src/libsyntax_expand/expand.rs

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