src/librustc_expand/expand.rs

   1 use crate::base::*;
   2 use crate::config::StripUnconfigured;
   3 use crate::configure;
   4 use crate::hygiene::{ExpnData, ExpnId, 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::ast::{self, AttrItem, Block, LitKind, NodeId, PatKind, Path};
  11 use rustc_ast::ast::{ItemKind, MacArgs, MacStmtStyle, StmtKind};
  12 use rustc_ast::mut_visit::*;
  13 use rustc_ast::ptr::P;
  14 use rustc_ast::token;
  15 use rustc_ast::tokenstream::TokenStream;
  16 use rustc_ast::visit::{self, AssocCtxt, Visitor};
  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_errors::{Applicability, PResult};
  21 use rustc_feature::Features;
  22 use rustc_parse::parser::Parser;
  23 use rustc_parse::validate_attr;
  24 use rustc_session::lint::builtin::UNUSED_DOC_COMMENTS;
  25 use rustc_session::lint::BuiltinLintDiagnostics;
  26 use rustc_session::parse::{feature_err, ParseSess};
  27 use rustc_span::source_map::respan;
  28 use rustc_span::symbol::{sym, Ident, Symbol};
  29 use rustc_span::{FileName, Span, DUMMY_SP};
  30
  31 use smallvec::{smallvec, SmallVec};
  32 use std::io::ErrorKind;
  33 use std::ops::DerefMut;
  34 use std::path::PathBuf;
  35 use std::rc::Rc;
  36 use std::{iter, mem, slice};
  37
  38 macro_rules! ast_fragments {
  39     (
  40         $($Kind:ident($AstTy:ty) {
  41             $kind_name:expr;
  42             $(one fn $mut_visit_ast:ident; fn $visit_ast:ident;)?
  43             $(many fn $flat_map_ast_elt:ident; fn $visit_ast_elt:ident($($args:tt)*);)?
  44             fn $make_ast:ident;
  45         })*
  46     ) => {
  47         /// A fragment of AST that can be produced by a single macro expansion.
  48         /// Can also serve as an input and intermediate result for macro expansion operations.
  49         pub enum AstFragment {
  50             OptExpr(Option<P<ast::Expr>>),
  51             $($Kind($AstTy),)*
  52         }
  53
  54         /// "Discriminant" of an AST fragment.
  55         #[derive(Copy, Clone, PartialEq, Eq)]
  56         pub enum AstFragmentKind {
  57             OptExpr,
  58             $($Kind,)*
  59         }
  60
  61         impl AstFragmentKind {
  62             pub fn name(self) -> &'static str {
  63                 match self {
  64                     AstFragmentKind::OptExpr => "expression",
  65                     $(AstFragmentKind::$Kind => $kind_name,)*
  66                 }
  67             }
  68
  69             fn make_from<'a>(self, result: Box<dyn MacResult + 'a>) -> Option<AstFragment> {
  70                 match self {
  71                     AstFragmentKind::OptExpr =>
  72                         result.make_expr().map(Some).map(AstFragment::OptExpr),
  73                     $(AstFragmentKind::$Kind => result.$make_ast().map(AstFragment::$Kind),)*
  74                 }
  75             }
  76         }
  77
  78         impl AstFragment {
  79             pub fn add_placeholders(&mut self, placeholders: &[NodeId]) {
  80                 if placeholders.is_empty() {
  81                     return;
  82                 }
  83                 match self {
  84                     $($(AstFragment::$Kind(ast) => ast.extend(placeholders.iter().flat_map(|id| {
  85                         // We are repeating through arguments with `many`, to do that we have to
  86                         // mention some macro variable from those arguments even if it's not used.
  87                         macro _repeating($flat_map_ast_elt) {}
  88                         placeholder(AstFragmentKind::$Kind, *id, None).$make_ast()
  89                     })),)?)*
  90                     _ => panic!("unexpected AST fragment kind")
  91                 }
  92             }
  93
  94             pub fn make_opt_expr(self) -> Option<P<ast::Expr>> {
  95                 match self {
  96                     AstFragment::OptExpr(expr) => expr,
  97                     _ => panic!("AstFragment::make_* called on the wrong kind of fragment"),
  98                 }
  99             }
 100
 101             $(pub fn $make_ast(self) -> $AstTy {
 102                 match self {
 103                     AstFragment::$Kind(ast) => ast,
 104                     _ => panic!("AstFragment::make_* called on the wrong kind of fragment"),
 105                 }
 106             })*
 107
 108             pub fn mut_visit_with<F: MutVisitor>(&mut self, vis: &mut F) {
 109                 match self {
 110                     AstFragment::OptExpr(opt_expr) => {
 111                         visit_clobber(opt_expr, |opt_expr| {
 112                             if let Some(expr) = opt_expr {
 113                                 vis.filter_map_expr(expr)
 114                             } else {
 115                                 None
 116                             }
 117                         });
 118                     }
 119                     $($(AstFragment::$Kind(ast) => vis.$mut_visit_ast(ast),)?)*
 120                     $($(AstFragment::$Kind(ast) =>
 121                         ast.flat_map_in_place(|ast| vis.$flat_map_ast_elt(ast)),)?)*
 122                 }
 123             }
 124
 125             pub fn visit_with<'a, V: Visitor<'a>>(&'a self, visitor: &mut V) {
 126                 match *self {
 127                     AstFragment::OptExpr(Some(ref expr)) => visitor.visit_expr(expr),
 128                     AstFragment::OptExpr(None) => {}
 129                     $($(AstFragment::$Kind(ref ast) => visitor.$visit_ast(ast),)?)*
 130                     $($(AstFragment::$Kind(ref ast) => for ast_elt in &ast[..] {
 131                         visitor.$visit_ast_elt(ast_elt, $($args)*);
 132                     })?)*
 133                 }
 134             }
 135         }
 136
 137         impl<'a> MacResult for crate::mbe::macro_rules::ParserAnyMacro<'a> {
 138             $(fn $make_ast(self: Box<crate::mbe::macro_rules::ParserAnyMacro<'a>>)
 139                            -> Option<$AstTy> {
 140                 Some(self.make(AstFragmentKind::$Kind).$make_ast())
 141             })*
 142         }
 143     }
 144 }
 145
 146 ast_fragments! {
 147     Expr(P<ast::Expr>) { "expression"; one fn visit_expr; fn visit_expr; fn make_expr; }
 148     Pat(P<ast::Pat>) { "pattern"; one fn visit_pat; fn visit_pat; fn make_pat; }
 149     Ty(P<ast::Ty>) { "type"; one fn visit_ty; fn visit_ty; fn make_ty; }
 150     Stmts(SmallVec<[ast::Stmt; 1]>) {
 151         "statement"; many fn flat_map_stmt; fn visit_stmt(); fn make_stmts;
 152     }
 153     Items(SmallVec<[P<ast::Item>; 1]>) {
 154         "item"; many fn flat_map_item; fn visit_item(); fn make_items;
 155     }
 156     TraitItems(SmallVec<[P<ast::AssocItem>; 1]>) {
 157         "trait item";
 158         many fn flat_map_trait_item;
 159         fn visit_assoc_item(AssocCtxt::Trait);
 160         fn make_trait_items;
 161     }
 162     ImplItems(SmallVec<[P<ast::AssocItem>; 1]>) {
 163         "impl item";
 164         many fn flat_map_impl_item;
 165         fn visit_assoc_item(AssocCtxt::Impl);
 166         fn make_impl_items;
 167     }
 168     ForeignItems(SmallVec<[P<ast::ForeignItem>; 1]>) {
 169         "foreign item";
 170         many fn flat_map_foreign_item;
 171         fn visit_foreign_item();
 172         fn make_foreign_items;
 173     }
 174     Arms(SmallVec<[ast::Arm; 1]>) {
 175         "match arm"; many fn flat_map_arm; fn visit_arm(); fn make_arms;
 176     }
 177     Fields(SmallVec<[ast::Field; 1]>) {
 178         "field expression"; many fn flat_map_field; fn visit_field(); fn make_fields;
 179     }
 180     FieldPats(SmallVec<[ast::FieldPat; 1]>) {
 181         "field pattern";
 182         many fn flat_map_field_pattern;
 183         fn visit_field_pattern();
 184         fn make_field_patterns;
 185     }
 186     GenericParams(SmallVec<[ast::GenericParam; 1]>) {
 187         "generic parameter";
 188         many fn flat_map_generic_param;
 189         fn visit_generic_param();
 190         fn make_generic_params;
 191     }
 192     Params(SmallVec<[ast::Param; 1]>) {
 193         "function parameter"; many fn flat_map_param; fn visit_param(); fn make_params;
 194     }
 195     StructFields(SmallVec<[ast::StructField; 1]>) {
 196         "field";
 197         many fn flat_map_struct_field;
 198         fn visit_struct_field();
 199         fn make_struct_fields;
 200     }
 201     Variants(SmallVec<[ast::Variant; 1]>) {
 202         "variant"; many fn flat_map_variant; fn visit_variant(); fn make_variants;
 203     }
 204 }
 205
 206 impl AstFragmentKind {
 207     crate fn dummy(self, span: Span) -> AstFragment {
 208         self.make_from(DummyResult::any(span)).expect("couldn't create a dummy AST fragment")
 209     }
 210
 211     fn expect_from_annotatables<I: IntoIterator<Item = Annotatable>>(
 212         self,
 213         items: I,
 214     ) -> AstFragment {
 215         let mut items = items.into_iter();
 216         match self {
 217             AstFragmentKind::Arms => {
 218                 AstFragment::Arms(items.map(Annotatable::expect_arm).collect())
 219             }
 220             AstFragmentKind::Fields => {
 221                 AstFragment::Fields(items.map(Annotatable::expect_field).collect())
 222             }
 223             AstFragmentKind::FieldPats => {
 224                 AstFragment::FieldPats(items.map(Annotatable::expect_field_pattern).collect())
 225             }
 226             AstFragmentKind::GenericParams => {
 227                 AstFragment::GenericParams(items.map(Annotatable::expect_generic_param).collect())
 228             }
 229             AstFragmentKind::Params => {
 230                 AstFragment::Params(items.map(Annotatable::expect_param).collect())
 231             }
 232             AstFragmentKind::StructFields => {
 233                 AstFragment::StructFields(items.map(Annotatable::expect_struct_field).collect())
 234             }
 235             AstFragmentKind::Variants => {
 236                 AstFragment::Variants(items.map(Annotatable::expect_variant).collect())
 237             }
 238             AstFragmentKind::Items => {
 239                 AstFragment::Items(items.map(Annotatable::expect_item).collect())
 240             }
 241             AstFragmentKind::ImplItems => {
 242                 AstFragment::ImplItems(items.map(Annotatable::expect_impl_item).collect())
 243             }
 244             AstFragmentKind::TraitItems => {
 245                 AstFragment::TraitItems(items.map(Annotatable::expect_trait_item).collect())
 246             }
 247             AstFragmentKind::ForeignItems => {
 248                 AstFragment::ForeignItems(items.map(Annotatable::expect_foreign_item).collect())
 249             }
 250             AstFragmentKind::Stmts => {
 251                 AstFragment::Stmts(items.map(Annotatable::expect_stmt).collect())
 252             }
 253             AstFragmentKind::Expr => AstFragment::Expr(
 254                 items.next().expect("expected exactly one expression").expect_expr(),
 255             ),
 256             AstFragmentKind::OptExpr => {
 257                 AstFragment::OptExpr(items.next().map(Annotatable::expect_expr))
 258             }
 259             AstFragmentKind::Pat | AstFragmentKind::Ty => {
 260                 panic!("patterns and types aren't annotatable")
 261             }
 262         }
 263     }
 264 }
 265
 266 pub struct Invocation {
 267     pub kind: InvocationKind,
 268     pub fragment_kind: AstFragmentKind,
 269     pub expansion_data: ExpansionData,
 270 }
 271
 272 pub enum InvocationKind {
 273     Bang {
 274         mac: ast::MacCall,
 275         span: Span,
 276     },
 277     Attr {
 278         attr: ast::Attribute,
 279         item: Annotatable,
 280         // Required for resolving derive helper attributes.
 281         derives: Vec<Path>,
 282         // We temporarily report errors for attribute macros placed after derives
 283         after_derive: bool,
 284     },
 285     Derive {
 286         path: Path,
 287         item: Annotatable,
 288     },
 289     /// "Invocation" that contains all derives from an item,
 290     /// broken into multiple `Derive` invocations when expanded.
 291     /// FIXME: Find a way to remove it.
 292     DeriveContainer {
 293         derives: Vec<Path>,
 294         item: Annotatable,
 295     },
 296 }
 297
 298 impl InvocationKind {
 299     fn placeholder_visibility(&self) -> Option<ast::Visibility> {
 300         // HACK: For unnamed fields placeholders should have the same visibility as the actual
 301         // fields because for tuple structs/variants resolve determines visibilities of their
 302         // constructor using these field visibilities before attributes on them are are expanded.
 303         // The assumption is that the attribute expansion cannot change field visibilities,
 304         // and it holds because only inert attributes are supported in this position.
 305         match self {
 306             InvocationKind::Attr { item: Annotatable::StructField(field), .. }
 307             | InvocationKind::Derive { item: Annotatable::StructField(field), .. }
 308             | InvocationKind::DeriveContainer { item: Annotatable::StructField(field), .. }
 309                 if field.ident.is_none() =>
 310             {
 311                 Some(field.vis.clone())
 312             }
 313             _ => None,
 314         }
 315     }
 316 }
 317
 318 impl Invocation {
 319     pub fn span(&self) -> Span {
 320         match &self.kind {
 321             InvocationKind::Bang { span, .. } => *span,
 322             InvocationKind::Attr { attr, .. } => attr.span,
 323             InvocationKind::Derive { path, .. } => path.span,
 324             InvocationKind::DeriveContainer { item, .. } => item.span(),
 325         }
 326     }
 327 }
 328
 329 pub struct MacroExpander<'a, 'b> {
 330     pub cx: &'a mut ExtCtxt<'b>,
 331     monotonic: bool, // cf. `cx.monotonic_expander()`
 332 }
 333
 334 impl<'a, 'b> MacroExpander<'a, 'b> {
 335     pub fn new(cx: &'a mut ExtCtxt<'b>, monotonic: bool) -> Self {
 336         MacroExpander { cx, monotonic }
 337     }
 338
 339     pub fn expand_crate(&mut self, mut krate: ast::Crate) -> ast::Crate {
 340         let mut module = ModuleData {
 341             mod_path: vec![Ident::from_str(&self.cx.ecfg.crate_name)],
 342             directory: match self.cx.source_map().span_to_unmapped_path(krate.span) {
 343                 FileName::Real(path) => path,
 344                 other => PathBuf::from(other.to_string()),
 345             },
 346         };
 347         module.directory.pop();
 348         self.cx.root_path = module.directory.clone();
 349         self.cx.current_expansion.module = Rc::new(module);
 350
 351         let orig_mod_span = krate.module.inner;
 352
 353         let krate_item = AstFragment::Items(smallvec![P(ast::Item {
 354             attrs: krate.attrs,
 355             span: krate.span,
 356             kind: ast::ItemKind::Mod(krate.module),
 357             ident: Ident::invalid(),
 358             id: ast::DUMMY_NODE_ID,
 359             vis: respan(krate.span.shrink_to_lo(), ast::VisibilityKind::Public),
 360             tokens: None,
 361         })]);
 362
 363         match self.fully_expand_fragment(krate_item).make_items().pop().map(P::into_inner) {
 364             Some(ast::Item { attrs, kind: ast::ItemKind::Mod(module), .. }) => {
 365                 krate.attrs = attrs;
 366                 krate.module = module;
 367             }
 368             None => {
 369                 // Resolution failed so we return an empty expansion
 370                 krate.attrs = vec![];
 371                 krate.module = ast::Mod { inner: orig_mod_span, items: vec![], inline: true };
 372             }
 373             Some(ast::Item { span, kind, .. }) => {
 374                 krate.attrs = vec![];
 375                 krate.module = ast::Mod { inner: orig_mod_span, items: vec![], inline: true };
 376                 self.cx.span_err(
 377                     span,
 378                     &format!(
 379                         "expected crate top-level item to be a module after macro expansion, found {} {}",
 380                         kind.article(), kind.descr()
 381                     ),
 382                 );
 383             }
 384         };
 385         self.cx.trace_macros_diag();
 386         krate
 387     }
 388
 389     // Recursively expand all macro invocations in this AST fragment.
 390     pub fn fully_expand_fragment(&mut self, input_fragment: AstFragment) -> AstFragment {
 391         let orig_expansion_data = self.cx.current_expansion.clone();
 392         self.cx.current_expansion.depth = 0;
 393
 394         // Collect all macro invocations and replace them with placeholders.
 395         let (mut fragment_with_placeholders, mut invocations) =
 396             self.collect_invocations(input_fragment, &[]);
 397
 398         // Optimization: if we resolve all imports now,
 399         // we'll be able to immediately resolve most of imported macros.
 400         self.resolve_imports();
 401
 402         // Resolve paths in all invocations and produce output expanded fragments for them, but
 403         // do not insert them into our input AST fragment yet, only store in `expanded_fragments`.
 404         // The output fragments also go through expansion recursively until no invocations are left.
 405         // Unresolved macros produce dummy outputs as a recovery measure.
 406         invocations.reverse();
 407         let mut expanded_fragments = Vec::new();
 408         let mut undetermined_invocations = Vec::new();
 409         let (mut progress, mut force) = (false, !self.monotonic);
 410         loop {
 411             let (invoc, res) = if let Some(invoc) = invocations.pop() {
 412                 invoc
 413             } else {
 414                 self.resolve_imports();
 415                 if undetermined_invocations.is_empty() {
 416                     break;
 417                 }
 418                 invocations = mem::take(&mut undetermined_invocations);
 419                 force = !mem::replace(&mut progress, false);
 420                 continue;
 421             };
 422
 423             let res = match res {
 424                 Some(res) => res,
 425                 None => {
 426                     let eager_expansion_root = if self.monotonic {
 427                         invoc.expansion_data.id
 428                     } else {
 429                         orig_expansion_data.id
 430                     };
 431                     match self.cx.resolver.resolve_macro_invocation(
 432                         &invoc,
 433                         eager_expansion_root,
 434                         force,
 435                     ) {
 436                         Ok(res) => res,
 437                         Err(Indeterminate) => {
 438                             // Cannot resolve, will retry this invocation later.
 439                             undetermined_invocations.push((invoc, None));
 440                             continue;
 441                         }
 442                     }
 443                 }
 444             };
 445
 446             let ExpansionData { depth, id: expn_id, .. } = invoc.expansion_data;
 447             self.cx.current_expansion = invoc.expansion_data.clone();
 448
 449             // FIXME(jseyfried): Refactor out the following logic
 450             let (expanded_fragment, new_invocations) = match res {
 451                 InvocationRes::Single(ext) => match self.expand_invoc(invoc, &ext.kind) {
 452                     ExpandResult::Ready(fragment) => self.collect_invocations(fragment, &[]),
 453                     ExpandResult::Retry(invoc, explanation) => {
 454                         if force {
 455                             // We are stuck, stop retrying and produce a dummy fragment.
 456                             let span = invoc.span();
 457                             self.cx.span_err(span, &explanation);
 458                             let fragment = invoc.fragment_kind.dummy(span);
 459                             self.collect_invocations(fragment, &[])
 460                         } else {
 461                             // Cannot expand, will retry this invocation later.
 462                             undetermined_invocations
 463                                 .push((invoc, Some(InvocationRes::Single(ext))));
 464                             continue;
 465                         }
 466                     }
 467                 },
 468                 InvocationRes::DeriveContainer(_exts) => {
 469                     // FIXME: Consider using the derive resolutions (`_exts`) immediately,
 470                     // instead of enqueuing the derives to be resolved again later.
 471                     let (derives, item) = match invoc.kind {
 472                         InvocationKind::DeriveContainer { derives, item } => (derives, item),
 473                         _ => unreachable!(),
 474                     };
 475                     if !item.derive_allowed() {
 476                         self.error_derive_forbidden_on_non_adt(&derives, &item);
 477                     }
 478
 479                     let mut item = self.fully_configure(item);
 480                     item.visit_attrs(|attrs| attrs.retain(|a| !a.has_name(sym::derive)));
 481
 482                     let mut derive_placeholders = Vec::with_capacity(derives.len());
 483                     invocations.reserve(derives.len());
 484                     for path in derives {
 485                         let expn_id = ExpnId::fresh(None);
 486                         derive_placeholders.push(NodeId::placeholder_from_expn_id(expn_id));
 487                         invocations.push((
 488                             Invocation {
 489                                 kind: InvocationKind::Derive { path, item: item.clone() },
 490                                 fragment_kind: invoc.fragment_kind,
 491                                 expansion_data: ExpansionData {
 492                                     id: expn_id,
 493                                     ..invoc.expansion_data.clone()
 494                                 },
 495                             },
 496                             None,
 497                         ));
 498                     }
 499                     let fragment =
 500                         invoc.fragment_kind.expect_from_annotatables(::std::iter::once(item));
 501                     self.collect_invocations(fragment, &derive_placeholders)
 502                 }
 503             };
 504
 505             progress = true;
 506             if expanded_fragments.len() < depth {
 507                 expanded_fragments.push(Vec::new());
 508             }
 509             expanded_fragments[depth - 1].push((expn_id, expanded_fragment));
 510             invocations.extend(new_invocations.into_iter().rev());
 511         }
 512
 513         self.cx.current_expansion = orig_expansion_data;
 514
 515         // Finally incorporate all the expanded macros into the input AST fragment.
 516         let mut placeholder_expander = PlaceholderExpander::new(self.cx, self.monotonic);
 517         while let Some(expanded_fragments) = expanded_fragments.pop() {
 518             for (expn_id, expanded_fragment) in expanded_fragments.into_iter().rev() {
 519                 placeholder_expander
 520                     .add(NodeId::placeholder_from_expn_id(expn_id), expanded_fragment);
 521             }
 522         }
 523         fragment_with_placeholders.mut_visit_with(&mut placeholder_expander);
 524         fragment_with_placeholders
 525     }
 526
 527     fn error_derive_forbidden_on_non_adt(&self, derives: &[Path], item: &Annotatable) {
 528         let attr = attr::find_by_name(item.attrs(), sym::derive);
 529         let span = attr.map_or(item.span(), |attr| attr.span);
 530         let mut err = self
 531             .cx
 532             .struct_span_err(span, "`derive` may only be applied to structs, enums and unions");
 533         if let Some(ast::Attribute { style: ast::AttrStyle::Inner, .. }) = attr {
 534             let trait_list = derives.iter().map(|t| pprust::path_to_string(t)).collect::<Vec<_>>();
 535             let suggestion = format!("#[derive({})]", trait_list.join(", "));
 536             err.span_suggestion(
 537                 span,
 538                 "try an outer attribute",
 539                 suggestion,
 540                 // We don't 𝑘𝑛𝑜𝑤 that the following item is an ADT
 541                 Applicability::MaybeIncorrect,
 542             );
 543         }
 544         err.emit();
 545     }
 546
 547     fn resolve_imports(&mut self) {
 548         if self.monotonic {
 549             self.cx.resolver.resolve_imports();
 550         }
 551     }
 552
 553     /// Collects all macro invocations reachable at this time in this AST fragment, and replace
 554     /// them with "placeholders" - dummy macro invocations with specially crafted `NodeId`s.
 555     /// Then call into resolver that builds a skeleton ("reduced graph") of the fragment and
 556     /// prepares data for resolving paths of macro invocations.
 557     fn collect_invocations(
 558         &mut self,
 559         mut fragment: AstFragment,
 560         extra_placeholders: &[NodeId],
 561     ) -> (AstFragment, Vec<(Invocation, Option<InvocationRes>)>) {
 562         // Resolve `$crate`s in the fragment for pretty-printing.
 563         self.cx.resolver.resolve_dollar_crates();
 564
 565         let invocations = {
 566             let mut collector = InvocationCollector {
 567                 cfg: StripUnconfigured {
 568                     sess: self.cx.parse_sess,
 569                     features: self.cx.ecfg.features,
 570                 },
 571                 cx: self.cx,
 572                 invocations: Vec::new(),
 573                 monotonic: self.monotonic,
 574             };
 575             fragment.mut_visit_with(&mut collector);
 576             fragment.add_placeholders(extra_placeholders);
 577             collector.invocations
 578         };
 579
 580         if self.monotonic {
 581             self.cx
 582                 .resolver
 583                 .visit_ast_fragment_with_placeholders(self.cx.current_expansion.id, &fragment);
 584         }
 585
 586         (fragment, invocations)
 587     }
 588
 589     fn fully_configure(&mut self, item: Annotatable) -> Annotatable {
 590         let mut cfg =
 591             StripUnconfigured { sess: self.cx.parse_sess, features: self.cx.ecfg.features };
 592         // Since the item itself has already been configured by the InvocationCollector,
 593         // we know that fold result vector will contain exactly one element
 594         match item {
 595             Annotatable::Item(item) => Annotatable::Item(cfg.flat_map_item(item).pop().unwrap()),
 596             Annotatable::TraitItem(item) => {
 597                 Annotatable::TraitItem(cfg.flat_map_trait_item(item).pop().unwrap())
 598             }
 599             Annotatable::ImplItem(item) => {
 600                 Annotatable::ImplItem(cfg.flat_map_impl_item(item).pop().unwrap())
 601             }
 602             Annotatable::ForeignItem(item) => {
 603                 Annotatable::ForeignItem(cfg.flat_map_foreign_item(item).pop().unwrap())
 604             }
 605             Annotatable::Stmt(stmt) => {
 606                 Annotatable::Stmt(stmt.map(|stmt| cfg.flat_map_stmt(stmt).pop().unwrap()))
 607             }
 608             Annotatable::Expr(mut expr) => Annotatable::Expr({
 609                 cfg.visit_expr(&mut expr);
 610                 expr
 611             }),
 612             Annotatable::Arm(arm) => Annotatable::Arm(cfg.flat_map_arm(arm).pop().unwrap()),
 613             Annotatable::Field(field) => {
 614                 Annotatable::Field(cfg.flat_map_field(field).pop().unwrap())
 615             }
 616             Annotatable::FieldPat(fp) => {
 617                 Annotatable::FieldPat(cfg.flat_map_field_pattern(fp).pop().unwrap())
 618             }
 619             Annotatable::GenericParam(param) => {
 620                 Annotatable::GenericParam(cfg.flat_map_generic_param(param).pop().unwrap())
 621             }
 622             Annotatable::Param(param) => {
 623                 Annotatable::Param(cfg.flat_map_param(param).pop().unwrap())
 624             }
 625             Annotatable::StructField(sf) => {
 626                 Annotatable::StructField(cfg.flat_map_struct_field(sf).pop().unwrap())
 627             }
 628             Annotatable::Variant(v) => Annotatable::Variant(cfg.flat_map_variant(v).pop().unwrap()),
 629         }
 630     }
 631
 632     fn error_recursion_limit_reached(&mut self) {
 633         let expn_data = self.cx.current_expansion.id.expn_data();
 634         let suggested_limit = self.cx.ecfg.recursion_limit * 2;
 635         self.cx
 636             .struct_span_err(
 637                 expn_data.call_site,
 638                 &format!("recursion limit reached while expanding `{}`", expn_data.kind.descr()),
 639             )
 640             .help(&format!(
 641                 "consider adding a `#![recursion_limit=\"{}\"]` attribute to your crate (`{}`)",
 642                 suggested_limit, self.cx.ecfg.crate_name,
 643             ))
 644             .emit();
 645         self.cx.trace_macros_diag();
 646     }
 647
 648     /// A macro's expansion does not fit in this fragment kind.
 649     /// For example, a non-type macro in a type position.
 650     fn error_wrong_fragment_kind(&mut self, kind: AstFragmentKind, mac: &ast::MacCall, span: Span) {
 651         let msg = format!(
 652             "non-{kind} macro in {kind} position: {path}",
 653             kind = kind.name(),
 654             path = pprust::path_to_string(&mac.path),
 655         );
 656         self.cx.span_err(span, &msg);
 657         self.cx.trace_macros_diag();
 658     }
 659
 660     fn expand_invoc(
 661         &mut self,
 662         invoc: Invocation,
 663         ext: &SyntaxExtensionKind,
 664     ) -> ExpandResult<AstFragment, Invocation> {
 665         let recursion_limit =
 666             self.cx.reduced_recursion_limit.unwrap_or(self.cx.ecfg.recursion_limit);
 667         if self.cx.current_expansion.depth > recursion_limit {
 668             if self.cx.reduced_recursion_limit.is_none() {
 669                 self.error_recursion_limit_reached();
 670             }
 671
 672             // Reduce the recursion limit by half each time it triggers.
 673             self.cx.reduced_recursion_limit = Some(recursion_limit / 2);
 674
 675             return ExpandResult::Ready(invoc.fragment_kind.dummy(invoc.span()));
 676         }
 677
 678         let (fragment_kind, span) = (invoc.fragment_kind, invoc.span());
 679         ExpandResult::Ready(match invoc.kind {
 680             InvocationKind::Bang { mac, .. } => match ext {
 681                 SyntaxExtensionKind::Bang(expander) => {
 682                     let tok_result = match expander.expand(self.cx, span, mac.args.inner_tokens()) {
 683                         Err(_) => return ExpandResult::Ready(fragment_kind.dummy(span)),
 684                         Ok(ts) => ts,
 685                     };
 686                     self.parse_ast_fragment(tok_result, fragment_kind, &mac.path, span)
 687                 }
 688                 SyntaxExtensionKind::LegacyBang(expander) => {
 689                     let prev = self.cx.current_expansion.prior_type_ascription;
 690                     self.cx.current_expansion.prior_type_ascription = mac.prior_type_ascription;
 691                     let tok_result = expander.expand(self.cx, span, mac.args.inner_tokens());
 692                     let result = if let Some(result) = fragment_kind.make_from(tok_result) {
 693                         result
 694                     } else {
 695                         self.error_wrong_fragment_kind(fragment_kind, &mac, span);
 696                         fragment_kind.dummy(span)
 697                     };
 698                     self.cx.current_expansion.prior_type_ascription = prev;
 699                     result
 700                 }
 701                 _ => unreachable!(),
 702             },
 703             InvocationKind::Attr { attr, mut item, derives, after_derive } => match ext {
 704                 SyntaxExtensionKind::Attr(expander) => {
 705                     self.gate_proc_macro_input(&item);
 706                     self.gate_proc_macro_attr_item(span, &item);
 707                     let tokens = item.into_tokens();
 708                     let attr_item = attr.unwrap_normal_item();
 709                     if let MacArgs::Eq(..) = attr_item.args {
 710                         self.cx.span_err(span, "key-value macro attributes are not supported");
 711                     }
 712                     let inner_tokens = attr_item.args.inner_tokens();
 713                     let tok_result = match expander.expand(self.cx, span, inner_tokens, tokens) {
 714                         Err(_) => return ExpandResult::Ready(fragment_kind.dummy(span)),
 715                         Ok(ts) => ts,
 716                     };
 717                     self.parse_ast_fragment(tok_result, fragment_kind, &attr_item.path, span)
 718                 }
 719                 SyntaxExtensionKind::LegacyAttr(expander) => {
 720                     match validate_attr::parse_meta(self.cx.parse_sess, &attr) {
 721                         Ok(meta) => {
 722                             let items = match expander.expand(self.cx, span, &meta, item) {
 723                                 ExpandResult::Ready(items) => items,
 724                                 ExpandResult::Retry(item, explanation) => {
 725                                     // Reassemble the original invocation for retrying.
 726                                     return ExpandResult::Retry(
 727                                         Invocation {
 728                                             kind: InvocationKind::Attr {
 729                                                 attr,
 730                                                 item,
 731                                                 derives,
 732                                                 after_derive,
 733                                             },
 734                                             ..invoc
 735                                         },
 736                                         explanation,
 737                                     );
 738                                 }
 739                             };
 740                             fragment_kind.expect_from_annotatables(items)
 741                         }
 742                         Err(mut err) => {
 743                             err.emit();
 744                             fragment_kind.dummy(span)
 745                         }
 746                     }
 747                 }
 748                 SyntaxExtensionKind::NonMacroAttr { mark_used } => {
 749                     attr::mark_known(&attr);
 750                     if *mark_used {
 751                         attr::mark_used(&attr);
 752                     }
 753                     item.visit_attrs(|attrs| attrs.push(attr));
 754                     fragment_kind.expect_from_annotatables(iter::once(item))
 755                 }
 756                 _ => unreachable!(),
 757             },
 758             InvocationKind::Derive { path, item } => match ext {
 759                 SyntaxExtensionKind::Derive(expander)
 760                 | SyntaxExtensionKind::LegacyDerive(expander) => {
 761                     if !item.derive_allowed() {
 762                         return ExpandResult::Ready(fragment_kind.dummy(span));
 763                     }
 764                     if let SyntaxExtensionKind::Derive(..) = ext {
 765                         self.gate_proc_macro_input(&item);
 766                     }
 767                     let meta = ast::MetaItem { kind: ast::MetaItemKind::Word, span, path };
 768                     let items = match expander.expand(self.cx, span, &meta, item) {
 769                         ExpandResult::Ready(items) => items,
 770                         ExpandResult::Retry(item, explanation) => {
 771                             // Reassemble the original invocation for retrying.
 772                             return ExpandResult::Retry(
 773                                 Invocation {
 774                                     kind: InvocationKind::Derive { path: meta.path, item },
 775                                     ..invoc
 776                                 },
 777                                 explanation,
 778                             );
 779                         }
 780                     };
 781                     fragment_kind.expect_from_annotatables(items)
 782                 }
 783                 _ => unreachable!(),
 784             },
 785             InvocationKind::DeriveContainer { .. } => unreachable!(),
 786         })
 787     }
 788
 789     fn gate_proc_macro_attr_item(&self, span: Span, item: &Annotatable) {
 790         let kind = match item {
 791             Annotatable::Item(_)
 792             | Annotatable::TraitItem(_)
 793             | Annotatable::ImplItem(_)
 794             | Annotatable::ForeignItem(_) => return,
 795             Annotatable::Stmt(_) => "statements",
 796             Annotatable::Expr(_) => "expressions",
 797             Annotatable::Arm(..)
 798             | Annotatable::Field(..)
 799             | Annotatable::FieldPat(..)
 800             | Annotatable::GenericParam(..)
 801             | Annotatable::Param(..)
 802             | Annotatable::StructField(..)
 803             | Annotatable::Variant(..) => panic!("unexpected annotatable"),
 804         };
 805         if self.cx.ecfg.proc_macro_hygiene() {
 806             return;
 807         }
 808         feature_err(
 809             self.cx.parse_sess,
 810             sym::proc_macro_hygiene,
 811             span,
 812             &format!("custom attributes cannot be applied to {}", kind),
 813         )
 814         .emit();
 815     }
 816
 817     fn gate_proc_macro_input(&self, annotatable: &Annotatable) {
 818         struct GateProcMacroInput<'a> {
 819             parse_sess: &'a ParseSess,
 820         }
 821
 822         impl<'ast, 'a> Visitor<'ast> for GateProcMacroInput<'a> {
 823             fn visit_item(&mut self, item: &'ast ast::Item) {
 824                 match &item.kind {
 825                     ast::ItemKind::Mod(module) if !module.inline => {
 826                         feature_err(
 827                             self.parse_sess,
 828                             sym::proc_macro_hygiene,
 829                             item.span,
 830                             "non-inline modules in proc macro input are unstable",
 831                         )
 832                         .emit();
 833                     }
 834                     _ => {}
 835                 }
 836
 837                 visit::walk_item(self, item);
 838             }
 839
 840             fn visit_mac(&mut self, _: &'ast ast::MacCall) {}
 841         }
 842
 843         if !self.cx.ecfg.proc_macro_hygiene() {
 844             annotatable.visit_with(&mut GateProcMacroInput { parse_sess: self.cx.parse_sess });
 845         }
 846     }
 847
 848     fn parse_ast_fragment(
 849         &mut self,
 850         toks: TokenStream,
 851         kind: AstFragmentKind,
 852         path: &Path,
 853         span: Span,
 854     ) -> AstFragment {
 855         let mut parser = self.cx.new_parser_from_tts(toks);
 856         match parse_ast_fragment(&mut parser, kind) {
 857             Ok(fragment) => {
 858                 ensure_complete_parse(&mut parser, path, kind.name(), span);
 859                 fragment
 860             }
 861             Err(mut err) => {
 862                 err.set_span(span);
 863                 annotate_err_with_kind(&mut err, kind, span);
 864                 err.emit();
 865                 self.cx.trace_macros_diag();
 866                 kind.dummy(span)
 867             }
 868         }
 869     }
 870 }
 871
 872 pub fn parse_ast_fragment<'a>(
 873     this: &mut Parser<'a>,
 874     kind: AstFragmentKind,
 875 ) -> PResult<'a, AstFragment> {
 876     Ok(match kind {
 877         AstFragmentKind::Items => {
 878             let mut items = SmallVec::new();
 879             while let Some(item) = this.parse_item()? {
 880                 items.push(item);
 881             }
 882             AstFragment::Items(items)
 883         }
 884         AstFragmentKind::TraitItems => {
 885             let mut items = SmallVec::new();
 886             while let Some(item) = this.parse_trait_item()? {
 887                 items.extend(item);
 888             }
 889             AstFragment::TraitItems(items)
 890         }
 891         AstFragmentKind::ImplItems => {
 892             let mut items = SmallVec::new();
 893             while let Some(item) = this.parse_impl_item()? {
 894                 items.extend(item);
 895             }
 896             AstFragment::ImplItems(items)
 897         }
 898         AstFragmentKind::ForeignItems => {
 899             let mut items = SmallVec::new();
 900             while let Some(item) = this.parse_foreign_item()? {
 901                 items.extend(item);
 902             }
 903             AstFragment::ForeignItems(items)
 904         }
 905         AstFragmentKind::Stmts => {
 906             let mut stmts = SmallVec::new();
 907             // Won't make progress on a `}`.
 908             while this.token != token::Eof && this.token != token::CloseDelim(token::Brace) {
 909                 if let Some(stmt) = this.parse_full_stmt()? {
 910                     stmts.push(stmt);
 911                 }
 912             }
 913             AstFragment::Stmts(stmts)
 914         }
 915         AstFragmentKind::Expr => AstFragment::Expr(this.parse_expr()?),
 916         AstFragmentKind::OptExpr => {
 917             if this.token != token::Eof {
 918                 AstFragment::OptExpr(Some(this.parse_expr()?))
 919             } else {
 920                 AstFragment::OptExpr(None)
 921             }
 922         }
 923         AstFragmentKind::Ty => AstFragment::Ty(this.parse_ty()?),
 924         AstFragmentKind::Pat => AstFragment::Pat(this.parse_pat(None)?),
 925         AstFragmentKind::Arms
 926         | AstFragmentKind::Fields
 927         | AstFragmentKind::FieldPats
 928         | AstFragmentKind::GenericParams
 929         | AstFragmentKind::Params
 930         | AstFragmentKind::StructFields
 931         | AstFragmentKind::Variants => panic!("unexpected AST fragment kind"),
 932     })
 933 }
 934
 935 pub fn ensure_complete_parse<'a>(
 936     this: &mut Parser<'a>,
 937     macro_path: &Path,
 938     kind_name: &str,
 939     span: Span,
 940 ) {
 941     if this.token != token::Eof {
 942         let token = pprust::token_to_string(&this.token);
 943         let msg = format!("macro expansion ignores token `{}` and any following", token);
 944         // Avoid emitting backtrace info twice.
 945         let def_site_span = this.token.span.with_ctxt(SyntaxContext::root());
 946         let mut err = this.struct_span_err(def_site_span, &msg);
 947         err.span_label(span, "caused by the macro expansion here");
 948         let msg = format!(
 949             "the usage of `{}!` is likely invalid in {} context",
 950             pprust::path_to_string(macro_path),
 951             kind_name,
 952         );
 953         err.note(&msg);
 954         let semi_span = this.sess.source_map().next_point(span);
 955
 956         let semi_full_span = semi_span.to(this.sess.source_map().next_point(semi_span));
 957         match this.sess.source_map().span_to_snippet(semi_full_span) {
 958             Ok(ref snippet) if &snippet[..] != ";" && kind_name == "expression" => {
 959                 err.span_suggestion(
 960                     semi_span,
 961                     "you might be missing a semicolon here",
 962                     ";".to_owned(),
 963                     Applicability::MaybeIncorrect,
 964                 );
 965             }
 966             _ => {}
 967         }
 968         err.emit();
 969     }
 970 }
 971
 972 struct InvocationCollector<'a, 'b> {
 973     cx: &'a mut ExtCtxt<'b>,
 974     cfg: StripUnconfigured<'a>,
 975     invocations: Vec<(Invocation, Option<InvocationRes>)>,
 976     monotonic: bool,
 977 }
 978
 979 impl<'a, 'b> InvocationCollector<'a, 'b> {
 980     fn collect(&mut self, fragment_kind: AstFragmentKind, kind: InvocationKind) -> AstFragment {
 981         // Expansion data for all the collected invocations is set upon their resolution,
 982         // with exception of the derive container case which is not resolved and can get
 983         // its expansion data immediately.
 984         let expn_data = match &kind {
 985             InvocationKind::DeriveContainer { item, .. } => Some(ExpnData {
 986                 parent: self.cx.current_expansion.id,
 987                 ..ExpnData::default(
 988                     ExpnKind::Macro(MacroKind::Attr, sym::derive),
 989                     item.span(),
 990                     self.cx.parse_sess.edition,
 991                     None,
 992                 )
 993             }),
 994             _ => None,
 995         };
 996         let expn_id = ExpnId::fresh(expn_data);
 997         let vis = kind.placeholder_visibility();
 998         self.invocations.push((
 999             Invocation {
1000                 kind,
1001                 fragment_kind,
1002                 expansion_data: ExpansionData {
1003                     id: expn_id,
1004                     depth: self.cx.current_expansion.depth + 1,
1005                     ..self.cx.current_expansion.clone()
1006                 },
1007             },
1008             None,
1009         ));
1010         placeholder(fragment_kind, NodeId::placeholder_from_expn_id(expn_id), vis)
1011     }
1012
1013     fn collect_bang(
1014         &mut self,
1015         mac: ast::MacCall,
1016         span: Span,
1017         kind: AstFragmentKind,
1018     ) -> AstFragment {
1019         self.collect(kind, InvocationKind::Bang { mac, span })
1020     }
1021
1022     fn collect_attr(
1023         &mut self,
1024         attr: Option<ast::Attribute>,
1025         derives: Vec<Path>,
1026         item: Annotatable,
1027         kind: AstFragmentKind,
1028         after_derive: bool,
1029     ) -> AstFragment {
1030         self.collect(
1031             kind,
1032             match attr {
1033                 Some(attr) => InvocationKind::Attr { attr, item, derives, after_derive },
1034                 None => InvocationKind::DeriveContainer { derives, item },
1035             },
1036         )
1037     }
1038
1039     fn find_attr_invoc(
1040         &self,
1041         attrs: &mut Vec<ast::Attribute>,
1042         after_derive: &mut bool,
1043     ) -> Option<ast::Attribute> {
1044         let attr = attrs
1045             .iter()
1046             .position(|a| {
1047                 if a.has_name(sym::derive) {
1048                     *after_derive = true;
1049                 }
1050                 !attr::is_known(a) && !is_builtin_attr(a)
1051             })
1052             .map(|i| attrs.remove(i));
1053         if let Some(attr) = &attr {
1054             if !self.cx.ecfg.custom_inner_attributes()
1055                 && attr.style == ast::AttrStyle::Inner
1056                 && !attr.has_name(sym::test)
1057             {
1058                 feature_err(
1059                     &self.cx.parse_sess,
1060                     sym::custom_inner_attributes,
1061                     attr.span,
1062                     "non-builtin inner attributes are unstable",
1063                 )
1064                 .emit();
1065             }
1066         }
1067         attr
1068     }
1069
1070     /// If `item` is an attr invocation, remove and return the macro attribute and derive traits.
1071     fn classify_item(
1072         &mut self,
1073         item: &mut impl HasAttrs,
1074     ) -> (Option<ast::Attribute>, Vec<Path>, /* after_derive */ bool) {
1075         let (mut attr, mut traits, mut after_derive) = (None, Vec::new(), false);
1076
1077         item.visit_attrs(|mut attrs| {
1078             attr = self.find_attr_invoc(&mut attrs, &mut after_derive);
1079             traits = collect_derives(&mut self.cx, &mut attrs);
1080         });
1081
1082         (attr, traits, after_derive)
1083     }
1084
1085     /// Alternative to `classify_item()` that ignores `#[derive]` so invocations fallthrough
1086     /// to the unused-attributes lint (making it an error on statements and expressions
1087     /// is a breaking change)
1088     fn classify_nonitem(
1089         &mut self,
1090         nonitem: &mut impl HasAttrs,
1091     ) -> (Option<ast::Attribute>, /* after_derive */ bool) {
1092         let (mut attr, mut after_derive) = (None, false);
1093
1094         nonitem.visit_attrs(|mut attrs| {
1095             attr = self.find_attr_invoc(&mut attrs, &mut after_derive);
1096         });
1097
1098         (attr, after_derive)
1099     }
1100
1101     fn configure<T: HasAttrs>(&mut self, node: T) -> Option<T> {
1102         self.cfg.configure(node)
1103     }
1104
1105     // Detect use of feature-gated or invalid attributes on macro invocations
1106     // since they will not be detected after macro expansion.
1107     fn check_attributes(&mut self, attrs: &[ast::Attribute]) {
1108         let features = self.cx.ecfg.features.unwrap();
1109         for attr in attrs.iter() {
1110             rustc_ast_passes::feature_gate::check_attribute(attr, self.cx.parse_sess, features);
1111             validate_attr::check_meta(self.cx.parse_sess, attr);
1112
1113             // macros are expanded before any lint passes so this warning has to be hardcoded
1114             if attr.has_name(sym::derive) {
1115                 self.cx
1116                     .parse_sess()
1117                     .span_diagnostic
1118                     .struct_span_warn(attr.span, "`#[derive]` does nothing on macro invocations")
1119                     .note("this may become a hard error in a future release")
1120                     .emit();
1121             }
1122
1123             if attr.doc_str().is_some() {
1124                 self.cx.parse_sess.buffer_lint_with_diagnostic(
1125                     &UNUSED_DOC_COMMENTS,
1126                     attr.span,
1127                     ast::CRATE_NODE_ID,
1128                     "unused doc comment",
1129                     BuiltinLintDiagnostics::UnusedDocComment(attr.span),
1130                 );
1131             }
1132         }
1133     }
1134 }
1135
1136 impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
1137     fn visit_expr(&mut self, expr: &mut P<ast::Expr>) {
1138         self.cfg.configure_expr(expr);
1139         visit_clobber(expr.deref_mut(), |mut expr| {
1140             self.cfg.configure_expr_kind(&mut expr.kind);
1141
1142             // ignore derives so they remain unused
1143             let (attr, after_derive) = self.classify_nonitem(&mut expr);
1144
1145             if let Some(ref attr_value) = attr {
1146                 // Collect the invoc regardless of whether or not attributes are permitted here
1147                 // expansion will eat the attribute so it won't error later.
1148                 self.cfg.maybe_emit_expr_attr_err(attr_value);
1149
1150                 // AstFragmentKind::Expr requires the macro to emit an expression.
1151                 return self
1152                     .collect_attr(
1153                         attr,
1154                         vec![],
1155                         Annotatable::Expr(P(expr)),
1156                         AstFragmentKind::Expr,
1157                         after_derive,
1158                     )
1159                     .make_expr()
1160                     .into_inner();
1161             }
1162
1163             if let ast::ExprKind::MacCall(mac) = expr.kind {
1164                 self.check_attributes(&expr.attrs);
1165                 self.collect_bang(mac, expr.span, AstFragmentKind::Expr).make_expr().into_inner()
1166             } else {
1167                 noop_visit_expr(&mut expr, self);
1168                 expr
1169             }
1170         });
1171     }
1172
1173     fn flat_map_arm(&mut self, arm: ast::Arm) -> SmallVec<[ast::Arm; 1]> {
1174         let mut arm = configure!(self, arm);
1175
1176         let (attr, traits, after_derive) = self.classify_item(&mut arm);
1177         if attr.is_some() || !traits.is_empty() {
1178             return self
1179                 .collect_attr(
1180                     attr,
1181                     traits,
1182                     Annotatable::Arm(arm),
1183                     AstFragmentKind::Arms,
1184                     after_derive,
1185                 )
1186                 .make_arms();
1187         }
1188
1189         noop_flat_map_arm(arm, self)
1190     }
1191
1192     fn flat_map_field(&mut self, field: ast::Field) -> SmallVec<[ast::Field; 1]> {
1193         let mut field = configure!(self, field);
1194
1195         let (attr, traits, after_derive) = self.classify_item(&mut field);
1196         if attr.is_some() || !traits.is_empty() {
1197             return self
1198                 .collect_attr(
1199                     attr,
1200                     traits,
1201                     Annotatable::Field(field),
1202                     AstFragmentKind::Fields,
1203                     after_derive,
1204                 )
1205                 .make_fields();
1206         }
1207
1208         noop_flat_map_field(field, self)
1209     }
1210
1211     fn flat_map_field_pattern(&mut self, fp: ast::FieldPat) -> SmallVec<[ast::FieldPat; 1]> {
1212         let mut fp = configure!(self, fp);
1213
1214         let (attr, traits, after_derive) = self.classify_item(&mut fp);
1215         if attr.is_some() || !traits.is_empty() {
1216             return self
1217                 .collect_attr(
1218                     attr,
1219                     traits,
1220                     Annotatable::FieldPat(fp),
1221                     AstFragmentKind::FieldPats,
1222                     after_derive,
1223                 )
1224                 .make_field_patterns();
1225         }
1226
1227         noop_flat_map_field_pattern(fp, self)
1228     }
1229
1230     fn flat_map_param(&mut self, p: ast::Param) -> SmallVec<[ast::Param; 1]> {
1231         let mut p = configure!(self, p);
1232
1233         let (attr, traits, after_derive) = self.classify_item(&mut p);
1234         if attr.is_some() || !traits.is_empty() {
1235             return self
1236                 .collect_attr(
1237                     attr,
1238                     traits,
1239                     Annotatable::Param(p),
1240                     AstFragmentKind::Params,
1241                     after_derive,
1242                 )
1243                 .make_params();
1244         }
1245
1246         noop_flat_map_param(p, self)
1247     }
1248
1249     fn flat_map_struct_field(&mut self, sf: ast::StructField) -> SmallVec<[ast::StructField; 1]> {
1250         let mut sf = configure!(self, sf);
1251
1252         let (attr, traits, after_derive) = self.classify_item(&mut sf);
1253         if attr.is_some() || !traits.is_empty() {
1254             return self
1255                 .collect_attr(
1256                     attr,
1257                     traits,
1258                     Annotatable::StructField(sf),
1259                     AstFragmentKind::StructFields,
1260                     after_derive,
1261                 )
1262                 .make_struct_fields();
1263         }
1264
1265         noop_flat_map_struct_field(sf, self)
1266     }
1267
1268     fn flat_map_variant(&mut self, variant: ast::Variant) -> SmallVec<[ast::Variant; 1]> {
1269         let mut variant = configure!(self, variant);
1270
1271         let (attr, traits, after_derive) = self.classify_item(&mut variant);
1272         if attr.is_some() || !traits.is_empty() {
1273             return self
1274                 .collect_attr(
1275                     attr,
1276                     traits,
1277                     Annotatable::Variant(variant),
1278                     AstFragmentKind::Variants,
1279                     after_derive,
1280                 )
1281                 .make_variants();
1282         }
1283
1284         noop_flat_map_variant(variant, self)
1285     }
1286
1287     fn filter_map_expr(&mut self, expr: P<ast::Expr>) -> Option<P<ast::Expr>> {
1288         let expr = configure!(self, expr);
1289         expr.filter_map(|mut expr| {
1290             self.cfg.configure_expr_kind(&mut expr.kind);
1291
1292             // Ignore derives so they remain unused.
1293             let (attr, after_derive) = self.classify_nonitem(&mut expr);
1294
1295             if let Some(ref attr_value) = attr {
1296                 self.cfg.maybe_emit_expr_attr_err(attr_value);
1297
1298                 return self
1299                     .collect_attr(
1300                         attr,
1301                         vec![],
1302                         Annotatable::Expr(P(expr)),
1303                         AstFragmentKind::OptExpr,
1304                         after_derive,
1305                     )
1306                     .make_opt_expr()
1307                     .map(|expr| expr.into_inner());
1308             }
1309
1310             if let ast::ExprKind::MacCall(mac) = expr.kind {
1311                 self.check_attributes(&expr.attrs);
1312                 self.collect_bang(mac, expr.span, AstFragmentKind::OptExpr)
1313                     .make_opt_expr()
1314                     .map(|expr| expr.into_inner())
1315             } else {
1316                 Some({
1317                     noop_visit_expr(&mut expr, self);
1318                     expr
1319                 })
1320             }
1321         })
1322     }
1323
1324     fn visit_pat(&mut self, pat: &mut P<ast::Pat>) {
1325         self.cfg.configure_pat(pat);
1326         match pat.kind {
1327             PatKind::MacCall(_) => {}
1328             _ => return noop_visit_pat(pat, self),
1329         }
1330
1331         visit_clobber(pat, |mut pat| match mem::replace(&mut pat.kind, PatKind::Wild) {
1332             PatKind::MacCall(mac) => {
1333                 self.collect_bang(mac, pat.span, AstFragmentKind::Pat).make_pat()
1334             }
1335             _ => unreachable!(),
1336         });
1337     }
1338
1339     fn flat_map_stmt(&mut self, stmt: ast::Stmt) -> SmallVec<[ast::Stmt; 1]> {
1340         let mut stmt = configure!(self, stmt);
1341
1342         // we'll expand attributes on expressions separately
1343         if !stmt.is_expr() {
1344             let (attr, derives, after_derive) = if stmt.is_item() {
1345                 self.classify_item(&mut stmt)
1346             } else {
1347                 // ignore derives on non-item statements so it falls through
1348                 // to the unused-attributes lint
1349                 let (attr, after_derive) = self.classify_nonitem(&mut stmt);
1350                 (attr, vec![], after_derive)
1351             };
1352
1353             if attr.is_some() || !derives.is_empty() {
1354                 return self
1355                     .collect_attr(
1356                         attr,
1357                         derives,
1358                         Annotatable::Stmt(P(stmt)),
1359                         AstFragmentKind::Stmts,
1360                         after_derive,
1361                     )
1362                     .make_stmts();
1363             }
1364         }
1365
1366         if let StmtKind::MacCall(mac) = stmt.kind {
1367             let (mac, style, attrs) = mac.into_inner();
1368             self.check_attributes(&attrs);
1369             let mut placeholder =
1370                 self.collect_bang(mac, stmt.span, AstFragmentKind::Stmts).make_stmts();
1371
1372             // If this is a macro invocation with a semicolon, then apply that
1373             // semicolon to the final statement produced by expansion.
1374             if style == MacStmtStyle::Semicolon {
1375                 if let Some(stmt) = placeholder.pop() {
1376                     placeholder.push(stmt.add_trailing_semicolon());
1377                 }
1378             }
1379
1380             return placeholder;
1381         }
1382
1383         // The placeholder expander gives ids to statements, so we avoid folding the id here.
1384         let ast::Stmt { id, kind, span } = stmt;
1385         noop_flat_map_stmt_kind(kind, self)
1386             .into_iter()
1387             .map(|kind| ast::Stmt { id, kind, span })
1388             .collect()
1389     }
1390
1391     fn visit_block(&mut self, block: &mut P<Block>) {
1392         let old_directory_ownership = self.cx.current_expansion.directory_ownership;
1393         self.cx.current_expansion.directory_ownership = DirectoryOwnership::UnownedViaBlock;
1394         noop_visit_block(block, self);
1395         self.cx.current_expansion.directory_ownership = old_directory_ownership;
1396     }
1397
1398     fn flat_map_item(&mut self, item: P<ast::Item>) -> SmallVec<[P<ast::Item>; 1]> {
1399         let mut item = configure!(self, item);
1400
1401         let (attr, traits, after_derive) = self.classify_item(&mut item);
1402         if attr.is_some() || !traits.is_empty() {
1403             return self
1404                 .collect_attr(
1405                     attr,
1406                     traits,
1407                     Annotatable::Item(item),
1408                     AstFragmentKind::Items,
1409                     after_derive,
1410                 )
1411                 .make_items();
1412         }
1413
1414         let mut attrs = mem::take(&mut item.attrs); // We do this to please borrowck.
1415         let ident = item.ident;
1416         let span = item.span;
1417
1418         match item.kind {
1419             ast::ItemKind::MacCall(..) => {
1420                 item.attrs = attrs;
1421                 self.check_attributes(&item.attrs);
1422                 item.and_then(|item| match item.kind {
1423                     ItemKind::MacCall(mac) => self
1424                         .collect(AstFragmentKind::Items, InvocationKind::Bang { mac, span })
1425                         .make_items(),
1426                     _ => unreachable!(),
1427                 })
1428             }
1429             ast::ItemKind::Mod(ref mut old_mod @ ast::Mod { .. }) if ident != Ident::invalid() => {
1430                 let sess = self.cx.parse_sess;
1431                 let orig_ownership = self.cx.current_expansion.directory_ownership;
1432                 let mut module = (*self.cx.current_expansion.module).clone();
1433
1434                 let pushed = &mut false; // Record `parse_external_mod` pushing so we can pop.
1435                 let dir = Directory { ownership: orig_ownership, path: module.directory };
1436                 let Directory { ownership, path } = if old_mod.inline {
1437                     // Inline `mod foo { ... }`, but we still need to push directories.
1438                     item.attrs = attrs;
1439                     push_directory(ident, &item.attrs, dir)
1440                 } else {
1441                     // We have an outline `mod foo;` so we need to parse the file.
1442                     let (new_mod, dir) =
1443                         parse_external_mod(sess, ident, span, dir, &mut attrs, pushed);
1444
1445                     let krate = ast::Crate {
1446                         span: new_mod.inner,
1447                         module: new_mod,
1448                         attrs,
1449                         proc_macros: vec![],
1450                     };
1451                     if let Some(extern_mod_loaded) = self.cx.extern_mod_loaded {
1452                         extern_mod_loaded(&krate);
1453                     }
1454
1455                     *old_mod = krate.module;
1456                     item.attrs = krate.attrs;
1457                     // File can have inline attributes, e.g., `#![cfg(...)]` & co. => Reconfigure.
1458                     item = match self.configure(item) {
1459                         Some(node) => node,
1460                         None => {
1461                             if *pushed {
1462                                 sess.included_mod_stack.borrow_mut().pop();
1463                             }
1464                             return Default::default();
1465                         }
1466                     };
1467                     dir
1468                 };
1469
1470                 // Set the module info before we flat map.
1471                 self.cx.current_expansion.directory_ownership = ownership;
1472                 module.directory = path;
1473                 module.mod_path.push(ident);
1474                 let orig_module =
1475                     mem::replace(&mut self.cx.current_expansion.module, Rc::new(module));
1476
1477                 let result = noop_flat_map_item(item, self);
1478
1479                 // Restore the module info.
1480                 self.cx.current_expansion.module = orig_module;
1481                 self.cx.current_expansion.directory_ownership = orig_ownership;
1482                 if *pushed {
1483                     sess.included_mod_stack.borrow_mut().pop();
1484                 }
1485                 result
1486             }
1487             _ => {
1488                 item.attrs = attrs;
1489                 noop_flat_map_item(item, self)
1490             }
1491         }
1492     }
1493
1494     fn flat_map_trait_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
1495         let mut item = configure!(self, item);
1496
1497         let (attr, traits, after_derive) = self.classify_item(&mut item);
1498         if attr.is_some() || !traits.is_empty() {
1499             return self
1500                 .collect_attr(
1501                     attr,
1502                     traits,
1503                     Annotatable::TraitItem(item),
1504                     AstFragmentKind::TraitItems,
1505                     after_derive,
1506                 )
1507                 .make_trait_items();
1508         }
1509
1510         match item.kind {
1511             ast::AssocItemKind::MacCall(..) => {
1512                 self.check_attributes(&item.attrs);
1513                 item.and_then(|item| match item.kind {
1514                     ast::AssocItemKind::MacCall(mac) => self
1515                         .collect_bang(mac, item.span, AstFragmentKind::TraitItems)
1516                         .make_trait_items(),
1517                     _ => unreachable!(),
1518                 })
1519             }
1520             _ => noop_flat_map_assoc_item(item, self),
1521         }
1522     }
1523
1524     fn flat_map_impl_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
1525         let mut item = configure!(self, item);
1526
1527         let (attr, traits, after_derive) = self.classify_item(&mut item);
1528         if attr.is_some() || !traits.is_empty() {
1529             return self
1530                 .collect_attr(
1531                     attr,
1532                     traits,
1533                     Annotatable::ImplItem(item),
1534                     AstFragmentKind::ImplItems,
1535                     after_derive,
1536                 )
1537                 .make_impl_items();
1538         }
1539
1540         match item.kind {
1541             ast::AssocItemKind::MacCall(..) => {
1542                 self.check_attributes(&item.attrs);
1543                 item.and_then(|item| match item.kind {
1544                     ast::AssocItemKind::MacCall(mac) => self
1545                         .collect_bang(mac, item.span, AstFragmentKind::ImplItems)
1546                         .make_impl_items(),
1547                     _ => unreachable!(),
1548                 })
1549             }
1550             _ => noop_flat_map_assoc_item(item, self),
1551         }
1552     }
1553
1554     fn visit_ty(&mut self, ty: &mut P<ast::Ty>) {
1555         match ty.kind {
1556             ast::TyKind::MacCall(_) => {}
1557             _ => return noop_visit_ty(ty, self),
1558         };
1559
1560         visit_clobber(ty, |mut ty| match mem::replace(&mut ty.kind, ast::TyKind::Err) {
1561             ast::TyKind::MacCall(mac) => {
1562                 self.collect_bang(mac, ty.span, AstFragmentKind::Ty).make_ty()
1563             }
1564             _ => unreachable!(),
1565         });
1566     }
1567
1568     fn visit_foreign_mod(&mut self, foreign_mod: &mut ast::ForeignMod) {
1569         self.cfg.configure_foreign_mod(foreign_mod);
1570         noop_visit_foreign_mod(foreign_mod, self);
1571     }
1572
1573     fn flat_map_foreign_item(
1574         &mut self,
1575         mut foreign_item: P<ast::ForeignItem>,
1576     ) -> SmallVec<[P<ast::ForeignItem>; 1]> {
1577         let (attr, traits, after_derive) = self.classify_item(&mut foreign_item);
1578
1579         if attr.is_some() || !traits.is_empty() {
1580             return self
1581                 .collect_attr(
1582                     attr,
1583                     traits,
1584                     Annotatable::ForeignItem(foreign_item),
1585                     AstFragmentKind::ForeignItems,
1586                     after_derive,
1587                 )
1588                 .make_foreign_items();
1589         }
1590
1591         match foreign_item.kind {
1592             ast::ForeignItemKind::MacCall(..) => {
1593                 self.check_attributes(&foreign_item.attrs);
1594                 foreign_item.and_then(|item| match item.kind {
1595                     ast::ForeignItemKind::MacCall(mac) => self
1596                         .collect_bang(mac, item.span, AstFragmentKind::ForeignItems)
1597                         .make_foreign_items(),
1598                     _ => unreachable!(),
1599                 })
1600             }
1601             _ => noop_flat_map_foreign_item(foreign_item, self),
1602         }
1603     }
1604
1605     fn visit_item_kind(&mut self, item: &mut ast::ItemKind) {
1606         match item {
1607             ast::ItemKind::MacroDef(..) => {}
1608             _ => {
1609                 self.cfg.configure_item_kind(item);
1610                 noop_visit_item_kind(item, self);
1611             }
1612         }
1613     }
1614
1615     fn flat_map_generic_param(
1616         &mut self,
1617         param: ast::GenericParam,
1618     ) -> SmallVec<[ast::GenericParam; 1]> {
1619         let mut param = configure!(self, param);
1620
1621         let (attr, traits, after_derive) = self.classify_item(&mut param);
1622         if attr.is_some() || !traits.is_empty() {
1623             return self
1624                 .collect_attr(
1625                     attr,
1626                     traits,
1627                     Annotatable::GenericParam(param),
1628                     AstFragmentKind::GenericParams,
1629                     after_derive,
1630                 )
1631                 .make_generic_params();
1632         }
1633
1634         noop_flat_map_generic_param(param, self)
1635     }
1636
1637     fn visit_attribute(&mut self, at: &mut ast::Attribute) {
1638         // turn `#[doc(include="filename")]` attributes into `#[doc(include(file="filename",
1639         // contents="file contents")]` attributes
1640         if !at.check_name(sym::doc) {
1641             return noop_visit_attribute(at, self);
1642         }
1643
1644         if let Some(list) = at.meta_item_list() {
1645             if !list.iter().any(|it| it.check_name(sym::include)) {
1646                 return noop_visit_attribute(at, self);
1647             }
1648
1649             let mut items = vec![];
1650
1651             for mut it in list {
1652                 if !it.check_name(sym::include) {
1653                     items.push({
1654                         noop_visit_meta_list_item(&mut it, self);
1655                         it
1656                     });
1657                     continue;
1658                 }
1659
1660                 if let Some(file) = it.value_str() {
1661                     let err_count = self.cx.parse_sess.span_diagnostic.err_count();
1662                     self.check_attributes(slice::from_ref(at));
1663                     if self.cx.parse_sess.span_diagnostic.err_count() > err_count {
1664                         // avoid loading the file if they haven't enabled the feature
1665                         return noop_visit_attribute(at, self);
1666                     }
1667
1668                     let filename = match self.cx.resolve_path(&*file.as_str(), it.span()) {
1669                         Ok(filename) => filename,
1670                         Err(mut err) => {
1671                             err.emit();
1672                             continue;
1673                         }
1674                     };
1675
1676                     match self.cx.source_map().load_file(&filename) {
1677                         Ok(source_file) => {
1678                             let src = source_file
1679                                 .src
1680                                 .as_ref()
1681                                 .expect("freshly loaded file should have a source");
1682                             let src_interned = Symbol::intern(src.as_str());
1683
1684                             let include_info = vec![
1685                                 ast::NestedMetaItem::MetaItem(attr::mk_name_value_item_str(
1686                                     Ident::with_dummy_span(sym::file),
1687                                     file,
1688                                     DUMMY_SP,
1689                                 )),
1690                                 ast::NestedMetaItem::MetaItem(attr::mk_name_value_item_str(
1691                                     Ident::with_dummy_span(sym::contents),
1692                                     src_interned,
1693                                     DUMMY_SP,
1694                                 )),
1695                             ];
1696
1697                             let include_ident = Ident::with_dummy_span(sym::include);
1698                             let item = attr::mk_list_item(include_ident, include_info);
1699                             items.push(ast::NestedMetaItem::MetaItem(item));
1700                         }
1701                         Err(e) => {
1702                             let lit =
1703                                 it.meta_item().and_then(|item| item.name_value_literal()).unwrap();
1704
1705                             if e.kind() == ErrorKind::InvalidData {
1706                                 self.cx
1707                                     .struct_span_err(
1708                                         lit.span,
1709                                         &format!("{} wasn't a utf-8 file", filename.display()),
1710                                     )
1711                                     .span_label(lit.span, "contains invalid utf-8")
1712                                     .emit();
1713                             } else {
1714                                 let mut err = self.cx.struct_span_err(
1715                                     lit.span,
1716                                     &format!("couldn't read {}: {}", filename.display(), e),
1717                                 );
1718                                 err.span_label(lit.span, "couldn't read file");
1719
1720                                 err.emit();
1721                             }
1722                         }
1723                     }
1724                 } else {
1725                     let mut err = self
1726                         .cx
1727                         .struct_span_err(it.span(), "expected path to external documentation");
1728
1729                     // Check if the user erroneously used `doc(include(...))` syntax.
1730                     let literal = it.meta_item_list().and_then(|list| {
1731                         if list.len() == 1 {
1732                             list[0].literal().map(|literal| &literal.kind)
1733                         } else {
1734                             None
1735                         }
1736                     });
1737
1738                     let (path, applicability) = match &literal {
1739                         Some(LitKind::Str(path, ..)) => {
1740                             (path.to_string(), Applicability::MachineApplicable)
1741                         }
1742                         _ => (String::from("<path>"), Applicability::HasPlaceholders),
1743                     };
1744
1745                     err.span_suggestion(
1746                         it.span(),
1747                         "provide a file path with `=`",
1748                         format!("include = \"{}\"", path),
1749                         applicability,
1750                     );
1751
1752                     err.emit();
1753                 }
1754             }
1755
1756             let meta = attr::mk_list_item(Ident::with_dummy_span(sym::doc), items);
1757             *at = ast::Attribute {
1758                 kind: ast::AttrKind::Normal(AttrItem {
1759                     path: meta.path,
1760                     args: meta.kind.mac_args(meta.span),
1761                 }),
1762                 span: at.span,
1763                 id: at.id,
1764                 style: at.style,
1765             };
1766         } else {
1767             noop_visit_attribute(at, self)
1768         }
1769     }
1770
1771     fn visit_id(&mut self, id: &mut ast::NodeId) {
1772         if self.monotonic {
1773             debug_assert_eq!(*id, ast::DUMMY_NODE_ID);
1774             *id = self.cx.resolver.next_node_id()
1775         }
1776     }
1777
1778     fn visit_fn_decl(&mut self, mut fn_decl: &mut P<ast::FnDecl>) {
1779         self.cfg.configure_fn_decl(&mut fn_decl);
1780         noop_visit_fn_decl(fn_decl, self);
1781     }
1782 }
1783
1784 pub struct ExpansionConfig<'feat> {
1785     pub crate_name: String,
1786     pub features: Option<&'feat Features>,
1787     pub recursion_limit: usize,
1788     pub trace_mac: bool,
1789     pub should_test: bool, // If false, strip `#[test]` nodes
1790     pub keep_macs: bool,
1791 }
1792
1793 impl<'feat> ExpansionConfig<'feat> {
1794     pub fn default(crate_name: String) -> ExpansionConfig<'static> {
1795         ExpansionConfig {
1796             crate_name,
1797             features: None,
1798             recursion_limit: 1024,
1799             trace_mac: false,
1800             should_test: false,
1801             keep_macs: false,
1802         }
1803     }
1804
1805     fn proc_macro_hygiene(&self) -> bool {
1806         self.features.map_or(false, |features| features.proc_macro_hygiene)
1807     }
1808     fn custom_inner_attributes(&self) -> bool {
1809         self.features.map_or(false, |features| features.custom_inner_attributes)
1810     }
1811 }