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, AttrItem, AttrStyle, Block, Inline, ItemKind, LitKind, MacArgs};
  16 use rustc_ast::{MacCallStmt, MacStmtStyle, MetaItemKind, ModKind, NestedMetaItem};
  17 use rustc_ast::{NodeId, PatKind, Path, StmtKind, Unsafe};
  18 use rustc_ast_pretty::pprust;
  19 use rustc_attr::{self as 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::{AttemptLocalParseRecovery, ForceCollect, GateOr, Parser, RecoverComma};
  26 use rustc_parse::validate_attr;
  27 use rustc_session::lint::builtin::UNUSED_DOC_COMMENTS;
  28 use rustc_session::lint::BuiltinLintDiagnostics;
  29 use rustc_session::parse::{feature_err, ParseSess};
  30 use rustc_session::Limit;
  31 use rustc_span::symbol::{sym, Ident, Symbol};
  32 use rustc_span::{ExpnId, FileName, Span, DUMMY_SP};
  33
  34 use smallvec::{smallvec, SmallVec};
  35 use std::io::ErrorKind;
  36 use std::ops::DerefMut;
  37 use std::path::PathBuf;
  38 use std::rc::Rc;
  39 use std::{iter, mem, slice};
  40
  41 macro_rules! ast_fragments {
  42     (
  43         $($Kind:ident($AstTy:ty) {
  44             $kind_name:expr;
  45             $(one fn $mut_visit_ast:ident; fn $visit_ast:ident;)?
  46             $(many fn $flat_map_ast_elt:ident; fn $visit_ast_elt:ident($($args:tt)*);)?
  47             fn $make_ast:ident;
  48         })*
  49     ) => {
  50         /// A fragment of AST that can be produced by a single macro expansion.
  51         /// Can also serve as an input and intermediate result for macro expansion operations.
  52         pub enum AstFragment {
  53             OptExpr(Option<P<ast::Expr>>),
  54             $($Kind($AstTy),)*
  55         }
  56
  57         /// "Discriminant" of an AST fragment.
  58         #[derive(Copy, Clone, PartialEq, Eq)]
  59         pub enum AstFragmentKind {
  60             OptExpr,
  61             $($Kind,)*
  62         }
  63
  64         impl AstFragmentKind {
  65             pub fn name(self) -> &'static str {
  66                 match self {
  67                     AstFragmentKind::OptExpr => "expression",
  68                     $(AstFragmentKind::$Kind => $kind_name,)*
  69                 }
  70             }
  71
  72             fn make_from<'a>(self, result: Box<dyn MacResult + 'a>) -> Option<AstFragment> {
  73                 match self {
  74                     AstFragmentKind::OptExpr =>
  75                         result.make_expr().map(Some).map(AstFragment::OptExpr),
  76                     $(AstFragmentKind::$Kind => result.$make_ast().map(AstFragment::$Kind),)*
  77                 }
  78             }
  79         }
  80
  81         impl AstFragment {
  82             pub fn add_placeholders(&mut self, placeholders: &[NodeId]) {
  83                 if placeholders.is_empty() {
  84                     return;
  85                 }
  86                 match self {
  87                     $($(AstFragment::$Kind(ast) => ast.extend(placeholders.iter().flat_map(|id| {
  88                         // We are repeating through arguments with `many`, to do that we have to
  89                         // mention some macro variable from those arguments even if it's not used.
  90                         macro _repeating($flat_map_ast_elt) {}
  91                         placeholder(AstFragmentKind::$Kind, *id, None).$make_ast()
  92                     })),)?)*
  93                     _ => panic!("unexpected AST fragment kind")
  94                 }
  95             }
  96
  97             pub fn make_opt_expr(self) -> Option<P<ast::Expr>> {
  98                 match self {
  99                     AstFragment::OptExpr(expr) => expr,
 100                     _ => panic!("AstFragment::make_* called on the wrong kind of fragment"),
 101                 }
 102             }
 103
 104             $(pub fn $make_ast(self) -> $AstTy {
 105                 match self {
 106                     AstFragment::$Kind(ast) => ast,
 107                     _ => panic!("AstFragment::make_* called on the wrong kind of fragment"),
 108                 }
 109             })*
 110
 111             pub fn mut_visit_with<F: MutVisitor>(&mut self, vis: &mut F) {
 112                 match self {
 113                     AstFragment::OptExpr(opt_expr) => {
 114                         visit_clobber(opt_expr, |opt_expr| {
 115                             if let Some(expr) = opt_expr {
 116                                 vis.filter_map_expr(expr)
 117                             } else {
 118                                 None
 119                             }
 120                         });
 121                     }
 122                     $($(AstFragment::$Kind(ast) => vis.$mut_visit_ast(ast),)?)*
 123                     $($(AstFragment::$Kind(ast) =>
 124                         ast.flat_map_in_place(|ast| vis.$flat_map_ast_elt(ast)),)?)*
 125                 }
 126             }
 127
 128             pub fn visit_with<'a, V: Visitor<'a>>(&'a self, visitor: &mut V) {
 129                 match *self {
 130                     AstFragment::OptExpr(Some(ref expr)) => visitor.visit_expr(expr),
 131                     AstFragment::OptExpr(None) => {}
 132                     $($(AstFragment::$Kind(ref ast) => visitor.$visit_ast(ast),)?)*
 133                     $($(AstFragment::$Kind(ref ast) => for ast_elt in &ast[..] {
 134                         visitor.$visit_ast_elt(ast_elt, $($args)*);
 135                     })?)*
 136                 }
 137             }
 138         }
 139
 140         impl<'a> MacResult for crate::mbe::macro_rules::ParserAnyMacro<'a> {
 141             $(fn $make_ast(self: Box<crate::mbe::macro_rules::ParserAnyMacro<'a>>)
 142                            -> Option<$AstTy> {
 143                 Some(self.make(AstFragmentKind::$Kind).$make_ast())
 144             })*
 145         }
 146     }
 147 }
 148
 149 ast_fragments! {
 150     Expr(P<ast::Expr>) { "expression"; one fn visit_expr; fn visit_expr; fn make_expr; }
 151     Pat(P<ast::Pat>) { "pattern"; one fn visit_pat; fn visit_pat; fn make_pat; }
 152     Ty(P<ast::Ty>) { "type"; one fn visit_ty; fn visit_ty; fn make_ty; }
 153     Stmts(SmallVec<[ast::Stmt; 1]>) {
 154         "statement"; many fn flat_map_stmt; fn visit_stmt(); fn make_stmts;
 155     }
 156     Items(SmallVec<[P<ast::Item>; 1]>) {
 157         "item"; many fn flat_map_item; fn visit_item(); fn make_items;
 158     }
 159     TraitItems(SmallVec<[P<ast::AssocItem>; 1]>) {
 160         "trait item";
 161         many fn flat_map_trait_item;
 162         fn visit_assoc_item(AssocCtxt::Trait);
 163         fn make_trait_items;
 164     }
 165     ImplItems(SmallVec<[P<ast::AssocItem>; 1]>) {
 166         "impl item";
 167         many fn flat_map_impl_item;
 168         fn visit_assoc_item(AssocCtxt::Impl);
 169         fn make_impl_items;
 170     }
 171     ForeignItems(SmallVec<[P<ast::ForeignItem>; 1]>) {
 172         "foreign item";
 173         many fn flat_map_foreign_item;
 174         fn visit_foreign_item();
 175         fn make_foreign_items;
 176     }
 177     Arms(SmallVec<[ast::Arm; 1]>) {
 178         "match arm"; many fn flat_map_arm; fn visit_arm(); fn make_arms;
 179     }
 180     Fields(SmallVec<[ast::ExprField; 1]>) {
 181         "field expression"; many fn flat_map_expr_field; fn visit_expr_field(); fn make_expr_fields;
 182     }
 183     FieldPats(SmallVec<[ast::PatField; 1]>) {
 184         "field pattern";
 185         many fn flat_map_pat_field;
 186         fn visit_pat_field();
 187         fn make_pat_fields;
 188     }
 189     GenericParams(SmallVec<[ast::GenericParam; 1]>) {
 190         "generic parameter";
 191         many fn flat_map_generic_param;
 192         fn visit_generic_param();
 193         fn make_generic_params;
 194     }
 195     Params(SmallVec<[ast::Param; 1]>) {
 196         "function parameter"; many fn flat_map_param; fn visit_param(); fn make_params;
 197     }
 198     StructFields(SmallVec<[ast::FieldDef; 1]>) {
 199         "field";
 200         many fn flat_map_field_def;
 201         fn visit_field_def();
 202         fn make_field_defs;
 203     }
 204     Variants(SmallVec<[ast::Variant; 1]>) {
 205         "variant"; many fn flat_map_variant; fn visit_variant(); fn make_variants;
 206     }
 207 }
 208
 209 impl AstFragmentKind {
 210     crate fn dummy(self, span: Span) -> AstFragment {
 211         self.make_from(DummyResult::any(span)).expect("couldn't create a dummy AST fragment")
 212     }
 213
 214     /// Fragment supports macro expansion and not just inert attributes, `cfg` and `cfg_attr`.
 215     pub fn supports_macro_expansion(self) -> bool {
 216         match self {
 217             AstFragmentKind::OptExpr
 218             | AstFragmentKind::Expr
 219             | AstFragmentKind::Pat
 220             | AstFragmentKind::Ty
 221             | AstFragmentKind::Stmts
 222             | AstFragmentKind::Items
 223             | AstFragmentKind::TraitItems
 224             | AstFragmentKind::ImplItems
 225             | AstFragmentKind::ForeignItems => true,
 226             AstFragmentKind::Arms
 227             | AstFragmentKind::Fields
 228             | AstFragmentKind::FieldPats
 229             | AstFragmentKind::GenericParams
 230             | AstFragmentKind::Params
 231             | AstFragmentKind::StructFields
 232             | AstFragmentKind::Variants => false,
 233         }
 234     }
 235
 236     fn expect_from_annotatables<I: IntoIterator<Item = Annotatable>>(
 237         self,
 238         items: I,
 239     ) -> AstFragment {
 240         let mut items = items.into_iter();
 241         match self {
 242             AstFragmentKind::Arms => {
 243                 AstFragment::Arms(items.map(Annotatable::expect_arm).collect())
 244             }
 245             AstFragmentKind::Fields => {
 246                 AstFragment::Fields(items.map(Annotatable::expect_expr_field).collect())
 247             }
 248             AstFragmentKind::FieldPats => {
 249                 AstFragment::FieldPats(items.map(Annotatable::expect_pat_field).collect())
 250             }
 251             AstFragmentKind::GenericParams => {
 252                 AstFragment::GenericParams(items.map(Annotatable::expect_generic_param).collect())
 253             }
 254             AstFragmentKind::Params => {
 255                 AstFragment::Params(items.map(Annotatable::expect_param).collect())
 256             }
 257             AstFragmentKind::StructFields => {
 258                 AstFragment::StructFields(items.map(Annotatable::expect_field_def).collect())
 259             }
 260             AstFragmentKind::Variants => {
 261                 AstFragment::Variants(items.map(Annotatable::expect_variant).collect())
 262             }
 263             AstFragmentKind::Items => {
 264                 AstFragment::Items(items.map(Annotatable::expect_item).collect())
 265             }
 266             AstFragmentKind::ImplItems => {
 267                 AstFragment::ImplItems(items.map(Annotatable::expect_impl_item).collect())
 268             }
 269             AstFragmentKind::TraitItems => {
 270                 AstFragment::TraitItems(items.map(Annotatable::expect_trait_item).collect())
 271             }
 272             AstFragmentKind::ForeignItems => {
 273                 AstFragment::ForeignItems(items.map(Annotatable::expect_foreign_item).collect())
 274             }
 275             AstFragmentKind::Stmts => {
 276                 AstFragment::Stmts(items.map(Annotatable::expect_stmt).collect())
 277             }
 278             AstFragmentKind::Expr => AstFragment::Expr(
 279                 items.next().expect("expected exactly one expression").expect_expr(),
 280             ),
 281             AstFragmentKind::OptExpr => {
 282                 AstFragment::OptExpr(items.next().map(Annotatable::expect_expr))
 283             }
 284             AstFragmentKind::Pat | AstFragmentKind::Ty => {
 285                 panic!("patterns and types aren't annotatable")
 286             }
 287         }
 288     }
 289 }
 290
 291 pub struct Invocation {
 292     pub kind: InvocationKind,
 293     pub fragment_kind: AstFragmentKind,
 294     pub expansion_data: ExpansionData,
 295 }
 296
 297 pub enum InvocationKind {
 298     Bang {
 299         mac: ast::MacCall,
 300         span: Span,
 301     },
 302     Attr {
 303         attr: ast::Attribute,
 304         // Re-insertion position for inert attributes.
 305         pos: usize,
 306         item: Annotatable,
 307         // Required for resolving derive helper attributes.
 308         derives: Vec<Path>,
 309     },
 310     Derive {
 311         path: Path,
 312         item: Annotatable,
 313     },
 314 }
 315
 316 impl InvocationKind {
 317     fn placeholder_visibility(&self) -> Option<ast::Visibility> {
 318         // HACK: For unnamed fields placeholders should have the same visibility as the actual
 319         // fields because for tuple structs/variants resolve determines visibilities of their
 320         // constructor using these field visibilities before attributes on them are are expanded.
 321         // The assumption is that the attribute expansion cannot change field visibilities,
 322         // and it holds because only inert attributes are supported in this position.
 323         match self {
 324             InvocationKind::Attr { item: Annotatable::FieldDef(field), .. }
 325             | InvocationKind::Derive { item: Annotatable::FieldDef(field), .. }
 326                 if field.ident.is_none() =>
 327             {
 328                 Some(field.vis.clone())
 329             }
 330             _ => None,
 331         }
 332     }
 333 }
 334
 335 impl Invocation {
 336     pub fn span(&self) -> Span {
 337         match &self.kind {
 338             InvocationKind::Bang { span, .. } => *span,
 339             InvocationKind::Attr { attr, .. } => attr.span,
 340             InvocationKind::Derive { path, .. } => path.span,
 341         }
 342     }
 343 }
 344
 345 pub struct MacroExpander<'a, 'b> {
 346     pub cx: &'a mut ExtCtxt<'b>,
 347     monotonic: bool, // cf. `cx.monotonic_expander()`
 348 }
 349
 350 impl<'a, 'b> MacroExpander<'a, 'b> {
 351     pub fn new(cx: &'a mut ExtCtxt<'b>, monotonic: bool) -> Self {
 352         MacroExpander { cx, monotonic }
 353     }
 354
 355     // FIXME: Avoid visiting the crate as a `Mod` item,
 356     // make crate a first class expansion target instead.
 357     pub fn expand_crate(&mut self, mut krate: ast::Crate) -> ast::Crate {
 358         let file_path = match self.cx.source_map().span_to_unmapped_path(krate.span) {
 359             FileName::Real(name) => name.into_local_path(),
 360             other => PathBuf::from(other.to_string()),
 361         };
 362         let dir_path = file_path.parent().unwrap_or(&file_path).to_owned();
 363         self.cx.root_path = dir_path.clone();
 364         self.cx.current_expansion.module = Rc::new(ModuleData {
 365             mod_path: vec![Ident::from_str(&self.cx.ecfg.crate_name)],
 366             file_path_stack: vec![file_path],
 367             dir_path,
 368         });
 369
 370         let krate_item = AstFragment::Items(smallvec![P(ast::Item {
 371             attrs: krate.attrs,
 372             span: krate.span,
 373             kind: ast::ItemKind::Mod(
 374                 Unsafe::No,
 375                 ModKind::Loaded(krate.items, Inline::Yes, krate.span)
 376             ),
 377             ident: Ident::invalid(),
 378             id: ast::DUMMY_NODE_ID,
 379             vis: ast::Visibility {
 380                 span: krate.span.shrink_to_lo(),
 381                 kind: ast::VisibilityKind::Public,
 382                 tokens: None,
 383             },
 384             tokens: None,
 385         })]);
 386
 387         match self.fully_expand_fragment(krate_item).make_items().pop().map(P::into_inner) {
 388             Some(ast::Item {
 389                 attrs,
 390                 kind: ast::ItemKind::Mod(_, ModKind::Loaded(items, ..)),
 391                 ..
 392             }) => {
 393                 krate.attrs = attrs;
 394                 krate.items = items;
 395             }
 396             None => {
 397                 // Resolution failed so we return an empty expansion
 398                 krate.attrs = vec![];
 399                 krate.items = vec![];
 400             }
 401             Some(ast::Item { span, kind, .. }) => {
 402                 krate.attrs = vec![];
 403                 krate.items = vec![];
 404                 self.cx.span_err(
 405                     span,
 406                     &format!(
 407                         "expected crate top-level item to be a module after macro expansion, found {} {}",
 408                         kind.article(), kind.descr()
 409                     ),
 410                 );
 411             }
 412         };
 413         self.cx.trace_macros_diag();
 414         krate
 415     }
 416
 417     // Recursively expand all macro invocations in this AST fragment.
 418     pub fn fully_expand_fragment(&mut self, input_fragment: AstFragment) -> AstFragment {
 419         let orig_expansion_data = self.cx.current_expansion.clone();
 420         let orig_force_mode = self.cx.force_mode;
 421         self.cx.current_expansion.depth = 0;
 422
 423         // Collect all macro invocations and replace them with placeholders.
 424         let (mut fragment_with_placeholders, mut invocations) =
 425             self.collect_invocations(input_fragment, &[]);
 426
 427         // Optimization: if we resolve all imports now,
 428         // we'll be able to immediately resolve most of imported macros.
 429         self.resolve_imports();
 430
 431         // Resolve paths in all invocations and produce output expanded fragments for them, but
 432         // do not insert them into our input AST fragment yet, only store in `expanded_fragments`.
 433         // The output fragments also go through expansion recursively until no invocations are left.
 434         // Unresolved macros produce dummy outputs as a recovery measure.
 435         invocations.reverse();
 436         let mut expanded_fragments = Vec::new();
 437         let mut undetermined_invocations = Vec::new();
 438         let (mut progress, mut force) = (false, !self.monotonic);
 439         loop {
 440             let (invoc, ext) = if let Some(invoc) = invocations.pop() {
 441                 invoc
 442             } else {
 443                 self.resolve_imports();
 444                 if undetermined_invocations.is_empty() {
 445                     break;
 446                 }
 447                 invocations = mem::take(&mut undetermined_invocations);
 448                 force = !mem::replace(&mut progress, false);
 449                 if force && self.monotonic {
 450                     self.cx.sess.delay_span_bug(
 451                         invocations.last().unwrap().0.span(),
 452                         "expansion entered force mode without producing any errors",
 453                     );
 454                 }
 455                 continue;
 456             };
 457
 458             let ext = match ext {
 459                 Some(ext) => ext,
 460                 None => {
 461                     let eager_expansion_root = if self.monotonic {
 462                         invoc.expansion_data.id
 463                     } else {
 464                         orig_expansion_data.id
 465                     };
 466                     match self.cx.resolver.resolve_macro_invocation(
 467                         &invoc,
 468                         eager_expansion_root,
 469                         force,
 470                     ) {
 471                         Ok(ext) => ext,
 472                         Err(Indeterminate) => {
 473                             // Cannot resolve, will retry this invocation later.
 474                             undetermined_invocations.push((invoc, None));
 475                             continue;
 476                         }
 477                     }
 478                 }
 479             };
 480
 481             let ExpansionData { depth, id: expn_id, .. } = invoc.expansion_data;
 482             self.cx.current_expansion = invoc.expansion_data.clone();
 483             self.cx.force_mode = force;
 484
 485             let fragment_kind = invoc.fragment_kind;
 486             let (expanded_fragment, new_invocations) = match self.expand_invoc(invoc, &ext.kind) {
 487                 ExpandResult::Ready(fragment) => {
 488                     let derive_placeholders = self
 489                         .cx
 490                         .resolver
 491                         .take_derive_resolutions(expn_id)
 492                         .map(|derives| {
 493                             enum AnnotatableRef<'a> {
 494                                 Item(&'a P<ast::Item>),
 495                                 Stmt(&'a ast::Stmt),
 496                             }
 497                             let item = match &fragment {
 498                                 AstFragment::Items(items) => match &items[..] {
 499                                     [item] => AnnotatableRef::Item(item),
 500                                     _ => unreachable!(),
 501                                 },
 502                                 AstFragment::Stmts(stmts) => match &stmts[..] {
 503                                     [stmt] => AnnotatableRef::Stmt(stmt),
 504                                     _ => unreachable!(),
 505                                 },
 506                                 _ => unreachable!(),
 507                             };
 508
 509                             invocations.reserve(derives.len());
 510                             derives
 511                                 .into_iter()
 512                                 .map(|(_exts, path)| {
 513                                     // FIXME: Consider using the derive resolutions (`_exts`)
 514                                     // instead of enqueuing the derives to be resolved again later.
 515                                     let expn_id = ExpnId::fresh(None);
 516                                     invocations.push((
 517                                         Invocation {
 518                                             kind: InvocationKind::Derive {
 519                                                 path,
 520                                                 item: match item {
 521                                                     AnnotatableRef::Item(item) => {
 522                                                         Annotatable::Item(item.clone())
 523                                                     }
 524                                                     AnnotatableRef::Stmt(stmt) => {
 525                                                         Annotatable::Stmt(P(stmt.clone()))
 526                                                     }
 527                                                 },
 528                                             },
 529                                             fragment_kind,
 530                                             expansion_data: ExpansionData {
 531                                                 id: expn_id,
 532                                                 ..self.cx.current_expansion.clone()
 533                                             },
 534                                         },
 535                                         None,
 536                                     ));
 537                                     NodeId::placeholder_from_expn_id(expn_id)
 538                                 })
 539                                 .collect::<Vec<_>>()
 540                         })
 541                         .unwrap_or_default();
 542
 543                     self.collect_invocations(fragment, &derive_placeholders)
 544                 }
 545                 ExpandResult::Retry(invoc) => {
 546                     if force {
 547                         self.cx.span_bug(
 548                             invoc.span(),
 549                             "expansion entered force mode but is still stuck",
 550                         );
 551                     } else {
 552                         // Cannot expand, will retry this invocation later.
 553                         undetermined_invocations.push((invoc, Some(ext)));
 554                         continue;
 555                     }
 556                 }
 557             };
 558
 559             progress = true;
 560             if expanded_fragments.len() < depth {
 561                 expanded_fragments.push(Vec::new());
 562             }
 563             expanded_fragments[depth - 1].push((expn_id, expanded_fragment));
 564             invocations.extend(new_invocations.into_iter().rev());
 565         }
 566
 567         self.cx.current_expansion = orig_expansion_data;
 568         self.cx.force_mode = orig_force_mode;
 569
 570         // Finally incorporate all the expanded macros into the input AST fragment.
 571         let mut placeholder_expander = PlaceholderExpander::new(self.cx, self.monotonic);
 572         while let Some(expanded_fragments) = expanded_fragments.pop() {
 573             for (expn_id, expanded_fragment) in expanded_fragments.into_iter().rev() {
 574                 placeholder_expander
 575                     .add(NodeId::placeholder_from_expn_id(expn_id), expanded_fragment);
 576             }
 577         }
 578         fragment_with_placeholders.mut_visit_with(&mut placeholder_expander);
 579         fragment_with_placeholders
 580     }
 581
 582     fn resolve_imports(&mut self) {
 583         if self.monotonic {
 584             self.cx.resolver.resolve_imports();
 585         }
 586     }
 587
 588     /// Collects all macro invocations reachable at this time in this AST fragment, and replace
 589     /// them with "placeholders" - dummy macro invocations with specially crafted `NodeId`s.
 590     /// Then call into resolver that builds a skeleton ("reduced graph") of the fragment and
 591     /// prepares data for resolving paths of macro invocations.
 592     fn collect_invocations(
 593         &mut self,
 594         mut fragment: AstFragment,
 595         extra_placeholders: &[NodeId],
 596     ) -> (AstFragment, Vec<(Invocation, Option<Lrc<SyntaxExtension>>)>) {
 597         // Resolve `$crate`s in the fragment for pretty-printing.
 598         self.cx.resolver.resolve_dollar_crates();
 599
 600         let invocations = {
 601             let mut collector = InvocationCollector {
 602                 cfg: StripUnconfigured {
 603                     sess: &self.cx.sess,
 604                     features: self.cx.ecfg.features,
 605                     modified: false,
 606                 },
 607                 cx: self.cx,
 608                 invocations: Vec::new(),
 609                 monotonic: self.monotonic,
 610             };
 611             fragment.mut_visit_with(&mut collector);
 612             fragment.add_placeholders(extra_placeholders);
 613             collector.invocations
 614         };
 615
 616         if self.monotonic {
 617             self.cx
 618                 .resolver
 619                 .visit_ast_fragment_with_placeholders(self.cx.current_expansion.id, &fragment);
 620         }
 621
 622         (fragment, invocations)
 623     }
 624
 625     fn error_recursion_limit_reached(&mut self) {
 626         let expn_data = self.cx.current_expansion.id.expn_data();
 627         let suggested_limit = self.cx.ecfg.recursion_limit * 2;
 628         self.cx
 629             .struct_span_err(
 630                 expn_data.call_site,
 631                 &format!("recursion limit reached while expanding `{}`", expn_data.kind.descr()),
 632             )
 633             .help(&format!(
 634                 "consider adding a `#![recursion_limit=\"{}\"]` attribute to your crate (`{}`)",
 635                 suggested_limit, self.cx.ecfg.crate_name,
 636             ))
 637             .emit();
 638         self.cx.trace_macros_diag();
 639     }
 640
 641     /// A macro's expansion does not fit in this fragment kind.
 642     /// For example, a non-type macro in a type position.
 643     fn error_wrong_fragment_kind(&mut self, kind: AstFragmentKind, mac: &ast::MacCall, span: Span) {
 644         let msg = format!(
 645             "non-{kind} macro in {kind} position: {path}",
 646             kind = kind.name(),
 647             path = pprust::path_to_string(&mac.path),
 648         );
 649         self.cx.span_err(span, &msg);
 650         self.cx.trace_macros_diag();
 651     }
 652
 653     fn expand_invoc(
 654         &mut self,
 655         invoc: Invocation,
 656         ext: &SyntaxExtensionKind,
 657     ) -> ExpandResult<AstFragment, Invocation> {
 658         let recursion_limit =
 659             self.cx.reduced_recursion_limit.unwrap_or(self.cx.ecfg.recursion_limit);
 660         if !recursion_limit.value_within_limit(self.cx.current_expansion.depth) {
 661             if self.cx.reduced_recursion_limit.is_none() {
 662                 self.error_recursion_limit_reached();
 663             }
 664
 665             // Reduce the recursion limit by half each time it triggers.
 666             self.cx.reduced_recursion_limit = Some(recursion_limit / 2);
 667
 668             return ExpandResult::Ready(invoc.fragment_kind.dummy(invoc.span()));
 669         }
 670
 671         let (fragment_kind, span) = (invoc.fragment_kind, invoc.span());
 672         ExpandResult::Ready(match invoc.kind {
 673             InvocationKind::Bang { mac, .. } => match ext {
 674                 SyntaxExtensionKind::Bang(expander) => {
 675                     let tok_result = match expander.expand(self.cx, span, mac.args.inner_tokens()) {
 676                         Err(_) => return ExpandResult::Ready(fragment_kind.dummy(span)),
 677                         Ok(ts) => ts,
 678                     };
 679                     self.parse_ast_fragment(tok_result, fragment_kind, &mac.path, span)
 680                 }
 681                 SyntaxExtensionKind::LegacyBang(expander) => {
 682                     let prev = self.cx.current_expansion.prior_type_ascription;
 683                     self.cx.current_expansion.prior_type_ascription = mac.prior_type_ascription;
 684                     let tok_result = expander.expand(self.cx, span, mac.args.inner_tokens());
 685                     let result = if let Some(result) = fragment_kind.make_from(tok_result) {
 686                         result
 687                     } else {
 688                         self.error_wrong_fragment_kind(fragment_kind, &mac, span);
 689                         fragment_kind.dummy(span)
 690                     };
 691                     self.cx.current_expansion.prior_type_ascription = prev;
 692                     result
 693                 }
 694                 _ => unreachable!(),
 695             },
 696             InvocationKind::Attr { attr, pos, mut item, derives } => match ext {
 697                 SyntaxExtensionKind::Attr(expander) => {
 698                     self.gate_proc_macro_input(&item);
 699                     self.gate_proc_macro_attr_item(span, &item);
 700                     let tokens = match attr.style {
 701                         AttrStyle::Outer => item.into_tokens(&self.cx.sess.parse_sess),
 702                         // FIXME: Properly collect tokens for inner attributes
 703                         AttrStyle::Inner => rustc_parse::fake_token_stream(
 704                             &self.cx.sess.parse_sess,
 705                             &item.into_nonterminal(),
 706                         ),
 707                     };
 708                     let attr_item = attr.unwrap_normal_item();
 709                     if let MacArgs::Eq(..) = attr_item.args {
 710                         self.cx.span_err(span, "key-value macro attributes are not supported");
 711                     }
 712                     let inner_tokens = attr_item.args.inner_tokens();
 713                     let tok_result = match expander.expand(self.cx, span, inner_tokens, tokens) {
 714                         Err(_) => return ExpandResult::Ready(fragment_kind.dummy(span)),
 715                         Ok(ts) => ts,
 716                     };
 717                     self.parse_ast_fragment(tok_result, fragment_kind, &attr_item.path, span)
 718                 }
 719                 SyntaxExtensionKind::LegacyAttr(expander) => {
 720                     match validate_attr::parse_meta(&self.cx.sess.parse_sess, &attr) {
 721                         Ok(meta) => {
 722                             let items = match expander.expand(self.cx, span, &meta, item) {
 723                                 ExpandResult::Ready(items) => items,
 724                                 ExpandResult::Retry(item) => {
 725                                     // Reassemble the original invocation for retrying.
 726                                     return ExpandResult::Retry(Invocation {
 727                                         kind: InvocationKind::Attr { attr, pos, item, derives },
 728                                         ..invoc
 729                                     });
 730                                 }
 731                             };
 732                             fragment_kind.expect_from_annotatables(items)
 733                         }
 734                         Err(mut err) => {
 735                             err.emit();
 736                             fragment_kind.dummy(span)
 737                         }
 738                     }
 739                 }
 740                 SyntaxExtensionKind::NonMacroAttr { mark_used } => {
 741                     self.cx.sess.mark_attr_known(&attr);
 742                     if *mark_used {
 743                         self.cx.sess.mark_attr_used(&attr);
 744                     }
 745                     item.visit_attrs(|attrs| attrs.insert(pos, attr));
 746                     fragment_kind.expect_from_annotatables(iter::once(item))
 747                 }
 748                 _ => unreachable!(),
 749             },
 750             InvocationKind::Derive { path, item } => match ext {
 751                 SyntaxExtensionKind::Derive(expander)
 752                 | SyntaxExtensionKind::LegacyDerive(expander) => {
 753                     if let SyntaxExtensionKind::Derive(..) = ext {
 754                         self.gate_proc_macro_input(&item);
 755                     }
 756                     let meta = ast::MetaItem { kind: ast::MetaItemKind::Word, span, path };
 757                     let items = match expander.expand(self.cx, span, &meta, item) {
 758                         ExpandResult::Ready(items) => items,
 759                         ExpandResult::Retry(item) => {
 760                             // Reassemble the original invocation for retrying.
 761                             return ExpandResult::Retry(Invocation {
 762                                 kind: InvocationKind::Derive { path: meta.path, item },
 763                                 ..invoc
 764                             });
 765                         }
 766                     };
 767                     fragment_kind.expect_from_annotatables(items)
 768                 }
 769                 _ => unreachable!(),
 770             },
 771         })
 772     }
 773
 774     fn gate_proc_macro_attr_item(&self, span: Span, item: &Annotatable) {
 775         let kind = match item {
 776             Annotatable::Item(_)
 777             | Annotatable::TraitItem(_)
 778             | Annotatable::ImplItem(_)
 779             | Annotatable::ForeignItem(_) => return,
 780             Annotatable::Stmt(stmt) => {
 781                 // Attributes are stable on item statements,
 782                 // but unstable on all other kinds of statements
 783                 if stmt.is_item() {
 784                     return;
 785                 }
 786                 "statements"
 787             }
 788             Annotatable::Expr(_) => "expressions",
 789             Annotatable::Arm(..)
 790             | Annotatable::ExprField(..)
 791             | Annotatable::PatField(..)
 792             | Annotatable::GenericParam(..)
 793             | Annotatable::Param(..)
 794             | Annotatable::FieldDef(..)
 795             | Annotatable::Variant(..) => panic!("unexpected annotatable"),
 796         };
 797         if self.cx.ecfg.proc_macro_hygiene() {
 798             return;
 799         }
 800         feature_err(
 801             &self.cx.sess.parse_sess,
 802             sym::proc_macro_hygiene,
 803             span,
 804             &format!("custom attributes cannot be applied to {}", kind),
 805         )
 806         .emit();
 807     }
 808
 809     fn gate_proc_macro_input(&self, annotatable: &Annotatable) {
 810         struct GateProcMacroInput<'a> {
 811             parse_sess: &'a ParseSess,
 812         }
 813
 814         impl<'ast, 'a> Visitor<'ast> for GateProcMacroInput<'a> {
 815             fn visit_item(&mut self, item: &'ast ast::Item) {
 816                 match &item.kind {
 817                     ast::ItemKind::Mod(_, mod_kind)
 818                         if !matches!(mod_kind, ModKind::Loaded(_, Inline::Yes, _)) =>
 819                     {
 820                         feature_err(
 821                             self.parse_sess,
 822                             sym::proc_macro_hygiene,
 823                             item.span,
 824                             "non-inline modules in proc macro input are unstable",
 825                         )
 826                         .emit();
 827                     }
 828                     _ => {}
 829                 }
 830
 831                 visit::walk_item(self, item);
 832             }
 833         }
 834
 835         if !self.cx.ecfg.proc_macro_hygiene() {
 836             annotatable
 837                 .visit_with(&mut GateProcMacroInput { parse_sess: &self.cx.sess.parse_sess });
 838         }
 839     }
 840
 841     fn parse_ast_fragment(
 842         &mut self,
 843         toks: TokenStream,
 844         kind: AstFragmentKind,
 845         path: &Path,
 846         span: Span,
 847     ) -> AstFragment {
 848         let mut parser = self.cx.new_parser_from_tts(toks);
 849         match parse_ast_fragment(&mut parser, kind) {
 850             Ok(fragment) => {
 851                 ensure_complete_parse(&mut parser, path, kind.name(), span);
 852                 fragment
 853             }
 854             Err(mut err) => {
 855                 if err.span.is_dummy() {
 856                     err.set_span(span);
 857                 }
 858                 annotate_err_with_kind(&mut err, kind, span);
 859                 err.emit();
 860                 self.cx.trace_macros_diag();
 861                 kind.dummy(span)
 862             }
 863         }
 864     }
 865 }
 866
 867 pub fn parse_ast_fragment<'a>(
 868     this: &mut Parser<'a>,
 869     kind: AstFragmentKind,
 870 ) -> PResult<'a, AstFragment> {
 871     Ok(match kind {
 872         AstFragmentKind::Items => {
 873             let mut items = SmallVec::new();
 874             while let Some(item) = this.parse_item(ForceCollect::No)? {
 875                 items.push(item);
 876             }
 877             AstFragment::Items(items)
 878         }
 879         AstFragmentKind::TraitItems => {
 880             let mut items = SmallVec::new();
 881             while let Some(item) = this.parse_trait_item()? {
 882                 items.extend(item);
 883             }
 884             AstFragment::TraitItems(items)
 885         }
 886         AstFragmentKind::ImplItems => {
 887             let mut items = SmallVec::new();
 888             while let Some(item) = this.parse_impl_item()? {
 889                 items.extend(item);
 890             }
 891             AstFragment::ImplItems(items)
 892         }
 893         AstFragmentKind::ForeignItems => {
 894             let mut items = SmallVec::new();
 895             while let Some(item) = this.parse_foreign_item()? {
 896                 items.extend(item);
 897             }
 898             AstFragment::ForeignItems(items)
 899         }
 900         AstFragmentKind::Stmts => {
 901             let mut stmts = SmallVec::new();
 902             // Won't make progress on a `}`.
 903             while this.token != token::Eof && this.token != token::CloseDelim(token::Brace) {
 904                 if let Some(stmt) = this.parse_full_stmt(AttemptLocalParseRecovery::Yes)? {
 905                     stmts.push(stmt);
 906                 }
 907             }
 908             AstFragment::Stmts(stmts)
 909         }
 910         AstFragmentKind::Expr => AstFragment::Expr(this.parse_expr()?),
 911         AstFragmentKind::OptExpr => {
 912             if this.token != token::Eof {
 913                 AstFragment::OptExpr(Some(this.parse_expr()?))
 914             } else {
 915                 AstFragment::OptExpr(None)
 916             }
 917         }
 918         AstFragmentKind::Ty => AstFragment::Ty(this.parse_ty()?),
 919         AstFragmentKind::Pat => {
 920             AstFragment::Pat(this.parse_pat_allow_top_alt(None, GateOr::Yes, RecoverComma::No)?)
 921         }
 922         AstFragmentKind::Arms
 923         | AstFragmentKind::Fields
 924         | AstFragmentKind::FieldPats
 925         | AstFragmentKind::GenericParams
 926         | AstFragmentKind::Params
 927         | AstFragmentKind::StructFields
 928         | AstFragmentKind::Variants => panic!("unexpected AST fragment kind"),
 929     })
 930 }
 931
 932 pub fn ensure_complete_parse<'a>(
 933     this: &mut Parser<'a>,
 934     macro_path: &Path,
 935     kind_name: &str,
 936     span: Span,
 937 ) {
 938     if this.token != token::Eof {
 939         let token = pprust::token_to_string(&this.token);
 940         let msg = format!("macro expansion ignores token `{}` and any following", token);
 941         // Avoid emitting backtrace info twice.
 942         let def_site_span = this.token.span.with_ctxt(SyntaxContext::root());
 943         let mut err = this.struct_span_err(def_site_span, &msg);
 944         err.span_label(span, "caused by the macro expansion here");
 945         let msg = format!(
 946             "the usage of `{}!` is likely invalid in {} context",
 947             pprust::path_to_string(macro_path),
 948             kind_name,
 949         );
 950         err.note(&msg);
 951         let semi_span = this.sess.source_map().next_point(span);
 952
 953         let semi_full_span = semi_span.to(this.sess.source_map().next_point(semi_span));
 954         match this.sess.source_map().span_to_snippet(semi_full_span) {
 955             Ok(ref snippet) if &snippet[..] != ";" && kind_name == "expression" => {
 956                 err.span_suggestion(
 957                     semi_span,
 958                     "you might be missing a semicolon here",
 959                     ";".to_owned(),
 960                     Applicability::MaybeIncorrect,
 961                 );
 962             }
 963             _ => {}
 964         }
 965         err.emit();
 966     }
 967 }
 968
 969 struct InvocationCollector<'a, 'b> {
 970     cx: &'a mut ExtCtxt<'b>,
 971     cfg: StripUnconfigured<'a>,
 972     invocations: Vec<(Invocation, Option<Lrc<SyntaxExtension>>)>,
 973     monotonic: bool,
 974 }
 975
 976 impl<'a, 'b> InvocationCollector<'a, 'b> {
 977     fn collect(&mut self, fragment_kind: AstFragmentKind, kind: InvocationKind) -> AstFragment {
 978         let expn_id = ExpnId::fresh(None);
 979         let vis = kind.placeholder_visibility();
 980         self.invocations.push((
 981             Invocation {
 982                 kind,
 983                 fragment_kind,
 984                 expansion_data: ExpansionData {
 985                     id: expn_id,
 986                     depth: self.cx.current_expansion.depth + 1,
 987                     ..self.cx.current_expansion.clone()
 988                 },
 989             },
 990             None,
 991         ));
 992         placeholder(fragment_kind, NodeId::placeholder_from_expn_id(expn_id), vis)
 993     }
 994
 995     fn collect_bang(
 996         &mut self,
 997         mac: ast::MacCall,
 998         span: Span,
 999         kind: AstFragmentKind,
1000     ) -> AstFragment {
1001         self.collect(kind, InvocationKind::Bang { mac, span })
1002     }
1003
1004     fn collect_attr(
1005         &mut self,
1006         (attr, pos, derives): (ast::Attribute, usize, Vec<Path>),
1007         item: Annotatable,
1008         kind: AstFragmentKind,
1009     ) -> AstFragment {
1010         self.collect(kind, InvocationKind::Attr { attr, pos, item, derives })
1011     }
1012
1013     /// If `item` is an attribute invocation, remove the attribute and return it together with
1014     /// its position and derives following it. We have to collect the derives in order to resolve
1015     /// legacy derive helpers (helpers written before derives that introduce them).
1016     fn take_first_attr(
1017         &mut self,
1018         item: &mut impl AstLike,
1019     ) -> Option<(ast::Attribute, usize, Vec<Path>)> {
1020         let mut attr = None;
1021
1022         item.visit_attrs(|attrs| {
1023             attr = attrs
1024                 .iter()
1025                 .position(|a| !self.cx.sess.is_attr_known(a) && !is_builtin_attr(a))
1026                 .map(|attr_pos| {
1027                     let attr = attrs.remove(attr_pos);
1028                     let following_derives = attrs[attr_pos..]
1029                         .iter()
1030                         .filter(|a| a.has_name(sym::derive))
1031                         .flat_map(|a| a.meta_item_list().unwrap_or_default())
1032                         .filter_map(|nested_meta| match nested_meta {
1033                             NestedMetaItem::MetaItem(ast::MetaItem {
1034                                 kind: MetaItemKind::Word,
1035                                 path,
1036                                 ..
1037                             }) => Some(path),
1038                             _ => None,
1039                         })
1040                         .collect();
1041
1042                     (attr, attr_pos, following_derives)
1043                 })
1044         });
1045
1046         attr
1047     }
1048
1049     fn configure<T: AstLike>(&mut self, node: T) -> Option<T> {
1050         self.cfg.configure(node)
1051     }
1052
1053     // Detect use of feature-gated or invalid attributes on macro invocations
1054     // since they will not be detected after macro expansion.
1055     fn check_attributes(&mut self, attrs: &[ast::Attribute]) {
1056         let features = self.cx.ecfg.features.unwrap();
1057         for attr in attrs.iter() {
1058             rustc_ast_passes::feature_gate::check_attribute(attr, self.cx.sess, features);
1059             validate_attr::check_meta(&self.cx.sess.parse_sess, attr);
1060             if attr.doc_str().is_some() {
1061                 self.cx.sess.parse_sess.buffer_lint_with_diagnostic(
1062                     &UNUSED_DOC_COMMENTS,
1063                     attr.span,
1064                     ast::CRATE_NODE_ID,
1065                     "unused doc comment",
1066                     BuiltinLintDiagnostics::UnusedDocComment(attr.span),
1067                 );
1068             }
1069         }
1070     }
1071 }
1072
1073 impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
1074     fn visit_expr(&mut self, expr: &mut P<ast::Expr>) {
1075         self.cfg.configure_expr(expr);
1076         visit_clobber(expr.deref_mut(), |mut expr| {
1077             if let Some(attr) = self.take_first_attr(&mut expr) {
1078                 // Collect the invoc regardless of whether or not attributes are permitted here
1079                 // expansion will eat the attribute so it won't error later.
1080                 self.cfg.maybe_emit_expr_attr_err(&attr.0);
1081
1082                 // AstFragmentKind::Expr requires the macro to emit an expression.
1083                 return self
1084                     .collect_attr(attr, Annotatable::Expr(P(expr)), AstFragmentKind::Expr)
1085                     .make_expr()
1086                     .into_inner();
1087             }
1088
1089             if let ast::ExprKind::MacCall(mac) = expr.kind {
1090                 self.check_attributes(&expr.attrs);
1091                 self.collect_bang(mac, expr.span, AstFragmentKind::Expr).make_expr().into_inner()
1092             } else {
1093                 ensure_sufficient_stack(|| noop_visit_expr(&mut expr, self));
1094                 expr
1095             }
1096         });
1097     }
1098
1099     fn flat_map_arm(&mut self, arm: ast::Arm) -> SmallVec<[ast::Arm; 1]> {
1100         let mut arm = configure!(self, arm);
1101
1102         if let Some(attr) = self.take_first_attr(&mut arm) {
1103             return self
1104                 .collect_attr(attr, Annotatable::Arm(arm), AstFragmentKind::Arms)
1105                 .make_arms();
1106         }
1107
1108         noop_flat_map_arm(arm, self)
1109     }
1110
1111     fn flat_map_expr_field(&mut self, field: ast::ExprField) -> SmallVec<[ast::ExprField; 1]> {
1112         let mut field = configure!(self, field);
1113
1114         if let Some(attr) = self.take_first_attr(&mut field) {
1115             return self
1116                 .collect_attr(attr, Annotatable::ExprField(field), AstFragmentKind::Fields)
1117                 .make_expr_fields();
1118         }
1119
1120         noop_flat_map_expr_field(field, self)
1121     }
1122
1123     fn flat_map_pat_field(&mut self, fp: ast::PatField) -> SmallVec<[ast::PatField; 1]> {
1124         let mut fp = configure!(self, fp);
1125
1126         if let Some(attr) = self.take_first_attr(&mut fp) {
1127             return self
1128                 .collect_attr(attr, Annotatable::PatField(fp), AstFragmentKind::FieldPats)
1129                 .make_pat_fields();
1130         }
1131
1132         noop_flat_map_pat_field(fp, self)
1133     }
1134
1135     fn flat_map_param(&mut self, p: ast::Param) -> SmallVec<[ast::Param; 1]> {
1136         let mut p = configure!(self, p);
1137
1138         if let Some(attr) = self.take_first_attr(&mut p) {
1139             return self
1140                 .collect_attr(attr, Annotatable::Param(p), AstFragmentKind::Params)
1141                 .make_params();
1142         }
1143
1144         noop_flat_map_param(p, self)
1145     }
1146
1147     fn flat_map_field_def(&mut self, sf: ast::FieldDef) -> SmallVec<[ast::FieldDef; 1]> {
1148         let mut sf = configure!(self, sf);
1149
1150         if let Some(attr) = self.take_first_attr(&mut sf) {
1151             return self
1152                 .collect_attr(attr, Annotatable::FieldDef(sf), AstFragmentKind::StructFields)
1153                 .make_field_defs();
1154         }
1155
1156         noop_flat_map_field_def(sf, self)
1157     }
1158
1159     fn flat_map_variant(&mut self, variant: ast::Variant) -> SmallVec<[ast::Variant; 1]> {
1160         let mut variant = configure!(self, variant);
1161
1162         if let Some(attr) = self.take_first_attr(&mut variant) {
1163             return self
1164                 .collect_attr(attr, Annotatable::Variant(variant), AstFragmentKind::Variants)
1165                 .make_variants();
1166         }
1167
1168         noop_flat_map_variant(variant, self)
1169     }
1170
1171     fn filter_map_expr(&mut self, expr: P<ast::Expr>) -> Option<P<ast::Expr>> {
1172         let expr = configure!(self, expr);
1173         expr.filter_map(|mut expr| {
1174             if let Some(attr) = self.take_first_attr(&mut expr) {
1175                 self.cfg.maybe_emit_expr_attr_err(&attr.0);
1176
1177                 return self
1178                     .collect_attr(attr, Annotatable::Expr(P(expr)), AstFragmentKind::OptExpr)
1179                     .make_opt_expr()
1180                     .map(|expr| expr.into_inner());
1181             }
1182
1183             if let ast::ExprKind::MacCall(mac) = expr.kind {
1184                 self.check_attributes(&expr.attrs);
1185                 self.collect_bang(mac, expr.span, AstFragmentKind::OptExpr)
1186                     .make_opt_expr()
1187                     .map(|expr| expr.into_inner())
1188             } else {
1189                 Some({
1190                     noop_visit_expr(&mut expr, self);
1191                     expr
1192                 })
1193             }
1194         })
1195     }
1196
1197     fn visit_pat(&mut self, pat: &mut P<ast::Pat>) {
1198         match pat.kind {
1199             PatKind::MacCall(_) => {}
1200             _ => return noop_visit_pat(pat, self),
1201         }
1202
1203         visit_clobber(pat, |mut pat| match mem::replace(&mut pat.kind, PatKind::Wild) {
1204             PatKind::MacCall(mac) => {
1205                 self.collect_bang(mac, pat.span, AstFragmentKind::Pat).make_pat()
1206             }
1207             _ => unreachable!(),
1208         });
1209     }
1210
1211     fn flat_map_stmt(&mut self, stmt: ast::Stmt) -> SmallVec<[ast::Stmt; 1]> {
1212         let mut stmt = configure!(self, stmt);
1213
1214         // we'll expand attributes on expressions separately
1215         if !stmt.is_expr() {
1216             if let Some(attr) = self.take_first_attr(&mut stmt) {
1217                 return self
1218                     .collect_attr(attr, Annotatable::Stmt(P(stmt)), AstFragmentKind::Stmts)
1219                     .make_stmts();
1220             }
1221         }
1222
1223         if let StmtKind::MacCall(mac) = stmt.kind {
1224             let MacCallStmt { mac, style, attrs, tokens: _ } = mac.into_inner();
1225             self.check_attributes(&attrs);
1226             let mut placeholder =
1227                 self.collect_bang(mac, stmt.span, AstFragmentKind::Stmts).make_stmts();
1228
1229             // If this is a macro invocation with a semicolon, then apply that
1230             // semicolon to the final statement produced by expansion.
1231             if style == MacStmtStyle::Semicolon {
1232                 if let Some(stmt) = placeholder.pop() {
1233                     placeholder.push(stmt.add_trailing_semicolon());
1234                 }
1235             }
1236
1237             return placeholder;
1238         }
1239
1240         // The placeholder expander gives ids to statements, so we avoid folding the id here.
1241         let ast::Stmt { id, kind, span } = stmt;
1242         noop_flat_map_stmt_kind(kind, self)
1243             .into_iter()
1244             .map(|kind| ast::Stmt { id, kind, span })
1245             .collect()
1246     }
1247
1248     fn visit_block(&mut self, block: &mut P<Block>) {
1249         let orig_dir_ownership = mem::replace(
1250             &mut self.cx.current_expansion.dir_ownership,
1251             DirOwnership::UnownedViaBlock,
1252         );
1253         noop_visit_block(block, self);
1254         self.cx.current_expansion.dir_ownership = orig_dir_ownership;
1255     }
1256
1257     fn flat_map_item(&mut self, item: P<ast::Item>) -> SmallVec<[P<ast::Item>; 1]> {
1258         let mut item = configure!(self, item);
1259
1260         if let Some(attr) = self.take_first_attr(&mut item) {
1261             return self
1262                 .collect_attr(attr, Annotatable::Item(item), AstFragmentKind::Items)
1263                 .make_items();
1264         }
1265
1266         let mut attrs = mem::take(&mut item.attrs); // We do this to please borrowck.
1267         let ident = item.ident;
1268         let span = item.span;
1269
1270         match item.kind {
1271             ast::ItemKind::MacCall(..) => {
1272                 item.attrs = attrs;
1273                 self.check_attributes(&item.attrs);
1274                 item.and_then(|item| match item.kind {
1275                     ItemKind::MacCall(mac) => {
1276                         self.collect_bang(mac, span, AstFragmentKind::Items).make_items()
1277                     }
1278                     _ => unreachable!(),
1279                 })
1280             }
1281             ast::ItemKind::Mod(_, ref mut mod_kind) if ident != Ident::invalid() => {
1282                 let (file_path, dir_path, dir_ownership) = match mod_kind {
1283                     ModKind::Loaded(_, inline, _) => {
1284                         // Inline `mod foo { ... }`, but we still need to push directories.
1285                         let (dir_path, dir_ownership) = mod_dir_path(
1286                             &self.cx.sess,
1287                             ident,
1288                             &attrs,
1289                             &self.cx.current_expansion.module,
1290                             self.cx.current_expansion.dir_ownership,
1291                             *inline,
1292                         );
1293                         item.attrs = attrs;
1294                         (None, dir_path, dir_ownership)
1295                     }
1296                     ModKind::Unloaded => {
1297                         // We have an outline `mod foo;` so we need to parse the file.
1298                         let old_attrs_len = attrs.len();
1299                         let ParsedExternalMod {
1300                             mut items,
1301                             inner_span,
1302                             file_path,
1303                             dir_path,
1304                             dir_ownership,
1305                         } = parse_external_mod(
1306                             &self.cx.sess,
1307                             ident,
1308                             span,
1309                             &self.cx.current_expansion.module,
1310                             self.cx.current_expansion.dir_ownership,
1311                             &mut attrs,
1312                         );
1313
1314                         if let Some(extern_mod_loaded) = self.cx.extern_mod_loaded {
1315                             (attrs, items) = extern_mod_loaded(ident, attrs, items, inner_span);
1316                         }
1317
1318                         *mod_kind = ModKind::Loaded(items, Inline::No, inner_span);
1319                         item.attrs = attrs;
1320                         if item.attrs.len() > old_attrs_len {
1321                             // If we loaded an out-of-line module and added some inner attributes,
1322                             // then we need to re-configure it and re-collect attributes for
1323                             // resolution and expansion.
1324                             item = configure!(self, item);
1325
1326                             if let Some(attr) = self.take_first_attr(&mut item) {
1327                                 return self
1328                                     .collect_attr(
1329                                         attr,
1330                                         Annotatable::Item(item),
1331                                         AstFragmentKind::Items,
1332                                     )
1333                                     .make_items();
1334                             }
1335                         }
1336                         (Some(file_path), dir_path, dir_ownership)
1337                     }
1338                 };
1339
1340                 // Set the module info before we flat map.
1341                 let mut module = self.cx.current_expansion.module.with_dir_path(dir_path);
1342                 module.mod_path.push(ident);
1343                 if let Some(file_path) = file_path {
1344                     module.file_path_stack.push(file_path);
1345                 }
1346
1347                 let orig_module =
1348                     mem::replace(&mut self.cx.current_expansion.module, Rc::new(module));
1349                 let orig_dir_ownership =
1350                     mem::replace(&mut self.cx.current_expansion.dir_ownership, dir_ownership);
1351
1352                 let result = noop_flat_map_item(item, self);
1353
1354                 // Restore the module info.
1355                 self.cx.current_expansion.dir_ownership = orig_dir_ownership;
1356                 self.cx.current_expansion.module = orig_module;
1357
1358                 result
1359             }
1360             _ => {
1361                 item.attrs = attrs;
1362                 noop_flat_map_item(item, self)
1363             }
1364         }
1365     }
1366
1367     fn flat_map_trait_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
1368         let mut item = configure!(self, item);
1369
1370         if let Some(attr) = self.take_first_attr(&mut item) {
1371             return self
1372                 .collect_attr(attr, Annotatable::TraitItem(item), AstFragmentKind::TraitItems)
1373                 .make_trait_items();
1374         }
1375
1376         match item.kind {
1377             ast::AssocItemKind::MacCall(..) => {
1378                 self.check_attributes(&item.attrs);
1379                 item.and_then(|item| match item.kind {
1380                     ast::AssocItemKind::MacCall(mac) => self
1381                         .collect_bang(mac, item.span, AstFragmentKind::TraitItems)
1382                         .make_trait_items(),
1383                     _ => unreachable!(),
1384                 })
1385             }
1386             _ => noop_flat_map_assoc_item(item, self),
1387         }
1388     }
1389
1390     fn flat_map_impl_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
1391         let mut item = configure!(self, item);
1392
1393         if let Some(attr) = self.take_first_attr(&mut item) {
1394             return self
1395                 .collect_attr(attr, Annotatable::ImplItem(item), AstFragmentKind::ImplItems)
1396                 .make_impl_items();
1397         }
1398
1399         match item.kind {
1400             ast::AssocItemKind::MacCall(..) => {
1401                 self.check_attributes(&item.attrs);
1402                 item.and_then(|item| match item.kind {
1403                     ast::AssocItemKind::MacCall(mac) => self
1404                         .collect_bang(mac, item.span, AstFragmentKind::ImplItems)
1405                         .make_impl_items(),
1406                     _ => unreachable!(),
1407                 })
1408             }
1409             _ => noop_flat_map_assoc_item(item, self),
1410         }
1411     }
1412
1413     fn visit_ty(&mut self, ty: &mut P<ast::Ty>) {
1414         match ty.kind {
1415             ast::TyKind::MacCall(_) => {}
1416             _ => return noop_visit_ty(ty, self),
1417         };
1418
1419         visit_clobber(ty, |mut ty| match mem::replace(&mut ty.kind, ast::TyKind::Err) {
1420             ast::TyKind::MacCall(mac) => {
1421                 self.collect_bang(mac, ty.span, AstFragmentKind::Ty).make_ty()
1422             }
1423             _ => unreachable!(),
1424         });
1425     }
1426
1427     fn flat_map_foreign_item(
1428         &mut self,
1429         foreign_item: P<ast::ForeignItem>,
1430     ) -> SmallVec<[P<ast::ForeignItem>; 1]> {
1431         let mut foreign_item = configure!(self, foreign_item);
1432
1433         if let Some(attr) = self.take_first_attr(&mut foreign_item) {
1434             return self
1435                 .collect_attr(
1436                     attr,
1437                     Annotatable::ForeignItem(foreign_item),
1438                     AstFragmentKind::ForeignItems,
1439                 )
1440                 .make_foreign_items();
1441         }
1442
1443         match foreign_item.kind {
1444             ast::ForeignItemKind::MacCall(..) => {
1445                 self.check_attributes(&foreign_item.attrs);
1446                 foreign_item.and_then(|item| match item.kind {
1447                     ast::ForeignItemKind::MacCall(mac) => self
1448                         .collect_bang(mac, item.span, AstFragmentKind::ForeignItems)
1449                         .make_foreign_items(),
1450                     _ => unreachable!(),
1451                 })
1452             }
1453             _ => noop_flat_map_foreign_item(foreign_item, self),
1454         }
1455     }
1456
1457     fn flat_map_generic_param(
1458         &mut self,
1459         param: ast::GenericParam,
1460     ) -> SmallVec<[ast::GenericParam; 1]> {
1461         let mut param = configure!(self, param);
1462
1463         if let Some(attr) = self.take_first_attr(&mut param) {
1464             return self
1465                 .collect_attr(
1466                     attr,
1467                     Annotatable::GenericParam(param),
1468                     AstFragmentKind::GenericParams,
1469                 )
1470                 .make_generic_params();
1471         }
1472
1473         noop_flat_map_generic_param(param, self)
1474     }
1475
1476     fn visit_attribute(&mut self, at: &mut ast::Attribute) {
1477         // turn `#[doc(include="filename")]` attributes into `#[doc(include(file="filename",
1478         // contents="file contents")]` attributes
1479         if !self.cx.sess.check_name(at, sym::doc) {
1480             return noop_visit_attribute(at, self);
1481         }
1482
1483         if let Some(list) = at.meta_item_list() {
1484             if !list.iter().any(|it| it.has_name(sym::include)) {
1485                 return noop_visit_attribute(at, self);
1486             }
1487
1488             let mut items = vec![];
1489
1490             for mut it in list {
1491                 if !it.has_name(sym::include) {
1492                     items.push({
1493                         noop_visit_meta_list_item(&mut it, self);
1494                         it
1495                     });
1496                     continue;
1497                 }
1498
1499                 if let Some(file) = it.value_str() {
1500                     let err_count = self.cx.sess.parse_sess.span_diagnostic.err_count();
1501                     self.check_attributes(slice::from_ref(at));
1502                     if self.cx.sess.parse_sess.span_diagnostic.err_count() > err_count {
1503                         // avoid loading the file if they haven't enabled the feature
1504                         return noop_visit_attribute(at, self);
1505                     }
1506
1507                     let filename = match self.cx.resolve_path(&*file.as_str(), it.span()) {
1508                         Ok(filename) => filename,
1509                         Err(mut err) => {
1510                             err.emit();
1511                             continue;
1512                         }
1513                     };
1514
1515                     match self.cx.source_map().load_file(&filename) {
1516                         Ok(source_file) => {
1517                             let src = source_file
1518                                 .src
1519                                 .as_ref()
1520                                 .expect("freshly loaded file should have a source");
1521                             let src_interned = Symbol::intern(src.as_str());
1522
1523                             let include_info = vec![
1524                                 ast::NestedMetaItem::MetaItem(attr::mk_name_value_item_str(
1525                                     Ident::with_dummy_span(sym::file),
1526                                     file,
1527                                     DUMMY_SP,
1528                                 )),
1529                                 ast::NestedMetaItem::MetaItem(attr::mk_name_value_item_str(
1530                                     Ident::with_dummy_span(sym::contents),
1531                                     src_interned,
1532                                     DUMMY_SP,
1533                                 )),
1534                             ];
1535
1536                             let include_ident = Ident::with_dummy_span(sym::include);
1537                             let item = attr::mk_list_item(include_ident, include_info);
1538                             items.push(ast::NestedMetaItem::MetaItem(item));
1539                         }
1540                         Err(e) => {
1541                             let lit_span = it.name_value_literal_span().unwrap();
1542
1543                             if e.kind() == ErrorKind::InvalidData {
1544                                 self.cx
1545                                     .struct_span_err(
1546                                         lit_span,
1547                                         &format!("{} wasn't a utf-8 file", filename.display()),
1548                                     )
1549                                     .span_label(lit_span, "contains invalid utf-8")
1550                                     .emit();
1551                             } else {
1552                                 let mut err = self.cx.struct_span_err(
1553                                     lit_span,
1554                                     &format!("couldn't read {}: {}", filename.display(), e),
1555                                 );
1556                                 err.span_label(lit_span, "couldn't read file");
1557
1558                                 err.emit();
1559                             }
1560                         }
1561                     }
1562                 } else {
1563                     let mut err = self
1564                         .cx
1565                         .struct_span_err(it.span(), "expected path to external documentation");
1566
1567                     // Check if the user erroneously used `doc(include(...))` syntax.
1568                     let literal = it.meta_item_list().and_then(|list| {
1569                         if list.len() == 1 {
1570                             list[0].literal().map(|literal| &literal.kind)
1571                         } else {
1572                             None
1573                         }
1574                     });
1575
1576                     let (path, applicability) = match &literal {
1577                         Some(LitKind::Str(path, ..)) => {
1578                             (path.to_string(), Applicability::MachineApplicable)
1579                         }
1580                         _ => (String::from("<path>"), Applicability::HasPlaceholders),
1581                     };
1582
1583                     err.span_suggestion(
1584                         it.span(),
1585                         "provide a file path with `=`",
1586                         format!("include = \"{}\"", path),
1587                         applicability,
1588                     );
1589
1590                     err.emit();
1591                 }
1592             }
1593
1594             let meta = attr::mk_list_item(Ident::with_dummy_span(sym::doc), items);
1595             *at = ast::Attribute {
1596                 kind: ast::AttrKind::Normal(
1597                     AttrItem { path: meta.path, args: meta.kind.mac_args(meta.span), tokens: None },
1598                     None,
1599                 ),
1600                 span: at.span,
1601                 id: at.id,
1602                 style: at.style,
1603             };
1604         } else {
1605             noop_visit_attribute(at, self)
1606         }
1607     }
1608
1609     fn visit_id(&mut self, id: &mut ast::NodeId) {
1610         if self.monotonic {
1611             debug_assert_eq!(*id, ast::DUMMY_NODE_ID);
1612             *id = self.cx.resolver.next_node_id()
1613         }
1614     }
1615 }
1616
1617 pub struct ExpansionConfig<'feat> {
1618     pub crate_name: String,
1619     pub features: Option<&'feat Features>,
1620     pub recursion_limit: Limit,
1621     pub trace_mac: bool,
1622     pub should_test: bool,          // If false, strip `#[test]` nodes
1623     pub span_debug: bool,           // If true, use verbose debugging for `proc_macro::Span`
1624     pub proc_macro_backtrace: bool, // If true, show backtraces for proc-macro panics
1625 }
1626
1627 impl<'feat> ExpansionConfig<'feat> {
1628     pub fn default(crate_name: String) -> ExpansionConfig<'static> {
1629         ExpansionConfig {
1630             crate_name,
1631             features: None,
1632             recursion_limit: Limit::new(1024),
1633             trace_mac: false,
1634             should_test: false,
1635             span_debug: false,
1636             proc_macro_backtrace: false,
1637         }
1638     }
1639
1640     fn proc_macro_hygiene(&self) -> bool {
1641         self.features.map_or(false, |features| features.proc_macro_hygiene)
1642     }
1643 }