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;
  14 use ast::Name;
  15 use codemap;
  16 use codemap::{CodeMap, Span, ExpnId, ExpnInfo, NO_EXPANSION, CompilerExpansion};
  17 use ext;
  18 use ext::expand;
  19 use ext::tt::macro_rules;
  20 use parse;
  21 use parse::parser;
  22 use parse::token;
  23 use parse::token::{InternedString, intern, str_to_ident};
  24 use ptr::P;
  25 use util::small_vector::SmallVector;
  26 use ext::mtwt;
  27 use fold::Folder;
  28
  29 use std::collections::HashMap;
  30 use std::rc::Rc;
  31 use std::default::Default;
  32
  33 #[unstable(feature = "rustc_private")]
  34 #[deprecated(since = "1.0.0", reason = "replaced by MultiItemDecorator")]
  35 pub trait ItemDecorator {
  36     fn expand(&self,
  37               ecx: &mut ExtCtxt,
  38               sp: Span,
  39               meta_item: &ast::MetaItem,
  40               item: &ast::Item,
  41               push: &mut FnMut(P<ast::Item>));
  42 }
  43
  44 #[allow(deprecated)]
  45 #[unstable(feature = "rustc_private")]
  46 #[deprecated(since = "1.0.0", reason = "replaced by MultiItemDecorator")]
  47 impl<F> ItemDecorator for F
  48     where F : Fn(&mut ExtCtxt, Span, &ast::MetaItem, &ast::Item, &mut FnMut(P<ast::Item>))
  49 {
  50     fn expand(&self,
  51               ecx: &mut ExtCtxt,
  52               sp: Span,
  53               meta_item: &ast::MetaItem,
  54               item: &ast::Item,
  55               push: &mut FnMut(P<ast::Item>)) {
  56         (*self)(ecx, sp, meta_item, item, push)
  57     }
  58 }
  59
  60 #[unstable(feature = "rustc_private")]
  61 #[deprecated(since = "1.0.0", reason = "replaced by MultiItemModifier")]
  62 pub trait ItemModifier {
  63     fn expand(&self,
  64               ecx: &mut ExtCtxt,
  65               span: Span,
  66               meta_item: &ast::MetaItem,
  67               item: P<ast::Item>)
  68               -> P<ast::Item>;
  69 }
  70
  71 #[allow(deprecated)]
  72 #[unstable(feature = "rustc_private")]
  73 #[deprecated(since = "1.0.0", reason = "replaced by MultiItemModifier")]
  74 impl<F> ItemModifier for F
  75     where F : Fn(&mut ExtCtxt, Span, &ast::MetaItem, P<ast::Item>) -> P<ast::Item>
  76 {
  77
  78     fn expand(&self,
  79               ecx: &mut ExtCtxt,
  80               span: Span,
  81               meta_item: &ast::MetaItem,
  82               item: P<ast::Item>)
  83               -> P<ast::Item> {
  84         (*self)(ecx, span, meta_item, item)
  85     }
  86 }
  87
  88 #[derive(Debug,Clone)]
  89 pub enum Annotatable {
  90     Item(P<ast::Item>),
  91     TraitItem(P<ast::TraitItem>),
  92     ImplItem(P<ast::ImplItem>),
  93 }
  94
  95 impl Annotatable {
  96     pub fn attrs(&self) -> &[ast::Attribute] {
  97         match *self {
  98             Annotatable::Item(ref i) => &i.attrs,
  99             Annotatable::TraitItem(ref ti) => &ti.attrs,
 100             Annotatable::ImplItem(ref ii) => &ii.attrs,
 101         }
 102     }
 103
 104     pub fn fold_attrs(self, attrs: Vec<ast::Attribute>) -> Annotatable {
 105         match self {
 106             Annotatable::Item(i) => Annotatable::Item(i.map(|i| ast::Item {
 107                 attrs: attrs,
 108                 ..i
 109             })),
 110             Annotatable::TraitItem(i) => Annotatable::TraitItem(i.map(|ti| {
 111                 ast::TraitItem { attrs: attrs, ..ti }
 112             })),
 113             Annotatable::ImplItem(i) => Annotatable::ImplItem(i.map(|ii| {
 114                 ast::ImplItem { attrs: attrs, ..ii }
 115             })),
 116         }
 117     }
 118
 119     pub fn expect_item(self) -> P<ast::Item> {
 120         match self {
 121             Annotatable::Item(i) => i,
 122             _ => panic!("expected Item")
 123         }
 124     }
 125
 126     pub fn map_item_or<F, G>(self, mut f: F, mut or: G) -> Annotatable
 127         where F: FnMut(P<ast::Item>) -> P<ast::Item>,
 128               G: FnMut(Annotatable) -> Annotatable
 129     {
 130         match self {
 131             Annotatable::Item(i) => Annotatable::Item(f(i)),
 132             _ => or(self)
 133         }
 134     }
 135
 136     pub fn expect_trait_item(self) -> P<ast::TraitItem> {
 137         match self {
 138             Annotatable::TraitItem(i) => i,
 139             _ => panic!("expected Item")
 140         }
 141     }
 142
 143     pub fn expect_impl_item(self) -> P<ast::ImplItem> {
 144         match self {
 145             Annotatable::ImplItem(i) => i,
 146             _ => panic!("expected Item")
 147         }
 148     }
 149 }
 150
 151 // A more flexible ItemDecorator.
 152 pub trait MultiItemDecorator {
 153     fn expand(&self,
 154               ecx: &mut ExtCtxt,
 155               sp: Span,
 156               meta_item: &ast::MetaItem,
 157               item: Annotatable,
 158               push: &mut FnMut(Annotatable));
 159 }
 160
 161 impl<F> MultiItemDecorator for F
 162     where F : Fn(&mut ExtCtxt, Span, &ast::MetaItem, Annotatable, &mut FnMut(Annotatable))
 163 {
 164     fn expand(&self,
 165               ecx: &mut ExtCtxt,
 166               sp: Span,
 167               meta_item: &ast::MetaItem,
 168               item: Annotatable,
 169               push: &mut FnMut(Annotatable)) {
 170         (*self)(ecx, sp, meta_item, item, push)
 171     }
 172 }
 173
 174 // A more flexible ItemModifier (ItemModifier should go away, eventually, FIXME).
 175 // meta_item is the annotation, item is the item being modified, parent_item
 176 // is the impl or trait item is declared in if item is part of such a thing.
 177 // FIXME Decorators should follow the same pattern too.
 178 pub trait MultiItemModifier {
 179     fn expand(&self,
 180               ecx: &mut ExtCtxt,
 181               span: Span,
 182               meta_item: &ast::MetaItem,
 183               item: Annotatable)
 184               -> Annotatable;
 185 }
 186
 187 impl<F> MultiItemModifier for F
 188     where F: Fn(&mut ExtCtxt,
 189                 Span,
 190                 &ast::MetaItem,
 191                 Annotatable) -> Annotatable
 192 {
 193     fn expand(&self,
 194               ecx: &mut ExtCtxt,
 195               span: Span,
 196               meta_item: &ast::MetaItem,
 197               item: Annotatable)
 198               -> Annotatable {
 199         (*self)(ecx, span, meta_item, item)
 200     }
 201 }
 202
 203 /// Represents a thing that maps token trees to Macro Results
 204 pub trait TTMacroExpander {
 205     fn expand<'cx>(&self,
 206                    ecx: &'cx mut ExtCtxt,
 207                    span: Span,
 208                    token_tree: &[ast::TokenTree])
 209                    -> Box<MacResult+'cx>;
 210 }
 211
 212 pub type MacroExpanderFn =
 213     for<'cx> fn(&'cx mut ExtCtxt, Span, &[ast::TokenTree]) -> Box<MacResult+'cx>;
 214
 215 impl<F> TTMacroExpander for F
 216     where F : for<'cx> Fn(&'cx mut ExtCtxt, Span, &[ast::TokenTree]) -> Box<MacResult+'cx>
 217 {
 218     fn expand<'cx>(&self,
 219                    ecx: &'cx mut ExtCtxt,
 220                    span: Span,
 221                    token_tree: &[ast::TokenTree])
 222                    -> Box<MacResult+'cx> {
 223         (*self)(ecx, span, token_tree)
 224     }
 225 }
 226
 227 pub trait IdentMacroExpander {
 228     fn expand<'cx>(&self,
 229                    cx: &'cx mut ExtCtxt,
 230                    sp: Span,
 231                    ident: ast::Ident,
 232                    token_tree: Vec<ast::TokenTree> )
 233                    -> Box<MacResult+'cx>;
 234 }
 235
 236 pub type IdentMacroExpanderFn =
 237     for<'cx> fn(&'cx mut ExtCtxt, Span, ast::Ident, Vec<ast::TokenTree>) -> Box<MacResult+'cx>;
 238
 239 impl<F> IdentMacroExpander for F
 240     where F : for<'cx> Fn(&'cx mut ExtCtxt, Span, ast::Ident,
 241                           Vec<ast::TokenTree>) -> Box<MacResult+'cx>
 242 {
 243     fn expand<'cx>(&self,
 244                    cx: &'cx mut ExtCtxt,
 245                    sp: Span,
 246                    ident: ast::Ident,
 247                    token_tree: Vec<ast::TokenTree> )
 248                    -> Box<MacResult+'cx>
 249     {
 250         (*self)(cx, sp, ident, token_tree)
 251     }
 252 }
 253
 254 // Use a macro because forwarding to a simple function has type system issues
 255 macro_rules! make_stmts_default {
 256     ($me:expr) => {
 257         $me.make_expr().map(|e| {
 258             SmallVector::one(P(codemap::respan(
 259                 e.span, ast::StmtExpr(e, ast::DUMMY_NODE_ID))))
 260         })
 261     }
 262 }
 263
 264 /// The result of a macro expansion. The return values of the various
 265 /// methods are spliced into the AST at the callsite of the macro.
 266 pub trait MacResult {
 267     /// Create an expression.
 268     fn make_expr(self: Box<Self>) -> Option<P<ast::Expr>> {
 269         None
 270     }
 271     /// Create zero or more items.
 272     fn make_items(self: Box<Self>) -> Option<SmallVector<P<ast::Item>>> {
 273         None
 274     }
 275
 276     /// Create zero or more impl items.
 277     fn make_impl_items(self: Box<Self>) -> Option<SmallVector<P<ast::ImplItem>>> {
 278         None
 279     }
 280
 281     /// Create a pattern.
 282     fn make_pat(self: Box<Self>) -> Option<P<ast::Pat>> {
 283         None
 284     }
 285
 286     /// Create zero or more statements.
 287     ///
 288     /// By default this attempts to create an expression statement,
 289     /// returning None if that fails.
 290     fn make_stmts(self: Box<Self>) -> Option<SmallVector<P<ast::Stmt>>> {
 291         make_stmts_default!(self)
 292     }
 293 }
 294
 295 macro_rules! make_MacEager {
 296     ( $( $fld:ident: $t:ty, )* ) => {
 297         /// `MacResult` implementation for the common case where you've already
 298         /// built each form of AST that you might return.
 299         #[derive(Default)]
 300         pub struct MacEager {
 301             $(
 302                 pub $fld: Option<$t>,
 303             )*
 304         }
 305
 306         impl MacEager {
 307             $(
 308                 pub fn $fld(v: $t) -> Box<MacResult> {
 309                     Box::new(MacEager {
 310                         $fld: Some(v),
 311                         ..Default::default()
 312                     })
 313                 }
 314             )*
 315         }
 316     }
 317 }
 318
 319 make_MacEager! {
 320     expr: P<ast::Expr>,
 321     pat: P<ast::Pat>,
 322     items: SmallVector<P<ast::Item>>,
 323     impl_items: SmallVector<P<ast::ImplItem>>,
 324     stmts: SmallVector<P<ast::Stmt>>,
 325 }
 326
 327 impl MacResult for MacEager {
 328     fn make_expr(self: Box<Self>) -> Option<P<ast::Expr>> {
 329         self.expr
 330     }
 331
 332     fn make_items(self: Box<Self>) -> Option<SmallVector<P<ast::Item>>> {
 333         self.items
 334     }
 335
 336     fn make_impl_items(self: Box<Self>) -> Option<SmallVector<P<ast::ImplItem>>> {
 337         self.impl_items
 338     }
 339
 340     fn make_stmts(self: Box<Self>) -> Option<SmallVector<P<ast::Stmt>>> {
 341         match self.stmts.as_ref().map_or(0, |s| s.len()) {
 342             0 => make_stmts_default!(self),
 343             _ => self.stmts,
 344         }
 345     }
 346
 347     fn make_pat(self: Box<Self>) -> Option<P<ast::Pat>> {
 348         if let Some(p) = self.pat {
 349             return Some(p);
 350         }
 351         if let Some(e) = self.expr {
 352             if let ast::ExprLit(_) = e.node {
 353                 return Some(P(ast::Pat {
 354                     id: ast::DUMMY_NODE_ID,
 355                     span: e.span,
 356                     node: ast::PatLit(e),
 357                 }));
 358             }
 359         }
 360         None
 361     }
 362 }
 363
 364 /// Fill-in macro expansion result, to allow compilation to continue
 365 /// after hitting errors.
 366 #[derive(Copy, Clone)]
 367 pub struct DummyResult {
 368     expr_only: bool,
 369     span: Span
 370 }
 371
 372 impl DummyResult {
 373     /// Create a default MacResult that can be anything.
 374     ///
 375     /// Use this as a return value after hitting any errors and
 376     /// calling `span_err`.
 377     pub fn any(sp: Span) -> Box<MacResult+'static> {
 378         Box::new(DummyResult { expr_only: false, span: sp })
 379     }
 380
 381     /// Create a default MacResult that can only be an expression.
 382     ///
 383     /// Use this for macros that must expand to an expression, so even
 384     /// if an error is encountered internally, the user will receive
 385     /// an error that they also used it in the wrong place.
 386     pub fn expr(sp: Span) -> Box<MacResult+'static> {
 387         Box::new(DummyResult { expr_only: true, span: sp })
 388     }
 389
 390     /// A plain dummy expression.
 391     pub fn raw_expr(sp: Span) -> P<ast::Expr> {
 392         P(ast::Expr {
 393             id: ast::DUMMY_NODE_ID,
 394             node: ast::ExprLit(P(codemap::respan(sp, ast::LitBool(false)))),
 395             span: sp,
 396         })
 397     }
 398
 399     /// A plain dummy pattern.
 400     pub fn raw_pat(sp: Span) -> ast::Pat {
 401         ast::Pat {
 402             id: ast::DUMMY_NODE_ID,
 403             node: ast::PatWild(ast::PatWildSingle),
 404             span: sp,
 405         }
 406     }
 407
 408 }
 409
 410 impl MacResult for DummyResult {
 411     fn make_expr(self: Box<DummyResult>) -> Option<P<ast::Expr>> {
 412         Some(DummyResult::raw_expr(self.span))
 413     }
 414     fn make_pat(self: Box<DummyResult>) -> Option<P<ast::Pat>> {
 415         Some(P(DummyResult::raw_pat(self.span)))
 416     }
 417     fn make_items(self: Box<DummyResult>) -> Option<SmallVector<P<ast::Item>>> {
 418         // this code needs a comment... why not always just return the Some() ?
 419         if self.expr_only {
 420             None
 421         } else {
 422             Some(SmallVector::zero())
 423         }
 424     }
 425     fn make_impl_items(self: Box<DummyResult>) -> Option<SmallVector<P<ast::ImplItem>>> {
 426         if self.expr_only {
 427             None
 428         } else {
 429             Some(SmallVector::zero())
 430         }
 431     }
 432     fn make_stmts(self: Box<DummyResult>) -> Option<SmallVector<P<ast::Stmt>>> {
 433         Some(SmallVector::one(P(
 434             codemap::respan(self.span,
 435                             ast::StmtExpr(DummyResult::raw_expr(self.span),
 436                                           ast::DUMMY_NODE_ID)))))
 437     }
 438 }
 439
 440 /// An enum representing the different kinds of syntax extensions.
 441 pub enum SyntaxExtension {
 442     /// A syntax extension that is attached to an item and creates new items
 443     /// based upon it.
 444     #[unstable(feature = "rustc_private")]
 445     #[deprecated(since = "1.0.0", reason = "replaced by MultiDecorator")]
 446     #[allow(deprecated)]
 447     Decorator(Box<ItemDecorator + 'static>),
 448
 449     /// A syntax extension that is attached to an item and creates new items
 450     /// based upon it.
 451     ///
 452     /// `#[derive(...)]` is a `MultiItemDecorator`.
 453     MultiDecorator(Box<MultiItemDecorator + 'static>),
 454
 455     /// A syntax extension that is attached to an item and modifies it
 456     /// in-place.
 457     #[unstable(feature = "rustc_private")]
 458     #[deprecated(since = "1.0.0", reason = "replaced by MultiModifier")]
 459     #[allow(deprecated)]
 460     Modifier(Box<ItemModifier + 'static>),
 461
 462     /// A syntax extension that is attached to an item and modifies it
 463     /// in-place. More flexible version than Modifier.
 464     MultiModifier(Box<MultiItemModifier + 'static>),
 465
 466     /// A normal, function-like syntax extension.
 467     ///
 468     /// `bytes!` is a `NormalTT`.
 469     ///
 470     /// The `bool` dictates whether the contents of the macro can
 471     /// directly use `#[unstable]` things (true == yes).
 472     NormalTT(Box<TTMacroExpander + 'static>, Option<Span>, bool),
 473
 474     /// A function-like syntax extension that has an extra ident before
 475     /// the block.
 476     ///
 477     IdentTT(Box<IdentMacroExpander + 'static>, Option<Span>, bool),
 478
 479     /// Represents `macro_rules!` itself.
 480     MacroRulesTT,
 481 }
 482
 483 pub type NamedSyntaxExtension = (Name, SyntaxExtension);
 484
 485 pub struct BlockInfo {
 486     /// Should macros escape from this scope?
 487     pub macros_escape: bool,
 488     /// What are the pending renames?
 489     pub pending_renames: mtwt::RenameList,
 490 }
 491
 492 impl BlockInfo {
 493     pub fn new() -> BlockInfo {
 494         BlockInfo {
 495             macros_escape: false,
 496             pending_renames: Vec::new(),
 497         }
 498     }
 499 }
 500
 501 /// The base map of methods for expanding syntax extension
 502 /// AST nodes into full ASTs
 503 fn initial_syntax_expander_table<'feat>(ecfg: &expand::ExpansionConfig<'feat>)
 504                                         -> SyntaxEnv {
 505     // utility function to simplify creating NormalTT syntax extensions
 506     fn builtin_normal_expander(f: MacroExpanderFn) -> SyntaxExtension {
 507         NormalTT(Box::new(f), None, false)
 508     }
 509
 510     let mut syntax_expanders = SyntaxEnv::new();
 511     syntax_expanders.insert(intern("macro_rules"), MacroRulesTT);
 512     syntax_expanders.insert(intern("format_args"),
 513                             // format_args uses `unstable` things internally.
 514                             NormalTT(Box::new(ext::format::expand_format_args), None, true));
 515     syntax_expanders.insert(intern("env"),
 516                             builtin_normal_expander(
 517                                     ext::env::expand_env));
 518     syntax_expanders.insert(intern("option_env"),
 519                             builtin_normal_expander(
 520                                     ext::env::expand_option_env));
 521     syntax_expanders.insert(intern("concat_idents"),
 522                             builtin_normal_expander(
 523                                     ext::concat_idents::expand_syntax_ext));
 524     syntax_expanders.insert(intern("concat"),
 525                             builtin_normal_expander(
 526                                     ext::concat::expand_syntax_ext));
 527     syntax_expanders.insert(intern("log_syntax"),
 528                             builtin_normal_expander(
 529                                     ext::log_syntax::expand_syntax_ext));
 530
 531     ext::deriving::register_all(&mut syntax_expanders);
 532
 533     if ecfg.enable_quotes() {
 534         // Quasi-quoting expanders
 535         syntax_expanders.insert(intern("quote_tokens"),
 536                            builtin_normal_expander(
 537                                 ext::quote::expand_quote_tokens));
 538         syntax_expanders.insert(intern("quote_expr"),
 539                            builtin_normal_expander(
 540                                 ext::quote::expand_quote_expr));
 541         syntax_expanders.insert(intern("quote_ty"),
 542                            builtin_normal_expander(
 543                                 ext::quote::expand_quote_ty));
 544         syntax_expanders.insert(intern("quote_item"),
 545                            builtin_normal_expander(
 546                                 ext::quote::expand_quote_item));
 547         syntax_expanders.insert(intern("quote_pat"),
 548                            builtin_normal_expander(
 549                                 ext::quote::expand_quote_pat));
 550         syntax_expanders.insert(intern("quote_arm"),
 551                            builtin_normal_expander(
 552                                 ext::quote::expand_quote_arm));
 553         syntax_expanders.insert(intern("quote_stmt"),
 554                            builtin_normal_expander(
 555                                 ext::quote::expand_quote_stmt));
 556         syntax_expanders.insert(intern("quote_matcher"),
 557                            builtin_normal_expander(
 558                                 ext::quote::expand_quote_matcher));
 559         syntax_expanders.insert(intern("quote_attr"),
 560                            builtin_normal_expander(
 561                                 ext::quote::expand_quote_attr));
 562     }
 563
 564     syntax_expanders.insert(intern("line"),
 565                             builtin_normal_expander(
 566                                     ext::source_util::expand_line));
 567     syntax_expanders.insert(intern("column"),
 568                             builtin_normal_expander(
 569                                     ext::source_util::expand_column));
 570     syntax_expanders.insert(intern("file"),
 571                             builtin_normal_expander(
 572                                     ext::source_util::expand_file));
 573     syntax_expanders.insert(intern("stringify"),
 574                             builtin_normal_expander(
 575                                     ext::source_util::expand_stringify));
 576     syntax_expanders.insert(intern("include"),
 577                             builtin_normal_expander(
 578                                     ext::source_util::expand_include));
 579     syntax_expanders.insert(intern("include_str"),
 580                             builtin_normal_expander(
 581                                     ext::source_util::expand_include_str));
 582     syntax_expanders.insert(intern("include_bytes"),
 583                             builtin_normal_expander(
 584                                     ext::source_util::expand_include_bytes));
 585     syntax_expanders.insert(intern("module_path"),
 586                             builtin_normal_expander(
 587                                     ext::source_util::expand_mod));
 588     syntax_expanders.insert(intern("asm"),
 589                             builtin_normal_expander(
 590                                     ext::asm::expand_asm));
 591     syntax_expanders.insert(intern("cfg"),
 592                             builtin_normal_expander(
 593                                     ext::cfg::expand_cfg));
 594     syntax_expanders.insert(intern("trace_macros"),
 595                             builtin_normal_expander(
 596                                     ext::trace_macros::expand_trace_macros));
 597     syntax_expanders
 598 }
 599
 600 /// One of these is made during expansion and incrementally updated as we go;
 601 /// when a macro expansion occurs, the resulting nodes have the backtrace()
 602 /// -> expn_info of their expansion context stored into their span.
 603 pub struct ExtCtxt<'a> {
 604     pub parse_sess: &'a parse::ParseSess,
 605     pub cfg: ast::CrateConfig,
 606     pub backtrace: ExpnId,
 607     pub ecfg: expand::ExpansionConfig<'a>,
 608     pub use_std: bool,
 609
 610     pub mod_path: Vec<ast::Ident> ,
 611     pub exported_macros: Vec<ast::MacroDef>,
 612
 613     pub syntax_env: SyntaxEnv,
 614     pub recursion_count: usize,
 615 }
 616
 617 impl<'a> ExtCtxt<'a> {
 618     pub fn new(parse_sess: &'a parse::ParseSess, cfg: ast::CrateConfig,
 619                ecfg: expand::ExpansionConfig<'a>) -> ExtCtxt<'a> {
 620         let env = initial_syntax_expander_table(&ecfg);
 621         ExtCtxt {
 622             parse_sess: parse_sess,
 623             cfg: cfg,
 624             backtrace: NO_EXPANSION,
 625             mod_path: Vec::new(),
 626             ecfg: ecfg,
 627             use_std: true,
 628             exported_macros: Vec::new(),
 629             syntax_env: env,
 630             recursion_count: 0,
 631         }
 632     }
 633
 634     #[unstable(feature = "rustc_private")]
 635     #[deprecated(since = "1.0.0",
 636                  reason = "Replaced with `expander().fold_expr()`")]
 637     pub fn expand_expr(&mut self, e: P<ast::Expr>) -> P<ast::Expr> {
 638         self.expander().fold_expr(e)
 639     }
 640
 641     /// Returns a `Folder` for deeply expanding all macros in a AST node.
 642     pub fn expander<'b>(&'b mut self) -> expand::MacroExpander<'b, 'a> {
 643         expand::MacroExpander::new(self)
 644     }
 645
 646     pub fn new_parser_from_tts(&self, tts: &[ast::TokenTree])
 647         -> parser::Parser<'a> {
 648         parse::tts_to_parser(self.parse_sess, tts.to_vec(), self.cfg())
 649     }
 650
 651     pub fn codemap(&self) -> &'a CodeMap { &self.parse_sess.span_diagnostic.cm }
 652     pub fn parse_sess(&self) -> &'a parse::ParseSess { self.parse_sess }
 653     pub fn cfg(&self) -> ast::CrateConfig { self.cfg.clone() }
 654     pub fn call_site(&self) -> Span {
 655         self.codemap().with_expn_info(self.backtrace, |ei| match ei {
 656             Some(expn_info) => expn_info.call_site,
 657             None => self.bug("missing top span")
 658         })
 659     }
 660     pub fn backtrace(&self) -> ExpnId { self.backtrace }
 661
 662     /// Original span that caused the current exapnsion to happen.
 663     pub fn original_span(&self) -> Span {
 664         let mut expn_id = self.backtrace;
 665         let mut call_site = None;
 666         loop {
 667             match self.codemap().with_expn_info(expn_id, |ei| ei.map(|ei| ei.call_site)) {
 668                 None => break,
 669                 Some(cs) => {
 670                     call_site = Some(cs);
 671                     expn_id = cs.expn_id;
 672                 }
 673             }
 674         }
 675         call_site.expect("missing expansion backtrace")
 676     }
 677
 678     /// Returns span for the macro which originally caused the current expansion to happen.
 679     ///
 680     /// Stops backtracing at include! boundary.
 681     pub fn expansion_cause(&self) -> Span {
 682         let mut expn_id = self.backtrace;
 683         let mut last_macro = None;
 684         loop {
 685             if self.codemap().with_expn_info(expn_id, |info| {
 686                 info.map_or(None, |i| {
 687                     if i.callee.name == "include" {
 688                         // Stop going up the backtrace once include! is encountered
 689                         return None;
 690                     }
 691                     expn_id = i.call_site.expn_id;
 692                     if i.callee.format != CompilerExpansion {
 693                         last_macro = Some(i.call_site)
 694                     }
 695                     return Some(());
 696                 })
 697             }).is_none() {
 698                 break
 699             }
 700         }
 701         last_macro.expect("missing expansion backtrace")
 702     }
 703
 704     pub fn mod_push(&mut self, i: ast::Ident) { self.mod_path.push(i); }
 705     pub fn mod_pop(&mut self) { self.mod_path.pop().unwrap(); }
 706     pub fn mod_path(&self) -> Vec<ast::Ident> {
 707         let mut v = Vec::new();
 708         v.push(token::str_to_ident(&self.ecfg.crate_name));
 709         v.extend(self.mod_path.iter().cloned());
 710         return v;
 711     }
 712     pub fn bt_push(&mut self, ei: ExpnInfo) {
 713         self.recursion_count += 1;
 714         if self.recursion_count > self.ecfg.recursion_limit {
 715             panic!(self.span_fatal(ei.call_site,
 716                             &format!("recursion limit reached while expanding the macro `{}`",
 717                                     ei.callee.name)));
 718         }
 719
 720         let mut call_site = ei.call_site;
 721         call_site.expn_id = self.backtrace;
 722         self.backtrace = self.codemap().record_expansion(ExpnInfo {
 723             call_site: call_site,
 724             callee: ei.callee
 725         });
 726     }
 727     pub fn bt_pop(&mut self) {
 728         match self.backtrace {
 729             NO_EXPANSION => self.bug("tried to pop without a push"),
 730             expn_id => {
 731                 self.recursion_count -= 1;
 732                 self.backtrace = self.codemap().with_expn_info(expn_id, |expn_info| {
 733                     expn_info.map_or(NO_EXPANSION, |ei| ei.call_site.expn_id)
 734                 });
 735             }
 736         }
 737     }
 738
 739     pub fn insert_macro(&mut self, def: ast::MacroDef) {
 740         if def.export {
 741             self.exported_macros.push(def.clone());
 742         }
 743         if def.use_locally {
 744             let ext = macro_rules::compile(self, &def);
 745             self.syntax_env.insert(def.ident.name, ext);
 746         }
 747     }
 748
 749     /// Emit `msg` attached to `sp`, and stop compilation immediately.
 750     ///
 751     /// `span_err` should be strongly preferred where-ever possible:
 752     /// this should *only* be used when
 753     /// - continuing has a high risk of flow-on errors (e.g. errors in
 754     ///   declaring a macro would cause all uses of that macro to
 755     ///   complain about "undefined macro"), or
 756     /// - there is literally nothing else that can be done (however,
 757     ///   in most cases one can construct a dummy expression/item to
 758     ///   substitute; we never hit resolve/type-checking so the dummy
 759     ///   value doesn't have to match anything)
 760     pub fn span_fatal(&self, sp: Span, msg: &str) -> ! {
 761         panic!(self.parse_sess.span_diagnostic.span_fatal(sp, msg));
 762     }
 763
 764     /// Emit `msg` attached to `sp`, without immediately stopping
 765     /// compilation.
 766     ///
 767     /// Compilation will be stopped in the near future (at the end of
 768     /// the macro expansion phase).
 769     pub fn span_err(&self, sp: Span, msg: &str) {
 770         self.parse_sess.span_diagnostic.span_err(sp, msg);
 771     }
 772     pub fn span_warn(&self, sp: Span, msg: &str) {
 773         self.parse_sess.span_diagnostic.span_warn(sp, msg);
 774     }
 775     pub fn span_unimpl(&self, sp: Span, msg: &str) -> ! {
 776         self.parse_sess.span_diagnostic.span_unimpl(sp, msg);
 777     }
 778     pub fn span_bug(&self, sp: Span, msg: &str) -> ! {
 779         self.parse_sess.span_diagnostic.span_bug(sp, msg);
 780     }
 781     pub fn span_note(&self, sp: Span, msg: &str) {
 782         self.parse_sess.span_diagnostic.span_note(sp, msg);
 783     }
 784     pub fn span_help(&self, sp: Span, msg: &str) {
 785         self.parse_sess.span_diagnostic.span_help(sp, msg);
 786     }
 787     pub fn fileline_help(&self, sp: Span, msg: &str) {
 788         self.parse_sess.span_diagnostic.fileline_help(sp, msg);
 789     }
 790     pub fn bug(&self, msg: &str) -> ! {
 791         self.parse_sess.span_diagnostic.handler().bug(msg);
 792     }
 793     pub fn trace_macros(&self) -> bool {
 794         self.ecfg.trace_mac
 795     }
 796     pub fn set_trace_macros(&mut self, x: bool) {
 797         self.ecfg.trace_mac = x
 798     }
 799     pub fn ident_of(&self, st: &str) -> ast::Ident {
 800         str_to_ident(st)
 801     }
 802     pub fn ident_of_std(&self, st: &str) -> ast::Ident {
 803         self.ident_of(if self.use_std { "std" } else { st })
 804     }
 805     pub fn name_of(&self, st: &str) -> ast::Name {
 806         token::intern(st)
 807     }
 808 }
 809
 810 /// Extract a string literal from the macro expanded version of `expr`,
 811 /// emitting `err_msg` if `expr` is not a string literal. This does not stop
 812 /// compilation on error, merely emits a non-fatal error and returns None.
 813 pub fn expr_to_string(cx: &mut ExtCtxt, expr: P<ast::Expr>, err_msg: &str)
 814                       -> Option<(InternedString, ast::StrStyle)> {
 815     // we want to be able to handle e.g. concat("foo", "bar")
 816     let expr = cx.expander().fold_expr(expr);
 817     match expr.node {
 818         ast::ExprLit(ref l) => match l.node {
 819             ast::LitStr(ref s, style) => return Some(((*s).clone(), style)),
 820             _ => cx.span_err(l.span, err_msg)
 821         },
 822         _ => cx.span_err(expr.span, err_msg)
 823     }
 824     None
 825 }
 826
 827 /// Non-fatally assert that `tts` is empty. Note that this function
 828 /// returns even when `tts` is non-empty, macros that *need* to stop
 829 /// compilation should call
 830 /// `cx.parse_sess.span_diagnostic.abort_if_errors()` (this should be
 831 /// done as rarely as possible).
 832 pub fn check_zero_tts(cx: &ExtCtxt,
 833                       sp: Span,
 834                       tts: &[ast::TokenTree],
 835                       name: &str) {
 836     if !tts.is_empty() {
 837         cx.span_err(sp, &format!("{} takes no arguments", name));
 838     }
 839 }
 840
 841 /// Extract the string literal from the first token of `tts`. If this
 842 /// is not a string literal, emit an error and return None.
 843 pub fn get_single_str_from_tts(cx: &mut ExtCtxt,
 844                                sp: Span,
 845                                tts: &[ast::TokenTree],
 846                                name: &str)
 847                                -> Option<String> {
 848     let mut p = cx.new_parser_from_tts(tts);
 849     if p.token == token::Eof {
 850         cx.span_err(sp, &format!("{} takes 1 argument", name));
 851         return None
 852     }
 853     let ret = cx.expander().fold_expr(p.parse_expr());
 854     if p.token != token::Eof {
 855         cx.span_err(sp, &format!("{} takes 1 argument", name));
 856     }
 857     expr_to_string(cx, ret, "argument must be a string literal").map(|(s, _)| {
 858         s.to_string()
 859     })
 860 }
 861
 862 /// Extract comma-separated expressions from `tts`. If there is a
 863 /// parsing error, emit a non-fatal error and return None.
 864 pub fn get_exprs_from_tts(cx: &mut ExtCtxt,
 865                           sp: Span,
 866                           tts: &[ast::TokenTree]) -> Option<Vec<P<ast::Expr>>> {
 867     let mut p = cx.new_parser_from_tts(tts);
 868     let mut es = Vec::new();
 869     while p.token != token::Eof {
 870         es.push(cx.expander().fold_expr(p.parse_expr()));
 871         if panictry!(p.eat(&token::Comma)){
 872             continue;
 873         }
 874         if p.token != token::Eof {
 875             cx.span_err(sp, "expected token: `,`");
 876             return None;
 877         }
 878     }
 879     Some(es)
 880 }
 881
 882 /// In order to have some notion of scoping for macros,
 883 /// we want to implement the notion of a transformation
 884 /// environment.
 885 ///
 886 /// This environment maps Names to SyntaxExtensions.
 887 pub struct SyntaxEnv {
 888     chain: Vec<MapChainFrame> ,
 889 }
 890
 891 // impl question: how to implement it? Initially, the
 892 // env will contain only macros, so it might be painful
 893 // to add an empty frame for every context. Let's just
 894 // get it working, first....
 895
 896 // NB! the mutability of the underlying maps means that
 897 // if expansion is out-of-order, a deeper scope may be
 898 // able to refer to a macro that was added to an enclosing
 899 // scope lexically later than the deeper scope.
 900
 901 struct MapChainFrame {
 902     info: BlockInfo,
 903     map: HashMap<Name, Rc<SyntaxExtension>>,
 904 }
 905
 906 impl SyntaxEnv {
 907     fn new() -> SyntaxEnv {
 908         let mut map = SyntaxEnv { chain: Vec::new() };
 909         map.push_frame();
 910         map
 911     }
 912
 913     pub fn push_frame(&mut self) {
 914         self.chain.push(MapChainFrame {
 915             info: BlockInfo::new(),
 916             map: HashMap::new(),
 917         });
 918     }
 919
 920     pub fn pop_frame(&mut self) {
 921         assert!(self.chain.len() > 1, "too many pops on MapChain!");
 922         self.chain.pop();
 923     }
 924
 925     fn find_escape_frame<'a>(&'a mut self) -> &'a mut MapChainFrame {
 926         for (i, frame) in self.chain.iter_mut().enumerate().rev() {
 927             if !frame.info.macros_escape || i == 0 {
 928                 return frame
 929             }
 930         }
 931         unreachable!()
 932     }
 933
 934     pub fn find(&self, k: &Name) -> Option<Rc<SyntaxExtension>> {
 935         for frame in self.chain.iter().rev() {
 936             match frame.map.get(k) {
 937                 Some(v) => return Some(v.clone()),
 938                 None => {}
 939             }
 940         }
 941         None
 942     }
 943
 944     pub fn insert(&mut self, k: Name, v: SyntaxExtension) {
 945         self.find_escape_frame().map.insert(k, Rc::new(v));
 946     }
 947
 948     pub fn info<'a>(&'a mut self) -> &'a mut BlockInfo {
 949         let last_chain_index = self.chain.len() - 1;
 950         &mut self.chain[last_chain_index].info
 951     }
 952 }