src/librustc_front/print/pprust.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 pub use self::AnnNode::*;
  12
  13 use syntax::abi::Abi;
  14 use syntax::ast;
  15 use syntax::codemap::{self, CodeMap, BytePos, Spanned};
  16 use syntax::errors;
  17 use syntax::parse::token::{self, BinOpToken};
  18 use syntax::parse::lexer::comments;
  19 use syntax::parse;
  20 use syntax::print::pp::{self, break_offset, word, space, hardbreak};
  21 use syntax::print::pp::{Breaks, eof};
  22 use syntax::print::pp::Breaks::{Consistent, Inconsistent};
  23 use syntax::print::pprust::{self as ast_pp, PrintState};
  24 use syntax::ptr::P;
  25
  26 use hir;
  27 use hir::{Crate, PatKind, RegionTyParamBound, TraitTyParamBound, TraitBoundModifier};
  28
  29 use std::io::{self, Write, Read};
  30
  31 pub enum AnnNode<'a> {
  32     NodeName(&'a ast::Name),
  33     NodeBlock(&'a hir::Block),
  34     NodeItem(&'a hir::Item),
  35     NodeSubItem(ast::NodeId),
  36     NodeExpr(&'a hir::Expr),
  37     NodePat(&'a hir::Pat),
  38 }
  39
  40 pub trait PpAnn {
  41     fn pre(&self, _state: &mut State, _node: AnnNode) -> io::Result<()> {
  42         Ok(())
  43     }
  44     fn post(&self, _state: &mut State, _node: AnnNode) -> io::Result<()> {
  45         Ok(())
  46     }
  47 }
  48
  49 #[derive(Copy, Clone)]
  50 pub struct NoAnn;
  51
  52 impl PpAnn for NoAnn {}
  53
  54
  55 pub struct State<'a> {
  56     krate: Option<&'a Crate>,
  57     pub s: pp::Printer<'a>,
  58     cm: Option<&'a CodeMap>,
  59     comments: Option<Vec<comments::Comment>>,
  60     literals: Option<Vec<comments::Literal>>,
  61     cur_cmnt_and_lit: ast_pp::CurrentCommentAndLiteral,
  62     boxes: Vec<pp::Breaks>,
  63     ann: &'a (PpAnn + 'a),
  64 }
  65
  66 impl<'a> PrintState<'a> for State<'a> {
  67     fn writer(&mut self) -> &mut pp::Printer<'a> {
  68         &mut self.s
  69     }
  70
  71     fn boxes(&mut self) -> &mut Vec<pp::Breaks> {
  72         &mut self.boxes
  73     }
  74
  75     fn comments(&mut self) -> &mut Option<Vec<comments::Comment>> {
  76         &mut self.comments
  77     }
  78
  79     fn cur_cmnt_and_lit(&mut self) -> &mut ast_pp::CurrentCommentAndLiteral {
  80         &mut self.cur_cmnt_and_lit
  81     }
  82
  83     fn literals(&self) -> &Option<Vec<comments::Literal>> {
  84         &self.literals
  85     }
  86 }
  87
  88 pub fn rust_printer<'a>(writer: Box<Write + 'a>, krate: Option<&'a Crate>) -> State<'a> {
  89     static NO_ANN: NoAnn = NoAnn;
  90     rust_printer_annotated(writer, &NO_ANN, krate)
  91 }
  92
  93 pub fn rust_printer_annotated<'a>(writer: Box<Write + 'a>,
  94                                   ann: &'a PpAnn,
  95                                   krate: Option<&'a Crate>)
  96                                   -> State<'a> {
  97     State {
  98         krate: krate,
  99         s: pp::mk_printer(writer, default_columns),
 100         cm: None,
 101         comments: None,
 102         literals: None,
 103         cur_cmnt_and_lit: ast_pp::CurrentCommentAndLiteral {
 104             cur_cmnt: 0,
 105             cur_lit: 0,
 106         },
 107         boxes: Vec::new(),
 108         ann: ann,
 109     }
 110 }
 111
 112 #[allow(non_upper_case_globals)]
 113 pub const indent_unit: usize = 4;
 114
 115 #[allow(non_upper_case_globals)]
 116 pub const default_columns: usize = 78;
 117
 118
 119 /// Requires you to pass an input filename and reader so that
 120 /// it can scan the input text for comments and literals to
 121 /// copy forward.
 122 pub fn print_crate<'a>(cm: &'a CodeMap,
 123                        span_diagnostic: &errors::Handler,
 124                        krate: &hir::Crate,
 125                        filename: String,
 126                        input: &mut Read,
 127                        out: Box<Write + 'a>,
 128                        ann: &'a PpAnn,
 129                        is_expanded: bool)
 130                        -> io::Result<()> {
 131     let mut s = State::new_from_input(cm, span_diagnostic, filename, input,
 132                                       out, ann, is_expanded, Some(krate));
 133
 134     // When printing the AST, we sometimes need to inject `#[no_std]` here.
 135     // Since you can't compile the HIR, it's not necessary.
 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: &errors::Handler,
 145                           filename: String,
 146                           input: &mut Read,
 147                           out: Box<Write + 'a>,
 148                           ann: &'a PpAnn,
 149                           is_expanded: bool,
 150                           krate: Option<&'a Crate>)
 151                           -> State<'a> {
 152         let (cmnts, lits) = comments::gather_comments_and_literals(span_diagnostic,
 153                                                                    filename,
 154                                                                    input);
 155
 156         State::new(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 {
 164                        None
 165                    } else {
 166                        Some(lits)
 167                    },
 168                    krate)
 169     }
 170
 171     pub fn new(cm: &'a CodeMap,
 172                out: Box<Write + 'a>,
 173                ann: &'a PpAnn,
 174                comments: Option<Vec<comments::Comment>>,
 175                literals: Option<Vec<comments::Literal>>,
 176                krate: Option<&'a Crate>)
 177                -> State<'a> {
 178         State {
 179             krate: krate,
 180             s: pp::mk_printer(out, default_columns),
 181             cm: Some(cm),
 182             comments: comments.clone(),
 183             literals: literals.clone(),
 184             cur_cmnt_and_lit: ast_pp::CurrentCommentAndLiteral {
 185                 cur_cmnt: 0,
 186                 cur_lit: 0,
 187             },
 188             boxes: Vec::new(),
 189             ann: ann,
 190         }
 191     }
 192 }
 193
 194 pub fn to_string<F>(f: F) -> String
 195     where F: FnOnce(&mut State) -> io::Result<()>
 196 {
 197     let mut wr = Vec::new();
 198     {
 199         let mut printer = rust_printer(Box::new(&mut wr), None);
 200         f(&mut printer).unwrap();
 201         eof(&mut printer.s).unwrap();
 202     }
 203     String::from_utf8(wr).unwrap()
 204 }
 205
 206 pub fn binop_to_string(op: BinOpToken) -> &'static str {
 207     match op {
 208         token::Plus => "+",
 209         token::Minus => "-",
 210         token::Star => "*",
 211         token::Slash => "/",
 212         token::Percent => "%",
 213         token::Caret => "^",
 214         token::And => "&",
 215         token::Or => "|",
 216         token::Shl => "<<",
 217         token::Shr => ">>",
 218     }
 219 }
 220
 221 pub fn ty_to_string(ty: &hir::Ty) -> String {
 222     to_string(|s| s.print_type(ty))
 223 }
 224
 225 pub fn bounds_to_string(bounds: &[hir::TyParamBound]) -> String {
 226     to_string(|s| s.print_bounds("", bounds))
 227 }
 228
 229 pub fn pat_to_string(pat: &hir::Pat) -> String {
 230     to_string(|s| s.print_pat(pat))
 231 }
 232
 233 pub fn arm_to_string(arm: &hir::Arm) -> String {
 234     to_string(|s| s.print_arm(arm))
 235 }
 236
 237 pub fn expr_to_string(e: &hir::Expr) -> String {
 238     to_string(|s| s.print_expr(e))
 239 }
 240
 241 pub fn lifetime_to_string(e: &hir::Lifetime) -> String {
 242     to_string(|s| s.print_lifetime(e))
 243 }
 244
 245 pub fn stmt_to_string(stmt: &hir::Stmt) -> String {
 246     to_string(|s| s.print_stmt(stmt))
 247 }
 248
 249 pub fn item_to_string(i: &hir::Item) -> String {
 250     to_string(|s| s.print_item(i))
 251 }
 252
 253 pub fn impl_item_to_string(i: &hir::ImplItem) -> String {
 254     to_string(|s| s.print_impl_item(i))
 255 }
 256
 257 pub fn trait_item_to_string(i: &hir::TraitItem) -> String {
 258     to_string(|s| s.print_trait_item(i))
 259 }
 260
 261 pub fn generics_to_string(generics: &hir::Generics) -> String {
 262     to_string(|s| s.print_generics(generics))
 263 }
 264
 265 pub fn where_clause_to_string(i: &hir::WhereClause) -> String {
 266     to_string(|s| s.print_where_clause(i))
 267 }
 268
 269 pub fn fn_block_to_string(p: &hir::FnDecl) -> String {
 270     to_string(|s| s.print_fn_block_args(p))
 271 }
 272
 273 pub fn path_to_string(p: &hir::Path) -> String {
 274     to_string(|s| s.print_path(p, false, 0))
 275 }
 276
 277 pub fn name_to_string(name: ast::Name) -> String {
 278     to_string(|s| s.print_name(name))
 279 }
 280
 281 pub fn fun_to_string(decl: &hir::FnDecl,
 282                      unsafety: hir::Unsafety,
 283                      constness: hir::Constness,
 284                      name: ast::Name,
 285                      opt_explicit_self: Option<&hir::ExplicitSelf_>,
 286                      generics: &hir::Generics)
 287                      -> String {
 288     to_string(|s| {
 289         try!(s.head(""));
 290         try!(s.print_fn(decl,
 291                         unsafety,
 292                         constness,
 293                         Abi::Rust,
 294                         Some(name),
 295                         generics,
 296                         opt_explicit_self,
 297                         hir::Inherited));
 298         try!(s.end()); // Close the head box
 299         s.end() // Close the outer box
 300     })
 301 }
 302
 303 pub fn block_to_string(blk: &hir::Block) -> String {
 304     to_string(|s| {
 305         // containing cbox, will be closed by print-block at }
 306         try!(s.cbox(indent_unit));
 307         // head-ibox, will be closed by print-block after {
 308         try!(s.ibox(0));
 309         s.print_block(blk)
 310     })
 311 }
 312
 313 pub fn explicit_self_to_string(explicit_self: &hir::ExplicitSelf_) -> String {
 314     to_string(|s| s.print_explicit_self(explicit_self, hir::MutImmutable).map(|_| {}))
 315 }
 316
 317 pub fn variant_to_string(var: &hir::Variant) -> String {
 318     to_string(|s| s.print_variant(var))
 319 }
 320
 321 pub fn arg_to_string(arg: &hir::Arg) -> String {
 322     to_string(|s| s.print_arg(arg, false))
 323 }
 324
 325 pub fn visibility_qualified(vis: hir::Visibility, s: &str) -> String {
 326     match vis {
 327         hir::Public => format!("pub {}", s),
 328         hir::Inherited => s.to_string(),
 329     }
 330 }
 331
 332 fn needs_parentheses(expr: &hir::Expr) -> bool {
 333     match expr.node {
 334         hir::ExprAssign(..) |
 335         hir::ExprBinary(..) |
 336         hir::ExprClosure(..) |
 337         hir::ExprAssignOp(..) |
 338         hir::ExprCast(..) |
 339         hir::ExprType(..) => true,
 340         _ => false,
 341     }
 342 }
 343
 344 impl<'a> State<'a> {
 345     pub fn cbox(&mut self, u: usize) -> io::Result<()> {
 346         self.boxes.push(pp::Breaks::Consistent);
 347         pp::cbox(&mut self.s, u)
 348     }
 349
 350     pub fn nbsp(&mut self) -> io::Result<()> {
 351         word(&mut self.s, " ")
 352     }
 353
 354     pub fn word_nbsp(&mut self, w: &str) -> io::Result<()> {
 355         try!(word(&mut self.s, w));
 356         self.nbsp()
 357     }
 358
 359     pub fn head(&mut self, w: &str) -> io::Result<()> {
 360         // outer-box is consistent
 361         try!(self.cbox(indent_unit));
 362         // head-box is inconsistent
 363         try!(self.ibox(w.len() + 1));
 364         // keyword that starts the head
 365         if !w.is_empty() {
 366             try!(self.word_nbsp(w));
 367         }
 368         Ok(())
 369     }
 370
 371     pub fn bopen(&mut self) -> io::Result<()> {
 372         try!(word(&mut self.s, "{"));
 373         self.end() // close the head-box
 374     }
 375
 376     pub fn bclose_(&mut self, span: codemap::Span, indented: usize) -> io::Result<()> {
 377         self.bclose_maybe_open(span, indented, true)
 378     }
 379     pub fn bclose_maybe_open(&mut self,
 380                              span: codemap::Span,
 381                              indented: usize,
 382                              close_box: bool)
 383                              -> io::Result<()> {
 384         try!(self.maybe_print_comment(span.hi));
 385         try!(self.break_offset_if_not_bol(1, -(indented as isize)));
 386         try!(word(&mut self.s, "}"));
 387         if close_box {
 388             try!(self.end()); // close the outer-box
 389         }
 390         Ok(())
 391     }
 392     pub fn bclose(&mut self, span: codemap::Span) -> io::Result<()> {
 393         self.bclose_(span, indent_unit)
 394     }
 395
 396     pub fn in_cbox(&self) -> bool {
 397         match self.boxes.last() {
 398             Some(&last_box) => last_box == pp::Breaks::Consistent,
 399             None => false,
 400         }
 401     }
 402     pub fn space_if_not_bol(&mut self) -> io::Result<()> {
 403         if !self.is_bol() {
 404             try!(space(&mut self.s));
 405         }
 406         Ok(())
 407     }
 408     pub fn break_offset_if_not_bol(&mut self, n: usize, off: isize) -> io::Result<()> {
 409         if !self.is_bol() {
 410             break_offset(&mut self.s, n, off)
 411         } else {
 412             if off != 0 && self.s.last_token().is_hardbreak_tok() {
 413                 // We do something pretty sketchy here: tuck the nonzero
 414                 // offset-adjustment we were going to deposit along with the
 415                 // break into the previous hardbreak.
 416                 self.s.replace_last_token(pp::hardbreak_tok_offset(off));
 417             }
 418             Ok(())
 419         }
 420     }
 421
 422     // Synthesizes a comment that was not textually present in the original source
 423     // file.
 424     pub fn synth_comment(&mut self, text: String) -> io::Result<()> {
 425         try!(word(&mut self.s, "/*"));
 426         try!(space(&mut self.s));
 427         try!(word(&mut self.s, &text[..]));
 428         try!(space(&mut self.s));
 429         word(&mut self.s, "*/")
 430     }
 431
 432
 433     pub fn commasep_cmnt<T, F, G>(&mut self,
 434                                   b: Breaks,
 435                                   elts: &[T],
 436                                   mut op: F,
 437                                   mut get_span: G)
 438                                   -> io::Result<()>
 439         where F: FnMut(&mut State, &T) -> io::Result<()>,
 440               G: FnMut(&T) -> codemap::Span
 441     {
 442         try!(self.rbox(0, b));
 443         let len = elts.len();
 444         let mut i = 0;
 445         for elt in elts {
 446             try!(self.maybe_print_comment(get_span(elt).hi));
 447             try!(op(self, elt));
 448             i += 1;
 449             if i < len {
 450                 try!(word(&mut self.s, ","));
 451                 try!(self.maybe_print_trailing_comment(get_span(elt), Some(get_span(&elts[i]).hi)));
 452                 try!(self.space_if_not_bol());
 453             }
 454         }
 455         self.end()
 456     }
 457
 458     pub fn commasep_exprs(&mut self, b: Breaks, exprs: &[P<hir::Expr>]) -> io::Result<()> {
 459         self.commasep_cmnt(b, exprs, |s, e| s.print_expr(&e), |e| e.span)
 460     }
 461
 462     pub fn print_mod(&mut self, _mod: &hir::Mod, attrs: &[ast::Attribute]) -> io::Result<()> {
 463         try!(self.print_inner_attributes(attrs));
 464         for item_id in &_mod.item_ids {
 465             try!(self.print_item_id(item_id));
 466         }
 467         Ok(())
 468     }
 469
 470     pub fn print_foreign_mod(&mut self,
 471                              nmod: &hir::ForeignMod,
 472                              attrs: &[ast::Attribute])
 473                              -> io::Result<()> {
 474         try!(self.print_inner_attributes(attrs));
 475         for item in &nmod.items {
 476             try!(self.print_foreign_item(item));
 477         }
 478         Ok(())
 479     }
 480
 481     pub fn print_opt_lifetime(&mut self, lifetime: &Option<hir::Lifetime>) -> io::Result<()> {
 482         if let Some(l) = *lifetime {
 483             try!(self.print_lifetime(&l));
 484             try!(self.nbsp());
 485         }
 486         Ok(())
 487     }
 488
 489     pub fn print_type(&mut self, ty: &hir::Ty) -> io::Result<()> {
 490         try!(self.maybe_print_comment(ty.span.lo));
 491         try!(self.ibox(0));
 492         match ty.node {
 493             hir::TyVec(ref ty) => {
 494                 try!(word(&mut self.s, "["));
 495                 try!(self.print_type(&ty));
 496                 try!(word(&mut self.s, "]"));
 497             }
 498             hir::TyPtr(ref mt) => {
 499                 try!(word(&mut self.s, "*"));
 500                 match mt.mutbl {
 501                     hir::MutMutable => try!(self.word_nbsp("mut")),
 502                     hir::MutImmutable => try!(self.word_nbsp("const")),
 503                 }
 504                 try!(self.print_type(&mt.ty));
 505             }
 506             hir::TyRptr(ref lifetime, ref mt) => {
 507                 try!(word(&mut self.s, "&"));
 508                 try!(self.print_opt_lifetime(lifetime));
 509                 try!(self.print_mt(mt));
 510             }
 511             hir::TyTup(ref elts) => {
 512                 try!(self.popen());
 513                 try!(self.commasep(Inconsistent, &elts[..], |s, ty| s.print_type(&ty)));
 514                 if elts.len() == 1 {
 515                     try!(word(&mut self.s, ","));
 516                 }
 517                 try!(self.pclose());
 518             }
 519             hir::TyBareFn(ref f) => {
 520                 let generics = hir::Generics {
 521                     lifetimes: f.lifetimes.clone(),
 522                     ty_params: hir::HirVec::new(),
 523                     where_clause: hir::WhereClause {
 524                         id: ast::DUMMY_NODE_ID,
 525                         predicates: hir::HirVec::new(),
 526                     },
 527                 };
 528                 try!(self.print_ty_fn(f.abi, f.unsafety, &f.decl, None, &generics, None));
 529             }
 530             hir::TyPath(None, ref path) => {
 531                 try!(self.print_path(path, false, 0));
 532             }
 533             hir::TyPath(Some(ref qself), ref path) => {
 534                 try!(self.print_qpath(path, qself, false))
 535             }
 536             hir::TyObjectSum(ref ty, ref bounds) => {
 537                 try!(self.print_type(&ty));
 538                 try!(self.print_bounds("+", &bounds[..]));
 539             }
 540             hir::TyPolyTraitRef(ref bounds) => {
 541                 try!(self.print_bounds("", &bounds[..]));
 542             }
 543             hir::TyFixedLengthVec(ref ty, ref v) => {
 544                 try!(word(&mut self.s, "["));
 545                 try!(self.print_type(&ty));
 546                 try!(word(&mut self.s, "; "));
 547                 try!(self.print_expr(&v));
 548                 try!(word(&mut self.s, "]"));
 549             }
 550             hir::TyTypeof(ref e) => {
 551                 try!(word(&mut self.s, "typeof("));
 552                 try!(self.print_expr(&e));
 553                 try!(word(&mut self.s, ")"));
 554             }
 555             hir::TyInfer => {
 556                 try!(word(&mut self.s, "_"));
 557             }
 558         }
 559         self.end()
 560     }
 561
 562     pub fn print_foreign_item(&mut self, item: &hir::ForeignItem) -> io::Result<()> {
 563         try!(self.hardbreak_if_not_bol());
 564         try!(self.maybe_print_comment(item.span.lo));
 565         try!(self.print_outer_attributes(&item.attrs));
 566         match item.node {
 567             hir::ForeignItemFn(ref decl, ref generics) => {
 568                 try!(self.head(""));
 569                 try!(self.print_fn(decl,
 570                                    hir::Unsafety::Normal,
 571                                    hir::Constness::NotConst,
 572                                    Abi::Rust,
 573                                    Some(item.name),
 574                                    generics,
 575                                    None,
 576                                    item.vis));
 577                 try!(self.end()); // end head-ibox
 578                 try!(word(&mut self.s, ";"));
 579                 self.end() // end the outer fn box
 580             }
 581             hir::ForeignItemStatic(ref t, m) => {
 582                 try!(self.head(&visibility_qualified(item.vis, "static")));
 583                 if m {
 584                     try!(self.word_space("mut"));
 585                 }
 586                 try!(self.print_name(item.name));
 587                 try!(self.word_space(":"));
 588                 try!(self.print_type(&t));
 589                 try!(word(&mut self.s, ";"));
 590                 try!(self.end()); // end the head-ibox
 591                 self.end() // end the outer cbox
 592             }
 593         }
 594     }
 595
 596     fn print_associated_const(&mut self,
 597                               name: ast::Name,
 598                               ty: &hir::Ty,
 599                               default: Option<&hir::Expr>,
 600                               vis: hir::Visibility)
 601                               -> io::Result<()> {
 602         try!(word(&mut self.s, &visibility_qualified(vis, "")));
 603         try!(self.word_space("const"));
 604         try!(self.print_name(name));
 605         try!(self.word_space(":"));
 606         try!(self.print_type(ty));
 607         if let Some(expr) = default {
 608             try!(space(&mut self.s));
 609             try!(self.word_space("="));
 610             try!(self.print_expr(expr));
 611         }
 612         word(&mut self.s, ";")
 613     }
 614
 615     fn print_associated_type(&mut self,
 616                              name: ast::Name,
 617                              bounds: Option<&hir::TyParamBounds>,
 618                              ty: Option<&hir::Ty>)
 619                              -> io::Result<()> {
 620         try!(self.word_space("type"));
 621         try!(self.print_name(name));
 622         if let Some(bounds) = bounds {
 623             try!(self.print_bounds(":", bounds));
 624         }
 625         if let Some(ty) = ty {
 626             try!(space(&mut self.s));
 627             try!(self.word_space("="));
 628             try!(self.print_type(ty));
 629         }
 630         word(&mut self.s, ";")
 631     }
 632
 633     pub fn print_item_id(&mut self, item_id: &hir::ItemId) -> io::Result<()> {
 634         if let Some(krate) = self.krate {
 635             // skip nested items if krate context was not provided
 636             let item = &krate.items[&item_id.id];
 637             self.print_item(item)
 638         } else {
 639             Ok(())
 640         }
 641     }
 642
 643     /// Pretty-print an item
 644     pub fn print_item(&mut self, item: &hir::Item) -> io::Result<()> {
 645         try!(self.hardbreak_if_not_bol());
 646         try!(self.maybe_print_comment(item.span.lo));
 647         try!(self.print_outer_attributes(&item.attrs));
 648         try!(self.ann.pre(self, NodeItem(item)));
 649         match item.node {
 650             hir::ItemExternCrate(ref optional_path) => {
 651                 try!(self.head(&visibility_qualified(item.vis, "extern crate")));
 652                 if let Some(p) = *optional_path {
 653                     let val = p.as_str();
 654                     if val.contains("-") {
 655                         try!(self.print_string(&val, ast::StrStyle::Cooked));
 656                     } else {
 657                         try!(self.print_name(p));
 658                     }
 659                     try!(space(&mut self.s));
 660                     try!(word(&mut self.s, "as"));
 661                     try!(space(&mut self.s));
 662                 }
 663                 try!(self.print_name(item.name));
 664                 try!(word(&mut self.s, ";"));
 665                 try!(self.end()); // end inner head-block
 666                 try!(self.end()); // end outer head-block
 667             }
 668             hir::ItemUse(ref vp) => {
 669                 try!(self.head(&visibility_qualified(item.vis, "use")));
 670                 try!(self.print_view_path(&vp));
 671                 try!(word(&mut self.s, ";"));
 672                 try!(self.end()); // end inner head-block
 673                 try!(self.end()); // end outer head-block
 674             }
 675             hir::ItemStatic(ref ty, m, ref expr) => {
 676                 try!(self.head(&visibility_qualified(item.vis, "static")));
 677                 if m == hir::MutMutable {
 678                     try!(self.word_space("mut"));
 679                 }
 680                 try!(self.print_name(item.name));
 681                 try!(self.word_space(":"));
 682                 try!(self.print_type(&ty));
 683                 try!(space(&mut self.s));
 684                 try!(self.end()); // end the head-ibox
 685
 686                 try!(self.word_space("="));
 687                 try!(self.print_expr(&expr));
 688                 try!(word(&mut self.s, ";"));
 689                 try!(self.end()); // end the outer cbox
 690             }
 691             hir::ItemConst(ref ty, ref expr) => {
 692                 try!(self.head(&visibility_qualified(item.vis, "const")));
 693                 try!(self.print_name(item.name));
 694                 try!(self.word_space(":"));
 695                 try!(self.print_type(&ty));
 696                 try!(space(&mut self.s));
 697                 try!(self.end()); // end the head-ibox
 698
 699                 try!(self.word_space("="));
 700                 try!(self.print_expr(&expr));
 701                 try!(word(&mut self.s, ";"));
 702                 try!(self.end()); // end the outer cbox
 703             }
 704             hir::ItemFn(ref decl, unsafety, constness, abi, ref typarams, ref body) => {
 705                 try!(self.head(""));
 706                 try!(self.print_fn(decl,
 707                                    unsafety,
 708                                    constness,
 709                                    abi,
 710                                    Some(item.name),
 711                                    typarams,
 712                                    None,
 713                                    item.vis));
 714                 try!(word(&mut self.s, " "));
 715                 try!(self.print_block_with_attrs(&body, &item.attrs));
 716             }
 717             hir::ItemMod(ref _mod) => {
 718                 try!(self.head(&visibility_qualified(item.vis, "mod")));
 719                 try!(self.print_name(item.name));
 720                 try!(self.nbsp());
 721                 try!(self.bopen());
 722                 try!(self.print_mod(_mod, &item.attrs));
 723                 try!(self.bclose(item.span));
 724             }
 725             hir::ItemForeignMod(ref nmod) => {
 726                 try!(self.head("extern"));
 727                 try!(self.word_nbsp(&nmod.abi.to_string()));
 728                 try!(self.bopen());
 729                 try!(self.print_foreign_mod(nmod, &item.attrs));
 730                 try!(self.bclose(item.span));
 731             }
 732             hir::ItemTy(ref ty, ref params) => {
 733                 try!(self.ibox(indent_unit));
 734                 try!(self.ibox(0));
 735                 try!(self.word_nbsp(&visibility_qualified(item.vis, "type")));
 736                 try!(self.print_name(item.name));
 737                 try!(self.print_generics(params));
 738                 try!(self.end()); // end the inner ibox
 739
 740                 try!(self.print_where_clause(&params.where_clause));
 741                 try!(space(&mut self.s));
 742                 try!(self.word_space("="));
 743                 try!(self.print_type(&ty));
 744                 try!(word(&mut self.s, ";"));
 745                 try!(self.end()); // end the outer ibox
 746             }
 747             hir::ItemEnum(ref enum_definition, ref params) => {
 748                 try!(self.print_enum_def(enum_definition, params, item.name, item.span, item.vis));
 749             }
 750             hir::ItemStruct(ref struct_def, ref generics) => {
 751                 try!(self.head(&visibility_qualified(item.vis, "struct")));
 752                 try!(self.print_struct(struct_def, generics, item.name, item.span, true));
 753             }
 754
 755             hir::ItemDefaultImpl(unsafety, ref trait_ref) => {
 756                 try!(self.head(""));
 757                 try!(self.print_visibility(item.vis));
 758                 try!(self.print_unsafety(unsafety));
 759                 try!(self.word_nbsp("impl"));
 760                 try!(self.print_trait_ref(trait_ref));
 761                 try!(space(&mut self.s));
 762                 try!(self.word_space("for"));
 763                 try!(self.word_space(".."));
 764                 try!(self.bopen());
 765                 try!(self.bclose(item.span));
 766             }
 767             hir::ItemImpl(unsafety,
 768                           polarity,
 769                           ref generics,
 770                           ref opt_trait,
 771                           ref ty,
 772                           ref impl_items) => {
 773                 try!(self.head(""));
 774                 try!(self.print_visibility(item.vis));
 775                 try!(self.print_unsafety(unsafety));
 776                 try!(self.word_nbsp("impl"));
 777
 778                 if generics.is_parameterized() {
 779                     try!(self.print_generics(generics));
 780                     try!(space(&mut self.s));
 781                 }
 782
 783                 match polarity {
 784                     hir::ImplPolarity::Negative => {
 785                         try!(word(&mut self.s, "!"));
 786                     }
 787                     _ => {}
 788                 }
 789
 790                 match opt_trait {
 791                     &Some(ref t) => {
 792                         try!(self.print_trait_ref(t));
 793                         try!(space(&mut self.s));
 794                         try!(self.word_space("for"));
 795                     }
 796                     &None => {}
 797                 }
 798
 799                 try!(self.print_type(&ty));
 800                 try!(self.print_where_clause(&generics.where_clause));
 801
 802                 try!(space(&mut self.s));
 803                 try!(self.bopen());
 804                 try!(self.print_inner_attributes(&item.attrs));
 805                 for impl_item in impl_items {
 806                     try!(self.print_impl_item(impl_item));
 807                 }
 808                 try!(self.bclose(item.span));
 809             }
 810             hir::ItemTrait(unsafety, ref generics, ref bounds, ref trait_items) => {
 811                 try!(self.head(""));
 812                 try!(self.print_visibility(item.vis));
 813                 try!(self.print_unsafety(unsafety));
 814                 try!(self.word_nbsp("trait"));
 815                 try!(self.print_name(item.name));
 816                 try!(self.print_generics(generics));
 817                 let mut real_bounds = Vec::with_capacity(bounds.len());
 818                 for b in bounds.iter() {
 819                     if let TraitTyParamBound(ref ptr, hir::TraitBoundModifier::Maybe) = *b {
 820                         try!(space(&mut self.s));
 821                         try!(self.word_space("for ?"));
 822                         try!(self.print_trait_ref(&ptr.trait_ref));
 823                     } else {
 824                         real_bounds.push(b.clone());
 825                     }
 826                 }
 827                 try!(self.print_bounds(":", &real_bounds[..]));
 828                 try!(self.print_where_clause(&generics.where_clause));
 829                 try!(word(&mut self.s, " "));
 830                 try!(self.bopen());
 831                 for trait_item in trait_items {
 832                     try!(self.print_trait_item(trait_item));
 833                 }
 834                 try!(self.bclose(item.span));
 835             }
 836         }
 837         self.ann.post(self, NodeItem(item))
 838     }
 839
 840     fn print_trait_ref(&mut self, t: &hir::TraitRef) -> io::Result<()> {
 841         self.print_path(&t.path, false, 0)
 842     }
 843
 844     fn print_formal_lifetime_list(&mut self, lifetimes: &[hir::LifetimeDef]) -> io::Result<()> {
 845         if !lifetimes.is_empty() {
 846             try!(word(&mut self.s, "for<"));
 847             let mut comma = false;
 848             for lifetime_def in lifetimes {
 849                 if comma {
 850                     try!(self.word_space(","))
 851                 }
 852                 try!(self.print_lifetime_def(lifetime_def));
 853                 comma = true;
 854             }
 855             try!(word(&mut self.s, ">"));
 856         }
 857         Ok(())
 858     }
 859
 860     fn print_poly_trait_ref(&mut self, t: &hir::PolyTraitRef) -> io::Result<()> {
 861         try!(self.print_formal_lifetime_list(&t.bound_lifetimes));
 862         self.print_trait_ref(&t.trait_ref)
 863     }
 864
 865     pub fn print_enum_def(&mut self,
 866                           enum_definition: &hir::EnumDef,
 867                           generics: &hir::Generics,
 868                           name: ast::Name,
 869                           span: codemap::Span,
 870                           visibility: hir::Visibility)
 871                           -> io::Result<()> {
 872         try!(self.head(&visibility_qualified(visibility, "enum")));
 873         try!(self.print_name(name));
 874         try!(self.print_generics(generics));
 875         try!(self.print_where_clause(&generics.where_clause));
 876         try!(space(&mut self.s));
 877         self.print_variants(&enum_definition.variants, span)
 878     }
 879
 880     pub fn print_variants(&mut self,
 881                           variants: &[hir::Variant],
 882                           span: codemap::Span)
 883                           -> io::Result<()> {
 884         try!(self.bopen());
 885         for v in variants {
 886             try!(self.space_if_not_bol());
 887             try!(self.maybe_print_comment(v.span.lo));
 888             try!(self.print_outer_attributes(&v.node.attrs));
 889             try!(self.ibox(indent_unit));
 890             try!(self.print_variant(v));
 891             try!(word(&mut self.s, ","));
 892             try!(self.end());
 893             try!(self.maybe_print_trailing_comment(v.span, None));
 894         }
 895         self.bclose(span)
 896     }
 897
 898     pub fn print_visibility(&mut self, vis: hir::Visibility) -> io::Result<()> {
 899         match vis {
 900             hir::Public => self.word_nbsp("pub"),
 901             hir::Inherited => Ok(()),
 902         }
 903     }
 904
 905     pub fn print_struct(&mut self,
 906                         struct_def: &hir::VariantData,
 907                         generics: &hir::Generics,
 908                         name: ast::Name,
 909                         span: codemap::Span,
 910                         print_finalizer: bool)
 911                         -> io::Result<()> {
 912         try!(self.print_name(name));
 913         try!(self.print_generics(generics));
 914         if !struct_def.is_struct() {
 915             if struct_def.is_tuple() {
 916                 try!(self.popen());
 917                 try!(self.commasep(Inconsistent, struct_def.fields(), |s, field| {
 918                     try!(s.print_visibility(field.vis));
 919                     try!(s.maybe_print_comment(field.span.lo));
 920                     s.print_type(&field.ty)
 921                 }));
 922                 try!(self.pclose());
 923             }
 924             try!(self.print_where_clause(&generics.where_clause));
 925             if print_finalizer {
 926                 try!(word(&mut self.s, ";"));
 927             }
 928             try!(self.end());
 929             self.end() // close the outer-box
 930         } else {
 931             try!(self.print_where_clause(&generics.where_clause));
 932             try!(self.nbsp());
 933             try!(self.bopen());
 934             try!(self.hardbreak_if_not_bol());
 935
 936             for field in struct_def.fields() {
 937                 try!(self.hardbreak_if_not_bol());
 938                 try!(self.maybe_print_comment(field.span.lo));
 939                 try!(self.print_outer_attributes(&field.attrs));
 940                 try!(self.print_visibility(field.vis));
 941                 try!(self.print_name(field.name));
 942                 try!(self.word_nbsp(":"));
 943                 try!(self.print_type(&field.ty));
 944                 try!(word(&mut self.s, ","));
 945             }
 946
 947             self.bclose(span)
 948         }
 949     }
 950
 951     pub fn print_variant(&mut self, v: &hir::Variant) -> io::Result<()> {
 952         try!(self.head(""));
 953         let generics = ::util::empty_generics();
 954         try!(self.print_struct(&v.node.data, &generics, v.node.name, v.span, false));
 955         match v.node.disr_expr {
 956             Some(ref d) => {
 957                 try!(space(&mut self.s));
 958                 try!(self.word_space("="));
 959                 self.print_expr(&d)
 960             }
 961             _ => Ok(()),
 962         }
 963     }
 964     pub fn print_method_sig(&mut self,
 965                             name: ast::Name,
 966                             m: &hir::MethodSig,
 967                             vis: hir::Visibility)
 968                             -> io::Result<()> {
 969         self.print_fn(&m.decl,
 970                       m.unsafety,
 971                       m.constness,
 972                       m.abi,
 973                       Some(name),
 974                       &m.generics,
 975                       Some(&m.explicit_self.node),
 976                       vis)
 977     }
 978
 979     pub fn print_trait_item(&mut self, ti: &hir::TraitItem) -> io::Result<()> {
 980         try!(self.ann.pre(self, NodeSubItem(ti.id)));
 981         try!(self.hardbreak_if_not_bol());
 982         try!(self.maybe_print_comment(ti.span.lo));
 983         try!(self.print_outer_attributes(&ti.attrs));
 984         match ti.node {
 985             hir::ConstTraitItem(ref ty, ref default) => {
 986                 try!(self.print_associated_const(ti.name,
 987                                                  &ty,
 988                                                  default.as_ref().map(|expr| &**expr),
 989                                                  hir::Inherited));
 990             }
 991             hir::MethodTraitItem(ref sig, ref body) => {
 992                 if body.is_some() {
 993                     try!(self.head(""));
 994                 }
 995                 try!(self.print_method_sig(ti.name, sig, hir::Inherited));
 996                 if let Some(ref body) = *body {
 997                     try!(self.nbsp());
 998                     try!(self.print_block_with_attrs(body, &ti.attrs));
 999                 } else {
1000                     try!(word(&mut self.s, ";"));
1001                 }
1002             }
1003             hir::TypeTraitItem(ref bounds, ref default) => {
1004                 try!(self.print_associated_type(ti.name,
1005                                                 Some(bounds),
1006                                                 default.as_ref().map(|ty| &**ty)));
1007             }
1008         }
1009         self.ann.post(self, NodeSubItem(ti.id))
1010     }
1011
1012     pub fn print_impl_item(&mut self, ii: &hir::ImplItem) -> io::Result<()> {
1013         try!(self.ann.pre(self, NodeSubItem(ii.id)));
1014         try!(self.hardbreak_if_not_bol());
1015         try!(self.maybe_print_comment(ii.span.lo));
1016         try!(self.print_outer_attributes(&ii.attrs));
1017         match ii.node {
1018             hir::ImplItemKind::Const(ref ty, ref expr) => {
1019                 try!(self.print_associated_const(ii.name, &ty, Some(&expr), ii.vis));
1020             }
1021             hir::ImplItemKind::Method(ref sig, ref body) => {
1022                 try!(self.head(""));
1023                 try!(self.print_method_sig(ii.name, sig, ii.vis));
1024                 try!(self.nbsp());
1025                 try!(self.print_block_with_attrs(body, &ii.attrs));
1026             }
1027             hir::ImplItemKind::Type(ref ty) => {
1028                 try!(self.print_associated_type(ii.name, None, Some(ty)));
1029             }
1030         }
1031         self.ann.post(self, NodeSubItem(ii.id))
1032     }
1033
1034     pub fn print_stmt(&mut self, st: &hir::Stmt) -> io::Result<()> {
1035         try!(self.maybe_print_comment(st.span.lo));
1036         match st.node {
1037             hir::StmtDecl(ref decl, _) => {
1038                 try!(self.print_decl(&decl));
1039             }
1040             hir::StmtExpr(ref expr, _) => {
1041                 try!(self.space_if_not_bol());
1042                 try!(self.print_expr(&expr));
1043             }
1044             hir::StmtSemi(ref expr, _) => {
1045                 try!(self.space_if_not_bol());
1046                 try!(self.print_expr(&expr));
1047                 try!(word(&mut self.s, ";"));
1048             }
1049         }
1050         if stmt_ends_with_semi(&st.node) {
1051             try!(word(&mut self.s, ";"));
1052         }
1053         self.maybe_print_trailing_comment(st.span, None)
1054     }
1055
1056     pub fn print_block(&mut self, blk: &hir::Block) -> io::Result<()> {
1057         self.print_block_with_attrs(blk, &[])
1058     }
1059
1060     pub fn print_block_unclosed(&mut self, blk: &hir::Block) -> io::Result<()> {
1061         self.print_block_unclosed_indent(blk, indent_unit)
1062     }
1063
1064     pub fn print_block_unclosed_indent(&mut self,
1065                                        blk: &hir::Block,
1066                                        indented: usize)
1067                                        -> io::Result<()> {
1068         self.print_block_maybe_unclosed(blk, indented, &[], false)
1069     }
1070
1071     pub fn print_block_with_attrs(&mut self,
1072                                   blk: &hir::Block,
1073                                   attrs: &[ast::Attribute])
1074                                   -> io::Result<()> {
1075         self.print_block_maybe_unclosed(blk, indent_unit, attrs, true)
1076     }
1077
1078     pub fn print_block_maybe_unclosed(&mut self,
1079                                       blk: &hir::Block,
1080                                       indented: usize,
1081                                       attrs: &[ast::Attribute],
1082                                       close_box: bool)
1083                                       -> io::Result<()> {
1084         match blk.rules {
1085             hir::UnsafeBlock(..) => try!(self.word_space("unsafe")),
1086             hir::PushUnsafeBlock(..) => try!(self.word_space("push_unsafe")),
1087             hir::PopUnsafeBlock(..) => try!(self.word_space("pop_unsafe")),
1088             hir::PushUnstableBlock => try!(self.word_space("push_unstable")),
1089             hir::PopUnstableBlock => try!(self.word_space("pop_unstable")),
1090             hir::DefaultBlock => (),
1091         }
1092         try!(self.maybe_print_comment(blk.span.lo));
1093         try!(self.ann.pre(self, NodeBlock(blk)));
1094         try!(self.bopen());
1095
1096         try!(self.print_inner_attributes(attrs));
1097
1098         for st in &blk.stmts {
1099             try!(self.print_stmt(st));
1100         }
1101         match blk.expr {
1102             Some(ref expr) => {
1103                 try!(self.space_if_not_bol());
1104                 try!(self.print_expr(&expr));
1105                 try!(self.maybe_print_trailing_comment(expr.span, Some(blk.span.hi)));
1106             }
1107             _ => (),
1108         }
1109         try!(self.bclose_maybe_open(blk.span, indented, close_box));
1110         self.ann.post(self, NodeBlock(blk))
1111     }
1112
1113     fn print_else(&mut self, els: Option<&hir::Expr>) -> io::Result<()> {
1114         match els {
1115             Some(_else) => {
1116                 match _else.node {
1117                     // "another else-if"
1118                     hir::ExprIf(ref i, ref then, ref e) => {
1119                         try!(self.cbox(indent_unit - 1));
1120                         try!(self.ibox(0));
1121                         try!(word(&mut self.s, " else if "));
1122                         try!(self.print_expr(&i));
1123                         try!(space(&mut self.s));
1124                         try!(self.print_block(&then));
1125                         self.print_else(e.as_ref().map(|e| &**e))
1126                     }
1127                     // "final else"
1128                     hir::ExprBlock(ref b) => {
1129                         try!(self.cbox(indent_unit - 1));
1130                         try!(self.ibox(0));
1131                         try!(word(&mut self.s, " else "));
1132                         self.print_block(&b)
1133                     }
1134                     // BLEAH, constraints would be great here
1135                     _ => {
1136                         panic!("print_if saw if with weird alternative");
1137                     }
1138                 }
1139             }
1140             _ => Ok(()),
1141         }
1142     }
1143
1144     pub fn print_if(&mut self,
1145                     test: &hir::Expr,
1146                     blk: &hir::Block,
1147                     elseopt: Option<&hir::Expr>)
1148                     -> io::Result<()> {
1149         try!(self.head("if"));
1150         try!(self.print_expr(test));
1151         try!(space(&mut self.s));
1152         try!(self.print_block(blk));
1153         self.print_else(elseopt)
1154     }
1155
1156     pub fn print_if_let(&mut self,
1157                         pat: &hir::Pat,
1158                         expr: &hir::Expr,
1159                         blk: &hir::Block,
1160                         elseopt: Option<&hir::Expr>)
1161                         -> io::Result<()> {
1162         try!(self.head("if let"));
1163         try!(self.print_pat(pat));
1164         try!(space(&mut self.s));
1165         try!(self.word_space("="));
1166         try!(self.print_expr(expr));
1167         try!(space(&mut self.s));
1168         try!(self.print_block(blk));
1169         self.print_else(elseopt)
1170     }
1171
1172
1173     fn print_call_post(&mut self, args: &[P<hir::Expr>]) -> io::Result<()> {
1174         try!(self.popen());
1175         try!(self.commasep_exprs(Inconsistent, args));
1176         self.pclose()
1177     }
1178
1179     pub fn print_expr_maybe_paren(&mut self, expr: &hir::Expr) -> io::Result<()> {
1180         let needs_par = needs_parentheses(expr);
1181         if needs_par {
1182             try!(self.popen());
1183         }
1184         try!(self.print_expr(expr));
1185         if needs_par {
1186             try!(self.pclose());
1187         }
1188         Ok(())
1189     }
1190
1191     fn print_expr_vec(&mut self, exprs: &[P<hir::Expr>]) -> io::Result<()> {
1192         try!(self.ibox(indent_unit));
1193         try!(word(&mut self.s, "["));
1194         try!(self.commasep_exprs(Inconsistent, &exprs[..]));
1195         try!(word(&mut self.s, "]"));
1196         self.end()
1197     }
1198
1199     fn print_expr_repeat(&mut self, element: &hir::Expr, count: &hir::Expr) -> io::Result<()> {
1200         try!(self.ibox(indent_unit));
1201         try!(word(&mut self.s, "["));
1202         try!(self.print_expr(element));
1203         try!(self.word_space(";"));
1204         try!(self.print_expr(count));
1205         try!(word(&mut self.s, "]"));
1206         self.end()
1207     }
1208
1209     fn print_expr_struct(&mut self,
1210                          path: &hir::Path,
1211                          fields: &[hir::Field],
1212                          wth: &Option<P<hir::Expr>>)
1213                          -> io::Result<()> {
1214         try!(self.print_path(path, true, 0));
1215         try!(word(&mut self.s, "{"));
1216         try!(self.commasep_cmnt(Consistent,
1217                                 &fields[..],
1218                                 |s, field| {
1219                                     try!(s.ibox(indent_unit));
1220                                     try!(s.print_name(field.name.node));
1221                                     try!(s.word_space(":"));
1222                                     try!(s.print_expr(&field.expr));
1223                                     s.end()
1224                                 },
1225                                 |f| f.span));
1226         match *wth {
1227             Some(ref expr) => {
1228                 try!(self.ibox(indent_unit));
1229                 if !fields.is_empty() {
1230                     try!(word(&mut self.s, ","));
1231                     try!(space(&mut self.s));
1232                 }
1233                 try!(word(&mut self.s, ".."));
1234                 try!(self.print_expr(&expr));
1235                 try!(self.end());
1236             }
1237             _ => if !fields.is_empty() {
1238                 try!(word(&mut self.s, ","))
1239             },
1240         }
1241         try!(word(&mut self.s, "}"));
1242         Ok(())
1243     }
1244
1245     fn print_expr_tup(&mut self, exprs: &[P<hir::Expr>]) -> io::Result<()> {
1246         try!(self.popen());
1247         try!(self.commasep_exprs(Inconsistent, &exprs[..]));
1248         if exprs.len() == 1 {
1249             try!(word(&mut self.s, ","));
1250         }
1251         self.pclose()
1252     }
1253
1254     fn print_expr_call(&mut self, func: &hir::Expr, args: &[P<hir::Expr>]) -> io::Result<()> {
1255         try!(self.print_expr_maybe_paren(func));
1256         self.print_call_post(args)
1257     }
1258
1259     fn print_expr_method_call(&mut self,
1260                               name: Spanned<ast::Name>,
1261                               tys: &[P<hir::Ty>],
1262                               args: &[P<hir::Expr>])
1263                               -> io::Result<()> {
1264         let base_args = &args[1..];
1265         try!(self.print_expr(&args[0]));
1266         try!(word(&mut self.s, "."));
1267         try!(self.print_name(name.node));
1268         if !tys.is_empty() {
1269             try!(word(&mut self.s, "::<"));
1270             try!(self.commasep(Inconsistent, tys, |s, ty| s.print_type(&ty)));
1271             try!(word(&mut self.s, ">"));
1272         }
1273         self.print_call_post(base_args)
1274     }
1275
1276     fn print_expr_binary(&mut self,
1277                          op: hir::BinOp,
1278                          lhs: &hir::Expr,
1279                          rhs: &hir::Expr)
1280                          -> io::Result<()> {
1281         try!(self.print_expr(lhs));
1282         try!(space(&mut self.s));
1283         try!(self.word_space(::util::binop_to_string(op.node)));
1284         self.print_expr(rhs)
1285     }
1286
1287     fn print_expr_unary(&mut self, op: hir::UnOp, expr: &hir::Expr) -> io::Result<()> {
1288         try!(word(&mut self.s, ::util::unop_to_string(op)));
1289         self.print_expr_maybe_paren(expr)
1290     }
1291
1292     fn print_expr_addr_of(&mut self,
1293                           mutability: hir::Mutability,
1294                           expr: &hir::Expr)
1295                           -> io::Result<()> {
1296         try!(word(&mut self.s, "&"));
1297         try!(self.print_mutability(mutability));
1298         self.print_expr_maybe_paren(expr)
1299     }
1300
1301     pub fn print_expr(&mut self, expr: &hir::Expr) -> io::Result<()> {
1302         try!(self.maybe_print_comment(expr.span.lo));
1303         try!(self.ibox(indent_unit));
1304         try!(self.ann.pre(self, NodeExpr(expr)));
1305         match expr.node {
1306             hir::ExprBox(ref expr) => {
1307                 try!(self.word_space("box"));
1308                 try!(self.print_expr(expr));
1309             }
1310             hir::ExprVec(ref exprs) => {
1311                 try!(self.print_expr_vec(&exprs[..]));
1312             }
1313             hir::ExprRepeat(ref element, ref count) => {
1314                 try!(self.print_expr_repeat(&element, &count));
1315             }
1316             hir::ExprStruct(ref path, ref fields, ref wth) => {
1317                 try!(self.print_expr_struct(path, &fields[..], wth));
1318             }
1319             hir::ExprTup(ref exprs) => {
1320                 try!(self.print_expr_tup(&exprs[..]));
1321             }
1322             hir::ExprCall(ref func, ref args) => {
1323                 try!(self.print_expr_call(&func, &args[..]));
1324             }
1325             hir::ExprMethodCall(name, ref tys, ref args) => {
1326                 try!(self.print_expr_method_call(name, &tys[..], &args[..]));
1327             }
1328             hir::ExprBinary(op, ref lhs, ref rhs) => {
1329                 try!(self.print_expr_binary(op, &lhs, &rhs));
1330             }
1331             hir::ExprUnary(op, ref expr) => {
1332                 try!(self.print_expr_unary(op, &expr));
1333             }
1334             hir::ExprAddrOf(m, ref expr) => {
1335                 try!(self.print_expr_addr_of(m, &expr));
1336             }
1337             hir::ExprLit(ref lit) => {
1338                 try!(self.print_literal(&lit));
1339             }
1340             hir::ExprCast(ref expr, ref ty) => {
1341                 try!(self.print_expr(&expr));
1342                 try!(space(&mut self.s));
1343                 try!(self.word_space("as"));
1344                 try!(self.print_type(&ty));
1345             }
1346             hir::ExprType(ref expr, ref ty) => {
1347                 try!(self.print_expr(&expr));
1348                 try!(self.word_space(":"));
1349                 try!(self.print_type(&ty));
1350             }
1351             hir::ExprIf(ref test, ref blk, ref elseopt) => {
1352                 try!(self.print_if(&test, &blk, elseopt.as_ref().map(|e| &**e)));
1353             }
1354             hir::ExprWhile(ref test, ref blk, opt_ident) => {
1355                 if let Some(ident) = opt_ident {
1356                     try!(self.print_name(ident.name));
1357                     try!(self.word_space(":"));
1358                 }
1359                 try!(self.head("while"));
1360                 try!(self.print_expr(&test));
1361                 try!(space(&mut self.s));
1362                 try!(self.print_block(&blk));
1363             }
1364             hir::ExprLoop(ref blk, opt_ident) => {
1365                 if let Some(ident) = opt_ident {
1366                     try!(self.print_name(ident.name));
1367                     try!(self.word_space(":"));
1368                 }
1369                 try!(self.head("loop"));
1370                 try!(space(&mut self.s));
1371                 try!(self.print_block(&blk));
1372             }
1373             hir::ExprMatch(ref expr, ref arms, _) => {
1374                 try!(self.cbox(indent_unit));
1375                 try!(self.ibox(4));
1376                 try!(self.word_nbsp("match"));
1377                 try!(self.print_expr(&expr));
1378                 try!(space(&mut self.s));
1379                 try!(self.bopen());
1380                 for arm in arms {
1381                     try!(self.print_arm(arm));
1382                 }
1383                 try!(self.bclose_(expr.span, indent_unit));
1384             }
1385             hir::ExprClosure(capture_clause, ref decl, ref body) => {
1386                 try!(self.print_capture_clause(capture_clause));
1387
1388                 try!(self.print_fn_block_args(&decl));
1389                 try!(space(&mut self.s));
1390
1391                 let default_return = match decl.output {
1392                     hir::DefaultReturn(..) => true,
1393                     _ => false,
1394                 };
1395
1396                 if !default_return || !body.stmts.is_empty() || body.expr.is_none() {
1397                     try!(self.print_block_unclosed(&body));
1398                 } else {
1399                     // we extract the block, so as not to create another set of boxes
1400                     match body.expr.as_ref().unwrap().node {
1401                         hir::ExprBlock(ref blk) => {
1402                             try!(self.print_block_unclosed(&blk));
1403                         }
1404                         _ => {
1405                             // this is a bare expression
1406                             try!(self.print_expr(body.expr.as_ref().map(|e| &**e).unwrap()));
1407                             try!(self.end()); // need to close a box
1408                         }
1409                     }
1410                 }
1411                 // a box will be closed by print_expr, but we didn't want an overall
1412                 // wrapper so we closed the corresponding opening. so create an
1413                 // empty box to satisfy the close.
1414                 try!(self.ibox(0));
1415             }
1416             hir::ExprBlock(ref blk) => {
1417                 // containing cbox, will be closed by print-block at }
1418                 try!(self.cbox(indent_unit));
1419                 // head-box, will be closed by print-block after {
1420                 try!(self.ibox(0));
1421                 try!(self.print_block(&blk));
1422             }
1423             hir::ExprAssign(ref lhs, ref rhs) => {
1424                 try!(self.print_expr(&lhs));
1425                 try!(space(&mut self.s));
1426                 try!(self.word_space("="));
1427                 try!(self.print_expr(&rhs));
1428             }
1429             hir::ExprAssignOp(op, ref lhs, ref rhs) => {
1430                 try!(self.print_expr(&lhs));
1431                 try!(space(&mut self.s));
1432                 try!(word(&mut self.s, ::util::binop_to_string(op.node)));
1433                 try!(self.word_space("="));
1434                 try!(self.print_expr(&rhs));
1435             }
1436             hir::ExprField(ref expr, name) => {
1437                 try!(self.print_expr(&expr));
1438                 try!(word(&mut self.s, "."));
1439                 try!(self.print_name(name.node));
1440             }
1441             hir::ExprTupField(ref expr, id) => {
1442                 try!(self.print_expr(&expr));
1443                 try!(word(&mut self.s, "."));
1444                 try!(self.print_usize(id.node));
1445             }
1446             hir::ExprIndex(ref expr, ref index) => {
1447                 try!(self.print_expr(&expr));
1448                 try!(word(&mut self.s, "["));
1449                 try!(self.print_expr(&index));
1450                 try!(word(&mut self.s, "]"));
1451             }
1452             hir::ExprPath(None, ref path) => {
1453                 try!(self.print_path(path, true, 0))
1454             }
1455             hir::ExprPath(Some(ref qself), ref path) => {
1456                 try!(self.print_qpath(path, qself, true))
1457             }
1458             hir::ExprBreak(opt_ident) => {
1459                 try!(word(&mut self.s, "break"));
1460                 try!(space(&mut self.s));
1461                 if let Some(ident) = opt_ident {
1462                     try!(self.print_name(ident.node.name));
1463                     try!(space(&mut self.s));
1464                 }
1465             }
1466             hir::ExprAgain(opt_ident) => {
1467                 try!(word(&mut self.s, "continue"));
1468                 try!(space(&mut self.s));
1469                 if let Some(ident) = opt_ident {
1470                     try!(self.print_name(ident.node.name));
1471                     try!(space(&mut self.s))
1472                 }
1473             }
1474             hir::ExprRet(ref result) => {
1475                 try!(word(&mut self.s, "return"));
1476                 match *result {
1477                     Some(ref expr) => {
1478                         try!(word(&mut self.s, " "));
1479                         try!(self.print_expr(&expr));
1480                     }
1481                     _ => (),
1482                 }
1483             }
1484             hir::ExprInlineAsm(ref a) => {
1485                 try!(word(&mut self.s, "asm!"));
1486                 try!(self.popen());
1487                 try!(self.print_string(&a.asm, a.asm_str_style));
1488                 try!(self.word_space(":"));
1489
1490                 try!(self.commasep(Inconsistent, &a.outputs, |s, out| {
1491                     match out.constraint.slice_shift_char() {
1492                         Some(('=', operand)) if out.is_rw => {
1493                             try!(s.print_string(&format!("+{}", operand), ast::StrStyle::Cooked))
1494                         }
1495                         _ => try!(s.print_string(&out.constraint, ast::StrStyle::Cooked)),
1496                     }
1497                     try!(s.popen());
1498                     try!(s.print_expr(&out.expr));
1499                     try!(s.pclose());
1500                     Ok(())
1501                 }));
1502                 try!(space(&mut self.s));
1503                 try!(self.word_space(":"));
1504
1505                 try!(self.commasep(Inconsistent, &a.inputs, |s, &(ref co, ref o)| {
1506                     try!(s.print_string(&co, ast::StrStyle::Cooked));
1507                     try!(s.popen());
1508                     try!(s.print_expr(&o));
1509                     try!(s.pclose());
1510                     Ok(())
1511                 }));
1512                 try!(space(&mut self.s));
1513                 try!(self.word_space(":"));
1514
1515                 try!(self.commasep(Inconsistent, &a.clobbers, |s, co| {
1516                     try!(s.print_string(&co, ast::StrStyle::Cooked));
1517                     Ok(())
1518                 }));
1519
1520                 let mut options = vec![];
1521                 if a.volatile {
1522                     options.push("volatile");
1523                 }
1524                 if a.alignstack {
1525                     options.push("alignstack");
1526                 }
1527                 if a.dialect == ast::AsmDialect::Intel {
1528                     options.push("intel");
1529                 }
1530
1531                 if !options.is_empty() {
1532                     try!(space(&mut self.s));
1533                     try!(self.word_space(":"));
1534                     try!(self.commasep(Inconsistent, &options, |s, &co| {
1535                         try!(s.print_string(co, ast::StrStyle::Cooked));
1536                         Ok(())
1537                     }));
1538                 }
1539
1540                 try!(self.pclose());
1541             }
1542         }
1543         try!(self.ann.post(self, NodeExpr(expr)));
1544         self.end()
1545     }
1546
1547     pub fn print_local_decl(&mut self, loc: &hir::Local) -> io::Result<()> {
1548         try!(self.print_pat(&loc.pat));
1549         if let Some(ref ty) = loc.ty {
1550             try!(self.word_space(":"));
1551             try!(self.print_type(&ty));
1552         }
1553         Ok(())
1554     }
1555
1556     pub fn print_decl(&mut self, decl: &hir::Decl) -> io::Result<()> {
1557         try!(self.maybe_print_comment(decl.span.lo));
1558         match decl.node {
1559             hir::DeclLocal(ref loc) => {
1560                 try!(self.space_if_not_bol());
1561                 try!(self.ibox(indent_unit));
1562                 try!(self.word_nbsp("let"));
1563
1564                 try!(self.ibox(indent_unit));
1565                 try!(self.print_local_decl(&loc));
1566                 try!(self.end());
1567                 if let Some(ref init) = loc.init {
1568                     try!(self.nbsp());
1569                     try!(self.word_space("="));
1570                     try!(self.print_expr(&init));
1571                 }
1572                 self.end()
1573             }
1574             hir::DeclItem(ref item) => {
1575                 self.print_item_id(item)
1576             }
1577         }
1578     }
1579
1580     pub fn print_usize(&mut self, i: usize) -> io::Result<()> {
1581         word(&mut self.s, &i.to_string())
1582     }
1583
1584     pub fn print_name(&mut self, name: ast::Name) -> io::Result<()> {
1585         try!(word(&mut self.s, &name.as_str()));
1586         self.ann.post(self, NodeName(&name))
1587     }
1588
1589     pub fn print_for_decl(&mut self, loc: &hir::Local, coll: &hir::Expr) -> io::Result<()> {
1590         try!(self.print_local_decl(loc));
1591         try!(space(&mut self.s));
1592         try!(self.word_space("in"));
1593         self.print_expr(coll)
1594     }
1595
1596     fn print_path(&mut self,
1597                   path: &hir::Path,
1598                   colons_before_params: bool,
1599                   depth: usize)
1600                   -> io::Result<()> {
1601         try!(self.maybe_print_comment(path.span.lo));
1602
1603         let mut first = !path.global;
1604         for segment in &path.segments[..path.segments.len() - depth] {
1605             if first {
1606                 first = false
1607             } else {
1608                 try!(word(&mut self.s, "::"))
1609             }
1610
1611             try!(self.print_name(segment.identifier.name));
1612
1613             try!(self.print_path_parameters(&segment.parameters, colons_before_params));
1614         }
1615
1616         Ok(())
1617     }
1618
1619     fn print_qpath(&mut self,
1620                    path: &hir::Path,
1621                    qself: &hir::QSelf,
1622                    colons_before_params: bool)
1623                    -> io::Result<()> {
1624         try!(word(&mut self.s, "<"));
1625         try!(self.print_type(&qself.ty));
1626         if qself.position > 0 {
1627             try!(space(&mut self.s));
1628             try!(self.word_space("as"));
1629             let depth = path.segments.len() - qself.position;
1630             try!(self.print_path(&path, false, depth));
1631         }
1632         try!(word(&mut self.s, ">"));
1633         try!(word(&mut self.s, "::"));
1634         let item_segment = path.segments.last().unwrap();
1635         try!(self.print_name(item_segment.identifier.name));
1636         self.print_path_parameters(&item_segment.parameters, colons_before_params)
1637     }
1638
1639     fn print_path_parameters(&mut self,
1640                              parameters: &hir::PathParameters,
1641                              colons_before_params: bool)
1642                              -> io::Result<()> {
1643         if parameters.is_empty() {
1644             return Ok(());
1645         }
1646
1647         if colons_before_params {
1648             try!(word(&mut self.s, "::"))
1649         }
1650
1651         match *parameters {
1652             hir::AngleBracketedParameters(ref data) => {
1653                 try!(word(&mut self.s, "<"));
1654
1655                 let mut comma = false;
1656                 for lifetime in &data.lifetimes {
1657                     if comma {
1658                         try!(self.word_space(","))
1659                     }
1660                     try!(self.print_lifetime(lifetime));
1661                     comma = true;
1662                 }
1663
1664                 if !data.types.is_empty() {
1665                     if comma {
1666                         try!(self.word_space(","))
1667                     }
1668                     try!(self.commasep(Inconsistent, &data.types, |s, ty| s.print_type(&ty)));
1669                     comma = true;
1670                 }
1671
1672                 for binding in data.bindings.iter() {
1673                     if comma {
1674                         try!(self.word_space(","))
1675                     }
1676                     try!(self.print_name(binding.name));
1677                     try!(space(&mut self.s));
1678                     try!(self.word_space("="));
1679                     try!(self.print_type(&binding.ty));
1680                     comma = true;
1681                 }
1682
1683                 try!(word(&mut self.s, ">"))
1684             }
1685
1686             hir::ParenthesizedParameters(ref data) => {
1687                 try!(word(&mut self.s, "("));
1688                 try!(self.commasep(Inconsistent, &data.inputs, |s, ty| s.print_type(&ty)));
1689                 try!(word(&mut self.s, ")"));
1690
1691                 match data.output {
1692                     None => {}
1693                     Some(ref ty) => {
1694                         try!(self.space_if_not_bol());
1695                         try!(self.word_space("->"));
1696                         try!(self.print_type(&ty));
1697                     }
1698                 }
1699             }
1700         }
1701
1702         Ok(())
1703     }
1704
1705     pub fn print_pat(&mut self, pat: &hir::Pat) -> io::Result<()> {
1706         try!(self.maybe_print_comment(pat.span.lo));
1707         try!(self.ann.pre(self, NodePat(pat)));
1708         // Pat isn't normalized, but the beauty of it
1709         // is that it doesn't matter
1710         match pat.node {
1711             PatKind::Wild => try!(word(&mut self.s, "_")),
1712             PatKind::Ident(binding_mode, ref path1, ref sub) => {
1713                 match binding_mode {
1714                     hir::BindByRef(mutbl) => {
1715                         try!(self.word_nbsp("ref"));
1716                         try!(self.print_mutability(mutbl));
1717                     }
1718                     hir::BindByValue(hir::MutImmutable) => {}
1719                     hir::BindByValue(hir::MutMutable) => {
1720                         try!(self.word_nbsp("mut"));
1721                     }
1722                 }
1723                 try!(self.print_name(path1.node.name));
1724                 match *sub {
1725                     Some(ref p) => {
1726                         try!(word(&mut self.s, "@"));
1727                         try!(self.print_pat(&p));
1728                     }
1729                     None => (),
1730                 }
1731             }
1732             PatKind::TupleStruct(ref path, ref args_) => {
1733                 try!(self.print_path(path, true, 0));
1734                 match *args_ {
1735                     None => try!(word(&mut self.s, "(..)")),
1736                     Some(ref args) => {
1737                         try!(self.popen());
1738                         try!(self.commasep(Inconsistent, &args[..], |s, p| s.print_pat(&p)));
1739                         try!(self.pclose());
1740                     }
1741                 }
1742             }
1743             PatKind::Path(ref path) => {
1744                 try!(self.print_path(path, true, 0));
1745             }
1746             PatKind::QPath(ref qself, ref path) => {
1747                 try!(self.print_qpath(path, qself, false));
1748             }
1749             PatKind::Struct(ref path, ref fields, etc) => {
1750                 try!(self.print_path(path, true, 0));
1751                 try!(self.nbsp());
1752                 try!(self.word_space("{"));
1753                 try!(self.commasep_cmnt(Consistent,
1754                                         &fields[..],
1755                                         |s, f| {
1756                                             try!(s.cbox(indent_unit));
1757                                             if !f.node.is_shorthand {
1758                                                 try!(s.print_name(f.node.name));
1759                                                 try!(s.word_nbsp(":"));
1760                                             }
1761                                             try!(s.print_pat(&f.node.pat));
1762                                             s.end()
1763                                         },
1764                                         |f| f.node.pat.span));
1765                 if etc {
1766                     if !fields.is_empty() {
1767                         try!(self.word_space(","));
1768                     }
1769                     try!(word(&mut self.s, ".."));
1770                 }
1771                 try!(space(&mut self.s));
1772                 try!(word(&mut self.s, "}"));
1773             }
1774             PatKind::Tup(ref elts) => {
1775                 try!(self.popen());
1776                 try!(self.commasep(Inconsistent, &elts[..], |s, p| s.print_pat(&p)));
1777                 if elts.len() == 1 {
1778                     try!(word(&mut self.s, ","));
1779                 }
1780                 try!(self.pclose());
1781             }
1782             PatKind::Box(ref inner) => {
1783                 try!(word(&mut self.s, "box "));
1784                 try!(self.print_pat(&inner));
1785             }
1786             PatKind::Ref(ref inner, mutbl) => {
1787                 try!(word(&mut self.s, "&"));
1788                 if mutbl == hir::MutMutable {
1789                     try!(word(&mut self.s, "mut "));
1790                 }
1791                 try!(self.print_pat(&inner));
1792             }
1793             PatKind::Lit(ref e) => try!(self.print_expr(&e)),
1794             PatKind::Range(ref begin, ref end) => {
1795                 try!(self.print_expr(&begin));
1796                 try!(space(&mut self.s));
1797                 try!(word(&mut self.s, "..."));
1798                 try!(self.print_expr(&end));
1799             }
1800             PatKind::Vec(ref before, ref slice, ref after) => {
1801                 try!(word(&mut self.s, "["));
1802                 try!(self.commasep(Inconsistent, &before[..], |s, p| s.print_pat(&p)));
1803                 if let Some(ref p) = *slice {
1804                     if !before.is_empty() {
1805                         try!(self.word_space(","));
1806                     }
1807                     if p.node != PatKind::Wild {
1808                         try!(self.print_pat(&p));
1809                     }
1810                     try!(word(&mut self.s, ".."));
1811                     if !after.is_empty() {
1812                         try!(self.word_space(","));
1813                     }
1814                 }
1815                 try!(self.commasep(Inconsistent, &after[..], |s, p| s.print_pat(&p)));
1816                 try!(word(&mut self.s, "]"));
1817             }
1818         }
1819         self.ann.post(self, NodePat(pat))
1820     }
1821
1822     fn print_arm(&mut self, arm: &hir::Arm) -> io::Result<()> {
1823         // I have no idea why this check is necessary, but here it
1824         // is :(
1825         if arm.attrs.is_empty() {
1826             try!(space(&mut self.s));
1827         }
1828         try!(self.cbox(indent_unit));
1829         try!(self.ibox(0));
1830         try!(self.print_outer_attributes(&arm.attrs));
1831         let mut first = true;
1832         for p in &arm.pats {
1833             if first {
1834                 first = false;
1835             } else {
1836                 try!(space(&mut self.s));
1837                 try!(self.word_space("|"));
1838             }
1839             try!(self.print_pat(&p));
1840         }
1841         try!(space(&mut self.s));
1842         if let Some(ref e) = arm.guard {
1843             try!(self.word_space("if"));
1844             try!(self.print_expr(&e));
1845             try!(space(&mut self.s));
1846         }
1847         try!(self.word_space("=>"));
1848
1849         match arm.body.node {
1850             hir::ExprBlock(ref blk) => {
1851                 // the block will close the pattern's ibox
1852                 try!(self.print_block_unclosed_indent(&blk, indent_unit));
1853
1854                 // If it is a user-provided unsafe block, print a comma after it
1855                 if let hir::UnsafeBlock(hir::UserProvided) = blk.rules {
1856                     try!(word(&mut self.s, ","));
1857                 }
1858             }
1859             _ => {
1860                 try!(self.end()); // close the ibox for the pattern
1861                 try!(self.print_expr(&arm.body));
1862                 try!(word(&mut self.s, ","));
1863             }
1864         }
1865         self.end() // close enclosing cbox
1866     }
1867
1868     // Returns whether it printed anything
1869     fn print_explicit_self(&mut self,
1870                            explicit_self: &hir::ExplicitSelf_,
1871                            mutbl: hir::Mutability)
1872                            -> io::Result<bool> {
1873         try!(self.print_mutability(mutbl));
1874         match *explicit_self {
1875             hir::SelfStatic => {
1876                 return Ok(false);
1877             }
1878             hir::SelfValue(_) => {
1879                 try!(word(&mut self.s, "self"));
1880             }
1881             hir::SelfRegion(ref lt, m, _) => {
1882                 try!(word(&mut self.s, "&"));
1883                 try!(self.print_opt_lifetime(lt));
1884                 try!(self.print_mutability(m));
1885                 try!(word(&mut self.s, "self"));
1886             }
1887             hir::SelfExplicit(ref typ, _) => {
1888                 try!(word(&mut self.s, "self"));
1889                 try!(self.word_space(":"));
1890                 try!(self.print_type(&typ));
1891             }
1892         }
1893         return Ok(true);
1894     }
1895
1896     pub fn print_fn(&mut self,
1897                     decl: &hir::FnDecl,
1898                     unsafety: hir::Unsafety,
1899                     constness: hir::Constness,
1900                     abi: Abi,
1901                     name: Option<ast::Name>,
1902                     generics: &hir::Generics,
1903                     opt_explicit_self: Option<&hir::ExplicitSelf_>,
1904                     vis: hir::Visibility)
1905                     -> io::Result<()> {
1906         try!(self.print_fn_header_info(unsafety, constness, abi, vis));
1907
1908         if let Some(name) = name {
1909             try!(self.nbsp());
1910             try!(self.print_name(name));
1911         }
1912         try!(self.print_generics(generics));
1913         try!(self.print_fn_args_and_ret(decl, opt_explicit_self));
1914         self.print_where_clause(&generics.where_clause)
1915     }
1916
1917     pub fn print_fn_args(&mut self,
1918                          decl: &hir::FnDecl,
1919                          opt_explicit_self: Option<&hir::ExplicitSelf_>,
1920                          is_closure: bool)
1921                          -> io::Result<()> {
1922         // It is unfortunate to duplicate the commasep logic, but we want the
1923         // self type and the args all in the same box.
1924         try!(self.rbox(0, Inconsistent));
1925         let mut first = true;
1926         if let Some(explicit_self) = opt_explicit_self {
1927             let m = match explicit_self {
1928                 &hir::SelfStatic => hir::MutImmutable,
1929                 _ => match decl.inputs[0].pat.node {
1930                     PatKind::Ident(hir::BindByValue(m), _, _) => m,
1931                     _ => hir::MutImmutable,
1932                 },
1933             };
1934             first = !try!(self.print_explicit_self(explicit_self, m));
1935         }
1936
1937         // HACK(eddyb) ignore the separately printed self argument.
1938         let args = if first {
1939             &decl.inputs[..]
1940         } else {
1941             &decl.inputs[1..]
1942         };
1943
1944         for arg in args {
1945             if first {
1946                 first = false;
1947             } else {
1948                 try!(self.word_space(","));
1949             }
1950             try!(self.print_arg(arg, is_closure));
1951         }
1952
1953         self.end()
1954     }
1955
1956     pub fn print_fn_args_and_ret(&mut self,
1957                                  decl: &hir::FnDecl,
1958                                  opt_explicit_self: Option<&hir::ExplicitSelf_>)
1959                                  -> io::Result<()> {
1960         try!(self.popen());
1961         try!(self.print_fn_args(decl, opt_explicit_self, false));
1962         if decl.variadic {
1963             try!(word(&mut self.s, ", ..."));
1964         }
1965         try!(self.pclose());
1966
1967         self.print_fn_output(decl)
1968     }
1969
1970     pub fn print_fn_block_args(&mut self, decl: &hir::FnDecl) -> io::Result<()> {
1971         try!(word(&mut self.s, "|"));
1972         try!(self.print_fn_args(decl, None, true));
1973         try!(word(&mut self.s, "|"));
1974
1975         if let hir::DefaultReturn(..) = decl.output {
1976             return Ok(());
1977         }
1978
1979         try!(self.space_if_not_bol());
1980         try!(self.word_space("->"));
1981         match decl.output {
1982             hir::Return(ref ty) => {
1983                 try!(self.print_type(&ty));
1984                 self.maybe_print_comment(ty.span.lo)
1985             }
1986             hir::DefaultReturn(..) => unreachable!(),
1987             hir::NoReturn(span) => {
1988                 try!(self.word_nbsp("!"));
1989                 self.maybe_print_comment(span.lo)
1990             }
1991         }
1992     }
1993
1994     pub fn print_capture_clause(&mut self, capture_clause: hir::CaptureClause) -> io::Result<()> {
1995         match capture_clause {
1996             hir::CaptureByValue => self.word_space("move"),
1997             hir::CaptureByRef => Ok(()),
1998         }
1999     }
2000
2001     pub fn print_bounds(&mut self, prefix: &str, bounds: &[hir::TyParamBound]) -> io::Result<()> {
2002         if !bounds.is_empty() {
2003             try!(word(&mut self.s, prefix));
2004             let mut first = true;
2005             for bound in bounds {
2006                 try!(self.nbsp());
2007                 if first {
2008                     first = false;
2009                 } else {
2010                     try!(self.word_space("+"));
2011                 }
2012
2013                 try!(match *bound {
2014                     TraitTyParamBound(ref tref, TraitBoundModifier::None) => {
2015                         self.print_poly_trait_ref(tref)
2016                     }
2017                     TraitTyParamBound(ref tref, TraitBoundModifier::Maybe) => {
2018                         try!(word(&mut self.s, "?"));
2019                         self.print_poly_trait_ref(tref)
2020                     }
2021                     RegionTyParamBound(ref lt) => {
2022                         self.print_lifetime(lt)
2023                     }
2024                 })
2025             }
2026             Ok(())
2027         } else {
2028             Ok(())
2029         }
2030     }
2031
2032     pub fn print_lifetime(&mut self, lifetime: &hir::Lifetime) -> io::Result<()> {
2033         self.print_name(lifetime.name)
2034     }
2035
2036     pub fn print_lifetime_def(&mut self, lifetime: &hir::LifetimeDef) -> io::Result<()> {
2037         try!(self.print_lifetime(&lifetime.lifetime));
2038         let mut sep = ":";
2039         for v in &lifetime.bounds {
2040             try!(word(&mut self.s, sep));
2041             try!(self.print_lifetime(v));
2042             sep = "+";
2043         }
2044         Ok(())
2045     }
2046
2047     pub fn print_generics(&mut self, generics: &hir::Generics) -> io::Result<()> {
2048         let total = generics.lifetimes.len() + generics.ty_params.len();
2049         if total == 0 {
2050             return Ok(());
2051         }
2052
2053         try!(word(&mut self.s, "<"));
2054
2055         let mut ints = Vec::new();
2056         for i in 0..total {
2057             ints.push(i);
2058         }
2059
2060         try!(self.commasep(Inconsistent, &ints[..], |s, &idx| {
2061             if idx < generics.lifetimes.len() {
2062                 let lifetime = &generics.lifetimes[idx];
2063                 s.print_lifetime_def(lifetime)
2064             } else {
2065                 let idx = idx - generics.lifetimes.len();
2066                 let param = &generics.ty_params[idx];
2067                 s.print_ty_param(param)
2068             }
2069         }));
2070
2071         try!(word(&mut self.s, ">"));
2072         Ok(())
2073     }
2074
2075     pub fn print_ty_param(&mut self, param: &hir::TyParam) -> io::Result<()> {
2076         try!(self.print_name(param.name));
2077         try!(self.print_bounds(":", &param.bounds));
2078         match param.default {
2079             Some(ref default) => {
2080                 try!(space(&mut self.s));
2081                 try!(self.word_space("="));
2082                 self.print_type(&default)
2083             }
2084             _ => Ok(()),
2085         }
2086     }
2087
2088     pub fn print_where_clause(&mut self, where_clause: &hir::WhereClause) -> io::Result<()> {
2089         if where_clause.predicates.is_empty() {
2090             return Ok(());
2091         }
2092
2093         try!(space(&mut self.s));
2094         try!(self.word_space("where"));
2095
2096         for (i, predicate) in where_clause.predicates.iter().enumerate() {
2097             if i != 0 {
2098                 try!(self.word_space(","));
2099             }
2100
2101             match predicate {
2102                 &hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate{ref bound_lifetimes,
2103                                                                               ref bounded_ty,
2104                                                                               ref bounds,
2105                                                                               ..}) => {
2106                     try!(self.print_formal_lifetime_list(bound_lifetimes));
2107                     try!(self.print_type(&bounded_ty));
2108                     try!(self.print_bounds(":", bounds));
2109                 }
2110                 &hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate{ref lifetime,
2111                                                                                 ref bounds,
2112                                                                                 ..}) => {
2113                     try!(self.print_lifetime(lifetime));
2114                     try!(word(&mut self.s, ":"));
2115
2116                     for (i, bound) in bounds.iter().enumerate() {
2117                         try!(self.print_lifetime(bound));
2118
2119                         if i != 0 {
2120                             try!(word(&mut self.s, ":"));
2121                         }
2122                     }
2123                 }
2124                 &hir::WherePredicate::EqPredicate(hir::WhereEqPredicate{ref path, ref ty, ..}) => {
2125                     try!(self.print_path(path, false, 0));
2126                     try!(space(&mut self.s));
2127                     try!(self.word_space("="));
2128                     try!(self.print_type(&ty));
2129                 }
2130             }
2131         }
2132
2133         Ok(())
2134     }
2135
2136     pub fn print_view_path(&mut self, vp: &hir::ViewPath) -> io::Result<()> {
2137         match vp.node {
2138             hir::ViewPathSimple(name, ref path) => {
2139                 try!(self.print_path(path, false, 0));
2140
2141                 if path.segments.last().unwrap().identifier.name != name {
2142                     try!(space(&mut self.s));
2143                     try!(self.word_space("as"));
2144                     try!(self.print_name(name));
2145                 }
2146
2147                 Ok(())
2148             }
2149
2150             hir::ViewPathGlob(ref path) => {
2151                 try!(self.print_path(path, false, 0));
2152                 word(&mut self.s, "::*")
2153             }
2154
2155             hir::ViewPathList(ref path, ref segments) => {
2156                 if path.segments.is_empty() {
2157                     try!(word(&mut self.s, "{"));
2158                 } else {
2159                     try!(self.print_path(path, false, 0));
2160                     try!(word(&mut self.s, "::{"));
2161                 }
2162                 try!(self.commasep(Inconsistent, &segments[..], |s, w| {
2163                     match w.node {
2164                         hir::PathListIdent { name, .. } => {
2165                             s.print_name(name)
2166                         }
2167                         hir::PathListMod { .. } => {
2168                             word(&mut s.s, "self")
2169                         }
2170                     }
2171                 }));
2172                 word(&mut self.s, "}")
2173             }
2174         }
2175     }
2176
2177     pub fn print_mutability(&mut self, mutbl: hir::Mutability) -> io::Result<()> {
2178         match mutbl {
2179             hir::MutMutable => self.word_nbsp("mut"),
2180             hir::MutImmutable => Ok(()),
2181         }
2182     }
2183
2184     pub fn print_mt(&mut self, mt: &hir::MutTy) -> io::Result<()> {
2185         try!(self.print_mutability(mt.mutbl));
2186         self.print_type(&mt.ty)
2187     }
2188
2189     pub fn print_arg(&mut self, input: &hir::Arg, is_closure: bool) -> io::Result<()> {
2190         try!(self.ibox(indent_unit));
2191         match input.ty.node {
2192             hir::TyInfer if is_closure => try!(self.print_pat(&input.pat)),
2193             _ => {
2194                 match input.pat.node {
2195                     PatKind::Ident(_, ref path1, _) if
2196                         path1.node.name ==
2197                             parse::token::special_idents::invalid.name => {
2198                         // Do nothing.
2199                     }
2200                     _ => {
2201                         try!(self.print_pat(&input.pat));
2202                         try!(word(&mut self.s, ":"));
2203                         try!(space(&mut self.s));
2204                     }
2205                 }
2206                 try!(self.print_type(&input.ty));
2207             }
2208         }
2209         self.end()
2210     }
2211
2212     pub fn print_fn_output(&mut self, decl: &hir::FnDecl) -> io::Result<()> {
2213         if let hir::DefaultReturn(..) = decl.output {
2214             return Ok(());
2215         }
2216
2217         try!(self.space_if_not_bol());
2218         try!(self.ibox(indent_unit));
2219         try!(self.word_space("->"));
2220         match decl.output {
2221             hir::NoReturn(_) => try!(self.word_nbsp("!")),
2222             hir::DefaultReturn(..) => unreachable!(),
2223             hir::Return(ref ty) => try!(self.print_type(&ty)),
2224         }
2225         try!(self.end());
2226
2227         match decl.output {
2228             hir::Return(ref output) => self.maybe_print_comment(output.span.lo),
2229             _ => Ok(()),
2230         }
2231     }
2232
2233     pub fn print_ty_fn(&mut self,
2234                        abi: Abi,
2235                        unsafety: hir::Unsafety,
2236                        decl: &hir::FnDecl,
2237                        name: Option<ast::Name>,
2238                        generics: &hir::Generics,
2239                        opt_explicit_self: Option<&hir::ExplicitSelf_>)
2240                        -> io::Result<()> {
2241         try!(self.ibox(indent_unit));
2242         if !generics.lifetimes.is_empty() || !generics.ty_params.is_empty() {
2243             try!(word(&mut self.s, "for"));
2244             try!(self.print_generics(generics));
2245         }
2246         let generics = hir::Generics {
2247             lifetimes: hir::HirVec::new(),
2248             ty_params: hir::HirVec::new(),
2249             where_clause: hir::WhereClause {
2250                 id: ast::DUMMY_NODE_ID,
2251                 predicates: hir::HirVec::new(),
2252             },
2253         };
2254         try!(self.print_fn(decl,
2255                            unsafety,
2256                            hir::Constness::NotConst,
2257                            abi,
2258                            name,
2259                            &generics,
2260                            opt_explicit_self,
2261                            hir::Inherited));
2262         self.end()
2263     }
2264
2265     pub fn maybe_print_trailing_comment(&mut self,
2266                                         span: codemap::Span,
2267                                         next_pos: Option<BytePos>)
2268                                         -> io::Result<()> {
2269         let cm = match self.cm {
2270             Some(cm) => cm,
2271             _ => return Ok(()),
2272         };
2273         match self.next_comment() {
2274             Some(ref cmnt) => {
2275                 if (*cmnt).style != comments::Trailing {
2276                     return Ok(());
2277                 }
2278                 let span_line = cm.lookup_char_pos(span.hi);
2279                 let comment_line = cm.lookup_char_pos((*cmnt).pos);
2280                 let mut next = (*cmnt).pos + BytePos(1);
2281                 match next_pos {
2282                     None => (),
2283                     Some(p) => next = p,
2284                 }
2285                 if span.hi < (*cmnt).pos && (*cmnt).pos < next &&
2286                    span_line.line == comment_line.line {
2287                     try!(self.print_comment(cmnt));
2288                     self.cur_cmnt_and_lit.cur_cmnt += 1;
2289                 }
2290             }
2291             _ => (),
2292         }
2293         Ok(())
2294     }
2295
2296     pub fn print_remaining_comments(&mut self) -> io::Result<()> {
2297         // If there aren't any remaining comments, then we need to manually
2298         // make sure there is a line break at the end.
2299         if self.next_comment().is_none() {
2300             try!(hardbreak(&mut self.s));
2301         }
2302         loop {
2303             match self.next_comment() {
2304                 Some(ref cmnt) => {
2305                     try!(self.print_comment(cmnt));
2306                     self.cur_cmnt_and_lit.cur_cmnt += 1;
2307                 }
2308                 _ => break,
2309             }
2310         }
2311         Ok(())
2312     }
2313
2314     pub fn print_opt_abi_and_extern_if_nondefault(&mut self,
2315                                                   opt_abi: Option<Abi>)
2316                                                   -> io::Result<()> {
2317         match opt_abi {
2318             Some(Abi::Rust) => Ok(()),
2319             Some(abi) => {
2320                 try!(self.word_nbsp("extern"));
2321                 self.word_nbsp(&abi.to_string())
2322             }
2323             None => Ok(()),
2324         }
2325     }
2326
2327     pub fn print_extern_opt_abi(&mut self, opt_abi: Option<Abi>) -> io::Result<()> {
2328         match opt_abi {
2329             Some(abi) => {
2330                 try!(self.word_nbsp("extern"));
2331                 self.word_nbsp(&abi.to_string())
2332             }
2333             None => Ok(()),
2334         }
2335     }
2336
2337     pub fn print_fn_header_info(&mut self,
2338                                 unsafety: hir::Unsafety,
2339                                 constness: hir::Constness,
2340                                 abi: Abi,
2341                                 vis: hir::Visibility)
2342                                 -> io::Result<()> {
2343         try!(word(&mut self.s, &visibility_qualified(vis, "")));
2344         try!(self.print_unsafety(unsafety));
2345
2346         match constness {
2347             hir::Constness::NotConst => {}
2348             hir::Constness::Const => try!(self.word_nbsp("const")),
2349         }
2350
2351         if abi != Abi::Rust {
2352             try!(self.word_nbsp("extern"));
2353             try!(self.word_nbsp(&abi.to_string()));
2354         }
2355
2356         word(&mut self.s, "fn")
2357     }
2358
2359     pub fn print_unsafety(&mut self, s: hir::Unsafety) -> io::Result<()> {
2360         match s {
2361             hir::Unsafety::Normal => Ok(()),
2362             hir::Unsafety::Unsafe => self.word_nbsp("unsafe"),
2363         }
2364     }
2365 }
2366
2367 // Dup'ed from parse::classify, but adapted for the HIR.
2368 /// Does this expression require a semicolon to be treated
2369 /// as a statement? The negation of this: 'can this expression
2370 /// be used as a statement without a semicolon' -- is used
2371 /// as an early-bail-out in the parser so that, for instance,
2372 ///     if true {...} else {...}
2373 ///      |x| 5
2374 /// isn't parsed as (if true {...} else {...} | x) | 5
2375 fn expr_requires_semi_to_be_stmt(e: &hir::Expr) -> bool {
2376     match e.node {
2377         hir::ExprIf(..) |
2378         hir::ExprMatch(..) |
2379         hir::ExprBlock(_) |
2380         hir::ExprWhile(..) |
2381         hir::ExprLoop(..) => false,
2382         _ => true,
2383     }
2384 }
2385
2386 /// this statement requires a semicolon after it.
2387 /// note that in one case (stmt_semi), we've already
2388 /// seen the semicolon, and thus don't need another.
2389 fn stmt_ends_with_semi(stmt: &hir::Stmt_) -> bool {
2390     match *stmt {
2391         hir::StmtDecl(ref d, _) => {
2392             match d.node {
2393                 hir::DeclLocal(_) => true,
2394                 hir::DeclItem(_) => false,
2395             }
2396         }
2397         hir::StmtExpr(ref e, _) => {
2398             expr_requires_semi_to_be_stmt(&e)
2399         }
2400         hir::StmtSemi(..) => {
2401             false
2402         }
2403     }
2404 }