compiler/rustc_expand/src/expand.rs

   1 use crate::base::*;
   2 use crate::config::StripUnconfigured;
   3 use crate::hygiene::SyntaxContext;
   4 use crate::mbe::macro_rules::annotate_err_with_kind;
   5 use crate::module::{mod_dir_path, parse_external_mod, DirOwnership, ParsedExternalMod};
   6 use crate::placeholders::{placeholder, PlaceholderExpander};
   7
   8 use rustc_ast as ast;
   9 use rustc_ast::mut_visit::*;
  10 use rustc_ast::ptr::P;
  11 use rustc_ast::token::{self, Delimiter};
  12 use rustc_ast::tokenstream::TokenStream;
  13 use rustc_ast::visit::{self, AssocCtxt, Visitor};
  14 use rustc_ast::{AssocItemKind, AstNodeWrapper, AttrStyle, ExprKind, ForeignItemKind};
  15 use rustc_ast::{HasAttrs, HasNodeId};
  16 use rustc_ast::{Inline, ItemKind, MacArgs, MacStmtStyle, MetaItemKind, ModKind};
  17 use rustc_ast::{NestedMetaItem, NodeId, PatKind, StmtKind, TyKind};
  18 use rustc_ast_pretty::pprust;
  19 use rustc_data_structures::map_in_place::MapInPlace;
  20 use rustc_data_structures::sync::Lrc;
  21 use rustc_errors::{Applicability, PResult};
  22 use rustc_feature::Features;
  23 use rustc_parse::parser::{
  24     AttemptLocalParseRecovery, CommaRecoveryMode, ForceCollect, Parser, RecoverColon, RecoverComma,
  25 };
  26 use rustc_parse::validate_attr;
  27 use rustc_session::lint::builtin::{UNUSED_ATTRIBUTES, UNUSED_DOC_COMMENTS};
  28 use rustc_session::lint::BuiltinLintDiagnostics;
  29 use rustc_session::parse::{feature_err, ParseSess};
  30 use rustc_session::Limit;
  31 use rustc_span::symbol::{sym, Ident};
  32 use rustc_span::{FileName, LocalExpnId, Span};
  33
  34 use smallvec::SmallVec;
  35 use std::ops::Deref;
  36 use std::path::PathBuf;
  37 use std::rc::Rc;
  38 use std::{iter, mem};
  39
  40 macro_rules! ast_fragments {
  41     (
  42         $($Kind:ident($AstTy:ty) {
  43             $kind_name:expr;
  44             $(one fn $mut_visit_ast:ident; fn $visit_ast:ident;)?
  45             $(many fn $flat_map_ast_elt:ident; fn $visit_ast_elt:ident($($args:tt)*);)?
  46             fn $make_ast:ident;
  47         })*
  48     ) => {
  49         /// A fragment of AST that can be produced by a single macro expansion.
  50         /// Can also serve as an input and intermediate result for macro expansion operations.
  51         pub enum AstFragment {
  52             OptExpr(Option<P<ast::Expr>>),
  53             $($Kind($AstTy),)*
  54         }
  55
  56         /// "Discriminant" of an AST fragment.
  57         #[derive(Copy, Clone, PartialEq, Eq)]
  58         pub enum AstFragmentKind {
  59             OptExpr,
  60             $($Kind,)*
  61         }
  62
  63         impl AstFragmentKind {
  64             pub fn name(self) -> &'static str {
  65                 match self {
  66                     AstFragmentKind::OptExpr => "expression",
  67                     $(AstFragmentKind::$Kind => $kind_name,)*
  68                 }
  69             }
  70
  71             fn make_from<'a>(self, result: Box<dyn MacResult + 'a>) -> Option<AstFragment> {
  72                 match self {
  73                     AstFragmentKind::OptExpr =>
  74                         result.make_expr().map(Some).map(AstFragment::OptExpr),
  75                     $(AstFragmentKind::$Kind => result.$make_ast().map(AstFragment::$Kind),)*
  76                 }
  77             }
  78         }
  79
  80         impl AstFragment {
  81             pub fn add_placeholders(&mut self, placeholders: &[NodeId]) {
  82                 if placeholders.is_empty() {
  83                     return;
  84                 }
  85                 match self {
  86                     $($(AstFragment::$Kind(ast) => ast.extend(placeholders.iter().flat_map(|id| {
  87                         ${ignore(flat_map_ast_elt)}
  88                         placeholder(AstFragmentKind::$Kind, *id, None).$make_ast()
  89                     })),)?)*
  90                     _ => panic!("unexpected AST fragment kind")
  91                 }
  92             }
  93
  94             pub fn make_opt_expr(self) -> Option<P<ast::Expr>> {
  95                 match self {
  96                     AstFragment::OptExpr(expr) => expr,
  97                     _ => panic!("AstFragment::make_* called on the wrong kind of fragment"),
  98                 }
  99             }
 100
 101             $(pub fn $make_ast(self) -> $AstTy {
 102                 match self {
 103                     AstFragment::$Kind(ast) => ast,
 104                     _ => panic!("AstFragment::make_* called on the wrong kind of fragment"),
 105                 }
 106             })*
 107
 108             fn make_ast<T: InvocationCollectorNode>(self) -> T::OutputTy {
 109                 T::fragment_to_output(self)
 110             }
 111
 112             pub fn mut_visit_with<F: MutVisitor>(&mut self, vis: &mut F) {
 113                 match self {
 114                     AstFragment::OptExpr(opt_expr) => {
 115                         visit_clobber(opt_expr, |opt_expr| {
 116                             if let Some(expr) = opt_expr {
 117                                 vis.filter_map_expr(expr)
 118                             } else {
 119                                 None
 120                             }
 121                         });
 122                     }
 123                     $($(AstFragment::$Kind(ast) => vis.$mut_visit_ast(ast),)?)*
 124                     $($(AstFragment::$Kind(ast) =>
 125                         ast.flat_map_in_place(|ast| vis.$flat_map_ast_elt(ast)),)?)*
 126                 }
 127             }
 128
 129             pub fn visit_with<'a, V: Visitor<'a>>(&'a self, visitor: &mut V) {
 130                 match *self {
 131                     AstFragment::OptExpr(Some(ref expr)) => visitor.visit_expr(expr),
 132                     AstFragment::OptExpr(None) => {}
 133                     $($(AstFragment::$Kind(ref ast) => visitor.$visit_ast(ast),)?)*
 134                     $($(AstFragment::$Kind(ref ast) => for ast_elt in &ast[..] {
 135                         visitor.$visit_ast_elt(ast_elt, $($args)*);
 136                     })?)*
 137                 }
 138             }
 139         }
 140
 141         impl<'a> MacResult for crate::mbe::macro_rules::ParserAnyMacro<'a> {
 142             $(fn $make_ast(self: Box<crate::mbe::macro_rules::ParserAnyMacro<'a>>)
 143                            -> Option<$AstTy> {
 144                 Some(self.make(AstFragmentKind::$Kind).$make_ast())
 145             })*
 146         }
 147     }
 148 }
 149
 150 ast_fragments! {
 151     Expr(P<ast::Expr>) { "expression"; one fn visit_expr; fn visit_expr; fn make_expr; }
 152     Pat(P<ast::Pat>) { "pattern"; one fn visit_pat; fn visit_pat; fn make_pat; }
 153     Ty(P<ast::Ty>) { "type"; one fn visit_ty; fn visit_ty; fn make_ty; }
 154     Stmts(SmallVec<[ast::Stmt; 1]>) {
 155         "statement"; many fn flat_map_stmt; fn visit_stmt(); fn make_stmts;
 156     }
 157     Items(SmallVec<[P<ast::Item>; 1]>) {
 158         "item"; many fn flat_map_item; fn visit_item(); fn make_items;
 159     }
 160     TraitItems(SmallVec<[P<ast::AssocItem>; 1]>) {
 161         "trait item";
 162         many fn flat_map_trait_item;
 163         fn visit_assoc_item(AssocCtxt::Trait);
 164         fn make_trait_items;
 165     }
 166     ImplItems(SmallVec<[P<ast::AssocItem>; 1]>) {
 167         "impl item";
 168         many fn flat_map_impl_item;
 169         fn visit_assoc_item(AssocCtxt::Impl);
 170         fn make_impl_items;
 171     }
 172     ForeignItems(SmallVec<[P<ast::ForeignItem>; 1]>) {
 173         "foreign item";
 174         many fn flat_map_foreign_item;
 175         fn visit_foreign_item();
 176         fn make_foreign_items;
 177     }
 178     Arms(SmallVec<[ast::Arm; 1]>) {
 179         "match arm"; many fn flat_map_arm; fn visit_arm(); fn make_arms;
 180     }
 181     ExprFields(SmallVec<[ast::ExprField; 1]>) {
 182         "field expression"; many fn flat_map_expr_field; fn visit_expr_field(); fn make_expr_fields;
 183     }
 184     PatFields(SmallVec<[ast::PatField; 1]>) {
 185         "field pattern";
 186         many fn flat_map_pat_field;
 187         fn visit_pat_field();
 188         fn make_pat_fields;
 189     }
 190     GenericParams(SmallVec<[ast::GenericParam; 1]>) {
 191         "generic parameter";
 192         many fn flat_map_generic_param;
 193         fn visit_generic_param();
 194         fn make_generic_params;
 195     }
 196     Params(SmallVec<[ast::Param; 1]>) {
 197         "function parameter"; many fn flat_map_param; fn visit_param(); fn make_params;
 198     }
 199     FieldDefs(SmallVec<[ast::FieldDef; 1]>) {
 200         "field";
 201         many fn flat_map_field_def;
 202         fn visit_field_def();
 203         fn make_field_defs;
 204     }
 205     Variants(SmallVec<[ast::Variant; 1]>) {
 206         "variant"; many fn flat_map_variant; fn visit_variant(); fn make_variants;
 207     }
 208     Crate(ast::Crate) { "crate"; one fn visit_crate; fn visit_crate; fn make_crate; }
 209 }
 210
 211 pub enum SupportsMacroExpansion {
 212     No,
 213     Yes { supports_inner_attrs: bool },
 214 }
 215
 216 impl AstFragmentKind {
 217     pub(crate) fn dummy(self, span: Span) -> AstFragment {
 218         self.make_from(DummyResult::any(span)).expect("couldn't create a dummy AST fragment")
 219     }
 220
 221     pub fn supports_macro_expansion(self) -> SupportsMacroExpansion {
 222         match self {
 223             AstFragmentKind::OptExpr
 224             | AstFragmentKind::Expr
 225             | AstFragmentKind::Stmts
 226             | AstFragmentKind::Ty
 227             | AstFragmentKind::Pat => SupportsMacroExpansion::Yes { supports_inner_attrs: false },
 228             AstFragmentKind::Items
 229             | AstFragmentKind::TraitItems
 230             | AstFragmentKind::ImplItems
 231             | AstFragmentKind::ForeignItems
 232             | AstFragmentKind::Crate => SupportsMacroExpansion::Yes { supports_inner_attrs: true },
 233             AstFragmentKind::Arms
 234             | AstFragmentKind::ExprFields
 235             | AstFragmentKind::PatFields
 236             | AstFragmentKind::GenericParams
 237             | AstFragmentKind::Params
 238             | AstFragmentKind::FieldDefs
 239             | AstFragmentKind::Variants => SupportsMacroExpansion::No,
 240         }
 241     }
 242
 243     fn expect_from_annotatables<I: IntoIterator<Item = Annotatable>>(
 244         self,
 245         items: I,
 246     ) -> AstFragment {
 247         let mut items = items.into_iter();
 248         match self {
 249             AstFragmentKind::Arms => {
 250                 AstFragment::Arms(items.map(Annotatable::expect_arm).collect())
 251             }
 252             AstFragmentKind::ExprFields => {
 253                 AstFragment::ExprFields(items.map(Annotatable::expect_expr_field).collect())
 254             }
 255             AstFragmentKind::PatFields => {
 256                 AstFragment::PatFields(items.map(Annotatable::expect_pat_field).collect())
 257             }
 258             AstFragmentKind::GenericParams => {
 259                 AstFragment::GenericParams(items.map(Annotatable::expect_generic_param).collect())
 260             }
 261             AstFragmentKind::Params => {
 262                 AstFragment::Params(items.map(Annotatable::expect_param).collect())
 263             }
 264             AstFragmentKind::FieldDefs => {
 265                 AstFragment::FieldDefs(items.map(Annotatable::expect_field_def).collect())
 266             }
 267             AstFragmentKind::Variants => {
 268                 AstFragment::Variants(items.map(Annotatable::expect_variant).collect())
 269             }
 270             AstFragmentKind::Items => {
 271                 AstFragment::Items(items.map(Annotatable::expect_item).collect())
 272             }
 273             AstFragmentKind::ImplItems => {
 274                 AstFragment::ImplItems(items.map(Annotatable::expect_impl_item).collect())
 275             }
 276             AstFragmentKind::TraitItems => {
 277                 AstFragment::TraitItems(items.map(Annotatable::expect_trait_item).collect())
 278             }
 279             AstFragmentKind::ForeignItems => {
 280                 AstFragment::ForeignItems(items.map(Annotatable::expect_foreign_item).collect())
 281             }
 282             AstFragmentKind::Stmts => {
 283                 AstFragment::Stmts(items.map(Annotatable::expect_stmt).collect())
 284             }
 285             AstFragmentKind::Expr => AstFragment::Expr(
 286                 items.next().expect("expected exactly one expression").expect_expr(),
 287             ),
 288             AstFragmentKind::OptExpr => {
 289                 AstFragment::OptExpr(items.next().map(Annotatable::expect_expr))
 290             }
 291             AstFragmentKind::Crate => {
 292                 AstFragment::Crate(items.next().expect("expected exactly one crate").expect_crate())
 293             }
 294             AstFragmentKind::Pat | AstFragmentKind::Ty => {
 295                 panic!("patterns and types aren't annotatable")
 296             }
 297         }
 298     }
 299 }
 300
 301 pub struct Invocation {
 302     pub kind: InvocationKind,
 303     pub fragment_kind: AstFragmentKind,
 304     pub expansion_data: ExpansionData,
 305 }
 306
 307 pub enum InvocationKind {
 308     Bang {
 309         mac: ast::MacCall,
 310         span: Span,
 311     },
 312     Attr {
 313         attr: ast::Attribute,
 314         // Re-insertion position for inert attributes.
 315         pos: usize,
 316         item: Annotatable,
 317         // Required for resolving derive helper attributes.
 318         derives: Vec<ast::Path>,
 319     },
 320     Derive {
 321         path: ast::Path,
 322         item: Annotatable,
 323     },
 324 }
 325
 326 impl InvocationKind {
 327     fn placeholder_visibility(&self) -> Option<ast::Visibility> {
 328         // HACK: For unnamed fields placeholders should have the same visibility as the actual
 329         // fields because for tuple structs/variants resolve determines visibilities of their
 330         // constructor using these field visibilities before attributes on them are are expanded.
 331         // The assumption is that the attribute expansion cannot change field visibilities,
 332         // and it holds because only inert attributes are supported in this position.
 333         match self {
 334             InvocationKind::Attr { item: Annotatable::FieldDef(field), .. }
 335             | InvocationKind::Derive { item: Annotatable::FieldDef(field), .. }
 336                 if field.ident.is_none() =>
 337             {
 338                 Some(field.vis.clone())
 339             }
 340             _ => None,
 341         }
 342     }
 343 }
 344
 345 impl Invocation {
 346     pub fn span(&self) -> Span {
 347         match &self.kind {
 348             InvocationKind::Bang { span, .. } => *span,
 349             InvocationKind::Attr { attr, .. } => attr.span,
 350             InvocationKind::Derive { path, .. } => path.span,
 351         }
 352     }
 353 }
 354
 355 pub struct MacroExpander<'a, 'b> {
 356     pub cx: &'a mut ExtCtxt<'b>,
 357     monotonic: bool, // cf. `cx.monotonic_expander()`
 358 }
 359
 360 impl<'a, 'b> MacroExpander<'a, 'b> {
 361     pub fn new(cx: &'a mut ExtCtxt<'b>, monotonic: bool) -> Self {
 362         MacroExpander { cx, monotonic }
 363     }
 364
 365     pub fn expand_crate(&mut self, krate: ast::Crate) -> ast::Crate {
 366         let file_path = match self.cx.source_map().span_to_filename(krate.spans.inner_span) {
 367             FileName::Real(name) => name
 368                 .into_local_path()
 369                 .expect("attempting to resolve a file path in an external file"),
 370             other => PathBuf::from(other.prefer_local().to_string()),
 371         };
 372         let dir_path = file_path.parent().unwrap_or(&file_path).to_owned();
 373         self.cx.root_path = dir_path.clone();
 374         self.cx.current_expansion.module = Rc::new(ModuleData {
 375             mod_path: vec![Ident::from_str(&self.cx.ecfg.crate_name)],
 376             file_path_stack: vec![file_path],
 377             dir_path,
 378         });
 379         let krate = self.fully_expand_fragment(AstFragment::Crate(krate)).make_crate();
 380         assert_eq!(krate.id, ast::CRATE_NODE_ID);
 381         self.cx.trace_macros_diag();
 382         krate
 383     }
 384
 385     // Recursively expand all macro invocations in this AST fragment.
 386     pub fn fully_expand_fragment(&mut self, input_fragment: AstFragment) -> AstFragment {
 387         let orig_expansion_data = self.cx.current_expansion.clone();
 388         let orig_force_mode = self.cx.force_mode;
 389
 390         // Collect all macro invocations and replace them with placeholders.
 391         let (mut fragment_with_placeholders, mut invocations) =
 392             self.collect_invocations(input_fragment, &[]);
 393
 394         // Optimization: if we resolve all imports now,
 395         // we'll be able to immediately resolve most of imported macros.
 396         self.resolve_imports();
 397
 398         // Resolve paths in all invocations and produce output expanded fragments for them, but
 399         // do not insert them into our input AST fragment yet, only store in `expanded_fragments`.
 400         // The output fragments also go through expansion recursively until no invocations are left.
 401         // Unresolved macros produce dummy outputs as a recovery measure.
 402         invocations.reverse();
 403         let mut expanded_fragments = Vec::new();
 404         let mut undetermined_invocations = Vec::new();
 405         let (mut progress, mut force) = (false, !self.monotonic);
 406         loop {
 407             let Some((invoc, ext)) = invocations.pop() else {
 408                 self.resolve_imports();
 409                 if undetermined_invocations.is_empty() {
 410                     break;
 411                 }
 412                 invocations = mem::take(&mut undetermined_invocations);
 413                 force = !mem::replace(&mut progress, false);
 414                 if force && self.monotonic {
 415                     self.cx.sess.delay_span_bug(
 416                         invocations.last().unwrap().0.span(),
 417                         "expansion entered force mode without producing any errors",
 418                     );
 419                 }
 420                 continue;
 421             };
 422
 423             let ext = match ext {
 424                 Some(ext) => ext,
 425                 None => {
 426                     let eager_expansion_root = if self.monotonic {
 427                         invoc.expansion_data.id
 428                     } else {
 429                         orig_expansion_data.id
 430                     };
 431                     match self.cx.resolver.resolve_macro_invocation(
 432                         &invoc,
 433                         eager_expansion_root,
 434                         force,
 435                     ) {
 436                         Ok(ext) => ext,
 437                         Err(Indeterminate) => {
 438                             // Cannot resolve, will retry this invocation later.
 439                             undetermined_invocations.push((invoc, None));
 440                             continue;
 441                         }
 442                     }
 443                 }
 444             };
 445
 446             let ExpansionData { depth, id: expn_id, .. } = invoc.expansion_data;
 447             let depth = depth - orig_expansion_data.depth;
 448             self.cx.current_expansion = invoc.expansion_data.clone();
 449             self.cx.force_mode = force;
 450
 451             let fragment_kind = invoc.fragment_kind;
 452             let (expanded_fragment, new_invocations) = match self.expand_invoc(invoc, &ext.kind) {
 453                 ExpandResult::Ready(fragment) => {
 454                     let mut derive_invocations = Vec::new();
 455                     let derive_placeholders = self
 456                         .cx
 457                         .resolver
 458                         .take_derive_resolutions(expn_id)
 459                         .map(|derives| {
 460                             derive_invocations.reserve(derives.len());
 461                             derives
 462                                 .into_iter()
 463                                 .map(|(path, item, _exts)| {
 464                                     // FIXME: Consider using the derive resolutions (`_exts`)
 465                                     // instead of enqueuing the derives to be resolved again later.
 466                                     let expn_id = LocalExpnId::fresh_empty();
 467                                     derive_invocations.push((
 468                                         Invocation {
 469                                             kind: InvocationKind::Derive { path, item },
 470                                             fragment_kind,
 471                                             expansion_data: ExpansionData {
 472                                                 id: expn_id,
 473                                                 ..self.cx.current_expansion.clone()
 474                                             },
 475                                         },
 476                                         None,
 477                                     ));
 478                                     NodeId::placeholder_from_expn_id(expn_id)
 479                                 })
 480                                 .collect::<Vec<_>>()
 481                         })
 482                         .unwrap_or_default();
 483
 484                     let (fragment, collected_invocations) =
 485                         self.collect_invocations(fragment, &derive_placeholders);
 486                     // We choose to expand any derive invocations associated with this macro invocation
 487                     // *before* any macro invocations collected from the output fragment
 488                     derive_invocations.extend(collected_invocations);
 489                     (fragment, derive_invocations)
 490                 }
 491                 ExpandResult::Retry(invoc) => {
 492                     if force {
 493                         self.cx.span_bug(
 494                             invoc.span(),
 495                             "expansion entered force mode but is still stuck",
 496                         );
 497                     } else {
 498                         // Cannot expand, will retry this invocation later.
 499                         undetermined_invocations.push((invoc, Some(ext)));
 500                         continue;
 501                     }
 502                 }
 503             };
 504
 505             progress = true;
 506             if expanded_fragments.len() < depth {
 507                 expanded_fragments.push(Vec::new());
 508             }
 509             expanded_fragments[depth - 1].push((expn_id, expanded_fragment));
 510             invocations.extend(new_invocations.into_iter().rev());
 511         }
 512
 513         self.cx.current_expansion = orig_expansion_data;
 514         self.cx.force_mode = orig_force_mode;
 515
 516         // Finally incorporate all the expanded macros into the input AST fragment.
 517         let mut placeholder_expander = PlaceholderExpander::default();
 518         while let Some(expanded_fragments) = expanded_fragments.pop() {
 519             for (expn_id, expanded_fragment) in expanded_fragments.into_iter().rev() {
 520                 placeholder_expander
 521                     .add(NodeId::placeholder_from_expn_id(expn_id), expanded_fragment);
 522             }
 523         }
 524         fragment_with_placeholders.mut_visit_with(&mut placeholder_expander);
 525         fragment_with_placeholders
 526     }
 527
 528     fn resolve_imports(&mut self) {
 529         if self.monotonic {
 530             self.cx.resolver.resolve_imports();
 531         }
 532     }
 533
 534     /// Collects all macro invocations reachable at this time in this AST fragment, and replace
 535     /// them with "placeholders" - dummy macro invocations with specially crafted `NodeId`s.
 536     /// Then call into resolver that builds a skeleton ("reduced graph") of the fragment and
 537     /// prepares data for resolving paths of macro invocations.
 538     fn collect_invocations(
 539         &mut self,
 540         mut fragment: AstFragment,
 541         extra_placeholders: &[NodeId],
 542     ) -> (AstFragment, Vec<(Invocation, Option<Lrc<SyntaxExtension>>)>) {
 543         // Resolve `$crate`s in the fragment for pretty-printing.
 544         self.cx.resolver.resolve_dollar_crates();
 545
 546         let mut invocations = {
 547             let mut collector = InvocationCollector {
 548                 // Non-derive macro invocations cannot see the results of cfg expansion - they
 549                 // will either be removed along with the item, or invoked before the cfg/cfg_attr
 550                 // attribute is expanded. Therefore, we don't need to configure the tokens
 551                 // Derive macros *can* see the results of cfg-expansion - they are handled
 552                 // specially in `fully_expand_fragment`
 553                 cx: self.cx,
 554                 invocations: Vec::new(),
 555                 monotonic: self.monotonic,
 556             };
 557             fragment.mut_visit_with(&mut collector);
 558             fragment.add_placeholders(extra_placeholders);
 559             collector.invocations
 560         };
 561
 562         if self.monotonic {
 563             self.cx
 564                 .resolver
 565                 .visit_ast_fragment_with_placeholders(self.cx.current_expansion.id, &fragment);
 566
 567             if self.cx.sess.opts.debugging_opts.incremental_relative_spans {
 568                 for (invoc, _) in invocations.iter_mut() {
 569                     let expn_id = invoc.expansion_data.id;
 570                     let parent_def = self.cx.resolver.invocation_parent(expn_id);
 571                     let span = match &mut invoc.kind {
 572                         InvocationKind::Bang { ref mut span, .. } => span,
 573                         InvocationKind::Attr { attr, .. } => &mut attr.span,
 574                         InvocationKind::Derive { path, .. } => &mut path.span,
 575                     };
 576                     *span = span.with_parent(Some(parent_def));
 577                 }
 578             }
 579         }
 580
 581         (fragment, invocations)
 582     }
 583
 584     fn error_recursion_limit_reached(&mut self) {
 585         let expn_data = self.cx.current_expansion.id.expn_data();
 586         let suggested_limit = match self.cx.ecfg.recursion_limit {
 587             Limit(0) => Limit(2),
 588             limit => limit * 2,
 589         };
 590         self.cx
 591             .struct_span_err(
 592                 expn_data.call_site,
 593                 &format!("recursion limit reached while expanding `{}`", expn_data.kind.descr()),
 594             )
 595             .help(&format!(
 596                 "consider increasing the recursion limit by adding a \
 597                  `#![recursion_limit = \"{}\"]` attribute to your crate (`{}`)",
 598                 suggested_limit, self.cx.ecfg.crate_name,
 599             ))
 600             .emit();
 601         self.cx.trace_macros_diag();
 602     }
 603
 604     /// A macro's expansion does not fit in this fragment kind.
 605     /// For example, a non-type macro in a type position.
 606     fn error_wrong_fragment_kind(&mut self, kind: AstFragmentKind, mac: &ast::MacCall, span: Span) {
 607         let msg = format!(
 608             "non-{kind} macro in {kind} position: {path}",
 609             kind = kind.name(),
 610             path = pprust::path_to_string(&mac.path),
 611         );
 612         self.cx.span_err(span, &msg);
 613         self.cx.trace_macros_diag();
 614     }
 615
 616     fn expand_invoc(
 617         &mut self,
 618         invoc: Invocation,
 619         ext: &SyntaxExtensionKind,
 620     ) -> ExpandResult<AstFragment, Invocation> {
 621         let recursion_limit =
 622             self.cx.reduced_recursion_limit.unwrap_or(self.cx.ecfg.recursion_limit);
 623         if !recursion_limit.value_within_limit(self.cx.current_expansion.depth) {
 624             if self.cx.reduced_recursion_limit.is_none() {
 625                 self.error_recursion_limit_reached();
 626             }
 627
 628             // Reduce the recursion limit by half each time it triggers.
 629             self.cx.reduced_recursion_limit = Some(recursion_limit / 2);
 630
 631             return ExpandResult::Ready(invoc.fragment_kind.dummy(invoc.span()));
 632         }
 633
 634         let (fragment_kind, span) = (invoc.fragment_kind, invoc.span());
 635         ExpandResult::Ready(match invoc.kind {
 636             InvocationKind::Bang { mac, .. } => match ext {
 637                 SyntaxExtensionKind::Bang(expander) => {
 638                     let Ok(tok_result) = expander.expand(self.cx, span, mac.args.inner_tokens()) else {
 639                         return ExpandResult::Ready(fragment_kind.dummy(span));
 640                     };
 641                     self.parse_ast_fragment(tok_result, fragment_kind, &mac.path, span)
 642                 }
 643                 SyntaxExtensionKind::LegacyBang(expander) => {
 644                     let prev = self.cx.current_expansion.prior_type_ascription;
 645                     self.cx.current_expansion.prior_type_ascription = mac.prior_type_ascription;
 646                     let tok_result = expander.expand(self.cx, span, mac.args.inner_tokens());
 647                     let result = if let Some(result) = fragment_kind.make_from(tok_result) {
 648                         result
 649                     } else {
 650                         self.error_wrong_fragment_kind(fragment_kind, &mac, span);
 651                         fragment_kind.dummy(span)
 652                     };
 653                     self.cx.current_expansion.prior_type_ascription = prev;
 654                     result
 655                 }
 656                 _ => unreachable!(),
 657             },
 658             InvocationKind::Attr { attr, pos, mut item, derives } => match ext {
 659                 SyntaxExtensionKind::Attr(expander) => {
 660                     self.gate_proc_macro_input(&item);
 661                     self.gate_proc_macro_attr_item(span, &item);
 662                     let tokens = match &item {
 663                         // FIXME: Collect tokens and use them instead of generating
 664                         // fake ones. These are unstable, so it needs to be
 665                         // fixed prior to stabilization
 666                         // Fake tokens when we are invoking an inner attribute, and
 667                         // we are invoking it on an out-of-line module or crate.
 668                         Annotatable::Crate(krate) => rustc_parse::fake_token_stream_for_crate(
 669                             &self.cx.sess.parse_sess,
 670                             krate,
 671                         ),
 672                         Annotatable::Item(item_inner)
 673                             if matches!(attr.style, AttrStyle::Inner)
 674                                 && matches!(
 675                                     item_inner.kind,
 676                                     ItemKind::Mod(
 677                                         _,
 678                                         ModKind::Unloaded | ModKind::Loaded(_, Inline::No, _),
 679                                     )
 680                                 ) =>
 681                         {
 682                             rustc_parse::fake_token_stream_for_item(
 683                                 &self.cx.sess.parse_sess,
 684                                 item_inner,
 685                             )
 686                         }
 687                         _ => item.to_tokens(),
 688                     };
 689                     let attr_item = attr.unwrap_normal_item();
 690                     if let MacArgs::Eq(..) = attr_item.args {
 691                         self.cx.span_err(span, "key-value macro attributes are not supported");
 692                     }
 693                     let inner_tokens = attr_item.args.inner_tokens();
 694                     let Ok(tok_result) = expander.expand(self.cx, span, inner_tokens, tokens) else {
 695                         return ExpandResult::Ready(fragment_kind.dummy(span));
 696                     };
 697                     self.parse_ast_fragment(tok_result, fragment_kind, &attr_item.path, span)
 698                 }
 699                 SyntaxExtensionKind::LegacyAttr(expander) => {
 700                     match validate_attr::parse_meta(&self.cx.sess.parse_sess, &attr) {
 701                         Ok(meta) => {
 702                             let items = match expander.expand(self.cx, span, &meta, item) {
 703                                 ExpandResult::Ready(items) => items,
 704                                 ExpandResult::Retry(item) => {
 705                                     // Reassemble the original invocation for retrying.
 706                                     return ExpandResult::Retry(Invocation {
 707                                         kind: InvocationKind::Attr { attr, pos, item, derives },
 708                                         ..invoc
 709                                     });
 710                                 }
 711                             };
 712                             if fragment_kind == AstFragmentKind::Expr && items.is_empty() {
 713                                 let msg =
 714                                     "removing an expression is not supported in this position";
 715                                 self.cx.span_err(span, msg);
 716                                 fragment_kind.dummy(span)
 717                             } else {
 718                                 fragment_kind.expect_from_annotatables(items)
 719                             }
 720                         }
 721                         Err(mut err) => {
 722                             err.emit();
 723                             fragment_kind.dummy(span)
 724                         }
 725                     }
 726                 }
 727                 SyntaxExtensionKind::NonMacroAttr => {
 728                     self.cx.expanded_inert_attrs.mark(&attr);
 729                     item.visit_attrs(|attrs| attrs.insert(pos, attr));
 730                     fragment_kind.expect_from_annotatables(iter::once(item))
 731                 }
 732                 _ => unreachable!(),
 733             },
 734             InvocationKind::Derive { path, item } => match ext {
 735                 SyntaxExtensionKind::Derive(expander)
 736                 | SyntaxExtensionKind::LegacyDerive(expander) => {
 737                     if let SyntaxExtensionKind::Derive(..) = ext {
 738                         self.gate_proc_macro_input(&item);
 739                     }
 740                     let meta = ast::MetaItem { kind: MetaItemKind::Word, span, path };
 741                     let items = match expander.expand(self.cx, span, &meta, item) {
 742                         ExpandResult::Ready(items) => items,
 743                         ExpandResult::Retry(item) => {
 744                             // Reassemble the original invocation for retrying.
 745                             return ExpandResult::Retry(Invocation {
 746                                 kind: InvocationKind::Derive { path: meta.path, item },
 747                                 ..invoc
 748                             });
 749                         }
 750                     };
 751                     fragment_kind.expect_from_annotatables(items)
 752                 }
 753                 _ => unreachable!(),
 754             },
 755         })
 756     }
 757
 758     fn gate_proc_macro_attr_item(&self, span: Span, item: &Annotatable) {
 759         let kind = match item {
 760             Annotatable::Item(_)
 761             | Annotatable::TraitItem(_)
 762             | Annotatable::ImplItem(_)
 763             | Annotatable::ForeignItem(_)
 764             | Annotatable::Crate(..) => return,
 765             Annotatable::Stmt(stmt) => {
 766                 // Attributes are stable on item statements,
 767                 // but unstable on all other kinds of statements
 768                 if stmt.is_item() {
 769                     return;
 770                 }
 771                 "statements"
 772             }
 773             Annotatable::Expr(_) => "expressions",
 774             Annotatable::Arm(..)
 775             | Annotatable::ExprField(..)
 776             | Annotatable::PatField(..)
 777             | Annotatable::GenericParam(..)
 778             | Annotatable::Param(..)
 779             | Annotatable::FieldDef(..)
 780             | Annotatable::Variant(..) => panic!("unexpected annotatable"),
 781         };
 782         if self.cx.ecfg.proc_macro_hygiene() {
 783             return;
 784         }
 785         feature_err(
 786             &self.cx.sess.parse_sess,
 787             sym::proc_macro_hygiene,
 788             span,
 789             &format!("custom attributes cannot be applied to {}", kind),
 790         )
 791         .emit();
 792     }
 793
 794     fn gate_proc_macro_input(&self, annotatable: &Annotatable) {
 795         struct GateProcMacroInput<'a> {
 796             parse_sess: &'a ParseSess,
 797         }
 798
 799         impl<'ast, 'a> Visitor<'ast> for GateProcMacroInput<'a> {
 800             fn visit_item(&mut self, item: &'ast ast::Item) {
 801                 match &item.kind {
 802                     ItemKind::Mod(_, mod_kind)
 803                         if !matches!(mod_kind, ModKind::Loaded(_, Inline::Yes, _)) =>
 804                     {
 805                         feature_err(
 806                             self.parse_sess,
 807                             sym::proc_macro_hygiene,
 808                             item.span,
 809                             "non-inline modules in proc macro input are unstable",
 810                         )
 811                         .emit();
 812                     }
 813                     _ => {}
 814                 }
 815
 816                 visit::walk_item(self, item);
 817             }
 818         }
 819
 820         if !self.cx.ecfg.proc_macro_hygiene() {
 821             annotatable
 822                 .visit_with(&mut GateProcMacroInput { parse_sess: &self.cx.sess.parse_sess });
 823         }
 824     }
 825
 826     fn parse_ast_fragment(
 827         &mut self,
 828         toks: TokenStream,
 829         kind: AstFragmentKind,
 830         path: &ast::Path,
 831         span: Span,
 832     ) -> AstFragment {
 833         let mut parser = self.cx.new_parser_from_tts(toks);
 834         match parse_ast_fragment(&mut parser, kind) {
 835             Ok(fragment) => {
 836                 ensure_complete_parse(&mut parser, path, kind.name(), span);
 837                 fragment
 838             }
 839             Err(mut err) => {
 840                 if err.span.is_dummy() {
 841                     err.set_span(span);
 842                 }
 843                 annotate_err_with_kind(&mut err, kind, span);
 844                 err.emit();
 845                 self.cx.trace_macros_diag();
 846                 kind.dummy(span)
 847             }
 848         }
 849     }
 850 }
 851
 852 pub fn parse_ast_fragment<'a>(
 853     this: &mut Parser<'a>,
 854     kind: AstFragmentKind,
 855 ) -> PResult<'a, AstFragment> {
 856     Ok(match kind {
 857         AstFragmentKind::Items => {
 858             let mut items = SmallVec::new();
 859             while let Some(item) = this.parse_item(ForceCollect::No)? {
 860                 items.push(item);
 861             }
 862             AstFragment::Items(items)
 863         }
 864         AstFragmentKind::TraitItems => {
 865             let mut items = SmallVec::new();
 866             while let Some(item) = this.parse_trait_item(ForceCollect::No)? {
 867                 items.extend(item);
 868             }
 869             AstFragment::TraitItems(items)
 870         }
 871         AstFragmentKind::ImplItems => {
 872             let mut items = SmallVec::new();
 873             while let Some(item) = this.parse_impl_item(ForceCollect::No)? {
 874                 items.extend(item);
 875             }
 876             AstFragment::ImplItems(items)
 877         }
 878         AstFragmentKind::ForeignItems => {
 879             let mut items = SmallVec::new();
 880             while let Some(item) = this.parse_foreign_item(ForceCollect::No)? {
 881                 items.extend(item);
 882             }
 883             AstFragment::ForeignItems(items)
 884         }
 885         AstFragmentKind::Stmts => {
 886             let mut stmts = SmallVec::new();
 887             // Won't make progress on a `}`.
 888             while this.token != token::Eof && this.token != token::CloseDelim(Delimiter::Brace) {
 889                 if let Some(stmt) = this.parse_full_stmt(AttemptLocalParseRecovery::Yes)? {
 890                     stmts.push(stmt);
 891                 }
 892             }
 893             AstFragment::Stmts(stmts)
 894         }
 895         AstFragmentKind::Expr => AstFragment::Expr(this.parse_expr()?),
 896         AstFragmentKind::OptExpr => {
 897             if this.token != token::Eof {
 898                 AstFragment::OptExpr(Some(this.parse_expr()?))
 899             } else {
 900                 AstFragment::OptExpr(None)
 901             }
 902         }
 903         AstFragmentKind::Ty => AstFragment::Ty(this.parse_ty()?),
 904         AstFragmentKind::Pat => AstFragment::Pat(this.parse_pat_allow_top_alt(
 905             None,
 906             RecoverComma::No,
 907             RecoverColon::Yes,
 908             CommaRecoveryMode::LikelyTuple,
 909         )?),
 910         AstFragmentKind::Crate => AstFragment::Crate(this.parse_crate_mod()?),
 911         AstFragmentKind::Arms
 912         | AstFragmentKind::ExprFields
 913         | AstFragmentKind::PatFields
 914         | AstFragmentKind::GenericParams
 915         | AstFragmentKind::Params
 916         | AstFragmentKind::FieldDefs
 917         | AstFragmentKind::Variants => panic!("unexpected AST fragment kind"),
 918     })
 919 }
 920
 921 pub fn ensure_complete_parse<'a>(
 922     this: &mut Parser<'a>,
 923     macro_path: &ast::Path,
 924     kind_name: &str,
 925     span: Span,
 926 ) {
 927     if this.token != token::Eof {
 928         let token = pprust::token_to_string(&this.token);
 929         let msg = format!("macro expansion ignores token `{}` and any following", token);
 930         // Avoid emitting backtrace info twice.
 931         let def_site_span = this.token.span.with_ctxt(SyntaxContext::root());
 932         let mut err = this.struct_span_err(def_site_span, &msg);
 933         err.span_label(span, "caused by the macro expansion here");
 934         let msg = format!(
 935             "the usage of `{}!` is likely invalid in {} context",
 936             pprust::path_to_string(macro_path),
 937             kind_name,
 938         );
 939         err.note(&msg);
 940         let semi_span = this.sess.source_map().next_point(span);
 941
 942         let semi_full_span = semi_span.to(this.sess.source_map().next_point(semi_span));
 943         match this.sess.source_map().span_to_snippet(semi_full_span) {
 944             Ok(ref snippet) if &snippet[..] != ";" && kind_name == "expression" => {
 945                 err.span_suggestion(
 946                     semi_span,
 947                     "you might be missing a semicolon here",
 948                     ";",
 949                     Applicability::MaybeIncorrect,
 950                 );
 951             }
 952             _ => {}
 953         }
 954         err.emit();
 955     }
 956 }
 957
 958 /// Wraps a call to `noop_visit_*` / `noop_flat_map_*`
 959 /// for an AST node that supports attributes
 960 /// (see the `Annotatable` enum)
 961 /// This method assigns a `NodeId`, and sets that `NodeId`
 962 /// as our current 'lint node id'. If a macro call is found
 963 /// inside this AST node, we will use this AST node's `NodeId`
 964 /// to emit lints associated with that macro (allowing
 965 /// `#[allow]` / `#[deny]` to be applied close to
 966 /// the macro invocation).
 967 ///
 968 /// Do *not* call this for a macro AST node
 969 /// (e.g. `ExprKind::MacCall`) - we cannot emit lints
 970 /// at these AST nodes, since they are removed and
 971 /// replaced with the result of macro expansion.
 972 ///
 973 /// All other `NodeId`s are assigned by `visit_id`.
 974 /// * `self` is the 'self' parameter for the current method,
 975 /// * `id` is a mutable reference to the `NodeId` field
 976 ///    of the current AST node.
 977 /// * `closure` is a closure that executes the
 978 ///   `noop_visit_*` / `noop_flat_map_*` method
 979 ///   for the current AST node.
 980 macro_rules! assign_id {
 981     ($self:ident, $id:expr, $closure:expr) => {{
 982         let old_id = $self.cx.current_expansion.lint_node_id;
 983         if $self.monotonic {
 984             debug_assert_eq!(*$id, ast::DUMMY_NODE_ID);
 985             let new_id = $self.cx.resolver.next_node_id();
 986             *$id = new_id;
 987             $self.cx.current_expansion.lint_node_id = new_id;
 988         }
 989         let ret = ($closure)();
 990         $self.cx.current_expansion.lint_node_id = old_id;
 991         ret
 992     }};
 993 }
 994
 995 enum AddSemicolon {
 996     Yes,
 997     No,
 998 }
 999
1000 /// A trait implemented for all `AstFragment` nodes and providing all pieces
1001 /// of functionality used by `InvocationCollector`.
1002 trait InvocationCollectorNode: HasAttrs + HasNodeId + Sized {
1003     type OutputTy = SmallVec<[Self; 1]>;
1004     type AttrsTy: Deref<Target = [ast::Attribute]> = Vec<ast::Attribute>;
1005     const KIND: AstFragmentKind;
1006     fn to_annotatable(self) -> Annotatable;
1007     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy;
1008     fn descr() -> &'static str {
1009         unreachable!()
1010     }
1011     fn noop_flat_map<V: MutVisitor>(self, _visitor: &mut V) -> Self::OutputTy {
1012         unreachable!()
1013     }
1014     fn noop_visit<V: MutVisitor>(&mut self, _visitor: &mut V) {
1015         unreachable!()
1016     }
1017     fn is_mac_call(&self) -> bool {
1018         false
1019     }
1020     fn take_mac_call(self) -> (ast::MacCall, Self::AttrsTy, AddSemicolon) {
1021         unreachable!()
1022     }
1023     fn pre_flat_map_node_collect_attr(_cfg: &StripUnconfigured<'_>, _attr: &ast::Attribute) {}
1024     fn post_flat_map_node_collect_bang(_output: &mut Self::OutputTy, _add_semicolon: AddSemicolon) {
1025     }
1026     fn wrap_flat_map_node_noop_flat_map(
1027         node: Self,
1028         collector: &mut InvocationCollector<'_, '_>,
1029         noop_flat_map: impl FnOnce(Self, &mut InvocationCollector<'_, '_>) -> Self::OutputTy,
1030     ) -> Result<Self::OutputTy, Self> {
1031         Ok(noop_flat_map(node, collector))
1032     }
1033 }
1034
1035 impl InvocationCollectorNode for P<ast::Item> {
1036     const KIND: AstFragmentKind = AstFragmentKind::Items;
1037     fn to_annotatable(self) -> Annotatable {
1038         Annotatable::Item(self)
1039     }
1040     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
1041         fragment.make_items()
1042     }
1043     fn noop_flat_map<V: MutVisitor>(self, visitor: &mut V) -> Self::OutputTy {
1044         noop_flat_map_item(self, visitor)
1045     }
1046     fn is_mac_call(&self) -> bool {
1047         matches!(self.kind, ItemKind::MacCall(..))
1048     }
1049     fn take_mac_call(self) -> (ast::MacCall, Self::AttrsTy, AddSemicolon) {
1050         let node = self.into_inner();
1051         match node.kind {
1052             ItemKind::MacCall(mac) => (mac, node.attrs, AddSemicolon::No),
1053             _ => unreachable!(),
1054         }
1055     }
1056     fn wrap_flat_map_node_noop_flat_map(
1057         mut node: Self,
1058         collector: &mut InvocationCollector<'_, '_>,
1059         noop_flat_map: impl FnOnce(Self, &mut InvocationCollector<'_, '_>) -> Self::OutputTy,
1060     ) -> Result<Self::OutputTy, Self> {
1061         if !matches!(node.kind, ItemKind::Mod(..)) {
1062             return Ok(noop_flat_map(node, collector));
1063         }
1064
1065         // Work around borrow checker not seeing through `P`'s deref.
1066         let (ident, span, mut attrs) = (node.ident, node.span, mem::take(&mut node.attrs));
1067         let ItemKind::Mod(_, mod_kind) = &mut node.kind else {
1068             unreachable!()
1069         };
1070
1071         let ecx = &mut collector.cx;
1072         let (file_path, dir_path, dir_ownership) = match mod_kind {
1073             ModKind::Loaded(_, inline, _) => {
1074                 // Inline `mod foo { ... }`, but we still need to push directories.
1075                 let (dir_path, dir_ownership) = mod_dir_path(
1076                     &ecx.sess,
1077                     ident,
1078                     &attrs,
1079                     &ecx.current_expansion.module,
1080                     ecx.current_expansion.dir_ownership,
1081                     *inline,
1082                 );
1083                 node.attrs = attrs;
1084                 (None, dir_path, dir_ownership)
1085             }
1086             ModKind::Unloaded => {
1087                 // We have an outline `mod foo;` so we need to parse the file.
1088                 let old_attrs_len = attrs.len();
1089                 let ParsedExternalMod { items, spans, file_path, dir_path, dir_ownership } =
1090                     parse_external_mod(
1091                         &ecx.sess,
1092                         ident,
1093                         span,
1094                         &ecx.current_expansion.module,
1095                         ecx.current_expansion.dir_ownership,
1096                         &mut attrs,
1097                     );
1098
1099                 if let Some(lint_store) = ecx.lint_store {
1100                     lint_store.pre_expansion_lint(
1101                         ecx.sess,
1102                         ecx.resolver.registered_tools(),
1103                         ecx.current_expansion.lint_node_id,
1104                         &attrs,
1105                         &items,
1106                         ident.name.as_str(),
1107                     );
1108                 }
1109
1110                 *mod_kind = ModKind::Loaded(items, Inline::No, spans);
1111                 node.attrs = attrs;
1112                 if node.attrs.len() > old_attrs_len {
1113                     // If we loaded an out-of-line module and added some inner attributes,
1114                     // then we need to re-configure it and re-collect attributes for
1115                     // resolution and expansion.
1116                     return Err(node);
1117                 }
1118                 (Some(file_path), dir_path, dir_ownership)
1119             }
1120         };
1121
1122         // Set the module info before we flat map.
1123         let mut module = ecx.current_expansion.module.with_dir_path(dir_path);
1124         module.mod_path.push(ident);
1125         if let Some(file_path) = file_path {
1126             module.file_path_stack.push(file_path);
1127         }
1128
1129         let orig_module = mem::replace(&mut ecx.current_expansion.module, Rc::new(module));
1130         let orig_dir_ownership =
1131             mem::replace(&mut ecx.current_expansion.dir_ownership, dir_ownership);
1132
1133         let res = Ok(noop_flat_map(node, collector));
1134
1135         collector.cx.current_expansion.dir_ownership = orig_dir_ownership;
1136         collector.cx.current_expansion.module = orig_module;
1137         res
1138     }
1139 }
1140
1141 struct TraitItemTag;
1142 impl InvocationCollectorNode for AstNodeWrapper<P<ast::AssocItem>, TraitItemTag> {
1143     type OutputTy = SmallVec<[P<ast::AssocItem>; 1]>;
1144     const KIND: AstFragmentKind = AstFragmentKind::TraitItems;
1145     fn to_annotatable(self) -> Annotatable {
1146         Annotatable::TraitItem(self.wrapped)
1147     }
1148     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
1149         fragment.make_trait_items()
1150     }
1151     fn noop_flat_map<V: MutVisitor>(self, visitor: &mut V) -> Self::OutputTy {
1152         noop_flat_map_assoc_item(self.wrapped, visitor)
1153     }
1154     fn is_mac_call(&self) -> bool {
1155         matches!(self.wrapped.kind, AssocItemKind::MacCall(..))
1156     }
1157     fn take_mac_call(self) -> (ast::MacCall, Self::AttrsTy, AddSemicolon) {
1158         let item = self.wrapped.into_inner();
1159         match item.kind {
1160             AssocItemKind::MacCall(mac) => (mac, item.attrs, AddSemicolon::No),
1161             _ => unreachable!(),
1162         }
1163     }
1164 }
1165
1166 struct ImplItemTag;
1167 impl InvocationCollectorNode for AstNodeWrapper<P<ast::AssocItem>, ImplItemTag> {
1168     type OutputTy = SmallVec<[P<ast::AssocItem>; 1]>;
1169     const KIND: AstFragmentKind = AstFragmentKind::ImplItems;
1170     fn to_annotatable(self) -> Annotatable {
1171         Annotatable::ImplItem(self.wrapped)
1172     }
1173     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
1174         fragment.make_impl_items()
1175     }
1176     fn noop_flat_map<V: MutVisitor>(self, visitor: &mut V) -> Self::OutputTy {
1177         noop_flat_map_assoc_item(self.wrapped, visitor)
1178     }
1179     fn is_mac_call(&self) -> bool {
1180         matches!(self.wrapped.kind, AssocItemKind::MacCall(..))
1181     }
1182     fn take_mac_call(self) -> (ast::MacCall, Self::AttrsTy, AddSemicolon) {
1183         let item = self.wrapped.into_inner();
1184         match item.kind {
1185             AssocItemKind::MacCall(mac) => (mac, item.attrs, AddSemicolon::No),
1186             _ => unreachable!(),
1187         }
1188     }
1189 }
1190
1191 impl InvocationCollectorNode for P<ast::ForeignItem> {
1192     const KIND: AstFragmentKind = AstFragmentKind::ForeignItems;
1193     fn to_annotatable(self) -> Annotatable {
1194         Annotatable::ForeignItem(self)
1195     }
1196     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
1197         fragment.make_foreign_items()
1198     }
1199     fn noop_flat_map<V: MutVisitor>(self, visitor: &mut V) -> Self::OutputTy {
1200         noop_flat_map_foreign_item(self, visitor)
1201     }
1202     fn is_mac_call(&self) -> bool {
1203         matches!(self.kind, ForeignItemKind::MacCall(..))
1204     }
1205     fn take_mac_call(self) -> (ast::MacCall, Self::AttrsTy, AddSemicolon) {
1206         let node = self.into_inner();
1207         match node.kind {
1208             ForeignItemKind::MacCall(mac) => (mac, node.attrs, AddSemicolon::No),
1209             _ => unreachable!(),
1210         }
1211     }
1212 }
1213
1214 impl InvocationCollectorNode for ast::Variant {
1215     const KIND: AstFragmentKind = AstFragmentKind::Variants;
1216     fn to_annotatable(self) -> Annotatable {
1217         Annotatable::Variant(self)
1218     }
1219     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
1220         fragment.make_variants()
1221     }
1222     fn noop_flat_map<V: MutVisitor>(self, visitor: &mut V) -> Self::OutputTy {
1223         noop_flat_map_variant(self, visitor)
1224     }
1225 }
1226
1227 impl InvocationCollectorNode for ast::FieldDef {
1228     const KIND: AstFragmentKind = AstFragmentKind::FieldDefs;
1229     fn to_annotatable(self) -> Annotatable {
1230         Annotatable::FieldDef(self)
1231     }
1232     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
1233         fragment.make_field_defs()
1234     }
1235     fn noop_flat_map<V: MutVisitor>(self, visitor: &mut V) -> Self::OutputTy {
1236         noop_flat_map_field_def(self, visitor)
1237     }
1238 }
1239
1240 impl InvocationCollectorNode for ast::PatField {
1241     const KIND: AstFragmentKind = AstFragmentKind::PatFields;
1242     fn to_annotatable(self) -> Annotatable {
1243         Annotatable::PatField(self)
1244     }
1245     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
1246         fragment.make_pat_fields()
1247     }
1248     fn noop_flat_map<V: MutVisitor>(self, visitor: &mut V) -> Self::OutputTy {
1249         noop_flat_map_pat_field(self, visitor)
1250     }
1251 }
1252
1253 impl InvocationCollectorNode for ast::ExprField {
1254     const KIND: AstFragmentKind = AstFragmentKind::ExprFields;
1255     fn to_annotatable(self) -> Annotatable {
1256         Annotatable::ExprField(self)
1257     }
1258     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
1259         fragment.make_expr_fields()
1260     }
1261     fn noop_flat_map<V: MutVisitor>(self, visitor: &mut V) -> Self::OutputTy {
1262         noop_flat_map_expr_field(self, visitor)
1263     }
1264 }
1265
1266 impl InvocationCollectorNode for ast::Param {
1267     const KIND: AstFragmentKind = AstFragmentKind::Params;
1268     fn to_annotatable(self) -> Annotatable {
1269         Annotatable::Param(self)
1270     }
1271     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
1272         fragment.make_params()
1273     }
1274     fn noop_flat_map<V: MutVisitor>(self, visitor: &mut V) -> Self::OutputTy {
1275         noop_flat_map_param(self, visitor)
1276     }
1277 }
1278
1279 impl InvocationCollectorNode for ast::GenericParam {
1280     const KIND: AstFragmentKind = AstFragmentKind::GenericParams;
1281     fn to_annotatable(self) -> Annotatable {
1282         Annotatable::GenericParam(self)
1283     }
1284     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
1285         fragment.make_generic_params()
1286     }
1287     fn noop_flat_map<V: MutVisitor>(self, visitor: &mut V) -> Self::OutputTy {
1288         noop_flat_map_generic_param(self, visitor)
1289     }
1290 }
1291
1292 impl InvocationCollectorNode for ast::Arm {
1293     const KIND: AstFragmentKind = AstFragmentKind::Arms;
1294     fn to_annotatable(self) -> Annotatable {
1295         Annotatable::Arm(self)
1296     }
1297     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
1298         fragment.make_arms()
1299     }
1300     fn noop_flat_map<V: MutVisitor>(self, visitor: &mut V) -> Self::OutputTy {
1301         noop_flat_map_arm(self, visitor)
1302     }
1303 }
1304
1305 impl InvocationCollectorNode for ast::Stmt {
1306     type AttrsTy = ast::AttrVec;
1307     const KIND: AstFragmentKind = AstFragmentKind::Stmts;
1308     fn to_annotatable(self) -> Annotatable {
1309         Annotatable::Stmt(P(self))
1310     }
1311     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
1312         fragment.make_stmts()
1313     }
1314     fn noop_flat_map<V: MutVisitor>(self, visitor: &mut V) -> Self::OutputTy {
1315         noop_flat_map_stmt(self, visitor)
1316     }
1317     fn is_mac_call(&self) -> bool {
1318         match &self.kind {
1319             StmtKind::MacCall(..) => true,
1320             StmtKind::Item(item) => matches!(item.kind, ItemKind::MacCall(..)),
1321             StmtKind::Semi(expr) => matches!(expr.kind, ExprKind::MacCall(..)),
1322             StmtKind::Expr(..) => unreachable!(),
1323             StmtKind::Local(..) | StmtKind::Empty => false,
1324         }
1325     }
1326     fn take_mac_call(self) -> (ast::MacCall, Self::AttrsTy, AddSemicolon) {
1327         // We pull macro invocations (both attributes and fn-like macro calls) out of their
1328         // `StmtKind`s and treat them as statement macro invocations, not as items or expressions.
1329         let (add_semicolon, mac, attrs) = match self.kind {
1330             StmtKind::MacCall(mac) => {
1331                 let ast::MacCallStmt { mac, style, attrs, .. } = mac.into_inner();
1332                 (style == MacStmtStyle::Semicolon, mac, attrs)
1333             }
1334             StmtKind::Item(item) => match item.into_inner() {
1335                 ast::Item { kind: ItemKind::MacCall(mac), attrs, .. } => {
1336                     (mac.args.need_semicolon(), mac, attrs.into())
1337                 }
1338                 _ => unreachable!(),
1339             },
1340             StmtKind::Semi(expr) => match expr.into_inner() {
1341                 ast::Expr { kind: ExprKind::MacCall(mac), attrs, .. } => {
1342                     (mac.args.need_semicolon(), mac, attrs)
1343                 }
1344                 _ => unreachable!(),
1345             },
1346             _ => unreachable!(),
1347         };
1348         (mac, attrs, if add_semicolon { AddSemicolon::Yes } else { AddSemicolon::No })
1349     }
1350     fn post_flat_map_node_collect_bang(stmts: &mut Self::OutputTy, add_semicolon: AddSemicolon) {
1351         // If this is a macro invocation with a semicolon, then apply that
1352         // semicolon to the final statement produced by expansion.
1353         if matches!(add_semicolon, AddSemicolon::Yes) {
1354             if let Some(stmt) = stmts.pop() {
1355                 stmts.push(stmt.add_trailing_semicolon());
1356             }
1357         }
1358     }
1359 }
1360
1361 impl InvocationCollectorNode for ast::Crate {
1362     type OutputTy = ast::Crate;
1363     const KIND: AstFragmentKind = AstFragmentKind::Crate;
1364     fn to_annotatable(self) -> Annotatable {
1365         Annotatable::Crate(self)
1366     }
1367     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
1368         fragment.make_crate()
1369     }
1370     fn noop_visit<V: MutVisitor>(&mut self, visitor: &mut V) {
1371         noop_visit_crate(self, visitor)
1372     }
1373 }
1374
1375 impl InvocationCollectorNode for P<ast::Ty> {
1376     type OutputTy = P<ast::Ty>;
1377     const KIND: AstFragmentKind = AstFragmentKind::Ty;
1378     fn to_annotatable(self) -> Annotatable {
1379         unreachable!()
1380     }
1381     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
1382         fragment.make_ty()
1383     }
1384     fn noop_visit<V: MutVisitor>(&mut self, visitor: &mut V) {
1385         noop_visit_ty(self, visitor)
1386     }
1387     fn is_mac_call(&self) -> bool {
1388         matches!(self.kind, ast::TyKind::MacCall(..))
1389     }
1390     fn take_mac_call(self) -> (ast::MacCall, Self::AttrsTy, AddSemicolon) {
1391         let node = self.into_inner();
1392         match node.kind {
1393             TyKind::MacCall(mac) => (mac, Vec::new(), AddSemicolon::No),
1394             _ => unreachable!(),
1395         }
1396     }
1397 }
1398
1399 impl InvocationCollectorNode for P<ast::Pat> {
1400     type OutputTy = P<ast::Pat>;
1401     const KIND: AstFragmentKind = AstFragmentKind::Pat;
1402     fn to_annotatable(self) -> Annotatable {
1403         unreachable!()
1404     }
1405     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
1406         fragment.make_pat()
1407     }
1408     fn noop_visit<V: MutVisitor>(&mut self, visitor: &mut V) {
1409         noop_visit_pat(self, visitor)
1410     }
1411     fn is_mac_call(&self) -> bool {
1412         matches!(self.kind, PatKind::MacCall(..))
1413     }
1414     fn take_mac_call(self) -> (ast::MacCall, Self::AttrsTy, AddSemicolon) {
1415         let node = self.into_inner();
1416         match node.kind {
1417             PatKind::MacCall(mac) => (mac, Vec::new(), AddSemicolon::No),
1418             _ => unreachable!(),
1419         }
1420     }
1421 }
1422
1423 impl InvocationCollectorNode for P<ast::Expr> {
1424     type OutputTy = P<ast::Expr>;
1425     type AttrsTy = ast::AttrVec;
1426     const KIND: AstFragmentKind = AstFragmentKind::Expr;
1427     fn to_annotatable(self) -> Annotatable {
1428         Annotatable::Expr(self)
1429     }
1430     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
1431         fragment.make_expr()
1432     }
1433     fn descr() -> &'static str {
1434         "an expression"
1435     }
1436     fn noop_visit<V: MutVisitor>(&mut self, visitor: &mut V) {
1437         noop_visit_expr(self, visitor)
1438     }
1439     fn is_mac_call(&self) -> bool {
1440         matches!(self.kind, ExprKind::MacCall(..))
1441     }
1442     fn take_mac_call(self) -> (ast::MacCall, Self::AttrsTy, AddSemicolon) {
1443         let node = self.into_inner();
1444         match node.kind {
1445             ExprKind::MacCall(mac) => (mac, node.attrs, AddSemicolon::No),
1446             _ => unreachable!(),
1447         }
1448     }
1449 }
1450
1451 struct OptExprTag;
1452 impl InvocationCollectorNode for AstNodeWrapper<P<ast::Expr>, OptExprTag> {
1453     type OutputTy = Option<P<ast::Expr>>;
1454     type AttrsTy = ast::AttrVec;
1455     const KIND: AstFragmentKind = AstFragmentKind::OptExpr;
1456     fn to_annotatable(self) -> Annotatable {
1457         Annotatable::Expr(self.wrapped)
1458     }
1459     fn fragment_to_output(fragment: AstFragment) -> Self::OutputTy {
1460         fragment.make_opt_expr()
1461     }
1462     fn noop_flat_map<V: MutVisitor>(mut self, visitor: &mut V) -> Self::OutputTy {
1463         noop_visit_expr(&mut self.wrapped, visitor);
1464         Some(self.wrapped)
1465     }
1466     fn is_mac_call(&self) -> bool {
1467         matches!(self.wrapped.kind, ast::ExprKind::MacCall(..))
1468     }
1469     fn take_mac_call(self) -> (ast::MacCall, Self::AttrsTy, AddSemicolon) {
1470         let node = self.wrapped.into_inner();
1471         match node.kind {
1472             ExprKind::MacCall(mac) => (mac, node.attrs, AddSemicolon::No),
1473             _ => unreachable!(),
1474         }
1475     }
1476     fn pre_flat_map_node_collect_attr(cfg: &StripUnconfigured<'_>, attr: &ast::Attribute) {
1477         cfg.maybe_emit_expr_attr_err(&attr);
1478     }
1479 }
1480
1481 struct InvocationCollector<'a, 'b> {
1482     cx: &'a mut ExtCtxt<'b>,
1483     invocations: Vec<(Invocation, Option<Lrc<SyntaxExtension>>)>,
1484     monotonic: bool,
1485 }
1486
1487 impl<'a, 'b> InvocationCollector<'a, 'b> {
1488     fn cfg(&self) -> StripUnconfigured<'_> {
1489         StripUnconfigured {
1490             sess: &self.cx.sess,
1491             features: self.cx.ecfg.features,
1492             config_tokens: false,
1493             lint_node_id: self.cx.current_expansion.lint_node_id,
1494         }
1495     }
1496
1497     fn collect(&mut self, fragment_kind: AstFragmentKind, kind: InvocationKind) -> AstFragment {
1498         let expn_id = LocalExpnId::fresh_empty();
1499         let vis = kind.placeholder_visibility();
1500         self.invocations.push((
1501             Invocation {
1502                 kind,
1503                 fragment_kind,
1504                 expansion_data: ExpansionData {
1505                     id: expn_id,
1506                     depth: self.cx.current_expansion.depth + 1,
1507                     ..self.cx.current_expansion.clone()
1508                 },
1509             },
1510             None,
1511         ));
1512         placeholder(fragment_kind, NodeId::placeholder_from_expn_id(expn_id), vis)
1513     }
1514
1515     fn collect_bang(&mut self, mac: ast::MacCall, kind: AstFragmentKind) -> AstFragment {
1516         // cache the macro call span so that it can be
1517         // easily adjusted for incremental compilation
1518         let span = mac.span();
1519         self.collect(kind, InvocationKind::Bang { mac, span })
1520     }
1521
1522     fn collect_attr(
1523         &mut self,
1524         (attr, pos, derives): (ast::Attribute, usize, Vec<ast::Path>),
1525         item: Annotatable,
1526         kind: AstFragmentKind,
1527     ) -> AstFragment {
1528         self.collect(kind, InvocationKind::Attr { attr, pos, item, derives })
1529     }
1530
1531     /// If `item` is an attribute invocation, remove the attribute and return it together with
1532     /// its position and derives following it. We have to collect the derives in order to resolve
1533     /// legacy derive helpers (helpers written before derives that introduce them).
1534     fn take_first_attr(
1535         &self,
1536         item: &mut impl HasAttrs,
1537     ) -> Option<(ast::Attribute, usize, Vec<ast::Path>)> {
1538         let mut attr = None;
1539
1540         let mut cfg_pos = None;
1541         let mut attr_pos = None;
1542         for (pos, attr) in item.attrs().iter().enumerate() {
1543             if !attr.is_doc_comment() && !self.cx.expanded_inert_attrs.is_marked(attr) {
1544                 let name = attr.ident().map(|ident| ident.name);
1545                 if name == Some(sym::cfg) || name == Some(sym::cfg_attr) {
1546                     cfg_pos = Some(pos); // a cfg attr found, no need to search anymore
1547                     break;
1548                 } else if attr_pos.is_none()
1549                     && !name.map_or(false, rustc_feature::is_builtin_attr_name)
1550                 {
1551                     attr_pos = Some(pos); // a non-cfg attr found, still may find a cfg attr
1552                 }
1553             }
1554         }
1555
1556         item.visit_attrs(|attrs| {
1557             attr = Some(match (cfg_pos, attr_pos) {
1558                 (Some(pos), _) => (attrs.remove(pos), pos, Vec::new()),
1559                 (_, Some(pos)) => {
1560                     let attr = attrs.remove(pos);
1561                     let following_derives = attrs[pos..]
1562                         .iter()
1563                         .filter(|a| a.has_name(sym::derive))
1564                         .flat_map(|a| a.meta_item_list().unwrap_or_default())
1565                         .filter_map(|nested_meta| match nested_meta {
1566                             NestedMetaItem::MetaItem(ast::MetaItem {
1567                                 kind: MetaItemKind::Word,
1568                                 path,
1569                                 ..
1570                             }) => Some(path),
1571                             _ => None,
1572                         })
1573                         .collect();
1574
1575                     (attr, pos, following_derives)
1576                 }
1577                 _ => return,
1578             });
1579         });
1580
1581         attr
1582     }
1583
1584     // Detect use of feature-gated or invalid attributes on macro invocations
1585     // since they will not be detected after macro expansion.
1586     fn check_attributes(&self, attrs: &[ast::Attribute], call: &ast::MacCall) {
1587         let features = self.cx.ecfg.features.unwrap();
1588         let mut attrs = attrs.iter().peekable();
1589         let mut span: Option<Span> = None;
1590         while let Some(attr) = attrs.next() {
1591             rustc_ast_passes::feature_gate::check_attribute(attr, self.cx.sess, features);
1592             validate_attr::check_meta(&self.cx.sess.parse_sess, attr);
1593
1594             let current_span = if let Some(sp) = span { sp.to(attr.span) } else { attr.span };
1595             span = Some(current_span);
1596
1597             if attrs.peek().map_or(false, |next_attr| next_attr.doc_str().is_some()) {
1598                 continue;
1599             }
1600
1601             if attr.is_doc_comment() {
1602                 self.cx.sess.parse_sess.buffer_lint_with_diagnostic(
1603                     &UNUSED_DOC_COMMENTS,
1604                     current_span,
1605                     self.cx.current_expansion.lint_node_id,
1606                     "unused doc comment",
1607                     BuiltinLintDiagnostics::UnusedDocComment(attr.span),
1608                 );
1609             } else if rustc_attr::is_builtin_attr(attr) {
1610                 let attr_name = attr.ident().unwrap().name;
1611                 // `#[cfg]` and `#[cfg_attr]` are special - they are
1612                 // eagerly evaluated.
1613                 if attr_name != sym::cfg && attr_name != sym::cfg_attr {
1614                     self.cx.sess.parse_sess.buffer_lint_with_diagnostic(
1615                         &UNUSED_ATTRIBUTES,
1616                         attr.span,
1617                         self.cx.current_expansion.lint_node_id,
1618                         &format!("unused attribute `{}`", attr_name),
1619                         BuiltinLintDiagnostics::UnusedBuiltinAttribute {
1620                             attr_name,
1621                             macro_name: pprust::path_to_string(&call.path),
1622                             invoc_span: call.path.span,
1623                         },
1624                     );
1625                 }
1626             }
1627         }
1628     }
1629
1630     fn expand_cfg_true(
1631         &mut self,
1632         node: &mut impl HasAttrs,
1633         attr: ast::Attribute,
1634         pos: usize,
1635     ) -> bool {
1636         let res = self.cfg().cfg_true(&attr);
1637         if res {
1638             // FIXME: `cfg(TRUE)` attributes do not currently remove themselves during expansion,
1639             // and some tools like rustdoc and clippy rely on that. Find a way to remove them
1640             // while keeping the tools working.
1641             self.cx.expanded_inert_attrs.mark(&attr);
1642             node.visit_attrs(|attrs| attrs.insert(pos, attr));
1643         }
1644         res
1645     }
1646
1647     fn expand_cfg_attr(&self, node: &mut impl HasAttrs, attr: ast::Attribute, pos: usize) {
1648         node.visit_attrs(|attrs| {
1649             attrs.splice(pos..pos, self.cfg().expand_cfg_attr(attr, false));
1650         });
1651     }
1652
1653     fn flat_map_node<Node: InvocationCollectorNode<OutputTy: Default>>(
1654         &mut self,
1655         mut node: Node,
1656     ) -> Node::OutputTy {
1657         loop {
1658             return match self.take_first_attr(&mut node) {
1659                 Some((attr, pos, derives)) => match attr.name_or_empty() {
1660                     sym::cfg => {
1661                         if self.expand_cfg_true(&mut node, attr, pos) {
1662                             continue;
1663                         }
1664                         Default::default()
1665                     }
1666                     sym::cfg_attr => {
1667                         self.expand_cfg_attr(&mut node, attr, pos);
1668                         continue;
1669                     }
1670                     _ => {
1671                         Node::pre_flat_map_node_collect_attr(&self.cfg(), &attr);
1672                         self.collect_attr((attr, pos, derives), node.to_annotatable(), Node::KIND)
1673                             .make_ast::<Node>()
1674                     }
1675                 },
1676                 None if node.is_mac_call() => {
1677                     let (mac, attrs, add_semicolon) = node.take_mac_call();
1678                     self.check_attributes(&attrs, &mac);
1679                     let mut res = self.collect_bang(mac, Node::KIND).make_ast::<Node>();
1680                     Node::post_flat_map_node_collect_bang(&mut res, add_semicolon);
1681                     res
1682                 }
1683                 None => {
1684                     match Node::wrap_flat_map_node_noop_flat_map(node, self, |mut node, this| {
1685                         assign_id!(this, node.node_id_mut(), || node.noop_flat_map(this))
1686                     }) {
1687                         Ok(output) => output,
1688                         Err(returned_node) => {
1689                             node = returned_node;
1690                             continue;
1691                         }
1692                     }
1693                 }
1694             };
1695         }
1696     }
1697
1698     fn visit_node<Node: InvocationCollectorNode<OutputTy = Node> + DummyAstNode>(
1699         &mut self,
1700         node: &mut Node,
1701     ) {
1702         loop {
1703             return match self.take_first_attr(node) {
1704                 Some((attr, pos, derives)) => match attr.name_or_empty() {
1705                     sym::cfg => {
1706                         let span = attr.span;
1707                         if self.expand_cfg_true(node, attr, pos) {
1708                             continue;
1709                         }
1710                         let msg =
1711                             format!("removing {} is not supported in this position", Node::descr());
1712                         self.cx.span_err(span, &msg);
1713                         continue;
1714                     }
1715                     sym::cfg_attr => {
1716                         self.expand_cfg_attr(node, attr, pos);
1717                         continue;
1718                     }
1719                     _ => visit_clobber(node, |node| {
1720                         self.collect_attr((attr, pos, derives), node.to_annotatable(), Node::KIND)
1721                             .make_ast::<Node>()
1722                     }),
1723                 },
1724                 None if node.is_mac_call() => {
1725                     visit_clobber(node, |node| {
1726                         // Do not clobber unless it's actually a macro (uncommon case).
1727                         let (mac, attrs, _) = node.take_mac_call();
1728                         self.check_attributes(&attrs, &mac);
1729                         self.collect_bang(mac, Node::KIND).make_ast::<Node>()
1730                     })
1731                 }
1732                 None => {
1733                     assign_id!(self, node.node_id_mut(), || node.noop_visit(self))
1734                 }
1735             };
1736         }
1737     }
1738 }
1739
1740 impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
1741     fn flat_map_item(&mut self, node: P<ast::Item>) -> SmallVec<[P<ast::Item>; 1]> {
1742         self.flat_map_node(node)
1743     }
1744
1745     fn flat_map_trait_item(&mut self, node: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
1746         self.flat_map_node(AstNodeWrapper::new(node, TraitItemTag))
1747     }
1748
1749     fn flat_map_impl_item(&mut self, node: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
1750         self.flat_map_node(AstNodeWrapper::new(node, ImplItemTag))
1751     }
1752
1753     fn flat_map_foreign_item(
1754         &mut self,
1755         node: P<ast::ForeignItem>,
1756     ) -> SmallVec<[P<ast::ForeignItem>; 1]> {
1757         self.flat_map_node(node)
1758     }
1759
1760     fn flat_map_variant(&mut self, node: ast::Variant) -> SmallVec<[ast::Variant; 1]> {
1761         self.flat_map_node(node)
1762     }
1763
1764     fn flat_map_field_def(&mut self, node: ast::FieldDef) -> SmallVec<[ast::FieldDef; 1]> {
1765         self.flat_map_node(node)
1766     }
1767
1768     fn flat_map_pat_field(&mut self, node: ast::PatField) -> SmallVec<[ast::PatField; 1]> {
1769         self.flat_map_node(node)
1770     }
1771
1772     fn flat_map_expr_field(&mut self, node: ast::ExprField) -> SmallVec<[ast::ExprField; 1]> {
1773         self.flat_map_node(node)
1774     }
1775
1776     fn flat_map_param(&mut self, node: ast::Param) -> SmallVec<[ast::Param; 1]> {
1777         self.flat_map_node(node)
1778     }
1779
1780     fn flat_map_generic_param(
1781         &mut self,
1782         node: ast::GenericParam,
1783     ) -> SmallVec<[ast::GenericParam; 1]> {
1784         self.flat_map_node(node)
1785     }
1786
1787     fn flat_map_arm(&mut self, node: ast::Arm) -> SmallVec<[ast::Arm; 1]> {
1788         self.flat_map_node(node)
1789     }
1790
1791     fn flat_map_stmt(&mut self, node: ast::Stmt) -> SmallVec<[ast::Stmt; 1]> {
1792         // FIXME: invocations in semicolon-less expressions positions are expanded as expressions,
1793         // changing that requires some compatibility measures.
1794         if node.is_expr() {
1795             // The only way that we can end up with a `MacCall` expression statement,
1796             // (as opposed to a `StmtKind::MacCall`) is if we have a macro as the
1797             // trailing expression in a block (e.g. `fn foo() { my_macro!() }`).
1798             // Record this information, so that we can report a more specific
1799             // `SEMICOLON_IN_EXPRESSIONS_FROM_MACROS` lint if needed.
1800             // See #78991 for an investigation of treating macros in this position
1801             // as statements, rather than expressions, during parsing.
1802             return match &node.kind {
1803                 StmtKind::Expr(expr)
1804                     if matches!(**expr, ast::Expr { kind: ExprKind::MacCall(..), .. }) =>
1805                 {
1806                     self.cx.current_expansion.is_trailing_mac = true;
1807                     // Don't use `assign_id` for this statement - it may get removed
1808                     // entirely due to a `#[cfg]` on the contained expression
1809                     let res = noop_flat_map_stmt(node, self);
1810                     self.cx.current_expansion.is_trailing_mac = false;
1811                     res
1812                 }
1813                 _ => noop_flat_map_stmt(node, self),
1814             };
1815         }
1816
1817         self.flat_map_node(node)
1818     }
1819
1820     fn visit_crate(&mut self, node: &mut ast::Crate) {
1821         self.visit_node(node)
1822     }
1823
1824     fn visit_ty(&mut self, node: &mut P<ast::Ty>) {
1825         self.visit_node(node)
1826     }
1827
1828     fn visit_pat(&mut self, node: &mut P<ast::Pat>) {
1829         self.visit_node(node)
1830     }
1831
1832     fn visit_expr(&mut self, node: &mut P<ast::Expr>) {
1833         // FIXME: Feature gating is performed inconsistently between `Expr` and `OptExpr`.
1834         if let Some(attr) = node.attrs.first() {
1835             self.cfg().maybe_emit_expr_attr_err(attr);
1836         }
1837         self.visit_node(node)
1838     }
1839
1840     fn filter_map_expr(&mut self, node: P<ast::Expr>) -> Option<P<ast::Expr>> {
1841         self.flat_map_node(AstNodeWrapper::new(node, OptExprTag))
1842     }
1843
1844     fn visit_block(&mut self, node: &mut P<ast::Block>) {
1845         let orig_dir_ownership = mem::replace(
1846             &mut self.cx.current_expansion.dir_ownership,
1847             DirOwnership::UnownedViaBlock,
1848         );
1849         noop_visit_block(node, self);
1850         self.cx.current_expansion.dir_ownership = orig_dir_ownership;
1851     }
1852
1853     fn visit_id(&mut self, id: &mut NodeId) {
1854         // We may have already assigned a `NodeId`
1855         // by calling `assign_id`
1856         if self.monotonic && *id == ast::DUMMY_NODE_ID {
1857             *id = self.cx.resolver.next_node_id();
1858         }
1859     }
1860 }
1861
1862 pub struct ExpansionConfig<'feat> {
1863     pub crate_name: String,
1864     pub features: Option<&'feat Features>,
1865     pub recursion_limit: Limit,
1866     pub trace_mac: bool,
1867     pub should_test: bool,          // If false, strip `#[test]` nodes
1868     pub span_debug: bool,           // If true, use verbose debugging for `proc_macro::Span`
1869     pub proc_macro_backtrace: bool, // If true, show backtraces for proc-macro panics
1870 }
1871
1872 impl<'feat> ExpansionConfig<'feat> {
1873     pub fn default(crate_name: String) -> ExpansionConfig<'static> {
1874         ExpansionConfig {
1875             crate_name,
1876             features: None,
1877             recursion_limit: Limit::new(1024),
1878             trace_mac: false,
1879             should_test: false,
1880             span_debug: false,
1881             proc_macro_backtrace: false,
1882         }
1883     }
1884
1885     fn proc_macro_hygiene(&self) -> bool {
1886         self.features.map_or(false, |features| features.proc_macro_hygiene)
1887     }
1888 }