src/libsyntax/ext/base.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 pub use self::SyntaxExtension::*;
  12
  13 use ast::{self, Attribute, Name, PatKind, MetaItem};
  14 use attr::HasAttrs;
  15 use codemap::{self, CodeMap, Spanned, respan};
  16 use syntax_pos::{Span, DUMMY_SP};
  17 use errors::DiagnosticBuilder;
  18 use ext::expand::{self, Expansion, Invocation};
  19 use ext::hygiene::{Mark, SyntaxContext};
  20 use fold::{self, Folder};
  21 use parse::{self, parser, DirectoryOwnership};
  22 use parse::token;
  23 use ptr::P;
  24 use symbol::Symbol;
  25 use util::small_vector::SmallVector;
  26
  27 use std::collections::HashMap;
  28 use std::path::PathBuf;
  29 use std::rc::Rc;
  30 use std::default::Default;
  31 use tokenstream::{self, TokenStream};
  32
  33
  34 #[derive(Debug,Clone)]
  35 pub enum Annotatable {
  36     Item(P<ast::Item>),
  37     TraitItem(P<ast::TraitItem>),
  38     ImplItem(P<ast::ImplItem>),
  39 }
  40
  41 impl HasAttrs for Annotatable {
  42     fn attrs(&self) -> &[Attribute] {
  43         match *self {
  44             Annotatable::Item(ref item) => &item.attrs,
  45             Annotatable::TraitItem(ref trait_item) => &trait_item.attrs,
  46             Annotatable::ImplItem(ref impl_item) => &impl_item.attrs,
  47         }
  48     }
  49
  50     fn map_attrs<F: FnOnce(Vec<Attribute>) -> Vec<Attribute>>(self, f: F) -> Self {
  51         match self {
  52             Annotatable::Item(item) => Annotatable::Item(item.map_attrs(f)),
  53             Annotatable::TraitItem(trait_item) => Annotatable::TraitItem(trait_item.map_attrs(f)),
  54             Annotatable::ImplItem(impl_item) => Annotatable::ImplItem(impl_item.map_attrs(f)),
  55         }
  56     }
  57 }
  58
  59 impl Annotatable {
  60     pub fn span(&self) -> Span {
  61         match *self {
  62             Annotatable::Item(ref item) => item.span,
  63             Annotatable::TraitItem(ref trait_item) => trait_item.span,
  64             Annotatable::ImplItem(ref impl_item) => impl_item.span,
  65         }
  66     }
  67
  68     pub fn expect_item(self) -> P<ast::Item> {
  69         match self {
  70             Annotatable::Item(i) => i,
  71             _ => panic!("expected Item")
  72         }
  73     }
  74
  75     pub fn map_item_or<F, G>(self, mut f: F, mut or: G) -> Annotatable
  76         where F: FnMut(P<ast::Item>) -> P<ast::Item>,
  77               G: FnMut(Annotatable) -> Annotatable
  78     {
  79         match self {
  80             Annotatable::Item(i) => Annotatable::Item(f(i)),
  81             _ => or(self)
  82         }
  83     }
  84
  85     pub fn expect_trait_item(self) -> ast::TraitItem {
  86         match self {
  87             Annotatable::TraitItem(i) => i.unwrap(),
  88             _ => panic!("expected Item")
  89         }
  90     }
  91
  92     pub fn expect_impl_item(self) -> ast::ImplItem {
  93         match self {
  94             Annotatable::ImplItem(i) => i.unwrap(),
  95             _ => panic!("expected Item")
  96         }
  97     }
  98 }
  99
 100 // A more flexible ItemDecorator.
 101 pub trait MultiItemDecorator {
 102     fn expand(&self,
 103               ecx: &mut ExtCtxt,
 104               sp: Span,
 105               meta_item: &ast::MetaItem,
 106               item: &Annotatable,
 107               push: &mut FnMut(Annotatable));
 108 }
 109
 110 impl<F> MultiItemDecorator for F
 111     where F : Fn(&mut ExtCtxt, Span, &ast::MetaItem, &Annotatable, &mut FnMut(Annotatable))
 112 {
 113     fn expand(&self,
 114               ecx: &mut ExtCtxt,
 115               sp: Span,
 116               meta_item: &ast::MetaItem,
 117               item: &Annotatable,
 118               push: &mut FnMut(Annotatable)) {
 119         (*self)(ecx, sp, meta_item, item, push)
 120     }
 121 }
 122
 123 // `meta_item` is the annotation, and `item` is the item being modified.
 124 // FIXME Decorators should follow the same pattern too.
 125 pub trait MultiItemModifier {
 126     fn expand(&self,
 127               ecx: &mut ExtCtxt,
 128               span: Span,
 129               meta_item: &ast::MetaItem,
 130               item: Annotatable)
 131               -> Vec<Annotatable>;
 132 }
 133
 134 impl<F, T> MultiItemModifier for F
 135     where F: Fn(&mut ExtCtxt, Span, &ast::MetaItem, Annotatable) -> T,
 136           T: Into<Vec<Annotatable>>,
 137 {
 138     fn expand(&self,
 139               ecx: &mut ExtCtxt,
 140               span: Span,
 141               meta_item: &ast::MetaItem,
 142               item: Annotatable)
 143               -> Vec<Annotatable> {
 144         (*self)(ecx, span, meta_item, item).into()
 145     }
 146 }
 147
 148 impl Into<Vec<Annotatable>> for Annotatable {
 149     fn into(self) -> Vec<Annotatable> {
 150         vec![self]
 151     }
 152 }
 153
 154 pub trait ProcMacro {
 155     fn expand<'cx>(&self,
 156                    ecx: &'cx mut ExtCtxt,
 157                    span: Span,
 158                    ts: TokenStream)
 159                    -> TokenStream;
 160 }
 161
 162 impl<F> ProcMacro for F
 163     where F: Fn(TokenStream) -> TokenStream
 164 {
 165     fn expand<'cx>(&self,
 166                    _ecx: &'cx mut ExtCtxt,
 167                    _span: Span,
 168                    ts: TokenStream)
 169                    -> TokenStream {
 170         // FIXME setup implicit context in TLS before calling self.
 171         (*self)(ts)
 172     }
 173 }
 174
 175 pub trait AttrProcMacro {
 176     fn expand<'cx>(&self,
 177                    ecx: &'cx mut ExtCtxt,
 178                    span: Span,
 179                    annotation: TokenStream,
 180                    annotated: TokenStream)
 181                    -> TokenStream;
 182 }
 183
 184 impl<F> AttrProcMacro for F
 185     where F: Fn(TokenStream, TokenStream) -> TokenStream
 186 {
 187     fn expand<'cx>(&self,
 188                    _ecx: &'cx mut ExtCtxt,
 189                    _span: Span,
 190                    annotation: TokenStream,
 191                    annotated: TokenStream)
 192                    -> TokenStream {
 193         // FIXME setup implicit context in TLS before calling self.
 194         (*self)(annotation, annotated)
 195     }
 196 }
 197
 198 /// Represents a thing that maps token trees to Macro Results
 199 pub trait TTMacroExpander {
 200     fn expand<'cx>(&self, ecx: &'cx mut ExtCtxt, span: Span, input: TokenStream)
 201                    -> Box<MacResult+'cx>;
 202 }
 203
 204 pub type MacroExpanderFn =
 205     for<'cx> fn(&'cx mut ExtCtxt, Span, &[tokenstream::TokenTree])
 206                 -> Box<MacResult+'cx>;
 207
 208 impl<F> TTMacroExpander for F
 209     where F: for<'cx> Fn(&'cx mut ExtCtxt, Span, &[tokenstream::TokenTree]) -> Box<MacResult+'cx>
 210 {
 211     fn expand<'cx>(&self, ecx: &'cx mut ExtCtxt, span: Span, input: TokenStream)
 212                    -> Box<MacResult+'cx> {
 213         struct AvoidInterpolatedIdents;
 214
 215         impl Folder for AvoidInterpolatedIdents {
 216             fn fold_tt(&mut self, tt: tokenstream::TokenTree) -> tokenstream::TokenTree {
 217                 if let tokenstream::TokenTree::Token(_, token::Interpolated(ref nt)) = tt {
 218                     if let token::NtIdent(ident) = nt.0 {
 219                         return tokenstream::TokenTree::Token(ident.span, token::Ident(ident.node));
 220                     }
 221                 }
 222                 fold::noop_fold_tt(tt, self)
 223             }
 224
 225             fn fold_mac(&mut self, mac: ast::Mac) -> ast::Mac {
 226                 fold::noop_fold_mac(mac, self)
 227             }
 228         }
 229
 230         let input: Vec<_> =
 231             input.trees().map(|tt| AvoidInterpolatedIdents.fold_tt(tt)).collect();
 232         (*self)(ecx, span, &input)
 233     }
 234 }
 235
 236 pub trait IdentMacroExpander {
 237     fn expand<'cx>(&self,
 238                    cx: &'cx mut ExtCtxt,
 239                    sp: Span,
 240                    ident: ast::Ident,
 241                    token_tree: Vec<tokenstream::TokenTree>)
 242                    -> Box<MacResult+'cx>;
 243 }
 244
 245 pub type IdentMacroExpanderFn =
 246     for<'cx> fn(&'cx mut ExtCtxt, Span, ast::Ident, Vec<tokenstream::TokenTree>)
 247                 -> Box<MacResult+'cx>;
 248
 249 impl<F> IdentMacroExpander for F
 250     where F : for<'cx> Fn(&'cx mut ExtCtxt, Span, ast::Ident,
 251                           Vec<tokenstream::TokenTree>) -> Box<MacResult+'cx>
 252 {
 253     fn expand<'cx>(&self,
 254                    cx: &'cx mut ExtCtxt,
 255                    sp: Span,
 256                    ident: ast::Ident,
 257                    token_tree: Vec<tokenstream::TokenTree>)
 258                    -> Box<MacResult+'cx>
 259     {
 260         (*self)(cx, sp, ident, token_tree)
 261     }
 262 }
 263
 264 // Use a macro because forwarding to a simple function has type system issues
 265 macro_rules! make_stmts_default {
 266     ($me:expr) => {
 267         $me.make_expr().map(|e| SmallVector::one(ast::Stmt {
 268             id: ast::DUMMY_NODE_ID,
 269             span: e.span,
 270             node: ast::StmtKind::Expr(e),
 271         }))
 272     }
 273 }
 274
 275 /// The result of a macro expansion. The return values of the various
 276 /// methods are spliced into the AST at the callsite of the macro.
 277 pub trait MacResult {
 278     /// Create an expression.
 279     fn make_expr(self: Box<Self>) -> Option<P<ast::Expr>> {
 280         None
 281     }
 282     /// Create zero or more items.
 283     fn make_items(self: Box<Self>) -> Option<SmallVector<P<ast::Item>>> {
 284         None
 285     }
 286
 287     /// Create zero or more impl items.
 288     fn make_impl_items(self: Box<Self>) -> Option<SmallVector<ast::ImplItem>> {
 289         None
 290     }
 291
 292     /// Create zero or more trait items.
 293     fn make_trait_items(self: Box<Self>) -> Option<SmallVector<ast::TraitItem>> {
 294         None
 295     }
 296
 297     /// Create a pattern.
 298     fn make_pat(self: Box<Self>) -> Option<P<ast::Pat>> {
 299         None
 300     }
 301
 302     /// Create zero or more statements.
 303     ///
 304     /// By default this attempts to create an expression statement,
 305     /// returning None if that fails.
 306     fn make_stmts(self: Box<Self>) -> Option<SmallVector<ast::Stmt>> {
 307         make_stmts_default!(self)
 308     }
 309
 310     fn make_ty(self: Box<Self>) -> Option<P<ast::Ty>> {
 311         None
 312     }
 313 }
 314
 315 macro_rules! make_MacEager {
 316     ( $( $fld:ident: $t:ty, )* ) => {
 317         /// `MacResult` implementation for the common case where you've already
 318         /// built each form of AST that you might return.
 319         #[derive(Default)]
 320         pub struct MacEager {
 321             $(
 322                 pub $fld: Option<$t>,
 323             )*
 324         }
 325
 326         impl MacEager {
 327             $(
 328                 pub fn $fld(v: $t) -> Box<MacResult> {
 329                     Box::new(MacEager {
 330                         $fld: Some(v),
 331                         ..Default::default()
 332                     })
 333                 }
 334             )*
 335         }
 336     }
 337 }
 338
 339 make_MacEager! {
 340     expr: P<ast::Expr>,
 341     pat: P<ast::Pat>,
 342     items: SmallVector<P<ast::Item>>,
 343     impl_items: SmallVector<ast::ImplItem>,
 344     trait_items: SmallVector<ast::TraitItem>,
 345     stmts: SmallVector<ast::Stmt>,
 346     ty: P<ast::Ty>,
 347 }
 348
 349 impl MacResult for MacEager {
 350     fn make_expr(self: Box<Self>) -> Option<P<ast::Expr>> {
 351         self.expr
 352     }
 353
 354     fn make_items(self: Box<Self>) -> Option<SmallVector<P<ast::Item>>> {
 355         self.items
 356     }
 357
 358     fn make_impl_items(self: Box<Self>) -> Option<SmallVector<ast::ImplItem>> {
 359         self.impl_items
 360     }
 361
 362     fn make_trait_items(self: Box<Self>) -> Option<SmallVector<ast::TraitItem>> {
 363         self.trait_items
 364     }
 365
 366     fn make_stmts(self: Box<Self>) -> Option<SmallVector<ast::Stmt>> {
 367         match self.stmts.as_ref().map_or(0, |s| s.len()) {
 368             0 => make_stmts_default!(self),
 369             _ => self.stmts,
 370         }
 371     }
 372
 373     fn make_pat(self: Box<Self>) -> Option<P<ast::Pat>> {
 374         if let Some(p) = self.pat {
 375             return Some(p);
 376         }
 377         if let Some(e) = self.expr {
 378             if let ast::ExprKind::Lit(_) = e.node {
 379                 return Some(P(ast::Pat {
 380                     id: ast::DUMMY_NODE_ID,
 381                     span: e.span,
 382                     node: PatKind::Lit(e),
 383                 }));
 384             }
 385         }
 386         None
 387     }
 388
 389     fn make_ty(self: Box<Self>) -> Option<P<ast::Ty>> {
 390         self.ty
 391     }
 392 }
 393
 394 /// Fill-in macro expansion result, to allow compilation to continue
 395 /// after hitting errors.
 396 #[derive(Copy, Clone)]
 397 pub struct DummyResult {
 398     expr_only: bool,
 399     span: Span
 400 }
 401
 402 impl DummyResult {
 403     /// Create a default MacResult that can be anything.
 404     ///
 405     /// Use this as a return value after hitting any errors and
 406     /// calling `span_err`.
 407     pub fn any(sp: Span) -> Box<MacResult+'static> {
 408         Box::new(DummyResult { expr_only: false, span: sp })
 409     }
 410
 411     /// Create a default MacResult that can only be an expression.
 412     ///
 413     /// Use this for macros that must expand to an expression, so even
 414     /// if an error is encountered internally, the user will receive
 415     /// an error that they also used it in the wrong place.
 416     pub fn expr(sp: Span) -> Box<MacResult+'static> {
 417         Box::new(DummyResult { expr_only: true, span: sp })
 418     }
 419
 420     /// A plain dummy expression.
 421     pub fn raw_expr(sp: Span) -> P<ast::Expr> {
 422         P(ast::Expr {
 423             id: ast::DUMMY_NODE_ID,
 424             node: ast::ExprKind::Lit(P(codemap::respan(sp, ast::LitKind::Bool(false)))),
 425             span: sp,
 426             attrs: ast::ThinVec::new(),
 427         })
 428     }
 429
 430     /// A plain dummy pattern.
 431     pub fn raw_pat(sp: Span) -> ast::Pat {
 432         ast::Pat {
 433             id: ast::DUMMY_NODE_ID,
 434             node: PatKind::Wild,
 435             span: sp,
 436         }
 437     }
 438
 439     pub fn raw_ty(sp: Span) -> P<ast::Ty> {
 440         P(ast::Ty {
 441             id: ast::DUMMY_NODE_ID,
 442             node: ast::TyKind::Infer,
 443             span: sp
 444         })
 445     }
 446 }
 447
 448 impl MacResult for DummyResult {
 449     fn make_expr(self: Box<DummyResult>) -> Option<P<ast::Expr>> {
 450         Some(DummyResult::raw_expr(self.span))
 451     }
 452
 453     fn make_pat(self: Box<DummyResult>) -> Option<P<ast::Pat>> {
 454         Some(P(DummyResult::raw_pat(self.span)))
 455     }
 456
 457     fn make_items(self: Box<DummyResult>) -> Option<SmallVector<P<ast::Item>>> {
 458         // this code needs a comment... why not always just return the Some() ?
 459         if self.expr_only {
 460             None
 461         } else {
 462             Some(SmallVector::new())
 463         }
 464     }
 465
 466     fn make_impl_items(self: Box<DummyResult>) -> Option<SmallVector<ast::ImplItem>> {
 467         if self.expr_only {
 468             None
 469         } else {
 470             Some(SmallVector::new())
 471         }
 472     }
 473
 474     fn make_trait_items(self: Box<DummyResult>) -> Option<SmallVector<ast::TraitItem>> {
 475         if self.expr_only {
 476             None
 477         } else {
 478             Some(SmallVector::new())
 479         }
 480     }
 481
 482     fn make_stmts(self: Box<DummyResult>) -> Option<SmallVector<ast::Stmt>> {
 483         Some(SmallVector::one(ast::Stmt {
 484             id: ast::DUMMY_NODE_ID,
 485             node: ast::StmtKind::Expr(DummyResult::raw_expr(self.span)),
 486             span: self.span,
 487         }))
 488     }
 489
 490     fn make_ty(self: Box<DummyResult>) -> Option<P<ast::Ty>> {
 491         Some(DummyResult::raw_ty(self.span))
 492     }
 493 }
 494
 495 pub type BuiltinDeriveFn =
 496     for<'cx> fn(&'cx mut ExtCtxt, Span, &MetaItem, &Annotatable, &mut FnMut(Annotatable));
 497
 498 /// Represents different kinds of macro invocations that can be resolved.
 499 #[derive(Clone, Copy, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 500 pub enum MacroKind {
 501     /// A bang macro - foo!()
 502     Bang,
 503     /// An attribute macro - #[foo]
 504     Attr,
 505     /// A derive attribute macro - #[derive(Foo)]
 506     Derive,
 507 }
 508
 509 /// An enum representing the different kinds of syntax extensions.
 510 pub enum SyntaxExtension {
 511     /// A syntax extension that is attached to an item and creates new items
 512     /// based upon it.
 513     ///
 514     /// `#[derive(...)]` is a `MultiItemDecorator`.
 515     ///
 516     /// Prefer ProcMacro or MultiModifier since they are more flexible.
 517     MultiDecorator(Box<MultiItemDecorator>),
 518
 519     /// A syntax extension that is attached to an item and modifies it
 520     /// in-place. Also allows decoration, i.e., creating new items.
 521     MultiModifier(Box<MultiItemModifier>),
 522
 523     /// A function-like procedural macro. TokenStream -> TokenStream.
 524     ProcMacro(Box<ProcMacro>),
 525
 526     /// An attribute-like procedural macro. TokenStream, TokenStream -> TokenStream.
 527     /// The first TokenSteam is the attribute, the second is the annotated item.
 528     /// Allows modification of the input items and adding new items, similar to
 529     /// MultiModifier, but uses TokenStreams, rather than AST nodes.
 530     AttrProcMacro(Box<AttrProcMacro>),
 531
 532     /// A normal, function-like syntax extension.
 533     ///
 534     /// `bytes!` is a `NormalTT`.
 535     NormalTT {
 536         expander: Box<TTMacroExpander>,
 537         def_info: Option<(ast::NodeId, Span)>,
 538         /// Whether the contents of the macro can
 539         /// directly use `#[unstable]` things (true == yes).
 540         allow_internal_unstable: bool,
 541         /// Whether the contents of the macro can use `unsafe`
 542         /// without triggering the `unsafe_code` lint.
 543         allow_internal_unsafe: bool,
 544     },
 545
 546     /// A function-like syntax extension that has an extra ident before
 547     /// the block.
 548     ///
 549     IdentTT(Box<IdentMacroExpander>, Option<Span>, bool),
 550
 551     /// An attribute-like procedural macro. TokenStream -> TokenStream.
 552     /// The input is the annotated item.
 553     /// Allows generating code to implement a Trait for a given struct
 554     /// or enum item.
 555     ProcMacroDerive(Box<MultiItemModifier>, Vec<Symbol> /* inert attribute names */),
 556
 557     /// An attribute-like procedural macro that derives a builtin trait.
 558     BuiltinDerive(BuiltinDeriveFn),
 559
 560     /// A declarative macro, e.g. `macro m() {}`.
 561     ///
 562     /// The second element is the definition site span.
 563     DeclMacro(Box<TTMacroExpander>, Option<(ast::NodeId, Span)>),
 564 }
 565
 566 impl SyntaxExtension {
 567     /// Return which kind of macro calls this syntax extension.
 568     pub fn kind(&self) -> MacroKind {
 569         match *self {
 570             SyntaxExtension::DeclMacro(..) |
 571             SyntaxExtension::NormalTT { .. } |
 572             SyntaxExtension::IdentTT(..) |
 573             SyntaxExtension::ProcMacro(..) =>
 574                 MacroKind::Bang,
 575             SyntaxExtension::MultiDecorator(..) |
 576             SyntaxExtension::MultiModifier(..) |
 577             SyntaxExtension::AttrProcMacro(..) =>
 578                 MacroKind::Attr,
 579             SyntaxExtension::ProcMacroDerive(..) |
 580             SyntaxExtension::BuiltinDerive(..) =>
 581                 MacroKind::Derive,
 582         }
 583     }
 584
 585     pub fn is_modern(&self) -> bool {
 586         match *self {
 587             SyntaxExtension::DeclMacro(..) |
 588             SyntaxExtension::ProcMacro(..) |
 589             SyntaxExtension::AttrProcMacro(..) |
 590             SyntaxExtension::ProcMacroDerive(..) => true,
 591             _ => false,
 592         }
 593     }
 594 }
 595
 596 pub type NamedSyntaxExtension = (Name, SyntaxExtension);
 597
 598 pub trait Resolver {
 599     fn next_node_id(&mut self) -> ast::NodeId;
 600     fn get_module_scope(&mut self, id: ast::NodeId) -> Mark;
 601     fn eliminate_crate_var(&mut self, item: P<ast::Item>) -> P<ast::Item>;
 602     fn is_whitelisted_legacy_custom_derive(&self, name: Name) -> bool;
 603
 604     fn visit_expansion(&mut self, mark: Mark, expansion: &Expansion, derives: &[Mark]);
 605     fn add_builtin(&mut self, ident: ast::Ident, ext: Rc<SyntaxExtension>);
 606
 607     fn resolve_imports(&mut self);
 608     // Resolves attribute and derive legacy macros from `#![plugin(..)]`.
 609     fn find_legacy_attr_invoc(&mut self, attrs: &mut Vec<Attribute>) -> Option<Attribute>;
 610     fn resolve_invoc(&mut self, invoc: &mut Invocation, scope: Mark, force: bool)
 611                      -> Result<Option<Rc<SyntaxExtension>>, Determinacy>;
 612     fn resolve_macro(&mut self, scope: Mark, path: &ast::Path, kind: MacroKind, force: bool)
 613                      -> Result<Rc<SyntaxExtension>, Determinacy>;
 614     fn check_unused_macros(&self);
 615 }
 616
 617 #[derive(Copy, Clone, Debug, PartialEq)]
 618 pub enum Determinacy {
 619     Determined,
 620     Undetermined,
 621 }
 622
 623 pub struct DummyResolver;
 624
 625 impl Resolver for DummyResolver {
 626     fn next_node_id(&mut self) -> ast::NodeId { ast::DUMMY_NODE_ID }
 627     fn get_module_scope(&mut self, _id: ast::NodeId) -> Mark { Mark::root() }
 628     fn eliminate_crate_var(&mut self, item: P<ast::Item>) -> P<ast::Item> { item }
 629     fn is_whitelisted_legacy_custom_derive(&self, _name: Name) -> bool { false }
 630
 631     fn visit_expansion(&mut self, _invoc: Mark, _expansion: &Expansion, _derives: &[Mark]) {}
 632     fn add_builtin(&mut self, _ident: ast::Ident, _ext: Rc<SyntaxExtension>) {}
 633
 634     fn resolve_imports(&mut self) {}
 635     fn find_legacy_attr_invoc(&mut self, _attrs: &mut Vec<Attribute>) -> Option<Attribute> { None }
 636     fn resolve_invoc(&mut self, _invoc: &mut Invocation, _scope: Mark, _force: bool)
 637                      -> Result<Option<Rc<SyntaxExtension>>, Determinacy> {
 638         Err(Determinacy::Determined)
 639     }
 640     fn resolve_macro(&mut self, _scope: Mark, _path: &ast::Path, _kind: MacroKind,
 641                      _force: bool) -> Result<Rc<SyntaxExtension>, Determinacy> {
 642         Err(Determinacy::Determined)
 643     }
 644     fn check_unused_macros(&self) {}
 645 }
 646
 647 #[derive(Clone)]
 648 pub struct ModuleData {
 649     pub mod_path: Vec<ast::Ident>,
 650     pub directory: PathBuf,
 651 }
 652
 653 #[derive(Clone)]
 654 pub struct ExpansionData {
 655     pub mark: Mark,
 656     pub depth: usize,
 657     pub module: Rc<ModuleData>,
 658     pub directory_ownership: DirectoryOwnership,
 659 }
 660
 661 /// One of these is made during expansion and incrementally updated as we go;
 662 /// when a macro expansion occurs, the resulting nodes have the `backtrace()
 663 /// -> expn_info` of their expansion context stored into their span.
 664 pub struct ExtCtxt<'a> {
 665     pub parse_sess: &'a parse::ParseSess,
 666     pub ecfg: expand::ExpansionConfig<'a>,
 667     pub crate_root: Option<&'static str>,
 668     pub resolver: &'a mut Resolver,
 669     pub resolve_err_count: usize,
 670     pub current_expansion: ExpansionData,
 671     pub expansions: HashMap<Span, Vec<String>>,
 672 }
 673
 674 impl<'a> ExtCtxt<'a> {
 675     pub fn new(parse_sess: &'a parse::ParseSess,
 676                ecfg: expand::ExpansionConfig<'a>,
 677                resolver: &'a mut Resolver)
 678                -> ExtCtxt<'a> {
 679         ExtCtxt {
 680             parse_sess,
 681             ecfg,
 682             crate_root: None,
 683             resolver,
 684             resolve_err_count: 0,
 685             current_expansion: ExpansionData {
 686                 mark: Mark::root(),
 687                 depth: 0,
 688                 module: Rc::new(ModuleData { mod_path: Vec::new(), directory: PathBuf::new() }),
 689                 directory_ownership: DirectoryOwnership::Owned,
 690             },
 691             expansions: HashMap::new(),
 692         }
 693     }
 694
 695     /// Returns a `Folder` for deeply expanding all macros in an AST node.
 696     pub fn expander<'b>(&'b mut self) -> expand::MacroExpander<'b, 'a> {
 697         expand::MacroExpander::new(self, false)
 698     }
 699
 700     /// Returns a `Folder` that deeply expands all macros and assigns all node ids in an AST node.
 701     /// Once node ids are assigned, the node may not be expanded, removed, or otherwise modified.
 702     pub fn monotonic_expander<'b>(&'b mut self) -> expand::MacroExpander<'b, 'a> {
 703         expand::MacroExpander::new(self, true)
 704     }
 705
 706     pub fn new_parser_from_tts(&self, tts: &[tokenstream::TokenTree]) -> parser::Parser<'a> {
 707         parse::stream_to_parser(self.parse_sess, tts.iter().cloned().collect())
 708     }
 709     pub fn codemap(&self) -> &'a CodeMap { self.parse_sess.codemap() }
 710     pub fn parse_sess(&self) -> &'a parse::ParseSess { self.parse_sess }
 711     pub fn cfg(&self) -> &ast::CrateConfig { &self.parse_sess.config }
 712     pub fn call_site(&self) -> Span {
 713         match self.current_expansion.mark.expn_info() {
 714             Some(expn_info) => expn_info.call_site,
 715             None => DUMMY_SP,
 716         }
 717     }
 718     pub fn backtrace(&self) -> SyntaxContext {
 719         SyntaxContext::empty().apply_mark(self.current_expansion.mark)
 720     }
 721
 722     /// Returns span for the macro which originally caused the current expansion to happen.
 723     ///
 724     /// Stops backtracing at include! boundary.
 725     pub fn expansion_cause(&self) -> Option<Span> {
 726         let mut ctxt = self.backtrace();
 727         let mut last_macro = None;
 728         loop {
 729             if ctxt.outer().expn_info().map_or(None, |info| {
 730                 if info.callee.name() == "include" {
 731                     // Stop going up the backtrace once include! is encountered
 732                     return None;
 733                 }
 734                 ctxt = info.call_site.ctxt;
 735                 last_macro = Some(info.call_site);
 736                 Some(())
 737             }).is_none() {
 738                 break
 739             }
 740         }
 741         last_macro
 742     }
 743
 744     pub fn struct_span_warn(&self,
 745                             sp: Span,
 746                             msg: &str)
 747                             -> DiagnosticBuilder<'a> {
 748         self.parse_sess.span_diagnostic.struct_span_warn(sp, msg)
 749     }
 750     pub fn struct_span_err(&self,
 751                            sp: Span,
 752                            msg: &str)
 753                            -> DiagnosticBuilder<'a> {
 754         self.parse_sess.span_diagnostic.struct_span_err(sp, msg)
 755     }
 756     pub fn struct_span_fatal(&self,
 757                              sp: Span,
 758                              msg: &str)
 759                              -> DiagnosticBuilder<'a> {
 760         self.parse_sess.span_diagnostic.struct_span_fatal(sp, msg)
 761     }
 762
 763     /// Emit `msg` attached to `sp`, and stop compilation immediately.
 764     ///
 765     /// `span_err` should be strongly preferred where-ever possible:
 766     /// this should *only* be used when
 767     /// - continuing has a high risk of flow-on errors (e.g. errors in
 768     ///   declaring a macro would cause all uses of that macro to
 769     ///   complain about "undefined macro"), or
 770     /// - there is literally nothing else that can be done (however,
 771     ///   in most cases one can construct a dummy expression/item to
 772     ///   substitute; we never hit resolve/type-checking so the dummy
 773     ///   value doesn't have to match anything)
 774     pub fn span_fatal(&self, sp: Span, msg: &str) -> ! {
 775         panic!(self.parse_sess.span_diagnostic.span_fatal(sp, msg));
 776     }
 777
 778     /// Emit `msg` attached to `sp`, without immediately stopping
 779     /// compilation.
 780     ///
 781     /// Compilation will be stopped in the near future (at the end of
 782     /// the macro expansion phase).
 783     pub fn span_err(&self, sp: Span, msg: &str) {
 784         self.parse_sess.span_diagnostic.span_err(sp, msg);
 785     }
 786     pub fn span_warn(&self, sp: Span, msg: &str) {
 787         self.parse_sess.span_diagnostic.span_warn(sp, msg);
 788     }
 789     pub fn span_unimpl(&self, sp: Span, msg: &str) -> ! {
 790         self.parse_sess.span_diagnostic.span_unimpl(sp, msg);
 791     }
 792     pub fn span_bug(&self, sp: Span, msg: &str) -> ! {
 793         self.parse_sess.span_diagnostic.span_bug(sp, msg);
 794     }
 795     pub fn trace_macros_diag(&self) {
 796         for (sp, notes) in self.expansions.iter() {
 797             let mut db = self.parse_sess.span_diagnostic.span_note_diag(*sp, "trace_macro");
 798             for note in notes {
 799                 db.note(note);
 800             }
 801             db.emit();
 802         }
 803     }
 804     pub fn bug(&self, msg: &str) -> ! {
 805         self.parse_sess.span_diagnostic.bug(msg);
 806     }
 807     pub fn trace_macros(&self) -> bool {
 808         self.ecfg.trace_mac
 809     }
 810     pub fn set_trace_macros(&mut self, x: bool) {
 811         self.ecfg.trace_mac = x
 812     }
 813     pub fn ident_of(&self, st: &str) -> ast::Ident {
 814         ast::Ident::from_str(st)
 815     }
 816     pub fn std_path(&self, components: &[&str]) -> Vec<ast::Ident> {
 817         let mut v = Vec::new();
 818         if let Some(s) = self.crate_root {
 819             v.push(self.ident_of(s));
 820         }
 821         v.extend(components.iter().map(|s| self.ident_of(s)));
 822         v
 823     }
 824     pub fn name_of(&self, st: &str) -> ast::Name {
 825         Symbol::intern(st)
 826     }
 827
 828     pub fn check_unused_macros(&self) {
 829         self.resolver.check_unused_macros();
 830     }
 831 }
 832
 833 /// Extract a string literal from the macro expanded version of `expr`,
 834 /// emitting `err_msg` if `expr` is not a string literal. This does not stop
 835 /// compilation on error, merely emits a non-fatal error and returns None.
 836 pub fn expr_to_spanned_string(cx: &mut ExtCtxt, expr: P<ast::Expr>, err_msg: &str)
 837                               -> Option<Spanned<(Symbol, ast::StrStyle)>> {
 838     // Update `expr.span`'s ctxt now in case expr is an `include!` macro invocation.
 839     let expr = expr.map(|mut expr| {
 840         expr.span.ctxt = expr.span.ctxt.apply_mark(cx.current_expansion.mark);
 841         expr
 842     });
 843
 844     // we want to be able to handle e.g. concat("foo", "bar")
 845     let expr = cx.expander().fold_expr(expr);
 846     match expr.node {
 847         ast::ExprKind::Lit(ref l) => match l.node {
 848             ast::LitKind::Str(s, style) => return Some(respan(expr.span, (s, style))),
 849             _ => cx.span_err(l.span, err_msg)
 850         },
 851         _ => cx.span_err(expr.span, err_msg)
 852     }
 853     None
 854 }
 855
 856 pub fn expr_to_string(cx: &mut ExtCtxt, expr: P<ast::Expr>, err_msg: &str)
 857                       -> Option<(Symbol, ast::StrStyle)> {
 858     expr_to_spanned_string(cx, expr, err_msg).map(|s| s.node)
 859 }
 860
 861 /// Non-fatally assert that `tts` is empty. Note that this function
 862 /// returns even when `tts` is non-empty, macros that *need* to stop
 863 /// compilation should call
 864 /// `cx.parse_sess.span_diagnostic.abort_if_errors()` (this should be
 865 /// done as rarely as possible).
 866 pub fn check_zero_tts(cx: &ExtCtxt,
 867                       sp: Span,
 868                       tts: &[tokenstream::TokenTree],
 869                       name: &str) {
 870     if !tts.is_empty() {
 871         cx.span_err(sp, &format!("{} takes no arguments", name));
 872     }
 873 }
 874
 875 /// Extract the string literal from the first token of `tts`. If this
 876 /// is not a string literal, emit an error and return None.
 877 pub fn get_single_str_from_tts(cx: &mut ExtCtxt,
 878                                sp: Span,
 879                                tts: &[tokenstream::TokenTree],
 880                                name: &str)
 881                                -> Option<String> {
 882     let mut p = cx.new_parser_from_tts(tts);
 883     if p.token == token::Eof {
 884         cx.span_err(sp, &format!("{} takes 1 argument", name));
 885         return None
 886     }
 887     let ret = panictry!(p.parse_expr());
 888     if p.token != token::Eof {
 889         cx.span_err(sp, &format!("{} takes 1 argument", name));
 890     }
 891     expr_to_string(cx, ret, "argument must be a string literal").map(|(s, _)| {
 892         s.to_string()
 893     })
 894 }
 895
 896 /// Extract comma-separated expressions from `tts`. If there is a
 897 /// parsing error, emit a non-fatal error and return None.
 898 pub fn get_exprs_from_tts(cx: &mut ExtCtxt,
 899                           sp: Span,
 900                           tts: &[tokenstream::TokenTree]) -> Option<Vec<P<ast::Expr>>> {
 901     let mut p = cx.new_parser_from_tts(tts);
 902     let mut es = Vec::new();
 903     while p.token != token::Eof {
 904         es.push(cx.expander().fold_expr(panictry!(p.parse_expr())));
 905         if p.eat(&token::Comma) {
 906             continue;
 907         }
 908         if p.token != token::Eof {
 909             cx.span_err(sp, "expected token: `,`");
 910             return None;
 911         }
 912     }
 913     Some(es)
 914 }