src/libsyntax_expand/expand.rs

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