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                         let attr = attr::find_by_name(item.attrs(), sym::derive)
 455                             .expect("`derive` attribute should exist");
 456                         let span = attr.span;
 457                         let mut err = self.cx.struct_span_err(
 458                             span,
 459                             "`derive` may only be applied to structs, enums and unions",
 460                         );
 461                         if let ast::AttrStyle::Inner = attr.style {
 462                             let trait_list = derives
 463                                 .iter()
 464                                 .map(|t| pprust::path_to_string(t))
 465                                 .collect::<Vec<_>>();
 466                             let suggestion = format!("#[derive({})]", trait_list.join(", "));
 467                             err.span_suggestion(
 468                                 span,
 469                                 "try an outer attribute",
 470                                 suggestion,
 471                                 // We don't 𝑘𝑛𝑜𝑤 that the following item is an ADT
 472                                 Applicability::MaybeIncorrect,
 473                             );
 474                         }
 475                         err.emit();
 476                     }
 477
 478                     let mut item = self.fully_configure(item);
 479                     item.visit_attrs(|attrs| attrs.retain(|a| !a.has_name(sym::derive)));
 480
 481                     let mut derive_placeholders = Vec::with_capacity(derives.len());
 482                     invocations.reserve(derives.len());
 483                     for path in derives {
 484                         let expn_id = ExpnId::fresh(None);
 485                         derive_placeholders.push(NodeId::placeholder_from_expn_id(expn_id));
 486                         invocations.push(Invocation {
 487                             kind: InvocationKind::Derive { path, item: item.clone() },
 488                             fragment_kind: invoc.fragment_kind,
 489                             expansion_data: ExpansionData {
 490                                 id: expn_id,
 491                                 ..invoc.expansion_data.clone()
 492                             },
 493                         });
 494                     }
 495                     let fragment =
 496                         invoc.fragment_kind.expect_from_annotatables(::std::iter::once(item));
 497                     self.collect_invocations(fragment, &derive_placeholders)
 498                 }
 499             };
 500
 501             if expanded_fragments.len() < depth {
 502                 expanded_fragments.push(Vec::new());
 503             }
 504             expanded_fragments[depth - 1].push((expn_id, expanded_fragment));
 505             if !self.cx.ecfg.single_step {
 506                 invocations.extend(new_invocations.into_iter().rev());
 507             }
 508         }
 509
 510         self.cx.current_expansion = orig_expansion_data;
 511
 512         // Finally incorporate all the expanded macros into the input AST fragment.
 513         let mut placeholder_expander = PlaceholderExpander::new(self.cx, self.monotonic);
 514         while let Some(expanded_fragments) = expanded_fragments.pop() {
 515             for (expn_id, expanded_fragment) in expanded_fragments.into_iter().rev() {
 516                 placeholder_expander
 517                     .add(NodeId::placeholder_from_expn_id(expn_id), expanded_fragment);
 518             }
 519         }
 520         fragment_with_placeholders.mut_visit_with(&mut placeholder_expander);
 521         fragment_with_placeholders
 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 expand_invoc(&mut self, invoc: Invocation, ext: &SyntaxExtensionKind) -> AstFragment {
 610         if self.cx.current_expansion.depth > self.cx.ecfg.recursion_limit {
 611             let expn_data = self.cx.current_expansion.id.expn_data();
 612             let suggested_limit = self.cx.ecfg.recursion_limit * 2;
 613             let mut err = self.cx.struct_span_err(
 614                 expn_data.call_site,
 615                 &format!("recursion limit reached while expanding `{}`", expn_data.kind.descr()),
 616             );
 617             err.help(&format!(
 618                 "consider adding a `#![recursion_limit=\"{}\"]` attribute to your crate (`{}`)",
 619                 suggested_limit, self.cx.ecfg.crate_name,
 620             ));
 621             err.emit();
 622             self.cx.trace_macros_diag();
 623             FatalError.raise();
 624         }
 625
 626         let (fragment_kind, span) = (invoc.fragment_kind, invoc.span());
 627         match invoc.kind {
 628             InvocationKind::Bang { mac, .. } => match ext {
 629                 SyntaxExtensionKind::Bang(expander) => {
 630                     self.gate_proc_macro_expansion_kind(span, fragment_kind);
 631                     let tok_result = expander.expand(self.cx, span, mac.args.inner_tokens());
 632                     self.parse_ast_fragment(tok_result, fragment_kind, &mac.path, span)
 633                 }
 634                 SyntaxExtensionKind::LegacyBang(expander) => {
 635                     let prev = self.cx.current_expansion.prior_type_ascription;
 636                     self.cx.current_expansion.prior_type_ascription = mac.prior_type_ascription;
 637                     let tok_result = expander.expand(self.cx, span, mac.args.inner_tokens());
 638                     let result = if let Some(result) = fragment_kind.make_from(tok_result) {
 639                         result
 640                     } else {
 641                         let msg = format!(
 642                             "non-{kind} macro in {kind} position: {path}",
 643                             kind = fragment_kind.name(),
 644                             path = pprust::path_to_string(&mac.path),
 645                         );
 646                         self.cx.span_err(span, &msg);
 647                         self.cx.trace_macros_diag();
 648                         fragment_kind.dummy(span)
 649                     };
 650                     self.cx.current_expansion.prior_type_ascription = prev;
 651                     result
 652                 }
 653                 _ => unreachable!(),
 654             },
 655             InvocationKind::Attr { attr, mut item, .. } => match ext {
 656                 SyntaxExtensionKind::Attr(expander) => {
 657                     self.gate_proc_macro_input(&item);
 658                     self.gate_proc_macro_attr_item(span, &item);
 659                     let item_tok = TokenTree::token(
 660                         token::Interpolated(Lrc::new(match item {
 661                             Annotatable::Item(item) => token::NtItem(item),
 662                             Annotatable::TraitItem(item) => token::NtTraitItem(item),
 663                             Annotatable::ImplItem(item) => token::NtImplItem(item),
 664                             Annotatable::ForeignItem(item) => token::NtForeignItem(item),
 665                             Annotatable::Stmt(stmt) => token::NtStmt(stmt.into_inner()),
 666                             Annotatable::Expr(expr) => token::NtExpr(expr),
 667                             Annotatable::Arm(..)
 668                             | Annotatable::Field(..)
 669                             | Annotatable::FieldPat(..)
 670                             | Annotatable::GenericParam(..)
 671                             | Annotatable::Param(..)
 672                             | Annotatable::StructField(..)
 673                             | Annotatable::Variant(..) => panic!("unexpected annotatable"),
 674                         })),
 675                         DUMMY_SP,
 676                     )
 677                     .into();
 678                     let item = attr.unwrap_normal_item();
 679                     if let MacArgs::Eq(..) = item.args {
 680                         self.cx.span_err(span, "key-value macro attributes are not supported");
 681                     }
 682                     let tok_result =
 683                         expander.expand(self.cx, span, item.args.inner_tokens(), item_tok);
 684                     self.parse_ast_fragment(tok_result, fragment_kind, &item.path, span)
 685                 }
 686                 SyntaxExtensionKind::LegacyAttr(expander) => {
 687                     match validate_attr::parse_meta(self.cx.parse_sess, &attr) {
 688                         Ok(meta) => {
 689                             let item = expander.expand(self.cx, span, &meta, item);
 690                             fragment_kind.expect_from_annotatables(item)
 691                         }
 692                         Err(mut err) => {
 693                             err.emit();
 694                             fragment_kind.dummy(span)
 695                         }
 696                     }
 697                 }
 698                 SyntaxExtensionKind::NonMacroAttr { mark_used } => {
 699                     attr::mark_known(&attr);
 700                     if *mark_used {
 701                         attr::mark_used(&attr);
 702                     }
 703                     item.visit_attrs(|attrs| attrs.push(attr));
 704                     fragment_kind.expect_from_annotatables(iter::once(item))
 705                 }
 706                 _ => unreachable!(),
 707             },
 708             InvocationKind::Derive { path, item } => match ext {
 709                 SyntaxExtensionKind::Derive(expander)
 710                 | SyntaxExtensionKind::LegacyDerive(expander) => {
 711                     if !item.derive_allowed() {
 712                         return fragment_kind.dummy(span);
 713                     }
 714                     if let SyntaxExtensionKind::Derive(..) = ext {
 715                         self.gate_proc_macro_input(&item);
 716                     }
 717                     let meta = ast::MetaItem { kind: ast::MetaItemKind::Word, span, path };
 718                     let items = expander.expand(self.cx, span, &meta, item);
 719                     fragment_kind.expect_from_annotatables(items)
 720                 }
 721                 _ => unreachable!(),
 722             },
 723             InvocationKind::DeriveContainer { .. } => unreachable!(),
 724         }
 725     }
 726
 727     fn gate_proc_macro_attr_item(&self, span: Span, item: &Annotatable) {
 728         let kind = match item {
 729             Annotatable::Item(_)
 730             | Annotatable::TraitItem(_)
 731             | Annotatable::ImplItem(_)
 732             | Annotatable::ForeignItem(_) => return,
 733             Annotatable::Stmt(_) => "statements",
 734             Annotatable::Expr(_) => "expressions",
 735             Annotatable::Arm(..)
 736             | Annotatable::Field(..)
 737             | Annotatable::FieldPat(..)
 738             | Annotatable::GenericParam(..)
 739             | Annotatable::Param(..)
 740             | Annotatable::StructField(..)
 741             | Annotatable::Variant(..) => panic!("unexpected annotatable"),
 742         };
 743         if self.cx.ecfg.proc_macro_hygiene() {
 744             return;
 745         }
 746         feature_err(
 747             self.cx.parse_sess,
 748             sym::proc_macro_hygiene,
 749             span,
 750             &format!("custom attributes cannot be applied to {}", kind),
 751         )
 752         .emit();
 753     }
 754
 755     fn gate_proc_macro_input(&self, annotatable: &Annotatable) {
 756         struct GateProcMacroInput<'a> {
 757             parse_sess: &'a ParseSess,
 758         }
 759
 760         impl<'ast, 'a> Visitor<'ast> for GateProcMacroInput<'a> {
 761             fn visit_item(&mut self, item: &'ast ast::Item) {
 762                 match &item.kind {
 763                     ast::ItemKind::Mod(module) if !module.inline => {
 764                         feature_err(
 765                             self.parse_sess,
 766                             sym::proc_macro_hygiene,
 767                             item.span,
 768                             "non-inline modules in proc macro input are unstable",
 769                         )
 770                         .emit();
 771                     }
 772                     _ => {}
 773                 }
 774
 775                 visit::walk_item(self, item);
 776             }
 777
 778             fn visit_mac(&mut self, _: &'ast ast::Mac) {}
 779         }
 780
 781         if !self.cx.ecfg.proc_macro_hygiene() {
 782             annotatable.visit_with(&mut GateProcMacroInput { parse_sess: self.cx.parse_sess });
 783         }
 784     }
 785
 786     fn gate_proc_macro_expansion_kind(&self, span: Span, kind: AstFragmentKind) {
 787         let kind = match kind {
 788             AstFragmentKind::Expr | AstFragmentKind::OptExpr => "expressions",
 789             AstFragmentKind::Pat => "patterns",
 790             AstFragmentKind::Stmts => "statements",
 791             AstFragmentKind::Ty
 792             | AstFragmentKind::Items
 793             | AstFragmentKind::TraitItems
 794             | AstFragmentKind::ImplItems
 795             | AstFragmentKind::ForeignItems => return,
 796             AstFragmentKind::Arms
 797             | AstFragmentKind::Fields
 798             | AstFragmentKind::FieldPats
 799             | AstFragmentKind::GenericParams
 800             | AstFragmentKind::Params
 801             | AstFragmentKind::StructFields
 802             | AstFragmentKind::Variants => panic!("unexpected AST fragment kind"),
 803         };
 804         if self.cx.ecfg.proc_macro_hygiene() {
 805             return;
 806         }
 807         feature_err(
 808             self.cx.parse_sess,
 809             sym::proc_macro_hygiene,
 810             span,
 811             &format!("procedural macros cannot be expanded to {}", kind),
 812         )
 813         .emit();
 814     }
 815
 816     fn parse_ast_fragment(
 817         &mut self,
 818         toks: TokenStream,
 819         kind: AstFragmentKind,
 820         path: &Path,
 821         span: Span,
 822     ) -> AstFragment {
 823         let mut parser = self.cx.new_parser_from_tts(toks);
 824         match parse_ast_fragment(&mut parser, kind) {
 825             Ok(fragment) => {
 826                 ensure_complete_parse(&mut parser, path, kind.name(), span);
 827                 fragment
 828             }
 829             Err(mut err) => {
 830                 err.set_span(span);
 831                 annotate_err_with_kind(&mut err, kind, span);
 832                 err.emit();
 833                 self.cx.trace_macros_diag();
 834                 kind.dummy(span)
 835             }
 836         }
 837     }
 838 }
 839
 840 pub fn parse_ast_fragment<'a>(
 841     this: &mut Parser<'a>,
 842     kind: AstFragmentKind,
 843 ) -> PResult<'a, AstFragment> {
 844     Ok(match kind {
 845         AstFragmentKind::Items => {
 846             let mut items = SmallVec::new();
 847             while let Some(item) = this.parse_item()? {
 848                 items.push(item);
 849             }
 850             AstFragment::Items(items)
 851         }
 852         AstFragmentKind::TraitItems => {
 853             let mut items = SmallVec::new();
 854             while this.token != token::Eof {
 855                 items.push(this.parse_trait_item(&mut false)?);
 856             }
 857             AstFragment::TraitItems(items)
 858         }
 859         AstFragmentKind::ImplItems => {
 860             let mut items = SmallVec::new();
 861             while this.token != token::Eof {
 862                 items.push(this.parse_impl_item(&mut false)?);
 863             }
 864             AstFragment::ImplItems(items)
 865         }
 866         AstFragmentKind::ForeignItems => {
 867             let mut items = SmallVec::new();
 868             while this.token != token::Eof {
 869                 items.push(this.parse_foreign_item()?);
 870             }
 871             AstFragment::ForeignItems(items)
 872         }
 873         AstFragmentKind::Stmts => {
 874             let mut stmts = SmallVec::new();
 875             // Won't make progress on a `}`.
 876             while this.token != token::Eof && this.token != token::CloseDelim(token::Brace) {
 877                 if let Some(stmt) = this.parse_full_stmt()? {
 878                     stmts.push(stmt);
 879                 }
 880             }
 881             AstFragment::Stmts(stmts)
 882         }
 883         AstFragmentKind::Expr => AstFragment::Expr(this.parse_expr()?),
 884         AstFragmentKind::OptExpr => {
 885             if this.token != token::Eof {
 886                 AstFragment::OptExpr(Some(this.parse_expr()?))
 887             } else {
 888                 AstFragment::OptExpr(None)
 889             }
 890         }
 891         AstFragmentKind::Ty => AstFragment::Ty(this.parse_ty()?),
 892         AstFragmentKind::Pat => AstFragment::Pat(this.parse_pat(None)?),
 893         AstFragmentKind::Arms
 894         | AstFragmentKind::Fields
 895         | AstFragmentKind::FieldPats
 896         | AstFragmentKind::GenericParams
 897         | AstFragmentKind::Params
 898         | AstFragmentKind::StructFields
 899         | AstFragmentKind::Variants => panic!("unexpected AST fragment kind"),
 900     })
 901 }
 902
 903 pub fn ensure_complete_parse<'a>(
 904     this: &mut Parser<'a>,
 905     macro_path: &Path,
 906     kind_name: &str,
 907     span: Span,
 908 ) {
 909     if this.token != token::Eof {
 910         let token = pprust::token_to_string(&this.token);
 911         let msg = format!("macro expansion ignores token `{}` and any following", token);
 912         // Avoid emitting backtrace info twice.
 913         let def_site_span = this.token.span.with_ctxt(SyntaxContext::root());
 914         let mut err = this.struct_span_err(def_site_span, &msg);
 915         err.span_label(span, "caused by the macro expansion here");
 916         let msg = format!(
 917             "the usage of `{}!` is likely invalid in {} context",
 918             pprust::path_to_string(macro_path),
 919             kind_name,
 920         );
 921         err.note(&msg);
 922         let semi_span = this.sess.source_map().next_point(span);
 923
 924         let semi_full_span = semi_span.to(this.sess.source_map().next_point(semi_span));
 925         match this.sess.source_map().span_to_snippet(semi_full_span) {
 926             Ok(ref snippet) if &snippet[..] != ";" && kind_name == "expression" => {
 927                 err.span_suggestion(
 928                     semi_span,
 929                     "you might be missing a semicolon here",
 930                     ";".to_owned(),
 931                     Applicability::MaybeIncorrect,
 932                 );
 933             }
 934             _ => {}
 935         }
 936         err.emit();
 937     }
 938 }
 939
 940 struct InvocationCollector<'a, 'b> {
 941     cx: &'a mut ExtCtxt<'b>,
 942     cfg: StripUnconfigured<'a>,
 943     invocations: Vec<Invocation>,
 944     monotonic: bool,
 945 }
 946
 947 impl<'a, 'b> InvocationCollector<'a, 'b> {
 948     fn collect(&mut self, fragment_kind: AstFragmentKind, kind: InvocationKind) -> AstFragment {
 949         // Expansion data for all the collected invocations is set upon their resolution,
 950         // with exception of the derive container case which is not resolved and can get
 951         // its expansion data immediately.
 952         let expn_data = match &kind {
 953             InvocationKind::DeriveContainer { item, .. } => Some(ExpnData {
 954                 parent: self.cx.current_expansion.id,
 955                 ..ExpnData::default(
 956                     ExpnKind::Macro(MacroKind::Attr, sym::derive),
 957                     item.span(),
 958                     self.cx.parse_sess.edition,
 959                 )
 960             }),
 961             _ => None,
 962         };
 963         let expn_id = ExpnId::fresh(expn_data);
 964         let vis = kind.placeholder_visibility();
 965         self.invocations.push(Invocation {
 966             kind,
 967             fragment_kind,
 968             expansion_data: ExpansionData {
 969                 id: expn_id,
 970                 depth: self.cx.current_expansion.depth + 1,
 971                 ..self.cx.current_expansion.clone()
 972             },
 973         });
 974         placeholder(fragment_kind, NodeId::placeholder_from_expn_id(expn_id), vis)
 975     }
 976
 977     fn collect_bang(&mut self, mac: ast::Mac, span: Span, kind: AstFragmentKind) -> AstFragment {
 978         self.collect(kind, InvocationKind::Bang { mac, span })
 979     }
 980
 981     fn collect_attr(
 982         &mut self,
 983         attr: Option<ast::Attribute>,
 984         derives: Vec<Path>,
 985         item: Annotatable,
 986         kind: AstFragmentKind,
 987         after_derive: bool,
 988     ) -> AstFragment {
 989         self.collect(
 990             kind,
 991             match attr {
 992                 Some(attr) => InvocationKind::Attr { attr, item, derives, after_derive },
 993                 None => InvocationKind::DeriveContainer { derives, item },
 994             },
 995         )
 996     }
 997
 998     fn find_attr_invoc(
 999         &self,
1000         attrs: &mut Vec<ast::Attribute>,
1001         after_derive: &mut bool,
1002     ) -> Option<ast::Attribute> {
1003         let attr = attrs
1004             .iter()
1005             .position(|a| {
1006                 if a.has_name(sym::derive) {
1007                     *after_derive = true;
1008                 }
1009                 !attr::is_known(a) && !is_builtin_attr(a)
1010             })
1011             .map(|i| attrs.remove(i));
1012         if let Some(attr) = &attr {
1013             if !self.cx.ecfg.custom_inner_attributes()
1014                 && attr.style == ast::AttrStyle::Inner
1015                 && !attr.has_name(sym::test)
1016             {
1017                 feature_err(
1018                     &self.cx.parse_sess,
1019                     sym::custom_inner_attributes,
1020                     attr.span,
1021                     "non-builtin inner attributes are unstable",
1022                 )
1023                 .emit();
1024             }
1025         }
1026         attr
1027     }
1028
1029     /// If `item` is an attr invocation, remove and return the macro attribute and derive traits.
1030     fn classify_item<T>(
1031         &mut self,
1032         item: &mut T,
1033     ) -> (Option<ast::Attribute>, Vec<Path>, /* after_derive */ bool)
1034     where
1035         T: HasAttrs,
1036     {
1037         let (mut attr, mut traits, mut after_derive) = (None, Vec::new(), false);
1038
1039         item.visit_attrs(|mut attrs| {
1040             attr = self.find_attr_invoc(&mut attrs, &mut after_derive);
1041             traits = collect_derives(&mut self.cx, &mut attrs);
1042         });
1043
1044         (attr, traits, after_derive)
1045     }
1046
1047     /// Alternative to `classify_item()` that ignores `#[derive]` so invocations fallthrough
1048     /// to the unused-attributes lint (making it an error on statements and expressions
1049     /// is a breaking change)
1050     fn classify_nonitem<T: HasAttrs>(
1051         &mut self,
1052         nonitem: &mut T,
1053     ) -> (Option<ast::Attribute>, /* after_derive */ bool) {
1054         let (mut attr, mut after_derive) = (None, false);
1055
1056         nonitem.visit_attrs(|mut attrs| {
1057             attr = self.find_attr_invoc(&mut attrs, &mut after_derive);
1058         });
1059
1060         (attr, after_derive)
1061     }
1062
1063     fn configure<T: HasAttrs>(&mut self, node: T) -> Option<T> {
1064         self.cfg.configure(node)
1065     }
1066
1067     // Detect use of feature-gated or invalid attributes on macro invocations
1068     // since they will not be detected after macro expansion.
1069     fn check_attributes(&mut self, attrs: &[ast::Attribute]) {
1070         let features = self.cx.ecfg.features.unwrap();
1071         for attr in attrs.iter() {
1072             rustc_ast_passes::feature_gate::check_attribute(attr, self.cx.parse_sess, features);
1073             validate_attr::check_meta(self.cx.parse_sess, attr);
1074
1075             // macros are expanded before any lint passes so this warning has to be hardcoded
1076             if attr.has_name(sym::derive) {
1077                 self.cx
1078                     .struct_span_warn(attr.span, "`#[derive]` does nothing on macro invocations")
1079                     .note("this may become a hard error in a future release")
1080                     .emit();
1081             }
1082         }
1083     }
1084 }
1085
1086 impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
1087     fn visit_expr(&mut self, expr: &mut P<ast::Expr>) {
1088         self.cfg.configure_expr(expr);
1089         visit_clobber(expr.deref_mut(), |mut expr| {
1090             self.cfg.configure_expr_kind(&mut expr.kind);
1091
1092             // ignore derives so they remain unused
1093             let (attr, after_derive) = self.classify_nonitem(&mut expr);
1094
1095             if attr.is_some() {
1096                 // Collect the invoc regardless of whether or not attributes are permitted here
1097                 // expansion will eat the attribute so it won't error later.
1098                 attr.as_ref().map(|a| self.cfg.maybe_emit_expr_attr_err(a));
1099
1100                 // AstFragmentKind::Expr requires the macro to emit an expression.
1101                 return self
1102                     .collect_attr(
1103                         attr,
1104                         vec![],
1105                         Annotatable::Expr(P(expr)),
1106                         AstFragmentKind::Expr,
1107                         after_derive,
1108                     )
1109                     .make_expr()
1110                     .into_inner();
1111             }
1112
1113             if let ast::ExprKind::Mac(mac) = expr.kind {
1114                 self.check_attributes(&expr.attrs);
1115                 self.collect_bang(mac, expr.span, AstFragmentKind::Expr).make_expr().into_inner()
1116             } else {
1117                 noop_visit_expr(&mut expr, self);
1118                 expr
1119             }
1120         });
1121     }
1122
1123     fn flat_map_arm(&mut self, arm: ast::Arm) -> SmallVec<[ast::Arm; 1]> {
1124         let mut arm = configure!(self, arm);
1125
1126         let (attr, traits, after_derive) = self.classify_item(&mut arm);
1127         if attr.is_some() || !traits.is_empty() {
1128             return self
1129                 .collect_attr(
1130                     attr,
1131                     traits,
1132                     Annotatable::Arm(arm),
1133                     AstFragmentKind::Arms,
1134                     after_derive,
1135                 )
1136                 .make_arms();
1137         }
1138
1139         noop_flat_map_arm(arm, self)
1140     }
1141
1142     fn flat_map_field(&mut self, field: ast::Field) -> SmallVec<[ast::Field; 1]> {
1143         let mut field = configure!(self, field);
1144
1145         let (attr, traits, after_derive) = self.classify_item(&mut field);
1146         if attr.is_some() || !traits.is_empty() {
1147             return self
1148                 .collect_attr(
1149                     attr,
1150                     traits,
1151                     Annotatable::Field(field),
1152                     AstFragmentKind::Fields,
1153                     after_derive,
1154                 )
1155                 .make_fields();
1156         }
1157
1158         noop_flat_map_field(field, self)
1159     }
1160
1161     fn flat_map_field_pattern(&mut self, fp: ast::FieldPat) -> SmallVec<[ast::FieldPat; 1]> {
1162         let mut fp = configure!(self, fp);
1163
1164         let (attr, traits, after_derive) = self.classify_item(&mut fp);
1165         if attr.is_some() || !traits.is_empty() {
1166             return self
1167                 .collect_attr(
1168                     attr,
1169                     traits,
1170                     Annotatable::FieldPat(fp),
1171                     AstFragmentKind::FieldPats,
1172                     after_derive,
1173                 )
1174                 .make_field_patterns();
1175         }
1176
1177         noop_flat_map_field_pattern(fp, self)
1178     }
1179
1180     fn flat_map_param(&mut self, p: ast::Param) -> SmallVec<[ast::Param; 1]> {
1181         let mut p = configure!(self, p);
1182
1183         let (attr, traits, after_derive) = self.classify_item(&mut p);
1184         if attr.is_some() || !traits.is_empty() {
1185             return self
1186                 .collect_attr(
1187                     attr,
1188                     traits,
1189                     Annotatable::Param(p),
1190                     AstFragmentKind::Params,
1191                     after_derive,
1192                 )
1193                 .make_params();
1194         }
1195
1196         noop_flat_map_param(p, self)
1197     }
1198
1199     fn flat_map_struct_field(&mut self, sf: ast::StructField) -> SmallVec<[ast::StructField; 1]> {
1200         let mut sf = configure!(self, sf);
1201
1202         let (attr, traits, after_derive) = self.classify_item(&mut sf);
1203         if attr.is_some() || !traits.is_empty() {
1204             return self
1205                 .collect_attr(
1206                     attr,
1207                     traits,
1208                     Annotatable::StructField(sf),
1209                     AstFragmentKind::StructFields,
1210                     after_derive,
1211                 )
1212                 .make_struct_fields();
1213         }
1214
1215         noop_flat_map_struct_field(sf, self)
1216     }
1217
1218     fn flat_map_variant(&mut self, variant: ast::Variant) -> SmallVec<[ast::Variant; 1]> {
1219         let mut variant = configure!(self, variant);
1220
1221         let (attr, traits, after_derive) = self.classify_item(&mut variant);
1222         if attr.is_some() || !traits.is_empty() {
1223             return self
1224                 .collect_attr(
1225                     attr,
1226                     traits,
1227                     Annotatable::Variant(variant),
1228                     AstFragmentKind::Variants,
1229                     after_derive,
1230                 )
1231                 .make_variants();
1232         }
1233
1234         noop_flat_map_variant(variant, self)
1235     }
1236
1237     fn filter_map_expr(&mut self, expr: P<ast::Expr>) -> Option<P<ast::Expr>> {
1238         let expr = configure!(self, expr);
1239         expr.filter_map(|mut expr| {
1240             self.cfg.configure_expr_kind(&mut expr.kind);
1241
1242             // Ignore derives so they remain unused.
1243             let (attr, after_derive) = self.classify_nonitem(&mut expr);
1244
1245             if attr.is_some() {
1246                 attr.as_ref().map(|a| self.cfg.maybe_emit_expr_attr_err(a));
1247
1248                 return self
1249                     .collect_attr(
1250                         attr,
1251                         vec![],
1252                         Annotatable::Expr(P(expr)),
1253                         AstFragmentKind::OptExpr,
1254                         after_derive,
1255                     )
1256                     .make_opt_expr()
1257                     .map(|expr| expr.into_inner());
1258             }
1259
1260             if let ast::ExprKind::Mac(mac) = expr.kind {
1261                 self.check_attributes(&expr.attrs);
1262                 self.collect_bang(mac, expr.span, AstFragmentKind::OptExpr)
1263                     .make_opt_expr()
1264                     .map(|expr| expr.into_inner())
1265             } else {
1266                 Some({
1267                     noop_visit_expr(&mut expr, self);
1268                     expr
1269                 })
1270             }
1271         })
1272     }
1273
1274     fn visit_pat(&mut self, pat: &mut P<ast::Pat>) {
1275         self.cfg.configure_pat(pat);
1276         match pat.kind {
1277             PatKind::Mac(_) => {}
1278             _ => return noop_visit_pat(pat, self),
1279         }
1280
1281         visit_clobber(pat, |mut pat| match mem::replace(&mut pat.kind, PatKind::Wild) {
1282             PatKind::Mac(mac) => self.collect_bang(mac, pat.span, AstFragmentKind::Pat).make_pat(),
1283             _ => unreachable!(),
1284         });
1285     }
1286
1287     fn flat_map_stmt(&mut self, stmt: ast::Stmt) -> SmallVec<[ast::Stmt; 1]> {
1288         let mut stmt = configure!(self, stmt);
1289
1290         // we'll expand attributes on expressions separately
1291         if !stmt.is_expr() {
1292             let (attr, derives, after_derive) = if stmt.is_item() {
1293                 self.classify_item(&mut stmt)
1294             } else {
1295                 // ignore derives on non-item statements so it falls through
1296                 // to the unused-attributes lint
1297                 let (attr, after_derive) = self.classify_nonitem(&mut stmt);
1298                 (attr, vec![], after_derive)
1299             };
1300
1301             if attr.is_some() || !derives.is_empty() {
1302                 return self
1303                     .collect_attr(
1304                         attr,
1305                         derives,
1306                         Annotatable::Stmt(P(stmt)),
1307                         AstFragmentKind::Stmts,
1308                         after_derive,
1309                     )
1310                     .make_stmts();
1311             }
1312         }
1313
1314         if let StmtKind::Mac(mac) = stmt.kind {
1315             let (mac, style, attrs) = mac.into_inner();
1316             self.check_attributes(&attrs);
1317             let mut placeholder =
1318                 self.collect_bang(mac, stmt.span, AstFragmentKind::Stmts).make_stmts();
1319
1320             // If this is a macro invocation with a semicolon, then apply that
1321             // semicolon to the final statement produced by expansion.
1322             if style == MacStmtStyle::Semicolon {
1323                 if let Some(stmt) = placeholder.pop() {
1324                     placeholder.push(stmt.add_trailing_semicolon());
1325                 }
1326             }
1327
1328             return placeholder;
1329         }
1330
1331         // The placeholder expander gives ids to statements, so we avoid folding the id here.
1332         let ast::Stmt { id, kind, span } = stmt;
1333         noop_flat_map_stmt_kind(kind, self)
1334             .into_iter()
1335             .map(|kind| ast::Stmt { id, kind, span })
1336             .collect()
1337     }
1338
1339     fn visit_block(&mut self, block: &mut P<Block>) {
1340         let old_directory_ownership = self.cx.current_expansion.directory_ownership;
1341         self.cx.current_expansion.directory_ownership = DirectoryOwnership::UnownedViaBlock;
1342         noop_visit_block(block, self);
1343         self.cx.current_expansion.directory_ownership = old_directory_ownership;
1344     }
1345
1346     fn flat_map_item(&mut self, item: P<ast::Item>) -> SmallVec<[P<ast::Item>; 1]> {
1347         let mut item = configure!(self, item);
1348
1349         let (attr, traits, after_derive) = self.classify_item(&mut item);
1350         if attr.is_some() || !traits.is_empty() {
1351             return self
1352                 .collect_attr(
1353                     attr,
1354                     traits,
1355                     Annotatable::Item(item),
1356                     AstFragmentKind::Items,
1357                     after_derive,
1358                 )
1359                 .make_items();
1360         }
1361
1362         match item.kind {
1363             ast::ItemKind::Mac(..) => {
1364                 self.check_attributes(&item.attrs);
1365                 item.and_then(|item| match item.kind {
1366                     ItemKind::Mac(mac) => self
1367                         .collect(
1368                             AstFragmentKind::Items,
1369                             InvocationKind::Bang { mac, span: item.span },
1370                         )
1371                         .make_items(),
1372                     _ => unreachable!(),
1373                 })
1374             }
1375             ast::ItemKind::Mod(ast::Mod { inner, .. }) => {
1376                 if item.ident == Ident::invalid() {
1377                     return noop_flat_map_item(item, self);
1378                 }
1379
1380                 let orig_directory_ownership = self.cx.current_expansion.directory_ownership;
1381                 let mut module = (*self.cx.current_expansion.module).clone();
1382                 module.mod_path.push(item.ident);
1383
1384                 // Detect if this is an inline module (`mod m { ... }` as opposed to `mod m;`).
1385                 // In the non-inline case, `inner` is never the dummy span (cf. `parse_item_mod`).
1386                 // Thus, if `inner` is the dummy span, we know the module is inline.
1387                 let inline_module = item.span.contains(inner) || inner.is_dummy();
1388
1389                 if inline_module {
1390                     if let Some(path) = attr::first_attr_value_str_by_name(&item.attrs, sym::path) {
1391                         self.cx.current_expansion.directory_ownership =
1392                             DirectoryOwnership::Owned { relative: None };
1393                         module.directory.push(&*path.as_str());
1394                     } else {
1395                         module.directory.push(&*item.ident.as_str());
1396                     }
1397                 } else {
1398                     let path = self.cx.parse_sess.source_map().span_to_unmapped_path(inner);
1399                     let mut path = match path {
1400                         FileName::Real(path) => path,
1401                         other => PathBuf::from(other.to_string()),
1402                     };
1403                     let directory_ownership = match path.file_name().unwrap().to_str() {
1404                         Some("mod.rs") => DirectoryOwnership::Owned { relative: None },
1405                         Some(_) => DirectoryOwnership::Owned { relative: Some(item.ident) },
1406                         None => DirectoryOwnership::UnownedViaMod,
1407                     };
1408                     path.pop();
1409                     module.directory = path;
1410                     self.cx.current_expansion.directory_ownership = directory_ownership;
1411                 }
1412
1413                 let orig_module =
1414                     mem::replace(&mut self.cx.current_expansion.module, Rc::new(module));
1415                 let result = noop_flat_map_item(item, self);
1416                 self.cx.current_expansion.module = orig_module;
1417                 self.cx.current_expansion.directory_ownership = orig_directory_ownership;
1418                 result
1419             }
1420
1421             _ => noop_flat_map_item(item, self),
1422         }
1423     }
1424
1425     fn flat_map_trait_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
1426         let mut item = configure!(self, item);
1427
1428         let (attr, traits, after_derive) = self.classify_item(&mut item);
1429         if attr.is_some() || !traits.is_empty() {
1430             return self
1431                 .collect_attr(
1432                     attr,
1433                     traits,
1434                     Annotatable::TraitItem(item),
1435                     AstFragmentKind::TraitItems,
1436                     after_derive,
1437                 )
1438                 .make_trait_items();
1439         }
1440
1441         match item.kind {
1442             ast::AssocItemKind::Macro(..) => {
1443                 self.check_attributes(&item.attrs);
1444                 item.and_then(|item| match item.kind {
1445                     ast::AssocItemKind::Macro(mac) => self
1446                         .collect_bang(mac, item.span, AstFragmentKind::TraitItems)
1447                         .make_trait_items(),
1448                     _ => unreachable!(),
1449                 })
1450             }
1451             _ => noop_flat_map_assoc_item(item, self),
1452         }
1453     }
1454
1455     fn flat_map_impl_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
1456         let mut item = configure!(self, item);
1457
1458         let (attr, traits, after_derive) = self.classify_item(&mut item);
1459         if attr.is_some() || !traits.is_empty() {
1460             return self
1461                 .collect_attr(
1462                     attr,
1463                     traits,
1464                     Annotatable::ImplItem(item),
1465                     AstFragmentKind::ImplItems,
1466                     after_derive,
1467                 )
1468                 .make_impl_items();
1469         }
1470
1471         match item.kind {
1472             ast::AssocItemKind::Macro(..) => {
1473                 self.check_attributes(&item.attrs);
1474                 item.and_then(|item| match item.kind {
1475                     ast::AssocItemKind::Macro(mac) => self
1476                         .collect_bang(mac, item.span, AstFragmentKind::ImplItems)
1477                         .make_impl_items(),
1478                     _ => unreachable!(),
1479                 })
1480             }
1481             _ => noop_flat_map_assoc_item(item, self),
1482         }
1483     }
1484
1485     fn visit_ty(&mut self, ty: &mut P<ast::Ty>) {
1486         match ty.kind {
1487             ast::TyKind::Mac(_) => {}
1488             _ => return noop_visit_ty(ty, self),
1489         };
1490
1491         visit_clobber(ty, |mut ty| match mem::replace(&mut ty.kind, ast::TyKind::Err) {
1492             ast::TyKind::Mac(mac) => self.collect_bang(mac, ty.span, AstFragmentKind::Ty).make_ty(),
1493             _ => unreachable!(),
1494         });
1495     }
1496
1497     fn visit_foreign_mod(&mut self, foreign_mod: &mut ast::ForeignMod) {
1498         self.cfg.configure_foreign_mod(foreign_mod);
1499         noop_visit_foreign_mod(foreign_mod, self);
1500     }
1501
1502     fn flat_map_foreign_item(
1503         &mut self,
1504         mut foreign_item: P<ast::ForeignItem>,
1505     ) -> SmallVec<[P<ast::ForeignItem>; 1]> {
1506         let (attr, traits, after_derive) = self.classify_item(&mut foreign_item);
1507
1508         if attr.is_some() || !traits.is_empty() {
1509             return self
1510                 .collect_attr(
1511                     attr,
1512                     traits,
1513                     Annotatable::ForeignItem(foreign_item),
1514                     AstFragmentKind::ForeignItems,
1515                     after_derive,
1516                 )
1517                 .make_foreign_items();
1518         }
1519
1520         match foreign_item.kind {
1521             ast::ForeignItemKind::Macro(..) => {
1522                 self.check_attributes(&foreign_item.attrs);
1523                 foreign_item.and_then(|item| match item.kind {
1524                     ast::ForeignItemKind::Macro(mac) => self
1525                         .collect_bang(mac, item.span, AstFragmentKind::ForeignItems)
1526                         .make_foreign_items(),
1527                     _ => unreachable!(),
1528                 })
1529             }
1530             _ => noop_flat_map_foreign_item(foreign_item, self),
1531         }
1532     }
1533
1534     fn visit_item_kind(&mut self, item: &mut ast::ItemKind) {
1535         match item {
1536             ast::ItemKind::MacroDef(..) => {}
1537             _ => {
1538                 self.cfg.configure_item_kind(item);
1539                 noop_visit_item_kind(item, self);
1540             }
1541         }
1542     }
1543
1544     fn flat_map_generic_param(
1545         &mut self,
1546         param: ast::GenericParam,
1547     ) -> SmallVec<[ast::GenericParam; 1]> {
1548         let mut param = configure!(self, param);
1549
1550         let (attr, traits, after_derive) = self.classify_item(&mut param);
1551         if attr.is_some() || !traits.is_empty() {
1552             return self
1553                 .collect_attr(
1554                     attr,
1555                     traits,
1556                     Annotatable::GenericParam(param),
1557                     AstFragmentKind::GenericParams,
1558                     after_derive,
1559                 )
1560                 .make_generic_params();
1561         }
1562
1563         noop_flat_map_generic_param(param, self)
1564     }
1565
1566     fn visit_attribute(&mut self, at: &mut ast::Attribute) {
1567         // turn `#[doc(include="filename")]` attributes into `#[doc(include(file="filename",
1568         // contents="file contents")]` attributes
1569         if !at.check_name(sym::doc) {
1570             return noop_visit_attribute(at, self);
1571         }
1572
1573         if let Some(list) = at.meta_item_list() {
1574             if !list.iter().any(|it| it.check_name(sym::include)) {
1575                 return noop_visit_attribute(at, self);
1576             }
1577
1578             let mut items = vec![];
1579
1580             for mut it in list {
1581                 if !it.check_name(sym::include) {
1582                     items.push({
1583                         noop_visit_meta_list_item(&mut it, self);
1584                         it
1585                     });
1586                     continue;
1587                 }
1588
1589                 if let Some(file) = it.value_str() {
1590                     let err_count = self.cx.parse_sess.span_diagnostic.err_count();
1591                     self.check_attributes(slice::from_ref(at));
1592                     if self.cx.parse_sess.span_diagnostic.err_count() > err_count {
1593                         // avoid loading the file if they haven't enabled the feature
1594                         return noop_visit_attribute(at, self);
1595                     }
1596
1597                     let filename = match self.cx.resolve_path(&*file.as_str(), it.span()) {
1598                         Ok(filename) => filename,
1599                         Err(mut err) => {
1600                             err.emit();
1601                             continue;
1602                         }
1603                     };
1604
1605                     match self.cx.source_map().load_file(&filename) {
1606                         Ok(source_file) => {
1607                             let src = source_file
1608                                 .src
1609                                 .as_ref()
1610                                 .expect("freshly loaded file should have a source");
1611                             let src_interned = Symbol::intern(src.as_str());
1612
1613                             let include_info = vec![
1614                                 ast::NestedMetaItem::MetaItem(attr::mk_name_value_item_str(
1615                                     Ident::with_dummy_span(sym::file),
1616                                     file,
1617                                     DUMMY_SP,
1618                                 )),
1619                                 ast::NestedMetaItem::MetaItem(attr::mk_name_value_item_str(
1620                                     Ident::with_dummy_span(sym::contents),
1621                                     src_interned,
1622                                     DUMMY_SP,
1623                                 )),
1624                             ];
1625
1626                             let include_ident = Ident::with_dummy_span(sym::include);
1627                             let item = attr::mk_list_item(include_ident, include_info);
1628                             items.push(ast::NestedMetaItem::MetaItem(item));
1629                         }
1630                         Err(e) => {
1631                             let lit =
1632                                 it.meta_item().and_then(|item| item.name_value_literal()).unwrap();
1633
1634                             if e.kind() == ErrorKind::InvalidData {
1635                                 self.cx
1636                                     .struct_span_err(
1637                                         lit.span,
1638                                         &format!("{} wasn't a utf-8 file", filename.display()),
1639                                     )
1640                                     .span_label(lit.span, "contains invalid utf-8")
1641                                     .emit();
1642                             } else {
1643                                 let mut err = self.cx.struct_span_err(
1644                                     lit.span,
1645                                     &format!("couldn't read {}: {}", filename.display(), e),
1646                                 );
1647                                 err.span_label(lit.span, "couldn't read file");
1648
1649                                 err.emit();
1650                             }
1651                         }
1652                     }
1653                 } else {
1654                     let mut err = self.cx.struct_span_err(
1655                         it.span(),
1656                         &format!("expected path to external documentation"),
1657                     );
1658
1659                     // Check if the user erroneously used `doc(include(...))` syntax.
1660                     let literal = it.meta_item_list().and_then(|list| {
1661                         if list.len() == 1 {
1662                             list[0].literal().map(|literal| &literal.kind)
1663                         } else {
1664                             None
1665                         }
1666                     });
1667
1668                     let (path, applicability) = match &literal {
1669                         Some(LitKind::Str(path, ..)) => {
1670                             (path.to_string(), Applicability::MachineApplicable)
1671                         }
1672                         _ => (String::from("<path>"), Applicability::HasPlaceholders),
1673                     };
1674
1675                     err.span_suggestion(
1676                         it.span(),
1677                         "provide a file path with `=`",
1678                         format!("include = \"{}\"", path),
1679                         applicability,
1680                     );
1681
1682                     err.emit();
1683                 }
1684             }
1685
1686             let meta = attr::mk_list_item(Ident::with_dummy_span(sym::doc), items);
1687             *at = ast::Attribute {
1688                 kind: ast::AttrKind::Normal(AttrItem {
1689                     path: meta.path,
1690                     args: meta.kind.mac_args(meta.span),
1691                 }),
1692                 span: at.span,
1693                 id: at.id,
1694                 style: at.style,
1695             };
1696         } else {
1697             noop_visit_attribute(at, self)
1698         }
1699     }
1700
1701     fn visit_id(&mut self, id: &mut ast::NodeId) {
1702         if self.monotonic {
1703             debug_assert_eq!(*id, ast::DUMMY_NODE_ID);
1704             *id = self.cx.resolver.next_node_id()
1705         }
1706     }
1707
1708     fn visit_fn_decl(&mut self, mut fn_decl: &mut P<ast::FnDecl>) {
1709         self.cfg.configure_fn_decl(&mut fn_decl);
1710         noop_visit_fn_decl(fn_decl, self);
1711     }
1712 }
1713
1714 pub struct ExpansionConfig<'feat> {
1715     pub crate_name: String,
1716     pub features: Option<&'feat Features>,
1717     pub recursion_limit: usize,
1718     pub trace_mac: bool,
1719     pub should_test: bool, // If false, strip `#[test]` nodes
1720     pub single_step: bool,
1721     pub keep_macs: bool,
1722 }
1723
1724 impl<'feat> ExpansionConfig<'feat> {
1725     pub fn default(crate_name: String) -> ExpansionConfig<'static> {
1726         ExpansionConfig {
1727             crate_name,
1728             features: None,
1729             recursion_limit: 1024,
1730             trace_mac: false,
1731             should_test: false,
1732             single_step: false,
1733             keep_macs: false,
1734         }
1735     }
1736
1737     fn proc_macro_hygiene(&self) -> bool {
1738         self.features.map_or(false, |features| features.proc_macro_hygiene)
1739     }
1740     fn custom_inner_attributes(&self) -> bool {
1741         self.features.map_or(false, |features| features.custom_inner_attributes)
1742     }
1743 }