src/libsyntax/print/pprust.rs

   1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 pub use self::AnnNode::*;
  12
  13 use abi;
  14 use ast;
  15 use ast::{RegionTyParamBound, TraitTyParamBound, TraitBoundModifier};
  16 use ast_util;
  17 use attr;
  18 use owned_slice::OwnedSlice;
  19 use attr::{AttrMetaMethods, AttributeMethods};
  20 use codemap::{self, CodeMap, BytePos};
  21 use diagnostic;
  22 use parse::token::{self, BinOpToken, Token, InternedString};
  23 use parse::lexer::comments;
  24 use parse;
  25 use print::pp::{self, break_offset, word, space, zerobreak, hardbreak};
  26 use print::pp::{Breaks, eof};
  27 use print::pp::Breaks::{Consistent, Inconsistent};
  28 use ptr::P;
  29 use std_inject;
  30
  31 use std::ascii;
  32 use std::io::{self, Write, Read};
  33 use std::iter;
  34
  35 pub enum AnnNode<'a> {
  36     NodeIdent(&'a ast::Ident),
  37     NodeName(&'a ast::Name),
  38     NodeBlock(&'a ast::Block),
  39     NodeItem(&'a ast::Item),
  40     NodeSubItem(ast::NodeId),
  41     NodeExpr(&'a ast::Expr),
  42     NodePat(&'a ast::Pat),
  43 }
  44
  45 pub trait PpAnn {
  46     fn pre(&self, _state: &mut State, _node: AnnNode) -> io::Result<()> { Ok(()) }
  47     fn post(&self, _state: &mut State, _node: AnnNode) -> io::Result<()> { Ok(()) }
  48 }
  49
  50 #[derive(Copy, Clone)]
  51 pub struct NoAnn;
  52
  53 impl PpAnn for NoAnn {}
  54
  55 #[derive(Copy, Clone)]
  56 pub struct CurrentCommentAndLiteral {
  57     pub cur_cmnt: usize,
  58     pub cur_lit: usize,
  59 }
  60
  61 pub struct State<'a> {
  62     pub s: pp::Printer<'a>,
  63     cm: Option<&'a CodeMap>,
  64     comments: Option<Vec<comments::Comment> >,
  65     literals: Option<Vec<comments::Literal> >,
  66     cur_cmnt_and_lit: CurrentCommentAndLiteral,
  67     boxes: Vec<pp::Breaks>,
  68     ann: &'a (PpAnn+'a),
  69 }
  70
  71 pub fn rust_printer<'a>(writer: Box<Write+'a>) -> State<'a> {
  72     static NO_ANN: NoAnn = NoAnn;
  73     rust_printer_annotated(writer, &NO_ANN)
  74 }
  75
  76 pub fn rust_printer_annotated<'a>(writer: Box<Write+'a>,
  77                                   ann: &'a PpAnn) -> State<'a> {
  78     State {
  79         s: pp::mk_printer(writer, default_columns),
  80         cm: None,
  81         comments: None,
  82         literals: None,
  83         cur_cmnt_and_lit: CurrentCommentAndLiteral {
  84             cur_cmnt: 0,
  85             cur_lit: 0
  86         },
  87         boxes: Vec::new(),
  88         ann: ann,
  89     }
  90 }
  91
  92 #[allow(non_upper_case_globals)]
  93 pub const indent_unit: usize = 4;
  94
  95 #[allow(non_upper_case_globals)]
  96 pub const default_columns: usize = 78;
  97
  98 /// Requires you to pass an input filename and reader so that
  99 /// it can scan the input text for comments and literals to
 100 /// copy forward.
 101 pub fn print_crate<'a>(cm: &'a CodeMap,
 102                        span_diagnostic: &diagnostic::SpanHandler,
 103                        krate: &ast::Crate,
 104                        filename: String,
 105                        input: &mut Read,
 106                        out: Box<Write+'a>,
 107                        ann: &'a PpAnn,
 108                        is_expanded: bool) -> io::Result<()> {
 109     let mut s = State::new_from_input(cm,
 110                                       span_diagnostic,
 111                                       filename,
 112                                       input,
 113                                       out,
 114                                       ann,
 115                                       is_expanded);
 116     if is_expanded && !std_inject::no_std(krate) {
 117         // We need to print `#![no_std]` (and its feature gate) so that
 118         // compiling pretty-printed source won't inject libstd again.
 119         // However we don't want these attributes in the AST because
 120         // of the feature gate, so we fake them up here.
 121
 122         let no_std_meta = attr::mk_word_item(InternedString::new("no_std"));
 123         let prelude_import_meta = attr::mk_word_item(InternedString::new("prelude_import"));
 124
 125         // #![feature(no_std)]
 126         let fake_attr = attr::mk_attr_inner(attr::mk_attr_id(),
 127                                             attr::mk_list_item(InternedString::new("feature"),
 128                                                                vec![no_std_meta.clone(),
 129                                                                     prelude_import_meta]));
 130         try!(s.print_attribute(&fake_attr));
 131
 132         // #![no_std]
 133         let fake_attr = attr::mk_attr_inner(attr::mk_attr_id(), no_std_meta);
 134         try!(s.print_attribute(&fake_attr));
 135     }
 136
 137     try!(s.print_mod(&krate.module, &krate.attrs));
 138     try!(s.print_remaining_comments());
 139     eof(&mut s.s)
 140 }
 141
 142 impl<'a> State<'a> {
 143     pub fn new_from_input(cm: &'a CodeMap,
 144                           span_diagnostic: &diagnostic::SpanHandler,
 145                           filename: String,
 146                           input: &mut Read,
 147                           out: Box<Write+'a>,
 148                           ann: &'a PpAnn,
 149                           is_expanded: bool) -> State<'a> {
 150         let (cmnts, lits) = comments::gather_comments_and_literals(
 151             span_diagnostic,
 152             filename,
 153             input);
 154
 155         State::new(
 156             cm,
 157             out,
 158             ann,
 159             Some(cmnts),
 160             // If the code is post expansion, don't use the table of
 161             // literals, since it doesn't correspond with the literals
 162             // in the AST anymore.
 163             if is_expanded { None } else { Some(lits) })
 164     }
 165
 166     pub fn new(cm: &'a CodeMap,
 167                out: Box<Write+'a>,
 168                ann: &'a PpAnn,
 169                comments: Option<Vec<comments::Comment>>,
 170                literals: Option<Vec<comments::Literal>>) -> State<'a> {
 171         State {
 172             s: pp::mk_printer(out, default_columns),
 173             cm: Some(cm),
 174             comments: comments,
 175             literals: literals,
 176             cur_cmnt_and_lit: CurrentCommentAndLiteral {
 177                 cur_cmnt: 0,
 178                 cur_lit: 0
 179             },
 180             boxes: Vec::new(),
 181             ann: ann,
 182         }
 183     }
 184 }
 185
 186 pub fn to_string<F>(f: F) -> String where
 187     F: FnOnce(&mut State) -> io::Result<()>,
 188 {
 189     let mut wr = Vec::new();
 190     {
 191         let mut printer = rust_printer(Box::new(&mut wr));
 192         f(&mut printer).unwrap();
 193         eof(&mut printer.s).unwrap();
 194     }
 195     String::from_utf8(wr).unwrap()
 196 }
 197
 198 pub fn binop_to_string(op: BinOpToken) -> &'static str {
 199     match op {
 200         token::Plus     => "+",
 201         token::Minus    => "-",
 202         token::Star     => "*",
 203         token::Slash    => "/",
 204         token::Percent  => "%",
 205         token::Caret    => "^",
 206         token::And      => "&",
 207         token::Or       => "|",
 208         token::Shl      => "<<",
 209         token::Shr      => ">>",
 210     }
 211 }
 212
 213 pub fn token_to_string(tok: &Token) -> String {
 214     match *tok {
 215         token::Eq                   => "=".to_string(),
 216         token::Lt                   => "<".to_string(),
 217         token::Le                   => "<=".to_string(),
 218         token::EqEq                 => "==".to_string(),
 219         token::Ne                   => "!=".to_string(),
 220         token::Ge                   => ">=".to_string(),
 221         token::Gt                   => ">".to_string(),
 222         token::Not                  => "!".to_string(),
 223         token::Tilde                => "~".to_string(),
 224         token::OrOr                 => "||".to_string(),
 225         token::AndAnd               => "&&".to_string(),
 226         token::BinOp(op)            => binop_to_string(op).to_string(),
 227         token::BinOpEq(op)          => format!("{}=", binop_to_string(op)),
 228
 229         /* Structural symbols */
 230         token::At                   => "@".to_string(),
 231         token::Dot                  => ".".to_string(),
 232         token::DotDot               => "..".to_string(),
 233         token::DotDotDot            => "...".to_string(),
 234         token::Comma                => ",".to_string(),
 235         token::Semi                 => ";".to_string(),
 236         token::Colon                => ":".to_string(),
 237         token::ModSep               => "::".to_string(),
 238         token::RArrow               => "->".to_string(),
 239         token::LArrow               => "<-".to_string(),
 240         token::FatArrow             => "=>".to_string(),
 241         token::OpenDelim(token::Paren) => "(".to_string(),
 242         token::CloseDelim(token::Paren) => ")".to_string(),
 243         token::OpenDelim(token::Bracket) => "[".to_string(),
 244         token::CloseDelim(token::Bracket) => "]".to_string(),
 245         token::OpenDelim(token::Brace) => "{".to_string(),
 246         token::CloseDelim(token::Brace) => "}".to_string(),
 247         token::Pound                => "#".to_string(),
 248         token::Dollar               => "$".to_string(),
 249         token::Question             => "?".to_string(),
 250
 251         /* Literals */
 252         token::Literal(lit, suf) => {
 253             let mut out = match lit {
 254                 token::Byte(b)           => format!("b'{}'", b),
 255                 token::Char(c)           => format!("'{}'", c),
 256                 token::Float(c)          => c.to_string(),
 257                 token::Integer(c)        => c.to_string(),
 258                 token::Str_(s)           => format!("\"{}\"", s),
 259                 token::StrRaw(s, n)      => format!("r{delim}\"{string}\"{delim}",
 260                                                     delim=repeat("#", n),
 261                                                     string=s),
 262                 token::ByteStr(v)         => format!("b\"{}\"", v),
 263                 token::ByteStrRaw(s, n)   => format!("br{delim}\"{string}\"{delim}",
 264                                                     delim=repeat("#", n),
 265                                                     string=s),
 266             };
 267
 268             if let Some(s) = suf {
 269                 out.push_str(&s.as_str())
 270             }
 271
 272             out
 273         }
 274
 275         /* Name components */
 276         token::Ident(s, _)          => s.to_string(),
 277         token::Lifetime(s)          => s.to_string(),
 278         token::Underscore           => "_".to_string(),
 279
 280         /* Other */
 281         token::DocComment(s)        => s.to_string(),
 282         token::SubstNt(s, _)        => format!("${}", s),
 283         token::MatchNt(s, t, _, _)  => format!("${}:{}", s, t),
 284         token::Eof                  => "<eof>".to_string(),
 285         token::Whitespace           => " ".to_string(),
 286         token::Comment              => "/* */".to_string(),
 287         token::Shebang(s)           => format!("/* shebang: {}*/", s),
 288
 289         token::SpecialVarNt(var)    => format!("${}", var.as_str()),
 290
 291         token::Interpolated(ref nt) => match *nt {
 292             token::NtExpr(ref e)        => expr_to_string(&**e),
 293             token::NtMeta(ref e)        => meta_item_to_string(&**e),
 294             token::NtTy(ref e)          => ty_to_string(&**e),
 295             token::NtPath(ref e)        => path_to_string(&**e),
 296             token::NtItem(ref e)        => item_to_string(&**e),
 297             token::NtBlock(ref e)       => block_to_string(&**e),
 298             token::NtStmt(ref e)        => stmt_to_string(&**e),
 299             token::NtPat(ref e)         => pat_to_string(&**e),
 300             token::NtIdent(ref e, _)    => ident_to_string(**e),
 301             token::NtTT(ref e)          => tt_to_string(&**e),
 302             token::NtArm(ref e)         => arm_to_string(&*e),
 303             token::NtImplItem(ref e)    => impl_item_to_string(&**e),
 304             token::NtTraitItem(ref e)   => trait_item_to_string(&**e),
 305             token::NtGenerics(ref e)    => generics_to_string(&*e),
 306             token::NtWhereClause(ref e) => where_clause_to_string(&*e),
 307         }
 308     }
 309 }
 310
 311 pub fn ty_to_string(ty: &ast::Ty) -> String {
 312     to_string(|s| s.print_type(ty))
 313 }
 314
 315 pub fn bounds_to_string(bounds: &[ast::TyParamBound]) -> String {
 316     to_string(|s| s.print_bounds("", bounds))
 317 }
 318
 319 pub fn pat_to_string(pat: &ast::Pat) -> String {
 320     to_string(|s| s.print_pat(pat))
 321 }
 322
 323 pub fn arm_to_string(arm: &ast::Arm) -> String {
 324     to_string(|s| s.print_arm(arm))
 325 }
 326
 327 pub fn expr_to_string(e: &ast::Expr) -> String {
 328     to_string(|s| s.print_expr(e))
 329 }
 330
 331 pub fn lifetime_to_string(e: &ast::Lifetime) -> String {
 332     to_string(|s| s.print_lifetime(e))
 333 }
 334
 335 pub fn tt_to_string(tt: &ast::TokenTree) -> String {
 336     to_string(|s| s.print_tt(tt))
 337 }
 338
 339 pub fn tts_to_string(tts: &[ast::TokenTree]) -> String {
 340     to_string(|s| s.print_tts(tts))
 341 }
 342
 343 pub fn stmt_to_string(stmt: &ast::Stmt) -> String {
 344     to_string(|s| s.print_stmt(stmt))
 345 }
 346
 347 pub fn attr_to_string(attr: &ast::Attribute) -> String {
 348     to_string(|s| s.print_attribute(attr))
 349 }
 350
 351 pub fn item_to_string(i: &ast::Item) -> String {
 352     to_string(|s| s.print_item(i))
 353 }
 354
 355 pub fn impl_item_to_string(i: &ast::ImplItem) -> String {
 356     to_string(|s| s.print_impl_item(i))
 357 }
 358
 359 pub fn trait_item_to_string(i: &ast::TraitItem) -> String {
 360     to_string(|s| s.print_trait_item(i))
 361 }
 362
 363 pub fn generics_to_string(generics: &ast::Generics) -> String {
 364     to_string(|s| s.print_generics(generics))
 365 }
 366
 367 pub fn where_clause_to_string(i: &ast::WhereClause) -> String {
 368     to_string(|s| s.print_where_clause(i))
 369 }
 370
 371 pub fn fn_block_to_string(p: &ast::FnDecl) -> String {
 372     to_string(|s| s.print_fn_block_args(p))
 373 }
 374
 375 pub fn path_to_string(p: &ast::Path) -> String {
 376     to_string(|s| s.print_path(p, false, 0))
 377 }
 378
 379 pub fn ident_to_string(id: ast::Ident) -> String {
 380     to_string(|s| s.print_ident(id))
 381 }
 382
 383 pub fn fun_to_string(decl: &ast::FnDecl,
 384                      unsafety: ast::Unsafety,
 385                      constness: ast::Constness,
 386                      name: ast::Ident,
 387                      opt_explicit_self: Option<&ast::ExplicitSelf_>,
 388                      generics: &ast::Generics)
 389                      -> String {
 390     to_string(|s| {
 391         try!(s.head(""));
 392         try!(s.print_fn(decl, unsafety, constness, abi::Rust, Some(name),
 393                         generics, opt_explicit_self, ast::Inherited));
 394         try!(s.end()); // Close the head box
 395         s.end() // Close the outer box
 396     })
 397 }
 398
 399 pub fn block_to_string(blk: &ast::Block) -> String {
 400     to_string(|s| {
 401         // containing cbox, will be closed by print-block at }
 402         try!(s.cbox(indent_unit));
 403         // head-ibox, will be closed by print-block after {
 404         try!(s.ibox(0));
 405         s.print_block(blk)
 406     })
 407 }
 408
 409 pub fn meta_item_to_string(mi: &ast::MetaItem) -> String {
 410     to_string(|s| s.print_meta_item(mi))
 411 }
 412
 413 pub fn attribute_to_string(attr: &ast::Attribute) -> String {
 414     to_string(|s| s.print_attribute(attr))
 415 }
 416
 417 pub fn lit_to_string(l: &ast::Lit) -> String {
 418     to_string(|s| s.print_literal(l))
 419 }
 420
 421 pub fn explicit_self_to_string(explicit_self: &ast::ExplicitSelf_) -> String {
 422     to_string(|s| s.print_explicit_self(explicit_self, ast::MutImmutable).map(|_| {}))
 423 }
 424
 425 pub fn variant_to_string(var: &ast::Variant) -> String {
 426     to_string(|s| s.print_variant(var))
 427 }
 428
 429 pub fn arg_to_string(arg: &ast::Arg) -> String {
 430     to_string(|s| s.print_arg(arg))
 431 }
 432
 433 pub fn mac_to_string(arg: &ast::Mac) -> String {
 434     to_string(|s| s.print_mac(arg, ::parse::token::Paren))
 435 }
 436
 437 pub fn visibility_qualified(vis: ast::Visibility, s: &str) -> String {
 438     match vis {
 439         ast::Public => format!("pub {}", s),
 440         ast::Inherited => s.to_string()
 441     }
 442 }
 443
 444 fn needs_parentheses(expr: &ast::Expr) -> bool {
 445     match expr.node {
 446         ast::ExprAssign(..) | ast::ExprBinary(..) |
 447         ast::ExprClosure(..) |
 448         ast::ExprAssignOp(..) | ast::ExprCast(..) => true,
 449         _ => false,
 450     }
 451 }
 452
 453 pub trait PrintState<'a> {
 454     fn writer(&mut self) -> &mut pp::Printer<'a>;
 455     fn boxes(&mut self) -> &mut Vec<pp::Breaks>;
 456     fn comments(&mut self) -> &mut Option<Vec<comments::Comment>>;
 457     fn cur_cmnt_and_lit(&mut self) -> &mut CurrentCommentAndLiteral;
 458     fn literals(&self) -> &Option<Vec<comments::Literal>>;
 459
 460     fn word_space(&mut self, w: &str) -> io::Result<()> {
 461         try!(word(self.writer(), w));
 462         space(self.writer())
 463     }
 464
 465     fn popen(&mut self) -> io::Result<()> { word(self.writer(), "(") }
 466
 467     fn pclose(&mut self) -> io::Result<()> { word(self.writer(), ")") }
 468
 469     fn is_begin(&mut self) -> bool {
 470         match self.writer().last_token() {
 471             pp::Token::Begin(_) => true,
 472             _ => false,
 473         }
 474     }
 475
 476     fn is_end(&mut self) -> bool {
 477         match self.writer().last_token() {
 478             pp::Token::End => true,
 479             _ => false,
 480         }
 481     }
 482
 483     // is this the beginning of a line?
 484     fn is_bol(&mut self) -> bool {
 485         self.writer().last_token().is_eof() || self.writer().last_token().is_hardbreak_tok()
 486     }
 487
 488     fn hardbreak_if_not_bol(&mut self) -> io::Result<()> {
 489         if !self.is_bol() {
 490             try!(hardbreak(self.writer()))
 491         }
 492         Ok(())
 493     }
 494
 495     // "raw box"
 496     fn rbox(&mut self, u: usize, b: pp::Breaks) -> io::Result<()> {
 497         self.boxes().push(b);
 498         pp::rbox(self.writer(), u, b)
 499     }
 500
 501     fn ibox(&mut self, u: usize) -> io::Result<()> {
 502         self.boxes().push(pp::Breaks::Inconsistent);
 503         pp::ibox(self.writer(), u)
 504     }
 505
 506     fn end(&mut self) -> io::Result<()> {
 507         self.boxes().pop().unwrap();
 508         pp::end(self.writer())
 509     }
 510
 511     fn commasep<T, F>(&mut self, b: Breaks, elts: &[T], mut op: F) -> io::Result<()>
 512         where F: FnMut(&mut Self, &T) -> io::Result<()>,
 513     {
 514         try!(self.rbox(0, b));
 515         let mut first = true;
 516         for elt in elts {
 517             if first { first = false; } else { try!(self.word_space(",")); }
 518             try!(op(self, elt));
 519         }
 520         self.end()
 521     }
 522
 523
 524     fn next_lit(&mut self, pos: BytePos) -> Option<comments::Literal> {
 525         let mut cur_lit = self.cur_cmnt_and_lit().cur_lit;
 526
 527         let mut result = None;
 528
 529         if let &Some(ref lits) = self.literals()
 530         {
 531             while cur_lit < lits.len() {
 532                 let ltrl = (*lits)[cur_lit].clone();
 533                 if ltrl.pos > pos { break; }
 534                 cur_lit += 1;
 535                 if ltrl.pos == pos {
 536                     result = Some(ltrl);
 537                     break;
 538                 }
 539             }
 540         }
 541
 542         self.cur_cmnt_and_lit().cur_lit = cur_lit;
 543         result
 544     }
 545
 546     fn maybe_print_comment(&mut self, pos: BytePos) -> io::Result<()> {
 547         loop {
 548             match self.next_comment() {
 549                 Some(ref cmnt) => {
 550                     if (*cmnt).pos < pos {
 551                         try!(self.print_comment(cmnt));
 552                         self.cur_cmnt_and_lit().cur_cmnt += 1;
 553                     } else { break; }
 554                 }
 555                 _ => break
 556             }
 557         }
 558         Ok(())
 559     }
 560
 561     fn print_comment(&mut self,
 562                      cmnt: &comments::Comment) -> io::Result<()> {
 563         match cmnt.style {
 564             comments::Mixed => {
 565                 assert_eq!(cmnt.lines.len(), 1);
 566                 try!(zerobreak(self.writer()));
 567                 try!(word(self.writer(), &cmnt.lines[0]));
 568                 zerobreak(self.writer())
 569             }
 570             comments::Isolated => {
 571                 try!(self.hardbreak_if_not_bol());
 572                 for line in &cmnt.lines {
 573                     // Don't print empty lines because they will end up as trailing
 574                     // whitespace
 575                     if !line.is_empty() {
 576                         try!(word(self.writer(), &line[..]));
 577                     }
 578                     try!(hardbreak(self.writer()));
 579                 }
 580                 Ok(())
 581             }
 582             comments::Trailing => {
 583                 try!(word(self.writer(), " "));
 584                 if cmnt.lines.len() == 1 {
 585                     try!(word(self.writer(), &cmnt.lines[0]));
 586                     hardbreak(self.writer())
 587                 } else {
 588                     try!(self.ibox(0));
 589                     for line in &cmnt.lines {
 590                         if !line.is_empty() {
 591                             try!(word(self.writer(), &line[..]));
 592                         }
 593                         try!(hardbreak(self.writer()));
 594                     }
 595                     self.end()
 596                 }
 597             }
 598             comments::BlankLine => {
 599                 // We need to do at least one, possibly two hardbreaks.
 600                 let is_semi = match self.writer().last_token() {
 601                     pp::Token::String(s, _) => ";" == s,
 602                     _ => false
 603                 };
 604                 if is_semi || self.is_begin() || self.is_end() {
 605                     try!(hardbreak(self.writer()));
 606                 }
 607                 hardbreak(self.writer())
 608             }
 609         }
 610     }
 611
 612     fn next_comment(&mut self) -> Option<comments::Comment> {
 613         let cur_cmnt = self.cur_cmnt_and_lit().cur_cmnt;
 614         match *self.comments() {
 615             Some(ref cmnts) => {
 616                 if cur_cmnt < cmnts.len() {
 617                     Some(cmnts[cur_cmnt].clone())
 618                 } else {
 619                     None
 620                 }
 621             }
 622             _ => None
 623         }
 624     }
 625
 626     fn print_literal(&mut self, lit: &ast::Lit) -> io::Result<()> {
 627         try!(self.maybe_print_comment(lit.span.lo));
 628         match self.next_lit(lit.span.lo) {
 629             Some(ref ltrl) => {
 630                 return word(self.writer(), &(*ltrl).lit);
 631             }
 632             _ => ()
 633         }
 634         match lit.node {
 635             ast::LitStr(ref st, style) => self.print_string(&st, style),
 636             ast::LitByte(byte) => {
 637                 let mut res = String::from("b'");
 638                 res.extend(ascii::escape_default(byte).map(|c| c as char));
 639                 res.push('\'');
 640                 word(self.writer(), &res[..])
 641             }
 642             ast::LitChar(ch) => {
 643                 let mut res = String::from("'");
 644                 res.extend(ch.escape_default());
 645                 res.push('\'');
 646                 word(self.writer(), &res[..])
 647             }
 648             ast::LitInt(i, t) => {
 649                 match t {
 650                     ast::SignedIntLit(st, ast::Plus) => {
 651                         word(self.writer(),
 652                              &ast_util::int_ty_to_string(st, Some(i as i64)))
 653                     }
 654                     ast::SignedIntLit(st, ast::Minus) => {
 655                         let istr = ast_util::int_ty_to_string(st, Some(-(i as i64)));
 656                         word(self.writer(),
 657                              &format!("-{}", istr))
 658                     }
 659                     ast::UnsignedIntLit(ut) => {
 660                         word(self.writer(), &ast_util::uint_ty_to_string(ut, Some(i)))
 661                     }
 662                     ast::UnsuffixedIntLit(ast::Plus) => {
 663                         word(self.writer(), &format!("{}", i))
 664                     }
 665                     ast::UnsuffixedIntLit(ast::Minus) => {
 666                         word(self.writer(), &format!("-{}", i))
 667                     }
 668                 }
 669             }
 670             ast::LitFloat(ref f, t) => {
 671                 word(self.writer(),
 672                      &format!(
 673                          "{}{}",
 674                          &f,
 675                          &ast_util::float_ty_to_string(t)))
 676             }
 677             ast::LitFloatUnsuffixed(ref f) => word(self.writer(), &f[..]),
 678             ast::LitBool(val) => {
 679                 if val { word(self.writer(), "true") } else { word(self.writer(), "false") }
 680             }
 681             ast::LitByteStr(ref v) => {
 682                 let mut escaped: String = String::new();
 683                 for &ch in v.iter() {
 684                     escaped.extend(ascii::escape_default(ch)
 685                                          .map(|c| c as char));
 686                 }
 687                 word(self.writer(), &format!("b\"{}\"", escaped))
 688             }
 689         }
 690     }
 691
 692     fn print_string(&mut self, st: &str,
 693                     style: ast::StrStyle) -> io::Result<()> {
 694         let st = match style {
 695             ast::CookedStr => {
 696                 (format!("\"{}\"", st.escape_default()))
 697             }
 698             ast::RawStr(n) => {
 699                 (format!("r{delim}\"{string}\"{delim}",
 700                          delim=repeat("#", n),
 701                          string=st))
 702             }
 703         };
 704         word(self.writer(), &st[..])
 705     }
 706
 707     fn print_inner_attributes(&mut self,
 708                                   attrs: &[ast::Attribute]) -> io::Result<()> {
 709         let mut count = 0;
 710         for attr in attrs {
 711             match attr.node.style {
 712                 ast::AttrStyle::Inner => {
 713                     try!(self.print_attribute(attr));
 714                     count += 1;
 715                 }
 716                 _ => {/* fallthrough */ }
 717             }
 718         }
 719         if count > 0 {
 720             try!(self.hardbreak_if_not_bol());
 721         }
 722         Ok(())
 723     }
 724
 725     fn print_outer_attributes(&mut self,
 726                               attrs: &[ast::Attribute]) -> io::Result<()> {
 727         let mut count = 0;
 728         for attr in attrs {
 729             match attr.node.style {
 730                 ast::AttrStyle::Outer => {
 731                     try!(self.print_attribute(attr));
 732                     count += 1;
 733                 }
 734                 _ => {/* fallthrough */ }
 735             }
 736         }
 737         if count > 0 {
 738             try!(self.hardbreak_if_not_bol());
 739         }
 740         Ok(())
 741     }
 742
 743     fn print_attribute(&mut self, attr: &ast::Attribute) -> io::Result<()> {
 744         try!(self.hardbreak_if_not_bol());
 745         try!(self.maybe_print_comment(attr.span.lo));
 746         if attr.node.is_sugared_doc {
 747             word(self.writer(), &attr.value_str().unwrap())
 748         } else {
 749             match attr.node.style {
 750                 ast::AttrStyle::Inner => try!(word(self.writer(), "#![")),
 751                 ast::AttrStyle::Outer => try!(word(self.writer(), "#[")),
 752             }
 753             try!(self.print_meta_item(&*attr.meta()));
 754             word(self.writer(), "]")
 755         }
 756     }
 757
 758     fn print_meta_item(&mut self, item: &ast::MetaItem) -> io::Result<()> {
 759         try!(self.ibox(indent_unit));
 760         match item.node {
 761             ast::MetaWord(ref name) => {
 762                 try!(word(self.writer(), &name));
 763             }
 764             ast::MetaNameValue(ref name, ref value) => {
 765                 try!(self.word_space(&name[..]));
 766                 try!(self.word_space("="));
 767                 try!(self.print_literal(value));
 768             }
 769             ast::MetaList(ref name, ref items) => {
 770                 try!(word(self.writer(), &name));
 771                 try!(self.popen());
 772                 try!(self.commasep(Consistent,
 773                                    &items[..],
 774                                    |s, i| s.print_meta_item(&**i)));
 775                 try!(self.pclose());
 776             }
 777         }
 778         self.end()
 779     }
 780 }
 781
 782 impl<'a> PrintState<'a> for State<'a> {
 783     fn writer(&mut self) -> &mut pp::Printer<'a> {
 784         &mut self.s
 785     }
 786
 787     fn boxes(&mut self) -> &mut Vec<pp::Breaks> {
 788         &mut self.boxes
 789     }
 790
 791     fn comments(&mut self) -> &mut Option<Vec<comments::Comment>> {
 792         &mut self.comments
 793     }
 794
 795     fn cur_cmnt_and_lit(&mut self) -> &mut CurrentCommentAndLiteral {
 796         &mut self.cur_cmnt_and_lit
 797     }
 798
 799     fn literals(&self) -> &Option<Vec<comments::Literal>> {
 800         &self.literals
 801     }
 802 }
 803
 804 impl<'a> State<'a> {
 805     pub fn cbox(&mut self, u: usize) -> io::Result<()> {
 806         self.boxes.push(pp::Breaks::Consistent);
 807         pp::cbox(&mut self.s, u)
 808     }
 809
 810     pub fn nbsp(&mut self) -> io::Result<()> { word(&mut self.s, " ") }
 811
 812     pub fn word_nbsp(&mut self, w: &str) -> io::Result<()> {
 813         try!(word(&mut self.s, w));
 814         self.nbsp()
 815     }
 816
 817     pub fn head(&mut self, w: &str) -> io::Result<()> {
 818         // outer-box is consistent
 819         try!(self.cbox(indent_unit));
 820         // head-box is inconsistent
 821         try!(self.ibox(w.len() + 1));
 822         // keyword that starts the head
 823         if !w.is_empty() {
 824             try!(self.word_nbsp(w));
 825         }
 826         Ok(())
 827     }
 828
 829     pub fn bopen(&mut self) -> io::Result<()> {
 830         try!(word(&mut self.s, "{"));
 831         self.end() // close the head-box
 832     }
 833
 834     pub fn bclose_(&mut self, span: codemap::Span,
 835                    indented: usize) -> io::Result<()> {
 836         self.bclose_maybe_open(span, indented, true)
 837     }
 838     pub fn bclose_maybe_open (&mut self, span: codemap::Span,
 839                               indented: usize, close_box: bool) -> io::Result<()> {
 840         try!(self.maybe_print_comment(span.hi));
 841         try!(self.break_offset_if_not_bol(1, -(indented as isize)));
 842         try!(word(&mut self.s, "}"));
 843         if close_box {
 844             try!(self.end()); // close the outer-box
 845         }
 846         Ok(())
 847     }
 848     pub fn bclose(&mut self, span: codemap::Span) -> io::Result<()> {
 849         self.bclose_(span, indent_unit)
 850     }
 851
 852     pub fn in_cbox(&self) -> bool {
 853         match self.boxes.last() {
 854             Some(&last_box) => last_box == pp::Breaks::Consistent,
 855             None => false
 856         }
 857     }
 858
 859     pub fn space_if_not_bol(&mut self) -> io::Result<()> {
 860         if !self.is_bol() { try!(space(&mut self.s)); }
 861         Ok(())
 862     }
 863     pub fn break_offset_if_not_bol(&mut self, n: usize,
 864                                    off: isize) -> io::Result<()> {
 865         if !self.is_bol() {
 866             break_offset(&mut self.s, n, off)
 867         } else {
 868             if off != 0 && self.s.last_token().is_hardbreak_tok() {
 869                 // We do something pretty sketchy here: tuck the nonzero
 870                 // offset-adjustment we were going to deposit along with the
 871                 // break into the previous hardbreak.
 872                 self.s.replace_last_token(pp::hardbreak_tok_offset(off));
 873             }
 874             Ok(())
 875         }
 876     }
 877
 878     // Synthesizes a comment that was not textually present in the original source
 879     // file.
 880     pub fn synth_comment(&mut self, text: String) -> io::Result<()> {
 881         try!(word(&mut self.s, "/*"));
 882         try!(space(&mut self.s));
 883         try!(word(&mut self.s, &text[..]));
 884         try!(space(&mut self.s));
 885         word(&mut self.s, "*/")
 886     }
 887
 888
 889
 890     pub fn commasep_cmnt<T, F, G>(&mut self,
 891                                   b: Breaks,
 892                                   elts: &[T],
 893                                   mut op: F,
 894                                   mut get_span: G) -> io::Result<()> where
 895         F: FnMut(&mut State, &T) -> io::Result<()>,
 896         G: FnMut(&T) -> codemap::Span,
 897     {
 898         try!(self.rbox(0, b));
 899         let len = elts.len();
 900         let mut i = 0;
 901         for elt in elts {
 902             try!(self.maybe_print_comment(get_span(elt).hi));
 903             try!(op(self, elt));
 904             i += 1;
 905             if i < len {
 906                 try!(word(&mut self.s, ","));
 907                 try!(self.maybe_print_trailing_comment(get_span(elt),
 908                                                     Some(get_span(&elts[i]).hi)));
 909                 try!(self.space_if_not_bol());
 910             }
 911         }
 912         self.end()
 913     }
 914
 915     pub fn commasep_exprs(&mut self, b: Breaks,
 916                           exprs: &[P<ast::Expr>]) -> io::Result<()> {
 917         self.commasep_cmnt(b, exprs, |s, e| s.print_expr(&**e), |e| e.span)
 918     }
 919
 920     pub fn print_mod(&mut self, _mod: &ast::Mod,
 921                      attrs: &[ast::Attribute]) -> io::Result<()> {
 922         try!(self.print_inner_attributes(attrs));
 923         for item in &_mod.items {
 924             try!(self.print_item(&**item));
 925         }
 926         Ok(())
 927     }
 928
 929     pub fn print_foreign_mod(&mut self, nmod: &ast::ForeignMod,
 930                              attrs: &[ast::Attribute]) -> io::Result<()> {
 931         try!(self.print_inner_attributes(attrs));
 932         for item in &nmod.items {
 933             try!(self.print_foreign_item(&**item));
 934         }
 935         Ok(())
 936     }
 937
 938     pub fn print_opt_lifetime(&mut self,
 939                               lifetime: &Option<ast::Lifetime>) -> io::Result<()> {
 940         if let Some(l) = *lifetime {
 941             try!(self.print_lifetime(&l));
 942             try!(self.nbsp());
 943         }
 944         Ok(())
 945     }
 946
 947     pub fn print_type(&mut self, ty: &ast::Ty) -> io::Result<()> {
 948         try!(self.maybe_print_comment(ty.span.lo));
 949         try!(self.ibox(0));
 950         match ty.node {
 951             ast::TyVec(ref ty) => {
 952                 try!(word(&mut self.s, "["));
 953                 try!(self.print_type(&**ty));
 954                 try!(word(&mut self.s, "]"));
 955             }
 956             ast::TyPtr(ref mt) => {
 957                 try!(word(&mut self.s, "*"));
 958                 match mt.mutbl {
 959                     ast::MutMutable => try!(self.word_nbsp("mut")),
 960                     ast::MutImmutable => try!(self.word_nbsp("const")),
 961                 }
 962                 try!(self.print_type(&*mt.ty));
 963             }
 964             ast::TyRptr(ref lifetime, ref mt) => {
 965                 try!(word(&mut self.s, "&"));
 966                 try!(self.print_opt_lifetime(lifetime));
 967                 try!(self.print_mt(mt));
 968             }
 969             ast::TyTup(ref elts) => {
 970                 try!(self.popen());
 971                 try!(self.commasep(Inconsistent, &elts[..],
 972                                    |s, ty| s.print_type(&**ty)));
 973                 if elts.len() == 1 {
 974                     try!(word(&mut self.s, ","));
 975                 }
 976                 try!(self.pclose());
 977             }
 978             ast::TyParen(ref typ) => {
 979                 try!(self.popen());
 980                 try!(self.print_type(&**typ));
 981                 try!(self.pclose());
 982             }
 983             ast::TyBareFn(ref f) => {
 984                 let generics = ast::Generics {
 985                     lifetimes: f.lifetimes.clone(),
 986                     ty_params: OwnedSlice::empty(),
 987                     where_clause: ast::WhereClause {
 988                         id: ast::DUMMY_NODE_ID,
 989                         predicates: Vec::new(),
 990                     },
 991                 };
 992                 try!(self.print_ty_fn(f.abi,
 993                                       f.unsafety,
 994                                       &*f.decl,
 995                                       None,
 996                                       &generics,
 997                                       None));
 998             }
 999             ast::TyPath(None, ref path) => {
1000                 try!(self.print_path(path, false, 0));
1001             }
1002             ast::TyPath(Some(ref qself), ref path) => {
1003                 try!(self.print_qpath(path, qself, false))
1004             }
1005             ast::TyObjectSum(ref ty, ref bounds) => {
1006                 try!(self.print_type(&**ty));
1007                 try!(self.print_bounds("+", &bounds[..]));
1008             }
1009             ast::TyPolyTraitRef(ref bounds) => {
1010                 try!(self.print_bounds("", &bounds[..]));
1011             }
1012             ast::TyFixedLengthVec(ref ty, ref v) => {
1013                 try!(word(&mut self.s, "["));
1014                 try!(self.print_type(&**ty));
1015                 try!(word(&mut self.s, "; "));
1016                 try!(self.print_expr(&**v));
1017                 try!(word(&mut self.s, "]"));
1018             }
1019             ast::TyTypeof(ref e) => {
1020                 try!(word(&mut self.s, "typeof("));
1021                 try!(self.print_expr(&**e));
1022                 try!(word(&mut self.s, ")"));
1023             }
1024             ast::TyInfer => {
1025                 try!(word(&mut self.s, "_"));
1026             }
1027             ast::TyMac(ref m) => {
1028                 try!(self.print_mac(m, token::Paren));
1029             }
1030         }
1031         self.end()
1032     }
1033
1034     pub fn print_foreign_item(&mut self,
1035                               item: &ast::ForeignItem) -> io::Result<()> {
1036         try!(self.hardbreak_if_not_bol());
1037         try!(self.maybe_print_comment(item.span.lo));
1038         try!(self.print_outer_attributes(&item.attrs));
1039         match item.node {
1040             ast::ForeignItemFn(ref decl, ref generics) => {
1041                 try!(self.head(""));
1042                 try!(self.print_fn(decl, ast::Unsafety::Normal,
1043                                    ast::Constness::NotConst,
1044                                    abi::Rust, Some(item.ident),
1045                                    generics, None, item.vis));
1046                 try!(self.end()); // end head-ibox
1047                 try!(word(&mut self.s, ";"));
1048                 self.end() // end the outer fn box
1049             }
1050             ast::ForeignItemStatic(ref t, m) => {
1051                 try!(self.head(&visibility_qualified(item.vis,
1052                                                     "static")));
1053                 if m {
1054                     try!(self.word_space("mut"));
1055                 }
1056                 try!(self.print_ident(item.ident));
1057                 try!(self.word_space(":"));
1058                 try!(self.print_type(&**t));
1059                 try!(word(&mut self.s, ";"));
1060                 try!(self.end()); // end the head-ibox
1061                 self.end() // end the outer cbox
1062             }
1063         }
1064     }
1065
1066     fn print_associated_const(&mut self,
1067                               ident: ast::Ident,
1068                               ty: &ast::Ty,
1069                               default: Option<&ast::Expr>,
1070                               vis: ast::Visibility)
1071                               -> io::Result<()>
1072     {
1073         try!(word(&mut self.s, &visibility_qualified(vis, "")));
1074         try!(self.word_space("const"));
1075         try!(self.print_ident(ident));
1076         try!(self.word_space(":"));
1077         try!(self.print_type(ty));
1078         if let Some(expr) = default {
1079             try!(space(&mut self.s));
1080             try!(self.word_space("="));
1081             try!(self.print_expr(expr));
1082         }
1083         word(&mut self.s, ";")
1084     }
1085
1086     fn print_associated_type(&mut self,
1087                              ident: ast::Ident,
1088                              bounds: Option<&ast::TyParamBounds>,
1089                              ty: Option<&ast::Ty>)
1090                              -> io::Result<()> {
1091         try!(self.word_space("type"));
1092         try!(self.print_ident(ident));
1093         if let Some(bounds) = bounds {
1094             try!(self.print_bounds(":", bounds));
1095         }
1096         if let Some(ty) = ty {
1097             try!(space(&mut self.s));
1098             try!(self.word_space("="));
1099             try!(self.print_type(ty));
1100         }
1101         word(&mut self.s, ";")
1102     }
1103
1104     /// Pretty-print an item
1105     pub fn print_item(&mut self, item: &ast::Item) -> io::Result<()> {
1106         try!(self.hardbreak_if_not_bol());
1107         try!(self.maybe_print_comment(item.span.lo));
1108         try!(self.print_outer_attributes(&item.attrs));
1109         try!(self.ann.pre(self, NodeItem(item)));
1110         match item.node {
1111             ast::ItemExternCrate(ref optional_path) => {
1112                 try!(self.head(&visibility_qualified(item.vis,
1113                                                      "extern crate")));
1114                 if let Some(p) = *optional_path {
1115                     let val = p.as_str();
1116                     if val.contains("-") {
1117                         try!(self.print_string(&val, ast::CookedStr));
1118                     } else {
1119                         try!(self.print_name(p));
1120                     }
1121                     try!(space(&mut self.s));
1122                     try!(word(&mut self.s, "as"));
1123                     try!(space(&mut self.s));
1124                 }
1125                 try!(self.print_ident(item.ident));
1126                 try!(word(&mut self.s, ";"));
1127                 try!(self.end()); // end inner head-block
1128                 try!(self.end()); // end outer head-block
1129             }
1130             ast::ItemUse(ref vp) => {
1131                 try!(self.head(&visibility_qualified(item.vis,
1132                                                      "use")));
1133                 try!(self.print_view_path(&**vp));
1134                 try!(word(&mut self.s, ";"));
1135                 try!(self.end()); // end inner head-block
1136                 try!(self.end()); // end outer head-block
1137             }
1138             ast::ItemStatic(ref ty, m, ref expr) => {
1139                 try!(self.head(&visibility_qualified(item.vis,
1140                                                     "static")));
1141                 if m == ast::MutMutable {
1142                     try!(self.word_space("mut"));
1143                 }
1144                 try!(self.print_ident(item.ident));
1145                 try!(self.word_space(":"));
1146                 try!(self.print_type(&**ty));
1147                 try!(space(&mut self.s));
1148                 try!(self.end()); // end the head-ibox
1149
1150                 try!(self.word_space("="));
1151                 try!(self.print_expr(&**expr));
1152                 try!(word(&mut self.s, ";"));
1153                 try!(self.end()); // end the outer cbox
1154             }
1155             ast::ItemConst(ref ty, ref expr) => {
1156                 try!(self.head(&visibility_qualified(item.vis,
1157                                                     "const")));
1158                 try!(self.print_ident(item.ident));
1159                 try!(self.word_space(":"));
1160                 try!(self.print_type(&**ty));
1161                 try!(space(&mut self.s));
1162                 try!(self.end()); // end the head-ibox
1163
1164                 try!(self.word_space("="));
1165                 try!(self.print_expr(&**expr));
1166                 try!(word(&mut self.s, ";"));
1167                 try!(self.end()); // end the outer cbox
1168             }
1169             ast::ItemFn(ref decl, unsafety, constness, abi, ref typarams, ref body) => {
1170                 try!(self.head(""));
1171                 try!(self.print_fn(
1172                     decl,
1173                     unsafety,
1174                     constness,
1175                     abi,
1176                     Some(item.ident),
1177                     typarams,
1178                     None,
1179                     item.vis
1180                 ));
1181                 try!(word(&mut self.s, " "));
1182                 try!(self.print_block_with_attrs(&**body, &item.attrs));
1183             }
1184             ast::ItemMod(ref _mod) => {
1185                 try!(self.head(&visibility_qualified(item.vis,
1186                                                     "mod")));
1187                 try!(self.print_ident(item.ident));
1188                 try!(self.nbsp());
1189                 try!(self.bopen());
1190                 try!(self.print_mod(_mod, &item.attrs));
1191                 try!(self.bclose(item.span));
1192             }
1193             ast::ItemForeignMod(ref nmod) => {
1194                 try!(self.head("extern"));
1195                 try!(self.word_nbsp(&nmod.abi.to_string()));
1196                 try!(self.bopen());
1197                 try!(self.print_foreign_mod(nmod, &item.attrs));
1198                 try!(self.bclose(item.span));
1199             }
1200             ast::ItemTy(ref ty, ref params) => {
1201                 try!(self.ibox(indent_unit));
1202                 try!(self.ibox(0));
1203                 try!(self.word_nbsp(&visibility_qualified(item.vis, "type")));
1204                 try!(self.print_ident(item.ident));
1205                 try!(self.print_generics(params));
1206                 try!(self.end()); // end the inner ibox
1207
1208                 try!(self.print_where_clause(&params.where_clause));
1209                 try!(space(&mut self.s));
1210                 try!(self.word_space("="));
1211                 try!(self.print_type(&**ty));
1212                 try!(word(&mut self.s, ";"));
1213                 try!(self.end()); // end the outer ibox
1214             }
1215             ast::ItemEnum(ref enum_definition, ref params) => {
1216                 try!(self.print_enum_def(
1217                     enum_definition,
1218                     params,
1219                     item.ident,
1220                     item.span,
1221                     item.vis
1222                 ));
1223             }
1224             ast::ItemStruct(ref struct_def, ref generics) => {
1225                 try!(self.head(&visibility_qualified(item.vis,"struct")));
1226                 try!(self.print_struct(&struct_def, generics, item.ident, item.span, true));
1227             }
1228
1229             ast::ItemDefaultImpl(unsafety, ref trait_ref) => {
1230                 try!(self.head(""));
1231                 try!(self.print_visibility(item.vis));
1232                 try!(self.print_unsafety(unsafety));
1233                 try!(self.word_nbsp("impl"));
1234                 try!(self.print_trait_ref(trait_ref));
1235                 try!(space(&mut self.s));
1236                 try!(self.word_space("for"));
1237                 try!(self.word_space(".."));
1238                 try!(self.bopen());
1239                 try!(self.bclose(item.span));
1240             }
1241             ast::ItemImpl(unsafety,
1242                           polarity,
1243                           ref generics,
1244                           ref opt_trait,
1245                           ref ty,
1246                           ref impl_items) => {
1247                 try!(self.head(""));
1248                 try!(self.print_visibility(item.vis));
1249                 try!(self.print_unsafety(unsafety));
1250                 try!(self.word_nbsp("impl"));
1251
1252                 if generics.is_parameterized() {
1253                     try!(self.print_generics(generics));
1254                     try!(space(&mut self.s));
1255                 }
1256
1257                 match polarity {
1258                     ast::ImplPolarity::Negative => {
1259                         try!(word(&mut self.s, "!"));
1260                     },
1261                     _ => {}
1262                 }
1263
1264                 match opt_trait {
1265                     &Some(ref t) => {
1266                         try!(self.print_trait_ref(t));
1267                         try!(space(&mut self.s));
1268                         try!(self.word_space("for"));
1269                     }
1270                     &None => {}
1271                 }
1272
1273                 try!(self.print_type(&**ty));
1274                 try!(self.print_where_clause(&generics.where_clause));
1275
1276                 try!(space(&mut self.s));
1277                 try!(self.bopen());
1278                 try!(self.print_inner_attributes(&item.attrs));
1279                 for impl_item in impl_items {
1280                     try!(self.print_impl_item(impl_item));
1281                 }
1282                 try!(self.bclose(item.span));
1283             }
1284             ast::ItemTrait(unsafety, ref generics, ref bounds, ref trait_items) => {
1285                 try!(self.head(""));
1286                 try!(self.print_visibility(item.vis));
1287                 try!(self.print_unsafety(unsafety));
1288                 try!(self.word_nbsp("trait"));
1289                 try!(self.print_ident(item.ident));
1290                 try!(self.print_generics(generics));
1291                 let mut real_bounds = Vec::with_capacity(bounds.len());
1292                 for b in bounds.iter() {
1293                     if let TraitTyParamBound(ref ptr, ast::TraitBoundModifier::Maybe) = *b {
1294                         try!(space(&mut self.s));
1295                         try!(self.word_space("for ?"));
1296                         try!(self.print_trait_ref(&ptr.trait_ref));
1297                     } else {
1298                         real_bounds.push(b.clone());
1299                     }
1300                 }
1301                 try!(self.print_bounds(":", &real_bounds[..]));
1302                 try!(self.print_where_clause(&generics.where_clause));
1303                 try!(word(&mut self.s, " "));
1304                 try!(self.bopen());
1305                 for trait_item in trait_items {
1306                     try!(self.print_trait_item(trait_item));
1307                 }
1308                 try!(self.bclose(item.span));
1309             }
1310             ast::ItemMac(codemap::Spanned { ref node, .. }) => {
1311                 try!(self.print_visibility(item.vis));
1312                 try!(self.print_path(&node.path, false, 0));
1313                 try!(word(&mut self.s, "! "));
1314                 try!(self.print_ident(item.ident));
1315                 try!(self.cbox(indent_unit));
1316                 try!(self.popen());
1317                 try!(self.print_tts(&node.tts[..]));
1318                 try!(self.pclose());
1319                 try!(word(&mut self.s, ";"));
1320                 try!(self.end());
1321             }
1322         }
1323         self.ann.post(self, NodeItem(item))
1324     }
1325
1326     fn print_trait_ref(&mut self, t: &ast::TraitRef) -> io::Result<()> {
1327         self.print_path(&t.path, false, 0)
1328     }
1329
1330     fn print_formal_lifetime_list(&mut self, lifetimes: &[ast::LifetimeDef]) -> io::Result<()> {
1331         if !lifetimes.is_empty() {
1332             try!(word(&mut self.s, "for<"));
1333             let mut comma = false;
1334             for lifetime_def in lifetimes {
1335                 if comma {
1336                     try!(self.word_space(","))
1337                 }
1338                 try!(self.print_lifetime_def(lifetime_def));
1339                 comma = true;
1340             }
1341             try!(word(&mut self.s, ">"));
1342         }
1343         Ok(())
1344     }
1345
1346     fn print_poly_trait_ref(&mut self, t: &ast::PolyTraitRef) -> io::Result<()> {
1347         try!(self.print_formal_lifetime_list(&t.bound_lifetimes));
1348         self.print_trait_ref(&t.trait_ref)
1349     }
1350
1351     pub fn print_enum_def(&mut self, enum_definition: &ast::EnumDef,
1352                           generics: &ast::Generics, ident: ast::Ident,
1353                           span: codemap::Span,
1354                           visibility: ast::Visibility) -> io::Result<()> {
1355         try!(self.head(&visibility_qualified(visibility, "enum")));
1356         try!(self.print_ident(ident));
1357         try!(self.print_generics(generics));
1358         try!(self.print_where_clause(&generics.where_clause));
1359         try!(space(&mut self.s));
1360         self.print_variants(&enum_definition.variants, span)
1361     }
1362
1363     pub fn print_variants(&mut self,
1364                           variants: &[P<ast::Variant>],
1365                           span: codemap::Span) -> io::Result<()> {
1366         try!(self.bopen());
1367         for v in variants {
1368             try!(self.space_if_not_bol());
1369             try!(self.maybe_print_comment(v.span.lo));
1370             try!(self.print_outer_attributes(&v.node.attrs));
1371             try!(self.ibox(indent_unit));
1372             try!(self.print_variant(&**v));
1373             try!(word(&mut self.s, ","));
1374             try!(self.end());
1375             try!(self.maybe_print_trailing_comment(v.span, None));
1376         }
1377         self.bclose(span)
1378     }
1379
1380     pub fn print_visibility(&mut self, vis: ast::Visibility) -> io::Result<()> {
1381         match vis {
1382             ast::Public => self.word_nbsp("pub"),
1383             ast::Inherited => Ok(())
1384         }
1385     }
1386
1387     pub fn print_struct(&mut self,
1388                         struct_def: &ast::StructDef,
1389                         generics: &ast::Generics,
1390                         ident: ast::Ident,
1391                         span: codemap::Span,
1392                         print_finalizer: bool) -> io::Result<()> {
1393         try!(self.print_ident(ident));
1394         try!(self.print_generics(generics));
1395         if struct_def.kind != ast::VariantKind::Dict {
1396             if struct_def.kind == ast::VariantKind::Tuple {
1397                 try!(self.popen());
1398                 try!(self.commasep(
1399                     Inconsistent, &struct_def.fields,
1400                     |s, field| {
1401                         match field.node.kind {
1402                             ast::NamedField(..) => panic!("unexpected named field"),
1403                             ast::UnnamedField(vis) => {
1404                                 try!(s.print_visibility(vis));
1405                                 try!(s.maybe_print_comment(field.span.lo));
1406                                 s.print_type(&*field.node.ty)
1407                             }
1408                         }
1409                     }
1410                 ));
1411                 try!(self.pclose());
1412             }
1413             try!(self.print_where_clause(&generics.where_clause));
1414             if print_finalizer {
1415                 try!(word(&mut self.s, ";"));
1416             }
1417             try!(self.end());
1418             self.end() // close the outer-box
1419         } else {
1420             try!(self.print_where_clause(&generics.where_clause));
1421             try!(self.nbsp());
1422             try!(self.bopen());
1423             try!(self.hardbreak_if_not_bol());
1424
1425             for field in &struct_def.fields {
1426                 match field.node.kind {
1427                     ast::UnnamedField(..) => panic!("unexpected unnamed field"),
1428                     ast::NamedField(ident, visibility) => {
1429                         try!(self.hardbreak_if_not_bol());
1430                         try!(self.maybe_print_comment(field.span.lo));
1431                         try!(self.print_outer_attributes(&field.node.attrs));
1432                         try!(self.print_visibility(visibility));
1433                         try!(self.print_ident(ident));
1434                         try!(self.word_nbsp(":"));
1435                         try!(self.print_type(&*field.node.ty));
1436                         try!(word(&mut self.s, ","));
1437                     }
1438                 }
1439             }
1440
1441             self.bclose(span)
1442         }
1443     }
1444
1445     /// This doesn't deserve to be called "pretty" printing, but it should be
1446     /// meaning-preserving. A quick hack that might help would be to look at the
1447     /// spans embedded in the TTs to decide where to put spaces and newlines.
1448     /// But it'd be better to parse these according to the grammar of the
1449     /// appropriate macro, transcribe back into the grammar we just parsed from,
1450     /// and then pretty-print the resulting AST nodes (so, e.g., we print
1451     /// expression arguments as expressions). It can be done! I think.
1452     pub fn print_tt(&mut self, tt: &ast::TokenTree) -> io::Result<()> {
1453         match *tt {
1454             ast::TtToken(_, ref tk) => {
1455                 try!(word(&mut self.s, &token_to_string(tk)));
1456                 match *tk {
1457                     parse::token::DocComment(..) => {
1458                         hardbreak(&mut self.s)
1459                     }
1460                     _ => Ok(())
1461                 }
1462             }
1463             ast::TtDelimited(_, ref delimed) => {
1464                 try!(word(&mut self.s, &token_to_string(&delimed.open_token())));
1465                 try!(space(&mut self.s));
1466                 try!(self.print_tts(&delimed.tts));
1467                 try!(space(&mut self.s));
1468                 word(&mut self.s, &token_to_string(&delimed.close_token()))
1469             },
1470             ast::TtSequence(_, ref seq) => {
1471                 try!(word(&mut self.s, "$("));
1472                 for tt_elt in &seq.tts {
1473                     try!(self.print_tt(tt_elt));
1474                 }
1475                 try!(word(&mut self.s, ")"));
1476                 match seq.separator {
1477                     Some(ref tk) => {
1478                         try!(word(&mut self.s, &token_to_string(tk)));
1479                     }
1480                     None => {},
1481                 }
1482                 match seq.op {
1483                     ast::ZeroOrMore => word(&mut self.s, "*"),
1484                     ast::OneOrMore => word(&mut self.s, "+"),
1485                 }
1486             }
1487         }
1488     }
1489
1490     pub fn print_tts(&mut self, tts: &[ast::TokenTree]) -> io::Result<()> {
1491         try!(self.ibox(0));
1492         let mut suppress_space = false;
1493         for (i, tt) in tts.iter().enumerate() {
1494             if i != 0 && !suppress_space {
1495                 try!(space(&mut self.s));
1496             }
1497             try!(self.print_tt(tt));
1498             // There should be no space between the module name and the following `::` in paths,
1499             // otherwise imported macros get re-parsed from crate metadata incorrectly (#20701)
1500             suppress_space = match tt {
1501                 &ast::TtToken(_, token::Ident(_, token::ModName)) |
1502                 &ast::TtToken(_, token::MatchNt(_, _, _, token::ModName)) |
1503                 &ast::TtToken(_, token::SubstNt(_, token::ModName)) => true,
1504                 _ => false
1505             }
1506         }
1507         self.end()
1508     }
1509
1510     pub fn print_variant(&mut self, v: &ast::Variant) -> io::Result<()> {
1511         try!(self.head(""));
1512         let generics = ast_util::empty_generics();
1513         try!(self.print_struct(&v.node.def, &generics, v.node.name, v.span, false));
1514         match v.node.disr_expr {
1515             Some(ref d) => {
1516                 try!(space(&mut self.s));
1517                 try!(self.word_space("="));
1518                 self.print_expr(&**d)
1519             }
1520             _ => Ok(())
1521         }
1522     }
1523
1524     pub fn print_method_sig(&mut self,
1525                             ident: ast::Ident,
1526                             m: &ast::MethodSig,
1527                             vis: ast::Visibility)
1528                             -> io::Result<()> {
1529         self.print_fn(&m.decl,
1530                       m.unsafety,
1531                       m.constness,
1532                       m.abi,
1533                       Some(ident),
1534                       &m.generics,
1535                       Some(&m.explicit_self.node),
1536                       vis)
1537     }
1538
1539     pub fn print_trait_item(&mut self, ti: &ast::TraitItem)
1540                             -> io::Result<()> {
1541         try!(self.ann.pre(self, NodeSubItem(ti.id)));
1542         try!(self.hardbreak_if_not_bol());
1543         try!(self.maybe_print_comment(ti.span.lo));
1544         try!(self.print_outer_attributes(&ti.attrs));
1545         match ti.node {
1546             ast::ConstTraitItem(ref ty, ref default) => {
1547                 try!(self.print_associated_const(ti.ident, &ty,
1548                                                  default.as_ref().map(|expr| &**expr),
1549                                                  ast::Inherited));
1550             }
1551             ast::MethodTraitItem(ref sig, ref body) => {
1552                 if body.is_some() {
1553                     try!(self.head(""));
1554                 }
1555                 try!(self.print_method_sig(ti.ident, sig, ast::Inherited));
1556                 if let Some(ref body) = *body {
1557                     try!(self.nbsp());
1558                     try!(self.print_block_with_attrs(body, &ti.attrs));
1559                 } else {
1560                     try!(word(&mut self.s, ";"));
1561                 }
1562             }
1563             ast::TypeTraitItem(ref bounds, ref default) => {
1564                 try!(self.print_associated_type(ti.ident, Some(bounds),
1565                                                 default.as_ref().map(|ty| &**ty)));
1566             }
1567         }
1568         self.ann.post(self, NodeSubItem(ti.id))
1569     }
1570
1571     pub fn print_impl_item(&mut self, ii: &ast::ImplItem) -> io::Result<()> {
1572         try!(self.ann.pre(self, NodeSubItem(ii.id)));
1573         try!(self.hardbreak_if_not_bol());
1574         try!(self.maybe_print_comment(ii.span.lo));
1575         try!(self.print_outer_attributes(&ii.attrs));
1576         match ii.node {
1577             ast::ConstImplItem(ref ty, ref expr) => {
1578                 try!(self.print_associated_const(ii.ident, &ty, Some(&expr), ii.vis));
1579             }
1580             ast::MethodImplItem(ref sig, ref body) => {
1581                 try!(self.head(""));
1582                 try!(self.print_method_sig(ii.ident, sig, ii.vis));
1583                 try!(self.nbsp());
1584                 try!(self.print_block_with_attrs(body, &ii.attrs));
1585             }
1586             ast::TypeImplItem(ref ty) => {
1587                 try!(self.print_associated_type(ii.ident, None, Some(ty)));
1588             }
1589             ast::MacImplItem(codemap::Spanned { ref node, .. }) => {
1590                 // code copied from ItemMac:
1591                 try!(self.print_path(&node.path, false, 0));
1592                 try!(word(&mut self.s, "! "));
1593                 try!(self.cbox(indent_unit));
1594                 try!(self.popen());
1595                 try!(self.print_tts(&node.tts[..]));
1596                 try!(self.pclose());
1597                 try!(word(&mut self.s, ";"));
1598                 try!(self.end())
1599             }
1600         }
1601         self.ann.post(self, NodeSubItem(ii.id))
1602     }
1603
1604     pub fn print_stmt(&mut self, st: &ast::Stmt) -> io::Result<()> {
1605         try!(self.maybe_print_comment(st.span.lo));
1606         match st.node {
1607             ast::StmtDecl(ref decl, _) => {
1608                 try!(self.print_decl(&**decl));
1609             }
1610             ast::StmtExpr(ref expr, _) => {
1611                 try!(self.space_if_not_bol());
1612                 try!(self.print_expr(&**expr));
1613             }
1614             ast::StmtSemi(ref expr, _) => {
1615                 try!(self.space_if_not_bol());
1616                 try!(self.print_expr(&**expr));
1617                 try!(word(&mut self.s, ";"));
1618             }
1619             ast::StmtMac(ref mac, style) => {
1620                 try!(self.space_if_not_bol());
1621                 let delim = match style {
1622                     ast::MacStmtWithBraces => token::Brace,
1623                     _ => token::Paren
1624                 };
1625                 try!(self.print_mac(&**mac, delim));
1626                 match style {
1627                     ast::MacStmtWithBraces => {}
1628                     _ => try!(word(&mut self.s, ";")),
1629                 }
1630             }
1631         }
1632         if parse::classify::stmt_ends_with_semi(&st.node) {
1633             try!(word(&mut self.s, ";"));
1634         }
1635         self.maybe_print_trailing_comment(st.span, None)
1636     }
1637
1638     pub fn print_block(&mut self, blk: &ast::Block) -> io::Result<()> {
1639         self.print_block_with_attrs(blk, &[])
1640     }
1641
1642     pub fn print_block_unclosed(&mut self, blk: &ast::Block) -> io::Result<()> {
1643         self.print_block_unclosed_indent(blk, indent_unit)
1644     }
1645
1646     pub fn print_block_unclosed_indent(&mut self, blk: &ast::Block,
1647                                        indented: usize) -> io::Result<()> {
1648         self.print_block_maybe_unclosed(blk, indented, &[], false)
1649     }
1650
1651     pub fn print_block_with_attrs(&mut self,
1652                                   blk: &ast::Block,
1653                                   attrs: &[ast::Attribute]) -> io::Result<()> {
1654         self.print_block_maybe_unclosed(blk, indent_unit, attrs, true)
1655     }
1656
1657     pub fn print_block_maybe_unclosed(&mut self,
1658                                       blk: &ast::Block,
1659                                       indented: usize,
1660                                       attrs: &[ast::Attribute],
1661                                       close_box: bool) -> io::Result<()> {
1662         match blk.rules {
1663             ast::UnsafeBlock(..) | ast::PushUnsafeBlock(..) => try!(self.word_space("unsafe")),
1664             ast::DefaultBlock    | ast::PopUnsafeBlock(..) => ()
1665         }
1666         try!(self.maybe_print_comment(blk.span.lo));
1667         try!(self.ann.pre(self, NodeBlock(blk)));
1668         try!(self.bopen());
1669
1670         try!(self.print_inner_attributes(attrs));
1671
1672         for st in &blk.stmts {
1673             try!(self.print_stmt(&**st));
1674         }
1675         match blk.expr {
1676             Some(ref expr) => {
1677                 try!(self.space_if_not_bol());
1678                 try!(self.print_expr(&**expr));
1679                 try!(self.maybe_print_trailing_comment(expr.span, Some(blk.span.hi)));
1680             }
1681             _ => ()
1682         }
1683         try!(self.bclose_maybe_open(blk.span, indented, close_box));
1684         self.ann.post(self, NodeBlock(blk))
1685     }
1686
1687     fn print_else(&mut self, els: Option<&ast::Expr>) -> io::Result<()> {
1688         match els {
1689             Some(_else) => {
1690                 match _else.node {
1691                     // "another else-if"
1692                     ast::ExprIf(ref i, ref then, ref e) => {
1693                         try!(self.cbox(indent_unit - 1));
1694                         try!(self.ibox(0));
1695                         try!(word(&mut self.s, " else if "));
1696                         try!(self.print_expr(&**i));
1697                         try!(space(&mut self.s));
1698                         try!(self.print_block(&**then));
1699                         self.print_else(e.as_ref().map(|e| &**e))
1700                     }
1701                     // "another else-if-let"
1702                     ast::ExprIfLet(ref pat, ref expr, ref then, ref e) => {
1703                         try!(self.cbox(indent_unit - 1));
1704                         try!(self.ibox(0));
1705                         try!(word(&mut self.s, " else if let "));
1706                         try!(self.print_pat(&**pat));
1707                         try!(space(&mut self.s));
1708                         try!(self.word_space("="));
1709                         try!(self.print_expr(&**expr));
1710                         try!(space(&mut self.s));
1711                         try!(self.print_block(&**then));
1712                         self.print_else(e.as_ref().map(|e| &**e))
1713                     }
1714                     // "final else"
1715                     ast::ExprBlock(ref b) => {
1716                         try!(self.cbox(indent_unit - 1));
1717                         try!(self.ibox(0));
1718                         try!(word(&mut self.s, " else "));
1719                         self.print_block(&**b)
1720                     }
1721                     // BLEAH, constraints would be great here
1722                     _ => {
1723                         panic!("print_if saw if with weird alternative");
1724                     }
1725                 }
1726             }
1727             _ => Ok(())
1728         }
1729     }
1730
1731     pub fn print_if(&mut self, test: &ast::Expr, blk: &ast::Block,
1732                     elseopt: Option<&ast::Expr>) -> io::Result<()> {
1733         try!(self.head("if"));
1734         try!(self.print_expr(test));
1735         try!(space(&mut self.s));
1736         try!(self.print_block(blk));
1737         self.print_else(elseopt)
1738     }
1739
1740     pub fn print_if_let(&mut self, pat: &ast::Pat, expr: &ast::Expr, blk: &ast::Block,
1741                         elseopt: Option<&ast::Expr>) -> io::Result<()> {
1742         try!(self.head("if let"));
1743         try!(self.print_pat(pat));
1744         try!(space(&mut self.s));
1745         try!(self.word_space("="));
1746         try!(self.print_expr(expr));
1747         try!(space(&mut self.s));
1748         try!(self.print_block(blk));
1749         self.print_else(elseopt)
1750     }
1751
1752     pub fn print_mac(&mut self, m: &ast::Mac, delim: token::DelimToken)
1753                      -> io::Result<()> {
1754         try!(self.print_path(&m.node.path, false, 0));
1755         try!(word(&mut self.s, "!"));
1756         match delim {
1757             token::Paren => try!(self.popen()),
1758             token::Bracket => try!(word(&mut self.s, "[")),
1759             token::Brace => try!(self.bopen()),
1760         }
1761         try!(self.print_tts(&m.node.tts));
1762         match delim {
1763             token::Paren => self.pclose(),
1764             token::Bracket => word(&mut self.s, "]"),
1765             token::Brace => self.bclose(m.span),
1766         }
1767     }
1768
1769
1770     fn print_call_post(&mut self, args: &[P<ast::Expr>]) -> io::Result<()> {
1771         try!(self.popen());
1772         try!(self.commasep_exprs(Inconsistent, args));
1773         self.pclose()
1774     }
1775
1776     pub fn check_expr_bin_needs_paren(&mut self, sub_expr: &ast::Expr,
1777                                       binop: ast::BinOp) -> bool {
1778         match sub_expr.node {
1779             ast::ExprBinary(ref sub_op, _, _) => {
1780                 if ast_util::operator_prec(sub_op.node) <
1781                     ast_util::operator_prec(binop.node) {
1782                     true
1783                 } else {
1784                     false
1785                 }
1786             }
1787             _ => true
1788         }
1789     }
1790
1791     pub fn print_expr_maybe_paren(&mut self, expr: &ast::Expr) -> io::Result<()> {
1792         let needs_par = needs_parentheses(expr);
1793         if needs_par {
1794             try!(self.popen());
1795         }
1796         try!(self.print_expr(expr));
1797         if needs_par {
1798             try!(self.pclose());
1799         }
1800         Ok(())
1801     }
1802
1803     fn print_expr_in_place(&mut self,
1804                            place: &ast::Expr,
1805                            expr: &ast::Expr) -> io::Result<()> {
1806         try!(self.word_space("in"));
1807         try!(self.print_expr(place));
1808         try!(space(&mut self.s));
1809         self.print_expr(expr)
1810     }
1811
1812     fn print_expr_vec(&mut self, exprs: &[P<ast::Expr>]) -> io::Result<()> {
1813         try!(self.ibox(indent_unit));
1814         try!(word(&mut self.s, "["));
1815         try!(self.commasep_exprs(Inconsistent, &exprs[..]));
1816         try!(word(&mut self.s, "]"));
1817         self.end()
1818     }
1819
1820     fn print_expr_repeat(&mut self,
1821                          element: &ast::Expr,
1822                          count: &ast::Expr) -> io::Result<()> {
1823         try!(self.ibox(indent_unit));
1824         try!(word(&mut self.s, "["));
1825         try!(self.print_expr(element));
1826         try!(self.word_space(";"));
1827         try!(self.print_expr(count));
1828         try!(word(&mut self.s, "]"));
1829         self.end()
1830     }
1831
1832     fn print_expr_struct(&mut self,
1833                          path: &ast::Path,
1834                          fields: &[ast::Field],
1835                          wth: &Option<P<ast::Expr>>) -> io::Result<()> {
1836         try!(self.print_path(path, true, 0));
1837         try!(word(&mut self.s, "{"));
1838         try!(self.commasep_cmnt(
1839             Consistent,
1840             &fields[..],
1841             |s, field| {
1842                 try!(s.ibox(indent_unit));
1843                 try!(s.print_ident(field.ident.node));
1844                 try!(s.word_space(":"));
1845                 try!(s.print_expr(&*field.expr));
1846                 s.end()
1847             },
1848             |f| f.span));
1849         match *wth {
1850             Some(ref expr) => {
1851                 try!(self.ibox(indent_unit));
1852                 if !fields.is_empty() {
1853                     try!(word(&mut self.s, ","));
1854                     try!(space(&mut self.s));
1855                 }
1856                 try!(word(&mut self.s, ".."));
1857                 try!(self.print_expr(&**expr));
1858                 try!(self.end());
1859             }
1860             _ => if !fields.is_empty() {
1861                 try!(word(&mut self.s, ","))
1862             }
1863         }
1864         try!(word(&mut self.s, "}"));
1865         Ok(())
1866     }
1867
1868     fn print_expr_tup(&mut self, exprs: &[P<ast::Expr>]) -> io::Result<()> {
1869         try!(self.popen());
1870         try!(self.commasep_exprs(Inconsistent, &exprs[..]));
1871         if exprs.len() == 1 {
1872             try!(word(&mut self.s, ","));
1873         }
1874         self.pclose()
1875     }
1876
1877     fn print_expr_call(&mut self,
1878                        func: &ast::Expr,
1879                        args: &[P<ast::Expr>]) -> io::Result<()> {
1880         try!(self.print_expr_maybe_paren(func));
1881         self.print_call_post(args)
1882     }
1883
1884     fn print_expr_method_call(&mut self,
1885                               ident: ast::SpannedIdent,
1886                               tys: &[P<ast::Ty>],
1887                               args: &[P<ast::Expr>]) -> io::Result<()> {
1888         let base_args = &args[1..];
1889         try!(self.print_expr(&*args[0]));
1890         try!(word(&mut self.s, "."));
1891         try!(self.print_ident(ident.node));
1892         if !tys.is_empty() {
1893             try!(word(&mut self.s, "::<"));
1894             try!(self.commasep(Inconsistent, tys,
1895                                |s, ty| s.print_type(&**ty)));
1896             try!(word(&mut self.s, ">"));
1897         }
1898         self.print_call_post(base_args)
1899     }
1900
1901     fn print_expr_binary(&mut self,
1902                          op: ast::BinOp,
1903                          lhs: &ast::Expr,
1904                          rhs: &ast::Expr) -> io::Result<()> {
1905         if self.check_expr_bin_needs_paren(lhs, op) {
1906             try!(self.print_expr_maybe_paren(lhs));
1907         } else {
1908             try!(self.print_expr(lhs));
1909         }
1910         try!(space(&mut self.s));
1911         try!(self.word_space(ast_util::binop_to_string(op.node)));
1912         if self.check_expr_bin_needs_paren(rhs, op) {
1913             self.print_expr_maybe_paren(rhs)
1914         } else {
1915             self.print_expr(rhs)
1916         }
1917     }
1918
1919     fn print_expr_unary(&mut self,
1920                         op: ast::UnOp,
1921                         expr: &ast::Expr) -> io::Result<()> {
1922         try!(word(&mut self.s, ast_util::unop_to_string(op)));
1923         self.print_expr_maybe_paren(expr)
1924     }
1925
1926     fn print_expr_addr_of(&mut self,
1927                           mutability: ast::Mutability,
1928                           expr: &ast::Expr) -> io::Result<()> {
1929         try!(word(&mut self.s, "&"));
1930         try!(self.print_mutability(mutability));
1931         self.print_expr_maybe_paren(expr)
1932     }
1933
1934     pub fn print_expr(&mut self, expr: &ast::Expr) -> io::Result<()> {
1935         try!(self.maybe_print_comment(expr.span.lo));
1936         try!(self.ibox(indent_unit));
1937         try!(self.ann.pre(self, NodeExpr(expr)));
1938         match expr.node {
1939             ast::ExprBox(ref expr) => {
1940                 try!(self.word_space("box"));
1941                 try!(self.print_expr(expr));
1942             }
1943             ast::ExprInPlace(ref place, ref expr) => {
1944                 try!(self.print_expr_in_place(place, expr));
1945             }
1946             ast::ExprVec(ref exprs) => {
1947                 try!(self.print_expr_vec(&exprs[..]));
1948             }
1949             ast::ExprRepeat(ref element, ref count) => {
1950                 try!(self.print_expr_repeat(&**element, &**count));
1951             }
1952             ast::ExprStruct(ref path, ref fields, ref wth) => {
1953                 try!(self.print_expr_struct(path, &fields[..], wth));
1954             }
1955             ast::ExprTup(ref exprs) => {
1956                 try!(self.print_expr_tup(&exprs[..]));
1957             }
1958             ast::ExprCall(ref func, ref args) => {
1959                 try!(self.print_expr_call(&**func, &args[..]));
1960             }
1961             ast::ExprMethodCall(ident, ref tys, ref args) => {
1962                 try!(self.print_expr_method_call(ident, &tys[..], &args[..]));
1963             }
1964             ast::ExprBinary(op, ref lhs, ref rhs) => {
1965                 try!(self.print_expr_binary(op, &**lhs, &**rhs));
1966             }
1967             ast::ExprUnary(op, ref expr) => {
1968                 try!(self.print_expr_unary(op, &**expr));
1969             }
1970             ast::ExprAddrOf(m, ref expr) => {
1971                 try!(self.print_expr_addr_of(m, &**expr));
1972             }
1973             ast::ExprLit(ref lit) => {
1974                 try!(self.print_literal(&**lit));
1975             }
1976             ast::ExprCast(ref expr, ref ty) => {
1977                 if let ast::ExprCast(..) = expr.node {
1978                     try!(self.print_expr(&**expr));
1979                 } else {
1980                     try!(self.print_expr_maybe_paren(&**expr));
1981                 }
1982                 try!(space(&mut self.s));
1983                 try!(self.word_space("as"));
1984                 try!(self.print_type(&**ty));
1985             }
1986             ast::ExprIf(ref test, ref blk, ref elseopt) => {
1987                 try!(self.print_if(&**test, &**blk, elseopt.as_ref().map(|e| &**e)));
1988             }
1989             ast::ExprIfLet(ref pat, ref expr, ref blk, ref elseopt) => {
1990                 try!(self.print_if_let(&**pat, &**expr, &** blk, elseopt.as_ref().map(|e| &**e)));
1991             }
1992             ast::ExprWhile(ref test, ref blk, opt_ident) => {
1993                 if let Some(ident) = opt_ident {
1994                     try!(self.print_ident(ident));
1995                     try!(self.word_space(":"));
1996                 }
1997                 try!(self.head("while"));
1998                 try!(self.print_expr(&**test));
1999                 try!(space(&mut self.s));
2000                 try!(self.print_block(&**blk));
2001             }
2002             ast::ExprWhileLet(ref pat, ref expr, ref blk, opt_ident) => {
2003                 if let Some(ident) = opt_ident {
2004                     try!(self.print_ident(ident));
2005                     try!(self.word_space(":"));
2006                 }
2007                 try!(self.head("while let"));
2008                 try!(self.print_pat(&**pat));
2009                 try!(space(&mut self.s));
2010                 try!(self.word_space("="));
2011                 try!(self.print_expr(&**expr));
2012                 try!(space(&mut self.s));
2013                 try!(self.print_block(&**blk));
2014             }
2015             ast::ExprForLoop(ref pat, ref iter, ref blk, opt_ident) => {
2016                 if let Some(ident) = opt_ident {
2017                     try!(self.print_ident(ident));
2018                     try!(self.word_space(":"));
2019                 }
2020                 try!(self.head("for"));
2021                 try!(self.print_pat(&**pat));
2022                 try!(space(&mut self.s));
2023                 try!(self.word_space("in"));
2024                 try!(self.print_expr(&**iter));
2025                 try!(space(&mut self.s));
2026                 try!(self.print_block(&**blk));
2027             }
2028             ast::ExprLoop(ref blk, opt_ident) => {
2029                 if let Some(ident) = opt_ident {
2030                     try!(self.print_ident(ident));
2031                     try!(self.word_space(":"));
2032                 }
2033                 try!(self.head("loop"));
2034                 try!(space(&mut self.s));
2035                 try!(self.print_block(&**blk));
2036             }
2037             ast::ExprMatch(ref expr, ref arms) => {
2038                 try!(self.cbox(indent_unit));
2039                 try!(self.ibox(4));
2040                 try!(self.word_nbsp("match"));
2041                 try!(self.print_expr(&**expr));
2042                 try!(space(&mut self.s));
2043                 try!(self.bopen());
2044                 for arm in arms {
2045                     try!(self.print_arm(arm));
2046                 }
2047                 try!(self.bclose_(expr.span, indent_unit));
2048             }
2049             ast::ExprClosure(capture_clause, ref decl, ref body) => {
2050                 try!(self.print_capture_clause(capture_clause));
2051
2052                 try!(self.print_fn_block_args(&**decl));
2053                 try!(space(&mut self.s));
2054
2055                 let default_return = match decl.output {
2056                     ast::DefaultReturn(..) => true,
2057                     _ => false
2058                 };
2059
2060                 if !default_return || !body.stmts.is_empty() || body.expr.is_none() {
2061                     try!(self.print_block_unclosed(&**body));
2062                 } else {
2063                     // we extract the block, so as not to create another set of boxes
2064                     match body.expr.as_ref().unwrap().node {
2065                         ast::ExprBlock(ref blk) => {
2066                             try!(self.print_block_unclosed(&**blk));
2067                         }
2068                         _ => {
2069                             // this is a bare expression
2070                             try!(self.print_expr(body.expr.as_ref().map(|e| &**e).unwrap()));
2071                             try!(self.end()); // need to close a box
2072                         }
2073                     }
2074                 }
2075                 // a box will be closed by print_expr, but we didn't want an overall
2076                 // wrapper so we closed the corresponding opening. so create an
2077                 // empty box to satisfy the close.
2078                 try!(self.ibox(0));
2079             }
2080             ast::ExprBlock(ref blk) => {
2081                 // containing cbox, will be closed by print-block at }
2082                 try!(self.cbox(indent_unit));
2083                 // head-box, will be closed by print-block after {
2084                 try!(self.ibox(0));
2085                 try!(self.print_block(&**blk));
2086             }
2087             ast::ExprAssign(ref lhs, ref rhs) => {
2088                 try!(self.print_expr(&**lhs));
2089                 try!(space(&mut self.s));
2090                 try!(self.word_space("="));
2091                 try!(self.print_expr(&**rhs));
2092             }
2093             ast::ExprAssignOp(op, ref lhs, ref rhs) => {
2094                 try!(self.print_expr(&**lhs));
2095                 try!(space(&mut self.s));
2096                 try!(word(&mut self.s, ast_util::binop_to_string(op.node)));
2097                 try!(self.word_space("="));
2098                 try!(self.print_expr(&**rhs));
2099             }
2100             ast::ExprField(ref expr, id) => {
2101                 try!(self.print_expr(&**expr));
2102                 try!(word(&mut self.s, "."));
2103                 try!(self.print_ident(id.node));
2104             }
2105             ast::ExprTupField(ref expr, id) => {
2106                 try!(self.print_expr(&**expr));
2107                 try!(word(&mut self.s, "."));
2108                 try!(self.print_usize(id.node));
2109             }
2110             ast::ExprIndex(ref expr, ref index) => {
2111                 try!(self.print_expr(&**expr));
2112                 try!(word(&mut self.s, "["));
2113                 try!(self.print_expr(&**index));
2114                 try!(word(&mut self.s, "]"));
2115             }
2116             ast::ExprRange(ref start, ref end) => {
2117                 if let &Some(ref e) = start {
2118                     try!(self.print_expr(&**e));
2119                 }
2120                 try!(word(&mut self.s, ".."));
2121                 if let &Some(ref e) = end {
2122                     try!(self.print_expr(&**e));
2123                 }
2124             }
2125             ast::ExprPath(None, ref path) => {
2126                 try!(self.print_path(path, true, 0))
2127             }
2128             ast::ExprPath(Some(ref qself), ref path) => {
2129                 try!(self.print_qpath(path, qself, true))
2130             }
2131             ast::ExprBreak(opt_ident) => {
2132                 try!(word(&mut self.s, "break"));
2133                 try!(space(&mut self.s));
2134                 if let Some(ident) = opt_ident {
2135                     try!(self.print_ident(ident.node));
2136                     try!(space(&mut self.s));
2137                 }
2138             }
2139             ast::ExprAgain(opt_ident) => {
2140                 try!(word(&mut self.s, "continue"));
2141                 try!(space(&mut self.s));
2142                 if let Some(ident) = opt_ident {
2143                     try!(self.print_ident(ident.node));
2144                     try!(space(&mut self.s))
2145                 }
2146             }
2147             ast::ExprRet(ref result) => {
2148                 try!(word(&mut self.s, "return"));
2149                 match *result {
2150                     Some(ref expr) => {
2151                         try!(word(&mut self.s, " "));
2152                         try!(self.print_expr(&**expr));
2153                     }
2154                     _ => ()
2155                 }
2156             }
2157             ast::ExprInlineAsm(ref a) => {
2158                 try!(word(&mut self.s, "asm!"));
2159                 try!(self.popen());
2160                 try!(self.print_string(&a.asm, a.asm_str_style));
2161                 try!(self.word_space(":"));
2162
2163                 try!(self.commasep(Inconsistent, &a.outputs,
2164                                    |s, &(ref co, ref o, is_rw)| {
2165                     match co.slice_shift_char() {
2166                         Some(('=', operand)) if is_rw => {
2167                             try!(s.print_string(&format!("+{}", operand),
2168                                                 ast::CookedStr))
2169                         }
2170                         _ => try!(s.print_string(&co, ast::CookedStr))
2171                     }
2172                     try!(s.popen());
2173                     try!(s.print_expr(&**o));
2174                     try!(s.pclose());
2175                     Ok(())
2176                 }));
2177                 try!(space(&mut self.s));
2178                 try!(self.word_space(":"));
2179
2180                 try!(self.commasep(Inconsistent, &a.inputs,
2181                                    |s, &(ref co, ref o)| {
2182                     try!(s.print_string(&co, ast::CookedStr));
2183                     try!(s.popen());
2184                     try!(s.print_expr(&**o));
2185                     try!(s.pclose());
2186                     Ok(())
2187                 }));
2188                 try!(space(&mut self.s));
2189                 try!(self.word_space(":"));
2190
2191                 try!(self.commasep(Inconsistent, &a.clobbers,
2192                                    |s, co| {
2193                     try!(s.print_string(&co, ast::CookedStr));
2194                     Ok(())
2195                 }));
2196
2197                 let mut options = vec!();
2198                 if a.volatile {
2199                     options.push("volatile");
2200                 }
2201                 if a.alignstack {
2202                     options.push("alignstack");
2203                 }
2204                 if a.dialect == ast::AsmDialect::Intel {
2205                     options.push("intel");
2206                 }
2207
2208                 if !options.is_empty() {
2209                     try!(space(&mut self.s));
2210                     try!(self.word_space(":"));
2211                     try!(self.commasep(Inconsistent, &*options,
2212                                        |s, &co| {
2213                         try!(s.print_string(co, ast::CookedStr));
2214                         Ok(())
2215                     }));
2216                 }
2217
2218                 try!(self.pclose());
2219             }
2220             ast::ExprMac(ref m) => try!(self.print_mac(m, token::Paren)),
2221             ast::ExprParen(ref e) => {
2222                 try!(self.popen());
2223                 try!(self.print_expr(&**e));
2224                 try!(self.pclose());
2225             }
2226         }
2227         try!(self.ann.post(self, NodeExpr(expr)));
2228         self.end()
2229     }
2230
2231     pub fn print_local_decl(&mut self, loc: &ast::Local) -> io::Result<()> {
2232         try!(self.print_pat(&*loc.pat));
2233         if let Some(ref ty) = loc.ty {
2234             try!(self.word_space(":"));
2235             try!(self.print_type(&**ty));
2236         }
2237         Ok(())
2238     }
2239
2240     pub fn print_decl(&mut self, decl: &ast::Decl) -> io::Result<()> {
2241         try!(self.maybe_print_comment(decl.span.lo));
2242         match decl.node {
2243             ast::DeclLocal(ref loc) => {
2244                 try!(self.space_if_not_bol());
2245                 try!(self.ibox(indent_unit));
2246                 try!(self.word_nbsp("let"));
2247
2248                 try!(self.ibox(indent_unit));
2249                 try!(self.print_local_decl(&**loc));
2250                 try!(self.end());
2251                 if let Some(ref init) = loc.init {
2252                     try!(self.nbsp());
2253                     try!(self.word_space("="));
2254                     try!(self.print_expr(&**init));
2255                 }
2256                 self.end()
2257             }
2258             ast::DeclItem(ref item) => self.print_item(&**item)
2259         }
2260     }
2261
2262     pub fn print_ident(&mut self, ident: ast::Ident) -> io::Result<()> {
2263         try!(word(&mut self.s, &ident.name.as_str()));
2264         self.ann.post(self, NodeIdent(&ident))
2265     }
2266
2267     pub fn print_usize(&mut self, i: usize) -> io::Result<()> {
2268         word(&mut self.s, &i.to_string())
2269     }
2270
2271     pub fn print_name(&mut self, name: ast::Name) -> io::Result<()> {
2272         try!(word(&mut self.s, &name.as_str()));
2273         self.ann.post(self, NodeName(&name))
2274     }
2275
2276     pub fn print_for_decl(&mut self, loc: &ast::Local,
2277                           coll: &ast::Expr) -> io::Result<()> {
2278         try!(self.print_local_decl(loc));
2279         try!(space(&mut self.s));
2280         try!(self.word_space("in"));
2281         self.print_expr(coll)
2282     }
2283
2284     fn print_path(&mut self,
2285                   path: &ast::Path,
2286                   colons_before_params: bool,
2287                   depth: usize)
2288                   -> io::Result<()>
2289     {
2290         try!(self.maybe_print_comment(path.span.lo));
2291
2292         let mut first = !path.global;
2293         for segment in &path.segments[..path.segments.len()-depth] {
2294             if first {
2295                 first = false
2296             } else {
2297                 try!(word(&mut self.s, "::"))
2298             }
2299
2300             try!(self.print_ident(segment.identifier));
2301
2302             try!(self.print_path_parameters(&segment.parameters, colons_before_params));
2303         }
2304
2305         Ok(())
2306     }
2307
2308     fn print_qpath(&mut self,
2309                    path: &ast::Path,
2310                    qself: &ast::QSelf,
2311                    colons_before_params: bool)
2312                    -> io::Result<()>
2313     {
2314         try!(word(&mut self.s, "<"));
2315         try!(self.print_type(&qself.ty));
2316         if qself.position > 0 {
2317             try!(space(&mut self.s));
2318             try!(self.word_space("as"));
2319             let depth = path.segments.len() - qself.position;
2320             try!(self.print_path(&path, false, depth));
2321         }
2322         try!(word(&mut self.s, ">"));
2323         try!(word(&mut self.s, "::"));
2324         let item_segment = path.segments.last().unwrap();
2325         try!(self.print_ident(item_segment.identifier));
2326         self.print_path_parameters(&item_segment.parameters, colons_before_params)
2327     }
2328
2329     fn print_path_parameters(&mut self,
2330                              parameters: &ast::PathParameters,
2331                              colons_before_params: bool)
2332                              -> io::Result<()>
2333     {
2334         if parameters.is_empty() {
2335             return Ok(());
2336         }
2337
2338         if colons_before_params {
2339             try!(word(&mut self.s, "::"))
2340         }
2341
2342         match *parameters {
2343             ast::AngleBracketedParameters(ref data) => {
2344                 try!(word(&mut self.s, "<"));
2345
2346                 let mut comma = false;
2347                 for lifetime in &data.lifetimes {
2348                     if comma {
2349                         try!(self.word_space(","))
2350                     }
2351                     try!(self.print_lifetime(lifetime));
2352                     comma = true;
2353                 }
2354
2355                 if !data.types.is_empty() {
2356                     if comma {
2357                         try!(self.word_space(","))
2358                     }
2359                     try!(self.commasep(
2360                         Inconsistent,
2361                         &data.types,
2362                         |s, ty| s.print_type(&**ty)));
2363                         comma = true;
2364                 }
2365
2366                 for binding in data.bindings.iter() {
2367                     if comma {
2368                         try!(self.word_space(","))
2369                     }
2370                     try!(self.print_ident(binding.ident));
2371                     try!(space(&mut self.s));
2372                     try!(self.word_space("="));
2373                     try!(self.print_type(&*binding.ty));
2374                     comma = true;
2375                 }
2376
2377                 try!(word(&mut self.s, ">"))
2378             }
2379
2380             ast::ParenthesizedParameters(ref data) => {
2381                 try!(word(&mut self.s, "("));
2382                 try!(self.commasep(
2383                     Inconsistent,
2384                     &data.inputs,
2385                     |s, ty| s.print_type(&**ty)));
2386                 try!(word(&mut self.s, ")"));
2387
2388                 match data.output {
2389                     None => { }
2390                     Some(ref ty) => {
2391                         try!(self.space_if_not_bol());
2392                         try!(self.word_space("->"));
2393                         try!(self.print_type(&**ty));
2394                     }
2395                 }
2396             }
2397         }
2398
2399         Ok(())
2400     }
2401
2402     pub fn print_pat(&mut self, pat: &ast::Pat) -> io::Result<()> {
2403         try!(self.maybe_print_comment(pat.span.lo));
2404         try!(self.ann.pre(self, NodePat(pat)));
2405         /* Pat isn't normalized, but the beauty of it
2406          is that it doesn't matter */
2407         match pat.node {
2408             ast::PatWild(ast::PatWildSingle) => try!(word(&mut self.s, "_")),
2409             ast::PatWild(ast::PatWildMulti) => try!(word(&mut self.s, "..")),
2410             ast::PatIdent(binding_mode, ref path1, ref sub) => {
2411                 match binding_mode {
2412                     ast::BindByRef(mutbl) => {
2413                         try!(self.word_nbsp("ref"));
2414                         try!(self.print_mutability(mutbl));
2415                     }
2416                     ast::BindByValue(ast::MutImmutable) => {}
2417                     ast::BindByValue(ast::MutMutable) => {
2418                         try!(self.word_nbsp("mut"));
2419                     }
2420                 }
2421                 try!(self.print_ident(path1.node));
2422                 match *sub {
2423                     Some(ref p) => {
2424                         try!(word(&mut self.s, "@"));
2425                         try!(self.print_pat(&**p));
2426                     }
2427                     None => ()
2428                 }
2429             }
2430             ast::PatEnum(ref path, ref args_) => {
2431                 try!(self.print_path(path, true, 0));
2432                 match *args_ {
2433                     None => try!(word(&mut self.s, "(..)")),
2434                     Some(ref args) => {
2435                         if !args.is_empty() {
2436                             try!(self.popen());
2437                             try!(self.commasep(Inconsistent, &args[..],
2438                                               |s, p| s.print_pat(&**p)));
2439                             try!(self.pclose());
2440                         }
2441                     }
2442                 }
2443             }
2444             ast::PatQPath(ref qself, ref path) => {
2445                 try!(self.print_qpath(path, qself, false));
2446             }
2447             ast::PatStruct(ref path, ref fields, etc) => {
2448                 try!(self.print_path(path, true, 0));
2449                 try!(self.nbsp());
2450                 try!(self.word_space("{"));
2451                 try!(self.commasep_cmnt(
2452                     Consistent, &fields[..],
2453                     |s, f| {
2454                         try!(s.cbox(indent_unit));
2455                         if !f.node.is_shorthand {
2456                             try!(s.print_ident(f.node.ident));
2457                             try!(s.word_nbsp(":"));
2458                         }
2459                         try!(s.print_pat(&*f.node.pat));
2460                         s.end()
2461                     },
2462                     |f| f.node.pat.span));
2463                 if etc {
2464                     if !fields.is_empty() { try!(self.word_space(",")); }
2465                     try!(word(&mut self.s, ".."));
2466                 }
2467                 try!(space(&mut self.s));
2468                 try!(word(&mut self.s, "}"));
2469             }
2470             ast::PatTup(ref elts) => {
2471                 try!(self.popen());
2472                 try!(self.commasep(Inconsistent,
2473                                    &elts[..],
2474                                    |s, p| s.print_pat(&**p)));
2475                 if elts.len() == 1 {
2476                     try!(word(&mut self.s, ","));
2477                 }
2478                 try!(self.pclose());
2479             }
2480             ast::PatBox(ref inner) => {
2481                 try!(word(&mut self.s, "box "));
2482                 try!(self.print_pat(&**inner));
2483             }
2484             ast::PatRegion(ref inner, mutbl) => {
2485                 try!(word(&mut self.s, "&"));
2486                 if mutbl == ast::MutMutable {
2487                     try!(word(&mut self.s, "mut "));
2488                 }
2489                 try!(self.print_pat(&**inner));
2490             }
2491             ast::PatLit(ref e) => try!(self.print_expr(&**e)),
2492             ast::PatRange(ref begin, ref end) => {
2493                 try!(self.print_expr(&**begin));
2494                 try!(space(&mut self.s));
2495                 try!(word(&mut self.s, "..."));
2496                 try!(self.print_expr(&**end));
2497             }
2498             ast::PatVec(ref before, ref slice, ref after) => {
2499                 try!(word(&mut self.s, "["));
2500                 try!(self.commasep(Inconsistent,
2501                                    &before[..],
2502                                    |s, p| s.print_pat(&**p)));
2503                 if let Some(ref p) = *slice {
2504                     if !before.is_empty() { try!(self.word_space(",")); }
2505                     try!(self.print_pat(&**p));
2506                     match **p {
2507                         ast::Pat { node: ast::PatWild(ast::PatWildMulti), .. } => {
2508                             // this case is handled by print_pat
2509                         }
2510                         _ => try!(word(&mut self.s, "..")),
2511                     }
2512                     if !after.is_empty() { try!(self.word_space(",")); }
2513                 }
2514                 try!(self.commasep(Inconsistent,
2515                                    &after[..],
2516                                    |s, p| s.print_pat(&**p)));
2517                 try!(word(&mut self.s, "]"));
2518             }
2519             ast::PatMac(ref m) => try!(self.print_mac(m, token::Paren)),
2520         }
2521         self.ann.post(self, NodePat(pat))
2522     }
2523
2524     fn print_arm(&mut self, arm: &ast::Arm) -> io::Result<()> {
2525         // I have no idea why this check is necessary, but here it
2526         // is :(
2527         if arm.attrs.is_empty() {
2528             try!(space(&mut self.s));
2529         }
2530         try!(self.cbox(indent_unit));
2531         try!(self.ibox(0));
2532         try!(self.print_outer_attributes(&arm.attrs));
2533         let mut first = true;
2534         for p in &arm.pats {
2535             if first {
2536                 first = false;
2537             } else {
2538                 try!(space(&mut self.s));
2539                 try!(self.word_space("|"));
2540             }
2541             try!(self.print_pat(&**p));
2542         }
2543         try!(space(&mut self.s));
2544         if let Some(ref e) = arm.guard {
2545             try!(self.word_space("if"));
2546             try!(self.print_expr(&**e));
2547             try!(space(&mut self.s));
2548         }
2549         try!(self.word_space("=>"));
2550
2551         match arm.body.node {
2552             ast::ExprBlock(ref blk) => {
2553                 // the block will close the pattern's ibox
2554                 try!(self.print_block_unclosed_indent(&**blk, indent_unit));
2555
2556                 // If it is a user-provided unsafe block, print a comma after it
2557                 if let ast::UnsafeBlock(ast::UserProvided) = blk.rules {
2558                     try!(word(&mut self.s, ","));
2559                 }
2560             }
2561             _ => {
2562                 try!(self.end()); // close the ibox for the pattern
2563                 try!(self.print_expr(&*arm.body));
2564                 try!(word(&mut self.s, ","));
2565             }
2566         }
2567         self.end() // close enclosing cbox
2568     }
2569
2570     // Returns whether it printed anything
2571     fn print_explicit_self(&mut self,
2572                            explicit_self: &ast::ExplicitSelf_,
2573                            mutbl: ast::Mutability) -> io::Result<bool> {
2574         try!(self.print_mutability(mutbl));
2575         match *explicit_self {
2576             ast::SelfStatic => { return Ok(false); }
2577             ast::SelfValue(_) => {
2578                 try!(word(&mut self.s, "self"));
2579             }
2580             ast::SelfRegion(ref lt, m, _) => {
2581                 try!(word(&mut self.s, "&"));
2582                 try!(self.print_opt_lifetime(lt));
2583                 try!(self.print_mutability(m));
2584                 try!(word(&mut self.s, "self"));
2585             }
2586             ast::SelfExplicit(ref typ, _) => {
2587                 try!(word(&mut self.s, "self"));
2588                 try!(self.word_space(":"));
2589                 try!(self.print_type(&**typ));
2590             }
2591         }
2592         return Ok(true);
2593     }
2594
2595     pub fn print_fn(&mut self,
2596                     decl: &ast::FnDecl,
2597                     unsafety: ast::Unsafety,
2598                     constness: ast::Constness,
2599                     abi: abi::Abi,
2600                     name: Option<ast::Ident>,
2601                     generics: &ast::Generics,
2602                     opt_explicit_self: Option<&ast::ExplicitSelf_>,
2603                     vis: ast::Visibility) -> io::Result<()> {
2604         try!(self.print_fn_header_info(unsafety, constness, abi, vis));
2605
2606         if let Some(name) = name {
2607             try!(self.nbsp());
2608             try!(self.print_ident(name));
2609         }
2610         try!(self.print_generics(generics));
2611         try!(self.print_fn_args_and_ret(decl, opt_explicit_self));
2612         self.print_where_clause(&generics.where_clause)
2613     }
2614
2615     pub fn print_fn_args(&mut self, decl: &ast::FnDecl,
2616                          opt_explicit_self: Option<&ast::ExplicitSelf_>)
2617         -> io::Result<()> {
2618         // It is unfortunate to duplicate the commasep logic, but we want the
2619         // self type and the args all in the same box.
2620         try!(self.rbox(0, Inconsistent));
2621         let mut first = true;
2622         if let Some(explicit_self) = opt_explicit_self {
2623             let m = match explicit_self {
2624                 &ast::SelfStatic => ast::MutImmutable,
2625                 _ => match decl.inputs[0].pat.node {
2626                     ast::PatIdent(ast::BindByValue(m), _, _) => m,
2627                     _ => ast::MutImmutable
2628                 }
2629             };
2630             first = !try!(self.print_explicit_self(explicit_self, m));
2631         }
2632
2633         // HACK(eddyb) ignore the separately printed self argument.
2634         let args = if first {
2635             &decl.inputs[..]
2636         } else {
2637             &decl.inputs[1..]
2638         };
2639
2640         for arg in args {
2641             if first { first = false; } else { try!(self.word_space(",")); }
2642             try!(self.print_arg(arg));
2643         }
2644
2645         self.end()
2646     }
2647
2648     pub fn print_fn_args_and_ret(&mut self, decl: &ast::FnDecl,
2649                                  opt_explicit_self: Option<&ast::ExplicitSelf_>)
2650         -> io::Result<()> {
2651         try!(self.popen());
2652         try!(self.print_fn_args(decl, opt_explicit_self));
2653         if decl.variadic {
2654             try!(word(&mut self.s, ", ..."));
2655         }
2656         try!(self.pclose());
2657
2658         self.print_fn_output(decl)
2659     }
2660
2661     pub fn print_fn_block_args(
2662             &mut self,
2663             decl: &ast::FnDecl)
2664             -> io::Result<()> {
2665         try!(word(&mut self.s, "|"));
2666         try!(self.print_fn_args(decl, None));
2667         try!(word(&mut self.s, "|"));
2668
2669         if let ast::DefaultReturn(..) = decl.output {
2670             return Ok(());
2671         }
2672
2673         try!(self.space_if_not_bol());
2674         try!(self.word_space("->"));
2675         match decl.output {
2676             ast::Return(ref ty) => {
2677                 try!(self.print_type(&**ty));
2678                 self.maybe_print_comment(ty.span.lo)
2679             }
2680             ast::DefaultReturn(..) => unreachable!(),
2681             ast::NoReturn(span) => {
2682                 try!(self.word_nbsp("!"));
2683                 self.maybe_print_comment(span.lo)
2684             }
2685         }
2686     }
2687
2688     pub fn print_capture_clause(&mut self, capture_clause: ast::CaptureClause)
2689                                 -> io::Result<()> {
2690         match capture_clause {
2691             ast::CaptureByValue => self.word_space("move"),
2692             ast::CaptureByRef => Ok(()),
2693         }
2694     }
2695
2696     pub fn print_bounds(&mut self,
2697                         prefix: &str,
2698                         bounds: &[ast::TyParamBound])
2699                         -> io::Result<()> {
2700         if !bounds.is_empty() {
2701             try!(word(&mut self.s, prefix));
2702             let mut first = true;
2703             for bound in bounds {
2704                 try!(self.nbsp());
2705                 if first {
2706                     first = false;
2707                 } else {
2708                     try!(self.word_space("+"));
2709                 }
2710
2711                 try!(match *bound {
2712                     TraitTyParamBound(ref tref, TraitBoundModifier::None) => {
2713                         self.print_poly_trait_ref(tref)
2714                     }
2715                     TraitTyParamBound(ref tref, TraitBoundModifier::Maybe) => {
2716                         try!(word(&mut self.s, "?"));
2717                         self.print_poly_trait_ref(tref)
2718                     }
2719                     RegionTyParamBound(ref lt) => {
2720                         self.print_lifetime(lt)
2721                     }
2722                 })
2723             }
2724             Ok(())
2725         } else {
2726             Ok(())
2727         }
2728     }
2729
2730     pub fn print_lifetime(&mut self,
2731                           lifetime: &ast::Lifetime)
2732                           -> io::Result<()>
2733     {
2734         self.print_name(lifetime.name)
2735     }
2736
2737     pub fn print_lifetime_def(&mut self,
2738                               lifetime: &ast::LifetimeDef)
2739                               -> io::Result<()>
2740     {
2741         try!(self.print_lifetime(&lifetime.lifetime));
2742         let mut sep = ":";
2743         for v in &lifetime.bounds {
2744             try!(word(&mut self.s, sep));
2745             try!(self.print_lifetime(v));
2746             sep = "+";
2747         }
2748         Ok(())
2749     }
2750
2751     pub fn print_generics(&mut self,
2752                           generics: &ast::Generics)
2753                           -> io::Result<()>
2754     {
2755         let total = generics.lifetimes.len() + generics.ty_params.len();
2756         if total == 0 {
2757             return Ok(());
2758         }
2759
2760         try!(word(&mut self.s, "<"));
2761
2762         let mut ints = Vec::new();
2763         for i in 0..total {
2764             ints.push(i);
2765         }
2766
2767         try!(self.commasep(Inconsistent, &ints[..], |s, &idx| {
2768             if idx < generics.lifetimes.len() {
2769                 let lifetime = &generics.lifetimes[idx];
2770                 s.print_lifetime_def(lifetime)
2771             } else {
2772                 let idx = idx - generics.lifetimes.len();
2773                 let param = &generics.ty_params[idx];
2774                 s.print_ty_param(param)
2775             }
2776         }));
2777
2778         try!(word(&mut self.s, ">"));
2779         Ok(())
2780     }
2781
2782     pub fn print_ty_param(&mut self, param: &ast::TyParam) -> io::Result<()> {
2783         try!(self.print_ident(param.ident));
2784         try!(self.print_bounds(":", &param.bounds));
2785         match param.default {
2786             Some(ref default) => {
2787                 try!(space(&mut self.s));
2788                 try!(self.word_space("="));
2789                 self.print_type(&**default)
2790             }
2791             _ => Ok(())
2792         }
2793     }
2794
2795     pub fn print_where_clause(&mut self, where_clause: &ast::WhereClause)
2796                               -> io::Result<()> {
2797         if where_clause.predicates.is_empty() {
2798             return Ok(())
2799         }
2800
2801         try!(space(&mut self.s));
2802         try!(self.word_space("where"));
2803
2804         for (i, predicate) in where_clause.predicates.iter().enumerate() {
2805             if i != 0 {
2806                 try!(self.word_space(","));
2807             }
2808
2809             match predicate {
2810                 &ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate{ref bound_lifetimes,
2811                                                                               ref bounded_ty,
2812                                                                               ref bounds,
2813                                                                               ..}) => {
2814                     try!(self.print_formal_lifetime_list(bound_lifetimes));
2815                     try!(self.print_type(&**bounded_ty));
2816                     try!(self.print_bounds(":", bounds));
2817                 }
2818                 &ast::WherePredicate::RegionPredicate(ast::WhereRegionPredicate{ref lifetime,
2819                                                                                 ref bounds,
2820                                                                                 ..}) => {
2821                     try!(self.print_lifetime(lifetime));
2822                     try!(word(&mut self.s, ":"));
2823
2824                     for (i, bound) in bounds.iter().enumerate() {
2825                         try!(self.print_lifetime(bound));
2826
2827                         if i != 0 {
2828                             try!(word(&mut self.s, ":"));
2829                         }
2830                     }
2831                 }
2832                 &ast::WherePredicate::EqPredicate(ast::WhereEqPredicate{ref path, ref ty, ..}) => {
2833                     try!(self.print_path(path, false, 0));
2834                     try!(space(&mut self.s));
2835                     try!(self.word_space("="));
2836                     try!(self.print_type(&**ty));
2837                 }
2838             }
2839         }
2840
2841         Ok(())
2842     }
2843
2844     pub fn print_view_path(&mut self, vp: &ast::ViewPath) -> io::Result<()> {
2845         match vp.node {
2846             ast::ViewPathSimple(ident, ref path) => {
2847                 try!(self.print_path(path, false, 0));
2848
2849                 if path.segments.last().unwrap().identifier.name !=
2850                         ident.name {
2851                     try!(space(&mut self.s));
2852                     try!(self.word_space("as"));
2853                     try!(self.print_ident(ident));
2854                 }
2855
2856                 Ok(())
2857             }
2858
2859             ast::ViewPathGlob(ref path) => {
2860                 try!(self.print_path(path, false, 0));
2861                 word(&mut self.s, "::*")
2862             }
2863
2864             ast::ViewPathList(ref path, ref idents) => {
2865                 if path.segments.is_empty() {
2866                     try!(word(&mut self.s, "{"));
2867                 } else {
2868                     try!(self.print_path(path, false, 0));
2869                     try!(word(&mut self.s, "::{"));
2870                 }
2871                 try!(self.commasep(Inconsistent, &idents[..], |s, w| {
2872                     match w.node {
2873                         ast::PathListIdent { name, rename, .. } => {
2874                             try!(s.print_ident(name));
2875                             if let Some(ident) = rename {
2876                                 try!(space(&mut s.s));
2877                                 try!(s.word_space("as"));
2878                                 try!(s.print_ident(ident));
2879                             }
2880                             Ok(())
2881                         },
2882                         ast::PathListMod { rename, .. } => {
2883                             try!(word(&mut s.s, "self"));
2884                             if let Some(ident) = rename {
2885                                 try!(space(&mut s.s));
2886                                 try!(s.word_space("as"));
2887                                 try!(s.print_ident(ident));
2888                             }
2889                             Ok(())
2890                         }
2891                     }
2892                 }));
2893                 word(&mut self.s, "}")
2894             }
2895         }
2896     }
2897
2898     pub fn print_mutability(&mut self,
2899                             mutbl: ast::Mutability) -> io::Result<()> {
2900         match mutbl {
2901             ast::MutMutable => self.word_nbsp("mut"),
2902             ast::MutImmutable => Ok(()),
2903         }
2904     }
2905
2906     pub fn print_mt(&mut self, mt: &ast::MutTy) -> io::Result<()> {
2907         try!(self.print_mutability(mt.mutbl));
2908         self.print_type(&*mt.ty)
2909     }
2910
2911     pub fn print_arg(&mut self, input: &ast::Arg) -> io::Result<()> {
2912         try!(self.ibox(indent_unit));
2913         match input.ty.node {
2914             ast::TyInfer => try!(self.print_pat(&*input.pat)),
2915             _ => {
2916                 match input.pat.node {
2917                     ast::PatIdent(_, ref path1, _) if
2918                         path1.node.name ==
2919                             parse::token::special_idents::invalid.name => {
2920                         // Do nothing.
2921                     }
2922                     _ => {
2923                         try!(self.print_pat(&*input.pat));
2924                         try!(word(&mut self.s, ":"));
2925                         try!(space(&mut self.s));
2926                     }
2927                 }
2928                 try!(self.print_type(&*input.ty));
2929             }
2930         }
2931         self.end()
2932     }
2933
2934     pub fn print_fn_output(&mut self, decl: &ast::FnDecl) -> io::Result<()> {
2935         if let ast::DefaultReturn(..) = decl.output {
2936             return Ok(());
2937         }
2938
2939         try!(self.space_if_not_bol());
2940         try!(self.ibox(indent_unit));
2941         try!(self.word_space("->"));
2942         match decl.output {
2943             ast::NoReturn(_) =>
2944                 try!(self.word_nbsp("!")),
2945             ast::DefaultReturn(..) => unreachable!(),
2946             ast::Return(ref ty) =>
2947                 try!(self.print_type(&**ty))
2948         }
2949         try!(self.end());
2950
2951         match decl.output {
2952             ast::Return(ref output) => self.maybe_print_comment(output.span.lo),
2953             _ => Ok(())
2954         }
2955     }
2956
2957     pub fn print_ty_fn(&mut self,
2958                        abi: abi::Abi,
2959                        unsafety: ast::Unsafety,
2960                        decl: &ast::FnDecl,
2961                        name: Option<ast::Ident>,
2962                        generics: &ast::Generics,
2963                        opt_explicit_self: Option<&ast::ExplicitSelf_>)
2964                        -> io::Result<()> {
2965         try!(self.ibox(indent_unit));
2966         if !generics.lifetimes.is_empty() || !generics.ty_params.is_empty() {
2967             try!(word(&mut self.s, "for"));
2968             try!(self.print_generics(generics));
2969         }
2970         let generics = ast::Generics {
2971             lifetimes: Vec::new(),
2972             ty_params: OwnedSlice::empty(),
2973             where_clause: ast::WhereClause {
2974                 id: ast::DUMMY_NODE_ID,
2975                 predicates: Vec::new(),
2976             },
2977         };
2978         try!(self.print_fn(decl,
2979                            unsafety,
2980                            ast::Constness::NotConst,
2981                            abi,
2982                            name,
2983                            &generics,
2984                            opt_explicit_self,
2985                            ast::Inherited));
2986         self.end()
2987     }
2988
2989     pub fn maybe_print_trailing_comment(&mut self, span: codemap::Span,
2990                                         next_pos: Option<BytePos>)
2991         -> io::Result<()> {
2992         let cm = match self.cm {
2993             Some(cm) => cm,
2994             _ => return Ok(())
2995         };
2996         match self.next_comment() {
2997             Some(ref cmnt) => {
2998                 if (*cmnt).style != comments::Trailing { return Ok(()) }
2999                 let span_line = cm.lookup_char_pos(span.hi);
3000                 let comment_line = cm.lookup_char_pos((*cmnt).pos);
3001                 let mut next = (*cmnt).pos + BytePos(1);
3002                 match next_pos { None => (), Some(p) => next = p }
3003                 if span.hi < (*cmnt).pos && (*cmnt).pos < next &&
3004                     span_line.line == comment_line.line {
3005                         try!(self.print_comment(cmnt));
3006                         self.cur_cmnt_and_lit.cur_cmnt += 1;
3007                     }
3008             }
3009             _ => ()
3010         }
3011         Ok(())
3012     }
3013
3014     pub fn print_remaining_comments(&mut self) -> io::Result<()> {
3015         // If there aren't any remaining comments, then we need to manually
3016         // make sure there is a line break at the end.
3017         if self.next_comment().is_none() {
3018             try!(hardbreak(&mut self.s));
3019         }
3020         loop {
3021             match self.next_comment() {
3022                 Some(ref cmnt) => {
3023                     try!(self.print_comment(cmnt));
3024                     self.cur_cmnt_and_lit.cur_cmnt += 1;
3025                 }
3026                 _ => break
3027             }
3028         }
3029         Ok(())
3030     }
3031
3032     pub fn print_opt_abi_and_extern_if_nondefault(&mut self,
3033                                                   opt_abi: Option<abi::Abi>)
3034         -> io::Result<()> {
3035         match opt_abi {
3036             Some(abi::Rust) => Ok(()),
3037             Some(abi) => {
3038                 try!(self.word_nbsp("extern"));
3039                 self.word_nbsp(&abi.to_string())
3040             }
3041             None => Ok(())
3042         }
3043     }
3044
3045     pub fn print_extern_opt_abi(&mut self,
3046                                 opt_abi: Option<abi::Abi>) -> io::Result<()> {
3047         match opt_abi {
3048             Some(abi) => {
3049                 try!(self.word_nbsp("extern"));
3050                 self.word_nbsp(&abi.to_string())
3051             }
3052             None => Ok(())
3053         }
3054     }
3055
3056     pub fn print_fn_header_info(&mut self,
3057                                 unsafety: ast::Unsafety,
3058                                 constness: ast::Constness,
3059                                 abi: abi::Abi,
3060                                 vis: ast::Visibility) -> io::Result<()> {
3061         try!(word(&mut self.s, &visibility_qualified(vis, "")));
3062         try!(self.print_unsafety(unsafety));
3063
3064         match constness {
3065             ast::Constness::NotConst => {}
3066             ast::Constness::Const => try!(self.word_nbsp("const"))
3067         }
3068
3069         if abi != abi::Rust {
3070             try!(self.word_nbsp("extern"));
3071             try!(self.word_nbsp(&abi.to_string()));
3072         }
3073
3074         word(&mut self.s, "fn")
3075     }
3076
3077     pub fn print_unsafety(&mut self, s: ast::Unsafety) -> io::Result<()> {
3078         match s {
3079             ast::Unsafety::Normal => Ok(()),
3080             ast::Unsafety::Unsafe => self.word_nbsp("unsafe"),
3081         }
3082     }
3083 }
3084
3085 fn repeat(s: &str, n: usize) -> String { iter::repeat(s).take(n).collect() }
3086
3087 #[cfg(test)]
3088 mod tests {
3089     use super::*;
3090
3091     use ast;
3092     use ast_util;
3093     use codemap;
3094     use parse::token;
3095     use ptr::P;
3096
3097     #[test]
3098     fn test_fun_to_string() {
3099         let abba_ident = token::str_to_ident("abba");
3100
3101         let decl = ast::FnDecl {
3102             inputs: Vec::new(),
3103             output: ast::DefaultReturn(codemap::DUMMY_SP),
3104             variadic: false
3105         };
3106         let generics = ast_util::empty_generics();
3107         assert_eq!(fun_to_string(&decl, ast::Unsafety::Normal,
3108                                  ast::Constness::NotConst,
3109                                  abba_ident,
3110                                  None, &generics),
3111                    "fn abba()");
3112     }
3113
3114     #[test]
3115     fn test_variant_to_string() {
3116         let ident = token::str_to_ident("principal_skinner");
3117
3118         let var = codemap::respan(codemap::DUMMY_SP, ast::Variant_ {
3119             name: ident,
3120             attrs: Vec::new(),
3121             // making this up as I go.... ?
3122             def: P(ast::StructDef { fields: Vec::new(),
3123                                     id: ast::DUMMY_NODE_ID,
3124                                     kind: ast::VariantKind::Unit }),
3125             id: 0,
3126             disr_expr: None,
3127         });
3128
3129         let varstr = variant_to_string(&var);
3130         assert_eq!(varstr, "principal_skinner");
3131     }
3132
3133     #[test]
3134     fn test_signed_int_to_string() {
3135         let pos_int = ast::LitInt(42, ast::SignedIntLit(ast::TyI32, ast::Plus));
3136         let neg_int = ast::LitInt((!42 + 1) as u64, ast::SignedIntLit(ast::TyI32, ast::Minus));
3137         assert_eq!(format!("-{}", lit_to_string(&codemap::dummy_spanned(pos_int))),
3138                    lit_to_string(&codemap::dummy_spanned(neg_int)));
3139     }
3140 }