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