src/librustc_expand/expand.rs

   1 use crate::base::*;
   2 use crate::config::StripUnconfigured;
   3 use crate::hygiene::{ExpnData, ExpnId, ExpnKind, SyntaxContext};
   4 use crate::mbe::macro_rules::annotate_err_with_kind;
   5 use crate::placeholders::{placeholder, PlaceholderExpander};
   6 use crate::proc_macro::collect_derives;
   7
   8 use rustc_ast_pretty::pprust;
   9 use rustc_attr::{self as attr, is_builtin_attr, HasAttrs};
  10 use rustc_data_structures::sync::Lrc;
  11 use rustc_errors::{Applicability, FatalError, PResult};
  12 use rustc_feature::Features;
  13 use rustc_parse::configure;
  14 use rustc_parse::parser::Parser;
  15 use rustc_parse::validate_attr;
  16 use rustc_parse::DirectoryOwnership;
  17 use rustc_session::lint::builtin::UNUSED_DOC_COMMENTS;
  18 use rustc_session::lint::BuiltinLintDiagnostics;
  19 use rustc_session::parse::{feature_err, ParseSess};
  20 use rustc_span::source_map::respan;
  21 use rustc_span::symbol::{sym, Symbol};
  22 use rustc_span::{FileName, Span, DUMMY_SP};
  23 use syntax::ast::{self, AttrItem, Block, Ident, LitKind, NodeId, PatKind, Path};
  24 use syntax::ast::{ItemKind, MacArgs, MacStmtStyle, StmtKind};
  25 use syntax::mut_visit::*;
  26 use syntax::ptr::P;
  27 use syntax::token;
  28 use syntax::tokenstream::{TokenStream, TokenTree};
  29 use syntax::util::map_in_place::MapInPlace;
  30 use syntax::visit::{self, AssocCtxt, Visitor};
  31
  32 use smallvec::{smallvec, SmallVec};
  33 use std::io::ErrorKind;
  34 use std::ops::DerefMut;
  35 use std::path::PathBuf;
  36 use std::rc::Rc;
  37 use std::{iter, mem, slice};
  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 $visit_ast_elt:ident($($args:tt)*);)?
  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::$Kind(ast) => ast.extend(placeholders.iter().flat_map(|id| {
  86                         // We are repeating through arguments with `many`, to do that we have to
  87                         // mention some macro variable from those arguments even if it's not used.
  88                         macro _repeating($flat_map_ast_elt) {}
  89                         placeholder(AstFragmentKind::$Kind, *id, None).$make_ast()
  90                     })),)?)*
  91                     _ => panic!("unexpected AST fragment kind")
  92                 }
  93             }
  94
  95             pub fn make_opt_expr(self) -> Option<P<ast::Expr>> {
  96                 match self {
  97                     AstFragment::OptExpr(expr) => expr,
  98                     _ => panic!("AstFragment::make_* called on the wrong kind of fragment"),
  99                 }
 100             }
 101
 102             $(pub fn $make_ast(self) -> $AstTy {
 103                 match self {
 104                     AstFragment::$Kind(ast) => ast,
 105                     _ => panic!("AstFragment::make_* called on the wrong kind of fragment"),
 106                 }
 107             })*
 108
 109             pub fn mut_visit_with<F: MutVisitor>(&mut self, vis: &mut F) {
 110                 match self {
 111                     AstFragment::OptExpr(opt_expr) => {
 112                         visit_clobber(opt_expr, |opt_expr| {
 113                             if let Some(expr) = opt_expr {
 114                                 vis.filter_map_expr(expr)
 115                             } else {
 116                                 None
 117                             }
 118                         });
 119                     }
 120                     $($(AstFragment::$Kind(ast) => vis.$mut_visit_ast(ast),)?)*
 121                     $($(AstFragment::$Kind(ast) =>
 122                         ast.flat_map_in_place(|ast| vis.$flat_map_ast_elt(ast)),)?)*
 123                 }
 124             }
 125
 126             pub fn visit_with<'a, V: Visitor<'a>>(&'a self, visitor: &mut V) {
 127                 match *self {
 128                     AstFragment::OptExpr(Some(ref expr)) => visitor.visit_expr(expr),
 129                     AstFragment::OptExpr(None) => {}
 130                     $($(AstFragment::$Kind(ref ast) => visitor.$visit_ast(ast),)?)*
 131                     $($(AstFragment::$Kind(ref ast) => for ast_elt in &ast[..] {
 132                         visitor.$visit_ast_elt(ast_elt, $($args)*);
 133                     })?)*
 134                 }
 135             }
 136         }
 137
 138         impl<'a> MacResult for crate::mbe::macro_rules::ParserAnyMacro<'a> {
 139             $(fn $make_ast(self: Box<crate::mbe::macro_rules::ParserAnyMacro<'a>>)
 140                            -> Option<$AstTy> {
 141                 Some(self.make(AstFragmentKind::$Kind).$make_ast())
 142             })*
 143         }
 144     }
 145 }
 146
 147 ast_fragments! {
 148     Expr(P<ast::Expr>) { "expression"; one fn visit_expr; fn visit_expr; fn make_expr; }
 149     Pat(P<ast::Pat>) { "pattern"; one fn visit_pat; fn visit_pat; fn make_pat; }
 150     Ty(P<ast::Ty>) { "type"; one fn visit_ty; fn visit_ty; fn make_ty; }
 151     Stmts(SmallVec<[ast::Stmt; 1]>) {
 152         "statement"; many fn flat_map_stmt; fn visit_stmt(); fn make_stmts;
 153     }
 154     Items(SmallVec<[P<ast::Item>; 1]>) {
 155         "item"; many fn flat_map_item; fn visit_item(); fn make_items;
 156     }
 157     TraitItems(SmallVec<[P<ast::AssocItem>; 1]>) {
 158         "trait item";
 159         many fn flat_map_trait_item;
 160         fn visit_assoc_item(AssocCtxt::Trait);
 161         fn make_trait_items;
 162     }
 163     ImplItems(SmallVec<[P<ast::AssocItem>; 1]>) {
 164         "impl item";
 165         many fn flat_map_impl_item;
 166         fn visit_assoc_item(AssocCtxt::Impl);
 167         fn make_impl_items;
 168     }
 169     ForeignItems(SmallVec<[P<ast::ForeignItem>; 1]>) {
 170         "foreign item";
 171         many fn flat_map_foreign_item;
 172         fn visit_foreign_item();
 173         fn make_foreign_items;
 174     }
 175     Arms(SmallVec<[ast::Arm; 1]>) {
 176         "match arm"; many fn flat_map_arm; fn visit_arm(); fn make_arms;
 177     }
 178     Fields(SmallVec<[ast::Field; 1]>) {
 179         "field expression"; many fn flat_map_field; fn visit_field(); fn make_fields;
 180     }
 181     FieldPats(SmallVec<[ast::FieldPat; 1]>) {
 182         "field pattern";
 183         many fn flat_map_field_pattern;
 184         fn visit_field_pattern();
 185         fn make_field_patterns;
 186     }
 187     GenericParams(SmallVec<[ast::GenericParam; 1]>) {
 188         "generic parameter";
 189         many fn flat_map_generic_param;
 190         fn visit_generic_param();
 191         fn make_generic_params;
 192     }
 193     Params(SmallVec<[ast::Param; 1]>) {
 194         "function parameter"; many fn flat_map_param; fn visit_param(); fn make_params;
 195     }
 196     StructFields(SmallVec<[ast::StructField; 1]>) {
 197         "field";
 198         many fn flat_map_struct_field;
 199         fn visit_struct_field();
 200         fn make_struct_fields;
 201     }
 202     Variants(SmallVec<[ast::Variant; 1]>) {
 203         "variant"; many fn flat_map_variant; fn visit_variant(); fn make_variants;
 204     }
 205 }
 206
 207 impl AstFragmentKind {
 208     fn dummy(self, span: Span) -> AstFragment {
 209         self.make_from(DummyResult::any(span)).expect("couldn't create a dummy AST fragment")
 210     }
 211
 212     fn expect_from_annotatables<I: IntoIterator<Item = Annotatable>>(
 213         self,
 214         items: I,
 215     ) -> AstFragment {
 216         let mut items = items.into_iter();
 217         match self {
 218             AstFragmentKind::Arms => {
 219                 AstFragment::Arms(items.map(Annotatable::expect_arm).collect())
 220             }
 221             AstFragmentKind::Fields => {
 222                 AstFragment::Fields(items.map(Annotatable::expect_field).collect())
 223             }
 224             AstFragmentKind::FieldPats => {
 225                 AstFragment::FieldPats(items.map(Annotatable::expect_field_pattern).collect())
 226             }
 227             AstFragmentKind::GenericParams => {
 228                 AstFragment::GenericParams(items.map(Annotatable::expect_generic_param).collect())
 229             }
 230             AstFragmentKind::Params => {
 231                 AstFragment::Params(items.map(Annotatable::expect_param).collect())
 232             }
 233             AstFragmentKind::StructFields => {
 234                 AstFragment::StructFields(items.map(Annotatable::expect_struct_field).collect())
 235             }
 236             AstFragmentKind::Variants => {
 237                 AstFragment::Variants(items.map(Annotatable::expect_variant).collect())
 238             }
 239             AstFragmentKind::Items => {
 240                 AstFragment::Items(items.map(Annotatable::expect_item).collect())
 241             }
 242             AstFragmentKind::ImplItems => {
 243                 AstFragment::ImplItems(items.map(Annotatable::expect_impl_item).collect())
 244             }
 245             AstFragmentKind::TraitItems => {
 246                 AstFragment::TraitItems(items.map(Annotatable::expect_trait_item).collect())
 247             }
 248             AstFragmentKind::ForeignItems => {
 249                 AstFragment::ForeignItems(items.map(Annotatable::expect_foreign_item).collect())
 250             }
 251             AstFragmentKind::Stmts => {
 252                 AstFragment::Stmts(items.map(Annotatable::expect_stmt).collect())
 253             }
 254             AstFragmentKind::Expr => AstFragment::Expr(
 255                 items.next().expect("expected exactly one expression").expect_expr(),
 256             ),
 257             AstFragmentKind::OptExpr => {
 258                 AstFragment::OptExpr(items.next().map(Annotatable::expect_expr))
 259             }
 260             AstFragmentKind::Pat | AstFragmentKind::Ty => {
 261                 panic!("patterns and types aren't annotatable")
 262             }
 263         }
 264     }
 265 }
 266
 267 pub struct Invocation {
 268     pub kind: InvocationKind,
 269     pub fragment_kind: AstFragmentKind,
 270     pub expansion_data: ExpansionData,
 271 }
 272
 273 pub enum InvocationKind {
 274     Bang {
 275         mac: ast::Mac,
 276         span: Span,
 277     },
 278     Attr {
 279         attr: ast::Attribute,
 280         item: Annotatable,
 281         // Required for resolving derive helper attributes.
 282         derives: Vec<Path>,
 283         // We temporarily report errors for attribute macros placed after derives
 284         after_derive: bool,
 285     },
 286     Derive {
 287         path: Path,
 288         item: Annotatable,
 289     },
 290     /// "Invocation" that contains all derives from an item,
 291     /// broken into multiple `Derive` invocations when expanded.
 292     /// FIXME: Find a way to remove it.
 293     DeriveContainer {
 294         derives: Vec<Path>,
 295         item: Annotatable,
 296     },
 297 }
 298
 299 impl InvocationKind {
 300     fn placeholder_visibility(&self) -> Option<ast::Visibility> {
 301         // HACK: For unnamed fields placeholders should have the same visibility as the actual
 302         // fields because for tuple structs/variants resolve determines visibilities of their
 303         // constructor using these field visibilities before attributes on them are are expanded.
 304         // The assumption is that the attribute expansion cannot change field visibilities,
 305         // and it holds because only inert attributes are supported in this position.
 306         match self {
 307             InvocationKind::Attr { item: Annotatable::StructField(field), .. }
 308             | InvocationKind::Derive { item: Annotatable::StructField(field), .. }
 309             | InvocationKind::DeriveContainer { item: Annotatable::StructField(field), .. }
 310                 if field.ident.is_none() =>
 311             {
 312                 Some(field.vis.clone())
 313             }
 314             _ => None,
 315         }
 316     }
 317 }
 318
 319 impl Invocation {
 320     pub fn span(&self) -> Span {
 321         match &self.kind {
 322             InvocationKind::Bang { span, .. } => *span,
 323             InvocationKind::Attr { attr, .. } => attr.span,
 324             InvocationKind::Derive { path, .. } => path.span,
 325             InvocationKind::DeriveContainer { item, .. } => item.span(),
 326         }
 327     }
 328 }
 329
 330 pub struct MacroExpander<'a, 'b> {
 331     pub cx: &'a mut ExtCtxt<'b>,
 332     monotonic: bool, // cf. `cx.monotonic_expander()`
 333 }
 334
 335 impl<'a, 'b> MacroExpander<'a, 'b> {
 336     pub fn new(cx: &'a mut ExtCtxt<'b>, monotonic: bool) -> Self {
 337         MacroExpander { cx, monotonic }
 338     }
 339
 340     pub fn expand_crate(&mut self, mut krate: ast::Crate) -> ast::Crate {
 341         let mut module = ModuleData {
 342             mod_path: vec![Ident::from_str(&self.cx.ecfg.crate_name)],
 343             directory: match self.cx.source_map().span_to_unmapped_path(krate.span) {
 344                 FileName::Real(path) => path,
 345                 other => PathBuf::from(other.to_string()),
 346             },
 347         };
 348         module.directory.pop();
 349         self.cx.root_path = module.directory.clone();
 350         self.cx.current_expansion.module = Rc::new(module);
 351
 352         let orig_mod_span = krate.module.inner;
 353
 354         let krate_item = AstFragment::Items(smallvec![P(ast::Item {
 355             attrs: krate.attrs,
 356             span: krate.span,
 357             kind: ast::ItemKind::Mod(krate.module),
 358             ident: Ident::invalid(),
 359             id: ast::DUMMY_NODE_ID,
 360             vis: respan(krate.span.shrink_to_lo(), ast::VisibilityKind::Public),
 361             tokens: None,
 362         })]);
 363
 364         match self.fully_expand_fragment(krate_item).make_items().pop().map(P::into_inner) {
 365             Some(ast::Item { attrs, kind: ast::ItemKind::Mod(module), .. }) => {
 366                 krate.attrs = attrs;
 367                 krate.module = module;
 368             }
 369             None => {
 370                 // Resolution failed so we return an empty expansion
 371                 krate.attrs = vec![];
 372                 krate.module = ast::Mod { inner: orig_mod_span, items: vec![], inline: true };
 373             }
 374             Some(ast::Item { span, kind, .. }) => {
 375                 krate.attrs = vec![];
 376                 krate.module = ast::Mod { inner: orig_mod_span, items: vec![], inline: true };
 377                 self.cx.span_err(
 378                     span,
 379                     &format!(
 380                         "expected crate top-level item to be a module after macro expansion, found a {}",
 381                         kind.descriptive_variant()
 382                     ),
 383                 );
 384             }
 385         };
 386         self.cx.trace_macros_diag();
 387         krate
 388     }
 389
 390     // Recursively expand all macro invocations in this AST fragment.
 391     pub fn fully_expand_fragment(&mut self, input_fragment: AstFragment) -> AstFragment {
 392         let orig_expansion_data = self.cx.current_expansion.clone();
 393         self.cx.current_expansion.depth = 0;
 394
 395         // Collect all macro invocations and replace them with placeholders.
 396         let (mut fragment_with_placeholders, mut invocations) =
 397             self.collect_invocations(input_fragment, &[]);
 398
 399         // Optimization: if we resolve all imports now,
 400         // we'll be able to immediately resolve most of imported macros.
 401         self.resolve_imports();
 402
 403         // Resolve paths in all invocations and produce output expanded fragments for them, but
 404         // do not insert them into our input AST fragment yet, only store in `expanded_fragments`.
 405         // The output fragments also go through expansion recursively until no invocations are left.
 406         // Unresolved macros produce dummy outputs as a recovery measure.
 407         invocations.reverse();
 408         let mut expanded_fragments = Vec::new();
 409         let mut undetermined_invocations = Vec::new();
 410         let (mut progress, mut force) = (false, !self.monotonic);
 411         loop {
 412             let invoc = if let Some(invoc) = invocations.pop() {
 413                 invoc
 414             } else {
 415                 self.resolve_imports();
 416                 if undetermined_invocations.is_empty() {
 417                     break;
 418                 }
 419                 invocations = mem::take(&mut undetermined_invocations);
 420                 force = !mem::replace(&mut progress, false);
 421                 continue;
 422             };
 423
 424             let eager_expansion_root =
 425                 if self.monotonic { invoc.expansion_data.id } else { orig_expansion_data.id };
 426             let res = match self.cx.resolver.resolve_macro_invocation(
 427                 &invoc,
 428                 eager_expansion_root,
 429                 force,
 430             ) {
 431                 Ok(res) => res,
 432                 Err(Indeterminate) => {
 433                     undetermined_invocations.push(invoc);
 434                     continue;
 435                 }
 436             };
 437
 438             progress = true;
 439             let ExpansionData { depth, id: expn_id, .. } = invoc.expansion_data;
 440             self.cx.current_expansion = invoc.expansion_data.clone();
 441
 442             // FIXME(jseyfried): Refactor out the following logic
 443             let (expanded_fragment, new_invocations) = match res {
 444                 InvocationRes::Single(ext) => {
 445                     let fragment = self.expand_invoc(invoc, &ext.kind);
 446                     self.collect_invocations(fragment, &[])
 447                 }
 448                 InvocationRes::DeriveContainer(_exts) => {
 449                     // FIXME: Consider using the derive resolutions (`_exts`) immediately,
 450                     // instead of enqueuing the derives to be resolved again later.
 451                     let (derives, item) = match invoc.kind {
 452                         InvocationKind::DeriveContainer { derives, item } => (derives, item),
 453                         _ => unreachable!(),
 454                     };
 455                     if !item.derive_allowed() {
 456                         self.error_derive_forbidden_on_non_adt(&derives, &item);
 457                     }
 458
 459                     let mut item = self.fully_configure(item);
 460                     item.visit_attrs(|attrs| attrs.retain(|a| !a.has_name(sym::derive)));
 461
 462                     let mut derive_placeholders = Vec::with_capacity(derives.len());
 463                     invocations.reserve(derives.len());
 464                     for path in derives {
 465                         let expn_id = ExpnId::fresh(None);
 466                         derive_placeholders.push(NodeId::placeholder_from_expn_id(expn_id));
 467                         invocations.push(Invocation {
 468                             kind: InvocationKind::Derive { path, item: item.clone() },
 469                             fragment_kind: invoc.fragment_kind,
 470                             expansion_data: ExpansionData {
 471                                 id: expn_id,
 472                                 ..invoc.expansion_data.clone()
 473                             },
 474                         });
 475                     }
 476                     let fragment =
 477                         invoc.fragment_kind.expect_from_annotatables(::std::iter::once(item));
 478                     self.collect_invocations(fragment, &derive_placeholders)
 479                 }
 480             };
 481
 482             if expanded_fragments.len() < depth {
 483                 expanded_fragments.push(Vec::new());
 484             }
 485             expanded_fragments[depth - 1].push((expn_id, expanded_fragment));
 486             if !self.cx.ecfg.single_step {
 487                 invocations.extend(new_invocations.into_iter().rev());
 488             }
 489         }
 490
 491         self.cx.current_expansion = orig_expansion_data;
 492
 493         // Finally incorporate all the expanded macros into the input AST fragment.
 494         let mut placeholder_expander = PlaceholderExpander::new(self.cx, self.monotonic);
 495         while let Some(expanded_fragments) = expanded_fragments.pop() {
 496             for (expn_id, expanded_fragment) in expanded_fragments.into_iter().rev() {
 497                 placeholder_expander
 498                     .add(NodeId::placeholder_from_expn_id(expn_id), expanded_fragment);
 499             }
 500         }
 501         fragment_with_placeholders.mut_visit_with(&mut placeholder_expander);
 502         fragment_with_placeholders
 503     }
 504
 505     fn error_derive_forbidden_on_non_adt(&self, derives: &[Path], item: &Annotatable) {
 506         let attr =
 507             attr::find_by_name(item.attrs(), sym::derive).expect("`derive` attribute should exist");
 508         let span = attr.span;
 509         let mut err = self
 510             .cx
 511             .struct_span_err(span, "`derive` may only be applied to structs, enums and unions");
 512         if let ast::AttrStyle::Inner = attr.style {
 513             let trait_list = derives.iter().map(|t| pprust::path_to_string(t)).collect::<Vec<_>>();
 514             let suggestion = format!("#[derive({})]", trait_list.join(", "));
 515             err.span_suggestion(
 516                 span,
 517                 "try an outer attribute",
 518                 suggestion,
 519                 // We don't 𝑘𝑛𝑜𝑤 that the following item is an ADT
 520                 Applicability::MaybeIncorrect,
 521             );
 522         }
 523         err.emit();
 524     }
 525
 526     fn resolve_imports(&mut self) {
 527         if self.monotonic {
 528             self.cx.resolver.resolve_imports();
 529         }
 530     }
 531
 532     /// Collects all macro invocations reachable at this time in this AST fragment, and replace
 533     /// them with "placeholders" - dummy macro invocations with specially crafted `NodeId`s.
 534     /// Then call into resolver that builds a skeleton ("reduced graph") of the fragment and
 535     /// prepares data for resolving paths of macro invocations.
 536     fn collect_invocations(
 537         &mut self,
 538         mut fragment: AstFragment,
 539         extra_placeholders: &[NodeId],
 540     ) -> (AstFragment, Vec<Invocation>) {
 541         // Resolve `$crate`s in the fragment for pretty-printing.
 542         self.cx.resolver.resolve_dollar_crates();
 543
 544         let invocations = {
 545             let mut collector = InvocationCollector {
 546                 cfg: StripUnconfigured {
 547                     sess: self.cx.parse_sess,
 548                     features: self.cx.ecfg.features,
 549                 },
 550                 cx: self.cx,
 551                 invocations: Vec::new(),
 552                 monotonic: self.monotonic,
 553             };
 554             fragment.mut_visit_with(&mut collector);
 555             fragment.add_placeholders(extra_placeholders);
 556             collector.invocations
 557         };
 558
 559         if self.monotonic {
 560             self.cx
 561                 .resolver
 562                 .visit_ast_fragment_with_placeholders(self.cx.current_expansion.id, &fragment);
 563         }
 564
 565         (fragment, invocations)
 566     }
 567
 568     fn fully_configure(&mut self, item: Annotatable) -> Annotatable {
 569         let mut cfg =
 570             StripUnconfigured { sess: self.cx.parse_sess, features: self.cx.ecfg.features };
 571         // Since the item itself has already been configured by the InvocationCollector,
 572         // we know that fold result vector will contain exactly one element
 573         match item {
 574             Annotatable::Item(item) => Annotatable::Item(cfg.flat_map_item(item).pop().unwrap()),
 575             Annotatable::TraitItem(item) => {
 576                 Annotatable::TraitItem(cfg.flat_map_trait_item(item).pop().unwrap())
 577             }
 578             Annotatable::ImplItem(item) => {
 579                 Annotatable::ImplItem(cfg.flat_map_impl_item(item).pop().unwrap())
 580             }
 581             Annotatable::ForeignItem(item) => {
 582                 Annotatable::ForeignItem(cfg.flat_map_foreign_item(item).pop().unwrap())
 583             }
 584             Annotatable::Stmt(stmt) => {
 585                 Annotatable::Stmt(stmt.map(|stmt| cfg.flat_map_stmt(stmt).pop().unwrap()))
 586             }
 587             Annotatable::Expr(mut expr) => Annotatable::Expr({
 588                 cfg.visit_expr(&mut expr);
 589                 expr
 590             }),
 591             Annotatable::Arm(arm) => Annotatable::Arm(cfg.flat_map_arm(arm).pop().unwrap()),
 592             Annotatable::Field(field) => {
 593                 Annotatable::Field(cfg.flat_map_field(field).pop().unwrap())
 594             }
 595             Annotatable::FieldPat(fp) => {
 596                 Annotatable::FieldPat(cfg.flat_map_field_pattern(fp).pop().unwrap())
 597             }
 598             Annotatable::GenericParam(param) => {
 599                 Annotatable::GenericParam(cfg.flat_map_generic_param(param).pop().unwrap())
 600             }
 601             Annotatable::Param(param) => {
 602                 Annotatable::Param(cfg.flat_map_param(param).pop().unwrap())
 603             }
 604             Annotatable::StructField(sf) => {
 605                 Annotatable::StructField(cfg.flat_map_struct_field(sf).pop().unwrap())
 606             }
 607             Annotatable::Variant(v) => Annotatable::Variant(cfg.flat_map_variant(v).pop().unwrap()),
 608         }
 609     }
 610
 611     fn error_recursion_limit_reached(&mut self) {
 612         let expn_data = self.cx.current_expansion.id.expn_data();
 613         let suggested_limit = self.cx.ecfg.recursion_limit * 2;
 614         self.cx
 615             .struct_span_err(
 616                 expn_data.call_site,
 617                 &format!("recursion limit reached while expanding `{}`", expn_data.kind.descr()),
 618             )
 619             .help(&format!(
 620                 "consider adding a `#![recursion_limit=\"{}\"]` attribute to your crate (`{}`)",
 621                 suggested_limit, self.cx.ecfg.crate_name,
 622             ))
 623             .emit();
 624         self.cx.trace_macros_diag();
 625         FatalError.raise();
 626     }
 627
 628     /// A macro's expansion does not fit in this fragment kind.
 629     /// For example, a non-type macro in a type position.
 630     fn error_wrong_fragment_kind(&mut self, kind: AstFragmentKind, mac: &ast::Mac, span: Span) {
 631         let msg = format!(
 632             "non-{kind} macro in {kind} position: {path}",
 633             kind = kind.name(),
 634             path = pprust::path_to_string(&mac.path),
 635         );
 636         self.cx.span_err(span, &msg);
 637         self.cx.trace_macros_diag();
 638     }
 639
 640     fn expand_invoc(&mut self, invoc: Invocation, ext: &SyntaxExtensionKind) -> AstFragment {
 641         if self.cx.current_expansion.depth > self.cx.ecfg.recursion_limit {
 642             self.error_recursion_limit_reached();
 643         }
 644
 645         let (fragment_kind, span) = (invoc.fragment_kind, invoc.span());
 646         match invoc.kind {
 647             InvocationKind::Bang { mac, .. } => match ext {
 648                 SyntaxExtensionKind::Bang(expander) => {
 649                     self.gate_proc_macro_expansion_kind(span, fragment_kind);
 650                     let tok_result = expander.expand(self.cx, span, mac.args.inner_tokens());
 651                     self.parse_ast_fragment(tok_result, fragment_kind, &mac.path, span)
 652                 }
 653                 SyntaxExtensionKind::LegacyBang(expander) => {
 654                     let prev = self.cx.current_expansion.prior_type_ascription;
 655                     self.cx.current_expansion.prior_type_ascription = mac.prior_type_ascription;
 656                     let tok_result = expander.expand(self.cx, span, mac.args.inner_tokens());
 657                     let result = if let Some(result) = fragment_kind.make_from(tok_result) {
 658                         result
 659                     } else {
 660                         self.error_wrong_fragment_kind(fragment_kind, &mac, span);
 661                         fragment_kind.dummy(span)
 662                     };
 663                     self.cx.current_expansion.prior_type_ascription = prev;
 664                     result
 665                 }
 666                 _ => unreachable!(),
 667             },
 668             InvocationKind::Attr { attr, mut item, .. } => match ext {
 669                 SyntaxExtensionKind::Attr(expander) => {
 670                     self.gate_proc_macro_input(&item);
 671                     self.gate_proc_macro_attr_item(span, &item);
 672                     let item_tok = TokenTree::token(
 673                         token::Interpolated(Lrc::new(match item {
 674                             Annotatable::Item(item) => token::NtItem(item),
 675                             Annotatable::TraitItem(item) => token::NtTraitItem(item),
 676                             Annotatable::ImplItem(item) => token::NtImplItem(item),
 677                             Annotatable::ForeignItem(item) => token::NtForeignItem(item),
 678                             Annotatable::Stmt(stmt) => token::NtStmt(stmt.into_inner()),
 679                             Annotatable::Expr(expr) => token::NtExpr(expr),
 680                             Annotatable::Arm(..)
 681                             | Annotatable::Field(..)
 682                             | Annotatable::FieldPat(..)
 683                             | Annotatable::GenericParam(..)
 684                             | Annotatable::Param(..)
 685                             | Annotatable::StructField(..)
 686                             | Annotatable::Variant(..) => panic!("unexpected annotatable"),
 687                         })),
 688                         DUMMY_SP,
 689                     )
 690                     .into();
 691                     let item = attr.unwrap_normal_item();
 692                     if let MacArgs::Eq(..) = item.args {
 693                         self.cx.span_err(span, "key-value macro attributes are not supported");
 694                     }
 695                     let tok_result =
 696                         expander.expand(self.cx, span, item.args.inner_tokens(), item_tok);
 697                     self.parse_ast_fragment(tok_result, fragment_kind, &item.path, span)
 698                 }
 699                 SyntaxExtensionKind::LegacyAttr(expander) => {
 700                     match validate_attr::parse_meta(self.cx.parse_sess, &attr) {
 701                         Ok(meta) => {
 702                             let item = expander.expand(self.cx, span, &meta, item);
 703                             fragment_kind.expect_from_annotatables(item)
 704                         }
 705                         Err(mut err) => {
 706                             err.emit();
 707                             fragment_kind.dummy(span)
 708                         }
 709                     }
 710                 }
 711                 SyntaxExtensionKind::NonMacroAttr { mark_used } => {
 712                     attr::mark_known(&attr);
 713                     if *mark_used {
 714                         attr::mark_used(&attr);
 715                     }
 716                     item.visit_attrs(|attrs| attrs.push(attr));
 717                     fragment_kind.expect_from_annotatables(iter::once(item))
 718                 }
 719                 _ => unreachable!(),
 720             },
 721             InvocationKind::Derive { path, item } => match ext {
 722                 SyntaxExtensionKind::Derive(expander)
 723                 | SyntaxExtensionKind::LegacyDerive(expander) => {
 724                     if !item.derive_allowed() {
 725                         return fragment_kind.dummy(span);
 726                     }
 727                     if let SyntaxExtensionKind::Derive(..) = ext {
 728                         self.gate_proc_macro_input(&item);
 729                     }
 730                     let meta = ast::MetaItem { kind: ast::MetaItemKind::Word, span, path };
 731                     let items = expander.expand(self.cx, span, &meta, item);
 732                     fragment_kind.expect_from_annotatables(items)
 733                 }
 734                 _ => unreachable!(),
 735             },
 736             InvocationKind::DeriveContainer { .. } => unreachable!(),
 737         }
 738     }
 739
 740     fn gate_proc_macro_attr_item(&self, span: Span, item: &Annotatable) {
 741         let kind = match item {
 742             Annotatable::Item(_)
 743             | Annotatable::TraitItem(_)
 744             | Annotatable::ImplItem(_)
 745             | Annotatable::ForeignItem(_) => return,
 746             Annotatable::Stmt(_) => "statements",
 747             Annotatable::Expr(_) => "expressions",
 748             Annotatable::Arm(..)
 749             | Annotatable::Field(..)
 750             | Annotatable::FieldPat(..)
 751             | Annotatable::GenericParam(..)
 752             | Annotatable::Param(..)
 753             | Annotatable::StructField(..)
 754             | Annotatable::Variant(..) => panic!("unexpected annotatable"),
 755         };
 756         if self.cx.ecfg.proc_macro_hygiene() {
 757             return;
 758         }
 759         feature_err(
 760             self.cx.parse_sess,
 761             sym::proc_macro_hygiene,
 762             span,
 763             &format!("custom attributes cannot be applied to {}", kind),
 764         )
 765         .emit();
 766     }
 767
 768     fn gate_proc_macro_input(&self, annotatable: &Annotatable) {
 769         struct GateProcMacroInput<'a> {
 770             parse_sess: &'a ParseSess,
 771         }
 772
 773         impl<'ast, 'a> Visitor<'ast> for GateProcMacroInput<'a> {
 774             fn visit_item(&mut self, item: &'ast ast::Item) {
 775                 match &item.kind {
 776                     ast::ItemKind::Mod(module) if !module.inline => {
 777                         feature_err(
 778                             self.parse_sess,
 779                             sym::proc_macro_hygiene,
 780                             item.span,
 781                             "non-inline modules in proc macro input are unstable",
 782                         )
 783                         .emit();
 784                     }
 785                     _ => {}
 786                 }
 787
 788                 visit::walk_item(self, item);
 789             }
 790
 791             fn visit_mac(&mut self, _: &'ast ast::Mac) {}
 792         }
 793
 794         if !self.cx.ecfg.proc_macro_hygiene() {
 795             annotatable.visit_with(&mut GateProcMacroInput { parse_sess: self.cx.parse_sess });
 796         }
 797     }
 798
 799     fn gate_proc_macro_expansion_kind(&self, span: Span, kind: AstFragmentKind) {
 800         let kind = match kind {
 801             AstFragmentKind::Expr | AstFragmentKind::OptExpr => "expressions",
 802             AstFragmentKind::Pat => "patterns",
 803             AstFragmentKind::Stmts => "statements",
 804             AstFragmentKind::Ty
 805             | AstFragmentKind::Items
 806             | AstFragmentKind::TraitItems
 807             | AstFragmentKind::ImplItems
 808             | AstFragmentKind::ForeignItems => return,
 809             AstFragmentKind::Arms
 810             | AstFragmentKind::Fields
 811             | AstFragmentKind::FieldPats
 812             | AstFragmentKind::GenericParams
 813             | AstFragmentKind::Params
 814             | AstFragmentKind::StructFields
 815             | AstFragmentKind::Variants => panic!("unexpected AST fragment kind"),
 816         };
 817         if self.cx.ecfg.proc_macro_hygiene() {
 818             return;
 819         }
 820         feature_err(
 821             self.cx.parse_sess,
 822             sym::proc_macro_hygiene,
 823             span,
 824             &format!("procedural macros cannot be expanded to {}", kind),
 825         )
 826         .emit();
 827     }
 828
 829     fn parse_ast_fragment(
 830         &mut self,
 831         toks: TokenStream,
 832         kind: AstFragmentKind,
 833         path: &Path,
 834         span: Span,
 835     ) -> AstFragment {
 836         let mut parser = self.cx.new_parser_from_tts(toks);
 837         match parse_ast_fragment(&mut parser, kind) {
 838             Ok(fragment) => {
 839                 ensure_complete_parse(&mut parser, path, kind.name(), span);
 840                 fragment
 841             }
 842             Err(mut err) => {
 843                 err.set_span(span);
 844                 annotate_err_with_kind(&mut err, kind, span);
 845                 err.emit();
 846                 self.cx.trace_macros_diag();
 847                 kind.dummy(span)
 848             }
 849         }
 850     }
 851 }
 852
 853 pub fn parse_ast_fragment<'a>(
 854     this: &mut Parser<'a>,
 855     kind: AstFragmentKind,
 856 ) -> PResult<'a, AstFragment> {
 857     Ok(match kind {
 858         AstFragmentKind::Items => {
 859             let mut items = SmallVec::new();
 860             while let Some(item) = this.parse_item()? {
 861                 items.push(item);
 862             }
 863             AstFragment::Items(items)
 864         }
 865         AstFragmentKind::TraitItems => {
 866             let mut items = SmallVec::new();
 867             while this.token != token::Eof {
 868                 items.push(this.parse_trait_item(&mut false)?);
 869             }
 870             AstFragment::TraitItems(items)
 871         }
 872         AstFragmentKind::ImplItems => {
 873             let mut items = SmallVec::new();
 874             while this.token != token::Eof {
 875                 items.push(this.parse_impl_item(&mut false)?);
 876             }
 877             AstFragment::ImplItems(items)
 878         }
 879         AstFragmentKind::ForeignItems => {
 880             let mut items = SmallVec::new();
 881             while this.token != token::Eof {
 882                 items.push(this.parse_foreign_item(&mut false)?);
 883             }
 884             AstFragment::ForeignItems(items)
 885         }
 886         AstFragmentKind::Stmts => {
 887             let mut stmts = SmallVec::new();
 888             // Won't make progress on a `}`.
 889             while this.token != token::Eof && this.token != token::CloseDelim(token::Brace) {
 890                 if let Some(stmt) = this.parse_full_stmt()? {
 891                     stmts.push(stmt);
 892                 }
 893             }
 894             AstFragment::Stmts(stmts)
 895         }
 896         AstFragmentKind::Expr => AstFragment::Expr(this.parse_expr()?),
 897         AstFragmentKind::OptExpr => {
 898             if this.token != token::Eof {
 899                 AstFragment::OptExpr(Some(this.parse_expr()?))
 900             } else {
 901                 AstFragment::OptExpr(None)
 902             }
 903         }
 904         AstFragmentKind::Ty => AstFragment::Ty(this.parse_ty()?),
 905         AstFragmentKind::Pat => AstFragment::Pat(this.parse_pat(None)?),
 906         AstFragmentKind::Arms
 907         | AstFragmentKind::Fields
 908         | AstFragmentKind::FieldPats
 909         | AstFragmentKind::GenericParams
 910         | AstFragmentKind::Params
 911         | AstFragmentKind::StructFields
 912         | AstFragmentKind::Variants => panic!("unexpected AST fragment kind"),
 913     })
 914 }
 915
 916 pub fn ensure_complete_parse<'a>(
 917     this: &mut Parser<'a>,
 918     macro_path: &Path,
 919     kind_name: &str,
 920     span: Span,
 921 ) {
 922     if this.token != token::Eof {
 923         let token = pprust::token_to_string(&this.token);
 924         let msg = format!("macro expansion ignores token `{}` and any following", token);
 925         // Avoid emitting backtrace info twice.
 926         let def_site_span = this.token.span.with_ctxt(SyntaxContext::root());
 927         let mut err = this.struct_span_err(def_site_span, &msg);
 928         err.span_label(span, "caused by the macro expansion here");
 929         let msg = format!(
 930             "the usage of `{}!` is likely invalid in {} context",
 931             pprust::path_to_string(macro_path),
 932             kind_name,
 933         );
 934         err.note(&msg);
 935         let semi_span = this.sess.source_map().next_point(span);
 936
 937         let semi_full_span = semi_span.to(this.sess.source_map().next_point(semi_span));
 938         match this.sess.source_map().span_to_snippet(semi_full_span) {
 939             Ok(ref snippet) if &snippet[..] != ";" && kind_name == "expression" => {
 940                 err.span_suggestion(
 941                     semi_span,
 942                     "you might be missing a semicolon here",
 943                     ";".to_owned(),
 944                     Applicability::MaybeIncorrect,
 945                 );
 946             }
 947             _ => {}
 948         }
 949         err.emit();
 950     }
 951 }
 952
 953 struct InvocationCollector<'a, 'b> {
 954     cx: &'a mut ExtCtxt<'b>,
 955     cfg: StripUnconfigured<'a>,
 956     invocations: Vec<Invocation>,
 957     monotonic: bool,
 958 }
 959
 960 impl<'a, 'b> InvocationCollector<'a, 'b> {
 961     fn collect(&mut self, fragment_kind: AstFragmentKind, kind: InvocationKind) -> AstFragment {
 962         // Expansion data for all the collected invocations is set upon their resolution,
 963         // with exception of the derive container case which is not resolved and can get
 964         // its expansion data immediately.
 965         let expn_data = match &kind {
 966             InvocationKind::DeriveContainer { item, .. } => Some(ExpnData {
 967                 parent: self.cx.current_expansion.id,
 968                 ..ExpnData::default(
 969                     ExpnKind::Macro(MacroKind::Attr, sym::derive),
 970                     item.span(),
 971                     self.cx.parse_sess.edition,
 972                 )
 973             }),
 974             _ => None,
 975         };
 976         let expn_id = ExpnId::fresh(expn_data);
 977         let vis = kind.placeholder_visibility();
 978         self.invocations.push(Invocation {
 979             kind,
 980             fragment_kind,
 981             expansion_data: ExpansionData {
 982                 id: expn_id,
 983                 depth: self.cx.current_expansion.depth + 1,
 984                 ..self.cx.current_expansion.clone()
 985             },
 986         });
 987         placeholder(fragment_kind, NodeId::placeholder_from_expn_id(expn_id), vis)
 988     }
 989
 990     fn collect_bang(&mut self, mac: ast::Mac, span: Span, kind: AstFragmentKind) -> AstFragment {
 991         self.collect(kind, InvocationKind::Bang { mac, span })
 992     }
 993
 994     fn collect_attr(
 995         &mut self,
 996         attr: Option<ast::Attribute>,
 997         derives: Vec<Path>,
 998         item: Annotatable,
 999         kind: AstFragmentKind,
1000         after_derive: bool,
1001     ) -> AstFragment {
1002         self.collect(
1003             kind,
1004             match attr {
1005                 Some(attr) => InvocationKind::Attr { attr, item, derives, after_derive },
1006                 None => InvocationKind::DeriveContainer { derives, item },
1007             },
1008         )
1009     }
1010
1011     fn find_attr_invoc(
1012         &self,
1013         attrs: &mut Vec<ast::Attribute>,
1014         after_derive: &mut bool,
1015     ) -> Option<ast::Attribute> {
1016         let attr = attrs
1017             .iter()
1018             .position(|a| {
1019                 if a.has_name(sym::derive) {
1020                     *after_derive = true;
1021                 }
1022                 !attr::is_known(a) && !is_builtin_attr(a)
1023             })
1024             .map(|i| attrs.remove(i));
1025         if let Some(attr) = &attr {
1026             if !self.cx.ecfg.custom_inner_attributes()
1027                 && attr.style == ast::AttrStyle::Inner
1028                 && !attr.has_name(sym::test)
1029             {
1030                 feature_err(
1031                     &self.cx.parse_sess,
1032                     sym::custom_inner_attributes,
1033                     attr.span,
1034                     "non-builtin inner attributes are unstable",
1035                 )
1036                 .emit();
1037             }
1038         }
1039         attr
1040     }
1041
1042     /// If `item` is an attr invocation, remove and return the macro attribute and derive traits.
1043     fn classify_item(
1044         &mut self,
1045         item: &mut impl HasAttrs,
1046     ) -> (Option<ast::Attribute>, Vec<Path>, /* after_derive */ bool) {
1047         let (mut attr, mut traits, mut after_derive) = (None, Vec::new(), false);
1048
1049         item.visit_attrs(|mut attrs| {
1050             attr = self.find_attr_invoc(&mut attrs, &mut after_derive);
1051             traits = collect_derives(&mut self.cx, &mut attrs);
1052         });
1053
1054         (attr, traits, after_derive)
1055     }
1056
1057     /// Alternative to `classify_item()` that ignores `#[derive]` so invocations fallthrough
1058     /// to the unused-attributes lint (making it an error on statements and expressions
1059     /// is a breaking change)
1060     fn classify_nonitem(
1061         &mut self,
1062         nonitem: &mut impl HasAttrs,
1063     ) -> (Option<ast::Attribute>, /* after_derive */ bool) {
1064         let (mut attr, mut after_derive) = (None, false);
1065
1066         nonitem.visit_attrs(|mut attrs| {
1067             attr = self.find_attr_invoc(&mut attrs, &mut after_derive);
1068         });
1069
1070         (attr, after_derive)
1071     }
1072
1073     fn configure<T: HasAttrs>(&mut self, node: T) -> Option<T> {
1074         self.cfg.configure(node)
1075     }
1076
1077     // Detect use of feature-gated or invalid attributes on macro invocations
1078     // since they will not be detected after macro expansion.
1079     fn check_attributes(&mut self, attrs: &[ast::Attribute]) {
1080         let features = self.cx.ecfg.features.unwrap();
1081         for attr in attrs.iter() {
1082             rustc_ast_passes::feature_gate::check_attribute(attr, self.cx.parse_sess, features);
1083             validate_attr::check_meta(self.cx.parse_sess, attr);
1084
1085             // macros are expanded before any lint passes so this warning has to be hardcoded
1086             if attr.has_name(sym::derive) {
1087                 self.cx
1088                     .struct_span_warn(attr.span, "`#[derive]` does nothing on macro invocations")
1089                     .note("this may become a hard error in a future release")
1090                     .emit();
1091             }
1092
1093             if attr.doc_str().is_some() {
1094                 self.cx.parse_sess.buffer_lint_with_diagnostic(
1095                     &UNUSED_DOC_COMMENTS,
1096                     attr.span,
1097                     ast::CRATE_NODE_ID,
1098                     "unused doc comment",
1099                     BuiltinLintDiagnostics::UnusedDocComment(attr.span),
1100                 );
1101             }
1102         }
1103     }
1104 }
1105
1106 impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
1107     fn visit_expr(&mut self, expr: &mut P<ast::Expr>) {
1108         self.cfg.configure_expr(expr);
1109         visit_clobber(expr.deref_mut(), |mut expr| {
1110             self.cfg.configure_expr_kind(&mut expr.kind);
1111
1112             // ignore derives so they remain unused
1113             let (attr, after_derive) = self.classify_nonitem(&mut expr);
1114
1115             if attr.is_some() {
1116                 // Collect the invoc regardless of whether or not attributes are permitted here
1117                 // expansion will eat the attribute so it won't error later.
1118                 attr.as_ref().map(|a| self.cfg.maybe_emit_expr_attr_err(a));
1119
1120                 // AstFragmentKind::Expr requires the macro to emit an expression.
1121                 return self
1122                     .collect_attr(
1123                         attr,
1124                         vec![],
1125                         Annotatable::Expr(P(expr)),
1126                         AstFragmentKind::Expr,
1127                         after_derive,
1128                     )
1129                     .make_expr()
1130                     .into_inner();
1131             }
1132
1133             if let ast::ExprKind::Mac(mac) = expr.kind {
1134                 self.check_attributes(&expr.attrs);
1135                 self.collect_bang(mac, expr.span, AstFragmentKind::Expr).make_expr().into_inner()
1136             } else {
1137                 noop_visit_expr(&mut expr, self);
1138                 expr
1139             }
1140         });
1141     }
1142
1143     fn flat_map_arm(&mut self, arm: ast::Arm) -> SmallVec<[ast::Arm; 1]> {
1144         let mut arm = configure!(self, arm);
1145
1146         let (attr, traits, after_derive) = self.classify_item(&mut arm);
1147         if attr.is_some() || !traits.is_empty() {
1148             return self
1149                 .collect_attr(
1150                     attr,
1151                     traits,
1152                     Annotatable::Arm(arm),
1153                     AstFragmentKind::Arms,
1154                     after_derive,
1155                 )
1156                 .make_arms();
1157         }
1158
1159         noop_flat_map_arm(arm, self)
1160     }
1161
1162     fn flat_map_field(&mut self, field: ast::Field) -> SmallVec<[ast::Field; 1]> {
1163         let mut field = configure!(self, field);
1164
1165         let (attr, traits, after_derive) = self.classify_item(&mut field);
1166         if attr.is_some() || !traits.is_empty() {
1167             return self
1168                 .collect_attr(
1169                     attr,
1170                     traits,
1171                     Annotatable::Field(field),
1172                     AstFragmentKind::Fields,
1173                     after_derive,
1174                 )
1175                 .make_fields();
1176         }
1177
1178         noop_flat_map_field(field, self)
1179     }
1180
1181     fn flat_map_field_pattern(&mut self, fp: ast::FieldPat) -> SmallVec<[ast::FieldPat; 1]> {
1182         let mut fp = configure!(self, fp);
1183
1184         let (attr, traits, after_derive) = self.classify_item(&mut fp);
1185         if attr.is_some() || !traits.is_empty() {
1186             return self
1187                 .collect_attr(
1188                     attr,
1189                     traits,
1190                     Annotatable::FieldPat(fp),
1191                     AstFragmentKind::FieldPats,
1192                     after_derive,
1193                 )
1194                 .make_field_patterns();
1195         }
1196
1197         noop_flat_map_field_pattern(fp, self)
1198     }
1199
1200     fn flat_map_param(&mut self, p: ast::Param) -> SmallVec<[ast::Param; 1]> {
1201         let mut p = configure!(self, p);
1202
1203         let (attr, traits, after_derive) = self.classify_item(&mut p);
1204         if attr.is_some() || !traits.is_empty() {
1205             return self
1206                 .collect_attr(
1207                     attr,
1208                     traits,
1209                     Annotatable::Param(p),
1210                     AstFragmentKind::Params,
1211                     after_derive,
1212                 )
1213                 .make_params();
1214         }
1215
1216         noop_flat_map_param(p, self)
1217     }
1218
1219     fn flat_map_struct_field(&mut self, sf: ast::StructField) -> SmallVec<[ast::StructField; 1]> {
1220         let mut sf = configure!(self, sf);
1221
1222         let (attr, traits, after_derive) = self.classify_item(&mut sf);
1223         if attr.is_some() || !traits.is_empty() {
1224             return self
1225                 .collect_attr(
1226                     attr,
1227                     traits,
1228                     Annotatable::StructField(sf),
1229                     AstFragmentKind::StructFields,
1230                     after_derive,
1231                 )
1232                 .make_struct_fields();
1233         }
1234
1235         noop_flat_map_struct_field(sf, self)
1236     }
1237
1238     fn flat_map_variant(&mut self, variant: ast::Variant) -> SmallVec<[ast::Variant; 1]> {
1239         let mut variant = configure!(self, variant);
1240
1241         let (attr, traits, after_derive) = self.classify_item(&mut variant);
1242         if attr.is_some() || !traits.is_empty() {
1243             return self
1244                 .collect_attr(
1245                     attr,
1246                     traits,
1247                     Annotatable::Variant(variant),
1248                     AstFragmentKind::Variants,
1249                     after_derive,
1250                 )
1251                 .make_variants();
1252         }
1253
1254         noop_flat_map_variant(variant, self)
1255     }
1256
1257     fn filter_map_expr(&mut self, expr: P<ast::Expr>) -> Option<P<ast::Expr>> {
1258         let expr = configure!(self, expr);
1259         expr.filter_map(|mut expr| {
1260             self.cfg.configure_expr_kind(&mut expr.kind);
1261
1262             // Ignore derives so they remain unused.
1263             let (attr, after_derive) = self.classify_nonitem(&mut expr);
1264
1265             if attr.is_some() {
1266                 attr.as_ref().map(|a| self.cfg.maybe_emit_expr_attr_err(a));
1267
1268                 return self
1269                     .collect_attr(
1270                         attr,
1271                         vec![],
1272                         Annotatable::Expr(P(expr)),
1273                         AstFragmentKind::OptExpr,
1274                         after_derive,
1275                     )
1276                     .make_opt_expr()
1277                     .map(|expr| expr.into_inner());
1278             }
1279
1280             if let ast::ExprKind::Mac(mac) = expr.kind {
1281                 self.check_attributes(&expr.attrs);
1282                 self.collect_bang(mac, expr.span, AstFragmentKind::OptExpr)
1283                     .make_opt_expr()
1284                     .map(|expr| expr.into_inner())
1285             } else {
1286                 Some({
1287                     noop_visit_expr(&mut expr, self);
1288                     expr
1289                 })
1290             }
1291         })
1292     }
1293
1294     fn visit_pat(&mut self, pat: &mut P<ast::Pat>) {
1295         self.cfg.configure_pat(pat);
1296         match pat.kind {
1297             PatKind::Mac(_) => {}
1298             _ => return noop_visit_pat(pat, self),
1299         }
1300
1301         visit_clobber(pat, |mut pat| match mem::replace(&mut pat.kind, PatKind::Wild) {
1302             PatKind::Mac(mac) => self.collect_bang(mac, pat.span, AstFragmentKind::Pat).make_pat(),
1303             _ => unreachable!(),
1304         });
1305     }
1306
1307     fn flat_map_stmt(&mut self, stmt: ast::Stmt) -> SmallVec<[ast::Stmt; 1]> {
1308         let mut stmt = configure!(self, stmt);
1309
1310         // we'll expand attributes on expressions separately
1311         if !stmt.is_expr() {
1312             let (attr, derives, after_derive) = if stmt.is_item() {
1313                 self.classify_item(&mut stmt)
1314             } else {
1315                 // ignore derives on non-item statements so it falls through
1316                 // to the unused-attributes lint
1317                 let (attr, after_derive) = self.classify_nonitem(&mut stmt);
1318                 (attr, vec![], after_derive)
1319             };
1320
1321             if attr.is_some() || !derives.is_empty() {
1322                 return self
1323                     .collect_attr(
1324                         attr,
1325                         derives,
1326                         Annotatable::Stmt(P(stmt)),
1327                         AstFragmentKind::Stmts,
1328                         after_derive,
1329                     )
1330                     .make_stmts();
1331             }
1332         }
1333
1334         if let StmtKind::Mac(mac) = stmt.kind {
1335             let (mac, style, attrs) = mac.into_inner();
1336             self.check_attributes(&attrs);
1337             let mut placeholder =
1338                 self.collect_bang(mac, stmt.span, AstFragmentKind::Stmts).make_stmts();
1339
1340             // If this is a macro invocation with a semicolon, then apply that
1341             // semicolon to the final statement produced by expansion.
1342             if style == MacStmtStyle::Semicolon {
1343                 if let Some(stmt) = placeholder.pop() {
1344                     placeholder.push(stmt.add_trailing_semicolon());
1345                 }
1346             }
1347
1348             return placeholder;
1349         }
1350
1351         // The placeholder expander gives ids to statements, so we avoid folding the id here.
1352         let ast::Stmt { id, kind, span } = stmt;
1353         noop_flat_map_stmt_kind(kind, self)
1354             .into_iter()
1355             .map(|kind| ast::Stmt { id, kind, span })
1356             .collect()
1357     }
1358
1359     fn visit_block(&mut self, block: &mut P<Block>) {
1360         let old_directory_ownership = self.cx.current_expansion.directory_ownership;
1361         self.cx.current_expansion.directory_ownership = DirectoryOwnership::UnownedViaBlock;
1362         noop_visit_block(block, self);
1363         self.cx.current_expansion.directory_ownership = old_directory_ownership;
1364     }
1365
1366     fn flat_map_item(&mut self, item: P<ast::Item>) -> SmallVec<[P<ast::Item>; 1]> {
1367         let mut item = configure!(self, item);
1368
1369         let (attr, traits, after_derive) = self.classify_item(&mut item);
1370         if attr.is_some() || !traits.is_empty() {
1371             return self
1372                 .collect_attr(
1373                     attr,
1374                     traits,
1375                     Annotatable::Item(item),
1376                     AstFragmentKind::Items,
1377                     after_derive,
1378                 )
1379                 .make_items();
1380         }
1381
1382         match item.kind {
1383             ast::ItemKind::Mac(..) => {
1384                 self.check_attributes(&item.attrs);
1385                 item.and_then(|item| match item.kind {
1386                     ItemKind::Mac(mac) => self
1387                         .collect(
1388                             AstFragmentKind::Items,
1389                             InvocationKind::Bang { mac, span: item.span },
1390                         )
1391                         .make_items(),
1392                     _ => unreachable!(),
1393                 })
1394             }
1395             ast::ItemKind::Mod(ast::Mod { inner, inline, .. })
1396                 if item.ident != Ident::invalid() =>
1397             {
1398                 let orig_directory_ownership = self.cx.current_expansion.directory_ownership;
1399                 let mut module = (*self.cx.current_expansion.module).clone();
1400                 module.mod_path.push(item.ident);
1401
1402                 if inline {
1403                     if let Some(path) = attr::first_attr_value_str_by_name(&item.attrs, sym::path) {
1404                         self.cx.current_expansion.directory_ownership =
1405                             DirectoryOwnership::Owned { relative: None };
1406                         module.directory.push(&*path.as_str());
1407                     } else {
1408                         module.directory.push(&*item.ident.as_str());
1409                     }
1410                 } else {
1411                     let path = self.cx.parse_sess.source_map().span_to_unmapped_path(inner);
1412                     let mut path = match path {
1413                         FileName::Real(path) => path,
1414                         other => PathBuf::from(other.to_string()),
1415                     };
1416                     let directory_ownership = match path.file_name().unwrap().to_str() {
1417                         Some("mod.rs") => DirectoryOwnership::Owned { relative: None },
1418                         Some(_) => DirectoryOwnership::Owned { relative: Some(item.ident) },
1419                         None => DirectoryOwnership::UnownedViaMod,
1420                     };
1421                     path.pop();
1422                     module.directory = path;
1423                     self.cx.current_expansion.directory_ownership = directory_ownership;
1424                 }
1425
1426                 let orig_module =
1427                     mem::replace(&mut self.cx.current_expansion.module, Rc::new(module));
1428                 let result = noop_flat_map_item(item, self);
1429                 self.cx.current_expansion.module = orig_module;
1430                 self.cx.current_expansion.directory_ownership = orig_directory_ownership;
1431                 result
1432             }
1433
1434             _ => noop_flat_map_item(item, self),
1435         }
1436     }
1437
1438     fn flat_map_trait_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
1439         let mut item = configure!(self, item);
1440
1441         let (attr, traits, after_derive) = self.classify_item(&mut item);
1442         if attr.is_some() || !traits.is_empty() {
1443             return self
1444                 .collect_attr(
1445                     attr,
1446                     traits,
1447                     Annotatable::TraitItem(item),
1448                     AstFragmentKind::TraitItems,
1449                     after_derive,
1450                 )
1451                 .make_trait_items();
1452         }
1453
1454         match item.kind {
1455             ast::AssocItemKind::Macro(..) => {
1456                 self.check_attributes(&item.attrs);
1457                 item.and_then(|item| match item.kind {
1458                     ast::AssocItemKind::Macro(mac) => self
1459                         .collect_bang(mac, item.span, AstFragmentKind::TraitItems)
1460                         .make_trait_items(),
1461                     _ => unreachable!(),
1462                 })
1463             }
1464             _ => noop_flat_map_assoc_item(item, self),
1465         }
1466     }
1467
1468     fn flat_map_impl_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
1469         let mut item = configure!(self, item);
1470
1471         let (attr, traits, after_derive) = self.classify_item(&mut item);
1472         if attr.is_some() || !traits.is_empty() {
1473             return self
1474                 .collect_attr(
1475                     attr,
1476                     traits,
1477                     Annotatable::ImplItem(item),
1478                     AstFragmentKind::ImplItems,
1479                     after_derive,
1480                 )
1481                 .make_impl_items();
1482         }
1483
1484         match item.kind {
1485             ast::AssocItemKind::Macro(..) => {
1486                 self.check_attributes(&item.attrs);
1487                 item.and_then(|item| match item.kind {
1488                     ast::AssocItemKind::Macro(mac) => self
1489                         .collect_bang(mac, item.span, AstFragmentKind::ImplItems)
1490                         .make_impl_items(),
1491                     _ => unreachable!(),
1492                 })
1493             }
1494             _ => noop_flat_map_assoc_item(item, self),
1495         }
1496     }
1497
1498     fn visit_ty(&mut self, ty: &mut P<ast::Ty>) {
1499         match ty.kind {
1500             ast::TyKind::Mac(_) => {}
1501             _ => return noop_visit_ty(ty, self),
1502         };
1503
1504         visit_clobber(ty, |mut ty| match mem::replace(&mut ty.kind, ast::TyKind::Err) {
1505             ast::TyKind::Mac(mac) => self.collect_bang(mac, ty.span, AstFragmentKind::Ty).make_ty(),
1506             _ => unreachable!(),
1507         });
1508     }
1509
1510     fn visit_foreign_mod(&mut self, foreign_mod: &mut ast::ForeignMod) {
1511         self.cfg.configure_foreign_mod(foreign_mod);
1512         noop_visit_foreign_mod(foreign_mod, self);
1513     }
1514
1515     fn flat_map_foreign_item(
1516         &mut self,
1517         mut foreign_item: P<ast::ForeignItem>,
1518     ) -> SmallVec<[P<ast::ForeignItem>; 1]> {
1519         let (attr, traits, after_derive) = self.classify_item(&mut foreign_item);
1520
1521         if attr.is_some() || !traits.is_empty() {
1522             return self
1523                 .collect_attr(
1524                     attr,
1525                     traits,
1526                     Annotatable::ForeignItem(foreign_item),
1527                     AstFragmentKind::ForeignItems,
1528                     after_derive,
1529                 )
1530                 .make_foreign_items();
1531         }
1532
1533         match foreign_item.kind {
1534             ast::ForeignItemKind::Macro(..) => {
1535                 self.check_attributes(&foreign_item.attrs);
1536                 foreign_item.and_then(|item| match item.kind {
1537                     ast::ForeignItemKind::Macro(mac) => self
1538                         .collect_bang(mac, item.span, AstFragmentKind::ForeignItems)
1539                         .make_foreign_items(),
1540                     _ => unreachable!(),
1541                 })
1542             }
1543             _ => noop_flat_map_foreign_item(foreign_item, self),
1544         }
1545     }
1546
1547     fn visit_item_kind(&mut self, item: &mut ast::ItemKind) {
1548         match item {
1549             ast::ItemKind::MacroDef(..) => {}
1550             _ => {
1551                 self.cfg.configure_item_kind(item);
1552                 noop_visit_item_kind(item, self);
1553             }
1554         }
1555     }
1556
1557     fn flat_map_generic_param(
1558         &mut self,
1559         param: ast::GenericParam,
1560     ) -> SmallVec<[ast::GenericParam; 1]> {
1561         let mut param = configure!(self, param);
1562
1563         let (attr, traits, after_derive) = self.classify_item(&mut param);
1564         if attr.is_some() || !traits.is_empty() {
1565             return self
1566                 .collect_attr(
1567                     attr,
1568                     traits,
1569                     Annotatable::GenericParam(param),
1570                     AstFragmentKind::GenericParams,
1571                     after_derive,
1572                 )
1573                 .make_generic_params();
1574         }
1575
1576         noop_flat_map_generic_param(param, self)
1577     }
1578
1579     fn visit_attribute(&mut self, at: &mut ast::Attribute) {
1580         // turn `#[doc(include="filename")]` attributes into `#[doc(include(file="filename",
1581         // contents="file contents")]` attributes
1582         if !at.check_name(sym::doc) {
1583             return noop_visit_attribute(at, self);
1584         }
1585
1586         if let Some(list) = at.meta_item_list() {
1587             if !list.iter().any(|it| it.check_name(sym::include)) {
1588                 return noop_visit_attribute(at, self);
1589             }
1590
1591             let mut items = vec![];
1592
1593             for mut it in list {
1594                 if !it.check_name(sym::include) {
1595                     items.push({
1596                         noop_visit_meta_list_item(&mut it, self);
1597                         it
1598                     });
1599                     continue;
1600                 }
1601
1602                 if let Some(file) = it.value_str() {
1603                     let err_count = self.cx.parse_sess.span_diagnostic.err_count();
1604                     self.check_attributes(slice::from_ref(at));
1605                     if self.cx.parse_sess.span_diagnostic.err_count() > err_count {
1606                         // avoid loading the file if they haven't enabled the feature
1607                         return noop_visit_attribute(at, self);
1608                     }
1609
1610                     let filename = match self.cx.resolve_path(&*file.as_str(), it.span()) {
1611                         Ok(filename) => filename,
1612                         Err(mut err) => {
1613                             err.emit();
1614                             continue;
1615                         }
1616                     };
1617
1618                     match self.cx.source_map().load_file(&filename) {
1619                         Ok(source_file) => {
1620                             let src = source_file
1621                                 .src
1622                                 .as_ref()
1623                                 .expect("freshly loaded file should have a source");
1624                             let src_interned = Symbol::intern(src.as_str());
1625
1626                             let include_info = vec![
1627                                 ast::NestedMetaItem::MetaItem(attr::mk_name_value_item_str(
1628                                     Ident::with_dummy_span(sym::file),
1629                                     file,
1630                                     DUMMY_SP,
1631                                 )),
1632                                 ast::NestedMetaItem::MetaItem(attr::mk_name_value_item_str(
1633                                     Ident::with_dummy_span(sym::contents),
1634                                     src_interned,
1635                                     DUMMY_SP,
1636                                 )),
1637                             ];
1638
1639                             let include_ident = Ident::with_dummy_span(sym::include);
1640                             let item = attr::mk_list_item(include_ident, include_info);
1641                             items.push(ast::NestedMetaItem::MetaItem(item));
1642                         }
1643                         Err(e) => {
1644                             let lit =
1645                                 it.meta_item().and_then(|item| item.name_value_literal()).unwrap();
1646
1647                             if e.kind() == ErrorKind::InvalidData {
1648                                 self.cx
1649                                     .struct_span_err(
1650                                         lit.span,
1651                                         &format!("{} wasn't a utf-8 file", filename.display()),
1652                                     )
1653                                     .span_label(lit.span, "contains invalid utf-8")
1654                                     .emit();
1655                             } else {
1656                                 let mut err = self.cx.struct_span_err(
1657                                     lit.span,
1658                                     &format!("couldn't read {}: {}", filename.display(), e),
1659                                 );
1660                                 err.span_label(lit.span, "couldn't read file");
1661
1662                                 err.emit();
1663                             }
1664                         }
1665                     }
1666                 } else {
1667                     let mut err = self.cx.struct_span_err(
1668                         it.span(),
1669                         &format!("expected path to external documentation"),
1670                     );
1671
1672                     // Check if the user erroneously used `doc(include(...))` syntax.
1673                     let literal = it.meta_item_list().and_then(|list| {
1674                         if list.len() == 1 {
1675                             list[0].literal().map(|literal| &literal.kind)
1676                         } else {
1677                             None
1678                         }
1679                     });
1680
1681                     let (path, applicability) = match &literal {
1682                         Some(LitKind::Str(path, ..)) => {
1683                             (path.to_string(), Applicability::MachineApplicable)
1684                         }
1685                         _ => (String::from("<path>"), Applicability::HasPlaceholders),
1686                     };
1687
1688                     err.span_suggestion(
1689                         it.span(),
1690                         "provide a file path with `=`",
1691                         format!("include = \"{}\"", path),
1692                         applicability,
1693                     );
1694
1695                     err.emit();
1696                 }
1697             }
1698
1699             let meta = attr::mk_list_item(Ident::with_dummy_span(sym::doc), items);
1700             *at = ast::Attribute {
1701                 kind: ast::AttrKind::Normal(AttrItem {
1702                     path: meta.path,
1703                     args: meta.kind.mac_args(meta.span),
1704                 }),
1705                 span: at.span,
1706                 id: at.id,
1707                 style: at.style,
1708             };
1709         } else {
1710             noop_visit_attribute(at, self)
1711         }
1712     }
1713
1714     fn visit_id(&mut self, id: &mut ast::NodeId) {
1715         if self.monotonic {
1716             debug_assert_eq!(*id, ast::DUMMY_NODE_ID);
1717             *id = self.cx.resolver.next_node_id()
1718         }
1719     }
1720
1721     fn visit_fn_decl(&mut self, mut fn_decl: &mut P<ast::FnDecl>) {
1722         self.cfg.configure_fn_decl(&mut fn_decl);
1723         noop_visit_fn_decl(fn_decl, self);
1724     }
1725 }
1726
1727 pub struct ExpansionConfig<'feat> {
1728     pub crate_name: String,
1729     pub features: Option<&'feat Features>,
1730     pub recursion_limit: usize,
1731     pub trace_mac: bool,
1732     pub should_test: bool, // If false, strip `#[test]` nodes
1733     pub single_step: bool,
1734     pub keep_macs: bool,
1735 }
1736
1737 impl<'feat> ExpansionConfig<'feat> {
1738     pub fn default(crate_name: String) -> ExpansionConfig<'static> {
1739         ExpansionConfig {
1740             crate_name,
1741             features: None,
1742             recursion_limit: 1024,
1743             trace_mac: false,
1744             should_test: false,
1745             single_step: false,
1746             keep_macs: false,
1747         }
1748     }
1749
1750     fn proc_macro_hygiene(&self) -> bool {
1751         self.features.map_or(false, |features| features.proc_macro_hygiene)
1752     }
1753     fn custom_inner_attributes(&self) -> bool {
1754         self.features.map_or(false, |features| features.custom_inner_attributes)
1755     }
1756 }