src/librustc_expand/expand.rs

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