compiler/rustc_expand/src/expand.rs

   1 use crate::base::*;
   2 use crate::config::StripUnconfigured;
   3 use crate::configure;
   4 use crate::hygiene::{ExpnData, ExpnKind, SyntaxContext};
   5 use crate::mbe::macro_rules::annotate_err_with_kind;
   6 use crate::module::{parse_external_mod, push_directory, Directory, DirectoryOwnership};
   7 use crate::placeholders::{placeholder, PlaceholderExpander};
   8 use crate::proc_macro::collect_derives;
   9
  10 use rustc_ast::mut_visit::*;
  11 use rustc_ast::ptr::P;
  12 use rustc_ast::token;
  13 use rustc_ast::tokenstream::TokenStream;
  14 use rustc_ast::visit::{self, AssocCtxt, Visitor};
  15 use rustc_ast::{self as ast, AttrItem, Block, LitKind, NodeId, PatKind, Path};
  16 use rustc_ast::{ItemKind, MacArgs, MacCallStmt, MacStmtStyle, StmtKind, Unsafe};
  17 use rustc_ast_pretty::pprust;
  18 use rustc_attr::{self as attr, is_builtin_attr, HasAttrs};
  19 use rustc_data_structures::map_in_place::MapInPlace;
  20 use rustc_data_structures::stack::ensure_sufficient_stack;
  21 use rustc_errors::{struct_span_err, Applicability, PResult};
  22 use rustc_feature::Features;
  23 use rustc_parse::parser::{AttemptLocalParseRecovery, Parser};
  24 use rustc_parse::validate_attr;
  25 use rustc_session::lint::builtin::UNUSED_DOC_COMMENTS;
  26 use rustc_session::lint::BuiltinLintDiagnostics;
  27 use rustc_session::parse::{feature_err, ParseSess};
  28 use rustc_session::Limit;
  29 use rustc_span::symbol::{sym, Ident, Symbol};
  30 use rustc_span::{ExpnId, FileName, Span, DUMMY_SP};
  31
  32 use smallvec::{smallvec, SmallVec};
  33 use std::io::ErrorKind;
  34 use std::ops::DerefMut;
  35 use std::path::PathBuf;
  36 use std::rc::Rc;
  37 use std::{iter, mem, slice};
  38
  39 macro_rules! ast_fragments {
  40     (
  41         $($Kind:ident($AstTy:ty) {
  42             $kind_name:expr;
  43             $(one fn $mut_visit_ast:ident; fn $visit_ast:ident;)?
  44             $(many fn $flat_map_ast_elt:ident; fn $visit_ast_elt:ident($($args:tt)*);)?
  45             fn $make_ast:ident;
  46         })*
  47     ) => {
  48         /// A fragment of AST that can be produced by a single macro expansion.
  49         /// Can also serve as an input and intermediate result for macro expansion operations.
  50         pub enum AstFragment {
  51             OptExpr(Option<P<ast::Expr>>),
  52             $($Kind($AstTy),)*
  53         }
  54
  55         /// "Discriminant" of an AST fragment.
  56         #[derive(Copy, Clone, PartialEq, Eq)]
  57         pub enum AstFragmentKind {
  58             OptExpr,
  59             $($Kind,)*
  60         }
  61
  62         impl AstFragmentKind {
  63             pub fn name(self) -> &'static str {
  64                 match self {
  65                     AstFragmentKind::OptExpr => "expression",
  66                     $(AstFragmentKind::$Kind => $kind_name,)*
  67                 }
  68             }
  69
  70             fn make_from<'a>(self, result: Box<dyn MacResult + 'a>) -> Option<AstFragment> {
  71                 match self {
  72                     AstFragmentKind::OptExpr =>
  73                         result.make_expr().map(Some).map(AstFragment::OptExpr),
  74                     $(AstFragmentKind::$Kind => result.$make_ast().map(AstFragment::$Kind),)*
  75                 }
  76             }
  77         }
  78
  79         impl AstFragment {
  80             pub fn add_placeholders(&mut self, placeholders: &[NodeId]) {
  81                 if placeholders.is_empty() {
  82                     return;
  83                 }
  84                 match self {
  85                     $($(AstFragment::$Kind(ast) => ast.extend(placeholders.iter().flat_map(|id| {
  86                         // We are repeating through arguments with `many`, to do that we have to
  87                         // mention some macro variable from those arguments even if it's not used.
  88                         macro _repeating($flat_map_ast_elt) {}
  89                         placeholder(AstFragmentKind::$Kind, *id, None).$make_ast()
  90                     })),)?)*
  91                     _ => panic!("unexpected AST fragment kind")
  92                 }
  93             }
  94
  95             pub fn make_opt_expr(self) -> Option<P<ast::Expr>> {
  96                 match self {
  97                     AstFragment::OptExpr(expr) => expr,
  98                     _ => panic!("AstFragment::make_* called on the wrong kind of fragment"),
  99                 }
 100             }
 101
 102             $(pub fn $make_ast(self) -> $AstTy {
 103                 match self {
 104                     AstFragment::$Kind(ast) => ast,
 105                     _ => panic!("AstFragment::make_* called on the wrong kind of fragment"),
 106                 }
 107             })*
 108
 109             pub fn mut_visit_with<F: MutVisitor>(&mut self, vis: &mut F) {
 110                 match self {
 111                     AstFragment::OptExpr(opt_expr) => {
 112                         visit_clobber(opt_expr, |opt_expr| {
 113                             if let Some(expr) = opt_expr {
 114                                 vis.filter_map_expr(expr)
 115                             } else {
 116                                 None
 117                             }
 118                         });
 119                     }
 120                     $($(AstFragment::$Kind(ast) => vis.$mut_visit_ast(ast),)?)*
 121                     $($(AstFragment::$Kind(ast) =>
 122                         ast.flat_map_in_place(|ast| vis.$flat_map_ast_elt(ast)),)?)*
 123                 }
 124             }
 125
 126             pub fn visit_with<'a, V: Visitor<'a>>(&'a self, visitor: &mut V) {
 127                 match *self {
 128                     AstFragment::OptExpr(Some(ref expr)) => visitor.visit_expr(expr),
 129                     AstFragment::OptExpr(None) => {}
 130                     $($(AstFragment::$Kind(ref ast) => visitor.$visit_ast(ast),)?)*
 131                     $($(AstFragment::$Kind(ref ast) => for ast_elt in &ast[..] {
 132                         visitor.$visit_ast_elt(ast_elt, $($args)*);
 133                     })?)*
 134                 }
 135             }
 136         }
 137
 138         impl<'a> MacResult for crate::mbe::macro_rules::ParserAnyMacro<'a> {
 139             $(fn $make_ast(self: Box<crate::mbe::macro_rules::ParserAnyMacro<'a>>)
 140                            -> Option<$AstTy> {
 141                 Some(self.make(AstFragmentKind::$Kind).$make_ast())
 142             })*
 143         }
 144     }
 145 }
 146
 147 ast_fragments! {
 148     Expr(P<ast::Expr>) { "expression"; one fn visit_expr; fn visit_expr; fn make_expr; }
 149     Pat(P<ast::Pat>) { "pattern"; one fn visit_pat; fn visit_pat; fn make_pat; }
 150     Ty(P<ast::Ty>) { "type"; one fn visit_ty; fn visit_ty; fn make_ty; }
 151     Stmts(SmallVec<[ast::Stmt; 1]>) {
 152         "statement"; many fn flat_map_stmt; fn visit_stmt(); fn make_stmts;
 153     }
 154     Items(SmallVec<[P<ast::Item>; 1]>) {
 155         "item"; many fn flat_map_item; fn visit_item(); fn make_items;
 156     }
 157     TraitItems(SmallVec<[P<ast::AssocItem>; 1]>) {
 158         "trait item";
 159         many fn flat_map_trait_item;
 160         fn visit_assoc_item(AssocCtxt::Trait);
 161         fn make_trait_items;
 162     }
 163     ImplItems(SmallVec<[P<ast::AssocItem>; 1]>) {
 164         "impl item";
 165         many fn flat_map_impl_item;
 166         fn visit_assoc_item(AssocCtxt::Impl);
 167         fn make_impl_items;
 168     }
 169     ForeignItems(SmallVec<[P<ast::ForeignItem>; 1]>) {
 170         "foreign item";
 171         many fn flat_map_foreign_item;
 172         fn visit_foreign_item();
 173         fn make_foreign_items;
 174     }
 175     Arms(SmallVec<[ast::Arm; 1]>) {
 176         "match arm"; many fn flat_map_arm; fn visit_arm(); fn make_arms;
 177     }
 178     Fields(SmallVec<[ast::Field; 1]>) {
 179         "field expression"; many fn flat_map_field; fn visit_field(); fn make_fields;
 180     }
 181     FieldPats(SmallVec<[ast::FieldPat; 1]>) {
 182         "field pattern";
 183         many fn flat_map_field_pattern;
 184         fn visit_field_pattern();
 185         fn make_field_patterns;
 186     }
 187     GenericParams(SmallVec<[ast::GenericParam; 1]>) {
 188         "generic parameter";
 189         many fn flat_map_generic_param;
 190         fn visit_generic_param();
 191         fn make_generic_params;
 192     }
 193     Params(SmallVec<[ast::Param; 1]>) {
 194         "function parameter"; many fn flat_map_param; fn visit_param(); fn make_params;
 195     }
 196     StructFields(SmallVec<[ast::StructField; 1]>) {
 197         "field";
 198         many fn flat_map_struct_field;
 199         fn visit_struct_field();
 200         fn make_struct_fields;
 201     }
 202     Variants(SmallVec<[ast::Variant; 1]>) {
 203         "variant"; many fn flat_map_variant; fn visit_variant(); fn make_variants;
 204     }
 205 }
 206
 207 impl AstFragmentKind {
 208     crate fn dummy(self, span: Span) -> AstFragment {
 209         self.make_from(DummyResult::any(span)).expect("couldn't create a dummy AST fragment")
 210     }
 211
 212     /// Fragment supports macro expansion and not just inert attributes, `cfg` and `cfg_attr`.
 213     pub fn supports_macro_expansion(self) -> bool {
 214         match self {
 215             AstFragmentKind::OptExpr
 216             | AstFragmentKind::Expr
 217             | AstFragmentKind::Pat
 218             | AstFragmentKind::Ty
 219             | AstFragmentKind::Stmts
 220             | AstFragmentKind::Items
 221             | AstFragmentKind::TraitItems
 222             | AstFragmentKind::ImplItems
 223             | AstFragmentKind::ForeignItems => true,
 224             AstFragmentKind::Arms
 225             | AstFragmentKind::Fields
 226             | AstFragmentKind::FieldPats
 227             | AstFragmentKind::GenericParams
 228             | AstFragmentKind::Params
 229             | AstFragmentKind::StructFields
 230             | AstFragmentKind::Variants => false,
 231         }
 232     }
 233
 234     fn expect_from_annotatables<I: IntoIterator<Item = Annotatable>>(
 235         self,
 236         items: I,
 237     ) -> AstFragment {
 238         let mut items = items.into_iter();
 239         match self {
 240             AstFragmentKind::Arms => {
 241                 AstFragment::Arms(items.map(Annotatable::expect_arm).collect())
 242             }
 243             AstFragmentKind::Fields => {
 244                 AstFragment::Fields(items.map(Annotatable::expect_field).collect())
 245             }
 246             AstFragmentKind::FieldPats => {
 247                 AstFragment::FieldPats(items.map(Annotatable::expect_field_pattern).collect())
 248             }
 249             AstFragmentKind::GenericParams => {
 250                 AstFragment::GenericParams(items.map(Annotatable::expect_generic_param).collect())
 251             }
 252             AstFragmentKind::Params => {
 253                 AstFragment::Params(items.map(Annotatable::expect_param).collect())
 254             }
 255             AstFragmentKind::StructFields => {
 256                 AstFragment::StructFields(items.map(Annotatable::expect_struct_field).collect())
 257             }
 258             AstFragmentKind::Variants => {
 259                 AstFragment::Variants(items.map(Annotatable::expect_variant).collect())
 260             }
 261             AstFragmentKind::Items => {
 262                 AstFragment::Items(items.map(Annotatable::expect_item).collect())
 263             }
 264             AstFragmentKind::ImplItems => {
 265                 AstFragment::ImplItems(items.map(Annotatable::expect_impl_item).collect())
 266             }
 267             AstFragmentKind::TraitItems => {
 268                 AstFragment::TraitItems(items.map(Annotatable::expect_trait_item).collect())
 269             }
 270             AstFragmentKind::ForeignItems => {
 271                 AstFragment::ForeignItems(items.map(Annotatable::expect_foreign_item).collect())
 272             }
 273             AstFragmentKind::Stmts => {
 274                 AstFragment::Stmts(items.map(Annotatable::expect_stmt).collect())
 275             }
 276             AstFragmentKind::Expr => AstFragment::Expr(
 277                 items.next().expect("expected exactly one expression").expect_expr(),
 278             ),
 279             AstFragmentKind::OptExpr => {
 280                 AstFragment::OptExpr(items.next().map(Annotatable::expect_expr))
 281             }
 282             AstFragmentKind::Pat | AstFragmentKind::Ty => {
 283                 panic!("patterns and types aren't annotatable")
 284             }
 285         }
 286     }
 287 }
 288
 289 pub struct Invocation {
 290     pub kind: InvocationKind,
 291     pub fragment_kind: AstFragmentKind,
 292     pub expansion_data: ExpansionData,
 293 }
 294
 295 pub enum InvocationKind {
 296     Bang {
 297         mac: ast::MacCall,
 298         span: Span,
 299     },
 300     Attr {
 301         attr: ast::Attribute,
 302         item: Annotatable,
 303         // Required for resolving derive helper attributes.
 304         derives: Vec<Path>,
 305         // We temporarily report errors for attribute macros placed after derives
 306         after_derive: bool,
 307     },
 308     Derive {
 309         path: Path,
 310         item: Annotatable,
 311     },
 312     /// "Invocation" that contains all derives from an item,
 313     /// broken into multiple `Derive` invocations when expanded.
 314     /// FIXME: Find a way to remove it.
 315     DeriveContainer {
 316         derives: Vec<Path>,
 317         item: Annotatable,
 318     },
 319 }
 320
 321 impl InvocationKind {
 322     fn placeholder_visibility(&self) -> Option<ast::Visibility> {
 323         // HACK: For unnamed fields placeholders should have the same visibility as the actual
 324         // fields because for tuple structs/variants resolve determines visibilities of their
 325         // constructor using these field visibilities before attributes on them are are expanded.
 326         // The assumption is that the attribute expansion cannot change field visibilities,
 327         // and it holds because only inert attributes are supported in this position.
 328         match self {
 329             InvocationKind::Attr { item: Annotatable::StructField(field), .. }
 330             | InvocationKind::Derive { item: Annotatable::StructField(field), .. }
 331             | InvocationKind::DeriveContainer { item: Annotatable::StructField(field), .. }
 332                 if field.ident.is_none() =>
 333             {
 334                 Some(field.vis.clone())
 335             }
 336             _ => None,
 337         }
 338     }
 339 }
 340
 341 impl Invocation {
 342     pub fn span(&self) -> Span {
 343         match &self.kind {
 344             InvocationKind::Bang { span, .. } => *span,
 345             InvocationKind::Attr { attr, .. } => attr.span,
 346             InvocationKind::Derive { path, .. } => path.span,
 347             InvocationKind::DeriveContainer { item, .. } => item.span(),
 348         }
 349     }
 350 }
 351
 352 pub struct MacroExpander<'a, 'b> {
 353     pub cx: &'a mut ExtCtxt<'b>,
 354     monotonic: bool, // cf. `cx.monotonic_expander()`
 355 }
 356
 357 impl<'a, 'b> MacroExpander<'a, 'b> {
 358     pub fn new(cx: &'a mut ExtCtxt<'b>, monotonic: bool) -> Self {
 359         MacroExpander { cx, monotonic }
 360     }
 361
 362     pub fn expand_crate(&mut self, mut krate: ast::Crate) -> ast::Crate {
 363         let mut module = ModuleData {
 364             mod_path: vec![Ident::from_str(&self.cx.ecfg.crate_name)],
 365             directory: match self.cx.source_map().span_to_unmapped_path(krate.span) {
 366                 FileName::Real(name) => name.into_local_path(),
 367                 other => PathBuf::from(other.to_string()),
 368             },
 369         };
 370         module.directory.pop();
 371         self.cx.root_path = module.directory.clone();
 372         self.cx.current_expansion.module = Rc::new(module);
 373
 374         let orig_mod_span = krate.module.inner;
 375
 376         let krate_item = AstFragment::Items(smallvec![P(ast::Item {
 377             attrs: krate.attrs,
 378             span: krate.span,
 379             kind: ast::ItemKind::Mod(krate.module),
 380             ident: Ident::invalid(),
 381             id: ast::DUMMY_NODE_ID,
 382             vis: ast::Visibility {
 383                 span: krate.span.shrink_to_lo(),
 384                 kind: ast::VisibilityKind::Public,
 385                 tokens: None,
 386             },
 387             tokens: None,
 388         })]);
 389
 390         match self.fully_expand_fragment(krate_item).make_items().pop().map(P::into_inner) {
 391             Some(ast::Item { attrs, kind: ast::ItemKind::Mod(module), .. }) => {
 392                 krate.attrs = attrs;
 393                 krate.module = module;
 394             }
 395             None => {
 396                 // Resolution failed so we return an empty expansion
 397                 krate.attrs = vec![];
 398                 krate.module = ast::Mod {
 399                     inner: orig_mod_span,
 400                     unsafety: Unsafe::No,
 401                     items: vec![],
 402                     inline: true,
 403                 };
 404             }
 405             Some(ast::Item { span, kind, .. }) => {
 406                 krate.attrs = vec![];
 407                 krate.module = ast::Mod {
 408                     inner: orig_mod_span,
 409                     unsafety: Unsafe::No,
 410                     items: vec![],
 411                     inline: true,
 412                 };
 413                 self.cx.span_err(
 414                     span,
 415                     &format!(
 416                         "expected crate top-level item to be a module after macro expansion, found {} {}",
 417                         kind.article(), kind.descr()
 418                     ),
 419                 );
 420             }
 421         };
 422         self.cx.trace_macros_diag();
 423         krate
 424     }
 425
 426     // Recursively expand all macro invocations in this AST fragment.
 427     pub fn fully_expand_fragment(&mut self, input_fragment: AstFragment) -> AstFragment {
 428         let orig_expansion_data = self.cx.current_expansion.clone();
 429         let orig_force_mode = self.cx.force_mode;
 430         self.cx.current_expansion.depth = 0;
 431
 432         // Collect all macro invocations and replace them with placeholders.
 433         let (mut fragment_with_placeholders, mut invocations) =
 434             self.collect_invocations(input_fragment, &[]);
 435
 436         // Optimization: if we resolve all imports now,
 437         // we'll be able to immediately resolve most of imported macros.
 438         self.resolve_imports();
 439
 440         // Resolve paths in all invocations and produce output expanded fragments for them, but
 441         // do not insert them into our input AST fragment yet, only store in `expanded_fragments`.
 442         // The output fragments also go through expansion recursively until no invocations are left.
 443         // Unresolved macros produce dummy outputs as a recovery measure.
 444         invocations.reverse();
 445         let mut expanded_fragments = Vec::new();
 446         let mut undetermined_invocations = Vec::new();
 447         let (mut progress, mut force) = (false, !self.monotonic);
 448         loop {
 449             let (invoc, res) = if let Some(invoc) = invocations.pop() {
 450                 invoc
 451             } else {
 452                 self.resolve_imports();
 453                 if undetermined_invocations.is_empty() {
 454                     break;
 455                 }
 456                 invocations = mem::take(&mut undetermined_invocations);
 457                 force = !mem::replace(&mut progress, false);
 458                 if force && self.monotonic {
 459                     self.cx.sess.delay_span_bug(
 460                         invocations.last().unwrap().0.span(),
 461                         "expansion entered force mode without producing any errors",
 462                     );
 463                 }
 464                 continue;
 465             };
 466
 467             let res = match res {
 468                 Some(res) => res,
 469                 None => {
 470                     let eager_expansion_root = if self.monotonic {
 471                         invoc.expansion_data.id
 472                     } else {
 473                         orig_expansion_data.id
 474                     };
 475                     match self.cx.resolver.resolve_macro_invocation(
 476                         &invoc,
 477                         eager_expansion_root,
 478                         force,
 479                     ) {
 480                         Ok(res) => res,
 481                         Err(Indeterminate) => {
 482                             // Cannot resolve, will retry this invocation later.
 483                             undetermined_invocations.push((invoc, None));
 484                             continue;
 485                         }
 486                     }
 487                 }
 488             };
 489
 490             let ExpansionData { depth, id: expn_id, .. } = invoc.expansion_data;
 491             self.cx.current_expansion = invoc.expansion_data.clone();
 492             self.cx.force_mode = force;
 493
 494             // FIXME(jseyfried): Refactor out the following logic
 495             let fragment_kind = invoc.fragment_kind;
 496             let (expanded_fragment, new_invocations) = match res {
 497                 InvocationRes::Single(ext) => match self.expand_invoc(invoc, &ext.kind) {
 498                     ExpandResult::Ready(fragment) => self.collect_invocations(fragment, &[]),
 499                     ExpandResult::Retry(invoc) => {
 500                         if force {
 501                             self.cx.span_bug(
 502                                 invoc.span(),
 503                                 "expansion entered force mode but is still stuck",
 504                             );
 505                         } else {
 506                             // Cannot expand, will retry this invocation later.
 507                             undetermined_invocations
 508                                 .push((invoc, Some(InvocationRes::Single(ext))));
 509                             continue;
 510                         }
 511                     }
 512                 },
 513                 InvocationRes::DeriveContainer(_exts) => {
 514                     // FIXME: Consider using the derive resolutions (`_exts`) immediately,
 515                     // instead of enqueuing the derives to be resolved again later.
 516                     let (derives, mut item) = match invoc.kind {
 517                         InvocationKind::DeriveContainer { derives, item } => (derives, item),
 518                         _ => unreachable!(),
 519                     };
 520                     let (item, derive_placeholders) = if !item.derive_allowed() {
 521                         self.error_derive_forbidden_on_non_adt(&derives, &item);
 522                         item.visit_attrs(|attrs| attrs.retain(|a| !a.has_name(sym::derive)));
 523                         (item, Vec::new())
 524                     } else {
 525                         let mut item = StripUnconfigured {
 526                             sess: self.cx.sess,
 527                             features: self.cx.ecfg.features,
 528                         }
 529                         .fully_configure(item);
 530                         item.visit_attrs(|attrs| attrs.retain(|a| !a.has_name(sym::derive)));
 531
 532                         invocations.reserve(derives.len());
 533                         let derive_placeholders = derives
 534                             .into_iter()
 535                             .map(|path| {
 536                                 let expn_id = ExpnId::fresh(None);
 537                                 invocations.push((
 538                                     Invocation {
 539                                         kind: InvocationKind::Derive { path, item: item.clone() },
 540                                         fragment_kind,
 541                                         expansion_data: ExpansionData {
 542                                             id: expn_id,
 543                                             ..self.cx.current_expansion.clone()
 544                                         },
 545                                     },
 546                                     None,
 547                                 ));
 548                                 NodeId::placeholder_from_expn_id(expn_id)
 549                             })
 550                             .collect::<Vec<_>>();
 551                         (item, derive_placeholders)
 552                     };
 553
 554                     let fragment = fragment_kind.expect_from_annotatables(::std::iter::once(item));
 555                     self.collect_invocations(fragment, &derive_placeholders)
 556                 }
 557             };
 558
 559             progress = true;
 560             if expanded_fragments.len() < depth {
 561                 expanded_fragments.push(Vec::new());
 562             }
 563             expanded_fragments[depth - 1].push((expn_id, expanded_fragment));
 564             invocations.extend(new_invocations.into_iter().rev());
 565         }
 566
 567         self.cx.current_expansion = orig_expansion_data;
 568         self.cx.force_mode = orig_force_mode;
 569
 570         // Finally incorporate all the expanded macros into the input AST fragment.
 571         let mut placeholder_expander = PlaceholderExpander::new(self.cx, self.monotonic);
 572         while let Some(expanded_fragments) = expanded_fragments.pop() {
 573             for (expn_id, expanded_fragment) in expanded_fragments.into_iter().rev() {
 574                 placeholder_expander
 575                     .add(NodeId::placeholder_from_expn_id(expn_id), expanded_fragment);
 576             }
 577         }
 578         fragment_with_placeholders.mut_visit_with(&mut placeholder_expander);
 579         fragment_with_placeholders
 580     }
 581
 582     fn error_derive_forbidden_on_non_adt(&self, derives: &[Path], item: &Annotatable) {
 583         let attr = self.cx.sess.find_by_name(item.attrs(), sym::derive);
 584         let span = attr.map_or(item.span(), |attr| attr.span);
 585         let mut err = struct_span_err!(
 586             self.cx.sess,
 587             span,
 588             E0774,
 589             "`derive` may only be applied to structs, enums and unions",
 590         );
 591         if let Some(ast::Attribute { style: ast::AttrStyle::Inner, .. }) = attr {
 592             let trait_list = derives.iter().map(|t| pprust::path_to_string(t)).collect::<Vec<_>>();
 593             let suggestion = format!("#[derive({})]", trait_list.join(", "));
 594             err.span_suggestion(
 595                 span,
 596                 "try an outer attribute",
 597                 suggestion,
 598                 // We don't 𝑘𝑛𝑜𝑤 that the following item is an ADT
 599                 Applicability::MaybeIncorrect,
 600             );
 601         }
 602         err.emit();
 603     }
 604
 605     fn resolve_imports(&mut self) {
 606         if self.monotonic {
 607             self.cx.resolver.resolve_imports();
 608         }
 609     }
 610
 611     /// Collects all macro invocations reachable at this time in this AST fragment, and replace
 612     /// them with "placeholders" - dummy macro invocations with specially crafted `NodeId`s.
 613     /// Then call into resolver that builds a skeleton ("reduced graph") of the fragment and
 614     /// prepares data for resolving paths of macro invocations.
 615     fn collect_invocations(
 616         &mut self,
 617         mut fragment: AstFragment,
 618         extra_placeholders: &[NodeId],
 619     ) -> (AstFragment, Vec<(Invocation, Option<InvocationRes>)>) {
 620         // Resolve `$crate`s in the fragment for pretty-printing.
 621         self.cx.resolver.resolve_dollar_crates();
 622
 623         let invocations = {
 624             let mut collector = InvocationCollector {
 625                 cfg: StripUnconfigured { sess: &self.cx.sess, features: self.cx.ecfg.features },
 626                 cx: self.cx,
 627                 invocations: Vec::new(),
 628                 monotonic: self.monotonic,
 629             };
 630             fragment.mut_visit_with(&mut collector);
 631             fragment.add_placeholders(extra_placeholders);
 632             collector.invocations
 633         };
 634
 635         if self.monotonic {
 636             self.cx
 637                 .resolver
 638                 .visit_ast_fragment_with_placeholders(self.cx.current_expansion.id, &fragment);
 639         }
 640
 641         (fragment, invocations)
 642     }
 643
 644     fn error_recursion_limit_reached(&mut self) {
 645         let expn_data = self.cx.current_expansion.id.expn_data();
 646         let suggested_limit = self.cx.ecfg.recursion_limit * 2;
 647         self.cx
 648             .struct_span_err(
 649                 expn_data.call_site,
 650                 &format!("recursion limit reached while expanding `{}`", expn_data.kind.descr()),
 651             )
 652             .help(&format!(
 653                 "consider adding a `#![recursion_limit=\"{}\"]` attribute to your crate (`{}`)",
 654                 suggested_limit, self.cx.ecfg.crate_name,
 655             ))
 656             .emit();
 657         self.cx.trace_macros_diag();
 658     }
 659
 660     /// A macro's expansion does not fit in this fragment kind.
 661     /// For example, a non-type macro in a type position.
 662     fn error_wrong_fragment_kind(&mut self, kind: AstFragmentKind, mac: &ast::MacCall, span: Span) {
 663         let msg = format!(
 664             "non-{kind} macro in {kind} position: {path}",
 665             kind = kind.name(),
 666             path = pprust::path_to_string(&mac.path),
 667         );
 668         self.cx.span_err(span, &msg);
 669         self.cx.trace_macros_diag();
 670     }
 671
 672     fn expand_invoc(
 673         &mut self,
 674         invoc: Invocation,
 675         ext: &SyntaxExtensionKind,
 676     ) -> ExpandResult<AstFragment, Invocation> {
 677         let recursion_limit =
 678             self.cx.reduced_recursion_limit.unwrap_or(self.cx.ecfg.recursion_limit);
 679         if !recursion_limit.value_within_limit(self.cx.current_expansion.depth) {
 680             if self.cx.reduced_recursion_limit.is_none() {
 681                 self.error_recursion_limit_reached();
 682             }
 683
 684             // Reduce the recursion limit by half each time it triggers.
 685             self.cx.reduced_recursion_limit = Some(recursion_limit / 2);
 686
 687             return ExpandResult::Ready(invoc.fragment_kind.dummy(invoc.span()));
 688         }
 689
 690         let (fragment_kind, span) = (invoc.fragment_kind, invoc.span());
 691         ExpandResult::Ready(match invoc.kind {
 692             InvocationKind::Bang { mac, .. } => match ext {
 693                 SyntaxExtensionKind::Bang(expander) => {
 694                     let tok_result = match expander.expand(self.cx, span, mac.args.inner_tokens()) {
 695                         Err(_) => return ExpandResult::Ready(fragment_kind.dummy(span)),
 696                         Ok(ts) => ts,
 697                     };
 698                     self.parse_ast_fragment(tok_result, fragment_kind, &mac.path, span)
 699                 }
 700                 SyntaxExtensionKind::LegacyBang(expander) => {
 701                     let prev = self.cx.current_expansion.prior_type_ascription;
 702                     self.cx.current_expansion.prior_type_ascription = mac.prior_type_ascription;
 703                     let tok_result = expander.expand(self.cx, span, mac.args.inner_tokens());
 704                     let result = if let Some(result) = fragment_kind.make_from(tok_result) {
 705                         result
 706                     } else {
 707                         self.error_wrong_fragment_kind(fragment_kind, &mac, span);
 708                         fragment_kind.dummy(span)
 709                     };
 710                     self.cx.current_expansion.prior_type_ascription = prev;
 711                     result
 712                 }
 713                 _ => unreachable!(),
 714             },
 715             InvocationKind::Attr { attr, mut item, derives, after_derive } => match ext {
 716                 SyntaxExtensionKind::Attr(expander) => {
 717                     self.gate_proc_macro_input(&item);
 718                     self.gate_proc_macro_attr_item(span, &item);
 719                     let tokens = item.into_tokens(&self.cx.sess.parse_sess);
 720                     let attr_item = attr.unwrap_normal_item();
 721                     if let MacArgs::Eq(..) = attr_item.args {
 722                         self.cx.span_err(span, "key-value macro attributes are not supported");
 723                     }
 724                     let inner_tokens = attr_item.args.inner_tokens();
 725                     let tok_result = match expander.expand(self.cx, span, inner_tokens, tokens) {
 726                         Err(_) => return ExpandResult::Ready(fragment_kind.dummy(span)),
 727                         Ok(ts) => ts,
 728                     };
 729                     self.parse_ast_fragment(tok_result, fragment_kind, &attr_item.path, span)
 730                 }
 731                 SyntaxExtensionKind::LegacyAttr(expander) => {
 732                     match validate_attr::parse_meta(&self.cx.sess.parse_sess, &attr) {
 733                         Ok(meta) => {
 734                             let items = match expander.expand(self.cx, span, &meta, item) {
 735                                 ExpandResult::Ready(items) => items,
 736                                 ExpandResult::Retry(item) => {
 737                                     // Reassemble the original invocation for retrying.
 738                                     return ExpandResult::Retry(Invocation {
 739                                         kind: InvocationKind::Attr {
 740                                             attr,
 741                                             item,
 742                                             derives,
 743                                             after_derive,
 744                                         },
 745                                         ..invoc
 746                                     });
 747                                 }
 748                             };
 749                             fragment_kind.expect_from_annotatables(items)
 750                         }
 751                         Err(mut err) => {
 752                             err.emit();
 753                             fragment_kind.dummy(span)
 754                         }
 755                     }
 756                 }
 757                 SyntaxExtensionKind::NonMacroAttr { mark_used } => {
 758                     self.cx.sess.mark_attr_known(&attr);
 759                     if *mark_used {
 760                         self.cx.sess.mark_attr_used(&attr);
 761                     }
 762                     item.visit_attrs(|attrs| attrs.push(attr));
 763                     fragment_kind.expect_from_annotatables(iter::once(item))
 764                 }
 765                 _ => unreachable!(),
 766             },
 767             InvocationKind::Derive { path, item } => match ext {
 768                 SyntaxExtensionKind::Derive(expander)
 769                 | SyntaxExtensionKind::LegacyDerive(expander) => {
 770                     if let SyntaxExtensionKind::Derive(..) = ext {
 771                         self.gate_proc_macro_input(&item);
 772                     }
 773                     let meta = ast::MetaItem { kind: ast::MetaItemKind::Word, span, path };
 774                     let items = match expander.expand(self.cx, span, &meta, item) {
 775                         ExpandResult::Ready(items) => items,
 776                         ExpandResult::Retry(item) => {
 777                             // Reassemble the original invocation for retrying.
 778                             return ExpandResult::Retry(Invocation {
 779                                 kind: InvocationKind::Derive { path: meta.path, item },
 780                                 ..invoc
 781                             });
 782                         }
 783                     };
 784                     fragment_kind.expect_from_annotatables(items)
 785                 }
 786                 _ => unreachable!(),
 787             },
 788             InvocationKind::DeriveContainer { .. } => unreachable!(),
 789         })
 790     }
 791
 792     fn gate_proc_macro_attr_item(&self, span: Span, item: &Annotatable) {
 793         let kind = match item {
 794             Annotatable::Item(_)
 795             | Annotatable::TraitItem(_)
 796             | Annotatable::ImplItem(_)
 797             | Annotatable::ForeignItem(_) => return,
 798             Annotatable::Stmt(stmt) => {
 799                 // Attributes are stable on item statements,
 800                 // but unstable on all other kinds of statements
 801                 if stmt.is_item() {
 802                     return;
 803                 }
 804                 "statements"
 805             }
 806             Annotatable::Expr(_) => "expressions",
 807             Annotatable::Arm(..)
 808             | Annotatable::Field(..)
 809             | Annotatable::FieldPat(..)
 810             | Annotatable::GenericParam(..)
 811             | Annotatable::Param(..)
 812             | Annotatable::StructField(..)
 813             | Annotatable::Variant(..) => panic!("unexpected annotatable"),
 814         };
 815         if self.cx.ecfg.proc_macro_hygiene() {
 816             return;
 817         }
 818         feature_err(
 819             &self.cx.sess.parse_sess,
 820             sym::proc_macro_hygiene,
 821             span,
 822             &format!("custom attributes cannot be applied to {}", kind),
 823         )
 824         .emit();
 825     }
 826
 827     fn gate_proc_macro_input(&self, annotatable: &Annotatable) {
 828         struct GateProcMacroInput<'a> {
 829             parse_sess: &'a ParseSess,
 830         }
 831
 832         impl<'ast, 'a> Visitor<'ast> for GateProcMacroInput<'a> {
 833             fn visit_item(&mut self, item: &'ast ast::Item) {
 834                 match &item.kind {
 835                     ast::ItemKind::Mod(module) if !module.inline => {
 836                         feature_err(
 837                             self.parse_sess,
 838                             sym::proc_macro_hygiene,
 839                             item.span,
 840                             "non-inline modules in proc macro input are unstable",
 841                         )
 842                         .emit();
 843                     }
 844                     _ => {}
 845                 }
 846
 847                 visit::walk_item(self, item);
 848             }
 849         }
 850
 851         if !self.cx.ecfg.proc_macro_hygiene() {
 852             annotatable
 853                 .visit_with(&mut GateProcMacroInput { parse_sess: &self.cx.sess.parse_sess });
 854         }
 855     }
 856
 857     fn parse_ast_fragment(
 858         &mut self,
 859         toks: TokenStream,
 860         kind: AstFragmentKind,
 861         path: &Path,
 862         span: Span,
 863     ) -> AstFragment {
 864         let mut parser = self.cx.new_parser_from_tts(toks);
 865         match parse_ast_fragment(&mut parser, kind) {
 866             Ok(fragment) => {
 867                 ensure_complete_parse(&mut parser, path, kind.name(), span);
 868                 fragment
 869             }
 870             Err(mut err) => {
 871                 err.set_span(span);
 872                 annotate_err_with_kind(&mut err, kind, span);
 873                 err.emit();
 874                 self.cx.trace_macros_diag();
 875                 kind.dummy(span)
 876             }
 877         }
 878     }
 879 }
 880
 881 pub fn parse_ast_fragment<'a>(
 882     this: &mut Parser<'a>,
 883     kind: AstFragmentKind,
 884 ) -> PResult<'a, AstFragment> {
 885     Ok(match kind {
 886         AstFragmentKind::Items => {
 887             let mut items = SmallVec::new();
 888             while let Some(item) = this.parse_item()? {
 889                 items.push(item);
 890             }
 891             AstFragment::Items(items)
 892         }
 893         AstFragmentKind::TraitItems => {
 894             let mut items = SmallVec::new();
 895             while let Some(item) = this.parse_trait_item()? {
 896                 items.extend(item);
 897             }
 898             AstFragment::TraitItems(items)
 899         }
 900         AstFragmentKind::ImplItems => {
 901             let mut items = SmallVec::new();
 902             while let Some(item) = this.parse_impl_item()? {
 903                 items.extend(item);
 904             }
 905             AstFragment::ImplItems(items)
 906         }
 907         AstFragmentKind::ForeignItems => {
 908             let mut items = SmallVec::new();
 909             while let Some(item) = this.parse_foreign_item()? {
 910                 items.extend(item);
 911             }
 912             AstFragment::ForeignItems(items)
 913         }
 914         AstFragmentKind::Stmts => {
 915             let mut stmts = SmallVec::new();
 916             // Won't make progress on a `}`.
 917             while this.token != token::Eof && this.token != token::CloseDelim(token::Brace) {
 918                 if let Some(stmt) = this.parse_full_stmt(AttemptLocalParseRecovery::Yes)? {
 919                     stmts.push(stmt);
 920                 }
 921             }
 922             AstFragment::Stmts(stmts)
 923         }
 924         AstFragmentKind::Expr => AstFragment::Expr(this.parse_expr()?),
 925         AstFragmentKind::OptExpr => {
 926             if this.token != token::Eof {
 927                 AstFragment::OptExpr(Some(this.parse_expr()?))
 928             } else {
 929                 AstFragment::OptExpr(None)
 930             }
 931         }
 932         AstFragmentKind::Ty => AstFragment::Ty(this.parse_ty()?),
 933         AstFragmentKind::Pat => AstFragment::Pat(this.parse_pat(None)?),
 934         AstFragmentKind::Arms
 935         | AstFragmentKind::Fields
 936         | AstFragmentKind::FieldPats
 937         | AstFragmentKind::GenericParams
 938         | AstFragmentKind::Params
 939         | AstFragmentKind::StructFields
 940         | AstFragmentKind::Variants => panic!("unexpected AST fragment kind"),
 941     })
 942 }
 943
 944 pub fn ensure_complete_parse<'a>(
 945     this: &mut Parser<'a>,
 946     macro_path: &Path,
 947     kind_name: &str,
 948     span: Span,
 949 ) {
 950     if this.token != token::Eof {
 951         let token = pprust::token_to_string(&this.token);
 952         let msg = format!("macro expansion ignores token `{}` and any following", token);
 953         // Avoid emitting backtrace info twice.
 954         let def_site_span = this.token.span.with_ctxt(SyntaxContext::root());
 955         let mut err = this.struct_span_err(def_site_span, &msg);
 956         err.span_label(span, "caused by the macro expansion here");
 957         let msg = format!(
 958             "the usage of `{}!` is likely invalid in {} context",
 959             pprust::path_to_string(macro_path),
 960             kind_name,
 961         );
 962         err.note(&msg);
 963         let semi_span = this.sess.source_map().next_point(span);
 964
 965         let semi_full_span = semi_span.to(this.sess.source_map().next_point(semi_span));
 966         match this.sess.source_map().span_to_snippet(semi_full_span) {
 967             Ok(ref snippet) if &snippet[..] != ";" && kind_name == "expression" => {
 968                 err.span_suggestion(
 969                     semi_span,
 970                     "you might be missing a semicolon here",
 971                     ";".to_owned(),
 972                     Applicability::MaybeIncorrect,
 973                 );
 974             }
 975             _ => {}
 976         }
 977         err.emit();
 978     }
 979 }
 980
 981 struct InvocationCollector<'a, 'b> {
 982     cx: &'a mut ExtCtxt<'b>,
 983     cfg: StripUnconfigured<'a>,
 984     invocations: Vec<(Invocation, Option<InvocationRes>)>,
 985     monotonic: bool,
 986 }
 987
 988 impl<'a, 'b> InvocationCollector<'a, 'b> {
 989     fn collect(&mut self, fragment_kind: AstFragmentKind, kind: InvocationKind) -> AstFragment {
 990         // Expansion data for all the collected invocations is set upon their resolution,
 991         // with exception of the derive container case which is not resolved and can get
 992         // its expansion data immediately.
 993         let expn_data = match &kind {
 994             InvocationKind::DeriveContainer { item, .. } => Some(ExpnData {
 995                 parent: self.cx.current_expansion.id,
 996                 ..ExpnData::default(
 997                     ExpnKind::Macro(MacroKind::Attr, sym::derive),
 998                     item.span(),
 999                     self.cx.sess.parse_sess.edition,
1000                     None,
1001                 )
1002             }),
1003             _ => None,
1004         };
1005         let expn_id = ExpnId::fresh(expn_data);
1006         let vis = kind.placeholder_visibility();
1007         self.invocations.push((
1008             Invocation {
1009                 kind,
1010                 fragment_kind,
1011                 expansion_data: ExpansionData {
1012                     id: expn_id,
1013                     depth: self.cx.current_expansion.depth + 1,
1014                     ..self.cx.current_expansion.clone()
1015                 },
1016             },
1017             None,
1018         ));
1019         placeholder(fragment_kind, NodeId::placeholder_from_expn_id(expn_id), vis)
1020     }
1021
1022     fn collect_bang(
1023         &mut self,
1024         mac: ast::MacCall,
1025         span: Span,
1026         kind: AstFragmentKind,
1027     ) -> AstFragment {
1028         self.collect(kind, InvocationKind::Bang { mac, span })
1029     }
1030
1031     fn collect_attr(
1032         &mut self,
1033         (attr, derives, after_derive): (Option<ast::Attribute>, Vec<Path>, bool),
1034         item: Annotatable,
1035         kind: AstFragmentKind,
1036     ) -> AstFragment {
1037         self.collect(
1038             kind,
1039             match attr {
1040                 Some(attr) => InvocationKind::Attr { attr, item, derives, after_derive },
1041                 None => InvocationKind::DeriveContainer { derives, item },
1042             },
1043         )
1044     }
1045
1046     fn find_attr_invoc(
1047         &self,
1048         attrs: &mut Vec<ast::Attribute>,
1049         after_derive: &mut bool,
1050     ) -> Option<ast::Attribute> {
1051         attrs
1052             .iter()
1053             .position(|a| {
1054                 if a.has_name(sym::derive) {
1055                     *after_derive = true;
1056                 }
1057                 !self.cx.sess.is_attr_known(a) && !is_builtin_attr(a)
1058             })
1059             .map(|i| attrs.remove(i))
1060     }
1061
1062     /// If `item` is an attr invocation, remove and return the macro attribute and derive traits.
1063     fn take_first_attr(
1064         &mut self,
1065         item: &mut impl HasAttrs,
1066     ) -> Option<(Option<ast::Attribute>, Vec<Path>, /* after_derive */ bool)> {
1067         let (mut attr, mut traits, mut after_derive) = (None, Vec::new(), false);
1068
1069         item.visit_attrs(|mut attrs| {
1070             attr = self.find_attr_invoc(&mut attrs, &mut after_derive);
1071             traits = collect_derives(&mut self.cx, &mut attrs);
1072         });
1073
1074         if attr.is_some() || !traits.is_empty() { Some((attr, traits, after_derive)) } else { None }
1075     }
1076
1077     /// Alternative to `take_first_attr()` that ignores `#[derive]` so invocations fallthrough
1078     /// to the unused-attributes lint (making it an error on statements and expressions
1079     /// is a breaking change)
1080     fn take_first_attr_no_derive(
1081         &mut self,
1082         nonitem: &mut impl HasAttrs,
1083     ) -> Option<(Option<ast::Attribute>, Vec<Path>, /* after_derive */ bool)> {
1084         let (mut attr, mut after_derive) = (None, false);
1085
1086         nonitem.visit_attrs(|mut attrs| {
1087             attr = self.find_attr_invoc(&mut attrs, &mut after_derive);
1088         });
1089
1090         attr.map(|attr| (Some(attr), Vec::new(), after_derive))
1091     }
1092
1093     fn configure<T: HasAttrs>(&mut self, node: T) -> Option<T> {
1094         self.cfg.configure(node)
1095     }
1096
1097     // Detect use of feature-gated or invalid attributes on macro invocations
1098     // since they will not be detected after macro expansion.
1099     fn check_attributes(&mut self, attrs: &[ast::Attribute]) {
1100         let features = self.cx.ecfg.features.unwrap();
1101         for attr in attrs.iter() {
1102             rustc_ast_passes::feature_gate::check_attribute(attr, self.cx.sess, features);
1103             validate_attr::check_meta(&self.cx.sess.parse_sess, attr);
1104
1105             // macros are expanded before any lint passes so this warning has to be hardcoded
1106             if attr.has_name(sym::derive) {
1107                 self.cx
1108                     .parse_sess()
1109                     .span_diagnostic
1110                     .struct_span_warn(attr.span, "`#[derive]` does nothing on macro invocations")
1111                     .note("this may become a hard error in a future release")
1112                     .emit();
1113             }
1114
1115             if attr.doc_str().is_some() {
1116                 self.cx.sess.parse_sess.buffer_lint_with_diagnostic(
1117                     &UNUSED_DOC_COMMENTS,
1118                     attr.span,
1119                     ast::CRATE_NODE_ID,
1120                     "unused doc comment",
1121                     BuiltinLintDiagnostics::UnusedDocComment(attr.span),
1122                 );
1123             }
1124         }
1125     }
1126 }
1127
1128 impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
1129     fn visit_expr(&mut self, expr: &mut P<ast::Expr>) {
1130         self.cfg.configure_expr(expr);
1131         visit_clobber(expr.deref_mut(), |mut expr| {
1132             self.cfg.configure_expr_kind(&mut expr.kind);
1133
1134             if let Some(attr) = self.take_first_attr_no_derive(&mut expr) {
1135                 // Collect the invoc regardless of whether or not attributes are permitted here
1136                 // expansion will eat the attribute so it won't error later.
1137                 if let Some(attr) = attr.0.as_ref() {
1138                     self.cfg.maybe_emit_expr_attr_err(attr)
1139                 }
1140
1141                 // AstFragmentKind::Expr requires the macro to emit an expression.
1142                 return self
1143                     .collect_attr(attr, Annotatable::Expr(P(expr)), AstFragmentKind::Expr)
1144                     .make_expr()
1145                     .into_inner();
1146             }
1147
1148             if let ast::ExprKind::MacCall(mac) = expr.kind {
1149                 self.check_attributes(&expr.attrs);
1150                 self.collect_bang(mac, expr.span, AstFragmentKind::Expr).make_expr().into_inner()
1151             } else {
1152                 ensure_sufficient_stack(|| noop_visit_expr(&mut expr, self));
1153                 expr
1154             }
1155         });
1156     }
1157
1158     fn flat_map_arm(&mut self, arm: ast::Arm) -> SmallVec<[ast::Arm; 1]> {
1159         let mut arm = configure!(self, arm);
1160
1161         if let Some(attr) = self.take_first_attr(&mut arm) {
1162             return self
1163                 .collect_attr(attr, Annotatable::Arm(arm), AstFragmentKind::Arms)
1164                 .make_arms();
1165         }
1166
1167         noop_flat_map_arm(arm, self)
1168     }
1169
1170     fn flat_map_field(&mut self, field: ast::Field) -> SmallVec<[ast::Field; 1]> {
1171         let mut field = configure!(self, field);
1172
1173         if let Some(attr) = self.take_first_attr(&mut field) {
1174             return self
1175                 .collect_attr(attr, Annotatable::Field(field), AstFragmentKind::Fields)
1176                 .make_fields();
1177         }
1178
1179         noop_flat_map_field(field, self)
1180     }
1181
1182     fn flat_map_field_pattern(&mut self, fp: ast::FieldPat) -> SmallVec<[ast::FieldPat; 1]> {
1183         let mut fp = configure!(self, fp);
1184
1185         if let Some(attr) = self.take_first_attr(&mut fp) {
1186             return self
1187                 .collect_attr(attr, Annotatable::FieldPat(fp), AstFragmentKind::FieldPats)
1188                 .make_field_patterns();
1189         }
1190
1191         noop_flat_map_field_pattern(fp, self)
1192     }
1193
1194     fn flat_map_param(&mut self, p: ast::Param) -> SmallVec<[ast::Param; 1]> {
1195         let mut p = configure!(self, p);
1196
1197         if let Some(attr) = self.take_first_attr(&mut p) {
1198             return self
1199                 .collect_attr(attr, Annotatable::Param(p), AstFragmentKind::Params)
1200                 .make_params();
1201         }
1202
1203         noop_flat_map_param(p, self)
1204     }
1205
1206     fn flat_map_struct_field(&mut self, sf: ast::StructField) -> SmallVec<[ast::StructField; 1]> {
1207         let mut sf = configure!(self, sf);
1208
1209         if let Some(attr) = self.take_first_attr(&mut sf) {
1210             return self
1211                 .collect_attr(attr, Annotatable::StructField(sf), AstFragmentKind::StructFields)
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         if let Some(attr) = self.take_first_attr(&mut variant) {
1222             return self
1223                 .collect_attr(attr, Annotatable::Variant(variant), AstFragmentKind::Variants)
1224                 .make_variants();
1225         }
1226
1227         noop_flat_map_variant(variant, self)
1228     }
1229
1230     fn filter_map_expr(&mut self, expr: P<ast::Expr>) -> Option<P<ast::Expr>> {
1231         let expr = configure!(self, expr);
1232         expr.filter_map(|mut expr| {
1233             self.cfg.configure_expr_kind(&mut expr.kind);
1234
1235             if let Some(attr) = self.take_first_attr_no_derive(&mut expr) {
1236                 if let Some(attr) = attr.0.as_ref() {
1237                     self.cfg.maybe_emit_expr_attr_err(attr)
1238                 }
1239
1240                 return self
1241                     .collect_attr(attr, Annotatable::Expr(P(expr)), AstFragmentKind::OptExpr)
1242                     .make_opt_expr()
1243                     .map(|expr| expr.into_inner());
1244             }
1245
1246             if let ast::ExprKind::MacCall(mac) = expr.kind {
1247                 self.check_attributes(&expr.attrs);
1248                 self.collect_bang(mac, expr.span, AstFragmentKind::OptExpr)
1249                     .make_opt_expr()
1250                     .map(|expr| expr.into_inner())
1251             } else {
1252                 Some({
1253                     noop_visit_expr(&mut expr, self);
1254                     expr
1255                 })
1256             }
1257         })
1258     }
1259
1260     fn visit_pat(&mut self, pat: &mut P<ast::Pat>) {
1261         self.cfg.configure_pat(pat);
1262         match pat.kind {
1263             PatKind::MacCall(_) => {}
1264             _ => return noop_visit_pat(pat, self),
1265         }
1266
1267         visit_clobber(pat, |mut pat| match mem::replace(&mut pat.kind, PatKind::Wild) {
1268             PatKind::MacCall(mac) => {
1269                 self.collect_bang(mac, pat.span, AstFragmentKind::Pat).make_pat()
1270             }
1271             _ => unreachable!(),
1272         });
1273     }
1274
1275     fn flat_map_stmt(&mut self, stmt: ast::Stmt) -> SmallVec<[ast::Stmt; 1]> {
1276         let mut stmt = configure!(self, stmt);
1277
1278         // we'll expand attributes on expressions separately
1279         if !stmt.is_expr() {
1280             let attr = if stmt.is_item() {
1281                 self.take_first_attr(&mut stmt)
1282             } else {
1283                 // Ignore derives on non-item statements for backwards compatibility.
1284                 // This will result in a unused attribute warning
1285                 self.take_first_attr_no_derive(&mut stmt)
1286             };
1287
1288             if let Some(attr) = attr {
1289                 return self
1290                     .collect_attr(attr, Annotatable::Stmt(P(stmt)), AstFragmentKind::Stmts)
1291                     .make_stmts();
1292             }
1293         }
1294
1295         if let StmtKind::MacCall(mac) = stmt.kind {
1296             let MacCallStmt { mac, style, attrs, tokens: _ } = mac.into_inner();
1297             self.check_attributes(&attrs);
1298             let mut placeholder =
1299                 self.collect_bang(mac, stmt.span, AstFragmentKind::Stmts).make_stmts();
1300
1301             // If this is a macro invocation with a semicolon, then apply that
1302             // semicolon to the final statement produced by expansion.
1303             if style == MacStmtStyle::Semicolon {
1304                 if let Some(stmt) = placeholder.pop() {
1305                     placeholder.push(stmt.add_trailing_semicolon());
1306                 }
1307             }
1308
1309             return placeholder;
1310         }
1311
1312         // The placeholder expander gives ids to statements, so we avoid folding the id here.
1313         let ast::Stmt { id, kind, span } = stmt;
1314         noop_flat_map_stmt_kind(kind, self)
1315             .into_iter()
1316             .map(|kind| ast::Stmt { id, kind, span })
1317             .collect()
1318     }
1319
1320     fn visit_block(&mut self, block: &mut P<Block>) {
1321         let old_directory_ownership = self.cx.current_expansion.directory_ownership;
1322         self.cx.current_expansion.directory_ownership = DirectoryOwnership::UnownedViaBlock;
1323         noop_visit_block(block, self);
1324         self.cx.current_expansion.directory_ownership = old_directory_ownership;
1325     }
1326
1327     fn flat_map_item(&mut self, item: P<ast::Item>) -> SmallVec<[P<ast::Item>; 1]> {
1328         let mut item = configure!(self, item);
1329
1330         if let Some(attr) = self.take_first_attr(&mut item) {
1331             return self
1332                 .collect_attr(attr, Annotatable::Item(item), AstFragmentKind::Items)
1333                 .make_items();
1334         }
1335
1336         let mut attrs = mem::take(&mut item.attrs); // We do this to please borrowck.
1337         let ident = item.ident;
1338         let span = item.span;
1339
1340         match item.kind {
1341             ast::ItemKind::MacCall(..) => {
1342                 item.attrs = attrs;
1343                 self.check_attributes(&item.attrs);
1344                 item.and_then(|item| match item.kind {
1345                     ItemKind::MacCall(mac) => {
1346                         self.collect_bang(mac, span, AstFragmentKind::Items).make_items()
1347                     }
1348                     _ => unreachable!(),
1349                 })
1350             }
1351             ast::ItemKind::Mod(ref mut old_mod @ ast::Mod { .. }) if ident != Ident::invalid() => {
1352                 let sess = &self.cx.sess.parse_sess;
1353                 let orig_ownership = self.cx.current_expansion.directory_ownership;
1354                 let mut module = (*self.cx.current_expansion.module).clone();
1355
1356                 let pushed = &mut false; // Record `parse_external_mod` pushing so we can pop.
1357                 let dir = Directory { ownership: orig_ownership, path: module.directory };
1358                 let Directory { ownership, path } = if old_mod.inline {
1359                     // Inline `mod foo { ... }`, but we still need to push directories.
1360                     item.attrs = attrs;
1361                     push_directory(&self.cx.sess, ident, &item.attrs, dir)
1362                 } else {
1363                     // We have an outline `mod foo;` so we need to parse the file.
1364                     let (new_mod, dir) = parse_external_mod(
1365                         &self.cx.sess,
1366                         ident,
1367                         span,
1368                         old_mod.unsafety,
1369                         dir,
1370                         &mut attrs,
1371                         pushed,
1372                     );
1373
1374                     let krate = ast::Crate {
1375                         span: new_mod.inner,
1376                         module: new_mod,
1377                         attrs,
1378                         proc_macros: vec![],
1379                     };
1380                     if let Some(extern_mod_loaded) = self.cx.extern_mod_loaded {
1381                         extern_mod_loaded(&krate);
1382                     }
1383
1384                     *old_mod = krate.module;
1385                     item.attrs = krate.attrs;
1386                     // File can have inline attributes, e.g., `#![cfg(...)]` & co. => Reconfigure.
1387                     item = match self.configure(item) {
1388                         Some(node) => node,
1389                         None => {
1390                             if *pushed {
1391                                 sess.included_mod_stack.borrow_mut().pop();
1392                             }
1393                             return Default::default();
1394                         }
1395                     };
1396                     dir
1397                 };
1398
1399                 // Set the module info before we flat map.
1400                 self.cx.current_expansion.directory_ownership = ownership;
1401                 module.directory = path;
1402                 module.mod_path.push(ident);
1403                 let orig_module =
1404                     mem::replace(&mut self.cx.current_expansion.module, Rc::new(module));
1405
1406                 let result = noop_flat_map_item(item, self);
1407
1408                 // Restore the module info.
1409                 self.cx.current_expansion.module = orig_module;
1410                 self.cx.current_expansion.directory_ownership = orig_ownership;
1411                 if *pushed {
1412                     sess.included_mod_stack.borrow_mut().pop();
1413                 }
1414                 result
1415             }
1416             _ => {
1417                 item.attrs = attrs;
1418                 noop_flat_map_item(item, self)
1419             }
1420         }
1421     }
1422
1423     fn flat_map_trait_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
1424         let mut item = configure!(self, item);
1425
1426         if let Some(attr) = self.take_first_attr(&mut item) {
1427             return self
1428                 .collect_attr(attr, Annotatable::TraitItem(item), AstFragmentKind::TraitItems)
1429                 .make_trait_items();
1430         }
1431
1432         match item.kind {
1433             ast::AssocItemKind::MacCall(..) => {
1434                 self.check_attributes(&item.attrs);
1435                 item.and_then(|item| match item.kind {
1436                     ast::AssocItemKind::MacCall(mac) => self
1437                         .collect_bang(mac, item.span, AstFragmentKind::TraitItems)
1438                         .make_trait_items(),
1439                     _ => unreachable!(),
1440                 })
1441             }
1442             _ => noop_flat_map_assoc_item(item, self),
1443         }
1444     }
1445
1446     fn flat_map_impl_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
1447         let mut item = configure!(self, item);
1448
1449         if let Some(attr) = self.take_first_attr(&mut item) {
1450             return self
1451                 .collect_attr(attr, Annotatable::ImplItem(item), AstFragmentKind::ImplItems)
1452                 .make_impl_items();
1453         }
1454
1455         match item.kind {
1456             ast::AssocItemKind::MacCall(..) => {
1457                 self.check_attributes(&item.attrs);
1458                 item.and_then(|item| match item.kind {
1459                     ast::AssocItemKind::MacCall(mac) => self
1460                         .collect_bang(mac, item.span, AstFragmentKind::ImplItems)
1461                         .make_impl_items(),
1462                     _ => unreachable!(),
1463                 })
1464             }
1465             _ => noop_flat_map_assoc_item(item, self),
1466         }
1467     }
1468
1469     fn visit_ty(&mut self, ty: &mut P<ast::Ty>) {
1470         match ty.kind {
1471             ast::TyKind::MacCall(_) => {}
1472             _ => return noop_visit_ty(ty, self),
1473         };
1474
1475         visit_clobber(ty, |mut ty| match mem::replace(&mut ty.kind, ast::TyKind::Err) {
1476             ast::TyKind::MacCall(mac) => {
1477                 self.collect_bang(mac, ty.span, AstFragmentKind::Ty).make_ty()
1478             }
1479             _ => unreachable!(),
1480         });
1481     }
1482
1483     fn visit_foreign_mod(&mut self, foreign_mod: &mut ast::ForeignMod) {
1484         self.cfg.configure_foreign_mod(foreign_mod);
1485         noop_visit_foreign_mod(foreign_mod, self);
1486     }
1487
1488     fn flat_map_foreign_item(
1489         &mut self,
1490         mut foreign_item: P<ast::ForeignItem>,
1491     ) -> SmallVec<[P<ast::ForeignItem>; 1]> {
1492         if let Some(attr) = self.take_first_attr(&mut foreign_item) {
1493             return self
1494                 .collect_attr(
1495                     attr,
1496                     Annotatable::ForeignItem(foreign_item),
1497                     AstFragmentKind::ForeignItems,
1498                 )
1499                 .make_foreign_items();
1500         }
1501
1502         match foreign_item.kind {
1503             ast::ForeignItemKind::MacCall(..) => {
1504                 self.check_attributes(&foreign_item.attrs);
1505                 foreign_item.and_then(|item| match item.kind {
1506                     ast::ForeignItemKind::MacCall(mac) => self
1507                         .collect_bang(mac, item.span, AstFragmentKind::ForeignItems)
1508                         .make_foreign_items(),
1509                     _ => unreachable!(),
1510                 })
1511             }
1512             _ => noop_flat_map_foreign_item(foreign_item, self),
1513         }
1514     }
1515
1516     fn visit_item_kind(&mut self, item: &mut ast::ItemKind) {
1517         match item {
1518             ast::ItemKind::MacroDef(..) => {}
1519             _ => {
1520                 self.cfg.configure_item_kind(item);
1521                 noop_visit_item_kind(item, self);
1522             }
1523         }
1524     }
1525
1526     fn flat_map_generic_param(
1527         &mut self,
1528         param: ast::GenericParam,
1529     ) -> SmallVec<[ast::GenericParam; 1]> {
1530         let mut param = configure!(self, param);
1531
1532         if let Some(attr) = self.take_first_attr(&mut param) {
1533             return self
1534                 .collect_attr(
1535                     attr,
1536                     Annotatable::GenericParam(param),
1537                     AstFragmentKind::GenericParams,
1538                 )
1539                 .make_generic_params();
1540         }
1541
1542         noop_flat_map_generic_param(param, self)
1543     }
1544
1545     fn visit_attribute(&mut self, at: &mut ast::Attribute) {
1546         // turn `#[doc(include="filename")]` attributes into `#[doc(include(file="filename",
1547         // contents="file contents")]` attributes
1548         if !self.cx.sess.check_name(at, sym::doc) {
1549             return noop_visit_attribute(at, self);
1550         }
1551
1552         if let Some(list) = at.meta_item_list() {
1553             if !list.iter().any(|it| it.has_name(sym::include)) {
1554                 return noop_visit_attribute(at, self);
1555             }
1556
1557             let mut items = vec![];
1558
1559             for mut it in list {
1560                 if !it.has_name(sym::include) {
1561                     items.push({
1562                         noop_visit_meta_list_item(&mut it, self);
1563                         it
1564                     });
1565                     continue;
1566                 }
1567
1568                 if let Some(file) = it.value_str() {
1569                     let err_count = self.cx.sess.parse_sess.span_diagnostic.err_count();
1570                     self.check_attributes(slice::from_ref(at));
1571                     if self.cx.sess.parse_sess.span_diagnostic.err_count() > err_count {
1572                         // avoid loading the file if they haven't enabled the feature
1573                         return noop_visit_attribute(at, self);
1574                     }
1575
1576                     let filename = match self.cx.resolve_path(&*file.as_str(), it.span()) {
1577                         Ok(filename) => filename,
1578                         Err(mut err) => {
1579                             err.emit();
1580                             continue;
1581                         }
1582                     };
1583
1584                     match self.cx.source_map().load_file(&filename) {
1585                         Ok(source_file) => {
1586                             let src = source_file
1587                                 .src
1588                                 .as_ref()
1589                                 .expect("freshly loaded file should have a source");
1590                             let src_interned = Symbol::intern(src.as_str());
1591
1592                             let include_info = vec![
1593                                 ast::NestedMetaItem::MetaItem(attr::mk_name_value_item_str(
1594                                     Ident::with_dummy_span(sym::file),
1595                                     file,
1596                                     DUMMY_SP,
1597                                 )),
1598                                 ast::NestedMetaItem::MetaItem(attr::mk_name_value_item_str(
1599                                     Ident::with_dummy_span(sym::contents),
1600                                     src_interned,
1601                                     DUMMY_SP,
1602                                 )),
1603                             ];
1604
1605                             let include_ident = Ident::with_dummy_span(sym::include);
1606                             let item = attr::mk_list_item(include_ident, include_info);
1607                             items.push(ast::NestedMetaItem::MetaItem(item));
1608                         }
1609                         Err(e) => {
1610                             let lit_span = it.name_value_literal_span().unwrap();
1611
1612                             if e.kind() == ErrorKind::InvalidData {
1613                                 self.cx
1614                                     .struct_span_err(
1615                                         lit_span,
1616                                         &format!("{} wasn't a utf-8 file", filename.display()),
1617                                     )
1618                                     .span_label(lit_span, "contains invalid utf-8")
1619                                     .emit();
1620                             } else {
1621                                 let mut err = self.cx.struct_span_err(
1622                                     lit_span,
1623                                     &format!("couldn't read {}: {}", filename.display(), e),
1624                                 );
1625                                 err.span_label(lit_span, "couldn't read file");
1626
1627                                 err.emit();
1628                             }
1629                         }
1630                     }
1631                 } else {
1632                     let mut err = self
1633                         .cx
1634                         .struct_span_err(it.span(), "expected path to external documentation");
1635
1636                     // Check if the user erroneously used `doc(include(...))` syntax.
1637                     let literal = it.meta_item_list().and_then(|list| {
1638                         if list.len() == 1 {
1639                             list[0].literal().map(|literal| &literal.kind)
1640                         } else {
1641                             None
1642                         }
1643                     });
1644
1645                     let (path, applicability) = match &literal {
1646                         Some(LitKind::Str(path, ..)) => {
1647                             (path.to_string(), Applicability::MachineApplicable)
1648                         }
1649                         _ => (String::from("<path>"), Applicability::HasPlaceholders),
1650                     };
1651
1652                     err.span_suggestion(
1653                         it.span(),
1654                         "provide a file path with `=`",
1655                         format!("include = \"{}\"", path),
1656                         applicability,
1657                     );
1658
1659                     err.emit();
1660                 }
1661             }
1662
1663             let meta = attr::mk_list_item(Ident::with_dummy_span(sym::doc), items);
1664             *at = ast::Attribute {
1665                 kind: ast::AttrKind::Normal(
1666                     AttrItem { path: meta.path, args: meta.kind.mac_args(meta.span), tokens: None },
1667                     None,
1668                 ),
1669                 span: at.span,
1670                 id: at.id,
1671                 style: at.style,
1672             };
1673         } else {
1674             noop_visit_attribute(at, self)
1675         }
1676     }
1677
1678     fn visit_id(&mut self, id: &mut ast::NodeId) {
1679         if self.monotonic {
1680             debug_assert_eq!(*id, ast::DUMMY_NODE_ID);
1681             *id = self.cx.resolver.next_node_id()
1682         }
1683     }
1684
1685     fn visit_fn_decl(&mut self, mut fn_decl: &mut P<ast::FnDecl>) {
1686         self.cfg.configure_fn_decl(&mut fn_decl);
1687         noop_visit_fn_decl(fn_decl, self);
1688     }
1689 }
1690
1691 pub struct ExpansionConfig<'feat> {
1692     pub crate_name: String,
1693     pub features: Option<&'feat Features>,
1694     pub recursion_limit: Limit,
1695     pub trace_mac: bool,
1696     pub should_test: bool, // If false, strip `#[test]` nodes
1697     pub keep_macs: bool,
1698     pub span_debug: bool, // If true, use verbose debugging for `proc_macro::Span`
1699     pub proc_macro_backtrace: bool, // If true, show backtraces for proc-macro panics
1700 }
1701
1702 impl<'feat> ExpansionConfig<'feat> {
1703     pub fn default(crate_name: String) -> ExpansionConfig<'static> {
1704         ExpansionConfig {
1705             crate_name,
1706             features: None,
1707             recursion_limit: Limit::new(1024),
1708             trace_mac: false,
1709             should_test: false,
1710             keep_macs: false,
1711             span_debug: false,
1712             proc_macro_backtrace: false,
1713         }
1714     }
1715
1716     fn proc_macro_hygiene(&self) -> bool {
1717         self.features.map_or(false, |features| features.proc_macro_hygiene)
1718     }
1719 }