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