compiler/rustc_expand/src/expand.rs

   1 use crate::base::*;
   2 use crate::config::StripUnconfigured;
   3 use crate::configure;
   4 use crate::hygiene::{ExpnData, ExpnKind, SyntaxContext};
   5 use crate::mbe::macro_rules::annotate_err_with_kind;
   6 use crate::module::{parse_external_mod, push_directory, Directory, DirectoryOwnership};
   7 use crate::placeholders::{placeholder, PlaceholderExpander};
   8 use crate::proc_macro::collect_derives;
   9
  10 use rustc_ast::mut_visit::*;
  11 use rustc_ast::ptr::P;
  12 use rustc_ast::token;
  13 use rustc_ast::tokenstream::TokenStream;
  14 use rustc_ast::visit::{self, AssocCtxt, Visitor};
  15 use rustc_ast::{self as ast, AttrItem, Block, LitKind, NodeId, PatKind, Path};
  16 use rustc_ast::{ItemKind, MacArgs, MacCallStmt, MacStmtStyle, StmtKind, Unsafe};
  17 use rustc_ast_pretty::pprust;
  18 use rustc_attr::{self as attr, is_builtin_attr, HasAttrs};
  19 use rustc_data_structures::map_in_place::MapInPlace;
  20 use rustc_data_structures::stack::ensure_sufficient_stack;
  21 use rustc_errors::{Applicability, PResult};
  22 use rustc_feature::Features;
  23 use rustc_parse::parser::Parser;
  24 use rustc_parse::validate_attr;
  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_session::Limit;
  29 use rustc_span::symbol::{sym, Ident, Symbol};
  30 use rustc_span::{ExpnId, 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     crate 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::MacCall,
 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(name) => name.into_local_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: ast::Visibility {
 361                 span: krate.span.shrink_to_lo(),
 362                 kind: ast::VisibilityKind::Public,
 363                 tokens: None,
 364             },
 365             tokens: None,
 366         })]);
 367
 368         match self.fully_expand_fragment(krate_item).make_items().pop().map(P::into_inner) {
 369             Some(ast::Item { attrs, kind: ast::ItemKind::Mod(module), .. }) => {
 370                 krate.attrs = attrs;
 371                 krate.module = module;
 372             }
 373             None => {
 374                 // Resolution failed so we return an empty expansion
 375                 krate.attrs = vec![];
 376                 krate.module = ast::Mod {
 377                     inner: orig_mod_span,
 378                     unsafety: Unsafe::No,
 379                     items: vec![],
 380                     inline: true,
 381                 };
 382             }
 383             Some(ast::Item { span, kind, .. }) => {
 384                 krate.attrs = vec![];
 385                 krate.module = ast::Mod {
 386                     inner: orig_mod_span,
 387                     unsafety: Unsafe::No,
 388                     items: vec![],
 389                     inline: true,
 390                 };
 391                 self.cx.span_err(
 392                     span,
 393                     &format!(
 394                         "expected crate top-level item to be a module after macro expansion, found {} {}",
 395                         kind.article(), kind.descr()
 396                     ),
 397                 );
 398             }
 399         };
 400         self.cx.trace_macros_diag();
 401         krate
 402     }
 403
 404     // Recursively expand all macro invocations in this AST fragment.
 405     pub fn fully_expand_fragment(&mut self, input_fragment: AstFragment) -> AstFragment {
 406         let orig_expansion_data = self.cx.current_expansion.clone();
 407         self.cx.current_expansion.depth = 0;
 408
 409         // Collect all macro invocations and replace them with placeholders.
 410         let (mut fragment_with_placeholders, mut invocations) =
 411             self.collect_invocations(input_fragment, &[]);
 412
 413         // Optimization: if we resolve all imports now,
 414         // we'll be able to immediately resolve most of imported macros.
 415         self.resolve_imports();
 416
 417         // Resolve paths in all invocations and produce output expanded fragments for them, but
 418         // do not insert them into our input AST fragment yet, only store in `expanded_fragments`.
 419         // The output fragments also go through expansion recursively until no invocations are left.
 420         // Unresolved macros produce dummy outputs as a recovery measure.
 421         invocations.reverse();
 422         let mut expanded_fragments = Vec::new();
 423         let mut undetermined_invocations = Vec::new();
 424         let (mut progress, mut force) = (false, !self.monotonic);
 425         loop {
 426             let (invoc, res) = if let Some(invoc) = invocations.pop() {
 427                 invoc
 428             } else {
 429                 self.resolve_imports();
 430                 if undetermined_invocations.is_empty() {
 431                     break;
 432                 }
 433                 invocations = mem::take(&mut undetermined_invocations);
 434                 force = !mem::replace(&mut progress, false);
 435                 continue;
 436             };
 437
 438             let res = match res {
 439                 Some(res) => res,
 440                 None => {
 441                     let eager_expansion_root = if self.monotonic {
 442                         invoc.expansion_data.id
 443                     } else {
 444                         orig_expansion_data.id
 445                     };
 446                     match self.cx.resolver.resolve_macro_invocation(
 447                         &invoc,
 448                         eager_expansion_root,
 449                         force,
 450                     ) {
 451                         Ok(res) => res,
 452                         Err(Indeterminate) => {
 453                             // Cannot resolve, will retry this invocation later.
 454                             undetermined_invocations.push((invoc, None));
 455                             continue;
 456                         }
 457                     }
 458                 }
 459             };
 460
 461             let ExpansionData { depth, id: expn_id, .. } = invoc.expansion_data;
 462             self.cx.current_expansion = invoc.expansion_data.clone();
 463
 464             // FIXME(jseyfried): Refactor out the following logic
 465             let (expanded_fragment, new_invocations) = match res {
 466                 InvocationRes::Single(ext) => match self.expand_invoc(invoc, &ext.kind) {
 467                     ExpandResult::Ready(fragment) => self.collect_invocations(fragment, &[]),
 468                     ExpandResult::Retry(invoc, explanation) => {
 469                         if force {
 470                             // We are stuck, stop retrying and produce a dummy fragment.
 471                             let span = invoc.span();
 472                             self.cx.span_err(span, &explanation);
 473                             let fragment = invoc.fragment_kind.dummy(span);
 474                             self.collect_invocations(fragment, &[])
 475                         } else {
 476                             // Cannot expand, will retry this invocation later.
 477                             undetermined_invocations
 478                                 .push((invoc, Some(InvocationRes::Single(ext))));
 479                             continue;
 480                         }
 481                     }
 482                 },
 483                 InvocationRes::DeriveContainer(_exts) => {
 484                     // FIXME: Consider using the derive resolutions (`_exts`) immediately,
 485                     // instead of enqueuing the derives to be resolved again later.
 486                     let (derives, item) = match invoc.kind {
 487                         InvocationKind::DeriveContainer { derives, item } => (derives, item),
 488                         _ => unreachable!(),
 489                     };
 490                     if !item.derive_allowed() {
 491                         self.error_derive_forbidden_on_non_adt(&derives, &item);
 492                     }
 493
 494                     let mut item = self.fully_configure(item);
 495                     item.visit_attrs(|attrs| attrs.retain(|a| !a.has_name(sym::derive)));
 496
 497                     let mut derive_placeholders = Vec::with_capacity(derives.len());
 498                     invocations.reserve(derives.len());
 499                     for path in derives {
 500                         let expn_id = ExpnId::fresh(None);
 501                         derive_placeholders.push(NodeId::placeholder_from_expn_id(expn_id));
 502                         invocations.push((
 503                             Invocation {
 504                                 kind: InvocationKind::Derive { path, item: item.clone() },
 505                                 fragment_kind: invoc.fragment_kind,
 506                                 expansion_data: ExpansionData {
 507                                     id: expn_id,
 508                                     ..invoc.expansion_data.clone()
 509                                 },
 510                             },
 511                             None,
 512                         ));
 513                     }
 514                     let fragment =
 515                         invoc.fragment_kind.expect_from_annotatables(::std::iter::once(item));
 516                     self.collect_invocations(fragment, &derive_placeholders)
 517                 }
 518             };
 519
 520             progress = true;
 521             if expanded_fragments.len() < depth {
 522                 expanded_fragments.push(Vec::new());
 523             }
 524             expanded_fragments[depth - 1].push((expn_id, expanded_fragment));
 525             invocations.extend(new_invocations.into_iter().rev());
 526         }
 527
 528         self.cx.current_expansion = orig_expansion_data;
 529
 530         // Finally incorporate all the expanded macros into the input AST fragment.
 531         let mut placeholder_expander = PlaceholderExpander::new(self.cx, self.monotonic);
 532         while let Some(expanded_fragments) = expanded_fragments.pop() {
 533             for (expn_id, expanded_fragment) in expanded_fragments.into_iter().rev() {
 534                 placeholder_expander
 535                     .add(NodeId::placeholder_from_expn_id(expn_id), expanded_fragment);
 536             }
 537         }
 538         fragment_with_placeholders.mut_visit_with(&mut placeholder_expander);
 539         fragment_with_placeholders
 540     }
 541
 542     fn error_derive_forbidden_on_non_adt(&self, derives: &[Path], item: &Annotatable) {
 543         let attr = self.cx.sess.find_by_name(item.attrs(), sym::derive);
 544         let span = attr.map_or(item.span(), |attr| attr.span);
 545         let mut err = rustc_errors::struct_span_err!(
 546             self.cx.sess,
 547             span,
 548             E0774,
 549             "`derive` may only be applied to structs, enums and unions",
 550         );
 551         if let Some(ast::Attribute { style: ast::AttrStyle::Inner, .. }) = attr {
 552             let trait_list = derives.iter().map(|t| pprust::path_to_string(t)).collect::<Vec<_>>();
 553             let suggestion = format!("#[derive({})]", trait_list.join(", "));
 554             err.span_suggestion(
 555                 span,
 556                 "try an outer attribute",
 557                 suggestion,
 558                 // We don't 𝑘𝑛𝑜𝑤 that the following item is an ADT
 559                 Applicability::MaybeIncorrect,
 560             );
 561         }
 562         err.emit();
 563     }
 564
 565     fn resolve_imports(&mut self) {
 566         if self.monotonic {
 567             self.cx.resolver.resolve_imports();
 568         }
 569     }
 570
 571     /// Collects all macro invocations reachable at this time in this AST fragment, and replace
 572     /// them with "placeholders" - dummy macro invocations with specially crafted `NodeId`s.
 573     /// Then call into resolver that builds a skeleton ("reduced graph") of the fragment and
 574     /// prepares data for resolving paths of macro invocations.
 575     fn collect_invocations(
 576         &mut self,
 577         mut fragment: AstFragment,
 578         extra_placeholders: &[NodeId],
 579     ) -> (AstFragment, Vec<(Invocation, Option<InvocationRes>)>) {
 580         // Resolve `$crate`s in the fragment for pretty-printing.
 581         self.cx.resolver.resolve_dollar_crates();
 582
 583         let invocations = {
 584             let mut collector = InvocationCollector {
 585                 cfg: StripUnconfigured { sess: &self.cx.sess, features: self.cx.ecfg.features },
 586                 cx: self.cx,
 587                 invocations: Vec::new(),
 588                 monotonic: self.monotonic,
 589             };
 590             fragment.mut_visit_with(&mut collector);
 591             fragment.add_placeholders(extra_placeholders);
 592             collector.invocations
 593         };
 594
 595         if self.monotonic {
 596             self.cx
 597                 .resolver
 598                 .visit_ast_fragment_with_placeholders(self.cx.current_expansion.id, &fragment);
 599         }
 600
 601         (fragment, invocations)
 602     }
 603
 604     fn fully_configure(&mut self, item: Annotatable) -> Annotatable {
 605         let mut cfg = StripUnconfigured { sess: &self.cx.sess, features: self.cx.ecfg.features };
 606         // Since the item itself has already been configured by the InvocationCollector,
 607         // we know that fold result vector will contain exactly one element
 608         match item {
 609             Annotatable::Item(item) => Annotatable::Item(cfg.flat_map_item(item).pop().unwrap()),
 610             Annotatable::TraitItem(item) => {
 611                 Annotatable::TraitItem(cfg.flat_map_trait_item(item).pop().unwrap())
 612             }
 613             Annotatable::ImplItem(item) => {
 614                 Annotatable::ImplItem(cfg.flat_map_impl_item(item).pop().unwrap())
 615             }
 616             Annotatable::ForeignItem(item) => {
 617                 Annotatable::ForeignItem(cfg.flat_map_foreign_item(item).pop().unwrap())
 618             }
 619             Annotatable::Stmt(stmt) => {
 620                 Annotatable::Stmt(stmt.map(|stmt| cfg.flat_map_stmt(stmt).pop().unwrap()))
 621             }
 622             Annotatable::Expr(mut expr) => Annotatable::Expr({
 623                 cfg.visit_expr(&mut expr);
 624                 expr
 625             }),
 626             Annotatable::Arm(arm) => Annotatable::Arm(cfg.flat_map_arm(arm).pop().unwrap()),
 627             Annotatable::Field(field) => {
 628                 Annotatable::Field(cfg.flat_map_field(field).pop().unwrap())
 629             }
 630             Annotatable::FieldPat(fp) => {
 631                 Annotatable::FieldPat(cfg.flat_map_field_pattern(fp).pop().unwrap())
 632             }
 633             Annotatable::GenericParam(param) => {
 634                 Annotatable::GenericParam(cfg.flat_map_generic_param(param).pop().unwrap())
 635             }
 636             Annotatable::Param(param) => {
 637                 Annotatable::Param(cfg.flat_map_param(param).pop().unwrap())
 638             }
 639             Annotatable::StructField(sf) => {
 640                 Annotatable::StructField(cfg.flat_map_struct_field(sf).pop().unwrap())
 641             }
 642             Annotatable::Variant(v) => Annotatable::Variant(cfg.flat_map_variant(v).pop().unwrap()),
 643         }
 644     }
 645
 646     fn error_recursion_limit_reached(&mut self) {
 647         let expn_data = self.cx.current_expansion.id.expn_data();
 648         let suggested_limit = self.cx.ecfg.recursion_limit * 2;
 649         self.cx
 650             .struct_span_err(
 651                 expn_data.call_site,
 652                 &format!("recursion limit reached while expanding `{}`", expn_data.kind.descr()),
 653             )
 654             .help(&format!(
 655                 "consider adding a `#![recursion_limit=\"{}\"]` attribute to your crate (`{}`)",
 656                 suggested_limit, self.cx.ecfg.crate_name,
 657             ))
 658             .emit();
 659         self.cx.trace_macros_diag();
 660     }
 661
 662     /// A macro's expansion does not fit in this fragment kind.
 663     /// For example, a non-type macro in a type position.
 664     fn error_wrong_fragment_kind(&mut self, kind: AstFragmentKind, mac: &ast::MacCall, span: Span) {
 665         let msg = format!(
 666             "non-{kind} macro in {kind} position: {path}",
 667             kind = kind.name(),
 668             path = pprust::path_to_string(&mac.path),
 669         );
 670         self.cx.span_err(span, &msg);
 671         self.cx.trace_macros_diag();
 672     }
 673
 674     fn expand_invoc(
 675         &mut self,
 676         invoc: Invocation,
 677         ext: &SyntaxExtensionKind,
 678     ) -> ExpandResult<AstFragment, Invocation> {
 679         let recursion_limit =
 680             self.cx.reduced_recursion_limit.unwrap_or(self.cx.ecfg.recursion_limit);
 681         if !recursion_limit.value_within_limit(self.cx.current_expansion.depth) {
 682             if self.cx.reduced_recursion_limit.is_none() {
 683                 self.error_recursion_limit_reached();
 684             }
 685
 686             // Reduce the recursion limit by half each time it triggers.
 687             self.cx.reduced_recursion_limit = Some(recursion_limit / 2);
 688
 689             return ExpandResult::Ready(invoc.fragment_kind.dummy(invoc.span()));
 690         }
 691
 692         let (fragment_kind, span) = (invoc.fragment_kind, invoc.span());
 693         ExpandResult::Ready(match invoc.kind {
 694             InvocationKind::Bang { mac, .. } => match ext {
 695                 SyntaxExtensionKind::Bang(expander) => {
 696                     let tok_result = match expander.expand(self.cx, span, mac.args.inner_tokens()) {
 697                         Err(_) => return ExpandResult::Ready(fragment_kind.dummy(span)),
 698                         Ok(ts) => ts,
 699                     };
 700                     self.parse_ast_fragment(tok_result, fragment_kind, &mac.path, span)
 701                 }
 702                 SyntaxExtensionKind::LegacyBang(expander) => {
 703                     let prev = self.cx.current_expansion.prior_type_ascription;
 704                     self.cx.current_expansion.prior_type_ascription = mac.prior_type_ascription;
 705                     let tok_result = expander.expand(self.cx, span, mac.args.inner_tokens());
 706                     let result = if let Some(result) = fragment_kind.make_from(tok_result) {
 707                         result
 708                     } else {
 709                         self.error_wrong_fragment_kind(fragment_kind, &mac, span);
 710                         fragment_kind.dummy(span)
 711                     };
 712                     self.cx.current_expansion.prior_type_ascription = prev;
 713                     result
 714                 }
 715                 _ => unreachable!(),
 716             },
 717             InvocationKind::Attr { attr, mut item, derives, after_derive } => match ext {
 718                 SyntaxExtensionKind::Attr(expander) => {
 719                     self.gate_proc_macro_input(&item);
 720                     self.gate_proc_macro_attr_item(span, &item);
 721                     let tokens = item.into_tokens(&self.cx.sess.parse_sess);
 722                     let attr_item = attr.unwrap_normal_item();
 723                     if let MacArgs::Eq(..) = attr_item.args {
 724                         self.cx.span_err(span, "key-value macro attributes are not supported");
 725                     }
 726                     let inner_tokens = attr_item.args.inner_tokens();
 727                     let tok_result = match expander.expand(self.cx, span, inner_tokens, tokens) {
 728                         Err(_) => return ExpandResult::Ready(fragment_kind.dummy(span)),
 729                         Ok(ts) => ts,
 730                     };
 731                     self.parse_ast_fragment(tok_result, fragment_kind, &attr_item.path, span)
 732                 }
 733                 SyntaxExtensionKind::LegacyAttr(expander) => {
 734                     match validate_attr::parse_meta(&self.cx.sess.parse_sess, &attr) {
 735                         Ok(meta) => {
 736                             let items = match expander.expand(self.cx, span, &meta, item) {
 737                                 ExpandResult::Ready(items) => items,
 738                                 ExpandResult::Retry(item, explanation) => {
 739                                     // Reassemble the original invocation for retrying.
 740                                     return ExpandResult::Retry(
 741                                         Invocation {
 742                                             kind: InvocationKind::Attr {
 743                                                 attr,
 744                                                 item,
 745                                                 derives,
 746                                                 after_derive,
 747                                             },
 748                                             ..invoc
 749                                         },
 750                                         explanation,
 751                                     );
 752                                 }
 753                             };
 754                             fragment_kind.expect_from_annotatables(items)
 755                         }
 756                         Err(mut err) => {
 757                             err.emit();
 758                             fragment_kind.dummy(span)
 759                         }
 760                     }
 761                 }
 762                 SyntaxExtensionKind::NonMacroAttr { mark_used } => {
 763                     self.cx.sess.mark_attr_known(&attr);
 764                     if *mark_used {
 765                         self.cx.sess.mark_attr_used(&attr);
 766                     }
 767                     item.visit_attrs(|attrs| attrs.push(attr));
 768                     fragment_kind.expect_from_annotatables(iter::once(item))
 769                 }
 770                 _ => unreachable!(),
 771             },
 772             InvocationKind::Derive { path, item } => match ext {
 773                 SyntaxExtensionKind::Derive(expander)
 774                 | SyntaxExtensionKind::LegacyDerive(expander) => {
 775                     if !item.derive_allowed() {
 776                         return ExpandResult::Ready(fragment_kind.dummy(span));
 777                     }
 778                     if let SyntaxExtensionKind::Derive(..) = ext {
 779                         self.gate_proc_macro_input(&item);
 780                     }
 781                     let meta = ast::MetaItem { kind: ast::MetaItemKind::Word, span, path };
 782                     let items = match expander.expand(self.cx, span, &meta, item) {
 783                         ExpandResult::Ready(items) => items,
 784                         ExpandResult::Retry(item, explanation) => {
 785                             // Reassemble the original invocation for retrying.
 786                             return ExpandResult::Retry(
 787                                 Invocation {
 788                                     kind: InvocationKind::Derive { path: meta.path, item },
 789                                     ..invoc
 790                                 },
 791                                 explanation,
 792                             );
 793                         }
 794                     };
 795                     fragment_kind.expect_from_annotatables(items)
 796                 }
 797                 _ => unreachable!(),
 798             },
 799             InvocationKind::DeriveContainer { .. } => unreachable!(),
 800         })
 801     }
 802
 803     fn gate_proc_macro_attr_item(&self, span: Span, item: &Annotatable) {
 804         let kind = match item {
 805             Annotatable::Item(_)
 806             | Annotatable::TraitItem(_)
 807             | Annotatable::ImplItem(_)
 808             | Annotatable::ForeignItem(_) => return,
 809             Annotatable::Stmt(_) => "statements",
 810             Annotatable::Expr(_) => "expressions",
 811             Annotatable::Arm(..)
 812             | Annotatable::Field(..)
 813             | Annotatable::FieldPat(..)
 814             | Annotatable::GenericParam(..)
 815             | Annotatable::Param(..)
 816             | Annotatable::StructField(..)
 817             | Annotatable::Variant(..) => panic!("unexpected annotatable"),
 818         };
 819         if self.cx.ecfg.proc_macro_hygiene() {
 820             return;
 821         }
 822         feature_err(
 823             &self.cx.sess.parse_sess,
 824             sym::proc_macro_hygiene,
 825             span,
 826             &format!("custom attributes cannot be applied to {}", kind),
 827         )
 828         .emit();
 829     }
 830
 831     fn gate_proc_macro_input(&self, annotatable: &Annotatable) {
 832         struct GateProcMacroInput<'a> {
 833             parse_sess: &'a ParseSess,
 834         }
 835
 836         impl<'ast, 'a> Visitor<'ast> for GateProcMacroInput<'a> {
 837             fn visit_item(&mut self, item: &'ast ast::Item) {
 838                 match &item.kind {
 839                     ast::ItemKind::Mod(module) if !module.inline => {
 840                         feature_err(
 841                             self.parse_sess,
 842                             sym::proc_macro_hygiene,
 843                             item.span,
 844                             "non-inline modules in proc macro input are unstable",
 845                         )
 846                         .emit();
 847                     }
 848                     _ => {}
 849                 }
 850
 851                 visit::walk_item(self, item);
 852             }
 853
 854             fn visit_mac(&mut self, _: &'ast ast::MacCall) {}
 855         }
 856
 857         if !self.cx.ecfg.proc_macro_hygiene() {
 858             annotatable
 859                 .visit_with(&mut GateProcMacroInput { parse_sess: &self.cx.sess.parse_sess });
 860         }
 861     }
 862
 863     fn parse_ast_fragment(
 864         &mut self,
 865         toks: TokenStream,
 866         kind: AstFragmentKind,
 867         path: &Path,
 868         span: Span,
 869     ) -> AstFragment {
 870         let mut parser = self.cx.new_parser_from_tts(toks);
 871         match parse_ast_fragment(&mut parser, kind) {
 872             Ok(fragment) => {
 873                 ensure_complete_parse(&mut parser, path, kind.name(), span);
 874                 fragment
 875             }
 876             Err(mut err) => {
 877                 err.set_span(span);
 878                 annotate_err_with_kind(&mut err, kind, span);
 879                 err.emit();
 880                 self.cx.trace_macros_diag();
 881                 kind.dummy(span)
 882             }
 883         }
 884     }
 885 }
 886
 887 pub fn parse_ast_fragment<'a>(
 888     this: &mut Parser<'a>,
 889     kind: AstFragmentKind,
 890 ) -> PResult<'a, AstFragment> {
 891     Ok(match kind {
 892         AstFragmentKind::Items => {
 893             let mut items = SmallVec::new();
 894             while let Some(item) = this.parse_item()? {
 895                 items.push(item);
 896             }
 897             AstFragment::Items(items)
 898         }
 899         AstFragmentKind::TraitItems => {
 900             let mut items = SmallVec::new();
 901             while let Some(item) = this.parse_trait_item()? {
 902                 items.extend(item);
 903             }
 904             AstFragment::TraitItems(items)
 905         }
 906         AstFragmentKind::ImplItems => {
 907             let mut items = SmallVec::new();
 908             while let Some(item) = this.parse_impl_item()? {
 909                 items.extend(item);
 910             }
 911             AstFragment::ImplItems(items)
 912         }
 913         AstFragmentKind::ForeignItems => {
 914             let mut items = SmallVec::new();
 915             while let Some(item) = this.parse_foreign_item()? {
 916                 items.extend(item);
 917             }
 918             AstFragment::ForeignItems(items)
 919         }
 920         AstFragmentKind::Stmts => {
 921             let mut stmts = SmallVec::new();
 922             // Won't make progress on a `}`.
 923             while this.token != token::Eof && this.token != token::CloseDelim(token::Brace) {
 924                 if let Some(stmt) = this.parse_full_stmt()? {
 925                     stmts.push(stmt);
 926                 }
 927             }
 928             AstFragment::Stmts(stmts)
 929         }
 930         AstFragmentKind::Expr => AstFragment::Expr(this.parse_expr()?),
 931         AstFragmentKind::OptExpr => {
 932             if this.token != token::Eof {
 933                 AstFragment::OptExpr(Some(this.parse_expr()?))
 934             } else {
 935                 AstFragment::OptExpr(None)
 936             }
 937         }
 938         AstFragmentKind::Ty => AstFragment::Ty(this.parse_ty()?),
 939         AstFragmentKind::Pat => AstFragment::Pat(this.parse_pat(None)?),
 940         AstFragmentKind::Arms
 941         | AstFragmentKind::Fields
 942         | AstFragmentKind::FieldPats
 943         | AstFragmentKind::GenericParams
 944         | AstFragmentKind::Params
 945         | AstFragmentKind::StructFields
 946         | AstFragmentKind::Variants => panic!("unexpected AST fragment kind"),
 947     })
 948 }
 949
 950 pub fn ensure_complete_parse<'a>(
 951     this: &mut Parser<'a>,
 952     macro_path: &Path,
 953     kind_name: &str,
 954     span: Span,
 955 ) {
 956     if this.token != token::Eof {
 957         let token = pprust::token_to_string(&this.token);
 958         let msg = format!("macro expansion ignores token `{}` and any following", token);
 959         // Avoid emitting backtrace info twice.
 960         let def_site_span = this.token.span.with_ctxt(SyntaxContext::root());
 961         let mut err = this.struct_span_err(def_site_span, &msg);
 962         err.span_label(span, "caused by the macro expansion here");
 963         let msg = format!(
 964             "the usage of `{}!` is likely invalid in {} context",
 965             pprust::path_to_string(macro_path),
 966             kind_name,
 967         );
 968         err.note(&msg);
 969         let semi_span = this.sess.source_map().next_point(span);
 970
 971         let semi_full_span = semi_span.to(this.sess.source_map().next_point(semi_span));
 972         match this.sess.source_map().span_to_snippet(semi_full_span) {
 973             Ok(ref snippet) if &snippet[..] != ";" && kind_name == "expression" => {
 974                 err.span_suggestion(
 975                     semi_span,
 976                     "you might be missing a semicolon here",
 977                     ";".to_owned(),
 978                     Applicability::MaybeIncorrect,
 979                 );
 980             }
 981             _ => {}
 982         }
 983         err.emit();
 984     }
 985 }
 986
 987 struct InvocationCollector<'a, 'b> {
 988     cx: &'a mut ExtCtxt<'b>,
 989     cfg: StripUnconfigured<'a>,
 990     invocations: Vec<(Invocation, Option<InvocationRes>)>,
 991     monotonic: bool,
 992 }
 993
 994 impl<'a, 'b> InvocationCollector<'a, 'b> {
 995     fn collect(&mut self, fragment_kind: AstFragmentKind, kind: InvocationKind) -> AstFragment {
 996         // Expansion data for all the collected invocations is set upon their resolution,
 997         // with exception of the derive container case which is not resolved and can get
 998         // its expansion data immediately.
 999         let expn_data = match &kind {
1000             InvocationKind::DeriveContainer { item, .. } => Some(ExpnData {
1001                 parent: self.cx.current_expansion.id,
1002                 ..ExpnData::default(
1003                     ExpnKind::Macro(MacroKind::Attr, sym::derive),
1004                     item.span(),
1005                     self.cx.sess.parse_sess.edition,
1006                     None,
1007                 )
1008             }),
1009             _ => None,
1010         };
1011         let expn_id = ExpnId::fresh(expn_data);
1012         let vis = kind.placeholder_visibility();
1013         self.invocations.push((
1014             Invocation {
1015                 kind,
1016                 fragment_kind,
1017                 expansion_data: ExpansionData {
1018                     id: expn_id,
1019                     depth: self.cx.current_expansion.depth + 1,
1020                     ..self.cx.current_expansion.clone()
1021                 },
1022             },
1023             None,
1024         ));
1025         placeholder(fragment_kind, NodeId::placeholder_from_expn_id(expn_id), vis)
1026     }
1027
1028     fn collect_bang(
1029         &mut self,
1030         mac: ast::MacCall,
1031         span: Span,
1032         kind: AstFragmentKind,
1033     ) -> AstFragment {
1034         self.collect(kind, InvocationKind::Bang { mac, span })
1035     }
1036
1037     fn collect_attr(
1038         &mut self,
1039         attr: Option<ast::Attribute>,
1040         derives: Vec<Path>,
1041         item: Annotatable,
1042         kind: AstFragmentKind,
1043         after_derive: bool,
1044     ) -> AstFragment {
1045         self.collect(
1046             kind,
1047             match attr {
1048                 Some(attr) => InvocationKind::Attr { attr, item, derives, after_derive },
1049                 None => InvocationKind::DeriveContainer { derives, item },
1050             },
1051         )
1052     }
1053
1054     fn find_attr_invoc(
1055         &self,
1056         attrs: &mut Vec<ast::Attribute>,
1057         after_derive: &mut bool,
1058     ) -> Option<ast::Attribute> {
1059         let attr = attrs
1060             .iter()
1061             .position(|a| {
1062                 if a.has_name(sym::derive) {
1063                     *after_derive = true;
1064                 }
1065                 !self.cx.sess.is_attr_known(a) && !is_builtin_attr(a)
1066             })
1067             .map(|i| attrs.remove(i));
1068         if let Some(attr) = &attr {
1069             if !self.cx.ecfg.custom_inner_attributes()
1070                 && attr.style == ast::AttrStyle::Inner
1071                 && !attr.has_name(sym::test)
1072             {
1073                 feature_err(
1074                     &self.cx.sess.parse_sess,
1075                     sym::custom_inner_attributes,
1076                     attr.span,
1077                     "non-builtin inner attributes are unstable",
1078                 )
1079                 .emit();
1080             }
1081         }
1082         attr
1083     }
1084
1085     /// If `item` is an attr invocation, remove and return the macro attribute and derive traits.
1086     fn classify_item(
1087         &mut self,
1088         item: &mut impl HasAttrs,
1089     ) -> (Option<ast::Attribute>, Vec<Path>, /* after_derive */ bool) {
1090         let (mut attr, mut traits, mut after_derive) = (None, Vec::new(), false);
1091
1092         item.visit_attrs(|mut attrs| {
1093             attr = self.find_attr_invoc(&mut attrs, &mut after_derive);
1094             traits = collect_derives(&mut self.cx, &mut attrs);
1095         });
1096
1097         (attr, traits, after_derive)
1098     }
1099
1100     /// Alternative to `classify_item()` that ignores `#[derive]` so invocations fallthrough
1101     /// to the unused-attributes lint (making it an error on statements and expressions
1102     /// is a breaking change)
1103     fn classify_nonitem(
1104         &mut self,
1105         nonitem: &mut impl HasAttrs,
1106     ) -> (Option<ast::Attribute>, /* after_derive */ bool) {
1107         let (mut attr, mut after_derive) = (None, false);
1108
1109         nonitem.visit_attrs(|mut attrs| {
1110             attr = self.find_attr_invoc(&mut attrs, &mut after_derive);
1111         });
1112
1113         (attr, after_derive)
1114     }
1115
1116     fn configure<T: HasAttrs>(&mut self, node: T) -> Option<T> {
1117         self.cfg.configure(node)
1118     }
1119
1120     // Detect use of feature-gated or invalid attributes on macro invocations
1121     // since they will not be detected after macro expansion.
1122     fn check_attributes(&mut self, attrs: &[ast::Attribute]) {
1123         let features = self.cx.ecfg.features.unwrap();
1124         for attr in attrs.iter() {
1125             rustc_ast_passes::feature_gate::check_attribute(attr, self.cx.sess, features);
1126             validate_attr::check_meta(&self.cx.sess.parse_sess, attr);
1127
1128             // macros are expanded before any lint passes so this warning has to be hardcoded
1129             if attr.has_name(sym::derive) {
1130                 self.cx
1131                     .parse_sess()
1132                     .span_diagnostic
1133                     .struct_span_warn(attr.span, "`#[derive]` does nothing on macro invocations")
1134                     .note("this may become a hard error in a future release")
1135                     .emit();
1136             }
1137
1138             if attr.doc_str().is_some() {
1139                 self.cx.sess.parse_sess.buffer_lint_with_diagnostic(
1140                     &UNUSED_DOC_COMMENTS,
1141                     attr.span,
1142                     ast::CRATE_NODE_ID,
1143                     "unused doc comment",
1144                     BuiltinLintDiagnostics::UnusedDocComment(attr.span),
1145                 );
1146             }
1147         }
1148     }
1149 }
1150
1151 impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
1152     fn visit_expr(&mut self, expr: &mut P<ast::Expr>) {
1153         self.cfg.configure_expr(expr);
1154         visit_clobber(expr.deref_mut(), |mut expr| {
1155             self.cfg.configure_expr_kind(&mut expr.kind);
1156
1157             // ignore derives so they remain unused
1158             let (attr, after_derive) = self.classify_nonitem(&mut expr);
1159
1160             if let Some(ref attr_value) = attr {
1161                 // Collect the invoc regardless of whether or not attributes are permitted here
1162                 // expansion will eat the attribute so it won't error later.
1163                 self.cfg.maybe_emit_expr_attr_err(attr_value);
1164
1165                 // AstFragmentKind::Expr requires the macro to emit an expression.
1166                 return self
1167                     .collect_attr(
1168                         attr,
1169                         vec![],
1170                         Annotatable::Expr(P(expr)),
1171                         AstFragmentKind::Expr,
1172                         after_derive,
1173                     )
1174                     .make_expr()
1175                     .into_inner();
1176             }
1177
1178             if let ast::ExprKind::MacCall(mac) = expr.kind {
1179                 self.check_attributes(&expr.attrs);
1180                 self.collect_bang(mac, expr.span, AstFragmentKind::Expr).make_expr().into_inner()
1181             } else {
1182                 ensure_sufficient_stack(|| noop_visit_expr(&mut expr, self));
1183                 expr
1184             }
1185         });
1186     }
1187
1188     fn flat_map_arm(&mut self, arm: ast::Arm) -> SmallVec<[ast::Arm; 1]> {
1189         let mut arm = configure!(self, arm);
1190
1191         let (attr, traits, after_derive) = self.classify_item(&mut arm);
1192         if attr.is_some() || !traits.is_empty() {
1193             return self
1194                 .collect_attr(
1195                     attr,
1196                     traits,
1197                     Annotatable::Arm(arm),
1198                     AstFragmentKind::Arms,
1199                     after_derive,
1200                 )
1201                 .make_arms();
1202         }
1203
1204         noop_flat_map_arm(arm, self)
1205     }
1206
1207     fn flat_map_field(&mut self, field: ast::Field) -> SmallVec<[ast::Field; 1]> {
1208         let mut field = configure!(self, field);
1209
1210         let (attr, traits, after_derive) = self.classify_item(&mut field);
1211         if attr.is_some() || !traits.is_empty() {
1212             return self
1213                 .collect_attr(
1214                     attr,
1215                     traits,
1216                     Annotatable::Field(field),
1217                     AstFragmentKind::Fields,
1218                     after_derive,
1219                 )
1220                 .make_fields();
1221         }
1222
1223         noop_flat_map_field(field, self)
1224     }
1225
1226     fn flat_map_field_pattern(&mut self, fp: ast::FieldPat) -> SmallVec<[ast::FieldPat; 1]> {
1227         let mut fp = configure!(self, fp);
1228
1229         let (attr, traits, after_derive) = self.classify_item(&mut fp);
1230         if attr.is_some() || !traits.is_empty() {
1231             return self
1232                 .collect_attr(
1233                     attr,
1234                     traits,
1235                     Annotatable::FieldPat(fp),
1236                     AstFragmentKind::FieldPats,
1237                     after_derive,
1238                 )
1239                 .make_field_patterns();
1240         }
1241
1242         noop_flat_map_field_pattern(fp, self)
1243     }
1244
1245     fn flat_map_param(&mut self, p: ast::Param) -> SmallVec<[ast::Param; 1]> {
1246         let mut p = configure!(self, p);
1247
1248         let (attr, traits, after_derive) = self.classify_item(&mut p);
1249         if attr.is_some() || !traits.is_empty() {
1250             return self
1251                 .collect_attr(
1252                     attr,
1253                     traits,
1254                     Annotatable::Param(p),
1255                     AstFragmentKind::Params,
1256                     after_derive,
1257                 )
1258                 .make_params();
1259         }
1260
1261         noop_flat_map_param(p, self)
1262     }
1263
1264     fn flat_map_struct_field(&mut self, sf: ast::StructField) -> SmallVec<[ast::StructField; 1]> {
1265         let mut sf = configure!(self, sf);
1266
1267         let (attr, traits, after_derive) = self.classify_item(&mut sf);
1268         if attr.is_some() || !traits.is_empty() {
1269             return self
1270                 .collect_attr(
1271                     attr,
1272                     traits,
1273                     Annotatable::StructField(sf),
1274                     AstFragmentKind::StructFields,
1275                     after_derive,
1276                 )
1277                 .make_struct_fields();
1278         }
1279
1280         noop_flat_map_struct_field(sf, self)
1281     }
1282
1283     fn flat_map_variant(&mut self, variant: ast::Variant) -> SmallVec<[ast::Variant; 1]> {
1284         let mut variant = configure!(self, variant);
1285
1286         let (attr, traits, after_derive) = self.classify_item(&mut variant);
1287         if attr.is_some() || !traits.is_empty() {
1288             return self
1289                 .collect_attr(
1290                     attr,
1291                     traits,
1292                     Annotatable::Variant(variant),
1293                     AstFragmentKind::Variants,
1294                     after_derive,
1295                 )
1296                 .make_variants();
1297         }
1298
1299         noop_flat_map_variant(variant, self)
1300     }
1301
1302     fn filter_map_expr(&mut self, expr: P<ast::Expr>) -> Option<P<ast::Expr>> {
1303         let expr = configure!(self, expr);
1304         expr.filter_map(|mut expr| {
1305             self.cfg.configure_expr_kind(&mut expr.kind);
1306
1307             // Ignore derives so they remain unused.
1308             let (attr, after_derive) = self.classify_nonitem(&mut expr);
1309
1310             if let Some(ref attr_value) = attr {
1311                 self.cfg.maybe_emit_expr_attr_err(attr_value);
1312
1313                 return self
1314                     .collect_attr(
1315                         attr,
1316                         vec![],
1317                         Annotatable::Expr(P(expr)),
1318                         AstFragmentKind::OptExpr,
1319                         after_derive,
1320                     )
1321                     .make_opt_expr()
1322                     .map(|expr| expr.into_inner());
1323             }
1324
1325             if let ast::ExprKind::MacCall(mac) = expr.kind {
1326                 self.check_attributes(&expr.attrs);
1327                 self.collect_bang(mac, expr.span, AstFragmentKind::OptExpr)
1328                     .make_opt_expr()
1329                     .map(|expr| expr.into_inner())
1330             } else {
1331                 Some({
1332                     noop_visit_expr(&mut expr, self);
1333                     expr
1334                 })
1335             }
1336         })
1337     }
1338
1339     fn visit_pat(&mut self, pat: &mut P<ast::Pat>) {
1340         self.cfg.configure_pat(pat);
1341         match pat.kind {
1342             PatKind::MacCall(_) => {}
1343             _ => return noop_visit_pat(pat, self),
1344         }
1345
1346         visit_clobber(pat, |mut pat| match mem::replace(&mut pat.kind, PatKind::Wild) {
1347             PatKind::MacCall(mac) => {
1348                 self.collect_bang(mac, pat.span, AstFragmentKind::Pat).make_pat()
1349             }
1350             _ => unreachable!(),
1351         });
1352     }
1353
1354     fn flat_map_stmt(&mut self, stmt: ast::Stmt) -> SmallVec<[ast::Stmt; 1]> {
1355         let mut stmt = configure!(self, stmt);
1356
1357         // we'll expand attributes on expressions separately
1358         if !stmt.is_expr() {
1359             let (attr, derives, after_derive) = if stmt.is_item() {
1360                 self.classify_item(&mut stmt)
1361             } else {
1362                 // ignore derives on non-item statements so it falls through
1363                 // to the unused-attributes lint
1364                 let (attr, after_derive) = self.classify_nonitem(&mut stmt);
1365                 (attr, vec![], after_derive)
1366             };
1367
1368             if attr.is_some() || !derives.is_empty() {
1369                 return self
1370                     .collect_attr(
1371                         attr,
1372                         derives,
1373                         Annotatable::Stmt(P(stmt)),
1374                         AstFragmentKind::Stmts,
1375                         after_derive,
1376                     )
1377                     .make_stmts();
1378             }
1379         }
1380
1381         if let StmtKind::MacCall(mac) = stmt.kind {
1382             let MacCallStmt { mac, style, attrs } = mac.into_inner();
1383             self.check_attributes(&attrs);
1384             let mut placeholder =
1385                 self.collect_bang(mac, stmt.span, AstFragmentKind::Stmts).make_stmts();
1386
1387             // If this is a macro invocation with a semicolon, then apply that
1388             // semicolon to the final statement produced by expansion.
1389             if style == MacStmtStyle::Semicolon {
1390                 if let Some(stmt) = placeholder.pop() {
1391                     placeholder.push(stmt.add_trailing_semicolon());
1392                 }
1393             }
1394
1395             return placeholder;
1396         }
1397
1398         // The placeholder expander gives ids to statements, so we avoid folding the id here.
1399         let ast::Stmt { id, kind, span, tokens } = stmt;
1400         noop_flat_map_stmt_kind(kind, self)
1401             .into_iter()
1402             .map(|kind| ast::Stmt { id, kind, span, tokens: tokens.clone() })
1403             .collect()
1404     }
1405
1406     fn visit_block(&mut self, block: &mut P<Block>) {
1407         let old_directory_ownership = self.cx.current_expansion.directory_ownership;
1408         self.cx.current_expansion.directory_ownership = DirectoryOwnership::UnownedViaBlock;
1409         noop_visit_block(block, self);
1410         self.cx.current_expansion.directory_ownership = old_directory_ownership;
1411     }
1412
1413     fn flat_map_item(&mut self, item: P<ast::Item>) -> SmallVec<[P<ast::Item>; 1]> {
1414         let mut item = configure!(self, item);
1415
1416         let (attr, traits, after_derive) = self.classify_item(&mut item);
1417         if attr.is_some() || !traits.is_empty() {
1418             return self
1419                 .collect_attr(
1420                     attr,
1421                     traits,
1422                     Annotatable::Item(item),
1423                     AstFragmentKind::Items,
1424                     after_derive,
1425                 )
1426                 .make_items();
1427         }
1428
1429         let mut attrs = mem::take(&mut item.attrs); // We do this to please borrowck.
1430         let ident = item.ident;
1431         let span = item.span;
1432
1433         match item.kind {
1434             ast::ItemKind::MacCall(..) => {
1435                 item.attrs = attrs;
1436                 self.check_attributes(&item.attrs);
1437                 item.and_then(|item| match item.kind {
1438                     ItemKind::MacCall(mac) => self
1439                         .collect(AstFragmentKind::Items, InvocationKind::Bang { mac, span })
1440                         .make_items(),
1441                     _ => unreachable!(),
1442                 })
1443             }
1444             ast::ItemKind::Mod(ref mut old_mod @ ast::Mod { .. }) if ident != Ident::invalid() => {
1445                 let sess = &self.cx.sess.parse_sess;
1446                 let orig_ownership = self.cx.current_expansion.directory_ownership;
1447                 let mut module = (*self.cx.current_expansion.module).clone();
1448
1449                 let pushed = &mut false; // Record `parse_external_mod` pushing so we can pop.
1450                 let dir = Directory { ownership: orig_ownership, path: module.directory };
1451                 let Directory { ownership, path } = if old_mod.inline {
1452                     // Inline `mod foo { ... }`, but we still need to push directories.
1453                     item.attrs = attrs;
1454                     push_directory(&self.cx.sess, ident, &item.attrs, dir)
1455                 } else {
1456                     // We have an outline `mod foo;` so we need to parse the file.
1457                     let (new_mod, dir) = parse_external_mod(
1458                         &self.cx.sess,
1459                         ident,
1460                         span,
1461                         old_mod.unsafety,
1462                         dir,
1463                         &mut attrs,
1464                         pushed,
1465                     );
1466
1467                     let krate = ast::Crate {
1468                         span: new_mod.inner,
1469                         module: new_mod,
1470                         attrs,
1471                         proc_macros: vec![],
1472                     };
1473                     if let Some(extern_mod_loaded) = self.cx.extern_mod_loaded {
1474                         extern_mod_loaded(&krate);
1475                     }
1476
1477                     *old_mod = krate.module;
1478                     item.attrs = krate.attrs;
1479                     // File can have inline attributes, e.g., `#![cfg(...)]` & co. => Reconfigure.
1480                     item = match self.configure(item) {
1481                         Some(node) => node,
1482                         None => {
1483                             if *pushed {
1484                                 sess.included_mod_stack.borrow_mut().pop();
1485                             }
1486                             return Default::default();
1487                         }
1488                     };
1489                     dir
1490                 };
1491
1492                 // Set the module info before we flat map.
1493                 self.cx.current_expansion.directory_ownership = ownership;
1494                 module.directory = path;
1495                 module.mod_path.push(ident);
1496                 let orig_module =
1497                     mem::replace(&mut self.cx.current_expansion.module, Rc::new(module));
1498
1499                 let result = noop_flat_map_item(item, self);
1500
1501                 // Restore the module info.
1502                 self.cx.current_expansion.module = orig_module;
1503                 self.cx.current_expansion.directory_ownership = orig_ownership;
1504                 if *pushed {
1505                     sess.included_mod_stack.borrow_mut().pop();
1506                 }
1507                 result
1508             }
1509             _ => {
1510                 item.attrs = attrs;
1511                 noop_flat_map_item(item, self)
1512             }
1513         }
1514     }
1515
1516     fn flat_map_trait_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
1517         let mut item = configure!(self, item);
1518
1519         let (attr, traits, after_derive) = self.classify_item(&mut item);
1520         if attr.is_some() || !traits.is_empty() {
1521             return self
1522                 .collect_attr(
1523                     attr,
1524                     traits,
1525                     Annotatable::TraitItem(item),
1526                     AstFragmentKind::TraitItems,
1527                     after_derive,
1528                 )
1529                 .make_trait_items();
1530         }
1531
1532         match item.kind {
1533             ast::AssocItemKind::MacCall(..) => {
1534                 self.check_attributes(&item.attrs);
1535                 item.and_then(|item| match item.kind {
1536                     ast::AssocItemKind::MacCall(mac) => self
1537                         .collect_bang(mac, item.span, AstFragmentKind::TraitItems)
1538                         .make_trait_items(),
1539                     _ => unreachable!(),
1540                 })
1541             }
1542             _ => noop_flat_map_assoc_item(item, self),
1543         }
1544     }
1545
1546     fn flat_map_impl_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
1547         let mut item = configure!(self, item);
1548
1549         let (attr, traits, after_derive) = self.classify_item(&mut item);
1550         if attr.is_some() || !traits.is_empty() {
1551             return self
1552                 .collect_attr(
1553                     attr,
1554                     traits,
1555                     Annotatable::ImplItem(item),
1556                     AstFragmentKind::ImplItems,
1557                     after_derive,
1558                 )
1559                 .make_impl_items();
1560         }
1561
1562         match item.kind {
1563             ast::AssocItemKind::MacCall(..) => {
1564                 self.check_attributes(&item.attrs);
1565                 item.and_then(|item| match item.kind {
1566                     ast::AssocItemKind::MacCall(mac) => self
1567                         .collect_bang(mac, item.span, AstFragmentKind::ImplItems)
1568                         .make_impl_items(),
1569                     _ => unreachable!(),
1570                 })
1571             }
1572             _ => noop_flat_map_assoc_item(item, self),
1573         }
1574     }
1575
1576     fn visit_ty(&mut self, ty: &mut P<ast::Ty>) {
1577         match ty.kind {
1578             ast::TyKind::MacCall(_) => {}
1579             _ => return noop_visit_ty(ty, self),
1580         };
1581
1582         visit_clobber(ty, |mut ty| match mem::replace(&mut ty.kind, ast::TyKind::Err) {
1583             ast::TyKind::MacCall(mac) => {
1584                 self.collect_bang(mac, ty.span, AstFragmentKind::Ty).make_ty()
1585             }
1586             _ => unreachable!(),
1587         });
1588     }
1589
1590     fn visit_foreign_mod(&mut self, foreign_mod: &mut ast::ForeignMod) {
1591         self.cfg.configure_foreign_mod(foreign_mod);
1592         noop_visit_foreign_mod(foreign_mod, self);
1593     }
1594
1595     fn flat_map_foreign_item(
1596         &mut self,
1597         mut foreign_item: P<ast::ForeignItem>,
1598     ) -> SmallVec<[P<ast::ForeignItem>; 1]> {
1599         let (attr, traits, after_derive) = self.classify_item(&mut foreign_item);
1600
1601         if attr.is_some() || !traits.is_empty() {
1602             return self
1603                 .collect_attr(
1604                     attr,
1605                     traits,
1606                     Annotatable::ForeignItem(foreign_item),
1607                     AstFragmentKind::ForeignItems,
1608                     after_derive,
1609                 )
1610                 .make_foreign_items();
1611         }
1612
1613         match foreign_item.kind {
1614             ast::ForeignItemKind::MacCall(..) => {
1615                 self.check_attributes(&foreign_item.attrs);
1616                 foreign_item.and_then(|item| match item.kind {
1617                     ast::ForeignItemKind::MacCall(mac) => self
1618                         .collect_bang(mac, item.span, AstFragmentKind::ForeignItems)
1619                         .make_foreign_items(),
1620                     _ => unreachable!(),
1621                 })
1622             }
1623             _ => noop_flat_map_foreign_item(foreign_item, self),
1624         }
1625     }
1626
1627     fn visit_item_kind(&mut self, item: &mut ast::ItemKind) {
1628         match item {
1629             ast::ItemKind::MacroDef(..) => {}
1630             _ => {
1631                 self.cfg.configure_item_kind(item);
1632                 noop_visit_item_kind(item, self);
1633             }
1634         }
1635     }
1636
1637     fn flat_map_generic_param(
1638         &mut self,
1639         param: ast::GenericParam,
1640     ) -> SmallVec<[ast::GenericParam; 1]> {
1641         let mut param = configure!(self, param);
1642
1643         let (attr, traits, after_derive) = self.classify_item(&mut param);
1644         if attr.is_some() || !traits.is_empty() {
1645             return self
1646                 .collect_attr(
1647                     attr,
1648                     traits,
1649                     Annotatable::GenericParam(param),
1650                     AstFragmentKind::GenericParams,
1651                     after_derive,
1652                 )
1653                 .make_generic_params();
1654         }
1655
1656         noop_flat_map_generic_param(param, self)
1657     }
1658
1659     fn visit_attribute(&mut self, at: &mut ast::Attribute) {
1660         // turn `#[doc(include="filename")]` attributes into `#[doc(include(file="filename",
1661         // contents="file contents")]` attributes
1662         if !self.cx.sess.check_name(at, sym::doc) {
1663             return noop_visit_attribute(at, self);
1664         }
1665
1666         if let Some(list) = at.meta_item_list() {
1667             if !list.iter().any(|it| it.has_name(sym::include)) {
1668                 return noop_visit_attribute(at, self);
1669             }
1670
1671             let mut items = vec![];
1672
1673             for mut it in list {
1674                 if !it.has_name(sym::include) {
1675                     items.push({
1676                         noop_visit_meta_list_item(&mut it, self);
1677                         it
1678                     });
1679                     continue;
1680                 }
1681
1682                 if let Some(file) = it.value_str() {
1683                     let err_count = self.cx.sess.parse_sess.span_diagnostic.err_count();
1684                     self.check_attributes(slice::from_ref(at));
1685                     if self.cx.sess.parse_sess.span_diagnostic.err_count() > err_count {
1686                         // avoid loading the file if they haven't enabled the feature
1687                         return noop_visit_attribute(at, self);
1688                     }
1689
1690                     let filename = match self.cx.resolve_path(&*file.as_str(), it.span()) {
1691                         Ok(filename) => filename,
1692                         Err(mut err) => {
1693                             err.emit();
1694                             continue;
1695                         }
1696                     };
1697
1698                     match self.cx.source_map().load_file(&filename) {
1699                         Ok(source_file) => {
1700                             let src = source_file
1701                                 .src
1702                                 .as_ref()
1703                                 .expect("freshly loaded file should have a source");
1704                             let src_interned = Symbol::intern(src.as_str());
1705
1706                             let include_info = vec![
1707                                 ast::NestedMetaItem::MetaItem(attr::mk_name_value_item_str(
1708                                     Ident::with_dummy_span(sym::file),
1709                                     file,
1710                                     DUMMY_SP,
1711                                 )),
1712                                 ast::NestedMetaItem::MetaItem(attr::mk_name_value_item_str(
1713                                     Ident::with_dummy_span(sym::contents),
1714                                     src_interned,
1715                                     DUMMY_SP,
1716                                 )),
1717                             ];
1718
1719                             let include_ident = Ident::with_dummy_span(sym::include);
1720                             let item = attr::mk_list_item(include_ident, include_info);
1721                             items.push(ast::NestedMetaItem::MetaItem(item));
1722                         }
1723                         Err(e) => {
1724                             let lit =
1725                                 it.meta_item().and_then(|item| item.name_value_literal()).unwrap();
1726
1727                             if e.kind() == ErrorKind::InvalidData {
1728                                 self.cx
1729                                     .struct_span_err(
1730                                         lit.span,
1731                                         &format!("{} wasn't a utf-8 file", filename.display()),
1732                                     )
1733                                     .span_label(lit.span, "contains invalid utf-8")
1734                                     .emit();
1735                             } else {
1736                                 let mut err = self.cx.struct_span_err(
1737                                     lit.span,
1738                                     &format!("couldn't read {}: {}", filename.display(), e),
1739                                 );
1740                                 err.span_label(lit.span, "couldn't read file");
1741
1742                                 err.emit();
1743                             }
1744                         }
1745                     }
1746                 } else {
1747                     let mut err = self
1748                         .cx
1749                         .struct_span_err(it.span(), "expected path to external documentation");
1750
1751                     // Check if the user erroneously used `doc(include(...))` syntax.
1752                     let literal = it.meta_item_list().and_then(|list| {
1753                         if list.len() == 1 {
1754                             list[0].literal().map(|literal| &literal.kind)
1755                         } else {
1756                             None
1757                         }
1758                     });
1759
1760                     let (path, applicability) = match &literal {
1761                         Some(LitKind::Str(path, ..)) => {
1762                             (path.to_string(), Applicability::MachineApplicable)
1763                         }
1764                         _ => (String::from("<path>"), Applicability::HasPlaceholders),
1765                     };
1766
1767                     err.span_suggestion(
1768                         it.span(),
1769                         "provide a file path with `=`",
1770                         format!("include = \"{}\"", path),
1771                         applicability,
1772                     );
1773
1774                     err.emit();
1775                 }
1776             }
1777
1778             let meta = attr::mk_list_item(Ident::with_dummy_span(sym::doc), items);
1779             *at = ast::Attribute {
1780                 kind: ast::AttrKind::Normal(AttrItem {
1781                     path: meta.path,
1782                     args: meta.kind.mac_args(meta.span),
1783                     tokens: None,
1784                 }),
1785                 span: at.span,
1786                 id: at.id,
1787                 style: at.style,
1788             };
1789         } else {
1790             noop_visit_attribute(at, self)
1791         }
1792     }
1793
1794     fn visit_id(&mut self, id: &mut ast::NodeId) {
1795         if self.monotonic {
1796             debug_assert_eq!(*id, ast::DUMMY_NODE_ID);
1797             *id = self.cx.resolver.next_node_id()
1798         }
1799     }
1800
1801     fn visit_fn_decl(&mut self, mut fn_decl: &mut P<ast::FnDecl>) {
1802         self.cfg.configure_fn_decl(&mut fn_decl);
1803         noop_visit_fn_decl(fn_decl, self);
1804     }
1805 }
1806
1807 pub struct ExpansionConfig<'feat> {
1808     pub crate_name: String,
1809     pub features: Option<&'feat Features>,
1810     pub recursion_limit: Limit,
1811     pub trace_mac: bool,
1812     pub should_test: bool, // If false, strip `#[test]` nodes
1813     pub keep_macs: bool,
1814     pub span_debug: bool, // If true, use verbose debugging for `proc_macro::Span`
1815     pub proc_macro_backtrace: bool, // If true, show backtraces for proc-macro panics
1816 }
1817
1818 impl<'feat> ExpansionConfig<'feat> {
1819     pub fn default(crate_name: String) -> ExpansionConfig<'static> {
1820         ExpansionConfig {
1821             crate_name,
1822             features: None,
1823             recursion_limit: Limit::new(1024),
1824             trace_mac: false,
1825             should_test: false,
1826             keep_macs: false,
1827             span_debug: false,
1828             proc_macro_backtrace: false,
1829         }
1830     }
1831
1832     fn proc_macro_hygiene(&self) -> bool {
1833         self.features.map_or(false, |features| features.proc_macro_hygiene)
1834     }
1835     fn custom_inner_attributes(&self) -> bool {
1836         self.features.map_or(false, |features| features.custom_inner_attributes)
1837     }
1838 }