let builtin = Res::NonMacroAttr(NonMacroAttrKind::Builtin);
 796                                 let is_derive_helper_compat = |res, flags: Flags| {
 797                                     res == Res::NonMacroAttr(NonMacroAttrKind::DeriveHelper)
 798                                         && flags.contains(Flags::DERIVE_HELPER_COMPAT)
 799                                 };
 800
 801                                 let ambiguity_error_kind = if is_import {
 802                                     Some(AmbiguityKind::Import)
 803                                 } else if innermost_res == builtin || res == builtin {
 804                                     Some(AmbiguityKind::BuiltinAttr)
 805                                 } else if is_derive_helper_compat(innermost_res, innermost_flags)
 806                                     || is_derive_helper_compat(res, flags)
 807                                 {
 808                                     Some(AmbiguityKind::DeriveHelper)
 809                                 } else if innermost_flags.contains(Flags::MACRO_RULES)
 810                                     && flags.contains(Flags::MODULE)
 811                                     && !this.disambiguate_macro_rules_vs_modularized(
 812                                         innermost_binding,
 813                                         binding,
 814                                     )
 815                                     || flags.contains(Flags::MACRO_RULES)
 816                                         && innermost_flags.contains(Flags::MODULE)
 817                                         && !this.disambiguate_macro_rules_vs_modularized(
 818                                             binding,
 819                                             innermost_binding,
 820                                         )
 821                                 {
 822                                     Some(AmbiguityKind::MacroRulesVsModularized)
 823                                 } else if innermost_binding.is_glob_import() {
 824                                     Some(AmbiguityKind::GlobVsOuter)
 825                                 } else if innermost_binding
 826                                     .may_appear_after(parent_scope.expansion, binding)
 827                                 {
 828                                     Some(AmbiguityKind::MoreExpandedVsOuter)
 829                                 } else {
 830                                     None
 831                                 };
 832                                 if let Some(kind) = ambiguity_error_kind {
 833                                     let misc = |f: Flags| {
 834                                         if f.contains(Flags::MISC_SUGGEST_CRATE) {
 835                                             AmbiguityErrorMisc::SuggestCrate
 836                                         } else if f.contains(Flags::MISC_SUGGEST_SELF) {
 837                                             AmbiguityErrorMisc::SuggestSelf
 838                                         } else if f.contains(Flags::MISC_FROM_PRELUDE) {
 839                                             AmbiguityErrorMisc::FromPrelude
 840                                         } else {
 841                                             AmbiguityErrorMisc::None
 842                                         }
 843                                     };
 844                                     this.ambiguity_errors.push(AmbiguityError {
 845                                         kind,
 846                                         ident: orig_ident,
 847                                         b1: innermost_binding,
 848                                         b2: binding,
 849                                         misc1: misc(innermost_flags),
 850                                         misc2: misc(flags),
 851                                     });
 852                                     return Some(Ok(innermost_binding));
 853                                 }
 854                             }
 855                         } else {
 856                             // Found the first solution.
 857                             innermost_result = Some((binding, flags));
 858                         }
 859                     }
 860                     Ok(..) | Err(Determinacy::Determined) => {}
 861                     Err(Determinacy::Undetermined) => determinacy = Determinacy::Undetermined,
 862                 }
 863
 864                 None
 865             },
 866         );
 867
 868         if let Some(break_result) = break_result {
 869             return break_result;
 870         }
 871
 872         // The first found solution was the only one, return it.
 873         if let Some((binding, _)) = innermost_result {
 874             return Ok(binding);
 875         }
 876
 877         Err(Determinacy::determined(determinacy == Determinacy::Determined || force))
 878     }
 879
 880     crate fn finalize_macro_resolutions(&mut self) {
 881         let check_consistency = |this: &mut Self,
 882                                  path: &[Segment],
 883                                  span,
 884                                  kind: MacroKind,
 885                                  initial_res: Option<Res>,
 886                                  res: Res| {
 887             if let Some(initial_res) = initial_res {
 888                 if res != initial_res && res != Res::Err && this.ambiguity_errors.is_empty() {
 889                     // Make sure compilation does not succeed if preferred macro resolution
 890                     // has changed after the macro had been expanded. In theory all such
 891                     // situations should be reported as ambiguity errors, so this is a bug.
 892                     span_bug!(span, "inconsistent resolution for a macro");
 893                 }
 894             } else {
 895                 // It's possible that the macro was unresolved (indeterminate) and silently
 896                 // expanded into a dummy fragment for recovery during expansion.
 897                 // Now, post-expansion, the resolution may succeed, but we can't change the
 898                 // past and need to report an error.
 899                 // However, non-speculative `resolve_path` can successfully return private items
 900                 // even if speculative `resolve_path` returned nothing previously, so we skip this
 901                 // less informative error if the privacy error is reported elsewhere.
 902                 if this.privacy_errors.is_empty() {
 903                     let msg = format!(
 904                         "cannot determine resolution for the {} `{}`",
 905                         kind.descr(),
 906                         Segment::names_to_string(path)
 907                     );
 908                     let msg_note = "import resolution is stuck, try simplifying macro imports";
 909                     this.session.struct_span_err(span, &msg).note(msg_note).emit();
 910                 }
 911             }
 912         };
 913
 914         let macro_resolutions = mem::take(&mut self.multi_segment_macro_resolutions);
 915         for (mut path, path_span, kind, parent_scope, initial_res) in macro_resolutions {
 916             // FIXME: Path resolution will ICE if segment IDs present.
 917             for seg in &mut path {
 918                 seg.id = None;
 919             }
 920             match self.resolve_path(
 921                 &path,
 922                 Some(MacroNS),
 923                 &parent_scope,
 924                 true,
 925                 path_span,
 926                 CrateLint::No,
 927             ) {
 928                 PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 => {
 929                     let res = path_res.base_res();
 930                     check_consistency(self, &path, path_span, kind, initial_res, res);
 931                 }
 932                 path_res @ PathResult::NonModule(..) | path_res @ PathResult::Failed { .. } => {
 933                     let (span, label) = if let PathResult::Failed { span, label, .. } = path_res {
 934                         (span, label)
 935                     } else {
 936                         (
 937                             path_span,
 938                             format!(
 939                                 "partially resolved path in {} {}",
 940                                 kind.article(),
 941                                 kind.descr()
 942                             ),
 943                         )
 944                     };
 945                     self.report_error(
 946                         span,
 947                         ResolutionError::FailedToResolve { label, suggestion: None },
 948                     );
 949                 }
 950                 PathResult::Module(..) | PathResult::Indeterminate => unreachable!(),
 951             }
 952         }
 953
 954         let macro_resolutions = mem::take(&mut self.single_segment_macro_resolutions);
 955         for (ident, kind, parent_scope, initial_binding) in macro_resolutions {
 956             match self.early_resolve_ident_in_lexical_scope(
 957                 ident,
 958                 ScopeSet::Macro(kind),
 959                 &parent_scope,
 960                 true,
 961                 true,
 962                 ident.span,
 963             ) {
 964                 Ok(binding) => {
 965                     let initial_res = initial_binding.map(|initial_binding| {
 966                         self.record_use(ident, MacroNS, initial_binding, false);
 967                         initial_binding.res()
 968                     });
 969                     let res = binding.res();
 970                     let seg = Segment::from_ident(ident);
 971                     check_consistency(self, &[seg], ident.span, kind, initial_res, res);
 972                 }
 973                 Err(..) => {
 974                     let expected = kind.descr_expected();
 975                     let msg = format!("cannot find {} `{}` in this scope", expected, ident);
 976                     let mut err = self.session.struct_span_err(ident.span, &msg);
 977                     self.unresolved_macro_suggestions(&mut err, kind, &parent_scope, ident);
 978                     err.emit();
 979                 }
 980             }
 981         }
 982
 983         let builtin_attrs = mem::take(&mut self.builtin_attrs);
 984         for (ident, parent_scope) in builtin_attrs {
 985             let _ = self.early_resolve_ident_in_lexical_scope(
 986                 ident,
 987                 ScopeSet::Macro(MacroKind::Attr),
 988                 &parent_scope,
 989                 true,
 990                 true,
 991                 ident.span,
 992             );
 993         }
 994     }
 995
 996     fn check_stability_and_deprecation(
 997         &mut self,
 998         ext: &SyntaxExtension,
 999         path: &ast::Path,
1000         node_id: NodeId,
1001     ) {
1002         let span = path.span;
1003         if let Some(stability) = &ext.stability {
1004             if let StabilityLevel::Unstable { reason, issue, is_soft } = stability.level {
1005                 let feature = stability.feature;
1006                 if !self.active_features.contains(&feature) && !span.allows_unstable(feature) {
1007                     let lint_buffer = &mut self.lint_buffer;
1008                     let soft_handler =
1009                         |lint, span, msg: &_| lint_buffer.buffer_lint(lint, node_id, span, msg);
1010                     stability::report_unstable(
1011                         self.session,
1012                         feature,
1013                         reason,
1014                         issue,
1015                         is_soft,
1016                         span,
1017                         soft_handler,
1018                     );
1019                 }
1020             }
1021         }
1022         if let Some(depr) = &ext.deprecation {
1023             let path = pprust::path_to_string(&path);
1024             let (message, lint) = stability::deprecation_message(depr, "macro", &path);
1025             stability::early_report_deprecation(
1026                 &mut self.lint_buffer,
1027                 &message,
1028                 depr.suggestion,
1029                 lint,
1030                 span,
1031             );
1032         }
1033     }
1034
1035     fn prohibit_imported_non_macro_attrs(
1036         &self,
1037         binding: Option<&'a NameBinding<'a>>,
1038         res: Option<Res>,
1039         span: Span,
1040     ) {
1041         if let Some(Res::NonMacroAttr(kind)) = res {
1042             if kind != NonMacroAttrKind::Tool && binding.map_or(true, |b| b.is_import()) {
1043                 let msg =
1044                     format!("cannot use {} {} through an import", kind.article(), kind.descr());
1045                 let mut err = self.session.struct_span_err(span, &msg);
1046                 if let Some(binding) = binding {
1047                     err.span_note(binding.span, &format!("the {} imported here", kind.descr()));
1048                 }
1049                 err.emit();
1050             }
1051         }
1052     }
1053
1054     crate fn check_reserved_macro_name(&mut self, ident: Ident, res: Res) {
1055         // Reserve some names that are not quite covered by the general check
1056         // performed on `Resolver::builtin_attrs`.
1057         if ident.name == sym::cfg || ident.name == sym::cfg_attr || ident.name == sym::derive {
1058             let macro_kind = self.get_macro(res).map(|ext| ext.macro_kind());
1059             if macro_kind.is_some() && sub_namespace_match(macro_kind, Some(MacroKind::Attr)) {
1060                 self.session.span_err(
1061                     ident.span,
1062                     &format!("name `{}` is reserved in attribute namespace", ident),
1063                 );
1064             }
1065         }
1066     }
1067
1068     /// Compile the macro into a `SyntaxExtension` and possibly replace
1069     /// its expander to a pre-defined one for built-in macros.
1070     crate fn compile_macro(&mut self, item: &ast::Item, edition: Edition) -> SyntaxExtension {
1071         let mut result = compile_declarative_macro(
1072             &self.session,
1073             self.session.features_untracked(),
1074             item,
1075             edition,
1076         );
1077
1078         if result.is_builtin {
1079             // The macro was marked with `#[rustc_builtin_macro]`.
1080             if let Some(builtin_macro) = self.builtin_macros.get_mut(&item.ident.name) {
1081                 // The macro is a built-in, replace its expander function
1082                 // while still taking everything else from the source code.
1083                 // If we already loaded this builtin macro, give a better error message than 'no such builtin macro'.
1084                 match mem::replace(builtin_macro, BuiltinMacroState::AlreadySeen(item.span)) {
1085                     BuiltinMacroState::NotYetSeen(ext) => result.kind = ext.kind,
1086                     BuiltinMacroState::AlreadySeen(span) => {
1087                         struct_span_err!(
1088                             self.session,
1089                             item.span,
1090                             E0773,
1091                             "attempted to define built-in macro more than once"
1092                         )
1093                         .span_note(span, "previously defined here")
1094                         .emit();
1095                     }
1096                 }
1097             } else {
1098                 let msg = format!("cannot find a built-in macro with name `{}`", item.ident);
1099                 self.session.span_err(item.span, &msg);
1100             }
1101         }
1102
1103         result
1104     }
1105 }