compiler/rustc_expand/src/expand.rs

   1 use crate::base::*;
   2 use crate::config::StripUnconfigured;
   3 use crate::configure;
   4 use crate::hygiene::SyntaxContext;
   5 use crate::mbe::macro_rules::annotate_err_with_kind;
   6 use crate::module::{mod_dir_path, parse_external_mod, DirOwnership, ParsedExternalMod};
   7 use crate::placeholders::{placeholder, PlaceholderExpander};
   8
   9 use rustc_ast as ast;
  10 use rustc_ast::mut_visit::*;
  11 use rustc_ast::ptr::P;
  12 use rustc_ast::token;
  13 use rustc_ast::tokenstream::TokenStream;
  14 use rustc_ast::visit::{self, AssocCtxt, Visitor};
  15 use rustc_ast::{AstLike, Block, Inline, ItemKind, MacArgs, MacCall};
  16 use rustc_ast::{MacCallStmt, MacStmtStyle, MetaItemKind, ModKind, NestedMetaItem};
  17 use rustc_ast::{NodeId, PatKind, Path, StmtKind};
  18 use rustc_ast_pretty::pprust;
  19 use rustc_attr::is_builtin_attr;
  20 use rustc_data_structures::map_in_place::MapInPlace;
  21 use rustc_data_structures::stack::ensure_sufficient_stack;
  22 use rustc_data_structures::sync::Lrc;
  23 use rustc_errors::{Applicability, PResult};
  24 use rustc_feature::Features;
  25 use rustc_parse::parser::{
  26     AttemptLocalParseRecovery, ForceCollect, Parser, RecoverColon, RecoverComma,
  27 };
  28 use rustc_parse::validate_attr;
  29 use rustc_session::lint::builtin::{UNUSED_ATTRIBUTES, UNUSED_DOC_COMMENTS};
  30 use rustc_session::lint::BuiltinLintDiagnostics;
  31 use rustc_session::parse::{feature_err, ParseSess};
  32 use rustc_session::Limit;
  33 use rustc_span::symbol::{sym, Ident};
  34 use rustc_span::{FileName, LocalExpnId, Span};
  35
  36 use smallvec::SmallVec;
  37 use std::ops::DerefMut;
  38 use std::path::PathBuf;
  39 use std::rc::Rc;
  40 use std::{iter, mem};
  41
  42 macro_rules! ast_fragments {
  43     (
  44         $($Kind:ident($AstTy:ty) {
  45             $kind_name:expr;
  46             $(one fn $mut_visit_ast:ident; fn $visit_ast:ident;)?
  47             $(many fn $flat_map_ast_elt:ident; fn $visit_ast_elt:ident($($args:tt)*);)?
  48             fn $make_ast:ident;
  49         })*
  50     ) => {
  51         /// A fragment of AST that can be produced by a single macro expansion.
  52         /// Can also serve as an input and intermediate result for macro expansion operations.
  53         pub enum AstFragment {
  54             OptExpr(Option<P<ast::Expr>>),
  55             $($Kind($AstTy),)*
  56         }
  57
  58         /// "Discriminant" of an AST fragment.
  59         #[derive(Copy, Clone, PartialEq, Eq)]
  60         pub enum AstFragmentKind {
  61             OptExpr,
  62             $($Kind,)*
  63         }
  64
  65         impl AstFragmentKind {
  66             pub fn name(self) -> &'static str {
  67                 match self {
  68                     AstFragmentKind::OptExpr => "expression",
  69                     $(AstFragmentKind::$Kind => $kind_name,)*
  70                 }
  71             }
  72
  73             fn make_from<'a>(self, result: Box<dyn MacResult + 'a>) -> Option<AstFragment> {
  74                 match self {
  75                     AstFragmentKind::OptExpr =>
  76                         result.make_expr().map(Some).map(AstFragment::OptExpr),
  77                     $(AstFragmentKind::$Kind => result.$make_ast().map(AstFragment::$Kind),)*
  78                 }
  79             }
  80         }
  81
  82         impl AstFragment {
  83             pub fn add_placeholders(&mut self, placeholders: &[NodeId]) {
  84                 if placeholders.is_empty() {
  85                     return;
  86                 }
  87                 match self {
  88                     $($(AstFragment::$Kind(ast) => ast.extend(placeholders.iter().flat_map(|id| {
  89                         // We are repeating through arguments with `many`, to do that we have to
  90                         // mention some macro variable from those arguments even if it's not used.
  91                         macro _repeating($flat_map_ast_elt) {}
  92                         placeholder(AstFragmentKind::$Kind, *id, None).$make_ast()
  93                     })),)?)*
  94                     _ => panic!("unexpected AST fragment kind")
  95                 }
  96             }
  97
  98             pub fn make_opt_expr(self) -> Option<P<ast::Expr>> {
  99                 match self {
 100                     AstFragment::OptExpr(expr) => expr,
 101                     _ => panic!("AstFragment::make_* called on the wrong kind of fragment"),
 102                 }
 103             }
 104
 105             $(pub fn $make_ast(self) -> $AstTy {
 106                 match self {
 107                     AstFragment::$Kind(ast) => ast,
 108                     _ => panic!("AstFragment::make_* called on the wrong kind of fragment"),
 109                 }
 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     Fields(SmallVec<[ast::ExprField; 1]>) {
 182         "field expression"; many fn flat_map_expr_field; fn visit_expr_field(); fn make_expr_fields;
 183     }
 184     FieldPats(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     StructFields(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     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::Fields
 235             | AstFragmentKind::FieldPats
 236             | AstFragmentKind::GenericParams
 237             | AstFragmentKind::Params
 238             | AstFragmentKind::StructFields
 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::Fields => {
 253                 AstFragment::Fields(items.map(Annotatable::expect_expr_field).collect())
 254             }
 255             AstFragmentKind::FieldPats => {
 256                 AstFragment::FieldPats(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::StructFields => {
 265                 AstFragment::StructFields(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<Path>,
 319     },
 320     Derive {
 321         path: 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.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                 cfg: StripUnconfigured {
 554                     sess: &self.cx.sess,
 555                     features: self.cx.ecfg.features,
 556                     config_tokens: false,
 557                 },
 558                 cx: self.cx,
 559                 invocations: Vec::new(),
 560                 monotonic: self.monotonic,
 561             };
 562             fragment.mut_visit_with(&mut collector);
 563             fragment.add_placeholders(extra_placeholders);
 564             collector.invocations
 565         };
 566
 567         if self.monotonic {
 568             self.cx
 569                 .resolver
 570                 .visit_ast_fragment_with_placeholders(self.cx.current_expansion.id, &fragment);
 571
 572             if self.cx.sess.opts.debugging_opts.incremental_relative_spans {
 573                 for (invoc, _) in invocations.iter_mut() {
 574                     let expn_id = invoc.expansion_data.id;
 575                     let parent_def = self.cx.resolver.invocation_parent(expn_id);
 576                     let span = match &mut invoc.kind {
 577                         InvocationKind::Bang { ref mut span, .. } => span,
 578                         InvocationKind::Attr { attr, .. } => &mut attr.span,
 579                         InvocationKind::Derive { path, .. } => &mut path.span,
 580                     };
 581                     *span = span.with_parent(Some(parent_def));
 582                 }
 583             }
 584         }
 585
 586         (fragment, invocations)
 587     }
 588
 589     fn error_recursion_limit_reached(&mut self) {
 590         let expn_data = self.cx.current_expansion.id.expn_data();
 591         let suggested_limit = match self.cx.ecfg.recursion_limit {
 592             Limit(0) => Limit(2),
 593             limit => limit * 2,
 594         };
 595         self.cx
 596             .struct_span_err(
 597                 expn_data.call_site,
 598                 &format!("recursion limit reached while expanding `{}`", expn_data.kind.descr()),
 599             )
 600             .help(&format!(
 601                 "consider increasing the recursion limit by adding a \
 602                  `#![recursion_limit = \"{}\"]` attribute to your crate (`{}`)",
 603                 suggested_limit, self.cx.ecfg.crate_name,
 604             ))
 605             .emit();
 606         self.cx.trace_macros_diag();
 607     }
 608
 609     /// A macro's expansion does not fit in this fragment kind.
 610     /// For example, a non-type macro in a type position.
 611     fn error_wrong_fragment_kind(&mut self, kind: AstFragmentKind, mac: &ast::MacCall, span: Span) {
 612         let msg = format!(
 613             "non-{kind} macro in {kind} position: {path}",
 614             kind = kind.name(),
 615             path = pprust::path_to_string(&mac.path),
 616         );
 617         self.cx.span_err(span, &msg);
 618         self.cx.trace_macros_diag();
 619     }
 620
 621     fn expand_invoc(
 622         &mut self,
 623         invoc: Invocation,
 624         ext: &SyntaxExtensionKind,
 625     ) -> ExpandResult<AstFragment, Invocation> {
 626         let recursion_limit =
 627             self.cx.reduced_recursion_limit.unwrap_or(self.cx.ecfg.recursion_limit);
 628         if !recursion_limit.value_within_limit(self.cx.current_expansion.depth) {
 629             if self.cx.reduced_recursion_limit.is_none() {
 630                 self.error_recursion_limit_reached();
 631             }
 632
 633             // Reduce the recursion limit by half each time it triggers.
 634             self.cx.reduced_recursion_limit = Some(recursion_limit / 2);
 635
 636             return ExpandResult::Ready(invoc.fragment_kind.dummy(invoc.span()));
 637         }
 638
 639         let (fragment_kind, span) = (invoc.fragment_kind, invoc.span());
 640         ExpandResult::Ready(match invoc.kind {
 641             InvocationKind::Bang { mac, .. } => match ext {
 642                 SyntaxExtensionKind::Bang(expander) => {
 643                     let tok_result = match expander.expand(self.cx, span, mac.args.inner_tokens()) {
 644                         Err(_) => return ExpandResult::Ready(fragment_kind.dummy(span)),
 645                         Ok(ts) => ts,
 646                     };
 647                     self.parse_ast_fragment(tok_result, fragment_kind, &mac.path, span)
 648                 }
 649                 SyntaxExtensionKind::LegacyBang(expander) => {
 650                     let prev = self.cx.current_expansion.prior_type_ascription;
 651                     self.cx.current_expansion.prior_type_ascription = mac.prior_type_ascription;
 652                     let tok_result = expander.expand(self.cx, span, mac.args.inner_tokens());
 653                     let result = if let Some(result) = fragment_kind.make_from(tok_result) {
 654                         result
 655                     } else {
 656                         self.error_wrong_fragment_kind(fragment_kind, &mac, span);
 657                         fragment_kind.dummy(span)
 658                     };
 659                     self.cx.current_expansion.prior_type_ascription = prev;
 660                     result
 661                 }
 662                 _ => unreachable!(),
 663             },
 664             InvocationKind::Attr { attr, pos, mut item, derives } => match ext {
 665                 SyntaxExtensionKind::Attr(expander) => {
 666                     self.gate_proc_macro_input(&item);
 667                     self.gate_proc_macro_attr_item(span, &item);
 668                     let tokens = match &item {
 669                         // FIXME: Collect tokens and use them instead of generating
 670                         // fake ones. These are unstable, so it needs to be
 671                         // fixed prior to stabilization
 672                         // Fake tokens when we are invoking an inner attribute, and
 673                         // we are invoking it on an out-of-line module or crate.
 674                         Annotatable::Crate(krate) => rustc_parse::fake_token_stream_for_crate(
 675                             &self.cx.sess.parse_sess,
 676                             krate,
 677                         ),
 678                         Annotatable::Item(item_inner)
 679                             if matches!(attr.style, ast::AttrStyle::Inner)
 680                                 && matches!(
 681                                     item_inner.kind,
 682                                     ItemKind::Mod(
 683                                         _,
 684                                         ModKind::Unloaded | ModKind::Loaded(_, Inline::No, _),
 685                                     )
 686                                 ) =>
 687                         {
 688                             rustc_parse::fake_token_stream(
 689                                 &self.cx.sess.parse_sess,
 690                                 &item.into_nonterminal(),
 691                             )
 692                         }
 693                         _ => item.into_tokens(&self.cx.sess.parse_sess),
 694                     };
 695                     let attr_item = attr.unwrap_normal_item();
 696                     if let MacArgs::Eq(..) = attr_item.args {
 697                         self.cx.span_err(span, "key-value macro attributes are not supported");
 698                     }
 699                     let inner_tokens = attr_item.args.inner_tokens();
 700                     let tok_result = match expander.expand(self.cx, span, inner_tokens, tokens) {
 701                         Err(_) => return ExpandResult::Ready(fragment_kind.dummy(span)),
 702                         Ok(ts) => ts,
 703                     };
 704                     self.parse_ast_fragment(tok_result, fragment_kind, &attr_item.path, span)
 705                 }
 706                 SyntaxExtensionKind::LegacyAttr(expander) => {
 707                     match validate_attr::parse_meta(&self.cx.sess.parse_sess, &attr) {
 708                         Ok(meta) => {
 709                             let items = match expander.expand(self.cx, span, &meta, item) {
 710                                 ExpandResult::Ready(items) => items,
 711                                 ExpandResult::Retry(item) => {
 712                                     // Reassemble the original invocation for retrying.
 713                                     return ExpandResult::Retry(Invocation {
 714                                         kind: InvocationKind::Attr { attr, pos, item, derives },
 715                                         ..invoc
 716                                     });
 717                                 }
 718                             };
 719                             if fragment_kind == AstFragmentKind::Expr && items.is_empty() {
 720                                 let msg =
 721                                     "removing an expression is not supported in this position";
 722                                 self.cx.span_err(span, msg);
 723                                 fragment_kind.dummy(span)
 724                             } else {
 725                                 fragment_kind.expect_from_annotatables(items)
 726                             }
 727                         }
 728                         Err(mut err) => {
 729                             err.emit();
 730                             fragment_kind.dummy(span)
 731                         }
 732                     }
 733                 }
 734                 SyntaxExtensionKind::NonMacroAttr => {
 735                     self.cx.expanded_inert_attrs.mark(&attr);
 736                     item.visit_attrs(|attrs| attrs.insert(pos, attr));
 737                     fragment_kind.expect_from_annotatables(iter::once(item))
 738                 }
 739                 _ => unreachable!(),
 740             },
 741             InvocationKind::Derive { path, item } => match ext {
 742                 SyntaxExtensionKind::Derive(expander)
 743                 | SyntaxExtensionKind::LegacyDerive(expander) => {
 744                     if let SyntaxExtensionKind::Derive(..) = ext {
 745                         self.gate_proc_macro_input(&item);
 746                     }
 747                     let meta = ast::MetaItem { kind: ast::MetaItemKind::Word, span, path };
 748                     let items = match expander.expand(self.cx, span, &meta, item) {
 749                         ExpandResult::Ready(items) => items,
 750                         ExpandResult::Retry(item) => {
 751                             // Reassemble the original invocation for retrying.
 752                             return ExpandResult::Retry(Invocation {
 753                                 kind: InvocationKind::Derive { path: meta.path, item },
 754                                 ..invoc
 755                             });
 756                         }
 757                     };
 758                     fragment_kind.expect_from_annotatables(items)
 759                 }
 760                 _ => unreachable!(),
 761             },
 762         })
 763     }
 764
 765     fn gate_proc_macro_attr_item(&self, span: Span, item: &Annotatable) {
 766         let kind = match item {
 767             Annotatable::Item(_)
 768             | Annotatable::TraitItem(_)
 769             | Annotatable::ImplItem(_)
 770             | Annotatable::ForeignItem(_)
 771             | Annotatable::Crate(..) => return,
 772             Annotatable::Stmt(stmt) => {
 773                 // Attributes are stable on item statements,
 774                 // but unstable on all other kinds of statements
 775                 if stmt.is_item() {
 776                     return;
 777                 }
 778                 "statements"
 779             }
 780             Annotatable::Expr(_) => "expressions",
 781             Annotatable::Arm(..)
 782             | Annotatable::ExprField(..)
 783             | Annotatable::PatField(..)
 784             | Annotatable::GenericParam(..)
 785             | Annotatable::Param(..)
 786             | Annotatable::FieldDef(..)
 787             | Annotatable::Variant(..) => panic!("unexpected annotatable"),
 788         };
 789         if self.cx.ecfg.proc_macro_hygiene() {
 790             return;
 791         }
 792         feature_err(
 793             &self.cx.sess.parse_sess,
 794             sym::proc_macro_hygiene,
 795             span,
 796             &format!("custom attributes cannot be applied to {}", kind),
 797         )
 798         .emit();
 799     }
 800
 801     fn gate_proc_macro_input(&self, annotatable: &Annotatable) {
 802         struct GateProcMacroInput<'a> {
 803             parse_sess: &'a ParseSess,
 804         }
 805
 806         impl<'ast, 'a> Visitor<'ast> for GateProcMacroInput<'a> {
 807             fn visit_item(&mut self, item: &'ast ast::Item) {
 808                 match &item.kind {
 809                     ast::ItemKind::Mod(_, mod_kind)
 810                         if !matches!(mod_kind, ModKind::Loaded(_, Inline::Yes, _)) =>
 811                     {
 812                         feature_err(
 813                             self.parse_sess,
 814                             sym::proc_macro_hygiene,
 815                             item.span,
 816                             "non-inline modules in proc macro input are unstable",
 817                         )
 818                         .emit();
 819                     }
 820                     _ => {}
 821                 }
 822
 823                 visit::walk_item(self, item);
 824             }
 825         }
 826
 827         if !self.cx.ecfg.proc_macro_hygiene() {
 828             annotatable
 829                 .visit_with(&mut GateProcMacroInput { parse_sess: &self.cx.sess.parse_sess });
 830         }
 831     }
 832
 833     fn parse_ast_fragment(
 834         &mut self,
 835         toks: TokenStream,
 836         kind: AstFragmentKind,
 837         path: &Path,
 838         span: Span,
 839     ) -> AstFragment {
 840         let mut parser = self.cx.new_parser_from_tts(toks);
 841         match parse_ast_fragment(&mut parser, kind) {
 842             Ok(fragment) => {
 843                 ensure_complete_parse(&mut parser, path, kind.name(), span);
 844                 fragment
 845             }
 846             Err(mut err) => {
 847                 if err.span.is_dummy() {
 848                     err.set_span(span);
 849                 }
 850                 annotate_err_with_kind(&mut err, kind, span);
 851                 err.emit();
 852                 self.cx.trace_macros_diag();
 853                 kind.dummy(span)
 854             }
 855         }
 856     }
 857 }
 858
 859 pub fn parse_ast_fragment<'a>(
 860     this: &mut Parser<'a>,
 861     kind: AstFragmentKind,
 862 ) -> PResult<'a, AstFragment> {
 863     Ok(match kind {
 864         AstFragmentKind::Items => {
 865             let mut items = SmallVec::new();
 866             while let Some(item) = this.parse_item(ForceCollect::No)? {
 867                 items.push(item);
 868             }
 869             AstFragment::Items(items)
 870         }
 871         AstFragmentKind::TraitItems => {
 872             let mut items = SmallVec::new();
 873             while let Some(item) = this.parse_trait_item(ForceCollect::No)? {
 874                 items.extend(item);
 875             }
 876             AstFragment::TraitItems(items)
 877         }
 878         AstFragmentKind::ImplItems => {
 879             let mut items = SmallVec::new();
 880             while let Some(item) = this.parse_impl_item(ForceCollect::No)? {
 881                 items.extend(item);
 882             }
 883             AstFragment::ImplItems(items)
 884         }
 885         AstFragmentKind::ForeignItems => {
 886             let mut items = SmallVec::new();
 887             while let Some(item) = this.parse_foreign_item(ForceCollect::No)? {
 888                 items.extend(item);
 889             }
 890             AstFragment::ForeignItems(items)
 891         }
 892         AstFragmentKind::Stmts => {
 893             let mut stmts = SmallVec::new();
 894             // Won't make progress on a `}`.
 895             while this.token != token::Eof && this.token != token::CloseDelim(token::Brace) {
 896                 if let Some(stmt) = this.parse_full_stmt(AttemptLocalParseRecovery::Yes)? {
 897                     stmts.push(stmt);
 898                 }
 899             }
 900             AstFragment::Stmts(stmts)
 901         }
 902         AstFragmentKind::Expr => AstFragment::Expr(this.parse_expr()?),
 903         AstFragmentKind::OptExpr => {
 904             if this.token != token::Eof {
 905                 AstFragment::OptExpr(Some(this.parse_expr()?))
 906             } else {
 907                 AstFragment::OptExpr(None)
 908             }
 909         }
 910         AstFragmentKind::Ty => AstFragment::Ty(this.parse_ty()?),
 911         AstFragmentKind::Pat => AstFragment::Pat(this.parse_pat_allow_top_alt(
 912             None,
 913             RecoverComma::No,
 914             RecoverColon::Yes,
 915         )?),
 916         AstFragmentKind::Crate => AstFragment::Crate(this.parse_crate_mod()?),
 917         AstFragmentKind::Arms
 918         | AstFragmentKind::Fields
 919         | AstFragmentKind::FieldPats
 920         | AstFragmentKind::GenericParams
 921         | AstFragmentKind::Params
 922         | AstFragmentKind::StructFields
 923         | AstFragmentKind::Variants => panic!("unexpected AST fragment kind"),
 924     })
 925 }
 926
 927 pub fn ensure_complete_parse<'a>(
 928     this: &mut Parser<'a>,
 929     macro_path: &Path,
 930     kind_name: &str,
 931     span: Span,
 932 ) {
 933     if this.token != token::Eof {
 934         let token = pprust::token_to_string(&this.token);
 935         let msg = format!("macro expansion ignores token `{}` and any following", token);
 936         // Avoid emitting backtrace info twice.
 937         let def_site_span = this.token.span.with_ctxt(SyntaxContext::root());
 938         let mut err = this.struct_span_err(def_site_span, &msg);
 939         err.span_label(span, "caused by the macro expansion here");
 940         let msg = format!(
 941             "the usage of `{}!` is likely invalid in {} context",
 942             pprust::path_to_string(macro_path),
 943             kind_name,
 944         );
 945         err.note(&msg);
 946         let semi_span = this.sess.source_map().next_point(span);
 947
 948         let semi_full_span = semi_span.to(this.sess.source_map().next_point(semi_span));
 949         match this.sess.source_map().span_to_snippet(semi_full_span) {
 950             Ok(ref snippet) if &snippet[..] != ";" && kind_name == "expression" => {
 951                 err.span_suggestion(
 952                     semi_span,
 953                     "you might be missing a semicolon here",
 954                     ";".to_owned(),
 955                     Applicability::MaybeIncorrect,
 956                 );
 957             }
 958             _ => {}
 959         }
 960         err.emit();
 961     }
 962 }
 963
 964 struct InvocationCollector<'a, 'b> {
 965     cx: &'a mut ExtCtxt<'b>,
 966     cfg: StripUnconfigured<'a>,
 967     invocations: Vec<(Invocation, Option<Lrc<SyntaxExtension>>)>,
 968     monotonic: bool,
 969 }
 970
 971 impl<'a, 'b> InvocationCollector<'a, 'b> {
 972     fn collect(&mut self, fragment_kind: AstFragmentKind, kind: InvocationKind) -> AstFragment {
 973         let expn_id = LocalExpnId::fresh_empty();
 974         let vis = kind.placeholder_visibility();
 975         self.invocations.push((
 976             Invocation {
 977                 kind,
 978                 fragment_kind,
 979                 expansion_data: ExpansionData {
 980                     id: expn_id,
 981                     depth: self.cx.current_expansion.depth + 1,
 982                     ..self.cx.current_expansion.clone()
 983                 },
 984             },
 985             None,
 986         ));
 987         placeholder(fragment_kind, NodeId::placeholder_from_expn_id(expn_id), vis)
 988     }
 989
 990     fn collect_bang(&mut self, mac: ast::MacCall, kind: AstFragmentKind) -> AstFragment {
 991         // cache the macro call span so that it can be
 992         // easily adjusted for incremental compilation
 993         let span = mac.span();
 994         self.collect(kind, InvocationKind::Bang { mac, span })
 995     }
 996
 997     fn collect_attr(
 998         &mut self,
 999         (attr, pos, derives): (ast::Attribute, usize, Vec<Path>),
1000         item: Annotatable,
1001         kind: AstFragmentKind,
1002     ) -> AstFragment {
1003         self.collect(kind, InvocationKind::Attr { attr, pos, item, derives })
1004     }
1005
1006     /// If `item` is an attribute invocation, remove the attribute and return it together with
1007     /// its position and derives following it. We have to collect the derives in order to resolve
1008     /// legacy derive helpers (helpers written before derives that introduce them).
1009     fn take_first_attr(
1010         &mut self,
1011         item: &mut impl AstLike,
1012     ) -> Option<(ast::Attribute, usize, Vec<Path>)> {
1013         let mut attr = None;
1014
1015         item.visit_attrs(|attrs| {
1016             attr = attrs
1017                 .iter()
1018                 .position(|a| !self.cx.expanded_inert_attrs.is_marked(a) && !is_builtin_attr(a))
1019                 .map(|attr_pos| {
1020                     let attr = attrs.remove(attr_pos);
1021                     let following_derives = attrs[attr_pos..]
1022                         .iter()
1023                         .filter(|a| a.has_name(sym::derive))
1024                         .flat_map(|a| a.meta_item_list().unwrap_or_default())
1025                         .filter_map(|nested_meta| match nested_meta {
1026                             NestedMetaItem::MetaItem(ast::MetaItem {
1027                                 kind: MetaItemKind::Word,
1028                                 path,
1029                                 ..
1030                             }) => Some(path),
1031                             _ => None,
1032                         })
1033                         .collect();
1034
1035                     (attr, attr_pos, following_derives)
1036                 })
1037         });
1038
1039         attr
1040     }
1041
1042     fn take_stmt_bang(
1043         &mut self,
1044         stmt: ast::Stmt,
1045     ) -> Result<(bool, MacCall, Vec<ast::Attribute>), ast::Stmt> {
1046         match stmt.kind {
1047             StmtKind::MacCall(mac) => {
1048                 let MacCallStmt { mac, style, attrs, .. } = mac.into_inner();
1049                 Ok((style == MacStmtStyle::Semicolon, mac, attrs.into()))
1050             }
1051             StmtKind::Item(item) if matches!(item.kind, ItemKind::MacCall(..)) => {
1052                 match item.into_inner() {
1053                     ast::Item { kind: ItemKind::MacCall(mac), attrs, .. } => {
1054                         Ok((mac.args.need_semicolon(), mac, attrs))
1055                     }
1056                     _ => unreachable!(),
1057                 }
1058             }
1059             StmtKind::Semi(expr) if matches!(expr.kind, ast::ExprKind::MacCall(..)) => {
1060                 match expr.into_inner() {
1061                     ast::Expr { kind: ast::ExprKind::MacCall(mac), attrs, .. } => {
1062                         Ok((mac.args.need_semicolon(), mac, attrs.into()))
1063                     }
1064                     _ => unreachable!(),
1065                 }
1066             }
1067             StmtKind::Local(..) | StmtKind::Empty | StmtKind::Item(..) | StmtKind::Semi(..) => {
1068                 Err(stmt)
1069             }
1070             StmtKind::Expr(..) => unreachable!(),
1071         }
1072     }
1073
1074     fn configure<T: AstLike>(&mut self, node: T) -> Option<T> {
1075         self.cfg.configure(node)
1076     }
1077
1078     // Detect use of feature-gated or invalid attributes on macro invocations
1079     // since they will not be detected after macro expansion.
1080     fn check_attributes(&self, attrs: &[ast::Attribute], call: &MacCall) {
1081         let features = self.cx.ecfg.features.unwrap();
1082         let mut attrs = attrs.iter().peekable();
1083         let mut span: Option<Span> = None;
1084         while let Some(attr) = attrs.next() {
1085             rustc_ast_passes::feature_gate::check_attribute(attr, self.cx.sess, features);
1086             validate_attr::check_meta(&self.cx.sess.parse_sess, attr);
1087
1088             let current_span = if let Some(sp) = span { sp.to(attr.span) } else { attr.span };
1089             span = Some(current_span);
1090
1091             if attrs.peek().map_or(false, |next_attr| next_attr.doc_str().is_some()) {
1092                 continue;
1093             }
1094
1095             if attr.is_doc_comment() {
1096                 self.cx.sess.parse_sess.buffer_lint_with_diagnostic(
1097                     &UNUSED_DOC_COMMENTS,
1098                     current_span,
1099                     self.cx.current_expansion.lint_node_id,
1100                     "unused doc comment",
1101                     BuiltinLintDiagnostics::UnusedDocComment(attr.span),
1102                 );
1103             } else if rustc_attr::is_builtin_attr(attr) {
1104                 let attr_name = attr.ident().unwrap().name;
1105                 // `#[cfg]` and `#[cfg_attr]` are special - they are
1106                 // eagerly evaluated.
1107                 if attr_name != sym::cfg && attr_name != sym::cfg_attr {
1108                     self.cx.sess.parse_sess.buffer_lint_with_diagnostic(
1109                         &UNUSED_ATTRIBUTES,
1110                         attr.span,
1111                         self.cx.current_expansion.lint_node_id,
1112                         &format!("unused attribute `{}`", attr_name),
1113                         BuiltinLintDiagnostics::UnusedBuiltinAttribute {
1114                             attr_name,
1115                             macro_name: pprust::path_to_string(&call.path),
1116                             invoc_span: call.path.span,
1117                         },
1118                     );
1119                 }
1120             }
1121         }
1122     }
1123 }
1124
1125 /// Wraps a call to `noop_visit_*` / `noop_flat_map_*`
1126 /// for an AST node that supports attributes
1127 /// (see the `Annotatable` enum)
1128 /// This method assigns a `NodeId`, and sets that `NodeId`
1129 /// as our current 'lint node id'. If a macro call is found
1130 /// inside this AST node, we will use this AST node's `NodeId`
1131 /// to emit lints associated with that macro (allowing
1132 /// `#[allow]` / `#[deny]` to be applied close to
1133 /// the macro invocation).
1134 ///
1135 /// Do *not* call this for a macro AST node
1136 /// (e.g. `ExprKind::MacCall`) - we cannot emit lints
1137 /// at these AST nodes, since they are removed and
1138 /// replaced with the result of macro expansion.
1139 ///
1140 /// All other `NodeId`s are assigned by `visit_id`.
1141 /// * `self` is the 'self' parameter for the current method,
1142 /// * `id` is a mutable reference to the `NodeId` field
1143 ///    of the current AST node.
1144 /// * `closure` is a closure that executes the
1145 ///   `noop_visit_*` / `noop_flat_map_*` method
1146 ///   for the current AST node.
1147 macro_rules! assign_id {
1148     ($self:ident, $id:expr, $closure:expr) => {{
1149         let old_id = $self.cx.current_expansion.lint_node_id;
1150         if $self.monotonic {
1151             debug_assert_eq!(*$id, ast::DUMMY_NODE_ID);
1152             let new_id = $self.cx.resolver.next_node_id();
1153             *$id = new_id;
1154             $self.cx.current_expansion.lint_node_id = new_id;
1155         }
1156         let ret = ($closure)();
1157         $self.cx.current_expansion.lint_node_id = old_id;
1158         ret
1159     }};
1160 }
1161
1162 impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
1163     fn visit_crate(&mut self, krate: &mut ast::Crate) {
1164         visit_clobber(krate, |krate| {
1165             let span = krate.span;
1166             let mut krate = match self.configure(krate) {
1167                 Some(krate) => krate,
1168                 None => {
1169                     return ast::Crate {
1170                         attrs: Vec::new(),
1171                         items: Vec::new(),
1172                         span,
1173                         id: self.cx.resolver.next_node_id(),
1174                         is_placeholder: false,
1175                     };
1176                 }
1177             };
1178
1179             if let Some(attr) = self.take_first_attr(&mut krate) {
1180                 return self
1181                     .collect_attr(attr, Annotatable::Crate(krate), AstFragmentKind::Crate)
1182                     .make_crate();
1183             }
1184
1185             assign_id!(self, &mut krate.id, || noop_visit_crate(&mut krate, self));
1186             krate
1187         })
1188     }
1189
1190     fn visit_expr(&mut self, expr: &mut P<ast::Expr>) {
1191         self.cfg.configure_expr(expr);
1192         visit_clobber(expr.deref_mut(), |mut expr| {
1193             if let Some(attr) = self.take_first_attr(&mut expr) {
1194                 // Collect the invoc regardless of whether or not attributes are permitted here
1195                 // expansion will eat the attribute so it won't error later.
1196                 self.cfg.maybe_emit_expr_attr_err(&attr.0);
1197
1198                 // AstFragmentKind::Expr requires the macro to emit an expression.
1199                 return self
1200                     .collect_attr(attr, Annotatable::Expr(P(expr)), AstFragmentKind::Expr)
1201                     .make_expr()
1202                     .into_inner();
1203             }
1204
1205             if let ast::ExprKind::MacCall(mac) = expr.kind {
1206                 self.check_attributes(&expr.attrs, &mac);
1207                 self.collect_bang(mac, AstFragmentKind::Expr).make_expr().into_inner()
1208             } else {
1209                 assign_id!(self, &mut expr.id, || {
1210                     ensure_sufficient_stack(|| noop_visit_expr(&mut expr, self));
1211                 });
1212                 expr
1213             }
1214         });
1215     }
1216
1217     fn flat_map_arm(&mut self, arm: ast::Arm) -> SmallVec<[ast::Arm; 1]> {
1218         let mut arm = configure!(self, arm);
1219
1220         if let Some(attr) = self.take_first_attr(&mut arm) {
1221             return self
1222                 .collect_attr(attr, Annotatable::Arm(arm), AstFragmentKind::Arms)
1223                 .make_arms();
1224         }
1225
1226         assign_id!(self, &mut arm.id, || noop_flat_map_arm(arm, self))
1227     }
1228
1229     fn flat_map_expr_field(&mut self, field: ast::ExprField) -> SmallVec<[ast::ExprField; 1]> {
1230         let mut field = configure!(self, field);
1231
1232         if let Some(attr) = self.take_first_attr(&mut field) {
1233             return self
1234                 .collect_attr(attr, Annotatable::ExprField(field), AstFragmentKind::Fields)
1235                 .make_expr_fields();
1236         }
1237
1238         assign_id!(self, &mut field.id, || noop_flat_map_expr_field(field, self))
1239     }
1240
1241     fn flat_map_pat_field(&mut self, fp: ast::PatField) -> SmallVec<[ast::PatField; 1]> {
1242         let mut fp = configure!(self, fp);
1243
1244         if let Some(attr) = self.take_first_attr(&mut fp) {
1245             return self
1246                 .collect_attr(attr, Annotatable::PatField(fp), AstFragmentKind::FieldPats)
1247                 .make_pat_fields();
1248         }
1249
1250         assign_id!(self, &mut fp.id, || noop_flat_map_pat_field(fp, self))
1251     }
1252
1253     fn flat_map_param(&mut self, p: ast::Param) -> SmallVec<[ast::Param; 1]> {
1254         let mut p = configure!(self, p);
1255
1256         if let Some(attr) = self.take_first_attr(&mut p) {
1257             return self
1258                 .collect_attr(attr, Annotatable::Param(p), AstFragmentKind::Params)
1259                 .make_params();
1260         }
1261
1262         assign_id!(self, &mut p.id, || noop_flat_map_param(p, self))
1263     }
1264
1265     fn flat_map_field_def(&mut self, sf: ast::FieldDef) -> SmallVec<[ast::FieldDef; 1]> {
1266         let mut sf = configure!(self, sf);
1267
1268         if let Some(attr) = self.take_first_attr(&mut sf) {
1269             return self
1270                 .collect_attr(attr, Annotatable::FieldDef(sf), AstFragmentKind::StructFields)
1271                 .make_field_defs();
1272         }
1273
1274         assign_id!(self, &mut sf.id, || noop_flat_map_field_def(sf, self))
1275     }
1276
1277     fn flat_map_variant(&mut self, variant: ast::Variant) -> SmallVec<[ast::Variant; 1]> {
1278         let mut variant = configure!(self, variant);
1279
1280         if let Some(attr) = self.take_first_attr(&mut variant) {
1281             return self
1282                 .collect_attr(attr, Annotatable::Variant(variant), AstFragmentKind::Variants)
1283                 .make_variants();
1284         }
1285
1286         assign_id!(self, &mut variant.id, || noop_flat_map_variant(variant, self))
1287     }
1288
1289     fn filter_map_expr(&mut self, expr: P<ast::Expr>) -> Option<P<ast::Expr>> {
1290         let expr = configure!(self, expr);
1291         expr.filter_map(|mut expr| {
1292             if let Some(attr) = self.take_first_attr(&mut expr) {
1293                 self.cfg.maybe_emit_expr_attr_err(&attr.0);
1294
1295                 return self
1296                     .collect_attr(attr, Annotatable::Expr(P(expr)), AstFragmentKind::OptExpr)
1297                     .make_opt_expr()
1298                     .map(|expr| expr.into_inner());
1299             }
1300
1301             if let ast::ExprKind::MacCall(mac) = expr.kind {
1302                 self.check_attributes(&expr.attrs, &mac);
1303                 self.collect_bang(mac, AstFragmentKind::OptExpr)
1304                     .make_opt_expr()
1305                     .map(|expr| expr.into_inner())
1306             } else {
1307                 assign_id!(self, &mut expr.id, || {
1308                     Some({
1309                         noop_visit_expr(&mut expr, self);
1310                         expr
1311                     })
1312                 })
1313             }
1314         })
1315     }
1316
1317     fn visit_pat(&mut self, pat: &mut P<ast::Pat>) {
1318         match pat.kind {
1319             PatKind::MacCall(_) => {}
1320             _ => return noop_visit_pat(pat, self),
1321         }
1322
1323         visit_clobber(pat, |mut pat| match mem::replace(&mut pat.kind, PatKind::Wild) {
1324             PatKind::MacCall(mac) => self.collect_bang(mac, AstFragmentKind::Pat).make_pat(),
1325             _ => unreachable!(),
1326         });
1327     }
1328
1329     fn flat_map_stmt(&mut self, stmt: ast::Stmt) -> SmallVec<[ast::Stmt; 1]> {
1330         let mut stmt = configure!(self, stmt);
1331
1332         // We pull macro invocations (both attributes and fn-like macro calls) out of their
1333         // `StmtKind`s and treat them as statement macro invocations, not as items or expressions.
1334         // FIXME: invocations in semicolon-less expressions positions are expanded as expressions,
1335         // changing that requires some compatibility measures.
1336         let mut stmt = if !stmt.is_expr() {
1337             if let Some(attr) = self.take_first_attr(&mut stmt) {
1338                 return self
1339                     .collect_attr(attr, Annotatable::Stmt(P(stmt)), AstFragmentKind::Stmts)
1340                     .make_stmts();
1341             }
1342
1343             match self.take_stmt_bang(stmt) {
1344                 Ok((add_semicolon, mac, attrs)) => {
1345                     self.check_attributes(&attrs, &mac);
1346                     let mut stmts = self.collect_bang(mac, AstFragmentKind::Stmts).make_stmts();
1347
1348                     // If this is a macro invocation with a semicolon, then apply that
1349                     // semicolon to the final statement produced by expansion.
1350                     if add_semicolon {
1351                         if let Some(stmt) = stmts.pop() {
1352                             stmts.push(stmt.add_trailing_semicolon());
1353                         }
1354                     }
1355
1356                     return stmts;
1357                 }
1358                 Err(stmt) => stmt,
1359             }
1360         } else {
1361             stmt
1362         };
1363
1364         // The only way that we can end up with a `MacCall` expression statement,
1365         // (as opposed to a `StmtKind::MacCall`) is if we have a macro as the
1366         // traiing expression in a block (e.g. `fn foo() { my_macro!() }`).
1367         // Record this information, so that we can report a more specific
1368         // `SEMICOLON_IN_EXPRESSIONS_FROM_MACROS` lint if needed.
1369         // See #78991 for an investigation of treating macros in this position
1370         // as statements, rather than expressions, during parsing.
1371         let res = match &stmt.kind {
1372             StmtKind::Expr(expr)
1373                 if matches!(**expr, ast::Expr { kind: ast::ExprKind::MacCall(..), .. }) =>
1374             {
1375                 self.cx.current_expansion.is_trailing_mac = true;
1376                 // Don't use `assign_id` for this statement - it may get removed
1377                 // entirely due to a `#[cfg]` on the contained expression
1378                 noop_flat_map_stmt(stmt, self)
1379             }
1380             _ => assign_id!(self, &mut stmt.id, || noop_flat_map_stmt(stmt, self)),
1381         };
1382         self.cx.current_expansion.is_trailing_mac = false;
1383         res
1384     }
1385
1386     fn visit_block(&mut self, block: &mut P<Block>) {
1387         let orig_dir_ownership = mem::replace(
1388             &mut self.cx.current_expansion.dir_ownership,
1389             DirOwnership::UnownedViaBlock,
1390         );
1391         noop_visit_block(block, self);
1392         self.cx.current_expansion.dir_ownership = orig_dir_ownership;
1393     }
1394
1395     fn flat_map_item(&mut self, item: P<ast::Item>) -> SmallVec<[P<ast::Item>; 1]> {
1396         let mut item = configure!(self, item);
1397
1398         if let Some(attr) = self.take_first_attr(&mut item) {
1399             return self
1400                 .collect_attr(attr, Annotatable::Item(item), AstFragmentKind::Items)
1401                 .make_items();
1402         }
1403
1404         let mut attrs = mem::take(&mut item.attrs); // We do this to please borrowck.
1405         let ident = item.ident;
1406         let span = item.span;
1407
1408         match item.kind {
1409             ast::ItemKind::MacCall(ref mac) => {
1410                 self.check_attributes(&attrs, &mac);
1411                 item.attrs = attrs;
1412                 item.and_then(|item| match item.kind {
1413                     ItemKind::MacCall(mac) => {
1414                         self.collect_bang(mac, AstFragmentKind::Items).make_items()
1415                     }
1416                     _ => unreachable!(),
1417                 })
1418             }
1419             ast::ItemKind::Mod(_, ref mut mod_kind) if ident != Ident::empty() => {
1420                 let (file_path, dir_path, dir_ownership) = match mod_kind {
1421                     ModKind::Loaded(_, inline, _) => {
1422                         // Inline `mod foo { ... }`, but we still need to push directories.
1423                         let (dir_path, dir_ownership) = mod_dir_path(
1424                             &self.cx.sess,
1425                             ident,
1426                             &attrs,
1427                             &self.cx.current_expansion.module,
1428                             self.cx.current_expansion.dir_ownership,
1429                             *inline,
1430                         );
1431                         item.attrs = attrs;
1432                         (None, dir_path, dir_ownership)
1433                     }
1434                     ModKind::Unloaded => {
1435                         // We have an outline `mod foo;` so we need to parse the file.
1436                         let old_attrs_len = attrs.len();
1437                         let ParsedExternalMod {
1438                             mut items,
1439                             inner_span,
1440                             file_path,
1441                             dir_path,
1442                             dir_ownership,
1443                         } = parse_external_mod(
1444                             &self.cx.sess,
1445                             ident,
1446                             span,
1447                             &self.cx.current_expansion.module,
1448                             self.cx.current_expansion.dir_ownership,
1449                             &mut attrs,
1450                         );
1451
1452                         if let Some(extern_mod_loaded) = self.cx.extern_mod_loaded {
1453                             (attrs, items) = extern_mod_loaded(ident, attrs, items, inner_span);
1454                         }
1455
1456                         *mod_kind = ModKind::Loaded(items, Inline::No, inner_span);
1457                         item.attrs = attrs;
1458                         if item.attrs.len() > old_attrs_len {
1459                             // If we loaded an out-of-line module and added some inner attributes,
1460                             // then we need to re-configure it and re-collect attributes for
1461                             // resolution and expansion.
1462                             item = configure!(self, item);
1463
1464                             if let Some(attr) = self.take_first_attr(&mut item) {
1465                                 return self
1466                                     .collect_attr(
1467                                         attr,
1468                                         Annotatable::Item(item),
1469                                         AstFragmentKind::Items,
1470                                     )
1471                                     .make_items();
1472                             }
1473                         }
1474                         (Some(file_path), dir_path, dir_ownership)
1475                     }
1476                 };
1477
1478                 // Set the module info before we flat map.
1479                 let mut module = self.cx.current_expansion.module.with_dir_path(dir_path);
1480                 module.mod_path.push(ident);
1481                 if let Some(file_path) = file_path {
1482                     module.file_path_stack.push(file_path);
1483                 }
1484
1485                 let orig_module =
1486                     mem::replace(&mut self.cx.current_expansion.module, Rc::new(module));
1487                 let orig_dir_ownership =
1488                     mem::replace(&mut self.cx.current_expansion.dir_ownership, dir_ownership);
1489
1490                 let result = assign_id!(self, &mut item.id, || noop_flat_map_item(item, self));
1491
1492                 // Restore the module info.
1493                 self.cx.current_expansion.dir_ownership = orig_dir_ownership;
1494                 self.cx.current_expansion.module = orig_module;
1495
1496                 result
1497             }
1498             _ => {
1499                 item.attrs = attrs;
1500                 // The crate root is special - don't assign an ID to it.
1501                 if !(matches!(item.kind, ast::ItemKind::Mod(..)) && ident == Ident::empty()) {
1502                     assign_id!(self, &mut item.id, || noop_flat_map_item(item, self))
1503                 } else {
1504                     noop_flat_map_item(item, self)
1505                 }
1506             }
1507         }
1508     }
1509
1510     fn flat_map_trait_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
1511         let mut item = configure!(self, item);
1512
1513         if let Some(attr) = self.take_first_attr(&mut item) {
1514             return self
1515                 .collect_attr(attr, Annotatable::TraitItem(item), AstFragmentKind::TraitItems)
1516                 .make_trait_items();
1517         }
1518
1519         match item.kind {
1520             ast::AssocItemKind::MacCall(ref mac) => {
1521                 self.check_attributes(&item.attrs, &mac);
1522                 item.and_then(|item| match item.kind {
1523                     ast::AssocItemKind::MacCall(mac) => {
1524                         self.collect_bang(mac, AstFragmentKind::TraitItems).make_trait_items()
1525                     }
1526                     _ => unreachable!(),
1527                 })
1528             }
1529             _ => {
1530                 assign_id!(self, &mut item.id, || noop_flat_map_assoc_item(item, self))
1531             }
1532         }
1533     }
1534
1535     fn flat_map_impl_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
1536         let mut item = configure!(self, item);
1537
1538         if let Some(attr) = self.take_first_attr(&mut item) {
1539             return self
1540                 .collect_attr(attr, Annotatable::ImplItem(item), AstFragmentKind::ImplItems)
1541                 .make_impl_items();
1542         }
1543
1544         match item.kind {
1545             ast::AssocItemKind::MacCall(ref mac) => {
1546                 self.check_attributes(&item.attrs, &mac);
1547                 item.and_then(|item| match item.kind {
1548                     ast::AssocItemKind::MacCall(mac) => {
1549                         self.collect_bang(mac, AstFragmentKind::ImplItems).make_impl_items()
1550                     }
1551                     _ => unreachable!(),
1552                 })
1553             }
1554             _ => {
1555                 assign_id!(self, &mut item.id, || noop_flat_map_assoc_item(item, self))
1556             }
1557         }
1558     }
1559
1560     fn visit_ty(&mut self, ty: &mut P<ast::Ty>) {
1561         match ty.kind {
1562             ast::TyKind::MacCall(_) => {}
1563             _ => return noop_visit_ty(ty, self),
1564         };
1565
1566         visit_clobber(ty, |mut ty| match mem::replace(&mut ty.kind, ast::TyKind::Err) {
1567             ast::TyKind::MacCall(mac) => self.collect_bang(mac, AstFragmentKind::Ty).make_ty(),
1568             _ => unreachable!(),
1569         });
1570     }
1571
1572     fn flat_map_foreign_item(
1573         &mut self,
1574         foreign_item: P<ast::ForeignItem>,
1575     ) -> SmallVec<[P<ast::ForeignItem>; 1]> {
1576         let mut foreign_item = configure!(self, foreign_item);
1577
1578         if let Some(attr) = self.take_first_attr(&mut foreign_item) {
1579             return self
1580                 .collect_attr(
1581                     attr,
1582                     Annotatable::ForeignItem(foreign_item),
1583                     AstFragmentKind::ForeignItems,
1584                 )
1585                 .make_foreign_items();
1586         }
1587
1588         match foreign_item.kind {
1589             ast::ForeignItemKind::MacCall(ref mac) => {
1590                 self.check_attributes(&foreign_item.attrs, &mac);
1591                 foreign_item.and_then(|item| match item.kind {
1592                     ast::ForeignItemKind::MacCall(mac) => {
1593                         self.collect_bang(mac, AstFragmentKind::ForeignItems).make_foreign_items()
1594                     }
1595                     _ => unreachable!(),
1596                 })
1597             }
1598             _ => {
1599                 assign_id!(self, &mut foreign_item.id, || noop_flat_map_foreign_item(
1600                     foreign_item,
1601                     self
1602                 ))
1603             }
1604         }
1605     }
1606
1607     fn flat_map_generic_param(
1608         &mut self,
1609         param: ast::GenericParam,
1610     ) -> SmallVec<[ast::GenericParam; 1]> {
1611         let mut param = configure!(self, param);
1612
1613         if let Some(attr) = self.take_first_attr(&mut param) {
1614             return self
1615                 .collect_attr(
1616                     attr,
1617                     Annotatable::GenericParam(param),
1618                     AstFragmentKind::GenericParams,
1619                 )
1620                 .make_generic_params();
1621         }
1622
1623         assign_id!(self, &mut param.id, || noop_flat_map_generic_param(param, self))
1624     }
1625
1626     fn visit_id(&mut self, id: &mut ast::NodeId) {
1627         // We may have already assigned a `NodeId`
1628         // by calling `assign_id`
1629         if self.monotonic && *id == ast::DUMMY_NODE_ID {
1630             *id = self.cx.resolver.next_node_id();
1631         }
1632     }
1633 }
1634
1635 pub struct ExpansionConfig<'feat> {
1636     pub crate_name: String,
1637     pub features: Option<&'feat Features>,
1638     pub recursion_limit: Limit,
1639     pub trace_mac: bool,
1640     pub should_test: bool,          // If false, strip `#[test]` nodes
1641     pub span_debug: bool,           // If true, use verbose debugging for `proc_macro::Span`
1642     pub proc_macro_backtrace: bool, // If true, show backtraces for proc-macro panics
1643 }
1644
1645 impl<'feat> ExpansionConfig<'feat> {
1646     pub fn default(crate_name: String) -> ExpansionConfig<'static> {
1647         ExpansionConfig {
1648             crate_name,
1649             features: None,
1650             recursion_limit: Limit::new(1024),
1651             trace_mac: false,
1652             should_test: false,
1653             span_debug: false,
1654             proc_macro_backtrace: false,
1655         }
1656     }
1657
1658     fn proc_macro_hygiene(&self) -> bool {
1659         self.features.map_or(false, |features| features.proc_macro_hygiene)
1660     }
1661 }