src/libsyntax/ext/expand.rs

   1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use ast::{self, Block, Ident, NodeId, PatKind, Path};
  12 use ast::{MacStmtStyle, StmtKind, ItemKind};
  13 use attr::{self, HasAttrs};
  14 use source_map::{ExpnInfo, MacroBang, MacroAttribute, dummy_spanned, respan};
  15 use config::StripUnconfigured;
  16 use errors::{Applicability, FatalError};
  17 use ext::base::*;
  18 use ext::derive::{add_derived_markers, collect_derives};
  19 use ext::hygiene::{self, Mark, SyntaxContext};
  20 use ext::placeholders::{placeholder, PlaceholderExpander};
  21 use feature_gate::{self, Features, GateIssue, is_builtin_attr, emit_feature_err};
  22 use fold;
  23 use fold::*;
  24 use parse::{DirectoryOwnership, PResult, ParseSess};
  25 use parse::token::{self, Token};
  26 use parse::parser::Parser;
  27 use ptr::P;
  28 use OneVector;
  29 use symbol::Symbol;
  30 use symbol::keywords;
  31 use syntax_pos::{Span, DUMMY_SP, FileName};
  32 use syntax_pos::hygiene::ExpnFormat;
  33 use tokenstream::{TokenStream, TokenTree};
  34 use visit::{self, Visitor};
  35
  36 use rustc_data_structures::fx::FxHashMap;
  37 use std::fs::File;
  38 use std::io::Read;
  39 use std::{iter, mem};
  40 use std::rc::Rc;
  41 use std::path::PathBuf;
  42
  43 macro_rules! ast_fragments {
  44     (
  45         $($Kind:ident($AstTy:ty) {
  46             $kind_name:expr;
  47             // FIXME: HACK: this should be `$(one ...)?` and `$(many ...)?` but `?` macro
  48             // repetition was removed from 2015 edition in #51587 because of ambiguities.
  49             $(one fn $fold_ast:ident; fn $visit_ast:ident;)*
  50             $(many fn $fold_ast_elt:ident; fn $visit_ast_elt:ident;)*
  51             fn $make_ast:ident;
  52         })*
  53     ) => {
  54         /// A fragment of AST that can be produced by a single macro expansion.
  55         /// Can also serve as an input and intermediate result for macro expansion operations.
  56         pub enum AstFragment {
  57             OptExpr(Option<P<ast::Expr>>),
  58             $($Kind($AstTy),)*
  59         }
  60
  61         /// "Discriminant" of an AST fragment.
  62         #[derive(Copy, Clone, PartialEq, Eq)]
  63         pub enum AstFragmentKind {
  64             OptExpr,
  65             $($Kind,)*
  66         }
  67
  68         impl AstFragmentKind {
  69             pub fn name(self) -> &'static str {
  70                 match self {
  71                     AstFragmentKind::OptExpr => "expression",
  72                     $(AstFragmentKind::$Kind => $kind_name,)*
  73                 }
  74             }
  75
  76             fn make_from<'a>(self, result: Box<dyn MacResult + 'a>) -> Option<AstFragment> {
  77                 match self {
  78                     AstFragmentKind::OptExpr =>
  79                         result.make_expr().map(Some).map(AstFragment::OptExpr),
  80                     $(AstFragmentKind::$Kind => result.$make_ast().map(AstFragment::$Kind),)*
  81                 }
  82             }
  83         }
  84
  85         impl AstFragment {
  86             pub fn make_opt_expr(self) -> Option<P<ast::Expr>> {
  87                 match self {
  88                     AstFragment::OptExpr(expr) => expr,
  89                     _ => panic!("AstFragment::make_* called on the wrong kind of fragment"),
  90                 }
  91             }
  92
  93             $(pub fn $make_ast(self) -> $AstTy {
  94                 match self {
  95                     AstFragment::$Kind(ast) => ast,
  96                     _ => panic!("AstFragment::make_* called on the wrong kind of fragment"),
  97                 }
  98             })*
  99
 100             pub fn fold_with<F: Folder>(self, folder: &mut F) -> Self {
 101                 match self {
 102                     AstFragment::OptExpr(expr) =>
 103                         AstFragment::OptExpr(expr.and_then(|expr| folder.fold_opt_expr(expr))),
 104                     $($(AstFragment::$Kind(ast) =>
 105                         AstFragment::$Kind(folder.$fold_ast(ast)),)*)*
 106                     $($(AstFragment::$Kind(ast) =>
 107                         AstFragment::$Kind(ast.into_iter()
 108                                               .flat_map(|ast| folder.$fold_ast_elt(ast))
 109                                               .collect()),)*)*
 110                 }
 111             }
 112
 113             pub fn visit_with<'a, V: Visitor<'a>>(&'a self, visitor: &mut V) {
 114                 match *self {
 115                     AstFragment::OptExpr(Some(ref expr)) => visitor.visit_expr(expr),
 116                     AstFragment::OptExpr(None) => {}
 117                     $($(AstFragment::$Kind(ref ast) => visitor.$visit_ast(ast),)*)*
 118                     $($(AstFragment::$Kind(ref ast) => for ast_elt in &ast[..] {
 119                         visitor.$visit_ast_elt(ast_elt);
 120                     })*)*
 121                 }
 122             }
 123         }
 124
 125         impl<'a, 'b> Folder for MacroExpander<'a, 'b> {
 126             fn fold_opt_expr(&mut self, expr: P<ast::Expr>) -> Option<P<ast::Expr>> {
 127                 self.expand_fragment(AstFragment::OptExpr(Some(expr))).make_opt_expr()
 128             }
 129             $($(fn $fold_ast(&mut self, ast: $AstTy) -> $AstTy {
 130                 self.expand_fragment(AstFragment::$Kind(ast)).$make_ast()
 131             })*)*
 132             $($(fn $fold_ast_elt(&mut self, ast_elt: <$AstTy as IntoIterator>::Item) -> $AstTy {
 133                 self.expand_fragment(AstFragment::$Kind(smallvec![ast_elt])).$make_ast()
 134             })*)*
 135         }
 136
 137         impl<'a> MacResult for ::ext::tt::macro_rules::ParserAnyMacro<'a> {
 138             $(fn $make_ast(self: Box<::ext::tt::macro_rules::ParserAnyMacro<'a>>)
 139                            -> Option<$AstTy> {
 140                 Some(self.make(AstFragmentKind::$Kind).$make_ast())
 141             })*
 142         }
 143     }
 144 }
 145
 146 ast_fragments! {
 147     Expr(P<ast::Expr>) { "expression"; one fn fold_expr; fn visit_expr; fn make_expr; }
 148     Pat(P<ast::Pat>) { "pattern"; one fn fold_pat; fn visit_pat; fn make_pat; }
 149     Ty(P<ast::Ty>) { "type"; one fn fold_ty; fn visit_ty; fn make_ty; }
 150     Stmts(OneVector<ast::Stmt>) { "statement"; many fn fold_stmt; fn visit_stmt; fn make_stmts; }
 151     Items(OneVector<P<ast::Item>>) { "item"; many fn fold_item; fn visit_item; fn make_items; }
 152     TraitItems(OneVector<ast::TraitItem>) {
 153         "trait item"; many fn fold_trait_item; fn visit_trait_item; fn make_trait_items;
 154     }
 155     ImplItems(OneVector<ast::ImplItem>) {
 156         "impl item"; many fn fold_impl_item; fn visit_impl_item; fn make_impl_items;
 157     }
 158     ForeignItems(OneVector<ast::ForeignItem>) {
 159         "foreign item"; many fn fold_foreign_item; fn visit_foreign_item; fn make_foreign_items;
 160     }
 161 }
 162
 163 impl AstFragmentKind {
 164     fn dummy(self, span: Span) -> Option<AstFragment> {
 165         self.make_from(DummyResult::any(span))
 166     }
 167
 168     fn expect_from_annotatables<I: IntoIterator<Item = Annotatable>>(self, items: I)
 169                                                                      -> AstFragment {
 170         let mut items = items.into_iter();
 171         match self {
 172             AstFragmentKind::Items =>
 173                 AstFragment::Items(items.map(Annotatable::expect_item).collect()),
 174             AstFragmentKind::ImplItems =>
 175                 AstFragment::ImplItems(items.map(Annotatable::expect_impl_item).collect()),
 176             AstFragmentKind::TraitItems =>
 177                 AstFragment::TraitItems(items.map(Annotatable::expect_trait_item).collect()),
 178             AstFragmentKind::ForeignItems =>
 179                 AstFragment::ForeignItems(items.map(Annotatable::expect_foreign_item).collect()),
 180             AstFragmentKind::Stmts =>
 181                 AstFragment::Stmts(items.map(Annotatable::expect_stmt).collect()),
 182             AstFragmentKind::Expr => AstFragment::Expr(
 183                 items.next().expect("expected exactly one expression").expect_expr()
 184             ),
 185             AstFragmentKind::OptExpr =>
 186                 AstFragment::OptExpr(items.next().map(Annotatable::expect_expr)),
 187             AstFragmentKind::Pat | AstFragmentKind::Ty =>
 188                 panic!("patterns and types aren't annotatable"),
 189         }
 190     }
 191 }
 192
 193 fn macro_bang_format(path: &ast::Path) -> ExpnFormat {
 194     // We don't want to format a path using pretty-printing,
 195     // `format!("{}", path)`, because that tries to insert
 196     // line-breaks and is slow.
 197     let mut path_str = String::with_capacity(64);
 198     for (i, segment) in path.segments.iter().enumerate() {
 199         if i != 0 {
 200             path_str.push_str("::");
 201         }
 202
 203         if segment.ident.name != keywords::CrateRoot.name() &&
 204             segment.ident.name != keywords::DollarCrate.name()
 205         {
 206             path_str.push_str(&segment.ident.as_str())
 207         }
 208     }
 209
 210     MacroBang(Symbol::intern(&path_str))
 211 }
 212
 213 pub struct Invocation {
 214     pub kind: InvocationKind,
 215     fragment_kind: AstFragmentKind,
 216     pub expansion_data: ExpansionData,
 217 }
 218
 219 pub enum InvocationKind {
 220     Bang {
 221         mac: ast::Mac,
 222         ident: Option<Ident>,
 223         span: Span,
 224     },
 225     Attr {
 226         attr: Option<ast::Attribute>,
 227         traits: Vec<Path>,
 228         item: Annotatable,
 229     },
 230     Derive {
 231         path: Path,
 232         item: Annotatable,
 233     },
 234 }
 235
 236 impl Invocation {
 237     pub fn span(&self) -> Span {
 238         match self.kind {
 239             InvocationKind::Bang { span, .. } => span,
 240             InvocationKind::Attr { attr: Some(ref attr), .. } => attr.span,
 241             InvocationKind::Attr { attr: None, .. } => DUMMY_SP,
 242             InvocationKind::Derive { ref path, .. } => path.span,
 243         }
 244     }
 245 }
 246
 247 pub struct MacroExpander<'a, 'b:'a> {
 248     pub cx: &'a mut ExtCtxt<'b>,
 249     monotonic: bool, // c.f. `cx.monotonic_expander()`
 250 }
 251
 252 impl<'a, 'b> MacroExpander<'a, 'b> {
 253     pub fn new(cx: &'a mut ExtCtxt<'b>, monotonic: bool) -> Self {
 254         MacroExpander { cx: cx, monotonic: monotonic }
 255     }
 256
 257     pub fn expand_crate(&mut self, mut krate: ast::Crate) -> ast::Crate {
 258         let mut module = ModuleData {
 259             mod_path: vec![Ident::from_str(&self.cx.ecfg.crate_name)],
 260             directory: match self.cx.source_map().span_to_unmapped_path(krate.span) {
 261                 FileName::Real(path) => path,
 262                 other => PathBuf::from(other.to_string()),
 263             },
 264         };
 265         module.directory.pop();
 266         self.cx.root_path = module.directory.clone();
 267         self.cx.current_expansion.module = Rc::new(module);
 268         self.cx.current_expansion.crate_span = Some(krate.span);
 269
 270         let orig_mod_span = krate.module.inner;
 271
 272         let krate_item = AstFragment::Items(smallvec![P(ast::Item {
 273             attrs: krate.attrs,
 274             span: krate.span,
 275             node: ast::ItemKind::Mod(krate.module),
 276             ident: keywords::Invalid.ident(),
 277             id: ast::DUMMY_NODE_ID,
 278             vis: respan(krate.span.shrink_to_lo(), ast::VisibilityKind::Public),
 279             tokens: None,
 280         })]);
 281
 282         match self.expand_fragment(krate_item).make_items().pop().map(P::into_inner) {
 283             Some(ast::Item { attrs, node: ast::ItemKind::Mod(module), .. }) => {
 284                 krate.attrs = attrs;
 285                 krate.module = module;
 286             },
 287             None => {
 288                 // Resolution failed so we return an empty expansion
 289                 krate.attrs = vec![];
 290                 krate.module = ast::Mod {
 291                     inner: orig_mod_span,
 292                     items: vec![],
 293                 };
 294             },
 295             _ => unreachable!(),
 296         };
 297         self.cx.trace_macros_diag();
 298         krate
 299     }
 300
 301     // Fully expand all macro invocations in this AST fragment.
 302     fn expand_fragment(&mut self, input_fragment: AstFragment) -> AstFragment {
 303         let orig_expansion_data = self.cx.current_expansion.clone();
 304         self.cx.current_expansion.depth = 0;
 305
 306         // Collect all macro invocations and replace them with placeholders.
 307         let (fragment_with_placeholders, mut invocations)
 308             = self.collect_invocations(input_fragment, &[]);
 309
 310         // Optimization: if we resolve all imports now,
 311         // we'll be able to immediately resolve most of imported macros.
 312         self.resolve_imports();
 313
 314         // Resolve paths in all invocations and produce output expanded fragments for them, but
 315         // do not insert them into our input AST fragment yet, only store in `expanded_fragments`.
 316         // The output fragments also go through expansion recursively until no invocations are left.
 317         // Unresolved macros produce dummy outputs as a recovery measure.
 318         invocations.reverse();
 319         let mut expanded_fragments = Vec::new();
 320         let mut derives: FxHashMap<Mark, Vec<_>> = FxHashMap::default();
 321         let mut undetermined_invocations = Vec::new();
 322         let (mut progress, mut force) = (false, !self.monotonic);
 323         loop {
 324             let invoc = if let Some(invoc) = invocations.pop() {
 325                 invoc
 326             } else {
 327                 self.resolve_imports();
 328                 if undetermined_invocations.is_empty() { break }
 329                 invocations = mem::replace(&mut undetermined_invocations, Vec::new());
 330                 force = !mem::replace(&mut progress, false);
 331                 continue
 332             };
 333
 334             let scope =
 335                 if self.monotonic { invoc.expansion_data.mark } else { orig_expansion_data.mark };
 336             let ext = match self.cx.resolver.resolve_macro_invocation(&invoc, scope, force) {
 337                 Ok(ext) => Some(ext),
 338                 Err(Determinacy::Determined) => None,
 339                 Err(Determinacy::Undetermined) => {
 340                     undetermined_invocations.push(invoc);
 341                     continue
 342                 }
 343             };
 344
 345             progress = true;
 346             let ExpansionData { depth, mark, .. } = invoc.expansion_data;
 347             self.cx.current_expansion = invoc.expansion_data.clone();
 348
 349             self.cx.current_expansion.mark = scope;
 350             // FIXME(jseyfried): Refactor out the following logic
 351             let (expanded_fragment, new_invocations) = if let Some(ext) = ext {
 352                 if let Some(ext) = ext {
 353                     let dummy = invoc.fragment_kind.dummy(invoc.span()).unwrap();
 354                     let fragment = self.expand_invoc(invoc, &*ext).unwrap_or(dummy);
 355                     self.collect_invocations(fragment, &[])
 356                 } else if let InvocationKind::Attr { attr: None, traits, item } = invoc.kind {
 357                     if !item.derive_allowed() {
 358                         let attr = attr::find_by_name(item.attrs(), "derive")
 359                             .expect("`derive` attribute should exist");
 360                         let span = attr.span;
 361                         let mut err = self.cx.mut_span_err(span,
 362                                                            "`derive` may only be applied to \
 363                                                             structs, enums and unions");
 364                         if let ast::AttrStyle::Inner = attr.style {
 365                             let trait_list = traits.iter()
 366                                 .map(|t| t.to_string()).collect::<Vec<_>>();
 367                             let suggestion = format!("#[derive({})]", trait_list.join(", "));
 368                             err.span_suggestion_with_applicability(
 369                                 span, "try an outer attribute", suggestion,
 370                                 // We don't 𝑘𝑛𝑜𝑤 that the following item is an ADT
 371                                 Applicability::MaybeIncorrect
 372                             );
 373                         }
 374                         err.emit();
 375                     }
 376
 377                     let item = self.fully_configure(item)
 378                         .map_attrs(|mut attrs| { attrs.retain(|a| a.path != "derive"); attrs });
 379                     let item_with_markers =
 380                         add_derived_markers(&mut self.cx, item.span(), &traits, item.clone());
 381                     let derives = derives.entry(invoc.expansion_data.mark).or_default();
 382
 383                     for path in &traits {
 384                         let mark = Mark::fresh(self.cx.current_expansion.mark);
 385                         derives.push(mark);
 386                         let item = match self.cx.resolver.resolve_macro_path(
 387                                 path, MacroKind::Derive, Mark::root(), &[], false) {
 388                             Ok(ext) => match *ext {
 389                                 BuiltinDerive(..) => item_with_markers.clone(),
 390                                 _ => item.clone(),
 391                             },
 392                             _ => item.clone(),
 393                         };
 394                         invocations.push(Invocation {
 395                             kind: InvocationKind::Derive { path: path.clone(), item: item },
 396                             fragment_kind: invoc.fragment_kind,
 397                             expansion_data: ExpansionData {
 398                                 mark,
 399                                 ..invoc.expansion_data.clone()
 400                             },
 401                         });
 402                     }
 403                     let fragment = invoc.fragment_kind
 404                         .expect_from_annotatables(::std::iter::once(item_with_markers));
 405                     self.collect_invocations(fragment, derives)
 406                 } else {
 407                     unreachable!()
 408                 }
 409             } else {
 410                 self.collect_invocations(invoc.fragment_kind.dummy(invoc.span()).unwrap(), &[])
 411             };
 412
 413             if expanded_fragments.len() < depth {
 414                 expanded_fragments.push(Vec::new());
 415             }
 416             expanded_fragments[depth - 1].push((mark, expanded_fragment));
 417             if !self.cx.ecfg.single_step {
 418                 invocations.extend(new_invocations.into_iter().rev());
 419             }
 420         }
 421
 422         self.cx.current_expansion = orig_expansion_data;
 423
 424         // Finally incorporate all the expanded macros into the input AST fragment.
 425         let mut placeholder_expander = PlaceholderExpander::new(self.cx, self.monotonic);
 426         while let Some(expanded_fragments) = expanded_fragments.pop() {
 427             for (mark, expanded_fragment) in expanded_fragments.into_iter().rev() {
 428                 let derives = derives.remove(&mark).unwrap_or_else(Vec::new);
 429                 placeholder_expander.add(NodeId::placeholder_from_mark(mark),
 430                                          expanded_fragment, derives);
 431             }
 432         }
 433         fragment_with_placeholders.fold_with(&mut placeholder_expander)
 434     }
 435
 436     fn resolve_imports(&mut self) {
 437         if self.monotonic {
 438             let err_count = self.cx.parse_sess.span_diagnostic.err_count();
 439             self.cx.resolver.resolve_imports();
 440             self.cx.resolve_err_count += self.cx.parse_sess.span_diagnostic.err_count() - err_count;
 441         }
 442     }
 443
 444     /// Collect all macro invocations reachable at this time in this AST fragment, and replace
 445     /// them with "placeholders" - dummy macro invocations with specially crafted `NodeId`s.
 446     /// Then call into resolver that builds a skeleton ("reduced graph") of the fragment and
 447     /// prepares data for resolving paths of macro invocations.
 448     fn collect_invocations(&mut self, fragment: AstFragment, derives: &[Mark])
 449                            -> (AstFragment, Vec<Invocation>) {
 450         let (fragment_with_placeholders, invocations) = {
 451             let mut collector = InvocationCollector {
 452                 cfg: StripUnconfigured {
 453                     sess: self.cx.parse_sess,
 454                     features: self.cx.ecfg.features,
 455                 },
 456                 cx: self.cx,
 457                 invocations: Vec::new(),
 458                 monotonic: self.monotonic,
 459             };
 460             (fragment.fold_with(&mut collector), collector.invocations)
 461         };
 462
 463         if self.monotonic {
 464             let err_count = self.cx.parse_sess.span_diagnostic.err_count();
 465             let mark = self.cx.current_expansion.mark;
 466             self.cx.resolver.visit_ast_fragment_with_placeholders(mark, &fragment_with_placeholders,
 467                                                                   derives);
 468             self.cx.resolve_err_count += self.cx.parse_sess.span_diagnostic.err_count() - err_count;
 469         }
 470
 471         (fragment_with_placeholders, invocations)
 472     }
 473
 474     fn fully_configure(&mut self, item: Annotatable) -> Annotatable {
 475         let mut cfg = StripUnconfigured {
 476             sess: self.cx.parse_sess,
 477             features: self.cx.ecfg.features,
 478         };
 479         // Since the item itself has already been configured by the InvocationCollector,
 480         // we know that fold result vector will contain exactly one element
 481         match item {
 482             Annotatable::Item(item) => {
 483                 Annotatable::Item(cfg.fold_item(item).pop().unwrap())
 484             }
 485             Annotatable::TraitItem(item) => {
 486                 Annotatable::TraitItem(item.map(|item| cfg.fold_trait_item(item).pop().unwrap()))
 487             }
 488             Annotatable::ImplItem(item) => {
 489                 Annotatable::ImplItem(item.map(|item| cfg.fold_impl_item(item).pop().unwrap()))
 490             }
 491             Annotatable::ForeignItem(item) => {
 492                 Annotatable::ForeignItem(
 493                     item.map(|item| cfg.fold_foreign_item(item).pop().unwrap())
 494                 )
 495             }
 496             Annotatable::Stmt(stmt) => {
 497                 Annotatable::Stmt(stmt.map(|stmt| cfg.fold_stmt(stmt).pop().unwrap()))
 498             }
 499             Annotatable::Expr(expr) => {
 500                 Annotatable::Expr(cfg.fold_expr(expr))
 501             }
 502         }
 503     }
 504
 505     fn expand_invoc(&mut self, invoc: Invocation, ext: &SyntaxExtension) -> Option<AstFragment> {
 506         if invoc.fragment_kind == AstFragmentKind::ForeignItems &&
 507            !self.cx.ecfg.macros_in_extern_enabled() {
 508             if let SyntaxExtension::NonMacroAttr { .. } = *ext {} else {
 509                 emit_feature_err(&self.cx.parse_sess, "macros_in_extern",
 510                                  invoc.span(), GateIssue::Language,
 511                                  "macro invocations in `extern {}` blocks are experimental");
 512             }
 513         }
 514
 515         let result = match invoc.kind {
 516             InvocationKind::Bang { .. } => self.expand_bang_invoc(invoc, ext)?,
 517             InvocationKind::Attr { .. } => self.expand_attr_invoc(invoc, ext)?,
 518             InvocationKind::Derive { .. } => self.expand_derive_invoc(invoc, ext)?,
 519         };
 520
 521         if self.cx.current_expansion.depth > self.cx.ecfg.recursion_limit {
 522             let info = self.cx.current_expansion.mark.expn_info().unwrap();
 523             let suggested_limit = self.cx.ecfg.recursion_limit * 2;
 524             let mut err = self.cx.struct_span_err(info.call_site,
 525                 &format!("recursion limit reached while expanding the macro `{}`",
 526                          info.format.name()));
 527             err.help(&format!(
 528                 "consider adding a `#![recursion_limit=\"{}\"]` attribute to your crate",
 529                 suggested_limit));
 530             err.emit();
 531             self.cx.trace_macros_diag();
 532             FatalError.raise();
 533         }
 534
 535         Some(result)
 536     }
 537
 538     fn expand_attr_invoc(&mut self,
 539                          invoc: Invocation,
 540                          ext: &SyntaxExtension)
 541                          -> Option<AstFragment> {
 542         let (attr, item) = match invoc.kind {
 543             InvocationKind::Attr { attr, item, .. } => (attr?, item),
 544             _ => unreachable!(),
 545         };
 546
 547         if let NonMacroAttr { mark_used: false } = *ext {} else {
 548             // Macro attrs are always used when expanded,
 549             // non-macro attrs are considered used when the field says so.
 550             attr::mark_used(&attr);
 551         }
 552         invoc.expansion_data.mark.set_expn_info(ExpnInfo {
 553             call_site: attr.span,
 554             def_site: None,
 555             format: MacroAttribute(Symbol::intern(&attr.path.to_string())),
 556             allow_internal_unstable: false,
 557             allow_internal_unsafe: false,
 558             local_inner_macros: false,
 559             edition: ext.edition(),
 560         });
 561
 562         match *ext {
 563             NonMacroAttr { .. } => {
 564                 attr::mark_known(&attr);
 565                 let item = item.map_attrs(|mut attrs| { attrs.push(attr); attrs });
 566                 Some(invoc.fragment_kind.expect_from_annotatables(iter::once(item)))
 567             }
 568             MultiModifier(ref mac) => {
 569                 let meta = attr.parse_meta(self.cx.parse_sess)
 570                                .map_err(|mut e| { e.emit(); }).ok()?;
 571                 let item = mac.expand(self.cx, attr.span, &meta, item);
 572                 Some(invoc.fragment_kind.expect_from_annotatables(item))
 573             }
 574             MultiDecorator(ref mac) => {
 575                 let mut items = Vec::new();
 576                 let meta = attr.parse_meta(self.cx.parse_sess)
 577                                .expect("derive meta should already have been parsed");
 578                 mac.expand(self.cx, attr.span, &meta, &item, &mut |item| items.push(item));
 579                 items.push(item);
 580                 Some(invoc.fragment_kind.expect_from_annotatables(items))
 581             }
 582             AttrProcMacro(ref mac, ..) => {
 583                 self.gate_proc_macro_attr_item(attr.span, &item);
 584                 let item_tok = TokenTree::Token(DUMMY_SP, Token::interpolated(match item {
 585                     Annotatable::Item(item) => token::NtItem(item),
 586                     Annotatable::TraitItem(item) => token::NtTraitItem(item.into_inner()),
 587                     Annotatable::ImplItem(item) => token::NtImplItem(item.into_inner()),
 588                     Annotatable::ForeignItem(item) => token::NtForeignItem(item.into_inner()),
 589                     Annotatable::Stmt(stmt) => token::NtStmt(stmt.into_inner()),
 590                     Annotatable::Expr(expr) => token::NtExpr(expr),
 591                 })).into();
 592                 let input = self.extract_proc_macro_attr_input(attr.tokens, attr.span);
 593                 let tok_result = mac.expand(self.cx, attr.span, input, item_tok);
 594                 let res = self.parse_ast_fragment(tok_result, invoc.fragment_kind,
 595                                                   &attr.path, attr.span);
 596                 self.gate_proc_macro_expansion(attr.span, &res);
 597                 res
 598             }
 599             ProcMacroDerive(..) | BuiltinDerive(..) => {
 600                 self.cx.span_err(attr.span, &format!("`{}` is a derive mode", attr.path));
 601                 self.cx.trace_macros_diag();
 602                 invoc.fragment_kind.dummy(attr.span)
 603             }
 604             _ => {
 605                 let msg = &format!("macro `{}` may not be used in attributes", attr.path);
 606                 self.cx.span_err(attr.span, msg);
 607                 self.cx.trace_macros_diag();
 608                 invoc.fragment_kind.dummy(attr.span)
 609             }
 610         }
 611     }
 612
 613     fn extract_proc_macro_attr_input(&self, tokens: TokenStream, span: Span) -> TokenStream {
 614         let mut trees = tokens.trees();
 615         match trees.next() {
 616             Some(TokenTree::Delimited(_, delim)) => {
 617                 if trees.next().is_none() {
 618                     return delim.tts.into()
 619                 }
 620             }
 621             Some(TokenTree::Token(..)) => {}
 622             None => return TokenStream::empty(),
 623         }
 624         self.cx.span_err(span, "custom attribute invocations must be \
 625             of the form #[foo] or #[foo(..)], the macro name must only be \
 626             followed by a delimiter token");
 627         TokenStream::empty()
 628     }
 629
 630     fn gate_proc_macro_attr_item(&self, span: Span, item: &Annotatable) {
 631         let (kind, gate) = match *item {
 632             Annotatable::Item(ref item) => {
 633                 match item.node {
 634                     ItemKind::Mod(_) if self.cx.ecfg.proc_macro_mod() => return,
 635                     ItemKind::Mod(_) => ("modules", "proc_macro_mod"),
 636                     _ => return,
 637                 }
 638             }
 639             Annotatable::TraitItem(_) => return,
 640             Annotatable::ImplItem(_) => return,
 641             Annotatable::ForeignItem(_) => return,
 642             Annotatable::Stmt(_) |
 643             Annotatable::Expr(_) if self.cx.ecfg.proc_macro_expr() => return,
 644             Annotatable::Stmt(_) => ("statements", "proc_macro_expr"),
 645             Annotatable::Expr(_) => ("expressions", "proc_macro_expr"),
 646         };
 647         emit_feature_err(
 648             self.cx.parse_sess,
 649             gate,
 650             span,
 651             GateIssue::Language,
 652             &format!("custom attributes cannot be applied to {}", kind),
 653         );
 654     }
 655
 656     fn gate_proc_macro_expansion(&self, span: Span, fragment: &Option<AstFragment>) {
 657         if self.cx.ecfg.proc_macro_gen() {
 658             return
 659         }
 660         let fragment = match fragment {
 661             Some(fragment) => fragment,
 662             None => return,
 663         };
 664
 665         fragment.visit_with(&mut DisallowMacros {
 666             span,
 667             parse_sess: self.cx.parse_sess,
 668         });
 669
 670         struct DisallowMacros<'a> {
 671             span: Span,
 672             parse_sess: &'a ParseSess,
 673         }
 674
 675         impl<'ast, 'a> Visitor<'ast> for DisallowMacros<'a> {
 676             fn visit_item(&mut self, i: &'ast ast::Item) {
 677                 if let ast::ItemKind::MacroDef(_) = i.node {
 678                     emit_feature_err(
 679                         self.parse_sess,
 680                         "proc_macro_gen",
 681                         self.span,
 682                         GateIssue::Language,
 683                         &format!("procedural macros cannot expand to macro definitions"),
 684                     );
 685                 }
 686                 visit::walk_item(self, i);
 687             }
 688
 689             fn visit_mac(&mut self, _mac: &'ast ast::Mac) {
 690                 // ...
 691             }
 692         }
 693     }
 694
 695     /// Expand a macro invocation. Returns the resulting expanded AST fragment.
 696     fn expand_bang_invoc(&mut self,
 697                          invoc: Invocation,
 698                          ext: &SyntaxExtension)
 699                          -> Option<AstFragment> {
 700         let (mark, kind) = (invoc.expansion_data.mark, invoc.fragment_kind);
 701         let (mac, ident, span) = match invoc.kind {
 702             InvocationKind::Bang { mac, ident, span } => (mac, ident, span),
 703             _ => unreachable!(),
 704         };
 705         let path = &mac.node.path;
 706
 707         let ident = ident.unwrap_or_else(|| keywords::Invalid.ident());
 708         let validate_and_set_expn_info = |this: &mut Self, // arg instead of capture
 709                                           def_site_span: Option<Span>,
 710                                           allow_internal_unstable,
 711                                           allow_internal_unsafe,
 712                                           local_inner_macros,
 713                                           // can't infer this type
 714                                           unstable_feature: Option<(Symbol, u32)>,
 715                                           edition| {
 716
 717             // feature-gate the macro invocation
 718             if let Some((feature, issue)) = unstable_feature {
 719                 let crate_span = this.cx.current_expansion.crate_span.unwrap();
 720                 // don't stability-check macros in the same crate
 721                 // (the only time this is null is for syntax extensions registered as macros)
 722                 if def_site_span.map_or(false, |def_span| !crate_span.contains(def_span))
 723                     && !span.allows_unstable() && this.cx.ecfg.features.map_or(true, |feats| {
 724                     // macro features will count as lib features
 725                     !feats.declared_lib_features.iter().any(|&(feat, _)| feat == feature)
 726                 }) {
 727                     let explain = format!("macro {}! is unstable", path);
 728                     emit_feature_err(this.cx.parse_sess, &*feature.as_str(), span,
 729                                      GateIssue::Library(Some(issue)), &explain);
 730                     this.cx.trace_macros_diag();
 731                     return Err(kind.dummy(span));
 732                 }
 733             }
 734
 735             if ident.name != keywords::Invalid.name() {
 736                 let msg = format!("macro {}! expects no ident argument, given '{}'", path, ident);
 737                 this.cx.span_err(path.span, &msg);
 738                 this.cx.trace_macros_diag();
 739                 return Err(kind.dummy(span));
 740             }
 741             mark.set_expn_info(ExpnInfo {
 742                 call_site: span,
 743                 def_site: def_site_span,
 744                 format: macro_bang_format(path),
 745                 allow_internal_unstable,
 746                 allow_internal_unsafe,
 747                 local_inner_macros,
 748                 edition,
 749             });
 750             Ok(())
 751         };
 752
 753         let opt_expanded = match *ext {
 754             DeclMacro { ref expander, def_info, edition, .. } => {
 755                 if let Err(dummy_span) = validate_and_set_expn_info(self, def_info.map(|(_, s)| s),
 756                                                                     false, false, false, None,
 757                                                                     edition) {
 758                     dummy_span
 759                 } else {
 760                     kind.make_from(expander.expand(self.cx, span, mac.node.stream()))
 761                 }
 762             }
 763
 764             NormalTT {
 765                 ref expander,
 766                 def_info,
 767                 allow_internal_unstable,
 768                 allow_internal_unsafe,
 769                 local_inner_macros,
 770                 unstable_feature,
 771                 edition,
 772             } => {
 773                 if let Err(dummy_span) = validate_and_set_expn_info(self, def_info.map(|(_, s)| s),
 774                                                                     allow_internal_unstable,
 775                                                                     allow_internal_unsafe,
 776                                                                     local_inner_macros,
 777                                                                     unstable_feature,
 778                                                                     edition) {
 779                     dummy_span
 780                 } else {
 781                     kind.make_from(expander.expand(self.cx, span, mac.node.stream()))
 782                 }
 783             }
 784
 785             IdentTT(ref expander, tt_span, allow_internal_unstable) => {
 786                 if ident.name == keywords::Invalid.name() {
 787                     self.cx.span_err(path.span,
 788                                     &format!("macro {}! expects an ident argument", path));
 789                     self.cx.trace_macros_diag();
 790                     kind.dummy(span)
 791                 } else {
 792                     invoc.expansion_data.mark.set_expn_info(ExpnInfo {
 793                         call_site: span,
 794                         def_site: tt_span,
 795                         format: macro_bang_format(path),
 796                         allow_internal_unstable,
 797                         allow_internal_unsafe: false,
 798                         local_inner_macros: false,
 799                         edition: hygiene::default_edition(),
 800                     });
 801
 802                     let input: Vec<_> = mac.node.stream().into_trees().collect();
 803                     kind.make_from(expander.expand(self.cx, span, ident, input))
 804                 }
 805             }
 806
 807             MultiDecorator(..) | MultiModifier(..) |
 808             AttrProcMacro(..) | SyntaxExtension::NonMacroAttr { .. } => {
 809                 self.cx.span_err(path.span,
 810                                  &format!("`{}` can only be used in attributes", path));
 811                 self.cx.trace_macros_diag();
 812                 kind.dummy(span)
 813             }
 814
 815             ProcMacroDerive(..) | BuiltinDerive(..) => {
 816                 self.cx.span_err(path.span, &format!("`{}` is a derive mode", path));
 817                 self.cx.trace_macros_diag();
 818                 kind.dummy(span)
 819             }
 820
 821             SyntaxExtension::ProcMacro { ref expander, allow_internal_unstable, edition } => {
 822                 if ident.name != keywords::Invalid.name() {
 823                     let msg =
 824                         format!("macro {}! expects no ident argument, given '{}'", path, ident);
 825                     self.cx.span_err(path.span, &msg);
 826                     self.cx.trace_macros_diag();
 827                     kind.dummy(span)
 828                 } else {
 829                     self.gate_proc_macro_expansion_kind(span, kind);
 830                     invoc.expansion_data.mark.set_expn_info(ExpnInfo {
 831                         call_site: span,
 832                         // FIXME procedural macros do not have proper span info
 833                         // yet, when they do, we should use it here.
 834                         def_site: None,
 835                         format: macro_bang_format(path),
 836                         // FIXME probably want to follow macro_rules macros here.
 837                         allow_internal_unstable,
 838                         allow_internal_unsafe: false,
 839                         local_inner_macros: false,
 840                         edition,
 841                     });
 842
 843                     let tok_result = expander.expand(self.cx, span, mac.node.stream());
 844                     let result = self.parse_ast_fragment(tok_result, kind, path, span);
 845                     self.gate_proc_macro_expansion(span, &result);
 846                     result
 847                 }
 848             }
 849         };
 850
 851         if opt_expanded.is_some() {
 852             opt_expanded
 853         } else {
 854             let msg = format!("non-{kind} macro in {kind} position: {name}",
 855                               name = path.segments[0].ident.name, kind = kind.name());
 856             self.cx.span_err(path.span, &msg);
 857             self.cx.trace_macros_diag();
 858             kind.dummy(span)
 859         }
 860     }
 861
 862     fn gate_proc_macro_expansion_kind(&self, span: Span, kind: AstFragmentKind) {
 863         let kind = match kind {
 864             AstFragmentKind::Expr => "expressions",
 865             AstFragmentKind::OptExpr => "expressions",
 866             AstFragmentKind::Pat => "patterns",
 867             AstFragmentKind::Ty => "types",
 868             AstFragmentKind::Stmts => "statements",
 869             AstFragmentKind::Items => return,
 870             AstFragmentKind::TraitItems => return,
 871             AstFragmentKind::ImplItems => return,
 872             AstFragmentKind::ForeignItems => return,
 873         };
 874         if self.cx.ecfg.proc_macro_non_items() {
 875             return
 876         }
 877         emit_feature_err(
 878             self.cx.parse_sess,
 879             "proc_macro_non_items",
 880             span,
 881             GateIssue::Language,
 882             &format!("procedural macros cannot be expanded to {}", kind),
 883         );
 884     }
 885
 886     /// Expand a derive invocation. Returns the resulting expanded AST fragment.
 887     fn expand_derive_invoc(&mut self,
 888                            invoc: Invocation,
 889                            ext: &SyntaxExtension)
 890                            -> Option<AstFragment> {
 891         let (path, item) = match invoc.kind {
 892             InvocationKind::Derive { path, item } => (path, item),
 893             _ => unreachable!(),
 894         };
 895         if !item.derive_allowed() {
 896             return None;
 897         }
 898
 899         let pretty_name = Symbol::intern(&format!("derive({})", path));
 900         let span = path.span;
 901         let attr = ast::Attribute {
 902             path, span,
 903             tokens: TokenStream::empty(),
 904             // irrelevant:
 905             id: ast::AttrId(0), style: ast::AttrStyle::Outer, is_sugared_doc: false,
 906         };
 907
 908         let mut expn_info = ExpnInfo {
 909             call_site: span,
 910             def_site: None,
 911             format: MacroAttribute(pretty_name),
 912             allow_internal_unstable: false,
 913             allow_internal_unsafe: false,
 914             local_inner_macros: false,
 915             edition: ext.edition(),
 916         };
 917
 918         match *ext {
 919             ProcMacroDerive(ref ext, ..) => {
 920                 invoc.expansion_data.mark.set_expn_info(expn_info);
 921                 let span = span.with_ctxt(self.cx.backtrace());
 922                 let dummy = ast::MetaItem { // FIXME(jseyfried) avoid this
 923                     ident: Path::from_ident(keywords::Invalid.ident()),
 924                     span: DUMMY_SP,
 925                     node: ast::MetaItemKind::Word,
 926                 };
 927                 let items = ext.expand(self.cx, span, &dummy, item);
 928                 Some(invoc.fragment_kind.expect_from_annotatables(items))
 929             }
 930             BuiltinDerive(func) => {
 931                 expn_info.allow_internal_unstable = true;
 932                 invoc.expansion_data.mark.set_expn_info(expn_info);
 933                 let span = span.with_ctxt(self.cx.backtrace());
 934                 let mut items = Vec::new();
 935                 func(self.cx, span, &attr.meta()?, &item, &mut |a| items.push(a));
 936                 Some(invoc.fragment_kind.expect_from_annotatables(items))
 937             }
 938             _ => {
 939                 let msg = &format!("macro `{}` may not be used for derive attributes", attr.path);
 940                 self.cx.span_err(span, msg);
 941                 self.cx.trace_macros_diag();
 942                 invoc.fragment_kind.dummy(span)
 943             }
 944         }
 945     }
 946
 947     fn parse_ast_fragment(&mut self,
 948                           toks: TokenStream,
 949                           kind: AstFragmentKind,
 950                           path: &Path,
 951                           span: Span)
 952                           -> Option<AstFragment> {
 953         let mut parser = self.cx.new_parser_from_tts(&toks.into_trees().collect::<Vec<_>>());
 954         match parser.parse_ast_fragment(kind, false) {
 955             Ok(fragment) => {
 956                 parser.ensure_complete_parse(path, kind.name(), span);
 957                 Some(fragment)
 958             }
 959             Err(mut err) => {
 960                 err.set_span(span);
 961                 err.emit();
 962                 self.cx.trace_macros_diag();
 963                 kind.dummy(span)
 964             }
 965         }
 966     }
 967 }
 968
 969 impl<'a> Parser<'a> {
 970     pub fn parse_ast_fragment(&mut self, kind: AstFragmentKind, macro_legacy_warnings: bool)
 971                               -> PResult<'a, AstFragment> {
 972         Ok(match kind {
 973             AstFragmentKind::Items => {
 974                 let mut items = OneVector::new();
 975                 while let Some(item) = self.parse_item()? {
 976                     items.push(item);
 977                 }
 978                 AstFragment::Items(items)
 979             }
 980             AstFragmentKind::TraitItems => {
 981                 let mut items = OneVector::new();
 982                 while self.token != token::Eof {
 983                     items.push(self.parse_trait_item(&mut false)?);
 984                 }
 985                 AstFragment::TraitItems(items)
 986             }
 987             AstFragmentKind::ImplItems => {
 988                 let mut items = OneVector::new();
 989                 while self.token != token::Eof {
 990                     items.push(self.parse_impl_item(&mut false)?);
 991                 }
 992                 AstFragment::ImplItems(items)
 993             }
 994             AstFragmentKind::ForeignItems => {
 995                 let mut items = OneVector::new();
 996                 while self.token != token::Eof {
 997                     if let Some(item) = self.parse_foreign_item()? {
 998                         items.push(item);
 999                     }
1000                 }
1001                 AstFragment::ForeignItems(items)
1002             }
1003             AstFragmentKind::Stmts => {
1004                 let mut stmts = OneVector::new();
1005                 while self.token != token::Eof &&
1006                       // won't make progress on a `}`
1007                       self.token != token::CloseDelim(token::Brace) {
1008                     if let Some(stmt) = self.parse_full_stmt(macro_legacy_warnings)? {
1009                         stmts.push(stmt);
1010                     }
1011                 }
1012                 AstFragment::Stmts(stmts)
1013             }
1014             AstFragmentKind::Expr => AstFragment::Expr(self.parse_expr()?),
1015             AstFragmentKind::OptExpr => {
1016                 if self.token != token::Eof {
1017                     AstFragment::OptExpr(Some(self.parse_expr()?))
1018                 } else {
1019                     AstFragment::OptExpr(None)
1020                 }
1021             },
1022             AstFragmentKind::Ty => AstFragment::Ty(self.parse_ty()?),
1023             AstFragmentKind::Pat => AstFragment::Pat(self.parse_pat()?),
1024         })
1025     }
1026
1027     pub fn ensure_complete_parse(&mut self, macro_path: &Path, kind_name: &str, span: Span) {
1028         if self.token != token::Eof {
1029             let msg = format!("macro expansion ignores token `{}` and any following",
1030                               self.this_token_to_string());
1031             // Avoid emitting backtrace info twice.
1032             let def_site_span = self.span.with_ctxt(SyntaxContext::empty());
1033             let mut err = self.diagnostic().struct_span_err(def_site_span, &msg);
1034             let msg = format!("caused by the macro expansion here; the usage \
1035                                of `{}!` is likely invalid in {} context",
1036                                macro_path, kind_name);
1037             err.span_note(span, &msg).emit();
1038         }
1039     }
1040 }
1041
1042 struct InvocationCollector<'a, 'b: 'a> {
1043     cx: &'a mut ExtCtxt<'b>,
1044     cfg: StripUnconfigured<'a>,
1045     invocations: Vec<Invocation>,
1046     monotonic: bool,
1047 }
1048
1049 impl<'a, 'b> InvocationCollector<'a, 'b> {
1050     fn collect(&mut self, fragment_kind: AstFragmentKind, kind: InvocationKind) -> AstFragment {
1051         let mark = Mark::fresh(self.cx.current_expansion.mark);
1052         self.invocations.push(Invocation {
1053             kind,
1054             fragment_kind,
1055             expansion_data: ExpansionData {
1056                 mark,
1057                 depth: self.cx.current_expansion.depth + 1,
1058                 ..self.cx.current_expansion.clone()
1059             },
1060         });
1061         placeholder(fragment_kind, NodeId::placeholder_from_mark(mark))
1062     }
1063
1064     fn collect_bang(&mut self, mac: ast::Mac, span: Span, kind: AstFragmentKind) -> AstFragment {
1065         self.collect(kind, InvocationKind::Bang { mac: mac, ident: None, span: span })
1066     }
1067
1068     fn collect_attr(&mut self,
1069                     attr: Option<ast::Attribute>,
1070                     traits: Vec<Path>,
1071                     item: Annotatable,
1072                     kind: AstFragmentKind)
1073                     -> AstFragment {
1074         self.collect(kind, InvocationKind::Attr { attr, traits, item })
1075     }
1076
1077     fn find_attr_invoc(&self, attrs: &mut Vec<ast::Attribute>) -> Option<ast::Attribute> {
1078         let attr = attrs.iter()
1079                         .position(|a| !attr::is_known(a) && !is_builtin_attr(a))
1080                         .map(|i| attrs.remove(i));
1081         if let Some(attr) = &attr {
1082             if !self.cx.ecfg.enable_custom_inner_attributes() &&
1083                attr.style == ast::AttrStyle::Inner && attr.path != "test" {
1084                 emit_feature_err(&self.cx.parse_sess, "custom_inner_attributes",
1085                                  attr.span, GateIssue::Language,
1086                                  "non-builtin inner attributes are unstable");
1087             }
1088         }
1089         attr
1090     }
1091
1092     /// If `item` is an attr invocation, remove and return the macro attribute and derive traits.
1093     fn classify_item<T>(&mut self, mut item: T) -> (Option<ast::Attribute>, Vec<Path>, T)
1094         where T: HasAttrs,
1095     {
1096         let (mut attr, mut traits) = (None, Vec::new());
1097
1098         item = item.map_attrs(|mut attrs| {
1099             if let Some(legacy_attr_invoc) = self.cx.resolver.find_legacy_attr_invoc(&mut attrs,
1100                                                                                      true) {
1101                 attr = Some(legacy_attr_invoc);
1102                 return attrs;
1103             }
1104
1105             attr = self.find_attr_invoc(&mut attrs);
1106             traits = collect_derives(&mut self.cx, &mut attrs);
1107             attrs
1108         });
1109
1110         (attr, traits, item)
1111     }
1112
1113     /// Alternative of `classify_item()` that ignores `#[derive]` so invocations fallthrough
1114     /// to the unused-attributes lint (making it an error on statements and expressions
1115     /// is a breaking change)
1116     fn classify_nonitem<T: HasAttrs>(&mut self, mut item: T) -> (Option<ast::Attribute>, T) {
1117         let mut attr = None;
1118
1119         item = item.map_attrs(|mut attrs| {
1120             if let Some(legacy_attr_invoc) = self.cx.resolver.find_legacy_attr_invoc(&mut attrs,
1121                                                                                      false) {
1122                 attr = Some(legacy_attr_invoc);
1123                 return attrs;
1124             }
1125
1126             attr = self.find_attr_invoc(&mut attrs);
1127             attrs
1128         });
1129
1130         (attr, item)
1131     }
1132
1133     fn configure<T: HasAttrs>(&mut self, node: T) -> Option<T> {
1134         self.cfg.configure(node)
1135     }
1136
1137     // Detect use of feature-gated or invalid attributes on macro invocations
1138     // since they will not be detected after macro expansion.
1139     fn check_attributes(&mut self, attrs: &[ast::Attribute]) {
1140         let features = self.cx.ecfg.features.unwrap();
1141         for attr in attrs.iter() {
1142             self.check_attribute_inner(attr, features);
1143
1144             // macros are expanded before any lint passes so this warning has to be hardcoded
1145             if attr.path == "derive" {
1146                 self.cx.struct_span_warn(attr.span, "`#[derive]` does nothing on macro invocations")
1147                     .note("this may become a hard error in a future release")
1148                     .emit();
1149             }
1150         }
1151     }
1152
1153     fn check_attribute(&mut self, at: &ast::Attribute) {
1154         let features = self.cx.ecfg.features.unwrap();
1155         self.check_attribute_inner(at, features);
1156     }
1157
1158     fn check_attribute_inner(&mut self, at: &ast::Attribute, features: &Features) {
1159         feature_gate::check_attribute(at, self.cx.parse_sess, features);
1160     }
1161 }
1162
1163 impl<'a, 'b> Folder for InvocationCollector<'a, 'b> {
1164     fn fold_expr(&mut self, expr: P<ast::Expr>) -> P<ast::Expr> {
1165         let mut expr = self.cfg.configure_expr(expr).into_inner();
1166         expr.node = self.cfg.configure_expr_kind(expr.node);
1167
1168         // ignore derives so they remain unused
1169         let (attr, expr) = self.classify_nonitem(expr);
1170
1171         if attr.is_some() {
1172             // collect the invoc regardless of whether or not attributes are permitted here
1173             // expansion will eat the attribute so it won't error later
1174             attr.as_ref().map(|a| self.cfg.maybe_emit_expr_attr_err(a));
1175
1176             // AstFragmentKind::Expr requires the macro to emit an expression
1177             return self.collect_attr(attr, vec![], Annotatable::Expr(P(expr)),
1178                                      AstFragmentKind::Expr).make_expr();
1179         }
1180
1181         if let ast::ExprKind::Mac(mac) = expr.node {
1182             self.check_attributes(&expr.attrs);
1183             self.collect_bang(mac, expr.span, AstFragmentKind::Expr).make_expr()
1184         } else {
1185             P(noop_fold_expr(expr, self))
1186         }
1187     }
1188
1189     fn fold_opt_expr(&mut self, expr: P<ast::Expr>) -> Option<P<ast::Expr>> {
1190         let mut expr = configure!(self, expr).into_inner();
1191         expr.node = self.cfg.configure_expr_kind(expr.node);
1192
1193         // ignore derives so they remain unused
1194         let (attr, expr) = self.classify_nonitem(expr);
1195
1196         if attr.is_some() {
1197             attr.as_ref().map(|a| self.cfg.maybe_emit_expr_attr_err(a));
1198
1199             return self.collect_attr(attr, vec![], Annotatable::Expr(P(expr)),
1200                                      AstFragmentKind::OptExpr)
1201                 .make_opt_expr();
1202         }
1203
1204         if let ast::ExprKind::Mac(mac) = expr.node {
1205             self.check_attributes(&expr.attrs);
1206             self.collect_bang(mac, expr.span, AstFragmentKind::OptExpr).make_opt_expr()
1207         } else {
1208             Some(P(noop_fold_expr(expr, self)))
1209         }
1210     }
1211
1212     fn fold_pat(&mut self, pat: P<ast::Pat>) -> P<ast::Pat> {
1213         let pat = self.cfg.configure_pat(pat);
1214         match pat.node {
1215             PatKind::Mac(_) => {}
1216             _ => return noop_fold_pat(pat, self),
1217         }
1218
1219         pat.and_then(|pat| match pat.node {
1220             PatKind::Mac(mac) => self.collect_bang(mac, pat.span, AstFragmentKind::Pat).make_pat(),
1221             _ => unreachable!(),
1222         })
1223     }
1224
1225     fn fold_stmt(&mut self, stmt: ast::Stmt) -> OneVector<ast::Stmt> {
1226         let mut stmt = match self.cfg.configure_stmt(stmt) {
1227             Some(stmt) => stmt,
1228             None => return OneVector::new(),
1229         };
1230
1231         // we'll expand attributes on expressions separately
1232         if !stmt.is_expr() {
1233             let (attr, derives, stmt_) = if stmt.is_item() {
1234                 self.classify_item(stmt)
1235             } else {
1236                 // ignore derives on non-item statements so it falls through
1237                 // to the unused-attributes lint
1238                 let (attr, stmt) = self.classify_nonitem(stmt);
1239                 (attr, vec![], stmt)
1240             };
1241
1242             if attr.is_some() || !derives.is_empty() {
1243                 return self.collect_attr(attr, derives,
1244                                          Annotatable::Stmt(P(stmt_)), AstFragmentKind::Stmts)
1245                     .make_stmts();
1246             }
1247
1248             stmt = stmt_;
1249         }
1250
1251         if let StmtKind::Mac(mac) = stmt.node {
1252             let (mac, style, attrs) = mac.into_inner();
1253             self.check_attributes(&attrs);
1254             let mut placeholder = self.collect_bang(mac, stmt.span, AstFragmentKind::Stmts)
1255                                         .make_stmts();
1256
1257             // If this is a macro invocation with a semicolon, then apply that
1258             // semicolon to the final statement produced by expansion.
1259             if style == MacStmtStyle::Semicolon {
1260                 if let Some(stmt) = placeholder.pop() {
1261                     placeholder.push(stmt.add_trailing_semicolon());
1262                 }
1263             }
1264
1265             return placeholder;
1266         }
1267
1268         // The placeholder expander gives ids to statements, so we avoid folding the id here.
1269         let ast::Stmt { id, node, span } = stmt;
1270         noop_fold_stmt_kind(node, self).into_iter().map(|node| {
1271             ast::Stmt { id, node, span }
1272         }).collect()
1273
1274     }
1275
1276     fn fold_block(&mut self, block: P<Block>) -> P<Block> {
1277         let old_directory_ownership = self.cx.current_expansion.directory_ownership;
1278         self.cx.current_expansion.directory_ownership = DirectoryOwnership::UnownedViaBlock;
1279         let result = noop_fold_block(block, self);
1280         self.cx.current_expansion.directory_ownership = old_directory_ownership;
1281         result
1282     }
1283
1284     fn fold_item(&mut self, item: P<ast::Item>) -> OneVector<P<ast::Item>> {
1285         let item = configure!(self, item);
1286
1287         let (attr, traits, item) = self.classify_item(item);
1288         if attr.is_some() || !traits.is_empty() {
1289             let item = Annotatable::Item(item);
1290             return self.collect_attr(attr, traits, item, AstFragmentKind::Items).make_items();
1291         }
1292
1293         match item.node {
1294             ast::ItemKind::Mac(..) => {
1295                 self.check_attributes(&item.attrs);
1296                 item.and_then(|item| match item.node {
1297                     ItemKind::Mac(mac) => {
1298                         self.collect(AstFragmentKind::Items, InvocationKind::Bang {
1299                             mac,
1300                             ident: Some(item.ident),
1301                             span: item.span,
1302                         }).make_items()
1303                     }
1304                     _ => unreachable!(),
1305                 })
1306             }
1307             ast::ItemKind::Mod(ast::Mod { inner, .. }) => {
1308                 if item.ident == keywords::Invalid.ident() {
1309                     return noop_fold_item(item, self);
1310                 }
1311
1312                 let orig_directory_ownership = self.cx.current_expansion.directory_ownership;
1313                 let mut module = (*self.cx.current_expansion.module).clone();
1314                 module.mod_path.push(item.ident);
1315
1316                 // Detect if this is an inline module (`mod m { ... }` as opposed to `mod m;`).
1317                 // In the non-inline case, `inner` is never the dummy span (c.f. `parse_item_mod`).
1318                 // Thus, if `inner` is the dummy span, we know the module is inline.
1319                 let inline_module = item.span.contains(inner) || inner.is_dummy();
1320
1321                 if inline_module {
1322                     if let Some(path) = attr::first_attr_value_str_by_name(&item.attrs, "path") {
1323                         self.cx.current_expansion.directory_ownership =
1324                             DirectoryOwnership::Owned { relative: None };
1325                         module.directory.push(&*path.as_str());
1326                     } else {
1327                         module.directory.push(&*item.ident.as_str());
1328                     }
1329                 } else {
1330                     let path = self.cx.parse_sess.source_map().span_to_unmapped_path(inner);
1331                     let mut path = match path {
1332                         FileName::Real(path) => path,
1333                         other => PathBuf::from(other.to_string()),
1334                     };
1335                     let directory_ownership = match path.file_name().unwrap().to_str() {
1336                         Some("mod.rs") => DirectoryOwnership::Owned { relative: None },
1337                         Some(_) => DirectoryOwnership::Owned {
1338                             relative: Some(item.ident),
1339                         },
1340                         None => DirectoryOwnership::UnownedViaMod(false),
1341                     };
1342                     path.pop();
1343                     module.directory = path;
1344                     self.cx.current_expansion.directory_ownership = directory_ownership;
1345                 }
1346
1347                 let orig_module =
1348                     mem::replace(&mut self.cx.current_expansion.module, Rc::new(module));
1349                 let result = noop_fold_item(item, self);
1350                 self.cx.current_expansion.module = orig_module;
1351                 self.cx.current_expansion.directory_ownership = orig_directory_ownership;
1352                 result
1353             }
1354
1355             _ => noop_fold_item(item, self),
1356         }
1357     }
1358
1359     fn fold_trait_item(&mut self, item: ast::TraitItem) -> OneVector<ast::TraitItem> {
1360         let item = configure!(self, item);
1361
1362         let (attr, traits, item) = self.classify_item(item);
1363         if attr.is_some() || !traits.is_empty() {
1364             let item = Annotatable::TraitItem(P(item));
1365             return self.collect_attr(attr, traits, item, AstFragmentKind::TraitItems)
1366                 .make_trait_items()
1367         }
1368
1369         match item.node {
1370             ast::TraitItemKind::Macro(mac) => {
1371                 let ast::TraitItem { attrs, span, .. } = item;
1372                 self.check_attributes(&attrs);
1373                 self.collect_bang(mac, span, AstFragmentKind::TraitItems).make_trait_items()
1374             }
1375             _ => fold::noop_fold_trait_item(item, self),
1376         }
1377     }
1378
1379     fn fold_impl_item(&mut self, item: ast::ImplItem) -> OneVector<ast::ImplItem> {
1380         let item = configure!(self, item);
1381
1382         let (attr, traits, item) = self.classify_item(item);
1383         if attr.is_some() || !traits.is_empty() {
1384             let item = Annotatable::ImplItem(P(item));
1385             return self.collect_attr(attr, traits, item, AstFragmentKind::ImplItems)
1386                 .make_impl_items();
1387         }
1388
1389         match item.node {
1390             ast::ImplItemKind::Macro(mac) => {
1391                 let ast::ImplItem { attrs, span, .. } = item;
1392                 self.check_attributes(&attrs);
1393                 self.collect_bang(mac, span, AstFragmentKind::ImplItems).make_impl_items()
1394             }
1395             _ => fold::noop_fold_impl_item(item, self),
1396         }
1397     }
1398
1399     fn fold_ty(&mut self, ty: P<ast::Ty>) -> P<ast::Ty> {
1400         let ty = match ty.node {
1401             ast::TyKind::Mac(_) => ty.into_inner(),
1402             _ => return fold::noop_fold_ty(ty, self),
1403         };
1404
1405         match ty.node {
1406             ast::TyKind::Mac(mac) => self.collect_bang(mac, ty.span, AstFragmentKind::Ty).make_ty(),
1407             _ => unreachable!(),
1408         }
1409     }
1410
1411     fn fold_foreign_mod(&mut self, foreign_mod: ast::ForeignMod) -> ast::ForeignMod {
1412         noop_fold_foreign_mod(self.cfg.configure_foreign_mod(foreign_mod), self)
1413     }
1414
1415     fn fold_foreign_item(&mut self,
1416                          foreign_item: ast::ForeignItem) -> OneVector<ast::ForeignItem> {
1417         let (attr, traits, foreign_item) = self.classify_item(foreign_item);
1418
1419         if attr.is_some() || !traits.is_empty() {
1420             let item = Annotatable::ForeignItem(P(foreign_item));
1421             return self.collect_attr(attr, traits, item, AstFragmentKind::ForeignItems)
1422                 .make_foreign_items();
1423         }
1424
1425         if let ast::ForeignItemKind::Macro(mac) = foreign_item.node {
1426             self.check_attributes(&foreign_item.attrs);
1427             return self.collect_bang(mac, foreign_item.span, AstFragmentKind::ForeignItems)
1428                 .make_foreign_items();
1429         }
1430
1431         noop_fold_foreign_item(foreign_item, self)
1432     }
1433
1434     fn fold_item_kind(&mut self, item: ast::ItemKind) -> ast::ItemKind {
1435         match item {
1436             ast::ItemKind::MacroDef(..) => item,
1437             _ => noop_fold_item_kind(self.cfg.configure_item_kind(item), self),
1438         }
1439     }
1440
1441     fn fold_generic_param(&mut self, param: ast::GenericParam) -> ast::GenericParam {
1442         self.cfg.disallow_cfg_on_generic_param(&param);
1443         noop_fold_generic_param(param, self)
1444     }
1445
1446     fn fold_attribute(&mut self, at: ast::Attribute) -> Option<ast::Attribute> {
1447         // turn `#[doc(include="filename")]` attributes into `#[doc(include(file="filename",
1448         // contents="file contents")]` attributes
1449         if !at.check_name("doc") {
1450             return noop_fold_attribute(at, self);
1451         }
1452
1453         if let Some(list) = at.meta_item_list() {
1454             if !list.iter().any(|it| it.check_name("include")) {
1455                 return noop_fold_attribute(at, self);
1456             }
1457
1458             let mut items = vec![];
1459
1460             for it in list {
1461                 if !it.check_name("include") {
1462                     items.push(noop_fold_meta_list_item(it, self));
1463                     continue;
1464                 }
1465
1466                 if let Some(file) = it.value_str() {
1467                     let err_count = self.cx.parse_sess.span_diagnostic.err_count();
1468                     self.check_attribute(&at);
1469                     if self.cx.parse_sess.span_diagnostic.err_count() > err_count {
1470                         // avoid loading the file if they haven't enabled the feature
1471                         return noop_fold_attribute(at, self);
1472                     }
1473
1474                     let mut buf = vec![];
1475                     let filename = self.cx.root_path.join(file.to_string());
1476
1477                     match File::open(&filename).and_then(|mut f| f.read_to_end(&mut buf)) {
1478                         Ok(..) => {}
1479                         Err(e) => {
1480                             self.cx.span_err(at.span,
1481                                              &format!("couldn't read {}: {}",
1482                                                       filename.display(),
1483                                                       e));
1484                         }
1485                     }
1486
1487                     match String::from_utf8(buf) {
1488                         Ok(src) => {
1489                             let src_interned = Symbol::intern(&src);
1490
1491                             // Add this input file to the code map to make it available as
1492                             // dependency information
1493                             self.cx.source_map().new_source_file(filename.into(), src);
1494
1495                             let include_info = vec![
1496                                 dummy_spanned(ast::NestedMetaItemKind::MetaItem(
1497                                         attr::mk_name_value_item_str(Ident::from_str("file"),
1498                                                                      dummy_spanned(file)))),
1499                                 dummy_spanned(ast::NestedMetaItemKind::MetaItem(
1500                                         attr::mk_name_value_item_str(Ident::from_str("contents"),
1501                                                             dummy_spanned(src_interned)))),
1502                             ];
1503
1504                             let include_ident = Ident::from_str("include");
1505                             let item = attr::mk_list_item(DUMMY_SP, include_ident, include_info);
1506                             items.push(dummy_spanned(ast::NestedMetaItemKind::MetaItem(item)));
1507                         }
1508                         Err(_) => {
1509                             self.cx.span_err(at.span,
1510                                              &format!("{} wasn't a utf-8 file",
1511                                                       filename.display()));
1512                         }
1513                     }
1514                 } else {
1515                     items.push(noop_fold_meta_list_item(it, self));
1516                 }
1517             }
1518
1519             let meta = attr::mk_list_item(DUMMY_SP, Ident::from_str("doc"), items);
1520             match at.style {
1521                 ast::AttrStyle::Inner =>
1522                     Some(attr::mk_spanned_attr_inner(at.span, at.id, meta)),
1523                 ast::AttrStyle::Outer =>
1524                     Some(attr::mk_spanned_attr_outer(at.span, at.id, meta)),
1525             }
1526         } else {
1527             noop_fold_attribute(at, self)
1528         }
1529     }
1530
1531     fn new_id(&mut self, id: ast::NodeId) -> ast::NodeId {
1532         if self.monotonic {
1533             assert_eq!(id, ast::DUMMY_NODE_ID);
1534             self.cx.resolver.next_node_id()
1535         } else {
1536             id
1537         }
1538     }
1539 }
1540
1541 pub struct ExpansionConfig<'feat> {
1542     pub crate_name: String,
1543     pub features: Option<&'feat Features>,
1544     pub recursion_limit: usize,
1545     pub trace_mac: bool,
1546     pub should_test: bool, // If false, strip `#[test]` nodes
1547     pub single_step: bool,
1548     pub keep_macs: bool,
1549 }
1550
1551 macro_rules! feature_tests {
1552     ($( fn $getter:ident = $field:ident, )*) => {
1553         $(
1554             pub fn $getter(&self) -> bool {
1555                 match self.features {
1556                     Some(&Features { $field: true, .. }) => true,
1557                     _ => false,
1558                 }
1559             }
1560         )*
1561     }
1562 }
1563
1564 impl<'feat> ExpansionConfig<'feat> {
1565     pub fn default(crate_name: String) -> ExpansionConfig<'static> {
1566         ExpansionConfig {
1567             crate_name,
1568             features: None,
1569             recursion_limit: 1024,
1570             trace_mac: false,
1571             should_test: false,
1572             single_step: false,
1573             keep_macs: false,
1574         }
1575     }
1576
1577     feature_tests! {
1578         fn enable_quotes = quote,
1579         fn enable_asm = asm,
1580         fn enable_custom_test_frameworks = custom_test_frameworks,
1581         fn enable_global_asm = global_asm,
1582         fn enable_log_syntax = log_syntax,
1583         fn enable_concat_idents = concat_idents,
1584         fn enable_trace_macros = trace_macros,
1585         fn enable_allow_internal_unstable = allow_internal_unstable,
1586         fn enable_custom_derive = custom_derive,
1587         fn enable_format_args_nl = format_args_nl,
1588         fn macros_in_extern_enabled = macros_in_extern,
1589         fn proc_macro_mod = proc_macro_mod,
1590         fn proc_macro_gen = proc_macro_gen,
1591         fn proc_macro_expr = proc_macro_expr,
1592         fn proc_macro_non_items = proc_macro_non_items,
1593     }
1594
1595     fn enable_custom_inner_attributes(&self) -> bool {
1596         self.features.map_or(false, |features| {
1597             features.custom_inner_attributes || features.custom_attribute || features.rustc_attrs
1598         })
1599     }
1600 }
1601
1602 // A Marker adds the given mark to the syntax context.
1603 #[derive(Debug)]
1604 pub struct Marker(pub Mark);
1605
1606 impl Folder for Marker {
1607     fn new_span(&mut self, span: Span) -> Span {
1608         span.apply_mark(self.0)
1609     }
1610
1611     fn fold_mac(&mut self, mac: ast::Mac) -> ast::Mac {
1612         noop_fold_mac(mac, self)
1613     }
1614 }