compiler/rustc_expand/src/expand.rs

   1 use crate::base::*;
   2 use crate::config::StripUnconfigured;
   3 use crate::configure;
   4 use crate::hygiene::{ExpnData, ExpnKind, SyntaxContext};
   5 use crate::mbe::macro_rules::annotate_err_with_kind;
   6 use crate::module::{parse_external_mod, push_directory, Directory, DirectoryOwnership};
   7 use crate::placeholders::{placeholder, PlaceholderExpander};
   8 use crate::proc_macro::collect_derives;
   9
  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::{self as ast, AttrItem, AttrStyle, Block, LitKind, NodeId, PatKind, Path};
  16 use rustc_ast::{ItemKind, MacArgs, MacCallStmt, MacStmtStyle, StmtKind, Unsafe};
  17 use rustc_ast_pretty::pprust;
  18 use rustc_attr::{self as attr, is_builtin_attr, HasAttrs};
  19 use rustc_data_structures::map_in_place::MapInPlace;
  20 use rustc_data_structures::stack::ensure_sufficient_stack;
  21 use rustc_errors::{struct_span_err, Applicability, PResult};
  22 use rustc_feature::Features;
  23 use rustc_parse::parser::{AttemptLocalParseRecovery, Parser};
  24 use rustc_parse::validate_attr;
  25 use rustc_session::lint::builtin::UNUSED_DOC_COMMENTS;
  26 use rustc_session::lint::BuiltinLintDiagnostics;
  27 use rustc_session::parse::{feature_err, ParseSess};
  28 use rustc_session::Limit;
  29 use rustc_span::symbol::{sym, Ident, Symbol};
  30 use rustc_span::{ExpnId, FileName, Span, DUMMY_SP};
  31
  32 use smallvec::{smallvec, SmallVec};
  33 use std::io::ErrorKind;
  34 use std::ops::DerefMut;
  35 use std::path::PathBuf;
  36 use std::rc::Rc;
  37 use std::{iter, mem, slice};
  38
  39 macro_rules! ast_fragments {
  40     (
  41         $($Kind:ident($AstTy:ty) {
  42             $kind_name:expr;
  43             $(one fn $mut_visit_ast:ident; fn $visit_ast:ident;)?
  44             $(many fn $flat_map_ast_elt:ident; fn $visit_ast_elt:ident($($args:tt)*);)?
  45             fn $make_ast:ident;
  46         })*
  47     ) => {
  48         /// A fragment of AST that can be produced by a single macro expansion.
  49         /// Can also serve as an input and intermediate result for macro expansion operations.
  50         pub enum AstFragment {
  51             OptExpr(Option<P<ast::Expr>>),
  52             $($Kind($AstTy),)*
  53         }
  54
  55         /// "Discriminant" of an AST fragment.
  56         #[derive(Copy, Clone, PartialEq, Eq)]
  57         pub enum AstFragmentKind {
  58             OptExpr,
  59             $($Kind,)*
  60         }
  61
  62         impl AstFragmentKind {
  63             pub fn name(self) -> &'static str {
  64                 match self {
  65                     AstFragmentKind::OptExpr => "expression",
  66                     $(AstFragmentKind::$Kind => $kind_name,)*
  67                 }
  68             }
  69
  70             fn make_from<'a>(self, result: Box<dyn MacResult + 'a>) -> Option<AstFragment> {
  71                 match self {
  72                     AstFragmentKind::OptExpr =>
  73                         result.make_expr().map(Some).map(AstFragment::OptExpr),
  74                     $(AstFragmentKind::$Kind => result.$make_ast().map(AstFragment::$Kind),)*
  75                 }
  76             }
  77         }
  78
  79         impl AstFragment {
  80             pub fn add_placeholders(&mut self, placeholders: &[NodeId]) {
  81                 if placeholders.is_empty() {
  82                     return;
  83                 }
  84                 match self {
  85                     $($(AstFragment::$Kind(ast) => ast.extend(placeholders.iter().flat_map(|id| {
  86                         // We are repeating through arguments with `many`, to do that we have to
  87                         // mention some macro variable from those arguments even if it's not used.
  88                         macro _repeating($flat_map_ast_elt) {}
  89                         placeholder(AstFragmentKind::$Kind, *id, None).$make_ast()
  90                     })),)?)*
  91                     _ => panic!("unexpected AST fragment kind")
  92                 }
  93             }
  94
  95             pub fn make_opt_expr(self) -> Option<P<ast::Expr>> {
  96                 match self {
  97                     AstFragment::OptExpr(expr) => expr,
  98                     _ => panic!("AstFragment::make_* called on the wrong kind of fragment"),
  99                 }
 100             }
 101
 102             $(pub fn $make_ast(self) -> $AstTy {
 103                 match self {
 104                     AstFragment::$Kind(ast) => ast,
 105                     _ => panic!("AstFragment::make_* called on the wrong kind of fragment"),
 106                 }
 107             })*
 108
 109             pub fn mut_visit_with<F: MutVisitor>(&mut self, vis: &mut F) {
 110                 match self {
 111                     AstFragment::OptExpr(opt_expr) => {
 112                         visit_clobber(opt_expr, |opt_expr| {
 113                             if let Some(expr) = opt_expr {
 114                                 vis.filter_map_expr(expr)
 115                             } else {
 116                                 None
 117                             }
 118                         });
 119                     }
 120                     $($(AstFragment::$Kind(ast) => vis.$mut_visit_ast(ast),)?)*
 121                     $($(AstFragment::$Kind(ast) =>
 122                         ast.flat_map_in_place(|ast| vis.$flat_map_ast_elt(ast)),)?)*
 123                 }
 124             }
 125
 126             pub fn visit_with<'a, V: Visitor<'a>>(&'a self, visitor: &mut V) {
 127                 match *self {
 128                     AstFragment::OptExpr(Some(ref expr)) => visitor.visit_expr(expr),
 129                     AstFragment::OptExpr(None) => {}
 130                     $($(AstFragment::$Kind(ref ast) => visitor.$visit_ast(ast),)?)*
 131                     $($(AstFragment::$Kind(ref ast) => for ast_elt in &ast[..] {
 132                         visitor.$visit_ast_elt(ast_elt, $($args)*);
 133                     })?)*
 134                 }
 135             }
 136         }
 137
 138         impl<'a> MacResult for crate::mbe::macro_rules::ParserAnyMacro<'a> {
 139             $(fn $make_ast(self: Box<crate::mbe::macro_rules::ParserAnyMacro<'a>>)
 140                            -> Option<$AstTy> {
 141                 Some(self.make(AstFragmentKind::$Kind).$make_ast())
 142             })*
 143         }
 144     }
 145 }
 146
 147 ast_fragments! {
 148     Expr(P<ast::Expr>) { "expression"; one fn visit_expr; fn visit_expr; fn make_expr; }
 149     Pat(P<ast::Pat>) { "pattern"; one fn visit_pat; fn visit_pat; fn make_pat; }
 150     Ty(P<ast::Ty>) { "type"; one fn visit_ty; fn visit_ty; fn make_ty; }
 151     Stmts(SmallVec<[ast::Stmt; 1]>) {
 152         "statement"; many fn flat_map_stmt; fn visit_stmt(); fn make_stmts;
 153     }
 154     Items(SmallVec<[P<ast::Item>; 1]>) {
 155         "item"; many fn flat_map_item; fn visit_item(); fn make_items;
 156     }
 157     TraitItems(SmallVec<[P<ast::AssocItem>; 1]>) {
 158         "trait item";
 159         many fn flat_map_trait_item;
 160         fn visit_assoc_item(AssocCtxt::Trait);
 161         fn make_trait_items;
 162     }
 163     ImplItems(SmallVec<[P<ast::AssocItem>; 1]>) {
 164         "impl item";
 165         many fn flat_map_impl_item;
 166         fn visit_assoc_item(AssocCtxt::Impl);
 167         fn make_impl_items;
 168     }
 169     ForeignItems(SmallVec<[P<ast::ForeignItem>; 1]>) {
 170         "foreign item";
 171         many fn flat_map_foreign_item;
 172         fn visit_foreign_item();
 173         fn make_foreign_items;
 174     }
 175     Arms(SmallVec<[ast::Arm; 1]>) {
 176         "match arm"; many fn flat_map_arm; fn visit_arm(); fn make_arms;
 177     }
 178     Fields(SmallVec<[ast::Field; 1]>) {
 179         "field expression"; many fn flat_map_field; fn visit_field(); fn make_fields;
 180     }
 181     FieldPats(SmallVec<[ast::FieldPat; 1]>) {
 182         "field pattern";
 183         many fn flat_map_field_pattern;
 184         fn visit_field_pattern();
 185         fn make_field_patterns;
 186     }
 187     GenericParams(SmallVec<[ast::GenericParam; 1]>) {
 188         "generic parameter";
 189         many fn flat_map_generic_param;
 190         fn visit_generic_param();
 191         fn make_generic_params;
 192     }
 193     Params(SmallVec<[ast::Param; 1]>) {
 194         "function parameter"; many fn flat_map_param; fn visit_param(); fn make_params;
 195     }
 196     StructFields(SmallVec<[ast::StructField; 1]>) {
 197         "field";
 198         many fn flat_map_struct_field;
 199         fn visit_struct_field();
 200         fn make_struct_fields;
 201     }
 202     Variants(SmallVec<[ast::Variant; 1]>) {
 203         "variant"; many fn flat_map_variant; fn visit_variant(); fn make_variants;
 204     }
 205 }
 206
 207 impl AstFragmentKind {
 208     crate fn dummy(self, span: Span) -> AstFragment {
 209         self.make_from(DummyResult::any(span)).expect("couldn't create a dummy AST fragment")
 210     }
 211
 212     /// Fragment supports macro expansion and not just inert attributes, `cfg` and `cfg_attr`.
 213     pub fn supports_macro_expansion(self) -> bool {
 214         match self {
 215             AstFragmentKind::OptExpr
 216             | AstFragmentKind::Expr
 217             | AstFragmentKind::Pat
 218             | AstFragmentKind::Ty
 219             | AstFragmentKind::Stmts
 220             | AstFragmentKind::Items
 221             | AstFragmentKind::TraitItems
 222             | AstFragmentKind::ImplItems
 223             | AstFragmentKind::ForeignItems => true,
 224             AstFragmentKind::Arms
 225             | AstFragmentKind::Fields
 226             | AstFragmentKind::FieldPats
 227             | AstFragmentKind::GenericParams
 228             | AstFragmentKind::Params
 229             | AstFragmentKind::StructFields
 230             | AstFragmentKind::Variants => false,
 231         }
 232     }
 233
 234     fn expect_from_annotatables<I: IntoIterator<Item = Annotatable>>(
 235         self,
 236         items: I,
 237     ) -> AstFragment {
 238         let mut items = items.into_iter();
 239         match self {
 240             AstFragmentKind::Arms => {
 241                 AstFragment::Arms(items.map(Annotatable::expect_arm).collect())
 242             }
 243             AstFragmentKind::Fields => {
 244                 AstFragment::Fields(items.map(Annotatable::expect_field).collect())
 245             }
 246             AstFragmentKind::FieldPats => {
 247                 AstFragment::FieldPats(items.map(Annotatable::expect_field_pattern).collect())
 248             }
 249             AstFragmentKind::GenericParams => {
 250                 AstFragment::GenericParams(items.map(Annotatable::expect_generic_param).collect())
 251             }
 252             AstFragmentKind::Params => {
 253                 AstFragment::Params(items.map(Annotatable::expect_param).collect())
 254             }
 255             AstFragmentKind::StructFields => {
 256                 AstFragment::StructFields(items.map(Annotatable::expect_struct_field).collect())
 257             }
 258             AstFragmentKind::Variants => {
 259                 AstFragment::Variants(items.map(Annotatable::expect_variant).collect())
 260             }
 261             AstFragmentKind::Items => {
 262                 AstFragment::Items(items.map(Annotatable::expect_item).collect())
 263             }
 264             AstFragmentKind::ImplItems => {
 265                 AstFragment::ImplItems(items.map(Annotatable::expect_impl_item).collect())
 266             }
 267             AstFragmentKind::TraitItems => {
 268                 AstFragment::TraitItems(items.map(Annotatable::expect_trait_item).collect())
 269             }
 270             AstFragmentKind::ForeignItems => {
 271                 AstFragment::ForeignItems(items.map(Annotatable::expect_foreign_item).collect())
 272             }
 273             AstFragmentKind::Stmts => {
 274                 AstFragment::Stmts(items.map(Annotatable::expect_stmt).collect())
 275             }
 276             AstFragmentKind::Expr => AstFragment::Expr(
 277                 items.next().expect("expected exactly one expression").expect_expr(),
 278             ),
 279             AstFragmentKind::OptExpr => {
 280                 AstFragment::OptExpr(items.next().map(Annotatable::expect_expr))
 281             }
 282             AstFragmentKind::Pat | AstFragmentKind::Ty => {
 283                 panic!("patterns and types aren't annotatable")
 284             }
 285         }
 286     }
 287 }
 288
 289 pub struct Invocation {
 290     pub kind: InvocationKind,
 291     pub fragment_kind: AstFragmentKind,
 292     pub expansion_data: ExpansionData,
 293 }
 294
 295 pub enum InvocationKind {
 296     Bang {
 297         mac: ast::MacCall,
 298         span: Span,
 299     },
 300     Attr {
 301         attr: ast::Attribute,
 302         item: Annotatable,
 303         // Required for resolving derive helper attributes.
 304         derives: Vec<Path>,
 305         // We temporarily report errors for attribute macros placed after derives
 306         after_derive: bool,
 307     },
 308     Derive {
 309         path: Path,
 310         item: Annotatable,
 311     },
 312     /// "Invocation" that contains all derives from an item,
 313     /// broken into multiple `Derive` invocations when expanded.
 314     /// FIXME: Find a way to remove it.
 315     DeriveContainer {
 316         derives: Vec<Path>,
 317         item: Annotatable,
 318     },
 319 }
 320
 321 impl InvocationKind {
 322     fn placeholder_visibility(&self) -> Option<ast::Visibility> {
 323         // HACK: For unnamed fields placeholders should have the same visibility as the actual
 324         // fields because for tuple structs/variants resolve determines visibilities of their
 325         // constructor using these field visibilities before attributes on them are are expanded.
 326         // The assumption is that the attribute expansion cannot change field visibilities,
 327         // and it holds because only inert attributes are supported in this position.
 328         match self {
 329             InvocationKind::Attr { item: Annotatable::StructField(field), .. }
 330             | InvocationKind::Derive { item: Annotatable::StructField(field), .. }
 331             | InvocationKind::DeriveContainer { item: Annotatable::StructField(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             InvocationKind::DeriveContainer { item, .. } => item.span(),
 348         }
 349     }
 350 }
 351
 352 pub struct MacroExpander<'a, 'b> {
 353     pub cx: &'a mut ExtCtxt<'b>,
 354     monotonic: bool, // cf. `cx.monotonic_expander()`
 355 }
 356
 357 impl<'a, 'b> MacroExpander<'a, 'b> {
 358     pub fn new(cx: &'a mut ExtCtxt<'b>, monotonic: bool) -> Self {
 359         MacroExpander { cx, monotonic }
 360     }
 361
 362     pub fn expand_crate(&mut self, mut krate: ast::Crate) -> ast::Crate {
 363         let mut module = ModuleData {
 364             mod_path: vec![Ident::from_str(&self.cx.ecfg.crate_name)],
 365             directory: match self.cx.source_map().span_to_unmapped_path(krate.span) {
 366                 FileName::Real(name) => name.into_local_path(),
 367                 other => PathBuf::from(other.to_string()),
 368             },
 369         };
 370         module.directory.pop();
 371         self.cx.root_path = module.directory.clone();
 372         self.cx.current_expansion.module = Rc::new(module);
 373
 374         let orig_mod_span = krate.module.inner;
 375
 376         let krate_item = AstFragment::Items(smallvec![P(ast::Item {
 377             attrs: krate.attrs,
 378             span: krate.span,
 379             kind: ast::ItemKind::Mod(krate.module),
 380             ident: Ident::invalid(),
 381             id: ast::DUMMY_NODE_ID,
 382             vis: ast::Visibility {
 383                 span: krate.span.shrink_to_lo(),
 384                 kind: ast::VisibilityKind::Public,
 385                 tokens: None,
 386             },
 387             tokens: None,
 388         })]);
 389
 390         match self.fully_expand_fragment(krate_item).make_items().pop().map(P::into_inner) {
 391             Some(ast::Item { attrs, kind: ast::ItemKind::Mod(module), .. }) => {
 392                 krate.attrs = attrs;
 393                 krate.module = module;
 394             }
 395             None => {
 396                 // Resolution failed so we return an empty expansion
 397                 krate.attrs = vec![];
 398                 krate.module = ast::Mod {
 399                     inner: orig_mod_span,
 400                     unsafety: Unsafe::No,
 401                     items: vec![],
 402                     inline: true,
 403                 };
 404             }
 405             Some(ast::Item { span, kind, .. }) => {
 406                 krate.attrs = vec![];
 407                 krate.module = ast::Mod {
 408                     inner: orig_mod_span,
 409                     unsafety: Unsafe::No,
 410                     items: vec![],
 411                     inline: true,
 412                 };
 413                 self.cx.span_err(
 414                     span,
 415                     &format!(
 416                         "expected crate top-level item to be a module after macro expansion, found {} {}",
 417                         kind.article(), kind.descr()
 418                     ),
 419                 );
 420             }
 421         };
 422         self.cx.trace_macros_diag();
 423         krate
 424     }
 425
 426     // Recursively expand all macro invocations in this AST fragment.
 427     pub fn fully_expand_fragment(&mut self, input_fragment: AstFragment) -> AstFragment {
 428         let orig_expansion_data = self.cx.current_expansion.clone();
 429         let orig_force_mode = self.cx.force_mode;
 430         self.cx.current_expansion.depth = 0;
 431
 432         // Collect all macro invocations and replace them with placeholders.
 433         let (mut fragment_with_placeholders, mut invocations) =
 434             self.collect_invocations(input_fragment, &[]);
 435
 436         // Optimization: if we resolve all imports now,
 437         // we'll be able to immediately resolve most of imported macros.
 438         self.resolve_imports();
 439
 440         // Resolve paths in all invocations and produce output expanded fragments for them, but
 441         // do not insert them into our input AST fragment yet, only store in `expanded_fragments`.
 442         // The output fragments also go through expansion recursively until no invocations are left.
 443         // Unresolved macros produce dummy outputs as a recovery measure.
 444         invocations.reverse();
 445         let mut expanded_fragments = Vec::new();
 446         let mut undetermined_invocations = Vec::new();
 447         let (mut progress, mut force) = (false, !self.monotonic);
 448         loop {
 449             let (invoc, res) = if let Some(invoc) = invocations.pop() {
 450                 invoc
 451             } else {
 452                 self.resolve_imports();
 453                 if undetermined_invocations.is_empty() {
 454                     break;
 455                 }
 456                 invocations = mem::take(&mut undetermined_invocations);
 457                 force = !mem::replace(&mut progress, false);
 458                 if force && self.monotonic {
 459                     self.cx.sess.delay_span_bug(
 460                         invocations.last().unwrap().0.span(),
 461                         "expansion entered force mode without producing any errors",
 462                     );
 463                 }
 464                 continue;
 465             };
 466
 467             let res = match res {
 468                 Some(res) => res,
 469                 None => {
 470                     let eager_expansion_root = if self.monotonic {
 471                         invoc.expansion_data.id
 472                     } else {
 473                         orig_expansion_data.id
 474                     };
 475                     match self.cx.resolver.resolve_macro_invocation(
 476                         &invoc,
 477                         eager_expansion_root,
 478                         force,
 479                     ) {
 480                         Ok(res) => res,
 481                         Err(Indeterminate) => {
 482                             // Cannot resolve, will retry this invocation later.
 483                             undetermined_invocations.push((invoc, None));
 484                             continue;
 485                         }
 486                     }
 487                 }
 488             };
 489
 490             let ExpansionData { depth, id: expn_id, .. } = invoc.expansion_data;
 491             self.cx.current_expansion = invoc.expansion_data.clone();
 492             self.cx.force_mode = force;
 493
 494             // FIXME(jseyfried): Refactor out the following logic
 495             let fragment_kind = invoc.fragment_kind;
 496             let (expanded_fragment, new_invocations) = match res {
 497                 InvocationRes::Single(ext) => match self.expand_invoc(invoc, &ext.kind) {
 498                     ExpandResult::Ready(fragment) => self.collect_invocations(fragment, &[]),
 499                     ExpandResult::Retry(invoc) => {
 500                         if force {
 501                             self.cx.span_bug(
 502                                 invoc.span(),
 503                                 "expansion entered force mode but is still stuck",
 504                             );
 505                         } else {
 506                             // Cannot expand, will retry this invocation later.
 507                             undetermined_invocations
 508                                 .push((invoc, Some(InvocationRes::Single(ext))));
 509                             continue;
 510                         }
 511                     }
 512                 },
 513                 InvocationRes::DeriveContainer(_exts) => {
 514                     // FIXME: Consider using the derive resolutions (`_exts`) immediately,
 515                     // instead of enqueuing the derives to be resolved again later.
 516                     let (derives, mut item) = match invoc.kind {
 517                         InvocationKind::DeriveContainer { derives, item } => (derives, item),
 518                         _ => unreachable!(),
 519                     };
 520                     let (item, derive_placeholders) = if !item.derive_allowed() {
 521                         self.error_derive_forbidden_on_non_adt(&derives, &item);
 522                         item.visit_attrs(|attrs| attrs.retain(|a| !a.has_name(sym::derive)));
 523                         (item, Vec::new())
 524                     } else {
 525                         let mut visitor = StripUnconfigured {
 526                             sess: self.cx.sess,
 527                             features: self.cx.ecfg.features,
 528                             modified: false,
 529                         };
 530                         let mut item = visitor.fully_configure(item);
 531                         item.visit_attrs(|attrs| attrs.retain(|a| !a.has_name(sym::derive)));
 532                         if visitor.modified && !derives.is_empty() {
 533                             // Erase the tokens if cfg-stripping modified the item
 534                             // This will cause us to synthesize fake tokens
 535                             // when `nt_to_tokenstream` is called on this item.
 536                             match &mut item {
 537                                 Annotatable::Item(item) => item.tokens = None,
 538                                 Annotatable::Stmt(stmt) => {
 539                                     if let StmtKind::Item(item) = &mut stmt.kind {
 540                                         item.tokens = None
 541                                     } else {
 542                                         panic!("Unexpected stmt {:?}", stmt);
 543                                     }
 544                                 }
 545                                 _ => panic!("Unexpected annotatable {:?}", item),
 546                             }
 547                         }
 548
 549                         invocations.reserve(derives.len());
 550                         let derive_placeholders = derives
 551                             .into_iter()
 552                             .map(|path| {
 553                                 let expn_id = ExpnId::fresh(None);
 554                                 invocations.push((
 555                                     Invocation {
 556                                         kind: InvocationKind::Derive { path, item: item.clone() },
 557                                         fragment_kind,
 558                                         expansion_data: ExpansionData {
 559                                             id: expn_id,
 560                                             ..self.cx.current_expansion.clone()
 561                                         },
 562                                     },
 563                                     None,
 564                                 ));
 565                                 NodeId::placeholder_from_expn_id(expn_id)
 566                             })
 567                             .collect::<Vec<_>>();
 568                         (item, derive_placeholders)
 569                     };
 570
 571                     let fragment = fragment_kind.expect_from_annotatables(::std::iter::once(item));
 572                     self.collect_invocations(fragment, &derive_placeholders)
 573                 }
 574             };
 575
 576             progress = true;
 577             if expanded_fragments.len() < depth {
 578                 expanded_fragments.push(Vec::new());
 579             }
 580             expanded_fragments[depth - 1].push((expn_id, expanded_fragment));
 581             invocations.extend(new_invocations.into_iter().rev());
 582         }
 583
 584         self.cx.current_expansion = orig_expansion_data;
 585         self.cx.force_mode = orig_force_mode;
 586
 587         // Finally incorporate all the expanded macros into the input AST fragment.
 588         let mut placeholder_expander = PlaceholderExpander::new(self.cx, self.monotonic);
 589         while let Some(expanded_fragments) = expanded_fragments.pop() {
 590             for (expn_id, expanded_fragment) in expanded_fragments.into_iter().rev() {
 591                 placeholder_expander
 592                     .add(NodeId::placeholder_from_expn_id(expn_id), expanded_fragment);
 593             }
 594         }
 595         fragment_with_placeholders.mut_visit_with(&mut placeholder_expander);
 596         fragment_with_placeholders
 597     }
 598
 599     fn error_derive_forbidden_on_non_adt(&self, derives: &[Path], item: &Annotatable) {
 600         let attr = self.cx.sess.find_by_name(item.attrs(), sym::derive);
 601         let span = attr.map_or(item.span(), |attr| attr.span);
 602         let mut err = struct_span_err!(
 603             self.cx.sess,
 604             span,
 605             E0774,
 606             "`derive` may only be applied to structs, enums and unions",
 607         );
 608         if let Some(ast::Attribute { style: ast::AttrStyle::Inner, .. }) = attr {
 609             let trait_list = derives.iter().map(|t| pprust::path_to_string(t)).collect::<Vec<_>>();
 610             let suggestion = format!("#[derive({})]", trait_list.join(", "));
 611             err.span_suggestion(
 612                 span,
 613                 "try an outer attribute",
 614                 suggestion,
 615                 // We don't 𝑘𝑛𝑜𝑤 that the following item is an ADT
 616                 Applicability::MaybeIncorrect,
 617             );
 618         }
 619         err.emit();
 620     }
 621
 622     fn resolve_imports(&mut self) {
 623         if self.monotonic {
 624             self.cx.resolver.resolve_imports();
 625         }
 626     }
 627
 628     /// Collects all macro invocations reachable at this time in this AST fragment, and replace
 629     /// them with "placeholders" - dummy macro invocations with specially crafted `NodeId`s.
 630     /// Then call into resolver that builds a skeleton ("reduced graph") of the fragment and
 631     /// prepares data for resolving paths of macro invocations.
 632     fn collect_invocations(
 633         &mut self,
 634         mut fragment: AstFragment,
 635         extra_placeholders: &[NodeId],
 636     ) -> (AstFragment, Vec<(Invocation, Option<InvocationRes>)>) {
 637         // Resolve `$crate`s in the fragment for pretty-printing.
 638         self.cx.resolver.resolve_dollar_crates();
 639
 640         let invocations = {
 641             let mut collector = InvocationCollector {
 642                 cfg: StripUnconfigured {
 643                     sess: &self.cx.sess,
 644                     features: self.cx.ecfg.features,
 645                     modified: false,
 646                 },
 647                 cx: self.cx,
 648                 invocations: Vec::new(),
 649                 monotonic: self.monotonic,
 650             };
 651             fragment.mut_visit_with(&mut collector);
 652             fragment.add_placeholders(extra_placeholders);
 653             collector.invocations
 654         };
 655
 656         if self.monotonic {
 657             self.cx
 658                 .resolver
 659                 .visit_ast_fragment_with_placeholders(self.cx.current_expansion.id, &fragment);
 660         }
 661
 662         (fragment, invocations)
 663     }
 664
 665     fn error_recursion_limit_reached(&mut self) {
 666         let expn_data = self.cx.current_expansion.id.expn_data();
 667         let suggested_limit = self.cx.ecfg.recursion_limit * 2;
 668         self.cx
 669             .struct_span_err(
 670                 expn_data.call_site,
 671                 &format!("recursion limit reached while expanding `{}`", expn_data.kind.descr()),
 672             )
 673             .help(&format!(
 674                 "consider adding a `#![recursion_limit=\"{}\"]` attribute to your crate (`{}`)",
 675                 suggested_limit, self.cx.ecfg.crate_name,
 676             ))
 677             .emit();
 678         self.cx.trace_macros_diag();
 679     }
 680
 681     /// A macro's expansion does not fit in this fragment kind.
 682     /// For example, a non-type macro in a type position.
 683     fn error_wrong_fragment_kind(&mut self, kind: AstFragmentKind, mac: &ast::MacCall, span: Span) {
 684         let msg = format!(
 685             "non-{kind} macro in {kind} position: {path}",
 686             kind = kind.name(),
 687             path = pprust::path_to_string(&mac.path),
 688         );
 689         self.cx.span_err(span, &msg);
 690         self.cx.trace_macros_diag();
 691     }
 692
 693     fn expand_invoc(
 694         &mut self,
 695         invoc: Invocation,
 696         ext: &SyntaxExtensionKind,
 697     ) -> ExpandResult<AstFragment, Invocation> {
 698         let recursion_limit =
 699             self.cx.reduced_recursion_limit.unwrap_or(self.cx.ecfg.recursion_limit);
 700         if !recursion_limit.value_within_limit(self.cx.current_expansion.depth) {
 701             if self.cx.reduced_recursion_limit.is_none() {
 702                 self.error_recursion_limit_reached();
 703             }
 704
 705             // Reduce the recursion limit by half each time it triggers.
 706             self.cx.reduced_recursion_limit = Some(recursion_limit / 2);
 707
 708             return ExpandResult::Ready(invoc.fragment_kind.dummy(invoc.span()));
 709         }
 710
 711         let (fragment_kind, span) = (invoc.fragment_kind, invoc.span());
 712         ExpandResult::Ready(match invoc.kind {
 713             InvocationKind::Bang { mac, .. } => match ext {
 714                 SyntaxExtensionKind::Bang(expander) => {
 715                     let tok_result = match expander.expand(self.cx, span, mac.args.inner_tokens()) {
 716                         Err(_) => return ExpandResult::Ready(fragment_kind.dummy(span)),
 717                         Ok(ts) => ts,
 718                     };
 719                     self.parse_ast_fragment(tok_result, fragment_kind, &mac.path, span)
 720                 }
 721                 SyntaxExtensionKind::LegacyBang(expander) => {
 722                     let prev = self.cx.current_expansion.prior_type_ascription;
 723                     self.cx.current_expansion.prior_type_ascription = mac.prior_type_ascription;
 724                     let tok_result = expander.expand(self.cx, span, mac.args.inner_tokens());
 725                     let result = if let Some(result) = fragment_kind.make_from(tok_result) {
 726                         result
 727                     } else {
 728                         self.error_wrong_fragment_kind(fragment_kind, &mac, span);
 729                         fragment_kind.dummy(span)
 730                     };
 731                     self.cx.current_expansion.prior_type_ascription = prev;
 732                     result
 733                 }
 734                 _ => unreachable!(),
 735             },
 736             InvocationKind::Attr { attr, mut item, derives, after_derive } => match ext {
 737                 SyntaxExtensionKind::Attr(expander) => {
 738                     self.gate_proc_macro_input(&item);
 739                     self.gate_proc_macro_attr_item(span, &item);
 740                     let tokens = match attr.style {
 741                         AttrStyle::Outer => item.into_tokens(&self.cx.sess.parse_sess),
 742                         // FIXME: Properly collect tokens for inner attributes
 743                         AttrStyle::Inner => rustc_parse::fake_token_stream(
 744                             &self.cx.sess.parse_sess,
 745                             &item.into_nonterminal(),
 746                             span,
 747                         ),
 748                     };
 749                     let attr_item = attr.unwrap_normal_item();
 750                     if let MacArgs::Eq(..) = attr_item.args {
 751                         self.cx.span_err(span, "key-value macro attributes are not supported");
 752                     }
 753                     let inner_tokens = attr_item.args.inner_tokens();
 754                     let tok_result = match expander.expand(self.cx, span, inner_tokens, tokens) {
 755                         Err(_) => return ExpandResult::Ready(fragment_kind.dummy(span)),
 756                         Ok(ts) => ts,
 757                     };
 758                     self.parse_ast_fragment(tok_result, fragment_kind, &attr_item.path, span)
 759                 }
 760                 SyntaxExtensionKind::LegacyAttr(expander) => {
 761                     match validate_attr::parse_meta(&self.cx.sess.parse_sess, &attr) {
 762                         Ok(meta) => {
 763                             let items = match expander.expand(self.cx, span, &meta, item) {
 764                                 ExpandResult::Ready(items) => items,
 765                                 ExpandResult::Retry(item) => {
 766                                     // Reassemble the original invocation for retrying.
 767                                     return ExpandResult::Retry(Invocation {
 768                                         kind: InvocationKind::Attr {
 769                                             attr,
 770                                             item,
 771                                             derives,
 772                                             after_derive,
 773                                         },
 774                                         ..invoc
 775                                     });
 776                                 }
 777                             };
 778                             fragment_kind.expect_from_annotatables(items)
 779                         }
 780                         Err(mut err) => {
 781                             err.emit();
 782                             fragment_kind.dummy(span)
 783                         }
 784                     }
 785                 }
 786                 SyntaxExtensionKind::NonMacroAttr { mark_used } => {
 787                     self.cx.sess.mark_attr_known(&attr);
 788                     if *mark_used {
 789                         self.cx.sess.mark_attr_used(&attr);
 790                     }
 791                     item.visit_attrs(|attrs| attrs.push(attr));
 792                     fragment_kind.expect_from_annotatables(iter::once(item))
 793                 }
 794                 _ => unreachable!(),
 795             },
 796             InvocationKind::Derive { path, item } => match ext {
 797                 SyntaxExtensionKind::Derive(expander)
 798                 | SyntaxExtensionKind::LegacyDerive(expander) => {
 799                     if let SyntaxExtensionKind::Derive(..) = ext {
 800                         self.gate_proc_macro_input(&item);
 801                     }
 802                     let meta = ast::MetaItem { kind: ast::MetaItemKind::Word, span, path };
 803                     let items = match expander.expand(self.cx, span, &meta, item) {
 804                         ExpandResult::Ready(items) => items,
 805                         ExpandResult::Retry(item) => {
 806                             // Reassemble the original invocation for retrying.
 807                             return ExpandResult::Retry(Invocation {
 808                                 kind: InvocationKind::Derive { path: meta.path, item },
 809                                 ..invoc
 810                             });
 811                         }
 812                     };
 813                     fragment_kind.expect_from_annotatables(items)
 814                 }
 815                 _ => unreachable!(),
 816             },
 817             InvocationKind::DeriveContainer { .. } => unreachable!(),
 818         })
 819     }
 820
 821     fn gate_proc_macro_attr_item(&self, span: Span, item: &Annotatable) {
 822         let kind = match item {
 823             Annotatable::Item(_)
 824             | Annotatable::TraitItem(_)
 825             | Annotatable::ImplItem(_)
 826             | Annotatable::ForeignItem(_) => return,
 827             Annotatable::Stmt(stmt) => {
 828                 // Attributes are stable on item statements,
 829                 // but unstable on all other kinds of statements
 830                 if stmt.is_item() {
 831                     return;
 832                 }
 833                 "statements"
 834             }
 835             Annotatable::Expr(_) => "expressions",
 836             Annotatable::Arm(..)
 837             | Annotatable::Field(..)
 838             | Annotatable::FieldPat(..)
 839             | Annotatable::GenericParam(..)
 840             | Annotatable::Param(..)
 841             | Annotatable::StructField(..)
 842             | Annotatable::Variant(..) => panic!("unexpected annotatable"),
 843         };
 844         if self.cx.ecfg.proc_macro_hygiene() {
 845             return;
 846         }
 847         feature_err(
 848             &self.cx.sess.parse_sess,
 849             sym::proc_macro_hygiene,
 850             span,
 851             &format!("custom attributes cannot be applied to {}", kind),
 852         )
 853         .emit();
 854     }
 855
 856     fn gate_proc_macro_input(&self, annotatable: &Annotatable) {
 857         struct GateProcMacroInput<'a> {
 858             parse_sess: &'a ParseSess,
 859         }
 860
 861         impl<'ast, 'a> Visitor<'ast> for GateProcMacroInput<'a> {
 862             fn visit_item(&mut self, item: &'ast ast::Item) {
 863                 match &item.kind {
 864                     ast::ItemKind::Mod(module) if !module.inline => {
 865                         feature_err(
 866                             self.parse_sess,
 867                             sym::proc_macro_hygiene,
 868                             item.span,
 869                             "non-inline modules in proc macro input are unstable",
 870                         )
 871                         .emit();
 872                     }
 873                     _ => {}
 874                 }
 875
 876                 visit::walk_item(self, item);
 877             }
 878         }
 879
 880         if !self.cx.ecfg.proc_macro_hygiene() {
 881             annotatable
 882                 .visit_with(&mut GateProcMacroInput { parse_sess: &self.cx.sess.parse_sess });
 883         }
 884     }
 885
 886     fn parse_ast_fragment(
 887         &mut self,
 888         toks: TokenStream,
 889         kind: AstFragmentKind,
 890         path: &Path,
 891         span: Span,
 892     ) -> AstFragment {
 893         let mut parser = self.cx.new_parser_from_tts(toks);
 894         match parse_ast_fragment(&mut parser, kind) {
 895             Ok(fragment) => {
 896                 ensure_complete_parse(&mut parser, path, kind.name(), span);
 897                 fragment
 898             }
 899             Err(mut err) => {
 900                 err.set_span(span);
 901                 annotate_err_with_kind(&mut err, kind, span);
 902                 err.emit();
 903                 self.cx.trace_macros_diag();
 904                 kind.dummy(span)
 905             }
 906         }
 907     }
 908 }
 909
 910 pub fn parse_ast_fragment<'a>(
 911     this: &mut Parser<'a>,
 912     kind: AstFragmentKind,
 913 ) -> PResult<'a, AstFragment> {
 914     Ok(match kind {
 915         AstFragmentKind::Items => {
 916             let mut items = SmallVec::new();
 917             while let Some(item) = this.parse_item()? {
 918                 items.push(item);
 919             }
 920             AstFragment::Items(items)
 921         }
 922         AstFragmentKind::TraitItems => {
 923             let mut items = SmallVec::new();
 924             while let Some(item) = this.parse_trait_item()? {
 925                 items.extend(item);
 926             }
 927             AstFragment::TraitItems(items)
 928         }
 929         AstFragmentKind::ImplItems => {
 930             let mut items = SmallVec::new();
 931             while let Some(item) = this.parse_impl_item()? {
 932                 items.extend(item);
 933             }
 934             AstFragment::ImplItems(items)
 935         }
 936         AstFragmentKind::ForeignItems => {
 937             let mut items = SmallVec::new();
 938             while let Some(item) = this.parse_foreign_item()? {
 939                 items.extend(item);
 940             }
 941             AstFragment::ForeignItems(items)
 942         }
 943         AstFragmentKind::Stmts => {
 944             let mut stmts = SmallVec::new();
 945             // Won't make progress on a `}`.
 946             while this.token != token::Eof && this.token != token::CloseDelim(token::Brace) {
 947                 if let Some(stmt) = this.parse_full_stmt(AttemptLocalParseRecovery::Yes)? {
 948                     stmts.push(stmt);
 949                 }
 950             }
 951             AstFragment::Stmts(stmts)
 952         }
 953         AstFragmentKind::Expr => AstFragment::Expr(this.parse_expr()?),
 954         AstFragmentKind::OptExpr => {
 955             if this.token != token::Eof {
 956                 AstFragment::OptExpr(Some(this.parse_expr()?))
 957             } else {
 958                 AstFragment::OptExpr(None)
 959             }
 960         }
 961         AstFragmentKind::Ty => AstFragment::Ty(this.parse_ty()?),
 962         AstFragmentKind::Pat => AstFragment::Pat(this.parse_pat(None)?),
 963         AstFragmentKind::Arms
 964         | AstFragmentKind::Fields
 965         | AstFragmentKind::FieldPats
 966         | AstFragmentKind::GenericParams
 967         | AstFragmentKind::Params
 968         | AstFragmentKind::StructFields
 969         | AstFragmentKind::Variants => panic!("unexpected AST fragment kind"),
 970     })
 971 }
 972
 973 pub fn ensure_complete_parse<'a>(
 974     this: &mut Parser<'a>,
 975     macro_path: &Path,
 976     kind_name: &str,
 977     span: Span,
 978 ) {
 979     if this.token != token::Eof {
 980         let token = pprust::token_to_string(&this.token);
 981         let msg = format!("macro expansion ignores token `{}` and any following", token);
 982         // Avoid emitting backtrace info twice.
 983         let def_site_span = this.token.span.with_ctxt(SyntaxContext::root());
 984         let mut err = this.struct_span_err(def_site_span, &msg);
 985         err.span_label(span, "caused by the macro expansion here");
 986         let msg = format!(
 987             "the usage of `{}!` is likely invalid in {} context",
 988             pprust::path_to_string(macro_path),
 989             kind_name,
 990         );
 991         err.note(&msg);
 992         let semi_span = this.sess.source_map().next_point(span);
 993
 994         let semi_full_span = semi_span.to(this.sess.source_map().next_point(semi_span));
 995         match this.sess.source_map().span_to_snippet(semi_full_span) {
 996             Ok(ref snippet) if &snippet[..] != ";" && kind_name == "expression" => {
 997                 err.span_suggestion(
 998                     semi_span,
 999                     "you might be missing a semicolon here",
1000                     ";".to_owned(),
1001                     Applicability::MaybeIncorrect,
1002                 );
1003             }
1004             _ => {}
1005         }
1006         err.emit();
1007     }
1008 }
1009
1010 struct InvocationCollector<'a, 'b> {
1011     cx: &'a mut ExtCtxt<'b>,
1012     cfg: StripUnconfigured<'a>,
1013     invocations: Vec<(Invocation, Option<InvocationRes>)>,
1014     monotonic: bool,
1015 }
1016
1017 impl<'a, 'b> InvocationCollector<'a, 'b> {
1018     fn collect(&mut self, fragment_kind: AstFragmentKind, kind: InvocationKind) -> AstFragment {
1019         // Expansion data for all the collected invocations is set upon their resolution,
1020         // with exception of the derive container case which is not resolved and can get
1021         // its expansion data immediately.
1022         let expn_data = match &kind {
1023             InvocationKind::DeriveContainer { item, .. } => {
1024                 let mut expn_data = ExpnData::default(
1025                     ExpnKind::Macro(MacroKind::Attr, sym::derive),
1026                     item.span(),
1027                     self.cx.sess.parse_sess.edition,
1028                     None,
1029                 );
1030                 expn_data.parent = self.cx.current_expansion.id;
1031                 Some(expn_data)
1032             }
1033             _ => None,
1034         };
1035         let expn_id = ExpnId::fresh(expn_data);
1036         let vis = kind.placeholder_visibility();
1037         self.invocations.push((
1038             Invocation {
1039                 kind,
1040                 fragment_kind,
1041                 expansion_data: ExpansionData {
1042                     id: expn_id,
1043                     depth: self.cx.current_expansion.depth + 1,
1044                     ..self.cx.current_expansion.clone()
1045                 },
1046             },
1047             None,
1048         ));
1049         placeholder(fragment_kind, NodeId::placeholder_from_expn_id(expn_id), vis)
1050     }
1051
1052     fn collect_bang(
1053         &mut self,
1054         mac: ast::MacCall,
1055         span: Span,
1056         kind: AstFragmentKind,
1057     ) -> AstFragment {
1058         self.collect(kind, InvocationKind::Bang { mac, span })
1059     }
1060
1061     fn collect_attr(
1062         &mut self,
1063         (attr, derives, after_derive): (Option<ast::Attribute>, Vec<Path>, bool),
1064         item: Annotatable,
1065         kind: AstFragmentKind,
1066     ) -> AstFragment {
1067         self.collect(
1068             kind,
1069             match attr {
1070                 Some(attr) => InvocationKind::Attr { attr, item, derives, after_derive },
1071                 None => InvocationKind::DeriveContainer { derives, item },
1072             },
1073         )
1074     }
1075
1076     fn find_attr_invoc(
1077         &self,
1078         attrs: &mut Vec<ast::Attribute>,
1079         after_derive: &mut bool,
1080     ) -> Option<ast::Attribute> {
1081         attrs
1082             .iter()
1083             .position(|a| {
1084                 if a.has_name(sym::derive) {
1085                     *after_derive = true;
1086                 }
1087                 !self.cx.sess.is_attr_known(a) && !is_builtin_attr(a)
1088             })
1089             .map(|i| attrs.remove(i))
1090     }
1091
1092     /// If `item` is an attr invocation, remove and return the macro attribute and derive traits.
1093     fn take_first_attr(
1094         &mut self,
1095         item: &mut impl HasAttrs,
1096     ) -> Option<(Option<ast::Attribute>, Vec<Path>, /* after_derive */ bool)> {
1097         let (mut attr, mut traits, mut after_derive) = (None, Vec::new(), false);
1098
1099         item.visit_attrs(|mut attrs| {
1100             attr = self.find_attr_invoc(&mut attrs, &mut after_derive);
1101             traits = collect_derives(&mut self.cx, &mut attrs);
1102         });
1103
1104         if attr.is_some() || !traits.is_empty() { Some((attr, traits, after_derive)) } else { None }
1105     }
1106
1107     /// Alternative to `take_first_attr()` that ignores `#[derive]` so invocations fallthrough
1108     /// to the unused-attributes lint (making it an error on statements and expressions
1109     /// is a breaking change)
1110     fn take_first_attr_no_derive(
1111         &mut self,
1112         nonitem: &mut impl HasAttrs,
1113     ) -> Option<(Option<ast::Attribute>, Vec<Path>, /* after_derive */ bool)> {
1114         let (mut attr, mut after_derive) = (None, false);
1115
1116         nonitem.visit_attrs(|mut attrs| {
1117             attr = self.find_attr_invoc(&mut attrs, &mut after_derive);
1118         });
1119
1120         attr.map(|attr| (Some(attr), Vec::new(), after_derive))
1121     }
1122
1123     fn configure<T: HasAttrs>(&mut self, node: T) -> Option<T> {
1124         self.cfg.configure(node)
1125     }
1126
1127     // Detect use of feature-gated or invalid attributes on macro invocations
1128     // since they will not be detected after macro expansion.
1129     fn check_attributes(&mut self, attrs: &[ast::Attribute]) {
1130         let features = self.cx.ecfg.features.unwrap();
1131         for attr in attrs.iter() {
1132             rustc_ast_passes::feature_gate::check_attribute(attr, self.cx.sess, features);
1133             validate_attr::check_meta(&self.cx.sess.parse_sess, attr);
1134
1135             // macros are expanded before any lint passes so this warning has to be hardcoded
1136             if attr.has_name(sym::derive) {
1137                 self.cx
1138                     .parse_sess()
1139                     .span_diagnostic
1140                     .struct_span_warn(attr.span, "`#[derive]` does nothing on macro invocations")
1141                     .note("this may become a hard error in a future release")
1142                     .emit();
1143             }
1144
1145             if attr.doc_str().is_some() {
1146                 self.cx.sess.parse_sess.buffer_lint_with_diagnostic(
1147                     &UNUSED_DOC_COMMENTS,
1148                     attr.span,
1149                     ast::CRATE_NODE_ID,
1150                     "unused doc comment",
1151                     BuiltinLintDiagnostics::UnusedDocComment(attr.span),
1152                 );
1153             }
1154         }
1155     }
1156 }
1157
1158 impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
1159     fn visit_expr(&mut self, expr: &mut P<ast::Expr>) {
1160         self.cfg.configure_expr(expr);
1161         visit_clobber(expr.deref_mut(), |mut expr| {
1162             self.cfg.configure_expr_kind(&mut expr.kind);
1163
1164             if let Some(attr) = self.take_first_attr_no_derive(&mut expr) {
1165                 // Collect the invoc regardless of whether or not attributes are permitted here
1166                 // expansion will eat the attribute so it won't error later.
1167                 if let Some(attr) = attr.0.as_ref() {
1168                     self.cfg.maybe_emit_expr_attr_err(attr)
1169                 }
1170
1171                 // AstFragmentKind::Expr requires the macro to emit an expression.
1172                 return self
1173                     .collect_attr(attr, Annotatable::Expr(P(expr)), AstFragmentKind::Expr)
1174                     .make_expr()
1175                     .into_inner();
1176             }
1177
1178             if let ast::ExprKind::MacCall(mac) = expr.kind {
1179                 self.check_attributes(&expr.attrs);
1180                 self.collect_bang(mac, expr.span, AstFragmentKind::Expr).make_expr().into_inner()
1181             } else {
1182                 ensure_sufficient_stack(|| noop_visit_expr(&mut expr, self));
1183                 expr
1184             }
1185         });
1186     }
1187
1188     fn flat_map_arm(&mut self, arm: ast::Arm) -> SmallVec<[ast::Arm; 1]> {
1189         let mut arm = configure!(self, arm);
1190
1191         if let Some(attr) = self.take_first_attr(&mut arm) {
1192             return self
1193                 .collect_attr(attr, Annotatable::Arm(arm), AstFragmentKind::Arms)
1194                 .make_arms();
1195         }
1196
1197         noop_flat_map_arm(arm, self)
1198     }
1199
1200     fn flat_map_field(&mut self, field: ast::Field) -> SmallVec<[ast::Field; 1]> {
1201         let mut field = configure!(self, field);
1202
1203         if let Some(attr) = self.take_first_attr(&mut field) {
1204             return self
1205                 .collect_attr(attr, Annotatable::Field(field), AstFragmentKind::Fields)
1206                 .make_fields();
1207         }
1208
1209         noop_flat_map_field(field, self)
1210     }
1211
1212     fn flat_map_field_pattern(&mut self, fp: ast::FieldPat) -> SmallVec<[ast::FieldPat; 1]> {
1213         let mut fp = configure!(self, fp);
1214
1215         if let Some(attr) = self.take_first_attr(&mut fp) {
1216             return self
1217                 .collect_attr(attr, Annotatable::FieldPat(fp), AstFragmentKind::FieldPats)
1218                 .make_field_patterns();
1219         }
1220
1221         noop_flat_map_field_pattern(fp, self)
1222     }
1223
1224     fn flat_map_param(&mut self, p: ast::Param) -> SmallVec<[ast::Param; 1]> {
1225         let mut p = configure!(self, p);
1226
1227         if let Some(attr) = self.take_first_attr(&mut p) {
1228             return self
1229                 .collect_attr(attr, Annotatable::Param(p), AstFragmentKind::Params)
1230                 .make_params();
1231         }
1232
1233         noop_flat_map_param(p, self)
1234     }
1235
1236     fn flat_map_struct_field(&mut self, sf: ast::StructField) -> SmallVec<[ast::StructField; 1]> {
1237         let mut sf = configure!(self, sf);
1238
1239         if let Some(attr) = self.take_first_attr(&mut sf) {
1240             return self
1241                 .collect_attr(attr, Annotatable::StructField(sf), AstFragmentKind::StructFields)
1242                 .make_struct_fields();
1243         }
1244
1245         noop_flat_map_struct_field(sf, self)
1246     }
1247
1248     fn flat_map_variant(&mut self, variant: ast::Variant) -> SmallVec<[ast::Variant; 1]> {
1249         let mut variant = configure!(self, variant);
1250
1251         if let Some(attr) = self.take_first_attr(&mut variant) {
1252             return self
1253                 .collect_attr(attr, Annotatable::Variant(variant), AstFragmentKind::Variants)
1254                 .make_variants();
1255         }
1256
1257         noop_flat_map_variant(variant, self)
1258     }
1259
1260     fn filter_map_expr(&mut self, expr: P<ast::Expr>) -> Option<P<ast::Expr>> {
1261         let expr = configure!(self, expr);
1262         expr.filter_map(|mut expr| {
1263             self.cfg.configure_expr_kind(&mut expr.kind);
1264
1265             if let Some(attr) = self.take_first_attr_no_derive(&mut expr) {
1266                 if let Some(attr) = attr.0.as_ref() {
1267                     self.cfg.maybe_emit_expr_attr_err(attr)
1268                 }
1269
1270                 return self
1271                     .collect_attr(attr, Annotatable::Expr(P(expr)), AstFragmentKind::OptExpr)
1272                     .make_opt_expr()
1273                     .map(|expr| expr.into_inner());
1274             }
1275
1276             if let ast::ExprKind::MacCall(mac) = expr.kind {
1277                 self.check_attributes(&expr.attrs);
1278                 self.collect_bang(mac, expr.span, AstFragmentKind::OptExpr)
1279                     .make_opt_expr()
1280                     .map(|expr| expr.into_inner())
1281             } else {
1282                 Some({
1283                     noop_visit_expr(&mut expr, self);
1284                     expr
1285                 })
1286             }
1287         })
1288     }
1289
1290     fn visit_pat(&mut self, pat: &mut P<ast::Pat>) {
1291         self.cfg.configure_pat(pat);
1292         match pat.kind {
1293             PatKind::MacCall(_) => {}
1294             _ => return noop_visit_pat(pat, self),
1295         }
1296
1297         visit_clobber(pat, |mut pat| match mem::replace(&mut pat.kind, PatKind::Wild) {
1298             PatKind::MacCall(mac) => {
1299                 self.collect_bang(mac, pat.span, AstFragmentKind::Pat).make_pat()
1300             }
1301             _ => unreachable!(),
1302         });
1303     }
1304
1305     fn flat_map_stmt(&mut self, stmt: ast::Stmt) -> SmallVec<[ast::Stmt; 1]> {
1306         let mut stmt = configure!(self, stmt);
1307
1308         // we'll expand attributes on expressions separately
1309         if !stmt.is_expr() {
1310             let attr = if stmt.is_item() {
1311                 self.take_first_attr(&mut stmt)
1312             } else {
1313                 // Ignore derives on non-item statements for backwards compatibility.
1314                 // This will result in a unused attribute warning
1315                 self.take_first_attr_no_derive(&mut stmt)
1316             };
1317
1318             if let Some(attr) = attr {
1319                 return self
1320                     .collect_attr(attr, Annotatable::Stmt(P(stmt)), AstFragmentKind::Stmts)
1321                     .make_stmts();
1322             }
1323         }
1324
1325         if let StmtKind::MacCall(mac) = stmt.kind {
1326             let MacCallStmt { mac, style, attrs, tokens: _ } = mac.into_inner();
1327             self.check_attributes(&attrs);
1328             let mut placeholder =
1329                 self.collect_bang(mac, stmt.span, AstFragmentKind::Stmts).make_stmts();
1330
1331             // If this is a macro invocation with a semicolon, then apply that
1332             // semicolon to the final statement produced by expansion.
1333             if style == MacStmtStyle::Semicolon {
1334                 if let Some(stmt) = placeholder.pop() {
1335                     placeholder.push(stmt.add_trailing_semicolon());
1336                 }
1337             }
1338
1339             return placeholder;
1340         }
1341
1342         // The placeholder expander gives ids to statements, so we avoid folding the id here.
1343         let ast::Stmt { id, kind, span } = stmt;
1344         noop_flat_map_stmt_kind(kind, self)
1345             .into_iter()
1346             .map(|kind| ast::Stmt { id, kind, span })
1347             .collect()
1348     }
1349
1350     fn visit_block(&mut self, block: &mut P<Block>) {
1351         let old_directory_ownership = self.cx.current_expansion.directory_ownership;
1352         self.cx.current_expansion.directory_ownership = DirectoryOwnership::UnownedViaBlock;
1353         noop_visit_block(block, self);
1354         self.cx.current_expansion.directory_ownership = old_directory_ownership;
1355     }
1356
1357     fn flat_map_item(&mut self, item: P<ast::Item>) -> SmallVec<[P<ast::Item>; 1]> {
1358         let mut item = configure!(self, item);
1359
1360         if let Some(attr) = self.take_first_attr(&mut item) {
1361             return self
1362                 .collect_attr(attr, Annotatable::Item(item), AstFragmentKind::Items)
1363                 .make_items();
1364         }
1365
1366         let mut attrs = mem::take(&mut item.attrs); // We do this to please borrowck.
1367         let ident = item.ident;
1368         let span = item.span;
1369
1370         match item.kind {
1371             ast::ItemKind::MacCall(..) => {
1372                 item.attrs = attrs;
1373                 self.check_attributes(&item.attrs);
1374                 item.and_then(|item| match item.kind {
1375                     ItemKind::MacCall(mac) => {
1376                         self.collect_bang(mac, span, AstFragmentKind::Items).make_items()
1377                     }
1378                     _ => unreachable!(),
1379                 })
1380             }
1381             ast::ItemKind::Mod(ref mut old_mod @ ast::Mod { .. }) if ident != Ident::invalid() => {
1382                 let sess = &self.cx.sess.parse_sess;
1383                 let orig_ownership = self.cx.current_expansion.directory_ownership;
1384                 let mut module = (*self.cx.current_expansion.module).clone();
1385
1386                 let pushed = &mut false; // Record `parse_external_mod` pushing so we can pop.
1387                 let dir = Directory { ownership: orig_ownership, path: module.directory };
1388                 let Directory { ownership, path } = if old_mod.inline {
1389                     // Inline `mod foo { ... }`, but we still need to push directories.
1390                     item.attrs = attrs;
1391                     push_directory(&self.cx.sess, ident, &item.attrs, dir)
1392                 } else {
1393                     // We have an outline `mod foo;` so we need to parse the file.
1394                     let (new_mod, dir) = parse_external_mod(
1395                         &self.cx.sess,
1396                         ident,
1397                         span,
1398                         old_mod.unsafety,
1399                         dir,
1400                         &mut attrs,
1401                         pushed,
1402                     );
1403
1404                     let krate = ast::Crate {
1405                         span: new_mod.inner,
1406                         module: new_mod,
1407                         attrs,
1408                         proc_macros: vec![],
1409                     };
1410                     if let Some(extern_mod_loaded) = self.cx.extern_mod_loaded {
1411                         extern_mod_loaded(&krate);
1412                     }
1413
1414                     *old_mod = krate.module;
1415                     item.attrs = krate.attrs;
1416                     // File can have inline attributes, e.g., `#![cfg(...)]` & co. => Reconfigure.
1417                     item = match self.configure(item) {
1418                         Some(node) => node,
1419                         None => {
1420                             if *pushed {
1421                                 sess.included_mod_stack.borrow_mut().pop();
1422                             }
1423                             return Default::default();
1424                         }
1425                     };
1426                     dir
1427                 };
1428
1429                 // Set the module info before we flat map.
1430                 self.cx.current_expansion.directory_ownership = ownership;
1431                 module.directory = path;
1432                 module.mod_path.push(ident);
1433                 let orig_module =
1434                     mem::replace(&mut self.cx.current_expansion.module, Rc::new(module));
1435
1436                 let result = noop_flat_map_item(item, self);
1437
1438                 // Restore the module info.
1439                 self.cx.current_expansion.module = orig_module;
1440                 self.cx.current_expansion.directory_ownership = orig_ownership;
1441                 if *pushed {
1442                     sess.included_mod_stack.borrow_mut().pop();
1443                 }
1444                 result
1445             }
1446             _ => {
1447                 item.attrs = attrs;
1448                 noop_flat_map_item(item, self)
1449             }
1450         }
1451     }
1452
1453     fn flat_map_trait_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
1454         let mut item = configure!(self, item);
1455
1456         if let Some(attr) = self.take_first_attr(&mut item) {
1457             return self
1458                 .collect_attr(attr, Annotatable::TraitItem(item), AstFragmentKind::TraitItems)
1459                 .make_trait_items();
1460         }
1461
1462         match item.kind {
1463             ast::AssocItemKind::MacCall(..) => {
1464                 self.check_attributes(&item.attrs);
1465                 item.and_then(|item| match item.kind {
1466                     ast::AssocItemKind::MacCall(mac) => self
1467                         .collect_bang(mac, item.span, AstFragmentKind::TraitItems)
1468                         .make_trait_items(),
1469                     _ => unreachable!(),
1470                 })
1471             }
1472             _ => noop_flat_map_assoc_item(item, self),
1473         }
1474     }
1475
1476     fn flat_map_impl_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
1477         let mut item = configure!(self, item);
1478
1479         if let Some(attr) = self.take_first_attr(&mut item) {
1480             return self
1481                 .collect_attr(attr, Annotatable::ImplItem(item), AstFragmentKind::ImplItems)
1482                 .make_impl_items();
1483         }
1484
1485         match item.kind {
1486             ast::AssocItemKind::MacCall(..) => {
1487                 self.check_attributes(&item.attrs);
1488                 item.and_then(|item| match item.kind {
1489                     ast::AssocItemKind::MacCall(mac) => self
1490                         .collect_bang(mac, item.span, AstFragmentKind::ImplItems)
1491                         .make_impl_items(),
1492                     _ => unreachable!(),
1493                 })
1494             }
1495             _ => noop_flat_map_assoc_item(item, self),
1496         }
1497     }
1498
1499     fn visit_ty(&mut self, ty: &mut P<ast::Ty>) {
1500         match ty.kind {
1501             ast::TyKind::MacCall(_) => {}
1502             _ => return noop_visit_ty(ty, self),
1503         };
1504
1505         visit_clobber(ty, |mut ty| match mem::replace(&mut ty.kind, ast::TyKind::Err) {
1506             ast::TyKind::MacCall(mac) => {
1507                 self.collect_bang(mac, ty.span, AstFragmentKind::Ty).make_ty()
1508             }
1509             _ => unreachable!(),
1510         });
1511     }
1512
1513     fn visit_foreign_mod(&mut self, foreign_mod: &mut ast::ForeignMod) {
1514         self.cfg.configure_foreign_mod(foreign_mod);
1515         noop_visit_foreign_mod(foreign_mod, self);
1516     }
1517
1518     fn flat_map_foreign_item(
1519         &mut self,
1520         mut foreign_item: P<ast::ForeignItem>,
1521     ) -> SmallVec<[P<ast::ForeignItem>; 1]> {
1522         if let Some(attr) = self.take_first_attr(&mut foreign_item) {
1523             return self
1524                 .collect_attr(
1525                     attr,
1526                     Annotatable::ForeignItem(foreign_item),
1527                     AstFragmentKind::ForeignItems,
1528                 )
1529                 .make_foreign_items();
1530         }
1531
1532         match foreign_item.kind {
1533             ast::ForeignItemKind::MacCall(..) => {
1534                 self.check_attributes(&foreign_item.attrs);
1535                 foreign_item.and_then(|item| match item.kind {
1536                     ast::ForeignItemKind::MacCall(mac) => self
1537                         .collect_bang(mac, item.span, AstFragmentKind::ForeignItems)
1538                         .make_foreign_items(),
1539                     _ => unreachable!(),
1540                 })
1541             }
1542             _ => noop_flat_map_foreign_item(foreign_item, self),
1543         }
1544     }
1545
1546     fn visit_item_kind(&mut self, item: &mut ast::ItemKind) {
1547         match item {
1548             ast::ItemKind::MacroDef(..) => {}
1549             _ => {
1550                 self.cfg.configure_item_kind(item);
1551                 noop_visit_item_kind(item, self);
1552             }
1553         }
1554     }
1555
1556     fn flat_map_generic_param(
1557         &mut self,
1558         param: ast::GenericParam,
1559     ) -> SmallVec<[ast::GenericParam; 1]> {
1560         let mut param = configure!(self, param);
1561
1562         if let Some(attr) = self.take_first_attr(&mut param) {
1563             return self
1564                 .collect_attr(
1565                     attr,
1566                     Annotatable::GenericParam(param),
1567                     AstFragmentKind::GenericParams,
1568                 )
1569                 .make_generic_params();
1570         }
1571
1572         noop_flat_map_generic_param(param, self)
1573     }
1574
1575     fn visit_attribute(&mut self, at: &mut ast::Attribute) {
1576         // turn `#[doc(include="filename")]` attributes into `#[doc(include(file="filename",
1577         // contents="file contents")]` attributes
1578         if !self.cx.sess.check_name(at, sym::doc) {
1579             return noop_visit_attribute(at, self);
1580         }
1581
1582         if let Some(list) = at.meta_item_list() {
1583             if !list.iter().any(|it| it.has_name(sym::include)) {
1584                 return noop_visit_attribute(at, self);
1585             }
1586
1587             let mut items = vec![];
1588
1589             for mut it in list {
1590                 if !it.has_name(sym::include) {
1591                     items.push({
1592                         noop_visit_meta_list_item(&mut it, self);
1593                         it
1594                     });
1595                     continue;
1596                 }
1597
1598                 if let Some(file) = it.value_str() {
1599                     let err_count = self.cx.sess.parse_sess.span_diagnostic.err_count();
1600                     self.check_attributes(slice::from_ref(at));
1601                     if self.cx.sess.parse_sess.span_diagnostic.err_count() > err_count {
1602                         // avoid loading the file if they haven't enabled the feature
1603                         return noop_visit_attribute(at, self);
1604                     }
1605
1606                     let filename = match self.cx.resolve_path(&*file.as_str(), it.span()) {
1607                         Ok(filename) => filename,
1608                         Err(mut err) => {
1609                             err.emit();
1610                             continue;
1611                         }
1612                     };
1613
1614                     match self.cx.source_map().load_file(&filename) {
1615                         Ok(source_file) => {
1616                             let src = source_file
1617                                 .src
1618                                 .as_ref()
1619                                 .expect("freshly loaded file should have a source");
1620                             let src_interned = Symbol::intern(src.as_str());
1621
1622                             let include_info = vec![
1623                                 ast::NestedMetaItem::MetaItem(attr::mk_name_value_item_str(
1624                                     Ident::with_dummy_span(sym::file),
1625                                     file,
1626                                     DUMMY_SP,
1627                                 )),
1628                                 ast::NestedMetaItem::MetaItem(attr::mk_name_value_item_str(
1629                                     Ident::with_dummy_span(sym::contents),
1630                                     src_interned,
1631                                     DUMMY_SP,
1632                                 )),
1633                             ];
1634
1635                             let include_ident = Ident::with_dummy_span(sym::include);
1636                             let item = attr::mk_list_item(include_ident, include_info);
1637                             items.push(ast::NestedMetaItem::MetaItem(item));
1638                         }
1639                         Err(e) => {
1640                             let lit_span = it.name_value_literal_span().unwrap();
1641
1642                             if e.kind() == ErrorKind::InvalidData {
1643                                 self.cx
1644                                     .struct_span_err(
1645                                         lit_span,
1646                                         &format!("{} wasn't a utf-8 file", filename.display()),
1647                                     )
1648                                     .span_label(lit_span, "contains invalid utf-8")
1649                                     .emit();
1650                             } else {
1651                                 let mut err = self.cx.struct_span_err(
1652                                     lit_span,
1653                                     &format!("couldn't read {}: {}", filename.display(), e),
1654                                 );
1655                                 err.span_label(lit_span, "couldn't read file");
1656
1657                                 err.emit();
1658                             }
1659                         }
1660                     }
1661                 } else {
1662                     let mut err = self
1663                         .cx
1664                         .struct_span_err(it.span(), "expected path to external documentation");
1665
1666                     // Check if the user erroneously used `doc(include(...))` syntax.
1667                     let literal = it.meta_item_list().and_then(|list| {
1668                         if list.len() == 1 {
1669                             list[0].literal().map(|literal| &literal.kind)
1670                         } else {
1671                             None
1672                         }
1673                     });
1674
1675                     let (path, applicability) = match &literal {
1676                         Some(LitKind::Str(path, ..)) => {
1677                             (path.to_string(), Applicability::MachineApplicable)
1678                         }
1679                         _ => (String::from("<path>"), Applicability::HasPlaceholders),
1680                     };
1681
1682                     err.span_suggestion(
1683                         it.span(),
1684                         "provide a file path with `=`",
1685                         format!("include = \"{}\"", path),
1686                         applicability,
1687                     );
1688
1689                     err.emit();
1690                 }
1691             }
1692
1693             let meta = attr::mk_list_item(Ident::with_dummy_span(sym::doc), items);
1694             *at = ast::Attribute {
1695                 kind: ast::AttrKind::Normal(
1696                     AttrItem { path: meta.path, args: meta.kind.mac_args(meta.span), tokens: None },
1697                     None,
1698                 ),
1699                 span: at.span,
1700                 id: at.id,
1701                 style: at.style,
1702             };
1703         } else {
1704             noop_visit_attribute(at, self)
1705         }
1706     }
1707
1708     fn visit_id(&mut self, id: &mut ast::NodeId) {
1709         if self.monotonic {
1710             debug_assert_eq!(*id, ast::DUMMY_NODE_ID);
1711             *id = self.cx.resolver.next_node_id()
1712         }
1713     }
1714
1715     fn visit_fn_decl(&mut self, mut fn_decl: &mut P<ast::FnDecl>) {
1716         self.cfg.configure_fn_decl(&mut fn_decl);
1717         noop_visit_fn_decl(fn_decl, self);
1718     }
1719 }
1720
1721 pub struct ExpansionConfig<'feat> {
1722     pub crate_name: String,
1723     pub features: Option<&'feat Features>,
1724     pub recursion_limit: Limit,
1725     pub trace_mac: bool,
1726     pub should_test: bool, // If false, strip `#[test]` nodes
1727     pub keep_macs: bool,
1728     pub span_debug: bool, // If true, use verbose debugging for `proc_macro::Span`
1729     pub proc_macro_backtrace: bool, // If true, show backtraces for proc-macro panics
1730 }
1731
1732 impl<'feat> ExpansionConfig<'feat> {
1733     pub fn default(crate_name: String) -> ExpansionConfig<'static> {
1734         ExpansionConfig {
1735             crate_name,
1736             features: None,
1737             recursion_limit: Limit::new(1024),
1738             trace_mac: false,
1739             should_test: false,
1740             keep_macs: false,
1741             span_debug: false,
1742             proc_macro_backtrace: false,
1743         }
1744     }
1745
1746     fn proc_macro_hygiene(&self) -> bool {
1747         self.features.map_or(false, |features| features.proc_macro_hygiene)
1748     }
1749 }