src/libsyntax/ext/expand.rs

   1 use crate::ast::{self, Block, Ident, LitKind, NodeId, PatKind, Path};
   2 use crate::ast::{MacStmtStyle, StmtKind, ItemKind};
   3 use crate::attr::{self, HasAttrs};
   4 use crate::source_map::{ExpnInfo, MacroBang, MacroAttribute, dummy_spanned, respan};
   5 use crate::config::StripUnconfigured;
   6 use crate::ext::base::*;
   7 use crate::ext::derive::{add_derived_markers, collect_derives};
   8 use crate::ext::hygiene::{Mark, SyntaxContext};
   9 use crate::ext::placeholders::{placeholder, PlaceholderExpander};
  10 use crate::feature_gate::{self, Features, GateIssue, is_builtin_attr, emit_feature_err};
  11 use crate::mut_visit::*;
  12 use crate::parse::{DirectoryOwnership, PResult, ParseSess};
  13 use crate::parse::token;
  14 use crate::parse::parser::Parser;
  15 use crate::ptr::P;
  16 use crate::symbol::Symbol;
  17 use crate::symbol::{kw, sym};
  18 use crate::tokenstream::{TokenStream, TokenTree};
  19 use crate::visit::{self, Visitor};
  20 use crate::util::map_in_place::MapInPlace;
  21
  22 use errors::{Applicability, FatalError};
  23 use smallvec::{smallvec, SmallVec};
  24 use syntax_pos::{Span, DUMMY_SP, FileName};
  25 use syntax_pos::hygiene::ExpnFormat;
  26
  27 use rustc_data_structures::fx::FxHashMap;
  28 use rustc_data_structures::sync::Lrc;
  29 use std::fs;
  30 use std::io::ErrorKind;
  31 use std::{iter, mem};
  32 use std::ops::DerefMut;
  33 use std::rc::Rc;
  34 use std::path::PathBuf;
  35
  36 macro_rules! ast_fragments {
  37     (
  38         $($Kind:ident($AstTy:ty) {
  39             $kind_name:expr;
  40             $(one fn $mut_visit_ast:ident; fn $visit_ast:ident;)?
  41             $(many fn $flat_map_ast_elt:ident; fn $visit_ast_elt:ident;)?
  42             fn $make_ast:ident;
  43         })*
  44     ) => {
  45         /// A fragment of AST that can be produced by a single macro expansion.
  46         /// Can also serve as an input and intermediate result for macro expansion operations.
  47         pub enum AstFragment {
  48             OptExpr(Option<P<ast::Expr>>),
  49             $($Kind($AstTy),)*
  50         }
  51
  52         /// "Discriminant" of an AST fragment.
  53         #[derive(Copy, Clone, PartialEq, Eq)]
  54         pub enum AstFragmentKind {
  55             OptExpr,
  56             $($Kind,)*
  57         }
  58
  59         impl AstFragmentKind {
  60             pub fn name(self) -> &'static str {
  61                 match self {
  62                     AstFragmentKind::OptExpr => "expression",
  63                     $(AstFragmentKind::$Kind => $kind_name,)*
  64                 }
  65             }
  66
  67             fn make_from<'a>(self, result: Box<dyn MacResult + 'a>) -> Option<AstFragment> {
  68                 match self {
  69                     AstFragmentKind::OptExpr =>
  70                         result.make_expr().map(Some).map(AstFragment::OptExpr),
  71                     $(AstFragmentKind::$Kind => result.$make_ast().map(AstFragment::$Kind),)*
  72                 }
  73             }
  74         }
  75
  76         impl AstFragment {
  77             pub fn make_opt_expr(self) -> Option<P<ast::Expr>> {
  78                 match self {
  79                     AstFragment::OptExpr(expr) => expr,
  80                     _ => panic!("AstFragment::make_* called on the wrong kind of fragment"),
  81                 }
  82             }
  83
  84             $(pub fn $make_ast(self) -> $AstTy {
  85                 match self {
  86                     AstFragment::$Kind(ast) => ast,
  87                     _ => panic!("AstFragment::make_* called on the wrong kind of fragment"),
  88                 }
  89             })*
  90
  91             pub fn mut_visit_with<F: MutVisitor>(&mut self, vis: &mut F) {
  92                 match self {
  93                     AstFragment::OptExpr(opt_expr) => {
  94                         visit_clobber(opt_expr, |opt_expr| {
  95                             if let Some(expr) = opt_expr {
  96                                 vis.filter_map_expr(expr)
  97                             } else {
  98                                 None
  99                             }
 100                         });
 101                     }
 102                     $($(AstFragment::$Kind(ast) => vis.$mut_visit_ast(ast),)*)*
 103                     $($(AstFragment::$Kind(ast) =>
 104                         ast.flat_map_in_place(|ast| vis.$flat_map_ast_elt(ast)),)*)*
 105                 }
 106             }
 107
 108             pub fn visit_with<'a, V: Visitor<'a>>(&'a self, visitor: &mut V) {
 109                 match *self {
 110                     AstFragment::OptExpr(Some(ref expr)) => visitor.visit_expr(expr),
 111                     AstFragment::OptExpr(None) => {}
 112                     $($(AstFragment::$Kind(ref ast) => visitor.$visit_ast(ast),)*)*
 113                     $($(AstFragment::$Kind(ref ast) => for ast_elt in &ast[..] {
 114                         visitor.$visit_ast_elt(ast_elt);
 115                     })*)*
 116                 }
 117             }
 118         }
 119
 120         impl<'a, 'b> MutVisitor for MacroExpander<'a, 'b> {
 121             fn filter_map_expr(&mut self, expr: P<ast::Expr>) -> Option<P<ast::Expr>> {
 122                 self.expand_fragment(AstFragment::OptExpr(Some(expr))).make_opt_expr()
 123             }
 124             $($(fn $mut_visit_ast(&mut self, ast: &mut $AstTy) {
 125                 visit_clobber(ast, |ast| self.expand_fragment(AstFragment::$Kind(ast)).$make_ast());
 126             })*)*
 127             $($(fn $flat_map_ast_elt(&mut self, ast_elt: <$AstTy as IntoIterator>::Item) -> $AstTy {
 128                 self.expand_fragment(AstFragment::$Kind(smallvec![ast_elt])).$make_ast()
 129             })*)*
 130         }
 131
 132         impl<'a> MacResult for crate::ext::tt::macro_rules::ParserAnyMacro<'a> {
 133             $(fn $make_ast(self: Box<crate::ext::tt::macro_rules::ParserAnyMacro<'a>>)
 134                            -> Option<$AstTy> {
 135                 Some(self.make(AstFragmentKind::$Kind).$make_ast())
 136             })*
 137         }
 138     }
 139 }
 140
 141 ast_fragments! {
 142     Expr(P<ast::Expr>) { "expression"; one fn visit_expr; fn visit_expr; fn make_expr; }
 143     Pat(P<ast::Pat>) { "pattern"; one fn visit_pat; fn visit_pat; fn make_pat; }
 144     Ty(P<ast::Ty>) { "type"; one fn visit_ty; fn visit_ty; fn make_ty; }
 145     Stmts(SmallVec<[ast::Stmt; 1]>) {
 146         "statement"; many fn flat_map_stmt; fn visit_stmt; fn make_stmts;
 147     }
 148     Items(SmallVec<[P<ast::Item>; 1]>) {
 149         "item"; many fn flat_map_item; fn visit_item; fn make_items;
 150     }
 151     TraitItems(SmallVec<[ast::TraitItem; 1]>) {
 152         "trait item"; many fn flat_map_trait_item; fn visit_trait_item; fn make_trait_items;
 153     }
 154     ImplItems(SmallVec<[ast::ImplItem; 1]>) {
 155         "impl item"; many fn flat_map_impl_item; fn visit_impl_item; fn make_impl_items;
 156     }
 157     ForeignItems(SmallVec<[ast::ForeignItem; 1]>) {
 158         "foreign item"; many fn flat_map_foreign_item; fn visit_foreign_item; fn make_foreign_items;
 159     }
 160 }
 161
 162 impl AstFragmentKind {
 163     fn dummy(self, span: Span) -> Option<AstFragment> {
 164         self.make_from(DummyResult::any(span))
 165     }
 166
 167     fn expect_from_annotatables<I: IntoIterator<Item = Annotatable>>(self, items: I)
 168                                                                      -> AstFragment {
 169         let mut items = items.into_iter();
 170         match self {
 171             AstFragmentKind::Items =>
 172                 AstFragment::Items(items.map(Annotatable::expect_item).collect()),
 173             AstFragmentKind::ImplItems =>
 174                 AstFragment::ImplItems(items.map(Annotatable::expect_impl_item).collect()),
 175             AstFragmentKind::TraitItems =>
 176                 AstFragment::TraitItems(items.map(Annotatable::expect_trait_item).collect()),
 177             AstFragmentKind::ForeignItems =>
 178                 AstFragment::ForeignItems(items.map(Annotatable::expect_foreign_item).collect()),
 179             AstFragmentKind::Stmts =>
 180                 AstFragment::Stmts(items.map(Annotatable::expect_stmt).collect()),
 181             AstFragmentKind::Expr => AstFragment::Expr(
 182                 items.next().expect("expected exactly one expression").expect_expr()
 183             ),
 184             AstFragmentKind::OptExpr =>
 185                 AstFragment::OptExpr(items.next().map(Annotatable::expect_expr)),
 186             AstFragmentKind::Pat | AstFragmentKind::Ty =>
 187                 panic!("patterns and types aren't annotatable"),
 188         }
 189     }
 190 }
 191
 192 fn macro_bang_format(path: &ast::Path) -> ExpnFormat {
 193     // We don't want to format a path using pretty-printing,
 194     // `format!("{}", path)`, because that tries to insert
 195     // line-breaks and is slow.
 196     let mut path_str = String::with_capacity(64);
 197     for (i, segment) in path.segments.iter().enumerate() {
 198         if i != 0 {
 199             path_str.push_str("::");
 200         }
 201         if segment.ident.name != kw::PathRoot {
 202             path_str.push_str(&segment.ident.as_str())
 203         }
 204     }
 205
 206     MacroBang(Symbol::intern(&path_str))
 207 }
 208
 209 pub struct Invocation {
 210     pub kind: InvocationKind,
 211     fragment_kind: AstFragmentKind,
 212     pub expansion_data: ExpansionData,
 213 }
 214
 215 pub enum InvocationKind {
 216     Bang {
 217         mac: ast::Mac,
 218         ident: Option<Ident>,
 219         span: Span,
 220     },
 221     Attr {
 222         attr: Option<ast::Attribute>,
 223         traits: Vec<Path>,
 224         item: Annotatable,
 225         // We temporarily report errors for attribute macros placed after derives
 226         after_derive: bool,
 227     },
 228     Derive {
 229         path: Path,
 230         item: Annotatable,
 231     },
 232 }
 233
 234 impl Invocation {
 235     pub 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, // cf. `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.source_map().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(smallvec![P(ast::Item {
 271             attrs: krate.attrs,
 272             span: krate.span,
 273             node: ast::ItemKind::Mod(krate.module),
 274             ident: Ident::invalid(),
 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                     inline: true,
 292                 };
 293             },
 294             _ => unreachable!(),
 295         };
 296         self.cx.trace_macros_diag();
 297         krate
 298     }
 299
 300     // Fully expand all macro invocations in this AST fragment.
 301     fn expand_fragment(&mut self, input_fragment: AstFragment) -> AstFragment {
 302         let orig_expansion_data = self.cx.current_expansion.clone();
 303         self.cx.current_expansion.depth = 0;
 304
 305         // Collect all macro invocations and replace them with placeholders.
 306         let (mut fragment_with_placeholders, mut invocations)
 307             = self.collect_invocations(input_fragment, &[]);
 308
 309         // Optimization: if we resolve all imports now,
 310         // we'll be able to immediately resolve most of imported macros.
 311         self.resolve_imports();
 312
 313         // Resolve paths in all invocations and produce output expanded fragments for them, but
 314         // do not insert them into our input AST fragment yet, only store in `expanded_fragments`.
 315         // The output fragments also go through expansion recursively until no invocations are left.
 316         // Unresolved macros produce dummy outputs as a recovery measure.
 317         invocations.reverse();
 318         let mut expanded_fragments = Vec::new();
 319         let mut derives: FxHashMap<Mark, Vec<_>> = FxHashMap::default();
 320         let mut undetermined_invocations = Vec::new();
 321         let (mut progress, mut force) = (false, !self.monotonic);
 322         loop {
 323             let invoc = if let Some(invoc) = invocations.pop() {
 324                 invoc
 325             } else {
 326                 self.resolve_imports();
 327                 if undetermined_invocations.is_empty() { break }
 328                 invocations = mem::replace(&mut undetermined_invocations, Vec::new());
 329                 force = !mem::replace(&mut progress, false);
 330                 continue
 331             };
 332
 333             let scope =
 334                 if self.monotonic { invoc.expansion_data.mark } else { orig_expansion_data.mark };
 335             let ext = match self.cx.resolver.resolve_macro_invocation(&invoc, scope, force) {
 336                 Ok(ext) => Some(ext),
 337                 Err(Determinacy::Determined) => None,
 338                 Err(Determinacy::Undetermined) => {
 339                     undetermined_invocations.push(invoc);
 340                     continue
 341                 }
 342             };
 343
 344             progress = true;
 345             let ExpansionData { depth, mark, .. } = invoc.expansion_data;
 346             self.cx.current_expansion = invoc.expansion_data.clone();
 347
 348             self.cx.current_expansion.mark = scope;
 349             // FIXME(jseyfried): Refactor out the following logic
 350             let (expanded_fragment, new_invocations) = if let Some(ext) = ext {
 351                 if let Some(ext) = ext {
 352                     let (invoc_fragment_kind, invoc_span) = (invoc.fragment_kind, invoc.span());
 353                     let fragment = self.expand_invoc(invoc, &*ext).unwrap_or_else(|| {
 354                         invoc_fragment_kind.dummy(invoc_span).unwrap()
 355                     });
 356                     self.collect_invocations(fragment, &[])
 357                 } else if let InvocationKind::Attr { attr: None, traits, item, .. } = invoc.kind {
 358                     if !item.derive_allowed() {
 359                         let attr = attr::find_by_name(item.attrs(), sym::derive)
 360                             .expect("`derive` attribute should exist");
 361                         let span = attr.span;
 362                         let mut err = self.cx.mut_span_err(span,
 363                                                            "`derive` may only be applied to \
 364                                                             structs, enums and unions");
 365                         if let ast::AttrStyle::Inner = attr.style {
 366                             let trait_list = traits.iter()
 367                                 .map(|t| t.to_string()).collect::<Vec<_>>();
 368                             let suggestion = format!("#[derive({})]", trait_list.join(", "));
 369                             err.span_suggestion(
 370                                 span, "try an outer attribute", suggestion,
 371                                 // We don't 𝑘𝑛𝑜𝑤 that the following item is an ADT
 372                                 Applicability::MaybeIncorrect
 373                             );
 374                         }
 375                         err.emit();
 376                     }
 377
 378                     let mut item = self.fully_configure(item);
 379                     item.visit_attrs(|attrs| attrs.retain(|a| a.path != sym::derive));
 380                     let mut item_with_markers = item.clone();
 381                     add_derived_markers(&mut self.cx, item.span(), &traits, &mut item_with_markers);
 382                     let derives = derives.entry(invoc.expansion_data.mark).or_default();
 383
 384                     derives.reserve(traits.len());
 385                     invocations.reserve(traits.len());
 386                     for path in &traits {
 387                         let mark = Mark::fresh(self.cx.current_expansion.mark);
 388                         derives.push(mark);
 389                         let item = match self.cx.resolver.resolve_macro_path(
 390                                 path, MacroKind::Derive, Mark::root(), Vec::new(), false) {
 391                             Ok(ext) => match *ext {
 392                                 BuiltinDerive(..) => item_with_markers.clone(),
 393                                 _ => item.clone(),
 394                             },
 395                             _ => item.clone(),
 396                         };
 397                         invocations.push(Invocation {
 398                             kind: InvocationKind::Derive { path: path.clone(), item: item },
 399                             fragment_kind: invoc.fragment_kind,
 400                             expansion_data: ExpansionData {
 401                                 mark,
 402                                 ..invoc.expansion_data.clone()
 403                             },
 404                         });
 405                     }
 406                     let fragment = invoc.fragment_kind
 407                         .expect_from_annotatables(::std::iter::once(item_with_markers));
 408                     self.collect_invocations(fragment, derives)
 409                 } else {
 410                     unreachable!()
 411                 }
 412             } else {
 413                 self.collect_invocations(invoc.fragment_kind.dummy(invoc.span()).unwrap(), &[])
 414             };
 415
 416             if expanded_fragments.len() < depth {
 417                 expanded_fragments.push(Vec::new());
 418             }
 419             expanded_fragments[depth - 1].push((mark, expanded_fragment));
 420             if !self.cx.ecfg.single_step {
 421                 invocations.extend(new_invocations.into_iter().rev());
 422             }
 423         }
 424
 425         self.cx.current_expansion = orig_expansion_data;
 426
 427         // Finally incorporate all the expanded macros into the input AST fragment.
 428         let mut placeholder_expander = PlaceholderExpander::new(self.cx, self.monotonic);
 429         while let Some(expanded_fragments) = expanded_fragments.pop() {
 430             for (mark, expanded_fragment) in expanded_fragments.into_iter().rev() {
 431                 let derives = derives.remove(&mark).unwrap_or_else(Vec::new);
 432                 placeholder_expander.add(NodeId::placeholder_from_mark(mark),
 433                                          expanded_fragment, derives);
 434             }
 435         }
 436         fragment_with_placeholders.mut_visit_with(&mut placeholder_expander);
 437         fragment_with_placeholders
 438     }
 439
 440     fn resolve_imports(&mut self) {
 441         if self.monotonic {
 442             self.cx.resolver.resolve_imports();
 443         }
 444     }
 445
 446     /// Collects all macro invocations reachable at this time in this AST fragment, and replace
 447     /// them with "placeholders" - dummy macro invocations with specially crafted `NodeId`s.
 448     /// Then call into resolver that builds a skeleton ("reduced graph") of the fragment and
 449     /// prepares data for resolving paths of macro invocations.
 450     fn collect_invocations(&mut self, mut fragment: AstFragment, derives: &[Mark])
 451                            -> (AstFragment, Vec<Invocation>) {
 452         // Resolve `$crate`s in the fragment for pretty-printing.
 453         self.cx.resolver.resolve_dollar_crates(&fragment);
 454
 455         let invocations = {
 456             let mut collector = InvocationCollector {
 457                 cfg: StripUnconfigured {
 458                     sess: self.cx.parse_sess,
 459                     features: self.cx.ecfg.features,
 460                 },
 461                 cx: self.cx,
 462                 invocations: Vec::new(),
 463                 monotonic: self.monotonic,
 464             };
 465             fragment.mut_visit_with(&mut collector);
 466             collector.invocations
 467         };
 468
 469         if self.monotonic {
 470             self.cx.resolver.visit_ast_fragment_with_placeholders(
 471                 self.cx.current_expansion.mark, &fragment, derives);
 472         }
 473
 474         (fragment, invocations)
 475     }
 476
 477     fn fully_configure(&mut self, item: Annotatable) -> Annotatable {
 478         let mut cfg = StripUnconfigured {
 479             sess: self.cx.parse_sess,
 480             features: self.cx.ecfg.features,
 481         };
 482         // Since the item itself has already been configured by the InvocationCollector,
 483         // we know that fold result vector will contain exactly one element
 484         match item {
 485             Annotatable::Item(item) => {
 486                 Annotatable::Item(cfg.flat_map_item(item).pop().unwrap())
 487             }
 488             Annotatable::TraitItem(item) => {
 489                 Annotatable::TraitItem(
 490                     item.map(|item| cfg.flat_map_trait_item(item).pop().unwrap()))
 491             }
 492             Annotatable::ImplItem(item) => {
 493                 Annotatable::ImplItem(item.map(|item| cfg.flat_map_impl_item(item).pop().unwrap()))
 494             }
 495             Annotatable::ForeignItem(item) => {
 496                 Annotatable::ForeignItem(
 497                     item.map(|item| cfg.flat_map_foreign_item(item).pop().unwrap())
 498                 )
 499             }
 500             Annotatable::Stmt(stmt) => {
 501                 Annotatable::Stmt(stmt.map(|stmt| cfg.flat_map_stmt(stmt).pop().unwrap()))
 502             }
 503             Annotatable::Expr(mut expr) => {
 504                 Annotatable::Expr({ cfg.visit_expr(&mut expr); expr })
 505             }
 506         }
 507     }
 508
 509     fn expand_invoc(&mut self, invoc: Invocation, ext: &SyntaxExtension) -> Option<AstFragment> {
 510         if invoc.fragment_kind == AstFragmentKind::ForeignItems &&
 511            !self.cx.ecfg.macros_in_extern_enabled() {
 512             if let SyntaxExtension::NonMacroAttr { .. } = *ext {} else {
 513                 emit_feature_err(&self.cx.parse_sess, sym::macros_in_extern,
 514                                  invoc.span(), GateIssue::Language,
 515                                  "macro invocations in `extern {}` blocks are experimental");
 516             }
 517         }
 518
 519         let result = match invoc.kind {
 520             InvocationKind::Bang { .. } => self.expand_bang_invoc(invoc, ext)?,
 521             InvocationKind::Attr { .. } => self.expand_attr_invoc(invoc, ext)?,
 522             InvocationKind::Derive { .. } => self.expand_derive_invoc(invoc, ext)?,
 523         };
 524
 525         if self.cx.current_expansion.depth > self.cx.ecfg.recursion_limit {
 526             let info = self.cx.current_expansion.mark.expn_info().unwrap();
 527             let suggested_limit = self.cx.ecfg.recursion_limit * 2;
 528             let mut err = self.cx.struct_span_err(info.call_site,
 529                 &format!("recursion limit reached while expanding the macro `{}`",
 530                          info.format.name()));
 531             err.help(&format!(
 532                 "consider adding a `#![recursion_limit=\"{}\"]` attribute to your crate",
 533                 suggested_limit));
 534             err.emit();
 535             self.cx.trace_macros_diag();
 536             FatalError.raise();
 537         }
 538
 539         Some(result)
 540     }
 541
 542     fn expand_attr_invoc(&mut self,
 543                          invoc: Invocation,
 544                          ext: &SyntaxExtension)
 545                          -> Option<AstFragment> {
 546         let (attr, mut item) = match invoc.kind {
 547             InvocationKind::Attr { attr, item, .. } => (attr?, item),
 548             _ => unreachable!(),
 549         };
 550
 551         if let NonMacroAttr { mark_used: false } = *ext {} else {
 552             // Macro attrs are always used when expanded,
 553             // non-macro attrs are considered used when the field says so.
 554             attr::mark_used(&attr);
 555         }
 556         invoc.expansion_data.mark.set_expn_info(ExpnInfo {
 557             call_site: attr.span,
 558             def_site: None,
 559             format: MacroAttribute(Symbol::intern(&attr.path.to_string())),
 560             allow_internal_unstable: None,
 561             allow_internal_unsafe: false,
 562             local_inner_macros: false,
 563             edition: ext.edition(self.cx.parse_sess.edition),
 564         });
 565
 566         match *ext {
 567             NonMacroAttr { .. } => {
 568                 attr::mark_known(&attr);
 569                 item.visit_attrs(|attrs| attrs.push(attr));
 570                 Some(invoc.fragment_kind.expect_from_annotatables(iter::once(item)))
 571             }
 572             MultiModifier(ref mac) => {
 573                 let meta = attr.parse_meta(self.cx.parse_sess)
 574                                .map_err(|mut e| { e.emit(); }).ok()?;
 575                 let item = mac.expand(self.cx, attr.span, &meta, item);
 576                 Some(invoc.fragment_kind.expect_from_annotatables(item))
 577             }
 578             MultiDecorator(ref mac) => {
 579                 let mut items = Vec::new();
 580                 let meta = attr.parse_meta(self.cx.parse_sess)
 581                                .expect("derive meta should already have been parsed");
 582                 mac.expand(self.cx, attr.span, &meta, &item, &mut |item| items.push(item));
 583                 items.push(item);
 584                 Some(invoc.fragment_kind.expect_from_annotatables(items))
 585             }
 586             AttrProcMacro(ref mac, ..) => {
 587                 self.gate_proc_macro_attr_item(attr.span, &item);
 588                 let item_tok = TokenTree::token(token::Interpolated(Lrc::new(match item {
 589                     Annotatable::Item(item) => token::NtItem(item),
 590                     Annotatable::TraitItem(item) => token::NtTraitItem(item.into_inner()),
 591                     Annotatable::ImplItem(item) => token::NtImplItem(item.into_inner()),
 592                     Annotatable::ForeignItem(item) => token::NtForeignItem(item.into_inner()),
 593                     Annotatable::Stmt(stmt) => token::NtStmt(stmt.into_inner()),
 594                     Annotatable::Expr(expr) => token::NtExpr(expr),
 595                 })), DUMMY_SP).into();
 596                 let input = self.extract_proc_macro_attr_input(attr.tokens, attr.span);
 597                 let tok_result = mac.expand(self.cx, attr.span, input, item_tok);
 598                 let res = self.parse_ast_fragment(tok_result, invoc.fragment_kind,
 599                                                   &attr.path, attr.span);
 600                 self.gate_proc_macro_expansion(attr.span, &res);
 601                 res
 602             }
 603             ProcMacroDerive(..) | BuiltinDerive(..) => {
 604                 self.cx.span_err(attr.span, &format!("`{}` is a derive macro", attr.path));
 605                 self.cx.trace_macros_diag();
 606                 invoc.fragment_kind.dummy(attr.span)
 607             }
 608             _ => {
 609                 let msg = &format!("macro `{}` may not be used in attributes", attr.path);
 610                 self.cx.span_err(attr.span, msg);
 611                 self.cx.trace_macros_diag();
 612                 invoc.fragment_kind.dummy(attr.span)
 613             }
 614         }
 615     }
 616
 617     fn extract_proc_macro_attr_input(&self, tokens: TokenStream, span: Span) -> TokenStream {
 618         let mut trees = tokens.trees();
 619         match trees.next() {
 620             Some(TokenTree::Delimited(_, _, tts)) => {
 621                 if trees.next().is_none() {
 622                     return tts.into()
 623                 }
 624             }
 625             Some(TokenTree::Token(..)) => {}
 626             None => return TokenStream::empty(),
 627         }
 628         self.cx.span_err(span, "custom attribute invocations must be \
 629             of the form #[foo] or #[foo(..)], the macro name must only be \
 630             followed by a delimiter token");
 631         TokenStream::empty()
 632     }
 633
 634     fn gate_proc_macro_attr_item(&self, span: Span, item: &Annotatable) {
 635         let (kind, gate) = match *item {
 636             Annotatable::Item(ref item) => {
 637                 match item.node {
 638                     ItemKind::Mod(_) if self.cx.ecfg.proc_macro_hygiene() => return,
 639                     ItemKind::Mod(_) => ("modules", sym::proc_macro_hygiene),
 640                     _ => return,
 641                 }
 642             }
 643             Annotatable::TraitItem(_) => return,
 644             Annotatable::ImplItem(_) => return,
 645             Annotatable::ForeignItem(_) => return,
 646             Annotatable::Stmt(_) |
 647             Annotatable::Expr(_) if self.cx.ecfg.proc_macro_hygiene() => return,
 648             Annotatable::Stmt(_) => ("statements", sym::proc_macro_hygiene),
 649             Annotatable::Expr(_) => ("expressions", sym::proc_macro_hygiene),
 650         };
 651         emit_feature_err(
 652             self.cx.parse_sess,
 653             gate,
 654             span,
 655             GateIssue::Language,
 656             &format!("custom attributes cannot be applied to {}", kind),
 657         );
 658     }
 659
 660     fn gate_proc_macro_expansion(&self, span: Span, fragment: &Option<AstFragment>) {
 661         if self.cx.ecfg.proc_macro_hygiene() {
 662             return
 663         }
 664         let fragment = match fragment {
 665             Some(fragment) => fragment,
 666             None => return,
 667         };
 668
 669         fragment.visit_with(&mut DisallowMacros {
 670             span,
 671             parse_sess: self.cx.parse_sess,
 672         });
 673
 674         struct DisallowMacros<'a> {
 675             span: Span,
 676             parse_sess: &'a ParseSess,
 677         }
 678
 679         impl<'ast, 'a> Visitor<'ast> for DisallowMacros<'a> {
 680             fn visit_item(&mut self, i: &'ast ast::Item) {
 681                 if let ast::ItemKind::MacroDef(_) = i.node {
 682                     emit_feature_err(
 683                         self.parse_sess,
 684                         sym::proc_macro_hygiene,
 685                         self.span,
 686                         GateIssue::Language,
 687                         "procedural macros cannot expand to macro definitions",
 688                     );
 689                 }
 690                 visit::walk_item(self, i);
 691             }
 692
 693             fn visit_mac(&mut self, _mac: &'ast ast::Mac) {
 694                 // ...
 695             }
 696         }
 697     }
 698
 699     /// Expand a macro invocation. Returns the resulting expanded AST fragment.
 700     fn expand_bang_invoc(&mut self,
 701                          invoc: Invocation,
 702                          ext: &SyntaxExtension)
 703                          -> Option<AstFragment> {
 704         let (mark, kind) = (invoc.expansion_data.mark, invoc.fragment_kind);
 705         let (mac, ident, span) = match invoc.kind {
 706             InvocationKind::Bang { mac, ident, span } => (mac, ident, span),
 707             _ => unreachable!(),
 708         };
 709         let path = &mac.node.path;
 710
 711         let ident = ident.unwrap_or_else(|| Ident::invalid());
 712         let validate_and_set_expn_info = |this: &mut Self, // arg instead of capture
 713                                           def_site_span: Option<Span>,
 714                                           allow_internal_unstable,
 715                                           allow_internal_unsafe,
 716                                           local_inner_macros,
 717                                           // can't infer this type
 718                                           unstable_feature: Option<(Symbol, u32)>,
 719                                           edition| {
 720
 721             // feature-gate the macro invocation
 722             if let Some((feature, issue)) = unstable_feature {
 723                 let crate_span = this.cx.current_expansion.crate_span.unwrap();
 724                 // don't stability-check macros in the same crate
 725                 // (the only time this is null is for syntax extensions registered as macros)
 726                 if def_site_span.map_or(false, |def_span| !crate_span.contains(def_span))
 727                     && !span.allows_unstable(feature)
 728                     && this.cx.ecfg.features.map_or(true, |feats| {
 729                     // macro features will count as lib features
 730                     !feats.declared_lib_features.iter().any(|&(feat, _)| feat == feature)
 731                 }) {
 732                     let explain = format!("macro {}! is unstable", path);
 733                     emit_feature_err(this.cx.parse_sess, feature, span,
 734                                      GateIssue::Library(Some(issue)), &explain);
 735                     this.cx.trace_macros_diag();
 736                 }
 737             }
 738
 739             if ident.name != kw::Invalid {
 740                 let msg = format!("macro {}! expects no ident argument, given '{}'", path, ident);
 741                 this.cx.span_err(path.span, &msg);
 742                 this.cx.trace_macros_diag();
 743                 return Err(kind.dummy(span));
 744             }
 745             mark.set_expn_info(ExpnInfo {
 746                 call_site: span,
 747                 def_site: def_site_span,
 748                 format: macro_bang_format(path),
 749                 allow_internal_unstable,
 750                 allow_internal_unsafe,
 751                 local_inner_macros,
 752                 edition,
 753             });
 754             Ok(())
 755         };
 756
 757         let opt_expanded = match *ext {
 758             DeclMacro { ref expander, def_info, edition, .. } => {
 759                 if let Err(dummy_span) = validate_and_set_expn_info(self, def_info.map(|(_, s)| s),
 760                                                                     None, false, false, None,
 761                                                                     edition) {
 762                     dummy_span
 763                 } else {
 764                     kind.make_from(expander.expand(self.cx, span, mac.node.stream(), None))
 765                 }
 766             }
 767
 768             NormalTT {
 769                 ref expander,
 770                 def_info,
 771                 ref allow_internal_unstable,
 772                 allow_internal_unsafe,
 773                 local_inner_macros,
 774                 unstable_feature,
 775                 edition,
 776             } => {
 777                 if let Err(dummy_span) = validate_and_set_expn_info(self, def_info.map(|(_, s)| s),
 778                                                                     allow_internal_unstable.clone(),
 779                                                                     allow_internal_unsafe,
 780                                                                     local_inner_macros,
 781                                                                     unstable_feature,
 782                                                                     edition) {
 783                     dummy_span
 784                 } else {
 785                     kind.make_from(expander.expand(
 786                         self.cx,
 787                         span,
 788                         mac.node.stream(),
 789                         def_info.map(|(_, s)| s),
 790                     ))
 791                 }
 792             }
 793
 794             IdentTT { ref expander, span: tt_span, ref allow_internal_unstable } => {
 795                 if ident.name == kw::Invalid {
 796                     self.cx.span_err(path.span,
 797                                     &format!("macro {}! expects an ident argument", path));
 798                     self.cx.trace_macros_diag();
 799                     kind.dummy(span)
 800                 } else {
 801                     invoc.expansion_data.mark.set_expn_info(ExpnInfo {
 802                         call_site: span,
 803                         def_site: tt_span,
 804                         format: macro_bang_format(path),
 805                         allow_internal_unstable: allow_internal_unstable.clone(),
 806                         allow_internal_unsafe: false,
 807                         local_inner_macros: false,
 808                         edition: self.cx.parse_sess.edition,
 809                     });
 810
 811                     let input: Vec<_> = mac.node.stream().into_trees().collect();
 812                     kind.make_from(expander.expand(self.cx, span, ident, input))
 813                 }
 814             }
 815
 816             MultiDecorator(..) | MultiModifier(..) |
 817             AttrProcMacro(..) | SyntaxExtension::NonMacroAttr { .. } => {
 818                 self.cx.span_err(path.span,
 819                                  &format!("`{}` can only be used in attributes", path));
 820                 self.cx.trace_macros_diag();
 821                 kind.dummy(span)
 822             }
 823
 824             ProcMacroDerive(..) | BuiltinDerive(..) => {
 825                 self.cx.span_err(path.span, &format!("`{}` is a derive macro", path));
 826                 self.cx.trace_macros_diag();
 827                 kind.dummy(span)
 828             }
 829
 830             SyntaxExtension::ProcMacro { ref expander, ref allow_internal_unstable, edition } => {
 831                 if ident.name != kw::Invalid {
 832                     let msg =
 833                         format!("macro {}! expects no ident argument, given '{}'", path, ident);
 834                     self.cx.span_err(path.span, &msg);
 835                     self.cx.trace_macros_diag();
 836                     kind.dummy(span)
 837                 } else {
 838                     self.gate_proc_macro_expansion_kind(span, kind);
 839                     invoc.expansion_data.mark.set_expn_info(ExpnInfo {
 840                         call_site: span,
 841                         // FIXME procedural macros do not have proper span info
 842                         // yet, when they do, we should use it here.
 843                         def_site: None,
 844                         format: macro_bang_format(path),
 845                         // FIXME probably want to follow macro_rules macros here.
 846                         allow_internal_unstable: allow_internal_unstable.clone(),
 847                         allow_internal_unsafe: false,
 848                         local_inner_macros: false,
 849                         edition,
 850                     });
 851
 852                     let tok_result = expander.expand(self.cx, span, mac.node.stream());
 853                     let result = self.parse_ast_fragment(tok_result, kind, path, span);
 854                     self.gate_proc_macro_expansion(span, &result);
 855                     result
 856                 }
 857             }
 858         };
 859
 860         if opt_expanded.is_some() {
 861             opt_expanded
 862         } else {
 863             let msg = format!("non-{kind} macro in {kind} position: {name}",
 864                               name = path.segments[0].ident.name, kind = kind.name());
 865             self.cx.span_err(path.span, &msg);
 866             self.cx.trace_macros_diag();
 867             kind.dummy(span)
 868         }
 869     }
 870
 871     fn gate_proc_macro_expansion_kind(&self, span: Span, kind: AstFragmentKind) {
 872         let kind = match kind {
 873             AstFragmentKind::Expr => "expressions",
 874             AstFragmentKind::OptExpr => "expressions",
 875             AstFragmentKind::Pat => "patterns",
 876             AstFragmentKind::Ty => "types",
 877             AstFragmentKind::Stmts => "statements",
 878             AstFragmentKind::Items => return,
 879             AstFragmentKind::TraitItems => return,
 880             AstFragmentKind::ImplItems => return,
 881             AstFragmentKind::ForeignItems => return,
 882         };
 883         if self.cx.ecfg.proc_macro_hygiene() {
 884             return
 885         }
 886         emit_feature_err(
 887             self.cx.parse_sess,
 888             sym::proc_macro_hygiene,
 889             span,
 890             GateIssue::Language,
 891             &format!("procedural macros cannot be expanded to {}", kind),
 892         );
 893     }
 894
 895     /// Expand a derive invocation. Returns the resulting expanded AST fragment.
 896     fn expand_derive_invoc(&mut self,
 897                            invoc: Invocation,
 898                            ext: &SyntaxExtension)
 899                            -> Option<AstFragment> {
 900         let (path, item) = match invoc.kind {
 901             InvocationKind::Derive { path, item } => (path, item),
 902             _ => unreachable!(),
 903         };
 904         if !item.derive_allowed() {
 905             return None;
 906         }
 907
 908         let pretty_name = Symbol::intern(&format!("derive({})", path));
 909         let span = path.span;
 910         let attr = ast::Attribute {
 911             path, span,
 912             tokens: TokenStream::empty(),
 913             // irrelevant:
 914             id: ast::AttrId(0), style: ast::AttrStyle::Outer, is_sugared_doc: false,
 915         };
 916
 917         let mut expn_info = ExpnInfo {
 918             call_site: span,
 919             def_site: None,
 920             format: MacroAttribute(pretty_name),
 921             allow_internal_unstable: None,
 922             allow_internal_unsafe: false,
 923             local_inner_macros: false,
 924             edition: ext.edition(self.cx.parse_sess.edition),
 925         };
 926
 927         match *ext {
 928             ProcMacroDerive(ref ext, ..) => {
 929                 invoc.expansion_data.mark.set_expn_info(expn_info);
 930                 let span = span.with_ctxt(self.cx.backtrace());
 931                 let dummy = ast::MetaItem { // FIXME(jseyfried) avoid this
 932                     path: Path::from_ident(Ident::invalid()),
 933                     span: DUMMY_SP,
 934                     node: ast::MetaItemKind::Word,
 935                 };
 936                 let items = ext.expand(self.cx, span, &dummy, item);
 937                 Some(invoc.fragment_kind.expect_from_annotatables(items))
 938             }
 939             BuiltinDerive(func) => {
 940                 expn_info.allow_internal_unstable = Some(vec![
 941                     sym::rustc_attrs,
 942                     Symbol::intern("derive_clone_copy"),
 943                     Symbol::intern("derive_eq"),
 944                     Symbol::intern("libstd_sys_internals"), // RustcDeserialize and RustcSerialize
 945                 ].into());
 946                 invoc.expansion_data.mark.set_expn_info(expn_info);
 947                 let span = span.with_ctxt(self.cx.backtrace());
 948                 let mut items = Vec::new();
 949                 func(self.cx, span, &attr.meta()?, &item, &mut |a| items.push(a));
 950                 Some(invoc.fragment_kind.expect_from_annotatables(items))
 951             }
 952             _ => {
 953                 let msg = &format!("macro `{}` may not be used for derive attributes", attr.path);
 954                 self.cx.span_err(span, msg);
 955                 self.cx.trace_macros_diag();
 956                 invoc.fragment_kind.dummy(span)
 957             }
 958         }
 959     }
 960
 961     fn parse_ast_fragment(&mut self,
 962                           toks: TokenStream,
 963                           kind: AstFragmentKind,
 964                           path: &Path,
 965                           span: Span)
 966                           -> Option<AstFragment> {
 967         let mut parser = self.cx.new_parser_from_tts(&toks.into_trees().collect::<Vec<_>>());
 968         match parser.parse_ast_fragment(kind, false) {
 969             Ok(fragment) => {
 970                 parser.ensure_complete_parse(path, kind.name(), span);
 971                 Some(fragment)
 972             }
 973             Err(mut err) => {
 974                 err.set_span(span);
 975                 err.emit();
 976                 self.cx.trace_macros_diag();
 977                 kind.dummy(span)
 978             }
 979         }
 980     }
 981 }
 982
 983 impl<'a> Parser<'a> {
 984     pub fn parse_ast_fragment(&mut self, kind: AstFragmentKind, macro_legacy_warnings: bool)
 985                               -> PResult<'a, AstFragment> {
 986         Ok(match kind {
 987             AstFragmentKind::Items => {
 988                 let mut items = SmallVec::new();
 989                 while let Some(item) = self.parse_item()? {
 990                     items.push(item);
 991                 }
 992                 AstFragment::Items(items)
 993             }
 994             AstFragmentKind::TraitItems => {
 995                 let mut items = SmallVec::new();
 996                 while self.token != token::Eof {
 997                     items.push(self.parse_trait_item(&mut false)?);
 998                 }
 999                 AstFragment::TraitItems(items)
1000             }
1001             AstFragmentKind::ImplItems => {
1002                 let mut items = SmallVec::new();
1003                 while self.token != token::Eof {
1004                     items.push(self.parse_impl_item(&mut false)?);
1005                 }
1006                 AstFragment::ImplItems(items)
1007             }
1008             AstFragmentKind::ForeignItems => {
1009                 let mut items = SmallVec::new();
1010                 while self.token != token::Eof {
1011                     items.push(self.parse_foreign_item()?);
1012                 }
1013                 AstFragment::ForeignItems(items)
1014             }
1015             AstFragmentKind::Stmts => {
1016                 let mut stmts = SmallVec::new();
1017                 while self.token != token::Eof &&
1018                       // won't make progress on a `}`
1019                       self.token != token::CloseDelim(token::Brace) {
1020                     if let Some(stmt) = self.parse_full_stmt(macro_legacy_warnings)? {
1021                         stmts.push(stmt);
1022                     }
1023                 }
1024                 AstFragment::Stmts(stmts)
1025             }
1026             AstFragmentKind::Expr => AstFragment::Expr(self.parse_expr()?),
1027             AstFragmentKind::OptExpr => {
1028                 if self.token != token::Eof {
1029                     AstFragment::OptExpr(Some(self.parse_expr()?))
1030                 } else {
1031                     AstFragment::OptExpr(None)
1032                 }
1033             },
1034             AstFragmentKind::Ty => AstFragment::Ty(self.parse_ty()?),
1035             AstFragmentKind::Pat => AstFragment::Pat(self.parse_pat(None)?),
1036         })
1037     }
1038
1039     pub fn ensure_complete_parse(&mut self, macro_path: &Path, kind_name: &str, span: Span) {
1040         if self.token != token::Eof {
1041             let msg = format!("macro expansion ignores token `{}` and any following",
1042                               self.this_token_to_string());
1043             // Avoid emitting backtrace info twice.
1044             let def_site_span = self.token.span.with_ctxt(SyntaxContext::empty());
1045             let mut err = self.diagnostic().struct_span_err(def_site_span, &msg);
1046             err.span_label(span, "caused by the macro expansion here");
1047             let msg = format!(
1048                 "the usage of `{}!` is likely invalid in {} context",
1049                 macro_path,
1050                 kind_name,
1051             );
1052             err.note(&msg);
1053             let semi_span = self.sess.source_map().next_point(span);
1054
1055             let semi_full_span = semi_span.to(self.sess.source_map().next_point(semi_span));
1056             match self.sess.source_map().span_to_snippet(semi_full_span) {
1057                 Ok(ref snippet) if &snippet[..] != ";" && kind_name == "expression" => {
1058                     err.span_suggestion(
1059                         semi_span,
1060                         "you might be missing a semicolon here",
1061                         ";".to_owned(),
1062                         Applicability::MaybeIncorrect,
1063                     );
1064                 }
1065                 _ => {}
1066             }
1067             err.emit();
1068         }
1069     }
1070 }
1071
1072 struct InvocationCollector<'a, 'b: 'a> {
1073     cx: &'a mut ExtCtxt<'b>,
1074     cfg: StripUnconfigured<'a>,
1075     invocations: Vec<Invocation>,
1076     monotonic: bool,
1077 }
1078
1079 impl<'a, 'b> InvocationCollector<'a, 'b> {
1080     fn collect(&mut self, fragment_kind: AstFragmentKind, kind: InvocationKind) -> AstFragment {
1081         let mark = Mark::fresh(self.cx.current_expansion.mark);
1082         self.invocations.push(Invocation {
1083             kind,
1084             fragment_kind,
1085             expansion_data: ExpansionData {
1086                 mark,
1087                 depth: self.cx.current_expansion.depth + 1,
1088                 ..self.cx.current_expansion.clone()
1089             },
1090         });
1091         placeholder(fragment_kind, NodeId::placeholder_from_mark(mark))
1092     }
1093
1094     fn collect_bang(&mut self, mac: ast::Mac, span: Span, kind: AstFragmentKind) -> AstFragment {
1095         self.collect(kind, InvocationKind::Bang { mac: mac, ident: None, span: span })
1096     }
1097
1098     fn collect_attr(&mut self,
1099                     attr: Option<ast::Attribute>,
1100                     traits: Vec<Path>,
1101                     item: Annotatable,
1102                     kind: AstFragmentKind,
1103                     after_derive: bool)
1104                     -> AstFragment {
1105         self.collect(kind, InvocationKind::Attr { attr, traits, item, after_derive })
1106     }
1107
1108     fn find_attr_invoc(&self, attrs: &mut Vec<ast::Attribute>, after_derive: &mut bool)
1109                        -> Option<ast::Attribute> {
1110         let attr = attrs.iter()
1111                         .position(|a| {
1112                             if a.path == sym::derive {
1113                                 *after_derive = true;
1114                             }
1115                             !attr::is_known(a) && !is_builtin_attr(a)
1116                         })
1117                         .map(|i| attrs.remove(i));
1118         if let Some(attr) = &attr {
1119             if !self.cx.ecfg.enable_custom_inner_attributes() &&
1120                attr.style == ast::AttrStyle::Inner && attr.path != sym::test {
1121                 emit_feature_err(&self.cx.parse_sess, sym::custom_inner_attributes,
1122                                  attr.span, GateIssue::Language,
1123                                  "non-builtin inner attributes are unstable");
1124             }
1125         }
1126         attr
1127     }
1128
1129     /// If `item` is an attr invocation, remove and return the macro attribute and derive traits.
1130     fn classify_item<T>(&mut self, item: &mut T)
1131                         -> (Option<ast::Attribute>, Vec<Path>, /* after_derive */ bool)
1132         where T: HasAttrs,
1133     {
1134         let (mut attr, mut traits, mut after_derive) = (None, Vec::new(), false);
1135
1136         item.visit_attrs(|mut attrs| {
1137             attr = self.find_attr_invoc(&mut attrs, &mut after_derive);
1138             traits = collect_derives(&mut self.cx, &mut attrs);
1139         });
1140
1141         (attr, traits, after_derive)
1142     }
1143
1144     /// Alternative to `classify_item()` that ignores `#[derive]` so invocations fallthrough
1145     /// to the unused-attributes lint (making it an error on statements and expressions
1146     /// is a breaking change)
1147     fn classify_nonitem<T: HasAttrs>(&mut self, nonitem: &mut T)
1148                                      -> (Option<ast::Attribute>, /* after_derive */ bool) {
1149         let (mut attr, mut after_derive) = (None, false);
1150
1151         nonitem.visit_attrs(|mut attrs| {
1152             attr = self.find_attr_invoc(&mut attrs, &mut after_derive);
1153         });
1154
1155         (attr, after_derive)
1156     }
1157
1158     fn configure<T: HasAttrs>(&mut self, node: T) -> Option<T> {
1159         self.cfg.configure(node)
1160     }
1161
1162     // Detect use of feature-gated or invalid attributes on macro invocations
1163     // since they will not be detected after macro expansion.
1164     fn check_attributes(&mut self, attrs: &[ast::Attribute]) {
1165         let features = self.cx.ecfg.features.unwrap();
1166         for attr in attrs.iter() {
1167             self.check_attribute_inner(attr, features);
1168
1169             // macros are expanded before any lint passes so this warning has to be hardcoded
1170             if attr.path == sym::derive {
1171                 self.cx.struct_span_warn(attr.span, "`#[derive]` does nothing on macro invocations")
1172                     .note("this may become a hard error in a future release")
1173                     .emit();
1174             }
1175         }
1176     }
1177
1178     fn check_attribute(&mut self, at: &ast::Attribute) {
1179         let features = self.cx.ecfg.features.unwrap();
1180         self.check_attribute_inner(at, features);
1181     }
1182
1183     fn check_attribute_inner(&mut self, at: &ast::Attribute, features: &Features) {
1184         feature_gate::check_attribute(at, self.cx.parse_sess, features);
1185     }
1186 }
1187
1188 impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
1189     fn visit_expr(&mut self, expr: &mut P<ast::Expr>) {
1190         self.cfg.configure_expr(expr);
1191         visit_clobber(expr.deref_mut(), |mut expr| {
1192             self.cfg.configure_expr_kind(&mut expr.node);
1193
1194             // ignore derives so they remain unused
1195             let (attr, after_derive) = self.classify_nonitem(&mut expr);
1196
1197             if attr.is_some() {
1198                 // Collect the invoc regardless of whether or not attributes are permitted here
1199                 // expansion will eat the attribute so it won't error later.
1200                 attr.as_ref().map(|a| self.cfg.maybe_emit_expr_attr_err(a));
1201
1202                 // AstFragmentKind::Expr requires the macro to emit an expression.
1203                 return self.collect_attr(attr, vec![], Annotatable::Expr(P(expr)),
1204                                           AstFragmentKind::Expr, after_derive)
1205                     .make_expr()
1206                     .into_inner()
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)
1212                     .make_expr()
1213                     .into_inner()
1214             } else {
1215                 noop_visit_expr(&mut expr, self);
1216                 expr
1217             }
1218         });
1219     }
1220
1221     fn filter_map_expr(&mut self, expr: P<ast::Expr>) -> Option<P<ast::Expr>> {
1222         let expr = configure!(self, expr);
1223         expr.filter_map(|mut expr| {
1224             self.cfg.configure_expr_kind(&mut expr.node);
1225
1226             // Ignore derives so they remain unused.
1227             let (attr, after_derive) = self.classify_nonitem(&mut expr);
1228
1229             if attr.is_some() {
1230                 attr.as_ref().map(|a| self.cfg.maybe_emit_expr_attr_err(a));
1231
1232                 return self.collect_attr(attr, vec![], Annotatable::Expr(P(expr)),
1233                                          AstFragmentKind::OptExpr, after_derive)
1234                     .make_opt_expr()
1235                     .map(|expr| expr.into_inner())
1236             }
1237
1238             if let ast::ExprKind::Mac(mac) = expr.node {
1239                 self.check_attributes(&expr.attrs);
1240                 self.collect_bang(mac, expr.span, AstFragmentKind::OptExpr)
1241                     .make_opt_expr()
1242                     .map(|expr| expr.into_inner())
1243             } else {
1244                 Some({ noop_visit_expr(&mut expr, self); expr })
1245             }
1246         })
1247     }
1248
1249     fn visit_pat(&mut self, pat: &mut P<ast::Pat>) {
1250         self.cfg.configure_pat(pat);
1251         match pat.node {
1252             PatKind::Mac(_) => {}
1253             _ => return noop_visit_pat(pat, self),
1254         }
1255
1256         visit_clobber(pat, |mut pat| {
1257             match mem::replace(&mut pat.node, PatKind::Wild) {
1258                 PatKind::Mac(mac) =>
1259                     self.collect_bang(mac, pat.span, AstFragmentKind::Pat).make_pat(),
1260                 _ => unreachable!(),
1261             }
1262         });
1263     }
1264
1265     fn flat_map_stmt(&mut self, stmt: ast::Stmt) -> SmallVec<[ast::Stmt; 1]> {
1266         let mut stmt = configure!(self, stmt);
1267
1268         // we'll expand attributes on expressions separately
1269         if !stmt.is_expr() {
1270             let (attr, derives, after_derive) = if stmt.is_item() {
1271                 self.classify_item(&mut stmt)
1272             } else {
1273                 // ignore derives on non-item statements so it falls through
1274                 // to the unused-attributes lint
1275                 let (attr, after_derive) = self.classify_nonitem(&mut stmt);
1276                 (attr, vec![], after_derive)
1277             };
1278
1279             if attr.is_some() || !derives.is_empty() {
1280                 return self.collect_attr(attr, derives, Annotatable::Stmt(P(stmt)),
1281                                          AstFragmentKind::Stmts, after_derive).make_stmts();
1282             }
1283         }
1284
1285         if let StmtKind::Mac(mac) = stmt.node {
1286             let (mac, style, attrs) = mac.into_inner();
1287             self.check_attributes(&attrs);
1288             let mut placeholder = self.collect_bang(mac, stmt.span, AstFragmentKind::Stmts)
1289                                         .make_stmts();
1290
1291             // If this is a macro invocation with a semicolon, then apply that
1292             // semicolon to the final statement produced by expansion.
1293             if style == MacStmtStyle::Semicolon {
1294                 if let Some(stmt) = placeholder.pop() {
1295                     placeholder.push(stmt.add_trailing_semicolon());
1296                 }
1297             }
1298
1299             return placeholder;
1300         }
1301
1302         // The placeholder expander gives ids to statements, so we avoid folding the id here.
1303         let ast::Stmt { id, node, span } = stmt;
1304         noop_flat_map_stmt_kind(node, self).into_iter().map(|node| {
1305             ast::Stmt { id, node, span }
1306         }).collect()
1307
1308     }
1309
1310     fn visit_block(&mut self, block: &mut P<Block>) {
1311         let old_directory_ownership = self.cx.current_expansion.directory_ownership;
1312         self.cx.current_expansion.directory_ownership = DirectoryOwnership::UnownedViaBlock;
1313         noop_visit_block(block, self);
1314         self.cx.current_expansion.directory_ownership = old_directory_ownership;
1315     }
1316
1317     fn flat_map_item(&mut self, item: P<ast::Item>) -> SmallVec<[P<ast::Item>; 1]> {
1318         let mut item = configure!(self, item);
1319
1320         let (attr, traits, after_derive) = self.classify_item(&mut item);
1321         if attr.is_some() || !traits.is_empty() {
1322             return self.collect_attr(attr, traits, Annotatable::Item(item),
1323                                      AstFragmentKind::Items, after_derive).make_items();
1324         }
1325
1326         match item.node {
1327             ast::ItemKind::Mac(..) => {
1328                 self.check_attributes(&item.attrs);
1329                 item.and_then(|item| match item.node {
1330                     ItemKind::Mac(mac) => {
1331                         self.collect(AstFragmentKind::Items, InvocationKind::Bang {
1332                             mac,
1333                             ident: Some(item.ident),
1334                             span: item.span,
1335                         }).make_items()
1336                     }
1337                     _ => unreachable!(),
1338                 })
1339             }
1340             ast::ItemKind::Mod(ast::Mod { inner, .. }) => {
1341                 if item.ident == Ident::invalid() {
1342                     return noop_flat_map_item(item, self);
1343                 }
1344
1345                 let orig_directory_ownership = self.cx.current_expansion.directory_ownership;
1346                 let mut module = (*self.cx.current_expansion.module).clone();
1347                 module.mod_path.push(item.ident);
1348
1349                 // Detect if this is an inline module (`mod m { ... }` as opposed to `mod m;`).
1350                 // In the non-inline case, `inner` is never the dummy span (cf. `parse_item_mod`).
1351                 // Thus, if `inner` is the dummy span, we know the module is inline.
1352                 let inline_module = item.span.contains(inner) || inner.is_dummy();
1353
1354                 if inline_module {
1355                     if let Some(path) = attr::first_attr_value_str_by_name(&item.attrs, sym::path) {
1356                         self.cx.current_expansion.directory_ownership =
1357                             DirectoryOwnership::Owned { relative: None };
1358                         module.directory.push(&*path.as_str());
1359                     } else {
1360                         module.directory.push(&*item.ident.as_str());
1361                     }
1362                 } else {
1363                     let path = self.cx.parse_sess.source_map().span_to_unmapped_path(inner);
1364                     let mut path = match path {
1365                         FileName::Real(path) => path,
1366                         other => PathBuf::from(other.to_string()),
1367                     };
1368                     let directory_ownership = match path.file_name().unwrap().to_str() {
1369                         Some("mod.rs") => DirectoryOwnership::Owned { relative: None },
1370                         Some(_) => DirectoryOwnership::Owned {
1371                             relative: Some(item.ident),
1372                         },
1373                         None => DirectoryOwnership::UnownedViaMod(false),
1374                     };
1375                     path.pop();
1376                     module.directory = path;
1377                     self.cx.current_expansion.directory_ownership = directory_ownership;
1378                 }
1379
1380                 let orig_module =
1381                     mem::replace(&mut self.cx.current_expansion.module, Rc::new(module));
1382                 let result = noop_flat_map_item(item, self);
1383                 self.cx.current_expansion.module = orig_module;
1384                 self.cx.current_expansion.directory_ownership = orig_directory_ownership;
1385                 result
1386             }
1387
1388             _ => noop_flat_map_item(item, self),
1389         }
1390     }
1391
1392     fn flat_map_trait_item(&mut self, item: ast::TraitItem) -> SmallVec<[ast::TraitItem; 1]> {
1393         let mut item = configure!(self, item);
1394
1395         let (attr, traits, after_derive) = self.classify_item(&mut item);
1396         if attr.is_some() || !traits.is_empty() {
1397             return self.collect_attr(attr, traits, Annotatable::TraitItem(P(item)),
1398                                      AstFragmentKind::TraitItems, after_derive).make_trait_items()
1399         }
1400
1401         match item.node {
1402             ast::TraitItemKind::Macro(mac) => {
1403                 let ast::TraitItem { attrs, span, .. } = item;
1404                 self.check_attributes(&attrs);
1405                 self.collect_bang(mac, span, AstFragmentKind::TraitItems).make_trait_items()
1406             }
1407             _ => noop_flat_map_trait_item(item, self),
1408         }
1409     }
1410
1411     fn flat_map_impl_item(&mut self, item: ast::ImplItem) -> SmallVec<[ast::ImplItem; 1]> {
1412         let mut item = configure!(self, item);
1413
1414         let (attr, traits, after_derive) = self.classify_item(&mut item);
1415         if attr.is_some() || !traits.is_empty() {
1416             return self.collect_attr(attr, traits, Annotatable::ImplItem(P(item)),
1417                                      AstFragmentKind::ImplItems, after_derive).make_impl_items();
1418         }
1419
1420         match item.node {
1421             ast::ImplItemKind::Macro(mac) => {
1422                 let ast::ImplItem { attrs, span, .. } = item;
1423                 self.check_attributes(&attrs);
1424                 self.collect_bang(mac, span, AstFragmentKind::ImplItems).make_impl_items()
1425             }
1426             _ => noop_flat_map_impl_item(item, self),
1427         }
1428     }
1429
1430     fn visit_ty(&mut self, ty: &mut P<ast::Ty>) {
1431         match ty.node {
1432             ast::TyKind::Mac(_) => {}
1433             _ => return noop_visit_ty(ty, self),
1434         };
1435
1436         visit_clobber(ty, |mut ty| {
1437             match mem::replace(&mut ty.node, ast::TyKind::Err) {
1438                 ast::TyKind::Mac(mac) =>
1439                     self.collect_bang(mac, ty.span, AstFragmentKind::Ty).make_ty(),
1440                 _ => unreachable!(),
1441             }
1442         });
1443     }
1444
1445     fn visit_foreign_mod(&mut self, foreign_mod: &mut ast::ForeignMod) {
1446         self.cfg.configure_foreign_mod(foreign_mod);
1447         noop_visit_foreign_mod(foreign_mod, self);
1448     }
1449
1450     fn flat_map_foreign_item(&mut self, mut foreign_item: ast::ForeignItem)
1451         -> SmallVec<[ast::ForeignItem; 1]>
1452     {
1453         let (attr, traits, after_derive) = self.classify_item(&mut foreign_item);
1454
1455         if attr.is_some() || !traits.is_empty() {
1456             return self.collect_attr(attr, traits, Annotatable::ForeignItem(P(foreign_item)),
1457                                      AstFragmentKind::ForeignItems, after_derive)
1458                                      .make_foreign_items();
1459         }
1460
1461         if let ast::ForeignItemKind::Macro(mac) = foreign_item.node {
1462             self.check_attributes(&foreign_item.attrs);
1463             return self.collect_bang(mac, foreign_item.span, AstFragmentKind::ForeignItems)
1464                 .make_foreign_items();
1465         }
1466
1467         noop_flat_map_foreign_item(foreign_item, self)
1468     }
1469
1470     fn visit_item_kind(&mut self, item: &mut ast::ItemKind) {
1471         match item {
1472             ast::ItemKind::MacroDef(..) => {}
1473             _ => {
1474                 self.cfg.configure_item_kind(item);
1475                 noop_visit_item_kind(item, self);
1476             }
1477         }
1478     }
1479
1480     fn visit_generic_param(&mut self, param: &mut ast::GenericParam) {
1481         self.cfg.disallow_cfg_on_generic_param(&param);
1482         noop_visit_generic_param(param, self)
1483     }
1484
1485     fn visit_attribute(&mut self, at: &mut ast::Attribute) {
1486         // turn `#[doc(include="filename")]` attributes into `#[doc(include(file="filename",
1487         // contents="file contents")]` attributes
1488         if !at.check_name(sym::doc) {
1489             return noop_visit_attribute(at, self);
1490         }
1491
1492         if let Some(list) = at.meta_item_list() {
1493             if !list.iter().any(|it| it.check_name(sym::include)) {
1494                 return noop_visit_attribute(at, self);
1495             }
1496
1497             let mut items = vec![];
1498
1499             for mut it in list {
1500                 if !it.check_name(sym::include) {
1501                     items.push({ noop_visit_meta_list_item(&mut it, self); it });
1502                     continue;
1503                 }
1504
1505                 if let Some(file) = it.value_str() {
1506                     let err_count = self.cx.parse_sess.span_diagnostic.err_count();
1507                     self.check_attribute(&at);
1508                     if self.cx.parse_sess.span_diagnostic.err_count() > err_count {
1509                         // avoid loading the file if they haven't enabled the feature
1510                         return noop_visit_attribute(at, self);
1511                     }
1512
1513                     let filename = self.cx.root_path.join(file.to_string());
1514                     match fs::read_to_string(&filename) {
1515                         Ok(src) => {
1516                             let src_interned = Symbol::intern(&src);
1517
1518                             // Add this input file to the code map to make it available as
1519                             // dependency information
1520                             self.cx.source_map().new_source_file(filename.into(), src);
1521
1522                             let include_info = vec![
1523                                 ast::NestedMetaItem::MetaItem(
1524                                     attr::mk_name_value_item_str(
1525                                         Ident::with_empty_ctxt(sym::file),
1526                                         dummy_spanned(file),
1527                                     ),
1528                                 ),
1529                                 ast::NestedMetaItem::MetaItem(
1530                                     attr::mk_name_value_item_str(
1531                                         Ident::with_empty_ctxt(sym::contents),
1532                                         dummy_spanned(src_interned),
1533                                     ),
1534                                 ),
1535                             ];
1536
1537                             let include_ident = Ident::with_empty_ctxt(sym::include);
1538                             let item = attr::mk_list_item(DUMMY_SP, include_ident, include_info);
1539                             items.push(ast::NestedMetaItem::MetaItem(item));
1540                         }
1541                         Err(e) => {
1542                             let lit = it
1543                                 .meta_item()
1544                                 .and_then(|item| item.name_value_literal())
1545                                 .unwrap();
1546
1547                             if e.kind() == ErrorKind::InvalidData {
1548                                 self.cx
1549                                     .struct_span_err(
1550                                         lit.span,
1551                                         &format!("{} wasn't a utf-8 file", filename.display()),
1552                                     )
1553                                     .span_label(lit.span, "contains invalid utf-8")
1554                                     .emit();
1555                             } else {
1556                                 let mut err = self.cx.struct_span_err(
1557                                     lit.span,
1558                                     &format!("couldn't read {}: {}", filename.display(), e),
1559                                 );
1560                                 err.span_label(lit.span, "couldn't read file");
1561
1562                                 if e.kind() == ErrorKind::NotFound {
1563                                     err.help("external doc paths are relative to the crate root");
1564                                 }
1565
1566                                 err.emit();
1567                             }
1568                         }
1569                     }
1570                 } else {
1571                     let mut err = self.cx.struct_span_err(
1572                         it.span(),
1573                         &format!("expected path to external documentation"),
1574                     );
1575
1576                     // Check if the user erroneously used `doc(include(...))` syntax.
1577                     let literal = it.meta_item_list().and_then(|list| {
1578                         if list.len() == 1 {
1579                             list[0].literal().map(|literal| &literal.node)
1580                         } else {
1581                             None
1582                         }
1583                     });
1584
1585                     let (path, applicability) = match &literal {
1586                         Some(LitKind::Str(path, ..)) => {
1587                             (path.to_string(), Applicability::MachineApplicable)
1588                         }
1589                         _ => (String::from("<path>"), Applicability::HasPlaceholders),
1590                     };
1591
1592                     err.span_suggestion(
1593                         it.span(),
1594                         "provide a file path with `=`",
1595                         format!("include = \"{}\"", path),
1596                         applicability,
1597                     );
1598
1599                     err.emit();
1600                 }
1601             }
1602
1603             let meta = attr::mk_list_item(DUMMY_SP, Ident::with_empty_ctxt(sym::doc), items);
1604             match at.style {
1605                 ast::AttrStyle::Inner => *at = attr::mk_spanned_attr_inner(at.span, at.id, meta),
1606                 ast::AttrStyle::Outer => *at = attr::mk_spanned_attr_outer(at.span, at.id, meta),
1607             }
1608         } else {
1609             noop_visit_attribute(at, self)
1610         }
1611     }
1612
1613     fn visit_id(&mut self, id: &mut ast::NodeId) {
1614         if self.monotonic {
1615             debug_assert_eq!(*id, ast::DUMMY_NODE_ID);
1616             *id = self.cx.resolver.next_node_id()
1617         }
1618     }
1619 }
1620
1621 pub struct ExpansionConfig<'feat> {
1622     pub crate_name: String,
1623     pub features: Option<&'feat Features>,
1624     pub recursion_limit: usize,
1625     pub trace_mac: bool,
1626     pub should_test: bool, // If false, strip `#[test]` nodes
1627     pub single_step: bool,
1628     pub keep_macs: bool,
1629 }
1630
1631 macro_rules! feature_tests {
1632     ($( fn $getter:ident = $field:ident, )*) => {
1633         $(
1634             pub fn $getter(&self) -> bool {
1635                 match self.features {
1636                     Some(&Features { $field: true, .. }) => true,
1637                     _ => false,
1638                 }
1639             }
1640         )*
1641     }
1642 }
1643
1644 impl<'feat> ExpansionConfig<'feat> {
1645     pub fn default(crate_name: String) -> ExpansionConfig<'static> {
1646         ExpansionConfig {
1647             crate_name,
1648             features: None,
1649             recursion_limit: 1024,
1650             trace_mac: false,
1651             should_test: false,
1652             single_step: false,
1653             keep_macs: false,
1654         }
1655     }
1656
1657     feature_tests! {
1658         fn enable_asm = asm,
1659         fn enable_custom_test_frameworks = custom_test_frameworks,
1660         fn enable_global_asm = global_asm,
1661         fn enable_log_syntax = log_syntax,
1662         fn enable_concat_idents = concat_idents,
1663         fn enable_trace_macros = trace_macros,
1664         fn enable_allow_internal_unstable = allow_internal_unstable,
1665         fn enable_format_args_nl = format_args_nl,
1666         fn macros_in_extern_enabled = macros_in_extern,
1667         fn proc_macro_hygiene = proc_macro_hygiene,
1668     }
1669
1670     fn enable_custom_inner_attributes(&self) -> bool {
1671         self.features.map_or(false, |features| {
1672             features.custom_inner_attributes || features.custom_attribute || features.rustc_attrs
1673         })
1674     }
1675 }
1676
1677 // A Marker adds the given mark to the syntax context.
1678 #[derive(Debug)]
1679 pub struct Marker(pub Mark);
1680
1681 impl MutVisitor for Marker {
1682     fn visit_span(&mut self, span: &mut Span) {
1683         *span = span.apply_mark(self.0)
1684     }
1685
1686     fn visit_mac(&mut self, mac: &mut ast::Mac) {
1687         noop_visit_mac(mac, self)
1688     }
1689 }