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, 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, 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 pub enum SupportsMacroExpansion {
 210     No,
 211     Yes { supports_inner_attrs: bool },
 212 }
 213
 214 impl AstFragmentKind {
 215     crate fn dummy(self, span: Span) -> AstFragment {
 216         self.make_from(DummyResult::any(span)).expect("couldn't create a dummy AST fragment")
 217     }
 218
 219     pub fn supports_macro_expansion(self) -> SupportsMacroExpansion {
 220         match self {
 221             AstFragmentKind::OptExpr
 222             | AstFragmentKind::Expr
 223             | AstFragmentKind::Stmts
 224             | AstFragmentKind::Ty
 225             | AstFragmentKind::Pat => SupportsMacroExpansion::Yes { supports_inner_attrs: false },
 226             AstFragmentKind::Items
 227             | AstFragmentKind::TraitItems
 228             | AstFragmentKind::ImplItems
 229             | AstFragmentKind::ForeignItems => {
 230                 SupportsMacroExpansion::Yes { supports_inner_attrs: true }
 231             }
 232             AstFragmentKind::Arms
 233             | AstFragmentKind::Fields
 234             | AstFragmentKind::FieldPats
 235             | AstFragmentKind::GenericParams
 236             | AstFragmentKind::Params
 237             | AstFragmentKind::StructFields
 238             | AstFragmentKind::Variants => SupportsMacroExpansion::No,
 239         }
 240     }
 241
 242     fn expect_from_annotatables<I: IntoIterator<Item = Annotatable>>(
 243         self,
 244         items: I,
 245     ) -> AstFragment {
 246         let mut items = items.into_iter();
 247         match self {
 248             AstFragmentKind::Arms => {
 249                 AstFragment::Arms(items.map(Annotatable::expect_arm).collect())
 250             }
 251             AstFragmentKind::Fields => {
 252                 AstFragment::Fields(items.map(Annotatable::expect_expr_field).collect())
 253             }
 254             AstFragmentKind::FieldPats => {
 255                 AstFragment::FieldPats(items.map(Annotatable::expect_pat_field).collect())
 256             }
 257             AstFragmentKind::GenericParams => {
 258                 AstFragment::GenericParams(items.map(Annotatable::expect_generic_param).collect())
 259             }
 260             AstFragmentKind::Params => {
 261                 AstFragment::Params(items.map(Annotatable::expect_param).collect())
 262             }
 263             AstFragmentKind::StructFields => {
 264                 AstFragment::StructFields(items.map(Annotatable::expect_field_def).collect())
 265             }
 266             AstFragmentKind::Variants => {
 267                 AstFragment::Variants(items.map(Annotatable::expect_variant).collect())
 268             }
 269             AstFragmentKind::Items => {
 270                 AstFragment::Items(items.map(Annotatable::expect_item).collect())
 271             }
 272             AstFragmentKind::ImplItems => {
 273                 AstFragment::ImplItems(items.map(Annotatable::expect_impl_item).collect())
 274             }
 275             AstFragmentKind::TraitItems => {
 276                 AstFragment::TraitItems(items.map(Annotatable::expect_trait_item).collect())
 277             }
 278             AstFragmentKind::ForeignItems => {
 279                 AstFragment::ForeignItems(items.map(Annotatable::expect_foreign_item).collect())
 280             }
 281             AstFragmentKind::Stmts => {
 282                 AstFragment::Stmts(items.map(Annotatable::expect_stmt).collect())
 283             }
 284             AstFragmentKind::Expr => AstFragment::Expr(
 285                 items.next().expect("expected exactly one expression").expect_expr(),
 286             ),
 287             AstFragmentKind::OptExpr => {
 288                 AstFragment::OptExpr(items.next().map(Annotatable::expect_expr))
 289             }
 290             AstFragmentKind::Pat | AstFragmentKind::Ty => {
 291                 panic!("patterns and types aren't annotatable")
 292             }
 293         }
 294     }
 295 }
 296
 297 pub struct Invocation {
 298     pub kind: InvocationKind,
 299     pub fragment_kind: AstFragmentKind,
 300     pub expansion_data: ExpansionData,
 301 }
 302
 303 pub enum InvocationKind {
 304     Bang {
 305         mac: ast::MacCall,
 306         span: Span,
 307     },
 308     Attr {
 309         attr: ast::Attribute,
 310         // Re-insertion position for inert attributes.
 311         pos: usize,
 312         item: Annotatable,
 313         // Required for resolving derive helper attributes.
 314         derives: Vec<Path>,
 315     },
 316     Derive {
 317         path: Path,
 318         item: Annotatable,
 319     },
 320 }
 321
 322 impl InvocationKind {
 323     fn placeholder_visibility(&self) -> Option<ast::Visibility> {
 324         // HACK: For unnamed fields placeholders should have the same visibility as the actual
 325         // fields because for tuple structs/variants resolve determines visibilities of their
 326         // constructor using these field visibilities before attributes on them are are expanded.
 327         // The assumption is that the attribute expansion cannot change field visibilities,
 328         // and it holds because only inert attributes are supported in this position.
 329         match self {
 330             InvocationKind::Attr { item: Annotatable::FieldDef(field), .. }
 331             | InvocationKind::Derive { item: Annotatable::FieldDef(field), .. }
 332                 if field.ident.is_none() =>
 333             {
 334                 Some(field.vis.clone())
 335             }
 336             _ => None,
 337         }
 338     }
 339 }
 340
 341 impl Invocation {
 342     pub fn span(&self) -> Span {
 343         match &self.kind {
 344             InvocationKind::Bang { span, .. } => *span,
 345             InvocationKind::Attr { attr, .. } => attr.span,
 346             InvocationKind::Derive { path, .. } => path.span,
 347         }
 348     }
 349 }
 350
 351 pub struct MacroExpander<'a, 'b> {
 352     pub cx: &'a mut ExtCtxt<'b>,
 353     monotonic: bool, // cf. `cx.monotonic_expander()`
 354 }
 355
 356 impl<'a, 'b> MacroExpander<'a, 'b> {
 357     pub fn new(cx: &'a mut ExtCtxt<'b>, monotonic: bool) -> Self {
 358         MacroExpander { cx, monotonic }
 359     }
 360
 361     // FIXME: Avoid visiting the crate as a `Mod` item,
 362     // make crate a first class expansion target instead.
 363     pub fn expand_crate(&mut self, mut krate: ast::Crate) -> ast::Crate {
 364         let file_path = match self.cx.source_map().span_to_unmapped_path(krate.span) {
 365             FileName::Real(name) => name.into_local_path(),
 366             other => PathBuf::from(other.to_string()),
 367         };
 368         let dir_path = file_path.parent().unwrap_or(&file_path).to_owned();
 369         self.cx.root_path = dir_path.clone();
 370         self.cx.current_expansion.module = Rc::new(ModuleData {
 371             mod_path: vec![Ident::from_str(&self.cx.ecfg.crate_name)],
 372             file_path_stack: vec![file_path],
 373             dir_path,
 374         });
 375
 376         let krate_item = AstFragment::Items(smallvec![P(ast::Item {
 377             attrs: krate.attrs,
 378             span: krate.span,
 379             kind: ast::ItemKind::Mod(
 380                 Unsafe::No,
 381                 ModKind::Loaded(krate.items, Inline::Yes, krate.span)
 382             ),
 383             ident: Ident::invalid(),
 384             id: ast::DUMMY_NODE_ID,
 385             vis: ast::Visibility {
 386                 span: krate.span.shrink_to_lo(),
 387                 kind: ast::VisibilityKind::Public,
 388                 tokens: None,
 389             },
 390             tokens: None,
 391         })]);
 392
 393         match self.fully_expand_fragment(krate_item).make_items().pop().map(P::into_inner) {
 394             Some(ast::Item {
 395                 attrs,
 396                 kind: ast::ItemKind::Mod(_, ModKind::Loaded(items, ..)),
 397                 ..
 398             }) => {
 399                 krate.attrs = attrs;
 400                 krate.items = items;
 401             }
 402             None => {
 403                 // Resolution failed so we return an empty expansion
 404                 krate.attrs = vec![];
 405                 krate.items = vec![];
 406             }
 407             Some(ast::Item { span, kind, .. }) => {
 408                 krate.attrs = vec![];
 409                 krate.items = vec![];
 410                 self.cx.span_err(
 411                     span,
 412                     &format!(
 413                         "expected crate top-level item to be a module after macro expansion, found {} {}",
 414                         kind.article(), kind.descr()
 415                     ),
 416                 );
 417             }
 418         };
 419         self.cx.trace_macros_diag();
 420         krate
 421     }
 422
 423     // Recursively expand all macro invocations in this AST fragment.
 424     pub fn fully_expand_fragment(&mut self, input_fragment: AstFragment) -> AstFragment {
 425         let orig_expansion_data = self.cx.current_expansion.clone();
 426         let orig_force_mode = self.cx.force_mode;
 427         self.cx.current_expansion.depth = 0;
 428
 429         // Collect all macro invocations and replace them with placeholders.
 430         let (mut fragment_with_placeholders, mut invocations) =
 431             self.collect_invocations(input_fragment, &[]);
 432
 433         // Optimization: if we resolve all imports now,
 434         // we'll be able to immediately resolve most of imported macros.
 435         self.resolve_imports();
 436
 437         // Resolve paths in all invocations and produce output expanded fragments for them, but
 438         // do not insert them into our input AST fragment yet, only store in `expanded_fragments`.
 439         // The output fragments also go through expansion recursively until no invocations are left.
 440         // Unresolved macros produce dummy outputs as a recovery measure.
 441         invocations.reverse();
 442         let mut expanded_fragments = Vec::new();
 443         let mut undetermined_invocations = Vec::new();
 444         let (mut progress, mut force) = (false, !self.monotonic);
 445         loop {
 446             let (invoc, ext) = if let Some(invoc) = invocations.pop() {
 447                 invoc
 448             } else {
 449                 self.resolve_imports();
 450                 if undetermined_invocations.is_empty() {
 451                     break;
 452                 }
 453                 invocations = mem::take(&mut undetermined_invocations);
 454                 force = !mem::replace(&mut progress, false);
 455                 if force && self.monotonic {
 456                     self.cx.sess.delay_span_bug(
 457                         invocations.last().unwrap().0.span(),
 458                         "expansion entered force mode without producing any errors",
 459                     );
 460                 }
 461                 continue;
 462             };
 463
 464             let ext = match ext {
 465                 Some(ext) => ext,
 466                 None => {
 467                     let eager_expansion_root = if self.monotonic {
 468                         invoc.expansion_data.id
 469                     } else {
 470                         orig_expansion_data.id
 471                     };
 472                     match self.cx.resolver.resolve_macro_invocation(
 473                         &invoc,
 474                         eager_expansion_root,
 475                         force,
 476                     ) {
 477                         Ok(ext) => ext,
 478                         Err(Indeterminate) => {
 479                             // Cannot resolve, will retry this invocation later.
 480                             undetermined_invocations.push((invoc, None));
 481                             continue;
 482                         }
 483                     }
 484                 }
 485             };
 486
 487             let ExpansionData { depth, id: expn_id, .. } = invoc.expansion_data;
 488             self.cx.current_expansion = invoc.expansion_data.clone();
 489             self.cx.force_mode = force;
 490
 491             let fragment_kind = invoc.fragment_kind;
 492             let (expanded_fragment, new_invocations) = match self.expand_invoc(invoc, &ext.kind) {
 493                 ExpandResult::Ready(fragment) => {
 494                     let mut derive_invocations = Vec::new();
 495                     let derive_placeholders = self
 496                         .cx
 497                         .resolver
 498                         .take_derive_resolutions(expn_id)
 499                         .map(|derives| {
 500                             enum AnnotatableRef<'a> {
 501                                 Item(&'a P<ast::Item>),
 502                                 Stmt(&'a ast::Stmt),
 503                             }
 504                             let item = match &fragment {
 505                                 AstFragment::Items(items) => match &items[..] {
 506                                     [item] => AnnotatableRef::Item(item),
 507                                     _ => unreachable!(),
 508                                 },
 509                                 AstFragment::Stmts(stmts) => match &stmts[..] {
 510                                     [stmt] => AnnotatableRef::Stmt(stmt),
 511                                     _ => unreachable!(),
 512                                 },
 513                                 _ => unreachable!(),
 514                             };
 515
 516                             derive_invocations.reserve(derives.len());
 517                             derives
 518                                 .into_iter()
 519                                 .map(|(path, _exts)| {
 520                                     // FIXME: Consider using the derive resolutions (`_exts`)
 521                                     // instead of enqueuing the derives to be resolved again later.
 522                                     let expn_id = ExpnId::fresh(None);
 523                                     derive_invocations.push((
 524                                         Invocation {
 525                                             kind: InvocationKind::Derive {
 526                                                 path,
 527                                                 item: match item {
 528                                                     AnnotatableRef::Item(item) => {
 529                                                         Annotatable::Item(item.clone())
 530                                                     }
 531                                                     AnnotatableRef::Stmt(stmt) => {
 532                                                         Annotatable::Stmt(P(stmt.clone()))
 533                                                     }
 534                                                 },
 535                                             },
 536                                             fragment_kind,
 537                                             expansion_data: ExpansionData {
 538                                                 id: expn_id,
 539                                                 ..self.cx.current_expansion.clone()
 540                                             },
 541                                         },
 542                                         None,
 543                                     ));
 544                                     NodeId::placeholder_from_expn_id(expn_id)
 545                                 })
 546                                 .collect::<Vec<_>>()
 547                         })
 548                         .unwrap_or_default();
 549
 550                     let (fragment, collected_invocations) =
 551                         self.collect_invocations(fragment, &derive_placeholders);
 552                     // We choose to expand any derive invocations associated with this macro invocation
 553                     // *before* any macro invocations collected from the output fragment
 554                     derive_invocations.extend(collected_invocations);
 555                     (fragment, derive_invocations)
 556                 }
 557                 ExpandResult::Retry(invoc) => {
 558                     if force {
 559                         self.cx.span_bug(
 560                             invoc.span(),
 561                             "expansion entered force mode but is still stuck",
 562                         );
 563                     } else {
 564                         // Cannot expand, will retry this invocation later.
 565                         undetermined_invocations.push((invoc, Some(ext)));
 566                         continue;
 567                     }
 568                 }
 569             };
 570
 571             progress = true;
 572             if expanded_fragments.len() < depth {
 573                 expanded_fragments.push(Vec::new());
 574             }
 575             expanded_fragments[depth - 1].push((expn_id, expanded_fragment));
 576             invocations.extend(new_invocations.into_iter().rev());
 577         }
 578
 579         self.cx.current_expansion = orig_expansion_data;
 580         self.cx.force_mode = orig_force_mode;
 581
 582         // Finally incorporate all the expanded macros into the input AST fragment.
 583         let mut placeholder_expander = PlaceholderExpander::new(self.cx, self.monotonic);
 584         while let Some(expanded_fragments) = expanded_fragments.pop() {
 585             for (expn_id, expanded_fragment) in expanded_fragments.into_iter().rev() {
 586                 placeholder_expander
 587                     .add(NodeId::placeholder_from_expn_id(expn_id), expanded_fragment);
 588             }
 589         }
 590         fragment_with_placeholders.mut_visit_with(&mut placeholder_expander);
 591         fragment_with_placeholders
 592     }
 593
 594     fn resolve_imports(&mut self) {
 595         if self.monotonic {
 596             self.cx.resolver.resolve_imports();
 597         }
 598     }
 599
 600     /// Collects all macro invocations reachable at this time in this AST fragment, and replace
 601     /// them with "placeholders" - dummy macro invocations with specially crafted `NodeId`s.
 602     /// Then call into resolver that builds a skeleton ("reduced graph") of the fragment and
 603     /// prepares data for resolving paths of macro invocations.
 604     fn collect_invocations(
 605         &mut self,
 606         mut fragment: AstFragment,
 607         extra_placeholders: &[NodeId],
 608     ) -> (AstFragment, Vec<(Invocation, Option<Lrc<SyntaxExtension>>)>) {
 609         // Resolve `$crate`s in the fragment for pretty-printing.
 610         self.cx.resolver.resolve_dollar_crates();
 611
 612         let invocations = {
 613             let mut collector = InvocationCollector {
 614                 // Non-derive macro invocations cannot see the results of cfg expansion - they
 615                 // will either be removed along with the item, or invoked before the cfg/cfg_attr
 616                 // attribute is expanded. Therefore, we don't need to configure the tokens
 617                 // Derive macros *can* see the results of cfg-expansion - they are handled
 618                 // specially in `fully_expand_fragment`
 619                 cfg: StripUnconfigured {
 620                     sess: &self.cx.sess,
 621                     features: self.cx.ecfg.features,
 622                     config_tokens: false,
 623                 },
 624                 cx: self.cx,
 625                 invocations: Vec::new(),
 626                 monotonic: self.monotonic,
 627             };
 628             fragment.mut_visit_with(&mut collector);
 629             fragment.add_placeholders(extra_placeholders);
 630             collector.invocations
 631         };
 632
 633         if self.monotonic {
 634             self.cx
 635                 .resolver
 636                 .visit_ast_fragment_with_placeholders(self.cx.current_expansion.id, &fragment);
 637         }
 638
 639         (fragment, invocations)
 640     }
 641
 642     fn error_recursion_limit_reached(&mut self) {
 643         let expn_data = self.cx.current_expansion.id.expn_data();
 644         let suggested_limit = self.cx.ecfg.recursion_limit * 2;
 645         self.cx
 646             .struct_span_err(
 647                 expn_data.call_site,
 648                 &format!("recursion limit reached while expanding `{}`", expn_data.kind.descr()),
 649             )
 650             .help(&format!(
 651                 "consider adding a `#![recursion_limit=\"{}\"]` attribute to your crate (`{}`)",
 652                 suggested_limit, self.cx.ecfg.crate_name,
 653             ))
 654             .emit();
 655         self.cx.trace_macros_diag();
 656     }
 657
 658     /// A macro's expansion does not fit in this fragment kind.
 659     /// For example, a non-type macro in a type position.
 660     fn error_wrong_fragment_kind(&mut self, kind: AstFragmentKind, mac: &ast::MacCall, span: Span) {
 661         let msg = format!(
 662             "non-{kind} macro in {kind} position: {path}",
 663             kind = kind.name(),
 664             path = pprust::path_to_string(&mac.path),
 665         );
 666         self.cx.span_err(span, &msg);
 667         self.cx.trace_macros_diag();
 668     }
 669
 670     fn expand_invoc(
 671         &mut self,
 672         invoc: Invocation,
 673         ext: &SyntaxExtensionKind,
 674     ) -> ExpandResult<AstFragment, Invocation> {
 675         let recursion_limit =
 676             self.cx.reduced_recursion_limit.unwrap_or(self.cx.ecfg.recursion_limit);
 677         if !recursion_limit.value_within_limit(self.cx.current_expansion.depth) {
 678             if self.cx.reduced_recursion_limit.is_none() {
 679                 self.error_recursion_limit_reached();
 680             }
 681
 682             // Reduce the recursion limit by half each time it triggers.
 683             self.cx.reduced_recursion_limit = Some(recursion_limit / 2);
 684
 685             return ExpandResult::Ready(invoc.fragment_kind.dummy(invoc.span()));
 686         }
 687
 688         let (fragment_kind, span) = (invoc.fragment_kind, invoc.span());
 689         ExpandResult::Ready(match invoc.kind {
 690             InvocationKind::Bang { mac, .. } => match ext {
 691                 SyntaxExtensionKind::Bang(expander) => {
 692                     let tok_result = match expander.expand(self.cx, span, mac.args.inner_tokens()) {
 693                         Err(_) => return ExpandResult::Ready(fragment_kind.dummy(span)),
 694                         Ok(ts) => ts,
 695                     };
 696                     self.parse_ast_fragment(tok_result, fragment_kind, &mac.path, span)
 697                 }
 698                 SyntaxExtensionKind::LegacyBang(expander) => {
 699                     let prev = self.cx.current_expansion.prior_type_ascription;
 700                     self.cx.current_expansion.prior_type_ascription = mac.prior_type_ascription;
 701                     let tok_result = expander.expand(self.cx, span, mac.args.inner_tokens());
 702                     let result = if let Some(result) = fragment_kind.make_from(tok_result) {
 703                         result
 704                     } else {
 705                         self.error_wrong_fragment_kind(fragment_kind, &mac, span);
 706                         fragment_kind.dummy(span)
 707                     };
 708                     self.cx.current_expansion.prior_type_ascription = prev;
 709                     result
 710                 }
 711                 _ => unreachable!(),
 712             },
 713             InvocationKind::Attr { attr, pos, mut item, derives } => match ext {
 714                 SyntaxExtensionKind::Attr(expander) => {
 715                     self.gate_proc_macro_input(&item);
 716                     self.gate_proc_macro_attr_item(span, &item);
 717                     let mut fake_tokens = false;
 718                     if let Annotatable::Item(item_inner) = &item {
 719                         if let ItemKind::Mod(_, mod_kind) = &item_inner.kind {
 720                             // FIXME: Collect tokens and use them instead of generating
 721                             // fake ones. These are unstable, so it needs to be
 722                             // fixed prior to stabilization
 723                             // Fake tokens when we are invoking an inner attribute, and:
 724                             fake_tokens = matches!(attr.style, ast::AttrStyle::Inner) &&
 725                                 // We are invoking an attribute on the crate root, or an outline
 726                                 // module
 727                                 (item_inner.ident.name.is_empty() || !matches!(mod_kind, ast::ModKind::Loaded(_, Inline::Yes, _)));
 728                         }
 729                     }
 730                     let tokens = if fake_tokens {
 731                         rustc_parse::fake_token_stream(
 732                             &self.cx.sess.parse_sess,
 733                             &item.into_nonterminal(),
 734                         )
 735                     } else {
 736                         item.into_tokens(&self.cx.sess.parse_sess)
 737                     };
 738                     let attr_item = attr.unwrap_normal_item();
 739                     if let MacArgs::Eq(..) = attr_item.args {
 740                         self.cx.span_err(span, "key-value macro attributes are not supported");
 741                     }
 742                     let inner_tokens = attr_item.args.inner_tokens();
 743                     let tok_result = match expander.expand(self.cx, span, inner_tokens, tokens) {
 744                         Err(_) => return ExpandResult::Ready(fragment_kind.dummy(span)),
 745                         Ok(ts) => ts,
 746                     };
 747                     self.parse_ast_fragment(tok_result, fragment_kind, &attr_item.path, span)
 748                 }
 749                 SyntaxExtensionKind::LegacyAttr(expander) => {
 750                     match validate_attr::parse_meta(&self.cx.sess.parse_sess, &attr) {
 751                         Ok(meta) => {
 752                             let items = match expander.expand(self.cx, span, &meta, item) {
 753                                 ExpandResult::Ready(items) => items,
 754                                 ExpandResult::Retry(item) => {
 755                                     // Reassemble the original invocation for retrying.
 756                                     return ExpandResult::Retry(Invocation {
 757                                         kind: InvocationKind::Attr { attr, pos, item, derives },
 758                                         ..invoc
 759                                     });
 760                                 }
 761                             };
 762                             if fragment_kind == AstFragmentKind::Expr && items.is_empty() {
 763                                 let msg =
 764                                     "removing an expression is not supported in this position";
 765                                 self.cx.span_err(span, msg);
 766                                 fragment_kind.dummy(span)
 767                             } else {
 768                                 fragment_kind.expect_from_annotatables(items)
 769                             }
 770                         }
 771                         Err(mut err) => {
 772                             err.emit();
 773                             fragment_kind.dummy(span)
 774                         }
 775                     }
 776                 }
 777                 SyntaxExtensionKind::NonMacroAttr { mark_used } => {
 778                     self.cx.sess.mark_attr_known(&attr);
 779                     if *mark_used {
 780                         self.cx.sess.mark_attr_used(&attr);
 781                     }
 782                     item.visit_attrs(|attrs| attrs.insert(pos, attr));
 783                     fragment_kind.expect_from_annotatables(iter::once(item))
 784                 }
 785                 _ => unreachable!(),
 786             },
 787             InvocationKind::Derive { path, item } => match ext {
 788                 SyntaxExtensionKind::Derive(expander)
 789                 | SyntaxExtensionKind::LegacyDerive(expander) => {
 790                     if let SyntaxExtensionKind::Derive(..) = ext {
 791                         self.gate_proc_macro_input(&item);
 792                     }
 793                     let meta = ast::MetaItem { kind: ast::MetaItemKind::Word, span, path };
 794                     let items = match expander.expand(self.cx, span, &meta, item) {
 795                         ExpandResult::Ready(items) => items,
 796                         ExpandResult::Retry(item) => {
 797                             // Reassemble the original invocation for retrying.
 798                             return ExpandResult::Retry(Invocation {
 799                                 kind: InvocationKind::Derive { path: meta.path, item },
 800                                 ..invoc
 801                             });
 802                         }
 803                     };
 804                     fragment_kind.expect_from_annotatables(items)
 805                 }
 806                 _ => unreachable!(),
 807             },
 808         })
 809     }
 810
 811     fn gate_proc_macro_attr_item(&self, span: Span, item: &Annotatable) {
 812         let kind = match item {
 813             Annotatable::Item(_)
 814             | Annotatable::TraitItem(_)
 815             | Annotatable::ImplItem(_)
 816             | Annotatable::ForeignItem(_) => return,
 817             Annotatable::Stmt(stmt) => {
 818                 // Attributes are stable on item statements,
 819                 // but unstable on all other kinds of statements
 820                 if stmt.is_item() {
 821                     return;
 822                 }
 823                 "statements"
 824             }
 825             Annotatable::Expr(_) => "expressions",
 826             Annotatable::Arm(..)
 827             | Annotatable::ExprField(..)
 828             | Annotatable::PatField(..)
 829             | Annotatable::GenericParam(..)
 830             | Annotatable::Param(..)
 831             | Annotatable::FieldDef(..)
 832             | Annotatable::Variant(..) => panic!("unexpected annotatable"),
 833         };
 834         if self.cx.ecfg.proc_macro_hygiene() {
 835             return;
 836         }
 837         feature_err(
 838             &self.cx.sess.parse_sess,
 839             sym::proc_macro_hygiene,
 840             span,
 841             &format!("custom attributes cannot be applied to {}", kind),
 842         )
 843         .emit();
 844     }
 845
 846     fn gate_proc_macro_input(&self, annotatable: &Annotatable) {
 847         struct GateProcMacroInput<'a> {
 848             parse_sess: &'a ParseSess,
 849         }
 850
 851         impl<'ast, 'a> Visitor<'ast> for GateProcMacroInput<'a> {
 852             fn visit_item(&mut self, item: &'ast ast::Item) {
 853                 match &item.kind {
 854                     ast::ItemKind::Mod(_, mod_kind)
 855                         if !matches!(mod_kind, ModKind::Loaded(_, Inline::Yes, _)) =>
 856                     {
 857                         feature_err(
 858                             self.parse_sess,
 859                             sym::proc_macro_hygiene,
 860                             item.span,
 861                             "non-inline modules in proc macro input are unstable",
 862                         )
 863                         .emit();
 864                     }
 865                     _ => {}
 866                 }
 867
 868                 visit::walk_item(self, item);
 869             }
 870         }
 871
 872         if !self.cx.ecfg.proc_macro_hygiene() {
 873             annotatable
 874                 .visit_with(&mut GateProcMacroInput { parse_sess: &self.cx.sess.parse_sess });
 875         }
 876     }
 877
 878     fn parse_ast_fragment(
 879         &mut self,
 880         toks: TokenStream,
 881         kind: AstFragmentKind,
 882         path: &Path,
 883         span: Span,
 884     ) -> AstFragment {
 885         let mut parser = self.cx.new_parser_from_tts(toks);
 886         match parse_ast_fragment(&mut parser, kind) {
 887             Ok(fragment) => {
 888                 ensure_complete_parse(&mut parser, path, kind.name(), span);
 889                 fragment
 890             }
 891             Err(mut err) => {
 892                 if err.span.is_dummy() {
 893                     err.set_span(span);
 894                 }
 895                 annotate_err_with_kind(&mut err, kind, span);
 896                 err.emit();
 897                 self.cx.trace_macros_diag();
 898                 kind.dummy(span)
 899             }
 900         }
 901     }
 902 }
 903
 904 pub fn parse_ast_fragment<'a>(
 905     this: &mut Parser<'a>,
 906     kind: AstFragmentKind,
 907 ) -> PResult<'a, AstFragment> {
 908     Ok(match kind {
 909         AstFragmentKind::Items => {
 910             let mut items = SmallVec::new();
 911             while let Some(item) = this.parse_item(ForceCollect::No)? {
 912                 items.push(item);
 913             }
 914             AstFragment::Items(items)
 915         }
 916         AstFragmentKind::TraitItems => {
 917             let mut items = SmallVec::new();
 918             while let Some(item) = this.parse_trait_item(ForceCollect::No)? {
 919                 items.extend(item);
 920             }
 921             AstFragment::TraitItems(items)
 922         }
 923         AstFragmentKind::ImplItems => {
 924             let mut items = SmallVec::new();
 925             while let Some(item) = this.parse_impl_item(ForceCollect::No)? {
 926                 items.extend(item);
 927             }
 928             AstFragment::ImplItems(items)
 929         }
 930         AstFragmentKind::ForeignItems => {
 931             let mut items = SmallVec::new();
 932             while let Some(item) = this.parse_foreign_item(ForceCollect::No)? {
 933                 items.extend(item);
 934             }
 935             AstFragment::ForeignItems(items)
 936         }
 937         AstFragmentKind::Stmts => {
 938             let mut stmts = SmallVec::new();
 939             // Won't make progress on a `}`.
 940             while this.token != token::Eof && this.token != token::CloseDelim(token::Brace) {
 941                 if let Some(stmt) = this.parse_full_stmt(AttemptLocalParseRecovery::Yes)? {
 942                     stmts.push(stmt);
 943                 }
 944             }
 945             AstFragment::Stmts(stmts)
 946         }
 947         AstFragmentKind::Expr => AstFragment::Expr(this.parse_expr()?),
 948         AstFragmentKind::OptExpr => {
 949             if this.token != token::Eof {
 950                 AstFragment::OptExpr(Some(this.parse_expr()?))
 951             } else {
 952                 AstFragment::OptExpr(None)
 953             }
 954         }
 955         AstFragmentKind::Ty => AstFragment::Ty(this.parse_ty()?),
 956         AstFragmentKind::Pat => {
 957             AstFragment::Pat(this.parse_pat_allow_top_alt(None, RecoverComma::No)?)
 958         }
 959         AstFragmentKind::Arms
 960         | AstFragmentKind::Fields
 961         | AstFragmentKind::FieldPats
 962         | AstFragmentKind::GenericParams
 963         | AstFragmentKind::Params
 964         | AstFragmentKind::StructFields
 965         | AstFragmentKind::Variants => panic!("unexpected AST fragment kind"),
 966     })
 967 }
 968
 969 pub fn ensure_complete_parse<'a>(
 970     this: &mut Parser<'a>,
 971     macro_path: &Path,
 972     kind_name: &str,
 973     span: Span,
 974 ) {
 975     if this.token != token::Eof {
 976         let token = pprust::token_to_string(&this.token);
 977         let msg = format!("macro expansion ignores token `{}` and any following", token);
 978         // Avoid emitting backtrace info twice.
 979         let def_site_span = this.token.span.with_ctxt(SyntaxContext::root());
 980         let mut err = this.struct_span_err(def_site_span, &msg);
 981         err.span_label(span, "caused by the macro expansion here");
 982         let msg = format!(
 983             "the usage of `{}!` is likely invalid in {} context",
 984             pprust::path_to_string(macro_path),
 985             kind_name,
 986         );
 987         err.note(&msg);
 988         let semi_span = this.sess.source_map().next_point(span);
 989
 990         let semi_full_span = semi_span.to(this.sess.source_map().next_point(semi_span));
 991         match this.sess.source_map().span_to_snippet(semi_full_span) {
 992             Ok(ref snippet) if &snippet[..] != ";" && kind_name == "expression" => {
 993                 err.span_suggestion(
 994                     semi_span,
 995                     "you might be missing a semicolon here",
 996                     ";".to_owned(),
 997                     Applicability::MaybeIncorrect,
 998                 );
 999             }
1000             _ => {}
1001         }
1002         err.emit();
1003     }
1004 }
1005
1006 struct InvocationCollector<'a, 'b> {
1007     cx: &'a mut ExtCtxt<'b>,
1008     cfg: StripUnconfigured<'a>,
1009     invocations: Vec<(Invocation, Option<Lrc<SyntaxExtension>>)>,
1010     monotonic: bool,
1011 }
1012
1013 impl<'a, 'b> InvocationCollector<'a, 'b> {
1014     fn collect(&mut self, fragment_kind: AstFragmentKind, kind: InvocationKind) -> AstFragment {
1015         let expn_id = ExpnId::fresh(None);
1016         let vis = kind.placeholder_visibility();
1017         self.invocations.push((
1018             Invocation {
1019                 kind,
1020                 fragment_kind,
1021                 expansion_data: ExpansionData {
1022                     id: expn_id,
1023                     depth: self.cx.current_expansion.depth + 1,
1024                     ..self.cx.current_expansion.clone()
1025                 },
1026             },
1027             None,
1028         ));
1029         placeholder(fragment_kind, NodeId::placeholder_from_expn_id(expn_id), vis)
1030     }
1031
1032     fn collect_bang(
1033         &mut self,
1034         mac: ast::MacCall,
1035         span: Span,
1036         kind: AstFragmentKind,
1037     ) -> AstFragment {
1038         self.collect(kind, InvocationKind::Bang { mac, span })
1039     }
1040
1041     fn collect_attr(
1042         &mut self,
1043         (attr, pos, derives): (ast::Attribute, usize, Vec<Path>),
1044         item: Annotatable,
1045         kind: AstFragmentKind,
1046     ) -> AstFragment {
1047         self.collect(kind, InvocationKind::Attr { attr, pos, item, derives })
1048     }
1049
1050     /// If `item` is an attribute invocation, remove the attribute and return it together with
1051     /// its position and derives following it. We have to collect the derives in order to resolve
1052     /// legacy derive helpers (helpers written before derives that introduce them).
1053     fn take_first_attr(
1054         &mut self,
1055         item: &mut impl AstLike,
1056     ) -> Option<(ast::Attribute, usize, Vec<Path>)> {
1057         let mut attr = None;
1058
1059         item.visit_attrs(|attrs| {
1060             attr = attrs
1061                 .iter()
1062                 .position(|a| !self.cx.sess.is_attr_known(a) && !is_builtin_attr(a))
1063                 .map(|attr_pos| {
1064                     let attr = attrs.remove(attr_pos);
1065                     let following_derives = attrs[attr_pos..]
1066                         .iter()
1067                         .filter(|a| a.has_name(sym::derive))
1068                         .flat_map(|a| a.meta_item_list().unwrap_or_default())
1069                         .filter_map(|nested_meta| match nested_meta {
1070                             NestedMetaItem::MetaItem(ast::MetaItem {
1071                                 kind: MetaItemKind::Word,
1072                                 path,
1073                                 ..
1074                             }) => Some(path),
1075                             _ => None,
1076                         })
1077                         .collect();
1078
1079                     (attr, attr_pos, following_derives)
1080                 })
1081         });
1082
1083         attr
1084     }
1085
1086     fn configure<T: AstLike>(&mut self, node: T) -> Option<T> {
1087         self.cfg.configure(node)
1088     }
1089
1090     // Detect use of feature-gated or invalid attributes on macro invocations
1091     // since they will not be detected after macro expansion.
1092     fn check_attributes(&mut self, attrs: &[ast::Attribute]) {
1093         let features = self.cx.ecfg.features.unwrap();
1094         let mut attrs = attrs.iter().peekable();
1095         let mut span: Option<Span> = None;
1096         while let Some(attr) = attrs.next() {
1097             rustc_ast_passes::feature_gate::check_attribute(attr, self.cx.sess, features);
1098             validate_attr::check_meta(&self.cx.sess.parse_sess, attr);
1099
1100             let current_span = if let Some(sp) = span { sp.to(attr.span) } else { attr.span };
1101             span = Some(current_span);
1102
1103             if attrs.peek().map_or(false, |next_attr| next_attr.doc_str().is_some()) {
1104                 continue;
1105             }
1106
1107             if attr.doc_str().is_some() {
1108                 self.cx.sess.parse_sess.buffer_lint_with_diagnostic(
1109                     &UNUSED_DOC_COMMENTS,
1110                     current_span,
1111                     ast::CRATE_NODE_ID,
1112                     "unused doc comment",
1113                     BuiltinLintDiagnostics::UnusedDocComment(attr.span),
1114                 );
1115             }
1116         }
1117     }
1118 }
1119
1120 impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
1121     fn visit_expr(&mut self, expr: &mut P<ast::Expr>) {
1122         self.cfg.configure_expr(expr);
1123         visit_clobber(expr.deref_mut(), |mut expr| {
1124             if let Some(attr) = self.take_first_attr(&mut expr) {
1125                 // Collect the invoc regardless of whether or not attributes are permitted here
1126                 // expansion will eat the attribute so it won't error later.
1127                 self.cfg.maybe_emit_expr_attr_err(&attr.0);
1128
1129                 // AstFragmentKind::Expr requires the macro to emit an expression.
1130                 return self
1131                     .collect_attr(attr, Annotatable::Expr(P(expr)), AstFragmentKind::Expr)
1132                     .make_expr()
1133                     .into_inner();
1134             }
1135
1136             if let ast::ExprKind::MacCall(mac) = expr.kind {
1137                 self.check_attributes(&expr.attrs);
1138                 self.collect_bang(mac, expr.span, AstFragmentKind::Expr).make_expr().into_inner()
1139             } else {
1140                 ensure_sufficient_stack(|| noop_visit_expr(&mut expr, self));
1141                 expr
1142             }
1143         });
1144     }
1145
1146     fn flat_map_arm(&mut self, arm: ast::Arm) -> SmallVec<[ast::Arm; 1]> {
1147         let mut arm = configure!(self, arm);
1148
1149         if let Some(attr) = self.take_first_attr(&mut arm) {
1150             return self
1151                 .collect_attr(attr, Annotatable::Arm(arm), AstFragmentKind::Arms)
1152                 .make_arms();
1153         }
1154
1155         noop_flat_map_arm(arm, self)
1156     }
1157
1158     fn flat_map_expr_field(&mut self, field: ast::ExprField) -> SmallVec<[ast::ExprField; 1]> {
1159         let mut field = configure!(self, field);
1160
1161         if let Some(attr) = self.take_first_attr(&mut field) {
1162             return self
1163                 .collect_attr(attr, Annotatable::ExprField(field), AstFragmentKind::Fields)
1164                 .make_expr_fields();
1165         }
1166
1167         noop_flat_map_expr_field(field, self)
1168     }
1169
1170     fn flat_map_pat_field(&mut self, fp: ast::PatField) -> SmallVec<[ast::PatField; 1]> {
1171         let mut fp = configure!(self, fp);
1172
1173         if let Some(attr) = self.take_first_attr(&mut fp) {
1174             return self
1175                 .collect_attr(attr, Annotatable::PatField(fp), AstFragmentKind::FieldPats)
1176                 .make_pat_fields();
1177         }
1178
1179         noop_flat_map_pat_field(fp, self)
1180     }
1181
1182     fn flat_map_param(&mut self, p: ast::Param) -> SmallVec<[ast::Param; 1]> {
1183         let mut p = configure!(self, p);
1184
1185         if let Some(attr) = self.take_first_attr(&mut p) {
1186             return self
1187                 .collect_attr(attr, Annotatable::Param(p), AstFragmentKind::Params)
1188                 .make_params();
1189         }
1190
1191         noop_flat_map_param(p, self)
1192     }
1193
1194     fn flat_map_field_def(&mut self, sf: ast::FieldDef) -> SmallVec<[ast::FieldDef; 1]> {
1195         let mut sf = configure!(self, sf);
1196
1197         if let Some(attr) = self.take_first_attr(&mut sf) {
1198             return self
1199                 .collect_attr(attr, Annotatable::FieldDef(sf), AstFragmentKind::StructFields)
1200                 .make_field_defs();
1201         }
1202
1203         noop_flat_map_field_def(sf, self)
1204     }
1205
1206     fn flat_map_variant(&mut self, variant: ast::Variant) -> SmallVec<[ast::Variant; 1]> {
1207         let mut variant = configure!(self, variant);
1208
1209         if let Some(attr) = self.take_first_attr(&mut variant) {
1210             return self
1211                 .collect_attr(attr, Annotatable::Variant(variant), AstFragmentKind::Variants)
1212                 .make_variants();
1213         }
1214
1215         noop_flat_map_variant(variant, self)
1216     }
1217
1218     fn filter_map_expr(&mut self, expr: P<ast::Expr>) -> Option<P<ast::Expr>> {
1219         let expr = configure!(self, expr);
1220         expr.filter_map(|mut expr| {
1221             if let Some(attr) = self.take_first_attr(&mut expr) {
1222                 self.cfg.maybe_emit_expr_attr_err(&attr.0);
1223
1224                 return self
1225                     .collect_attr(attr, Annotatable::Expr(P(expr)), AstFragmentKind::OptExpr)
1226                     .make_opt_expr()
1227                     .map(|expr| expr.into_inner());
1228             }
1229
1230             if let ast::ExprKind::MacCall(mac) = expr.kind {
1231                 self.check_attributes(&expr.attrs);
1232                 self.collect_bang(mac, expr.span, AstFragmentKind::OptExpr)
1233                     .make_opt_expr()
1234                     .map(|expr| expr.into_inner())
1235             } else {
1236                 Some({
1237                     noop_visit_expr(&mut expr, self);
1238                     expr
1239                 })
1240             }
1241         })
1242     }
1243
1244     fn visit_pat(&mut self, pat: &mut P<ast::Pat>) {
1245         match pat.kind {
1246             PatKind::MacCall(_) => {}
1247             _ => return noop_visit_pat(pat, self),
1248         }
1249
1250         visit_clobber(pat, |mut pat| match mem::replace(&mut pat.kind, PatKind::Wild) {
1251             PatKind::MacCall(mac) => {
1252                 self.collect_bang(mac, pat.span, AstFragmentKind::Pat).make_pat()
1253             }
1254             _ => unreachable!(),
1255         });
1256     }
1257
1258     fn flat_map_stmt(&mut self, stmt: ast::Stmt) -> SmallVec<[ast::Stmt; 1]> {
1259         let mut stmt = configure!(self, stmt);
1260
1261         // we'll expand attributes on expressions separately
1262         if !stmt.is_expr() {
1263             if let Some(attr) = self.take_first_attr(&mut stmt) {
1264                 return self
1265                     .collect_attr(attr, Annotatable::Stmt(P(stmt)), AstFragmentKind::Stmts)
1266                     .make_stmts();
1267             }
1268         }
1269
1270         if let StmtKind::MacCall(mac) = stmt.kind {
1271             let MacCallStmt { mac, style, attrs, tokens: _ } = mac.into_inner();
1272             self.check_attributes(&attrs);
1273             let mut placeholder =
1274                 self.collect_bang(mac, stmt.span, AstFragmentKind::Stmts).make_stmts();
1275
1276             // If this is a macro invocation with a semicolon, then apply that
1277             // semicolon to the final statement produced by expansion.
1278             if style == MacStmtStyle::Semicolon {
1279                 if let Some(stmt) = placeholder.pop() {
1280                     placeholder.push(stmt.add_trailing_semicolon());
1281                 }
1282             }
1283
1284             return placeholder;
1285         }
1286
1287         // The placeholder expander gives ids to statements, so we avoid folding the id here.
1288         let ast::Stmt { id, kind, span } = stmt;
1289         noop_flat_map_stmt_kind(kind, self)
1290             .into_iter()
1291             .map(|kind| ast::Stmt { id, kind, span })
1292             .collect()
1293     }
1294
1295     fn visit_block(&mut self, block: &mut P<Block>) {
1296         let orig_dir_ownership = mem::replace(
1297             &mut self.cx.current_expansion.dir_ownership,
1298             DirOwnership::UnownedViaBlock,
1299         );
1300         noop_visit_block(block, self);
1301         self.cx.current_expansion.dir_ownership = orig_dir_ownership;
1302     }
1303
1304     fn flat_map_item(&mut self, item: P<ast::Item>) -> SmallVec<[P<ast::Item>; 1]> {
1305         let mut item = configure!(self, item);
1306
1307         if let Some(attr) = self.take_first_attr(&mut item) {
1308             return self
1309                 .collect_attr(attr, Annotatable::Item(item), AstFragmentKind::Items)
1310                 .make_items();
1311         }
1312
1313         let mut attrs = mem::take(&mut item.attrs); // We do this to please borrowck.
1314         let ident = item.ident;
1315         let span = item.span;
1316
1317         match item.kind {
1318             ast::ItemKind::MacCall(..) => {
1319                 item.attrs = attrs;
1320                 self.check_attributes(&item.attrs);
1321                 item.and_then(|item| match item.kind {
1322                     ItemKind::MacCall(mac) => {
1323                         self.collect_bang(mac, span, AstFragmentKind::Items).make_items()
1324                     }
1325                     _ => unreachable!(),
1326                 })
1327             }
1328             ast::ItemKind::Mod(_, ref mut mod_kind) if ident != Ident::invalid() => {
1329                 let (file_path, dir_path, dir_ownership) = match mod_kind {
1330                     ModKind::Loaded(_, inline, _) => {
1331                         // Inline `mod foo { ... }`, but we still need to push directories.
1332                         let (dir_path, dir_ownership) = mod_dir_path(
1333                             &self.cx.sess,
1334                             ident,
1335                             &attrs,
1336                             &self.cx.current_expansion.module,
1337                             self.cx.current_expansion.dir_ownership,
1338                             *inline,
1339                         );
1340                         item.attrs = attrs;
1341                         (None, dir_path, dir_ownership)
1342                     }
1343                     ModKind::Unloaded => {
1344                         // We have an outline `mod foo;` so we need to parse the file.
1345                         let old_attrs_len = attrs.len();
1346                         let ParsedExternalMod {
1347                             mut items,
1348                             inner_span,
1349                             file_path,
1350                             dir_path,
1351                             dir_ownership,
1352                         } = parse_external_mod(
1353                             &self.cx.sess,
1354                             ident,
1355                             span,
1356                             &self.cx.current_expansion.module,
1357                             self.cx.current_expansion.dir_ownership,
1358                             &mut attrs,
1359                         );
1360
1361                         if let Some(extern_mod_loaded) = self.cx.extern_mod_loaded {
1362                             (attrs, items) = extern_mod_loaded(ident, attrs, items, inner_span);
1363                         }
1364
1365                         *mod_kind = ModKind::Loaded(items, Inline::No, inner_span);
1366                         item.attrs = attrs;
1367                         if item.attrs.len() > old_attrs_len {
1368                             // If we loaded an out-of-line module and added some inner attributes,
1369                             // then we need to re-configure it and re-collect attributes for
1370                             // resolution and expansion.
1371                             item = configure!(self, item);
1372
1373                             if let Some(attr) = self.take_first_attr(&mut item) {
1374                                 return self
1375                                     .collect_attr(
1376                                         attr,
1377                                         Annotatable::Item(item),
1378                                         AstFragmentKind::Items,
1379                                     )
1380                                     .make_items();
1381                             }
1382                         }
1383                         (Some(file_path), dir_path, dir_ownership)
1384                     }
1385                 };
1386
1387                 // Set the module info before we flat map.
1388                 let mut module = self.cx.current_expansion.module.with_dir_path(dir_path);
1389                 module.mod_path.push(ident);
1390                 if let Some(file_path) = file_path {
1391                     module.file_path_stack.push(file_path);
1392                 }
1393
1394                 let orig_module =
1395                     mem::replace(&mut self.cx.current_expansion.module, Rc::new(module));
1396                 let orig_dir_ownership =
1397                     mem::replace(&mut self.cx.current_expansion.dir_ownership, dir_ownership);
1398
1399                 let result = noop_flat_map_item(item, self);
1400
1401                 // Restore the module info.
1402                 self.cx.current_expansion.dir_ownership = orig_dir_ownership;
1403                 self.cx.current_expansion.module = orig_module;
1404
1405                 result
1406             }
1407             _ => {
1408                 item.attrs = attrs;
1409                 noop_flat_map_item(item, self)
1410             }
1411         }
1412     }
1413
1414     fn flat_map_trait_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
1415         let mut item = configure!(self, item);
1416
1417         if let Some(attr) = self.take_first_attr(&mut item) {
1418             return self
1419                 .collect_attr(attr, Annotatable::TraitItem(item), AstFragmentKind::TraitItems)
1420                 .make_trait_items();
1421         }
1422
1423         match item.kind {
1424             ast::AssocItemKind::MacCall(..) => {
1425                 self.check_attributes(&item.attrs);
1426                 item.and_then(|item| match item.kind {
1427                     ast::AssocItemKind::MacCall(mac) => self
1428                         .collect_bang(mac, item.span, AstFragmentKind::TraitItems)
1429                         .make_trait_items(),
1430                     _ => unreachable!(),
1431                 })
1432             }
1433             _ => noop_flat_map_assoc_item(item, self),
1434         }
1435     }
1436
1437     fn flat_map_impl_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
1438         let mut item = configure!(self, item);
1439
1440         if let Some(attr) = self.take_first_attr(&mut item) {
1441             return self
1442                 .collect_attr(attr, Annotatable::ImplItem(item), AstFragmentKind::ImplItems)
1443                 .make_impl_items();
1444         }
1445
1446         match item.kind {
1447             ast::AssocItemKind::MacCall(..) => {
1448                 self.check_attributes(&item.attrs);
1449                 item.and_then(|item| match item.kind {
1450                     ast::AssocItemKind::MacCall(mac) => self
1451                         .collect_bang(mac, item.span, AstFragmentKind::ImplItems)
1452                         .make_impl_items(),
1453                     _ => unreachable!(),
1454                 })
1455             }
1456             _ => noop_flat_map_assoc_item(item, self),
1457         }
1458     }
1459
1460     fn visit_ty(&mut self, ty: &mut P<ast::Ty>) {
1461         match ty.kind {
1462             ast::TyKind::MacCall(_) => {}
1463             _ => return noop_visit_ty(ty, self),
1464         };
1465
1466         visit_clobber(ty, |mut ty| match mem::replace(&mut ty.kind, ast::TyKind::Err) {
1467             ast::TyKind::MacCall(mac) => {
1468                 self.collect_bang(mac, ty.span, AstFragmentKind::Ty).make_ty()
1469             }
1470             _ => unreachable!(),
1471         });
1472     }
1473
1474     fn flat_map_foreign_item(
1475         &mut self,
1476         foreign_item: P<ast::ForeignItem>,
1477     ) -> SmallVec<[P<ast::ForeignItem>; 1]> {
1478         let mut foreign_item = configure!(self, foreign_item);
1479
1480         if let Some(attr) = self.take_first_attr(&mut foreign_item) {
1481             return self
1482                 .collect_attr(
1483                     attr,
1484                     Annotatable::ForeignItem(foreign_item),
1485                     AstFragmentKind::ForeignItems,
1486                 )
1487                 .make_foreign_items();
1488         }
1489
1490         match foreign_item.kind {
1491             ast::ForeignItemKind::MacCall(..) => {
1492                 self.check_attributes(&foreign_item.attrs);
1493                 foreign_item.and_then(|item| match item.kind {
1494                     ast::ForeignItemKind::MacCall(mac) => self
1495                         .collect_bang(mac, item.span, AstFragmentKind::ForeignItems)
1496                         .make_foreign_items(),
1497                     _ => unreachable!(),
1498                 })
1499             }
1500             _ => noop_flat_map_foreign_item(foreign_item, self),
1501         }
1502     }
1503
1504     fn flat_map_generic_param(
1505         &mut self,
1506         param: ast::GenericParam,
1507     ) -> SmallVec<[ast::GenericParam; 1]> {
1508         let mut param = configure!(self, param);
1509
1510         if let Some(attr) = self.take_first_attr(&mut param) {
1511             return self
1512                 .collect_attr(
1513                     attr,
1514                     Annotatable::GenericParam(param),
1515                     AstFragmentKind::GenericParams,
1516                 )
1517                 .make_generic_params();
1518         }
1519
1520         noop_flat_map_generic_param(param, self)
1521     }
1522
1523     fn visit_attribute(&mut self, at: &mut ast::Attribute) {
1524         // turn `#[doc(include="filename")]` attributes into `#[doc(include(file="filename",
1525         // contents="file contents")]` attributes
1526         if !self.cx.sess.check_name(at, sym::doc) {
1527             return noop_visit_attribute(at, self);
1528         }
1529
1530         if let Some(list) = at.meta_item_list() {
1531             if !list.iter().any(|it| it.has_name(sym::include)) {
1532                 return noop_visit_attribute(at, self);
1533             }
1534
1535             let mut items = vec![];
1536
1537             for mut it in list {
1538                 if !it.has_name(sym::include) {
1539                     items.push({
1540                         noop_visit_meta_list_item(&mut it, self);
1541                         it
1542                     });
1543                     continue;
1544                 }
1545
1546                 if let Some(file) = it.value_str() {
1547                     let err_count = self.cx.sess.parse_sess.span_diagnostic.err_count();
1548                     self.check_attributes(slice::from_ref(at));
1549                     if self.cx.sess.parse_sess.span_diagnostic.err_count() > err_count {
1550                         // avoid loading the file if they haven't enabled the feature
1551                         return noop_visit_attribute(at, self);
1552                     }
1553
1554                     let filename = match self.cx.resolve_path(&*file.as_str(), it.span()) {
1555                         Ok(filename) => filename,
1556                         Err(mut err) => {
1557                             err.emit();
1558                             continue;
1559                         }
1560                     };
1561
1562                     match self.cx.source_map().load_file(&filename) {
1563                         Ok(source_file) => {
1564                             let src = source_file
1565                                 .src
1566                                 .as_ref()
1567                                 .expect("freshly loaded file should have a source");
1568                             let src_interned = Symbol::intern(src.as_str());
1569
1570                             let include_info = vec![
1571                                 ast::NestedMetaItem::MetaItem(attr::mk_name_value_item_str(
1572                                     Ident::with_dummy_span(sym::file),
1573                                     file,
1574                                     DUMMY_SP,
1575                                 )),
1576                                 ast::NestedMetaItem::MetaItem(attr::mk_name_value_item_str(
1577                                     Ident::with_dummy_span(sym::contents),
1578                                     src_interned,
1579                                     DUMMY_SP,
1580                                 )),
1581                             ];
1582
1583                             let include_ident = Ident::with_dummy_span(sym::include);
1584                             let item = attr::mk_list_item(include_ident, include_info);
1585                             items.push(ast::NestedMetaItem::MetaItem(item));
1586                         }
1587                         Err(e) => {
1588                             let lit_span = it.name_value_literal_span().unwrap();
1589
1590                             if e.kind() == ErrorKind::InvalidData {
1591                                 self.cx
1592                                     .struct_span_err(
1593                                         lit_span,
1594                                         &format!("{} wasn't a utf-8 file", filename.display()),
1595                                     )
1596                                     .span_label(lit_span, "contains invalid utf-8")
1597                                     .emit();
1598                             } else {
1599                                 let mut err = self.cx.struct_span_err(
1600                                     lit_span,
1601                                     &format!("couldn't read {}: {}", filename.display(), e),
1602                                 );
1603                                 err.span_label(lit_span, "couldn't read file");
1604
1605                                 err.emit();
1606                             }
1607                         }
1608                     }
1609                 } else {
1610                     let mut err = self
1611                         .cx
1612                         .struct_span_err(it.span(), "expected path to external documentation");
1613
1614                     // Check if the user erroneously used `doc(include(...))` syntax.
1615                     let literal = it.meta_item_list().and_then(|list| {
1616                         if list.len() == 1 {
1617                             list[0].literal().map(|literal| &literal.kind)
1618                         } else {
1619                             None
1620                         }
1621                     });
1622
1623                     let (path, applicability) = match &literal {
1624                         Some(LitKind::Str(path, ..)) => {
1625                             (path.to_string(), Applicability::MachineApplicable)
1626                         }
1627                         _ => (String::from("<path>"), Applicability::HasPlaceholders),
1628                     };
1629
1630                     err.span_suggestion(
1631                         it.span(),
1632                         "provide a file path with `=`",
1633                         format!("include = \"{}\"", path),
1634                         applicability,
1635                     );
1636
1637                     err.emit();
1638                 }
1639             }
1640
1641             let meta = attr::mk_list_item(Ident::with_dummy_span(sym::doc), items);
1642             *at = ast::Attribute {
1643                 kind: ast::AttrKind::Normal(
1644                     AttrItem { path: meta.path, args: meta.kind.mac_args(meta.span), tokens: None },
1645                     None,
1646                 ),
1647                 span: at.span,
1648                 id: at.id,
1649                 style: at.style,
1650             };
1651         } else {
1652             noop_visit_attribute(at, self)
1653         }
1654     }
1655
1656     fn visit_id(&mut self, id: &mut ast::NodeId) {
1657         if self.monotonic {
1658             debug_assert_eq!(*id, ast::DUMMY_NODE_ID);
1659             *id = self.cx.resolver.next_node_id()
1660         }
1661     }
1662 }
1663
1664 pub struct ExpansionConfig<'feat> {
1665     pub crate_name: String,
1666     pub features: Option<&'feat Features>,
1667     pub recursion_limit: Limit,
1668     pub trace_mac: bool,
1669     pub should_test: bool,          // If false, strip `#[test]` nodes
1670     pub span_debug: bool,           // If true, use verbose debugging for `proc_macro::Span`
1671     pub proc_macro_backtrace: bool, // If true, show backtraces for proc-macro panics
1672 }
1673
1674 impl<'feat> ExpansionConfig<'feat> {
1675     pub fn default(crate_name: String) -> ExpansionConfig<'static> {
1676         ExpansionConfig {
1677             crate_name,
1678             features: None,
1679             recursion_limit: Limit::new(1024),
1680             trace_mac: false,
1681             should_test: false,
1682             span_debug: false,
1683             proc_macro_backtrace: false,
1684         }
1685     }
1686
1687     fn proc_macro_hygiene(&self) -> bool {
1688         self.features.map_or(false, |features| features.proc_macro_hygiene)
1689     }
1690 }