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::{BuiltinMacroState, Determinacy};
   7 use crate::{DeriveData, Finalize, ParentScope, ResolutionError, Resolver, ScopeSet};
   8 use crate::{ModuleKind, ModuleOrUniformRoot, NameBinding, PathResult, Segment};
   9 use rustc_ast::{self as ast, Inline, ItemKind, ModKind, 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_data_structures::intern::Interned;
  15 use rustc_data_structures::sync::Lrc;
  16 use rustc_errors::struct_span_err;
  17 use rustc_expand::base::{Annotatable, DeriveResolutions, Indeterminate, ResolverExpand};
  18 use rustc_expand::base::{SyntaxExtension, SyntaxExtensionKind};
  19 use rustc_expand::compile_declarative_macro;
  20 use rustc_expand::expand::{AstFragment, Invocation, InvocationKind, SupportsMacroExpansion};
  21 use rustc_hir::def::{self, DefKind, NonMacroAttrKind};
  22 use rustc_hir::def_id::{CrateNum, LocalDefId};
  23 use rustc_middle::middle::stability;
  24 use rustc_middle::ty::RegisteredTools;
  25 use rustc_session::lint::builtin::{LEGACY_DERIVE_HELPERS, SOFT_UNSTABLE, UNUSED_MACROS};
  26 use rustc_session::lint::BuiltinLintDiagnostics;
  27 use rustc_session::parse::feature_err;
  28 use rustc_session::Session;
  29 use rustc_span::edition::Edition;
  30 use rustc_span::hygiene::{self, ExpnData, ExpnKind, LocalExpnId};
  31 use rustc_span::hygiene::{AstPass, MacroKind};
  32 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  33 use rustc_span::{Span, DUMMY_SP};
  34 use std::cell::Cell;
  35 use std::mem;
  36
  37 type Res = def::Res<NodeId>;
  38
  39 /// Binding produced by a `macro_rules` item.
  40 /// Not modularized, can shadow previous `macro_rules` bindings, etc.
  41 #[derive(Debug)]
  42 pub struct MacroRulesBinding<'a> {
  43     crate binding: &'a NameBinding<'a>,
  44     /// `macro_rules` scope into which the `macro_rules` item was planted.
  45     crate parent_macro_rules_scope: MacroRulesScopeRef<'a>,
  46     crate ident: Ident,
  47 }
  48
  49 /// The scope introduced by a `macro_rules!` macro.
  50 /// This starts at the macro's definition and ends at the end of the macro's parent
  51 /// module (named or unnamed), or even further if it escapes with `#[macro_use]`.
  52 /// Some macro invocations need to introduce `macro_rules` scopes too because they
  53 /// can potentially expand into macro definitions.
  54 #[derive(Copy, Clone, Debug)]
  55 pub enum MacroRulesScope<'a> {
  56     /// Empty "root" scope at the crate start containing no names.
  57     Empty,
  58     /// The scope introduced by a `macro_rules!` macro definition.
  59     Binding(&'a MacroRulesBinding<'a>),
  60     /// The scope introduced by a macro invocation that can potentially
  61     /// create a `macro_rules!` macro definition.
  62     Invocation(LocalExpnId),
  63 }
  64
  65 /// `macro_rules!` scopes are always kept by reference and inside a cell.
  66 /// The reason is that we update scopes with value `MacroRulesScope::Invocation(invoc_id)`
  67 /// in-place after `invoc_id` gets expanded.
  68 /// This helps to avoid uncontrollable growth of `macro_rules!` scope chains,
  69 /// which usually grow linearly with the number of macro invocations
  70 /// in a module (including derives) and hurt performance.
  71 pub(crate) type MacroRulesScopeRef<'a> = Interned<'a, Cell<MacroRulesScope<'a>>>;
  72
  73 /// Macro namespace is separated into two sub-namespaces, one for bang macros and
  74 /// one for attribute-like macros (attributes, derives).
  75 /// We ignore resolutions from one sub-namespace when searching names in scope for another.
  76 crate fn sub_namespace_match(candidate: Option<MacroKind>, requirement: Option<MacroKind>) -> bool {
  77     #[derive(PartialEq)]
  78     enum SubNS {
  79         Bang,
  80         AttrLike,
  81     }
  82     let sub_ns = |kind| match kind {
  83         MacroKind::Bang => SubNS::Bang,
  84         MacroKind::Attr | MacroKind::Derive => SubNS::AttrLike,
  85     };
  86     let candidate = candidate.map(sub_ns);
  87     let requirement = requirement.map(sub_ns);
  88     // "No specific sub-namespace" means "matches anything" for both requirements and candidates.
  89     candidate.is_none() || requirement.is_none() || candidate == requirement
  90 }
  91
  92 // We don't want to format a path using pretty-printing,
  93 // `format!("{}", path)`, because that tries to insert
  94 // line-breaks and is slow.
  95 fn fast_print_path(path: &ast::Path) -> Symbol {
  96     if path.segments.len() == 1 {
  97         path.segments[0].ident.name
  98     } else {
  99         let mut path_str = String::with_capacity(64);
 100         for (i, segment) in path.segments.iter().enumerate() {
 101             if i != 0 {
 102                 path_str.push_str("::");
 103             }
 104             if segment.ident.name != kw::PathRoot {
 105                 path_str.push_str(segment.ident.as_str())
 106             }
 107         }
 108         Symbol::intern(&path_str)
 109     }
 110 }
 111
 112 /// The code common between processing `#![register_tool]` and `#![register_attr]`.
 113 fn registered_idents(
 114     sess: &Session,
 115     attrs: &[ast::Attribute],
 116     attr_name: Symbol,
 117     descr: &str,
 118 ) -> FxHashSet<Ident> {
 119     let mut registered = FxHashSet::default();
 120     for attr in sess.filter_by_name(attrs, attr_name) {
 121         for nested_meta in attr.meta_item_list().unwrap_or_default() {
 122             match nested_meta.ident() {
 123                 Some(ident) => {
 124                     if let Some(old_ident) = registered.replace(ident) {
 125                         let msg = format!("{} `{}` was already registered", descr, ident);
 126                         sess.struct_span_err(ident.span, &msg)
 127                             .span_label(old_ident.span, "already registered here")
 128                             .emit();
 129                     }
 130                 }
 131                 None => {
 132                     let msg = format!("`{}` only accepts identifiers", attr_name);
 133                     let span = nested_meta.span();
 134                     sess.struct_span_err(span, &msg).span_label(span, "not an identifier").emit();
 135                 }
 136             }
 137         }
 138     }
 139     registered
 140 }
 141
 142 crate fn registered_attrs_and_tools(
 143     sess: &Session,
 144     attrs: &[ast::Attribute],
 145 ) -> (FxHashSet<Ident>, FxHashSet<Ident>) {
 146     let registered_attrs = registered_idents(sess, attrs, sym::register_attr, "attribute");
 147     let mut registered_tools = registered_idents(sess, attrs, sym::register_tool, "tool");
 148     // We implicitly add `rustfmt` and `clippy` to known tools,
 149     // but it's not an error to register them explicitly.
 150     let predefined_tools = [sym::clippy, sym::rustfmt];
 151     registered_tools.extend(predefined_tools.iter().cloned().map(Ident::with_dummy_span));
 152     (registered_attrs, registered_tools)
 153 }
 154
 155 // Some feature gates for inner attributes are reported as lints for backward compatibility.
 156 fn soft_custom_inner_attributes_gate(path: &ast::Path, invoc: &Invocation) -> bool {
 157     match &path.segments[..] {
 158         // `#![test]`
 159         [seg] if seg.ident.name == sym::test => return true,
 160         // `#![rustfmt::skip]` on out-of-line modules
 161         [seg1, seg2] if seg1.ident.name == sym::rustfmt && seg2.ident.name == sym::skip => {
 162             if let InvocationKind::Attr { item, .. } = &invoc.kind {
 163                 if let Annotatable::Item(item) = item {
 164                     if let ItemKind::Mod(_, ModKind::Loaded(_, Inline::No, _)) = item.kind {
 165                         return true;
 166                     }
 167                 }
 168             }
 169         }
 170         _ => {}
 171     }
 172     false
 173 }
 174
 175 impl<'a> ResolverExpand for Resolver<'a> {
 176     fn next_node_id(&mut self) -> NodeId {
 177         self.next_node_id()
 178     }
 179
 180     fn invocation_parent(&self, id: LocalExpnId) -> LocalDefId {
 181         self.invocation_parents[&id].0
 182     }
 183
 184     fn resolve_dollar_crates(&mut self) {
 185         hygiene::update_dollar_crate_names(|ctxt| {
 186             let ident = Ident::new(kw::DollarCrate, DUMMY_SP.with_ctxt(ctxt));
 187             match self.resolve_crate_root(ident).kind {
 188                 ModuleKind::Def(.., name) if name != kw::Empty => name,
 189                 _ => kw::Crate,
 190             }
 191         });
 192     }
 193
 194     fn visit_ast_fragment_with_placeholders(
 195         &mut self,
 196         expansion: LocalExpnId,
 197         fragment: &AstFragment,
 198     ) {
 199         // Integrate the new AST fragment into all the definition and module structures.
 200         // We are inside the `expansion` now, but other parent scope components are still the same.
 201         let parent_scope = ParentScope { expansion, ..self.invocation_parent_scopes[&expansion] };
 202         let output_macro_rules_scope = self.build_reduced_graph(fragment, parent_scope);
 203         self.output_macro_rules_scopes.insert(expansion, output_macro_rules_scope);
 204
 205         parent_scope.module.unexpanded_invocations.borrow_mut().remove(&expansion);
 206     }
 207
 208     fn register_builtin_macro(&mut self, name: Symbol, ext: SyntaxExtensionKind) {
 209         if self.builtin_macros.insert(name, BuiltinMacroState::NotYetSeen(ext)).is_some() {
 210             self.session
 211                 .diagnostic()
 212                 .bug(&format!("built-in macro `{}` was already registered", name));
 213         }
 214     }
 215
 216     // Create a new Expansion with a definition site of the provided module, or
 217     // a fake empty `#[no_implicit_prelude]` module if no module is provided.
 218     fn expansion_for_ast_pass(
 219         &mut self,
 220         call_site: Span,
 221         pass: AstPass,
 222         features: &[Symbol],
 223         parent_module_id: Option<NodeId>,
 224     ) -> LocalExpnId {
 225         let parent_module =
 226             parent_module_id.map(|module_id| self.local_def_id(module_id).to_def_id());
 227         let expn_id = LocalExpnId::fresh(
 228             ExpnData::allow_unstable(
 229                 ExpnKind::AstPass(pass),
 230                 call_site,
 231                 self.session.edition(),
 232                 features.into(),
 233                 None,
 234                 parent_module,
 235             ),
 236             self.create_stable_hashing_context(),
 237         );
 238
 239         let parent_scope =
 240             parent_module.map_or(self.empty_module, |def_id| self.expect_module(def_id));
 241         self.ast_transform_scopes.insert(expn_id, parent_scope);
 242
 243         expn_id
 244     }
 245
 246     fn resolve_imports(&mut self) {
 247         ImportResolver { r: self }.resolve_imports()
 248     }
 249
 250     fn resolve_macro_invocation(
 251         &mut self,
 252         invoc: &Invocation,
 253         eager_expansion_root: LocalExpnId,
 254         force: bool,
 255     ) -> Result<Lrc<SyntaxExtension>, Indeterminate> {
 256         let invoc_id = invoc.expansion_data.id;
 257         let parent_scope = match self.invocation_parent_scopes.get(&invoc_id) {
 258             Some(parent_scope) => *parent_scope,
 259             None => {
 260                 // If there's no entry in the table, then we are resolving an eagerly expanded
 261                 // macro, which should inherit its parent scope from its eager expansion root -
 262                 // the macro that requested this eager expansion.
 263                 let parent_scope = *self
 264                     .invocation_parent_scopes
 265                     .get(&eager_expansion_root)
 266                     .expect("non-eager expansion without a parent scope");
 267                 self.invocation_parent_scopes.insert(invoc_id, parent_scope);
 268                 parent_scope
 269             }
 270         };
 271
 272         let (path, kind, inner_attr, derives) = match invoc.kind {
 273             InvocationKind::Attr { ref attr, ref derives, .. } => (
 274                 &attr.get_normal_item().path,
 275                 MacroKind::Attr,
 276                 attr.style == ast::AttrStyle::Inner,
 277                 self.arenas.alloc_ast_paths(derives),
 278             ),
 279             InvocationKind::Bang { ref mac, .. } => (&mac.path, MacroKind::Bang, false, &[][..]),
 280             InvocationKind::Derive { ref path, .. } => (path, MacroKind::Derive, false, &[][..]),
 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 supports_macro_expansion = invoc.fragment_kind.supports_macro_expansion();
 286         let node_id = invoc.expansion_data.lint_node_id;
 287         let (ext, res) = self.smart_resolve_macro_path(
 288             path,
 289             kind,
 290             supports_macro_expansion,
 291             inner_attr,
 292             parent_scope,
 293             node_id,
 294             force,
 295             soft_custom_inner_attributes_gate(path, invoc),
 296         )?;
 297
 298         let span = invoc.span();
 299         let def_id = res.opt_def_id();
 300         invoc_id.set_expn_data(
 301             ext.expn_data(
 302                 parent_scope.expansion,
 303                 span,
 304                 fast_print_path(path),
 305                 def_id,
 306                 def_id.map(|def_id| self.macro_def_scope(def_id).nearest_parent_mod()),
 307             ),
 308             self.create_stable_hashing_context(),
 309         );
 310
 311         Ok(ext)
 312     }
 313
 314     fn check_unused_macros(&mut self) {
 315         for (_, &(node_id, ident)) in self.unused_macros.iter() {
 316             self.lint_buffer.buffer_lint(
 317                 UNUSED_MACROS,
 318                 node_id,
 319                 ident.span,
 320                 &format!("unused macro definition: `{}`", ident.as_str()),
 321             );
 322         }
 323     }
 324
 325     fn has_derive_copy(&self, expn_id: LocalExpnId) -> bool {
 326         self.containers_deriving_copy.contains(&expn_id)
 327     }
 328
 329     fn resolve_derives(
 330         &mut self,
 331         expn_id: LocalExpnId,
 332         force: bool,
 333         derive_paths: &dyn Fn() -> DeriveResolutions,
 334     ) -> Result<(), Indeterminate> {
 335         // Block expansion of the container until we resolve all derives in it.
 336         // This is required for two reasons:
 337         // - Derive helper attributes are in scope for the item to which the `#[derive]`
 338         //   is applied, so they have to be produced by the container's expansion rather
 339         //   than by individual derives.
 340         // - Derives in the container need to know whether one of them is a built-in `Copy`.
 341         // Temporarily take the data to avoid borrow checker conflicts.
 342         let mut derive_data = mem::take(&mut self.derive_data);
 343         let entry = derive_data.entry(expn_id).or_insert_with(|| DeriveData {
 344             resolutions: derive_paths(),
 345             helper_attrs: Vec::new(),
 346             has_derive_copy: false,
 347         });
 348         let parent_scope = self.invocation_parent_scopes[&expn_id];
 349         for (i, (path, _, opt_ext)) in entry.resolutions.iter_mut().enumerate() {
 350             if opt_ext.is_none() {
 351                 *opt_ext = Some(
 352                     match self.resolve_macro_path(
 353                         &path,
 354                         Some(MacroKind::Derive),
 355                         &parent_scope,
 356                         true,
 357                         force,
 358                     ) {
 359                         Ok((Some(ext), _)) => {
 360                             if !ext.helper_attrs.is_empty() {
 361                                 let last_seg = path.segments.last().unwrap();
 362                                 let span = last_seg.ident.span.normalize_to_macros_2_0();
 363                                 entry.helper_attrs.extend(
 364                                     ext.helper_attrs
 365                                         .iter()
 366                                         .map(|name| (i, Ident::new(*name, span))),
 367                                 );
 368                             }
 369                             entry.has_derive_copy |= ext.builtin_name == Some(sym::Copy);
 370                             ext
 371                         }
 372                         Ok(_) | Err(Determinacy::Determined) => self.dummy_ext(MacroKind::Derive),
 373                         Err(Determinacy::Undetermined) => {
 374                             assert!(self.derive_data.is_empty());
 375                             self.derive_data = derive_data;
 376                             return Err(Indeterminate);
 377                         }
 378                     },
 379                 );
 380             }
 381         }
 382         // Sort helpers in a stable way independent from the derive resolution order.
 383         entry.helper_attrs.sort_by_key(|(i, _)| *i);
 384         self.helper_attrs
 385             .insert(expn_id, entry.helper_attrs.iter().map(|(_, ident)| *ident).collect());
 386         // Mark this derive as having `Copy` either if it has `Copy` itself or if its parent derive
 387         // has `Copy`, to support cases like `#[derive(Clone, Copy)] #[derive(Debug)]`.
 388         if entry.has_derive_copy || self.has_derive_copy(parent_scope.expansion) {
 389             self.containers_deriving_copy.insert(expn_id);
 390         }
 391         assert!(self.derive_data.is_empty());
 392         self.derive_data = derive_data;
 393         Ok(())
 394     }
 395
 396     fn take_derive_resolutions(&mut self, expn_id: LocalExpnId) -> Option<DeriveResolutions> {
 397         self.derive_data.remove(&expn_id).map(|data| data.resolutions)
 398     }
 399
 400     // The function that implements the resolution logic of `#[cfg_accessible(path)]`.
 401     // Returns true if the path can certainly be resolved in one of three namespaces,
 402     // returns false if the path certainly cannot be resolved in any of the three namespaces.
 403     // Returns `Indeterminate` if we cannot give a certain answer yet.
 404     fn cfg_accessible(
 405         &mut self,
 406         expn_id: LocalExpnId,
 407         path: &ast::Path,
 408     ) -> Result<bool, Indeterminate> {
 409         let span = path.span;
 410         let path = &Segment::from_path(path);
 411         let parent_scope = self.invocation_parent_scopes[&expn_id];
 412
 413         let mut indeterminate = false;
 414         for ns in [TypeNS, ValueNS, MacroNS].iter().copied() {
 415             match self.maybe_resolve_path(path, Some(ns), &parent_scope) {
 416                 PathResult::Module(ModuleOrUniformRoot::Module(_)) => return Ok(true),
 417                 PathResult::NonModule(partial_res) if partial_res.unresolved_segments() == 0 => {
 418                     return Ok(true);
 419                 }
 420                 PathResult::Indeterminate => indeterminate = true,
 421                 // FIXME: `resolve_path` is not ready to report partially resolved paths
 422                 // correctly, so we just report an error if the path was reported as unresolved.
 423                 // This needs to be fixed for `cfg_accessible` to be useful.
 424                 PathResult::NonModule(..) | PathResult::Failed { .. } => {}
 425                 PathResult::Module(_) => panic!("unexpected path resolution"),
 426             }
 427         }
 428
 429         if indeterminate {
 430             return Err(Indeterminate);
 431         }
 432
 433         self.session
 434             .struct_span_err(span, "not sure whether the path is accessible or not")
 435             .span_note(span, "`cfg_accessible` is not fully implemented")
 436             .emit();
 437         Ok(false)
 438     }
 439
 440     fn get_proc_macro_quoted_span(&self, krate: CrateNum, id: usize) -> Span {
 441         self.crate_loader.cstore().get_proc_macro_quoted_span_untracked(krate, id, self.session)
 442     }
 443
 444     fn declare_proc_macro(&mut self, id: NodeId) {
 445         self.proc_macros.push(id)
 446     }
 447
 448     fn registered_tools(&self) -> &RegisteredTools {
 449         &self.registered_tools
 450     }
 451 }
 452
 453 impl<'a> Resolver<'a> {
 454     /// Resolve macro path with error reporting and recovery.
 455     /// Uses dummy syntax extensions for unresolved macros or macros with unexpected resolutions
 456     /// for better error recovery.
 457     fn smart_resolve_macro_path(
 458         &mut self,
 459         path: &ast::Path,
 460         kind: MacroKind,
 461         supports_macro_expansion: SupportsMacroExpansion,
 462         inner_attr: bool,
 463         parent_scope: &ParentScope<'a>,
 464         node_id: NodeId,
 465         force: bool,
 466         soft_custom_inner_attributes_gate: bool,
 467     ) -> Result<(Lrc<SyntaxExtension>, Res), Indeterminate> {
 468         let (ext, res) = match self.resolve_macro_path(path, Some(kind), parent_scope, true, force)
 469         {
 470             Ok((Some(ext), res)) => (ext, res),
 471             Ok((None, res)) => (self.dummy_ext(kind), res),
 472             Err(Determinacy::Determined) => (self.dummy_ext(kind), Res::Err),
 473             Err(Determinacy::Undetermined) => return Err(Indeterminate),
 474         };
 475
 476         // Report errors for the resolved macro.
 477         for segment in &path.segments {
 478             if let Some(args) = &segment.args {
 479                 self.session.span_err(args.span(), "generic arguments in macro path");
 480             }
 481             if kind == MacroKind::Attr && segment.ident.as_str().starts_with("rustc") {
 482                 self.session.span_err(
 483                     segment.ident.span,
 484                     "attributes starting with `rustc` are reserved for use by the `rustc` compiler",
 485                 );
 486             }
 487         }
 488
 489         match res {
 490             Res::Def(DefKind::Macro(_), def_id) => {
 491                 if let Some(def_id) = def_id.as_local() {
 492                     self.unused_macros.remove(&def_id);
 493                     if self.proc_macro_stubs.contains(&def_id) {
 494                         self.session.span_err(
 495                             path.span,
 496                             "can't use a procedural macro from the same crate that defines it",
 497                         );
 498                     }
 499                 }
 500             }
 501             Res::NonMacroAttr(..) | Res::Err => {}
 502             _ => panic!("expected `DefKind::Macro` or `Res::NonMacroAttr`"),
 503         };
 504
 505         self.check_stability_and_deprecation(&ext, path, node_id);
 506
 507         let unexpected_res = if ext.macro_kind() != kind {
 508             Some((kind.article(), kind.descr_expected()))
 509         } else if matches!(res, Res::Def(..)) {
 510             match supports_macro_expansion {
 511                 SupportsMacroExpansion::No => Some(("a", "non-macro attribute")),
 512                 SupportsMacroExpansion::Yes { supports_inner_attrs } => {
 513                     if inner_attr && !supports_inner_attrs {
 514                         Some(("a", "non-macro inner attribute"))
 515                     } else {
 516                         None
 517                     }
 518                 }
 519             }
 520         } else {
 521             None
 522         };
 523         if let Some((article, expected)) = unexpected_res {
 524             let path_str = pprust::path_to_string(path);
 525             let msg = format!("expected {}, found {} `{}`", expected, res.descr(), path_str);
 526             self.session
 527                 .struct_span_err(path.span, &msg)
 528                 .span_label(path.span, format!("not {} {}", article, expected))
 529                 .emit();
 530             return Ok((self.dummy_ext(kind), Res::Err));
 531         }
 532
 533         // We are trying to avoid reporting this error if other related errors were reported.
 534         if res != Res::Err
 535             && inner_attr
 536             && !self.session.features_untracked().custom_inner_attributes
 537         {
 538             let msg = match res {
 539                 Res::Def(..) => "inner macro attributes are unstable",
 540                 Res::NonMacroAttr(..) => "custom inner attributes are unstable",
 541                 _ => unreachable!(),
 542             };
 543             if soft_custom_inner_attributes_gate {
 544                 self.session.parse_sess.buffer_lint(SOFT_UNSTABLE, path.span, node_id, msg);
 545             } else {
 546                 feature_err(&self.session.parse_sess, sym::custom_inner_attributes, path.span, msg)
 547                     .emit();
 548             }
 549         }
 550
 551         Ok((ext, res))
 552     }
 553
 554     pub fn resolve_macro_path(
 555         &mut self,
 556         path: &ast::Path,
 557         kind: Option<MacroKind>,
 558         parent_scope: &ParentScope<'a>,
 559         trace: bool,
 560         force: bool,
 561     ) -> Result<(Option<Lrc<SyntaxExtension>>, Res), Determinacy> {
 562         let path_span = path.span;
 563         let mut path = Segment::from_path(path);
 564
 565         // Possibly apply the macro helper hack
 566         if kind == Some(MacroKind::Bang)
 567             && path.len() == 1
 568             && path[0].ident.span.ctxt().outer_expn_data().local_inner_macros
 569         {
 570             let root = Ident::new(kw::DollarCrate, path[0].ident.span);
 571             path.insert(0, Segment::from_ident(root));
 572         }
 573
 574         let res = if path.len() > 1 {
 575             let res = match self.maybe_resolve_path(&path, Some(MacroNS), parent_scope) {
 576                 PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 => {
 577                     Ok(path_res.base_res())
 578                 }
 579                 PathResult::Indeterminate if !force => return Err(Determinacy::Undetermined),
 580                 PathResult::NonModule(..)
 581                 | PathResult::Indeterminate
 582                 | PathResult::Failed { .. } => Err(Determinacy::Determined),
 583                 PathResult::Module(..) => unreachable!(),
 584             };
 585
 586             if trace {
 587                 let kind = kind.expect("macro kind must be specified if tracing is enabled");
 588                 self.multi_segment_macro_resolutions.push((
 589                     path,
 590                     path_span,
 591                     kind,
 592                     *parent_scope,
 593                     res.ok(),
 594                 ));
 595             }
 596
 597             self.prohibit_imported_non_macro_attrs(None, res.ok(), path_span);
 598             res
 599         } else {
 600             let scope_set = kind.map_or(ScopeSet::All(MacroNS, false), ScopeSet::Macro);
 601             let binding = self.early_resolve_ident_in_lexical_scope(
 602                 path[0].ident,
 603                 scope_set,
 604                 parent_scope,
 605                 None,
 606                 force,
 607                 false,
 608                 None,
 609             );
 610             if let Err(Determinacy::Undetermined) = binding {
 611                 return Err(Determinacy::Undetermined);
 612             }
 613
 614             if trace {
 615                 let kind = kind.expect("macro kind must be specified if tracing is enabled");
 616                 self.single_segment_macro_resolutions.push((
 617                     path[0].ident,
 618                     kind,
 619                     *parent_scope,
 620                     binding.ok(),
 621                 ));
 622             }
 623
 624             let res = binding.map(|binding| binding.res());
 625             self.prohibit_imported_non_macro_attrs(binding.ok(), res.ok(), path_span);
 626             res
 627         };
 628
 629         res.map(|res| (self.get_macro(res), res))
 630     }
 631
 632     crate fn finalize_macro_resolutions(&mut self) {
 633         let check_consistency = |this: &mut Self,
 634                                  path: &[Segment],
 635                                  span,
 636                                  kind: MacroKind,
 637                                  initial_res: Option<Res>,
 638                                  res: Res| {
 639             if let Some(initial_res) = initial_res {
 640                 if res != initial_res {
 641                     // Make sure compilation does not succeed if preferred macro resolution
 642                     // has changed after the macro had been expanded. In theory all such
 643                     // situations should be reported as errors, so this is a bug.
 644                     this.session.delay_span_bug(span, "inconsistent resolution for a macro");
 645                 }
 646             } else {
 647                 // It's possible that the macro was unresolved (indeterminate) and silently
 648                 // expanded into a dummy fragment for recovery during expansion.
 649                 // Now, post-expansion, the resolution may succeed, but we can't change the
 650                 // past and need to report an error.
 651                 // However, non-speculative `resolve_path` can successfully return private items
 652                 // even if speculative `resolve_path` returned nothing previously, so we skip this
 653                 // less informative error if the privacy error is reported elsewhere.
 654                 if this.privacy_errors.is_empty() {
 655                     let msg = format!(
 656                         "cannot determine resolution for the {} `{}`",
 657                         kind.descr(),
 658                         Segment::names_to_string(path)
 659                     );
 660                     let msg_note = "import resolution is stuck, try simplifying macro imports";
 661                     this.session.struct_span_err(span, &msg).note(msg_note).emit();
 662                 }
 663             }
 664         };
 665
 666         let macro_resolutions = mem::take(&mut self.multi_segment_macro_resolutions);
 667         for (mut path, path_span, kind, parent_scope, initial_res) in macro_resolutions {
 668             // FIXME: Path resolution will ICE if segment IDs present.
 669             for seg in &mut path {
 670                 seg.id = None;
 671             }
 672             match self.resolve_path(
 673                 &path,
 674                 Some(MacroNS),
 675                 &parent_scope,
 676                 Finalize::SimplePath(ast::CRATE_NODE_ID, path_span),
 677                 None,
 678             ) {
 679                 PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 => {
 680                     let res = path_res.base_res();
 681                     check_consistency(self, &path, path_span, kind, initial_res, res);
 682                 }
 683                 path_res @ PathResult::NonModule(..) | path_res @ PathResult::Failed { .. } => {
 684                     let (span, label) = if let PathResult::Failed { span, label, .. } = path_res {
 685                         (span, label)
 686                     } else {
 687                         (
 688                             path_span,
 689                             format!(
 690                                 "partially resolved path in {} {}",
 691                                 kind.article(),
 692                                 kind.descr()
 693                             ),
 694                         )
 695                     };
 696                     self.report_error(
 697                         span,
 698                         ResolutionError::FailedToResolve { label, suggestion: None },
 699                     );
 700                 }
 701                 PathResult::Module(..) | PathResult::Indeterminate => unreachable!(),
 702             }
 703         }
 704
 705         let macro_resolutions = mem::take(&mut self.single_segment_macro_resolutions);
 706         for (ident, kind, parent_scope, initial_binding) in macro_resolutions {
 707             match self.early_resolve_ident_in_lexical_scope(
 708                 ident,
 709                 ScopeSet::Macro(kind),
 710                 &parent_scope,
 711                 Some(ident.span),
 712                 true,
 713                 false,
 714                 None,
 715             ) {
 716                 Ok(binding) => {
 717                     let initial_res = initial_binding.map(|initial_binding| {
 718                         self.record_use(ident, initial_binding, false);
 719                         initial_binding.res()
 720                     });
 721                     let res = binding.res();
 722                     let seg = Segment::from_ident(ident);
 723                     check_consistency(self, &[seg], ident.span, kind, initial_res, res);
 724                     if res == Res::NonMacroAttr(NonMacroAttrKind::DeriveHelperCompat) {
 725                         let node_id = self
 726                             .invocation_parents
 727                             .get(&parent_scope.expansion)
 728                             .map_or(ast::CRATE_NODE_ID, |id| self.def_id_to_node_id[id.0]);
 729                         self.lint_buffer.buffer_lint_with_diagnostic(
 730                             LEGACY_DERIVE_HELPERS,
 731                             node_id,
 732                             ident.span,
 733                             "derive helper attribute is used before it is introduced",
 734                             BuiltinLintDiagnostics::LegacyDeriveHelpers(binding.span),
 735                         );
 736                     }
 737                 }
 738                 Err(..) => {
 739                     let expected = kind.descr_expected();
 740                     let msg = format!("cannot find {} `{}` in this scope", expected, ident);
 741                     let mut err = self.session.struct_span_err(ident.span, &msg);
 742                     self.unresolved_macro_suggestions(&mut err, kind, &parent_scope, ident);
 743                     err.emit();
 744                 }
 745             }
 746         }
 747
 748         let builtin_attrs = mem::take(&mut self.builtin_attrs);
 749         for (ident, parent_scope) in builtin_attrs {
 750             let _ = self.early_resolve_ident_in_lexical_scope(
 751                 ident,
 752                 ScopeSet::Macro(MacroKind::Attr),
 753                 &parent_scope,
 754                 Some(ident.span),
 755                 true,
 756                 false,
 757                 None,
 758             );
 759         }
 760     }
 761
 762     fn check_stability_and_deprecation(
 763         &mut self,
 764         ext: &SyntaxExtension,
 765         path: &ast::Path,
 766         node_id: NodeId,
 767     ) {
 768         let span = path.span;
 769         if let Some(stability) = &ext.stability {
 770             if let StabilityLevel::Unstable { reason, issue, is_soft } = stability.level {
 771                 let feature = stability.feature;
 772                 if !self.active_features.contains(&feature) && !span.allows_unstable(feature) {
 773                     let lint_buffer = &mut self.lint_buffer;
 774                     let soft_handler =
 775                         |lint, span, msg: &_| lint_buffer.buffer_lint(lint, node_id, span, msg);
 776                     stability::report_unstable(
 777                         self.session,
 778                         feature,
 779                         reason,
 780                         issue,
 781                         None,
 782                         is_soft,
 783                         span,
 784                         soft_handler,
 785                     );
 786                 }
 787             }
 788         }
 789         if let Some(depr) = &ext.deprecation {
 790             let path = pprust::path_to_string(&path);
 791             let (message, lint) = stability::deprecation_message_and_lint(depr, "macro", &path);
 792             stability::early_report_deprecation(
 793                 &mut self.lint_buffer,
 794                 &message,
 795                 depr.suggestion,
 796                 lint,
 797                 span,
 798                 node_id,
 799             );
 800         }
 801     }
 802
 803     fn prohibit_imported_non_macro_attrs(
 804         &self,
 805         binding: Option<&'a NameBinding<'a>>,
 806         res: Option<Res>,
 807         span: Span,
 808     ) {
 809         if let Some(Res::NonMacroAttr(kind)) = res {
 810             if kind != NonMacroAttrKind::Tool && binding.map_or(true, |b| b.is_import()) {
 811                 let msg =
 812                     format!("cannot use {} {} through an import", kind.article(), kind.descr());
 813                 let mut err = self.session.struct_span_err(span, &msg);
 814                 if let Some(binding) = binding {
 815                     err.span_note(binding.span, &format!("the {} imported here", kind.descr()));
 816                 }
 817                 err.emit();
 818             }
 819         }
 820     }
 821
 822     crate fn check_reserved_macro_name(&mut self, ident: Ident, res: Res) {
 823         // Reserve some names that are not quite covered by the general check
 824         // performed on `Resolver::builtin_attrs`.
 825         if ident.name == sym::cfg || ident.name == sym::cfg_attr {
 826             let macro_kind = self.get_macro(res).map(|ext| ext.macro_kind());
 827             if macro_kind.is_some() && sub_namespace_match(macro_kind, Some(MacroKind::Attr)) {
 828                 self.session.span_err(
 829                     ident.span,
 830                     &format!("name `{}` is reserved in attribute namespace", ident),
 831                 );
 832             }
 833         }
 834     }
 835
 836     /// Compile the macro into a `SyntaxExtension` and possibly replace
 837     /// its expander to a pre-defined one for built-in macros.
 838     crate fn compile_macro(&mut self, item: &ast::Item, edition: Edition) -> SyntaxExtension {
 839         let mut result = compile_declarative_macro(
 840             &self.session,
 841             self.session.features_untracked(),
 842             item,
 843             edition,
 844         );
 845
 846         if let Some(builtin_name) = result.builtin_name {
 847             // The macro was marked with `#[rustc_builtin_macro]`.
 848             if let Some(builtin_macro) = self.builtin_macros.get_mut(&builtin_name) {
 849                 // The macro is a built-in, replace its expander function
 850                 // while still taking everything else from the source code.
 851                 // If we already loaded this builtin macro, give a better error message than 'no such builtin macro'.
 852                 match mem::replace(builtin_macro, BuiltinMacroState::AlreadySeen(item.span)) {
 853                     BuiltinMacroState::NotYetSeen(ext) => {
 854                         result.kind = ext;
 855                         if item.id != ast::DUMMY_NODE_ID {
 856                             self.builtin_macro_kinds
 857                                 .insert(self.local_def_id(item.id), result.macro_kind());
 858                         }
 859                     }
 860                     BuiltinMacroState::AlreadySeen(span) => {
 861                         struct_span_err!(
 862                             self.session,
 863                             item.span,
 864                             E0773,
 865                             "attempted to define built-in macro more than once"
 866                         )
 867                         .span_note(span, "previously defined here")
 868                         .emit();
 869                     }
 870                 }
 871             } else {
 872                 let msg = format!("cannot find a built-in macro with name `{}`", item.ident);
 873                 self.session.span_err(item.span, &msg);
 874             }
 875         }
 876
 877         result
 878     }
 879 }