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::ast::{self, AttrItem, Block, Ident, LitKind, NodeId, PatKind, Path};
   9 use rustc_ast::ast::{ItemKind, MacArgs, MacStmtStyle, StmtKind};
  10 use rustc_ast::mut_visit::*;
  11 use rustc_ast::ptr::P;
  12 use rustc_ast::token;
  13 use rustc_ast::tokenstream::{TokenStream, TokenTree};
  14 use rustc_ast::util::map_in_place::MapInPlace;
  15 use rustc_ast::visit::{self, AssocCtxt, Visitor};
  16 use rustc_ast_pretty::pprust;
  17 use rustc_attr::{self as attr, is_builtin_attr, HasAttrs};
  18 use rustc_data_structures::sync::Lrc;
  19 use rustc_errors::{Applicability, FatalError, PResult};
  20 use rustc_feature::Features;
  21 use rustc_parse::configure;
  22 use rustc_parse::parser::Parser;
  23 use rustc_parse::validate_attr;
  24 use rustc_parse::DirectoryOwnership;
  25 use rustc_session::lint::builtin::UNUSED_DOC_COMMENTS;
  26 use rustc_session::lint::BuiltinLintDiagnostics;
  27 use rustc_session::parse::{feature_err, ParseSess};
  28 use rustc_span::source_map::respan;
  29 use rustc_span::symbol::{sym, Symbol};
  30 use rustc_span::{FileName, Span, DUMMY_SP};
  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 {} {}",
 381                         kind.article(), kind.descr()
 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 = attr::find_by_name(item.attrs(), sym::derive);
 507         let span = attr.map_or(item.span(), |attr| attr.span);
 508         let mut err = self
 509             .cx
 510             .struct_span_err(span, "`derive` may only be applied to structs, enums and unions");
 511         if let Some(ast::Attribute { style: ast::AttrStyle::Inner, .. }) = attr {
 512             let trait_list = derives.iter().map(|t| pprust::path_to_string(t)).collect::<Vec<_>>();
 513             let suggestion = format!("#[derive({})]", trait_list.join(", "));
 514             err.span_suggestion(
 515                 span,
 516                 "try an outer attribute",
 517                 suggestion,
 518                 // We don't 𝑘𝑛𝑜𝑤 that the following item is an ADT
 519                 Applicability::MaybeIncorrect,
 520             );
 521         }
 522         err.emit();
 523     }
 524
 525     fn resolve_imports(&mut self) {
 526         if self.monotonic {
 527             self.cx.resolver.resolve_imports();
 528         }
 529     }
 530
 531     /// Collects all macro invocations reachable at this time in this AST fragment, and replace
 532     /// them with "placeholders" - dummy macro invocations with specially crafted `NodeId`s.
 533     /// Then call into resolver that builds a skeleton ("reduced graph") of the fragment and
 534     /// prepares data for resolving paths of macro invocations.
 535     fn collect_invocations(
 536         &mut self,
 537         mut fragment: AstFragment,
 538         extra_placeholders: &[NodeId],
 539     ) -> (AstFragment, Vec<Invocation>) {
 540         // Resolve `$crate`s in the fragment for pretty-printing.
 541         self.cx.resolver.resolve_dollar_crates();
 542
 543         let invocations = {
 544             let mut collector = InvocationCollector {
 545                 cfg: StripUnconfigured {
 546                     sess: self.cx.parse_sess,
 547                     features: self.cx.ecfg.features,
 548                 },
 549                 cx: self.cx,
 550                 invocations: Vec::new(),
 551                 monotonic: self.monotonic,
 552             };
 553             fragment.mut_visit_with(&mut collector);
 554             fragment.add_placeholders(extra_placeholders);
 555             collector.invocations
 556         };
 557
 558         if self.monotonic {
 559             self.cx
 560                 .resolver
 561                 .visit_ast_fragment_with_placeholders(self.cx.current_expansion.id, &fragment);
 562         }
 563
 564         (fragment, invocations)
 565     }
 566
 567     fn fully_configure(&mut self, item: Annotatable) -> Annotatable {
 568         let mut cfg =
 569             StripUnconfigured { sess: self.cx.parse_sess, features: self.cx.ecfg.features };
 570         // Since the item itself has already been configured by the InvocationCollector,
 571         // we know that fold result vector will contain exactly one element
 572         match item {
 573             Annotatable::Item(item) => Annotatable::Item(cfg.flat_map_item(item).pop().unwrap()),
 574             Annotatable::TraitItem(item) => {
 575                 Annotatable::TraitItem(cfg.flat_map_trait_item(item).pop().unwrap())
 576             }
 577             Annotatable::ImplItem(item) => {
 578                 Annotatable::ImplItem(cfg.flat_map_impl_item(item).pop().unwrap())
 579             }
 580             Annotatable::ForeignItem(item) => {
 581                 Annotatable::ForeignItem(cfg.flat_map_foreign_item(item).pop().unwrap())
 582             }
 583             Annotatable::Stmt(stmt) => {
 584                 Annotatable::Stmt(stmt.map(|stmt| cfg.flat_map_stmt(stmt).pop().unwrap()))
 585             }
 586             Annotatable::Expr(mut expr) => Annotatable::Expr({
 587                 cfg.visit_expr(&mut expr);
 588                 expr
 589             }),
 590             Annotatable::Arm(arm) => Annotatable::Arm(cfg.flat_map_arm(arm).pop().unwrap()),
 591             Annotatable::Field(field) => {
 592                 Annotatable::Field(cfg.flat_map_field(field).pop().unwrap())
 593             }
 594             Annotatable::FieldPat(fp) => {
 595                 Annotatable::FieldPat(cfg.flat_map_field_pattern(fp).pop().unwrap())
 596             }
 597             Annotatable::GenericParam(param) => {
 598                 Annotatable::GenericParam(cfg.flat_map_generic_param(param).pop().unwrap())
 599             }
 600             Annotatable::Param(param) => {
 601                 Annotatable::Param(cfg.flat_map_param(param).pop().unwrap())
 602             }
 603             Annotatable::StructField(sf) => {
 604                 Annotatable::StructField(cfg.flat_map_struct_field(sf).pop().unwrap())
 605             }
 606             Annotatable::Variant(v) => Annotatable::Variant(cfg.flat_map_variant(v).pop().unwrap()),
 607         }
 608     }
 609
 610     fn error_recursion_limit_reached(&mut self) {
 611         let expn_data = self.cx.current_expansion.id.expn_data();
 612         let suggested_limit = self.cx.ecfg.recursion_limit * 2;
 613         self.cx
 614             .struct_span_err(
 615                 expn_data.call_site,
 616                 &format!("recursion limit reached while expanding `{}`", expn_data.kind.descr()),
 617             )
 618             .help(&format!(
 619                 "consider adding a `#![recursion_limit=\"{}\"]` attribute to your crate (`{}`)",
 620                 suggested_limit, self.cx.ecfg.crate_name,
 621             ))
 622             .emit();
 623         self.cx.trace_macros_diag();
 624         FatalError.raise();
 625     }
 626
 627     /// A macro's expansion does not fit in this fragment kind.
 628     /// For example, a non-type macro in a type position.
 629     fn error_wrong_fragment_kind(&mut self, kind: AstFragmentKind, mac: &ast::Mac, span: Span) {
 630         let msg = format!(
 631             "non-{kind} macro in {kind} position: {path}",
 632             kind = kind.name(),
 633             path = pprust::path_to_string(&mac.path),
 634         );
 635         self.cx.span_err(span, &msg);
 636         self.cx.trace_macros_diag();
 637     }
 638
 639     fn expand_invoc(&mut self, invoc: Invocation, ext: &SyntaxExtensionKind) -> AstFragment {
 640         if self.cx.current_expansion.depth > self.cx.ecfg.recursion_limit {
 641             self.error_recursion_limit_reached();
 642         }
 643
 644         let (fragment_kind, span) = (invoc.fragment_kind, invoc.span());
 645         match invoc.kind {
 646             InvocationKind::Bang { mac, .. } => match ext {
 647                 SyntaxExtensionKind::Bang(expander) => {
 648                     self.gate_proc_macro_expansion_kind(span, fragment_kind);
 649                     let tok_result = expander.expand(self.cx, span, mac.args.inner_tokens());
 650                     self.parse_ast_fragment(tok_result, fragment_kind, &mac.path, span)
 651                 }
 652                 SyntaxExtensionKind::LegacyBang(expander) => {
 653                     let prev = self.cx.current_expansion.prior_type_ascription;
 654                     self.cx.current_expansion.prior_type_ascription = mac.prior_type_ascription;
 655                     let tok_result = expander.expand(self.cx, span, mac.args.inner_tokens());
 656                     let result = if let Some(result) = fragment_kind.make_from(tok_result) {
 657                         result
 658                     } else {
 659                         self.error_wrong_fragment_kind(fragment_kind, &mac, span);
 660                         fragment_kind.dummy(span)
 661                     };
 662                     self.cx.current_expansion.prior_type_ascription = prev;
 663                     result
 664                 }
 665                 _ => unreachable!(),
 666             },
 667             InvocationKind::Attr { attr, mut item, .. } => match ext {
 668                 SyntaxExtensionKind::Attr(expander) => {
 669                     self.gate_proc_macro_input(&item);
 670                     self.gate_proc_macro_attr_item(span, &item);
 671                     // `Annotatable` can be converted into tokens directly, but we are packing it
 672                     // into a nonterminal as a piece of AST to make the produced token stream
 673                     // look nicer in pretty-printed form. This may be no longer necessary.
 674                     let item_tok = TokenTree::token(
 675                         token::Interpolated(Lrc::new(match item {
 676                             Annotatable::Item(item) => token::NtItem(item),
 677                             Annotatable::TraitItem(item)
 678                             | Annotatable::ImplItem(item)
 679                             | Annotatable::ForeignItem(item) => {
 680                                 token::NtItem(P(item.and_then(ast::AssocItem::into_item)))
 681                             }
 682                             Annotatable::Stmt(stmt) => token::NtStmt(stmt.into_inner()),
 683                             Annotatable::Expr(expr) => token::NtExpr(expr),
 684                             Annotatable::Arm(..)
 685                             | Annotatable::Field(..)
 686                             | Annotatable::FieldPat(..)
 687                             | Annotatable::GenericParam(..)
 688                             | Annotatable::Param(..)
 689                             | Annotatable::StructField(..)
 690                             | Annotatable::Variant(..) => panic!("unexpected annotatable"),
 691                         })),
 692                         DUMMY_SP,
 693                     )
 694                     .into();
 695                     let item = attr.unwrap_normal_item();
 696                     if let MacArgs::Eq(..) = item.args {
 697                         self.cx.span_err(span, "key-value macro attributes are not supported");
 698                     }
 699                     let tok_result =
 700                         expander.expand(self.cx, span, item.args.inner_tokens(), item_tok);
 701                     self.parse_ast_fragment(tok_result, fragment_kind, &item.path, span)
 702                 }
 703                 SyntaxExtensionKind::LegacyAttr(expander) => {
 704                     match validate_attr::parse_meta(self.cx.parse_sess, &attr) {
 705                         Ok(meta) => {
 706                             let item = expander.expand(self.cx, span, &meta, item);
 707                             fragment_kind.expect_from_annotatables(item)
 708                         }
 709                         Err(mut err) => {
 710                             err.emit();
 711                             fragment_kind.dummy(span)
 712                         }
 713                     }
 714                 }
 715                 SyntaxExtensionKind::NonMacroAttr { mark_used } => {
 716                     attr::mark_known(&attr);
 717                     if *mark_used {
 718                         attr::mark_used(&attr);
 719                     }
 720                     item.visit_attrs(|attrs| attrs.push(attr));
 721                     fragment_kind.expect_from_annotatables(iter::once(item))
 722                 }
 723                 _ => unreachable!(),
 724             },
 725             InvocationKind::Derive { path, item } => match ext {
 726                 SyntaxExtensionKind::Derive(expander)
 727                 | SyntaxExtensionKind::LegacyDerive(expander) => {
 728                     if !item.derive_allowed() {
 729                         return fragment_kind.dummy(span);
 730                     }
 731                     if let SyntaxExtensionKind::Derive(..) = ext {
 732                         self.gate_proc_macro_input(&item);
 733                     }
 734                     let meta = ast::MetaItem { kind: ast::MetaItemKind::Word, span, path };
 735                     let items = expander.expand(self.cx, span, &meta, item);
 736                     fragment_kind.expect_from_annotatables(items)
 737                 }
 738                 _ => unreachable!(),
 739             },
 740             InvocationKind::DeriveContainer { .. } => unreachable!(),
 741         }
 742     }
 743
 744     fn gate_proc_macro_attr_item(&self, span: Span, item: &Annotatable) {
 745         let kind = match item {
 746             Annotatable::Item(_)
 747             | Annotatable::TraitItem(_)
 748             | Annotatable::ImplItem(_)
 749             | Annotatable::ForeignItem(_) => return,
 750             Annotatable::Stmt(_) => "statements",
 751             Annotatable::Expr(_) => "expressions",
 752             Annotatable::Arm(..)
 753             | Annotatable::Field(..)
 754             | Annotatable::FieldPat(..)
 755             | Annotatable::GenericParam(..)
 756             | Annotatable::Param(..)
 757             | Annotatable::StructField(..)
 758             | Annotatable::Variant(..) => panic!("unexpected annotatable"),
 759         };
 760         if self.cx.ecfg.proc_macro_hygiene() {
 761             return;
 762         }
 763         feature_err(
 764             self.cx.parse_sess,
 765             sym::proc_macro_hygiene,
 766             span,
 767             &format!("custom attributes cannot be applied to {}", kind),
 768         )
 769         .emit();
 770     }
 771
 772     fn gate_proc_macro_input(&self, annotatable: &Annotatable) {
 773         struct GateProcMacroInput<'a> {
 774             parse_sess: &'a ParseSess,
 775         }
 776
 777         impl<'ast, 'a> Visitor<'ast> for GateProcMacroInput<'a> {
 778             fn visit_item(&mut self, item: &'ast ast::Item) {
 779                 match &item.kind {
 780                     ast::ItemKind::Mod(module) if !module.inline => {
 781                         feature_err(
 782                             self.parse_sess,
 783                             sym::proc_macro_hygiene,
 784                             item.span,
 785                             "non-inline modules in proc macro input are unstable",
 786                         )
 787                         .emit();
 788                     }
 789                     _ => {}
 790                 }
 791
 792                 visit::walk_item(self, item);
 793             }
 794
 795             fn visit_mac(&mut self, _: &'ast ast::Mac) {}
 796         }
 797
 798         if !self.cx.ecfg.proc_macro_hygiene() {
 799             annotatable.visit_with(&mut GateProcMacroInput { parse_sess: self.cx.parse_sess });
 800         }
 801     }
 802
 803     fn gate_proc_macro_expansion_kind(&self, span: Span, kind: AstFragmentKind) {
 804         let kind = match kind {
 805             AstFragmentKind::Expr | AstFragmentKind::OptExpr => "expressions",
 806             AstFragmentKind::Pat => "patterns",
 807             AstFragmentKind::Stmts => "statements",
 808             AstFragmentKind::Ty
 809             | AstFragmentKind::Items
 810             | AstFragmentKind::TraitItems
 811             | AstFragmentKind::ImplItems
 812             | AstFragmentKind::ForeignItems => return,
 813             AstFragmentKind::Arms
 814             | AstFragmentKind::Fields
 815             | AstFragmentKind::FieldPats
 816             | AstFragmentKind::GenericParams
 817             | AstFragmentKind::Params
 818             | AstFragmentKind::StructFields
 819             | AstFragmentKind::Variants => panic!("unexpected AST fragment kind"),
 820         };
 821         if self.cx.ecfg.proc_macro_hygiene() {
 822             return;
 823         }
 824         feature_err(
 825             self.cx.parse_sess,
 826             sym::proc_macro_hygiene,
 827             span,
 828             &format!("procedural macros cannot be expanded to {}", kind),
 829         )
 830         .emit();
 831     }
 832
 833     fn parse_ast_fragment(
 834         &mut self,
 835         toks: TokenStream,
 836         kind: AstFragmentKind,
 837         path: &Path,
 838         span: Span,
 839     ) -> AstFragment {
 840         let mut parser = self.cx.new_parser_from_tts(toks);
 841         match parse_ast_fragment(&mut parser, kind) {
 842             Ok(fragment) => {
 843                 ensure_complete_parse(&mut parser, path, kind.name(), span);
 844                 fragment
 845             }
 846             Err(mut err) => {
 847                 err.set_span(span);
 848                 annotate_err_with_kind(&mut err, kind, span);
 849                 err.emit();
 850                 self.cx.trace_macros_diag();
 851                 kind.dummy(span)
 852             }
 853         }
 854     }
 855 }
 856
 857 pub fn parse_ast_fragment<'a>(
 858     this: &mut Parser<'a>,
 859     kind: AstFragmentKind,
 860 ) -> PResult<'a, AstFragment> {
 861     Ok(match kind {
 862         AstFragmentKind::Items => {
 863             let mut items = SmallVec::new();
 864             while let Some(item) = this.parse_item()? {
 865                 items.push(item);
 866             }
 867             AstFragment::Items(items)
 868         }
 869         AstFragmentKind::TraitItems => {
 870             let mut items = SmallVec::new();
 871             while let Some(item) = this.parse_trait_item()? {
 872                 items.extend(item);
 873             }
 874             AstFragment::TraitItems(items)
 875         }
 876         AstFragmentKind::ImplItems => {
 877             let mut items = SmallVec::new();
 878             while let Some(item) = this.parse_impl_item()? {
 879                 items.extend(item);
 880             }
 881             AstFragment::ImplItems(items)
 882         }
 883         AstFragmentKind::ForeignItems => {
 884             let mut items = SmallVec::new();
 885             while let Some(item) = this.parse_foreign_item()? {
 886                 items.extend(item);
 887             }
 888             AstFragment::ForeignItems(items)
 889         }
 890         AstFragmentKind::Stmts => {
 891             let mut stmts = SmallVec::new();
 892             // Won't make progress on a `}`.
 893             while this.token != token::Eof && this.token != token::CloseDelim(token::Brace) {
 894                 if let Some(stmt) = this.parse_full_stmt()? {
 895                     stmts.push(stmt);
 896                 }
 897             }
 898             AstFragment::Stmts(stmts)
 899         }
 900         AstFragmentKind::Expr => AstFragment::Expr(this.parse_expr()?),
 901         AstFragmentKind::OptExpr => {
 902             if this.token != token::Eof {
 903                 AstFragment::OptExpr(Some(this.parse_expr()?))
 904             } else {
 905                 AstFragment::OptExpr(None)
 906             }
 907         }
 908         AstFragmentKind::Ty => AstFragment::Ty(this.parse_ty()?),
 909         AstFragmentKind::Pat => AstFragment::Pat(this.parse_pat(None)?),
 910         AstFragmentKind::Arms
 911         | AstFragmentKind::Fields
 912         | AstFragmentKind::FieldPats
 913         | AstFragmentKind::GenericParams
 914         | AstFragmentKind::Params
 915         | AstFragmentKind::StructFields
 916         | AstFragmentKind::Variants => panic!("unexpected AST fragment kind"),
 917     })
 918 }
 919
 920 pub fn ensure_complete_parse<'a>(
 921     this: &mut Parser<'a>,
 922     macro_path: &Path,
 923     kind_name: &str,
 924     span: Span,
 925 ) {
 926     if this.token != token::Eof {
 927         let token = pprust::token_to_string(&this.token);
 928         let msg = format!("macro expansion ignores token `{}` and any following", token);
 929         // Avoid emitting backtrace info twice.
 930         let def_site_span = this.token.span.with_ctxt(SyntaxContext::root());
 931         let mut err = this.struct_span_err(def_site_span, &msg);
 932         err.span_label(span, "caused by the macro expansion here");
 933         let msg = format!(
 934             "the usage of `{}!` is likely invalid in {} context",
 935             pprust::path_to_string(macro_path),
 936             kind_name,
 937         );
 938         err.note(&msg);
 939         let semi_span = this.sess.source_map().next_point(span);
 940
 941         let semi_full_span = semi_span.to(this.sess.source_map().next_point(semi_span));
 942         match this.sess.source_map().span_to_snippet(semi_full_span) {
 943             Ok(ref snippet) if &snippet[..] != ";" && kind_name == "expression" => {
 944                 err.span_suggestion(
 945                     semi_span,
 946                     "you might be missing a semicolon here",
 947                     ";".to_owned(),
 948                     Applicability::MaybeIncorrect,
 949                 );
 950             }
 951             _ => {}
 952         }
 953         err.emit();
 954     }
 955 }
 956
 957 struct InvocationCollector<'a, 'b> {
 958     cx: &'a mut ExtCtxt<'b>,
 959     cfg: StripUnconfigured<'a>,
 960     invocations: Vec<Invocation>,
 961     monotonic: bool,
 962 }
 963
 964 impl<'a, 'b> InvocationCollector<'a, 'b> {
 965     fn collect(&mut self, fragment_kind: AstFragmentKind, kind: InvocationKind) -> AstFragment {
 966         // Expansion data for all the collected invocations is set upon their resolution,
 967         // with exception of the derive container case which is not resolved and can get
 968         // its expansion data immediately.
 969         let expn_data = match &kind {
 970             InvocationKind::DeriveContainer { item, .. } => Some(ExpnData {
 971                 parent: self.cx.current_expansion.id,
 972                 ..ExpnData::default(
 973                     ExpnKind::Macro(MacroKind::Attr, sym::derive),
 974                     item.span(),
 975                     self.cx.parse_sess.edition,
 976                 )
 977             }),
 978             _ => None,
 979         };
 980         let expn_id = ExpnId::fresh(expn_data);
 981         let vis = kind.placeholder_visibility();
 982         self.invocations.push(Invocation {
 983             kind,
 984             fragment_kind,
 985             expansion_data: ExpansionData {
 986                 id: expn_id,
 987                 depth: self.cx.current_expansion.depth + 1,
 988                 ..self.cx.current_expansion.clone()
 989             },
 990         });
 991         placeholder(fragment_kind, NodeId::placeholder_from_expn_id(expn_id), vis)
 992     }
 993
 994     fn collect_bang(&mut self, mac: ast::Mac, span: Span, kind: AstFragmentKind) -> AstFragment {
 995         self.collect(kind, InvocationKind::Bang { mac, span })
 996     }
 997
 998     fn collect_attr(
 999         &mut self,
1000         attr: Option<ast::Attribute>,
1001         derives: Vec<Path>,
1002         item: Annotatable,
1003         kind: AstFragmentKind,
1004         after_derive: bool,
1005     ) -> AstFragment {
1006         self.collect(
1007             kind,
1008             match attr {
1009                 Some(attr) => InvocationKind::Attr { attr, item, derives, after_derive },
1010                 None => InvocationKind::DeriveContainer { derives, item },
1011             },
1012         )
1013     }
1014
1015     fn find_attr_invoc(
1016         &self,
1017         attrs: &mut Vec<ast::Attribute>,
1018         after_derive: &mut bool,
1019     ) -> Option<ast::Attribute> {
1020         let attr = attrs
1021             .iter()
1022             .position(|a| {
1023                 if a.has_name(sym::derive) {
1024                     *after_derive = true;
1025                 }
1026                 !attr::is_known(a) && !is_builtin_attr(a)
1027             })
1028             .map(|i| attrs.remove(i));
1029         if let Some(attr) = &attr {
1030             if !self.cx.ecfg.custom_inner_attributes()
1031                 && attr.style == ast::AttrStyle::Inner
1032                 && !attr.has_name(sym::test)
1033             {
1034                 feature_err(
1035                     &self.cx.parse_sess,
1036                     sym::custom_inner_attributes,
1037                     attr.span,
1038                     "non-builtin inner attributes are unstable",
1039                 )
1040                 .emit();
1041             }
1042         }
1043         attr
1044     }
1045
1046     /// If `item` is an attr invocation, remove and return the macro attribute and derive traits.
1047     fn classify_item(
1048         &mut self,
1049         item: &mut impl HasAttrs,
1050     ) -> (Option<ast::Attribute>, Vec<Path>, /* after_derive */ bool) {
1051         let (mut attr, mut traits, mut after_derive) = (None, Vec::new(), false);
1052
1053         item.visit_attrs(|mut attrs| {
1054             attr = self.find_attr_invoc(&mut attrs, &mut after_derive);
1055             traits = collect_derives(&mut self.cx, &mut attrs);
1056         });
1057
1058         (attr, traits, after_derive)
1059     }
1060
1061     /// Alternative to `classify_item()` that ignores `#[derive]` so invocations fallthrough
1062     /// to the unused-attributes lint (making it an error on statements and expressions
1063     /// is a breaking change)
1064     fn classify_nonitem(
1065         &mut self,
1066         nonitem: &mut impl HasAttrs,
1067     ) -> (Option<ast::Attribute>, /* after_derive */ bool) {
1068         let (mut attr, mut after_derive) = (None, false);
1069
1070         nonitem.visit_attrs(|mut attrs| {
1071             attr = self.find_attr_invoc(&mut attrs, &mut after_derive);
1072         });
1073
1074         (attr, after_derive)
1075     }
1076
1077     fn configure<T: HasAttrs>(&mut self, node: T) -> Option<T> {
1078         self.cfg.configure(node)
1079     }
1080
1081     // Detect use of feature-gated or invalid attributes on macro invocations
1082     // since they will not be detected after macro expansion.
1083     fn check_attributes(&mut self, attrs: &[ast::Attribute]) {
1084         let features = self.cx.ecfg.features.unwrap();
1085         for attr in attrs.iter() {
1086             rustc_ast_passes::feature_gate::check_attribute(attr, self.cx.parse_sess, features);
1087             validate_attr::check_meta(self.cx.parse_sess, attr);
1088
1089             // macros are expanded before any lint passes so this warning has to be hardcoded
1090             if attr.has_name(sym::derive) {
1091                 self.cx
1092                     .struct_span_warn(attr.span, "`#[derive]` does nothing on macro invocations")
1093                     .note("this may become a hard error in a future release")
1094                     .emit();
1095             }
1096
1097             if attr.doc_str().is_some() {
1098                 self.cx.parse_sess.buffer_lint_with_diagnostic(
1099                     &UNUSED_DOC_COMMENTS,
1100                     attr.span,
1101                     ast::CRATE_NODE_ID,
1102                     "unused doc comment",
1103                     BuiltinLintDiagnostics::UnusedDocComment(attr.span),
1104                 );
1105             }
1106         }
1107     }
1108 }
1109
1110 impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
1111     fn visit_expr(&mut self, expr: &mut P<ast::Expr>) {
1112         self.cfg.configure_expr(expr);
1113         visit_clobber(expr.deref_mut(), |mut expr| {
1114             self.cfg.configure_expr_kind(&mut expr.kind);
1115
1116             // ignore derives so they remain unused
1117             let (attr, after_derive) = self.classify_nonitem(&mut expr);
1118
1119             if attr.is_some() {
1120                 // Collect the invoc regardless of whether or not attributes are permitted here
1121                 // expansion will eat the attribute so it won't error later.
1122                 attr.as_ref().map(|a| self.cfg.maybe_emit_expr_attr_err(a));
1123
1124                 // AstFragmentKind::Expr requires the macro to emit an expression.
1125                 return self
1126                     .collect_attr(
1127                         attr,
1128                         vec![],
1129                         Annotatable::Expr(P(expr)),
1130                         AstFragmentKind::Expr,
1131                         after_derive,
1132                     )
1133                     .make_expr()
1134                     .into_inner();
1135             }
1136
1137             if let ast::ExprKind::Mac(mac) = expr.kind {
1138                 self.check_attributes(&expr.attrs);
1139                 self.collect_bang(mac, expr.span, AstFragmentKind::Expr).make_expr().into_inner()
1140             } else {
1141                 noop_visit_expr(&mut expr, self);
1142                 expr
1143             }
1144         });
1145     }
1146
1147     fn flat_map_arm(&mut self, arm: ast::Arm) -> SmallVec<[ast::Arm; 1]> {
1148         let mut arm = configure!(self, arm);
1149
1150         let (attr, traits, after_derive) = self.classify_item(&mut arm);
1151         if attr.is_some() || !traits.is_empty() {
1152             return self
1153                 .collect_attr(
1154                     attr,
1155                     traits,
1156                     Annotatable::Arm(arm),
1157                     AstFragmentKind::Arms,
1158                     after_derive,
1159                 )
1160                 .make_arms();
1161         }
1162
1163         noop_flat_map_arm(arm, self)
1164     }
1165
1166     fn flat_map_field(&mut self, field: ast::Field) -> SmallVec<[ast::Field; 1]> {
1167         let mut field = configure!(self, field);
1168
1169         let (attr, traits, after_derive) = self.classify_item(&mut field);
1170         if attr.is_some() || !traits.is_empty() {
1171             return self
1172                 .collect_attr(
1173                     attr,
1174                     traits,
1175                     Annotatable::Field(field),
1176                     AstFragmentKind::Fields,
1177                     after_derive,
1178                 )
1179                 .make_fields();
1180         }
1181
1182         noop_flat_map_field(field, self)
1183     }
1184
1185     fn flat_map_field_pattern(&mut self, fp: ast::FieldPat) -> SmallVec<[ast::FieldPat; 1]> {
1186         let mut fp = configure!(self, fp);
1187
1188         let (attr, traits, after_derive) = self.classify_item(&mut fp);
1189         if attr.is_some() || !traits.is_empty() {
1190             return self
1191                 .collect_attr(
1192                     attr,
1193                     traits,
1194                     Annotatable::FieldPat(fp),
1195                     AstFragmentKind::FieldPats,
1196                     after_derive,
1197                 )
1198                 .make_field_patterns();
1199         }
1200
1201         noop_flat_map_field_pattern(fp, self)
1202     }
1203
1204     fn flat_map_param(&mut self, p: ast::Param) -> SmallVec<[ast::Param; 1]> {
1205         let mut p = configure!(self, p);
1206
1207         let (attr, traits, after_derive) = self.classify_item(&mut p);
1208         if attr.is_some() || !traits.is_empty() {
1209             return self
1210                 .collect_attr(
1211                     attr,
1212                     traits,
1213                     Annotatable::Param(p),
1214                     AstFragmentKind::Params,
1215                     after_derive,
1216                 )
1217                 .make_params();
1218         }
1219
1220         noop_flat_map_param(p, self)
1221     }
1222
1223     fn flat_map_struct_field(&mut self, sf: ast::StructField) -> SmallVec<[ast::StructField; 1]> {
1224         let mut sf = configure!(self, sf);
1225
1226         let (attr, traits, after_derive) = self.classify_item(&mut sf);
1227         if attr.is_some() || !traits.is_empty() {
1228             return self
1229                 .collect_attr(
1230                     attr,
1231                     traits,
1232                     Annotatable::StructField(sf),
1233                     AstFragmentKind::StructFields,
1234                     after_derive,
1235                 )
1236                 .make_struct_fields();
1237         }
1238
1239         noop_flat_map_struct_field(sf, self)
1240     }
1241
1242     fn flat_map_variant(&mut self, variant: ast::Variant) -> SmallVec<[ast::Variant; 1]> {
1243         let mut variant = configure!(self, variant);
1244
1245         let (attr, traits, after_derive) = self.classify_item(&mut variant);
1246         if attr.is_some() || !traits.is_empty() {
1247             return self
1248                 .collect_attr(
1249                     attr,
1250                     traits,
1251                     Annotatable::Variant(variant),
1252                     AstFragmentKind::Variants,
1253                     after_derive,
1254                 )
1255                 .make_variants();
1256         }
1257
1258         noop_flat_map_variant(variant, self)
1259     }
1260
1261     fn filter_map_expr(&mut self, expr: P<ast::Expr>) -> Option<P<ast::Expr>> {
1262         let expr = configure!(self, expr);
1263         expr.filter_map(|mut expr| {
1264             self.cfg.configure_expr_kind(&mut expr.kind);
1265
1266             // Ignore derives so they remain unused.
1267             let (attr, after_derive) = self.classify_nonitem(&mut expr);
1268
1269             if attr.is_some() {
1270                 attr.as_ref().map(|a| self.cfg.maybe_emit_expr_attr_err(a));
1271
1272                 return self
1273                     .collect_attr(
1274                         attr,
1275                         vec![],
1276                         Annotatable::Expr(P(expr)),
1277                         AstFragmentKind::OptExpr,
1278                         after_derive,
1279                     )
1280                     .make_opt_expr()
1281                     .map(|expr| expr.into_inner());
1282             }
1283
1284             if let ast::ExprKind::Mac(mac) = expr.kind {
1285                 self.check_attributes(&expr.attrs);
1286                 self.collect_bang(mac, expr.span, AstFragmentKind::OptExpr)
1287                     .make_opt_expr()
1288                     .map(|expr| expr.into_inner())
1289             } else {
1290                 Some({
1291                     noop_visit_expr(&mut expr, self);
1292                     expr
1293                 })
1294             }
1295         })
1296     }
1297
1298     fn visit_pat(&mut self, pat: &mut P<ast::Pat>) {
1299         self.cfg.configure_pat(pat);
1300         match pat.kind {
1301             PatKind::Mac(_) => {}
1302             _ => return noop_visit_pat(pat, self),
1303         }
1304
1305         visit_clobber(pat, |mut pat| match mem::replace(&mut pat.kind, PatKind::Wild) {
1306             PatKind::Mac(mac) => self.collect_bang(mac, pat.span, AstFragmentKind::Pat).make_pat(),
1307             _ => unreachable!(),
1308         });
1309     }
1310
1311     fn flat_map_stmt(&mut self, stmt: ast::Stmt) -> SmallVec<[ast::Stmt; 1]> {
1312         let mut stmt = configure!(self, stmt);
1313
1314         // we'll expand attributes on expressions separately
1315         if !stmt.is_expr() {
1316             let (attr, derives, after_derive) = if stmt.is_item() {
1317                 self.classify_item(&mut stmt)
1318             } else {
1319                 // ignore derives on non-item statements so it falls through
1320                 // to the unused-attributes lint
1321                 let (attr, after_derive) = self.classify_nonitem(&mut stmt);
1322                 (attr, vec![], after_derive)
1323             };
1324
1325             if attr.is_some() || !derives.is_empty() {
1326                 return self
1327                     .collect_attr(
1328                         attr,
1329                         derives,
1330                         Annotatable::Stmt(P(stmt)),
1331                         AstFragmentKind::Stmts,
1332                         after_derive,
1333                     )
1334                     .make_stmts();
1335             }
1336         }
1337
1338         if let StmtKind::Mac(mac) = stmt.kind {
1339             let (mac, style, attrs) = mac.into_inner();
1340             self.check_attributes(&attrs);
1341             let mut placeholder =
1342                 self.collect_bang(mac, stmt.span, AstFragmentKind::Stmts).make_stmts();
1343
1344             // If this is a macro invocation with a semicolon, then apply that
1345             // semicolon to the final statement produced by expansion.
1346             if style == MacStmtStyle::Semicolon {
1347                 if let Some(stmt) = placeholder.pop() {
1348                     placeholder.push(stmt.add_trailing_semicolon());
1349                 }
1350             }
1351
1352             return placeholder;
1353         }
1354
1355         // The placeholder expander gives ids to statements, so we avoid folding the id here.
1356         let ast::Stmt { id, kind, span } = stmt;
1357         noop_flat_map_stmt_kind(kind, self)
1358             .into_iter()
1359             .map(|kind| ast::Stmt { id, kind, span })
1360             .collect()
1361     }
1362
1363     fn visit_block(&mut self, block: &mut P<Block>) {
1364         let old_directory_ownership = self.cx.current_expansion.directory_ownership;
1365         self.cx.current_expansion.directory_ownership = DirectoryOwnership::UnownedViaBlock;
1366         noop_visit_block(block, self);
1367         self.cx.current_expansion.directory_ownership = old_directory_ownership;
1368     }
1369
1370     fn flat_map_item(&mut self, item: P<ast::Item>) -> SmallVec<[P<ast::Item>; 1]> {
1371         let mut item = configure!(self, item);
1372
1373         let (attr, traits, after_derive) = self.classify_item(&mut item);
1374         if attr.is_some() || !traits.is_empty() {
1375             return self
1376                 .collect_attr(
1377                     attr,
1378                     traits,
1379                     Annotatable::Item(item),
1380                     AstFragmentKind::Items,
1381                     after_derive,
1382                 )
1383                 .make_items();
1384         }
1385
1386         match item.kind {
1387             ast::ItemKind::Mac(..) => {
1388                 self.check_attributes(&item.attrs);
1389                 item.and_then(|item| match item.kind {
1390                     ItemKind::Mac(mac) => self
1391                         .collect(
1392                             AstFragmentKind::Items,
1393                             InvocationKind::Bang { mac, span: item.span },
1394                         )
1395                         .make_items(),
1396                     _ => unreachable!(),
1397                 })
1398             }
1399             ast::ItemKind::Mod(ast::Mod { inner, inline, .. })
1400                 if item.ident != Ident::invalid() =>
1401             {
1402                 let orig_directory_ownership = self.cx.current_expansion.directory_ownership;
1403                 let mut module = (*self.cx.current_expansion.module).clone();
1404                 module.mod_path.push(item.ident);
1405
1406                 if inline {
1407                     if let Some(path) = attr::first_attr_value_str_by_name(&item.attrs, sym::path) {
1408                         self.cx.current_expansion.directory_ownership =
1409                             DirectoryOwnership::Owned { relative: None };
1410                         module.directory.push(&*path.as_str());
1411                     } else {
1412                         module.directory.push(&*item.ident.as_str());
1413                     }
1414                 } else {
1415                     let path = self.cx.parse_sess.source_map().span_to_unmapped_path(inner);
1416                     let mut path = match path {
1417                         FileName::Real(path) => path,
1418                         other => PathBuf::from(other.to_string()),
1419                     };
1420                     let directory_ownership = match path.file_name().unwrap().to_str() {
1421                         Some("mod.rs") => DirectoryOwnership::Owned { relative: None },
1422                         Some(_) => DirectoryOwnership::Owned { relative: Some(item.ident) },
1423                         None => DirectoryOwnership::UnownedViaMod,
1424                     };
1425                     path.pop();
1426                     module.directory = path;
1427                     self.cx.current_expansion.directory_ownership = directory_ownership;
1428                 }
1429
1430                 let orig_module =
1431                     mem::replace(&mut self.cx.current_expansion.module, Rc::new(module));
1432                 let result = noop_flat_map_item(item, self);
1433                 self.cx.current_expansion.module = orig_module;
1434                 self.cx.current_expansion.directory_ownership = orig_directory_ownership;
1435                 result
1436             }
1437
1438             _ => noop_flat_map_item(item, self),
1439         }
1440     }
1441
1442     fn flat_map_trait_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
1443         let mut item = configure!(self, item);
1444
1445         let (attr, traits, after_derive) = self.classify_item(&mut item);
1446         if attr.is_some() || !traits.is_empty() {
1447             return self
1448                 .collect_attr(
1449                     attr,
1450                     traits,
1451                     Annotatable::TraitItem(item),
1452                     AstFragmentKind::TraitItems,
1453                     after_derive,
1454                 )
1455                 .make_trait_items();
1456         }
1457
1458         match item.kind {
1459             ast::AssocItemKind::Macro(..) => {
1460                 self.check_attributes(&item.attrs);
1461                 item.and_then(|item| match item.kind {
1462                     ast::AssocItemKind::Macro(mac) => self
1463                         .collect_bang(mac, item.span, AstFragmentKind::TraitItems)
1464                         .make_trait_items(),
1465                     _ => unreachable!(),
1466                 })
1467             }
1468             _ => noop_flat_map_assoc_item(item, self),
1469         }
1470     }
1471
1472     fn flat_map_impl_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
1473         let mut item = configure!(self, item);
1474
1475         let (attr, traits, after_derive) = self.classify_item(&mut item);
1476         if attr.is_some() || !traits.is_empty() {
1477             return self
1478                 .collect_attr(
1479                     attr,
1480                     traits,
1481                     Annotatable::ImplItem(item),
1482                     AstFragmentKind::ImplItems,
1483                     after_derive,
1484                 )
1485                 .make_impl_items();
1486         }
1487
1488         match item.kind {
1489             ast::AssocItemKind::Macro(..) => {
1490                 self.check_attributes(&item.attrs);
1491                 item.and_then(|item| match item.kind {
1492                     ast::AssocItemKind::Macro(mac) => self
1493                         .collect_bang(mac, item.span, AstFragmentKind::ImplItems)
1494                         .make_impl_items(),
1495                     _ => unreachable!(),
1496                 })
1497             }
1498             _ => noop_flat_map_assoc_item(item, self),
1499         }
1500     }
1501
1502     fn visit_ty(&mut self, ty: &mut P<ast::Ty>) {
1503         match ty.kind {
1504             ast::TyKind::Mac(_) => {}
1505             _ => return noop_visit_ty(ty, self),
1506         };
1507
1508         visit_clobber(ty, |mut ty| match mem::replace(&mut ty.kind, ast::TyKind::Err) {
1509             ast::TyKind::Mac(mac) => self.collect_bang(mac, ty.span, AstFragmentKind::Ty).make_ty(),
1510             _ => unreachable!(),
1511         });
1512     }
1513
1514     fn visit_foreign_mod(&mut self, foreign_mod: &mut ast::ForeignMod) {
1515         self.cfg.configure_foreign_mod(foreign_mod);
1516         noop_visit_foreign_mod(foreign_mod, self);
1517     }
1518
1519     fn flat_map_foreign_item(
1520         &mut self,
1521         mut foreign_item: P<ast::ForeignItem>,
1522     ) -> SmallVec<[P<ast::ForeignItem>; 1]> {
1523         let (attr, traits, after_derive) = self.classify_item(&mut foreign_item);
1524
1525         if attr.is_some() || !traits.is_empty() {
1526             return self
1527                 .collect_attr(
1528                     attr,
1529                     traits,
1530                     Annotatable::ForeignItem(foreign_item),
1531                     AstFragmentKind::ForeignItems,
1532                     after_derive,
1533                 )
1534                 .make_foreign_items();
1535         }
1536
1537         match foreign_item.kind {
1538             ast::ForeignItemKind::Macro(..) => {
1539                 self.check_attributes(&foreign_item.attrs);
1540                 foreign_item.and_then(|item| match item.kind {
1541                     ast::ForeignItemKind::Macro(mac) => self
1542                         .collect_bang(mac, item.span, AstFragmentKind::ForeignItems)
1543                         .make_foreign_items(),
1544                     _ => unreachable!(),
1545                 })
1546             }
1547             _ => noop_flat_map_foreign_item(foreign_item, self),
1548         }
1549     }
1550
1551     fn visit_item_kind(&mut self, item: &mut ast::ItemKind) {
1552         match item {
1553             ast::ItemKind::MacroDef(..) => {}
1554             _ => {
1555                 self.cfg.configure_item_kind(item);
1556                 noop_visit_item_kind(item, self);
1557             }
1558         }
1559     }
1560
1561     fn flat_map_generic_param(
1562         &mut self,
1563         param: ast::GenericParam,
1564     ) -> SmallVec<[ast::GenericParam; 1]> {
1565         let mut param = configure!(self, param);
1566
1567         let (attr, traits, after_derive) = self.classify_item(&mut param);
1568         if attr.is_some() || !traits.is_empty() {
1569             return self
1570                 .collect_attr(
1571                     attr,
1572                     traits,
1573                     Annotatable::GenericParam(param),
1574                     AstFragmentKind::GenericParams,
1575                     after_derive,
1576                 )
1577                 .make_generic_params();
1578         }
1579
1580         noop_flat_map_generic_param(param, self)
1581     }
1582
1583     fn visit_attribute(&mut self, at: &mut ast::Attribute) {
1584         // turn `#[doc(include="filename")]` attributes into `#[doc(include(file="filename",
1585         // contents="file contents")]` attributes
1586         if !at.check_name(sym::doc) {
1587             return noop_visit_attribute(at, self);
1588         }
1589
1590         if let Some(list) = at.meta_item_list() {
1591             if !list.iter().any(|it| it.check_name(sym::include)) {
1592                 return noop_visit_attribute(at, self);
1593             }
1594
1595             let mut items = vec![];
1596
1597             for mut it in list {
1598                 if !it.check_name(sym::include) {
1599                     items.push({
1600                         noop_visit_meta_list_item(&mut it, self);
1601                         it
1602                     });
1603                     continue;
1604                 }
1605
1606                 if let Some(file) = it.value_str() {
1607                     let err_count = self.cx.parse_sess.span_diagnostic.err_count();
1608                     self.check_attributes(slice::from_ref(at));
1609                     if self.cx.parse_sess.span_diagnostic.err_count() > err_count {
1610                         // avoid loading the file if they haven't enabled the feature
1611                         return noop_visit_attribute(at, self);
1612                     }
1613
1614                     let filename = match self.cx.resolve_path(&*file.as_str(), it.span()) {
1615                         Ok(filename) => filename,
1616                         Err(mut err) => {
1617                             err.emit();
1618                             continue;
1619                         }
1620                     };
1621
1622                     match self.cx.source_map().load_file(&filename) {
1623                         Ok(source_file) => {
1624                             let src = source_file
1625                                 .src
1626                                 .as_ref()
1627                                 .expect("freshly loaded file should have a source");
1628                             let src_interned = Symbol::intern(src.as_str());
1629
1630                             let include_info = vec![
1631                                 ast::NestedMetaItem::MetaItem(attr::mk_name_value_item_str(
1632                                     Ident::with_dummy_span(sym::file),
1633                                     file,
1634                                     DUMMY_SP,
1635                                 )),
1636                                 ast::NestedMetaItem::MetaItem(attr::mk_name_value_item_str(
1637                                     Ident::with_dummy_span(sym::contents),
1638                                     src_interned,
1639                                     DUMMY_SP,
1640                                 )),
1641                             ];
1642
1643                             let include_ident = Ident::with_dummy_span(sym::include);
1644                             let item = attr::mk_list_item(include_ident, include_info);
1645                             items.push(ast::NestedMetaItem::MetaItem(item));
1646                         }
1647                         Err(e) => {
1648                             let lit =
1649                                 it.meta_item().and_then(|item| item.name_value_literal()).unwrap();
1650
1651                             if e.kind() == ErrorKind::InvalidData {
1652                                 self.cx
1653                                     .struct_span_err(
1654                                         lit.span,
1655                                         &format!("{} wasn't a utf-8 file", filename.display()),
1656                                     )
1657                                     .span_label(lit.span, "contains invalid utf-8")
1658                                     .emit();
1659                             } else {
1660                                 let mut err = self.cx.struct_span_err(
1661                                     lit.span,
1662                                     &format!("couldn't read {}: {}", filename.display(), e),
1663                                 );
1664                                 err.span_label(lit.span, "couldn't read file");
1665
1666                                 err.emit();
1667                             }
1668                         }
1669                     }
1670                 } else {
1671                     let mut err = self
1672                         .cx
1673                         .struct_span_err(it.span(), "expected path to external documentation");
1674
1675                     // Check if the user erroneously used `doc(include(...))` syntax.
1676                     let literal = it.meta_item_list().and_then(|list| {
1677                         if list.len() == 1 {
1678                             list[0].literal().map(|literal| &literal.kind)
1679                         } else {
1680                             None
1681                         }
1682                     });
1683
1684                     let (path, applicability) = match &literal {
1685                         Some(LitKind::Str(path, ..)) => {
1686                             (path.to_string(), Applicability::MachineApplicable)
1687                         }
1688                         _ => (String::from("<path>"), Applicability::HasPlaceholders),
1689                     };
1690
1691                     err.span_suggestion(
1692                         it.span(),
1693                         "provide a file path with `=`",
1694                         format!("include = \"{}\"", path),
1695                         applicability,
1696                     );
1697
1698                     err.emit();
1699                 }
1700             }
1701
1702             let meta = attr::mk_list_item(Ident::with_dummy_span(sym::doc), items);
1703             *at = ast::Attribute {
1704                 kind: ast::AttrKind::Normal(AttrItem {
1705                     path: meta.path,
1706                     args: meta.kind.mac_args(meta.span),
1707                 }),
1708                 span: at.span,
1709                 id: at.id,
1710                 style: at.style,
1711             };
1712         } else {
1713             noop_visit_attribute(at, self)
1714         }
1715     }
1716
1717     fn visit_id(&mut self, id: &mut ast::NodeId) {
1718         if self.monotonic {
1719             debug_assert_eq!(*id, ast::DUMMY_NODE_ID);
1720             *id = self.cx.resolver.next_node_id()
1721         }
1722     }
1723
1724     fn visit_fn_decl(&mut self, mut fn_decl: &mut P<ast::FnDecl>) {
1725         self.cfg.configure_fn_decl(&mut fn_decl);
1726         noop_visit_fn_decl(fn_decl, self);
1727     }
1728 }
1729
1730 pub struct ExpansionConfig<'feat> {
1731     pub crate_name: String,
1732     pub features: Option<&'feat Features>,
1733     pub recursion_limit: usize,
1734     pub trace_mac: bool,
1735     pub should_test: bool, // If false, strip `#[test]` nodes
1736     pub single_step: bool,
1737     pub keep_macs: bool,
1738 }
1739
1740 impl<'feat> ExpansionConfig<'feat> {
1741     pub fn default(crate_name: String) -> ExpansionConfig<'static> {
1742         ExpansionConfig {
1743             crate_name,
1744             features: None,
1745             recursion_limit: 1024,
1746             trace_mac: false,
1747             should_test: false,
1748             single_step: false,
1749             keep_macs: false,
1750         }
1751     }
1752
1753     fn proc_macro_hygiene(&self) -> bool {
1754         self.features.map_or(false, |features| features.proc_macro_hygiene)
1755     }
1756     fn custom_inner_attributes(&self) -> bool {
1757         self.features.map_or(false, |features| features.custom_inner_attributes)
1758     }
1759 }