src/librustc_expand/expand.rs

   1 use crate::base::*;
   2 use crate::config::StripUnconfigured;
   3 use crate::hygiene::{ExpnData, ExpnId, ExpnKind, SyntaxContext};
   4 use crate::mbe::macro_rules::annotate_err_with_kind;
   5 use crate::placeholders::{placeholder, PlaceholderExpander};
   6 use crate::proc_macro::collect_derives;
   7
   8 use rustc_ast_pretty::pprust;
   9 use rustc_attr::{self as attr, is_builtin_attr, HasAttrs};
  10 use rustc_data_structures::sync::Lrc;
  11 use rustc_errors::{Applicability, FatalError, PResult};
  12 use rustc_feature::Features;
  13 use rustc_parse::configure;
  14 use rustc_parse::parser::Parser;
  15 use rustc_parse::validate_attr;
  16 use rustc_parse::DirectoryOwnership;
  17 use rustc_session::parse::{feature_err, ParseSess};
  18 use rustc_span::source_map::respan;
  19 use rustc_span::symbol::{sym, Symbol};
  20 use rustc_span::{FileName, Span, DUMMY_SP};
  21 use syntax::ast::{self, AttrItem, Block, Ident, LitKind, NodeId, PatKind, Path};
  22 use syntax::ast::{ItemKind, MacArgs, MacStmtStyle, StmtKind};
  23 use syntax::mut_visit::*;
  24 use syntax::ptr::P;
  25 use syntax::token;
  26 use syntax::tokenstream::{TokenStream, TokenTree};
  27 use syntax::util::map_in_place::MapInPlace;
  28 use syntax::visit::{self, AssocCtxt, Visitor};
  29
  30 use smallvec::{smallvec, SmallVec};
  31 use std::io::ErrorKind;
  32 use std::ops::DerefMut;
  33 use std::path::PathBuf;
  34 use std::rc::Rc;
  35 use std::{iter, mem, slice};
  36
  37 macro_rules! ast_fragments {
  38     (
  39         $($Kind:ident($AstTy:ty) {
  40             $kind_name:expr;
  41             $(one fn $mut_visit_ast:ident; fn $visit_ast:ident;)?
  42             $(many fn $flat_map_ast_elt:ident; fn $visit_ast_elt:ident($($args:tt)*);)?
  43             fn $make_ast:ident;
  44         })*
  45     ) => {
  46         /// A fragment of AST that can be produced by a single macro expansion.
  47         /// Can also serve as an input and intermediate result for macro expansion operations.
  48         pub enum AstFragment {
  49             OptExpr(Option<P<ast::Expr>>),
  50             $($Kind($AstTy),)*
  51         }
  52
  53         /// "Discriminant" of an AST fragment.
  54         #[derive(Copy, Clone, PartialEq, Eq)]
  55         pub enum AstFragmentKind {
  56             OptExpr,
  57             $($Kind,)*
  58         }
  59
  60         impl AstFragmentKind {
  61             pub fn name(self) -> &'static str {
  62                 match self {
  63                     AstFragmentKind::OptExpr => "expression",
  64                     $(AstFragmentKind::$Kind => $kind_name,)*
  65                 }
  66             }
  67
  68             fn make_from<'a>(self, result: Box<dyn MacResult + 'a>) -> Option<AstFragment> {
  69                 match self {
  70                     AstFragmentKind::OptExpr =>
  71                         result.make_expr().map(Some).map(AstFragment::OptExpr),
  72                     $(AstFragmentKind::$Kind => result.$make_ast().map(AstFragment::$Kind),)*
  73                 }
  74             }
  75         }
  76
  77         impl AstFragment {
  78             pub fn add_placeholders(&mut self, placeholders: &[NodeId]) {
  79                 if placeholders.is_empty() {
  80                     return;
  81                 }
  82                 match self {
  83                     $($(AstFragment::$Kind(ast) => ast.extend(placeholders.iter().flat_map(|id| {
  84                         // We are repeating through arguments with `many`, to do that we have to
  85                         // mention some macro variable from those arguments even if it's not used.
  86                         macro _repeating($flat_map_ast_elt) {}
  87                         placeholder(AstFragmentKind::$Kind, *id, None).$make_ast()
  88                     })),)?)*
  89                     _ => panic!("unexpected AST fragment kind")
  90                 }
  91             }
  92
  93             pub fn make_opt_expr(self) -> Option<P<ast::Expr>> {
  94                 match self {
  95                     AstFragment::OptExpr(expr) => expr,
  96                     _ => panic!("AstFragment::make_* called on the wrong kind of fragment"),
  97                 }
  98             }
  99
 100             $(pub fn $make_ast(self) -> $AstTy {
 101                 match self {
 102                     AstFragment::$Kind(ast) => ast,
 103                     _ => panic!("AstFragment::make_* called on the wrong kind of fragment"),
 104                 }
 105             })*
 106
 107             pub fn mut_visit_with<F: MutVisitor>(&mut self, vis: &mut F) {
 108                 match self {
 109                     AstFragment::OptExpr(opt_expr) => {
 110                         visit_clobber(opt_expr, |opt_expr| {
 111                             if let Some(expr) = opt_expr {
 112                                 vis.filter_map_expr(expr)
 113                             } else {
 114                                 None
 115                             }
 116                         });
 117                     }
 118                     $($(AstFragment::$Kind(ast) => vis.$mut_visit_ast(ast),)?)*
 119                     $($(AstFragment::$Kind(ast) =>
 120                         ast.flat_map_in_place(|ast| vis.$flat_map_ast_elt(ast)),)?)*
 121                 }
 122             }
 123
 124             pub fn visit_with<'a, V: Visitor<'a>>(&'a self, visitor: &mut V) {
 125                 match *self {
 126                     AstFragment::OptExpr(Some(ref expr)) => visitor.visit_expr(expr),
 127                     AstFragment::OptExpr(None) => {}
 128                     $($(AstFragment::$Kind(ref ast) => visitor.$visit_ast(ast),)?)*
 129                     $($(AstFragment::$Kind(ref ast) => for ast_elt in &ast[..] {
 130                         visitor.$visit_ast_elt(ast_elt, $($args)*);
 131                     })?)*
 132                 }
 133             }
 134         }
 135
 136         impl<'a> MacResult for crate::mbe::macro_rules::ParserAnyMacro<'a> {
 137             $(fn $make_ast(self: Box<crate::mbe::macro_rules::ParserAnyMacro<'a>>)
 138                            -> Option<$AstTy> {
 139                 Some(self.make(AstFragmentKind::$Kind).$make_ast())
 140             })*
 141         }
 142     }
 143 }
 144
 145 ast_fragments! {
 146     Expr(P<ast::Expr>) { "expression"; one fn visit_expr; fn visit_expr; fn make_expr; }
 147     Pat(P<ast::Pat>) { "pattern"; one fn visit_pat; fn visit_pat; fn make_pat; }
 148     Ty(P<ast::Ty>) { "type"; one fn visit_ty; fn visit_ty; fn make_ty; }
 149     Stmts(SmallVec<[ast::Stmt; 1]>) {
 150         "statement"; many fn flat_map_stmt; fn visit_stmt(); fn make_stmts;
 151     }
 152     Items(SmallVec<[P<ast::Item>; 1]>) {
 153         "item"; many fn flat_map_item; fn visit_item(); fn make_items;
 154     }
 155     TraitItems(SmallVec<[P<ast::AssocItem>; 1]>) {
 156         "trait item";
 157         many fn flat_map_trait_item;
 158         fn visit_assoc_item(AssocCtxt::Trait);
 159         fn make_trait_items;
 160     }
 161     ImplItems(SmallVec<[P<ast::AssocItem>; 1]>) {
 162         "impl item";
 163         many fn flat_map_impl_item;
 164         fn visit_assoc_item(AssocCtxt::Impl);
 165         fn make_impl_items;
 166     }
 167     ForeignItems(SmallVec<[P<ast::ForeignItem>; 1]>) {
 168         "foreign item";
 169         many fn flat_map_foreign_item;
 170         fn visit_foreign_item();
 171         fn make_foreign_items;
 172     }
 173     Arms(SmallVec<[ast::Arm; 1]>) {
 174         "match arm"; many fn flat_map_arm; fn visit_arm(); fn make_arms;
 175     }
 176     Fields(SmallVec<[ast::Field; 1]>) {
 177         "field expression"; many fn flat_map_field; fn visit_field(); fn make_fields;
 178     }
 179     FieldPats(SmallVec<[ast::FieldPat; 1]>) {
 180         "field pattern";
 181         many fn flat_map_field_pattern;
 182         fn visit_field_pattern();
 183         fn make_field_patterns;
 184     }
 185     GenericParams(SmallVec<[ast::GenericParam; 1]>) {
 186         "generic parameter";
 187         many fn flat_map_generic_param;
 188         fn visit_generic_param();
 189         fn make_generic_params;
 190     }
 191     Params(SmallVec<[ast::Param; 1]>) {
 192         "function parameter"; many fn flat_map_param; fn visit_param(); fn make_params;
 193     }
 194     StructFields(SmallVec<[ast::StructField; 1]>) {
 195         "field";
 196         many fn flat_map_struct_field;
 197         fn visit_struct_field();
 198         fn make_struct_fields;
 199     }
 200     Variants(SmallVec<[ast::Variant; 1]>) {
 201         "variant"; many fn flat_map_variant; fn visit_variant(); fn make_variants;
 202     }
 203 }
 204
 205 impl AstFragmentKind {
 206     fn dummy(self, span: Span) -> AstFragment {
 207         self.make_from(DummyResult::any(span)).expect("couldn't create a dummy AST fragment")
 208     }
 209
 210     fn expect_from_annotatables<I: IntoIterator<Item = Annotatable>>(
 211         self,
 212         items: I,
 213     ) -> AstFragment {
 214         let mut items = items.into_iter();
 215         match self {
 216             AstFragmentKind::Arms => {
 217                 AstFragment::Arms(items.map(Annotatable::expect_arm).collect())
 218             }
 219             AstFragmentKind::Fields => {
 220                 AstFragment::Fields(items.map(Annotatable::expect_field).collect())
 221             }
 222             AstFragmentKind::FieldPats => {
 223                 AstFragment::FieldPats(items.map(Annotatable::expect_field_pattern).collect())
 224             }
 225             AstFragmentKind::GenericParams => {
 226                 AstFragment::GenericParams(items.map(Annotatable::expect_generic_param).collect())
 227             }
 228             AstFragmentKind::Params => {
 229                 AstFragment::Params(items.map(Annotatable::expect_param).collect())
 230             }
 231             AstFragmentKind::StructFields => {
 232                 AstFragment::StructFields(items.map(Annotatable::expect_struct_field).collect())
 233             }
 234             AstFragmentKind::Variants => {
 235                 AstFragment::Variants(items.map(Annotatable::expect_variant).collect())
 236             }
 237             AstFragmentKind::Items => {
 238                 AstFragment::Items(items.map(Annotatable::expect_item).collect())
 239             }
 240             AstFragmentKind::ImplItems => {
 241                 AstFragment::ImplItems(items.map(Annotatable::expect_impl_item).collect())
 242             }
 243             AstFragmentKind::TraitItems => {
 244                 AstFragment::TraitItems(items.map(Annotatable::expect_trait_item).collect())
 245             }
 246             AstFragmentKind::ForeignItems => {
 247                 AstFragment::ForeignItems(items.map(Annotatable::expect_foreign_item).collect())
 248             }
 249             AstFragmentKind::Stmts => {
 250                 AstFragment::Stmts(items.map(Annotatable::expect_stmt).collect())
 251             }
 252             AstFragmentKind::Expr => AstFragment::Expr(
 253                 items.next().expect("expected exactly one expression").expect_expr(),
 254             ),
 255             AstFragmentKind::OptExpr => {
 256                 AstFragment::OptExpr(items.next().map(Annotatable::expect_expr))
 257             }
 258             AstFragmentKind::Pat | AstFragmentKind::Ty => {
 259                 panic!("patterns and types aren't annotatable")
 260             }
 261         }
 262     }
 263 }
 264
 265 pub struct Invocation {
 266     pub kind: InvocationKind,
 267     pub fragment_kind: AstFragmentKind,
 268     pub expansion_data: ExpansionData,
 269 }
 270
 271 pub enum InvocationKind {
 272     Bang {
 273         mac: ast::Mac,
 274         span: Span,
 275     },
 276     Attr {
 277         attr: ast::Attribute,
 278         item: Annotatable,
 279         // Required for resolving derive helper attributes.
 280         derives: Vec<Path>,
 281         // We temporarily report errors for attribute macros placed after derives
 282         after_derive: bool,
 283     },
 284     Derive {
 285         path: Path,
 286         item: Annotatable,
 287     },
 288     /// "Invocation" that contains all derives from an item,
 289     /// broken into multiple `Derive` invocations when expanded.
 290     /// FIXME: Find a way to remove it.
 291     DeriveContainer {
 292         derives: Vec<Path>,
 293         item: Annotatable,
 294     },
 295 }
 296
 297 impl InvocationKind {
 298     fn placeholder_visibility(&self) -> Option<ast::Visibility> {
 299         // HACK: For unnamed fields placeholders should have the same visibility as the actual
 300         // fields because for tuple structs/variants resolve determines visibilities of their
 301         // constructor using these field visibilities before attributes on them are are expanded.
 302         // The assumption is that the attribute expansion cannot change field visibilities,
 303         // and it holds because only inert attributes are supported in this position.
 304         match self {
 305             InvocationKind::Attr { item: Annotatable::StructField(field), .. }
 306             | InvocationKind::Derive { item: Annotatable::StructField(field), .. }
 307             | InvocationKind::DeriveContainer { item: Annotatable::StructField(field), .. }
 308                 if field.ident.is_none() =>
 309             {
 310                 Some(field.vis.clone())
 311             }
 312             _ => None,
 313         }
 314     }
 315 }
 316
 317 impl Invocation {
 318     pub fn span(&self) -> Span {
 319         match &self.kind {
 320             InvocationKind::Bang { span, .. } => *span,
 321             InvocationKind::Attr { attr, .. } => attr.span,
 322             InvocationKind::Derive { path, .. } => path.span,
 323             InvocationKind::DeriveContainer { item, .. } => item.span(),
 324         }
 325     }
 326 }
 327
 328 pub struct MacroExpander<'a, 'b> {
 329     pub cx: &'a mut ExtCtxt<'b>,
 330     monotonic: bool, // cf. `cx.monotonic_expander()`
 331 }
 332
 333 impl<'a, 'b> MacroExpander<'a, 'b> {
 334     pub fn new(cx: &'a mut ExtCtxt<'b>, monotonic: bool) -> Self {
 335         MacroExpander { cx, monotonic }
 336     }
 337
 338     pub fn expand_crate(&mut self, mut krate: ast::Crate) -> ast::Crate {
 339         let mut module = ModuleData {
 340             mod_path: vec![Ident::from_str(&self.cx.ecfg.crate_name)],
 341             directory: match self.cx.source_map().span_to_unmapped_path(krate.span) {
 342                 FileName::Real(path) => path,
 343                 other => PathBuf::from(other.to_string()),
 344             },
 345         };
 346         module.directory.pop();
 347         self.cx.root_path = module.directory.clone();
 348         self.cx.current_expansion.module = Rc::new(module);
 349
 350         let orig_mod_span = krate.module.inner;
 351
 352         let krate_item = AstFragment::Items(smallvec![P(ast::Item {
 353             attrs: krate.attrs,
 354             span: krate.span,
 355             kind: ast::ItemKind::Mod(krate.module),
 356             ident: Ident::invalid(),
 357             id: ast::DUMMY_NODE_ID,
 358             vis: respan(krate.span.shrink_to_lo(), ast::VisibilityKind::Public),
 359             tokens: None,
 360         })]);
 361
 362         match self.fully_expand_fragment(krate_item).make_items().pop().map(P::into_inner) {
 363             Some(ast::Item { attrs, kind: ast::ItemKind::Mod(module), .. }) => {
 364                 krate.attrs = attrs;
 365                 krate.module = module;
 366             }
 367             None => {
 368                 // Resolution failed so we return an empty expansion
 369                 krate.attrs = vec![];
 370                 krate.module = ast::Mod { inner: orig_mod_span, items: vec![], inline: true };
 371             }
 372             Some(ast::Item { span, kind, .. }) => {
 373                 krate.attrs = vec![];
 374                 krate.module = ast::Mod { inner: orig_mod_span, items: vec![], inline: true };
 375                 self.cx.span_err(
 376                     span,
 377                     &format!(
 378                         "expected crate top-level item to be a module after macro expansion, found a {}",
 379                         kind.descriptive_variant()
 380                     ),
 381                 );
 382             }
 383         };
 384         self.cx.trace_macros_diag();
 385         krate
 386     }
 387
 388     // Recursively expand all macro invocations in this AST fragment.
 389     pub fn fully_expand_fragment(&mut self, input_fragment: AstFragment) -> AstFragment {
 390         let orig_expansion_data = self.cx.current_expansion.clone();
 391         self.cx.current_expansion.depth = 0;
 392
 393         // Collect all macro invocations and replace them with placeholders.
 394         let (mut fragment_with_placeholders, mut invocations) =
 395             self.collect_invocations(input_fragment, &[]);
 396
 397         // Optimization: if we resolve all imports now,
 398         // we'll be able to immediately resolve most of imported macros.
 399         self.resolve_imports();
 400
 401         // Resolve paths in all invocations and produce output expanded fragments for them, but
 402         // do not insert them into our input AST fragment yet, only store in `expanded_fragments`.
 403         // The output fragments also go through expansion recursively until no invocations are left.
 404         // Unresolved macros produce dummy outputs as a recovery measure.
 405         invocations.reverse();
 406         let mut expanded_fragments = Vec::new();
 407         let mut undetermined_invocations = Vec::new();
 408         let (mut progress, mut force) = (false, !self.monotonic);
 409         loop {
 410             let invoc = if let Some(invoc) = invocations.pop() {
 411                 invoc
 412             } else {
 413                 self.resolve_imports();
 414                 if undetermined_invocations.is_empty() {
 415                     break;
 416                 }
 417                 invocations = mem::take(&mut undetermined_invocations);
 418                 force = !mem::replace(&mut progress, false);
 419                 continue;
 420             };
 421
 422             let eager_expansion_root =
 423                 if self.monotonic { invoc.expansion_data.id } else { orig_expansion_data.id };
 424             let res = match self.cx.resolver.resolve_macro_invocation(
 425                 &invoc,
 426                 eager_expansion_root,
 427                 force,
 428             ) {
 429                 Ok(res) => res,
 430                 Err(Indeterminate) => {
 431                     undetermined_invocations.push(invoc);
 432                     continue;
 433                 }
 434             };
 435
 436             progress = true;
 437             let ExpansionData { depth, id: expn_id, .. } = invoc.expansion_data;
 438             self.cx.current_expansion = invoc.expansion_data.clone();
 439
 440             // FIXME(jseyfried): Refactor out the following logic
 441             let (expanded_fragment, new_invocations) = match res {
 442                 InvocationRes::Single(ext) => {
 443                     let fragment = self.expand_invoc(invoc, &ext.kind);
 444                     self.collect_invocations(fragment, &[])
 445                 }
 446                 InvocationRes::DeriveContainer(_exts) => {
 447                     // FIXME: Consider using the derive resolutions (`_exts`) immediately,
 448                     // instead of enqueuing the derives to be resolved again later.
 449                     let (derives, item) = match invoc.kind {
 450                         InvocationKind::DeriveContainer { derives, item } => (derives, item),
 451                         _ => unreachable!(),
 452                     };
 453                     if !item.derive_allowed() {
 454                         self.error_derive_forbidden_on_non_adt(&derives, &item);
 455                     }
 456
 457                     let mut item = self.fully_configure(item);
 458                     item.visit_attrs(|attrs| attrs.retain(|a| !a.has_name(sym::derive)));
 459
 460                     let mut derive_placeholders = Vec::with_capacity(derives.len());
 461                     invocations.reserve(derives.len());
 462                     for path in derives {
 463                         let expn_id = ExpnId::fresh(None);
 464                         derive_placeholders.push(NodeId::placeholder_from_expn_id(expn_id));
 465                         invocations.push(Invocation {
 466                             kind: InvocationKind::Derive { path, item: item.clone() },
 467                             fragment_kind: invoc.fragment_kind,
 468                             expansion_data: ExpansionData {
 469                                 id: expn_id,
 470                                 ..invoc.expansion_data.clone()
 471                             },
 472                         });
 473                     }
 474                     let fragment =
 475                         invoc.fragment_kind.expect_from_annotatables(::std::iter::once(item));
 476                     self.collect_invocations(fragment, &derive_placeholders)
 477                 }
 478             };
 479
 480             if expanded_fragments.len() < depth {
 481                 expanded_fragments.push(Vec::new());
 482             }
 483             expanded_fragments[depth - 1].push((expn_id, expanded_fragment));
 484             if !self.cx.ecfg.single_step {
 485                 invocations.extend(new_invocations.into_iter().rev());
 486             }
 487         }
 488
 489         self.cx.current_expansion = orig_expansion_data;
 490
 491         // Finally incorporate all the expanded macros into the input AST fragment.
 492         let mut placeholder_expander = PlaceholderExpander::new(self.cx, self.monotonic);
 493         while let Some(expanded_fragments) = expanded_fragments.pop() {
 494             for (expn_id, expanded_fragment) in expanded_fragments.into_iter().rev() {
 495                 placeholder_expander
 496                     .add(NodeId::placeholder_from_expn_id(expn_id), expanded_fragment);
 497             }
 498         }
 499         fragment_with_placeholders.mut_visit_with(&mut placeholder_expander);
 500         fragment_with_placeholders
 501     }
 502
 503     fn error_derive_forbidden_on_non_adt(&self, derives: &[Path], item: &Annotatable) {
 504         let attr =
 505             attr::find_by_name(item.attrs(), sym::derive).expect("`derive` attribute should exist");
 506         let span = attr.span;
 507         let mut err = self
 508             .cx
 509             .struct_span_err(span, "`derive` may only be applied to structs, enums and unions");
 510         if let ast::AttrStyle::Inner = attr.style {
 511             let trait_list = derives.iter().map(|t| pprust::path_to_string(t)).collect::<Vec<_>>();
 512             let suggestion = format!("#[derive({})]", trait_list.join(", "));
 513             err.span_suggestion(
 514                 span,
 515                 "try an outer attribute",
 516                 suggestion,
 517                 // We don't 𝑘𝑛𝑜𝑤 that the following item is an ADT
 518                 Applicability::MaybeIncorrect,
 519             );
 520         }
 521         err.emit();
 522     }
 523
 524     fn resolve_imports(&mut self) {
 525         if self.monotonic {
 526             self.cx.resolver.resolve_imports();
 527         }
 528     }
 529
 530     /// Collects all macro invocations reachable at this time in this AST fragment, and replace
 531     /// them with "placeholders" - dummy macro invocations with specially crafted `NodeId`s.
 532     /// Then call into resolver that builds a skeleton ("reduced graph") of the fragment and
 533     /// prepares data for resolving paths of macro invocations.
 534     fn collect_invocations(
 535         &mut self,
 536         mut fragment: AstFragment,
 537         extra_placeholders: &[NodeId],
 538     ) -> (AstFragment, Vec<Invocation>) {
 539         // Resolve `$crate`s in the fragment for pretty-printing.
 540         self.cx.resolver.resolve_dollar_crates();
 541
 542         let invocations = {
 543             let mut collector = InvocationCollector {
 544                 cfg: StripUnconfigured {
 545                     sess: self.cx.parse_sess,
 546                     features: self.cx.ecfg.features,
 547                 },
 548                 cx: self.cx,
 549                 invocations: Vec::new(),
 550                 monotonic: self.monotonic,
 551             };
 552             fragment.mut_visit_with(&mut collector);
 553             fragment.add_placeholders(extra_placeholders);
 554             collector.invocations
 555         };
 556
 557         if self.monotonic {
 558             self.cx
 559                 .resolver
 560                 .visit_ast_fragment_with_placeholders(self.cx.current_expansion.id, &fragment);
 561         }
 562
 563         (fragment, invocations)
 564     }
 565
 566     fn fully_configure(&mut self, item: Annotatable) -> Annotatable {
 567         let mut cfg =
 568             StripUnconfigured { sess: self.cx.parse_sess, features: self.cx.ecfg.features };
 569         // Since the item itself has already been configured by the InvocationCollector,
 570         // we know that fold result vector will contain exactly one element
 571         match item {
 572             Annotatable::Item(item) => Annotatable::Item(cfg.flat_map_item(item).pop().unwrap()),
 573             Annotatable::TraitItem(item) => {
 574                 Annotatable::TraitItem(cfg.flat_map_trait_item(item).pop().unwrap())
 575             }
 576             Annotatable::ImplItem(item) => {
 577                 Annotatable::ImplItem(cfg.flat_map_impl_item(item).pop().unwrap())
 578             }
 579             Annotatable::ForeignItem(item) => {
 580                 Annotatable::ForeignItem(cfg.flat_map_foreign_item(item).pop().unwrap())
 581             }
 582             Annotatable::Stmt(stmt) => {
 583                 Annotatable::Stmt(stmt.map(|stmt| cfg.flat_map_stmt(stmt).pop().unwrap()))
 584             }
 585             Annotatable::Expr(mut expr) => Annotatable::Expr({
 586                 cfg.visit_expr(&mut expr);
 587                 expr
 588             }),
 589             Annotatable::Arm(arm) => Annotatable::Arm(cfg.flat_map_arm(arm).pop().unwrap()),
 590             Annotatable::Field(field) => {
 591                 Annotatable::Field(cfg.flat_map_field(field).pop().unwrap())
 592             }
 593             Annotatable::FieldPat(fp) => {
 594                 Annotatable::FieldPat(cfg.flat_map_field_pattern(fp).pop().unwrap())
 595             }
 596             Annotatable::GenericParam(param) => {
 597                 Annotatable::GenericParam(cfg.flat_map_generic_param(param).pop().unwrap())
 598             }
 599             Annotatable::Param(param) => {
 600                 Annotatable::Param(cfg.flat_map_param(param).pop().unwrap())
 601             }
 602             Annotatable::StructField(sf) => {
 603                 Annotatable::StructField(cfg.flat_map_struct_field(sf).pop().unwrap())
 604             }
 605             Annotatable::Variant(v) => Annotatable::Variant(cfg.flat_map_variant(v).pop().unwrap()),
 606         }
 607     }
 608
 609     fn error_recursion_limit_reached(&mut self) {
 610         let expn_data = self.cx.current_expansion.id.expn_data();
 611         let suggested_limit = self.cx.ecfg.recursion_limit * 2;
 612         self.cx
 613             .struct_span_err(
 614                 expn_data.call_site,
 615                 &format!("recursion limit reached while expanding `{}`", expn_data.kind.descr()),
 616             )
 617             .help(&format!(
 618                 "consider adding a `#![recursion_limit=\"{}\"]` attribute to your crate (`{}`)",
 619                 suggested_limit, self.cx.ecfg.crate_name,
 620             ))
 621             .emit();
 622         self.cx.trace_macros_diag();
 623         FatalError.raise();
 624     }
 625
 626     /// A macro's expansion does not fit in this fragment kind.
 627     /// For example, a non-type macro in a type position.
 628     fn error_wrong_fragment_kind(&mut self, kind: AstFragmentKind, mac: &ast::Mac, span: Span) {
 629         let msg = format!(
 630             "non-{kind} macro in {kind} position: {path}",
 631             kind = kind.name(),
 632             path = pprust::path_to_string(&mac.path),
 633         );
 634         self.cx.span_err(span, &msg);
 635         self.cx.trace_macros_diag();
 636     }
 637
 638     fn expand_invoc(&mut self, invoc: Invocation, ext: &SyntaxExtensionKind) -> AstFragment {
 639         if self.cx.current_expansion.depth > self.cx.ecfg.recursion_limit {
 640             self.error_recursion_limit_reached();
 641         }
 642
 643         let (fragment_kind, span) = (invoc.fragment_kind, invoc.span());
 644         match invoc.kind {
 645             InvocationKind::Bang { mac, .. } => match ext {
 646                 SyntaxExtensionKind::Bang(expander) => {
 647                     self.gate_proc_macro_expansion_kind(span, fragment_kind);
 648                     let tok_result = expander.expand(self.cx, span, mac.args.inner_tokens());
 649                     self.parse_ast_fragment(tok_result, fragment_kind, &mac.path, span)
 650                 }
 651                 SyntaxExtensionKind::LegacyBang(expander) => {
 652                     let prev = self.cx.current_expansion.prior_type_ascription;
 653                     self.cx.current_expansion.prior_type_ascription = mac.prior_type_ascription;
 654                     let tok_result = expander.expand(self.cx, span, mac.args.inner_tokens());
 655                     let result = if let Some(result) = fragment_kind.make_from(tok_result) {
 656                         result
 657                     } else {
 658                         self.error_wrong_fragment_kind(fragment_kind, &mac, span);
 659                         fragment_kind.dummy(span)
 660                     };
 661                     self.cx.current_expansion.prior_type_ascription = prev;
 662                     result
 663                 }
 664                 _ => unreachable!(),
 665             },
 666             InvocationKind::Attr { attr, mut item, .. } => match ext {
 667                 SyntaxExtensionKind::Attr(expander) => {
 668                     self.gate_proc_macro_input(&item);
 669                     self.gate_proc_macro_attr_item(span, &item);
 670                     let item_tok = TokenTree::token(
 671                         token::Interpolated(Lrc::new(match item {
 672                             Annotatable::Item(item) => token::NtItem(item),
 673                             Annotatable::TraitItem(item) => token::NtTraitItem(item),
 674                             Annotatable::ImplItem(item) => token::NtImplItem(item),
 675                             Annotatable::ForeignItem(item) => token::NtForeignItem(item),
 676                             Annotatable::Stmt(stmt) => token::NtStmt(stmt.into_inner()),
 677                             Annotatable::Expr(expr) => token::NtExpr(expr),
 678                             Annotatable::Arm(..)
 679                             | Annotatable::Field(..)
 680                             | Annotatable::FieldPat(..)
 681                             | Annotatable::GenericParam(..)
 682                             | Annotatable::Param(..)
 683                             | Annotatable::StructField(..)
 684                             | Annotatable::Variant(..) => panic!("unexpected annotatable"),
 685                         })),
 686                         DUMMY_SP,
 687                     )
 688                     .into();
 689                     let item = attr.unwrap_normal_item();
 690                     if let MacArgs::Eq(..) = item.args {
 691                         self.cx.span_err(span, "key-value macro attributes are not supported");
 692                     }
 693                     let tok_result =
 694                         expander.expand(self.cx, span, item.args.inner_tokens(), item_tok);
 695                     self.parse_ast_fragment(tok_result, fragment_kind, &item.path, span)
 696                 }
 697                 SyntaxExtensionKind::LegacyAttr(expander) => {
 698                     match validate_attr::parse_meta(self.cx.parse_sess, &attr) {
 699                         Ok(meta) => {
 700                             let item = expander.expand(self.cx, span, &meta, item);
 701                             fragment_kind.expect_from_annotatables(item)
 702                         }
 703                         Err(mut err) => {
 704                             err.emit();
 705                             fragment_kind.dummy(span)
 706                         }
 707                     }
 708                 }
 709                 SyntaxExtensionKind::NonMacroAttr { mark_used } => {
 710                     attr::mark_known(&attr);
 711                     if *mark_used {
 712                         attr::mark_used(&attr);
 713                     }
 714                     item.visit_attrs(|attrs| attrs.push(attr));
 715                     fragment_kind.expect_from_annotatables(iter::once(item))
 716                 }
 717                 _ => unreachable!(),
 718             },
 719             InvocationKind::Derive { path, item } => match ext {
 720                 SyntaxExtensionKind::Derive(expander)
 721                 | SyntaxExtensionKind::LegacyDerive(expander) => {
 722                     if !item.derive_allowed() {
 723                         return fragment_kind.dummy(span);
 724                     }
 725                     if let SyntaxExtensionKind::Derive(..) = ext {
 726                         self.gate_proc_macro_input(&item);
 727                     }
 728                     let meta = ast::MetaItem { kind: ast::MetaItemKind::Word, span, path };
 729                     let items = expander.expand(self.cx, span, &meta, item);
 730                     fragment_kind.expect_from_annotatables(items)
 731                 }
 732                 _ => unreachable!(),
 733             },
 734             InvocationKind::DeriveContainer { .. } => unreachable!(),
 735         }
 736     }
 737
 738     fn gate_proc_macro_attr_item(&self, span: Span, item: &Annotatable) {
 739         let kind = match item {
 740             Annotatable::Item(_)
 741             | Annotatable::TraitItem(_)
 742             | Annotatable::ImplItem(_)
 743             | Annotatable::ForeignItem(_) => return,
 744             Annotatable::Stmt(_) => "statements",
 745             Annotatable::Expr(_) => "expressions",
 746             Annotatable::Arm(..)
 747             | Annotatable::Field(..)
 748             | Annotatable::FieldPat(..)
 749             | Annotatable::GenericParam(..)
 750             | Annotatable::Param(..)
 751             | Annotatable::StructField(..)
 752             | Annotatable::Variant(..) => panic!("unexpected annotatable"),
 753         };
 754         if self.cx.ecfg.proc_macro_hygiene() {
 755             return;
 756         }
 757         feature_err(
 758             self.cx.parse_sess,
 759             sym::proc_macro_hygiene,
 760             span,
 761             &format!("custom attributes cannot be applied to {}", kind),
 762         )
 763         .emit();
 764     }
 765
 766     fn gate_proc_macro_input(&self, annotatable: &Annotatable) {
 767         struct GateProcMacroInput<'a> {
 768             parse_sess: &'a ParseSess,
 769         }
 770
 771         impl<'ast, 'a> Visitor<'ast> for GateProcMacroInput<'a> {
 772             fn visit_item(&mut self, item: &'ast ast::Item) {
 773                 match &item.kind {
 774                     ast::ItemKind::Mod(module) if !module.inline => {
 775                         feature_err(
 776                             self.parse_sess,
 777                             sym::proc_macro_hygiene,
 778                             item.span,
 779                             "non-inline modules in proc macro input are unstable",
 780                         )
 781                         .emit();
 782                     }
 783                     _ => {}
 784                 }
 785
 786                 visit::walk_item(self, item);
 787             }
 788
 789             fn visit_mac(&mut self, _: &'ast ast::Mac) {}
 790         }
 791
 792         if !self.cx.ecfg.proc_macro_hygiene() {
 793             annotatable.visit_with(&mut GateProcMacroInput { parse_sess: self.cx.parse_sess });
 794         }
 795     }
 796
 797     fn gate_proc_macro_expansion_kind(&self, span: Span, kind: AstFragmentKind) {
 798         let kind = match kind {
 799             AstFragmentKind::Expr | AstFragmentKind::OptExpr => "expressions",
 800             AstFragmentKind::Pat => "patterns",
 801             AstFragmentKind::Stmts => "statements",
 802             AstFragmentKind::Ty
 803             | AstFragmentKind::Items
 804             | AstFragmentKind::TraitItems
 805             | AstFragmentKind::ImplItems
 806             | AstFragmentKind::ForeignItems => return,
 807             AstFragmentKind::Arms
 808             | AstFragmentKind::Fields
 809             | AstFragmentKind::FieldPats
 810             | AstFragmentKind::GenericParams
 811             | AstFragmentKind::Params
 812             | AstFragmentKind::StructFields
 813             | AstFragmentKind::Variants => panic!("unexpected AST fragment kind"),
 814         };
 815         if self.cx.ecfg.proc_macro_hygiene() {
 816             return;
 817         }
 818         feature_err(
 819             self.cx.parse_sess,
 820             sym::proc_macro_hygiene,
 821             span,
 822             &format!("procedural macros cannot be expanded to {}", kind),
 823         )
 824         .emit();
 825     }
 826
 827     fn parse_ast_fragment(
 828         &mut self,
 829         toks: TokenStream,
 830         kind: AstFragmentKind,
 831         path: &Path,
 832         span: Span,
 833     ) -> AstFragment {
 834         let mut parser = self.cx.new_parser_from_tts(toks);
 835         match parse_ast_fragment(&mut parser, kind) {
 836             Ok(fragment) => {
 837                 ensure_complete_parse(&mut parser, path, kind.name(), span);
 838                 fragment
 839             }
 840             Err(mut err) => {
 841                 err.set_span(span);
 842                 annotate_err_with_kind(&mut err, kind, span);
 843                 err.emit();
 844                 self.cx.trace_macros_diag();
 845                 kind.dummy(span)
 846             }
 847         }
 848     }
 849 }
 850
 851 pub fn parse_ast_fragment<'a>(
 852     this: &mut Parser<'a>,
 853     kind: AstFragmentKind,
 854 ) -> PResult<'a, AstFragment> {
 855     Ok(match kind {
 856         AstFragmentKind::Items => {
 857             let mut items = SmallVec::new();
 858             while let Some(item) = this.parse_item()? {
 859                 items.push(item);
 860             }
 861             AstFragment::Items(items)
 862         }
 863         AstFragmentKind::TraitItems => {
 864             let mut items = SmallVec::new();
 865             while this.token != token::Eof {
 866                 items.push(this.parse_trait_item(&mut false)?);
 867             }
 868             AstFragment::TraitItems(items)
 869         }
 870         AstFragmentKind::ImplItems => {
 871             let mut items = SmallVec::new();
 872             while this.token != token::Eof {
 873                 items.push(this.parse_impl_item(&mut false)?);
 874             }
 875             AstFragment::ImplItems(items)
 876         }
 877         AstFragmentKind::ForeignItems => {
 878             let mut items = SmallVec::new();
 879             while this.token != token::Eof {
 880                 items.push(this.parse_foreign_item(&mut false)?);
 881             }
 882             AstFragment::ForeignItems(items)
 883         }
 884         AstFragmentKind::Stmts => {
 885             let mut stmts = SmallVec::new();
 886             // Won't make progress on a `}`.
 887             while this.token != token::Eof && this.token != token::CloseDelim(token::Brace) {
 888                 if let Some(stmt) = this.parse_full_stmt()? {
 889                     stmts.push(stmt);
 890                 }
 891             }
 892             AstFragment::Stmts(stmts)
 893         }
 894         AstFragmentKind::Expr => AstFragment::Expr(this.parse_expr()?),
 895         AstFragmentKind::OptExpr => {
 896             if this.token != token::Eof {
 897                 AstFragment::OptExpr(Some(this.parse_expr()?))
 898             } else {
 899                 AstFragment::OptExpr(None)
 900             }
 901         }
 902         AstFragmentKind::Ty => AstFragment::Ty(this.parse_ty()?),
 903         AstFragmentKind::Pat => AstFragment::Pat(this.parse_pat(None)?),
 904         AstFragmentKind::Arms
 905         | AstFragmentKind::Fields
 906         | AstFragmentKind::FieldPats
 907         | AstFragmentKind::GenericParams
 908         | AstFragmentKind::Params
 909         | AstFragmentKind::StructFields
 910         | AstFragmentKind::Variants => panic!("unexpected AST fragment kind"),
 911     })
 912 }
 913
 914 pub fn ensure_complete_parse<'a>(
 915     this: &mut Parser<'a>,
 916     macro_path: &Path,
 917     kind_name: &str,
 918     span: Span,
 919 ) {
 920     if this.token != token::Eof {
 921         let token = pprust::token_to_string(&this.token);
 922         let msg = format!("macro expansion ignores token `{}` and any following", token);
 923         // Avoid emitting backtrace info twice.
 924         let def_site_span = this.token.span.with_ctxt(SyntaxContext::root());
 925         let mut err = this.struct_span_err(def_site_span, &msg);
 926         err.span_label(span, "caused by the macro expansion here");
 927         let msg = format!(
 928             "the usage of `{}!` is likely invalid in {} context",
 929             pprust::path_to_string(macro_path),
 930             kind_name,
 931         );
 932         err.note(&msg);
 933         let semi_span = this.sess.source_map().next_point(span);
 934
 935         let semi_full_span = semi_span.to(this.sess.source_map().next_point(semi_span));
 936         match this.sess.source_map().span_to_snippet(semi_full_span) {
 937             Ok(ref snippet) if &snippet[..] != ";" && kind_name == "expression" => {
 938                 err.span_suggestion(
 939                     semi_span,
 940                     "you might be missing a semicolon here",
 941                     ";".to_owned(),
 942                     Applicability::MaybeIncorrect,
 943                 );
 944             }
 945             _ => {}
 946         }
 947         err.emit();
 948     }
 949 }
 950
 951 struct InvocationCollector<'a, 'b> {
 952     cx: &'a mut ExtCtxt<'b>,
 953     cfg: StripUnconfigured<'a>,
 954     invocations: Vec<Invocation>,
 955     monotonic: bool,
 956 }
 957
 958 impl<'a, 'b> InvocationCollector<'a, 'b> {
 959     fn collect(&mut self, fragment_kind: AstFragmentKind, kind: InvocationKind) -> AstFragment {
 960         // Expansion data for all the collected invocations is set upon their resolution,
 961         // with exception of the derive container case which is not resolved and can get
 962         // its expansion data immediately.
 963         let expn_data = match &kind {
 964             InvocationKind::DeriveContainer { item, .. } => Some(ExpnData {
 965                 parent: self.cx.current_expansion.id,
 966                 ..ExpnData::default(
 967                     ExpnKind::Macro(MacroKind::Attr, sym::derive),
 968                     item.span(),
 969                     self.cx.parse_sess.edition,
 970                 )
 971             }),
 972             _ => None,
 973         };
 974         let expn_id = ExpnId::fresh(expn_data);
 975         let vis = kind.placeholder_visibility();
 976         self.invocations.push(Invocation {
 977             kind,
 978             fragment_kind,
 979             expansion_data: ExpansionData {
 980                 id: expn_id,
 981                 depth: self.cx.current_expansion.depth + 1,
 982                 ..self.cx.current_expansion.clone()
 983             },
 984         });
 985         placeholder(fragment_kind, NodeId::placeholder_from_expn_id(expn_id), vis)
 986     }
 987
 988     fn collect_bang(&mut self, mac: ast::Mac, span: Span, kind: AstFragmentKind) -> AstFragment {
 989         self.collect(kind, InvocationKind::Bang { mac, span })
 990     }
 991
 992     fn collect_attr(
 993         &mut self,
 994         attr: Option<ast::Attribute>,
 995         derives: Vec<Path>,
 996         item: Annotatable,
 997         kind: AstFragmentKind,
 998         after_derive: bool,
 999     ) -> AstFragment {
1000         self.collect(
1001             kind,
1002             match attr {
1003                 Some(attr) => InvocationKind::Attr { attr, item, derives, after_derive },
1004                 None => InvocationKind::DeriveContainer { derives, item },
1005             },
1006         )
1007     }
1008
1009     fn find_attr_invoc(
1010         &self,
1011         attrs: &mut Vec<ast::Attribute>,
1012         after_derive: &mut bool,
1013     ) -> Option<ast::Attribute> {
1014         let attr = attrs
1015             .iter()
1016             .position(|a| {
1017                 if a.has_name(sym::derive) {
1018                     *after_derive = true;
1019                 }
1020                 !attr::is_known(a) && !is_builtin_attr(a)
1021             })
1022             .map(|i| attrs.remove(i));
1023         if let Some(attr) = &attr {
1024             if !self.cx.ecfg.custom_inner_attributes()
1025                 && attr.style == ast::AttrStyle::Inner
1026                 && !attr.has_name(sym::test)
1027             {
1028                 feature_err(
1029                     &self.cx.parse_sess,
1030                     sym::custom_inner_attributes,
1031                     attr.span,
1032                     "non-builtin inner attributes are unstable",
1033                 )
1034                 .emit();
1035             }
1036         }
1037         attr
1038     }
1039
1040     /// If `item` is an attr invocation, remove and return the macro attribute and derive traits.
1041     fn classify_item(
1042         &mut self,
1043         item: &mut impl HasAttrs,
1044     ) -> (Option<ast::Attribute>, Vec<Path>, /* after_derive */ bool) {
1045         let (mut attr, mut traits, mut after_derive) = (None, Vec::new(), false);
1046
1047         item.visit_attrs(|mut attrs| {
1048             attr = self.find_attr_invoc(&mut attrs, &mut after_derive);
1049             traits = collect_derives(&mut self.cx, &mut attrs);
1050         });
1051
1052         (attr, traits, after_derive)
1053     }
1054
1055     /// Alternative to `classify_item()` that ignores `#[derive]` so invocations fallthrough
1056     /// to the unused-attributes lint (making it an error on statements and expressions
1057     /// is a breaking change)
1058     fn classify_nonitem(
1059         &mut self,
1060         nonitem: &mut impl HasAttrs,
1061     ) -> (Option<ast::Attribute>, /* after_derive */ bool) {
1062         let (mut attr, mut after_derive) = (None, false);
1063
1064         nonitem.visit_attrs(|mut attrs| {
1065             attr = self.find_attr_invoc(&mut attrs, &mut after_derive);
1066         });
1067
1068         (attr, after_derive)
1069     }
1070
1071     fn configure<T: HasAttrs>(&mut self, node: T) -> Option<T> {
1072         self.cfg.configure(node)
1073     }
1074
1075     // Detect use of feature-gated or invalid attributes on macro invocations
1076     // since they will not be detected after macro expansion.
1077     fn check_attributes(&mut self, attrs: &[ast::Attribute]) {
1078         let features = self.cx.ecfg.features.unwrap();
1079         for attr in attrs.iter() {
1080             rustc_ast_passes::feature_gate::check_attribute(attr, self.cx.parse_sess, features);
1081             validate_attr::check_meta(self.cx.parse_sess, attr);
1082
1083             // macros are expanded before any lint passes so this warning has to be hardcoded
1084             if attr.has_name(sym::derive) {
1085                 self.cx
1086                     .struct_span_warn(attr.span, "`#[derive]` does nothing on macro invocations")
1087                     .note("this may become a hard error in a future release")
1088                     .emit();
1089             }
1090         }
1091     }
1092 }
1093
1094 impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
1095     fn visit_expr(&mut self, expr: &mut P<ast::Expr>) {
1096         self.cfg.configure_expr(expr);
1097         visit_clobber(expr.deref_mut(), |mut expr| {
1098             self.cfg.configure_expr_kind(&mut expr.kind);
1099
1100             // ignore derives so they remain unused
1101             let (attr, after_derive) = self.classify_nonitem(&mut expr);
1102
1103             if attr.is_some() {
1104                 // Collect the invoc regardless of whether or not attributes are permitted here
1105                 // expansion will eat the attribute so it won't error later.
1106                 attr.as_ref().map(|a| self.cfg.maybe_emit_expr_attr_err(a));
1107
1108                 // AstFragmentKind::Expr requires the macro to emit an expression.
1109                 return self
1110                     .collect_attr(
1111                         attr,
1112                         vec![],
1113                         Annotatable::Expr(P(expr)),
1114                         AstFragmentKind::Expr,
1115                         after_derive,
1116                     )
1117                     .make_expr()
1118                     .into_inner();
1119             }
1120
1121             if let ast::ExprKind::Mac(mac) = expr.kind {
1122                 self.check_attributes(&expr.attrs);
1123                 self.collect_bang(mac, expr.span, AstFragmentKind::Expr).make_expr().into_inner()
1124             } else {
1125                 noop_visit_expr(&mut expr, self);
1126                 expr
1127             }
1128         });
1129     }
1130
1131     fn flat_map_arm(&mut self, arm: ast::Arm) -> SmallVec<[ast::Arm; 1]> {
1132         let mut arm = configure!(self, arm);
1133
1134         let (attr, traits, after_derive) = self.classify_item(&mut arm);
1135         if attr.is_some() || !traits.is_empty() {
1136             return self
1137                 .collect_attr(
1138                     attr,
1139                     traits,
1140                     Annotatable::Arm(arm),
1141                     AstFragmentKind::Arms,
1142                     after_derive,
1143                 )
1144                 .make_arms();
1145         }
1146
1147         noop_flat_map_arm(arm, self)
1148     }
1149
1150     fn flat_map_field(&mut self, field: ast::Field) -> SmallVec<[ast::Field; 1]> {
1151         let mut field = configure!(self, field);
1152
1153         let (attr, traits, after_derive) = self.classify_item(&mut field);
1154         if attr.is_some() || !traits.is_empty() {
1155             return self
1156                 .collect_attr(
1157                     attr,
1158                     traits,
1159                     Annotatable::Field(field),
1160                     AstFragmentKind::Fields,
1161                     after_derive,
1162                 )
1163                 .make_fields();
1164         }
1165
1166         noop_flat_map_field(field, self)
1167     }
1168
1169     fn flat_map_field_pattern(&mut self, fp: ast::FieldPat) -> SmallVec<[ast::FieldPat; 1]> {
1170         let mut fp = configure!(self, fp);
1171
1172         let (attr, traits, after_derive) = self.classify_item(&mut fp);
1173         if attr.is_some() || !traits.is_empty() {
1174             return self
1175                 .collect_attr(
1176                     attr,
1177                     traits,
1178                     Annotatable::FieldPat(fp),
1179                     AstFragmentKind::FieldPats,
1180                     after_derive,
1181                 )
1182                 .make_field_patterns();
1183         }
1184
1185         noop_flat_map_field_pattern(fp, self)
1186     }
1187
1188     fn flat_map_param(&mut self, p: ast::Param) -> SmallVec<[ast::Param; 1]> {
1189         let mut p = configure!(self, p);
1190
1191         let (attr, traits, after_derive) = self.classify_item(&mut p);
1192         if attr.is_some() || !traits.is_empty() {
1193             return self
1194                 .collect_attr(
1195                     attr,
1196                     traits,
1197                     Annotatable::Param(p),
1198                     AstFragmentKind::Params,
1199                     after_derive,
1200                 )
1201                 .make_params();
1202         }
1203
1204         noop_flat_map_param(p, self)
1205     }
1206
1207     fn flat_map_struct_field(&mut self, sf: ast::StructField) -> SmallVec<[ast::StructField; 1]> {
1208         let mut sf = configure!(self, sf);
1209
1210         let (attr, traits, after_derive) = self.classify_item(&mut sf);
1211         if attr.is_some() || !traits.is_empty() {
1212             return self
1213                 .collect_attr(
1214                     attr,
1215                     traits,
1216                     Annotatable::StructField(sf),
1217                     AstFragmentKind::StructFields,
1218                     after_derive,
1219                 )
1220                 .make_struct_fields();
1221         }
1222
1223         noop_flat_map_struct_field(sf, self)
1224     }
1225
1226     fn flat_map_variant(&mut self, variant: ast::Variant) -> SmallVec<[ast::Variant; 1]> {
1227         let mut variant = configure!(self, variant);
1228
1229         let (attr, traits, after_derive) = self.classify_item(&mut variant);
1230         if attr.is_some() || !traits.is_empty() {
1231             return self
1232                 .collect_attr(
1233                     attr,
1234                     traits,
1235                     Annotatable::Variant(variant),
1236                     AstFragmentKind::Variants,
1237                     after_derive,
1238                 )
1239                 .make_variants();
1240         }
1241
1242         noop_flat_map_variant(variant, self)
1243     }
1244
1245     fn filter_map_expr(&mut self, expr: P<ast::Expr>) -> Option<P<ast::Expr>> {
1246         let expr = configure!(self, expr);
1247         expr.filter_map(|mut expr| {
1248             self.cfg.configure_expr_kind(&mut expr.kind);
1249
1250             // Ignore derives so they remain unused.
1251             let (attr, after_derive) = self.classify_nonitem(&mut expr);
1252
1253             if attr.is_some() {
1254                 attr.as_ref().map(|a| self.cfg.maybe_emit_expr_attr_err(a));
1255
1256                 return self
1257                     .collect_attr(
1258                         attr,
1259                         vec![],
1260                         Annotatable::Expr(P(expr)),
1261                         AstFragmentKind::OptExpr,
1262                         after_derive,
1263                     )
1264                     .make_opt_expr()
1265                     .map(|expr| expr.into_inner());
1266             }
1267
1268             if let ast::ExprKind::Mac(mac) = expr.kind {
1269                 self.check_attributes(&expr.attrs);
1270                 self.collect_bang(mac, expr.span, AstFragmentKind::OptExpr)
1271                     .make_opt_expr()
1272                     .map(|expr| expr.into_inner())
1273             } else {
1274                 Some({
1275                     noop_visit_expr(&mut expr, self);
1276                     expr
1277                 })
1278             }
1279         })
1280     }
1281
1282     fn visit_pat(&mut self, pat: &mut P<ast::Pat>) {
1283         self.cfg.configure_pat(pat);
1284         match pat.kind {
1285             PatKind::Mac(_) => {}
1286             _ => return noop_visit_pat(pat, self),
1287         }
1288
1289         visit_clobber(pat, |mut pat| match mem::replace(&mut pat.kind, PatKind::Wild) {
1290             PatKind::Mac(mac) => self.collect_bang(mac, pat.span, AstFragmentKind::Pat).make_pat(),
1291             _ => unreachable!(),
1292         });
1293     }
1294
1295     fn flat_map_stmt(&mut self, stmt: ast::Stmt) -> SmallVec<[ast::Stmt; 1]> {
1296         let mut stmt = configure!(self, stmt);
1297
1298         // we'll expand attributes on expressions separately
1299         if !stmt.is_expr() {
1300             let (attr, derives, after_derive) = if stmt.is_item() {
1301                 self.classify_item(&mut stmt)
1302             } else {
1303                 // ignore derives on non-item statements so it falls through
1304                 // to the unused-attributes lint
1305                 let (attr, after_derive) = self.classify_nonitem(&mut stmt);
1306                 (attr, vec![], after_derive)
1307             };
1308
1309             if attr.is_some() || !derives.is_empty() {
1310                 return self
1311                     .collect_attr(
1312                         attr,
1313                         derives,
1314                         Annotatable::Stmt(P(stmt)),
1315                         AstFragmentKind::Stmts,
1316                         after_derive,
1317                     )
1318                     .make_stmts();
1319             }
1320         }
1321
1322         if let StmtKind::Mac(mac) = stmt.kind {
1323             let (mac, style, attrs) = mac.into_inner();
1324             self.check_attributes(&attrs);
1325             let mut placeholder =
1326                 self.collect_bang(mac, stmt.span, AstFragmentKind::Stmts).make_stmts();
1327
1328             // If this is a macro invocation with a semicolon, then apply that
1329             // semicolon to the final statement produced by expansion.
1330             if style == MacStmtStyle::Semicolon {
1331                 if let Some(stmt) = placeholder.pop() {
1332                     placeholder.push(stmt.add_trailing_semicolon());
1333                 }
1334             }
1335
1336             return placeholder;
1337         }
1338
1339         // The placeholder expander gives ids to statements, so we avoid folding the id here.
1340         let ast::Stmt { id, kind, span } = stmt;
1341         noop_flat_map_stmt_kind(kind, self)
1342             .into_iter()
1343             .map(|kind| ast::Stmt { id, kind, span })
1344             .collect()
1345     }
1346
1347     fn visit_block(&mut self, block: &mut P<Block>) {
1348         let old_directory_ownership = self.cx.current_expansion.directory_ownership;
1349         self.cx.current_expansion.directory_ownership = DirectoryOwnership::UnownedViaBlock;
1350         noop_visit_block(block, self);
1351         self.cx.current_expansion.directory_ownership = old_directory_ownership;
1352     }
1353
1354     fn flat_map_item(&mut self, item: P<ast::Item>) -> SmallVec<[P<ast::Item>; 1]> {
1355         let mut item = configure!(self, item);
1356
1357         let (attr, traits, after_derive) = self.classify_item(&mut item);
1358         if attr.is_some() || !traits.is_empty() {
1359             return self
1360                 .collect_attr(
1361                     attr,
1362                     traits,
1363                     Annotatable::Item(item),
1364                     AstFragmentKind::Items,
1365                     after_derive,
1366                 )
1367                 .make_items();
1368         }
1369
1370         match item.kind {
1371             ast::ItemKind::Mac(..) => {
1372                 self.check_attributes(&item.attrs);
1373                 item.and_then(|item| match item.kind {
1374                     ItemKind::Mac(mac) => self
1375                         .collect(
1376                             AstFragmentKind::Items,
1377                             InvocationKind::Bang { mac, span: item.span },
1378                         )
1379                         .make_items(),
1380                     _ => unreachable!(),
1381                 })
1382             }
1383             ast::ItemKind::Mod(ast::Mod { inner, inline, .. })
1384                 if item.ident != Ident::invalid() =>
1385             {
1386                 let orig_directory_ownership = self.cx.current_expansion.directory_ownership;
1387                 let mut module = (*self.cx.current_expansion.module).clone();
1388                 module.mod_path.push(item.ident);
1389
1390                 if inline {
1391                     if let Some(path) = attr::first_attr_value_str_by_name(&item.attrs, sym::path) {
1392                         self.cx.current_expansion.directory_ownership =
1393                             DirectoryOwnership::Owned { relative: None };
1394                         module.directory.push(&*path.as_str());
1395                     } else {
1396                         module.directory.push(&*item.ident.as_str());
1397                     }
1398                 } else {
1399                     let path = self.cx.parse_sess.source_map().span_to_unmapped_path(inner);
1400                     let mut path = match path {
1401                         FileName::Real(path) => path,
1402                         other => PathBuf::from(other.to_string()),
1403                     };
1404                     let directory_ownership = match path.file_name().unwrap().to_str() {
1405                         Some("mod.rs") => DirectoryOwnership::Owned { relative: None },
1406                         Some(_) => DirectoryOwnership::Owned { relative: Some(item.ident) },
1407                         None => DirectoryOwnership::UnownedViaMod,
1408                     };
1409                     path.pop();
1410                     module.directory = path;
1411                     self.cx.current_expansion.directory_ownership = directory_ownership;
1412                 }
1413
1414                 let orig_module =
1415                     mem::replace(&mut self.cx.current_expansion.module, Rc::new(module));
1416                 let result = noop_flat_map_item(item, self);
1417                 self.cx.current_expansion.module = orig_module;
1418                 self.cx.current_expansion.directory_ownership = orig_directory_ownership;
1419                 result
1420             }
1421
1422             _ => noop_flat_map_item(item, self),
1423         }
1424     }
1425
1426     fn flat_map_trait_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
1427         let mut item = configure!(self, item);
1428
1429         let (attr, traits, after_derive) = self.classify_item(&mut item);
1430         if attr.is_some() || !traits.is_empty() {
1431             return self
1432                 .collect_attr(
1433                     attr,
1434                     traits,
1435                     Annotatable::TraitItem(item),
1436                     AstFragmentKind::TraitItems,
1437                     after_derive,
1438                 )
1439                 .make_trait_items();
1440         }
1441
1442         match item.kind {
1443             ast::AssocItemKind::Macro(..) => {
1444                 self.check_attributes(&item.attrs);
1445                 item.and_then(|item| match item.kind {
1446                     ast::AssocItemKind::Macro(mac) => self
1447                         .collect_bang(mac, item.span, AstFragmentKind::TraitItems)
1448                         .make_trait_items(),
1449                     _ => unreachable!(),
1450                 })
1451             }
1452             _ => noop_flat_map_assoc_item(item, self),
1453         }
1454     }
1455
1456     fn flat_map_impl_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
1457         let mut item = configure!(self, item);
1458
1459         let (attr, traits, after_derive) = self.classify_item(&mut item);
1460         if attr.is_some() || !traits.is_empty() {
1461             return self
1462                 .collect_attr(
1463                     attr,
1464                     traits,
1465                     Annotatable::ImplItem(item),
1466                     AstFragmentKind::ImplItems,
1467                     after_derive,
1468                 )
1469                 .make_impl_items();
1470         }
1471
1472         match item.kind {
1473             ast::AssocItemKind::Macro(..) => {
1474                 self.check_attributes(&item.attrs);
1475                 item.and_then(|item| match item.kind {
1476                     ast::AssocItemKind::Macro(mac) => self
1477                         .collect_bang(mac, item.span, AstFragmentKind::ImplItems)
1478                         .make_impl_items(),
1479                     _ => unreachable!(),
1480                 })
1481             }
1482             _ => noop_flat_map_assoc_item(item, self),
1483         }
1484     }
1485
1486     fn visit_ty(&mut self, ty: &mut P<ast::Ty>) {
1487         match ty.kind {
1488             ast::TyKind::Mac(_) => {}
1489             _ => return noop_visit_ty(ty, self),
1490         };
1491
1492         visit_clobber(ty, |mut ty| match mem::replace(&mut ty.kind, ast::TyKind::Err) {
1493             ast::TyKind::Mac(mac) => self.collect_bang(mac, ty.span, AstFragmentKind::Ty).make_ty(),
1494             _ => unreachable!(),
1495         });
1496     }
1497
1498     fn visit_foreign_mod(&mut self, foreign_mod: &mut ast::ForeignMod) {
1499         self.cfg.configure_foreign_mod(foreign_mod);
1500         noop_visit_foreign_mod(foreign_mod, self);
1501     }
1502
1503     fn flat_map_foreign_item(
1504         &mut self,
1505         mut foreign_item: P<ast::ForeignItem>,
1506     ) -> SmallVec<[P<ast::ForeignItem>; 1]> {
1507         let (attr, traits, after_derive) = self.classify_item(&mut foreign_item);
1508
1509         if attr.is_some() || !traits.is_empty() {
1510             return self
1511                 .collect_attr(
1512                     attr,
1513                     traits,
1514                     Annotatable::ForeignItem(foreign_item),
1515                     AstFragmentKind::ForeignItems,
1516                     after_derive,
1517                 )
1518                 .make_foreign_items();
1519         }
1520
1521         match foreign_item.kind {
1522             ast::ForeignItemKind::Macro(..) => {
1523                 self.check_attributes(&foreign_item.attrs);
1524                 foreign_item.and_then(|item| match item.kind {
1525                     ast::ForeignItemKind::Macro(mac) => self
1526                         .collect_bang(mac, item.span, AstFragmentKind::ForeignItems)
1527                         .make_foreign_items(),
1528                     _ => unreachable!(),
1529                 })
1530             }
1531             _ => noop_flat_map_foreign_item(foreign_item, self),
1532         }
1533     }
1534
1535     fn visit_item_kind(&mut self, item: &mut ast::ItemKind) {
1536         match item {
1537             ast::ItemKind::MacroDef(..) => {}
1538             _ => {
1539                 self.cfg.configure_item_kind(item);
1540                 noop_visit_item_kind(item, self);
1541             }
1542         }
1543     }
1544
1545     fn flat_map_generic_param(
1546         &mut self,
1547         param: ast::GenericParam,
1548     ) -> SmallVec<[ast::GenericParam; 1]> {
1549         let mut param = configure!(self, param);
1550
1551         let (attr, traits, after_derive) = self.classify_item(&mut param);
1552         if attr.is_some() || !traits.is_empty() {
1553             return self
1554                 .collect_attr(
1555                     attr,
1556                     traits,
1557                     Annotatable::GenericParam(param),
1558                     AstFragmentKind::GenericParams,
1559                     after_derive,
1560                 )
1561                 .make_generic_params();
1562         }
1563
1564         noop_flat_map_generic_param(param, self)
1565     }
1566
1567     fn visit_attribute(&mut self, at: &mut ast::Attribute) {
1568         // turn `#[doc(include="filename")]` attributes into `#[doc(include(file="filename",
1569         // contents="file contents")]` attributes
1570         if !at.check_name(sym::doc) {
1571             return noop_visit_attribute(at, self);
1572         }
1573
1574         if let Some(list) = at.meta_item_list() {
1575             if !list.iter().any(|it| it.check_name(sym::include)) {
1576                 return noop_visit_attribute(at, self);
1577             }
1578
1579             let mut items = vec![];
1580
1581             for mut it in list {
1582                 if !it.check_name(sym::include) {
1583                     items.push({
1584                         noop_visit_meta_list_item(&mut it, self);
1585                         it
1586                     });
1587                     continue;
1588                 }
1589
1590                 if let Some(file) = it.value_str() {
1591                     let err_count = self.cx.parse_sess.span_diagnostic.err_count();
1592                     self.check_attributes(slice::from_ref(at));
1593                     if self.cx.parse_sess.span_diagnostic.err_count() > err_count {
1594                         // avoid loading the file if they haven't enabled the feature
1595                         return noop_visit_attribute(at, self);
1596                     }
1597
1598                     let filename = match self.cx.resolve_path(&*file.as_str(), it.span()) {
1599                         Ok(filename) => filename,
1600                         Err(mut err) => {
1601                             err.emit();
1602                             continue;
1603                         }
1604                     };
1605
1606                     match self.cx.source_map().load_file(&filename) {
1607                         Ok(source_file) => {
1608                             let src = source_file
1609                                 .src
1610                                 .as_ref()
1611                                 .expect("freshly loaded file should have a source");
1612                             let src_interned = Symbol::intern(src.as_str());
1613
1614                             let include_info = vec![
1615                                 ast::NestedMetaItem::MetaItem(attr::mk_name_value_item_str(
1616                                     Ident::with_dummy_span(sym::file),
1617                                     file,
1618                                     DUMMY_SP,
1619                                 )),
1620                                 ast::NestedMetaItem::MetaItem(attr::mk_name_value_item_str(
1621                                     Ident::with_dummy_span(sym::contents),
1622                                     src_interned,
1623                                     DUMMY_SP,
1624                                 )),
1625                             ];
1626
1627                             let include_ident = Ident::with_dummy_span(sym::include);
1628                             let item = attr::mk_list_item(include_ident, include_info);
1629                             items.push(ast::NestedMetaItem::MetaItem(item));
1630                         }
1631                         Err(e) => {
1632                             let lit =
1633                                 it.meta_item().and_then(|item| item.name_value_literal()).unwrap();
1634
1635                             if e.kind() == ErrorKind::InvalidData {
1636                                 self.cx
1637                                     .struct_span_err(
1638                                         lit.span,
1639                                         &format!("{} wasn't a utf-8 file", filename.display()),
1640                                     )
1641                                     .span_label(lit.span, "contains invalid utf-8")
1642                                     .emit();
1643                             } else {
1644                                 let mut err = self.cx.struct_span_err(
1645                                     lit.span,
1646                                     &format!("couldn't read {}: {}", filename.display(), e),
1647                                 );
1648                                 err.span_label(lit.span, "couldn't read file");
1649
1650                                 err.emit();
1651                             }
1652                         }
1653                     }
1654                 } else {
1655                     let mut err = self.cx.struct_span_err(
1656                         it.span(),
1657                         &format!("expected path to external documentation"),
1658                     );
1659
1660                     // Check if the user erroneously used `doc(include(...))` syntax.
1661                     let literal = it.meta_item_list().and_then(|list| {
1662                         if list.len() == 1 {
1663                             list[0].literal().map(|literal| &literal.kind)
1664                         } else {
1665                             None
1666                         }
1667                     });
1668
1669                     let (path, applicability) = match &literal {
1670                         Some(LitKind::Str(path, ..)) => {
1671                             (path.to_string(), Applicability::MachineApplicable)
1672                         }
1673                         _ => (String::from("<path>"), Applicability::HasPlaceholders),
1674                     };
1675
1676                     err.span_suggestion(
1677                         it.span(),
1678                         "provide a file path with `=`",
1679                         format!("include = \"{}\"", path),
1680                         applicability,
1681                     );
1682
1683                     err.emit();
1684                 }
1685             }
1686
1687             let meta = attr::mk_list_item(Ident::with_dummy_span(sym::doc), items);
1688             *at = ast::Attribute {
1689                 kind: ast::AttrKind::Normal(AttrItem {
1690                     path: meta.path,
1691                     args: meta.kind.mac_args(meta.span),
1692                 }),
1693                 span: at.span,
1694                 id: at.id,
1695                 style: at.style,
1696             };
1697         } else {
1698             noop_visit_attribute(at, self)
1699         }
1700     }
1701
1702     fn visit_id(&mut self, id: &mut ast::NodeId) {
1703         if self.monotonic {
1704             debug_assert_eq!(*id, ast::DUMMY_NODE_ID);
1705             *id = self.cx.resolver.next_node_id()
1706         }
1707     }
1708
1709     fn visit_fn_decl(&mut self, mut fn_decl: &mut P<ast::FnDecl>) {
1710         self.cfg.configure_fn_decl(&mut fn_decl);
1711         noop_visit_fn_decl(fn_decl, self);
1712     }
1713 }
1714
1715 pub struct ExpansionConfig<'feat> {
1716     pub crate_name: String,
1717     pub features: Option<&'feat Features>,
1718     pub recursion_limit: usize,
1719     pub trace_mac: bool,
1720     pub should_test: bool, // If false, strip `#[test]` nodes
1721     pub single_step: bool,
1722     pub keep_macs: bool,
1723 }
1724
1725 impl<'feat> ExpansionConfig<'feat> {
1726     pub fn default(crate_name: String) -> ExpansionConfig<'static> {
1727         ExpansionConfig {
1728             crate_name,
1729             features: None,
1730             recursion_limit: 1024,
1731             trace_mac: false,
1732             should_test: false,
1733             single_step: false,
1734             keep_macs: false,
1735         }
1736     }
1737
1738     fn proc_macro_hygiene(&self) -> bool {
1739         self.features.map_or(false, |features| features.proc_macro_hygiene)
1740     }
1741     fn custom_inner_attributes(&self) -> bool {
1742         self.features.map_or(false, |features| features.custom_inner_attributes)
1743     }
1744 }