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