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, InvocationRes, ResolverExpand};
  18 use rustc_expand::base::{SyntaxExtension, SyntaxExtensionKind};
  19 use rustc_expand::compile_declarative_macro;
  20 use rustc_expand::expand::{AstFragment, Invocation, InvocationKind};
  21 use rustc_feature::is_builtin_attr_name;
  22 use rustc_hir::def::{self, DefKind, NonMacroAttrKind};
  23 use rustc_hir::def_id;
  24 use rustc_hir::PrimTy;
  25 use rustc_middle::middle::stability;
  26 use rustc_middle::ty;
  27 use rustc_session::lint::builtin::{SOFT_UNSTABLE, UNUSED_MACROS};
  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<InvocationRes, 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, after_derive) = match invoc.kind {
 248             InvocationKind::Attr { ref attr, ref derives, after_derive, .. } => (
 249                 &attr.get_normal_item().path,
 250                 MacroKind::Attr,
 251                 attr.style == ast::AttrStyle::Inner,
 252                 self.arenas.alloc_ast_paths(derives),
 253                 after_derive,
 254             ),
 255             InvocationKind::Bang { ref mac, .. } => {
 256                 (&mac.path, MacroKind::Bang, false, &[][..], false)
 257             }
 258             InvocationKind::Derive { ref path, .. } => {
 259                 (path, MacroKind::Derive, false, &[][..], false)
 260             }
 261             InvocationKind::DeriveContainer { ref derives, .. } => {
 262                 // Block expansion of the container until we resolve all derives in it.
 263                 // This is required for two reasons:
 264                 // - Derive helper attributes are in scope for the item to which the `#[derive]`
 265                 //   is applied, so they have to be produced by the container's expansion rather
 266                 //   than by individual derives.
 267                 // - Derives in the container need to know whether one of them is a built-in `Copy`.
 268                 // FIXME: Try to avoid repeated resolutions for derives here and in expansion.
 269                 let mut exts = Vec::new();
 270                 let mut helper_attrs = Vec::new();
 271                 for path in derives {
 272                     exts.push(
 273                         match self.resolve_macro_path(
 274                             path,
 275                             Some(MacroKind::Derive),
 276                             &parent_scope,
 277                             true,
 278                             force,
 279                         ) {
 280                             Ok((Some(ext), _)) => {
 281                                 let span = path
 282                                     .segments
 283                                     .last()
 284                                     .unwrap()
 285                                     .ident
 286                                     .span
 287                                     .normalize_to_macros_2_0();
 288                                 helper_attrs.extend(
 289                                     ext.helper_attrs.iter().map(|name| Ident::new(*name, span)),
 290                                 );
 291                                 if ext.builtin_name == Some(sym::Copy) {
 292                                     self.containers_deriving_copy.insert(invoc_id);
 293                                 }
 294                                 ext
 295                             }
 296                             Ok(_) | Err(Determinacy::Determined) => {
 297                                 self.dummy_ext(MacroKind::Derive)
 298                             }
 299                             Err(Determinacy::Undetermined) => return Err(Indeterminate),
 300                         },
 301                     )
 302                 }
 303                 self.helper_attrs.insert(invoc_id, helper_attrs);
 304                 return Ok(InvocationRes::DeriveContainer(exts));
 305             }
 306         };
 307
 308         // Derives are not included when `invocations` are collected, so we have to add them here.
 309         let parent_scope = &ParentScope { derives, ..parent_scope };
 310         let require_inert = !invoc.fragment_kind.supports_macro_expansion();
 311         let node_id = self.lint_node_id(eager_expansion_root);
 312         let (ext, res) = self.smart_resolve_macro_path(
 313             path,
 314             kind,
 315             require_inert,
 316             inner_attr,
 317             parent_scope,
 318             node_id,
 319             force,
 320         )?;
 321
 322         let span = invoc.span();
 323         invoc_id.set_expn_data(ext.expn_data(
 324             parent_scope.expansion,
 325             span,
 326             fast_print_path(path),
 327             res.opt_def_id(),
 328         ));
 329
 330         if let Res::Def(_, _) = res {
 331             if after_derive {
 332                 self.session.span_err(span, "macro attributes must be placed before `#[derive]`");
 333             }
 334             let normal_module_def_id = self.macro_def_scope(invoc_id).nearest_parent_mod;
 335             self.definitions.add_parent_module_of_macro_def(invoc_id, normal_module_def_id);
 336         }
 337
 338         Ok(InvocationRes::Single(ext))
 339     }
 340
 341     fn check_unused_macros(&mut self) {
 342         for (_, &(node_id, span)) in self.unused_macros.iter() {
 343             self.lint_buffer.buffer_lint(UNUSED_MACROS, node_id, span, "unused macro definition");
 344         }
 345     }
 346
 347     fn lint_node_id(&mut self, expn_id: ExpnId) -> NodeId {
 348         // FIXME - make this more precise. This currently returns the NodeId of the
 349         // nearest closing item - we should try to return the closest parent of the ExpnId
 350         self.invocation_parents
 351             .get(&expn_id)
 352             .map_or(ast::CRATE_NODE_ID, |id| self.def_id_to_node_id[*id])
 353     }
 354
 355     fn has_derive_copy(&self, expn_id: ExpnId) -> bool {
 356         self.containers_deriving_copy.contains(&expn_id)
 357     }
 358
 359     // The function that implements the resolution logic of `#[cfg_accessible(path)]`.
 360     // Returns true if the path can certainly be resolved in one of three namespaces,
 361     // returns false if the path certainly cannot be resolved in any of the three namespaces.
 362     // Returns `Indeterminate` if we cannot give a certain answer yet.
 363     fn cfg_accessible(&mut self, expn_id: ExpnId, path: &ast::Path) -> Result<bool, Indeterminate> {
 364         let span = path.span;
 365         let path = &Segment::from_path(path);
 366         let parent_scope = self.invocation_parent_scopes[&expn_id];
 367
 368         let mut indeterminate = false;
 369         for ns in [TypeNS, ValueNS, MacroNS].iter().copied() {
 370             match self.resolve_path(path, Some(ns), &parent_scope, false, span, CrateLint::No) {
 371                 PathResult::Module(ModuleOrUniformRoot::Module(_)) => return Ok(true),
 372                 PathResult::NonModule(partial_res) if partial_res.unresolved_segments() == 0 => {
 373                     return Ok(true);
 374                 }
 375                 PathResult::Indeterminate => indeterminate = true,
 376                 // FIXME: `resolve_path` is not ready to report partially resolved paths
 377                 // correctly, so we just report an error if the path was reported as unresolved.
 378                 // This needs to be fixed for `cfg_accessible` to be useful.
 379                 PathResult::NonModule(..) | PathResult::Failed { .. } => {}
 380                 PathResult::Module(_) => panic!("unexpected path resolution"),
 381             }
 382         }
 383
 384         if indeterminate {
 385             return Err(Indeterminate);
 386         }
 387
 388         self.session
 389             .struct_span_err(span, "not sure whether the path is accessible or not")
 390             .span_note(span, "`cfg_accessible` is not fully implemented")
 391             .emit();
 392         Ok(false)
 393     }
 394 }
 395
 396 impl<'a> Resolver<'a> {
 397     /// Resolve macro path with error reporting and recovery.
 398     /// Uses dummy syntax extensions for unresolved macros or macros with unexpected resolutions
 399     /// for better error recovery.
 400     fn smart_resolve_macro_path(
 401         &mut self,
 402         path: &ast::Path,
 403         kind: MacroKind,
 404         require_inert: bool,
 405         inner_attr: bool,
 406         parent_scope: &ParentScope<'a>,
 407         node_id: NodeId,
 408         force: bool,
 409     ) -> Result<(Lrc<SyntaxExtension>, Res), Indeterminate> {
 410         let (ext, res) = match self.resolve_macro_path(path, Some(kind), parent_scope, true, force)
 411         {
 412             Ok((Some(ext), res)) => (ext, res),
 413             Ok((None, res)) => (self.dummy_ext(kind), res),
 414             Err(Determinacy::Determined) => (self.dummy_ext(kind), Res::Err),
 415             Err(Determinacy::Undetermined) => return Err(Indeterminate),
 416         };
 417
 418         // Report errors for the resolved macro.
 419         for segment in &path.segments {
 420             if let Some(args) = &segment.args {
 421                 self.session.span_err(args.span(), "generic arguments in macro path");
 422             }
 423             if kind == MacroKind::Attr && segment.ident.as_str().starts_with("rustc") {
 424                 self.session.span_err(
 425                     segment.ident.span,
 426                     "attributes starting with `rustc` are reserved for use by the `rustc` compiler",
 427                 );
 428             }
 429         }
 430
 431         match res {
 432             Res::Def(DefKind::Macro(_), def_id) => {
 433                 if let Some(def_id) = def_id.as_local() {
 434                     self.unused_macros.remove(&def_id);
 435                     if self.proc_macro_stubs.contains(&def_id) {
 436                         self.session.span_err(
 437                             path.span,
 438                             "can't use a procedural macro from the same crate that defines it",
 439                         );
 440                     }
 441                 }
 442             }
 443             Res::NonMacroAttr(..) | Res::Err => {}
 444             _ => panic!("expected `DefKind::Macro` or `Res::NonMacroAttr`"),
 445         };
 446
 447         self.check_stability_and_deprecation(&ext, path, node_id);
 448
 449         let unexpected_res = if ext.macro_kind() != kind {
 450             Some((kind.article(), kind.descr_expected()))
 451         } else if require_inert && matches!(res, Res::Def(..)) {
 452             Some(("a", "non-macro attribute"))
 453         } else {
 454             None
 455         };
 456         if let Some((article, expected)) = unexpected_res {
 457             let path_str = pprust::path_to_string(path);
 458             let msg = format!("expected {}, found {} `{}`", expected, res.descr(), path_str);
 459             self.session
 460                 .struct_span_err(path.span, &msg)
 461                 .span_label(path.span, format!("not {} {}", article, expected))
 462                 .emit();
 463             return Ok((self.dummy_ext(kind), Res::Err));
 464         }
 465
 466         // We are trying to avoid reporting this error if other related errors were reported.
 467         if res != Res::Err
 468             && inner_attr
 469             && !self.session.features_untracked().custom_inner_attributes
 470         {
 471             let msg = match res {
 472                 Res::Def(..) => "inner macro attributes are unstable",
 473                 Res::NonMacroAttr(..) => "custom inner attributes are unstable",
 474                 _ => unreachable!(),
 475             };
 476             if path == &sym::test {
 477                 self.session.parse_sess.buffer_lint(SOFT_UNSTABLE, path.span, node_id, msg);
 478             } else {
 479                 feature_err(&self.session.parse_sess, sym::custom_inner_attributes, path.span, msg)
 480                     .emit();
 481             }
 482         }
 483
 484         Ok((ext, res))
 485     }
 486
 487     pub fn resolve_macro_path(
 488         &mut self,
 489         path: &ast::Path,
 490         kind: Option<MacroKind>,
 491         parent_scope: &ParentScope<'a>,
 492         trace: bool,
 493         force: bool,
 494     ) -> Result<(Option<Lrc<SyntaxExtension>>, Res), Determinacy> {
 495         let path_span = path.span;
 496         let mut path = Segment::from_path(path);
 497
 498         // Possibly apply the macro helper hack
 499         if kind == Some(MacroKind::Bang)
 500             && path.len() == 1
 501             && path[0].ident.span.ctxt().outer_expn_data().local_inner_macros
 502         {
 503             let root = Ident::new(kw::DollarCrate, path[0].ident.span);
 504             path.insert(0, Segment::from_ident(root));
 505         }
 506
 507         let res = if path.len() > 1 {
 508             let res = match self.resolve_path(
 509                 &path,
 510                 Some(MacroNS),
 511                 parent_scope,
 512                 false,
 513                 path_span,
 514                 CrateLint::No,
 515             ) {
 516                 PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 => {
 517                     Ok(path_res.base_res())
 518                 }
 519                 PathResult::Indeterminate if !force => return Err(Determinacy::Undetermined),
 520                 PathResult::NonModule(..)
 521                 | PathResult::Indeterminate
 522                 | PathResult::Failed { .. } => Err(Determinacy::Determined),
 523                 PathResult::Module(..) => unreachable!(),
 524             };
 525
 526             if trace {
 527                 let kind = kind.expect("macro kind must be specified if tracing is enabled");
 528                 self.multi_segment_macro_resolutions.push((
 529                     path,
 530                     path_span,
 531                     kind,
 532                     *parent_scope,
 533                     res.ok(),
 534                 ));
 535             }
 536
 537             self.prohibit_imported_non_macro_attrs(None, res.ok(), path_span);
 538             res
 539         } else {
 540             let scope_set = kind.map_or(ScopeSet::All(MacroNS, false), ScopeSet::Macro);
 541             let binding = self.early_resolve_ident_in_lexical_scope(
 542                 path[0].ident,
 543                 scope_set,
 544                 parent_scope,
 545                 false,
 546                 force,
 547                 path_span,
 548             );
 549             if let Err(Determinacy::Undetermined) = binding {
 550                 return Err(Determinacy::Undetermined);
 551             }
 552
 553             if trace {
 554                 let kind = kind.expect("macro kind must be specified if tracing is enabled");
 555                 self.single_segment_macro_resolutions.push((
 556                     path[0].ident,
 557                     kind,
 558                     *parent_scope,
 559                     binding.ok(),
 560                 ));
 561             }
 562
 563             let res = binding.map(|binding| binding.res());
 564             self.prohibit_imported_non_macro_attrs(binding.ok(), res.ok(), path_span);
 565             res
 566         };
 567
 568         res.map(|res| (self.get_macro(res), res))
 569     }
 570
 571     // Resolve an identifier in lexical scope.
 572     // This is a variation of `fn resolve_ident_in_lexical_scope` that can be run during
 573     // expansion and import resolution (perhaps they can be merged in the future).
 574     // The function is used for resolving initial segments of macro paths (e.g., `foo` in
 575     // `foo::bar!(); or `foo!();`) and also for import paths on 2018 edition.
 576     crate fn early_resolve_ident_in_lexical_scope(
 577         &mut self,
 578         orig_ident: Ident,
 579         scope_set: ScopeSet,
 580         parent_scope: &ParentScope<'a>,
 581         record_used: bool,
 582         force: bool,
 583         path_span: Span,
 584     ) -> Result<&'a NameBinding<'a>, Determinacy> {
 585         bitflags::bitflags! {
 586             struct Flags: u8 {
 587                 const MACRO_RULES          = 1 << 0;
 588                 const MODULE               = 1 << 1;
 589                 const MISC_SUGGEST_CRATE   = 1 << 2;
 590                 const MISC_SUGGEST_SELF    = 1 << 3;
 591                 const MISC_FROM_PRELUDE    = 1 << 4;
 592             }
 593         }
 594
 595         assert!(force || !record_used); // `record_used` implies `force`
 596
 597         // Make sure `self`, `super` etc produce an error when passed to here.
 598         if orig_ident.is_path_segment_keyword() {
 599             return Err(Determinacy::Determined);
 600         }
 601
 602         let (ns, macro_kind, is_import) = match scope_set {
 603             ScopeSet::All(ns, is_import) => (ns, None, is_import),
 604             ScopeSet::AbsolutePath(ns) => (ns, None, false),
 605             ScopeSet::Macro(macro_kind) => (MacroNS, Some(macro_kind), false),
 606         };
 607
 608         // This is *the* result, resolution from the scope closest to the resolved identifier.
 609         // However, sometimes this result is "weak" because it comes from a glob import or
 610         // a macro expansion, and in this case it cannot shadow names from outer scopes, e.g.
 611         // mod m { ... } // solution in outer scope
 612         // {
 613         //     use prefix::*; // imports another `m` - innermost solution
 614         //                    // weak, cannot shadow the outer `m`, need to report ambiguity error
 615         //     m::mac!();
 616         // }
 617         // So we have to save the innermost solution and continue searching in outer scopes
 618         // to detect potential ambiguities.
 619         let mut innermost_result: Option<(&NameBinding<'_>, Flags)> = None;
 620         let mut determinacy = Determinacy::Determined;
 621
 622         // Go through all the scopes and try to resolve the name.
 623         let break_result = self.visit_scopes(
 624             scope_set,
 625             parent_scope,
 626             orig_ident.span.ctxt(),
 627             |this, scope, use_prelude, ctxt| {
 628                 let ident = Ident::new(orig_ident.name, orig_ident.span.with_ctxt(ctxt));
 629                 let ok = |res, span, arenas| {
 630                     Ok((
 631                         (res, ty::Visibility::Public, span, ExpnId::root()).to_name_binding(arenas),
 632                         Flags::empty(),
 633                     ))
 634                 };
 635                 let result = match scope {
 636                     Scope::DeriveHelpers(expn_id) => {
 637                         if let Some(attr) = this
 638                             .helper_attrs
 639                             .get(&expn_id)
 640                             .and_then(|attrs| attrs.iter().rfind(|i| ident == **i))
 641                         {
 642                             let binding = (
 643                                 Res::NonMacroAttr(NonMacroAttrKind::DeriveHelper),
 644                                 ty::Visibility::Public,
 645                                 attr.span,
 646                                 expn_id,
 647                             )
 648                                 .to_name_binding(this.arenas);
 649                             Ok((binding, Flags::empty()))
 650                         } else {
 651                             Err(Determinacy::Determined)
 652                         }
 653                     }
 654                     Scope::DeriveHelpersCompat => {
 655                         let mut result = Err(Determinacy::Determined);
 656                         for derive in parent_scope.derives {
 657                             let parent_scope = &ParentScope { derives: &[], ..*parent_scope };
 658                             match this.resolve_macro_path(
 659                                 derive,
 660                                 Some(MacroKind::Derive),
 661                                 parent_scope,
 662                                 true,
 663                                 force,
 664                             ) {
 665                                 Ok((Some(ext), _)) => {
 666                                     if ext.helper_attrs.contains(&ident.name) {
 667                                         result = ok(
 668                                             Res::NonMacroAttr(NonMacroAttrKind::DeriveHelperCompat),
 669                                             derive.span,
 670                                             this.arenas,
 671                                         );
 672                                         break;
 673                                     }
 674                                 }
 675                                 Ok(_) | Err(Determinacy::Determined) => {}
 676                                 Err(Determinacy::Undetermined) => {
 677                                     result = Err(Determinacy::Undetermined)
 678                                 }
 679                             }
 680                         }
 681                         result
 682                     }
 683                     Scope::MacroRules(macro_rules_scope) => match macro_rules_scope.get() {
 684                         MacroRulesScope::Binding(macro_rules_binding)
 685                             if ident == macro_rules_binding.ident =>
 686                         {
 687                             Ok((macro_rules_binding.binding, Flags::MACRO_RULES))
 688                         }
 689                         MacroRulesScope::Invocation(_) => Err(Determinacy::Undetermined),
 690                         _ => Err(Determinacy::Determined),
 691                     },
 692                     Scope::CrateRoot => {
 693                         let root_ident = Ident::new(kw::PathRoot, ident.span);
 694                         let root_module = this.resolve_crate_root(root_ident);
 695                         let binding = this.resolve_ident_in_module_ext(
 696                             ModuleOrUniformRoot::Module(root_module),
 697                             ident,
 698                             ns,
 699                             parent_scope,
 700                             record_used,
 701                             path_span,
 702                         );
 703                         match binding {
 704                             Ok(binding) => Ok((binding, Flags::MODULE | Flags::MISC_SUGGEST_CRATE)),
 705                             Err((Determinacy::Undetermined, Weak::No)) => {
 706                                 return Some(Err(Determinacy::determined(force)));
 707                             }
 708                             Err((Determinacy::Undetermined, Weak::Yes)) => {
 709                                 Err(Determinacy::Undetermined)
 710                             }
 711                             Err((Determinacy::Determined, _)) => Err(Determinacy::Determined),
 712                         }
 713                     }
 714                     Scope::Module(module) => {
 715                         let adjusted_parent_scope = &ParentScope { module, ..*parent_scope };
 716                         let binding = this.resolve_ident_in_module_unadjusted_ext(
 717                             ModuleOrUniformRoot::Module(module),
 718                             ident,
 719                             ns,
 720                             adjusted_parent_scope,
 721                             true,
 722                             record_used,
 723                             path_span,
 724                         );
 725                         match binding {
 726                             Ok(binding) => {
 727                                 let misc_flags = if ptr::eq(module, this.graph_root) {
 728                                     Flags::MISC_SUGGEST_CRATE
 729                                 } else if module.is_normal() {
 730                                     Flags::MISC_SUGGEST_SELF
 731                                 } else {
 732                                     Flags::empty()
 733                                 };
 734                                 Ok((binding, Flags::MODULE | misc_flags))
 735                             }
 736                             Err((Determinacy::Undetermined, Weak::No)) => {
 737                                 return Some(Err(Determinacy::determined(force)));
 738                             }
 739                             Err((Determinacy::Undetermined, Weak::Yes)) => {
 740                                 Err(Determinacy::Undetermined)
 741                             }
 742                             Err((Determinacy::Determined, _)) => Err(Determinacy::Determined),
 743                         }
 744                     }
 745                     Scope::RegisteredAttrs => match this.registered_attrs.get(&ident).cloned() {
 746                         Some(ident) => ok(
 747                             Res::NonMacroAttr(NonMacroAttrKind::Registered),
 748                             ident.span,
 749                             this.arenas,
 750                         ),
 751                         None => Err(Determinacy::Determined),
 752                     },
 753                     Scope::MacroUsePrelude => {
 754                         match this.macro_use_prelude.get(&ident.name).cloned() {
 755                             Some(binding) => Ok((binding, Flags::MISC_FROM_PRELUDE)),
 756                             None => Err(Determinacy::determined(
 757                                 this.graph_root.unexpanded_invocations.borrow().is_empty(),
 758                             )),
 759                         }
 760                     }
 761                     Scope::BuiltinAttrs => {
 762                         if is_builtin_attr_name(ident.name) {
 763                             ok(
 764                                 Res::NonMacroAttr(NonMacroAttrKind::Builtin(ident.name)),
 765                                 DUMMY_SP,
 766                                 this.arenas,
 767                             )
 768                         } else {
 769                             Err(Determinacy::Determined)
 770                         }
 771                     }
 772                     Scope::ExternPrelude => match this.extern_prelude_get(ident, !record_used) {
 773                         Some(binding) => Ok((binding, Flags::empty())),
 774                         None => Err(Determinacy::determined(
 775                             this.graph_root.unexpanded_invocations.borrow().is_empty(),
 776                         )),
 777                     },
 778                     Scope::ToolPrelude => match this.registered_tools.get(&ident).cloned() {
 779                         Some(ident) => ok(Res::ToolMod, ident.span, this.arenas),
 780                         None => Err(Determinacy::Determined),
 781                     },
 782                     Scope::StdLibPrelude => {
 783                         let mut result = Err(Determinacy::Determined);
 784                         if let Some(prelude) = this.prelude {
 785                             if let Ok(binding) = this.resolve_ident_in_module_unadjusted(
 786                                 ModuleOrUniformRoot::Module(prelude),
 787                                 ident,
 788                                 ns,
 789                                 parent_scope,
 790                                 false,
 791                                 path_span,
 792                             ) {
 793                                 if use_prelude || this.is_builtin_macro(binding.res()) {
 794                                     result = Ok((binding, Flags::MISC_FROM_PRELUDE));
 795                                 }
 796                             }
 797                         }
 798                         result
 799                     }
 800                     Scope::BuiltinTypes => match PrimTy::from_name(ident.name) {
 801                         Some(prim_ty) => ok(Res::PrimTy(prim_ty), DUMMY_SP, this.arenas),
 802                         None => Err(Determinacy::Determined),
 803                     },
 804                 };
 805
 806                 match result {
 807                     Ok((binding, flags))
 808                         if sub_namespace_match(binding.macro_kind(), macro_kind) =>
 809                     {
 810                         if !record_used {
 811                             return Some(Ok(binding));
 812                         }
 813
 814                         if let Some((innermost_binding, innermost_flags)) = innermost_result {
 815                             // Found another solution, if the first one was "weak", report an error.
 816                             let (res, innermost_res) = (binding.res(), innermost_binding.res());
 817                             if res != innermost_res {
 818                                 let is_builtin = |res| {
 819                                     matches!(res, Res::NonMacroAttr(NonMacroAttrKind::Builtin(..)))
 820                                 };
 821                                 let derive_helper_compat =
 822                                     Res::NonMacroAttr(NonMacroAttrKind::DeriveHelperCompat);
 823
 824                                 let ambiguity_error_kind = if is_import {
 825                                     Some(AmbiguityKind::Import)
 826                                 } else if is_builtin(innermost_res) || is_builtin(res) {
 827                                     Some(AmbiguityKind::BuiltinAttr)
 828                                 } else if innermost_res == derive_helper_compat
 829                                     || res == derive_helper_compat
 830                                 {
 831                                     Some(AmbiguityKind::DeriveHelper)
 832                                 } else if innermost_flags.contains(Flags::MACRO_RULES)
 833                                     && flags.contains(Flags::MODULE)
 834                                     && !this.disambiguate_macro_rules_vs_modularized(
 835                                         innermost_binding,
 836                                         binding,
 837                                     )
 838                                     || flags.contains(Flags::MACRO_RULES)
 839                                         && innermost_flags.contains(Flags::MODULE)
 840                                         && !this.disambiguate_macro_rules_vs_modularized(
 841                                             binding,
 842                                             innermost_binding,
 843                                         )
 844                                 {
 845                                     Some(AmbiguityKind::MacroRulesVsModularized)
 846                                 } else if innermost_binding.is_glob_import() {
 847                                     Some(AmbiguityKind::GlobVsOuter)
 848                                 } else if innermost_binding
 849                                     .may_appear_after(parent_scope.expansion, binding)
 850                                 {
 851                                     Some(AmbiguityKind::MoreExpandedVsOuter)
 852                                 } else {
 853                                     None
 854                                 };
 855                                 if let Some(kind) = ambiguity_error_kind {
 856                                     let misc = |f: Flags| {
 857                                         if f.contains(Flags::MISC_SUGGEST_CRATE) {
 858                                             AmbiguityErrorMisc::SuggestCrate
 859                                         } else if f.contains(Flags::MISC_SUGGEST_SELF) {
 860                                             AmbiguityErrorMisc::SuggestSelf
 861                                         } else if f.contains(Flags::MISC_FROM_PRELUDE) {
 862                                             AmbiguityErrorMisc::FromPrelude
 863                                         } else {
 864                                             AmbiguityErrorMisc::None
 865                                         }
 866                                     };
 867                                     this.ambiguity_errors.push(AmbiguityError {
 868                                         kind,
 869                                         ident: orig_ident,
 870                                         b1: innermost_binding,
 871                                         b2: binding,
 872                                         misc1: misc(innermost_flags),
 873                                         misc2: misc(flags),
 874                                     });
 875                                     return Some(Ok(innermost_binding));
 876                                 }
 877                             }
 878                         } else {
 879                             // Found the first solution.
 880                             innermost_result = Some((binding, flags));
 881                         }
 882                     }
 883                     Ok(..) | Err(Determinacy::Determined) => {}
 884                     Err(Determinacy::Undetermined) => determinacy = Determinacy::Undetermined,
 885                 }
 886
 887                 None
 888             },
 889         );
 890
 891         if let Some(break_result) = break_result {
 892             return break_result;
 893         }
 894
 895         // The first found solution was the only one, return it.
 896         if let Some((binding, _)) = innermost_result {
 897             return Ok(binding);
 898         }
 899
 900         Err(Determinacy::determined(determinacy == Determinacy::Determined || force))
 901     }
 902
 903     crate fn finalize_macro_resolutions(&mut self) {
 904         let check_consistency = |this: &mut Self,
 905                                  path: &[Segment],
 906                                  span,
 907                                  kind: MacroKind,
 908                                  initial_res: Option<Res>,
 909                                  res: Res| {
 910             if let Some(initial_res) = initial_res {
 911                 if res != initial_res {
 912                     // Make sure compilation does not succeed if preferred macro resolution
 913                     // has changed after the macro had been expanded. In theory all such
 914                     // situations should be reported as errors, so this is a bug.
 915                     this.session.delay_span_bug(span, "inconsistent resolution for a macro");
 916                 }
 917             } else {
 918                 // It's possible that the macro was unresolved (indeterminate) and silently
 919                 // expanded into a dummy fragment for recovery during expansion.
 920                 // Now, post-expansion, the resolution may succeed, but we can't change the
 921                 // past and need to report an error.
 922                 // However, non-speculative `resolve_path` can successfully return private items
 923                 // even if speculative `resolve_path` returned nothing previously, so we skip this
 924                 // less informative error if the privacy error is reported elsewhere.
 925                 if this.privacy_errors.is_empty() {
 926                     let msg = format!(
 927                         "cannot determine resolution for the {} `{}`",
 928                         kind.descr(),
 929                         Segment::names_to_string(path)
 930                     );
 931                     let msg_note = "import resolution is stuck, try simplifying macro imports";
 932                     this.session.struct_span_err(span, &msg).note(msg_note).emit();
 933                 }
 934             }
 935         };
 936
 937         let macro_resolutions = mem::take(&mut self.multi_segment_macro_resolutions);
 938         for (mut path, path_span, kind, parent_scope, initial_res) in macro_resolutions {
 939             // FIXME: Path resolution will ICE if segment IDs present.
 940             for seg in &mut path {
 941                 seg.id = None;
 942             }
 943             match self.resolve_path(
 944                 &path,
 945                 Some(MacroNS),
 946                 &parent_scope,
 947                 true,
 948                 path_span,
 949                 CrateLint::No,
 950             ) {
 951                 PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 => {
 952                     let res = path_res.base_res();
 953                     check_consistency(self, &path, path_span, kind, initial_res, res);
 954                 }
 955                 path_res @ PathResult::NonModule(..) | path_res @ PathResult::Failed { .. } => {
 956                     let (span, label) = if let PathResult::Failed { span, label, .. } = path_res {
 957                         (span, label)
 958                     } else {
 959                         (
 960                             path_span,
 961                             format!(
 962                                 "partially resolved path in {} {}",
 963                                 kind.article(),
 964                                 kind.descr()
 965                             ),
 966                         )
 967                     };
 968                     self.report_error(
 969                         span,
 970                         ResolutionError::FailedToResolve { label, suggestion: None },
 971                     );
 972                 }
 973                 PathResult::Module(..) | PathResult::Indeterminate => unreachable!(),
 974             }
 975         }
 976
 977         let macro_resolutions = mem::take(&mut self.single_segment_macro_resolutions);
 978         for (ident, kind, parent_scope, initial_binding) in macro_resolutions {
 979             match self.early_resolve_ident_in_lexical_scope(
 980                 ident,
 981                 ScopeSet::Macro(kind),
 982                 &parent_scope,
 983                 true,
 984                 true,
 985                 ident.span,
 986             ) {
 987                 Ok(binding) => {
 988                     let initial_res = initial_binding.map(|initial_binding| {
 989                         self.record_use(ident, MacroNS, initial_binding, false);
 990                         initial_binding.res()
 991                     });
 992                     let res = binding.res();
 993                     let seg = Segment::from_ident(ident);
 994                     check_consistency(self, &[seg], ident.span, kind, initial_res, res);
 995                 }
 996                 Err(..) => {
 997                     let expected = kind.descr_expected();
 998                     let msg = format!("cannot find {} `{}` in this scope", expected, ident);
 999                     let mut err = self.session.struct_span_err(ident.span, &msg);
1000                     self.unresolved_macro_suggestions(&mut err, kind, &parent_scope, ident);
1001                     err.emit();
1002                 }
1003             }
1004         }
1005
1006         let builtin_attrs = mem::take(&mut self.builtin_attrs);
1007         for (ident, parent_scope) in builtin_attrs {
1008             let _ = self.early_resolve_ident_in_lexical_scope(
1009                 ident,
1010                 ScopeSet::Macro(MacroKind::Attr),
1011                 &parent_scope,
1012                 true,
1013                 true,
1014                 ident.span,
1015             );
1016         }
1017     }
1018
1019     fn check_stability_and_deprecation(
1020         &mut self,
1021         ext: &SyntaxExtension,
1022         path: &ast::Path,
1023         node_id: NodeId,
1024     ) {
1025         let span = path.span;
1026         if let Some(stability) = &ext.stability {
1027             if let StabilityLevel::Unstable { reason, issue, is_soft } = stability.level {
1028                 let feature = stability.feature;
1029                 if !self.active_features.contains(&feature) && !span.allows_unstable(feature) {
1030                     let lint_buffer = &mut self.lint_buffer;
1031                     let soft_handler =
1032                         |lint, span, msg: &_| lint_buffer.buffer_lint(lint, node_id, span, msg);
1033                     stability::report_unstable(
1034                         self.session,
1035                         feature,
1036                         reason,
1037                         issue,
1038                         is_soft,
1039                         span,
1040                         soft_handler,
1041                     );
1042                 }
1043             }
1044         }
1045         if let Some(depr) = &ext.deprecation {
1046             let path = pprust::path_to_string(&path);
1047             let (message, lint) = stability::deprecation_message(depr, "macro", &path);
1048             stability::early_report_deprecation(
1049                 &mut self.lint_buffer,
1050                 &message,
1051                 depr.suggestion,
1052                 lint,
1053                 span,
1054                 node_id,
1055             );
1056         }
1057     }
1058
1059     fn prohibit_imported_non_macro_attrs(
1060         &self,
1061         binding: Option<&'a NameBinding<'a>>,
1062         res: Option<Res>,
1063         span: Span,
1064     ) {
1065         if let Some(Res::NonMacroAttr(kind)) = res {
1066             if kind != NonMacroAttrKind::Tool && binding.map_or(true, |b| b.is_import()) {
1067                 let msg =
1068                     format!("cannot use {} {} through an import", kind.article(), kind.descr());
1069                 let mut err = self.session.struct_span_err(span, &msg);
1070                 if let Some(binding) = binding {
1071                     err.span_note(binding.span, &format!("the {} imported here", kind.descr()));
1072                 }
1073                 err.emit();
1074             }
1075         }
1076     }
1077
1078     crate fn check_reserved_macro_name(&mut self, ident: Ident, res: Res) {
1079         // Reserve some names that are not quite covered by the general check
1080         // performed on `Resolver::builtin_attrs`.
1081         if ident.name == sym::cfg || ident.name == sym::cfg_attr || ident.name == sym::derive {
1082             let macro_kind = self.get_macro(res).map(|ext| ext.macro_kind());
1083             if macro_kind.is_some() && sub_namespace_match(macro_kind, Some(MacroKind::Attr)) {
1084                 self.session.span_err(
1085                     ident.span,
1086                     &format!("name `{}` is reserved in attribute namespace", ident),
1087                 );
1088             }
1089         }
1090     }
1091
1092     /// Compile the macro into a `SyntaxExtension` and possibly replace
1093     /// its expander to a pre-defined one for built-in macros.
1094     crate fn compile_macro(&mut self, item: &ast::Item, edition: Edition) -> SyntaxExtension {
1095         let mut result = compile_declarative_macro(
1096             &self.session,
1097             self.session.features_untracked(),
1098             item,
1099             edition,
1100         );
1101
1102         if let Some(builtin_name) = result.builtin_name {
1103             // The macro was marked with `#[rustc_builtin_macro]`.
1104             if let Some(builtin_macro) = self.builtin_macros.get_mut(&builtin_name) {
1105                 // The macro is a built-in, replace its expander function
1106                 // while still taking everything else from the source code.
1107                 // If we already loaded this builtin macro, give a better error message than 'no such builtin macro'.
1108                 match mem::replace(builtin_macro, BuiltinMacroState::AlreadySeen(item.span)) {
1109                     BuiltinMacroState::NotYetSeen(ext) => result.kind = ext,
1110                     BuiltinMacroState::AlreadySeen(span) => {
1111                         struct_span_err!(
1112                             self.session,
1113                             item.span,
1114                             E0773,
1115                             "attempted to define built-in macro more than once"
1116                         )
1117                         .span_note(span, "previously defined here")
1118                         .emit();
1119                     }
1120                 }
1121             } else {
1122                 let msg = format!("cannot find a built-in macro with name `{}`", item.ident);
1123                 self.session.span_err(item.span, &msg);
1124             }
1125         }
1126
1127         result
1128     }
1129 }