src/libsyntax/ext/expand.rs

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