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;
  14 use syntax::ast;
  15 use syntax::owned_slice::OwnedSlice;
  16 use syntax::codemap::{self, CodeMap, BytePos, Spanned};
  17 use syntax::diagnostic;
  18 use syntax::parse::token::{self, BinOpToken};
  19 use syntax::parse::lexer::comments;
  20 use syntax::parse;
  21 use syntax::print::pp::{self, break_offset, word, space, hardbreak};
  22 use syntax::print::pp::{Breaks, eof};
  23 use syntax::print::pp::Breaks::{Consistent, Inconsistent};
  24 use syntax::print::pprust::{self as ast_pp, PrintState};
  25 use syntax::ptr::P;
  26
  27 use hir;
  28 use hir::{RegionTyParamBound, TraitTyParamBound, TraitBoundModifier};
  29
  30 use std::io::{self, Write, Read};
  31
  32 pub enum AnnNode<'a> {
  33     NodeName(&'a ast::Name),
  34     NodeBlock(&'a hir::Block),
  35     NodeItem(&'a hir::Item),
  36     NodeSubItem(ast::NodeId),
  37     NodeExpr(&'a hir::Expr),
  38     NodePat(&'a hir::Pat),
  39 }
  40
  41 pub trait PpAnn {
  42     fn pre(&self, _state: &mut State, _node: AnnNode) -> io::Result<()> {
  43         Ok(())
  44     }
  45     fn post(&self, _state: &mut State, _node: AnnNode) -> io::Result<()> {
  46         Ok(())
  47     }
  48 }
  49
  50 #[derive(Copy, Clone)]
  51 pub struct NoAnn;
  52
  53 impl PpAnn for NoAnn {}
  54
  55
  56 pub struct State<'a> {
  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>) -> State<'a> {
  89     static NO_ANN: NoAnn = NoAnn;
  90     rust_printer_annotated(writer, &NO_ANN)
  91 }
  92
  93 pub fn rust_printer_annotated<'a>(writer: Box<Write + 'a>, ann: &'a PpAnn) -> State<'a> {
  94     State {
  95         s: pp::mk_printer(writer, default_columns),
  96         cm: None,
  97         comments: None,
  98         literals: None,
  99         cur_cmnt_and_lit: ast_pp::CurrentCommentAndLiteral {
 100             cur_cmnt: 0,
 101             cur_lit: 0,
 102         },
 103         boxes: Vec::new(),
 104         ann: ann,
 105     }
 106 }
 107
 108 #[allow(non_upper_case_globals)]
 109 pub const indent_unit: usize = 4;
 110
 111 #[allow(non_upper_case_globals)]
 112 pub const default_columns: usize = 78;
 113
 114
 115 /// Requires you to pass an input filename and reader so that
 116 /// it can scan the input text for comments and literals to
 117 /// copy forward.
 118 pub fn print_crate<'a>(cm: &'a CodeMap,
 119                        span_diagnostic: &diagnostic::SpanHandler,
 120                        krate: &hir::Crate,
 121                        filename: String,
 122                        input: &mut Read,
 123                        out: Box<Write + 'a>,
 124                        ann: &'a PpAnn,
 125                        is_expanded: bool)
 126                        -> io::Result<()> {
 127     let mut s = State::new_from_input(cm, span_diagnostic, filename, input, out, ann, is_expanded);
 128
 129     // When printing the AST, we sometimes need to inject `#[no_std]` here.
 130     // Since you can't compile the HIR, it's not necessary.
 131
 132     try!(s.print_mod(&krate.module, &krate.attrs));
 133     try!(s.print_remaining_comments());
 134     eof(&mut s.s)
 135 }
 136
 137 impl<'a> State<'a> {
 138     pub fn new_from_input(cm: &'a CodeMap,
 139                           span_diagnostic: &diagnostic::SpanHandler,
 140                           filename: String,
 141                           input: &mut Read,
 142                           out: Box<Write + 'a>,
 143                           ann: &'a PpAnn,
 144                           is_expanded: bool)
 145                           -> State<'a> {
 146         let (cmnts, lits) = comments::gather_comments_and_literals(span_diagnostic,
 147                                                                    filename,
 148                                                                    input);
 149
 150         State::new(cm,
 151                    out,
 152                    ann,
 153                    Some(cmnts),
 154                    // If the code is post expansion, don't use the table of
 155                    // literals, since it doesn't correspond with the literals
 156                    // in the AST anymore.
 157                    if is_expanded {
 158                        None
 159                    } else {
 160                        Some(lits)
 161                    })
 162     }
 163
 164     pub fn new(cm: &'a CodeMap,
 165                out: Box<Write + 'a>,
 166                ann: &'a PpAnn,
 167                comments: Option<Vec<comments::Comment>>,
 168                literals: Option<Vec<comments::Literal>>)
 169                -> State<'a> {
 170         State {
 171             s: pp::mk_printer(out, default_columns),
 172             cm: Some(cm),
 173             comments: comments.clone(),
 174             literals: literals.clone(),
 175             cur_cmnt_and_lit: ast_pp::CurrentCommentAndLiteral {
 176                 cur_cmnt: 0,
 177                 cur_lit: 0,
 178             },
 179             boxes: Vec::new(),
 180             ann: ann,
 181         }
 182     }
 183 }
 184
 185 pub fn to_string<F>(f: F) -> String
 186     where F: FnOnce(&mut State) -> io::Result<()>
 187 {
 188     let mut wr = Vec::new();
 189     {
 190         let mut printer = rust_printer(Box::new(&mut wr));
 191         f(&mut printer).unwrap();
 192         eof(&mut printer.s).unwrap();
 193     }
 194     String::from_utf8(wr).unwrap()
 195 }
 196
 197 pub fn binop_to_string(op: BinOpToken) -> &'static str {
 198     match op {
 199         token::Plus => "+",
 200         token::Minus => "-",
 201         token::Star => "*",
 202         token::Slash => "/",
 203         token::Percent => "%",
 204         token::Caret => "^",
 205         token::And => "&",
 206         token::Or => "|",
 207         token::Shl => "<<",
 208         token::Shr => ">>",
 209     }
 210 }
 211
 212 pub fn ty_to_string(ty: &hir::Ty) -> String {
 213     to_string(|s| s.print_type(ty))
 214 }
 215
 216 pub fn bounds_to_string(bounds: &[hir::TyParamBound]) -> String {
 217     to_string(|s| s.print_bounds("", bounds))
 218 }
 219
 220 pub fn pat_to_string(pat: &hir::Pat) -> String {
 221     to_string(|s| s.print_pat(pat))
 222 }
 223
 224 pub fn arm_to_string(arm: &hir::Arm) -> String {
 225     to_string(|s| s.print_arm(arm))
 226 }
 227
 228 pub fn expr_to_string(e: &hir::Expr) -> String {
 229     to_string(|s| s.print_expr(e))
 230 }
 231
 232 pub fn lifetime_to_string(e: &hir::Lifetime) -> String {
 233     to_string(|s| s.print_lifetime(e))
 234 }
 235
 236 pub fn stmt_to_string(stmt: &hir::Stmt) -> String {
 237     to_string(|s| s.print_stmt(stmt))
 238 }
 239
 240 pub fn item_to_string(i: &hir::Item) -> String {
 241     to_string(|s| s.print_item(i))
 242 }
 243
 244 pub fn impl_item_to_string(i: &hir::ImplItem) -> String {
 245     to_string(|s| s.print_impl_item(i))
 246 }
 247
 248 pub fn trait_item_to_string(i: &hir::TraitItem) -> String {
 249     to_string(|s| s.print_trait_item(i))
 250 }
 251
 252 pub fn generics_to_string(generics: &hir::Generics) -> String {
 253     to_string(|s| s.print_generics(generics))
 254 }
 255
 256 pub fn where_clause_to_string(i: &hir::WhereClause) -> String {
 257     to_string(|s| s.print_where_clause(i))
 258 }
 259
 260 pub fn fn_block_to_string(p: &hir::FnDecl) -> String {
 261     to_string(|s| s.print_fn_block_args(p))
 262 }
 263
 264 pub fn path_to_string(p: &hir::Path) -> String {
 265     to_string(|s| s.print_path(p, false, 0))
 266 }
 267
 268 pub fn name_to_string(name: ast::Name) -> String {
 269     to_string(|s| s.print_name(name))
 270 }
 271
 272 pub fn fun_to_string(decl: &hir::FnDecl,
 273                      unsafety: hir::Unsafety,
 274                      constness: hir::Constness,
 275                      name: ast::Name,
 276                      opt_explicit_self: Option<&hir::ExplicitSelf_>,
 277                      generics: &hir::Generics)
 278                      -> String {
 279     to_string(|s| {
 280         try!(s.head(""));
 281         try!(s.print_fn(decl,
 282                         unsafety,
 283                         constness,
 284                         abi::Rust,
 285                         Some(name),
 286                         generics,
 287                         opt_explicit_self,
 288                         hir::Inherited));
 289         try!(s.end()); // Close the head box
 290         s.end() // Close the outer box
 291     })
 292 }
 293
 294 pub fn block_to_string(blk: &hir::Block) -> String {
 295     to_string(|s| {
 296         // containing cbox, will be closed by print-block at }
 297         try!(s.cbox(indent_unit));
 298         // head-ibox, will be closed by print-block after {
 299         try!(s.ibox(0));
 300         s.print_block(blk)
 301     })
 302 }
 303
 304 pub fn explicit_self_to_string(explicit_self: &hir::ExplicitSelf_) -> String {
 305     to_string(|s| s.print_explicit_self(explicit_self, hir::MutImmutable).map(|_| {}))
 306 }
 307
 308 pub fn variant_to_string(var: &hir::Variant) -> String {
 309     to_string(|s| s.print_variant(var))
 310 }
 311
 312 pub fn arg_to_string(arg: &hir::Arg) -> String {
 313     to_string(|s| s.print_arg(arg))
 314 }
 315
 316 pub fn visibility_qualified(vis: hir::Visibility, s: &str) -> String {
 317     match vis {
 318         hir::Public => format!("pub {}", s),
 319         hir::Inherited => s.to_string(),
 320     }
 321 }
 322
 323 fn needs_parentheses(expr: &hir::Expr) -> bool {
 324     match expr.node {
 325         hir::ExprAssign(..) |
 326         hir::ExprBinary(..) |
 327         hir::ExprClosure(..) |
 328         hir::ExprAssignOp(..) |
 329         hir::ExprCast(..) => true,
 330         _ => false,
 331     }
 332 }
 333
 334 impl<'a> State<'a> {
 335     pub fn cbox(&mut self, u: usize) -> io::Result<()> {
 336         self.boxes.push(pp::Breaks::Consistent);
 337         pp::cbox(&mut self.s, u)
 338     }
 339
 340     pub fn nbsp(&mut self) -> io::Result<()> {
 341         word(&mut self.s, " ")
 342     }
 343
 344     pub fn word_nbsp(&mut self, w: &str) -> io::Result<()> {
 345         try!(word(&mut self.s, w));
 346         self.nbsp()
 347     }
 348
 349     pub fn head(&mut self, w: &str) -> io::Result<()> {
 350         // outer-box is consistent
 351         try!(self.cbox(indent_unit));
 352         // head-box is inconsistent
 353         try!(self.ibox(w.len() + 1));
 354         // keyword that starts the head
 355         if !w.is_empty() {
 356             try!(self.word_nbsp(w));
 357         }
 358         Ok(())
 359     }
 360
 361     pub fn bopen(&mut self) -> io::Result<()> {
 362         try!(word(&mut self.s, "{"));
 363         self.end() // close the head-box
 364     }
 365
 366     pub fn bclose_(&mut self, span: codemap::Span, indented: usize) -> io::Result<()> {
 367         self.bclose_maybe_open(span, indented, true)
 368     }
 369     pub fn bclose_maybe_open(&mut self,
 370                              span: codemap::Span,
 371                              indented: usize,
 372                              close_box: bool)
 373                              -> io::Result<()> {
 374         try!(self.maybe_print_comment(span.hi));
 375         try!(self.break_offset_if_not_bol(1, -(indented as isize)));
 376         try!(word(&mut self.s, "}"));
 377         if close_box {
 378             try!(self.end()); // close the outer-box
 379         }
 380         Ok(())
 381     }
 382     pub fn bclose(&mut self, span: codemap::Span) -> io::Result<()> {
 383         self.bclose_(span, indent_unit)
 384     }
 385
 386     pub fn in_cbox(&self) -> bool {
 387         match self.boxes.last() {
 388             Some(&last_box) => last_box == pp::Breaks::Consistent,
 389             None => false,
 390         }
 391     }
 392     pub fn space_if_not_bol(&mut self) -> io::Result<()> {
 393         if !self.is_bol() {
 394             try!(space(&mut self.s));
 395         }
 396         Ok(())
 397     }
 398     pub fn break_offset_if_not_bol(&mut self, n: usize, off: isize) -> io::Result<()> {
 399         if !self.is_bol() {
 400             break_offset(&mut self.s, n, off)
 401         } else {
 402             if off != 0 && self.s.last_token().is_hardbreak_tok() {
 403                 // We do something pretty sketchy here: tuck the nonzero
 404                 // offset-adjustment we were going to deposit along with the
 405                 // break into the previous hardbreak.
 406                 self.s.replace_last_token(pp::hardbreak_tok_offset(off));
 407             }
 408             Ok(())
 409         }
 410     }
 411
 412     // Synthesizes a comment that was not textually present in the original source
 413     // file.
 414     pub fn synth_comment(&mut self, text: String) -> io::Result<()> {
 415         try!(word(&mut self.s, "/*"));
 416         try!(space(&mut self.s));
 417         try!(word(&mut self.s, &text[..]));
 418         try!(space(&mut self.s));
 419         word(&mut self.s, "*/")
 420     }
 421
 422
 423     pub fn commasep_cmnt<T, F, G>(&mut self,
 424                                   b: Breaks,
 425                                   elts: &[T],
 426                                   mut op: F,
 427                                   mut get_span: G)
 428                                   -> io::Result<()>
 429         where F: FnMut(&mut State, &T) -> io::Result<()>,
 430               G: FnMut(&T) -> codemap::Span
 431     {
 432         try!(self.rbox(0, b));
 433         let len = elts.len();
 434         let mut i = 0;
 435         for elt in elts {
 436             try!(self.maybe_print_comment(get_span(elt).hi));
 437             try!(op(self, elt));
 438             i += 1;
 439             if i < len {
 440                 try!(word(&mut self.s, ","));
 441                 try!(self.maybe_print_trailing_comment(get_span(elt), Some(get_span(&elts[i]).hi)));
 442                 try!(self.space_if_not_bol());
 443             }
 444         }
 445         self.end()
 446     }
 447
 448     pub fn commasep_exprs(&mut self, b: Breaks, exprs: &[P<hir::Expr>]) -> io::Result<()> {
 449         self.commasep_cmnt(b, exprs, |s, e| s.print_expr(&**e), |e| e.span)
 450     }
 451
 452     pub fn print_mod(&mut self, _mod: &hir::Mod, attrs: &[ast::Attribute]) -> io::Result<()> {
 453         try!(self.print_inner_attributes(attrs));
 454         for item in &_mod.items {
 455             try!(self.print_item(&**item));
 456         }
 457         Ok(())
 458     }
 459
 460     pub fn print_foreign_mod(&mut self,
 461                              nmod: &hir::ForeignMod,
 462                              attrs: &[ast::Attribute])
 463                              -> io::Result<()> {
 464         try!(self.print_inner_attributes(attrs));
 465         for item in &nmod.items {
 466             try!(self.print_foreign_item(&**item));
 467         }
 468         Ok(())
 469     }
 470
 471     pub fn print_opt_lifetime(&mut self, lifetime: &Option<hir::Lifetime>) -> io::Result<()> {
 472         if let Some(l) = *lifetime {
 473             try!(self.print_lifetime(&l));
 474             try!(self.nbsp());
 475         }
 476         Ok(())
 477     }
 478
 479     pub fn print_type(&mut self, ty: &hir::Ty) -> io::Result<()> {
 480         try!(self.maybe_print_comment(ty.span.lo));
 481         try!(self.ibox(0));
 482         match ty.node {
 483             hir::TyVec(ref ty) => {
 484                 try!(word(&mut self.s, "["));
 485                 try!(self.print_type(&**ty));
 486                 try!(word(&mut self.s, "]"));
 487             }
 488             hir::TyPtr(ref mt) => {
 489                 try!(word(&mut self.s, "*"));
 490                 match mt.mutbl {
 491                     hir::MutMutable => try!(self.word_nbsp("mut")),
 492                     hir::MutImmutable => try!(self.word_nbsp("const")),
 493                 }
 494                 try!(self.print_type(&*mt.ty));
 495             }
 496             hir::TyRptr(ref lifetime, ref mt) => {
 497                 try!(word(&mut self.s, "&"));
 498                 try!(self.print_opt_lifetime(lifetime));
 499                 try!(self.print_mt(mt));
 500             }
 501             hir::TyTup(ref elts) => {
 502                 try!(self.popen());
 503                 try!(self.commasep(Inconsistent, &elts[..], |s, ty| s.print_type(&**ty)));
 504                 if elts.len() == 1 {
 505                     try!(word(&mut self.s, ","));
 506                 }
 507                 try!(self.pclose());
 508             }
 509             hir::TyParen(ref typ) => {
 510                 try!(self.popen());
 511                 try!(self.print_type(&**typ));
 512                 try!(self.pclose());
 513             }
 514             hir::TyBareFn(ref f) => {
 515                 let generics = hir::Generics {
 516                     lifetimes: f.lifetimes.clone(),
 517                     ty_params: OwnedSlice::empty(),
 518                     where_clause: hir::WhereClause {
 519                         id: ast::DUMMY_NODE_ID,
 520                         predicates: Vec::new(),
 521                     },
 522                 };
 523                 try!(self.print_ty_fn(f.abi, f.unsafety, &*f.decl, None, &generics, None));
 524             }
 525             hir::TyPath(None, ref path) => {
 526                 try!(self.print_path(path, false, 0));
 527             }
 528             hir::TyPath(Some(ref qself), ref path) => {
 529                 try!(self.print_qpath(path, qself, false))
 530             }
 531             hir::TyObjectSum(ref ty, ref bounds) => {
 532                 try!(self.print_type(&**ty));
 533                 try!(self.print_bounds("+", &bounds[..]));
 534             }
 535             hir::TyPolyTraitRef(ref bounds) => {
 536                 try!(self.print_bounds("", &bounds[..]));
 537             }
 538             hir::TyFixedLengthVec(ref ty, ref v) => {
 539                 try!(word(&mut self.s, "["));
 540                 try!(self.print_type(&**ty));
 541                 try!(word(&mut self.s, "; "));
 542                 try!(self.print_expr(&**v));
 543                 try!(word(&mut self.s, "]"));
 544             }
 545             hir::TyTypeof(ref e) => {
 546                 try!(word(&mut self.s, "typeof("));
 547                 try!(self.print_expr(&**e));
 548                 try!(word(&mut self.s, ")"));
 549             }
 550             hir::TyInfer => {
 551                 try!(word(&mut self.s, "_"));
 552             }
 553         }
 554         self.end()
 555     }
 556
 557     pub fn print_foreign_item(&mut self, item: &hir::ForeignItem) -> io::Result<()> {
 558         try!(self.hardbreak_if_not_bol());
 559         try!(self.maybe_print_comment(item.span.lo));
 560         try!(self.print_outer_attributes(&item.attrs));
 561         match item.node {
 562             hir::ForeignItemFn(ref decl, ref generics) => {
 563                 try!(self.head(""));
 564                 try!(self.print_fn(decl,
 565                                    hir::Unsafety::Normal,
 566                                    hir::Constness::NotConst,
 567                                    abi::Rust,
 568                                    Some(item.name),
 569                                    generics,
 570                                    None,
 571                                    item.vis));
 572                 try!(self.end()); // end head-ibox
 573                 try!(word(&mut self.s, ";"));
 574                 self.end() // end the outer fn box
 575             }
 576             hir::ForeignItemStatic(ref t, m) => {
 577                 try!(self.head(&visibility_qualified(item.vis, "static")));
 578                 if m {
 579                     try!(self.word_space("mut"));
 580                 }
 581                 try!(self.print_name(item.name));
 582                 try!(self.word_space(":"));
 583                 try!(self.print_type(&**t));
 584                 try!(word(&mut self.s, ";"));
 585                 try!(self.end()); // end the head-ibox
 586                 self.end() // end the outer cbox
 587             }
 588         }
 589     }
 590
 591     fn print_associated_const(&mut self,
 592                               name: ast::Name,
 593                               ty: &hir::Ty,
 594                               default: Option<&hir::Expr>,
 595                               vis: hir::Visibility)
 596                               -> io::Result<()> {
 597         try!(word(&mut self.s, &visibility_qualified(vis, "")));
 598         try!(self.word_space("const"));
 599         try!(self.print_name(name));
 600         try!(self.word_space(":"));
 601         try!(self.print_type(ty));
 602         if let Some(expr) = default {
 603             try!(space(&mut self.s));
 604             try!(self.word_space("="));
 605             try!(self.print_expr(expr));
 606         }
 607         word(&mut self.s, ";")
 608     }
 609
 610     fn print_associated_type(&mut self,
 611                              name: ast::Name,
 612                              bounds: Option<&hir::TyParamBounds>,
 613                              ty: Option<&hir::Ty>)
 614                              -> io::Result<()> {
 615         try!(self.word_space("type"));
 616         try!(self.print_name(name));
 617         if let Some(bounds) = bounds {
 618             try!(self.print_bounds(":", bounds));
 619         }
 620         if let Some(ty) = ty {
 621             try!(space(&mut self.s));
 622             try!(self.word_space("="));
 623             try!(self.print_type(ty));
 624         }
 625         word(&mut self.s, ";")
 626     }
 627
 628     /// Pretty-print an item
 629     pub fn print_item(&mut self, item: &hir::Item) -> io::Result<()> {
 630         try!(self.hardbreak_if_not_bol());
 631         try!(self.maybe_print_comment(item.span.lo));
 632         try!(self.print_outer_attributes(&item.attrs));
 633         try!(self.ann.pre(self, NodeItem(item)));
 634         match item.node {
 635             hir::ItemExternCrate(ref optional_path) => {
 636                 try!(self.head(&visibility_qualified(item.vis, "extern crate")));
 637                 if let Some(p) = *optional_path {
 638                     let val = p.as_str();
 639                     if val.contains("-") {
 640                         try!(self.print_string(&val, ast::CookedStr));
 641                     } else {
 642                         try!(self.print_name(p));
 643                     }
 644                     try!(space(&mut self.s));
 645                     try!(word(&mut self.s, "as"));
 646                     try!(space(&mut self.s));
 647                 }
 648                 try!(self.print_name(item.name));
 649                 try!(word(&mut self.s, ";"));
 650                 try!(self.end()); // end inner head-block
 651                 try!(self.end()); // end outer head-block
 652             }
 653             hir::ItemUse(ref vp) => {
 654                 try!(self.head(&visibility_qualified(item.vis, "use")));
 655                 try!(self.print_view_path(&**vp));
 656                 try!(word(&mut self.s, ";"));
 657                 try!(self.end()); // end inner head-block
 658                 try!(self.end()); // end outer head-block
 659             }
 660             hir::ItemStatic(ref ty, m, ref expr) => {
 661                 try!(self.head(&visibility_qualified(item.vis, "static")));
 662                 if m == hir::MutMutable {
 663                     try!(self.word_space("mut"));
 664                 }
 665                 try!(self.print_name(item.name));
 666                 try!(self.word_space(":"));
 667                 try!(self.print_type(&**ty));
 668                 try!(space(&mut self.s));
 669                 try!(self.end()); // end the head-ibox
 670
 671                 try!(self.word_space("="));
 672                 try!(self.print_expr(&**expr));
 673                 try!(word(&mut self.s, ";"));
 674                 try!(self.end()); // end the outer cbox
 675             }
 676             hir::ItemConst(ref ty, ref expr) => {
 677                 try!(self.head(&visibility_qualified(item.vis, "const")));
 678                 try!(self.print_name(item.name));
 679                 try!(self.word_space(":"));
 680                 try!(self.print_type(&**ty));
 681                 try!(space(&mut self.s));
 682                 try!(self.end()); // end the head-ibox
 683
 684                 try!(self.word_space("="));
 685                 try!(self.print_expr(&**expr));
 686                 try!(word(&mut self.s, ";"));
 687                 try!(self.end()); // end the outer cbox
 688             }
 689             hir::ItemFn(ref decl, unsafety, constness, abi, ref typarams, ref body) => {
 690                 try!(self.head(""));
 691                 try!(self.print_fn(decl,
 692                                    unsafety,
 693                                    constness,
 694                                    abi,
 695                                    Some(item.name),
 696                                    typarams,
 697                                    None,
 698                                    item.vis));
 699                 try!(word(&mut self.s, " "));
 700                 try!(self.print_block_with_attrs(&**body, &item.attrs));
 701             }
 702             hir::ItemMod(ref _mod) => {
 703                 try!(self.head(&visibility_qualified(item.vis, "mod")));
 704                 try!(self.print_name(item.name));
 705                 try!(self.nbsp());
 706                 try!(self.bopen());
 707                 try!(self.print_mod(_mod, &item.attrs));
 708                 try!(self.bclose(item.span));
 709             }
 710             hir::ItemForeignMod(ref nmod) => {
 711                 try!(self.head("extern"));
 712                 try!(self.word_nbsp(&nmod.abi.to_string()));
 713                 try!(self.bopen());
 714                 try!(self.print_foreign_mod(nmod, &item.attrs));
 715                 try!(self.bclose(item.span));
 716             }
 717             hir::ItemTy(ref ty, ref params) => {
 718                 try!(self.ibox(indent_unit));
 719                 try!(self.ibox(0));
 720                 try!(self.word_nbsp(&visibility_qualified(item.vis, "type")));
 721                 try!(self.print_name(item.name));
 722                 try!(self.print_generics(params));
 723                 try!(self.end()); // end the inner ibox
 724
 725                 try!(self.print_where_clause(&params.where_clause));
 726                 try!(space(&mut self.s));
 727                 try!(self.word_space("="));
 728                 try!(self.print_type(&**ty));
 729                 try!(word(&mut self.s, ";"));
 730                 try!(self.end()); // end the outer ibox
 731             }
 732             hir::ItemEnum(ref enum_definition, ref params) => {
 733                 try!(self.print_enum_def(enum_definition, params, item.name, item.span, item.vis));
 734             }
 735             hir::ItemStruct(ref struct_def, ref generics) => {
 736                 try!(self.head(&visibility_qualified(item.vis, "struct")));
 737                 try!(self.print_struct(struct_def, generics, item.name, item.span, true));
 738             }
 739
 740             hir::ItemDefaultImpl(unsafety, ref trait_ref) => {
 741                 try!(self.head(""));
 742                 try!(self.print_visibility(item.vis));
 743                 try!(self.print_unsafety(unsafety));
 744                 try!(self.word_nbsp("impl"));
 745                 try!(self.print_trait_ref(trait_ref));
 746                 try!(space(&mut self.s));
 747                 try!(self.word_space("for"));
 748                 try!(self.word_space(".."));
 749                 try!(self.bopen());
 750                 try!(self.bclose(item.span));
 751             }
 752             hir::ItemImpl(unsafety,
 753                           polarity,
 754                           ref generics,
 755                           ref opt_trait,
 756                           ref ty,
 757                           ref impl_items) => {
 758                 try!(self.head(""));
 759                 try!(self.print_visibility(item.vis));
 760                 try!(self.print_unsafety(unsafety));
 761                 try!(self.word_nbsp("impl"));
 762
 763                 if generics.is_parameterized() {
 764                     try!(self.print_generics(generics));
 765                     try!(space(&mut self.s));
 766                 }
 767
 768                 match polarity {
 769                     hir::ImplPolarity::Negative => {
 770                         try!(word(&mut self.s, "!"));
 771                     }
 772                     _ => {}
 773                 }
 774
 775                 match opt_trait {
 776                     &Some(ref t) => {
 777                         try!(self.print_trait_ref(t));
 778                         try!(space(&mut self.s));
 779                         try!(self.word_space("for"));
 780                     }
 781                     &None => {}
 782                 }
 783
 784                 try!(self.print_type(&**ty));
 785                 try!(self.print_where_clause(&generics.where_clause));
 786
 787                 try!(space(&mut self.s));
 788                 try!(self.bopen());
 789                 try!(self.print_inner_attributes(&item.attrs));
 790                 for impl_item in impl_items {
 791                     try!(self.print_impl_item(impl_item));
 792                 }
 793                 try!(self.bclose(item.span));
 794             }
 795             hir::ItemTrait(unsafety, ref generics, ref bounds, ref trait_items) => {
 796                 try!(self.head(""));
 797                 try!(self.print_visibility(item.vis));
 798                 try!(self.print_unsafety(unsafety));
 799                 try!(self.word_nbsp("trait"));
 800                 try!(self.print_name(item.name));
 801                 try!(self.print_generics(generics));
 802                 let mut real_bounds = Vec::with_capacity(bounds.len());
 803                 for b in bounds.iter() {
 804                     if let TraitTyParamBound(ref ptr, hir::TraitBoundModifier::Maybe) = *b {
 805                         try!(space(&mut self.s));
 806                         try!(self.word_space("for ?"));
 807                         try!(self.print_trait_ref(&ptr.trait_ref));
 808                     } else {
 809                         real_bounds.push(b.clone());
 810                     }
 811                 }
 812                 try!(self.print_bounds(":", &real_bounds[..]));
 813                 try!(self.print_where_clause(&generics.where_clause));
 814                 try!(word(&mut self.s, " "));
 815                 try!(self.bopen());
 816                 for trait_item in trait_items {
 817                     try!(self.print_trait_item(trait_item));
 818                 }
 819                 try!(self.bclose(item.span));
 820             }
 821         }
 822         self.ann.post(self, NodeItem(item))
 823     }
 824
 825     fn print_trait_ref(&mut self, t: &hir::TraitRef) -> io::Result<()> {
 826         self.print_path(&t.path, false, 0)
 827     }
 828
 829     fn print_formal_lifetime_list(&mut self, lifetimes: &[hir::LifetimeDef]) -> io::Result<()> {
 830         if !lifetimes.is_empty() {
 831             try!(word(&mut self.s, "for<"));
 832             let mut comma = false;
 833             for lifetime_def in lifetimes {
 834                 if comma {
 835                     try!(self.word_space(","))
 836                 }
 837                 try!(self.print_lifetime_def(lifetime_def));
 838                 comma = true;
 839             }
 840             try!(word(&mut self.s, ">"));
 841         }
 842         Ok(())
 843     }
 844
 845     fn print_poly_trait_ref(&mut self, t: &hir::PolyTraitRef) -> io::Result<()> {
 846         try!(self.print_formal_lifetime_list(&t.bound_lifetimes));
 847         self.print_trait_ref(&t.trait_ref)
 848     }
 849
 850     pub fn print_enum_def(&mut self,
 851                           enum_definition: &hir::EnumDef,
 852                           generics: &hir::Generics,
 853                           name: ast::Name,
 854                           span: codemap::Span,
 855                           visibility: hir::Visibility)
 856                           -> io::Result<()> {
 857         try!(self.head(&visibility_qualified(visibility, "enum")));
 858         try!(self.print_name(name));
 859         try!(self.print_generics(generics));
 860         try!(self.print_where_clause(&generics.where_clause));
 861         try!(space(&mut self.s));
 862         self.print_variants(&enum_definition.variants, span)
 863     }
 864
 865     pub fn print_variants(&mut self,
 866                           variants: &[P<hir::Variant>],
 867                           span: codemap::Span)
 868                           -> io::Result<()> {
 869         try!(self.bopen());
 870         for v in variants {
 871             try!(self.space_if_not_bol());
 872             try!(self.maybe_print_comment(v.span.lo));
 873             try!(self.print_outer_attributes(&v.node.attrs));
 874             try!(self.ibox(indent_unit));
 875             try!(self.print_variant(&**v));
 876             try!(word(&mut self.s, ","));
 877             try!(self.end());
 878             try!(self.maybe_print_trailing_comment(v.span, None));
 879         }
 880         self.bclose(span)
 881     }
 882
 883     pub fn print_visibility(&mut self, vis: hir::Visibility) -> io::Result<()> {
 884         match vis {
 885             hir::Public => self.word_nbsp("pub"),
 886             hir::Inherited => Ok(()),
 887         }
 888     }
 889
 890     pub fn print_struct(&mut self,
 891                         struct_def: &hir::VariantData,
 892                         generics: &hir::Generics,
 893                         name: ast::Name,
 894                         span: codemap::Span,
 895                         print_finalizer: bool)
 896                         -> io::Result<()> {
 897         try!(self.print_name(name));
 898         try!(self.print_generics(generics));
 899         if !struct_def.is_struct() {
 900             if struct_def.is_tuple() {
 901                 try!(self.popen());
 902                 try!(self.commasep(Inconsistent, struct_def.fields(), |s, field| {
 903                     match field.node.kind {
 904                         hir::NamedField(..) => panic!("unexpected named field"),
 905                         hir::UnnamedField(vis) => {
 906                             try!(s.print_visibility(vis));
 907                             try!(s.maybe_print_comment(field.span.lo));
 908                             s.print_type(&*field.node.ty)
 909                         }
 910                     }
 911                 }));
 912                 try!(self.pclose());
 913             }
 914             try!(self.print_where_clause(&generics.where_clause));
 915             if print_finalizer {
 916                 try!(word(&mut self.s, ";"));
 917             }
 918             try!(self.end());
 919             self.end() // close the outer-box
 920         } else {
 921             try!(self.print_where_clause(&generics.where_clause));
 922             try!(self.nbsp());
 923             try!(self.bopen());
 924             try!(self.hardbreak_if_not_bol());
 925
 926             for field in struct_def.fields() {
 927                 match field.node.kind {
 928                     hir::UnnamedField(..) => panic!("unexpected unnamed field"),
 929                     hir::NamedField(name, visibility) => {
 930                         try!(self.hardbreak_if_not_bol());
 931                         try!(self.maybe_print_comment(field.span.lo));
 932                         try!(self.print_outer_attributes(&field.node.attrs));
 933                         try!(self.print_visibility(visibility));
 934                         try!(self.print_name(name));
 935                         try!(self.word_nbsp(":"));
 936                         try!(self.print_type(&*field.node.ty));
 937                         try!(word(&mut self.s, ","));
 938                     }
 939                 }
 940             }
 941
 942             self.bclose(span)
 943         }
 944     }
 945
 946     pub fn print_variant(&mut self, v: &hir::Variant) -> io::Result<()> {
 947         try!(self.head(""));
 948         let generics = ::util::empty_generics();
 949         try!(self.print_struct(&v.node.data, &generics, v.node.name, v.span, false));
 950         match v.node.disr_expr {
 951             Some(ref d) => {
 952                 try!(space(&mut self.s));
 953                 try!(self.word_space("="));
 954                 self.print_expr(&**d)
 955             }
 956             _ => Ok(()),
 957         }
 958     }
 959
 960     pub fn print_method_sig(&mut self,
 961                             name: ast::Name,
 962                             m: &hir::MethodSig,
 963                             vis: hir::Visibility)
 964                             -> io::Result<()> {
 965         self.print_fn(&m.decl,
 966                       m.unsafety,
 967                       m.constness,
 968                       m.abi,
 969                       Some(name),
 970                       &m.generics,
 971                       Some(&m.explicit_self.node),
 972                       vis)
 973     }
 974
 975     pub fn print_trait_item(&mut self, ti: &hir::TraitItem) -> io::Result<()> {
 976         try!(self.ann.pre(self, NodeSubItem(ti.id)));
 977         try!(self.hardbreak_if_not_bol());
 978         try!(self.maybe_print_comment(ti.span.lo));
 979         try!(self.print_outer_attributes(&ti.attrs));
 980         match ti.node {
 981             hir::ConstTraitItem(ref ty, ref default) => {
 982                 try!(self.print_associated_const(ti.name,
 983                                                  &ty,
 984                                                  default.as_ref().map(|expr| &**expr),
 985                                                  hir::Inherited));
 986             }
 987             hir::MethodTraitItem(ref sig, ref body) => {
 988                 if body.is_some() {
 989                     try!(self.head(""));
 990                 }
 991                 try!(self.print_method_sig(ti.name, sig, hir::Inherited));
 992                 if let Some(ref body) = *body {
 993                     try!(self.nbsp());
 994                     try!(self.print_block_with_attrs(body, &ti.attrs));
 995                 } else {
 996                     try!(word(&mut self.s, ";"));
 997                 }
 998             }
 999             hir::TypeTraitItem(ref bounds, ref default) => {
1000                 try!(self.print_associated_type(ti.name,
1001                                                 Some(bounds),
1002                                                 default.as_ref().map(|ty| &**ty)));
1003             }
1004         }
1005         self.ann.post(self, NodeSubItem(ti.id))
1006     }
1007
1008     pub fn print_impl_item(&mut self, ii: &hir::ImplItem) -> io::Result<()> {
1009         try!(self.ann.pre(self, NodeSubItem(ii.id)));
1010         try!(self.hardbreak_if_not_bol());
1011         try!(self.maybe_print_comment(ii.span.lo));
1012         try!(self.print_outer_attributes(&ii.attrs));
1013         match ii.node {
1014             hir::ConstImplItem(ref ty, ref expr) => {
1015                 try!(self.print_associated_const(ii.name, &ty, Some(&expr), ii.vis));
1016             }
1017             hir::MethodImplItem(ref sig, ref body) => {
1018                 try!(self.head(""));
1019                 try!(self.print_method_sig(ii.name, sig, ii.vis));
1020                 try!(self.nbsp());
1021                 try!(self.print_block_with_attrs(body, &ii.attrs));
1022             }
1023             hir::TypeImplItem(ref ty) => {
1024                 try!(self.print_associated_type(ii.name, None, Some(ty)));
1025             }
1026         }
1027         self.ann.post(self, NodeSubItem(ii.id))
1028     }
1029
1030     pub fn print_stmt(&mut self, st: &hir::Stmt) -> io::Result<()> {
1031         try!(self.maybe_print_comment(st.span.lo));
1032         match st.node {
1033             hir::StmtDecl(ref decl, _) => {
1034                 try!(self.print_decl(&**decl));
1035             }
1036             hir::StmtExpr(ref expr, _) => {
1037                 try!(self.space_if_not_bol());
1038                 try!(self.print_expr(&**expr));
1039             }
1040             hir::StmtSemi(ref expr, _) => {
1041                 try!(self.space_if_not_bol());
1042                 try!(self.print_expr(&**expr));
1043                 try!(word(&mut self.s, ";"));
1044             }
1045         }
1046         if stmt_ends_with_semi(&st.node) {
1047             try!(word(&mut self.s, ";"));
1048         }
1049         self.maybe_print_trailing_comment(st.span, None)
1050     }
1051
1052     pub fn print_block(&mut self, blk: &hir::Block) -> io::Result<()> {
1053         self.print_block_with_attrs(blk, &[])
1054     }
1055
1056     pub fn print_block_unclosed(&mut self, blk: &hir::Block) -> io::Result<()> {
1057         self.print_block_unclosed_indent(blk, indent_unit)
1058     }
1059
1060     pub fn print_block_unclosed_indent(&mut self,
1061                                        blk: &hir::Block,
1062                                        indented: usize)
1063                                        -> io::Result<()> {
1064         self.print_block_maybe_unclosed(blk, indented, &[], false)
1065     }
1066
1067     pub fn print_block_with_attrs(&mut self,
1068                                   blk: &hir::Block,
1069                                   attrs: &[ast::Attribute])
1070                                   -> io::Result<()> {
1071         self.print_block_maybe_unclosed(blk, indent_unit, attrs, true)
1072     }
1073
1074     pub fn print_block_maybe_unclosed(&mut self,
1075                                       blk: &hir::Block,
1076                                       indented: usize,
1077                                       attrs: &[ast::Attribute],
1078                                       close_box: bool)
1079                                       -> io::Result<()> {
1080         match blk.rules {
1081             hir::UnsafeBlock(..) => try!(self.word_space("unsafe")),
1082             hir::PushUnsafeBlock(..) => try!(self.word_space("push_unsafe")),
1083             hir::PopUnsafeBlock(..) => try!(self.word_space("pop_unsafe")),
1084             hir::PushUnstableBlock => try!(self.word_space("push_unstable")),
1085             hir::PopUnstableBlock => try!(self.word_space("pop_unstable")),
1086             hir::DefaultBlock => (),
1087         }
1088         try!(self.maybe_print_comment(blk.span.lo));
1089         try!(self.ann.pre(self, NodeBlock(blk)));
1090         try!(self.bopen());
1091
1092         try!(self.print_inner_attributes(attrs));
1093
1094         for st in &blk.stmts {
1095             try!(self.print_stmt(&**st));
1096         }
1097         match blk.expr {
1098             Some(ref expr) => {
1099                 try!(self.space_if_not_bol());
1100                 try!(self.print_expr(&**expr));
1101                 try!(self.maybe_print_trailing_comment(expr.span, Some(blk.span.hi)));
1102             }
1103             _ => (),
1104         }
1105         try!(self.bclose_maybe_open(blk.span, indented, close_box));
1106         self.ann.post(self, NodeBlock(blk))
1107     }
1108
1109     fn print_else(&mut self, els: Option<&hir::Expr>) -> io::Result<()> {
1110         match els {
1111             Some(_else) => {
1112                 match _else.node {
1113                     // "another else-if"
1114                     hir::ExprIf(ref i, ref then, ref e) => {
1115                         try!(self.cbox(indent_unit - 1));
1116                         try!(self.ibox(0));
1117                         try!(word(&mut self.s, " else if "));
1118                         try!(self.print_expr(&**i));
1119                         try!(space(&mut self.s));
1120                         try!(self.print_block(&**then));
1121                         self.print_else(e.as_ref().map(|e| &**e))
1122                     }
1123                     // "final else"
1124                     hir::ExprBlock(ref b) => {
1125                         try!(self.cbox(indent_unit - 1));
1126                         try!(self.ibox(0));
1127                         try!(word(&mut self.s, " else "));
1128                         self.print_block(&**b)
1129                     }
1130                     // BLEAH, constraints would be great here
1131                     _ => {
1132                         panic!("print_if saw if with weird alternative");
1133                     }
1134                 }
1135             }
1136             _ => Ok(()),
1137         }
1138     }
1139
1140     pub fn print_if(&mut self,
1141                     test: &hir::Expr,
1142                     blk: &hir::Block,
1143                     elseopt: Option<&hir::Expr>)
1144                     -> io::Result<()> {
1145         try!(self.head("if"));
1146         try!(self.print_expr(test));
1147         try!(space(&mut self.s));
1148         try!(self.print_block(blk));
1149         self.print_else(elseopt)
1150     }
1151
1152     pub fn print_if_let(&mut self,
1153                         pat: &hir::Pat,
1154                         expr: &hir::Expr,
1155                         blk: &hir::Block,
1156                         elseopt: Option<&hir::Expr>)
1157                         -> io::Result<()> {
1158         try!(self.head("if let"));
1159         try!(self.print_pat(pat));
1160         try!(space(&mut self.s));
1161         try!(self.word_space("="));
1162         try!(self.print_expr(expr));
1163         try!(space(&mut self.s));
1164         try!(self.print_block(blk));
1165         self.print_else(elseopt)
1166     }
1167
1168
1169     fn print_call_post(&mut self, args: &[P<hir::Expr>]) -> io::Result<()> {
1170         try!(self.popen());
1171         try!(self.commasep_exprs(Inconsistent, args));
1172         self.pclose()
1173     }
1174
1175     pub fn print_expr_maybe_paren(&mut self, expr: &hir::Expr) -> io::Result<()> {
1176         let needs_par = needs_parentheses(expr);
1177         if needs_par {
1178             try!(self.popen());
1179         }
1180         try!(self.print_expr(expr));
1181         if needs_par {
1182             try!(self.pclose());
1183         }
1184         Ok(())
1185     }
1186
1187     fn print_expr_vec(&mut self, exprs: &[P<hir::Expr>]) -> io::Result<()> {
1188         try!(self.ibox(indent_unit));
1189         try!(word(&mut self.s, "["));
1190         try!(self.commasep_exprs(Inconsistent, &exprs[..]));
1191         try!(word(&mut self.s, "]"));
1192         self.end()
1193     }
1194
1195     fn print_expr_repeat(&mut self, element: &hir::Expr, count: &hir::Expr) -> io::Result<()> {
1196         try!(self.ibox(indent_unit));
1197         try!(word(&mut self.s, "["));
1198         try!(self.print_expr(element));
1199         try!(self.word_space(";"));
1200         try!(self.print_expr(count));
1201         try!(word(&mut self.s, "]"));
1202         self.end()
1203     }
1204
1205     fn print_expr_struct(&mut self,
1206                          path: &hir::Path,
1207                          fields: &[hir::Field],
1208                          wth: &Option<P<hir::Expr>>)
1209                          -> io::Result<()> {
1210         try!(self.print_path(path, true, 0));
1211         try!(word(&mut self.s, "{"));
1212         try!(self.commasep_cmnt(Consistent,
1213                                 &fields[..],
1214                                 |s, field| {
1215                                     try!(s.ibox(indent_unit));
1216                                     try!(s.print_name(field.name.node));
1217                                     try!(s.word_space(":"));
1218                                     try!(s.print_expr(&*field.expr));
1219                                     s.end()
1220                                 },
1221                                 |f| f.span));
1222         match *wth {
1223             Some(ref expr) => {
1224                 try!(self.ibox(indent_unit));
1225                 if !fields.is_empty() {
1226                     try!(word(&mut self.s, ","));
1227                     try!(space(&mut self.s));
1228                 }
1229                 try!(word(&mut self.s, ".."));
1230                 try!(self.print_expr(&**expr));
1231                 try!(self.end());
1232             }
1233             _ => if !fields.is_empty() {
1234                 try!(word(&mut self.s, ","))
1235             },
1236         }
1237         try!(word(&mut self.s, "}"));
1238         Ok(())
1239     }
1240
1241     fn print_expr_tup(&mut self, exprs: &[P<hir::Expr>]) -> io::Result<()> {
1242         try!(self.popen());
1243         try!(self.commasep_exprs(Inconsistent, &exprs[..]));
1244         if exprs.len() == 1 {
1245             try!(word(&mut self.s, ","));
1246         }
1247         self.pclose()
1248     }
1249
1250     fn print_expr_call(&mut self, func: &hir::Expr, args: &[P<hir::Expr>]) -> io::Result<()> {
1251         try!(self.print_expr_maybe_paren(func));
1252         self.print_call_post(args)
1253     }
1254
1255     fn print_expr_method_call(&mut self,
1256                               name: Spanned<ast::Name>,
1257                               tys: &[P<hir::Ty>],
1258                               args: &[P<hir::Expr>])
1259                               -> io::Result<()> {
1260         let base_args = &args[1..];
1261         try!(self.print_expr(&*args[0]));
1262         try!(word(&mut self.s, "."));
1263         try!(self.print_name(name.node));
1264         if !tys.is_empty() {
1265             try!(word(&mut self.s, "::<"));
1266             try!(self.commasep(Inconsistent, tys, |s, ty| s.print_type(&**ty)));
1267             try!(word(&mut self.s, ">"));
1268         }
1269         self.print_call_post(base_args)
1270     }
1271
1272     fn print_expr_binary(&mut self,
1273                          op: hir::BinOp,
1274                          lhs: &hir::Expr,
1275                          rhs: &hir::Expr)
1276                          -> io::Result<()> {
1277         try!(self.print_expr(lhs));
1278         try!(space(&mut self.s));
1279         try!(self.word_space(::util::binop_to_string(op.node)));
1280         self.print_expr(rhs)
1281     }
1282
1283     fn print_expr_unary(&mut self, op: hir::UnOp, expr: &hir::Expr) -> io::Result<()> {
1284         try!(word(&mut self.s, ::util::unop_to_string(op)));
1285         self.print_expr_maybe_paren(expr)
1286     }
1287
1288     fn print_expr_addr_of(&mut self,
1289                           mutability: hir::Mutability,
1290                           expr: &hir::Expr)
1291                           -> io::Result<()> {
1292         try!(word(&mut self.s, "&"));
1293         try!(self.print_mutability(mutability));
1294         self.print_expr_maybe_paren(expr)
1295     }
1296
1297     pub fn print_expr(&mut self, expr: &hir::Expr) -> io::Result<()> {
1298         try!(self.maybe_print_comment(expr.span.lo));
1299         try!(self.ibox(indent_unit));
1300         try!(self.ann.pre(self, NodeExpr(expr)));
1301         match expr.node {
1302             hir::ExprBox(ref expr) => {
1303                 try!(self.word_space("box"));
1304                 try!(self.print_expr(expr));
1305             }
1306             hir::ExprVec(ref exprs) => {
1307                 try!(self.print_expr_vec(&exprs[..]));
1308             }
1309             hir::ExprRepeat(ref element, ref count) => {
1310                 try!(self.print_expr_repeat(&**element, &**count));
1311             }
1312             hir::ExprStruct(ref path, ref fields, ref wth) => {
1313                 try!(self.print_expr_struct(path, &fields[..], wth));
1314             }
1315             hir::ExprTup(ref exprs) => {
1316                 try!(self.print_expr_tup(&exprs[..]));
1317             }
1318             hir::ExprCall(ref func, ref args) => {
1319                 try!(self.print_expr_call(&**func, &args[..]));
1320             }
1321             hir::ExprMethodCall(name, ref tys, ref args) => {
1322                 try!(self.print_expr_method_call(name, &tys[..], &args[..]));
1323             }
1324             hir::ExprBinary(op, ref lhs, ref rhs) => {
1325                 try!(self.print_expr_binary(op, &**lhs, &**rhs));
1326             }
1327             hir::ExprUnary(op, ref expr) => {
1328                 try!(self.print_expr_unary(op, &**expr));
1329             }
1330             hir::ExprAddrOf(m, ref expr) => {
1331                 try!(self.print_expr_addr_of(m, &**expr));
1332             }
1333             hir::ExprLit(ref lit) => {
1334                 try!(self.print_literal(&**lit));
1335             }
1336             hir::ExprCast(ref expr, ref ty) => {
1337                 try!(self.print_expr(&**expr));
1338                 try!(space(&mut self.s));
1339                 try!(self.word_space("as"));
1340                 try!(self.print_type(&**ty));
1341             }
1342             hir::ExprIf(ref test, ref blk, ref elseopt) => {
1343                 try!(self.print_if(&**test, &**blk, elseopt.as_ref().map(|e| &**e)));
1344             }
1345             hir::ExprWhile(ref test, ref blk, opt_ident) => {
1346                 if let Some(ident) = opt_ident {
1347                     try!(self.print_name(ident.name));
1348                     try!(self.word_space(":"));
1349                 }
1350                 try!(self.head("while"));
1351                 try!(self.print_expr(&**test));
1352                 try!(space(&mut self.s));
1353                 try!(self.print_block(&**blk));
1354             }
1355             hir::ExprLoop(ref blk, opt_ident) => {
1356                 if let Some(ident) = opt_ident {
1357                     try!(self.print_name(ident.name));
1358                     try!(self.word_space(":"));
1359                 }
1360                 try!(self.head("loop"));
1361                 try!(space(&mut self.s));
1362                 try!(self.print_block(&**blk));
1363             }
1364             hir::ExprMatch(ref expr, ref arms, _) => {
1365                 try!(self.cbox(indent_unit));
1366                 try!(self.ibox(4));
1367                 try!(self.word_nbsp("match"));
1368                 try!(self.print_expr(&**expr));
1369                 try!(space(&mut self.s));
1370                 try!(self.bopen());
1371                 for arm in arms {
1372                     try!(self.print_arm(arm));
1373                 }
1374                 try!(self.bclose_(expr.span, indent_unit));
1375             }
1376             hir::ExprClosure(capture_clause, ref decl, ref body) => {
1377                 try!(self.print_capture_clause(capture_clause));
1378
1379                 try!(self.print_fn_block_args(&**decl));
1380                 try!(space(&mut self.s));
1381
1382                 let default_return = match decl.output {
1383                     hir::DefaultReturn(..) => true,
1384                     _ => false,
1385                 };
1386
1387                 if !default_return || !body.stmts.is_empty() || body.expr.is_none() {
1388                     try!(self.print_block_unclosed(&**body));
1389                 } else {
1390                     // we extract the block, so as not to create another set of boxes
1391                     match body.expr.as_ref().unwrap().node {
1392                         hir::ExprBlock(ref blk) => {
1393                             try!(self.print_block_unclosed(&**blk));
1394                         }
1395                         _ => {
1396                             // this is a bare expression
1397                             try!(self.print_expr(body.expr.as_ref().map(|e| &**e).unwrap()));
1398                             try!(self.end()); // need to close a box
1399                         }
1400                     }
1401                 }
1402                 // a box will be closed by print_expr, but we didn't want an overall
1403                 // wrapper so we closed the corresponding opening. so create an
1404                 // empty box to satisfy the close.
1405                 try!(self.ibox(0));
1406             }
1407             hir::ExprBlock(ref blk) => {
1408                 // containing cbox, will be closed by print-block at }
1409                 try!(self.cbox(indent_unit));
1410                 // head-box, will be closed by print-block after {
1411                 try!(self.ibox(0));
1412                 try!(self.print_block(&**blk));
1413             }
1414             hir::ExprAssign(ref lhs, ref rhs) => {
1415                 try!(self.print_expr(&**lhs));
1416                 try!(space(&mut self.s));
1417                 try!(self.word_space("="));
1418                 try!(self.print_expr(&**rhs));
1419             }
1420             hir::ExprAssignOp(op, ref lhs, ref rhs) => {
1421                 try!(self.print_expr(&**lhs));
1422                 try!(space(&mut self.s));
1423                 try!(word(&mut self.s, ::util::binop_to_string(op.node)));
1424                 try!(self.word_space("="));
1425                 try!(self.print_expr(&**rhs));
1426             }
1427             hir::ExprField(ref expr, name) => {
1428                 try!(self.print_expr(&**expr));
1429                 try!(word(&mut self.s, "."));
1430                 try!(self.print_name(name.node));
1431             }
1432             hir::ExprTupField(ref expr, id) => {
1433                 try!(self.print_expr(&**expr));
1434                 try!(word(&mut self.s, "."));
1435                 try!(self.print_usize(id.node));
1436             }
1437             hir::ExprIndex(ref expr, ref index) => {
1438                 try!(self.print_expr(&**expr));
1439                 try!(word(&mut self.s, "["));
1440                 try!(self.print_expr(&**index));
1441                 try!(word(&mut self.s, "]"));
1442             }
1443             hir::ExprRange(ref start, ref end) => {
1444                 if let &Some(ref e) = start {
1445                     try!(self.print_expr(&**e));
1446                 }
1447                 try!(word(&mut self.s, ".."));
1448                 if let &Some(ref e) = end {
1449                     try!(self.print_expr(&**e));
1450                 }
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, &(ref co, ref o, is_rw)| {
1491                     match co.slice_shift_char() {
1492                         Some(('=', operand)) if is_rw => {
1493                             try!(s.print_string(&format!("+{}", operand), ast::CookedStr))
1494                         }
1495                         _ => try!(s.print_string(&co, ast::CookedStr)),
1496                     }
1497                     try!(s.popen());
1498                     try!(s.print_expr(&**o));
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::CookedStr));
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::CookedStr));
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::CookedStr));
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) => self.print_item(&**item),
1575         }
1576     }
1577
1578     pub fn print_usize(&mut self, i: usize) -> io::Result<()> {
1579         word(&mut self.s, &i.to_string())
1580     }
1581
1582     pub fn print_name(&mut self, name: ast::Name) -> io::Result<()> {
1583         try!(word(&mut self.s, &name.as_str()));
1584         self.ann.post(self, NodeName(&name))
1585     }
1586
1587     pub fn print_for_decl(&mut self, loc: &hir::Local, coll: &hir::Expr) -> io::Result<()> {
1588         try!(self.print_local_decl(loc));
1589         try!(space(&mut self.s));
1590         try!(self.word_space("in"));
1591         self.print_expr(coll)
1592     }
1593
1594     fn print_path(&mut self,
1595                   path: &hir::Path,
1596                   colons_before_params: bool,
1597                   depth: usize)
1598                   -> io::Result<()> {
1599         try!(self.maybe_print_comment(path.span.lo));
1600
1601         let mut first = !path.global;
1602         for segment in &path.segments[..path.segments.len() - depth] {
1603             if first {
1604                 first = false
1605             } else {
1606                 try!(word(&mut self.s, "::"))
1607             }
1608
1609             try!(self.print_name(segment.identifier.name));
1610
1611             try!(self.print_path_parameters(&segment.parameters, colons_before_params));
1612         }
1613
1614         Ok(())
1615     }
1616
1617     fn print_qpath(&mut self,
1618                    path: &hir::Path,
1619                    qself: &hir::QSelf,
1620                    colons_before_params: bool)
1621                    -> io::Result<()> {
1622         try!(word(&mut self.s, "<"));
1623         try!(self.print_type(&qself.ty));
1624         if qself.position > 0 {
1625             try!(space(&mut self.s));
1626             try!(self.word_space("as"));
1627             let depth = path.segments.len() - qself.position;
1628             try!(self.print_path(&path, false, depth));
1629         }
1630         try!(word(&mut self.s, ">"));
1631         try!(word(&mut self.s, "::"));
1632         let item_segment = path.segments.last().unwrap();
1633         try!(self.print_name(item_segment.identifier.name));
1634         self.print_path_parameters(&item_segment.parameters, colons_before_params)
1635     }
1636
1637     fn print_path_parameters(&mut self,
1638                              parameters: &hir::PathParameters,
1639                              colons_before_params: bool)
1640                              -> io::Result<()> {
1641         if parameters.is_empty() {
1642             return Ok(());
1643         }
1644
1645         if colons_before_params {
1646             try!(word(&mut self.s, "::"))
1647         }
1648
1649         match *parameters {
1650             hir::AngleBracketedParameters(ref data) => {
1651                 try!(word(&mut self.s, "<"));
1652
1653                 let mut comma = false;
1654                 for lifetime in &data.lifetimes {
1655                     if comma {
1656                         try!(self.word_space(","))
1657                     }
1658                     try!(self.print_lifetime(lifetime));
1659                     comma = true;
1660                 }
1661
1662                 if !data.types.is_empty() {
1663                     if comma {
1664                         try!(self.word_space(","))
1665                     }
1666                     try!(self.commasep(Inconsistent, &data.types, |s, ty| s.print_type(&**ty)));
1667                     comma = true;
1668                 }
1669
1670                 for binding in data.bindings.iter() {
1671                     if comma {
1672                         try!(self.word_space(","))
1673                     }
1674                     try!(self.print_name(binding.name));
1675                     try!(space(&mut self.s));
1676                     try!(self.word_space("="));
1677                     try!(self.print_type(&*binding.ty));
1678                     comma = true;
1679                 }
1680
1681                 try!(word(&mut self.s, ">"))
1682             }
1683
1684             hir::ParenthesizedParameters(ref data) => {
1685                 try!(word(&mut self.s, "("));
1686                 try!(self.commasep(Inconsistent, &data.inputs, |s, ty| s.print_type(&**ty)));
1687                 try!(word(&mut self.s, ")"));
1688
1689                 match data.output {
1690                     None => {}
1691                     Some(ref ty) => {
1692                         try!(self.space_if_not_bol());
1693                         try!(self.word_space("->"));
1694                         try!(self.print_type(&**ty));
1695                     }
1696                 }
1697             }
1698         }
1699
1700         Ok(())
1701     }
1702
1703     pub fn print_pat(&mut self, pat: &hir::Pat) -> io::Result<()> {
1704         try!(self.maybe_print_comment(pat.span.lo));
1705         try!(self.ann.pre(self, NodePat(pat)));
1706         // Pat isn't normalized, but the beauty of it
1707         // is that it doesn't matter
1708         match pat.node {
1709             hir::PatWild => try!(word(&mut self.s, "_")),
1710             hir::PatIdent(binding_mode, ref path1, ref sub) => {
1711                 match binding_mode {
1712                     hir::BindByRef(mutbl) => {
1713                         try!(self.word_nbsp("ref"));
1714                         try!(self.print_mutability(mutbl));
1715                     }
1716                     hir::BindByValue(hir::MutImmutable) => {}
1717                     hir::BindByValue(hir::MutMutable) => {
1718                         try!(self.word_nbsp("mut"));
1719                     }
1720                 }
1721                 try!(self.print_name(path1.node.name));
1722                 match *sub {
1723                     Some(ref p) => {
1724                         try!(word(&mut self.s, "@"));
1725                         try!(self.print_pat(&**p));
1726                     }
1727                     None => (),
1728                 }
1729             }
1730             hir::PatEnum(ref path, ref args_) => {
1731                 try!(self.print_path(path, true, 0));
1732                 match *args_ {
1733                     None => try!(word(&mut self.s, "(..)")),
1734                     Some(ref args) => {
1735                         if !args.is_empty() {
1736                             try!(self.popen());
1737                             try!(self.commasep(Inconsistent, &args[..], |s, p| s.print_pat(&**p)));
1738                             try!(self.pclose());
1739                         }
1740                     }
1741                 }
1742             }
1743             hir::PatQPath(ref qself, ref path) => {
1744                 try!(self.print_qpath(path, qself, false));
1745             }
1746             hir::PatStruct(ref path, ref fields, etc) => {
1747                 try!(self.print_path(path, true, 0));
1748                 try!(self.nbsp());
1749                 try!(self.word_space("{"));
1750                 try!(self.commasep_cmnt(Consistent,
1751                                         &fields[..],
1752                                         |s, f| {
1753                                             try!(s.cbox(indent_unit));
1754                                             if !f.node.is_shorthand {
1755                                                 try!(s.print_name(f.node.name));
1756                                                 try!(s.word_nbsp(":"));
1757                                             }
1758                                             try!(s.print_pat(&*f.node.pat));
1759                                             s.end()
1760                                         },
1761                                         |f| f.node.pat.span));
1762                 if etc {
1763                     if !fields.is_empty() {
1764                         try!(self.word_space(","));
1765                     }
1766                     try!(word(&mut self.s, ".."));
1767                 }
1768                 try!(space(&mut self.s));
1769                 try!(word(&mut self.s, "}"));
1770             }
1771             hir::PatTup(ref elts) => {
1772                 try!(self.popen());
1773                 try!(self.commasep(Inconsistent, &elts[..], |s, p| s.print_pat(&**p)));
1774                 if elts.len() == 1 {
1775                     try!(word(&mut self.s, ","));
1776                 }
1777                 try!(self.pclose());
1778             }
1779             hir::PatBox(ref inner) => {
1780                 try!(word(&mut self.s, "box "));
1781                 try!(self.print_pat(&**inner));
1782             }
1783             hir::PatRegion(ref inner, mutbl) => {
1784                 try!(word(&mut self.s, "&"));
1785                 if mutbl == hir::MutMutable {
1786                     try!(word(&mut self.s, "mut "));
1787                 }
1788                 try!(self.print_pat(&**inner));
1789             }
1790             hir::PatLit(ref e) => try!(self.print_expr(&**e)),
1791             hir::PatRange(ref begin, ref end) => {
1792                 try!(self.print_expr(&**begin));
1793                 try!(space(&mut self.s));
1794                 try!(word(&mut self.s, "..."));
1795                 try!(self.print_expr(&**end));
1796             }
1797             hir::PatVec(ref before, ref slice, ref after) => {
1798                 try!(word(&mut self.s, "["));
1799                 try!(self.commasep(Inconsistent, &before[..], |s, p| s.print_pat(&**p)));
1800                 if let Some(ref p) = *slice {
1801                     if !before.is_empty() {
1802                         try!(self.word_space(","));
1803                     }
1804                     if p.node != hir::PatWild {
1805                         try!(self.print_pat(&**p));
1806                     }
1807                     try!(word(&mut self.s, ".."));
1808                     if !after.is_empty() {
1809                         try!(self.word_space(","));
1810                     }
1811                 }
1812                 try!(self.commasep(Inconsistent, &after[..], |s, p| s.print_pat(&**p)));
1813                 try!(word(&mut self.s, "]"));
1814             }
1815         }
1816         self.ann.post(self, NodePat(pat))
1817     }
1818
1819     fn print_arm(&mut self, arm: &hir::Arm) -> io::Result<()> {
1820         // I have no idea why this check is necessary, but here it
1821         // is :(
1822         if arm.attrs.is_empty() {
1823             try!(space(&mut self.s));
1824         }
1825         try!(self.cbox(indent_unit));
1826         try!(self.ibox(0));
1827         try!(self.print_outer_attributes(&arm.attrs));
1828         let mut first = true;
1829         for p in &arm.pats {
1830             if first {
1831                 first = false;
1832             } else {
1833                 try!(space(&mut self.s));
1834                 try!(self.word_space("|"));
1835             }
1836             try!(self.print_pat(&**p));
1837         }
1838         try!(space(&mut self.s));
1839         if let Some(ref e) = arm.guard {
1840             try!(self.word_space("if"));
1841             try!(self.print_expr(&**e));
1842             try!(space(&mut self.s));
1843         }
1844         try!(self.word_space("=>"));
1845
1846         match arm.body.node {
1847             hir::ExprBlock(ref blk) => {
1848                 // the block will close the pattern's ibox
1849                 try!(self.print_block_unclosed_indent(&**blk, indent_unit));
1850
1851                 // If it is a user-provided unsafe block, print a comma after it
1852                 if let hir::UnsafeBlock(hir::UserProvided) = blk.rules {
1853                     try!(word(&mut self.s, ","));
1854                 }
1855             }
1856             _ => {
1857                 try!(self.end()); // close the ibox for the pattern
1858                 try!(self.print_expr(&*arm.body));
1859                 try!(word(&mut self.s, ","));
1860             }
1861         }
1862         self.end() // close enclosing cbox
1863     }
1864
1865     // Returns whether it printed anything
1866     fn print_explicit_self(&mut self,
1867                            explicit_self: &hir::ExplicitSelf_,
1868                            mutbl: hir::Mutability)
1869                            -> io::Result<bool> {
1870         try!(self.print_mutability(mutbl));
1871         match *explicit_self {
1872             hir::SelfStatic => {
1873                 return Ok(false);
1874             }
1875             hir::SelfValue(_) => {
1876                 try!(word(&mut self.s, "self"));
1877             }
1878             hir::SelfRegion(ref lt, m, _) => {
1879                 try!(word(&mut self.s, "&"));
1880                 try!(self.print_opt_lifetime(lt));
1881                 try!(self.print_mutability(m));
1882                 try!(word(&mut self.s, "self"));
1883             }
1884             hir::SelfExplicit(ref typ, _) => {
1885                 try!(word(&mut self.s, "self"));
1886                 try!(self.word_space(":"));
1887                 try!(self.print_type(&**typ));
1888             }
1889         }
1890         return Ok(true);
1891     }
1892
1893     pub fn print_fn(&mut self,
1894                     decl: &hir::FnDecl,
1895                     unsafety: hir::Unsafety,
1896                     constness: hir::Constness,
1897                     abi: abi::Abi,
1898                     name: Option<ast::Name>,
1899                     generics: &hir::Generics,
1900                     opt_explicit_self: Option<&hir::ExplicitSelf_>,
1901                     vis: hir::Visibility)
1902                     -> io::Result<()> {
1903         try!(self.print_fn_header_info(unsafety, constness, abi, vis));
1904
1905         if let Some(name) = name {
1906             try!(self.nbsp());
1907             try!(self.print_name(name));
1908         }
1909         try!(self.print_generics(generics));
1910         try!(self.print_fn_args_and_ret(decl, opt_explicit_self));
1911         self.print_where_clause(&generics.where_clause)
1912     }
1913
1914     pub fn print_fn_args(&mut self,
1915                          decl: &hir::FnDecl,
1916                          opt_explicit_self: Option<&hir::ExplicitSelf_>)
1917                          -> io::Result<()> {
1918         // It is unfortunate to duplicate the commasep logic, but we want the
1919         // self type and the args all in the same box.
1920         try!(self.rbox(0, Inconsistent));
1921         let mut first = true;
1922         if let Some(explicit_self) = opt_explicit_self {
1923             let m = match explicit_self {
1924                 &hir::SelfStatic => hir::MutImmutable,
1925                 _ => match decl.inputs[0].pat.node {
1926                     hir::PatIdent(hir::BindByValue(m), _, _) => m,
1927                     _ => hir::MutImmutable,
1928                 },
1929             };
1930             first = !try!(self.print_explicit_self(explicit_self, m));
1931         }
1932
1933         // HACK(eddyb) ignore the separately printed self argument.
1934         let args = if first {
1935             &decl.inputs[..]
1936         } else {
1937             &decl.inputs[1..]
1938         };
1939
1940         for arg in args {
1941             if first {
1942                 first = false;
1943             } else {
1944                 try!(self.word_space(","));
1945             }
1946             try!(self.print_arg(arg));
1947         }
1948
1949         self.end()
1950     }
1951
1952     pub fn print_fn_args_and_ret(&mut self,
1953                                  decl: &hir::FnDecl,
1954                                  opt_explicit_self: Option<&hir::ExplicitSelf_>)
1955                                  -> io::Result<()> {
1956         try!(self.popen());
1957         try!(self.print_fn_args(decl, opt_explicit_self));
1958         if decl.variadic {
1959             try!(word(&mut self.s, ", ..."));
1960         }
1961         try!(self.pclose());
1962
1963         self.print_fn_output(decl)
1964     }
1965
1966     pub fn print_fn_block_args(&mut self, decl: &hir::FnDecl) -> io::Result<()> {
1967         try!(word(&mut self.s, "|"));
1968         try!(self.print_fn_args(decl, None));
1969         try!(word(&mut self.s, "|"));
1970
1971         if let hir::DefaultReturn(..) = decl.output {
1972             return Ok(());
1973         }
1974
1975         try!(self.space_if_not_bol());
1976         try!(self.word_space("->"));
1977         match decl.output {
1978             hir::Return(ref ty) => {
1979                 try!(self.print_type(&**ty));
1980                 self.maybe_print_comment(ty.span.lo)
1981             }
1982             hir::DefaultReturn(..) => unreachable!(),
1983             hir::NoReturn(span) => {
1984                 try!(self.word_nbsp("!"));
1985                 self.maybe_print_comment(span.lo)
1986             }
1987         }
1988     }
1989
1990     pub fn print_capture_clause(&mut self, capture_clause: hir::CaptureClause) -> io::Result<()> {
1991         match capture_clause {
1992             hir::CaptureByValue => self.word_space("move"),
1993             hir::CaptureByRef => Ok(()),
1994         }
1995     }
1996
1997     pub fn print_bounds(&mut self, prefix: &str, bounds: &[hir::TyParamBound]) -> io::Result<()> {
1998         if !bounds.is_empty() {
1999             try!(word(&mut self.s, prefix));
2000             let mut first = true;
2001             for bound in bounds {
2002                 try!(self.nbsp());
2003                 if first {
2004                     first = false;
2005                 } else {
2006                     try!(self.word_space("+"));
2007                 }
2008
2009                 try!(match *bound {
2010                     TraitTyParamBound(ref tref, TraitBoundModifier::None) => {
2011                         self.print_poly_trait_ref(tref)
2012                     }
2013                     TraitTyParamBound(ref tref, TraitBoundModifier::Maybe) => {
2014                         try!(word(&mut self.s, "?"));
2015                         self.print_poly_trait_ref(tref)
2016                     }
2017                     RegionTyParamBound(ref lt) => {
2018                         self.print_lifetime(lt)
2019                     }
2020                 })
2021             }
2022             Ok(())
2023         } else {
2024             Ok(())
2025         }
2026     }
2027
2028     pub fn print_lifetime(&mut self, lifetime: &hir::Lifetime) -> io::Result<()> {
2029         self.print_name(lifetime.name)
2030     }
2031
2032     pub fn print_lifetime_def(&mut self, lifetime: &hir::LifetimeDef) -> io::Result<()> {
2033         try!(self.print_lifetime(&lifetime.lifetime));
2034         let mut sep = ":";
2035         for v in &lifetime.bounds {
2036             try!(word(&mut self.s, sep));
2037             try!(self.print_lifetime(v));
2038             sep = "+";
2039         }
2040         Ok(())
2041     }
2042
2043     pub fn print_generics(&mut self, generics: &hir::Generics) -> io::Result<()> {
2044         let total = generics.lifetimes.len() + generics.ty_params.len();
2045         if total == 0 {
2046             return Ok(());
2047         }
2048
2049         try!(word(&mut self.s, "<"));
2050
2051         let mut ints = Vec::new();
2052         for i in 0..total {
2053             ints.push(i);
2054         }
2055
2056         try!(self.commasep(Inconsistent, &ints[..], |s, &idx| {
2057             if idx < generics.lifetimes.len() {
2058                 let lifetime = &generics.lifetimes[idx];
2059                 s.print_lifetime_def(lifetime)
2060             } else {
2061                 let idx = idx - generics.lifetimes.len();
2062                 let param = &generics.ty_params[idx];
2063                 s.print_ty_param(param)
2064             }
2065         }));
2066
2067         try!(word(&mut self.s, ">"));
2068         Ok(())
2069     }
2070
2071     pub fn print_ty_param(&mut self, param: &hir::TyParam) -> io::Result<()> {
2072         try!(self.print_name(param.name));
2073         try!(self.print_bounds(":", &param.bounds));
2074         match param.default {
2075             Some(ref default) => {
2076                 try!(space(&mut self.s));
2077                 try!(self.word_space("="));
2078                 self.print_type(&**default)
2079             }
2080             _ => Ok(()),
2081         }
2082     }
2083
2084     pub fn print_where_clause(&mut self, where_clause: &hir::WhereClause) -> io::Result<()> {
2085         if where_clause.predicates.is_empty() {
2086             return Ok(());
2087         }
2088
2089         try!(space(&mut self.s));
2090         try!(self.word_space("where"));
2091
2092         for (i, predicate) in where_clause.predicates.iter().enumerate() {
2093             if i != 0 {
2094                 try!(self.word_space(","));
2095             }
2096
2097             match predicate {
2098                 &hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate{ref bound_lifetimes,
2099                                                                               ref bounded_ty,
2100                                                                               ref bounds,
2101                                                                               ..}) => {
2102                     try!(self.print_formal_lifetime_list(bound_lifetimes));
2103                     try!(self.print_type(&**bounded_ty));
2104                     try!(self.print_bounds(":", bounds));
2105                 }
2106                 &hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate{ref lifetime,
2107                                                                                 ref bounds,
2108                                                                                 ..}) => {
2109                     try!(self.print_lifetime(lifetime));
2110                     try!(word(&mut self.s, ":"));
2111
2112                     for (i, bound) in bounds.iter().enumerate() {
2113                         try!(self.print_lifetime(bound));
2114
2115                         if i != 0 {
2116                             try!(word(&mut self.s, ":"));
2117                         }
2118                     }
2119                 }
2120                 &hir::WherePredicate::EqPredicate(hir::WhereEqPredicate{ref path, ref ty, ..}) => {
2121                     try!(self.print_path(path, false, 0));
2122                     try!(space(&mut self.s));
2123                     try!(self.word_space("="));
2124                     try!(self.print_type(&**ty));
2125                 }
2126             }
2127         }
2128
2129         Ok(())
2130     }
2131
2132     pub fn print_view_path(&mut self, vp: &hir::ViewPath) -> io::Result<()> {
2133         match vp.node {
2134             hir::ViewPathSimple(name, ref path) => {
2135                 try!(self.print_path(path, false, 0));
2136
2137                 if path.segments.last().unwrap().identifier.name != name {
2138                     try!(space(&mut self.s));
2139                     try!(self.word_space("as"));
2140                     try!(self.print_name(name));
2141                 }
2142
2143                 Ok(())
2144             }
2145
2146             hir::ViewPathGlob(ref path) => {
2147                 try!(self.print_path(path, false, 0));
2148                 word(&mut self.s, "::*")
2149             }
2150
2151             hir::ViewPathList(ref path, ref segments) => {
2152                 if path.segments.is_empty() {
2153                     try!(word(&mut self.s, "{"));
2154                 } else {
2155                     try!(self.print_path(path, false, 0));
2156                     try!(word(&mut self.s, "::{"));
2157                 }
2158                 try!(self.commasep(Inconsistent, &segments[..], |s, w| {
2159                     match w.node {
2160                         hir::PathListIdent { name, .. } => {
2161                             s.print_name(name)
2162                         }
2163                         hir::PathListMod { .. } => {
2164                             word(&mut s.s, "self")
2165                         }
2166                     }
2167                 }));
2168                 word(&mut self.s, "}")
2169             }
2170         }
2171     }
2172
2173     pub fn print_mutability(&mut self, mutbl: hir::Mutability) -> io::Result<()> {
2174         match mutbl {
2175             hir::MutMutable => self.word_nbsp("mut"),
2176             hir::MutImmutable => Ok(()),
2177         }
2178     }
2179
2180     pub fn print_mt(&mut self, mt: &hir::MutTy) -> io::Result<()> {
2181         try!(self.print_mutability(mt.mutbl));
2182         self.print_type(&*mt.ty)
2183     }
2184
2185     pub fn print_arg(&mut self, input: &hir::Arg) -> io::Result<()> {
2186         try!(self.ibox(indent_unit));
2187         match input.ty.node {
2188             hir::TyInfer => try!(self.print_pat(&*input.pat)),
2189             _ => {
2190                 match input.pat.node {
2191                     hir::PatIdent(_, ref path1, _) if
2192                         path1.node.name ==
2193                             parse::token::special_idents::invalid.name => {
2194                         // Do nothing.
2195                     }
2196                     _ => {
2197                         try!(self.print_pat(&*input.pat));
2198                         try!(word(&mut self.s, ":"));
2199                         try!(space(&mut self.s));
2200                     }
2201                 }
2202                 try!(self.print_type(&*input.ty));
2203             }
2204         }
2205         self.end()
2206     }
2207
2208     pub fn print_fn_output(&mut self, decl: &hir::FnDecl) -> io::Result<()> {
2209         if let hir::DefaultReturn(..) = decl.output {
2210             return Ok(());
2211         }
2212
2213         try!(self.space_if_not_bol());
2214         try!(self.ibox(indent_unit));
2215         try!(self.word_space("->"));
2216         match decl.output {
2217             hir::NoReturn(_) => try!(self.word_nbsp("!")),
2218             hir::DefaultReturn(..) => unreachable!(),
2219             hir::Return(ref ty) => try!(self.print_type(&**ty)),
2220         }
2221         try!(self.end());
2222
2223         match decl.output {
2224             hir::Return(ref output) => self.maybe_print_comment(output.span.lo),
2225             _ => Ok(()),
2226         }
2227     }
2228
2229     pub fn print_ty_fn(&mut self,
2230                        abi: abi::Abi,
2231                        unsafety: hir::Unsafety,
2232                        decl: &hir::FnDecl,
2233                        name: Option<ast::Name>,
2234                        generics: &hir::Generics,
2235                        opt_explicit_self: Option<&hir::ExplicitSelf_>)
2236                        -> io::Result<()> {
2237         try!(self.ibox(indent_unit));
2238         if !generics.lifetimes.is_empty() || !generics.ty_params.is_empty() {
2239             try!(word(&mut self.s, "for"));
2240             try!(self.print_generics(generics));
2241         }
2242         let generics = hir::Generics {
2243             lifetimes: Vec::new(),
2244             ty_params: OwnedSlice::empty(),
2245             where_clause: hir::WhereClause {
2246                 id: ast::DUMMY_NODE_ID,
2247                 predicates: Vec::new(),
2248             },
2249         };
2250         try!(self.print_fn(decl,
2251                            unsafety,
2252                            hir::Constness::NotConst,
2253                            abi,
2254                            name,
2255                            &generics,
2256                            opt_explicit_self,
2257                            hir::Inherited));
2258         self.end()
2259     }
2260
2261     pub fn maybe_print_trailing_comment(&mut self,
2262                                         span: codemap::Span,
2263                                         next_pos: Option<BytePos>)
2264                                         -> io::Result<()> {
2265         let cm = match self.cm {
2266             Some(cm) => cm,
2267             _ => return Ok(()),
2268         };
2269         match self.next_comment() {
2270             Some(ref cmnt) => {
2271                 if (*cmnt).style != comments::Trailing {
2272                     return Ok(());
2273                 }
2274                 let span_line = cm.lookup_char_pos(span.hi);
2275                 let comment_line = cm.lookup_char_pos((*cmnt).pos);
2276                 let mut next = (*cmnt).pos + BytePos(1);
2277                 match next_pos {
2278                     None => (),
2279                     Some(p) => next = p,
2280                 }
2281                 if span.hi < (*cmnt).pos && (*cmnt).pos < next &&
2282                    span_line.line == comment_line.line {
2283                     try!(self.print_comment(cmnt));
2284                     self.cur_cmnt_and_lit.cur_cmnt += 1;
2285                 }
2286             }
2287             _ => (),
2288         }
2289         Ok(())
2290     }
2291
2292     pub fn print_remaining_comments(&mut self) -> io::Result<()> {
2293         // If there aren't any remaining comments, then we need to manually
2294         // make sure there is a line break at the end.
2295         if self.next_comment().is_none() {
2296             try!(hardbreak(&mut self.s));
2297         }
2298         loop {
2299             match self.next_comment() {
2300                 Some(ref cmnt) => {
2301                     try!(self.print_comment(cmnt));
2302                     self.cur_cmnt_and_lit.cur_cmnt += 1;
2303                 }
2304                 _ => break,
2305             }
2306         }
2307         Ok(())
2308     }
2309
2310     pub fn print_opt_abi_and_extern_if_nondefault(&mut self,
2311                                                   opt_abi: Option<abi::Abi>)
2312                                                   -> io::Result<()> {
2313         match opt_abi {
2314             Some(abi::Rust) => Ok(()),
2315             Some(abi) => {
2316                 try!(self.word_nbsp("extern"));
2317                 self.word_nbsp(&abi.to_string())
2318             }
2319             None => Ok(()),
2320         }
2321     }
2322
2323     pub fn print_extern_opt_abi(&mut self, opt_abi: Option<abi::Abi>) -> io::Result<()> {
2324         match opt_abi {
2325             Some(abi) => {
2326                 try!(self.word_nbsp("extern"));
2327                 self.word_nbsp(&abi.to_string())
2328             }
2329             None => Ok(()),
2330         }
2331     }
2332
2333     pub fn print_fn_header_info(&mut self,
2334                                 unsafety: hir::Unsafety,
2335                                 constness: hir::Constness,
2336                                 abi: abi::Abi,
2337                                 vis: hir::Visibility)
2338                                 -> io::Result<()> {
2339         try!(word(&mut self.s, &visibility_qualified(vis, "")));
2340         try!(self.print_unsafety(unsafety));
2341
2342         match constness {
2343             hir::Constness::NotConst => {}
2344             hir::Constness::Const => try!(self.word_nbsp("const")),
2345         }
2346
2347         if abi != abi::Rust {
2348             try!(self.word_nbsp("extern"));
2349             try!(self.word_nbsp(&abi.to_string()));
2350         }
2351
2352         word(&mut self.s, "fn")
2353     }
2354
2355     pub fn print_unsafety(&mut self, s: hir::Unsafety) -> io::Result<()> {
2356         match s {
2357             hir::Unsafety::Normal => Ok(()),
2358             hir::Unsafety::Unsafe => self.word_nbsp("unsafe"),
2359         }
2360     }
2361 }
2362
2363 // Dup'ed from parse::classify, but adapted for the HIR.
2364 /// Does this expression require a semicolon to be treated
2365 /// as a statement? The negation of this: 'can this expression
2366 /// be used as a statement without a semicolon' -- is used
2367 /// as an early-bail-out in the parser so that, for instance,
2368 ///     if true {...} else {...}
2369 ///      |x| 5
2370 /// isn't parsed as (if true {...} else {...} | x) | 5
2371 fn expr_requires_semi_to_be_stmt(e: &hir::Expr) -> bool {
2372     match e.node {
2373         hir::ExprIf(..) |
2374         hir::ExprMatch(..) |
2375         hir::ExprBlock(_) |
2376         hir::ExprWhile(..) |
2377         hir::ExprLoop(..) => false,
2378         _ => true,
2379     }
2380 }
2381
2382 /// this statement requires a semicolon after it.
2383 /// note that in one case (stmt_semi), we've already
2384 /// seen the semicolon, and thus don't need another.
2385 fn stmt_ends_with_semi(stmt: &hir::Stmt_) -> bool {
2386     match *stmt {
2387         hir::StmtDecl(ref d, _) => {
2388             match d.node {
2389                 hir::DeclLocal(_) => true,
2390                 hir::DeclItem(_) => false,
2391             }
2392         }
2393         hir::StmtExpr(ref e, _) => {
2394             expr_requires_semi_to_be_stmt(&**e)
2395         }
2396         hir::StmtSemi(..) => {
2397             false
2398         }
2399     }
2400 }