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