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, FatalError, 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                 // FIXME: this workaround issue #84569
 418                 FatalError.raise();
 419             }
 420         };
 421         self.cx.trace_macros_diag();
 422         krate
 423     }
 424
 425     // Recursively expand all macro invocations in this AST fragment.
 426     pub fn fully_expand_fragment(&mut self, input_fragment: AstFragment) -> AstFragment {
 427         let orig_expansion_data = self.cx.current_expansion.clone();
 428         let orig_force_mode = self.cx.force_mode;
 429         self.cx.current_expansion.depth = 0;
 430
 431         // Collect all macro invocations and replace them with placeholders.
 432         let (mut fragment_with_placeholders, mut invocations) =
 433             self.collect_invocations(input_fragment, &[]);
 434
 435         // Optimization: if we resolve all imports now,
 436         // we'll be able to immediately resolve most of imported macros.
 437         self.resolve_imports();
 438
 439         // Resolve paths in all invocations and produce output expanded fragments for them, but
 440         // do not insert them into our input AST fragment yet, only store in `expanded_fragments`.
 441         // The output fragments also go through expansion recursively until no invocations are left.
 442         // Unresolved macros produce dummy outputs as a recovery measure.
 443         invocations.reverse();
 444         let mut expanded_fragments = Vec::new();
 445         let mut undetermined_invocations = Vec::new();
 446         let (mut progress, mut force) = (false, !self.monotonic);
 447         loop {
 448             let (invoc, ext) = if let Some(invoc) = invocations.pop() {
 449                 invoc
 450             } else {
 451                 self.resolve_imports();
 452                 if undetermined_invocations.is_empty() {
 453                     break;
 454                 }
 455                 invocations = mem::take(&mut undetermined_invocations);
 456                 force = !mem::replace(&mut progress, false);
 457                 if force && self.monotonic {
 458                     self.cx.sess.delay_span_bug(
 459                         invocations.last().unwrap().0.span(),
 460                         "expansion entered force mode without producing any errors",
 461                     );
 462                 }
 463                 continue;
 464             };
 465
 466             let ext = match ext {
 467                 Some(ext) => ext,
 468                 None => {
 469                     let eager_expansion_root = if self.monotonic {
 470                         invoc.expansion_data.id
 471                     } else {
 472                         orig_expansion_data.id
 473                     };
 474                     match self.cx.resolver.resolve_macro_invocation(
 475                         &invoc,
 476                         eager_expansion_root,
 477                         force,
 478                     ) {
 479                         Ok(ext) => ext,
 480                         Err(Indeterminate) => {
 481                             // Cannot resolve, will retry this invocation later.
 482                             undetermined_invocations.push((invoc, None));
 483                             continue;
 484                         }
 485                     }
 486                 }
 487             };
 488
 489             let ExpansionData { depth, id: expn_id, .. } = invoc.expansion_data;
 490             self.cx.current_expansion = invoc.expansion_data.clone();
 491             self.cx.force_mode = force;
 492
 493             let fragment_kind = invoc.fragment_kind;
 494             let (expanded_fragment, new_invocations) = match self.expand_invoc(invoc, &ext.kind) {
 495                 ExpandResult::Ready(fragment) => {
 496                     let mut derive_invocations = Vec::new();
 497                     let derive_placeholders = self
 498                         .cx
 499                         .resolver
 500                         .take_derive_resolutions(expn_id)
 501                         .map(|derives| {
 502                             enum AnnotatableRef<'a> {
 503                                 Item(&'a P<ast::Item>),
 504                                 Stmt(&'a ast::Stmt),
 505                             }
 506                             let item = match &fragment {
 507                                 AstFragment::Items(items) => match &items[..] {
 508                                     [item] => AnnotatableRef::Item(item),
 509                                     _ => unreachable!(),
 510                                 },
 511                                 AstFragment::Stmts(stmts) => match &stmts[..] {
 512                                     [stmt] => AnnotatableRef::Stmt(stmt),
 513                                     _ => unreachable!(),
 514                                 },
 515                                 _ => unreachable!(),
 516                             };
 517
 518                             derive_invocations.reserve(derives.len());
 519                             derives
 520                                 .into_iter()
 521                                 .map(|(path, _exts)| {
 522                                     // FIXME: Consider using the derive resolutions (`_exts`)
 523                                     // instead of enqueuing the derives to be resolved again later.
 524                                     let expn_id = ExpnId::fresh(None);
 525                                     derive_invocations.push((
 526                                         Invocation {
 527                                             kind: InvocationKind::Derive {
 528                                                 path,
 529                                                 item: match item {
 530                                                     AnnotatableRef::Item(item) => {
 531                                                         Annotatable::Item(item.clone())
 532                                                     }
 533                                                     AnnotatableRef::Stmt(stmt) => {
 534                                                         Annotatable::Stmt(P(stmt.clone()))
 535                                                     }
 536                                                 },
 537                                             },
 538                                             fragment_kind,
 539                                             expansion_data: ExpansionData {
 540                                                 id: expn_id,
 541                                                 ..self.cx.current_expansion.clone()
 542                                             },
 543                                         },
 544                                         None,
 545                                     ));
 546                                     NodeId::placeholder_from_expn_id(expn_id)
 547                                 })
 548                                 .collect::<Vec<_>>()
 549                         })
 550                         .unwrap_or_default();
 551
 552                     let (fragment, collected_invocations) =
 553                         self.collect_invocations(fragment, &derive_placeholders);
 554                     // We choose to expand any derive invocations associated with this macro invocation
 555                     // *before* any macro invocations collected from the output fragment
 556                     derive_invocations.extend(collected_invocations);
 557                     (fragment, derive_invocations)
 558                 }
 559                 ExpandResult::Retry(invoc) => {
 560                     if force {
 561                         self.cx.span_bug(
 562                             invoc.span(),
 563                             "expansion entered force mode but is still stuck",
 564                         );
 565                     } else {
 566                         // Cannot expand, will retry this invocation later.
 567                         undetermined_invocations.push((invoc, Some(ext)));
 568                         continue;
 569                     }
 570                 }
 571             };
 572
 573             progress = true;
 574             if expanded_fragments.len() < depth {
 575                 expanded_fragments.push(Vec::new());
 576             }
 577             expanded_fragments[depth - 1].push((expn_id, expanded_fragment));
 578             invocations.extend(new_invocations.into_iter().rev());
 579         }
 580
 581         self.cx.current_expansion = orig_expansion_data;
 582         self.cx.force_mode = orig_force_mode;
 583
 584         // Finally incorporate all the expanded macros into the input AST fragment.
 585         let mut placeholder_expander = PlaceholderExpander::new(self.cx, self.monotonic);
 586         while let Some(expanded_fragments) = expanded_fragments.pop() {
 587             for (expn_id, expanded_fragment) in expanded_fragments.into_iter().rev() {
 588                 placeholder_expander
 589                     .add(NodeId::placeholder_from_expn_id(expn_id), expanded_fragment);
 590             }
 591         }
 592         fragment_with_placeholders.mut_visit_with(&mut placeholder_expander);
 593         fragment_with_placeholders
 594     }
 595
 596     fn resolve_imports(&mut self) {
 597         if self.monotonic {
 598             self.cx.resolver.resolve_imports();
 599         }
 600     }
 601
 602     /// Collects all macro invocations reachable at this time in this AST fragment, and replace
 603     /// them with "placeholders" - dummy macro invocations with specially crafted `NodeId`s.
 604     /// Then call into resolver that builds a skeleton ("reduced graph") of the fragment and
 605     /// prepares data for resolving paths of macro invocations.
 606     fn collect_invocations(
 607         &mut self,
 608         mut fragment: AstFragment,
 609         extra_placeholders: &[NodeId],
 610     ) -> (AstFragment, Vec<(Invocation, Option<Lrc<SyntaxExtension>>)>) {
 611         // Resolve `$crate`s in the fragment for pretty-printing.
 612         self.cx.resolver.resolve_dollar_crates();
 613
 614         let invocations = {
 615             let mut collector = InvocationCollector {
 616                 // Non-derive macro invocations cannot see the results of cfg expansion - they
 617                 // will either be removed along with the item, or invoked before the cfg/cfg_attr
 618                 // attribute is expanded. Therefore, we don't need to configure the tokens
 619                 // Derive macros *can* see the results of cfg-expansion - they are handled
 620                 // specially in `fully_expand_fragment`
 621                 cfg: StripUnconfigured {
 622                     sess: &self.cx.sess,
 623                     features: self.cx.ecfg.features,
 624                     config_tokens: false,
 625                 },
 626                 cx: self.cx,
 627                 invocations: Vec::new(),
 628                 monotonic: self.monotonic,
 629             };
 630             fragment.mut_visit_with(&mut collector);
 631             fragment.add_placeholders(extra_placeholders);
 632             collector.invocations
 633         };
 634
 635         if self.monotonic {
 636             self.cx
 637                 .resolver
 638                 .visit_ast_fragment_with_placeholders(self.cx.current_expansion.id, &fragment);
 639         }
 640
 641         (fragment, invocations)
 642     }
 643
 644     fn error_recursion_limit_reached(&mut self) {
 645         let expn_data = self.cx.current_expansion.id.expn_data();
 646         let suggested_limit = self.cx.ecfg.recursion_limit * 2;
 647         self.cx
 648             .struct_span_err(
 649                 expn_data.call_site,
 650                 &format!("recursion limit reached while expanding `{}`", expn_data.kind.descr()),
 651             )
 652             .help(&format!(
 653                 "consider adding a `#![recursion_limit=\"{}\"]` attribute to your crate (`{}`)",
 654                 suggested_limit, self.cx.ecfg.crate_name,
 655             ))
 656             .emit();
 657         self.cx.trace_macros_diag();
 658     }
 659
 660     /// A macro's expansion does not fit in this fragment kind.
 661     /// For example, a non-type macro in a type position.
 662     fn error_wrong_fragment_kind(&mut self, kind: AstFragmentKind, mac: &ast::MacCall, span: Span) {
 663         let msg = format!(
 664             "non-{kind} macro in {kind} position: {path}",
 665             kind = kind.name(),
 666             path = pprust::path_to_string(&mac.path),
 667         );
 668         self.cx.span_err(span, &msg);
 669         self.cx.trace_macros_diag();
 670     }
 671
 672     fn expand_invoc(
 673         &mut self,
 674         invoc: Invocation,
 675         ext: &SyntaxExtensionKind,
 676     ) -> ExpandResult<AstFragment, Invocation> {
 677         let recursion_limit =
 678             self.cx.reduced_recursion_limit.unwrap_or(self.cx.ecfg.recursion_limit);
 679         if !recursion_limit.value_within_limit(self.cx.current_expansion.depth) {
 680             if self.cx.reduced_recursion_limit.is_none() {
 681                 self.error_recursion_limit_reached();
 682             }
 683
 684             // Reduce the recursion limit by half each time it triggers.
 685             self.cx.reduced_recursion_limit = Some(recursion_limit / 2);
 686
 687             return ExpandResult::Ready(invoc.fragment_kind.dummy(invoc.span()));
 688         }
 689
 690         let (fragment_kind, span) = (invoc.fragment_kind, invoc.span());
 691         ExpandResult::Ready(match invoc.kind {
 692             InvocationKind::Bang { mac, .. } => match ext {
 693                 SyntaxExtensionKind::Bang(expander) => {
 694                     let tok_result = match expander.expand(self.cx, span, mac.args.inner_tokens()) {
 695                         Err(_) => return ExpandResult::Ready(fragment_kind.dummy(span)),
 696                         Ok(ts) => ts,
 697                     };
 698                     self.parse_ast_fragment(tok_result, fragment_kind, &mac.path, span)
 699                 }
 700                 SyntaxExtensionKind::LegacyBang(expander) => {
 701                     let prev = self.cx.current_expansion.prior_type_ascription;
 702                     self.cx.current_expansion.prior_type_ascription = mac.prior_type_ascription;
 703                     let tok_result = expander.expand(self.cx, span, mac.args.inner_tokens());
 704                     let result = if let Some(result) = fragment_kind.make_from(tok_result) {
 705                         result
 706                     } else {
 707                         self.error_wrong_fragment_kind(fragment_kind, &mac, span);
 708                         fragment_kind.dummy(span)
 709                     };
 710                     self.cx.current_expansion.prior_type_ascription = prev;
 711                     result
 712                 }
 713                 _ => unreachable!(),
 714             },
 715             InvocationKind::Attr { attr, pos, mut item, derives } => match ext {
 716                 SyntaxExtensionKind::Attr(expander) => {
 717                     self.gate_proc_macro_input(&item);
 718                     self.gate_proc_macro_attr_item(span, &item);
 719                     let mut fake_tokens = false;
 720                     if let Annotatable::Item(item_inner) = &item {
 721                         if let ItemKind::Mod(_, mod_kind) = &item_inner.kind {
 722                             // FIXME: Collect tokens and use them instead of generating
 723                             // fake ones. These are unstable, so it needs to be
 724                             // fixed prior to stabilization
 725                             // Fake tokens when we are invoking an inner attribute, and:
 726                             fake_tokens = matches!(attr.style, ast::AttrStyle::Inner) &&
 727                                 // We are invoking an attribute on the crate root, or an outline
 728                                 // module
 729                                 (item_inner.ident.name.is_empty() || !matches!(mod_kind, ast::ModKind::Loaded(_, Inline::Yes, _)));
 730                         }
 731                     }
 732                     let tokens = if fake_tokens {
 733                         rustc_parse::fake_token_stream(
 734                             &self.cx.sess.parse_sess,
 735                             &item.into_nonterminal(),
 736                         )
 737                     } else {
 738                         item.into_tokens(&self.cx.sess.parse_sess)
 739                     };
 740                     let attr_item = attr.unwrap_normal_item();
 741                     if let MacArgs::Eq(..) = attr_item.args {
 742                         self.cx.span_err(span, "key-value macro attributes are not supported");
 743                     }
 744                     let inner_tokens = attr_item.args.inner_tokens();
 745                     let tok_result = match expander.expand(self.cx, span, inner_tokens, tokens) {
 746                         Err(_) => return ExpandResult::Ready(fragment_kind.dummy(span)),
 747                         Ok(ts) => ts,
 748                     };
 749                     self.parse_ast_fragment(tok_result, fragment_kind, &attr_item.path, span)
 750                 }
 751                 SyntaxExtensionKind::LegacyAttr(expander) => {
 752                     match validate_attr::parse_meta(&self.cx.sess.parse_sess, &attr) {
 753                         Ok(meta) => {
 754                             let items = match expander.expand(self.cx, span, &meta, item) {
 755                                 ExpandResult::Ready(items) => items,
 756                                 ExpandResult::Retry(item) => {
 757                                     // Reassemble the original invocation for retrying.
 758                                     return ExpandResult::Retry(Invocation {
 759                                         kind: InvocationKind::Attr { attr, pos, item, derives },
 760                                         ..invoc
 761                                     });
 762                                 }
 763                             };
 764                             if fragment_kind == AstFragmentKind::Expr && items.is_empty() {
 765                                 let msg =
 766                                     "removing an expression is not supported in this position";
 767                                 self.cx.span_err(span, msg);
 768                                 fragment_kind.dummy(span)
 769                             } else {
 770                                 fragment_kind.expect_from_annotatables(items)
 771                             }
 772                         }
 773                         Err(mut err) => {
 774                             err.emit();
 775                             fragment_kind.dummy(span)
 776                         }
 777                     }
 778                 }
 779                 SyntaxExtensionKind::NonMacroAttr { mark_used } => {
 780                     self.cx.sess.mark_attr_known(&attr);
 781                     if *mark_used {
 782                         self.cx.sess.mark_attr_used(&attr);
 783                     }
 784                     item.visit_attrs(|attrs| attrs.insert(pos, attr));
 785                     fragment_kind.expect_from_annotatables(iter::once(item))
 786                 }
 787                 _ => unreachable!(),
 788             },
 789             InvocationKind::Derive { path, item } => match ext {
 790                 SyntaxExtensionKind::Derive(expander)
 791                 | SyntaxExtensionKind::LegacyDerive(expander) => {
 792                     if let SyntaxExtensionKind::Derive(..) = ext {
 793                         self.gate_proc_macro_input(&item);
 794                     }
 795                     let meta = ast::MetaItem { kind: ast::MetaItemKind::Word, span, path };
 796                     let items = match expander.expand(self.cx, span, &meta, item) {
 797                         ExpandResult::Ready(items) => items,
 798                         ExpandResult::Retry(item) => {
 799                             // Reassemble the original invocation for retrying.
 800                             return ExpandResult::Retry(Invocation {
 801                                 kind: InvocationKind::Derive { path: meta.path, item },
 802                                 ..invoc
 803                             });
 804                         }
 805                     };
 806                     fragment_kind.expect_from_annotatables(items)
 807                 }
 808                 _ => unreachable!(),
 809             },
 810         })
 811     }
 812
 813     fn gate_proc_macro_attr_item(&self, span: Span, item: &Annotatable) {
 814         let kind = match item {
 815             Annotatable::Item(_)
 816             | Annotatable::TraitItem(_)
 817             | Annotatable::ImplItem(_)
 818             | Annotatable::ForeignItem(_) => return,
 819             Annotatable::Stmt(stmt) => {
 820                 // Attributes are stable on item statements,
 821                 // but unstable on all other kinds of statements
 822                 if stmt.is_item() {
 823                     return;
 824                 }
 825                 "statements"
 826             }
 827             Annotatable::Expr(_) => "expressions",
 828             Annotatable::Arm(..)
 829             | Annotatable::ExprField(..)
 830             | Annotatable::PatField(..)
 831             | Annotatable::GenericParam(..)
 832             | Annotatable::Param(..)
 833             | Annotatable::FieldDef(..)
 834             | Annotatable::Variant(..) => panic!("unexpected annotatable"),
 835         };
 836         if self.cx.ecfg.proc_macro_hygiene() {
 837             return;
 838         }
 839         feature_err(
 840             &self.cx.sess.parse_sess,
 841             sym::proc_macro_hygiene,
 842             span,
 843             &format!("custom attributes cannot be applied to {}", kind),
 844         )
 845         .emit();
 846     }
 847
 848     fn gate_proc_macro_input(&self, annotatable: &Annotatable) {
 849         struct GateProcMacroInput<'a> {
 850             parse_sess: &'a ParseSess,
 851         }
 852
 853         impl<'ast, 'a> Visitor<'ast> for GateProcMacroInput<'a> {
 854             fn visit_item(&mut self, item: &'ast ast::Item) {
 855                 match &item.kind {
 856                     ast::ItemKind::Mod(_, mod_kind)
 857                         if !matches!(mod_kind, ModKind::Loaded(_, Inline::Yes, _)) =>
 858                     {
 859                         feature_err(
 860                             self.parse_sess,
 861                             sym::proc_macro_hygiene,
 862                             item.span,
 863                             "non-inline modules in proc macro input are unstable",
 864                         )
 865                         .emit();
 866                     }
 867                     _ => {}
 868                 }
 869
 870                 visit::walk_item(self, item);
 871             }
 872         }
 873
 874         if !self.cx.ecfg.proc_macro_hygiene() {
 875             annotatable
 876                 .visit_with(&mut GateProcMacroInput { parse_sess: &self.cx.sess.parse_sess });
 877         }
 878     }
 879
 880     fn parse_ast_fragment(
 881         &mut self,
 882         toks: TokenStream,
 883         kind: AstFragmentKind,
 884         path: &Path,
 885         span: Span,
 886     ) -> AstFragment {
 887         let mut parser = self.cx.new_parser_from_tts(toks);
 888         match parse_ast_fragment(&mut parser, kind) {
 889             Ok(fragment) => {
 890                 ensure_complete_parse(&mut parser, path, kind.name(), span);
 891                 fragment
 892             }
 893             Err(mut err) => {
 894                 if err.span.is_dummy() {
 895                     err.set_span(span);
 896                 }
 897                 annotate_err_with_kind(&mut err, kind, span);
 898                 err.emit();
 899                 self.cx.trace_macros_diag();
 900                 kind.dummy(span)
 901             }
 902         }
 903     }
 904 }
 905
 906 pub fn parse_ast_fragment<'a>(
 907     this: &mut Parser<'a>,
 908     kind: AstFragmentKind,
 909 ) -> PResult<'a, AstFragment> {
 910     Ok(match kind {
 911         AstFragmentKind::Items => {
 912             let mut items = SmallVec::new();
 913             while let Some(item) = this.parse_item(ForceCollect::No)? {
 914                 items.push(item);
 915             }
 916             AstFragment::Items(items)
 917         }
 918         AstFragmentKind::TraitItems => {
 919             let mut items = SmallVec::new();
 920             while let Some(item) = this.parse_trait_item(ForceCollect::No)? {
 921                 items.extend(item);
 922             }
 923             AstFragment::TraitItems(items)
 924         }
 925         AstFragmentKind::ImplItems => {
 926             let mut items = SmallVec::new();
 927             while let Some(item) = this.parse_impl_item(ForceCollect::No)? {
 928                 items.extend(item);
 929             }
 930             AstFragment::ImplItems(items)
 931         }
 932         AstFragmentKind::ForeignItems => {
 933             let mut items = SmallVec::new();
 934             while let Some(item) = this.parse_foreign_item(ForceCollect::No)? {
 935                 items.extend(item);
 936             }
 937             AstFragment::ForeignItems(items)
 938         }
 939         AstFragmentKind::Stmts => {
 940             let mut stmts = SmallVec::new();
 941             // Won't make progress on a `}`.
 942             while this.token != token::Eof && this.token != token::CloseDelim(token::Brace) {
 943                 if let Some(stmt) = this.parse_full_stmt(AttemptLocalParseRecovery::Yes)? {
 944                     stmts.push(stmt);
 945                 }
 946             }
 947             AstFragment::Stmts(stmts)
 948         }
 949         AstFragmentKind::Expr => AstFragment::Expr(this.parse_expr()?),
 950         AstFragmentKind::OptExpr => {
 951             if this.token != token::Eof {
 952                 AstFragment::OptExpr(Some(this.parse_expr()?))
 953             } else {
 954                 AstFragment::OptExpr(None)
 955             }
 956         }
 957         AstFragmentKind::Ty => AstFragment::Ty(this.parse_ty()?),
 958         AstFragmentKind::Pat => {
 959             AstFragment::Pat(this.parse_pat_allow_top_alt(None, RecoverComma::No)?)
 960         }
 961         AstFragmentKind::Arms
 962         | AstFragmentKind::Fields
 963         | AstFragmentKind::FieldPats
 964         | AstFragmentKind::GenericParams
 965         | AstFragmentKind::Params
 966         | AstFragmentKind::StructFields
 967         | AstFragmentKind::Variants => panic!("unexpected AST fragment kind"),
 968     })
 969 }
 970
 971 pub fn ensure_complete_parse<'a>(
 972     this: &mut Parser<'a>,
 973     macro_path: &Path,
 974     kind_name: &str,
 975     span: Span,
 976 ) {
 977     if this.token != token::Eof {
 978         let token = pprust::token_to_string(&this.token);
 979         let msg = format!("macro expansion ignores token `{}` and any following", token);
 980         // Avoid emitting backtrace info twice.
 981         let def_site_span = this.token.span.with_ctxt(SyntaxContext::root());
 982         let mut err = this.struct_span_err(def_site_span, &msg);
 983         err.span_label(span, "caused by the macro expansion here");
 984         let msg = format!(
 985             "the usage of `{}!` is likely invalid in {} context",
 986             pprust::path_to_string(macro_path),
 987             kind_name,
 988         );
 989         err.note(&msg);
 990         let semi_span = this.sess.source_map().next_point(span);
 991
 992         let semi_full_span = semi_span.to(this.sess.source_map().next_point(semi_span));
 993         match this.sess.source_map().span_to_snippet(semi_full_span) {
 994             Ok(ref snippet) if &snippet[..] != ";" && kind_name == "expression" => {
 995                 err.span_suggestion(
 996                     semi_span,
 997                     "you might be missing a semicolon here",
 998                     ";".to_owned(),
 999                     Applicability::MaybeIncorrect,
1000                 );
1001             }
1002             _ => {}
1003         }
1004         err.emit();
1005     }
1006 }
1007
1008 struct InvocationCollector<'a, 'b> {
1009     cx: &'a mut ExtCtxt<'b>,
1010     cfg: StripUnconfigured<'a>,
1011     invocations: Vec<(Invocation, Option<Lrc<SyntaxExtension>>)>,
1012     monotonic: bool,
1013 }
1014
1015 impl<'a, 'b> InvocationCollector<'a, 'b> {
1016     fn collect(&mut self, fragment_kind: AstFragmentKind, kind: InvocationKind) -> AstFragment {
1017         let expn_id = ExpnId::fresh(None);
1018         let vis = kind.placeholder_visibility();
1019         self.invocations.push((
1020             Invocation {
1021                 kind,
1022                 fragment_kind,
1023                 expansion_data: ExpansionData {
1024                     id: expn_id,
1025                     depth: self.cx.current_expansion.depth + 1,
1026                     ..self.cx.current_expansion.clone()
1027                 },
1028             },
1029             None,
1030         ));
1031         placeholder(fragment_kind, NodeId::placeholder_from_expn_id(expn_id), vis)
1032     }
1033
1034     fn collect_bang(
1035         &mut self,
1036         mac: ast::MacCall,
1037         span: Span,
1038         kind: AstFragmentKind,
1039     ) -> AstFragment {
1040         self.collect(kind, InvocationKind::Bang { mac, span })
1041     }
1042
1043     fn collect_attr(
1044         &mut self,
1045         (attr, pos, derives): (ast::Attribute, usize, Vec<Path>),
1046         item: Annotatable,
1047         kind: AstFragmentKind,
1048     ) -> AstFragment {
1049         self.collect(kind, InvocationKind::Attr { attr, pos, item, derives })
1050     }
1051
1052     /// If `item` is an attribute invocation, remove the attribute and return it together with
1053     /// its position and derives following it. We have to collect the derives in order to resolve
1054     /// legacy derive helpers (helpers written before derives that introduce them).
1055     fn take_first_attr(
1056         &mut self,
1057         item: &mut impl AstLike,
1058     ) -> Option<(ast::Attribute, usize, Vec<Path>)> {
1059         let mut attr = None;
1060
1061         item.visit_attrs(|attrs| {
1062             attr = attrs
1063                 .iter()
1064                 .position(|a| !self.cx.sess.is_attr_known(a) && !is_builtin_attr(a))
1065                 .map(|attr_pos| {
1066                     let attr = attrs.remove(attr_pos);
1067                     let following_derives = attrs[attr_pos..]
1068                         .iter()
1069                         .filter(|a| a.has_name(sym::derive))
1070                         .flat_map(|a| a.meta_item_list().unwrap_or_default())
1071                         .filter_map(|nested_meta| match nested_meta {
1072                             NestedMetaItem::MetaItem(ast::MetaItem {
1073                                 kind: MetaItemKind::Word,
1074                                 path,
1075                                 ..
1076                             }) => Some(path),
1077                             _ => None,
1078                         })
1079                         .collect();
1080
1081                     (attr, attr_pos, following_derives)
1082                 })
1083         });
1084
1085         attr
1086     }
1087
1088     fn configure<T: AstLike>(&mut self, node: T) -> Option<T> {
1089         self.cfg.configure(node)
1090     }
1091
1092     // Detect use of feature-gated or invalid attributes on macro invocations
1093     // since they will not be detected after macro expansion.
1094     fn check_attributes(&mut self, attrs: &[ast::Attribute]) {
1095         let features = self.cx.ecfg.features.unwrap();
1096         let mut attrs = attrs.iter().peekable();
1097         let mut span: Option<Span> = None;
1098         while let Some(attr) = attrs.next() {
1099             rustc_ast_passes::feature_gate::check_attribute(attr, self.cx.sess, features);
1100             validate_attr::check_meta(&self.cx.sess.parse_sess, attr);
1101
1102             let current_span = if let Some(sp) = span { sp.to(attr.span) } else { attr.span };
1103             span = Some(current_span);
1104
1105             if attrs.peek().map_or(false, |next_attr| next_attr.doc_str().is_some()) {
1106                 continue;
1107             }
1108
1109             if attr.doc_str().is_some() {
1110                 self.cx.sess.parse_sess.buffer_lint_with_diagnostic(
1111                     &UNUSED_DOC_COMMENTS,
1112                     current_span,
1113                     ast::CRATE_NODE_ID,
1114                     "unused doc comment",
1115                     BuiltinLintDiagnostics::UnusedDocComment(attr.span),
1116                 );
1117             }
1118         }
1119     }
1120 }
1121
1122 impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
1123     fn visit_expr(&mut self, expr: &mut P<ast::Expr>) {
1124         self.cfg.configure_expr(expr);
1125         visit_clobber(expr.deref_mut(), |mut expr| {
1126             if let Some(attr) = self.take_first_attr(&mut expr) {
1127                 // Collect the invoc regardless of whether or not attributes are permitted here
1128                 // expansion will eat the attribute so it won't error later.
1129                 self.cfg.maybe_emit_expr_attr_err(&attr.0);
1130
1131                 // AstFragmentKind::Expr requires the macro to emit an expression.
1132                 return self
1133                     .collect_attr(attr, Annotatable::Expr(P(expr)), AstFragmentKind::Expr)
1134                     .make_expr()
1135                     .into_inner();
1136             }
1137
1138             if let ast::ExprKind::MacCall(mac) = expr.kind {
1139                 self.check_attributes(&expr.attrs);
1140                 self.collect_bang(mac, expr.span, AstFragmentKind::Expr).make_expr().into_inner()
1141             } else {
1142                 ensure_sufficient_stack(|| noop_visit_expr(&mut expr, self));
1143                 expr
1144             }
1145         });
1146     }
1147
1148     fn flat_map_arm(&mut self, arm: ast::Arm) -> SmallVec<[ast::Arm; 1]> {
1149         let mut arm = configure!(self, arm);
1150
1151         if let Some(attr) = self.take_first_attr(&mut arm) {
1152             return self
1153                 .collect_attr(attr, Annotatable::Arm(arm), AstFragmentKind::Arms)
1154                 .make_arms();
1155         }
1156
1157         noop_flat_map_arm(arm, self)
1158     }
1159
1160     fn flat_map_expr_field(&mut self, field: ast::ExprField) -> SmallVec<[ast::ExprField; 1]> {
1161         let mut field = configure!(self, field);
1162
1163         if let Some(attr) = self.take_first_attr(&mut field) {
1164             return self
1165                 .collect_attr(attr, Annotatable::ExprField(field), AstFragmentKind::Fields)
1166                 .make_expr_fields();
1167         }
1168
1169         noop_flat_map_expr_field(field, self)
1170     }
1171
1172     fn flat_map_pat_field(&mut self, fp: ast::PatField) -> SmallVec<[ast::PatField; 1]> {
1173         let mut fp = configure!(self, fp);
1174
1175         if let Some(attr) = self.take_first_attr(&mut fp) {
1176             return self
1177                 .collect_attr(attr, Annotatable::PatField(fp), AstFragmentKind::FieldPats)
1178                 .make_pat_fields();
1179         }
1180
1181         noop_flat_map_pat_field(fp, self)
1182     }
1183
1184     fn flat_map_param(&mut self, p: ast::Param) -> SmallVec<[ast::Param; 1]> {
1185         let mut p = configure!(self, p);
1186
1187         if let Some(attr) = self.take_first_attr(&mut p) {
1188             return self
1189                 .collect_attr(attr, Annotatable::Param(p), AstFragmentKind::Params)
1190                 .make_params();
1191         }
1192
1193         noop_flat_map_param(p, self)
1194     }
1195
1196     fn flat_map_field_def(&mut self, sf: ast::FieldDef) -> SmallVec<[ast::FieldDef; 1]> {
1197         let mut sf = configure!(self, sf);
1198
1199         if let Some(attr) = self.take_first_attr(&mut sf) {
1200             return self
1201                 .collect_attr(attr, Annotatable::FieldDef(sf), AstFragmentKind::StructFields)
1202                 .make_field_defs();
1203         }
1204
1205         noop_flat_map_field_def(sf, self)
1206     }
1207
1208     fn flat_map_variant(&mut self, variant: ast::Variant) -> SmallVec<[ast::Variant; 1]> {
1209         let mut variant = configure!(self, variant);
1210
1211         if let Some(attr) = self.take_first_attr(&mut variant) {
1212             return self
1213                 .collect_attr(attr, Annotatable::Variant(variant), AstFragmentKind::Variants)
1214                 .make_variants();
1215         }
1216
1217         noop_flat_map_variant(variant, self)
1218     }
1219
1220     fn filter_map_expr(&mut self, expr: P<ast::Expr>) -> Option<P<ast::Expr>> {
1221         let expr = configure!(self, expr);
1222         expr.filter_map(|mut expr| {
1223             if let Some(attr) = self.take_first_attr(&mut expr) {
1224                 self.cfg.maybe_emit_expr_attr_err(&attr.0);
1225
1226                 return self
1227                     .collect_attr(attr, Annotatable::Expr(P(expr)), AstFragmentKind::OptExpr)
1228                     .make_opt_expr()
1229                     .map(|expr| expr.into_inner());
1230             }
1231
1232             if let ast::ExprKind::MacCall(mac) = expr.kind {
1233                 self.check_attributes(&expr.attrs);
1234                 self.collect_bang(mac, expr.span, AstFragmentKind::OptExpr)
1235                     .make_opt_expr()
1236                     .map(|expr| expr.into_inner())
1237             } else {
1238                 Some({
1239                     noop_visit_expr(&mut expr, self);
1240                     expr
1241                 })
1242             }
1243         })
1244     }
1245
1246     fn visit_pat(&mut self, pat: &mut P<ast::Pat>) {
1247         match pat.kind {
1248             PatKind::MacCall(_) => {}
1249             _ => return noop_visit_pat(pat, self),
1250         }
1251
1252         visit_clobber(pat, |mut pat| match mem::replace(&mut pat.kind, PatKind::Wild) {
1253             PatKind::MacCall(mac) => {
1254                 self.collect_bang(mac, pat.span, AstFragmentKind::Pat).make_pat()
1255             }
1256             _ => unreachable!(),
1257         });
1258     }
1259
1260     fn flat_map_stmt(&mut self, stmt: ast::Stmt) -> SmallVec<[ast::Stmt; 1]> {
1261         let mut stmt = configure!(self, stmt);
1262
1263         // we'll expand attributes on expressions separately
1264         if !stmt.is_expr() {
1265             if let Some(attr) = self.take_first_attr(&mut stmt) {
1266                 return self
1267                     .collect_attr(attr, Annotatable::Stmt(P(stmt)), AstFragmentKind::Stmts)
1268                     .make_stmts();
1269             }
1270         }
1271
1272         if let StmtKind::MacCall(mac) = stmt.kind {
1273             let MacCallStmt { mac, style, attrs, tokens: _ } = mac.into_inner();
1274             self.check_attributes(&attrs);
1275             let mut placeholder =
1276                 self.collect_bang(mac, stmt.span, AstFragmentKind::Stmts).make_stmts();
1277
1278             // If this is a macro invocation with a semicolon, then apply that
1279             // semicolon to the final statement produced by expansion.
1280             if style == MacStmtStyle::Semicolon {
1281                 if let Some(stmt) = placeholder.pop() {
1282                     placeholder.push(stmt.add_trailing_semicolon());
1283                 }
1284             }
1285
1286             return placeholder;
1287         }
1288
1289         // The placeholder expander gives ids to statements, so we avoid folding the id here.
1290         let ast::Stmt { id, kind, span } = stmt;
1291         noop_flat_map_stmt_kind(kind, self)
1292             .into_iter()
1293             .map(|kind| ast::Stmt { id, kind, span })
1294             .collect()
1295     }
1296
1297     fn visit_block(&mut self, block: &mut P<Block>) {
1298         let orig_dir_ownership = mem::replace(
1299             &mut self.cx.current_expansion.dir_ownership,
1300             DirOwnership::UnownedViaBlock,
1301         );
1302         noop_visit_block(block, self);
1303         self.cx.current_expansion.dir_ownership = orig_dir_ownership;
1304     }
1305
1306     fn flat_map_item(&mut self, item: P<ast::Item>) -> SmallVec<[P<ast::Item>; 1]> {
1307         let mut item = configure!(self, item);
1308
1309         if let Some(attr) = self.take_first_attr(&mut item) {
1310             return self
1311                 .collect_attr(attr, Annotatable::Item(item), AstFragmentKind::Items)
1312                 .make_items();
1313         }
1314
1315         let mut attrs = mem::take(&mut item.attrs); // We do this to please borrowck.
1316         let ident = item.ident;
1317         let span = item.span;
1318
1319         match item.kind {
1320             ast::ItemKind::MacCall(..) => {
1321                 item.attrs = attrs;
1322                 self.check_attributes(&item.attrs);
1323                 item.and_then(|item| match item.kind {
1324                     ItemKind::MacCall(mac) => {
1325                         self.collect_bang(mac, span, AstFragmentKind::Items).make_items()
1326                     }
1327                     _ => unreachable!(),
1328                 })
1329             }
1330             ast::ItemKind::Mod(_, ref mut mod_kind) if ident != Ident::invalid() => {
1331                 let (file_path, dir_path, dir_ownership) = match mod_kind {
1332                     ModKind::Loaded(_, inline, _) => {
1333                         // Inline `mod foo { ... }`, but we still need to push directories.
1334                         let (dir_path, dir_ownership) = mod_dir_path(
1335                             &self.cx.sess,
1336                             ident,
1337                             &attrs,
1338                             &self.cx.current_expansion.module,
1339                             self.cx.current_expansion.dir_ownership,
1340                             *inline,
1341                         );
1342                         item.attrs = attrs;
1343                         (None, dir_path, dir_ownership)
1344                     }
1345                     ModKind::Unloaded => {
1346                         // We have an outline `mod foo;` so we need to parse the file.
1347                         let old_attrs_len = attrs.len();
1348                         let ParsedExternalMod {
1349                             mut items,
1350                             inner_span,
1351                             file_path,
1352                             dir_path,
1353                             dir_ownership,
1354                         } = parse_external_mod(
1355                             &self.cx.sess,
1356                             ident,
1357                             span,
1358                             &self.cx.current_expansion.module,
1359                             self.cx.current_expansion.dir_ownership,
1360                             &mut attrs,
1361                         );
1362
1363                         if let Some(extern_mod_loaded) = self.cx.extern_mod_loaded {
1364                             (attrs, items) = extern_mod_loaded(ident, attrs, items, inner_span);
1365                         }
1366
1367                         *mod_kind = ModKind::Loaded(items, Inline::No, inner_span);
1368                         item.attrs = attrs;
1369                         if item.attrs.len() > old_attrs_len {
1370                             // If we loaded an out-of-line module and added some inner attributes,
1371                             // then we need to re-configure it and re-collect attributes for
1372                             // resolution and expansion.
1373                             item = configure!(self, item);
1374
1375                             if let Some(attr) = self.take_first_attr(&mut item) {
1376                                 return self
1377                                     .collect_attr(
1378                                         attr,
1379                                         Annotatable::Item(item),
1380                                         AstFragmentKind::Items,
1381                                     )
1382                                     .make_items();
1383                             }
1384                         }
1385                         (Some(file_path), dir_path, dir_ownership)
1386                     }
1387                 };
1388
1389                 // Set the module info before we flat map.
1390                 let mut module = self.cx.current_expansion.module.with_dir_path(dir_path);
1391                 module.mod_path.push(ident);
1392                 if let Some(file_path) = file_path {
1393                     module.file_path_stack.push(file_path);
1394                 }
1395
1396                 let orig_module =
1397                     mem::replace(&mut self.cx.current_expansion.module, Rc::new(module));
1398                 let orig_dir_ownership =
1399                     mem::replace(&mut self.cx.current_expansion.dir_ownership, dir_ownership);
1400
1401                 let result = noop_flat_map_item(item, self);
1402
1403                 // Restore the module info.
1404                 self.cx.current_expansion.dir_ownership = orig_dir_ownership;
1405                 self.cx.current_expansion.module = orig_module;
1406
1407                 result
1408             }
1409             _ => {
1410                 item.attrs = attrs;
1411                 noop_flat_map_item(item, self)
1412             }
1413         }
1414     }
1415
1416     fn flat_map_trait_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
1417         let mut item = configure!(self, item);
1418
1419         if let Some(attr) = self.take_first_attr(&mut item) {
1420             return self
1421                 .collect_attr(attr, Annotatable::TraitItem(item), AstFragmentKind::TraitItems)
1422                 .make_trait_items();
1423         }
1424
1425         match item.kind {
1426             ast::AssocItemKind::MacCall(..) => {
1427                 self.check_attributes(&item.attrs);
1428                 item.and_then(|item| match item.kind {
1429                     ast::AssocItemKind::MacCall(mac) => self
1430                         .collect_bang(mac, item.span, AstFragmentKind::TraitItems)
1431                         .make_trait_items(),
1432                     _ => unreachable!(),
1433                 })
1434             }
1435             _ => noop_flat_map_assoc_item(item, self),
1436         }
1437     }
1438
1439     fn flat_map_impl_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
1440         let mut item = configure!(self, item);
1441
1442         if let Some(attr) = self.take_first_attr(&mut item) {
1443             return self
1444                 .collect_attr(attr, Annotatable::ImplItem(item), AstFragmentKind::ImplItems)
1445                 .make_impl_items();
1446         }
1447
1448         match item.kind {
1449             ast::AssocItemKind::MacCall(..) => {
1450                 self.check_attributes(&item.attrs);
1451                 item.and_then(|item| match item.kind {
1452                     ast::AssocItemKind::MacCall(mac) => self
1453                         .collect_bang(mac, item.span, AstFragmentKind::ImplItems)
1454                         .make_impl_items(),
1455                     _ => unreachable!(),
1456                 })
1457             }
1458             _ => noop_flat_map_assoc_item(item, self),
1459         }
1460     }
1461
1462     fn visit_ty(&mut self, ty: &mut P<ast::Ty>) {
1463         match ty.kind {
1464             ast::TyKind::MacCall(_) => {}
1465             _ => return noop_visit_ty(ty, self),
1466         };
1467
1468         visit_clobber(ty, |mut ty| match mem::replace(&mut ty.kind, ast::TyKind::Err) {
1469             ast::TyKind::MacCall(mac) => {
1470                 self.collect_bang(mac, ty.span, AstFragmentKind::Ty).make_ty()
1471             }
1472             _ => unreachable!(),
1473         });
1474     }
1475
1476     fn flat_map_foreign_item(
1477         &mut self,
1478         foreign_item: P<ast::ForeignItem>,
1479     ) -> SmallVec<[P<ast::ForeignItem>; 1]> {
1480         let mut foreign_item = configure!(self, foreign_item);
1481
1482         if let Some(attr) = self.take_first_attr(&mut foreign_item) {
1483             return self
1484                 .collect_attr(
1485                     attr,
1486                     Annotatable::ForeignItem(foreign_item),
1487                     AstFragmentKind::ForeignItems,
1488                 )
1489                 .make_foreign_items();
1490         }
1491
1492         match foreign_item.kind {
1493             ast::ForeignItemKind::MacCall(..) => {
1494                 self.check_attributes(&foreign_item.attrs);
1495                 foreign_item.and_then(|item| match item.kind {
1496                     ast::ForeignItemKind::MacCall(mac) => self
1497                         .collect_bang(mac, item.span, AstFragmentKind::ForeignItems)
1498                         .make_foreign_items(),
1499                     _ => unreachable!(),
1500                 })
1501             }
1502             _ => noop_flat_map_foreign_item(foreign_item, self),
1503         }
1504     }
1505
1506     fn flat_map_generic_param(
1507         &mut self,
1508         param: ast::GenericParam,
1509     ) -> SmallVec<[ast::GenericParam; 1]> {
1510         let mut param = configure!(self, param);
1511
1512         if let Some(attr) = self.take_first_attr(&mut param) {
1513             return self
1514                 .collect_attr(
1515                     attr,
1516                     Annotatable::GenericParam(param),
1517                     AstFragmentKind::GenericParams,
1518                 )
1519                 .make_generic_params();
1520         }
1521
1522         noop_flat_map_generic_param(param, self)
1523     }
1524
1525     fn visit_attribute(&mut self, at: &mut ast::Attribute) {
1526         // turn `#[doc(include="filename")]` attributes into `#[doc(include(file="filename",
1527         // contents="file contents")]` attributes
1528         if !self.cx.sess.check_name(at, sym::doc) {
1529             return noop_visit_attribute(at, self);
1530         }
1531
1532         if let Some(list) = at.meta_item_list() {
1533             if !list.iter().any(|it| it.has_name(sym::include)) {
1534                 return noop_visit_attribute(at, self);
1535             }
1536
1537             let mut items = vec![];
1538
1539             for mut it in list {
1540                 if !it.has_name(sym::include) {
1541                     items.push({
1542                         noop_visit_meta_list_item(&mut it, self);
1543                         it
1544                     });
1545                     continue;
1546                 }
1547
1548                 if let Some(file) = it.value_str() {
1549                     let err_count = self.cx.sess.parse_sess.span_diagnostic.err_count();
1550                     self.check_attributes(slice::from_ref(at));
1551                     if self.cx.sess.parse_sess.span_diagnostic.err_count() > err_count {
1552                         // avoid loading the file if they haven't enabled the feature
1553                         return noop_visit_attribute(at, self);
1554                     }
1555
1556                     let filename = match self.cx.resolve_path(&*file.as_str(), it.span()) {
1557                         Ok(filename) => filename,
1558                         Err(mut err) => {
1559                             err.emit();
1560                             continue;
1561                         }
1562                     };
1563
1564                     match self.cx.source_map().load_file(&filename) {
1565                         Ok(source_file) => {
1566                             let src = source_file
1567                                 .src
1568                                 .as_ref()
1569                                 .expect("freshly loaded file should have a source");
1570                             let src_interned = Symbol::intern(src.as_str());
1571
1572                             let include_info = vec![
1573                                 ast::NestedMetaItem::MetaItem(attr::mk_name_value_item_str(
1574                                     Ident::with_dummy_span(sym::file),
1575                                     file,
1576                                     DUMMY_SP,
1577                                 )),
1578                                 ast::NestedMetaItem::MetaItem(attr::mk_name_value_item_str(
1579                                     Ident::with_dummy_span(sym::contents),
1580                                     src_interned,
1581                                     DUMMY_SP,
1582                                 )),
1583                             ];
1584
1585                             let include_ident = Ident::with_dummy_span(sym::include);
1586                             let item = attr::mk_list_item(include_ident, include_info);
1587                             items.push(ast::NestedMetaItem::MetaItem(item));
1588                         }
1589                         Err(e) => {
1590                             let lit_span = it.name_value_literal_span().unwrap();
1591
1592                             if e.kind() == ErrorKind::InvalidData {
1593                                 self.cx
1594                                     .struct_span_err(
1595                                         lit_span,
1596                                         &format!("{} wasn't a utf-8 file", filename.display()),
1597                                     )
1598                                     .span_label(lit_span, "contains invalid utf-8")
1599                                     .emit();
1600                             } else {
1601                                 let mut err = self.cx.struct_span_err(
1602                                     lit_span,
1603                                     &format!("couldn't read {}: {}", filename.display(), e),
1604                                 );
1605                                 err.span_label(lit_span, "couldn't read file");
1606
1607                                 err.emit();
1608                             }
1609                         }
1610                     }
1611                 } else {
1612                     let mut err = self
1613                         .cx
1614                         .struct_span_err(it.span(), "expected path to external documentation");
1615
1616                     // Check if the user erroneously used `doc(include(...))` syntax.
1617                     let literal = it.meta_item_list().and_then(|list| {
1618                         if list.len() == 1 {
1619                             list[0].literal().map(|literal| &literal.kind)
1620                         } else {
1621                             None
1622                         }
1623                     });
1624
1625                     let (path, applicability) = match &literal {
1626                         Some(LitKind::Str(path, ..)) => {
1627                             (path.to_string(), Applicability::MachineApplicable)
1628                         }
1629                         _ => (String::from("<path>"), Applicability::HasPlaceholders),
1630                     };
1631
1632                     err.span_suggestion(
1633                         it.span(),
1634                         "provide a file path with `=`",
1635                         format!("include = \"{}\"", path),
1636                         applicability,
1637                     );
1638
1639                     err.emit();
1640                 }
1641             }
1642
1643             let meta = attr::mk_list_item(Ident::with_dummy_span(sym::doc), items);
1644             *at = ast::Attribute {
1645                 kind: ast::AttrKind::Normal(
1646                     AttrItem { path: meta.path, args: meta.kind.mac_args(meta.span), tokens: None },
1647                     None,
1648                 ),
1649                 span: at.span,
1650                 id: at.id,
1651                 style: at.style,
1652             };
1653         } else {
1654             noop_visit_attribute(at, self)
1655         }
1656     }
1657
1658     fn visit_id(&mut self, id: &mut ast::NodeId) {
1659         if self.monotonic {
1660             debug_assert_eq!(*id, ast::DUMMY_NODE_ID);
1661             *id = self.cx.resolver.next_node_id()
1662         }
1663     }
1664 }
1665
1666 pub struct ExpansionConfig<'feat> {
1667     pub crate_name: String,
1668     pub features: Option<&'feat Features>,
1669     pub recursion_limit: Limit,
1670     pub trace_mac: bool,
1671     pub should_test: bool,          // If false, strip `#[test]` nodes
1672     pub span_debug: bool,           // If true, use verbose debugging for `proc_macro::Span`
1673     pub proc_macro_backtrace: bool, // If true, show backtraces for proc-macro panics
1674 }
1675
1676 impl<'feat> ExpansionConfig<'feat> {
1677     pub fn default(crate_name: String) -> ExpansionConfig<'static> {
1678         ExpansionConfig {
1679             crate_name,
1680             features: None,
1681             recursion_limit: Limit::new(1024),
1682             trace_mac: false,
1683             should_test: false,
1684             span_debug: false,
1685             proc_macro_backtrace: false,
1686         }
1687     }
1688
1689     fn proc_macro_hygiene(&self) -> bool {
1690         self.features.map_or(false, |features| features.proc_macro_hygiene)
1691     }
1692 }