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_data_structures::ptr_key::PtrKey;
  15 use rustc_data_structures::sync::Lrc;
  16 use rustc_errors::struct_span_err;
  17 use rustc_expand::base::{Indeterminate, ResolverExpand, SyntaxExtension, SyntaxExtensionKind};
  18 use rustc_expand::compile_declarative_macro;
  19 use rustc_expand::expand::{AstFragment, Invocation, InvocationKind};
  20 use rustc_feature::is_builtin_attr_name;
  21 use rustc_hir::def::{self, DefKind, NonMacroAttrKind};
  22 use rustc_hir::def_id;
  23 use rustc_hir::PrimTy;
  24 use rustc_middle::middle::stability;
  25 use rustc_middle::ty;
  26 use rustc_session::lint::builtin::{LEGACY_DERIVE_HELPERS, SOFT_UNSTABLE, UNUSED_MACROS};
  27 use rustc_session::lint::BuiltinLintDiagnostics;
  28 use rustc_session::parse::feature_err;
  29 use rustc_session::Session;
  30 use rustc_span::edition::Edition;
  31 use rustc_span::hygiene::{self, ExpnData, ExpnId, ExpnKind};
  32 use rustc_span::hygiene::{AstPass, MacroKind};
  33 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  34 use rustc_span::{Span, DUMMY_SP};
  35 use std::cell::Cell;
  36 use std::{mem, ptr};
  37
  38 type Res = def::Res<NodeId>;
  39
  40 /// Binding produced by a `macro_rules` item.
  41 /// Not modularized, can shadow previous `macro_rules` bindings, etc.
  42 #[derive(Debug)]
  43 pub struct MacroRulesBinding<'a> {
  44     crate binding: &'a NameBinding<'a>,
  45     /// `macro_rules` scope into which the `macro_rules` item was planted.
  46     crate parent_macro_rules_scope: MacroRulesScopeRef<'a>,
  47     crate ident: Ident,
  48 }
  49
  50 /// The scope introduced by a `macro_rules!` macro.
  51 /// This starts at the macro's definition and ends at the end of the macro's parent
  52 /// module (named or unnamed), or even further if it escapes with `#[macro_use]`.
  53 /// Some macro invocations need to introduce `macro_rules` scopes too because they
  54 /// can potentially expand into macro definitions.
  55 #[derive(Copy, Clone, Debug)]
  56 pub enum MacroRulesScope<'a> {
  57     /// Empty "root" scope at the crate start containing no names.
  58     Empty,
  59     /// The scope introduced by a `macro_rules!` macro definition.
  60     Binding(&'a MacroRulesBinding<'a>),
  61     /// The scope introduced by a macro invocation that can potentially
  62     /// create a `macro_rules!` macro definition.
  63     Invocation(ExpnId),
  64 }
  65
  66 /// `macro_rules!` scopes are always kept by reference and inside a cell.
  67 /// The reason is that we update scopes with value `MacroRulesScope::Invocation(invoc_id)`
  68 /// in-place after `invoc_id` gets expanded.
  69 /// This helps to avoid uncontrollable growth of `macro_rules!` scope chains,
  70 /// which usually grow lineraly with the number of macro invocations
  71 /// in a module (including derives) and hurt performance.
  72 pub(crate) type MacroRulesScopeRef<'a> = PtrKey<'a, Cell<MacroRulesScope<'a>>>;
  73
  74 // Macro namespace is separated into two sub-namespaces, one for bang macros and
  75 // one for attribute-like macros (attributes, derives).
  76 // We ignore resolutions from one sub-namespace when searching names in scope for another.
  77 fn sub_namespace_match(candidate: Option<MacroKind>, requirement: Option<MacroKind>) -> bool {
  78     #[derive(PartialEq)]
  79     enum SubNS {
  80         Bang,
  81         AttrLike,
  82     }
  83     let sub_ns = |kind| match kind {
  84         MacroKind::Bang => SubNS::Bang,
  85         MacroKind::Attr | MacroKind::Derive => SubNS::AttrLike,
  86     };
  87     let candidate = candidate.map(sub_ns);
  88     let requirement = requirement.map(sub_ns);
  89     // "No specific sub-namespace" means "matches anything" for both requirements and candidates.
  90     candidate.is_none() || requirement.is_none() || candidate == requirement
  91 }
  92
  93 // We don't want to format a path using pretty-printing,
  94 // `format!("{}", path)`, because that tries to insert
  95 // line-breaks and is slow.
  96 fn fast_print_path(path: &ast::Path) -> Symbol {
  97     if path.segments.len() == 1 {
  98         path.segments[0].ident.name
  99     } else {
 100         let mut path_str = String::with_capacity(64);
 101         for (i, segment) in path.segments.iter().enumerate() {
 102             if i != 0 {
 103                 path_str.push_str("::");
 104             }
 105             if segment.ident.name != kw::PathRoot {
 106                 path_str.push_str(&segment.ident.as_str())
 107             }
 108         }
 109         Symbol::intern(&path_str)
 110     }
 111 }
 112
 113 /// The code common between processing `#![register_tool]` and `#![register_attr]`.
 114 fn registered_idents(
 115     sess: &Session,
 116     attrs: &[ast::Attribute],
 117     attr_name: Symbol,
 118     descr: &str,
 119 ) -> FxHashSet<Ident> {
 120     let mut registered = FxHashSet::default();
 121     for attr in sess.filter_by_name(attrs, attr_name) {
 122         for nested_meta in attr.meta_item_list().unwrap_or_default() {
 123             match nested_meta.ident() {
 124                 Some(ident) => {
 125                     if let Some(old_ident) = registered.replace(ident) {
 126                         let msg = format!("{} `{}` was already registered", descr, ident);
 127                         sess.struct_span_err(ident.span, &msg)
 128                             .span_label(old_ident.span, "already registered here")
 129                             .emit();
 130                     }
 131                 }
 132                 None => {
 133                     let msg = format!("`{}` only accepts identifiers", attr_name);
 134                     let span = nested_meta.span();
 135                     sess.struct_span_err(span, &msg).span_label(span, "not an identifier").emit();
 136                 }
 137             }
 138         }
 139     }
 140     registered
 141 }
 142
 143 crate fn registered_attrs_and_tools(
 144     sess: &Session,
 145     attrs: &[ast::Attribute],
 146 ) -> (FxHashSet<Ident>, FxHashSet<Ident>) {
 147     let registered_attrs = registered_idents(sess, attrs, sym::register_attr, "attribute");
 148     let mut registered_tools = registered_idents(sess, attrs, sym::register_tool, "tool");
 149     // We implicitly add `rustfmt` and `clippy` to known tools,
 150     // but it's not an error to register them explicitly.
 151     let predefined_tools = [sym::clippy, sym::rustfmt];
 152     registered_tools.extend(predefined_tools.iter().cloned().map(Ident::with_dummy_span));
 153     (registered_attrs, registered_tools)
 154 }
 155
 156 impl<'a> ResolverExpand for Resolver<'a> {
 157     fn next_node_id(&mut self) -> NodeId {
 158         self.next_node_id()
 159     }
 160
 161     fn resolve_dollar_crates(&mut self) {
 162         hygiene::update_dollar_crate_names(|ctxt| {
 163             let ident = Ident::new(kw::DollarCrate, DUMMY_SP.with_ctxt(ctxt));
 164             match self.resolve_crate_root(ident).kind {
 165                 ModuleKind::Def(.., name) if name != kw::Empty => name,
 166                 _ => kw::Crate,
 167             }
 168         });
 169     }
 170
 171     fn visit_ast_fragment_with_placeholders(&mut self, expansion: ExpnId, fragment: &AstFragment) {
 172         // Integrate the new AST fragment into all the definition and module structures.
 173         // We are inside the `expansion` now, but other parent scope components are still the same.
 174         let parent_scope = ParentScope { expansion, ..self.invocation_parent_scopes[&expansion] };
 175         let output_macro_rules_scope = self.build_reduced_graph(fragment, parent_scope);
 176         self.output_macro_rules_scopes.insert(expansion, output_macro_rules_scope);
 177
 178         parent_scope.module.unexpanded_invocations.borrow_mut().remove(&expansion);
 179     }
 180
 181     fn register_builtin_macro(&mut self, name: Symbol, ext: SyntaxExtensionKind) {
 182         if self.builtin_macros.insert(name, BuiltinMacroState::NotYetSeen(ext)).is_some() {
 183             self.session
 184                 .diagnostic()
 185                 .bug(&format!("built-in macro `{}` was already registered", name));
 186         }
 187     }
 188
 189     // Create a new Expansion with a definition site of the provided module, or
 190     // a fake empty `#[no_implicit_prelude]` module if no module is provided.
 191     fn expansion_for_ast_pass(
 192         &mut self,
 193         call_site: Span,
 194         pass: AstPass,
 195         features: &[Symbol],
 196         parent_module_id: Option<NodeId>,
 197     ) -> ExpnId {
 198         let expn_id = ExpnId::fresh(Some(ExpnData::allow_unstable(
 199             ExpnKind::AstPass(pass),
 200             call_site,
 201             self.session.edition(),
 202             features.into(),
 203             None,
 204         )));
 205
 206         let parent_scope = if let Some(module_id) = parent_module_id {
 207             let parent_def_id = self.local_def_id(module_id);
 208             self.definitions.add_parent_module_of_macro_def(expn_id, parent_def_id.to_def_id());
 209             self.module_map[&parent_def_id]
 210         } else {
 211             self.definitions.add_parent_module_of_macro_def(
 212                 expn_id,
 213                 def_id::DefId::local(def_id::CRATE_DEF_INDEX),
 214             );
 215             self.empty_module
 216         };
 217         self.ast_transform_scopes.insert(expn_id, parent_scope);
 218         expn_id
 219     }
 220
 221     fn resolve_imports(&mut self) {
 222         ImportResolver { r: self }.resolve_imports()
 223     }
 224
 225     fn resolve_macro_invocation(
 226         &mut self,
 227         invoc: &Invocation,
 228         eager_expansion_root: ExpnId,
 229         force: bool,
 230     ) -> Result<Lrc<SyntaxExtension>, Indeterminate> {
 231         let invoc_id = invoc.expansion_data.id;
 232         let parent_scope = match self.invocation_parent_scopes.get(&invoc_id) {
 233             Some(parent_scope) => *parent_scope,
 234             None => {
 235                 // If there's no entry in the table, then we are resolving an eagerly expanded
 236                 // macro, which should inherit its parent scope from its eager expansion root -
 237                 // the macro that requested this eager expansion.
 238                 let parent_scope = *self
 239                     .invocation_parent_scopes
 240                     .get(&eager_expansion_root)
 241                     .expect("non-eager expansion without a parent scope");
 242                 self.invocation_parent_scopes.insert(invoc_id, parent_scope);
 243                 parent_scope
 244             }
 245         };
 246
 247         let (path, kind, inner_attr, derives) = match invoc.kind {
 248             InvocationKind::Attr { ref attr, ref derives, .. } => (
 249                 &attr.get_normal_item().path,
 250                 MacroKind::Attr,
 251                 attr.style == ast::AttrStyle::Inner,
 252                 self.arenas.alloc_ast_paths(derives),
 253             ),
 254             InvocationKind::Bang { ref mac, .. } => (&mac.path, MacroKind::Bang, false, &[][..]),
 255             InvocationKind::Derive { ref path, .. } => (path, MacroKind::Derive, false, &[][..]),
 256         };
 257
 258         // Derives are not included when `invocations` are collected, so we have to add them here.
 259         let parent_scope = &ParentScope { derives, ..parent_scope };
 260         let require_inert = !invoc.fragment_kind.supports_macro_expansion();
 261         let node_id = self.lint_node_id(eager_expansion_root);
 262         let (ext, res) = self.smart_resolve_macro_path(
 263             path,
 264             kind,
 265             require_inert,
 266             inner_attr,
 267             parent_scope,
 268             node_id,
 269             force,
 270         )?;
 271
 272         let span = invoc.span();
 273         invoc_id.set_expn_data(ext.expn_data(
 274             parent_scope.expansion,
 275             span,
 276             fast_print_path(path),
 277             res.opt_def_id(),
 278         ));
 279
 280         if let Res::Def(_, _) = res {
 281             let normal_module_def_id = self.macro_def_scope(invoc_id).nearest_parent_mod;
 282             self.definitions.add_parent_module_of_macro_def(invoc_id, normal_module_def_id);
 283
 284             // Gate macro attributes in `#[derive]` output.
 285             if !self.session.features_untracked().macro_attributes_in_derive_output
 286                 && kind == MacroKind::Attr
 287                 && ext.builtin_name != Some(sym::derive)
 288             {
 289                 let mut expn_id = parent_scope.expansion;
 290                 loop {
 291                     // Helper attr table is a quick way to determine whether the attr is `derive`.
 292                     if self.helper_attrs.contains_key(&expn_id) {
 293                         feature_err(
 294                             &self.session.parse_sess,
 295                             sym::macro_attributes_in_derive_output,
 296                             path.span,
 297                             "macro attributes in `#[derive]` output are unstable",
 298                         )
 299                         .emit();
 300                         break;
 301                     } else {
 302                         let expn_data = expn_id.expn_data();
 303                         match expn_data.kind {
 304                             ExpnKind::Root
 305                             | ExpnKind::Macro(MacroKind::Bang | MacroKind::Derive, _) => {
 306                                 break;
 307                             }
 308                             _ => expn_id = expn_data.parent,
 309                         }
 310                     }
 311                 }
 312             }
 313         }
 314
 315         Ok(ext)
 316     }
 317
 318     fn check_unused_macros(&mut self) {
 319         for (_, &(node_id, span)) in self.unused_macros.iter() {
 320             self.lint_buffer.buffer_lint(UNUSED_MACROS, node_id, span, "unused macro definition");
 321         }
 322     }
 323
 324     fn lint_node_id(&self, expn_id: ExpnId) -> NodeId {
 325         // FIXME - make this more precise. This currently returns the NodeId of the
 326         // nearest closing item - we should try to return the closest parent of the ExpnId
 327         self.invocation_parents
 328             .get(&expn_id)
 329             .map_or(ast::CRATE_NODE_ID, |id| self.def_id_to_node_id[*id])
 330     }
 331
 332     fn has_derive_copy(&self, expn_id: ExpnId) -> bool {
 333         self.containers_deriving_copy.contains(&expn_id)
 334     }
 335
 336     fn resolve_derives(
 337         &mut self,
 338         expn_id: ExpnId,
 339         derives: Vec<ast::Path>,
 340         force: bool,
 341     ) -> Result<(), Indeterminate> {
 342         // Block expansion of the container until we resolve all derives in it.
 343         // This is required for two reasons:
 344         // - Derive helper attributes are in scope for the item to which the `#[derive]`
 345         //   is applied, so they have to be produced by the container's expansion rather
 346         //   than by individual derives.
 347         // - Derives in the container need to know whether one of them is a built-in `Copy`.
 348         // FIXME: Try to cache intermediate results to avoid resolving same derives multiple times.
 349         let parent_scope = self.invocation_parent_scopes[&expn_id];
 350         let mut exts = Vec::new();
 351         let mut helper_attrs = Vec::new();
 352         let mut has_derive_copy = false;
 353         for path in derives {
 354             exts.push((
 355                 match self.resolve_macro_path(
 356                     &path,
 357                     Some(MacroKind::Derive),
 358                     &parent_scope,
 359                     true,
 360                     force,
 361                 ) {
 362                     Ok((Some(ext), _)) => {
 363                         let span =
 364                             path.segments.last().unwrap().ident.span.normalize_to_macros_2_0();
 365                         helper_attrs
 366                             .extend(ext.helper_attrs.iter().map(|name| Ident::new(*name, span)));
 367                         has_derive_copy |= ext.builtin_name == Some(sym::Copy);
 368                         ext
 369                     }
 370                     Ok(_) | Err(Determinacy::Determined) => self.dummy_ext(MacroKind::Derive),
 371                     Err(Determinacy::Undetermined) => return Err(Indeterminate),
 372                 },
 373                 path,
 374             ))
 375         }
 376         self.derive_resolutions.insert(expn_id, exts);
 377         self.helper_attrs.insert(expn_id, helper_attrs);
 378         // Mark this derive as having `Copy` either if it has `Copy` itself or if its parent derive
 379         // has `Copy`, to support cases like `#[derive(Clone, Copy)] #[derive(Debug)]`.
 380         if has_derive_copy || self.has_derive_copy(parent_scope.expansion) {
 381             self.containers_deriving_copy.insert(expn_id);
 382         }
 383         Ok(())
 384     }
 385
 386     fn take_derive_resolutions(
 387         &mut self,
 388         expn_id: ExpnId,
 389     ) -> Option<Vec<(Lrc<SyntaxExtension>, ast::Path)>> {
 390         self.derive_resolutions.remove(&expn_id)
 391     }
 392
 393     // The function that implements the resolution logic of `#[cfg_accessible(path)]`.
 394     // Returns true if the path can certainly be resolved in one of three namespaces,
 395     // returns false if the path certainly cannot be resolved in any of the three namespaces.
 396     // Returns `Indeterminate` if we cannot give a certain answer yet.
 397     fn cfg_accessible(&mut self, expn_id: ExpnId, path: &ast::Path) -> Result<bool, Indeterminate> {
 398         let span = path.span;
 399         let path = &Segment::from_path(path);
 400         let parent_scope = self.invocation_parent_scopes[&expn_id];
 401
 402         let mut indeterminate = false;
 403         for ns in [TypeNS, ValueNS, MacroNS].iter().copied() {
 404             match self.resolve_path(path, Some(ns), &parent_scope, false, span, CrateLint::No) {
 405                 PathResult::Module(ModuleOrUniformRoot::Module(_)) => return Ok(true),
 406                 PathResult::NonModule(partial_res) if partial_res.unresolved_segments() == 0 => {
 407                     return Ok(true);
 408                 }
 409                 PathResult::Indeterminate => indeterminate = true,
 410                 // FIXME: `resolve_path` is not ready to report partially resolved paths
 411                 // correctly, so we just report an error if the path was reported as unresolved.
 412                 // This needs to be fixed for `cfg_accessible` to be useful.
 413                 PathResult::NonModule(..) | PathResult::Failed { .. } => {}
 414                 PathResult::Module(_) => panic!("unexpected path resolution"),
 415             }
 416         }
 417
 418         if indeterminate {
 419             return Err(Indeterminate);
 420         }
 421
 422         self.session
 423             .struct_span_err(span, "not sure whether the path is accessible or not")
 424             .span_note(span, "`cfg_accessible` is not fully implemented")
 425             .emit();
 426         Ok(false)
 427     }
 428 }
 429
 430 impl<'a> Resolver<'a> {
 431     /// Resolve macro path with error reporting and recovery.
 432     /// Uses dummy syntax extensions for unresolved macros or macros with unexpected resolutions
 433     /// for better error recovery.
 434     fn smart_resolve_macro_path(
 435         &mut self,
 436         path: &ast::Path,
 437         kind: MacroKind,
 438         require_inert: bool,
 439         inner_attr: bool,
 440         parent_scope: &ParentScope<'a>,
 441         node_id: NodeId,
 442         force: bool,
 443     ) -> Result<(Lrc<SyntaxExtension>, Res), Indeterminate> {
 444         let (ext, res) = match self.resolve_macro_path(path, Some(kind), parent_scope, true, force)
 445         {
 446             Ok((Some(ext), res)) => (ext, res),
 447             Ok((None, res)) => (self.dummy_ext(kind), res),
 448             Err(Determinacy::Determined) => (self.dummy_ext(kind), Res::Err),
 449             Err(Determinacy::Undetermined) => return Err(Indeterminate),
 450         };
 451
 452         // Report errors for the resolved macro.
 453         for segment in &path.segments {
 454             if let Some(args) = &segment.args {
 455                 self.session.span_err(args.span(), "generic arguments in macro path");
 456             }
 457             if kind == MacroKind::Attr && segment.ident.as_str().starts_with("rustc") {
 458                 self.session.span_err(
 459                     segment.ident.span,
 460                     "attributes starting with `rustc` are reserved for use by the `rustc` compiler",
 461                 );
 462             }
 463         }
 464
 465         match res {
 466             Res::Def(DefKind::Macro(_), def_id) => {
 467                 if let Some(def_id) = def_id.as_local() {
 468                     self.unused_macros.remove(&def_id);
 469                     if self.proc_macro_stubs.contains(&def_id) {
 470                         self.session.span_err(
 471                             path.span,
 472                             "can't use a procedural macro from the same crate that defines it",
 473                         );
 474                     }
 475                 }
 476             }
 477             Res::NonMacroAttr(..) | Res::Err => {}
 478             _ => panic!("expected `DefKind::Macro` or `Res::NonMacroAttr`"),
 479         };
 480
 481         self.check_stability_and_deprecation(&ext, path, node_id);
 482
 483         let unexpected_res = if ext.macro_kind() != kind {
 484             Some((kind.article(), kind.descr_expected()))
 485         } else if require_inert && matches!(res, Res::Def(..)) {
 486             Some(("a", "non-macro attribute"))
 487         } else {
 488             None
 489         };
 490         if let Some((article, expected)) = unexpected_res {
 491             let path_str = pprust::path_to_string(path);
 492             let msg = format!("expected {}, found {} `{}`", expected, res.descr(), path_str);
 493             self.session
 494                 .struct_span_err(path.span, &msg)
 495                 .span_label(path.span, format!("not {} {}", article, expected))
 496                 .emit();
 497             return Ok((self.dummy_ext(kind), Res::Err));
 498         }
 499
 500         // We are trying to avoid reporting this error if other related errors were reported.
 501         if res != Res::Err
 502             && inner_attr
 503             && !self.session.features_untracked().custom_inner_attributes
 504         {
 505             let msg = match res {
 506                 Res::Def(..) => "inner macro attributes are unstable",
 507                 Res::NonMacroAttr(..) => "custom inner attributes are unstable",
 508                 _ => unreachable!(),
 509             };
 510             if path == &sym::test {
 511                 self.session.parse_sess.buffer_lint(SOFT_UNSTABLE, path.span, node_id, msg);
 512             } else {
 513                 feature_err(&self.session.parse_sess, sym::custom_inner_attributes, path.span, msg)
 514                     .emit();
 515             }
 516         }
 517
 518         Ok((ext, res))
 519     }
 520
 521     pub fn resolve_macro_path(
 522         &mut self,
 523         path: &ast::Path,
 524         kind: Option<MacroKind>,
 525         parent_scope: &ParentScope<'a>,
 526         trace: bool,
 527         force: bool,
 528     ) -> Result<(Option<Lrc<SyntaxExtension>>, Res), Determinacy> {
 529         let path_span = path.span;
 530         let mut path = Segment::from_path(path);
 531
 532         // Possibly apply the macro helper hack
 533         if kind == Some(MacroKind::Bang)
 534             && path.len() == 1
 535             && path[0].ident.span.ctxt().outer_expn_data().local_inner_macros
 536         {
 537             let root = Ident::new(kw::DollarCrate, path[0].ident.span);
 538             path.insert(0, Segment::from_ident(root));
 539         }
 540
 541         let res = if path.len() > 1 {
 542             let res = match self.resolve_path(
 543                 &path,
 544                 Some(MacroNS),
 545                 parent_scope,
 546                 false,
 547                 path_span,
 548                 CrateLint::No,
 549             ) {
 550                 PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 => {
 551                     Ok(path_res.base_res())
 552                 }
 553                 PathResult::Indeterminate if !force => return Err(Determinacy::Undetermined),
 554                 PathResult::NonModule(..)
 555                 | PathResult::Indeterminate
 556                 | PathResult::Failed { .. } => Err(Determinacy::Determined),
 557                 PathResult::Module(..) => unreachable!(),
 558             };
 559
 560             if trace {
 561                 let kind = kind.expect("macro kind must be specified if tracing is enabled");
 562                 self.multi_segment_macro_resolutions.push((
 563                     path,
 564                     path_span,
 565                     kind,
 566                     *parent_scope,
 567                     res.ok(),
 568                 ));
 569             }
 570
 571             self.prohibit_imported_non_macro_attrs(None, res.ok(), path_span);
 572             res
 573         } else {
 574             let scope_set = kind.map_or(ScopeSet::All(MacroNS, false), ScopeSet::Macro);
 575             let binding = self.early_resolve_ident_in_lexical_scope(
 576                 path[0].ident,
 577                 scope_set,
 578                 parent_scope,
 579                 false,
 580                 force,
 581                 path_span,
 582             );
 583             if let Err(Determinacy::Undetermined) = binding {
 584                 return Err(Determinacy::Undetermined);
 585             }
 586
 587             if trace {
 588                 let kind = kind.expect("macro kind must be specified if tracing is enabled");
 589                 self.single_segment_macro_resolutions.push((
 590                     path[0].ident,
 591                     kind,
 592                     *parent_scope,
 593                     binding.ok(),
 594                 ));
 595             }
 596
 597             let res = binding.map(|binding| binding.res());
 598             self.prohibit_imported_non_macro_attrs(binding.ok(), res.ok(), path_span);
 599             res
 600         };
 601
 602         res.map(|res| (self.get_macro(res), res))
 603     }
 604
 605     // Resolve an identifier in lexical scope.
 606     // This is a variation of `fn resolve_ident_in_lexical_scope` that can be run during
 607     // expansion and import resolution (perhaps they can be merged in the future).
 608     // The function is used for resolving initial segments of macro paths (e.g., `foo` in
 609     // `foo::bar!(); or `foo!();`) and also for import paths on 2018 edition.
 610     crate fn early_resolve_ident_in_lexical_scope(
 611         &mut self,
 612         orig_ident: Ident,
 613         scope_set: ScopeSet,
 614         parent_scope: &ParentScope<'a>,
 615         record_used: bool,
 616         force: bool,
 617         path_span: Span,
 618     ) -> Result<&'a NameBinding<'a>, Determinacy> {
 619         bitflags::bitflags! {
 620             struct Flags: u8 {
 621                 const MACRO_RULES          = 1 << 0;
 622                 const MODULE               = 1 << 1;
 623                 const MISC_SUGGEST_CRATE   = 1 << 2;
 624                 const MISC_SUGGEST_SELF    = 1 << 3;
 625                 const MISC_FROM_PRELUDE    = 1 << 4;
 626             }
 627         }
 628
 629         assert!(force || !record_used); // `record_used` implies `force`
 630
 631         // Make sure `self`, `super` etc produce an error when passed to here.
 632         if orig_ident.is_path_segment_keyword() {
 633             return Err(Determinacy::Determined);
 634         }
 635
 636         let (ns, macro_kind, is_import) = match scope_set {
 637             ScopeSet::All(ns, is_import) => (ns, None, is_import),
 638             ScopeSet::AbsolutePath(ns) => (ns, None, false),
 639             ScopeSet::Macro(macro_kind) => (MacroNS, Some(macro_kind), false),
 640         };
 641
 642         // This is *the* result, resolution from the scope closest to the resolved identifier.
 643         // However, sometimes this result is "weak" because it comes from a glob import or
 644         // a macro expansion, and in this case it cannot shadow names from outer scopes, e.g.
 645         // mod m { ... } // solution in outer scope
 646         // {
 647         //     use prefix::*; // imports another `m` - innermost solution
 648         //                    // weak, cannot shadow the outer `m`, need to report ambiguity error
 649         //     m::mac!();
 650         // }
 651         // So we have to save the innermost solution and continue searching in outer scopes
 652         // to detect potential ambiguities.
 653         let mut innermost_result: Option<(&NameBinding<'_>, Flags)> = None;
 654         let mut determinacy = Determinacy::Determined;
 655
 656         // Go through all the scopes and try to resolve the name.
 657         let break_result = self.visit_scopes(
 658             scope_set,
 659             parent_scope,
 660             orig_ident.span.ctxt(),
 661             |this, scope, use_prelude, ctxt| {
 662                 let ident = Ident::new(orig_ident.name, orig_ident.span.with_ctxt(ctxt));
 663                 let ok = |res, span, arenas| {
 664                     Ok((
 665                         (res, ty::Visibility::Public, span, ExpnId::root()).to_name_binding(arenas),
 666                         Flags::empty(),
 667                     ))
 668                 };
 669                 let result = match scope {
 670                     Scope::DeriveHelpers(expn_id) => {
 671                         if let Some(attr) = this
 672                             .helper_attrs
 673                             .get(&expn_id)
 674                             .and_then(|attrs| attrs.iter().rfind(|i| ident == **i))
 675                         {
 676                             let binding = (
 677                                 Res::NonMacroAttr(NonMacroAttrKind::DeriveHelper),
 678                                 ty::Visibility::Public,
 679                                 attr.span,
 680                                 expn_id,
 681                             )
 682                                 .to_name_binding(this.arenas);
 683                             Ok((binding, Flags::empty()))
 684                         } else {
 685                             Err(Determinacy::Determined)
 686                         }
 687                     }
 688                     Scope::DeriveHelpersCompat => {
 689                         let mut result = Err(Determinacy::Determined);
 690                         for derive in parent_scope.derives {
 691                             let parent_scope = &ParentScope { derives: &[], ..*parent_scope };
 692                             match this.resolve_macro_path(
 693                                 derive,
 694                                 Some(MacroKind::Derive),
 695                                 parent_scope,
 696                                 true,
 697                                 force,
 698                             ) {
 699                                 Ok((Some(ext), _)) => {
 700                                     if ext.helper_attrs.contains(&ident.name) {
 701                                         result = ok(
 702                                             Res::NonMacroAttr(NonMacroAttrKind::DeriveHelperCompat),
 703                                             derive.span,
 704                                             this.arenas,
 705                                         );
 706                                         break;
 707                                     }
 708                                 }
 709                                 Ok(_) | Err(Determinacy::Determined) => {}
 710                                 Err(Determinacy::Undetermined) => {
 711                                     result = Err(Determinacy::Undetermined)
 712                                 }
 713                             }
 714                         }
 715                         result
 716                     }
 717                     Scope::MacroRules(macro_rules_scope) => match macro_rules_scope.get() {
 718                         MacroRulesScope::Binding(macro_rules_binding)
 719                             if ident == macro_rules_binding.ident =>
 720                         {
 721                             Ok((macro_rules_binding.binding, Flags::MACRO_RULES))
 722                         }
 723                         MacroRulesScope::Invocation(_) => Err(Determinacy::Undetermined),
 724                         _ => Err(Determinacy::Determined),
 725                     },
 726                     Scope::CrateRoot => {
 727                         let root_ident = Ident::new(kw::PathRoot, ident.span);
 728                         let root_module = this.resolve_crate_root(root_ident);
 729                         let binding = this.resolve_ident_in_module_ext(
 730                             ModuleOrUniformRoot::Module(root_module),
 731                             ident,
 732                             ns,
 733                             parent_scope,
 734                             record_used,
 735                             path_span,
 736                         );
 737                         match binding {
 738                             Ok(binding) => Ok((binding, Flags::MODULE | Flags::MISC_SUGGEST_CRATE)),
 739                             Err((Determinacy::Undetermined, Weak::No)) => {
 740                                 return Some(Err(Determinacy::determined(force)));
 741                             }
 742                             Err((Determinacy::Undetermined, Weak::Yes)) => {
 743                                 Err(Determinacy::Undetermined)
 744                             }
 745                             Err((Determinacy::Determined, _)) => Err(Determinacy::Determined),
 746                         }
 747                     }
 748                     Scope::Module(module) => {
 749                         let adjusted_parent_scope = &ParentScope { module, ..*parent_scope };
 750                         let binding = this.resolve_ident_in_module_unadjusted_ext(
 751                             ModuleOrUniformRoot::Module(module),
 752                             ident,
 753                             ns,
 754                             adjusted_parent_scope,
 755                             true,
 756                             record_used,
 757                             path_span,
 758                         );
 759                         match binding {
 760                             Ok(binding) => {
 761                                 let misc_flags = if ptr::eq(module, this.graph_root) {
 762                                     Flags::MISC_SUGGEST_CRATE
 763                                 } else if module.is_normal() {
 764                                     Flags::MISC_SUGGEST_SELF
 765                                 } else {
 766                                     Flags::empty()
 767                                 };
 768                                 Ok((binding, Flags::MODULE | misc_flags))
 769                             }
 770                             Err((Determinacy::Undetermined, Weak::No)) => {
 771                                 return Some(Err(Determinacy::determined(force)));
 772                             }
 773                             Err((Determinacy::Undetermined, Weak::Yes)) => {
 774                                 Err(Determinacy::Undetermined)
 775                             }
 776                             Err((Determinacy::Determined, _)) => Err(Determinacy::Determined),
 777                         }
 778                     }
 779                     Scope::RegisteredAttrs => match this.registered_attrs.get(&ident).cloned() {
 780                         Some(ident) => ok(
 781                             Res::NonMacroAttr(NonMacroAttrKind::Registered),
 782                             ident.span,
 783                             this.arenas,
 784                         ),
 785                         None => Err(Determinacy::Determined),
 786                     },
 787                     Scope::MacroUsePrelude => {
 788                         match this.macro_use_prelude.get(&ident.name).cloned() {
 789                             Some(binding) => Ok((binding, Flags::MISC_FROM_PRELUDE)),
 790                             None => Err(Determinacy::determined(
 791                                 this.graph_root.unexpanded_invocations.borrow().is_empty(),
 792                             )),
 793                         }
 794                     }
 795                     Scope::BuiltinAttrs => {
 796                         if is_builtin_attr_name(ident.name) {
 797                             ok(
 798                                 Res::NonMacroAttr(NonMacroAttrKind::Builtin(ident.name)),
 799                                 DUMMY_SP,
 800                                 this.arenas,
 801                             )
 802                         } else {
 803                             Err(Determinacy::Determined)
 804                         }
 805                     }
 806                     Scope::ExternPrelude => match this.extern_prelude_get(ident, !record_used) {
 807                         Some(binding) => Ok((binding, Flags::empty())),
 808                         None => Err(Determinacy::determined(
 809                             this.graph_root.unexpanded_invocations.borrow().is_empty(),
 810                         )),
 811                     },
 812                     Scope::ToolPrelude => match this.registered_tools.get(&ident).cloned() {
 813                         Some(ident) => ok(Res::ToolMod, ident.span, this.arenas),
 814                         None => Err(Determinacy::Determined),
 815                     },
 816                     Scope::StdLibPrelude => {
 817                         let mut result = Err(Determinacy::Determined);
 818                         if let Some(prelude) = this.prelude {
 819                             if let Ok(binding) = this.resolve_ident_in_module_unadjusted(
 820                                 ModuleOrUniformRoot::Module(prelude),
 821                                 ident,
 822                                 ns,
 823                                 parent_scope,
 824                                 false,
 825                                 path_span,
 826                             ) {
 827                                 if use_prelude || this.is_builtin_macro(binding.res()) {
 828                                     result = Ok((binding, Flags::MISC_FROM_PRELUDE));
 829                                 }
 830                             }
 831                         }
 832                         result
 833                     }
 834                     Scope::BuiltinTypes => match PrimTy::from_name(ident.name) {
 835                         Some(prim_ty) => ok(Res::PrimTy(prim_ty), DUMMY_SP, this.arenas),
 836                         None => Err(Determinacy::Determined),
 837                     },
 838                 };
 839
 840                 match result {
 841                     Ok((binding, flags))
 842                         if sub_namespace_match(binding.macro_kind(), macro_kind) =>
 843                     {
 844                         if !record_used {
 845                             return Some(Ok(binding));
 846                         }
 847
 848                         if let Some((innermost_binding, innermost_flags)) = innermost_result {
 849                             // Found another solution, if the first one was "weak", report an error.
 850                             let (res, innermost_res) = (binding.res(), innermost_binding.res());
 851                             if res != innermost_res {
 852                                 let is_builtin = |res| {
 853                                     matches!(res, Res::NonMacroAttr(NonMacroAttrKind::Builtin(..)))
 854                                 };
 855                                 let derive_helper =
 856                                     Res::NonMacroAttr(NonMacroAttrKind::DeriveHelper);
 857                                 let derive_helper_compat =
 858                                     Res::NonMacroAttr(NonMacroAttrKind::DeriveHelperCompat);
 859
 860                                 let ambiguity_error_kind = if is_import {
 861                                     Some(AmbiguityKind::Import)
 862                                 } else if is_builtin(innermost_res) || is_builtin(res) {
 863                                     Some(AmbiguityKind::BuiltinAttr)
 864                                 } else if innermost_res == derive_helper_compat
 865                                     || res == derive_helper_compat && innermost_res != derive_helper
 866                                 {
 867                                     Some(AmbiguityKind::DeriveHelper)
 868                                 } else if innermost_flags.contains(Flags::MACRO_RULES)
 869                                     && flags.contains(Flags::MODULE)
 870                                     && !this.disambiguate_macro_rules_vs_modularized(
 871                                         innermost_binding,
 872                                         binding,
 873                                     )
 874                                     || flags.contains(Flags::MACRO_RULES)
 875                                         && innermost_flags.contains(Flags::MODULE)
 876                                         && !this.disambiguate_macro_rules_vs_modularized(
 877                                             binding,
 878                                             innermost_binding,
 879                                         )
 880                                 {
 881                                     Some(AmbiguityKind::MacroRulesVsModularized)
 882                                 } else if innermost_binding.is_glob_import() {
 883                                     Some(AmbiguityKind::GlobVsOuter)
 884                                 } else if innermost_binding
 885                                     .may_appear_after(parent_scope.expansion, binding)
 886                                 {
 887                                     Some(AmbiguityKind::MoreExpandedVsOuter)
 888                                 } else {
 889                                     None
 890                                 };
 891                                 if let Some(kind) = ambiguity_error_kind {
 892                                     let misc = |f: Flags| {
 893                                         if f.contains(Flags::MISC_SUGGEST_CRATE) {
 894                                             AmbiguityErrorMisc::SuggestCrate
 895                                         } else if f.contains(Flags::MISC_SUGGEST_SELF) {
 896                                             AmbiguityErrorMisc::SuggestSelf
 897                                         } else if f.contains(Flags::MISC_FROM_PRELUDE) {
 898                                             AmbiguityErrorMisc::FromPrelude
 899                                         } else {
 900                                             AmbiguityErrorMisc::None
 901                                         }
 902                                     };
 903                                     this.ambiguity_errors.push(AmbiguityError {
 904                                         kind,
 905                                         ident: orig_ident,
 906                                         b1: innermost_binding,
 907                                         b2: binding,
 908                                         misc1: misc(innermost_flags),
 909                                         misc2: misc(flags),
 910                                     });
 911                                     return Some(Ok(innermost_binding));
 912                                 }
 913                             }
 914                         } else {
 915                             // Found the first solution.
 916                             innermost_result = Some((binding, flags));
 917                         }
 918                     }
 919                     Ok(..) | Err(Determinacy::Determined) => {}
 920                     Err(Determinacy::Undetermined) => determinacy = Determinacy::Undetermined,
 921                 }
 922
 923                 None
 924             },
 925         );
 926
 927         if let Some(break_result) = break_result {
 928             return break_result;
 929         }
 930
 931         // The first found solution was the only one, return it.
 932         if let Some((binding, _)) = innermost_result {
 933             return Ok(binding);
 934         }
 935
 936         Err(Determinacy::determined(determinacy == Determinacy::Determined || force))
 937     }
 938
 939     crate fn finalize_macro_resolutions(&mut self) {
 940         let check_consistency = |this: &mut Self,
 941                                  path: &[Segment],
 942                                  span,
 943                                  kind: MacroKind,
 944                                  initial_res: Option<Res>,
 945                                  res: Res| {
 946             if let Some(initial_res) = initial_res {
 947                 if res != initial_res {
 948                     // Make sure compilation does not succeed if preferred macro resolution
 949                     // has changed after the macro had been expanded. In theory all such
 950                     // situations should be reported as errors, so this is a bug.
 951                     this.session.delay_span_bug(span, "inconsistent resolution for a macro");
 952                 }
 953             } else {
 954                 // It's possible that the macro was unresolved (indeterminate) and silently
 955                 // expanded into a dummy fragment for recovery during expansion.
 956                 // Now, post-expansion, the resolution may succeed, but we can't change the
 957                 // past and need to report an error.
 958                 // However, non-speculative `resolve_path` can successfully return private items
 959                 // even if speculative `resolve_path` returned nothing previously, so we skip this
 960                 // less informative error if the privacy error is reported elsewhere.
 961                 if this.privacy_errors.is_empty() {
 962                     let msg = format!(
 963                         "cannot determine resolution for the {} `{}`",
 964                         kind.descr(),
 965                         Segment::names_to_string(path)
 966                     );
 967                     let msg_note = "import resolution is stuck, try simplifying macro imports";
 968                     this.session.struct_span_err(span, &msg).note(msg_note).emit();
 969                 }
 970             }
 971         };
 972
 973         let macro_resolutions = mem::take(&mut self.multi_segment_macro_resolutions);
 974         for (mut path, path_span, kind, parent_scope, initial_res) in macro_resolutions {
 975             // FIXME: Path resolution will ICE if segment IDs present.
 976             for seg in &mut path {
 977                 seg.id = None;
 978             }
 979             match self.resolve_path(
 980                 &path,
 981                 Some(MacroNS),
 982                 &parent_scope,
 983                 true,
 984                 path_span,
 985                 CrateLint::No,
 986             ) {
 987                 PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 => {
 988                     let res = path_res.base_res();
 989                     check_consistency(self, &path, path_span, kind, initial_res, res);
 990                 }
 991                 path_res @ PathResult::NonModule(..) | path_res @ PathResult::Failed { .. } => {
 992                     let (span, label) = if let PathResult::Failed { span, label, .. } = path_res {
 993                         (span, label)
 994                     } else {
 995                         (
 996                             path_span,
 997                             format!(
 998                                 "partially resolved path in {} {}",
 999                                 kind.article(),
1000                                 kind.descr()
1001                             ),
1002                         )
1003                     };
1004                     self.report_error(
1005                         span,
1006                         ResolutionError::FailedToResolve { label, suggestion: None },
1007                     );
1008                 }
1009                 PathResult::Module(..) | PathResult::Indeterminate => unreachable!(),
1010             }
1011         }
1012
1013         let macro_resolutions = mem::take(&mut self.single_segment_macro_resolutions);
1014         for (ident, kind, parent_scope, initial_binding) in macro_resolutions {
1015             match self.early_resolve_ident_in_lexical_scope(
1016                 ident,
1017                 ScopeSet::Macro(kind),
1018                 &parent_scope,
1019                 true,
1020                 true,
1021                 ident.span,
1022             ) {
1023                 Ok(binding) => {
1024                     let initial_res = initial_binding.map(|initial_binding| {
1025                         self.record_use(ident, MacroNS, initial_binding, false);
1026                         initial_binding.res()
1027                     });
1028                     let res = binding.res();
1029                     let seg = Segment::from_ident(ident);
1030                     check_consistency(self, &[seg], ident.span, kind, initial_res, res);
1031                     if res == Res::NonMacroAttr(NonMacroAttrKind::DeriveHelperCompat) {
1032                         self.lint_buffer.buffer_lint_with_diagnostic(
1033                             LEGACY_DERIVE_HELPERS,
1034                             self.lint_node_id(parent_scope.expansion),
1035                             ident.span,
1036                             "derive helper attribute is used before it is introduced",
1037                             BuiltinLintDiagnostics::LegacyDeriveHelpers(binding.span),
1038                         );
1039                     }
1040                 }
1041                 Err(..) => {
1042                     let expected = kind.descr_expected();
1043                     let msg = format!("cannot find {} `{}` in this scope", expected, ident);
1044                     let mut err = self.session.struct_span_err(ident.span, &msg);
1045                     self.unresolved_macro_suggestions(&mut err, kind, &parent_scope, ident);
1046                     err.emit();
1047                 }
1048             }
1049         }
1050
1051         let builtin_attrs = mem::take(&mut self.builtin_attrs);
1052         for (ident, parent_scope) in builtin_attrs {
1053             let _ = self.early_resolve_ident_in_lexical_scope(
1054                 ident,
1055                 ScopeSet::Macro(MacroKind::Attr),
1056                 &parent_scope,
1057                 true,
1058                 true,
1059                 ident.span,
1060             );
1061         }
1062     }
1063
1064     fn check_stability_and_deprecation(
1065         &mut self,
1066         ext: &SyntaxExtension,
1067         path: &ast::Path,
1068         node_id: NodeId,
1069     ) {
1070         let span = path.span;
1071         if let Some(stability) = &ext.stability {
1072             if let StabilityLevel::Unstable { reason, issue, is_soft } = stability.level {
1073                 let feature = stability.feature;
1074                 if !self.active_features.contains(&feature) && !span.allows_unstable(feature) {
1075                     let lint_buffer = &mut self.lint_buffer;
1076                     let soft_handler =
1077                         |lint, span, msg: &_| lint_buffer.buffer_lint(lint, node_id, span, msg);
1078                     stability::report_unstable(
1079                         self.session,
1080                         feature,
1081                         reason,
1082                         issue,
1083                         is_soft,
1084                         span,
1085                         soft_handler,
1086                     );
1087                 }
1088             }
1089         }
1090         if let Some(depr) = &ext.deprecation {
1091             let path = pprust::path_to_string(&path);
1092             let (message, lint) = stability::deprecation_message(depr, "macro", &path);
1093             stability::early_report_deprecation(
1094                 &mut self.lint_buffer,
1095                 &message,
1096                 depr.suggestion,
1097                 lint,
1098                 span,
1099                 node_id,
1100             );
1101         }
1102     }
1103
1104     fn prohibit_imported_non_macro_attrs(
1105         &self,
1106         binding: Option<&'a NameBinding<'a>>,
1107         res: Option<Res>,
1108         span: Span,
1109     ) {
1110         if let Some(Res::NonMacroAttr(kind)) = res {
1111             if kind != NonMacroAttrKind::Tool && binding.map_or(true, |b| b.is_import()) {
1112                 let msg =
1113                     format!("cannot use {} {} through an import", kind.article(), kind.descr());
1114                 let mut err = self.session.struct_span_err(span, &msg);
1115                 if let Some(binding) = binding {
1116                     err.span_note(binding.span, &format!("the {} imported here", kind.descr()));
1117                 }
1118                 err.emit();
1119             }
1120         }
1121     }
1122
1123     crate fn check_reserved_macro_name(&mut self, ident: Ident, res: Res) {
1124         // Reserve some names that are not quite covered by the general check
1125         // performed on `Resolver::builtin_attrs`.
1126         if ident.name == sym::cfg || ident.name == sym::cfg_attr {
1127             let macro_kind = self.get_macro(res).map(|ext| ext.macro_kind());
1128             if macro_kind.is_some() && sub_namespace_match(macro_kind, Some(MacroKind::Attr)) {
1129                 self.session.span_err(
1130                     ident.span,
1131                     &format!("name `{}` is reserved in attribute namespace", ident),
1132                 );
1133             }
1134         }
1135     }
1136
1137     /// Compile the macro into a `SyntaxExtension` and possibly replace
1138     /// its expander to a pre-defined one for built-in macros.
1139     crate fn compile_macro(&mut self, item: &ast::Item, edition: Edition) -> SyntaxExtension {
1140         let mut result = compile_declarative_macro(
1141             &self.session,
1142             self.session.features_untracked(),
1143             item,
1144             edition,
1145         );
1146
1147         if let Some(builtin_name) = result.builtin_name {
1148             // The macro was marked with `#[rustc_builtin_macro]`.
1149             if let Some(builtin_macro) = self.builtin_macros.get_mut(&builtin_name) {
1150                 // The macro is a built-in, replace its expander function
1151                 // while still taking everything else from the source code.
1152                 // If we already loaded this builtin macro, give a better error message than 'no such builtin macro'.
1153                 match mem::replace(builtin_macro, BuiltinMacroState::AlreadySeen(item.span)) {
1154                     BuiltinMacroState::NotYetSeen(ext) => result.kind = ext,
1155                     BuiltinMacroState::AlreadySeen(span) => {
1156                         struct_span_err!(
1157                             self.session,
1158                             item.span,
1159                             E0773,
1160                             "attempted to define built-in macro more than once"
1161                         )
1162                         .span_note(span, "previously defined here")
1163                         .emit();
1164                     }
1165                 }
1166             } else {
1167                 let msg = format!("cannot find a built-in macro with name `{}`", item.ident);
1168                 self.session.span_err(item.span, &msg);
1169             }
1170         }
1171
1172         result
1173     }
1174 }