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 // Needed for feature-gating attributes used after derives or together with test/bench
 220 #[derive(Clone, Copy, PartialEq)]
 221 pub enum TogetherWith {
 222     None,
 223     Derive,
 224     TestBench,
 225 }
 226
 227 pub enum InvocationKind {
 228     Bang {
 229         mac: ast::Mac,
 230         ident: Option<Ident>,
 231         span: Span,
 232     },
 233     Attr {
 234         attr: Option<ast::Attribute>,
 235         traits: Vec<Path>,
 236         item: Annotatable,
 237         together_with: TogetherWith,
 238     },
 239     Derive {
 240         path: Path,
 241         item: Annotatable,
 242     },
 243 }
 244
 245 impl Invocation {
 246     pub fn span(&self) -> Span {
 247         match self.kind {
 248             InvocationKind::Bang { span, .. } => span,
 249             InvocationKind::Attr { attr: Some(ref attr), .. } => attr.span,
 250             InvocationKind::Attr { attr: None, .. } => DUMMY_SP,
 251             InvocationKind::Derive { ref path, .. } => path.span,
 252         }
 253     }
 254 }
 255
 256 pub struct MacroExpander<'a, 'b:'a> {
 257     pub cx: &'a mut ExtCtxt<'b>,
 258     monotonic: bool, // c.f. `cx.monotonic_expander()`
 259 }
 260
 261 impl<'a, 'b> MacroExpander<'a, 'b> {
 262     pub fn new(cx: &'a mut ExtCtxt<'b>, monotonic: bool) -> Self {
 263         MacroExpander { cx: cx, monotonic: monotonic }
 264     }
 265
 266     pub fn expand_crate(&mut self, mut krate: ast::Crate) -> ast::Crate {
 267         let mut module = ModuleData {
 268             mod_path: vec![Ident::from_str(&self.cx.ecfg.crate_name)],
 269             directory: match self.cx.source_map().span_to_unmapped_path(krate.span) {
 270                 FileName::Real(path) => path,
 271                 other => PathBuf::from(other.to_string()),
 272             },
 273         };
 274         module.directory.pop();
 275         self.cx.root_path = module.directory.clone();
 276         self.cx.current_expansion.module = Rc::new(module);
 277         self.cx.current_expansion.crate_span = Some(krate.span);
 278
 279         let orig_mod_span = krate.module.inner;
 280
 281         let krate_item = AstFragment::Items(smallvec![P(ast::Item {
 282             attrs: krate.attrs,
 283             span: krate.span,
 284             node: ast::ItemKind::Mod(krate.module),
 285             ident: keywords::Invalid.ident(),
 286             id: ast::DUMMY_NODE_ID,
 287             vis: respan(krate.span.shrink_to_lo(), ast::VisibilityKind::Public),
 288             tokens: None,
 289         })]);
 290
 291         match self.expand_fragment(krate_item).make_items().pop().map(P::into_inner) {
 292             Some(ast::Item { attrs, node: ast::ItemKind::Mod(module), .. }) => {
 293                 krate.attrs = attrs;
 294                 krate.module = module;
 295             },
 296             None => {
 297                 // Resolution failed so we return an empty expansion
 298                 krate.attrs = vec![];
 299                 krate.module = ast::Mod {
 300                     inner: orig_mod_span,
 301                     items: vec![],
 302                 };
 303             },
 304             _ => unreachable!(),
 305         };
 306         self.cx.trace_macros_diag();
 307         krate
 308     }
 309
 310     // Fully expand all macro invocations in this AST fragment.
 311     fn expand_fragment(&mut self, input_fragment: AstFragment) -> AstFragment {
 312         let orig_expansion_data = self.cx.current_expansion.clone();
 313         self.cx.current_expansion.depth = 0;
 314
 315         // Collect all macro invocations and replace them with placeholders.
 316         let (fragment_with_placeholders, mut invocations)
 317             = self.collect_invocations(input_fragment, &[]);
 318
 319         // Optimization: if we resolve all imports now,
 320         // we'll be able to immediately resolve most of imported macros.
 321         self.resolve_imports();
 322
 323         // Resolve paths in all invocations and produce output expanded fragments for them, but
 324         // do not insert them into our input AST fragment yet, only store in `expanded_fragments`.
 325         // The output fragments also go through expansion recursively until no invocations are left.
 326         // Unresolved macros produce dummy outputs as a recovery measure.
 327         invocations.reverse();
 328         let mut expanded_fragments = Vec::new();
 329         let mut derives: FxHashMap<Mark, Vec<_>> = FxHashMap::default();
 330         let mut undetermined_invocations = Vec::new();
 331         let (mut progress, mut force) = (false, !self.monotonic);
 332         loop {
 333             let invoc = if let Some(invoc) = invocations.pop() {
 334                 invoc
 335             } else {
 336                 self.resolve_imports();
 337                 if undetermined_invocations.is_empty() { break }
 338                 invocations = mem::replace(&mut undetermined_invocations, Vec::new());
 339                 force = !mem::replace(&mut progress, false);
 340                 continue
 341             };
 342
 343             let scope =
 344                 if self.monotonic { invoc.expansion_data.mark } else { orig_expansion_data.mark };
 345             let ext = match self.cx.resolver.resolve_macro_invocation(&invoc, scope, force) {
 346                 Ok(ext) => Some(ext),
 347                 Err(Determinacy::Determined) => None,
 348                 Err(Determinacy::Undetermined) => {
 349                     undetermined_invocations.push(invoc);
 350                     continue
 351                 }
 352             };
 353
 354             progress = true;
 355             let ExpansionData { depth, mark, .. } = invoc.expansion_data;
 356             self.cx.current_expansion = invoc.expansion_data.clone();
 357
 358             self.cx.current_expansion.mark = scope;
 359             // FIXME(jseyfried): Refactor out the following logic
 360             let (expanded_fragment, new_invocations) = if let Some(ext) = ext {
 361                 if let Some(ext) = ext {
 362                     let dummy = invoc.fragment_kind.dummy(invoc.span()).unwrap();
 363                     let fragment = self.expand_invoc(invoc, &*ext).unwrap_or(dummy);
 364                     self.collect_invocations(fragment, &[])
 365                 } else if let InvocationKind::Attr { attr: None, traits, item, .. } = invoc.kind {
 366                     if !item.derive_allowed() {
 367                         let attr = attr::find_by_name(item.attrs(), "derive")
 368                             .expect("`derive` attribute should exist");
 369                         let span = attr.span;
 370                         let mut err = self.cx.mut_span_err(span,
 371                                                            "`derive` may only be applied to \
 372                                                             structs, enums and unions");
 373                         if let ast::AttrStyle::Inner = attr.style {
 374                             let trait_list = traits.iter()
 375                                 .map(|t| t.to_string()).collect::<Vec<_>>();
 376                             let suggestion = format!("#[derive({})]", trait_list.join(", "));
 377                             err.span_suggestion_with_applicability(
 378                                 span, "try an outer attribute", suggestion,
 379                                 // We don't 𝑘𝑛𝑜𝑤 that the following item is an ADT
 380                                 Applicability::MaybeIncorrect
 381                             );
 382                         }
 383                         err.emit();
 384                     }
 385
 386                     let item = self.fully_configure(item)
 387                         .map_attrs(|mut attrs| { attrs.retain(|a| a.path != "derive"); attrs });
 388                     let item_with_markers =
 389                         add_derived_markers(&mut self.cx, item.span(), &traits, item.clone());
 390                     let derives = derives.entry(invoc.expansion_data.mark).or_default();
 391
 392                     for path in &traits {
 393                         let mark = Mark::fresh(self.cx.current_expansion.mark);
 394                         derives.push(mark);
 395                         let item = match self.cx.resolver.resolve_macro_path(
 396                                 path, MacroKind::Derive, Mark::root(), Vec::new(), false) {
 397                             Ok(ext) => match *ext {
 398                                 BuiltinDerive(..) => item_with_markers.clone(),
 399                                 _ => item.clone(),
 400                             },
 401                             _ => item.clone(),
 402                         };
 403                         invocations.push(Invocation {
 404                             kind: InvocationKind::Derive { path: path.clone(), item: item },
 405                             fragment_kind: invoc.fragment_kind,
 406                             expansion_data: ExpansionData {
 407                                 mark,
 408                                 ..invoc.expansion_data.clone()
 409                             },
 410                         });
 411                     }
 412                     let fragment = invoc.fragment_kind
 413                         .expect_from_annotatables(::std::iter::once(item_with_markers));
 414                     self.collect_invocations(fragment, derives)
 415                 } else {
 416                     unreachable!()
 417                 }
 418             } else {
 419                 self.collect_invocations(invoc.fragment_kind.dummy(invoc.span()).unwrap(), &[])
 420             };
 421
 422             if expanded_fragments.len() < depth {
 423                 expanded_fragments.push(Vec::new());
 424             }
 425             expanded_fragments[depth - 1].push((mark, expanded_fragment));
 426             if !self.cx.ecfg.single_step {
 427                 invocations.extend(new_invocations.into_iter().rev());
 428             }
 429         }
 430
 431         self.cx.current_expansion = orig_expansion_data;
 432
 433         // Finally incorporate all the expanded macros into the input AST fragment.
 434         let mut placeholder_expander = PlaceholderExpander::new(self.cx, self.monotonic);
 435         while let Some(expanded_fragments) = expanded_fragments.pop() {
 436             for (mark, expanded_fragment) in expanded_fragments.into_iter().rev() {
 437                 let derives = derives.remove(&mark).unwrap_or_else(Vec::new);
 438                 placeholder_expander.add(NodeId::placeholder_from_mark(mark),
 439                                          expanded_fragment, derives);
 440             }
 441         }
 442         fragment_with_placeholders.fold_with(&mut placeholder_expander)
 443     }
 444
 445     fn resolve_imports(&mut self) {
 446         if self.monotonic {
 447             let err_count = self.cx.parse_sess.span_diagnostic.err_count();
 448             self.cx.resolver.resolve_imports();
 449             self.cx.resolve_err_count += self.cx.parse_sess.span_diagnostic.err_count() - err_count;
 450         }
 451     }
 452
 453     /// Collect all macro invocations reachable at this time in this AST fragment, and replace
 454     /// them with "placeholders" - dummy macro invocations with specially crafted `NodeId`s.
 455     /// Then call into resolver that builds a skeleton ("reduced graph") of the fragment and
 456     /// prepares data for resolving paths of macro invocations.
 457     fn collect_invocations(&mut self, fragment: AstFragment, derives: &[Mark])
 458                            -> (AstFragment, Vec<Invocation>) {
 459         let (fragment_with_placeholders, invocations) = {
 460             let mut collector = InvocationCollector {
 461                 cfg: StripUnconfigured {
 462                     sess: self.cx.parse_sess,
 463                     features: self.cx.ecfg.features,
 464                 },
 465                 cx: self.cx,
 466                 invocations: Vec::new(),
 467                 monotonic: self.monotonic,
 468             };
 469             (fragment.fold_with(&mut collector), collector.invocations)
 470         };
 471
 472         if self.monotonic {
 473             let err_count = self.cx.parse_sess.span_diagnostic.err_count();
 474             let mark = self.cx.current_expansion.mark;
 475             self.cx.resolver.visit_ast_fragment_with_placeholders(mark, &fragment_with_placeholders,
 476                                                                   derives);
 477             self.cx.resolve_err_count += self.cx.parse_sess.span_diagnostic.err_count() - err_count;
 478         }
 479
 480         (fragment_with_placeholders, invocations)
 481     }
 482
 483     fn fully_configure(&mut self, item: Annotatable) -> Annotatable {
 484         let mut cfg = StripUnconfigured {
 485             sess: self.cx.parse_sess,
 486             features: self.cx.ecfg.features,
 487         };
 488         // Since the item itself has already been configured by the InvocationCollector,
 489         // we know that fold result vector will contain exactly one element
 490         match item {
 491             Annotatable::Item(item) => {
 492                 Annotatable::Item(cfg.fold_item(item).pop().unwrap())
 493             }
 494             Annotatable::TraitItem(item) => {
 495                 Annotatable::TraitItem(item.map(|item| cfg.fold_trait_item(item).pop().unwrap()))
 496             }
 497             Annotatable::ImplItem(item) => {
 498                 Annotatable::ImplItem(item.map(|item| cfg.fold_impl_item(item).pop().unwrap()))
 499             }
 500             Annotatable::ForeignItem(item) => {
 501                 Annotatable::ForeignItem(
 502                     item.map(|item| cfg.fold_foreign_item(item).pop().unwrap())
 503                 )
 504             }
 505             Annotatable::Stmt(stmt) => {
 506                 Annotatable::Stmt(stmt.map(|stmt| cfg.fold_stmt(stmt).pop().unwrap()))
 507             }
 508             Annotatable::Expr(expr) => {
 509                 Annotatable::Expr(cfg.fold_expr(expr))
 510             }
 511         }
 512     }
 513
 514     fn expand_invoc(&mut self, invoc: Invocation, ext: &SyntaxExtension) -> Option<AstFragment> {
 515         if invoc.fragment_kind == AstFragmentKind::ForeignItems &&
 516            !self.cx.ecfg.macros_in_extern_enabled() {
 517             if let SyntaxExtension::NonMacroAttr { .. } = *ext {} else {
 518                 emit_feature_err(&self.cx.parse_sess, "macros_in_extern",
 519                                  invoc.span(), GateIssue::Language,
 520                                  "macro invocations in `extern {}` blocks are experimental");
 521             }
 522         }
 523
 524         let result = match invoc.kind {
 525             InvocationKind::Bang { .. } => self.expand_bang_invoc(invoc, ext)?,
 526             InvocationKind::Attr { .. } => self.expand_attr_invoc(invoc, ext)?,
 527             InvocationKind::Derive { .. } => self.expand_derive_invoc(invoc, ext)?,
 528         };
 529
 530         if self.cx.current_expansion.depth > self.cx.ecfg.recursion_limit {
 531             let info = self.cx.current_expansion.mark.expn_info().unwrap();
 532             let suggested_limit = self.cx.ecfg.recursion_limit * 2;
 533             let mut err = self.cx.struct_span_err(info.call_site,
 534                 &format!("recursion limit reached while expanding the macro `{}`",
 535                          info.format.name()));
 536             err.help(&format!(
 537                 "consider adding a `#![recursion_limit=\"{}\"]` attribute to your crate",
 538                 suggested_limit));
 539             err.emit();
 540             self.cx.trace_macros_diag();
 541             FatalError.raise();
 542         }
 543
 544         Some(result)
 545     }
 546
 547     fn expand_attr_invoc(&mut self,
 548                          invoc: Invocation,
 549                          ext: &SyntaxExtension)
 550                          -> Option<AstFragment> {
 551         let (attr, item) = match invoc.kind {
 552             InvocationKind::Attr { attr, item, .. } => (attr?, item),
 553             _ => unreachable!(),
 554         };
 555
 556         if let NonMacroAttr { mark_used: false } = *ext {} else {
 557             // Macro attrs are always used when expanded,
 558             // non-macro attrs are considered used when the field says so.
 559             attr::mark_used(&attr);
 560         }
 561         invoc.expansion_data.mark.set_expn_info(ExpnInfo {
 562             call_site: attr.span,
 563             def_site: None,
 564             format: MacroAttribute(Symbol::intern(&attr.path.to_string())),
 565             allow_internal_unstable: false,
 566             allow_internal_unsafe: false,
 567             local_inner_macros: false,
 568             edition: ext.edition(),
 569         });
 570
 571         match *ext {
 572             NonMacroAttr { .. } => {
 573                 attr::mark_known(&attr);
 574                 let item = item.map_attrs(|mut attrs| { attrs.push(attr); attrs });
 575                 Some(invoc.fragment_kind.expect_from_annotatables(iter::once(item)))
 576             }
 577             MultiModifier(ref mac) => {
 578                 let meta = attr.parse_meta(self.cx.parse_sess)
 579                                .map_err(|mut e| { e.emit(); }).ok()?;
 580                 let item = mac.expand(self.cx, attr.span, &meta, item);
 581                 Some(invoc.fragment_kind.expect_from_annotatables(item))
 582             }
 583             MultiDecorator(ref mac) => {
 584                 let mut items = Vec::new();
 585                 let meta = attr.parse_meta(self.cx.parse_sess)
 586                                .expect("derive meta should already have been parsed");
 587                 mac.expand(self.cx, attr.span, &meta, &item, &mut |item| items.push(item));
 588                 items.push(item);
 589                 Some(invoc.fragment_kind.expect_from_annotatables(items))
 590             }
 591             AttrProcMacro(ref mac, ..) => {
 592                 self.gate_proc_macro_attr_item(attr.span, &item);
 593                 let item_tok = TokenTree::Token(DUMMY_SP, Token::interpolated(match item {
 594                     Annotatable::Item(item) => token::NtItem(item),
 595                     Annotatable::TraitItem(item) => token::NtTraitItem(item.into_inner()),
 596                     Annotatable::ImplItem(item) => token::NtImplItem(item.into_inner()),
 597                     Annotatable::ForeignItem(item) => token::NtForeignItem(item.into_inner()),
 598                     Annotatable::Stmt(stmt) => token::NtStmt(stmt.into_inner()),
 599                     Annotatable::Expr(expr) => token::NtExpr(expr),
 600                 })).into();
 601                 let input = self.extract_proc_macro_attr_input(attr.tokens, attr.span);
 602                 let tok_result = mac.expand(self.cx, attr.span, input, item_tok);
 603                 let res = self.parse_ast_fragment(tok_result, invoc.fragment_kind,
 604                                                   &attr.path, attr.span);
 605                 self.gate_proc_macro_expansion(attr.span, &res);
 606                 res
 607             }
 608             ProcMacroDerive(..) | BuiltinDerive(..) => {
 609                 self.cx.span_err(attr.span, &format!("`{}` is a derive mode", attr.path));
 610                 self.cx.trace_macros_diag();
 611                 invoc.fragment_kind.dummy(attr.span)
 612             }
 613             _ => {
 614                 let msg = &format!("macro `{}` may not be used in attributes", attr.path);
 615                 self.cx.span_err(attr.span, msg);
 616                 self.cx.trace_macros_diag();
 617                 invoc.fragment_kind.dummy(attr.span)
 618             }
 619         }
 620     }
 621
 622     fn extract_proc_macro_attr_input(&self, tokens: TokenStream, span: Span) -> TokenStream {
 623         let mut trees = tokens.trees();
 624         match trees.next() {
 625             Some(TokenTree::Delimited(_, delim)) => {
 626                 if trees.next().is_none() {
 627                     return delim.tts.into()
 628                 }
 629             }
 630             Some(TokenTree::Token(..)) => {}
 631             None => return TokenStream::empty(),
 632         }
 633         self.cx.span_err(span, "custom attribute invocations must be \
 634             of the form #[foo] or #[foo(..)], the macro name must only be \
 635             followed by a delimiter token");
 636         TokenStream::empty()
 637     }
 638
 639     fn gate_proc_macro_attr_item(&self, span: Span, item: &Annotatable) {
 640         let (kind, gate) = match *item {
 641             Annotatable::Item(ref item) => {
 642                 match item.node {
 643                     ItemKind::Mod(_) if self.cx.ecfg.proc_macro_mod() => return,
 644                     ItemKind::Mod(_) => ("modules", "proc_macro_mod"),
 645                     _ => return,
 646                 }
 647             }
 648             Annotatable::TraitItem(_) => return,
 649             Annotatable::ImplItem(_) => return,
 650             Annotatable::ForeignItem(_) => return,
 651             Annotatable::Stmt(_) |
 652             Annotatable::Expr(_) if self.cx.ecfg.proc_macro_expr() => return,
 653             Annotatable::Stmt(_) => ("statements", "proc_macro_expr"),
 654             Annotatable::Expr(_) => ("expressions", "proc_macro_expr"),
 655         };
 656         emit_feature_err(
 657             self.cx.parse_sess,
 658             gate,
 659             span,
 660             GateIssue::Language,
 661             &format!("custom attributes cannot be applied to {}", kind),
 662         );
 663     }
 664
 665     fn gate_proc_macro_expansion(&self, span: Span, fragment: &Option<AstFragment>) {
 666         if self.cx.ecfg.proc_macro_gen() {
 667             return
 668         }
 669         let fragment = match fragment {
 670             Some(fragment) => fragment,
 671             None => return,
 672         };
 673
 674         fragment.visit_with(&mut DisallowMacros {
 675             span,
 676             parse_sess: self.cx.parse_sess,
 677         });
 678
 679         struct DisallowMacros<'a> {
 680             span: Span,
 681             parse_sess: &'a ParseSess,
 682         }
 683
 684         impl<'ast, 'a> Visitor<'ast> for DisallowMacros<'a> {
 685             fn visit_item(&mut self, i: &'ast ast::Item) {
 686                 if let ast::ItemKind::MacroDef(_) = i.node {
 687                     emit_feature_err(
 688                         self.parse_sess,
 689                         "proc_macro_gen",
 690                         self.span,
 691                         GateIssue::Language,
 692                         &format!("procedural macros cannot expand to macro definitions"),
 693                     );
 694                 }
 695                 visit::walk_item(self, i);
 696             }
 697
 698             fn visit_mac(&mut self, _mac: &'ast ast::Mac) {
 699                 // ...
 700             }
 701         }
 702     }
 703
 704     /// Expand a macro invocation. Returns the resulting expanded AST fragment.
 705     fn expand_bang_invoc(&mut self,
 706                          invoc: Invocation,
 707                          ext: &SyntaxExtension)
 708                          -> Option<AstFragment> {
 709         let (mark, kind) = (invoc.expansion_data.mark, invoc.fragment_kind);
 710         let (mac, ident, span) = match invoc.kind {
 711             InvocationKind::Bang { mac, ident, span } => (mac, ident, span),
 712             _ => unreachable!(),
 713         };
 714         let path = &mac.node.path;
 715
 716         let ident = ident.unwrap_or_else(|| keywords::Invalid.ident());
 717         let validate_and_set_expn_info = |this: &mut Self, // arg instead of capture
 718                                           def_site_span: Option<Span>,
 719                                           allow_internal_unstable,
 720                                           allow_internal_unsafe,
 721                                           local_inner_macros,
 722                                           // can't infer this type
 723                                           unstable_feature: Option<(Symbol, u32)>,
 724                                           edition| {
 725
 726             // feature-gate the macro invocation
 727             if let Some((feature, issue)) = unstable_feature {
 728                 let crate_span = this.cx.current_expansion.crate_span.unwrap();
 729                 // don't stability-check macros in the same crate
 730                 // (the only time this is null is for syntax extensions registered as macros)
 731                 if def_site_span.map_or(false, |def_span| !crate_span.contains(def_span))
 732                     && !span.allows_unstable() && this.cx.ecfg.features.map_or(true, |feats| {
 733                     // macro features will count as lib features
 734                     !feats.declared_lib_features.iter().any(|&(feat, _)| feat == feature)
 735                 }) {
 736                     let explain = format!("macro {}! is unstable", path);
 737                     emit_feature_err(this.cx.parse_sess, &*feature.as_str(), span,
 738                                      GateIssue::Library(Some(issue)), &explain);
 739                     this.cx.trace_macros_diag();
 740                     return Err(kind.dummy(span));
 741                 }
 742             }
 743
 744             if ident.name != keywords::Invalid.name() {
 745                 let msg = format!("macro {}! expects no ident argument, given '{}'", path, ident);
 746                 this.cx.span_err(path.span, &msg);
 747                 this.cx.trace_macros_diag();
 748                 return Err(kind.dummy(span));
 749             }
 750             mark.set_expn_info(ExpnInfo {
 751                 call_site: span,
 752                 def_site: def_site_span,
 753                 format: macro_bang_format(path),
 754                 allow_internal_unstable,
 755                 allow_internal_unsafe,
 756                 local_inner_macros,
 757                 edition,
 758             });
 759             Ok(())
 760         };
 761
 762         let opt_expanded = match *ext {
 763             DeclMacro { ref expander, def_info, edition, .. } => {
 764                 if let Err(dummy_span) = validate_and_set_expn_info(self, def_info.map(|(_, s)| s),
 765                                                                     false, false, false, None,
 766                                                                     edition) {
 767                     dummy_span
 768                 } else {
 769                     kind.make_from(expander.expand(self.cx, span, mac.node.stream()))
 770                 }
 771             }
 772
 773             NormalTT {
 774                 ref expander,
 775                 def_info,
 776                 allow_internal_unstable,
 777                 allow_internal_unsafe,
 778                 local_inner_macros,
 779                 unstable_feature,
 780                 edition,
 781             } => {
 782                 if let Err(dummy_span) = validate_and_set_expn_info(self, def_info.map(|(_, s)| s),
 783                                                                     allow_internal_unstable,
 784                                                                     allow_internal_unsafe,
 785                                                                     local_inner_macros,
 786                                                                     unstable_feature,
 787                                                                     edition) {
 788                     dummy_span
 789                 } else {
 790                     kind.make_from(expander.expand(self.cx, span, mac.node.stream()))
 791                 }
 792             }
 793
 794             IdentTT(ref expander, tt_span, allow_internal_unstable) => {
 795                 if ident.name == keywords::Invalid.name() {
 796                     self.cx.span_err(path.span,
 797                                     &format!("macro {}! expects an ident argument", path));
 798                     self.cx.trace_macros_diag();
 799                     kind.dummy(span)
 800                 } else {
 801                     invoc.expansion_data.mark.set_expn_info(ExpnInfo {
 802                         call_site: span,
 803                         def_site: tt_span,
 804                         format: macro_bang_format(path),
 805                         allow_internal_unstable,
 806                         allow_internal_unsafe: false,
 807                         local_inner_macros: false,
 808                         edition: hygiene::default_edition(),
 809                     });
 810
 811                     let input: Vec<_> = mac.node.stream().into_trees().collect();
 812                     kind.make_from(expander.expand(self.cx, span, ident, input))
 813                 }
 814             }
 815
 816             MultiDecorator(..) | MultiModifier(..) |
 817             AttrProcMacro(..) | SyntaxExtension::NonMacroAttr { .. } => {
 818                 self.cx.span_err(path.span,
 819                                  &format!("`{}` can only be used in attributes", path));
 820                 self.cx.trace_macros_diag();
 821                 kind.dummy(span)
 822             }
 823
 824             ProcMacroDerive(..) | BuiltinDerive(..) => {
 825                 self.cx.span_err(path.span, &format!("`{}` is a derive mode", path));
 826                 self.cx.trace_macros_diag();
 827                 kind.dummy(span)
 828             }
 829
 830             SyntaxExtension::ProcMacro { ref expander, allow_internal_unstable, edition } => {
 831                 if ident.name != keywords::Invalid.name() {
 832                     let msg =
 833                         format!("macro {}! expects no ident argument, given '{}'", path, ident);
 834                     self.cx.span_err(path.span, &msg);
 835                     self.cx.trace_macros_diag();
 836                     kind.dummy(span)
 837                 } else {
 838                     self.gate_proc_macro_expansion_kind(span, kind);
 839                     invoc.expansion_data.mark.set_expn_info(ExpnInfo {
 840                         call_site: span,
 841                         // FIXME procedural macros do not have proper span info
 842                         // yet, when they do, we should use it here.
 843                         def_site: None,
 844                         format: macro_bang_format(path),
 845                         // FIXME probably want to follow macro_rules macros here.
 846                         allow_internal_unstable,
 847                         allow_internal_unsafe: false,
 848                         local_inner_macros: false,
 849                         edition,
 850                     });
 851
 852                     let tok_result = expander.expand(self.cx, span, mac.node.stream());
 853                     let result = self.parse_ast_fragment(tok_result, kind, path, span);
 854                     self.gate_proc_macro_expansion(span, &result);
 855                     result
 856                 }
 857             }
 858         };
 859
 860         if opt_expanded.is_some() {
 861             opt_expanded
 862         } else {
 863             let msg = format!("non-{kind} macro in {kind} position: {name}",
 864                               name = path.segments[0].ident.name, kind = kind.name());
 865             self.cx.span_err(path.span, &msg);
 866             self.cx.trace_macros_diag();
 867             kind.dummy(span)
 868         }
 869     }
 870
 871     fn gate_proc_macro_expansion_kind(&self, span: Span, kind: AstFragmentKind) {
 872         let kind = match kind {
 873             AstFragmentKind::Expr => "expressions",
 874             AstFragmentKind::OptExpr => "expressions",
 875             AstFragmentKind::Pat => "patterns",
 876             AstFragmentKind::Ty => "types",
 877             AstFragmentKind::Stmts => "statements",
 878             AstFragmentKind::Items => return,
 879             AstFragmentKind::TraitItems => return,
 880             AstFragmentKind::ImplItems => return,
 881             AstFragmentKind::ForeignItems => return,
 882         };
 883         if self.cx.ecfg.proc_macro_non_items() {
 884             return
 885         }
 886         emit_feature_err(
 887             self.cx.parse_sess,
 888             "proc_macro_non_items",
 889             span,
 890             GateIssue::Language,
 891             &format!("procedural macros cannot be expanded to {}", kind),
 892         );
 893     }
 894
 895     /// Expand a derive invocation. Returns the resulting expanded AST fragment.
 896     fn expand_derive_invoc(&mut self,
 897                            invoc: Invocation,
 898                            ext: &SyntaxExtension)
 899                            -> Option<AstFragment> {
 900         let (path, item) = match invoc.kind {
 901             InvocationKind::Derive { path, item } => (path, item),
 902             _ => unreachable!(),
 903         };
 904         if !item.derive_allowed() {
 905             return None;
 906         }
 907
 908         let pretty_name = Symbol::intern(&format!("derive({})", path));
 909         let span = path.span;
 910         let attr = ast::Attribute {
 911             path, span,
 912             tokens: TokenStream::empty(),
 913             // irrelevant:
 914             id: ast::AttrId(0), style: ast::AttrStyle::Outer, is_sugared_doc: false,
 915         };
 916
 917         let mut expn_info = ExpnInfo {
 918             call_site: span,
 919             def_site: None,
 920             format: MacroAttribute(pretty_name),
 921             allow_internal_unstable: false,
 922             allow_internal_unsafe: false,
 923             local_inner_macros: false,
 924             edition: ext.edition(),
 925         };
 926
 927         match *ext {
 928             ProcMacroDerive(ref ext, ..) => {
 929                 invoc.expansion_data.mark.set_expn_info(expn_info);
 930                 let span = span.with_ctxt(self.cx.backtrace());
 931                 let dummy = ast::MetaItem { // FIXME(jseyfried) avoid this
 932                     ident: Path::from_ident(keywords::Invalid.ident()),
 933                     span: DUMMY_SP,
 934                     node: ast::MetaItemKind::Word,
 935                 };
 936                 let items = ext.expand(self.cx, span, &dummy, item);
 937                 Some(invoc.fragment_kind.expect_from_annotatables(items))
 938             }
 939             BuiltinDerive(func) => {
 940                 expn_info.allow_internal_unstable = true;
 941                 invoc.expansion_data.mark.set_expn_info(expn_info);
 942                 let span = span.with_ctxt(self.cx.backtrace());
 943                 let mut items = Vec::new();
 944                 func(self.cx, span, &attr.meta()?, &item, &mut |a| items.push(a));
 945                 Some(invoc.fragment_kind.expect_from_annotatables(items))
 946             }
 947             _ => {
 948                 let msg = &format!("macro `{}` may not be used for derive attributes", attr.path);
 949                 self.cx.span_err(span, msg);
 950                 self.cx.trace_macros_diag();
 951                 invoc.fragment_kind.dummy(span)
 952             }
 953         }
 954     }
 955
 956     fn parse_ast_fragment(&mut self,
 957                           toks: TokenStream,
 958                           kind: AstFragmentKind,
 959                           path: &Path,
 960                           span: Span)
 961                           -> Option<AstFragment> {
 962         let mut parser = self.cx.new_parser_from_tts(&toks.into_trees().collect::<Vec<_>>());
 963         match parser.parse_ast_fragment(kind, false) {
 964             Ok(fragment) => {
 965                 parser.ensure_complete_parse(path, kind.name(), span);
 966                 Some(fragment)
 967             }
 968             Err(mut err) => {
 969                 err.set_span(span);
 970                 err.emit();
 971                 self.cx.trace_macros_diag();
 972                 kind.dummy(span)
 973             }
 974         }
 975     }
 976 }
 977
 978 impl<'a> Parser<'a> {
 979     pub fn parse_ast_fragment(&mut self, kind: AstFragmentKind, macro_legacy_warnings: bool)
 980                               -> PResult<'a, AstFragment> {
 981         Ok(match kind {
 982             AstFragmentKind::Items => {
 983                 let mut items = OneVector::new();
 984                 while let Some(item) = self.parse_item()? {
 985                     items.push(item);
 986                 }
 987                 AstFragment::Items(items)
 988             }
 989             AstFragmentKind::TraitItems => {
 990                 let mut items = OneVector::new();
 991                 while self.token != token::Eof {
 992                     items.push(self.parse_trait_item(&mut false)?);
 993                 }
 994                 AstFragment::TraitItems(items)
 995             }
 996             AstFragmentKind::ImplItems => {
 997                 let mut items = OneVector::new();
 998                 while self.token != token::Eof {
 999                     items.push(self.parse_impl_item(&mut false)?);
1000                 }
1001                 AstFragment::ImplItems(items)
1002             }
1003             AstFragmentKind::ForeignItems => {
1004                 let mut items = OneVector::new();
1005                 while self.token != token::Eof {
1006                     if let Some(item) = self.parse_foreign_item()? {
1007                         items.push(item);
1008                     }
1009                 }
1010                 AstFragment::ForeignItems(items)
1011             }
1012             AstFragmentKind::Stmts => {
1013                 let mut stmts = OneVector::new();
1014                 while self.token != token::Eof &&
1015                       // won't make progress on a `}`
1016                       self.token != token::CloseDelim(token::Brace) {
1017                     if let Some(stmt) = self.parse_full_stmt(macro_legacy_warnings)? {
1018                         stmts.push(stmt);
1019                     }
1020                 }
1021                 AstFragment::Stmts(stmts)
1022             }
1023             AstFragmentKind::Expr => AstFragment::Expr(self.parse_expr()?),
1024             AstFragmentKind::OptExpr => {
1025                 if self.token != token::Eof {
1026                     AstFragment::OptExpr(Some(self.parse_expr()?))
1027                 } else {
1028                     AstFragment::OptExpr(None)
1029                 }
1030             },
1031             AstFragmentKind::Ty => AstFragment::Ty(self.parse_ty()?),
1032             AstFragmentKind::Pat => AstFragment::Pat(self.parse_pat()?),
1033         })
1034     }
1035
1036     pub fn ensure_complete_parse(&mut self, macro_path: &Path, kind_name: &str, span: Span) {
1037         if self.token != token::Eof {
1038             let msg = format!("macro expansion ignores token `{}` and any following",
1039                               self.this_token_to_string());
1040             // Avoid emitting backtrace info twice.
1041             let def_site_span = self.span.with_ctxt(SyntaxContext::empty());
1042             let mut err = self.diagnostic().struct_span_err(def_site_span, &msg);
1043             let msg = format!("caused by the macro expansion here; the usage \
1044                                of `{}!` is likely invalid in {} context",
1045                                macro_path, kind_name);
1046             err.span_note(span, &msg).emit();
1047         }
1048     }
1049 }
1050
1051 struct InvocationCollector<'a, 'b: 'a> {
1052     cx: &'a mut ExtCtxt<'b>,
1053     cfg: StripUnconfigured<'a>,
1054     invocations: Vec<Invocation>,
1055     monotonic: bool,
1056 }
1057
1058 impl<'a, 'b> InvocationCollector<'a, 'b> {
1059     fn collect(&mut self, fragment_kind: AstFragmentKind, kind: InvocationKind) -> AstFragment {
1060         let mark = Mark::fresh(self.cx.current_expansion.mark);
1061         self.invocations.push(Invocation {
1062             kind,
1063             fragment_kind,
1064             expansion_data: ExpansionData {
1065                 mark,
1066                 depth: self.cx.current_expansion.depth + 1,
1067                 ..self.cx.current_expansion.clone()
1068             },
1069         });
1070         placeholder(fragment_kind, NodeId::placeholder_from_mark(mark))
1071     }
1072
1073     fn collect_bang(&mut self, mac: ast::Mac, span: Span, kind: AstFragmentKind) -> AstFragment {
1074         self.collect(kind, InvocationKind::Bang { mac: mac, ident: None, span: span })
1075     }
1076
1077     fn collect_attr(&mut self,
1078                     attr: Option<ast::Attribute>,
1079                     traits: Vec<Path>,
1080                     item: Annotatable,
1081                     kind: AstFragmentKind,
1082                     together_with: TogetherWith)
1083                     -> AstFragment {
1084         self.collect(kind, InvocationKind::Attr { attr, traits, item, together_with })
1085     }
1086
1087     fn find_attr_invoc(&self, attrs: &mut Vec<ast::Attribute>, together_with: &mut TogetherWith)
1088                        -> Option<ast::Attribute> {
1089         let attr = attrs.iter()
1090                         .position(|a| {
1091                             if a.path == "derive" {
1092                                 *together_with = TogetherWith::Derive
1093                             } else if a.path == "rustc_test_marker2" {
1094                                 *together_with = TogetherWith::TestBench
1095                             }
1096                             !attr::is_known(a) && !is_builtin_attr(a)
1097                         })
1098                         .map(|i| attrs.remove(i));
1099         if let Some(attr) = &attr {
1100             if !self.cx.ecfg.enable_custom_inner_attributes() &&
1101                attr.style == ast::AttrStyle::Inner && attr.path != "test" {
1102                 emit_feature_err(&self.cx.parse_sess, "custom_inner_attributes",
1103                                  attr.span, GateIssue::Language,
1104                                  "non-builtin inner attributes are unstable");
1105             }
1106         }
1107         if together_with == &TogetherWith::None &&
1108            attrs.iter().any(|a| a.path == "rustc_test_marker2") {
1109             *together_with = TogetherWith::TestBench;
1110         }
1111         attr
1112     }
1113
1114     /// If `item` is an attr invocation, remove and return the macro attribute and derive traits.
1115     fn classify_item<T>(&mut self, mut item: T)
1116                         -> (Option<ast::Attribute>, Vec<Path>, T, TogetherWith)
1117         where T: HasAttrs,
1118     {
1119         let (mut attr, mut traits, mut together_with) = (None, Vec::new(), TogetherWith::None);
1120
1121         item = item.map_attrs(|mut attrs| {
1122             if let Some(legacy_attr_invoc) = self.cx.resolver.find_legacy_attr_invoc(&mut attrs,
1123                                                                                      true) {
1124                 attr = Some(legacy_attr_invoc);
1125                 return attrs;
1126             }
1127
1128             attr = self.find_attr_invoc(&mut attrs, &mut together_with);
1129             traits = collect_derives(&mut self.cx, &mut attrs);
1130             attrs
1131         });
1132
1133         (attr, traits, item, together_with)
1134     }
1135
1136     /// Alternative of `classify_item()` that ignores `#[derive]` so invocations fallthrough
1137     /// to the unused-attributes lint (making it an error on statements and expressions
1138     /// is a breaking change)
1139     fn classify_nonitem<T: HasAttrs>(&mut self, mut item: T)
1140                                      -> (Option<ast::Attribute>, T, TogetherWith) {
1141         let (mut attr, mut together_with) = (None, TogetherWith::None);
1142
1143         item = item.map_attrs(|mut attrs| {
1144             if let Some(legacy_attr_invoc) = self.cx.resolver.find_legacy_attr_invoc(&mut attrs,
1145                                                                                      false) {
1146                 attr = Some(legacy_attr_invoc);
1147                 return attrs;
1148             }
1149
1150             attr = self.find_attr_invoc(&mut attrs, &mut together_with);
1151             attrs
1152         });
1153
1154         (attr, item, together_with)
1155     }
1156
1157     fn configure<T: HasAttrs>(&mut self, node: T) -> Option<T> {
1158         self.cfg.configure(node)
1159     }
1160
1161     // Detect use of feature-gated or invalid attributes on macro invocations
1162     // since they will not be detected after macro expansion.
1163     fn check_attributes(&mut self, attrs: &[ast::Attribute]) {
1164         let features = self.cx.ecfg.features.unwrap();
1165         for attr in attrs.iter() {
1166             self.check_attribute_inner(attr, features);
1167
1168             // macros are expanded before any lint passes so this warning has to be hardcoded
1169             if attr.path == "derive" {
1170                 self.cx.struct_span_warn(attr.span, "`#[derive]` does nothing on macro invocations")
1171                     .note("this may become a hard error in a future release")
1172                     .emit();
1173             }
1174         }
1175     }
1176
1177     fn check_attribute(&mut self, at: &ast::Attribute) {
1178         let features = self.cx.ecfg.features.unwrap();
1179         self.check_attribute_inner(at, features);
1180     }
1181
1182     fn check_attribute_inner(&mut self, at: &ast::Attribute, features: &Features) {
1183         feature_gate::check_attribute(at, self.cx.parse_sess, features);
1184     }
1185 }
1186
1187 impl<'a, 'b> Folder for InvocationCollector<'a, 'b> {
1188     fn fold_expr(&mut self, expr: P<ast::Expr>) -> P<ast::Expr> {
1189         let mut expr = self.cfg.configure_expr(expr).into_inner();
1190         expr.node = self.cfg.configure_expr_kind(expr.node);
1191
1192         // ignore derives so they remain unused
1193         let (attr, expr, together_with) = self.classify_nonitem(expr);
1194
1195         if attr.is_some() {
1196             // collect the invoc regardless of whether or not attributes are permitted here
1197             // expansion will eat the attribute so it won't error later
1198             attr.as_ref().map(|a| self.cfg.maybe_emit_expr_attr_err(a));
1199
1200             // AstFragmentKind::Expr requires the macro to emit an expression
1201             return self.collect_attr(attr, vec![], Annotatable::Expr(P(expr)),
1202                                      AstFragmentKind::Expr, together_with).make_expr();
1203         }
1204
1205         if let ast::ExprKind::Mac(mac) = expr.node {
1206             self.check_attributes(&expr.attrs);
1207             self.collect_bang(mac, expr.span, AstFragmentKind::Expr).make_expr()
1208         } else {
1209             P(noop_fold_expr(expr, self))
1210         }
1211     }
1212
1213     fn fold_opt_expr(&mut self, expr: P<ast::Expr>) -> Option<P<ast::Expr>> {
1214         let mut expr = configure!(self, expr).into_inner();
1215         expr.node = self.cfg.configure_expr_kind(expr.node);
1216
1217         // ignore derives so they remain unused
1218         let (attr, expr, together_with) = self.classify_nonitem(expr);
1219
1220         if attr.is_some() {
1221             attr.as_ref().map(|a| self.cfg.maybe_emit_expr_attr_err(a));
1222
1223             return self.collect_attr(attr, vec![], Annotatable::Expr(P(expr)),
1224                                      AstFragmentKind::OptExpr, together_with).make_opt_expr();
1225         }
1226
1227         if let ast::ExprKind::Mac(mac) = expr.node {
1228             self.check_attributes(&expr.attrs);
1229             self.collect_bang(mac, expr.span, AstFragmentKind::OptExpr).make_opt_expr()
1230         } else {
1231             Some(P(noop_fold_expr(expr, self)))
1232         }
1233     }
1234
1235     fn fold_pat(&mut self, pat: P<ast::Pat>) -> P<ast::Pat> {
1236         let pat = self.cfg.configure_pat(pat);
1237         match pat.node {
1238             PatKind::Mac(_) => {}
1239             _ => return noop_fold_pat(pat, self),
1240         }
1241
1242         pat.and_then(|pat| match pat.node {
1243             PatKind::Mac(mac) => self.collect_bang(mac, pat.span, AstFragmentKind::Pat).make_pat(),
1244             _ => unreachable!(),
1245         })
1246     }
1247
1248     fn fold_stmt(&mut self, stmt: ast::Stmt) -> OneVector<ast::Stmt> {
1249         let mut stmt = match self.cfg.configure_stmt(stmt) {
1250             Some(stmt) => stmt,
1251             None => return OneVector::new(),
1252         };
1253
1254         // we'll expand attributes on expressions separately
1255         if !stmt.is_expr() {
1256             let (attr, derives, stmt_, together_with) = if stmt.is_item() {
1257                 self.classify_item(stmt)
1258             } else {
1259                 // ignore derives on non-item statements so it falls through
1260                 // to the unused-attributes lint
1261                 let (attr, stmt, together_with) = self.classify_nonitem(stmt);
1262                 (attr, vec![], stmt, together_with)
1263             };
1264
1265             if attr.is_some() || !derives.is_empty() {
1266                 return self.collect_attr(attr, derives, Annotatable::Stmt(P(stmt_)),
1267                                          AstFragmentKind::Stmts, together_with).make_stmts();
1268             }
1269
1270             stmt = stmt_;
1271         }
1272
1273         if let StmtKind::Mac(mac) = stmt.node {
1274             let (mac, style, attrs) = mac.into_inner();
1275             self.check_attributes(&attrs);
1276             let mut placeholder = self.collect_bang(mac, stmt.span, AstFragmentKind::Stmts)
1277                                         .make_stmts();
1278
1279             // If this is a macro invocation with a semicolon, then apply that
1280             // semicolon to the final statement produced by expansion.
1281             if style == MacStmtStyle::Semicolon {
1282                 if let Some(stmt) = placeholder.pop() {
1283                     placeholder.push(stmt.add_trailing_semicolon());
1284                 }
1285             }
1286
1287             return placeholder;
1288         }
1289
1290         // The placeholder expander gives ids to statements, so we avoid folding the id here.
1291         let ast::Stmt { id, node, span } = stmt;
1292         noop_fold_stmt_kind(node, self).into_iter().map(|node| {
1293             ast::Stmt { id, node, span }
1294         }).collect()
1295
1296     }
1297
1298     fn fold_block(&mut self, block: P<Block>) -> P<Block> {
1299         let old_directory_ownership = self.cx.current_expansion.directory_ownership;
1300         self.cx.current_expansion.directory_ownership = DirectoryOwnership::UnownedViaBlock;
1301         let result = noop_fold_block(block, self);
1302         self.cx.current_expansion.directory_ownership = old_directory_ownership;
1303         result
1304     }
1305
1306     fn fold_item(&mut self, item: P<ast::Item>) -> OneVector<P<ast::Item>> {
1307         let item = configure!(self, item);
1308
1309         let (attr, traits, item, together_with) = self.classify_item(item);
1310         if attr.is_some() || !traits.is_empty() {
1311             return self.collect_attr(attr, traits, Annotatable::Item(item),
1312                                      AstFragmentKind::Items, together_with).make_items();
1313         }
1314
1315         match item.node {
1316             ast::ItemKind::Mac(..) => {
1317                 self.check_attributes(&item.attrs);
1318                 item.and_then(|item| match item.node {
1319                     ItemKind::Mac(mac) => {
1320                         self.collect(AstFragmentKind::Items, InvocationKind::Bang {
1321                             mac,
1322                             ident: Some(item.ident),
1323                             span: item.span,
1324                         }).make_items()
1325                     }
1326                     _ => unreachable!(),
1327                 })
1328             }
1329             ast::ItemKind::Mod(ast::Mod { inner, .. }) => {
1330                 if item.ident == keywords::Invalid.ident() {
1331                     return noop_fold_item(item, self);
1332                 }
1333
1334                 let orig_directory_ownership = self.cx.current_expansion.directory_ownership;
1335                 let mut module = (*self.cx.current_expansion.module).clone();
1336                 module.mod_path.push(item.ident);
1337
1338                 // Detect if this is an inline module (`mod m { ... }` as opposed to `mod m;`).
1339                 // In the non-inline case, `inner` is never the dummy span (c.f. `parse_item_mod`).
1340                 // Thus, if `inner` is the dummy span, we know the module is inline.
1341                 let inline_module = item.span.contains(inner) || inner.is_dummy();
1342
1343                 if inline_module {
1344                     if let Some(path) = attr::first_attr_value_str_by_name(&item.attrs, "path") {
1345                         self.cx.current_expansion.directory_ownership =
1346                             DirectoryOwnership::Owned { relative: None };
1347                         module.directory.push(&*path.as_str());
1348                     } else {
1349                         module.directory.push(&*item.ident.as_str());
1350                     }
1351                 } else {
1352                     let path = self.cx.parse_sess.source_map().span_to_unmapped_path(inner);
1353                     let mut path = match path {
1354                         FileName::Real(path) => path,
1355                         other => PathBuf::from(other.to_string()),
1356                     };
1357                     let directory_ownership = match path.file_name().unwrap().to_str() {
1358                         Some("mod.rs") => DirectoryOwnership::Owned { relative: None },
1359                         Some(_) => DirectoryOwnership::Owned {
1360                             relative: Some(item.ident),
1361                         },
1362                         None => DirectoryOwnership::UnownedViaMod(false),
1363                     };
1364                     path.pop();
1365                     module.directory = path;
1366                     self.cx.current_expansion.directory_ownership = directory_ownership;
1367                 }
1368
1369                 let orig_module =
1370                     mem::replace(&mut self.cx.current_expansion.module, Rc::new(module));
1371                 let result = noop_fold_item(item, self);
1372                 self.cx.current_expansion.module = orig_module;
1373                 self.cx.current_expansion.directory_ownership = orig_directory_ownership;
1374                 result
1375             }
1376
1377             _ => noop_fold_item(item, self),
1378         }
1379     }
1380
1381     fn fold_trait_item(&mut self, item: ast::TraitItem) -> OneVector<ast::TraitItem> {
1382         let item = configure!(self, item);
1383
1384         let (attr, traits, item, together_with) = self.classify_item(item);
1385         if attr.is_some() || !traits.is_empty() {
1386             return self.collect_attr(attr, traits, Annotatable::TraitItem(P(item)),
1387                                      AstFragmentKind::TraitItems, together_with).make_trait_items()
1388         }
1389
1390         match item.node {
1391             ast::TraitItemKind::Macro(mac) => {
1392                 let ast::TraitItem { attrs, span, .. } = item;
1393                 self.check_attributes(&attrs);
1394                 self.collect_bang(mac, span, AstFragmentKind::TraitItems).make_trait_items()
1395             }
1396             _ => fold::noop_fold_trait_item(item, self),
1397         }
1398     }
1399
1400     fn fold_impl_item(&mut self, item: ast::ImplItem) -> OneVector<ast::ImplItem> {
1401         let item = configure!(self, item);
1402
1403         let (attr, traits, item, together_with) = self.classify_item(item);
1404         if attr.is_some() || !traits.is_empty() {
1405             return self.collect_attr(attr, traits, Annotatable::ImplItem(P(item)),
1406                                      AstFragmentKind::ImplItems, together_with).make_impl_items();
1407         }
1408
1409         match item.node {
1410             ast::ImplItemKind::Macro(mac) => {
1411                 let ast::ImplItem { attrs, span, .. } = item;
1412                 self.check_attributes(&attrs);
1413                 self.collect_bang(mac, span, AstFragmentKind::ImplItems).make_impl_items()
1414             }
1415             _ => fold::noop_fold_impl_item(item, self),
1416         }
1417     }
1418
1419     fn fold_ty(&mut self, ty: P<ast::Ty>) -> P<ast::Ty> {
1420         let ty = match ty.node {
1421             ast::TyKind::Mac(_) => ty.into_inner(),
1422             _ => return fold::noop_fold_ty(ty, self),
1423         };
1424
1425         match ty.node {
1426             ast::TyKind::Mac(mac) => self.collect_bang(mac, ty.span, AstFragmentKind::Ty).make_ty(),
1427             _ => unreachable!(),
1428         }
1429     }
1430
1431     fn fold_foreign_mod(&mut self, foreign_mod: ast::ForeignMod) -> ast::ForeignMod {
1432         noop_fold_foreign_mod(self.cfg.configure_foreign_mod(foreign_mod), self)
1433     }
1434
1435     fn fold_foreign_item(&mut self,
1436                          foreign_item: ast::ForeignItem) -> OneVector<ast::ForeignItem> {
1437         let (attr, traits, foreign_item, together_with) = self.classify_item(foreign_item);
1438
1439         if attr.is_some() || !traits.is_empty() {
1440             return self.collect_attr(attr, traits, Annotatable::ForeignItem(P(foreign_item)),
1441                                      AstFragmentKind::ForeignItems, together_with)
1442                                      .make_foreign_items();
1443         }
1444
1445         if let ast::ForeignItemKind::Macro(mac) = foreign_item.node {
1446             self.check_attributes(&foreign_item.attrs);
1447             return self.collect_bang(mac, foreign_item.span, AstFragmentKind::ForeignItems)
1448                 .make_foreign_items();
1449         }
1450
1451         noop_fold_foreign_item(foreign_item, self)
1452     }
1453
1454     fn fold_item_kind(&mut self, item: ast::ItemKind) -> ast::ItemKind {
1455         match item {
1456             ast::ItemKind::MacroDef(..) => item,
1457             _ => noop_fold_item_kind(self.cfg.configure_item_kind(item), self),
1458         }
1459     }
1460
1461     fn fold_generic_param(&mut self, param: ast::GenericParam) -> ast::GenericParam {
1462         self.cfg.disallow_cfg_on_generic_param(&param);
1463         noop_fold_generic_param(param, self)
1464     }
1465
1466     fn fold_attribute(&mut self, at: ast::Attribute) -> Option<ast::Attribute> {
1467         // turn `#[doc(include="filename")]` attributes into `#[doc(include(file="filename",
1468         // contents="file contents")]` attributes
1469         if !at.check_name("doc") {
1470             return noop_fold_attribute(at, self);
1471         }
1472
1473         if let Some(list) = at.meta_item_list() {
1474             if !list.iter().any(|it| it.check_name("include")) {
1475                 return noop_fold_attribute(at, self);
1476             }
1477
1478             let mut items = vec![];
1479
1480             for it in list {
1481                 if !it.check_name("include") {
1482                     items.push(noop_fold_meta_list_item(it, self));
1483                     continue;
1484                 }
1485
1486                 if let Some(file) = it.value_str() {
1487                     let err_count = self.cx.parse_sess.span_diagnostic.err_count();
1488                     self.check_attribute(&at);
1489                     if self.cx.parse_sess.span_diagnostic.err_count() > err_count {
1490                         // avoid loading the file if they haven't enabled the feature
1491                         return noop_fold_attribute(at, self);
1492                     }
1493
1494                     let mut buf = vec![];
1495                     let filename = self.cx.root_path.join(file.to_string());
1496
1497                     match File::open(&filename).and_then(|mut f| f.read_to_end(&mut buf)) {
1498                         Ok(..) => {}
1499                         Err(e) => {
1500                             self.cx.span_err(at.span,
1501                                              &format!("couldn't read {}: {}",
1502                                                       filename.display(),
1503                                                       e));
1504                         }
1505                     }
1506
1507                     match String::from_utf8(buf) {
1508                         Ok(src) => {
1509                             let src_interned = Symbol::intern(&src);
1510
1511                             // Add this input file to the code map to make it available as
1512                             // dependency information
1513                             self.cx.source_map().new_source_file(filename.into(), src);
1514
1515                             let include_info = vec![
1516                                 dummy_spanned(ast::NestedMetaItemKind::MetaItem(
1517                                         attr::mk_name_value_item_str(Ident::from_str("file"),
1518                                                                      dummy_spanned(file)))),
1519                                 dummy_spanned(ast::NestedMetaItemKind::MetaItem(
1520                                         attr::mk_name_value_item_str(Ident::from_str("contents"),
1521                                                             dummy_spanned(src_interned)))),
1522                             ];
1523
1524                             let include_ident = Ident::from_str("include");
1525                             let item = attr::mk_list_item(DUMMY_SP, include_ident, include_info);
1526                             items.push(dummy_spanned(ast::NestedMetaItemKind::MetaItem(item)));
1527                         }
1528                         Err(_) => {
1529                             self.cx.span_err(at.span,
1530                                              &format!("{} wasn't a utf-8 file",
1531                                                       filename.display()));
1532                         }
1533                     }
1534                 } else {
1535                     items.push(noop_fold_meta_list_item(it, self));
1536                 }
1537             }
1538
1539             let meta = attr::mk_list_item(DUMMY_SP, Ident::from_str("doc"), items);
1540             match at.style {
1541                 ast::AttrStyle::Inner =>
1542                     Some(attr::mk_spanned_attr_inner(at.span, at.id, meta)),
1543                 ast::AttrStyle::Outer =>
1544                     Some(attr::mk_spanned_attr_outer(at.span, at.id, meta)),
1545             }
1546         } else {
1547             noop_fold_attribute(at, self)
1548         }
1549     }
1550
1551     fn new_id(&mut self, id: ast::NodeId) -> ast::NodeId {
1552         if self.monotonic {
1553             assert_eq!(id, ast::DUMMY_NODE_ID);
1554             self.cx.resolver.next_node_id()
1555         } else {
1556             id
1557         }
1558     }
1559 }
1560
1561 pub struct ExpansionConfig<'feat> {
1562     pub crate_name: String,
1563     pub features: Option<&'feat Features>,
1564     pub recursion_limit: usize,
1565     pub trace_mac: bool,
1566     pub should_test: bool, // If false, strip `#[test]` nodes
1567     pub single_step: bool,
1568     pub keep_macs: bool,
1569 }
1570
1571 macro_rules! feature_tests {
1572     ($( fn $getter:ident = $field:ident, )*) => {
1573         $(
1574             pub fn $getter(&self) -> bool {
1575                 match self.features {
1576                     Some(&Features { $field: true, .. }) => true,
1577                     _ => false,
1578                 }
1579             }
1580         )*
1581     }
1582 }
1583
1584 impl<'feat> ExpansionConfig<'feat> {
1585     pub fn default(crate_name: String) -> ExpansionConfig<'static> {
1586         ExpansionConfig {
1587             crate_name,
1588             features: None,
1589             recursion_limit: 1024,
1590             trace_mac: false,
1591             should_test: false,
1592             single_step: false,
1593             keep_macs: false,
1594         }
1595     }
1596
1597     feature_tests! {
1598         fn enable_quotes = quote,
1599         fn enable_asm = asm,
1600         fn enable_custom_test_frameworks = custom_test_frameworks,
1601         fn enable_global_asm = global_asm,
1602         fn enable_log_syntax = log_syntax,
1603         fn enable_concat_idents = concat_idents,
1604         fn enable_trace_macros = trace_macros,
1605         fn enable_allow_internal_unstable = allow_internal_unstable,
1606         fn enable_custom_derive = custom_derive,
1607         fn enable_format_args_nl = format_args_nl,
1608         fn macros_in_extern_enabled = macros_in_extern,
1609         fn proc_macro_mod = proc_macro_mod,
1610         fn proc_macro_gen = proc_macro_gen,
1611         fn proc_macro_expr = proc_macro_expr,
1612         fn proc_macro_non_items = proc_macro_non_items,
1613     }
1614
1615     fn enable_custom_inner_attributes(&self) -> bool {
1616         self.features.map_or(false, |features| {
1617             features.custom_inner_attributes || features.custom_attribute || features.rustc_attrs
1618         })
1619     }
1620 }
1621
1622 // A Marker adds the given mark to the syntax context.
1623 #[derive(Debug)]
1624 pub struct Marker(pub Mark);
1625
1626 impl Folder for Marker {
1627     fn new_span(&mut self, span: Span) -> Span {
1628         span.apply_mark(self.0)
1629     }
1630
1631     fn fold_mac(&mut self, mac: ast::Mac) -> ast::Mac {
1632         noop_fold_mac(mac, self)
1633     }
1634 }