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::build::AstBuilder;
  19 use ext::derive::{add_derived_markers, collect_derives};
  20 use ext::hygiene::{self, Mark, SyntaxContext};
  21 use ext::placeholders::{placeholder, PlaceholderExpander};
  22 use feature_gate::{self, Features, GateIssue, is_builtin_attr, emit_feature_err};
  23 use fold;
  24 use fold::*;
  25 use parse::{DirectoryOwnership, PResult, ParseSess};
  26 use parse::token::{self, Token};
  27 use parse::parser::Parser;
  28 use ptr::P;
  29 use OneVector;
  30 use symbol::Symbol;
  31 use symbol::keywords;
  32 use syntax_pos::{Span, DUMMY_SP, FileName};
  33 use syntax_pos::hygiene::ExpnFormat;
  34 use tokenstream::{TokenStream, TokenTree};
  35 use visit::{self, Visitor};
  36
  37 use std::collections::HashMap;
  38 use std::fs::File;
  39 use std::io::Read;
  40 use std::{iter, mem};
  41 use std::rc::Rc;
  42 use std::path::PathBuf;
  43
  44 macro_rules! ast_fragments {
  45     (
  46         $($Kind:ident($AstTy:ty) {
  47             $kind_name:expr;
  48             // FIXME: HACK: this should be `$(one ...)?` and `$(many ...)?` but `?` macro
  49             // repetition was removed from 2015 edition in #51587 because of ambiguities.
  50             $(one fn $fold_ast:ident; fn $visit_ast:ident;)*
  51             $(many fn $fold_ast_elt:ident; fn $visit_ast_elt:ident;)*
  52             fn $make_ast:ident;
  53         })*
  54     ) => {
  55         /// A fragment of AST that can be produced by a single macro expansion.
  56         /// Can also serve as an input and intermediate result for macro expansion operations.
  57         pub enum AstFragment {
  58             OptExpr(Option<P<ast::Expr>>),
  59             $($Kind($AstTy),)*
  60         }
  61
  62         /// "Discriminant" of an AST fragment.
  63         #[derive(Copy, Clone, PartialEq, Eq)]
  64         pub enum AstFragmentKind {
  65             OptExpr,
  66             $($Kind,)*
  67         }
  68
  69         impl AstFragmentKind {
  70             pub fn name(self) -> &'static str {
  71                 match self {
  72                     AstFragmentKind::OptExpr => "expression",
  73                     $(AstFragmentKind::$Kind => $kind_name,)*
  74                 }
  75             }
  76
  77             fn make_from<'a>(self, result: Box<dyn MacResult + 'a>) -> Option<AstFragment> {
  78                 match self {
  79                     AstFragmentKind::OptExpr =>
  80                         result.make_expr().map(Some).map(AstFragment::OptExpr),
  81                     $(AstFragmentKind::$Kind => result.$make_ast().map(AstFragment::$Kind),)*
  82                 }
  83             }
  84         }
  85
  86         impl AstFragment {
  87             pub fn make_opt_expr(self) -> Option<P<ast::Expr>> {
  88                 match self {
  89                     AstFragment::OptExpr(expr) => expr,
  90                     _ => panic!("AstFragment::make_* called on the wrong kind of fragment"),
  91                 }
  92             }
  93
  94             $(pub fn $make_ast(self) -> $AstTy {
  95                 match self {
  96                     AstFragment::$Kind(ast) => ast,
  97                     _ => panic!("AstFragment::make_* called on the wrong kind of fragment"),
  98                 }
  99             })*
 100
 101             pub fn fold_with<F: Folder>(self, folder: &mut F) -> Self {
 102                 match self {
 103                     AstFragment::OptExpr(expr) =>
 104                         AstFragment::OptExpr(expr.and_then(|expr| folder.fold_opt_expr(expr))),
 105                     $($(AstFragment::$Kind(ast) =>
 106                         AstFragment::$Kind(folder.$fold_ast(ast)),)*)*
 107                     $($(AstFragment::$Kind(ast) =>
 108                         AstFragment::$Kind(ast.into_iter()
 109                                               .flat_map(|ast| folder.$fold_ast_elt(ast))
 110                                               .collect()),)*)*
 111                 }
 112             }
 113
 114             pub fn visit_with<'a, V: Visitor<'a>>(&'a self, visitor: &mut V) {
 115                 match *self {
 116                     AstFragment::OptExpr(Some(ref expr)) => visitor.visit_expr(expr),
 117                     AstFragment::OptExpr(None) => {}
 118                     $($(AstFragment::$Kind(ref ast) => visitor.$visit_ast(ast),)*)*
 119                     $($(AstFragment::$Kind(ref ast) => for ast_elt in &ast[..] {
 120                         visitor.$visit_ast_elt(ast_elt);
 121                     })*)*
 122                 }
 123             }
 124         }
 125
 126         impl<'a, 'b> Folder for MacroExpander<'a, 'b> {
 127             fn fold_opt_expr(&mut self, expr: P<ast::Expr>) -> Option<P<ast::Expr>> {
 128                 self.expand_fragment(AstFragment::OptExpr(Some(expr))).make_opt_expr()
 129             }
 130             $($(fn $fold_ast(&mut self, ast: $AstTy) -> $AstTy {
 131                 self.expand_fragment(AstFragment::$Kind(ast)).$make_ast()
 132             })*)*
 133             $($(fn $fold_ast_elt(&mut self, ast_elt: <$AstTy as IntoIterator>::Item) -> $AstTy {
 134                 self.expand_fragment(AstFragment::$Kind(OneVector::one(ast_elt))).$make_ast()
 135             })*)*
 136         }
 137
 138         impl<'a> MacResult for ::ext::tt::macro_rules::ParserAnyMacro<'a> {
 139             $(fn $make_ast(self: Box<::ext::tt::macro_rules::ParserAnyMacro<'a>>)
 140                            -> Option<$AstTy> {
 141                 Some(self.make(AstFragmentKind::$Kind).$make_ast())
 142             })*
 143         }
 144     }
 145 }
 146
 147 ast_fragments! {
 148     Expr(P<ast::Expr>) { "expression"; one fn fold_expr; fn visit_expr; fn make_expr; }
 149     Pat(P<ast::Pat>) { "pattern"; one fn fold_pat; fn visit_pat; fn make_pat; }
 150     Ty(P<ast::Ty>) { "type"; one fn fold_ty; fn visit_ty; fn make_ty; }
 151     Stmts(OneVector<ast::Stmt>) { "statement"; many fn fold_stmt; fn visit_stmt; fn make_stmts; }
 152     Items(OneVector<P<ast::Item>>) { "item"; many fn fold_item; fn visit_item; fn make_items; }
 153     TraitItems(OneVector<ast::TraitItem>) {
 154         "trait item"; many fn fold_trait_item; fn visit_trait_item; fn make_trait_items;
 155     }
 156     ImplItems(OneVector<ast::ImplItem>) {
 157         "impl item"; many fn fold_impl_item; fn visit_impl_item; fn make_impl_items;
 158     }
 159     ForeignItems(OneVector<ast::ForeignItem>) {
 160         "foreign item"; many fn fold_foreign_item; fn visit_foreign_item; fn make_foreign_items;
 161     }
 162 }
 163
 164 impl AstFragmentKind {
 165     fn dummy(self, span: Span) -> Option<AstFragment> {
 166         self.make_from(DummyResult::any(span))
 167     }
 168
 169     fn expect_from_annotatables<I: IntoIterator<Item = Annotatable>>(self, items: I)
 170                                                                      -> AstFragment {
 171         let mut items = items.into_iter();
 172         match self {
 173             AstFragmentKind::Items =>
 174                 AstFragment::Items(items.map(Annotatable::expect_item).collect()),
 175             AstFragmentKind::ImplItems =>
 176                 AstFragment::ImplItems(items.map(Annotatable::expect_impl_item).collect()),
 177             AstFragmentKind::TraitItems =>
 178                 AstFragment::TraitItems(items.map(Annotatable::expect_trait_item).collect()),
 179             AstFragmentKind::ForeignItems =>
 180                 AstFragment::ForeignItems(items.map(Annotatable::expect_foreign_item).collect()),
 181             AstFragmentKind::Stmts =>
 182                 AstFragment::Stmts(items.map(Annotatable::expect_stmt).collect()),
 183             AstFragmentKind::Expr => AstFragment::Expr(
 184                 items.next().expect("expected exactly one expression").expect_expr()
 185             ),
 186             AstFragmentKind::OptExpr =>
 187                 AstFragment::OptExpr(items.next().map(Annotatable::expect_expr)),
 188             AstFragmentKind::Pat | AstFragmentKind::Ty =>
 189                 panic!("patterns and types aren't annotatable"),
 190         }
 191     }
 192 }
 193
 194 fn macro_bang_format(path: &ast::Path) -> ExpnFormat {
 195     // We don't want to format a path using pretty-printing,
 196     // `format!("{}", path)`, because that tries to insert
 197     // line-breaks and is slow.
 198     let mut path_str = String::with_capacity(64);
 199     for (i, segment) in path.segments.iter().enumerate() {
 200         if i != 0 {
 201             path_str.push_str("::");
 202         }
 203
 204         if segment.ident.name != keywords::CrateRoot.name() &&
 205             segment.ident.name != keywords::DollarCrate.name()
 206         {
 207             path_str.push_str(&segment.ident.as_str())
 208         }
 209     }
 210
 211     MacroBang(Symbol::intern(&path_str))
 212 }
 213
 214 pub struct Invocation {
 215     pub kind: InvocationKind,
 216     fragment_kind: AstFragmentKind,
 217     pub expansion_data: ExpansionData,
 218 }
 219
 220 pub enum InvocationKind {
 221     Bang {
 222         mac: ast::Mac,
 223         ident: Option<Ident>,
 224         span: Span,
 225     },
 226     Attr {
 227         attr: Option<ast::Attribute>,
 228         traits: Vec<Path>,
 229         item: Annotatable,
 230     },
 231     Derive {
 232         path: Path,
 233         item: Annotatable,
 234     },
 235 }
 236
 237 impl Invocation {
 238     pub fn span(&self) -> Span {
 239         match self.kind {
 240             InvocationKind::Bang { span, .. } => span,
 241             InvocationKind::Attr { attr: Some(ref attr), .. } => attr.span,
 242             InvocationKind::Attr { attr: None, .. } => DUMMY_SP,
 243             InvocationKind::Derive { ref path, .. } => path.span,
 244         }
 245     }
 246
 247     pub fn path(&self) -> Option<&Path> {
 248         match self.kind {
 249             InvocationKind::Bang { ref mac, .. } => Some(&mac.node.path),
 250             InvocationKind::Attr { attr: Some(ref attr), .. } => Some(&attr.path),
 251             InvocationKind::Attr { attr: None, .. } => None,
 252             InvocationKind::Derive { ref path, .. } => Some(path),
 253         }
 254     }
 255 }
 256
 257 pub struct MacroExpander<'a, 'b:'a> {
 258     pub cx: &'a mut ExtCtxt<'b>,
 259     monotonic: bool, // c.f. `cx.monotonic_expander()`
 260 }
 261
 262 impl<'a, 'b> MacroExpander<'a, 'b> {
 263     pub fn new(cx: &'a mut ExtCtxt<'b>, monotonic: bool) -> Self {
 264         MacroExpander { cx: cx, monotonic: monotonic }
 265     }
 266
 267     pub fn expand_crate(&mut self, mut krate: ast::Crate) -> ast::Crate {
 268         let mut module = ModuleData {
 269             mod_path: vec![Ident::from_str(&self.cx.ecfg.crate_name)],
 270             directory: match self.cx.codemap().span_to_unmapped_path(krate.span) {
 271                 FileName::Real(path) => path,
 272                 other => PathBuf::from(other.to_string()),
 273             },
 274         };
 275         module.directory.pop();
 276         self.cx.root_path = module.directory.clone();
 277         self.cx.current_expansion.module = Rc::new(module);
 278         self.cx.current_expansion.crate_span = Some(krate.span);
 279
 280         let orig_mod_span = krate.module.inner;
 281
 282         let krate_item = AstFragment::Items(OneVector::one(P(ast::Item {
 283             attrs: krate.attrs,
 284             span: krate.span,
 285             node: ast::ItemKind::Mod(krate.module),
 286             ident: keywords::Invalid.ident(),
 287             id: ast::DUMMY_NODE_ID,
 288             vis: respan(krate.span.shrink_to_lo(), ast::VisibilityKind::Public),
 289             tokens: None,
 290         })));
 291
 292         match self.expand_fragment(krate_item).make_items().pop().map(P::into_inner) {
 293             Some(ast::Item { attrs, node: ast::ItemKind::Mod(module), .. }) => {
 294                 krate.attrs = attrs;
 295                 krate.module = module;
 296             },
 297             None => {
 298                 // Resolution failed so we return an empty expansion
 299                 krate.attrs = vec![];
 300                 krate.module = ast::Mod {
 301                     inner: orig_mod_span,
 302                     items: vec![],
 303                 };
 304             },
 305             _ => unreachable!(),
 306         };
 307         self.cx.trace_macros_diag();
 308         krate
 309     }
 310
 311     // Fully expand all macro invocations in this AST fragment.
 312     fn expand_fragment(&mut self, input_fragment: AstFragment) -> AstFragment {
 313         let orig_expansion_data = self.cx.current_expansion.clone();
 314         self.cx.current_expansion.depth = 0;
 315
 316         // Collect all macro invocations and replace them with placeholders.
 317         let (fragment_with_placeholders, mut invocations)
 318             = self.collect_invocations(input_fragment, &[]);
 319
 320         // Optimization: if we resolve all imports now,
 321         // we'll be able to immediately resolve most of imported macros.
 322         self.resolve_imports();
 323
 324         // Resolve paths in all invocations and produce ouput expanded fragments for them, but
 325         // do not insert them into our input AST fragment yet, only store in `expanded_fragments`.
 326         // The output fragments also go through expansion recursively until no invocations are left.
 327         // Unresolved macros produce dummy outputs as a recovery measure.
 328         invocations.reverse();
 329         let mut expanded_fragments = Vec::new();
 330         let mut derives = HashMap::new();
 331         let mut undetermined_invocations = Vec::new();
 332         let (mut progress, mut force) = (false, !self.monotonic);
 333         loop {
 334             let invoc = if let Some(invoc) = invocations.pop() {
 335                 invoc
 336             } else {
 337                 self.resolve_imports();
 338                 if undetermined_invocations.is_empty() { break }
 339                 invocations = mem::replace(&mut undetermined_invocations, Vec::new());
 340                 force = !mem::replace(&mut progress, false);
 341                 continue
 342             };
 343
 344             let scope =
 345                 if self.monotonic { invoc.expansion_data.mark } else { orig_expansion_data.mark };
 346             let ext = match self.cx.resolver.resolve_invoc(&invoc, scope, force) {
 347                 Ok(ext) => Some(ext),
 348                 Err(Determinacy::Determined) => None,
 349                 Err(Determinacy::Undetermined) => {
 350                     undetermined_invocations.push(invoc);
 351                     continue
 352                 }
 353             };
 354
 355             progress = true;
 356             let ExpansionData { depth, mark, .. } = invoc.expansion_data;
 357             self.cx.current_expansion = invoc.expansion_data.clone();
 358
 359             self.cx.current_expansion.mark = scope;
 360             // FIXME(jseyfried): Refactor out the following logic
 361             let (expanded_fragment, new_invocations) = if let Some(ext) = ext {
 362                 if let Some(ext) = ext {
 363                     let dummy = invoc.fragment_kind.dummy(invoc.span()).unwrap();
 364                     let fragment = self.expand_invoc(invoc, &*ext).unwrap_or(dummy);
 365                     self.collect_invocations(fragment, &[])
 366                 } else if let InvocationKind::Attr { attr: None, traits, item } = invoc.kind {
 367                     if !item.derive_allowed() {
 368                         let attr = attr::find_by_name(item.attrs(), "derive")
 369                             .expect("`derive` attribute should exist");
 370                         let span = attr.span;
 371                         let mut err = self.cx.mut_span_err(span,
 372                                                            "`derive` may only be applied to \
 373                                                             structs, enums and unions");
 374                         if let ast::AttrStyle::Inner = attr.style {
 375                             let trait_list = traits.iter()
 376                                 .map(|t| t.to_string()).collect::<Vec<_>>();
 377                             let suggestion = format!("#[derive({})]", trait_list.join(", "));
 378                             err.span_suggestion_with_applicability(
 379                                 span, "try an outer attribute", suggestion,
 380                                 // We don't 𝑘𝑛𝑜𝑤 that the following item is an ADT
 381                                 Applicability::MaybeIncorrect
 382                             );
 383                         }
 384                         err.emit();
 385                     }
 386
 387                     let item = self.fully_configure(item)
 388                         .map_attrs(|mut attrs| { attrs.retain(|a| a.path != "derive"); attrs });
 389                     let item_with_markers =
 390                         add_derived_markers(&mut self.cx, item.span(), &traits, item.clone());
 391                     let derives = derives.entry(invoc.expansion_data.mark).or_insert_with(Vec::new);
 392
 393                     for path in &traits {
 394                         let mark = Mark::fresh(self.cx.current_expansion.mark);
 395                         derives.push(mark);
 396                         let item = match self.cx.resolver.resolve_macro(
 397                                 Mark::root(), path, MacroKind::Derive, false) {
 398                             Ok(ext) => match *ext {
 399                                 BuiltinDerive(..) => item_with_markers.clone(),
 400                                 _ => item.clone(),
 401                             },
 402                             _ => item.clone(),
 403                         };
 404                         invocations.push(Invocation {
 405                             kind: InvocationKind::Derive { path: path.clone(), item: item },
 406                             fragment_kind: invoc.fragment_kind,
 407                             expansion_data: ExpansionData {
 408                                 mark,
 409                                 ..invoc.expansion_data.clone()
 410                             },
 411                         });
 412                     }
 413                     let fragment = invoc.fragment_kind
 414                         .expect_from_annotatables(::std::iter::once(item_with_markers));
 415                     self.collect_invocations(fragment, derives)
 416                 } else {
 417                     unreachable!()
 418                 }
 419             } else {
 420                 self.collect_invocations(invoc.fragment_kind.dummy(invoc.span()).unwrap(), &[])
 421             };
 422
 423             if expanded_fragments.len() < depth {
 424                 expanded_fragments.push(Vec::new());
 425             }
 426             expanded_fragments[depth - 1].push((mark, expanded_fragment));
 427             if !self.cx.ecfg.single_step {
 428                 invocations.extend(new_invocations.into_iter().rev());
 429             }
 430         }
 431
 432         self.cx.current_expansion = orig_expansion_data;
 433
 434         // Finally incorporate all the expanded macros into the input AST fragment.
 435         let mut placeholder_expander = PlaceholderExpander::new(self.cx, self.monotonic);
 436         while let Some(expanded_fragments) = expanded_fragments.pop() {
 437             for (mark, expanded_fragment) in expanded_fragments.into_iter().rev() {
 438                 let derives = derives.remove(&mark).unwrap_or_else(Vec::new);
 439                 placeholder_expander.add(NodeId::placeholder_from_mark(mark),
 440                                          expanded_fragment, derives);
 441             }
 442         }
 443         fragment_with_placeholders.fold_with(&mut placeholder_expander)
 444     }
 445
 446     fn resolve_imports(&mut self) {
 447         if self.monotonic {
 448             let err_count = self.cx.parse_sess.span_diagnostic.err_count();
 449             self.cx.resolver.resolve_imports();
 450             self.cx.resolve_err_count += self.cx.parse_sess.span_diagnostic.err_count() - err_count;
 451         }
 452     }
 453
 454     /// Collect all macro invocations reachable at this time in this AST fragment, and replace
 455     /// them with "placeholders" - dummy macro invocations with specially crafted `NodeId`s.
 456     /// Then call into resolver that builds a skeleton ("reduced graph") of the fragment and
 457     /// prepares data for resolving paths of macro invocations.
 458     fn collect_invocations(&mut self, fragment: AstFragment, derives: &[Mark])
 459                            -> (AstFragment, Vec<Invocation>) {
 460         let (fragment_with_placeholders, invocations) = {
 461             let mut collector = InvocationCollector {
 462                 cfg: StripUnconfigured {
 463                     should_test: self.cx.ecfg.should_test,
 464                     sess: self.cx.parse_sess,
 465                     features: self.cx.ecfg.features,
 466                 },
 467                 cx: self.cx,
 468                 invocations: Vec::new(),
 469                 monotonic: self.monotonic,
 470                 tests_nameable: true,
 471             };
 472             (fragment.fold_with(&mut collector), collector.invocations)
 473         };
 474
 475         if self.monotonic {
 476             let err_count = self.cx.parse_sess.span_diagnostic.err_count();
 477             let mark = self.cx.current_expansion.mark;
 478             self.cx.resolver.visit_ast_fragment_with_placeholders(mark, &fragment_with_placeholders,
 479                                                                   derives);
 480             self.cx.resolve_err_count += self.cx.parse_sess.span_diagnostic.err_count() - err_count;
 481         }
 482
 483         (fragment_with_placeholders, invocations)
 484     }
 485
 486     fn fully_configure(&mut self, item: Annotatable) -> Annotatable {
 487         let mut cfg = StripUnconfigured {
 488             should_test: self.cx.ecfg.should_test,
 489             sess: self.cx.parse_sess,
 490             features: self.cx.ecfg.features,
 491         };
 492         // Since the item itself has already been configured by the InvocationCollector,
 493         // we know that fold result vector will contain exactly one element
 494         match item {
 495             Annotatable::Item(item) => {
 496                 Annotatable::Item(cfg.fold_item(item).pop().unwrap())
 497             }
 498             Annotatable::TraitItem(item) => {
 499                 Annotatable::TraitItem(item.map(|item| cfg.fold_trait_item(item).pop().unwrap()))
 500             }
 501             Annotatable::ImplItem(item) => {
 502                 Annotatable::ImplItem(item.map(|item| cfg.fold_impl_item(item).pop().unwrap()))
 503             }
 504             Annotatable::ForeignItem(item) => {
 505                 Annotatable::ForeignItem(
 506                     item.map(|item| cfg.fold_foreign_item(item).pop().unwrap())
 507                 )
 508             }
 509             Annotatable::Stmt(stmt) => {
 510                 Annotatable::Stmt(stmt.map(|stmt| cfg.fold_stmt(stmt).pop().unwrap()))
 511             }
 512             Annotatable::Expr(expr) => {
 513                 Annotatable::Expr(cfg.fold_expr(expr))
 514             }
 515         }
 516     }
 517
 518     fn expand_invoc(&mut self, invoc: Invocation, ext: &SyntaxExtension) -> Option<AstFragment> {
 519         if invoc.fragment_kind == AstFragmentKind::ForeignItems &&
 520            !self.cx.ecfg.macros_in_extern_enabled() {
 521             if let SyntaxExtension::NonMacroAttr { .. } = *ext {} else {
 522                 emit_feature_err(&self.cx.parse_sess, "macros_in_extern",
 523                                  invoc.span(), GateIssue::Language,
 524                                  "macro invocations in `extern {}` blocks are experimental");
 525             }
 526         }
 527
 528         let result = match invoc.kind {
 529             InvocationKind::Bang { .. } => self.expand_bang_invoc(invoc, ext)?,
 530             InvocationKind::Attr { .. } => self.expand_attr_invoc(invoc, ext)?,
 531             InvocationKind::Derive { .. } => self.expand_derive_invoc(invoc, ext)?,
 532         };
 533
 534         if self.cx.current_expansion.depth > self.cx.ecfg.recursion_limit {
 535             let info = self.cx.current_expansion.mark.expn_info().unwrap();
 536             let suggested_limit = self.cx.ecfg.recursion_limit * 2;
 537             let mut err = self.cx.struct_span_err(info.call_site,
 538                 &format!("recursion limit reached while expanding the macro `{}`",
 539                          info.format.name()));
 540             err.help(&format!(
 541                 "consider adding a `#![recursion_limit=\"{}\"]` attribute to your crate",
 542                 suggested_limit));
 543             err.emit();
 544             self.cx.trace_macros_diag();
 545             FatalError.raise();
 546         }
 547
 548         Some(result)
 549     }
 550
 551     fn expand_attr_invoc(&mut self,
 552                          invoc: Invocation,
 553                          ext: &SyntaxExtension)
 554                          -> Option<AstFragment> {
 555         let (attr, item) = match invoc.kind {
 556             InvocationKind::Attr { attr, item, .. } => (attr?, item),
 557             _ => unreachable!(),
 558         };
 559
 560         if let NonMacroAttr { mark_used: false } = *ext {} else {
 561             // Macro attrs are always used when expanded,
 562             // non-macro attrs are considered used when the field says so.
 563             attr::mark_used(&attr);
 564         }
 565         invoc.expansion_data.mark.set_expn_info(ExpnInfo {
 566             call_site: attr.span,
 567             def_site: None,
 568             format: MacroAttribute(Symbol::intern(&attr.path.to_string())),
 569             allow_internal_unstable: false,
 570             allow_internal_unsafe: false,
 571             local_inner_macros: false,
 572             edition: ext.edition(),
 573         });
 574
 575         match *ext {
 576             NonMacroAttr { .. } => {
 577                 attr::mark_known(&attr);
 578                 let item = item.map_attrs(|mut attrs| { attrs.push(attr); attrs });
 579                 Some(invoc.fragment_kind.expect_from_annotatables(iter::once(item)))
 580             }
 581             MultiModifier(ref mac) => {
 582                 let meta = attr.parse_meta(self.cx.parse_sess)
 583                                .map_err(|mut e| { e.emit(); }).ok()?;
 584                 let item = mac.expand(self.cx, attr.span, &meta, item);
 585                 Some(invoc.fragment_kind.expect_from_annotatables(item))
 586             }
 587             MultiDecorator(ref mac) => {
 588                 let mut items = Vec::new();
 589                 let meta = attr.parse_meta(self.cx.parse_sess)
 590                                .expect("derive meta should already have been parsed");
 591                 mac.expand(self.cx, attr.span, &meta, &item, &mut |item| items.push(item));
 592                 items.push(item);
 593                 Some(invoc.fragment_kind.expect_from_annotatables(items))
 594             }
 595             AttrProcMacro(ref mac, ..) => {
 596                 self.gate_proc_macro_attr_item(attr.span, &item);
 597                 let item_tok = TokenTree::Token(DUMMY_SP, Token::interpolated(match item {
 598                     Annotatable::Item(item) => token::NtItem(item),
 599                     Annotatable::TraitItem(item) => token::NtTraitItem(item.into_inner()),
 600                     Annotatable::ImplItem(item) => token::NtImplItem(item.into_inner()),
 601                     Annotatable::ForeignItem(item) => token::NtForeignItem(item.into_inner()),
 602                     Annotatable::Stmt(stmt) => token::NtStmt(stmt.into_inner()),
 603                     Annotatable::Expr(expr) => token::NtExpr(expr),
 604                 })).into();
 605                 let input = self.extract_proc_macro_attr_input(attr.tokens, attr.span);
 606                 let tok_result = mac.expand(self.cx, attr.span, input, item_tok);
 607                 let res = self.parse_ast_fragment(tok_result, invoc.fragment_kind,
 608                                                   &attr.path, attr.span);
 609                 self.gate_proc_macro_expansion(attr.span, &res);
 610                 res
 611             }
 612             ProcMacroDerive(..) | BuiltinDerive(..) => {
 613                 self.cx.span_err(attr.span, &format!("`{}` is a derive mode", attr.path));
 614                 self.cx.trace_macros_diag();
 615                 invoc.fragment_kind.dummy(attr.span)
 616             }
 617             _ => {
 618                 let msg = &format!("macro `{}` may not be used in attributes", attr.path);
 619                 self.cx.span_err(attr.span, msg);
 620                 self.cx.trace_macros_diag();
 621                 invoc.fragment_kind.dummy(attr.span)
 622             }
 623         }
 624     }
 625
 626     fn extract_proc_macro_attr_input(&self, tokens: TokenStream, span: Span) -> TokenStream {
 627         let mut trees = tokens.trees();
 628         match trees.next() {
 629             Some(TokenTree::Delimited(_, delim)) => {
 630                 if trees.next().is_none() {
 631                     return delim.tts.into()
 632                 }
 633             }
 634             Some(TokenTree::Token(..)) => {}
 635             None => return TokenStream::empty(),
 636         }
 637         self.cx.span_err(span, "custom attribute invocations must be \
 638             of the form #[foo] or #[foo(..)], the macro name must only be \
 639             followed by a delimiter token");
 640         TokenStream::empty()
 641     }
 642
 643     fn gate_proc_macro_attr_item(&self, span: Span, item: &Annotatable) {
 644         let (kind, gate) = match *item {
 645             Annotatable::Item(ref item) => {
 646                 match item.node {
 647                     ItemKind::Mod(_) if self.cx.ecfg.proc_macro_mod() => return,
 648                     ItemKind::Mod(_) => ("modules", "proc_macro_mod"),
 649                     _ => return,
 650                 }
 651             }
 652             Annotatable::TraitItem(_) => return,
 653             Annotatable::ImplItem(_) => return,
 654             Annotatable::ForeignItem(_) => return,
 655             Annotatable::Stmt(_) |
 656             Annotatable::Expr(_) if self.cx.ecfg.proc_macro_expr() => return,
 657             Annotatable::Stmt(_) => ("statements", "proc_macro_expr"),
 658             Annotatable::Expr(_) => ("expressions", "proc_macro_expr"),
 659         };
 660         emit_feature_err(
 661             self.cx.parse_sess,
 662             gate,
 663             span,
 664             GateIssue::Language,
 665             &format!("custom attributes cannot be applied to {}", kind),
 666         );
 667     }
 668
 669     fn gate_proc_macro_expansion(&self, span: Span, fragment: &Option<AstFragment>) {
 670         if self.cx.ecfg.proc_macro_gen() {
 671             return
 672         }
 673         let fragment = match fragment {
 674             Some(fragment) => fragment,
 675             None => return,
 676         };
 677
 678         fragment.visit_with(&mut DisallowModules {
 679             span,
 680             parse_sess: self.cx.parse_sess,
 681         });
 682
 683         struct DisallowModules<'a> {
 684             span: Span,
 685             parse_sess: &'a ParseSess,
 686         }
 687
 688         impl<'ast, 'a> Visitor<'ast> for DisallowModules<'a> {
 689             fn visit_item(&mut self, i: &'ast ast::Item) {
 690                 let name = match i.node {
 691                     ast::ItemKind::Mod(_) => Some("modules"),
 692                     ast::ItemKind::MacroDef(_) => Some("macro definitions"),
 693                     _ => None,
 694                 };
 695                 if let Some(name) = name {
 696                     emit_feature_err(
 697                         self.parse_sess,
 698                         "proc_macro_gen",
 699                         self.span,
 700                         GateIssue::Language,
 701                         &format!("procedural macros cannot expand to {}", name),
 702                     );
 703                 }
 704                 visit::walk_item(self, i);
 705             }
 706
 707             fn visit_mac(&mut self, _mac: &'ast ast::Mac) {
 708                 // ...
 709             }
 710         }
 711     }
 712
 713     /// Expand a macro invocation. Returns the resulting expanded AST fragment.
 714     fn expand_bang_invoc(&mut self,
 715                          invoc: Invocation,
 716                          ext: &SyntaxExtension)
 717                          -> Option<AstFragment> {
 718         let (mark, kind) = (invoc.expansion_data.mark, invoc.fragment_kind);
 719         let (mac, ident, span) = match invoc.kind {
 720             InvocationKind::Bang { mac, ident, span } => (mac, ident, span),
 721             _ => unreachable!(),
 722         };
 723         let path = &mac.node.path;
 724
 725         let ident = ident.unwrap_or_else(|| keywords::Invalid.ident());
 726         let validate_and_set_expn_info = |this: &mut Self, // arg instead of capture
 727                                           def_site_span: Option<Span>,
 728                                           allow_internal_unstable,
 729                                           allow_internal_unsafe,
 730                                           local_inner_macros,
 731                                           // can't infer this type
 732                                           unstable_feature: Option<(Symbol, u32)>,
 733                                           edition| {
 734
 735             // feature-gate the macro invocation
 736             if let Some((feature, issue)) = unstable_feature {
 737                 let crate_span = this.cx.current_expansion.crate_span.unwrap();
 738                 // don't stability-check macros in the same crate
 739                 // (the only time this is null is for syntax extensions registered as macros)
 740                 if def_site_span.map_or(false, |def_span| !crate_span.contains(def_span))
 741                     && !span.allows_unstable() && this.cx.ecfg.features.map_or(true, |feats| {
 742                     // macro features will count as lib features
 743                     !feats.declared_lib_features.iter().any(|&(feat, _)| feat == feature)
 744                 }) {
 745                     let explain = format!("macro {}! is unstable", path);
 746                     emit_feature_err(this.cx.parse_sess, &*feature.as_str(), span,
 747                                      GateIssue::Library(Some(issue)), &explain);
 748                     this.cx.trace_macros_diag();
 749                     return Err(kind.dummy(span));
 750                 }
 751             }
 752
 753             if ident.name != keywords::Invalid.name() {
 754                 let msg = format!("macro {}! expects no ident argument, given '{}'", path, ident);
 755                 this.cx.span_err(path.span, &msg);
 756                 this.cx.trace_macros_diag();
 757                 return Err(kind.dummy(span));
 758             }
 759             mark.set_expn_info(ExpnInfo {
 760                 call_site: span,
 761                 def_site: def_site_span,
 762                 format: macro_bang_format(path),
 763                 allow_internal_unstable,
 764                 allow_internal_unsafe,
 765                 local_inner_macros,
 766                 edition,
 767             });
 768             Ok(())
 769         };
 770
 771         let opt_expanded = match *ext {
 772             DeclMacro { ref expander, def_info, edition, .. } => {
 773                 if let Err(dummy_span) = validate_and_set_expn_info(self, def_info.map(|(_, s)| s),
 774                                                                     false, false, false, None,
 775                                                                     edition) {
 776                     dummy_span
 777                 } else {
 778                     kind.make_from(expander.expand(self.cx, span, mac.node.stream()))
 779                 }
 780             }
 781
 782             NormalTT {
 783                 ref expander,
 784                 def_info,
 785                 allow_internal_unstable,
 786                 allow_internal_unsafe,
 787                 local_inner_macros,
 788                 unstable_feature,
 789                 edition,
 790             } => {
 791                 if let Err(dummy_span) = validate_and_set_expn_info(self, def_info.map(|(_, s)| s),
 792                                                                     allow_internal_unstable,
 793                                                                     allow_internal_unsafe,
 794                                                                     local_inner_macros,
 795                                                                     unstable_feature,
 796                                                                     edition) {
 797                     dummy_span
 798                 } else {
 799                     kind.make_from(expander.expand(self.cx, span, mac.node.stream()))
 800                 }
 801             }
 802
 803             IdentTT(ref expander, tt_span, allow_internal_unstable) => {
 804                 if ident.name == keywords::Invalid.name() {
 805                     self.cx.span_err(path.span,
 806                                     &format!("macro {}! expects an ident argument", path));
 807                     self.cx.trace_macros_diag();
 808                     kind.dummy(span)
 809                 } else {
 810                     invoc.expansion_data.mark.set_expn_info(ExpnInfo {
 811                         call_site: span,
 812                         def_site: tt_span,
 813                         format: macro_bang_format(path),
 814                         allow_internal_unstable,
 815                         allow_internal_unsafe: false,
 816                         local_inner_macros: false,
 817                         edition: hygiene::default_edition(),
 818                     });
 819
 820                     let input: Vec<_> = mac.node.stream().into_trees().collect();
 821                     kind.make_from(expander.expand(self.cx, span, ident, input))
 822                 }
 823             }
 824
 825             MultiDecorator(..) | MultiModifier(..) |
 826             AttrProcMacro(..) | SyntaxExtension::NonMacroAttr { .. } => {
 827                 self.cx.span_err(path.span,
 828                                  &format!("`{}` can only be used in attributes", path));
 829                 self.cx.trace_macros_diag();
 830                 kind.dummy(span)
 831             }
 832
 833             ProcMacroDerive(..) | BuiltinDerive(..) => {
 834                 self.cx.span_err(path.span, &format!("`{}` is a derive mode", path));
 835                 self.cx.trace_macros_diag();
 836                 kind.dummy(span)
 837             }
 838
 839             SyntaxExtension::ProcMacro { ref expander, allow_internal_unstable, edition } => {
 840                 if ident.name != keywords::Invalid.name() {
 841                     let msg =
 842                         format!("macro {}! expects no ident argument, given '{}'", path, ident);
 843                     self.cx.span_err(path.span, &msg);
 844                     self.cx.trace_macros_diag();
 845                     kind.dummy(span)
 846                 } else {
 847                     self.gate_proc_macro_expansion_kind(span, kind);
 848                     invoc.expansion_data.mark.set_expn_info(ExpnInfo {
 849                         call_site: span,
 850                         // FIXME procedural macros do not have proper span info
 851                         // yet, when they do, we should use it here.
 852                         def_site: None,
 853                         format: macro_bang_format(path),
 854                         // FIXME probably want to follow macro_rules macros here.
 855                         allow_internal_unstable,
 856                         allow_internal_unsafe: false,
 857                         local_inner_macros: false,
 858                         edition,
 859                     });
 860
 861                     let tok_result = expander.expand(self.cx, span, mac.node.stream());
 862                     let result = self.parse_ast_fragment(tok_result, kind, path, span);
 863                     self.gate_proc_macro_expansion(span, &result);
 864                     result
 865                 }
 866             }
 867         };
 868
 869         if opt_expanded.is_some() {
 870             opt_expanded
 871         } else {
 872             let msg = format!("non-{kind} macro in {kind} position: {name}",
 873                               name = path.segments[0].ident.name, kind = kind.name());
 874             self.cx.span_err(path.span, &msg);
 875             self.cx.trace_macros_diag();
 876             kind.dummy(span)
 877         }
 878     }
 879
 880     fn gate_proc_macro_expansion_kind(&self, span: Span, kind: AstFragmentKind) {
 881         let kind = match kind {
 882             AstFragmentKind::Expr => "expressions",
 883             AstFragmentKind::OptExpr => "expressions",
 884             AstFragmentKind::Pat => "patterns",
 885             AstFragmentKind::Ty => "types",
 886             AstFragmentKind::Stmts => "statements",
 887             AstFragmentKind::Items => return,
 888             AstFragmentKind::TraitItems => return,
 889             AstFragmentKind::ImplItems => return,
 890             AstFragmentKind::ForeignItems => return,
 891         };
 892         if self.cx.ecfg.proc_macro_non_items() {
 893             return
 894         }
 895         emit_feature_err(
 896             self.cx.parse_sess,
 897             "proc_macro_non_items",
 898             span,
 899             GateIssue::Language,
 900             &format!("procedural macros cannot be expanded to {}", kind),
 901         );
 902     }
 903
 904     /// Expand a derive invocation. Returns the resulting expanded AST fragment.
 905     fn expand_derive_invoc(&mut self,
 906                            invoc: Invocation,
 907                            ext: &SyntaxExtension)
 908                            -> Option<AstFragment> {
 909         let (path, item) = match invoc.kind {
 910             InvocationKind::Derive { path, item } => (path, item),
 911             _ => unreachable!(),
 912         };
 913         if !item.derive_allowed() {
 914             return None;
 915         }
 916
 917         let pretty_name = Symbol::intern(&format!("derive({})", path));
 918         let span = path.span;
 919         let attr = ast::Attribute {
 920             path, span,
 921             tokens: TokenStream::empty(),
 922             // irrelevant:
 923             id: ast::AttrId(0), style: ast::AttrStyle::Outer, is_sugared_doc: false,
 924         };
 925
 926         let mut expn_info = ExpnInfo {
 927             call_site: span,
 928             def_site: None,
 929             format: MacroAttribute(pretty_name),
 930             allow_internal_unstable: false,
 931             allow_internal_unsafe: false,
 932             local_inner_macros: false,
 933             edition: ext.edition(),
 934         };
 935
 936         match *ext {
 937             ProcMacroDerive(ref ext, ..) => {
 938                 invoc.expansion_data.mark.set_expn_info(expn_info);
 939                 let span = span.with_ctxt(self.cx.backtrace());
 940                 let dummy = ast::MetaItem { // FIXME(jseyfried) avoid this
 941                     ident: Path::from_ident(keywords::Invalid.ident()),
 942                     span: DUMMY_SP,
 943                     node: ast::MetaItemKind::Word,
 944                 };
 945                 let items = ext.expand(self.cx, span, &dummy, item);
 946                 Some(invoc.fragment_kind.expect_from_annotatables(items))
 947             }
 948             BuiltinDerive(func) => {
 949                 expn_info.allow_internal_unstable = true;
 950                 invoc.expansion_data.mark.set_expn_info(expn_info);
 951                 let span = span.with_ctxt(self.cx.backtrace());
 952                 let mut items = Vec::new();
 953                 func(self.cx, span, &attr.meta()?, &item, &mut |a| items.push(a));
 954                 Some(invoc.fragment_kind.expect_from_annotatables(items))
 955             }
 956             _ => {
 957                 let msg = &format!("macro `{}` may not be used for derive attributes", attr.path);
 958                 self.cx.span_err(span, msg);
 959                 self.cx.trace_macros_diag();
 960                 invoc.fragment_kind.dummy(span)
 961             }
 962         }
 963     }
 964
 965     fn parse_ast_fragment(&mut self,
 966                           toks: TokenStream,
 967                           kind: AstFragmentKind,
 968                           path: &Path,
 969                           span: Span)
 970                           -> Option<AstFragment> {
 971         let mut parser = self.cx.new_parser_from_tts(&toks.into_trees().collect::<Vec<_>>());
 972         match parser.parse_ast_fragment(kind, false) {
 973             Ok(fragment) => {
 974                 parser.ensure_complete_parse(path, kind.name(), span);
 975                 Some(fragment)
 976             }
 977             Err(mut err) => {
 978                 err.set_span(span);
 979                 err.emit();
 980                 self.cx.trace_macros_diag();
 981                 kind.dummy(span)
 982             }
 983         }
 984     }
 985 }
 986
 987 impl<'a> Parser<'a> {
 988     pub fn parse_ast_fragment(&mut self, kind: AstFragmentKind, macro_legacy_warnings: bool)
 989                               -> PResult<'a, AstFragment> {
 990         Ok(match kind {
 991             AstFragmentKind::Items => {
 992                 let mut items = OneVector::new();
 993                 while let Some(item) = self.parse_item()? {
 994                     items.push(item);
 995                 }
 996                 AstFragment::Items(items)
 997             }
 998             AstFragmentKind::TraitItems => {
 999                 let mut items = OneVector::new();
1000                 while self.token != token::Eof {
1001                     items.push(self.parse_trait_item(&mut false)?);
1002                 }
1003                 AstFragment::TraitItems(items)
1004             }
1005             AstFragmentKind::ImplItems => {
1006                 let mut items = OneVector::new();
1007                 while self.token != token::Eof {
1008                     items.push(self.parse_impl_item(&mut false)?);
1009                 }
1010                 AstFragment::ImplItems(items)
1011             }
1012             AstFragmentKind::ForeignItems => {
1013                 let mut items = OneVector::new();
1014                 while self.token != token::Eof {
1015                     if let Some(item) = self.parse_foreign_item()? {
1016                         items.push(item);
1017                     }
1018                 }
1019                 AstFragment::ForeignItems(items)
1020             }
1021             AstFragmentKind::Stmts => {
1022                 let mut stmts = OneVector::new();
1023                 while self.token != token::Eof &&
1024                       // won't make progress on a `}`
1025                       self.token != token::CloseDelim(token::Brace) {
1026                     if let Some(stmt) = self.parse_full_stmt(macro_legacy_warnings)? {
1027                         stmts.push(stmt);
1028                     }
1029                 }
1030                 AstFragment::Stmts(stmts)
1031             }
1032             AstFragmentKind::Expr => AstFragment::Expr(self.parse_expr()?),
1033             AstFragmentKind::OptExpr => {
1034                 if self.token != token::Eof {
1035                     AstFragment::OptExpr(Some(self.parse_expr()?))
1036                 } else {
1037                     AstFragment::OptExpr(None)
1038                 }
1039             },
1040             AstFragmentKind::Ty => AstFragment::Ty(self.parse_ty()?),
1041             AstFragmentKind::Pat => AstFragment::Pat(self.parse_pat()?),
1042         })
1043     }
1044
1045     pub fn ensure_complete_parse(&mut self, macro_path: &Path, kind_name: &str, span: Span) {
1046         if self.token != token::Eof {
1047             let msg = format!("macro expansion ignores token `{}` and any following",
1048                               self.this_token_to_string());
1049             // Avoid emitting backtrace info twice.
1050             let def_site_span = self.span.with_ctxt(SyntaxContext::empty());
1051             let mut err = self.diagnostic().struct_span_err(def_site_span, &msg);
1052             let msg = format!("caused by the macro expansion here; the usage \
1053                                of `{}!` is likely invalid in {} context",
1054                                macro_path, kind_name);
1055             err.span_note(span, &msg).emit();
1056         }
1057     }
1058 }
1059
1060 struct InvocationCollector<'a, 'b: 'a> {
1061     cx: &'a mut ExtCtxt<'b>,
1062     cfg: StripUnconfigured<'a>,
1063     invocations: Vec<Invocation>,
1064     monotonic: bool,
1065
1066     /// Test functions need to be nameable. Tests inside functions or in other
1067     /// unnameable locations need to be ignored. `tests_nameable` tracks whether
1068     /// any test functions found in the current context would be nameable.
1069     tests_nameable: bool,
1070 }
1071
1072 impl<'a, 'b> InvocationCollector<'a, 'b> {
1073     fn collect(&mut self, fragment_kind: AstFragmentKind, kind: InvocationKind) -> AstFragment {
1074         let mark = Mark::fresh(self.cx.current_expansion.mark);
1075         self.invocations.push(Invocation {
1076             kind,
1077             fragment_kind,
1078             expansion_data: ExpansionData {
1079                 mark,
1080                 depth: self.cx.current_expansion.depth + 1,
1081                 ..self.cx.current_expansion.clone()
1082             },
1083         });
1084         placeholder(fragment_kind, NodeId::placeholder_from_mark(mark))
1085     }
1086
1087     /// Folds the item allowing tests to be expanded because they are still nameable.
1088     /// This should probably only be called with module items
1089     fn fold_nameable(&mut self, item: P<ast::Item>) -> OneVector<P<ast::Item>> {
1090         fold::noop_fold_item(item, self)
1091     }
1092
1093     /// Folds the item but doesn't allow tests to occur within it
1094     fn fold_unnameable(&mut self, item: P<ast::Item>) -> OneVector<P<ast::Item>> {
1095         let was_nameable = mem::replace(&mut self.tests_nameable, false);
1096         let items = fold::noop_fold_item(item, self);
1097         self.tests_nameable = was_nameable;
1098         items
1099     }
1100
1101     fn collect_bang(&mut self, mac: ast::Mac, span: Span, kind: AstFragmentKind) -> AstFragment {
1102         self.collect(kind, InvocationKind::Bang { mac: mac, ident: None, span: span })
1103     }
1104
1105     fn collect_attr(&mut self,
1106                     attr: Option<ast::Attribute>,
1107                     traits: Vec<Path>,
1108                     item: Annotatable,
1109                     kind: AstFragmentKind)
1110                     -> AstFragment {
1111         self.collect(kind, InvocationKind::Attr { attr, traits, item })
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) -> (Option<ast::Attribute>, Vec<Path>, T)
1116         where T: HasAttrs,
1117     {
1118         let (mut attr, mut traits) = (None, Vec::new());
1119
1120         item = item.map_attrs(|mut attrs| {
1121             if let Some(legacy_attr_invoc) = self.cx.resolver.find_legacy_attr_invoc(&mut attrs,
1122                                                                                      true) {
1123                 attr = Some(legacy_attr_invoc);
1124                 return attrs;
1125             }
1126
1127             attr = find_attr_invoc(&mut attrs);
1128             traits = collect_derives(&mut self.cx, &mut attrs);
1129             attrs
1130         });
1131
1132         (attr, traits, item)
1133     }
1134
1135     /// Alternative of `classify_item()` that ignores `#[derive]` so invocations fallthrough
1136     /// to the unused-attributes lint (making it an error on statements and expressions
1137     /// is a breaking change)
1138     fn classify_nonitem<T: HasAttrs>(&mut self, mut item: T) -> (Option<ast::Attribute>, T) {
1139         let mut attr = None;
1140
1141         item = item.map_attrs(|mut attrs| {
1142             if let Some(legacy_attr_invoc) = self.cx.resolver.find_legacy_attr_invoc(&mut attrs,
1143                                                                                      false) {
1144                 attr = Some(legacy_attr_invoc);
1145                 return attrs;
1146             }
1147
1148             attr = find_attr_invoc(&mut attrs);
1149             attrs
1150         });
1151
1152         (attr, item)
1153     }
1154
1155     fn configure<T: HasAttrs>(&mut self, node: T) -> Option<T> {
1156         self.cfg.configure(node)
1157     }
1158
1159     // Detect use of feature-gated or invalid attributes on macro invocations
1160     // since they will not be detected after macro expansion.
1161     fn check_attributes(&mut self, attrs: &[ast::Attribute]) {
1162         let features = self.cx.ecfg.features.unwrap();
1163         for attr in attrs.iter() {
1164             self.check_attribute_inner(attr, features);
1165
1166             // macros are expanded before any lint passes so this warning has to be hardcoded
1167             if attr.path == "derive" {
1168                 self.cx.struct_span_warn(attr.span, "`#[derive]` does nothing on macro invocations")
1169                     .note("this may become a hard error in a future release")
1170                     .emit();
1171             }
1172         }
1173     }
1174
1175     fn check_attribute(&mut self, at: &ast::Attribute) {
1176         let features = self.cx.ecfg.features.unwrap();
1177         self.check_attribute_inner(at, features);
1178     }
1179
1180     fn check_attribute_inner(&mut self, at: &ast::Attribute, features: &Features) {
1181         feature_gate::check_attribute(at, self.cx.parse_sess, features);
1182     }
1183 }
1184
1185 pub fn find_attr_invoc(attrs: &mut Vec<ast::Attribute>) -> Option<ast::Attribute> {
1186     attrs.iter()
1187          .position(|a| !attr::is_known(a) && !is_builtin_attr(a))
1188          .map(|i| attrs.remove(i))
1189 }
1190
1191 impl<'a, 'b> Folder for InvocationCollector<'a, 'b> {
1192     fn fold_expr(&mut self, expr: P<ast::Expr>) -> P<ast::Expr> {
1193         let mut expr = self.cfg.configure_expr(expr).into_inner();
1194         expr.node = self.cfg.configure_expr_kind(expr.node);
1195
1196         // ignore derives so they remain unused
1197         let (attr, expr) = self.classify_nonitem(expr);
1198
1199         if attr.is_some() {
1200             // collect the invoc regardless of whether or not attributes are permitted here
1201             // expansion will eat the attribute so it won't error later
1202             attr.as_ref().map(|a| self.cfg.maybe_emit_expr_attr_err(a));
1203
1204             // AstFragmentKind::Expr requires the macro to emit an expression
1205             return self.collect_attr(attr, vec![], Annotatable::Expr(P(expr)),
1206                                      AstFragmentKind::Expr).make_expr();
1207         }
1208
1209         if let ast::ExprKind::Mac(mac) = expr.node {
1210             self.check_attributes(&expr.attrs);
1211             self.collect_bang(mac, expr.span, AstFragmentKind::Expr).make_expr()
1212         } else {
1213             P(noop_fold_expr(expr, self))
1214         }
1215     }
1216
1217     fn fold_opt_expr(&mut self, expr: P<ast::Expr>) -> Option<P<ast::Expr>> {
1218         let mut expr = configure!(self, expr).into_inner();
1219         expr.node = self.cfg.configure_expr_kind(expr.node);
1220
1221         // ignore derives so they remain unused
1222         let (attr, expr) = self.classify_nonitem(expr);
1223
1224         if attr.is_some() {
1225             attr.as_ref().map(|a| self.cfg.maybe_emit_expr_attr_err(a));
1226
1227             return self.collect_attr(attr, vec![], Annotatable::Expr(P(expr)),
1228                                      AstFragmentKind::OptExpr)
1229                 .make_opt_expr();
1230         }
1231
1232         if let ast::ExprKind::Mac(mac) = expr.node {
1233             self.check_attributes(&expr.attrs);
1234             self.collect_bang(mac, expr.span, AstFragmentKind::OptExpr).make_opt_expr()
1235         } else {
1236             Some(P(noop_fold_expr(expr, self)))
1237         }
1238     }
1239
1240     fn fold_pat(&mut self, pat: P<ast::Pat>) -> P<ast::Pat> {
1241         let pat = self.cfg.configure_pat(pat);
1242         match pat.node {
1243             PatKind::Mac(_) => {}
1244             _ => return noop_fold_pat(pat, self),
1245         }
1246
1247         pat.and_then(|pat| match pat.node {
1248             PatKind::Mac(mac) => self.collect_bang(mac, pat.span, AstFragmentKind::Pat).make_pat(),
1249             _ => unreachable!(),
1250         })
1251     }
1252
1253     fn fold_stmt(&mut self, stmt: ast::Stmt) -> OneVector<ast::Stmt> {
1254         let mut stmt = match self.cfg.configure_stmt(stmt) {
1255             Some(stmt) => stmt,
1256             None => return OneVector::new(),
1257         };
1258
1259         // we'll expand attributes on expressions separately
1260         if !stmt.is_expr() {
1261             let (attr, derives, stmt_) = if stmt.is_item() {
1262                 self.classify_item(stmt)
1263             } else {
1264                 // ignore derives on non-item statements so it falls through
1265                 // to the unused-attributes lint
1266                 let (attr, stmt) = self.classify_nonitem(stmt);
1267                 (attr, vec![], stmt)
1268             };
1269
1270             if attr.is_some() || !derives.is_empty() {
1271                 return self.collect_attr(attr, derives,
1272                                          Annotatable::Stmt(P(stmt_)), AstFragmentKind::Stmts)
1273                     .make_stmts();
1274             }
1275
1276             stmt = stmt_;
1277         }
1278
1279         if let StmtKind::Mac(mac) = stmt.node {
1280             let (mac, style, attrs) = mac.into_inner();
1281             self.check_attributes(&attrs);
1282             let mut placeholder = self.collect_bang(mac, stmt.span, AstFragmentKind::Stmts)
1283                                         .make_stmts();
1284
1285             // If this is a macro invocation with a semicolon, then apply that
1286             // semicolon to the final statement produced by expansion.
1287             if style == MacStmtStyle::Semicolon {
1288                 if let Some(stmt) = placeholder.pop() {
1289                     placeholder.push(stmt.add_trailing_semicolon());
1290                 }
1291             }
1292
1293             return placeholder;
1294         }
1295
1296         // The placeholder expander gives ids to statements, so we avoid folding the id here.
1297         let ast::Stmt { id, node, span } = stmt;
1298         noop_fold_stmt_kind(node, self).into_iter().map(|node| {
1299             ast::Stmt { id, node, span }
1300         }).collect()
1301
1302     }
1303
1304     fn fold_block(&mut self, block: P<Block>) -> P<Block> {
1305         let old_directory_ownership = self.cx.current_expansion.directory_ownership;
1306         self.cx.current_expansion.directory_ownership = DirectoryOwnership::UnownedViaBlock;
1307         let result = noop_fold_block(block, self);
1308         self.cx.current_expansion.directory_ownership = old_directory_ownership;
1309         result
1310     }
1311
1312     fn fold_item(&mut self, item: P<ast::Item>) -> OneVector<P<ast::Item>> {
1313         let item = configure!(self, item);
1314
1315         let (attr, traits, mut item) = self.classify_item(item);
1316         if attr.is_some() || !traits.is_empty() {
1317             let item = Annotatable::Item(item);
1318             return self.collect_attr(attr, traits, item, AstFragmentKind::Items).make_items();
1319         }
1320
1321         match item.node {
1322             ast::ItemKind::Mac(..) => {
1323                 self.check_attributes(&item.attrs);
1324                 item.and_then(|item| match item.node {
1325                     ItemKind::Mac(mac) => {
1326                         self.collect(AstFragmentKind::Items, InvocationKind::Bang {
1327                             mac,
1328                             ident: Some(item.ident),
1329                             span: item.span,
1330                         }).make_items()
1331                     }
1332                     _ => unreachable!(),
1333                 })
1334             }
1335             ast::ItemKind::Mod(ast::Mod { inner, .. }) => {
1336                 if item.ident == keywords::Invalid.ident() {
1337                     return self.fold_nameable(item);
1338                 }
1339
1340                 let orig_directory_ownership = self.cx.current_expansion.directory_ownership;
1341                 let mut module = (*self.cx.current_expansion.module).clone();
1342                 module.mod_path.push(item.ident);
1343
1344                 // Detect if this is an inline module (`mod m { ... }` as opposed to `mod m;`).
1345                 // In the non-inline case, `inner` is never the dummy span (c.f. `parse_item_mod`).
1346                 // Thus, if `inner` is the dummy span, we know the module is inline.
1347                 let inline_module = item.span.contains(inner) || inner.is_dummy();
1348
1349                 if inline_module {
1350                     if let Some(path) = attr::first_attr_value_str_by_name(&item.attrs, "path") {
1351                         self.cx.current_expansion.directory_ownership =
1352                             DirectoryOwnership::Owned { relative: None };
1353                         module.directory.push(&*path.as_str());
1354                     } else {
1355                         module.directory.push(&*item.ident.as_str());
1356                     }
1357                 } else {
1358                     let path = self.cx.parse_sess.codemap().span_to_unmapped_path(inner);
1359                     let mut path = match path {
1360                         FileName::Real(path) => path,
1361                         other => PathBuf::from(other.to_string()),
1362                     };
1363                     let directory_ownership = match path.file_name().unwrap().to_str() {
1364                         Some("mod.rs") => DirectoryOwnership::Owned { relative: None },
1365                         Some(_) => DirectoryOwnership::Owned {
1366                             relative: Some(item.ident),
1367                         },
1368                         None => DirectoryOwnership::UnownedViaMod(false),
1369                     };
1370                     path.pop();
1371                     module.directory = path;
1372                     self.cx.current_expansion.directory_ownership = directory_ownership;
1373                 }
1374
1375                 let orig_module =
1376                     mem::replace(&mut self.cx.current_expansion.module, Rc::new(module));
1377                 let result = self.fold_nameable(item);
1378                 self.cx.current_expansion.module = orig_module;
1379                 self.cx.current_expansion.directory_ownership = orig_directory_ownership;
1380                 result
1381             }
1382             // Ensure that test functions are accessible from the test harness.
1383             // #[test] fn foo() {}
1384             // becomes:
1385             // #[test] pub fn foo_gensym(){}
1386             // #[allow(unused)]
1387             // use foo_gensym as foo;
1388             ast::ItemKind::Fn(..) if self.cx.ecfg.should_test => {
1389                 if self.tests_nameable && item.attrs.iter().any(|attr| is_test_or_bench(attr)) {
1390                     let orig_ident = item.ident;
1391                     let orig_vis   = item.vis.clone();
1392
1393                     // Publicize the item under gensymed name to avoid pollution
1394                     item = item.map(|mut item| {
1395                         item.vis = respan(item.vis.span, ast::VisibilityKind::Public);
1396                         item.ident = item.ident.gensym();
1397                         item
1398                     });
1399
1400                     // Use the gensymed name under the item's original visibility
1401                     let mut use_item = self.cx.item_use_simple_(
1402                         item.ident.span,
1403                         orig_vis,
1404                         Some(orig_ident),
1405                         self.cx.path(item.ident.span,
1406                             vec![keywords::SelfValue.ident(), item.ident]));
1407
1408                     // #[allow(unused)] because the test function probably isn't being referenced
1409                     use_item = use_item.map(|mut ui| {
1410                         ui.attrs.push(
1411                             self.cx.attribute(DUMMY_SP, attr::mk_list_item(DUMMY_SP,
1412                                 Ident::from_str("allow"), vec![
1413                                     attr::mk_nested_word_item(Ident::from_str("unused"))
1414                                 ]
1415                             ))
1416                         );
1417
1418                         ui
1419                     });
1420
1421                     OneVector::many(
1422                         self.fold_unnameable(item).into_iter()
1423                             .chain(self.fold_unnameable(use_item)))
1424                 } else {
1425                     self.fold_unnameable(item)
1426                 }
1427             }
1428             _ => self.fold_unnameable(item),
1429         }
1430     }
1431
1432     fn fold_trait_item(&mut self, item: ast::TraitItem) -> OneVector<ast::TraitItem> {
1433         let item = configure!(self, item);
1434
1435         let (attr, traits, item) = self.classify_item(item);
1436         if attr.is_some() || !traits.is_empty() {
1437             let item = Annotatable::TraitItem(P(item));
1438             return self.collect_attr(attr, traits, item, AstFragmentKind::TraitItems)
1439                 .make_trait_items()
1440         }
1441
1442         match item.node {
1443             ast::TraitItemKind::Macro(mac) => {
1444                 let ast::TraitItem { attrs, span, .. } = item;
1445                 self.check_attributes(&attrs);
1446                 self.collect_bang(mac, span, AstFragmentKind::TraitItems).make_trait_items()
1447             }
1448             _ => fold::noop_fold_trait_item(item, self),
1449         }
1450     }
1451
1452     fn fold_impl_item(&mut self, item: ast::ImplItem) -> OneVector<ast::ImplItem> {
1453         let item = configure!(self, item);
1454
1455         let (attr, traits, item) = self.classify_item(item);
1456         if attr.is_some() || !traits.is_empty() {
1457             let item = Annotatable::ImplItem(P(item));
1458             return self.collect_attr(attr, traits, item, AstFragmentKind::ImplItems)
1459                 .make_impl_items();
1460         }
1461
1462         match item.node {
1463             ast::ImplItemKind::Macro(mac) => {
1464                 let ast::ImplItem { attrs, span, .. } = item;
1465                 self.check_attributes(&attrs);
1466                 self.collect_bang(mac, span, AstFragmentKind::ImplItems).make_impl_items()
1467             }
1468             _ => fold::noop_fold_impl_item(item, self),
1469         }
1470     }
1471
1472     fn fold_ty(&mut self, ty: P<ast::Ty>) -> P<ast::Ty> {
1473         let ty = match ty.node {
1474             ast::TyKind::Mac(_) => ty.into_inner(),
1475             _ => return fold::noop_fold_ty(ty, self),
1476         };
1477
1478         match ty.node {
1479             ast::TyKind::Mac(mac) => self.collect_bang(mac, ty.span, AstFragmentKind::Ty).make_ty(),
1480             _ => unreachable!(),
1481         }
1482     }
1483
1484     fn fold_foreign_mod(&mut self, foreign_mod: ast::ForeignMod) -> ast::ForeignMod {
1485         noop_fold_foreign_mod(self.cfg.configure_foreign_mod(foreign_mod), self)
1486     }
1487
1488     fn fold_foreign_item(&mut self,
1489                          foreign_item: ast::ForeignItem) -> OneVector<ast::ForeignItem> {
1490         let (attr, traits, foreign_item) = self.classify_item(foreign_item);
1491
1492         if attr.is_some() || !traits.is_empty() {
1493             let item = Annotatable::ForeignItem(P(foreign_item));
1494             return self.collect_attr(attr, traits, item, AstFragmentKind::ForeignItems)
1495                 .make_foreign_items();
1496         }
1497
1498         if let ast::ForeignItemKind::Macro(mac) = foreign_item.node {
1499             self.check_attributes(&foreign_item.attrs);
1500             return self.collect_bang(mac, foreign_item.span, AstFragmentKind::ForeignItems)
1501                 .make_foreign_items();
1502         }
1503
1504         noop_fold_foreign_item(foreign_item, self)
1505     }
1506
1507     fn fold_item_kind(&mut self, item: ast::ItemKind) -> ast::ItemKind {
1508         match item {
1509             ast::ItemKind::MacroDef(..) => item,
1510             _ => noop_fold_item_kind(self.cfg.configure_item_kind(item), self),
1511         }
1512     }
1513
1514     fn fold_generic_param(&mut self, param: ast::GenericParam) -> ast::GenericParam {
1515         self.cfg.disallow_cfg_on_generic_param(&param);
1516         noop_fold_generic_param(param, self)
1517     }
1518
1519     fn fold_attribute(&mut self, at: ast::Attribute) -> Option<ast::Attribute> {
1520         // turn `#[doc(include="filename")]` attributes into `#[doc(include(file="filename",
1521         // contents="file contents")]` attributes
1522         if !at.check_name("doc") {
1523             return noop_fold_attribute(at, self);
1524         }
1525
1526         if let Some(list) = at.meta_item_list() {
1527             if !list.iter().any(|it| it.check_name("include")) {
1528                 return noop_fold_attribute(at, self);
1529             }
1530
1531             let mut items = vec![];
1532
1533             for it in list {
1534                 if !it.check_name("include") {
1535                     items.push(noop_fold_meta_list_item(it, self));
1536                     continue;
1537                 }
1538
1539                 if let Some(file) = it.value_str() {
1540                     let err_count = self.cx.parse_sess.span_diagnostic.err_count();
1541                     self.check_attribute(&at);
1542                     if self.cx.parse_sess.span_diagnostic.err_count() > err_count {
1543                         // avoid loading the file if they haven't enabled the feature
1544                         return noop_fold_attribute(at, self);
1545                     }
1546
1547                     let mut buf = vec![];
1548                     let filename = self.cx.root_path.join(file.to_string());
1549
1550                     match File::open(&filename).and_then(|mut f| f.read_to_end(&mut buf)) {
1551                         Ok(..) => {}
1552                         Err(e) => {
1553                             self.cx.span_err(at.span,
1554                                              &format!("couldn't read {}: {}",
1555                                                       filename.display(),
1556                                                       e));
1557                         }
1558                     }
1559
1560                     match String::from_utf8(buf) {
1561                         Ok(src) => {
1562                             let src_interned = Symbol::intern(&src);
1563
1564                             // Add this input file to the code map to make it available as
1565                             // dependency information
1566                             self.cx.codemap().new_filemap(filename.into(), src);
1567
1568                             let include_info = vec![
1569                                 dummy_spanned(ast::NestedMetaItemKind::MetaItem(
1570                                         attr::mk_name_value_item_str(Ident::from_str("file"),
1571                                                                      dummy_spanned(file)))),
1572                                 dummy_spanned(ast::NestedMetaItemKind::MetaItem(
1573                                         attr::mk_name_value_item_str(Ident::from_str("contents"),
1574                                                             dummy_spanned(src_interned)))),
1575                             ];
1576
1577                             let include_ident = Ident::from_str("include");
1578                             let item = attr::mk_list_item(DUMMY_SP, include_ident, include_info);
1579                             items.push(dummy_spanned(ast::NestedMetaItemKind::MetaItem(item)));
1580                         }
1581                         Err(_) => {
1582                             self.cx.span_err(at.span,
1583                                              &format!("{} wasn't a utf-8 file",
1584                                                       filename.display()));
1585                         }
1586                     }
1587                 } else {
1588                     items.push(noop_fold_meta_list_item(it, self));
1589                 }
1590             }
1591
1592             let meta = attr::mk_list_item(DUMMY_SP, Ident::from_str("doc"), items);
1593             match at.style {
1594                 ast::AttrStyle::Inner =>
1595                     Some(attr::mk_spanned_attr_inner(at.span, at.id, meta)),
1596                 ast::AttrStyle::Outer =>
1597                     Some(attr::mk_spanned_attr_outer(at.span, at.id, meta)),
1598             }
1599         } else {
1600             noop_fold_attribute(at, self)
1601         }
1602     }
1603
1604     fn new_id(&mut self, id: ast::NodeId) -> ast::NodeId {
1605         if self.monotonic {
1606             assert_eq!(id, ast::DUMMY_NODE_ID);
1607             self.cx.resolver.next_node_id()
1608         } else {
1609             id
1610         }
1611     }
1612 }
1613
1614 pub struct ExpansionConfig<'feat> {
1615     pub crate_name: String,
1616     pub features: Option<&'feat Features>,
1617     pub recursion_limit: usize,
1618     pub trace_mac: bool,
1619     pub should_test: bool, // If false, strip `#[test]` nodes
1620     pub single_step: bool,
1621     pub keep_macs: bool,
1622 }
1623
1624 macro_rules! feature_tests {
1625     ($( fn $getter:ident = $field:ident, )*) => {
1626         $(
1627             pub fn $getter(&self) -> bool {
1628                 match self.features {
1629                     Some(&Features { $field: true, .. }) => true,
1630                     _ => false,
1631                 }
1632             }
1633         )*
1634     }
1635 }
1636
1637 impl<'feat> ExpansionConfig<'feat> {
1638     pub fn default(crate_name: String) -> ExpansionConfig<'static> {
1639         ExpansionConfig {
1640             crate_name,
1641             features: None,
1642             recursion_limit: 1024,
1643             trace_mac: false,
1644             should_test: false,
1645             single_step: false,
1646             keep_macs: false,
1647         }
1648     }
1649
1650     feature_tests! {
1651         fn enable_quotes = quote,
1652         fn enable_asm = asm,
1653         fn enable_global_asm = global_asm,
1654         fn enable_log_syntax = log_syntax,
1655         fn enable_concat_idents = concat_idents,
1656         fn enable_trace_macros = trace_macros,
1657         fn enable_allow_internal_unstable = allow_internal_unstable,
1658         fn enable_custom_derive = custom_derive,
1659         fn enable_format_args_nl = format_args_nl,
1660         fn macros_in_extern_enabled = macros_in_extern,
1661         fn proc_macro_mod = proc_macro_mod,
1662         fn proc_macro_gen = proc_macro_gen,
1663         fn proc_macro_expr = proc_macro_expr,
1664         fn proc_macro_non_items = proc_macro_non_items,
1665     }
1666 }
1667
1668 // A Marker adds the given mark to the syntax context.
1669 #[derive(Debug)]
1670 pub struct Marker(pub Mark);
1671
1672 impl Folder for Marker {
1673     fn new_span(&mut self, span: Span) -> Span {
1674         span.apply_mark(self.0)
1675     }
1676
1677     fn fold_mac(&mut self, mac: ast::Mac) -> ast::Mac {
1678         noop_fold_mac(mac, self)
1679     }
1680 }