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};
  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::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                     self.parse_ast_fragment(tok_result, fragment_kind, &mac.path, span)
 581                 }
 582                 SyntaxExtensionKind::LegacyBang(expander) => {
 583                     let prev = self.cx.current_expansion.prior_type_ascription;
 584                     self.cx.current_expansion.prior_type_ascription = mac.prior_type_ascription;
 585                     let tok_result = expander.expand(self.cx, span, mac.stream());
 586                     let result = if let Some(result) = fragment_kind.make_from(tok_result) {
 587                         result
 588                     } else {
 589                         let msg = format!(
 590                             "non-{kind} macro in {kind} position: {path}",
 591                             kind = fragment_kind.name(),
 592                             path = pprust::path_to_string(&mac.path),
 593                         );
 594                         self.cx.span_err(span, &msg);
 595                         self.cx.trace_macros_diag();
 596                         fragment_kind.dummy(span)
 597                     };
 598                     self.cx.current_expansion.prior_type_ascription = prev;
 599                     result
 600                 }
 601                 _ => unreachable!()
 602             }
 603             InvocationKind::Attr { attr, mut item, .. } => match ext {
 604                 SyntaxExtensionKind::Attr(expander) => {
 605                     self.gate_proc_macro_attr_item(span, &item);
 606                     let item_tok = TokenTree::token(token::Interpolated(Lrc::new(match item {
 607                         Annotatable::Item(item) => token::NtItem(item),
 608                         Annotatable::TraitItem(item) => token::NtTraitItem(item.into_inner()),
 609                         Annotatable::ImplItem(item) => token::NtImplItem(item.into_inner()),
 610                         Annotatable::ForeignItem(item) => token::NtForeignItem(item.into_inner()),
 611                         Annotatable::Stmt(stmt) => token::NtStmt(stmt.into_inner()),
 612                         Annotatable::Expr(expr) => token::NtExpr(expr),
 613                         Annotatable::Arm(..)
 614                         | Annotatable::Field(..)
 615                         | Annotatable::FieldPat(..)
 616                         | Annotatable::GenericParam(..)
 617                         | Annotatable::Param(..)
 618                         | Annotatable::StructField(..)
 619                         | Annotatable::Variant(..)
 620                             => panic!("unexpected annotatable"),
 621                     })), DUMMY_SP).into();
 622                     let input = self.extract_proc_macro_attr_input(attr.item.tokens, span);
 623                     let tok_result = expander.expand(self.cx, span, input, item_tok);
 624                     self.parse_ast_fragment(tok_result, fragment_kind, &attr.item.path, span)
 625                 }
 626                 SyntaxExtensionKind::LegacyAttr(expander) => {
 627                     match attr.parse_meta(self.cx.parse_sess) {
 628                         Ok(meta) => {
 629                             let item = expander.expand(self.cx, span, &meta, item);
 630                             fragment_kind.expect_from_annotatables(item)
 631                         }
 632                         Err(mut err) => {
 633                             err.emit();
 634                             fragment_kind.dummy(span)
 635                         }
 636                     }
 637                 }
 638                 SyntaxExtensionKind::NonMacroAttr { mark_used } => {
 639                     attr::mark_known(&attr);
 640                     if *mark_used {
 641                         attr::mark_used(&attr);
 642                     }
 643                     item.visit_attrs(|attrs| attrs.push(attr));
 644                     fragment_kind.expect_from_annotatables(iter::once(item))
 645                 }
 646                 _ => unreachable!()
 647             }
 648             InvocationKind::Derive { path, item } => match ext {
 649                 SyntaxExtensionKind::Derive(expander) |
 650                 SyntaxExtensionKind::LegacyDerive(expander) => {
 651                     if !item.derive_allowed() {
 652                         return fragment_kind.dummy(span);
 653                     }
 654                     let meta = ast::MetaItem { kind: ast::MetaItemKind::Word, span, path };
 655                     let items = expander.expand(self.cx, span, &meta, item);
 656                     fragment_kind.expect_from_annotatables(items)
 657                 }
 658                 _ => unreachable!()
 659             }
 660             InvocationKind::DeriveContainer { .. } => unreachable!()
 661         }
 662     }
 663
 664     fn extract_proc_macro_attr_input(&self, tokens: TokenStream, span: Span) -> TokenStream {
 665         let mut trees = tokens.trees();
 666         match trees.next() {
 667             Some(TokenTree::Delimited(_, _, tts)) => {
 668                 if trees.next().is_none() {
 669                     return tts.into()
 670                 }
 671             }
 672             Some(TokenTree::Token(..)) => {}
 673             None => return TokenStream::default(),
 674         }
 675         self.cx.span_err(span, "custom attribute invocations must be \
 676             of the form `#[foo]` or `#[foo(..)]`, the macro name must only be \
 677             followed by a delimiter token");
 678         TokenStream::default()
 679     }
 680
 681     fn gate_proc_macro_attr_item(&self, span: Span, item: &Annotatable) {
 682         let (kind, gate) = match *item {
 683             Annotatable::Item(ref item) => {
 684                 match item.kind {
 685                     ItemKind::Mod(_) if self.cx.ecfg.proc_macro_hygiene() => return,
 686                     ItemKind::Mod(_) => ("modules", sym::proc_macro_hygiene),
 687                     _ => return,
 688                 }
 689             }
 690             Annotatable::TraitItem(_) => return,
 691             Annotatable::ImplItem(_) => return,
 692             Annotatable::ForeignItem(_) => return,
 693             Annotatable::Stmt(_) |
 694             Annotatable::Expr(_) if self.cx.ecfg.proc_macro_hygiene() => return,
 695             Annotatable::Stmt(_) => ("statements", sym::proc_macro_hygiene),
 696             Annotatable::Expr(_) => ("expressions", sym::proc_macro_hygiene),
 697             Annotatable::Arm(..)
 698             | Annotatable::Field(..)
 699             | Annotatable::FieldPat(..)
 700             | Annotatable::GenericParam(..)
 701             | Annotatable::Param(..)
 702             | Annotatable::StructField(..)
 703             | Annotatable::Variant(..)
 704             => panic!("unexpected annotatable"),
 705         };
 706         emit_feature_err(
 707             self.cx.parse_sess,
 708             gate,
 709             span,
 710             GateIssue::Language,
 711             &format!("custom attributes cannot be applied to {}", kind),
 712         );
 713     }
 714
 715     fn gate_proc_macro_expansion_kind(&self, span: Span, kind: AstFragmentKind) {
 716         let kind = match kind {
 717             AstFragmentKind::Expr |
 718             AstFragmentKind::OptExpr => "expressions",
 719             AstFragmentKind::Pat => "patterns",
 720             AstFragmentKind::Stmts => "statements",
 721             AstFragmentKind::Ty |
 722             AstFragmentKind::Items |
 723             AstFragmentKind::TraitItems |
 724             AstFragmentKind::ImplItems |
 725             AstFragmentKind::ForeignItems => return,
 726             AstFragmentKind::Arms
 727             | AstFragmentKind::Fields
 728             | AstFragmentKind::FieldPats
 729             | AstFragmentKind::GenericParams
 730             | AstFragmentKind::Params
 731             | AstFragmentKind::StructFields
 732             | AstFragmentKind::Variants
 733                 => panic!("unexpected AST fragment kind"),
 734         };
 735         if self.cx.ecfg.proc_macro_hygiene() {
 736             return
 737         }
 738         emit_feature_err(
 739             self.cx.parse_sess,
 740             sym::proc_macro_hygiene,
 741             span,
 742             GateIssue::Language,
 743             &format!("procedural macros cannot be expanded to {}", kind),
 744         );
 745     }
 746
 747     fn parse_ast_fragment(
 748         &mut self,
 749         toks: TokenStream,
 750         kind: AstFragmentKind,
 751         path: &Path,
 752         span: Span,
 753     ) -> AstFragment {
 754         let mut parser = self.cx.new_parser_from_tts(toks);
 755         match parser.parse_ast_fragment(kind, false) {
 756             Ok(fragment) => {
 757                 parser.ensure_complete_parse(path, kind.name(), span);
 758                 fragment
 759             }
 760             Err(mut err) => {
 761                 err.set_span(span);
 762                 annotate_err_with_kind(&mut err, kind, span);
 763                 err.emit();
 764                 self.cx.trace_macros_diag();
 765                 kind.dummy(span)
 766             }
 767         }
 768     }
 769 }
 770
 771 impl<'a> Parser<'a> {
 772     pub fn parse_ast_fragment(&mut self, kind: AstFragmentKind, macro_legacy_warnings: bool)
 773                               -> PResult<'a, AstFragment> {
 774         Ok(match kind {
 775             AstFragmentKind::Items => {
 776                 let mut items = SmallVec::new();
 777                 while let Some(item) = self.parse_item()? {
 778                     items.push(item);
 779                 }
 780                 AstFragment::Items(items)
 781             }
 782             AstFragmentKind::TraitItems => {
 783                 let mut items = SmallVec::new();
 784                 while self.token != token::Eof {
 785                     items.push(self.parse_trait_item(&mut false)?);
 786                 }
 787                 AstFragment::TraitItems(items)
 788             }
 789             AstFragmentKind::ImplItems => {
 790                 let mut items = SmallVec::new();
 791                 while self.token != token::Eof {
 792                     items.push(self.parse_impl_item(&mut false)?);
 793                 }
 794                 AstFragment::ImplItems(items)
 795             }
 796             AstFragmentKind::ForeignItems => {
 797                 let mut items = SmallVec::new();
 798                 while self.token != token::Eof {
 799                     items.push(self.parse_foreign_item(DUMMY_SP)?);
 800                 }
 801                 AstFragment::ForeignItems(items)
 802             }
 803             AstFragmentKind::Stmts => {
 804                 let mut stmts = SmallVec::new();
 805                 while self.token != token::Eof &&
 806                       // won't make progress on a `}`
 807                       self.token != token::CloseDelim(token::Brace) {
 808                     if let Some(stmt) = self.parse_full_stmt(macro_legacy_warnings)? {
 809                         stmts.push(stmt);
 810                     }
 811                 }
 812                 AstFragment::Stmts(stmts)
 813             }
 814             AstFragmentKind::Expr => AstFragment::Expr(self.parse_expr()?),
 815             AstFragmentKind::OptExpr => {
 816                 if self.token != token::Eof {
 817                     AstFragment::OptExpr(Some(self.parse_expr()?))
 818                 } else {
 819                     AstFragment::OptExpr(None)
 820                 }
 821             },
 822             AstFragmentKind::Ty => AstFragment::Ty(self.parse_ty()?),
 823             AstFragmentKind::Pat => AstFragment::Pat(self.parse_pat(None)?),
 824             AstFragmentKind::Arms
 825             | AstFragmentKind::Fields
 826             | AstFragmentKind::FieldPats
 827             | AstFragmentKind::GenericParams
 828             | AstFragmentKind::Params
 829             | AstFragmentKind::StructFields
 830             | AstFragmentKind::Variants
 831                 => panic!("unexpected AST fragment kind"),
 832         })
 833     }
 834
 835     pub fn ensure_complete_parse(&mut self, macro_path: &Path, kind_name: &str, span: Span) {
 836         if self.token != token::Eof {
 837             let msg = format!("macro expansion ignores token `{}` and any following",
 838                               self.this_token_to_string());
 839             // Avoid emitting backtrace info twice.
 840             let def_site_span = self.token.span.with_ctxt(SyntaxContext::root());
 841             let mut err = self.diagnostic().struct_span_err(def_site_span, &msg);
 842             err.span_label(span, "caused by the macro expansion here");
 843             let msg = format!(
 844                 "the usage of `{}!` is likely invalid in {} context",
 845                 pprust::path_to_string(&macro_path),
 846                 kind_name,
 847             );
 848             err.note(&msg);
 849             let semi_span = self.sess.source_map().next_point(span);
 850
 851             let semi_full_span = semi_span.to(self.sess.source_map().next_point(semi_span));
 852             match self.sess.source_map().span_to_snippet(semi_full_span) {
 853                 Ok(ref snippet) if &snippet[..] != ";" && kind_name == "expression" => {
 854                     err.span_suggestion(
 855                         semi_span,
 856                         "you might be missing a semicolon here",
 857                         ";".to_owned(),
 858                         Applicability::MaybeIncorrect,
 859                     );
 860                 }
 861                 _ => {}
 862             }
 863             err.emit();
 864         }
 865     }
 866 }
 867
 868 struct InvocationCollector<'a, 'b> {
 869     cx: &'a mut ExtCtxt<'b>,
 870     cfg: StripUnconfigured<'a>,
 871     invocations: Vec<Invocation>,
 872     monotonic: bool,
 873 }
 874
 875 impl<'a, 'b> InvocationCollector<'a, 'b> {
 876     fn collect(&mut self, fragment_kind: AstFragmentKind, kind: InvocationKind) -> AstFragment {
 877         // Expansion data for all the collected invocations is set upon their resolution,
 878         // with exception of the derive container case which is not resolved and can get
 879         // its expansion data immediately.
 880         let expn_data = match &kind {
 881             InvocationKind::DeriveContainer { item, .. } => Some(ExpnData {
 882                 parent: self.cx.current_expansion.id,
 883                 ..ExpnData::default(
 884                     ExpnKind::Macro(MacroKind::Attr, sym::derive),
 885                     item.span(), self.cx.parse_sess.edition,
 886                 )
 887             }),
 888             _ => None,
 889         };
 890         let expn_id = ExpnId::fresh(expn_data);
 891         self.invocations.push(Invocation {
 892             kind,
 893             fragment_kind,
 894             expansion_data: ExpansionData {
 895                 id: expn_id,
 896                 depth: self.cx.current_expansion.depth + 1,
 897                 ..self.cx.current_expansion.clone()
 898             },
 899         });
 900         placeholder(fragment_kind, NodeId::placeholder_from_expn_id(expn_id))
 901     }
 902
 903     fn collect_bang(&mut self, mac: ast::Mac, span: Span, kind: AstFragmentKind) -> AstFragment {
 904         self.collect(kind, InvocationKind::Bang { mac, span })
 905     }
 906
 907     fn collect_attr(&mut self,
 908                     attr: Option<ast::Attribute>,
 909                     derives: Vec<Path>,
 910                     item: Annotatable,
 911                     kind: AstFragmentKind,
 912                     after_derive: bool)
 913                     -> AstFragment {
 914         self.collect(kind, match attr {
 915             Some(attr) => InvocationKind::Attr { attr, item, derives, after_derive },
 916             None => InvocationKind::DeriveContainer { derives, item },
 917         })
 918     }
 919
 920     fn find_attr_invoc(&self, attrs: &mut Vec<ast::Attribute>, after_derive: &mut bool)
 921                        -> Option<ast::Attribute> {
 922         let attr = attrs.iter()
 923                         .position(|a| {
 924                             if a.path == sym::derive {
 925                                 *after_derive = true;
 926                             }
 927                             !attr::is_known(a) && !is_builtin_attr(a)
 928                         })
 929                         .map(|i| attrs.remove(i));
 930         if let Some(attr) = &attr {
 931             if !self.cx.ecfg.custom_inner_attributes() &&
 932                attr.style == ast::AttrStyle::Inner && attr.path != sym::test {
 933                 emit_feature_err(&self.cx.parse_sess, sym::custom_inner_attributes,
 934                                  attr.span, GateIssue::Language,
 935                                  "non-builtin inner attributes are unstable");
 936             }
 937         }
 938         attr
 939     }
 940
 941     /// If `item` is an attr invocation, remove and return the macro attribute and derive traits.
 942     fn classify_item<T>(&mut self, item: &mut T)
 943                         -> (Option<ast::Attribute>, Vec<Path>, /* after_derive */ bool)
 944         where T: HasAttrs,
 945     {
 946         let (mut attr, mut traits, mut after_derive) = (None, Vec::new(), false);
 947
 948         item.visit_attrs(|mut attrs| {
 949             attr = self.find_attr_invoc(&mut attrs, &mut after_derive);
 950             traits = collect_derives(&mut self.cx, &mut attrs);
 951         });
 952
 953         (attr, traits, after_derive)
 954     }
 955
 956     /// Alternative to `classify_item()` that ignores `#[derive]` so invocations fallthrough
 957     /// to the unused-attributes lint (making it an error on statements and expressions
 958     /// is a breaking change)
 959     fn classify_nonitem<T: HasAttrs>(&mut self, nonitem: &mut T)
 960                                      -> (Option<ast::Attribute>, /* after_derive */ bool) {
 961         let (mut attr, mut after_derive) = (None, false);
 962
 963         nonitem.visit_attrs(|mut attrs| {
 964             attr = self.find_attr_invoc(&mut attrs, &mut after_derive);
 965         });
 966
 967         (attr, after_derive)
 968     }
 969
 970     fn configure<T: HasAttrs>(&mut self, node: T) -> Option<T> {
 971         self.cfg.configure(node)
 972     }
 973
 974     // Detect use of feature-gated or invalid attributes on macro invocations
 975     // since they will not be detected after macro expansion.
 976     fn check_attributes(&mut self, attrs: &[ast::Attribute]) {
 977         let features = self.cx.ecfg.features.unwrap();
 978         for attr in attrs.iter() {
 979             feature_gate::check_attribute(attr, self.cx.parse_sess, features);
 980
 981             // macros are expanded before any lint passes so this warning has to be hardcoded
 982             if attr.path == sym::derive {
 983                 self.cx.struct_span_warn(attr.span, "`#[derive]` does nothing on macro invocations")
 984                     .note("this may become a hard error in a future release")
 985                     .emit();
 986             }
 987         }
 988     }
 989 }
 990
 991 impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
 992     fn visit_expr(&mut self, expr: &mut P<ast::Expr>) {
 993         self.cfg.configure_expr(expr);
 994         visit_clobber(expr.deref_mut(), |mut expr| {
 995             self.cfg.configure_expr_kind(&mut expr.kind);
 996
 997             // ignore derives so they remain unused
 998             let (attr, after_derive) = self.classify_nonitem(&mut expr);
 999
1000             if attr.is_some() {
1001                 // Collect the invoc regardless of whether or not attributes are permitted here
1002                 // expansion will eat the attribute so it won't error later.
1003                 attr.as_ref().map(|a| self.cfg.maybe_emit_expr_attr_err(a));
1004
1005                 // AstFragmentKind::Expr requires the macro to emit an expression.
1006                 return self.collect_attr(attr, vec![], Annotatable::Expr(P(expr)),
1007                                           AstFragmentKind::Expr, after_derive)
1008                     .make_expr()
1009                     .into_inner()
1010             }
1011
1012             if let ast::ExprKind::Mac(mac) = expr.kind {
1013                 self.check_attributes(&expr.attrs);
1014                 self.collect_bang(mac, expr.span, AstFragmentKind::Expr)
1015                     .make_expr()
1016                     .into_inner()
1017             } else {
1018                 noop_visit_expr(&mut expr, self);
1019                 expr
1020             }
1021         });
1022     }
1023
1024     fn flat_map_arm(&mut self, arm: ast::Arm) -> SmallVec<[ast::Arm; 1]> {
1025         let mut arm = configure!(self, arm);
1026
1027         let (attr, traits, after_derive) = self.classify_item(&mut arm);
1028         if attr.is_some() || !traits.is_empty() {
1029             return self.collect_attr(attr, traits, Annotatable::Arm(arm),
1030                                      AstFragmentKind::Arms, after_derive)
1031                                      .make_arms();
1032         }
1033
1034         noop_flat_map_arm(arm, self)
1035     }
1036
1037     fn flat_map_field(&mut self, field: ast::Field) -> SmallVec<[ast::Field; 1]> {
1038         let mut field = configure!(self, field);
1039
1040         let (attr, traits, after_derive) = self.classify_item(&mut field);
1041         if attr.is_some() || !traits.is_empty() {
1042             return self.collect_attr(attr, traits, Annotatable::Field(field),
1043                                      AstFragmentKind::Fields, after_derive)
1044                                      .make_fields();
1045         }
1046
1047         noop_flat_map_field(field, self)
1048     }
1049
1050     fn flat_map_field_pattern(&mut self, fp: ast::FieldPat) -> SmallVec<[ast::FieldPat; 1]> {
1051         let mut fp = configure!(self, fp);
1052
1053         let (attr, traits, after_derive) = self.classify_item(&mut fp);
1054         if attr.is_some() || !traits.is_empty() {
1055             return self.collect_attr(attr, traits, Annotatable::FieldPat(fp),
1056                                      AstFragmentKind::FieldPats, after_derive)
1057                                      .make_field_patterns();
1058         }
1059
1060         noop_flat_map_field_pattern(fp, self)
1061     }
1062
1063     fn flat_map_param(&mut self, p: ast::Param) -> SmallVec<[ast::Param; 1]> {
1064         let mut p = configure!(self, p);
1065
1066         let (attr, traits, after_derive) = self.classify_item(&mut p);
1067         if attr.is_some() || !traits.is_empty() {
1068             return self.collect_attr(attr, traits, Annotatable::Param(p),
1069                                      AstFragmentKind::Params, after_derive)
1070                                      .make_params();
1071         }
1072
1073         noop_flat_map_param(p, self)
1074     }
1075
1076     fn flat_map_struct_field(&mut self, sf: ast::StructField) -> SmallVec<[ast::StructField; 1]> {
1077         let mut sf = configure!(self, sf);
1078
1079         let (attr, traits, after_derive) = self.classify_item(&mut sf);
1080         if attr.is_some() || !traits.is_empty() {
1081             return self.collect_attr(attr, traits, Annotatable::StructField(sf),
1082                                      AstFragmentKind::StructFields, after_derive)
1083                                      .make_struct_fields();
1084         }
1085
1086         noop_flat_map_struct_field(sf, self)
1087     }
1088
1089     fn flat_map_variant(&mut self, variant: ast::Variant) -> SmallVec<[ast::Variant; 1]> {
1090         let mut variant = configure!(self, variant);
1091
1092         let (attr, traits, after_derive) = self.classify_item(&mut variant);
1093         if attr.is_some() || !traits.is_empty() {
1094             return self.collect_attr(attr, traits, Annotatable::Variant(variant),
1095                                      AstFragmentKind::Variants, after_derive)
1096                                      .make_variants();
1097         }
1098
1099         noop_flat_map_variant(variant, self)
1100     }
1101
1102     fn filter_map_expr(&mut self, expr: P<ast::Expr>) -> Option<P<ast::Expr>> {
1103         let expr = configure!(self, expr);
1104         expr.filter_map(|mut expr| {
1105             self.cfg.configure_expr_kind(&mut expr.kind);
1106
1107             // Ignore derives so they remain unused.
1108             let (attr, after_derive) = self.classify_nonitem(&mut expr);
1109
1110             if attr.is_some() {
1111                 attr.as_ref().map(|a| self.cfg.maybe_emit_expr_attr_err(a));
1112
1113                 return self.collect_attr(attr, vec![], Annotatable::Expr(P(expr)),
1114                                          AstFragmentKind::OptExpr, after_derive)
1115                     .make_opt_expr()
1116                     .map(|expr| expr.into_inner())
1117             }
1118
1119             if let ast::ExprKind::Mac(mac) = expr.kind {
1120                 self.check_attributes(&expr.attrs);
1121                 self.collect_bang(mac, expr.span, AstFragmentKind::OptExpr)
1122                     .make_opt_expr()
1123                     .map(|expr| expr.into_inner())
1124             } else {
1125                 Some({ noop_visit_expr(&mut expr, self); expr })
1126             }
1127         })
1128     }
1129
1130     fn visit_pat(&mut self, pat: &mut P<ast::Pat>) {
1131         self.cfg.configure_pat(pat);
1132         match pat.kind {
1133             PatKind::Mac(_) => {}
1134             _ => return noop_visit_pat(pat, self),
1135         }
1136
1137         visit_clobber(pat, |mut pat| {
1138             match mem::replace(&mut pat.kind, PatKind::Wild) {
1139                 PatKind::Mac(mac) =>
1140                     self.collect_bang(mac, pat.span, AstFragmentKind::Pat).make_pat(),
1141                 _ => unreachable!(),
1142             }
1143         });
1144     }
1145
1146     fn flat_map_stmt(&mut self, stmt: ast::Stmt) -> SmallVec<[ast::Stmt; 1]> {
1147         let mut stmt = configure!(self, stmt);
1148
1149         // we'll expand attributes on expressions separately
1150         if !stmt.is_expr() {
1151             let (attr, derives, after_derive) = if stmt.is_item() {
1152                 self.classify_item(&mut stmt)
1153             } else {
1154                 // ignore derives on non-item statements so it falls through
1155                 // to the unused-attributes lint
1156                 let (attr, after_derive) = self.classify_nonitem(&mut stmt);
1157                 (attr, vec![], after_derive)
1158             };
1159
1160             if attr.is_some() || !derives.is_empty() {
1161                 return self.collect_attr(attr, derives, Annotatable::Stmt(P(stmt)),
1162                                          AstFragmentKind::Stmts, after_derive).make_stmts();
1163             }
1164         }
1165
1166         if let StmtKind::Mac(mac) = stmt.kind {
1167             let (mac, style, attrs) = mac.into_inner();
1168             self.check_attributes(&attrs);
1169             let mut placeholder = self.collect_bang(mac, stmt.span, AstFragmentKind::Stmts)
1170                                         .make_stmts();
1171
1172             // If this is a macro invocation with a semicolon, then apply that
1173             // semicolon to the final statement produced by expansion.
1174             if style == MacStmtStyle::Semicolon {
1175                 if let Some(stmt) = placeholder.pop() {
1176                     placeholder.push(stmt.add_trailing_semicolon());
1177                 }
1178             }
1179
1180             return placeholder;
1181         }
1182
1183         // The placeholder expander gives ids to statements, so we avoid folding the id here.
1184         let ast::Stmt { id, kind, span } = stmt;
1185         noop_flat_map_stmt_kind(kind, self).into_iter().map(|kind| {
1186             ast::Stmt { id, kind, span }
1187         }).collect()
1188
1189     }
1190
1191     fn visit_block(&mut self, block: &mut P<Block>) {
1192         let old_directory_ownership = self.cx.current_expansion.directory_ownership;
1193         self.cx.current_expansion.directory_ownership = DirectoryOwnership::UnownedViaBlock;
1194         noop_visit_block(block, self);
1195         self.cx.current_expansion.directory_ownership = old_directory_ownership;
1196     }
1197
1198     fn flat_map_item(&mut self, item: P<ast::Item>) -> SmallVec<[P<ast::Item>; 1]> {
1199         let mut item = configure!(self, item);
1200
1201         let (attr, traits, after_derive) = self.classify_item(&mut item);
1202         if attr.is_some() || !traits.is_empty() {
1203             return self.collect_attr(attr, traits, Annotatable::Item(item),
1204                                      AstFragmentKind::Items, after_derive).make_items();
1205         }
1206
1207         match item.kind {
1208             ast::ItemKind::Mac(..) => {
1209                 self.check_attributes(&item.attrs);
1210                 item.and_then(|item| match item.kind {
1211                     ItemKind::Mac(mac) => self.collect(
1212                         AstFragmentKind::Items, InvocationKind::Bang { mac, span: item.span }
1213                     ).make_items(),
1214                     _ => unreachable!(),
1215                 })
1216             }
1217             ast::ItemKind::Mod(ast::Mod { inner, .. }) => {
1218                 if item.ident == Ident::invalid() {
1219                     return noop_flat_map_item(item, self);
1220                 }
1221
1222                 let orig_directory_ownership = self.cx.current_expansion.directory_ownership;
1223                 let mut module = (*self.cx.current_expansion.module).clone();
1224                 module.mod_path.push(item.ident);
1225
1226                 // Detect if this is an inline module (`mod m { ... }` as opposed to `mod m;`).
1227                 // In the non-inline case, `inner` is never the dummy span (cf. `parse_item_mod`).
1228                 // Thus, if `inner` is the dummy span, we know the module is inline.
1229                 let inline_module = item.span.contains(inner) || inner.is_dummy();
1230
1231                 if inline_module {
1232                     if let Some(path) = attr::first_attr_value_str_by_name(&item.attrs, sym::path) {
1233                         self.cx.current_expansion.directory_ownership =
1234                             DirectoryOwnership::Owned { relative: None };
1235                         module.directory.push(&*path.as_str());
1236                     } else {
1237                         module.directory.push(&*item.ident.as_str());
1238                     }
1239                 } else {
1240                     let path = self.cx.parse_sess.source_map().span_to_unmapped_path(inner);
1241                     let mut path = match path {
1242                         FileName::Real(path) => path,
1243                         other => PathBuf::from(other.to_string()),
1244                     };
1245                     let directory_ownership = match path.file_name().unwrap().to_str() {
1246                         Some("mod.rs") => DirectoryOwnership::Owned { relative: None },
1247                         Some(_) => DirectoryOwnership::Owned {
1248                             relative: Some(item.ident),
1249                         },
1250                         None => DirectoryOwnership::UnownedViaMod(false),
1251                     };
1252                     path.pop();
1253                     module.directory = path;
1254                     self.cx.current_expansion.directory_ownership = directory_ownership;
1255                 }
1256
1257                 let orig_module =
1258                     mem::replace(&mut self.cx.current_expansion.module, Rc::new(module));
1259                 let result = noop_flat_map_item(item, self);
1260                 self.cx.current_expansion.module = orig_module;
1261                 self.cx.current_expansion.directory_ownership = orig_directory_ownership;
1262                 result
1263             }
1264
1265             _ => noop_flat_map_item(item, self),
1266         }
1267     }
1268
1269     fn flat_map_trait_item(&mut self, item: ast::TraitItem) -> SmallVec<[ast::TraitItem; 1]> {
1270         let mut item = configure!(self, item);
1271
1272         let (attr, traits, after_derive) = self.classify_item(&mut item);
1273         if attr.is_some() || !traits.is_empty() {
1274             return self.collect_attr(attr, traits, Annotatable::TraitItem(P(item)),
1275                                      AstFragmentKind::TraitItems, after_derive).make_trait_items()
1276         }
1277
1278         match item.kind {
1279             ast::TraitItemKind::Macro(mac) => {
1280                 let ast::TraitItem { attrs, span, .. } = item;
1281                 self.check_attributes(&attrs);
1282                 self.collect_bang(mac, span, AstFragmentKind::TraitItems).make_trait_items()
1283             }
1284             _ => noop_flat_map_trait_item(item, self),
1285         }
1286     }
1287
1288     fn flat_map_impl_item(&mut self, item: ast::ImplItem) -> SmallVec<[ast::ImplItem; 1]> {
1289         let mut item = configure!(self, item);
1290
1291         let (attr, traits, after_derive) = self.classify_item(&mut item);
1292         if attr.is_some() || !traits.is_empty() {
1293             return self.collect_attr(attr, traits, Annotatable::ImplItem(P(item)),
1294                                      AstFragmentKind::ImplItems, after_derive).make_impl_items();
1295         }
1296
1297         match item.kind {
1298             ast::ImplItemKind::Macro(mac) => {
1299                 let ast::ImplItem { attrs, span, .. } = item;
1300                 self.check_attributes(&attrs);
1301                 self.collect_bang(mac, span, AstFragmentKind::ImplItems).make_impl_items()
1302             }
1303             _ => noop_flat_map_impl_item(item, self),
1304         }
1305     }
1306
1307     fn visit_ty(&mut self, ty: &mut P<ast::Ty>) {
1308         match ty.kind {
1309             ast::TyKind::Mac(_) => {}
1310             _ => return noop_visit_ty(ty, self),
1311         };
1312
1313         visit_clobber(ty, |mut ty| {
1314             match mem::replace(&mut ty.kind, ast::TyKind::Err) {
1315                 ast::TyKind::Mac(mac) =>
1316                     self.collect_bang(mac, ty.span, AstFragmentKind::Ty).make_ty(),
1317                 _ => unreachable!(),
1318             }
1319         });
1320     }
1321
1322     fn visit_foreign_mod(&mut self, foreign_mod: &mut ast::ForeignMod) {
1323         self.cfg.configure_foreign_mod(foreign_mod);
1324         noop_visit_foreign_mod(foreign_mod, self);
1325     }
1326
1327     fn flat_map_foreign_item(&mut self, mut foreign_item: ast::ForeignItem)
1328         -> SmallVec<[ast::ForeignItem; 1]>
1329     {
1330         let (attr, traits, after_derive) = self.classify_item(&mut foreign_item);
1331
1332         if attr.is_some() || !traits.is_empty() {
1333             return self.collect_attr(attr, traits, Annotatable::ForeignItem(P(foreign_item)),
1334                                      AstFragmentKind::ForeignItems, after_derive)
1335                                      .make_foreign_items();
1336         }
1337
1338         if let ast::ForeignItemKind::Macro(mac) = foreign_item.kind {
1339             self.check_attributes(&foreign_item.attrs);
1340             return self.collect_bang(mac, foreign_item.span, AstFragmentKind::ForeignItems)
1341                 .make_foreign_items();
1342         }
1343
1344         noop_flat_map_foreign_item(foreign_item, self)
1345     }
1346
1347     fn visit_item_kind(&mut self, item: &mut ast::ItemKind) {
1348         match item {
1349             ast::ItemKind::MacroDef(..) => {}
1350             _ => {
1351                 self.cfg.configure_item_kind(item);
1352                 noop_visit_item_kind(item, self);
1353             }
1354         }
1355     }
1356
1357     fn flat_map_generic_param(
1358         &mut self,
1359         param: ast::GenericParam
1360     ) -> SmallVec<[ast::GenericParam; 1]>
1361     {
1362         let mut param = configure!(self, param);
1363
1364         let (attr, traits, after_derive) = self.classify_item(&mut param);
1365         if attr.is_some() || !traits.is_empty() {
1366             return self.collect_attr(attr, traits, Annotatable::GenericParam(param),
1367                                      AstFragmentKind::GenericParams, after_derive)
1368                                      .make_generic_params();
1369         }
1370
1371         noop_flat_map_generic_param(param, self)
1372     }
1373
1374     fn visit_attribute(&mut self, at: &mut ast::Attribute) {
1375         // turn `#[doc(include="filename")]` attributes into `#[doc(include(file="filename",
1376         // contents="file contents")]` attributes
1377         if !at.check_name(sym::doc) {
1378             return noop_visit_attribute(at, self);
1379         }
1380
1381         if let Some(list) = at.meta_item_list() {
1382             if !list.iter().any(|it| it.check_name(sym::include)) {
1383                 return noop_visit_attribute(at, self);
1384             }
1385
1386             let mut items = vec![];
1387
1388             for mut it in list {
1389                 if !it.check_name(sym::include) {
1390                     items.push({ noop_visit_meta_list_item(&mut it, self); it });
1391                     continue;
1392                 }
1393
1394                 if let Some(file) = it.value_str() {
1395                     let err_count = self.cx.parse_sess.span_diagnostic.err_count();
1396                     self.check_attributes(slice::from_ref(at));
1397                     if self.cx.parse_sess.span_diagnostic.err_count() > err_count {
1398                         // avoid loading the file if they haven't enabled the feature
1399                         return noop_visit_attribute(at, self);
1400                     }
1401
1402                     let filename = self.cx.resolve_path(&*file.as_str(), it.span());
1403                     match self.cx.source_map().load_file(&filename) {
1404                         Ok(source_file) => {
1405                             let src = source_file.src.as_ref()
1406                                 .expect("freshly loaded file should have a source");
1407                             let src_interned = Symbol::intern(src.as_str());
1408
1409                             let include_info = vec![
1410                                 ast::NestedMetaItem::MetaItem(
1411                                     attr::mk_name_value_item_str(
1412                                         Ident::with_dummy_span(sym::file),
1413                                         file,
1414                                         DUMMY_SP,
1415                                     ),
1416                                 ),
1417                                 ast::NestedMetaItem::MetaItem(
1418                                     attr::mk_name_value_item_str(
1419                                         Ident::with_dummy_span(sym::contents),
1420                                         src_interned,
1421                                         DUMMY_SP,
1422                                     ),
1423                                 ),
1424                             ];
1425
1426                             let include_ident = Ident::with_dummy_span(sym::include);
1427                             let item = attr::mk_list_item(include_ident, include_info);
1428                             items.push(ast::NestedMetaItem::MetaItem(item));
1429                         }
1430                         Err(e) => {
1431                             let lit = it
1432                                 .meta_item()
1433                                 .and_then(|item| item.name_value_literal())
1434                                 .unwrap();
1435
1436                             if e.kind() == ErrorKind::InvalidData {
1437                                 self.cx
1438                                     .struct_span_err(
1439                                         lit.span,
1440                                         &format!("{} wasn't a utf-8 file", filename.display()),
1441                                     )
1442                                     .span_label(lit.span, "contains invalid utf-8")
1443                                     .emit();
1444                             } else {
1445                                 let mut err = self.cx.struct_span_err(
1446                                     lit.span,
1447                                     &format!("couldn't read {}: {}", filename.display(), e),
1448                                 );
1449                                 err.span_label(lit.span, "couldn't read file");
1450
1451                                 err.emit();
1452                             }
1453                         }
1454                     }
1455                 } else {
1456                     let mut err = self.cx.struct_span_err(
1457                         it.span(),
1458                         &format!("expected path to external documentation"),
1459                     );
1460
1461                     // Check if the user erroneously used `doc(include(...))` syntax.
1462                     let literal = it.meta_item_list().and_then(|list| {
1463                         if list.len() == 1 {
1464                             list[0].literal().map(|literal| &literal.kind)
1465                         } else {
1466                             None
1467                         }
1468                     });
1469
1470                     let (path, applicability) = match &literal {
1471                         Some(LitKind::Str(path, ..)) => {
1472                             (path.to_string(), Applicability::MachineApplicable)
1473                         }
1474                         _ => (String::from("<path>"), Applicability::HasPlaceholders),
1475                     };
1476
1477                     err.span_suggestion(
1478                         it.span(),
1479                         "provide a file path with `=`",
1480                         format!("include = \"{}\"", path),
1481                         applicability,
1482                     );
1483
1484                     err.emit();
1485                 }
1486             }
1487
1488             let meta = attr::mk_list_item(Ident::with_dummy_span(sym::doc), items);
1489             *at = attr::Attribute {
1490                 item: AttrItem { path: meta.path, tokens: meta.kind.tokens(meta.span) },
1491                 span: at.span,
1492                 id: at.id,
1493                 style: at.style,
1494                 is_sugared_doc: false,
1495             };
1496         } else {
1497             noop_visit_attribute(at, self)
1498         }
1499     }
1500
1501     fn visit_id(&mut self, id: &mut ast::NodeId) {
1502         if self.monotonic {
1503             debug_assert_eq!(*id, ast::DUMMY_NODE_ID);
1504             *id = self.cx.resolver.next_node_id()
1505         }
1506     }
1507
1508     fn visit_fn_decl(&mut self, mut fn_decl: &mut P<ast::FnDecl>) {
1509         self.cfg.configure_fn_decl(&mut fn_decl);
1510         noop_visit_fn_decl(fn_decl, self);
1511     }
1512 }
1513
1514 pub struct ExpansionConfig<'feat> {
1515     pub crate_name: String,
1516     pub features: Option<&'feat Features>,
1517     pub recursion_limit: usize,
1518     pub trace_mac: bool,
1519     pub should_test: bool, // If false, strip `#[test]` nodes
1520     pub single_step: bool,
1521     pub keep_macs: bool,
1522 }
1523
1524 impl<'feat> ExpansionConfig<'feat> {
1525     pub fn default(crate_name: String) -> ExpansionConfig<'static> {
1526         ExpansionConfig {
1527             crate_name,
1528             features: None,
1529             recursion_limit: 1024,
1530             trace_mac: false,
1531             should_test: false,
1532             single_step: false,
1533             keep_macs: false,
1534         }
1535     }
1536
1537     fn proc_macro_hygiene(&self) -> bool {
1538         self.features.map_or(false, |features| features.proc_macro_hygiene)
1539     }
1540     fn custom_inner_attributes(&self) -> bool {
1541         self.features.map_or(false, |features| features.custom_inner_attributes)
1542     }
1543 }