src/librustc_resolve/macros.rs

   1 // Copyright 2016 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use {AmbiguityError, CrateLint, Resolver, ResolutionError, is_known_tool, resolve_error};
  12 use {Module, ModuleKind, NameBinding, NameBindingKind, PathResult, ToNameBinding};
  13 use ModuleOrUniformRoot;
  14 use Namespace::{self, TypeNS, MacroNS};
  15 use build_reduced_graph::{BuildReducedGraphVisitor, IsMacroExport};
  16 use resolve_imports::ImportResolver;
  17 use rustc::hir::def_id::{DefId, BUILTIN_MACROS_CRATE, CRATE_DEF_INDEX, DefIndex,
  18                          DefIndexAddressSpace};
  19 use rustc::hir::def::{Def, NonMacroAttrKind};
  20 use rustc::hir::map::{self, DefCollector};
  21 use rustc::{ty, lint};
  22 use rustc::middle::cstore::CrateStore;
  23 use syntax::ast::{self, Name, Ident};
  24 use syntax::attr;
  25 use syntax::errors::DiagnosticBuilder;
  26 use syntax::ext::base::{self, Determinacy, MultiModifier, MultiDecorator};
  27 use syntax::ext::base::{MacroKind, SyntaxExtension, Resolver as SyntaxResolver};
  28 use syntax::ext::expand::{AstFragment, Invocation, InvocationKind};
  29 use syntax::ext::hygiene::{self, Mark};
  30 use syntax::ext::tt::macro_rules;
  31 use syntax::feature_gate::{self, feature_err, emit_feature_err, is_builtin_attr_name, GateIssue};
  32 use syntax::feature_gate::EXPLAIN_DERIVE_UNDERSCORE;
  33 use syntax::fold::{self, Folder};
  34 use syntax::parse::parser::PathStyle;
  35 use syntax::parse::token::{self, Token};
  36 use syntax::ptr::P;
  37 use syntax::symbol::{Symbol, keywords};
  38 use syntax::tokenstream::{TokenStream, TokenTree, Delimited};
  39 use syntax::util::lev_distance::find_best_match_for_name;
  40 use syntax_pos::{Span, DUMMY_SP};
  41
  42 use std::cell::Cell;
  43 use std::mem;
  44 use rustc_data_structures::sync::Lrc;
  45
  46 #[derive(Clone)]
  47 pub struct InvocationData<'a> {
  48     pub module: Cell<Module<'a>>,
  49     pub def_index: DefIndex,
  50     // The scope in which the invocation path is resolved.
  51     pub legacy_scope: Cell<LegacyScope<'a>>,
  52     // The smallest scope that includes this invocation's expansion,
  53     // or `Empty` if this invocation has not been expanded yet.
  54     pub expansion: Cell<LegacyScope<'a>>,
  55 }
  56
  57 impl<'a> InvocationData<'a> {
  58     pub fn root(graph_root: Module<'a>) -> Self {
  59         InvocationData {
  60             module: Cell::new(graph_root),
  61             def_index: CRATE_DEF_INDEX,
  62             legacy_scope: Cell::new(LegacyScope::Empty),
  63             expansion: Cell::new(LegacyScope::Empty),
  64         }
  65     }
  66 }
  67
  68 #[derive(Copy, Clone)]
  69 pub enum LegacyScope<'a> {
  70     Empty,
  71     Invocation(&'a InvocationData<'a>), // The scope of the invocation, not including its expansion
  72     Expansion(&'a InvocationData<'a>), // The scope of the invocation, including its expansion
  73     Binding(&'a LegacyBinding<'a>),
  74 }
  75
  76 pub struct LegacyBinding<'a> {
  77     pub parent: Cell<LegacyScope<'a>>,
  78     pub ident: Ident,
  79     def_id: DefId,
  80     pub span: Span,
  81 }
  82
  83 pub struct ProcMacError {
  84     crate_name: Symbol,
  85     name: Symbol,
  86     module: ast::NodeId,
  87     use_span: Span,
  88     warn_msg: &'static str,
  89 }
  90
  91 #[derive(Copy, Clone)]
  92 pub enum MacroBinding<'a> {
  93     Legacy(&'a LegacyBinding<'a>),
  94     Global(&'a NameBinding<'a>),
  95     Modern(&'a NameBinding<'a>),
  96 }
  97
  98 impl<'a> MacroBinding<'a> {
  99     pub fn span(self) -> Span {
 100         match self {
 101             MacroBinding::Legacy(binding) => binding.span,
 102             MacroBinding::Global(binding) | MacroBinding::Modern(binding) => binding.span,
 103         }
 104     }
 105
 106     pub fn binding(self) -> &'a NameBinding<'a> {
 107         match self {
 108             MacroBinding::Global(binding) | MacroBinding::Modern(binding) => binding,
 109             MacroBinding::Legacy(_) => panic!("unexpected MacroBinding::Legacy"),
 110         }
 111     }
 112
 113     pub fn def_ignoring_ambiguity(self) -> Def {
 114         match self {
 115             MacroBinding::Legacy(binding) => Def::Macro(binding.def_id, MacroKind::Bang),
 116             MacroBinding::Global(binding) | MacroBinding::Modern(binding) =>
 117                 binding.def_ignoring_ambiguity(),
 118         }
 119     }
 120 }
 121
 122 impl<'a, 'crateloader: 'a> base::Resolver for Resolver<'a, 'crateloader> {
 123     fn next_node_id(&mut self) -> ast::NodeId {
 124         self.session.next_node_id()
 125     }
 126
 127     fn get_module_scope(&mut self, id: ast::NodeId) -> Mark {
 128         let mark = Mark::fresh(Mark::root());
 129         let module = self.module_map[&self.definitions.local_def_id(id)];
 130         self.invocations.insert(mark, self.arenas.alloc_invocation_data(InvocationData {
 131             module: Cell::new(module),
 132             def_index: module.def_id().unwrap().index,
 133             legacy_scope: Cell::new(LegacyScope::Empty),
 134             expansion: Cell::new(LegacyScope::Empty),
 135         }));
 136         mark
 137     }
 138
 139     fn eliminate_crate_var(&mut self, item: P<ast::Item>) -> P<ast::Item> {
 140         struct EliminateCrateVar<'b, 'a: 'b, 'crateloader: 'a>(
 141             &'b mut Resolver<'a, 'crateloader>, Span
 142         );
 143
 144         impl<'a, 'b, 'crateloader> Folder for EliminateCrateVar<'a, 'b, 'crateloader> {
 145             fn fold_path(&mut self, path: ast::Path) -> ast::Path {
 146                 match self.fold_qpath(None, path) {
 147                     (None, path) => path,
 148                     _ => unreachable!(),
 149                 }
 150             }
 151
 152             fn fold_qpath(&mut self, mut qself: Option<ast::QSelf>, mut path: ast::Path)
 153                           -> (Option<ast::QSelf>, ast::Path) {
 154                 qself = qself.map(|ast::QSelf { ty, path_span, position }| {
 155                     ast::QSelf {
 156                         ty: self.fold_ty(ty),
 157                         path_span: self.new_span(path_span),
 158                         position,
 159                     }
 160                 });
 161
 162                 if path.segments[0].ident.name == keywords::DollarCrate.name() {
 163                     let module = self.0.resolve_crate_root(path.segments[0].ident);
 164                     path.segments[0].ident.name = keywords::CrateRoot.name();
 165                     if !module.is_local() {
 166                         let span = path.segments[0].ident.span;
 167                         path.segments.insert(1, match module.kind {
 168                             ModuleKind::Def(_, name) => ast::PathSegment::from_ident(
 169                                 ast::Ident::with_empty_ctxt(name).with_span_pos(span)
 170                             ),
 171                             _ => unreachable!(),
 172                         });
 173                         if let Some(qself) = &mut qself {
 174                             qself.position += 1;
 175                         }
 176                     }
 177                 }
 178                 (qself, path)
 179             }
 180
 181             fn fold_mac(&mut self, mac: ast::Mac) -> ast::Mac {
 182                 fold::noop_fold_mac(mac, self)
 183             }
 184         }
 185
 186         EliminateCrateVar(self, item.span).fold_item(item).expect_one("")
 187     }
 188
 189     fn is_whitelisted_legacy_custom_derive(&self, name: Name) -> bool {
 190         self.whitelisted_legacy_custom_derives.contains(&name)
 191     }
 192
 193     fn visit_ast_fragment_with_placeholders(&mut self, mark: Mark, fragment: &AstFragment,
 194                                             derives: &[Mark]) {
 195         let invocation = self.invocations[&mark];
 196         self.collect_def_ids(mark, invocation, fragment);
 197
 198         self.current_module = invocation.module.get();
 199         self.current_module.unresolved_invocations.borrow_mut().remove(&mark);
 200         self.current_module.unresolved_invocations.borrow_mut().extend(derives);
 201         for &derive in derives {
 202             self.invocations.insert(derive, invocation);
 203         }
 204         let mut visitor = BuildReducedGraphVisitor {
 205             resolver: self,
 206             legacy_scope: LegacyScope::Invocation(invocation),
 207             expansion: mark,
 208         };
 209         fragment.visit_with(&mut visitor);
 210         invocation.expansion.set(visitor.legacy_scope);
 211     }
 212
 213     fn add_builtin(&mut self, ident: ast::Ident, ext: Lrc<SyntaxExtension>) {
 214         let def_id = DefId {
 215             krate: BUILTIN_MACROS_CRATE,
 216             index: DefIndex::from_array_index(self.macro_map.len(),
 217                                               DefIndexAddressSpace::Low),
 218         };
 219         let kind = ext.kind();
 220         self.macro_map.insert(def_id, ext);
 221         let binding = self.arenas.alloc_name_binding(NameBinding {
 222             kind: NameBindingKind::Def(Def::Macro(def_id, kind), false),
 223             span: DUMMY_SP,
 224             vis: ty::Visibility::Invisible,
 225             expansion: Mark::root(),
 226         });
 227         self.macro_prelude.insert(ident.name, binding);
 228     }
 229
 230     fn resolve_imports(&mut self) {
 231         ImportResolver { resolver: self }.resolve_imports()
 232     }
 233
 234     // Resolves attribute and derive legacy macros from `#![plugin(..)]`.
 235     fn find_legacy_attr_invoc(&mut self, attrs: &mut Vec<ast::Attribute>, allow_derive: bool)
 236                               -> Option<ast::Attribute> {
 237         for i in 0..attrs.len() {
 238             let name = attrs[i].name();
 239
 240             if self.session.plugin_attributes.borrow().iter()
 241                     .any(|&(ref attr_nm, _)| name == &**attr_nm) {
 242                 attr::mark_known(&attrs[i]);
 243             }
 244
 245             match self.macro_prelude.get(&name).cloned() {
 246                 Some(binding) => match *binding.get_macro(self) {
 247                     MultiModifier(..) | MultiDecorator(..) | SyntaxExtension::AttrProcMacro(..) => {
 248                         return Some(attrs.remove(i))
 249                     }
 250                     _ => {}
 251                 },
 252                 None => {}
 253             }
 254         }
 255
 256         if !allow_derive { return None }
 257
 258         // Check for legacy derives
 259         for i in 0..attrs.len() {
 260             let name = attrs[i].name();
 261
 262             if name == "derive" {
 263                 let result = attrs[i].parse_list(&self.session.parse_sess, |parser| {
 264                     parser.parse_path_allowing_meta(PathStyle::Mod)
 265                 });
 266
 267                 let mut traits = match result {
 268                     Ok(traits) => traits,
 269                     Err(mut e) => {
 270                         e.cancel();
 271                         continue
 272                     }
 273                 };
 274
 275                 for j in 0..traits.len() {
 276                     if traits[j].segments.len() > 1 {
 277                         continue
 278                     }
 279                     let trait_name = traits[j].segments[0].ident.name;
 280                     let legacy_name = Symbol::intern(&format!("derive_{}", trait_name));
 281                     if !self.macro_prelude.contains_key(&legacy_name) {
 282                         continue
 283                     }
 284                     let span = traits.remove(j).span;
 285                     self.gate_legacy_custom_derive(legacy_name, span);
 286                     if traits.is_empty() {
 287                         attrs.remove(i);
 288                     } else {
 289                         let mut tokens = Vec::new();
 290                         for (j, path) in traits.iter().enumerate() {
 291                             if j > 0 {
 292                                 tokens.push(TokenTree::Token(attrs[i].span, Token::Comma).into());
 293                             }
 294                             for (k, segment) in path.segments.iter().enumerate() {
 295                                 if k > 0 {
 296                                     tokens.push(TokenTree::Token(path.span, Token::ModSep).into());
 297                                 }
 298                                 let tok = Token::from_ast_ident(segment.ident);
 299                                 tokens.push(TokenTree::Token(path.span, tok).into());
 300                             }
 301                         }
 302                         attrs[i].tokens = TokenTree::Delimited(attrs[i].span, Delimited {
 303                             delim: token::Paren,
 304                             tts: TokenStream::concat(tokens).into(),
 305                         }).into();
 306                     }
 307                     return Some(ast::Attribute {
 308                         path: ast::Path::from_ident(Ident::new(legacy_name, span)),
 309                         tokens: TokenStream::empty(),
 310                         id: attr::mk_attr_id(),
 311                         style: ast::AttrStyle::Outer,
 312                         is_sugared_doc: false,
 313                         span,
 314                     });
 315                 }
 316             }
 317         }
 318
 319         None
 320     }
 321
 322     fn resolve_macro_invocation(&mut self, invoc: &Invocation, scope: Mark, force: bool)
 323                                 -> Result<Option<Lrc<SyntaxExtension>>, Determinacy> {
 324         let (path, kind, derives_in_scope) = match invoc.kind {
 325             InvocationKind::Attr { attr: None, .. } =>
 326                 return Ok(None),
 327             InvocationKind::Attr { attr: Some(ref attr), ref traits, .. } =>
 328                 (&attr.path, MacroKind::Attr, &traits[..]),
 329             InvocationKind::Bang { ref mac, .. } =>
 330                 (&mac.node.path, MacroKind::Bang, &[][..]),
 331             InvocationKind::Derive { ref path, .. } =>
 332                 (path, MacroKind::Derive, &[][..]),
 333         };
 334
 335         let (def, ext) = self.resolve_macro_to_def(path, kind, scope, derives_in_scope, force)?;
 336
 337         if let Def::Macro(def_id, _) = def {
 338             self.macro_defs.insert(invoc.expansion_data.mark, def_id);
 339             let normal_module_def_id =
 340                 self.macro_def_scope(invoc.expansion_data.mark).normal_ancestor_id;
 341             self.definitions.add_parent_module_of_macro_def(invoc.expansion_data.mark,
 342                                                             normal_module_def_id);
 343             invoc.expansion_data.mark.set_default_transparency(ext.default_transparency());
 344             invoc.expansion_data.mark.set_is_builtin(def_id.krate == BUILTIN_MACROS_CRATE);
 345         }
 346
 347         Ok(Some(ext))
 348     }
 349
 350     fn resolve_macro_path(&mut self, path: &ast::Path, kind: MacroKind, scope: Mark,
 351                           derives_in_scope: &[ast::Path], force: bool)
 352                           -> Result<Lrc<SyntaxExtension>, Determinacy> {
 353         Ok(self.resolve_macro_to_def(path, kind, scope, derives_in_scope, force)?.1)
 354     }
 355
 356     fn check_unused_macros(&self) {
 357         for did in self.unused_macros.iter() {
 358             let id_span = match *self.macro_map[did] {
 359                 SyntaxExtension::NormalTT { def_info, .. } |
 360                 SyntaxExtension::DeclMacro { def_info, .. } => def_info,
 361                 _ => None,
 362             };
 363             if let Some((id, span)) = id_span {
 364                 let lint = lint::builtin::UNUSED_MACROS;
 365                 let msg = "unused macro definition";
 366                 self.session.buffer_lint(lint, id, span, msg);
 367             } else {
 368                 bug!("attempted to create unused macro error, but span not available");
 369             }
 370         }
 371     }
 372 }
 373
 374 impl<'a, 'cl> Resolver<'a, 'cl> {
 375     fn resolve_macro_to_def(&mut self, path: &ast::Path, kind: MacroKind, scope: Mark,
 376                             derives_in_scope: &[ast::Path], force: bool)
 377                             -> Result<(Def, Lrc<SyntaxExtension>), Determinacy> {
 378         let def = self.resolve_macro_to_def_inner(path, kind, scope, derives_in_scope, force);
 379
 380         // Report errors and enforce feature gates for the resolved macro.
 381         if def != Err(Determinacy::Undetermined) {
 382             // Do not report duplicated errors on every undetermined resolution.
 383             for segment in &path.segments {
 384                 if let Some(args) = &segment.args {
 385                     self.session.span_err(args.span(), "generic arguments in macro path");
 386                 }
 387             }
 388         }
 389
 390         let def = def?;
 391
 392         if path.segments.len() > 1 {
 393             if kind != MacroKind::Bang {
 394                 if def != Def::NonMacroAttr(NonMacroAttrKind::Tool) &&
 395                    !self.session.features_untracked().proc_macro_path_invoc {
 396                     let msg = format!("non-ident {} paths are unstable", kind.descr());
 397                     emit_feature_err(&self.session.parse_sess, "proc_macro_path_invoc",
 398                                      path.span, GateIssue::Language, &msg);
 399                 }
 400             }
 401         }
 402
 403         match def {
 404             Def::Macro(def_id, macro_kind) => {
 405                 self.unused_macros.remove(&def_id);
 406                 if macro_kind == MacroKind::ProcMacroStub {
 407                     let msg = "can't use a procedural macro from the same crate that defines it";
 408                     self.session.span_err(path.span, msg);
 409                     return Err(Determinacy::Determined);
 410                 }
 411             }
 412             Def::NonMacroAttr(attr_kind) => {
 413                 if kind == MacroKind::Attr {
 414                     let features = self.session.features_untracked();
 415                     if attr_kind == NonMacroAttrKind::Tool && !features.tool_attributes {
 416                         feature_err(&self.session.parse_sess, "tool_attributes", path.span,
 417                                     GateIssue::Language, "tool attributes are unstable").emit();
 418                     }
 419                     if attr_kind == NonMacroAttrKind::Custom {
 420                         assert!(path.segments.len() == 1);
 421                         let name = path.segments[0].ident.name.as_str();
 422                         if name.starts_with("rustc_") {
 423                             if !features.rustc_attrs {
 424                                 let msg = "unless otherwise specified, attributes with the prefix \
 425                                            `rustc_` are reserved for internal compiler diagnostics";
 426                                 feature_err(&self.session.parse_sess, "rustc_attrs", path.span,
 427                                             GateIssue::Language, &msg).emit();
 428                             }
 429                         } else if name.starts_with("derive_") {
 430                             if !features.custom_derive {
 431                                 feature_err(&self.session.parse_sess, "custom_derive", path.span,
 432                                             GateIssue::Language, EXPLAIN_DERIVE_UNDERSCORE).emit();
 433                             }
 434                         } else if !features.custom_attribute {
 435                             let msg = format!("The attribute `{}` is currently unknown to the \
 436                                                compiler and may have meaning added to it in the \
 437                                                future", path);
 438                             feature_err(&self.session.parse_sess, "custom_attribute", path.span,
 439                                         GateIssue::Language, &msg).emit();
 440                         }
 441                     }
 442                 } else {
 443                     // Not only attributes, but anything in macro namespace can result in
 444                     // `Def::NonMacroAttr` definition (e.g. `inline!()`), so we must report
 445                     // an error for those cases.
 446                     let msg = format!("expected a macro, found {}", def.kind_name());
 447                     self.session.span_err(path.span, &msg);
 448                     return Err(Determinacy::Determined);
 449                 }
 450             }
 451             _ => panic!("expected `Def::Macro` or `Def::NonMacroAttr`"),
 452         }
 453
 454         Ok((def, self.get_macro(def)))
 455     }
 456
 457     pub fn resolve_macro_to_def_inner(&mut self, path: &ast::Path, kind: MacroKind, scope: Mark,
 458                                       derives_in_scope: &[ast::Path], force: bool)
 459                                       -> Result<Def, Determinacy> {
 460         let ast::Path { ref segments, span } = *path;
 461         let mut path: Vec<_> = segments.iter().map(|seg| seg.ident).collect();
 462         let invocation = self.invocations[&scope];
 463         let module = invocation.module.get();
 464         self.current_module = if module.is_trait() { module.parent.unwrap() } else { module };
 465
 466         // Possibly apply the macro helper hack
 467         if kind == MacroKind::Bang && path.len() == 1 &&
 468            path[0].span.ctxt().outer().expn_info().map_or(false, |info| info.local_inner_macros) {
 469             let root = Ident::new(keywords::DollarCrate.name(), path[0].span);
 470             path.insert(0, root);
 471         }
 472
 473         if path.len() > 1 {
 474             let res = self.resolve_path(None, &path, Some(MacroNS), false, span, CrateLint::No);
 475             let def = match res {
 476                 PathResult::NonModule(path_res) => match path_res.base_def() {
 477                     Def::Err => Err(Determinacy::Determined),
 478                     def @ _ => {
 479                         if path_res.unresolved_segments() > 0 {
 480                             self.found_unresolved_macro = true;
 481                             self.session.span_err(span, "fail to resolve non-ident macro path");
 482                             Err(Determinacy::Determined)
 483                         } else {
 484                             Ok(def)
 485                         }
 486                     }
 487                 },
 488                 PathResult::Module(..) => unreachable!(),
 489                 PathResult::Indeterminate if !force => return Err(Determinacy::Undetermined),
 490                 _ => {
 491                     self.found_unresolved_macro = true;
 492                     Err(Determinacy::Determined)
 493                 },
 494             };
 495             self.current_module.nearest_item_scope().macro_resolutions.borrow_mut()
 496                 .push((path.into_boxed_slice(), span));
 497             return def;
 498         }
 499
 500         let legacy_resolution = self.resolve_legacy_scope(&invocation.legacy_scope, path[0], false);
 501         let result = if let Some(MacroBinding::Legacy(binding)) = legacy_resolution {
 502             Ok(Def::Macro(binding.def_id, MacroKind::Bang))
 503         } else {
 504             match self.resolve_lexical_macro_path_segment(path[0], MacroNS, false, force,
 505                                                           kind == MacroKind::Attr, span) {
 506                 Ok(binding) => Ok(binding.binding().def_ignoring_ambiguity()),
 507                 Err(Determinacy::Undetermined) => return Err(Determinacy::Undetermined),
 508                 Err(Determinacy::Determined) => {
 509                     self.found_unresolved_macro = true;
 510                     Err(Determinacy::Determined)
 511                 }
 512             }
 513         };
 514
 515         self.current_module.nearest_item_scope().legacy_macro_resolutions.borrow_mut()
 516             .push((scope, path[0], kind, result.ok()));
 517
 518         if let Ok(Def::NonMacroAttr(NonMacroAttrKind::Custom)) = result {} else {
 519             return result;
 520         }
 521
 522         // At this point we've found that the `attr` is determinately unresolved and thus can be
 523         // interpreted as a custom attribute. Normally custom attributes are feature gated, but
 524         // it may be a custom attribute whitelisted by a derive macro and they do not require
 525         // a feature gate.
 526         //
 527         // So here we look through all of the derive annotations in scope and try to resolve them.
 528         // If they themselves successfully resolve *and* one of the resolved derive macros
 529         // whitelists this attribute's name, then this is a registered attribute and we can convert
 530         // it from a "generic custom attrite" into a "known derive helper attribute".
 531         assert!(kind == MacroKind::Attr);
 532         enum ConvertToDeriveHelper { Yes, No, DontKnow }
 533         let mut convert_to_derive_helper = ConvertToDeriveHelper::No;
 534         for derive in derives_in_scope {
 535             match self.resolve_macro_path(derive, MacroKind::Derive, scope, &[], force) {
 536                 Ok(ext) => if let SyntaxExtension::ProcMacroDerive(_, ref inert_attrs, _) = *ext {
 537                     if inert_attrs.contains(&path[0].name) {
 538                         convert_to_derive_helper = ConvertToDeriveHelper::Yes;
 539                         break
 540                     }
 541                 },
 542                 Err(Determinacy::Undetermined) =>
 543                     convert_to_derive_helper = ConvertToDeriveHelper::DontKnow,
 544                 Err(Determinacy::Determined) => {}
 545             }
 546         }
 547
 548         match convert_to_derive_helper {
 549             ConvertToDeriveHelper::Yes => Ok(Def::NonMacroAttr(NonMacroAttrKind::DeriveHelper)),
 550             ConvertToDeriveHelper::No => result,
 551             ConvertToDeriveHelper::DontKnow => Err(Determinacy::determined(force)),
 552         }
 553     }
 554
 555     // Resolve the initial segment of a non-global macro path
 556     // (e.g. `foo` in `foo::bar!(); or `foo!();`).
 557     // This is a variation of `fn resolve_ident_in_lexical_scope` that can be run during
 558     // expansion and import resolution (perhaps they can be merged in the future).
 559     pub fn resolve_lexical_macro_path_segment(&mut self,
 560                                               mut ident: Ident,
 561                                               ns: Namespace,
 562                                               record_used: bool,
 563                                               force: bool,
 564                                               is_attr: bool,
 565                                               path_span: Span)
 566                                               -> Result<MacroBinding<'a>, Determinacy> {
 567         // General principles:
 568         // 1. Not controlled (user-defined) names should have higher priority than controlled names
 569         //    built into the language or standard library. This way we can add new names into the
 570         //    language or standard library without breaking user code.
 571         // 2. "Closed set" below means new names can appear after the current resolution attempt.
 572         // Places to search (in order of decreasing priority):
 573         // (Type NS)
 574         // 1. FIXME: Ribs (type parameters), there's no necessary infrastructure yet
 575         //    (open set, not controlled).
 576         // 2. Names in modules (both normal `mod`ules and blocks), loop through hygienic parents
 577         //    (open, not controlled).
 578         // 3. Extern prelude (closed, not controlled).
 579         // 4. Tool modules (closed, controlled right now, but not in the future).
 580         // 5. Standard library prelude (de-facto closed, controlled).
 581         // 6. Language prelude (closed, controlled).
 582         // (Macro NS)
 583         // 1. Names in modules (both normal `mod`ules and blocks), loop through hygienic parents
 584         //    (open, not controlled).
 585         // 2. Macro prelude (language, standard library, user-defined legacy plugins lumped into
 586         //    one set) (open, the open part is from macro expansions, not controlled).
 587         // 2a. User-defined prelude from macro-use
 588         //    (open, the open part is from macro expansions, not controlled).
 589         // 2b. Standard library prelude, currently just a macro-use (closed, controlled)
 590         // 2c. Language prelude, perhaps including builtin attributes
 591         //    (closed, controlled, except for legacy plugins).
 592         // 3. Builtin attributes (closed, controlled).
 593
 594         assert!(ns == TypeNS  || ns == MacroNS);
 595         assert!(force || !record_used); // `record_used` implies `force`
 596         ident = ident.modern();
 597
 598         // Names from inner scope that can't shadow names from outer scopes, e.g.
 599         // mod m { ... }
 600         // {
 601         //     use prefix::*; // if this imports another `m`, then it can't shadow the outer `m`
 602         //                    // and we have and ambiguity error
 603         //     m::mac!();
 604         // }
 605         // This includes names from globs and from macro expansions.
 606         let mut potentially_ambiguous_result: Option<MacroBinding> = None;
 607
 608         enum WhereToResolve<'a> {
 609             Module(Module<'a>),
 610             MacroPrelude,
 611             BuiltinAttrs,
 612             ExternPrelude,
 613             ToolPrelude,
 614             StdLibPrelude,
 615             PrimitiveTypes,
 616         }
 617
 618         // Go through all the scopes and try to resolve the name.
 619         let mut where_to_resolve = WhereToResolve::Module(self.current_module);
 620         let mut use_prelude = !self.current_module.no_implicit_prelude;
 621         loop {
 622             let result = match where_to_resolve {
 623                 WhereToResolve::Module(module) => {
 624                     let orig_current_module = mem::replace(&mut self.current_module, module);
 625                     let binding = self.resolve_ident_in_module_unadjusted(
 626                         ModuleOrUniformRoot::Module(module),
 627                         ident,
 628                         ns,
 629                         true,
 630                         record_used,
 631                         path_span,
 632                     );
 633                     self.current_module = orig_current_module;
 634                     binding.map(MacroBinding::Modern)
 635                 }
 636                 WhereToResolve::MacroPrelude => {
 637                     match self.macro_prelude.get(&ident.name).cloned() {
 638                         Some(binding) => Ok(MacroBinding::Global(binding)),
 639                         None => Err(Determinacy::Determined),
 640                     }
 641                 }
 642                 WhereToResolve::BuiltinAttrs => {
 643                     // FIXME: Only built-in attributes are not considered as candidates for
 644                     // non-attributes to fight off regressions on stable channel (#53205).
 645                     // We need to come up with some more principled approach instead.
 646                     if is_attr && is_builtin_attr_name(ident.name) {
 647                         let binding = (Def::NonMacroAttr(NonMacroAttrKind::Builtin),
 648                                        ty::Visibility::Public, ident.span, Mark::root())
 649                                        .to_name_binding(self.arenas);
 650                         Ok(MacroBinding::Global(binding))
 651                     } else {
 652                         Err(Determinacy::Determined)
 653                     }
 654                 }
 655                 WhereToResolve::ExternPrelude => {
 656                     if use_prelude && self.extern_prelude.contains(&ident.name) {
 657                         if !self.session.features_untracked().extern_prelude &&
 658                            !self.ignore_extern_prelude_feature {
 659                             feature_err(&self.session.parse_sess, "extern_prelude",
 660                                         ident.span, GateIssue::Language,
 661                                         "access to extern crates through prelude is experimental")
 662                                         .emit();
 663                         }
 664
 665                         let crate_id =
 666                             self.crate_loader.process_path_extern(ident.name, ident.span);
 667                         let crate_root =
 668                             self.get_module(DefId { krate: crate_id, index: CRATE_DEF_INDEX });
 669                         self.populate_module_if_necessary(crate_root);
 670
 671                         let binding = (crate_root, ty::Visibility::Public,
 672                                        ident.span, Mark::root()).to_name_binding(self.arenas);
 673                         Ok(MacroBinding::Global(binding))
 674                     } else {
 675                         Err(Determinacy::Determined)
 676                     }
 677                 }
 678                 WhereToResolve::ToolPrelude => {
 679                     if use_prelude && is_known_tool(ident.name) {
 680                         let binding = (Def::ToolMod, ty::Visibility::Public,
 681                                        ident.span, Mark::root()).to_name_binding(self.arenas);
 682                         Ok(MacroBinding::Global(binding))
 683                     } else {
 684                         Err(Determinacy::Determined)
 685                     }
 686                 }
 687                 WhereToResolve::StdLibPrelude => {
 688                     let mut result = Err(Determinacy::Determined);
 689                     if use_prelude {
 690                         if let Some(prelude) = self.prelude {
 691                             if let Ok(binding) = self.resolve_ident_in_module_unadjusted(
 692                                 ModuleOrUniformRoot::Module(prelude),
 693                                 ident,
 694                                 ns,
 695                                 false,
 696                                 false,
 697                                 path_span,
 698                             ) {
 699                                 result = Ok(MacroBinding::Global(binding));
 700                             }
 701                         }
 702                     }
 703                     result
 704                 }
 705                 WhereToResolve::PrimitiveTypes => {
 706                     if let Some(prim_ty) =
 707                             self.primitive_type_table.primitive_types.get(&ident.name).cloned() {
 708                         let binding = (Def::PrimTy(prim_ty), ty::Visibility::Public,
 709                                        ident.span, Mark::root()).to_name_binding(self.arenas);
 710                         Ok(MacroBinding::Global(binding))
 711                     } else {
 712                         Err(Determinacy::Determined)
 713                     }
 714                 }
 715             };
 716
 717             macro_rules! continue_search { () => {
 718                 where_to_resolve = match where_to_resolve {
 719                     WhereToResolve::Module(module) => {
 720                         match self.hygienic_lexical_parent(module, &mut ident.span) {
 721                             Some(parent_module) => WhereToResolve::Module(parent_module),
 722                             None => {
 723                                 use_prelude = !module.no_implicit_prelude;
 724                                 if ns == MacroNS {
 725                                     WhereToResolve::MacroPrelude
 726                                 } else {
 727                                     WhereToResolve::ExternPrelude
 728                                 }
 729                             }
 730                         }
 731                     }
 732                     WhereToResolve::MacroPrelude => WhereToResolve::BuiltinAttrs,
 733                     WhereToResolve::BuiltinAttrs => break, // nowhere else to search
 734                     WhereToResolve::ExternPrelude => WhereToResolve::ToolPrelude,
 735                     WhereToResolve::ToolPrelude => WhereToResolve::StdLibPrelude,
 736                     WhereToResolve::StdLibPrelude => WhereToResolve::PrimitiveTypes,
 737                     WhereToResolve::PrimitiveTypes => break, // nowhere else to search
 738                 };
 739
 740                 continue;
 741             }}
 742
 743             match result {
 744                 Ok(result) => {
 745                     if !record_used {
 746                         return Ok(result);
 747                     }
 748
 749                     let binding = result.binding();
 750
 751                     // Found a solution that is ambiguous with a previously found solution.
 752                     // Push an ambiguity error for later reporting and
 753                     // return something for better recovery.
 754                     if let Some(previous_result) = potentially_ambiguous_result {
 755                         if binding.def() != previous_result.binding().def() {
 756                             self.ambiguity_errors.push(AmbiguityError {
 757                                 span: path_span,
 758                                 name: ident.name,
 759                                 b1: previous_result.binding(),
 760                                 b2: binding,
 761                                 lexical: true,
 762                             });
 763                             return Ok(previous_result);
 764                         }
 765                     }
 766
 767                     // Found a solution that's not an ambiguity yet, but is "suspicious" and
 768                     // can participate in ambiguities later on.
 769                     // Remember it and go search for other solutions in outer scopes.
 770                     if binding.is_glob_import() || binding.expansion != Mark::root() {
 771                         potentially_ambiguous_result = Some(result);
 772
 773                         continue_search!();
 774                     }
 775
 776                     // Found a solution that can't be ambiguous, great success.
 777                     return Ok(result);
 778                 },
 779                 Err(Determinacy::Determined) => {
 780                     continue_search!();
 781                 }
 782                 Err(Determinacy::Undetermined) => return Err(Determinacy::determined(force)),
 783             }
 784         }
 785
 786         // Previously found potentially ambiguous result turned out to not be ambiguous after all.
 787         if let Some(previous_result) = potentially_ambiguous_result {
 788             return Ok(previous_result);
 789         }
 790
 791         let determinacy = Determinacy::determined(force);
 792         if determinacy == Determinacy::Determined && is_attr {
 793             // For single-segment attributes interpret determinate "no resolution" as a custom
 794             // attribute. (Lexical resolution implies the first segment and is_attr should imply
 795             // the last segment, so we are certainly working with a single-segment attribute here.)
 796             assert!(ns == MacroNS);
 797             let binding = (Def::NonMacroAttr(NonMacroAttrKind::Custom),
 798                            ty::Visibility::Public, ident.span, Mark::root())
 799                            .to_name_binding(self.arenas);
 800             Ok(MacroBinding::Global(binding))
 801         } else {
 802             Err(determinacy)
 803         }
 804     }
 805
 806     pub fn resolve_legacy_scope(&mut self,
 807                                 mut scope: &'a Cell<LegacyScope<'a>>,
 808                                 ident: Ident,
 809                                 record_used: bool)
 810                                 -> Option<MacroBinding<'a>> {
 811         let ident = ident.modern();
 812         let mut relative_depth: u32 = 0;
 813         let mut binding = None;
 814         loop {
 815             match scope.get() {
 816                 LegacyScope::Empty => break,
 817                 LegacyScope::Expansion(invocation) => {
 818                     match invocation.expansion.get() {
 819                         LegacyScope::Invocation(_) => scope.set(invocation.legacy_scope.get()),
 820                         LegacyScope::Empty => {
 821                             scope = &invocation.legacy_scope;
 822                         }
 823                         _ => {
 824                             relative_depth += 1;
 825                             scope = &invocation.expansion;
 826                         }
 827                     }
 828                 }
 829                 LegacyScope::Invocation(invocation) => {
 830                     relative_depth = relative_depth.saturating_sub(1);
 831                     scope = &invocation.legacy_scope;
 832                 }
 833                 LegacyScope::Binding(potential_binding) => {
 834                     if potential_binding.ident == ident {
 835                         if record_used && relative_depth > 0 {
 836                             self.disallowed_shadowing.push(potential_binding);
 837                         }
 838                         binding = Some(potential_binding);
 839                         break
 840                     }
 841                     scope = &potential_binding.parent;
 842                 }
 843             };
 844         }
 845
 846         let binding = if let Some(binding) = binding {
 847             MacroBinding::Legacy(binding)
 848         } else if let Some(binding) = self.macro_prelude.get(&ident.name).cloned() {
 849             MacroBinding::Global(binding)
 850         } else {
 851             return None;
 852         };
 853
 854         Some(binding)
 855     }
 856
 857     pub fn finalize_current_module_macro_resolutions(&mut self) {
 858         let module = self.current_module;
 859         for &(ref path, span) in module.macro_resolutions.borrow().iter() {
 860             match self.resolve_path(None, &path, Some(MacroNS), true, span, CrateLint::No) {
 861                 PathResult::NonModule(_) => {},
 862                 PathResult::Failed(span, msg, _) => {
 863                     resolve_error(self, span, ResolutionError::FailedToResolve(&msg));
 864                 }
 865                 _ => unreachable!(),
 866             }
 867         }
 868
 869         for &(mark, ident, kind, def) in module.legacy_macro_resolutions.borrow().iter() {
 870             let span = ident.span;
 871             let legacy_scope = &self.invocations[&mark].legacy_scope;
 872             let legacy_resolution = self.resolve_legacy_scope(legacy_scope, ident, true);
 873             let resolution = self.resolve_lexical_macro_path_segment(ident, MacroNS, true, true,
 874                                                                      kind == MacroKind::Attr, span);
 875
 876             let check_consistency = |this: &Self, binding: MacroBinding| {
 877                 if let Some(def) = def {
 878                     if this.ambiguity_errors.is_empty() && this.disallowed_shadowing.is_empty() &&
 879                        binding.def_ignoring_ambiguity() != def {
 880                         // Make sure compilation does not succeed if preferred macro resolution
 881                         // has changed after the macro had been expanded. In theory all such
 882                         // situations should be reported as ambiguity errors, so this is span-bug.
 883                         span_bug!(span, "inconsistent resolution for a macro");
 884                     }
 885                 } else {
 886                     // It's possible that the macro was unresolved (indeterminate) and silently
 887                     // expanded into a dummy fragment for recovery during expansion.
 888                     // Now, post-expansion, the resolution may succeed, but we can't change the
 889                     // past and need to report an error.
 890                     let msg =
 891                         format!("cannot determine resolution for the {} `{}`", kind.descr(), ident);
 892                     let msg_note = "import resolution is stuck, try simplifying macro imports";
 893                     this.session.struct_span_err(span, &msg).note(msg_note).emit();
 894                 }
 895             };
 896
 897             match (legacy_resolution, resolution) {
 898                 (Some(MacroBinding::Legacy(legacy_binding)), Ok(MacroBinding::Modern(binding))) => {
 899                     if legacy_binding.def_id != binding.def_ignoring_ambiguity().def_id() {
 900                         let msg1 = format!("`{}` could refer to the macro defined here", ident);
 901                         let msg2 =
 902                             format!("`{}` could also refer to the macro imported here", ident);
 903                         self.session.struct_span_err(span, &format!("`{}` is ambiguous", ident))
 904                             .span_note(legacy_binding.span, &msg1)
 905                             .span_note(binding.span, &msg2)
 906                             .emit();
 907                     }
 908                 },
 909                 (None, Err(_)) => {
 910                     assert!(def.is_none());
 911                     let bang = if kind == MacroKind::Bang { "!" } else { "" };
 912                     let msg =
 913                         format!("cannot find {} `{}{}` in this scope", kind.descr(), ident, bang);
 914                     let mut err = self.session.struct_span_err(span, &msg);
 915                     self.suggest_macro_name(&ident.as_str(), kind, &mut err, span);
 916                     err.emit();
 917                 },
 918                 (Some(MacroBinding::Modern(_)), _) | (_, Ok(MacroBinding::Legacy(_))) => {
 919                     span_bug!(span, "impossible macro resolution result");
 920                 }
 921                 // OK, unambiguous resolution
 922                 (Some(binding), Err(_)) | (None, Ok(binding)) |
 923                 // OK, legacy wins over global even if their definitions are different
 924                 (Some(binding @ MacroBinding::Legacy(_)), Ok(MacroBinding::Global(_))) |
 925                 // OK, modern wins over global even if their definitions are different
 926                 (Some(MacroBinding::Global(_)), Ok(binding @ MacroBinding::Modern(_))) => {
 927                     check_consistency(self, binding);
 928                 }
 929                 (Some(MacroBinding::Global(binding1)), Ok(MacroBinding::Global(binding2))) => {
 930                     if binding1.def() != binding2.def() {
 931                         span_bug!(span, "mismatch between same global macro resolutions");
 932                     }
 933                     check_consistency(self, MacroBinding::Global(binding1));
 934
 935                     self.record_use(ident, MacroNS, binding1, span);
 936                     self.err_if_macro_use_proc_macro(ident.name, span, binding1);
 937                 },
 938             };
 939         }
 940     }
 941
 942     fn suggest_macro_name(&mut self, name: &str, kind: MacroKind,
 943                           err: &mut DiagnosticBuilder<'a>, span: Span) {
 944         // First check if this is a locally-defined bang macro.
 945         let suggestion = if let MacroKind::Bang = kind {
 946             find_best_match_for_name(self.macro_names.iter().map(|ident| &ident.name), name, None)
 947         } else {
 948             None
 949         // Then check global macros.
 950         }.or_else(|| {
 951             // FIXME: get_macro needs an &mut Resolver, can we do it without cloning?
 952             let macro_prelude = self.macro_prelude.clone();
 953             let names = macro_prelude.iter().filter_map(|(name, binding)| {
 954                 if binding.get_macro(self).kind() == kind {
 955                     Some(name)
 956                 } else {
 957                     None
 958                 }
 959             });
 960             find_best_match_for_name(names, name, None)
 961         // Then check modules.
 962         }).or_else(|| {
 963             let is_macro = |def| {
 964                 if let Def::Macro(_, def_kind) = def {
 965                     def_kind == kind
 966                 } else {
 967                     false
 968                 }
 969             };
 970             let ident = Ident::new(Symbol::intern(name), span);
 971             self.lookup_typo_candidate(&[ident], MacroNS, is_macro, span)
 972         });
 973
 974         if let Some(suggestion) = suggestion {
 975             if suggestion != name {
 976                 if let MacroKind::Bang = kind {
 977                     err.span_suggestion(span, "you could try the macro", suggestion.to_string());
 978                 } else {
 979                     err.span_suggestion(span, "try", suggestion.to_string());
 980                 }
 981             } else {
 982                 err.help("have you added the `#[macro_use]` on the module/import?");
 983             }
 984         }
 985     }
 986
 987     fn collect_def_ids(&mut self,
 988                        mark: Mark,
 989                        invocation: &'a InvocationData<'a>,
 990                        fragment: &AstFragment) {
 991         let Resolver { ref mut invocations, arenas, graph_root, .. } = *self;
 992         let InvocationData { def_index, .. } = *invocation;
 993
 994         let visit_macro_invoc = &mut |invoc: map::MacroInvocationData| {
 995             invocations.entry(invoc.mark).or_insert_with(|| {
 996                 arenas.alloc_invocation_data(InvocationData {
 997                     def_index: invoc.def_index,
 998                     module: Cell::new(graph_root),
 999                     expansion: Cell::new(LegacyScope::Empty),
1000                     legacy_scope: Cell::new(LegacyScope::Empty),
1001                 })
1002             });
1003         };
1004
1005         let mut def_collector = DefCollector::new(&mut self.definitions, mark);
1006         def_collector.visit_macro_invoc = Some(visit_macro_invoc);
1007         def_collector.with_parent(def_index, |def_collector| {
1008             fragment.visit_with(def_collector)
1009         });
1010     }
1011
1012     pub fn define_macro(&mut self,
1013                         item: &ast::Item,
1014                         expansion: Mark,
1015                         legacy_scope: &mut LegacyScope<'a>) {
1016         self.local_macro_def_scopes.insert(item.id, self.current_module);
1017         let ident = item.ident;
1018         if ident.name == "macro_rules" {
1019             self.session.span_err(item.span, "user-defined macros may not be named `macro_rules`");
1020         }
1021
1022         let def_id = self.definitions.local_def_id(item.id);
1023         let ext = Lrc::new(macro_rules::compile(&self.session.parse_sess,
1024                                                &self.session.features_untracked(),
1025                                                item, hygiene::default_edition()));
1026         self.macro_map.insert(def_id, ext);
1027
1028         let def = match item.node { ast::ItemKind::MacroDef(ref def) => def, _ => unreachable!() };
1029         if def.legacy {
1030             let ident = ident.modern();
1031             self.macro_names.insert(ident);
1032             *legacy_scope = LegacyScope::Binding(self.arenas.alloc_legacy_binding(LegacyBinding {
1033                 parent: Cell::new(*legacy_scope), ident: ident, def_id: def_id, span: item.span,
1034             }));
1035             let def = Def::Macro(def_id, MacroKind::Bang);
1036             self.all_macros.insert(ident.name, def);
1037             if attr::contains_name(&item.attrs, "macro_export") {
1038                 let module = self.graph_root;
1039                 let vis = ty::Visibility::Public;
1040                 self.define(module, ident, MacroNS,
1041                             (def, vis, item.span, expansion, IsMacroExport));
1042             } else {
1043                 self.unused_macros.insert(def_id);
1044             }
1045         } else {
1046             let module = self.current_module;
1047             let def = Def::Macro(def_id, MacroKind::Bang);
1048             let vis = self.resolve_visibility(&item.vis);
1049             if vis != ty::Visibility::Public {
1050                 self.unused_macros.insert(def_id);
1051             }
1052             self.define(module, ident, MacroNS, (def, vis, item.span, expansion));
1053         }
1054     }
1055
1056     /// Error if `ext` is a Macros 1.1 procedural macro being imported by `#[macro_use]`
1057     fn err_if_macro_use_proc_macro(&mut self, name: Name, use_span: Span,
1058                                    binding: &NameBinding<'a>) {
1059         let krate = binding.def().def_id().krate;
1060
1061         // Plugin-based syntax extensions are exempt from this check
1062         if krate == BUILTIN_MACROS_CRATE { return; }
1063
1064         let ext = binding.get_macro(self);
1065
1066         match *ext {
1067             // If `ext` is a procedural macro, check if we've already warned about it
1068             SyntaxExtension::AttrProcMacro(..) | SyntaxExtension::ProcMacro { .. } =>
1069                 if !self.warned_proc_macros.insert(name) { return; },
1070             _ => return,
1071         }
1072
1073         let warn_msg = match *ext {
1074             SyntaxExtension::AttrProcMacro(..) =>
1075                 "attribute procedural macros cannot be imported with `#[macro_use]`",
1076             SyntaxExtension::ProcMacro { .. } =>
1077                 "procedural macros cannot be imported with `#[macro_use]`",
1078             _ => return,
1079         };
1080
1081         let def_id = self.current_module.normal_ancestor_id;
1082         let node_id = self.definitions.as_local_node_id(def_id).unwrap();
1083
1084         self.proc_mac_errors.push(ProcMacError {
1085             crate_name: self.cstore.crate_name_untracked(krate),
1086             name,
1087             module: node_id,
1088             use_span,
1089             warn_msg,
1090         });
1091     }
1092
1093     pub fn report_proc_macro_import(&mut self, krate: &ast::Crate) {
1094         for err in self.proc_mac_errors.drain(..) {
1095             let (span, found_use) = ::UsePlacementFinder::check(krate, err.module);
1096
1097             if let Some(span) = span {
1098                 let found_use = if found_use { "" } else { "\n" };
1099                 self.session.struct_span_err(err.use_span, err.warn_msg)
1100                     .span_suggestion(
1101                         span,
1102                         "instead, import the procedural macro like any other item",
1103                         format!("use {}::{};{}", err.crate_name, err.name, found_use),
1104                     ).emit();
1105             } else {
1106                 self.session.struct_span_err(err.use_span, err.warn_msg)
1107                     .help(&format!("instead, import the procedural macro like any other item: \
1108                                     `use {}::{};`", err.crate_name, err.name))
1109                     .emit();
1110             }
1111         }
1112     }
1113
1114     fn gate_legacy_custom_derive(&mut self, name: Symbol, span: Span) {
1115         if !self.session.features_untracked().custom_derive {
1116             let sess = &self.session.parse_sess;
1117             let explain = feature_gate::EXPLAIN_CUSTOM_DERIVE;
1118             emit_feature_err(sess, "custom_derive", span, GateIssue::Language, explain);
1119         } else if !self.is_whitelisted_legacy_custom_derive(name) {
1120             self.session.span_warn(span, feature_gate::EXPLAIN_DEPR_CUSTOM_DERIVE);
1121         }
1122     }
1123 }