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         self.cx.trace_macros_diag();
 381         krate
 382     }
 383
 384     // Recursively expand all macro invocations in this AST fragment.
 385     pub fn fully_expand_fragment(&mut self, input_fragment: AstFragment) -> AstFragment {
 386         let orig_expansion_data = self.cx.current_expansion.clone();
 387         let orig_force_mode = self.cx.force_mode;
 388
 389         // Collect all macro invocations and replace them with placeholders.
 390         let (mut fragment_with_placeholders, mut invocations) =
 391             self.collect_invocations(input_fragment, &[]);
 392
 393         // Optimization: if we resolve all imports now,
 394         // we'll be able to immediately resolve most of imported macros.
 395         self.resolve_imports();
 396
 397         // Resolve paths in all invocations and produce output expanded fragments for them, but
 398         // do not insert them into our input AST fragment yet, only store in `expanded_fragments`.
 399         // The output fragments also go through expansion recursively until no invocations are left.
 400         // Unresolved macros produce dummy outputs as a recovery measure.
 401         invocations.reverse();
 402         let mut expanded_fragments = Vec::new();
 403         let mut undetermined_invocations = Vec::new();
 404         let (mut progress, mut force) = (false, !self.monotonic);
 405         loop {
 406             let Some((invoc, ext)) = invocations.pop() else {
 407                 self.resolve_imports();
 408                 if undetermined_invocations.is_empty() {
 409                     break;
 410                 }
 411                 invocations = mem::take(&mut undetermined_invocations);
 412                 force = !mem::replace(&mut progress, false);
 413                 if force && self.monotonic {
 414                     self.cx.sess.delay_span_bug(
 415                         invocations.last().unwrap().0.span(),
 416                         "expansion entered force mode without producing any errors",
 417                     );
 418                 }
 419                 continue;
 420             };
 421
 422             let ext = match ext {
 423                 Some(ext) => ext,
 424                 None => {
 425                     let eager_expansion_root = if self.monotonic {
 426                         invoc.expansion_data.id
 427                     } else {
 428                         orig_expansion_data.id
 429                     };
 430                     match self.cx.resolver.resolve_macro_invocation(
 431                         &invoc,
 432                         eager_expansion_root,
 433                         force,
 434                     ) {
 435                         Ok(ext) => ext,
 436                         Err(Indeterminate) => {
 437                             // Cannot resolve, will retry this invocation later.
 438                             undetermined_invocations.push((invoc, None));
 439                             continue;
 440                         }
 441                     }
 442                 }
 443             };
 444
 445             let ExpansionData { depth, id: expn_id, .. } = invoc.expansion_data;
 446             let depth = depth - orig_expansion_data.depth;
 447             self.cx.current_expansion = invoc.expansion_data.clone();
 448             self.cx.force_mode = force;
 449
 450             let fragment_kind = invoc.fragment_kind;
 451             let (expanded_fragment, new_invocations) = match self.expand_invoc(invoc, &ext.kind) {
 452                 ExpandResult::Ready(fragment) => {
 453                     let mut derive_invocations = Vec::new();
 454                     let derive_placeholders = self
 455                         .cx
 456                         .resolver
 457                         .take_derive_resolutions(expn_id)
 458                         .map(|derives| {
 459                             derive_invocations.reserve(derives.len());
 460                             derives
 461                                 .into_iter()
 462                                 .map(|(path, item, _exts)| {
 463                                     // FIXME: Consider using the derive resolutions (`_exts`)
 464                                     // instead of enqueuing the derives to be resolved again later.
 465                                     let expn_id = LocalExpnId::fresh_empty();
 466                                     derive_invocations.push((
 467                                         Invocation {
 468                                             kind: InvocationKind::Derive { path, item },
 469                                             fragment_kind,
 470                                             expansion_data: ExpansionData {
 471                                                 id: expn_id,
 472                                                 ..self.cx.current_expansion.clone()
 473                                             },
 474                                         },
 475                                         None,
 476                                     ));
 477                                     NodeId::placeholder_from_expn_id(expn_id)
 478                                 })
 479                                 .collect::<Vec<_>>()
 480                         })
 481                         .unwrap_or_default();
 482
 483                     let (fragment, collected_invocations) =
 484                         self.collect_invocations(fragment, &derive_placeholders);
 485                     // We choose to expand any derive invocations associated with this macro invocation
 486                     // *before* any macro invocations collected from the output fragment
 487                     derive_invocations.extend(collected_invocations);
 488                     (fragment, derive_invocations)
 489                 }
 490                 ExpandResult::Retry(invoc) => {
 491                     if force {
 492                         self.cx.span_bug(
 493                             invoc.span(),
 494                             "expansion entered force mode but is still stuck",
 495                         );
 496                     } else {
 497                         // Cannot expand, will retry this invocation later.
 498                         undetermined_invocations.push((invoc, Some(ext)));
 499                         continue;
 500                     }
 501                 }
 502             };
 503
 504             progress = true;
 505             if expanded_fragments.len() < depth {
 506                 expanded_fragments.push(Vec::new());
 507             }
 508             expanded_fragments[depth - 1].push((expn_id, expanded_fragment));
 509             invocations.extend(new_invocations.into_iter().rev());
 510         }
 511
 512         self.cx.current_expansion = orig_expansion_data;
 513         self.cx.force_mode = orig_force_mode;
 514
 515         // Finally incorporate all the expanded macros into the input AST fragment.
 516         let mut placeholder_expander = PlaceholderExpander::default();
 517         while let Some(expanded_fragments) = expanded_fragments.pop() {
 518             for (expn_id, expanded_fragment) in expanded_fragments.into_iter().rev() {
 519                 placeholder_expander
 520                     .add(NodeId::placeholder_from_expn_id(expn_id), expanded_fragment);
 521             }
 522         }
 523         fragment_with_placeholders.mut_visit_with(&mut placeholder_expander);
 524         fragment_with_placeholders
 525     }
 526
 527     fn resolve_imports(&mut self) {
 528         if self.monotonic {
 529             self.cx.resolver.resolve_imports();
 530         }
 531     }
 532
 533     /// Collects all macro invocations reachable at this time in this AST fragment, and replace
 534     /// them with "placeholders" - dummy macro invocations with specially crafted `NodeId`s.
 535     /// Then call into resolver that builds a skeleton ("reduced graph") of the fragment and
 536     /// prepares data for resolving paths of macro invocations.
 537     fn collect_invocations(
 538         &mut self,
 539         mut fragment: AstFragment,
 540         extra_placeholders: &[NodeId],
 541     ) -> (AstFragment, Vec<(Invocation, Option<Lrc<SyntaxExtension>>)>) {
 542         // Resolve `$crate`s in the fragment for pretty-printing.
 543         self.cx.resolver.resolve_dollar_crates();
 544
 545         let mut invocations = {
 546             let mut collector = InvocationCollector {
 547                 // Non-derive macro invocations cannot see the results of cfg expansion - they
 548                 // will either be removed along with the item, or invoked before the cfg/cfg_attr
 549                 // attribute is expanded. Therefore, we don't need to configure the tokens
 550                 // Derive macros *can* see the results of cfg-expansion - they are handled
 551                 // specially in `fully_expand_fragment`
 552                 cfg: StripUnconfigured {
 553                     sess: &self.cx.sess,
 554                     features: self.cx.ecfg.features,
 555                     config_tokens: false,
 556                 },
 557                 cx: self.cx,
 558                 invocations: Vec::new(),
 559                 monotonic: self.monotonic,
 560             };
 561             fragment.mut_visit_with(&mut collector);
 562             fragment.add_placeholders(extra_placeholders);
 563             collector.invocations
 564         };
 565
 566         if self.monotonic {
 567             self.cx
 568                 .resolver
 569                 .visit_ast_fragment_with_placeholders(self.cx.current_expansion.id, &fragment);
 570
 571             if self.cx.sess.opts.debugging_opts.incremental_relative_spans {
 572                 for (invoc, _) in invocations.iter_mut() {
 573                     let expn_id = invoc.expansion_data.id;
 574                     let parent_def = self.cx.resolver.invocation_parent(expn_id);
 575                     let span = match &mut invoc.kind {
 576                         InvocationKind::Bang { ref mut span, .. } => span,
 577                         InvocationKind::Attr { attr, .. } => &mut attr.span,
 578                         InvocationKind::Derive { path, .. } => &mut path.span,
 579                     };
 580                     *span = span.with_parent(Some(parent_def));
 581                 }
 582             }
 583         }
 584
 585         (fragment, invocations)
 586     }
 587
 588     fn error_recursion_limit_reached(&mut self) {
 589         let expn_data = self.cx.current_expansion.id.expn_data();
 590         let suggested_limit = match self.cx.ecfg.recursion_limit {
 591             Limit(0) => Limit(2),
 592             limit => limit * 2,
 593         };
 594         self.cx
 595             .struct_span_err(
 596                 expn_data.call_site,
 597                 &format!("recursion limit reached while expanding `{}`", expn_data.kind.descr()),
 598             )
 599             .help(&format!(
 600                 "consider increasing the recursion limit by adding a \
 601                  `#![recursion_limit = \"{}\"]` attribute to your crate (`{}`)",
 602                 suggested_limit, self.cx.ecfg.crate_name,
 603             ))
 604             .emit();
 605         self.cx.trace_macros_diag();
 606     }
 607
 608     /// A macro's expansion does not fit in this fragment kind.
 609     /// For example, a non-type macro in a type position.
 610     fn error_wrong_fragment_kind(&mut self, kind: AstFragmentKind, mac: &ast::MacCall, span: Span) {
 611         let msg = format!(
 612             "non-{kind} macro in {kind} position: {path}",
 613             kind = kind.name(),
 614             path = pprust::path_to_string(&mac.path),
 615         );
 616         self.cx.span_err(span, &msg);
 617         self.cx.trace_macros_diag();
 618     }
 619
 620     fn expand_invoc(
 621         &mut self,
 622         invoc: Invocation,
 623         ext: &SyntaxExtensionKind,
 624     ) -> ExpandResult<AstFragment, Invocation> {
 625         let recursion_limit =
 626             self.cx.reduced_recursion_limit.unwrap_or(self.cx.ecfg.recursion_limit);
 627         if !recursion_limit.value_within_limit(self.cx.current_expansion.depth) {
 628             if self.cx.reduced_recursion_limit.is_none() {
 629                 self.error_recursion_limit_reached();
 630             }
 631
 632             // Reduce the recursion limit by half each time it triggers.
 633             self.cx.reduced_recursion_limit = Some(recursion_limit / 2);
 634
 635             return ExpandResult::Ready(invoc.fragment_kind.dummy(invoc.span()));
 636         }
 637
 638         let (fragment_kind, span) = (invoc.fragment_kind, invoc.span());
 639         ExpandResult::Ready(match invoc.kind {
 640             InvocationKind::Bang { mac, .. } => match ext {
 641                 SyntaxExtensionKind::Bang(expander) => {
 642                     let tok_result = match expander.expand(self.cx, span, mac.args.inner_tokens()) {
 643                         Err(_) => return ExpandResult::Ready(fragment_kind.dummy(span)),
 644                         Ok(ts) => ts,
 645                     };
 646                     self.parse_ast_fragment(tok_result, fragment_kind, &mac.path, span)
 647                 }
 648                 SyntaxExtensionKind::LegacyBang(expander) => {
 649                     let prev = self.cx.current_expansion.prior_type_ascription;
 650                     self.cx.current_expansion.prior_type_ascription = mac.prior_type_ascription;
 651                     let tok_result = expander.expand(self.cx, span, mac.args.inner_tokens());
 652                     let result = if let Some(result) = fragment_kind.make_from(tok_result) {
 653                         result
 654                     } else {
 655                         self.error_wrong_fragment_kind(fragment_kind, &mac, span);
 656                         fragment_kind.dummy(span)
 657                     };
 658                     self.cx.current_expansion.prior_type_ascription = prev;
 659                     result
 660                 }
 661                 _ => unreachable!(),
 662             },
 663             InvocationKind::Attr { attr, pos, mut item, derives } => match ext {
 664                 SyntaxExtensionKind::Attr(expander) => {
 665                     self.gate_proc_macro_input(&item);
 666                     self.gate_proc_macro_attr_item(span, &item);
 667                     let tokens = match &item {
 668                         // FIXME: Collect tokens and use them instead of generating
 669                         // fake ones. These are unstable, so it needs to be
 670                         // fixed prior to stabilization
 671                         // Fake tokens when we are invoking an inner attribute, and
 672                         // we are invoking it on an out-of-line module or crate.
 673                         Annotatable::Crate(krate) => rustc_parse::fake_token_stream_for_crate(
 674                             &self.cx.sess.parse_sess,
 675                             krate,
 676                         ),
 677                         Annotatable::Item(item_inner)
 678                             if matches!(attr.style, ast::AttrStyle::Inner)
 679                                 && matches!(
 680                                     item_inner.kind,
 681                                     ItemKind::Mod(
 682                                         _,
 683                                         ModKind::Unloaded | ModKind::Loaded(_, Inline::No, _),
 684                                     )
 685                                 ) =>
 686                         {
 687                             rustc_parse::fake_token_stream(
 688                                 &self.cx.sess.parse_sess,
 689                                 &item.into_nonterminal(),
 690                             )
 691                         }
 692                         _ => item.into_tokens(&self.cx.sess.parse_sess),
 693                     };
 694                     let attr_item = attr.unwrap_normal_item();
 695                     if let MacArgs::Eq(..) = attr_item.args {
 696                         self.cx.span_err(span, "key-value macro attributes are not supported");
 697                     }
 698                     let inner_tokens = attr_item.args.inner_tokens();
 699                     let tok_result = match expander.expand(self.cx, span, inner_tokens, tokens) {
 700                         Err(_) => return ExpandResult::Ready(fragment_kind.dummy(span)),
 701                         Ok(ts) => ts,
 702                     };
 703                     self.parse_ast_fragment(tok_result, fragment_kind, &attr_item.path, span)
 704                 }
 705                 SyntaxExtensionKind::LegacyAttr(expander) => {
 706                     match validate_attr::parse_meta(&self.cx.sess.parse_sess, &attr) {
 707                         Ok(meta) => {
 708                             let items = match expander.expand(self.cx, span, &meta, item) {
 709                                 ExpandResult::Ready(items) => items,
 710                                 ExpandResult::Retry(item) => {
 711                                     // Reassemble the original invocation for retrying.
 712                                     return ExpandResult::Retry(Invocation {
 713                                         kind: InvocationKind::Attr { attr, pos, item, derives },
 714                                         ..invoc
 715                                     });
 716                                 }
 717                             };
 718                             if fragment_kind == AstFragmentKind::Expr && items.is_empty() {
 719                                 let msg =
 720                                     "removing an expression is not supported in this position";
 721                                 self.cx.span_err(span, msg);
 722                                 fragment_kind.dummy(span)
 723                             } else {
 724                                 fragment_kind.expect_from_annotatables(items)
 725                             }
 726                         }
 727                         Err(mut err) => {
 728                             err.emit();
 729                             fragment_kind.dummy(span)
 730                         }
 731                     }
 732                 }
 733                 SyntaxExtensionKind::NonMacroAttr => {
 734                     self.cx.expanded_inert_attrs.mark(&attr);
 735                     item.visit_attrs(|attrs| attrs.insert(pos, attr));
 736                     fragment_kind.expect_from_annotatables(iter::once(item))
 737                 }
 738                 _ => unreachable!(),
 739             },
 740             InvocationKind::Derive { path, item } => match ext {
 741                 SyntaxExtensionKind::Derive(expander)
 742                 | SyntaxExtensionKind::LegacyDerive(expander) => {
 743                     if let SyntaxExtensionKind::Derive(..) = ext {
 744                         self.gate_proc_macro_input(&item);
 745                     }
 746                     let meta = ast::MetaItem { kind: ast::MetaItemKind::Word, span, path };
 747                     let items = match expander.expand(self.cx, span, &meta, item) {
 748                         ExpandResult::Ready(items) => items,
 749                         ExpandResult::Retry(item) => {
 750                             // Reassemble the original invocation for retrying.
 751                             return ExpandResult::Retry(Invocation {
 752                                 kind: InvocationKind::Derive { path: meta.path, item },
 753                                 ..invoc
 754                             });
 755                         }
 756                     };
 757                     fragment_kind.expect_from_annotatables(items)
 758                 }
 759                 _ => unreachable!(),
 760             },
 761         })
 762     }
 763
 764     fn gate_proc_macro_attr_item(&self, span: Span, item: &Annotatable) {
 765         let kind = match item {
 766             Annotatable::Item(_)
 767             | Annotatable::TraitItem(_)
 768             | Annotatable::ImplItem(_)
 769             | Annotatable::ForeignItem(_)
 770             | Annotatable::Crate(..) => return,
 771             Annotatable::Stmt(stmt) => {
 772                 // Attributes are stable on item statements,
 773                 // but unstable on all other kinds of statements
 774                 if stmt.is_item() {
 775                     return;
 776                 }
 777                 "statements"
 778             }
 779             Annotatable::Expr(_) => "expressions",
 780             Annotatable::Arm(..)
 781             | Annotatable::ExprField(..)
 782             | Annotatable::PatField(..)
 783             | Annotatable::GenericParam(..)
 784             | Annotatable::Param(..)
 785             | Annotatable::FieldDef(..)
 786             | Annotatable::Variant(..) => panic!("unexpected annotatable"),
 787         };
 788         if self.cx.ecfg.proc_macro_hygiene() {
 789             return;
 790         }
 791         feature_err(
 792             &self.cx.sess.parse_sess,
 793             sym::proc_macro_hygiene,
 794             span,
 795             &format!("custom attributes cannot be applied to {}", kind),
 796         )
 797         .emit();
 798     }
 799
 800     fn gate_proc_macro_input(&self, annotatable: &Annotatable) {
 801         struct GateProcMacroInput<'a> {
 802             parse_sess: &'a ParseSess,
 803         }
 804
 805         impl<'ast, 'a> Visitor<'ast> for GateProcMacroInput<'a> {
 806             fn visit_item(&mut self, item: &'ast ast::Item) {
 807                 match &item.kind {
 808                     ast::ItemKind::Mod(_, mod_kind)
 809                         if !matches!(mod_kind, ModKind::Loaded(_, Inline::Yes, _)) =>
 810                     {
 811                         feature_err(
 812                             self.parse_sess,
 813                             sym::proc_macro_hygiene,
 814                             item.span,
 815                             "non-inline modules in proc macro input are unstable",
 816                         )
 817                         .emit();
 818                     }
 819                     _ => {}
 820                 }
 821
 822                 visit::walk_item(self, item);
 823             }
 824         }
 825
 826         if !self.cx.ecfg.proc_macro_hygiene() {
 827             annotatable
 828                 .visit_with(&mut GateProcMacroInput { parse_sess: &self.cx.sess.parse_sess });
 829         }
 830     }
 831
 832     fn parse_ast_fragment(
 833         &mut self,
 834         toks: TokenStream,
 835         kind: AstFragmentKind,
 836         path: &Path,
 837         span: Span,
 838     ) -> AstFragment {
 839         let mut parser = self.cx.new_parser_from_tts(toks);
 840         match parse_ast_fragment(&mut parser, kind) {
 841             Ok(fragment) => {
 842                 ensure_complete_parse(&mut parser, path, kind.name(), span);
 843                 fragment
 844             }
 845             Err(mut err) => {
 846                 if err.span.is_dummy() {
 847                     err.set_span(span);
 848                 }
 849                 annotate_err_with_kind(&mut err, kind, span);
 850                 err.emit();
 851                 self.cx.trace_macros_diag();
 852                 kind.dummy(span)
 853             }
 854         }
 855     }
 856 }
 857
 858 pub fn parse_ast_fragment<'a>(
 859     this: &mut Parser<'a>,
 860     kind: AstFragmentKind,
 861 ) -> PResult<'a, AstFragment> {
 862     Ok(match kind {
 863         AstFragmentKind::Items => {
 864             let mut items = SmallVec::new();
 865             while let Some(item) = this.parse_item(ForceCollect::No)? {
 866                 items.push(item);
 867             }
 868             AstFragment::Items(items)
 869         }
 870         AstFragmentKind::TraitItems => {
 871             let mut items = SmallVec::new();
 872             while let Some(item) = this.parse_trait_item(ForceCollect::No)? {
 873                 items.extend(item);
 874             }
 875             AstFragment::TraitItems(items)
 876         }
 877         AstFragmentKind::ImplItems => {
 878             let mut items = SmallVec::new();
 879             while let Some(item) = this.parse_impl_item(ForceCollect::No)? {
 880                 items.extend(item);
 881             }
 882             AstFragment::ImplItems(items)
 883         }
 884         AstFragmentKind::ForeignItems => {
 885             let mut items = SmallVec::new();
 886             while let Some(item) = this.parse_foreign_item(ForceCollect::No)? {
 887                 items.extend(item);
 888             }
 889             AstFragment::ForeignItems(items)
 890         }
 891         AstFragmentKind::Stmts => {
 892             let mut stmts = SmallVec::new();
 893             // Won't make progress on a `}`.
 894             while this.token != token::Eof && this.token != token::CloseDelim(token::Brace) {
 895                 if let Some(stmt) = this.parse_full_stmt(AttemptLocalParseRecovery::Yes)? {
 896                     stmts.push(stmt);
 897                 }
 898             }
 899             AstFragment::Stmts(stmts)
 900         }
 901         AstFragmentKind::Expr => AstFragment::Expr(this.parse_expr()?),
 902         AstFragmentKind::OptExpr => {
 903             if this.token != token::Eof {
 904                 AstFragment::OptExpr(Some(this.parse_expr()?))
 905             } else {
 906                 AstFragment::OptExpr(None)
 907             }
 908         }
 909         AstFragmentKind::Ty => AstFragment::Ty(this.parse_ty()?),
 910         AstFragmentKind::Pat => AstFragment::Pat(this.parse_pat_allow_top_alt(
 911             None,
 912             RecoverComma::No,
 913             RecoverColon::Yes,
 914         )?),
 915         AstFragmentKind::Crate => AstFragment::Crate(this.parse_crate_mod()?),
 916         AstFragmentKind::Arms
 917         | AstFragmentKind::Fields
 918         | AstFragmentKind::FieldPats
 919         | AstFragmentKind::GenericParams
 920         | AstFragmentKind::Params
 921         | AstFragmentKind::StructFields
 922         | AstFragmentKind::Variants => panic!("unexpected AST fragment kind"),
 923     })
 924 }
 925
 926 pub fn ensure_complete_parse<'a>(
 927     this: &mut Parser<'a>,
 928     macro_path: &Path,
 929     kind_name: &str,
 930     span: Span,
 931 ) {
 932     if this.token != token::Eof {
 933         let token = pprust::token_to_string(&this.token);
 934         let msg = format!("macro expansion ignores token `{}` and any following", token);
 935         // Avoid emitting backtrace info twice.
 936         let def_site_span = this.token.span.with_ctxt(SyntaxContext::root());
 937         let mut err = this.struct_span_err(def_site_span, &msg);
 938         err.span_label(span, "caused by the macro expansion here");
 939         let msg = format!(
 940             "the usage of `{}!` is likely invalid in {} context",
 941             pprust::path_to_string(macro_path),
 942             kind_name,
 943         );
 944         err.note(&msg);
 945         let semi_span = this.sess.source_map().next_point(span);
 946
 947         let semi_full_span = semi_span.to(this.sess.source_map().next_point(semi_span));
 948         match this.sess.source_map().span_to_snippet(semi_full_span) {
 949             Ok(ref snippet) if &snippet[..] != ";" && kind_name == "expression" => {
 950                 err.span_suggestion(
 951                     semi_span,
 952                     "you might be missing a semicolon here",
 953                     ";".to_owned(),
 954                     Applicability::MaybeIncorrect,
 955                 );
 956             }
 957             _ => {}
 958         }
 959         err.emit();
 960     }
 961 }
 962
 963 struct InvocationCollector<'a, 'b> {
 964     cx: &'a mut ExtCtxt<'b>,
 965     cfg: StripUnconfigured<'a>,
 966     invocations: Vec<(Invocation, Option<Lrc<SyntaxExtension>>)>,
 967     monotonic: bool,
 968 }
 969
 970 impl<'a, 'b> InvocationCollector<'a, 'b> {
 971     fn collect(&mut self, fragment_kind: AstFragmentKind, kind: InvocationKind) -> AstFragment {
 972         let expn_id = LocalExpnId::fresh_empty();
 973         let vis = kind.placeholder_visibility();
 974         self.invocations.push((
 975             Invocation {
 976                 kind,
 977                 fragment_kind,
 978                 expansion_data: ExpansionData {
 979                     id: expn_id,
 980                     depth: self.cx.current_expansion.depth + 1,
 981                     ..self.cx.current_expansion.clone()
 982                 },
 983             },
 984             None,
 985         ));
 986         placeholder(fragment_kind, NodeId::placeholder_from_expn_id(expn_id), vis)
 987     }
 988
 989     fn collect_bang(&mut self, mac: ast::MacCall, kind: AstFragmentKind) -> AstFragment {
 990         // cache the macro call span so that it can be
 991         // easily adjusted for incremental compilation
 992         let span = mac.span();
 993         self.collect(kind, InvocationKind::Bang { mac, span })
 994     }
 995
 996     fn collect_attr(
 997         &mut self,
 998         (attr, pos, derives): (ast::Attribute, usize, Vec<Path>),
 999         item: Annotatable,
1000         kind: AstFragmentKind,
1001     ) -> AstFragment {
1002         self.collect(kind, InvocationKind::Attr { attr, pos, item, derives })
1003     }
1004
1005     /// If `item` is an attribute invocation, remove the attribute and return it together with
1006     /// its position and derives following it. We have to collect the derives in order to resolve
1007     /// legacy derive helpers (helpers written before derives that introduce them).
1008     fn take_first_attr(
1009         &mut self,
1010         item: &mut impl AstLike,
1011     ) -> Option<(ast::Attribute, usize, Vec<Path>)> {
1012         let mut attr = None;
1013
1014         item.visit_attrs(|attrs| {
1015             attr = attrs
1016                 .iter()
1017                 .position(|a| !self.cx.expanded_inert_attrs.is_marked(a) && !is_builtin_attr(a))
1018                 .map(|attr_pos| {
1019                     let attr = attrs.remove(attr_pos);
1020                     let following_derives = attrs[attr_pos..]
1021                         .iter()
1022                         .filter(|a| a.has_name(sym::derive))
1023                         .flat_map(|a| a.meta_item_list().unwrap_or_default())
1024                         .filter_map(|nested_meta| match nested_meta {
1025                             NestedMetaItem::MetaItem(ast::MetaItem {
1026                                 kind: MetaItemKind::Word,
1027                                 path,
1028                                 ..
1029                             }) => Some(path),
1030                             _ => None,
1031                         })
1032                         .collect();
1033
1034                     (attr, attr_pos, following_derives)
1035                 })
1036         });
1037
1038         attr
1039     }
1040
1041     fn take_stmt_bang(
1042         &mut self,
1043         stmt: ast::Stmt,
1044     ) -> Result<(bool, MacCall, Vec<ast::Attribute>), ast::Stmt> {
1045         match stmt.kind {
1046             StmtKind::MacCall(mac) => {
1047                 let MacCallStmt { mac, style, attrs, .. } = mac.into_inner();
1048                 Ok((style == MacStmtStyle::Semicolon, mac, attrs.into()))
1049             }
1050             StmtKind::Item(item) if matches!(item.kind, ItemKind::MacCall(..)) => {
1051                 match item.into_inner() {
1052                     ast::Item { kind: ItemKind::MacCall(mac), attrs, .. } => {
1053                         Ok((mac.args.need_semicolon(), mac, attrs))
1054                     }
1055                     _ => unreachable!(),
1056                 }
1057             }
1058             StmtKind::Semi(expr) if matches!(expr.kind, ast::ExprKind::MacCall(..)) => {
1059                 match expr.into_inner() {
1060                     ast::Expr { kind: ast::ExprKind::MacCall(mac), attrs, .. } => {
1061                         Ok((mac.args.need_semicolon(), mac, attrs.into()))
1062                     }
1063                     _ => unreachable!(),
1064                 }
1065             }
1066             StmtKind::Local(..) | StmtKind::Empty | StmtKind::Item(..) | StmtKind::Semi(..) => {
1067                 Err(stmt)
1068             }
1069             StmtKind::Expr(..) => unreachable!(),
1070         }
1071     }
1072
1073     fn configure<T: AstLike>(&mut self, node: T) -> Option<T> {
1074         self.cfg.configure(node)
1075     }
1076
1077     // Detect use of feature-gated or invalid attributes on macro invocations
1078     // since they will not be detected after macro expansion.
1079     fn check_attributes(&self, attrs: &[ast::Attribute], call: &MacCall) {
1080         let features = self.cx.ecfg.features.unwrap();
1081         let mut attrs = attrs.iter().peekable();
1082         let mut span: Option<Span> = None;
1083         while let Some(attr) = attrs.next() {
1084             rustc_ast_passes::feature_gate::check_attribute(attr, self.cx.sess, features);
1085             validate_attr::check_meta(&self.cx.sess.parse_sess, attr);
1086
1087             let current_span = if let Some(sp) = span { sp.to(attr.span) } else { attr.span };
1088             span = Some(current_span);
1089
1090             if attrs.peek().map_or(false, |next_attr| next_attr.doc_str().is_some()) {
1091                 continue;
1092             }
1093
1094             if attr.is_doc_comment() {
1095                 self.cx.sess.parse_sess.buffer_lint_with_diagnostic(
1096                     &UNUSED_DOC_COMMENTS,
1097                     current_span,
1098                     self.cx.current_expansion.lint_node_id,
1099                     "unused doc comment",
1100                     BuiltinLintDiagnostics::UnusedDocComment(attr.span),
1101                 );
1102             } else if rustc_attr::is_builtin_attr(attr) {
1103                 let attr_name = attr.ident().unwrap().name;
1104                 // `#[cfg]` and `#[cfg_attr]` are special - they are
1105                 // eagerly evaluated.
1106                 if attr_name != sym::cfg && attr_name != sym::cfg_attr {
1107                     self.cx.sess.parse_sess.buffer_lint_with_diagnostic(
1108                         &UNUSED_ATTRIBUTES,
1109                         attr.span,
1110                         self.cx.current_expansion.lint_node_id,
1111                         &format!("unused attribute `{}`", attr_name),
1112                         BuiltinLintDiagnostics::UnusedBuiltinAttribute {
1113                             attr_name,
1114                             macro_name: pprust::path_to_string(&call.path),
1115                             invoc_span: call.path.span,
1116                         },
1117                     );
1118                 }
1119             }
1120         }
1121     }
1122 }
1123
1124 /// Wraps a call to `noop_visit_*` / `noop_flat_map_*`
1125 /// for an AST node that supports attributes
1126 /// (see the `Annotatable` enum)
1127 /// This method assigns a `NodeId`, and sets that `NodeId`
1128 /// as our current 'lint node id'. If a macro call is found
1129 /// inside this AST node, we will use this AST node's `NodeId`
1130 /// to emit lints associated with that macro (allowing
1131 /// `#[allow]` / `#[deny]` to be applied close to
1132 /// the macro invocation).
1133 ///
1134 /// Do *not* call this for a macro AST node
1135 /// (e.g. `ExprKind::MacCall`) - we cannot emit lints
1136 /// at these AST nodes, since they are removed and
1137 /// replaced with the result of macro expansion.
1138 ///
1139 /// All other `NodeId`s are assigned by `visit_id`.
1140 /// * `self` is the 'self' parameter for the current method,
1141 /// * `id` is a mutable reference to the `NodeId` field
1142 ///    of the current AST node.
1143 /// * `closure` is a closure that executes the
1144 ///   `noop_visit_*` / `noop_flat_map_*` method
1145 ///   for the current AST node.
1146 macro_rules! assign_id {
1147     ($self:ident, $id:expr, $closure:expr) => {{
1148         let old_id = $self.cx.current_expansion.lint_node_id;
1149         if $self.monotonic {
1150             debug_assert_eq!(*$id, ast::DUMMY_NODE_ID);
1151             let new_id = $self.cx.resolver.next_node_id();
1152             *$id = new_id;
1153             $self.cx.current_expansion.lint_node_id = new_id;
1154         }
1155         let ret = ($closure)();
1156         $self.cx.current_expansion.lint_node_id = old_id;
1157         ret
1158     }};
1159 }
1160
1161 impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
1162     fn visit_crate(&mut self, krate: &mut ast::Crate) {
1163         let span = krate.span;
1164         let empty_crate =
1165             || ast::Crate { attrs: Vec::new(), items: Vec::new(), span, is_placeholder: None };
1166         let mut fold_crate = |krate: ast::Crate| {
1167             let mut krate = match self.configure(krate) {
1168                 Some(krate) => krate,
1169                 None => return empty_crate(),
1170             };
1171
1172             if let Some(attr) = self.take_first_attr(&mut krate) {
1173                 return self
1174                     .collect_attr(attr, Annotatable::Crate(krate), AstFragmentKind::Crate)
1175                     .make_crate();
1176             }
1177
1178             noop_visit_crate(&mut krate, self);
1179             krate
1180         };
1181
1182         // Cannot use `visit_clobber` here, see the FIXME on it.
1183         *krate = fold_crate(mem::replace(krate, empty_crate()));
1184     }
1185
1186     fn visit_expr(&mut self, expr: &mut P<ast::Expr>) {
1187         self.cfg.configure_expr(expr);
1188         visit_clobber(expr.deref_mut(), |mut expr| {
1189             if let Some(attr) = self.take_first_attr(&mut expr) {
1190                 // Collect the invoc regardless of whether or not attributes are permitted here
1191                 // expansion will eat the attribute so it won't error later.
1192                 self.cfg.maybe_emit_expr_attr_err(&attr.0);
1193
1194                 // AstFragmentKind::Expr requires the macro to emit an expression.
1195                 return self
1196                     .collect_attr(attr, Annotatable::Expr(P(expr)), AstFragmentKind::Expr)
1197                     .make_expr()
1198                     .into_inner();
1199             }
1200
1201             if let ast::ExprKind::MacCall(mac) = expr.kind {
1202                 self.check_attributes(&expr.attrs, &mac);
1203                 self.collect_bang(mac, AstFragmentKind::Expr).make_expr().into_inner()
1204             } else {
1205                 assign_id!(self, &mut expr.id, || {
1206                     ensure_sufficient_stack(|| noop_visit_expr(&mut expr, self));
1207                 });
1208                 expr
1209             }
1210         });
1211     }
1212
1213     fn flat_map_arm(&mut self, arm: ast::Arm) -> SmallVec<[ast::Arm; 1]> {
1214         let mut arm = configure!(self, arm);
1215
1216         if let Some(attr) = self.take_first_attr(&mut arm) {
1217             return self
1218                 .collect_attr(attr, Annotatable::Arm(arm), AstFragmentKind::Arms)
1219                 .make_arms();
1220         }
1221
1222         assign_id!(self, &mut arm.id, || noop_flat_map_arm(arm, self))
1223     }
1224
1225     fn flat_map_expr_field(&mut self, field: ast::ExprField) -> SmallVec<[ast::ExprField; 1]> {
1226         let mut field = configure!(self, field);
1227
1228         if let Some(attr) = self.take_first_attr(&mut field) {
1229             return self
1230                 .collect_attr(attr, Annotatable::ExprField(field), AstFragmentKind::Fields)
1231                 .make_expr_fields();
1232         }
1233
1234         assign_id!(self, &mut field.id, || noop_flat_map_expr_field(field, self))
1235     }
1236
1237     fn flat_map_pat_field(&mut self, fp: ast::PatField) -> SmallVec<[ast::PatField; 1]> {
1238         let mut fp = configure!(self, fp);
1239
1240         if let Some(attr) = self.take_first_attr(&mut fp) {
1241             return self
1242                 .collect_attr(attr, Annotatable::PatField(fp), AstFragmentKind::FieldPats)
1243                 .make_pat_fields();
1244         }
1245
1246         assign_id!(self, &mut fp.id, || noop_flat_map_pat_field(fp, self))
1247     }
1248
1249     fn flat_map_param(&mut self, p: ast::Param) -> SmallVec<[ast::Param; 1]> {
1250         let mut p = configure!(self, p);
1251
1252         if let Some(attr) = self.take_first_attr(&mut p) {
1253             return self
1254                 .collect_attr(attr, Annotatable::Param(p), AstFragmentKind::Params)
1255                 .make_params();
1256         }
1257
1258         assign_id!(self, &mut p.id, || noop_flat_map_param(p, self))
1259     }
1260
1261     fn flat_map_field_def(&mut self, sf: ast::FieldDef) -> SmallVec<[ast::FieldDef; 1]> {
1262         let mut sf = configure!(self, sf);
1263
1264         if let Some(attr) = self.take_first_attr(&mut sf) {
1265             return self
1266                 .collect_attr(attr, Annotatable::FieldDef(sf), AstFragmentKind::StructFields)
1267                 .make_field_defs();
1268         }
1269
1270         assign_id!(self, &mut sf.id, || noop_flat_map_field_def(sf, self))
1271     }
1272
1273     fn flat_map_variant(&mut self, variant: ast::Variant) -> SmallVec<[ast::Variant; 1]> {
1274         let mut variant = configure!(self, variant);
1275
1276         if let Some(attr) = self.take_first_attr(&mut variant) {
1277             return self
1278                 .collect_attr(attr, Annotatable::Variant(variant), AstFragmentKind::Variants)
1279                 .make_variants();
1280         }
1281
1282         assign_id!(self, &mut variant.id, || noop_flat_map_variant(variant, self))
1283     }
1284
1285     fn filter_map_expr(&mut self, expr: P<ast::Expr>) -> Option<P<ast::Expr>> {
1286         let expr = configure!(self, expr);
1287         expr.filter_map(|mut expr| {
1288             if let Some(attr) = self.take_first_attr(&mut expr) {
1289                 self.cfg.maybe_emit_expr_attr_err(&attr.0);
1290
1291                 return self
1292                     .collect_attr(attr, Annotatable::Expr(P(expr)), AstFragmentKind::OptExpr)
1293                     .make_opt_expr()
1294                     .map(|expr| expr.into_inner());
1295             }
1296
1297             if let ast::ExprKind::MacCall(mac) = expr.kind {
1298                 self.check_attributes(&expr.attrs, &mac);
1299                 self.collect_bang(mac, AstFragmentKind::OptExpr)
1300                     .make_opt_expr()
1301                     .map(|expr| expr.into_inner())
1302             } else {
1303                 assign_id!(self, &mut expr.id, || {
1304                     Some({
1305                         noop_visit_expr(&mut expr, self);
1306                         expr
1307                     })
1308                 })
1309             }
1310         })
1311     }
1312
1313     fn visit_pat(&mut self, pat: &mut P<ast::Pat>) {
1314         match pat.kind {
1315             PatKind::MacCall(_) => {}
1316             _ => return noop_visit_pat(pat, self),
1317         }
1318
1319         visit_clobber(pat, |mut pat| match mem::replace(&mut pat.kind, PatKind::Wild) {
1320             PatKind::MacCall(mac) => self.collect_bang(mac, AstFragmentKind::Pat).make_pat(),
1321             _ => unreachable!(),
1322         });
1323     }
1324
1325     fn flat_map_stmt(&mut self, stmt: ast::Stmt) -> SmallVec<[ast::Stmt; 1]> {
1326         let mut stmt = configure!(self, stmt);
1327
1328         // We pull macro invocations (both attributes and fn-like macro calls) out of their
1329         // `StmtKind`s and treat them as statement macro invocations, not as items or expressions.
1330         // FIXME: invocations in semicolon-less expressions positions are expanded as expressions,
1331         // changing that requires some compatibility measures.
1332         let mut stmt = if !stmt.is_expr() {
1333             if let Some(attr) = self.take_first_attr(&mut stmt) {
1334                 return self
1335                     .collect_attr(attr, Annotatable::Stmt(P(stmt)), AstFragmentKind::Stmts)
1336                     .make_stmts();
1337             }
1338
1339             match self.take_stmt_bang(stmt) {
1340                 Ok((add_semicolon, mac, attrs)) => {
1341                     self.check_attributes(&attrs, &mac);
1342                     let mut stmts = self.collect_bang(mac, AstFragmentKind::Stmts).make_stmts();
1343
1344                     // If this is a macro invocation with a semicolon, then apply that
1345                     // semicolon to the final statement produced by expansion.
1346                     if add_semicolon {
1347                         if let Some(stmt) = stmts.pop() {
1348                             stmts.push(stmt.add_trailing_semicolon());
1349                         }
1350                     }
1351
1352                     return stmts;
1353                 }
1354                 Err(stmt) => stmt,
1355             }
1356         } else {
1357             stmt
1358         };
1359
1360         // The only way that we can end up with a `MacCall` expression statement,
1361         // (as opposed to a `StmtKind::MacCall`) is if we have a macro as the
1362         // traiing expression in a block (e.g. `fn foo() { my_macro!() }`).
1363         // Record this information, so that we can report a more specific
1364         // `SEMICOLON_IN_EXPRESSIONS_FROM_MACROS` lint if needed.
1365         // See #78991 for an investigation of treating macros in this position
1366         // as statements, rather than expressions, during parsing.
1367         let res = match &stmt.kind {
1368             StmtKind::Expr(expr)
1369                 if matches!(**expr, ast::Expr { kind: ast::ExprKind::MacCall(..), .. }) =>
1370             {
1371                 self.cx.current_expansion.is_trailing_mac = true;
1372                 // Don't use `assign_id` for this statement - it may get removed
1373                 // entirely due to a `#[cfg]` on the contained expression
1374                 noop_flat_map_stmt(stmt, self)
1375             }
1376             _ => assign_id!(self, &mut stmt.id, || noop_flat_map_stmt(stmt, self)),
1377         };
1378         self.cx.current_expansion.is_trailing_mac = false;
1379         res
1380     }
1381
1382     fn visit_block(&mut self, block: &mut P<Block>) {
1383         let orig_dir_ownership = mem::replace(
1384             &mut self.cx.current_expansion.dir_ownership,
1385             DirOwnership::UnownedViaBlock,
1386         );
1387         noop_visit_block(block, self);
1388         self.cx.current_expansion.dir_ownership = orig_dir_ownership;
1389     }
1390
1391     fn flat_map_item(&mut self, item: P<ast::Item>) -> SmallVec<[P<ast::Item>; 1]> {
1392         let mut item = configure!(self, item);
1393
1394         if let Some(attr) = self.take_first_attr(&mut item) {
1395             return self
1396                 .collect_attr(attr, Annotatable::Item(item), AstFragmentKind::Items)
1397                 .make_items();
1398         }
1399
1400         let mut attrs = mem::take(&mut item.attrs); // We do this to please borrowck.
1401         let ident = item.ident;
1402         let span = item.span;
1403
1404         match item.kind {
1405             ast::ItemKind::MacCall(ref mac) => {
1406                 self.check_attributes(&attrs, &mac);
1407                 item.attrs = attrs;
1408                 item.and_then(|item| match item.kind {
1409                     ItemKind::MacCall(mac) => {
1410                         self.collect_bang(mac, AstFragmentKind::Items).make_items()
1411                     }
1412                     _ => unreachable!(),
1413                 })
1414             }
1415             ast::ItemKind::Mod(_, ref mut mod_kind) if ident != Ident::empty() => {
1416                 let (file_path, dir_path, dir_ownership) = match mod_kind {
1417                     ModKind::Loaded(_, inline, _) => {
1418                         // Inline `mod foo { ... }`, but we still need to push directories.
1419                         let (dir_path, dir_ownership) = mod_dir_path(
1420                             &self.cx.sess,
1421                             ident,
1422                             &attrs,
1423                             &self.cx.current_expansion.module,
1424                             self.cx.current_expansion.dir_ownership,
1425                             *inline,
1426                         );
1427                         item.attrs = attrs;
1428                         (None, dir_path, dir_ownership)
1429                     }
1430                     ModKind::Unloaded => {
1431                         // We have an outline `mod foo;` so we need to parse the file.
1432                         let old_attrs_len = attrs.len();
1433                         let ParsedExternalMod {
1434                             mut items,
1435                             inner_span,
1436                             file_path,
1437                             dir_path,
1438                             dir_ownership,
1439                         } = parse_external_mod(
1440                             &self.cx.sess,
1441                             ident,
1442                             span,
1443                             &self.cx.current_expansion.module,
1444                             self.cx.current_expansion.dir_ownership,
1445                             &mut attrs,
1446                         );
1447
1448                         if let Some(extern_mod_loaded) = self.cx.extern_mod_loaded {
1449                             (attrs, items) = extern_mod_loaded(ident, attrs, items, inner_span);
1450                         }
1451
1452                         *mod_kind = ModKind::Loaded(items, Inline::No, inner_span);
1453                         item.attrs = attrs;
1454                         if item.attrs.len() > old_attrs_len {
1455                             // If we loaded an out-of-line module and added some inner attributes,
1456                             // then we need to re-configure it and re-collect attributes for
1457                             // resolution and expansion.
1458                             item = configure!(self, item);
1459
1460                             if let Some(attr) = self.take_first_attr(&mut item) {
1461                                 return self
1462                                     .collect_attr(
1463                                         attr,
1464                                         Annotatable::Item(item),
1465                                         AstFragmentKind::Items,
1466                                     )
1467                                     .make_items();
1468                             }
1469                         }
1470                         (Some(file_path), dir_path, dir_ownership)
1471                     }
1472                 };
1473
1474                 // Set the module info before we flat map.
1475                 let mut module = self.cx.current_expansion.module.with_dir_path(dir_path);
1476                 module.mod_path.push(ident);
1477                 if let Some(file_path) = file_path {
1478                     module.file_path_stack.push(file_path);
1479                 }
1480
1481                 let orig_module =
1482                     mem::replace(&mut self.cx.current_expansion.module, Rc::new(module));
1483                 let orig_dir_ownership =
1484                     mem::replace(&mut self.cx.current_expansion.dir_ownership, dir_ownership);
1485
1486                 let result = assign_id!(self, &mut item.id, || noop_flat_map_item(item, self));
1487
1488                 // Restore the module info.
1489                 self.cx.current_expansion.dir_ownership = orig_dir_ownership;
1490                 self.cx.current_expansion.module = orig_module;
1491
1492                 result
1493             }
1494             _ => {
1495                 item.attrs = attrs;
1496                 // The crate root is special - don't assign an ID to it.
1497                 if !(matches!(item.kind, ast::ItemKind::Mod(..)) && ident == Ident::empty()) {
1498                     assign_id!(self, &mut item.id, || noop_flat_map_item(item, self))
1499                 } else {
1500                     noop_flat_map_item(item, self)
1501                 }
1502             }
1503         }
1504     }
1505
1506     fn flat_map_trait_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
1507         let mut item = configure!(self, item);
1508
1509         if let Some(attr) = self.take_first_attr(&mut item) {
1510             return self
1511                 .collect_attr(attr, Annotatable::TraitItem(item), AstFragmentKind::TraitItems)
1512                 .make_trait_items();
1513         }
1514
1515         match item.kind {
1516             ast::AssocItemKind::MacCall(ref mac) => {
1517                 self.check_attributes(&item.attrs, &mac);
1518                 item.and_then(|item| match item.kind {
1519                     ast::AssocItemKind::MacCall(mac) => {
1520                         self.collect_bang(mac, AstFragmentKind::TraitItems).make_trait_items()
1521                     }
1522                     _ => unreachable!(),
1523                 })
1524             }
1525             _ => {
1526                 assign_id!(self, &mut item.id, || noop_flat_map_assoc_item(item, self))
1527             }
1528         }
1529     }
1530
1531     fn flat_map_impl_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
1532         let mut item = configure!(self, item);
1533
1534         if let Some(attr) = self.take_first_attr(&mut item) {
1535             return self
1536                 .collect_attr(attr, Annotatable::ImplItem(item), AstFragmentKind::ImplItems)
1537                 .make_impl_items();
1538         }
1539
1540         match item.kind {
1541             ast::AssocItemKind::MacCall(ref mac) => {
1542                 self.check_attributes(&item.attrs, &mac);
1543                 item.and_then(|item| match item.kind {
1544                     ast::AssocItemKind::MacCall(mac) => {
1545                         self.collect_bang(mac, AstFragmentKind::ImplItems).make_impl_items()
1546                     }
1547                     _ => unreachable!(),
1548                 })
1549             }
1550             _ => {
1551                 assign_id!(self, &mut item.id, || noop_flat_map_assoc_item(item, self))
1552             }
1553         }
1554     }
1555
1556     fn visit_ty(&mut self, ty: &mut P<ast::Ty>) {
1557         match ty.kind {
1558             ast::TyKind::MacCall(_) => {}
1559             _ => return noop_visit_ty(ty, self),
1560         };
1561
1562         visit_clobber(ty, |mut ty| match mem::replace(&mut ty.kind, ast::TyKind::Err) {
1563             ast::TyKind::MacCall(mac) => self.collect_bang(mac, AstFragmentKind::Ty).make_ty(),
1564             _ => unreachable!(),
1565         });
1566     }
1567
1568     fn flat_map_foreign_item(
1569         &mut self,
1570         foreign_item: P<ast::ForeignItem>,
1571     ) -> SmallVec<[P<ast::ForeignItem>; 1]> {
1572         let mut foreign_item = configure!(self, foreign_item);
1573
1574         if let Some(attr) = self.take_first_attr(&mut foreign_item) {
1575             return self
1576                 .collect_attr(
1577                     attr,
1578                     Annotatable::ForeignItem(foreign_item),
1579                     AstFragmentKind::ForeignItems,
1580                 )
1581                 .make_foreign_items();
1582         }
1583
1584         match foreign_item.kind {
1585             ast::ForeignItemKind::MacCall(ref mac) => {
1586                 self.check_attributes(&foreign_item.attrs, &mac);
1587                 foreign_item.and_then(|item| match item.kind {
1588                     ast::ForeignItemKind::MacCall(mac) => {
1589                         self.collect_bang(mac, AstFragmentKind::ForeignItems).make_foreign_items()
1590                     }
1591                     _ => unreachable!(),
1592                 })
1593             }
1594             _ => {
1595                 assign_id!(self, &mut foreign_item.id, || noop_flat_map_foreign_item(
1596                     foreign_item,
1597                     self
1598                 ))
1599             }
1600         }
1601     }
1602
1603     fn flat_map_generic_param(
1604         &mut self,
1605         param: ast::GenericParam,
1606     ) -> SmallVec<[ast::GenericParam; 1]> {
1607         let mut param = configure!(self, param);
1608
1609         if let Some(attr) = self.take_first_attr(&mut param) {
1610             return self
1611                 .collect_attr(
1612                     attr,
1613                     Annotatable::GenericParam(param),
1614                     AstFragmentKind::GenericParams,
1615                 )
1616                 .make_generic_params();
1617         }
1618
1619         assign_id!(self, &mut param.id, || noop_flat_map_generic_param(param, self))
1620     }
1621
1622     fn visit_id(&mut self, id: &mut ast::NodeId) {
1623         // We may have already assigned a `NodeId`
1624         // by calling `assign_id`
1625         if self.monotonic && *id == ast::DUMMY_NODE_ID {
1626             *id = self.cx.resolver.next_node_id();
1627         }
1628     }
1629 }
1630
1631 pub struct ExpansionConfig<'feat> {
1632     pub crate_name: String,
1633     pub features: Option<&'feat Features>,
1634     pub recursion_limit: Limit,
1635     pub trace_mac: bool,
1636     pub should_test: bool,          // If false, strip `#[test]` nodes
1637     pub span_debug: bool,           // If true, use verbose debugging for `proc_macro::Span`
1638     pub proc_macro_backtrace: bool, // If true, show backtraces for proc-macro panics
1639 }
1640
1641 impl<'feat> ExpansionConfig<'feat> {
1642     pub fn default(crate_name: String) -> ExpansionConfig<'static> {
1643         ExpansionConfig {
1644             crate_name,
1645             features: None,
1646             recursion_limit: Limit::new(1024),
1647             trace_mac: false,
1648             should_test: false,
1649             span_debug: false,
1650             proc_macro_backtrace: false,
1651         }
1652     }
1653
1654     fn proc_macro_hygiene(&self) -> bool {
1655         self.features.map_or(false, |features| features.proc_macro_hygiene)
1656     }
1657 }